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Optimal Combination (optimal + combination)
Selected AbstractsEstimation for the Optimal Combination of Markers without Modeling the Censoring DistributionBIOMETRICS, Issue 1 2009Chin-Tsang Chiang Summary In the time-dependent receiver operating characteristic curve analysis with several baseline markers, research interest focuses on seeking appropriate composite markers to enhance the accuracy in predicting the vital status of individuals over time. Based on censored survival data, we proposed a more flexible estimation procedure for the optimal combination of markers under the validity of a time-varying coefficient generalized linear model for the event time without restrictive assumptions on the censoring pattern. The consistency of the proposed estimators is also established in this article. In contrast, the inverse probability weighting (IPW) approach might introduce a bias when the selection probabilities are misspecified in the estimating equations. The performance of both estimation procedures are examined and compared through a class of simulations. It is found from the simulation study that the proposed estimators are far superior to the IPW ones. Applying these methods to an angiography cohort, our estimation procedure is shown to be useful in predicting the time to all-cause and coronary artery disease related death. [source] Optimal combinations of ultrasound-based and serum markers of disease severity in patients with chronic hepatitis CJOURNAL OF VIRAL HEPATITIS, Issue 8 2010J. F. L. Cobbold Summary., Combinations of noninvasive markers may improve discrimination of chronic liver disease severity. The aims of this study were to compare four validated serum and ultrasound-based markers of hepatic disease severity head-to-head with liver biopsy and to assess optimal combinations with consideration of cost. A total of 67 patients with biopsy-proven chronic hepatitis C underwent all four techniques on the same visit [aspartate aminotransferase (AST) to platelet ratio index (APRI); Enhanced Liver Fibrosis (ELF) panel; transient elastography (TE) and ultrasound microbubble hepatic transit times (HTT)]. Markers were combined according to increasing financial cost and ordinal regression used to determine contributions. APRI, ELF, TE and HTT predicted cirrhosis with diagnostic accuracy of 86%, 91%, 90% and 83% respectively. ELF and TE were the most reliable tests with an intra-class correlation of 0.94 each. Either ELF or TE significantly enhanced the prediction of fibrosis stage when combined with APRI, but when combined together, did not improve the model further. Addition of third or fourth markers did not significantly improve prediction of fibrosis. Combination of APRI with either ELF or TE effectively predicts fibrosis stage, but combinations of three or more tests lead to redundancy of information and increased cost. [source] Evaluation of the participant-support method for information acquisition in the "Multiplex Risk Communicator"ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 9 2009Tomohiro Watanabe Abstract In this paper, we propose a smooth risk communication support method for the Multiplex Risk Communicator. There has been a diversification of the social risks to the information-based society, leading to complex social issues, and risk communication is necessary in order to solve the complicated social problems that arise concerning stakeholders with various levels of knowledge and differing standards regarding risks. We introduce a portal system that assists participants to achieve an optimal combination of countermeasures. The characteristics of the proposed method are: first, to classify the stage when participants acquire information; second, to enable smooth transitions during the information acquisition stage; and third, to support information acquisition by offering information portals. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(9): 24,35, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10092 [source] Species-specific differences in oak foliage affect preference and performance of gypsy moth caterpillarsENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2003L. K. Foss Abstract The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), is an introduced defoliator that preferentially feeds on oaks, Quercus spp. (Fagaceae) in the north-eastern USA. As the gypsy moth expands its geographic range, the extensive oak component in forests and urban environments of the USA assure its successful establishment. Given their economic and ecological importance, and the gypsy moth's potential to cause mortality, we evaluated caterpillar preference and performance on various oaks prevalent in the central hardwoods region. Most of the physical and chemical characteristics we measured, from budbreak phenology to foliar chemistry, varied significantly among the oak species tested. Similarly, insect preference and performance varied significantly, though not always in predictable ways. Caterpillar preference was compared for black, Q. velutina Lamarck, burr, Q. macrocarpa Michaux, cherrybark, Q. pagoda Rafinesque, northern red, Q. rubra L., pin, Q. palustris Muenchhausen, swamp white, Q. bicolor Willdenow, white, Q. alba L., and willow, Q. phellos L., oaks. Gypsy moth preference was greatest for black and burr, and least for northern red, pin, and willow oaks. We assessed foliar characteristics and caterpillar performance on foliage from burr, cherrybark, northern red, pin, and willow oaks. Caterpillar preference did not always correlate with performance. Gypsy moth consumption and growth were highest, and development most rapid, on pin oak, which had high