Resonant Raman scattering on graphene: SERS and gap-mode TERS.

Nanoscale deformations and corrugations occur in graphene-like two-dimensional materials during their incorporation into hybrid structures and real devices, such as sensors based on surface-enhanced Raman scattering (SERS-based sensors). The structural features mentioned above are known to affect the electronic properties of graphene, thus highly sensitive and high-resolution techniques are required to reveal and characterize arising local defects, mechanical deformations, and phase transformations. In this study, we demonstrate that gap-mode tip-enhanced Raman Scattering (gm-TERS), which offers the benefits of structural and chemical analytical methods, allows variations in the structure and mechanical state of a two-dimensional material to be probed with nanoscale spatial resolution. In this work, we demonstrate locally enhanced gm-TERS on a monolayer graphene film placed on a plasmonic substrate with specific diameter gold nanodisks. SERS measurements are employed to determine the optimal disk diameter and excitation wavelength for further realization of gm-TERS. A significant local plasmonic enhancement of the main vibrational modes in graphene by a factor of 100 and a high spatial resolution of 10 nm are achieved in the gm-TERS experiment, making gm-TERS chemical mapping possible. By analyzing the gm-TERS spectra of the graphene film in the local area of a nanodisk, the local tensile mechanical strain in graphene was detected, resulting in a split of the G mode into two components, G+ and G-. Using the frequency split in the positions of G+ and G- modes in the TERS spectra, the stress was estimated to be up to 1.5%. The results demonstrate that gap-mode TERS mapping allows rapid and precise characterization of local structural defects in two-dimensional materials on the nanoscale.

[Assessment of the role of nutritional and genetic determinants in the formation of the risk of diseases associated with folate cycle disorders in the population of the Omsk region].

A number of essential nutrients are involved in the folate cycle, and its effectiveness depends on the sufficient intake of them. In addition, polymorphic variants of the methylenetetrahydrofolate reductase (MTHFR), methionine synthase reductase (MTRR) and methionine synthase (MTR) genes affect a wide range of biochemical reactions of the folate cycle and should also be considered as a risk factor for the development of a number of diseases. The purpose of this research was to study the prevalence of these risk factors. Material and methods. The prevalence of polymorphisms of the folate cycle genes: C677T polymorphism of the MTHFR gene and A66G polymorphism of the MTRR gene in a random stratified (by sex and age) sample of the adult population of the Omsk region [n=139, 51 men, 88 women, aged 18 to 75 years, median age 37 (26; 48) years] was studied. The identification of polymorphisms was carried out by the method of allele-specific polymerase chain reaction with an electrophoretic detection scheme. Using the food intake frequency questionnaire, the dietary intake of nutrients involved in the folate cycle was determined: B vitamins (B6, B2, B9, B12), methionine, choline, in a representative stratified sample of residents of the Omsk region [n=421, 177 men, 244 women, aged 18 to 83 years, median age 37 (23; 57) years]. Results. MTHFR genotypes (A222V С677T C>T) were distributed as follows: CC-type - 51.3%, CT - 41.0%, TT - 7.7%; MTRR genotypes (I22M A>G): AA type - 57.9%, AG - 30.3%, GG - 11.8%. The analysis of actual nutrition showed consumption below the recommended dietary intake of folates in 88.2% persons, vitamin B2 and choline - in 40.5%, vitamin B6 - in 29.2%, methionine - in 22.0%. Vitamin B12 intake was within the recommended range. Conclusion. The totality of the data presented indicates the combined influence and wide distribution of factors that determine the low efficiency of the folate cycle, and, as a result, a high risk of developing a characteristic pathology for the adult population of the region, which determines the need and priorities for prevention measures, including healthy nutrition.

Electrochemically exfoliated thin Bi2Se3 films and van der Waals heterostructures Bi2Se3/graphene.

Thin Bi2Se3 flakes with few nanometer thicknesses and sized up to 350 µm were created by using electrochemical splitting from high-quality Bi2Se3 bulk monocrystals. The dependence of film resistance on the Bi2Se3 flake thickness demonstrates that, at room temperature, the bulk conductivity becomes negligible in comparison with the surface conductivity for films with thicknesses lower than 80 nm. Unexpectedly, all these films demonstrated p-type conductivity. The doping effect with sulfur or sulfur-related radicals during electrochemical exfoliation is suggested for the p-type conductivity of the exfoliated Bi2Se3 films. The formation of 2-8 nm films was predominantly found. Van der Waals (vdW) heterostructures of Bi2Se3/Graphene/SiO2/Si were created and their properties were compared with that of Bi2Se3 on the SiO2/Si substrate. The increase of the conductivity and carrier mobility in Bi2Se3 flakes of 3-5 times was found for vdW heterostructures with graphene. Thin Bi2Se3 films are potentially interesting for applications for spintronics, nano- and optoelectronics.

[Gastric damage in systemic sarcoidosis]. / Porazhenie zheludka pri sistemnom sarkoidoze.

