Diffusion in stationary flow from mesoscopic nonequilibrium thermodynamics

We analyze the diffusion of a Brownian particle in a fluid under stationary flow. By using the scheme of nonequilibrium thermodynamics in phase space, we obtain the Fokker-Planck equation that is compared with others derived from the kinetic theory and projector operator techniques. This equation exhibits violation of the fluctuation-dissipation theorem. By implementing the hydrodynamic regime described by the first moments of the nonequilibrium distribution, we find relaxation equations for the diffusion current and pressure tensor, allowing us to arrive at a complete description of the system in the inertial and diffusion regimes. The simplicity and generality of the method we propose makes it applicable to more complex situations, often encountered in problems of soft-condensed matter, in which not only one but more degrees of freedom are coupled to a nonequilibrium bath.

Sex-chromosome turnovers induced by deleterious mutation load.

In sharp contrast with mammals and birds, many cold-blooded vertebrates present homomorphic sex chromosomes. Empirical evidence supports a role for frequent turnovers, which replace nonrecombining sex chromosomes before they have time to decay. Three main mechanisms have been proposed for such turnovers, relying either on neutral processes, sex-ratio selection, or intrinsic benefits of the new sex-determining genes (due, e.g., to linkage with sexually antagonistic mutations). Here, we suggest an additional mechanism, arising from the load of deleterious mutations that accumulate on nonrecombining sex chromosomes. In the absence of dosage compensation, this load should progressively lower survival rate in the heterogametic sex. Turnovers should occur when this cost outweighs the benefits gained from any sexually antagonistic genes carried by the nonrecombining sex chromosome. We use individual-based simulations of a Muller's ratchet process to test this prediction, and investigate how the relevant parameters (effective population size, strength and dominance of deleterious mutations, size of nonrecombining segment, and strength of sexually antagonistic selection) are expected to affect the rate of turnovers.

Impaired chemical coupling of cerebral blood flow is compatible with intact neurological outcome in neonates with perinatal risk factors.

Early detection of pathophysiological factors associated with permanent brain damage is a major issue in neonatal medicine. The aim of our study was to evaluate the significance of the CO2 reactivity of cerebral blood flow (CBF) in neonates with perinatal risk factors. Fourteen ventilated neonates with perinatal risk factors (pathological cardiotocogramm, low cord pH, postpartal encephalopathy) were enrolled into this prospective study. The study was performed 18-123 h after birth. CBF was measured using the noninvasive intravenous 133Xe method. Two measurements were taken with a minimal PaCO2-difference of 5 mm Hg. From the two CBF values the CO2 reactivity was calculated. Outcome was evaluated 1 year after birth. The CBF values at a lower PaCO2 ranged from 6.6 to 115. 2 ml/100 g brain issue/min (median = 18.2) and at a higher PaCO2 level from 7.1 to 125.7 ml/100 g brain tissue/min (median = 18.75). The calculated CO2 reactivity ranged from -9.6 to 6.6% (median 1.1%) change in CBF/mm Hg change in PaCO2. CO2 reactivity correlated with lowest pH (r2 = 0.35, p = 0.02). Two infants died, one of neonatal sepsis, the other of heart failure. Neurological outcome at the age of 1 year was normal in 11 patients, 1 had severe cerebral palsy. From the 12 surviving patients the patient with severe neurological deficit showed the highest CBF values (125.7 ml/100 g/min). Impaired chemical coupling of cerebral blood flow is compatible with intact neurological outcome in neonates with perinatal risk factors. CO2 reactivity in these newborns correlates with the lowest pH and may reflect the severity of perinatal asphyxia.

A hybrid algorithm combining metaheuristic with Monte Carlo simulation for solving the Stochastic Flow Shop problem

In this paper, a hybrid simulation-based algorithm is proposed for the StochasticFlow Shop Problem. The main idea of the methodology is to transform the stochastic problem into a deterministic problem and then apply simulation to the latter. In order to achieve this goal, we rely on Monte Carlo Simulation and an adapted version of a deterministic heuristic. This approach aims to provide flexibility and simplicity due to the fact that it is not constrained by any previous assumption and relies in well-tested heuristics.

