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Kinds of Split Terms modified by Split Selected AbstractsProjection and partitioned solution for two-phase flow problemsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2005Andrea Comerlati Abstract Multiphase flow through porous media is a highly nonlinear process that can be solved numerically with the aid of finite elements (FE) in space and finite differences (FD) in time. For an accurate solution much refined FE grids are generally required with the major computational effort consisting of the resolution to the nonlinearity frequently obtained with the classical Picard linearization approach. The efficiency of the repeated solution to the linear systems within each individual time step represents the key to improve the performance of a multiphase flow simulator. The present paper discusses the performance of the projection solvers (GMRES with restart, TFQMR, and BiCGSTAB) for two global schemes based on a different nodal ordering of the unknowns (ORD1 and ORD2) and a scheme (SPLIT) based on the straightforward inversion of the lumped mass matrix which allows for the preliminary elimination and substitution of the unknown saturations. It is shown that SPLIT is between two and three time faster than ORD1 and ORD2, irrespective of the solver used. Copyright © 2005 John Wiley & Sons, Ltd. [source] The notch-responsive transcription factor Hes-1 attenuates osteocalcin promoter activity in osteoblastic cellsJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 3 2009Ying Zhang Abstract Notch signaling plays a key role in osteoblast differentiation. A major transcriptional downstream regulator of this pathway is the helix,loop,helix (HLH) transcription factor Hairy/Enhancer of Split 1 (Hes-1). Here we investigated the function of Hes-1 in osteoblastic cells. Endogenous Hes-1 gene expression decreases during progression of bone cell phenotype development in MC3T3-E1 osteoblasts suggesting that it is a negative regulator of osteoblast differentiation. Forced expression of Hes-1 inhibits osteocalcin (OC) mRNA levels, and luciferase assays indicate that Hes-1 directly represses OC promoter activity. In vitro and in vivo protein/DNA interaction assays reveal that recombinant Hes-1 binds specifically to an E-box in the proximal promoter of the OC gene. Deletion of the Hes-1 WRPW domain (MHes-1) that recruits the co-repressor Groucho abrogates repression of OC promoter activity by Hes-1, but also blocks Hes-1 binding to the promoter. The latter result suggests that exogenous Hes-1 may be recruited to the OC promoter by both protein/DNA and protein/protein interactions. We conclude that the Notch-responsive Hes-1 protein is capable of repressing OC gene transcription in osteoblastic cells through an E-box in the proximal promoter. Hes-1 may contribute to osteoblast growth and differentiation by controlling basal bone-specific transcription directly through interactions with transcriptional regulators that are known to bind to the OC gene promoter. J. Cell. Biochem. 108: 651,659, 2009. © 2009 Wiley-Liss, Inc. [source] Genetic control over grain damage in a spring barley mapping populationPLANT BREEDING, Issue 1 2004P. Rajasekaran Abstract A genetic map was constructed using DNA-based markers in a barley mapping population derived from the cross ,Tankard'×,Livet', that was developed to explore the genetic control over grain damage in spring barley cultivars. Quantitative trait loci (QTL) were located for husk skinning, gape between the lemma and palea and splitting of the fused pericarp/testa/aleurone tissues. The QTL accounted for 70% of the genetic variation in Split and 60% of the genetic variation in Gape and Skinning. The QTL were clustered on chromosomes 1H, 4H, 5H, 6H and 7H. QTL analysis indicates the possibility of transgressive segregation for grain splitting and so the breeding of lines with more extreme splitting. This is of concern to the malting industry as, without extensive phenotypic assessment, such lines could be commercialized, as was the case of Landlord, and put malting barley supplies at risk. These findings are discussed in relation to the genetic control over traits including grain length and width. [source] Reversible and Noncompetitive Inhibition of ,-Tryptase by Protein Surface Binding of Tetravalent Peptide Ligands Identified from a Combinatorial Split,Mix Library,ANGEWANDTE CHEMIE, Issue 24 2010Peter Molekulare Stöpsel: Das On-Bead-Screening einer kombinatorischen Bibliothek von 216 vierarmigen Oligopeptiden lieferte hoch spezifische, nichtkompetitive Inhibitoren der Serinprotease ,-Tryptase mit nanomolarer Affinität. Die Liganden binden sehr wahrscheinlich an die Proteinoberfläche und wirken als molekulare ,Stöpsel", indem sie den Zugang zu den aktiven Zentren blockieren, die sich im Innern einer zentralen Kavität befinden (siehe Bild). [source] Party Mergers and Splits in New Democracies: The Case of South Korea (1987,2007)GOVERNMENT AND OPPOSITION, Issue 4 2010Kyungmee Park This study explores how a party's organizational mode affects its stability in new democracies. A party organization was stable under these three conditions: when the relationship from lower to upper organizations has institutionalized a strong vertical organization mode; when the central party power is concentrated on the leadership; and when the leadership has been safely shifted after elections. In the case of two ruling parties in South Korea, each mode produced differences in party stability. The dissimilar organization modes of two parties resulted in different organizational stability. [source] Artefacts produced by suture traction during incisional biopsy of oral lesionsCLINICAL OTOLARYNGOLOGY, Issue 6 2002J. Seoane The aim of this study