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.

Ozone in ambient air at a tropical megacity, Delhi: characteristics, trends and cumulative ozone exposure indices

Abstract: Seven year data of hourly surface ozone concentration is analyzed to study diurnal cycle, trends, excess of ozone levels above threshold value and cumulative ozone exposure indices at a tropical megacity, Delhi. The ozone levels clearly exhibit a diurnal cycle, similar to what has been found in other urban places. A sharp increase in the ozone levels during forenoon and a sharp decrease in the early afternoon can be observed. The average rate of increase in ozone concentration between 09 and 12 h has been observed to be 7.1 ppb h−1. We find that the daily maximum and daytime 8-h (10–17 h) ozone levels are increasing at a rate of about 1.7 (± 0.7) and 1.3 (± 0.56) ppb y−1, respectively. The directives on ozone pollution in ambient air provided by United Nations Economic Commission for Europe and World Health Organization for vegetation (AOT40) and human health protection were used to assess the air quality. The present surface ozone levels in the city are high enough to exceed “Critical Levels” which are considered to be safe for human health, vegetation and forest. The human health threshold was exceeded for up to ~45 days per year. The AOT40 (Accumulated exposure Over a Threshold of 40 ppb) threshold was exceeded significantly during winter (D-J-F) and pre-monsoon (M-A-M) (Rabi crop growing season) season in India. Translating AOT40 exceedances during pre-monsoon into relative yield loss we estimate yield loss of 22.7%, 22.5%, 16.3% and 5.5% for wheat, cotton, soybean and rice, respectively.

Advances in gold nanoparticle–liquid crystal composites

Abstract: We present the advancement in the research of the dispersion of gold nanoparticles (GNPs) in thermotropic calamitic liquid crystals. The formation/behavior of surface plasmon resonance (SPR) in GNPs is briefly described. The uniform dispersion of GNPs into liquid crystals along with two important aspects, i.e. tuning of GNP properties by liquid crystal and vice versa, are widely discussed. Overall, the article highlights the advances in the research into GNP-liquid crystal composites in terms of their scientific and technological aspects.

Force-insensitive optical cavity

Abstract: We describe a rigidly mounted optical cavity that is insensitive to inertial forces acting in any direction and to the compressive force used to constrain it. The design is based on a cubic geometry with four supports placed symmetrically about the optical axis in a tetrahedral configuration. To measure the inertial force sensitivity, a laser is locked to the cavity while it is inverted about three orthogonal axes. The maximum acceleration sensitivity is 2.5×10−11/g (where g=9.81 ms−2), the lowest passive sensitivity to be reported for an optical cavity.

Electrochemical Cholesterol Sensor Based on Tin Oxide‐Chitosan Nanobiocomposite Film

Abstract: A chitosan (CS)-tin oxide (SnO2) nanobiocomposite film has been deposited onto an indium-tin-oxide glass plate to immobilize cholesterol oxidase (ChOx) for cholesterol detection. The value of the Michaelis–Menten constant (Km) obtained as 3.8 mM for ChOx/CS-SnO2/ITO is lower (8 mM) than that of a ChOx/CS/ITO bioelectrode revealing enhancement in affinity and/or activity of ChOx towards cholesterol and also revealing strong binding of ChOx onto CS-SnO2/ITO electrode. This ChOx/CS-SnO2/ITO cholesterol sensor retains 95% of enzyme activity after 4–6 weeks at 4 °C with response time of 5 s, sensitivity of 34.7 μA/mg dL−1 cm2 and detection limit of 5 mg/dL.

A Stimulated Emission Source at 0.34 Millimetre Wave-length

Abstract: THE investigation of far infra-red stimulated emission sources at the National Physical Laboratory continues, and some results obtained using hydrogen cyanide and related molecules in pulsed electrical discharges are reported here. The interest attaching to these results is in the long wave-length of the emission and particularly its relation to the wave-length of water vapour absorption lines in the atmosphere.