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Negative Slope (negative + slope)

Distribution by Scientific Domains

Medical Sciences	40%
Life Sciences	40%

Selected Abstracts

Energy input and zooplankton species richness

ECOGRAPHY, Issue 6 2007
Dag O. Hessen
What are the relative contribution of temperature and solar irradiance as types of energy deliveries for species richness at the ecosystem level? In order to reveal this question in lake ecosystems, we assessed zooplankton species richness in 1891 Norwegian lakes covering a wide range in latitude, altitude, and lake area. Geographical variables could largely be replaced by temperature-related variables, e.g. annual monthly maximum temperature or growth season. Multivariate analysis (PCA) revealed that not only maximum monthly temperature, but also energy input in terms of solar radiation were closely associated with species richness. This was confirmed by stepwise, linear regression analysis in which lake area was also found to be significant. We tested the predictive power of the "metabolic scaling laws" for species richness by regressing Ln of species richness over the inverse of the air temperature (in Kelvin), corrected for the activation energy (eV) as predicted by the Boltzmann constant. A significant, negative slope of 0.78 for ln richness over temperature, given as 1/kT, was found, thus slightly higher than the range of slopes predicted from the scaling law (0.60,0.70). Temperature basically constrained the upper bound of species number, but it was only a modest predictor of actual richness. Both PCA-analysis and linear regression models left a large unexplained variance probably due to lake-specific properties such as catchment influence, lake productivity, food-web structure, immigration constraints or more stochastic effects. [source]

A slowly inactivating sodium current (INa2) in the plateau range in canine cardiac Purkinje single cells

EXPERIMENTAL PHYSIOLOGY, Issue 1 2007
Mario Vassalle
The action potential of Purkinje fibres is markedly shortened by tetrodotoxin, suggesting the possibility that a slowly inactivating sodium current might flow during the plateau. The aim of the present experiments was to investigate, in canine cardiac Purkinje single cells by means of a whole cell patch clamp technique, whether a sodium current slowly inactivates at less negative potentials and (if so) some of its distinctive characteristics. The results showed that a 500 ms depolarizing step from a holding potential of ,90 mV to ,50 mV induced the fast inward current INa (labelled here INa1). With steps to ,40 mV or less negative values, a slowly decaying component (tentatively labelled here INa2) appeared, which peaked at ,30 to ,20 mV and decayed slowly and incompletely during the 500 ms steps. The INa2 was present also during steps to ,10 mV, but then the transient outward current (Ito) appeared. When the holding potential (Vh) was decreased to ,60 to ,50 mV, INa2 disappeared even if a small INa1 might still be present. Tetrodotoxin (30 ,m), lignocaine (100 ,m) and cadmium (0.2 mm; but not manganese, 1 mm) blocked INa2. During fast depolarizing ramps, the rapid inactivation of INa1 was followed by a negative slope region. During repolarizing ramps, a region of positive slope was present, whereas INa1 was absent. At less negative values of Vh, the amplitude of the negative and positive slopes became gradually smaller. Gradually faster ramps increased the magnitude of the negative slope, and tetrodotoxin (30 ,m) reduced or abolished it. Thus, Purkinje cells have a slowly decaying inward current owing to Na+ entry (INa2) that is different in several ways from the fast INa1 and that appears important for the duration of the plateau. [source]

FIRMNESS OF THERMAL PROCESSED ONION AS AFFECTED BY BLANCHING

JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 6 2006
JAE C. KIM
ABSTRACT The pectin methyl esterase enzyme system was shown to be involved in firmness of thermally treated onion in the temperature range 50,70C. Thermal softening of onion at 90 and 100C showed an initial steep negative slope with a shallow negative slope at longer heating time. Low-temperature blanching at 70C was effective to maintain firm onion tissue exposed to excessive heating. Physical strength of onion was substantially diminished when exposed to a commercial sterilization condition where F0, extent of thermal sterilization, was 3, and/or more. Blanching in water for 120 min at 70C resulted in a maximum value for the firmness of commercially sterilized onion. Firmness of onion, blanched in calcium brine at a concentration range of 0.0,1.0% (wt) prior to heat treatment, decreased with increasing severity of thermal sterilization treatment. At F0 = 6, blanching in 0.5% calcium brine resulted in maximum firmness of thermally sterilized onion, approximately 70% of that of raw onion. [source]

