Solid source MBE growth of InAsP/InP quantum wells

Strained InAsP multiquantum wells (MWQs) were grown on InP(100) substrates by solid source molecular beam epitaxy and were characterized to relate structural and optical quality to growth conditions. The multiquantum wells were grown using either dimer or tetramer arsenic (As₂ or As₄) over the substrate temperature range of 420–535°C. θ-2θ x-ray diffraction measurements showed only slight differences between arsenic compositions in the quantum wells grown with As₂ or As₄. 300K and 8K photoluminescence full width at half max (FWHM) decreased at higher growth temperatures regardless of the arsenic species used. The 8K photoluminescence FWHM and the surface roughness measured by atomic force microscopy are found to be less sensitive to substrate growth temperature for the multiquantum wells growth with As₂ as opposed to As₄.     

Sericin Enhances the Bioperformance of Collagen-Based Matrices Preseeded with Human-Adipose Derived Stem Cells (hADSCs)

Current clinical strategies for adipose tissue engineering (ATE), including autologous fat implants or the use of synthetic surrogates, not only are failing in the long term, but also can’t face the latest requirements regarding the aesthetic restoration of the resulted imperfections. In this context, modern strategies in current ATE applications are based on the implantation of 3D cell-scaffold bioconstructs, designed for prospective achievement of in situ functional de novo tissue. Thus, in this paper, we reported for the first time the evaluation of a spongious 60% collagen and 40% sericin scaffold preseeded with human adipose-derived stem cells (hADSCs) in terms of biocompatibility and adipogenic potential in vitro. We showed that the addition of the sticky protein sericin in the composition of a classical collagen sponge enhanced the adhesion and also the proliferation rate of the seeded cells, thus improving the biocompatibility of the novel scaffold. In addition, sericin stimulated PPARγ2 overexpression, triggering a subsequent upregulated expression profile of FAS, aP2 and perilipin adipogenic markers. These features, together with the already known sericin stimulatory potential on cellular collagen production, promote collagen-sericin biomatrix as a good candidate for soft tissue reconstruction and wound healing applications.     

The origin of shallow n-type conductivity in boron-doped diamond with H or S co-doping: Density functional theory study

The ionization potentials and the electron affinities of doped diamond were calculated using B3LYP hybrid density functional theory and nanocrystalline cluster models, while taking into account the quantum confinement of the charge carriers. In many cases donor and acceptor levels were created in the middle of the gap between the conduction and valence bands. A possible explanation for the n-type behavior created by co-doping diamond films with boron and sulfur is given in terms of thermally activated electron donation from an SVS (V is vacancy) donor to a BB acceptor band. Both lie deep in the band gap. It is proposed that electrons in the BB acceptor band are mobile charge carriers. It is also proposed that the conversion of boron-doped diamond from p-type conductivity, with hole charge carriers in the top of the valence band, to n-type conductivity, following treatment in a deuterium plasma, may arise from formation of interstitial hydrogen donor levels and B_nH_m acceptor levels that create an acceptor band in which electrons are mobile. Again, both are deep in the band gap of pure diamond. In a prior attempt to explain this n-type behavior, BH_n defects with unrelaxed structures were proposed to be shallow donors to the diamond conduction band. This paper shows that these defects become deep donors when their structures are optimized. Finally, defects created from vacancies with 1 to 4 H in them are shown to be deep donors to the diamond conduction band.     

KINETICS OF CADMIUM ION SORPTION ON ION EXCHANGE AND CHELATING RESINS

ABSTRACT

Cadmium sorption from aqueous solutions on sulfonic (C-150) and iminodiacetic (S-930) Purolite macroporous resins was investigated. The influence of operating variables such as initial pH, Cd(H) concentration, time and temperature on the equilibrium parameters was measured. The ion preference and sorption ability of resins, i.e. binding constant (b) and saturation capacity {x_m), derived from sorption isotherm, depend on the functional group structure. The Cd(II) uptake is only particle diffusion controlled. The kinetic parameters, i.e. t_1/2 values for 50 % attainment of equilibrium sorption, rate constant (K¯ ) and diffusion coefficient (D¯) are higher on the sulfonic resin. The “moving boundary” particle diffusion model fits the entire ion sorption process on chelating resin, but only the initial sorption on the sulfonic resin, confirming the difference in chemistry between chelation and ion exchange.     

