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1
Brugnara, C., T. Van Ha, and D. C. Tosteson. "Properties of K+ transport in resealed human erythrocyte ghosts." American Journal of Physiology-Cell Physiology 255, no. 3 (September 1, 1988): C346—C356. http://dx.doi.org/10.1152/ajpcell.1988.255.3.c346.
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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.
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James, D. E., K. M. Burleigh, L. H. Storlien, S. P. Bennett, and E. W. Kraegen. "Heterogeneity of insulin action in muscle: influence of blood flow." American Journal of Physiology-Endocrinology and Metabolism 251, no. 4 (October 1, 1986): E422—E430. http://dx.doi.org/10.1152/ajpendo.1986.251.4.e422.
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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)
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Li, Dan, Gabriel G. Katul, and Sergej S. Zilitinkevich. "Revisiting the Turbulent Prandtl Number in an Idealized Atmospheric Surface Layer." Journal of the Atmospheric Sciences 72, no. 6 (May 27, 2015): 2394–410. http://dx.doi.org/10.1175/jas-d-14-0335.1.
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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.
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Ayala, Julio E., Deanna P. Bracy, Freyja D. James, Brianna M. Julien, David H. Wasserman, and Daniel J. Drucker. "The Glucagon-Like Peptide-1 Receptor Regulates Endogenous Glucose Production and Muscle Glucose Uptake Independent of Its Incretin Action." Endocrinology 150, no. 3 (November 13, 2008): 1155–64. http://dx.doi.org/10.1210/en.2008-0945.
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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.
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Mei, Baoling, Hongyu Yue, Xunhua Zheng, William McDowell, Qingshan Zhao, Zaixing Zhou, and Zhisheng Yao. "Effects of Grazing Pattern on Ecosystem Respiration and Methane Flux in a Sown Pasture in Inner Mongolia, China." Atmosphere 10, no. 1 (December 26, 2018): 5. http://dx.doi.org/10.3390/atmos10010005.
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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.
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Garcia, Rolando R., and Jadwiga H. Richter. "On the Momentum Budget of the Quasi-Biennial Oscillation in the Whole Atmosphere Community Climate Model." Journal of the Atmospheric Sciences 76, no. 1 (December 18, 2018): 69–87. http://dx.doi.org/10.1175/jas-d-18-0088.1.
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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.
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Sun, Xiaochen, and Xue-Ning Bai. "Particle diffusion and acceleration in magnetorotational instability turbulence." Monthly Notices of the Royal Astronomical Society 506, no. 1 (June 11, 2021): 1128–47. http://dx.doi.org/10.1093/mnras/stab1643.
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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.
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Mey, Jacob, and John Kirwan. "A Whole-Grain Diet Improves Whole-Body Protein Turnover Compared to a Macronutrient-Matched Refined-Grain Diet in Adults with Overweight/Obesity." Current Developments in Nutrition 4, Supplement_2 (May 29, 2020): 1661. http://dx.doi.org/10.1093/cdn/nzaa063_059.
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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.
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Huston, Kyle J., Christina E. Rice, and Ronald G. Larson. "Forward Flux Sampling of Polymer Desorption Paths from a Solid Surface into Dilute Solution." Polymers 12, no. 10 (October 3, 2020): 2275. http://dx.doi.org/10.3390/polym12102275.
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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.
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Smith, K. F., R. A. Harrison, and S. J. Perkins. "Structural comparisons of the native and reactive-centre-cleaved forms of α1-antitrypsin by neutron- and X-ray-scattering in solution." Biochemical Journal 267, no. 1 (April 1, 1990): 203–12. http://dx.doi.org/10.1042/bj2670203.
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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.
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Scepi, Nicolas, Mitchell C. Begelman, and Jason Dexter. "Magnetic flux inversion in a peculiar changing look AGN." Monthly Notices of the Royal Astronomical Society: Letters 502, no. 1 (January 9, 2021): L50—L54. http://dx.doi.org/10.1093/mnrasl/slab002.
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ABSTRACT We argue that the changing-look event in the active galactic nucleus (AGN) 1ES 1927+654, followed by a dip of three orders of magnitude in the X-ray luminosity, is controlled by a change in the accretion rate and an inversion of magnetic flux in a magnetically arrested disc (MAD). Before the changing-look event, strong magnetic flux on the black hole powers X-ray emission via the Blandford–Znajek process, while the UV emission is produced by a radiatively inefflcient magnetized disc. An advection event, bringing flux of the opposite polarity, propagates inward leading, first, to a rise in the UV/optical luminosity and, then, to a dip in the X-ray luminosity. We find that the observed time-scale between the beginning of the changing-look event and the minimum in the X-ray luminosity, ≈200 d, is in agreement with the time needed to cancel the magnetic flux in a MAD extending to ≈180 rg. Although flux inversion events might be rare due to the large ratio of flux-to-mass that is needed, we argue that AGN showing an unusually high ratio of X-ray to UV luminosity are prime candidates for such events. We suggest that similar events may lead to jet interruptions in radio-loud objects.
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Mazdab, F. K. "CHARACTERIZATION OF FLUX-GROWN TRACE-ELEMENT-DOPED TITANITE USING THE HIGH-MASS-RESOLUTION ION MICROPROBE (SHRIMP-RG)." Canadian Mineralogist 47, no. 4 (August 1, 2009): 813–31. http://dx.doi.org/10.3749/canmin.47.4.813.
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Meyer, D. F., A. S. Nealis, K. R. Bruckdorfer, and S. J. Perkins. "Characterization of the structure of polydisperse human low-density lipoprotein by neutron scattering." Biochemical Journal 310, no. 2 (September 1, 1995): 407–15. http://dx.doi.org/10.1042/bj3100407.
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Low-density lipoproteins (LDL) in plasma are constructed from a single molecule of apolipoprotein B-100 (M(r) 512000) in association with lipid (approximate M(r) 2-3 x 10(6)). The gross structure was studied using an updated pulsed-neutron camera LOQ with an area detector to establish the basis for the interpretation of structural changes seen during dynamic studies of LDL oxidation. Neutron-scattering data for LDL in 100% 2H2O buffers emphasize their external appearance. Guinier analysis on a continuous-flux neutron camera D17 revealed pronounced concentration-dependences in the radius of gyration, RG, and the intensity of forward scattering, I(0) (equivalent to the M(r) of LDL) between 0.5 and 11 mg of LDL protein/ml. LDL preparations from different donors gave different RG values. When extrapolated to zero concentration, RG values ranged between 8.3 and 10.6 nm and were linearly correlated with M(r), which is consistent with a spherical structure. The distance-distribution function P(r) in real space showed a single maximum at 9.1-10.9 nm, which is just under half the observed maximum dimension of 23.1 +/- 1.2 nm expected for a spherical structure. The neutron radial-density function p(r) exhibited a plateau of high and featureless density at the centre of LDL. LDL can be modelled by a polydisperse assembly of spheres with two internal densities and a mean radius close to 10.0 nm in a normal distribution of radii with a standard deviation of 2.0 nm. The data are consistent with recent electron-microscopy and ultracentrifugation data.(ABSTRACT TRUNCATED AT 250 WORDS)
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Lawler, J. M., S. K. Powers, T. Visser, H. Van Dijk, M. J. Kordus, and L. L. Ji. "Acute exercise and skeletal muscle antioxidant and metabolic enzymes: effects of fiber type and age." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 265, no. 6 (December 1, 1993): R1344—R1350. http://dx.doi.org/10.1152/ajpregu.1993.265.6.r1344.
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Inhibition of metabolic enzyme activity has been associated with free radical stress in locomotor muscle with prolonged or intense exercise. However, it is not known whether such alterations with acute exercise in skeletal muscle are influenced by muscle fiber type or age. Twenty 4-mo-old and twenty 24-mo-old female Fischer-344 rats were divided at random into young exercised (YE; n = 10), old exercised (OE; n = 10), young control (YC; n = 10), and old control (OC; n = 10) groups. Animals in both YE and OE groups ran on a treadmill (10% uphill grade) for 40 min at approximately 75% of each age-group's maximal O2 consumption. Immediately after the treadmill run, white gastrocnemius (WG), red gastrocnemius (RG), and soleus (SOL) muscles were removed and quick-frozen in liquid nitrogen. Malondialdehyde was significantly increased (P < 0.05) in RG of YE vs. YC rats. Glutathione peroxidase activity was significantly elevated (P < 0.05) in the WG of YE rats. Analysis of variance revealed a significant over-all increase in superoxide dismutase activity with exercise. Activities of phosphofructokinase (PFK), citrate synthase, succinate dehydrogenase, and 3-hydroxyacyl-CoA dehydrogenase were unchanged (P > 0.05) with acute exercise in the SOL. However, PFK activity was decreased in the WG by 60% in OE but only 33% in YE, and in the RG by 41% in OE but only 21% in YE. We conclude that maximal glycolytic flux in the gastrocnemius may be adversely affected by acute exercise, and this effect was more pronounced in the 24-mo-old group.
