Structural transformations and thermal stability of RhGe synthesized under high temperature and pressure.

Here, we study B20-type RhGe, a representative of a class of non-centrosymmetric monosilicides and monogermanides, which possess unique topological and magnetic properties important for many possible applications. The stability and phase transitions of the non-equilibrium B20-RhGe phase that can only be obtained under high pressure, are investigated theoretically usingab initiocalculations and experimentally by means of differential scanning calorimetry. For RhGe and, for comparison, for its analogue RhSi, we conducted an evolutionary search for low-energy polymorphic modifications at zero temperature and then performed simulations of their behavior at finite temperatures. The (P,T) conditions of stability for the found polymorphs are determined. Our calorimetric studies on high-pressure-synthesized RhGe samples allowed us to reveal peculiarities in thermal stability and heating-induced phase transformations. X-ray diffraction analysis and microstructure analysis of the samples were carried out before and after the heating. We also determined the specific heat from calorimetric measurements and compared the results with our calculations in the quasi-harmonic approximation.

Is icosahedral short-range order presented in supercooled transition metals?

Supercooled transition metals are characterized by the absence of long-range order and the presence of a specific short-range order in the arrangement of atoms. So, the presence of shoulders and broadenings at the second maximum in the experimentally measured quantity-in the static structure factorS(k)-is usually interpreted as a manifestation of the icosahedral (ideal or distorted) short-range order (ISRO-Icosahedral Short-Range Order). Icosahedral short-range order is a structure with fivefold symmetry in the arrangement of atoms, which can lead to the possibility of achieving deep supercooling. In this work, we study the local structural features of equilibrium and supercooled nickel melts under various cooling protocols (γ∈1010,1014 K s-1) in order to clarify the mechanism of formation of the icosahedral short-range order in pure transition metals. Comprehensive studies of the properties of nickel melts were carried out using experiments on x-ray diffraction, large-scale molecular dynamics (MD) simulations with subsequent structural and cluster analysis. A good agreement was found between the results of x-ray diffraction data and the MD simulations results for an equilibrium nickel melt. It was found that the nickel melt is characterized by a short-range order, formed by fragments of icosahedra and distorted icosahedral clusters. It was revealed that the 'liquid-crystal' phase transition in nickel is accompanied by the transformation of distorted icosahedral clusters into clusters with thefcc/hcp-symmetry. It is shown that, in contrast to the Voronoi tessellation method, the cluster analysis method based on the (q4,q6) rotational invariants does not allow sufficiently correct identification of the distorted icosahedral short-range order in metal melts.

[Identification by enzyme immunoassay of escape mutants S143L and G145R of hepatitis B virus (Hepadnaviridae: Orthohepadnavirus: Hepatitis B virus)].

INTRODUCTION: The achievement of the goal of the World Health Organization to eliminate viral hepatitis B by 2030 seems to be problematic partly due to the presence of escape mutants of its etiological agent, hepatitis B virus (HBV) (<i>Hepadnaviridae: Orthohepadnavirus: Hepatitis B virus</i>), that are spreading mainly in the risk groups. Specific routine diagnostic assays aimed at identification of HBV escape mutants do not exist.The study aimed the evaluation of the serological fingerprinting method adapted for routine detection of escape mutations in 143 and 145 aa positions of HBV surface antigen (HBsAg). MATERIAL AND METHODS: HBV DNA from 56 samples of HBsAg-positive blood sera obtained from donors, chronic HBsAg carriers and oncohematology patients has been sequenced. After the identification of mutations in HBsAg, the samples were tested in the enzyme-linked immunosorbent assay (ELISA) kit «Hepastrip-mutant-3K¼. RESULTS AND DISCUSSION: Escape mutations were detected mainly in patients with hematologic malignancies. Substitutions in 143 and 145 aa were found in 10.81% and in 8.11% of such patients, respectively. The G145R mutation was recognized using ELISA kit in almost all cases. The kit specifically recognized the S143L substitution in contrast to the S143T variant. The presence of neighbor mutation D144E can be assumed due to it special serological fingerprint. CONCLUSION: ELISA-based detection of escape mutations S143L, D144E and G145R can be used for routine diagnostics, especially in the risk groups. The diagnostic parameters of the kit can be refined in additional studies. This immunoassay and methodology are applicable for the development and quality control of vaccines against escape mutants.

Molecular Pathogenesis and the Possible Role of Mitochondrial Heteroplasmy in Thoracic Aortic Aneurysm.

