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Shape
Kinds of Shape Terms modified by Shape Selected AbstractsJ -SHAPE OR LINEAR RELATIONSHIP BETWEEN ALCOHOL CONSUMPTION AND DEPRESSION: DOES IT MATTER?ADDICTION, Issue 6 2005BENJAMIN TAYLOR No abstract is available for this article. [source] ALCOHOL AND IN-PATIENT UTILIZATION: WHAT IS THE SHAPE OF THE RELATIONSHIP?ADDICTION, Issue 1 2005MARY ANNE ARMSTRONG No abstract is available for this article. [source] EVOLUTION OF SCAPULA SIZE AND SHAPE IN DIDELPHID MARSUPIALS (DIDELPHIMORPHIA: DIDELPHIDAE)EVOLUTION, Issue 9 2009Diego Astúa The New World family Didelphidae, the basal lineage within marsupials, is commonly viewed as morphologically conservative, yet includes aquatic, terrestrial, scansorial, and arboreal species. Here, I quantitatively estimated the existing variability in size and shape of the Didelphidae scapula (1076 specimens from 56 species) using geometric morphometrics, and compared size and shape differences to evolutionary and ecologic distances. I found considerable variation in the scapula morphology, most of it related to size differences between species. This results in morphologic divergence between different locomotor habits in larger species (resulting from increased mechanical loads), but most smaller species present similarly shaped scapulae. The only exceptions are the water opossum and the short-tailed opossums, and the functional explanations for these differences remain unclear. Scapula size and shape were mapped onto a molecular phylogeny for 32 selected taxa and ancestral size and shapes were reconstructed using squared-changed parsimony. Results indicate that the Didelphidae evolved from a medium- to small-sized ancestor with a generalized scapula, slightly more similar to arboreal ones, but strikingly different from big-bodied present arboreal species, suggesting that the ancestral Didelphidae was a small scansorial animal with no particular adaptations for arboreal or terrestrial habits, and these specializations evolved only in larger-bodied clades. [source] DOES VARIATION IN SELECTION IMPOSED BY BEARS DRIVE DIVERGENCE AMONG POPULATIONS IN THE SIZE AND SHAPE OF SOCKEYE SALMON?EVOLUTION, Issue 5 2009Stephanie M. Carlson Few studies have determined whether formal estimates of selection explain patterns of trait divergence among populations, yet this is one approach for evaluating whether the populations are in equilibria. If adaptive divergence is complete, directional selection should be absent and stabilizing selection should prevail. We estimated natural selection, due to bear predation, acting on the body size and shape of male salmon in three breeding populations that experience differing predation regimes. Our approach was to (1) estimate selection acting within each population on each trait based on an empirical estimate of reproductive activity, (2) test for trait divergence among populations, and (3) test whether selection coefficients were correlated with trait divergence among populations. Stabilizing selection was never significant, indicating that these populations have yet to attain equilibria. Directional selection varied among populations in a manner consistent with trait divergence, indicating ongoing population differentiation. Specifically, the rank order of the creeks in terms of patterns of selection paralleled the rank order in terms of size and shape. The shortest and least deep-bodied males had the highest reproductive activity in the creek with the most intense predation and longer and deeper-bodied males were favored in the creeks with lower predation risk. [source] CONVERGENCE AND REMARKABLY CONSISTENT CONSTRAINT IN THE EVOLUTION OF CARNIVORE SKULL SHAPEEVOLUTION, Issue 5 2007Stephen Wroe Phenotypic similarities between distantly related marsupials and placentals are commonly presented as examples of convergence and support for the role of adaptive evolution in shaping morphological and ecological diversity. Here we compare skull shape in a wide range of carnivoran placentals (Carnivora) and nonherbivorous marsupials using a three-dimensional (3-D) geometric morphometric approach. Morphological and ecological diversity among extant carnivorans is considerably greater than is evident in the marsupial order Dasyuromorphia with which they have most commonly been compared. To examine convergence across a wider, but broadly comparable range of feeding ecologies, a dataset inclusive of nondasyuromorphian marsupials and extinct taxa representing morphotypes no longer present was assembled. We found support for the adaptive paradigm, with correlations between morphology, feeding behavior, and bite force, although skull shape better predicted feeding ecology in the phylogenetically diverse marsupial sample than in carnivorans. However, we also show that remarkably consistent but differing