Superplastic deformation of Ti-6Al-4V extruded tube

Superplastic forming using conventional alloys and product forms may be a cost effective route for component manufacture. In this paper superplastic deformation of Ti-3Al-4V extruded tube is examined in terms of the strain anisotropy, microstructural changes, the texture and the post-formed tensile properties. Superplastic deformation with low flow stresses over a wide range of strain rates was observed. Strain anisotropy and surface roughening occurred during deformation and was associated with the two-phase, aligned and banded microstructure. A small reduction in the tensile properties was found and changes in the texture were noted after superplastic deformation.     

Yodel: A Yield Stress Model for Suspensions

A model for the yield stress of particulate suspensions is presented that incorporates microstructural parameters taking into account volume fraction of solids, particle size, particle size distribution, maximum packing, percolation threshold, and interparticle forces. The model relates the interparticle forces between particles of dissimilar size and the statistical distribution of particle pairs expected for measured or log-normal size distributions. The model is tested on published data of sub-micron ceramic suspensions and represents the measured data very well, over a wide range of volume fractions of solids. The model shows the variation of the yield stress of particulate suspensions to be inversely proportional to the particle diameter. Not all the parameters in the model could be directly evaluated; thus, two were used as adjustable variables: the maximum packing fraction and the minimum interparticle separation distance. The values for these two adjustable variables provided by the model are in good agreement with separate determinations of these parameters. This indicates that the model and the approximations used in its derivation capture the main parameters that influence the yield stress of particulate suspensions and should help us to better predict changes in the rheological properties of complex suspensions. The model predicts the variation of the yield stress of particulate suspensions to be inversely proportional to the particle diameter, but the experimental results do not show a clear dependence on diameter. This result is consistent with previous evaluations, which have shown significant variations in this dependence, and the reasons behind the yield stress dependence on particle size are discussed in the context of the radius of curvature of particles at contact.     

Plasma viral RNA load predicts disease progression in accelerated feline immunodeficiency virus infection

Viral RNA load has been shown to indicate disease stage and predict the rapidity of disease progression in human immunodeficiency virus type 1 (HIV-1)-infected individuals. We had previously demonstrated that feline immunodeficiency virus (FIV) RNA levels in plasma correlate with disease stage in infected cats. Here we expand upon those observations by demonstrating that plasma virus load is 1 to 2 logs higher in cats with rapidly progressive FIV disease than in long-term survivors. Differences in plasma FIV RNA levels are evident by 1 to 2 weeks after infection and are consistent throughout infection. We also evaluated humoral immune responses in FIV-infected cats for correlation with survival times. Total anti-FIV antibody titers did not differ between cats with rapidly progressive FIV disease and long-term survivors. These findings indicate that virus replication plays an important role in FIV disease progression, as it does in HIV-1 disease progression. The parallels in virus loads and disease progressions between HIV-1 and FIV support the idea that the accelerated disease model is well suited for the study of therapeutic agents directed at reducing lentiviral replication.     

Endothelium-dependent effect of perindopril and enalaprilat in rat thoracic aorta

AIM: To study the effect of the angiotensin-converting enzyme (ACE) inhibitors perindopril (Per) and enalaprilat (Ena) on the reactivity of the endothelium in normal rats. METHODS: Male rats were treated intragastrically with Per (2 mg.kg-1.d-1) or placebo (n = 18) for 6 wk. Aorta was isolated for experiment. Another set of isolated aortic rings with and without endothelium were incubated with Ena (0.1 mumol.L-1) for 30 min. Responses to acetylcholine, serotonin, phenylephrine, sodium nitroprusside (SN), and nitroglycerin (Nit) were observed. RESULTS: Endothelium-dependent relaxation to acetylcholine was augmented in aortic rings from rats treated with Per in comparison with control. The IC50 value (95% confidence limits) decreased from 3.8 (0.56-26.1) mumol.L-1 (control group) to 0.98 (0.28-3.41) mumol.L-1 (Per-treated group). The maximal relaxation was augmented from 62 +/- 9% to 78 +/- 10% (P < 0.01). However, the responses to the endothelium-independent vasodilators, SN and Nit, were similar. Serotonin- and phenylephrine-induced contractions were decreased, which were influenced by basal release of endothelium-derived relaxing factor (EDRF). EC50 values was 6.1 (2.6-14.4) nmol.L-1 vs 8.3 (3.6-18.8) nmol.L-1 in comparison with control group and Per-treated group. The maximal contraction was decreased from 2.42 +/- 0.29 g (control group) to 1.96 +/- 0.25 g (treated group) (P < 0.01). Similar results were found in incubation with Ena. CONCLUSION: Ena and Per enhanced the basic release of EDRF from vascular endothelium.     

水溶液中硅酸溶解和胶结的实验研究

本研究了几种不酸ＰＨ值对硅酸胶结的影响。结果表明，草酸浓度增大时，硅酸胶结速度变缓，至ＰＨ３－４时，硅酸不再胶结；而ＨＣＬ浓度增大，虽然胶结速度变缓，但最终仍胶结。     

Complications of care in a pediatric intensive care unit: a prospective study

OBJECTIVES: (a) To examine the frequency, type, and severity of complications occurring in a pediatric intensive care unit; (b) to identify populations at risk; and (c) to study the impact of complications on morbidity and mortality. DESIGN: Prospective survey. SETTING: Pediatric intensive care unit (PICU) of a university-affiliated hospital. PATIENTS: 1035 consecutive admissions over an 18-month period. RESULTS: 115 complications occurred during 83 (8.0%) admissions, for 2.7 complications per 100 PICU-days; 48 (42%) complications were major, 45 (39%) moderate, and 22 (19%) minor. Sixty complications (52%) were ventilator-related, 14 were drug-related, 13 procedure-related, 24 infectious, and 22 involved invasive devices (18 vascular catheters). Human error was involved in 41 (36%) cases, 21 of which were major (18%). Treatments included reintubation < 24 h (28), intravenous antimicrobials (24), and invasive bedside procedures (14). Cardiopulmonary resuscitation was required in 6 patients. Thirteen patients with complications died (15.7%); 2 deaths were directly due to complications. Patients with complications were younger, had longer lengths of stay, and had a higher mortality. Length of stay was a positive risk factor for complication risk (odds ratio = 1.09, 95% confidence interval: 1.05 to 1.13; p = 0.0001); other patient characteristics had no predictive effect. Kaplan-Meier estimates showed that the most severe complications occurred early in the PICU stay. The best indicators of patient mortality were number of complications (odds ratio = 2.96, 95% confidence interval 1.72 to 5.08; p = 0.0001), and mortality risk derived from the Pediatric Risk of Mortality Score (odds ratio = 1.08, 95% confidence interval 1.06 to 1.10; p = 0.0001). Mortality was correlated with increasing severity of complications. CONCLUSION: Complications have a significant impact on patient care. Patients may be at increased risk earlier in their PICU course, when the number of interventions may be greatest. Complications may increase patient mortality and predict patient death better than other patient variables.