Academic literature on the topic 'Flux RG'

We report here our studies on K+ transport in resealed human red cell ghosts (RG) in the presence of 0.1 mM ouabain and 0.01 mM bumetanide, inhibitors of the Na+-K+ pump and Na+-K+-Cl- cotransport, respectively. RG were obtained with the gel-filtration method. K+ efflux from RG was dependent on the pH used in the lysis buffer and increased when the pH used in the lysis buffer and increased when the pH was raised from 5.5 to 8.0. As in intact red cells, RG made from cells of the least dense fraction had a much higher K+ efflux than RG made from cells of the densest fraction. This K+ flux is volume independent and increases when the pH of the flux medium is increased from 6.0 to 8.0. K+ efflux (60-70%) at pH 7.40 from RG made from cells of the least dense fraction is inhibited when Cl- is substituted by nitrate or when the ghosts are resealed in the absence of ATP. This chloride- and ATP-dependent component is markedly reduced in RG made from cells of the densest fraction. An increase in the internal Mg2+ concentration in RG from the least dense fraction induced marked inhibition of K+ efflux. Contrary to intact cells, N-ethylmaleimide (NEM) did not affect K+ efflux from RG. Thus the effects of pH, osmolarity, and NEM on K+ transport in RG are markedly different from those reported in intact erythrocytes.

The influence of blood flow (BF) and basal neuromotor tone on in vivo insulin-stimulated glucose uptake (Rg') in muscle was examined using the euglycemic clamp plus deoxyglucose/glucose tracer (insulin action) and labeled microsphere (BF) techniques. Anesthesia was used to produce perturbations in BF and/or activity compared with conscious rats. An index of muscle glycolytic flux (Gf) was estimated from Rg' in excess of glycogen synthesis. Gf and glycogen synthesis were significantly increased in soleus and red gastrocnemius (RG) during insulin infusion (150 mU/l) in conscious rats. Rg' was related to muscle BF in conscious rats (r = 0.92). In anesthetized rats, Rg' and BF were reduced in soleus, RG, red quadriceps, and plantaris (e.g., soleus 69%, P less than 0.001, and 80%, P less than 0.001, respectively). However, it is unlikely that Rg' and BF are causally related because fractional extraction of glucose by muscle was low (approximately 9%); fractional extraction increased during anesthesia (17%, P less than 0.01); BF but not Rg' was reduced by anesthesia in extensor digitorum longus, white gastrocnemius, and white quadriceps; and reduced Rg' during anesthesia in soleus and RG was mainly due to reduced GF. In conclusion, BF is not a major contributor to the heterogeneity in insulin-stimulated glucose uptake among individual muscles under basal conditions. These data suggest that neuromotor tone may indirectly influence the magnitude of muscle glucose uptake during insulin elevation via a substrate switching effect. This may give rise to a significant increase in glycolytic flux of glucose in those muscles that exhibit elevated activity even at rest (e.g., soleus).(ABSTRACT TRUNCATED AT 250 WORDS)

Abstract Cospectral budgets are used to link the kinetic and potential energy distributions of turbulent eddies, as measured by their spectra, to macroscopic relations between the turbulent Prandtl number (Prt) and atmospheric stability measures such as the stability parameter ζ, the gradient Richardson number Rg, or the flux Richardson number Rf in the atmospheric surface layer. The dependence of Prt on ζ, Rg, or Rf is shown to be primarily controlled by the ratio of Kolmogorov and Kolmogorov–Obukhov–Corrsin phenomenological constants and a constant associated with isotropization of turbulent flux production that can be independently determined using rapid distortion theory in homogeneous turbulence. Changes in scaling laws of the vertical velocity and air temperature spectra are also shown to affect the Prt–ζ (or Prt–Rg or Prt–Rf) relation. Results suggest that departure of Prt from unity under neutral conditions is induced by dissimilarity between momentum and heat in terms of Rotta constants, isotropization constants, and constants in the flux transfer terms. A maximum flux Richardson number Rfm predicted from the cospectral budgets method (=0.25) is in good agreement with values in the literature, suggesting that Rfm may be tied to the collapse of Kolmogorov spectra instead of laminarization of turbulent flows under stable stratification. The linkages between microscale energy distributions of turbulent eddies and macroscopic relations that are principally determined by dimensional considerations or similarity theories suggest that when these scalewise energy distributions of eddies experience a “transition” to other distributions (e.g., when Rf is increased over Rfm), dimensional considerations or similarity theories may fail to predict bulk flow properties.