Crystallization of Silicate Magmas Deciphered Using Crystal Size Distributions

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007
Bruce D. Marsh
The remoteness and inhospitable nature of natural silicate magma make it exceedingly difficult to study in its natural setting deep beneath volcanoes. Although laboratory experiments involving molten rock are routinely performed, it is the style and nature of crystallization under natural conditions that is important to understand. This is where the crystal size distributions (CSD) method becomes fundamentally valuable. Just as chemical thermodynamics offers a quantitative macroscopic means of investigating chemical processes that occur at the atomic level, crystal size distribution theory quantitatively relates the overall observed spectrum of crystal sizes to both the kinetics of crystallization and the physical processes affecting the population of crystals themselves. Petrography, which is the qualitative study of rock textures, is the oldest, most comprehensively developed, and perhaps most beautiful aspect of studying magmatic rocks. It is the ultimate link to the kinetics of crystallization and the integrated space,time history of evolution of every magma. CSD analysis offers a quantitative inroad to unlocking and quantifying the observed textures of magmatic rocks. Perhaps the most stunning feature of crystal-rich magmatic rocks is that the constituent crystal populations show smooth and often quasi-linear log-normal distributions of negative slope when plotted as population density against crystal size. These patterns are decipherable using CSD theory, and this method has proven uniquely valuable in deciphering the kinetics of crystallization of magma. The CSD method has been largely developed in chemical engineering by Randolph and Larson,1,2 among many others, for use in understanding industrial crystallization processes, and its introduction to natural magmatic systems began in 1988. The CSD approach is particularly valuable in its ease of application to complex systems. It is an aid to classical kinetic theory by being, in its purest form, free of any atomistic assumptions regarding crystal nucleation and growth. Yet the CSD method provides kinetic information valuable to understanding the connection between crystal nucleation and growth and the overall cooling and dynamics of magma. It offers a means of investigating crystallization in dynamic systems, involving both physical and chemical processes, independent of an exact kinetic theory. The CSD method applied to rocks shows a systematic and detailed history of crystal nucleation and growth that forms the foundation of a comprehensive and general model of magma solidification. [source]

Impact of Cyclosporine Reduction With MMF: A Randomized Trial in Chronic Allograft Dysfunction.

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 11 2006
Reference' Study
Long-term use of calcineurine inhibitors (CNIs) may contribute to the development of chronic allograft dysfunction (CAD). We investigate the impact of the introduction of MMF combined with cyclosporine (CsA) 50% dose reduction. An open, randomized, controlled, multicenter, prospective study was conducted in 103 patients, receiving a CsA-based therapy with a serum creatinine between 1.7,3.4 mg/dL, more than 1 year after transplantation. They were randomized to receive MMF with half dose of CsA (MMF group) or to continue their maintenance CsA dose (control group). A total of 96 weeks after randomization, the evolution of renal function assessed by regression line analysis of 1/SeCr improved in the MMF group (positive slope) vs. the control group (negative slope), 4.2 × 10,4 vs. ,3.0 × 10,4, respectively (p < 0.001). Concurrently, the absolute renal function improved significantly in the MMF group. No episode of biopsy-proven acute rejection occurred. One patient in each group lost his graft because of biopsy-proven chronic allograft nephropathy. There was a significant decrease of triglycerides level in the MMF group. Anemia and diarrhea were statistically more frequent in the MMF group. In CAD, the reduction of CsA in the presence of MMF results in significant improvement in renal function during a 2-year follow-up. [source]

Risk factors for rising creatinine in renal allografts with 1 and 3 yr survival

CLINICAL TRANSPLANTATION, Issue 6 2006
Steven Paraskevas
Abstract:, Background:, Determining factors associated with negative slope of inverse creatinine vs. time (1/Cr vs. t) may help prevent a decline in renal allograft function. Methods:, A total of 1389 adult recipients of primary renal transplants were divided into quartiles based on the slope of 1/Cr vs. t calculated from 6 and 12 months post transplant. A multivariate analysis of risk factors for being in the worst vs. best quartile employed these variables: donor source, HLA mismatch, recipient age, donor age, panel-reactive antibody (PRA), acute rejection (AR), 3-month cyclosporin A (CsA) level, 1-yr CsA level and acute tubular necrosis. Two separate analyses compared risk factors in patients with 1 and 3 yr survival, respectively. Results:, In recipients with ,1 yr graft survival, high PRA and AR were associated with negative slopes of 1/Cr vs. t. For those with ,3 yr graft survival, both AR and 3-month CsA level >150 ng/mL were significant risk factors, using both 6- and 12-month slopes. Stratification of AR showed 1 AR episode ,6 months and multiple AR episodes carried significant risk for negative slopes. Conclusion:, Optimization of allograft function invokes a conundrum between the needs to avoid both AR and high early CsA levels. We support a policy of carefully balancing these two risks. [source]

