Studies of the growth and mineral nutrition of barley varieties. II. Potassium uptake and its regulation

1983 ◽  
Vol 61 (6) ◽  
pp. 1551-1558 ◽  
Author(s):  
M. Yaeesh Siddiqi ◽  
Anthony D. M. Glass
Keyword(s):  
Steady State ◽  
Kinetic Constants ◽  
Growth Responses ◽  
Short Term ◽  
Potential Growth ◽  
Wide Range ◽  
Rapid Loading ◽  
State Growth ◽  
Complete Nutrient Solution ◽  
Growth Experiments

Short-term K+ (86Rb) influx and its regulation by root K+ concentration was studied in barley varieties, using plants grown in complete nutrient solution at constant concentrations. The varieties employed in this study exhibited substantial differences not only in K+ influx but also in the intensity and the pattern of regulation of K+ influx. In the high-potential growth-rate varieties these K+ uptake characteristics were found to correlate well with their growth responses to K+ supply reported earlier by Siddiqi and Glass. Predictions of K+ influx, based upon kinetic constants and internal K+ concentrations derived from steady-state growth experiments, were found to correspond well with the observed fluxes for plants grown under these conditions over a wide range of root K+ concentrations. These predictions also provided good estimates of influx in CaSO4-grown plants for intermediate levels of root K+ concentration. However, at low root K+ concentration, predictions greatly overestimated observed fluxes, while at high root K+, influx was underestimated. Similarly, when kinetic constants derived from CaSO4-grown plants (whose root K+ concentrations were increased by rapid loading) were applied to steady-state plants, predicted influx values were close to observed in the intermediate range of root K+ concentration. However, at high root K+, influx was overestimated. These adjustments serve, in the steady state, to maintain tissue K+ concentration within rather narrow limits.

V˙o 2 kinetics of mild exercise are altered by RER

1999 ◽  
Vol 87 (6) ◽  
pp. 2097-2106 ◽  
Author(s):  
Paul A. Molé ◽  
James J. Hoffmann
Keyword(s):  
Steady State ◽  
Time Course ◽  
Respiratory Exchange Ratio ◽  
Short Term ◽  
Men And Women ◽  
Adult Men ◽  
Wide Range ◽  
Leg Cycling ◽  
Biexponential Model ◽  
Kinetics Of

We propose that variations in fat and carbohydrate (CHO) oxidation by working muscle alter O2 uptake (V˙o 2) kinetics. This hypothesis provides two predictions: 1) the kinetics should comprise two exponential components, one fast and the other slow, and 2) their contribution should change with variations in fat and CHO oxidation, as predicted by steady-state respiratory exchange ratio (RER). The purpose of this study was to test these predictions by evaluating theV˙o 2 kinetic model:V˙o 2( t) = αR + αF{1 − exp[( t − TD)/−τF]} + αC{1 − exp[( t − TD)/−τC]} for short-term, mild leg cycling in 38 women and 44 men, whereV˙o 2( t) describes the time course, αR is resting V˙o 2, t is time after onset of exercise, TD is time delay, αF and τF are asymptote and time constant, respectively, for the fast (fat) oxidative term, and αC and τC are the corresponding parameters for the slow (CHO) oxidative term. We found that 1) this biexponential model accurately described the V˙o 2kinetics over a wide range of RERs, 2) the contribution of the fast (αF, fat) component was inversely related to RER, whereas the slow (αC, CHO) component was positively related to RER, and 3) this assignment of the fast and slow terms accurately predicted steady-state respiratory quotient and CO2 output. Therefore, the kinetic model can quantify the dynamics of fat and CHO oxidation over the first 5–10 min of mild exercise in young adult men and women.

Simulation of C1 fluxes in cyanobacteria: comparison between the carboxysome hypothesis and the equilibrium proposal

1997 ◽  
Vol 75 (12) ◽  
pp. 2117-2130 ◽  
Author(s):  
Christophe Salon ◽  
David Thomas Canvin
Keyword(s):  
Mathematical Model ◽  
Steady State ◽  
Kinetic Constants ◽  
Experimental Conditions ◽  
Extracellular Medium ◽  
Blue Green Algae ◽  
Permeability Coefficients ◽  
Inorganic Species ◽  
Wide Range ◽  
Entire Cell

