Virus Transmission in Gypsy Moths is not a Simple Mass Action Process

Ecology ◽  
1996 ◽  
Vol 77 (1) ◽  
pp. 201-206 ◽  
Author(s):  
Vincent D'Amico ◽  
Joseph S. Elkinton ◽  
Greg Dwyer ◽  
John P. Burand ◽  
John P. Buonaccorsi
Keyword(s):  
Virus Transmission ◽  
Mass Action ◽  
Gypsy Moths ◽  
Simple Mass ◽  
Action Process

Modelling and Experimental Studies of Sorption in the Near Field of a Cementitious Repository

1989 ◽  
Vol 176 ◽  
Author(s):  
P.L. Brown ◽  
A. Haworth ◽  
R. McCrohon ◽  
S.M. Sharland ◽  
C.J. Tweed
Keyword(s):  
Near Field ◽  
Experimental Studies ◽  
Mass Action ◽  
Chemical Equilibria ◽  
Transport Code ◽  
Mass Action Model ◽  
Action Model ◽  
Modelling Studies ◽  
Simple Mass

ABSTRACTA joint experimental and modelling programme is reported, which aims to improve our understanding of sorption processes of radionuclides onto repository materials. Diffusion/sorption experiments of sorption onto cement are described, although results are limited at this stage. The modelling studies use the coupled chemical equilibria and transport code CHEQMATE to simulate some of these experiments. The chemical part of the model is based on a simple mass-action model of sorption. More detailed comparisons will continue when the experiments are terminated, and the samples are sectioned.

scholarly journals The infection rate of Daphnia magna by Pasteuria ramosa conforms with the mass-action principle

2003 ◽  
Vol 131 (2) ◽  
pp. 957-966 ◽  
Author(s):  
R. R. REGOES ◽  
J. W. HOTTINGER ◽  
L. SYGNARSKI ◽  
D. EBERT
Keyword(s):  
Daphnia Magna ◽  
Infection Rate ◽  
Infection Process ◽  
Action Principle ◽  
Mass Action ◽  
Infection Model ◽  
Susceptibility To Infection ◽  
Pasteuria Ramosa ◽  
Simple Mass ◽  
Host Parasite

In simple epidemiological models that describe the interaction between hosts with their parasites, the infection process is commonly assumed to be governed by the law of mass action, i.e. it is assumed that the infection rate depends linearly on the densities of the host and the parasite. The mass-action assumption, however, can be problematic if certain aspects of the host–parasite interaction are very pronounced, such as spatial compartmentalization, host immunity which may protect from infection with low doses, or host heterogeneity with regard to susceptibility to infection. As deviations from a mass-action infection rate have consequences for the dynamics of the host–parasite system, it is important to test for the appropriateness of the mass-action assumption in a given host–parasite system. In this paper, we examine the relationship between the infection rate and the parasite inoculum for the water flee Daphnia magna and its bacterial parasite Pasteuria ramosa. We measured the fraction of infected hosts after exposure to 14 different doses of the parasite. We find that the observed relationship between the fraction of infected hosts and the parasite dose is largely consistent with an infection process governed by the mass-action principle. However, we have evidence for a subtle but significant deviation from a simple mass-action infection model, which can be explained either by some antagonistic effects of the parasite spores during the infection process, or by heterogeneity in the hosts' susceptibility with regard to infection.

