Reciprocal Ratio Research Articles

Reduction of the environmental impact of pesticides: waxy microspheres encapsulating the insecticide carbaryl.

A controlled-release system with reduced environmental impact was produced by encapsulating the pesticide carbaryl in the waxy lipophilic material Gelucire 54/02. The microspheres were prepared by a modified hydrophobic congealable disperse-phase method. The influence of experimental parameters, such as the reciprocal ratio between the amounts of pesticide and wax employed, on size, morphology, loading efficiency, and release behavior of the particles was evaluated. Microspheres were free-flowing and showed a nonporous scaly surface at SEM analysis. The mean particle size ranged from 15.8 to 19.8 microm and was independent of the amount of Gelucire used to prepare the microspheres. At a fixed Gelucire content, the increase in theoretical carbaryl content yielded up to 72% loading efficiency, whereas at a fixed carbaryl content the increase in Gelucire amount produced a 64% increase in encapsulation efficiency. These data were accounted for by the carbaryl leakage from molten Gelucire toward the dispersing aqueous phase. The release profiles of carbaryl from microspheres showed that the use of increasing amounts of waxy material decreased the carbaryl release rate, whereas at a fixed Gelucire content, the release was the slowest when carbaryl was not completely dissolved within the matrix. The possibility to achieve different burst effects by simply varying the formulation parameters offers an efficient tool to ensure the fast release of an active dose of insecticide. The lower vertical mobility of carbaryl encapsulated in waxy microspheres compared to the vertical mobility of the technical-grade product showed that the controlled-release system has a lower potential risk for groundwater contamination.

Crystallochemistry and Kondo-like behaviour of the thorium and uranium arsenoselenides

We have grown single crystals of uranium and thorium arsenoselenide and arsenosulphide by the chemical vapour transport method. The crystals show a Kondo-like effect and its contribution to the resistivity was estimated by the determination of the reciprocal residual resistivity ratio (RRRR) ρ(4,2)/ ρ(300). The ratio varied from 0.70 (for UAsS) to 2.10 (for ThAsSe). A high resolution transmission electron microscopy study of ThAsSe crystals reveals a perfect ordering of cations. The X-ray diffraction examination showed that the unit cells of the examined crystals belong to a tetragonal system with the PbFCl-type structure (space group P4/nmm (no. 129)). Anomalously large anisotropic displacement factors have been observed for all the atoms composing the compounds examined. An interdependence between the displacement factor and RRRR has allowed to ascribe both phenomena to the same source. It indicates that the two-level system Kondo model is most suitable for the theoretical description of the systems.

The AHP approach for selecting an automobile purchase model

The analytic hierarchy process (AHP) provides a structure on decision-making processes where there are a limited numbers of choices but each has a number of attributes. This paper explores the use of AHP for deciding on car purchase. In the context of shopping, it is important to include elements that provide attributes that make consumer decision-making easier, comfortable and therefore, lead to a car purchase. As the car market becomes more competitive, there is a greater demand for innovation that provides better customer service and strategic competition in the business management. This paper presents a new methodological extension of the AHP by focusing on two issues. One combines pairwise comparison with a spreadsheet method using a 5-point rating scale. The other applies the group weight to a reciprocal consistency ratio. Three newly formed car models of midsize are used to show how the method allows choice to be prioritized and analyzed statistically.

Hepatic microvascular features in experimental cirrhosis: a structural and morphometrical study in CCl 4-treated rats

Background/Aims: In this study, a detailed morphometrical analysis of the hepatic microvasculature in the different zones of hepatic parenchyma was performed in normal and cirrhotic rat liver (CCl 4-induced). The aims were to detect, in CCl 4-induced cirrhosis, the real presence of the“capillarization” of hepatic sinusoids and to assess alterations of the sinusoid/parenchyma ratio within the nodule. Methods: Cirrhosis was promoted by controlled intragastric CCl 4 administration. Scanning electron microscopy of the vascular corrosion cast technique associated with light microscopy and transmission electron microscopy were used. Results: Evidence of connective tissue in the space of Disse was found only in sinusoids located near portal tracts or large fibrotic areas, and this was also confirmed by laminin immunohistochemistry. In contrast, all the intranodular sinusoids lacked real basal membrane and connective fibers in the space of Disse and, displayed normal fenestrations. The parenchymal area, sinusoidal area, mean sinusoidal area, sinusoidal perimeter, hepatocyte area and the reciprocal ratios were all considered in the morphometrical analysis. The sinusoids were of uniform size in the periportal, periseptal and pericentral areas of the cirrhotic liver without the typical zonal differences of the normal liver. The areas occupied by sinusoids per unit of parenchyma and the sinusoid/hepatocyte interfaces disposable for metabolic exchanges were markedly smaller ( p<0.01) in cirrhotic than normal liver. Conclusion: Our findings indicate that capillarization of hepatic sinusoids occurs only in very limited regions of the cirrhotic parenchyma, and thus this phenomenon does not have relevant functional consequences. Furthermore, the cirrhotic parenchyma appears not to be supplied by sinusoids and lacks features of zonation, which is a condition that could play a major role in the development and progression of liver failure.

