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.

XPS: binding energy calibration of electron spectrometers 5—re-evaluation of the reference energies

Abstract: The binding energies of the calibration peaks for x-ray photoelectron spectroscopy—Cu 2p3/2, Ag 3d5/2 and Au 4f7/2—have been reassessed based on the traceable data recorded in 1984 using unmonochromated x-rays and an analyser resolution of 0.3 eV. The changes in those energies, for different x-ray sources and analyser resolutions, have been calculated and the results compared with further data. This includes work with monochromatic Al x-rays recorded at high energy resolution, allowing the binding energies to be referred to a new zero value set at the Fermi edge measured for Ag. A consistent set of data is presented for the calibration and assessment of photoelectron spectrometers with energy resolutions in the range 0.2–1.5 eV, when used with unmonochromated Al or Mg x-rays or monochromated Al x-rays. © 1998 John Wiley & Sons, Ltd.

Evolution of Hierarchical Hexagonal Stacked Plates of CuS from Liquid−Liquid Interface and its Photocatalytic Application for Oxidative Degradation of Different Dyes under Indoor Lighting

Abstract: Blue solution of copper(II) acetylacetonate complex, [Cu(acac)2] in dichloromethane (DCM) and an aqueous alkaline solution of thioacetamide (TAA) constitute a biphasic system. The system in a screw cap test tube under a modified hydrothermal (MHT) reaction condition produces a greenish black solid at the liquid−liquid interface. It has been characterized that the solid mass is an assembly of hexagonal copper sulfide (CuS) nanoplates representing a hierarchical structure. The as-synthesized CuS nanoplates are well characterized by several physical techniques. An ethanolic dispersion of CuS presents a high band gap energy (2.2 eV) which assists visible light photocatalytic mineralization of different dye molecules. Thus a cleanup measure of dye contaminated water body even under indoor light comes true.

Application of Thiolated Gold Nanoparticles for the Enhancement of Glucose Oxidase Activity

Abstract: Glucose oxidase (GOx) has been covalently immobilized onto chemically synthesized thiolated gold nanoparticles (5−8 nm) via N-ethyl-N‘-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS). The lower value of the Michaelis−Menton constant obtained for the immobilized (3.74 mM) GOx compared with that for the free (5.85 mM) GOx suggests significant enhancement in the activity of GOx attached to thiolated gold nanoparticles. The covalently immobilized GOx thiolated nanoparticles exhibit a response time of 30 s, a shelf life of more than 6 months, and improved tolerance to both pH and temperature.

How to tell the difference between a model and a digital twin

Abstract: “When I use a word, it means whatever I want it to mean”: Humpty Dumpty in Alice’s Adventures Through The Looking Glass, Lewis Carroll. “Digital twin” is currently a term applied in a wide variety of ways. Some differences are variations from sector to sector, but definitions within a sector can also vary significantly. Within engineering, claims are made regarding the benefits of using digital twinning for design, optimisation, process control, virtual testing, predictive maintenance, and lifetime estimation. In many of its usages, the distinction between a model and a digital twin is not made clear. The danger of this variety and vagueness is that a poor or inconsistent definition and explanation of a digital twin may lead people to reject it as just hype, so that once the hype and the inevitable backlash are over the final level of interest and use (the “plateau of productivity”) may fall well below the maximum potential of the technology. The basic components of a digital twin (essentially a model and some data) are generally comparatively mature and well-understood. Many of the aspects of using data in models are similarly well-understood, from long experience in model validation and verification and from development of boundary, initial and loading conditions from measured values. However, many interesting open questions exist, some connected with the volume and speed of data, some connected with reliability and uncertainty, and some to do with dynamic model updating. In this paper we highlight the essential differences between a model and a digital twin, outline some of the key benefits of using digital twins, and suggest directions for further research to fully exploit the potential of the approach.

The Nature of the Electronic States in Disordered One-Dimensional Systems

Abstract: We consider an electron moving in the field of a one-dimensional infinite chain of identical potentials separated by regions of zero potential, the lengths s of these regions being distributed according to a probability density function p(8) . If we define the reduced phase of a real solution of the wave equation as the principal value of arctan ( — ψ9/kψ ) and є i as the reduced phase at the point x i immediately to the left of the i th atomic potential, it is shown for all bounded p(s) and sufficiently high electron energies that the є i are distributed according to a probability density function which depends on the direction of integration from a specified homogeneous boundary condition. This result is shown to imply that the eigenfunctions for such systems are localized in the sense that the envelope of such a function decays on average in an exponential manner on either side of some region. An analytical calculation for a random chain of δ-functions gives the decay of the nodes explicitly for high energies, and numerical calculations of the decay for a liquid model are presented. Further support for the theory is provided by computer calculations of some of the eigenfunctions of a chain of 1000 randomly placed δ-functions.