constraints have influenced the evolution of cranial shape in both groups. These differences between carnivorans and marsupials, which correlate with brain size and bite force, are maintained across the full gamut of morphologies and feeding categories, from small insectivores and omnivores to large meat-specialists. [source] QUANTITATIVE GENETICS OF PLASTRON SHAPE IN SLIDER TURTLES (TRACHEMYS SCRIPTA)EVOLUTION, Issue 3 2006Erin M. Myers Abstract Shape variation is widespread in nature and embodies both a response to and a source for evolution and natural selection. To detect patterns of shape evolution, one must assess the quantitative genetic underpinnings of shape variation as well as the selective environment that the organisms have experienced. Here we used geometric morphometrics to assess variation in plastron shell shape in 1314 neonatal slider turtles (Trachemys scripta) from 162 clutches of laboratory-incubated eggs from two nesting areas. Multivariate analysis of variance indicated that nesting area has a limited role in describing plastron shape variation among clutches, whereas differences between individual clutches were highly significant, suggesting a prominent clutch effect. The covariation between plastron shape and several possible maternal effect variables (yolk hormone levels and egg dimensions) was assessed for a subset of clutches and found to be negligible. We subsequently employed several recently proposed methods for estimating heritability from shape variables, and generalized a univariate approach to accommodate unequal sample sizes. Univariate estimates of shape heritability based on Procrustes distances yielded large values for both nesting populations (h2, 0.86), and multivariate estimates of maximal additive heritability were also large for both nesting populations (h2max, 0.57). We also estimated the dominant trend in heritable shape change for each nesting population and found that the direction of shape evolution was not the same for the two sites. Therefore, although the magnitude of shape evolution was similar between nesting populations, the manner in which plastron shape is evolving is not. We conclude that the univariate approach for assessing quantitative genetic parameters from geometric morphometric data has limited utility, because it is unable to accurately describe how shape is evolving. [source] SEXUAL SELECTION, GENETIC ARCHITECTURE, AND THE CONDITION DEPENDENCE OF BODY SHAPE IN THE SEXUALLY DIMORPHIC FLY PROCHYLIZA XANTHOSTOMA (PIOPHILIDAE)EVOLUTION, Issue 1 2005Russell Bonduriansky Abstract The hypothesis that sexual selection drives the evolution of condition dependence is not firmly supported by empirical evidence, and the process remains poorly understood. First, even though sexual competition typically involves multiple traits, studies usually compare a single sexual trait with a single "control" trait, ignoring variation among sexual traits and raising the possibility of sampling bias. Second, few studies have addressed the genetic basis of condition dependence. Third, even though condition dependence is thought to result from a form of sex-specific epistasis, the evolution of condition dependence has never been considered in relation to intralocus sexual conflict. We argue that condition dependence may weaken intersexual genetic correlations and facilitate the evolution of sexual dimorphism. To address these questions, we manipulated an environmental factor affecting condition (larval diet) and examined its effects on four sexual and four nonsexual traits in Prochyliza xanthostoma adults. As predicted by theory, the strength of condition dependence increased with degree of exaggeration among male traits. Body shape was more condition dependent in males than in females and, perhaps as a result, genetic and environmental effects on body shape were congruent in males, but not in females. However, of the four male sexual traits, only head length was significantly larger in high-condition males after controlling for body size. Strong condition dependence was associated with reduced intersexual genetic correlation. However, homologous male and female traits exhibited correlated responses to condition, suggesting an intersexual genetic correlation for condition dependence itself. Our findings support the role of sexual selection in the evolution of condition dependence, but reveal considerable variation in condition dependence among sexual traits. It is not clear whether the evolution of condition dependence has mitigated or exacerbated intralocus sexual conflict in this species. [source] VARIATION OF SHELL SHAPE IN THE CLONAL SNAIL MELANOIDES TUBERCULATA AND ITS CONSEQUENCES FOR THE INTERPRETATION OF FOSSIL SERIESEVOLUTION, Issue 2 2000Sarah Samadi Abstract., Interpreting paleontological data is difficult because the genetic nature of observed