# Moldova State University

• Chisinau, Moldova
Recent publications
This work is devoted to the study of the effect of a substrate chemical bonding type on the mechanical properties of coated systems (CSs) of a soft film/hard substrate type. The Cu/MgO and Cu/Si coated systems, as well as MgO and Si substrate crystals, which have similar hardness values but different types of chemical bonds, were studied. Various elastoplastic parameters were compared. The general and specific features of the deformation process under nanomicroindentation were identified. It has been established that general properties, such as ‘pop-in’, ‘pop-out’, ‘elbow’ effects, indentation size effect (ISE), are determined by the stress state created in the material during the indenter penetration and depend on the magnitude of the applied load and the film thickness. The specific properties, Young's modulus, hardness, relaxation parameters depend on the crystal structure and elastoplastic properties of the film and substrate material. The difference in the type of chemical bonding of the substrates, despite the close values of hardness, changes the elastoplastic properties and deformation mechanism of the composite structure as a whole, thereby expanding the possibility of creating new materials required for modern technology. • Highlights • Study of the effect of a substrate chemical bonding type on the mechanical properties of soft film/hard substrate (Cu/MgO, Cu/Si) coated systems. • The difference in the type of chemical bonding of the substrates, despite the close values ⁣⁣of hardness, changes the elastoplastic properties and deformation mechanism of the composite structure as a whole.
For decades, bovine jugular vein conduits (BJV) and classic cryopreserved homografts have been the two most widely used options for pulmonary valve replacement (PVR) in congenital heart disease. More recently, decellularized pulmonary homografts (DPH) have provided an alternative avenue for PVR. Matched comparison of patients who received DPH for PVR with patients who received bovine jugular vein conduits (BJV) considering patient age group, type of heart defect, and previous procedures. 319 DPH patients were matched to 319 BJV patients; the mean age of BJV patients was 15.3 (SD 9.5) years versus 19.1 (12.4) years in DPH patients (p = 0.001). The mean conduit diameter was 24.5 (3.5) mm for DPH and 20.3 (2.5) mm for BJV (p < 0.001). There was no difference in survival rates between the two groups after 10 years (97.0 vs. 98.1%, p = 0.45). The rate of freedom from endocarditis was significantly lower for BJV patients (87.1 vs. 96.5%, p = 0.006). Freedom from explantation was significantly lower for BJV at 10 years (81.7 vs. 95.5%, p = 0.001) as well as freedom from any significant degeneration at 10 years (39.6 vs. 65.4%, p < 0.001). 140 Patients, matched for age, heart defect type, prior procedures, and conduit sizes of 20–22 mm (± 2 mm), were compared separately; mean age BJV 8.7 (4.9) and DPH 9.5 (7.3) years (p = n.s.). DPH showed 20% higher freedom from explantation and degeneration in this subgroup (p = 0.232). Decellularized pulmonary homografts exhibit superior 10-year results to bovine jugular vein conduits in PVR.
The palaeontological material from the Dacian Basin provides a complete and well-represented record of faunal succession during the important faunal turnover called the Pachycrocuta event. The present study describes fossil remains of ruminants (Cervidae, Bovidae, Giraffidae) from the Early Pleistocene of Valea Grăunceanului, Fântâna lui Mitilan and other smaller sites from the Olteț River Valley. The article discuss the taxonomic context, eco-morphology and functional morphology of the described taxa and dynamics of biogeographic distribution. The commutity of ruminant species from the Dacian Basin before the Pachycrocuta event is dominated by Pliocene holdovers: Pliotragus ardeus, Gazellospira torticornis, Rucervus radulescui, Metacervocerus rhenanus and Mitilanotherium inexspectatum. This assemblage also contains new forms for Western Eurasia as Dama eurygonos, Eucladoceros dicranios, Eucladoceros ctenoides, Alces sp. and Bison (Eobison) sp. This specific regional fauna of ruminants became extinct during the Pachycrocuta faunal turnover and was replaced by a more cold-adapted assemblage of ruminants (Megalovis latifrons, Eucladoceros sp., Dama sp., Praemegaceros obscurus and its specialised diminished form Praemegaceros cf. mosbachensis) that show a greater affinity with coeval Levant faunas. The revealed dynamics of paleobiogeographic zones from the Early Pleistocene of southeastern Europe supports the hypothesis of early hominin dispersals in Western Eurasia via Balkan-Anatolia path.
