Modification of crystal anisotropy and enhancement of magnetic moment of Co-doped SnO2 thin films annealed under magnetic field

Co-doped SnO₂ thin films were grown by sputtering technique on SiO₂/Si(001) substrates at room temperature, and then, thermal treatments with and without an applied magnetic field (H_TT) were performed in vacuum at 600°C for 20 min. H_TT was applied parallel and perpendicular to the substrate surface. Magnetic M(H) measurements reveal the coexistence of a strong antiferromagnetic (AFM) signal and a ferromagnetic (FM) component. The AFM component has a Néel temperature higher than room temperature, the spin axis lies parallel to the substrate surface, and the highest magnetic moment m =7 μ_B/Co at. is obtained when H_TT is applied parallel to the substrate surface. Our results show an enhancement of FM moment per Co⁺² from 0.06 to 0.42 μ_B/Co at. for the sample on which H_TT was applied perpendicular to the surface. The FM order is attributed to the coupling of Co⁺² ions through electrons trapped at the site of oxygen vacancies, as described by the bound magnetic polaron model. Our results suggest that FM order is aligned along [101] direction of Co-doped SnO₂ nanocrystals, which is proposed to be the easy magnetization axis.     

Effects of polymer doping on dielectric and electro‐optical parameters of nematic liquid crystal

Poly(isobutyl methacrylate) (PiBMA) polymer doped in pure p‐Ethoxybenzylidene p‐Heptylaniline (EBHA) mesomaterial has been investigated in the present study. The dielectric and electro‐optical parameters of EBHA having nematic phase were altered due to the addition of polymer in different concentration. The strong dopant concentration dependent nature of negative dielectric anisotropy and conductivity are the interesting results of the present polymer doped nematic liquid crystal (NLC) system. The present composite shows its useful application in low charge consumable devices due to the easy charge transportation phenomenon. The investigated polymer doped‐NLC system exhibiting increased negative dielectric anisotropy and high conductivity may prove to be advantageous for video applications in vertically aligned cells. POLYM. ENG. SCI., 55:414–420, 2015. © 2014 Society of Plastics Engineers     

Brønsted Acid‐Catalyzed Enantioselective Synthesis of Isatin‐ Derived N,S‐Acetals

The enantioselective organocatalytic nucleophilic addition of thiols to isatin‐derived ketimines has been developed utilizing only 1 mol% of an enantiopure BINOL‐derived phosphoric acid. The new protocol provides a series of isatin‐derived N,S‐acetals in high yields (up to 98%) and high enantioselectivities (up to 93% ee).

     

Detailed kinetic analysis of oil shale pyrolysis TGA data

There are significant resources of oil shale in the western United States, which if exploited in an environmentally responsible manner would provide secure access to transportation fuels. Understanding the kinetics of kerogen decomposition to oil is critical to designing a viable process. A dataset of thermogravimetric analysis (TGA) of the Green River oil shale is provided and two distinct data analysis approaches—advanced isoconversional method and parameter fitting are used to analyze the data. Activation energy distributions with conversion calculated using the isoconversional method (along with uncertainties) ranged between 93 and 245 kJ/mol. Root mean square errors between the model and experimental data were the lowest for the isoconversional method, but the distributed reactivity models also produced reasonable results. When using parameter fitting approaches, a number of models produce similar results making model choice difficult. Advanced isoconversional method is better in this regard, but maybe applicable to a limited number of reaction pathways. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Impact of p‐toluenesulfonate on polypyrrole–cobalt catalyst for oxygen reduction reaction

Polypyrrole (PPy) and polypyrrole p‐toluenesulfonate (PPy/pTS) supported cobalt (Co) catalysts have been synthesized using in situ surfactant modified chemical oxidative polymerization. These catalysts have been characterized for their structure and electrocatalytic activity employing FT‐IR, Raman, SEM, HRTEM, and electrochemical techniques. The influence of pTS on the morphology and oxygen reduction reaction (ORR) activity has been discussed in respect of the formation of polaronic and bipolaronic species. The impact of these species on the electrochemical performance has been studied using continuous cycling in acidic media. Overall, PPy/pTS‐Co is found to be the best suitable candidate among the catalysts synthesized for this study and can become an attractive substitute as a non‐noble catalyst material for cathode applications in fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2645–2651, 2013     

Change-Point Detection in Binomial Thinning Processes,with Applications in Epidemiology

Abstract

Most of the classical change-point detection schemes are designed for the sequences of independent and identically distributed (i.i.d.) random variables. In this article, motivated by the outbreak of 2009 H1N1 pandemic influenza, we develop change-point detection procedures for the susceptible–infected–recovered (SIR) epidemic model, where a change-point in the infection rate parameter signifies either the beginning or the end of an epidemic trend.

