On the stochastic theory of compartments: I. A single-compartment system

1972 ◽  
Vol 34 (1) ◽  
pp. 53-63 ◽  
Author(s):  
A. K. Thakur ◽  
A. Rescigno ◽  
D. E. Schafer
Keyword(s):  
Stochastic Theory ◽  
Compartment System ◽  
Single Compartment

Sodium Regulation in the Crayfish Astacus Fluviatilis

1960 ◽  
Vol 37 (1) ◽  
pp. 83-99 ◽  
Author(s):  
G. W. BRYAN
Keyword(s):  
Tap Water ◽  
Sodium Concentration ◽  
The Body ◽  
Urine Sodium ◽  
Compartment System ◽  
Single Compartment ◽  
Blood And Urine Samples ◽  
Astacus Fluviatilis ◽  
Sodium Regulation ◽  
Total Sodium

1. In Bristol tap water containing 0.4 mM./l. sodium and artificial tap water containing 2 mM./l. sodium, Astacus maintains a blood sodium concentration of about 203 mM./l. This value was not markedly affected by starvation periods of up to a month. 2. Methods of taking small blood and urine samples from individual crayfish at intervals over several hundred hours have been described. 3. Under steady state conditions, curves for the uptake and loss of 22Na by the blood are described by equations derived for a one-compartment system. 4. The volume of this single compartment, which exchanges sodium with the medium, is larger than the actual blood volume by an amount roughly equivalent to the sodium in the tissues. Exchange of sodium between the blood and tissues is probably very rapid. 5. Sodium losses in the urine account for about 6% of the total sodium outflux found using 22Na. The urine sodium concentration of about 6 mM./l. was temporarily increased by conditions such as heavy feeding when the blood may have gained additional sodium. 6. Potential difference measurements across the body surface indicate that the high blood sodium concentration is maintained by active uptake of sodium.

Voltage cycling process for the electroconversion of biomass-derived polyols

2021 ◽  
Vol 118 (41) ◽  
pp. e2113382118
Author(s):  
Dohyung Kim ◽  
Chengshuang Zhou ◽  
Miao Zhang ◽  
Matteo Cargnello
Keyword(s):  
Secondary Alcohol ◽  
Pt Nanoparticles ◽  
Chemical Processes ◽  
High Rate ◽  
Thermal Processes ◽  
Turnover Frequency ◽  
Renewable Electricity ◽  
Compartment System ◽  
Single Compartment ◽  
Potential Conditions

Electrification of chemical reactions is crucial to fundamentally transform our society that is still heavily dependent on fossil resources and unsustainable practices. In addition, electrochemistry-based approaches offer a unique way of catalyzing reactions by the fast and continuous alteration of applied potentials, unlike traditional thermal processes. Here, we show how the continuous cyclic application of electrode potential allows Pt nanoparticles to electrooxidize biomass-derived polyols with turnover frequency improved by orders of magnitude compared with the usual rates at fixed potential conditions. Moreover, secondary alcohol oxidation is enhanced, with a ketoses-to-aldoses ratio increased up to sixfold. The idea has been translated into the construction of a symmetric single-compartment system in a two-electrode configuration. Its operation via voltage cycling demonstrates high-rate sorbitol electrolysis with the formation of H2 as a desired coproduct at operating voltages below 1.4 V. The devised method presents a potential approach to using renewable electricity to drive chemical processes.

scholarly journals Mathematical modelling of concentration profiles for species transport through the single and the interconnected multiple-compartment systems

2020 ◽  
pp. 61-68
Author(s):  
Oludare Adedire ◽  
J. N. Ndam
Keyword(s):  
Discrete System ◽  
Research Work ◽  
Method Of Lines ◽  
Chemical Species ◽  
Concentration Profiles ◽  
Compartment System ◽  
Chemical Reaction Kinetics ◽  
Single Compartment ◽  
The Method Of Lines ◽  
Order Chemical Reaction

In this research work, we investigate the concentration profiles in the single and the interconnected multiple-compartment systems with sieve partitions for the transport of chemical species with second order chemical reaction kinetics. With assumption of unidirectional transport of chemical species and constant physical properties with same equilibrium contant, the developed partial differential equations representing the two systems are spatially discretized using the Method of Lines (MOL) technique and the resulting semi-discrete system of ODEs are solved using MATLAB ode15s solver. The results show that the interconnected multiple-compartment system has lower concentration profile than the single-compartment system for different values of diffusivities.

