Stochastic indicator analysis of contaminated sites

1997 ◽  
Vol 34 (4) ◽  
pp. 988-1008 ◽  
Author(s):  
George Christakos ◽  
Dionissios T. Hristopulos
Keyword(s):  
Threshold Level ◽  
Critical Threshold ◽  
Environmental Standards ◽  
Pollution Levels ◽  
Observation Scale ◽  
Geographical Regions ◽  
Indicator Analysis ◽  
Fractal Characteristics ◽  
Ergodicity Breaking ◽  
Analytical Expressions

We formulate stochastic indicator parameters that characterize pollution levels in geographical regions with heterogeneous contaminant distributions. The indicator parameters are expressed in terms of the random fields representing the contaminant distributions and the critical threshold level specified by health and environmental standards. Certain theoretical results are proven regarding univariate and bivariate indicator parameters. The analytical expressions obtained are general and can be used in practice for various types of contaminant distributions. A test of ergodicity-breaking is suggested for scientific and engineering applications in terms of the indicator parameters. Fractal characteristics of the indicator parameters are discussed. The effects of modelling and observation scale on exceedance contamination analysis are examined. Indicator random field parameters are studied on both continuum and lattice domains using analytical means and numerical simulations.

Stochastic indicator analysis of contaminated sites

1997 ◽  
Vol 34 (04) ◽  
pp. 988-1008
Author(s):  
George Christakos ◽  
Dionissios T. Hristopulos
Keyword(s):  
Threshold Level ◽  
Critical Threshold ◽  
Environmental Standards ◽  
Pollution Levels ◽  
Observation Scale ◽  
Geographical Regions ◽  
Indicator Analysis ◽  
Fractal Characteristics ◽  
Ergodicity Breaking ◽  
Analytical Expressions

We formulate stochastic indicator parameters that characterize pollution levels in geographical regions with heterogeneous contaminant distributions. The indicator parameters are expressed in terms of the random fields representing the contaminant distributions and the critical threshold level specified by health and environmental standards. Certain theoretical results are proven regarding univariate and bivariate indicator parameters. The analytical expressions obtained are general and can be used in practice for various types of contaminant distributions. A test of ergodicity-breaking is suggested for scientific and engineering applications in terms of the indicator parameters. Fractal characteristics of the indicator parameters are discussed. The effects of modelling and observation scale on exceedance contamination analysis are examined. Indicator random field parameters are studied on both continuum and lattice domains using analytical means and numerical simulations.

Temporal patterns of tissue glycogen, glucose, and glycogen phosphorylase activity prior to hibernation in freeze-tolerant chorus frogs, Pseudacris triseriata

2008 ◽  
Vol 86 (10) ◽  
pp. 1095-1100 ◽  
Author(s):  
Steve C. Dinsmore ◽  
David L. Swanson
Keyword(s):  
Glycogen Phosphorylase ◽  
Threshold Level ◽  
Liver Glycogen ◽  
Critical Threshold ◽  
Hepatic Glycogen ◽  
Phosphorylase Activity ◽  
Continuous Increase ◽  
Glycogen Accumulation ◽  
Chorus Frogs ◽  
Glycogen Stores

Freezing survival may differ among winters in chorus frogs ( Pseudacris triseriata (Wied-Neuwied, 1838)), and low freezing survival is associated with low hepatic glycogen stores. The pattern of prehibernation liver glycogen accumulation in chorus frogs is unknown. Frogs might accumulate hepatic glycogen stores until a threshold level sufficient for winter survival is attained, after which frogs enter hibernation (critical threshold hypothesis). According to this model, frogs active late in the season should only be those with low hepatic glycogen stores. Alternatively, hepatic glycogen levels might continue to increase throughout the fall as long as frogs remain active (continuous increase hypothesis). We tested these hypotheses by measuring liver and leg muscle glycogen, glucose, and glycogen phosphorylase activities in chorus frogs throughout the fall prehibernation period in southeastern South Dakota. Hepatic glycogen levels were significantly related to date and increased throughout the fall period, consistent with the continuous increase hypothesis. This suggests that hepatic glycogen levels do not serve as a cue for entrance into hibernation. Liver phosphorylase activity did not vary significantly with progression of the fall season and activity was lower than in winter, suggesting that the winter increment of phosphorylase activity requires some stimulus during hibernation (e.g., low temperatures).

