Article describes how blending of ceramic constituent phases enhances sinterability and performance in high strength ceramics. The authors describe how a near fully dense blended boron carbide (B4C)-titanium diboride (TiB2) composite produced through spark plasma sintering (SPS) is probed to understand the mechanical performance under dynamic uniaxial strain, or shock compression.

Article discusses the Mexican cavefish Astyanax mexicanus, has lost moderate-to-vigorous activity following cave colonization, reaching basal swim speeds ~3.7-fold slower than their river-dwelling counterpart. Collectively, the authors reveal broad skeletal muscle changes following cave colonization, displaying an adaptive skeletal muscle phenotype reminiscent to mammalian disuse and high-fat models while simultaneously maintaining a unique capacity for sustained muscle contraction via enhanced glycogen metabolism.

Article tests a hypothesized path model of Theory of Planned Behavior (TPB) variables (i.e., attitude toward behavior, subjective norm, perceived behavioral control, and intention) with physical activity (PA) and depressive symptoms. The findings support the theoretical tenets of TPB and provide empirical evidence of the psychosocial mechanism of PA and depressive symptoms in Chinese adolescents. It suggests that building PA intervention strategies while considering the TPB framework may promote adolescents’ physical and mental health.

Article describes study analyzing the effects of a new purine derivative drug, PDD005, in attenuating mechanisms involved in the pathogenesis of neurodegenerative diseases, using both in vivo and in vitro models.

Article describes study investigating spin Hall effect (SHE) in two prototypical Ferroelectric Rashba semiconductors (FERSCs), GeTe and SnTe, and show that it can be large either in ferroelectric or paraelectric structure.

Abstract: Errors are found in the mathematical correlation based on the combined Jouyban-Acree and Modified Apelblat model for describing the variation in the mole fraction solubility of cefpiramide with temperature and solvent composition for the binary aqueous-ethanol solvent system. The equation coefficents given by Tang and coworkers, when substituted into the model equation, do not yield the authors' calculated mole fraction solubilities of cefpiramide.

A task was undertaken to characterize glovebox gloves that are currently used in the facilities at Savannah River Site (SRS) as well as some experimental and advanced compound gloves that have been proposed for use. Gloves from four manufacturers were tested for permeation in hydrogen and air, thermal stability, tensile properties, puncture resistance and dynamic mechanical response. The gloves were compared to each other within the type and also to the butyl rubber glove that is widely used at the SRS. The permeation testing demonstrated that the butyl compounds from three of the vendors behaved similarly and exhibited hydrogen permeabilities of .52‐.84 x10{sup ‐7} cc H{sub 2}*cm / (cm{sup 2}*atm). The Viton� glove performed at the lower edge of this bound, while the more advanced composite gloves exhibited permeabilities greater than a factor of two compared to butyl. Thermogravimetric analysis was used to determine the amount of material lost under slightly aggressive conditions. Glove losses are important since they can affect the life of glovebox stripper systems. During testing at 90, 120, and 150�C, the samples lost most of the mass in the initial 60 minutes of thermal exposure and as expected increasing the temperature increased the mass loss and …

Supported catalysts are widely used in industry and can be optimized by tuning the composition and interface of the metal nanoparticles and oxide supports. Rational design of metal-metal oxide interfaces in nanostructured catalysts is critical to achieve better reaction activities and selectivities. We introduce here a new class of nanocrystal tandem catalysts that have multiple metal-metal oxide interfaces for the catalysis of sequential reactions. We utilized a nanocrystal bilayer structure formed by assembling platinum and cerium oxide nanocube monolayers of less than 10 nm on a silica substrate. The two distinct metal-metal oxide interfaces, CeO2-Pt and Pt-SiO2, can be used to catalyse two distinct sequential reactions. The CeO2-Pt interface catalysed methanol decomposition to produce CO and H2, which were subsequently used for ethylene hydroformylation catalysed by the nearby Pt-SiO2 interface. Consequently, propanal was produced selectively from methanol and ethylene on the nanocrystal bilayer tandem catalyst. This new concept of nanocrystal tandem catalysis represents a powerful approach towards designing high-performance, multifunctional nanostructured catalysts

By analyzing the pulse to pulse intensity fluctuations of the radiation emitted by a charge particle in the incoherent part of the spectrum, it is possible to extract information about the spatial distribution of the beam. At the Advanced Light Source (ALS) of the Lawrence Berkeley National Laboratory, we have developed and tested a simple scheme based on this principle that allows for the absolute measurement of the bunch length. A description of the method and the experimental results are presented.

Clouds of low energy electrons in the vacuum beam pipes of accelerators of positively charged particle beams present a serious limitation for operation at high currents. Furthermore, it is difficult to probe their density over substantial lengths of the beam pipe. We have developed a novel technique to directly measure the electron cloud density via the phase shift induced in a TE wave transmitted over a section of the accelerator and used it to measure the average electron cloud density over a 50 m section in the positron ring of the PEP-II collider at the Stanford Linear Accelerator Center.

