Low frequency shear electromagnetic modes in strongly coupled, relativistic-degenerate, astrophysical electron-positron-ion plasmas

Starting from appropriate fluid equations, a dispersion relation describing the properties of low frequency (as compared to the ion gyrofrequency) shear electromagnetic mode in an ultra-dense, relativistic-degenerate plasma is derived and examined. The plasma constituents are fully degenerate electrons and positrons, and strongly correlated non-degenerate ions. It is found that the shear mode can couple with the electrostatic ion mode under certain circumstances. The electron and positron relativistic degeneracy and ion correlations significantly affect the waves. However, the electron degeneracy pressure is dominant because the density balance changes due to the presence of ions in electron-positron pair plasma. The results are discussed numerically in the ultra-relativistic and weakly-relativistic limits, indicating relevance to the dense plasmas, produced in laboratory (e.g., super-intense laser-dense matter experiments), and astrophysical regimes.     

Hot plasma waves in Veselago medium around Reissner-Nordström black hole

We investigate the general relativistic magnetohydronadynamic (GRMHD) equations for hot plasmas in a Veselago medium around the Reissner-Nordström (RN) black hole. Using the 3+1 formalisms of spacetime, we write the GRMHD equations and perturb them linearly. These are then Fourier analyzed for the magnetized and nonmagnetized plasmas in rotating and nonrotating backgrounds. We derive dispersion relations and analyze the wave properties by the graphs of wave vector, refractive index and change in refractive. The results confirm the presence of Veselago medium for rotating magnetized/nonmagnetized and nonrotating nonmagnetized plasmas.     

Neural network model for discharge and water-level prediction for Ramganga River catchment of Ganga Basin,India

ABSTRACT

Discharges and water levels are essential components of river hydrodynamics. In unreachable terrains and ungauged locations, it is quite difficult to measure these parameters due to rugged topography. In the present study an artificial neural network model has been developed for the Ramganga River catchment of the Ganga Basin. The modelled network is trained, validated and tested using daily water flow and level data pertaining to 4 years (2010–2013). The network has been optimized using an enumeration technique and a network topology of 4-10-2 with a learning rate set at 0.06, which was found optimum for predicting discharge and water-level values for the considered river. The mean square error values obtained for discharge and water level for the tested data were found to be 0.046 and 0.012, respectively. Thus, monsoon flow patterns can be estimated with an accuracy of about 93.42%.

Editor M.C. Acreman; Associate editor E. Gargouri     

On the use of horizontal acoustic Doppler profilers for continuous bed shear stress monitoring

Continuous monitoring of bed shear stress in large river systems may serve to better estimate alluvial sediment transport to the coastal ocean.Here we explore the possibility of using a horizontally deployed acoustic Doppler current profiler(ADCP) to monitor bed shear stress,applying a prescribed boundary layer model,previously used for discharge estimation.The model parameters include the local roughness length and a dip correction factor to account for sidewall effects.Both these parameters depend on river stage and on the position in the cross-section, and were estimated from shipborne ADCP data.We applied the calibrated boundary layer model to obtain bed shear stress estimates over the measuring range of the HADCP.To validate the results,co-located coupled ADCPs were used to infer bed shear stress,both from Reynolds stress profiles and from mean velocity profiles. From HADCP data collected over a period of 1.5 years,a time series of width profiles of bed shear stress was obtained for a tidal reach of the Mahakam River,East Kalimantan,Indonesia.A smaller dataset covering 25 hours was used for comparison with results from the coupled ADCPs.The bed shear stress estimates derived from Reynolds stress profiles appeared to be strongly affected by local effects causing upflow and downflow,which are not included in the boundary layer model used to derive bed shear stress with the horizontal ADCP.Bed shear stresses from the coupled ADCP are representative of a much more localized flow,while those derived with the horizontal ADCP resemble the net effect of the flow over larger scales.Bed shear stresses obtained from mean velocity profiles from the coupled ADCPs show a good agreement between the two methods,and highlight the robustness of the method to uncertainty in the estimates of the roughness length.     

Non-linear fuzzy-set based uncertainty propagation for improved DO prediction using multiple-linear regression

In this paper, a new non-linear fuzzy-set based methodology is proposed to characterize and propagate uncertainty through a multiple linear regression (MLR) model to predict DO using flow and water temperature as the regressors. The output is depicted as probabilistic rather than deterministic and is used to calculate the risk of low DO concentration. To demonstrate the new method, data from the Bow River in Calgary, Alberta from 2006 to 2008 are used. Low DO concentration has been occasionally observed in the river and correctly predicting, and quantifying the associated uncertainty and variability of DO is of interest to the City of Calgary. Flow, temperature and DO data were used to construct five MLR models, using different combinations of linear and non-linear fuzzy membership functions. The results show that non-linear representation of variance is superior to the linear approach based on model performance. Normal and Gumbel based membership functions produced the best results. The outputs from two non-linear fuzzy membership models were used to calculate risk of low DO. The predicted risk was between 3.9 and 4.9 %. This is an improvement over the traditional method, which can not indicate a risk of low DO for the same time period. This study demonstrates that water resource managers can adequately use MLR models to predict the risk of low DO using abiotic factors.     

