Body size and latitudinal gradients in regional diversity of New World birds

Axe latitudinal gradients in regional diversity random or biased with respect to body size? Using data for the New World avifauna, I show that the slope of the increase in regional species richness from the Arctic to the equator is not independent of body size. The increase is steepest among small and medium-sized species, and shallowest among the largest species. This is reflected in latitudinal variation in the shape of frequency distributions of body sizes in regional subsets of the New World avifauna. Because species are added disproportionately in small and medium size classes towards low latitudes, distributions become less widely spread along the body size axis than expected from the number of species. These patterns suggest an interaction between the effects of latitude and body size on species richness, implying that mechanisms which vary with both latitude and body size may be important determinants of high tropical diversity in New World birds.

Determinants of tissue Doppler measures of regional diastolic function during dobutamine stress echocardiography

Background Diastolic dysfunction induced by ischemia may alter transmitral blood flow, but this reflects global ventricular function, and pseudonormalization may occur with increased preload. Tissue Doppler may assess regional diastolic function and is relatively load-independent, but limited data exist regarding its application to stress testing. We sought to examine the stress response of regional diastolic parameters to dobutomine echocardiography (DbE). Methods Sixty-three patients underwent study with DbE: 20 with low probability of coronary artery disease (CAD) and 43 with CAD who underwent angiography. A standard DbE protocol was used, and segments were categorized as ischemic, scar, or normal. Color tissue Doppler was acquired at baseline and peak stress, and waveforms in the basal and mid segments were used to measure early filling (Em), late filling (Am), and E deceleration time. Significant CAD was defined by stenoses >50% vessel diameter. Results Diastolic parameters had limited feasibility because of merging of Em and Am waves at high heart rates and limited reproducibility. Nonetheless, compared with normal segments, segments subtended with significant stenoses showed a lower Em velocity at rest (6.2 +/- 2.6 cm/s vs 4.8 +/- 2.2 cm/s, P < .0001) and peak (7.5 +/- 4.2 cm/s vs 5.1 +/- 3.6 cm/s, P < .0001), Abnormal segments also showed a shorter E deceleration time (51 +/- 27 ms vs 41 +/- 27 ms, P = .0001) at base and peak. No changes were documented in Am. The same pattern was seen with segments identified as ischemic with wall motion score. However, in the absence of ischemia, segments of patients with left ventricular hypertrophy showed a lower Em velocity, with blunted Em responses to stress. Conclusion Regional diastolic function is sensitive to ischemia. However, a number of practical limitations limit the applicability of diastolic parameters for the quantification of stress echocardiography.

Automated regional myocardial displacement for facilitating the interpretation of dobutamine echocardiography

Quantification of stress echocardiography may overcome the training requirements and subjective nature of visual wall motion score (WMS) assessment, but quantitative approaches may be difficult to apply and require significant time for image processing. The integral of long-axis myocardial velocity is displacement, which may be represented as a color map over the left ventricular myocardium. This study was designed to explore the feasibility and accuracy of measuring long-axis myocardial displacement, derived from tissue Doppler, for the detection of coronary artery disease (CAD) during dobutamine stress echocardiography (DBE). One hundred thirty patients underwent standard DBE, including 30 patients at low risk of CAD, 30 patients with normal coronary angiography (both groups studied to define normal ranges of displacement), and 70 patients who underwent coronary angiography in whom the accuracy of normal ranges was tested. Regional myocardial displacement was obtained by analysis of color tissue Doppler apical images acquired at peak stress. Displacement was compared with WMS, and with the presence of CAD by angiography. The analysis time was 3.2 +/- 1.5 minutes per patient. Segmental displacement was correlated with wall motion (normal 7.4 +/- 3.2 mm, ischemia 5.8 +/- 4.2 mm, viability 4.6 +/- 3.0 mm, scar 4.5 +/- 3.5 mm, p <0.001). Reversal of normal base-apex displacement was an insensitive (19%) but specific (90%) marker of CAD. The sum of displacements within each vascular territory had a sensitivity and specificity of 89% and 79%, respectively, for prediction of significant CAD, compared with 86% and 78%, respectively, for WMS (p = NS). The displacements in the basal segments had a sensitivity and specificity of 83% and 78%, respectively (p = NS). Regional myocardial displacement during DBE is feasible and offers a fast and accurate method for the diagnosis of CAD. (C),2002 by Excerpta Medica, Inc.

