bluuebunny/crossref_metadata_2025 huggingface dataset:
The chromatin of differentiating erythroblasts is cleaved into large size fragments independent of caspase activated DNase and apoptosis inducing factor
Authors: Hristoskova Sashka , Holzgreve Wolfgang , Hahn Sinuhe , Rusterholz Corinne
Published: May 2007

Erythroblast cell differentiation involves self‐controlled and limited nuclear proteolysis prior nucleus loss. Early evidence suggests that apoptotic‐like pathways are activated during this process. The chromatin of developing erythroblasts becomes fragmented in vivo, however, the exact mechanisms and molecules involved remain elusive. In this study, erythroblasts were differentiated in culture from CD34‐enriched umbilical cord blood progenitor cells and the characteristics of DNA fragmentation were examined. This analysis shows that the chromatin of differentiating erythroblasts is cleaved into discrete fragments of 50–200 kb. This process most likely involves one or several endonucleases as we detect in vivo double strand DNA cleavage. However, major players of the apoptotic DNA degradation, caspase activated DNase and apoptosis inducing factor, are not activated in these cells. Therefore, our data suggests that erythroblast chromatin degradation may involve enzymes distinct form those active in apoptotic cells. J. Cell. Physiol. 213: 490–494, 2007. © 2007 Wiley‐Liss, Inc.
Chromatin compaction and cell death by high molecular weight FGF‐2 depend on its nuclear localization, intracrine ERK activation, and engagement of mitochondria
Authors: Ma Xin , Dang Xitong , Claus Peter , Hirst Cheryl , Fandrich Robert R. , Jin Yan , Grothe Claudia , Kirshenbaum Lorrie A. , Cattini Peter A. , Kardami Elissavet
Published: May 2007

Fibroblast growth factor 2 (FGF‐2) is produced as CUG‐initiated, 22–34 kDa or AUG‐initiated 18 kDa isoforms (hi‐ and lo‐FGF‐2, respectively), with potentially distinct functions. We report that expression of hi‐FGF‐2 in HEK293 cells elicited chromatin compaction preceding cell death with apoptotic features. Nuclear localization of the intact protein was required as expression of a non‐nuclear hi‐FGF‐2 mutant failed to elicit chromatin compaction. Equally ineffective, despite nuclear localization, was the over‐expression of the 18 kDa core sequence (lo‐FGF‐2). Chromatin compaction by hi‐FGF‐2 was accompanied by increased cytosolic cytochrome C, and was attenuated either by over‐expression of Bcl‐2 or by a peptide inhibitor of the pro‐apoptotic protein Bax. In addition hi‐FGF‐2 elicited sustained activation of total and nuclear extracellular signal regulated kinase (ERK1/2) by an intracrine route, as it was not prevented by neutralizing anti‐FGF‐2 antibodies. Inhibition of the ERK1/2 activating pathway by dominant negative upstream activating kinase, or by PD 98059, prevented chromatin compaction by hi‐FGF‐2. ERK1/2 activation was not affected by the Bax‐inhibiting peptide suggesting that it occurred upstream of mitochondrial involvement. We conclude that the hi‐FGF‐2‐induced chromatin compaction and cell death requires its nuclear localization, intracrine ERK1/2 activation and mitochondrial engagement. J. Cell. Physiol. 213:690–698. © 2007 Wiley‐Liss, Inc.
Sperm morphology of the eurasian beaver, Castor fiber: An example of a species of rodent with highly derived and pleiomorphic sperm populations
Authors: Bierla Joanna B. , Gizejewski Zygmunt , Leigh Christopher M. , Ekwall Hans , Söderquist Lennart , Rodriguez‐Martinez Heriberto , Zalewski Kazimierz , Breed William G.
Published: May 2007

The structural organization of the spermatozoon from the Eurasian beaver, Castor fiber (Family: Castoridae), was determined and compared to that of other sciuromorph rodents. The beaver spermatozoon has a head, which is variable in form but usually paddle‐shaped, with a small nucleus and very large acrosome, and a tail that is relatively short compared to that of most other rodents. Transmission electron microscopy indicates that in most testicular spermatozoa the acrosome projects apically, although in a few it becomes partly flexed. During the final stages of maturation, however, the acrosome becomes highly folded so that the apical segment comes to lie alongside part of the acrosome that occurs lateral to the nucleus, with, in some cases, fusion taking place between the outer acrosomal membranes. The sperm nucleus is wedge‐shaped, being broader basally and narrowing apically with an occasional large nuclear vacuole occurring. This spermatozoon structure is markedly different from that found in the other species of Geomyoidea, which is the sister group of the Castoridae. The findings thus emphasize the highly divergent nature of the beaver spermatozoon and demonstrate that, within the proposed Infraorder Castorimorpha, very large differences in sperm structure have evolved. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
P2Y receptor‐activating nucleotides modulate cellular reactive oxygen species production in dissociated hippocampal astrocytes and neurons in culture independent of parallel cytosolic Ca2+ rise and change in mitochondrial potential
Authors: Kahlert Stefan , Blaser Till , Tulapurkar Mohan , Reiser Georg
Published: May 2007

