Home About us Contact
|
Home About us Contact | ||
|
|
||
Possible Combinations (possible + combination)
Selected AbstractsProper Splitting of Interconnected Power SystemsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2010S. Najafi Non-member Abstract Power system islanding is the last defense line to protect power grids from incidence of wide-area blackout. As a wide-area control action, power system splitting is a comprehensive decision making problem that includes different subproblems. This paper introduces a novel approach for separation of the entire power system into several stable islands in different loading levels. The proposed method combines both the dynamic and the static characteristics of interconnected power network and determines the proper splitting schemes. The presented algorithm searches for proper islanding strategy in the boundary of primary determined coherent machines using Krylov subspace method and finds the proper splitting points by transferring some of the buses in one island to another island such that total load shedding is minimized. A spanning tree-based depth first search algorithm is used to find all possible combination of transferred buses. The presented method reduces the huge initial search space of islanding strategy considering dynamic characteristics of integrated power system and reduction of search space to only boundary network. The speed of the proposed algorithm is remarkably high and can be applied for islanding the power system in real-time. The presented algorithm is applied to IEEE 118 BUS test system. Results show the robustness, effectiveness, and capability of the algorithm to determine fast and accurate proper islanding strategy. Time domain simulation of the islanding strategies confirms that all the islands which are specified by the proposed method are stable. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Introducing natural-convective chilling to food engineering undergraduate freshmen: Case studied assisted by CFD simulation and field visualizationCOMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 1 2009J. A. Rabi Abstract A computational fluid dynamics (CFD)-assisted didactic activity has been applied to Food Engineering freshmen aiming at introducing basic concepts of process modeling and simulation towards the food industry. Evoking natural convection, a relatively simple case study was proposed involving two initially room temperature porous samples (identified as two fruits) that were placed inside a refrigeration chamber. Three different configurations were suggested for placing such warmer samples so that students were asked to order them with respect to their chilling capability, that is, to their ability to chill samples as fast as possible. Freshmen's written answers were collected before CFD was used to simulate and visualize each distinct chilling scenario. Accordingly, a finite-volume FORTRAN simulator for transport phenomena in domains fully or partially filled up with porous matrix was used to help compare each chilling performance. Among all possible combinations, answer distribution is presented and discussed in the light of freshmen's scholar background as well as based on the way natural convection concepts were introduced. © 2008 Wiley Periodicals, Inc. Comput Appl Eng Educ 17: 34,43, 2009; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae20161 [source] Folate deficiency in human peripheral blood lymphocytes induces chromosome 8 aneuploidy but this effect is not modified by riboflavinENVIRONMENTAL AND MOLECULAR MUTAGENESIS, Issue 1 2010Juan Ni Abstract Chromosome 8 aneuploidy is a common event in certain cancers but whether folate (F) deficiency induces chromosome 8 aneuploidy is not known. Furthermore the impact of riboflavin (R) deficiency, which may alter activity of a key enzyme in folate metabolism, on these events is unknown. Therefore, the aim of our research was to test the following hypotheses: (a) F deficiency induces chromosome 8 aneuploidy; (b) chromosome 8 aneuploidy is affected by F deficiency to a similar degree as chromosome 17 and (c) R deficiency aggravates the risk of aneuploidy caused by F deficiency. These hypotheses were tested in long-term cultures of lymphocytes from twenty female healthy volunteers (aged 30,48 years). Lymphocytes were cultured in each of the four possible combinations of low (L) and high (H) F (LF, 20 nmol/L, HF 200 nmol/L, respectively) and L and H R (LR 1 nmol/L, HR 500 nmol/L, respectively) media (LFLR, LFHR, HFLR, HFHR) for 9 days. Chromosomes 8 and 17 aneuploidy was measured in mononucleated (MONO) and cytokinesis-blocked binucleated (BN) cells using dual-color fluorescence in situ hybridization (FISH) with fluorescent centromeric probes specific for chromosomes 8 and 17. Culture in LF media (LFLR or LFHR) induced significant and similar increases in frequencies of aneuploidy of chromosomes 8 and 17 (P < 0.001) relative to culture in HF media (HFLR or HFHR). There was no significant effect of R concentration on aneuploidy frequency for either chromosome. We conclude that F deficiency is a possible cause of chromosome 8 aneuploidy. Environ. Mol. Mutagen. 2010. © 2009 Wiley-Liss, Inc. [source] Adenosine A1 Antagonism Attenuates Atropine-resistant Hypoxic Bradycardia in RatsACADEMIC EMERGENCY MEDICINE, Issue 9 2003Justin L. Kaplan MD Abstract Objectives: To test the following hypotheses: Hypoxia induces bradycardia and hemodynamic compromise that are resistant to atropine but responsive to selective antagonism of the adenosine A1 receptor (A1AdoR). The mechanism for such attenuation is independent of the vagus nerve. Methods: Ten minutes after sham or actual bilateral cervical vagotomy, paralyzed ventilated rats were made hypoxic (5% fractional inspired oxygen, continued until death). Five minutes after beginning hypoxia, intravenous treatment with BG-9719, a selective A1AdoR antagonist (0.1 mg/kg); atropine (0.1 mg/kg); BG-9719 vehicle; or saline was initiated. These drug doses were based on pilot studies. Of the eight treatment groups (eight possible combinations of vagotomy status and drug/vehicle treatment), n= 8 in all except nonvagotomized, vehicle-treated rats (where n= 7). Results: Heart rate and left ventricular contractility decreased rapidly with hypoxia. Atropine had minimal effects in prolonging survival (from mean ± SEM of 15.5 ± 2.1 minutes to 20.2 ± 2.5 minutes, p = 0.94) and attenuating posthypoxic decreases in heart rate (p = 0.89) and contractility (p = 0.83) compared with saline. BG-9719 prolonged survival, however, from 14.4 ± 1.9 minutes (with vehicle treatment) to 37.2 ± 6.8 minutes (p < 0.001). Survival, heart rate, and contractility were preserved with BG-9719 compared with atropine and vehicle (p < 0.05, all comparisons). Vagotomy prevented the effects of BG-9719 on survival prolongation (p = 0.003), heart rate (p = 0.01), and contractility (p < 0.001) but did not affect those outcomes in saline-treated rats. Conclusions: Survival, heart rate, and contractility were better preserved with BG-9719 than atropine. A1AdoR selective antagonism, possibly because of its multiple mechanisms for attenuating hypoxic cardiac insufficiency, resulted in better hemodynamic and clinical outcomes. That attenuation seems to have a component of vagal mediation. [source] Selection of Antiepileptic Drug Polytherapy Based on Mechanisms of Action: The Evidence ReviewedEPILEPSIA, Issue 11 2000Charles L. P. Deckers Summary: Purpose: When monotherapy with antiepileptic drugs (AEDs) fails, combination therapy is tried in an attempt to improve effectiveness by improving efficacy, tolerability, or both. We reviewed the available studies (both animal and human) on AED polytherapy to determine whether AEDs can be selected for combination therapy based on their mechanisms of action, and if so, which combinations are associated with increased effectiveness. Because various designs and methods of analysis were used in these studies, it was also necessary to evaluate the appropriateness of these approaches. Methods: Published papers reporting on AED polytherapy in animals or humans were identified by Medline search and by checking references cited in these papers. Results: Thirty-nine papers were identified reporting on two-drug AED combinations. Several combinations were reported to offer improved effectiveness, but no uniform approach was used in either animal or human studies for the evaluation of pharmacodynamic drug interactions; efficacy was often the only end point. Conclusions: There is evidence that AED polytherapy based on mechanisms of action may enhance effectiveness. In particular, combining a sodium channel blocker with a drug enhancing GABAergic inhibition appears to be advantageous. Combining two GABA mimetic drugs or combining an AMPA antagonist with an NMDA antagonist may enhance efficacy, but tolerability is sometimes reduced. Combining two sodium channel blockers seems less promising. However, given the incomplete knowledge of the pathophysiology of seizures and indeed of the exact mechanisms of action of AEDs, an empirical but rational approach for evaluating AED combinations is of fundamental importance. This would involve appropriate testing of all possible combinations in animal models and subsequent evaluation of advantageous combinations in clinical trials. Testing procedures in animals should include the isobologram method, and the concept of drug load should be the basis of studies in patients with epilepsy. [source] Zero-sequence-based relaying technique for protecting power transformers and its performance assessment using unsupervised learning ANNEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 2 2006Guzmán Díaz Abstract In this paper a simple and robust new relaying technique for protecting transformers from internal winding faults is proposed. Based on the measurement of zero sequence current inside a delta winding, the technique greatly simplifies the conventional differential relaying arrangement when a delta winding is available. Despite the number of windings of the transformer and the location of the fault, only measurement of induced zero sequence current within the delta winding is needed. Since the proposed technique has been shown to be prone to generate false pick-up signals during inrush, a simple restraining criterion is proposed and analysed. Additionally, use of projection techniques based on self-organizing maps (SOM) is proposed in this paper as a valuable tool for analysing multivariable data which are generated from the huge number of possible combinations existing between switching instant and fault location. Finite element simulations and laboratory tests have been combined into SOM to validate the proposed relaying technique and the restraining criterion. Copyright © 2005 John Wiley & Sons, Ltd. [source] THE ECOLOGY AND GENETICS OF FITNESS IN CHLAMYDOMONAS.EVOLUTION, Issue 1 2002VIII. Abstract According to classical evolutionary theory, sexual recombination can generate the variation necessary to adapt to changing environments and thereby confer an evolutionary advantage of sexual over asexual reproduction. Using the green alga, Chlamydomonas reinhardtii, we investigated the effect of a single sexual episode on adaptation of heterotrophic growth on different carbon sources. In an initial mixture of isolates, sex was induced and the resulting offspring constituted the sexual populations, along with any unmated vegetative cells; the unmated mixture of isolates represented the asexual populations. Mean and variance in division rates (i.e., fitness) were measured four times during approximately 50 generations of vegetative growth in the dark on all possible combinations of four carbon sources. Consistent with effects of recombination of epistatic genes in linkage disequilibrium, sexual populations initially had a higher variance in fitness, but their mean fitness was lower than that of asexual populations, possibly due to recombinational load. Subsequently, fitness of sexual populations exceeded that of asexual ones, but finally they regained parity in both mean and variance of fitness. Although recombination was not more effective on more complex substrates, these results generally support the idea that sex can accelerate adaptation to novel environments. [source] Role of the surface charges D72 and K8 in the function and structural stability of the cytochrome c6 from Nostoc sp.FEBS JOURNAL, Issue 13 2005PCC 711 We investigated the role of electrostatic charges at positions D72 and K8 in the function and structural stability of cytochrome c6 from Nostoc sp. PCC 7119 (cyt c6). A series of mutant forms was generated to span the possible combinations of charge neutralization (by mutation to alanine) and charge inversion (by mutation to lysine and aspartate, respectively) in these positions. All forms of cyt c6 were functionally characterized by laser flash absorption spectroscopy, and their stability was probed by urea-induced folding equilibrium relaxation experiments and differential scanning calorimetry. Neutralization or inversion of the positive charge at position K8 reduced the efficiency of electron transfer to photosystem I. This effect could not be reversed by compensating for the change in global charge that had been introduced by the mutation, indicating a specific role for K8 in the formation of the electron transfer complex between cyt c6 and photosystem I. Replacement of D72 by asparagine or lysine increased the efficiency