morphological variation is generally unknown. Indeed, it is hardly possible to distinguish among several sources of morphological variation including phenotypic plasticity, sexual dimorphism, within-species genetic variation or differences among species. This can be addressed using fossil organisms with recent representatives. The freshwater snail Melanoides tuberculata ranks in this category. A fossil series of this and other species have been studied in the Turkana Basin (Kenya) and is presented as one of the best examples illustrating the punctuated pattern of evolution by the tenants of this theory. Melanoides tuberculata today occupies most of the tropics. We studied variation of shell shape in natural populations of this parthenogenetic snail using Raup's model of shell coiling. We considered different sources of variation on estimates of three relevant parameters of Raup's model: (1) variation in shell shape was detected among clones, and had both genetic and environmental bases; (2) sexual dimorphism, in those clones in which males occur, appeared as an additional source of shell variation; and (3) ecophenotypic variation was detected by comparing samples from different sites and years within two clones. We then tested the performance of discriminant function analyses, a classical tool in paleontological studies, using several datasets. Although the three sources of variation cited above contributed significantly to the observed morphological variance, they could not be detected without a priori knowledge of the biological entities studied. However, it was possible to distinguish between M. tuberculata and a related thiarid species using these analyses. Overall, this suggests that the tools classically used in paleontological studies are poorly efficient when distinguishing between important sources of within-species variation. Our study also gives some empirical bases to the doubts cast on the interpretation of the molluscan series of the Turkana Basin. [source] INFLUENCE OF SAMPLE SIZE AND SHAPE ON TRANSPORT PARAMETERS DURING DRYING OF SHRINKING BODIESJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2007NAJMUR RAHMAN ABSTRACT An experimental investigation on the influence of sample size and shape on heat and mass transport parameters under natural convection air-drying is presented. Potato cylinders with length of 0.05 m and thicknesses of 0.005, 0.008, 0.010 and 0.016 m, and circular slices with diameter of 0.05 m and thickness of 0.01 m were dried in a laboratory scale hot-air cabinet dryer. Results indicate that each transport parameter exhibits a linear relationship with sample thickness. Convective heat and mass transfer coefficients (hcand hm) decreased whereas moisture diffusion coefficient (Deff) increased with increasing thickness. Considering no sample shrinkage effect in the parameter analysis, for the thickness range considered, the values of hcare found to be underestimated in the range of 29.0,30.6%, whereas those of hmand Deff are overestimated in the range of 33.7,38.0% and 75.9,128.1%, respectively. Using Levenberg,Marquardt algorithm for optimization, a correlation for Biot number for mass transfer (Bim) as a function of drying time and sample thickness is proposed. A close agreement was observed between dimensionless moisture contents predicted by this relation and those obtained from experiments for different sample thicknesses at drying air temperature of 60C. For the same thickness and drying conditions, circular slices caused an increase in each transport parameter significantly. [source] INFLUENCE OF GLASS SHAPE ON WINE AROMAJOURNAL OF SENSORY STUDIES, Issue 1 2002J.F. DELWICHE ABSTRACT Differences in the physical shape of glasses could potentially influence proportions of aromatic compounds trapped in the headspace of a wine glass, altering the perception of a wine. Blindfolded, naïve subjects assessed the aroma of a California Cabernet Sauvignon presented in 4 different glasses. Two of these were from a speciality line of crystal wine glasses, one designed for Chardonnay, the other for Bordeaux/Cabernet Sauvignon. A restaurant-style wine glass and a leaded crystal goblet were the remaining vessels used. The nonexpert judges assessed wine aroma for total intensity, fruitiness, vinegariness, oakiness, and mustiness, as well as liking. The only significant difference found in the aroma intensity ratings was for the Bordeaux glass, which was rated as having a significantly lower total intensity than the other three glasses. However, several significant correlations were found between the attribute intensity ratings and physical characteristics of the glasses. This suggests that the glass does have a limited, but subtle, impact upon the olfactory experience of wines. [source] IS BLOOD PRESSURE RELATED TO KIDNEY SHAPE AND SIZE?NEPHROLOGY, Issue 1 2002Singh