bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced list costings: Examination of an informed short cut in mental health research
Authors: Knapp M. , Beecham J.
Published: May 2007

The demands for cost information in health services are many and various but the supply of such information is less than might be expected and is compounded by the expense of undertaking costs research. This paper examines a short cut to mental health research which, if certain rules and conventions are obeyed, can still produce valid costs data. By distilling evidence from previous research a reduced list of services is identified which accounts for the greater part of the total costs of care packages. By concentrating on these key services, 94 per cent of the total costs of care were predicted for discharged long‐stay patients and no less than 91 per cent for people supported by community psychiatric nurses. The results suggest that this reduced list method can work well where the aim is to obtain broad orders of magnitude for the costs of care. By reducing the resources required for research, the approach could expand the current costs information base and move towards meeting the pressing practice demands for costs data.
Monitoring health in Sweden: On the rationale for working environment regulations
Authors: Lyttkens Carl Hampus
Published: May 2007

The quality of the working environment affects the health status of a population. In the absence of government intervention this quality would be determined by market forces, but the market outcome is generally not accepted. Instead public policy attempts to carefully monitor the level of occupational hazards, which are invariably subject to regulation in industrialized countries. However, this study demonstrates that the welfare implications of this monitoring of health are not self‐evident. In the presence of a tax on labour and, for example, a tax‐financed social insurance system, it is shown that market forces may lead either to excessive or to sub‐optimal investments in injury prevention. Both private and (local) public safety goods are considered.
Is malaria control a priority? Evidence from Nepal
Authors: Mills Anne
Published: May 2007

The research reported here assessed the value of malaria control through a cost‐effectiveness study of the vertically‐organized malaria control programme in Nepal. It presents a methodological framework for analysing cost‐effectiveness which includes resource‐saving consequences as well as health consequences. The methods used to collect data on control costs, cases and deaths prevented, treatment costs averted and production gains are described and the assumptions required by the analysis are made explicit. A variety of cost‐effectiveness ratios are calculated, sensitivity analysis applied and the policy implications of the results considered. The results from Nepal are compared to estimates for parasitic disease and other health programmes in other countries: it is concluded that the Nepalese programme appears no less cost‐effective than many other health interventions. It can also be justified by reference to the population groups benefiting from malaria control.
Measuring utility values for QALYs: Two methodological issues
Authors: Smith Richard , Dobson Matthew
Published: May 2007

Two methodological concerns in utility estimation, the development of health state descriptions (scenarios) and the interpretation of interval scale anchor points, are examined in the context of disease‐specific cost utility analyses (CUA). It is contended that results in CUA can be fundamentally biased by: (i) how the information presented in a scenario is generated; and (ii) the researcher's ‘definition’ of anchor points, when these are used as bounds to the interval scale. A number of recommendations are made, in particular for a more explicit reporting of these issues in CUA, to facilitate greater consistency in the application of utility measurement techniques.
Appraising the use of contingent valuation: A note in response
Authors: Fox‐Rushby Julia
Published: May 2007

This paper reviews the guidelines and recommendations propounded by Morrison and Gyldmark in relation to the use of contingent valuation (CV) to value health states. The issues raised are: that QALYs may not be sufficiently sensitive to changes in health thus requiring the use of CV formulation; the questionable practice of reinterpreting monetary values; and the possibility of income bias. It is concluded that further empirical research, at least, is needed to verify whether this approach should be rejected in favour of quality adjusted life years (QALYs) or healthy year equivalents (HYEs).
Cost‐effectiveness of endoscopic surgery
Authors: Cuschieri A.
Published: May 2007

Endoscopic surgery is a rapidly defusing treatment approach subject to continual technological advance. It offers great potential for economic benefits as well as health gains, but as shown in the article in this issue by Kesteloot and Penninckx, the relative cost of open versus endoscopic surgery is a quite complex issue. The main factors influencing the costs and effectiveness of endoscopic surgery are reviewed and the need for more and better evaluation studies highlighted.
Persons vs years: Two ways of eliciting implicit weights
Authors: Olsen Jan Abel
Published: May 2007

The paper presents two methods for eliciting individuals' implicit weights to be attached to health benefits which extend over time. The first is a person‐trade‐off type which implies that social weights are attached to years with improved health when these are distributed between different groups of people. The second method is based on time‐trade‐off which yields private weights to succeeding years with improved health for oneself. Emphasis is placed on methodological issues, but some preliminary results obtained from small samples are also presented.
Variations in general practice prescribing costs and implications for budget setting
Authors: Healey Andrew T. , Yule Brian F. , Reid John P.
Published: May 2007

Indicative prescribing amounts, and the equivalent prescribing element of funds in the case of fundholding practices, are now an established part of UK general practice. This paper examines the implications of variations in GP prescribing behaviour for the determination of prescribing budgets. Using regression analysis, the extent to which variations in total practice prescribing costs can be explained by factors suggested for inclusion in a weighted capitation formula is established. The results indicate that 97% of the variation in practice prescribing costs can be explained by differences in practice list size, the proportion of patients aged 65 years and over, the proportion of patients living in ‘deprived areas’ and whether or not the practice qualifies for ‘inducement payments’. The implications of the results for budget setting are discussed. A resource allocation formula based on regression analysis of expenditures can be used to promote horizontal equity in terms of equal budgets for equal need. However, its implications for vertical equity and efficiency are more ambiguous.
BMP7 promotes adipogenic but not osteo‐/chondrogenic differentiation of adult human bone marrow‐derived stem cells in high‐density micro‐mass culture
Authors: Neumann Katja , Endres Michaela , Ringe Jochen , Flath Bernd , Manz Rudi , Häupl Thomas , Sittinger Michael , Kaps Christian
Published: May 2007

