单纤维刺扎人体皮肤的弯曲力学行为分析

伸出织物表面的短、粗纤维末梢是产生贴身纺织品针刺感的主要原因,本质是纤维末梢刺扎并诱发皮肤伤害性机械刺激感受器.通常基于固定-铰接约束条件下弹性压杆轴向压缩稳定性理论,计算纤维末梢的临界压力判断这种感受器的诱发可能性.然而,这种方法忽略了织物握持纤维末梢的强度、纤维末梢接触皮肤的滑动阻力及其柔韧性特征.本文以伸出织物表面的直立纤维末梢为对象,假设其织物握持端为线弹性转动约束、另一端受皮肤的接触反作用力和滑动阻力作用,建立纤维末梢刺扎人体皮肤的弯曲变形力学模型.通过参数化模拟,本文比较分析了纤维末梢在弹性-支撑约束和固定-铰接约束条件下的弯曲变形行为.研究发现,纤维末梢在弹性-支撑约束条件下的弯曲力学行为才能解释其刺扎皮肤产生的大多数力学现象及针刺感现象.     

A conjugate gradient iterative method

A strongly implicit pre-conditioned form of the conjugate gradient method is considered. The resulting iterative technique is applicable for sparse systems of difference equations arising from boundary value problems. The method is used to solve two- and three-dimensional potential flows. In addition, it is extended to a 2 x 2 coupled system to solve the Navier-Stokes equations in stream function-vorticity form.     

Putative association between a new polymorphism in exon 3 (Arg109Cys) of the pancreatic colipase gene and type 2 diabetes mellitus in two independent Caucasian study populations

The protein encoded by the pancreatic colipase (CLPS) gene is an essential cofactor needed by pancreatic triglyceride lipase (PNLIP) for efficient dietary lipid hydrolysis. Since the inhibition of lipase activity was shown to reduce the incidence of type 2 diabetes mellitus, we tested the hypothesis that genetic variations in the CLPS and PNLIP genes are associated with type 2 diabetes; 47 unrelated subjects were screened for polymorphisms of the CLPS and PNLIP genes. A nested-case control study of 192 incident type 2 diabetes subjects and 384 sex- and age-matched controls taken from the European Prospective Investigation into Cancer and Nutrition Potsdam Cohort (EPIC) was employed for association studies. The Metabolic Intervention Cohort Kiel (MICK) consisting of 716 males was used for verification. A novel putative functional polymorphism (Arg109Cys) was identified in the CLPS gene. The frequencies of the Arg/Cys genotype were 2.6% in EPIC and 2.2% in MICK study subjects. No homozygotes for the Cys/Cys genotype were found in either study population. Logistic regression analysis showed a statistically significant association of the Arg/Cys genotype with an increased risk of type 2 diabetes. The odds ratios estimated by the model were 3.75 (95%CI = 1.13-12.49, p = 0.03) in EPIC and 4.86 (95%CI = 1.13-20.95, p = 0.03) in MICK. No comparable associations were found with other traits of the insulin-resistance syndrome (e. g.; body mass index, waist to hip ratio). In conclusion, we obtained evidence in two German Caucasian study populations that the variant of the rare CLPS Arg109Cys polymorphism might contribute to increased susceptibility of type 2 diabetes.     

Effect of government actions on technological innovation for SO2 control

The relationship between government actions and innovation in environmental control technology is important for the design of cost-effective policies to achieve environmental goals. This paper examines such relationships for the case of sulfur dioxide control technology for U.S. coal-fired power plants. The study employs several complementary research methods, including analyses of key government actions, technology patenting activity, technology performance and cost trends, knowledge transfer activities, and expert elicitations. Our results indicate that government regulation appears to be a greater stimulus to inventive activity than government-sponsored research support alone, and that the anticipation of regulation also spurs inventive activity. Regulatory stringency focuses this activity along particular technical pathways and is a key factor in creating markets for environmental technologies. We also find that with greater technology adoption, both new and existing systems experience notable efficiency improvements and capital cost reductions. The important role of government in fostering knowledge transfer via technical conferences and other measures is also seen as an important factor in promoting environmental technology innovation.     