Regulation of plasma free fatty acid turnover

1961 ◽  
Vol 201 (1) ◽  
pp. 9-15 ◽  
Author(s):  
D. T. Armstrong ◽  
R. Steele ◽  
N. Altszuler ◽  
A. Dunn ◽  
J. S. Bishop ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Free Fatty Acid ◽  
Plasma Free Fatty Acid ◽  
Mass Action ◽  
Turnover Rates ◽  
Pharmacological Treatments ◽  
Simple Mass ◽  
Plasma Ffa ◽  
Specific Activities ◽  
The Relationship

Plasma free fatty acid (FFA) turnover rates have been estimated in dogs by a technique involving measurement of FFA specific activities during constant intravenous infusion of trace amounts of C14-labeled palmitic acid. In order to determine the relationship between FFA concentration and turnover, variations in plasma FFA levels ranging from 0.081 to 3.31 µEq/ml were induced by a variety of physiological and pharmacological treatments. Calculated FFA turnover rates ranged from 2.1 to 58.8 µEq/kg/min, with a highly significant linear regression of FFA turnover on FFA level. It is concluded that under a variety of conditions changes in FFA concentration are brought about by changes in FFA production rate and that changes in FFA uptake are simple mass-action effects of changes in FFA concentration. Respiratory C14O2 data are presented indicating that about one-fourth of the total expired CO2 is derived from FFA in the postabsorptive state. This accounts for the immediate fate of about one-fourth of the total FFA leaving the plasma.

Accelerated triacylglycerol turnover kinetics in hearts of diabetic rats include evidence for compartmented lipid storage

2006 ◽  
Vol 290 (3) ◽  
pp. E448-E455 ◽  
Author(s):  
J. Michael O’Donnell ◽  
Manuela Zampino ◽  
Nathaniel M. Alpert ◽  
Matthew J. Fasano ◽  
David L. Geenen ◽  
...  
Keyword(s):  
Turnover Rate ◽  
Exponential Model ◽  
Diabetic Rats ◽  
Mass Action ◽  
Dynamic Mode ◽  
Turnover Rates ◽  
High Substrate ◽  
Isolated Hearts ◽  
Simple Mass ◽  
Exponential Enrichment

Triacylglycerol (TAG) storage and turnover rates in the intact, beating rat heart were determined for the first time using dynamic mode 13C- NMR spectroscopy to elucidate profound differences between hearts from diabetic rats (DR, streptozotocin treatment) and normal rats (NR). The incorporation of [2,4,6,8,10,12,14,16-13C8]palmitate into the TAG pool was monitored in isolated hearts perfused with physiological (0.5 mM palmitate, 5 mM glucose) and elevated substrate levels (1.2 mM palmitate, 11 mM glucose) characteristic of the diabetic condition. Surprisingly, although the normal hearts were enriched at a near-linear profile for ≥2 h before exponential characterization, exponential enrichment of TAG in diabetic hearts reached steady state after only 45 min. Consequently, TAG turnover rate was determined by fitting an exponential model to enrichment data rather than conventional two-point linear analysis. In the high-substrate group, both turnover rate (DR 820 ± 330, NR 190 ± 150 nmol·min−1·g−1 dry wt; P < 0.001) and [TAG] content (DR 78 ± 10, NR 32 ± 4 μmol/g dry wt; P < 0.001) were greater in the diabetic group. At lower substrate concentrations, turnover was greater in diabetics (DR 530 ± 300, NR 160 ± 30; P < 0.05). However, this could not be explained by simple mass action, because [TAG] content was similar between groups [DR 34 ± 7, NR 39 ± 9 μmol/g dry wt; not significant (NS)]. Consistent with exponential enrichment data, 13C fractional enrichment of TAG was lower in diabetics (low- substrate groups: DR 4 ± 1%, NR 10 ± 4%, P < 0.05; high-substrate groups: DR 8 ± 3%, NR 14 ± 9%, NS), thereby supporting earlier speculation that TAG is compartmentalized in the diabetic heart.

