Effect of the plasma production rate on the implosion dynamics of cylindrical wire/fiber arrays with a profiled linear mass

Results are presented from experimental studies on the implosion of arrays made of wires and metalized fibers under the action of current pulses with an amplitude of up to 3.5 MA at the Angara-5-1 facility. The effect of the parameters of an additional linear mass of bismuth and gold deposited on the wires/fibers is investigated. It is examined how the material of the wires/fibers and the metal coating deposited on them affect the penetration of the plasma with the frozen-in magnetic field into a cylindrical array. Information on the plasma production rate $\dot m_{Bi}$ for different metals is obtained by analyzing optical streak images of imploding arrays. The plasma production rate for cylindrical arrays made of the kapron fibers coated with bismuth is determined. For the initial array radius of R ₀ = 1 cm and discharge current of I = 1 MA, the plasma production rate is found to be $\dot m_{Bi} \approx 0.095 \pm 0.015$ μg/(cm² ns).     

Study of the implosion characteristics of quasi-spherical wire arrays on the Angara-5-1 facility at currents of up to 4 MA

Results are presented from experimental studies of the spatial distribution of the density of matter in the central part of the discharge gap and the formation of the temporal profile of the X-ray power in the course of implosion of quasi-spherical wire arrays at discharge currents of up to 4 MA. The spatial distribution of the X-ray intensity in the central part of the discharge gap and the temporal profile of the X-ray power are used as implosion characteristics of quasi-spherical wire arrays. The quasi-spherical arrays were formed by the radial stretching of unstrained wires of initially cylindrical and conical wire arrays under the action of the electrostatic field. The temporal profile of the output X-ray pulse in the photon energy range of 0.1–1 keV is shown to depend on both the geometrical parameters of the quasi-spherical array and the longitudinal distribution of its mass. It is found that a 40% increase in the wire mass due to deposition of an additional mass in the equatorial region of a quasi-spherical array leads to a 15% increase in the average current radius of the pinch and a 30% decrease in the X-ray yield. Experiments with quasi-spherical arrays made of kapron fibers with deposited Al and Bi conducting layers were also carried out. It is demonstrated that application of such arrays makes it possible to control the profile and duration of the generated X-ray pulse by varying the mass, material, and location of the deposited layer. It is found that deposition of an additional mass in the form of a thin Bi stripe on tungsten wires near the cathode end of the array allows one to mitigate the influence of the cathode zipper effect on the pinch compression and formation of the X-ray pulse in tungsten arrays.     

Salt dynamics in soil profiles during long-term evaporation under different groundwater conditions

To study salt dynamics in soil profiles under different groundwater conditions, a 3-year indoor experiment was carried out under conditions of open-air evaporation. Silt loam soil was treated under three groundwater table depths (0.85, 1.05, and 1.55 m) combined with three groundwater salinities: 0.40 dS m^? 1 (2 g l^? 1), 0.80 dS m^? 1 (4 g l^? 1), and 1.60 dS m^? 1 (8 g l^? 1). A total of nine soil columns (0.14 m internal diameter) were used to simulate different combinations of groundwater depths and salinities. The results obtained showed that salt first accumulated at the bottom of the soil column, and only when soil salinity in this layer had remained relatively stable with time, salt began to accumulate in the adjacent upper soil layers. When all subsoil layers had reached dynamic salinity equilibrium, electrical conductivity (EC) of soils in the surface layer began to increase drastically. With increasing salt accumulation in the surface soil, EC of the subsoil began to rise tardily. The further up the soil layer, the earlier EC started to increase, although the redistribution of salts in the soil profile tended to be homogenous. Groundwater depth did not significantly change subsoil EC values at the same depth; however, it distinctly affected the time needed for the subsoil to reach dynamic salinity equilibrium. Groundwater salinity, on the other hand, did not significantly alter the time point at which soil salinity at the same depth began to increase rapidly or the time period needed to reach dynamic salinity equilibrium. This study explored salt transport processes in the soil profile through a long-term experiment, enabling us to reveal some general laws governing salt dynamics that will be very important to understand the mechanism of soil salinization. The results could be further used to set up strategies to prevent salinization or to improve salt-affected soils.     