The considered model falls into a general class of binomial thinning processes, which is a Markov chain. The cumulative sum (CUSUM) change-point detection procedure is developed for this class, and its performance is evaluated. Apparently, the CUSUM stopping rule is no longer optimal for this non-i.i.d. case. It can be improved by introducing a non constant adaptive threshold. The resulting modified scheme attains a shorter mean delay and at the same time a longer expected time of a false alarm, given that a false alarm eventually occurs.

Proposed detection procedures are applied to the 2001–2012 influenza data published by the Centers for Disease Control and Prevention.     

表面改性处理钛增强纤维连接蛋白介导的成骨细胞MG-63黏附和增殖(英文)

采用化学抛光处理钛、阳极氧化和微弧氧化处理钛作为生物材料模型,研究成骨细胞MG-63在其表面的黏附和增殖机理。结果表明,阳极氧化和微弧氧化处理的钛表面通过促进MG-63细胞分泌纤维连接蛋白形成细胞外基质从而使其快速附着和伸展。另外,阳极氧化和微弧氧化处理的钛表面通过Outside-in信号传导通路,上调纤维连接蛋白及与其相关的整合素α5的转录水平,促进成骨细胞MG-63在其表面的增殖。     

Fabrication and Corrosion Resistance Evaluation of Novel Epoxy/Oxide Layer (MgO) Coating on Mg Alloy

Protection of Metals and Physical Chemistry of Surfaces - A protective novel (MgO) oxide layer (with 91.92% corrosion protection efficiency) was successfully applied on Mg–0.4%Ca alloy using...     

An electrochemical method for measurement of mass transport in polymer membranes using acetaminophen as a model system

An electrochemical approach has been used to model and measure acetaminophen transport through a microporous polycarbonate membrane. The dynamic response of a membrane covered planar electrode system was investigated to derive a simplified middle point formula, the time at which amperometric current reaches half steady state value, that provided reliable solute diffusion coefficients. Experimental values may be noise-contaminated; when this noise is significant, the diffusion coefficient by this method needs to be refined. Here a direct simulation method with a bipartite mathematical expression for current transient was used, which fitted calculated current transients to experimental data. A best fit was reached by minimising the standard deviation between the simulated and experimental current profiles. Mathematically, the simulated curve was linear operated, i.e. shifted and stretched vertically, as well as shifted and stretched horizontally to coincide with the experimental curve. The single point formula, bipartite expression and simulation approach allowed extraction of accurate diffusion values from a previously reported approximated method. The computation approach is not only valid for membrane covered electrodes, but is suitable for other experimental set ups where a one-dimensional Fickian diffusion model is valid, for example, for axial diffusion through cylindrical geometries.     

Design of Packaging Vents for Cooling Fresh Horticultural Produce

This review focuses on the design of vents in packages used for handling horticulture produce. The studies on vent designs that are conducted to obtain fundamental understanding of the mechanisms by which different parameters affect the rate and homogeneity of the airflow and the cooling process are presented. Ventilated packages should be designed in such a way that they can provide a uniform airflow distribution and consequently uniform produce cooling. Total opening area and opening size and position show a significant effect on pressure drop, air distribution uniformity and cooling efficiency. Recent advances in measurement and mathematical modelling techniques have provided powerful tools to develop detailed investigations of local airflow rate and heat and mass transfer processes within complex packaging structures. The complexity of the physical structure of the packed systems and the biological variability of the produce make both experimental and model-based studies of transport processes challenging. In many of the available mathematical models, the packed structure is assumed as a porous medium; the limitations of the porous media approach are evident during vented package design studies principally when the container-to-produce dimension ratio is below a certain value. The complex and chaotic structure within horticultural produce ventilated packages during a forced-air precooling process complicates the numerical study of energy and mass transfer considering each individual produce. Future research efforts should be directed to detailed models of the vented package, the complex produce stacking within the package, as well as their interaction with adjacent produce, stacks and surrounding environment. For the validation of the numerical models, the development of better experimental techniques taking into account the complex packaging system is also very important.