Hepatic microvascular features in experimental cirrhosis: a structural and morphometrical study in CCl4-treated rats

In this study, a detailed morphometrical analysis of the hepatic microvasculature in the different zones of hepatic parenchyma was performed in normal and cirrhotic rat liver (CCl4-induced). The aims were to detect, in CCl4-induced cirrhosis, the real presence of the "capillarization" of hepatic sinusoids and to assess alterations of the sinusoid/parenchyma ratio within the nodule. Cirrhosis was promoted by controlled intragastric CCl4 administration. Scanning electron microscopy of the vascular corrosion cast technique associated with light microscopy and transmission electron microscopy were used. Evidence of connective tissue in the space of Disse was found only in sinusoids located near portal tracts or large fibrotic areas, and this was also confirmed by laminin immunohistochemistry. In contrast, all the intranodular sinusoids lacked real basal membrane and connective fibers in the space of Disse and, displayed normal fenestrations. The parenchymal area, sinusoidal area, mean sinusoidal area, sinusoidal perimeter, hepatocyte area and the reciprocal ratios were all considered in the morphometrical analysis. The sinusoids were of uniform size in the periportal, periseptal and pericentral areas of the cirrhotic liver without the typical zonal differences of the normal liver. The areas occupied by sinusoids per unit of parenchyma and the sinusoid/hepatocyte interfaces disposable for metabolic exchanges were markedly smaller (p<0.01) in cirrhotic than normal liver. Our findings indicate that capillarization of hepatic sinusoids occurs only in very limited regions of the cirrhotic parenchyma, and thus this phenomenon does not have relevant functional consequences. Furthermore, the cirrhotic parenchyma appears not to be supplied by sinusoids and lacks features of zonation, which is a condition that could play a major role in the development and progression of liver failure.

Flurbiprofen and enantiomers in ophthalmic solution tested as inhibitors of prostanoid synthesis in human blood.

The purpose of this study was to assess the selectivity and potency of the nonsteroidal anti-inflammatory drug (NSAID), flurbiprofen, and its enantiomers in their inhibition of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). An assay was used with freshly drawn, heparinized human whole blood, incubated with 25 microM calcium ionophore A23187 during 60 min to produce thromboxane B2 (TXB2) by activity of COX-1 in platelets. Incubation with E. coli lipopolysaccharide (LPS) during 24 hr produced prostaglandin E2 (PGE2) by induction of COX-2 in monocytes, suppressing any possible contribution of COX-1 activity by the addition of acetylsalicylic acid. Concentration inhibition curves were determined with racemic, S(+), and R(-) flurbiprofen in final concentrations ranging from 10(-3) to 10(-10) M. The stereoselectivity of S(+) flurbiprofen vs. R(-) flurbiprofen, expressed as the reciprocal of the ratio of the concentrations giving 50% inhibition (IC50), is 340 for COX-1 and 56 for COX-2. The selectivity for COX-1 vs. COX-2, expressed as the reciprocal ratio of the IC50, was 32 for racemic, 16 for S(+), and 5.3 for R(-) flurbiprofen. Meloxicam in the same assay showed COX-2 selectivity with a ratio of 0.19.

Nonlinear dynamics of electron flows with density gradient in spherical diodes

A variety of Pierce diodes formed by a pair of grounded concentric spheres with electrons streaming radially are investigated with particle-in-cell simulations and analytical models. The electrons flow parallel or antiparallel to a density gradient in convergent or divergent diodes, respectively. The existence and stability (or instability) of laminar steady states with space charge and nonuniform velocity that are possible for a given set of diode parameters, are crucial to determine the outcome of the numerical experiments. The dispersion relation for the stability of the initial constant velocity states and the concomitant energy flow balance are examined in relation to the nonlinear dynamical evolution. Spherical diodes have properties that are common to a dual pair of diodes with reciprocal ratios of collector to emitter radii. Stable oscillatory electrostatic states, associated with Hopf bifurcations, are observed in the simulations. The breakdown of the laminar electron flow has completely different physical characteristics in divergent and convergent diodes.