nitrogen and tannin levels, and was among the least preferred. Northern red and willow oaks were also among the least preferred and were the least suitable tested, producing caterpillars with moderate to low consumption and growth rates, as well as the longest development. Northern red oak contained the lowest foliar tannins; willow oak foliage was lowest in carbohydrates and nitrogen. Our results suggest that a combination of foliar characteristics may be responsible for gypsy moth preference and performance, and that an optimal combination of foliar components serves to maximize host suitability. These data will provide information useful for planning and managing urban forests in the presence of expanding gypsy moth populations. [source] Tolerability and Safety of Frovatriptan With Short- and Long-term Use for Treatment of Migraine and in Comparison With SumatriptanHEADACHE, Issue 2002Gilles Géraud MD Objective.,To evaluate the tolerability and safety of frovatriptan 2.5 mg in patients with migraine. Background.,Frovatriptan is a new, selective serotonin agonist (triptan) developed for the acute treatment of migraine. Dose range-finding studies identified 2.5 mg as the dose that conferred the optimal combination of efficacy and tolerability. Methods.,The tolerability and safety of frovatriptan 2.5 mg were assessed during controlled, acute migraine treatment studies, including a study that compared frovatriptan 2.5 mg with sumatriptan 100 mg, as well as a 12-month open-label study during which patients could take up to three doses of frovatriptan 2.5 mg within a 24-hour period. Safety and tolerability were assessed through the collection of adverse events, monitoring of heart rate and blood pressure performance of 12-lead electrocardiogram, hematology screen, and blood chemistry studies. Results.,In the short-term studies, 1554 patients took frovatriptan 2.5 mg and 838 took placebo. In the 12-month study, 496 patients treated 13 878 migraine attacks. Frovatriptan was well tolerated in the short- and long-term studies with 1% of patients in the short-term studies and 5% of patients in the long-term study withdrawing due to lack of tolerability. The incidence of adverse events was higher in the frovatriptan-treated patients than in the patients who took placebo (47% versus 34%) and the spectrum of adverse events was similar. When compared to sumatriptan 100 mg, significantly fewer patients taking frovatriptan experienced adverse events (43% versus 36%; P=.03) and the number of adverse events was lower (0.62 versus 0.91), there were also fewer adverse events suggestive of cardiovascular symptoms in the frovatriptan group. Analysis of the entire clinical database (n=2392) demonstrated that frovatriptan was well tolerated by the patients regardless of their age, gender, race, concomitant medication, or the presence of cardiovascular risk factors. No effects of frovatriptan on heart rate, blood pressure, 12-lead electrocardiogram, hematology screen, or blood chemistry were observed. No patient suffered any treatment-related serious adverse event. Conclusions.,Short- and long-term use of frovatriptan 2.5 mg was well tolerated by a wide variety of patients. Frovatriptan treatment produced an adverse events profile similar to that of placebo, and in a direct comparison study was better tolerated than sumatriptan 100 mg. [source] Analysis of the parameters of the sintered loop heat pipeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2004K.J. Zan Abstract The purpose of this paper is to establish an experimental formula for sintered dendritic nickel powder. For this reason, wick structures with different porosity ranging from 65 to 80% were fabricated by cold pressing sintering process at fixed porosity and their parameters that included porosity, pore radius, and permeability were also measured. According to both the capillary limitation and the present experimental formula of the sintered dendritic nickel powder, the wick structure parameters that would affect the heat transfer capacity of the loop heat pipe (LHP) were analyzed theoretically and then investigated experimentally. The results showed that there exists an optimal combination of wick structure parameters by which the performance of the LHP would achieve optimization. The maximum heat transfer capacity was up to 500 W and the thermal resistance was 0.12°C/W at the allowable working temperature 80°C. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(8): 515,526, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20034 [source] State-space time integration with energy control and fourth-order accuracy for linear dynamic systemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2006Steen Krenk Abstract A fourth-order accurate time integration algorithm with exact energy conservation for linear structural dynamics is presented. It is derived by integrating the phase-space representation and evaluating the resulting displacement and velocity integrals via integration by parts, substituting the time derivatives from the original differential equations. The resulting algorithm has an exact energy equation, in which the change of energy is equal to the work of the external forces minus a quadratic form of the damping matrix. This implies unconditional stability of the algorithm, and the relative phase error is of fourth-order. An optional high-frequency algorithmic damping is constructed by optimal combination of three different damping matrices, each proportional to either the mass or the stiffness matrix. This leads to a modified form of the undamped algorithm with scalar weights on some of the matrices introducing damping of fourth-order in the frequency. Thus, the low-frequency response