A parallel implementation of the nested decomposition algorithm for multistage stochastic linear programs

Multistage stochastic linear programs can represent a variety of practical decision problems. Solving a multistage stochastic program can be viewed as solving a large tree of linear programs. A common approach for solving these problems is the nested decomposition algorithm, which moves up down the tree by solving nodes and passing information among nodes. The natural independence of subtrees suggests that much of the computational effort of the nested decomposition algorithm can run in parallel across small numbers of fast processors. This paper explores the advantages of such parallel implementations over serial implementations and compares alternative sequencing protocols for parallel processors. Computational experience on a large test set of practical problems with up to 1.5 million constraints and almost 5 million variables suggests that parallel implementations may indeed work well, but they require careful attention to processor load balancing. Supported in part by the National Science Foundation under Grants DDM-9215921 and SES-9211937.     

Infinite joins that are finitely join-irreducible

Complete lattices are studied which contain an element u which is not the join of a finite set of smaller elements, but is the join of all elements <u.This work was done while the first author was partly supported by NSF contract DMS 85-02330; during the completion of the article the second author was partly supported by NSF grant DMS 88-07043.     

Scheduling problems with random processing times under expected earliness/tardiness costs

This work is concerned with scheduling problems for a single machine. Taking earliness and tardiness of completion time and due–date value into consideration, the objective function with a common due date is considered. The processing time of each job is random. Sufficient conditions guaranteeing an optimal SEPT sequence are derived. Under exponential and normal processing times, further results are obtained     

Biotin-, fluorescein- and 'clickable' conjugates of phospha-oseltamivir as probes for the influenza virus which utilize selective binding to the neuraminidase

The synthesis of conjugates of phospha-oseltamivir to the well established reporter groups fluorescein and biotin and an approach to multimeric inhibitors is described. We report powerful inhibition of the influenza neuraminidase by these probes and quantify fluorescence quenching during binding of the fluorescein conjugate through titration with the neuraminidase. Thus, we show that they could be useful tools to efficiently inhibit, detect and quantify the virus and the neuraminidase in biological systems.     

Supercurrent-induced temperature gradient across a nonequilibrium SNS Josephson junction

Using tunneling spectroscopy, we have measured the local electron energy distribution function in the normal part of a superconductor-normal metal-superconductor (SNS) Josephson junction containing an extra lead to a normal reservoir. In the presence of simultaneous supercurrent and injected quasiparticle current, the distribution function exhibits a sharp feature at very low energy. The feature is odd in energy and odd under reversal of either the supercurrent or the quasiparticle current direction. The feature represents an effective temperature gradient across the SNS Josephson junction that is controllable by the supercurrent.     

Magnetization-dependent shift in ferromagnet/superconductor/ferromagnet trilayers with a strong ferromagnet

We have measured the superconducting transition temperature Tc of Ni/Nb/Ni trilayers when the magnetizations of the two outer Ni layers are parallel (P) and antiparallel (AP). The largest difference in occurs when the Nb thickness is just above the critical thickness at which superconductivity disappears completely. We have observed a difference in Tc between the P and AP states as large as 41 mK--a significant increase over earlier results in samples with higher Tc and with a CuNi alloy in place of the Ni. Our result also demonstrates that strong elemental ferromagnets are promising candidates for future investigations of ferromagnet/superconductor heterostructures.