Inorganic carbon fluxes were simulated by a mathematical model using an equilibrium hypothesis for a wide range of conditions in a closed system composed of air-grown cells of Synechococcus UTEX 625 in a reaction vessel connected to a mass spectrometer. The metabolic scheme took into account the input fluxes of CO2 and HCO3− transport into the cells, the output fluxes of CO2 and HCO3− efflux, the diversion of Q toward the formation of the internal C2 pool, and photosynthetic CO2 fixation. The equations expressed the variation in concentration of each inorganic species outside and inside the cell as a function of time. The input fluxes were previously characterized by their kinetic constants (K1/2 and Vm) both during initial uptake occurring upon illumination of the cells and under steady-state photosynthesis conditions. The efflux rates of the various Ci species from the cells were investigated under a wide variety of experimental conditions. Using these efflux rates, the permeability coefficients of the cell for CO2 and HCO3− were calculated previously. Using the kinetic constants for CO2 and HCO3− transport, the permeability coefficients of the cell for CO2 and HCO3− and the geometrical characteristics of the cells, the model simulated precisely the [HCO3−]/[CO2] ratio and the [CO2] and [O2] changes in the extracellular medium as well as the rate of filling of the internal Ci pool under various conditions. Accurate fitting of experimental data with calculated values were possible only when the intracellular Ci species were assumed to be in equilibrium throughout the entire cell volume. Results are discussed and compared with those given by previous hypotheses. Key words: Synechococcus UTEX 625, blue green algae, cyanobacteria, mathematical model, active CO2 transport, active HCO3− transport, steady state, photosynthesis, Ci concentrating mechanism.

scholarly journals The Light Growth Response of Phycomyces

1973 ◽  
Vol 62 (5) ◽  
pp. 590-617 ◽  
Author(s):  
K. W. Foster ◽  
E. D. Lipson
Keyword(s):  
Growth Response ◽  
Tracking System ◽  
Action Spectrum ◽  
Response Patterns ◽  
Growth Responses ◽  
Wide Range ◽  
Variable Damping ◽  
State Growth ◽  
Gradual Variation ◽  
Constant Period

With the help of an automated tracking system we have studied the characteristics of the transient light growth response of Phycomyces. The response shows a sharply defined latency. The Q10 of the reciprocal latency is 2.4. Response patterns at different peaks of the action spectrum are the same. The gradual variation of response magnitude over a wide range of adapted intensifies parallels that of phototropism. The responses to saturating stimuli exhibit a strong oscillation with a constant period of 1.6 min and variable damping. The growth responses to sinusoidally varying light intensities show a system bandwidth of 2.5 x 10-3 Hz. The linear dependence of phase shift on frequency is largely attributable to the latency observed with pulse stimuli. In the high intensity range a previously suspected increase of the steady-state growth rate with intensity has been confirmed. The light growth responses of mutants selected for diminished phototropism have been investigated. Many of these mutants have sizable but grossly distorted growth responses.

Validation of On-line Respiration Meter and its Applications by Computer Simulation

1992 ◽  
Vol 26 (5-6) ◽  
pp. 1355-1363 ◽  
Author(s):  
C-W. Kim ◽  
H. Spanjers ◽  
A. Klapwijk
Keyword(s):  
Steady State ◽  
Activated Sludge ◽  
Respiration Rate ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Mass Balances ◽  
Short Term ◽  
Respiration Rates ◽  
On Line ◽  
Made In

An on-line respiration meter is presented to monitor three types of respiration rates of activated sludge and to calculate effluent and influent short term biochemical oxygen demand (BODst) in the continuous activated sludge process. This work is to verify if the calculated BODst is reliable and the assumptions made in the course of developing the proposed procedure were acceptable. A mathematical model and a dynamic simulation program are written for an activated sludge model plant along with the respiration meter based on mass balances of BODst and DO. The simulation results show that the three types of respiration rate reach steady state within 15 minutes under reasonable operating conditions. As long as the respiration rate reaches steady state the proposed procedure calculates the respiration rate that is equal to the simulated. Under constant and dynamic BODst loading, the proposed procedure is capable of calculating the effluent and influent BODst with reasonable accuracy.

