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We apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv-plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167–197 MHz; z = 6.2–7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.
The purpose of the study examined in this article was to understand how non-physician health care professionals working in Canadian primary health care settings facilitate older persons’ access to community support services (CSSs). The use of CSSs has positive impacts for clients, yet they are underused from lack of awareness. Using a qualitative description approach, we interviewed 20 health care professionals from various disciplines and primary health care models about the processes they use to link older patients to CSSs. Participants collaborated extensively with interprofessional colleagues within and outside their organizations to find relevant CSSs. They actively engaged patients and families in making these linkages and ensured follow-up. It was troubling to find that they relied on out-of-date resources and inefficient search strategies to find CSSs. Our findings can be used to develop resources and approaches to better support primary health care providers in linking older adults to relevant CSSs.
In a recent article in Social Science History, Professor Alan Bogue, former president of the Association and one of its founding fathers, has reviewed the first ten years of SSHA. In it he presents from the constitution the major purpose of the Association as “improving ‘the quality of historical explanation in every manner possible, but particularly by encouraging the selective use and adaptation in historical research and teaching of relevant social science’” (Bogue, 1987: 336). In this paper, we review the first ten years of the Social Science History journal in the context of an association formed to promote social science applications to the analysis of historical data. One indicator of the success of this enterprise is the extent to which historians are applying social science methods. Another indicator is the involvement of non-historians in social science history.
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.
The distributions of discrete, continuous and conditional multiple window scan statistics are studied. The finite Markov chain imbedding technique has been applied to obtain the distributions of fixed window scan statistics defined from a sequence of Bernoulli trials. In this manuscript the technique is extended to compute the distributions of multiple window scan statistics and the exact powers for multiple pulse and Markov dependent alternatives. An application in blood component quality monitoring is provided. Numerical results are also given to illustrate our theoretical results.
Heterosexuality continues to be regarded and adopted as a norm in the majority of Asian societies. In Hong Kong, lesbians and gay men are still encountering unfavourable attitudes from the general public (such as stereotyping and discrimination). This paper briefly reviews the legal and cultural context and notes in particular the situation in schools.
A centre manifold theory for reaction-diffusion equations with temporal delays is developed. Besides an existence proof, we also show that the equation on the centre manifold is a coupled system of scalar ordinary differential equations of higher order. As an illustration, this reduction procedure is applied to the Hutchinson equation with diffusion.
Half-Heusler (HH) phases, a versatile class of alloys with promising functional properties, have recently gained attention as emerging thermoelectric materials. These materials are investigated from the perspective of thermal and electronic transport properties for enhancing the dimensionless figure of merit (ZT) at 800–1000 K. The electronic origin of thermopower enhancement is reviewed. Grain refinement and embedment of nanoparticles in HH alloy hosts were used to produce fine-grained as well as nanocomposites and monolithic nanostructured materials. Present experiments indicated that n-type Hf0.6Zr0.4NiSn0.995Sb0.005 HH alloys and p-type Hf0.3Zr0.7CoSn0.3Sb0.7/nano-ZrO2 composites can attain ZT = 1.05 and 0.8 near 900–1000 K, respectively. The observed ZT enhancements could be attributed to multiple origins; in particular, the electronic origin was identified. The prospect for higher ZT was investigated in light of a recently developed nanostructure model of lattice thermal conductivity. Tests performed on p–n couple devices from the newly developed HH materials showed good power generation efficiencies—achieving 8.7% efficiency for hot-side temperatures of about 700 °C.
We report a study on the properties of Ionized Metal Plasma (IMP) Ta, Ta(N) and multi-layer Ta/Ta(N) based on a comparative evaluation of their performance as diffusion barriers in Cu based metallization schemes. The film structures used in this study are: IMP Cu(2000Å)/IMP Ta(250Å)/Si; IMP Cu(2000Å)/IMP Ta(N)(250Å)/Si; and IMP Cu(2000Å)/IMP multi-layer Ta/Ta(N)(250Å)/Si. The samples were annealed in N2 ambient at 500 °C, 550°C, 600°C and 650°C, respectively, for 30 minutes. The failure behavior and film properties of different barriers were investigated using MetaPULSE, Film stress measurement (FSM), Four-point probe (FPP), X-ray diffractometry (XRD), Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM). It has been observed clearly from the sheet resistance measurements that failures of Ta(N) and Ta barriers occurred at 550°C and 600°C respectively, whereas the multi-layer Ta/Ta(N) could still survive from the annealing up to 650°C. Evidence showing the formation of Cu3Si in the failed film stacks was found from XRD spectra. Based on our studies, it can be concluded that microstructures of the barriers has the major effects on preventing Cu from diffusing through them to react with Si and this makes the multi-layer Ta/Ta(N), in overall, superior to the other two Ta and Ta(N) barriers.
To determine the compatibility between the rigid rod and the flexible chain polyquinolines, both small angle x-ray and neutron scattering measurements were conducted on a sample containing deuterated flexible components. The scattering intensities from both x-ray and neutron were reduced to absolute scale in order to remove the scattering contribution from microvoids which tended to overshadow the signal of molecular origin. Quantitative information regarding the extent of molecular segregation in a polyquinoline multi-block copolymer was obtained, the result indicated that the material was strongly associated but not segregated into single component phases.
To determine the compatibility between the rigid rod and the flexible chain polyquinolines, both small angle x-ray and neutron scattering measurements were conducted on blends containing deuterated flexible chains. The scattering intensities from both x-ray and neutron were reduced to their absolute scales in order to remove the scattering contribution from microvoids which tended to overshadow the signal of molecular origin. Quantitative information regarding the molecular dispersion in a 50/50 rigid rod and flexible chain blend was obtained. The result indicated that this material was partially segregated but not to the point of single component phases.
Transmission electron microscopy (TEM) has been used to study the effects of 200 keV proton and 1 MeV fluorine ion irradiation on the microstructure of YBa2Cu3O7-δ (YBCO). Proton irradiation at fluences on the order of 1016 cm−2 results in more visible defects than can reasonably be expected solely from high energy transfer events; medium energy transfer events also contribute to visible defects. Defects arising from cascade events can be as large as 2 to 3 nm, and high resolution imaging suggests that they consist of small volumes of structurally disordered material. Fluorine irradiation to similar displacement levels results in significantly more visible defects.