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Motivated by the manufacture of carbon fibre components, this paper considers the smooth draping of loosely woven fabric over rigid obstacles, both smooth and nonsmooth. The draped fabric is modelled as the continuum limit of a Chebyshev net of two families of short rigid rods that are freely pivoted at their joints. This approach results in a system of nonlinear hyperbolic partial differential equations whose characteristics are the fibres in the fabric. The analysis of this system gives useful information about the drapability of obstacles of many shapes and also poses interesting theoretical questions concerning well-posedness, smoothness and computability of the solutions.
Gravitational waves from coalescing neutron stars encode information about nuclear matter at extreme densities, inaccessible by laboratory experiments. The late inspiral is influenced by the presence of tides, which depend on the neutron star equation of state. Neutron star mergers are expected to often produce rapidly rotating remnant neutron stars that emit gravitational waves. These will provide clues to the extremely hot post-merger environment. This signature of nuclear matter in gravitational waves contains most information in the 2–4 kHz frequency band, which is outside of the most sensitive band of current detectors. We present the design concept and science case for a Neutron Star Extreme Matter Observatory (NEMO): a gravitational-wave interferometer optimised to study nuclear physics with merging neutron stars. The concept uses high-circulating laser power, quantum squeezing, and a detector topology specifically designed to achieve the high-frequency sensitivity necessary to probe nuclear matter using gravitational waves. Above 1 kHz, the proposed strain sensitivity is comparable to full third-generation detectors at a fraction of the cost. Such sensitivity changes expected event rates for detection of post-merger remnants from approximately one per few decades with two A+ detectors to a few per year and potentially allow for the first gravitational-wave observations of supernovae, isolated neutron stars, and other exotica.
The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
During the past 20 years, the idea that non-spherical planetary nebulae might need a binary or planetary interaction to be shaped was discussed by various authors. It is now generally agreed that the varied morphologies of planetary nebulae cannot be fully explained solely by single star evolution. Observationally, more binary central stars of planetary nebulae have been discovered, opening new possibilities to understand the connections between binarity and morphology. So far, ≃45 binary central stars of planetary nebulae have been detected, most being close systems detected via flux variability. In order to determine the PN binary fraction, one needs a method that can detect wider binaries. We present here recent results concentrating on binary infrared excess observations aimed at detecting binaries of any separation.
An investigation into the cause of bacterial contamination of bottles of non-injectable water has been reported. A method of monitoring such bottles has also been described. The roles played by autoclave spray-cooling water and inadequate bottle seals in the contamination of fluids have been examined. Possible methods of reducing the risk of contamination are discussed and the design of an improved method of closure of sterile bottled fluids is stressed. Bacteriological examination is shown to be a more accurate index of the true rate of contamination than measurement of dye concentrations of bottle contents.
As we have noted before, the WG-IR was created following a Joint Commission Meeting at the IAU General Assembly in Baltimore in 1988, a meeting that provided both diagnosis and prescription for the perceived ailments of infrared photometry at the time. The results were summarized in Milone (1989). The challenges involve how to explain the failure to systematically achieve the milli-magnitude precision expected of infrared photometry and an apparent 3% limit on system transformability. The proposed solution was to re-define the broadband Johnson system, the passbands of which had proven so unsatisfactory that over time effectively different systems proliferated although bearing the same JHKLMNQ designations; the new system needed to be better positioned and centered in the atmospheric windows of the Earth's atmosphere, and the variable water vapour content of the atmosphere needed to be measured in real time to better correct for atmospheric extinction.
We present the results of eighteen non-continuous nights of time series photometric observations of a 1.25 deg2 field in Cygnus centered on the NASA Kepler Mission field of view. Using the Case Western Burrell Schmidt telescope we gathered a dataset containing light curves of roughly 30,000 stars with 14 < r < 19. We have statistically examined each light curve to test for variability, periodicity, and unusual light curve trends, including exoplanet transits. We present a summary of our photometric project including a characterization of the level and content of stellar variability in this field. We will also discuss our potential exoplanet candidates.