G [source] SHAPE OF THINGS: UNDERSTANDING A LOOM WEIGHTOXFORD JOURNAL OF ARCHAEOLOGY, Issue 4 2009LINDA MÅRTENSSON If there is one thing to be learnt from watching people work in old traditional crafts it is this: The tools and the working procedures are never clumsy, never impractical (Hoffmann 1988) Summary Loom weights are common finds in archaeological excavations in Europe and the Near East. They represent the only remains of warp-weighted looms. The function of the warp-weighted loom is well known from ethnographic studies. The function of loom weights, however, has not been investigated and cannot be deduced directly from ethnographical data, since loom weights in antiquity were very different from those used in the twentieth century AD. This paper reviews the functional elements of a loom weight. The weight and thickness of loom weights are established as the defining functional parameters for the operation of the warp-weighted loom. A series of systematic tests demonstrated that the weight of a loom weight defines what yarn to use and the thread density. The thickness of a loom weight, and thus the width of the row of loom weights hanging closely together, defines the width of a fabric and , together with the weight of the loom weight , the thread count and density of the fabric. This new knowledge provides the methodological framework for archaeologists to calculate textile production possibilities from any given loom weight, as long as the weight and thickness are preserved. Furthermore, it allows scholars to assess textile production on sites where no textiles are preserved. [source] THE SHAPE OF THE PHANEROZOIC MARINE PALAEODIVERSITY CURVE: HOW MUCH CAN BE PREDICTED FROM THE SEDIMENTARY ROCK RECORD OF WESTERN EUROPE?PALAEONTOLOGY, Issue 4 2007ANDREW B. SMITH Abstract:, Palaeodiversity curves are constructed from counts of fossils collected at outcrop and thus potentially biased by variation in the rock record, specifically by the amount of sedimentary rock representative of different time intervals that has been preserved at outcrop. To investigate how much of a problem this poses we have compiled a high-resolution record of marine rock outcrop area in Western Europe for the Phanerozoic and use this to generate a model that predicts the sampled diversity curve. We find that we can predict with high accuracy the variance of the marine genus diversity curve (itself dominated by European taxa) from rock outcrop data and a three-step model of diversity that tracks supercontinent fragmentation, coalescence and fragmentation. The size and position of two of the five major mass extinction spikes are largely predicted by rock outcrop data. We conclude that the long-term trends in taxonomic diversity and the end-Cretaceous extinction are not the result of rock area bias, but cannot rule out that rock outcrop area bias explains many of the short-term rises and falls in sampled diversity that palaeontologists have previously sought to explain biologically. [source] THE SHAPES OF NEUTRAL GENE GENEALOGIES IN TWO SPECIES: PROBABILITIES OF MONOPHYLY, PARAPHYLY, AND POLYPHYLY IN A COALESCENT MODELEVOLUTION, Issue 7 2003Noah A. Rosenberg Abstract., The genealogies of samples of orthologous regions from multiple species can be classified by their shapes. Using a neutral coalescent model of two species, I give exact probabilities of each of four possible genealogical shapes: reciprocal monophyly, two types of paraphyly, and polyphyly. After the divergence that forms two species, each of which has population size N, polyphyly is the most likely genealogical shape for the lineages of the two species. At , 1.300N generations after divergence, paraphyly becomes most likely, and reciprocal monophyly becomes most likely at ,1.665N generations. For a given species, the time at which 99% of its loci acquire monophyletic genealogies is ,5.298N generations, assuming all loci in its sister species are monophyletic. The probability that all lineages of two species are reciprocally monophyletic given that a sample from the two species has a reciprocally monophyletic genealogy increases rapidly with sample size, as does the probability that the most recent common ancestor (MRCA) for a sample is also the MRCA for all lineages from the two species. The results have potential applications for the testing of evolutionary hypotheses. [source] Stylet Bend Angles and Tracheal Tube Passage Using a Straight-to-cuff ShapeACADEMIC EMERGENCY MEDICINE, Issue 12 2006Richard M. Levitan MD Abstract Objectives Malleable stylets improve maneuverability and control during tube insertion, but after passage through the vocal cords the stiffened tracheal tube may impinge on the tracheal rings, preventing passage. The goal of this study was to assess insertion difficulty with styletted tubes of different bend angles. Methods Tube