Cosmic Needles versus Cosmic Microwave Background Radiation

It has been suggested by a number of authors that the 2.7K cosmic microwave background (CMB) radiation might have arisen from the radiation from Population III objects thermalized by conducting cosmic graphite/iron needle-shaped dust. Due to lack of an accurate solution to the absorption properties of exceedingly elongated grains, in existing literature which studies the CMB thermalizing process they are generally modelled as (1) needle-like spheroids in terms of the Rayleigh approximation; (2) infinite cylinders; and (3) the antenna theory. We show here that the Rayleigh approximation is not valid since the Rayleigh criterion is not satisfied for highly conducting needles. We also show that the available intergalactic iron dust, if modelled as infinite cylinders, is not sufficient to supply the required opacity at long wavelengths to obtain the observed isotropy and Planckian nature of the CMB. If appealing to the antenna theory, conducting iron needles with exceedingly large elongations (10^4) appear able to provide sufficient opacity to thermalize the CMB within the iron density limit. But the applicability of the antenna theory to exceedingly thin needles of nanometer/micrometer in thickness needs to be justified.Comment: 13 pages, 4 figures; submitted to ApJ

The Detection of Cold Dust in Cas A: Evidence for the Formation of Metallic Needles in the Ejecta

Recently, Dunne et al. (2003) obtained 450 and 850 micron SCUBA images of CasA, and reported the detection of 2-4 M_sun of cold, 18K, dust in the remnant. Here we show that their interpretation of the observations faces serious difficulties. Their inferred dust mass is larger than the mass of refractory material in the ejecta of a 10 to 30 M_sun star. The cold dust model faces even more difficulties if the 170 micron observations of the remnant are included in the analysis, decreasing the cold dust temperature to ~ 8K, and increasing its mass to > 20 M_sun. We offer here a more plausible interpretation of their observation, in which the cold dust emission is generated by conducting needles with properties that are completely determined by the combined submillimeter and X-ray observations of the remnant. The needles consist of metallic whiskers with <1% of embedded impurities that may have condensed out of blobs of material that were expelled at high velocities from the inner metal-rich layers of the star in an asymmetric explosion. The needles are collisionally heated by the shocked gas to a temperature of 8K. Taking the destruction of needles into account, a dust mass of only 1E-4 to 1E-3M_sun is needed to account for the observed SCUBA emission. Aligned in the magnetic field, needles may give rise to observable polarized emission. The detection of submillimeter polarization will therefore offer definitive proof for a needle origin for the cold dust emission. Supernovae may still be proven to be important sources of interstellar dust, but the evidence is still inconclusive.Comment: 18 pages including 4 figures. Accepted for publication in the ApJ. Missing reference adde

Formal Process of Managerial Learning: Empirical Evidence from Apparel Manufacturing Industry

This paper reports results of an empirical investigation into the formal processes that apparel manufacturing companies use to develop their managers. The findings of the study shed light on the formal development processes that are commonly used in the industry and on differences across companies of different ownership. The investigations revealed that not all human resource managers actively engage in the provision of different formal management development processes. Instead, some development processes are solely provided by the heads of the departments within their departments without having any specific organisation-led development initiative. The implications of the findings are discussed. Key words: Apparel Industry, Management Development, Ownershi

