Half-Life of a Water Column as a Laboratory Exercise in Exponential Decay

1960 ◽  
Vol 28 (8) ◽  
pp. 740-742 ◽  
Author(s):  
J. R. Smithson ◽  
E. R. Pinkston
Keyword(s):  
Water Column ◽  
Exponential Decay ◽  
Half Life ◽  
Laboratory Exercise

Tree windthrow and forest soil turnover

1989 ◽  
Vol 19 (3) ◽  
pp. 386-389 ◽  
Author(s):  
D. A. Norton
Keyword(s):  
Forest Soil ◽  
Exponential Decay ◽  
Half Life ◽  
Soil Development ◽  
Turnover Time ◽  
Important Influence ◽  
Plant Distribution ◽  
Canopy Trees ◽  
Decay Model ◽  
Exponential Decay Model

Soil turnover as a result of tree windthrow has an important influence on soil development and plant distribution in forests. Estimates of the time needed for soil turnover in a given area are often made, but unless these take into account the potential for reestablishment of canopy trees onto sites previously affected by windthrow, they are likely to substantially underestimate turnover time. Soil turnover is not a regular, uniform process, but rather results in a mosaic of soils with different turnover histories. Because soil turnover follows an exponential decay model, some area of soil will never be turned over. As it is therefore not possible to define the time when all the soil in an area has been turned over, it is proposed that soil turnover half-life (the time at which half the soil has been turned over) be used as a measure of soil turnover.

scholarly journals Radiocesium in the Taiwan Strait and the Kuroshio east of Taiwan from 2018 to 2019

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wei-Jen Huang ◽  
Ming-Ta Lee ◽  
Kuei-Chen Huang ◽  
Kai-Jung Kao ◽  
Ming-An Lee ◽  
...  
Keyword(s):  
Water Column ◽  
Surface Waters ◽  
Half Life ◽  
North Pacific Ocean ◽  
Taiwan Strait ◽  
Depth Range ◽  
Near Surface ◽  
Activity Concentrations ◽  
The Taiwan Strait ◽  
The Kuroshio

AbstractThe release of anthropogenic radiocesium to the North Pacific Ocean (NPO) has occurred in the past 60 years. Factors controlling 137Cs (half-life, 30.2 year) and 134Cs (half-life, 2.06 year) activity concentrations in the Kuroshio east of Taiwan and the Taiwan Strait (latitude 20° N–27° N, longitude 116° E–123° E) remain unclear. This study collected seawater samples throughout this region and analyzed 134Cs and 137Cs activity concentrations between 2018 and 2019. A principal component analysis (PCA) was performed to analyze the controlling factors of radiocesium. Results of all 134Cs activity concentrations were below the detection limit (0.5 Bq m−3). Analyses of water column 137Cs profiles revealed a primary concentration peak (2.1–2.2 Bq m−3) at a depth range of 200–400 m (potential density σθ: 25.3 to 26.1 kg m−3). The PCA result suggests that this primary peak was related to density layers in the water column. A secondary 137Cs peak (1.90 Bq m−3) was observed in the near-surface waters (σθ = 18.8 to 21.4 kg m−3) and was possibly related to upwelling and river-to-sea mixing on the shelf. In the Taiwan Strait, 137Cs activity concentrations in the near-surface waters were higher in the summer than in the winter. We suggest that upwelling facilitates the vertical transport of 137Cs at the shelf break of the western NPO.

scholarly journals Exploring the Environmental Exposure to Methoxychlor, α-HCH and Endosulfan–sulfate Residues in Lake Naivasha (Kenya) Using a Multimedia Fate Modeling Approach

2020 ◽  
Vol 17 (8) ◽  
pp. 2727
Author(s):  
Yasser Abbasi ◽  
Chris M. Mannaerts
Keyword(s):  
Sensitivity Analysis ◽  
Water Column ◽  
Environmental Exposure ◽  
Pesticide Residues ◽  
Half Life ◽  
Mass Fraction ◽  
Passive Sampling ◽  
Lake Naivasha ◽  
Endosulfan Sulfate ◽  
Modeling Approach