With mixed cultures of hippocampal astrocytes and neurons, we investigated the influence of nucleotides on cytosolic Ca2+ level, generation of reactive oxygen species (ROS), and mitochondrial potential. We employed ATP and four purine/pyrimidine derivates, which are P2Y receptor subtype‐preferring agonists. Stimulation with ATP, a P2Y1/2/4 receptor agonist in rat, caused a large cytosolic Ca2+ increase in astrocytes and a considerably smaller Ca2+ response in neighboring neurons. The P2Y1 receptor antagonist MRS2179 completely blocked the ATP‐induced Ca2+ response in astrocytes and neurons. Application of ATP significantly reduced the mitochondrial potential in neurons, which was not inhibited by MRS2179. Interestingly, MRS2179 mediated a mitochondrial depolarization without affecting the cytosolic Ca2+ level. Stimulation with UDP, a P2Y6 receptor agonist; UTP, a P2Y2/4 receptor agonist; 2MeSATP, a P2Y1 receptor agonist; or 2MeSADP, a P2Y1/12/13 receptor agonist, evoked significant Ca2+ responses in astrocytes but small Ca2+ responses in neurons. In astrocytes, there was an inverse relationship between the amplitude of the cytosolic Ca2+ peak and the rate of ROS generation in response to nucleotide application. Activation with UDP resulted in the highest ROS generation that we detected, whereas 2MeSADP and 2MeSATP reduced the ROS generation below the basal level. 2MeSADP and UDP caused mitochondrial depolarization of comparable size. Thus, neither in astrocytes nor in neurons did the degree of mitochondrial depolarization correlate with ROS generation. Nucleotides acting via P2Y receptors can modulate ROS generation of hippocampal neurons without acutely changing the cytosolic Ca2+ level. Thus, ROS might function as a signaling molecule upon nucleotide‐induced P2Y receptor activation in brain. © 2007 Wiley‐Liss, Inc.
Neuroprotective effects of pituitary adenylate cyclase–activating polypeptide (PACAP) in MPP+‐induced alteration of translational control in Neuro‐2a neuroblastoma cells
Authors: Deguil Julie , Jailloux David , Page Guylène , Fauconneau Bernard , Houeto Jean‐Luc , Philippe Michel , Muller Jean‐Marc , Pain Stéphanie
Published: May 2007

Parkinson's disease (PD) and 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) toxicity are both associated with dopaminergic neuron death in the substantia nigra. Although a variety of evidence has shown that degenerative cells have apoptotic features, the role of apoptosis in disease pathology remains controversial. The 1‐methyl‐4‐phenylpyridinium ion (MPP+), a metabolite of MPTP, was recently shown to alter the expression of proteins involved in translational control. The initiation step of translational control is regulated by a cascade of phosphorylation affecting proteins of the antiapoptotic way controlled by mammalian target of rapamycin (mTOR) and of the proapoptotic way controlled by double‐stranded RNA protein–dependent kinase (PKR). A study showed that MPP+induced an increase in eIF2α phosphorylation, leading to inhibition of protein synthesis. The aims of our study were: (1) to assess the effects of MPP+toxicity on molecular factors of PKR and mTOR signaling pathways in murine neuroblastoma cells, and (2) to examine the ability of VIP and PACAP peptides to counteract the MPP+toxicity. Our findings showed that MPP+induced phosphorylation of eIF2α and significantly reduced the expression of phosphorylated mTOR, p70S6K, eIF4E, and 4E‐BP1, suggesting its toxicity in controlling protein synthesis. Furthermore, the VIP peptide had no effect on either the PKR or the mTOR signaling pathway. On the contrary, the PACAP 27 neuropeptide prevented MPP+‐induced eIF2α phosphorylation and blocked MPP+toxicity in molecular factors of the mTOR pathway. And last, PACAP 27 seemed to protect Neuro‐2a cells from the apoptotic process as assessed by the decreased nuclear condensation after DAPI staining. These results could open new paths of research of PACAP in PD. © 2007 Wiley‐Liss, Inc.
Delayed neurotrophin treatment following deafness rescues spiral ganglion cells from death and promotes regrowth of auditory nerve peripheral processes: Effects of brain‐derived neurotrophic factor and fibroblast growth factor
Authors: Miller Josef M. , Le Prell Colleen G. , Prieskorn Diane M. , Wys Noel L. , Altschuler Richard A.
Published: May 2007