The scientific school of Alexander Frumkin, a world-renowned electrochemist born in Chisinau, was at the origin of the electrochemical science in the Republic of Moldova. Research directions, such as high-rate anodic dissolution, plasma electrochemical treatment, electrical methods for mass transfer control, identified as “extreme electrochemistry”, and the electrochemical nanostructuring, have been significantly developed at the national level from both fundamental and applicative viewpoints. Moreover, the European cooperation considerably broadened the opportunities for Moldovan electrochemists in the related areas such as materials science and surface engineering. The present review highlights the main scientific contributions of Moldovan researchers to the world information process related to the above mentioned domains and to the academic–industrial collaboration.
Rolled‐up nanostructures provide new opportunities to control and modify thermal properties. The topology and geometry of nanoscale architectures have a strong influence on phonon spectrum and thermal conductivity. In the theoretical description, rolled‐up nanotubes are often approximated with nanotubes constructed from concentric multiwalled nanotubes. In this paper, the phonon spectrum is shown not to differ for these two nanotubes if the radius of the nanotube is much larger than the lattice constant. If the contact between layers of the rolled‐up or concentric nanotubes is weak, the thermal conductivity is not influenced by the contact, and it can be approximated by the conductivity of the one‐layered flat membrane. In the limit of weak contact, the diffusive heat transfer is shown to demonstrate an appreciable difference between rolled‐up and concentric nanotubes with large radii. The experimental measurements can be significantly distorted by the effects of the weak interlayer contact. This article is protected by copyright. All rights reserved.
This paper describes technological processes developed for less studied ZnTe thin films prepared by close space sublimation method, without an additional transport agent gas, for controlling their structural and optical properties. The enhanced oxygen incorporation depends on the source–substrate growth conditions. ZnTe thin films fabricated in the source-substrate temperature interval mentioned here crystallize in a cubic zincblende structure preferentially oriented along the [111] reflection plane. As the source temperature increases, the energy dispersive X-ray spectroscopy shows that the tellurium content increases, while the oxygen decreases. The values of the optical band gaps vary in interval from 2.21 eV up to 2.22 eV with variation of the source temperature, while variation of the substrate temperature leads to the band gap value decrease from 2.24 to 2.14 eV. The photoluminescence spectra of the ZnTe:O thin films are dominated by the red emission bands localized at 1.73 eV and 1.82 eV. This study will serve as a basis for future efforts to develop intermediate-band solar cells with improved conversion efficiency.
The titanium carbide MXenes currently attract an extreme amount of interest from the material science community due to their promising functional properties arising from the two-dimensionality of these layered structures. In particular, the interaction between MXene and gaseous molecules, even at the physisorption level, yields a substantial shift in electrical parameters, which makes it possible to design gas sensors working at RT as a prerequisite to low-powered detection units. Herein, we consider to review such sensors, primarily based on Ti3C2Tx and Ti2CTx crystals as the most studied ones to date, delivering a chemiresistive type of signal. We analyze the ways reported in the literature to modify these 2D nanomaterials for (i) detecting various analyte gases, (ii) improving stability and sensitivity, (iii) reducing response/recovery times, and (iv) advancing a sensitivity to atmospheric humidity. The most powerful approach based on designing hetero-layers of MXenes with other crystals is discussed with regard to employing semiconductor metal oxides and chalcogenides, noble metal nanoparticles, carbon materials (graphene and nanotubes), and polymeric components. The current concepts on the detection mechanisms of MXenes and their hetero-composites are considered, and the background reasons for improving gas-sensing functionality in the hetero-composite when compared with pristine MXenes are classified. We formulate state-of-the-art advances and challenges in the field while proposing some possible solutions, in particular via employing a multisensor array paradigm.