Thoracic aortic aneurysm (TAA) is a life-threatening condition associated with high mortality, in which the aortic wall is deformed due to congenital or age-associated pathological changes. The mechanisms of TAA development remain to be studied in detail, and are the subject of active research. In this review, we describe the morphological changes of the aortic wall in TAA. We outline the genetic disorders associated with aortic enlargement and discuss the potential role of mitochondrial pathology, in particular mitochondrial DNA heteroplasmy, in the disease pathogenesis.

Effect of copper concentration on the structure and properties of Al-Cu-Fe and Al-Cu-Ni melts.

We address a relationship between properties of liquid and solid states by comparing structural characteristics and viscosity in Al-Cu-Fe and Al-Cu-Ni melts. The former system forms an equilibrium quasicrystalline phase but the latter does not. We show that the concentration behavior of the viscosity, melting temperature and characteristics of the chemical short-range order correlate with each other. The main structural differences between the melts are related to the peculiarities of their electronic structure, which is the same for liquid and solid states near the melting temperature.

Electronic band structure in n-type GaAs/AlGaAs wide quantum wells in tilted magnetic field.

Oscillations of the real component of AC conductivity [Formula: see text] in a magnetic field were measured in the n-AlGaAs/GaAs structure with a wide (75 nm) quantum well by contactless acoustic methods at [Formula: see text] mK. In a wide quantum well, the electronic band structure is associated with the two-subband electron spectrum, namely the symmetric (S) and antisymmetric (AS) subbands formed due to electrostatic repulsion of electrons. A change of the oscillations amplitude in tilted magnetic field observed in the experiments occurs due to crossings of Landau levels of different subbands (S and AS) at the Fermi level. The theory developed in this work shows that these crossings are caused by the difference in the cyclotron energies in the S and AS subbands induced by the in-plane magnetic field.

[Detection of Epstein-Barr virus genome in oral cavity squamous cell carcinoma samples of russian patients.]

INTRODUCTION: Oral cavity squamous cell carcinoma (OC-SCC) is the most common and aggressive malignancy of the oral cavity. Recent studies have revealed infections with human papilloma virus (HPV) as an additional risk factor for oral squamous cell carcinoma development, while distinguished role of Epstein-Barr virus (EBV) remains still uncertain. However, the evidence for association between virus infection and risk of oral squamous cell carcinoma is controversially and varies significantly by geographic regions and race. PURPOSE: The aim of the present study was to elucidate the prevalence of HPV and EBV in OC-SCC samples of Russian patients from Moscow region. MATERIAL AND METHODS: We investigated fresh-frozen tumor tissue fragments obtained from 11 patients with OC-SCC. DNA was extracted and the viral genome was examined by quantitative PCR assays with highrisk type-specific HPV and EBV specific markers followed by sequencing-based analysis. RESULTS: No HPV infection in analyzed OC-SCC samples was observed, while EBV was identified in 70.0% (7/10) of patients. Further based on Q-PCR amplification of the EBV targets including BamHI-W, EBNA1 and C-terminal fragment of LMP1 gene, EBV infection and measurement of virus load in the tumor samples was assessed. Sequencing LMP1-positive products revealed that the most samples (5/6) contained variants LMP1 with Cao deletion characterized by an increased transforming potential. CONCLUSION: These data suggest that prevalence of EBV infections is common and may influence cancer development, although detected LMP1 variants of EBV are not necessarily associated with the pathogenesis of OC-SCC. Further studies are necessary to determine the potential role of EBV and its possible importance as an infection factor in OC-SCC.

Linear magnetoresistance in the low-field limit in density-wave materials.

The magnetoresistance (MR) of a material is typically insensitive to reversing the applied field direction and varies quadratically with magnetic field in the low-field limit. Quantum effects, unusual topological band structures, and inhomogeneities that lead to wandering current paths can induce a cross-over from quadratic to linear MR with increasing magnetic field. Here we explore a series of metallic charge- and spin-density-wave systems that exhibit extremely large positive linear MR. By contrast to other linear MR mechanisms, this effect remains robust down to miniscule magnetic fields of tens of Oersted at low temperature. We frame an explanation of this phenomenon in a semiclassical narrative for a broad category of materials with partially gapped Fermi surfaces due to density waves.

Pretreatment with Antiviral Preparation Kagocel Normalizes the Content of Bone Marrow Multipotent Stromal Cells and TNFα in Blood Serum of CBA Mice Disturbed by Administration of S. typhimurium Antigen Complex In Vivo and Maintains High Concentration of IL-10 and Th1 Cytokines.

