Use of wolfram trioxide for setting off preparations of nucleic acids

The use of tungsten trioxide for shadowing nucleic acids is shown to be possible. Approximately 20 mg of tungsten trioxide could be prepared by heating (25 s, 2 V) a coil (4 turns, 1.5 mm i.d.) made of tungsten wire 0.5 mm diameter in a vacuum evaporator at atmospheric pressure. As revealed by electron microscopy, this amount of tungsten trioxide is sufficient for qualitative rotary shadowing phage lambda DNA.     

Return current in encephalography. Variational principles.

The encephalographic problem of finding the electric potential V and the return current associated with any assumed primary current, Jp, is put in the form of a variational principle. With Jp and the conductivity specified, the correct V is one which makes an integral quantity P[V] a maximum. The terms in P[V] are related to the rates at which work is done by the electric field on the primary and return currents. It is shown that there is a unique solution for the electric field, and it satisfies the conservation of energy; this condition can serve as a check on any numerical solution. With the conductivity a different constant in different regions, the variational principle is recast in terms of the charge density on the surfaces of discontinuity. An iteration-variation method for finding the solution is outlined, and possible computational advantages over other approaches are discussed.     

An analysis of membrane phase transition theories based on kink and jog defects

We derive the geometric properties of isomeric defects referred to as kinks and jogs. With the aid of these geometric properties we are able to list in tabular form according to energy and area all possible kink and jog configurations. This information is the kink and jog single chain density of states in discrete form. We relate the properties of the single chain density of states to the thermodynamic bilayer system. Based on the single chain information, we calculate an upper bound on the entropy change of the membrane phase transition and show that it is less than one half the experimental entropy change of the transition. Finally we show that the discrepancy in the macroscopic value of the entropy results from the fact that the total number of single chain kink and jog defects is orders of magnitude too small.     

Dynamics of kinks in inhomogeneous polynucleotide chains

In the present paper the dynamics of the nonlinear conformational excitations — kinks, in inhomogeneous polynucleotide DNA chains is investigated. To calculate the kink rest energy E₀ and its size d the method of dynamical interval is used. This makes it possible to take into account that all coefficients of the model dynamic equation — the sine-Gordon equation depend on the sequence of bases. It is shown that the method gives an opportunity to calculate dynamical characteristics of any artificial and real sequences that is important for implementing tasks associated with the search and analysis of functionally important DNA sites.     

Diagnostics of plasma oscillations by the field of surface waves guided by a dielectric waveguide

The potentialities of the diagnostic method for determining the plasma parameters by recording the surface waves guided by a dielectric waveguide and scattered by plasma oscillations are discussed. The use of surface (slowed) waves makes it possible to improve both the sensitivity and spatial resolution of measurements. The scattering is the most intense near the waveguide cutoff, at which the dependence of the wave propagation constant on the plasma density is the steepest. It is shown experimentally that the method proposed makes it possible to determine the discharge plasma density and electron energy and to estimate the amplitude of the RF field of the plasma waves forming the discharge and the amplitude of plasma density oscillations in these waves. The data obtained from the measurements of the amplitudes of both high-and low-frequency plasma density oscillations by the proposed method agree satisfactorily with theoretical predictions. The experimental data on the plasma density are confirmed by other diagnostic measurements. The ways of reducing measurement errors are proposed.     

Real-time measurements of quartz erosion in experiments modeling heat loads on divertor plates during disruption in tokamaks

