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We describe an ultra-wide-bandwidth, low-frequency receiver recently installed on the Parkes radio telescope. The receiver system provides continuous frequency coverage from 704 to 4032 MHz. For much of the band (
), the system temperature is approximately 22 K and the receiver system remains in a linear regime even in the presence of strong mobile phone transmissions. We discuss the scientific and technical aspects of the new receiver, including its astronomical objectives, as well as the feed, receiver, digitiser, and signal processor design. We describe the pipeline routines that form the archive-ready data products and how those data files can be accessed from the archives. The system performance is quantified, including the system noise and linearity, beam shape, antenna efficiency, polarisation calibration, and timing stability.
The most important factors known to influence the eating quality of beef are well established and include both pre- and post-slaughter events with many of the determinants interacting with each other. A substantial programme of work has been conducted by the Agri-Food and Biosciences Institute in Northern Ireland aimed at quantifying those factors of most importance to the local beef industry. Post-slaughter effects such as carcase chilling and electrical stimulation, ageing, carcase hanging and cooking method have been shown to have a significant impact on eating quality when compared with pre-slaughter activities such as animal handling and lairage time in the Northern Ireland studies. However, the effect of animal breed, particularly the use of dairy breed animals, was shown to significantly improve eating quality. Many of these factors were found to interact with each other.
We investigate to what extent the current helicity distribution observed in solar active regions is compatible with solar dynamo models. We use an advanced 2D mean-field dynamo model with dynamo action largely concentrated near the bottom of the convective zone, and dynamo saturation based on the evolution of the magnetic helicity and algebraic quenching. For comparison, we also studied a more basic 2D mean-field dynamo model with simple algebraic alpha quenching only. Using these numerical models we obtain butterfly diagrams for both the small-scale current helicity and the large-scale magnetic helicity, and compare them with the butterfly diagram for the current helicity in active regions obtained from observations. This comparison shows that the current helicity of active regions, as estimated by −A·B evaluated at the depth from which the active region arises, resembles the observational data much better than the small-scale current helicity calculated directly from the helicity evolution equation. Here B and A are respectively the dynamo generated mean magnetic field and its vector potential.
Intravenous amphotericin or intravenous voriconazole, both followed by oral voriconazole, have previously been given to treat invasive aspergillosis of the skull base.
Exclusively oral voriconazole was used in an immunocompetent patient with biopsy-proven, invasive aspergillosis. She had a large, erosive lesion extending from the central skull base to the right orbit and ethmoid sinus, and displacing the right internal carotid artery. After four months of oral treatment as an out-patient, a repeated computed tomography scan showed a fully treated infection with post-infectious changes only, and treatment was terminated. Two years later, there had been no recurrence.
Substantial cost savings were made by using exclusively oral treatment, compared with the use of intravenous voriconazole or amphotericin, or a switch strategy.
Mixing of cattle prior to slaughter which results in aggressive activity (Mohan Raj et al 1992) leads to glycogen depletion pre-slaughter and subsequently meat with a higher ultimate pH (pHu). Purchas et al (1990) reported a quadratic relationship between pHu and tenderness with highest shear force values recorded between pHu 5.8 to 6.2. The aim of this study was to determine the effect of fasting and mixing of steers prior to slaughter on the meat eating quality of longissimus dorsi (LD) muscle.
There is now good agreement between the various methods of estimating the space density of the star-formation rate (SFRD) at low redshifts (z < 1), with uncertainties around 30–50%. However, the situation at higher redshifts remains much less clear, with uncertainties in the SFRD, due to e.g. poorly known dust absorption corrections, of as much as 300–500%. Radio emission from star-forming galaxies is unaffected by absorption and scales linearly with star-formation rate, thus the radio luminosity of star-forming galaxies provides an excellent independent, unbiased measure of their star-formation rate. The current deepest ‘blank field’ radio surveys (reaching <10 μJy rms at 1.4 GHz) are sensitive enough to detect starburst galaxies out to z ~ 3, and so potentially offer an excellent way to measure the SFRD. Indeed, modelling of the sub-mJy source counts requires an additional population of faint steep spectrum objects, that are very likely to be starburst galaxies.
The true nature of the faint radio population remains elusive despite the many observations of the “sub-mJy” bump over the last two decades. This lack of information is largely due to the faint magnitudes of the optical counterparts to the radio sources. There are strong theoretical reasons (and a few observational ones) to believe that this rise in the counts is due to the emergence of a rapidly evolving star-forming population. Now, for the first time, we are able to separate the AGN and star-forming populations below 1mJy using a combination of multi-wavelength data from Spitzer, GMRT, MERLIN, CFHT, Keck, UKIRT, Subaru, Chandra and XMM-Newton. The many discriminators between these emission mechanisms include MIR colours, MIR/radio flux ratios, X-ray luminosities/spectra, optical spectra, radio morphologies and radio spectra. We can now derive the source counts separately for AGN and star-forming galaxies confirming that the latter population rise sharply at faint flux densities.