The objective of our study was to elucidate the potential of bone morphogenetic protein‐7 (BMP7) to initiate distinct mesenchymal lineage development of human adult mesenchymal stem cells (MSC) in three‐dimensional micro‐mass culture. Expanded MSC were cultured in high‐density micro‐masses under serum‐free conditions that favor chondrogenic differentiation and were stimulated with 50–200 ng/ml BMP7 or 10 ng/ml transforming growth factor‐β3 (TGFβ3) as control. Histological staining of proteoglycan with alcian blue, mineralized matrix according to von Kossa, and lipids with Oil Red O, immunostaining of type II collagen as well as real‐time gene expression analysis of typical chondrogenic, adipogenic, and osteogenic marker genes showed that BMP7 promoted adipogenic differentiation of MSC. Micro‐masses stimulated with BMP7 developed adipocytic cells filled with lipid droplets and showed an enhanced expression of the adipocyte marker genes fatty acid binding protein 4 (FABP4) and the adipose most abundant transcript 1 (apM1). Development along the chondrogenic lineage or stimulation of osteogenic differentiation were not evident upon stimulation with BMP7 in different concentrations. In contrast, TGFβ3 directed MSC to form a cartilaginous matrix that is rich in proteoglycan and type II collagen. Gene expression analysis of typical chondrocyte marker genes like cartilage oligomeric matrix protein (COMP), link protein, aggrecan, and types IIα1 and IXα3 collagen confirmed chondrogenic differentiation of MSC treated with TGFβ3. These results suggest that BMP7 promotes the adipogenic and not the osteogenic or chondrogenic lineage development of human stem cells when assembled three‐dimensionally in micro‐masses. J. Cell. Biochem. 102: 626–637, 2007. © 2007 Wiley‐Liss, Inc.
Expression of key substrate cycle enzymes in rat spermatogenic cells: Fructose 1,6 bisphosphatase and 6 phosphofructose 1‐kinase
Authors: Yáñez Alejandro J. , Bustamante Ximena , Bertinat Romina , Werner Enrique , Rauch Maria Cecilia , Concha Ilona I. , Reyes Juan G. , Slebe Juan C.
Published: May 2007

A substrate cycle composed of phosphofructo 1‐kinase I (PFK) and fructose 1,6 bisphosphatase I (FBPase) has been proposed in rat spermatids. This substrate cycle can explain the ability of glucose to induce a decrease in intracellular ATP, a phenomenon that was related to regulation of [Ca2+]i in these cells. In spite of the importance of this metabolic cycle, the expression and activities of the enzymes that compose such cycle have not been systematically studied in spermatogenic cells. Here, we show that PFK and FBPase activities were present in pachytene spermatocytes and round spermatids extracts. Expression of PFK at the mRNA and protein levels showed a relatively similar expression in spermatogenic cells, but a stronger expression in Sertoli cells. Instead, expression of FBPase at the mRNA and protein levels was stronger in round and elongating spermatids as compared to other spermatogenic cells. A similar pattern was observed when evidencing FBPase activity by a NADPH‐nitroblue tetrazolium‐linked cytochemical assay in isolated pachytene spermatocytes and round spermatids. Rat spermatids also showed the ability to convert lactate to fructose‐ and glucose‐6‐P, indicating that both glycolytic and gluconeogenic fluxes are present in these cells. Our results indicate that a coordinated expression of key substrate cycle enzymes, at the level of PFK/FBPase, appear in the last stages of spermatogenic cell differentiation, suggesting that the co‐regulation of these enzymes are required for the ability of these cells to respond to glucose and induce metabolic and Ca2+ signals that can be important for sperm development and function. J. Cell. Physiol. 212:807–816, 2007. © 2007 Wiley‐Liss, Inc.
Regulation of chondrocyte differentiation by the actin cytoskeleton and adhesive interactions
Authors: Woods Anita , Wang Guoyan , Beier Frank
Published: May 2007