Time-resolved measurements of quartz erosion are carried out to determine the density of the energy flux incident onto the sample surface. These data are needed to create a reliable code describing the interaction of a thermonuclear plasma with a solid surface. Experiments were performed in the 2MK-200 facilityunder the program of modeling heat loads on divertor plates during disruptions in tokamaks. A 10-mm-thick plate of fused quartz was exposed to a high-temperature deuterium-plasma stream with the temperature T _i +T _e ≤1 keV, density (5–10)×10¹⁵ cm⁻³ β=0.25, energy density up to 200 J/cm², and power density ∼10 MW/cm². It is shown that the quartz erosion begins almost immediately after the stream reaches the surface. The eroded material shields the quartz surface from further destruction. Under the given experimental conditions, the integral shielding factor (the ratio of the stream energy to the energy reaching the surface) was rather high (about seventeen). As a result, at a stream energy density of ∼150 J/cm², the total erosion depth was about 0.75 μm over 35 μs. Based on the measured time dependence of the erosion depth and the reference data on the thermal conductivity of the fused quartz, the power density incident onto the quartz sample was numerically calculated. __________ Translated from Fizika Plazmy, Vol. 27, No. 3, 2001, pp. 243–250. Original Russian Text Copyright ? 2001 by Arkhipov, Bakhtin, Vasenin, Zhitlukhin, Safronov, Toporkov.     

Temperature dependence of the dielectric properties of blood

The aim of the work was to investigate the temperature effect in physiological range on the dielectric properties of a fish (Cyprinus carpio) blood. By applying an empirical non-damaging method and statistical analysis of the dielectric data, it is observed that a heating of carp blood induces an almost linear value variation of the electrical conductivity and permittivity of the intracellular matter of carp red blood cells. The dielectric data, however, reveal anomalous behaviour for conductivity and permittivity of the interior of carp erythrocytes at 23 degrees C and 23 degrees, 37 degrees C, respectively and for both volume fraction and dielectric loss factor tg delta at 30 degrees, 35 degrees, 37 degrees C. For the presented dielectric parameters the temperature coefficient and the Arrhenius activation energy were estimated. Moreover, this work led to conclusion that the changes of the volume fraction of carp erythrocytes induce corresponding variations of the maximum of the dielectric loss factor tg delta determined for a whole blood.     

Rapid and uniform electromagnetic heating of aqueous cryoprotectant solutions from cryogenic temperatures

Devitrification (ice formation during warming) is one of the primary obstacles to successful organ vitrification (solidification without ice formation). The only feasible approach to overcoming either devitrification or its damaging effects in a large organ appears at present to be the use of some form of electromagnetic heating (EH) to achieve the required high heating rates. One complication of EH in this application is the need for warming within a steel pressure vessel. We have previously reported that resonant radiofrequency (RF) helical coils provide very uniform heating at ambient temperatures and low heating rates and can be modified for coaxial power transmission, which is necessary if only one cable is to penetrate through the wall of the pressure vessel. We now report our initial studies using a modified helical coil, high RF input power, and cryogenic aqueous cryoprotectant solutions [60% (w/v) solution of 4.37 M dimethylsulfoxide and 4.37 M acetamide in water and 50% (w/w) 1,2-propanediol]. We also describe the electronic equipment required for this type of research. Temperatures were monitored during high-power conditions with Luxtron fiberoptic probes. Thermometry was complicated by the use of catheters needed for probe insertion and guidance. The highest heating rates we observed using catheters occurred at temperatures ranging from about -70 to -40 degrees C, the temperature zone where devitrification usually appears in unstable solutions during slow warming. We find that in this range we can achieve measured heating rates of approximately 300 degrees C/min in 30- to 130-ml samples using 200 to 700 W of RF power without overheating the sample at any point. However, energy conservation calculations imply that our measured peak heating rates may be considerably higher than the true heating rates occurring in the bulk of our solutions. We were able to estimate the overall true heating rates, obtaining an average value of about 20 degrees C/min/100 W/100 ml, which implies a heating efficiency close to 100%. It appears that it should be possible to warm vitrified rabbit kidneys rapidly enough under high-pressure conditions to protect them from devitrification.     