Sarcoidosis is a multisystem disease of unknown etiology, characterized by specific granulomas without caseous necrosis in the affected organs and tissues. Along with respiratory organs, the gastrointestinal tract may be affected by sarcoidosis. Due to the rarity of gastric involvement of sarcoidosis, substantial difficulties arise in verifying the diagnosis, making a differential diagnosis, and examining gastric biopsy specimens. The paper describes in detail pathological changes in the gastric wall tissue specimen in sarcoidosis and comparatively analyzes the findings with the data available in the literature.

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).

Two-layer and composite films based on oxidized and fluorinated graphene.

This study is devoted to the production and investigation of dielectric films, based on oxidized and fluorinated graphene suspensions. The properties of the graphene oxide films may be greatly improved by adding fluorographene. FG films have transmission in the visible and near infrared ranges equal to 96-98%. Two-layer films of fluorinated graphene on graphene oxide and composite films (composite suspension of fluorinated and oxidized graphene) exhibit good insulating properties. Their leakage currents are lower than that in the graphene oxide or fluorinated graphene by 3-5 orders of magnitude. A significant increase in thermal stability and relatively low charge in the film and at the interface with silicon (3 × 1010-1.4 × 1011 cm-2) are also found for these films. An application of thin fluorographene films (a few nanometers) decorates and eliminates structural defects in the graphene oxide films, resulting in conductivity blocking in graphene oxide. The built-in charge density in the composite film of 10-20% fluorographene in the graphene oxide is much less than in the two-layer film (<1 × 1010 cm-2). The created two-layer and composite films may be practically applied in 2D printed and flexible electronics as insulating films (gate dielectric and interlayer insulator), as well as materials showing the resistive effect.

Graphene-based humidity sensors: the origin of alternating resistance change.

The response of a graphene-based humidity sensor is considered as a function of film structures. Analysis of the resistance changes due to water molecule adsorption on the graphene or multi-layer graphene (MLG) surface is performed for films with different structures and resistivities from hundreds of ohms/sq to hundreds of kilo-ohms/sq. The results revealed possible increase, decrease and non-monotonous behavior of resistance with changes in film structure. Adsorption of water molecules at grain boundary defects is assumed to lead to an increase in film resistivity due to the donor property of water and the p-type conductivity of graphene. Another type of conductive center with a higher capture cross-section is realized in the case of water molecule adsorption at edge defects in MLG films (the formation of conductive chains with ionic conductivity). If these chains form a continuous network the film resistivity decreases. The result of the competition between the opposite effects of the conductivity compensation and formation of the water-based conductive chains depends on the film structure and determines the response of humidity sensors. Sensor sensitivity is found to increase when only one type of defect determines water adsorption (edge defects or grain boundary defects).

Fluorinated graphene suspension for inkjet printed technologies.

The possibility to control the size of the flakes of graphene suspension in the course of their fluorination in an aqueous hydrofluoric acid solution was demonstrated. The effect of the suspension composition, the fluorination time, temperature and thermal stress on the fragmentation process was investigated. The corrugation of suspension flakes, which occurs at fluorination due to a difference in the constants of graphene and fluorographene lattices, leads to the appearance of nonuniform mechanical stresses. The fact that the flake size after fragmentation is determined by the size of corrugation allows the assumption that the driving force of fragmentation is this mechanical stress. This assumption is confirmed by the break of the corrugated layers from flakes under thermal stress. Moreover, fluorination treatment at elevated temperatures (∼70 °C) significantly accelerates the fragmentation process. Suspensions of fluorinated graphene with nanometer size flakes are of interest for the development of 2D ink-jet printing technologies and production of thermally and chemically stable dielectric films for nanoelectronics. The printed fluorinated graphene films on silicon and flexible substrates have been demonstrated and the charges in metal-insulator-semiconductor structures have been estimated as the ultra low values of (0.5-2) × 10(10) cm(-2).

[Primary and secondary hypophysitis: A clinicomorphological study]. / Pervichnyi i vtorichnyi gipofizit. Kliniko-morfologicheskoe issledovanie.

The paper describes 6 cases of the rare disease - primary and secondary hypophysitis detected by a morphological examination of the material of endoscopic transsphenoidal resection of pituitary neoplasms. It also provides clinical and morphological comparisons and analyzes the data available in the literature.

Fluorinated graphene dielectric films obtained from functionalized graphene suspension: preparation and properties.

In the present study, we have examined the interaction between a suspension of graphene in dimethylformamide and an aqueous solution of hydrofluoric acid, which was found to result in partial fluorination of suspension flakes. A considerable decrease in the thickness and lateral size of the graphene flakes (up to 1-5 monolayers in thickness and 100-300 nm in diameter) with increasing duration of fluorination treatment is found to be accompanied by a simultaneous transition of the flakes from the conducting to the insulating state. Smooth and uniform insulating films with a roughness of ∼2 nm and thicknesses down to 20 nm were deposited from the suspension on silicon. The electrical and structural properties of the films suggest their use as insulating elements in thin-film nano- and microelectronic device structures. In particular, it was found that the films prepared from the fluorinated suspension display rather high breakdown voltages (field strength of (1-3) × 10(6) V cm(-1)), ultralow densities of charges in the film and at the interface with the silicon substrate in metal-insulator-semiconductor structures (∼(1-5) × 10(10) cm(-2)). Such excellent characteristics of the dielectric film can be compared only to well-developed SiO2 layers. The films from the fluorinated suspension are cheap, practically feasible and easy to produce.

