1,019 research outputs found
Phase equilibrium modelling of the amphibolite to granulite facies transition in metabasic rocks (Ivrea Zone, NW Italy)
The development of thermodynamic models for tonalitic melt and the updated clinopyroxene and amphibole models now allow the use of phase equilibrium modelling to estimate PâT conditions and melt production for anatectic mafic and intermediate rock types at highâtemperature conditions.
The Permian midâlower crustal section of the Ivrea Zone preserves a metamorphic field gradient from mid amphibolite facies to granulite facies, and thus records the onset of partial melting in metabasic rocks. Interlayered metabasic and metapelitic rocks allows the direct comparison of PâT estimates and partial melting between both rock types with the same metamorphic evolution. Pseudosections for metabasic compositions calculated in the Na2OâCaOâK2OâFeOâMgOâAl2O3âSiO2âH2OâTiO2âO (NCKFMASHTO) system are presented and compared with those of metapelitic rocks calculated with consistent endmember data and aâx models. The results presented in this study show that PâT conditions obtained by phase equilibria modelling of both metabasic and metapelitic rocks give consistent results within uncertainties, allowing integration of results obtained for both rock types. In combination, the calculations for both metabasic and metapelitic rocks allows an updated and more precisely constrained metamorphic field gradient for Val Strona di Omegna to be defined. The new field gradient has a slightly lower dP/dT which is in better agreement with the onset of crustal thinning of the Adriatic margin during the Permian inferred in recent studies
Supersoft X-ray sources in M31: II. ROSAT-detected supersoft sources in the ROSAT, Chandra and XMM eras
We have performed Chandra observations during the past 3 years of 5 of the
M31 supersoft X-ray sources (SSS) discovered with ROSAT. Surprisingly, only one
of these sources has been detected, despite a predicted detection of about
20-80 counts. This has motivated a thorough check of the ROSAT M31 survey I
data, including a relaxation of the hardness ratio requirement used to select
SSS. This increases the number of SSS identified in survey I by 7. We then
carried out a comparison with the ROSAT M31 survey II dataset which had
hitherto not been explicitly investigated for SSS. We find that most of the
ROSAT survey I sources are not detected, and only two new SSS are identified.
The low detection rate in the ROSAT survey II and our Chandra observations
implies that the variability time scale of SSS is a few months. If the majority
of these sources are close-binary SSS with shell hydrogen burning, it further
implies that half of these sources predominantly experience large mass transfer
rates.Comment: accepted for publ. in ApJ; 2 ps-figures; high-quality figures
available at http://www.mpe.mpg.de/~jcg/publis.htm
Kinematic Orbits and the Structure of the Internal Space for Systems of Five or More Bodies
The internal space for a molecule, atom, or other n-body system can be
conveniently parameterised by 3n-9 kinematic angles and three kinematic
invariants. For a fixed set of kinematic invariants, the kinematic angles
parameterise a subspace, called a kinematic orbit, of the n-body internal
space. Building on an earlier analysis of the three- and four-body problems, we
derive the form of these kinematic orbits (that is, their topology) for the
general n-body problem. The case n=5 is studied in detail, along with the
previously studied cases n=3,4.Comment: 38 pages, submitted to J. Phys.
Evolution of the polarization of the optical afterglow of the gamma-ray burst GRB 030329
We report 31 polarimetric observations of the afterglow of GRB 030329 with
high signal-to-noise and high sampling frequency. We establish the polarization
light curve, detect sustained polarization at the percent level, and find
significant variability of polarization degree and angle. The data imply that
the afterglow magnetic field has small coherence length and is mostly random,
probably generated by turbulence.Comment: Nature 426 (13. Nov. 2003), 2 figure
Temperature dependent characterization of optical fibres for distributed temperature sensing in hot geothermal wells
This study was performed in order to select a proper fibre for the
application of a distributed temperature sensing system within a hot geothermal
well in Iceland. Commercially available high temperature graded index fibres
have been tested under in-situ temperature conditions. Experiments have been
performed with four different polyimide coated fibres, a fibre with an aluminum
coating and a fibre with a gold coating. To select a fibre, the relationship
between attenuation, temperature, and time has been analyzed together with SEM
micrographs. On the basis of these experiments, polyimide fibres have been
chosen for utilisation. Further tests in ambient and inert atmosphere have been
conducted with two polyimide coated fibres to set an operating temperature
limit for these fibres. SEM micrographs, together with coating colour changes
have been used to characterize the high temperature performance of the fibres.
