Competing causes of failure and reliability tests for Weibull lifetimes under type I progressive censoring

For many high reliability products where very few items are expected to fail during the test period, testing under normal conditions is not feasible. Further, the requirement for high reliability increases the need for test procedures which yield valuable degradation and other useful information for improving product reliability. Thus in some manufacturing and other experiments, various types of failure censored and accelerated life tests are commonly employed for life testing. In this paper we discuss Type I progressively censored variable-sampling plans for Weibull lifetime distributions under competing causes of failure. The proposed procedure is attractive as it yields useful degradation-related information for improving product quality. In addition, the procedure is useful when a test is conducted under severe time constraint and/or when the experimenter wishes to save costly specimens or scarce test facilities for other use.     

Effect of band 3 subunit equilibrium on the kinetics and affinity of ankyrin binding to erythrocyte membrane vesicles

The membrane-spanning protein, band 3, anchors the spectrin-based membrane skeleton to the lipid bilayer via the bridging protein, ankyrin. To understand how band 3 subunit stoichiometry influences this membrane-skeletal junction, we have induced changes in the band 3 association equilibrium and assayed the kinetics and equilibrium properties of ankyrin binding. We observe that band 3 oligomers convert slowly to dimers and ultimately monomers following removal of ankyrin. Addition of excess ankyrin back to these membranes enriched in dissociated band 3 then shifts band 3 almost entirely to tetramers, confirming that the tetrameric form of band 3 constitutes the preferred oligomeric state of ankyrin binding. 4, 4'-Diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) labeling of band 3, which is shown to shift most of the band 3 population to dimers, eliminates the majority of ankyrin-binding sites on the membrane and greatly reduces retention of band 3 in detergent-extracted membrane skeletons. Furthermore, DIDS- modified membranes lack all low affinity ankyrin-binding sites and roughly half of all high affinity sites. Since labeled membranes lack the rapid kinetic phase of ankyrin binding and exhibit only half of the normal amplitude of the slow kinetic phase, it can be concluded that the rapid phase of ankyrin association involves low affinity sites and the slow phase involves high affinity sites. A model accounting for these data and most previous data on ankyrin-band 3 interactions is provided.     

Management of sternal and abdominal wounds in a pediatric heart transplant patient

A 14-year-old girl with congenital heart disease underwent ventricular assist device placement before cardiac transplantation. The inability to close her abdominal fascia necessitated the placement of Prolene mesh, which subsequently became exposed and contaminated when her incision dehisced. Stable closure was obtained with Vicryl mesh and a rectus abdominis turnover flap. Her posttransplant course was notable for compression of the donor heart, necessitating prolonged open sternotomy. She failed an attempt at delayed sternal closure due to compression of the right ventricle by the sternum. In addition to standard pectoralis advancement flaps, a pedicled osseous sternal flap based on her left internal mammary artery was developed to avoid ventricular compression yet still provide some protection to the mediastinum. Alternative uses of this vascularized bone flap to assist with chest wall reconstruction are discussed.     

Racial variation of factor VII activity and antigen levels and their correlates in healthy Chinese and Indians at low and high risk for coronary artery disease

We examined the genotypes of ALDH2, ADH2, ADH3 and P-4502E1 loci of alcoholics and nonalcoholics. Also we compared the frequencies of the homozygous ALDH2*1/1 genotype and heterozygous ALDH2*1/2 genotypes in alcoholics. Our study reported differences in the allelic frequencies of ALDH2, ADH2 and ADH3 loci between alcoholics and nonalcoholics. For alcoholics, it was indicated that ADH2 and ADH3 plays an important role for alcoholism. For genotypes of P-4502E1, no significant difference was observed between alcoholics and nonalcoholics. Alcoholics with the heterozygous ALDH2*1/2 genotype had significantly higher frequency of the ADH2*1 than that of alcoholics with ALDH2*1/1 genotype. Concerning the alcoholics with the heterozygous ALDH2*1/2 genotype, we assumed that ADH2*1 plays a role for the development of alcoholism.     

