Forts, (fractional) zero forcing, and Cartesian products of graphs

The (disjoint) fort number and fractional zero forcing number are introduced and related to existing parameters including the (standard) zero forcing number. The fort hypergraph is introduced and hypergraph results on transversals and matchings are applied to the zero forcing number and fort number. These results are used to establish a Vizing-like lower bound for the zero forcing number of a Cartesian product of graphs for certain families of graphs, and a family of graphs achieving this lower bound is exhibited

The Strong Spectral Property of Graphs: Graph Operations and Barbell Partitions

The utility of a matrix satisfying the Strong Spectral Property has been well established particularly in connection with the inverse eigenvalue problem for graphs. More recently the class of graphs in which all associated symmetric matrices possess the Strong Spectral Property (denoted $G^{SSP}$) were studied, and along these lines we aim to study properties of graphs that exhibit a so-called barbell partition. Such a partition is a known impediment to membership in the class $G^{SSP}$. In particular we consider the existence of barbell partitions under various standard and useful graph operations

Degradation of Organics in a Glow Discharge Under Martian Conditions

The primary objective of this project is to understand the consequences of glow electrical discharges on the chemistry and biology of Mars. The possibility was raised some time ago that the absence of organic material and carbonaceous matter in the Martian soil samples studied by the VikinG Landers might be due in part to an intrinsic atmospheric mechanism such as glow discharge. The high probability for dust interactions during Martian dust storms and dust devils, combined with the cold, dry climate of Mars most likely results in airborne dust that is highly charged. Such high electrostatic potentials generated during dust storms on Earth are not permitted in the low-pressure CO2 environment on Mars; therefore electrostatic energy released in the form of glow discharges is a highly likely phenomenon. Since glow discharge methods are used for cleaning and sterilizing surfaces throughout industry, the idea that dust in the Martian atmosphere undergoes a cleaning action many times over geologic time scales appears to be a plausible one

Centerscope

Centerscope, formerly Scope, was published by the Boston University Medical Center "to communicate the concern of the Medical Center for the development and maintenance of improved health care in contemporary society.

The Methane Diurnal Variation and Microseepage Flux at Gale Crater, Mars as Constrained by the ExoMars Trace Gas Orbiter and Curiosity Observations

The upper bound of 50 parts per trillion by volume for Mars methane above 5 km established by the ExoMars Trace Gas Orbiter, substantially lower than the 410 parts per trillion by volume average measured overnight by the Curiosity Rover, places a strong constraint on the daytime methane flux at the Gale crater. We propose that these measurements may be largely reconciled by the inhibition of mixing near the surface overnight, whereby methane emitted from the subsurface accumulates within meters of the surface before being mixed below detection limits at dawn. A model of this scenario allows the first precise calculation of microseepage fluxes at Gale to be derived, consistent with a constant 1.5 à 10â 10 kg·mâ 2·solâ 1 (5.4 à 10â 5 tonnes·kmâ 2·yearâ 1) source at depth. Under this scenario, only 2.7 à 104 km2 of Mars’s surface may be emitting methane, unless a fast destruction mechanism exists.Plain Language SummaryThe ExoMars Trace Gas Orbiter and the Curiosity Rover have recorded different amounts of methane in the atmosphere on Mars. The Trace Gas Orbiter measured very little methane (<50 parts per trillion by volume) above 5 km in the sunlit atmosphere, while Curiosity measured substantially more (410 parts per trillion by volume) near the surface at night. In this paper we describe a framework which explains both measurements by suggesting that a small amount of methane seeps out of the ground constantly. During the day, this small amount of methane is rapidly mixed and diluted by vigorous convection, leading to low overall levels within the atmosphere. During the night, convection lessens, allowing methane to build up near the surface. At dawn, convection intensifies and the nearâ surface methane is mixed and diluted with much more atmosphere. Using this model and methane concentrations from both approaches, we are ableâ for the first timeâ to place a single number on the rate of seepage of methane at Gale crater which we find equivalent to 2.8 kg per Martian day. Future spacecraft measuring methane near the surface of Mars could determine how much methane seeps out of the ground in different locations, providing insight into what processes create that methane in the subsurface.Key PointsNighttime SAMâ TLS seasonal cycle enrichment measurements and TGO sunset/sunrise measurements are not in oppositionMicroseepage fluxes must be local to Gale, range from 0.82 to 4.6 kg/sol, and are consistent with a constant source at depthLittle of Mars experiences microseepage unless a fast destruction mechanism exists or Gale is very unusualPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151840/1/grl59471-sup-0001-2019GL083800-SI.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151840/2/grl59471_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151840/3/grl59471.pd

Centerscope

Centerscope, formerly Scope, was published by the Boston University Medical Center "to communicate the concern of the Medical Center for the development and maintenance of improved health care in contemporary society.

