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Using the data obtained from Kepler satellite, we have analyzed an F-type ultra-fast rotator KIC 6791060. We derive a rotational period of 0.34365±0.00004 d. Multiple periodicity with a period separation of ~0.00016 d was detected, which appears to be a result of the relative velocity between the multiple spot-groups in different stellar latitudes due to the surface differential rotation. Modeling of the surface inhomogeneities using the light curve of 3899 epochs shows the evidence of single active longitude region. The active longitude is found to drift along the longitude at a rate similar to the detected period separation of the F-type star. The surface coverage of cool spots is found to be in the range of ~0.07–0.44%. The low value of the spottedness can be interpreted probably due to the thinner convection zone on the F-type star.
We study the motion of a bubble driven by buoyancy and thermocapillarity in a tube with a non-uniformly heated walls, containing a so-called ‘self-rewetting fluid’; the surface tension of the latter exhibits a parabolic dependence on temperature, with a well-defined minimum. In the Stokes flow limit, we derive the conditions under which a spherical bubble can come to rest in a self-rewetting fluid whose temperature varies linearly in the vertical direction, and demonstrate that this is possible for both positive and negative temperature gradients. This is in contrast to the case of simple fluids whose surface tension decreases linearly with temperature, for which bubble motion is arrested only for negative temperature gradients. In the case of self-rewetting fluids, we propose an analytical expression for the position of bubble arrestment as a function of other dimensionless numbers. We also perform direct numerical simulation of axisymmetric bubble motion in a fluid whose temperature increases linearly with vertical distance from the bottom of the tube; this is done for a range of Bond and Galileo numbers, as well as for various parameters that govern the functional dependence of surface tension on temperature. We demonstrate that bubble motion can be reversed and then arrested only in self-rewetting fluids, and not in linear fluids, for sufficiently small Bond numbers. We also demonstrate that considerable bubble elongation is possible under significant wall confinement, and for strongly self-rewetting fluids and large Bond numbers. The mechanisms underlying the phenomena observed are elucidated by considering how the surface tension dependence on temperature affects the thermocapillary stresses in the flow.
We report on the effect of the International Nosocomial Infection Control Consortium's (INICC) multidimensional approach for the reduction of ventilator-associated pneumonia (VAP) in adult patients hospitalized in 21 intensive-care units (ICUs), from 14 hospitals in 10 Indian cities. A quasi-experimental study was conducted, which was divided into baseline and intervention periods. During baseline, prospective surveillance of VAP was performed applying the Centers for Disease Control and Prevention/National Healthcare Safety Network definitions and INICC methods. During intervention, our approach in each ICU included a bundle of interventions, education, outcome and process surveillance, and feedback of VAP rates and performance. Crude stratified rates were calculated, and by using random-effects Poisson regression to allow for clustering by ICU, the incidence rate ratio for each time period compared with the 3-month baseline was determined. The VAP rate was 17·43/1000 mechanical ventilator days during baseline, and 10·81 for intervention, showing a 38% VAP rate reduction (relative risk 0·62, 95% confidence interval 0·5–0·78, P = 0·0001).
UBVRI photometry and low resolution optical spectroscopy of the type IIb SN 2011dh in M51 are presented, covering the first year after the explosion. The peak absolute magnitude in V-band of −17.12±0.18 mag indicates SN 2011dh to be a normal bright type IIb event. The peak quasi-bolometric luminosity indicates that ~ 0.06 M⊙ of 56Ni was synthesized in the explosion. The He I lines were detected in the spectra much before the maximum light in B-band. The nebular spectra of SN 2011dh show a box shaped emission in the red wing of [OI] 6300, 6363 line due to Hα emission excited because of shock-wave interaction. The analysis of the nebular spectra indicates a progenitor with a main sequence mass of 10-15 M⊙.
The UBVRI photometric follow-up of SN 2011fu has been initiated a few days after the explosion, shows a rise followed by steep decay in all bands and shares properties very similar to that seen in case of SN 1993J, with a possible detection of the adiabatic cooling phase at very early epochs. The spectral modeling performed with SYNOW suggests that the early-phase line velocities for H and Fe ii features were ~ 16000 km s−1 and ~ 14000 km s−1, respectively. Studies of rare class of type IIb SNe are important to understand the evolution of the possible progenitors of core-collapse SNe in more details.
Using an ab initio density functional theory (DFT), we study thin film electronic properties of topological insulators (TIs) based on ternary compounds of Tl (thallium) and Bi (bismuth). We consider TlBiX2 (X=Se, Te) and Bi2X2Y (X, Y=Se, Te) compounds. Here we discuss the nature of surface states, their locations in the Brillouin Zone (BZ) and their interactions within the bulk region. Our calculations suggest a critical film thickness to maintain the Dirac cone which is smaller than that in binary Bi-based compounds. Atomic relaxations are found to affect the Dirac cone in some of these compounds. We discuss the penetration depth of surface states into the bulk region.
UBVRI photometry and medium resolution spectroscopy of two Type Ia supernovae, SN 2009an and SN 2009ig, are presented. Their Δm15(B) indicate these two SNe marginally deviate from “normal” Type Ia events. Spectroscopically, both SNe belong to the low velocity gradient group. The estimated mass of 56Ni ejected is almost a factor of two different for these two objects, with the estimates being ~0.4M⊙ for SN 2009an and ~0.8 M⊙ for SN 2009ig.