Chondrocyte differentiation is a multi‐step process characterized by successive changes in cell morphology and gene expression. In addition to tight regulation by numerous soluble factors, these processes are controlled by adhesive events. During the early phase of the chondrocyte life cycle, cell–cell adhesion through molecules such as N‐cadherin and neural cell adhesion molecule (N‐CAM) is required for differentiation of mesenchymal precursor cells to chondrocytes. At later stages, for example in growth plate chondrocytes, adhesion signaling from extracellular matrix (ECM) proteins through integrins and other ECM receptors such as the discoidin domain receptor (DDR) 2 (a collagen receptor) and Annexin V is necessary for normal chondrocyte proliferation and hypertrophy. Cell–matrix interactions are also important for chondrogenesis, for example through the activity of CD44, a receptor for Hyaluronan and collagens. The roles of several signaling molecules involved in adhesive signaling, such as integrin‐linked kinase (ILK) and Rho GTPases, during chondrocyte differentiation are beginning to be understood, and the actin cytoskeleton has been identified as a common target of these adhesive pathways. Complete elucidation of the pathways connecting adhesion receptors to downstream effectors and the mechanisms integrating adhesion signaling with growth factor‐ and hormone‐induced pathways is required for a better understanding of physiological and pathological skeletal development. J. Cell. Physiol. 213: 1–8, 2007. © 2007 Wiley‐Liss, Inc.
Low levels of DNA ligases III and IV sufficient for effective NHEJ
Authors: Windhofer Frank , Wu Wenqi , Iliakis George
Published: May 2007

Cells of higher eukaryotes rejoin double strand breaks (DSBs) in their DNA predominantly by a non‐homologous DNA end joining (NHEJ) pathway that utilizes the products of DNA‐PKcs, Ku, LIG4, XRCC4, XLF/Cernunnos, Artemis as well as DNA polymerase lambda (termed D‐NHEJ). Mutants with defects in these proteins remove a large proportion of DSBs from their genome utilizing an alternative pathway of NHEJ that operates as a backup (B‐NHEJ). While D‐NHEJ relies exclusively on DNA ligase IV, recent work points to DNA ligase III as a component of B‐NHEJ. Here, we use RNA interference (RNAi) to further investigate the activity requirements for DNA ligase III and IV in the pathways of NHEJ. We report that 70–80% knock down of LIG3 expression has no detectable effect on DSB rejoining, either in D‐NHEJ proficient cells, or in cells where D‐NHEJ has been chemically or genetically compromised. Surprisingly, also LIG4 knock down has no effect on repair proficient cells, but inhibits DSB rejoining in a radiosensitive cell line with a hypomorphic LIG4 mutation that severely compromises its activity. The results suggest that complete coverage for D‐NHEJ or B‐NHEJ is afforded by very low ligase levels and demonstrate residual end joining by DNA ligase IV in cells of patients with mutations in LIG4. J. Cell. Physiol. 213: 475–483, 2007. © 2007 Wiley‐Liss, Inc.
Hormonal regulation of IGFBP‐2 proteolysis is attenuated with progression to androgen insensitivity in the LNCaP progression model
Authors: DeGraff David J. , Malik Manisha , Chen Qian , Miyako Kenichi , Rejto Lidia , Aguiar Adam A. , Bancroft Diccon R.E. , Cohen Pinchas , Sikes Robert A.
Published: May 2007

The identification of molecular determinants involved in the promotion of metastasis and development of androgen insensitive prostate cancer (AI‐PCa) is necessary to discriminate aggressive from indolent disease and to identify therapeutic targets for advanced disease. Overexpression of one particular member of the insulin like growth factor (IGF) axis, IGFBP‐2, is implicated in the development of AI‐PCa and other cancers. Using the LNCaP human PCa progression model, we show that the AI and metastatic prostate cancer cell line C4‐2B4 expresses greater amounts of secreted IGFBP‐2 than the androgen sensitive (AS), non‐metastatic LNCaP progenitor cell line. Further, the ability of androgens to decrease extracellular IGFBP‐2 levels is attenuated in the AI and metastatic C4‐2 cell line. The ability of androgen to negatively regulate extracellular IGFBP‐2 levels was blocked by Casodex in a dose‐dependent manner. The mechanism underlying the androgen‐induced downregulation of secreted IGFBP‐2 appears to involve extracellular proteolysis, resulting in the production of IGFBP‐2 fragments lacking the ability to bind IGF‐I and IGF‐II. As C4‐2 cells have an attenuated ability to proteolyze IGFBP‐2 in response to androgen and C4‐2B4 cells express greater amounts of IGFBP‐2, our data implies that the diminished regulation of IGFBP‐2 and loss of associated proteolytic fragments play a role in the increased metastatic behavior of these cells in vivo. Furthermore, our results suggest that either increased levels of intact IGFBP‐2 or decreased levels of IGFBP‐2 proteolytic fragments could serve as a biomarker to monitor for progression to AI‐PCa. J. Cell. Physiol. 213: 261–268, 2007. © 2007 Wiley‐Liss, Inc.
Serous cutaneous glands in the South American horned frog Ceratophrys ornata (Leptodactylformes, Chthonobatrachia, Ceratophrydae): Ultrastructural expression of poison biosynthesis and maturation
Authors: Arifulova Irina , Delfino Giovanni , Dujsebayeva Tatjana , Fedotovskikh Galina , Nosi Daniele , Terreni Alessandro
Published: May 2007

