The 2D wavelet transform modulus maxima method is used to obtain quantitative information on the fractal/multifractal nature and anisotropic structure of Galactic atomic hydrogen (H I) from the ...Canadian Galactic Plane Survey. Five mosaics were analyzed in the second quadrant of the Milky Way, corresponding to the Local, Perseus, and Outer spiral arms, as well as two "interarm" regions located between these three spiral arms. A monofractal signature is found for all five mosaics. An anisotropic signature is detected: the rms roughness fluctuations of the mosaics in the latitude direction differ from those in the longitude direction. This anisotropy is scale-independent for the interarm regions while it is scale-dependent for the spiral arms. The longitudinal matter distribution of H I structure is similar for all five mosaics while the latitudinal distribution is smoother in the spiral arms. These results hold for all physical length scales studied, from 62 pc in the Local arm to 644 pc in the Outer arm. Several hypotheses are investigated to provide a physical explanation: the scale-height gradient, the density wave, star formation activity, photolevitation of dusty clouds, random motion of H I clouds, corrugation, and turbulence. The slopes of the power spectra for an increasing number of velocity channels were compared for 11 sections of the Local arm column density mosaic. All slopes are identical within the uncertainties (-3.0) and we do not detect for the Galactic plane the change in the power law index predicted by Lazarian and Pogosyan.
Preventing virological failure following HIV treatment remains a difficult task that is further complicated by the emergence of drug resistance. We have developed a mathematical model able to explain ...and predict HIV virological outcomes for various compounds and patients' drug intake patterns. Compared to current approaches, this model considers, altogether, drug penetration into lymph nodes, a refined adherence representation accounting for the propensity for long drug holidays, population pharmacokinetic and pharmacodynamic variability, drug interaction, and crossresistance. In silico results are consistent with clinical observations for treatment with efavirenz, efavirenz in association with tenofovir DF and emtricitabine, or boosted darunavir. Our findings indicate that limited lymph node drug penetration can account for a large proportion of cases of virological failure and drug resistance. Since a limited amount of information is required by the model, it can be of use in the process of drug discovery and to guide clinical treatment strategies.
Our knowledge of dinosaurs comes primarily from the fossil record. Notwithstanding the condition of these vestiges, paleontologists reconstruct early reptilian life by comparison to previously ...discovered specimens. When relics are missing, reasonable deductions are used to fill in the gaps.
This is the first of two papers on the morphological analysis of H I features. In this first paper, we use the so-called metric space technique, developed by F. C. Adams and J. Wiseman. The metric ...space technique is an image analysis, mathematical formalism used to quantitatively compare astrophysical maps according to complexity. Instead of comparing maps on a pixel-by-pixel basis, we compare the maps' one-dimensional "output functions," which characterize specific morphological/physical aspects of the maps. The tool is used to analyze 28 H I features of known origin taken from the Canadian Galactic Plane Survey (CGPS), where the maps are scaled at 18arc sec per pixel (resolution of 1 cos delta arcmin). Technical and mathematical improvements to the formalism are presented. After classifying the 28 maps according to complexity, we searched for correlations between this complexity ranking and other quantifiable aspects of the H I features such as age, area, H I area, distance, flux from the ionizing star(s), fractal dimension, H I mass, and |z| (the absolute value of the height of the objects, above or below the Galactic plane). The most interesting correlations are (1) the higher the flux of UV photons, the more complex is the photodissociated H I feature, and (2) the older the supernova remnant, the more complex the H I associated with it. There is no correlation between the fractal dimension of the maps and their complexity or their physical characteristics, thus showing that the metric space technique could be used as a solution to the degeneracy of the fractal dimension.
