László P. Biró(1), Gábor Piszter(1), Krisztián Kertész(1), Zsófia Baji(1), Zofia Vértesy(1), Zsolt E. Horváth(1), Géza I. Márk(1), Dávid Kovács(1), Dániel Zámbó(1), Zsolt Bálint(2), Gergely Nagy(3), József S. Pap(3)

(1)HUN-REN, Centre for Energy Research, Institute of Technical Physics and Materials Science, Budapest, Hungary
(2)Hungarian Natural History Museum, Budapest, Hungary
(3)HUN-REN, Centre for Energy Research, Surface Chemistry and Catalysis Department, Budapest, Hungary

Color in reflected light arises from the spectral changes suffered by white light when reflected from a given surface. There are two very different ways of generating reflected colors: by selective absorption of light (“chemical color” of atoms and molecules), or by selective reflection of light (“physical, or structural color” of photonic crystal type nanoarchitectures).
The photonic crystal type nanoarchitectures are nanocomposites of two transparent materials, with different enough refractive indexes to produce a so-called photonic band gap (PBG) [1]. The PBG is analogous to the electronic band gap, well-known from solid state physics, but it is produced when the periodicity of modulation of the refractive index in the photonic nanocomposite is in the wavelength range of the light falling on the PBG material. If the refractive index contrast between the constituent materials is large enough than light within a wavelength range cannot propagate in the PBG material and is reflected from its surface.
Quite remarkably, natural evolution discovered PBG materials many millennia before mankind. The blue and green colors of butterfly wings originate from photonic nanoarchitectures. The PBG nanocomposite is formed between chitin and air. Sophisticated nanoarchitectures in the cover scales of many butterfly species generate an amazing range of beautiful structural colors from UV to green [2]. Most frequently, the structural colors are occurring on the wings of male butterflies and are used in prezygotic sexual communication.
Photocatalysis is the process in which the abundant solar energy is directly converted into chemical transformations - using photogenerated charge carriers - in molecules adsorbed on a semiconductor surface. Photogeneration of charge carriers can take place when the energy of the light falling on the surface is large enough to excite electrons over the band gap of the semiconductor, or appropriate conditions are created for the absorption of multiple photons. This latter process can be enhanced by the so-called “slow light effect” occurring on the surface of the PBG materials. Using this, the visible light efficiency of UV photocatalyst: ZnO - a cheap, abundant, and environmentally safe material - can be enhanced in the visible range. Conformal coating of the butterfly wings possessing structural color by a few nanometers of ZnO layer and doping by Cu2O type nanoparticles can achieve this goal [3].

[1] Biró, L. P., & Vigneron, J. P. (2011). Photonic nanoarchitectures in butterflies and beetles: Valuable sources for bioinspiration. Laser and Photonics Reviews, 5(1), 27–51. https://doi.org/10.1002/lpor.200900018
[2] Piszter, G., Kertész, K., Bálint, Z., & Biró, L. P. (2023). Wide-gamut structural colours on oakblue butterflies by naturally tuned photonic nanoarchitectures. Royal Society Open Science, 10(4). https://doi.org/10.1098/rsos.221487
[3] Piszter, G., Kertész, K., Kovács, D., Zámbó, D., Baji, Z., Illés, L., Nagy, G., Pap, J. S., Bálint, Z., & Biró, L. P. (2022). Spectral Engineering of Hybrid Biotemplated Photonic/Photocatalytic Nanoarchitectures. Nanomaterials, 12(24), 4490. https://doi.org/10.3390/nano12244490

Viktor Kilin(1), Róbert Lunacsek(1), Gergely Vetési(1), Hargita Hegyesi(2), Márk Kozsurek(1), Tamás Ferenc Polgár(3), Roland Patai(3) Alán Alpár(1), Zita Puskár(1)

(1)Semmelweis University, Department of Anatomy, Histology and Embryology
(2)Semmelweis University, Department of Genetics, Cell- and Immunobiology
(3)Biological Research Centre, Institute of Biophysics

Coming to know the communication between the periphery and the central nervous system may be the key in understanding the development of neuropsychiatric and neurodegenerative diseases. The main goal of this work was to investigate the spinal representation of peritoneal inflammation (peritonitis) induced by Complete Freund's Adjuvant (CFA).
According to our previous studies, inflammation induced by intraplantar carrageenan led to increased expression and interaction of multifunctional membrane proteins such as dipeptidyl peptidase 4 enzyme (DPP4), Toll-like receptor 4 (TLR4), and caveolin, resulting in increased production of inflammatory cytokines. Using confocal microscopy and western blot, morphological alterations and changes in the expression of the membrane proteins were examined simultaneously in the mesentery and in the spinal cord during inflammation.
Peripheral blood mononuclear cells (PBMCs) play a key role in inflammatory processes. To investigate the mediators by which the PBMCs communicate with each other and other cell types, an in vitro inflammatory model was established. PBMC cell cultures were treated with the TLR4 agonist LPS and the released mediators were extracted from the supernatant and added to native PBMCs and non-blood-derived dorsal root ganglion cells.
In line with the morphological changes in mesothelial cells, glial cells in the spinal cord also showed morphological alterations during CFA-induced inflammation. The expression of DPP4, TLR4, and caveolin increased in both the peritoneum and the spinal cord. Mediators released upon TLR4 activation by LPS stimulus were taken up in large quantities by both native PBMCs and dorsal root ganglion cells. These results indicate that during peripheral inflammation PBMCs and cells of the peripheral and central nervous systems communicate intensively with each other.

Aicha Elaouni(1,2), Gergő Ballai(2), Ákos Szamosvölgyi(2), Zoltán Kovács(2), Zsolt Pap(2), Henrik Haspel(2,3), Zoltán Kónya(2,3), Hassan Ait Ahsaine(1), Mohamed Saadi(1)

(1)Mohammed V University in Rabat - Faculty of Science, Centre des Sciences des Matériaux, Laboratoire de Chimie Appliquée des Matériaux, Rabat, Morocco
(2)Department of Applied and Environmental Chemistry, University of Szeged, Szeged, Hungary
(3)HUN-REN-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Szeged, Hungary

A facile hydrothermal reaction was employed to construct Bi₂WO₆ of a 3D flowerlike morphology, utilizing two different surfactants: hexadecyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVP). Commercial ZnO was loaded onto the resulting product, and the formation mechanism of ZnO/Bi₂WO₆ was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV-vis spectroscopy. Photocatalytic performance was characterized by the degradation of the model pollutant phenol under UV light irradiation followed by high-performance liquid chromatography (HPLC). It was revealed, that beyond morphological control, the introduction of CTAB surfactant induced an unnoticed doping effect. The latter significantly impacts both the structure and the photoactivity of the photocatalyst. Consequently, this led to an extension of its optical absorption upon loading with ZnO. This study provides novel insights into the roles of surfactants in the synthesis of Bi₂WO₆-based photocatalyst, and on their photocatalytic activity.

Ádám Soós(1), Emőke Szőcs(1), Nándor Nagy(1)

(1)Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary

The enteric nervous system (ENS) governs the function of the gastrointestinal tract. Numerous developmental disorders underlie its defective function, affecting neural stem cells derived from the neural crest. Regenerative medicine offers promising opportunities for personalized stem cell therapy for congenital neurointestinal diseases. Our research explores the possibilities of using dental pulp-derived mesenchymal stem cells (DPSCs) for tissue regeneration. Similar to the ENS, the DPSCs isolated from adult teeth are neural crest derived stem cells, which can be directly reprogrammed towards a neural lineage by viral vector transfection. Isolation of DPSCs alleviates ethical concerns associated with other sources of human stem cells. In our experimental work, we have created neural cell aggregates (neurospheres) from DPSCs directly reprogrammed towards a neural fate using cell culture techniques. Using immunocytochemical methods we have characterized the phenotype of the neurospheres and followed their tissue differentiation by transplanting neurospheres into aganglionic segments of the 5-day-old chicken embryonic hindgut. Utilizing DPSCs, our research aims to restore the nervous tissue in neurocristopathies affecting the ENS.

Pialy Sen, Anshu Kumar Sharma, László Imre, Péter Viktor Nagy, Gábor Szabó, Katalin Tóth*, György Vámosi*

Department of Biophysics and Cell Biology, Faculty of Medicine, Doctoral School of Molecular Cell and Immune Biology, University of Debrecen, Debrecen, Hungary
*Senior authors

Introduction: Lamin A is a component of the nuclear lamina encoded by the LMNA/C gene, which forms a meshwork at the periphery of the nucleus and interacts with hetero- and euchromatin. It is also present in nucleoplasm. PPARγ is a nuclear receptor regulating lipid homeostasis. It heterodimerizes with RXR and works in a ligand-dependent manner.
Aims: Previous findings showed that Lamin A plays an important role in maintaining the viscoelastic properties of chromatin. Lamin A mutation or KO inhibits adipogenesis by reducing PPARγ expression in mouse cells. We were interested in whether Lamin A affects PPARγ mobility and DNA-binding, chromatin dynamics, and hetero/euchromatin distribution in the nucleus.
Methods: We cloned EGFP-tagged PPARγ and created stable cell lines by viral transduction of mouse adult WT (MAF-LMN A+/+) and KO (MAF-LMN A-/-) cells. We studied the mobility of PPARγ by fluorescence correlation spectroscopy (FCS) and chromatin distribution by immunolabelling and confocal imaging.
Results: By using FCS, we identified a slow DNA-bound and a fast freely diffusing or transiently bound PPARγ population. In the absence of ligand, the slow fraction of PPARγ decreased in KO compared to WT cells. Ligand treatment (rosiglitazone, RSG, 1 μM) caused a significant increase of the slow fraction in both cells, which overrode the decrease caused by the lack of lamin A, but the diffusion coefficients remained unchanged. To study the different states of the chromatin we used agarose-embedded MAF (WT/KO) cells and performed immunofluorescence labeling modified histones in the euchromatin (H3K4me3), constitutive (H3K9me3) and facultative heterochromatin (H3K27me3). The average granule size of euchromatin and constitutive heterochromatin decreased in KO cells, while that of facultative heterochromatin did not change relative to the WT. Pearson’s correlation analysis revealed that the PPARγ has a lower colocalization with constitutive and facultative heterochromatin in KO cells than in WT cells, whereas colocalization with euchromatin did not change.
Conclusion: Lamin A plays a role in the distribution and granularity of euchromatin and heterochromatin and its absence weakens PPARγ-DNA binding.

