Using tritium to document the mean transit time and sources of water contributing to a chain-of-ponds river system: Implications for resource protection

2016 ◽  
Vol 75 ◽  
pp. 9-19 ◽  
Author(s):  
I. Cartwright ◽  
U. Morgenstern
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
River System ◽  
Resource Protection ◽  
The Mean ◽  
A Chain

scholarly journals Application of Water Stable Isotopes for Hydrological Characterization of the Red River (Asia)

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2051
Author(s):  
Nho Lan Nguyen ◽  
Thu Nga Do ◽  
Anh Duc Trinh
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
River System ◽  
Red River ◽  
Catchment Hydrology ◽  
Natural Conditions ◽  
Reservoir Volume ◽  
The Mean ◽  
Hydrological Station

Fraction of young water (Fyw) and mean transit time (MTT, τ) calculated from water isotope profiles are valuable information for catchment hydrological assessment, especially in anthropogenically impacted region where natural conditions may not be decisive to catchment hydrology. The calculation of Fyw and MTT were performed on three subsets of δ18O_H2O data collected at the Hanoi meteo-hydrological station, Red River, in three periods; 2002–2005, 2015, and 2018–2019. The mean (min and max) values of δ18O_H2O in rainwater over the three periods are, respectively, −5.3‰ (−11.0 and −1.2‰), −5.4‰ (−10.7 and −1.4‰), and −4.5‰ (−13.9 and 1.7‰). The corresponding values in river water are −8.4‰ (−9.8 and −6.9‰), −8.5‰ (−9.1 and −7.7‰), and −8.4‰ (−9.5 and −7.2‰), respectively. The mean of Fyw calculated from the δ18O_H2O data for different periods is 22 ± 9%, 10 ± 5%, and 8 ± 3%. Mean transit time is 4.69 ± 15.57, 1.65 ± 1.53, and 2.06 ± 1.87 years. The calculated Fyw (MTT) is negatively (positively) proportional to change in reservoir volume over the three periods, which is logical, since reservoirs tend to keep more water in the catchment and slower down water flow. The strong variation of Fyw and τ, two essential variables characterizing the catchment hydrology, represents an anthropogenic impact in the Red River system.

scholarly journals Use of the mean transit time of an intravascular contrast agent as an exchange-insensitive index of myocardial perfusion

1999 ◽  
Vol 9 (3) ◽  
pp. 402-408 ◽  
Author(s):  
Massimo Lombardi ◽  
Richard A. Jones ◽  
J�rgen Westby ◽  
Geir Torheim ◽  
Timothy E. Southon ◽  
...  
Keyword(s):  
Myocardial Perfusion ◽  
Contrast Agent ◽  
Transit Time ◽  
Mean Transit Time ◽  
Intravascular Contrast Agent ◽  
The Mean

Lung water measurements with the mean transit time approach

1985 ◽  
Vol 59 (3) ◽  
pp. 673-683 ◽  
Author(s):  
R. M. Effros
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Tissue Perfusion ◽  
Time Data ◽  
Lung Water ◽  
Thermal Signal ◽  
The Mean ◽  
Points Of View ◽  
Vascular Obstruction ◽  
Pulmonary Vascular Obstruction

The potential usefulness and limitations of the double-indicator mean transit time approach for measuring lung water are evaluated from both theoretical and empirical points of view. It is concluded that poor tissue perfusion is the most serious factor that can compromise the reliability of this approach. Replacement of the conventional water isotopes with a thermal signal enhances indicator delivery to ischemic areas but the diffusion of heat is not sufficiently rapid to permit measurements of water in macroscopic collections of fluid which remain unperfused. The frequency of pulmonary vascular obstruction in patients with pulmonary edema related to lung injury suggests that interpretation of transit time data will be complicated by uncertainties concerning perfusion. Thermal-dye measurements of lung water may prove more helpful in situations where pulmonary blood flow remains relatively uniform.

scholarly journals Modeling radiocarbon dynamics in soils: SoilR version 1.1

2014 ◽  
Vol 7 (3) ◽  
pp. 3161-3192 ◽  
Author(s):  
C. A. Sierra ◽  
M. Müller ◽  
S. E. Trumbore
Keyword(s):  
Organic Matter ◽  
Soil Organic Matter ◽  
Transit Time ◽  
Mean Transit Time ◽  
Time Data ◽  
Soil System ◽  
Linear Dynamical Systems ◽  
Natural Systems ◽  
Radiocarbon Data ◽  
The Mean

Abstract. Radiocarbon is an important tracer of the global carbon cycle that helps to understand carbon dynamics in soils. It is useful to estimate rates of organic matter cycling as well as the mean residence or transit time of carbon in soils. We included a set of functions to model the fate of radiocarbon in soil organic matter within the SoilR package for the R environment for computing. Here we present the main system equations and functions to calculate the transfer and release of radiocarbon from different soil organic matter pools. Similarly, we present functions to calculate the mean transit time for different pools and the entire soil system. This new version of SoilR also includes a group of datasets describing the amount of radiocarbon in the atmosphere over time, data necessary to estimate the incorporation of radiocarbon in soils. Also, we present examples on how to obtain parameters of pool-based models from radiocarbon data using inverse parameter estimation. This implementation is general enough so it can also be used to trace the incorporation of radiocarbon in other natural systems that can be represented as linear dynamical systems.