Economic Comparison of Two Energy-Efficient Design Strategies for Mechanical Ventilation Systems

Two systems, one with air re-circulation alone and the other a combination of air re-circulation and energy recovery using plate heat exchangers have been analysed. For these systems, a set of equations was derived for partial or full re-circulation of air with and without plate heat exchangers. Also, as part of the analysis, the reciprocal ratio of investment and running costs was considered. In this analysis, the re-circulation factor provided by ventilation units, a bypass factor and the efficiency of a plate heat exchanger were considered to be variables. For the sake of simplicity, the outdoor temperature was assumed to change uniformly throughout the year from a winter time minimum to a summer time maximum. All the final mathematical expressions derived are non-dimensional. The technical and economic estimations proposed were those which gave the most pessimistic outcome, that is, those for which the outcome gave the lowest guaranteed common profit. The numerical calculations showed that quite different results were obtained depending on specific applications. Several economic indexes were estimated including payback times and capital and running costs for typical examples. The expected payback time for a system with plate heat exchanger is something like 2.0 years for an installation in the climate zone of Saint Petersburg, installed and run in accordance with Russian legislation.

Economic Comparison of Two Energy-Efficient Design Strategies for Mechanical Ventilation Systems

Two systems, one with air re-circulation alone and the other a combination of air re-circulation and energy recovery using plate heat exchangers have been ana lysed. For these systems, a set of equations was derived for partial or full re-circulation of air with and without plate heat exchangers. Also, as part of the analysis, the reciprocal ratio of investment and running costs was considered. In this analysis, the re-circulation factor pro vided by ventilation units, a bypass factor and the effi ciency of a plate heat exchanger were considered to be variables. For the sake of simplicity, the outdoor temper ature was assumed to change uniformly throughout the year from a winter time minimum to a summer time maximum. All the final mathematical expressions de rived are non-dimensional. The technical and economic estimations proposed were those which gave the most pessimistic outcome, that is, those for which the out come gave the lowest guaranteed common profit. The numerical calculations showed that quite different re sults were obtained depending on specific applications. Several economic indexes were estimated including payback times and capital and running costs for typical examples. The expected payback time for a system with plate heat exchanger is something like 2.0 years for an installation in the climate zone of Saint Petersburg, installed and run in accordance with Russian legislation.

Dependence estimation over a finite bivariate failure time region.

This article concerns nonparametric estimation of association between bivariate failure times. In the presence of independent right censoring, the support for failure time variates may be restricted and measures of dependence over a finite failure time region may be of particular interest. To this end, the reciprocal cross ratio function, weighted by the bivariate failure time density, is proposed as a summary measure of dependence over a failure time region. This 'relative risk' estimator is shown to be consistent and asymptotically normally distributed, with consistent bootstrap variance estimator. A finite-region version of Kendall's tau, which is suitable for censored failure time data, is also proposed, and corresponding asymptotic distribution theory is noted. The accuracy of these asymptotic approximations is studied in simulations and an illustration is provided.

Reliability of Isokinetic Concentric and Eccentric Strength in Circumpubertal Soccer Players

The reliable examination of isokinetic parameters in young athletes is important for the establishment of appropriate strength testing protocols. The purpose of this study was to examine the reliability of peak moments, non-preferred/preferred leg and reciprocal ratios during isokinetic knee efforts in young soccer players. Thirteen circumpubertal (age = 13.0 ± 0.4 years) soccer players performed maximum knee extension and flexion efforts at 30, 120 and 180°·s1 in two occasions, a week apart. The reliability of the peak moments was high, with reliability coefficients ranging from 0.71 to 0.98. The non-preferred/preferred leg and reciprocal ratios demonstrated moderate to high reliability (coefficients ranged from 0.42 to 0.87). The reliable examination of moments of force and ratio measurements during eccentric tests and at fast angular velocities in young soccer players requires extensive familiarization of the subjects prior to the main test.

Fourier transform infrared spectroscopy characterisation of carotid plaques. II

A histological and spectroscopic study on carotid plaques was performed. Based on the analysis of band shape of important groups like amides, their convolution and their reciprocal intensity ratio, we were able to draw a map of the distribution of intima, homogeneous, dishomogeneous and ulcerated parts of the plaque and to characterise various components (cholesterol etc.). When present, the nature of the thrombus was clarified.