is to compare the artefacts ascribed to the technique of incisional biopsy using a punch or scalpel and the influence of suture use for traction and delivery of the specimen. A total of 160 samples were obtained from 10 fresh pig tongues by four experienced oral surgeons. Handling artefacts (squeeze artefacts): crush, splits, fragmentation and pseudocysts were assessed. No differences were identified in terms of crush, fragmentation or pseudocysts between samples obtained with a punch or scalpel. Splits were more frequent in those biopsies taken with a scalpel (,2 = 9.26; P=,0.0023). Artefacts in the punch biopsy group were significantly less than in the group that combined punch and suture traction (P < 0.01). The scalpel and suture traction group showed significantly more artefacts than the group without suture. It is concluded the use of a stitch for traction in small incisional biopsies causes squeeze artefacts, so its use should be restricted to specimen orientation. [source] BqR-Tree: A Data Structure for Flights and Walkthroughs in Urban Scenes with Mobile ElementsCOMPUTER GRAPHICS FORUM, Issue 6 2010J.L. Pina I.3.6 [Computer Graphics]: Graphics data structures and data types Abstract BqR-Tree, the data structure presented in this paper is an improved R-Tree data structure based on a quadtree spatial partitioning which improves the rendering speed of the usual R-trees when view-culling is implemented, especially in urban scenes. The city is split by means of a spatial quadtree partition and the block is adopted as the basic urban unit. One advantage of blocks is that they can be easily identified in any urban environment, regardless of the origins and structure of the input data. The aim of the structure is to accelerate the visualization of complex scenes containing not only static but dynamic elements. The usefulness of the structure has been tested with low structured data, which makes its application appropriate to almost all city data. The results of the tests show that when using the BqR-Tree structure to perform walkthroughs and flights, rendering times vastly improve in comparison to the data structures which have yielded best results to date, with average improvements of around 30%. [source] Exact and Robust (Self-)Intersections for Polygonal MeshesCOMPUTER GRAPHICS FORUM, Issue 2 2010Marcel Campen Abstract We present a new technique to implement operators that modify the topology of polygonal meshes at intersections and self-intersections. Depending on the modification strategy, this effectively results in operators for Boolean combinations or for the construction of outer hulls that are suited for mesh repair tasks and accurate mesh-based front tracking of deformable materials that split and merge. By combining an adaptive octree with nested binary space partitions (BSP), we can guarantee exactness (= correctness) and robustness (= completeness) of the algorithm while still achieving higher performance and less memory consumption than previous approaches. The efficiency and scalability in terms of runtime and memory is obtained by an operation localization scheme. We restrict the essential computations to those cells in the adaptive octree where intersections actually occur. Within those critical cells, we convert the input geometry into a plane-based BSP-representation which allows us to perform all computations exactly even with fixed precision arithmetics. We carefully analyze the precision requirements of the involved geometric data and predicates in order to guarantee correctness and show how minimal input mesh quantization can be used to safely rely on computations with standard floating point numbers. We properly evaluate our method with respect to precision, robustness, and efficiency. [source] CAD-Based Photogrammetry for Reverse Engineering of Industrial InstallationsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2003Johan W. H. Tangelder For instance, in the case of a servicing plant, such a library contains descriptions of simple components such as straight pipes, elbows, and T-junctions. A new installation is constructed by selecting and connecting the appropriate components from the library. This article demonstrates that one can use the same approach for reverse engineering by photogrammetry. In our technique, the operator interprets images and selects the appropriate CAD component from a library. By aligning the edges of the component's wire frame to the visible edges in the images, we implicitly determine the position, orientation, and shape of the real component. For a fast object reconstruction the alignment process has been split in two parts. Initially, the operator approximately aligns a component to the images. In a second step a fitting algorithm is invoked for an automatic and precise alignment. Further improvement in the efficiency of the reconstruction is obtained by imposing geometric constraints on the CAD components of adjacent object parts. [source] Identity in Flexible Organizations: Experiences in Dutch OrganizationsCREATIVITY AND INNOVATION MANAGEMENT, Issue 4 2003Michiel Schoemaker In the information economy, flexible organizations have evolved. Work and labour relations have become more flexible than in industrial organizations. This has consequences for the identity of organizations. Organizations tend to become opportunity coalitions when the identity is too fragmented or neglected. The key questions this article adresses is what is identity in a flexible organization and to what extent is it possible to ,manage' the construction of identity in flexible organizations? This key question was split up into three sub-questions. We were interested in how (1) organizations organize their talent management, (2) how organizations manage