Karyotyping of Saccharomyces strains with different temperature profiles

This study examined the karyotype, the fermentation performance and the optimum growth temperature (Topt) of 28 yeast strains all identified as species belonging to Saccharomyces sensu stricto . The strains were isolated from fermented musts, which had not been inoculated, at two temperature ranges: 20–40 °C and approximately 0–6 °C. The results demonstrated a correlation between the Topt and the chromosome organization. In particular, strains with Topt of less than 30 °C showed only two bands in the region between 365 and 225 kb, while those with a Topt greater than 30 °C had three bands in this size range. From a taxonomic viewpoint, the Topt is a better indicator for the Saccharomyces sp. than the ceiling temperature of 37 °C currently used to differentiate cryotolerant Saccharomyces bayanus and S. pastorianus from non-cryotolerant S. cerevisiae and S. paradoxus strains.     

Use of conical wire arrays for modeling three-dimensional MHD implosion effects

Results are presented from experimental studies and numerical simulations of three-dimensional dynamics of the plasma produced in the Angara-5-1 facility by the electrical implosion of conical wire arrays at currents of up to 3 MA. The arrays were made of 6-to 8-μm-diameter tungsten wires, the inclination angle of the generatrix with respect to the axis being from 15° to 42°. The results of two-dimensional MHD simulations are compared with experimental data. The formation dynamics of the plasma precursor is found to be different for cylindrical and conical arrays. As the cone angle increases, the duration of the X-ray pulse increases, while the height of the pinch radiating zone decreases.     

Study of the implosion of wire arrays at the PF-3 facility

Results of experiments on the compression of tungsten wire arrays by the plasma current sheath (PCS) of the PF-3 facility at currents of up to 2 MA are presented. The efficiency of current transportation to the wire array and switching-over of the discharge current to the array were studied. Information on the penetration of the magnetic field into the wire array obtained using microprobes made it possible to compare the obtained experimental data with the results of magnetic field measurements carried out at other high-power electrophysical devices. The intensity of plasma production from tungsten wires under the action of the plasma focus PCS is estimated. The experimental results are tested against the existing models of wire array implosion with prolonged plasma production.     

Circulation of methicillin-resistant staphylococci in hospitals with different profiles

Analysis of prevalence of methicillin-resistant staphylococci in hospitals with different specializations was performed. 2584 strains were isolated. Methicillin-resistant (MR) strains were present in different profile hospitals and their total prevalence between isolated strains was 12.3% while significantly varied in different hospitals (from 8% to 37%). Along with MRSA (methicillin-resistant Staphylococcus aureus), MRSE (methicillin-resistant Staphylococcus epidermidis) and MRSS (methicillin-resistant Staphylococcus saprophyticus) were presented in all studied hospitals. The prevalence of MR strains was highest among strains isolated from flame burn wounds (37%), while in samples from newborns in maternity hospital resistant strains represented 12% of isolates, and in general clinical hospital--not more than 9% of isolates. Relationship between rates of isolation of methicillin-resistant staphylococci and specialization of hospital unit was noted. For example, prevalence of MR staphylococci in isolates from newborns in ICU (47.5%) differed from the same one in maternity hospital (11.6%).     

Characterising biomolecular interactions and dynamics with mass photometry

We review recent advances in our ability to characterise biomolecular structure, interactions and associated dynamics by mass photometry (MP), the label-free detection and mass measurement of individual biomolecules in solution. Molecular counting and identification provides direct access to relative abundance, and thereby affinities, while associated dynamics yield on- and off-rates. The molecular resolution afforded by MP enables these measurements as a function of stoichiometry and assembly at equilibrium, as opposed to the majority of existing solution-based methods. Together with future improvements in terms of assays and technological performance, MP is likely to provide mechanistic details of complex biomolecular processes.     