Borbála Kertész(1), Anna Jász(1), Helén Bartók(1), Péter Kovács(3), Zoltán Szadai(1), Zsolt Mezriczky(3), Balázs Chiovini(3), J. Balázs Rózsa(1, 2, 3)

(1)BrainVisionCenter, Budapest, Hungary
(2)Laboratory of 3D Functional Network and Dendritic Imaging, Institute of Experimental Medicine, Budapest, Hungary
(3)Pazmany Peter Catholic University, Faculty Of Information Technology and Bionics, Budapest

Although dendritic signaling strongly influences sensory processing and learning, the connection between dendritic integration and somatic output is not yet fully understood. The aim of this project is to examine the relationship between various aspects of a visual learning paradigm and different dendritic events, such as action potentials, bursts, or subthreshold events. To achieve this goal, we recorded and analyzed both voltage and calcium signal responses, with particular emphasis on the timing, co-occurrence, and propagation of these signals across different depths of the cortex.
We used 3D acousto-optic two-photon laser scanning microscopy to observe the apical dendrites of layer 5 and layer 2-3 pyramidal cells from the trunk to the distal tuft in the primary visual cortex of mice with controlled water access during various visual discrimination tasks. We imaged either jRGECO1a (calcium) and JEDI-2p (voltage) signals simultaneously, or only JEDI-2p or ASAP3 (voltage) sensors. To investigate dendritic events during visual stimuli, we employed a visual task with randomly given rewards in half of the trials. We presented drifting grating visual stimuli of different orientations and directions. The dendrites were measured by 3D lines and square fields utilizing the 3D drift-scanning feature of the AO microscope. This method allows for quick drifting of the excitation spot in 3D space while continuously recording fluorescence data without the need to maintain the same scanning position during the recording.
Our findings indicate that during visual stimuli, there are various types of voltage signals that seem analogous to calcium signals and appear throughout the entire dendrite. This suggests the possibility of determining the source and direction of the signals shown by the calcium and voltage sensors. During the training phase, we measured the dendritic activity of the animals as they were leaning to distinguish between rewarded and non-rewarded visual stimuli. Our measurements detected dendritic events related to different conditions, such as the presence or lack of visual cues, as well as reward or error signals. Our next step will be an in-depth analysis of the composition and propagation of these voltage signals.

Boglárka Tóth(1), Hajnalka Bokor(1), Nóra Hádinger(1), László Acsády(1)

(1)Institute of Experimental Medicine, HUN-REN, Budapest, Hungary

Frontal and sensory layer 5 (L5) cortico-thalamic pathways have several anatomical differences. Layer 5 pathways originating from sensory cortices form large boutons on proximal dendrites of the thalamic cells and pass through the GABAergic interface of the thalamus, the reticular nucleus without giving off collaterals. Our group recently investigated the L5 corticothalamic pathway of various frontal cortical regions and discovered multiple differences compared to sensory corticothalamic L5 pathways. Frontal corticothalamic L5 afferents formed small boutons and innervated the reticular nucleus of the thalamus (Hádinger et al. 2023).
To analyse the size difference of L5 boutons in the thalamus quantitatively, we injected adeno-associated virus containing code for YFP protein into the primary sensory cortex (n=3) and into the secondary motor cortex (n=2) of RBP4-cre, layer 5 specific mice. After 3 weeks of survival period mice were sacrificed and brains were prepared for light microscopical imaging. For imaging we used a Nikon C2 microscope; (60x objective oil immersion, NA = 1.40; image dimensions: 70 x 70 x 10 m, pixel size: x, y: 0.087 m z: 0.125 m). Confocal images were taken from the somatosensory thalamic nucleus, nucleus posterior (PO) nucleus of the thalamus to sample boutons from the primary sensory cortex and from the ventromedial nucleus of the thalamus (VM) which is innervated by the frontal cortical region, the secondary motor cortex (M2). Confocal image stacks were deconvolved using Huygens software. On confocal Z-stack images boutons were marked and outlined by hand on their biggest cross-section, for image analysis with Fiji ImageJ software.
In case of the sensory L5 corticothalamic afferents we found not only the earlier described giant, “rose bud like” boutons, but surprisingly numerous small boutons too, average size of boutons in the area was 0.84 ± 0.46 mm2 (n=714). In the case of the M2 L5 corticothalamic boutons we exclusively found small boutons, average size of boutons in the area was 0.47 ± 0.11 mm2 (n= 429). Boutons in the two area did not show normal distribution (Kolmogorov-Smirnov test pPO« 0.0001; pVM=0.006) and we found the size distribution of the sensory S1 and frontal, motor M2 pathways to be significantly different using the Mann-Whitney test (p« 0.0001).
Our results show that the size of the L5 boutons in the thalamus is dependent upon the cortical region at the origin of the afferents. It suggests that L5-thalamus communication is fine tuned in terms of anatomical features to subserve the network requirements of the given cortico-thalamic circuit.

Gábor Fazekas, Gábor Steinbach

HUN-REN Biological Research Centre, Szeged

The history of microscopes goes back more than 400 years. Over the centuries, technology and science have developed a lot, together with microscopy. And with the appearance of various sensors, it became possible to capture the images seen in the microscope. By now, with our microscopic measurements, we would like to be able to examine our sample in 3D, the images would be ready as soon as possible and the quality of the images would be outstanding. With the help of confocal microscopes, we can get a glimpse of the inside of most biological samples. With laser scanning microscopes, excellent images can be taken, but the acquisition takes a relatively long time, so it is difficult to take a large, high-resolution, three-dimensional images with them. The solution could be the spinning disk microscope, which produces high-quality images extremely quickly. While using a laser scanning microscope it is possible to have optical slices of the sample with 1 pinhole, in the case of a spinning disk there are approximately 20,000 pinholes on a disk that we rotate. In the case of the spinning disk microscope, we use a camera as a sensor instead of a detector, this also promotes the fastest possible imaging, which depends on the speed of the disk rotation in addition to the speed of the camera. It also happens that our sample is very sensitive to light, and the spinning disk microscope is also a good solution for this, because in addition to the fast imaging, the laser intensity does not have to be as strong as in the case of the laser scanning microscope. In my presentation, I will introduce how the spinning disk microscope works, what advantages it has in addition to those listed so far, and why they are possible with this type of microscope.

Anett Schwarcz(1,2), Csaba Cserép(1), Eszter Szabadits(1), Ádám Dénes(1)

(1)Neuroimmunology Laboratory, HUN-REN KOKI, Budapest, Hungary.
(2)János Szentágothai, Semmelweis University Doctoral School of Neuroscience, Budapest, Hungary

The dynamic development of microscopic techniques offers new opportunities for the comprehensive study of biological processes. However, the application of methods covering a wide resolution range requires the right questions to be asked and the definition of a precise target, without which it is difficult to obtain relevant results. In the following, I would like to demonstrate the application of microscopic modalities with different resolution capabilities in the field of neuroscience by highlighting examples from my own work.
Our research focuses on microglial cells which are the main immune cells of the brain. These cells are essential for the normal functioning of the brain and play an important role in maintaining brain homeostasis, proper development and function of neurons, the formation of their synaptic connections and the regulation of inflammatory processes. They also play a role in the control of cerebral blood flow. Carrying out these complex tasks requires continuous communication between the microglia and the other cells of the brain. However, our current understanding of the cell-cell interactions of microglia with neurons, other glial cells and blood vessel cells is rather incomplete.
We uses different microscopic methods, ranging from micrometre magnification to nanometre resolution, to reveal the connectivity of microglial cells. Starting from the lower resolution, we first investigated the location and heterogeneity of glial cells (microglia, astrocytes, oligodendrocytes) and neurons in the cerebral cortex using slide scanning microscope. With this method, we can obtain information on the distribution and quantity of the cells under investigation in a small but fast way for many samples. We then used a higher-resolution confocal laser scanning microscope to take a closer look at how many different cells a microglial cell interacts with at a given time point and how many different cells it interacts with. Then, to achieve nanometre resolution, we used scanning electron microscopy serial section tomography to verify that the putative contact sites visualised by diffraction-limited confocal microscopy are real direct contacts, where the plasma membranes of microglia and other cells are brought within nanometre proximity of each other. Furthermore, these images can be used to reveal the intracellular ultrastructure characteristic of the different contacts. In order to study the dynamics and function of these connections, we use two-photon microscopy in vivo, in a departure from the mainly anatomical microscopy techniques used so far.Our studies will allow us to determine the lifetime, stability and signalling pathway involved in the connection of each contact.
By combining these different microscopic techniques, we can gain a complete view of both the anatomical structure and the functional role of microglial cells in their interactions with other cells. Our studies will be carried out in mouse, human adult and elderly samples, which will help us to understand the subcellular processes underlying ageing and related neurodegenerative neurodegenerative diseases such as Alzheimer's disease.
The project KDP-12-10/PALY-2022 was funded by the Ministry of Culture and Innovation with support from the National Research Development and Innovation Fund under the KDP-2021 grant scheme. The project was supported by the Richter Gedeon Talentum Foundation (1103 Budapest, Gyömrői u. 19-21.).

Péter Faludi(1), Ferenc Lengyel(1), Klaudia Barabás(1), Ildikó Udvarácz(1), Dániel Pham(2), Dóra Reglődi(2), Zsuzsanna Nagy(1), Gergely Kovács(1)

(1)Institute of Physiology, Medical School, University of Pécs, Pécs, Hungary
(2)Department of Anatomy, Medical School, University of Pécs, Pécs, Hungary

Introduction: Pituitary adenylate cyclase-activating polypeptide (PACAP) is a member of the vasoactive intestinal peptide (VIP) neuropeptide family that is involved in the regulation of several releasing hormones and trop-hormones by stimulating intracellular cAMP production. The hypothalamic-pituitary-gonadal (HPG) axis regulates the synthesis and the release of sex hormones and the gametogenesis in all mammals. Although, the effect of PACAP on fertility is well documented, the mechanism of the effect of PACAP on hypothalamic GnRH and kisspeptin neurons, which are key elements at the highest regulatory level of the HPG axis, is not known in detail. In our previous study, we demonstrated hypothalamic changes that could contribute to the irregular oestrous cycle observed in PACAP knockout (KO) female mice.
Aim: In our present experiments, we examined structural changes in the hypothalamus that might underlie the fertility problems found in male PACAP KO mice.
Methods: Our experiments were performed in brain samples obtained from wild-type (WT) and PACAP KO animals using immunohistochemistry techniques. Immunohistochemistry was applied to determine the number and fiber density of GnRH neurons in WT and PACAP KO mice. Using the RNAscope technique, kisspeptin mRNA-positive cells were counted in the rostral periventricular region of the third ventricle (RP3V) and arcuate nucleus (ARC). Finally, the mRNA and protein expression of estrogen receptor alpha (ERα) and the protein expression of androgen receptor (AR) were also examined.
Results: In our experiments, with immunohistochemistry of the hypothalamus, we found that in PACAP KO animals, that the number and fiber density of GnRH neurons decreased in the medial preoptic area. Furthermore, the number of kisspeptin neurons increased in R3PV and the mid-portion of the arcuate nucleus. The amount of ERα mRNA increased in both the anteroventral periventricular nucleus (AVPV) and the arcuate nucleus, in regions where kisspeptin neurons regulating GnRH neurons are located. Interestingly, the number of AR+ cells decreased while the number of ERα+ cells increased in the medial preoptic area (MPOA) region, demonstrating a misbalance between effects exerted by estrogen and testosterone.
Conclusion: Our results suggest that the observed changes in the hypothalamus might be involved in the development of fertility problems in PACAP-deficient males by altering the normal function of the HPG axis. Further experiments are needed to elucidate the exact pathomechanism.