of electron transfer to photosystem I, but destabilized the protein. D72 apparently participates in electrostatic interactions that stabilize the structure of cyt c6. The destabilizing effect was reduced when aspartate was replaced by the small amino acid alanine. Complementing the mutation D72A with a charge neutralization or inversion at position K8 led to mutant forms of cyt c6 that were more stable than the wild-type under all tested conditions. [source] Predicting the emergence of resistance to antifungal drugsFEMS MICROBIOLOGY LETTERS, Issue 1 2001Leah E Cowen Abstract The emergence of antifungal drug resistance is inevitable. Here I discuss antibiotic resistance in the context of the adaptive potential of fungi and I propose an approach to predicting the evolution of antifungal resistance using experimental evolution of DNA sequences and microbial populations. Prediction is based on determination of evolutionary potential at two levels, the gene and the genome. At the level of the gene, evolutionary potential depends on the sequence space of candidate resistance genes defined by the fitness effects of all possible mutations in all possible combinations. At the level of the genome, evolutionary potential depends on the adaptive landscape defined by the fitness effects of all possible interactions among alleles constituting the genotype. [source] Interfertility between North American and European strains of Phlebiopsis giganteaFOREST PATHOLOGY, Issue 3 2005R. Grillo Summary Thirteen homokaryotic strains of Phlebiopsis gigantea from Canada, six strains from the US and 10 strains from Europe were paired in all possible combinations in order to determine the degree of interfertility between them. The diagnosis of interfertility was based on the production of heterokaryotic fruit bodies in the pairings. Among the resulting 406 pairings, 253 (62%) fruited. Within the strains originating from Canada, USA and Europe, 64, 80 and 64% of the pairings fruited, respectively. The fruiting frequency in pairings between the Canadian and US strains was 65%, between the Canadian and European strains 55%, and between the US and European strains 67%. True hybridization between the European and North American P. gigantea was shown by analysing the single-spore progeny using DNA fingerprinting. In spite of the relatively low interfertility in pairings within and between continents, no clear indication of the existence of intersterility groups was found. The low interfertility is probably due to the ageing of the pure cultures and to deficient fruiting ability of certain heterokaryons on agar medium. The results strongly suggest that although the North American and European strains of P. gigantea show some differentiation they can be regarded as belonging to the same biological species. Résumé Treize souches homocaryotiques de Phlebiopsis gigantea du Canada, 6 des Etats-Unis et 10 d'Europe ont été confrontées par paires selon toutes les combinaisons possibles pour déterminer leur degré d'interfertilité. Le diagnostic d'interfertilité est basé sur la production de fructifications hétérocaryotiques dans les confrontations. Parmi les 406 paires, 253 (62%) ont fructifié. Ce pourcentage est de 64, 80 et 64% respectivement pour les souches du Canada, des Etats-Unis ou d'Europe entre elles. La fréquence de fructification pour les confrontations entre souches du Canada et des Etats-Unis est de 65%, entre souches européennes et canadiennes de 55% et entre souches des USA et d'Europe de 67%. La réalité de l'hybridation entre souches européennes et nord américaines a été démontrée par analyse de la descendance de spores par empreinte génétique. Malgré la relativement faible interfertilité dans les confrontations intra ou inter continents, l'existence de groupes d'interstérilité n'a pu être montrée. La faible interfertilité est probablement due au vieillissement des cultures pures et à une faible capacitéà fructifier sur milieu gélosé de certains hétérocaryons. Les résultats suggèrent fortement que malgré une certaine différenciation entre souches nord américaines et européennes de P. gigantea, celles-ci peuvent être considérées comme appartenant à la même espèce. Zusammenfassung Zur Bestimmung der Interfertilität wurden 13 homokaryotische Isolate von Phlebiopsis gigantea aus Kanada, 6 aus den USA und 10 aus Europa in allen möglichen Kombinationen miteinander gekreuzt. Der Erfolg der Kreuzungen wurde anhand der Bildung von heterokaryotischen Fruchtkörpern beurteilt. Bei insgesamt 406 Kreuzungen wurden in 253 Fällen (62%) Fruchtkörper gebildet. Unter den Stämmen aus Kanada, den USA und Europa kam es in 64, 80 und 64% der Fälle zur Fruchtkörperbildung. Bei Paarungen zwischen Isolaten aus Kanada und den USA fruktifizierten 65%, bei Paarungen zwischen Isolaten aus Kanada und Europa waren dies 55%, Paarungen zwischen Isolaten aus den USA und Europa fruktifizierten zu 67%. Die echte Hybridisierung zwischen europäischen und nordamerikanischen Isolaten von P. gigantea wurde durch Analysen der Einzelsporisolate aus den Fruchtkörpern durch DNA-Fingerprinting nachgewiesen. Trotz der relativ geringen Interfertilität innerhalb und zwischen den Kontinenten wurden keine klaren Hinweise auf die Existenz von Intersterilitätsgruppen gefunden. Die geringe Interfertilität ist möglicherweise durch eine Degeneration der Kulturen in vitro und durch die fehlende Fähigkeit mancher Heterokaryen zur Fruchtkörperbildung auf Agarmedien erklärbar. Die Ergebnisse zeigen, dass Isolate von P. gigantea aus Nordamerika und Europa trotz einer gewissen geographischen Differenzierung zu einer einzigen biologischen Art gehören. [source] Selecting discriminant function models for predicting the expected richness of aquatic macroinvertebratesFRESHWATER BIOLOGY, Issue 2 2006JOHN VAN SICKLE Summary 1. The predictive modelling approach to bioassessment estimates the macroinvertebrate assemblage expected at a stream site if it were in a minimally disturbed reference condition. The difference between expected and observed assemblages then measures the departure of the site from reference condition. 2. Most predictive models employ site classification, followed by discriminant function (DF) modelling, to predict the expected assemblage from a suite of environmental variables. Stepwise DF analysis is normally used to choose a single subset of DF predictor variables with a high accuracy for classifying sites. An alternative is to screen all possible combinations of predictor variables, in order to identify several ,best' subsets that yield good overall performance of the predictive model. 