National Physical Laboratory

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.

The thermal conductivity of ice new data on the temperature coefficient

Abstract: The thermal conductivity of ice in the form of cylindrical specimens has been measured by a steady-state method, the temperature gradients being measured by thermocouples in drill-holes in the ice. The temperature range covered is from 0°C to −180°C, and the results are compared with those of previous observers. Using the most probable values given, there is a linear relationship within 1 or 2% between the thermal conductivity of ice and the reciprocal of the absolute temperature, down to about 120°K. A quadratic equation is proposed, giving the thermal conductivity as a function of temperature. Lees' work in 1905 is shown to be unsubstantiated, his values being lower than the present ones by about a factor of two, although the possibility of anisotropy at low temperatures is still to be considered.

Recent developments in dimensional nanometrology using AFMs

Abstract: Scanning probe microscopes, in particular the atomic force microscope (AFM), have developed into sophisticated instruments that, throughout the world, are no longer used just for imaging, but for quantitative measurements. A role of the national measurement institutes has been to provide traceable metrology for these instruments. This paper presents a brief overview as to how this has been achieved, highlights the future requirements for metrology to support developments in AFM technology and describes work in progress to meet this need.

Statistical aspects of the independent joint action of poisons, particularly insecticides; the toxicity of a mixture of poisons.

Abstract: Methods are described for discovering whether a mixture of two poisons is as toxic as predicted on the hypothesis of independent joint action. These include X2tests and a procedure for finding the maximum likelihood estimate of the coefficient of correlation in resistance to the poisons. The methods are illustrated using data from insecticidal tests. In the insecticidal tests, flour beetles, Tribolium castaneum Herbst, were sprayed with, or exposed to films of, different insecticides in solution in Shell oil P 31. The insecticides were pyrethrins, D.D.T., and B.H.C., singly and in pairs. The statistical analysis of the results showed that pyrethrins and D.D.T. could have acted independently both as films and as direct sprays; D.D.T. and B.H.C. could have acted independently as films but not as direct sprays; and B.H.C. and pyrethrins could not have acted independently either as films or as direct sprays. These findings are discussed, and it is concluded that independent action should be regarded as a special case of a more general type of joint action for which the term dissimilar is proposed. A general method of approach is suggested for the conception and development of hypotheses of the joint action of poisons.

Binding of chloroquine-conjugated gold nanoparticles with bovine serum albumin.

Abstract: We have conjugated chloroquine, an anti-malarial, antiviral and anti-tumor drug, with thiol-functionalized gold nanoparticles and studied their binding interaction with bovine serum albumin (BSA) protein. Gold nanoparticles have been synthesized using sodium borohydride as reducing agent and 11-mercaptoundecanoic acid as thiol functionalizing ligand in aqueous medium. The formation of gold nanoparticles was confirmed from the characteristic surface plasmon absorption band at 522 nm and transmission electron microscopy revealed the average particle size to be ~7 nm. Chloroquine was conjugated to thiolated gold nanoparticles by using EDC/NHS chemistry and the binding was analyzed using optical density measurement and Fourier transform infrared spectroscopy. The chloroquine-conjugated gold nanoparticles (GNP-Chl) were found to interact efficiently with BSA. Thermodynamic parameters suggest that the binding is driven by both enthalpy and entropy, accompanied with only a minor alteration in protein's structure. Competitive drug binding assay revealed that the GNP-Chl bind at warfarin binding site I in subdomain IIA of BSA and was further supported by Trp212 fluorescence quenching measurements. Unraveling the nature of interactions of GNP-Chl with BSA would pave the way for the design of nanotherapeutic agents with improved functionality, enriching the field of nanomedicine.