Distribution of pesticide residues in the environment and their transport to surface water bodies is one of the most important environmental challenges. Fate of pesticides in the complex environments, especially in aquatic phases such as lakes and rivers, is governed by the main properties of the contaminants and the environmental properties. In this study, a multimedia mass modeling approach using the Quantitative Water Air Sediment Interaction (QWASI) model was applied to explore the fate of organochlorine pesticide residues of methoxychlor, α-HCH and endosulfan–sulfate in the lake Naivasha (Kenya). The required physicochemical data of the pesticides such as molar mass, vapor pressure, air–water partitioning coefficient (KAW), solubility, and the Henry’s law constant were provided as the inputs of the model. The environment data also were collected using field measurements and taken from the literature. The sensitivity analysis of the model was applied using One At a Time (OAT) approach and calibrated using measured pesticide residues by passive sampling method. Finally, the calibrated model was used to estimate the fate and distribution of the pesticide residues in different media of the lake. The result of sensitivity analysis showed that the five most sensitive parameters were KOC, logKow, half-life of the pollutants in water, half-life of the pollutants in sediment, and KAW. The variations of outputs for the three studied pesticide residues against inputs were noticeably different. For example, the range of changes in the concentration of α-HCH residue was between 96% to 102%, while for methoxychlor and endosulfan-sulfate it was between 65% to 125%. The results of calibration demonstrated that the model was calibrated reasonably with the R2 of 0.65 and RMSE of 16.4. It was found that methoxychlor had a mass fraction of almost 70% in water column and almost 30% of mass fraction in the sediment. In contrast, endosulfan–sulfate had highest most fraction in the water column (>99%) and just a negligible percentage in the sediment compartment. α-HCH also had the same situation like endosulfan–sulfate (e.g., 99% and 1% in water and sediment, respectively). Finally, it was concluded that the application of QWASI in combination with passive sampling technique allowed an insight to the fate process of the studied OCPs and helped actual concentration predictions. Therefore, the results of this study can also be used to perform risk assessment and investigate the environmental exposure of pesticide residues.

Activities: An Interest in Radioactivity

1996 ◽  
Vol 89 (3) ◽  
pp. 209-230
Author(s):  
Jane B. Kennedy
Keyword(s):  
Exponential Decay ◽  
Exponential Growth ◽  
Half Life ◽  
Core Curriculum ◽  
Equal Access ◽  
Compound Interest

Introduction: This activity explores exponential growth and decay, emphasizing the paired concepts of doubling and half-life. Exponential growth is derived from actual computations to obtain compound interest, whereas exponential decay is modeled by the use of “radioactive” dice. The activity is based on the concept of the differentiated core curriculum, which asserts that all students should be guaranteed equal access to the same curricular topics but recognizes that all students may not explore the content to the same depth or at the same level of formalism.

An algorithm for filtering detector instabilities in search of novel non-exponential decay and in conventional half-life determinations

2017 ◽  
Vol 127 ◽  
pp. 179-185 ◽  
Author(s):  
G.W. Hitt ◽  
B. Goddard ◽  
A.A. Solodov ◽  
D. Bridi ◽  
A.F. Isakovic ◽  
...  
Keyword(s):  
Exponential Decay ◽  
Half Life

The circulatory half-lives of α -profibrin and α-fibrin monomer, and comparisons with other fibrin(ogen) derivatives

2003 ◽  
Vol 89 (01) ◽  
pp. 48-52 ◽  
Author(s):  
Patricia DiBello ◽  
John Shainoff
Keyword(s):  
Vascular Disease ◽  
Exponential Decay ◽  
Half Life ◽  
Decay Curve ◽  
Human Fibrinogen ◽  
Extravascular Space ◽  
Plasma Decay ◽  
Exponential Decay Curve ◽  
Fibrin Monomer ◽  
Double Exponential

