A finite element method for thermo-mechanical coupling analysis of shape memory alloys

Due to strong thermo-mechanical coupling in shape memory alloys (SMAs), heat generation/absorption during forward/reverse phase transformation can cause temperature variations in the material; influencing its mechanical behaviour. It is usually assumed that this coupling is only affected by the loading rate. But, recently studies have shown that the size of the structure and the boundary conditions are also important. Therefore, only the definition of quasistatic or slow loading rate can not guarantee an isothermal process and so further considerations need to be made. Based on the powerful model, proposed by Lagoudas et al. [1] and later improved for computer programming using the return mapping algorithm by Qidwai and Lagoudas [2], this contribution presents a three-dimensional thermo-mechanically coupled extension which describes two important typical phenomena of material model of SMAs: superelasticity and superplasticity (shape memory effect). An algorithm is then proposed to implement the coupled model into a finite element code. Performed simulations with different boundary conditions demonstrate that the both loading rate and the size dependency can be captured within the proposed framework. The results are in good agreement with available data in the literature

The effective mass of atom-radiation field system and the cavity-field Wigner distribution in the presence of a homogeneous gravitational field in the Jaynes-Cummings model

The effective mass that approximately describes the effect of a classical homogeneous gravitational field on an interacting atom-radiation field system is determined within the framework of the Jaynes-Cummings model. By taking into account both the atomic motion and gravitational field, a full quantum treatment of the internal and external dynamics of the atom is presented. By solving exactly the Schrodinger equation in the interaction picture, the evolving state of the system is found. Influence of a classical homogeneous gravitational field on the energy eigenvalues, the effective mass of atom-radiation field system and the Wigner distribution of the radiation field are studied, when initially the radiation field is prepared in a coherent state and the two-level atom is in a coherent superposition of the excited and ground states.Comment: 12 pages, 9 figure

Rapid one-step separation and purification of recombinant phenylalanine dehydrogenase in aqueous two-phase systems

Background: Phenylalanine dehydrogenase (PheDH; EC 1.4.1.20) is a NAD +-dependent enzyme that performs the reversible oxidative deamination of L-phenylalanine to phenylpyruvate. It plays an important role in detection and screening of phenylketonuria (PKU) diseases and production of chiral intermediates as well. The main goal of this study was to find a simple and rapid alternative method for purifying PheDH. Methods: The purification of recombinant Bacillus sphaericus PheDH was investigated in polyethylene glycol (PEG) and ammonium sulfate aqueous two-phase systems (ATPS). The influences of system parameters including PEG molecular weight and concentration, pH and (NH4)2SO4 concentration on enzyme partitioning were also studied. The purity of enzyme was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Results: A single extraction process was developed for separation and purification of recombinant PheDH from E. coli BL21 (DE3). The optimized conditions for partitioning and purification of PheDH were 9% (w/w) PEG-6,000 and 16% (w/w) (NH4)2SO4 at pH 8.0. The partition coefficient, recovery, yield, purification factor and specific activity values were achieved 58.7, 135%, 94.42%, 491.93 and 9828.88 U/mg, respectively. Also, the Km values for L-phenylalanine and NAD+ in oxidative deamination were 0.21 and 0.13 mM, respectively. Conclusion: The data presented in this paper demonstrated the potential of ATPS as a versatile and scaleable process for downstream processing of recombinant PheDH

Outage Probability of Wireless Ad Hoc Networks with Cooperative Relaying

In this paper, we analyze the performance of cooperative transmissions in wireless ad hoc networks with random node locations. According to a contention probability for message transmission, each source node can either transmits its own message signal or acts as a potential relay for others. Hence, each destination node can potentially receive two copies of the message signal, one from the direct link and the other from the relay link. Taking the random node locations and interference into account, we derive closed-form expressions for the outage probability with different combining schemes at the destination nodes. In particular, the outage performance of optimal combining, maximum ratio combining, and selection combining strategies are studied and quantified.Comment: 7 pages; IEEE Globecom 201

Epidemiology and the agreement rate of serological tests in human brucellosis in North East of Iran

Background: Brucellosis still remains a major health problem with different symptoms and various diagnostic methods. Diagnostic methods of brucellosis are usually based on detecting specific antibodies in the patient’s serum. Nowadays, many serological tests are applied for the diagnosis of human brucellosis. Most routine tests are serum agglutination tests based on Wright and 2-Mercaptoethanol (2-ME). Objectives: The aim of this study (cross sectional study) was to evaluate the prevalence of brucellosis and assess the degree of agreement among serum samples of suspected brucellosis serological tests routinely performed in Mashhad, Iran. Patients and Methods: This study was conducted in Mashhad from August 2011 to September 2012. Sera (2 - 3 mL) were collected from 83 cases suspected of brucellosis among 594 patients. Ten serum samples were collected from healthy subjects as control sera. Rose Bengal test for initial screening and Wright and 2 ME as standard tests were conducted to determine antibody titers. Thereafter, IgG and IgM levels were determined by the Enzyme Linked Immunosorbent Assay (ELISA) method. Results: Among 83 serum samples, Rose Bengal test was able to identify 20 (12%) positive specimens; the standard tube agglutination test was able to detect 30 (18%) positive samples, and the ELISA IgG and ELISA IgM were able to trace 42 (21%) and 13 (6.5%) positive samples, respectively. Ten control samples had negative results for the ELISA method. The results were calculated by the Kappa formula. The highest level of agreement was among 1 = KRB-SAT tests and the lowest level of agreement was among tests K ELISA IgM-IgG = 0.30. Conclusions: According to the results, brucellosis has remained endemic in this region. Most cases were detected by ELISA IgG. The highest kappa agreements were between tests KRB-SAT, KRB-IgG and KSAT-IgG, while the lowest levels of agreement were between tests SAT-IgM and ELISA IgM-IgG. Considering that ELISA IgM results are covered by SAT and ELISA IgG test results, applications of this test do not seem necessary. © 2015, Infectious Diseases and Tropical Medicine Research Center