Effect of Age-Hardening Temperature on Mechanical and Wear Behavior of Furnace-Cooled Al7075-Tungsten Carbide Composite

In this study, aluminum alloy (Al7075) composites with a 4% weight fraction of tungsten carbide (WC) were manufactured using a stir casting process and the developed composites were subjected to various ageing temperatures. An attempt has been made to predict the age-hardening temperature with the enhanced mechanical and wear properties of Al7075-WC. The result shows that the composite specimen aged at 250 °C offered maximum tensile strength and the Brinell hardness number was increased by 37.1% and 50.5%, respectively; the maximum impact energy was observed to be 92.2% for the 450 °C aged composites, compared to the non-aged Al7075-WC composites. The strength properties of the Al7075-WC composite decreased to 30.86%, 4.7%, and 24.9% when the composite specimens aged at 350 °C. The mechanical properties of the Al7075-WC composite were increased at the age-hardening temperatures from 150 °C to 250 °C and decreased from 250 °C to 350 °C. The wear testing pin-on-disc setup utilized to determine the wear characteristics of the prepared MMC with wear parameters of load and sliding distance and the wear resistance of the composite specimens increased due to ageing. The fractography analysis of the composite samples carried out by scanning electron microscope (SEM) images revealed that the fracture of the composite during the tensile test is a mixture of ductile and brittle modes.     

Biochar Synthesis from Mineral- and Ash-Rich Waste Biomass,Part 1: Investigation of Thermal Decomposition Mechanism during Slow Pyrolysis

Synthesizing biochar from mineral- and ash-rich waste biomass (MWB), a by-product of human activities in urban areas, can result in renewable and versatile multi-functional materials, which can also cater to the need of solid waste management. Hybridizing biochar with minerals, silicates, and metals is widely investigated to improve parent functionalities. MWB intrinsically possesses such foreign materials. The pyrolysis of such MWB is kinetically complex and requires detailed investigation. Using TGA-FTIR, this study investigates and compares the kinetics and decomposition mechanism during pyrolysis of three types of MWB: (i) mineral-rich banana peduncle (BP), (ii) ash-rich sewage sludge (SS), and (iii) mineral and ash-rich anaerobic digestate (AD). The results show that the pyrolysis of BP, SS, and AD is exothermic, catalyzed by its mineral content, with heat of pyrolysis 5480, 4066, and 1286 kJ/kg, respectively. The pyrolysis favors char formation kinetics mainly releasing CO₂ and H₂O. The secondary tar reactions initiate from ≈318 °C (BP), 481 °C (SS), and 376 °C (AD). Moreover, negative apparent activation energies are intrinsic to their kinetics after 313 °C (BP), 448 °C (SS), and 339 °C (AD). The results can support in tailoring and controlling sustainable biochar synthesis from slow pyrolysis of MWB.     

Correlates of carotid artery stiffness in young adults: The Bogalusa Heart Study

Decreased arterial elasticity, an independent risk factor for cardiovascular (C-V) disease, is associated with C-V risk factors in middle-aged and older individuals. However, information is limited in this regard in young adults. This aspect was examined in a community-based sample of 516 black and white subjects aged 25-38 years (71% white, 39% male). The common carotid artery elasticity was measured from M-mode ultrasonography as Peterson's elastic modulus (Ep) and relative wall thickness-adjusted Young's elastic modulus (YEM). Blacks and males had higher Ep (P < 0.05); males had higher YEM (P < 0.0001); and blacks had higher wall thickness (P < 0.01). For the entire sample adjusted for race and gender both Ep and YEM correlated significantly (P < 0.05-0.0001) with age, BMI, waist, systolic and diastolic blood pressures, heart rate, product of heart rate and pulse pressure, triglycerides, total cholesterol to HDL cholesterol ratio, insulin and glucose. In a multivariate regression model that included hemodynamic variables, systolic blood pressure, product of heart rate and pulse pressure, age, triglycerides, BMI, and male gender (for YEM only) were independent correlates of Ep (R2 = 0.38) and YEM (R2 = 0.25). When the hemodynamic variables were excluded from the model, age, triglycerides, BMI, black race (Ep only), male gender, parental history of hypertension, HDL cholesterol (inverse association), and insulin (marginal significance) remained independent correlates of Ep (R2 = 0.20) and YEM (R2 = 16). Both Ep and YEM increased (P for trend P < 0.0001) with increasing number of independent continuous risk factors (defined as values above or below the age, race, and gender-specific extreme quintiles) that were retained in the regression models. The observed increasing arterial stiffness (or decreased elasticity) with increasing number of risk factors related to insulin resistance syndrome in free-living, asymptomatic young adults has important implications for prevention.     