The proportion of beef cattle originating from the suckler herd is projected to decrease, relative to the proportion from the dairy herd. Sinclair et al., (2001) found no difference between eating quality of Holstein and Charolais when hung tenderstretch. Most genotype comparisons in relation to meat quality have used the longissimus dorsi muscle and very few have considered more than one particular post slaughter process (ie hanging technique, aging period). The present study was undertaken to investigate the effect of genotype and post slaughter processing (hanging technique and aging time) on the eating quality of a range of hindquarter muscles.
Recent data on meat quality indicates that dairy genotypes produce more tender meat than beef genotypes. The relationships between carcass parameters and instrumental measures of meat quality depend on the method of hanging (Lively et al., 2005). The present study was undertaken to evaluate the impact of some carcass parameters on meat eating quality of two genotypes when two carcass hanging methods are used.
We study a simple model for the solar dynamo in the framework of the Parker dynamo, with a nonlinear dynamo saturation mechanism based on magnetic helicity conservation arguments. We find a parameter range in which the model demonstrates a cyclic behaviour with properties similar to that of Parker dynamo with the simplest form of algebraic $\alpha$-quenching. We compare the nonlinear current helicity evolution in this model with data for the current helicity evolution obtained during 10 years of observations at the Huairou Solar Station of China. We conclude that, in spite of the very preliminary state of the observations and the crude nature of the model, the idea of using observational data to constrain our ideas concerning magnetic field generation in the framework of the solar dynamo appears promising.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html
Fossil magnetic fields (i.e. fields that survive
from one stage of
stellar evolution to a significantly later epoch without
being regenerated) have been invoked to explain
phenomena in the Sun, magnetic CP stars, white dwarfs
and neutron stars. The feasibility of such processes is
discussed critically. Estimates are made that suggest that flux survival
through pre-main sequence evolution is more likely to occur in stars with
M > 1 M⊙. Any link between CP star and white dwarf magnetism is argued
to favour the fossil field origin of CP star fields.
We describe the operation of lasers having active regions composed of InP self-assembled quantum dots embedded in In0.5Al0.3Ga0.2P grown on GaAs (100) substrates by MOCVD. InP quantum dots grown on In0.5Al0.3Ga0.2P have a high density on the order of about 1-2x10 cm-2 with a dominant size of about 10-15 nm for 7.5 ML growth. These In0.5Al0.3Ga0.2P/InP quantum dots have previously been characterized by atomic-force microscopy, high-resolution transmission electron microscopy, and photoluminescence. We report here the 300K operation of optically pumped red-emitting quantum dots using both double quantum-dot active regions and quantum-dot coupled with InGaP quantum-well active regions. Optically and electrically pumped 300K lasers have been obtained using this active region design; these lasers show improved operation compared to the lasers having QD-based active regions with threshold current densities as low as Jth ∼ 0.5 KA/cm2.
Three hundred and twenty pigs were reared from birth to slaughter at 21 weeks in either barren or enriched environments. The barren environments were defined as intensive housing (slatted floors and minimum recommended space allowances) and the enriched environments incorporated extra space including an area which contained peat and straw in a rack. Behavioural observations showed that environmental enrichment reduced time spent inactive and time spent involved in harmful social and aggressive behaviour (P < 0·001). Each pig was individually exposed to a novel object during a novel pen test at 18 weeks of age and behavioural, heart rate and plasma cortisol responses were recorded. At slaughter plasma cortisol levels were measured, adrenal glands were weighed and hearts were examined for endothelial haemorrhages. Pigs from enriched environments appeared less fearful during the novel pen test by showing a shorter latency to contact the novel object (P < 0·001) and spending more time in contact with it (P < 0·05). Plasma cortisol responses to the novel pen test tended to be higher in pigs from enriched environments (P > 0·05) and pigs from enriched environments had significantly higher cortisol levels at slaughter (P < 0·05). Adrenal weights were greater in pigs from barren environments (P < 0·05) and it is suggested that chronic activation of the pituitary-adrenal axis in barren environments led to a suppression of cortisol responses to acute stress. The higher cortisol responses to the novel pen test in pigs from enriched environments may also have resulted from greater levels of behavioural activity. This could also explain the higher maximum heart rates in pigs from enriched environments during the 1st min of the test (P < 0-05) and during the period prior to the test when they were being driven towards the test arena (P < 0-05). However, the fact that enriched pigs also showed a greater number of lesions to the endothelium of the heart (P < 0-05) may mean they had a more reactive sympathetic nervous system.
Langmuir-Blodgett (LB) films of poly(p-phenylene vinylene) (PPV) were prepared using an amphiphilic precursor, where the counterion chloride was partially replaced by a long chain dodecylbenzenesulfonate ion. These LB-PPV films are highly ordered along the dipping direction as demonstrated by linear dichroism experiments using linearly polarized optical absorption and emission. The intensity ratio between emitted light parallel and perpendicular to the dipping direction was ca. 17, which is much higher than the dichroic ratio of 3.6 found in the polarized absorption experiment. These values indicate an efficient energy and/or charge transfer between low conjugated segments (disordered) and highly conjugated (ordered) ones after excitation. In addition, the LB films displayed large circular polarization with an asymmetry factor ge which varies from 0.6 to –0.2 when the sample temperature is increased from 30 to 300 K.
