1,958 research outputs found
A Description of the Third Instar of Platambus flavovittaus (Larson and Wolfe, 1998) with Comments on the Larval Morphology of Platambus stagninus (Say, 1823) and a Key to the Agabini (Coleoptera: Dytiscidae) of Georgia
Mature Agabini larvae collected from a small temporary road-side habitat were reared to the adult stage and identified as Platambus flavovittattus (Larson and Wolfe, 1998). The mature larva is described and illustrated with an emphasis on leg morphology. Important differences between cranial temporal curvatures of P. flavovittatus and P. stagninus (Say, 1823) are described. A larval key is constructed to facilitate identification of Georgia agabine genera and species
Structure and evolution of the first CoRoT exoplanets: Probing the Brown Dwarf/Planet overlapping mass regime
We present detailed structure and evolution calculations for the first
transiting extrasolar planets discovered by the space-based CoRoT mission.
Comparisons between theoretical and observed radii provide information on the
internal composition of the CoRoT objects. We distinguish three different
categories of planets emerging from these discoveries and from previous
ground-based surveys: (i) planets explained by standard planetary models
including irradiation, (ii) abnormally bloated planets and (iii) massive
objects belonging to the overlapping mass regime between planets and brown
dwarfs. For the second category, we show that tidal heating can explain the
relevant CoRoT objects, providing non-zero eccentricities. We stress that the
usual assumption of a quick circularization of the orbit by tides, as usually
done in transit light curve analysis, is not justified a priori, as suggested
recently by Levrard et al. (2009), and that eccentricity analysis should be
carefully redone for some observations. Finally, special attention is devoted
to CoRoT-3b and to the identification of its very nature: giant planet or brown
dwarf ? The radius determination of this object confirms the theoretical
mass-radius predictions for gaseous bodies in the substellar regime but, given
the present observational uncertainties, does not allow an unambiguous
identification of its very nature. This opens the avenue, however, to an
observational identification of these two distinct astrophysical populations,
brown dwarfs and giant planets, in their overlapping mass range, as done for
the case of the 8 Jupiter-mass object Hat-P-2b. (abridged)Comment: 6 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Rotational Velocities of Very Low Mass Binaries
We present rotational velocities for individual components of eleven very low mass (VLM) binaries with spectral types between M7.5 and L4. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics (LGS AO) system. The binaries were targeted as part of a dynamical mass program, and their orbital inclinations are used to translate vsini into a rotational velocity for each component. We find that the observed sources tend to be rapid rotators (vsini > 10 km s^(-1)), consistent with previous measurements for ultracool objects. Five systems have component vsini's that are statistically different, with three binaries having velocity differences greater than 25 km s^(-1). To bring these discrepant rotational velocities into agreement would require their rotational axes to be inclined between 10 to 40° with respect to each other, and that at least one component has a significant inclination with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have interesting implications for binary star formation. Two of the binaries with large differences in rotational velocity are also known radio sources, LP 349-25AB and 2MASS 0746+20AB. LP 349-25B is rotating at ∼95 km s^(-1), within a factor of ∼3 of the break up speed, and is one of the most rapidly rotating VLM objects known
Cationic vacancy induced room-temperature ferromagnetism in transparent conducting anatase Ti_{1-x}Ta_xO_2 (x~0.05) thin films
We report room-temperature ferromagnetism in highly conducting transparent
anatase Ti1-xTaxO2 (x~0.05) thin films grown by pulsed laser deposition on
LaAlO3 substrates. Rutherford backscattering spectrometry (RBS), x-ray
diffraction (XRD), proton induced x-ray emission (PIXE), x-ray absorption
spectroscopy (XAS) and time-of-flight secondary ion mass spectrometry
(TOF-SIMS) indicated negligible magnetic contaminants in the films. The
presence of ferromagnetism with concomitant large carrier densities was
determined by a combination of superconducting quantum interference device
(SQUID) magnetometry, electrical transport measurements, soft x-ray magnetic
circular dichroism (SXMCD), XAS, and optical magnetic circular dichroism (OMCD)
and was supported by first-principle calculations. SXMCD and XAS measurements
revealed a 90% contribution to ferromagnetism from the Ti ions and a 10%
contribution from the O ions. RBS/channelling measurements show complete Ta
substitution in the Ti sites though carrier activation was only 50% at 5% Ta
concentration implying compensation by cationic defects. The role of Ti vacancy
and Ti3+ was studied via XAS and x-ray photoemission spectroscopy (XPS)
respectively. It was found that in films with strong ferromagnetism, the Ti
vacancy signal was strong while Ti3+ signal was absent. We propose (in the
absence of any obvious exchange mechanisms) that the localised magnetic
moments, Ti vacancy sites, are ferromagnetically ordered by itinerant carriers.