The extent to which neurotrophic factors are able to not only rescue the auditory nerve from deafferentation‐induced degeneration but also promote process regrowth is of basic and clinical interest, as regrowth may enhance the therapeutic efficacy of cochlear prostheses. The use of neurotrophic factors is also relevant to interventions to promote regrowth and repair at other sites of nerve trauma. Therefore, auditory nerve survival and peripheral process regrowth were assessed in the guinea pig cochlea following chronic infusion of BDNF + FGF1 into scala tympani, with treatment initiated 4 days, 3 weeks, or 6 weeks after deafferentation from deafening. Survival of auditory nerve somata (spiral ganglion neurons) was assessed from midmodiolar sections. Peripheral process regrowth was assessed using pan‐Trk immunostaining to selectively label afferent fibers. Significantly enhanced survival was seen in each of the treatment groups compared to controls receiving artificial perilymph. A large increase in peripheral processes was found with BDNF + FGF1 treatment after a 3‐week delay compared to the artificial perilymph controls and a smaller enhancement after a 6‐week delay. Neurotrophic factor treatment therefore has the potential to improve the benefits of cochlear implants by maintaining a larger excitable population of neurons and inducing neural regrowth. © 2007 Wiley‐Liss, Inc.
Morphometric analysis of oligodendrocytes in the adult mouse frontal cortex
Authors: Murtie Joshua C. , Macklin Wendy B. , Corfas Gabriel
Published: May 2007

Oligodendrocytes (OLs), the myelinating cells of the central nervous system, have specialized morphologies that subserve their function. Numerous qualitative studies suggest that OLs in different brain regions can differ in their morphological characteristics, including number of branches and internodes, internode length, etc. However, progress in identifying and characterizing the diverse types of OLs and their distribution in the brain has been made difficult by several technical constraints. Here we report a new strategy to analyze OL morphology with a high degree of quantitative power and throughput. We used confocal microscopy and three‐dimensional cell tracing software to study OLs in the frontal cortex of mice expressing enhanced green fluorescent protein (eGFP) under the control of the proteolipid protein (Plp) gene promoter. Three‐dimensional reconstructions were then used to analyze and quantify cell morphology, including total process length, total process surface area, total internode length, number of primary processes, number of branch points, and number of internodes. In addition, these reconstructions were subjected to Sholl analysis, which allows for the quantitative measure of OL arbor complexity. By using this approach, we identified and characterized a previously undescribed population of small OLs with a compact but complex morphology that includes numerous branching processes and a large number of short internodes. Our data suggest that other populations of OLs remain to be identified and characterized and that the tools we have developed could help in the process of characterizing them. © 2007 Wiley‐Liss, Inc.
Optimizing human post‐mortem brain tissue gene expression profiling in Parkinson's disease and other neurodegenerative disorders: From target “fishing” to translational breakthroughs
Authors: Papapetropoulos Spiridon , Shehadeh Lina , McCorquodale Donald
Published: May 2007

Insights on the etiopathogenesis of common neurodegenerative disorders such as Parkinson's disease (PD) and Alzheimer's disease (AD) have been largely based on the discovery of gene mutations in genetically determined forms. Although these discoveries have been helpful in elucidating the basic molecular pathogenesis of familial forms, they represent a small fraction of cases, leaving the large majority classified as idiopathic. In the postgenomic era, brain tissue gene expression profiling has allowed relative quantitative assessment of thousands of genes simultaneously from one tissue sample, providing clues for novel candidate genes and processes implicated in neurodegenerative disorders. Some remain critical of “fishing expedition” science, but gene expression profiling is a discovery‐based procedure well suited for the study of largely idiopathic and multifactorial diseases. However, the technology is still under development, and many methodological and biological aspects contribute to the heterogeneous results obtained from gene expression profiling. In this Review, we discuss the advantages and limitations of this technology in simple terms and identify the key variables that influence/limit gene expression profiling‐derived translational breakthroughs in neurodegenerative diseases. © 2007 Wiley‐Liss, Inc.
High‐pressure Raman and photoluminescence of highly anisotropic CdS nanowires
Authors: Fan H. M. , Ni Z. H. , Feng Y. P. , Fan X. F. , Shen Z. X. , Zou B. S.
Published: May 2007

Raman and photoluminescence of CdS nanowires of diameter 80 nm and lengths up to several tens of micrometers were studied at pressure up to 60 kbar using a Jobin‐Yvon T64000 micro‐Raman system in conjunction with the diamond‐anvil cell technique. The phase transition pressure of wurtzite to rock salt was observed at 38 kbar, which is higher than that of bulk CdS. In contrast with the transition pressure of different‐sized CdS nanocrystal, this elevated phase transition pressure cannot be explained well by the size effect. Thus the contribution of particle morphology of such a system, which represents the low‐energy surface structure, should be considered. The pressure dependence of photoluminescence is also discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Raman and infrared studies of synthetic Maya pigments as a function of heating time and dye concentration
Authors: Manciu F. S. , Reza L. , Polette L. A. , Torres B. , Chianelli R. R.
Published: May 2007

Maya Blue is a famous indigo‐based pigment produced by the ancient Mayas. The organic/inorganic complexes inspired by Maya Blue have led to a new class of surface compounds that have novel applications to pigment industries. Materials analyzed in the present work are made by a synthetic route, and demonstrate chemical stability similar to that of the ancient Maya Blue samples. However, we have learned that stable complexes can be synthesized at much higher dye concentrations than used by the Mayas. Analysis by FT‐Raman and FT‐IR spectroscopy demonstrates the partial elimination of the selection rules for the centrosymmetric indigo, indicating distortion of the molecule. This distortion accounts for the observed color changes, as the molecular orbital structure is modified, allowing the complex to stabilize. The spectroscopic data also shows the disappearance of the indigo NH bonding, as the organic molecules incorporate into palygorskite material. A structural change of indigo to dehydroindigo during heating is suggested by this result. Infrared data confirm the loss of zeolitic water and a partial removal of structural water after the heating process. Evidence of bonding between cationic aluminum and dehydroindigo through oxygen and nitrogen is revealed by FT‐Raman measurements at higher dye concentrations. Copyright © 2007 John Wiley & Sons, Ltd.
Expression of enhanced green fluorescent protein in porcine‐ and bovine‐cloned embryos following interspecies somatic cell nuclear transfer of fibroblasts transfected by retrovirus vector
Authors: Uhm Sang Jun , Gupta Mukesh Kumar , Kim Teoan , Lee Hoon Taek
Published: May 2007

