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Institution

National Physical Laboratory

FacilityLondon, United Kingdom
About: National Physical Laboratory is a facility organization based out in London, United Kingdom. It is known for research contribution in the topics: Dielectric & Thin film. The organization has 7615 authors who have published 13327 publications receiving 319381 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, the degree of hydration and the kinetics of water uptake depend crucially on the preparation and aging conditions of graphite oxide (GO) compounds, and the best sample they have ever got shows layer distances of 8, 9 and 11.5 A u at relative humidities of 45, 75 and 100%, respectively.

399 citations

Journal ArticleDOI
TL;DR: In this article, the electronic properties of liquid polyvalent metals are discussed in relation to the nearly free-electron model and the optical properties fit a simple Drude formula, with the same density of states as for free electrons.
Abstract: The electronic properties of liquid polyvalent metals are discussed in relation to the nearly-free-electron model. The observed Hall effect (including some new measurements on Hg, In and Sn) is consistent in most cases with a spherical Fermi surface for the valence electrons. The optical properties fit a simple Drude formula, with the same density of states as for free electrons. The evidence from the magnetic susceptibility and its change at the melting point is only qualitative, but is consistent with a free-electron sphere in the liquid. Only the observed small change in the Knight shift on melting is difficult to interpret in our model. As in I (Ziman 1961) the electrical resistivity is assumed to be represented, in first approximation, by an integral over the angle of scattering of a conduction electron, where the integrand contains the x-ray scattering function of the liquid and the Fourier transform of a ‘pseudo-potential’ for each ion. The formula adequately describes the data, with a pse...

393 citations

Book ChapterDOI
TL;DR: Methods are described to provide information on how to analyze protein concentration using UV protein spectroscopy measurements, traditional dye-based absorbance measurements; BCA, Lowry, and Bradford assays and the fluorescent dye- based assays; amine derivatization and detergent partition assays.
Abstract: The measurement of protein concentration in an aqueous sample is an important assay in biochemistry research and development labs for applications ranging from enzymatic studies to providing data for biopharmaceutical lot release. Spectrophotometric protein quantitation assays are methods that use UV and visible spectroscopy to rapidly determine the concentration of protein, relative to a standard, or using an assigned extinction coefficient. Methods are described to provide information on how to analyze protein concentration using UV protein spectroscopy measurements, traditional dye-based absorbance measurements; BCA, Lowry, and Bradford assays and the fluorescent dye-based assays; amine derivatization and detergent partition assays. The observation that no single assay dominates the market is due to specific limitations of certain methods that investigators need to consider before selecting the most appropriate assay for their sample. Many of the dye-based assays have unique chemical mechanisms that are prone to interference from chemicals prevalent in many biological buffer preparations. A discussion of which assays are prone to interference and the selection of alternative methods is included.

387 citations

Journal ArticleDOI
TL;DR: In this article, the authors extended Lighthill's theory for the purpose of estimating the sound radiated from a turbulent fluid flow to deal with both the transonic and supersonic ranges of eddy convection speed.
Abstract: The theory initiated by Lighthill (1952) for the purpose of estimating the sound radiated from a turbulent fluid flow is extended to deal with both the transonic and supersonic ranges of eddy convection speed. The sound is that which would be produced by a distribution of convected acoustic quadrupoles whose instantaneous strength per unit volume is given by a turbulence stress tensor, T {j. At low subsonic speeds the radiated intensity increases with the eighth power of velocity although quadrupole convection augments this basic dependence by a factor 11 — cos | ~5, where M is the eddy convection Mach number and Q the angular position of an observation point measured from the direction of eddy motion. At supersonic speeds the augmentation factor becomes singular whenever the eddy approaches the observation point at sonic velocity, Mcos At that condition a quadrupole degenerates into its constituent simple sources, for each quadrupole element moves with the acoustic wave front it generates and cancelling contributions from opposing sources, so essential in determining quadrupole behaviour, cannot combine but are heard independently. This simple-source radiation is likened to a type of eddy Mach wave whose strength increases with the cube of a typical flow velocity. When quadrupoles approach the observer with supersonic speed sound is heard in reverse time, but is once again of a quadrupole nature and the general low-speed result is again applicable. The limiting high-speed form of the convection augmentation factor is | Mcos 6|-5 which combines with the basic eighth power velocity law to yield the result that radiation intensity increases only as the cube of velocity at high supersonic speed. The mathematical theory is developed in some detail and supported by more physical arguments, and the paper is concluded by a section where some relevant experimental evidence is discussed.

385 citations

Journal ArticleDOI
TL;DR: Guidelines containing two procedures are proposed for the evaluation of key comparison data, based on the use of the weighted mean and consistency checks based on classical statistics regarding its applicability, to the simple circulation of a single travelling standard around all the participants.
Abstract: Guidelines containing two procedures are proposed for the evaluation of key comparison data. They apply to the simple circulation of a single travelling standard around all the participants. The application of the procedures to a specific set of key comparison data provides a key comparison reference value (KCRV) and the associated uncertainty, the degree of equivalence of the measurement made by each participating national institute and the degrees of equivalence between measurements made by all pairs of participating institutes. Procedure A is based on the use of the weighted mean, together with consistency checks based on classical statistics regarding its applicability. Should the checks fail, action to remedy the situation is suggested. If the remedy is inappropriate, Procedure B can be applied instead. It is based on the use of the median (or any another informed choice) as a more robust estimator in the circumstances.

384 citations


Authors

Showing all 7655 results

NameH-indexPapersCitations
Rajesh Kumar1494439140830
Akhilesh Pandey10052953741
A. S. Bell9030561177
David R. Clarke9055336039
Praveen Kumar88133935718
Richard C. Thompson8738045702
Xin-She Yang8544461136
Andrew J. Pollard7967326295
Krishnendu Chakrabarty7999627583
Vinod Kumar7781526882
Bansi D. Malhotra7537519419
Matthew Hall7582724352
Sanjay K. Srivastava7336615587
Michael Jones7233118889
Sanjay Singh71113322099
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
202315
202242
2021356
2020438
2019434
2018406