Incoherent electron effects could seriously limit the beam lifetime in proton or ion storage rings, such as LHC, SPS, or RHIC, or blow up the vertical emittance of positron beams, e.g., at the B factories or in linear-collider damping rings. Different approaches to modeling these effects each have their own merits and drawbacks. We describe several simulation codes which simplify the descriptions of the beam-electron interaction and of the accelerator structure in various different ways, and present results for a toy model of the SPS. In addition, we present evidence that for positron beams the interplay of incoherent electron-cloud effects and synchrotron radiation can lead to a significant increase in vertical equilibrium emittance. The magnitude of a few incoherent e{sup +}e{sup -} scattering processes is also estimated. Options for future code development are reviewed.

High brightness electron beam sources such as rf photo-injectors as proposed for SASE FELs must consistently produce the desired beam quality. We report the results of a study in which a combined neural network (NN) and first-principles (FP) model is used to model the transverse phase space of the beam as a function of quadrupole strength, while beam charge, solenoid field, accelerator gradient, and linac voltage and phase are kept constant. The parametric transport matrix between the exit of the linac section and the spectrometer screen constitutes the FP component of the combined model. The NN block provides the parameters of the transport matrix as functions of quad current. Using real data from SLAC Gun Test Facility, we will highlight the significance of the constrained training of the NN block and show that the phase space of the beam is accurately modeled by the combined NN and FP model, while variations of beam matrix parameters with the quad current are correctly captured. We plan to extend the combined model in the future to capture the effects of variations in beam charge, solenoid field, and accelerator voltage and phase.

We present a novel Morse Theory approach for the analysis of the complex topology of the Rayleigh-Taylor mixing layer. We automatically extract bubble structures at multiple scales and identify the resolution of interest. Quantitative analysis of bubble counts over time highlights distinct mixing trends for a high-resolution Direct Numerical Simulation (DNS) [1].

We describe the use of image analysis to count bubbles in 3-D, large-scale, LES [1] and DNS [2] of the Rayleigh-Taylor instability. We analyze these massive datasets by first converting the 3-D data to 2-D, then counting the bubbles in the 2-D data. Our plots for the bubble count indicate there are four distinct regimes in the process of the mixing of the two fluids. We also show that our results are relatively insensitive to the choice of parameters in our analysis algorithms.

Complexation of U(VI) with 1-hydroxyethane-1,1-diphosphonic acid (HEDPA) in acidic to basic solutions has been studied with multiple techniques. A number of 1:1 (UO{sub 2}H{sub 3}L), 1:2 (UO{sub 2}H{sub j}L{sub 2} where j = 4, 3, 2, 1, 0 and -1) and 2:2 ((UO{sub 2}){sub 2}H{sub j}L{sub 2} where j = 1, 0 and -1) complexes form, but the 1:2 complexes are the major species in a wide pH range. Thermodynamic parameters (formation constants, enthalpy and entropy of complexation) were determined by potentiometry and calorimetry. Data indicate that the complexation of U(VI) with HEDPA is exothermic, favored by the enthalpy of complexation. This is in contrast to the complexation of U(VI) with dicarboxylic acids in which the enthalpy term usually is unfavorable. Results from electrospray ionization mass spectrometry (ESI-MS) and {sup 31}P NMR have confirmed the presence of 1:1, 1:2 and 2:2 U(VI)-HEDPA complexes.

This article discusses strong tantalum-to-boron dative interactions in (silox)3Ta(BH3) and (silox)3Ta(ɳ2-B,CI-BCI2Ph) (silox = tBu3SiO)1.

We consider the properties of {Omega} graphs ({Omega} vs f(z)) obtained from Gouy interferometry on multicomponent systems with constant diffusion coefficients. We show that they must have (a) either a maximum or else a minimum between f(z)=0 and f(z)=1 and (b) an inflection point between the f(z) value at the extremum and f(z)=1. Consequently, an {Omega} graph cannot have both positive and negative {Omega} values.

Metal-containing tetrahedral amorphous carbon films wereproduced by dual filtered cathodic vacuum arc plasma sources operatedinsequentially pulsed mode. Negatively pulsed bias was applied to thesubstrate when carbon plasma was generated, whereas it was absentwhen themolybdenum plasma was presented. Film thickness was measured afterdeposition by profilometry. Glass slides with silver padswere used assubstrates for the measurement of the sheet resistance. Themicrostructure and composition of the films were characterizedbyRamanspectroscopy and Rutherford backscattering, respectively. It was foundthat the electrical resistivity decreases with an increaseof the Mocontent, which can be ascribed to an increase of the sp2 content and anincrease of the sp2 cluster size.