不同交配型马尔尼菲篮状菌的抗真菌药物敏感性

马尔尼菲篮状菌是马尔尼菲篮状菌病的致病菌,具有不同交配型,且交配型分布具有地域差异.交配型是影响某些真菌药物敏感性的因素之一,但是否影响马尔尼菲篮状菌的药物敏感性不详.为了解马尔尼菲篮状菌交配型和其药物敏感性的关系,本研究检测了不同交配型马尔尼菲篮状菌对7种抗真菌药物的敏感性.结果显示,与MAT-1型马尔尼菲篮状菌相比...     

Physiological and environmental parameters associated with mass spectrometry-based salivary metabolomic profiles

Mass spectrometry (MS)-based metabolomic methods enable simultaneous profiling of hundreds of salivary metabolites, and may be useful to diagnose a wide range of diseases using saliva. However, few studies have evaluated the effects of physiological or environmental factors on salivary metabolomic profiles. Therefore, we used capillary electrophoresis-MS to analyze saliva metabolite profiles in 155 subjects with reasonable oral hygiene, and examined the effects of physiological and environmental factors on the metabolite profiles. Overall, 257 metabolites were identified and quantified. The global profiles and individual metabolites were evaluated by principle component analysis and univariate tests, respectively. Collection method, collection time, sex, body mass index, and smoking affected the global metabolite profiles. However, age also might contribute to the bias in sex and collection time. The profiles were relatively unaffected by other parameters, such as alcohol consumption and smoking, tooth brushing, or the use of medications or nutritional supplements. Temporomandibular joint disorders had relatively greater effects on salivary metabolites than other dental abnormalities (e.g., stomatitis, tooth alignment, and dental caries). These findings provide further insight into the diversity and stability of salivary metabolomic profiles, as well as the generalizability of disease-specific biomarkers.     

Experiments on the implosion of heterogeneous wire arrays on the S-300 facility

Results are presented from experiments on the implosion of simple and nested wire arrays of different mass and material composition (W and/or Al). The experiments were performed on the S-300 facility (a high-current pulsed power generator with a voltage pulse amplitude of 700 kV, current amplitude of 2.5–3.5 MA, and pulse duration of 100 ns) at the Kurchatov Institute (Moscow). The imploding arrays were recorded using five-frame laser shadowgraphy, three-frame image-tube photography, an optical streak camera, X-ray pinhole cameras with different filters, X-ray polychromator, and X-ray spectrometer on the basis of a convex mica crystal. Laser probing measurements indicate that the current-carrying structure undergoes a fast (over a time shorter than 10 ns) global rearrangement, which manifests itself as the emergence of transparent regions. This effect is presumably related to the grouping of the wires, which carry currents of a few tens of kiloamperes, or to the current filamentation in their common plasma corona. The radiation of liners of different chemical composition in the final compressed state has been investigated. Electric measurements performed in experiments with nested arrays (e.g., with an aluminum outer liner and a tungsten inner liner) indicate that the inner array, which is still at rest, intercepts the electric current from the outer array when the latter penetrates through it. The effect of the “fall” of the outer liner through the inner one in the course of magnetic implosion has been revealed for the first time by analyzing X-ray emission spectra.     

Discovery of glycosyltransferases using carbohydrate arrays and mass spectrometry

Glycosyltransferases catalyze the reaction between an activated sugar donor and an acceptor to form a new glycosidic linkage. Glycosyltransferases are responsible for the assembly of oligosaccharides in vivo and are also important for the in vitro synthesis of these biomolecules. However, the functional identification and characterization of new glycosyltransferases is difficult and tedious. This paper describes an approach that combines arrays of reactions on an immobilized array of acceptors with an analysis by mass spectrometry to screen putative glycosyltransferases. A total of 14,280 combinations of a glycosyltransferase, an acceptor and a donor in four buffer conditions were screened, leading to the identification and characterization of four new glycosyltransferases. This work is notable because it provides a label-free method for the rapid functional annotation of putative enzymes.     

