Propagating intensity disturbances in polar corona as seen from AIA/SDO

Context. Polar corona is often explored to find the energy source for the acceleration of the fast solar wind. Earlier observations show omni-presence of quasi-periodic disturbances, traveling outward, which is believed to be caused by the ubiquitous presence of outward propagating waves. These waves, mostly of compressional type, might provide the additional momentum and heat required for the fast solar wind acceleration. It has been conjectured that these disturbances are not due to waves but high speed plasma outflows, which are difficult to distinguish using the current available techniques. Aims. With the unprecedented high spatial and temporal resolution of AIA/SDO, we search for these quasi-periodic disturbances in both plume and interplume regions of the polar corona. We investigate their nature of propagation and search for a plausible interpretation. We also aim to study their multi-thermal nature by using three different coronal passbands of AIA. Methods. We chose several clean plume and interplume structures and studied the time evolution of specific channels by making artificial slits along them. Taking the average across the slits, space-time maps are constructed and then filtration techniques are applied to amplify the low-amplitude oscillations. To suppress the effect of fainter jets, we chose wider slits than usual. Results. In almost all the locations chosen, in both plume and interplume regions we find the presence of propagating quasi-periodic disturbances, of periodicities ranging from 10-30 min. These are clearly seen in two channels and in a few cases out to very large distances (approximate to 250 `') off-limb, almost to the edge of the AIA field of view. The propagation speeds are in the range of 100-170 km s(-1). The average speeds are different for different passbands and higher in interplume regions. Conclusions. Propagating disturbances are observed, even after removing the effects of jets and are insensitive to changes in slit width. This indicates that a coherent mechanism is involved. In addition, the observed propagation speed varies between the different passpands, implying that these quasi-periodic intensity disturbances are possibly due to magneto-acoustic waves. The propagation speeds in interplume region are higher than in the plume region.

How fast is ultrafast chemistry

The field of ultrafast chemistry has seen a string of remarkable discoveries in the recent years. In this article we briefly discuss some of the problems solved recently. The understanding that has emerged from these studies has important consequences non only in chemistry but also in diverse biological processes.

Effect of chronic administration of Tamoxifen on fertility in male bonnet monkeys (Macaca radiata)

Administration of Tamoxifen via the Alzet pump at a rate of 50 mu g hr(-1) for 90 days in the adult male bonnet monkeys Macaca radiata had no effect on the serum testosterone concentration determined at 10 AM and 10 PM as well as total sperm count determined at 15-day intervals over a period of 260 days. However, a significant reduction in sperm motility was observed beyond 90 days up until the 225th day. Breeding studies conducted from day 90 to 260 revealed that these males were infertile.

Lopsidedness in WHISP galaxies I. Rotation curves and kinematic lopsidedness

The frequently observed lopsidedness of the distribution of stars and gas in disc galaxies is still considered as a major problem in galaxy dynamics. It is even discussed as an imprint of the formation history of discs and the evolution of baryons in dark matter haloes. Here, we analyse a selected sample of 70 galaxies from the Westerbork Hi Survey of Spiral and Irregular Galaxies. The Hi data allow us to follow the morphology and the kinematics out to very large radii. In the present paper, we present the rotation curves and study the kinematic asymmetry. We extract the rotation curves of the receding and approaching sides separately and show that the kinematic behaviour of disc galaxies can be classified into five different types: symmetric velocity fields where the rotation curves of the receding and approaching sides are almost identical; global distortions where the rotation velocities of the receding and approaching sides have an offset that is constant with radius; local distortions leading to large deviations in the inner and negligible deviations in the outer parts (and vice versa); and distortions that divide the galaxies into two kinematic systems that are visible in terms of the different behaviour of the rotation curves of the receding and approaching sides, which leads to a crossing and a change in side. The kinematic lopsidedness is measured from the maximum rotation velocities, averaged over the plateau of the rotation curves. This gives a good estimate of the global lopsidedness in the outer parts of the sample galaxies. We find that the mean value of the perturbation parameter denoting the lopsided potential as obtained from the kinematic data is 0.056. Altogether, 36% of the sample galaxies are globally lopsided, which can be interpreted as the disc responding to a halo that was distorted by a tidal encounter. In Paper II, we study the morphological lopsidedness of the same sample of galaxies.