Serous cutaneous glands are described in newly metamorphosed and juvenile specimens of the horned frog Ceratophrys ornata using light and transmission electron microscopy. We report patterns of biosynthesis and maturation of the specific product of the gland secretory unit. The syncytial, secretory compartment possesses a complex of endoplasmic reticulum (predominantly smooth endoplasmic reticulum after metamorphosis) and Golgi stacks. The serous product is weak in density and is contained in vesicles involved in repeating merging processes. During this maturation activity, secondary lysosomes are observed, which derive from autophagic processes (crinophagy) involving the secretory materials. Ceratophrys ornata, a species representative of the type genus of the family Ceratophrydae, belongs to the heterogeneous group of anurans that, possibly as the result of convergence, all produce cutaneous poisons consisting of vesicles or faint density granules. J. Morphol., 2007. © 2007 Wiley‐Liss, Inc.
Electrospray tandem mass spectrometry of epipolythiodioxopiperazines
Authors: Wu Zhi‐Jun , Li Guo‐You , Fang Dong‐Mei , Qi Hua‐Yi , Ren Wei‐Jian , Zhang Guo‐Lin
Published: May 2007

Low‐energy collision‐induced electrospray ionization tandem mass spectrometry ESI‐CID‐MS/MS (in the positive ion mode) was used for the structural characterization of a series of five representative epioplythiodioxopipreazines: dethiotetra(methylthio)chemotin, chaetocochins A, B and C, and chemotin isolated from the fungus Chaetomium cochliodes. The fragmentation pathways were elucidated by ESI‐IT‐MSn. The elemental compositions of most of the product ions were confirmed by low‐energy ESI‐CID‐QTOF‐MS/MS analyses. The loss of the S2 molecule seems always to be the first when the SS bond is present. The loss of 77 Da corresponding to the loss of the [CH3SCH2O]' radical was diagnostic for chaetocochins A and B, in which the two piperazines rings are linked by an acetal group. It was found that a McLafferty rearrangement plays a significant role in the skeleton fragmentation of theses series of studied complex multicyclic piperazine compounds. This MacLafferty rearrangement affords the product ions at m/z 416 and 400, containing the two piperazine rings belonging to the epipolythiodioxopipreazines. In addition, the pentacyclic rearrangement involving the loss of the SMe· radical seems to occur in the presence of the unfused ring. Finally the product ions at m/z 635 and 591 seem to be the characteristic ions for chaetocochin A. Copyright © 2007 John Wiley & Sons, Ltd.
On the Raman scattering from semiconducting nanowires
Authors: Cao L. , Laim L. , Valenzuela P. D. , Nabet B. , Spanier J. E.
Published: May 2007

We present a short review of recent work on the unusual Raman scattering characteristics in semiconductor nanowires, focusing on the dependence of the intensity, spectral and spatial character of the scattering response on the size, shape and composition of the nanowires. Results of Raman scattering collected from individual Si and nanowires and nanocones indicate that the observed enhancement is dependent on the diameter (d), the excitation wavelength (λlaser) and the incident polarization state. Strong agreement between experimental data and model calculations of scattering from an infinite dielectric cylinder is found. This size dependence is in accordance with other recent findings in which a diameter‐dependent dipolar ‘antenna’ pattern for the scattered intensity and a cross‐sectional shape dependence of the surface optic (SO) phonon dispersions were seen. Further providing evidence of the nanowire shape and size dependence on Raman scattering, these results suggest manipulation of classical electromagnetic scattering signatures, thereby expanding opportunities for engineering the photonic and sensing properties of nanowires. Copyright © 2007 John Wiley & Sons, Ltd.
Rapid identification of purified enteropathogenic Escherichia coli by microchip electrophoresis
Authors: Law Wai Siang , Teng Teng Tay Elaine , Feng Huatao , Yu Lijun , Zhao Jian Hong , Li Sam Fong Yau
Published: May 2007

In this work, the potential of PDMS‐based microchip electrophoresis in the identifications and characterizations of microorganism was evaluated. Enteropathogenic E. coli (EPEC) was selected as the model microorganism. In this study, separation parameters such as applied voltage, concentrations of buffer and buffer modifier, injection voltage, and duration of injection had been investigated and optimized. Determination of EPEC bacteria could be completed within 2 min with good reproducibility. RSDs were less than 0.5 and 5% in migration time and peak area, respectively. Separation efficiency corresponding to plate number of more than 100 000 was achieved. In order to obtain reproducible separations, sample pretreatment was found to be essential. Microchip electrophoresis with LIF detection could potentially revolutionize certain aspects of microbiology involving diagnosis, profiling of pathogens, environmental analysis, and many other areas of study.
Microchip‐based capillary electrophoresis for determination of lactate dehydrogenase isoenzymes
Authors: Zhuang Gui‐Sheng , Liu Jing , Jia Chun‐Ping , Jin Qing‐Hui , Zhao Jian‐Long , Wang Hui‐Min
Published: May 2007

This article describes a novel microchip‐based capillary electrophoresis and on‐column enzymatic reaction analysis protocol for lactate dehydrogenase (LDH) isoenzymes with a home‐made xenon lamp‐induced fluorescence detection system. A microchip integrated with a temperature‐control unit is designed and fabricated for low‐temperature electrophoretic separation of LDH isoenzymes, optimal enzyme reaction temperature control, and product detection. A four‐step operation and temperature control are employed for the determination of LDH activity by on‐chip monitoring of the amount of incubation product of NADH during the fixed incubation period and at a fixed temperature. Experiments on the determination of LDH standard sample and serum LDH isoenzymes from a healthy adult donor are carried out. The results are comparable with those obtained by conventional CE. Shorter analysis times and a more stable and lower background baseline can be achieved. The efficient separation of different LDH forms indicates the potential of microfluidic devices for isoenzyme assay.
Pipetting causes shear stress and elevation of phosphorylated stress‐activated protein kinase/jun kinase in preimplantation embryos
Authors: Xie Y. , Wang F. , Puscheck E.E. , Rappolee D.A.
Published: May 2007