3. We applied best-subsets DF analysis to assemblage and environmental data from 199 reference sites in Oregon, U.S.A. Two sets of 66 best DF models containing between one and 14 predictor variables (that is, having model orders from one to 14) were developed, for five-group and 11-group site classifications. 4. Resubstitution classification accuracy of the DF models increased consistently with model order, but cross-validated classification accuracy did not improve beyond seventh or eighth-order models, suggesting that the larger models were overfitted. 5. Overall predictive model performance at model training sites, measured by the root-mean-squared error of the observed/expected species richness ratio, also improved steadily with DF model order. But high-order DF models usually performed poorly at an independent set of validation sites, another sign of model overfitting. 6. Models selected by stepwise DF analysis showed evidence of overfitting and were outperformed by several of the best-subsets models. 7. The group separation strength of a DF model, as measured by Wilks',, was more strongly correlated with overall predictive model performance at training sites than was DF classification accuracy. 8. Our results suggest improved strategies for developing reliable, parsimonious predictive models. We emphasise the value of independent validation data for obtaining a realistic picture of model performance. We also recommend assessing not just one or two, but several, candidate models based on their overall performance as well as the performance of their DF component. 9. We provide links to our free software for stepwise and best-subsets DF analysis. [source] Sensitivity analysis of prior model probabilities and the value of prior knowledge in the assessment of conceptual model uncertainty in groundwater modellingHYDROLOGICAL PROCESSES, Issue 8 2009Rodrigo Rojas Abstract A key point in the application of multi-model Bayesian averaging techniques to assess the predictive uncertainty in groundwater modelling applications is the definition of prior model probabilities, which reflect the prior perception about the plausibility of alternative models. In this work the influence of prior knowledge and prior model probabilities on posterior model probabilities, multi-model predictions, and conceptual model uncertainty estimations is analysed. The sensitivity to prior model probabilities is assessed using an extensive numerical analysis in which the prior probability space of a set of plausible conceptualizations is discretized to obtain a large ensemble of possible combinations of prior model probabilities. Additionally, the value of prior knowledge about alternative models in reducing conceptual model uncertainty is assessed by considering three example knowledge states, expressed as quantitative relations among the alternative models. A constrained maximum entropy approach is used to find the set of prior model probabilities that correspond to the different prior knowledge states. For illustrative purposes, a three-dimensional hypothetical setup approximated by seven alternative conceptual models is employed. Results show that posterior model probabilities, leading moments of the predictive distributions and estimations of conceptual model uncertainty are very sensitive to prior model probabilities, indicating the relevance of selecting proper prior probabilities. Additionally, including proper prior knowledge improves the predictive performance of the multi-model approach, expressed by reductions of the multi-model prediction variances by up to 60% compared with a non-informative case. However, the ratio between-model to total variance does not substantially decrease. This suggests that the contribution of conceptual model uncertainty to the total variance cannot be further reduced based only on prior knowledge about the plausibility of alternative models. These results advocate including proper prior knowledge about alternative conceptualizations in combination with extra conditioning data to further reduce conceptual model uncertainty in groundwater modelling predictions. Copyright © 2009 John Wiley & Sons, Ltd. [source] DSC-Ritz method for high-mode frequency analysis of thick shallow shellsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2005C. W. Lim Abstract This paper addresses a challenging problem in computational mechanics,the analysis of thick shallow shells vibrating at high modes. Existing methods encounter significant difficulties for such a problem due to numerical instability. A new numerical approach, DSC-Ritz method, is developed by taking the advantages of both the discrete singular convolution (DSC) wavelet kernels of the Dirichlet type and the Ritz method for the numerical solution of thick shells with all possible combinations of commonly occurred boundary conditions. As wavelets are localized in both frequency and co-ordinate domains, they give rise to numerical schemes with optimal accurate, stability and flexibility. Numerical examples are considered for Mindlin plates and shells with various edge supports. Benchmark solutions are obtained and analyzed in detail. Experimental results validate the convergence, stability, accuracy and reliability of the proposed approach. In particular, with a reasonable number of grid points, the new DSC-Ritz method is capable of producing highly accurate numerical results for high-mode vibration frequencies, which are hitherto unavailable to engineers. Moreover, the capability of predicting high modes endows us the privilege to reveal a discrepancy between natural higher-order vibration modes of a Mindlin plate and those calculated via an analytical relationship linking Kirchhoff and Mindlin plates. Copyright © 2004 John Wiley & Sons, Ltd. [source] A lumped mass numerical model for cellular materials deformed by impactINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 11 2001Z. H. Tu Abstract When impacted by a relatively rigid body, cellular materials undergo severe deformation and extensive material failure. However, such behaviour may not be well described using traditional numerical approaches such as the finite element method. This paper presents a lumped mass numerical model which can accommodate high degrees of deformation and material failure. The essence of this model is to discretize a block of material into contiguous element volumes, each represented by a mass point. Interactions between a node and its neighbours are accounted for by defining ,connections' that represent their interfaces which transmit stresses. Strains at a node are calculated from the co-ordinates of the surrounding nodes; these also determine the stresses on the interfaces. The governing equations for the entire solution domain are then converted into a system of equations of motion with nodal positions as unknowns. Failure criteria and possible combinations of ,connection' breakage are incorporated to model the occurrence of damage. A practical contact algorithm is also developed to describe the contact interactions between cellular materials and rigid bodies. Simulations for normal and oblique impacts of rigid rectangular, cylindrical and wedge-tipped impactors on crushable foam blocks are presented to substantiate the validity of the model. The generally good correlation between the numerical and experimental results demonstrates that the proposed numerical approach is able to model the impact response of the crushable foam. However, some limitations in modelling crack propagation in oblique impacts by a rigid impactor on foam blocks are observed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Differential Contribution of Osteoclast- and Osteoblast-Lineage Cells to CpG-Oligodeoxynucleotide (CpG-ODN) Modulation of Osteoclastogenesis,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 9 2005Alla Amcheslavsky Abstract CpG-ODNs modulate osteoclast differentiation through Toll-like receptor 9 (TLR9). Using TLR9-deficient mice, we found that activation of TLR9 on both osteoclast precursors and osteoblasts mediate the osteoclastogenic effect of CpG-ODN. Osteoclastic TLR9 is more important for this activity. Introduction: Bacterial infections cause pathological bone loss by accelerating differentiation and activation of the osteoclast. A variety of bacteria-derived molecules have been shown to enhance osteoclast differentiation through activation of Toll-like receptors (TLRs). We have shown that CpG-oligodeoxynucleotides (CpG-ODNs), mimicking bacterial DNA and exerting their cellular activities through TLR9, modulate osteoclast differentiation in a complex manner: the ODNs inhibit the activity of the physiological osteoclast differentiation factor RANKL in early osteoclast precursors (OCPs) but markedly stimulate osteoclastogenesis in cells primed by RANKL. Materials and Methods: Osteoclast precursors and osteoblasts from TLR9-deficient (TLR9,/,) and wildtype (TLR9+/+) mice were used for in vitro analyses of osteoclast differentiation and modulation of signal transduction and gene expression. Results: As expected CpG-ODN did not exert any activity in cells derived from TLR9,/,mice; these cells, however, responded in a normal manner to other stimuli. Using bone marrow/osteoblasts co-cultures from all possible combinations of TLR9,/, and TLR9+/+ mice-derived cells, we showed that TLR9 in the two lineages is required for CpG-ODN induction of osteoclastogenesis. Conclusions: CpG-ODN modulates osteoclastogenesis in a TLR9-dependent manner. Activation of TLR9 in bone marrow-derived osteoclasts precursors is more crucial to induction of osteoclastogenesis than activation of the osteoblastic TLR9. [source] A novel approach for screening discrete variations in organic synthesisJOURNAL OF CHEMOMETRICS, Issue 5 2001Rolf Carlson Abstract In this paper we present a general strategy for screening discrete variations in organic synthesis. The strategy is based upon principal properties, i.e. principal component characterization of the constituents defining the reaction system. The first step is to select subsets of test items from each class of constituents defining the reaction space, i.e. substrates, reagents, solvents, catalysts, etc., so that the selected items from each class cover the properties considered. The second step is to construct a candidate matrix which contains all possible combinations of the items in the subsets. This matrix is a full multilevel factorial design. The third step is to assign a tentative model for the screening experiment and to construct the corresponding candidate model matrix. The fourth step is to select experiments to yield an experimental design that spans the variable space efficiently and that also gives good estimates of the model parameters. We present an algorithm that uses singular value decomposition to select experiments. The proposed strategy is then illustrated with an example of the Fischer indole synthesis. Copyright © 2001 John Wiley & Sons, Ltd. [source] A multi-objective optimization approach to polygeneration energy systems designAICHE JOURNAL, Issue 5 2010Pei Liu Abstract Polygeneration, typically involving co-production of methanol and electricity, is a promising energy conversion technology which provides opportunities for high energy utilization efficiency and low/zero emissions. The optimal design of such a complex, large-scale and highly nonlinear process system poses significant challenges. In this article, we present a multiobjective optimization model for the optimal design of a methanol/electricity polygeneration plant. Economic and environmental criteria are simultaneously optimized over a superstructure capturing a number of possible combinations of technologies and types of equipment. Aggregated models are considered, including a detailed methanol synthesis step with chemical kinetics and phase equilibrium considerations. The resulting model is formulated as a non-convex mixed-integer nonlinear programming problem. Global optimization and parallel computation techniques are employed to generate an optimal Pareto frontier. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Proton magnetic resonance spectroscopic imaging to differentiate between nonneoplastic lesions and brain tumors in children,JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2006Roula Hourani MD Abstract Purpose To investigate whether in vivo proton magnetic resonance spectroscopic imaging (MRSI) can differentiate between 1) tumors and nonneoplastic brain lesions, and 2) high- and low-grade tumors in children. Materials and Methods Thirty-two children (20 males and 12 females, mean age = 10 ± 5 years) with primary brain lesions were evaluated retrospectively. Nineteen patients had a neuropathologically confirmed brain tumor, and 13 patients had a benign lesion. Multislice proton MRSI was performed at TE = 280 msec. Ratios of N-acetyl aspartate/choline (NAA/Cho), NAA/creatine (Cr), and Cho/Cr were evaluated in the lesion and the contralateral hemisphere. Normalized lesion peak areas (Chonorm, Crnorm, and NAAnorm) expressed relative to the contralateral hemisphere were also calculated. Discriminant function analysis was used for statistical evaluation. Results Considering all possible combinations of metabolite ratios, the best discriminant function to differentiate between nonneoplastic lesions and brain tumors was found to include only the ratio of Cho/Cr (Wilks' lambda, P = 0.012; 78.1% of original grouped cases correctly classified). The best discriminant function to differentiate between high- and low-grade tumors included the ratios of NAA/Cr and Chonorm (Wilks' lambda, P = 0.001; 89.5% of original