Males of numerous species of harvestman have been reported to be dimorphic with respect to size of the weapon that is used in aggressive encounters with conspecific males. The claim of dimorphism was ...based in every instance on finite mixture modeling of the frequency distribution for size of the weapon, with the detection of bimodality being equated with the detection of dimorphism. I used the Hartigan dip test and frequency histograms to re-examine the original data for size of the weapon in males of five species of harvestman. Distributions for two of the species are unimodal by both dip test and graphical display; distributions for two others have an appearance of bimodality in frequency diagrams but do not depart significantly from unimodality by the dip test; and the distribution for the remaining species is multimodal by the dip test but appears to be unimodal in graphical display. Patterns of bivariate (allometric) variation follow sigmoidal curves for all five species, with the steep part of the curve corresponding with the low point in the histogram for the two species that give an appearance of bimodality. Thus, bimodality — when it can be detected and confirmed — is most likely to be a consequence of an unexpected pattern of allometric variation and not dimorphism.
Instrumented contact experiments are performed on three metallic glasses to systematically study shear band formation near a stress concentration. The results suggest that high local stresses at a ...point in the glass are insufficient to initiate a shear band. Rather, the yield strength must be exceeded along the entire length of a viable shear path in order for a shear band to form. Because of this, conventional analyses to extract shear yield stresses from Hertzian contact experiments overestimate the glass strength by a factor of three or more. In contrast, the interpretation of shear band initiation as yield on a plane agrees with recent experimental observations on metallic glasses that pertain to the slip-line field, and can rationalize the experimental contact load measurements as well as the shear band path.
Several investigations in recent years have reported patterns of discontinuous, biphasic, loglinear variation in the metabolic allometry of aquatic animals. These putative shifts in pattern of ...allometry have been attributed to changes in the primary site for gas exchange from cutaneous to branchial as animals undergo ontogenetic changes in size, shape, and surface area. Because of the important implications of the earlier research with regard to both physiology and evolution, I re-examined data that purportedly support claims of discontinuous, biphasic allometry in oxygen consumption versus body size of American eels (Anguilla rostrata) and spiny lobsters (Sagmariasus verreauxi). I used ANCOVA to fit three different statistical models to each set of logarithmic transformations and then assessed the fits by Akaike's Information Criterion. The observations for both species were described better by a single straight line fitted to the full distribution than by a biphasic model. Eels, lobsters, and other aquatic animals undergo changes in shape and surface area as they grow, but such changes are not necessarily accompanied by changes in the pattern of metabolic allometry.
Nanoindentation measurements were obtained on eight commercially-produced DP980 dual-phase steels to quantify the hardness of the individual constituents, ferrite and martensite, in each steel. Each ...microstructure was also evaluated to determine grain size, martensite volume fraction (MVF), and retained austenite content. Nanoindentation hardnesses and quantitative microstructural measurements were correlated with tensile properties and performance in hole expansion tests to assess the importance of the individual constituent properties. Hole expansion samples were prepared with both sheared edges produced by mechanical punching, and non-deformed edges produced by electric discharge machining (EDM). Average material hardness based on nanoindentation data correlated directly to Vickers hardness measurements, verifying the capability of the nanoindentation technique to produce data consistent with traditional hardness measurements. Yield strength (YS) correlated directly to ferrite hardness indicating that, for a similar MVF and microstructural morphology, the YS is controlled by the strength of the softer matrix phase (ferrite). Hole expansion ratios (HER) on EDM samples decreased with an increase in both martensite and ferrite hardness, indicating that EDM HER values can be enhanced by softening both constituents. Punched-hole HER values decreased with increasing martensite hardness and martensite-to-ferrite hardness ratio, but were independent of ferrite hardness, indicating that softening the martensite while increasing the ferrite hardness could produce a higher HER.
What is complex allometry? Packard, Gary C
Biology open,
12/2023, Letnik:
12, Številka:
12
Journal Article
Recenzirano
Odprti dostop
Complex allometry describes a smooth, curvilinear relationship between logarithmic transformations of a biological variable and a corresponding measure for body size when the observations are ...displayed on a bivariate graph with linear scaling. The curvature in such a display is commonly captured by fitting a quadratic equation to the distribution; and the quadratic term is typically interpreted, in turn, to mean that the mathematically equivalent equation for describing the arithmetic distribution is a two-parameter power equation with an exponent that changes with body size. A power equation with an exponent that is itself a function of body size is virtually uninterpretable, yet numerous attempts have been made in recent years to incorporate such an exponent into theoretical models for the evolution of form and function in both plants and animals. However, the curvature that is described by a quadratic equation fitted to logarithms usually means that an explicit, non-zero intercept is required in the power equation describing the untransformed distribution - not that the exponent in the power equation varies with body size. Misperceptions that commonly accompany reports of complex allometry can be avoided by using nonlinear regression to examine untransformed data.
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Apolipoproteins AI and B are structural components of lipoprotein particles, and also determinants of the metabolic fate of the encapsulated lipid, cholesterol and triglyceride. Development of ...accurate assays for these apolipoproteins has opened the way for their use as predictors of coronary heart disease risk. Interpretation of AI and apo B levels is best undertaken with background knowledge of the metabolic status of an individual, especially the lipolytic capacity as reflected in the triglyceride concentration. Those with raised triglyceride, in general, not only have an elevated apo B/apo AI ratio, but also apo B‐containing lipoproteins with a prolonged residence time and hence ample opportunity for modification and damage. Assessment of apolipoprotein levels is an aid to risk prediction and can be useful in tailoring treatment.
