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Southern pine beetles (Dendroctonus frontalis Zimmermann) and symbiotic fungi are associated with mass mortality in stands of Caribbean pine (Pinus caribaea Morelet). This study provides a 12.7-year assessment of semiochemical mediation between southern pine beetle and Caribbean pine in relation to concentrations of 4-allylanisole (estragole, methyl chavicol) and monoterpenes measured by gas chromatography–mass spectrometry in different seasons in premontane and coastal pine stands of Belize and Guatemala. Individual trees and stands with >2.5% (relative mass %) of 4-allylanisole in the xylem oleoresin exhibited significantly less beetle-induced mortality than those with <2.5%. Changes in relative levels of 4-allylanisole and monoterpenes during this study are consistent with seasonal temperature and cumulative water deficit effects and suggest bark beetle attack of P. caribaea may intensify in the future.
Phased VLA observations of the Galactic center magnetar J1745-2900 over 8-12 GHz reveal rich single pulse behavior. The average profile is comprised of several distinct components and is fairly stable over day timescales and GHz frequencies. The average profile is dominated by the jitter of relatively narrow pulses. The pulses in each of the four profile components are uncorrelated in phase and amplitude, although the occurrence of pulse components 1 and 2 appear to be correlated. Using a collection of the brightest individual pulses, we verify that the index of the dispersion law is consistent with the expected cold plasma value of 2. The scattering time is weakly constrained, but consistent with previous measurements, while the dispersion measure DM = 1763+3−10 pc cm−3 is lower than previous measurements, which could be a result of time variability in the line-of-sight column density or changing pulse profile shape over time or frequency.
A new high rate deposition method has been used to fabricate thin film CdTe
photovoltaic devices using pulsed dc magnetron sputtering. The devices have been
deposited in superstrate configuration on to a commercial fluorine doped tin
oxide transparent conductor on soda lime glass. The cadmium sulphide and cadmium
telluride thin films were deposited from compound targets. The magnetrons were
mounted vertically around a cylindrical chamber and the substrate carrier
rotates so that the layers can be deposited sequentially. The substrates were
held at 200°C during deposition, a process condition previously found
to minimize the stress in the coatings. Optimization of the process involved a
number of parameters including control of pulse frequency, power and working gas
pressure. The devices deposited using the process are exceptionally uniform
enabling the CdTe absorber thickness to be reduced to ∼1um. The
as-deposited material is dense and columnar. The cadmium chloride treatment
increases the grain size and removes planar defects. The microstructure of the
films before and after activation has been characterized using a number of
techniques including transmission electron microscopy, Energy Dispersive mapping
and these measurements have been correlated to device performance. The
deposition rate is much higher than can be obtained with radio-frequency
sputtering and is comparable with methods currently used in thin film CdTe
module manufacturing such as Vapour Transport Deposition and Close Space
A detailed understanding of the response of mineral phases to the radiation fields experienced in a geological disposal facility (GDF) is currently poorly constrained. Prolongued ion irradiation has the potential to affect both the physical integrity and oxidation state of materials and therefore may alter a structure's ability to react with radionuclides. Radiohalos (spheres of radiation damage in minerals surrounding radioactive (α-emitting) inclusions) provide useful analogues for studying long term α-particle damage accumulation. In this study, silicate minerals adjacent to Th- and U-rich monazite and zircon were probed for redox changes and long/short range disorder using microfocus X-ray absorption spectroscopy (XAS) and high resolution X-ray diffraction (XRD) at Beamline I18, Diamond Light Source. Fe3+ → Fe2+ reduction has been demonstrated in an amphibole sample containing structural OH– groups – a trend not observed in anhydrous phases such as garnet. Coincident with the findings of Pattrick et al. (2013), the radiolytic breakdown of OH– groups is postulated to liberate Fe3+ reducing electrons. Across all samples, high point defect densities and minor lattice aberrations are apparent adjacent to the radioactive inclusion, demonstrated by micro-XRD.
Human anthrax cases reported in the country of Georgia increased 75% from 2011 (n = 81) to 2012 (n = 142). This increase prompted a case-control investigation using 67 culture- or PCR-confirmed cases and 134 controls matched by residence and gender to investigate risk factor(s) for infection during the month before case onset. Independent predictors most strongly associated with disease in the multivariable modelling were slaughtering animals [odds ratio (OR) 7·3, 95% confidence interval (CI) 2·9–18·1, P < 0·001] and disposing of dead animals (OR 13·6, 95% CI 1·5–119·8, P = 0·02). Participants owning or working with livestock (n = 131) were additionally interviewed about livestock management practices during the previous 6 months: 53 (44%) of 121 respondents vaccinated livestock against anthrax; 19 (16%) of 116 moved livestock >1 km; 15 (12%) of 125 had sick livestock; and 11 (9%) of 128 respondents reported finding dead livestock. We recommend joint public health and veterinary anthrax case investigations to identify areas of increased risk for livestock anthrax outbreaks, annual anthrax vaccination of livestock in those areas, and public awareness education.
