Surface Topography and Electrical Signaling: Single and Synergistic Effects on Neural Differentiation of Stem Cells

Incomplete regeneration and restoration of function in damaged nerves is a major clinical challenge. In this regard, stem cells hold much promise in nerve tissue engineering, with advantages such as prevention of scar‐tissue ingrowth and guidance of axonal regrowth. Engineering 3D and patterned microenvironments using biomaterials with chemical and mechanical characteristics close to those of normal nervous tissue has enabled new approaches for guided differentiation of various stem cells toward neural cells and possible treatment of neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's diseases. Differentiation of stem cells in a neurogenic lineage is largely affected by signals from the surrounding microenvironment (niche). The stem cell niche refers to a specific microenvironment around the stem cells, which provides specific biochemical (soluble factors) and biophysical signals (topography, electrical, and mechanical). This specified niche regulates the stem cells' behavior and fate. While the role of chemical cues in neural differentiation is well appreciated, recently, the cues presented by the physical microenvironment are increasingly documented to be important regulators of nerve cell differentiation. The single and synergistic effects of surface topography and electrical signals on neural differentiation of stem cells are reviewed.     

Improvement of UF/fiberglass mat properties used in roofing shingles through emulsion polymers and nanoclay addition

Modification of urea–formaldehyde (UF) resin binder for making fiberglass mats was aimed as a route to enhance its brittleness and improve its mechanical properties. The UF resin modifiers were chosen among pure acrylate emulsion polymers having different glass transition temperatures (T _g). Blends of 10% w/w based on dry modifiers and UF resin were prepared. The most effective modifier was chosen and 4 wt% of nanoclay was added to the UF resin for improvement of its mechanical properties. Morphologies of the fractured surface of the UF-modified films were investigated by scanning electron microscopy (SEM). Coarser texture of the fractured surface was regarded as an increased toughness of the modified UF resin. Investigation of gel time at 100 °C on various modified urea–formaldehyde resins showed that the gel time of the modified UF resins generally decreases with adding polymeric emulsions. It is decreased further when less film forming latex (higher T _g) is used in UF resin. Less film formation on the other hand, promotes easier water release during UF resin curing. Tensile and tear strength of the fiberglass mat composites have been increased up to 300 and 50%, respectively, while additional increase of 33% in tensile strength was obtained when nanoclay was incorporated into the composites. X-ray diffraction (XRD) analysis and Si-mapping through SEM were employed in order to show the dispersion and the distribution of nanoclay in the composites, respectively. The disappearance of the peak at 2θ = 7.22 confirmed the exfoliation of the employed nanoclay.     

Quality Management in Pakistan's Knitwear Industry

Although quality is a critical success factor for all types of business, its salience is to be driven home in Pakistan's business environment in general and its export-oriented business segment in Pakistan in particular. As a first part of this effort, we chose to study quality management in Pakistan's knitwear industry, whose combined share with readymade garments in Pakistan's total exports rose to 16.7% by 1997/1998. We mailed a postal self-completion questionnaire to 59 members of the Pakistan Knitwear and Sweaters Exporters Association. The response rate was 29%. It was found that Pakistan's knitwear industry was in various stages of development in quality management, with greater concentration in the quality inspection mode. Although there are attempts to graduate to quality assurance and beyond, it was found that considerable distance has yet to be traversed before Pakistan's knitwear industry acquires a quality philosophy as a part of its overall business approach industrywide. As part of a statistical test, however, advanced quality management concepts were found applicable in Pakistan, although the application is currently limited. These concepts must gain in popularity.     

Molecular dynamics simulations of transport and separation of supercritical carbon dioxide-alkane mixtures in supported membranes

The results of extensive nonequilibrium molecular dynamics (MD) simulations of flow and transport of several binary mixtures of CO₂ and an n-alkane chain, from CH₄ to C₄H₁₀, through a model porous membrane composed of three pores in series with significantly different sizes and in the presence of an external pressure gradient, are reported. The technique that we use for the simulations is a combination of the configurational-bias Monte Carlo method (used for efficient generation of molecular models of n-alkane chains) and the dual control-volume grand-canonical MD method. The selectivity of the membrane changes qualitatively as the length of the alkane chain increases, resulting in high separation factors in favor of the alkanes. Moreover, we find that, under supercritical conditions, unusual phenomena occur that give rise to direction- and pressure-dependent permeabilities for the fluids. The results, which are also in agreement with a continuum formulation of the problem, indicate that the composite nature of the membrane gives rise to the direction-dependent permeabilities. Hence, modeling flow and transport of supercritical fluid mixtures in porous materials with the type of morphology considered in this paper (such as supported porous membranes) would require using effective permeabilities that depend on both the external pressure drop and the direction along which it is applied to the materials.     

Secure FSM-based arithmetic codes

Recently, arithmetic coding has attracted the attention of many scholars because of its high compression capability. Accordingly, in this paper, a method that adds secrecy to this well-known source code is proposed. Finite state arithmetic code is used as source code to add security. Its finite state machine characteristic is exploited to insert some random jumps during source coding process. In addition, a Huffman code is designed for each state to make decoding possible even in jumps. Being prefix-free, Huffman codes are useful in tracking correct states for an authorized user when he/she decodes with correct symmetric pseudo-random key. The robustness of our proposed scheme is further reinforced by adding another extra uncertainty by swapping outputs of Huffman codes in each state. Several test images are used for inspecting the validity of the proposed Huffman finite state arithmetic coding (HFSAC). The results of several experimental key space analyses, statistical analyses, key and plaintext sensitivity tests show that HFSAC with a little effect on compression efficiency provides an efficient and secure method for real-time image encryption and transmission.     