MUSCULAR DYSBALANCES IN DIFFERENT SHOULDER EXERCISES

229 Functionally, the shoulder is considered a ball joint, whereby high mobility is attended by low stability. Therefore, muscular balance is decisive for stability. Altered strength ratios are frequently described as "muscular dysbalances" and considered one of the causes of various shoulder pathologies, whereby objective quantification is difficult. In order to define muscular balance first, the strength ratios of reciprocal muscle groups (quotient of peak torque) for extension/flexion (EX/FL), abduction/adduction (AB/AD) and rotation movements (ERO/IRO) were determined in 166 untrained men (UM) and 83 untrained women (UF). Determination was made isometric, concentric (60°/s, 180°/s) and eccentric (60°/s, 120°/s, LIDO-Active). The influence on this norm of one-sided (25 high-performance tennis players, TPH; 18 leisure tennis players, TPL) and two-sided (32 gymnasts, GY) athletic exercise, altered daily exercise (11 paraplegics with paralysis time < 4 mo., PP; 11 Paraplegics with paralysis time > 2 years, PU) and a combination of longer existing, altered daily exercise and increased athletic exercise (16 trained paraplegics, PT) was examined (ANOVA, α=0.05). The definition of the sex-specific norm showed no differences in reciprocal strength ratios between UM and UF (p>0.05) in spite of different absolute torque values (p<0.05). EX, AD and ERO showed higher torques, so that the quotients were < 1. Morcover, there was a decrease in the sequence AB/AD > FL/EX > ERO/IRO. Shoulder stress in sports led to a decrease in quotients compared to UM due to a relatively increased maximum strength in EX, AD and ERO (p<0.01). At the beginning of a paraplegia (PP), the quotient of FL/EX and AB/AD is elevated (p<0.05). This altered ratio decreases with increasing duration of paralysis (PU). The combination of paraplegia and athletic exercise (PT) showed no difference in ratios to UM. With increased shoulder stress, the altered strength ratios reflect specific requirements of the performance attained. However, the importance of muscular dysbalances for the onset of shoulder complaints must be considered more important than their influence on athletic performance capacity.

Morphometry and Quality Control For a May-Grunwald Giemsa Stained Preparation. A 40 Centers Cooperative Study

A multicentric study including 40 medical centers has been done on May-Gmnwald Giemsa (MGG) stain, to obtain precise information concerning the size, shape and color of cellular elements. A number of factors are taken into consideration including the zone of microscopic observation, the quality of staining, condition of grabbing images and the size of the sample. Morphometric and colorimetric measurements have been applied as objective tools for demonstrating the predominance of each Red/Green/Blue component, and more particularly their reciprocal ratio. The results obtained for each center may constitute a guideline for adjusting their procedure, in order to reach a consensus regarding similar staining by all centers.

Consistency of gas hold-up determinations

The retention of methane on poly(dimethylsiloxane) capillary columns was studied focusing its relation with the gas hold-up time t M, which was derived from the retention of n-alkanes. The [ideal gas/Van der Waals fluid] partition equation was applied in order to provide the mathematical expression for the retention factor of the n-alkanes as a function of the carbon number n. In this context the partial molar free energy of solution is a non-linear function of the chain length Δ G s( n) ( n≥5). The resultant retention factor k of methane, determined from its retention time and the calculated t M, approaches an almost constant value when the temperature is increased beyond 100°C. This value of k has the order of the reciprocal column phase ratio 1/ β. Precisely, this is the theoretically expected limit of a non-interacting solute or inert marker.

Philopatry, male presence and grooming reciprocation among female primates: a comparative perspective

Competition for food and a safe location in a group are considered to be the main determinants of variation in social relationships among female primates. The effect of the presence of males is usually overlooked, however. Here we put forward two hypotheses connecting the (relative) number of males in a group, a statistic measuring the strength of positive relationships among females (the degree of reciprocity of grooming) and female residence. Under the first hypothesis, we assumed that philopatric females suffer especially from competition for males. Because females of these species are restrained to their native group and thus do not move to groups where better conditions (i.e. more males) prevail, a higher socionomic sex ratio would imply reduced competition and this should be reflected in better relationships among females (i.e. in a higher degree of reciprocation). The second hypothesis is based on the contention of Wrangham (1987) that groups with more males are better able to defend large food sources: in these groups female relationships would suffer less from within-group competition for food. We therefore also expected a positive correlation between the absolute number of males and grooming reciprocation. To test the hypotheses, matrices of grooming interactions were collected by going through the primatological literature. For ten female-resident and four female-transfer primate species, the degree of grooming reciprocation was quantified using a specially adapted matrix statistic. The results favoured the first (competition for males) hypothesis. The degree of grooming reciprocation among females was positively correlated with socionomic sex ratio, but neither with group size nor with the absolute number of males. Correlations between the degree of reciprocity and sex ratio were confirmed at three levels: within the same group at different points in time, between groups of the same species, and between species. In addition, the degree of reciprocation increased with sex ratio more strongly in typical single/variable male than in multi-male species. This we interpreted as a direct consequence of the lower social availability of males for females in multi-male groups than single-male groups. In turn, this effect may be due to males competing for females in multi-male groups.

