Home About us Contact
|
Home About us Contact | ||
|
|
||
Asymmetry
Kinds of Asymmetry Terms modified by Asymmetry Selected AbstractsON THE ADAPTIVE ACCURACY OF DIRECTIONAL ASYMMETRY IN INSECT WING SIZEEVOLUTION, Issue 11 2008Christophe Pélabon Subtle left,right biases are often observed in organisms with an overall bilateral symmetry. The evolutionary significance of these directional asymmetries remains uncertain, however, and scenarios of both developmental constraints and adaptation have been suggested. Reviewing the literature on asymmetry in insect wings, we analyze patterns of directional asymmetry in wing size to evaluate the possible adaptive significance of this character. We found that directional asymmetry in wing size is widespread among insects, with left- and right-biased asymmetries commonly observed. The direction of the asymmetry does not appear to be evolutionarily conserved above the species level. Overall, we argue that the very small magnitude of directional asymmetry, 0.7% of the wing size on average, associated with an extremely imprecise expression, precludes directional asymmetry from playing any major adaptive role. [source] ASYMMETRY IN STRUCTURAL DEFENSES: INSIGHTS INTO SELECTIVE PREDATION IN THE WILDEVOLUTION, Issue 9 2003C. A. Bergstrom Abstract Assessment of geographical patterns in fluctuating asymmetry (small, random differences between sides of bilateral characters) among populations shows promise as a tool to resolve the relative biomechanical importance of traits, in addition to being a possible indicator of habitat quality. We used 115 endemic freshwater populations of threespine stickleback (Gasterosteus aculeatus) from Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada, to explore the degree of concordance between geographical variation of asymmetry in a predator defense structure (bony lateral plates) and geographical variation in several indirect measures of predation regime as well as several abiotic habitat variables. We found a geographical cline in the population frequency of lateral plate asymmetries, with reduced asymmetry in the southern clear-water regions of the archipelago characterized by long reaction distances and greater chance of capture by predators, and elevated asymmetry in the northern stained-water regions with poor visibility and low chances of capture. Lateral plate asymmetry was strongly correlated with expression of several defensive armor traits, including total plate numbers among populations, mean cross-sectional diameter of stickleback with the dorsal and pelvic spines erect, and mean degree of overlap between the plates and spine supports. There were no significant correlations between frequency of asymmetric fish and any of our abiotic habitat variables. Stickleback with structural plate asymmetries had fewer trout-induced scars than symmetric fish in the significant majority of populations, and there was a decrease in structural plate asymmetry with age in stained-water habitats, suggesting that trout predators may be selectively removing asymmetric fish in some lakes. This study provides evidence that geographical variation in developmental stability of threespine stickleback, as seen in the frequencies of asymmetry, reflects differences among populations in the importance of structural defenses to fitness rather than differences in habitat quality, and that asymmetry may be a target of selection by predators in wild populations. [source] SHAPE ANALYSIS OF SYMMETRIC STRUCTURES: QUANTIFYING VARIATION AMONG INDIVIDUALS AND ASYMMETRYEVOLUTION, Issue 10 2002Christian Peter Klingenberg Abstract., Morphometric studies often consider parts with internal left-right symmetry, for instance, the vertebrate skull. This type of symmetry is called object symmetry and is distinguished from matching symmetry, in which two separate structures exist as mirror images of each other, one on each body side. We explain a method for partitioning the total shape variation of landmark configurations with object symmetry into components of symmetric variation among individuals and asymmetry. This method is based on the Procrustes superimposition of the original and a reflected copy of each landmark configuration and is compatible with the two-factor ANOVA model customary in studies of fluctuating asymmetry. We show a fully multivariate framework for testing the effects in the two-factor model with MANOVA statistics, which also applies to shapes with matching symmetry. We apply the new methods in a small case study of pharyngeal jaws of the Neotropical cichlid fish Amphilophus citrinellus. The analysis revealed that the symmetric component of variation in the pharyngeal jaws is dominated by the contrast between two alternative trophic morphs in this species and that there is subtle but statistically significant directional asymmetry. Finally, we provide some general recommendations for morphometric studies of symmetric shapes. [source] BILATERAL DIRECTIONAL ASYMMETRY OF THE APPENDICULAR SKELETON OF THE HARBOR PORPOISE (PHOCOENA PHOCOENA)MARINE