Interaction between myoglobin and hyaluronic acid in layer-by-layer structures—An electrochemical study

The layer-by-layer (LBL) self-assembled film construction of the biocompatible polymer hyaluronic acid (HA) and single heme redox protein, myoglobin (Mb) is described. The films were built upon gold electrode substrates, both gold quartz crystal electrodes and bulk gold (Au(bulk)) electrodes, and formation of the LBL films was gravimetrically monitored by an electrochemical quartz crystal microbalance. The electrochemical properties of the hyaluronic acid/myoglobin films ({HA/Mb}_n) were investigated after each deposition step using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The CV response presented an oxidation peak at +0.3 V vs. SCE, not characteristic of the redox protein myoglobin, and, the peak current decreased slightly with each additional bilayer. CV at Au(bulk) electrodes in pH 5.0 acetate buffer solution, containing Mb, presented the same oxidation peak as observed at {HA/Mb}_n modified electrodes, confirming the presence of the same electroactive species. The Mb oxidation peak current depends linearly on scan rate, characteristic of adsorbed thin-layer electrochemical systems, attributed to free adsorbed heme. Impedance spectra, recorded after deposition of each bilayer, were in agreement with the cyclic voltammetry observations.     

Morphological instability leading to formation of porous anodic oxide films

Electrochemical oxidation of metals, in solutions where the oxide is somewhat soluble, produces anodic oxides with highly regular arrangements of pores. Although porous aluminium and titanium oxides have found extensive use in functional nanostructures, pore initiation and self-ordering are not yet understood. Here we present an analysis that examines the roles of oxide dissolution and ionic conduction in the morphological stability of anodic films. We show that patterns of pores with a minimum spacing are possible only within a narrow range of the oxide formation efficiency (the fraction of oxidized metal atoms retained in the film), which should exist when the metal ion charge exceeds two. Experimentally measured efficiencies, over diverse anodizing conditions on both aluminium and titanium, lie within the different ranges predicted for each metal. On the basis of these results, the relationship between dissolution chemistry and the conditions for pore initiation can now be understood in quantitative terms.     

Copolymerization of a bisanthracene compound with bismaleimides by Diels–Alder cycloaddition

Four new polymers have been synthesized via succesive Diels–Alder cycloadditions of a bisdiene compound bearing two anthracene groups and four bisdienophiles, all containing bismaleimide functions. The polycondensation reaction was performed in N,N‐dimethylacetamide at 120 °C leading to polymers soluble in polar solvents having molecular weights lower than 6000 g mol^?1. © 2001 Society of Chemical Industry     

Remote calibration using mobile, multiagent technology

Instrument calibration, though unavoidable, is extensively time and resource consuming. It often involves a distinct layer of data management and security. Since many of the available digital instruments are provided with communication interfaces, one can build a remote calibration system from the actual hardware and a computing unit with Internet connection capabilities. This paper, after showing a simple client-server architecture, discusses how the use of mobile, multiagent techniques is expected to solve most of the security issues, working as well and effectively as a traditional, agent-free client-server architecture.     

Quantitative prediction of body diameter in severely obese individuals

The prevalence of obesity and severe obesity continues to increase in the developed world. Apart from obesity's strong association with a variety of health conditions, severely obese individuals (i.e. > or = 300 lb [136 kg]) sometimes have difficulty with ambulation, and often cannot use regular sized clothes, furniture, and assistive devices such as walkers and wheelchairs. The purpose of this study was to assess the relationship between linear body measurements (anthropometry) and weight in severely obese people in order to generate equations to predict such measurements from weight alone. Various body size measurements were obtained from three independent data sets (74 severely obese individuals evaluated at the New York Obesity Research Center, 103 severely obese individuals who participated in the National Center for Health Statistics' National Health and Nutrition Examination Survey III, and a further 90 severely obese individuals evaluated at the New York Obesity Research Center). Linear regression analyses revealed that for each increase of 10 kg (22.04 lb) above 136 kg (300 lb), body diameter measurements increase by 0.9-1.1 cm. These analyses provide body size-to-weight estimates that may help manufacturers develop products and services that are more appropriate for increasing numbers of severely obese individuals.