Glucagon-like peptide-1 (GLP-1) diminishes postmeal glucose excursions by enhancing insulin secretion via activation of the β-cell GLP-1 receptor (Glp1r). GLP-1 may also control glucose levels through mechanisms that are independent of this incretin effect. The hyperinsulinemic-euglycemic clamp (insulin clamp) and exercise were used to examine the incretin-independent glucoregulatory properties of the Glp1r because both perturbations stimulate glucose flux independent of insulin secretion. Chow-fed mice with a functional disruption of the Glp1r (Glp1r−/−) were compared with wild-type littermates (Glp1r+/+). Studies were performed on 5-h-fasted mice implanted with arterial and venous catheters for sampling and infusions, respectively. During insulin clamps, [3-3H]glucose and 2[14C]deoxyglucose were used to determine whole-body glucose turnover and glucose metabolic index (Rg), an indicator of glucose uptake. Rg in sedentary and treadmill exercised mice was determined using 2[3H]deoxyglucose. Glp1r−/− mice exhibited increased glucose disappearance, muscle Rg, and muscle glycogen levels during insulin clamps. This was not associated with enhanced muscle insulin signaling. Glp1r−/− mice exhibited impaired suppression of endogenous glucose production and hepatic glycogen accumulation during insulin clamps. This was associated with impaired liver insulin signaling. Glp1r−/− mice became significantly hyperglycemic during exercise. Muscle Rg was normal in exercised Glp1r−/− mice, suggesting that hyperglycemia resulted from an added drive to stimulate glucose production. Muscle AMP-activated protein kinase phosphorylation was higher in exercised Glp1r−/− mice. This was associated with increased relative exercise intensity and decreased exercise endurance. In conclusion, these results show that the endogenous Glp1r regulates hepatic and muscle glucose flux independent of its ability to enhance insulin secretion. During increased glucose flux, the glucagon-like peptide-1 receptor regulates endogenous glucose production and muscle glucose uptake independent of its ability to stimulate insulin secretion.

The establishment of sown pasture is an important agricultural practice in many landscapes. Although both native grassland and sown pasture play a key role in the global carbon cycle, due to lack of data and field experiments, our understanding of grassland CH4 fluxes and CO2 emissions remains limited, especially when it comes to sown pasture. We measured ecosystem respiration and CH4 fluxes in response to a variety of potential drivers (soil temperature, soil moisture, ammonium nitrogen, nitrate nitrogen and dissolved organic carbon) in CG (continuous grazing), RG (rotational grazing) and UG (ungrazed) plots in sown grassland for one year in Inner Mongolia. Fluxes of CH4 and ecosystem respiration were measured using static opaque chambers and gas chromatography. Grazing significantly reduced ecosystem respiration (p < 0.01), and grazing pattern significantly influenced respiration in CG and RG plots (p < 0.01). We find that the sown grassland is a net sink for atmospheric CH4. No influence of grazing pattern was observed on CH4 flux in CG, RG and UG (p > 0.05). Soil temperature is the most important factor influencing ecosystem respiration and CH4 flux in the sown grassland, with soil moisture playing a secondary role to soil temperature. Variation in levels of ammonium nitrogen, nitrate nitrogen and dissolved organic carbon had little influence on ecosystem respiration or CH4 flux (except in UG plots). The values obtained for ecosystem respiration of grasslands have a large uncertainty range, which may be due to spatial variability as well as differences in research methods. Mean CH4 fluxes measured only during the growing season were much higher than the annual mean CH4 fluxes.

Abstract This study documents the contribution of equatorial waves and mesoscale gravity waves to the momentum budget of the quasi-biennial oscillation (QBO) in a 110-level version of the Whole Atmosphere Community Climate Model. The model has high vertical resolution, 500 m, above the boundary layer and through the lower and middle stratosphere, decreasing gradually to about 1.5 km near the stratopause. Parameterized mesoscale gravity waves and resolved equatorial waves contribute comparable easterly and westerly accelerations near the equator. Westerly acceleration by resolved waves is due mainly to Kelvin waves of zonal wavenumber in the range k = 1–15 and is broadly distributed about the equator. Easterly acceleration near the equator is due mainly to Rossby–gravity (RG) waves with zonal wavenumbers in the range k = 4–12. These RG waves appear to be generated in situ during both the easterly and westerly phases of the QBO, wherever the meridional curvature of the equatorial westerly jet is large enough to produce reversals of the zonal-mean barotropic vorticity gradient, suggesting that they are excited by the instability of the jet. The RG waves produce a characteristic pattern of Eliassen–Palm flux divergence that includes strong easterly acceleration close to the equator and westerly acceleration farther from the equator, suggesting that the role of the RG waves is to redistribute zonal-mean vorticity such as to neutralize the instability of the westerly jet. Insofar as unstable RG waves might be present in the real atmosphere, mixing due to these waves could have important implications for transport in the tropical stratosphere.