MAMMAL SCIENCE, Issue 3 2005Anders Galatius Abstract Directional asymmetry (DA) of the lengths, diameters, and masses of the scapula, humerus, radius, and ulna were analyzed on a sample of 213 harbor porpoises from Denmark and West Greenland. The levels of DA were consistent across yearlings and older animals, mature and immature animals, sexes, and populations. All investigated variables showed significant DA favoring the right side. For the pooled sample, DA of lengths ranged from 0.2% SE 0.1 (ulna) to 1.2% SE 0.1 (scapula). DAs of diameters were 1.5% SE 0.2 for the humerus, 0.6% SE 0.1 for the radius, and 1.3% SE 0.2 for the ulna. DA of mass ranged from 2.8% SE 0.5 (humerus) to 4.3% SE 0.7 (ulna). The humerus and ulna had significantly larger mean diameter/ length ratios on the right side than the left, making them more robust. The large DA of scapula length indicates larger muscle mass associated with the right flipper, while the generally more robust right humerii and ulnae may be designed for higher levels of mechanical stress. These DAs and the examples of lateralized behavior recorded in cetaceans, point to the existence of lateralized use of the flippers at the population level in harbor porpoises and possibly other cetacean species. [source] Latitudinal patterns in abundance and life-history traits of the mole crab Emerita brasiliensis on South American sandy beachesDIVERSITY AND DISTRIBUTIONS, Issue 2 2004Omar Defeo ABSTRACT Demographic and life-history attributes of the mole crab Emerita brasiliensis were analysed along 2700 km of the Atlantic coast of South America, including sandy beaches at the southernmost limit (Uruguay) and at the core of its geographical range (Brazil). Population features varied markedly within this range and exhibited systematic geographical patterns of variation. Abundance significantly increased from temperate to subtropical beaches, and the same held true for the asymptotic weight of males. Conversely, length at maturity and asymptotic weight of females increased from subtropical to temperate beaches, being inversely related to sea water temperature. Macroecological patterns in abundance and body weight showed the first large-scale evidence of scaling of population density to body size for a sandy beach population. Mortality rates (both sexes) followed a nonlinear increase from low-density temperate beaches to high-density subtropical beaches. The effect of habitat quality and availability could explain discontinuities in the species distribution within its range, and also differential responses in life-history attributes at a local scale. Asymmetries and converse latitudinal trends between sexes suggest that there is not a single general factor determining large-scale patterns in life-history traits of this species. Our results reinforce the view that density-dependent and environmental factors operating together regulate sandy beach populations. The need to develop macroecological studies in sandy beach ecology is highlighted, as knowledge acquired from local to large spatial scales throws light on population structure and regulation mechanisms. [source] Mollusk species diversity in the Southeastern Pacific: why are there more species towards the pole?ECOGRAPHY, Issue 2 2003Claudio Valdovinos The most ubiquitous and well recognized diversity pattern at large spatial scales is the latitudinal increase in species richness near the equator and decline towards the poles. Although several exceptions to this pattern have been documented, shallow water mollusks, the most specious group of marine invertebrates, are the epitome of the monotonic decline in species diversity toward higher latitudes along the Pacific and Atlantic coasts of North America. Here we analyze the geographic diversity of 629 mollusk species along the Pacific South American shelf. Our analyses are based on the most complete database of invertebrates assembled for this region of the world, consisting of latitudinal ranges of over 95% of all described mollusks between 10° and 55°S. Along this coast, mollusk diversity did not follow the typical latitudinal trend. The number of species remained constant and relatively low at intermediate latitudes and sharply increased toward higher latitudes, south of 42°S. This trend was explained by changes in shelf area, but not by sea surface temperature, unlike the pattern documented for Northern Hemisphere mollusks. Direct sampling of soft bottom communities along the gradient suggests that regional trends in species richness are produced by increased alpha diversity, and not only by artifacts produced by the increase in sampling area. We hypothesize that increased shelf area south of 42°S, geographic isolation produced by divergence of major oceanic currents, and the existence of refugia during glaciations, enabled species diversification. Radiation could have been limited by narrow continental shelves between 10°,42°. Asymmetries in latitudinal diversity trends between hemispheres show that there is not a single general factor determining large-scale