Helga Fanni Schubert(1), Adél Sóti(1), Richard Hembrom(1), Roumaissa Ounoki(1), Enkhjin Enkhbileg(1), Emilija Dukic(2), Cornelia Spetea(2), Katalin Solymosi(1)

(1)Department of Plant Anatomy, ELTE Eötvös Loránd University, Budapest, Hungary
(2)Department of Biological and Environmental Sciences, University of Gothenburg, Göteborg, Sweden

Due to improper irrigation practices, seawater or soil water seepage, high soil salinity represents an important threat to agricultural productivity in several areas of the world. Salt stress affects crops in a complex manner and negatively influences the structure and function of their plastids. In this respect, most studies deal with leaf chloroplasts, and report the swelling of the intrathylakoidal space of chloroplast inner membranes under salt stress. Our previous investigations (Ounoki et al. 2023) indicated that shrinkage may be observed in chloroplasts under salt stress, and swelling is present only in etioplasts. Yet, it is fully unclear what causes this swelling, and whether thylakoid located ion channels or transporters are involved in it or not.
Therefore, in this work, plastid ultrastructure was compared in the cotyledons or leaves of dark- or light-grown thale cress (Arabidopsis thaliana L.) plants of different developmental stages under control conditions and after being exposed to short-term (30 min; 200 or 300 mM NaCl) or long-term salt stress treatments (4 h, 600 mM NaCl:KCl, 1:1). In addition to the wild-type (WT) plants, we had single, double, and triple mutants of the thylakoid-located CLCe chloride ion channel (C), KEA3 K⁺/H⁺ antiporter (K) and VCCN voltage-gated chloride ion channel (V), which were lacking these components.
Based on our transmission electron microscopic analyses, we can conclude that salt stress does not affect the structure of the photosynthetic apparatus of mature chloroplasts in old leaves. However, in the etioplasts of the cotyledons of dark-grown triple (kvc) mutant seedlings salt stress induced the formation of vesicles, and in the cotyledon chloroplasts of young light-grown seedlings it also caused the swelling of the lumen of the stroma thylakoids. In the young chloroplasts of the cotyledons, membrane reorganization processes indicating selective chloroplast autophagy in both wild-type and triple (kvc) mutant plants started already after 4 hours of salt shock (600 mM NaCl:KCl) treatment.
Our results confirmed the sensitivity of etioplasts and young chloroplasts to salt stress, and also outlined the complex role of the various thylakoid ion transport components in the preservation of the structural and functional stability of the photosynthetic apparatus and thylakoid membranes under salt stress.

Acknowledgments
The work was funded by the grant OTKA FK124748, and supported by the ÚNKP-23-5 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund (to K.S.) and by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences (to K.S.). Project no. C2299457 has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under the KDP-2023 funding scheme (to H.F.S).

References: Ounoki et al. (2023) Physiol Plant 175(6):e14100. doi: 10.1111/ppl.14100.

Henrik Haspel(1,2), Henrik Fülöp(2), Koppány Tóth-Kőrösi(2), Gergő Ballai(2), Dániel Sebők(2), Imre Szenti(2), Dorina Gabriella Dobó(3), Ákos Kukovecz(1,2), Zoltán Kónya(1,2)

(1)HUN-REN-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Szeged, Hungary
(2)Department of Applied and Environmental Chemistry, University of Szeged, Szeged, Hungary
(3)Institute of Pharmaceutical Technology and Regulatory Affairs, University of Szeged, Szeged, Hungary

Coordination polymers (CPs) and their porous counterparts, metal organic frameworks (MOFs), are composed of metallic nodes connected mostly by oxygen polydentate organic ligands or aromatic acids, where the repeating coordination extends into 1, 2, or 3 dimensions. Both CPs and MOFs were investigated in a wide range of catalytic processes as catalysts or catalyst precursors. The latter implies the decomposition of the ordered structure into well-dispersed supported nanoparticles by thermal, chemical, or electrochemical reduction. Formerly, we designed and constructed a CO2RR gas-diffusion electrode by the in-situ electrochemical transformation of a silver coordination polymer (Ag-CP) into a carbon-supported silver electrocatalyst [1], whereas the underlying mechanism of the CP/MOF-derived nanoparticle formation remained unknown. In this study, we synthesized the same AgCP in its unsupported form by the reaction of Ag+ and the 2,5-pyridinedicarboxylic acid linker, and the thermal CP decomposition steps were followed by in-situ X-ray diffraction (XRD) and in-situ Raman microscopy under inert, reductive and oxidative atmospheres. Morphology changes were studied by transmission and scanning electron microscopies (HRTEM, SEM), while the thermodynamics of the structural transformation was examined by thermal methods (TGA, DSC). A detailed description of the multi-step Ag nanoparticle formation contributes to the better understanding of the CP/MOF-derived catalyst formation.

Zsombor Molnár(1,2), Máté Hegedűs(3), Péter Németh(1,4), Mihály Pósfai(1,2)

(1)University of Pannonia, Research Institute of Biomolecular and Chemical Engineering, Nanolab
(2)HUN-REN–PE Environmental Mineralogy Research Group, Veszprém
(3)Eötvös Loránd University, Department of Material Physics, Budapest
(4)HUN-REN Research Centre for Astronomy and Earth Sciences, Institute for Geological and Geochemical Research, Budapest

The different CaCO₃ polymorphs, especially the trigonal calcite and the orthorhombic aragonite are the most well-known crystalline alkaline earth carbonate minerals, mostly due to their widespread occurrence in rocks and in the solid frameworks of living organisms. Cation substitutions are very common in both minerals and are widely used for reconstructing environmental changes and geochemical processes. According to basic principles of crystallography and coordination chemistry, only certain cations can be incorporated in large amounts in certain crystal structures, e.g., Mg²⁺ prefers trigonal, calcite-related structures, while the larger Sr²⁺ and Ba²⁺ cations prefer orthorhombic, aragonite-related structures. Here we focused on the extent these basic assumptions apply to amorphous Ca–Sr–Ba-carbonate phases which are precursors of crystalline phases, and how these amorphous precursors transform into crystalline polymorphs.
In our experimental work, we synthesized amorphous Ca–Sr, Ca–Ba and Ca–Sr–Ba-carbonate phases under laboratory conditions from solutions with defined cation compositions. We monitored the kinetic stability of the amorphous phases with a pH electrode, and studied the morphological, compositional and structural features of the solid phases using scanning electron microscopy (SEM), various scanning transmission electron microscopy (STEM) techniques, and Raman spectroscopy measurements were performed on the crystallized end-products. Our observations showed that the amorphous phases incorporated more Ca and had a higher Ba/Sr ratio in all cases than the stochiometric cation ratios of the mother solutions. The incorporated Sr and Ba cations significantly modified the structural properties of the amorphous phases and increased their kinetic stability. Our results show that the presence of amorphous precursors during crystallization leads to a much higher incorporation of Sr²+ and Ba²⁺ cations into calcite-type structures that a priori assumptions would suggest.
This research was supported by NKFIH under grant no. SNN-139585.

Roumaissa Ounoki(1), Adél Sóti(1), Renáta Ünnep(2), Katalin Solymosi(1)

(1)Department of Plant Anatomy, ELTE Eötvös Loránd University, Budapest, Hungary
(2)Neutron Spectroscopy Department, HUN-REN Centre for Energy Research, Budapest, Hungary

Water-soluble salts are accumulating in high concentrations in the soil of approx. 830 million hectares of land, influencing agricultural production, and thus affecting 1.5 billion inhabitants at the global level. Salts present in the soil may directly interact with leaves of seedlings developing in the soil, but are also taken up by plants and accumulate in their above-ground organs, including leaves, where they may interact with the structure and metabolism of their plastids. Literature data about salt stressed plants often report the swelling of the thylakoid lumen as a result of salt stress.
So far, it is not fully clear whether the observed swelling is not an artefact or not associated with osmotic changes occurring before or during chemical fixation. In this work, we compared granum ultrastructure (i.e. granum repeat distance – RD - values) using transmission electron microscopy of chemically fixed and conventionally embedded samples and using small-angle neutron scattering of in vivo samples (Ounoki et al. 2021, 2023). Both methods provided consistent data and similar tendencies in the studied two species. Under salt stress, in spearmint leaves we observed the disorganization of the regular granum structure, while the granum RD values decreased in wheat leaves treated with salt stress in the light, indicating the shrinkage of the granum structure. While our data showed that fully differentiated chloroplasts are not prone to swelling, we have observed that salt stress, and especially high concentrations of Na⁺, induce the swelling of the prothylakoid membranes of the etioplasts of dark-grown seedlings and inhibit their greening (Sóti et al. 2023).
Our data outlined the importance of understanding the potential negative impact of soil salinity on the plastids of seedlings germinating in the soil in the absence of light, and also proved that K⁺ salts (e.g. wood ash) as well as CaCl₂ may represent more environment-friendly snow- and ice-melting compounds on roads during winter.

Acknowledgments:
The work was funded by the grant OTKA FK124748, and supported by the ÚNKP-23-5 New National Excellence Program of the Ministry for Culture and Innovation from the source of the National Research, Development and Innovation Fund (to K.S.) and by the Bolyai János Research Scholarship of the Hungarian Academy of Sciences (to K.S.). The work was also financed from the OTKA PD 138540 grant (to U.R.)

