11,683 research outputs found
Thruster maintenance system Patent
System for removing and repairing spacecraft control thrusters by use of portable air lock
Periodicities In The X-Ray Intensity Variations of TV Columbae: An Intermediate Polar
We present results from a temporal analysis of the longest and the most
sensitive X-ray observations of TV Columbae--an intermediate polar. The
observations were carried out with the RXTE PCA, ROSAT PSPC, and ASCA. Data
were analyzed using a 1-dimensional CLEAN and Bayesian algorithms. The presence
of a nearly sinusoidal modulation due to the spin of the white dwarf is seen
clearly in all the data, confirming the previous reports based on the EXOSAT
data. An improved period of 1909.7+/-2.5s is derived for the spin from the RXTE
data.The binary period of 5.5hr is detected unambiguously in X-rays for the
first time. Several side-bands due to the interaction of these periods are
observed in the power spectra, thereby suggesting contributions from both the
disk-fed and the stream-fed accretion for TV Col. The accretion disk could
perhaps be precessing as side-bands due to the influence of 4 day period on the
orbital period are seen. The presence of a significant power at certain
side-bands of the spin frequency indicates that the emission poles are
asymmetrically located. The strong power at the orbital side-bands seen in both
the RXTE and ROSAT data gives an indication for an absorption site fixed in the
orbital frame. Both the spin and the binary modulation are found to be
energy-dependent. Increased hardness ratio during a broad dip in the intensity
at binary phase of 0.75--1.0 confirms the presence of a strong attenuation due
to additional absorbers probably from an impact site of the accretion stream
with the disk or magnetosphere. Hardness ratio variations and the energy
dependent modulation depth during the spin modulation can be explained by
partially covered absorbers in the path of X-ray emission region in the
accretion stream.Comment: 34 pages, including 12 figures, Accepted for publication in
Astronomical Journal, scheduled for January 2004 issue (vol. 127
VAMP: A computer program for calculating volume, area, and mass properties of aerospace vehicles
A computerized procedure developed for analyzing aerospace vehicles evaluates the properties of elemental surface areas with specified thickness by accumulating and combining them with arbitrarily specified mass elements to form a complete evaluation. Picture-like images of the geometric description are capable of being generated
High mass X-ray binaries in the NIRorbital solutions of two highly obscured systems
The maximum mass of a neutron star (NS) is poorly defined. Theoretical
attempts to define this mass have thus far been unsuccessful. Observational
results currently provide the only means of narrowing this mass range down.
Eclipsing X-ray binary (XRB) pulsar systems are the only interacting binaries
in which the mass of the NS may be measured directly. Only 10 such systems are
known to exist, 6 of which have yielded NS masses in the range 1.06 - 1.86
M.We present the first orbital solutions of two further eclipsing
systems, OAO 1657-415 and EXO 1722-363, whose donor stars have only recently
been identified. Using observations obtained using the VLT/ISAAC NIR
spectrograph, our initial work was concerned with providing an accurate
spectral classification of the two counterpart stars, leading to a consistent
explanation of the mechanism for spin period evolution of OAO 1657-415.
Calculating radial velocities allowed orbital solutions for both systems to be
computed. These are the first accurate determinations of the NS and counterpart
masses in XRB pulsar systems to be made employing NIR spectroscopy.Comment: 5 pages, 3 figures, contribution to the proceedings of "The
multi-wavelength view of hot, massive stars", 39th Li`ege Int. Astroph.