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Porth, O., Y. Mizuno, Z. Younsi, and C. M. Fromm. "Flares in the Galactic Centre – I. Orbiting flux tubes in magnetically arrested black hole accretion discs." Monthly Notices of the Royal Astronomical Society 502, no. 2 (January 29, 2021): 2023–32. http://dx.doi.org/10.1093/mnras/stab163.
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ABSTRACT Recent observations of Sgr A* by the GRAVITY instrument have astrometrically tracked infrared (IR) flares at distances of ∼10 gravitational radii (rg). In this paper, we study a model for the flares based on 3D general relativistic magnetohydrodynamic (GRMHD) simulations of magnetically arrested accretion discs (MADs) that exhibit violent episodes of flux escape from the black hole magnetosphere. These events are attractive for flare modelling for several reasons: (i) the magnetically dominant regions can resist being disrupted via magnetorotational turbulence and shear; (ii) the orientation of the magnetic field is predominantly vertical as suggested by the GRAVITY data; and (iii) the magnetic reconnection associated with the flux eruptions could yield a self-consistent means of particle heating/acceleration during the flare events. In this analysis, we track erupted flux bundles and provide distributions of sizes, energies, and plasma parameter. In our simulations, the orbits tend to circularize at a range of radii from ${\sim} 5\hbox{ to }40\, r_{\rm g}$. The magnetic energy contained within the flux bundles ranges up to ${\sim} 10^{40}\,\rm erg$, enough to power IR and X-ray flares. We find that the motion within the magnetically supported flow is substantially sub-Keplerian, in tension with the inferred period–radius relation of the three GRAVITY flares.
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Bezaire, Veronic, George J. F. Heigenhauser, and Lawrence L. Spriet. "Regulation of CPT I activity in intermyofibrillar and subsarcolemmal mitochondria from human and rat skeletal muscle." American Journal of Physiology-Endocrinology and Metabolism 286, no. 1 (January 2004): E85—E91. http://dx.doi.org/10.1152/ajpendo.00237.2003.
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Carnitine palmitoyltransferase I (CPT I) is considered the rate-limiting enzyme in the transfer of long-chain fatty acids (LCFA) into the mitochondria and is reversibly inhibited by malonyl-CoA (M-CoA) in vitro. In rat skeletal muscle, M-CoA levels decrease during exercise, releasing the inhibition of CPT I and increasing LCFA oxidation. However, in human skeletal muscle, M-CoA levels do not change during moderate-intensity exercise despite large increases in fat oxidation, suggesting that M-CoA is not the sole regulator of increased CPT I activity during exercise. In the present study, we measured CPT I activity in intermyofibrillar (IMF) and subsarcolemmal (SS) mitochondria isolated from human vastus lateralis (VL), rat soleus (Sol), and red gastrocnemius (RG) muscles. We tested whether exercise-related levels (∼65% maximal O2 uptake) of calcium and adenylate charge metabolites (free AMP, ADP, and Pi) could override the M-CoA-induced inhibition of CPT I activity and explain the increased CPT I flux during exercise. Protein content was ∼25-40% higher in IMF than in SS mitochondria in all muscles. Maximal CPT I activity was similar in IMF and SS mitochondria in all muscles (VL: 282 ± 46 vs. 280 ± 51; Sol: 390 ± 81 vs. 368 ± 82; RG: 252 ± 71 vs. 278 ± 44 nmol·min-1·mg protein-1). Sensitivity to M-CoA did not differ between IMF and SS mitochondria in all muscles (25-31% inhibition in VL, 52-70% in Sol and RG). Calcium and adenylate charge metabolites did not override the M-CoA-induced inhibition of CPT I activity in mitochondria isolated from VL, Sol, and RG muscles. Decreasing pH from 7.1 to 6.8 reduced CPT I activity by ∼34-40% in both VL mitochondrial fractions. In summary, this study reports no differences in CPT I activity or sensitivity to M-CoA between IMF and SS mitochondria isolated from human and rat skeletal muscles. Exercise-induced increases in calcium and adenylate charge metabolites do not appear responsible for upregulating CPT I activity in human or rat skeletal muscle during moderate aerobic exercise.
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Petersen, Hilary Ann, Patrick T. Fueger, Deanna P. Bracy, David H. Wasserman, and Amy E. Halseth. "Fiber type-specific determinants of V maxfor insulin-stimulated muscle glucose uptake in vivo." American Journal of Physiology-Endocrinology and Metabolism 284, no. 3 (March 1, 2003): E541—E548. http://dx.doi.org/10.1152/ajpendo.00323.2002.
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The aim of this study was to determine barriers limiting muscle glucose uptake (MGU) during increased glucose flux created by raising blood glucose in the presence of fixed insulin. The determinants of the maximal velocity ( V max) of MGU in muscles of different fiber types were defined. Conscious rats were studied during a 4 mU · kg−1 · min−1insulin clamp with plasma glucose at 2.5, 5.5, and 8.5 mM. [U-14C]mannitol and 3- O-methyl-[3H]glucose ([3H]MG) were infused to steady-state levels ( t = −180 to 0 min). These isotope infusions were continued from 0 to 40 min with the addition of a 2-deoxy-[3H]glucose ([3H]DG) infusion. Muscles were excised at t = 40 min. Glucose metabolic index (Rg) was calculated from muscle-phosphorylated [3H]DG. [U-14C]mannitol was used to determine extracellular (EC) H2O. Glucose at the outer ([G]om) and inner ([G]im) sarcolemmal surfaces was determined by the ratio of [3H]MG in intracellular to EC H2O and muscle glucose. Rg was comparable at the two higher glucose concentrations, suggesting that rates of uptake near V max were reached. In summary, by defining the relationship of arterial glucose to [G]om and [G]im in the presence of fixed hyperinsulinemia, it is concluded that 1) V max for MGU is limited by extracellular and intracellular barriers in type I fibers, as the sarcolemma is freely permeable to glucose; 2) V max is limited in muscles with predominantly type IIb fibers by extracellular resistance and transport resistance; and 3) limits to Rg are determined by resistance at multiple steps and are better defined by distributed control rather than by a single rate-limiting step.
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Sasi, M. N., and V. Deepa. "Seasonal variation of equatorial wave momentum fluxes at Gadanki (13.5° N, 79.2° E)." Annales Geophysicae 19, no. 8 (August 31, 2001): 985–90. http://dx.doi.org/10.5194/angeo-19-985-2001.
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Abstract. The vertical flux of the horizontal momentum associated with the equatorial Kelvin and Rossby-gravity waves are estimated from the winds measured by the Indian MST radar located at Gadanki (13.5° N, 79.2° E) during September 1995 to August 1996 in the tropospheric and lower stratospheric regions for all four seasons. The present study shows that momentum flux values are greater during equinox seasons than solstices, with values near the tropopause level being 16 × 10-3, 7.4 × 10-3, 27 × 10-3 and 5.5 × 10-3 m2 s-2 for Kelvin waves and 5.5 × 10-3, 3.5 × 10-3, 6.7 × 10-3 and 2.1 × 10-3 m2 s-2 for RG waves during autumnal equinox, winter, vernal equinox and summer seasons, respectively. Using these momentum flux values near the tropopause level, acceleration of the mean flow in the stratosphere up to a 29 km height were computed following Plumb (1984), by considering the wave-meanflow interaction and the deposition of the momentum through the radiative dissipation of the waves. A comparison of the estimated mean-flow acceleration in the stratosphere compares well, except at a few height levels, with the observed mean-flow accelerations in the stratosphere derived from the radiosonde data from a nearby station.Key words. Meteorology and atmosphenic dynamics (tropical meteorology; waves and tides)
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Chevalier, R. A., and R. T. Emmering. "The Structure of Pulsar Nebulae." Symposium - International Astronomical Union 125 (1987): 122. http://dx.doi.org/10.1017/s0074180900160577.
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We have found solutions to the problem of a relativistic pulsar wind interacting with a nebula moving at constant velocity vn. The wind is assumed to contain a toroidal magnetic field; the ratio of Poynting flux to particle flux in the wind is a constant σ. Under these assumptions, the wind is shocked at a radius rs that moves out at constant velocity. Solutions for the shocked wind are only possible if σ < σc = 1/(−1 + c/vn). For a given value of vn, rs → as σ → σc. Kennel and Coroniti (1984) have calculated similar models for the Crab Nebula but they assume that rs is a constant; i.e. they calculate steady-state models. The steady-state approximation is expected to be good close to the shock wave, but it breaks down in the outer parts of the nebula. For vn = 2000 km s−1 and rn/rg = 20, Kennel and Coroniti find σ = 0.003. For the same Crab Nebula pmeters, our time-dependent model yields σ = 0.0016. There may be times in the evolution of Crab Nebula or of other pulsar nebulae when a model with a shocked relativistic wind and a toroidal magnetic field cannot apply. It appears that a wide variety of structures are possible for pulsar nebulae.