is virtually undamped, and the algorithm remains third-order accurate even when algorithmic damping is included. The accuracy of the algorithm is illustrated by an application to pulse propagation in an elastic medium, where the algorithmic damping is used to reduce dispersion due to the spatial discretization, leading to a smooth solution with a clearly defined wave front. Copyright © 2005 John Wiley & Sons, Ltd. [source] Transcoding media for bandwidth constrained mobile devicesINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 2 2005Kevin Curran Bandwidth is an important consideration when dealing with streaming media. More bandwidth is required for complex data such as video as opposed to a simple audio file. When delivering streaming media, sufficient bandwidth is required to achieve an acceptable level of performance. If the information streamed exceeds the bandwidth capacity of the client the result will be ,choppy' and incomplete with possible loss of transmission. Transcoding typically refers to the adaptation of streaming content. Typical transcoding scenarios exploit content-negotiation to negotiate between different formats in order to obtain the most optimal combination of requested quality and available resources. It is possible to transcode media to a lesser quality or size upon encountering adverse bandwidth conditions. This can be accomplished without the need to encode multiple versions of the same file at differing quality levels. This study investigates the capability of transcoding for coping with restrictions in client devices. In addition, the properties of transcoded media files are examined and evaluated to determine their applicability for streaming in relation to a range of broad device types capable of receiving streaming media.,Copyright © 2005 John Wiley & Sons, Ltd. [source] Structure,Activity Relationship Studies in Single-Site Esterase Peptide DendrimersISRAEL JOURNAL OF CHEMISTRY, Issue 1 2009Sacha Javor We recently reported on peptide dendrimers with a single catalytic site at the dendrimer core catalyzing the hydrolysis of acetoxy- and butyryloxy-pyrene trisulfonate 1a/b in aqueous buffer with Michaelis,Menten kinetics. Substrate binding is mediated by a pair of protonated arginine or histidine residues in the first generation branch, and esterolysis is performed by the imidazole side-chain of a histidine residue in the core acting as a general base or nucleophile. Herein we report on a structure,activity relationship study searching for an optimal combination between amino acid sequence and catalytic machinery. Installation of histidine residues onto the aromatic dendrimer framework "R" leads to 10-fold higher rate acceleration up to kcat/kuncat = 1.5 * 103 at pH 5.5 with dendrimers RG3H (AcYT)8 (BWG)4 (BHS)2BHS and RMG3H (AcYT)8(BWG)4(BHSG)2BHS (one-letter codes for L -amino acids; Ac = acetyl, B = L -2,3-diaminopropionic acid branching point, C-terminus is amide -CONH2). These dendrimers reach the compactness of a native folded protein. [source] New Approach to Biphasic Waveforms for Internal Defibrillation:JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 8 2000Fully Discharging Capacitors Internal Defibrillation with Fully Discharging Capacitors. Introduction: The use of two independent, fully discharging capacitors for each phase of a biphasic defibrillation waveform may lead to the design of a simpler, smaller, internal defibrillator. The goal of this study was to determine the optimal combination of capacitor sizes for such a waveform. Methods and Results: Eight full-discharge (95/95% tilt), biphasic waveforms produced by several combinations of phase-1 capacitors (30, 60, and 90 ,F) and phase-2 capacitors (1/3, 2/3, and 1.0 times the phase-1 capacitor) were tested and compared to a single-capacitor waveform (120 ,F, 65/65% tilt) in a pig ventricular fibrillation model (n = 12, 23 ± 2 kg). In the full-discharge waveforms, phase-2 peak voltage was equal to phase-1 peak voltage. Shocks were delivered between a right ventricular lead and a left pectoral can electrode. E50s and V50s were determined using a ten-step Bayesian process. Full-discharge waveforms with phase-2 capacitors of ,40 ,F had the same E50 (6.7 ± 1.7 J to 7.3 ± 3.9 J) as the single-capacitor truncated waveform (7.3 ± 3.7 J), whereas waveforms with phase-2 capacitors of ,60 ,F had an extremely high E50 (14.5 ± 10.8 J or greater, P < 0.05). Moreover, of the former set of energy-efficient waveforms, those with phase-1 capacitors of ,60 ,F additionally exhibited V50s that were equivalent to the V50 of the single-capacitor waveform (344 ± 65 V to 407 ± 50 V vs 339 ± 83 V). Conclusion: Defibrillation efficacy can be maintained in a full-discharge, two-capacitor waveform with the proper choice of capacitors. [source] The relative effectiveness of practice change interventions in overcoming common barriers to change: a survey of 14 hospitals with experience implementing evidence-based guidelinesJOURNAL OF EVALUATION IN CLINICAL PRACTICE, Issue 5 2007Fiona Simpson MND Abstract Aims and objectives, Changing practice to reflect current best evidence can be costly and time-consuming. The purpose of this survey was to determine the optimal combination of practice change interventions needed to overcome barriers to practice change commonly encountered in the intensive care unit (ICU). Design, A survey instrument delivered by mail with email follow-up reminders. Setting, Fourteen hospitals throughout Australia and New Zealand. Subjects, Individuals responsible for implementing an evidence-based guideline for nutritional support in the ICU. Survey, Practice change interventions were ranked in order of effectiveness and barriers to change were