PtAu Nanoparticles Supported by Reduced Graphene Oxide as a Highly Active Catalyst for Hydrogen Evolution

PtAu nanoparticles spontaneously deposited on graphene support, PtAu/rGO, have shown remarkably high catalytic activity for hydrogen evolution reaction (HER) in sulfuric acid solution. SEM images of the PtAu/rGO electrode surface showed that Pt nanoparticles that are non-uniform in size occupy both the edges of previously deposited uniform Au nanoparticles and the edges of graphene support. XPS analysis showed that the atomic percentages of Au and Pt in PtAu/rGO were 0.6% and 0.3%, respectively. The atomic percentage of Au alone on previously prepared Au/rGO was 0.7%. Outstanding HER activity was achieved for the PtAu/rGO electrode, showing the initial potential close to the equilibrium potential for HER and a low Tafel slope of −38 mV/dec. This was confirmed by electrochemical impedance spectroscopy. The chronoamperometric measurement performed for 40 min for hydrogen evolution at a constant potential indicated good stability and durability of the PtAu/rGO electrode.

Passivation of Recirculating Open Water Cooling Systems Using New Organic Passivator

It is well know that recirculating open cooling water system at metal/ water surface contact appear frequent corrosion products, like scales, foaling and material losses which are have great effect on cooling process. Passivation helps to maintain clean heat transfer surface by inhibiting oxides scales through creating outer passive layer. Passivators are substances which usually have a sufficiently high equilibrium potential and sufficiently low over potential decrease corrosion rate on attainment of passivity. One of the most popular passivator is organic phosphate Phosphinosuccinic oligomer C15H14O4P component (PSO) The study of passivation of carbon steel pipe line in recirculating open cooling water system was the aim of this present work. Maximum efficiency of passivator was determined and surface morphology were investigated using optical, scanning microscopy, phase analysis of the formed protective layer was exam by XRD and EDX. Corrosion in running water with and without PSO at 2 m3/hr flow rate was investigated using corrosion coupon rack. It was found that 200 ppm (PSO) decreases corrosion rate of carbon steel pipe in 3.5% NaCL solution from 23 to 7 mpy in stagnate water corrosion testing, while in running water in 3.5% NaCL solution it decreases from 45 to 18 mpy. XDR showed that the protective layer due to passivation is mainly Magnetite (Fe3O4) compound.

Post-Annealing Effects on the Structure and Semiconductor Performance of Nanocrystalline ZnTe Thin Films Electrodeposited from an Aqueous Solution Containing Citric Acid

Using the potentiostatic electrodeposition technique, zinc telluride nanocrystalline thin films and an array of nanowires were synthesized in a citric acid bath. Electrodeposited zinc telluride thin films with stoichiometric compositions were obtained at a cathode potential of approximately −0.8 V versus Ag/AgCl, which was in a more noble region compared with the equilibrium potential of zinc. The average thickness of the zinc telluride thin films was approximately 3 μm, and the average growth rate was approximately 3 nm s−1. The as-deposited zinc telluride thin films had an amorphous phase with a black tint. By contrast, the zinc telluride thin films annealed at 683 K had a crystalline phase with a reddish-brown tint. The electrodeposited single-phase zinc telluride exhibited an optical absorption performance in a wavelength region that was shorter than 559 nm. At the annealing temperature of 683 K, the zinc telluride films exhibited an energy band gap of 2.3 eV, which was almost identical to that of single-crystal zinc telluride. The resistivity of the as-deposited amorphous-like zinc telluride thin films was approximately 2 × 105 Ω·m, whereas that of the samples annealed at 683 K was around 2 × 103 Ω·m, which was smaller than that of single-crystal zinc telluride. A three-dimensional nanostructure constructed with the zinc telluride nanowire array was also demonstrated using a template synthesis technique.

Channelopathies an Approach to Elevate Level of Cure- A Review

Channelopathies is group of diseases which is concerned with changes occur in the structural unit i.e., cell and its subunits (channels). Particularly disturbances in equilibrium potential in cell membrane carry toward the major cause of disease. Study of channel physiology with its mechanism is essential methodology to establish the differential factor in between normal phenomenon and disorder. Specific channels permit movement of selected ions through cellular membranes and are of important importance during variety of physiological processes, particularly in excitable tissues. In this review channelopathies in diseases like Central nervous system, Cardiovascular system, Renal system with their mechanism of action of channel disruption and treatment approaches have been covered.