passage was assessed with four different bend angles (25°, 35°, 45°, and 60°) using straight-to-cuff,shaped tubes. In two separate airway procedure classes, 16 operators in each class (32 total) placed randomly ordered styletted tubes of the different angles into eight cadavers (16 total). Operators subjectively graded the ease of tube passage as no resistance, some resistance, or impossible to advance. Results No resistance was reported in 69.1% (177/256) at 25°, in 63.7% (163/256) at 35°, in 39.4% (101/256) at 45°, and in 8.9% (22/256) at 60°. Tube passage was impossible in 2.3% of insertions (6/256) at 25°, in 3.5% (9/256) at 35°, in 11.3% (29/256) at 45°, and in 53.9% (138/256) at 60°. The odds ratios of impossible tube passage for 35°, 45°, and 60° vs. 25° were 1.52 (95% confidence interval [CI] = 0.55 to 4.16), 5.32 (95% CI = 2.22 to 12.71), and 48.72 (95% CI = 21.35 to 111.03), respectively. Conclusions Bend angles beyond 35° with straight-to-cuff styletted tracheal tubes increase the risk of difficult and impossible tube passage into the trachea. The authors did not compare different stylet stopping points, stylets of different stiffness, or tracheal tubes with different tip designs, all variables that can affect tube passage. [source] The Relationship Between Left Ventricular Shape and QT Interval DispersionECHOCARDIOGRAPHY, Issue 8 2002F.A.C.C., Kishore J. Harjai M.D. Left ventricular geometry is suspected to affect heterogeneity of myocardial repolarization; therefore, it is plausible but unproven that increased sphericity of the left ventricle is associated with greater QT interval dispersion. In 60 patients with dilated cardiomyopathy with left ventricular ejection fraction , 30%, we found that spherical distortion of the left ventricle was associated with increased QT dispersion, implying increased heterogeneity of myocardial repolarization. [source] Analysis of affective factors of colored three-dimensional shapesELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 5 2009Takeshi Miura Abstract "Shape" has been regarded as one of the fundamental elements of plastic art, together with "color" and "material." The purpose of this paper is to investigate the influence of shape on affective meanings, when the visual stimulus is a three-dimensional shape. The semantic differential technique is used for the extraction of affective factors, with samples of stimuli produced by three-dimensional computer graphics (3DCG). Since it is difficult to separate the stimuli of shape and color in the visual stimulus of a three-dimensional shape, both single-color experiments and colored three-dimensional-shape experiments were performed; the influence of shape is investigated by comparison of the respective results. A total of 33 single colors and 132 colored three-dimensional shapes with simple geometrical form (cube, cylinder, cone, and sphere) were used as samples. Four factors are extracted for single-color stimuli by factor analysis: "showiness," "pleasantness," "strength," and "warmth." The factor of "looseness" is also added to the above factors in the case of a three-dimensional-shape stimulus. The following tendencies of these factors are obtained: among the single-color factors, the factors of "pleasantness" and "warmth" show marked variation caused by the influence of shape, and the factor score of "looseness" depends on the straightness or roundness of the shape. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(5): 41,54, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10001 [source] The Role of Functionalisation, Asymmetry and Shape of a New Macrocyclic Compartmental Ligand in the Formation of Mononuclear, Homo- and Heterodinuclear Lanthanide(III) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2009Sergio Tamburini Abstract The compartmental [1+1] macrocycle H3L, obtained by self-condensation of the formyl precursor 3,3,-(3,6-dioxaoctane-1,8-diyldioxy)bis(2-hydroxybenzaldehyde) with the amine precursor N,N -bis(2-aminoethyl)-2-hydroxybenzylamine, contains one inner ON3O2 Schiff base and one outer O2O4 crown-like chamber. According to the experimental conditions it forms, by a template process, the stable mononuclear complexes Ln(H3L)(Cl)2(CH3COO)·nS·mHCl or [Ln(L)]·nS (Ln = La, Lu, Y, Yb, Er, Dy, Tb, Gd, Eu, Ce) with the lanthanide(III) ion encapsulated in the crown-ether-like and in the Schiff base site. The mononuclear complexes Ln(H3L)(Cl)2(CH3COO)·nS·mHCl, by further complexation with a different lanthanide(III) ion, give rise to the related heterodinuclear complexes [LnLn,(L)(Cl)2(CH3COO)]·nS while the homodinuclear and the heterodinuclear complexes [Ln2(L)](Cl)3·nH2O and [LnLn,(L)](Cl)3·nS could be prepared by a template reaction using the appropriate molar ratio of reactants. Their properties have been studied by using SEM-EDS microscopy, IR and NMR spectroscopy and