Study on the influence of temperature on the surface asperity in micro cross wedge rolling

When the common deformation processes are scaled down to micro/meso dimensions, size effect is the particular phenomena in microforming, which is related to the dominant influence of single grains inside the micropart. The conventional cross wedge rolling (CWR) is introduced into the micro scale in order to take the advantages of CWR. The micro cross wedge rolling (MCWR) has to confront with the phenomena of size effect that occurs in the common microforming processes inevitably. One of the approaches to compensate size effect is to increase the deforming temperature. An increased formability is achieved because more slip systems of polycrystal metal are activated at the elevated temperature. This reduces the anisotropic material behavior resulting in a more homogeneous forming with improved reproducibility. In this study, a YAG laser beam is applied to heat the workpiece. Finite element model (FEM) associated with a material constitutive formulation considering dislocation mechanics is set up to simulate the MCWR of pure copper utilizing the laser heating. The surface asperity as an indication of material heterogeneity in micro scale is quantitatively analysed. The simulation results show a good agreement with experimental results in terms of the surface asperity. © 2013 AIP Publishing LLC

Purification and biochemical characterization of a serine alkaline protease TC4 from a new isolated Bacillus alcalophilus TCCC11004 in detergent formulations

An extracellular alkaline protease producing strain was isolated from alkaline soil and identified as Bacillus alcalophilus TCCC11004 on the basis of 16S rDNA gene sequencing and biochemical properties. The most appropriate medium for the protease production was composed of (g/l): maltodextrin 110, yeast extract 17.5, cotton seed meal 29.3, K2HPO4 18, trisodium citrate 3.3 and CaCl2 2.6. The alkaline protease TC4 was purified from the culture supernatant by ammonium sulfate precipitation, Sephadex G-75 gel filtration and SP-Sepharose HP ion exchange chromatography, with a 6.8 fold increase in specific activity and 15.2% recovery. The molecular weight was estimated to be 26 kDa on SDS-PAGE. The protease was highly active from pH 9.0-12.0 with an optimal at pH 11.0. It was active at 30 - 60°C and exhibited maximal activity at 50°C. The thermostability of the protease was increased by the addition of CaCl2. It retained 70 and 81% of its initial activity after heating for 2 h at 50°C, in the absence or presence of 2 mM CaCl2, respectively. The enzyme was inactivated by diisopropyl fluorophosphate and phenylmethylsulfonyl fluoride, suggesting that it is a serine protease. The protease was stable in 0.5% SDS and retained 70.3% of its initial activity after 1 h of incubation. It was active in the presence of 3% Triton X-100 with 100% activity and stable towards oxidizing agent with 69.2% activity in the presence of 1% H2O2. The enzyme showed excellent compatibility with commercial detergents such as TaiZi, BiLang, DiaoPai and TianQing, retaining more than 90% of its initial activity in the tested detergents after 1 h of preincubation at 40°C.Keywords: Serine alkaline protease, Bacillus alcalophilus, stability, detergent compatibility

Scalp acupuncture for acute ischemic stroke: a meta-analysis of randomized controlled trials

Scalp acupuncture (SA) is a commonly used therapeutic approach for stroke throughout China and elsewhere in the world. The objective of this study was to assess clinical efficacy and safety of SA for acute ischemic stroke. A systematical literature search of 6 databases was conducted to identify randomized controlled trials (RCTs) of SA for acute ischemic stroke compared with western conventional medicines (WCMs). All statistical analyses were performed by the Rev Man Version 5.0. Eight studies with 538 participants were included in the studies. The studies were deemed to have an unclear risk of bias based on the Cochrane Back Review Group. Compared with the WCM, 6 RCTs showed significant effects of SA for improving neurological deficit scores (P < 0.01); 4 RCTs showed significant effects of SA for favoring the clinical effective rate (P < 0.01) However, the adverse events have not been documented. In conclusion, SA appears to be able to improve neurological deficit score and the clinical effective rate when compared with WCM, though the beneficial effect from SA is possibly overvalued because of generally low methodology of the included trials. No evidence is available for adverse effects. Rigorous well-designed clinical trials are needed.published_or_final_versio