Necessary Conditions for Interpolation by Multivariate Polynomials

Let $$\Omega $$ Ω be a smooth, bounded, convex domain in $${\mathbb {R}}^n$$ R n and let $$\Lambda _k$$ Λ k be a finite subset of $$\Omega $$ Ω . We find necessary geometric conditions for $$\Lambda _k$$ Λ k to be interpolating for the space of multivariate polynomials of degree at most k. Our results are asymptotic in k. The density conditions obtained match precisely the necessary geometric conditions that sampling sets are known to satisfy and are expressed in terms of the equilibrium potential of the convex set. Moreover we prove that in the particular case of the unit ball, for k large enough, there are no bases of orthogonal reproducing kernels in the space of polynomials of degree at most k.

Compositional Indicators for a Dynamical Barrier within Saturn’s E-ring

<p><strong>Abstract</strong></p> <p>Mass spectra from the Cosmic Dust Analyzer (CDA) [1] onboard the Cassini spacecraft revealed the existence of different compositional types of icy dust particles in Saturn’s E-ring. Most of these µm to sub-µm water ice grains were ejected from the cryo-volcanoes at the southern polar region of Enceladus and carry different constituents, for example organic compounds or salts [2-5]. These particles are subject to ongoing plasma sputtering during their lifetime in the E-ring [6,7].</p> <p>Recent modelling of the dynamics of E-ring particles has shown that, in the region between the orbital distances of Dione and Rhea, the outwards migration of a proportion of the E-ring dust slows down and almost comes to a halt [8]. Due to the minimum of the V-shaped electrostatic grain equilibrium potential [9] and a polarity reversal of the dust surface charges [10], the semi-major axes of the dust particles’ orbits actually stop growing, forcing the particles to spend a significant part of their lifetime at this distance from Saturn. Therefore, this phenomenon should allow plasma sputtering to operate much longer on the dust particles residing in this region, potentially resulting in detectable alterations to the dust particle properties, e.g. particle composition and size, in this region.</p> <p>Here we present the discovery of a new population of grains within the E ring, which show signs of compositional alteration, best explained by plasma sputtering. The radial frequency distribution of these grains shows a distinct accumulation in the region between the orbits of Dione and Rhea, and may provide evidence of prolonged residence there. Analyses of CDA mass spectra of the grains, interpreted via comparison with laboratory Laser‐Induced Liquid Beam Ion Desorption (LILBID) [11] analogue experiments, indicate the particles to be very salt-rich water ice. In comparison to the previously reported salt-rich particle types, generated from Enceladus’ subsurface ocean [3,4] this new population must possess a far higher salt concentration to explain its observed spectral appearance. We propose that the increase in salt concentration arises from sputtering-induced removal of water from less salty oceanic grains (Type 3) [3,4], during their extended time in the region between Dione and Rhea. This population may therefore represent the first confirmation of the proposed dynamical barrier within Saturn’s E-ring.</p> <p><strong>References</strong></p> <p>[1] Srama, R. et al., The Cassini Cosmic Dust Analyzer, Space Science Reviews, 114, 465-518, 2004.</p> <p>[2] Hillier, J. et al., The composition of Saturn’s E ring, Mon. Not. R. Astron. Soc., 377, 1588–1596, 2007</p> <p>[3] Postberg, F. et al., The E-ring in the vicinity of Enceladus II. Probing the moon’s interior-The composition of E-ring particles, Icarus, 193, 438-454, 2008.</p> <p>[4] Postberg, F. et al., Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus, Nature, 459, 1098-1101, 2009.</p> <p>[5] Postberg, F. et al., A salt-water reservoir as the source of a compositionally stratified plume on Enceladus, Nature, 474, 620–622, 2011</p> <p>[6] Jurac, S. et al., Saturn’s E Ring and Production of the Neutral Torus, Icarus, 149, 384–396, 2001</p> <p>[7] Johnson, R. E. et al., Sputtering of ice grains and icy satellites in Saturn’s inner magnetosphere, Planetary and Space Science, 56, 1238–1243, 2008</p> <p>[8] Kempf & Beckmann, Dynamics and long-term evolution of Saturn's E ring particles (in prep.)</p> <p>[9] Mitchell, C. J. et al., Tenuous ring formation by the capture of interplanetary dust at Saturn, JOURNAL OF GEOPHYSICAL RESEARCH, 110, 2005</p> <p>[10] Kempf, S. et al., The electrostatic potential of E ring particles, Planetary and Space Science, 54, 999-1006, 2006</p> <p>[11] Klenner, F. et al., Analogue spectra for impact ionization mass spectra of water ice grains obtained at different impact speeds in space, Rapid Commun Mass Spectrom., 33, 1751–1760, 2019</p>

