Parametric Integer Programming: The Right-Hand-Side-Case

A family of integer programs is considered whose right-hand-sides lie on a given line segment L. This family is called a parametric integer program(PIP). Solving a (PIP) means finding an optimal solution for every program in the family. It is shown how a simple generalization of the conventional branch-and-bound approach to integer programming makes it possible to solve such a (PIP). The usual bounding test is extended from a comparison of two point values to a comparison of two functions defined on the line segment L. The method is illustrated on a small example and computational results for some larger problems are reported.Supported in part by the U.S. Army Research Office (Durham) under Contract DAHC04-73-C-0032

Proof of the perpetuity equation

AbstractA perpetuity is a perpetual annuity. Although there have been a number of different derivations, which we discuss in detail, we present what appears to be the first mathematical proof of the perpetuity equation based on the fundamental properties of the real numbers (Result (2.2.1) of Dieudonne (1960) [14])

An Electrochemical Analysis of Fretting Corrosion in Metal-on-Metal Hip Implants Subjected to High Impaction Loads

The metal-on-metal total hip arthroplasty, a procedure where the hip joint is replaced by a femoral prosthesis with a metal femoral head and a metal socket, has been a popular option for patients requiring a hip joint replacement. Metal on metal hip implants have been a successful implant design until recently where there has been an increased number of failures of this type of implant due to fretting corrosion, believed to be caused from the use of large femoral heads. Fretting corrosion in hip implants results from cyclic micromotion at the taper-trunnion interface; this interface motion removes the protective oxidation layer from the metal allowing the fluid environment of the body to react with the metal and ultimately leads to the release of metal ions into the surrounding tissue and bloodstream. The objective of this research is to quantify the amount of fretting corrosion at the taper-trunnion interface after a static load of 991 lbs is applied, and compare results to a previous study where 450 lbs impaction force was applied. For both studies all specimens are cyclically loaded between 10 lbs and 460 lbs while fretting corrosion data is collected. Fretting corrosion was characterized through the implementation of an electrochemical experiment in order to measure the amount of metal ions released from the implant during loading, which is directly correlated to the amount of fretting corrosion. Results of this study will elucidate the importance of impaction load in the process of fretting corrosion at the metal taper-trunnion interface

A hybrid approach to discrete mathematical programming

The dynamic programming and branch-and-bound approaches are combined to produce a hybrid algorithm for separable discrete mathematical programs. The hybrid algorithm uses linear programming in a novel way to compute bounds and is readily extended to solve a family of parametric integer programs with related right-hand-sides. Computational experience is reported on a number of linear and nonlinear integer programs.Supported in part by the U.S. Army Research Office (Durham) under Contract DAHC04-73-C-0032

The optimality of balancing workloads in certain types of flexible manufacturing systems

Symmetric mathematical programming is used to analyze the optimality of balancing workloads to maximize the expected production in a single-server closed queuing network model of a flexible manufacturing system (FMS). In particular, using generalized concavity we prove that, even though the production function is not concave, balancing workloads maximizes the expected production in certain types of m-machine FMS's with n parts in the system. Our results are compared and contrasted with previous models of production systems.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25713/1/0000270.pd

Optimal operation of flood control systems

The management and control of multiple-reservoir flood control systems is studied. Our objective is to devise operating policies which minimize flood damages as determined by the flood peaks. Methodologies are presented that employ dynamic programming and stochastic dynamic programming for the optimal operation of multiple-reservoir flood control systems with deterministic and stochastic inflows, respectively. The methodologies are applied to a number of real-world problems involving river basins in Illinois and elsewhere. We then study the effects of parametrically varying a number of the input parameters. A Markov renewal flood synthesis model and a methodology for determining the optimal capacity of a new flood control reservoir are also presented.U.S. Geological SurveyU.S. Department of the InteriorOpe

First isolation of a rhabdovirus from perch Perca fluviatilis in Switzerland

Perca fluviatilis is a fish species of increasing interest to the Swiss fish farming industry. In recent years, recirculation systems have been specifically set up to increase production. In one of these farms, abnormal spiral swimming associated with elevated mortalities occurred in repeated batches of imported perch shortly after stocking on several occasions. No bacterial or parasitic etiology was detected, but a virus grown in bluegill fry (BF-2) cells was identified as perch rhabdovirus. Subsequent investigations of other samples suggested a viral tropism for the central nervous system (CNS). Phylogenetic analysis of the partial N and entire G gene sequences positioned this isolate in genogroup C of the species Perch rhabdovirus, with high nucleotide and amino acid (aa) sequence identities with the DK5533 strain isolated in Denmark in 1989. Comparative studies using other closely related isolates allowed the distinction of 2 serological Patterns among perch rhabdoviruses and the identification of a proline substitution by a serine in Position 147 of the glycoprotein potentially involved in antigenic differentiation. Even if perch imported onto the farm tested negative by virus isolation prior to transport, they may have been the origin of this outbreak since CNS tissue was not included in the samples that were analyzed. Another possibility might be a sub-clinical infection with a viral load in resident fish too low to be detected. This study reports the first isolation of a perch rhabdovirus in Switzerland, and emphasizes the necessity of optimizing diagnostic tools that facilitate better control of the risks associated with fish translocation

Motility Screen Identifies Drosophila IGF-II mRNA-Binding Protein—Zipcode-Binding Protein Acting in Oogenesis and Synaptogenesis

The localization of specific mRNAs can establish local protein gradients that generate and control the development of cellular asymmetries. While all evidence underscores the importance of the cytoskeleton in the transport and localization of RNAs, we have limited knowledge of how these events are regulated. Using a visual screen for motile proteins in a collection of GFP protein trap lines, we identified the Drosophila IGF-II mRNA-binding protein (Imp), an ortholog of Xenopus Vg1 RNA binding protein and chicken zipcode-binding protein. In Drosophila, Imp is part of a large, RNase-sensitive complex that is enriched in two polarized cell types, the developing oocyte and the neuron. Using time-lapse confocal microscopy, we establish that both dynein and kinesin contribute to the transport of GFP-Imp particles, and that regulation of transport in egg chambers appears to differ from that in neurons. In Drosophila, loss-of-function Imp mutations are zygotic lethal, and mutants die late as pharate adults. Imp has a function in Drosophila oogenesis that is not essential, as well as functions that are essential during embryogenesis and later development. Germline clones of Imp mutations do not block maternal mRNA localization or oocyte development, but overexpression of a specific Imp isoform disrupts dorsal/ventral polarity. We report here that loss-of-function Imp mutations, as well as Imp overexpression, can alter synaptic terminal growth. Our data show that Imp is transported to the neuromuscular junction, where it may modulate the translation of mRNA targets. In oocytes, where Imp function is not essential, we implicate a specific Imp domain in the establishment of dorsoventral polarity