their labour relations and (3) how organizations manage identity. These three subjects come forward in recent publications in the field of organizational development and HRM as being critical of management of a flexible and innovative organization. In the article, the characteristics of flexible organizations are defined. These characteristics are translated into the relationship between these organization and individual: the way flexible organizations manage their work, labour relations and identity is studied in 20 Dutch organizations. Striving for an optimum in flexible work and flexible labour relations, combined with managing a specific organizational identity seems to be the HR-strategy Dutch organizations implement to reach flexibility and innovation. [source] Possible role of Hes5 for the rostrocaudal polarity formation of the tectumDEVELOPMENT GROWTH & DIFFERENTIATION, Issue 3 2004Jun Kimura The alar plate of the mesencephalon differentiates into the optic tectum. Retinal fibers project to the tectum topographically in a retinotopic manner. Engrailed (En) is responsible for the tectum polarity formation and regionalization. Former study indicated the presence of the molecule whose expression is repressed by En and that represses the isthmus-related gene expression. To isolate such molecules, we constructed a subtracted library between cDNA population of the normal rostral mesencephalon and of the rostral mesencephalon that misexpresses En2. From the library, we isolated cHes5, a chicken homolog of Drosophila hairy/Enhancer of split. cHes5 begins to be expressed in the rostral part of the E2 mesencephalon, and spreads to caudal mesencephalon by E3. To our expectation, cHes5 expression was repressed by En2. Furthermore, misexpression of cHes5 in the mesencephalon inhibited expression of ephrinA2, a marker of caudal mesencephalon. An active repressor form of Hes5, which is a chimeric molecule of Hes5 and repressor domain of En2, showed a similar but more severe phenotype. The results indicate that Hes5 is regulated by En and is responsible for rostral identity of mesencephalon by repressing ephrinA2. [source] Insulin, insulin propeptides and intima-media thickness in the carotid artery in 58-year-old clinically healthy men.DIABETIC MEDICINE, Issue 2 2002Insulin Resistance study (AIR), The Atherosclerosis Abstract Aims To examine the relationship between specific (intact) insulin, insulin propeptides and subclinical atherosclerosis. Methods A cross-sectional study based on a stratified sampling of randomly selected, clinically healthy 58-year-old men (n = 391). Ultrasound examinations of the carotid arteries were performed with measurement of intima-media thickness (IMT) in the common carotid artery and in the carotid artery bulb. Fasting, cross-reacting plasma insulin (RIA), specific (intact) insulin, proinsulin, 32,33 split proinsulin and C-peptide were measured. Results Plasma concentrations of cross-reacting plasma insulin, specific insulin, proinsulin, 32,33 split proinsulin and C-peptide were univariately associated with common carotid artery IMT. Established risk factors such as blood pressure, smoking, apoB, triglycerides, body mass index (BMI), and waist,hip ratio were also related to IMT. After adjustment for smoking, apoB, blood pressure and triglycerides, cross-reacting plasma insulin, proinsulin and C-peptide but not specific insulin and split 32,33 proinsulin remained associated with carotid artery IMT. No associations remained after adjustment for BMI. Conclusions Fasting plasma proinsulin, C-peptide, and insulin by cross-reacting RIA was associated with common carotid artery IMT independent of several conventional risk factors for atherosclerosis. The multicollinearity between the insulin peptides and propeptides makes it difficult to clarify the exact role of each peptide. [source] Cognitive subprocesses and schizophrenia.ACTA PSYCHIATRICA SCANDINAVICA, Issue 2001Objective:,The aim of the study is to demonstrate that deficits of information processing in schizophrenic patients can be isolated with reaction-time (RT) decomposition paradigms. Method:,Three types of visually presented tasks were applied: simple, disjunctive and choice RT-tasks. RT were split into movement latency and time necessary to execute movements. Comparisons of three samples of schizophrenic patients (295.3) with individually matched (age, sex, education and handedness) healthy controls are presented: Sample 1: 10 drug-naive first-onset patients, Sample 2: 10 neuroleptically treated first-onset patients, Sample 3: 10 neuroleptically treated chronically ill patients. Results:,Findings indicate that schizophrenia affects primarily subprocesses in which percepts are translated into appropriate actions (response-selection). Neuroleptic treatment improves processing at this stage but is accompanied by slowing of movement execution. Conclusion:,Response-selection is selectively impaired in first-onset patients. This disturbance, which might be specific for schizophrenia, can be regarded as indication of a disconnection between frontal and posterior areas. [source] Split sample comparison of ThinPrep and conventional smears in endoscopic retrograde cholangiopancreatography-guided pancreatic fine-needle aspirations,DIAGNOSTIC CYTOPATHOLOGY, Issue 2 2005Momin T. Siddiqui M.D. Abstract Fine-needle aspiration (FNA) of pancreatic lesions is a common procedure to establish a tissue diagnosis before chemotherapy or surgery. In this study, the authors attempt to compare the diagnostic value of the ThinPrep (TP) method with conventional smears (CSs) in samples obtained by endoscopic retrograde cholangiopancreatography (ERCP)-guided pancreatic FNAs. Material obtained, prospectively, from ERCP-guided pancreatic FNAs