The shielding effect of small-scale martian surface geometry on ultraviolet flux

The atmosphere of Mars does little to attenuate incoming ultraviolet (UV) radiation. Large amounts of UV radiation sterilize the hardiest of terrestrial organisms within minutes, and chemically alter the soil such that organic molecules at or near the surface are rapidly destroyed. Thus the survival of any putative martian life near the surface depends to a large extent on how much UV radiation it receives. Variations in small-scale geometry of the surface such as pits, trenches, flat faces and overhangs can have a significant effect on the incident UV flux and may create “safe havens” for organisms and organic molecules. In order to examine this effect, a 1-D radiative transfer sky model with 836 meshed points (plus the Sun) was developed which includes both diffuse and direct components of the surface irradiance. This model derives the variation of UV flux with latitude and an object's Geometric Shielding Ratio (a ratio which describes the geometry of each situation). The best protection is offered by overhangs with flux reduced to a factor of 1.8±0.2×10⁻⁵ of the unprotected value, a reduction which does not vary significantly by latitude. Pits and cracks are less effective with a reduction in UV flux of only up to 4.5±0.5×10⁻³ for the modeled scenarios; however, they are more effective for the same geometric shielding ratio than overhangs at high latitudes due to the low height of the Sun in the sky. Lastly, polar faces of rocks have the least effective shielding geometry with at most a 1.1±0.1×10⁻¹ reduction in UV flux. Polar faces of rocks are most effective at mid latitudes where the Sun is never directly overhead, as at tropical latitudes, and never exposes the back of the rock, as at polar latitudes. In the most favorable cases, UV flux is sufficiently reduced such that organic in-fall could accumulate beneath overhanging surfaces and in pits and cracks. As well, hardy terrestrial microorganisms such as Bacillus pumilus could persist for up to 100 sols on the outer surfaces of typical spacecraft or several tens of martian years in the most shielded surface niches.     

Exploring and Visualizing Differences in Geographic and Linguistic Web Coverage

This article reports on a study performed to understand the geographic and linguistic coverage of web resources, focusing on the example of tourism‐related themes in Switzerland. Search engine queries of web documents were used to gather counts for phrases in four different languages. The study focused on selected populated places and tourist attractions in Switzerland from three gazetteer datasets: topographic gazetteer data from the Swiss national mapping agency (SwissTopo); POI data from a commercial data provider (Tele Atlas) and user generated geographic content (geonames.org). The web counts illustrate the geographic extent and trends of web coverage of tourism for different languages. Results show that coverage for local languages, i.e. German, French and Italian, is more strongly related to the region of the spoken language. Correlation of the web counts to typical tourism indicators, e.g. population and number of hotel nights rented per year, are also computed and compared.     

Rapid inactivation of seven Bacillus spp. under simulated Mars UV irradiation

Seven Bacillus spp. were exposed to simulations of Mars-normal UV fluence rates in order to study the effects of UV irradiation on microbial survival. A UV illumination system was calibrated to deliver 9.78 W m⁻² (35.2 kJ m⁻² h⁻¹) of UVC + UVB irradiation (200-320 nm) to microbial samples, thus creating a clear-sky simulation (0.5 optical depth) of equatorial Mars. The Bacillus spp. studied were: B. licheniformis KL-196, B. megaterium KL-197, B. nealsonii FO-092, B. pumilus FO-36B, B. pumilus SAFR-032, B. subtilis 42HS1, and B. subtilis HA101. The bacteria were prepared as thin monolayers of endospores on aluminum coupons in order to simulate contaminated spacecraft surfaces. Bacterial monolayers were exposed to Mars UV irradiation for time-steps of 0, 0.25, 0.5, 1, 5, 15, 30, 60, 120, or 180 min. The surviving endospores were then assayed with a Most Probable Numbers (MPN) procedure and with a culture-based assay that utilized a bacillus spore germination medium. Results indicated that B. pumilus SAFR-032 was the most resistant, and B. subtilis 42HS-1 and B. megaterium were the most sensitive of the seven strains exposed to martian UV fluence rates. Bacillus subtilis 42HS1 and B. megaterium were inactivated after 30 min exposure to Mars UV, while B. pumilus SAFR-032 required 180 min for full inactivation in both assays. Spores of B. pumilus SAFR-032 exhibited significantly different inactivation kinetics suggesting that this wild type isolate also was more resistant than the standard dosimetric strain, B. subtilis HA101. Although the various Bacillus spp. exhibited diverse levels of UV resistance, none were immune to UV irradiation, and, thus, all species would be expected to be inactivated on Sun-exposed spacecraft surfaces within a few tens-of-minutes to a few hours on sol 1 under clear-sky conditions on equatorial Mars. The inactivation kinetics of all seven Bacillus spp. support the conclusion that significant levels of bioload reductions are possible on Sun-exposed spacecraft surfaces in very short time periods under clear-sky conditions on Mars. However, the presence of UV resistant microbes on spacecraft surfaces rapidly covered in dust during landing operations, and non-Sun-exposed surfaces of spacecraft remain concerns that must continue to be addressed through adequate spacecraft sanitizing procedures prior to launch.     