Coll., 12-16 July 201
Parton distribution functions and nuclear EMC effect in a statistical model
A new and simple statistical approach is performed to calculate the parton
distribution functions (PDFs) of the nucleon in terms of light-front kinematic
variables. Analytic expressions of x-dependent PDFs are obtained in the whole x
region. And thereafter, we treat the temperature T as a parameter of the atomic
number A to explain the nuclear EMC effect in the region . We
give the predictions of PDF ratios, and they are very different from those by
other models, thus experiments aiming at measuring PDF ratios are suggested to
provide a discrimination of different models.Comment: 4 pages, no figure; talk given at the 5th International Conference On
Quarks and Nuclear Physics (QNP09), Sep 2009, Beijing Chin
New observations of stratospheric N2O5
The unequivocal detection of N2O5 in the stratosphere was reported by Toon et al. based on measurements of the absorption by the N2O5 bands at 1246 and 1720/cm in solar occulation spectra recorded at sunrise near 47 S latitude by the Atmospheric Trace Molecule Spectroscopy (ATMOS) experiment during the Spacelab 3 (SL3) shuttle mission. Additional measurements and analysis of stratospheric N2O5 derived from the ATMOS/SL3 spectra are reported. The primary results are the detection and measurement of N2O5 absorption at sunset in the lower stratosphere, the inversion of a precise (approximately 10 percent) N2O5 sunrise vertical distribution between 25.5 and 37.5 km altitude, and the identification and measurement of absorption by the N2O5 743/cm band at sunrise. Assuming 4.32 x 10(sup -17) and 4.36 x 10(sup -17)/cm/molecule/sq cm respectively for the integrated intensities of the 1246 and 743/cm bands at stratospheric temperatures, retrieved volume mixing ratios in parts per billion by volume (ppbv) at sunrise (47 S latitude) are 1.32 + or - 0.34 at 37.5 km, 1.53 + or - 0.35 at 35.5 km, 1.63 + or - 0.36 at 33.5 km, 1.60 + or - 0.34 at 31.5 km, 1.43 + or - 0.30 at 29.5 km, 1.15 + or - 0.24 at 27.5 km, and 0.73 + or - 0.15 at 25.5 km. Retrieved VMRs in ppbv at sunset (30 N latitude) are 0.13 + or - 0.05 at 29.5 km, 0.14 + or - 0.05 at 27.5 km, and 0.10 + or - 0.04 at 25.5 km. Quoted error limits (1 sigma) include the error in the assumed band intensities (approximately 20 percent). Within the error limits of the measurements, the inferred mixing ratios at sunrise agree with diurnal photochemical model predictions obtained by two groups using current photochemical data. The measured mixing ratios at sunset are lower than the model predictions with differences of about a factor of 2 at 25 km altitude
OAO1657-415 : A `Missing Link' in High Mass X-ray Binaries?
OAO1657-415 is only the seventh eclipsing X-ray pulsar known and therefore
has the potential to yield only the seventh mass of a neutron star in an X-ray
binary. Here we report photometric and spectroscopic observations of candidates
for the optical counterpart to the system and identify a B6V or B5III star as a
possible companion to the neutron star. We measure the observational parameters
of the star and suggest reasons why OAO1657-415 may be unlike other high mass
X-ray binaries.Comment: 5 pages, 5 figures, to be published in 'Evolution of binary and
multiple star systems', proceedings of conference, Bormi
Remission vs low disease activity: function, quality of life and structural outcomes in the Early Rheumatoid Arthritis Study and Network
Objectives To examine associations between function, quality of life and structural outcomes in patients achieving remission vs low disease activity in early RA. Methods Demographic, clinical and radiographic variables were collected at baseline and then annually from the Early Rheumatoid Arthritis Study (ERAS) and Early Rheumatoid Arthritis Network (ERAN) inception cohorts in routine care from 1986 to 2012. Disease activity was categorized: mean DAS28 score between years 1 and 5: remission [mean remission DAS (mRDAS) <2.6] or low [mean low DAS (mLDAS) 2.6–3.2]; sustained low/remission DAS28 (sLDAS/sRDAS) at years 1 and 2; and sustained Boolean remission (sBR) at years 1 and 2. Changes in HAQ and Short Form 36 Health Survey Questionnaire [SF-36; physical (PCS) and mental (MCS) component score]) and total Sharp van der Heijde (SvdH) scores for each disease activity category were modelled using multi-level models. Covariates included year of onset, age, gender and DMARD use at first visit. Results Of 2701 patients, 562 (21%) were categorized mRDAS, 330 (12%) mLDAS, 279 (10%) sRDAS, 203 (7.5%) sLDAS and 93 (3%) sBR. Patients categorized as mRDAS had increasingly divergent improved HAQ, SF-36 PCS, MCS and total SvdH scores compared with mLDAS (P-values 0.001 to <0.0001, all time points). Patients categorized as sRDAS had better HAQ, SF-36 PCS and MCS scores (P-values 0.05 to <0.0001, all time points) and SvdH scores (P = 0.05, years 3–5) over sLDAS. sBR was associated with better HAQ, and SF-36 PCS and MCS scores over sLDAS (P-values 0.002 to <0.0001, all time points). Conclusion These findings from routine care support ACR/EULAR guidelines that remission is a preferable goal over low disease activity in early RA.Peer reviewedFinal Published versio
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