Cationic-defect-induced magnetism is an alternative route to ferromagnetism in
wide-band-gap semiconducting oxides without any magnetic elements.Comment: 21 pages, 10 figures, to appear in Philosophical Transaction - Royal
Soc.
Mental health status and perceived burden in caregiving spouses of persons with psychotic illness (a study from India)
Mental illness poses a great deal of burden on other family members, particularly the primary caregiver. In the Indian context for a married person with mental illness, the caregiving burden is usually experienced by the spouse, who is considered to be the ‘natural’ option. This quantitative study used survey methodology to assess caregiving burden in fifty spouses of persons diagnosed with a psychotic illness. Data was collected at a neuro-psychiatric facility in Tiruchirappalli, India. The Depression, Anxiety and Stress Scale and the Burden Assessment Schedule were the instruments administered to assess the mental health status of the spouse and their perceived burden. Findings revealed that the majority of spouses were classified as experiencing ‘severe’ and ‘extremely severe’ in terms of their depression, anxiety and stress levels and ‘high’ in terms of perceived burden. The specific ‘type’ of clinical diagnosis, however, did not differentiate the spouses on the key variables studied. The correlation of these key variables with other background variables has also been examined. The implications of the results of this study for psychosocial intervention have also been discussed in this article
Is tidal heating sufficient to explain bloated exoplanets? Consistent calculations accounting for finite initial eccentricity
In this paper, we present the consistent evolution of short-period exoplanets
coupling the tidal and gravothermal evolution of the planet. Contrarily to
previous similar studies, our calculations are based on the complete tidal
evolution equations of the Hut model, valid at any order in eccentricity,
obliquity and spin. We demonstrate, both analytically and numerically, that,
except if the system was formed with a nearly circular orbit (e<0.2), solving
consistently the complete tidal equations is mandatory to derive correct tidal
evolution histories. We show that calculations based on tidal models truncated
at second order in eccentricity, as done in all previous studies, lead to
erroneous tidal evolutions. As a consequence, tidal energy dissipation rates
are severely underestimated in all these calculations and the characteristic
timescales for the various orbital parameters evolutions can be wrong by up to
three orders in magnitude.
Based on these complete, consistent calculations, we revisit the viability of
the tidal heating hypothesis to explain the anomalously large radius of
transiting giant planets. We show that, even though tidal dissipation does
provide a substantial contribution to the planet's heat budget and can explain
some of the moderately bloated hot-Jupiters, this mechanism can not explain
alone the properties of the most inflated objects, including HD 209458b.
Indeed, solving the complete tidal equations shows that enhanced tidal
dissipation and thus orbit circularization occur too early during the planet's
evolution to provide enough extra energy at the present epoch. In that case
another mechanisms, such as stellar irradiation induced surface winds
dissipating in the planet's tidal bulges, or inefficient convection in the
planet's interior must be invoked, together with tidal dissipation, to provide
all the pieces of the abnormally large exoplanet puzzle.Comment: 14 pages, 10 figures, Accepted for publication in Astronomy and
Astrophysics
Estimates of electronic interaction parameters for LaO compounds (=Ti-Ni) from ab-initio approaches
We have analyzed the ab-initio local density approximation band structure
calculations for the family of perovskite oxides, LaO with =Ti-Ni
within a parametrized nearest neighbor tight-binding model and extracted
various interaction strengths. We study the systematics in these interaction
parameters across the transition metal series and discuss the relevance of
these in a many-body description of these oxides. The results obtained here
compare well with estimates of these parameters obtained via analysis of
electron spectroscopic results in conjunction with the Anderson impurity model.