Thermal Performance Prediction of Two-Phase Closed Thermosyphon Using Adaptive Neuro-Fuzzy Inference System

In this paper the Adaptive Neuro-Fuzzy Inference System (ANFIS) is used for the prediction of thermal efficiency and thermal resistance of a two-phase closed thermosyphon (TPCT). Aqueous suspensions of pristine multiwalled carbon nanotubes (CNTs) and functionalized CNTs with ethylene diamine were used as nanofluid in the TPCT. The experimental results regarding the TPCT performance including thermal efficiency and thermal resistance were modeled by the ANFIS technique. The ANFIS network was initiated by 70% of experimental data, and 30% of primary data were considered for testing and checking the suitability of the ANFIS model. The modeling results were compared with five arithmetical criteria. The arithmetical criteria suggested that the obtained modeling by ANFIS is valid and it could be expanded for other conditions. Also, to determine optimal ranges of experimental conditions, three-dimensional diagrams were traced by the modeling data. The proposed method of ANFIS modeling may be applied for optimization of other TPCTs with different configurations.     

Removal of malachite green (a toxic dye) from water by cobalt ferrite silica magnetic nanocomposite: Herbal and green sol-gel autocombustion synthesis

Cobalt ferrite-silica nanocomposites were synthesized in the presence of various amounts of Salix alba bark extract via the self-propagating sol-gel process. The structure, morphology and magnetic property of nanostructures was investigated and the adsorbent ability for the removal of malachite green (MG) dye from water through CoFe₂O₄SiO₂ has been reported. The products were characterized by XRD, SEM, TEM, FTIR and VSM techniques. The samples that were synthesized in the presence of more extract (20 mg extract) revealed no trace of impurity in XRD pattern and indicated more spherical and agglomerated particles on SEM images; in contrast other samples indicated Co₃O₄ as impurity besides rough and irregular spherical shapes. TEM images for sample SA20 (15.41 ± 0.65 nm size) illustrated narrow size distribution which is consistent with the SEM analysis. The saturation magnetization values continuously increase with the increasing Salix alba bark extract amount and reaches to 2.89 emu/g for SA20 sample. Investigation on MG adsorption isotherm and kinetic onto the nanocomposites were carried out as well. The experimental data best fitted to the Langmuir model and revealed a monolayer adsorption capacity of 75.5 ± 1.21 mg g^?1. The adsorption kinetic was found to follow pseudo-second-order kinetic model. Consequently, prepared nanocomposite can be used as an effective magnetic adsorbent for the MG removal from water.     

Highly Efficient Dye Removal from Aqueous Solutions Using Simple Chemical Modification of Wood Sawdust

Abstract

This study examined the efficiency of oxidized wood meal for removal of methylene blue (MB) as a typical basic dye from aqueous waste streams. The adsorption process was performed using sawdust treated with KMnO₄, K₂Cr₂O₇, and H₂O₂ oxidants. Among the tested chemical oxidants, KMnO₄ was found to be more effective for modification of sawdust for dye uptake. Based on the breakthrough analysis, the highest column capacity of 227 mg g^?1 was obtained for the KMnO₄/SD. Sorption capacity of KMnO₄ treated sawdust for dye uptake was about seven times that of untreated sawdust (SD). The nature and morphology of adsorbents were characterized by SEM, XRD, and FTIR analysis. The adsorption behavior of KMnO₄/SD was found to be a strongly pH-dependent process and the maximum adsorption efficiency was obtained at pH 10. Dye-loaded KMnO₄/SD sorbent can be regenerated using low-cost chemicals.     

Robust adaptive actuator failure compensation for a class of uncertain nonlinear systems

This paper presents a robust adaptive state feedback control scheme for a class of parametric-strict-feedback nonlinear systems in the presence of time varying actuator failures. The designed adaptive controller compensates a general class of actuator failures without any need for explicit fault detection. The parameters, times, and patterns of the considered failures are completely unknown. The proposed controller is constructed based on a backstepping design method. The global boundedness of all the closed-loop signals is guaranteed and the tracking error is proved to converge to a small neighborhood of the origin. The proposed approach is employed for a two-axis positioning stage system as well as an aircraft wing system. The simulation results show the correctness and effectiveness of the proposed robust adaptive actuator failure compensation approach.     

Water‐silver nanofluid application in a TPCT under an external magnetic field

The efficiency of a two‐phase closed thermosyphon (TPCT) with a nanofluid as the working fluid under the effects of a magnetic field is investigated experimentally. In this study the silver/water nanofluid with different concentrations (20 ppm–80 ppm) was tested. Also a magnetic field with various strengths (0.12, 0.35, and 1.2 T) was exerted on the TPCT by a permanent magnet. It was seen that the TPCT heat transfer performance and the thermophysical properties of the base fluid are affected considerably by the nanoparticle addition and magnetic field. According to the experimental results the thermal efficiency of the thermosyphon increased significantly with the nanoparticle concentration increasing as well as the magnetic field strength. The TPCT showed better performance for the highest value of concentration (80 ppm) and magnetic field (1.2 T). Moreover, the experimental results present that the thermal efficiency in the presence of a magnetic field is somewhat increased. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21006