ABSTRACT Hot accretion flows contain collisionless plasmas that are believed to be capable of accelerating particles to very high energies, as a result of turbulence generated by the magnetorotational instability (MRI). We conduct unstratified shearing-box simulations of the MRI turbulence in ideal magnetohydrodynamic (MHD), and inject energetic relativistic test particles in simulation snapshots to conduct a detailed investigation on particle diffusion and stochastic acceleration. We consider different amount of net vertical magnetic flux, with sufficiently high resolution to resolve the gyro-radii (Rg) of most particles. Particles with large Rg (≳ 0.03 disc scale height H) show spatial diffusion coefficients of ∼30 and ∼5 times Bohm values in the azimuthal and poloidal directions, respectively. We further measure particle momentum diffusion coefficient D(p) by applying the Fokker–Planck equation, finding that contribution from turbulent fluctuations scales as D(p) ∝ p, and shear acceleration takes over when Rg ≳ 0.1H, characterized by D(p) ∝ p3. For particles with smaller Rg (≲ 0.03H), their spatial diffusion coefficients roughly scale as ∼p−1, and show evidence of D(p) ∝ p2 scaling in momentum diffusion but with large uncertainties. We find that multiple effects contribute to stochastic acceleration/deceleration, and the process is likely affected by intermittency in the MRI turbulence. We also discuss the potential of accelerating PeV cosmic rays in hot accretion flows around supermassive black holes.

Abstract Objectives We investigated the effect of consuming a whole-grain diet on whole-body protein metabolism compared to a macronutrient-matched refined-grain diet in adults with overweight/obesity using labelled amino acids (ClinicalTrials.gov Identifier: NCT01411540). Methods We conducted a randomized, controlled crossover trial in 14 adults with overweight/obesity (age: 40 ± 7 yrs, BMI: 33 ± 5 kg/m2) in which isocaloric, macronutrient-matched whole-grain (WG) and refined-grain (RG) diets were fully provided for two 8-week periods (with a 10-week washout period). Diets differed only in the inclusion of whole grains (50 g/1000 kcal). Body composition was measured via DEXA. Whole-body protein kinetics were assessed before and after each diet in the fasted state (13C-Leucine, primed, constant infusion) and over 24 hours (15N-Glycine, bolus). Protein kinetics were normalized to fat-free mass (FFM). Results Both diets resulted in mild weight loss (WG: −2.0 ± 2.5 kg; RG: −2.9 ± 3.3 kg; both P = 0.01 compared to baseline). Fasted-state leucine kinetics revealed greater protein synthesis (WG: 205 ± 61 µmol/kgFFM/hr; RG: 178 ± 36 µmol/kgFFM/hr; P = 0.04) and protein breakdown (WG: 235 ± 68 µmol/kgFFM/hr; RG: 203 ± 40 µmol/kgFFM/hr, P = 0.03) on a WG vs RG diet. This resulted in a more negative fasted-state net balance on a WG diet (WG: −30 ± 8 µmol/kg/hr; RG: −25 ± 6 µmol/kg/hr, P = 0.02). In contrast, 24-hour whole-body protein turnover measured by the end-product method (15N-Glycine), revealed greater protein synthesis (WG: 316 ± 135 mg protein/kgFFM/hr; RG: 250 ± 94 mg protein/kgFFM/hr) with no difference in protein breakdown, yielding a more positive 24-hr net balance on a WG diet (WG: 31 ± 21 mg protein/kgFFM/hr; RG: 10 ± 34 mg protein/kgFFM/hr). Conclusions A whole-grain diet increases whole-body leucine flux and results in a greater 24-hr net protein balance in adults with overweight/obesity compared to a refined-grain diet. This trial suggests whole-grains have an independent effect on protein metabolism and may benefit adults with overweight/obesity. Funding Sources This research was supported by the NIH (UL1 RR024989, T32DK007319 (JPK); T32AT004094 (JTM – trainee)) and an investigator-initiated grant from Nestle (JPK). Nestle Product Technology Center and Cereal Partners Worldwide provided the study meals and foods.