ranked in order of how frequently they were encountered. Results, A response rate of 100% was achieved. Interventions traditionally regarded as strong (academic detailing, active reminders) were ranked higher than those traditionally regarded as moderate (audit and feedback), or weak (posters, mouse mats). The high ranks of the site initiation visit (educational outreach, modest) and in-servicing (didactic lectures, weak) were unexpected, as was the relatively low rank of educationally influential, peer-nominated opinion leaders. Four hospitals reported the same doctor-related barrier as ,most common' and the remaining 10 hospitals reported three different doctor-related barriers, two nursing-related barriers and three organizational barriers as most common. Conclusions, When designing a multifaceted, multi-centre change strategy, the selection of individual practice change interventions should be based on: (1) an assessment of available resources; (2) recognition of the importance of different types of barriers to different sites; (3) the potential for combinations of interventions to have a synergistic effect on practice change, and (4) the potential for combinations of interventions to actually reduce workload. [source] Influence of Storage Atmosphere and Temperature on Quality Evolution of Cut Belgian EndivesJOURNAL OF FOOD SCIENCE, Issue 8 2001M.D. Van de Velde ABSTRACT: An optimal combination of O2, CO2, and N2 for storage of cut Belgian Endive was defined, investigating visual quality aspects. In the experimental design, principles of mixture theory were used. The acceptability of cut endives stored under different gas combinations, selected in the range where both CO2 and O2 were varied between 2% and 18%, was evaluated by a consumer panel at different time intervals during storage. The response was modeled with a second-degree polynomial, the response surface pointed in the direction of a gas mixture 10% CO2, 10% O2, and 80% N2 for maximum acceptability or best quality during storage. Repeated experiments, including different varieties from 2 different growers, confirmed the optimal gas concentration, (10% CO2, 10% O2, and 80% N2). In a second step, the effect of temperature on quality degradation of cut endives stored under optimal atmosphere conditions, was quantified using the Arrhenius equation. An activation energy of 16.3 kcal/mol was obtained. [source] IMPACT OF FREEZING TEMPERATURE ON QUALITY OF FARMED ATLANTIC COD (GADUS MORHUA L.)JOURNAL OF TEXTURE STUDIES, Issue 4 2007TURID MØRKØRE ABSTRACT This study evaluates the impact of freezing temperature (,10,,25,,40,,55 or,70C) on thaw exudates, liquid leakage during freeze-chilling, appearance, gaping and mechanical properties of farmed Atlantic cod fillets. Freezing temperature significantly influenced each of the characteristics studied. High temperatures (,10 and,25C) gave increased thaw exudates, and freezing at,10C gave the highest liquid leakage during freeze-chilling. Fillets frozen at,10C had the lowest gaping and the whitest appearance. The results indicated the highest degree of toughening upon freezing at,10 or,55C, whereas the degree of toughening appeared to be similar and lower for fillets frozen at,25,,40 or,70C. The impact of freezing temperatures on the quality of farmed cod therefore appeared to be complex, but no overall beneficial effects were found by decreasing the freezing temperature below,40C. PRACTICAL APPLICATIONS For the fish processing industry, it is important to define optimal freezing and frozen storage regimes that are cost efficient and at the same time preserve the fresh fillet quality. Farmed cod differ from their wild counterparts by having lower water content, lower muscle pH and thicker fillets. Hence, industrial guidelines for wild cod may not be transferable to farmed cod. This study showed no beneficial effects by decreasing the freezing temperature below ,40C. Freezing and frozen storage are usually separated commercially. Results from the present study give valuable contribution to future studies aiming at defining optimal combination of freezing and frozen storage temperatures for farmed Atlantic cod. [source] Enhanced Clinical Utility of ,-CDT in a General PopulationALCOHOLISM, Issue 8 2000Pekka Sillanaukee Background: The use of a combination of markers to detect excessive alcohol consumption has been reported to provide better sensitivity in the diagnosis of alcohol abuse than single markers. However, the optimal combination of markers for the diagnosis of alcohol abuse has not yet been found. The aim of this study was to compare the diagnostic value of carbohydrate-deficient transferrin (CDT) and ,-glutamyltransferase (GGT) to discriminate among heavy drinkers (>280 g/week), moderate drinkers (105,280 g/week), and light drinkers (<105 g/week). Their mathematical combination, named ,-CDT, which has been found to be a strong marker of alcohol abuse in a former study, was also evaluated. Methods: The study was conducted in a group of 6962 subjects (3974 males and 2988 females), between the ages of 25 and 74 years, who participated in a large cross-sectional risk factor survey carried out in five geographic areas in Finland. In each study area, an age- and gender-stratified random sample was drawn from the general population. Sensitivity, specificity, positive and negative predictive values, and receiver operating characteristic curves were used to evaluate the performance of CDT, GGT, and ,-CDT. Results: For both sexes, the combined marker had the highest specificity (95%) and sensitivity in detecting heavy drinkers. In all cases, ,-CDT had the highest area under ROC plots. Our results also showed that GGT and CDT have similar, and