was split to prepare CSs (2,5 slides) first, the remainder being rinsed in PreservCyte, and in the laboratory, 1 TP slide was prepared. The diagnostic categories of unsatisfactory, benign, reactive, suspicious for malignancy, and malignant were compared. Fifty-one pancreatic FNAs prepared by split sample method yielded the following results: TP yielded unsatisfactory, 6 cases; benign, 3 cases; reactive, 5 cases; suspicious for malignancy, 11 cases; and malignant, 26 cases; in contrast, CS yielded unsatisfactory, 13 cases; benign, 4 cases; reactive, 3 cases; suspicious for malignancy, 13 cases; and malignant, 18 cases. Histological follow-up was available in 21 cases (reactive, 8 cases; suspicious for malignancy, 1 case, and malignant, 12 cases). The foregoing data indicate a higher sensitivity in detection of pancreatic adenocarcinoma by the TP method (TP, 91% vs. 58% CS) with equivalent specificity (100%). In addition, TP provides better preservation and cytological detail. Diagn. Cytopathol. 2005;32:70,75. © 2005 Wiley-Liss, Inc. [source] The cranial morphology of Kayentachelys, an Early Jurassic cryptodire, and the early history of turtlesACTA ZOOLOGICA, Issue 3 2010Eugene S. Gaffney Abstract Gaffney, E.S. and Jenkins, F.A., Jr. 2010. The cranial morphology of Kayentachelys, an Early Jurassic cryptodire, and the early history of turtles. , Acta Zoologica (Stockholm) 91: 335,368 The skull morphology of Kayentachelys aprixGaffney et al., 1987, a turtle from the Early Jurassic Kayenta Fm of northern Arizona, demonstrates the presence of cryptodiran synapomorphies in agreement with Gaffney et al. (1987, 1991, 2007), and contrary to the conclusions of Sterli and Joyce (2007), Joyce (2007), Sterli (2008), and Anquetin et al. (2008). Specific characters found in Kayentachelys and diagnostic of cryptodires include the processus trochlearis oticum, the curved processus pterygoideus externus with a vertical plate, and the prefrontal,vomer contact, which are confirmed as absent in the outgroups, specifically the Late Triassic Proganochelys. The Joyce (2007) analysis suffers from the reduction of the signal from skull characters, with a consequently greater reliance on shell characters, resulting in pleurodires being resolved at various positions within the cryptodires. Kayentachelys reveals what a primitive cryptodire would be expected to look like: a combination of primitive and derived characters, with the fewer derived characters providing the best test of its relationships to other turtles. Although incompletely known, the Mid-Late Jurassic Condorchelys, Heckeremys, and Eileanchelys may be early cryptodires close to Kayentachelys. We confirm the Late Triassic Proterochersis as a pleurodire, dating the pleurodire,cryptodire split as Late Triassic or earlier. [source] Evolution of invertebrate nervous systems: the Chaetognatha as a case studyACTA ZOOLOGICA, Issue 1 2010Steffen Harzsch Abstract Harzsch, S. and Wanninger, A. 2010. Evolution of invertebrate nervous systems: the Chaetognatha as a case study. ,Acta Zoologica (Stockholm) 91: 35,43 Although recent molecular studies indicate that Chaetognatha may be one of the earliest Bilaterian offshoots, the phylogenetic position of this taxon still is a matter of ongoing debate. In this contribution, we review recent attempts to contribute phylogenetic information on the Chaetognatha by analysing structure and development of their nervous system (neurophylogeny). Analysing this group of organisms also has a major impact on our understanding of nervous system evolution in Bilateria. We review recent evidence from this field and suggest that Urbilateria already was equipped with the genetic toolkit required to build a complex, concentrated central nervous system (CNS), although this was not expressed phenotypically so that Urbilateria was equipped with a nerve plexus and not a CNS. This implies that in the deep metazoan nodes, concentration of the ancestral plexus occurred twice independently, namely once after the protostome,deuterostome split on the branch leading to the protostomes (resulting in a ventrally positioned nerve cord) and once along the chordate line (with a dorsal nerve cord). [source] Osteoderm morphology in recent and fossil euphractine xenarthransACTA ZOOLOGICA, Issue 4 2009C. M. Krmpotic Abstract The presence of osteoderms within the integument, forming a carapace, is one of the most distinctive features of armadillos with the external morphology of these elements forming the basis of most systematic schemes. This is especially true for fossil taxa, where these elements are most frequent in the palaeontological record. A detailed study of osteoderms from the cephalic shield and different regions of the dorsal armour of Chaetophractus villosus (Euphractinae, Xenarthra) was made and compared to those of the extant genus Dasypus (Dasypodinae, Xenarthra), and the extinct genus ,Eutatus. Three distinct histological zones were recognized: outer and inner zones are thin, formed by regular compact bone, the middle zone is thicker, with large cavities that contain mainly adipose tissue, hair follicles, and sweat and sebaceous glands. The internal structure of ,Eutatus (also a member of Euphractinae) osteoderms is close to that of C. villosus, consistent with the notion that these taxa are phylogenetically closely related. In contrast, Dasypus shows marked differences. Dasypus shows hair follicles associated with both gland types (sweat and sebaceous) and connected to foramina on the external surface. Although not observed in adult C. villosus, it has been documented during embryonic development, only to atrophy later in ontogeny. Furthermore, the presence of red bone marrow is rare in C. villosus, but widespread in Dasypus novemcinctus