Microbubble-enhanced hemorrhage control using high intensity focused ultrasound

Our objective was to investigate whether hemorrhage control can be achieved faster when high-intensity focused ultrasound (HIFU) is applied in the presence of ultrasound contrast agents (UCA) as compared to HIFU only application. Incisions (3 cm long and 0.5 cm deep) were produced in the livers of anesthetized rabbits. UCA Optison (0.18 ml/kg) was injected into the mesenteric vein. A HIFU applicator (5.5 MHz, 6800 W/cm² in situ) was scanned at a rate of 1–2 mm/s in one direction over the incision (with multiple passes if needed), until hemostasis was achieved. Hemostasis times were 59 ± 23 s (n = 21) in the presence of Optison and 70 ± 23 s (n = 29) without Optison. The presence of Optison produced on average 37% reduction in hemostasis times normalized to initial bleeding rates (p < 0.05), as well as 60% faster formation of the coagulum seal over the incision (p < 0.05). Gross and histological observations showed similar appearance of HIFU lesions produced in the presence of Optison and HIFU lesions produced without Optison. Our results suggest potential utility of UCA for increasing efficiency of HIFU-induced hemostasis of solid organ injuries.     

Ferromagnetic properties of Fe-substituted ZnO-based magnetic semiconductor

The diluted magnetic semiconductor Zn_1−x⁵⁷Fe_xO (x=0.01, 0.02, 0.03) compounds were prepared by the solid-state reaction method. The crystal structure of _Zn0.97⁵⁷_Fe0.03O${\mathrm{Zn}}_{0.97}{}^{57}{\mathrm{Fe}}_{0.03}\mathrm{O}$ at room temperature is determined to be a hexagonal structure of P6₃mc with lattice constants a₀=3.252 Å and c₀=5.205 Å by Rietveld refinement. The Bragg factors R_B and R_F were determined as 3.23% and 2.81%. From the inverse susceptibility versus T curve, the paramagnetic Curie temperature is found to be 2.7 K and effective moment is found to be 4.01 μ_B, thereby suggesting that the exchange interactions between Fe ions are ferromagnetic. Mössbauer spectra of _Zn0.97⁵⁷_Fe0.03O${\mathrm{Zn}}_{0.97}{}^{57}{\mathrm{Fe}}_{0.03}\mathrm{O}$ have been taken at various temperatures ranging from 4.2 to 295 K. Mössbauer spectrum for _Zn0.97⁵⁷_Fe0.03O${\mathrm{Zn}}_{0.97}{}^{57}{\mathrm{Fe}}_{0.03}\mathrm{O}$ at 4.2 K has shown ferromagnetic phase (sextet), and the spectra were fitted based on a random distribution model of Fe ions.     

The charge structure and interaction mechanism on In-doped sulphur spinel

The charge structure and interaction mechanism on In-doped sulphur spinel FeIn_xCr_2−xS₄ are studied. The temperature dependence of magnetization μ_B, measured from 60 K to room temperature, suggests that FeIn_xCr_2−xS₄ (x=0.1$x=0.1$, 0.3) are ferrimagnetic. The Néel temperature is decreased with increasing non-magnetic In substitution as consequence of reduction of superexchange interaction for increased lattice parameter. FeIn_xCr_2−xS₄ is investigated by Mössbauer spectra from 4.2 K to room temperature. The asymmetric line broadening is observed for the sample FeIn_xCr_2−xS₄ and considered to be dynamic Jahn–Teller relaxation. The charge state of Fe ions is ferrous in character.     

An effective stochastic excitation strategy for finding elusive NMR signals from solids

The versatility of using a stochastic pulse sequence to elucidate peaks with a wide range of shifts, peak widths, and T(1) relaxation times is demonstrated. A stochastic sequence is combined with high speed magic angle spinning (MAS) to obtain the broad and largely shifted peak associated with (31)P in LiNiPO(4). A stochastic sequence is also used to obtain a spectrum of 85% H(3)PO(4), which has a much longer T(1) value. The signal-to-noise was comparable for spectra of 85% H(3)PO(4) obtained with either a stochastic sequence or an optimized Ernst angle experiment. Experimental parameters for the stochastic experiment are set depending only on the ringdown of the probe and not on any inherent qualities of the sample. A stochastic sequence, therefore, combined with MAS provides a useful strategy for finding peaks with unknown T(1) relaxation constants, peak widths, and shifts.     

