Antibacterial electrospun chitosan/poly(vinyl alcohol) nanofibers containing silver nitrate and titanium dioxide

Chitosan/poly(vinyl alcohol) (PVA) nanofibers with antibacterial activity were prepared by the electrospinning of a chitosan/PVA solution with a small amount of silver nitrate (AgNO₃) and titanium dioxide (TiO₂). Nanofibers with diameters of 270–360 nm were obtained. The yield of low‐viscosity chitosan (LCS)/PVA nanofibers was higher than that of high‐viscosity chitosan (HCS)/PVA, and the water content of the HCS/PVA nanofibers and the LCS/PVA nanofibers were 430 and 390%, respectively. The nanofibers developed in this study exhibited antibacterial activities of 99 and 98% against Staphylococcus aureus and Escherichia coli, respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Prediction of bitumen content in oil sand based on FT-IR measurement

FT-IR spectra of bitumen are utilized to propose simple prediction method of bitumen content in oil sand. Analysis and fractionation of Athabasca oil sand were carried out by standard method. A fraction of bitumen dissolved in tetrahydrofuran (THF) was 9.1 wt% and insoluble fraction was found as concomitantly clean clay (sand). The asphaltene fraction of oil sand was 1.42 wt%, which has higher sulfur content and lower H/C molar ratio than that of maltene. The clean clay and bitumen were used to prepare clay/bitumen composites. FT-IR spectra of different clay/bitumen composite were measured and compared. From analysis of the absorbance data, the empirical equation to predict bitumen content in oil sand was acquired using linear least square fitting. Using this equation, bitumen content of Athabasca oil sand was predicted to have a value of 10.5 wt% which is similar to 9.1 wt% of bitumen content extracted by THF solvent from oil sand.     

Investigation into High-Temperature Interfacial Strength of Heat-Resisting Alloy Deposited by Laser Melting Process

Metals and Materials International - This paper presents an investigation of the interfacial strength between a material deposited on a substrate via direct energy deposition (DED) process. Using...     

In situ sintered silver decorated 3D structure of cellulose scaffold for highly thermoconductive electromagnetic interference shielding epoxy nanocomposites

This study presents a 3-dimensional (3D) network structure of cellulose scaffold (CS), which was in situ decorated with silver nanoparticles (AgNPs). The scaffold was then infiltrated with epoxy matrix and cured at elevated temperature to sinter the AgNPs; finally, highly thermoconductive epoxy composites (Ag@CS/epoxy) was obtained. The resultant Ag@CS20/epoxy composite reached a thermal conductivity of 2.52 W·m⁻¹·K⁻¹ at 2.2 vol% of filler loading, which shows an enhancement of over 11-folds in the thermal conductivity compared to the neat epoxy. The superb electrical conductivity value of over 53,691 S·m⁻¹ of the Ag@CS20/epoxy was achieved, which led to exceptional EMI SE values of 69.1 dB. Furthermore, surface temperatures during heating and cooling were also investigated to demonstrate the superior heat dissipating capacity of the Ag@CS/epoxy composite, which can be potentially put an application as thermal dissipating material in the next generation of electronics.     

The Role of the Gut Microbiota in the Gut–Brain Axis in Obesity: Mechanisms and Future Implications

Interaction between the gut and the brain is essential for energy homeostasis. In obesity, this homeostasis is disrupted, leading to a positive energy balance and weight gain. Obesity is a global epidemic that affects individual health and strains the socioeconomic system. Microbial dysbiosis has long been reported in obesity and obesity-related disorders. More recent literature has focused on the interaction of the gut microbiota and its metabolites on human brain and behavior. Developing strategies that target the gut microbiota could be a future approach for the treatment of obesity. Here, we review the microbiota–gut–brain axis and possible therapeutic options.     

Residual stress characteristics in a non-circular drawing sequence of pearlitic steel wire

In this paper, characteristics of residual stress in pearlitic steel wire drawn by a non-circular drawing (NCD) sequence with two processing routes, NCDA and NCDB, were experimentally and numerically investigated up to the 12th pass in comparison with conventional wire drawing (WD). For experimental investigation of the axial residual stress at the surface of the drawn wire, destructive (deflection) and non-destructive methods were employed. According to the experimental results, axial surface residual stress of the drawn wire by the NCD sequence was lower and more homogeneous compared to the conventional WD. Based on the elasto-plastic numerical simulation results from the surface to the center of the drawn wire using a commercial DEFORM-3D, an empirical relationship between residual stress and reduction of area was determined to predict the residual stress evolution in the multi-pass WD, NCDA, and NCDB, in that order. From the results of this investigation, it can be construed that the NCD sequence, especially the NCDB, might be helpful in improving the residual stress characteristics of pearlitic steel wire to improve its mechanical behavior and service life.     

Design and dynamic analysis of an arch-type desktop reconfigurable machine

This paper describes the development of a three-degrees-of-freedom (DOF) desktop reconfigurable machine tool. Recently, numerous micro-components or systems in various areas such as biomedical micro-electro-mechanical systems (MEMS) often require dedicated, precise, and cost-efficient manufacturing processes to cope with large product demand fluctuations in the global market. A downscaled desktop manufacturing machine that can control multi-DOF motions rapidly and smoothly on the basis of a reduced machine size was developed to meeting this demand. In this paper, the conceptual design of a desktop reconfigurable machine, which is capable of controlling the three DOF orientation of a spindle, is presented. Then, static and dynamic structural analyses are performed to characterize the effect of vibration on the manufacturing performance. The results demonstrate the feasibility of simultaneously controlling the position and orientation of the machine tool during the machining operation. Dynamic simulations and experimental results using a closed-loop control with position feedback are presented to illustrate the performance and features of the system. Unlike conventional full-scale manufacturing machines, the developed machine provides a number of advantages, including fast dynamic response, simple design, low cost, and a compact but relatively large workspace without motion singularities.     

Synthesis,electrochemical, and spectroelectrochemical properties of conductive poly-[2,5-di-(2-thienyl)-1H-pyrrole-1-(p-benzoic acid)]

Poly(ter-heteroaromatic(thiophene-pyrrole-thiophene)), PDPB, was electrochemically prepared from the 2,5-di(2-thienyl)-1H-pyrrole-1-(p-benzoic acid) (DPB) monomer using the Paal-Knorr pyrrole condensation reaction. The structure of the monomer was confirmed using ¹H-, ¹³C NMR, FT-IR and mass spectroscopy. The maximum UV–visible absorption and PL emission bands of DPB were observed at 330 nm and 500 nm, respectively. The cyclic voltammograms (CVs) recorded for the electrochemically polymerized DPB revealed a set of redox peaks at 0.65/0.53 V. The conductivity monotonically increased with respect to the applied potential from 0.0 V to 1.0 V, exhibiting a maximum conductivity of 0.18 S/cm at +0.80 V. The in situ UV–visible spectroelectrochemical analysis of PDPB revealed electronic transitions at 420 nm, 654 nm, and 870 nm corresponding to the π–π* transition, polaron, and bipolaron states, respectively. The optical band-gap (E_g) of PDPB was 2.16 eV. The color of the PDPB film transitioned yellow (at 0.0 V) to blue (at 1.0 V) when the potential was switched between the reduced and oxidized states with a good electrochromic response time (0.95 s).