osteoderms. These results suggest an early split of both subfamilies and support the hypothesis that the Euphractinae are more derived than the Dasypodinae. [source] Integrating species life-history traits and patterns of deforestation in amphibian conservation planningDIVERSITY AND DISTRIBUTIONS, Issue 1 2010C. G. Becker Abstract Aim, To identify priority areas for amphibian conservation in southeastern Brazil, by integrating species life-history traits and patterns of deforestation. Location, State of São Paulo, Brazil. Methods, We used the software Marxan to evaluate different scenarios of amphibian conservation planning. Our approach differs from previous methods by explicitly including two different landscape metrics; habitat split for species with aquatic larvae, and habitat loss for species with terrestrial development. We evaluated the effect of habitat requirements by classifying species breeding habitats in five categories (flowing water, still water permanent, still water temporary, bromeliad or bamboo, and terrestrial). We performed analyses using two scales, grid cells and watersheds and also considered nature preserves as protected areas. Results, We found contrasting patterns of deforestation between coastal and inland regions. Seventy-six grid cells and 14 watersheds are capable of representing each species at least once. When accounting for grid cells already protected in state and national parks and considering species habitat requirements we found 16 high-priority grid cells for species with one or two reproductive habitats, and only one cell representing species with four habitat requirements. Key areas for the conservation of species breeding in flowing and permanent still waters are concentrated in southern state, while those for amphibians breeding in temporary ponds are concentrated in central to eastern zones. Eastern highland zones are key areas for preserving species breeding terrestrially by direct or indirect development. Species breeding in bromeliads and bamboos are already well represented in protected areas. Main conclusions, Our results emphasize the need to integrate information on landscape configuration and species life-history traits to produce more ecologically relevant conservation strategies. [source] Limited phylogeographic structure in the flightless ground beetle, Calathus ruficollis, in southern CaliforniaDIVERSITY AND DISTRIBUTIONS, Issue 5 2007Stylianos Chatzimanolis ABSTRACT The California Floristic Province is home to more than 8000 species of beetles, yet their geographical patterns of supra- and infraspecific diversity remain largely unexplored. In this paper, we investigate the phylogeography and population demographics of a flightless ground beetle, Calathus ruficollis (Coleoptera: Carabidae), in southern California. We sampled 136 specimens from 25 localities divided into 10 populations using a fragment of the mitochondrial cytochrome oxidase I gene. We tested several hypotheses, including the association of geography with particular clades and populations, the degree of differentiation among regions, and the expansion of populations. Parsimony and Bayesian phylogenetic analyses along with nested clade analysis and amova indicate a deep split between the southern Sierra Nevada population and populations south and west. This split corresponds closely to the split between subspecies C. ruficollis ignicollis (southern Sierra Nevada) and C. ruficollis ruficollis. Populations otherwise exhibit limited geographical structure, though Fst values indicate some local differentiation. Mismatch distributions and Fu's Fs indicate range expansion of several populations, suggesting that some structure may have been obscured by recent exchange. The population of C. ruficollis on Santa Cruz Island, which might have been expected to be isolated, shares several haplotypes with mainland populations, appearing to represent multiple colonizations. [source] Are there general mechanisms of animal home range behaviour?ECOLOGY LETTERS, Issue 6 2008A review, prospects for future research Abstract Home range behaviour is a common pattern of space use, having fundamental consequences for ecological processes. However, a general mechanistic explanation is still lacking. Research is split into three separate areas of inquiry , movement models based on random walks, individual-based models based on optimal foraging theory, and a statistical modelling approach , which have developed without much productive contact. Here we review recent advances in modelling home range behaviour, focusing particularly on the problem of identifying mechanisms that lead to the emergence of stable home ranges from unbounded movement paths. We discuss the issue of spatiotemporal scale, which is rarely considered in modelling studies, as well as highlighting the need to consider more closely the dynamical nature of home ranges. Recent methodological and theoretical advances may soon lead to a unified approach, however, conceptually unifying our understanding of linkages among home range behaviour and ecological or evolutionary processes. [source] Decision Theory Applied to an Instrumental Variables ModelECONOMETRICA, Issue 3 2007Gary Chamberlain This paper applies some general concepts in decision theory to a simple instrumental variables model. There are two endogenous variables linked by a single structural equation; k of the exogenous variables are excluded from this structural equation and provide the instrumental variables (IV). The reduced-form distribution of the endogenous variables conditional on the exogenous variables corresponds to independent draws from a bivariate normal distribution with linear regression functions and a known covariance matrix. A canonical form of the model has parameter