Level of economic security of NATO Eastern flank countries

2018 ◽  
Vol 32 (32) ◽  
pp. 202-221
Author(s):  
Agnieszka Sałek-Imińska
Keyword(s):  
Economic Recession ◽  
Economic Factor ◽  
Threshold Level ◽  
Economic Security ◽  
Critical Threshold ◽  
Modern World ◽  
Gdp Growth ◽  
Value Judgments ◽  
Eastern Flank ◽  
National Economies

In the modern world an undoubted increase in the economic factor of maintaining the security of states is observed. Economic security is an important element of the functioning of national economies, including the states of the eastern flank of NATO. Perceiving economic security as a balance of development needs of these states we can identify several areas of activity of its quantifiers, which can include development, infrastructure and balance opportunities and needs. To determine the levels of these quantifiers, we must use a carefully selected set of meters. One of them is Gross Domestic Product (GDP) which clearly describes the measurable features present in the analyzed national economies. The objective of this article is to attempt to indicate the level of the economic security of NATO’s eastern flank states in terms of the level of economic growth measured by GDP. From an autonomous perspective, this meter does not give grounds for expressing value judgments in the context of the widely understood level of economic security, but it constitutes their necessary component and basis for further analyzes and evaluations. For the needs of the elaboration, an assumption was made, being a simplification of the economic reality, indicating that changes in annual GDP will show the level of the economic security of NATO’s eastern flank states. Hence, an increase in GDP growth lower than 1.9% in a period, which the analysis refers to, is a sign of a decrease in the level of economic security of a given state and vice versa. In all the states of NATO’s eastern flank, an improvement in its level was observed, where in 2017 in all the states of NATO’s eastern flank the rate of GDP growth was higher than the assumed critical threshold level of 1.9%. Years 2014–2016 also constitute a period of improvement in the level of the economic security of the analyzed states, except for Bulgaria in 2014, Estonia and Lithuania in 2015 and Estonia in 2016. While the period from 2008 to 2013 is a period when the level of the economic security of the states of NATO’s eastern flank is diverse and there are no indications that it improved. In the context of the analyzed problem, the best years were 2008 and 2011, for which GDP growth was the highest. In 2008 Estonia, Latvia and Hungary were those that did not reach the critical threshold (decline in economic security). The other six states were characterized by an increase in the level of economic security. The following year is a period when all the states (except for Poland) did not register any improvement. This resulted from a general economic recession, which was observed in the region of Central and Eastern Europe. Considering the number of years for which the assumed critical threshold level of 1.9% was not reached, we can claim that the economy of Poland (2 periods: 2012–2013), and then Czech Republic, Lithuania, Latvia and Slovakia (3 periods), Romania (4 years) and Bulgaria, Estonia and Hungary (5 years) were characterized by the highest level of economic security in the analyzed period.

scholarly journals Frequency, Diversity, and Activity of 2,4-Diacetylphloroglucinol-Producing Fluorescent Pseudomonas spp. in Dutch Take-all Decline Soils

2003 ◽  
Vol 93 (1) ◽  
pp. 54-63 ◽  
Author(s):  
Jorge T. de Souza ◽  
David M. Weller ◽  
Jos M. Raaijmakers
Keyword(s):  
Threshold Level ◽  
Washington State ◽  
Frequency Diversity ◽  
Population Densities ◽  
Pseudomonas Spp ◽  
Fluorescent Pseudomonas ◽  
Geographical Regions ◽  
First Time ◽  
Conducive Soil ◽  
Take All

