scholarly journals Cosmogenic 3He in terrestrial rocks: a review

2021 ◽  
Author(s):  
Pierre-Henri BLARD
Keyword(s):  
Production Rate ◽  
Noble Gas ◽  
Size Fraction ◽  
Cosmogenic Nuclides ◽  
Absolute Calibration ◽  
Calibration Data ◽  
Production Rates ◽  
Accuracy And Precision ◽  
The Impact

This review article summarizes the state of the art of cosmogenic 3He (3Hec), with a focus on the most efficient methods for measuring this cosmogenic noble gas in terrestrial samples. After briefly reviewing the scientific applications and production pathways of cosmogenic 3He, I summarize the most important theoretical and practical aspects of 3He analyses and describe the best strategies for correcting for non-cosmogenic 3He components in minerals. I also review our knowledge of 3Hec production rates and explore potential new applications for future studies.Our ability to accurately and precisely measure cosmogenic 3He is mainly constrained by the level of the non-cosmogenic 3He background (i.e., magmatic, radiogenic, nucleogenic, and atmospheric 3He), and thus by the geological characteristics of the samples. Constructing 3He vs. 4He isochrons by analyzing several aliquots from the same sample constitutes a useful and overlooked method that is advantageous because it obviates the often-complicated step of vacuum crushing. This method also allows the direct and joint determination of cosmogenic 3He and the magmatic 3He/4He ratio. I perform numerical modeling to explore the impact of the non-cosmogenic 3He components on the final uncertainties and detection limits of 3He dating. Reducing the magmatic component by selecting phenocrysts in the 100–500 m size fraction improves the precision of cosmogenic 3He analyses. Moreover, it is important to measure U, Th, and Li concentrations in the analyzed minerals and their host rocks to ensure proper corrections for radiogenic 4He and nucleogenic 3He, improving both the accuracy and precision of the method.After summarizing the most important aspects of 3He analytical techniques, including the best 3Hec extraction techniques and the key parameters of noble gas mass spectrometry that result in accurate and precise helium isotopic measurements, I also review 3Hec production rates and their spatial variability. The global database of absolute calibration sites yields a world-wide average 3Hec production rate in olivine and pyroxene of 124 ± 11 at g−1 yr−1 using the LSD scaling and the online CREp calculator (https://crep.otelo.univ-lorraine.fr/#/). Cross-calibrations against 10Be indicate that the ratio of the production rate of 3Hec in olivine/pyroxene to that of 10Be in quartz is 33 ± 2 and increases by less than 7% between sea level and 5,000 m elevation. This important observation demonstrates that 3He in olivine/pyroxene and 10Be in quartz can be considered as synchronized chronometers. However, 3Hec/10Be cross-calibrations based on 3Hec in accessory minerals (zircon, garnet, kyanite, apatite) yield unexpectedly high 3He/10Be production ratios of 40–60 above 3,000 m elevation. As the capture of cosmogenic thermal neutrons by 6Li is unlikely to explain this excess, I discuss other plausible mechanisms that should be explored, such as 3Hec inherited from previous exposure episodes, unrecognized specific reaction pathways, or the impact of snow cover. New cross-calibration data obtained by measuring 3Hec against other cosmogenic nuclides in different settings will advance our understanding of cosmogenic nuclide production rates and improve the accuracy and precision of applications relying on cosmogenic 3He. Other improvements could extend the applicability of the 3He geoscientific toolbox; for example, coupling 3He with radioactive cosmogenic nuclides (10Be, 36Cl, 53Mn) will allow paleoaltimetry or the determination of burial ages or paleo-depths in intermediate and mafic terrains.

scholarly journals Asteroseismic potential of CHEOPS

2018 ◽  
Vol 620 ◽  
pp. A203 ◽  
Author(s):  
A. Moya ◽  
S. Barceló Forteza ◽  
A. Bonfanti ◽  
S. J. A. J. Salmon ◽  
V. Van Grootel ◽  
...  
Keyword(s):  
Time Series ◽  
Main Sequence ◽  
Uncertainty Reduction ◽  
Light Curves ◽  
Accuracy And Precision ◽  
Mass Uncertainty ◽  
The Impact ◽  
Host Stars