vector (,, ,, ,), where ,is the parameter of interest and is normalized to be a point on the unit circle. The reduced-form coefficients on the instrumental variables are split into a scalar parameter ,and a parameter vector ,, which is normalized to be a point on the (k,1)-dimensional unit sphere; ,measures the strength of the association between the endogenous variables and the instrumental variables, and ,is a measure of direction. A prior distribution is introduced for the IV model. The parameters ,, ,, and ,are treated as independent random variables. The distribution for ,is uniform on the unit circle; the distribution for ,is uniform on the unit sphere with dimension k-1. These choices arise from the solution of a minimax problem. The prior for ,is left general. It turns out that given any positive value for ,, the Bayes estimator of ,does not depend on ,; it equals the maximum-likelihood estimator. This Bayes estimator has constant risk; because it minimizes average risk with respect to a proper prior, it is minimax. The same general concepts are applied to obtain confidence intervals. The prior distribution is used in two ways. The first way is to integrate out the nuisance parameter ,in the IV model. This gives an integrated likelihood function with two scalar parameters, ,and ,. Inverting a likelihood ratio test, based on the integrated likelihood function, provides a confidence interval for ,. This lacks finite sample optimality, but invariance arguments show that the risk function depends only on ,and not on ,or ,. The second approach to confidence sets aims for finite sample optimality by setting up a loss function that trades off coverage against the length of the interval. The automatic uniform priors are used for ,and ,, but a prior is also needed for the scalar ,, and no guidance is offered on this choice. The Bayes rule is a highest posterior density set. Invariance arguments show that the risk function depends only on ,and not on ,or ,. The optimality result combines average risk and maximum risk. The confidence set minimizes the average,with respect to the prior distribution for ,,of the maximum risk, where the maximization is with respect to ,and ,. [source] Sample Splitting and Threshold EstimationECONOMETRICA, Issue 3 2000Bruce E. Hansen Threshold models have a wide variety of applications in economics. Direct applications include models of separating and multiple equilibria. Other applications include empirical sample splitting when the sample split is based on a continuously-distributed variable such as firm size. In addition, threshold models may be used as a parsimonious strategy for nonparametric function estimation. For example, the threshold autoregressive model (TAR) is popular in the nonlinear time series literature. Threshold models also emerge as special cases of more complex statistical frameworks, such as mixture models, switching models, Markov switching models, and smooth transition threshold models. It may be important to understand the statistical properties of threshold models as a preliminary step in the development of statistical tools to handle these more complicated structures. Despite the large number of potential applications, the statistical theory of threshold estimation is undeveloped. It is known that threshold estimates are super-consistent, but a distribution theory useful for testing and inference has yet to be provided. This paper develops a statistical theory for threshold estimation in the regression context. We allow for either cross-section or time series observations. Least squares estimation of the regression parameters is considered. An asymptotic distribution theory for the regression estimates (the threshold and the regression slopes) is developed. It is found that the distribution of the threshold estimate is nonstandard. A method to construct asymptotic confidence intervals is developed by inverting the likelihood ratio statistic. It is shown that this yields asymptotically conservative confidence regions. Monte Carlo simulations are presented to assess the accuracy of the asymptotic approximations. The empirical relevance of the theory is illustrated through an application to the multiple equilibria growth model of Durlauf and Johnson (1995). [source] Effects of hunger level and nutrient balance on survival and acetylcholinesterase activity of dimethoate exposed wolf spidersENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 3 2002Lars-Flemming Pedersen Abstract The influence of two nutritional factors (food quantity and quality) on the responses of a wolf spider, Pardosa prativaga (L.K.), to a high dose of the insecticide dimethoate, was investigated in a fully factorial experimental design. Spider groups with different (good and bad) nutrient balance were created by feeding them fruit flies of either high or low nutrient content for 28 days. Both groups were then split into satiated and 14 days starved subgroups. Each of these was further divided into insecticide treated and control halves. Survivorship and acetylcholinesterase (AChE) activity measured on the survivors were used as response variables. Survivorship after topical dimethoate exposure (LD50; 48 h) was influenced by spider body weight, nutrient balance, and starvation. Furthermore, AChE activity was significantly inhibited by dimethoate exposure. A significant interaction between nutrient balance, starvation, and dimethoate exposure revealed synergistic effects of starvation and nutrient imbalance on AChE inhibition by dimethoate in surviving spiders. These results show that the tolerance of non-target arthropods to dimethoate may vary depending on the nutritional history of the animal. [source] Fluctuating Asymmetry of Responders Affects Offers in the