Search

Platinum supported on glassy carbon (GC) was used as a model system for studying the influence of the surface morphology of a Pt catalyst on methanol oxidation in alkaline and acidic solutions. Platinum was deposited by the potential step method on GC samples from H2SO4 + H2PtCl6 solution under the same conditions with loadings from 10 to 80 mg cm-2. AFM and STM images of the GC/Pt electrodes showed that the Pt was deposited in the form of 3D agglomerates composed of spherical particles. Longer deposition times resulted in increased growth of Pt forms and a decrease in the specific area of the Pt. The real surface area of Pt increased with loading but the changes were almost negligible at higher loadings. Nevertheless, both the specific and mass activity of platinum supported on glassy carbon for methanol oxidation in acidic and in alkaline solutions exhibit a volcanic dependence with respect to the platinum loading. The increase in the activity can be explained by the increasing the particle size with the loading and thus an increase in the contiguous Pt sites available for adsorption and decomposition of methanol. However, the decrease in the activity of the catalyst with further increase of loading and particle size after reaching the maximum is related to the decrease of active sites available for methanol adsorption and their accessibility as a result of more close proximity and pronounced coalescence of the Pt particles.

Application of dynamic 1H-NMR spectroscopy added to the understanding of the hydrogen bonds existing in the structurally related 5-substituted-2-alkylidene-4-oxothiazolidines in polar and apolar solvents. The equilibrated mixtures of these typical push-pull alkenes in CDCl3 consist of the intramolecularly H-bonded (E)-isomer and intermolecularly H-bonded (Z)-isomer in varying proportions which depend on the solvent polarity. For the representative of the series, (Z)-2-(5-ethoxycarbonylmethyl-4-oxothiazolidin-2-ylidene)-1-phenylethanone, a concentration effect on the degree of intermolecular hydrogen bonding in apolar CDCl3 has been studied.

The miсrоstruсture, hаrdnеss, аnd elесtrical соnductivity of the alloys from tеrnаry systеms bаsed on Bi and Gе hаve nоt been studied so fаr. This pаper prеsents the rеsults of experimental and anаlytical investigation of Bi-Cu-Gе, Bi-Ga-Gе, and Bi-Gе-Zn ternary systems. Following experimental techniques were applied: optical microscopy (LOM), scаnning еlесtron miсrosсоpy (SEM) with enеrgy dispersivе spесtrometry (EDS), X-rаy diffrасtometric anаlysis (XRD), Brinеll hаrdness measurements and electrical conductivity mеаsurements. Among the analytical methods, the Cаlphаd mеthod and the software Pandаt ver. 8.1 were used. In all three investigated ternary systems an isothermal section at 25°C was selected for experimental testing. Based on the optimized thermodynamic parameters for the constitutive binary systems, the calculation was performed. The experimentally obtained results were compared with the results of thermodynamic calculations and gооd agreement wаs noticed. Also, in all three tested systems hardness and electrical conductivity were measured and using appropriate mathematical models these properties were guided in the entire range of the composition. The obtained results include determination of isothermal sections, identification of co-existing phases, electrical conductivity and hardness measurements and development of mathematical models for prediction of electrical conductivity and hardness.

Myopathies decrease muscle functionality. Mutations in ryanodine receptor 1 (RyR1) are often associated with myopathies with microscopic core-like structures in the muscle fiber. In this study, we identify a mouse RyR1 model in which heterozygous animals display clinical and pathological hallmarks of myopathy with core-like structures. The RyR1 mutation decreases sensitivity to activated calcium release and myoplasmic calcium levels, subsequently affecting mitochondrial calcium and ATP production. Mutant muscle shows a persistent potassium leak and disrupted expression of regulators of potassium homeostasis. Inhibition of KATP channels or increasing interstitial potassium by diet or FDA-approved drugs can reverse the muscle weakness, fatigue-like physiology and pathology. We identify regulators of potassium homeostasis as biomarkers of disease that may reveal therapeutic targets in human patients with myopathy of central core disease (CCD). Altogether, our results suggest that amelioration of potassium leaks through potassium homeostasis mechanisms may minimize muscle damage of myopathies due to certain RyR1 mutations.

