High-magnification Faraday rotation imaging and analysis of X-pinch implosion dynamics.

An X-pinch load driven by an intense current pulse (>100 kA in ∼100 ns) can result in the formation of a small radius, runaway compressional micro-pinch. A micro-pinch is characterized by a hot (>1 keV), current-driven (>100 kA), high-density plasma column (near solid density) with a small neck diameter (1-10 µm), a short axial extent (<1 mm), and a short duration (≲1 ns). With material pressures often well into the multi-Mbar regime, a micro-pinch plasma often radiates an intense, sub-ns burst of sub-keV to multi-keV x rays. A low-density coronal plasma immediately surrounding the dense plasma neck could potentially shunt current away from the neck and thus reduce the magnetic drive pressure applied to the neck. To study the current distribution in the coronal plasma, a Faraday rotation imaging diagnostic (1064 nm) capable of producing simultaneous high-magnification polarimetric and interferometric images has been developed for the MAIZE facility at the University of Michigan. Designed with a variable magnification (1-10×), this diagnostic achieves a spatial resolution of ∼35 µm, which is useful for resolving the ∼100-µm-scale coronal plasma immediately surrounding the dense core. This system has now been used on a reduced-output MAIZE (100-200 kA, 150 ns) to assess the radial distribution of drive current immediately surrounding the dense micro-pinch neck. The total current enclosed was found to increase as a function of radius, r, from a value of ≈50±25 kA at r ≈ 140 µm (at the edge of the dense neck) to a maximal value of ≈150±75 kA for r ≥ 225 µm. This corresponds to a peak magnetic drive pressure of ≈75±50 kbar at r ≈ 225 µm. The limitations of these measurements are discussed in the paper.

Plasmoid Formation and Strong Radiative Cooling in a Driven Magnetic Reconnection Experiment.

We present the first experimental study of plasmoid formation in a magnetic reconnection layer undergoing rapid radiative cooling, a regime relevant to extreme astrophysical plasmas. Two exploding aluminum wire arrays, driven by the Z machine, generate a reconnection layer (S_{L}≈120) in which the cooling rate far exceeds the hydrodynamic transit rate (τ_{hydro}/τ_{cool}>100). The reconnection layer generates a transient burst of >1 keV x-ray emission, consistent with the formation and subsequent rapid cooling of the layer. Time-gated x-ray images show fast-moving (up to 50 km s^{-1}) hotspots in the layer, consistent with the presence of plasmoids in 3D resistive magnetohydrodynamic simulations. X-ray spectroscopy shows that these hotspots generate the majority of Al K-shell emission (around 1.6 keV) prior to the onset of cooling, and exhibit temperatures (170 eV) much greater than that of the plasma inflows and the rest of the reconnection layer, thus providing insight into the generation of high-energy radiation in radiatively cooled reconnection events.

Effect of IGF-1 C472T, GH C2141G, and GHR T914A polymorphisms on growth performance and feed efficiency in young Kazakh white-headed cattle.

Background and Aim: Improving the feed efficiency of beef cattle is necessary to increase the profitability of meat production. Implementing marker-assisted selection breeding systems can improve the genetic potential of beef cattle for increased productivity. This research aimed to study the effects of insulin-like growth factor (IGF)-1 C472T, growth hormone (GH) C2141G, and GH receptor (GHR) T914A polymorphisms on growth performance and feed efficiency in young Kazakh white-headed cattle. Materials and Methods: Young Kazakh white-headed cattle (n = 50) were grouped after weaning according to sex (28 bulls and 22 heifers) and they were genotyped according to the IGF-1 C472T, GH C2141G, and GHR T914A polymorphisms. The test period was conducted from 8 to 15 months of age. The experimental animals were evaluated for live weight (LW) at the beginning and end of the test period. They were also assessed for average daily gain, hip height, metabolic mid-weight (MMWT), actual dry matter intake (DMI), and residual feed intake (RFI). Results: Significant differences in MMWT were found between the bulls with the IGF-1TT and IGF-1CT genotypes, which was a 2.2 kg increase in heterozygous cattle (p < 0.05). Heterozygous IGF-1CT bulls differed with a higher DMI of 0.087 kg/day (p < 0.05) compared to IGF-1TT homozygotes. Carriers of the IGF-1TT genotype had the greatest feed efficiency at 0.068 kg/day (p < 0.05). Heifers with the GHCC genotype differed in their maximum DMI with an increase of 1.17%-1.57% (p < 0.05) relative to the other genotypes. The G allele in the GH C2141G polymorphism was associated with better (p < 0.05) feed efficiency in the Kazakh white-headed breed. The minimum DMI and RFI in GHR T914A heterozygous heifers were significantly inferior (p < 0.05) to the other genotypes. Conclusion: Association studies of the IGF-1 C472T, GH C2141G, and GHR T914A polymorphisms indicate a relationship between growth, development, and feed efficiency with the genetic characteristics of young Kazakh white-headed cattle. A significant (p < 0.05) dominant effect was found in the IGF-1 gene in bulls and in the GHR gene in heifers, which should be considered when breeding with heterogeneous parental pairs. The negative effect of the allele substitution in the IGF-1 C472T polymorphism was observed in the LW of heifers (-3.25 kg) at the age of 8 months and bulls (-6.05 kg) at 15 months. The substitution in the GH C2141G polymorphism was associated with a significant reduction in DMI by 0.036 kg (p < 0.05) and an increase in feed efficiency by 0.023 kg (p < 0.05) during the rearing of heifers. These results can improve the production efficiency of mature herds of Kazakh white-headed cattle.