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Wilson, Nat, Fiammetta Straneo, and Patrick Heimbach. "Satellite-derived submarine melt rates and mass balance (2011–2015) for Greenland's largest remaining ice tongues." Cryosphere 11, no. 6 (December 5, 2017): 2773–82. http://dx.doi.org/10.5194/tc-11-2773-2017.
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Abstract. Ice-shelf-like floating extensions at the termini of Greenland glaciers are undergoing rapid changes with potential implications for the stability of upstream glaciers and the ice sheet as a whole. While submarine melting is recognized as a major contributor to mass loss, the spatial distribution of submarine melting and its contribution to the total mass balance of these floating extensions is incompletely known and understood. Here, we use high-resolution WorldView satellite imagery collected between 2011 and 2015 to infer the magnitude and spatial variability of melt rates under Greenland's largest remaining ice tongues – Nioghalvfjerdsbræ (79 North Glacier, 79N), Ryder Glacier (RG), and Petermann Glacier (PG). Submarine melt rates under the ice tongues vary considerably, exceeding 50 m a−1 near the grounding zone and decaying rapidly downstream. Channels, likely originating from upstream subglacial channels, give rise to large melt variations across the ice tongues. We compare the total melt rates to the influx of ice to the ice tongue to assess their contribution to the current mass balance. At Petermann Glacier and Ryder Glacier, we find that the combined submarine and aerial melt approximately balances the ice flux from the grounded ice sheet. At Nioghalvfjerdsbræ the total melt flux (14.2 ± 0.96 km3 a−1 w.e., water equivalent) exceeds the inflow of ice (10.2 ± 0.59 km3 a−1 w.e.), indicating present thinning of the ice tongue.
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Aguilos, Maricar, Clément Stahl, Benoit Burban, Bruno Hérault, Elodie Courtois, Sabrina Coste, Fabien Wagner, Camille Ziegler, Kentaro Takagi, and Damien Bonal. "Interannual and Seasonal Variations in Ecosystem Transpiration and Water Use Efficiency in a Tropical Rainforest." Forests 10, no. 1 (December 26, 2018): 14. http://dx.doi.org/10.3390/f10010014.
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Warmer and drier climates over Amazonia have been predicted for the next century with expected changes in regional water and carbon cycles. We examined the impact of interannual and seasonal variations in climate conditions on ecosystem-level evapotranspiration (ET) and water use efficiency (WUE) to determine key climatic drivers and anticipate the response of these ecosystems to climate change. We used daily climate and eddyflux data recorded at the Guyaflux site in French Guiana from 2004 to 2014. ET and WUE exhibited weak interannual variability. The main climatic driver of ET and WUE was global radiation (Rg), but relative extractable water (REW) and soil temperature (Ts) did also contribute. At the seasonal scale, ET and WUE showed a modal pattern driven by Rg, with maximum values for ET in July and August and for WUE at the beginning of the year. By removing radiation effects during water depleted periods, we showed that soil water stress strongly reduced ET. In contrast, drought conditions enhanced radiation-normalized WUE in almost all the years, suggesting that the lack of soil water had a more severe effect on ecosystem evapotranspiration than on photosynthesis. Our results are of major concern for tropical ecosystem modeling because they suggest that under future climate conditions, tropical forest ecosystems will be able to simultaneously adjust CO2 and H2O fluxes. Yet, for tropical forests under future conditions, the direction of change in WUE at the ecosystem scale is hard to predict, since the impact of radiation on WUE is counterbalanced by adjustments to soil water limitations. Developing mechanistic models that fully integrate the processes associated with CO2 and H2O flux control should help researchers understand and simulate future functional adjustments in these ecosystems.
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van der Molen, M. K., J. van Huissteden, F. J. W. Parmentier, A. M. R. Petrescu, A. J. Dolman, T. C. Maximov, A. V. Kononov, S. V. Karsanaev, and D. A. Suzdalov. "The growing season greenhouse gas balance of a continental tundra site in the Indigirka lowlands, NE Siberia." Biogeosciences 4, no. 6 (November 14, 2007): 985–1003. http://dx.doi.org/10.5194/bg-4-985-2007.
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Abstract. Carbon dioxide and methane fluxes were measured at a tundra site near Chokurdakh, in the lowlands of the Indigirka river in north-east Siberia. This site is one of the few stations on Russian tundra and it is different from most other tundra flux stations in its continentality. A suite of methods was applied to determine the fluxes of NEE, GPP, Reco and methane, including eddy covariance, chambers and leaf cuvettes. Net carbon dioxide fluxes were high compared with other tundra sites, with NEE=−92 g C m−2 yr−1, which is composed of an Reco=+141 g C m−2 yr−1 and GPP=−232 g C m−2 yr−1. This large carbon dioxide sink may be explained by the continental climate, that is reflected in low winter soil temperatures (−14°C), reducing the respiration rates, and short, relatively warm summers, stimulating high photosynthesis rates. Interannual variability in GPP was dominated by the frequency of light limitation (Rg<200 W m−2), whereas Reco depends most directly on soil temperature and time in the growing season, which serves as a proxy of the combined effects of active layer depth, leaf area index, soil moisture and substrate availability. The methane flux, in units of global warming potential, was +28 g C-CO2e m−2 yr−1, so that the greenhouse gas balance was −64 g C-CO2e m−2 yr−1. Methane fluxes depended only slightly on soil temperature and were highly sensitive to hydrological conditions and vegetation composition.
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van der Molen, M. K., J. C. van Huissteden, F. J. Parmentier, A. M. R. Petrescu, A. J. Dolman, T. C. Maximov, A. V. Kononov, S. V. Karsanaev, and D. A. Suzdalov. "The seasonal cycle of the greenhouse gas balance of a continental tundra site in the Indigirka lowlands, NE Siberia." Biogeosciences Discussions 4, no. 4 (July 17, 2007): 2329–84. http://dx.doi.org/10.5194/bgd-4-2329-2007.
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Abstract. Carbon dioxide and methane fluxes were measured at a tundra site near Chokurdakh, in the lowlands of the Indigirka river in north-east Siberia. This site is one of the few stations on Russian tundra and it is different from most other tundra flux stations in its continentality. A suite of methods was applied to determine the fluxes of NEE, GPP, Reco and methane, including eddy covariance, chambers and leaf cuvettes. Net carbon dioxide fluxes were unusually high, compared with other tundra sites, with NEE=–92 g C m−2 yr−1, which is composed of an Reco=+141 g C m−2 yr−1 and GPP=–232 g C m−2 yr−1. This large carbon dioxide sink may be explained by the continental climate, that is reflected in low winter soil temperatures (–14°C), reducing the respiration rates, and short, relatively warm summers, stimulating high photosynthesis rates. Interannual variability in GPP was dominated by the frequency of light limitation (Rg <200 W m−2), whereas Reco depends most directly on soil temperature and time in the growing season, which serves as a proxy of the combined effects of active layer depth, leaf area index, soil moisture and substrate availability. The methane flux, in units of global warming potential, was +28 g C-CO2e m−2 yr−1, so that the greenhouse gas balance was –64 g C-CO2e m−2 yr−1. Methane fluxes depended only slightly on soil temperature and were highly sensitive to hydrological conditions and vegetation composition.
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Haisch, M., N. K. Fukagawa, and D. E. Matthews. "Oxidation of glutamine by the splanchnic bed in humans." American Journal of Physiology-Endocrinology and Metabolism 278, no. 4 (April 1, 2000): E593—E602. http://dx.doi.org/10.1152/ajpendo.2000.278.4.e593.
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[1,2-13C2]glutamine and [ ring-2H5]phenylalanine were infused for 7 h into five postabsorptive healthy subjects on two occasions. On one occasion, the tracers were infused intravenously for 3.5 h and then by a nasogastric tube for 3.5 h. The order of infusion was reversed on the other occasion. From the plasma tracer enrichment measurements at plateau during the intravenous and nasogastric infusion periods, we determined that 27 ± 2% of the enterally delivered phenylalanine and 64 ± 2% of the glutamine were removed on the first pass by the splanchnic bed. Glutamine flux was 303 ± 8 μmol ⋅ kg− 1 ⋅ h− 1. Of the enterally delivered [13C]glutamine tracer, 73 ± 2% was recovered as exhaled CO2 compared with 58 ± 1% of the intravenously infused tracer. The fraction of the enterally delivered tracer that was oxidized specifically on the first pass by the splanchnic bed was 53 ± 2%, comprising 83% of the total tracer extracted. From the appearance of 13C in plasma glucose, we estimated that 7 and 10% of the intravenously and nasogastrically infused glutamine tracers, respectively, were converted to glucose. The results for glutamine flux and first-pass extraction were similar to our previously reported values when a [2-15N]glutamine tracer [Matthews DE, Morano MA, and Campbell RG, Am J Physiol Endocrinol Metab 264: E848–E854, 1993] was used. The results of [13C]glutamine tracer disposal demonstrate that the major fate of enteral glutamine extraction is for oxidation and that only a minor portion is used for gluconeogenesis.