diversity patterns. [source] Numerical modelling of 3D fluid flow and oxygen isotope exchange in fractured media: spatial distribution of isotope patternsGEOFLUIDS (ELECTRONIC), Issue 4 2007C. SAVARD Abstract An understanding of fluid flow, mass transport and isotopic exchange in fractured rock is required to understand the origin of several geological processes including hydrothermal mineral deposits. The numerical model HydroGeoSphere simulates 3D advection, molecular diffusion, mechanical dispersion and isotopic exchange in a discretely fractured porous media, and can be used to better understand the processes of mass transport and isotopic exchange in fractured rocks. Study of 18O isopleth patterns for different types of fractures and fracture networks with a range of structural complexity and hydraulic properties shows that fracture properties and geometry control mass transport and isotopic exchange. The hydraulic properties, as well as the density, spacing, and connectivity of fractures determine the isotopic patterns. Asymmetries in the geometry of oxygen isotope patterns could be used to determine the direction of hydrothermal fluid flow. [source] Geomorphic constraints on the active tectonics of southern TaiwanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2007Lucy A. Ramsey SUMMARY Taiwan is a region of rapid active tectonics, yet the study of the tectonic processes that shape the interior of the island is difficult due to the high rates of erosion and dense vegetation. We use digital topography to look for indications of active deformation preserved in the local geomorphology. In particular, anomalies in the regional pattern of drainage are used to infer zones of enhanced tectonic activity. The apparent anticlockwise rotation of major river systems in plan view indicates the presence of a diffuse zone of left-lateral shear running down the southeastern side of Taiwan. Asymmetries in the catchments of individual drainage basins show the influence of varying rates of uplift across southern Taiwan, with the most rapid uplift close to Taitung at the indentation point of the Luzon arc with the Chinese continental margin. Our interpretations, though based predominantly on remote-sensing observations, are consistent with the available field evidence. This study demonstrates the usefulness of drainage basins as tectonic markers in the quantification of regional strain and uplift, which may have wider applicability in other deforming parts of the world. [source] Accruals quality and corporate cash holdingsACCOUNTING & FINANCE, Issue 1 2009Pedro J. García-Teruel G31; G32 Abstract This Work Uses Panel Data For Firms Listed In The Spanish Stock Exchange Over The Period From 1995 To 2001 To Analyse The Effect Of Accounting Quality On Cash Holdings. The Results Show That Firms With Good Accruals Quality Hold Lower Cash Levels Than Firms With Poor Accruals Quality. This Finding Suggests That The Quality Of Accounting Information May Reduce The Negative Effects Of Information Asymmetries And Adverse Selection Costs, Allowing Firms To Reduce Their Level Of Corporate Cash Holdings. The Results Also Show That Cash Holdings Decrease When Firms Increase Their Use Of Bank Debt And In The Presence Of Cash Substitutes. In Contrast With This, Firms With Higher Cash Flow Hold Higher Levels Of Cash. [source] Asymmetries in Transatlantic Monetary Policy-making: Does the ECB Follow the Fed?,JCMS: JOURNAL OF COMMON MARKET STUDIES, Issue 5 2005ANSGAR BELKE The belief that the European Central Bank (ECB) follows the US Federal Reserve (the Fed) in setting its policy is so entrenched with market participants and commentators that the search for empirical support would seem to be a trivial task. However, this is not the case. We find that the ECB is indeed often influenced by the Fed, but the reverse is true at least as often if one considers longer sample periods. There is empirically little support for the proposition that there has for a long time been a systematic asymmetric leader-follower relationship between the ECB and the Fed. Only after September 2001 is there more evidence of such an asymmetry. There is a clear-cut structural break between the period pre-economic and monetary union (EMU) and EMU itself in terms of the relationship between short-term interest rates on both sides of the Atlantic. [source] Monetary Policies in the Presence of AsymmetriesJCMS: JOURNAL OF COMMON MARKET STUDIES, Issue 4 2000Paul De Grauwe In this article we study the theory of monetary policy when the monetary authority faces asymmetries in the countries constituting the monetary union. We identify two asymmetries (shocks and transmission) in the context of a two-country model. A general finding is that, as the degree of asymmetries increases, the effectiveness of stabilization of output and unemployment is reduced. As a result, when asymmetries increase, the stabilization effort of the central bank declines for given preferences about stabilization. We also find that the central bank can improve the efficiency of its