Influence of dietary linoleic acid intake with different fat intakes on arachidonic acid concentrations in plasma and platelet lipids and eicosanoid biosynthesis in female volunteers

Background/Aim: N-6 fatty acids are considered to promote diseases prevalent in industrialized countries and characterized by an increased eicosanoid biosynthesis from arachidonic acid (AA). We investigated the impact of the linoleic acid (LA) intake on AA levels in humans. Methods: Six healthy female volunteers (age range 2334 years) were given liquid formula diets (LFD) devoid of AA for 6 weeks, providing a constant intake of zero energy% (LFD 0: protein 15%, carbohydrates 85%) or 20 energy% (LFD 20: protein 15%, carbohydrates 55%, fat 30%) LA, for 3 weeks each. Fatty acids of plasma cholesteryl esters and platelet lipids were determined each week, and the prostaglandin biosynthesis was measured in 24-hour urine samples. Results: LFD 0 increased (+31% of initial value) and LFD 20 lowered (-30% of initial value) the percentage of AA in plasma cholesteryl esters and platelet lipids. Moreover, absence of dietary AA lowered the percentages of AA in plasma (-31% week 0 vs. week 6) and platelet (-11%) lipids, indicating a low transformation of LA. LFD 0 reduced urinary metabolite levels of prostaglandins D, E, and F in 24-hour urine samples (-48%, p < 0.001) within 24 h, but did not significantly affect platelet aggregation (-10%) and thromboxane formation (-25%). LFD 20 significantly lowered platelet aggregation (-25%) and thromboxane formation (-43%). The prostaglandin metabolite levels increased during the first 10 days, declined thereafter, and were lower than the preexperimental values at the end of the 3-week period. Conclusions: The results show that dietary LA does not increase the AA levels in plasma or platelet lipids and does not persistently contribute to prostaglandin biosynthesis which is increased by AA intake with Western diets

Two-fluid tokamak equilibria with reversed magnetic shear and sheared flow

The aim of the present work is to investigate tokamak equilibria with reversed magnetic shear and sheared flow, which may play a role in the formation of internal transport barriers (ITBs), within the framework of two-fluid model. The study is based on exact self-consistent solutions in cylindrical geometry by means of which the impact of the magnetic shear, s, and the "toroidal" (axial) and "poloidal" (azimuthal) ion velocity components on the radial electric field, its shear and the shear of the ExB velocity is examined. For a wide parametric regime of experimental concern it turns out that the contributions of the toroidal and poloidal velocity and pressure gradient terms to the electric field, its shear and ExB velocity shear are of the same order of magnitude. The impact of s on ExB velocity shear through the pressure gradient term is stronger than that through the velocity terms. The results indicate that, alike MHD, the magnetic shear and the sheared toroidal and poloidal velocities act synergetically in producing electric fields and therefore ExB velocity shear profiles compatible with ones observed in discharges with ITBs; owing to the pressure gadient term, however, the impact of s on the electic field, its shear and the shear of ExB velocity is stronger than that in MHD.Comment: 25 pages, 21 figure

Parameter estimation for macroscopic pedestrian dynamics models from microscopic data

In this paper we develop a framework for parameter estimation in macroscopic pedestrian models using individual trajectories -- microscopic data. We consider a unidirectional flow of pedestrians in a corridor and assume that the velocity decreases with the average density according to the fundamental diagram. Our model is formed from a coupling between a density dependent stochastic differential equation and a nonlinear partial differential equation for the density, and is hence of McKean--Vlasov type. We discuss identifiability of the parameters appearing in the fundamental diagram from trajectories of individuals, and we introduce optimization and Bayesian methods to perform the identification. We analyze the performance of the developed methodologies in various situations, such as for different in- and outflow conditions, for varying numbers of individual trajectories and for differing channel geometries

On computational irreducibility and the predictability of complex physical systems

Using elementary cellular automata (CA) as an example, we show how to coarse-grain CA in all classes of Wolfram's classification. We find that computationally irreducible (CIR) physical processes can be predictable and even computationally reducible at a coarse-grained level of description. The resulting coarse-grained CA which we construct emulate the large-scale behavior of the original systems without accounting for small-scale details. At least one of the CA that can be coarse-grained is irreducible and known to be a universal Turing machine.Comment: 4 pages, 2 figures, to be published in PR

Ergodic and Nonergodic Anomalous Diffusion in Coupled Stochastic Processes

Inspired by problems in biochemical kinetics, we study statistical properties of an overdamped Langevin process whose friction coefficient depends on the state of a similar, unobserved process. Integrating out the latter, we derive the long time behaviour of the mean square displacement. Anomalous diffusion is found. Since the diffusion exponent can not be predicted using a simple scaling argument, anomalous scaling appears as well. We also find that the coupling can lead to ergodic or non-ergodic behaviour of the studied process. We compare our theoretical predictions with numerical simulations and find an excellent agreement. The findings caution against treating biochemical systems coupled with unobserved dynamical degrees of freedom by means of standard, diffusive Langevin descriptions

Max-plus analysis on some binary particle systems

We concern with a special class of binary cellular automata, i.e., the so-called particle cellular automata (PCA) in the present paper. We first propose max-plus expressions to PCA of 4 neighbors. Then, by utilizing basic operations of the max-plus algebra and appropriate transformations, PCA4-1, 4-2 and 4-3 are solved exactly and their general solutions are found in terms of max-plus expressions. Finally, we analyze the asymptotic behaviors of general solutions and prove the fundamental diagrams exactly.Comment: 24 pages, 5 figures, submitted to J. Phys.

