Electrode position scaling in realistic laplacian computation

This note discusses the effects of the electrode position scaling on the realistic Laplacian (RL) computation. It is shown that when the RL is estimated with the help of Tikhonov regularization and the generalized cross-validation (GCV) criterion, improper electrode position scaling may influence the GCV criterion, which results in the decrease of RL precision. We identify what the proper scaling should be, and we provide a closer examination of how the GCV criterion is affected by the electrode position scaling.      

An expanding carbon cap-and-trade regime? A decade of experience with RGGI charts a path forward

On carbon, states have been forced by federal inaction to take matters into their own hands. Over a dozen states are participating in or considering CO₂ cap-and-trade regimes. The oldest – the Regional Greenhouse Gas Initiative – has in a decade achieved emission reductions through joint state implementation and efficient market-based carbon pollution control. The initiative also has yielded $5 billion in economic benefits and tens of thousands of jobs. RGGI thus charts a path forward for states seeking a practical approach to carbon reduction in the absence of federal leadership.     

Synthesis and In Vitro Evaluation of C-7 and C-8 Luteolin Derivatives as Influenza Endonuclease Inhibitors

The part of the influenza polymerase PA subunit featuring endonuclease activity is a target for anti-influenza therapies, including the FDA-approved drug Xofluza. A general feature of endonuclease inhibitors is their ability to chelate Mg²⁺ or Mn²⁺ ions located in the enzyme’s catalytic site. Previously, we screened a panel of flavonoids for PA inhibition and found luteolin and its C-glucoside orientin to be potent inhibitors. Through structural analysis, we identified the presence of a 3′,4′-dihydroxyphenyl moiety as a crucial feature for sub-micromolar inhibitory activity. Here, we report results from a subsequent investigation exploring structural changes at the C-7 and C-8 positions of luteolin. Experimental IC₅₀ values were determined by AlphaScreen technology. The most potent inhibitors were C-8 derivatives with inhibitory potencies comparable to that of luteolin. Bio-isosteric replacement of the C-7 hydroxyl moiety of luteolin led to a series of compounds with one-order-of-magnitude-lower inhibitory potencies. Using X-ray crystallography, we solved structures of the wild-type PA-N-terminal domain and its I38T mutant in complex with orientin at 1.9 Å and 2.2 Å resolution, respectively.     

In situ Y2Si2O7 coatings on SiC fibers: Thermodynamic analysis and processing

It is shown using thermodynamic analysis and kinetic modeling that a processing window exists for the formation of Y₂Si₂O₇ coatings on SiC. The proposed method is validated using an experimental procedure in which the in situ formation of Y₂Si₂O₇ on a commercial SiC-based fiber is demonstrated. The method involves the deposition of YPO₄ on preoxidized fine diameter SiC-based fibers, and heat treating the coated fibers within a calculated processing window of oxygen partial pressure, temperature, degree of preoxidation, and coating thickness. The results are promising for the development of environmentally resistant interfacial coatings for SiC-fiber reinforced SiC-based matrix composites. The proposed and validated approach allows a low-cost method to obtain continuous hermetic coatings on SiC fibers with interfacial properties adequate for tough composite behavior that resists degradation under turbine engine conditions.     

Minimization of the Theoretical Error of Input Parameters for a Vapor Permeation Apparatus

All input experimental errors for membrane flux determination were analyzed. The overall error in pressure did not largely influence the determination of membrane flux. The main contribution to errors was ascribed to flow meters and membrane thickness. The choice of an optimal operational range for input parameters led to elimination of at least 2/3 of the theoretical relative error for subsequent evaluation of the permeability of individual species. This is especially valuable for low‐permeable membranes, whereas a very low relative theoretical error can be obtained in the case of highly permeable materials.     

Evidence of Strict Stereospecificity in the Structure of sn‐1,2‐Diacyl‐3‐Acetyl‐Glycerols from Euonymus maximowiczianus Seeds Using Nuclear Magnetic Resonance Spectroscopy

Asymmetric, optically active sn‐1,2‐diacyl‐3‐acetyl‐glycerols (AcDAG) have been known to scientists for several decades. However, to date, the problem of their structure has not been definitely resolved, which has led to a vast diversity of terms used for their designation in the literature. Using two‐dimensional nuclear magnetic resonance, we have investigated AcDAG from the mature seeds of Euonymus maximowiczianus, from which we have been able to both identify a correlation of the methyl group in acetic acid residue with protons at the carbon atom at sn‐3 position in the glycerol residue of the AcDAG molecule and, for the first time, demonstrate that this correlation is observed exclusively with one carbon atom at the α‐position, but not with two as would have been expected in case of a racemic mixture. Moreover, results of our analysis of AcDAG isolated from the seeds of E. maximowiczianus directly confirm that diacylglycerol‐3‐acetyl‐transferase is responsible for their biosynthesis, which reveals a strict specificity not only to acetyl‐CoA as one of the substrates but also to the sn‐3‐position of the glycerol residue in sn‐1,2‐diacylglycerol during their biosynthesis.     

Molecular dynamics simulation of diffusion of O2 and CO2 in amorphous poly(ethylene terephthalate) and related aromatic polyesters

The diffusion of small molecules through polymers is important in many areas of polymer science, such as gas barrier and separation membrane materials, polymeric foams, and in the processing and properties of polymers. Molecular simulation techniques have been applied to study the diffusion of oxygen and dioxide of carbon as small molecule penetrants in models of bulk amorphous poly(ethylene terephthalate) and related aromatic polyesters. A bulk amorphous configuration with periodic boundary conditions is generated into a unit cell whose dimensions are determined for each of the simulated aromatic polyesters in the cell to have the experimental density. The aim for this research is to explore and investigate the diffusion of gases through bulk amorphous poly(ethylene terephthalate) and related aromatic polyesters. The diffusion coefficients for O₂ and CO₂ were determined via NVE molecular dynamics simulations using the Dreiding 2.21 molecular mechanics force field over a range of temperatures (300, 500 and 600 K) using up to 30 ns simulation time. We have focussed on the influence of the temperature, polymer dynamics, number of aromatic rings, ortho-, meta-, para-isomers, density and free volume distribution on the diffusion properties. Correlation of diffusion coefficients with free volume, temperature, number of aromatic rings, ortho-, meta- and para-isomers was found.     

Morphological features of porous silicon carbide obtained via a carbothermal method

Samples of porous silicon carbide were obtained using sucrose or carbon and aerosil or silica mesoporous molecular sieves (SBA‐3, SBA‐15, KIT‐6 and MCF). Fibers content in silicon carbide samples is higher when the mesopore surface area of carbon materials derived from carbon‐silica composites is lower. Based on the found correlation between the morphology and porosity of SiC and mesopore surface area of the carbon component in the composites, a templating action of carbon in carbothermal reduction was suggested.     

Corrosion of YBCO bulk superconductor in air

A corrosion process caused by reaction of surfaces of oxygenation cracks of YBCO bulk single‐grain superconductor with air moisture was studied. X‐ray photo‐emission spectroscopy, done on air exposed (001) surfaces, confirmed oxygen bonds related to barium hydroxide. Thermal analyses and mass spectrometry of exposed samples has shown a release of water caused by decomposition of barium hydroxide hydrates during sample heating. The sample weight increase versus time was related to formation of barium hydroxide phases at the surfaces of oxygenation cracks. The morphological changes of these phases at heating were observed with scanning electron microscope.