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The degradation of biopolymers such as polylactic acid (PLA) has been studied for several years; however, the results regarding the mechanism of degradation are not completely understood yet. PLA is easily processed by traditional techniques including injection molding, blow molding, extrusion, and thermoforming; in this research, the extrusion and injection molding processes were used to produce PLA samples for accelerated destructive testing. The methodology employed consisted of carrying out material testing under the guidelines of several ASTM standards; this research hypothesized that the effects of UV light, humidity, and temperature exposure have a statistical difference in the PLA degradation rate. The multivariate analysis of non-parametric data is presented as an alternative to multivariate analysis, in which the data do not satisfy the essential assumptions of a regular MANOVA, such as multivariate normality. A package in the R software that allows the user to perform a non-parametric multivariate analysis when necessary was used. This paper presents a study to determine if there is a significant difference in the degradation rate after 2000 h of accelerated degradation of a biopolymer using the multivariate and non-parametric analyses of variance. The combination of the statistical techniques, multivariate analysis of variance and repeated measures, provided information for a better understanding of the degradation path of the biopolymer.

RESUMO

While the degradation of Polylactic Acid (PLA) has been studied for several years, results regarding the mechanism for determining degradation are not completely understood. Through accelerated degradation testing, data can be extrapolated and modeled to test parameters such as temperature, voltage, time, and humidity. Accelerated lifetime testing is used as an alternative to experimentation under normal conditions. The methodology to create this model consisted of fabricating series of ASTM specimens using extrusion and injection molding. These specimens were tested through accelerated degradation; tensile and flexural testing were conducted at different points of time. Nonparametric inference tests for multivariate data are presented. The results indicate that the effect of the independent variable or treatment effect (time) is highly significant. This research intends to provide a better understanding of biopolymer degradation. The findings indicated that the proposed statistical models can be used as a tool for characterization of the material regarding the durability of the biopolymer as an engineering material. Having multiple models, one for each individual accelerating variable, allow deciding which parameter is critical in the characterization of the material.

Assuntos

RESUMO

Sipid mediators of inflammation have been implicated in the pathogenesis of Pseudomonas aeruginosa (PA) related pulmonary damage in patients with cystic fibrosis. We studied the role of these mediators in a rat model of PA endobronchitis using essential fatty acid deficient (EFAD) animals. Whole blood from EFAD animals produced significantly less leukotriene B4 (LTB4) and hydroxyheptadecatrienoic acid when stimulated ex vivo than did whole blood from control animals (p less than 0.005). Similarly, lung lavage fluid from EFAD animals infected with PA contained less LTB4 and thromboxane B2 (TXB2) than that from control animals. Despite these differences, cellular infiltration of airways in response to PA infection was virtually identical in animals from the regular diet and the EFAD groups. Both EFAD and control animals had a significant increase in white blood cells (WBC) in lung lavage fluid at 1, 3 and 6 days following infection with PA when compared to animals receiving sterile beads. Localized areas of consolidation and nodularity were grossly evident in the lungs of all PA infected animals irrespective of their ability to generate the lipid inflammatory mediators. Microscopic examination of lung sections demonstrated similar changes in all infected animals. We conclude that LTB4 and TXB2 production occurs early in the course of PA pulmonary infection in rats. This early rise in lipid mediators is temporally associated with an influx of WBC into the airways. However, attenuation of eicosanoid production by use of an EFAD diet does not lead to a reduction in the inflammatory response to PA infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Assuntos

RESUMO

In a multicenter, double-blind, randomized, longitudinal study, 252 children received licensed Lederle diphtheria-tetanus toxoids and pertussis vaccine adsorbed (DTP) at 2, 4, and 6 months of age, and 245 children received a DTP vaccine with the Lederle/Takeda acellular pertussis component (APDT) at the same ages. Both groups of children received APDT vaccine at 18 months of age. After each of the first three immunizations, APDT vaccine recipients had fewer local and systemic reactions than did DTP vaccinees. Reactions after the 18-month APDT vaccination were minimal in severity regardless of the vaccine previously received. Antibody responses to lymphocytosis-promoting factor and agglutinogens were more pronounced in DTP recipients; however, APDT recipients had a better serologic response to filamentous hemagglutinin, and responses to the 69K protein were equivalent. This APDT vaccine produces fewer reactions than the standard whole-cell DTP vaccine. The protective significance of the serologic responses to the APDT vaccine is unknown, but the greater response to filamentous hemagglutinin and equivalent response to the 69K protein compared with those to DTP vaccine seem promising.

Assuntos

Assuntos

RESUMO

To determine the efficacy of rifampin chemoprophylaxis in eradication of oropharyngeal carriage of Haemophilus influenzae type b, we conducted a multicenter, double-blind, placebo-controlled trial among household contacts of patients hospitalized for invasive HIB infection. Seventy-nine index patients and 400 close contacts were studied; 26.5% of contacts were colonized. The efficacy of rifampin (10 mg/kg/dose, 600 mg/dose maximum, twice daily for two days) in eradicating carriage was 52% and varied with age (75.6% in persons greater than or equal to 5 and 27% in those less than 5 years). Eradication rates in those less than 5 years were not significantly better than for placebo. No resistant isolates were encountered in sensitivity testing. The low efficacy of this rifampin regimen in young children precludes its routine use as a chemoprophylactic agent for family contacts. The occurrence of three cases of invasive HIB infection in individuals outside the defined contact group raises concern regarding the efficacy of any chemoprophylactic regimen.

Assuntos