We present the first principles study of cubic In2O3 with a diatomic defect composed of a Sn atom substituting the In atom at the b-site and a Ga atom embedded in the nearest c-site (structural vacancy) with lattice positions according to the Wyckoff notations. Structural, electronic, phononic and thermal properties were investigated within density functional theory formalism. The lattice anharmonicity effects were taken into account for all possible three-phonon scattering processes. The phonon transport was considered within the Peierls-Boltzmann transport equation with relaxation time approximation. In the relaxed lattice, a strong rearrangement of the initial positions of the atoms in the defect vicinity was revealed, which primarily manifests itself in the displacement of the Sn atom toward another interstitial site. Thus, a cage is formed around the defect by 12 O and 12 In atoms. The calculations of elastic constants and mean square displacements of cage region atoms showed the rattling-like behavior of the Sn atom. Bader charge analysis and electron localization function allowed a deeper understanding and explanation of such behavior. Phonon spectra as compared to In2O3 and In2O3:(Sn) demonstrated flattening of mode branches with spatial localization. They also revealed a decrease in average group velocities of phonons, including those of acoustic type, the presence of avoided-crossing features in the low energy range, and an increase of available phase space for three-phonon scattering. Accounting for all these vibrational features due to defect atoms resulted in a thermal conductivity drop at room temperature by more than 7 times compared to In2O3.
Background The research was aimed at comparing the effect of using two types of training load different in intensity and energy supply. We studied the influence of the proposed load variations (machine and free weight exercises) on long-term adaptation of the body at the stage of specialized basic training in bodybuilding. Methods A total of 64 athletes aged 18–20 years were examined. The research participants were randomly divided into four groups, 16 athletes in each group. Athletes of group 1 and 3 used a complex of free weight exercises. Group 2 and 4 participants performed machine exercises. Bodybuilders of group 1 and 2 were trained in conditions of medium intensity training load ( R a = 0.58) in the anaerobic-glycolytic mode of energy supply. Athletes of the 3rd and 4th groups used high intensity load ( R a = 0.71) in the anaerobic-alactate mode of energy supply. We managed to determine the nature of adaptation processes using methods of control testing of strength capabilities, bioimpedansometry, anthropometry, biochemical analysis of blood serum (LDH, creatinine). Results The study showed that the difference in the dynamics of the participants’ maximum strength development (on example of chest muscles) did not depend on the content of machine or free weight exercises, but on the features of training load regimes. Thus, the controlled indicator of strength capabilities in athletes of groups 3 and 4 increased by 5.1% compared to groups 1 and 2. During all stages of the study, the indicators of the projectile working mass in athletes of groups 3 and 4 exceeded the results observed in groups 1 and 2 by 25.9%. At the same time, the amount of load in a set is on average 2 times higher in athletes of groups 1 and 2. Group 4 athletes, who used machine exercises and high intensity training load, increased the circumferential body measurements by 3.8 times (the chest), compared to the results recorded in group 1 athletes. Athletes of group 1 and 2 showed increasing in body fat by 3.4% compared to the initial level on the background of large load volume. The basal creatine level in bodybuilders of groups 3 and 4 increased by 3.7 times after 12 weeks of study, which indicates an accelerated growth of muscle mass. Conclusion The most pronounced adaptive body changes in bodybuilders at the stage of specialized basic training occurred during high intensity training load and anaerobic-alactate energy supply mode. Machine exercises contributed to increasing the morpho functional indicators of athletes more than free weight exercises.
[MoV2O2S2]2+-based thiosemicarbazone complexes appear as very promising molecules for biological applications due to the intrinsic properties of their components. This paper deals with the synthesis and characterization of six coordination complexes obtained by the reaction of [MoV2O2S2]2+ clusters with bis-thiosemicarbazone ligands that contain flexible or rigid spacers between the two thiosemicarbazone units. Interestingly, structural characterization by single-crystal X-ray diffraction, MALDI-TOF MS technique and NMR spectroscopy revealed that the nuclearity of the complex is controlled by the nature of the spacer between the thiosemicarbazone units. Binuclear complexes, namely [MoV2O2S2(L1-3)], are isolated with flexible spacers while tetranuclear complexes [(MoV2O2S2)2(L4-6)2] are formed when the bis-thiosemicarbazone ligands are built on rigid spacers.