Interspecies somatic cell nuclear transfer (iSCNT) has emerged as an important tool for studying nucleo‐cytoplasmic interactions and cloning of animals whose oocytes are difficult to obtain. This study was designed to explore the feasibility of employing transgenic fibroblasts as donor cells for iSCNT. The study examined the chromatin morphology, in vitro development, and expression of an enhanced green fluorescent protein (EGFP) gene in porcine‐ and bovine‐cloned embryos produced by iSCNT of fetal fibroblast transfected with a pLNβ‐EGFP retroviral vector. Parthenogenetic and transfected or nontransfected intraspecies SCNT embryos were used as controls for comparison. Analysis of data revealed that xenogenic oocyte was able to reprogram somatic cells of different genus and supports their in vitro development to the blastocyst stage. However, the developmental rates of transgenic iSCNT embryos to the blastocyst stage were significantly lower than those of intraspecies SCNT embryos. The reduction in development rates was however, not due to integration of the transgene as the lower (P < 0.05) development rates of the intraspecies SCNT porcine or bovine embryos did not differ between transgenic and nontransgenic groups. Expression of EGFP was observed in 100% of blastocysts and mosaicism was not observed. Furthermore, after iSCNT of porcine or bovine donor nuclei into xenogenic ooplasm, patterns of nuclear remodeling in reconstructed embryos were similar. In conclusion, our data demonstrated the feasibility of producing transgenic iSCNT embryos. To our knowledge, this is the first report of transgenic cloned embryo production by iSCNT approach. In the future, this may provide a powerful research tool for studying developmental events in domestic animals and provide marked cell lines for other genetic manipulations. Mol. Reprod. Dev. 74: 1538–1547, 2007. © 2007 Wiley‐Liss, Inc.
Numerical analysis of 1‐D compression wave propagation in saturated poroelastic media
Authors: Qiu Tong , Fox Patrick J.
Published: May 2007

A numerical procedure is presented for the simulation of 1‐D compression wave propagation in saturated poroelastic media. The media are modelled as a two‐phase system consisting of compressible fluid and solids. Viscous coupling forces resulting from the relative motion between phases are characterized as Darcy type. The numerical procedure can account for effects of axial strain, nonlinear material behaviour, and various drained and undrained boundary conditions. Time integration is carried out explicitly and isothermal conditions are assumed. The method is capable of modelling shock
wave fronts without introducing artificial viscosity. Numerical results are in close agreement with analytical solutions for several simplified cases and indicate that mass coupling may have important effects on fluid velocity and wave speed. Corresponding effects on solid velocity and wave speed are much smaller. Numerical results also indicate that damping occurs in a saturated poroelastic column and is dependent on the value of hydraulic conductivity. Copyright © 2007 John Wiley & Sons, Ltd.
Evaluation of commonly used rules for detecting “steady state” in computer simulation
Authors: Gafarian A. V. , Ancker C. J. , Morisaku T.
Published: May 2007

A definition of the problem of the initial transient with respect to the steady‐state mean value has been formulated. A set of criteria has been set forth by which the efficaacy of any proposed rule may be assessed. Within this framework, five heuristic rules for predicting the approximate end of transiency, four of which have been quoted extensively in the simulation literature, have been evaluated in the M/M/1 situation. All performed poorly and are not suitable for their intended use.
Predicting the cost performance of inventory control systems by retrospective simulation
Authors: MacCormick Alastair
Published: May 2007

When an inventory‐control system is designed to utilized statistical demand information in computing an (s,S) policy, it may be necessary to use performance forecasts to calibrate the relationship between control parameters and performance measures. Using a simulation model to test prediction by retrospective simulation we estimated the bias and variance of forecasts for expected costs and other operating characteristics. The results show the sensitivity of the prediction bias to changes in demand, cost, and lead time parameters and to choices made in system design.
The optimum design of multivariate acceptance sampling plans
Authors: Chapman S. C. , Schmidt J. W. , Bennett G. K.
Published: May 2007

A model is developed which may be used to determine the expected total cost of quality control per inspection lot under acceptance sampling by variables where several characteristics are to be simultaneously controlled. Optimization of the model is accomplished through the application of a conventional search procedure. The sensitivity of the model and the optimum solution to the shape of the underlying probability distributions is discussed and associated analyses are presented through an example.
Markov chain with taboo states and reliability
Authors: Sriwastav G. L. , Pandit S. N. N.
Published: May 2007