Extremely high response of electrostatically exfoliated few layer graphene to ammonia adsorption.

Extremely high gas sensing properties of p-type few layer graphene flakes exfoliated from highly oriented pyrolytic graphite have been demonstrated. The current response to ammonia adsorption is strongly dependent on film thickness and is higher than that for graphene by 1-8 orders of magnitude. A maximal response was found for sample thickness ∼ 2 nm. The effect is attributed to the formation of multiple p-n-p junctions at the grain boundaries in the polycrystalline graphene flakes exposed to ammonia-containing ambient.

[Maternal serum screening: possibilities of using in the complex diagnosis of fetal malformation].

Along with ultrasonography, maternal serum screening is an initial stage of a diagnostic process of genetically determined fetal malformation. Based on the performed clinical and statistical study, the author estimated the values of alpha-fetoprotein and beta-subunit of chorionic gonadotropin if the fetus has malformations of the central nervous system, heart, anterior abdominal wall, and urinary tract and Down's syndrome. The informative value of alpha-fetoprotein was confirmed in malformations of the anterior abdominal wall (gastroschisis, omphalocele) and the central nervous system (hydrocephalus, spinal hernia) and that of chorionic gonadotropin in Down's syndrome in a fetus of 15 to 24 weeks gestation.

The modification of Si nanocrystallites embedded in a dielectric matrix by high energy ion irradiation.

We have followed the effects of heavy ion irradiation on the structural, electrical, and photoluminescence properties of ensembles of silicon nanocrystallites embedded in a dielectric (SiO(2)) matrix. This was done as a function of the irradiation dose and the content of the Si phase. The results obtained can be accounted for self-consistently assuming that a relatively small dose of the irradiation enhances the crystallization while for higher doses the irradiation enhances the amorphization. The corresponding processes suggest that tuning of the above properties can be achieved by swift heavy ion irradiation.

Low-dimensional effects in a three-dimensional system of Si quantum dots modified by high-energy ion irradiation.

Modification of films containing Si nanocrystallites embedded in SiO2 by irradiation with high-energy ions was found to induce peaks in their low-frequency capacitance-voltage characteristics. Considering the nanocrystallite spatial distribution that follows the ion tracks we interpret these peaks as due to the charge transfer along these tracks, similar to the process that was reported previously for two-dimensional arrays of such crystallites. The ion irradiation of the above three-dimensional system appears to be useful then for the fabrication of nanostructures, which have also the properties of low-dimensional arrays.

[Hygienic risk factors of congenital malformations].

The frequency of multiple congenital malformations, central nervous system and genital malformations were found to be associated to the magnitude and duration of ecological load. Xenobiotics identified in the ambient air of a large industrial center pose an increased risk for antenatal malformations. The largest number of statistically significant correlation coefficients was established between the study variables at a delay lag of 2 years. It is assumed that high ambient air pollution adversely affects the mechanisms of inheritance in future parents long before birth of a child.

[Primary lung osteosarcoma simulating gastric carcinoma].

The rarest case of primary lung osteosarcoma is described. Despite the fact that an extended clinicoinstrumental study was conducted, the clinicians who interpreted the process to be a destructive gastric carcinoma did not diagnose the site of the tumor. Autopsy identified the unusual form of primary lung malignancy progression with an advanced invasion into the organs on both sides of the diaphragm, including the gastric wall.

[Characterization of the sanitary situation in the Kurgan Region].

The aim of this survey was to study the ecological state in the Kurgan Region in the period of 1993 to 2003. The survey showed the west and northwest part of the Kurgan Region to be areas at risk for environment-dependent diseases. The major risk factors included a high pollution of water sources with limited water resources due to the radioactive pollution occurring in the 1940s to the 1950s in some areas of the region; transformation of natural landscapes caused by spring floods and soil erosions among other things.

[Mast cells in photolesion of the skin and basal cell cancer associated with it].

Morphofunctional features of skin mast cells located in the areas subjected to chronic UV-radiation and in the associated basal cell carcinoma with photoinjure have been studied. Various immunohistochemical methods (chromogranin A, CDla, HLA-DR, CD35, Ki67, P53, Bcl-2, Mcl-1, involucrine) were used. It is found that chronic UV-damage leads to mast cell hyperplasia as well as activation of their synthetic, absorption and secretory functions. It is suggested that mast cell hyperplasia and increase of mast cells neuroendocrine activity provide a risk of basal cell carcinoma development.