The ALICE Transition Radiation Detector

In this talk an overview of the ALICE TRD is presented. The ALICE TRD consists of 540 individual detector modules with a total of 1.2 million readout channels. It allows electron identification above a momentum of 1 GeV/c and is capable of providing a very fast and efficient trigger on electrons with large transverse momentum pt. It will operate in a very high multiplicity environment. The rapidity density of charged particles in collisions of Pb nuclei at ps = 5:5 ATeV is expected to be as high as dN/dy = 8000

Venous thromboembolism in pregnancy

Pregnancy-related venous thromboembolic events are important preventable causes of morbidity and mortality in South Africa. All pregnant patients should be evaluated for thrombotic risk at different stages of their pregnancy and appropriate preventive steps taken. Maternal and fetal wellbeing must be kept in mind, as well as physiological changes leading to altered drug pharmacokinetics. Managing the patient with thrombotic risk in pregnancy, diagnosing venous thromboembolism (VTE) during pregnancy and treatment of venous thromboembolic events should be managed by a team. Excellent recent reviews on this subject are available, including risk factor stratification in anticoagulant therapy; managing the patient at time of labour; diagnosing VTE; and managing neuraxial anaesthesia in the pregnant patient on anticoagulant therapy

Flow-gauging structures in South African rivers Part 1: An overview

Accurate hydrological information is of paramount importance in a dry country such as South Africa. Flow measurements in rivers are complicated by the high variability of flows as well as by sediment and debris loads. It has been found necessary to modify and even substitute certain internationally accepted gauging structure designs to overcome local practical problems and improve accuracies.This, Part 1 of a paper in 2 parts, concentrates on the attributes of different types of gauging structures and the informationprovided on the different structures will assist the reader with the selection of an appropriate structure. The historical development of the gauging structure network in South African rivers is briefly discussed. Gauging structures used in South African rivers and basic design criteria for the preferred structures at this stage, based on past experience, are discussed:• Crump weirs• Sharp-crested weirs• Sluicing flumes.This paper reflects the lessons that have been learnt by DWAF and other South African organisations and should be of value to others who have to perform flow measurements under similar climatic conditions. Factors that may adversely impact on gauging accuracy are also pointed out in the conclusion. Part 2 of the paper contains information on the calibration theory and techniques to rate the preferred gauging structures

Optical properties of Mn4+ ions in GaN:Mn codoped with Mg acceptors

The optical properties of Mn-Mg codoped epitaxial GaN were studied. Addition of Mg acceptors quenches the weak manganese-related photoluminescence (PL) band at 1.3 eV in GaN:Mn and a series of sharp PL peaks are observed at 1 eV in codoped epilayers. The change in PL spectra indicates that Mg addition stabilizes the Mn4+ charge state by decreasing the Fermi level. The 1 eV PL peaks are tentatively attributed to intra center transitions involving Mn4+ ions. Spin allowed 3d-shell 4T2-4T1 transitions and their phonon replicas are involved. The relative intensities of the sharp peaks are strongly dependent on the excitation wavelength, indicating the optically active Mn4+ centers involved in the separate peaks are different. The temperature dependence of the PL spectrum suggests the presence of at least three distinct Mn4+ complex centers.Comment: 14 pages, 3 figures, 1 table, accepted by Appl. Phys. Let

Flow-gauging structures in South African rivers Part 2: Calibration

Accurate hydrological information is of paramount importance in a dry country such as South Africa. Flow measurements in rivers are complicated by the high variability of flows as well as by sediment loads and debris. It has been found necessary to modify and even substitute certain internationally accepted gauging station designs to overcome practical problems and to improve accuracies.Part 1 of this paper concentrated on the attributes of different types of gauging structures and provided guidance onthe design criteria applicable for selected structures. Part 2 of this paper in 2 parts contains information required to rate orcalibrate the gauging structures that are most likely to be selected in the foreseeable future:• Crump weirs• Sharp-crested weirs• Sluicing flumes.This paper and its linked predecessor reflect the lessons that have been learnt by DWAF and other South African organisationsand should be of value to others who have to perform flow measurements under similar conditions. The problems associatedwith the use of compound weir structures to gauge discharge and techniques that may be used to overcome some of theseproblems are also discussed

Mid-IR continuous-wave fiber-laser-pumped optical parametric oscillators

We review recent developments in continuous-wave mid-infrared optical parametric oscillators pumped by fiber lasers. Such devices are potentially valuable spectroscopic sources providing high output powers and rapid, wide-range tuning in the mid-infrared molecular fingerprint region