402 research outputs found
Construction and properties of a mutant of herpes simplex virus type 1 with glycoprotein H coding sequences deleted
A mutant of herpes simplex virus type 1 (HSV-1) in which glycoprotein H (gH) coding sequences were deleted and replaced by the Escherichia coli lacZ gene under the control of the human cytomegalovirus IE-1 gene promoter was constructed. The mutant was propagated in Vero cells which contained multiple copies of the HSV-1 gH gene under the control of the HSV-1 gD promoter and which therefore provide gH in trans following HSV-1 infection. Phenotypically gH-negative virions were obtained by a single growth cycle in Vero cells. These virions were noninfectious, as judged by plaque assay and by expression of I-galactosidase following high-multiplicity infection, but partial recovery of infectivity was achieved by using the fusogenic agent polyethylene glycol. Adsorption of gH-negative virions to cells blocked the adsorption of superinfecting wild-type virus, a result in contrast to that obtained with gD-negative virions (D. C. Johnson and M. W. Ligas, J. Virol. 62:4605-4612, 1988). The simplest conclusion is that gH is required for membrane fusion but not for receptor binding, a conclusion consistent with the conservation of gH in all herpesviruses
AAO Starbugs: software control and associated algorithms
The Australian Astronomical Observatory's TAIPAN instrument deploys 150
Starbug robots to position optical fibres to accuracies of 0.3 arcsec, on a 32
cm glass field plate on the focal plane of the 1.2 m UK-Schmidt telescope. This
paper describes the software system developed to control and monitor the
Starbugs, with particular emphasis on the automated path-finding algorithms,
and the metrology software which keeps track of the position and motion of
individual Starbugs as they independently move in a crowded field. The software
employs a tiered approach to find a collision-free path for every Starbug, from
its current position to its target location. This consists of three
path-finding stages of increasing complexity and computational cost. For each
Starbug a path is attempted using a simple method. If unsuccessful,
subsequently more complex (and expensive) methods are tried until a valid path
is found or the target is flagged as unreachable.Comment: 10 pages, to be published in Proc. SPIE 9913, Software and
Cyberinfrastructure for Astronomy IV; 201
CYCLOPS2: the fibre image slicer upgrade for the UCLES high resolution spectrograph
CYCLOPS2 is an upgrade for the UCLES high resolution spectrograph on the
Anglo-Australian Telescope, scheduled for commissioning in semester 2012A. By
replacing the 5 mirror Coud\'e train with a Cassegrain mounted fibre-based
image slicer CYCLOPS2 simultaneously provides improved throughput, reduced
aperture losses and increased spectral resolution. Sixteen optical fibres
collect light from a 5.0 arcsecond^2 area of sky and reformat it into the
equivalent of a 0.6 arcsecond wide slit, delivering a spectral resolution of R
= 70000 and up to twice as much flux as the standard 1 arcsecond slit of the
Coud\'e train. CYCLOPS2 also adds support for simultaneous ThAr wavelength
calibration via a dedicated fibre. CYCLOPS2 consists of three main components,
the fore-optics unit, fibre bundle and slit unit. The fore optics unit
incorporates magnification optics and a lenslet array and is designed to mount
to the CURE Cassegrain instrument interface, which provides acquisition,
guiding and calibration facilities. The fibre bundle transports the light from
the Cassegrain focus to the UCLES spectrograph at Coud\'e and also includes a
fibre mode scrambler. The slit unit consists of the fibre slit and relay optics
to project an image of the slit onto the entrance aperture of the UCLES
spectrograph. CYCLOPS2 builds on experience with the first generation CYCLOPS
fibre system, which we also describe in this paper. We present the science case
for an image slicing fibre feed for echelle spectroscopy and describe the
design of CYCLOPS and CYCLOPS2.Comment: 9 pages, 6 figures, published in Proc. SPIE 844
The ecology of exercise: mechanisms underlying Individual variation in behavior, activity, and performance: an introduction to symposium
Wild animals often engage in intense physical activity while performing tasks vital for their survival and reproduction associated with foraging, avoiding predators, fighting, providing parental care, and migrating. In this theme issue we consider how viewing these tasks as “exercise”—analogous to that performed by human athletes—may help provide insight into the mechanisms underlying individual variation in these types of behaviors and the importance of physical activity in an ecological context. In this article and throughout this issue, we focus on four key questions relevant to the study of behavioral ecology that may be addressed by studying wild animal behavior from the perspective of exercise physiology: (1) How hard do individual animals work in response to ecological (or evolutionary) demands?; (2) Do lab-based studies of activity provide good models for understanding activity in free-living animals and individual variation in traits?; (3) Can animals work too hard during “routine” activities?; and (4) Can paradigms of “exercise” and “training” be applied to free-living animals? Attempts to address these issues are currently being facilitated by rapid technological developments associated with physiological measurements and the remote tracking of wild animals, to provide mechanistic insights into the behavior of free-ranging animals at spatial and temporal scales that were previously impossible. We further suggest that viewing the behaviors of non-human animals in terms of the physical exercise performed will allow us to fully take advantage of these technological advances, draw from knowledge and conceptual frameworks already in use by human exercise physiologists, and identify key traits that constrain performance and generate variation in performance among individuals. It is our hope that, by highlighting mechanisms of behavior and performance, the articles in this issue will spur on further synergies between physiologists and ecologists, to take advantage of emerging cross-disciplinary perspectives and technologies
Identifying Stars of Mass >150 Msun from Their Eclipse by a Binary Companion
We examine the possibility that very massive stars greatly exceeding the
commonly adopted stellar mass limit of 150 Msun may be present in young star
clusters in the local universe. We identify ten candidate clusters, some of
which may host stars with masses up to 600 Msun formed via runaway collisions.
