Data assimilation for the Martian atmosphere using MGS Thermal Emission Spectrometer observations

From the introduction: Given the quantity of data expected from current and forthcoming spacecraft missions to Mars, it is now possible to use data assimilation as a means of atmospheric analysis for the first time for a planet other than the Earth. Several groups have described plans to develop assimilation schemes for Mars [Banfield et al., 1995; Houben, 1999; Lewis and Read, 1995; Lewis et al., 1996, 1997; Zhang et al., 2001]. Data assimilation is a technique for the analysis of atmospheric observations which combines currently valid information with prior knowledge from previous observations and dynamical and physical constraints, via the use of a numerical model. Despite the number of new missions, observations of the atmosphere of Mars in the near future are still likely to be sparse when compared to those of the Earth, perhaps comprising one orbiter and a few surface stations at best at any one time. Data assimilation is useful as a means to extract the maximum information from such observations, both by a form of interpolation in space and time using model constraints and by the combination of information from different observations, e.g. temperature profiles and surface pressure measurements which may be irregularly distributed. The procedure can produce a dynamically consistent set of meteorological fields and can be used directly to test and to refine an atmospheric model against observations

Assimilation of TES data from the Mars Global Surveyor scientifc mapping phase

The Thermal Emission Spectrometer (TES)aboard Mars Global Surveyor has produced data which cover almost two Martian years so far (during its scientific mapping phase). Thermal profiles for the atmosphere below 40 km and total dust opacities can be retrieved from TES nadir spectra and assimilated into a Mars general circulation model (MGCM), by using the assimilation techniques described in detail by Lewis et al. (2002). This paper describes some preliminary results from assimilations of temperature data from the period Ls=141°- 270° corresponding to late northern summer until winter solstice on Mars. Work in progress is devoted to assimilate both temperature and total dust opacity data for the full period for which they are already available

Effect of recoil on the velocity distribution of metastable atoms produced by electron impact

We have shown both experimentally and by a simple kinematic argument that the velocity distribution in a beam of metastable atoms produced by electron bombardment of ground state atoms deviates strongly from the velocity distribution of the ground state atoms.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32886/1/0000264.pd

The Major Histocompatibility Complex–related Fc Receptor for IgG (FcRn) Binds Albumin and Prolongs Its Lifespan

The inverse relationship between serum albumin concentration and its half-life suggested to early workers that albumin would be protected from a catabolic fate by a receptor-mediated mechanism much like that proposed for IgG. We show here that albumin binds FcRn in a pH dependent fashion, that the lifespan of albumin is shortened in FcRn-deficient mice, and that the plasma albumin concentration of FcRn-deficient mice is less than half that of wild-type mice. These results affirm the hypothesis that the major histocompatibility complex–related Fc receptor protects albumin from degradation just as it does IgG, prolonging the half-lives of both

Correspondence between T. Melden, George C. Stokes, and John Shary

Correspondence regarding lot 282, Shary Subdivision between November 1, 1930 and October 15, 1942 between T. Melden, George C. Stokes, John Shary, Pearl Stokes, and attorneys for the United Irrigation Company.https://scholarworks.utrgv.edu/johnshary/1024/thumbnail.jp

Assimilation of Mars Global Surveyor atmospheric temperature data into a general circulation model

We examined the observed temperature data from Thermal Emission Spectrometer (TES) between heliocentric longitude L_s = 141° and 146° (∼10 Martian days in northern summer) during the mapping phase, then compared them with the simulated results using the NASA/Ames Mars general circulation model. Both show a strong polar vortex at the winter pole, higher equatorial temperatures near the ground and larger tropospheric lapse rates during daytime than at night. However, the simulation is colder than the observation at the bottom and top of the atmosphere and warmer in the middle. The highest wave activities are found in the polar front in both the simulations and the observations, but it is at a much higher altitude in the former. Experiments show that larger dust opacity improves the temperature field in the lower atmospheric levels. Using a steady state Kalman filter, we attempted to obtain a model state that is consistent with the observations. The assimilation did achieve better agreement with the observations overall, especially over the north pole. However, it is hard to make any further improvement. Dust opacity is the key factor in determining the temperature field; correcting temperature alone improves the spatial and temporal variations, it degrades the mean state in the south pole. Assimilation cannot improve the simulation further, unless more realistic dust opacity and its vertical profile are considered