Pretreatment with the active substance of antiviral preparation Kagocel, inductor of type I endogenous IFN, in a daily therapeutic dose (30 µg/mouse) 3 h prior to administration of S. typhimurium antigens to CBA mice reduced the number of bone marrow multipotent stromal cell (significantly increased by 3.2 times on the next day after antigen injection) to the initial level. Thus, activation of the stromal tissue induced by administration of the bacterial antigen was blocked. In addition, preliminary administration of Kagocel modulated the cytokine profile of the blood serum affected by S. typhimurium antigens: reduced 1.6-fold elevated concentration a proinflammatory cytokine TNFα to the control level (in 4 h after antigen injection) and maintained this level in 20 h after antigen administration. Kagocel also maintained the concentration of anti-inflammatory cytokine IL-10 at the level surpassing the normal by 1.6 times and high concentrations of Th1 cytokines (IL-2, IFNγ, and IL-12). These results suggest that Kagocel can reduce the immune response to bacterial antigens (similar to type I IFN [7]), which can contribute to its therapeutic and preventive effects in addition to its well documented antiviral activity and then this preparation can be used for the therapy of diseases accompanied by excessive or chronic inflammation.

Modified Pechini Processing of Barium and Lanthanum-Lithium Titanate Nanoparticles and Thin Films.

Barium-strontium titanate (BST) Ba0.6Sr 0.4 TiO3 and lanthanum-lithium titanate (LLT) La0.5Li0.5TiO3 nanopowders and thin films have been obtained via the modified Pechini route. Polyesterification and complexation processes of gel formation have been examined. Hypothetical models of coordinative polymers formed in sol-gel system have been suggested. It has been shown that BST and LLT solid solutions form in one step at relatively low temperature. X-ray diffraction confirms that the final products, which are single phases and have cubic shape, are formed at 600 and 700 °C for BST and LLT respectively. It has been found that use of thermal shock as pretreatment allows to increase the density of BST- and LLT-based thin films.

Hepatitis B virus covalently closed circular DNA homeostasis is independent of the lymphotoxin pathway during chronic HBV infection.

Current treatment options for patients with chronic hepatitis B virus (HBV) infection are not curative as they are not effective in eliminating covalently closed circular DNA (cccDNA). cccDNA is a stable template for HBV transcription in the nucleus of hepatocytes and is thought to be one of the main factors responsible for HBV persistence. Recently, activation of the lymphotoxin beta receptor (LTßR) has been shown to trigger degradation of cccDNA through induction of cytidine deaminases of the APOBEC3 family in HBV cell culture model systems. To assess the presence and relevance of such mechanisms in the liver of chronically HBV-infected patients, we compared intrahepatic cccDNA levels with the expression levels of lymphotoxins and some of their target genes (eg APOBEC deaminases) in liver biopsy tissue. Our results confirm elevated gene expression levels of components of the lymphotoxin pathway including lymphotoxin alpha (LTα), lymphotoxin beta (LTß), APOBEC3B (A3B) and APOBEC3G (A3G) in the chronically HBV-infected liver compared to uninfected liver. Furthermore, expression levels of the genes of the APOBEC deaminase family were correlated with those of LTα and LTß gene expression, consistent with lymphotoxin-mediated upregulation of APOBEC gene expression. However, intrahepatic cccDNA and HBV replication levels were not correlated with LTα, LTß and APOBEC gene expression. In conclusion, these results suggest that although the lymphotoxin pathway is activated in the chronically HBV-infected liver, it has no major impact on HBV cccDNA metabolism in chronic HBV infection.

[A comparative characteristic of antigenic properties of recombinant and native hbs-antigens with G145R mutation and evaluation of their immunogenicity].

BACKGROUND: One of the important reasons for spreading of hepatitis B virus (HBV) under conditions of vaccinepressure is emergence of escape mutations. Prevalent G145R mutation in S-gene leads to the most expressed changes of serological properties of HBV. Consequently, HBsAg is modifed so thoroughly that it cannot be recognized by the majority of anti-HBs. Mutant G145R also differs from a wild type HBsAg by its immunogenic properties. At present, the relevance of enhancement of hepatitis B vaccine in view of mutant virus variants has been recognized. OBJECTIVES: a comparative study of antigenic and immunogenic properties of native and recombinant G145R mutants and an estimation of possibility for developing antigenic component of hepatitis B vaccine with G145R mutation in HBsAg. METHODS: antigenic properties of recombinant HBsAg with G145R mutation were compared with each other and with native mutants by serological fngerprinting method. Then, BALB/c mice and sheep were immunized with selected recombinant antigen under different protocols. Titers of antibodies specifc to wild type or mutant G145R type of HBsAg in sera of immunized animals were measured. RESULTS: it was found that not all the recombinant HBsAg variants with G145R substitution have the same antigenic properties as native HBsAg with similar mutation. Recombinant HBsAg selected according to the principle of antigenic similarity possesses immunogenicity in mice and sheep causing the production of antibodies reacting with native wild and mutant type HBsAg. It was shown that mutant antigen is less immunogenic, requires larger doses and more time for the development of immune response; however, it is capable of causing an antibody level comparable with wild type antigen. CONCLUSIONS: preliminary selection of recombinant HBsAg containing G145R mutation with antigenic and immunogenic properties similar to the native analogue creates the basis for development of a specifc component of hepatitis B vaccine with escape mutation G145R in HBsAg.