References:
Ounoki et al. (2023) Physiol Plant 175(6):e14100. doi: 10.1111/ppl.14100.
Ounoki et al. (2021) Front Plant Sci 12: 738467. doi: 10.3389/fpls.2021.739467
Sóti et al. (2023) Planta 258, 102 (2023). https://doi.org/10.1007/s00425-023-04255-4

Ilona Nyirő-Kósa(1,2), Zsombor Molnár(1,2), Kornél Rácz(1,2), Mihály Pósfai(1,2)
(1)University of Pannonia, Veszprém, Hungary,
(2)HUN-REN–PE Environmental Mineralogy Research Group, Veszprém, Hungary

Our decade-long research on carbonate formation in Lake Balaton showed that the formation of Mg-calcite, the major constituent mineral of the sediment, is a multi-step process influenced indirectly by algal blooms. Through samples taken during algal blooms and observations from laboratory carbonate precipitation experiments, we could observe and describe certain stages of this process. However, questions remained regarding the specific sub-processes and their timescales involved in the formation of Mg-calcite. In order to understand the complete process of carbonate formation in Lake Balaton, we modeled carbonate precipitation on a mesocosm scale, in a month-long experiment. We controlled the experimental parameters in 12 basins (5 m³ each), with 4 triplets of the basins treated in the same way. Algal blooms were induced, with photosynthesis resulting in changes in water chemistry that led to the precipitation of carbonates. We examined the specific properties of the carbonates that precipitated both in the presence of montmorillonite (a clay mineral) and in a sediment-free environment. The samples were characterized using a Thermo Scientific Talos F200X G2 scanning transmission electron microscope, both in transmission (TEM) and scanning transmission (STEM) modes. High-resolution TEM and high-angle annular dark-field (HAADF) STEM images were obtained and elemental maps were acquired using energy-dispersive X-ray spectroscopy (EDS) in STEM mode. We found that photosynthesis created high supersaturation near the cells, resulting in the fast nucleation of amorphous calcium carbonate (ACC). ACC particles then attached to nm-scale smectite flakes where they instantly transformed into calcite. By the aging of calcite, the crystals grew and clearly visible crystal faces developed (Fig. 1). The process of Mg-calcite formation involved at least two dissolution/reprecipitation cycles. The Mg content of calcite changed parallel with the water chemistry parameters; in particular, dilution caused by a heavy rain resulted in partial dissolution and less Mg in the calcite, while higher temperatures and evaporation increased the Mg content in the solid product. The entire process of Mg-calcite formation took place within hours to days; thus, the properties of Mg-calcite particles in the lake sediment are directly influenced by marked weather changes.
This research was supported by the RRF-2.3.1-21-2022-00014 grant.

Miroslav Ovečka(1), Kateřina Hlaváčková(1), Jiří Sojka(1), Olga Šamajová(1), Jozef Šamaj(1)
(1)Department of Biotechnology, Faculty of Science, Palacký University Olomouc, Šlechtitelů 27, CZ-783 71 Olomouc, Czech Republic, e-mail: miroslav.ovecka@upol.cz

Plants can be visualized by different microscopy methods, but their growth and development are highly dynamic spatio-temporal processes, which make live imaging of plants challenging. The main limitations depend on optical properties of plant cell surfaces, presence of vacuoles, and their bulky size, creating different refractive indexes. There is a need to alleviate out-of-focus fluorescence, phototoxicity, photobleaching, restricted temporal resolution and limitations in imaging depth. In addition, plants have special environmental requirements for undisturbed growth and development during imaging, compromising the possibility to mount them on a glass slide covered by coverslip used in classical microscopy. We analyse diverse processes, such as visualization of microtubule and actin dynamics during plant morphogenesis, signalling by mitogen-activated protein kinases, contribution of vesicular trafficking to the cellular dynamics, and we solve these scientific questions with regard to the tissue- and organ-specific, and developmentally relevant regulations. To address these aims, we utilize (and co-develop) different advanced microscopy methods and techniques. Subcellular architecture, organization and dynamics of most organelles in cells of living plants can be monitored at the nanoscale using super-resolution microscopy methods, such as structured illumination microscopy (SIM) and Airyscan confocal laser scanning microscopy (ACLSM). On the other hand, light-sheet fluorescence microscopy (LSFM) is an ideal method for long-term bioimaging of living plants depicting their development at physiological conditions (Ovečka et al. 2018, 2022). We developed reliable and broadly applicable protocols for short-term bioimaging of plant cells using SIM (Komis et al. 2015) and long-term developmental imaging of plants using LSFM (Ovečka et al. 2015). ACLSM improves lateral resolution up to 120 nm, enabling fast super-resolution imaging. LSFM provides multi-dimensional volumetric observations of intact plants with high efficiency of optical sectioning throughout the sample volume, enabling observation of fast events in living plants with high temporal and spatial resolution. All these parameters favour ACLSM and LSFM for developmental plant imaging at the subcellular, cellular, tissue, organ, and whole-organism levels. Importantly, we insert intact plants into the observation chambers of both ACLSM and LSFM systems vertically, providing natural plant orientation according to the gravitational vector during imaging. To maintain undisturbed plant growth in near-environmental conditions, both systems are coupled with accessory devices developed exclusively in our laboratory that precisely control illumination, temperature and plant perfusion during imaging. These devices enable to collect liquid media fractions for multi-omics analyses, allowing also the direct application of any compound of interest with simultaneous image acquisition. Together with the model plant Arabidopsis thaliana (L.) Heynh., we adapted this approach also for robust crop species Medicago sativa L. and Hordeum vulgare L., documenting growth and development of their roots including the events of plant-microbe interactions. Better understanding of early plant development is indispensable for crop biotechnological research and therefore, these new microscopy approaches significantly broadened our view on how molecular and cellular mechanisms in plants are organized and regulated.
References
Komis et al. (2015) Nature Protocols 10, 1248-1263.
Ovečka et al. (2015) Nature Protocols 10, 1234-1247.
Ovečka et al. (2018) Nature Plants 4, 639-650.
Ovečka et al. (2022) Plant Physiology 188, 683-702.

György Zoltán Radnóczi

HUN-REN Centre for Energy Research, Budapest, Hungary

The annual conference of the Hungarian Microscopy Society is traditionally an interdisciplinary event where researchers working in various fields within microscopy gather to share fresh and interesting results. Since most presentations assume a deeper understanding of the topic, there is often a discussion about the need for less specialized presentations that explain the basics of a given topic for colleagues who are less familiar with it. In this presentation, I will attempt to explain the basics of electron diffraction, commonly discussed by mineralogists, materials scientists, and physicists, for colleagues who rarely encounter this phenomenon while working in other fields.

Csaba Cserép(1)

(1)HUN-REN Institute of Experimental Medicine, Laboratory of Neutoimmunology

Epitope localisation methods based on specific antibody-antigen binding are of fundamental importance in life science research. This is particularly true for two large groups of techniques, pre-embedding and post-embedding immunohistochemical labeling. In my presentation, I will briefly describe the principles, main characteristics, advantages and disadvantages of these techniques and some of their variants, with an indication of their potential applications.

Paulina Nowak

Abbelight, Paris, France

Super-resolution microscopy is a Nobel prize-awarded optical imaging technique that allows crossing the diffraction limit. Among the three super-resolution methods, Single Molecule Localization Microscopy (SMLM) achieves the best resolution. This capability opens new possibilities for studying biological structures and processes at the nanoscale.
Since its creation in 2016, Abbelight’s researchers and engineers have developed cutting-edge solutions to overcome SMLM’s limitations. The talk will cover key advancements from Abbelight. For instance, 1) ASTER - the largest and most homogenous field of view available. The technology results in the speckle-free TIRF illumination required for high-quality SMLM imaging. 2) Spectral Demixing - the unique approach for multi-color SMLM imaging. This technology allows fast simultaneous multi-color imaging, which, combined with the large field of view, helps the user achieve the highest quality data in significantly less time compared to typical SMLM acquisitions.
Overall, Abbelight's SMLM and TIRF solutions provide cutting-edge technologies to advance biological and biomedical research, making super-resolution imaging easy and accessible to everyone.

L.Vassé(1)

(1)JEOL (EUROPE) SAS, 1 Allée de Giverny, 78290 Croissy-sur-Seine, France

Keywords: FIB-SEM,Cryo-prep,Cryo-FIB,Cryo-TEM lamella prep, TEM lamella preparation, 3D analysis, EDS, EBSD

Since 1949, JEOL's legacy has been one of the most remarkable innovations in the development of instruments used to advance scientific research and technology. JEOL has 60 years of expertise in the field of electron.
After a successful introduction of the JIB-PS500i last year , JEOL introduces a new generation of Cryo-FIB this year , the IB-Z200021CFS&IB-Z200022CPC.
This CRYO-FIB-SEM system incorporates a liquid nitrogen cooling stage and a cryocooled specimen transfer mechanism for frozen specimens, making it possible to prepare TEM specimens such as biopolymers.
The specimen transfer mechanism has a built-in sputter coating function. Therefore, this CRYO-FIB-SEM system alone can perform a series of processes to create TEM specimens from frozen specimens including conductivity coating, protective film forming, and FIB processing.
In addition, by using JEOL's CRYO ARM™ cartridge, direct specimen transfer to the CRYO ARM™ after TEM specimen preparation becomes easier.Other features will be also introduced during the presentation:
- High-resolution & High-contrast SEM Imaging
- High-power & High-quality FIB processing
- New Chamber & Stage Design
- Cryo specimen transfer using CRYO ARM™ cartridge
- Highly stable cooling Stage
- JEOL’s unique anti contamination device

Peter Pekker(1)

(1)Nanolab, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Veszprém, Hungary

The degree of Ca:Mg cation ordering is an important parameter in the classification of Ca-Mg carbonates and for understanding their formation. Earlier TEM studies revealed inhomogeneity in cation ordering, suggesting the importance of further studies at the nano- and atomic scales. Despite the experienced difficulties in data collection and processing, STEM HAADF imaging appears to be the most suitable method for the analysis of local ordering phenomena. Due to the beam sensitivity of these minerals, obtaining images with an interpretable signal-to-noise ratio was the most challenging aspect of data collection and processing; therefore, we collected image stacks of hundreds of single frames by applying a low beam current and fast scanning, and summed the individual frames after correcting for the sample drift with image registration methods. Since the signal-to-noise ratio of single frames was very low, we combined the cross-correlation method (Fig. 1A) with manual registration to align atomic columns accurately (Fig. 1B), and for correcting the effect of slow sample drift as well. Based on the crystal chemical information extracted from the corrected and summed HAADF images and STEM EDS elemental maps, the degree of cation ordering was found to be heterogeneous in these mineral grains (Fig. 1C). In a coherent crystal lattice the ordered and disordered areas join along sharp borders and form domains on the nanometer scale, displaying a strong correlation between changes in chemical composition, lattice parameters, and the degree of ordering. These results characterize the nanotexture of these carbonates providing additional information for the understanding of crystallization processes of Ca-Mg carbonates.

