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This paper describes the system architecture of a newly constructed radio telescope – the Boolardy engineering test array, which is a prototype of the Australian square kilometre array pathfinder telescope. Phased array feed technology is used to form multiple simultaneous beams per antenna, providing astronomers with unprecedented survey speed. The test array described here is a six-antenna interferometer, fitted with prototype signal processing hardware capable of forming at least nine dual-polarisation beams simultaneously, allowing several square degrees to be imaged in a single pointed observation. The main purpose of the test array is to develop beamforming and wide-field calibration methods for use with the full telescope, but it will also be capable of limited early science demonstrations.
In this paper, we establish bounds on the norm of multiplication operators on the Bloch space of the unit disk via weighted composition operators. In doing so, we characterize the isometric multiplication operators to be precisely those induced by constant functions of modulus 1. We then describe the spectrum of the multiplication operators in terms of the range of the symbol. Lastly, we identify the isometries and spectra of a particular class of weighted composition operators on the Bloch space.
Carbon nanotubes have the potential of being used as interconnects and active semiconducting material in future electronic circuits. It is necessary to study such nano-scale circuits with probes that can make measurements with molecular precision. We describe results using two nanoprobe techniques, namely scanning surface potential microscopy (SSPM), and conductive tip atomic force microscopy (CT-AFM), in the investigation of electrical properties of nanotube circuits. Vertical arrays of multi-walled nanotubes, grown in a porous alumina template with a metal back contact were analyzed. Current mapping confirmed that the nanotubes were electrically connected to the back contact. Isolated single-walled nanotube bundles deposited on an oxidized silicon wafer, and contacted electrically through chromium electrodes were also studied. Contact potential differences between the metal and nanotubes, and the current in some connected nanotubes were measured. Measurements of contact potential with different metals, and the nature of microscopic transport is crucial. Contact potential measurements can also provide fast and reliable characterization of junctions between metallic and semiconducting nanotubes and metals electrodes.
We have fabricated ordered arrays of gold nanocrystals on FIB-processed silicon substrates using electroless deposition. We have also fabricated ordered arrays of silver nanocrystals on silicon with diameters 40–60 nm separated by 180 nm center-to-center, using pulsed-laser deposition (PLD) to deposit silver on the substrate. The metal nanocrystal arrays are characterized using SEM as well as AFM and energy dispersive x-ray (EDX) analysis. AFM confirms particle sizes measured in SEM, and EDX analysis demonstrates that Ag preferentially clusters at sites that have been damaged by the ion beam. These results suggest that the FIB-PLD combination can be used to create ordered arrays of Ag nanocrystals with diameters of 10 nm or less.
Almost as long as African studies has been a recognized intellectual enterprise in U.S. higher education, scholars have sought to establish its credentials as an academic pursuit and have debated its characteristics. To take the most obvious example, the home page of the African Studies Association (ASA) Web site (http://www.africanstudies.org/) declares, “The African Studies Association was founded in 1957 as a non-profit organization open to all individuals and institutions interested in African affairs. Its mission is to bring together people with a scholarly and professional interest in Africa.”
Michael F. Murphy, National Blood Service, Oxford, UK, University of Oxford, Oxford, UK,
Rachel Rayment, National Blood Service, Oxford, UK,
David Allen, National Blood Service, Oxford, UK,
David Roberts, National Blood Service, Oxford, UK, University of Oxford, Oxford, UK
Alloimmune thrombocytopenia is the commonest cause of neonatal thrombocytopenia, occurring in one in 1000–2000 live births; this is equivalent to 400–800 cases per year in the UK. The pathogenesis of alloimmune thrombocytopenia is similar to HDFN (Chapter 1):
• The mother is negative for a platelet alloantigen which the fetus has inherited from the father, and maternal alloimmunization occurs in a proportion of women who may have a genetic predisposition to become immunized (Section 1.3.3).
• Placental transfer of IgG antibodies may result in moderate to severe thrombocytopenia as early as 16 weeks’ gestation.
• The most clinically significant incompatibility is for HPA-1a, the frequency of this antigen being 97.5% in Caucasians (Section 12.3).
• HPA-1a alloimmunization is HLA class II restricted; there is a strong association with HLA-DRw52a (HLA-DR3*0101), which is present in one in three of Caucasian women. Although the negative predictive value of the absence of HLA-DR3*0101 for HPA-1a alloimmunization in HPA-1a-negative women is >99%, the positive predictive value of its presence for alloimmunization has been estimated to be only 35%, and not all alloimmunized mothers will have babies with thrombocytopenia (Section 4.2).
• The antibody titre and isotype have not been shown to correlate consistently with the development or severity of disease (Section 184.108.40.206).