5,211 research outputs found
Microstructures in Two Alkali Feldspar Megacrysts from the Papuk Mt., Croatia
Two types of megacrysts, one from Pakra Creek and the other from the Slobostina Creek locality proved to be low microcline in association with low albite and quartz. A sample from Pakra Creek is a vein filling megacryst characterised by the absence of twinning. The deduced crystallization temperature is below 460°C. The sample from Sloboština Creek is a pocket forming megacryst which shows tweed-like texture, with deduced crystallization temperature near to but above 460°C. Both samples are characterized by a continuously modulated lattice on the submicroscopic scale
Microstructures in Two Alkali Feldspar Megacrysts from the Papuk Mt., Croatia
Two types of megacrysts, one from Pakra Creek and the other from the Slobostina Creek locality proved to be low microcline in association with low albite and quartz. A sample from Pakra Creek is a vein filling megacryst characterised by the absence of twinning. The deduced crystallization temperature is below 460°C. The sample from Sloboština Creek is a pocket forming megacryst which shows tweed-like texture, with deduced crystallization temperature near to but above 460°C. Both samples are characterized by a continuously modulated lattice on the submicroscopic scale
Near infrared and optical emission of WASP-5 b
CONTEXT: Thermal emission from extrasolar planets makes it possible to study
important physical processes in their atmospheres and derive more precise
orbital elements. AIMS: By using new near infrared and optical data, we examine
how these data constrain the orbital eccentricity and the thermal properties of
the planet atmosphere. METHODS: The full light curves acquired by the TESS
satellite from two sectors are used to put upper limit on the amplitude of the
planet's phase variation and estimate the occultation depth. Two, already
published and one, yet unpublished followup observations in the 2MASS K (Ks)
band are employed to derive a more precise occultation light curve in this near
infrared waveband. RESULTS: The merged occultation light curve in the Ks band
comprises 4515 data points. The data confirm the results of the earlier
eccentricity estimates, suggesting circular orbit: e=0.005+/-0.015. The high
value of the flux depression of (2.70+/-0.14) ppt in the Ks band excludes
simple black body emission at the 10 sigma level and disagrees also with
current atmospheric models at the (4-7) sigma level. From the analysis of the
TESS data, in the visual band we found tentative evidence for a near noise
level detection of the secondary eclipse, and placed constraints on the
associated amplitude of the planet's phase variation. A formal box fit yields
an occultation depth of (0.157+/-0.056) ppt. This implies a relatively high
geometric albedo of Ag=0.43+/-0.15 for fully efficient atmospheric circulation
and Ag=0.29+/-0.15 for no circulation at all. No preference can be seen either
for the oxygen-enhanced, or for the carbon-enhanced atmosphere models.Comment: After the 2nd referee report. Wrong citation of e*cos(w) by Baskin et
al. (2013) has been corrected. Appendix B is supplied by another figur
Design Patterns for Description-Driven Systems
In data modelling, product information has most often been handled separately
from process information. The integration of product and process models in a
unified data model could provide the means by which information could be shared
across an enterprise throughout the system lifecycle from design through to
production. Recently attempts have been made to integrate these two separate
views of systems through identifying common data models. This paper relates
description-driven systems to multi-layer architectures and reveals where
existing design patterns facilitate the integration of product and process
models and where patterns are missing or where existing patterns require
enrichment for this integration. It reports on the construction of a so-called
description-driven system which integrates Product Data Management (PDM) and
Workflow Management (WfM) data models through a common meta-model.Comment: 14 pages, 13 figures. Presented at the 3rd Enterprise Distributed
Object Computing EDOC'99 conference. Mannheim, Germany. September 199
Theoretical mass sensitivity of Love wave and layer guided acoustic plate mode sensors
A model for the mass sensitivity of Love wave and layer guided shear horizontal acoustic plate mode (SH–APM) sensors is developed by considering the propagation of shear horizontally polarized acoustic waves in a three layer system. A dispersion equation is derived for this three layer system and this is shown to contain the dispersion equation for the two layer system of the substrate and the guiding layer plus a term involving the third layer, which is regarded as a perturbing mass layer. This equation is valid for an arbitrary thickness perturbing mass layer. The perturbation, Δν, of the wave speed for the two-layer system by a thin third layer of density, ρp and thickness Δh is shown to be equal to the mass per unit area multiplied by a function dependent only on the properties of the substrate and the guiding layer, and the operating frequency of the sensor. The independence of the function from the properties of the third layer means that the mass sensitivity of the bare, two-layer, sensor operated about any thickness of the guiding layer can be deduced from the slope of the numerically or experimentally determined dispersion curve. Formulas are also derived for a Love wave on an infinite thickness substrate describing the change in mass sensitivity due to a change in frequency. The consequences of the various formulas for mass sensing applications are illustrated using numerical calculations with parameters describing a (rigid) poly(methylmethacrylate) wave-guiding layer on a finite thickness quartz substrate. These calculations demonstrate that a layer-guided SH–APM can have a mass sensitivity comparable to, or higher, than that of Love waves propagating on the same substrate. The increase in mass sensitivity of the layer guided SH–APMs over previously studied SH–APM sensors is of significance, particularly for liquid sensing applications. The relevance of the dispersion curve to experiments using higher frequencies or frequency hopping and to experiments using thick guiding layers is discussed
The Evolution Of LMC X-4 Flares: Evidence For Super-Eddington Radiation Oozing Through Inhomogeneous Polar Cap Accretion Flows ?