Context. Asteroseismology has been impressively boosted during the last decade mainly thanks to space missions such as Kepler/K2 and CoRoT. This has a large impact, in particular, in exoplanetary sciences since the accurate characterization of the exoplanets is convoluted in most cases with the characterization of their hosting star. In the decade before the expected launch of the ESA mission PLATO 2.0, only two important missions will provide short-cadence high-precision photometric time-series: NASA–TESS and ESA–CHEOPS missions, both having high capabilities for exoplanetary sciences. Aims. In this work we want to explore the asteroseismic potential of CHEOPS time-series. Methods. Following the works estimating the asteroseismic potential of Kepler and TESS, we have analysed the probability of detecting solar-like pulsations using CHEOPS light-curves. Since CHEOPS will collect runs with observational times from hours up to a few days, we have analysed the accuracy and precision we can obtain for the estimation of νmax. This is the only asteroseismic observable we can recover using CHEOPS observations. Finally, we have analysed the impact of knowing νmax in the characterization of exoplanet host stars. Results. Using CHEOPS light-curves with the expected observational times we can determine νmax for massive G and F-type stars from late main sequence (MS) on, and for F, G, and K-type stars from post-main sequence on with an uncertainty lower than a 5%. For magnitudes V <  12 and observational times from eight hours up to two days, the HR zone of potential detectability changes. The determination of νmax leads to an internal age uncertainty reduction in the characterization of exoplanet host stars from 52% to 38%; mass uncertainty reduction from 2.1% to 1.8%; radius uncertainty reduction from 1.8% to 1.6%; density uncertainty reduction from 5.6% to 4.7%, in our best scenarios.

scholarly journals The impact of biogenic, anthropogenic, and biomass burning volatile organic compound emissions on regional and seasonal variations in secondary organic aerosol

2018 ◽  
Vol 18 (10) ◽  
pp. 7393-7422 ◽  
Author(s):  
Jamie M. Kelly ◽  
Ruth M. Doherty ◽  
Fiona M. O'Connor ◽  
Graham W. Mann
Keyword(s):  
Production Rate ◽  
Biomass Burning ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Anthropogenic Source ◽  
Reaction Yield ◽  
Production Rates ◽  
Depth Analysis ◽  
The Impact ◽  
Model Agreement

Abstract. The global secondary organic aerosol (SOA) budget is highly uncertain, with global annual SOA production rates, estimated from global models, ranging over an order of magnitude and simulated SOA concentrations underestimated compared to observations. In this study, we use a global composition-climate model (UKCA) with interactive chemistry and aerosol microphysics to provide an in-depth analysis of the impact of each VOC source on the global SOA budget and its seasonality. We further quantify the role of each source on SOA spatial distributions, and evaluate simulated seasonal SOA concentrations against a comprehensive set of observations. The annual global SOA production rates from monoterpene, isoprene, biomass burning, and anthropogenic precursor sources is 19.9, 19.6, 9.5, and 24.6 Tg (SOA) a−1, respectively. When all sources are included, the SOA production rate from all sources is 73.6 Tg (SOA) a−1, which lies within the range of estimates from previous modelling studies. SOA production rates and SOA burdens from biogenic and biomass burning SOA sources peak during Northern Hemisphere (NH) summer. In contrast, the anthropogenic SOA production rate is fairly constant all year round. However, the global anthropogenic SOA burden does have a seasonal cycle which is lowest during NH summer, which is probably due to enhanced wet removal. Inclusion of the new SOA sources also accelerates the ageing by condensation of primary organic aerosol (POA), making it more hydrophilic, leading to a reduction in the POA lifetime. With monoterpene as the only source of SOA, simulated SOA and total organic aerosol (OA) concentrations are underestimated by the model when compared to surface and aircraft measurements. Model agreement with observations improves with all new sources added, primarily due to the inclusion of the anthropogenic source of SOA, although a negative bias remains. A further sensitivity simulation was performed with an increased anthropogenic SOA reaction yield, corresponding to an annual global SOA production rate of 70.0 Tg (SOA) a−1. Whilst simulated SOA concentrations improved relative to observations, they were still underestimated in urban environments and overestimated further downwind and in remote environments. In contrast, the inclusion of SOA from isoprene and biomass burning did not improve model–observations biases substantially except at one out of two tropical locations. However, these findings may reflect the very limited availability of observations to evaluate the model, which are primarily located in the NH mid-latitudes where anthropogenic emissions are high. Our results highlight that, within the current uncertainty limits in SOA sources and reaction yields, over the NH mid-latitudes, a large anthropogenic SOA source results in good agreement with observations. However, more observations are needed to establish the importance of biomass burning and biogenic sources of SOA in model agreement with observations.

