Alterations In Material Properties Research Articles

Cellular mechanisms of captopril-induced matrix remodeling in Syrian hamster cardiomyopathy.

Although angiotensin-converting enzyme (ACE) inhibitors have become a mainstay of treatment for chronic congestive heart failure (CHF), it is not known whether the cardiac remodeling effects are a secondary phenomenon, resulting from ACE inhibitors' hemodynamic actions of afterload reduction, or occur through an independent mechanism. We used ultrasonic tissue characterization to define potentially salutary effects of treatment with ACE inhibitors on the material properties of the heart and its potential influence on cardiac remodeling at the cellular level. Ten 1-month-old, cardiomyopathic (CM) Syrian hamsters and 6 normal (NL) hamsters were treated with captopril (2 g/L water ad libitum), and 10 CM hamsters and 10 NL hamsters were maintained untreated for 3 months. Hearts were excised, and backscattered radiofrequency data were acquired from 1200 independent sites from each specimen with a high-resolution 50-MHz acoustic microscope for calculation of integrated backscatter (IB). Treatment with captopril reduced left ventricular mass, calcium concentration, and IB in CM hearts without affecting myofiber size or collagen concentration. The IB from grossly normal regions of myocardium in NL hamsters, treated CM hamsters, and untreated CM hamsters was not significantly different. The IB from the microscopic regions of scar tissue in treated CM hamsters was significantly less (P = .0004) than that from scar tissue in untreated CM hamsters. The reduced IB from treated scar tissue components reflects specific alterations in the material properties (elastic stiffness, density) of fibrous regions in CM hearts induced by captopril. This is the first report that defines specific cellular effects of ACE inhibitors on the material properties of isolated components of cardiac tissue in experimental cardiomyopathy. These alterations in material properties of scar tissue components represent a potential mechanism for the salutary actions of ACE inhibitors in heart failure.

Ultrasonically determined elasticity and cortical density in canine femora after hip arthroplasty

Effects of canine hip replacement (with a porous-coated femoral component) on the material properties of surrounding cortical bone were evaluated. The hypotheses were: (1) after four months of implantation, mechanical properties of the cortex would change, and (2) a collared implant would be associated with smaller changes than a collarless design. Unilateral total hip arthroplasty was performed in 15 mixed-breed dogs. Nine received a collared and six received a collarless femoral component. Four months after implantation, longitudinal ultrasonic wave propagation velocities and bone mineral densities (from dual energy X-ray absorptiometry) were measured in harvested femora and used to calculate the axial elastic constitutive coefficients for the cortex surrounding the implants. Results showed no difference in bone elasticity or bone density between collared and collarless designs. Significant velocity decreases from control values ( p<0.0001) were noted in all implanted femora at four months. Bone mineral densities also displayed decreased values after four months of implantation ( p<0.0145). Elastic coefficients were consistently less after four months of implantation when compared to control values ( p<0.0001). This alteration in material properties would affect load transfer into the implanted femur via the increased disparity between implant and bone stiffnesses regardless of the component design. Significant differences in the elastic coefficients between implanted and control femora support hypothesis 1. However, no group differences were found between collared and collarless implantations; thus, the study does not support hypothesis 2.

Fatigue analysis of laser welded lap joints

Metal fabrication industries have shown increased interest in laser welding of sheet steel products in recent years. A lap joint is often selected because this joint configuration allows quality welding with less restrictive joint dimensional tolerances. Recent experiments in the fatigue performance of laser welded lap joints show that fatigue performance is dependent on weld pattern. This investigation establishes a technique for predicting the fatigue response of laser welded lap joints. A static stress analysis (Goland and Reissner) is combined with a cyclic stress-strain analysis (Nuber) to establish a model for calculating joint stress under cyclic loading. The model accounts for about 3 4 of the reduction in fatigue stress when comparing laser welded lap joints to unwelded, smooth material. The remaining 1 4 reduction is attributed to residual stress and/or material property alterations resulting from welding.