Determination of alpha-helix and beta-sheet stability in the solid state: a solid-state NMR investigation of poly(L-alanine)

The relative stability of alpha-helix and beta-sheet secondary structure in the solid state was investigated using poly(L-alanine) (PLA) as a model system. Protein folding and stability has been well studied in solution, but little is known about solid-state environments, such as the core of a folded protein, where peptide packing interactions are the dominant factor in determining structural stability. (13)C cross-polarization with magic angle spinning (CPMAS) NMR spectroscopy was used to determine the backbone conformation of solid powder samples of 15-kDa and 21.4-kDa PLA before and after various sample treatments. Reprecipitation from helix-inducing solvents traps the alpha-helical conformation of PLA, although the method of reprecipitation also affects the conformational distribution. Grinding converts the secondary structure of PLA to a final steady-state mixture of 55% beta-sheet and 45% alpha-helix at room temperature regardless of the initial secondary structure. Grinding PLA at liquid nitrogen temperatures leads to a similar steady-state mixture with 60% beta-sheet and 40% alpha-helix, indicating that mechanical shear force is sufficient to induce secondary structure interconversion. Cooling the sample in liquid nitrogen or subjecting it to high pressure has no effect on secondary structure. Heating the sample without grinding results in equilibration of secondary structure to 50% alpha-helix/50% beta-sheet at 100 degrees C when starting from a mostly alpha-helical state. No change was observed upon heating a beta-sheet sample, perhaps due to kinetic effects and the different heating rate used in the experiments. These results are consistent with beta-sheet approximately 260 J/mol more stable than alpha-helix in solid-state PLA.     

Sulfide Solid Electrolytes for Lithium Battery Applications

The use of solid electrolytes is a promising direction to improve the energy density of lithium‐ion batteries. However, the low ionic conductivity of many solid electrolytes currently hinders the performance of solid‐state batteries. Sulfide solid electrolytes can be processed in a number of forms (glass, glass‐ceramic, and crystalline) and have a wide range of available chemistries. Crystalline sulfide materials demonstrate ionic conductivity on par with those of liquid electrolytes through the utilization of near ideal conduction pathways. Low‐temperature processing is also possible for these materials due to their favorable mechanical properties. The main drawback of sulfide solid electrolytes remains their electrochemical stability, but this can be addressed through compositional tuning or the use of artificial solid electrolyte interphase (SEI). Implementation of sulfide solid electrolytes, with proper treatment for stability, can lead to substantial improvements in solid‐state battery performance leading to significant advancement in electric vehicle technology.     

Description of turbulent convection in a plasma with the help of interacting Lorentz oscillators

A four-field model is proposed that describes turbulent plasma convection inside the separatrix during the L-H transition. It is shown that the Braginskii four-field hydrodynamic equations, which describe fluctuations of the electron and ion temperatures, plasma density, and electrostatic potential in tokamak edge plasmas, can be reduced to three Lorentz-like systems of equations coupled through the equation for the kinetic energy of the fluctuations, i.e., to a four-field edge turbulent layer model describing the nonlinear dynamics of convective cells in the presence of a sheared flow. For three coupled oscillators, the critical pressure gradient corresponding to transitions to both L-and H-modes is found to be much lower than that for an individual oscillator, which describes turbulent convection driven by fluctuations of one type. The edge turbulent layer model makes it possible to describe the formation of a transport barrier inside the separatrix during the L-H transition; calculate heat and particle fluxes via ion and electron channels; and, in combination with the transport code for a core plasma, compute the auxiliary heating power required for a transition to the H-mode.     

Sodium Plating from Na‐β″‐Alumina Ceramics at Room Temperature,Paving the Way for Fast‐Charging All‐Solid‐State Batteries

All‐solid‐state batteries with an alkali metal anode have the potential to achieve high energy density. However, the onset of dendrite formation limits the maximum plating current density across the solid electrolyte and prevents fast charging. It is shown that the maximum plating current density is related to the interfacial resistance between the solid electrolyte and the metal anode. Due to their high ionic conductivity, low electronic conductivity, and stability against sodium metal, Na‐β″‐alumina ceramics are excellent candidates as electrolytes for room‐temperature all‐solid‐state batteries. Here, it is demonstrated that a heat treatment of Na‐β″‐alumina ceramics in argon atmosphere enables an interfacial resistance <10 Ω cm² and current densities up to 12 mA cm^?2 at room temperature. The current density obtained for Na‐β″‐alumina is ten times higher than that measured on a garnet‐type Li₇La₃Zr₂O₁₂ electrolyte under equivalent conditions. X‐ray photoelectron spectroscopy shows that eliminating hydroxyl groups and carbon contaminations at the interface between Na‐β″‐alumina and sodium metal is key to reach such values. By comparing the temperature‐dependent stripping/plating behavior of Na‐β″‐alumina and Li₇La₃Zr₂O₁₂, the role of the alkali metal in governing interface kinetics is discussed. This study provides new insights into dendrite formation and paves the way for fast‐charging all‐solid‐state batteries.     