Tellurium quantum dots: Preparation and optical properties

Herein, we report an effective and simple method for producing Tellurium Quantum dots (TeQDs), zero-dimensional nanomaterials with great prospects for biomedical applications. Their preparation is based on the ultrasonic exfoliation of Te powder dispersed in 1-methyl-2-pyrrolidone. Sonication causes the van der Waals forces between the structural hexagons of Te to break so that the relatively coarse powder breaks down into nanoscale particles. The TeQDs have an average size of about 4 nm. UV-Vis absorption spectra of the TeQDs showed an absorption peak at 288 nm. Photoluminescence excitation (PLE) and photoluminescence (PL) are used to study the optical properties of TeQDs. Both the PLE and PL peaks revealed a linear relationship against the emission and excitation energies, respectively. TeQDs have important potential applications in biological imaging and catalysis as well as optoelectronics

Failure mechanisms of a SiC particles 2024Al composite under dynamic loading

Dynamic mechanical response of a 20 vol% silicon carbide particles (SiCp) reinforced 2024 Al composite prepared by powder metallurgy techniques were studied with a split Hopkinson bar. The fracture mechanisms and the deformation microstructure were examined with Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). The present results indicate that the composite has a strong SiC-Al interfacial bonding; failure of the material is mainly caused by fracture of SiC particles and tearing failure of the SiC-Al interface. This failure by interface tearing with adhesion of an aluminium layer on SiC particles on the fracture surfaces has not been reported in SiC particle-reinforced aluminium composites. High-resolution transmission electron microscopy studies showed that many of the SiC-Al interfaces have coincident site lattice structures, which are considered to make a significant contribution to the strong interfacial bonding

New plasma surface-treated memory alloys: Towards a new generation of "smart" orthopaedic materials

This paper describes the corrosion resistance, surface mechanical properties, cyto-compatibility, and in-vivo performance of plasma-treated and untreated NiTi samples. Nickel-titanium discs containing 50.8% Ni were treated by nitrogen and carbon plasma immersion ion implantation (PIII). After nitrogen plasma treatment, a layer of stable titanium nitride is formed on the NiTi surface. Titanium carbide is also found at the surface after carbon plasma implantation. Compared to the untreated samples, the corrosion resistances of the plasma PIII samples are better by a factor of five and the surface hardness and elastic modulus are better by a factor of two. The concentration of Ni leached into the simulated body fluids from the untreated samples is 30 ppm, whereas that from the plasma-treated PIII are undetectable. Although there is no significant difference in the ability of cells to grow on either surface, bone formation is found to be better on the nitrogen and carbon PIII sample surfaces at post-operation 2 weeks. All these improvements can be attributed to the formation of titanium nitride and titanium carbide on the surface. © 2007 Elsevier B.V. All rights reserved.postprin

Acupuncture for chronic neck pain: a pilot for a randomised controlled trial

Background: Acupuncture is increasingly being used for many conditions including chronic neck pain. However the evidence remains inconclusive, indicating the need for further well-designed research. The aim of this study was to conduct a pilot randomised controlled parallel arm trial, to establish key features required for the design and implementation of a large-scale trial on acupuncture for chronic neck pain. Methods: Patients whose GPs had diagnosed neck pain were recruited from one general practice, and randomised to receive usual GP care only, or acupuncture ( up to 10 treatments over 3 months) as an adjunctive treatment to usual GP care. The primary outcome measure was the Northwick Park Neck Pain Questionnaire (NPQ) at 3 months. The primary analysis was to determine the sample size for the full scale study. Results: Of the 227 patients with neck pain identified from the GP database, 28 (12.3%) consenting patients were eligible to participate in the pilot and 24 (10.5%) were recruited to the trial. Ten patients were randomised to acupuncture, receiving an average of eight treatments from one of four acupuncturists, and 14 were randomised to usual GP care alone. The sample size for the full scale trial was calculated from a clinically meaningful difference of 5% on the NPQ and, from this pilot, an adjusted standard deviation of 15.3%. Assuming 90% power at the 5% significance level, a sample size of 229 would be required in each arm in a large-scale trial when allowing for a loss to follow-up rate of 14%. In order to achieve this sample, one would need to identify patients from databases of GP practices with a total population of 230,000 patients, or approximately 15 GP practices roughly equal in size to the one involved in this study (i.e. 15,694 patients). Conclusion: This pilot study has allowed a number of recommendations to be made to facilitate the design of a large-scale trial, which in turn will help to clarify the existing evidence base on acupuncture for neck pain

High pseudocapacitive cobalt carbonate hydroxide films derived from CoAl layered double hydroxides

A thin nanosheet of mesoporous cobalt carbonate hydroxide (MPCCH) has been fabricated from a CoAl-LDH nanosheet following removal of the Al cations by alkali etching. The basic etched electrode exhibits enhanced specific capacitance (1075 F g−1 at 5 mA cm−2) and higher rate capability and cycling stability (92% maintained after 2000 cycles)