16,259 research outputs found
Measurements of the composition of aerosol component of Venusian atmosphere with Vega 1 lander, preliminary data
Preliminary investigation of mass spectra of gaseous products of pyrolyzed Venusian cloud particles collected and analyzed by the complex device of mass-spectrometer and collector pyrolyzer on board Vega 1 lander revealed the presence of heavy particles in the upper cloud layer. Based on 64 amu peak (SO2+), an estimate of the lower limit of the sulfuric acid aerosol content at the 62 to 54 km heights of approximately 2.0 mg/cu m is obtained. A chlorine line (35 and 37 amu) is also present in the mass spectrum with a lower limit of the chlorine concentration of approximately 0.3 mg/ cu m
Determination of the Far-Infrared Cosmic Background Using COBE/DIRBE and WHAM Data
Determination of the cosmic infrared background (CIB) at far infrared
wavelengths using COBE/DIRBE data is limited by the accuracy to which
foreground interplanetary and Galactic dust emission can be modeled and
subtracted. Previous determinations of the far infrared CIB (e.g., Hauser et
al. 1998) were based on the detection of residual isotropic emission in skymaps
from which the emission from interplanetary dust and the neutral interstellar
medium were removed. In this paper we use the Wisconsin H-alpha Mapper (WHAM)
Northern Sky Survey as a tracer of the ionized medium to examine the effect of
this foreground component on determination of the CIB. We decompose the DIRBE
far infrared data for five high Galactic latitude regions into H I and H-alpha
correlated components and a residual component. We find the H-alpha correlated
component to be consistent with zero for each region, and we find that addition
of an H-alpha correlated component in modeling the foreground emission has
negligible effect on derived CIB results. Our CIB detections and 2 sigma upper
limits are essentially the same as those derived by Hauser et al. and are given
by nu I_nu (nW m-2 sr-1) < 75, < 32, 25 +- 8, and 13 +- 3 at 60, 100, 140, and
240 microns, respectively. Our residuals have not been subjected to a detailed
anisotropy test, so our CIB results do not supersede those of Hauser et al. We
derive upper limits on the 100 micron emissivity of the ionized medium that are
typically about 40% of the 100 micron emissivity of the neutral atomic medium.
This low value may be caused in part by a lower dust-to-gas mass ratio in the
ionized medium than in the neutral medium, and in part by a shortcoming of
using H-alpha intensity as a tracer of far infrared emission.Comment: 38 pages, 8 figures. Accepted for publication in Ap
Imperfect Homoclinic Bifurcations
Experimental observations of an almost symmetric electronic circuit show
complicated sequences of bifurcations. These results are discussed in the light
of a theory of imperfect global bifurcations. It is shown that much of the
dynamics observed in the circuit can be understood by reference to imperfect
homoclinic bifurcations without constructing an explicit mathematical model of
the system.Comment: 8 pages, 11 figures, submitted to PR
Solution generating with perfect fluids
We apply a technique, due to Stephani, for generating solutions of the
Einstein-perfect fluid equations. This technique is similar to the vacuum
solution generating techniques of Ehlers, Harrison, Geroch and others. We start
with a ``seed'' solution of the Einstein-perfect fluid equations with a Killing
vector. The seed solution must either have (i) a spacelike Killing vector and
equation of state P=rho or (ii) a timelike Killing vector and equation of state
rho+3P=0. The new solution generated by this technique then has the same
Killing vector and the same equation of state. We choose several simple seed
solutions with these equations of state and where the Killing vector has no
twist. The new solutions are twisting versions of the seed solutions
A Measurement of the Angular Power Spectrum of the CMB Temperature Anisotropy from the 2003 Flight of Boomerang