monetary policies when asymmetries in the transmission exist, by using national information in the setting of optimal policies. The declared strategy of the ECB conflicts with this prescription. However, in practice the ECB is likely to follow this prescription. [source] Financial Markets, Development and Economic Growth: Tales of Informational AsymmetriesJOURNAL OF ECONOMIC SURVEYS, Issue 3 2004Salvatore Capasso Abstract., The development of financial systems is very often characterised by the development of innovative financial contracts which allow a more efficient allocation of resources and a higher level of capital productivity and economic growth. By exploiting the microeconomic theory of the optimal financial contract under asymmetric information, economists have recently managed to shed new light on the well studied issue of the relationship between financial market development and economic growth. This paper reviews the most recent progress of this literature which shows that the amount of information asymmetry in the credit market and the degree of heterogeneity between borrowers (typically firms) and lenders (typically workers or savers) determine the nature of the financial system. Differences in endowments and in the level of information distribution can give rise to very different financial contracts which affect, and in turn are affected, by capital accumulation and growth. [source] Revisiting Hrdli,ka and Boas: Asymmetries of Race and Anti-Imperialism in Interwar AnthropologyAMERICAN ANTHROPOLOGIST, Issue 1 2010Robert Oppenheim ABSTRACT, Physical anthropologist Ale, Hrdli,ka is often remembered as an institutional and political opponent of Franz Boas and as an advocate of racial typology against which the Boasian antiracialist position in American anthropology developed. I argue that Hrdli,ka nonetheless also has more subtle lessons to offer about the political limits of Boasian antiracism. Examining Hrdli,ka's engagement with the politics of Europe and East Asia from the 1920s to the 1940s, particularly with the intellectual grounding of Japanese imperialism, I suggest that he was perhaps uniquely cognizant of a "second problem of race in the world",the racist assimilationism of the Japanese empire,vis-à-vis the Boasian grasp of race, rooted in a response to U.S. and Nazi racisms, as a category of invidious difference. Moreover, I contend that the lacuna that Hrdli,ka helps us identify has continued to haunt the discipline at certain key moments of Boasian critique of other ideological forces. [source] Deciduous tooth crown size and asymmetry in strabismic childrenORTHODONTICS & CRANIOFACIAL RESEARCH, Issue 4 2002T Heikkinen Structured Abstract Authors , Heikkinen T, Alvesalo L, Tienari J Objectives , To explore deciduous tooth crown dimensions in strabismic children and the relationship between the type of strabismus and tooth crown mesio-distal (M-D) and labio-lingual (L-L) size asymmetries. Material , Dental casts at mixed dentition of 2159 Collaborative Perinatal Study black and white children were measured, 123 of them strabismic at 1 year of age, age ranging from 6 to 12 years. Methods, Directional and fluctuating asymmetries in antimeric teeth were explored in various types of strabismus having unilateral, bilateral or alternating expression. ANOVA and T-square test were used for size comparisons and calculated asymmetries were explored by comparing the variances and Pearson correlations. Results , Strabismus was associated with significant M-D size increase of deciduous maxillary canines in black boys and white girls, black girls had size reduction in their mandibular canine, but white boys were unaffected. Right side size dominance was found in the strabismic children in the lower second deciduous molar M-D dimensions and in the children with alternating strabismus in their upper deciduous canine M-D dimensions. Children with unilateral strabismus had random fluctuating dental asymmetry in their upper deciduous second molar L-L dimensions when compared with healthy normals. Higher left-right correlations were found in lower second deciduous molar dimensions in strabismic girls when compared with that in controls and in strabismic boys, suggesting better developmental canalization in female. Conclusions , Asymmetries in the head area, such as promoted here in strabismic children, may have associations with asymmetries in the dentition, focusing the embryonal origins and timing of developmental processes. [source] On Business Cycle Asymmetries in G7 CountriesOXFORD BULLETIN OF ECONOMICS & STATISTICS, Issue 3 2004Khurshid M. Kiani Abstract We investigate whether business cycle dynamics in seven industrialized countries (the G7) are characterized by asymmetries in conditional mean. We provide evidence on this issue using a variety of time series models. Our approach is fully parametric. Our testing strategy is robust to any conditional heteroskedasticity, outliers, and/or long memory that may be present. Our results indicate fairly strong evidence of nonlinearities in the