MORPHOLOGICAL ANALYSIS OF HEPATITIS B VIRUS WITH ESCAPE MUTATIONS IN S-gene G145R AND S143L.

BACKGROUND: In terms of serological properties and immunization, the wild type of HBsAg HBV and its G145R mutant behave as different antigens. This testifies to serious structural changes, which presumably could have a significant impact on the morphogenesis of virions and subviral particles. Nevertheless, morphological and ultrastructural investigations of HBV with G145R mutation have not been carried yet. OBJECTIVES: Research of structural and morphological organization of HBV in the presence of the G145R escape mutation. METHODS: Studies of sera, purified viruses and recombinant HBsAg were carried out by transmission electron microscopy by the method of negative staining and indirect reaction of immunelabeling using monoclonal antibodies of different specificity. Specimens of wild type HBV and HBV with S143L mutation obtained in an identical manner were used as the control. RESULTS: The presence of typical virus particles of HBV was shown in the specimens of wild strain and HBV with S143L mutation. Specimens of HBV with G145R mutation were characterized by expressed morphological heterogeneity. In the initial serum and in the specimen of purified virus containing G145R mutant, large oval particles 60-70 nm and up to 200 nm in size, respectively, were found. The presence of antigen structures of HBV in all heterogeneous forms was confirmed. It was shown that forming of subviral particles in the process of expression of the recombinant HBsAg with G145R mutation depends on conditions of expression and purification of the protein. They can vary from well-formed circular and oval particles to practically unstructured fine-grained masses. CONCLUSION: Direct data on the impact of G145R escape-mutation in S-gene, in contrast to S143L mutation, on the morphogenesis of virions and subviral particles of HBV were obtained.

Fractional Quantum Hall States in a Ge Quantum Well.

Measurements of the Hall and dissipative conductivity of a strained Ge quantum well on a SiGe/(001)Si substrate in the quantum Hall regime are reported. We analyze the results in terms of thermally activated quantum tunneling of carriers from one internal edge state to another across saddle points in the long-range impurity potential. This shows that the gaps for different filling fractions closely follow the dependence predicted by theory. We also find that the estimates of the separation of the edge states at the saddle are in line with the expectations of an electrostatic model in the lowest spin-polarized Landau level (LL), but not in the spin-reversed LL where the density of quasiparticle states is not high enough to accommodate the carriers required.

Effects of Kagocel® on the Counts of Multipotent Stromal Cells, Expression of Cytokine Genes in Primary Cultures of Bone Marrow Stromal Cells, and Serum Cytokine Concentrations in CBA Mice.

The efficiency of cloning of bone marrow multipotent stromal cells (ECF-MSC) from CBA mice and the MSC counts in the femoral bone increased 24 h after a single in vivo (but not in vitro) injection of kagocel (active substance of antiviral drug Kagocel (®) ) 1.4 times (in response to 50-80 µg) and 4.6 times (in response to 250 µg). The maximum increase of ECF-MSC in response to 50 µg per mouse was detected just 1 h after Kagocel injection to intact mice and to mice previously receiving the drug for 3 days (2 and 1.7 times, respectively). The increase of ECF-MSC was 3-fold less intense in response to oral Kagocel in a dose of 250 µg/mouse vs. intraperitoneal Kagocel, ECF-MSC corresponding to its level in response to oral Poly (I:C). In vivo Kagocel led to emergence of proinflammatory cytokine IFN-γ, IL-1ß, and IL-8 mRNA in primary cultures of bone marrow stromal cells. Serum concentrations of IL-2, IL-5, IL-10, GM-CSF, IFN-γ, TNF-α, IL-4, and IL-12 increased 1.5 and 2 times just 1 h after Kagocel injection in doses of 30-50 and 250 µg, respectively, to intact mice and to animals previously treated with the drug for 3 days. The cytokine concentrations normalized after 3 h and increased again after 24 h, though did not reach the levels recorded 1 h after the drug injection. These data indicated that the therapeutic and preventive effects of Kagocel, together with its previously demonstrated stimulation of α- and ß-interferon production during several days, could be due to the capacity of this drug to increase the bone marrow ECF-MSC, serum cytokine concentrations, and induce the expression of proinflammatory cytokine genes in the bone marrow stromal cells 1 h after its injection.