grouped cases correctly classified). Cr levels in low-grade tumors were slightly lower than or comparable to control regions and ranged from 53% to 165% of the control values in high-grade tumors. Conclusion Proton MRSI may have a promising role in differentiating pediatric brain lesions, and an important diagnostic value, particularly for inoperable or inaccessible lesions. J. Magn. Reson. Imaging 2006. Published 2005 Wiley-Liss, Inc. [source] A new methodology for the definition of odor zones in perfumery ternary diagramsAICHE JOURNAL, Issue 8 2006Vera G. Mata Abstract The new methodology called "Perfumery Ternary Diagram" helps perfumers in odor prediction, allowing a fast evaluation of the odor value in the headspace for all possible combinations of a non-ideal perfume liquid mixture with three fragrant components and one or more solvents. In this work, the determination of Perfumery Ternary Points (PTP) and Perfumery Binary Lines (PBL) is described, allowing a complete definition of Perfumery Ternary Diagram (PTD) odor zones, without the need to calculate a large number of points inside the triangle region. The methodology of PTP and PBL determination was applied to the system: limonene, geraniol, vanillin, and ethanol. The effect of solvent,ethanol,on the odor zones, namely on the number of PTP and on the shape of the PBL was studied, as well as the effect of the non-idealities. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Antagonists in Mutual Antipathies: A Person-Oriented ApproachJOURNAL OF RESEARCH ON ADOLESCENCE, Issue 1 2009Berna Güro This study investigated the heterogeneity of mutual antipathy relationships. Separate cluster analyses of peer interactions of early adolescents (mean age 11 years) and adolescents (mean age of 14) yielded 3 types of individuals in each age group, namely Prosocial, Antisocial, and Withdrawn. Prevalence analysis of the 6 possible combinations of types of individuals constituting mutual antipathy dyads yielded antipathy dyad types. The majority of these dyads consisted of a combination of 2 dissimilar types of individuals. Implications of the high prevalence of the Antisocial,Withdrawn antipathy dyad type are discussed. [source] A Qualitative and Quantitative Approach to Determine the Optimum Combination of Feeding Stimulants for Striped Bass Morone saxatilis Using an Agar Gel CarrierJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 1 2002Elias Papatryphon A series of experiments was conducted to determine the optimum combination of previously identified feeding stimulants (FS), namely L-alanine (Ala), L-serine (Ser), inosine-5,-monophosphate (IMP), and betaine (Bet), for striped bass Morone saxatilis. Three experiments were conducted to determine the optimum combination of FS using an agar gel matrix as a carrier. In the first experiment a 24 factorial experiment was conducted to test all possible combinations of the four FS at two levels, 0 and 0.1 M. Significant interactions between the FS were found, suggesting the complexity of gustatory stimulation and palatability. In the second experiment a 4 × 6 factorial design was employed to test each FS alone and at concentrations ranging from 0 to 8% in order to determine the minimum level at which maximal stimulation is achieved. The results suggest that there is no significant improvement in feed intake beyond the 1 % level of supplementation for all the FS. In addition, Ala produced a significantly greater response compared to all other FS. In the last experiment, a modified single factor method was used to estimate the optimum levels for each FS in a mixture. The range of the concentrations tested was 0,1% of the agar gel for each FS. Combining all four compounds yielded maximal stimulation. The levels of each compound in the final optimum combination of FS were: Ala, 0.4; Ser, 0.6; Bet, 0.4; and IMP, 0.3% of the agar gel. [source] Individual signatures in scent gland secretions of Eurasian deerJOURNAL OF ZOOLOGY, Issue 3 2000R. E. Lawson Abstract Evidence for individuality of odour profile, coding for individual identity, was sought in scent profiles derived from natural secretions of the preorbital gland of red deer Cervus elaphus (n= 26), sika deer C. nippon (15), fallow deer Dama dama (50), Chinese muntjac Muntiacus reevesi (23) and Chinese water deer Hydropotes inermis (53); from metatarsal secretions from red deer (n= 35), sika (30), fallow (193) and roe deer Capreolus capreolus (26), and from roe deer interdigital glands (n= 48). Volatiles were eluted from sample materials at body temperature, to restrict analysis to those elements that would occur within the natural odour signal; the different volatile elements were then separated by gas chromatography. For each species considered, secretions from at least one scent gland were individually distinct and sufficiently complex to code for identity. Within our samples no two individuals produced identical odour profiles; yet in analysis of metatarsal gland secretions of individual fallow deer sampled in successive years, odour signatures of individuals remained consistent over time. The wider potential for individual coding was assessed through calculation of the number of different possible combinations of all volatiles recovered in any species×gland system. Every secretion considered seems to have the potential to provide individually characteristic signals (with the exception of secretions from the fallow deer preorbital gland, which notably contained no odour information under any analytical system). Complexity of signals differed markedly between species as did the gland-type responsible for production of the most complex or distinctive signal. No simple evolutionary patterns are apparent to account for this variation and we suggest that the form of gland selected for production of a signal carrying information about individual identity is a function of habitat type and sociality. [source] RT-GROG: parallelized self-calibrating GROG for real-time MRIMAGNETIC RESONANCE IN MEDICINE, Issue 1 2010Haris Saybasili Abstract A real-time implementation of self-calibrating Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) operator gridding for radial acquisitions is presented. Self-calibrating GRAPPA operator gridding is a parallel-imaging-based, parameter-free gridding algorithm, where coil sensitivity profiles are used to calculate gridding weights. Self-calibrating GRAPPA operator gridding's weight-set calculation and image reconstruction steps are decoupled into two distinct processes, implemented in C++ and parallelized. This decoupling allows the weights to be updated adaptively in the background while image reconstruction threads use the most recent gridding weights to grid and reconstruct images. All