Microwave switch: LAMPS (light-activated microwave photoconductive switch)

A new microwave switch, the light-activated microwave photoconductive switch consisting of a heterostructure photoconductive switch (HPCS) with a flip-chip bonded vertical-cavity surface-emitting laser is reported. An insertion loss of 0.17 dB at a laser power of 15 mW and an isolation of 25 dB were obtained at 1 GHz. Excellent linearity was obtained with second and third order intercepts measured at 960 MHz of SOI=115 dBm and TOI=65 dBm at 960 MHz, respectively.     

Rate and temperature effects on crack blunting mechanisms in pure and modified epoxies

The failure mechanisms of several epoxy polymers (including pure, rubber- and particulatemodified, as well as rubber/particulate hybrid epoxies) were investigated over a wide range of strain rates (10^–6 to 10² sec^–1) and temperatures (–80 to 60° C). A substantial variation in fracture toughness, G_Ic, with rate was observed at both very high and very low strain rates. Under impact testing conditions, G_Ic for both pure and rubber-modified epoxies displayed peaks at about 23 and –80° C which appeared to correlate with the corresponding size of the crack tip plastic zone. In order to explain these rate and temperature-dependent G_Ic results, two separate crack blunting mechanisms were proposed: thermal blunting due to crack tip adiabatic heating and plastic blunting associated with shear yield/flow processes. Thermal blunting was found to occur in the pure- and rubber-modified epoxies under all impact testing conditions and temperatures above 0° C. For temperatures below –20° C under impact conditions, the fracture toughness is dependent on viscoelastic loss processes and not thermal blunting. Plastic blunting was predominant at very slow strain rates less than 10^–2 sec^–1 for the pure- and rubber-modified epoxies and at impact strain rates for the fibre and hybrid epoxies. Microstructural studies of fracture surfaces provided some essential support for the two proposed crack blunting mechanisms.     

Integrating communication services

The need for communication services which span multiple communication technologies is growing. Communication services are being developed in three areas: in the public switched telephony networks, on the Internet in the form of integrated multimedia including voice-over-Internet, and in private switched telephony networks in the form of enterprise computer-telephony integration applications. This article shows it is plausible to create unified services which span the Internet and public switched telephony networks, and goes on to describe Nexus, an architecture and prototype for integrated communication services     

Dynamic group multicast routing with bandwidth reservations

Multicasting refers to the transmission of data from a source node to multiple destination nodes in a network. Group multicasting is a generalization of multicasting whereby every member of a group is allowed to multicast messages to other members that belong to the same group. The routing problem in this case involves the construction of a set of low cost multicast trees with bandwidth requirements, one for each member of the group for multicasting messages to other members of the group. In this paper, we examine this routing problem with an additional requirement that member nodes are allowed to join and leave the multicasting group anytime during a session. We call this problem, the dynamic group multicast routing problem (DGMRP). In this paper, we proposed three heuristic algorithms to generate a set of low cost multicast trees with dynamic group membership. Results from our empirical study shows that the one of the proposed algorithms, called Maximum bandwidth bottleneck path selection algorithm (MBBPS), achieves better utilization of bandwidth resources as compared with the other two algorithms which are based on a greedy approach. In addition MBBPS performs better in terms of cost when the bandwidth is not sufficient in the network. Copyright © 2002 John Wiley & Sons, Ltd.     

Structural identification of a new acetildenafil analogue from pre-mixed bulk powder intended as a dietary supplement

An analogue of acetildenafil was detected in an extract of pre-mixed bulk powder. To our knowledge, the powder was destined to be encapsulated and sold as a dietary supplement. The structure was identified by NMR, HR-ESI-MS, ESI-MSⁿ and FTIR analyses. Owing to the inclusion of a hydroxyl group in acetildenafil, the detected compound was called 'hydroxyacetildenafil'. With increasing use of dietary supplements marketed for penile erectile dysfunction, the detection of analogues of sexual performance enhancers is important and timely.