Shear stress at 1.2 dynes/cm2 induces stress‐activated protein kinase/jun kinase phosphorylation that precedes and causes apoptosis in embryos (Xie et al., 2006b, Biol Reprod). Pipetting embryos is necessary for many protocols, from in vitro fertilization to collecting embryos prior to analyzing gene expression by microarrays. We sought to determine if pipetting upregulates phosphorylated MAPK8/9 (formerly known as stress‐activated protein kinase/jun kinase/SAPK/JNK1, 2). We found that phosphorylated MAPK8/9, a marker of MAPK8/9 activation, is upregulated in a dose‐dependent manner by pipetting. Whereas embryos with the zona pellucida removed were more sensitive to stress‐induced lethality mediated by 1.2 dynes/cm2 shear force, phosphorylated MAPK8/9 was induced at lower numbers of pipet triturations in hatched embryos at E4.5. E4.5 embryos were more sensitive to induction of MAPK8/9 than unhatched embryos at E2.5 or E3.5. E3.5 embryos also showed a pipetting dose‐dependent induction of FOS protein (formerly known as c‐fos), a marker of shear stress in many cell types. Phosphorylated MAPK8/9 measured in ex vivo embryos from E1.5 to E4.5 were expressed at low levels. Embryos that had been pipetted sufficiently to induce phosphorylated MAPK8/9 and FOS had the same number of cells as untreated embryos 24 hr later. This suggests that rapid phosphorylation of MAPK8/9 due to transient shear stress does not mediate long‐term negative biological outcomes. But, it is possible that techniques requiring multiple handling events would induce MAPK8/9 and cause biological outcomes or that other biological outcomes are affected by low amounts of transient shear stress. This study suggests that embryo handling prior to experimental measurement of signal transduction phosphoproteins, proteins and mRNA should be performed with care. Indeed, it is likely that shear stress may cause rapid transient changes in hundreds of proteins and mRNA. Mol. Reprod. Dev. 74: 1287–1294, 2007. © 2007 Wiley‐Liss, Inc.
A heterogeneous arrival and service queueing loss model
Authors: Fond Simson , Ross Sheldon M.
Published: May 2007

Consider a single‐server exponential queueing loss system in which the arrival and service rates alternate between the paris (γ1, γ1), and (γ2, μ2), spending an exponential amount of time with rate cμi in (γi, μi), i = 1.2. It is shown that if all arrivals finding the server busy are lost, then the percentage of arrivals lost is a decreasing function of c. This is in line with a general conjecture of Ross to the effect that the “more nonstationary” a Poisson arrival process is, the greater the average customer delay (in infinite capacity models) or the greater the precentage of lost customers (in finite capacity models). We also study the limiting cases when c approaches 0 or infinity.
Permutation flow‐shop theory revisited
Authors: Szwarc Wlodzimierz
Published: May 2007

The paper provides a new theoretical framework for generating dominance conditions and lower bounds and for solving special cases. All existing and new results have been derived in a routine and simple manner.
Return policies for an inventory system with positive and negative demands
Authors: Heyman Daniel P.
Published: May 2007

We consider a single item inventory system with positive and negative stock fluctuations. Items can be purchased from a central stock, n items can be returned for a cost R + rn, and a linear inventory carrying cost is charged. It is shown that for minimizing the asymptotic cost rate when returns are a significant fraction of stock usage, a two‐critical‐number policy (a,b) is optimal, where b is the trigger level for returns and b – a is the return quantity. The values for a and b are found, as well as the operating characteristics of the system. We also consider the optimal return decision to make at time zero and show that it is partially determined by a and b.
The distribution of recoverable inventory items from a repair center when the number of consumption centers is large
Authors: Miller Bruce L. , Modarres‐Yazdi Mohammad
Published: May 2007

This paper considers real‐time decision rules for an inventory system where items are repaired than “used up.” The problem is to decide which user in the system has the greatest need for the newly available inventory items coming out of repair. The main result shows that two published approahes, the Transportation Time Look Ahead policy and METRIC, are optimal when the number of users gets large. A useful byproduct of the proof is a lower bound on the average backorder rate for a repair‐inventory system of any size.
Optimal sampling and the right‐hand side of a linear program: Sensitivity analysis revisited
Authors: Daughety Andrew F.
Published: May 2007

This paper examines right‐hand side sensitivity analysis in linear programming as a problem in optimal sampling. Specifically, the insensitivity point of a solution is defined as the point at which the expected gain from increased accuracy in the prediction of a resource level is equal to the expected cost of procuring the information. The problem is structured using the rudiments of optimal statistical decision theory.
Two queueing systems sharing the same finite waiting room
Authors: Fischer M. J.
Published: May 2007