We have applied mechanical exfoliation for the preparation of ultra-thin
samples of the phyllosilicate mineral biotite. We demonstrate that the
'scotch tape' approach, which was made famous as an early method for
production of single-atom-thick graphene, can be used for production of
sheet-silicate specimens that are sufficiently thin to allow high-resolution
transmission electron microscope (HRTEM) imaging to be achieved successfully
while also being free from the specimen preparation artefacts that are often
caused by ion-beam milling techniques. Exfoliation of the biotite parallel
to the (001) planes has produced layers as thin as two structural TOT units
thick (∼2 nm). The minimal specimen thickness enabled not only HRTEM imaging
but also the application of subsequent exit wavefunction restoration to
reveal the pristine biotite lattice. Exit wavefunction restoration recovers
the full complex electron wave from a focal series of HRTEM images, removing
the effects of coherent lens aberrations. This combination of methods
therefore produces images in which the observed features are readily
interpreted to obtain atomic resolution structural information.
The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunity to investigate the transient sky at radio wavelengths. In this paper we present VAST, an ASKAP survey for Variables and Slow Transients. VAST will exploit the wide-field survey capabilities of ASKAP to enable the discovery and investigation of variable and transient phenomena from the local to the cosmological, including flare stars, intermittent pulsars, X-ray binaries, magnetars, extreme scattering events, interstellar scintillation, radio supernovae, and orphan afterglows of gamma-ray bursts. In addition, it will allow us to probe unexplored regions of parameter space where new classes of transient sources may be detected. In this paper we review the known radio transient and variable populations and the current results from blind radio surveys. We outline a comprehensive program based on a multi-tiered survey strategy to characterise the radio transient sky through detection and monitoring of transient and variable sources on the ASKAP imaging timescales of 5 s and greater. We also present an analysis of the expected source populations that we will be able to detect with VAST.
We are developing a purely commensal survey experiment for fast (<5 s) transient radio sources. Short-timescale transients are associated with the most energetic and brightest single events in the Universe. Our objective is to cover the enormous volume of transients parameter space made available by ASKAP, with an unprecedented combination of sensitivity and field of view. Fast timescale transients open new vistas on the physics of high brightness temperature emission, extreme states of matter and the physics of strong gravitational fields. In addition, the detection of extragalactic objects affords us an entirely new and extremely sensitive probe on the huge reservoir of baryons present in the IGM. We outline here our approach to the considerable challenge involved in detecting fast transients, particularly the development of hardware fast enough to dedisperse and search the ASKAP data stream at or near real-time rates. Through CRAFT, ASKAP will provide the testbed of many of the key technologies and survey modes proposed for high time resolution science with the SKA.
Cupric oxide thin films were sputtered onto soda-lime glass slides from a single pre-formed ceramic target using a radio-frequency power supply. The effects of oxygen partial pressure and substrate temperature on the optical, electrical and structural properties of the films were studied. It was found that increasing temperature resulted in increased crystallinity and crystal size but also increased film resistivity. The most conductive films were those deposited at room temperature. Increasing oxygen partial pressure was found to reduce resistivity dramatically. This is thought to be due to higher charge carrier concentrations resulting from increased copper vacancies. Increasing oxygen partial pressure causes an increase in the optical band gap from a minimum of 0.8eV up to a maximum of 1.42eV. Oxygen-rich films display reduced crystallinity, becoming increasingly amorphous with increased oxygen content. These results show that the optical, electrical and structural properties of sputtered cupric oxide films can be controlled by alteration of the deposition environment.
