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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 microstructure-property relations were evaluated for a nominally Ti-25Al-17Nb orthorhombic alloy, in terms of the deformation and failure mechanisms of the constituent ordered phases (orthorhombic, alpha-2, and B2). The mechanisms were characterized through observation of slip traces, crack initiation sites, and TEM. Properties of interest were the room temperature elongation, fatigue crack growth (FCG) resistance, and creep resistance.
A brief overview of the research activities at the Thermionic Energy Conversion (TEC) Center is given. The goal is to achieve direct thermal to electric energy conversion with >20% efficiency and >1W/cm2 power density at a hot side temperature of 300–650C. Thermionic emission in both vacuum and solid-state devices is investigated. In the case of solid-state devices, hot electron filtering using heterostructure barriers is used to increase the thermoelectric power factor. In order to study electron transport above the barriers and lateral momentum conservation in thermionic emission process, the current-voltage characteristic of ballistic transistor structures is investigated. Embedded ErAs nanoparticles and metal/semiconductor multilayers are used to reduce the lattice thermal conductivity. Cross-plane thermoelectric properties and the effective ZT of the thin film are analyzed using the transient Harman technique. Integrated circuit fabrication techniques are used to transfer the n- and p-type thin films on AlN substrates and make power generation modules with hundreds of thin film elements. For vacuum devices, nitrogen-doped diamond and carbon nanotubes are studied for emitters. Sb-doped highly oriented diamond and low electron affinity AlGaN are investigated for collectors. Work functions below 1.6eV and vacuum thermionic power generation at temperatures below 700C have been demonstrated.
In this report we study the morphology and chemical composition of a nanocomposite memory device where the active device layer is sandwiched between two aluminum electrodes and consists of a nanocomposite of polystyrene (PS) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM). The morphology of the active layer is imaged both in plan-view and cross-sectional view by using transmission electron microscopy (TEM). We introduce two techniques to prepare the cross-sections from the active layer, namely, a conventional technique based on microtoming and secondly nanostructural processing with focused ion beam (FIB). Based on the morphology studies we deduce that within the used concentrations the PCBM forms spherical nanoscale clusters within the continuous PS matrix. The chemical composition of the device is determined by using X-ray photoelectron spectroscopy (XPS) and it shows that the thermal evaporation of the aluminum electrodes does not lead to observable inclusion of the aluminum into the active material layer.
We have investigated a mode-coupling mechanism between kinetic Alfvén waves and a collisional drift wave in an inhomogeneous cylindrical plasma. Drift waves satisfying the condition k⊥D > 1/r0 (where r0 is the radius of the plasma cylinder) are stabilized by the low-frequency ponderomotive force generated by the kinetic Alfvén waves. For typical plasma parameters and a moderate level of Alfven-wave intensity the stabilization factor is comparable to the destabilization mechanism due to collisions.
Giardia, a common enteric protozoan parasite is a well-recognized cause of diarrhoeal illness. The detailed mechanism of diarrhoea due to this infection is not well understood. A 58 kDa enterotoxin (ESP) was purified from the excretory–secretory product of the parasite. The present study was designed to investigate the mode of action of this enterotoxin of G. lamblia in mice enterocytes. An increase in cyclic adenosine monophosphate level, as well as intracellular Ca2+ concentration, was observed in the ESP-triggered enterocytes. The levels of phospholipase Cγ1 and inositol triphosphate were found to be upregulated. The activity of protein kinase C (PKC) in the enterocytes was also enhanced following stimulation with the ESP. An increase in the level of reactive oxygen species in ESP-stimulated cells correlated well with the decline in the activity of antioxidant enzymes (superoxide dismutase and catalase). The significantly high levels of nitrite and citrulline indicated the generation of reactive nitrogen intermediates in the ESP-triggered enterocytes. Thus, ESP could induce cross-talk among the different signal transduction pathways in the enterocytes, which could together bring about a common secretory response.
The mechanism by which Giardia lamblia exerts its pathogenicity is likely to be multifactorial. A 58 kDa enterotoxin was purified and characterized from the excretory–secretory product (ESP) of the parasite (Kaur et al. 2001). In the present study an attempt has been made to elucidate the mechanism of action of the ESP, a potentially important enterotoxin. A 41 kDa glycoprotein was identified in the mouse enterocyte membrane fraction with which the ESP interacted in a GM1-specific manner. The GTPase activity was reduced in enterocytes stimulated with the ESP, resulting in an increase in the level of adenylate cyclase-dependent cyclic adenosine monophosphate (cAMP). The activity of protein kinase A (PKA) in the enterocytes was also upregulated after ESP treatment. Ultimately, a significant increase in intracellular Ca2+ concentration and decrease in cytosolic Cl− level were noticed in ESP-stimulated mouse enterocytes. Thus it is possible that the enterotoxic ESP could bind to the 41 kDa glycoprotein (receptor?) on the enterocytes and activate the G-protein-mediated signal transduction pathway resulting in alteration of electrolyte transport.