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Souza, Vanessa de Arruda, Débora Regina Roberti, Anderson Luis Ruhoff, Tamíres Zimmer, Daniela Santini Adamatti, Luis Gustavo G. de Gonçalves, Marcelo Bortoluzzi Diaz, Rita de Cássia Marques Alves, and Osvaldo L. L. de Moraes. "Evaluation of MOD16 Algorithm over Irrigated Rice Paddy Using Flux Tower Measurements in Southern Brazil." Water 11, no. 9 (September 13, 2019): 1911. http://dx.doi.org/10.3390/w11091911.
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Evapotranspiration (ET) is an important component of the hydrological cycle. Understanding the ET process has become of fundamental importance given the scenario of global change and increasing water use, especially in the agricultural sector. Determining ET over large agricultural areas is a limiting factor due to observational data availability. In this regard, remote sensing data has been used to estimate ET. In this study, we evaluated the Moderate-Resolution Imaging Spectroradiometer (MODIS) land surface ET product estimates (hereafter MOD16 ET – MODIS Global Terrestrial Evapotranspiration Product) over two rice paddy areas in Southern Brazil, through the ET measured using the eddy covariance technique (hereafter EC). The energy balance components were evaluated during fallow and flooded seasons showing latent heat flux dominates in both seasons. The results showed that MOD16 ET underestimated EC measurements. Overall, the RMSE (root mean square error) ranged between 13.40 and 16.35 mm 8-day−1 and percent bias (PBIAS) ranged between −33.7% and −38.7%. We also assessed the ET (measured and estimated) main drivers, with EC yielding higher correlation against observed net radiation (Rn) and global radiation (Rg), followed by air temperature (Temp) and vapor pressure deficit (VPD), whilst MOD16 ET estimates yielded higher correlation against leaf area index (LAI) and fraction of photosynthetically active radiation (fPAR). The MOD16 algorithm was forced with meteorological measurements but the results did not improve as expected, suggesting a low sensitivity to meteorological inputs. Our results indicated when a water layer was present over the soil surface without vegetation (LAI around zero), the largest differences between EC measurements and MOD16 ET were found. In this period, the expected domain of soil evaporation was not observed in MOD16 ET physical processes partition, indicating the algorithm was not able to detect areas with high soil moisture. In general, the MOD16 ET product presented low accuracy when compared against experimental measurements over flooded rice paddy, suggesting more studies are necessary, in order to reduce uncertainties associated to the land cover conditions.
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Petropoulos, G. P., M. R. North, G. Ireland, P. K. Srivastava, and D. V. Rendall. "Validating a 1-D SVAT model in a range of USA and Australian ecosystems: evidence towards its use as a tool to study Earth's system interactions." Geoscientific Model Development Discussions 8, no. 3 (March 5, 2015): 2437–95. http://dx.doi.org/10.5194/gmdd-8-2437-2015.
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Abstract. This paper describes the validation of the SimSphere SVAT model conducted at different ecosystem types in the USA and Australia. Specific focus was given to examining the models' ability in predicting Shortwave Incoming Solar Radiation (Rg), Net Radiation (Rnet), Latent Heat (LE), Sensible Heat (H), Air Temperature at 1.3 m (Tair 1.3 m) and Air Temperature at 50 m (Tair 50 m). Model predictions were compared against corresponding in situ measurements acquired for a total of 72 selected days of the year 2011 obtained from 8 sites belonging to the AmeriFlux (USA) and OzFlux (Australia) monitoring networks. Selected sites were representative of a variety of environmental, biome and climatic conditions, to allow for the inclusion of contrasting conditions in the model evaluation. The application of the model confirmed its high capability in representing the multifarious and complex interactions of the Earth system. Comparisons showed a good agreement between modelled and measured fluxes, especially for the days with smoothed daily flux trends. A good to excellent agreement between the model predictions and the in situ measurements was reported, particularly so for the LE, H, T1.3 m and T 50 m parameters (RMSD = 39.47, 55.06 W m−2, 3.23, 3.77 °C respectively). A systematic underestimation of Rg and Rnet (RMSD = 67.83, 58.69 W m−2, MBE = 67.83, 58.69 W m−2 respectively) was also found. Highest simulation accuracies were obtained for the open woodland savannah and mulga woodland sites for most of the compared parameters. Very high values of the Nash–Sutcliffe efficiency index were also reported for all parameters ranging from 0.720 to 0.998, suggesting a very good model representation of the observations. To our knowledge, this study presents the first comprehensive validation of SimSphere, particularly so in USA and Australian ecosystem types. Findings are important and timely, given the rapidly expanding use of this model worldwide both as an educational and research tool. This includes ongoing research by different Space Agencies examining its synergistic use with Earth Observation data towards the development of global operational products.
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Borok, Z., A. Hami, S. I. Danto, R. L. Lubman, K. J. Kim, and E. D. Crandall. "Effects of EGF on alveolar epithelial junctional permeability and active sodium transport." American Journal of Physiology-Lung Cellular and Molecular Physiology 270, no. 4 (April 1, 1996): L559—L565. http://dx.doi.org/10.1152/ajplung.1996.270.4.l559.
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We evaluated the effects of epidermal growth factor (EGF) on transepithelial resistance (Rt) and active ion transport by alveolar epithelial cell (AEC) monolayers on tissue culture-treated polycarbonate filters. Rat type II cells were cultured in completely defined serum-free medium (MDSF) or MDSF supplemented with EGF. The addition of EGF from either day 0 (chronic) or day 4 (subacute) resulted in significant increases in Rt and short-circuit current (ISC) on day 5. After subacute exposure, these effects were delayed in onset by 6-12 h and sustained for > 24 h. Basolateral (but not apical) EGF was responsible for these effects, which were prevented by preincubation with tyrphostin RG-50864, a reversible specific inhibitor of the EGF receptor tyrosine kinase. ISC decreased, with a sensitivity to apical inhibitors of sodium transport in the order benzamil > amiloride > 5-(N-ethyl-N-isopropyl) amiloride in MDSF +/- EGF, and was completely inhibited by the addition of basolateral ouabain. Net sodium flux and Na+, K+ -ATPase activity both increased approximately 50% in the presence of EGF. These results indicate that 1) EGF decreases tight junctional permeability and increases active sodium transport by AEC monolayers via basolaterally located EGF receptors, and 2) the pathways for AEC sodium entry and exit (+/- EGF) are apical high amiloride affinity sodium channels and basolateral sodium pumps.
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Mondal, Aditya S., G. C. Dewangan, and B. Raychaudhuri. "Study of the reflection spectrum of the bright atoll source GX 3 + 1 with NuSTAR." Monthly Notices of the Royal Astronomical Society 487, no. 4 (June 14, 2019): 5441–49. http://dx.doi.org/10.1093/mnras/stz1658.
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ABSTRACT We report on the NuSTAR observation of the atoll type neutron star (NS) low-mass X-ray binary GX 3 + 1 performed on 2017 October 17. The source was found in a soft X-ray spectral state with 3–70 keV luminosity of LX ∼ 3 × 1037 erg s−1 (${\sim } 16{{\ \rm per\ cent}}$ of the Eddington luminosity), assuming a distance of 6 kpc. A positive correlation between intensity and hardness ratio suggests that the source was in the banana branch during this observation. The broad-band 3–70 keV NuSTAR spectral data can be described by a two-component continuum model consisting of a disc blackbody (kTdisc ∼ 1.8 keV) and a single temperature blackbody model (kTbb ∼ 2.7 keV). The spectrum shows a clear and robust indication of relativistic reflection from the inner disc which is modelled with a self-consistent relativistic reflection model. The accretion disc is viewed at an inclination of i ≃ 22°–26° and extended close to the NS, down to $R_\text{in}=(1.2\!-\!1.8) R_\text{ISCO}\:(\simeq 6.1\!-\!9.1\, R_{\mathrm{ g}}\: \text{or}\: 14\!-\!20.5$ km) which allows an upper limit on the NS radius (≤13.5 km). Based on the measured flux and the mass accretion rate, the maximum radial extension for the boundary layer is estimated to be ∼6.3 Rg from the NS surface. However, if the disc is not truncated by the boundary layer but by the magnetosphere, an estimated upper limit on the polar magnetic field would be of B ≤ 6 × 108 G.