scholarly journals The impact of biogenic, anthropogenic and biomass burning emissions on regional and seasonal variations in secondary organic aerosol

2017 ◽  
Author(s):  
Jamie M. Kelly ◽  
Ruth M. Doherty ◽  
Fiona M. O'Connor ◽  
Graham W. Mann
Keyword(s):  
Production Rate ◽  
Biomass Burning ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol ◽  
Anthropogenic Source ◽  
Reaction Yield ◽  
Production Rates ◽  
Depth Analysis ◽  
The Impact ◽  
Model Agreement

Abstract. The global secondary organic aerosol (SOA) budget is highly uncertain, with global annual SOA production rates, estimated from global models, ranging over an order of magnitude and simulated SOA concentrations underestimated compared to observations. In this study, we use a global composition-climate model (UKCA) with interactive chemistry and aerosol microphysics to provide an in-depth analysis of the impact of each SOA source on the global SOA budget and its seasonality. We further quantify the role of each source on SOA spatial distributions, and evaluate simulated seasonal SOA concentrations against a comprehensive set of observations. The annual global SOA production rates from monoterpene, isoprene, biomass burning and anthropogenic precursor sources is 19.9 19.6, 9.5 and 24.6 Tg (SOA) a−1 respectively. When all sources are included, the SOA production rate from all sources is 73.6 Tg (SOA) a−1, which lies within the range of estimates from previous modelling studies. SOA production rates and SOA burdens from biogenic and biomass burning SOA sources peak during northern hemisphere (NH) summer. In contrast, the an thropogenic SOA production rate is fairly constant all year round. However, the global anthropogenic SOA burden does have a seasonal cycle which is lowest during NH summer, which is probably due to enhanced wet removal. Inclusion of the new SOA sources also accelerates the ageing by condensation of primary organic aerosol (POA), making it more hydrophilic, leading to a reduction in the POA lifetime. With monoterpene as the only source of SOA, simulated SOA and total organic aerosol (OA) concentrations are underestimated by the model when compared to surface and aircraft measurements. Model agreement with observations improves with all new sources added, primarily due to the inclusion of the anthropogenic source of SOA, although a negative bias remains. A further sensitivity simulation was performed with an increased anthropogenic SOA reaction yield, corresponding to an annual global SOA production rate of 70.0 Tg (SOA) a−1. Whilst simulated SOA concentrations improved relative to observations, they were still underestimated in urban environments and overestimated further downwind and in remote environments respectively. On the other hand, the inclusion of SOA from isoprene and biomass burning did not improve model–observations biases substantially except at one out of two tropical locations. However, these findings may reflect the very limited availability of observations to evaluate the model, which are primarily located in the NH mid-latitudes where anthropogenic emissions are high. Our results highlight that, within the current uncertainty limits in SOA sources and reaction yields, over the NH mid-latitudes, a large anthropogenic SOA source results in good agreement with observations. However, more observations are needed to establish the importance of biomass burning and biogenic sources of SOA in model agreement with observations.

Assessment of Measuring Errors in Strain Fields Obtained via DIC on Planar Sheet Metal Specimens with a Non-Perpendicular Camera Alignment

2011 ◽  
Vol 70 ◽  
pp. 165-170 ◽  
Author(s):  
Pascal Lava ◽  
Sam Coppieters ◽  
Yue Qi Wang ◽  
Paul van Houtte ◽  
Dimitri Debruyne
Keyword(s):  
Sheet Metal ◽  
Biaxial Loading ◽  
Image Plane ◽  
Displacement Fields ◽  
Strain Fields ◽  
Accuracy And Precision ◽  
Camera View ◽  
Plane Displacement ◽  
The Impact

The determination of strain fields based on displacement components obtained via 2D-DIC is subject to several errors that originate from various sources. In this contribution, we study the impact of a non-perpendicular camera alignment to a planar sheet metal specimen’s surface subject to biaxial loading conditions. The errors are estimated in a numerical experiment. To this purpose, deformed images - that were obtained by imposing finite element (FE) displacement fields on an undeformed image - are numerically rotated for various Euler angles. It is shown that a 3D-DIC stereo configuration induces a substantial compensation for the introduced image-plane displacement gradients. However, higher strain accuracy and precision are obtained - up to the level of a perfect perpendicular alignment - in a proposed ”rectified” 2D-DIC setup. This compensating technique gains benefit from both 2D-DIC (single camera view, basic amount of correlation runs, no cross-camera matching nor triangulation) and 3D-DIC (oblique angle compensation).