Spectroscopic Studies of Asparaginyl-tRNA Synthetase from Entamoeba histolytica

2019 ◽  
Vol 26 (6) ◽  
pp. 435-448
Author(s):  
Priyanka Biswas ◽  
Dillip K. Sahu ◽  
Kalyanasis Sahu ◽  
Rajat Banerjee
Keyword(s):  
Circular Dichroism ◽  
Steady State ◽  
Entamoeba Histolytica ◽  
Protein Concentration ◽  
Trna Synthetase ◽  
Solvent Exposure ◽  
Steady State Fluorescence ◽  
State Process ◽  
Wide Range ◽  
Circular Dichroïsm

Background: Aminoacyl-tRNA synthetases play an important role in catalyzing the first step in protein synthesis by attaching the appropriate amino acid to its cognate tRNA which then transported to the growing polypeptide chain. Asparaginyl-tRNA Synthetase (AsnRS) from Brugia malayi, Leishmania major, Thermus thermophilus, Trypanosoma brucei have been shown to play an important role in survival and pathogenesis. Entamoeba histolytica (Ehis) is an anaerobic eukaryotic pathogen that infects the large intestines of humans. It is a major cause of dysentery and has the potential to cause life-threatening abscesses in the liver and other organs making it the second leading cause of parasitic death after malaria. Ehis-AsnRS has not been studied in detail, except the crystal structure determined at 3 Å resolution showing that it is primarily α-helical and dimeric. It is a homodimer, with each 52 kDa monomer consisting of 451 amino acids. It has a relatively short N-terminal as compared to its human and yeast counterparts. Objective: Our study focusses to understand certain structural characteristics of Ehis-AsnRS using biophysical tools to decipher the thermodynamics of unfolding and its binding properties. Methods: Ehis-AsnRS was cloned and expressed in E. coli BL21DE3 cells. Protein purification was performed using Ni-NTA affinity chromatography, following which the protein was used for biophysical studies. Various techniques such as steady-state fluorescence, quenching, circular dichroism, differential scanning fluorimetry, isothermal calorimetry and fluorescence lifetime studies were employed for the conformational characterization of Ehis-AsnRS. Protein concentration for far-UV and near-UV circular dichroism experiments was 8 µM and 20 µM respectively, while 4 µM protein was used for the rest of the experiments. Results: The present study revealed that Ehis-AsnRS undergoes unfolding when subjected to increasing concentration of GdnHCl and the process is reversible. With increasing temperature, it retains its structural compactness up to 45ºC before it unfolds. Steady-state fluorescence, circular dichroism and hydrophobic dye binding experiments cumulatively suggest that Ehis-AsnRS undergoes a two-state transition during unfolding. Shifting of the transition mid-point with increasing protein concentration further illustrate that dissociation and unfolding processes are coupled indicating the absence of any detectable folded monomer. Conclusion: This article indicates that GdnHCl induced denaturation of Ehis-AsnRS is a two – state process and does not involve any intermediate; unfolding occurs directly from native dimer to unfolded monomer. The solvent exposure of the tryptophan residues is biphasic, indicating selective quenching. Ehis-AsnRS also exhibits a structural as well as functional stability over a wide range of pH.

scholarly journals Identification of DC Thermal Steady-State Differential Inductance of Ferrite Power Inductors

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3854
Author(s):  
Salvatore Musumeci ◽  
Luigi Solimene ◽  
Carlo Stefano Ragusa
Keyword(s):  
Steady State ◽  
Input Voltage ◽  
Switching Frequency ◽  
Ohmic Losses ◽  
Steady State Temperature ◽  
Wide Range ◽  
Average Current ◽  
Power Inductors ◽  
Saturable Inductor ◽  
Thermal Steady State

In this paper, we propose a method for the identification of the differential inductance of saturable ferrite inductors adopted in DC–DC converters, considering the influence of the operating temperature. The inductor temperature rise is caused mainly by its losses, neglecting the heating contribution by the other components forming the converter layout. When the ohmic losses caused by the average current represent the principal portion of the inductor power losses, the steady-state temperature of the component can be related to the average current value. Under this assumption, usual for saturable inductors in DC–DC converters, the presented experimental setup and characterization method allow identifying a DC thermal steady-state differential inductance profile of a ferrite inductor. The curve is obtained from experimental measurements of the inductor voltage and current waveforms, at different average current values, that lead the component to operate from the linear region of the magnetization curve up to the saturation. The obtained inductance profile can be adopted to simulate the current waveform of a saturable inductor in a DC–DC converter, providing accurate results under a wide range of switching frequency, input voltage, duty cycle, and output current values.

scholarly journals The Survival of Haloferax mediterranei under Stressful Conditions