Probiotic bacteria are antagonistic to Salmonella enterica and Campylobacter jejuni and influence host lymphocyte responses in human microbiota‐associated immunodeficient and immunocompetent mice

A defined human microbiota‐associated (HMA) mouse model in BALB/c and immunodeficient Tgε26 mice was used to assess the ability of probiotic lactobacilli and bifidobacteria to enhance colonization resistance to gastrointestinal (GI) tract pathogens. Probiotic bacteria (1×10⁸ colony forming unit (CFU)/mL) successfully excluded Campylobacter jejuni from both strains of mice 7 days after challenge. The probiotic bacteria also reduced the number of Salmonella in the large intestines of both mouse strains. The nylon wool fractionated spleen lymphocyte populations were incubated with Salmonella or C. jejuni antigens. The probiotic treatments did not affect lymphocyte proliferation to C. jejuni antigens, but significantly increased proliferation of lymphocytes to Salmonella antigens by 68 and 55%, respectively, over untreated mice. Caspase 3/7 activation was significantly reduced 33 and 38% in the T and B lymphocyte fractions, respectively, of probiotic‐treated, Salmonella‐challenged HMA BALB/c mice, suggesting that lymphocyte rescue from apoptosis was occurring as a result of probiotic bacteria activity. These results revealed an immunosuppressive activity by Salmonella that was inhibited by the presence of probiotic bacteria. In summary, lactobacilli and bifidobacteria competitively excluded C. jejuni from immunocompetent and immunodeficient mice and antagonized an observable Salmonella‐induced immunosuppression in immunocompetent mice.     

Multiple phases of expression and regulation of mouse Hoxc8 during early embryogenesis

Hox genes are expressed in dynamic patterns during embryogenesis consistent with their role in axial specifications. To study the distribution of mouse Hoxc8, a homeodomain containing protein, we raised monoclonal antibodies against the least conserved portion of Hoxc8. Using these antibodies, we have examined early and mid-gestation embryos for the distribution of the protein. At the end of gastrulation Hoxc8 is expressed in the caudal portion of the embryo. In the neural tube, an early phase when all cells express Hoxc8 is distinguished from a late phase with predominant expression in differentiating neurons. A comparison of this expression pattern with that of a reporter gene under the control of the early Hoxc8 enhancer demarcates three separate regulatory components: (1) initiation and establishment; (2) maintenance; and (3) downregulation. We propose that Hoxc8 expression during embryogenesis is established in multiple phases. Possible regulatory mechanisms involved in generating such a complex domain of Hox gene expression are discussed.     

Psychological characteristics of South African street children

Research has shown that no treatment program designed for street children can succeed unless the community is prepared to respect, protect, and provide opportunities for them (Tacon, cited in Schurink & Rip, 1993). Unfortunately, these children are abused in many parts of the world (Aptekar, 1994). This paper investigates why the general public, as well as those charged with enforcing the law, often treat street children with scorn and hostility.     

Effects of ibuprofen on airway vascular response to cotton smoke injury

We studied the effects of ibuprofen on bronchial blood flow and myocardial function after inhalation injury. Sheep (n = 12) were chronically instrumented with cardiovascular and pulmonary catheters. After 5 days of recovery period, baseline data were collected and the sheep were divided into two groups. Group S (n = 6) were insufflated with 48 breaths of cotton smoke; while group I (n = 6) were pretreated with ibuprofen (12mg/kg bolus followed by 3 mg/kg/h continuous infusion for 24 h) and challenged with the same dose of smoke. All the animals were studied for 24h. Bronchial blood flow increased significantly in both groups throughout the experimental period; while stroke volume as well as right and left ventricular stroke work indices of both groups were significantly decreased (group I worse than group S) in the second half of the experimental period. These data suggest that vasodilatory prostaglandins do not play a major role in the bronchial vascular response to smoke inhalation injury and myocardial depression seen post injury is worse in animals treated with ibuprofen.