V405 Aurigae: A High Magnetic Field Intermediate Polar

Our simultaneous multicolor (UBVRI) circular polarimetry has revealed nearly sinusoidal variation over the WD spin cycle, and almost symmetric positive and negative polarization excursions. Maximum amplitudes are observed in the B and V bands (+-3 %). This is the first time that polarization peaking in the blue has been discovered in an IP, and suggests that V405 Aur is the highest magnetic field IP found so far. The polarized flux spectrum is similar to those found in polars with magnetic fields in the range B ~ 25-50 MG. Our low resolution circular spectropolarimetry has given evidence of transient features which can be fitted by cyclotron harmonics n = 6, 7, and 8, at a field of B = 31.5 +- 0.8 MG, consistent with the broad-band polarized flux spectrum. Timings of the circular polarization zero crossovers put strict upper limits on WD spin period changes and indicate that the WD in V405 Aur is currently accreting closely at the spin equilibrium rate, with very long synchronization timescales, T_s > 10^9 yr. For the observed spin to orbital period ratio, P_{spin}/P_{orb} = 0.0365, and P_{orb} ~ 4.15 hr, existing numerical accretion models predict spin equilibrium condition with B ~ 30 MG if the mass ratio of the binary components is q_1 ~ 0.4. The high magnetic field makes V405 Aur a likely candidate as a progenitor of a polar.Comment: To appear in The Astrophysical Journal, September 1 Issue (2008), 9 pages, 10 figure

Non-sister Sri Lankan White-eyes (genus Zosterops) are a Result of Independent Colonizations

Co-occurrence of closely related taxa on islands could be attributed to sympatric speciation or multiple colonization. Sympatric speciation is considered to be rare in small islands, however multiple colonizations are known to be common in both oceanic and continental islands. In this study we investigated the phylogenetic relatedness and means of origin of the two sympatrically co-occurring Zosterops white-eyes, the endemic Zosterops ceylonensis and its widespread regional congener Z. palpebrosus, in the island of Sri Lanka. Sri Lanka is a continental island in the Indian continental shelf of the Northern Indian Ocean. Our multivariate morphometric analyses confirmed the phenotypic distinctness of the two species. Maximum Likelihood and Bayesian phylogenetic analyses with ~2000bp from two mitochondrial (ND2 and ND3) and one nuclear (TGF) gene indicated that they are phylogenetically distinct, and not sister to each other. The two subspecies of the peninsula India; Z. p. egregius of Sri Lanka and India and Z. p. nilgiriensis of Western Ghats (India) clustered within the Z. palpebrosus clade having a common ancestor. In contrast, the divergence of the endemic Z. ceylonensis appears to be much deeper and is basal to the other Zosterops white-eyes. Therefore we conclude that the two Zosterops species originated in the island through independent colonizations from different ancestral lineages, and not through island speciation or multiple colonization from the same continental ancestral population. Despite high endemism, Sri Lankan biodiversity is long considered to be a subset of southern India. This study on a speciose group with high dispersal ability and rapid diversification rate provide evidence for the contribution of multiple colonizations in shaping Sri Lanka’s biodiversity. It also highlights the complex biogeographic patterns of the South Asian region, reflected even in highly vagile groups such as birds

Detection of microorganisms at high altitudes

This article does not have an abstract

Pulse time modulation for subcarrier multiplexed systems.

Subcarrier multiplexed (SCM) systems are an attractive alternative to the evolving digital technology for transmitting broadband services, at an affordable price. However, the majority of existing systems are based on analogue signal transmission and therefore, the strict noise and nonlinear requirements undermine the system performance. The work carried out in this thesis presents the feasibility of pulse time modulation (PTM), as a second stage modulator, in SCM systems.PTM techniques offer simplicity and low cost, and with the additional bandwidth available on optical fibres can trade bandwidth to significantly higher signal-to-noise ratio (SNR) levels, compared to analogue systems. Three different PTM techniques, square wave frequency modulation (SWFM), pulse frequency modulation (PFM) and pulse position modulation (PPM) has been investigated. A prototype system capable of transmitting a video channel, two audio channels and a data channel is implemented for each technique in order to evaluate the performance potential of PTM as a second stage modulator in SCM systems.The SNR expressions for all three schemes are derived from the first principles and the obtained results were verified experimentally. The optimum SNR performance is delivered by a raised cosine shaped pulse and the PPM technique delivers 5 dB SNR improvement over PFM. For SWFM systems a 3 dB SNR advantage is gained over single-edge detection technique and PFM systems by employing double-edge detection at the receiver. PPM spectrum contains a clock component which could be employed at the receiver for signal recovery. Demodulation technique, based on clock recovery using a phase locked loop (PLL) is proposed and implemented. This technique is cost effective and less complex compared to the existing demodulation schemes.The PFM implementation shows a 6 dB improvement in the receiver sensitivity compared to conventional SCM systems, while the PPM system offers an extra 2.5 dB improvement. The improved receiver sensitivity of the SCM-PTM technique, results in an increased optical power budget, where the transmission distance, number of subscribers and the number of channels in a network can be optimized. The nonlinear performance of the overall system is also shown to be within the specified performance levels