scholarly journals Mathematical modeling of the effects of Wnt-10b on bone metabolism

2021 ◽  
Author(s):  
Carley V. Cook ◽  
Mohammad Aminul Islam ◽  
Brenda J. Smith ◽  
Ashlee N. Ford Versypt
Keyword(s):  
Bone Metabolism ◽  
Bone Health ◽  
Bone Volume ◽  
Original Model ◽  
Osteoblast Proliferation ◽  
Compartment System ◽  
Single Compartment ◽  
Proliferation And Differentiation ◽  
Osteoblast Apoptosis ◽  
Expected Increase

Bone health is determined by many factors including bone metabolism or remodeling. Wnt-10b has been shown to alter osteoblastogenesis through pre-osteoblast proliferation and differentiation as well as the osteoblast apoptosis rate, which collectively lead to the increase of bone density. To model this change, we adapted a previously published model of bone remodeling. The resulting model is a single compartment system that includes ordinary differential equations for active osteoclasts, pre-osteoblasts, osteoblasts, and osteocytes and a differential equation that tracks the amount of bone present at the remodeling site. Our alterations to the original model consist of extending it past a single remodeling cycle and implementing a direct relationship to Wnt-10b. Four new parameters were estimated and validated using normalized data from mice. The model connects Wnt-10b to bone metabolism and predicts the change in bone volume caused by a change in Wnt-10b. We find that this model predicts the expected increase in pre-osteoblasts and osteoblasts while also pointing to a decrease in osteoclasts when Wnt-10b is increased.

Description of a Simple Model for the Study of Bone Calcium Metabolism

1980 ◽  
Vol 19 (01) ◽  
pp. 11-15
Author(s):  
G. Roncari ◽  
L. Rapisardi ◽  
L. Conte ◽  
G. Pedroli
Keyword(s):  
Simple Model ◽  
Calcium Metabolism ◽  
Good Description ◽  
Radioactive Tracer ◽  
Normal Subjects ◽  
Bone Diseases ◽  
Compartment System ◽  
Bone Calcium ◽  
Finite Period ◽  
Kinetics Of

A simple model for the study of bone calcium metabolism is proposed. It describes the kinetics of a radioactive tracer in terms of an open single compartment system with an expanding volume for a finite period of time. In addition to the simplicity of the hypotheses introduced, the model is able to give a good description of the biological processes which regulate calcium kinetics. Moreover the functional parameters can be easily calculated, even just graphically. 15 normal subjects and 22 patients affected by various bone diseases were studied. The results were compared with those obtained by using the model proposed by Burkinshaw et al. and the method described by Reeve et al.

Volume Sensor Development Test. Series 5 - Multi-Compartment System

2005 ◽  
Author(s):  
James A. Lynch ◽  
Daniel T. Gottuk ◽  
Jeffrey C. Owrutsky ◽  
Daniel A. Steinhurst ◽  
Christian P. Minor ◽  
...  
Keyword(s):  
Test Series ◽  
Compartment System ◽  
Sensor Development ◽  
Volume Sensor

scholarly journals Analysis of Stochastic Generation and Shifts of Phantom Attractors in a Climate–Vegetation Dynamical Model

Mathematics ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 1329
Author(s):  
Lev Ryashko ◽  
Dmitri V. Alexandrov ◽  
Irina Bashkirtseva
Keyword(s):  
Multiplicative Noise ◽  
Nonlinear Dynamical Systems ◽  
Stochastic Theory ◽  
Slow Variable ◽  
Theoretical Description ◽  
Mathematical Study ◽  
Stochastic Generation ◽  
Nonlinear Dynamical ◽  
Additive And Multiplicative Noise ◽  
And Shifts

A problem of the noise-induced generation and shifts of phantom attractors in nonlinear dynamical systems is considered. On the basis of the model describing interaction of the climate and vegetation we study the probabilistic mechanisms of noise-induced systematic shifts in global temperature both upward (“warming”) and downward (“freezing”). These shifts are associated with changes in the area of Earth covered by vegetation. The mathematical study of these noise-induced phenomena is performed within the framework of the stochastic theory of phantom attractors in slow-fast systems. We give a theoretical description of stochastic generation and shifts of phantom attractors based on the method of freezing a slow variable and averaging a fast one. The probabilistic mechanisms of oppositely directed shifts caused by additive and multiplicative noise are discussed.

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