Since its discovery in 1985, the celebrated geodesic cage structure of the C{sub 60} molecule has been recognized: a truncated icosahedron in which all sixty vertices are equivalent and has the full I{sub h} symmetry, making it thus far the most spherical of all known molecules. Inherent in this high symmetry is an intricate network of electron-phonon coupling, evident in phonon progressions and vibronic peak broadening, and resulting in structural distortions of neutral C{sub 60} in the presence of solvent. Within the I{sub h} symmetry group of this molecule, of the forty-six distinct vibrational frequencies only ten are Raman-active and four are IR-active (in the first order), while the remaining 32 modes are optically silent. Symmetry-reduced structures of C{sub 60} would activate some of these silent modes, which could then be amenable to experimental verification such as in resonance Raman scattering. Here, quantum chemical calculations within density functional theory establish for the first times (1) lower-symmetry, energetically more stable structures for C{sub 60}, the lowest of which is of D{sub 3d} symmetry, and with a new assignment of the ground state as the {sup 1}A{sub 1g} state, (2) the activation of some IR and Raman I{sub h} silent modes: the …

We propose a new scheme for an approximate solution of the Schroedinger equation for a many-body interacting system, based on the use of pairs of walkers. Trial wavefunctions for these pairs are combinations of standard symmetric and antisymmetric wavefunctions. The method consists in applying a fixed-node restriction in the enlarged space, and computing the energy of the antisymmetric state from the knowledge of the exact ground state energy for the symmetric state. We made two conjectures: first, that this fixed-hypernode energy is an upper bound to the true fermion energy; second that this bound would necessarily be lower than the usual fixed-node energy using the same antisymmetric trial function. The first conjecture is true, and is proved in this paper. The second is not, and numerical and analytical counterexamples are given. The question of whether the fixed-hypernode energy can be better than the usual bound remains open.

The orientation relationship, habit plane, parent-product interface at the atomic level, twin relationship, and plastic deformation resulting from the {delta} {yields} {alpha}{prime} isothermal martensitic transformation in Pu-Ga alloys are examined using optical microscopy, transmission electron microscopy, and finite element calculations. The {delta} {yields} {alpha}{prime} transformation exhibits a {approx}20% volume collapse when the face-centered cubic {delta} phase transforms to the monoclinic {alpha}{prime} phase, which results in unique and intriguing crystallography and morphology. Here, we show that the orientation relationship is very close to that previously reported by Zocco et al. (1990), but has small rotational misalignments between the two phases both parallel and perpendicular to the [110]{sub {delta}} {parallel}[100]{sub {alpha}{prime}} direction. The amount of plastic deformation is exceedingly large due to the {approx}20% volume collapse and transmission electron microscopy is used to quantify the difference in dislocation density between untransformed {delta}-matrix and regions of {delta} adjacent to the transformed {alpha}{prime}. The twins contained in {alpha}{prime} plates are shown to have a (205){sub {alpha}} orientation as the lattice invariant deformation and are found to be composed of two alternating variants that share a common <020>{sub {alpha}{prime}} direction, but differ by a 60 degree rotation about <020>{sub {alpha}{prime}}. A combination of electron diffraction …

Our approach to the solution of the Schroedinger Equation for many-fermion systems has been extensively revised. We have devised a generalization of ''acceptance/rejection'' that applies to signed random walkers. We have introduced a new class of importance functions for two walkers that better reflects the structure of the enlarged Euclidean space of the pair. For greater flexibility, we no longer rely on the ''local energy'' of the importance function to determine the dynamics of the walk. We sketch these technical changes and give new results for the two-dimensional electron gas.

By implementing a large-area, gain-stabilized microcalorimeter array on an electron beam ion trap, the electron-impact excitation cross sections for the dominant x-ray lines in the Fe XVII spectrum have been measured as a function of electron energy up to greater than three times the threshold energy, establishing a benchmark for atomic calculations. The results reveal a consistent overestimation by recent calculations of the excitation cross section of the resonance transition, which is shown to be at the root of several long-standing problems associated with modeling solar and astrophysical Fe XVII spectra. The data do not show strong contributions from resonance excitation contrary to recent statements in the literature.

A general analysis of poroelasticity for hexagonal, tetragonal, and cubic symmetry shows that four eigenvectors are pure shear modes with no coupling to the pore-fluid mechanics. The remaining two eigenvectors are linear combinations of pure compression and uniaxial shear, both of which are coupled to the fluid mechanics. The analysis proceeds by first reducing the problem to a 2 x 2 system. The poroelastic system including both anisotropy in the solid elastic frame (i.e., with ''hard anisotropy''), and also anisotropy of the poroelastic coefficients (''soft anisotropy'') is then studied in some detail. In the presence of anisotropy and spatial heterogeneity, mechanics of the pore fluid produces shear dependence on fluid bulk modulus in the overall poroelastic system. This effect is always present (though sometimes small in magnitude) in the systems studied, and can be comparatively large (up to a maximum increase of about 20 per cent) in some porous media--including porous glass and Schuler-Cotton Valley sandstone. General conclusions about poroelastic shear behavior are also related to some recently derived product formulas that determine overall shear response of these systems. Another method is also introduced based on rigorous Hashin-Shtrikman-style bounds for nonporous random polycrystals, followed by related self-consistent estimates of mineral …