In this paper, we consider the analysis of two M/G/1 queueing systems sharing the same finite waiting room. An exact analysis is given for several special cases, and then an algorithm is developed which approximates the system behavior for the general problem. Comparisons are made between the special cases and the algorithm.
A streamlined simplex approach to the singly constrained transportation problem
Authors: Klingman D. , Russell R.
Published: May 2007

A primal simplex procedure is developed to solve transportation problems with an arbitrary additional linear constraint. The approach is a specialization of the Double Reverse Method of Charnes and Cooper. Efficient procedures for pricing‐out the basis, determining representations, and implementing the change of basis are presented. These procedures exploit the pure transportation substructure in such a manner that full advantage may be taken of the computational schemes and list structures used to store and update the basis in codifying the MODI method. Furthermore, the pricing‐out and change‐of‐basis procedures are organized in a manner that permits the calculations for one to be utilized in the other. Computational results are presented which indicate that this method is at least 50 times faster than the state‐of‐the‐art LP code, APEX‐III. Methods for obtaining basic primal “feasible” starts and “good” feasible integer solutions are also presented.
Refined prediction for linear regression models
Authors: Hess J. L. , Gunst R. F.
Published: May 2007

Adequate prediction of a response variable using a multiple linear regression model is shown in this article to be related to the presence of multicollinearities among the predictor variables. If strong multicollinearities are present in the data, this information can be used to determine when prediction is likely to be accurate. A region of prediction,R, is proposed as a guide for prediction purposes. This region is related to a prediction interval when the matrix of predictor variables is of full column rank, but it can also be used when the sample is undersized. The Gorman‐Toman ten‐variable data is used to illustrate the effectiveness of the regionR.
A note on the stochastic shortest‐route problem
Authors: Croucher John S.
Published: May 2007

This paper develops an algorithm for a “shortest route” network problem in which it is desired to find the path which yields the shortest expected distance through the network. It is assumed that if a particular arc is chosen, then there is a finite probability that an adjacent arc will be traversed instead. Backward induction is used and appropriate recursion formulae are developed. A numerical example is provided.
Survey of approaches to readiness
Authors: Barzily Zeev , Marlow W. H. , Zacks S.
Published: May 2007

About thirty references that feature naval logistics environments are considered. All are unclassified and all appear in the open literature or are available from the Defense Logistics Studies Information Exchange. Three approaches are identified–data analysis, theoretical models, and readiness indexes–and conclusions are presented as to possibilities for answering two questions: (a) Can the unit do the job? (b) How does readiness depend on resources? Four cases are treated in detail to illustrate methodology.
Computational results with a branch‐and‐bound algorithm for the general knapsack problem
Authors: Bulfin R. L. , Parker R. G. , Shetty C. M.
Published: May 2007

In this paper, a branch‐and‐bound procedure is presented for treating the general knapsack problem. The fundamental notion of the procedure involves a variation of traditional branching strategies as well as the incorporation of penalties in order to improve bounds. Substantial computational experience has been obtained, the results of which would indicate the feasibility of the procedure for problems of large size.
Confidence intervals related to sequential test for the exponential distribution
Authors: Siegmund D.
Published: May 2007

One‐sided sequential tests for the mean of an exponential distribution are proposed, and the related confidence intervals are computed. The tests behave like the classical sequential probability‐ration test when the mean is small and like a fixed‐time test when the mean is large and accurate estimation is important.
Multiproduct lot‐size scheduling with proportional product demands
Authors: Murphy F. H. , Soyster A. L.
Published: May 2007

In this paper we consider the multiproduct, multiperiod production‐scheduling model of Manne under the assumption that, across products, demands are interrelated over time. When demand requirements are proportional we show that the solution has a specific structure determined by the ratio of setup to production‐run time of each product. This structure holds for any length horizon and may permit a substantial (time) savings for column generation solution procedures.
An exact branch‐and‐bound procedure for the quadratic‐assignment problem
Authors: Bazaraa M. S. , Elshafei A. N.
Published: May 2007

The quadratic‐assignment problem is a difficult combinatorial problem which still remains unsolved. In this study, an exact branch‐and‐bound procedure, which is able to produce optimal solutions for problems with twelve facilities or less, is developed. The method incorporates the concept of stepped fathoming to reduce the effort expended in searching the decision trees. Computational experience with the procedure is presented.
Coordinated replenishments of items under time‐varying demand: Dynamic programming formulation
Authors: Silver Edward A
Published: May 2007

We consider a group (or family) of items having deterministic, but time‐varying, demand patterns. The group is defined by a setup‐cost structure that makes coordination attractive (a major setup cost for each group replenishment regardless of how many of the items are involved). The problem is to determine the timing and sizes of the replenishments of all of the items so as to satisfy the demand out to a given horizon in a cost‐minimizing fashion. A dynamic programming formulation is illustrated for the case of a two‐item family. It is demonstrated that the dynamic programming approach is computationally reasonable, in an operational sense, only for small family sizes. For large families heuristic solution methods appear necessary.
A note on duality in homogeneous fractional programming
Authors: Craven B. D. , Mond B.
Published: May 2007