2021 ◽  
Vol 9 (2) ◽  
pp. 336
Author(s):  
Laura Matarredona ◽  
Mónica Camacho ◽  
Basilio Zafrilla ◽  
Gloria Bravo-Barrales ◽  
Julia Esclapez ◽  
...  
Keyword(s):  
Inductively Coupled Plasma ◽  
Sea Water ◽  
Industrial Applications ◽  
Growth Responses ◽  
Haloferax Mediterranei ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Wide Range ◽  
High Metal ◽  
Plasma Mass Spectrometry

Haloarchaea can survive and thrive under exposure to a wide range of extreme environmental factors, which represents a potential interest to biotechnology. Growth responses to different stressful conditions were examined in the haloarchaeon Haloferax mediterranei R4. It has been demonstrated that this halophilic archaeon is able to grow between 10 and 32.5% (w/v) of sea water, at 32–52 °C, although it is expected to grow in temperatures lower than 32 °C, and between 5.75 and 8.75 of pH. Moreover, it can also grow under high metal concentrations (nickel, lithium, cobalt, arsenic), which are toxic to most living beings, making it a promising candidate for future biotechnological purposes and industrial applications. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) analysis quantified the intracellular ion concentrations of these four metals in Hfx. mediterranei, concluding that this haloarchaeon can accumulate Li+, Co2+, As5+, and Ni2+ within the cell. This paper is the first report on Hfx. mediterranei in which multiple stress conditions have been studied to explore the mechanism of stress resistance. It constitutes the most detailed study in Haloarchaea, and, as a consequence, new biotechnological and industrial applications have emerged.

SET-VALUED PERFORMANCE APPROXIMATIONS FOR THE QUEUE GIVEN PARTIAL INFORMATION

2020 ◽  
pp. 1-23
Author(s):  
Yan Chen ◽  
Ward Whitt
Keyword(s):  
Steady State ◽  
Decay Rate ◽  
Waiting Time ◽  
Partial Information ◽  
Upper And Lower Bounds ◽  
Interarrival Time ◽  
Limited Information ◽  
Wide Range ◽  
The Mean ◽  
Third Moment

In order to understand queueing performance given only partial information about the model, we propose determining intervals of likely values of performance measures given that limited information. We illustrate this approach for the mean steady-state waiting time in the $GI/GI/K$ queue. We start by specifying the first two moments of the interarrival-time and service-time distributions, and then consider additional information about these underlying distributions, in particular, a third moment and a Laplace transform value. As a theoretical basis, we apply extremal models yielding tight upper and lower bounds on the asymptotic decay rate of the steady-state waiting-time tail probability. We illustrate by constructing the theoretically justified intervals of values for the decay rate and the associated heuristically determined interval of values for the mean waiting times. Without extra information, the extremal models involve two-point distributions, which yield a wide range for the mean. Adding constraints on the third moment and a transform value produces three-point extremal distributions, which significantly reduce the range, producing practical levels of accuracy.

scholarly journals Modelling the atmosphere of lava planet K2-141b: implications for low- and high-resolution spectroscopy

2020 ◽  
Vol 499 (4) ◽  
pp. 4605-4612
Author(s):  
T Giang Nguyen ◽  
Nicolas B Cowan ◽  
Agnibha Banerjee ◽  
John E Moores
Keyword(s):  
Steady State ◽  
Ocean Circulation ◽  
Scale Height ◽  
High Resolution Spectroscopy ◽  
Return Flow ◽  
High Dispersion ◽  
Magma Ocean ◽  
Steady State Flow ◽  
Wide Range ◽  
Very High

ABSTRACT Transit searches have uncovered Earth-size planets orbiting so close to their host star that their surface should be molten, so-called lava planets. We present idealized simulations of the atmosphere of lava planet K2-141b and calculate the return flow of material via circulation in the magma ocean. We then compare how pure Na, SiO, or SiO2 atmospheres would impact future observations. The more volatile Na atmosphere is thickest followed by SiO and SiO2, as expected. Despite its low vapour pressure, we find that a SiO2 atmosphere is easier to observe via transit spectroscopy due to its greater scale height near the day–night terminator and the planetary radial velocity and acceleration are very high, facilitating high dispersion spectroscopy. The special geometry that arises from very small orbits allows for a wide range of limb observations for K2-141b. After determining the magma ocean depth, we infer that the ocean circulation required for SiO steady-state flow is only 10−4 m s−1, while the equivalent return flow for Na is several orders of magnitude greater. This suggests that a steady-state Na atmosphere cannot be sustained and that the surface will evolve over time.

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