scholarly journals Altered Cortisol Metabolism in Polycystic Ovary Syndrome: Insulin Enhances 5α-Reduction But Not the Elevated Adrenal Steroid Production Rates

2003 ◽  
Vol 88 (12) ◽  
pp. 5907-5913 ◽  
Author(s):  
Tasoula Tsilchorozidou ◽  
John W. Honour ◽  
Gerard S. Conway
Keyword(s):  
Polycystic Ovary Syndrome ◽  
Urinary Excretion ◽  
Production Rate ◽  
Polycystic Ovary ◽  
Resistance Index ◽  
Production Rates ◽  
Androgen Excess ◽  
Ovary Syndrome ◽  
Cortisol Metabolism ◽  
The Impact

Abstract Androgen excess in women with polycystic ovary syndrome (PCOS) may be ovarian and/or adrenal in origin, and one proposed contributing mechanism is altered cortisol metabolism. Increased peripheral metabolism of cortisol may occur by enhanced inactivation of cortisol by 5α-reductase (5α-R) or impaired reactivation of cortisol from cortisone by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) resulting in decreased negative feedback suppression of ACTH secretion maintaining normal plasma cortisol concentrations at the expense of androgen excess. We have tested whether any enzyme dysregulation was related to circulating insulin or androgen concentrations in women with PCOS and have sought to clarify their relationship with obesity. First, to avoid obesity-related effects on cortisol metabolism, 18 lean women with PCOS were compared with 19 lean controls who were closely matched for body mass index (BMI). Second, the impact of obesity was studied in a cross-section of 42 PCOS women of a broad range of BMI. We measured 24-h urinary excretion of steroid metabolites by gas chromatography/mass spectrometry and fasting metabolic and hormone profiles. Urinary excretion of androgens [androsterone (P = 0.003), etiocholanolone (P = 0.02), and C19 steroid sulfates (P = 0.009)], cortisone metabolites [tetrahydrocortisone (THE) (P = 0.02), α-cortolone (P &lt; 0.001), β-cortol + β-cortolone (P &lt; 0.001), cortolones (P &lt; 0.001), and E metabolites (P &lt; 0.001)], and TCM (P = 0.002) were raised in lean PCOS subjects when compared with controls. A significantly higher 5α-tetrahydrocortisol (5α-THF)/5β-THF ratio (P = 0.04) and a significantly lower α-THF + THF + α-cortol/THE + cortolones ratio (P = 0.01) were found in lean PCOS women compared with lean controls, indicating both enhanced 5α-R and reduced 11β-HSD1 activities. A decreased THE/cortolones ratio (P = 0.03) was also found in lean PCOS women compared with lean controls, indicating increased 20 α/β-HSD activity. In the group of 42 PCOS subjects, measures of 5α/5β reduction were positively correlated with the homeostasis model insulin resistance index (HOMA-R): α-THF/THF and HOMA-R (r = 0.34; P = 0.03), androsterone/etiocholanolone and HOMA-R (r = 0.32; P = 0.04), and total 5α /total 5β and HOMA-R (r = 0.37; P = 0.02). A positive correlation was also found between measures of 5α-R and BMI (r = 0.37; P = 0.02). No correlation was found between measures of 11β-HSD1 activity and indices of insulin sensitivity or BMI. We have demonstrated that there is an increased production rate of cortisol and androgens as measured in vivo in lean PCOS women. Insulin seems to enhance 5α reduction of steroids in PCOS but was not associated with the elevated cortisol production rate. The changes in 5α-R, 11β-HSD1, and 20α/β-HSD enzyme activities observed in PCOS may contribute to the increased production rates of cortisol and androgens, supporting the concept of a widespread dysregulation of steroid metabolism. This dysregulation does not seem to be the primary cause of PCOS because no correlation was found between serum androgen levels or urinary excretion of androgens with measurements of either 5α-R or 11β-HSD1 activities.

scholarly journals Kinetic studies and production rate of equine (e) FSH in ovariectomized pony mares. Application to the determination of a dosage regimen for eFSH in a superovulation treatment

2004 ◽  
Vol 182 (1) ◽  
pp. 43-54 ◽  
Author(s):  
C Briant ◽  
PL Toutain ◽  
M Ottogalli ◽  
T Magallon ◽  
D Guillaume
Keyword(s):  
Kinetic Parameters ◽  
Production Rate ◽  
Dosage Regimen ◽  
Latin Square ◽  
Kinetic Studies ◽  
Production Rates ◽  
Daily Production ◽  
Dosage Regimens ◽  
Dose Levels