Effects of meconium aspiration in isolated perfused rat lungs

Our objective was to study meconium-induced lung injury in isolated perfused rat lungs exposed to anoxia. Our working hypothesis was that meconium-induced lung injury is independent of preexisting hypoxia, and that hypoxia will increase severity of lung injury observed after meconium aspiration. We compared five different groups of animals (n = 5) for pulmonary arterial pressure (PAP), weight lung changes, and TNFalpha expression. Group I had lungs instilled with 4 ml of normal saline. Group II had lungs exposed to 5 min of anoxia. Group III had lungs instilled with 4 ml of 30% filtered human meconium. Group IV had lungs exposed to 5 min of anoxia and then instilled with 4 ml of 30% filtered human meconium. Group V had lungs instilled with 4 ml of 30% unfiltered human meconium. Our subjects were adult Sprague-Dawley rats. The isolated rat lung model was prepared according to Levey and Gast (J Appl Physiol 1966;21:313-316). Lungs were ventilated with room air. Anoxia was caused by the use of N(2). The pulmonary artery was cannulated, and pulmonary arterial pressure and lung weight were measured. Lung weight and pulmonary arterial pressure were monitored for 120 min, and TNFalpha levels were measured in effluent at 15, 30, 60, and 120 min. Experiments were done at the Michael Reese Hospital (Chicago, IL). At the end of the experiment, PAP reached its highest values in group V (10.0 +/- 1.7 mmHg). Final PAPs in groups I-IV were: 4.85 +/- 0.3, 4.99 +/- 0.4, 5.93 +/- 0.3, and 7.25 +/- 0.51 mmHg, respectively). Lung wet weight increased significantly only in groups IV and V vs. group I; at 120 min, they were: 0.96 +/- 0.3 g, P < 0.01, and 1.5 g +/- 0.2 g, P < 0.01, respectively. TNFalpha levels did not change significantly over time in group I. TNFalpha is a marker as well as proprietor of pulmonary inflammatory response. TNFalpha reached its highest levels in groups IV and V: 595 and 753 pg/ml at 120 min, respectively. In conclusion, a short episode of anoxia prior to meconium aspiration may increase lung sensitivity to meconium-induced lung injury. This effect may be moderated by the TNFalpha present in the pulmonary circulation.     

A survey of knowledge, attitudes, and beliefs of house staff physicians from various specialties concerning antimicrobial use and resistance

BACKGROUND: Examination of knowledge, attitudes, and beliefs of house staff physicians will be important in developing interventions to improve antimicrobial use and prevent resistance. METHODS: A 75-item survey was distributed to house staff physicians on nonpediatric services in a university teaching hospital. Knowledge was assessed with a 10-question quiz. RESULTS: The survey was completed by 179 (67%) of 269 house staff physicians on 5 specialties. Outside and inside the intensive care unit, 21% and 25% of respondents, respectively, reported that they were using antibiotics optimally. Surgeons were significantly more likely than other physicians to report that they were regularly seeking input into antimicrobial selections (P<.001). Of the 170 physicians who completed the survey, 88% agreed antibiotics are overused in general and 72% also agreed this was the case at their institution (r = 0.56; P<.05); 96% agreed that hospitals in general face serious problems with antibiotic resistance and 93% agreed that their hospital faces these same problems (r = 0.57; P<.05); 97% agreed that better use of antibiotics would reduce resistance; 32% stated that they had not had formal teaching on antimicrobial agents in the last year (medicine residents reported significantly more formal teaching than others [P =.001]); and 90% wanted more education about antimicrobials and 67% wanted more feedback on antimicrobial selections. The mean antimicrobial quiz score was 28%, with medicine residents scoring significantly higher than others (P =.04). Upper-level residents did not perform better than interns. CONCLUSIONS: This survey (1) revealed that house staff are aware of the importance of antimicrobial resistance and believe better antimicrobial use will help this problem and (2) demonstrated differences between specialties with respect to antimicrobial use and knowledge. House staff at our hospital have suboptimal knowledge about antimicrobials, and this knowledge did not increase appreciably over the course of their training. Antimicrobial education is needed and is likely to be well received by house staff physicians in academic centers but may be more effective if it is tailored to specific specialties.     

Gastroparesis after combined heart and lung transplantation.

GOALS: To determine the prevalence, severity, and outcome of gastroparesis after heart and lung transplantation (HLT). STUDY: Ten patients (five women; age range, 27-57 years) underwent HLT at Temple University Hospital from 1996 to 1999. The charts of these patients were reviewed, including results from gastric emptying scans and upper endoscopies. Symptoms were assessed with a standardized questionnaire. RESULTS: The indications for HLT included pulmonary hypertension in six patients, Eisenmenger syndrome in two, and dilated cardiomyopathy and congenital heart disease in two. Four patients died before the start of this clinical analysis. The six surviving patients constituted our study population. The patients' posttransplantation follow-up period ranged from 1.4 to 4.4 years (average, 2.6 years). Five patients (83%) were symptomatic with nausea, vomiting, and postprandial abdominal distension. Solid phase gastric emptying was delayed in all five patients with mean gastric retention of 93% at 2 hours (normal <50%). Patients generally did not respond to prokinetic agents. Four patients required pyloroplasty with J tube placement for symptom control, nutrition, and delivery of immunosuppressive medication. CONCLUSIONS: There is a high prevalence of symptomatic gastroparesis in patients after HLT. The gastroparesis is severe and often resistant to prokinetic agents.     

Effect of adiponectin on expression of vascular endothelial growth factor and pigment epithelium-derived factor: An in vitro study

Aim:This study was carried out to identify the role of adiponectin (APN) in modulating the expression of vascular endothelial growth factor (VEGF) and pigment epithelial-derived factor (PEDF) in relation to ocular angiogenesis.Results:ARPE cells exposed to APN showed decreased expression of VEGF mRNA, protein whereas PEDF protein is unaltered and PEDF mRNA was increased.Conclusion:Our in vitro study on ARPE exposed to APN showed a negative correlation with VEGF levels. Thus indicating the protective role for APN in angiogenesis-related diseases.KEY WORDS: Adiponectin, pigment epithelium derived factor, proliferative diabetic retinopathy, vascular endothelial growth factor