conditional mean dynamics of the GDP growth rates for Canada, Germany, Italy, Japan, and the US. For France and the UK, the conditional mean dynamics appear to be largely linear. Our study shows that while the existence of conditional heteroskedasticity and long memory does not have much effect on testing for linearity in the conditional mean, accounting for outliers does reduce the evidence against linearity. [source] Hair Whorls in the Dog (Canis familiaris), Part II: AsymmetriesTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 3 2010Lisa M. Tomkins Abstract In horses and cattle, hair whorls have been shown to act as a structural marker of reactivity and behavioral lateralization. Few studies on canine whorls have been reported and none have assessed whorl position or direction of flow. This study describes the distribution and characteristics of whorl in each of 10 regions in which whorls are typically located in dogs. Hair whorls were assessed in dogs (n = 120) and were recorded as clockwise or counterclockwise in the cephalic, cervical (dorsal, lateral, ventral), thoracic and brachial axillary, chest, shoulders, elbows, abdominal, and ischiatic regions. Bilateral whorls, including brachial axillary, elbow, abdominal and ischiatic whorls, rotated in opposing directions, allowing the dog's overall hair coat to be symmetrical. Cephalic, brachial axillary, and ischiatic whorls were consistent in their direction; cephalic and ischiatic whorls were clockwise on the right side of the body, and counterclockwise on the left, whereas right brachial axillary whorls were counterclockwise and left were clockwise. The central chest whorl was predominantly counterclockwise (91.21%). Direction of whorls was associated with several factors, including coat length, coat thickness, sex and source of the dog. Anat Rec, 2010. © 2009 Wiley-Liss, Inc. [source] Technology Adoption and the Emergence of Regional AsymmetriesTHE JOURNAL OF INDUSTRIAL ECONOMICS, Issue 1 2000Emanuele Giovannetti The model explains the emergence of asymmetric productive structures among regions based on adoption of a quality improving technology. Firms' products are differentiated both in location and quality, location is given. We characterize symmetric and asymmetric equilibria of the two stage game in price and adoption. Asymmetric equilibria display partial adoption frequencies and regular geographical patterns of adoptions. The asymmetry of the economy has, often, a reverse U-shaped relation with the innovation size. Market integration is an obstacle for the full adoption of the new technology and favours the emergence of regional asymmetries. [source] Commentary: Is It Possible to Determine the Extent to Which Informational Asymmetries and Prejudice Bias Responses?THE JOURNAL OF LAW, MEDICINE & ETHICS, Issue 4 2009Terrance HurleyArticle first published online: 17 DEC 200 This commentary provides a brief overview of the methods and results presented by Jennifer Kuzma, Pouya Najmaie, and Joel Larson in "Evaluating Oversight Systems for Emerging Technologies: A Case Study of Genetically Engineered Organisms." It offers suggestions regarding how supplemental information might be used to gain additional insights into the authors' results and how future research could further enhance our understanding of the attributes and outcomes of regulatory oversight for genetically engineered organisms. [source] Asymmetries in the nucleosome core particle at 2.5,Å resolutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2000Joel M. Harp The 2.5,Å X-ray crystal structure of the nucleosome core particle presented here provides significant additions to the understanding of the nucleosome, the fundamental unit of chromatin structure. Extensions are made to the structure of the N-terminal histone tails and details are provided on hydration and ion binding. The structure is composed of twofold symmetric molecules, native chicken histone octamer cores and the DNA palindrome, which were expected to form a perfectly twofold symmetric nucleosome core particle. In fact, the result is asymmetric owing to the binding of the DNA to the protein surface and to the packing of the particles in the crystal lattice. An analysis is made of the asymmetries by comparisons both within the nucleosome core particle and to the structure of the histone octamer core of the nucleosome. [source] Temperament, Tympanum, and Temperature: Four Provisional Studies of the Biobehavioral Correlates of Tympanic Membrane Temperature AsymmetriesCHILD DEVELOPMENT, Issue 3 2002W. Thomas Boyce Previous research in both humans and nonhuman primates suggests that subtle asymmetries in tympanic membrane (TM) temperatures may be related to aspects of cognition and socioaffective behavior. Such associations could plausibly reflect lateralities in cerebral blood flow that support side-to-side differences in regional cortical activation. Asymmetries in activation of the left and right frontal cortex, for example, are correlates of temperamental differences in child behavior and markers of risk