Variance Of Residence Time Research Articles

Inferring detailed space use from movement paths: A unifying, residence time-based framework.

The residence time is the amount of time spent within a predefined circle surrounding each point along the movement path of an animal, reflecting its response to resource availability/quality. Two main residence time‐based methods exist in the literature: (1) The variance of residence times along the path plotted against the radius of the circle was suggested to indicate the scale at which the animal perceives its resources; and (2) segments of the path with homogeneous residence times were suggested to indicate distinct behavioral modes, at a certain scale. Here, we modify and integrate these two methods to one framework with two steps of analysis: (1) identifying several distinct, nested scales of area‐restricted search (ARS), providing an indication of how animals view complex resource landscapes, and also the resolutions at which the analysis should proceed; and (2) identifying places which the animal revisits multiple times and performs ARS; for these, we extract two scale‐dependent statistical measures—the mean visit duration and the number of revisits in each place. The association between these measures is suggested as a signature of how animals utilize different habitats or resource types. The framework is validated through computer simulations combining different movement strategies and resource maps. We suggest that the framework provides information that is especially relevant when interpreting movement data in light of optimal behavior models, and which would have remained uncovered by either coarser or finer analyses.

Effect of lifter shape and operating parameters on the flow of materials in a pilot rotary kiln: Part III. Up-scaling considerations and segregation analysis

Up-scaling tracer experiments were carried out in a pilot-scale rotary kiln twice as big as the kiln used in the first two Parts of this study. Internal fixtures such as grid, or lifter structure arranged in 3 and 6 rows of single throughout lifters were used. The effects of these removable fixtures and other usual operating conditions, namely, mass flow rate of granular biomass materials, rotational speed and slope of the kiln on the residence time distribution (RTD), the mean and variance of residence time (MRT and VRT), the hold-up (HU), the Peclet number (Pe) and corresponding axial dispersion coefficient (D), were investigated. Scaling-up rules were derived for the MRT, HU volume fraction and D from the results of a comprehensive experimental work. Good agreement was found between the experimental data and the calculated values. The wide size distribution of the beech chips used in the present study allows analysis of particle segregation, which may further increase understanding of the flow characteristics of granular materials, notably within flighted rotary kilns. The results show that while significantly increasing the dispersion, ipso facto, enhancing the mixing, the lifters limit the extent of particle segregation.

Movement is the glue connecting home ranges and habitat selection.

Animal space use has been studied by focusing either on geographic (e.g. home ranges, species' distribution) or on environmental (e.g. habitat use and selection) space. However, all patterns of space use emerge from individual movements, which are the primary means by which animals change their environment. Individuals increase their use of a given area by adjusting two key movement components: the duration of their visit and/or the frequency of revisits. Thus, in spatially heterogeneous environments, animals exploit known, high-quality resource areas by increasing their residence time (RT) in and/or decreasing their time to return (TtoR) to these areas. We expected that spatial variation in these two movement properties should lead to observed patterns of space use in both geographic and environmental spaces. We derived a set of nine predictions linking spatial distribution of movement properties to emerging space-use patterns. We predicted that, at a given scale, high variation in RT and TtoR among habitats leads to strong habitat selection and that long RT and short TtoR result in a small home range size. We tested these predictions using moose (Alces alces) GPS tracking data. We first modelled the relationship between landscape characteristics and movement properties. Then, we investigated how the spatial distribution of predicted movement properties (i.e. spatial autocorrelation, mean, and variance of RT and TtoR) influences home range size and hierarchical habitat selection. In landscapes with high spatial autocorrelation of RT and TtoR, a high variation in both RT and TtoR occurred in home ranges. As expected, home range location was highly selective in such landscapes (i.e. second-order habitat selection); RT was higher and TtoR lower within the selected home range than outside, and moose home ranges were small. Within home ranges, a higher variation in both RT and TtoR was associated with higher selectivity among habitat types (i.e. third-order habitat selection). Our findings show how patterns of geographic and environmental space use correspond to the two sides of a coin, linked by movement responses of individuals to environmental heterogeneity. By demonstrating the potential to assess the consequences of altering RT or TtoR (e.g. through human disturbance or climatic changes) on home range size and habitat selection, our work sets the basis for new theoretical and methodological advances in movement ecology.

