Modeling slip base mechanisms Hiser, N R; Reid, J D
International journal of crashworthiness,
01/2005, Letnik:
10, Številka:
5
Journal Article
Recenzirano
Slip base mechanisms are commonly used in breakaway devices for the roadside safety industry; for example, the base of structures such as sign posts, luminaire poles, and guardrail system posts are ...often slip base mechanisms. Due to the breakaway feature of the slip base, it has considerable potential for reducing the amount of crash resistance, and thus occupant injury, when vehicles inadvertently leave the roadway and strike these objects. The objective of this study was to develop improved methods of modeling slip base structures using nonlinear, finite element analysis. Two bolt preloading techniques were developed and evaluated, including one method which utilized a discrete spring element, and a second method which utilized pre-stressed bolt shaft elements. Both methods produced desired bolt preload, as well as acceptable slip behavior when impacted in a simple shear scenario. However, when the impact conditions became more severe, the model using pre-stressed solid elements was significantly more accurate. The stress-based clamping model was then incorporated into a new cable guardrail system model. Performance of the slip base model was acceptable in both end-on impact and length-of-need impact simulations. Thus, the model was deemed appropriate for use in further development and analysis of existing cable systems, as well as alternate slip base applications.
A membranous structure causing functional stenosis at the mouth of the left atrial appendage (LAA) has been reported. In this study we describe the presence of nonobstructive membranes traversing the ...cavity of the LAA found incidentally on transesophageal echocardiography (TEE).
Stimulation of sensory nerves in the airway mucosa causes local release of the neuropeptides substance P and calcitonin gene-related peptide (CGRP). In this study we used a modification of the ...reference-sample microsphere technique to measure changes in regional blood flow and cardiac output distribution produced in the rat by substance P, CGRP, and capsaicin (a drug that releases endogenous neuropeptides from sensory nerves). Three sets of microspheres labeled with different radionuclides were injected into the left ventricle of anesthetized F344 rats before, immediately after, and 5 min after left ventricular injections of capsaicin, substance P, or CGRP. The reference blood sample was withdrawn from the abdominal aorta and was simultaneously replaced with 0.9% NaCl at 37 degrees C. We found that stimulation of sensory nerves with a low dose of capsaicin causes a large and selective increase in microvascular blood flow in the extrapulmonary airways. The effect of capsaicin is mimicked by systemic injection of substance P but not by CGRP, suggesting that substance P is the main agent of neurogenic vasodilation in rat airways.
The cytochrome c oxidase enzyme from Rhodobacter sphaeroides bacteria exists as a complex of four peptide subunits, two hemes and a variety of lipids and metal ions held together by non-covalent ...forces. Although the native enzyme functions as an associated unit, this complex usually dissociates during matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry analysis. Through the use of matrix additives such as sucrose, the complete complex and partial complexes can be stabilized in the MALDI-ToF experiment. The dissociation of the complex allows the detection of the components of the enzyme. The direct detection of associated lipids from an aqueous solution of the intact enzyme may eliminate the need for enzyme disruption and lipid extraction. The partial dissociation of multi-subunit enzymes in such experiments may allow the determination of subunit–subunit and subunit–lipid interactions.
Hospitals in the US are increasingly concerned with the rising number of hospital-acquired pressure ulcers. To reduce its 2002-2003 average hospital-acquired pressure ulcer prevalence rate of 9.2%, a ...regional medical center in southeastern US initiated a process improvement and education program. Quarterly pressure ulcer prevalence studies were conducted and the Medical Intensive Care Unit was found to have the highest number of hospital-acquired pressure ulcers among the five units participating in the study. As part of a new Pressure Ulcer Strategic Plan, significant changes were made to the organizational infrastructure and processes, which included implementing the Braden Risk Scale Assessment Tool in place of the Norton Risk Scale, developing a pressure ulcer prevention protocol, creating Pressure Ulcer/Skin Tear Physician orders for nurses, establishing a Skin Resource Team, and providing additional education, training, and other relevant resources. Better appreciation for and enhanced utilization of Certified Wound Ostomy Continence Nurses were encouraged. New support surfaces were purchased. Implementing these changes resulted in a decrease in the quarterly hospital-acquired pressure ulcer prevalence in participating units, including the Medical Intensive Care Unit where rates dropped from a high of 29% to near 0%. Clinicians now approach pressure ulcers as preventable rather than inevitable and view Certified Wound Ostomy Continence Nurses as resources and clinical experts for prevention and treatment. Overall quality of care and financial resource utilization also have substantially improved.