status for affective and anxiety disorders. Tympanic membrane temperatures might thus reflect the neural asymmetries that subserve individual differences in temperament and behavior. This report merged findings from four geographically and demographically distinctive studies, which utilized identical thermometry methods to examine associations between TM temperature asymmetries and biobehavioral attributes of 4- to 8-year-old children (N= 468). The four studies produced shared patterns of associations that linked TM temperature lateralities to individual differences in behavior and socioaffective difficulties. Warmer left TMs were associated with "surgent," affectively positive behaviors, whereas warmer right TMs were related to problematic, affectively negative behaviors. Taken together, these findings suggest that asymmetries in TM temperatures could be associated with behavior problems that signal risk for developmental psychopathology. [source] Asymmetry of the active nonweightbearing foot and ankle range of motion for dorsiflexion-plantar flexion and its coupled movements in adultsCLINICAL ANATOMY, Issue 7 2007Virgilio F. Ferrario Abstract Asymmetries in ankle range of motion (ROM) have been reported, but often the uninvolved limb is used as a reference in clinical practice. The study wanted to quantify the intraindividual asymmetries in dorsi-plantar flexion foot and ankle ROM and its coupled foot movements. Active triplanar nonweightbearing ROM of the foot and ankle was recorded in young healthy adults (30 male volunteers, mean age 22.8 years; 35 female volunteers, mean age 23.8 years) using an optoelectronic set-up. The sagittal plane movement (mean ROM female subjects right side 71.3°, left side 71.4°, P > 0.05; mean ROM male subjects right side 69°, left side 68.9°, P > 0.05; sex difference, P < 0.001) was coupled with frontal (mean ROM female subjects right side 16.6°, left side 14.8°, P > 0.05; male subjects right side 17°, left side 15.3°; P > 0.05; no sex difference) and horizontal (mean ROM female subjects right side 19.6°, left side 18.8°, P < 0.001; male subjects right side 17.6°, left side 16.2°, P < 0.001; sex < 0.001) plane motions. Individual fluctuating asymmetries up to 15° (principal movement), and up to 29° (associated movements) were measured. Overall, 20% of female and 34% of male subjects had principal plane asymmetries >5°, and 50% of the subjects had asymmetries >5° in the associated movements. In young adults, individual asymmetries in ankle joint complex dorsi-plantar flexion should be taken into account when using the uninvolved, contralateral limb as a reference for clinical examination. Clin. Anat. 20:834,842, 2007. © 2007 Wiley-Liss, Inc. [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] Fluctuating Asymmetry, Sexual Selection, and Survivorship in Male Dark-Winged DamselfliesETHOLOGY, Issue 9 2002Michelle L. Beck We examined fluctuating asymmetry and morphology as they relate to reproductive success, territoriality, and relative survivorship in the dark-winged damselfly Calopteryx maculata. Fluctuating asymmetry was not correlated with any aspect of morphology in males, but it did predict mating status in males. Mating males showed significantly lower levels of forewing asymmetry than did non-mating males holding adjacent territories. While fluctuating asymmetry did not relate to survivorship or resource holding ability, body size did. Larger males were able to hold territories longer and lived longer than smaller individuals. We suggest that size is of greater importance in this species with regards to fitness and that fluctuating asymmetry may play a minor role by impacting short-term mating success. [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] Tensile-Compressive Creep Asymmetry of Recent Die Cast Magnesium Alloys,ADVANCED ENGINEERING MATERIALS, Issue 9 2007S. Xu The tensile-compressive creep asymmetry of die cast magnesium alloys is experimentally explored and the possible deformation mechanisms are discussed. Creep tests were performed under tension and compression at 125,°C and 150,°C on die cast Mg alloys AM50, AE44 and AJ62A. Higher tensile than compressive creep strengths were observed for all alloys except for low pressure die cast AM50 at a low creep stress of 35 MPa at 125,°C. An aging treatment of 250 hours at 180,°C was employed for AM50 samples to obtain an over-aged microstructure that would minimize the effects of dynamic precipitation of ,-Mg17Al12 on creep. The creep data for the aged samples showed significant scatter, and the trend in tensile-compressive creep asymmetry of the aged samples is not clear for the short-term creep tests under high creep stresses. [source] Market Segmentation and Information Asymmetry in Chinese Stock Markets: A VAR AnalysisFINANCIAL REVIEW, Issue 4 2003Jian Yang G15/G32 Abstract This study examines the market segmentation and information asymmetry patterns in Chinese stock markets. The recursive cointegration analysis confirms that each of six markets is not linked with other markets in the long