A computationally feasible matrix method is presented to find the first‐passage probabilities in a Markov chain where a set of states is taboo during transit. This concept has been used to evaluate the reliability of a system whose changes in strength can be thought of as a Markov chain, while the environment in which it is functioning generates stresses which can also be envisaged as another Markov chain.
A note on the limitations of goal programming as observed in resource allocation for marine environmental protection
Authors: Harrald J. , Leotta J. , Wallace W. A. , Wendell R. E.
Published: May 2007

After first formulating the problem of the Marine Environmental Protection program of the Coast Guard as a multiple‐objective linear program, we investigate the applicability and limitations of goal programming. We point out how the preemptive goal‐programming approach is incompatible with utility preferences. Then we observe the tendency of optimal solutions for standard linear goal programs to occur at extreme points. We also note problems of more general approaches, such as dealing with additively separable approximations to preferences.
M/M/1 queues with interdependent arrival and service processes
Authors: Mitchell C. R. , Paulson A. S.
Published: May 2007

We study via simulation an M/M/1 queueing system with the assumption that a customer's service time and the interarrival interval separating his arrival from that of his predecessor are correlated random variables having a bivariate exponential distribution. We show that positive correlation reduces the mean and variance of the total waiting time and that negative correlation has the opposite effect. By using spectral analysis and a nonparametric test applied to the sample power spectra associated with certain simulated waiting times we show the effect to be statistically significant.
Interval estimation of a global optimum for large combinatorial problems
Authors: Golden Bruce L. , Alt Frank B.
Published: May 2007

Consider an “intractable” optimization problem for which no efficient solution technique exists. Given a systematic procedure for generating independent heuristic solutions, we seek to obtain interval estimates for the globally optimal solution using statistical inference. In previous work, accurate point estimates have been derived. Determining interval estimates, however, is a considerably more difficult task. In this paper, we develop straightforward procedures which compute confidence intervals efficiently in order to evaluate heuristic solutions and assess deviations from optimality. The strategy presented is applicable to a host of combinatorial optimization problems. The assumptions of our model, along with computational experience, are discussed.
The enumeration of all efficient solutions for a linear multiple‐objective transportation problem
Authors: Isermann Heinz
Published: May 2007

An algorithm is presented by which the set of all efficient solutions for a linear multiple‐objective transportation problem can be enumerated. First the algorithm determines an initial efficient basic solution. In a second step all efficient basic solutions are enumerated. Finally, the set of all efficient solutions is constructed as a union of a minimal number of convex sets of efficient solutions. The algorithm is illustrated by a numerical example.
Bayesian estimation and optimal designs in partially accelerated life testing
Authors: Degroot Morris H. , Goel Prem K.
Published: May 2007

A method of life testing is proposed which combines both ordinary and accelerated life‐testing procedures. It is assumed that an item can be tested either in a standard environment or under stress. The amount of stress is fixed in advance and is the same for all items to be tested However, the time x at which an item on lest is taken out of the standard environment and put under stress can be chosen by the experimenter subject to a given cost structure. When an item is put under stress its lifetime is changed by the factor α. Let the random variable T denote the lifetime of an item in the standard environment, and let γ denote its lifetime under the partially accelerated test procedure just described. Then Y = T if T ≦ x, and Y = x + α (T > x) if T > x. It is assumed that T has an exponential distribution with parameter θ. The estimation of θ and α and the optimal design of a partially accelerated life test are studied in the framework of Bayesian decision theory.
Optimal state‐dependent pricing policies for a class of stochastic multiunit service systems
Authors: Gupta R. K. , Srinivasan V. , Yu P. L.
Published: May 2007

This paper models a k‐unit service system (e.g., a repair, maintenance, or rental facility) with Poisson arrivals, exponential service times, and no queue. If we denote the number of units that are busy as the state of the system, the state‐dependent pricing model formalizes the intuitive notion that when most units are idle, the price (i.e., the service charge per unit time) should be low, and when most units are busy, the price should be higher than the average. A computationally efficient algorithm based on a nonlinear programming formulation of the problem is provided for determination of the optimal state‐dependent prices. The procedure ultimately reduces to the search on a single variable in an interval to determine the unique intersection point of a concave increasing function and a linear decreasing function. The algorithm takes, on the average, only about 1/2 second per problem on the IBM 360/65 (FORTRAN G Compiler). A discrete optimal‐control approach to the problem is shown to result in essentially the same procedure as the nonlinear‐programming formulation. Several properties of the optimal state‐dependent prices are given. Comparisons of the optimal values of the objective function for the state‐dependent and state‐independent pricing policies show that the former is on the average, only about 0.7% better than the latter, which may explain partly why state‐dependent pricing is not prevalent in many service systems. Potential generalizations of the model are discussed.
On the first time a separately maintained parallel system has been down for a fixed time
Authors: Ross Sheldon M. , Schechtman Jack
Published: May 2007

