Microwave spectroscopy of the Mars atmosphere

A study of the use of millimeter-wavelength spectral transitions to investigate the atmosphere of Mars is presented. In the model experiments investigated it is assumed that a spectrometer in the frequency range from 100 to 260 GHz looks into a modest-sized telescope of from 30 to 50 cm aperture from a near-Mars orbit. The molecules H2O, CO, O2, O3, and H2O2 all have intense spectral lines in the Mars atmosphere in this frequency range and in addition are all very important in understanding the water cycle, the photochemistry, and the circularization in that atmosphere. It is shown that the altitude and the zonal distribution of H2O can be mapped even in atmospheric columns as dry as 0.25 precipital μm. Ozone can be mapped over the entire planet, independent of solar-lighting conditions, dust loading, or clouds in the atmosphere, because millimeter waves are insensitive to any particles that can be suspended in the Mars atmosphere. Because the signal-receiving techniques use superheterodyne devices and narrow spectral lines, zonal and meridional winds can be measured at altitudes above 10 km with a precision approaching approximately 3 m/s by the use of Doppler shifts. Temperature–pressure profiles can be measured to altitudes of 100 km by the use of CO lines in the limb-sounding mode

The effects of atmospheric dust on observations of Martian surface albedo

The Mariner 9 and Viking missions provided abundant evidence that aeolian processes are active over much of surface of Mars. A radiative transfer model was developed which allows the effects of atmospheric dust loading and variable surface albedo to be investigated. This model incorporated atmospheric dust opacity, the single scattering albedo, and particle phase function of atmospheric dust, the bidirectional; reflectance of the surface, and variable lighting and viewing geometry. The Cerberus albedo feature was examined in detail using this technique

Properties of dust and clouds in the Mars atmosphere: Analysis of Viking IRTM emission phase function sequences

An analysis of emission-phase-function (EPF) observations from the Viking Orbiter Infrared Thermal Mapper (IRTM) yields a wide variety of results regarding dust and cloud scattering in the Mars atmosphere and atmospheric-corrected albedos for the surface of Mars. A multiple scattering radiative transfer model incorporating a bidirectional phase function for the surface and atmospheric scattering by dust and clouds is used to derive surface albedos and dust and ice optical properties and optical depths for these various conditions on Mars

Infrared signature of active massive black holes in nearby dwarf galaxies

We investigate the possible presence of active galactic nuclei (AGN) in dwarf galaxies and other nearby galaxies to identify candidates for follow-up confirmation and dynamical mass measurements. We use the Wide-field Infrared Survey Explorer (WISE) All-Sky Release Source Catalog and examine the infrared colours of a sample of dwarf galaxies and other nearby galaxies in order to identify both unobscured and obscured candidate AGN by applying the infrared colour diagnostic. Stellar masses of galaxies are obtained using a combination of three independent methods. Black hole masses are estimated using the bolometric luminosity of the AGN candidates and computed for three cases of the bolometric-to-Eddington luminosity ratio. We identify 303 candidate AGN, of which 276 were subsequently found to have been independently identified as AGN via other methods. The remaining 9% require follow-up observations for confirmation. The activity is detected in galaxies with stellar masses from ~ 10^6 to 10^9 solar masses; assuming the candidates are AGN, the black hole masses are estimated to be ~ 10^3 - 10^6 solar masses, adopting L_bol = 0.1 L_Edd. The black hole masses probed are several orders of magnitude smaller than previously reported for centrally located massive black holes. We examine the stellar mass versus black hole mass relationship in this low galaxy mass regime. We find that it is consistent with the existing relation extending linearly (in log-log space) into the lower mass regime. These findings suggest that CMBH are present in low-mass galaxies and in the Local Universe, and provide new impetus for follow-up dynamical studies of quiescent black holes in local dwarf galaxies.Comment: 14 pages, 9 figures, 4 tables, accepted for publication in Astronomy & Astrophysics. The first version of this paper appeared on astro-ph in 2014 (arXiv:1411.3844). The new version includes 3 new tables, 1 new figure and updated discussio