We investigate the transient ventilation flow within a confined ventilated space, with high- and low-level openings, when the strength of a low-level point source of heat is changed instantaneously. The steady-flow regime in the space involves a turbulent buoyant plume, which rises from the point source to a well-mixed warm upper layer. The steady-state height of the interface between this layer and the lower layer of exterior fluid is independent of the heat flux, but the upper layer becomes progressively warmer with heat flux. New analogue laboratory experiments of the transient adjustment between steady states identify that if the heat flux is increased, the continuing plume propagates to the top of the room forming a new, warmer layer. This layer gradually deepens, and as the turbulent plume entrains fluid from the original warm layer, the original layer is gradually depleted and disappears, and a new steady state is established. In contrast, if the source buoyancy flux is decreased, the continuing plume is cooler than the original plume, so that on reaching the interface it is of intermediate density between the original warm layer and the external fluid. The plume supplies a new intermediate layer, which gradually deepens with the continuing flow. In turn, the original upper layer becomes depleted, both as a result of being vented through the upper opening of the space, but also due to some penetrative entrainment of this layer by the plume, as the plume overshoots the interface before falling back to supply the new intermediate layer. We develop quantitative models which are in good accord with our experimental data, by combining classical plume theory with models of the penetrative entrainment for the case of a decrease in heating. Typically, we find that the effect of penetrative entrainment on the density of the intruding layer is relatively weak, provided the change in source strength is sufficiently large. However, penetrative entrainment measurably increases the rate at which the depth of the draining layer decreases. We conclude with a discussion of the importance of these results for the control of naturally ventilated spaces.
The introduction of voluntary fortification of some foods with folic acid in Australia has been implemented since evidence of the prevention of neural tube defects with periconceptional folic acid was published. Our objectives were to determine how many women were aware of folate and when they became aware, what was the awareness of labels on foods that mentioned folate, and how much folate-fortified food women ate.
To address these objectives we collected data by self-administered questionnaire from a random sample of 578 recently pregnant women in Western Australia between September 1997 and March 2000.
Overall, 89% of women had heard, seen or read anything about the link between folate and birth defects such as spina bifida, 62% first became aware of the folate message before their recent pregnancy and 42% of women noticed any labels on foods that mention folate before or during their recent pregnancy. Overall, 53% of women were aware of foods that have folate added to them and 33% usually or always read the labels on food packaging. The folate-fortified foods most often consumed by women were cereals (69%), breads (34%) and milk (15%). Of the women who consumed folate-fortified foods (78%), the earlier they became aware of the folate message and noticed labels on food, the more fortified foods they consumed.
These results indicate that staple foods fortified with folate are consumed by almost 80% of women in the population. Therefore, mandatory fortification of staple foods may reach most women, providing improved opportunity for the prevention of neural tube defects in Australia.
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.
Deficits in visual-spatial ability can be associated with
Parkinson's disease (PD), and there are several possible reasons
for these deficits. Dysfunction in frontal–striatal and/or
frontal–parietal systems, associated with dopamine deficiency,
might disrupt cognitive processes either supporting (e.g., working
memory) or subserving visual-spatial computations. The goal of this
study was to assess visual–spatial orientation ability in
individuals with PD using the Mental Rotations Test (MRT), along with
other measures of cognitive function. Non-demented men with PD were
significantly less accurate on this test than matched control men. In
contrast, women with PD performed similarly to matched control women,
but both groups of women did not perform much better than chance.
Further, mental rotation accuracy in men correlated with their
executive skills involving mental processing and psychomotor speed. In
women with PD, however, mental rotation accuracy correlated negatively
with verbal memory, indicating that higher mental rotation performance
was associated with lower ability in verbal memory. These results
indicate that PD is associated with visual–spatial orientation
deficits in men. Women with PD and control women both performed poorly
on the MRT, possibly reflecting a floor effect. Although men and women
with PD appear to engage different cognitive processes in this task,
the reason for the sex difference remains to be elucidated.
(JINS, 2003, 9, 1078–1087.)
A variety of carbon nanotube films have been fabricated and tested as cold cathodes. A spray deposition technique was developed for processing as-grown bulk nanotubes, both single-walled and multi-walled, into films of randomly oriented nanotubes. Films of randomly oriented multi-walled nanotubes were grown using thermal chemical vapor deposition, and arrays of well-aligned multi-walled nanotubes have been fabricated using a microwave plasma enhanced chemical vapor deposition technique. The emission current-voltage (I-V) characteristics of these nanotube cathodes have been measured. Both multi-walled (random and aligned) and single-walled carbon nanotubes exhibit low turn-on fields (∼ 2 V/μm to generate 1 nA) and threshold fields (< 5 V/μm to generate 10 mA/cm2). Significantly, these cathodes were capable of operation at very large current densities (> 1A/cm2), making them candidates for application in a variety of vacuum microelectronic devices.
The efficacy of residual photoresist removal on the top surface of the InGaAs QWW grating and the effects of surface oxides on the optical property of quantum well wires (QWWs) were examined through atomic force microscopy (AFM) and photoluminescence (PL) spectroscopy. Different resist removal treatments, including acetone, ozone and diluted HC1 were evaluated. Both AFM and PL measurements reveal that with the surface cleaning processing we have developed, high luminescence efficiency from the QWWs is conserved after removal of the residual photoresist.