Failure Evaluation of Galvanized High Carbon Steel Spring Wires

High carbon steel wires are subjected to patented heat treatment after the surface cleaning process to obtain sufficient mechanical strength and toughness properties. As a result of this process, thin lamellar pearlitic microstructural features suitable for subsequent diameter reduction processes are obtained. Before entering the hot dip zinc bath, the surface is again subjected to pre-surface preparation. Afterwards, the wires reach the targeted coating thickness depending upon the dipping time in the molten zinc bath at 450 degrees C and a bright and smooth surface finish is obtained by cooling with air or water after stripping at the exit of the bath. Various discontinuities can be observed in the galvanized layer depending on the cooling rate and surface preparation process quality. The risk of failure to the galvanized wire due to these discontinuities during subsequent shaping or during diameter reduction is very high. In this study, a failure analysis was carried out on galvanized spring steel. The results showed that the failure is related to two main factors: the relatively poor surface quality and the unsuitable cooling rate of the wires after exiting from the galvanizing bath. In order to explain the origin of the failure, systematic metallographic investigations were performed by means of scanning electron microscope on both the wire surface and zinc layer cross-section. Mechanical behavior of wire was investigated on lifespan testing

Oxidation kinetics of hercynite spinels for solar thermochemical fuel production

The development of an economically viable solar thermochemical fuel production process relies largely on identifying redox active materials with optimized thermodynamic and kinetic properties. Iron aluminate (FeAl2O4, hercynite) and cobalt-iron aluminate (CoxFe1-xAl2O4) have both been demonstrated as viable redox-active materials for this process. However, doping with cobalt creates a tradeoff between the thermodynamics and kinetics of H2 production mediated by hercynite in which the kinetics are improved at the expense of lowering the yield. In this work, we evaluate four spinel aluminate materials with varying cobalt contents (FeAl2O4, Co0.05Fe0.95Al2O4, Co0.25Fe0.75Al2O4, and Co0.40Fe0.60Al2O4) to better understand the role of cobalt in the redox mediating properties of these materials and to quantify its effect on the thermodynamic and kinetic properties for CO2 reduction. A solid-state kinetic analysis was performed on each sample to model its CO2 reduction kinetics at temperatures ranging from 1200 °C to 1350 °C. An F1 model representative of first-order reaction kinetics was found to most accurately represent the experimental data for all materials evaluated. The computed rate constants, activation energies, and pre-exponential factors all increase with increasing cobalt content. High temperature in-situ XPS was utilized to characterize the spinel surfaces and indicated the presence of metallic states of the reduced cobalt-iron spinel, which are not present in un-doped hercynite. These species provide a new site for the CO2 reduction reaction and enhance its rate through an increased pre-exponential factor

Prevalence, characteristics, and impacts of work-related musculoskeletal disorders: a survey among physical therapists in the State of Kuwait

<p>Abstract</p> <p>Background</p> <p>Physical therapists working in the State of Kuwait are at risk of work-related musculoskeletal disorders (WMSDs). However, prevalence rates and risk factors are not well documented. The objective of this study was to determine the prevalence, characteristics, and impacts of WMSDs among physical therapists in the State of Kuwait.</p> <p>Methods</p> <p>A self-administered questionnaire was distributed to 350 physical therapists. The questionnaire gathered demographic data as well as information on occurrence of musculoskeletal complaints in the previous 12 months. Descriptive statistics, frequency, and Chi-square analyses were used.</p> <p>Results</p> <p>The response rate to the questionnaire was 63% (222/350). Of the 212 responders included in the study, the one-year prevalence of WMSDs was 47.6%, with lower back complaints as the most common (32%). This was followed by neck (21%), upper back (19%), shoulder (13%), hand/wrist (11%), knee (11%), ankle/foot (6%), elbow (4%), and hip/thigh (3%) complaints. The frequency of WMSDs was not gender related (except lower back, neck, and shoulder complaints) nor was it related to age (except lower back complaints), working venues (except hand/wrist), working hours, area of specialty, or exercise. WMSDs' impact on work was minor.</p> <p>Conclusions</p> <p>WMSDs among physical therapists in Kuwait were common, with lower back and neck affected most. Lower back and neck WMSDs were related to the participant's demographics. Hand/wrist WMSDs were related to work settings. Further research is needed to investigate the effect of risk factors as physical load, psychosocial load, and general health status on prevalence musculoskeletal disorders.</p

Work-related musculoskeletal disorders among Nigerian Physiotherapists

<p>Abstract</p> <p>Background</p> <p>Physiotherapists are known to be prone to Work- related musculoskeletal disorders (WRMDs) but its prevalence among physiotherapists in Nigeria has not been reported. This study investigated the prevalence and work factors of WRMDs among physiotherapists in Nigeria.</p> <p>Methods</p> <p>A cross- sectional survey was administered to physiotherapists in different parts of Nigeria using a 2- part questionnaire with items adopted from questionnaires used for similar studies around the world. Two hundred and seventeen copies of the questionnaire were distributed for self administration but 126 physiotherapists returned completed surveys for a 58.1% response. The data were analyzed using SPPS version 10 at alpha level of 0.05. Descriptive statistics of frequency and percentages and inferential statistics of <it>x</it>²were used as appropriate for data analysis.</p> <p>Results</p> <p>Reported 12- month prevalence of WRMDs among Nigerian physiotherapists was 91.3%. Prevalence of WRMDs was significantly higher in female physiotherapists (p = 0.007) and those with lower body mass index (p = 0.045). The low back (69.8%) was the most commonly affected body part, followed by the neck (34.1%). Fifty percent of the physiotherapists first experienced their WRMDs within five years of graduation and the highest prevalence (61.7%) was found among physiotherapists younger than 30 years. Treating large number of patients in a day was cited by most (83.5%) of the respondents as the most important work factor for their WRMDs. The most commonly adopted coping strategy identified was for the therapists to modify their position and/or the patient's position (64.3%). Majority of the respondents (87.0%) did not leave the profession but 62.6% changed and/or modified their treatment because of their WRMDs.</p> <p>Conclusion</p> <p>The prevalence of WRMDs among physiotherapists in Nigeria is higher than most values reported for their counterparts around the world. The coping strategies and work factors of WRMDs among Nigerian physiotherapists are mostly similar to those of their counterparts elsewhere.</p