A novel cable design has been developed, a deployment strategy has been worked
out and a suitable well for deployment has been selected.Comment: PACS: 42.81.Pa, 93.85.Fg, 47.80.Fg, 91.35.Dc, 07.20.Dt, 07.60.V
An EUV Study of the Intermediate Polar EX Hydrae
On 2000 May 5, we began a large multi-wavelength campaign to study the
intermediate polar, EX Hydrae. The simultaneous observations from six
satellites and four telescopes were centered around a one million second
observation with EUVE. Although EX Hydrae has been studied previously with
EUVE, our higher signal-to-noise observations present new results and challenge
the current IP models. Previously unseen dips in the light curve are
reminiscent of the stream dips seen in polar light curves. Also of interest is
the temporal extent of the bulge dip; approximately 0.5 in phase, implying that
the bulge extends over half of the accretion disk. We propose that the magnetic
field in EX Hydrae is strong enough (a few MG) to begin pulling material
directly from the outer edge of the disk, thereby forming a large accretion
curtain which would produce a very broad bulge dip. This would also result in
magnetically controlled accretion streams originating from the outer edge of
the disk. We also present a period analysis of the photometric data which shows
numerous beat frequencies with strong power and also intermittent and wandering
frequencies, an indication that physical conditions within EX Hya changed over
the course of the observation. Iron spectral line ratios give a temperature of
log T=6.5-6.9 K for all spin phases and a poorly constrained density of
n_e=10^10-10^11 cm^-3 for the emitting plasma. This paper is the first in a
series detailing our results from this multi-wavelength observational campaign.Comment: 27 pages, 7 figures, accepted for publication in Ap
Six supersoft X-ray binaries: system parameters and twin-jet outflows
A comparison is made between the properties of CAL 83, CAL 87, RX
J0513.9-6951, 1E 0035.4-7230 (SMC 13), RX J0019.8+2156, and RX J0925.7-4758,
all supersoft X-ray binaries. Spectra with the same resolution and wavelength
coverage of these systems are compared and contrasted. Some new photometry is
also presented. The equivalent widths of the principal emission lines of H and
He II differ by more than an order of magnitude among these sources, although
those of the highest ionization lines (e.g. O VI) are very similar. In
individual systems, the velocity curves derived from various ions often differ
in phasing and amplitude, but those whose phasing is consistent with the light
curves (implying the lines are formed near the compact star) give masses of
and for the degenerate and mass-losing
stars, respectively. This finding is in conflict with currently prevailing
theoretical models for supersoft binaries. The three highest luminosity sources
show evidence of "jet" outflows, with velocities of .
In CAL 83 the shape of the He II 4686\AA profile continues to show evidence
that these jets may precess with a period of days.Comment: 27 pages including 5 tables, plus 6 figures. To appear in Ap
The limit of N=(2,2) superconformal minimal models
The limit of families of two-dimensional conformal field theories has
recently attracted attention in the context of AdS/CFT dualities. In our work
we analyse the limit of N=(2,2) superconformal minimal models when the central
charge approaches c=3. The limiting theory is a non-rational N=(2,2)
superconformal theory, in which there is a continuum of chiral primary fields.
We determine the spectrum of the theory, the three-point functions on the
sphere, and the disc one-point functions.Comment: 37 pages, 3 figures; v2: minor corrections in section 5.3, version to
be published in JHE
Attention deficit hyperactivity symptoms predict problematic mobile phone use
Attention-deficit-hyperactivity disorder (ADHD) is the most commonly diagnosed childhood disorder characterised by inattention, hyperactivity/impulsivity, or both. Some of the key traits of ADHD have previously been linked to addictive and problematic behaviours. The aim of the present study was to examine the relationship between problematic mobile phone use, smartphone
addiction risk and ADHD symptoms in an adult population. A sample of 273 healthy adult volunteers completed the Adult
ADHD Self-Report Scale (ASRS), the Mobile Phone Problem Usage Scale (MPPUS), and the Smartphone Addiction Scale
(SAS). A significant positive correlation was found between the ASRS and both scales. More specifically, inattention symptoms
and age predicted smartphone addiction risk and problematic mobile phone use. Our results suggest that there is a positive
relationship between ADHD traits and problematic mobile phone use. In particular, younger adults with higher level of inattention symptoms could be at higher risk of developing smartphone addiction. The implication of our findings for theoretical
frameworks of problematic mobile phone use and clinical practice are discussed
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