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Curve Fit (curve + fit)
Selected AbstractsGrain-scale permeabilities of faceted polycrystalline aggregatesGEOFLUIDS (ELECTRONIC), Issue 4 2006J. D. PRICE Abstract Porous synthetic quartzites and amphibolites, each with faceted pore walls, were synthesized and evaluated to examine the permeability of pore networks similar to those of the lower crust and mantle. Quartzite with a fluid in equilibrium with an Mg,clinopyroxene contained connected networks of pores with a dihedral angle of 30° bounded by walls that were 10,50% faceted. The relationship of their permeability (k) to porosity (,) is approximated by the previously determined relationship for relatively nonfaceted synthetic quartzite Amphibolite with an HF fluid contained fluorotremolite and a connected network of pores bounded by walls exhibiting 78,90% faceting. These materials showed much lower k for a given ,, with an apparent permeability threshold at ,c = 0.04. A curve fit to these data yields The results suggest that moderate faceting has little effect on the transmission of fluids through rocks, but extensive faceting significantly alters permeability. This difference is most likely produced through isolation of the fluid to the grain corners at low , with extensive faceting. Rocks with pores that tend toward faceting may impede the flow of fluids and melt. [source] Seasonal variations in [3H]citalopram platelet binding between healthy controls and violent offenders in FinlandHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 7 2005James Callaway Abstract Monthly binding densities (Bmax) of [3H]citalopram to the platelet serotonin transporter (SERT) was measured longitudinally over 1 year in a control group of 18 healthy Finnish male volunteers. Single platelet samples were also analysed from 33 men who were incarcerated for violent crimes during the same calendar year. A statistically significant seasonal variation in SERT Bmax was observed in both data sets, and bi-monthly floating averages for SERT Bmax were calculated and then fit to an annual sinusoidal curve for both groups. The Bmax for platelet [3H]citalopram binding showed a statistically significant (p,=,0.001) seasonal variance between a winter (January,February) maximum of 1590 fmol/mg protein and a summer (July,August) minimum of 1216 fmol/mg protein for the control group, with an R2 of 70% for the annual sinusoidal curve fit. A statistically significant (p,=,0.007) seasonal variance was also observed between a winter (January,February) maximum of 1980 fmol/mg protein and an autumnal (August,September) minimum of 1234 fmol/mg protein for the violent offenders, again with an R2 of 70% for the annual sinusoidal curve fit. This observation lends additional support to the idea that violent human behavior and impulsivity may be directly linked to values of SERT Bmax, which can be affected by various psychoactive drugs and also varies with the natural change of seasons. Copyright © 2005 John Wiley & Sons, Ltd. [source] The relationship of total and per-gram rankings in competitive effect to the natural abundance of herbaceous perennialsJOURNAL OF ECOLOGY, Issue 1 2001Timothy G. Howard Summary 1,Using a field experiment and a garden experiment, I estimated the rankings in total and per-gram competitive effect of non-woody perennial old-field species. 2,Total competitive effects were defined as the relative reduction in growth of a target from no-neighbour to with-neighbour conditions. Per-gram competitive effects were defined as the per-unit relative reduction in target growth among increasing neighbour densities, and were determined from the shape of a nonlinear curve fit through a distribution of normalized target performance against neighbour mass. 3,In both experiments, mean total competitive effect differed significantly among species, indicating a strong competitive hierarchy. In the garden experiment only species at opposite ends of the ranking differed significantly in per-gram competitive effect, resulting in a weaker competitive hierarchy based on this measure. 4,Nonetheless, rankings of per-gram competitive effect were more strongly correlated with rank in abundance than were rankings of total competitive effect. 5,Per-gram competitive effect may be more predictive of natural abundance than total competitive effect for at least two reasons. The effects of neighbour abundance on targets are nonlinear, and unlike total effects, per-gram estimates of competitive effect may therefore indicate how competition changes over time with changing neighbour densities. Also, if higher per-gram competitive effect reflects higher per-unit nutrient uptake rates, it would probably be advantageous to a species throughout the individual's life span, rather than only when the individual is larger than its surrounding neighbours. [source] A simple pharmacokinetics subroutine for modeling double peak phenomenonBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 3 2006Ahmad Mirfazaelian Abstract Double peak absorption has been described with several orally administered drugs. Numerous reasons have been implicated in causing the double peak. DRUG-KNT,a pharmacokinetic software developed previously for fitting one and two compartment kinetics using the iterative curve stripping method,was modified and a revised subroutine was incorporated to solve double-peak models. This subroutine considers the double peak as two hypothetical doses administered with a time gap. The fitting capability of the presented model was verified using four sets of data showing double peak profiles extracted from the literature (piroxicam, ranitidine, phenazopyridine and talinolol). Visual inspection and statistical diagnostics showed that the present algorithm provided adequate curve fit disregarding the mechanism involved in the emergence of the secondary peaks. Statistical diagnostic parameters (RSS, AIC and R2) generally showed good fitness in the plasma profile prediction by this model. It was concluded that the algorithm presented herein provides adequate predicted curves in cases of the double peak phenomenon. Copyright © 2006 John Wiley & Sons, Ltd. [source] Cell Detachment Model for an Antibody-Based Microfluidic Cancer Screening SystemBIOTECHNOLOGY PROGRESS, Issue 5 2006Swapnil P. Wankhede We consider cells bound to the floor of a microfluidic channel and present a model of their flow-induced detachment. We approximate hydrodynamic force and cell elastic response using static finite-element simulation of a single cell. Detachment is assumed to occur when hydrodynamic and adhesive forces are roughly equal. The result is extended to multiple cells at the device level using a sigmoidal curve fit. The model is applied to a microfluidic cancer-screening device that discriminates between normal epithelial cells and cells infected with human papillomavirus (HPV), on the basis of increased expression of the transmembrane protein ,6 integrin in the latter. Here, the cells to be tested are bound to a microchannel floor coated with anti ,6 integrin antibodies. In an appropriate flow rate range, normal cells are washed away while HPV-infected cells remain bound. The model allows interpolation between data points to choose the optimal flow rate and provides insight into interaction of cell mechanical properties and the flow-induced detachment mechanism. Notably, the results suggest a significant influence of cell elastic response on detachment. [source] | |||||||||||||