Characterization of Quasi-Keplerian, Differentially Rotating, Free-Boundary Laboratory Plasmas.

We present results from pulsed-power driven differentially rotating plasma experiments designed to simulate physics relevant to astrophysical disks and jets. In these experiments, angular momentum is injected by the ram pressure of the ablation flows from a wire array Z pinch. In contrast to previous liquid metal and plasma experiments, rotation is not driven by boundary forces. Axial pressure gradients launch a rotating plasma jet upward, which is confined by a combination of ram, thermal, and magnetic pressure of a surrounding plasma halo. The jet has subsonic rotation, with a maximum rotation velocity 23±3 km/s. The rotational velocity profile is quasi-Keplerian with a positive Rayleigh discriminant κ^{2}∝r^{-2.8±0.8} rad^{2}/s^{2}. The plasma completes 0.5-2 full rotations in the experimental time frame (∼150 ns).

Speciation analysis of manganese against the background of its different content in the blood serum of dairy cows.

Studies in the field of microelement speciation in the body of farm animals, in particular dairy cattle, are almost completely absent. The average concentration of Mn in the blood serum of all the studied animals (n = 80) was 2.5 µg/L, which corresponds to normal values. Of the total number of animals, 21% were the cows with the low normal values (serum Mn concentration ≤ 2 µg/L, i.e. less than Q25 of the total sample) and 25% were the animals with the high normal values (serum Mn concentration ≥ 2.72 µg/L, i.e. more than Q75 of the total sample). The data obtained in the course of the study indicate that the change in the Mn level, even in the range of normal values, is accompanied by the redistribution of this element over various protein fractions. The six found Mn blood serum forms are presumably represented by α2-macroglobulin (tetramer, dimer, and monomer), transferrin/albumine, manganese citrates, and "free" metal ions. The analyzed fractions of Mn found in the blood serum of cows had the following hierarchy of concentrations: in the group with low-normal values of Mn ("free" Mn >> tetrameric form of α2-macroglobulin >> transferrin/albumine >> dimeric form of α2-macroglobulin >> monomeric form of α2-macroglobulin >> citrate), in the group with high normal manganese values ("free" Mn >> monomeric form of α2-macroglobulin >> transferring/albumine >> citrate >> tetrameric form of α2-macroglobulin >> dimeric form of α2-macroglobulin). In the group with high normal Mn values relative to the group with low normal values, there was a percentage decrease in the tetrameric fraction of a2-macroglobulin from 17.2 to 4.4%, dimeric fraction of a2-macroglobulin from 6.9 to 2.2%, "free" Mn from 54.3 to 44.4% and an increase in monomeric fraction of a2-macroglobulin from 6.7 to 23.1%, transferrin/albumine from 10.1 to 17.7%, citrate from 4.8 to 8.2%. Our data demonstrate the features of Mn redistribution of dairy cows, which can be used for an extended assessment of the microelement status of animals.

Perpendicular Subcritical Shock Structure in a Collisional Plasma Experiment.

We present a study of perpendicular subcritical shocks in a collisional laboratory plasma. Shocks are produced by placing obstacles into the supermagnetosonic outflow from an inverse wire array z pinch. We demonstrate the existence of subcritical shocks in this regime and find that secondary shocks form in the downstream. Detailed measurements of the subcritical shock structure confirm the absence of a hydrodynamic jump. We calculate the classical (Spitzer) resistive diffusion length and show that it is approximately equal to the shock width. We measure little heating across the shock (<10% of the ion kinetic energy) which is consistent with an absence of viscous dissipation.

Time-resolved velocity and ion sound speed measurements from simultaneous bow shock imaging and inductive probe measurements.

