The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by counting the atoms in 1 kg single-crystal spheres, which are highly enriched with the 28Si isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, NA = 6.022,140,78(18) × 10(23) mol(-1), is the most accurate input datum for a new definition of the kilogram.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1103/PhysRevLett.106.030801 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Viscoelastic Behavior of Aqueous Hydroxypropyl Cellulose Solutions Due to Entanglements.
Biomacromolecules
January 2025
Cellulose Research Unit, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
Hydroxypropyl cellulose (HpC) forms a liquid crystalline phase and is thought to have a rod-like shape in aqueous solution. The viscoelastic behaviors of aqueous solutions of HpC samples with average molar substitution numbers ( ∼ 3.8) and weight-average molar masses ( = 36-740 kg mol) were examined over a wide concentration () range, and the results were discussed based on a concept of rod particle suspension rheology.
View Article and Find Full Text PDFOn the temperature dependence of surface tension: Historical perspective on the Eötvös equation of capillarity, celebrating his 175th anniversary.
Adv Colloid Interface Sci
October 2024
University of Miskolc, 3515 Miskolc, Egyetemvaros, Hungary; HUN-REN-ME Materials Science Research Group, 3515 Miskolc, Egyetemvaros, Hungary. Electronic address:
The Hungarian baron Roland Eötvös (Eötvös Loránd, 1848-1919) lived in the difficult period between two revolutions in Hungary, but nevertheless he achieved revolutionary results in two fields of science: capillarity (1875-1886) and gravity (after 1886). This paper describes his famous capillary equation published in 1886 in the world-language of the time (German) and in one of the most famous scientific journals of the time (Annalen der Physik und Chemie). In his paper he showed a simple equation for the temperature dependence of surface tension of one-component liquids and more importantly he showed that this quantity approaches zero as temperature tends towards the critical temperature.
View Article and Find Full Text PDFPython-Based Algorithm for Estimating the Parameters of Physical Property Models for Substances Not Available in Database.
ACS Omega
March 2024
CJ BIO Research Institute, CJ CheilJedang Corp., Suwon-Si, Gyeonggi-do 16495, Republic of Korea.
An in-house Python-based algorithm was developed using simplified molecular-input line-entry specification (SMILES) strings and a dipole moment for estimating the normal boiling point, critical properties, standard enthalpy, vapor pressure, liquid molar volume, enthalpy of vaporization, heat capacity, viscosity, thermal conductivity, and surface tension of molecules. Normal boiling point, critical properties, and standard enthalpy were estimated by using the Joback group contribution method. Vapor pressure, liquid molar volume, enthalpy of vaporization, heat capacity, and surface tension were estimated by using the Riedel model, Gunn-Yamada model, Clausius-Clapeyron equation, Joback group contribution method, and Brock-Bird model, respectively.
View Article and Find Full Text PDFRigid Rod-like Viscoelastic Behaviors of Methyl Cellulose Samples with a Wide Range of Molar Masses Dissolved in Aqueous Solutions.
Molecules
January 2024
Cellulose Research Unit, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
The viscoelastic behaviors of aqueous solutions of commercially available methyl cellulose (MC) samples with a degree of substitution of 1.8 and a wide range of weight average molar masses () were investigated over a wide concentration () range at some temperatures from -10 to 25 °C. The viscoelastic parameters useful to discuss the structure and dynamics of MC-forming particles in aqueous solutions were precisely determined, such as the zero-shear viscosity (), the steady-state compliance (), the average relaxation time (), and the activation energy (*) of .
View Article and Find Full Text PDFHydrogen production and storage through adsorption and dissociation of HO on pristine and functionalized SWCNT: a DFT approach.
J Mol Model
September 2023
School of Interdisciplinary Engineering & Sciences (SINES), National University of Sciences and Technology (NUST), Sector H-12, Islamabad, 44000, Pakistan.
Adsorption of 1 and 2 HO molecules for hydrogen production and storage on the surface of pristine, carbamic acid and 2-amino 3-acetylpyridine functionalized SWCNTs with the dimensionality of (2, 4), (5, 5), and (6, 0) at various positions, i.e., center and edges were investigated by using computational DFT calculations.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!