7,213 research outputs found
Protein tyrosine kinase but not protein kinase C inhibition blocks receptor induced alveolar macrophage activation
The selective enzyme inhibitors genistein and Ro 31-8220 were used to assess the importance of protein tyrosine kinase (PTK) and protein kinase C (PKC), respectively, in N-formyl-methionyl-leucyl-phenylalanine (FMLP) induced generation of superoxide anion and thromboxane B2 (TXB2) in guinea-pig alveolar macrophages (AM). Genistein (3–100 μM) dose dependently inhibited FMLP (3 nM) induced superoxide generation in non-primed AM and TXB2 release in non-primed or in lipopolysaccharide (LPS) (10 ng/ml) primed AM to a level > 80% but had litle effect up to 100 μM on phorbol myristate acetate (PMA) (10 nM) induced superoxide release. Ro 31-8220 inhibited PMA induced superoxide generation (IC50 0.21 ± 0.10 μM) but had no effect on or potentiated (at 3 and 10 μM) FMLP responses in non-primed AM. In contrast, when present during LPS priming as well as during FMLP challenge Ro 31-8220 (10 μM) inhibited primed TXB2 release by > 80%. The results indicate that PTK activation is required for the generation of these inflammatory mediators by FMLP in AM. PKC activation appears to be required for LPS priming but not for transducing the FMLP signal; rather, PKC activation may modulate the signal by a negative feedback mechanism
A search in the COS-B data base for correlated time variability in regions containing objects of interest
As is well known, association of the gamma-ray sources with celestial objects is, in general, difficult on a pure positional basis, while correlated time variability could obviously provide such proof. This technique can be employed on regions of the gamma-ray sky containing interesting objects of known variability at some wavelength even in the absence of a recognized gamma-ray excess with the aim to extract a weak but predictable signal from the surrounding noise. This technique is applied here on a longer variability time scale, generally of the order of days. Photons coming from the sky regions centered on the various celestial objects considered were selected with energies 100 MeV and with arrival directions within an energy-dependent area of radius of approx 6 deg at 100 MeV. In order to construct a time profile of such photons, their arrival times were grouped in bins of dimensions defined by the available photons number and by the value of the period searched for
Graviton n-point functions for UV-complete theories in Anti-de Sitter space
We calculate graviton n-point functions in an anti-de Sitter black brane
background for effective gravity theories whose linearized equations of motion
have at most two time derivatives. We compare the n-point functions in Einstein
gravity to those in theories whose leading correction is quadratic in the
Riemann tensor. The comparison is made for any number of gravitons and for all
physical graviton modes in a kinematic region for which the leading correction
can significantly modify the Einstein result. We find that the n-point
functions of Einstein gravity depend on at most a single angle, whereas those
of the corrected theories may depend on two angles. For the four-point
functions, Einstein gravity exhibits linear dependence on the Mandelstam
variable s versus a quadratic dependence on s for the corrected theory.Comment: 29 page
The XMM-Newton EPIC X-ray Light Curve Analysis of WR 6
We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet
star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the
results of spectral analysis, this follow-up highlights the X-ray variability
clearly detected in all four pointings. However, phased light curves fail to
confirm obvious cyclic behavior on the well-established 3.766 d period widely
found at longer wavelengths. The data are of such quality that we were able to
conduct a search for "event clustering" in the arrival times of X-ray photons.
However, we fail to detect any such clustering. One possibility is that X-rays
are generated in a stationary shock structure. In this context we favor a
co-rotating interaction region (CIR) and present a phenomenological model for
X-rays from a CIR structure. We show that a CIR has the potential to account
simultaneously for the X-ray variability and constraints provided by the
spectral analysis. Ultimately, the viability of the CIR model will require both
intermittent long-term X-ray monitoring of WR 6 and better physical models of
CIR X-ray production at large radii in stellar winds.Comment: to appear in Ap
Grass and Forage Improvement: Temperate Forages
Key points
1. Plant breeding has contributed significantly to the development of effective grassland production systems.
2. New technologies offer enhanced precision in breeding and access to wider genetic variation.
3. The requirement for more sustainable production systems will require genetic improvements in complex traits where the use of new technology will be vital
Grass and Forage Improvement: Temperate Forages
Plant breeding has contributed significantly to the development of effective grassland production systems. New technologies offer enhanced precision in breeding and access to wider genetic variation. The requirement for more sustainable production systems will require genetic improvements in complex traits where the use of new technology will be vital
The EXOSAT medium-energy slew survey catalog
We present a catalog of X-ray sources observed during slew maneuvers by the
Medium Energy Detector Array onboard the EXOSAT Observatory. The EXOSAT Medium
Energy slew-survey catalog (EXMS) provides a unique record of the 1--8 keV
X-ray sky between 1983 and 1986. 98% of the sky was observed, with 85%
receiving an exposure of >60 s. 1210 sources were detected. By comparing these
source positions with other catalogs, identifications are given for 992
detections (82% of the sample). These identifications consist of 250 distinct
objects, including 95 different X-ray binary systems, and 14 different AGN. A
further 58 detections have multiple candidates, while 160 detections remain
unidentified. Collimator transmission corrected 1-8 keV count rates are given
for the identified sources, together with raw count rates for the other
detections. The construction of the EXMS and the checks performed to ensure the
validity of the derived source properties are discussed. A publically available
version of this catalog is maintained on the EXOSAT database and archive system
(telnet://[email protected]).Comment: 52 pages. 22 Figures. To be published in A&AS. For more information,
see http://astro.estec.esa.nl/SA-general/Projects/Exosat/exmsintro.htm
Radio-frequency dressed lattices for ultracold alkali atoms
Ultracold atomic gases in periodic potentials are powerful platforms for exploring quantum physics in regimes dominated by many-body effects as well as for developing applications that benefit from quantum mechanical effects. Further advances face a range of challenges including the realization of potentials with lattice constants smaller than optical wavelengths as well as creating schemes for effective addressing and manipulation of single sites. In this paper we propose a dressed-based scheme for creating periodic potential landscapes for ultracold alkali atoms with the capability of overcoming such difficulties. The dressed approach has the advantage of operating in a low-frequency regime where decoherence and heating effects due to spontaneous emission do not take place. These results highlight the possibilities of atom-chip technology in the future development of quantum simulations and quantum technologies, and provide a realistic scheme for starting such an exploration
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