Charm Lifetimes and Mixing

A review of the latest results on charm lifetimes and D-mixing is presented. The e+e- collider experiments are now able to measure charm lifetimes quite precisely, however comparisons with the latest results from fixed-target experiments show that possible systematic effects could be evident. The new D-mixing results from the B-factories have changed the picture that is emerging. Although the new world averaged value of y_CP is now consistent with zero, there is still a very interesting and favoured scenario if the strong phase difference between the Doubly-Cabibbo-suppressed and the Cabibbo-flavoured D0 -> Kpi decay is large.Comment: Presented at the 9th International Symposium on Heavy Flavors, Caltech, Pasadena, 10-13 Sept. 2001. To appear in proceeding

NeuroFlow: A General Purpose Spiking Neural Network Simulation Platform using Customizable Processors

© 2016 Cheung, Schultz and Luk.NeuroFlow is a scalable spiking neural network simulation platform for off-the-shelf high performance computing systems using customizable hardware processors such as Field-Programmable Gate Arrays (FPGAs). Unlike multi-core processors and application-specific integrated circuits, the processor architecture of NeuroFlow can be redesigned and reconfigured to suit a particular simulation to deliver optimized performance, such as the degree of parallelism to employ. The compilation process supports using PyNN, a simulator-independent neural network description language, to configure the processor. NeuroFlow supports a number of commonly used current or conductance based neuronal models such as integrate-and-fire and Izhikevich models, and the spike-timing-dependent plasticity (STDP) rule for learning. A 6-FPGA system can simulate a network of up to ~600,000 neurons and can achieve a real-time performance of 400,000 neurons. Using one FPGA, NeuroFlow delivers a speedup of up to 33.6 times the speed of an 8-core processor, or 2.83 times the speed of GPU-based platforms. With high flexibility and throughput, NeuroFlow provides a viable environment for large-scale neural network simulation

Stopping powers and cross sections due to two-photon processes in relativistic nucleus-nucleus collision

The radiation dose received from high energy galactic cosmic rays (GCR) is a limiting factor in the design of long duration space flights and the building of lunar and martian habitats. It is of vital importance to have an accurate understanding of the interactions of GCR in order to assess the radiation environment that the astronauts will be exposed to. Although previous studies have concentrated on the strong interaction process in GCR, there are also very large effects due to electromagnetic (EM) interactions. In this report we describe our first efforts at understanding these EM production processes due to two-photon collisions. More specifically, we shall consider particle production processes in relativistic heavy ion collisions (RHICs) through two-photon exchange

On the dynamics of stochastic nonlinear dispersive partial differential equations

This thesis contributes towards the well-posedness theory of stochastic dispersive partial differential equations. Our investigation focuses on initial value problems as sociated with the stochastic nonlinear Schro¨dinger (SNLS) and stochastic Korteweg de Vries (SKdV) equations. We divide this thesis into four main topics, which are the contents of Chapters 2–5. Chapter 2 is concerned with the SNLS posed on the d-dimensional tori with either additive or multiplicative stochastic forcing. In particular, we prove local-in time well-posedness for initial data and noise at subcritical regularities. We are also able to extend this to global-in-time well-posedness at energy subcritical regularity for certain cases. In the next two chapters, we focus on SNLS posed on the d dimensional Euclidean space with additive noise. In Chapter 3, we prove local well posedness with the noise at supercritical regularity while the initial data stays at critical regularity. In Chapter 4, we restrict our attention to dimension 4 and study SNLS with non-vanishing boundary conditions. In particular, we use perturbative techniques to prove global well-posedness with data in H1(R4) + 1. In Chapter 5, we move on from SNLS to SKdV, where we prove L2(T)-global well-posedness of SKdV with multiplicative noise on the circle. We also verify that a result on the stabilisation of noise by Tsutsumi [84] continues to hold in our low regularity setting

Review of charm and beauty lifetimes

A review of the latest experimental results on charm and beauty particle lifetimes is presented together with a brief summary of measurement methods used for beauty particle lifetime measurements. There have been significant updates to the D{sub s}{sup +}/D{sup 0}, B{sup +}/B{sub d}{sup 0} and {Lambda}{sub b}{sup 0}/B{sub d}{sup 0} lifetime ratios which have some theoretical implications. However more precise measurements are still needed before one can make conclusive statements about the theory used to calculate the particle lifetimes

Confocal microscopic analysis of optical crosstalk in GaN micro-pixel light-emitting diodes

© 2015 AIP Publishing LLC. The optical crosstalk phenomenon in GaN micro-pixel light-emitting diodes (LED) has been investigated by confocal microscopy. Depth-resolved confocal emission images indicate light channeling along the GaN and sapphire layers as the source of crosstalk. Thin-film micro-pixel devices are proposed, whereby the light-trapping sapphire layers are removed by laser lift-off. Optical crosstalk is significantly reduced but not eliminated due to the remaining GaN layer. Another design involving micro-pixels which are completely isolated is further proposed; such devices exhibited low-noise and enhanced optical performances, which are important attributes for high-density micro-pixel LED applications including micro-displays and multi-channel optical communications.published_or_final_versio