Calibration of the Pseudo-Reaction-Zone model for detonation wave propagation

An approach for the calibration of an advanced programmed burn (PB) model for detonation performance calculations in high explosive systems is detailed. Programmed burn methods split the detonation performance calculation into two components: timing and energy release. For the timing, the PB model uses a Detonation Shock Dynamics (DSD) surface propagation model, where the normal surface speed is a function of local surface curvature. For the energy release calculation and subsequent hydrodynamic flow evolution, a Pseudo-Reaction-Zone (PRZ) model is used. The PRZ model is similar to a reactive burn model in that it converts reactants into products at a finite rate, but it has a reaction rate dependent on the normal surface speed derived from the DSD calculation. The PRZ reaction rate parameters must be calibrated in such a way that the rate of energy release due to reaction in multi-dimensional geometries is consistent with the timing calculation provided by the DSD model. Our strategy for achieving this is to run the PRZ model in a detonation shock-attached frame in a compliant 2D planar slab geometry in an equivalent way to a reactive burn model, from which we can generate detonation front shapes and detonation phase speed variations with slab thickness. In this case, the D _n field used by the PRZ model is then simply the normal detonation shock speed rather than the DSD surface normal speed. The PRZ rate parameters are then iterated on to match the equivalent surface front shapes and surface phase speed variations with slab thickness derived from the target DSD model. For the purposes of this paper, the target DSD model is fitted to the performance properties of an idealised condensed-phase reactive burn model, which allows us to compare the detonation structure of the calibrated PRZ model to that of the originating idealised-condensed phase model.     

Chiral magnetic effect without chirality source in asymmetric Weyl semimetals

We describe a new type of the chiral magnetic effect (CME) that should occur in Weyl semimetals (WSMs) with an asymmetry in the dispersion relations of the left- and right-handed (LH and RH) chiral Weyl fermions. In such materials, time-dependent pumping of electrons from a non-chiral external source can generate a non-vanishing chiral chemical potential. This is due to the different capacities of the LH and RH chiral Weyl cones arising from the difference in the density of states in the LH and RH cones. The chiral chemical potential then generates, via the chiral anomaly, a current along the direction of an applied magnetic field even in the absence of an external electric field. The source of chirality imbalance in this new setup is thus due to the band structure of the system and the presence of (non-chiral) electron source, and not due to the parallel electric and magnetic fields. We illustrate the effect by an argument based on the effective field theory, and by the chiral kinetic theory calculation for a rotationally invariant WSM with different Fermi velocities in the left and right chiral Weyl cones; we also consider the case of a WSM with Weyl nodes at different energies. We argue that this effect is generically present in WSMs with different dispersion relations for LH and RH chiral Weyl cones, such as SrSi₂ recently predicted as a WSM with broken inversion and mirror symmetries, as long as the chiral relaxation time is much longer than the transport scattering time.     

Experimental and Numerical Simulations of Spray Impingement and Combustion Characteristics in Gasoline Direct Injection Engines under Variable Driving Conditions

Gasoline direct injection (GDI) increases engine power output and reduces emissions. In GDI engines, increasing injection pressure improves atomization, which increases thermal efficiency at the cost of wall wetting. When wall wetting occurs, both soot emissions and fuel consumption increase. Wall wetting in GDI engines under cold driving conditions has rarely been considered. In this study, experimental data characterizing droplet splashing/spreading phenomena were collected to inform numerical simulations of combustion characteristics and wall wetting subject to variable driving conditions and excess air ratio, λ. Fully 3D and unsteady numerical simulations were carried out to predict flow-field, combustion, and spray-impingement characteristics. To simulate a GDI engine, a spray-impingement model was developed using both experimental data and previous modeling efforts. The excess air ratio and driving-condition temperature were the variable parameters considered in this study. When decreasing λ from 1.0 to 0.7 by increasing the fuel-injection rate (fuel rich), the cylinder pressure increases to 61 % of the pressure when λ=1.0. Because of increasing the fuel-injection rate, the increased momentum in the fuel spray increases both wall wetting and soot generation. At low driving-condition temperatures, the cylinder pressure was up to 63 % less than that under warm conditions, but with increased soot generation. Simulations revealed a correlation between wall wetting and the soot emissions. Soot generation was most sensitive to changes in wall wetting.     