Hajnalka Ábrahám, Abigél Molnár, László Seress

Central Electron Microscopic Laboratory, István Ábrahám Nano-Bio-Imaging Center, University of Pécs Medical School, Pécs

Thanks to the possibility of acquisitions of large-scale equipment in recent decades, several universities and research centers could purchase instruments that are unique in the country or in the region. As a result, many institutions have established (or plan to establish) core-facilities to make large-scale instruments available to researchers in the region. On the experience of an electron microscopic laboratory that has been operating as a core-facility for more than 25 years, we present the challenges of service function from the past period through interesting requests that needed certain level of innovations.
The Central Electron Microscopic Laboratory was established in 1998 as an independent service unit at the University of Pécs (predecessor in title of the University of Pécs Medical School (UPMS)) under the leadership of Dr. László Seress. Although it was operating in different organizational forms over the years, it has maintained its core-facility character.
In the past more than 2 decades, the unit, which is part of the UPMS and supported by it, has received numerous requests from other faculties of the University, in addition to the institutes and clinics of the UPMS. The laboratory have also made several contracts with other institutions.
The work involved a wide variety of samples, in addition to the routine ultra-thin sections of human tissue in used medical diagnostics. The samples examined with transmission electron microscope included dairy products, plant cells, cultured animal and human cells, organoids from 3D cell culture, human and mouse oocytes, extracellular vesicles, thrombocytes, zebrafish embryo nanotubes and viruses (e.g. bacteriophages, herpes and coronavirus). Scanning electron microscopy was also used to examine a diverse range of samples, including meteorite debris, dental drills and fillings, dental prosthetic materials, bacterial biofilm, components of chromatography instrument, plant structures and nasal mucosa from experimental animals underwent treatment used in oto- rhino- laryngology.
Since the laboratory staff not only performs electron microscopic examinations, but in most cases also carries out pre-treatments (fixation, embedding, sectioning, contrasting) prior to examinations, methodological challenges were encountered in several cases. In addition, in many cases, interpretation of the results, generation of a data set suitable for statistical analysis, was also the task of the laboratory staff.
In addition to general advice, this involved finding the optimal solution, modifying laboratory protocols, and setting optimal parameters.
The presentation will show some of the interesting but challenging cases described above, which, in addition to the modified protocols, may be useful for laboratories with similar core facilities.

The acquisition of the JEOL JEM-1400Flash TEM electron microscope for the laboratory was supported by GINOP-2.3.3-15-2016-0002.

Erzsébet Dodony(1,2), István Dódony(3), Péter Pekker(3), György Sáfrán(1)

(1)HUN-REN, Center for Energy Research, Institute of Technical Physics and Materials Science, Thin Film Physics Laboratory, Budapest, Hungary
(2)Department of Material Physics, Eötvös Loránd University, Budapest, Hungary
(3)NANOLAB, Research Institute of Biomolecular and Chemical Engineering, University of Pannonia, Veszprém, Hungary

The composition range of the γ-nickel-silicide span between Ni₅Si₂-Ni₃₁Si₁₂. The early structure determination [1] resulted relatively high reliability value (R=0.13), indicating some uncertainties in structural parameters. The increasing efficiency of TEM in crystallography has revealed [2] how inhomogeneous γ-nickel silicide is. Our in-situ HRTEM study [3] revealed several new structural modifications of γ-nickel-silicide.
Using different techniques in microscopy (HRTEM, STEM, HAADF, SAED) and image processing as well as HRTEM simulations (Digital Micrograph, CRISP, JEMS) we determined the modular nature of the γ-nickel-silicide.
The HRTEM micrograph in Figure 1. illustrates how different the γ-nickel silicide can be within the nanoscale regions, despite the fact that FFT and SAED patterns are very similar. In the lecture we are going to discuss the structural features (like stacking, twinning, etc.) responsible for the structural variability of γ-nickel-silicide.

[1] K. Frank and K. Schubert, Kristallstruktur von Ni31Si12, Acta Crystallographica B, 1971, 27, 916-920.
[2] S. H. Chen, C., Carter, Z. Elgat, L R, Zheng, and J. W. Mayer, The structure of Ni5Si2 formed in Ni-Si thin film lateral diffusion couples, J. Appl. Phys. 62 (4), (1987) 1189-1194.
[3] E. Dodony, A. Rečnik, I. Dódony, Gy. Sáfrán, Journal of Alloys and Compounds, 2022, 918, 165466

Titanilla Szögi(1), Barbara Nikolett Borsos(1,2), Dejana Masic(1), Nóra Ördög(1), Nikolett Barta(1), László Tiszlavicz(1), Tibor Pankotai(1,2,3)

(1)Department of Pathology, Albert Szent-Györgyi Medical School, University of Szeged, Állomás utca 1, Szeged H-6725
(2)Competence Centre of the Life Sciences Cluster of the Centre of Excellence for Interdisciplinary Research, Development and Innovation, University of Szeged, Dugonics tér 13, Szeged H-6720, Hungary
(3)Hungarian Centre of Excellence for Molecular Medicine (HCEMM), Genome Integrity and DNA Repair Core Group, Budapesti út 9, Szeged H-6728, Hungary

As of January 13, 2023, over 671 million cases of the coronavirus disease 2019 (COVID-19) have been reported, with more than 67.1 million lives lost globally. The COVID-19 pandemic is caused by infection with the SARS-CoV-2 virus. The COVID-19 disease can be divided into two phases based on the onset of the symptoms: acute (first 4 weeks) and long or post-COVID (4–12 weeks) stage. So, we talk about post-COVID syndrome when the so-called post-COVID symptoms such as fatigue, shortness of breath, hampered respiration, cough, loss of taste or smell and cognitive impairment persist for an extended period of time. Similar symptoms can be observed in individuals diagnosed with genetic mitochondrial disease. Previous experiments have shown that COVID-19 can alter the metabolism of the mitochondria. The overproduction of reactive oxygen species (ROS) due to dysfunction causes a cytokine storm, which then results in a robust immune response. The aim of our research is to examine the structural and mechanical changes of mitochondria and study the effects of oxidative damage and mitophagy-related processes using transmission electron microscopy on tissue samples from the bronchial and nasal mucosa of post-COVID syndrome and control subjects.
For the post-embedding immunohistochemistry, we utilized antibodies targeting proteins involved in mitochondrial fusion (MFN1, MFN2) and fission (FIS1, DRP1), mitophagy (ATG4B), oxidative phosphorylation (LDH), and neutralization of ROS on tissue samples from post-COVID and control groups. Then, we examined the structural and mechanical changes of mitochondria using transmission electron microscopy (JEOL-1400).
We can observe significant differences in the level of proteins involved in fusion and fission in post-COVID individuals compared to control subjects. In addition, we detected significant differences in the level of ATG4B, a protein involved in mitophagy, and LDH, an enzyme crucial for oxidative phosphorylation.
In a healthy body, damaged mitochondria are degraded by mitophagy. The absence of this process in post-COVID individuals may explain the development of acute symptoms. Our experiments demonstrate that the equilibrium between mitochondrial fusion and fission is disrupted during COVID-19 infection. The resulting mitochondrial dysfunction is related to the fact that glycolysis is favored over oxidative phosphorylation during COVID-19 infection.

Ildikó Cora(1), Zsolt Fogarassy(1), Alexander Azarov(2), György Z. Radnóczi(1), Béla Pécz(1), Andrej Kuznetsov(2)

(1)HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Konkoly Thege M út 29-33., 1121 Budapest Hungary
(2)University of Oslo, Department of Physics, Centre for Materials Science and Nanotechnology, PO Box 1048 Blindern, N-0316 Oslo, Norway

Intrinsic properties of Ga₂O₃, like very wide bandgap (Eg > 4.5 eV) and high critical breakdown field (8 MV/cm) higher than SiC or GaN have, makes it a promising candidate for high power electronics, suitable for fabrication of solar-blind detectors for UV-C radiation (wavelength below 280 nm)
In literature six Ga₂O₃ polymorphs were mentioned, from which three have full crystallographic description. β is the one with thermodynamically stable at high temperature, as well with monoclinic structure. All the others are metastable and tend to convert during high temperature treatments. Metastable polymorphs usually appear in mixed form and show nm-scaled ordering, which makes it hard to describe them individually by conventional techniques. First goal is to understand their structure at the nm scale. Second is to reveal the structural development and transformations between the polymorphs. Transmission electron microscopy (electron diffraction, conventional, high resolution and HAADF TEM, and connected simulations) is the primary adequate tool for answering these questions.
Recently, it was revealed that ε phase with disordered Ga in a hexagonal cell does not exist, the Ga is ordered in 5-20 nm large rotational twin domains, which has the orthorhombic κ structure. γ polymorph thought to be of defect spinel structure, however several crystallographic questions are opened, which strongly affects its macroscopic properties and phase transformations.
δ is thought to have bixbyite structure. It is important to understand the crystallographic background of the polymorphism of Ga₂O₃ for their formation mechanism.
Our experiments were done on radiation induced phase transformation of β. First the β → γ phase transformation was crystallographically described. Later the structural and textural development of the γ→ β transformation was monitored by ex situ and in situ annealing experiments (from RT up to 1100°C) applying ED, HRTEM, HAADF techniques combined with simulations. First, the co-existence of β and γ drastically affect the later developed texture of the transformed β layer, and afterwards at higher annealing temperature the presence of the implanted ion dominantly affects the texture development of the β layer.

Bence Radics(1), Viktória Nagy(2), Dániel Vidács(2), Titanilla Szilágyi-Szögi(1), Enikő Budai(1), Róbert Sepp(2)

(1)Department of Pathology, University of Szeged, Szeged, Hungary.
(2)Cardiology Center of the Albert Szent-Györgyi Health Centre, University of Szeged, Szeged, Hungary.

Introduction
Chloroquine is an anti-malarial drug frequently used as immunomodulatory treatment in many systemic autoimmune diseases. It is considered to be a safe and effective alternative of corticosteroids. A rare but severe side effect of long-term chloroquine treatment is cardiomyopathy (CMP), which is characterized by histological changes resembling lysosomal storage diseases (e.g. Fabry disease). The pathognomic ultrastructural changes are the accumulation of lamellar bodies (LB) and curvilinear bodies (CB) (see abstract image A and B) in the cytoplasm of cardiomyocytes. The aim of our study were: 1) to find other disease- or severity specific ultrastructural changes and 2) to correlate the ultrastructural findings with clinical data in patients diagnosed with chloroquine CMP.
Methods
The retrospective analysis included endomyocardial biopsy specimens collected for diagnostic purposes from patients with suspected chloroquine cardiomyopathy from the archive of the Department of Pathology, University of Szeged (from 2013-2024). The ultrathin slides were reanalyzed with a JEOL 1400 transmission electron microscope. Each slide was divided into five zones (1 central and 4 peripheral quadrants) and at least 2 random cardiomyocytes were picked for detailed analysis. We established definitions and registered the presence of the following ultrastructural features in each cell (0 or 1): group forming LB, isolated LB, CB, Z-line streaming (ZLS), dense filamentous cytoplasmic bodies (DFD) and floating nucleus (FN). The normalized ratio of each morphological abnormality (0-1) was calculated from at least 10 cells. Relevant clinical and laboratory data were collected from the integrated hospital information system.
Results
15 cases were found (females: 14) and reanalyzed. Patient age was (median [min-max]) 64 years [38-72]. The most common indication of chloroquine treatment was SLE (n=10), with a duration of 7 years [2-27]. A mild (n=6) and a severe (n=9) cardiomyopathy (CMP) group was distinguished based on the frequency of group forming and isolated LB with k-means cluster analysis. The frequency of CB (1 [0.8-1] and 0.6 [0.2-0.9]); ZLS (1 [0.6-1] and 0.65 [0.5-0.8]) and DFD (0.8 [0.6-1] and 0.4 [0.3-0.7]) were significantly (p<0.05) higher in the severe than in the mild group, respectively (Mann-Whitney U-test). Higher levels of serum proBNP were detected in the severe CMP group (3614 pmol.L-1 [980-11038] vs 896 [275-30930]; p<0.05). The most common ECG abnormality was type III AV-block (n=6/9) in the severe, and bundle branch block (n=4/6) in the mild CMP group.
Discussion
This is the first systematic analysis assessing the severity of chloroquine CMP based on the electron microscopic findings on endomyocardial biopsy specimens in the scientific literature. We could define a mild and a severe CMP group based on the frequency of different ultrastructural abnormalities of cardiomyocytes. The ultrastructural severity of chloroquine cardiotoxicity correlated with various clinical and laboratory data underlying the importance of electron microscopic investigation of heart biopsy specimens.