The dependence of the hopping interaction strength, t, is found to be
approximately .Comment: 18 pages; 1 tex file+9 postscript files (appeared in Phys Rev B Oct
15,1996
Stabilnost amlodipin besilata i atenolola u jednoslojnim i dvoslojnim tabletama
Multi-drug tablets of amlodipine besylate and atenolol were prepared as either mono-layer (mixed matrix) or bi-layer tablets containing each drug in a separate layer by using similar excipients and processing. Each tablet batch was packed in strip and blister packs and kept under accelerated temperature and humidity conditions. The stability of two tablet and packaging types was compared by HPLC analysis after 0, 1, 3 and 4.5 months and expressed as the content of intact amlodipine and atenolol.
The content of atenolol did not decline regardless of tablet and packaging type. Amlodipine content in bi-layer tablets decreased to about 95 and 88% when packed in strips and blisters, respectively. When prepared as mono-layer tablets, the content decreased to 72 and 32%, respectively.
The study revealed that the bi-layer tablet formulation was more stable than the mono-layer type. Further, the stability was increased when the tablets were packed in aluminium strips as compared to PVC blisters.Tablete s amlodipinom i atenololom pripremljene su ili u obliku jednoslojne tablete (miješani matriks) ili kao dvoslojne tablete (lijekovi u zasebnim slojevima) koristeći slične pomoćne tvari i uvjete tabletiranja. Tablete su pakirane u dvije vrste pakiranja, aluminijske folije (strip) ili PVC (blister) i čuvane u uvjetima ubrzanog starenja. Stabilnost je određivana pomoću HPLC metode nakon 0, 1, 2, 3 i 4,5 mjeseci i izražena kao sadržaj intaktnog lijeka.
Sadržaj atenolola nije se značajno promijenio bez obzira na tip tablete ili pakiranje. Sadržaj amlodipina u dvoslojnim tabletama smanjio se na 95 % (tablete u strip pakiranju) i 88 % (tablete u blister pakiranju). Istodobno, u jednoslojnom tipu kombiniranih tableta sadržaj se smanjio na 72 % (strip pakiranje) i 32 % (blister pakiranje).
Rezultati pokazuju da su dvoslojne tablete s amlodipinom i atenololom stabilnije od jednoslojnih. Štoviše, pakiranje tableta u aluminijsku foliju u obliku strip pakiranja povećava njihovu stabilnost u usporedbi s PVC pakirnim materijalom (blister)
Low Temperature Opacities
Previous computations of low temperature Rosseland and Planck mean opacities
from Alexander & Ferguson (1994) are updated and expanded. The new computations
include a more complete equation of state with more grain species and updated
optical constants. Grains are now explicitly included in thermal equilibrium in
the equation of state calculation, which allows for a much wider range of grain
compositions to be accurately included than was previously the case. The
inclusion of high temperature condensates such as AlO and CaTiO
significantly affects the total opacity over a narrow range of temperatures
before the appearance of the first silicate grains.
The new opacity tables are tabulated for temperatures ranging from 30000 K to
500 K with gas densities from 10 g cm to 10 g cm.
Comparisons with previous Rosseland mean opacity calculations are discussed. At
high temperatures, the agreement with OPAL and Opacity Project is quite good.
Comparisons at lower temperatures are more divergent as a result of differences
in molecular and grain physics included in different calculations. The
computation of Planck mean opacities performed with the opacity sampling method
are shown to require a very large number of opacity sampling wavelength points;
previously published results obtained with fewer wavelength points are shown to
be significantly in error. Methods for requesting or obtaining the new tables
are provided.Comment: 39 pages with 12 figures. To be published in ApJ, April 200
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