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Fueger, Patrick T., Sami Heikkinen, Deanna P. Bracy, Carlo M. Malabanan, R. Richard Pencek, Markku Laakso, and David H. Wasserman. "Hexokinase II partial knockout impairs exercise-stimulated glucose uptake in oxidative muscles of mice." American Journal of Physiology-Endocrinology and Metabolism 285, no. 5 (November 2003): E958—E963. http://dx.doi.org/10.1152/ajpendo.00190.2003.
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Muscle glucose uptake (MGU) is distributively controlled by three serial steps: delivery of glucose to the muscle membrane, transport across the muscle membrane, and intracellular phosphorylation to glucose 6-phosphate by hexokinase (HK). During states of high glucose fluxes such as moderate exercise, the HK activity is of increased importance, since augmented muscle perfusion increases glucose delivery, and increased GLUT4 at the cell membrane increases glucose transport. Because HK II overexpression augments exercise-stimulated MGU, it was hypothesized that a reduction in HK II activity would impair exercise-stimulated MGU and that the magnitude of this impairment would be greatest in tissues with the largest glucose requirement. To this end, mice with a HK II partial knockout ( HK+/–) were compared with their wild-type control (WT) littermates during either sedentary or moderate exercise periods. Rg, an index of glucose metabolism, was measured using 2-deoxy-[3H]glucose. No differences in glucose metabolism were detected between sedentary groups. The increase in Rgdue to exercise was impaired in the highly oxidative heart and soleus muscles of HK+/–compared with WT mice (7 ± 10 vs. 29 ± 9 and 8 ± 3 vs. 25 ± 7 μmol · 100 g–1· min–1, respectively). However, the increase in Rgdue to exercise was not altered in gastrocnemius and superficial vastus lateralis muscles in HK+/–and WT mice (8 ± 2 vs. 12 ± 3 and 5 ± 2 vs. 8 ± 2 μmol · 100 g–1· min–1, respectively). In conclusion, MGU is impaired by reductions in HK activity during exercise, a physiological condition characterized by high glucose flux. This impairment is critically dependent on the tissue's glucose metabolic rate and correlates with tissue oxidative capacity.
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Mondal, Aditya S., G. C. Dewangan, and B. Raychaudhuri. "On the disc reflection spectroscopy of NS LMXB Serpens X-1: analysis of a recent NuSTAR observation." Monthly Notices of the Royal Astronomical Society 494, no. 3 (April 24, 2020): 3177–85. http://dx.doi.org/10.1093/mnras/staa1001.
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ABSTRACT We present NuSTAR observation of the atoll type neutron star (NS) low-mass X-ray binary (LMXB) Serpens X-1 (Ser X-1) performed on 2018 February 17. We observed Ser X-1 in a soft X-ray spectral state with 3–79 keV luminosity of LX ∼ 0.4 × 1038 erg s−1 (${\sim}23{{\ \rm per\ cent}}$ of the Eddington luminosity), assuming a distance of 7.7 kpc. A positive correlation between intensity and hardness ratio suggests that the source was in the banana branch during this observation. The broad-band 3–30 keV NuSTAR energy spectrum can be well described either by a three-component continuum model consisting of a disc blackbody, a single temperature blackbody, and a power law or by a two-component continuum model consisting of a disc blackbody and a Comptonization component. A broad iron line ∼5–8 keV and the Compton back-scattering hump peaking at ∼10–20 keV band are clearly detected in the X-ray spectrum. These features are best interpreted by a self-consistent relativistic reflection model. Fits with relativistically blurred disc reflection model suggests that the inner disc radius Rin is truncated prior to the ISCO at (1.9–2.5) RISCO (${\simeq}11.4\!-\!15\, R_{g}\: \text{or}\: 26\!-\!34$ km) and the accretion disc is viewed at a low inclination of i ≃ 16°−20°. The disc is likely to be truncated either by a boundary layer or by the magnetosphere. Based on the measured flux and the mass accretion rate, the maximum radial extension for the boundary layer is estimated to be ∼6.4 Rg from the NS surface. The truncated inner disc in association with pressure from a magnetic field sets an upper limit of B ≤ 1.9 × 109 G.
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O’Doherty, Robert M., Amy E. Halseth, Daryl K. Granner, Deanna P. Bracy, and David H. Wasserman. "Analysis of insulin-stimulated skeletal muscle glucose uptake in conscious rat using isotopic glucose analogs." American Journal of Physiology-Endocrinology and Metabolism 274, no. 2 (February 1, 1998): E287—E296. http://dx.doi.org/10.1152/ajpendo.1998.274.2.e287.
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An isotopic method was used in conscious rats to determine the roles of glucose transport and the transsarcolemmal glucose gradient (TSGG) in control of basal and insulin-stimulated muscle glucose uptake. Rats received an intravenous 3- O-[3H]methylglucose (3- O-[3H]MG) infusion from −100 to 40 min and a 2-deoxy-[3H]glucose infusion from 0 to 40 min to calculate a glucose metabolic index (Rg). Insulin was infused from −100 to 40 min at rates of 0.0, 0.6, 1.0, and 4.0 mU ⋅ kg−1⋅ min−1, and glucose was clamped at basal concentrations. The ratios of soleus intracellular to extracellular 3- O-[3H]MG concentration and soleus glucose concentrations were used to estimate the TSGG using principles of glucose countertransport. Tissue glucose concentrations were compared in well-perfused, slow-twitch muscle (soleus) and poorly perfused, fast-twitch muscle (vastus lateralis, gastrocnemius). Data show that 1) small increases in insulin increase soleus Rgwithout decreasing TSGG, suggesting that muscle glucose delivery and phosphorylation can accommodate the increased flux; 2) due to a limitation in soleus glucose phosphorylation and possibly delivery, insulin at high physiological levels decreases TSGG, and at supraphysiological insulin levels the TSGG is not significantly different from 0; 3) maximum Rgis maintained even though TSGG decreases with increasing insulin levels, indicating that glucose transport continues to increase and is not rate limiting for maximal insulin-stimulated glucose uptake; and 4) muscle consisting of fast-twitch fibers that are poorly perfused exhibits a 35–45% fall in tissue glucose with insulin, suggesting that glucose delivery is a major limitation in sustaining the TSGG. In conclusion, control of glucose uptake is distributed between glucose transport and factors that determine the TSGG. Insulin stimulation of glucose transport increases the demands on the factors that maintain glucose delivery to the muscle membrane and glucose phosphorylation inside the muscle.
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Melland, A. R., M. R. Mc Caskill, R. E. White, and D. F. Chapman. "Loss of phosphorus and nitrogen in runoff and subsurface drainage from high and low input pastures grazed by sheep in southern Australia." Soil Research 46, no. 2 (2008): 161. http://dx.doi.org/10.1071/sr07084.
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High rates of fertiliser applied to boost pasture growth in the southern Australian sheep industry may lead to eutrophication of waterways and groundwater degradation. A field study was used to investigate whether higher fertiliser and stocking rates would increase nutrient loss in runoff and subsurface flow from pastures. Phosphorus (P) and nitrogen (N) concentrations in surface and subsurface flow were measured from 1998–2000 in four 0.5-ha hillslope plots. Surface flow volume was measured directly and subsurface water flux was estimated using soil moisture data and a water balance model. A simulated rainfall study was also conducted using 0.64-m2 plots. The treatments represented were: a low-P set-stocked sown pasture (SS low P), a high-P set-stocked sown pasture (SS high P), a high-P sown pasture in a 4-paddock rotation (RG 4-pdk), and an unsown set-stocked pasture (Low P volunteer). No runoff from the hillslope occurred in 1999, while the volume of runoff in 1998 and 2000 varied from 0.1 to 68 mm/year across the 4 hillslope plots. More P was lost via surface runoff (up to 0.25 kg P/ha.year) than subsurface flow (up to 0.027 kg P/ha.year). However, N loads were greater in subsurface flows (3.2–10.6 kg N/ha.year) than surface runoff (0.04–2.74 kg N/ha.year). Phosphorus concentrations were higher in runoff from the high P treatments (0.34–0.83 mg P/L) than the set-stocked low P treatment (0.19–0.22 mg P/L). Higher TP concentrations in runoff from the high P treatments were associated with greater labile P contents in the soil, dung, and herbage. However, the volume of runoff, rather than the pasture treatment, was the primary determinant of nutrient loss. Avoiding high nutrient inputs in seasonally waterlogged areas, sowing perennial pastures, and minimising stock camping helps minimise P losses to waterways and N losses to groundwater.
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Seo, G. T., S. W. Jang, S. H. Lee, and C. H. Yoon. "The fouling characterization and control in the high concentration PAC membrane bioreactor HCPAC-MBR." Water Science and Technology 51, no. 6-7 (March 1, 2005): 77–84. http://dx.doi.org/10.2166/wst.2005.0624.