Age Distribution in the Kenics Static Micromixer with Convection and Diffusion

Age distribution in a Kenics static micromixer is studied by mean age solution of a steady transport equation. The spatial distribution of mean age reveals locations of older material that could potentially cause process fouling and product defects. At the microscales of the mixer, both convection and diffusion strongly affect age distribution. A method is developed to compute an average effective diffusivity to measure false diffusion due to numerical errors. The range of Peclet number is found so that the scalar solution is not affected by false diffusion. The effect of convection and diffusion is studied for Re numbers that cover the full range of laminar flows in the mixer. Diffusion broadening is found to have a strong effect on the striation structures in the mixer. Age distribution in the mixer is quantitatively measured with a frequency distribution function and two different variances, the variance of residence time and the variance of mean age. It is found that the mean age variance decay rate i...

Hemodynamic Changes with Liver Fibrosis Measured by Dynamic Contrast-Enhanced MRI in the Rat

To evaluate the hemodynamic changes of liver cirrhosis in the rat and investigate the relationship between hemodynamic changes and properties of fibrotic change in the liver. Three rats with cirrhosis induced by thioacetamide (TAA), three with disease induced by carbon tetrachloride (CCl4), and three with no treatment were measured on dynamic MRI using a 1.5T scanner. Compartment and moment analysis were used to quantitate hemodynamic changes. Compartment model analysis showed that increased transition speed from vessels to the liver correlated with grade of liver fibrosis. Moment analysis demonstrated that decrease of area under the curve (AUC), mean residence time (MRT), variance of residence time (VRT), half life (T1/2) and increased total clearance (CL) correlated with grade of liver fibrosis. Hemodynamic changes in injured fibrotic liver may be influenced by the grade of fibrosis. Compartment model and moment analysis may be useful for evaluating hemodynamic changes in injured liver.

Intraarterial infusion chemotherapy with lipiodol-CDDP suspension for hepatocellular carcinoma.

To quantitatively evaluate the usefulness of lipiodol-CDDP suspension (LCS) chemotherapy in hepatocellular carcinoma (HCC). CDDP (cis-diamminedichloroplatinum) powder was prepared by removing the water and NaCl from aqueous CDDP. Two quantities of prepared CDDP powder, 10 mg and 20 mg, were mixed with 1 ml each of iopamidol 300 mgI/ml (IP300) and lipiodol (LPD) using a high pressure pumping method, thus producing LCS. Thirty-two patients with HCC, who had good renal function [creatinine clearance (Ccr) 50 ml/min or more], received additional intraarterial infusion chemotherapy with LCS or LCS alone. The most frequently observed CDDP powder sizes were 5.95-10.90 microm (average: 11.59 microm). The LCS obtained demonstrated a suspension of 2-12 microm (average 3.69 microm) immediately after mixing, and no significant changes were observed in LCS particle sizes 3 hr after mixing. Moreover, the sustained release with LCS was observed for up to 3 hr. Meanwhile, the peripheral free platinum concentration between intraarterial infusion chemotherapy with LCS and intraarterial infusion with the aqueous solution of CDDP, with respect to variance residence time (VRT), showed a significant difference, with a p value of 0.0382. The survival rate was 89.84% at 1 year, 73.78% at 2 years, and 68.51% at 3 years. Furthermore, the platinum concentration in the tumor was 25-95 times the concentration in the surrounding liver parenchyma. Good clinical results can be expected by applying LCS to HCC.