Abstract This paper deals with the study of Fe-W powders, which were prepared by electrolyzing, and their stabilized properties. The synthesized Fe-W powders were studied using X-ray diffraction, thermal analysis, Mossbauer spectroscopy and thermomagnetic measurement. A poor hydrogen absorption occurred. After the heat treatment at 800°C, the amorphous and α-Fe(W) phases were decomposed into prevailing α-Fe with approx. 3 at.% W accompanied by the W(Fe), λ-Fe2W, and Fe2+ in oxide phases. [ABSTRACT FROM AUTHOR]

Infants with Down syndrome (DS) or Trisomy 21, are at high risk for developing pulmonary arterial hypertension (PAH), but mechanisms that increase susceptibility are poorly understood. Laboratory studies have shown that early disruption of angiogenesis during development impairs vascular and alveolar growth and causes PAH. Human chromosome 21 encodes known anti-angiogenic factors, including collagen18a1 (endostatin, ES), ß-amyloid peptide (BAP) and Down Syndrome Critical Region 1 (DSCR-1). Therefore, we hypothesized that fetal lungs from subjects with DS are characterized by early over-expression of anti-angiogenic factors and have abnormal lung vascular growth in utero.Human fetal lung tissue from DS and non-DS subjects were obtained from a biorepository. Quantitative reverse transcriptase PCR (qRT-PCR) was performed to assay 84 angiogenesis-associated genes and individual qRT-PCR was performed for ES, amyloid protein precursor (APP) and DSCR1. Western blot analysis (WBA) was used to assay lung ES, APP and DSCR-1 protein contents. Lung vessel density and wall thickness were determined by morphometric analysis.The angiogenesis array identified up-regulation of three anti-angiogenic genes: COL18A1 (ES), COL4A3 (tumstatin) and TIMP3 (tissue inhibitor of metallopeptidase 3) in DS lungs. Single qRT-PCR and WBA showed striking elevations of ES and APP mRNA (p = 0.022 and p = 0.001) and protein (p = 0.040 and p = 0.002; respectively). Vessel density was reduced (p = 0.041) and vessel wall thickness was increased in DS lung tissue (p = 0.033) when compared to non-DS subjects.We conclude that lung anti-angiogenic factors, including COL18A1 (ES), COL4A3, TIMP3 and APP are over-expressed and fetal lung vessel growth is decreased in subjects with DS. We speculate that increased fetal lung anti-angiogenic factor expression due to trisomy 21 impairs lung vascular growth and signaling, which impairs alveolarization and contributes to high risk for PAH during infancy.

We study the dynamics of genetic code evolution. The model of Vetsigian et al. [Proc. Natl. Acad. Sci. USA 103, 10696 (2006)PNASA60027-842410.1073/pnas.0603780103] and Vetsigian [Collective evolution of biological and physical systems, Ph.D. thesis, 2005] uses the mechanism of horizontal gene transfer to demonstrate convergence of the genetic code to a near universal solution. We reproduce and analyze the algorithm as a dynamical system. All the parameters used in the model are varied to assess their impact on convergence and optimality score. We show that by allowing specific parameters to vary with time, the solution exhibits attractor dynamics. Finally, we study automorphisms of the genetic code arising due to this model. We use this to examine the scaling of the solutions to re-examine universality and find that there is a direct link to mutation rate.

Weyl semimetals are predicted to realize the three-dimensional axial anomaly first discussed in particle physics. The anomaly leads to unusual transport phenomena such as the chiral magnetic effect in which an applied magnetic field induces a current parallel to the field. Here we investigate diagnostics of the axial anomaly based on the fundamental equations of axion electrodynamics. We find that materials with Weyl nodes of opposite chirality and finite energy separation immersed in a uniform magnetic field exhibit an anomaly-induced oscillatory magnetic field with a period set by the chemical potential difference of the nodes. In the case where a chemical potential imbalance is created by applying parallel electric and magnetic fields, we find a suppression of the magnetic-field component parallel to the electric field inside the material for rectangular samples, suggesting that the chiral magnetic current opposes this imbalance. For cylindrical geometries, we instead find an enhancement of this magnetic-field component along with an anomaly-induced azimuthal component. We propose experiments to detect such magnetic signatures of the axial anomaly.

Motivated by the question of stability, in this letter we argue that an effective quantum-like theory can emerge in complex adaptive systems. In the concrete example of stochastic Lotka-Volterra dynamics, the relevant effective "Planck constant" associated with such emergent "quantum" theory has the dimensions of the square of the unit of time. Such an emergent quantum-like theory has inherently non-classical stability as well as coherent properties that are not, in principle, endangered by thermal fluctuations and therefore might be of crucial importance in complex adaptive systems.