The Effects of Thromboxane Antagonism on the Transit Time of Platelets Through the Spleen

1985 ◽  
Vol 54 (02) ◽  
pp. 495-497 ◽  
Author(s):  
A M Peters ◽  
I F Lane ◽  
M Sinclair ◽  
J T C Irwin ◽  
C N McCollum
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Thromboxane A2 ◽  
Time Measurement ◽  
Thromboxane A2 Receptor ◽  
Group Research ◽  
The Mean ◽  
A Site ◽  
Kinetics Of ◽  
Transit Time Measurement

SummaryThe spleen is well-known as a site for platelet pooling, although the mechanisms controlling intrasplenic platelet transit are essentially unknown. We tested the possibility that thromboxane A2 might be involved in this control by measuring intrasplenic platelet transit time in 10 subjects receiving a specific thromboxane A2 receptor antagonist (AH23848B; 70 mg; Glaxo Group Research Ltd), in 10 receiving aspirin (300 mg) plus dipyridamole (75 mg), and in 9 receiving placebo. All doses were administered 3 times daily commencing 4 days prior to transit time measurement.Mean intrasplenic platelet transit time was measured by monitoring the kinetics of equilibration of 111In radiolabelled platelets between blood and spleen following intravenous injection. There was no difference between the mean transit time in the 3 groups of subjects, lending no support to the hypothesis that thromboxane A2 is involved in the control of platelet traffic through the spleen.

Comparison of methods for analyzing gastric isotope emptying

1982 ◽  
Vol 243 (3) ◽  
pp. G237-G242 ◽  
Author(s):  
M. C. Dugas ◽  
R. R. Schade ◽  
D. Lhotsky ◽  
D. Van Thiel
Keyword(s):  
Gastric Emptying ◽  
Transit Time ◽  
Gamma Camera ◽  
Statistical Difference ◽  
Mean Transit Time ◽  
Comparison Of Methods ◽  
Sulfur Colloid ◽  
The Mean ◽  
Linear Regressions ◽  
99Mtc Sulfur Colloid

The gastric emptying of 99mTc-sulfur colloid, ingested in a nutrient liquid test meal, was followed by gamma camera for normals, diabetics, and diabetics receiving intravenous metoclopramide. Gastric emptying patterns of 99mTc by these groups present as normal, slow, and rapid on simple graphic inspection. Half times of indicator emptying were computed from inspection and from least-squares linear regressions of log(base e) residue versus time for the total postpeak curve and for the remainder of the 15-min postpeak curve. In addition, the percent of 99mTc residue leaving at, and the area under, the residue curve until 6, 12, 24, and 60 min postpeak and the indicator mean transit time (MTT) were computed. Standard half-time determinations revealed no significant differences among the three groups, despite obvious visual differences among them. In contrast, the mean transit time of the rapid group was significantly less than that of the slow (P less than 0.01) and normal (P less than 0.05) groups. However, no statistical difference was noted between the slow and the normal emptiers (P greater than 0.1) using the MTT measure. The percent of particles leaving the stomach and the area under the residue curves demonstrated significant differences among the three groups, reflecting the obvious visual perceptions gained from simple curve inspection. Because the percent of indicator particles leaving the stomach region at a given time reflects a single time, it was concluded that the residue area represents the most reliable, objective, and quantifiable parameter for testing of significant differences.

scholarly journals A proof of the occupancy principle and the mean-transit-time theorem for compartmental models

1984 ◽  
Vol 68 (1) ◽  
pp. 121-136 ◽  
Author(s):  
Rajasekhar Ramakrishnan ◽  
Edward F. Leonard ◽  
Ralph B. Dell
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Compartmental Models ◽  
The Mean

scholarly journals High cadence near-infrared transit timing observations of extrasolar planets

2009 ◽  
Vol 5 (H15) ◽  
pp. 688-689
Author(s):  
Claudio Cáceres ◽  
Valentin D. Ivanov ◽  
Dante ~Minniti ◽  
Dominique Naef ◽  
Claudio Melo ◽  
...  
Keyword(s):  
High Precision ◽  
Transit Time ◽  
Near Infrared ◽  
Extrasolar Planets ◽  
Mean Transit Time ◽  
Infrared Observations ◽  
Nearby Stars ◽  
Time Variations ◽  
The Mean ◽  
High Cadence

AbstractCurrently the only technique sensitive to Earth mass planets around nearby stars (that are too close for microlensing) is the monitoring of the transit time variations of the transiting extrasolar planets. We search for additional planets in the systems of the hot-Neptune GJ-436 b, and the hot-Jupiter XO-1 b, using high cadence observations in the J and KS bands, with the SofI and ISAAC instruments from La Silla Paranal Observatory. New high-precision transit timing measurements were used to derive new ephemeris. No statistically significant timing deviations were detected. We demonstrate that the high cadence ground based near-infrared observations are successful in constraining the mean transit time to 30 sec, and are a viable alternative to space missions.

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