Estimation of the sub-iron-iron flux ratio in cosmic rays over alice springs using a balloon flight experiment with a CR-39 detector

The sub-iron-iron flux ratio in cosmic rays at an atmospheric depth of 9.8 g cm^–2 has been estimated using a balloon-borne CR-39 (HCB) stack launched from Alice Springs for 32 hours. The recovered and chemically etched plates were analysed optically and the measured etch pit diameters yielded the sub-iron-iron flux ratio at the flight altitude. The sub-iron-iron flux ratio has been corrected for the top of the atmosphere by considering the loss of heavy ions due to nuclear interaction and fragmentation. The present result has been compared with the result expected from the source composition derived by Protheroeet al. as well as other authors.     

P–T–fO2 controls on a partly inverse chromite-bearing ultramafic intrusive: an evaluation from the Sukinda Massif, India

The chromites from the alpine type ultramafic intrusive of Sukinda, India, display a typical partly inverse spinel form and occur in two distinct zones: Brown Ore Zone (BOZ) and Grey Ore Zone (GOZ). The host ultramafites are mostly altered and are represented by the serpentinite, tremolite-talc(chlorite) schist, talc-serpentine schist and chlorite rock. The less altered variants are dunite, harzburgite and websterite. A dyke of orthopyroxenite runs through the main ultramafic body.The composition of olivine (Fo₉₂), orthopyroxene (En_92–89) and Al₂O₃ contents of the parental liquid (10.40–11.45%) determined from chromites, suggest that the parent melt is of boninitic affinity. The chemical plot of TiO₂ content against cr# of chromites corroborates a boninitic parental melt. The Fe–Mg partitioning in olivine and chromite depicts the temperature for chromitites as 1200 °C. A compositional plot of mg# and cr# suggests crystallization at high pressure conditions, corresponding to the kimberlite xenolith field. From the P–T diagram of pyrolite melting and mineral assemblage, the pressure of crystallization is stipulated to be ≥1.2 GPa. The f_O2 values estimated from Fe³⁺/Cr+Al+Fe³⁺ ratios range from 10^−8.3 to 10^−9.3 for the GOZ and 10^−7.1 to 10^−7.3 for the BOZ. The f_O2 values together with the pressure range suggest crystallization at upper mantle conditions. The heterogeneity in chemical composition and f_O2 conditions for the GOZ and BOZ could be linked to heterogeneity in the upper mantle.     

Field based index of flood vulnerability(IFV): A new validation technique for flood susceptible models

The flood hazard management is one of the major challenges in the floodplain regions worldwide. With the rise in population growth and the spread of infrastructural development, the level of risk has increased over time.Therefore, the prediction of flood susceptible area is a key challenge for the adoption of management plans.Flood susceptibility modeling is technically a common work, but it is still a very tough job to validate flood susceptible models in a very rigorous and scientific manner. Therefore, the present work in the Atreyee River Basin of India and Bangladesh was planned to establish artificial neural network(ANN), radial basis function(RBF), random forest(RF) and their ensemble-based flood susceptibility models. The flood susceptible models were constructed based on nine flood conditioning parameters. The flood susceptibility models were validated in a conventional way using the receiver operating curve(ROC). To validate the flood-susceptible models, a two dimensional(2 D) hydraulic flood simulation model was developed. Also, the index of flood vulnerability model was developed and applied for validating the flood susceptible models, which was a very unique way to validate the predictive models. Friedman test and Wilcoxon Signed rank test were employed to compare the generated flood susceptible models. Results showed that 11.95%–12.99% of the entire basin area(10188.4 km2) comes under very high flood-susceptible zones. Accuracy evaluation results have shown that the performance of ensemble flood susceptible models outperforms other standalone machine learning models. The flood simulation model and IFV model were also spatially adjusted with the flood susceptibility models. Therefore, the present study recommended for the ensemble flood susceptibility prediction and IFV based validation along with conventional ways.     