We report on observations of the Cosmic Microwave Background (CMB) obtained
during the January 2003 flight of Boomerang . These results are derived from
195 hours of observation with four 145 GHz Polarization Sensitive Bolometer
(PSB) pairs, identical in design to the four 143 GHz Planck HFI polarized
pixels. The data include 75 hours of observations distributed over 1.84% of the
sky with an additional 120 hours concentrated on the central portion of the
field, itself representing 0.22% of the full sky. From these data we derive an
estimate of the angular power spectrum of temperature fluctuations of the CMB
in 24 bands over the multipole range (50 < l < 1500). A series of features,
consistent with those expected from acoustic oscillations in the primordial
photon-baryon fluid, are clearly evident in the power spectrum, as is the
exponential damping of power on scales smaller than the photon mean free path
at the epoch of last scattering (l > 900). As a consistency check, the
collaboration has performed two fully independent analyses of the time ordered
data, which are found to be in excellent agreement.Comment: 11 pages, 7 figures, 3 tables. High resolution figures and data are
available at http://cmb.phys.cwru.edu/boomerang/ and
http://oberon.roma1.infn.it/boomerang/b2
Damage to the prefrontal cortex increases utilitarian moral judgements
The psychological and neurobiological processes underlying moral judgement have been the focus of many recent empirical studies1â11. Of central interest is whether emotions play a causal role in moral judgement, and, in parallel, how emotion-related areas of the brain contribute to moral judgement. Here we show that six patients with focal bilateral damage to the ventromedial prefrontal cortex (VMPC), a brain region necessary for the normal generation of emotions and, in particular, social emotions12â14, produce an abnor- mally âutilitarianâ pattern of judgements on moral dilemmas that pit compelling considerations of aggregate welfare against highly emotionally aversive behaviours (for example, having to sacrifice one personâs life to save a number of other lives)7,8. In contrast, the VMPC patientsâ judgements were normal in other classes of moral dilemmas. These findings indicate that, for a selective set of moral dilemmas, the VMPC is critical for normal judgements of right and wrong. The findings support a necessary role for emotion in the generation of those judgements
Unusual Flaring Activity in the Blazar PKS 1424-418 during 2008-2011
Context. Blazars are a subset of active galactic nuclei (AGN) with jets that
are oriented along our line of sight. Variability and spectral energy
distribution (SED) studies are crucial tools for understanding the physical
processes responsible for observed AGN emission.
Aims. We report peculiar behaviour in the bright gamma-ray blazar PKS
1424-418 and use its strong variability to reveal information about the
particle acceleration and interactions in the jet. Methods. Correlation
analysis of the extensive optical coverage by the ATOM telescope and nearly
continuous gamma-ray coverage by the Fermi Large Area Telescope is combined
with broadband, time-dependent modeling of the SED incorporating supplemental
information from radio and X-ray observations of this blazar.
Results. We analyse in detail four bright phases at optical-GeV energies.
These flares of PKS 1424-418 show high correlation between these energy ranges,
with the exception of one large optical flare that coincides with relatively
low gamma-ray activity. Although the optical/gamma-ray behaviour of PKS
1424-418 shows variety, the multiwavelength modeling indicates that these
differences can largely be explained by changes in the flux and energy spectrum
of the electrons in the jet that are radiating. We find that for all flares the
SED is adequately represented by a leptonic model that includes inverse Compton
emission from external radiation fields with similar parameters.