Natural suppressiveness of soils to take-all disease of wheat, referred to as take-all decline (TAD), occurs worldwide. It has been postulated that different microbial genera and mechanisms are responsible for TAD in soils from different geographical regions. In growth chamber experiments, we demonstrated that fluorescent Pseudomonas spp. that produce the antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG) play a key role in the natural suppressiveness of two Dutch TAD soils. First, 2,4-DAPG-producing fluorescent Pseudomonas spp. were present on roots of wheat grown in both of the TAD soils at densities at or above the threshold density required to control take-all of wheat; in a complementary take-all conducive soil, population densities of 2,4-DAPG-producing Pseudomonas spp. were below this threshold level. Second, introduction of 2,4-DAPG-producing strain SSB17, a representative of the dominant geno-typic group found in the Dutch TAD soils, into the take-all conducive soil at population densities similar to the densities of indigenous 2,4-DAPG producers found in TAD soils provided control of take-all similar to that observed in the TAD soil. Third, a mutant of strain SSB17 deficient in 2,4-DAPG production was not able to control take-all of wheat, indicating that 2,4-DAPG is a key determinant in take-all suppression. These results show that in addition to the physicochemically different TAD soils from Washington State, 2,4-DAPG-producing fluorescent Pseudomonas spp. are also a key component of the natural suppressiveness found in Dutch TAD soils. Furthermore, it is the first time since the initial studies of Gerlagh (1968) that at least part of the mechanisms and microorganisms that operate in Dutch TAD soils are identified. Although quantitatively similar, the genotypic composition of 2,4-DAPG-producing Pseudomonas spp. varied between the Dutch TAD soils and the TAD soils from Washington State.

A cost analysis of alternative culling strategies for the eradication of classical swine fever in wildlife

2007 ◽  
Vol 12 (5) ◽  
pp. 653-671 ◽  
Author(s):  
LUCA BOLZONI ◽  
GIULIO A. DE LEO
Keyword(s):  
Cost Benefit ◽  
Classical Swine Fever ◽  
Threshold Level ◽  
Host Population ◽  
Critical Threshold ◽  
Optimal Time ◽  
Health Authorities ◽  
Optimal Value ◽  
The Cost ◽  
Traditional Strategy

In the epidemiological literature, the eradication of a wildlife disease through culling is usually described in terms of a constant hunting rate to simulate the selective removal of animals from the population. By using simple SI (susceptible–infected) models, it is easy to prove that, if the hunting rate is high enough, the population eventually drops below a critical threshold level under which the pathogen is deemed to be extinct. However, hunting costs as well as the monetary benefits of disease control are almost systematically neglected. Moreover, the hunting rate is usually assumed to be constant over time, while in reality health authorities can implement more flexible culling policies. In this work we examine a class of more realistic time-variant culling strategies in a cost–benefit framework. Culling strategies differ in the way decisions are made about when and how much to cull; that is, whether hunting occurs when disease prevalence, host population density, or the number of carcasses exceeds (or is below) a given threshold. For each culling strategy, the optimal value of the control parameters and the hunting rate are those that minimize the sum of the culling costs and the sanitary costs associated with infection over a specific period of time. Classical swine fever (CSF) in wild boar populations has been taken as a reference example because of its potential economic impact on industrialized and developing countries.We show that the optimal time-flexible culling strategy is invariably more efficient than the best traditional strategy in which the hunting rate is held constant through time. We also show that the type of hunting strategy that is selected as optimal depends on the shape of the cost functions.

scholarly journals The role of incoherent feedforward circuits in regulating precision of event timing

2020 ◽  
Author(s):  
Supravat Dey ◽  
Sherin Kannoly ◽  
Pavol Bokes ◽  
John J Dennehy ◽  
Abhyudai Singh
Keyword(s):  
Single Cells ◽  
Threshold Level ◽  
Cellular Growth ◽  
Critical Threshold ◽  
E Coli ◽  
Cellular Events ◽  
Event Timing ◽  
Simple Model System ◽  
Cell Data

AbstractTriggering of cellular events often relies on the level of a key gene product crossing a critical threshold. Achieving precision in event timing in spite of noisy gene expression facilitates high-fidelity functioning of diverse processes from biomolecular clocks, apoptosis and cellular differentiation. Here we investigate the role of an incoherent feedforward circuit in regulating the time taken by a bacterial virus (bacteriophage lambda) to lyse an infected Escherichia coli cell. Lysis timing is the result of expression and accumulation of a single lambda protein (holin) in the E. coli cell membrane up to a critical threshold level, which triggers the formation of membrane lesions. This easily visualized process provides a simple model system for characterizing event-timing stochasticity in single cells. Intriguingly, lambda’s lytic pathway synthesizes two functionally opposite proteins: holin and antiholin from the same mRNA in a 2:1 ratio. Antiholin sequesters holin and inhibits the formation of lethal membrane lesions, thus creating an incoherent feedforward circuit. We develop and analyze a stochastic model for this feedforward circuit that considers correlated bursty expression of holin/antiholin, and their concentrations are diluted from cellular growth. Interestingly, our analysis shows the noise in timing is minimized when both proteins are expressed at an optimal ratio, hence revealing an important regulatory role for antiholin. These results are in agreement with single cell data, where removal of antiholin results in enhanced stochasticity in lysis timing.