Wall slip and wall divergence are known to have large and opposing effects on the stability of flow in a two-dimensional channel. While divergence
hugely destabilises, slip dramatically stabilizes the linear mode.
In a non-parallel stability analysis, we study a combination of these
two effects, since both
will coexist in small-scale flows with wall roughness.
Our main results are (i) that the stabilising effect of slip
is reversed at higher angles of divergence,
(ii) transient growth of disturbances
is unaffected by either wall-divergence, or by slip at any divergence.
Moreover, at the
Reynolds numbers relevant here, transient growth is too low to be a
significant player in transition to turbulence,
which is more likely to be driven by linear instability.
The results would have implications for the onset of unsteadiness and
mixing in small scale flows.
PLANET, the Probing Lensing Anomaly NETwork, is an international team
conducting observations of on-going gravitational microlensing
events from five sites in the southern hemisphere. Our primary goal is to
detect or to put constraints on sub-stellar companions of M dwarfs from the galactic disk.
We report the current status and discuss the future prospects.
A 2 m robotic telescope at Dome C which would benefit from continuous coverage and dream like seeing
(median of 0.27 arcsec) is currently the best option for a
ground based aggressive search for Earth-mass planets in the habitable zone.
Due to their extremely small luminosity compared to the stars they orbit, planets outside our own Solar System are extraordinarily difficult to detect directly in optical light. Careful photometric monitoring of distant stars, however, can reveal the presence of exoplanets via the microlensing or eclipsing effects they induce. The international PLANET collaboration is performing such monitoring using a cadre of semi-dedicated telescopes around the world. Their results constrain the number of gas giants orbiting 1–7 AU from the most typical stars in the Galaxy. Upgrades in the program are opening regions of “exoplanet discovery space” – toward smaller masses and larger orbital radii – that are inaccessible to the Doppler velocity technique.
We review the current status and future prospects of the PLANET collaboration, an international team of astronomers performing high-precision photometric monitoring of microlensing events. Our photometric precision and sampling is characterised and the suitability of the database for variable star studies is discussed. Preliminary results on K-giant stability are presented.
During the ESO key-program on gravitational lenses, the light curves of two images (A and B) of the lensed quasar UM 425 were obtained (from 1987 to 1995). This poster presents a possible interpretation of the light curves in terms of a micro-lensing event in the faint B component of the system, without ruling out a possible intrinsic variation of the source.
Three new objects have been found, when carrying out a survey of IRAS sources with colours like planetary nebulae, via low resolution spectroscopy. IRAS 14592-6311 and IRAS 07173-1733 are bright cometary nebulae, showing metal line emission very similar to V1331 Cyg (LkHα 120), which is the prototype of a certain number of T Tauri stars. They present strong P-Cygni profiles and some other peculiar characteristics. IRAS 14592-6311 is associated with a molecular cloud at a distance of 2.9 kpc, while IRAS 07173-1733 is located at the edge of the dark cloud KHAV 201. In the case of IRAS 05506+2414, it presents a bipolar structure with Herbig-Haro emission characteristics in one of the lobes, produces by shocked gas, and is located near Orion.
We have undertaken a programme of kinematic study of southern planetary nebulae by obtaining high-resolution (R ≥ 50,000) spectra, using the ESO 1.5-m telescope + the Coudé Echelle Spectrograph. As first results of this study, this paper presents previously unknown expansion velocities of 16 planetary nebulae. This result increases the total number of planetary nebulae for which the expansion velocities are now known by about 10%. Further, reliable distance measurements and other physical properties are available for most of these sources. Hence this sample significantly improves the previously available data for statistical analysis related to the dynamics and evolution of planetary nebulae. Some preliminary results based on such statistical analysis are presented. The details of the results will be published in Astron. Astrophys.
Kinematic study of the multiple shell PN NGC 3242 was carried out by obtaining Hα and [O III] line profiles at 9 positions of the nebula using a high-resolution (R ≅ 50,000) Fabry-Pérot spectrometer. The positions cover both the bright inner shell and the faint outer shell. It is shown here that the two apparently continuous shells are kinematically separate: the faint outer shell was ejected ∼ 5000 years earlier and has less expansion velocity than the bright inner shell.
Psychiatric manifestations were studied in 72 amputees in the post-operative period. All were right handed. Besides phantom limb phenomena, which were observed in nearly four-fifths of the cases and are described in another paper, nearly two-thirds had psychiatric symptoms in the form of depression (45 patients), anxiety (38), crying spells (38), insomnia (34), loss of appetite (23), suicidal ideas (21) and psychotic behaviour (2). Right arm amputees had phantom phenomena and insomnia significantly more often than left.
Nearly one-fifth of the cases were diagnosed as having psychotic depressive reactions, two-fifths as having depressive neurosis and two, both with right upper limb amputations, as schizophrenic.
Phantom limb phenomena during the post-operative period were studied in 72 amputees. All were right handed. Phantom limb was present in 86.1 per cent of the cases, significantly more commonly following amputation of the right arm. Nearly half of the phantoms developed within the first 24 hours and another quarter in the next 24 hours, appearing earlier in lower limb amputees. Movements in the phantom were felt by three-quarters of the cases, an incidence unaffected by site or side of amputation. Telescopy was present in nearly two-thirds and phantom limb pain in over two-thirds, significantly more commonly in the upper limb amputees but uninfluenced by the side of amputation. Thirty-one of the patients dreamed that their limbs were intact.
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