The appropriate dosage regimen for equine FSH (eFSH) (dose, dosing interval) administration in a superovulation treatment in pony mares was determined by a kinetic approach using production rates and kinetic parameters of elimination of the hormone. Two dosage regimens were then tested in superovulation protocols. The eFSH production rates were determined by sampling four ovariectomized pony mares every 10 min for 8 h during the breeding season. Kinetic parameters were determined by administering four dose levels of a preparation of eFSH (4.4, 8.8, 17.6 and 35.2 micro g/kg) by the i.v. route to the same mares, in a randomized 4x4 Latin Square protocol. The overall mean plasma clearance was 0.256+/- 0.07 ml.kg(-1).min(-1), and was independent of the dose. The mean residence time ranged from 5.5 to 10.8 h and increased with the dose. The estimated FSH production rates were 8.6 to 15.3 micro g.kg(-1).day(-1) (i.e. 2.89 to 3.45 mg per day per mare). Two dosage regimens of eFSH were then tested in cyclic mares (ten treated mares in each trial): 3.45 mg per day (4.4 micro g/kg three times a day by the i.v. route), which corresponds to the maximal daily production rate of the native hormone in ovariectomized mares, and 1.72 mg per day (2.2 micro g/kg three times a day), which corresponds to half of that production rate. The dosage regimen of 2.2 micro g/kg three times a day gave satisfactory results in terms of efficacy (numbers of ovulations and embryos) with minimal unwanted effects (luteinized or anovulatory follicles).

Regolith production rates from 238U-234U-230Th disequilibrium in a deep granitic weathering profile (Longnan, SE China)

2020 ◽  
Author(s):  
Guodong Jia ◽  
François Chabaux ◽  
Jérôme van der Woerd ◽  
Eric Pelt ◽  
Raphaël di Chiara ◽  
...  
Keyword(s):  
Production Rate ◽  
Jiangxi Province ◽  
Subtropical Climate ◽  
Production Rates ◽  
Denudation Rates ◽  
History Of ◽  
One Step ◽  
Deep Profile

&lt;p&gt;The present study seeks to evaluate the application of the &lt;sup&gt;238&lt;/sup&gt;U-&lt;sup&gt;234&lt;/sup&gt;U-&lt;sup&gt;230&lt;/sup&gt;Th radioactive disequilibrium methodology for the determination of the regolith production rates in thick weathering profiles marked by long histories, encountered under various climate regimes, but still very little studied by these techniques. For this purpose, &lt;sup&gt;238&lt;/sup&gt;U-&lt;sup&gt;234&lt;/sup&gt;U-&lt;sup&gt;230&lt;/sup&gt;Th disequilibria have been analyzed in a &amp;#8776; 11 m-deep profile developed on a granitic bedrock in south China (Longnan, Jiangxi Province) under a subtropical climate. The results demonstrate that in such deep weathering profiles the determination of weathering rates from the analysis of U-series nuclides in bulk rock samples cannot be recovered by applying in one step to the entire alteration profile the modeling approach classically used to interpret the U-series nuclides, i.e. the &amp;#8220;gain and loss&amp;#8221; model. The modeling has to be made on subsections of relatively small size (&lt;1 or 2 meters of thickness), so that the model assumptions can be met, especially the constancy of the mobility parameters along the weathering zone. The results also confirm that the upper part of the weathering profiles marked by the vegetation/biological influences and responding to the short-term climate variations is not well adapted for applying the U-series nuclides methodology for recovering regolith production rates. Based on the data, regolith production rates were estimated independently on four different zones of the profile. Similar values of ~2m/Ma have been obtained whatever the level, suggesting that such a profile of more than 5 million years would be formed at a relatively stable long-term production rate (averaged over several thousand years). This slow production rate of 2 m/Ma can be reconciled with the previously published in situ &lt;sup&gt;10&lt;/sup&gt;Be data from the same profile, when assuming non steady-state erosion of the upper part of the profile. Slow denudation rates similar to the U-series derived production rates of 2 m/Ma can thus be obtained with a minimum exposure time of 40 ky, and an inherited component of 20-25*10&lt;sup&gt;4&lt;/sup&gt; at/g originating from the exhumed deeper part of the profile. Altogether the data demonstrate that the combined analysis of U-series and cosmogenic nuclides, which has the potential to become a relevant approach to constrain the dynamics of continental surfaces, requires (a) dense and deep sampling for both nuclides studies, and (b) also to consider more systematically the polyphased and variable history of erosion of the continental surface during the Quaternary. These results have implications for the interpretation of long-term accumulation of &lt;sup&gt;10&lt;/sup&gt;Be at depth and &lt;sup&gt;10&lt;/sup&gt;Be data variations in granitic alteration profiles.&lt;/p&gt;

scholarly journals A Complementary and Revised View on the N-Acylation of Chitosan with Hexanoyl Chloride