For a linear fractional programming problem, Sharma and Swarup have constructed a dual problem, also a linear fractional program, in which the objective functions of both primal and dual problems are the same. Craven and Mond have extended this result to a nonlinear fractional programming problem with linear constraints, and a dual problem for which the objective function is the same as that of the primal. This theorem is now further extended from linear to differentiable convex constraints.
A note on a modified block replacement policy for units with increasing marginal running costs
Authors: Berg Menachem , Epstein Benjamin
Published: May 2007

The model for a modified block replacement policy (MBRP) is extended to include running costs. An illustrative example is worked out for the case when item life is exponentially distributed and marginal running cost per unit time increases linearly with the age of the item.
A note on optimal inventory management under inflation
Authors: Misra Ram B.
Published: May 2007

This paper develops a discounted‐cost model that is similar to the classical economic order quantity model but includes inflation rates as parameters of the inventory system. A numerical problem is solved to illustrate the effects.
A methodology for studying the dynamics of extended logistic systems
Authors: Graves Stephen C. , Keilson Julian
Published: May 2007

An extended logistic system is a well‐defined configuration of equipment, modules, inventories, and repair and replacement facilities modeling a complex, repairable system with on‐going repair. The design of such systems has been based largely on the static tools of inventory theory and reliability theory, i.e., on steady‐state distributions and on associated means and variances. Such static tools suppress the scale of real lime and ignore system persistence time in up‐states and persistence time in down‐states.

A reasonably simple dynamic methodology is presented, focusing on system failure time as a more meaningful objective function for system‐design tradeoff studies. In the presence of good reliability, it is shown that different candidates for system failure time effectively merge to yield an unambiguous, single system failure time. Examples illustrating the importance of dynamic information for system design are given.
A three‐echelon, multi‐item model for recoverable items
Authors: Muckstadt J. A.
Published: May 2007

The main objective of this paper is to develop a mathematical model for a particular type of three‐echelon inventory system. The proposed model is being used by the Air Force to evaluate inventory investment requirements for alternative logistic structures. The system we will model consists of a group of locations, called bases, and a central depot. The items of concern in our analysis are called recoverable items, that is, items that can be repaired when they fail. Furthermore, each item has a modular or hierarchical design. Briefly, the model is used to determine the stock levels at each location for each item so as to achieve optimum inventory‐system performance for a given level of investment. An algorithm for the computation of stock levels for each item and location is developed and illustrated. Some of the ways the model can be used are illustrated with Air Force data.
Some bayes tests and their asymptotic properties for the multivariate, multisample goodness‐of‐fit problem
Authors: Ramani K. V.
Published: May 2007

Independent samples are taken from C multivariate populations with continuous but unknown cumulative distribution function c.d.f.). The problem is to test the hypothesis that the C population c.d.f's are identical to a specified c.d.f. We approach this problem by first transforming the data so that the hypothesis being tested is that the common distribution is uniform over a unit hypercube. We then construct some Bayes tests and investigate their asymptotic properties. These tests are based on the asymptotic normality of the number of observations falling in the “asymptotically sufficient groupings”.
Multiple‐attribute decision making with partial information: The expected‐value criterion
Authors: Charnetski Johnnie R. , Soland Richard M.
Published: May 2007

We consider the multiple‐attribute decision problem with finite action set and additive utility function. We suppose that the decision maker cannot specify nonnegative weights for the various attributes which would resolve the problem, but that he/she supplies ordinal information about these weights which can be translated into a set of linear constraints restricting their values. A bounded polytope W of feasible weight vectors is thus determined. Supposing that each element of W has the same chance of being the “appropriate one,” we compute the expected utility value of each action. The computation method uses a combination of numerical integration and Monte Carlo simulation and is equivalent to finding the center of mass of the bounded polytope W. Comparisons are made with another criterion already presented, the comparative hyper‐volume criterion, and two small examples are presented.
A capacity‐expansion model for two facility types
Authors: Luss Hanan
Published: May 2007

This paper describes a deterministic capacity‐expansion model for two facility types with a finite number of discrete time periods. Capacity expansions are initialed either by new construction or by the conversion of idle capacity from one facility type to the other. Once converted, the capacity becomes an integral part of the new facility type. The costs incurred include construction, conversion, and holding costs. All cost functions are assumed to be nondecreasing and concave. Using a network flow approach, the paper develops an efficient dynamic‐programming algorithm to minimize the total costs when the demands for additional capacity are nonnegative in each period. Thereafter, the algorithm is extended for arbitrary demands. The model is applied to a cable‐sizing problem that occurs in communication networks, and numerical examples are discussed.
Distribution of sample correlation coefficients
Authors: Alam Khursheed
Published: May 2007

Let (Y, Xl,…, XK) be a random vector distributed according to a multivariate normal distribution where Xl,…, XK are considered as predictor variables and y is the predictand. Let ri, and Ri denote the population and sample correlation coefficients, respectively, between Y and Xi. The population correlation coefficient ri is a measure of the predictive power of Xi. The author has derived the joint distribution of Rl,…, RK and its asymptotic property. The given result is useful in the problem of selecting the most important predictor variable corresponding to the largest absolute value of ri.
A new analysis of a lot‐size model with partial backlogging
Authors: Rosenberg David
Published: May 2007