Concentration fluctuations and dilution in aquifers

The concentration of solute undergoing advection and local dispersion in a random hydraulic conductivity field is analyzed to quantify its variability and dilution. Detailed numerical evaluations of the concentration variance σc2 are compared to an approximate analytical description, which is based on a characteristic variance residence time (VRT), over which local dispersion destroys concentration fluctuations, and effective dispersion coefficients that quantify solute spreading rates. Key features of the analytical description for a finite size impulse input of solute are (1) initially, the concentration fields become more irregular with time, i.e., coefficient of variation, CV=σc/〈c〉, increases with time (〈c〉 being the mean concentration); (2) owing to the action of local dispersion, at large times (t > VRT), σc2 is a linear combination of 〈c〉2 and (∂〈c〉/∂xi)2, and the CV decreases with time (at the center, CV ≅ (N)1/2 VRT/t, N being the macroscopic dimensionality of the plume); (3) at early time, dilution and spreading can be severely disconnected; however, at large time the volume occupied by solute approaches that apparent from its spatial second moments; and (4) in contrast to the advection‐local dispersion case, under advection alone, the CV grows unboundedly with time (at the center, CV ∝ tN/4), and spatial second moment is increasingly disconnected from dilution, as time progresses. The predicted large time evolution of dilution and concentration fluctuation measures is observed in the numerical simulations.

Concentration fluctuations and dilution in two-dimensionally periodic heterogeneous porous media

Dilution of solute in two-dimensionally periodic heterogeneous porous media is assessed by numerically simulating advection-dispersion. The concentration fluctuations, created by advective heterogeneity, are destroyed by local dispersion, over a characteristic variance residence time (VRT). For an impulse introduction of solute, initially, plumes become increasingly irregular with time—the coefficient of variation (CV) of concentration grows with time. A priori, the spatial second moment and mean concentrations are insufficient measures of dilution, because concentration fluctuations can be large. At large times (t > VRT) the relative concentration fluctuations weaken—the concentration CV was observed to slowly decrease with time. At the center of mass the general trend of the decreasing CV follows VRT/t (predicted by Kapoor and Gelhar). The VRT is found to be an increasing function of the log hydraulic conductivity microscale. In employing effective dispersion coefficents to model the mean concentration, it needs to be recognized that excursions of concentrations around the mean are singularly determined by local dispersion.

Temporal Moments for Nonergodic Solute Transport in Heterogeneous Aquifers

The first two temporal moments, i.e., mean value and variance of residence time, are used to characterize nonergodic transport in heterogeneous porous media. Due to the nonergodicity stemming from small initial solute sources relative to the hydraulic conductivity integral scale, only statistical moments of the temporal moments can be obtained. The expected value and variance of the first temporal moment and the expected value of the second temporal moment are derived for both conservative solute and solute subject to sorption governed by linear kinetics. The nonergodic temporal moments incorporating sorption kinetics can be expressed in terms of the corresponding conservative moments and the constant rate parameters. The methodology is exemplified for a two‐dimensional aquifer using first‐order results for the velocity statistics. The analytical results compare reasonably well with the simulations for a variability in the hydraulic conductivity up to σlnK2 = 1. The results indicate that the relative difference between nonergodic and ergodic conditions, expressed through the second temporal moment, clearly is diminished for a kinetically sorbing solute as compared to a conservative one.

Numerical Estimation of the Noncompartmental Pharmacokinetic Parameters Variance and Coefficient of Variation of Residence Times

Noncompartmental investigation of the distribution of residence times from concentration-time data requires estimation of the second noncentral moment (AUM2C) as well as the area under the curve (AUC) and the area under the moment curve (AUMC). The accuracy and precision of 12 numerical integration methods for AUM2C were tested on simulated noisy data sets representing bolus, oral, and infusion concentration-time profiles. The root-mean-squared errors given by the best methods were only slightly larger than the corresponding errors in the estimation of AUC and AUMC. AUM2C extrapolated "tail" areas as estimated from a log-linear fit are biased, but the bias is minimized by application of a simple correction factor. The precision of estimates of variance of residence times (VRT) can be severely impaired by the variance of the extrapolated tails. VRT is therefore not a useful parameter unless the tail areas are small or can be shown to be estimated with little error. Estimates of the coefficient of variation of residence times (CVRT) and its square (CV2) are robust in the sense of being little affected by errors in the concentration values. The accuracy of estimates of CVRT obtained by optimum numerical methods is equal to or better than that of AUC and mean residence time estimates, even in data sets with large tail areas.