Retroactive Anti-Jamming for MISO Broadcast Channels

Jamming attacks can significantly impact the performance of wireless communication systems. In addition to reducing the capacity, such attacks may lead to insurmountable overhead in terms of re-transmissions and increased power consumption. In this paper, we consider the multiple-input single-output (MISO) broadcast channel (BC) in the presence of a jamming attack in which a subset of the receivers can be jammed at any given time. Further, countermeasures for mitigating the effects of such jamming attacks are presented. The effectiveness of these anti-jamming countermeasures is quantified in terms of the degrees-of-freedom (DoF) of the MISO BC under various assumptions regarding the availability of the channel state information (CSIT) and the jammer state information at the transmitter (JSIT). The main contribution of this paper is the characterization of the DoF region of the two user MISO BC under various assumptions on the availability of CSIT and JSIT. Partial extensions to the multi-user broadcast channels are also presented.Comment: submitted to IEEE Transactions on Information Theor

Wind mapping in Venus' upper mesosphere with the IRAM-Plateau de Bure interferometer

The dynamics of the upper mesosphere of Venus (~85-115 km) have been characterized as a combination of a retrograde superrotating zonal wind (RSZ) with a subsolar-to-antisolar flow (SSAS). Numerous mm-wave single-dish observations have been obtained and could directly measure mesospheric line-of-sight winds by mapping Doppler-shifts on CO rotational lines, but their limited spatial resolution makes their interpretation difficult. By using interferometric facilities, one can obtain better resolution on Doppler-shifts maps, allowing in particular to put firmer constraints on the respective contributions of the SSAS and RSZ circulations to the global mesospheric wind field. We report on interferometric observations of the CO(1-0) line obtained with the IRAM-Plateau de Bure interferometer in November 2007 and June 2009, that could map the upper mesosphere dynamics on the morning hemisphere with a very good spatial resolution (3.5-5.5"). All the obtained measurements show, with a remarkably good temporal stability, that the wind globally flows in the (sky) East-West direction, corresponding in the observed geometry either to an unexpected prograde zonal wind or a SSAS flow. A very localized inversion of the wind direction, that could correspond to a RSZ wind, is also repeatedly detected in the night hemisphere. The presence of significant meridional winds is not evidenced. Using models with different combinations of zonal and SSAS winds, we find that the data is best reproduced by a dominant SSAS flow with a maximal velocity at the terminator of ~200 m/s, displaying large diurnal and latitudinal asymmetries, combined with an equatorial RSZ wind of 70-100 m/s, overall indicating a wind-field structure consistent with but much more complex than the usual representation of the mesospheric dynamics.Comment: Accepted for publication in A&

Platelet Transcriptome Heterogeneity: A Role for RNA Uptake in Vascular Health and Disease

As our understanding of the platelet’s systemic role continues to expand beyond hemostasis and thrombosis, interrogation of the platelet’s ability to affect diverse biological processes is required. Studies of the platelet’s non-traditional roles have focused on developing our understanding of the platelet’s relation to specific disease phenotypes as well as elucidation of platelet characteristics, content, and function. The generic content, traditional function and heterogeneity of platelets have long been accepted; more ambiguous and controversial has been how these factors are interrelated. Investigation of platelet content revealed the presence of biologically functional RNA in anucleated platelets, the correlation of platelet RNA to distinct phenotypes, and the ability of platelets to transfer RNA to other vascular cells; however how these processes occur is unclear. To further interrogate platelet RNA processes, we utilized sorting and RNA sequencing to develop platelet subpopulation transcriptome profiles. We found that platelet heterogeneity extends to the platelet transcriptome: distinct RNA profiles exist dependent on platelet size. We hypothesized that this RNA heterogeneity is the result of RNA transfer between platelets and vascular cells. Using in vitro and in vivo modeling, we were able to show the novel ability of platelets to take up RNA from vascular cells, correlating to the unique functional profile associated with small platelet transcriptomes. These findings reveal a role for platelet RNA transfer in platelet RNA heterogeneity, with potential correlation to platelet functional diversity previously proposed. The ability of the platelet to bidirectionally transfer RNA within circulation has implications for vascular health and beyond

Topology Driven Improvement of FDC Build Parameters

The likeliest failure origin for advanced ceramics parts, prepared by fused deposition, is a void from improper fill. Adequate filling of each cross-section is dependent upon the deposition toolpath. Cross-sectional spaces are conventionally filled with pre-defined parameters. We propose that adaptive build parameters will control variations in geometry and property of a part. Voids, overfilling, incomplete bonding and excess traversing can be suppressed by adjusting the fill parameters for cross-sectional areas. Improved build parameters and toolpath allows for faster build time and components ofj full density. Some implementations are discussed and presented.Mechanical Engineerin