Durham University

About: Durham University is a education organization based out in Durham, United Kingdom. It is known for research contribution in the topics: Population & Galaxy. The organization has 39385 authors who have published 82311 publications receiving 3110994 citations. The organization is also known as: University of Durham & Gallery of Durham University.

Charm quark contribution to K+ ---> pi+ nu anti-nu at next-to-next-to-leading order

Abstract: We calculate the complete next-to-next-to-leading (NNLO) order QCD corrections to the charm contribution of the rare decay K+??+?. We present the results for the two-loop matching conditions of the Wilson coefficients, the three-loop anomalous dimensions, and the two-loop matrix elements of the relevant operators entering the NNLO renormalization group analysis of the Z-penguin and the electroweak box contribution. The NNLO QCD corrections reduce the theoretical uncertainty from ?9.8% at NLO to ?2.4% in the relevant parameter Pc(X), implying the leftover scale uncertainties in (K+??+?) and in the determination of |Vtd|, sin 2?, and ? from the K??? system to be ?1.3%, ?1.0%, ?0.006, and ?1.2?, respectively. For the charm quark mass mc(mc) = (1.30?0.05)GeV and |Vus| = 0.2248 the NLO value Pc(X) = 0.37?0.06 is modified to Pc(X) = 0.38?0.04 at NNLO and the error is fully dominated by the uncertainty in mc(mc). We tabulate Pc(X) in terms of mc(mc) and ?s(MZ) and express the dependences of Pc(X) on these and other parameters by an accurate approximate analytic formula. We find (K+??+?) = (8.0?1.1) ? 10?11 and the quoted uncertainty mainly stems from mc(mc) and the Cabibbo-Kobayashi-Maskawa elements. We also emphasize that improved calculations of the long-distance contributions to K+??+? and of the isospin breaking in the weak current matrix element will further sharpen the sensitivity of the two golden K??? decays to new physics.

The Importance of Vibronic Coupling for Efficient Reverse Intersystem Crossing in Thermally Activated Delayed Fluorescence Molecules

Abstract: Factors influencing the rate of reverse intersystem crossing (krISC ) in thermally activated delayed fluorescence (TADF) emitters are critical for improving the efficiency and performance of third-generation heavy-metal-free organic light-emitting diodes (OLEDs). However, present understanding of the TADF mechanism does not extend far beyond a thermal equilibrium between the lowest singlet and triplet states and consequently research has focused almost exclusively on the energy gap between these two states. Herein, we use a model spin-vibronic Hamiltonian to reveal the crucial role of non-Born-Oppenheimer effects in determining krISC . We demonstrate that vibronic (nonadiabatic) coupling between the lowest local excitation triplet (3 LE) and lowest charge transfer triplet (3 CT) opens the possibility for significant second-order coupling effects and increases krISC by about four orders of magnitude. Crucially, these simulations reveal the dynamical mechanism for highly efficient TADF and opens design routes that go beyond the Born-Oppenheimer approximation for the future development of high-performing systems.

Review of condition monitoring of rotating electrical machines

Abstract: Condition monitoring of rotating electrical machinery has received intense research interest for more than 30 years. However, electrical machinery has been considered reliable and the application of fast-acting digital electrical protection has rather reduced the attention operators pay to the equipment. The area based upon current literature and the author's experience is reviewed. There are three restrictions: only on-line techniques for rotating machines are dealt with; specific problems of variable speed drives are not dealt with, except in passing; conventional rather than emerging brushless, reluctance and permanent magnet machines of unusual topology are concentrated upon. The art of condition monitoring is minimalist, to take minimum measurements from a machine necessary to extract a diagnosis, so that a condition can be rapidly inferred, giving a clear indication of incipient failure modes. The current state of the art is reviewed in the following ways: survey developments in condition monitoring of machines, mechanically and electrically, over the last 30 years; put that work in context alongside the known failure mechanisms; review those developments which have proved successful and identify areas of research which require attention in the future to advance the subject.

Mood-congruent judgment is a general effect.

Abstract: Mood congruency refers to a match in affective content between a person's mood and his or her thoughts. The mood-congruent judgment effect states in part that attributes will be judged more characteristic, and events more likely, under conditions of mood congruence. Thus, the happy person will believe good weather is more likely than bad weather (relative to such a judgment in a state of mood incongruence). Three studies showed that the effect generalizes to non-self-relevant judgments with natural mood