Temporary fluoride concentration changes in groundwater in the context of impact assessment in the Vaniyar sub-basin,South India

India’s surface water and groundwater distribution is temporally variable due to the monsoon. Agriculture is one of the dominant economic sectors in India. Groundwater quality is regularly assessed to determine usability for drinking and irrigation. In this study, World Health Organization and Bureau of Indian Standards guidelines were used to determine suitability of groundwater near artificial recharge structures (ARS) with a focus on the structures´ impact on groundwater quality. Groundwater resources were evaluated for irrigation suitability using electrical conductivity (EC), sodium adsorption ratio, the US Salinity Laboratory diagram, sodium concentration, Wilcox’s diagram, Kelly’s index, and Doneen’s permeability index. EC and major ions were tested in recharge areas at different distances from the ARS. The construction of ARS at optimal distances along major streams has improved groundwater quantity and quality in the sub-basin. Before construction of ARS, fluoride concentrations were higher; after construction, fluoride was reduced in most locations. Water stored in the check dam and groundwater in the wells closer to the structure were suitable for both drinking and irrigation purposes. Impact of ARS on nearby groundwater quality was observed at Pallipatti, Mulayanur, Venkadasamuthram, Pudupatti, Poyyappatti, Harur1, and Sekkampatti. More distant sites included Pappiredipatti, Nambiyappati, Menasi, Harur, Todampatti, and Adikarapatti. Data demonstrated improved groundwater quality in the area of the ARS. Through recharge, the non-potable fluoride in the region is reduced to the permissible limit for human consumption.     

XUV image of the sun from eclipse observations of the ionospheric E-region

Ionospheric E-region observations from Boulder (40.0 N, 105.3 W), Grand Bahama (26.6 N, 78.2 W), Mexico City (19.3 N, 99.2 W), Vandenberg (35.6 N, 120.6 W), and Wallops Island (37.9 N, 75.5 W) during the total solar eclipse of 7 March, 1970 are used for reconstructing the distribution of the ionizing XUV radiation over the solar disk. The derived solar image compares reasonably well with the EUV and X-ray pictures of the Sun obtained from rockets.     

Speciation of heavy metals in electroplating industry sludge and wastewater residue using inductively coupled plasma

The speciation of metals in environmental samples is a critical factor in assessing the potential environmental impacts, before their disposal. The distribution and speciation of toxic heavy metals in plating wastewater residues and sludge was investigated for four samples using sequential extraction method. Tessier method was used to fractionate the metal content into exchangeable, acid extractable, reducible and oxidizable fractions. Residual and total metal contents were determined in aqua regia digest. The extracts were analysed for metals using inductively coupled plasma -atomic emission spectrometry. The bioavailable fraction (exchangeable and acid extractable fractions) is comprised less than the other forms. The oxidisable and reducible forms are dominants for all the four samples studied. The major metal constitute in the samples is iron, the wastewater residue contains (12.3 and 7.4 g/Kg respectively on dry basis) and the sludge contains (31.5 and 41.6 g /Kg) respectively. Cr concentration is higher in wastewater residue of second electroplating industry. The descending order of the average total metal contents for these four samples were Fe > Cr > Sn > Zn >Cu > Ni > Mn > Pb > Cd > Ag. Based on the average of absolute values for the four samples the highest bioavailability order of metals is Cr (39 %) in wastewater residues and Zn (32 %) in sludge samples. Metal recovery was good, with < 10 % difference between the total metal recovered through the extractant steps and the total metal determined using aqua regia extract.     

Performance Comparison of Multiwavelet and Multicontourlet Frame Based Features for Improving Classification Accuracy in Remote Sensing Images

Scalar wavelet based contourlet frame based features are used for improving the classification of remote sensing images. Multiwavelet an extension to scalar wavelets provides higher degree of freedom, which possess two or more scaling function and wavelet function. Unlike scalar wavelets, which has single scaling and wavelet function. Multiwavelet satisfies several mathematical properties simultaneously such as orthogonality, compact support, linear phase symmetry and higher order approximation. The multiwavelets considered here are Geronimo-Hardin-Massopust (GHM) and Chui Lian (CL). In this paper the performance of GHM and CL multiwavelet is compared. Finally CL based multicontourlet frame based features are used for improving the classification accuracy of remote sensing images as it has directional filter banks. Principal component analysis based feature reduction is performed and Gaussian Kernel Fuzzy C means classifiers are used to improve the classification accuracy. The experimental results shows that the CL based multicontourlet overall accuracy is improved to 5.3% (for LISS-IV(i)), 2.09% (for LISS IV(ii)) 4.17% (for LISS IV(iii)) and 4.2% (for LISS IV-(iv)) the kappa coefficient is improved to 0.04 (for LISS IV-(i)), 0.029 (for LISS IV-(ii)), 0.031 (for LISS IV-(iii)) and 0.05 (for LISS IV-(iv)) compared to Wavelet based Contourlet transform.     

A Combined Detail Enhancing Algorithm and Texture Feature Extraction Method for Supervised Classification of Remote Sensing Images

In this paper, we propose a supervised classification in multispectral satellite images based on a novel detail enhancing texture feature extraction algorithm. The multispectral training and test images are first given for pre-processing, which is decomposed into low-pass approximation and high-pass multi-directional subbands by wavelet based contourlet transform. High pass subbands are easily interfered by noise. Based upon the Normal Shrink technique, thresholding is applied in high frequency images to eliminate the noise. The intra and inter scale fusion rule is used to combine the approximation and detail subbands to form the enhanced image. The co-occurrence features are calculated by forming the gray level co-occurrence matrix on training and test images. Mahalanobis distance classifier is applied on the training and test data sets for effective classification. The experiment result shows that the overall accuracy is improved to 2.2% for (Test-1) 2% for (Test-2) and 3.2 5% for (Test-3) and kappa coefficient is improved to 0.02 for (Test-1) image 0.03 for (Test-2) image and 0.03 (Test-3) image.