We report on the influence of Bias-Temperature Stress (BTS) on the pentacene Thin Film Transistors (TFTs) electrical characteristics and on their 1/f noise level. The gate BTS primarily affects the TFT threshold voltage, leaving both mobility and sub-threshold slope values almost unchanged. The degree of the threshold voltage shift induced by the positive or negative BTS depends on the TFT design and the BTS parameters. The current-voltage characteristics time dependence of the organic TFTs, subjected to the BTS, resembles that for amorphous-Si TFTs. The results of the 1/f noise measurements in the organic TFTs allowed us to conclude that the gate BTS primarily affects the TFT contact regions, resulting in the increase of both the contact noise and the contact resistance.
Surface processing of microelectronic materials by bombardment with nanoparticles of condensed gases (i.e., clusters) in the form of an ion beam, makes possible etching and smoothing of those surfaces to very high figures of merit. As this is not possible with any conventional ion method, gas-cluster ion-beam systems have great potential in manufacturing. The formation of gas clusters and their collision with surfaces provides an interesting arena for novel physics and surface science. This paper outlines a physical model for the clusters and surface interactions, and provides examples of surface processing. In particular, the reduction of surface roughness while etching by cluster-ion bombardment is illustrated for various materials utilized in microelectronics.
In the present work we study the effect of vertical alignment in the quantum dot array formed by successive deposition of several rows of InAlAs and InGaAs quantum dots separated by thin AIGaAs spacer layers. Transmission electron microscopy and photoluminescence studies revealed that the InAlAs QDs characterized by high areal density force InGaAs to be transformed into the denser array as compared to the case of spontaneous transformation. Using denser array of composite quantum dots in the active region of a diode laser leads to the increase in modal gain, decrease in internal loss, and decrease in the threshold current density for short cavity diodes. Room temperature continuous wave output power as high as 3.3 W at 0.87 µm is achieved.
Quantum dot structures containing 2 and 7 layers of small coherent InAs clusters embedded into a Si single crystal matrix were grown by MBE. The structure of these clusters was investigated by high resolution transmission electron microscopy. The crystallographic quality of the structure severely depends on the substrate temperature, growth sequence, and the geometrical parameters of the sample. The investigation demonstrates that Si can incorporate a limited volume of InAs in a form of small coherent clusters about 3 nm in diameter. If the deposited InAs layer exceeds a critical thickness, large dislocated InAs precipitates are formed during Si overgrowth accumulating the excess of InAs.
The principal interests in this work are energetic-beam control of carbon-film properties and the roles of doping and surface morphology in field emission. Carbon films with variable sp3-bonding fraction were deposited on n-type Si substrates by ArF (193 nm) pulsed-laser ablation (PLA) of a pyrolytic graphite target, and by direct metal ion beam deposition (DMIBD) using a primary Cs+ beam to generate the secondary C- deposition beam. The PLA films are undoped while the DMIBD films are doped with Cs. The kinetic energy (KE) of the incident C atoms/ions was controlled and varied over the range from ∼25 eV to ∼175 eV. Earlier studies have shown that C films' sp3-bonding fraction and diamond-like properties can be maximized by using KE values near 90 eV. The films' surface morphology, sp3–bonding fraction, and Cs-content were determined as a function of KE using atomic force microscopy, TEM/EELS, Rutherford backscattering and nuclear reaction measurements, respectively. Field emission (FE) from these very smooth undoped and Cs-containing films is compared with the FE from two types of deliberately nanostructured carbon films, namely hot-filament chemical vapor deposition (HF-CVD) carbon and carbon nanotubes grown by plasma-enhanced CVD. Electron field emission (FE) characteristics were measured using ∼25-μm, ∼5-μm and ∼1-μm diameter probes that were scanned with ∼75 nm resolution in the x-, y-, and z-directions in a vacuum chamber (∼5 × 10-7 torr base pressure) equipped with a video camera for viewing. The hydrogen-free and very smooth a-D or a-C films (with high or low sp3 content, and with or without ∼1% Cs doping) produced by PLD and DMIBD are not good field emitters. Conditioning accompanied by arcing was required to obtain emission, so that their subsequent FE is characteristic of the arc-produced damage site. However, deliberate surface texturing can eliminate the need for conditioning, apparently by geometrical enhancement of the local electric field. But the most promising approach for producing macroscopically flat FE cathodes is to use materials that are highly nanostructured, either by the deposition process (e.g. HF-CVD carbon) or intrinsically (e.g. carbon nanotubes). HF-CVD films were found to combine a number of desirable properties for FE displays and vacuum microelectronics, including the absence of conditioning, low turn-on fields, high emission site density, and apparent stability and durability during limited long-term testing. Preliminary FE measurements revealed that vertically aligned carbon nanotubes are equally promising.