326 research outputs found
Photometric monitoring of the doubly imaged quasar UM673: possible evidence for chromatic microlensing
We present the results of two-band CCD photometric monitoring of the
gravitationally lensed quasar Q 0142-100 (UM 673).The data, obtained at ESO-La
Silla with the 1.54 m Danish telescope in the Gunn i-band (October 1998 -
September 1999) and in the Johnson V-band (October 1998 to December 2001), were
analyzed using three different photometric methods. The light-curves obtained
with all methods show variations, with a peak-to-peak amplitude of 0.14
magnitude in . Although it was not possible to measure the time delay
between the two lensed QSO images, the brighter component displays possible
evidence for microlensing: it becomes bluer as it gets brighter, as expected
under the assumption of differential magnification of a quasar accretion diskComment: Accepted for publication in Astronomy & Astrophysics; 8 pages, 7
figure
The mediating role of alliances in the international market orientation-performance relationship of SMEs
Enhancing international performance is a critical issue for internationalizing SMEs. Researchers have suggested that firms need to enhance their international market orientation (IMO) in order to increase performance; but the way this association works is rather unexplored. This is important for both theory and practice since its exploration would lead to a better understanding on how SMEs can effectively enhance their international performance. In this paper, we examine whether alliances through which firms access knowledge and resources play a mediating role in the IMO and performance relationship. We investigate our hypothesis on a sample of 94 companies based in the United Arab Emirates. We discovered that alliances mediate the IMO-performance relationship and we extend the knowledge- and resource-based views of the firm
Recommended from our members
Uncertainty analysis of heat flux measurements estimated using a one-dimensional, inverse heat-conduction program.
The measurement of heat flux in hydrocarbon fuel fires (e.g., diesel or JP-8) is difficult due to high temperatures and the sooty environment. Un-cooled commercially available heat flux gages do not survive in long duration fires, and cooled gages often become covered with soot, thus changing the gage calibration. An alternate method that is rugged and relatively inexpensive is based on inverse heat conduction methods. Inverse heat-conduction methods estimate absorbed heat flux at specific material interfaces using temperature/time histories, boundary conditions, material properties, and usually an assumption of one-dimensional (1-D) heat flow. This method is commonly used at Sandia.s fire test facilities. In this report, an uncertainty analysis was performed for a specific example to quantify the effect of input parameter variations on the estimated heat flux when using the inverse heat conduction method. The approach used was to compare results from a number of cases using modified inputs to a base-case. The response of a 304 stainless-steel cylinder [about 30.5 cm (12-in.) in diameter and 0.32-cm-thick (1/8-in.)] filled with 2.5-cm-thick (1-in.) ceramic fiber insulation was examined. Input parameters of an inverse heat conduction program varied were steel-wall thickness, thermal conductivity, and volumetric heat capacity; insulation thickness, thermal conductivity, and volumetric heat capacity, temperature uncertainty, boundary conditions, temperature sampling period; and numerical inputs. One-dimensional heat transfer was assumed in all cases. Results of the analysis show that, at the maximum heat flux, the most important parameters were temperature uncertainty, steel thickness and steel volumetric heat capacity. The use of a constant thermal properties rather than temperature dependent values also made a significant difference in the resultant heat flux; therefore, temperature-dependent values should be used. As an example, several parameters were varied to estimate the uncertainty in heat flux. The result was 15-19% uncertainty to 95% confidence at the highest flux, neglecting multidimensional effects
Study of DDO 68: nearest candidate for a young galaxy?
We present the results of optical spectroscopy and imaging with the SAO 6m
telescope for the dwarf galaxy DDO 68 (UGC 5340 = VV 542), falling into the
region of very low density of luminous (L > L*) galaxies (Lynx-Cancer void).
Its deep images in V,R bands and in the narrow H-alpha-filter show that the
galaxy has the very irregular morphology, with a long curved tail on the South
and a ring-like structure at the Northern edge. The latter consists of 5
separate regions, in three of which we could measure O/H by the classical T_e
method. Their weighted mean oxygen abundance corresponds to
12+log(O/H)=7.21+-0.03, coincident within uncertainties with those for IZw18.
The (V-R) colour of DDO 68 is rather blue all over the galaxy, indicating the
youth of its stellar populations. Comparing the (V-R)_0 colour of the
underlying exponential disk of 0.12+-0.04 with the PEGASE.2 models for the
evolving stellar clusters, we give the first estimate of the ages of the oldest
stellar population, which needs confirmation by the other colours and the
photometry of resolved stars. These ages are in the range of 200-900 Myr for
continuous star formation law, and 100-115 Myr for the instantaneous starburst.