We estimate the probabilities of these very massive stars being in eclipsing
binaries to be >30%. Although most of these systems cannot be resolved at
present, their transits can be detected at distances of 3 Mpc even under the
contamination of the background cluster light, due to the large associated
luminosities ~10^7 Lsun and mean transit depths of ~10^6 Lsun. Discovery of
very massive eclipsing binaries would flag possible progenitors of
pair-instability supernovae and intermediate-mass black holes.Comment: 5 pages, 1 figure, 1 table. Submitted to MNRA
Non-Uniform Channelization Methods for Next Generation SDR PMR Base Stations
Channelization in multi-standard Software-Defined
Radio base stations presents a significant challenge. In this
paper, two different channelization structures designed for a
multi-standard SDR base station are studied. As a basis for
comparing their computational efficiency and
reconfigurability, both are applied to a specific case study of a
TETRA and TEDS standards base station. Uniform narrow
band spectrum division followed by channel recombination
demonstrates greater flexibility than a non-uniform parallel
spectrum division alternative. However, computational
advantages between both structures depend on the channel
allocation patterns considered
Law, Liquor, and Love
This article discusses attempts at alcohol law reform in New Zealand between 2008 and 2017. First, it describes a major review of alcohol by the New Zealand Law Commission, headed by Sir Geoffrey Palmer, who had overseen liberalisation of alcohol regulation 25 years earlier. The main recommendations of the commission’s final report featured progressive reform of the alcohol laws regulating marketing, price, accessibility and age of purchase. Second, it outlines the response to the commission’s report by the Nationalled government, including an Alcohol Reform Bill that ignored the key recommendations of the commission. This ‘non-reform’ bill was the outcome of a political process of obfuscation, delay and inaction led by then prime minister, John Key. Third, the article describes the factors that have contributed to the lack of effective alcohol law reform, despite the review and high public support for change over the past decade. We conclude that ‘the love of money’ is at the heart of the barriers to change. Finally, we propose three main policies that would make a significant difference to reducing alcohol-related harm in New Zealand and suggest how these could be advanced
The Influence of Particle Content on the Equi-Biaxial Fatigue Behaviour of Magnetorheological Elastomers
The equi-biaxial fatigue behaviour of silicone based magnetorheological elastomers (MREs) with various volume fractions of carbonyl iron particles ranging between 15% and 35% was studied. Wöhler curves for each material were derived by cycling test samples to failure over a range of stress amplitudes. Changes in complex modulus (E*) and dynamic stored energy during the fatigue process were observed. As for other elastic solids, fatigue resistance of MREs with different particle contents was shown to be dependent on the stress amplitudes applied. MREs with low particle content showed the highest fatigue life at high stress amplitudes while MREs with high particle content exhibited the highest fatigue resistance at low stress amplitudes. E* fell with the accumulation of cycles for each material, but the change was dependent on the particle content and stress amplitude applied. However, each material failed in a range suggesting a limiting value of E* for the material between 1.22 MPa and 1.38 MPa regardless of the particle content and the magnitude of the stress amplitude. In keeping with results from previous testing, it was shown that dynamic stored energy can be used to predict the fatigue life of MREs having a wide variation in particle content
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