Associations between height, body mass, and frequency of decayed, extracted, and filled deciduous teeth among two cohorts of Taiwanese first graders

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2009
B. Floyd
Abstract In this study, heights, weights, and numbers of decayed, extracted, and filled (DEF) deciduous teeth of 300 first-graders from a less affluent area of Taipei were compared with those of 277 first-graders from a more affluent one. Parents of all children self-identified as having ancestors from Fujian. This study tested the hypothesis that synergisms between under-nutrition and disease form part of a causal pathway contributing to the risk of deciduous caries. Within the less affluent community significant inverse associations between height and body mass index, as proxies for nutritional status, and the frequency of DEF deciduous teeth were anticipated. These associations were not expected in the more affluent community where nutritional status was adequate. An alternative hypothesis, that parental behavior potentially correlated with parental education, occupational backgrounds, housing, or family size contributed independently to offspring nutritional status and caries risk, was evaluated with available data. Consistent with the primary hypothesis, regression analyses revealed significant negative slopes of height (P = 0.002) and log BMI (P = 0.036) on total DEF deciduous teeth in the less affluent group, but not in the more affluent one. Direct tests of slope coefficients in the two groups indicate a significant difference for height (P = 0.041) but not log BMI (P = 0.29). Inclusion of parental education, occupational categories, housing, and numbers of siblings in the regression model provided no support to the alternative hypothesis. Results suggest that improving nutritional status significantly lowers caries risk, though most variation is probably attributable to other factors. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source]

Effect of age on anterior chamber angle configuration in Asians determined by anterior segment optical coherence tomography; clinic-based study

ACTA OPHTHALMOLOGICA, Issue 6 2010
Mi Hyun Cheon
Acta Ophthalmol. 2010: 88: e205,e210 Abstract. Purpose:, To evaluate the distribution of anterior chamber angle (ACA) parameters and to assess association of these parameters with age in Asian subjects. Methods:, Four hundred and thirty-nine consecutive Korean subjects aged from 30 to 89 were enrolled from a university clinic. All participants were scanned using anterior segment optical coherence tomography (AS-OCT, Visante, version 2.0). We measured ACA parameters such as anterior chamber depth (ACD), angle opening distance at 500 and 750 ,m (AOD500,750), angle recess area at 500 and 750 ,m (ARA500,750), trabecular iris space area at 500 and 750 ,m (TISA500,750), and determined age-related changes in these parameters with use of a linear mixed effect model that adjusted for gender, axial length, intraocular pressure, and keratometry data. Slopes of ACA parameters as a function of age were determined. For various AS-OCT parameters, the normalized slope was calculated by dividing the slope by the mean value. Results:, All analysed ACA parameters decreased with age in both nasal and temporal quadrants. Axial length and keratometry data were significant covariates for ACA changes. The slopes of ACD were ,0.02396 mm/year, AOD500, ARA500, and TISA500 measured at the temporal angle were ,0.00634 mm/year, ,0.0019 mm2/year, and ,0.00177 mm2/year, respectively. There was no age-dependent difference in central corneal thickness (p value; 0.4597) Based on the normalized slopes, the AOD showed the steepest slope at both temporal and nasal sectors. Conclusion:, All ACA parameters assessed by AS-OCT, which accounted for other ocular biometric parameters, showed significant negative slopes with increasing age. These results should be considered when assessing changes in the anterior chamber over time. [source]

Improvements to resampling measures of group support

CLADISTICS, Issue 4 2003
Pablo A Goloboff
Several aspects of current resampling methods to assess group support are reviewed. When the characters have different prior weights or some state transformation costs are different, the frequencies under either bootstrapping or jackknifing can be distorted, producing either under- or overestimations of the actual group support. This is avoided by symmetric resampling, where the probability p of increasing the weight of a character equals the probability of decreasing it. Problems with interpreting absolute group frequencies as a measure of the support are discussed; group support does not necessarily vary with the frequency itself, since in some cases groups with positive support may have much lower frequencies than groups with no support at all. Three possible solutions for this problem are suggested. The first is measuring the support as the difference in frequency between the group and its most frequent contradictory group. The second is calculating frequencies for values of p below the threshold under which the frequency ranks the groups in the right order of support (this threshold may vary from data set to data set). The third is estimating the support by using the slope of the frequency as a function of different (low) values of p; when p is low, groups with actual support have negative slopes (closer to 0 when the support is higher), and groups with no support have positive slopes (larger when evidence for and against the group is more abundant). [source]