The phenomenon of globalization becomes a component of the artistic literature. Writers felt the need to create their own universe based on recognizable symbols. This launch from inside an asteroid of ancient myth offers opportunities to climb Mount Olympus in his personal dissection. Thus, the authors are tempted to extract from myths fragments in which they can mirror their reality. The fragment holds in the work the part of the whole, similar to a starfish that reconstructs its body after a fragment. In the same way, the writer of our century creates his hybrid from the myth he cuts out in order to involve him in the situations of multiculturalism. Thus the ancient spirit is selected in the virtual test tube with all the perspectives of the dream game proper to the hologram of the intellectual character.
Background and purpose: All previous rodent models lacking the peptide hormone angiotensin II (Ang II) were hypotensive. A mixed background strain with global deletion of the angiotensinogen gene was backcrossed to the FVB/N background (Agt-KO), a strain preferred for transgenic generation. Surprisingly, the resulting line turned out to be normotensive. Therefore, this study aimed to understand the unique blood pressure regulation of FVB/N mice without angiotensin peptides. Experimental approach: Acute and chronic recordings of BP in freely-moving adult mice were performed to establish baseline BP. The pressure responses to sympatholytic and sympathomimetic as well as nitric oxide inhibitor and donor compounds were used to quantify the neurogenic tone and endothelial function. The role of the renal nerves on baseline BP maintenance was tested by renal denervation. Finally, further phenotyping was done by gene expression analysis, histology and measurement of metabolites in plasma, urine and tissues. Key results: Baseline BP in adult FVB/N Agt-KO was unexpectedly unaltered. As compensatory mechanisms Agt-KO presented an increased sympathetic nerve activity and reduced endothelial nitric oxide production. However, FVB/N Agt-KO exhibited the renal morphological and physiological alterations previously found in mice lacking the production of Ang II including polyuria and hydronephrosis. The hypotensive effect of bilateral renal denervation was blunted in Agt-KO compared to wildtype FVB/N mice. Conclusion and implications: We describe a germline Agt-KO line that challenges all previous knowledge on BP regulation in mice with deletion of the classical RAS. This line may represent a model of drug-resistant hypertension because it lacks hypotension.
Background Numerous studies and their meta-analysis have shown a high prevalence of anxiety and depression in patients with inflammatory bowel disease (IBD): up to a third of patients with anxiety symptoms and a quarter with depression symptoms. These rates increase even more with high disease activity: up to half of patients with anxiety criteria and up to a third with depression symptoms. Data on the frequency and severity of depression and anxiety in patients with Clostridioides difficile infection (CDI) are not so numerous and unambiguous. During the Covid-19 pandemic, the frequency of depression and anxiety increased among healthy individuals and, even more so, among patients with intestinal diseases. The aim of the study was to evaluate the degree of anxiety and depression in patients with IBD and those with CDI during the Covid-19 pandemic. Methods Thirty patients with IBD and 30 patients with CDI were included in the study. IBD was confirmed by endoscopy and histology. CDI was confirmed by enzyme analysis for glutamate dehydrogenase and toxins A and B in the feces of patients with nosocomial infection. Hamilton scale (17 items) was used in order to assess the depression grade. This scale divides patients into four groups: no depression, mild, moderate and severe depression. Anxiety was diagnosed by the Spielberger scale (40 items) which includes analysis of State anxiety (SA) and Trait anxiety (TA). Results Depression was determined in 56.7% of patients in the IBD group: 46.7% had mild depression, and 10% moderate depression. In the CDI group depression was diagnosed significantly more frequently – 86.7% of cases: mild grade in 76.6% and moderate in 10%, predominantly among women. SA was identified in 46.7% of patients in IBD group, and severe SA in 10.0%. In CDI group the frequency and grade of SA were similar: 40.0% and 13.3% respectively. The of TA was extremely high in both groups: 93.3% in the IBD group, of which 50.0% with severe TA, and 96.7% in the CDI group, of which 40.0% with severe TA. Conclusion The results of the study confirm the presence of anxiety and depression in an extremely large number of patients with IBD and CDI during the Covid-19 pandemic. The frequency of anxiety and depression in this study is significantly higher than previously reported. Patients with IBD and CDI should be monitored for early diagnosis and adequate treatment of depression and anxiety.
