255 research outputs found
New investigations into the stability of Mesna using LC-MS/MS and NMR
Both LC-MS/MS and NMR analyses confirmed the instability of Mesna and its conversion into Dimesna
INTEGRAL/SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane
The center of our Galaxy is a known strong source of electron-positron
511-keV annihilation radiation. Thus far, however, there have been no reliable
detections of annihilation radiation outside of the central radian of our
Galaxy. One of the primary objectives of the INTEGRAL (INTErnational Gamma-RAy
Astrophysics Laboratory) mission, launched in Oct. 2002, is the detailed study
of this radiation. The Spectrometer on INTEGRAL (SPI) is a high resolution
coded-aperture gamma-ray telescope with an unprecedented combination of
sensitivity, angular resolution and energy resolution. We report results from
the first 10 months of observation. During this period a significant fraction
of the observing time was spent in or near the Galactic Plane. No positive
annihilation flux was detected outside of the central region (|l| > 40 deg) of
our Galaxy. In this paper we describe the observations and data analysis
methods and give limits on the 511-keV flux.Comment: Accepted for publication in the Astrophysical Journal. 13 pages, 3
figure
The experience of long-term opiate maintenance treatment and reported barriers to recovery: A qualitative systematic review
Background/Aim: To inform understanding of the experience of long-term opiate maintenance and identify barriers to recovery. Methods: A qualitative systematic review. Results: 14 studies in 17 papers, mainly from the USA (65%), met inclusion criteria, involving 1,088 participants. Studies focused on methadone prescribing. Participants reported stability; however, many disliked methadone. Barriers to full recovery were primarily âinward focused'. Conclusion: This is the first review of qualitative literature on long-term maintenance, finding that universal service improvements could be made to address reported barriers to recovery, including involving ex-users as positive role models, and increasing access to psychological support. Treatment policies combining harm minimisation and abstinence-orientated approaches may best support individualised recovery
Sequence of two gonadotropin releasing hormones from tunicate suggest an important role of conformation in receptor activation
AbstractThe primary structure of two forms of gonadotropin releasing hormone (GnRH) from tunicate (Chelyosoma productum) have been determined based on mass spectrometric and chemical sequence analyses. The peptides, tunicate GnRH-I and -II, contain features unprecedented in vertebrate GnRH. Tunicate GnRH-I contains a putative salt bridge between Asp5 and Lys8. A GnRH analog containing a lactam bridge between Asp5 and Lys8 was found to increase release of estradiol compared with that of the native tunicate GnRH-I and -II. Tunicate GnRH-II contains a cysteine residue and was isolated as a dimeric peptide. These motifs suggest that the conformation plays an important role in receptor activation
Swift observations of the 2006 outburst of the recurrent nova RS Ophiuchi: I. Early X-ray emission from the shocked ejecta and red giant wind
RS Ophiuchi began its latest outburst on 2006 February 12. Previous outbursts
have indicated that high velocity ejecta interact with a pre-existing red giant
wind, setting up shock systems analogous to those seen in Supernova Remnants.
However, in the previous outburst in 1985, X-ray observations did not commence
until 55 days after the initial explosion. Here we report on Swift observations
covering the first month of the 2006 outburst with the Burst Alert (BAT) and
X-ray Telescope (XRT) instruments. RS Oph was clearly detected in the BAT 14-25
keV band from t=0 to days. XRT observationsfrom 0.3-10 keV, started at
3.17 days after outburst. The rapidly evolving XRT spectra clearly show the
presence of both line and continuum emission which can be fitted by thermal
emission from hot gas whose characteristic temperature, overlying absorbing
column, , and resulting unabsorbed total flux decline monotonically
after the first few days. Derived shock velocities are in good agreement with
those found from observations at other wavelengths. Similarly, is in
accord with that expected from the red giant wind ahead of the forward shock.
