26,250 research outputs found
Pressure letdown method and device for coal conversion systems
In combination with a reactor for a coal utilization system, a pressure letdown device accepts from a reactor, a polyphase fluid at an entrance pressure and an entrance velocity, and discharges the fluid from the device at a discharge pressure substantially lower than the entrance pressure and at a discharge temperature and a discharge velocity substantially equal to the entrance temperature and entrance velocity. The device is characterized by a series of pressure letdown stages including several symmetrical baffles, disposed in coaxially nested alignment. In each baffle several ports or apertures of uniform dimensions are defined. The number of ports or apertures for each baffle plate is unique with respect to the number of ports or apertures defined in each of the other baffles. The mass rate of flow for each port is a function of the area of the port, the pressure of the fluid as applied to the port, and a common pressure ratio established across the ports
Maser Source Finding Methods in HOPS
The {\bf H}{\bf O} Southern Galactic {\bf P}lane {\bf S}urvey (HOPS) has
observed 100 square degrees of the Galactic plane, using the Mopra radio
telescope to search for emission from multiple spectral lines in the 12\,mm
band (19.5\,--\,27.5\,GHz). Perhaps the most important of these spectral lines
is the 22.2\,GHz water maser transition. We describe the methods used to
identify water maser candidates and subsequent confirmation of the sources. Our
methods involve a simple determination of likely candidates by searching peak
emission maps, utilising the intrinsic nature of water maser emission -
spatially unresolved and spectrally narrow-lined. We estimate completeness
limits and compare our method with results from the {\sc Duchamp} source
finder. We find that the two methods perform similarly. We conclude that the
similarity in performance is due to the intrinsic limitation of the noise
characteristics of the data. The advantages of our method are that it is
slightly more efficient in eliminating spurious detections and is simple to
implement. The disadvantage is that it is a manual method of finding sources
and so is not practical on datasets much larger than HOPS, or for datasets with
extended emission that needs to be characterised. We outline a two-stage method
for the most efficient means of finding masers, using {\sc Duchamp}.Comment: 8 pages, 1 table, 4 figures. Accepted for publication in PASA special
issue on Source Finding & Visualisatio
Organising evidence for environmental management decisions: a '4S' hierarchy.
Making decisions informed by the best-available science is an objective for many organisations managing the environment or natural resources. Yet, available science is still not widely used in environmental policy and practice. We describe a '4S' hierarchy for organising relevant science to inform decisions. This hierarchy has already revolutionised clinical practice. It is beginning to emerge for environmental management, although all four levels need substantial development before environmental decision-makers can reliably and efficiently find the evidence they need. We expose common bypass routes that currently lead to poor or biased representation of scientific knowledge. We argue that the least developed level of the hierarchy is that closest to decision-makers, placing synthesised scientific knowledge into environmental decision support systems.L.V.D. is funded by the Natural Environment Research Council (Grant code NE/K015419/1). J.C.W. is funded by the UK Commonwealth Scholarship Commission and the Cambridge Commonwealth, European and International Trust. W.J.S. is funded by Arcadia.This is the final version of the article. It first appeared from Cell Press/Elsevier via http://dx.doi.org/10.1016/j.tree.2014.09.00
Effects of aging on vibration detection thresholds at various body regions
Background: The ability to detect sinusoidal vibrations on the skin surface is dependent on the activation of two classes of receptors. The density of such receptors varies across the skin surface and is a factor in determining the sensory acuity of each skin area. However, the acuity of many sensory systems is known to deteriorate with advancing age. The aim of this study was to determine if vibrotactile sensibility of several skin surfaces deteriorated equally with advancing age. Methods: Vibration detection thresholds for two frequencies of vibration (30 Hz and 200 Hz) were determined using a method of limits protocol, in two groups of healthy adults, one group aged 17 to 27 years and the other aged 55 to 90 years. Sinusoidal vibrations were generated by a computer and delivered to the skin surface via the probe (diameter = 2 mm) of a mechanical vibrator. Four skin sites (palmar surface of the tip of the middle finger, volar surface of the forearm, lateral aspect of the shoulder, cheek just caudal to the zygoma) were tested. Results: The fingertip was the most sensitive site for vibrotactile detection at both frequencies in a substantial majority of subjects. The older group of subjects showed significantly higher detection thresholds for both frequencies at all sites, except the fingertip, when compared to young subjects. Conclusion: The study confirms the deterioration of vibrotactile acuity at several skin sites previously reported in the literature. However, there appears to be no significant reduction in vibrotactile detection at the fingertips in older subjects. This may reflect the high receptor density of this area, or the functional importance of vibrotactile sensibility of the fingertips or some combination of both of these factors