possible combinations of two-dimensional gridding weights GG are evaluated for m,n = {,0.5, ,0.4, ,, 0, 0.1, ,, 0.5} and stored in a look-up table. Consequently, the per-sample two-dimensional weights calculation during gridding is eliminated from the reconstruction process and replaced by a simple look-up table access. In practice, up to 34× faster reconstruction than conventional (parallelized) self-calibrating GRAPPA operator gridding is achieved. On a 32-coil dataset of size 128 × 64, reconstruction performance is 14.5 frames per second (fps), while the data acquisition is 6.6 fps. Magn Reson Med 64:306,312, 2010. © 2010 Wiley-Liss, Inc. [source] Intimately linked or hardly speaking?MOLECULAR ECOLOGY, Issue 3 2001The relationship between genotype, environmental gradients in a Louisiana Iris hybrid population Abstract Several models of hybrid zone evolution predict the same spatial patterns of genotypic distribution whether or not structuring is due to environment-dependent or -independent selection. In this study, we tested for evidence of environment-dependent selection in an Iris fulva×Iris brevicaulis hybrid population by examining the distribution of genotypes in relation to environmental gradients. We selected 201 Louisiana Iris plants from within a known hybrid population (80 m × 80 m) and placed them in four different genotypic classes (I. fulva, I. fulva -like hybrid, I. brevicaulis -like hybrid and I. brevicaulis) based on seven species-specific random amplified polymorphic DNA (RAPD) markers and two chloroplast DNA haplotypes. Environmental variables were then measured. These variables included percentage cover by tree canopy, elevation from the high water mark, soil pH and percentage soil organic matter. Each variable was sampled for all 201 plants. Canonical discriminant analysis (CDA) was used to infer the environmental factors most strongly associated with the different genotypic groups. Slight differences in elevation (,0.5 m to +0.4 m) were important for distinguishing habitat distributions described by CDA, even though there were no statistical differences between mean elevations alone. I. brevicaulis occurred in a broad range of habitats, while I. fulva had a narrower distribution. Of all the possible combinations, I. fulva -like hybrids and I. brevicaulis -like hybrids occurred in the most distinct habitat types relative to one another. Each hybrid class was not significantly different from its closest parent with regard to habitat occupied, but was statistically unique from its more distant parental species. Within the hybrid genotypes, most, but not all, RAPD loci were individually correlated with environmental variables. This study suggests that, at a very fine spatial scale, environment-dependent selection contributed to the genetic structuring of this hybrid zone. [source] Periodontal pathogens in subgingival plaque of HIV-positive subjects with chronic periodontitisMOLECULAR ORAL MICROBIOLOGY, Issue 3 2003M Patel Many putative periodontal pathogens associated with periodontal disease in human immunodeficiency virus (HIV)-infected patients also occur in non-HIV-infected individuals. This study examined the prevalence of eight periodontal pathogens in HIV-positive and HIV-negative patients with chronic periodontitis using the 16s RNA polymerase chain reaction technique. The results showed a significant prevalence of Porphyromonas gingivalis and Treponema denticola among HIV-negative patients compared to HIV-positive patients. Sixty percent of the patients in both groups were colonized by five to six species. Odds ratio analysis revealed a statistically significant positive association between three of the 28 possible combinations in the HIV-positive group. They included Prevotella nigrescens/Campylobacter rectus, P. nigrescens/P. gingivalis and P. nigrescens/T. denticola. Although the prevalence of periodontal pathogens is similar in both the groups, the combination of certain periodontal pathogens may be responsible for chronic periodontitis seen in HIV-infected adults. [source] Nearest-neighbor tree species combinations in tropical forest: the role of chance, and some consequences of high diversityOIKOS, Issue 3 2007Milton Lieberman In three permanent inventory plots comprising 12.4 ha of undisturbed forest at La Selva, Costa Rica, all stems ,10 cm dbh were mapped and identified to species. There were 1628, 1478 and 1954 trees in the plots, representing 168, 166 and 171 species respectively. We determined the species of each nearest-neighbor pair of trees, and asked whether the occurrence of species pairs conforms to a simple random mixing model. If trees are randomly mixed in terms of species, the expected frequency of any nearest neighbor species combination is a function of the relative abundance of the two species. Departures from random mixing could arise from species interactions, differential responses to habitat, or both. The number of possible ij species combinations increases approximately as the square of the number of species. For the 168 species in plot 1, for example, there are 14 196 possible combinations. We compared the expected frequency of each species combination in the three plots (42,736 combinations in all) with observed frequencies. Over 98% of the combinations had observed frequencies of zero and expected frequencies close to zero. A consequence of high diversity is low density of most individual species, and exceedingly low frequencies of the vast majority of species combinations. For each of the 805 combinations with observed frequencies >0, we used simulation to generate a distribution of expected frequencies. We used a t-test to compare the observed frequency with the mean of the simulated distribution for each combination. Only 40 combinations (0.09% of the possible species combinations in the plots) departed from expected frequencies; 39 combinations were more common, and one less common than expected. The overwhelming majority of nearest neighbor species combinations occur at frequencies predictable from their individual abundances. [source] Diversity loss, recruitment limitation, and ecosystem functioning: lessons learned from a removal experimentOIKOS, Issue 3 2001Amy J. Symstad A five-year removal experiment in which plant functional group diversity was manipulated found strong limitation of ecosystem functioning caused by the differing abilities of remaining functional groups to recruit into space left unoccupied by the plants removed. We manipulated functional group diversity and composition by removing all possible combinations of zero, one, or two plant functional groups (forbs, C3 graminoids, and C4 graminoids), as well as randomly chosen biomass at levels corresponding to the functional group