Removal of Bromate from Water Using De‐Acidite FF‐IP Resin and Determination by Ultra‐Performance Liquid Chromatography‐Tandem Mass Spectrometry

Contamination of water due to bromate is a severe health hazard. The aim of the present study was to remove bromate from water using a crosslinked polystyrene based strongly basic anion exchange resin De‐Acidite FF‐IP. Batch experiments were performed to study the influence of various experimental parameters such as effect of pH, contact time, temperature, and effect of competing anions on bromate removal by De‐Acidite FF‐IP resin. At optimum parameters, the removal rate of bromate was very fast and 90% removal took place in 5 min and equilibrium was established within 10 min. The presence of competitive anions reduced the bromate adsorption in the order of Cl^? > F^? > CO > SO > NO > PO. The practical utility of this resin has been demonstrated by removing bromate in some of the commercial bottled water from Saudi Arabia. The level of bromate was determined using a very sensitive, precise and rapid method based on ultra‐performance liquid chromatography‐tendem mass spectrometry (UPLC‐MS/MS).     

Recognition of the time and level of emplacement of the Sillai Patti carbonatite complex,Malakand Division,Northwest Pakistan: Constraints from fission-track dating

The Sillai Patti carbonatite complex represents the second largest carbonatite body of the Peshawar Plain Alkaline Igneous Province of northern Pakistan. It is situated about 20 km west of Malakand, near Sillai Patti village. Here, the carbonatite occurs along a fault in the form of a sheet striking in the NNE–SSW direction and dipping towards south. The carbonatite body is about 12 km long and 2–20 m thick, predominantly intruded along the faulted contact of metasediments and granite gneiss but locally, within the metasediments.A fission-track age of 29.40 ± 1.47 Ma was obtained for the Sillai Patti carbonatite complex. Close resemblance of fission-track apatite age of this study with the fission-track as well as other high temperature radiometric ages from the same and the neighboring carbonatite complexes of the alkaline belt of northern Pakistan suggests emplacement of the Sillai Patti carbonatite complex at higher crustal level and subsequent extremely fast cooling to near ambient temperatures (<60 °C) required for the complete retention of fission tracks in apatite. The age data also point out that the fission-track age of 29.40 ± 1.47 Ma of this study is the age of intrusion of the carbonatitic magma of Sillai Patti carbonatite complex to shallow, near-surface level.Comparison of the uplift induced denudation rates of the region with the world data clearly reflects the presence of a post collisonal extensional environment in the region south of Main Mantle Thrust during Oligocene time. This strongly negates the idea of the earlier workers of emplacement of the carbonatite complexes of the Loe-Shilman and Sillai Patti areas along thrust faults during Oligocene.     

Principal component analysis of lithologic variables in Early Permian Barakar coal-measures,western Singrauli Gondwana sub-basin of central India

The quantitative relationships between lithological variables of Early Permian Barakar coal measures of western Singrauli Gondwana sub-basin are investigated using principal component analysis in an attempt to reveal simple relationships undetected by conventional quantitative methods. The results not only confirm and amplify those of the simple regression analysis described in Casshyap et.al. (1988), but are also interpreted in terms of evolution of coal swamps. If the total thickness of strata, total thickness of clastic sediments, total thickness of coal seams, number of sandstone beds, number of shale beds, number of coal seams and clastic ratio are considered, the first three components accounts for 80% of the total variance and the lithological variables generally fall into two groups. One group contains the first four variables, namely, total thickness of strata, total thickness of sandstone, total thickness of shale and total thickness of coal seams, all of which have basin-like regional patterns of sedimentation linked to net subsidence. The other group of variables, which are somewhat less closely related to net subsidence such as number of sandstone beds, number of shale beds and number of coal seam. The sand/shale ratio and clastic ratio are dependent on the other variables and seem to be unrelated to net subsidence. The principal component results, at best in geological term, may be explained by the to and fro lateral migration of a river channel across its flood plain coupled with a gradual isostatic adjustment of the basin floor in response to the weight of the sediments and differential subsidence through space and time.