Transition from fractal-dendritic to compact islands for the 2D-ferroelectric SnSe on graphene/Ir(111).

Epitaxial growth is a versatile method to prepare two-dimensional van der Waals ferroelectrics like group IV monochalcogenides which have potential for novel electronic devices and sensors. We systematically study SnSe monolayer islands grown by molecular beam epitaxy, especially the effect of annealing temperature on shape and morphology of the edges. Characterization of the samples by scanning tunneling microscopy reveals that the shape of the islands changes from fractal-dendritic after deposition at room temperature to a compact rhombic shape through annealing, but ripening processes are absent up to the desorption temperature. A two-step growth process leads to large, epitaxially aligned rhombic islands bounded by well-defined110-edges (armchair-like), which we claim to be the equilibrium shape of the stoichiometric SnSe monolayer islands. The relaxation of the energetically favorable edges is detected in atomically resolved STM images. The experimental findings are supported by the results of our first-principles calculations, which provide insights into the energetics of the edges, their reconstructions, and yields the equilibrium shapes of the islands which are in good agreement with the experiment.

[The interdisciplinary approach as tool of pharmaceutical education of children: from theory to practice].

The pharmaceutical literacy is a necessary element of ensuring quality of human life that is to be formed at early age. The article demonstrates that key direction of development of health literacy is pharmaceutical education involving pharmaceutical workers. The necessity of development of pharmaceutical literacy in children through involvement into process of pharmaceutical education pedagogues and parents/legal representatives of child. The article presents analysis of normative legal documents regulating strategic directions of state and international policy in the field of protection of health and rights of minor citizen/children that regulate organization of pharmaceutical and educational activities and requirements to pharmaceutical and pedagogical workers within the framework of their professional role. The problematic zones in organization of pharmaceutical counseling of minors citizen were discovered. The necessity to improve professional competence of pharmaceutical and pedagogical workers in organization of pharmaceutical education of children of preschool and school age is established. The results of sociological survey of minor citizen and their parents demonstrated inadequate level of pharmaceutical literacy of respondents. On the basis of research results structural model of interaction of participants of pharmaceutical education of children (pharmaceutical workers - parents - pedagogues). The communication relations at the stage of transferring pharmaceutical knowledge to minor personality were revealed. The main result of the study is original structural functional model of organization of pharmaceutical education of children implementing interdisciplinary approach in forming pharmaceutical knowledge in children of preschool and school age. The stages of interaction of participants and professional tasks of pharmaceutical and pedagogical specialists in process of teaching children skills of pharmaceutical safety are determined.

[NORMATIVE AND LEGAL ASPECTS OF THE FORMATION OF THE BASIC PREREQUISITES OF PUBLIC HEALTH (PUBLICATIONS REVIEW)].

Preservation of public health is the main goal of social progress and development of the society. The search for potential opportunities to improve individual and public health indicators is a positive predictor of increasing the socio-economic efficiency of the society and increasing the healthy life expectancy of citizens. The scientific review provides arguments in favor of the need for professional collaboration of specialists from various industries in order to universally realize the most important right of citizens to protect their own and public health. Regulatory legal documents defining national and international policy in the field of health protection and forming the general vector of development of health care activities were used as the sources of information for the formation of the basis of the study. As a result of a logical generalization of global and national priorities and trends in the development of the healthcare sector, the main prerequisites (determinants) of health saving of citizens, adopted by the world community and reflected in domestic documents, are formulated. The main prerequisites (determinants) of health are defined as: promotion of activities that advantage health protection; creation of a single preventive space; specification of the concept of "responsible attitude to health"; coverage of the entire life cycle of a person and all spheres of his activity in the formation of a responsible attitude to health and motivation for its preservation; development of information technologies in the field of health protection; expansion of intersectoral and interdisciplinary cooperation in order to maintain and strengthen health; improvement of public health literacy; transformation of health services from the standpoint of health protection; development of human resources to ensure health-saving activities. The identified determinants of the preservation of individual and public health can act as a theoretical basis for the development of a scientific and practical methodology aimed at solving problems of improving health through the potential of interdisciplinary interaction of specialists in various fields of activity.