We discuss the properties and the possible youth of this nearby object (2.3
times closer than the famous young galaxy IZw18) in the context of its atypical
environment.Comment: 13 pages, including 7 tables and 3 postscript figures. Accepted for
publication in Astron.Astrophys. Small language corrections are made after
the A&A Language Edito
A multi-wavelength survey of AGN in the XMM-LSS field: I. Quasar selection via the KX technique
AIMS: We present a sample of candidate quasars selected using the
KX-technique. The data cover 0.68 deg^2 of the X-ray Multi-Mirror (XMM)
Large-Scale Structure (LSS) survey area where overlapping multi-wavelength
imaging data permits an investigation of the physical nature of selected
sources. METHODS: The KX method identifies quasars on the basis of their
optical (R and z') to near-infrared (Ks) photometry and point-like morphology.
We combine these data with optical (u*,g'r',i',z') and mid-infrared (3.6-24
micron) wavebands to reconstruct the spectral energy distributions (SEDs) of
candidate quasars. RESULTS: Of 93 sources selected as candidate quasars by the
KX method, 25 are classified as quasars by the subsequent SED analysis.
Spectroscopic observations are available for 12/25 of these sources and confirm
the quasar hypothesis in each case. Even more, 90% of the SED-classified
quasars show X-ray emission, a property not shared by any of the false
candidates in the KX-selected sample. Applying a photometric redshift analysis
to the sources without spectroscopy indicates that the 25 sources classified as
quasars occupy the interval 0.7 < z < 2.5. The remaining 68/93 sources are
classified as stars and unresolved galaxies.Comment: 13 pages, 9 figures, A&A 494, p. 579-589. Replaced with published
version. Fig. 9 in first astro-ph submission has been update
Endoscopic resection of giant lipoma mimicking colonic neoplasm initially presenting with massive haemorrhage: a case report
Lipomas of the colon are benign tumors that rarely occur. Their size ranges from 2 mm to several cm. They are usually asymptomatic but occasionally they present with clinical manifestations depending on tumor size, localization and complications, which often lead to diagnostic difficulty. A 40-year-old man presented with massive rectal haemorrhage. During colonoscopy a giant polyp of over 50 mm in its bigger diameter, with a thick stalk of 2 cm, located in the transverse colon, was revealed. Endoscopic resection was performed with success. Histologic examination demonstrated a giant lipoma. In this report discussion over endoscopic resection of colonic lipomas mimicking neoplasms is also performed
Strange Quark Contributions to Parity-Violating Asymmetries in the Forward G0 Electron-Proton Scattering Experiment
We have measured parity-violating asymmetries in elastic electron-proton
scattering over the range of momentum transfers 0.12 < Q^2 < 1.0 GeV^2. These
asymmetries, arising from interference of the electromagnetic and neutral weak
interactions, are sensitive to strange quark contributions to the currents of
the proton. The measurements were made at JLab using a toroidal spectrometer to
detect the recoiling protons from a liquid hydrogen target. The results
indicate non-zero, Q^2 dependent, strange quark contributions and provide new
information beyond that obtained in previous experiments.Comment: 5 pages, 2 figure
Effect of low tidal volume ventilation on lung function and inflammation in mice
<p>Abstract</p> <p>Background</p> <p>A large number of studies have investigated the effects of high tidal volume ventilation in mouse models. In contrast data on very short term effects of low tidal volume ventilation are sparse. Therefore we investigated the functional and structural effects of low tidal volume ventilation in mice.</p> <p>Methods</p> <p>38 Male C57/Bl6 mice were ventilated with different tidal volumes (Vt 5, 7, and 10 ml/kg) without or with application of PEEP (2 cm H<sub>2</sub>O). Four spontaneously breathing animals served as controls. Oxygen saturation and pulse rate were monitored. Lung function was measured every 5 min for at least 30 min. Afterwards lungs were removed and histological sections were stained for measurement of infiltration with polymorphonuclear leukocytes (PMN). Moreover, mRNA expression of macrophage inflammatory protein (MIP)-2 and tumor necrosis factor (TNF)α in the lungs was quantified using real time PCR.</p> <p>Results</p> <p>Oxygen saturation did not change significantly over time of ventilation in all groups (P > 0.05). Pulse rate dropped in all groups without PEEP during mechanical ventilation. In contrast, in the groups with PEEP pulse rate increased over time. These effects were not statistically significant (P > 0.05). Tissue damping (G) and tissue elastance (H) were significantly increased in all groups after 30 min of ventilation (P < 0.05). Only the group with a Vt of 10 ml/kg and PEEP did not show a significant increase in H (P > 0.05). Mechanical ventilation significantly increased infiltration of the lungs with PMN (P < 0.05). Expression of MIP-2 was significantly induced by mechanical ventilation in all groups (P < 0.05). MIP-2 mRNA expression was lowest in the group with a Vt of 10 ml/kg + PEEP.</p> <p>Conclusions</p> <p>Our data show that very short term mechanical ventilation with lower tidal volumes than 10 ml/kg did not reduce inflammation additionally. Formation of atelectasis and inadequate oxygenation with very low tidal volumes may be important factors. Application of PEEP attenuated inflammation.</p
- …