The kinetics of conjugative plasmid transmission: Fit of a simple mass action model

Plasmid ◽  
1979 ◽  
Vol 2 (2) ◽  
pp. 247-260 ◽  
Author(s):  
Bruce R. Levin ◽  
Frank M. Stewart ◽  
Virginia A. Rice
Keyword(s):  
Mass Action ◽  
Conjugative Plasmid ◽  
Mass Action Model ◽  
Action Model ◽  
Simple Mass ◽  
Kinetics Of

The Origin of Reversible Hydroxide Uptake on Reservoir Rock

1985 ◽  
Vol 25 (05) ◽  
pp. 711-718 ◽  
Author(s):  
A.L. Bunge ◽  
C.J. Radke
Keyword(s):  
Ion Exchange ◽  
Oil Recovery ◽  
Hydrogen Exchange ◽  
Weak Acid ◽  
Ion Uptake ◽  
Mass Action ◽  
Hydroxide Ion ◽  
Sodium Hydrogen ◽  
Simple Mass ◽  
Sodium Exchange

Abstract When reservoir solids reversibly consume hydroxide, the impact on alkaline-waterflood performance can be significant. Only recently has this reaction been recognized as a principal factor influencing oil recovery rates and chemical-pulse depletion. This paper considers the origin of the reversible hydroxide uptake to be ion exchange of sodium for hydrogen ions. Using a simple, mass-action equilibrium model, we describe the alkali exchange isotherm. Because hydronium and hydroxide concentrations in water are never zero, hydroxide uptake must be reported relative to a reference pH and salinity. With the recognition of a reference state pH and salinity. With the recognition of a reference state and with the mass-action model, we predict qualitatively the effects of pH, salt concentration, and temperature on the measured hydroxide uptake isotherms for the Wilmington, Ranger-zone sand. Mineral sites that exchange ions of sodium for hydrogen may also exchange calcium for hydrogen or for sodium. Using simple mass-action equilibria again, we demonstrate that reversible hydroxide uptake depends on hardness concentration and that calcium/sodium exchange is pH dependent. Introduction Alkaline flooding is a technique in which chemical interactions with reservoir minerals are of paramount importance to success or failure. Hydroxide consumption falls into three broad categories:reversible rock adsorption or ion exchange,congruent and incongruent mineral dissolution, andprecipitation of insoluble hydroxides. All three loss mechanisms have been considered in various levels of detail. Reversible hydroxide ion uptake, which was overlooked in earlier work on alkali/rock interactions, is, perhaps, the least transparent consumption reaction. Its perhaps, the least transparent consumption reaction. Its existence and importance have come to light only recently. In modeling the alkaline oil recovery process, de Zabala et al. point out that equilibrium hydroxide ion uptake causes a chromographic lag in caustic and in the accompanying in-situ generated surfactants, which in turn slows oil-production rates. Likewise, Bunge and Radke demonstrate that hydroxide ion uptake alone can diminish an alkaline chemical pulse to ineffective concentration levels. Thus, even if caustic consumption by dissolution and precipitation could be eliminated, ion-exchange delay can precipitation could be eliminated, ion-exchange delay can limit the success of alkaline EOR. Therefore, when a reservoir is considered for possible alkaline flooding, understanding and quantifying any alkali/rock ion exchange is necessary. This paper presents a simple, mass-action treatment of reversible hydroxide ion uptake by sodium/hydrogen ion exchange followed by a reaction to form or dissociate water. We refer to this overall reaction scheme as hydroxide uptake, or reversible hydroxide consumption. By using the mass-action model and by paying careful attention to the measurement of alkali exchange isotherms, we show how the effects of pH, salt content, and temperature on the hydroxide uptake isotherms may be explained. The relationship between sodium/hydrogen exchange and calcium/sodium exchange is also explored. We demonstrate that calcium/sodium exchange is a combination of sodium/hydrogen and calcium/hydrogen exchange. Therefore, calcium/sodium exchange isotherms generally must be a function of pH, and hydroxide exchange isotherms must depend on calcium concentration. Finally, the connection between the hydrogen exchange capacity (HEC) and the calcium exchange capacity (CEC) is elucidated. Sodium/Hydrogen Exchange Fig. 1 gives the reversible hydroxide uptake on Wilmington, Ranger-zone sand as a function of hydroxide concentration at three temperatures with and without NaCl. Although there is considerable scatter in the data and few points at the lower pH values, the uptake isotherms appear Langmuir in shape. Also, alkali exchange increases with increasing temperature but decreases when salt is added. Reversible alkali exchange occurs not only with the unconsolidated reservoir materials shown here but also on consolidated Berea sandstone. To quantify the behavior of reversible surface uptake of hydroxide ions on reservoir minerals, we adopt our previous. ture of weak-acid sodium/hydrogen cation previous. ture of weak-acid sodium/hydrogen cation exchange: MOH+Na+ + MONa+H+................... (1) where M represents a mineral exchange site. For oxides (such as silica) MOH denotes a hydrolyzable acid site, while for clay minerals (such as kaolinite or montmorillonite MOH denotes a negative lattice exchange site occupied by a hydronium ion. SPEJ P. 711