Star Formation in the Field and Clusters of NGC 5253
We investigate the star formation history of both the bright star clusters
and the diffuse `field star' population in the dwarf starburst galaxy NGC 5253
using STIS longslit ultraviolet spectroscopy. Our slit covers a physical area
of 370 x 1.6 pc and includes 8 apparent clusters and several inter-cluster
regions of diffuse light which we take to be the field. The diffuse light
spectrum lacks the strong O-star wind features which are clearly visible in
spectra of the brightest clusters. This discrepancy provides compelling
evidence that the diffuse light is not reflected light from nearby clusters,
but originates in a UV-bright field star population, and it raises the issue of
whether the star formation process may be operating differently in the field
than in clusters. We compare our spectra to STARBURST99 evolutionary synthesis
models which incorporate a new low metallicity atlas of O-star spectra. We
favor a scenario which accounts for the paucity of O-stars in the field without
requiring the field to have a different IMF than the clusters: stellar clusters
form continuously and then dissolve on ~10 Myr timescales and disperse their
remaining stars into the field. We consider the probable contribution of an
O-star deficient field population to the spatially unresolved spectra of high
redshift galaxies. (Abridged)Comment: 26 pages, 10 figures, accepted for publication in Ap
The space physics environment data analysis system (SPEDAS)
With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (www.spedas.org), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have “crib-sheets,” user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer’s Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its “modes of use” with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans.Published versio
First Irish pregnancies after IVF with gestational carrier
In this report, our early experience with screening, monitoring and coordinating IVF utilising gestational carrier treatment is described. Although congenital and iatrogenic etiologies for uterine factor infertility manifest distinctly different reasons for considering a gestational carrier approach, we outline a unified management strategy for both conditions. One patient had congenital absence of the uterus and proximal vagina (Mayer-Rokitansky-Kuster-Hauser syndrome variant), while another patient presented post-hysterectomy and adjuvant brachytherapy for invasive squamous cervical carcinoma. Conception was established for both patients, the first pregnancies to be achieved using an IVF/gestational carrier technique in Ireland. As demonstrated here, selected patients with at least one intact ovary who suffer from uterine factor infertility can be excellent candidates for IVF with embryo transfer to a carefully screened gestational carrier. The role of individual and group counselling is reviewed; professional legal advice is prudent in complex cases
Physical and chemical conditions in methanol maser selected hot-cores and UCHII regions
We present the results of a targeted 3-mm spectral line survey towards the
eighty-three 6.67 GHz methanol maser selected star forming clumps observed by
Purcell et al. 2006. In addition to the previously reported measurements of
HCO+ (1 - 0), H13CO+ (1 - 0), and CH3CN (5 - 4) & (6 -5), we used the Mopra
antenna to detect emission lines of N2H+ (1 - 0), HCN (1 - 0) and HNC (1 - 0)
towards 82/83 clumps (99 per cent), and CH3OH (2 - 1) towards 78/83 clumps (94
per cent). The molecular line data have been used to derive virial and LTE
masses, rotational temperatures and chemical abundances in the clumps, and
these properties have been compared between sub-samples associated with
different indicators of evolution. The greatest differences are found between
clumps associated with 8.6 GHz radio emission, indicating the presence of an
Ultra-Compact HII region, and `isolated' masers (without associated radio
emission), and between clumps exhibiting CH3CN emission and those without. In
particular, thermal CH3OH is found to be brighter and more abundant in
Ultra-Compact HII (UCHII) regions and in sources with detected CH3CN, and may
constitute a crude molecular clock in single dish observations. Clumps
associated with 8.6 GHz radio emission tend to be more massive and more
luminous than clumps without radio emission. This is likely because the most
massive clumps evolve so rapidly that a Hyper-Compact HII or UCHII region is
the first visible tracer of star-formation. The gas-mass to sub-mm/IR
luminosity relation for the combined sample was found to be L proportional to
M**0.68, considerably shallower than expected for massive main-sequence stars
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