We present a technique to measure the time-resolved velocity and ion sound speed in magnetized, supersonic high-energy-density plasmas. We place an inductive ("b-dot") probe in a supersonic pulsed-power-driven plasma flow and measure the magnetic field advected by the plasma. As the magnetic Reynolds number is large (RM > 10), the plasma flow advects a magnetic field proportional to the current at the load. This enables us to estimate the flow velocity as a function of time from the delay between the current at the load and the signal at the probe. The supersonic flow also generates a hydrodynamic bow shock around the probe, the structure of which depends on the upstream sonic Mach number. By imaging the shock around the probe with a Mach-Zehnder interferometer, we determine the upstream Mach number from the shock Mach angle, which we then use to determine the ion sound speed from the known upstream velocity. We use the sound speed to infer the value of Z̄Te, where Z̄ is the average ionization and Te is the electron temperature. We use this diagnostic to measure the time-resolved velocity and sound speed of a supersonic (MS ∼ 8), super-Alfvénic (MA ∼ 2) aluminum plasma generated during the ablation stage of an exploding wire array on the Magpie generator (1.4 MA, 250 ns). The velocity and Z̄Te measurements agree well with the optical Thompson scattering measurements reported in the literature and with 3D resistive magnetohydrodynamic simulations in GORGON.

Effect of leptin C528T and leptin C73T polymorphisms and pregnancy on adipose tissue formation and carcass grade in Aberdeen Angus heifers and first-calf cows.

Background and Aim: The leptin (LEP) gene plays a role in the regulation of the activity required to obtain food, energy metabolism, and fat deposition and affects the body composition of animals. Lipogenesis is an ineffective process. A lot of energy from feed is expended on the synthesis of adipose tissue. This study aimed to determine the effect of LEP C528T and LEP C73T polymorphisms and pregnancy on adipose tissue formation and carcass grade in Aberdeen Angus heifers and first-calf cows. Materials and Methods: Heifers (n = 49) and first-calf cows (n = 30) were grouped according to their genotype for LEP C528T and LEP C73T polymorphisms at the age of 24 months. DNA samples were isolated from whole blood. Experimental animals were slaughtered at the age of 24 months, and a chemical analysis of samples of longissimus dorsi muscle and ground beef was performed. Results: The maximum internal fat weight, back-fat thickness, and fat content of the longissimus dorsi muscle and ground beef were determined in heifers heterozygous for both LEP C528T and LEP C73T polymorphisms. The ranking of genotypes in terms of adipose tissue formation did not change in first-calf cows compared to heifers carrying the same LEP gene variants. Pregnancy had a more significant (p < 0.05-0.001) effect on slaughter parameters and lipogenesis in animals of different genotypes than studied polymorphisms. Heterozygosity of the LEP gene was much more strongly expressed in the carcass grade of heifers. "Prime" grades were assigned to 66.7% of carcasses heterozygous for LEP C528T and "Top Choice" to 58.8% of carcasses with LEP C73T nucleotide substitutions. Conclusion: LEP C528T and LEP C73T polymorphisms were shown to affect the extent of fat formation in Aberdeen Angus heifers and first-calf cows. Animals with heterozygous genotypes exhibited the maximum development of internal fat, back-fat, and intramuscular fat. Pregnancy had a more significant effect on slaughter parameters and adipose tissue formation than studied polymorphisms. First-calf cows had a significantly lower fat content in carcasses than heifers. These results can aid in the production of efficient mature herds of Aberdeen Angus cattle.

Measurements of neutron fluxes from tokamak plasmas using a compact neutron spectrometer.

A compact neutron spectrometer based on the BC-501A liquid organic scintillator was applied to neutron measurements at the TUMAN-3M tokamak. The spectrometer was calibrated using measurements from the ion beam of the cyclotron accelerator. Neutron spectra were measured during discharges using a neutral deuterium beam injection into the TUMAN-3M D-plasma. An energy distribution of the neutrons from the plasma that hit the spectrometer was obtained from the measured BC-501A instrumental spectra by the DeGaSum code using detector response functions obtained in the course of the calibration. This allowed for the estimation of the 2.45 MeV neutron yield and the evaluation of both the time evolution of the DD fusion rate and the characteristic time of the injected deuterium slowing down in discharges with neutral beam injection heating.

Collective optical Thomson scattering in pulsed-power driven high energy density physics experiments (invited).