A hybrid algorithm combining metaheuristic with Monte Carlo simulation for solving the Stochastic Flow Shop problem

In this paper, a hybrid simulation-based algorithm is proposed for the StochasticFlow Shop Problem. The main idea of the methodology is to transform the stochastic problem into a deterministic problem and then apply simulation to the latter. In order to achieve this goal, we rely on Monte Carlo Simulation and an adapted version of a deterministic heuristic. This approach aims to provide flexibility and simplicity due to the fact that it is not constrained by any previous assumption and relies in well-tested heuristics.

Trust region versus line search for computing the optical flow

We consider the numerical treatment of the optical flow problem by evaluating the performance of the trust region method versus the line search method. To the best of our knowledge, the trust region method is studied here for the first time for variational optical flow computation. Four different optical flow models are used to test the performance of the proposed algorithm combining linear and nonlinear data terms with quadratic and TV regularization. We show that trust region often performs better than line search; especially in the presence of non-linearity and non-convexity in the model.

Estimating gene flow across hybrid zones: how reliable are microsatellites?

Due to their high polymorphism, microsatellites have become one of the most valued genetic markers in population biology. We review the first two published studies on hybrid zones of the common shrew based on microsatellites. Both reveal surprisingly high interracial gene flow. It can be shown that these are overestimates. Indeed, in classical population genetics models as F-statistics, mutation is neglected. This constitutes an acceptable assumption as long as migration is higher than mutation. However, in hybrid zones where genetic exchanges can be rare, neglecting mutation will lead to strong overestimates of migration when working with microsatellites which display mutation rates up to 10(-3). As there seems to be no straightforward way to correct for this bias, interracial gene flow estimates based on microsatellites should be taken with caution. This problem should however not conceal the enormous potential of microsatellites to unravel the genetics of hybrid zones.

Milk flow, teat morphology and subclinical mastitis prevalence in Gir cows

The aim of this work was to evaluate the association between milk flow, teat morphological measurements and subclinical mastitis prevalence in Gir cows. Eighty cows in the 2nd and 3rd lactations, with 90 to 200 days of lactation, were divided according to milk flow during milking into fast or slow groups. Teat morphometry was assessed by ultrasound scanning of the right anterior teat and external measurements. Milk samples were collected for somatic cells count (SCC) and microbiological culture. The effect of milk flow during milking was evaluated by analysis of variance of milk yield, SCC, morphometry and external measurements. The association of morphometry and external measurements of the teats with the SCC and microorganisms found in milk were analysed. Milk flow was significantly correlated to milk production. Gir cows with slower milk flow had longer teat canal and greater milk yield, in comparison to cows with fast milk flow. Teat-end to floor distance influenced SCC of Gir cows. Prevalence of subclinical mastitis and the type of mastitis-causing pathogens were not affected by milk flow during milking

A study of the effect of sartorius transposition on lymph flow after ilioinguinal node dissection.

Ilioinguinal dissection is associated with a high rate of lymphatic complications. Prolonged lymph flow causes greatest concern and preventive strategies are needed. A retrospective study of 28 consecutive patients undergoing groin dissection for melanoma metastases was performed to evaluate the influence of sartorius muscle transposition on lymph flow. Modification of the surgical technique with transposition of the sartorius muscle was not associated with reduced drainage time (P = 0.66). A 2-staged approach, with initial sentinel lymph node resection and lymph node dissection in a second operation, however, lead to shortened duration of the lymph flow (P = 0.01). Prolonged lymphorrhea was more frequent in older (P = 0.03), obese (P = 0.02) patients affected by diabetes mellitus (P = 0.03) and hypertension (P = 0.04).