A mathematical model for neutral sulfite pulping of various broadleaved wood species

A mathematical model for neutral sulfite pulping process was derived. This model represented by a linear logarithmic relationship of the main pulping characteristics (yield and lignin content) to time and temperature parameters, both determined by the H-factor, is expressed by a logarithmic straight line equation. The relationship of yield to lignin content in the high yield pulps after neutral sulfite pulping is also expressed by a logarithmic straight line equation. A suitable way to calculate the main characteristics of neutral sulfite pulping is the power form of the logarithmic straight line equation for the dependence of the ratio yield/lignin vs. lignin content, yield/H-factor vs. H-factor, lignin/H-factor vs. H-factor and their mathematical equivalents (i.e. reciprocal ratio and/or product). A set of power equations characterizing the relationships yield vs. lignin content as well as yield and lignin content vs. H-factor for woodpulps prepared by neutral sulfite pulping of various broadleaved wood species are given.

Concentric and eccentric isokinetic measurements in knee muscles during the menstrual cycle: A special reference to reciprocal moment ratios

Objective: To investigate the effects of menstrual cycle on the reliability of concentric (CON) and eccentric (ECC) isokinetic measurements and reciprocal moment ratios in knee muscles. Design: Repeated measurements. Setting: A university exercise physiology laboratory. Participants: Sixteen healthy sedentary women volunteers, aged 24 to 35 years, who had regular menstrual cycle (ranging from 24 to 32 days). Methods: Subjects were tested at 60°/sec (4 repetitions) and 180°/sec (20 repetitions) of angular velocities for CON and ECC tests at the menstrual (MP, days 1 to 3), follicular (FP, days 7 to 10), and luteal phases (LP, 19 to 21). Blood samples were analyzed for sex hormones at the FP and LP. Results: ECC and CON peak torques and total works, and their reciprocal ratios in dominant knee muscles, were not significantly different among the phases by ANOVA. Intraclass correlation coefficients (ICCs) among the phases for peak torque and total work of knee extensors in both angular velocities were in the range of .68 to .91 and .45 to .84 for CON and ECC tests, respectively. However, it was in the range of .03 to .72 and .65 to .94 for CON and ECC tests of knee flexors, respectively. In addition, there were no significant correlations between sex hormones and tested variables. Conclusion: The results suggest that the phase of the menstrual cycle should not be taken into account in isokinetic measurements.

Layered excipient suppositories: The possibility of modulating drug availability

The release rate of a drug dose from suppositories is affected by characteristics of the excipient (melting temperature and rate, viscosity at rectal temperature, hydro-lipophilic characteristics). Release kinetics from excipients commonly available do not always respond to clinical requirements, even after the introduction of auxiliary agents. Release curves which were differentiated and adaptable to therapeutic conditions were obtained by vehicling a drug in suppositories of two superimposed layers of lipophilic excipients with different characteristics and hence with a difference in drug availability. The two distinct excipient layers release the drug from these suppositories contemporaneously but independently. The amount of drug released in the time course is the sum of the single amounts individually released by the two suppository layers. By previously mixing the two excipients, release rate becomes uniform in the suppository body overall and is conditioned only by the assumed characteristics of the mixture. The release mechanism for superimposed layer suppositories is confirmed by the good agreement between experimental and calculated curves. By using a pair of excipients with different characteristics in superimposed layers between which the drug is distributed, it is possible to modulate drug release kinetics by regulating the reciprocal ratio between the two suppository fractions.

Transport of nitrullin, a new nitrosoalkylurea derivative, into tumor and normal cells

The interaction between the antitumor drug nitrullin and the system providing the transport ofl-lysine into P388 leukemic cells and murine enterocytes is studied. Two types of lysine carriers with low and high affinity for the substrate are identified. Nitrullin competitively inhibits the transport of3H-lysine and shows the same affinity for both carriers. It is similar to that of lysine for the low-affinity carrier and is 80-fold lower than lysine affinity for the high-affinity carrier. Kinetic characteristics of the low-affinity transport of3H-lysine and Ki of nitrullin are similar to those obtained at a reciprocal substrate-inhibitor ratio. Nitrullin does not inhibit active transport of3H-lysine into enterocytes against the background of considerable (70%) passive diffusion.