scholarly journals Intracellular Complexes of Viral Spike and Cellular Receptor Accumulate during Cytopathic Murine Coronavirus Infections

1998 ◽  
Vol 72 (4) ◽  
pp. 3278-3288 ◽  
Author(s):  
Pasupuleti V. Rao ◽  
Thomas M. Gallagher
Keyword(s):  
Trypan Blue ◽  
Hepatitis Virus ◽  
Syncytium Formation ◽  
Threshold Level ◽  
Inducible Promoter ◽  
Critical Threshold ◽  
Murine Hepatitis Virus ◽  
Trypan Blue Exclusion ◽  
Hela Cell Lines

ABSTRACT Murine hepatitis virus (MHV) infections exhibit remarkable variability in cytopathology, ranging from acutely cytolytic to essentially asymptomatic levels. In this report, we assess the role of the MHV receptor (MHVR) in controlling this variable virus-induced cytopathology. We developed human (HeLa) cell lines in which the MHVR was produced in a regulated fashion by placing MHVR cDNA under the control of an inducible promoter. Depending on the extent of induction, MHVR levels ranged from less than ∼1,500 molecules per cell (designated Rlo) to ∼300,000 molecules per cell (designated Rhi). Throughout this range, the otherwise MHV-resistant HeLa cells were rendered susceptible to infection. However, infection in the Rlo cells occurred without any overt evidence of cytopathology, while the corresponding Rhi cells died within 14 h after infection. When the HeLa-MHVR cells were infected with vaccinia virus recombinants encoding MHV spike (S) proteins, the Rhi cells succumbed within 12 h postinfection; Rlo cells infected in parallel were intact, as judged by trypan blue exclusion. This acute cytopathology was not due solely to syncytium formation between the cells producing S and MHVR, because fusion-blocking antiviral antibodies did not prevent it. These findings raised the possibility of an intracellular interaction between S and MHVR in the acute cell death. Indeed, we identified intracellular complexes of S and MHVR via coimmunoprecipitation of endoglycosidase H-sensitive forms of the two proteins. We suggest that MHV infections can become acutely cytopathic once these intracellular complexes rise above a critical threshold level.

scholarly journals Passive Transfer of Antiserum Specific for Immunogens Derived from a Nontypeable Haemophilus influenzaeAdhesin and Lipoprotein D Prevents Otitis Media after Heterologous Challenge

2000 ◽  
Vol 68 (5) ◽  
pp. 2756-2765 ◽  
Author(s):  
Bobbie-Jo Kennedy ◽  
Laura A. Novotny ◽  
Joseph A. Jurcisek ◽  
Yves Lobet ◽  
Lauren O. Bakaletz
Keyword(s):  
Otitis Media ◽  
Bacterial Load ◽  
Threshold Level ◽  
Passive Transfer ◽  
Critical Threshold ◽  
Upper Respiratory Tract ◽  
Functional Activities ◽  
Exposed Region ◽  
Heterologous Challenge ◽  
Upper Respiratory