Ultimatum Game Oppositely According to Attractiveness or Need as Perceived by ProposersETHOLOGY, Issue 7 2009Darine Zaatari The Ultimatum Game (UG) measures cooperative tendencies in humans. A proposer offers to split a given sum of money between self and a responder, who may accept or reject the offer. If accepted, each receives the proposed split; if rejected, nobody receives anything. We studied the effect of the putative responder's degree of facial symmetry (fluctuating asymmetry, FA) on the offer he/she received in opposite-sexed UGs. Symmetry is an important measure of biological quality so subjects were expected to receive higher offers when symmetrical than asymmetrical. In a sample of Jamaicans, individuals played two UGs with opposite-sexed responders, a symmetrical photo of a Lebanese and an asymmetrical one. Individuals do indeed give more to symmetrical responders (p = 0.032). When subjects are asked their motivation, a striking dichotomy emerges: those who cite ,attractiveness' as a motive, give strongly to symmetrical responders while those citing ,need' invariably give more to asymmetrical ones (p < 0.0001). Females also show a nearly significant tendency to cite need as a motive more often than do males. [source] Anti-Predator Strategies and Grouping Patterns in White-Tailed Deer and Mule DeerETHOLOGY, Issue 4 2001Susan Lingle White-tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) are closely related species of similar size that differ in their anti-predator behavior. White-tails flee from coyotes (Canis latrans), whereas mule deer typically stand their ground and attack this predator. I used observations of coyotes hunting deer to identify: (i) changes in group structure made in response to coyotes; and (ii) the relationship between group structure and the risk of predation for each species. In response to coyotes, groups of mule deer merged with other groups and individuals bunched together. Predation attempts were more likely to escalate when groups split and individuals failed to bunch. Coyotes typically attacked mule deer that were in outlying positions, and these deer had to move to central positions to end attacks. Due to the high frequency of attacks on small groups as well as to the level of dilution of risk, individuals in small mule deer groups were at high risk of being attacked compared with those in larger groups. In contrast to mule deer, white-tails made no consistent changes in group size or formation, and coyotes attacked individuals in central as well as in outlying positions. Variation in aspects of group cohesion was not related to the vulnerability of white-tails, and there was no obvious difference in the risk of attack facing individuals in groups of different size. These results suggest that coyote predation selects for relatively large, cohesive groups in mule deer, apparently because this type of group improves their ability to deter coyotes. Coyote predation does not have similar effects on groups formed by white-tails, which use flight rather than deterrence to avoid predation. The benefits of responding cohesively, occupying certain positions within groups, and forming groups of a certain size can vary widely depending on the anti-predator strategies used by an animal. [source] Pivotal role of Notch signaling in regulation of erythroid maturation and proliferationEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 4 2006Yoshimichi Tachikawa Abstract:, Notch signaling plays an important role in cell fate decisions in developmental systems. To clarify its role in committed hematopoietic progenitor cells, we investigated the effects of Notch signaling in erythroid colony forming cells (ECFCs) generated from peripheral blood. ECFCs express Notch receptors, Notch1 and Notch2, and Notch ligands Delta1, Delta4, and Jagged1. When we assayed the effects of Notch ligands on erythroid maturation by flow cytometry, we found that immobilized Delta1 and immobilized Delta4 in particular inhibited maturation, whereas Jagged1 had no effect. In addition, Delta4 inhibited proliferation without reducing cell viability. Increases in expression levels of the Notch target gene hairy enhancer of split (HES) -1 were evident by real-time PCR after stimulation with immobilized Delta4. The effect of soluble Delta4 on expression of HES-1 was less pronounced than that seen with the immobilized form, indicating that all surface-bound ligands are important for effective signal transduction. When ECFCs were cultured in the presence of soluble Delta4 at a low cell concentration, erythroid maturation was slightly inhibited, but at a high concentration, maturation was promoted via competition of soluble Delta4 with endogenous ligands. These results indicate a pivotal role of Notch signaling in regulating erythroid maturation and proliferation, and further suggest that cell,cell interactions modulate growth of erythroid progenitor cells via Notch system. [source] Multicomponent Supramolecular Devices: Synthesis, Optical, and Electronic Properties of Bridged Bis-dirhodium and -diruthenium Complexes,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 19 2006Anne Petitjean Abstract Four ruthenium- and rhodium-based metal,metal-bonded multicomponent systems have been synthesized, and their absorption, redox, spectroelectrochemical and structural properties have been studied. The absorption spectra of the four bis-dimetallic compounds M2LM2, where L is a bridging ligand and M is rhodium or ruthenium, exhibit very strong bands in the UV, visible and, for the diruthenium species, near-IR region. The low-energy absorption bands are assigned to charge-transfer transitions involving a metal,metal bonding orbital as the donor and an orbital centered on the bis-tetradentate aromatic