5,570 research outputs found
The PAX 2 picture processing system
PAX 2 digital picture processing program written in FORTRAN - subroutine annotation
Jet-Induced Nucleosynthesis in Misaligned Microquasars
The jet axes and the orbital planes of microquasar systems are usually
assumed to be approximately perpendicular, eventhough this is not currently an
observational requirement. On the contrary, in one of the few systems where the
relative orientations are well-constrained, V4641Sgr, the jet axis is known to
lie not more than ~36 degrees from the binary plane. Such a jet, lying close to
the binary plane, and traveling at a significant fraction of the speed of light
may periodically impact the secondary star initiating nuclear reactions on its
surface. The integrated yield of such nuclear reactions over the age of the
binary system (less the radiative mass loss) will detectably alter the
elemental abundances of the companion star. This scenario may explain the
anomalously high Li enhancements (roughly ~20-200 times the sun's photospheric
value; or, equivalently, 0.1-1 times the average solar system value) seen in
the companions of some black-hole X-ray binary systems. (Such enhancements are
puzzling since Li nuclei are exceedingly fragile - being easily destroyed in
the interiors of stars - and Li would be expected to be depleted rather than
enhanced there.) Gamma-ray line signatures of the proposed process could
include the 2.22 MeV neutron capture line as well as the 0.478 MeV 7Li*
de-excitation line, both of which may be discernable with the INTEGRAL
satellite if produced in an optically thin region during a large outburst. For
very energetic jets, a relatively narrow neutral pion gamma-decay signature at
67.5 MeV could also be measurable with the GLAST satellite. We argue that about
10-20% of all microquasar systems ought to be sufficiently misaligned as to be
undergoing the proposed jet-secondary impacts.Comment: ApJ, accepted. Includes referee's suggestions and some minor
clarifications over previous versio
Design, Synthesis, and Characterization of Poly(trimethylsilylmethyl methaciylate-co-chloromethyl styrene) for 193 nm Exposure
Requirements of materials for lithography at 193 am limit single layer resist candidates to those with high optical transmission. A random copolymer of trimethylsilymethyl methacrylate (SI) and chloromethyl styrene (CMS), [P(SI-CMS)], has been shown to be highly sensitive negative 193 nm resist in both bi-layer and single layer modes. Such resists show maximum sensitivity with an optical absorbance of the coating oflog10e, or 0.434. Through control of the mole ratio of the monomers in the P(SI-CMS) copolymer, absorbance values have been optimized for film thicknesses of0.2 - 0.3 micrometers for 90: 10 SI:CMS, 0.35 - 0.45 m for 95:5 SI:CMS and 0.55 -0.65 pm for 98:2 SI:CMS. Optical absorbance ofthe CMS is at a maximum in the 190 to 205 nm range, allowing the copolymer to be tailored for a large degree of crosslinking at a relatively low CMS concentration. Spray development of these materials is performed with ethanol, followed by a two step methanol I isopropanol-water rinse. Sensitivities are on the order of 4 to 20 mj/cm^2 at M near 40 000 g/mol. Furthermore, these ratios have been found to produce optimum 02 etch resistance
Discrete breathers in a two-dimensional hexagonal Fermi-Pasta-Ulam lattice
We consider a two-dimensional Fermi-Pasta-Ulam (FPU) lattice with hexagonal
symmetry. Using asymptotic methods based on small amplitude ansatz, at third
order we obtain a reduction to a cubic nonlinear Schrodinger equation (NLS) for
the breather envelope. However, this does not support stable soliton solutions,
so we pursue a higher-order analysis yielding a generalised NLS, which includes
known stabilising terms. We present numerical results which suggest that
long-lived stationary and moving breathers are supported by the lattice. We
find breather solutions which move in an arbitrary direction, an ellipticity
criterion for the wavenumbers of the carrier wave, asymptotic estimates for the
breather energy, and a minimum threshold energy below which breathers cannot be
found. This energy threshold is maximised for stationary breathers, and becomes
vanishingly small near the boundary of the elliptic domain where breathers
attain a maximum speed. Several of the results obtained are similar to those
obtained for the square FPU lattice (Butt & Wattis, J Phys A, 39, 4955,
(2006)), though we find that the square and hexagonal lattices exhibit
different properties in regard to the generation of harmonics, and the isotropy
of the generalised NLS equation.Comment: 29 pages, 14 Figure
Ethical dilemmas are not simply black and white
This is an Accepted Manuscript of an article published by Taylor & Francis Group in Ethics and Social Practice on 1 July 2008, available online at: http://dx.doi.org/10.1080/17496530801948838.This article aims to highlight some of the ethical issues that arise when social work educators plan to involve service users and carers from black and minority ethnic (BME) communities in the teaching of social work students. Between 2005 and 2007, the authors carried out a two-part project that involved working with service users and carers from BME communities in the area around Liverpool in Britain. The article first discusses the background for this two-part project, highlighting two themes relating to the ethical dilemmas we experienced. The first of these themes concerned conducting a project in a political context based on short and intermittent funding and intransigent bureaucracy. Our second theme concerned how to reconcile bringing together a group of people because they were recognized as having a shared experience while at the same time there were a myriad differences within the group. We then discuss these issues in light of the ethical approach we adopted, based on being open and honest, flexible in a respectful and meaningful way, and on anti-oppressive ethics and shared responsibility.Peer reviewe
