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]

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).

[Primary and secondary hypophysitis: A clinicomorphological study]

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.

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.

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).

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

The fluorinated graphene suspension films were found to have excellent characteristics and be 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.

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.

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.

[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.

[Analysis of the influenza situation in the USSR and the GDR in nonepidemic (1978-1979) and epidemic (1979-1980) seasons]

Analysis of comparative surveillance on influenza carried out in the USSR and the GDR is presented. It was shown that both in the nonepidemic and epidemic seasons the incidence of influenza in the USSR increased considerably earlier than in the GDR. In the nonepidemic season of 1978-1979, strains of different antigenic structure were in circulation in the USSR and the GDR, whereas the epidemic of 1979-1980 was induced by new drift variants of A(H3N2) virus, A/Bangkok/1/79 and A/Bangkok/2/79. The epidemic strains circulating in both countries were dissimilar biologically and antigenically. In the nonepidemic period in the USSR and GDR the circulating A(H1N1) strains were represented not only by drift variants A/USSR/90/77 and A/Brazil/11/78 but also by natural recombinants of A(H1N1), A/USSR/61/79, in which the internal proteins (P, NP, NS, and M) were analogous to those of A(H3N2).

[Characteristics of the distribution of influenza A and B in various geographical regions of the USSR]

The results of a comparative analysis of laboratory-confirmed cases of influenza A and B recorded annually in October-May from 1977 to 1981 in four towns located in different geographical regions of the country are reported. During this period, influenza A represented by varieties A (H1N1) and A (H3N2) and B were found to have been recorded in all the towns under study. The periods of the maximum number of the laboratory-confirmed cases recorded coincided generally with the periods of increased clinical incidence of ARD. There were instances, however, when during the periods of elevated ARD morbidity the number of laboratory-confirmed cases of influenza increased insignificantly. Peculiar features were found in fluctuations of the incidence of laboratory-confirmed influenza cases in different geographical regions of the country.

[Comparative analysis of the dynamics of antibodies to influenza A (H1N1) and A/Hong Kong/1/68 (H3N2) in the sera of a healthy population]

A comparative analysis of the dynamics of antibodies against A(H1N1) and A/Hong Kong/I/68 (H3N2) influenza viruses was carried out in the blood sera of healthy population in some cities of the USSR. The data obtained suggest that anamnestic antibody production can be stimulated only by the drift- and not by the shift-variants of viruses, i.e. by those with varying hemagglutinin serotypes.

[Etiological study of the fatal cases in the period of the influenza A epidemic of 1977-1978]

The etiology of the disease, the age structure of fatalities, the time of death were studied in 34 fatal cases in the period of influenza A (H1N1) epidemic in December 1977-February 1978 and in 33 fatal cases during influenza A/Victoria/3/75 (H3N2) epidemic in January-March, 1975 (data from some autopsy offices of Kiev). The results of the investigation of the etiology by immunofluorescence and the histological methods were mostly similar. The polyetiological structure of the diseases in the influenza epidemic of 1975 and rather monoetiological one in the influenza epidemic of 1977-1978 were observed. In 1975, fatal cases were found mostly in 2 age groups: infants under 1 year and adults over 20, in 1977-1978 in 4 age groups: infants under 1, children of 1-3, over 9, and adults. In both epidemics the maximum number of fatal cases coincided with the beginning of a decline in the epidemic wave and subsequently they were registered evenly for over one month. A high infection rate with a new influenza A virus variant (H1N1) was found among normal subjects in all age groups.

Epidemiology of influenza during 1957--75 in the Union of Soviet Socialist Republics and the German Democratic Republic

Analysis of clinical data collected by the epidemiological services in both countries showed that each shift or drift in the antigenic structure of the influenza virus resulted in epidemics in both countries. Depending on the degree of antigenic change, both shifts and drifts influenced the speed of epidemic spread and the time of occurrence and the intensity of the epidemics. However, the analyses did not reveal a direct relation between degree of antigenic variation and the attack rate or the severity of the epidemic. The mean attack rate in both countries was about 13% depending on the pathogenicity of the circulating virus. The severity of the epidemics varied in the two countries but the fourth epidemic after each shift was severe in both countries. The reasons for this and other features of the epidemiology are discussed.

Influenza in the USSR in 1977: recurrence of influenzavirus A subtype H1N1

Early in November 1977, several outbreaks of influenza were reported in the far eastern region of the USSR. The epidemic spread rapidly throughout the country affecting mainly people under the age of 20 years. Most of the strains of virus isolated were found to be influenza A subtype H1N1. The serological characterization of the strains is described in this paper.