Ultimate Load Behavior of Full-Scale Highway Truss Bridges: Phase I - Ultimate Load Tests of the Hubby Bridge - Boone County, Interim Report, HR-169, 1975

As a result of the construction of the Saylorville Dam and Reservoir on the Des Moines River, six highway bridges crossing the river were scheduled for removal. One of these, an old pinconnected high-truss single-lane bridge, was selected for a testing program which included ultimate load tests. The purpose of the ultimate load tests, which are summarized in this report, was to relate design and rating procedures presently used in bridge design to the field behavior of this type of truss bridge. The ultimate load tests consisted of ultimate load testing of one span of the bridge, of two I-shaped floorbeams, and of two panels of the timber deck. The theoretical capacity of each of these components is compared with the results from the field tests.

Spatiotemporal adaptive multiscale multiphysics simulations of two-phase flow

We present a spatiotemporal adaptive multiscale algorithm, which is based on the Multiscale Finite Volume method. The algorithm offers a very efficient framework to deal with multiphysics problems and to couple regions with different spatial resolution. We employ the method to simulate two-phase flow through porous media. At the fine scale, we consider a pore-scale description of the flow based on the Volume Of Fluid method. In order to construct a global problem that describes the coarse-scale behavior, the equations are averaged numerically with respect to auxiliary control volumes, and a Darcy-like coarse-scale model is obtained. The space adaptivity is based on the idea that a fine-scale description is only required in the front region, whereas the resolution can be coarsened elsewhere. Temporal adaptivity relies on the fact that the fine-scale and the coarse-scale problems can be solved with different temporal resolution (longer time steps can be used at the coarse scale). By simulating drainage under unstable flow conditions, we show that the method is able to capture the coarse-scale behavior outside the front region and to reproduce complex fluid patterns in the front region.

Sex differences in lipid and glucose kinetics after ingestion of an acute oral fructose load.

The increase in VLDL TAG concentration after ingestion of a high-fructose diet is more pronounced in men than in pre-menopausal women. We hypothesised that this may be due to a lower fructose-induced stimulation of de novo lipogenesis (DNL) in pre-menopausal women. To evaluate this hypothesis, nine healthy male and nine healthy female subjects were studied after ingestion of oral loads of fructose enriched with 13C6 fructose. Incorporation of 13C into breath CO2, plasma glucose and plasma VLDL palmitate was monitored to evaluate total fructose oxidation, gluconeogenesis and hepatic DNL, respectively. Substrate oxidation was assessed by indirect calorimetry. After 13C fructose ingestion, 44.0 (sd 3.2)% of labelled carbons were recovered in plasma glucose in males v. 41.9 (sd 2.3)% in females (NS), and 42.9 (sd 3.7)% of labelled carbons were recovered in breath CO2 in males v. 43.0 (sd 4.5)% in females (NS), indicating similar gluconeogenesis from fructose and total fructose oxidation in males and females. The area under the curve for 13C VLDL palmitate tracer-to-tracee ratio was four times lower in females (P < 0.05), indicating a lower DNL. Furthermore, lipid oxidation was significantly suppressed in males (by 16.4 (sd 5.2), P < 0.05), but it was not suppressed in females ( -1.3 (sd 4.7)%). These results support the hypothesis that females may be protected against fructose-induced hypertriglyceridaemia because of a lower stimulation of DNL and a lower suppression of lipid oxidation.

Ultimate Load Behavior of Full-Scale Highway Truss Bridges: Phase II - Service Load and Supplementary Tests, Interim Report, HR-169, 1975

As a result of the construction of the Saylorville Dam and Reservoir on the Des Moines River, six highway bridges crossing the river were scheduled for removal. Two of these were incorporated into a comprehensive test program to study the behavior of old pin-connected high-truss single-lane bridges. The test program consisted of ultimate load tests, service load tests and a supplementary test program. The results reported in this report cover the service load tests on the two bridges as well as the supplementary tests, both static and fatigue, of eyebar members removed from the two bridges. The field test results of the service loading are compared with theoretical results of the truss analysis.