their compositions confirmed by thermal and ESI-Mass spectrometric analyses. In the heterodinuclear complexes, the site occupancy of the different lanthanide(III) ions was determined by 1H and 13C NMR spectroscopy in CD3OD or (CD3)2SO , it was found that heterodinuclear complexation occurs in methanol with the smaller lanthanide(III) ion mainly coordinating to the Schiff base site and the larger lanthanide(III) ion to the crown site whereas, in dimethyl sulfoxide, demetalation of the weaker coordinated lanthanide(III) ion into the crown ether chamber occurs with the subsequent formation of mononuclear species in solution. The thermal decomposition of the heterodinuclear complexes forms the related mixed oxides, the stoichiometries and properties of which were determined by SEM-EDS microscopy and X-ray powder diffraction studies (XRD). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] The Effect of Nanoparticle Shape on the Photocarrier Dynamics and Photovoltaic Device Performance of Poly(3-hexylthiophene):CdSe Nanoparticle Bulk Heterojunction Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 16 2010Smita Dayal Abstract The charge separation and transport dynamics in CdSe nanoparticle:poly(3-hexylthiophene) (P3HT) blends are reported as a function of the shape of the CdSe-nanoparticle electron acceptor (dot, rod, and tetrapod). For optimization of organic photovoltaic device performance it is crucial to understand the role of various nanostructures in the generation and transport of charge carriers. The sample processing conditions are carefully controlled to eliminate any processing-related effects on the carrier generation and on device performance with the aim of keeping the conjugated polymer phase constant and only varying the shape of the inorganic nanoparticle acceptor phase. The electrodeless, flash photolysis time-resolved microwave conductivity (FP-TRMC) technique is used and the results are compared to the efficiency of photovoltaic devices that incorporate the same active layer. It is observed that in nanorods and tetrapods blended with P3HT, the high aspect ratios provide a pathway for the electrons to move away from the dissociation site even in the absence of an applied electric field, resulting in enhanced carrier lifetimes that correlate to increased efficiencies in devices. The processing conditions that yield optimum performance in high aspect ratio CdSe nanoparticles blended with P3HT result in poorly performing quantum dot CdSe:P3HT devices, indicating that the latter devices are inherently limited by the absence of the dimensionality that allows for efficient, prolonged charge separation at the polymer:CdSe interface. [source] Morphometric Analysis on the Size, Shape and Areal Distribution of Glacial Cirques in the Maritime Alps (Western French-Italian Alps)GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 3 2004Paolo Roberto Federici Abstract The morphometry of 432 glacial cirques in the Maritime Alps (Western French-Italian Alps), studied over several years of fieldwork, was analysed with the use of a geographical information system. Some of the parameters automatically evaluated from digital elevation models required an objective and relatively new definition. In particular, cirque length was measured along a line that, from the threshold midpoint, splits the cirque into two equivalent surfaces; cirque width was automatically drawn as the longest line inscribed in the cirque and perpendicular to the length line. Significant correlations were found among the different factors and parameters analysed. In particular, cirque shape analysis showed that cirques develop allometrically in the three dimensions, i.e. more in length and width than in altitudinal range. Nevertheless cirques of the Maritime Alps have a regular, almost circular shape (mean L/W value = 1.07). The correlations among length, width and area are all very high (r2= 0.8,0.9). In terms of size, cirques show a wide range in area from 0.06 to 5.2 km2 with a mean value of 0.4 km2. The largest cirques are found on SSW-facing slopes and at high elevations. Small cirques can be found at all altitudes but all those at high elevation are part of compound cirques at the main head valleys. Most cirques (37%) are characterized by a northern aspect; NE and SW are also frequent directions. [source] The impact of state physical education requirements on youth physical activity and overweightHEALTH ECONOMICS, Issue 12 2007John Cawley Abstract To combat childhood overweight in the US, which has risen dramatically in the past three decades, many medical and public health organizations have called for students to spend more time in physical education (PE) classes. This paper is the first to examine the impact of state PE requirements on student PE exercise time. It also exploits variation in state laws as