We compute desorption rates for isolated polymers adsorbed to a solid wall with a rare event sampling technique called multilevel splitting, also known as forward flux sampling. We interpret computed rates with theories based on the conjecture that the product tdesDRg2 of the desorption time tdes and diffusivity D divided by squared radius of gyration Rg scales with exp(h/Rg) where h is the equilibrium ratio of adsorbed surface concentration of polymer Γ to bulk concentration of polymer c. As the polymer–wall interaction energy is increased, the slope of lntdesDRg2 vs. NVMFkBT nearly approaches unity, as expected for strongly-adsorbing chains, where N is the degree of polymerization and VMF is the height-averaged monomer–wall interaction energy for a strongly adsorbed chain. However, we also find that this scaling law is only accurate when adsorption strength per monomer exceeds a threshold value on the order of 0.3–0.5 kBT for a freely jointed chain without or with excluded volume effects. Below the critical value, we observe that tdesDRg2 becomes nearly constant with N, so that tdes∝Nα, with α≈2. This suggests a crossover from “strong” detachment-controlled to a “weak” diffusion-controlled desorption rate as VMF/kBT drops below some threshold. These results may partially explain experimental data, that in some cases show “strong” exponential dependence of desorption time on chain length, while in others a “weak” power-law dependence is found. However, in the “strong” adsorption case, our results suggest much longer desorption times than those measured, while the reverse is true in the weak adsorption limit. We discuss possible reasons for these discrepancies.

alpha 1-Antitrypsin is the best-characterized member of the serpin (serine-proteinase inhibitor) superfamily. Its solution structure was studied by high-flux neutron-scattering and synchrotron X-ray-scattering. Neutron data show that its absorption coefficient A1% 280,1cm is 5.4. The neutron radius of gyration RG at infinite contrast for native alpha 1-antitrypsin is 2.61 nm, characteristic of a moderately elongated structure, and its cross-sectional RG is 1.34 nm. The internal inhomogeneity of scattering densities within alpha 1-antitrypsin is high at 29 x 10(-5). The X-ray RG is 2.91 nm, in good agreement with the neutron RG of 2.82 nm in 1H2O. This RG is unchanged in reactive-centre-cleaved alpha 1-antitrypsin. These parameters are also unchanged at pH 8 in sodium/potassium phosphate buffers up to 0.6 M. The neutron and X-ray curves for native alpha 1-antitrypsin were compared with Debye simulation based on the crystal structure of reactive-centre-cleaved (papain) alpha 1-antitrypsin. After allowance for residues not visible in the crystallographic electron-density map, and rejoining the proteolysed site between Met-358 and Ser-359 by means of a relatively minor conformational re-arrangement, good agreement to a structural resolution of 4 nm is obtained with the neutron data in two contrasts and with the X-ray data. The structures of the native and cleaved forms of alpha 1-antitrypsin are thus similar within the resolution of solution scattering. This places an upper limit on the magnitude of the presumed conformational changes that occur in alpha 1-antitrypsin on reactive-centre cleavage, as indicated in earlier spectroscopic investigations of the Met-358-Ser-359 peptide-bond cleavage. Methods for scattering-curve simulations from crystal structures are critically assessed. The RG data lead to dimensions of 7.8 nm x 4.9 nm x 2.2 nm for native alpha 1-antitrypsin. The high internal inhomogeneity and the asymmetric shorter semi-axes of 4.9 nm and 2.2 nm suggest that the three oligosaccharide chains of alpha 1-antitrypsin are essentially freely extended into solvent in physiological conditions. This conclusion is also supported by the Debye simulations, and by modelling based on hydrodynamic parameters.

Women’s views of antenatal screening have been widely researched, but men’s remain under-explored. The original contribution of this research was to conduct a mixed-methods study about men’s experiences specifically. In-depth interviews were firstly conducted with twelve men. Six women were interviewed about their views on men’s involvement. A grounded theory was developed, which was that men began developing a prenatal paternal identity and a schema of their child. These conceptualisations were reinforced or distorted by screening, causing their ideas and feelings about their growing family to be in a state of flux. To explore this theory with a more diverse group, a questionnaire was designed, pretested (n=30), piloted (n=53) and administered to 200 men. Exploratory factor analysis showed prenatal paternal identity and child-schema consisted of ‘bonding and closeness’, ‘genetic relationship’ and ‘imagined interactions’. Regression analyses showed investing time in screening, seeing more ultrasound scans, and making screening decisions, predicted higher scores on ‘bonding and closeness’. Investing time and being younger predicted higher scores on ‘genetic relationship’. Investing time, feeling fetal movements, being of a higher socioeconomic status and being younger predicted higher scores on ‘imagined interactions’. Longitudinal research is now required to identify implications for men, women and children.