Downregulation of Integrin β4 Decreases the Ability of Airway Epithelial Cells to Present Antigens

Airway epithelial cells have been demonstrated to be accessory antigen presentation cells (APC) capable of activating T cells and may play an important role in the development of allergic airway inflammation of asthma. In asthmatic airways, loss of expression of the adhesion molecule integrin β4 (ITGB4) and an increase in Th2 inflammation bias has been observed in our previous study. Given that ITGB4 is engaged in multiple signaling pathways, we studied whether disruption of ITGB4-mediated cell adhesion may contribute to the adaptive immune response of epithelial cells, including their ability to present antigens, induce the activate and differentiate of T cells. We silenced ITGB4 expression in bronchial epithelial cells with an effective siRNA vector and studied the effects of ITGB4 silencing on the antigen presentation ability of airway epithelial cells. T cell proliferation and cytokine production was investigated after co-culturing with ITGB4-silenced epithelial cells. Surface expression of B7 homologs and the major histocompatibility complex (MHC) class II was also detected after ITGB4 was silenced. Our results demonstrated that silencing of ITGB4 resulted in impaired antigen presentation processes and suppressed T cell proliferation. Meanwhile, decrease in Th1 cytokine production and increase in Th17 cytokine production was induced after co-culturing with ITGB4-silenced epithelial cells. Moreover, HLA-DR was decreased and the B7 homologs expression was different after ITGB4 silencing. Overall, this study suggested that downregulation of ITGB4 expression in airway epithelial cells could impair the antigen presentation ability of these cells, which further regulate airway inflammation reaction in allergic asthma

The Role of Alveolar Epithelial Cells in Initiating and Shaping Pulmonary Immune Responses: Communication between Innate and Adaptive Immune Systems

Macrophages and dendritic cells have been recognized as key players in the defense against mycobacterial infection. However, more recently, other cells in the lungs such as alveolar epithelial cells (AEC) have been found to play important roles in the defense and pathogenesis of infection. In the present study we first compared AEC with pulmonary macrophages (PuM) isolated from mice in their ability to internalize and control Bacillus Calmette-Guérin (BCG) growth and their capacity as APCs. AEC were able to internalize and control bacterial growth as well as present antigen to primed T cells. Secondly, we compared both cell types in their capacity to secrete cytokines and chemokines upon stimulation with various molecules including mycobacterial products. Activated PuM and AEC displayed different patterns of secretion. Finally, we analyzed the profile of response of AEC to diverse stimuli. AEC responded to both microbial and internal stimuli exemplified by TLR ligands and IFNs, respectively. The response included synthesis by AEC of several factors, known to have various effects in other cells. Interestingly, TNF could stimulate the production of CCL2/MCP-1. Since MCP-1 plays a role in the recruitment of monocytes and macrophages to sites of infection and macrophages are the main producers of TNF, we speculate that both cell types can stimulate each other. Also, another cell-cell interaction was suggested when IFNs (produced mainly by lymphocytes) were able to induce expression of chemokines (IP-10 and RANTES) by AEC involved in the recruitment of circulating lymphocytes to areas of injury, inflammation, or viral infection. In the current paper we confirm previous data on the capacity of AEC regarding internalization of mycobacteria and their role as APC, and extend the knowledge of AEC as a multifunctional cell type by assessing the secretion of a broad array of factors in response to several different types of stimuli

Isolation and Characterization of Intestinal Epithelial Cells from Normal and SIV-Infected Rhesus Macaques

Impairment of intestinal epithelial barriers contributes to the progression of HIV/SIV infection and leads to generalized HIV-induced immune-cell activation during chronic infection. Rhesus macaques are the major animal model for studying HIV pathogenesis. However, detailed characterization of isolated rhesus epithelial cells (ECs) from intestinal tissues is not well defined. It is also not well documented whether isolated ECs had any other cell contaminants from intestinal tissues during the time of processing that might hamper interpretation of EC preparations or cultures. In this study, we identify and characterize ECs based on flow cytometry and immunohistochemistry methods using various enzymatic and mechanical isolation techniques to enrich ECs from intestinal tissues. This study shows that normal healthy ECs differentially express HLA-DR, CD23, CD27, CD90, CD95 and IL-10R markers. Early apoptosis and upregulation of ICAM-1 and HLA-DR in intestinal ECs are thought to be the key features in SIV mediated enteropathy. The data suggest that intestinal ECs might be playing an important role in mucosal immune responses by regulating the expression of different important regulatory and adhesion molecules and their function