scholarly journals THE KINETICS OF TRYPSIN DIGESTION

1924 ◽  
Vol 6 (4) ◽  
pp. 417-428 ◽  
Author(s):  
John H. Northrop
Keyword(s):  
Good Reason ◽  
Mass Action ◽  
Trypsin Digestion ◽  
Anomalous Effect ◽  
Enzyme Reactions ◽  
Consecutive Reactions ◽  
Prolonged Contact ◽  
Secondary Reactions ◽  
Simple Mass ◽  
Kinetics Of

1. The kinetics of enzyme reactions diverge more or less from the simple mass action expression for a monomolecular reaction. There is good reason to believe that these discrepancies are due to other secondary reactions which also agree with the law of mass action. Attempts to incorporate all these reactions in one equation, however, are unsatisfactory owing to the complexity of the relations involved. 2. It is possible, however, to regulate conditions experimentally so that these secondary reactions are reduced to a minimum. This has been done in the case of trypsin digestion by working at a low temperature, which prevents inactivation of the trypsin, by using a large amount of trypsin, which prevents the inhibiting effect of the products from becoming noticeable, and by using the disappearance of the protein as the indicator which obviates the complicating effects of the consecutive reactions. 3. Under these conditions the hydrolysis, for any initial concentration of casein is accurately represented by the monomolecular formula, See PDF for Equation The effect of variations in the initial trypsin concentration are also correctly predicted. 4. If the initial casein concentration is varied, however, the value of the constant changes for each casein concentration, becoming less as the casein increases and eventually becoming nearly inversely proportional to the casein concentration. It is pointed out that this cannot be due to a compound between enzyme and casein, nor to the viscosity, but is probably owing to an equilibrium between the casein and water, in which the casein can be replaced by the first cleavage products. This is corroborated by the fact that if the casein is dissolved in a freshly prepared solution of digested casein, the anomalous effect of the substrate concentration disappears and the reaction is typically monomolecular in every respect. A solution of digested casein which has been in prolonged contact with trypsin does not have this effect. 5. It is pointed out that the various equations that have been proposed to account for the enzyme reactions on the basis of a compound between the enzyme and substrate could be applied equally well on the basis of a compound between water and the substrate which is attacked by the enzyme.

scholarly journals The Relationship Between School Holidays and Transmission of Influenza in England and Wales

2016 ◽  
Vol 184 (9) ◽  
pp. 644-651 ◽  
Author(s):  
Charlotte Jackson ◽  
Emilia Vynnycky ◽  
Punam Mangtani
Keyword(s):  
Control Measure ◽  
Meta Analysis ◽  
School Closure ◽  
Mass Action ◽  
Contact Parameter ◽  
England And Wales ◽  
Percentage Difference ◽  
Action Model ◽  
Simple Mass ◽  
The Difference