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This study focuses on the experimental investigation to identify the effect of PAC at high concentrations on the fouling of membranes. A pilot-scale experimental apparatus was installed at a water treatment plant located downstream of Nakdong river basin, Korea. Effluent of rapid sand filter was used as influent of the system, which consists of PAC bio-reactor, submerged membrane module (hollow fiber with pore size 0.1 μm) and air supply facility. PAC was dosed at 40 g/L initially and it was not replaced during the operation period. Suction type filtration was carried out at intervals of 12 min. suction and 3 min. idling. At the initial flux 0.36 m/d, the system could be operated stably for around 90 days at target trans-membrane pressure (TMP) of 40 kPa. Among total resistance of membrane filtration, cake and gel layer resistance, Rc+Rg, was the dominant fraction (more than 90% of the total) to increase the filtration pressure, which means that the filtration resistance could be controlled by the PAC cake layer and then irreversible membrane fouling could be prevented. Three minutes air backwashing every 3 days could extend the operation period to 127 days. Organics were analyzed in terms of molecular weight structure. The influent of the system consists of 15.0% and 74.4% of hydrophobic and hydrophilic natural organic matter (NOM), respectively. Hydrophobic and hydrophilic (electrostatic) interaction was the main factor on fouling of the membrane in the reactor. Hydrophobic fraction decreased slightly in the effluent, which means hydrophobic NOM removal in the reactor by adsorption. Organics accumulated in the membrane were extracted for analysis after a certain period of operation. The fraction of hydrophobic and hydrophilic organics was 41.4% and 38.9%, respectively. On the basis of the experimental results, the hydrophobic organics were the major materials causing the fouling of the membrane, which should be changed to other types of material.
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Parijskij, Y. N., N. S. Soboleva, W. M. Goss, A. I. Kopylov, O. V. Verkhodanov, A. V. Temirova, and O. P. Zhelenkova. "The RATAN-600 - VLA − 6m Russian telescope: Early Universe Project." Symposium - International Astronomical Union 175 (1996): 591–92. http://dx.doi.org/10.1017/s007418090008195x.
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We present the preliminary results of the “BIG TRIO” project of penetration into the “Dark Age” of the Universe, between the recombination epoch and the epoch of the first QSO using RATAN-600 “Cold Experiment” deep (few mJy) multi-frequency strip survey (Parijskij, Korolkov, 1986; Parijskij et.al,1991,1992). Our general approach is close to the classical SS FRII RG selection rules of very distant galaxies with old stellar population (McCarthy, 1993) with small improvements. Details may be found in (Kopylov et al, 1995). Mean estimated z of our SS FRII RG's is about 1.5, 20% of all objects have z larger than 3. Before the direct spectroscopy of all SS FRII objects we have estimated their redshifts by different methods: using the updated Hubble diagram, θ-z and flux density-z relations and now begun to use multi-color measuring all our objects to estimate “color z” and a stellar age of the parent galaxies using available models of stellar population evolution in such objects (gE class). The first subgroup of 16 objects (not the weakest ones) measured in BVRI gave us the following preliminary results using Bruzual-Charlot model (Bruzual et al., 1993). Looking at this Table, we can make the following statements: mean color z occurred to be very close (within 15%) to the photometric z, but individual redshifts may differ. A mean age of the stellar population is about 1 Gyr, and, at least in some objects, star formation began when the Universe was only 1 Gyr old (Ω0 = 1, H0 = 50), that is older than the most distant QSOs. One object, RC0934+0505, happened to be the oldest object found up to now. We estimate, that there are about 10000 objects with such an age on the sky which can be easily selected (especially with new generation of radio and optical catalogs now in preparation) and fully studied spectroscopically even by present day facilities. The only evolution effect we have noticed is that more distant objects have smaller ages of stellar populations. There is weak z-dependence of the ratio of radio to optical luminosities in the objects of our list, which disappears when we take into account the K- correction to the SED in gE.
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DUMITRESCU, Horia, Vladimir CARDOS, and Radu BOGATEANU. "Gravitational waves on Earth and their warming effects." INCAS BULLETIN 13, no. 1 (March 5, 2021): 43–54. http://dx.doi.org/10.13111/2066-8201.2021.13.1.5.
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The gravity or reactive bundle energy is the outlet of the morphogenetic impact, known as “BIG BANG”, creating a bounded ordered/structured universe along with the solar system, including the EARTH-world with its human race. Post-impact, the huge kinetic energy is spread into stellar bodies associated with the light flux under strong mutual connections or gravitational bundle. Einstein’s general relativity theory including the gravitational field can be expressed under a condensed tensor formulation as E R − Rg = T where E defines the geometry via a curved space-time structure (R) over the gravity field (1/2Rg), embedded in a matter distribution T The fundamental (ten non-linear partial differential) equations of the gravitational field are a kind of the space-time machine using the curvature of a four-dimensional space-time to engender the gravity field carrying away material structures. Gravity according to the curved space-time theory is not seen as a gravitational force, but it manifests itself in the relativistic form of the space-time curvature needing the constancy of the light speed. But the constant light velocity makes the tidal wave/pulsating energy, a characteristic of solar energy, impossible. The Einstein’s field equation, expressed in terms of tensor formulation along with the constant light speed postulate, needs two special space-time tensors (curvature and torsion) in 4 dimensions, where for the simplicity the torsion/twist tensor is less well approximated (Bianchi identity) leading to a constant/frozen gravity (twist-free gravity).The non-zero torsion tensor plays a significant physical role in the planetary dynamics as a finest gear of a planet, where its spinning rotation is directly connected to the own work and space-time structure (or clock), controlled by light fluctuations (or tidal effect of gravity). The spin correction of Einstein’s gravitational field refers to the curvature-torsion effect coupled with fluctuating light speed. The mutual curvature-torsion bundle self-sustained by the quantum fluctuations of light speed engenders helical gravitational wave fields of a quantum nature where bodies orbit freely in the light speed field (cosmic wind). In contrast to the Einstein’s field equation describing a gravitational frozen field, a quantum tidal gravity model is proposed in the paper.
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Porquet, D., C. Done, J. N. Reeves, N. Grosso, A. Marinucci, G. Matt, A. Lobban, et al. "A deep X-ray view of the bare AGN Ark 120." Astronomy & Astrophysics 623 (February 25, 2019): A11. http://dx.doi.org/10.1051/0004-6361/201834448.
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Context. The spin of supermassive black holes (SMBH) in active galactic nuclei (AGN) can be determined from spectral signature(s) of relativistic reflection such as the X-ray iron Kα line profile, but this can be rather uncertain when the line of sight intersects the so-called warm absorber and/or other wind components as these distort the continuum shape. Therefore, AGN showing no (or very weak) intrinsic absorption along the line-of-sight such as Ark 120, a so-called bare AGN, are the ideal targets for SMBH spin measurements. However, in our previous work on Ark 120, we found that its 2014 X-ray spectrum is dominated by Comptonisation, while the relativistic reflection emission only originates at tens of gravitational radii from the SMBH. As a result, we could not constrain the SMBH spin from disc reflection alone. Aims. Our aim is to determine the SMBH spin in Ark 120 from an alternative technique based on the global energetics of the disc-corona system. Indeed, the mass accretion rate (Ṁ) through the outer disc can be measured from the optical-UV emission, while the bolometric luminosity (Lbol) can be fairly well constrained from the optical to hard X-rays spectral energy distribution, giving access to the accretion efficiency η = Lbol/(Ṁc2) which depends on the SMBH spin. Methods. The spectral analysis uses simultaneous XMM-Newton (OM and pn) and NuSTAR observations on 2014 March 22 and 2013 February 18. We applied the OPTXCONV model (based on OPTXAGNF) to self consistently reproduce the emission from the inner corona (warm and hot thermal Comptonisation) and the outer disc (colour temperature corrected black body), taking into account both the disc inclination angle and relativistic effects. For self-consistency, we modelled the mild relativistic reflection of the incident Comptonisation components using the XILCONV convolution model. Results. We infer a SMBH spin of 0.83+0.05−0.03, adopting the SMBH reverberation mass of 1.50 × 108 M⊙. In addition, we find that the coronal radius decreases with increasing flux (by about a factor of two), from 85+13−10Rg in 2013 to 14 ± 3 Rg in 2014. Conclusions. This is the first time that such a constraint is obtained for a SMBH spin from this technique, thanks to the bare properties of Ark 120, its well determined SMBH reverberation mass, and the presence of a mild relativistic reflection component in 2014 which allows us to constrain the disc inclination angle. We caution that these results depend on the detailed disc-corona structure, which is not yet fully established. However, the realistic parameter values (e.g. Lbol/LEdd, disc inclination angle) found suggest that this is a promising method to determine spin in moderate-Ṁ AGN.