We reformulate the cost equation for the lot‐size model with partial back‐logging. The formulation is in terms of “fictitious demand rate,” a new inventory decision variable that simplifies the analysis. Using decomposition by projection, we obtain an optimal solution in a straightforward manner. The form of the solution sheds additional light on the behavior of the model. Some of these insights are elucidated by numerical examples.
Optimal betting strategies for favorable games
Authors: Subelman Eduardo J.
Published: May 2007

We examine the problem of a gambler interested in maximizing the expected value of a convex utility function of his fortune after n plays of a game. We allow any probability distribution to rule the outcome of each play, and this distribution may change from play to play according to a Markov process. We present results regarding the existence of an optimal policy and its structural dependence on the gambler's fortune. The well‐known results of Bellman and Kalaba for exponential and logarithmic utility functions and coin‐tossing games are generalized. We also examine the situation of general stale spaces and show that the same structural results hold.
Geometry of the total time on test transform
Authors: Barlow Richard E.
Published: May 2007

Total time on test (TTT) plots provide a useful graphical method for tentative identification of failure distribution models. Identification is based on properties of the TTT transform. New properties of the TTT transform distribution are obtained. These results are useful to the user of TTT plots. Although IFR (DFR) distributions are particularly easy to identify from TTT plots, the user must exercise caution relative to identification of IFR A (DFRA) distributions.
Simulation of nonhomogeneous poisson processes by thinning
Authors: Lewis P. A. W , Shedler G. S.
Published: May 2007

A simple and relatively efficient method for simulating one‐dimensional and two‐dimensional nonhomogeneous Poisson processes is presented The method is applicable for any rate function and is based on controlled deletion of points in a Poisson process whose rate function dominates the given rate function In its simplest implementation, the method obviates the need for numerical integration of the rate function, for ordering of points, and for generation of Poisson variates.
Bounds on optimal cost for a replacement problem with partial observations
Authors: White Chelsea C.
Published: May 2007

This paper characterizes the structure of optimal strategies for a replacement problem for two special cases of observation quality. It is shown that when the state of the system is either completely observed or completely unobserved at every decision epoch by the controller, reasonable assumptions are sufficient for the existence of optimal replacement strategies composed of policies having a generalized, control‐limit form. These structural results are of particular interest since the optimal cost functions for the two special cases represent bounds on the optimal cost function for the general partially observed case, significant computational simplification can result for the two special cases due to their optimal strategy structure, and optimal strategies possessing a control‐limit structure do not necessarily exist for the general partially observed case.
Survival distributions in crossing fields containing clusters of mines with possible detection and uncertain activation or kill
Authors: Zacks S.
Published: May 2007

The present paper presents an algorithm for the exact determination of survival distributions in crossing mine fields. The model under consideration considers clusters of mines, scattered at random in the field around specified aim points. The scatter distributions of the various clusters are assumed to be known The encounter process allows for a possible detection and destruction of the mines, for inactivation of the mines and for the possibility that an activated mine will not destroy the object. Recursive formulae for the determination of the survival probabilities of each object (tank) in a column of n crossing at the same path are given. The distribution of the number of survivors out of n objects in a column is also determined. Numerical examples are given.
Design of a process control scheme for defects per 100 units based on aoql
Authors: Leavenworth Richard S. , Scheaffer Richard L.
Published: May 2007

A process control scheme is developed in which decisions as to the frequency of sampling are made based upon the choice of an Average Outgoing Quality Limit. The scheme utilizes plotted points on a U‐control chart for defects and the theory of runs to determine when to switch among Reduced, Normal, Tightened, and 100 percent inspection. The scheme is formulated as a semi‐Markov process to derive steady stale equations for the probabilities of being in Reduced, Normal, Tightened, or 100 percent inspection and for Average Outgoing Quality and Average Fraction Inspected. The resulting system and the computer programs used to derive it are discussed.
A single server queue with arrival rate dependent on server breakdowns
Authors: Shogan Andrew W.
Published: May 2007

This paper considers a single server queueing system that alternates stochastically between two states: operational and failed. When operational, the system functions as anM/Ek/1 queue. When the system is failed, no service takes place but customers continue to arrive according to a Poisson process; however, the arrival rate is different from that when the system is operational. The durations of the operating and failed periods are exponential with mean 1/cβ and Erlang with mean 1/cβ, respectively. Generating functions are used to derive the steady‐state quantitiesLandW, both of which, when viewed as functions ofc, decrease at a rate inversely proportional to c2. The paper includes an analysis of several special and extreme cases and an application to a production‐storage system.
Statistical tests for exponential service from m/g/1 waiting‐time data
Authors: Thiagarajan T. R. , Harris Carl M.
Published: May 2007

From an original motivation in quantitative inventory modeling, we develop methods for testing the hypothesis that the service times of an M/G/1 queue are exponentially distributed, given a sequence of observations of customer line and/or system waits. The approaches are mostly extensions of the well‐known exponential goodness‐of‐fit test popularized by Gnedenko, which results from the observation that the sum of a random exponential sample is Erlang distributed and thus that the quotient of two independent exponential sample means is F distributed.