Resources for security and stability? The politics of regional cooperation on the Mekong, 1957-2001

This article tells about the relationship between resource politics and security in international relations. Using the Mekong River Basin as its case study, the article examines the place of resource and development issues in attempts to develop regional institutions. The question of whether a resource development regime with apparently low productivity in terms of technical output, but high levels of resilience and longevity, should be considered a failure or not, is considered. This question is examined within the broader context of Southeast Asian politics during the First, Second, and Third Indochina conflicts as well as the post-cold war era. The article argues that survival and a capacity to change to meet the challenges of extreme broader events are clear evidence of regime success. From this standpoint, the article explores ways in which the Mekong resource regime is linked to more general concerns for political security and stability and may in fact reflect political concerns for subregional neighborhood maintenance.

Intrinsic regional differences in androgen receptors and dihydrotestosterone metabolism in human preadipocytes

Androgens play an important role in regulating the central obesity that is a strong risk factor for cardiovascular disease and insulin resistance. This study confirms that androgen receptors are present in subcultured human preadipocytes, with androgen receptor gene expression and saturable specific dihydrotestosterone binding, dissociation constant 1.02 - 2.56 nM and maximal binding capacity 30.8 - 55.7 fmol/mg protein. There was an intrinsic regional difference in androgen receptor complement, with more androgen receptors in visceral than in subcutaneous preadipocytes. Dihydrotestosterone was metabolised by human preadipocytes, with more androstanediol produced by subcutaneous than visceral preadipocytes. While dihydrotestosterone metabolism was insufficient to explain the regional variation in androgen binding, both of these differences would reduce the androgen responsiveness of the subcutaneous preadipocytes compared with visceral preadipocytes. There were no gender differences in androgen binding or metabolism. While the direct effects of androgens on human PAS remain uncertain, these regional differences suggest that AR-mediated regulation of certain PA functions influences adipose tissue distribution.

Density functional theory analysis of the influence of pore wall heterogeneity on adsorption in carbons

Density functional theory for adsorption in carbons is adapted here to incorporate a random distribution of pore wall thickness in the solid, and it is shown that the mean pore wall thickness is intimately related to the pore size distribution characteristics. For typical carbons the pore walls are estimated to comprise only about two graphene layers, and application of the modified density functional theory approach shows that the commonly used assumption of infinitely thick walls can severely affect the results for adsorption in small pores under both supercritical and subcritical conditions. Under supercritical conditions the Henry's law coefficient is overpredicted by as much as a factor of 2, while under subcritical conditions pore wall heterogeneity appears to modify transitions in small pores into a sequence of smaller ones corresponding to pores with different wall thicknesses. The results suggest the need to improve current pore size distrubution analysis methods to allow for pore wall heterogeneity. The density functional theory is further extended here to allow for interpore adsorbate interactions, and it appears that these interaction are negligible for small molecules such as nitrogen but significant for more strongly interacting heavier molecules such as butane, for which the traditional independent pore model may not be adequate.

Mixed gas equilibrium adsorption on zeolites and energetic heterogeneity of adsorption volume

A model for binary mixture adsorption accounting for energetic heterogeneity and intermolecular interactions is proposed in this paper. The model is based on statistical thermodynamics, and it is able to describe molecular rearrangement of a mixture in a nonuniform adsorption field inside a cavity. The Helmholtz free energy obtained in the framework of this approach has upper and lower limits, which define a permissible range in which all possible solutions will be found. One limit corresponds to a completely chaotic distribution of molecules within a cavity, while the other corresponds to a maximum ordered molecular structure. Comparison of the nearly ideal O-2-N-2-zeolite NaX system at ambient temperature with the system Of O-2-N-2-zeolite CaX at 144 K has shown that a decrease of temperature leads to a molecular rearrangement in the cavity volume, which results from the difference in the fluid-solid interactions. The model is able to describe this behavior and therefore allows predicting mixture adsorption more accurately compared to those assuming energetic uniformity of the adsorption volume. Another feature of the model is its ability to correctly describe the negative deviations from Raoult's law exhibited by the O-2-N-2-CaX system at 144 K. Analysis of the highly nonideal CO2-C2H6-zeolite NaX system has shown that the spatial molecular rearrangement in separate cavities is induced by not only the ion-quadrupole interaction of the CO2 molecule but also the significant difference in molecular size and the difference between the intermolecular interactions of molecules of the same species and those of molecules of different species. This leads to the highly ordered structure of this system.