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Reis, Ligia S., José L. de Souza, Carlos A. V. de Azevedo, Gustavo B. Lyra, Ricardo A. Ferreira Junior, and Vera L. A. de Lima. "Componentes da radiação solar em cultivo de tomate sob condições de ambiente protegido." Revista Brasileira de Engenharia Agrícola e Ambiental 16, no. 7 (July 2012): 739–44. http://dx.doi.org/10.1590/s1415-43662012000700006.
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Objetivou-se, com este trabalho, avaliar o saldo de radiação e a irradiação solar e fotossintética em condições de ambiente protegido cultivado com o tomateiro e suas relações com a irradiação solar do ambiente externo. O tomateiro foi cultivado em casa de vegetação não climatizada, com cobertura de polietileno de 0,12 mm de espessura. A irradiação solar (Rgi), o saldo de radiação (Rni) e a densidade de fluxo de fótons fotossintéticos foram obtidos por radiômetros ligados a um datalogger instalado no interior do ambiente protegido. Os dados externos (irradiância solar global, Rg) foram coletados na Estação Agrometeorológica do Centro de Ciências Agrárias da Universidade Federal de Alagoas. O ambiente protegido promoveu redução na irradiação solar expressa como a transmitância do polietileno em 62%. As relações entre os componentes de radiação do ambiente interno e externo foram expressas satisfatoriamente por regressões lineares, com coeficientes de determinação (R²) superiores a 0,88 enquanto para a irradiação fotossintética (PARi) os R² foram maiores que 0,52. As relações obtidas mostraram que Rni representa 0,60 da Rgi e a PARi é proporcional a 0,28 da Rg e 0,44 da Rgi. O albedo médio da cultura durante o ciclo foi de 0,15.
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His, Isabelle, Christine Andème-Onzighi, Claudine Morvan, and Azeddine Driouich. "Microscopic Studies on Mature Flax Fibers Embedded in LR White." Journal of Histochemistry & Cytochemistry 49, no. 12 (December 2001): 1525–35. http://dx.doi.org/10.1177/002215540104901206.
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Flax fibers have been the subject of many biochemical studies, which revealed that cellulose and pectins are the major constituents of their walls. In contrast, little is known about the location of these polymers within the walls of mature fibers by microscopic methods. This has been technically hampered by the very thick secondary wall of fibers, resulting in inadequate tissue preservation unsuitable for immunogold microscopy. In this study, we adapted the basic chemical fixation, dehydration and infiltration methods to achieve a good preservation of the cell structures of mature fibers and reduced damage to antigens. We were able to apply postembedding immunocytochemical techniques to map the location of various pectic epitopes within the walls of mature fibers. Our immunolabeling data show that homogalacturonans were exclusively found in the middle lamellae and the cell junctions but were not detectable in the secondary wall. In contrast, rhamnogalacturonan I (RG I)-associated epitopes, as well as galactan and arabinan epitopes, were abundantly distributed over the secondary wall of mature fibers.
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Silva, Thieres G. F. da, Magna S. B. de Moura, Sérgio Zolnier, José M. Soares, Luciana S. B. de Souza, and Elieth O. Brandão. "Variação do balanço de radiação e de energia da cana-de-açúcar irrigada no semiárido brasileiro." Revista Brasileira de Engenharia Agrícola e Ambiental 15, no. 2 (February 2011): 139–47. http://dx.doi.org/10.1590/s1415-43662011000200005.
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O objetivo deste trabalho foi analisar as variações nas magnitudes e nas partições dos componentes do balanço de radiação e de energia, obtidos durante o período de crescimento da cana-de-açúcar irrigada (variedade RB92579). O experimento foi conduzido em Juazeiro, BA, localizado na região do Semiárido brasileiro. Os fluxos de calor sensível (H) e calor latente (LE) no ar foram estimados por meio do balanço de energia, com base na razão de Bowen (BERB). Concomitantemente, o crescimento da cultura também foi monitorado. Em análise preliminar deste método, constatou-se que 62,7% dos dados coletados apresentaram consistência física para serem utilizados nas estimativas dos componentes H e LE. Observou-se que o valor médio da relação Rn/Rg foi igual a 59±5%, com os menores valores ocorrendo no início e final do ciclo de cultivo da cana-de-açúcar, enquanto a magnitude dos valores do balanço de radiação de ondas longas (BOL) foi intensificada quando o índice de área foliar (IAF) era reduzido. Além disso, verificou-se também que o valor médio do albedo foi de 23±3% e que 81% da energia disponível foram destinados ao fluxo de calor latente, enquanto os valores do fluxo de calor sensível no ar (H) e no solo (G) representaram 16 e 3%, respectivamente.
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Reis, Fabrício de Oliveira, Eliemar Campostrini, and Elias Fernandes de Sousa. "Fluxo de seiva xilemática em mamoeiro 'Golden' cultivado por microaspersão sobre copa: relações com as variáveis ambientais." Bragantia 68, no. 2 (2009): 285–94. http://dx.doi.org/10.1590/s0006-87052009000200001.
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As técnicas de irrigação, bem como o uso de espécies adaptadas às condições de deficiência hídrica, têm sido cada vez mais importantes para o sucesso da produção vegetal. De fato, a adequada irrigação em plantas cultivadas pode melhorar a eficiência no uso da água, refletindo na qualidade do produto agrícola e no custo de produção. O estresse hídrico em fruteiras pode ser causado por deficiência de água no solo, na atmosfera ou em ambos. As variáveis ambientais regulam a perda de água pelas plantas, e os elevados valores de déficit de pressão de vapor entre a folha e o ar (DPVfolha-ar) podem causar fechamento estomático e reduzir o processo transpiratório, principalmente em plantas de grande porte. Neste trabalho, utilizou-se o método de dissipação de calor no caule proposto por GRANIER (1985) para a medição do fluxo de seiva xilemática (FS). Assim, objetivou-se obter possíveis relações entre os valores de FS e os valores de evapotranspiração de referência (ET0) em mamoeiros cultivados com e sem microaspersão sobre copa (MASC) em condição de campo, assim como investigar as relações entre os valores do FS e a radiação global (RG) e déficit de pressão de vapor do ar (DPVar). Constatou-se uma defasagem entre a perda de água pelas folhas e o movimento de água através do tronco (fase lag). De janeiro a março, obteve-se uma boa correlação entre FS e DPVar, fato não observado de junho a agosto, provavelmente devido a esta fase lag. De janeiro a março, as plantas que receberam MASC tiveram o FS aumentado em relação às plantas-controle, época em que o ET0 foi maior.
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Sabag, Evyatar. "Non minimal D-type conformal matter compactified on three punctured spheres." Journal of High Energy Physics 2020, no. 10 (October 2020). http://dx.doi.org/10.1007/jhep10(2020)139.
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Abstract We study compactifications of 6d non minimal (Dp+3, Dp+3) type conformal matter. These can be described by N M5-branes probing a Dp+3-type singularity. We derive 4d Lagrangians corresponding to compactifications of such 6d SCFTs on three punctured spheres (trinions) with two maximal punctures and one minimal puncture. The trinion models are described by simple $$ \mathcal{N} $$ N = 1 quivers with SU(2N) gauge nodes. We derive the trinion Lagrangians using RG flows between the aforementioned 6d SCFTs with different values of p and their relations to matching RG flows in their compactifications to 4d. The suggested trinions are shown to reduce to known models in the minimal case of N = 1. Additional checks are made to show the new minimal punctures uphold the expected S-duality between models in which we exchange two such punctures. We also show that closing the new minimal puncture leads to expected flux tube models.
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Calderón-Infante, José, Angel M. Uranga, and Irene Valenzuela. "The convex hull swampland distance conjecture and bounds on non-geodesics." Journal of High Energy Physics 2021, no. 3 (March 2021). http://dx.doi.org/10.1007/jhep03(2021)299.
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Abstract The Swampland Distance Conjecture (SDC) restricts the geodesic distances that scalars can traverse in effective field theories as they approach points at infinite distance in moduli space. We propose that, when applied to the subset of light fields in effective theories with scalar potentials, the SDC restricts the amount of non-geodesicity allowed for trajectories along valleys of the potential. This is necessary to ensure consistency of the SDC as a valid swampland criterion at any energy scale across the RG flow. We provide a simple description of this effect in moduli space of hyperbolic space type, and products thereof, and obtain critical trajectories which lead to maximum non-geodesicity compatible with the SDC. We recover and generalize these results by expressing the SDC as a new Convex Hull constraint on trajectories, characterizing towers by their scalar charge to mass ratio in analogy to the Scalar Weak Gravity Conjecture. We show that recent results on the asymptotic scalar potential of flux compatifications near infinity in moduli space precisely realize these critical amounts of non-geodesicity. Our results suggest that string theory flux compactifications lead to the most generic potentials allowing for maximum non-geodesicity of the potential valleys while respecting the SDC along them.