[The organizational aspects of security support of participants of clinical testing of vaccine "Gam-COVID-Vac"].

The COVID-19 pandemic resulted in many aftermaths, economic crisis and extra charging of health care. The development of vaccine against SARS-nCoV-2 agent turned out as the priority task of world and Russian medicine and pharmaceutics. The investigation of efficiency and safety of vaccines can be prolonged for many years that can aggravate the observed crisis. Having regard to the global scope and speed of pandemic spreading, the vaccine "Gam-COVID-Vac" was registered with special procedure by the Decree of the Government of the Russian Federation No. 441 of 03.04.2020 for accelerated access to civic turn-over. To monitor safety of vaccine on the basis of international experience, the decision was made to organize the independent Committee of monitoring data concerning efficacy and safety of vaccines applied to prevent COVID-19. The article presents rationale for necessity to create independent committee and to implement such a practice.

[Adverse drug reactions of local anesthetics used in dentistry]. / Nezhelatel'nye reaktsii na mestnye anestetiki pri ikh primenenii v stomatologii.

The aim. Study the adverse drug reactions (ADR) that occur when using local anesthetics (LA) in patients living in the Republic of Crimea and registered during the period 2010-2018. MATERIAL AND METHODS: The objects of the study were 122 notification forms about LA ADR recorded in the regional base (Register) of spontaneous reports called ARCADe (Adverse Reactions in Crimea, Autonomic Database). In most cases, ADR was associated with the use of amide LA Lidocaine - 69 cases (56.55% of the total number of cases for LA ADR), less often, ADR was caused by combinations containing Articaine (34 cases, 27.87%). Rare cases of ADR were reported for Novocaine/Procaine (9 cases, 7.38%), Bupivacaine (8 cases, 6.56%) and Mepivacaine (2 cases, 1.64%). The main clinical manifestations of reactions were hypersensitivity-like reactions (38 cases), cardiac and vascular disorders (29 cases) and central nervous system disorders (19 cases). Lack of effectiveness of LA occurred in 13 cases (10.66%). RESULTS: A study of the outcome of ADR revealed a high incidence of life-threatening conditions associated with LA use - 31 cases (25.4%), which indicates the severity of the event and the need to cancel the suspected drug and prescribe additional medications for correction. The need for hospitalization or prolongation of hospitalization was necessary in 7 cases (5.8%), and temporary disability of patients was revealed in 5 cases (4.1%). Of particular interest are 2 cases (1.6%) of the development of a fatal outcome as a result of the suspected anaphylactic shock (1 case) and disorders of the central nervous system (convulsions, development of respiratory failure). CONCLUSION: The high frequency and severity of unwanted effects resulted from the use of LA requires healthcare professionals to make rational choices and strictly monitor patient safety.

Electron-Beam Induced Transformations of Layered Tin Dichalcogenides.

By combining high-resolution transmission electron microscopy and associated analytical methods with first-principles calculations, we study the behavior of layered tin dichalcogenides under electron beam irradiation. We demonstrate that the controllable removal of chalcogen atoms due to electron irradiation, at both room and elevated temperatures, gives rise to transformations in the atomic structure of Sn-S and Sn-Se systems so that new phases with different properties can be induced. In particular, rhombohedral layered SnS2 and SnSe2 can be transformed via electron beam induced loss of chalcogen atoms into highly anisotropic orthorhombic layered SnS and SnSe. A striking dependence of the layer orientation of the resulting SnS-parallel to the layers of ultrathin SnS2 starting material, but slanted for transformations of thicker few-layer SnS2-is rationalized by a transformation pathway in which vacancies group into ordered S-vacancy lines, which convert via a Sn2S3 intermediate to SnS. Absence of a stable Sn2Se3 intermediate precludes this pathway for the selenides, hence SnSe2 always transforms into basal plane oriented SnSe. Our results provide microscopic insights into the transformation mechanism and show how irradiation can be used to tune the properties of layered tin chalcogenides for applications in electronics, catalysis, or energy storage.