Tb3+ luminescence enhancement of YAG:Tb3+ nanocrystals embedded in silica xerogel

The luminescence behavior of composite materials consisting of nanocrystals of Y_3?xAl₅O₁₂:Tb (YAG:Tb³⁺) embedded into silica xerogel has been studied. Blue and green luminescence of the materials is due to a cross-relaxation effect in Tb³⁺ ions doped into a YAG lattice. The materials with YAG:Tb³⁺ nanocrystals immobilized in silica exhibit enhancement of Tb³⁺ luminescence in comparison with the macrocrystalline YAG:Tb³⁺ powder. The Tb³⁺ luminescence intensity of a composite material dried at room temperature can be improved when higher aliphatic alcohols are applied in a one-pot procedure during a sol–gel synthesis. On the other hand, the Tb³⁺ luminescence is quenched in the presence of Ag nanoparticles in the material. The composite material (YAG:Tb³⁺ in silica) exhibits thermal stability at higher temperatures and achieves the highest emission intensity after having been annealed at 700 °C.     

X-band Electron Spin Relaxation Times for Four Aromatic Radicals in Fluid Solution and Comparison with Other Organic Radicals

X-band electron spin relaxation times of BDPA (1:1 α,γ-bisdiphenylene-β-phenylallyl), galvinoxyl 2,6-di-tert-butyl-α-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxy, DPPH (2,2-diphenyl-1-picrylhydrazyl) and thianthrene radicals in fluid solution were measured by electron spin echo and inversion recovery at ambient temperature. Tumbling correlation times are estimated to be in the range of 20–30 ps. In this fast tumbling regime T ₁ ~ T ₂. Relaxation times are compared with previously reported values for symmetrically substituted triarylmethyl, semiquinone, and nitroxide radicals. The concentration dependence of spin lattice relaxation for neutral BDPA in toluene is about 10³ times greater than for anionic trityl radicals in water. T ₁ decreases in the order carbon-center BDPA > galvinoxyl > DPPH > thianthrene. The dominant relaxation mechanisms are proposed to be a local mode for BDPA, spin rotation, local mode and modulation of anisotropic proton hyperfine coupling for galvinoxyl, modulation of anisotropic nitrogen hyperfine for DPPH, and spin rotation plus modulation of anisotropic proton hyperfine coupling for thianthrene.     

Metabolomic applications of electrochemistry/Mass spectrometry

Analytical techniques used for multivariate analysis of endogenous metabolites in biological systems (e.g., metabolomics, metabonomics) must be capable of accurately and selectively monitoring many known and unknown molecules that span a diverse chemical spectrum and over extremely large dynamic concentration ranges. Mass spectrometric (MS) and electrochemical array (EC-Array) detection have been widely used for multi-component analysis with applicability to low-level (fmol) metabolites. Described here are practical considerations and results obtained with the combined use of EC-Array and MS for HPLC-based multivariate metabolomic analysis. Data presented include the study of changes in rat urinary metabolite profiles associated with xenobiotic toxin exposure analyzed by HPLC using water:acetonitrile binary gradient conditions and post-column flow splitting between EC-Array and MS detectors. Results show complementary quantitative and qualitative analysis and the ability to differentiate sample groups consistent with xenobiotic-induced histopathological changes. The potential applicability of this hyphenated technique for biomarker elucidation through measurement of redox active compounds that are commonly associated with disease pathology and xenobiotic toxicity is discussed. The use of EC reactor cells in series with MS is also presented as a means of producing likely metabolites to facilitate structural elucidation and confirmation.