quasi-natural experiments in order to estimate the causal impact of PE on overall student physical activity and weight. We study nationwide data from the Youth Risk Behavior Surveillance System for 1999, 2001, and 2003 merged with data on state minimum PE requirements from the 2001 Shape of the Nation Report. We find that high school students with a binding PE requirement report an average of 31 additional minutes per week spent physically active in PE class. Our results also indicate that additional PE time raises the number of days per week that girls report having exercised vigorously or having engaged in strength-building activity. We find no evidence that PE lowers BMI or the probability that a student is overweight. We conclude that raising PE credit requirements may make girls more physically active overall but there is not yet the scientific base to declare raising PE requirements an anti-obesity initiative for either boys or girls. Copyright © 2007 John Wiley & Sons, Ltd. [source] Mechanisms Controlling Crystal Habits of Gold and Silver ColloidsADVANCED FUNCTIONAL MATERIALS, Issue 7 2005C. Lofton Abstract Examples of gold and silver anisotropic colloids, such as prisms and rods, have appeared in the literature for many years. In most cases, the morphologies of these thermodynamically unfavorable particles have been explained by the particular reaction environment in which they were synthesized. The mechanisms used to explain the growth generally fall into two categories, one in which chemically adsorbed molecules regulate the growth of specific crystal faces kinetically, and the other where micelle-forming surfactants physically direct the shape of the particle. This paper raises questions about the growth of anisotropic metal colloids that the current mechanisms cannot adequately address, specifically, the formation of multiple shapes in a single homogeneous reaction and the appearance of similar structures in very different synthesis schemes. These observations suggest that any growth mechanism should primarily take into consideration nucleation and kinetics, and not only thermodynamics or physical constrictions. The authors suggest an alternative mechanism where the presence and orientation of twin planes in these face-centered cubic (fcc) metals direct the shape of the growing particles. This explanation follows that used for silver halide crystals, and has the advantage of explaining particle growth in many synthesis methods. In this mechanism, twin planes generate reentrant grooves, favorable sites for the attachment of adatoms. Shape and structural data are presented for gold and silver particles synthesized using several different techniques to support this new model. Triangular prisms are suggested to contain a single twin plane which directs that growth of the initial seed in two dimensions, but limits the final size of the prism. Hexagonal platelets are suggested to contain two parallel twin planes that allow the fast growing edges to regenerate one another, allowing large sizes and aspect ratios to form. Rods and wires were found to have a fivefold symmetry, which may only allow growth in one dimension. It is expected that a superior mechanistic understanding will permit shape-selective synthesis schemes to be developed. [source] Shape of isolated bubble in intermittent flows in a horizontal pipeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 5 2007Gu Hanyang Abstract An experimental study on the shape of a single bubble similar to those observed in a horizontal plug/slug flow was performed using visual observation and conductance probes. The results indicated that the shapes of the bubble nose and the bubble body depend on the Froude number defined by gas/liquid mixture velocity, whereas the shape of the back region of the bubble depends on both the Froude number and bubble length. The photographic images showed that the structural feature of the bubble head is related to the motion characteristics of the bubble. The transition from plug flow to slug flow occurs when the tail of the bubble changes from a staircase to hydraulic jump pattern with the increasing of the Froude number and bubble length. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 276, 285, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20161 [source] Shape of "True" transition boiling curve and two-mode boilingHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2003Duu-Jong Lee Abstract Two-mode boiling could occur on the same heating element, which provided information on the criterion separating the stable and metastable boiling regimes. The "equal-area" criterion based on the complete boiling curve interpreted the criterion of coexistence of the two boiling modes. However, the transition boiling curve could not be constructed by the pool boiling tests. Literature works adopted various correlations of transition boiling curves for analysis, but failed to recognize the possible errors incorporated in such an approximation. This paper demonstrated the relative errors embedded in calculating the equal-area criterion by assuming various shapes of the transition boiling curve. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(7): 593,601, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10113 [source] Microfluidic Endoskeletons: Materials of Controlled Shape and Stiffness with Photocurable Microfluidic Endoskeleton (Adv. Mater.ADVANCED MATERIALS, Issue 27 200927/2009) Photocurable microfluidic channel networks in thin layers of polydimethylsiloxane can act as on-demand endoskeletons to lock-in specific shapes, report Orlin Velev and co-workers on p. 2803. The light-induced solidification of photopolymer inside the microchannel networks leads to drastic increases in the elastic and bending moduli of the elastomeric material. The fabrication process is simple and scalable, and could make use of other shape-memory materials, creating the potential to fabricate custom shapes (e.g., containers, protective exoskeletons, or supports) using simple heat, light, or magnetic/electric field triggers. [source] Materials of Controlled Shape and Stiffness with Photocurable Microfluidic EndoskeletonADVANCED MATERIALS, Issue 27 2009Suk Tai Chang Photocurable microfluidic channel networks in thin layers of polydimethylsiloxane can act as on-demand endoskeletons to lock-in specific shapes. The light-induced solidification of photopolymer inside the microchannel networks leads to drastic increases in the elastic and bending moduli of the elastomeric material. [source] Near-Net Shape ,-Si4Al2O2N6 Parts by Hydrolysis Induced Aqueous Gelcasting ProcessINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 1 2009Ibram Ganesh In this paper, a new net-shaping process, an hydrolysis-induced aqueous gelcasting (GC) (GCHAS) has been reported for consolidation of ,-Si4Al2O2N6 ceramics from aqueous slurries containing 48,50 vol%,-Si3N4, ,-Al2O3, AlN, and Y2O3 powders mixture. Dense ceramics of same composition were also consolidated by aqueous GC and hydrolysis assisted solidification routes. Among three techniques used, the GCHAS process was found to be superior for fabricating defect-free thin wall ,-Si4Al2O2N6 crucibles and tubes. Before use, the as purchased AlN powder was passivated against hydrolysis. The sintered ,-Si4Al2O2N6 ceramics exhibited comparable properties with those reported for similar materials in the literature. [source] Self-Assembly and Self-Orientation of Truncated Octahedral Magnetite Nanocrystals,ADVANCED MATERIALS, Issue 18 2006K. Zheng Monodisperse magnetite nanoparticles (12,nm) in the shape of Wigner,Seitz crystals self-assemble into a body-centered cubic superlattice (see figure) in which the nanoparticles possess the same crystallographic orientations. Shape plays a critical role in controlling the orientation of the nanoparticles in self-assembly. Both self-assembly and self-orientation of nanoparticles are important for technical applications such as high-density magnetic storage. [source] Optically Anisotropic Colloids of Controllable Shape,ADVANCED MATERIALS, Issue 6 2005A. Fernández-Nieves Solid spheres, disks, and ellipsoids with micrometer-scale bipolar anisotropic character respond to external electric fields by aligning their mean optical axes parallel to the field. The monodisperse, optically anisotropic colloids (see Figure) are synthesized by photopolymerization of a monodisperse liquid-crystal emulsion after mechanical deformation of the drops. [source] The effects of muscular dystrophy on the craniofacial shape of Mus musculusJOURNAL OF ANATOMY, Issue 6 2007Donna Carlson Jones Abstract Skeletal anomalies are common in patients with muscular dystrophy, despite an absence of mutations to genes that specifically direct skeletogenesis. In order to understand these anomalies further, we examined two strains of muscular dystrophy (laminin- and merosin-deficient) relative to controls, to determine how the weakened muscle forces affected skull shape in a mouse model. Shape was characterized with geometric morphometric techniques, improving upon the limited analytical power of the standard linear measurements. Through these techniques, we document the specific types of cranial skeletal deformation produced by the two strains, each with individual shape abnormalities. The mice with merosin deficiency (with an earlier age of onset) developed skulls with more deformation, probably related to the earlier ontogenetic timing of disease onset. Future examinations of these mouse models may provide insight regarding the impact of muscular forces and the production and maintenance of craniofacial integration and modularity. [source] | ||||||||||||||||||||||||||||||||||||||||||||||