ligands as the acceptor (metal,metal to ligand charge transfer, M2LCT). Each compound exhibits reversible bridging-ligand-centered reductions at mild potentials and several reversible oxidation processes. The oxidation signals of the two equivalent dimetallic centers of each bis-dimetallic compound are split, with the splitting , a measure of the electronic coupling , depending on both the metal and bridging ligand. The mixed-valence species of the dirhodium species was investigated, and the electronic coupling matrix element calculated from the experimental intervalence band parameters for one of them (86 cm,1) indicates a significant inter-component electronic interaction which compares well with good electron conducting anionic bridges such as cyanides. Although none of these compounds is luminescent, the M2LCT excited state of one of the bis-dirhodium complexes is relatively long-lived (about 6 ,s) in degassed acetonitrile at room temperature. The results presented here are promising for the development of linear poly-dimetallic complexes built on longer naphthyridine-based strands, with significant long-range electronic coupling and molecular-wire-like behavior. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Equal Channel Angular Pressing of a Mg,3Al,1Zn Alloy with Back Pressure,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Feng Kang Abstract An extruded Mg,3Al,1Zn alloy bar is subjected to 1,4 passes equal channel angular pressing (ECAP) with or without 125,MPa backpressure via route Bc at 200,°C. Both strength and ductility are significantly increased after ECAP with backpressure; this is in strong contrast to the case of ECAP without backpressure, where significant improvement in ductility is accompanied by obvious decrease in yield strength from texture softening. Compared to ECAP without backpressure, much enhanced grain refinement, and the split of the dominant texture component of (0002) pole were observed with scatter intensity peaks in the case after ECAP with backpressure. This turns out to be resulted mainly from the activation of new slip system together with enhanced dynamic recrystallization under the effect of backpressure. The improvement of both strength and ductility in Mg,3Al,1Zn alloy through ECAP with back pressure provides a better approach to meet the engineering requests on comprehensive performance of this light alloy. [source] Adaptation of normal and hypofunctional masseter muscle after bite-raising in growing ratsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 6 2000Andrea Bresin The aim of this study was to analyze the effects of prolonged muscular elongation induced by bite-raising on the length of the muscle belly, sarcomeres and aponeurosis of the anterior deep masseter in the growing rat. Another aim was to determine the role of different functional conditions of this muscle in the adaptation process. Ninety-six young male rats were split into two groups: one was fed a hard diet and the other a soft diet to develop different functional capacities in the masticatory muscles. After 2 wk, half of the rats in both groups were fitted with an appliance that raised the bite by 2 mm. The measurements on the muscles were performed in situ. The insertion of the appliance stretched the anterior masseter muscle. After 4 wk, the vertical dentoskeletal dimension, the muscle belly, and the sarcomeres showed no difference in length among the groups. However, the aponeurosis was longer in the rats wearing the appliance compared to the controls, and among the bite block groups it was longer in the rats fed a hard diet. Length adaptation occurred in the aponeurosis. Clinically this may imply a need for reactivation of functional appliances to increase their efficiency, at a rate possibly depending on masseter muscles functional condition. [source] Towards a Selective Functionalization of Amino-Terminated DendrimersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 22 2004Fritz Vögtle Abstract Selective functionalization of the periphery of commercial polypropyleneamine (POPAM) and polyamidoamine (PAMAM) dendrimers has been investigated in preparative scale. The first generation (G1) POPAM dendrimer was for the first time selectively N,N -bis(sulfonylated) with tosyl chloride and the corresponding mono-, di-, tri-, and tetra- N -tosylsulfonamides were isolated and fully characterized. Unexpectedly, similar persulfonylation of G2 POPAM results in splitting of a central C,N bond and only fully and partially sulfonylated halves of the initial dendrimer could be isolated. Higher generations of POPAM are also split during the persulfonylation yielding complex mixtures of persulfonylated dendritic fragments which could hardly be identified. A plausible mechanism of the POPAM decomposition on the basis of the reaction product analysis is proposed. N -Sulfonylation of a peripheral octasulfonamide of G2 POPAM with tosyl chloride also leads to the destruction of the dendrimer, while its N -alkylation with benzyl bromide proved to be not selective yielding a completely alkylated derivative. Unlike POPAM dendrimers, PAMAM dendrimers were shown to be more stable during their sulfonylation and no decomposition of the dendritic backbone was detected. In contrast to the POPAM dendrimers, PAMAM dendrimers were shown to be rather inert with respect to the formation of N -tosylsulfonamides since they could only be N -monosulfonylated at all peripheral amino groups. The combination of MALDI-TOF and ESI-FT-ICR tandem mass spectrometry has been shown to be an effective method for structure assignment and purity check of selectively or fully persulfonylated dendritic oligoamines. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] | ||||||||||||||||||||||||||||||||||||||||