Diurnal properties of Tonic and Synaptic GABAA receptor-mediated currents in Suprachiasmatic Nucleus neurons

Synaptic and extrasynaptic GABAA receptor (GABAAR)-mediated neurotransmission is a critical component of the suprachiasmatic nucleus (SCN) neuronal network. However, the properties of the GABAA tonic current (Itonic) and its origin remain unexplored. Spontaneous GABAA postsynaptic currents (sGPSC) and Itonic were recorded from SCN neurons using the whole-cell voltage-clamp technique at different times of the day. GABAAR antagonists (bicuculline, gabazine, and picrotoxin) inhibited sGPSC and induced an outward shift of the holding current, which defined the Itonic amplitude. The sGPSC frequency, synaptic charge transfer, and the Itonic amplitude all demonstrated significant diurnal rhythms with peaks in the middle of the day (Zeitgeber Time, ZT8) and nadirs at night (ZT19). The Itonic amplitude increased proportionally with the sGPSC frequency and synaptic charge transfer during the day and required action potential-mediated GABA release, which was confirmed by TTX application. The activation of presynaptic GABAB receptors by baclofen did not significantly alter the Itonic of neurons with low-frequency sGPSC. The equilibrium potential (Eq) for Itonic was similar to the Eq for chloride and GABAA receptor-activated currents. Itonic showed outward rectification at membrane potentials over the range of -70 mV to -10 mV, then was linear at voltages greater than -10 mV. GABAAR containing α4-, α5- and δ- subunits were expressed in SCN, and their contribution to Itonic was confirmed by application of the GABAAR agonist THIP and the GABAAR inverse agonist L655,708. Thus, the Itonic was mediated by extrasynaptic GABAARs activated predominantly by GABA diffusing out of GABAergic synapses.

The Role of the Molecular Hydrogen Formation in the Process of Metal-Ion Reduction on Multicrystalline Silicon in a Hydrofluoric Acid Matrix

Metal deposition on silicon in hydrofluoric acid (HF) solutions is a well-established process for the surface patterning of silicon. The reactions behind this process, especially the formation or the absence of molecular hydrogen (H2), are controversially discussed in the literature. In this study, several batch experiments with Ag+, Cu2+, AuCl4– and PtCl62– in HF matrix and multicrystalline silicon were performed. The stoichiometric amounts of the metal depositions, the silicon dissolution and the molecular hydrogen formation were determined analytically. Based on these data and theoretical considerations of the valence transfer, four reasons for the formation of H2 could be identified. First, H2 is generated in a consecutive reaction after a monovalent hole transfer (h+) to a Si–Si bond. Second, H2 is produced due to a monovalent hole transfer to the Si–H bonds. Third, H2 occurs if Si–Si back bonds of the hydrogen-terminated silicon are attacked by Cu2+ reduction resulting in the intermediate species HSiF3, which is further degraded to H2 and SiF62–. The fourth H2-forming reaction reduces oxonium ions (H3O+) on the silver/, copper/ and gold/silicon contacts via monovalent hole transfer to silicon. In the case of (cumulative) even-numbered valence transfers to silicon, no H2 is produced. The formation of H2 also fails to appear if the equilibrium potential of the 2H3O+/H2 half-cell does not reach the energetic level of the valence bands of the bulk or hydrogen-terminated silicon. Non-hydrogen-forming reactions in silver, copper and gold deposition always occur with at least one H2-forming process. The PtCl62– reduction to Pt proceeds exclusively via even-numbered valence transfers to silicon. This also applies to the reaction of H3O+ at the platinum/silicon contact. Consequently, no H2 is formed during platinum deposition.