227 research outputs found
Analysis of combustion instability in liquid propellant engines with or without acoustic cavities
Analytical studies have been made of the relative combustion stability of various propellant combinations when used with hardware configurations representative of current design practices and with or without acoustic cavities. Two combustion instability models, a Priem-type model and a modification of the Northern Research and Engineering (NREC) instability model, were used to predict the variation in engine stability with changes in operating conditions, hardware characteristics or propellant combination, exclusive of acoustic cavity effects. The NREC model was developed for turbojet engines but is applicable to liquid propellant engines. A steady-state combustion model was used to predict the needed input for the instability models. In addition, preliminary development was completed on a new model to predict the influence of an acoustic cavity with specific allowance for the effects the nozzle, steady flow and combustion
GAS DIFFUSION INTO A BUBBLE OF FIXED RADIUS
The problem of radiolytic gas diffusion into a bubble of fixed radius is solved. A constant source of radiolytic gas is assumed. The concentration of gas at the bubble surface is related to the pressure within the bubble by Henry's constant. (W. L.H.
Seeing Galaxies though Thick and Thin. IV. The Superimposed Spiral Galaxies of NGC 3314
The superimposed pair of spiral galaxies NGC 3314 offers a unique opportunity
to trace the dust properties in a spiral galaxy. We analyze multicolor HST
imaging, supported by ground-based near-IR imaging and fiber-array spectroscopy
to measure dust extinction in the foreground Sc galaxy NGC 3314A, which is
backlit by the Sb system NGC 3314B. We can measure extinctions over a wide
range of galactocentric radii in the foreground galaxy, from 0.4-4.5 kpc. In
the outer disk, the extinction is strongly localized in discrete dust lanes.
These dust features show an extinction curve with a slope close to the Galactic
mean (R = 3.5+/-0.3) from 1.6 to 3.8 kpc, with no radial trend. Using the I-K
color of the background nucleus, we derive an extinction A(I) = 3.3 through the
disk at a projected distance 400 pc from the nucleus of NGC 3314A. The
extinction in even the inner disk of NGC 3314A is quite patchy, since
background H-alpha emission is detected from all parts of the system. Local
anticorrelations between foreground and background line emission demonstrate
that the dust is concentrated to star-forming regions, as has been found for
the blue light in several systems. Colors of dust lanes in NGC 3314A which are
projected only partially against the background disk indicate that the dust
scale height in the foreground disk is substantially smaller than that of the
stars.Comment: 12 figures; accepted for Astronomical Journal (Sept. 2001
Comment on "Evidence for Neutrinoless Double Beta Decay"
We comment on the recent claim for the experimental observation of
neutrinoless double-beta decay. We discuss several limitations in the analysis
provided in that paper and conclude that there is no basis for the presented
claim.Comment: A comment written to Modern Physics Letters A. 4 pages, no figures.
Updated version, accepted for publicatio
Taqman Real-Time PCR Detects Avipoxvirus DNA in Blood of Hawaìi `Amakihi (Hemignathus virens)
Margaret E. M. Farias et al...Background
Avipoxvirus sp. is a significant threat to endemic bird populations on several groups of islands worldwide, including Hawaìi, the Galapagos Islands, and the Canary Islands. Accurate identification and genotyping of Avipoxvirus is critical to the study of this disease and how it interacts with other pathogens, but currently available methods rely on invasive sampling of pox-like lesions and may be especially harmful in smaller birds.
Methodology/Principal Findings
Here, we present a nested TaqMan Real-Time PCR for the detection of the Avipoxvirus 4b core protein gene in archived blood samples from Hawaiian birds. The method was successful in amplifying Avipoxvirus DNA from packed blood cells of one of seven Hawaiian honeycreepers with confirmed Avipoxvirus infections and 13 of 28 Hawaìi `amakihi (Hemignathus virens) with suspected Avipoxvirus infections based on the presence of pox-like lesions. Mixed genotype infections have not previously been documented in Hawaìi but were observed in two individuals in this study.