This paper considers a paradigm large-Prandtl-number, large-Rayleigh-number forced convection problem suggested by the batch melting process in the glass industry. Although the fluid is heated from above, non-uniform heating in the horizontal direction induces thermal boundary layers in which colder liquid is driven over hotter liquid. This leads to an interesting selection problem in the boundary layer analysis, whose resolution is suggested by a combination of analytical and numerical evidence.
The authors have developed, implemented and assessed an on-line, open-book quizzing environment for the introductory materials science course, “Materials In Today’s World”. The course is offered as an E-Education course and students may complete the course from anywhere that permits access to our course management system, ANGEL. For reasons that were both pragmatic and philosophical, we decided that the exams/quizzes would not be proctored, they would be delivered wholly on-line, and would be open-book.
In the current paper, we will present and justify our philosophy, of on-line, open-book quizzes: the rich feedback, which is a feature or our quizzing system, QuestionMark Perception, is used both as a teaching tool, and as a means to refine the quiz database. We have replaced the original “high-stakes” midterm and final exam, with a series of lower-stakes, weekly quizzes, which are generated from a large question database. Student response to the quizzing environment is generally very positive.
In addition to a hard-copy textbook, Power-Point presentations and videos, the authors have developed a series of Flash modules and on-line quizzing tools for use in teaching and assessing the fundamentals of Materials Science and Engineering. The original thrust was aimed at non-science majors at university, but the modules are also designed for ease of use in high school curricula. In the current paper, we present our philosophy for the presentation of materials' related subject material, using different learning objects, by describing one particular module: on electronic materials.
Performance on some neuropsychological tests is best expressed as an
intra-individual measure of association (such as a parametric or
non-parametric correlation coefficient or the slope of a regression
line). Examples of the use of intra-individual measures of association
(IIMAs) include the quantification of performance on tests designed to
assess temporal order memory or the accuracy of time estimation. The
present paper presents methods for comparing a patient's
performance with a control or normative sample when performance is
expressed as an IIMA. The methods test if there is a significant
difference between a patient's IIMA and those obtained from
controls, yield an estimate of the abnormality of the patient's
IIMA, and provide confidence limits on the level of abnormality. The
methods can be used with normative or control samples of any size and
will therefore be of particular relevance to single-case researchers. A
method for comparing the difference between a patient's scores on
two measures with the differences observed in controls is also
described (one or both measures can be IIMAs). All the methods require
only summary statistics (rather than the raw data from the normative or
control sample); it is hoped that this feature will encourage the
development of norms for tasks that use IIMAs to quantify performance.
Worked examples of the statistical methods are provided using data from
a clinical case and controls. A computer program (for PCs) that
implements the methods is described and made available. (JINS,
2003, 9, 989–1000.)
The free volume of metallic glasses has a significant effect on atomic relaxation processes, although a detailed understanding of the nature and distribution of free volume sites is currently lacking. Positron annihilation spectroscopy was employed to study free volume in a Zr–Ti–Ni–Cu–Be bulk metallic glass following plastic straining and cathodic charging with atomic hydrogen. Multiple techniques were used to show that strained samples had more open volume, while moderate hydrogen charging resulted in a free volume decrease. It was also shown that the free volume is associated with zirconium and titanium at the expense of nickel, copper, and beryllium. Plastic straining led to a slight chemical reordering.