The role of parental investments for cognitive and noncognitive skill formation : evidence for the first 11 years of life

This paper examines the impact of parental investments on the development of cognitive, mental and emotional skills during childhood using data from a longitudinal study, the Mannheim Study of Children at Risk, starting at birth. Our work offers three important innovations. First, we use reliable measures of the child’s cognitive, mental and emotional skills as well as accurate measures of parental investment. Second, we estimate latent factor models to account for unobserved characteristics of children. Third, we examine the skill development for girls and boys separately, as well as for children who were born with either organic or psychosocial risk. We find a decreasing impact of parental investments on cognitive and mental skills, while emotional skills seem to be unaffected by parental investment throughout childhood. Thus, initial inequality persists during childhood. Since families are the main sources of education during the first years of life, our results have important implications for the quality of the parent-child relationship

Numerical modelling of the transport of trace gases including methane in the subsurface of Mars

We model the transport of gas through the martian subsurface in order to quantify the timescales of release of a trace gas with a source at depth using a Fickian model of diffusion through a putative martian regolith column. The model is then applied to the case of methane previously observed in the martian atmosphere. We investigate which parameters in the model have the greatest effect on transport timescales and find that transport is very sensitive to the pressure profile of the subsurface, but relatively insensitive to the temperature profile. Uncertainties in the composition, structure and physical conditions of the martian subsurface also introduce uncertainties in the timescales calculated. It was found that methane may take several hundred thousand Mars-years to diffuse from a source at depth. Purely diffusive transport cannot explain transient release that varies on timescales of less than one martian year from sources such as serpentinization or methanogenic organisms at depths of more than 2 km. However, diffusion of gas released by the destabilisation of methane clathrate hydrates close to the surface, for example caused by transient mass wasting events or erosion, could produce a rapidly varying flux of methane into the atmosphere of more than 10-3 kg m-2 s-1 over a duration of less than half a martian year, consistent with observations of martian methane variability. Seismic events, magmatic intrusions or impacts could also potentially produce similar patterns of release, but are far more complex to simulate

Vegetation Cover Analysis of Hazardous Waste Sites in Utah and Arizona Using Hyperspectral Remote Sensing

This study investigated the usability of hyperspectral remote sensing for characterizing vegetation at hazardous waste sites. The specific objectives of this study were to: (1) estimate leaf-area-index (LAI) of the vegetation using three different methods (i.e., vegetation indices, red-edge positioning (REP), and machine learning regression trees), and (2) map the vegetation cover using machine learning decision trees based on either the scaled reflectance data or mixture tuned matched filtering (MTMF)-derived metrics and vegetation indices. HyMap airborne data (126 bands at 2.3 x 2.3 m spatial resolution), collected over the U. S. Department of Energy uranium processing sites near Monticello, Utah and Monument Valley, Arizona, were used. Grass and shrub species were mixed on an engineered disposal cell cover at the Monticello site while shrub species were dominant in the phytoremediation plantings at the Monument Valley site. Regression trees resulted in the best calibration performance of LAI estimation (R-2 > 0.80. The use of REPs failed to accurately predict LAI (R-2 < 0.2). The use of the MTMF-derived metrics (matched filter scores and infeasibility) and a range of vegetation indices in decision trees improved the vegetation mapping when compared to the decision tree classification using just the scaled reflectance. Results suggest that hyperspectral imagery are useful for characterizing biophysical characteristics (LAI) and vegetation cover on capped hazardous waste sites. However, it is believed that the vegetation mapping would benefit from the use of higher spatial resolution hyperspectral data due to the small size of many of the vegetation patches (<1 m) found on the sites.open111

SOLID2: An Antibody Array-Based Life-Detector Instrument in a Mars Drilling Simulation Experiment (MARTE)

A field prototype of an antibody array-based life-detector instrument, Signs Of LIfe Detector (SOLID2), has been tested in a Mars drilling mission simulation called MARTE (Mars Astrobiology Research and Technology Experiment). As one of the analytical instruments on the MARTE robotic drilling rig, SOLID2 performed automatic sample processing and analysis of ground core samples (0.5 g) with protein microarrays that contained 157 different antibodies. Core samples from different depths (down to 5.5 m) were analyzed, and positive reactions were obtained in antibodies raised against the Gram-negative bacterium Leptospirillum ferrooxidans, a species of the genus Acidithiobacillus (both common microorganisms in the Río Tinto area), and extracts from biofilms and other natural samples from the Río Tinto area. These positive reactions were absent when the samples were previously subjected to a high-temperature treatment, which indicates the biological origin and structural dependency of the antibody-antigen reactions. We conclude that an antibody array-based life-detector instrument like SOLID2 can detect complex biological material, and it should be considered as a potential analytical instrument for future planetary missions that search for life.The work was funded by the Spanish Ministerio de Educación y Ciencia (ESP2004-05008), the Centro de Astrobiología (CAB), the Instituto Nacional de Técnica Aeroespacial (INTA), and by the National Aeronautics and Space Administration (NASA) Astrobiology Science and Technology for Exploring Planets (ASTEP) program under NRA 02-OSS-01.Peer reviewe