833 research outputs found
A Faddeev Calculation for Pentaquark in Diquark Picture with Nambu-Jona-Lasinio Type Interaction
A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark
in the diquark picture of Jaffe and Wilczek in which is a
diquark-diquark- three-body system.
Nambu-Jona-Lasinio (NJL) model is used to calculate the lowest order diagrams
in the two-body scatterings of and . With the use of coupling
constants determined from the meson sector, we find that
interaction is attractive while interaction is repulsive, and there is no
bound pentaquark state. A bound pentaquark can only be
obtained with unphysically strong vector mesonic coupling constants.Comment: 4 pages, 4 figure
Rapidly quantifying the relative distention of a human bladder
A device and method was developed to rapidly quantify the relative distention of the bladder of a human subject. An ultrasonic transducer is positioned on the human subject near the bladder. A microprocessor controlled pulser excites the transducer by sending an acoustic wave into the human subject. This wave interacts with the bladder walls and is reflected back to the ultrasonic transducer where it is received, amplified, and processed by the receiver. The resulting signal is digitized by an analog to digital converter, controlled by the microprocessor again, and is stored in data memory. The software in the microprocessor determines the relative distention of the bladder as a function of the propagated ultrasonic energy. Based on programmed scientific measurements and the human subject's past history as contained in program memory, the microprocessor sends out a signal to turn on any or all of the available alarms. The alarm system includes and audible alarm, the visible alarm, the tactile alarm, and the remote wireless alarm
Rapidly quantifying the relative distention of a human bladder
A device and method of rapidly quantifying the relative distention of the bladder in a human subject are disclosed. The ultrasonic transducer which is positioned on the subject in proximity to the bladder is excited by a pulser under the command of a microprocessor to launch an acoustic wave into the patient. This wave interacts with the bladder walls and is reflected back to the ultrasonic transducer, when it is received, amplified and processed by the receiver. The resulting signal is digitized by an analog-to-digital converter under the command of the microprocessor and is stored in the data memory. The software in the microprocessor determines the relative distention of the bladder as a function of the propagated ultrasonic energy; and based on programmed scientific measurements and individual, anatomical, and behavioral characterists of the specific subject as contained in the program memory, sends out a signal to turn on any or all of the audible alarm, the visible alarm, the tactile alarm, and the remote wireless alarm
X-ray spectroscopy of the ADC source X1822-371 with Chandra and XMM-Newton
The eclipsing low-mass X-ray binary X1822-371 is the prototype of the
accretion disc corona (ADC) sources. We analyse two Chandra observations and
one XMM-Newton observation to study the discrete features and their variation
as a function of the orbital phase, deriving constraints on the temperature,
density, and location of the plasma responsible for emission lines. The HETGS
and XMM/Epic-pn observed X1822-371 for 140 and 50 ks, respectively. We
extracted an averaged spectrum and five spectra from five selected
orbital-phase intervals that are 0.04-0.25, 0.25-0.50, 0.50-0.75, 0.75-0.95,
and, finally, 0.95-1.04; the orbital phase zero corresponds to the eclipse
time. All spectra cover the energy band between 0.35 and 12 keV. We confirm the
presence of local neutral matter that partially covers the X-ray emitting
region; the equivalent hydrogen column is cm and the
covered fraction is about 60-65%. We identify emission lines from highly
ionised elements, and a prominent fluorescence iron line associated with a
blending of FeI-FeXV resonant transitions. The transitions of He-like ions show
that the intercombination dominates over the forbidden and resonance lines. The
line fluxes are the highest during the orbital phases between 0.04 and 0.75. We
discuss the presence of an extended, optically thin corona with optical depth
of about 0.01 that scatters the X-ray photons from the innermost region into
the line of sight. The photoionised plasma producing most of the observed lines
is placed in the bulge at the outer radius of the disc distant from the central
source of cm. The OVII and the fluorescence iron line are
probably produced in the photoionised surface of the disc at inner radii.
(Abridged)Comment: 18 pages including 12 figures. Accepted for publication in A&
A BeppoSAX observation of the super-soft source CAL87
We report on a BeppoSAX Concentrator Spectrometer observation of the
super-soft source (SSS) CAL87. The X-ray emission in SSS is believed to arise
from nuclear burning of accreted material on the surface of a white dwarf (WD).
An absorbed blackbody spectral model gives a chi^2_v of 1.18 and a temperature
of 42 +/- ^13 _11 eV. However, the derived luminosity and radius are greater
than the Eddington limit and radius of a WD. Including an O viii edge at 0.871
keV gives a significantly better fit (at > 95% confidence) and results in more
realistic values of the source luminosity and radius. We also fit WD atmosphere
models to the CAL87 spectrum. These also give reasonable bolometric
luminosities and radii in the ranges 2.7-4.8 10^{36} erg/s and 8-20 10^7 cm,
respectively. These results support the view that the X-ray emission from CAL87
results from nuclear burning in the atmosphere of a WD.Comment: 4 pages. Accepted for publication in A&A (Letters
An extreme, blueshifted iron line profile in the Narrow Line Seyfert 1 PG 1402+261; an edge-on accretion disk or highly ionized absorption?
We report on a short XMM-Newton observation of the radio-quiet Narrow Line
Seyfert 1 PG 1402+261. The EPIC X-ray spectrum of PG 1402+261 shows a strong
excess of counts between 6-9 keV in the rest frame. This feature can be modeled
by an unusually strong (equivalent width 2 keV) and very broad (FWHM velocity
of 110000 km/s) iron K-shell emission line. The line centroid energy at 7.3 keV
appears blue-shifted with respect to the iron Kalpha emission band between
6.4-6.97 keV, while the blue-wing of the line extends to 9 keV in the quasar
rest frame. The line profile can be fitted by reflection from the inner
accretion disk, but an inclination angle of >60 deg is required to model the
extreme blue-wing of the line. Furthermore the extreme strength of the line
requires a geometry whereby the hard X-ray emission from PG 1402+261 above 2
keV is dominated by the pure-reflection component from the disk, while little
or none of the direct hard power-law is observed. Alternatively the spectrum
above 2 keV may instead be explained by an ionized absorber, if the column
density is sufficiently high (N_H > 3 x 10^23 cm^-2) and if the matter is
ionized enough to produce a deep (tau~1) iron K-shell absorption edge at 9 keV.
This absorber could originate in a large column density, high velocity outflow,
perhaps similar to those which appear to be observed in several other high
accretion rate AGN. Further observations, especially at higher spectral
resolution, are required to distinguish between the accretion disk reflection
or outflow scenarios.Comment: Accepted for publication in ApJ (18 pages, 5 figures, 1 table
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