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Peterzan, M. A., W. T. Clarke, C. A. Lygate, H. A. Lake, J. J. Rayner, M. J. Hundertmark, A. P. Apps, et al. "P1611Non-invasive predictors of LV biopsy-obtained creatine kinase activity in patients with non-failing and failing myocardial hypertrophy." European Heart Journal 40, Supplement_1 (October 1, 2019). http://dx.doi.org/10.1093/eurheartj/ehz748.0370.
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Abstract Introduction Myocardial creatine kinase (CK) activity represents an important metabolic reserve: it correlates closely with contractile reserve and post-ischaemic function, keeps cytosolic [ADP] low, and optimises the free energy for ATP hydrolysis. It may also contribute to the transition to failure in the heart hypertrophied by chronic haemodynamic overload; modest up-regulation has been shown to be cardio-protective. Total CK activity measurement requires chemical freeze-and-extract methods, which destroy tissue, precluding repeated measures. To date, non-invasive assessments of human myocardial CK flux (calculated as kf × [PCr], where kf is the pseudo-first-order forward rate constant measured by 31P-magnetic resonance spectroscopy (MRS) have not assessed creatine content or total CK activity. Thus we aimed to validate kf measurement against total CK activity and investigate predictors of CK activity. Methods 39 subjects (median age 71, range 43–84) undergoing clinically indicated cardiac surgery had CK total activity measured from LV biopsy. 31 had severe AS (10 with impaired LVEF); 2 had severe primary MR; 5 had severe mitral stenosis (2 with impaired LVEF) and 1 had an LA mass. 35 of 39 contributed triplicate datasets: CK total activity, kf (31P-MRS TRiST sequence at 3T) and LV volumes (cine-MRI, 3T Siemens). 27 had severe AS (8 with impaired LVEF); other groups were the same. Exclusion criteria were prior myocardial infarction and flow-limiting coronary disease. Flash-frozen LV biopsies obtained within 15 min of cardiopulmonary bypass were analysed for CK total activity, total creatine, and citrate synthase (CS) activity (a marker of oxidative phosphorylation capacity). Results Multiple, novel correlations were observed between CK total activity (IU/mg protein) and CS activity (r=0.87, p=9e-13), total creatine (r=0.59, p=8e-5), kf (r=0.42, p=0.013), total creatine × kf (r=0.64, p=4e-5), LVESVi (r=−0.52, p=8e-4), LVEF (r=0.48, p=0.002) and LVMi (r=−0.42, p=0.009) (Panels A-E) (LVEDVi and non-indexed counterparts were also significant correlates.) The most predictive linear regression model incorporating elements of the CK rate equation included total creatine (nmol/mg protein), kf (/s), and kf × LVESVi (ml/m2) (adjusted R2=0.56, beta=0.426, 0.618, −1.968 and p=0.001, 5e-5, 0.003 respectively, Panel F). Figure 1 Conclusions These results are the first evidence of agreement between non-invasive estimates of human cardiac CK activity (kf) and freeze-extracted chemical methods. The key original finding is that it is feasible to attempt to predict CK capacity in vivo by using a combination of techniques (creatine by 1H MRS, CK kf by 31P-MRS and LVESVi by cine imaging). The key insight is that CK capacity is best estimated not simply from what the rate equation would predict (creatine and kf), but that other factors relating to failing contractility reduce CK activity independently from creatine content and enzyme kf. Acknowledgement/Funding British Heart Foundation Clinical Research Training Fellowship (FS/15/80/31803) and Programme Grant (RG/18/12/34040).
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Peterzan, M. A., W. T. Clarke, C. A. Lygate, H. A. Lake, J. Y. C. Lau, E. Johnson, J. J. Rayner, et al. "P2272Determinants of left ventricular ATP availability measured in vivo and ex vivo in patients with severe aortic stenosis: correlation of creatine kinase activity with LVEF and ATP diffusion distance." European Heart Journal 40, Supplement_1 (October 1, 2019). http://dx.doi.org/10.1093/eurheartj/ehz748.0749.
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Abstract Introduction The transition to systolic failure in severe aortic stenosis (AS) increases mortality. There are currently no reliable markers of transition, and the guideline LVEF <50% threshold for intervention in asymptomatic severe AS does not capture all subjects at increased risk. In animal models, reduced ATP delivery capacity through creatine kinase (CK) is important, with modest increases in CK capacity conferring cardioprotection. ATP may also diffuse (independent of CK) from mitochondria to the contractile site. We have performed the first human study to test whether ATP diffusion distance relates to CK activity and whether CK activity is reduced in low LVEF severe AS. Methods 19 patients with severe AS, LVEF ≥55% (AS-pEF, mean±SD LVEF 63±5%, mean gradient 48±14 mmHg) and 10 with severe AS, LVEF <55% (AS-rEF, LVEF 42±8%, mean gradient 32±11) underwent 31P-MRS for CK rate constant (kf) and phosphocreatine/ATP (PCr/ATP) ratio, and MRI for LV volumes. LV biopsies were taken during AVR and analysed for CK total activity, CK isoforms, total creatine, and citrate synthase (CS) activity. 9 biopsies also underwent serial block face scanning electron microscopy and mitochondria-sarcomere 3D distance distributions were plotted. Results were compared to 24 controls (LVEF 61±4%), of which 4 had LV biopsy (3 severe MS, 1 LA myxoma, MS-pEF). Surgical patients had flow-limiting atheroma excluded with invasive angiography and prior myocardial infarction excluded with late gadolinium enhancement MRI. Results When compared to controls, both CK total activity and CS activity were lower in AS-pEF (by 27% and 23% respectively, both p<0.05, Panels A-B). Although PCr/ATP reduced in AS-pEF (by 20%, p<0.001, panel C), kf (panel D) and CK flux estimated by kf × total creatine were not different. CK-MB expression reduced in AS-pEF (19 vs 27% of total CK, p=0.003), reflecting compensatory increases in CK-MM (p=0.26) and CK-BB (p=0.18) in the face of reduced CK activity. AS-rEF was associated with further reduction in both CK and CS activities (by 32% and 22% respectively, both p<0.05, Panels A-B), but no differences in PCr/ATP, CK kf or relative CK isozyme expression were seen. There were no significant between-group differences in total creatine (Panel E). Overall this suggests that CK reserve and oxidative capacity potentially reduce in pressure overload, with further falls commensurate with systolic dysfunction. When median mitochondria-sarcomere ATP diffusion distances were plotted against CK total activity a strong positive correlation was observed (r=0.86, p=0.003, Panel F). This suggests a compensatory reduction in diffusion distance develops when CK activity falls. Conclusions Transition to failure in severe AS is associated with lower oxidative capacity and maximal ATP delivery capacity through CK. Despite compensatory falls in ATP diffusion distance and altered CK isozyme expression, these changes may underlie susceptibility to EF decline in AS. Acknowledgement/Funding British Heart Foundation Clinical Research Training Fellowship (FS/15/80/31803) and Programme Grant (RG/18/12/34040).
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Petrova, Anna, Liudmila Kozlova, Oleg Gorshkov, Alsu Nazipova, Marina Ageeva, and Tatyana Gorshkova. "Cell Wall Layer Induced in Xylem Fibers of Flax Upon Gravistimulation Is Similar to Constitutively Formed Cell Walls of Bast Fibers." Frontiers in Plant Science 12 (April 6, 2021). http://dx.doi.org/10.3389/fpls.2021.660375.
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In the fibers of many plant species after the formation of secondary cell walls, cellulose-enriched cell wall layers (often named G-layers or tertiary cell walls) are deposited which are important in many physiological situations. Flax (Linum usitatissimum L.) phloem fibers constitutively develop tertiary cell walls during normal plant growth. During the gravitropic response after plant inclination, the deposition of a cellulose-enriched cell wall layer is induced in xylem fibers on one side of the stem, providing a system similar to that of tension wood in angiosperm trees. Atomic force microscopy (AFM), immunochemistry, and transcriptomic analyses demonstrated that the G-layer induced in flax xylem fibers was similar to the constitutively formed tertiary cell wall of bast (phloem) fibers but different from the secondary cell wall. The tertiary cell walls, independent of tissue of origin and inducibility, were twice as stiff as the secondary cell walls. In the gravitropic response, the tertiary cell wall deposition rate in xylem was higher than that of the secondary cell wall. Rhamnogalacturonan I (RG-I) with galactan side chains was a prominent component in cellulose-rich layers of both phloem and xylem flax fibers. Transcriptomic events underlying G-layer deposition in phloem and xylem fibers had much in common. At the induction of tertiary cell wall deposition, several genes for rhamnosyltransferases of the GT106 family were activated in xylem samples. The same genes were expressed in the isolated phloem fibers depositing the tertiary cell wall. The comparison of transcriptomes in fibers with both inducible and constitutive tertiary cell wall deposition and xylem tissues that formed the secondary cell walls is an effective system that revealed important molecular players involved in the formation of cellulose-enriched cell walls.