rather low, sensitivity but high specificity in a general population. Conclusions: Compared with single markers, a significant improvement of sensitivity was obtained when the combination of both markers was used, especially in females. [source] Cosmic microwave background signal in Wilkinson Microwave Anisotropy Probe three-year data with fasticaMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2007D. Maino ABSTRACT We present an application of the fast Independent Component Analysis (fastica) to the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data with the goal of extracting the cosmic microwave background (CMB) signal. We evaluate the confidence of our results by means of Monte Carlo simulations including the CMB, foreground contaminations and instrumental noise specific to each WMAP frequency band. We perform a complete analysis involving all or a subset of the WMAP channels in order to select the optimal combination for CMB extraction, using the frequency scaling of the reconstructed component as a figure of merit. We find that the combination KQVW provides the best CMB frequency scaling, indicating that the low-frequency foreground contamination in Q, V and W bands is better traced by the emission in the K band. The CMB angular power spectrum is recovered up to the degree scale; it is consistent within errors for all WMAP channel combinations considered, and in close agreement with the WMAP three-year results. A power spectrum analysis is made of the sky map divided into two hemispheres that have been previously reported as showing evidence of an asymmetric ratio of power on large angular scales. We then confirm the findings of several previous works with independent techniques. [source] Synergistic antitumor effects of lenalidomide and rituximab on mantle cell lymphoma in vitro and in vivo,AMERICAN JOURNAL OF HEMATOLOGY, Issue 9 2009Liang Zhang Rituximab (RTX), a chimeric anti-CD20 antibody, is associated with direct induction of apoptosis and antibody-dependent cell-mediated cytotoxicity (ADCC) with clinical efficacy in mantle cell lymphoma (MCL). Lenalidomide (LEN), a novel immunomodulatory agent, sensitizes tumor cells and enhances ADCC. Our study attempted to elucidate the mechanism of LEN-enhanced RTX-mediated cytotoxicity of MCL cells. We found that LEN and RTX induced growth inhibition of both cultured and fresh primary MCL cells. LEN enhanced RTX-induced apoptosis via upregulating phosphorylation of c-Jun N-terminal protein kinases (JNK), Bcl-2, Bad; increasing release of cytochrome-c; enhancing activation of caspase-3, -8, -9 and cleavage of PARP. Meanwhile, LEN activated NK cells and increased CD16 expression on CD56lowCD16+ NK cells. Whole PBMCs but not NK cell-depleted PBMCs treated with LEN augmented 30% of RTX-dependent cytotoxicity. Daily treatment with LEN increased NK cells by 10-folds in SCID mice, and combination of LEN and RTX decreased tumor burden and prolonged survival of MCL-bearing SCID mice. Taken together, our study demonstrates that LEN plus RTX provides a synergistically therapeutic effect on MCL cells by enhancing apoptosis and RTX-dependent NK cell-mediated cytotoxicity and may be an optimal combination in the clinical trial of relapsed or refractory MCL. Am. J. Hematol. 2009. © 2009 Wiley-Liss, Inc. [source] DoE in engine developmentQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 6 2008Karsten Röpke Abstract Stricter legal emission limits and increasing customer expectations lead to a growing number of controllable engine components and thus to a higher engine control complexity. For engine development, however, this means much greater time and effort is required to find the optimal combination of all selectable parameters. This trend can be observed in the field of Gasoline as well as for Diesel engines. At the same time, the development time from the first idea up to the introduction of a new production engine has become even shorter, and the costs have to be reduced. Since the number of measuring points required for complete operational-test measurements rises exponentially with the number of input variables, it is quite obvious that full factorial measurements are no longer possible. Therefore the method ,Design of Experiments' (DoE) is widely accepted as a suitable tool in the automotive sector and among its suppliers. In the meantime the term ,DoE'/,DoE-Process' covers often also the measurement procedure and the modeling. Likewise, this method is broadly applied in the IAV (author's note: IAV is a German provider of engineering services to the automotive industry) during the advanced development stage up to the production engine applications. Whereas DoE is used mainly in the area of steady-state applications recent research work shows a great potential also to optimize transient engine behavior. This paper will give an overview about the usage of statistical methods (mainly Design of Experiments) in the production engine calibration. ,Engine calibration' is the term for finding the optimal settings of the engine controller unit; optimal in terms of minimal emissions, minimal fuel consumption, good drivability and other brand specific goals. Copyright © 2008 John Wiley & Sons, Ltd. [source] Designing an accelerated degradation experiment by optimizing the estimation of the percentileQUALITY AND RELIABILITY ENGINEERING INTERNATIONAL, Issue 3 2003Hong-Fwu Yu Abstract Degradation tests are widely used to assess the reliability of highly reliable products which are not likely to fail under traditional life tests or accelerated life tests. However, for some highly reliable products, the degradation may be very slow and hence it is impossible to have a precise assessment within a