A Compartment Model for Percutaneous Absorption: Compatibility of Lag Time and Steady-State Flux with Diffusion Model

The lag times and steady-state flux predicted by a specific case of the compartment model, which was recently proposed to generate finite-dose percutaneous permeation pharmacokinetics, are compared with those predicted by the diffusion model. When the intercompartmental transfer rate constants are defined so that the three statistical moments of the compartmental model (the mean residence times of a drug in the vehicle and that in the skin and the variance of residence time in the vehicle) are identical to those in the diffusion model, the lag times and steady-state flux values predicted by the two models are the same.

徐放性バルプロ酸製剤（デパケンＲ錠，ＮＩＫ‐２４０）の生物学的同等性と体内動態の比較検討

Bioavailability and pharmacokinetic study of slow release preparations of sodium valproate (Depakene-R Tablets, NIK-240) were investigated by a cross-over design in six healthy volunteers. When bioavailability parameters were compared between two preparations after a single dose of 600mg of each drug was administered orally, there was difference in maximum serum concentration (Cmax), but no difference was found in areas under the serum concentration-time curve (AUC), peak time (Tmax), mean residence time (MRT) and variance of residence time (VRT). The pharmacokinetic parameters were estimated according to one-compartment open models with three different absorption steps (first-order or zero-order absorption step with lag time, two first-order input steps) by simultaneous least squares curve fitting method.The firstorder absorption with lag time model fitted better to describe pharmacokinetics of the two preparations than the other models, but pharmacokinetic parameters (Ke, Ka, Vd, lag time) showed no differences in the two preparations.These results indicate that two preparations were comparable to the extent of bioavailability, but not comparable to the rate of bioavailability. NIK-240 was released more slowly than Depakene-R Tablets and predictions regarding multiple dosing show that NIK-240 can provide smaller fluctuations in plasma valproic acid level than Depakene-R Tablets.These results were important for the administration of slowrelease preparations in the drug monitoring and the drug administration regimen.

Pharmacokinetics of trace elements by noncompartmental analysis in rats. Part 1. Significance of the pharmacokinetic parameters.

Six-week-old male Wistar rats were administrated the radioisotopes of five trace elements (iron, zinc, copper, manganese and iodine) intravenously in order to elucidate the significance of their pharmacokinetics by noncompartmental analysis. The mean residence time (MRT) and variance of residence time (VRT) increased in the order Mn, Cu, I, Fe and Zn. Neither MRT nor VRT indicated any statistical significance between I and Fe. These results suggested that Mn and Cu were voided rapidly from the plasma, whereas Zn persisted in the plasma for the longest time among these elements. Though I and Fe showed quite different plasma disappearance curves, both were considered to diminish at almost the same speed. The volume of distribution at steady state (Vdss) increased in the order Cu (32 ml), Fe (62 ml), I (149 ml), Mn (185 ml) and Zn (1012 ml). The distribution coefficient (Kd) of these elements increased in the same order as Vdss did. For Cu and Fe, Vdss was intermediate between the plasma volume and total body fluid volume of the rat, while, for the others, Vdss was greater than the total body fluid volume. In particular, Vdss of Zn was the greatest among these elements. Hence, the present study suggested that the plasma concentrations of Cu and Fe may reflect their body contents fairy well, though those of I, Fe and Zn can hardly do so. Vdss and Kd are, therefore, considered to be useful as supplementary diagnostic indices to understand the plasma concentrations of trace elements. Systemic clearance (CLs) increased in the order Fe (0.02 ml/min), Zn (0.07 ml/min), I (0.21 ml/min), Cu (0.37 ml/min) and Mn (4.61 ml/min). The CLs of Mn was similar to the hepatic plasma flow rate of the rat in size, indicating that the Cls of Mn may be one of the greatest among trace elements. It appeared, therefore, that when administered intravenously, Mn may be transferred from the plasma to the tissues more easily than the other elements.

Investigations of the Residence Time and the Longitudinal Mixing Behavior in Counter-rotating Twin Screw Extruders

Abstract This paper presents a distribution function which allows to calculate the residence time distribution in a counter rotating twin screw extruder. Only the minimum and mean residence time appear in this function. The agreement between calculated and experimentally determined residence times is satisfactory. Longitudinal mixing capacity is discribed with the aid of the residence time variance.