Zoltán Dankházi(1), Márk Windisch(1,2)

(1)Eötvös Loránd University, Faculty of Science, Department of Materials Physics, Budapest, Hungary
(2)Zoltán Bay Applied Research Nonprofit Kft., Budapest, Hungary

Just as wind blows on desert sand, waves can also appear on surfaces treated with ions. The first reports on this effect were published in the early 1960s. The surface waviness produced by ion beam treatment is sometimes a problem (e.g. TEM lamella fabrication), but this technology is becoming more and more widespread and used. In order to create and avoid periodic structures in a controlled manner, several theoretical descriptions have been developed in the last decades. As a consequence of the boom in micro- and nanotechnology, the number of publications related to the study of surface structures created by ion bombardment has multiplied since the end of the 20th century. The experimental works can be grouped according to the type of ions used, their energy or the electrical conductivity of the irradiated material, as well as its composition, structure and morphology. Behavior according to the latter aspects can be observed in the figure, where a completely different pattern was formed in adjacent parts of the same sample as a result of Ga+ irradiation.
We have created surface structures with Ar+ and Ga+ irradiation in the 100 eV and 30 keV energy and 0°-85° angle ranges using a conventional ion gun or a focused ion beam, mostly on Si single crystals. The surface morphology was investigated with a scanning electron microscope and an atomic force microscope.
In the first part of the talk, we will briefly review the most important experimental and theoretical results published on the subject, and then, after presenting our own measurements, I will compare them with the data found in the literature.

András Kovács

Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons, Forschungszentrum Jülich, Germany

A modern transmission electron microscope (TEM) allows spatial and spectroscopic imaging at 1 Å (or below) on a daily base, with a wide range of possibilities in control sample temperature, environment, electrical biasing, magnetic field. This makes TEM essential in materials science, physics, chemistry, structural biology and industrial research. One of the perhaps less well known applications is the measurement of magnetic properties of materials, for which several TEM techniques are available, such as Lorentz TEM, electron holography, differential phase contrast mapping. However, in order to characterise and understand magnetic properties such as domain wall width, magnetisation, induction mapping, the structure, chemical composition and functional property measurements should all be conducted, in which the specimen preparation plays an important role.
Compared to different material systems, the preparation of magnetic materials for TEM studies is more challenging. In addition to the structural degradation that occurs during ion sputtering, the sample is easily oxidized, which alters the functional magnetic properties of the surface. For this type of measurement, the sample must have a uniform thickness (±10%) and a large surface area (about 10x10 µm). For holographic measurements, a vacuum is required in the immediate vicinity of the sample. Nowadays, solid state bulk and thin film samples are prepared using focused Ga ion beam (FIB) thinning, which induces significant surface damage making post-cleaning process important as ever. The low-energy argon ion beam(<1 keV) thinning technology and approach developed by Árpád Barna and co-workers can still be successfully applied today for the non-destructive preparation of TEM samples. In this talk, two research topics will be presented , in which careful TEM specimen preparation is coupled with the application of modern electron microscopy techniques to (1) understand the structural and magnetic properties of high entropy magnetic alloys (Fig.1) and (2) directly investigate the effect of mechanical strain on magnetization by in situ electron holography measurements.

Tamás Zagyva(1,2), Anamul Haq Mir(3), Robert W. Harrison(4)

(1)Dalton Cumbrian Facility, Dalton Nuclear Institute, The University of Manchester, UK
(2)Department of Chemistry, The University of Manchester, Manchester, UK
(3)MIAMI Irradiation Facility, University of Huddersfield, UK
(4)Nuclear Fuel Centre of Excellence, Department of Mechanical, The University of Manchester, UK

Heavy ion irradiation experiments (using particle accelerators) are commonly used to examine the radiation tolerance of materials for various applications (e.g., shielding materials in nuclear and fusion reactors, the behaviour of high-level waste materials, etc). The MIAMI-2 (Microscope and Ion Accelerator for Materials Investigation) in situ ion irradiation facility at the University of Huddersfield (UK) allows to study radiation damage in materials in real time. The samples can be irradiated with ions inside a transmission electron microscope (TEM) and images can be captured either at regular time intervals or continuously as the material is being damaged by the ion beam.
However, in order to accurately determine the ion radiation-induced damage, the electron beam must not cause additional microstructural changes during the TEM analysis. My PhD research aimed to provide a comprehensive study of electron beam-induced effects in ion-irradiated powellite (CaMoO₄) as a function of temperature and electron flux using the MIAMI-2 facility.
When the powellite grains were exposed to a high electron flux during the TEM measurements, recrystallisation occurred. The electron flux (threshold) where recrystallisation occurs was determined by the following procedure at various temperatures. After Xe irradiation, amorphised powellite grains were exposed to an electron beam with a low electron flux. The electron flux was then gradually increased with 1–3-minute holding steps. The appearance of the first diffraction spots on the selected area electron diffraction (SAED) patterns served as a marker of where recrystallisation occurs.
Our study highlights the importance of systematically studying the electron-material interaction before characterising the heavy ion irradiation-induced changes in the sample. We found that powellite (and other materials) can be studied safely at cryogenic temperatures without causing unwanted electron beam-induced microstructural changes. We suggest cooling the beam-sensitive samples to cryogenic temperatures for TEM analysis between the high-temperature ion irradiation steps.
Focused (very high flux) electron beam irradiation studies have been widely used to predict the material’s behaviour under beta irradiation. However, we have demonstrated that low flux electron beam irradiations (which are more representative to simulate beta irradiation conditions) can often cause substantially different responses (i.e., recrystallisation instead of amorphization). Therefore, previous focused (high-flux) electron irradiation studies should be revised as they could provide misleading predictions.

Andrius Plauška(1), Gergely Szalay(1), Abhrajyoti Chakrabarti(1), Juhász Gábor (2), Tarján Balázs(2), Katalin Ócsai(2,3), Fehér András(4), Máté Veress(4), Szepesi Áron(1), Wéber Katalin(1), Balázs Rózsa(1,2,3)

(1)Laboratory of 3D functional network and dendritic imaging, Institute of Experimental Medicine, Budapest
(2)Brain Vision Center Nonprofit Kft, Budapest
(3)The Faculty of Information Technology, Pázmány Péter Catholic University, Budapest

A neuronal ensemble comprises a synchronized group of neurons firing in unison, theorized to underlie complex cognitive processes and serve as fundamental units of perception. Despite their presumed significance, empirical evidence elucidating their precise roles in behavior and cognition remains sparse. The advent of rapid, high-resolution imaging techniques, coupled with advanced photostimulation methods, novel optogenetic tools, and enhanced computational capabilities, has spurred a surge in research aimed at probing the functional implications of neuronal ensembles. A prominent frontier in neuroscience involves leveraging an "all-optical" methodology to investigate the interplay between network dynamics and behavior. This cutting-edge approach enables the exploration of how the activity of functional neuronal circuits modulates behavior and the dynamics of neuronal ensembles during learning processes.
Here, we used a two-photon acousto-optic (AO) stimulation technique that allows imaging and stimulation of hundreds of cells. Our goal was to identify neurons in mouse V1 that are visually responsive, attribute them to functional ensembles, and evoke conditioned behavior by backstimulating these ensembles. To this end, we recorded neuronal activity of hundreds of cells from multiple depth levels in mouse V1 in the presence of varying visual stimuli. Then, using a well-established singular value decomposition method, we grouped the cells into ensembles and selected those that showed the peak presence during visual stimulation. The core (or pattern completion) neurons from the chosen ensembles were then backstimulated, which resulted in reproduced neuronal response kinetics and enhanced behavioral effect.

Dóra Zalka(1,2,3), Zoltán Dankházi(3), Gábor Varga(3), Márk Windisch(3,4), Karel Saksl(5)

(1)Institute of Materials Research Slovak Academy of Sciences, Watsonova 47, 04001 Košice, Slovak Republic
(2)Department of Physics of Condensed Matters, Faculty of Sciences, Pavol Jozef Šafárik University in Košice, Park Angelinum 9, 041 54 Košice, Slovak Republic
(3)Department of Materials Physics, Eötvös Loránd University, Pázmány Péter stny. 1/A, 1117 Budapest, Hungary
(4)Department of Development, Bay Zoltán Nonprofit Ltd. for Applied Research, Kondorfa utca 1, 1116 Budapest
(5)Faculty of Materials Metallurgy and Recycling, Technical University of Košice, Letna 9, 042 00 Košice, Slovak Republic

The focus of this work is to demonstrate the surprising behavior of silver chalcogenides in the interaction with electron irradiation. During the scanning electron microscopy analysis, originally intended as a routine control of the synthetic granulate’s particle sizes and their stoichiometry, we observed the formation of silver outcrops. By surprise, said protrusions can be removed by varying only the current densities applied during the electron irradiation. Moreover, by adjusting the intensity of the electron beam, silver can be repeatedly regrown and then, by changing the intensity again, removed from the surface. These findings inspired us to make videos about the phenomenon. We intend to serve the microscopist community by presenting how we managed to prepare the movies in case of these dynamically changing samples. An interesting aspect of our study is that we maintained the accelerating voltage at constant 20 kV while varying only the beam current (4, 8, 16 nA). Previous research has primarily focused on the relationship between the accelerating voltage and its effect on material behavior during electron beam interactions. Beside investigating the effect of the current density and the accelerating voltage, we also applied moderate cooling to the stage to study the Ag2S particles under different temperature conditions.