Properties of mesoscopic superconducting thin-film rings. London approach

Superconducting thin-film rings smaller than the film penetration depth (the Pearl length) are considered. The current distribution, magnetic moment, and thermodynamic potential ${\cal F}(H,N,v)$ for a flat, washer-shaped annular ring in a uniform applied field $H$ perpendicular to the film are solved analytically within the London approach for a state with winding number $N$ and a vortex at radius $v$ between the inner and outer radii.Comment: Submitted to Phys. Rev.

Homophily and Contagion Are Generically Confounded in Observational Social Network Studies

We consider processes on social networks that can potentially involve three factors: homophily, or the formation of social ties due to matching individual traits; social contagion, also known as social influence; and the causal effect of an individual's covariates on their behavior or other measurable responses. We show that, generically, all of these are confounded with each other. Distinguishing them from one another requires strong assumptions on the parametrization of the social process or on the adequacy of the covariates used (or both). In particular we demonstrate, with simple examples, that asymmetries in regression coefficients cannot identify causal effects, and that very simple models of imitation (a form of social contagion) can produce substantial correlations between an individual's enduring traits and their choices, even when there is no intrinsic affinity between them. We also suggest some possible constructive responses to these results.Comment: 27 pages, 9 figures. V2: Revised in response to referees. V3: Ditt

Dynamic Impedance of Two-Dimensional Superconducting Films Near the Superconducting Transition

The sheet impedances, Z(w,T), of several superconducting a-Mo77Ge23 films and one In/InOx film have been measured in zero field using a two-coil mutual inductance technique at frequencies from 100 Hz to 100 kHz. Z(w,T) is found to have three contributions: the inductive superfluid, renormalized by nonvortex phase fluctuations; conventional vortex-antivortex pairs, whose contribution turns on very rapidly just below the usual Kosterlitz-Thouless-Berezinskii unbinding temperature; and an anomalous contribution. The latter is predominantly resistive, persists well below the KTB temperature, and is weakly dependent on frequency down to remarkably low frequencies, at least 100 Hz. It increases with T as e-U'(T)/kT, where the activation energy, U'(T), is about half the energy to create a vortex-antivortex pair, indicating that the frequency dependence is that of individual excitations, rather than critical behavior.Comment: 10 pages, 10 figs; subm PR

Phenomenology of GUT-less Supersymmetry Breaking

We study models in which supersymmetry breaking appears at an intermediate scale, M_{in}, below the GUT scale. We assume that the soft supersymmetry-breaking parameters of the MSSM are universal at M_{in}, and analyze the morphology of the constraints from cosmology and collider experiments on the allowed regions of parameter space as M_{in} is reduced from the GUT scale. We present separate analyses of the (m_{1/2},m_0) planes for tan(beta)=10 and tan(beta)=50, as well as a discussion of non-zero trilinear couplings, A_0. Specific scenarios where the gaugino and scalar masses appear to be universal below the GUT scale have been found in mirage-mediation models, which we also address here. We demand that the lightest neutralino be the LSP, and that the relic neutralino density not conflict with measurements by WMAP and other observations. At moderate values of M_{in}, we find that the allowed regions of the (m_{1/2},m_0) plane are squeezed by the requirements of electroweak symmetry breaking and that the lightest neutralino be the LSP, whereas the constraint on the relic density is less severe. At very low M_{in}, the electroweak vacuum conditions become the dominant constraint, and a secondary source of astrophysical cold dark matter would be necessary to explain the measured relic density for nearly all values of the soft SUSY-breaking parameters and tan(beta). We calculate the neutralino-nucleon cross sections for viable scenarios and compare them with the present and projected limits from direct dark matter searches.Comment: 35 pages, 9 figures; typos corrected, references adde