Marine Drugs ◽  
2021 ◽  
Vol 19 (7) ◽  
pp. 385
Author(s):  
Berthold Reis ◽  
Niklas Gerlach ◽  
Christine Steinbach ◽  
Karina Haro Carrasco ◽  
Marina Oelmann ◽  
...  
Keyword(s):  
Potentiometric Titration ◽  
1H Nmr ◽  
Accurate Method ◽  
Strong Impact ◽  
Ph Variation ◽  
Accuracy And Precision ◽  
Low Molecular Weight Chitosan ◽  
The Impact ◽  
Reaction Media

The modification of the biobased polymer chitosan is a broad and widely studied field. Herein, an insight into the hydrophobization of low-molecular-weight chitosan by substitution of amino functionalities with hexanoyl chloride is reported. Thereby, the influence of the pH of the reaction media was investigated. Further, methods for the determination of the degree of substitution based on 1H-NMR, FTIR, and potentiometric titration were compared and discussed regarding their accuracy and precision. 1H-NMR was the most accurate method, while FTIR and the potentiometric titration, though precise and reproducible, underlie the influence of complete protonation and solubility issues. Additionally, the impact of the pH variation during the synthesis on the properties of the samples was investigated by Cd2+ sorption experiments. The adjusted pH values during the synthesis and, therefore, the obtained degrees of substitution possessed a strong impact on the adsorption properties of the final material.

scholarly journals Technical note: On the reliability of laboratory beta-source calibration for luminescence dating

2020 ◽  
Author(s):  
Barbara Mauz ◽  
Loïc Martin ◽  
Michael Discher ◽  
Chantal Tribolo ◽  
Sebastian Kreutzer ◽  
...  
Keyword(s):  
Grain Size ◽  
Dose Rate ◽  
Size Fraction ◽  
Absorbed Dose ◽  
Technical Note ◽  
Luminescence Dating ◽  
Body Of Knowledge ◽  
Accuracy And Precision ◽  
Beta Source ◽  
The Impact

Abstract. The dose rate of the 90Sr / 90Y beta source used in most luminescence readers is a laboratory key parameter. There is a well-established body of knowledge about parameters controlling accuracy and precision of the calibration value but some hard to explain inconsistencies still exist. Here we have investigated the impact of grain size, aliquot size and irradiation geometry on the resulting calibration value through experiments and simulations. The resulting data indicate that the dose rate of an individual beta source results from the interplay of a number of parameters, most of which are well established by previous studies. Our study provides evidence for an additionally complicating parameter which is aliquot size in particular for grain sizes of 50–200 μm. For this grain-size fraction the absorbed dose is enhanced by ~10–20 % as aliquot size decreases. This enhancement is most variable for 50–100 μm grains mounted as aliquots of

VARIATION OF CORTISOL METABOLISM AS A CONTRIBUTING FACTOR TO DISCREPANCIES IN THE MEASUREMENT OF CORTISOL PRODUCTION RATE

1972 ◽  
Vol 70 (1) ◽  
pp. 89-96 ◽  
Author(s):  
M. J. Levell
Keyword(s):  
Production Rate ◽  
Isotope Dilution ◽  
Normal Subjects ◽  
Contributory Factor ◽  
Morning Dose ◽  
Production Rates ◽  
Evening Dose ◽  
Cortisol Metabolism

ABSTRACT Five normal subjects were given [14C] cortisol in the morning and [3H] cortisol in the evening, in both cases by mouth. The excretion of radioactivity in tetrahydrocortisol (THF) and tetrahydrocortisone (THE) was measured by a modified form of reverse isotope dilution. In 2 subjects, the ratio of isotopic THF/isotopic THE was higher after the evening dose than after the morning dose. In 1 subject the ratio decreased. In 2 subjects it did not change. Cortisol production rates calculated from THF were usually higher than those calculated from THE. The observed variations of metabolism were only a contributory factor to these discrepancies.

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