Cagdas Yavuz(1), Henrik Haspel(1,2), Zoltán Kónya(1,2)

(1)Department of Applied and Environmental Chemistry, University of Szeged, Szeged, Hungary
(2)HUN-REN-SZTE Reaction Kinetics and Surface Chemistry Research Group

The continuous application of renewable energy sources, such as solar, wind, wave, and geothermal systems, is limited due to climatic and geographical conditions. Electrochemical water splitting is a method of producing oxygen and hydrogen without the need for scaling devices or certain geological conditions, where slow water oxidation, the so-called oxygen-evolution reaction (OER), is the bottleneck of its practical use. OER electrocatalysts facilitate a 4-electron process working in a harsh environment, thus efficiency, cost and stability are critical factors to investigate. Metal-organic frameworks (MOFs) have porous structures produced by assorted coordination of metal clusters with polytopic organic linkers, and MOFs can act like OER catalysts using, e.g., 3d transition metals Fe, Co, Ni (Fe-Co-Ni-MOFs). In this study, we fabricated bimetallic nickel/cobalt-metal organic framework (Ni/Co-MOF) water oxidation electrocatalysts by a simple wet-chemical method, and subsequently deposited them onto porous Nickel foam and carbon paper (CP) substrates via drop casting and electrochemical deposition, respectively. The physical-chemical properties of Ni/Co-MOF electrodes were investigated by a series of techniques (XRD, SEM-EDS, FT-IR, Raman spectroscopy etc.), and their electrocatalytic activity was characterized in a 3-electrode setup (CV, LSV, EIS etc.) under alkaline conditions. According to LSV results which were performed in 1.0 M KOH electrolyte with a scan rate of 20 mV s-1 the over potential of Ni/Co-MOF was 84 mV to attain a current density of 10 mA cm-2 and maintains it‘s current more than 24 h. The electrochemically deposited Ni/Co-MOF on Ni foam substrate showed the highest activity along with the lowest overpotential among all the systems tested here, while it maintained stable oxygen evolution through the strong interaction between the linker with metal nodes. The obtained results are comparable to the single metal MOFs and show promise in water electrolysis.

János László Lábár(1), Béla Pécz(1), Yao Yao(2), Daniel F. Fernandes(2), Tereza Košutová(2), Tomas Kubart(2), Zhen Zhang(2), Francois Lefloch(3), Frédéric Gustavo(3), Axel Leblanc(3), Shi-Li Zhang(2)
(1)HUN-REN Centre for Energy Research, Institute of Technical Physics and Materials Science, Budapest
(2)Division of Solid-State Electronics, Department of Electrical Engineering, Uppsala University, Uppsala, Sveden
(3)Université Grenoble Alpes, CEA, Grenoble INP, IRIG, PHELIQS, Grenoble, France

PtSi is a known contact material in microelectronics, usually formed by the self-aligned silicidation (SALICIDE) process in Si CMOS technology. At very low temperatures (< 1 K) this compound becomes superconducting. Its superconductivity is exploited in the creation of gatemon type qubits, which is the target of the SIQUOS project.
In the present talk we report on creation of superconducting sub-5 nm PtSi films. The problem of standard CMOS fabrication technology with very thin PtSi films that they break into discrete islands. To avoid this unwanted process a new technology step was developed in the project. STEM HAADF images and EDS elemental maps prove that the formed 5 nm PtSi films remain continuous. These continuous thin films are needed to achieve the targeted nanoscale JoFETs. The critical temperature of the thin films is also determined as parameters of the thin PtSi film.
This project was partially funded within the QuantERA II Program that has received funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No 101017733. Additional funding was provided by the Hungarian National Research, Development and Innovation Office (2019 2.1.7-ERA-NET-2022-00032). The authors are grateful to Levente Illés and Noémi Szász for the preparation of the TEM samples.

Bence Pál Barta(1), Benita Onhausz(1), Afnan AL Doghmi(1), Abigél Egyed-Kolumbán(1), Zita Szalai(1), János Balázs(1), Mária Bagyánszki(1) and Nikolett Bódi(1)

(1)Department of Physiology, Anatomy and Neuroscience, University of Szeged, Szeged, Hungary

The balance between the production and scavenging of reactive oxygen species is important to maintain the cellular homeostasis. However, the balance which is shifted towards the accumulation of reactive oxygen species will lead to cell and tissue damage. Cytokines are important members in the regulation of cellular homeostasis, and they have key role in modulation of neuroinflammation in different diseases, such as type 1 diabetes. Altered expression of inflammatory cytokines have effects on cell survival or death, and they can modify the neurochemical phenotype and plasticity of neurons. Moreover, they have impact on the activation of nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB), or its negative regulator, nuclear factor-2 erythroid related factor-2 (Nrf2) signalling pathway. NFκB has a pivotal role to transfer the oxidative stress signals into the cells, and the balance between the NFκB and the antioxidative Nrf2 are crucial in the future fate of cells.
Therefore, our goal was to investigate the effect of chronic hyperglycaemia and immediate insulin treatment on the expression of NFκB (p65 component, which has transactivation effect) and its negative regulator protein Nrf2 in the myenteric ganglia and their muscular environment of rat duodenum.
Adult male Wistar rats were used in our experiments. Hyperglycaemia was induced with a single intraperitoneal injection of streptozotocin (STZ; 60 mg/kg). Insulin was subcutaneously injected twice a day to insulin-treated diabetic rats. Ten weeks after the onset of hyperglycaemia, the animals were sacrificed. Myenteric whole-mounts were prepared for NFκB p65-HuC/HuD double-labelling fluorescent immunohistochemistry. Duodenal ultrathin sections were used for NFκB p65 and Nrf2 post-embedding immunogold electron microscopy. Protein and mRNA expression of NFκB p65 and Nrf2 were examined in gut tissue homogenates by enzyme-linked immunosorbent assay and quantitative polymerase chain reaction.
The proportion of NFκB p65-immunoreactive (IR) myenteric neurons were 2% in the duodenal ganglia of controls, while it decreased significantly (less than 1%) in the diabetic rats. Moreover, the ratio of NFκB p65-labelling gold particles’ density between the ganglia’s perikarya and nuclei were also decreased in diabetics, compared to controls. The density of Nrf2 gold labels significantly increased in the myenteric ganglia of diabetic duodenum. In the intestinal smooth muscle, both the NFκB p65 and Nrf2 density were enhanced significantly in diabetic rats. NFκB p65 and Nrf2 tissue levels were changed in the opposite way in smooth muscle/myenteric plexus homogenates. We observed elevated level of both NFκB p65 and Nrf2 mRNA expression, in the diabetic animals. The insulin treatment prevented all hyperglycaemia-related alterations in NFκB p65 and Nrf2 expression.
These findings support that diabetes-related NFκB p65 and Nrf2 expression changed in an opposite way in myenteric ganglia. In addition, the ganglionic muscular environment is also affected in diabetic damage of NFκB signalling, which may contribute to diabetic motility disturbances.

Zsolt Czigány(1), Jaroslav Ženíšek(2), Pavel Souček(2), Pavel Ondračka(2), Vilma Buršíková(3), David Holec(3), Katalin Balázsi(1), Petr Vašina(2)
(1)Institute of Technical Physics and Materials Science, HUN-REN Centre for Energy Research, Konkoly Thege M. út 29-33, Budapest H-1121, Hungary
(2)Department of Plasma Physics and Technology, Masaryk University, Kotlářská 2, Brno 61137, Czech Republic
(3)Department of Materials Science, Montanuniversität Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria

We have investigated the stability of the orthorhombic (Mo_1−xNb_x)₂BC phase [1], when molybdenum is gradually replaced by niobium. During the interpretation of the electron diffraction patterns, difficulties arose in distinguishing the cubic and orthorhombic phases. TEM investigations were made by a Cs corrected Themis (Thermo Fisher) microscope at 200kV. The strong reflections in the SAED pattern of Mo₂BC (Fig 1) can be indexed as an fcc phase which has a 111 preferred orientation. However, if we want to interpret all the reflections of Mo₂BC, it can be better indexed as orthorhombic Mo₂BC (PDF Card No.: 00-029-0913). The strong reflections of the orthorhombic phase coincide with the allowed reflections of the fcc structure, while the weak reflections coincide with cubic reflections forbidden in fcc structure. This orthorhombic structure was proposed by Jeitschko et al. in 1963 [2], who has already remarked that “the shape of the cell reveals a certain resemblance to MoB type; the reflection system also indicates the existence of pseudocubic sub cell”. Between the cell parameters of the orthorhombic and cubic structure the following relation can be recognized: the two short sides of the orthorhombic cell are almost equal and equal with 110 plane distance of cubic structure while the long side is four times the cubic cell parameter. Therefore, the orthorhombic cell can be interpreted as a supercell generated from the fcc cell. Indeed, the orthorhombic cell is a supercell of cubic carbide for metallic sublattice: within the orthorhombic unit cell, the arrangement of heavy metal atoms (Mo, Nb) resemble an fcc arrangement characteristic for cubic transition metal carbides (Fig 1). Meanwhile, the layered long range ordering of B and C atoms create the special orthorhombic unit cell, resulting an elongated cell with close to tetragonal shape, but due to the symmetry of the site occupation of B and C atoms the short edges are not exchangeable (Fig 1). Due to low scattering power of the light elements, this ordering have weak effect on the diffraction pattern, i.e. some weak reflections appear in addition to the strong fcc pattern. Consequently, cubic and orthorhombic structures may not be distinguished for very small grain sizes. However, this is not exclusively a technical question. Unambiguous distinction between fcc and orthorhombic structure may be elusive for very small grains because structural elements with cubic ordering are precursors of the orthorhombic supercell. This may be the case for Nb₂BC sample (indexed as cubic), where minor shifts of reflections compared to cubic system (e.g. 111 and 311 spacing are 1.7 and 1% higher, respectively) may indicate the onset of medium scale orthorhombic ordering.

References:
[1] J. Ženíšek et al., Effect of Nb incorporation in Mo₂BC coatings on structural and mechanical properties — ab initio modelling and experiment, Acta Materialia 268 (2024) 119741
[2] W. Jeitschko et al., Die Kristallstruktur von Mo₂BC, Monatshefte für Chemie und verwandte Teile anderer Wissenschaften. 94 (1963) 565–568

Arvin Taghizadeh Tabrizi(1), Gergő Ballai(1), Henrik Haspel(1,2), Zoltán Kónya(1,2)

(1)Department of Applied and Environmental Chemistry, University of Szeged, Szeged, Hungary
(2)HUN-REN Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Szeged, Hungary