Variability in drug intake is increasingly recognized as a major source of variability in drug response. The non-uniform access to medicated feed, influenced by swine individual feeding behaviour, is ...a determinant of antibiotic exposure, recalling the intrinsic similarity with human compliance to drug regimens. In this paper, we developed a feeding behaviour–pharmacokinetic (FBPK) model of in-feed chlortetracycline (CTC) and established, in a definite way, the effect of feeding behaviour and its induced pharmacokinetic (PK) variability. Based on reported animal behaviour, we mathematically formulated swine feeding behaviour by incorporating its main characteristics: intense feeding periods that repeat on a daily basis and random feeding periods of free access to feed, along with growth stage factors. This behaviour model was then integrated into a PK model of CTC. Moreover, we analysed the effect of each feeding behaviour component and assessed the corresponding PK variability. We have been able to delineate the impact of different feeding behaviour components and characterize the induced PK variability. We have compared different therapeutic assumptions to our model and shown that random features underlying the feeding behaviour have dramatic influence on the PK variability. A practical tool to adopt the dosing regimen in terms of dose and age has been proposed. The method developed here can be generalized to other therapeutic contexts and incorporated into medical practice, particularly to make long-term projections of drug-intake behaviour, to explain possible treatment failure and guide practitioners in adjusting the dosing regimen.
The influence of several physicochemical parameters on enzymatic hydrolysis and the in vitro release of sodium diclofenac (SDic) from cross-linked high amylose starch (Contramid) (CLA) tablets was ...evaluated. These parameters included pH, ionic strength of the medium, enzyme concentration, compression force and incorporation of gel-forming polymers such as hydroxypropyl methylcellulose (HPMC), poly(ethylene oxide) (PEO) and poly(vinyl alcohol) into the tablet. Pure CLA tablets were incubated in phosphate buffer (pH 6.8) containing α-amylase and the extent of enzymatic erosion was determined by gravimetry. Release of SDic from CLA tablets, in the presence of α-amylase, was measured using a USP type III dissolution apparatus. For low α-amylase concentrations (<2250 IU/l), the drug release was mainly diffusion-controlled. At higher α-amylase concentrations (>4500 IU/l) both diffusion and erosion contributed to the release of SDic. The hydrolysis kinetics of CLA tablets by α-amylase was biphasic. During the first phase (2–4 h), the hydrolysis rate was hyperbolically related to the α-amylase concentration but was practically α-amylase concentration-independent during the second phase. Enzymatic erosion and drug release kinetics appear to be relatively independent of ionic strength, pre-incubation time in simulated gastric fluid, and compression force of the tablets (6–34 kN). Incorporation of HPMC or PEO into the tablet resulted in a significant decrease of both tablet erosion and drug release rates.
Attempts to obtain estimates of pharmacokinetic-pharmacodynamic (PK-PD) parameters for mivacurium with traditional central link models were unsuccessful in many patients. We hypothesized that a link ...model with the peripheral compartment would be more appropriate for mivacurium in view of its extremely rapid plasma clearance and its potential elimination by tissue pseudocholinesterases. For validation purposes, the peripheral link model was applied to other neuromuscular blocking agents (NMBA), i.e., atracurium and doxacurium which have respectively an intermediate and a long elimination half-life. Assuming peripheral elimination in PK-PD modeling was investigated but found to have no impact on the estimation of PK-PD parameters. Our results indicate that, for drugs having intermediate and long elimination half-lives, EC50 values are similar with either the central or peripheral link model. For mivacurium, a peripheral link model enables PK-PD modeling in all subjects, with more precision in the PK-PD parameter estimates and a better fitting of the effect data when compared to the central link model. For these reasons, a peripheral link model should be preferred for mivacurium.
One of the most popular ways of estimating fractal dimension (Df) is the box-counting method (BCM). The major problem with this method is that it leads to results with a very high percentage of ...error. The modified box-counting method (MBCM) was developed as a methodic procedure to set sequence and range. The procedure eliminates two problems of the computerized BCM, the border effect and noninteger values of ε. The MBCM is a new, powerful tool, very simple to use, allowing accurate estimation of D
f.
Increasing attention is being paid to the configuration and development of vascular structures and their possible correlations with physiological events. The study of angiogenesis in normal and ...pathological states as well as in embryo and adult has provided new insights into the mechanism of vessel growth and organization of the vasculature. Various mathematical branching models have been developed. These constructions are mainly geometrical and only involve a branching phenomenon. We propose the use of a deterministic non-linear model based on physiological laws and hydrodynamics. Growth, branching and anastomosis, the three actual main events occurring in vascular growth, are included in this model. Space growth, including cells and vessels, is defined by a decreasing transformation. Space density and the length of new sprouts are controlled by a set of parameters. The conditions on these parameters are well established, which allows the production of realistic patterns.
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