Ganymede crater dimensions – Implications for central peak and central pit formation and development

The morphology of impact craters on the icy Galilean satellites differs from craters on rocky bodies. The differences are thought due to the relative weakness of ice and the possible presence of sub-surface water layers. Digital elevation models constructed from Galileo images were used to measure a range of dimensions of craters on the dark and bright terrains of Ganymede. Measurements were made from multiple profiles across each crater, so that natural variation in crater dimensions could be assessed and averaged scaling trends constructed. The additional depth, slope and volume information reported in this work has enabled study of central peak formation and development, and allowed a quantitative assessment of the various theories for central pit formation. We note a possible difference in the size-morphology progression between small craters on icy and silicate bodies, where central peaks occur in small craters before there is any slumping of the crater rim, which is the opposite to the observed sequence on the Moon. Conversely, our crater dimension analyses suggest that the size-morphology progression of large lunar craters from central peak to peak-ring is mirrored on Ganymede, but that the peak-ring is subsequently modified to a central pit morphology. Pit formation may occur via the collapse of surface material into a void left by the gradual release of impact-induced volatiles or the drainage of impact melt into sub-crater fractures.     

GIS techniques for regional-scale landslide susceptibility assessment: the Sicily (Italy) case study

This study describes the assessment of landslide susceptibility in Sicily (Italy) at a 1:100,000 scale using a multivariate logistic regression model. The model was implemented in a GIS environment by using the ArcSDM (Arc Spatial Data Modeller) module, modified to develop spatial prediction through regional data sets. A newly developed algorithm was used to automatically extract the detachment area from mapped landslide polygons. The following factors were selected as independent variables of the logistic regression model: slope gradient, lithology, land cover, a curve number derived index and a pluviometric anomaly index. The above-described configuration has been verified to be the best one among others employing from three to eight factors. All the regression coefficients and parameters were calculated using selected landslide training data sets. The results of the analysis were validated using an independent landslide data set. On an average, 82% of the area affected by instability and 79% of the not affected area were correctly classified by the model, which proved to be a useful tool for planners and decision-makers.     

Late-Stage Breast Cancer Diagnosis and Health Care Access in Illinois∗

The variations of breast cancer mortality rates from place to place reflect both underlying differences in breast cancer prevalence and differences in diagnosis and treatment that affect the risk of death. This article examines the role of access to health care in explaining the variation of late-stage diagnosis of breast cancer. We use cancer registry data for the state of Illinois by zip code to investigate spatial variation in late diagnosis. Geographic information systems and spatial analysis methods are used to create detailed measures of spatial access to health care such as convenience of visiting primary care physicians and travel time from the nearest mammography facility. The effects of spatial access, in combination with the influences of socioeconomic factors, on late-stage breast cancer diagnosis are assessed using statistical methods. The results suggest that for breast cancer, poor geographical access to primary health care significantly increases the risk of late diagnosis for persons living outside the city of Chicago. Disadvantaged population groups including those with low income and racial and ethnic minorities tend to experience high rates of late diagnosis. In Illinois, poor spatial access to primary health care is more strongly associated with late diagnosis than is spatial access to mammography. This suggests the importance of primary care physicians as gatekeepers in early breast cancer detection.     

The structure and intensity evolution of a solar burst at 2.8 cm and the relation with the soft X-ray emitting region

The decay phase of a microwave burst was observed with a one-dimensional angular resolution of 16″ at 2.8 cm. The structure was found to be composed of several bursting regions with different evolution. The event was also observed in soft X-rays by full-disk detectors. The joint analysis of these data suggests that the complete event has thermal origin and that the soft X-ray emission is associated with the rapidly varying component of the radio structure. From these results the average values of the electron temperatures and densities were computed for each component.     

Eutrophication and the rate of net nitrification in a coastal marine ecosystem

Rates of net nitrification were calculated for four large (13 m³) estuarine-based microcosms that had been subjected to inorganic nutrient enrichment. Calculated rates were based on two years of weekly nitrate and nitrite measurements and ranged from a maximum of 0·55 μmol NO₂₊₃⁻ produced l⁻¹ day⁻¹ in the control tank (no enrichment) to over 13 μmol NO₂₊₃⁻ produced l⁻¹ day⁻¹ in the most enriched tank (receiving 18·6 μmol NH₄ l⁻¹ day⁻¹). Almost all NO₂₊₃⁻ production was pelagic, little was benthic. Net NO₃⁻ production or net NO₂⁻ production dominated the net nitrification rates during different seasons. Good correlations were found between various oxidation rates and substrate concentrations. The calculated net nitrite production rates were 10 to 1000 times higher than previously reported rates for open ocean systems, demonstrating the potential importance of nitrification to estuarine systems.     

Robe’s circular restricted three-body problem under oblate primaries with perturbations in Coriolis and centrifugal forces

This paper examines the existence and linear stability of equilibrium points in the perturbed Robe’s circular restricted three-body problem under the assumption that the hydrostatic equilibrium figure of the first primary is an oblate spheroid, and the shape of the second primary is also an oblate spheroid. The problem is perturbed in the sense that small perturbations given to the Coriolis and centrifugal forces are being considered. Results of the analysis found two axial equilibrium points on the line joining the centre of both primaries. It is further observed that under certain conditions, points on the circle within the first primary are also equilibrium points. The linear stability of this configuration is examined; it is observed that the first axial point is unstable while the second one is conditionally stable and the circular points are unstable.     

Rock-magnetic and archeomagnetic survey from some classical settlements at Chapultepec archeological site (western Mesoamerica)

Many archaeological artifacts contain magnetic minerals that may record the direction and strength of the Earth’s magnetic field. The geomagnetic field parameters (declination, inclination and intensity) change through time and then may be used as a dating tool. Over the last three decades, the archeomagnetic method was successfully applied in Europe. Still, no systematic studies are devoted to the American sites. We report here, a detailed rock-magnetic and archeomagnetic investigation of some pre-Columbian settlements at Chapultepec archeological site (western Mesoamerica). Continuous low-field susceptibility vs. temperature curves performed in air point to Ti-poor titanomagnetites as remanence carriers. Hysteresis ratios fall essentially in the pseudo-single-domain region. The twelve oriented samples taken from the furnace located in the habitation area were demagnetized applying pick alternative fields. In most cases, a stable uni-vectorial remanent magnetization was found yielding a reasonably well defined mean characteristic direction: inclination I = 32.8°, declination D = 353.4°, and parameters of Fisherian statistics α₉₅ = 10.4° and k = 14. Still poorly defined directional master curves for Mesoamerica, together with relatively dispersed mean directions obtained in this study, make dating targets difficult. Archaeomagnetic dating was carried out on the basis of Bayessian statistics. This established a most probable time interval from 512 to 634 A.D. with an average of 573 ± 61 A.D.     

A framework for addressing health disparities in vulnerable populations with the help of Esri Community Analyst

Increasingly, health outcomes are tied to nutritional opportunities based on the availability of foods and cultural patterns of consumption. This paper demonstrates how Esri Community Analyst can help in identifying at-risk communities. The methodology that results argues a means by which national data made available by Esri in a “one-stop shop” can be utilized in a simplified, user-friendly way to identify specific populations with higher prevalence of certain diseases and areas where nutritional needs are likely unmet. For demonstration purposes, this paper presents a case study for South Carolina, USA.