Singular spectrum analysis,harmonic regression and El-Nino effect on total ozone (1979–1993) over India and surrounding regions

The Total Ozone Mapping Spectrometer (TOMS) is a satellite instrument that records Total Column Ozone (TCO) concentration (in DB) of the atmosphere in the form of different overpass files. We have selected 23 sites over India (15), Pakistan (4), Bangladesh (1) and adjoining China (3) to investigate the TCO scenario over this region. About 114,000 historical records (1979M1–1992M12) from 23 overpass files were processed to generate 23 monthly mean time series (TS) of TCO. Statistical analysis followed by singular spectrum analysis (SSA), harmonic regression (HR) and spatial interpolation have been used to accomplish the investigation. Four dominant signals; quasi-biennial signal (QBI, \(\hbox {T} = 30.12\) months), quasi-annual signal (QAN, \(\hbox {T} = 19.69\) months), annual signal (ANN, \(\hbox {T} = 12\) months) and semi-annual signal (SAN, \(\hbox {T} = 6\) months) were discerned to explain the variability. Direct latitudinal effect on the TCO distribution was observed. The variance was limited between 80.53 and 90.13%; ANN contributes 65.93–93.22% followed by SAN 0.58–5.69%, QAN 0.33–5.48%, and QBI 0.06–5.94%. Peak values of the oscillations are estimated from phasor diagrams: QBI, March to May in the mid-latitude; QAN, April, and May; ANN, February to April; SAN, March to May. Incisive pictures of the average distribution and variability of four sinusoids were investigated from contour plots. Two ozone valley were discerned from Spatial interpolation; one over Deccan Plateau in low and other over Tibetan Plateau in high latitude. 179 outliers from \(23 \times 168\) observations have been identified after harmonic regression. The appearance of the outliers is highly consistent with extreme phases of multivariate ENSO Index and Dipole Mode Index.     

A simple approach for the determination of bulk modulus and equation of state under the effect of high temperature for minerals

A simple theoretical method for the determination of bulk modulus and equation of state is investigated and applied for six minerals of geophysical importance. The results obtained at different temperatures are found to present a good agreement with the experimental data. The simplicity of the method is discussed in the light of other methods in high temperature research on minerals. Received: 7 January 1996 / Revised, accepted: 11 June 1997     

Influence of biotic-abiotic factors on the degradation of novaluron in tropical soil

In this study, the degradation of novaluron (benzoylphenyl urea insect growth regulator) was investigated under controlled laboratory conditions in clay loam alluvial and coastal saline soils of West Bengal, India. The application rates were field rate (FR); 2FR and 10FR. The incubation study was carried out at 30 °C and 60% of maximum water holding capacity of both the soils. Degradation of novaluron in both the soils followed first order reaction kinetics at all application rates under non-sterile and sterile conditions. The half-lives of novaluron in non-sterilized soils ranged from 17.0–17.8 days (alluvial soil) and 11.4–12.7 days (coastal saline soil), while the values in case of the sterilized soils were 53.7–59.0 days (alluvial soil) and 28.9–29.8 days (coastal saline soil) respectively. The novaluron degradation patterns were found to be highly influenced by soil types, application rates, and biotic abiotic factors. Abiotic factors strongly influenced novaluron degradation in both the soils. Biotic degradation was higher in alluvial soil compared to the coastal saline soil.     

Deformation behavior of migmatites: insights from microstructural analysis of a garnet–sillimanite–mullite–quartz–feldspar-bearing anatectic migmatite at Rampura–Agucha,Aravalli–Delhi Fold Belt,NW India

International Journal of Earth Sciences - In the present study we investigate the microstructural development in mullite, quartz and garnet in an anatectic migmatite hosted within a Grenvillian-age...     

Study of subsurface geology in locating arsenic-free groundwater in Bengal delta,West Bengal,India

Over a large area of the Bengal delta in West Bengal, India, arsenic distribution patterns in groundwater were studied. One hundred and ten boreholes at different target locations were made, subsurface sediments were logged and analysed, and arsenic values in sediments vis-à-vis groundwater were compared. The study elucidates the subsurface geology of the western part of Bengal delta and characterises the sediments that were intersected in different boreholes with contrasting values of arsenic in groundwater. It reveals an existence of multiple aquifers stacked over each other. Depending on the color and nature of aquifer-sands and their overlying clay beds six aquifer types (Type-1 to Type-6) are classified and described. Sediment-arsenic for all the varieties of aquifer sands are near similar but the groundwater-arsenic of these six aquifers varies widely. Type-2 and Type-5 aquifers host arsenic-contaminated groundwater whereas the other four aquifers are arsenic-free. Type-2 and Type-5 aquifers are capped by a grey to dark grey soft organic matter-rich clay unit which makes these aquifers semi-confined to leaky-confined. These contribute in releasing arsenic from the sediments. The results of this study are employed in a proposed georemedial measure against this hazardous toxic element.