非鉄金属の抵抗熱源応用蒸気シールド加圧接合法及びその品質のインプロセス制御に関する研究 Ｖ 溶融・排出量検出方式による接合部品質の制御

The bonds in various electric devices are recently required high precision and high quality at bonds.To control the material deformation, thermo-characteristics by resistance heating while bonding are examined, and the optimum electrode materials and their constitution are selected as described in the report-1 and the report-2.To get high quality for bonds, examinations about defects at the interface are done, and then the vapor shield process for cleaning interface is newly developed. Moreover, the effects of the vapor shield process on preventing defect formation is successfully proved as described in the report-3 and in the report-4.In this study, to apply the above process named Vapor Shielded Pressure Bonding on mass-production line of contact-bars of electromagnetic switchgears, the monitoring process of metal expulsion which is conclusive fatter of bonding quality and inprocess quality control system are examined.The main results obtained are as follows;1) Metal expulsion volumes fluctuate in continuous bonding of a number of contact-bars, because both the alterations of material properties and supplied power bring fluctuation of heat inputs.2) In finding metal expulsion volume of each bonding by electrode displacement, the correct volume can be detected by employing forging stage before bonding. For, alteration of surface confiugration of contact materials which obstruct the correct detecting of expulsion can be effectively neglected by forging.3) The beginning point of expulsion while bonding can be found accurately in real time by monitoring electrode displacement.4) The inprocess control system by monitoring electrode displacement is successfully developed. The system can continuously produce the sound bonds of contactbars without any bad one.

Effects of a 1-wk spaceflight on morphological and mechanical properties of growing bone.

The morphological and mechanical responses of tibia and humerus were assessed in growing male rats after a 1-wk spaceflight aboard NASA Spacelab 3. In contrast to flights of longer duration, changes in middiaphysial cross-sectional morphology were minimal. Inhibition of longitudinal growth was not found in the tibia but was apparent in the humerus. The normal age-related increase in tibial middiaphysial density was not observed in the flight animals. Three-point bending tests indicated that a 1-wk spaceflight impeded the maturation of bone strength and stiffness, with the effects more pronounced in the tibia than in the humerus. Material property alterations in bone thus overshadowed morphological factors in determining the bone's mechanical response. It is likely that deprivation of normal weight-bearing loads was a major factor contributing to the observed changes, but endocrine and other local factors must also be considered.

Thin film narrow band optical filters

Narrow band filters are interesting for a number of reasons. Firstly there is the simple reason that we want to be able to make them better with a higher process yield. Secondly there is the reason that their performance is very sensitive to alterations in material properties and so they could be useful test beds for materials and especially for detecting small instabilities with time. Techniques for design of thin film narrow band optical filters are well established. The filters may be considered as arrangements of tuned cavities: the simplest type, the Fabry-Perot, consists of just one cavity; the double half-wave (DHW) has two cavities; the triple half-wave (THW) consists of three cavities; and so on. The narrowest filters are constructed completely from dielectric materials to keep dissipative losses as low as possible. Almost all the all-dielectric filter designs in common use employ layers that have optical thicknesses which are integral multiples of quarter of the peak wavelength. This is because both the theoretical treatment and the control of deposition are rather simpler for quarter-waves than for non-integral thicknesses. From time to time proposals have been made for new narrow band filter designs which involve nonintegral thicknesses but these do not seem to have been taken up to any extent by manufacturers, probably because the additional complication outweighs any advantage which they might have in performance. The theory and techniques of layer thickness control are apparently rather less well organized than design. These are central to the production of coatings and so manufacturers are naturally reluctant to discuss their methods in detail. There has not been a great deal of interest in this aspect by academics and as a result relatively little has been published. In this review we consider briefly a few of the problems which occur in the production of narrow band all-dielectric thin film optical filters. For the reasons mentioned above we shall consider only designs composed entirely of optical thicknesses which are integral multiples of a quarter-wave. Assuming that we have stable thin film materials with accurately predictable losses then we can estimate the best performance which should be achieved with a particular design. Real manufactured filters will always have poorer performance than this because errors in the layers will disturb the optimum matching. The resulting decrease in peak transmittance will be accompanied by a corresponding increase in reflectance which is always a good test of whether low transmittance is due to losses or to manufacturing inaccuracies. This leads us directly to the idea of tolerances. How accurately