Lopsidedness in WHISP galaxies II. Morphological lopsidedness

The distribution of stars and gas in many galaxies is asymmetric. This so-called lopsidedness is expected to significantly affect the dynamics and evolution of the disc, including the star formation activity. Here, we measure the degree of lopsidedness for the gas distribution in a selected sample of 70 galaxies from the Westerbork Hi Survey of Spiral and Irregular Galaxies. This complements our earlier work (Paper I) where the kinematic lopsidedness was derived for the same galaxies. The morphological lopsidedness is measured by performing a harmonic decomposition of the surface density maps. The amplitude of lopsidedness A(1), the fractional value of the first Fourier component, is typically quite high (about 0.1) within the optical disc and has a constant phase. Thus, lopsidedness is a common feature in galaxies and indicates a global mode. We measure A(1) out to typically one to four optical radii, sometimes even further. This is, on average, four times larger than the distance to which lopsidedness was measured in the past using near-IR as a tracer of the old stellar component, and therefore provides a new, more stringent constraint on the mechanism for the origin of lopsidedness. Interestingly, the value of A(1) saturates beyond the optical radius. Furthermore, the plot of A(1) versus radius shows fluctuations that we argue are due to local spiral features. We also try to explain the physical origin of this observed disc lopsidedness. No clear trend is found when the degree of lopsidedness is compared to a measure of the isolation or interaction probability of the sample galaxies. However, this does not rule out a tidal origin if the lopsidedness is long-lived. In addition, we find that the early-type galaxies tend to be more morphologically lopsided than the late-type galaxies. Both results together indicate that lopsidedness has a tidal origin.

Effect of fluctuations on the freezing of a colloidal suspension in an external periodic potential

We incorporate the effects of fluctuations in a density functional analysis of the freezing of a colloidal liquid in the presence of an external potential generated by interfering laser beams. A mean-field treatment, using a density functional theory, predicts that with the increase in the strength of the modulating potential, the freezing transition changes from a first order to a continuous one via a tricritical point for a suitable choice of the modulating wavevectors. We demonstrate here that the continuous nature of the freezing transition at large values of the external potential V-e survives the presence of fluctuations. We also show that fluctuations tend to stabilize the liquid phase in the large V-e regime.

Symplectic integration of nonlinear Hamiltonian systems

There exist several standard numerical methods for integrating ordinary differential equations. However, if one is interested in integration of Hamiltonian systems, these methods can lead to wrong results. This is due to the fact that these methods do not explicitly preserve the so-called 'symplectic condition' (that needs to be satisfied for Hamiltonian systems) at every integration step. In this paper, we look at various methods for integration that preserve the symplectic condition.

The nature of charge ordering in rare earth manganates and its strong dependence on the size of the A-site cations

Charge ordering in rare earth manganates of the type Ln(0.5)A(0.5)MnO(3) (Ln = rare earth, A = alkaline earth) is highly sensitive to the average radius of the A-site cations, [r(A)]. Tn the small [r(A)] regime (e.g., Y0.5Ca0.5MnO3), charge ordering occurs in the paramagnetic state, the transformation to an antiferromagnetic state occurring at still lower temperatures. At moderate [r(A)] values (e.g., Nd0.5Sr0.5MnO3), a ferromagnetic metallic state transforms to a charge-ordered antiferromagnetic state with cooling. These two distinct types of charge ordering and associated properties are explained in terms of the variation of the exchange couplings J(FM) and J(AFM) with [r(A)] and the invariance of the single-ion Jahn-Teller energy with [r(A)]. A qualitative temperature-[r(A)] phase diagram, consistent with the experimental observations, has been constructed to describe the properties of the manganates in the different [r(A)] regimes. (C) 1997 Academic Press.

Combinatorial logic synthesis using technology directed decomposition

The aim of logic synthesis is to produce circuits which satisfy the given boolean function while meeting timing constraints and requiring the minimum silicon area. Logic synthesis involves two steps namely logic decomposition and technology mapping. Existing methods treat the two as separate operation. The traditional approach is to minimize the number of literals without considering the target technology during the decomposition phase. The decomposed expressions are then mapped on to the target technology to optimize the area, Timing optimization is carried out subsequently, A new approach which treats logic decomposition and technology maping as a single operation is presented. The logic decomposition is based on the parameters of the target technology. The area and timing optimization is carried out during logic decomposition phase itself. Results using MCNC circuits are presented to show that this method produces circuits which are 38% faster while requiring 14% increase in area.