Consider a system consisting of n separately maintained independent components where the components alternate between intervals in which they are “up” and in which they are “down”. When the ith component goes up [down] then, independent of the past, it remains up [down] for a random length of time, having distribution Fi[Gi], and then goes down [up]. We say that component i is failed at time t if it has been “down” at all time points s ϵ[t‐A.t]: otherwise it is said to be working. Thus, a component is failed if it is down and has been down for the previous A time units. Assuming that all components initially start “up,” let T denote the first time they are all failed, at which point we say the system is failed. We obtain the moment‐generating function of T when n = l, for general F and G, thus generalizing previous results which assumed that at least one of these distributions be exponential. In addition, we present a condition under which T is an NBU (new better than used) random variable. Finally we assume that all the up and down distributions Fi and Gi i = l,….n, are exponential, and we obtain an exact expression for E(T) for general n; in addition we obtain bounds for all higher moments of T by showing that T is NBU.
On a single‐server queue with state‐dependent service
Authors: Shanthikumar J. G.
Published: May 2007

This paper discusses a class of queueing models in which the service time of a customer al a single server facility is dependent on the queue size at the onset of its service. The Laplace transform for the wait in queue distribution is derived and the utilization of the server is given when the arrival is a homogeneous Poisson process.
Approximation techniques in the solution of queueing problems
Authors: Bhat U. Narayan , Shalaby Mohamed , Fischer Martin J.
Published: May 2007

In the study of complex queueing systems, analysis techniques aimed al providing exact solutions become ineffective. Approximation techniques provide an attractive alternative in such cases. This paper gives an overview of different types of approximation techniques available in the literature and points out their relative merits. Also, the need for proper validation procedures of approximation techniques is emphasized.
Optimal project compression with due‐dated events
Authors: Elmaghraby S. E. , Pulat P. S.
Published: May 2007

The paper proposes an algorithm for the determination of the solution of the activities to be shortened and the amount by which they are to be shortened in order to minimize the total cost of project completion. This cost involves a linear penalty for tardienss of a set of key events and a linear cost of activity compression from its normal duration. The procedure is a generalization of the work of Fulkerson.
Some simple victory‐prediction conditions for lanchester‐type combat between two homogeneous forces with supporting fires
Authors: Taylor James G.
Published: May 2007

This paper develops new “simple” victory‐prediction conditions for a linear Lanchester‐type model of combat between two homogeneous forces with superimposed effects of supporting fires not subject to attrition. These simple victory‐prediction conditions involve only the initial conditions of battle and certain assumptions about the nature of temporal variations in the attrition‐rate coefficients. They are developed for a fixed‐force‐ratio‐breakpoint battle by studying the force‐ratio equation for the linear combat model. An important consideration is shown to be required for developing such simple victory‐prediction conditions: victory is not guaranteed in a fixed‐force‐ratio‐breakpoint battle even when the force ratio is always changing to the advantage of one of the combatants. One must specify additional conditions to hold for the cumulative fire effectivenesses of the primary weapon systems in order to develop correct victory‐prediction conditions. The inadequacy of previous victory‐prediction results is explained by examining (for the linear combat model without the supporting fires) new “exact” victory‐prediction conditions, which show that even the range of possible battle outcomes may be significantly different for variable‐coefficient and constant‐coefficients models.
A comparison of waiting time approximations in series queueing systems
Authors: Shimshak Daniel G.
Published: May 2007

The determination of steady‐state characteristics in systems of tandem queues has been left to computer simulation because of the lack of exact solutions in all but the simplest newtorks. In this paper, several methods developed for approximating the average waiting time in single‐server queues are extended to systems of queues in series. Three methods, due to Fraker, Page, and Marchal, are compared along with results gathered through GPSS simulation. Various queueing networks with Erlangian service distributions are investigated.
Scheduling jobs to two machines subject to batch arrival ordering
Authors: Tamir Arie
Published: May 2007

The problem considered is to assign n jobs to two processors so as to minimize the total flow time, with the constraint that a predetermined partial ordering (induced by batch arrivals) must be preserved within the subset of jobs assigned to each processor. An efficient algorithm of time 0(n5) is developed, and computational experience is reported.
Scheduling of stochastic tasks on two parallel processors
Authors: Pinedo Michael , Weiss Gideon
Published: May 2007

We consider the problem of scheduling n tasks on two identical parallel processors. We show both in the case when the processing times for the n tasks are independent exponential random variables, and when they are independent hyperexponentials which are mixtures of two fixed exponentials, that the policy of performing tasks with longest expected processing time (LEPT) first minimizes the expected makespan, and that in the hyperexponential case the policy of performing tasks with shortest expected processing time (SEPT) first minimizes the expected flow time. The approach is simpler than the dynamic programming approach recently employed by Bruno and Downey.
Optimal maintenance‐repair policies for the machine repair problem
Authors: Albright S. Christian
Published: May 2007

We consider a model with M + N identical machines. As many as N of these can be working at any given time and the others act as standby spares. Working machines fail at exponential rate λ, spares fail at exponential rale γ, and failed machines are repaired at exponential rate μ. The control variables are λ. μ, and the number of removable repairman, S, to be operated at any given time. Using the criterion of total expected discounted cost, we show that λ, S, and μ are monotonic functions of the number of failed machines M, N, the discount factor, and for the finite time horizon model, the amount of time remaining.
Benders' partitioning scheme applied to a new formulation of the quadratic assignment problem
Authors: Bazaraa Mokhtar S. , Sherali Hanif D.
Published: May 2007