Atomic layer deposition (ALD) is a unique method for the fabrication of thin layer structures. It utilizes self-terminating surface half-reactions through the repeated decomposition of multiple (usually two) reactants (the so-called precursors) on the surface of the target substrate. Due to their beneficial electronic, electrochemical, and catalytic characteristics, vanadium oxide is suitable for various applications, such as electrochemical energy storage, electrocatalysis etc. VO_x thin layers can be fabricated via ALD, however, the formation of multiple oxide phases of diverse physical properties, e.g. VO₂, V₂O₅, V₂O₃ etc., undermines their direct applicability. Certain phases can be stabilized by the addition of further interlayers, such as zinc oxide, obtaining multilayer electrodes. In this study, VO_x/ZnO multilayers were fabricated by ALD, and the effect of zinc oxide on VO_x phase selection was investigated. First, V_xO_y thin film was deposited onto nickel foam (NiF) at 150 °C through 280 cycles using tetrakis(ethylmethylamino)vanadium(IV) (TEMAV) and water as vanadium and oxygen precursors, respectively. In the second step, zinc oxide was deposited using diethylzinc (DEZ) and water precursors at 170 °C through 280 cycles, followed by an additional V_xO_y thin layer. The phase formation and phase transition in subsequent annealing were studied by X-ray Diffraction (XRD), while morphology of the as-synthesized and annealed thin layers was characterized using scanning electron microscopy (SEM), and atomic force microscopy (AFM). It is known that vanadium oxide has a high potential to be utilized as electrocatalyst in hydrogen evolution reactions (HER). Therefore, the constructed multilayer electrodes were tested in HER by using linear scanning voltammetry (LSV) in 1 M KOH solution at room temperature. Results on the three-layer VO_x/ZnO electrode demonstrated improved HER performance of −0.15 V (vs. RHE) onset potential and −125.6 mA cm⁻² current density at -0.45 V (vs. RHE).
Keywords: Vanadium Oxide, Atomic Layer Deposition, Multilayer Electrode, Zinc Oxide, Hydrogen Evolution Reaction

Henriett Halász(1), Viktória Tárnai(1), Miklós Nyitrai(1), János Matkó(2), Edina Szabó-Meleg(1)

(1)University of Pécs, Medical School, Department of Biophysics, Pécs, Hungary
(2)Eötvös Loránd University, Faculty of Sciences, Department of Immunology, Budapest, Hungary

Membrane nanotubes (NTs) are transient and dynamic actin-driven protrusions, which physically connect spatially separated cells over long distances. The actin network plays an essential role in the structure and function of NTs, however, microtubules and intermediate filaments can also be observed within them. NTs allow the direct transport of different cellular cargo, genetic information or even proteins between distant cells. NTs have a role in the progression of numerous neurodegenerative disorders, e.g. Alzheimer’s and Parkinson’s diseases, and they are also involved in the development of resistance against chemotherapeutic agents and antibiotics. At the same time, the presence of NTs can serve as a form of aid for damaged cells. For example, healthy cells may transfer mitochondria to damaged cells, thus enhancing their energetic status.
We examined the role and function of the microtubules between B-lymphoma cell NTs by using specific cytoskeletal inhibitors, gene silencing method and different microscopic techniques. Our results verify that NTs facilitate the direct transport of mitochondria bidirectionally between interconnected cells through the cooperation of two motor proteins: microtubule-based kinesin and actin-based myosin VI. We also confirmed an additional potential role of microtubules, which could be associated with the mechanical stability and prolonged lifetime of NTs. Understanding the molecular background of mitochondrial transport via NTs can form an important basis for their subsequent therapeutic application.

Marcell Gajdics(1), Ildikó Cora(1), Béla Pécz(1)

(1)Institute for Technical Physics and Materials Science, HUN-REN Centre for Energy Research, Budapest, Hungary

Ga₂O₃, as an ultrawide bandgap semiconductor material, has numerous potential applications in the field of electronics and optoelectronics. One of the commonly used deposition methods is radio frequency sputtering, which results in amorphous layers when deposited at room temperatures. Thus post-deposition heat treatment is needed to achieve a crystalline material, which is important in many applications. In the current work, the crystallization of radio frequency sputtered gallium oxide thin films was investigated by in situ transmission electron microscopy (TEM). The layers were deposited by reactive sputtering of a liquid Ga target using different oxygen flows. In this way, samples with different oxygen content were achieved and the effect of the Ga/O atomic ratio on the crystallization of the films was studied. Lamellas were prepared by focused ion beam technique, which were then mounted on a sample holder (Protochips) for the heating experiment. A constant heating rate was applied (2 °C/min) and the transition was followed in high-resolution imaging mode. The first crystal seeds appeared at the film/substrate interface; by the growth of these seeds a crystallization front was formed. The sample was quenched at this point in order to further study the crystal structure. The images below show the sample in this state at lower magnification (a) and at high resolution (b). Based on our observations, for the sample with composition close to the stoichiometry the crystal growth starts at around 530 °C, while for the sample with oxygen deficit the transformation starts at around 550 °C.

S.A. Raheem(1), G. Ballai(1), I. Szenti(2), H. Haspel(1,2), Z. Kónya(1,2*)

(1)Department of Applied and Environmental Chemistry, University of Szeged, Szeged, Hungary
(2)HUN-REN-SZTE Reaction Kinetics and Surface Chemistry Research Group, University of Szeged, Szeged, Hungary

Ammonia (NH3) is an important feedstock in modern industry, as it is used for the production of a wide range of materials, like chemical fertilizers, pharmaceuticals, synthetic fiber to name a few. On the other hand, ammonia could serve as an energy vector storing hydrogen in chemical bonds. Currently ammonia is produced by the energy- and carbon-intensive Haber-Bosch process, which alone is responsible for 1-2% of the global annual energy consumption. The electrocatalytic reduction of nitrate (NO3RR) to ammonia represents a compelling avenue for effectively and sustainably transforming a hazardous environmental pollutant (NO3−) into a valuable chemical feedstock (NH3) at ambient conditions, and thus developing highly active and selective NO3RR electrocatalysts is important. To this end, tungsten-doped cobalt oxyhydroxide nanostructures (W-CoOOHOv) were synthesized via a direct hydrothermal method, followed by a subsequent NaBH4 reduction to form oxygen vacancies (W-CoOOHOv) therein. The formed W-CoOOHOv demonstrated a high ammonia yield of 355.6 µg cm−1 h−1 along with a NH3 Faradaic efficiency of 89.4%. The observed enhanced performance could be attributed to the synergistic effects between tungsten and oxygen vacancies through modifying the adsorption energies of NO3−. This work suggests an avenue for the design of cost-effective and highly selective electrocatalysts for nitrate reduction to ammonia.

Viktória Varga(1), Viktória Cseh(1), Benjámin Fógel(1), Kadosa Sajdik(1), Dr. Tamás Szabó(1)
(1)University of Szeged, Department of Physical Chemistry and Materials Science, Szeged, Hungary

Thin layers can be created on various surfaces by various ways e.g. by spray-coating, spin-coating or Langmuir-Blodgett techniques. In addition to the above-mentioned techniques, the so-called LbL, i.e. layer-by-layer is outstanding for its simplicity and also for the possibility of relatively ordered layer formation, where the substrate (e.g. glass plate) is immersed in a solution/dispersion of one component and then the other. The immersion step is followed by rinsing and drying steps. The resulting thing films have a wide range of applications, in the form of packaging materials, membrane filters and anti-reflective coatings to drug-delivery systems. One of the most prominent, unique and demanding applications is the coating of lenses for medical instruments, e.g. endoscopes. Such layers should provide abrasion resistance, antifogging effect and protein adsorption resistance as well. It is therefore important to study the adsorption of proteins on glass surface. In addition, from and industrial point of view, it is also interesting to study the thin films formed by the components of milk proteins, due to the milk content of food products. For our experiments, we therefore chose two natural proteins, the serum albumin and the lactalbumin.
The formation of the protein thin films was investigated on a quartz plate by optimizing several parameters such as pH, ionic strength, protein concentration and immersion time. The results of spectrophotometric measurements were compared with images obtained by atomic force microscopy (AFM). The UV spectrophotometric adsorption can be used to follow the process but sometimes gives high error and do not provide sufficient information on the homogeneity of the thin films and the fine structure and morphology of the resulting layers. In addition to the formation of monolayers, the properties of bovine serum albumin (BSA) and graphene oxide (GO) bilayers were also investigated. The AFM results were used to determine the optimum immersion time for the two components for layer formation.
AFM characterization of the LbL protein-GO thin films revealed that a few seconds adsorption time was sufficient for the formation of BSA layers, while more time (10 min) was required for lactalbumin and GO. This time may be unique for different proteins. The initial concentration and pH of the protein solution also have a significant effect on the amount of material bound on the substrate. We also examined the morphology and coverage of the bilayers, the formed BSA/GO bilayers are relatively smooth and well formed - ideal for study by AFM.
Keywords: protein, albumin, graphene oxide, AFM, thin layer, immersion technique, layer-by-layer
Acknowledgement: This paper was supported by the Bolyai János Research Fellowship of the Hungarian Academy of Sciences. This research received funding from the ERA-NET COFUND/EJP COFUND Programme with co-funding from the European Union Horizon 2020 research and innovation programme and the NKFIH (project No. 2019-2.1.7-ERA-NET-2021-00029) in the frame of supporting the AtomDeC Consortium by the Visegrad Group-Japan 2021 Joint Call on Advanced Materials in cooperation with the International Visegrad Fund.

Klára Hajagos-Nagy, Zsolt Czigány, Fanni Misják, György Radnóczi
HUN-REN Centre for Energy Research
Bulk Mn-Cu alloys are well-known magnetic and shape-memory alloys, which are created from γ-Mn(Cu) solid solution by martensitic (fcc-->fct) transformation. The stable form of Mn at room temperature, α-Mn, is considered problematic due to its brittleness, even though the α-Mn structure contains many possibilities of use, such as para-, antiferro- and weakly ferromagnetic behaviour, anomalous Hall effect and high pressure (220 GPa) stability. α-Mn owes these properties to its unique crystal structure among elements: it is made up of atoms of different valence states and sizes.
The usability of α-Mn can presumably be expanded by alloying. Cu does not dissolve in it under equilibrium conditions, however, in our previous work [1] we produced an α-Mn(Cu) solid solution under non-equilibrium conditions - by DC magnetron sputtering. In this research, we investigated the non-equilibrium solubility limit of Cu in α-Mn, the growth and microstructure of α-Mn(Cu) layers.
The non-equilibrium solubility was investigated on a 50 nm thick combinatorial sample grown by DC magnetron sputtering, where the composition varied linearly between pure Mn and 50 at% Cu content. The films contain a crystalline phase up to 30 at% Cu content; the grain size varies between 5-20 nm. The electron diffraction intensity distributions showed that α-Mn can dissolve 30 at% Cu. Film growth was examined on 0.5-1 μm thick films, comparing discrete and variable composition (gradient) layers. At 10 at% Cu content a single-phase α-Mn(Cu) solid solution layer grows with a columnar structure (figure a). As the Cu content increases, an amorphous minority phase appears and hinders the growth of the α-Mn(Cu) grains (figure b). Examination of gradient films showed that the columnar structure characteristic of single-phase growth can be maintained at higher Cu content (figure c). The composition of the film shown in figure c was pure Mn at the beginning of the growth and the Cu content increased linearly up to 60 at%. The layer grew in a columnar way, a sharp crystalline-amorphous transition can be observed at a Cu content of 30 at%. The gradient film retained the columnar structure even in the composition range showing two-phase growth in the discrete case (10-30 at% Cu), which can be beneficial in many applications where the minimization of grain boundaries is required.

[1] F. Misják, K.H. Nagy, P. Lobotka, G. Radnóczi, Journal of Applied Physics, 116(8) 2014