Unraveling the dynamics of protein interactions with quantitative mass spectrometry

Knowledge of structure and dynamics of proteins and protein complexes is important to unveil the molecular basis and mechanisms involved in most biological processes. Protein complex dynamics can be defined as the changes in the composition of a protein complex during a cellular process. Protein dynamics can be defined as conformational changes in a protein during enzyme activation, for example, when a protein binds to a ligand or when a protein binds to another protein. Mass spectrometry (MS) combined with affinity purification has become the analytical tool of choice for mapping protein-protein interaction networks and the recent developments in the quantitative proteomics field has made it possible to identify dynamically interacting proteins. Furthermore, hydrogen/deuterium exchange MS is emerging as a powerful technique to study structure and conformational dynamics of proteins or protein assemblies in solution. Methods have been developed and applied for the identification of transient and/or weak dynamic interaction partners and for the analysis of conformational dynamics of proteins or protein complexes. This review is an overview of existing and recent developments in studying the overall dynamics of in vivo protein interaction networks and protein complexes using MS-based methods.     

Unraveling the dynamics of protein interactions with quantitative mass spectrometry

Knowledge of structure and dynamics of proteins and protein complexes is important to unveil the molecular basis and mechanisms involved in most biological processes. Protein complex dynamics can be defined as the changes in the composition of a protein complex during a cellular process. Protein dynamics can be defined as conformational changes in a protein during enzyme activation, for example, when a protein binds to a ligand or when a protein binds to another protein. Mass spectrometry (MS) combined with affinity purification has become the analytical tool of choice for mapping protein–protein interaction networks and the recent developments in the quantitative proteomics field has made it possible to identify dynamically interacting proteins. Furthermore, hydrogen/deuterium exchange MS is emerging as a powerful technique to study structure and conformational dynamics of proteins or protein assemblies in solution. Methods have been developed and applied for the identification of transient and/or weak dynamic interaction partners and for the analysis of conformational dynamics of proteins or protein complexes. This review is an overview of existing and recent developments in studying the overall dynamics of in vivo protein interaction networks and protein complexes using MS-based methods.     

两性具有不同出生率和死亡率的种群动态

以往的种群动力学模型均隐含假设性比为1：1,而实际上并非总如此,不同性别的出生和死亡是不完全相同的。文中就考虑了两性具有不同出生率和死亡率的种群动态问题。可以知道种群动态只是受雌性控制,与雄性无关。     

Proteome analysis of antibody-producing CHO cell lines with different metabolic profiles

Two-dimensional gel electrophoresis and tandem mass spectrometry were used to identify proteins associated with a metabolic shift during fed-batch cultures of two recombinant antibody-producing CHO cell lines. The first cell line underwent a marked change in lactate metabolism during culture, initially producing lactate and then consuming it, while the second cell line produced lactate for a similar duration but did not later consume it. The first cell line displayed a declining specific antibody productivity during culture, correlating to the 2-D gel results and the intracellular antibody concentration determined by HPLC. Several statistical analysis methods were compared during this work, including a fixed fold-change criterion and t-tests using standard deviations determined in several ways from the raw data and mathematically transformed data. Application of a variance-stabilizing transformation enabled the use of a global empirical standard deviation in the t-tests. Most of the protein spots changing in each cell line did not change significantly in the other cell line. A substantial fraction of the changing proteins were glycolytic enzymes; others included proteins related to antibody production, protein processing, and cell structure. Enolase, pyruvate kinase, BiP/GRP78, and protein disulfide isomerase were found in spots that changed over time in both cell lines, and some protein changes differed from previous reports. These data provide a foundation for future investigation of metabolism in industrially relevant mammalian cell culture processes, and suggest that along with differences between cell types, the proteins expressed in cultures with low lactate concentrations may depend on how those conditions were generated.