Pharmacological studies on puerariae flos. I. The effects of puerariae flos on alcoholic metabolism and spontaneous movement in mice

In the general rule, Puerariae Flos or it's combination drugs are used in traditional medicinal system for counteraction to drinking among Japanese and Chinese therapy. One of such drugs is Kakkakaiseito. Here we report the results of investigation on some pharmacological actions including alcoholic metabolism. The experiments were carried out to confirm its actual effect on alcohol, acetaldehyde and ketone body metabolism in the blood and the alteration of behaviour pattern of mice. Drugs used in this study were methanolic extract (PF-ME), isoflavonoid fraction (PF-IF) and triterpenoid saponin fraction (PF-SP) isolated from Puerariae Flos. Each drug was orally administrated to mice. These results were shown as follows: the concentrations of blood alcohol and acetaldehyde decreased more after the treatment with PF-IF (800 mg/kg) than those of the control group. This fact was evidenced remarkable effects with area under the blood concentration-time curve, mean residence time, and variance residence time and values on the moment analysis. However, a reduction effect was not recognized by the treatment with PF-SP (1000 mg/kg). Moreover, PF-ME and PF-IF suppressed the increment of spontaneous movement induced by alcohol administration, whereas PF-SP did not prevent the decrease in the increment caused by alcohol administration. These results support the basis that Puerariae Flos or its combination drugs is used in a traditional medicinal system for counteraction to drinking. However, further investigation is necessary.

Microcomputer-based programs for calculating mean and variance residence time by the method of prospective areas

A published package of microcomputer-based pharmacokinetic programs has been expanded to include programs to calculate mean and variance above the residence time (MRT and VRT) using the method of prospective areas. Three programs, one for plasma concentration time data, one for urinary excretion data, and one for in-vitro dissolution data, are available. All programs were tested with the data obtained from original articles or from simulated theoretical data. These programs were written in a modular fashion in such a way that they form an integrated software package. In conjunction with the programs previously developed, the user can choose/select how extensively the data are to be analyzed without reentry of data. This is particularly important since proper pharmacokinetic data analysis can only be made by using different calculations with different assumptions. Graphic display and linear regression subroutines are included in each module to simplify operation for the user. The modular design also facilitates modifications, upkeep, and accommodation to new methods of calculation.

The absolute bioavailability of rabbit muscle creatine phosphokinase after intramuscular administration.

A two-period crossover study was carried out to determine the rate and the extent of bioavailability of rabbit muscle creatine phosphokinase (CPK) after intramuscular administration to six male rabbits. The plasma profile of CPK after intramuscular administration (500 U/kg body weight in 0.8 ml of 2% rabbit serum albumin solution into the vastus lateralis muscle) showed a plateau around 4-12 h. Intravenous administration of CPK was performed at doses of 300 and 500 U/kg body weight. The mean clearance/body weight and Vdss/body weight were 0.00604±0.00094 l/h/kg (mean±S.D., n=6) and 5.32±1.47%, respectively. The mean residence time (MRTim) and mean absorption time (MATim) of CPK after intramuscular administration were 20.7±4.2 and 11.9±5.1 h, respectively. Since MATim was long relative to MRTim, the rate of bioavailability was slow and the residence time distribution appeared to be skewed. The value of MATim/MRTim, reflecting the contribution of moment of input function to the plasma activity of CPK, was 55.4±11.6%. The variance of residence time (VRTim) and variance of absorption time (VATim) were 608±107 and 505±122h2. The results imply that the aborption and disposition of CPK after intramuscular administration were rather complicated. The mean fraction of CPK absorbed was 0.311±0.149. Presumably, the incomplete access of CPK to the systemic circulation was due to extravascular inactivation.

Statistical moments in pharmacokinetics

Statistical moments are parameters that describe the characteristics of the time courses of plasma concentration (area, mean residence time, and variance of residence time) and of the urinary excretion rate that follow administration of a single dose of a drug. The relationship between the moments of a time-course curve and pharmacokinetic profiles of drug disposition, i.e., absorption, distribution, metabolism, and excretion, is described. The moments are related to the extent and rate of bioavailability, and it is shown that they can be effectively applied to the deconvolution operation.

On the theory of the indicator-dilution method for measurement of blood flow and volume.

On the theory of the indicator-dilution method for measurement of blood flow and volume.