[Biomarkers of prostate cancer sensitivity to the Sendai virus].

Metastatic prostate cancer is often associated with either primary or intractable castration-resistant prostate cancer (CRPC), thus justifying the search for entirely new ways of treatment. Oncolytic viruses are able to selectively induce the death of tumor cells without affecting normal cells. A murine Sendai virus has potential to be used as an oncolytic agent. However, tumors vary in their sensitivity to different viruses, prompting us to attempt to identify corresponding biomarkers that reflect the interaction of cancer cells and the virus. Here, we show that the sensitivity of primary prostatic adenocarcinoma cell lines to Sendai virus strain (SeVM) vary substantially. Using quantitative PCR, we evaluated expression levels of genes that encode RIG-1-like and Toll-like receptors (TLRs) in cell lines and showed that the levels of mRNAs that encode TLR3 and TLR7 correlate with a degree of sensitivity of the cells to Sendai virus. The lines with lower levels of TLR3 and TLR7 expression are more sensitive to the virus.

van der Waals bonding in layered compounds from advanced density-functional first-principles calculations.

Although the precise microscopic knowledge of van der Waals interactions is crucial for understanding bonding in weakly bonded layered compounds, very little quantitative information on the strength of interlayer interaction in these materials is available, either from experiments or simulations. Here, using many-body perturbation and advanced density-functional theory techniques, we calculate the interlayer binding and exfoliation energies for a large number of layered compounds and show that, independent of the electronic structure of the material, the energies for most systems are around 20 meV/Å2. This universality explains the successful exfoliation of a wide class of layered materials to produce two-dimensional systems, and furthers our understanding the properties of layered compounds in general.

From point defects in graphene to two-dimensional amorphous carbon.

While crystalline two-dimensional materials have become an experimental reality during the past few years, an amorphous 2D material has not been reported before. Here, using electron irradiation we create an sp2-hybridized one-atom-thick flat carbon membrane with a random arrangement of polygons, including four-membered carbon rings. We show how the transformation occurs step by step by nucleation and growth of low-energy multivacancy structures constructed of rotated hexagons and other polygons. Our observations, along with first-principles calculations, provide new insights to the bonding behavior of carbon and dynamics of defects in graphene. The created domains possess a band gap, which may open new possibilities for engineering graphene-based electronic devices.

Cutting and controlled modification of graphene with ion beams.

Using atomistic computer simulations, we study how ion irradiation can be used to alter the morphology of a graphene monolayer, by introducing defects of specific type, and to cut graphene sheets. Based on the results of our analytical potential molecular dynamics simulations, a kinetic Monte Carlo code is developed for modeling morphological changes in a graphene monolayer under irradiation at macroscopic time scales. Impacts of He, Ne, Ar, Kr, Xe, and Ga ions with kinetic energies ranging from tens of eV to 10 MeV and angles of incidence between 0° and 88° are studied. Our results provide microscopic insights into the response of graphene to ion irradiation and can directly be used for the optimization of graphene cutting and patterning with focused ion beams.

Controlled generation of luminescent centers in hexagonal boron nitride by irradiation engineering.

Luminescent centers in the two-dimensional material hexagonal boron nitride have the potential to enable quantum applications at room temperature. To be used for applications, it is crucial to generate these centers in a controlled manner and to identify their microscopic nature. Here, we present a method inspired by irradiation engineering with oxygen atoms. We systematically explore the influence of the kinetic energy and the irradiation fluence on the generation of luminescent centers. We find modifications of their density for both parameters, while a fivefold enhancement is observed with increasing fluence. Molecular dynamics simulations clarify the generation mechanism of these centers and their microscopic nature. We infer that VNCB and [Formula: see text] are the most likely centers formed. Ab initio calculations of their optical properties show excellent agreement with our experiments. Our methodology generates quantum emitters in a controlled manner and provides insights into their microscopic nature.

