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Absolute Size (absolute + size)
Selected AbstractsBelow-ground carbon flux and partitioning: global patterns and response to temperatureFUNCTIONAL ECOLOGY, Issue 6 2008C. M. Litton Summary 1The fraction of gross primary production (GPP) that is total below-ground carbon flux (TBCF) and the fraction of TBCF that is below-ground net primary production (BNPP) represent globally significant C fluxes that are fundamental in regulating ecosystem C balance. However, global estimates of the partitioning of GPP to TBCF and of TBCF to BNPP, as well as the absolute size of these fluxes, remain highly uncertain. 2Efforts to model below-ground processes are hindered by methodological difficulties for estimating below-ground C cycling, the complexity of below-ground interactions, and an incomplete understanding of the response of GPP, TBCF and BNPP to climate change. Due to a paucity of available data, many terrestrial ecosystem models and ecosystem-level studies of whole stand C use efficiency rely on assumptions that: (i) C allocation patterns across large geographic, climatic and taxonomic scales are fixed; and (ii) c. 50% of TBCF is BNPP. 3Here, we examine available information on GPP, TBCF, BNPP, TBCF : GPP and BNPP : TBCF from a diverse global data base of forest ecosystems to understand patterns in below-ground C flux and partitioning, and their response to mean annual temperature (MAT). 4MAT and mean annual precipitation (MAP) covaried strongly across the global forest data base (37 mm increase in MAP for every 1 °C increase in MAT). In all analyses, however, MAT was the most important variable explaining observed patterns in below-ground C processes. 5GPP, TBCF and BNPP all increased linearly across the global scale range of MAT. TBCF : GPP increased significantly with MAT for temperate and tropical ecosystems (> 5 °C), but variability was high across the data set. BNPP : TBCF varied from 0·26 to 0·53 across the entire MAT gradient (,5 to 30 °C), with a much narrower range of 0·42 to 0·53 for temperate and tropical ecosystems (5 to 30 °C). 6Variability in the data sets was moderate and clear exceptions to the general patterns exist that likely relate to other factors important for determining below-ground C flux and partitioning, in particular water availability and nutrient supply. Still, our results highlight global patterns in below-ground C flux and partitioning in forests in response to MAT that in part confirm previously held assumptions. [source] Evolution of M1 crown size and cusp proportions in the genus HomoJOURNAL OF ANATOMY, Issue 5 2009Rolf Quam Abstract Previous research into tooth crown dimensions and cusp proportions has proved to be a useful way to identify taxonomic differences in Pliocene and Pleistocene fossil hominins. The present study has identified changes in both M1 crown size and cusp proportions within the genus Homo, with M1 overall crown size reduction apparently occurring in two main stages. The first stage (a reduction of ca. 17%) is associated with the emergence of Homo ergaster and Homo erectus sensu stricto. The second stage (a reduction of ca. 10%) occurs in Homo sapiens, but the reduced modern human M1 tooth crown size was only attained in Upper Paleolithic times. The absolute sizes of the individual cusps are highly positively correlated with overall crown size and dental reduction produces a reduction in the absolute size of each of the cusps. Most of the individual cusps scale isometrically with crown size, but the paracone shows a negative allometric relationship, indicating that the reduction in paracone size is less than in the other M1 cusps. Thus, the phylogenetically oldest cusp in the upper molars also seems to be the most stable cusp (at least in the M1). The most striking change in M1 cusp proportions is a change in the relative size of the areas of the paracone and metacone. The combination of a small relative paracone and a large relative metacone generally characterizes specimens attributed to early Homo, and the presence of this character state in Australopithecus and Paranthropus suggests it may represent the primitive condition for the later part of the hominin clade. In contrast, nearly all later Homo taxa, with the exception of Homo antecessor, show the opposite condition (i.e. a relatively large paracone and a relatively small metacone). This change in the relationship between the relative sizes of the paracone and metacone is related to an isometric reduction of the absolute size of the metacone. This metacone reduction occurs in the context of relative stability in the paracone as crown size decreases. Among later Homo taxa, both Homo heidelbergensis and Homo neanderthalensis show a further reduction of the metacone and an enlargement of the hypocone. Fossil and contemporary H. sapiens samples show a trend toward increasing the relative size of the protocone and decreasing the relative size of the hypocone. In Europe, modern human M1 cusp proportions are essentially reached during the Upper Paleolithic. Although some variation was documented among the fossil taxa, we suggest that the relative size of the M1 paracone and metacone areas may be useful for differentiating the earliest members of our genus from subsequent Homo species. [source] Magnetic Resonance Imaging Outcomes From a Comprehensive Magnetic Resonance Study of Children With Fetal Alcohol Spectrum DisordersALCOHOLISM, Issue 10 2009Susan J. Astley