All Pseudocapacitive MXene‐RuO2 Asymmetric Supercapacitors

2D transition metal carbides and nitrides, known as MXenes, are an emerging class of 2D materials with a wide spectrum of potential applications, in particular in electrochemical energy storage. The hydrophilicity of MXenes combined with their metallic conductivity and surface redox reactions is the key for high‐rate pseudocapacitive energy storage in MXene electrodes. However, symmetric MXene supercapacitors have a limited voltage window of around 0.6 V due to possible oxidation at high anodic potentials. In this study, the fact that titanium carbide MXene (Ti₃C₂T_x) can operate at negative potentials in acidic electrolyte is exploited, to design an all‐pseudocapacitive asymmetric device by combining it with a ruthenium oxide (RuO₂) positive electrode. This asymmetric device operates at a voltage window of 1.5 V, which is about two times wider than the operating voltage window of symmetric MXene supercapacitors, and is the widest voltage window reported to date for MXene‐based supercapacitors. The complementary working potential windows of MXene and RuO₂, along with proton‐induced pseudocapacitance, significantly enhance the device performance. As a result, the asymmetric devices can deliver an energy density of 37 µW h cm^?2 at a power density of 40 mW cm^?2, with 86% capacitance retention after 20 000 charge–discharge cycles. These results show that pseudocapacitive negative MXene electrodes can potentially replace carbon‐based materials in asymmetric electrochemical capacitors, leading to an increased energy density.     

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.     

THE CELL SAP OF HYDRODICTYON

Analysis of the cell sap of Hydrodictyon patenaeforme Pocock, from California indicates the usual marked accumulation of potassium, which is 4000 times as concentrated as in the surrounding pond water. Small amounts of sodium and calcium were found. Chloride makes up about three-fourths of the anions, with a very high sulfate, and much lower bicarbonate concentration accounting for most of the remainder. Electrical conductivity and osmotic studies indicate that the analyzed elements are ionized, and account for most of the sap''s osmotic pressure. pH is 5.5 to 6.0. The analytical procedure was designed to determine as many of the cations as possible on one small sample. Hydrodictyon is a large multinucleate cell belonging to an order (Chlorococcales) new to permeability and accumulation studies.     

Numerical analysis of the safety factor and effective ion mass in a tokamak plasma with the help of the discrete alfvén wave spectrum

Numerical aspects of the method for diagnosing a tokamak plasma with the help of the discrete Alfvén wave spectrum are considered. It is shown that this diagnostics should be supported with highly accurate computational tools. A code suitable for implementing the relevant calculation scheme is developed, which makes it possible to identify the eigenmodes numerically with the desired accuracy. The code can also provide recommendations for performing tokamak experiments and can be used to study the possibility of auxiliary plasma heating by Alfvén waves. The discrete Alfvén wave spectrum, radial profiles of the energy deposited in the plasma, and the dependence of the Alfvén mode frequencies on the damping rate and on the class of the current-density profiles chosen are calculated for the first time for the T-10 tokamak. It is also shown that the diagnostic method proposed makes it possible to obtain reliable information about the plasma parameters.     