Nanostructuring few-layer graphene films with swift heavy ions for electronic application: tuning of electronic and transport properties.

The morphology and electronic properties of single and few-layer graphene films nanostructured by the impact of heavy high-energy ions have been studied. It is found that ion irradiation leads to the formation of nano-sized pores, or antidots, with sizes ranging from 20 to 60 nm, in the upper one or two layers. The sizes of the pores proved to be roughly independent of the energy of the ions, whereas the areal density of the pores increased with the ion dose. With increasing ion energy (>70 MeV), a profound reduction in the concentration of structural defects (by a factor of 2-5), relatively high mobility values of charge carriers (700-1200 cm2 V-1 s-1) and a transport band gap of about 50 meV were observed in the nanostructured films. The experimental data were rationalized through atomistic simulations of ion impact onto few-layer graphene structures with a thickness matching the experimental samples. We showed that even a single Xe atom with energy in the experimental range produces a considerable amount of damage in the graphene lattice, whereas high dose ion irradiation allows one to propose a high probability of consecutive impacts of several ions onto an area already amorphized by the previous ions, which increases the average radius of the pore to match the experimental results. We also found that the formation of "welded" sheets due to interlayer covalent bonds at the edges and, hence, defect-free antidot arrays is likely at high ion energies (above 70 MeV).

Tailoring the optical properties of atomically-thin WS2via ion irradiation.

Two-dimensional transition metal dichalcogenides (TMDCs) exhibit excellent optoelectronic properties. However, the large band gaps in many semiconducting TMDCs make optical absorption in the near-infrared (NIR) wavelength regime impossible, which prevents applications of these materials in optical communications. In this work, we demonstrate that Ar+ ion irradiation is a powerful post-synthesis technique to tailor the optical properties of the semiconducting tungsten disulfide (WS2) by creating S-vacancies and thus controlling material stoichiometry. First-principles calculations reveal that the S-vacancies give rise to deep states in the band gap, which determine the NIR optical absorption of the WS2 monolayer. As the density of the S-vacancies increases, the enhanced NIR linear and saturable absorption of WS2 is observed, which is explained by the results of first-principles calculations. We further demonstrate that by using the irradiated WS2 as a saturable absorber in a waveguide system, the passively Q-switched laser operations can be optimized, thus opening new avenues for tailoring the optical response of TMDCs by defect-engineering through ion irradiation.

Substitutional carbon doping of free-standing and Ru-supported BN sheets: a first-principles study.

The development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open the possibility of creating stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0 0 0 1), but the stabilization mechanism is still unknown. With the use of density-functional theory we study the energetics of BN/Ru slabs, with different types of configurations of C substitutional defects introduced to the h-BN overlayer. The results are compared to the energetics of free-standing BCN materials. We found that the substrate facilitates the C substitution process in the h-BN overlayer. Thus, more homogeneous BCN material can be grown, overcoming the segregation into graphene and h-BN. In addition, we investigate the electronic and transport gaps in free-standing BCN structures, and assess their mechanical properties and stability. The band gap in mixed BCN free-standing material depends on the concentration of the constituent elements and ranges from zero in pristine graphene to nearly 5 eV in free-standing h-BN. This makes BCN attractive for application in modern electronics.

Mechanical properties and current-carrying capacity of Al reinforced with graphene/BN nanoribbons: a computational study.