ABSTRACT We recently determined that passive transfer of serum directed against a synthetic peptide called LB1 or a recombinant fusion protein immunogen [LPD-LB1(f)2,1,3] could prevent otitis media after challenge with a homologous nontypeable Haemophilus influenzae (NTHI) isolate. NTHI residing in the nasopharynx was rapidly cleared from this site, thus preventing it from ascending the eustachian tube and inducing otitis media in chinchillas compromised by an ongoing viral upper respiratory tract infection. While LB1 is based solely on one NTHI adhesin, the latter immunogen, LPD-LB1(f)2,1,3, was designed to incorporate two NTHI antigens shown to play a role in the pathogenesis of otitis media; lipoprotein D (LPD) and the P5-homologous fimbrin adhesin. The design of LPD-LB1(f)2,1,3 also accommodated for the recently demonstrated existence of three major groupings, based on amino acid sequence diversity, in the third surface-exposed region of P5-fimbrin. LPD-LB1(f)2,1,3 was thus designed to potentially confer broader protection against challenge by diverse strains of NTHI. Chinchillas were passively immunized here with serum specific for either LB1 or for LPD-LB1(f)2,1,3 prior to challenge with a member of all three groups of NTHI relative to diversity in region 3. The transferred serum pools were also analyzed for titer, specificity, and several functional activities. We found that both serum pools had equivalent ability to mediate C′-dependent killing and to inhibit adherence of NTHI strains to human oropharyngeal cells. When passively transferred, both serum pools significantly inhibited the signs and incidence of otitis media (P ≤ 0.01) induced by any of the three challenge isolates. Despite providing protection against disease, the ability of these antisera to induce total eradication of NTHI from the nasopharynx was not equivalent among NTHI groups. These data thus suggested that while early, complete eradication of NTHI from the nasopharynx was highly protective, reduction of the bacterial load to below a critical threshold level appeared to be similarly effective.

Relation Between Microscopic and Macroscopic Mechanical Properties in Random Mixtures of Elastic Media

2006 ◽  
Vol 129 (3) ◽  
pp. 453-461 ◽  
Author(s):  
Stefano Giordano
Keyword(s):  
Convergence Properties ◽  
Observation Scale ◽  
Random Mixture ◽  
Specific Analysis ◽  
Mixture Characterization ◽  
Homogeneous Media ◽  
Analytical Expressions ◽  
Large Observation

A material composed of a mixture of distinct homogeneous media can be considered as a homogeneous one at a sufficiently large observation scale. In this work, the problem of the elastic mixture characterization is solved in the case of linear random mixtures, that is, materials for which the various components are isotropic, linear, and mixed together as an ensemble of particles having completely random shapes and positions. The proposed solution of this problem has been obtained in terms of the elastic properties of each constituent and of the stoichiometric coefficients. In other words, we have explicitly given the features of the micro-macro transition for a random mixture of elastic material. This result, in a large number of limiting cases, reduces to various analytical expressions that appear in earlier literature. Moreover, some comparisons with the similar problem concerning the electric characterization of random mixtures have been drawn. The specific analysis of porous random materials has been performed and largely discussed. Such an analysis leads to the evaluation of the percolation threshold, to the determination of the convergence properties of Poisson’s ratio, and to good agreements with experimental data.

scholarly journals Tension-dependent stabilization of E-cadherin limits cell-cell contact expansion

2020 ◽  
Author(s):  
Jana Slováková ◽  
Mateusz Sikora ◽  
Silvia Caballero-Mancebo ◽  
S.F. Gabriel Krens ◽  
Walter A. Kaufmann ◽  
...  
Keyword(s):  
Threshold Level ◽  
Critical Threshold ◽  
Cell Cortex ◽  
Cell Contact ◽  
Total Size ◽  
Cortical Tension ◽  
Pulling Forces ◽  
Contact Size ◽  
E Cadherin ◽  
Cell Cell

AbstractTension of the actomyosin cell cortex plays a key role in determining cell-cell contact growth and size. The level of cortical tension outside of the cell-cell contact, when pulling at the contact edge, scales with the total size to which a cell-cell contact can grow1,2. Here we show in zebrafish primary germ layer progenitor cells that this monotonic relationship only applies to a narrow range of cortical tension increase, and that above a critical threshold, contact size inversely scales with cortical tension. This switch from cortical tension increasing to decreasing progenitor cell-cell contact size is caused by cortical tension promoting E-cadherin anchoring to the actomyosin cytoskeleton, thereby increasing clustering and stability of E-cadherin at the contact. Once tension-mediated E-cadherin stabilization at the contact exceeds a critical threshold level, the rate by which the contact expands in response to pulling forces from the cortex sharply drops, leading to smaller contacts at physiologically relevant timescales of contact formation. Thus, the activity of cortical tension in expanding cell-cell contact size is limited by tension stabilizing E-cadherin-actin complexes at the contact.

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