We present the results of two extensive Rossi X-ray Timing Explorer
observations of large X-ray flaring episodes from the high-mass X-ray binary
pulsar LMC X-4. Light curves during the flaring episodes comprise bright peaks
embedded in relatively fainter regions, with complex patterns of recurrence and
clustering of flares. We identify precursors preceding the flaring activity.
Pulse profiles during the flares appear to be simple sinusoids, and pulsed
fractions are proportional to the flare intensities. We fit Gaussian functions
to flare peaks to estimate the mean full-width-half-maximum to be 68 s.
Significant rapid aperiodic variability exists up to a few hertz during the
flares, which is related to the appearance of narrow, spiky peaks in the light
curves. While spectral fits and softness ratios show overall spectral softening
as the flare intensity increases, the narrow, spiky peaks do not follow this
trend. The mean fluence of the flare peaks is (3.1 2.9)
10 ergs in the 2.5--25 keV energy range, with its maximum at 1.9
10 ergs. The flare peak luminosity reaches up to (2.1
0.2) 10 ergs s, far above the Eddington luminosity of a
neutron star. We discuss possible origins of the flares, and we also propose
that inhomogeneous accretion columns onto the neutron star polar caps are
responsible for the observed properties.Comment: 39 pages (including figures and tables), accepted for publication in
Ap
Relationships Among HIV/AIDS Orphanhood, Stigma, and Symptoms of Anxiety and Depression in South African Youth: A Longitudinal Investigation Using a Path Analysis Framework
Cross-sectional research has demonstrated that HIV/AIDS orphanhood is associated with anxiety and depression and that HIV/AIDS-related stigma is a risk factor for these outcomes. This study used a longitudinal data set to determine whether relationships between HIV/AIDS orphanhood and anxiety/depression scores (measured at 4-year follow-up) operate indirectly via perceived stigma. Youths from poor communities around Cape Town were interviewed in 2005 (n = 1,025) and followed up in 2009 (n = 723). At baseline, HIV/AIDS-orphaned youth reported significantly higher stigma and depression scores than youth not orphaned by HIV/AIDS. At follow-up, HIV/AIDS-orphaned youth reported significantly higher stigma, anxiety, and depression scores. However, HIV/AIDS orphanhood was not directly associated with anxiety or depression. Instead, significant indirect effects (operating through perceived stigma) were obtained for both assessment periods. Results demonstrate that stigma persists across time and appears to mediate relationships between HIV/AIDS orphanhood and psychological distress. Interventions aiming to reduce stigma may help promote the mental health of HIV/AIDS-orphaned youth
Beat Cepheids as Probes of Stellar and Galactic Metallicity
The mere location of a Beat Cepheid model in a Period Ratio vs. Period
diagram (Petersen diagram) puts very tight constraints on its metallicity Z.
The Beat Cepheid Peterson diagrams are revisited with linear nonadiabatic
turbulent convective models, and their accuracy as a probe for stellar
metallicity is evaluated. They are shown to be largely independent of the
helium content Y, and they are also only weakly dependent on the
mass-luminosity relation that is used in their construction. However, they are
found to show sensitivity to the relative abundances of the elements that are
lumped into the metallicity parameter Z. Rotation is estimated to have but a
small effect on the 'pulsation metallicities'. A composite Petersen diagram is
presented that allows one to read off upper and lower limits on the metallicity
Z from the measured period P0 and period ratio P1/P0.Comment: 9 pages, 12 color figures (black and white version available from 1st
author's website). With minor revisions. to appear in Ap
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