SummaryPrevious studies showed that α-fibrin monomer (lacking both A-fibrinopeptides, FPA) is normally cleared from the circulation before it assembles into a clot. Recent studies indicate that substantial quantities of an intermediate, α-profibrin lacking only one of the two FPA are produced in the course of conversion of human fibrinogen to fibrin. Since clearance of the α-fibrin monomer is saturable and receptor mediated, the extent to which α-profibrin or other fibrin(ogen) derivatives might compete for monomer uptake was deemed important. We compared plasma decay of injected human α-fibrin, fibrinogen, and α-profibrin in rabbits using rabbit anti-human fibrinogen for assays. The circulatory half-life of human α-fibrin monomer was short (t1/2 = 2.3 h) and followed a simple exponential decay curve, as anticipated from clearance of rabbit α-fibrin. It was absorbed as fast as it permeated the extravascular space with no redistribution. Human fibrinogen had a long half-life (t1/2 = 39.5 h), calculated from the double exponential plasma decay curves (redistribution + catabolism) observed over 28 h. The α-profibrin had an intermediary half-life (t1/2 = 11 h) determined from double exponential decay curves. Since redistribution accompanied the slow clearance of α-profibrin, its binding by the fibrin receptor(s) must be weak, probably too weak to compete with the clearance of α-fibrin monomer. The initial production of α-fibrin monomer is only partially dependent on prior formation of α-profibrin, as recently shown. Thus, it is the slow clearance and the weak competition from α-profibrin that underlie the occurrence of substantial levels of α-profibrin unaccompanied by detectable levels of α-fibrin monomer in many subjects with vascular disease.

Accumulation of Cd by a freshwater mussel (Pyganodon grandis) is reduced in the presence of Cu, Zn, Pb, and Ni

1999 ◽  
Vol 56 (3) ◽  
pp. 467-478 ◽  
Author(s):  
A R Stewart
Keyword(s):  
Water Column ◽  
Half Life ◽  
Metal Uptake ◽  
Freshwater Mussel ◽  
Laboratory Studies ◽  
Metal Mixture ◽  
Nonequilibrium Conditions ◽  
Pyganodon Grandis ◽  
Anodonta Grandis ◽  
Concentration Levels

The effects of a metal mixture on Cd bioavailability and uptake in the freshwater mussel Pyganodon grandis (formerly Anodonta grandis grandis) were investigated in a limnocorral experiment in a Precambrian Shield lake during the summer of 1992. Differences in the partitioning of Cd in water, sediment, and mussels were identified between limnocorrals treated with Cd alone or with Cd and a mixture of metals (Cu, Zn, Pb, and Ni) at three concentration levels. Loss of Cd from the water column was slower in treatments with the metal mixture (22- to 34-day half-life) than in the treatment with Cd alone (11-day half-life). Despite the higher concentrations of Cd in the water column in treatments with the mixture of metals, the mussels accumulated proportionally less Cd as the metal concentrations increased. These relationships were observed in mussels exposed for 40 days ([Cd] <4.4 µg·L-1) and 80 days ([Cd] = 4-14 µg·L-1). The uncoupling of the effects of the metal mixture on Cd bioavailability and uptake suggests that laboratory studies may be appropriate for characterizing metal uptake in mussels exposed to mixtures of metals under nonequilibrium conditions. The significant deviation in the behavior of Cd in the presence of the metal mixture emphasizes the need to further investigate regulatory approaches that focus on individual contaminants.

scholarly journals Half-life of Ingested Antibodies in Anopheles Stephensi Mosquito Is Less Than 10 Hours

