31,491 research outputs found
A real-time digital computer program for the simulation of a single rotor helicopter
A computer program was developed for the study of a single-rotor helicopter on the Langley Research Center real-time digital simulation system. Descriptions of helicopter equations and data, program subroutines (including flow charts and listings), real-time simulation system routines, and program operation are included. Program usage is illustrated by standard check cases and a representative flight case
Single-level resonance parameters fit nuclear cross-sections
Least squares analyses of experimental differential cross-section data for the U-235 nucleus have yielded single level Breit-Wigner resonance parameters that fit, simultaneously, three nuclear cross sections of capture, fission, and total
Assembly and force measurement with SPM-like probes in holographic optical tweezers
We report a high fidelity tomographic reconstruction of the quantum state of photon pairs generated by parametric down-conversion with orbital angular momentum (OAM) entanglement. Our tomography method allows us to estimate an upper and lower bound for the entanglement between the down-converted photons. We investigate the two-dimensional state subspace defined by the OAM states ±ℓ and superpositions thereof, with ℓ=1, 2, ..., 30. We find that the reconstructed density matrix, even for OAMs up to around ℓ=20, is close to that of a maximally entangled Bell state with a fidelity in the range between F=0.979 and F=0.814. This demonstrates that, although the single count-rate diminishes with increasing ℓ, entanglement persists in a large dimensional state space
Properties of simulated Milky Way-mass galaxies in loose group and field environments
We test the validity of comparing simulated field disk galaxies with the
empirical properties of systems situated within environments more comparable to
loose groups, including the Milky Way's Local Group. Cosmological simulations
of Milky Way-mass galaxies have been realised in two different environment
samples: in the field and in environments with similar properties to the Local
Group. Apart from the environments of the galaxies, the samples are kept as
homogeneous as possible with equivalent ranges in last major merger time, halo
mass and halo spin. Comparison of these two samples allow for systematic
differences in the simulations to be identified. Metallicity gradients, disk
scale lengths, colours, magnitudes and age-velocity dispersion relations are
studied for each galaxy in the suite and the strength of the link between these
and environment of the galaxies is studied. The bulge-to-disk ratio of the
galaxies show that these galaxies are less spheroid dominated than many other
simulated galaxies in literature with the majority of both samples being disk
dominated. We find that secular evolution and mergers dominate the spread of
morphologies and metallicity gradients with no visible differences between the
two environment samples. In contrast with this consistency in the two samples
there is tentative evidence for a systematic difference in the velocity
dispersion-age relations of galaxies in the different environments. Loose group
galaxies appear to have more discrete steps in their velocity dispersion-age
relations. We conclude that at the current resolution of cosmological galaxy
simulations field environment galaxies are sufficiently similar to those in
loose groups to be acceptable proxies for comparison with the Milky Way
provided that a similar assembly history is considered.Comment: 16 pages, 11 figures, abstract abridged for arXiv. Accepted for
publication in Astronomy & Astrophysic
An evaluation: The potential of discarded tires as a source of fuel
The destructive distillation of rubber tire samples was studied by thermogravimetry, differential scanning calorimetry, combustion calorimetry, and mass spectroscopy. The decomposition reaction was found to be exothermic and produced a mass loss of 65 percent. The gas evolution curves that were obtained indicate that a variety of organic materials are evolved simultaneously during the decomposition of the rubber polymer
Investigation of macrocyclisation routes to 1,4,7-triazacyclononanes : efficient syntheses from 1,2-ditosylamides
Two routes to the synthesis of a cyclohexyl-fused 1,4,7-triazacyclononane involving macrocyclisations of tosamides have been investigated. In the first approach, using a classic Richman-Atkins-type cyclisation of a cyclohexyl-substituted 1,4,7-tritosamide with ethylene glycol ditosylate, afforded the cyclohexyl-fused 1,4,7-triazacyclononane in 5.86% overall yield in four steps. The second, more concise, approach involving the macrocyclisation of trans-cyclohexane-1,2-ditosamide with the tritosyl derivative of diethanolamine initially gave poor yields (< 25%). The well-documented problems with efficiencies in macrocyclisations using 1,2-ditosamides led to the use of a wider range of 1,2-ditosamides including ethane-1,2-ditosamide and propane-1,2-ditosamide. These extended studies led to the development of an efficient macrocyclisation protocol using lithium hydride. This new method afforded 1,4,7-tritosyl-1,4,7-triazacyclononanes in good yield (57-90%) from 1,2-ditosamides in a single step. These efficient methods were then applied to the preparation of a chiral cyclohexyl-fused 1,4,7-tritosyl-1,4,7-triazacyclononane (65-70%). This key chiral intermediate was then converted into a copper(II) complex following detosylation and N-methylation. The resulting chiral copper(II) complex catalysed the aziridination of styrene but it did so in a racemic fashion
Human fur gene encodes a yeast KEX2-like endoprotease that cleaves pro-beta-NGF in vivo.
