3,062 research outputs found
Library inventory using a RFID wand: contribution of tag and book specific factors on the read rate
Library inventory using a RFID wand: contribution of tag and book specific factors on the read rate
Purpose Low read rates are a general problem in library inventories. The purpose of this study is to examine the factors that contribute to the success of library inventory by means of a radio-frequency identification (RFID) inventory taker. The factors investigated were tag position, tag orientation, book thickness, tag density (related to thickness of a sequence of books) and position on the shelf. Design/methodology/approach A total of 210 books were placed in eight random permutations on three fixed book shelves. For each configuration, the RFID tags were read forty times. The resulting data were analysed by means of a generalized linear model, relating the combined contribution of tag position, tag orientation, book thickness and position on the bookshelf to the read rate. Findings The tags positioned directly next to the spine were always read, but those near the opening of the book (far from the spine and inventory reader) were not always read. Considering only books with tags near the opening, tag orientation and position on the shelf appeared not to be related to the read rate, while book thickness, thickness over three books and spine tag density appeared to have a small positive contribution to the read rate. Practical implications Low read rates during a library inventory can be prevented by placing the tags near the book spine – the other book specific factors (listed in the previous paragraph) are of little influence. When not scanned during a first sweep, repeated scanning can increase the read rate with 0.15. Originality/value This paper is one of the first to analyse the influence of tag location and book specific factors on the read rate of RFID tags in library books. The experimental approach sets an example for future work
Discovery of long-period variable stars in the very-metal-poor globular cluster M15
We present a search for long-period variable (LPV) stars among giant branch
stars in M15 which, at [Fe/H] ~ -2.3, is one of the most metal-poor Galactic
globular clusters. We use multi-colour optical photometry from the 0.6-m Keele
Thornton and 2-m Liverpool Telescopes. Variability of delta-V ~ 0.15 mag is
detected in K757 and K825 over unusually-long timescales of nearly a year,
making them the most metal-poor LPVs found in a Galactic globular cluster. K825
is placed on the long secondary period sequence, identified for metal-rich
LPVs, though no primary period is detectable. We discuss this variability in
the context of dust production and stellar evolution at low metallicity, using
additional spectra from the 6.5-m Magellan (Las Campanas) telescope. A lack of
dust production, despite the presence of gaseous mass loss raises questions
about the production of dust and the intra-cluster medium of this cluster.Comment: 13 pages, 9 figures, accepted by MNRA
Radiographic and ultrasonographic evaluation of the esophagus in the horse
The purpose of this study was to describe the radiographic and ultrasonographic appearance of the esophagus of ten healthy horses. Contrast radiography showed variations in the long-axis shape of the esophagus at the thoracic inlet. Administration of a large volume contrast medium by intubation showed stasis of contrast material for several minutes in two of the ten horses. The wall thickness of the non-distended esophagus on ultrasound was 2.6 +/- 0.3 mm with significant differences depending on the location. Distention of the esophagus by intubation or by a bolus of water or concentrate resulted in a decrease in wall thickness and it facilitated measuring with less variation. Stasis at the thoracic inlet was seen in five of the ten horses, when a water bolus was administered. Ultrasonographic evaluation of 100g spontaneously swallowed commercial concentrate was better than fluid (water bolus or 2.5mL/kg contrast medium) administration via intubation to assess esophageal motility at the thoracic inlet. Stasis seen at the thoracic inlet after bolus administration by intubation should not be regarded as an abnormal finding, and swallowing, with the subsequent peristaltic wave, has a positive influence on the bolus passage time
The M33 Variable Star Population Revealed by Spitzer
We analyze five epochs of Spitzer Space Telescope/Infrared Array Camera
(IRAC) observations of the nearby spiral galaxy M33. Each epoch covered nearly
a square degree at 3.6, 4.5, and 8.0 microns. The point source catalog from the
full dataset contains 37,650 stars. The stars have luminosities characteristic
of the asymptotic giant branch and can be separated into oxygen-rich and
carbon-rich populations by their [3.6] - [4.5] colors. The [3.6] - [8.0] colors
indicate that over 80% of the stars detected at 8.0 microns have dust shells.
Photometric comparison of epochs using conservative criteria yields a catalog
of 2,923 variable stars. These variables are most likely long-period variables
amidst an evolved stellar population. At least one-third of the identified
carbon stars are variable.Comment: Accepted for publication in ApJ. See published article for full
resolution figures and electronic table
Intense Mass Loss from C-rich AGB Stars at low Metallicity?
We argue that the energy injection of pulsations may be of greater importance
to the mass-loss rate of AGB stars than metallicity, and that the mass-loss
trend with metallicity is not as simple as sometimes assumed. Using our
detailed radiation hydrodynamical models that include dust formation, we
illustrate the effects of pulsation energy on wind properties. We find that the
mass-loss rate scales with the kinetic energy input by pulsations as long as a
dust-saturated wind does not occur, and all other stellar parameters are kept
constant. This includes the absolute abundance of condensible carbon (not bound
in CO), which is more relevant than keeping the C/O-ratio constant when
comparing stars of different metallicity. The pressure and temperature
gradients in the atmospheres of stars, become steeper and flatter,
respectively, when the metallicity is reduced, while the radius where the
atmosphere becomes opaque is typically associated with a higher gas pressure.