The NATO SPS Workshop (https://ephysimlab.usm.md/spsatcg5816/) on monitoring and protection of critical infrastructure by unmanned systems provided participants the opportunity to consider state-of-the-art ways of the use of Unmanned Vehicle Systems (UVS) and sensor network technology for threats monitoring of critical infrastructures. Also, sessions on the monitoring, data analysis and structural modelling, monitoring, and forecasting of natural catastrophes, as well as on the cybersecurity and protection of IT infrastructure were of special interests for students and experts working in the ICT field. We present a drone-based platform for the monitoring of air pollution with gaseous pollutants and solid microparticles, PM2.5 and PM10, as well as chemical and radiological contaminations. In addition, results on air pollution analysis for particulate matter including Atomic Force Microscopy (AFM) and Fluorescence Lifetime Imaging Microscopy (FLIM) are provided in this paper.
A new technological approach for sintering Al-doped ZnO ceramics using chemical vapor transport (CVT) based on HCl has been developed. Among the advantages of the proposed sintering approach are: the low sintering temperature of 1070 °C; the absence of deviation in the diameter of ceramics after sintering; and the presence of Zn excess in the resulting material. The influence of dopant powder, concentration of Al, powder compacting pressure, and stoichiometric deviation on the density and conductive properties of ceramics has been investigated. Due to the relatively weak interaction of Al2O3 with HCl and limited solubility of Al in ZnO, a doping level about 2 at.% is recommended. A further increase in the dopant concentration significantly reduces the density and conductivity of the resulting material. A theoretical and experimental comparative analysis of the features of CVT sintering of ZnO doped with Al, Ga, and In was also carried out. ZnO:Al:Cl CVT ceramics with the resistivity of 9.5 × 10–3 Ω cm can be used as stable magnetron targets for ZnO thin films deposition with improved conductive properties. The influence of dopant powder, Al concentration, deposition temperature, and the gaseous medium of sintering target on the electrical properties of films are investigated and discussed.
Antimicrobial resistance (AMR) is a major threat to global health. Understanding the emergence, evolution, and transmission of individual antibiotic resistance genes (ARGs) is essential to develop sustainable strategies combatting this threat. Here, we use metagenomic sequencing to analyse ARGs in 757 sewage samples from 243 cities in 101 countries, collected from 2016 to 2019.We find regional patterns in resistomes, and these differ between subsets corresponding to drug classes and are partly driven by taxonomic variation. The genetic environments of 49 common ARGs are highly diverse, with most common ARGs carried by multiple distinct genomic contexts globally and sometimes on plasmids. Analysis of flanking sequence revealed ARG-specific patterns of dispersal limitation and global transmission. Our data furthermore suggest certain geographies are more prone to transmission events and should receive additional attention.