We confirm the basic models of the 1985 outburst and conclude that standard
Phase I remnant evolution terminated by days and the remnant then
rapidly evolved to display behaviour characteristic of Phase III. Around t=26
days however, a new, luminous and highly variable soft X-ray source began to
appear whose origin will be explored in a subsequent paper.Comment: 20 pages, 4 figures (2 updated), accepted by Ap
INTEGRAL/SPI Limits on Electron-Positron Annihilation Radiation from the Galactic Plane
The center of our Galaxy is a known strong source of electron-positron 511 keV annihilation radiation. Thus far, however, there have been no reliable detection of annihilation radiation outside of the central radian of our Galaxy. One of the primary objectives of the INTEGRAL (International Gamma-Ray Astrophysics Laboratory mission, resolution, coded-apeture gamma-ray telescope with an unprecedented combination of sensitivity, angular resolution, and energy resolution. We resport results from the first 10 months of observation. During this period a significant fraction of the observing time was spent in or near the Galactic plan. No positive annihilation flux was detected outside of the central regin ( l \u3e 40°) of our Galaxy. In this paper we describe observation and data analysis method and give limits on the 511 keV flu
Gamma-Ray Emission Concurrent with the Nova in the Symbiotic Binary V407 Cygni
Novae are thermonuclear explosions on a white dwarf surface fueled by mass
accreted from a companion star. Current physical models posit that shocked
expanding gas from the nova shell can produce X-ray emission but emission at
higher energies has not been widely expected. Here, we report the Fermi Large
Area Telescope detection of variable gamma-ray (0.1-10 GeV) emission from the
recently-detected optical nova of the symbiotic star V407 Cygni. We propose
that the material of the nova shell interacts with the dense ambient medium of
the red giant primary, and that particles can be accelerated effectively to
produce pi0 decay gamma-rays from proton-proton interactions. Emission
involving inverse Compton scattering of the red giant radiation is also
considered and is not ruled out.Comment: 38 pages, includes Supplementary Online Material; corresponding
authors: C.C. Cheung, A.B. Hill, P. Jean, S. Razzaque, K.S. Woo
INTEGRAL/SPI ground calibration
Three calibration campaigns of the spectrometer SPI have been performed
before launch in order to determine the instrument characteristics, such as the
effective detection area, the spectral resolution and the angular resolution.
Absolute determination of the effective area has been obtained from simulations
and measurements. At 1 MeV, the effective area is 65 cm^2 for a point source on
the optical axis, the spectral resolution ~2.3 keV. The angular resolution is
better than 2.5 deg and the source separation capability about 1 deg. Some
temperature dependant parameters will require permanent in-flight calibration.Comment: 9 pages, 12 figures, 2 tables. Accepted for publication in A&AL
(INTEGRAL Special issue
Calibration of the Spectrometer aboard the INTEGRAL satellite
SPI, the Spectrometer on board the ESA INTEGRAL satellite, to be launched in
October 2002, will study the gamma-ray sky in the 20 keV to 8 MeV energy band
with a spectral resolution of 2 keV for photons of 1 MeV, thanks to its 19
germanium detectors spanning an active area of 500 cm2. A coded mask imaging
technique provides a 2 deg angular resolution. The 16 deg field of view is
defined by an active BGO veto shield, furthermore used for background
rejection. In April 2001 the flight model of SPI underwent a one-month
calibration campaign at CEA in Bruy\`eres le Ch\^atel using low intensity
radioactive sources and the CEA accelerator for homogeneity measurements and
high intensity radioactive sources for imaging performance measurements. After
integration of all scientific payloads (the spectrometer SPI, the imager IBIS
and the monitors JEM-X and OMC) on the INTEGRAL satellite, a cross-calibration
campaign has been performed at the ESA center in Noordwijk. A set of sources
has been placed in the field of view of the different instruments in order to
compare their performances and determine their mutual influence. Some of those
sources had already been used in Bruy\`eres during the SPI standalone test. For
the lowest energy band calibration an X-ray generator has been used. We report
on the scientific goals of this calibration activity, and present the
measurements performed as well as some preliminary results.Comment: 12 pages, 19 figures, Published in Proceedings of SPIE conference,
24-28 August 2002, Waikoloa, Hawaii, US
- âŠ