Background:, Magnetic resonance (MR) technology offers noninvasive methods for in vivo assessment of neuroabnormalities. Methods:, A comprehensive neuropsychological/psychiatric battery, coupled with MR imaging, (MRI), MR spectroscopy (MRS), and functional MRI (fMRI) assessments, were administered to children with fetal alcohol spectrum disorders (FASD) to determine if global and/or focal abnormalities could be identified, and distinguish diagnostic subclassifications across the spectrum. The 4 study groups included: (i) fetal alcohol syndrome (FAS)/partial FAS (PFAS); (ii) static encephalopathy/alcohol exposed (SE/AE); (iii) neurobehavioral disorder/alcohol exposed (ND/AE) as diagnosed with the FASD 4-Digit Code; and (iv) healthy peers with no prenatal alcohol exposure. Presented here are the MRI assessments that were used to compare the sizes of brain regions between the 4 groups. The neuropsychological/behavioral, MRS, and fMRI outcomes are reported separately. Results:, Progressing across the 4 study groups from Controls to ND/AE to SE/AE to FAS/PFAS, the mean absolute size of the total brain, frontal lobe, caudate, putamen, hippocampus, cerebellar vermis, and corpus callosum length decreased incrementally and significantly. The FAS/PFAS group (the only group with the 4-Digit FAS facial phenotype) had disproportionately smaller frontal lobes relative to all other groups. The FAS/PFAS and SE/AE groups [the 2 groups with the most severe central nervous system (CNS) dysfunction] had disproportionately smaller caudate regions relative to the ND/AE and Control groups. The prevalence of subjects in the FAS/PFAS, SE/AE, and ND/AE groups that had 1 or more brain regions, 2 or more SDs below the mean size observed in the Control group was 78, 58, and 43%, respectively. Significant correlations were observed between size of brain regions and level of prenatal alcohol exposure, magnitude of FAS facial phenotype, and level of CNS dysfunction. Conclusions:, Magnetic resonance imaging provided further validation that ND/AE, SE/AE, and FAS/PFAS as defined by the FASD 4-Digit Code are 3 clinically distinct and increasingly more affected diagnostic subclassifications under the umbrella of FASD. Neurostructural abnormalities are present across the spectrum. MRI could importantly augment diagnosis of conditions under the umbrella of FASD, once population-based norms for structural development of the human brain are established. [source] A structure and energy dissipation efficiency of relativistic reconfinement shocksMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009Krzysztof Nalewajko ABSTRACT We present a semi-analytical hydrodynamical model for the structure of reconfinement shocks formed in astrophysical relativistic jets interacting with external medium. We take into account exact conservation laws, both across the shock front and in the zone of the shocked matter, and exact angular relations. Our results confirm a good accuracy of the approximate formulae derived by Komissarov & Falle. However, including the transverse pressure gradient in the shocked jet, we predict an absolute size of the shock to be about twice larger. We calculate the efficiency of the kinetic energy dissipation in the shock and show a strong dependence on both the bulk Lorentz factor and opening angle of the jet. [source] New perspectives for estimating body condition from mass/length data: the scaled mass index as an alternative methodOIKOS, Issue 12 2009Jordi Peig Body condition is assumed to influence an animal's health and fitness. Various non-destructive methods based on body mass and a measure of body length have been used as condition indices (CIs), but the dominant method amongst ecologists is currently the calculation of residuals from an ordinary least squares (OLS) regression of body mass against length. Recent studies of energy reserves in small mammals and starlings claimed to validate this method, although we argue that they did not include the most appropriate tests since they compared the CI with the absolute size of energy reserves. We present a novel CI (the ,scaled mass index') based on the central principle of scaling, with important methodological, biological and conceptual advantages. Through a reanalysis of data from small mammals, starlings and snakes, we show that the scaled mass index is a better indicator of the relative size of energy reserves and other body components than OLS residuals, performing better in all seven species and in 19 out of 20 analyses. We also present an empirical and theoretical comparison of the scaled mass index and OLS residuals as CIs. We argue that the scaled mass index is a useful new tool for ecologists. [source] Comparison of optical coherence tomography and fundus photography for measuring the optic disc sizeOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2006Aljoscha S. Neubauer Abstract Purpose:, To assess the agreement and repeatability of optic nerve head (ONH) size measurements by optical coherence tomography (OCT) as compared to conventional planimetry of fundus photographs in normal eyes. Methods:, For comparison with planimetry the absolute size of the ONH of 25 eyes from 25 normal subjects were measured by both OCT and digital fundus photography (Zeiss FF camera 450). Repeatability of automated Stratus OCT measurements were investigated by repeatedly measuring the optic disc in five normal subjects. Results:, Mean disc size was 1763 ± 186 vertically and 1632 ± 160 ,m horizontally on