Reconstructing the prior probabilities of allelic phylogenies

In general when a phylogeny is reconstructed from DNA or protein sequence data, it makes use only of the probabilities of obtaining some phylogeny given a collection of data. It is also possible to determine the prior probabilities of different phylogenies. This information can be of use in analyzing the biological causes for the observed divergence of sampled taxa. Unusually "rare" topologies for a given data set may be indicative of different biological forces acting. A recursive algorithm is presented that calculates the prior probabilities of a phylogeny for different allelic samples and for different phylogenies. This method is a straightforward extension of Ewens' sample distribution. The probability of obtaining each possible sample according to Ewens' distribution is further subdivided into each of the possible phylogenetic topologies. These probabilities depend not only on the identity of the alleles and on 4N(mu) (four times the effective population size times the neutral mutation rate) but also on the phylogenetic relationships among the alleles. Illustrations of the algorithm are given to demonstrate how different phylogenies are favored under different conditions.     

Simulation of the Planetary Interior Differentiation Processes in the Laboratory

A planetary interior is under high-pressure and high-temperature conditions and it has a layered structure. There are two important processes that led to that layered structure, (1) percolation of liquid metal in a solid silicate matrix by planet differentiation, and (2) inner core crystallization by subsequent planet cooling. We conduct high-pressure and high-temperature experiments to simulate both processes in the laboratory. Formation of percolative planetary core depends on the efficiency of melt percolation, which is controlled by the dihedral (wetting) angle. The percolation simulation includes heating the sample at high pressure to a target temperature at which iron-sulfur alloy is molten while the silicate remains solid, and then determining the true dihedral angle to evaluate the style of liquid migration in a crystalline matrix by 3D visualization. The 3D volume rendering is achieved by slicing the recovered sample with a focused ion beam (FIB) and taking SEM image of each slice with a FIB/SEM crossbeam instrument. The second set of experiments is designed to understand the inner core crystallization and element distribution between the liquid outer core and solid inner core by determining the melting temperature and element partitioning at high pressure. The melting experiments are conducted in the multi-anvil apparatus up to 27 GPa and extended to higher pressure in the diamond-anvil cell with laser-heating. We have developed techniques to recover small heated samples by precision FIB milling and obtain high-resolution images of the laser-heated spot that show melting texture at high pressure. By analyzing the chemical compositions of the coexisting liquid and solid phases, we precisely determine the liquidus curve, providing necessary data to understand the inner core crystallization process.     

Comparison of simple perturbation-theory estimates for the liquid–solid and the liquid–vapor interfacial free energies of Lennard-Jones systems

The most naive perturbation method to estimate interfacial free energies is based on the assumption that the interface between coexisting phases is infinitely sharp. Although this approximation does not yield particularly accurate estimates for the liquid–vapor surface tension, we find that it works surprisingly well for the interface between a dense liquid and a solid. As an illustration we estimate the liquid–solid interfacial free energy of a Lennard-Jones system with truncated and shifted interactions and compare the results with numerical data that have been reported in the literature. We find that the agreement between theory and simulation is excellent. In contrast, if we apply the same procedure to estimate the variation of the liquid–vapor surface tension, for different variants of the Lennard-Jones potential (truncated/shifted/force-shifted), we find that the agreement with the available simulation data is, at best, fair. The present method makes it possible to obtain quick and easy estimate of the effect on the surface free energy of different potential-truncation schemes used in computer simulations.     

Fast ignition of an inertial fusion target with a solid noncryogenic fuel by an ion beam

The burning efficiency of a preliminarily compressed inertial confinement fusion (ICF) target with a solid noncryogenic fuel (deuterium-tritium beryllium hydride) upon fast central ignition by a fast ion beam is studied. The main aim of the study was to determine the extent to which the spatial temperature distribution formed under the heating of an ICF target by ion beams with different particle energy spectra affects the thermonuclear gain. The study is based on a complex numerical modeling including computer simulations of (i) the heating of a compressed target with a spatially nonuniform density and temperature distributions by a fast ion beam and (ii) the burning of the target with the initial spatial density distribution formed at the instant of maximum compression of the target and the initial spatial temperature distribution formed as a result of heating of the compressed target by the ion beam. The threshold energy of the igniting ion beam and the dependence of the thermonuclear gain on the energy deposited in the target are determined.