Conclusions/Significance
We anticipate that this method will be applicable to other closely related strains of Avipoxvirus and will become an important and useful tool in global studies of the epidemiology of Avipoxvirus.Funding for this study was provided by: U.S. Geological Survey, Pacific Island Ecosystems Research Center (biology.usgs.gov/pierc/); U.S. Geological Survey Wildlife (biology.usgs.gov/wter/) and Invasive Species (biology.usgs.gov/invasive/) Programs; National Science Foundation (DEB0083944, www.nsf.gov); NIH/NCRR IDeA Networks of Biomedical Research Excellence (INBRE), P20RR016467 (http://www.ncrr.nih.gov/research_infrastructure/institutional_development_award/idea_networks_of_biomedical_research_excellence/). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewe
110 Years of Avipoxvirus in the Galapagos Islands
The role of disease in regulating populations is controversial, partly owing to the absence of good disease records in historic wildlife populations. We examined birds collected in the Galapagos Islands between 1891 and 1906 that are currently held at the California Academy of Sciences and the Zoologisches Staatssammlung Muenchen, including 3973 specimens representing species from two well-studied families of endemic passerine birds: finches and mockingbirds. Beginning with samples collected in 1899, we observed cutaneous lesions consistent with Avipoxvirus on 226 (6.3%) specimens. Histopathology and viral genotyping of 59 candidate tissue samples from six islands showed that 21 (35.6%) were positive for Avipoxvirus, while alternative diagnoses for some of those testing negative by both methods were feather follicle cysts, non-specific dermatitis, or post mortem fungal colonization. Positive specimens were significantly nonrandomly distributed among islands both for mockingbirds (San Cristobal vs. Espanola, Santa Fe and Santa Cruz) and for finches (San Cristobal and Isabela vs. Santa Cruz and Floreana), and overall highly significantly distributed toward islands that were inhabited by humans (San Cristobal, Isabela, Floreana) vs. uninhabited at the time of collection (Santa Cruz, Santa Fe, Espanola), with only one positive individual on an uninhabited island. Eleven of the positive specimens sequenced successfully were identical at four diagnostic sites to the two canarypox variants previously described in contemporary Galapagos passerines. We conclude that this virus was introduced late in 1890′s and was dispersed among islands by a variety of mechanisms, including regular human movements among colonized islands. At present, this disease represents an ongoing threat to the birds on the Galapagos Islands
The Journal of Microelectronic Research 2005
https://scholarworks.rit.edu/meec_archive/1014/thumbnail.jp
The Majorana Project
Building a \BBz experiment with the ability to probe neutrino mass in the
inverted hierarchy region requires the combination of a large detector mass
sensitive to \BBz, on the order of 1-tonne, and unprecedented background
levels, on the order of or less than 1 count per year in the \BBz signal
region. The MAJORANA Collaboration proposes a design based on using high-purity
enriched Ge-76 crystals deployed in ultra-low background electroformed Cu
cryostats and using modern analysis techniques that should be capable of
reaching the required sensitivity while also being scalable to a 1-tonne size.
To demonstrate feasibility, the collaboration plans to construct a prototype
system, the MAJORANA DEMONSTRATOR, consisting of 30 kg of 86% enriched \Ge-76
detectors and 30 kg of natural or isotope-76-depleted Ge detectors. We plan to
deploy and evaluate two different Ge detector technologies, one based on a
p-type configuration and the other on n-type.Comment: paper submitted for the 2008 Carolina International Symposium on
Neutrino Physic
The Majorana Neutrinoless Double-Beta Decay Experiment
The proposed Majorana double-beta decay experiment is based on an array of
segmented intrinsic Ge detectors with a total mass of 500 kg of Ge isotopically
enriched to 86% in 76Ge. A discussion is given of background reduction by:
material selection, detector segmentation, pulse shape analysis, and
electro-formation of copper parts and granularity. Predictions of the
experimental sensitivity are given. For an experimental running time of 10
years over the construction and operation of Majorana, a half-life sensitivity
of ~4x10^27 y (neutrinoless) is predicted. This corresponds to an effective
Majorana mass of the electron neutrino of ~0.03-0.04 eV, according to recent
QRPA and RQRPA matrix element calculations.Comment: 10 pages, 7 figure
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