Extracts from BSC-40 cells infected with vaccinia recombinants expressing either the yeast KEX2 prohormone endoprotease or a human structural homologue (fur gene product) contained an elevated level of a membrane-associated endoproteolytic activity that could cleave at pairs of basic amino acids (-LysArg- and -ArgArg-). The fur-directed activity (furin) shared many properties with Kex2p including activity at pH 7.3 and a requirement for calcium. By using antifurin antibodies, immunoblot analysis detected two furin translation products (90 and 96 kD), while immunofluorescence indicated localization to the Golgi apparatus. Coexpression of either Kex2p or furin with the mouse beta-nerve growth factor precursor (pro-beta-NGF) resulted in greatly enhanced conversion of the precursor to mature nerve growth factor. Thus, the sequence homology shared by furin and the yeast KEX2 prohormone processing enzyme is reflected by significant functional homology both in vitro and in vivo
On Dwarf Galaxies as the Source of Intracluster Gas
Recent observational evidence for steep dwarf galaxy luminosity functions in
several rich clusters has led to speculation that their precursors may be the
source of the majority of gas and metals inferred from intracluster medium
(ICM) x-ray observations. Their deposition into the ICM is presumed to occur
through early supernovae-driven winds, the resultant systems reflecting the
photometric and chemical properties of the low luminosity dwarf spheroidals and
ellipticals we observe locally. We consider this scenario, utilising a
self-consistent model for spheroidal photo-chemical evolution and gas ejection
via galactic superwinds. Insisting that post-wind dwarfs obey the observed
colour-luminosity-metallicity relations, we conclude that the bulk of the ICM
gas and metals does not originate within their precursors.Comment: 43 pages, 8 figures, LaTeX, also available at
http://msowww.anu.edu.au/~gibson/publications.html, to appear in ApJ, Vol
473, 1997, in pres
Preoperative neutrophil-lymphocyte ratio and outcome from coronary artery bypass grafting
Background: An elevated preoperative white blood cell count has been associated with a worse outcome after coronary artery bypass grafting (CABG). Leukocyte subtypes, and particularly the neutrophil-lymphocyte (N/L) ratio, may however, convey superior prognostic information. We hypothesized that the N/L ratio would predict the outcome of patients undergoing surgical revascularization. Methods: Baseline clinical details were obtained prospectively in 1938 patients undergoing CABG. The differential leukocyte was measured before surgery, and patients were followed-up 3.6 years later. The primary end point was all-cause mortality. Results: The preoperative N/L ratio was a powerful univariable predictor of mortality (hazard ratio [HR] 1.13 per unit, P 3.36). Conclusion: An elevated N/L ratio is associated with a poorer survival after CABG. This prognostic utility is independent of other recognized risk factors.Peer reviewedAuthor versio
The optical transmission spectrum of the hot Jupiter HAT-P-32b: clouds explain the absence of broad spectral features?
We report Gemini-North GMOS observations of the inflated hot Jupiter
HAT-P-32b during two primary transits. We simultaneously observed two
comparison stars and used differential spectro-photometry to produce
multi-wavelength light curves. 'White' light curves and 29 'spectral' light
curves were extracted for each transit and analysed to refine the system
parameters and produce transmission spectra from 520-930nm in ~14nm bins. The
light curves contain time-varying white noise as well as time-correlated noise,
and we used a Gaussian process model to fit this complex noise model. Common
mode corrections derived from the white light curve fits were applied to the
spectral light curves which significantly improved our precision, reaching
typical uncertainties in the transit depth of ~2x10^-4, corresponding to about
half a pressure scale height. The low resolution transmission spectra are
consistent with a featureless model, and we can confidently rule out broad
features larger than about one scale height. The absence of Na/K wings or
prominent TiO/VO features is most easily explained by grey absorption from
clouds in the upper atmosphere, masking the spectral features. However, we
cannot confidently rule out clear atmosphere models with low abundances (~10^-3
solar) of TiO, VO or even metal hydrides masking the Na and K wings. A smaller
scale height or ionisation could also contribute to muted spectral features,
but alone are unable to to account for the absence of features reported here.Comment: 17 pages, 11 figures, 2 tables, accepted for publication in MNRA
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