2021 ◽  
Author(s):  
Kazutoyo Miura ◽  
Deng Bingbing ◽  
Yonas T Gebremicale ◽  
Thao P Pham ◽  
Ababacar Diouf ◽  
...  
Keyword(s):  
Exponential Decay ◽  
Mechanism Of Action ◽  
Half Life ◽  
Human Monoclonal Antibody ◽  
Critical Role ◽  
Target Antigen ◽  
Multiple Time ◽  
Human Red Blood Cells ◽  
Exponential Decay Model ◽  
Multiple Time Points

Abstract Background: A transmission-blocking vaccine (TBV) can be a useful tool to reduce malaria infection in an endemic area. For a TBV, elicited antibody (either by itself or working with complement) has a critical role in the mechanism of action, which for most known TBV targets, blockade will occur within the mosquito. However, no study has quantitively assessed the longevity of ingested antibody in Anopheles mosquito vectors. Methods: A mixture of mouse or human monoclonal antibody (mAb), human red blood cells and human serum were fed to An. stephensi mosquitoes, and their midguts were collected at multiple time points (0 to 48 hours; 12 mosquitoes at each time point) after feeds. The reactivity of antibodies against target antigen (integrity of antigen-binding region of the antibody) in each midgut was assessed by ELISA. For one mouse mAb, integrity of antibody constant region was also determined by western blot (WB) with a mouse-specific secondary antibody.Results: First, the half-life of mouse anti-Pfs25 mAb, 4B7, was determined both by ELISA and WB in three independent assays. When the ELISA and WB signals were plotted against time after feed, both data reasonably fit one-phase exponential decay models (R2 B 0.70), and the half-lives were estimated as 8.6 hours by ELISA and 4.7 hours by WB. To determine whether the longevity was affected by target antigens or species of antibody, two human anti-Pfs25 mAbs (AB1245 and AB2544), one human anti-Pfs48/45 mAb (TB31F), and one mouse anti-Pfs230 mAb (15A4-1B12) were examined by ELISA in two or three independent assays. The ELISA results of each additional mAb also reasonably fit to a one-phase exponential decay model (R2 a 0.78), and the half-lives of those mAbs were similar to that of 4B7 (7.2 to 9.3 hours), except AB1245 which showed a half-life of 4.6 hours. Conclusions: Depending on the methods of detection and mAbs used, the longevity of ingested antibody varied around 2-fold, but all estimated half-lives were < 10 hours. These data suggest a TBV with antibody dependent mechanism of action(s) is more likely to succeed when targeting earlier stages of parasites (or parasite interaction) in mosquitoes.

Estimation of Half-life and Exponential Decay Using a Nomogram

1983 ◽  
Vol 40 (10) ◽  
pp. 1696-1698
Author(s):  
Stanley W. Carson ◽  
C. Lindsay DeVane
Keyword(s):  
Exponential Decay ◽  
Half Life

scholarly journals Pharmacokinetics of Intracameral Voriconazole Injection

2009 ◽  
Vol 53 (5) ◽  
pp. 2156-2157 ◽  
Author(s):  
Ying-Cheng Shen ◽  
Mei-Yen Wang ◽  
Chun-Yuan Wang ◽  
Tsun-Chung Tsai ◽  
Hin-Yeung Tsai ◽  
...  
Keyword(s):  
Exponential Decay ◽  
Half Life ◽  
Vitreous Humor ◽  
Rapid Decline ◽  
Clinical Settings ◽  
Fungal Endophthalmitis ◽  
Detectable Limit ◽  
Intracameral Injection

ABSTRACT Elimination of voriconazole after intracameral injection exhibited an exponential decay with a half-life of 22 min. Voriconazole levels in the vitreous humor were below the detectable limit. The aqueous concentrations achieved with a 25-μg dose during the first 2 h were greater than the previously reported MICs of organisms most involved in fungal endophthalmitis. A rapid decline in intracameral concentration suggests that frequent supplementation of intracameral voriconazole may be required in clinical settings.

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