Three-dimensional Simulations of Accretion to Stars with Complex Magnetic Fields

Disk accretion to rotating stars with complex magnetic fields is investigated using full three-dimensional magnetohydrodynamic (MHD) simulations. The studied magnetic configurations include superpositions of misaligned dipole and quadrupole fields and off-centre dipoles. The simulations show that when the quadrupole component is comparable to the dipole component, the magnetic field has a complex structure with three major magnetic poles on the surface of the star and three sets of loops of field lines connecting them. A significant amount of matter flows to the quadrupole "belt", forming a ring-like hot spot on the star. If the maximum strength of the magnetic field on the star is fixed, then we observe that the mass accretion rate, the torque on the star, and the area covered by hot spots are several times smaller in the quadrupole-dominant cases than in the pure dipole cases. The influence of the quadrupole component on the shape of the hot spots becomes noticeable when the ratio of the quadrupole and dipole field strengths $B_q/B_d\gtrsim0.5$, and becomes dominant when $B_q/B_d\gtrsim1$. In the case of an off-centre dipole field, most of the matter flows through a one-armed accretion stream, forming a large hot spot on the surface, with a second much smaller secondary spot. The light curves may have simple, sinusoidal shapes, thus mimicking stars with pure dipole fields. Or, they may be complex and unusual. In some cases the light curves may be indicators of a complex field, in particular if the inclination angle is known independently. We also note that in the case of complex fields, magnetospheric gaps are often not empty, and this may be important for the survival of close-in exosolar planets.Comment: 13 pages, 21 figures, accepted for publication in MNRA

Three-dimensional Simulations of Disk Accretion to an Inclined Dipole: I. Magnetospheric Flow at Different Theta

We present results of fully three-dimensional MHD simulations of disk accretion to a rotating magnetized star with its dipole moment inclined at an angle Theta to the rotation axis of the disk. We observed that matter accretes from the disk to a star in two or several streams depending on Theta. Streams may precess around the star at small Theta. The inner regions of the disk are warped. The warping is due to the tendency of matter to co-rotate with inclined magnetosphere. The accreting matter brings positive angular momentum to the (slowly rotating) star tending to spin it up. The corresponding torque N_z depends only weakly on Theta. The angular momentum flux to the star is transported predominantly by the magnetic field; the matter component contributes < 1 % of the total flux. Results of simulations are important for understanding the nature of classical T Tauri stars, cataclysmic variables, and X-ray pulsars.Comment: 26 pages, 22 figures, LaTeX, macros: emulapj.sty, avi simulations are available at http://www.astro.cornell.edu/us-rus/inclined.ht

Possible interpretations of the magnitude-redshift relation for supernovae of type Ia

It has been shown by Riess et al. and Perlmutter et al. that the observed redshift-magnitude relation for supernovae of type Ia, which suggests that the deceleration parameter q0 is negative, can be explained in a Friedmann model with a positive cosmological constant. We show that a quasi-steady state cosmology (QSSC) model can also fit the supernova data. Since most of the emphasis and publicity have been concentrated on explanations involving the Friedmann model, we show how a good fit can be obtained to the observations in the framework of the QSSC. Using this model, we show that absorption due to intergalactic dust may play an important role. This may explain why a few of the supernovae observed show large deviations from the curve determined by the majority of the data