run. Further, the result from data-determined forecast error variance decomposition clearly shows that foreign investors in the Shanghai B-share market are better informed than Chinese domestic investors in two A-share markets and foreign investors in Shenzhen and Hong Kong markets over time. The finding challenges a widespread assumption of less informed foreign investors in the literature, but suggests that foreign investors could be more informed in emerging markets. [source] Institutional Investors and Information Asymmetry: An Event Study of Self-Tender OffersFINANCIAL REVIEW, Issue 2 2003Michele O'Neill G14/G20/G32 Abstract Our research compares the asymmetric information costs of firms with low levels of institutional ownership to those with high levels. We use self-tender offers as an information event. Our results show that higher institutional ownership, particularly a higher number of institutional investors, is associated with a lower degree of informed trading. These results persist even after we control for differences in trading activity among our sample firms. [source] Bone remodelling following a lower leg fracture in the 11,000-year-old hunter-gatherer from Vado all' Arancio (Italy)INTERNATIONAL JOURNAL OF OSTEOARCHAEOLOGY, Issue 6 2002B. M. Holt Abstract The Upper Palaeolithic skeleton from Vado all'Arancio (Italy), dated to about 11,330 BP, exhibits a severe ankle fracture healed with residual deformation. Following recovery, this young hunter-gatherer continued to walk for an extended period of time, albeit in a mechanically altered manner. While right-left differences in external lower limb bone measurements are relatively low, biomechanical analysis of femur and tibia indicates unusually pronounced asymmetry in all cross-sectional measures of diaphyseal strength. Asymmetry results primarily from normal side endosteal hypertrophy, and not from hypotrophy of the injured limb, suggesting that this individual resumed active life following recovery. This pattern of asymmetry underscores the role of physical activity in maintaining bone mass. Copyright © 2002 John Wiley & Sons, Ltd. [source] Asymmetry in the detection of shapes from shading in infants,JAPANESE PSYCHOLOGICAL RESEARCH, Issue 3 2008TOMOKO IMURA Abstract:, We investigated 3- and 4-month-old infants' sensitivity to differences defined by shading using a paired-comparison familiarity/novelty preference procedure. Infants were familiarized with a pair of displays consisting of homogeneous shaded disks, and then were tested with two displays: the familiar display and a novel one containing shaded disks with reversed polarity (defined as the target). Experiment 1 examined two assumptions on discerning shapes from shading in infants by manipulating the orientations in the shading gradient of stimuli. When the orientation of the shading gradient was vertical, 4-month-old infants looked at the novel display for a longer time during the test trial. However, they failed to detect differences when the orientation of shading gradients was horizontal. Three-month-old infants did not detect differences in either orientation of the shading gradient. Experiment 2 examined asymmetry in the detection of convex versus concave shapes. Four-month-old infants failed to detect the target when the orientation of the shading grating was vertical and the target was convex. Taken with the results of Experiment 1, concave shapes were much easier to detect than convex shapes for 4-month-olds. This asymmetry suggests that 4-month-old infants process shading information in the same manner as adults. [source] IAS Versus U.S. GAAP: Information Asymmetry,Based Evidence from Germany's New MarketJOURNAL OF ACCOUNTING RESEARCH, Issue 3 2003CHRISTIAN LEUZ abstract Motivated by the debate about globally uniform accounting standards, this study investigates whether firms using U.S. generally accepted accounting principles (GAAP) vis-à-vis international accounting standards (IAS) exhibit differences in several proxies for information asymmetry. It exploits a unique setting in which the two sets of standards are put on a level playing field. Firms trading in Germany's New Market must choose between IAS and U.S. GAAP for financial reporting, but face the same regulatory environment otherwise. Thus, institutional factors such as listing requirements, market microstructure, and standards enforcement are held constant. In this setting, differences in the bid-ask spread and share turnover between IAS and U.S. GAAP firms are statistically insignificant and economically small. Subsequent analyses of analysts' forecast dispersion, initial public offering underpricing, and firms' standard choices corroborate these findings. Thus, at least for New Market firms, the choice between IAS and U.S. GAAP appears to be of little consequence for information asymmetry and market liquidity. These findings do not support widespread claims that U.S. GAAP produce financial statements of higher informational quality than IAS. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||