Lifetime modelling with aid of a modified complementary weibull distribution

The complementary Weibull distribution may serve as a lifetime model for various applications. A modification of this distribution is introduced. Its purpose is to enable the calculation of the MTBF integral, which does not exist for the regular complementary Weibull function. An efficient quadrature technique is provided. Its utility is validated through some examples.     

Determination of green‐bond strength in tacky poly(vinyl alcohol) hydrogels

Pressure‐sensitive tack is the adhesive property related to bond formation. It is a key issue when formulating hydrogel poultices for transdermal delivery, dressings, and bioelectrodes. Quantitative tack gives an indication of the potential ease and success of application when gels are brought into contact with skin. The effects of different dwell times and constant pressures on bond formation between tacky poly(vinyl alcohol) (PVA) hydrogels and a skin model were explored in the current study; these were correlated with viscoelastic properties in order to elucidate structure–function relationships. A rolling tack test was performed using a novel apparatus capable of simultaneously controlling the pressure and dwell time in a hydrogel/skin‐model‐probe system. PVA gels were formed via the freeze–thaw technique using Ca²⁺ ions. Lower calcium availability in PVA gels resulted in longer dwell times required to complete bond formation, decreased creep compliance (at 0.01 s) and a decreased G′_{(ω = 40)}/G′_{(ω = 0.01)} ratio, all three leading to a loss in tack strength. All tested gels were found to have pressure‐sensitive tack. The results of this study support the applicability of a rheological methodology and a novel tack‐testing procedure to quantify green‐bond formation in pressure‐sensitive‐adhesive PVA hydrogels. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2130–2135, 2003     

Structural Basis of Microtubule Stabilization by Discodermolide

Microtubule‐stabilizing agents (MSAs) are widely used in chemotherapy. Using X‐ray crystallography we elucidated the detailed binding modes of two potent MSAs, (+)‐discodermolide (DDM) and the DDM–paclitaxel hybrid KS‐1‐199‐32, in the taxane pocket of β‐tubulin. The two compounds bind in a very similar hairpin conformation, as previously observed in solution. However, they stabilize the M‐loop of β‐tubulin differently: KS‐1‐199‐32 induces an M‐loop helical conformation that is not observed for DDM. In the context of the microtubule structure, both MSAs connect the β‐tubulin helices H6 and H7 and loop S9–S10 with the M‐loop. This is similar to the structural effects elicited by epothilone A, but distinct from paclitaxel. Together, our data reveal differential binding mechanisms of DDM and KS‐1‐199‐32 on tubulin.     

An intelligent Quality of Service brokering model for e-commerce

A fuzzy logic based Quality of Service (QoS) brokering model for e-commerce to manage system and network resources is presented in this study. This model takes into consideration limited bandwidth between clients and their Internet Service Providers; and similarly the client’s system capabilities. The QoS brokering system was modelled, developed, and simulated using Matlab 7.0. Its performance was evaluated using two QoS performance metrics namely the response time and the throughput. The proposed QoS brokering model is simple to implement as well as robust due to the nature of fuzzy controller. Simulation results of the proposed QoS brokering system demonstrate the effectiveness of the model in managing resources optimally and also improving the user-perceived QoS of e-commerce application.     

Laboratory evaluation of malathion, chlorpyrifos and chlorpyrifos-methyl for use against beetles infesting stored wheat

The relative toxicities of malathion; chlorpyrifos, 0,0-diethyl 0-(3,5,6-trichloro-2-pyridyl) phosphorothioate; and chlorpyrifos-methyl, 0,0 dimethyl 0-(3,5,6-trichloro-2-pyridyl) phosphorothioate to stored product beetles were determined using an impregnated filter paper technique. Chlorpyrifos-methyl was the most toxic compound to the 5 species tested and like chlorpyrifos was equally effective against malathion resistant and susceptible strains of Tribolium. On wheat of 12% moisture content chlorpyrifos-methyl was the most effective of the 3 compounds as a protectant against Sitophilus oryzae (L.).     

An improved algorithm for online coloring of intervals with bandwidth

We present an improved online algorithm for coloring interval graphs with bandwidth. This problem has recently been studied by Adamy and Erlebach and a 195-competitive online strategy has been presented. We improve this by presenting a 10-competitive strategy. To achieve this result, we use variants of an optimal online coloring algorithm due to Kierstead and Trotter.