The upper tolerance limits of nonepidemic daily morbidity for influenza and other acute respiratory diseases in the epidemic season

The start of an influenza epidemic may be detected by comparing actual daily morbidity from influenza and other acute respiratory infections with the upper tolerance limits of this morbidity for nonepidemic years. A method of constructing such tolerance limits for the autumn-winter season, when the probability of an influenza epidemic is greatest, is described. The results are illustrated by data relating to Moscow.

Influenza A2 and B in the USSR in 1966-67, and some aspects of global epidemiology of influenza

An epidemic wave of influenza caused by the A2 virus was recorded in the USSR in the winter of 1966-67; this was the fifth wave since this pandemic strain first appeared. In contrast to the last wave of 1965, it developed simultaneously with, or followed, an epidemic of influenza B. The epidemic spread of influenza was observed for a period of 2 years in the USSR; influenza B prevailed in 1966, influenza A2 in 1967, and the two viruses spread at different speeds. A slow spread and a gradual increase in intensity during most of the year was characteristic of influenza B while influenza A2 spread rapidly and involved a considerable part of the country within 3 months.Although the influenza B started to spread almost 9 months before influenza A2 became active, the periods of maximum intensity of both outbreaks coincided in most parts of the USSR in the winter of 1966-67. The approach of summer temporarily stopped the spread of influenza B but did not bring the outbreak to an end nor lessen the intensity of the next wave in the autumn. Among the haemagglutinating agents isolated in the USSR in 1966-67 were 121 strains of virus B and 132 strains of virus A2. A study of the antigenic structure of the B strains showed that they were not all similar; some of them were closely related to B/Johannesburg/33/58, a greater number were more closely related to B/Singapore/3/64 and a number of strains differed from both varieties.Among the A2 viruses isolated and investigated were strains similar to those of pandemic prototype A2/Singapore/1/57, strains close to A2/England/12/64 and A2/USSR, Gor/62/65, strains antigenically different from all those strains but still related to the A2 subtype and strains that had S-antigen of A-type but which were not inhibited by antisera to the prototypes A2/57, A2/64 or A2/67.Outbreaks of influenza A2 and B recorded in the USSR are considered to be parts of the global influenza epidemics.

The Hong Kong influenza virus epidemic in the USSR

An epidemic wave of influenza associated with the A2/Hong Kong/68 virus reached the USSR in the second 10-day period of December 1968. During the first quarter of 1969 the epidemic involved almost all cities of the Soviet Union. The intensities of the rise and of the fall of the 1969 epidemic wave were less pronounced than those of the 1965 influenza A2 epidemic, but were more extended. In most towns the epidemic lasted 50-80 days whereas in 1965 the epidemic in towns lasted 25-30 days.The influenza caused by A2/Hong Kong/68 was characterized by an unusual age-group distribution. Children under 7 years of age made up only one-quarter of the total influenza cases during the peak of the epidemic wave in most communities. The clinical course of the disease was, in the main, of average severity, there being no significant differences in symptoms compared with influenza caused by virus A2.Analysing the influenza epidemics associated with influenza A2 virus during recent years one may note peculiar features of the A2 Hong Kong/68 influenza epidemic. On the one hand, these are apparently connected with the shifts in antigenic character of the virus, and, on the other hand, with the timely arrangements undertaken by public health services to prepare for the influenza epidemic, i.e., the carrying out of prophy actic and anti-epidemic measures.

The 1965 A2 influenza epidemic in the USSR and the natural history of Asian influenza

An epidemic of Asian (A2) influenza that occurred in the USSR early in 1965 was the fourth wave of Asian influenza there since 1957, when the disease became pandemic, spreading through all countries and continents. The 1965 epidemic was severe, in several cities even more so than the 1957 pandemic. Study of the antigenic structure of the viruses isolated during the latest epidemic indicated that the viruses were similar to those isolated in western Europe in 1964 (A2/England 12/64) but that their structure showed a further shift away from that of the prototype virus (A2/Singapore 1/57). The 1957 and 1959 pandemics followed similar courses, starting in China. The third wave affected Europe. North Africa and Asia in winter 1960-61, but did not reach the USSR until the following winter. The fourth wave was more complex, spreading in Asia in 1962-63 and in Europe and America in 1963-64; it reached the USSR at the beginning of 1965. The way in which the structure of the A2 virus has changed since 1957 is discussed.