planimetry. On OCT, values of 1772 ± 317 ,m vertically (p = 0.82) and a significantly smaller horizontal diameter of 1492 ± 302 ,m (p = 0.04) were obtained. The 95% limits of agreement were (,546 ,m; +527 ,m) for vertical and (,502 ,m; +782 ,m) for horizontal planimetric compared to OCT measurements. In some cases large discrepancies existed. Repeatability of automatic measurements of the optic disc by OCT was moderately good with intra-class correlation coefficients (ICC) of 0.78 horizontally and 0.83 vertically. The coefficient of repeatability indicating instrument precision was 80 ,m for horizontal and 168 ,m for vertical measurements. Conclusions:, OCT can be used to determine optic disc margins in moderate agreement with planimetry in normal subjects. However, in some cases significant disagreement with photographic assessment may occur making manual inspection advisable. Automatic disc detection by OCT is moderately repeatable. [source] The South, Medium-Sized Cities, and a New Look at the Determinants of African-American RepresentationPOLITICS & POLICY, Issue 4 2003Peter F. Burns This paper examines the determinants of African-American representation on city councils in medium-sized urban areas to provide greater insight into the strategies African-Americans use to achieve political incorporation and the extent to which traditionally excluded groups have access to elected positions in the United States. I argue that previous studies generate varied conclusions about the determinants of African-American representation on city councils because scholars fail to recognize that minority political strategies may vary based on the relative and absolute size of the minority population. I examine the determinants of African-American representation in medium-sized cities to consider whether African-Americans employ an electoral mobilization strategy when they make up a large percentage of the electorate but lack the large absolute numbers necessary to sustain demand-protest activities. A regression analysis indicates that the percentage of African-Americans in the electorate is the only factor that significantly affects African-American descriptive representation. This finding supports the hypothesis that African-Americans use an electoral strategy when they lack large absolute numbers. This research also confirms Guinier's (1994) claims that African-Americans fail to achieve proportional representation in the current electoral system and suggests that the plurality system comes with high start-up costs for a traditionally excluded group. [source] Epidermal kinetic alterations required to generate the psoriatic phenotype: a reappraisalCELL PROLIFERATION, Issue 3 2010T. Simonart Objectives:, Although there have been major advances in understanding immunopathogenesis of psoriasis, the basic processes causing psoriatic morphology remain to be identified. Materials and methods:, Our group has designed a systematic review of studies (1962,2009) on keratinocyte kinetics in psoriasis. We obtained data from MEDLINE, PubMed, Current Contents, reference lists and specialist textbooks. A general equation for evolution of the differentiated epidermis has been analysed. Necessary conditions for observed qualitative change in homeostasis between normal skin and established psoriatic lesions were determined. Results and discussion:, Increase in the number of cell divisions (or imbalance in symmetric division rates of committed progenitor cells) and/or decrease in physiological apoptosis in the germinative compartment, together with feedback loops that limit thickening of the skin, are required to generate psoriatic morphology, that is, to increase the absolute size but decrease relative size of the differentiated cell compartment with respect to the germinative compartment. [source] HAVE MALE AND FEMALE GENITALIA COEVOLVED?EVOLUTION, Issue 9 2005A PHYLOGENETIC ANALYSIS OF GENITALIC MORPHOLOGY AND SEXUAL SIZE DIMORPHISM IN WEB-BUILDING SPIDERS (ARANEAE: ARANEOIDEA) Abstract Sexual size dimorphism (SSD) can strongly influence the evolution of reproductive strategies and life history. If SSD is extreme, and other characters (e.g., genitalic size) also increase with size, then functional conflicts may arise between the sexes. Spiders offer an excellent opportunity to investigate this issue because of their wide range of SSD. By using modern phylogenetic methods with 16 species of orb-weaving spiders, we provide strong evidence for the "positive genitalic divergence" model, implying that sexual genitalic dimorphism (SGD) increases as SSD increases. This pattern is supported by an evolutionary mismatch between the absolute sizes of male and female genitalia across species. Indeed, our findings reveal a dramatic reversal from male genitalia that are up to 87X larger than female genitalia in size-monomorphic species to female genitalia that are up to 2.8X larger in extremely size-dimorphic species. We infer that divergence in SGD could limit SSD both in spiders, and potentially in other taxa as well. Further, male and female body size, as well as male and female genitalia size, are decoupled evolutionarily. Finally, we show a negative scaling (hypoallometry) of male and female genitalic morphology within sexes. Evolutionary forces specific to each sex, such as larger female size (increased fecundity) or smaller male size (enhanced mate-searching ability), may be balanced by stabilizing selection on relative genitalic size. [source] | |||||||||||||