La correspondance CFT (Anti-De Sitter) (AdS) / Théorie des champs conformes (CFT), également connue sous le nom de dualité holographique, constitue un lien remarquable entre la théorie des cordes (qui inclut la gravité) et les théories de jauge. Elle relie une CFT dans un espace-temps d-dimensionnel à une théorie de la gravité dans un espace-temps dimension supérieur, également appelé bloc. Ce dernier a une limite dans laquelle réside la théorie du champ conforme.Dans cette thèse, le sujet d'étude est la description holographique des flux de groupes de renormalisation (RG) des théories (de champ) sur les espaces-temps à symétrie maximale. Le cadre théorique que j'ai utilisé est la théorie d'Einstein-scalaire. L'inclusion du champ scalaire dynamique correspond à la rupture de l'invariance conforme aux limites. Dans ce travail, les limites et les tranches du bloc sont choisies pour être des espaces-temps à symétrie maximale et l'évolution des champs en bloc est étudiée. Il décrit les écoulements RG holographiques sur des variétés courbes. De plus, deux applications sont présentées dans cette thèse. La première application s'inscrit dans le contexte des théorèmes F et la seconde concerne un défaut incurvé dans les flux RG holographiques en masse.Les théorèmes F pour les théories de champs quantiques (QFT) définies dans des espaces-temps tridimensionnels exigent l'existence de fonctions dites F. Ce sont des fonctions décroissantes de façon monotone le long du flux RG. Dans ce travail, de nouvelles fonctions F pour les théories holographiques ont été découvertes. Elles sont construites à partir de l'action sur la parois d'une solution de flux holographique RG sur une sphère à 3-sphères. Ils permettent une interprétation entropique, fournissant ainsi un lien direct entre la formulation entropique du théorème F et sa définition en termes d’énergie libre.La deuxième application des flux RG holographiques explorée dans cette thèse se situe dans le contexte de modèles affichant un mécanisme d'auto-ajustement en tant que résolution proposée du problème de la constante cosmologique (CC). Dans ces modèles, notre univers à 4-dimensions est réalisé comme une brane intégrée dans un volume à 5-dimensions. Ce cadre permet des solutions où la géométrie de la brane est plate malgré la présence d'une énergie de vide non triviale sur son worldvolume. Ceci est appelé réglage automatique. De chaque côté de la brane, les solutions sont des flux RG holographiques. Le nouvel aspect introduit dans cette thèse consiste à utiliser les flux RG holographiques sur des variétés courbes, ce qui permet à son tour d’étudier des solutions à réglage automatique dans lesquelles la brane est également courbe
The Anti-de Sitter (AdS)/Conformal Field Theory (CFT) correspondence, also known as holographic duality, is a remarkable connection between string theory (which includes gravity) and gauge theories. It relates a CFT in a d-dimensional space-time to a gravity theory in higher dimensional space-time which is also referred to as the bulk. The latter has a boundary on which the conformal eld theory may be thought to reside. In this thesis, the subject of study is the holographic description of Renormalization Group (RG) fows of (field) theories on maximally symmetric space-times. The theoretical framework I used is Einstein-scalar theory. Inclusion of the dynamical scalar field corresponds to breaking boundary conformal invariance. In this work, both the boundary and bulk slices are chosen to be maximally symmetric space-times and the evolution of bulk fields is studied. It describes holographic RG flows on curved manifolds. Furthermore, two applications are presented in this thesis. The first application is in the context of F-theorems and the second is regarding a curved defect in the bulk holographic RG flows.F-theorems for Quantum Field Theories (QFT) defined on 3-dimensional space-times demand the existence of so-called F-functions. These are monotonically decreasing functions along the RG flow. In this work, new F-functions for holographic theories have been found which are constructed from the on-shell action of a holographic RG flow solution on a 3-sphere. They allow an entropic interpretation, therefore providing a direct connection between the entropic formulation of the F-theorem and its definition in terms of free energy. The second application of holographic RG flows explored in this thesis is in the context of models displaying a self-tuning mechanism as a proposed resolution of the cosmological constant (CC) problem. In these models, our 4-dimensional universe is realized as a brane embedded in a 5-dimensional bulk. This framework allows solutions where the brane geometry is flat despite of the presence of non-trivial vacuum energy on its worldvolume. This is referred to as self-tuning. On each side of the brane, the solutions are holographic RG flows. The new aspect introduced in this thesis is to use the holographic RG flows on curved manifolds, which in turn allows the study of self-tuning solutions where the brane is also curved