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CODATA Recommended Values of the Fundamental Physical Constants: 2018.

ABSTRACT: We report the 2018 self-consistent values of constants and conversion factors of physics and chemistry recommended by the Committee on Data of the International Science Council. The recommended values can also be found at physics.nist.gov/constants. The values are based on a least-squares adjustment that takes into account all theoretical and experimental data available through 31 December 2018. A discussion of the major improvements as well as inconsistencies within the data is given. The former include a decrease in the uncertainty of the dimensionless fine-structure constant and a nearly two orders of magnitude improvement of particle masses expressed in units of kg due to the transition to the revised International System of Units (SI) with an exact value for the Planck constant. Further, because the elementary charge, Boltzmann constant, and Avogadro constant also have exact values in the revised SI, many other constants are either exact or have significantly reduced uncertainties. Inconsistencies remain for the gravitational constant and the muon magnetic-moment anomaly. The proton charge radius puzzle has been partially resolved by improved measurements of hydrogen energy levels.

SUBMITTER: Tiesinga E

PROVIDER: S-EPMC9888147 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature

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CODATA Recommended Values of the Fundamental Physical Constants: 2018.

Tiesinga Eite E Mohr Peter J PJ Newell David B DB Taylor Barry N BN

Journal of physical and chemical reference data 20210923 3

We report the 2018 self-consistent values of constants and conversion factors of physics and chemistry recommended by the Committee on Data of the International Science Council. The recommended values can also be found at physics.nist.gov/constants. The values are based on a least-squares adjustment that takes into account all theoretical and experimental data available through 31 December 2018. A discussion of the major improvements as well as inconsistencies within the data is given. The forme ...[more]

PMID: 36726646

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Project description:BackgroundPhysical activity (PA) and its health benefits are a continuous point of discussion. Recommendations for children's daily PA vary between guidelines. To better define the amount of PA necessary to prevent overweight and obesity in children, further research is needed. The present study investigates children's compliance to physical activity guidelines (PAGs) and the association between objectively measured PA and body mass index (BMI).MethodsParticipating children were 11 years old (n = 419) and part of the European CHOP trial, which was conducted in Germany, Belgium, Poland, Spain, Italy. At least 2 days of PA measurements were collected from each child using a SenseWear™ armband. BMI was calculated from children's height and weight. Thresholds of min·day-1 in PA needed to differentiate between normal and excess weight (overweight/obesity) were determined with Receiver Operator Characteristics (ROC) analysis. Additionally, adjusted linear and logistic regressions models were calculated for group differences and effects of a 5, 15 and 60 min·day-1 increases in PA on BMI.ResultsMedian time spent in total PA was 462 min·day-1 (25th percentile; 75th percentile: 389; 534) and 75 min·day-1 (41; 115) in moderate to vigorous PA (MVPA). Girls spent 36 min·day-1 less in MVPA than boys and overweight/obese children 24 min·day-1 less than normal weight children (linear regression, p < 0.001). 63.2% of the children met PAGs of 60 min·day-1 in MVPA. The optimal threshold for min·day-1 in MVPA determined with ROC analysis was 46 min·day-1. Comparing 5, 15 and 60 min·day-1 increases in PA revealed that an additional 15 min·day-1 of vigorous PA had the same effect as 60 min·day-1 of MVPA. Sedentary time and light PA showed contrary associations to one another, with light PA being negatively and sedentary time being positively associated with excessive weight.ConclusionsCurrent PAGs are met by 2/3 of children and seem appropriate to prevent excess weight in children. An official recommendation of daily 15-20 min of vigorous PA and further reduction of sedentary time could help to fight youth overweight and thus be of potential public health importance.Trial registrationClinicalTrials.gov Identifier: NCT00338689 . Registered: June 19, 2006 (retrospectively registered).

Project description:Hydroxycinnamic acid derivatives (HCA) are a type of phenolic acid that occurs naturally. HCA are widely known for their anti-inflammatory, anti-cancer, and especially antioxidant capabilities; however, a comprehensive study of the mechanism and kinetics of the antiradical activity of these compounds has not been performed. Here, we report a study on the mechanisms and kinetics of hydroperoxyl radical scavenging activity of HCA by density functional theory (DFT) calculations. The ability of HCA to scavenge hydroperoxyl radicals in physiological environments was studied. The results showed that HCA had moderate and weak HOO˙ antiradical activity in pentyl ethanoate solvent, with the overall rate constant k overall = 8.60 × 101 - 3.40 × 104 M-1 s-1. The formal hydrogen transfer mechanism of phenyl hydroxyl groups defined this action. However, in water at physiological pH, 2-coumaric acid (1), 4-coumaric acid (2), caffeic acid (3), ferulic acid (4), sinapic acid (5) and 4-hydroxyphenylpyruvic acid (7) exhibit a significant HOO˙ antiradical activity with k total = 105 - 108 M-1 s-1 by the electron transfer reaction of the phenolate anions. Following a rise in pH levels in most of the studied substances, the overall rate constant varied. The acid 5 exhibited the highest HOO˙ radical scavenging activity (log(k overall) = 4.6-5.1) at pH < 5; however, at pH = 5.4-8.8, the highest HOO˙ radical scavenging activity were observed for 3 with log(k overall) = 5.2-5.7. At pH > 6.2, acids 2, 3, 4, and 5 presented the largest radical scavenging activity. By contrast, acid 3-coumaric acid (8) had the lowest antiradical activity at most pH values. Thus, the hydroperoxyl radical scavenging activity in pentyl ethanoate follows the order 3 > 5 > 1 ∼ 2 ∼ 4 ∼ 6 (homovanillic acid) ∼ 7 > 8, whereas it follows the order 3 > 2 ∼ 4 ∼ 5 > 6 ∼ 7 > 1 > 8 in water at pH = 7.40. The activity of 1, 2, 3, 4, 5, 6, and 7 are faster than those of the reference Trolox, suggesting that these HCA could be useful natural antioxidants in the aqueous physiological environment.

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CODATA Recommended Values of the Fundamental Physical Constants: 2018.

Publications

CODATA Recommended Values of the Fundamental Physical Constants: 2018.

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