Background: Precise knowledge of the topographic features of the splenic artery and its branches in the hilum region is of practical interest due to the various interventions on the vessels of the spleen. Materials and methods: The anatomy of the spleen was studied by means of macroscopic dissection on 330 organ complexes, which were carefully documented and analyzed statistically. Results: The analysis of the splenic artery trajectory led to identification of four types: straight (43.03%), sinusoidal (27.58%), serpentine (20.91%) and alternating (8.48%). To assess the relation between the trajectory of the splenic artery and its branches we performed a chi square test. Sinuous or serpentine trajectory was associated with the presence of long splenic artery branches (dorsal pancreatic artery or the great pancreatic artery), X2 (2, N = 330) = 12.85, p = 0.001. The artery was located suprapancreatic in 70.30% of cases, anteropancreatic in 4.55%, the vessel had an intrapancreatic course in 14.85% and in 10.00% of cases the artery was located retropancreatic. The presence of inferior polar arteries was associated with a longer pancreas (Spearman's correlation; r = 0.37; p = 0.037). In a multiple regression analysis, inferior polar arteries predicted the length of the pancreas although only a small number of cases could be explained by this model (R2 = 0.127, Adjusted R2 = 0.098; Betta = 0.357; t(330) = 2.091; p = 0.045). There were 30 (9.09%) cases of accessory spleens. Conclusions: The arterial supply of the spleen is highly variable in its trajectory, terminal branches, and relation to other organs. The splenic artery tends to be sinuous or serpentine in zones when a large artery branches off (e.g., the dorsal pancreatic or greater pancreatic artery). Multiple short branches tend to stabilize the trajectory of the splenic artery. Inferior polar arteries and accessory spleens contribute to the length of the pancreas, most likely due to increased vascular supply to the tail of the gland.
Transition metal dichalcogenide (TMD) semiconductors are two-dimensional materials with great potential for the future of nano-optics and nano-optoelectronics as well as the rich and exciting development of basic research. The influence of an external magnetic field on a TMD monolayer raises a new question: to unveil the behavior of the magneto-polaron resonances (MPRs) associated with the phonon symmetry inherent in the system. It is shown that the renormalized Landau energy levels are modified by the interplay of the long-range Pekar–Fröhlich (PF) and short-range deformation potential (DP) interactions. This leads to a new series of MPRs involving the optical phonons at the center of the Brillouin zone. The coupling of the two Landau levels with the LO and A1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$A_1$$\end{document} optical phonon modes provokes resonant splittings of double avoided-crossing levels giving rise to three excitation branches. This effect appears as bigger energy gaps at the anticrossing points in the renormalized Landau levels. To explore the interplay between the MPRs, the electron-phonon interactions (PF and DP) and the couplings between adjacent Landau levels, a full Green’s function treatment for the evaluation of the energy and its life-time broadening is developed. A generalization of the two-level approach is performed for the description of the new MPR branches. The obtained results are a guideline for the magneto-optical experiments in TMDs, where three MPR peaks should be observable.
This article discusses the features of the synthesis and application of porous two-dimensional nanomaterials in developing conductometric gas sensors based on metal oxides. It is concluded that using porous 2D nanomaterials and 3D structures based on them is a promising approach to improving the parameters of gas sensors, such as sensitivity and the rate of response. The limitations that may arise when using 2D structures in gas sensors intended for the sensor market are considered.
(1) Background: In the context of the COVID-19 pandemic, the educational system in Romania faced major challenges. Online knowledge development was necessary and mandatory during this time; (2) Methods: our study included a group of 140 preadolescents and used a phenomenology qualitative method to investigate if the novel online teaching, implemented in a hurry during the pandemic without any previous teacher training, managed to replace face-to-face teaching; (3) Results: The students have expressed their joy for online courses, as long as they are kept interactive. Even though they feel nervous and worried when it comes to evaluation, the students claim they feel capable to learn all of the learning materials. Most of them are pleased by classes and do not get bored during them, feeling constantly motivated to actively participate in dialogue; (4) Discussions: Despite the lack of teaching-method standardization, our learning providers succeeded in accomplishing their tasks during online courses. Even in remote rural areas, they managed to assure the means for these children to access and take part in online courses; (5) Conclusions: our learning system must offer teachers the possibility to emphasize online education using adequate training programs aiming to develop technical and online pedagogical skills.
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220 members
• Department of History
• of Theoretical Physics
• Department of Theoretical Physics
• Faculty of Physics and Engineering
• Laboratory of "Fundamental and Applied Mathematics"
Information
Address
Mateevici 60, 2009, Chisinau, Moldova
Head of institution
prof. Igor Sarov
Website
www.usm.md