In this paper we present a new formulation of the quadratic assignment problem. This is done by transforming the quadratic objective function into a linear objective function by introducing a number of new variables and constraints. The resulting problem is a 0‐1 linear integer program with a highly specialized structure. This permits the use of the partitioning scheme of Benders where only the original variables need be considered. The algorithm described thus iterates between two problems. The master problem is a pure 0‐1 integer program, and the subproblem is a transportation problem whose optimal solution is shown to be readily available from the master problem in closed form. Computational experience on problems available in the literature is provided.
The dynamic transportation problem: A survey
Authors: Bookbinder James H. , Sethi Suresh P.
Published: May 2007

The dynamic transportation problem is a transportation problem over time. That is, a problem of selecting at each instant of time t, the optimal flow of commodities from various sources to various sinks in a given network so as to minimize the total cost of transportation subject to some supply and demand constraints. While the earliest formulation of the problem dates back to 1958 as a problem of finding the maximal flow through a dynamic network in a given time, the problem has received wider attention only in the last ten years. During these years, the problem has been tackled by network techniques, linear programming, dynamic programming, combinational methods, nonlinear programming and finally, the optimal control theory. This paper is an up‐to‐date survey of the various analyses of the problem along with a critical discussion, comparison, and extensions of various formulations and techniques used. The survey concludes with a number of important suggestions for future work.
Statistical analysis of the output data from terminating simulations
Authors: Law Averill M.
Published: May 2007

In this paper we precisely define the two types of simulations (terminating and steady‐state) with regard to analysis of simulation output and discuss some common measures of performance for each type. In addition, we conclude, on the basis of discussions with many simulation practitioners, that both types of simulations are important in practice. This is contrary to the impression one gets from reading the simulation literature, where the steady‐state case is almost exclusively considered.

Although analyses of terminating simulations are considerably easier than are those of steady‐state simulations, they have not received a careful treatment in the literature. We discuss and give empirical results for fixed sample size, relative width, and absolute width procedures that can be used for constructing confidence intervals for measures of performance in the terminating case.
A note on the “value” of bounds on EVPI in stochastic programming
Authors: Morris J. G. , Thompson H. E.
Published: May 2007

The existing literature concentrates on determining sharp upper bounds for EVPI in stochastic programming problems. This seems to be a problem without an application. Lower bounds, which we view as having an important application, are only the incidental subject of study and in the few instances that are available are obtained at an extremely high cost.

In order to suggest a rethinking of the course of this research, we analyze the need for bounds on EVPI in the context of its significance in decision problems.
Optimal replacement of parts having observable correlated stages of deterioration
Authors: Shaw L. , Hsu C‐L , Tyan S. G.
Published: May 2007

A single component system is assumed to progress through a finite number of increasingly bad levels of deterioration. The system with level i (0 ≤ i ≤ n) starts in state 0 when new, and is definitely replaced upon reaching the worthless state n. It is assumed that the transition times are directly monitored and the admissible class of strategies allows substitution of a new component only at such transition times. The durations in various deterioration levels are dependent random variables with exponential marginal distributions and a particularly convenient joint distribution. Strategies are chosen to maximize the average rewards per unit time. For some reward functions (with the reward rate depending on the state and the duration in this state) the knowledge of previous state duration provides useful information about the rate of deterioration.
On the generation of deep disjunctive cutting planes
Authors: Sherali Hanif D. , Shetty C. M.
Published: May 2007

In this paper we address the question of deriving deep cuts for nonconvex disjunctive programs. These problems include logical constraints which restrict the variables to at least one of a finite number of constraint sets. Based on the works of Balas. Glover, and Jeroslow, we examine the set of valid inequalities or cuts which one may derive in this context, and defining reasonable criteria to measure depth of a cut we demonstrate how one may obtain the “deepest” cut. The analysis covers the case where each constraint set in the logical statement has only one constraint and is also extended for the case where each of these constraint sets may have more than one constraint.
Storage problems when demand is “all or nothing”
Authors: Gaver D. P. , Jacobs P. A.
Published: May 2007

An inventory of physical goods or storage space (in a communications system buffer, for instance) often experiences “all or nothing” demand: if a demand of random size D can be immediately and entirely filled from stock it is satisfied, but otherwise it vanishes. Probabilistic properties of the resulting inventory level are discussed analytically, both for the single buffer and for multiple buffer problems. Numerical results are presented.
A network flow approach for capacity expansion problems with two facility types
Authors: Luss Hanan
Published: May 2007

A deterministic capacity expansion model for two facility types with a finite number of discrete time periods is described. The model generalizes previous work by allowing for capacity disposals, in addition to capacity expansions and conversions from one facility type to the other. Furthermore, shortages of capacity are allowed and upper bounds on both shortages and idle capacities can be imposed. The demand increments for additional capacity of any type in any time period can be negative. All cost functions are assumed to be piecewise, concave and nondecreasing away from zero. The model is formulated as a shortest path problem for an acyclic network, and an efficient search procedure is developed to determine the costs associated with the links of this network.
Solving multifacility location problems involving euclidean distances
Authors: Calamai Paul , Charalambous Christakis
Published: May 2007