Dispersion force for materials relevant for micro and nanodevices fabrication
The dispersion (van der Waals and Casimir) force between two semi-spaces are
calculated using the Lifshitz theory for different materials relevant for micro
and nanodevices fabrication, namely, gold, silicon, gallium arsenide, diamond
and two types of diamond-like carbon (DLC), silicon carbide, silicon nitride
and silicon dioxide. The calculations were performed using recent experimental
optical data available in the literature, usually ranging from the far infrared
up to the extreme ultraviolet bands of the electromagnetic spectrum. The
results are presented in the form of a correction factor to the Casimir force
predicted between perfect conductors, for the separation between the
semi-spaces varying from 1 nanometre up to 1 micrometre. The relative
importance of the contributions to the dispersion force of the optical
properties in different spectral ranges is analyzed. The role of the
temperature for semiconductors and insulators is also addressed. The results
are meant to be useful for the estimation of the impact of the Casimir and van
der Waals forces on the operational parameters of micro and nanodevices
INTEGRAL and XMM-Newton observations towards the unidentified MeV source GRO J1411-64
The COMPTEL unidentified source GRO J1411-64 was observed by INTEGRAL, and
its central part, also by XMM-Newton. The data analysis shows no hint for new
detections at hard X-rays. The upper limits in flux herein presented constrain
the energy spectrum of whatever was producing GRO J1411-64, imposing, in the
framework of earlier COMPTEL observations, the existence of a peak in power
output located somewhere between 300-700 keV for the so-called low state. The
Circinus Galaxy is the only source detected within the 4 location error
of GRO J1411-64, but can be safely excluded as the possible counterpart: the
extrapolation of the energy spectrum is well below the one for GRO J1411-64 at
MeV energies. 22 significant sources (likelihood ) were extracted and
analyzed from XMM-Newton data. Only one of these sources, XMMU
J141255.6-635932, is spectrally compatible with GRO J1411-64 although the fact
the soft X-ray observations do not cover the full extent of the COMPTEL source
position uncertainty make an association hard to quantify and thus risky. The
unique peak of the power output at high energies (hard X-rays and gamma-rays)
resembles that found in the SED seen in blazars or microquasars. However, an
analysis using a microquasar model consisting on a magnetized conical jet
filled with relativistic electrons which radiate through synchrotron and
inverse Compton scattering with star, disk, corona and synchrotron photons
shows that it is hard to comply with all observational constrains. This and the
non-detection at hard X-rays introduce an a-posteriori question mark upon the
physical reality of this source, which is discussed in some detail
The Extraordinary X-ray Light Curve of the Classical Nova V1494 Aquilae (1999 #2) in Outburst: The Discovery of Pulsations and a "Burst"
V1494 Aql (Nova Aql 1999 No. 2) was discovered on 2 December 1999. We
obtained Chandra ACIS-I spectra on 15 April and 7 June 2000 which appear to
show only emission lines. Our third observation, on 6 August, showed that its
spectrum had evolved to that characteristic of a Super Soft X-ray Source. We
then obtained Chandra LETG+HRC-S spectra on 28 September (8 ksec) and 1 October
(17 ksec). We analyzed the X-ray light curve of our grating observations and
found both a short time scale ``burst'' and oscillations. Neither of these
phenomena have previously been seen in the light curve of a nova in outburst.
The ``burst'' was a factor of 10 rise in X-ray counts near the middle of the
second observation, and which lasted about 1000 sec; it exhibited at least two
peaks, in addition to other structure. Our time series analysis of the combined
25 ksec observation shows a peak at 2500 s which is present in independent
analyses of both the zeroth order image and the dispersed spectrum and is not
present in similar analyses of grating data for HZ 43 and Sirius B. Further
analyses of the V1494 Aql data find other periods present which implies that we
are observing non-radial g+ modes from the pulsating, rekindled white dwarf.Comment: ApJ accepte
Probing a Complex of Cytochromecand Cardiolipin by Magnetic Circular Dichroism Spectroscopy: Implications for the Initial Events in Apoptosis
Oxidation of cardiolipin (CL) by its complex with cytochrome c (cyt c) plays a crucial role in triggering apoptosis. Through a combination of magnetic circular dichroism spectroscopy and potentiometric titrations, we show that both the ferric and ferrous forms of the heme group of a CL:cyt c complex exist as multiple conformers at a physiologically relevant pH of 7.4. For the ferric state, these conformers are His/Lys- and His/OH–-ligated. The ferrous state is predominantly high-spin and, most likely, His/–. Interconversion of the ferric and ferrous conformers is described by a single midpoint potential of -80 ± 9 mV vs SHE. These results suggest that CL oxidation in mitochondria could occur by the reaction of molecular oxygen with the ferrous CL:cyt c complex in addition to the well-described reaction of peroxides with the ferric form
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