Directional Distribution of Observable Comets Induced by A Star Passage Through the Oort Cloud

We simulated the passage of a star through the Oort cometary cloud andanalyzed the resulting sample of observable long period comets, noting strong asymmetries in the directional distribution of the perihelion points of thosecomets. We discuss the results previously published byWeissman (1996) for the same case. An explanation is suggestedwhy the isotropic output can be obtained only for a very peculiar case. The``cometary shower' density variation with time is also presented and thetime-dependence of the directional distribution is discussed.     

Interfacing the DIGICO flux-gate spinner magnetometer to an APPLE IIe microcomputer

Summary. A hardware configuration and program are described for interfacing a DIGICO spinner rock magnetometer to an APPLE microcomputer. This configuration provides full control of measurements and permits storage of the results on floppy or hard discs. A similar configuration can be used to operate the anisotropy unit.     

Period Change of CU Pegasi

On the basis of the published times of minima and our own observations, we analysed the period change of the Algol-type eclipsing binary CU Pegasi. Over almost seventy years of observations, the parabolic period change has been clearly seen as dP/dt = 1.38 × 10⁻⁶ d/year. The estimated mass transfer in the system is about 1 × 10⁻⁷ M_M⊙/year.     

Groundwater quality as a geoindicator of organochlorine pesticide contamination after pesticide tomb reclamation: a case study of Franciszkowo, northwestern Poland

The need of surface soil removal during reclamation of the former underground landfills makes environmental monitoring difficult to perform. Environmental quality assessment after reclamation is very important because it provides information about: (1) the efficiency of remediation, (2) the rate of biodegradation of contaminants which were not removed during reclamation works and (3) the possible migration of contaminants from soil and permeable host rocks to surface waters and groundwaters. The concept of geoindicators, which was introduced to facilitate the assessment of environmental changes, can help assess environmental quality at sites previously subjected to reclamation. The groundwater quality is usually used as a geoindicator of inorganic contaminants. This concept was applied to find changes in organochlorine pesticide concentrations in groundwaters after toxic pesticide burial ground reclamation. The aim of this study was to monitor the concentrations of organochlorine pesticides and their metabolites in groundwaters at the former pesticide landfill site after its remediation. The study showed that very high concentrations of organochlorine pesticides and their metabolites in a contaminated soil had a small influence on pesticide concentrations in groundwaters and that this influence decreased in time. It has been 2 years since reclamation of the landfill took place, and the concentrations of organochlorine pesticides in groundwaters dropped to acceptable levels within the current environmental quality standards.     

The Electrostatic Blow-Off of Cometary Grains and Variations and Outbursts of Brightness of Comets at Large Heliocentric Distances

Interaction between the strong solar wind and the dark side of a cometary nucleus was considered. It was calculated that the potential of the dark side of the cometary nucleus could be numerically large and negative. Assuming that the nucleus of the comet has surface mantle which consists of loose, fine dust-ice particles, it was shown that cometary particles could electrostatically levitate over the nucleus. It was examined how this phenomenon affected the changes in the cometary brightness. Calculations were carried out for realistically assumed values of a large range of cometary parameters. It was shown that the considered mechanism could lead to the variations of cometary brightness, sometimes even to the outbursts of brightness.     

Numerical simulations of three-dimensional magnetic swirls in a solar flux-tube

We aim to numerically study evolution of Alfv′en waves that accompany short-lasting swirl events in a solar magnetic flux-tube that can be a simple model of a magnetic pore or a sunspot. With the use of the FLASH code we numerically solve three-dimensional ideal magnetohydrodynamic equations to simulate twists which are implemented at the top of the photosphere in magnetic field lines of the flux-tube. Our numerical results exhibit swirl events and Alfv′en waves with associated clockwise and counterclockwise rotation of magnetic lines, with the largest values of vorticity at the bottom of the chromosphere, and a certain amount of energy flux.     

Measuring visual pollution by outdoor advertisements in an urban street using intervisibilty analysis and public surveys

Debates on the encroaching commercialization of public space by outdoor advertising highlight its possible negative impact on local quality of life and enjoyment of public spaces. These overstimulating outdoor advertisements are often considered a source of visual pollution, but cities have no standard way of measuring where it exists and its local impact, and thus cannot regulate it effectively. This study illustrates that visual pollution can be measured in a useful way by relating public opinion to the number of visible advertisements (intervisibility analysis). Using a 2.5D outdoor advertisement (OA) dataset (location and height) of a busy urban street in Lublin, Poland, this preliminary experiment translates visibility into visual pollution. It was found that streetscape views with more than seven visible OAs created visual pollution in this case study. The GIS-based methodology proposed could provide Lublin officials with a basic tool to assess and manage visual pollution, by informing permitting decisions on OAs.     

Spatial Prediction of Landslide Hazard Using Fuzzy k-means and Dempster-Shafer Theory

Landslide databases and input parameters used for modeling landslide hazard often contain imprecisions and uncertainties inherent in the decision‐making process. Dealing with imprecision and uncertainty requires techniques that go beyond classical logic. In this paper, methods of fuzzy k‐means classification were used to assign digital terrain attributes to continuous landform classes whereas the Dempster‐Shafer theory of evidence was used to represent and manage imprecise information and to deal with uncertainties. The paper introduces the integration of the fuzzy k‐means classification method and the Dempster‐Shafer theory of evidence to model landslide hazard in roaded and roadless areas illustrated through a case study in the Clearwater National Forest in central Idaho, USA. Sample probabilistic maps of landslide hazard potential and uncertainties are presented. The probabilistic maps are intended to help decision‐making in effective forest management and planning.     

Analysis of the influence of parameter and scale uncertainties on a local multi-criteria land use evaluation model

Land use evaluation involves careful consideration of several environmental factors and their relative importance quantified by factor weights. Local multi-criteria evaluation provides a mechanism for computing factor (criteria) weights within local neighborhoods that capture spatial heterogeneity and contribute to more accurate evaluation results. The accuracy of results, however, is tempered by the potential uncertainty of criteria weights. The paper presents a spatially explicit approach to uncertainty and sensitivity analysis of local criteria weights and modeling scale on the variability of model output. The efficacy of the approach is presented on the example of Environmental Benefit Index (EBI) model used by the U.S. Department of Agriculture Conservation Reserve Program (CRP) to select environmentally sensitive agricultural areas for conservation. The uncertainty analysis resulted in identifying robust areas for CRP selection characterized by high suitability and low uncertainty. The sensitivity analysis focused on the next-best group of candidates characterized by high suitability and high uncertainty. The results show that there is a relationship between spatial heterogeneity, data representation scale, and the level of uncertainty in the results of EBI model. The sensitivity of model output can be attributed to both the uncertainty of criteria weights and the modeling scale. A potential practical value of this approach is the improved analytical support for land suitability evaluation requiring a consideration of sub-optimal land units (high suitability/high uncertainty). Also, this approach can guide modelling effort by allowing the analyst to visualize spatial distribution and patterns of model output uncertainty and focus data collection on influential model input factors.