Optical collective Thomson scattering (TS) is used to diagnose magnetized high energy density physics experiments at the Magpie pulsed-power generator at Imperial College London. The system uses an amplified pulse from the second harmonic of a Nd:YAG laser (3 J, 8 ns, 532 nm) to probe a wide diversity of high-temperature plasma objects, with densities in the range of 1017-1019 cm-3 and temperatures between 10 eV and a few keV. The scattered light is collected from 100 µm-scale volumes within the plasmas, which are imaged onto optical fiber arrays. Multiple collection systems observe these volumes from different directions, providing simultaneous probing with different scattering K-vectors (and different associated α-parameters, typically in the range of 0.5-3), allowing independent measurements of separate velocity components of the bulk plasma flow. The fiber arrays are coupled to an imaging spectrometer with a gated intensified charge coupled device. The spectrometer is configured to view the ion-acoustic waves of the collective Thomson scattered spectrum. Fits to the spectra with the theoretical spectral density function S(K, ω) yield measurements of the local plasma temperatures and velocities. Fitting is constrained by independent measurements of the electron density from laser interferometry and the corresponding spectra for different scattering vectors. This TS diagnostic has been successfully implemented on a wide range of experiments, revealing temperature and flow velocity transitions across magnetized shocks, inside rotating plasma jets and imploding wire arrays, as well as providing direct measurements of drift velocities inside a magnetic reconnection current sheet.

An imaging refractometer for density fluctuation measurements in high energy density plasmas.

We report on a recently developed laser-probing diagnostic, which allows direct measurements of ray-deflection angles in one axis while retaining imaging capabilities in the other axis. This allows us to measure the spectrum of angular deflections from a laser beam, which passes through a turbulent high-energy-density plasma. This spectrum contains information about the density fluctuations within the plasma, which deflect the probing laser over a range of angles. We create synthetic diagnostics using ray-tracing to compare this new diagnostic with standard shadowgraphy and schlieren imaging approaches, which demonstrates the enhanced sensitivity of this new diagnostic over standard techniques. We present experimental data from turbulence behind a reverse shock in a plasma and demonstrate that this technique can measure angular deflections between 0.06 and 34 mrad, corresponding to a dynamic range of over 500.

Counterpropagating Radiative Shock Experiments on the Orion Laser.

We present new experiments to study the formation of radiative shocks and the interaction between two counterpropagating radiative shocks. The experiments are performed at the Orion laser facility, which is used to drive shocks in xenon inside large aspect ratio gas cells. The collision between the two shocks and their respective radiative precursors, combined with the formation of inherently three-dimensional shocks, provides a novel platform particularly suited for the benchmarking of numerical codes. The dynamics of the shocks before and after the collision are investigated using point-projection x-ray backlighting while, simultaneously, the electron density in the radiative precursor was measured via optical laser interferometry. Modeling of the experiments using the 2D radiation hydrodynamic codes nym and petra shows very good agreement with the experimental results.

Influence of atomic kinetics in the simulation of plasma microscopic properties and thermal instabilities for radiative bow shock experiments.

Numerical simulations of laboratory astrophysics experiments on plasma flows require plasma microscopic properties that are obtained by means of an atomic kinetic model. This fact implies a careful choice of the most suitable model for the experiment under analysis. Otherwise, the calculations could lead to inaccurate results and inappropriate conclusions. First, a study of the validity of the local thermodynamic equilibrium in the calculation of the average ionization, mean radiative properties, and cooling times of argon plasmas in a range of plasma conditions of interest in laboratory astrophysics experiments on radiative shocks is performed in this work. In the second part, we have made an analysis of the influence of the atomic kinetic model used to calculate plasma microscopic properties of experiments carried out on magpie on radiative bow shocks propagating in argon. The models considered were developed assuming both local and nonlocal thermodynamic equilibrium and, for the latter situation, we have considered in the kinetic model different effects such as external radiation field and plasma mixture. The microscopic properties studied were the average ionization, the charge state distributions, the monochromatic opacities and emissivities, the Planck mean opacity, and the radiative power loss. The microscopic study was made as a postprocess of a radiative-hydrodynamic simulation of the experiment. We have also performed a theoretical analysis of the influence of these atomic kinetic models in the criteria for the onset possibility of thermal instabilities due to radiative cooling in those experiments in which small structures were experimentally observed in the bow shock that could be due to this kind of instability.

Anomalous Heating and Plasmoid Formation in a Driven Magnetic Reconnection Experiment.

We present a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power driven laboratory experiment. Oppositely directed magnetic fields (B=3 T), advected by supersonic, sub-Alfvénic carbon plasma flows (V_{in}=50 km/s), are brought together and mutually annihilate inside a thin current layer (δ=0.6 mm). Temporally and spatially resolved optical diagnostics, including interferometry, Faraday rotation imaging, and Thomson scattering, allow us to determine the structure and dynamics of this layer, the nature of the inflows and outflows, and the detailed energy partition during the reconnection process. We measure high electron and ion temperatures (T_{e}=100 eV, T_{i}=600 eV), far in excess of what can be attributed to classical (Spitzer) resistive and viscous dissipation. We observe the repeated formation and ejection of plasmoids, consistent with the predictions from semicollisional plasmoid theory.