This effect can be compensated for by adjusting the velocity amplitude of the
variable inner boundary (piston), which is used to simulate the effects of
pulsation, to obtain models with comparable kinetic-energy input. Hence, it is
more relevant to compare models with similar energy-injections than of similar
velocity amplitude. Since there is no evidence for weaker pulsations in
low-metallicity AGB stars, we conclude that it is unlikely that low-metallicity
C-stars have a lower mass-loss rate, than their more metal-rich counterparts
with similar stellar parameters, as long as they have a comparable amount of
condensible carbon.Comment: 4 pages, 3 figures. Accepted for publication in A&A. Updated after
language editing. Additional typos fixe
Spitzer SAGE-SMC Infrared Photometry of Massive Stars in the Small Magellanic Cloud
We present a catalog of 5324 massive stars in the Small Magellanic Cloud
(SMC), with accurate spectral types compiled from the literature, and a
photometric catalog for a subset of 3654 of these stars, with the goal of
exploring their infrared properties. The photometric catalog consists of stars
with infrared counterparts in the Spitzer, SAGE-SMC survey database, for which
we present uniform photometry from 0.3-24 um in the UBVIJHKs+IRAC+MIPS24 bands.
We compare the color magnitude diagrams and color-color diagrams to those of
the Large Magellanic Cloud (LMC), finding that the brightest infrared sources
in the SMC are also the red supergiants, supergiant B[e] (sgB[e]) stars,
luminous blue variables, and Wolf-Rayet stars, with the latter exhibiting less
infrared excess, the red supergiants being less dusty and the sgB[e] stars
being on average less luminous. Among the objects detected at 24 um are a few
very luminous hypergiants, 4 B-type stars with peculiar, flat spectral energy
distributions, and all 3 known luminous blue variables. We detect a distinct Be
star sequence, displaced to the red, and suggest a novel method of confirming
Be star candidates photometrically. We find a higher fraction of Oe and Be
stars among O and early-B stars in the SMC, respectively, when compared to the
LMC, and that the SMC Be stars occur at higher luminosities. We estimate
mass-loss rates for the red supergiants, confirming the correlation with
luminosity even at the metallicity of the SMC. Finally, we confirm the new
class of stars displaying composite A & F type spectra, the sgB[e] nature of
2dFS1804 and find the F0 supergiant 2dFS3528 to be a candidate luminous blue
variable with cold dust.Comment: 23 pages, 17 figures, 5 tables, accepted for publication in the
Astronomical Journa
Chemical evolution of star clusters
I discuss the chemical evolution of star clusters, with emphasis on old
globular clusters, in relation to their formation histories. Globular clusters
clearly formed in a complex fashion, under markedly different conditions from
any younger clusters presently known. Those special conditions must be linked
to the early formation epoch of the Galaxy and must not have occurred since.
While a link to the formation of globular clusters in dwarf galaxies has been
suggested, present-day dwarf galaxies are not representative of the
gravitational potential wells within which the globular clusters formed.
Instead, a formation deep within the proto-Galaxy or within dark-matter
minihaloes might be favoured. Not all globular clusters may have formed and
evolved similarly. In particular, we may need to distinguish Galactic halo from
Galactic bulge clusters.Comment: 27 pages, 2 figures. To appear as invited review article in a special
issue of the Phil. Trans. Royal Soc. A: Ch. 6 "Star clusters as tracers of
galactic star-formation histories" (ed. R. de Grijs). Fully peer reviewed.
LaTeX, requires rspublic.cls style fil
Rapid Communication: Evidence for the Existence of Complexes between Th(IV) and α-Isosaccharinic Acid under Alkaline Conditions
Evaluation of textile substrates for dispensing synthetic attractants for malaria mosquitoes
Background: The full-scale impact of odour-baited technology on the surveillance, sampling and control of vectors of infectious diseases is partly limited by the lack of methods for the efficient and sustainable dispensing of attractants. In this study we investigated whether locally-available and commonly used textiles are efficient substrates for the release of synthetic odorant blends attracting malaria mosquitoes.
Methods: The relative efficacy of (a) polyester, (b) cotton, (c) cellulose + polyacrylate, and (d) nylon textiles as substrates for dispensing a synthetic odour blend (Ifakara blend 1(IB1)) that attracts malaria mosquitoes was evaluated in western Kenya. The study was conducted through completely randomized Latin square experimental designs under semi-field and field conditions.
Results: Traps charged with IB1-impregnated polyester, cotton and cellulose + polyacrylate materials caught significantly more female Anopheles gambiae sensu stricto (semi-field conditions) and An. gambiae sensu lato (field conditions) mosquitoes than IB1-treated nylon (P = 0.001). The IB1-impregnated cellulose + polyacrylate material was the most attractive to female An. funestus mosquitoes compared to all other dispensing textile substrates (P < 0.001). The responses of female An. funestus mosquitoes to IB1-treated cotton and polyester were equal (P = 0.45). Significantly more female Culex mosquitoes were attracted to IB1-treated cotton than to the other treatments (P < 0.001). Whereas IB1-impregnated cotton and cellulose + polyacrylate material attracted equal numbers of female Mansonia mosquitoes (P = 0.44), the catches due to these two substrates were significantly higher than those associated with the other substrates (P < 0.001).
Conclusion: The number and species of mosquitoes attracted to a synthetic odour blend is influenced by the type of odour-dispensing material used. Thus, surveillance and intervention programmes for malaria and other mosquito vectors using attractive odour baits should select an odour-release material that optimizes the odour blend
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