LDL (low-density lipoprotein) is the major carrier of cholesterol in human plasma, and as such is intimately involved in the process of atherosclerosis. The lipoprotein class comprises a number of ...distinct subfractions, and is commonly divided into large, intermediate and small sized particles. Small, dense LDLs are held to be particularly atherogenic, since these particles are retained preferentially by the artery wall, are readily oxidized and carry an enzyme believed to have an important role in atherosclerosis, i.e. lipoprotein-associated phospholipase A(2). Generation of small, dense LDL occurs by intravascular lipoprotein remodelling as a result of disturbances such as Type II diabetes, metabolic syndrome, renal disease and pre-eclampsia. The key predisposing factor is the development of hypertriglyceridaemia, in particular elevation in the plasma concentration of large, triacylglycerol-rich VLDL (very-low-density lipoprotein). This leads to the formation of slowly metabolized LDL particles (5-day residence time), which are subject to exchange processes that remove cholesteryl ester from the particle core and replace it with triacylglycerol. LDL, so altered, is a potential substrate for hepatic lipase; if the activity of the enzyme is high enough, lipolysis will generate smaller, denser particles. Correction of the dyslipidaemia associated with small, dense LDL is possible using fibrates and statins, and this may contribute to the clinical benefits seen with these drugs. Fibrates act to lower plasma triacylglycerol (VLDL) levels, and so correct the underlying metabolic disturbance. Statins remove VLDL particles via receptor-mediated pathways and reduce the residence time (and hence limit the potential for remodelling) of LDL in the circulation.
Background
Triglyceride‐rich lipoproteins and their remnants have emerged as major risk factors for cardiovascular disease. New experimental approaches are required that permit simultaneous ...investigation of the dynamics of chylomicrons (CM) and apoB48 metabolism and of apoB100 in very low‐density lipoproteins (VLDL).
Methods
Mass spectrometric techniques were used to determine the masses and tracer enrichments of apoB48 in the CM, VLDL1 and VLDL2 density intervals. An integrated non‐steady‐state multicompartmental model was constructed to describe the metabolism of apoB48‐ and apoB100‐containing lipoproteins following a fat‐rich meal, as well as during prolonged fasting.
Results
The kinetic model described the metabolism of apoB48 in CM, VLDL1 and VLDL2. It predicted a low level of basal apoB48 secretion and, during fat absorption, an increment in apoB48 release into not only CM but also directly into VLDL1 and VLDL2. ApoB48 particles with a long residence time were present in VLDL, and in subjects with high plasma triglycerides, these lipoproteins contributed to apoB48 measured during fasting conditions. Basal apoB48 secretion was about 50 mg day−1, and the increment during absorption was about 230 mg day−1. The fractional catabolic rates for apoB48 in VLDL1 and VLDL2 were substantially lower than for apoB48 in CM.
Discussion
This novel non‐steady‐state model integrates the metabolic properties of both apoB100 and apoB48 and the kinetics of triglyceride. The model is physiologically relevant and provides insight not only into apoB48 release in the basal and postabsorptive states but also into the contribution of the intestine to VLDL pool size and kinetics.
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There is abundant evidence that the risk of atherosclerotic vascular disease is directly related to plasma cholesterol levels. Accordingly, all of the national and transnational screening and ...therapeutic guidelines are based on total or LDL cholesterol. This presumes that cholesterol is the most important lipoprotein‐related proatherogenic risk variable. On the contrary, risk appears to be more directly related to the number of circulating atherogenic particles that contact and enter the arterial wall than to the measured concentration of cholesterol in these lipoprotein fractions. Each of the atherogenic lipoprotein particles contains a single molecule of apolipoprotein (apo) B and therefore the concentration of apo B provides a direct measure of the number of circulating atherogenic lipoproteins. Evidence from fundamental, epidemiological and clinical trial studies indicates that apo B is superior to any of the cholesterol indices to recognize those at increased risk of vascular disease and to judge the adequacy of lipid‐lowering therapy. On the basis of this evidence, we believe that apo B should be included in all guidelines as an indicator of cardiovascular risk. In addition, the present target adopted by the Canadian guideline groups of an apo B <90 mg dL−1 in high‐risk patients should be reassessed in the light of the new clinical trial results and a new ultra‐low target of <80 mg dL−1 be considered. The evidence also indicates that the apo B/apo A‐I ratio is superior to any of the conventional cholesterol ratios in patients without symptomatic vascular disease or diabetes to evaluate the lipoprotein‐related risk of vascular disease.
Evidence is accumulating about the association between strong family ties and the emotional and physical welfare of older adults, and researchers have identified negative consequences of being ...unmarried, being childless, and/or living alone. These associations have been recognized in multiple contexts, including in Asia where living with a spouse and/or grown children has been shown in some studies to improve elderly well-being. Social support, especially family support, is expected to continue to be important where populations are aging and social safety nets are weak. Using longitudinal data from the 2010 and 2012 waves of the China Family Panel Studies, we focus on the effects of marital status at times 1 and 2, changes in marital status between the two surveys, and other family-related indicators of social connectedness on ratings of depression, levels of life satisfaction, and self-reported physical health among those aged 50 and over. Our sample includes 9831 respondents who have valid data on wellbeing indicators for Wave 1 and Wave 2, as well as complete information on the other covariates controlled in our analysis. In analyses of the full sample, those who were married at both points in time reported lower
scores than those who were never-married, divorced, or widowed at both time points, and those whose unions dissolved in the interval. Those who were married at both times also generally reported greater levels of
than those who were never married at both time points and those who became divorced during the interval. Important underlying gender differences are observed both for life satisfaction and depression. In addition, those who were married at both time points reported being in better
than those who became widowed during the interval (significant primarily for women), and those who had never been married (significant primarily for men). Our study contributes to the literature on social ties and the wellbeing by highlighting the importance of marital status and changing marital status, net of child co-residence and proximity, in China.
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