A facility for X-ray diffraction in magnetic fields up to 25 T and temperatures between 15 and 295 K.

A facility for X-ray diffraction has been developed at the National High Magnetic Field Laboratory. It brings diffraction capability to the 25 T Florida split coil magnet and implements temperature control in a range of 15-295 K using a cold finger helium cryostat. This instrument represents an alternative to pulsed magnetic field systems, and it exceeds the static magnetic fields currently available at synchrotron facilities. Magnetic field compatibility of an X-ray source and detectors with the sizable magnetic fringe fields emanating from the magnet constrained the design of the diffractometer.

[IMMUNOPATHOGENESIS OF OCCULT INFECTION CAUSED BY HEPATITIS B VIRUS].

The concept of occult infection caused by hepatitis B virus (HBV) is determined as the presence of HBV DNA in blood sera or liver with the absence of detectable HBsAg. The actuality of this problem is associated with the fact, that occult hepatitis B (OHB) can be transmitted during hemotransfusions, cause reactivation of chronic hepatitis B in immune compromised individuals, facilitate development of liver cirrhosis and hepatocellular carcinoma. Several different hypotheses of OHB immunopathogenesis have been proposed, including a low number of copies of HBV DNA, altered immune response of the macroorganism, genetic variability of the S gene, integration of viral DNA into host genome, infection of mononuclear cells of peripheral blood, presence of immune complexes that hide HBsAg, and interference by other viruses such as HCV and HIV. Molecular mechanisms of HBV virus in HBsAg-negative individuals are not fully understood, however, viral mutations seem a very significant factor. Approaches of OHB prophylaxis including use of a polyvalent vaccine, that allows vaccination against wild and mutant HBV viruses, are examined.

[Migration of a nociogenic zone in human somatosensory system].

The article reviews the process of migration of nociogenic zones and principles of their integrative switching - off from the point of systematic approach and the informational-structural theory of pain. The phenomenon of migration of nociogenic zones underlies the development of clinical manifestations of pain.

[Multidirectional effect of MIF and sodium polyprenyl phosphate on the course of experimental flavivirus infection in mice].

AIM: Study of macrophage migration inhibiting factor (MIF) effect after intracerebral administration on the course of experimental infection induced in mice by tick borne encephalitis virus (TEV), and study of sodium polyprenyl phosphate (PPP) and/or antibodies against MIF on the course of this infection against the background of MIF administration. MATERIALS AND METHODS: Phosprenil preparation was used as a source of PPP. PPP was administered intracerebrally. MIF--human recombinant (R&D, USA), mice--Balb/c line. RESULTS: In the sera of mice infected with TEV, MIF production stimulation was detected at days 8 through 10 after the infection--against the background of clinical signs presentation of tick borne encephalitis (TE). Administration of PPP to infected mice, on the contrary, resulted in MIF production suppression at the specified period. After administration of 20 ng of MIF to mice, lethality increased by 40% and average life span decreased by 2.3 days. Thus, MIF at high doses caused an increase of infection course severity, induced by TEV in mice, and administration of 60 microg of PPP resulted in the protection from infection in 100% of cases. Intracerebral administrationto mice of antibodies against MIF resulted in a decrease of lethality indicator up to 26% as compared with control and an increase of averagelife span by 5.5 days. During simultaneous administration into the brain of infected mice of MIF, PPP and antibodies against MIF, prevention of MIF-induced increase of TE course severity was registered. CONCLUSION: The data obtained allow to conclude that MIF may serve as an indicator of TE course severity, and possible prognostic indicator of meningo-encephalitic form development in humans.

Stand alone experimental setup for dc transport measurements.

Described is a system consisted of Keithley's current source Model 6221 and nanovoltmeter Model 2182A pairs. That pair was developed by Keithley for precise measurements of a sample's one electrical parameter by the dc current-reversal transport technique. Nonstandard synchronization method employed in the presented setup allows assembling several pairs together for low level electrical measurements of a sample's several parameters associated with the same current, thus expanding the applications of these devices. The equipment was tested by simultaneous measurements of such two parameters as transverse magnetoresistance and Hall voltage on the following materials: Si/SiGe, Ge:Mn; HgTe/HgCdTe, and InMnSb.