reasonable amount of testing time. In such cases, an alternative is to use higher stresses to extrapolate the product's reliability at the design stress. This is called an accelerated degradation test (ADT). In conducting an ADT, several decision variables, such s the inspection frequency, sample size and termination time, at each stress level are influential on the experimental efficiency. An inappropriate choice of these decision variables not only wastes experimental resources but also reduces the precision of the estimation of the product's reliability at the use condition. The main purpose of this paper is to deal with the problem of designing an ADT. By using the criterion of minimizing the mean-squared error of the estimated 100th percentile of the product's lifetime distribution at the use condition subject to the constraint that the total experimental cost does not exceed a predetermined budget, a nonlinear integer programming problem is built to derive the optimal combination of the sample size, inspection frequency and the termination time at each stress level. A numerical example is provided to illustrate the proposed method. Copyright © 2003 John Wiley & Sons, Ltd. [source] Retirement Incomes: Private Savings versus Social TransfersTHE MANCHESTER SCHOOL, Issue 5 2000John Creedy It has long been known, from the work of Samuelson and Aaron, that if (approximately) the sum of the population and real earnings growth rates exceeds the real interest rate, all individuals can be made better off by using a pay-as-you-go pension scheme. The basic overlapping generations model that is typically used to examine such intergenerational transfers makes no allowance for labour supply responses to taxes and transfers, and so cannot be used to examine optimal tax and pension levels. The present paper allows for labour supply effects, whereby a tax imposed to finance current pensions introduces distortions to labour supply and a reduction in the tax base. The optimal proportional tax rate, and therefore the optimal combination of private savings and social transfers, is derived in terms of the time preference rate, the taste for leisure, real interest and productivity and population growth rates. It is found that the condition under which the optimal tax is positive is the same as the Samuelson,Aaron condition. A crucial ingredient in obtaining this result is an assumption that pension levels are adjusted in line with the growth of wage rates rather than, for example, being held constant in real terms. This in turn is found to imply that earnings grow at the same rate as the wage, so long as preferences are such that leisure can be expressed as a proportion of full income. [source] Controversies in the treatment of high-risk prostate cancer,what is the optimal combination of hormonal therapy and radiotherapy: a review of literature,THE PROSTATE, Issue 7 2010Abrahim Al-Mamgani Abstract BACKGROUND In high-risk prostate carcinoma, there is controversy whether these patients should be treated with escalated-dose (,74 Gy) or conventional-dose radiotherapy (<74 Gy) combined with hormonal therapy. Furthermore, the issue of the optimal duration and timing of hormonal therapy are not well crystallized. PATIENTS AND METHODS A search for evidence from randomized- and large non-randomized studies in order to address these issues, was therefore initiated. For this purpose, MedLine, EMbase, and PubMed and the data base of the Dutch randomized dose-escalation trial, were consulted. RESULTS AND CONCLUSIONS From this search it was concluded that the benefit of hormonal therapy in combination with conventional-dose radiotherapy (<74 Gy) in high-risk prostate cancer is evident (Level 2 evidence); Levels 2 and 3 evidence were provided by several studies supporting the use of escalated-dose radiotherapy in high-risk prostate cancer. For the combination of hormonal therapy with escalated-dose radiotherapy in these patients, there is Level 2 evidence for moderately escalated dose (74 Gy) and high escalated dose (,78 Gy). The optimal duration and timing of hormonal therapy are not well defined. More randomized-controlled trials and meta-analyses are therefore needed to clearly determine the independent role of dose-escalation in high-risk patients treated with hormonal therapy and the optimal duration and timing of hormonal therapy. Prostate 70: 701,709, 2010. © 2009 Wiley-Liss, Inc. [source] Improved conception rates in sows inseminated with cryopreserved boar spermatozoa prepared with a more optimal combination of osmolality and glycerol in the freezing extenderANIMAL SCIENCE JOURNAL, Issue 2 2009Tetsuji OKAZAKI ABSTRACT Cryoprotectant agents (CPAs) are added in freezing extenders to prevent intracellular ice crystal formation. However, it has been reported that high dose of CPAs confer toxicity on spermatozoa. Recently, the reduction of intracellular water by a high osmolality solution has also resulted in the suppression of ice crystal formation in spermatozoa, suggesting that the optimal combination of glycerol concentration and freezing extender osmolality could contribute to the development of effective sperm cryopreservation techniques. In this study, we investigated the motility, membrane and acrosomal integrity of frozen-thawed boar spermatozoa treated with freezing extender (NSF) of varying osmolalities (300, 400, 500 mOsm/kg) and final concentrations of glycerol (0.5, 1, 2, 3%). The spermatozoa that were treated at 400 mOsm/kg and 2% glycerol showed significantly higher rates of motility and membrane integrity compared with those in other treatment groups. In addition, the conception and implantation rates of swine artificially inseminated with spermatozoa frozen