Scaled laboratory experiments explain the kink behaviour of the Crab Nebula jet.

The remarkable discovery by the Chandra X-ray observatory that the Crab nebula's jet periodically changes direction provides a challenge to our understanding of astrophysical jet dynamics. It has been suggested that this phenomenon may be the consequence of magnetic fields and magnetohydrodynamic instabilities, but experimental demonstration in a controlled laboratory environment has remained elusive. Here we report experiments that use high-power lasers to create a plasma jet that can be directly compared with the Crab jet through well-defined physical scaling laws. The jet generates its own embedded toroidal magnetic fields; as it moves, plasma instabilities result in multiple deflections of the propagation direction, mimicking the kink behaviour of the Crab jet. The experiment is modelled with three-dimensional numerical simulations that show exactly how the instability develops and results in changes of direction of the jet.

Structure of a Magnetic Flux Annihilation Layer Formed by the Collision of Supersonic, Magnetized Plasma Flows.

We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure-two narrow current sheets running along the outside surfaces of the layer. Measurements with Thomson scattering show a fast outflow of plasma along the layer and a high ion temperature (T_{i}∼Z[over ¯]T_{e}, with average ionization Z[over ¯]=7). Analysis of the spatially resolved plasma parameters indicates that the advection and subsequent annihilation of the inflowing magnetic flux determines the structure of the layer, while the ion heating could be due to the development of kinetic, current-driven instabilities.

Monochromatic radiography of high energy density physics experiments on the MAGPIE generator.

A monochromatic X-ray backlighter based on Bragg reflection from a spherically bent quartz crystal has been developed for the MAGPIE pulsed power generator at Imperial College (1.4 MA, 240 ns) [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (2005)]. This instrument has been used to diagnose high energy density physics experiments with 1.865 keV radiation (Silicon He-α) from a laser plasma source driven by a ∼7 J, 1 ns pulse from the Cerberus laser. The design of the diagnostic, its characterisation and performance, and initial results in which the instrument was used to radiograph a shock physics experiment on MAGPIE are discussed.

Diagnosing collisions of magnetized, high energy density plasma flows using a combination of collective Thomson scattering, Faraday rotation, and interferometry (invited).

A suite of laser based diagnostics is used to study interactions of magnetised, supersonic, radiatively cooled plasma flows produced using the Magpie pulse power generator (1.4 MA, 240 ns rise time). Collective optical Thomson scattering measures the time-resolved local flow velocity and temperature across 7-14 spatial positions. The scattering spectrum is recorded from multiple directions, allowing more accurate reconstruction of the flow velocity vectors. The areal electron density is measured using 2D interferometry; optimisation and analysis are discussed. The Faraday rotation diagnostic, operating at 1053 nm, measures the magnetic field distribution in the plasma. Measurements obtained simultaneously by these diagnostics are used to constrain analysis, increasing the accuracy of interpretation.

Interpenetration, deflection, and stagnation of cylindrically convergent magnetized supersonic tungsten plasma flows.

The interpenetration and interaction of supersonic, magnetized tungsten plasma flows has been directly observed via spatially and temporally resolved measurements of the Thomson scattering ion feature. A novel scattering geometry allows independent measurements of the axial and radial velocity components of the ions. The plasma flows are produced via the pulsed power driven ablation of fine tungsten wires in a cylindrical wire array z pinch. Fits of the data reveal the variations in radial velocity, axial velocity, and temperature of the ion streams as they interpenetrate and interact. A previously unobserved increase in axial velocity is measured near the array axis. This may be the result of v[over →]×B[over →] bending of the ion streams by a toroidal magnetic field, advected to and accumulated about the axis by the streams.

[Cell therapy of critical lower limb ischemia (problems and prospects)].

Critical limb ischemia is a syndrome that combines several peripheral artery diseases with different ethiology and pathogenesis but with similar prognosis, high morbidity and mortality. Possibility of surgical and conservative treatment of critical limb ischemia almost completely exhausted. Some hopes have arisen due to progress in cell technology. The article provides a critical analysis of pathogenic prerequisites of stem/progenitor cells for the treatment of patients with a critical limb ischemia in detail the basic results of preclinical and clinical studies on the safety and efficacy of cell technology. Unsolved problems and prospects of practical application are also discussed.