Record high values of Young's modulus and tensile strength of graphene and BN nanoribbons as well as their chemically active edges make them promising candidates for serving as fillers in metal-based composite materials. Herein, using ab initio and analytical potential calculations we carry out a systematic study of the mechanical properties of nanocomposites constructed by reinforcing an Al matrix with BN and graphene nanoribbons. We consider a simple case of uniform distribution of nanoribbons in an Al matrix under the assumption that such configuration will lead to the maximum enhancement of mechanical characteristics. We estimate the bonding energy and the interfacial critical shear stress at the ribbon/metal interface as functions of ribbon width and show that the introduction of nanoribbons into the metal leads to a substantial increase in the mechanical characteristics of the composite material, as strong covalent bonding between the ribbon edges and Al matrix provides efficient load transfer from the metal to the ribbons. Using the obtained data, we apply the rule of mixtures in order to analytically assess the relationship between the composite strength and concentration of nanoribbons. Finally, we study carbon chains, which can be referred to as the ultimately narrow ribbons, and find that they are not the best fillers due to their weak interaction with the Al matrix. Simulations of the electronic transport properties of the composites with graphene nanoribbons and carbyne chains embedded into Al show that the inclusion of the C phase gives rise to deterioration in the current carrying capacity of the material, but the drop is relatively small, so that the composite material can still transmit current well, if required.

Atomic scale study of the life cycle of a dislocation in graphene from birth to annihilation.

Dislocations, one of the key entities in materials science, govern the properties of any crystalline material. Thus, understanding their life cycle, from creation to annihilation via motion and interaction with other dislocations, point defects and surfaces, is of fundamental importance. Unfortunately, atomic-scale investigations of dislocation evolution in a bulk object are well beyond the spatial and temporal resolution limits of current characterization techniques. Here we overcome the experimental limits by investigating the two-dimensional graphene in an aberration-corrected transmission electron microscope, exploiting the impinging energetic electrons both to image and stimulate atomic-scale morphological changes in the material. The resulting transformations are followed in situ, atom-by-atom, showing the full life cycle of a dislocation from birth to annihilation. Our experiments, combined with atomistic simulations, reveal the evolution of dislocations in two-dimensional systems to be governed by markedly long-ranging out-of-plane buckling.

Dual origin of defect magnetism in graphene and its reversible switching by molecular doping.

Control of magnetism by applied voltage is desirable for spintronics applications. Finding a suitable material remains an elusive goal, with only a few candidates found so far. Graphene is one of them and attracts interest because of its weak spin-orbit interaction, the ability to control electronic properties by the electric field effect and the possibility to introduce paramagnetic centres such as vacancies and adatoms. Here we show that the magnetism of adatoms in graphene is itinerant and can be controlled by doping, so that magnetic moments are switched on and off. The much-discussed vacancy magnetism is found to have a dual origin, with two approximately equal contributions; one from itinerant magnetism and the other from dangling bonds. Our work suggests that graphene's spin transport can be controlled by the field effect, similar to its electronic and optical properties, and that spin diffusion can be significantly enhanced above a certain carrier density.

Are we van der Waals ready?

We apply a range of density-functional-theory-based methods capable of describing van der Waals interactions with weakly bonded layered solids in order to investigate their accuracy for extended systems. The methods under investigation are the local-density approximation, semi-empirical force fields, non-local van der Waals density functionals and the random-phase approximation. We investigate the equilibrium geometries, elastic constants and binding energies of a large and diverse set of compounds and arrive at conclusions about the reliability of the different methods. The study also points to some directions of further development for the non-local van der Waals density functionals.

Embedding transition-metal atoms in graphene: structure, bonding, and magnetism.

We present a density-functional-theory study of transition-metal atoms (Sc-Zn, Pt, and Au) embedded in single and double vacancies (SV and DV) in a graphene sheet. We show that for most metals, the bonding is strong and the metal-vacancy complexes exhibit interesting magnetic behavior. In particular, an Fe atom on a SV is not magnetic, while the Fe@DV complex has a high magnetic moment. Surprisingly, Au and Cu atoms at SV are magnetic. Both bond strengths and magnetic moments can be understood within a simple local-orbital picture, involving carbon sp(2) hybrids and the metal spd orbitals. We further calculate the barriers for impurity-atom migration, and they agree well with available experimental data. We discuss the experimental realization of such systems in the context of spintronics and nanocatalysis.