Aging can be realized as a subalgebra of Schrödinger algebra by discarding the time-translation generator. While the two-point functions of the age algebra have been known for some time, little else was known about the higher n-point correlators. In this Letter, we present novel three-point correlators of scalar primary operators. We find that the aging correlators are distinct from the Schrödinger correlators by more than certain dressings with time-dependent factors, as was the case with two-point functions. In the existing literature, the holographic geometry of aging is obtained by performing certain general coordinate transformations on the holographic dual of the Schrödinger theory. Consequently, the aging two-point functions derived from holography look as the Schrödinger two-point functions dressed by time-dependent factors. However, since the three-point functions obtained in this Letter are not merely dressed Schrödinger correlators and instead, depend on an additional time-translation breaking variable, we conclude that the most general holographic realization of aging is yet to be found. We also comment on various extensions of the Schrödinger and aging algebras.

Bulk Bi2Te3 is known to be a topological insulator. We investigate surface states of Bi2Te3(111) thin films of one to six quintuple layers using density-functional theory including spin-orbit coupling. We construct a method to identify topologically protected surface states of thin film topological insulators. Applying this method to Bi2Te3 thin films, we find that the topological nature of the surface states remains robust with the film thickness and that the films of three or more quintuple layers have topologically nontrivial surface states, which agrees with experiments.

We present a class of classically marginal N-vector models in d=4 and d=3 whose scalar potentials can be written as subdeterminants of symmetric matrices. The d=3 case can be thought of as a generalization of the scalar sector of the Bagger-Lambert-Gustavsson model. Using the Hubbard-Stratonovich transformation we calculate their effective potentials which exhibit intriguing large-N scaling behaviors. We comment on the possible relevance of our models to strings, membranes, and also to a class of novel spin systems that are based on ternary commutation relations.

We point out that the recent discussion of nonrelativistic anti-de Sitter space and conformal field theory correspondence has a direct application in nonequilibrium statistical physics, a fact which has not been emphasized in the recent literature on the subject. In particular, we propose a duality between aging in systems far from equilibrium characterized by the dynamical exponent z=2 and gravity in a specific background. The key ingredient in our proposal is the recent geometric realization of the Schrödinger group. We also discuss the relevance of the proposed correspondence for the more general aging phenomena in systems where the value of the dynamical exponent is different from 2.

We analytically compute the spectrum of the spin zero glueballs in the planar limit of pure Yang-Mills theory in 2 + 1 dimensions. The new ingredient is provided by our computation of a new nontrivial form of the ground state wave functional. The mass spectrum of the theory is determined by the zeroes of Bessel functions, and the agreement with large lattice data is excellent.

A multifactor optimisation technique is successfully applied to develop a new HPLC method in which methyldopa, hydrochlorothiazide and amiloride were analysed and determined on a C18 column with detection at 286 nm. The optimal conditions of HPLC separation were determined with the aid of the response surface diagram -- 'window diagram'. The effect of simultaneously varying the pH, proportion aqueous acetic acidum and methanol in the mobile phase were studied to optimise the separation. The mobile phase composition that provides an acceptable resolution methyldopa, hydrochlorothiazide and amiloride in a short elution time is water--methanol (75:25) and pH 3.60. The k' values for methyldopa, hydrochlorothiazide and amiloride after optimisation were 1.40, 2.50 and 5.33, respectively. Relative retention (alpha) for ratio hydrochlorothiazide/methyldopa and amiloride/hydrochlorothiazide were 1.767 and 2.159, respectively. Correlation coefficients of the calibration curves for all analytes were greater than 0.995 and the R.S.D. values for the slope and the intercept with respect to the linearity were less than 2%. A method is applied for the quantitative analysis of Alatan tablets (Lek-Ljubljana). The powdered tablets are extracted with methanol, containing caffeine as the internal standard and assayed by comparison of peak areas after liquid chromatography. The high recovery (for all analytes about 100%) and the low R.S.D. (<2%) confirm good precision and reproducibility of the chromatographic method.

We point out that for a large class of universes, holography implies that the most probable value for the cosmological constant is zero. In four space-time dimensions, the probability distribution takes the Baum-Hawking form, dP approximately exp(cM(2)(p)/Lambda)dLambda.