by the novel freezing extender (conception; 79%, implantation; 57.5%) were significantly higher than those of frozen-thawed spermatozoa treated in the conventional NSF (300 mOsm/kg, 3% glycerol) (conception; 29%, implantation; 33.8%). From these results, we concluded that the novel hyperosmotic (400 mOsm/kg) and low-glycerol (final concentration 2%) freezing extender is beneficial for the cryopreservation of boar spermatozoa. [source] Estimation for the Optimal Combination of Markers without Modeling the Censoring DistributionBIOMETRICS, Issue 1 2009Chin-Tsang Chiang Summary In the time-dependent receiver operating characteristic curve analysis with several baseline markers, research interest focuses on seeking appropriate composite markers to enhance the accuracy in predicting the vital status of individuals over time. Based on censored survival data, we proposed a more flexible estimation procedure for the optimal combination of markers under the validity of a time-varying coefficient generalized linear model for the event time without restrictive assumptions on the censoring pattern. The consistency of the proposed estimators is also established in this article. In contrast, the inverse probability weighting (IPW) approach might introduce a bias when the selection probabilities are misspecified in the estimating equations. The performance of both estimation procedures are examined and compared through a class of simulations. It is found from the simulation study that the proposed estimators are far superior to the IPW ones. Applying these methods to an angiography cohort, our estimation procedure is shown to be useful in predicting the time to all-cause and coronary artery disease related death. [source] Statistical approaches in landscape genetics: an evaluation of methods for linking landscape and genetic dataECOGRAPHY, Issue 5 2009Niko Balkenhol The goal of landscape genetics is to detect and explain landscape effects on genetic diversity and structure. Despite the increasing popularity of landscape genetic approaches, the statistical methods for linking genetic and landscape data remain largely untested. This lack of method evaluation makes it difficult to compare studies utilizing different statistics, and compromises the future development and application of the field. To investigate the suitability and comparability of various statistical approaches used in landscape genetics, we simulated data sets corresponding to five landscape-genetic scenarios. We then analyzed these data with eleven methods, and compared the methods based on their statistical power, type-1 error rates, and their overall ability to lead researchers to accurate conclusions about landscape-genetic relationships. Results suggest that some of the most commonly applied techniques (e.g. Mantel and partial Mantel tests) have high type-1 error rates, and that multivariate, non-linear methods are better suited for landscape genetic data analysis. Furthermore, different methods generally show only moderate levels of agreement. Thus, analyzing a data set with only one method could yield method-dependent results, potentially leading to erroneous conclusions. Based on these findings, we give recommendations for choosing optimal combinations of statistical methods, and identify future research needs for landscape genetic data analyses. [source] Pharmacodynamic and Pharmacokinetic Interaction Studies of Loreclezole with Felbamate, Lamotrigine, Topiramate, and Oxcarbazepine in the Mouse Maximal Electroshock Seizure ModelEPILEPSIA, Issue 3 2005Jarogniew J. Luszczki Summary:,Purpose: The study investigated the types of interactions between loreclezole (LCZ) and a variety of newly licensed antiepileptic drugs (AEDs) with different mechanisms of actions [felbamate (FBM), lamotrigine (LTG), topiramate (TPM), and oxcarbazepine (OXC)] by isobolographic analysis. Methods: Anticonvulsant and adverse-effect profiles of combinations of LCZ with other AEDs at fixed ratios of 1:3, 1:1, and 3:1 were investigated in the maximal electroshock (MES)-induced seizures and the chimney test (as a measure of motor impairment) in mice so as to identify optimal combinations. Protective indices (PIs) and benefit indices (BIs) were calculated so that a ranking in relation to advantageous combinations could be established. Results: With isobolography, it was observed that the combination of LCZ and TPM, at the fixed ratios of 1:1 and 3:1, was supraadditive (synergistic; p < 0.05), whereas LCZ with TPM at the fixed ratio of 1:3 and LCZ combined with LTG, FBM, or OXC at the fixed ratios of 1:3, 1:1, and 3:1 were associated with additive interactions. Moreover, the isobolographic analysis in the chimney test revealed that only one combination tested (LCZ and TPM at the fixed ratio of 1:1) was subadditive (antagonistic; p < 0.05), whereas the remaining combinations of LCZ with LTG, FBM, or OXC (at the fixed ratios of 1:3, 1:1, and 3:1) barely displayed additivity. However, these combinations were associated with significant pharmacokinetic interactions, in that LCZ increased brain TPM (94%), OXC (21%), FBM (46%), and LTG (8%) concentrations. In addition, brain LCZ concentrations were decreased by TPM (26%), OXC (37%), LTG (42%), and FBM (19%). None of the examined combinations between LCZ and TPM, OXC, LTG, and FBM altered long-term memory in the step-through passive-avoidance task. Conclusions: LCZ plus TPM appears to be a particularly favorable combination, based on the MES test and the chimney test. LCZ and OXC also is a favorable combination. However, these conclusions are confounded by the fact that LCZ is associated with significant pharmacokinetic interactions. [source] Optimal combinations of ultrasound-based