The dietary protein requirements of patients with insulin-dependent diabetes mellitus (IDDM) are unknown. We studied the metabolic adaptation of IDDM patients with early nephropathy to therapeutic, ...low-protein diets. Six patients were studied at baseline and following 1 and 12 weeks of consuming 0.6 g/kg-1 ideal body weight.day-1 protein. Outcome variables included quadriceps muscle strength, body composition, nitrogen balance, and estimates of whole body protein turnover using an infusion of L-1-13Cleucine. All subjects experienced decreased muscle strength (6.6% decline in maximal torque, P = 0.05) and increased body fatness (11% increase in fat mass, P = 0.03) with no change in total body weight. This was accompanied by an initial 40% decrease in the rate of whole-body leucine oxidation after 1 week of dietary restriction which returned almost to baseline rates by 12 weeks (P less than 0.001, 1 week vs. 12 weeks). Nitrogen balance remained negative throughout the period of protein restriction. We conclude that IDDM subjects with early nephropathy experience protein undernutrition during the first 3 months of the dietary protein restriction currently recommended for the treatment of nephropathy. This may result, in part, from an inability to conserve essential amino acids from oxidative loss over the time period of the study.
Assembly of the core subunits of the aa sub(3)-type cytochrome c oxidase in mitochondria and aerobic bacteria such as Rhodobacter sphaeroides requires the association of three subunits and the ...formation of five to seven metal centers. Several assembly proteins are required for the late stages of oxidase assembly in eukaryotes; some of these are also present in Rb. sphaeroides. To investigate the role of one of these proteins, Cox11p, the mitochondrial- like oxidase of Rb. sphaeroides was overexpressed and purified from cells that lacked cox11, the gene for Cox11p. The oxidase that assembled in the absence of Cox11p lacked Cu sub(B) at the active site and contained greatly reduced amounts of metal at the magnesium/manganese-binding site between subunits I and II. This inactive oxidase, however, did contain hemes a and a sub(3), Cu sub(A), and all three subunits. These results indicate that Cox11p is required at a late, perhaps final, step in the assembly of cytochrome oxidase, most likely the insertion of Cu sub(B). Oxidase which assembled in a strain with a low copy number of cox11 appeared nearly wild type, suggesting that Cox11p is required in substoichiometric amounts for its role in oxidase assembly.
Type 2 diabetes is a major cause of death among American Indians and obesity and physical inactivity are modifiable risk factors in the development of type 2 diabetes. Physical activity may have both ...a preventive effect and a secondary preventive effect of lessening insulin resistance in persons with type 2 diabetes. Moreover, for some individuals participation in daily regimens of physical activity is very difficult. Culture-specific physical activity may be an intervention to reduce obesity and prevent diabetes-related complications. Therefore, the research questions for this study were: (1) What is the body fat percentage of diabetic and non-diabetic Mskoke Indians?, (2) How does body fat percentage of Mvskoke Indians compare with recommended percentages for age and gender?, (3) What is the caloric use of Mvskoke Indians during daily and traditional cultural activities of dancing and stickball?, and (4) Are there relationships among body fat percentage, calorie use, gender, and diabetic status? The findings revealed that female diabetics' percentage of body fat in three age cohorts (40-49, 50-59, and 70+) was higher than that of non-diabetic females. By contrast, male diabetics had lower percentage of body fat than non-diabetic males. The actual mean percentage of body fat of the female participants ranged from 38.5% to 44%, roughly twice the standard recommended percentages of body fat of 20-24%. No significant difference was found in calorie use by gender or diabetic status. Analysis of calories during traditional activities revealed that 30 minutes of stickball used an average of 135.7 calories. Dancing for 33 minutes used an average of 149 calories. No significant relationship was found among percentage of body fat, caloric use, gender, and diabetic status.
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