This paper considers the problem of locating multiple new facilities in order to minimize a total cost function consisting of the sum of weighted Euclidean distances among the new facilities and between the new and existing facilities, the locations of which are known. A new procedure is derived from a set of results pertaining to necessary conditions for a minimum of the objective function. The results from a number of sample problems which have been executed on a programmed version of this algorithm are used to illustrate the effectiveness of the new technique.
The United States Coast Guard Computer‐Assisted Search Planning system (CASP)
Authors: Richardson Henry R. , Discenza Joseph H.
Published: May 2007

This paper provides an overview of the Computer‐Assisted Search Planning (CASP) system developed for the United States Coast Guard. The CASP information processing methodology is based upon Monte Carlo simulation to obtain an initial probability distribution for target location and to update this distribution to account for drift due to currents and winds. A multiple scenario approach is employed to generate the initial probability distribution. Bayesian updating is used to reflect negative information obtained from unsuccessful search. The principal output of the CASP system is a sequence of probability “maps” which display the current target location probability distributions throughout the time period of interest. CASP also provides guidance for allocating search effort based upon optimal search theory.
Spike swapping in basis reinversion
Authors: Helgason R. V. , Kennington J. L.
Published: May 2007

During basis reinversion of either a product form or elimination form linear programming system, it may become necessary to swap spike columns to effect the reinversion and maintain the desired sparsity characteristics. This note shows that the only spikes which need be examined when an interchange is required are those not yet processed in the current external bump.
An alternative proof of the IFRA property of some shock models
Authors: Derman C. , Smith D. R.
Published: May 2007

Let , where A (t)/t is nondecreasing in t, {P(k)1/k} is nonincreasing. It is known that H(t) = 1 — H(t) is an increasing failure rate on the average (IFRA) distribution. A proof based on the IFRA closure theorem is given. H(t) is the distribution of life for systems undergoing shocks occurring according to a Poisson process where P(k) is the probability that the system survives k shocks. The proof given herein shows there is an underlying connection between such models and monotone systems of independent components that explains the IFRA life distribution occurring in both models.
Surrogate duality in a branch‐and‐bound procedure
Authors: Karwan Mark H. , Rardin Ronald L.
Published: May 2007

Recent research has led to several surrogate multiplier search procedures for use in a primal branch‐and‐bound procedure. As single constrained integer programming problems, the surrogate subproblems are also solved via branch‐and‐bound. This paper develops the inner play between the surrogate subproblem and the primal branch‐and‐bound trees which can be exploited to produce a number of computational efficiencies. Most important is a restarting procedure which precludes the need to solve numerous surrogate subproblems at each node of a primal branch‐and‐bound tree. Empirical evidence suggests that this procedure greatly reduces total computation time.
Extreme solutions of the two machine flow‐shop problem
Authors: Szwarc Wlodzimierz
Published: May 2007

The paper provides a new theoretical framework to identify extreme solutions of the two machine flow‐shop problem. Some remarkable properties of these solutions have been developed. As a result the problem of generating minimal solutions can be decomposed into a number of smaller subproblems.
A characterization of the value of zero‐sum two‐person games
Authors: Tijs S. H.
Published: May 2007

For the family D, consisting of those zero‐sum two‐person games which have a value, the value‐function on D is characterized by four properties called objectivity, monotony, symmetry and sufficiency.
Manpower modeling in cost effectiveness studies of usaf program to reduce the incidence of heart disease
Authors: Petersen Clifford C.
Published: May 2007

Planning for a cardiovascular disease reduction program, soon to be initiated by the United States Air Force, has required an evaluation of its expected cost effectiveness. During the course of this evaluation, it was necessary to consider manpower flows and their expected changes in response to the disease reduction program. This paper describes several manpower models that were applied: a simple expected value equilibrium model; a cross‐sectional model that considered the length of service of personnel; and a staffing model used to optimize the allocation of paramedics to the many Air Force bases of various sizes. The relevance of these models to the cost effectiveness evaluation is shown but the detailed cost effectiveness results are not presented.
Applications of renewal theory in analysis of the free‐replacement warranty
Authors: Blischke Wallace R. , Scheuer Ernest M.
Published: May 2007

Under a free‐replacement warranty of durationW, the customer is provided, for an initial cost ofC, as many replacement items as needed to provide service for a periodW. Payments ofCare not made at fixed intervals of lengthW, but in random cycles of lengthY = W + γ(W), whereγ(W)is the (random) remaining life‐time of the item in serviceWtime units after the beginning of a cycle. The expected number of payments over the life cycle,L, of the item is given byMY(L), the renewal function for the random variableY. We investigate this renewal function analytically and numerically and compare the latter with known asymptotic results. The distribution ofY, and hence the renewal function, depends on the underlying failure distribution of the items. Several choices for this distribution, including the exponential, uniform, gamma and Weibull, are considered.