Conclusions. Detailed studies of individual blazars like PKS 1424-418 during
periods of enhanced activity in different wavebands are helping us identify
underlying patterns in the physical parameters in this class of AGN.Comment: accepted for publication in A&
Development and Characterization of a Precisely Adjustable Fiber Polishing Arm
The development of bare fiber or air-gapped microlens-fiber coupled Integral
Field Units (IFUs) for astronomical applications requires careful treatment of
the fiber end-faces (terminations). Previous studies suggest that minimization
of fiber end face irregularity leads to better optical performance in terms of
the diminishing effect of focal ratio degradation. Polishing has typically been
performed using commercial rotary polishers with multiple gradually decreasing
grit sizes. These polishers generally lack the ability to carefully adjust
angular position and polishing force. Control of these parameters vastly help
in getting a repeatable and controllable polish over a variety of
glass/epoxy/metal matrices that make up integral filed units and fiber slits. A
polishing arm is developed to polish the fiber terminations (IFU, mini-bundles
and v-grooves) of the NIR Fiber System for the RSS spectrograph at SALT. The
polishing arm angular adjustments ensure the correct position and orientation
of each termination on the polishing surface during the polish. Various studies
have indicated that the fiber focal ratio also degrades if the fiber end face
comes under excessive stress. The polishing arm is fitted with a load cell to
enable control of the polishing force. We have explored the minimal applicable
end stress by applying different loads while polishing. The arm is modular to
hold a variety of fiber termination styles. The polishing arm is also designed
to access a fiber inspection microscope without removing the fiber termination
from the arm. This enables inspection of the finish quality at various stages
through polishing process
Iridium complexes of the conformationally rigid IBioxMe4Ligand : hydride complexes and dehydrogenation of cyclooctene
A method for accessing the formally 14 VE iridium(III) hydride fragment {Ir(IBioxMe4)2(H)2}+ (2), containing the conformationally rigid NHC ligand IBioxMe4, is reported. Hydrogenation of trans-[Ir(IBioxMe4)2(COE)Cl] (1) in the presence of excess Na[BArF4] leads to the formation of dimeric [{Ir(IBioxMe4)2(H)2}2Cl][BArF4] (3), which is structurally fluxional in solution and acts as a reservoir of monomeric 2 in the presence of excess halogen ion abstractor. Stable dihydride complexes trans-[Ir(IBioxMe4)2(2,2âČ-bipyridine)(H)2][BArF4] (4) and [Ir(IBioxMe4)3(H)2][BArF4] (5) were subsequently isolated through in situ trapping of 2 using 2,2âČ-bipyridine and IBioxMe4, respectively, and fully characterized. Using mixtures of 3 and Na[BArF4] as a latent source of 2, the reactive monomeric fragmentâs reactivity was explored with excess ethylene and cyclooctene, and trans-[Ir(IBioxMe4)2(C2H4)2][BArF4] (6) and cis-[Ir(IBioxMe4)2(COD)][BArF4] (7) were isolated, respectively, through sacrificial hydrogenation of the alkenes. Complex 6 is notable for the adoption of a very unusual orthogonal arrangement of the trans-ethylene ligands in the solid state, which has been analyzed computationally using energy and charge decomposition (EDA-NOCV). The formation of 7 via transfer dehydrogenation of COE highlights the ability to partner IBioxMe4 with reactive metal centers capable of CâH bond activation, without intramolecular activation. Reaction of 7 with CO slowly formed trans-[Ir(IBioxMe4)2(CO)2][BArF4] (8), but the equivalent reaction with bis-ethylene 6 was an order of magnitude faster, quantifying the strong coordination of COD in 7
Negotiating daughterhood and strangerhood: retrospective accounts of serial migration
Most considerations of daughtering and mothering take for granted that the subjectivities of mothers and daughters are negotiated in contexts of physical proximity throughout daughtersâ childhoods. Yet many mothers and daughters spend periods separated from each other, sometimes across national borders. Globally, an increasing number of children experience life in transnational families.
This paper examines the retrospective narratives of four women who were serial migrants as children (whose parents migrated before they did) . It focuses on their accounts of the reunion with their mothers and how these fit with the ways in which they construct their mother-daughter relationships. We take a psychosocial approach by using a psychoanalytically-informed reading of these narratives to acknowledge the complexities of the attachments produced in the context of migration and to attend to the multi-layered psychodynamics of the resulting relationships. The paper argues that serial migration positioned many of the daughters in a conflictual emotional landscape from which they had to negotiate âstrangerhoodâ in the context of sadness at leaving people to whom they were attached in order to join their mothers (or parents). As a result, many were resistant to being positioned as daughters, doing daughtering and being mothered in their new homes
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