Abstract School closure is often considered as an influenza control measure, but its effects on transmission are poorly understood. We used 2 approaches to estimate how school holidays affect the contact parameter (the per capita rate of contact sufficient for infection transmission) for influenza using primary care data from England and Wales (1967–2000). Firstly, we fitted an age-structured susceptible-infectious-recovered model to each year's data to estimate the proportional change in the contact parameter during school holidays as compared with termtime. Secondly, we calculated the percentage difference in the contact parameter between holidays and termtime from weekly values of the contact parameter, estimated directly from simple mass-action models. Estimates were combined using random-effects meta-analysis, where appropriate. From fitting to the data, the difference in the contact parameter among children aged 5–14 years during holidays as compared with termtime ranged from a 36% reduction to a 17% increase; estimates were too heterogeneous for meta-analysis. Based on the simple mass-action model, the contact parameter was 17% (95% confidence interval: 10, 25) lower during holidays than during termtime. Results were robust to the assumed proportions of infections that were reported and individuals who were susceptible when the influenza season started. We conclude that school closure may reduce transmission during influenza outbreaks.

scholarly journals Community structure mediates Sabin 2 polio vaccine virus transmission

2020 ◽  
Author(s):  
M Famulare ◽  
W Wong ◽  
R Haque ◽  
JA Platts-Mills ◽  
P Saha ◽  
...  
Keyword(s):  
Community Structure ◽  
Contact Structure ◽  
Virus Transmission ◽  
Social Contact ◽  
Vaccine Virus ◽  
Mass Action ◽  
Routine Immunization ◽  
Disease Forecasting ◽  
Forecasting Models

AbstractSince the global withdrawal of Sabin 2 oral poliovirus vaccine (OPV) from routine immunization, the Global Polio Eradication Initiative (GPEI) has reported multiple circulating vaccine-derived poliovirus type 2 (cVDPV2) outbreaks. cVDPV2 outbreaks are controlled using mass vaccination with Sabin 2 OPV, which carries a small, but serious risk of seeding future cVDPV2 outbreaks in settings of low population immunity. Accurate forecasting models are essential to quantify transmission and reversion risk to optimize effectiveness of mass OPV2 campaigns and minimize cVDPV2 emergence risk. Here, we developed an agent-based model of Sabin 2 vaccine transmission to simulate and to assess the role of household community structure on transmission during a clinical trial designed to monitor community transmission following a mass OPV campaign in Matlab, Bangladesh. Our results emphasize the role of household and community membership and shows that vaccine virus transmission occurs primarily between local community members. When constructing disease forecasting models, ignoring community structure and asserting mass action systematically overestimates emergence probability, duration, and epidemic size due to mechanistic differences in how transmissions are distributed. Model forecasting of vaccine transmission and cVDPV2 emergence risk must incorporate existing knowledge regarding community and social contact structure to provide accurate assessments of transmission risk and ensure the efficacy of future cVDPV2 containment and prevention strategies.Significance StatementThe emergence of multiple Sabin 2 circulating, vaccine-derived poliovirus (cVDPV2) outbreaks since the withdrawal of Sabin 2 oral poliovirus from routine immunization scales threatens to undermine global eradication efforts. Disease forecasting models are invaluable tools for evaluating transmission and outbreak risk but it is unclear how relevant social behavior and household community model is for cVDPV2 outbreak forecasting. Understanding the interaction between social contact structure and disease transmission is critical for accurate risk assessment but is frequently ignored in outbreak forecast models. Our study utilizes data from a cluster-randomized vaccine trial designed to trace Sabin 2 vaccine virus transmission to assess whether model forecasts that ignore social community structure are appropriate for informing public policy.

A simple mass-action model for the eukaryotic heat shock response and its mathematical validation

2010 ◽  
Vol 10 (1) ◽  
pp. 595-612 ◽  
Author(s):  
Ion Petre ◽  
Andrzej Mizera ◽  
Claire L. Hyder ◽  
Annika Meinander ◽  
Andrey Mikhailov ◽  
...  
Keyword(s):  
Heat Shock ◽  
Heat Shock Response ◽  
Mass Action ◽  
Mass Action Model ◽  
Shock Response ◽  
Action Model ◽  
Simple Mass
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