Higher-order nonlinear and dispersive effects on ion-acoustic solitons in
a plasma consisting of two types of cold positive ions and two-temperature non-isothermal
electrons are studied using a reductive perturbation method. An integrated
form of the basic sets of fluid equations consisting of two types of positive
ions and two types of non-isothermal electrons is derived in terms of a pseudo-potential.
A perturbation solution of this equation is obtained by the Bogoliubov–Mitropolsky method.
At the lowest order, we obtain a modified Korteweg–de Vries
solitary-wave solution, which has a sech4 profile. Calculations are carried out at
the next two higher orders. The secularity-removing condition at each order gives
a correction to the velocity of the solitary wave at the corresponding order. The
variations of Mach number and width of the ion-acoustic soliton with amplitude at
each order are shown graphically for plasmas with H+ and He+ or with He+ and
Ar+ ions, with two-temperature non-isothermal electrons.
ZrO2–Al2O3 powders were synthesized by spray pyrolysis. These powders were sintered at 1 GPa in the temperature range of 700–1100 °C. The microstructural evolution and densification are reported in this paper. The application of 1 Gpa pressure lowers the crystallization temperature from ∼850 to <700 °C. Similarly, the transformation temperature under 1 GPa pressure for γ → α–Al2O3 reduces from ∼1100 to 700–800 °C range, and that for t → m ZrO2 reduces from ∼1050 to 700–800 °C range. It was possible to obtain highly dense nanocrystalline ZrO2–Al2O3 composite at temperatures as low as 700 °C. The effect of high pressure on nucleation and transformation of phases is discussed.
The aim was to investigate the effect of tiapride (100 mg three times a day for at least one month) on outcome following detoxification.
The setting was a tertiary referral centre. The study design was randomised, double-blind, and placebo-controlled. One hundred routinely admitted alcohol-dependent patients were entered, and 54 completed the trial. Outcome was assessed by considering drinking status at three months and six months follow-up, and by comparing psychological status at intake and follow-up using the Crown-Crisp Experiential Index, the Litman Self-esteem scale and a Satisfaction with Life Situations scale. We also compared performance over the six months before admission with the three and six months of follow-up on measures of health, social and drinking variables.
Tiapride proved better (usually at statistically highly significant levels) than placebo at promoting: abstinence, self-esteem, and satisfaction with life situations; and at reducing: alcohol consumption, use of health service resources, and levels of neuroticism.
Tiapride merits serious consideration in the longer-term treatment of alcoholic patients.
Thirty-two chemically dependent alcoholics with significant levels of anxiety or depression were admitted to a double-blind randomised study in which the effect of the substituted benzamide tiapride was compared with that of placebo over a 6-month period. Twenty patients completed the study. Assessments included relevant biochemical and haematological tests, drinking levels and associated behaviour, expressed satisfaction with various areas of life, the Crown-Crisp Experiential Index of neurotic symptoms and questionnaires on self-esteem and alcohol dependence. The results indicated that in comparison with the placebo group, patients treated with tiapride drank less and had longer periods of abstinence. This was associated with improvements in laboratory tests, reduction in neurotic symptoms, gains in self-esteem and increased levels of expressed satisfaction with life situation. The drug was well tolerated and no deleterious effects were noted, suggesting its potential usefulness for this patient group.
For an operator on a Hilbert space, points in the closure of its numerical range are characterized as either extreme, non-extreme boundary, or interior in terms of various associated sets of bounded sequences of vectors. These generalize similar results due to Embry, for points in the numerical range.
The problem of capillary–gravity waves generated by certain moving oscillatory surface-pressure distributions is investigated. The main difficulty of the problem lies in finding the real roots of the modified frequency equations. This is dealt with by the use of certain geometric considerations. The critical condition that results from the formation of double roots of the modified frequency equations is represented as a surface. This surface divides the whole space into several distinct regions. For points in different regions the propagation of waves is different. The waves are determined in all cases.
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