Analgesia and sedation in the intensive care unit: an overview of the issues

Analgesic and sedative medications are widely used in intensive care units to achieve patient comfort and tolerance of the intensive care unit environment, and to eliminate pain, anxiety, delirium and other forms of distress. Surveys and prospective cohort studies have revealed wide variability in medication selection, monitoring using sedation scales, and implementation of structured treatment algorithms among practitioners in different countries and regions of the world. Successful management of analgesia and sedation incorporates a patient-based approach that includes detection and management of predisposing and causative factors, including delirium; monitoring using analgesia and sedation scales and other instruments; proper medication selection, with an emphasis on analgesia-based drugs; and incorporation of structured strategies that have been demonstrated to reduce likelihood of excessive or prolonged sedation

Variation of magnetic properties of Sr2_2FeMoO6_6 due to oxygen vacancies

Oxygen vacancies can be of utmost importance for improving or deteriorating physical properties of oxide materials. Here, we studied from first-principles the electronic and magnetic properties of oxygen vacancies in the double perovskite Sr$_2$FeMoO$_6$ (SFMO). We show that oxygen vacancies can increase the Curie temperature in SFMO, although the total magnetic moment is reduced at the same time. We found also that the experimentally observed valence change of the Fe ions from $3+$ to $2+$ in the x-ray magnetic circular dichroism (XMCD) measurements is better explained by oxygen vacancies than by the assumed mixed valence state. The agreement of the calculated x-ray absorption spectra and XMCD results with experimental data is considerably improved by inclusion of oxygen vacancies.Comment: submitted to PRB but rejected, major revision, submitting to JPC

Neuronal Distortions of Reward Probability without Choice

Reward probability crucially determines the value of outcomes. A basic phenomenon, defying explanation by traditional decision theories, is that people often overweigh small and underweigh large probabilities in choices under uncertainty. However, the neuronal basis of such reward probability distortions and their position in the decision process are largely unknown. We assessed individual probability distortions with behavioral pleasantness ratings and brain imaging in the absence of choice. Dorsolateral frontal cortex regions showed experience dependent overweighting of small, and underweighting of large, probabilities whereas ventral frontal regions showed the opposite pattern. These results demonstrate distorted neuronal coding of reward probabilities in the absence of choice, stress the importance of experience with probabilistic outcomes and contrast with linear probability coding in the striatum. Input of the distorted probability estimations to decision-making mechanisms are likely to contribute to well known inconsistencies in preferences formalized in theories of behavioral economics

Sodium and mineralocorticoids in normal pregnancy

For many years clinicians have speculated that abnormal sodium metabolism plays an important role in the pathogenesis of hypertension. This consideration probably has been most evident in obstetrical practices directed toward preventing hypertensive disorders of pregnancy. It was commonly assumed that normal gestation was associated with sodium-retaining tendencies, which were thought to be causally related to the development of preeclampsia. Accordingly, pregnant women customarily were treated as though threatened by excessive sodium retention; dietary salt restriction and diuretics were prescribed routinely as precautionary measures.In view of this concern, it is quite understandable that the discovery of aldosterone and the recognition of its causal relationship to hypertension in Conn's syndrome quickly led early investigators to study the possible pathogenic role of this potent mineralocorticoid in the hypertensive disorders of pregnancy. Initial reports suggesting that aldosterone levels were higher in preeclamptic than in nonpregnant women generated considerable excitement, which quickly was tempered by the observation that aldosterone secretion was increased to an even greater extent in normal gravidas [1]. Since then, results of numerous studies have provided confirmation that aldosterone levels are markedly elevated in normal gravidas compared with nonpregnant women on similar salt intakes [2, 3]. More recently, it has been shown that secretion of another potent mineralocorticoid, desoxycorticosterone, also is increased substantially during normal pregnancy [4, 5]. Nonetheless, normal gravidas do not demonstrate clinical evidence of mineralocorticoid excess, and the blood pressure falls below pregnancy values during the first two trimesters.Although the regulation of aldosterone secretion in pregnancy has been studied extensively, the physiologic significance of the markedly increased secretion of aldosterone remains controversial. There is considerable evidence that normal pregnancy results in a tendency towards a reduced effective blood volume, despite the high levels not only of aldosterone and desoxycorticosterone, but also of estrogens, which have sodium-retaining effects in man. Thus, some propose that the enhanced secretion of aldosterone is a compensatory response required to maintain normal volume homeostasis [6]. Others argue that the augmented extracellular and intravascular fluid volumes measured in normal pregnancy, as well as the accompanying rise in cardiac output and in the GFR, are inconsistent with functional hypovolemia, and suggest that these changes more likely reflect sodium retention induced by aldosterone hypersecretion [7].Questions regarding the role of increased aldosterone in pregnancy, whether it is associated with a tendency to lose or to retain sodium, not only have a bearing upon routine management of pregnant women, but are also of fundamental importance to our understanding of the pathophysiology of the gestational hypertensive disorders. In attempting to resolve these issues, it would seem appropriate to review studies that might help to define the role of increased mineralocorticoids in normal pregnancy