Radiation embrittlement of nuclear reactor pressure vessel steels results from a high number density of nanometer sized Cu-Mn-Ni rich precipitates (CRPs) and sub-nanometer matrix features, thought to be vacancy-solute cluster complexes (VSC). However, questions exist regarding both the composition of the precipitates and the defect character and composition of the matrix features. We present results of positron annihilation spectroscopy (PAS) and small angle neutron scattering (SANS) characterization of irradiated and thermally aged Fe-Cu and Fe-Cu-Mn alloys. These complementary techniques provide insight into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of CRPs and VSCs in both alloys. The CRPs are coarser in the Fe-Cu alloy and the number densities of CRP and VSC increase with the addition of Mn. The PAS involved measuring both the positron lifetimes and the Doppler broadened annihilation spectra in the high momentum region to provide elemental sensitivity at the annihilation site. The spectra in Fe-Cu-Mn specimens thermally aged to peak hardness at 450°C and irradiated at 288°C are nearly identical to elemental Cu. Positron lifetime and spectrum measurements in Fe-Cu specimens irradiated at 288°C clearly show the existence of long lifetime (∼500 ps) open volume defects, which also contain Cu. Thus the SANS and PAS provide a self-consistent picture of nanostructures composed of CRPs and VSCs and tend to discount high Fe concentrations in the CRPs.
Progressive inefficacy of chemoprophylactic therapy to control gastro-intestinal (GI) nematode infection in sheep has been a major contributory factor in stimulating research into the development of alternative means of internal parasite control. This research aims to investigate the possibilities for selecting UK sheep for increased genetic resistance to naturally acquired GI nematode parasite infections.
The electrostatic surface potential of self-assembled monolayers (SAMs) of aliphatic and aromatic thiols has been measured using electrostatic force microscopy. The variation of the surface potential of chemisorbed alkanethiols, with respect to bare Au(111), is observed to increase with increasing chain length. The trend is similar to that observed in the literature. A preliminary theoretical model, based on treating the monolayer as a sheet of dipoles, has been used to calculate the surface potential of alkanethiols. Similar measurements on several aromatic thiols, with a symmetric and non-symmetric molecular structure, reveal that non-symmetric systems have significantly higher potential (≥ 170mV) than the symmetric molecules.
We provide direct experimental evidence for a non-random distribution of atomic constituents in Zr-based multi-component bulk metallic glasses using positron annihilation spectroscopy. The Ti content around the open-volume regions is significantly enhanced at the expense of Cu and Ni, indicating that Cu and Ni occupy most of the volume bounded by their neighboring atoms while Ti and Zr are less closely packed and more likely to be associated with open-volume regions. Temperature-dependent measurements indicate the presence of at least two different characteristic sizes for the open volume regions. Measurements on hydrogen- charged samples show that the larger open-volume regions can be filled by hydrogen up to a critical density. Beyond this critical density, local atomic-scale open-volume damage is created in the sample to accommodate additional hydrogen. The onset of this local damage in positron annihilation data coincides with the onset of volume expansion in X-ray diffraction data.
Films of Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 have been grown using Atomic-Layer-by-Layer Molecular Beam Epitaxy (ALL-MBE) on lattice-matched substrates. These materials have been combined with layers of closely related metastable compounds like Bi2Sr2Ca7Cu8O20 (2278) and rare-earth-doped compounds like Bi2Sr2DyxCa1–xCu2O8 (Dy: 2212) to form heterostructures with unique superconducting properties, including superconductor/insulator multilayers and tunnel junctions. Transmission electron microscopy (TEM) has been used to study the morphology and microstructure of these heterostructures. These TEM studies shed light on the physical properties of the films, and give insight into the growth mode of highly anisotropic solids like Bi2Sr2CaCu2O8.
The effects of the insect hormones, ecdysone and 20-hydroxyecdysone, certain non-steroidal ecdysteroid agonists (RH compounds) and the inhibitor, azadirachtin, on the timing of the 3rd-stage moult of Dirofilaria immitis were investigated. 20-Hydroxyecdysone and RH 5849 when used at a concentration of 10−5 M, resulted in a premature timing of this moult. Azadiracthin, at a similar concentration, prevented moulting of most of the larvae to the 4th stage. The results are discussed in relation to the possibility of a hormonal role for ecdysteroids and neuropeptide-like compounds in the control of ecdysis in filarial nematodes, that maybe somewhat comparable to the system which is found in insects.