and serum markers of disease severity in patients with chronic hepatitis CJOURNAL OF VIRAL HEPATITIS, Issue 8 2010J. F. L. Cobbold Summary., Combinations of noninvasive markers may improve discrimination of chronic liver disease severity. The aims of this study were to compare four validated serum and ultrasound-based markers of hepatic disease severity head-to-head with liver biopsy and to assess optimal combinations with consideration of cost. A total of 67 patients with biopsy-proven chronic hepatitis C underwent all four techniques on the same visit [aspartate aminotransferase (AST) to platelet ratio index (APRI); Enhanced Liver Fibrosis (ELF) panel; transient elastography (TE) and ultrasound microbubble hepatic transit times (HTT)]. Markers were combined according to increasing financial cost and ordinal regression used to determine contributions. APRI, ELF, TE and HTT predicted cirrhosis with diagnostic accuracy of 86%, 91%, 90% and 83% respectively. ELF and TE were the most reliable tests with an intra-class correlation of 0.94 each. Either ELF or TE significantly enhanced the prediction of fibrosis stage when combined with APRI, but when combined together, did not improve the model further. Addition of third or fourth markers did not significantly improve prediction of fibrosis. Combination of APRI with either ELF or TE effectively predicts fibrosis stage, but combinations of three or more tests lead to redundancy of information and increased cost. [source] TECHNOLOGY TRANSFER UNDER RETURNS TO SCALE*THE MANCHESTER SCHOOL, Issue 3 2009DEBAPRIYA SEN In this paper we consider the licensing of a cost-reducing innovation by an outside innovator that uses optimal combinations of upfront fees and royalties in a Cournot duopoly characterized by non-constant returns to scale. The main conclusion of our theoretical analysis is that incidence of positive royalties and diffusion of innovations are both inversely related to economies of scale. Our analysis provides a plausible explanation of the variation of licensing policies across industries. [source] Effect of combined fish meal : soybean meal ratio, vitamin C and fish oil supplementations in diet on the growth and reproduction of red swamp crayfish, Procambarus clarkii (Crustacea: Decapoda)AQUACULTURE RESEARCH, Issue 9 2010Jia-Yuan Xu Abstract Fish meal (FM), vitamin C (VC) and fish oil (FO) play important roles in the growth and reproduction in aquatic animals. To determine the optimum dietary combinations of FM:SM (soybean meal) ratio, VC and FO supplementations for the growth and reproduction of female crayfish Procambarus clarkii, we used the L9 (33) orthogonal array, which arranged three factors varied at three levels (FM:SM at 1:3, 1:2 and 1:1.5; VC supplementation at 0.02%, 0.04% and 0.06%; FO inclusion at 1.90%, 2.85% and 3.80%). Range analysis showed that the highest weight gain (WG) of the crayfish occurred at FM:SM of 1:1.5, VC supplementation of 0.04% and FO inclusion of 1.90%, and the maximum gonadosomatic index (GSI), egg laying amount (ELA) and spawning rate (SR) were obtained at FM:SM 1:1.5, VC supplementation 0.06% and FO inclusion 3.80%. Analysis of variance indicated that all the three factors had no significant effects on WG. Fish oil supplementation significantly affected GSI, ELA and SR (P<0.05), while FM:SM did not significantly influence any of these indicators. Taking the cost into consideration, we suggest that a dietary FM:SM of 1:3, VC supplementation 0.06% and FO inclusion 3.80% might be the optimal combinations for the reproduction of P. clarkii. [source] Cophylogeny of the Ficus microcosmBIOLOGICAL REVIEWS, Issue 4 2004Andrew P. Jackson ABSTRACT The various mutualistic and antagonistic symbioses between fig trees (Ficus: Moraceae) and chalcid wasps comprise a community in microcosm. Phylogenetic estimates of figs and fig wasps show general topological correspondence, making the microcosm a model system for cophylogeny. Incongruence between phylogenies from associated organisms can be reconciled through a combination of evolutionary events. Cophylogeny mapping reconciles phylogenies by embedding an associate tree into a host tree, finding the optimal combinations of events capable of explaining incongruence and evaluating the level of codivergence. This review addresses the results of cophylogeny analysis concerning Ficus and discusses the plausibility of different evolutionary events. Five different associations encompassing fig-pollinator, fig-parasite and pollinator-parasitoid interactions are reconciled. The method improves on previous comparisons by employing,jungles'to provide an exhaustive and quantitative analysis of cophylogeny. A jungle is a mechanism for inferring host switches and obtaining all potentially optimal solutions to the reconciliation problem. The results support the consensus that figs codiverge significantly with pollinators but not non-pollinators. However, pollinators still appear to have switched between hosts in contradiction to the traditional model of faithful codivergence. This emphasises the growing realisation that evolutionary transitions in the microcosm are more flexible than previously thought and host specificity is necessary but not sufficient for codivergence. The importance of sampling strategy is emphasised by the influence of taxon set on the fig-pollinator and fig-parasite jungles. Spurious significant results for fig-parasite and fig-parasitoid jungles indicate that the choice of congruence measure influences significance; the total number of events required to reconcile two trees ('total cost') is not a good measure of congruence when switches cannot be realistically weighted. [source] | ||||||||||||||||||||||