MOCVD of aluminium oxide films using aluminiurn beta-diketonates as precursors

Deposition of Al2O3 coatings by CVD is of importance because they are often used as abrading material in cemented carbide cutting tools. The conventionally used CVD process for Al2O3 involves the corrosive reactant AlCl3. In this paper, we report on the thermal characterisation of the metalorganic precursors namely aluminium tristetramethyl-heptanedionate [Al(thd)(3)] and aluminium tris-acetylacetonate [Al(acac)(3)] and their application to the CVD of Al2O3 films. Crystalline Al2O3 films were deposited by MOCVD at low temperatures by the pyrolysis of Al(thd)(3) and Al(acac)(3). The films were deposited on a TiN-coated tungsten carbide (TiN/WC) and Si(100) substrates in the temperature range 500-1100degreesC. The as-deposited films were characterised by x-ray diffraction, optical microscopy, scanning and transmission electron microscopy, Auger electron spectroscopy. The observed crystallinity of films grown at low temperatures, their microstructure, and composition may be interpreted in terms of a growth process that involves the melting of the metalorganic precursor on the hot growth surface.

Search for sub-mm, mm and radio continuum emission from extremely red objects

We present the results of sub-mm, mm (850 mum, 450 mum and 1250 mum) and radio (1.4 and 4.8 GHz) continuum observations of a sample of 27 K-selected Extremely Red Objects, or EROs, (14 of which form a complete sample with K < 20 and I - K > 5) aimed at detecting dusty starbursts, deriving the fraction of UltraLuminous Infrared Galaxies (ULIGs) in ERO samples, and constraining their redshifts using the radio-FIR correlation. One ERO was tentatively detected at 1250 mum and two were detected at 1.4 GHz, one of which has a less secure identification as an ERO counterpart. Limits on their redshifts and their star forming properties are derived and discussed. We stacked the observations of the undetected objects at 850 mum, 1250 mum and 4.8 GHz in order to search for possible statistical emission from the ERO population as a whole, but no significant detections were derived either for the whole sample or as a function of the average NIR colours. These results strongly suggest that the dominant population of EROs with K < 20 is not comprised of ULIGs like HR 10, but is probably made of radio-quiet ellipticals and weaker starburst galaxies with L < 10(12) L . and SFR < few hundred M. yr(-1).

Cobalt oxide thin films prepared by metalorganic chemical vapor deposition from cobalt acetylacetonate

Thin films of cobalt oxide have been deposited on various substrates, such as glass, Si(100), SrTiO3(100), and LaAlO3(100), by low pressure metalorganic chemical vapor deposition (MOCVD) using cobalt(IL), acetylacetonate as the precursor. Films obtained in the temperature range 400-600 degreesC were uniform and highly crystalline having Co3O4 phase as revealed by x-ray diffraction. Under similar conditions of growth, highly oriented thin films of cobalt oxide grow on SrTiO3(100) and LaAlO3(100). The microstructure and the surface morphology of cobalt oxide films on glass, Si(100) and single crystalline substrates, SrTiO3(100) and LaAlO3(100) were studied by scanning electron microscopy. Optical properties of the films were studied by uv-visible-near IR spectrophotometry.

Electronic structure of ${\rm Ca}_{1-x}{\rm Sr}_x{\rm VO}_3$: A tale of two energy scales

We investigate the electronic structure of Ca1-xSrxVO3 using photoemission spectroscopy. Core level spectra establish an electronic phase separation at the surface, leading to a distinctly different surface electronic structure compared to the bulk. Analysis of the photoemission spectra of this system allowed us to separate the surface and bulk contributions. These results help us to understand properties related to two vastly differing energy scales, namely the low-energy scale of thermal excitations ( $\sim\!k_{\rm B}T$) and the high-energy scale related to Coulomb and other electronic interactions.

Temperature profiles of accretion discs around rapidly rotating strange stars in general relativity: A comparison with neutron stars

We compute the temperature profiles of accretion discs around rapidly rotating strange stars, using constant gravitational mass equilibrium sequences of these objects, considering the full effect of general relativity. Beyond a certain critical value of stellar angular momentum (J), we observe the radius ( $r_{\rm orb}$) of the innermost stable circular orbit (ISCO) to increase with J (a property seen neither in rotating black holes nor in rotating neutron stars). The reason for this is traced to the crucial dependence of ${\rm d}r_{\rm orb}/{\rm d}J$ on the rate of change of the radial gradient of the Keplerian angular velocity at $r_{\rm orb}$ with respect to J. The structure parameters and temperature profiles obtained are compared with those of neutron stars, as an attempt to provide signatures for distinguishing between the two. We show that when the full gamut of strange star equation of state models, with varying degrees of stiffness are considered, there exists a substantial overlap in properties of both neutron stars and strange stars. However, applying accretion disc model constraints to rule out stiff strange star equation of state models, we notice that neutron stars and strange stars exclusively occupy certain parameter spaces. This result implies the possibility of distinguishing these objects from each other by sensitive observations through future X-ray detectors.