removals, from a prairie grassland community. Although random biomass removal treatments showed no significant effect of removing biomass in general on ecosystem functions measured (P>0.05), the loss of particular functional groups led to significant differences in above- (P<0.001) and belowground (P<0.001) biomass, rooting-zone (P=0.001) and leached (P=0.01) nitrogen, nitrogen mineralization (P<0.001), and community drought resistance (P=0.002). Many of these differences stemmed from the marked difference in the ways remaining functional groups responded to the experimental removals. Strong recruitment limitation of C4 graminoids resulted in large areas of open ground, high nutrient leaching, and high community drought resistance in plots containing just this functional group. In contrast, rhizomatous C3 graminoids quickly colonized space and used soil resources made available by the removal of other groups, leading to lower soil nitrate in plots containing C3 graminoids. These effects of recruitment limitation on ecosystem functioning illustrate possible effects of diversity loss not captured by synthetic experiments in which diversity gradients are created by adding high densities of seeds to bare soil. [source] Technical note: Prediction of sex based on five skull traits using decision analysis (CHAID)AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 3 2009Joan C. Stevenson Abstract Osteologists commonly assess the sex of skeletal remains found in forensic and archaeological contexts based on ordinal scores of subjectively assessed sexually dimorphic traits. Using known-sex samples, logistic regression (LR) discriminant functions have been recently developed, which allow sex probabilities to be determined. A limitation of LR is that it emphasizes main effects and not interactions. Chi-square automatic interaction detection (CHAID) is an alternative classification strategy that emphasizes the information in variable interactions and uses decision trees to maximize the probability of correct sex determinations. We used CHAID to analyze the predictive value of the 31 possible combinations of five sexually dimorphic skull traits that Walker used previously to develop logistic regression sex determination equations. The samples consisted of 304 individuals of known sex of English, African American, and European American origin. Based on practical considerations, selection criteria for the best sex predictive trait combinations (SPTCs) were set at accuracies for both sexes of 75% or greater and sex biases lower than 5%. Although several of the trees meeting these criteria were produced for the English and European American samples, none met them for the African American sample. In the series of out-of-sample tests we performed, the trees from the English and combined sample of all groups predicted best. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] Efficiency of quantitative trait loci-assisted selection in correlations between identified and residual genotypesANIMAL SCIENCE JOURNAL, Issue 1 2008Ching Y. LIN ABSTRACT This study quantified the efficiency of quantitative traits loci (QTL)-assisted selection in the presence of correlations (,qr) between identified (q) and residual (r) genotypes. Two levels of heritability (h2 = 0.1 or 0.3), two levels of correlation (,qr = ,0.3 or 0.3) and five proportions of genetic variance explained by QTL detected (= 0.1, 0.2, 0.4, 0.6 or 0.8) were combined to give 20 scenarios in all. QTL-assisted selection placed a larger index weight on the QTL genotype than on the phenotype in 17 of 20 scenarios, yielding a greater response in the QTL genotype than in residual genotype. Although QTL-assisted selection was superior to phenotypic selection in all 20 scenarios, QTL-assisted selection showed a greater advantage over phenotypic selection when ,qr was positive than when ,qr was negative. Doubling the proportion of detected QTL variance to genetic variance does not result in a twofold increase in the genetic response to QTL-assisted selection, suggesting that economic returns diminish for each additional cost of detecting extra QTL. The correlation between q and r would make the interpretation (or prediction) of QTL effects difficult and QTL-assisted selection strategy must consider the joint effect of q and r. When q and r are not independent, a failure to account for ,qr in QTL-assisted selection would underestimate the genetic responses when ,qr is positive, but overestimate the genetic responses when ,qr is negative. Estimation bias is more serious at high heritability than at low heritability. Accounting for ,qr would improve the efficiency of QTL-assisted selection and the accuracy of QTL detection. The generalized procedure developed in this study allows for quantifying the efficiency of QTL-assisted selection and assessing estimation bias for ignoring the correlation between q and r for all possible combinations of h2, ,qr, and . [source] Noncorrelated effects of seed predation and pollination on the perennial herb Ruellia nudiflora remain spatially consistentBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009LUIS ABDALA-ROBERTS By simultaneously manipulating both seed predator and pollinator effects on the perennial herb Ruellia nudiflora at two sites in Yucatan (Mexico), the present study evaluated (1) whether a correlation (interaction) existed between seed predator and pollinator effects on R. nudiflora seed production and (2) whether such an interaction varied geographically. We used three populations per site, and a total of 20 plants per population (N = 120). Groups of five plants were randomly chosen at each population to simultaneously receive one of two seed predator and pollinator exclosure levels (present or excluded in each case). These two factors were fully crossed, resulting in each group being subjected to one of four possible combinations: pollinators excluded/herbivores present; herbivores excluded/pollinators present; herbivores excluded/pollinators excluded; or control (neither excluded). Response variables were the number of seeds produced per plant and the proportion of attacked fruits by seed predators per plant. Seed predators had a large impact on R. nudiflora seed production but did not show any preference for fruits from plants not excluded from pollinators. In addition, the pollination treatment was not significant, indicating no effect of pollinators on reproductive success. These findings resulted in a nonsignificant herbivory × pollination interaction, which was consistent across sites, indicating lack of correlated selection of these two guilds on R. nudiflora seed production. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 800,807. [source] | ||||||||||||||||||||||||||||||||||