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 depth dependence of the depth resolution in composition–depth profiling with Auger Electron Spectroscopy

Abstract: The depth dependence of the depth resolution in composition–depth profiles using Auger electron spectroscopy is briefly appraised to emphasize some of the different mechanisms operating for different classes of material and to show how the use of a characterized Ta2O5 on Ta reference material can help to optimize the depth resolution. In addition it is shown that, even for flat uniformly-layered samples sputtered under ideal conditions where the ion beam crater is flat and impurities may be ignored, five factors still limit the depth resolution: information depth, statistical effects and cascade mixing, electron stimulated desorption and sample roughening. These may each be observed to dominate at the appropriate depth for amorphous materials but, for evaporated polycrystalline metal films, the last term dominates for depths greater than 10 nm.

Turbulence Damping and Drag Reduction Produced by Certain Additives in Water

Abstract: seasonal variations in the air activity ratio may then be connected with the variations in the precipitation ratio and in the wind variability. The apparent connexion between air activity and precipitation in Norway makes it of interest to look for similar tendencies in more world-wide observations. The U.S. Naval Research Laboratory has published data. on gross beta and strontium-90 activity in ground-level air along the 80th meridian West I957-62 (ref. 2). The strontium-90 activity at the measuring stations in the northern hemisphere follows the same overall seasonal pattern as shown by the ca.esium-137 concentration in Fig. 2A. The precipitation in the northern hemisphere also shows a seasonal variation, with a minimum in spring and a maximum in autumns. The data in refs. 2 and 3 thus indicate a correlation between air activity and precipitation in the northern hemisphere similar to that of the model in Fig. I. From ref. 2 it seems that the spring peaks in the northern hemisphere tend to appear later at 39° and 51° than at the stations north and south of these latitudes. The minimum in mean precipitation as estimated in ref. 3 also appears later in the middle latitudes. This apparent correlation may be due to the larger exchange of air in zonal than in meridional direction in the troposphere. It might then be expected that latitudinal variations in precipitation would lead to latitudinal, inverse variations in air activity. Such an effect might be deduced from Fig. 4. Curve A shows mean annual precipitation (December-November) from 5° N to 90° N, based on ref. 3. Curve E, which is the most complete Naval Research Laboratory profile available over 12 months, shows the average beta activity in air over the period December 1958 to November 1959 at six Naval Research Laboratory stations. A seasonal variation in the latitudinal distribution of precipitation is evident from curves Band 0. In December-May there is a precipitation minimum at 15°-20° N. In June-November the minimum is found at 30°-35° N. It appears from curves D and F that there is a corresponding shift of the air activity maximum from around 25° N in December 1958-May 1959 to around 40°-50° N in June-November 1959. Summarizing, it may be said that seasonal and latitudinal variations in ground-level air activity appear to be correlated to seasonal and latitudinal variations in precipitation. It is realized that other geophysical processes also cause variations in air activity. However, the effect discussed in the present article seems to form a necessary part of the complete fall-out picture.

Revision of the ?Guide to the Expression of Uncertainty in Measurement?

Abstract: The Joint Committee for Guides in Metrology, Working Group 1, JCGM-WG1, is currently revising the 'Guide to the Expression of Uncertainty in Measurement'. In this communication, the motivation for undertaking such a revision is given and the main changes with respect to the current, 2008 edition are outlined.