Disparate MG II absorption statistics towards quasars and gamma-ray bursts: a possible explanation

We examine the recent report by Prochter et al. that gamma-ray burst (GRB) sight lines have a much higher incidence of strong Mg II absorption than quasar sight lines. We propose that the discrepancy is due to the different beam sizes of GRBs and quasars, and that the intervening Mg II systems are clumpy with the dense part of each cloudlet of a similar size as the quasars, i.e. ≲10¹⁶ cm, but bigger than GRBs. We also discuss observational predictions of our proposed model. Most notably, in some cases the intervening Mg II absorbers in GRB spectra should be seen varying, and quasars with smaller sizes should show an increased rate of strong Mg II absorbers. In fact, our prediction of variable Mg II lines in the GRB spectra has been now confirmed by Hao et al., who observed intervening Fe II and Mg II lines at z=1.48 to be strongly variable in the multi-epoch spectra of z=4.05 GRB 060206.     

A new scenario framework for Climate Change Research: scenario matrix architecture

This paper describes the scenario matrix architecture that underlies a framework for developing new scenarios for climate change research. The matrix architecture facilitates addressing key questions related to current climate research and policy-making: identifying the effectiveness of different adaptation and mitigation strategies (in terms of their costs, risks and other consequences) and the possible trade-offs and synergies. The two main axes of the matrix are: 1) the level of radiative forcing of the climate system (as characterised by the representative concentration pathways) and 2) a set of alternative plausible trajectories of future global development (described as shared socio-economic pathways). The matrix can be used to guide scenario development at different scales. It can also be used as a heuristic tool for classifying new and existing scenarios for assessment. Key elements of the architecture, in particular the shared socio-economic pathways and shared policy assumptions (devices for incorporating explicit mitigation and adaptation policies), are elaborated in other papers in this special issue.     

Development of isopluvial map using L-moment approach for Tehri-Garhwal Himalaya

Estimation of design rainfall intensity is crucial for design and planning of water resources engineering projects. The intent of the present study is to develop regional IDF curves for Tehri-Garhwal Himalayan region in India, wherein numbers of hydropower projects are in planning and execution stage. Self Recording Rain Gauge (SRRG) stations are generally not so frequent in the project locations. Under this situation, the engineers are forced to use regional intensity duration frequency (IDF) curves. Under this study, four stations viz. Tehri M.T.Lab, Mukhim, Pilkhi and Dhuttu were available with SRRG data. These data are used to develop the regional IDF curve for entire Tehri-Garwal region. After selection of the most intensive storms, return periods has been determined using regionalized L-moment method. After developing IDF curves for above four raingauge stations, Thiessen Ploygon method is applied to find out average IDF curve. To show the spatial variability, Isopluvial maps have been generated using ArcGIS and a relation equation has been developed.     

Influence of Low-Degree High-Order p-Mode Splittings on the Solar Rotation Profile

The solar rotation profile is well constrained down to about 0.25R _⊙ thanks to the study of acoustic modes. Since the radius of the inner turning point of a resonant acoustic mode is inversely proportional to the ratio of its frequency to its degree, only the low-degree p modes reach the core. The higher the order of these modes, the deeper they penetrate into the Sun and thus they carry more diagnostic information on the inner regions. Unfortunately, the estimates of frequency splittings at high frequency from Sun-as-a-star measurements have higher observational errors because of mode blending, resulting in weaker constraints on the rotation profile in the inner core. Therefore inversions for the solar internal rotation use only modes below 2.4 mHz for ?≤3. In the work presented here, we used an 11.5-year-long time series to compute the rotational frequency splittings for modes ?≤3 using velocities measured with the GOLF instrument. We carried out a theoretical study of the influence of the low-degree modes in the region from 2 to 3.5 mHz on the inferred rotation profile as a function of their error bars.     

Magnetized string cosmological model in cylindrically symmetric inhomogeneous universe-revisited

Cylindrically symmetric inhomogeneous magnetized string cosmological model is investigated. The source of the magnetic field is due to an electric current produced along x-axis. F ₂₃ is the only non-vanishing component of electromagnetic field tensor. To get the deterministic solution, it has been assumed that the expansion (θ) in the model is proportional to the eigen value σ ₁ ¹ of the shear tensor σ _j ⁱ . The physical and geometric properties of the model are also discussed in presence and absence of magnetic field.     

Cloud height determination using satellite stereoscopy from Along Track Scanning Radiometer onboard ERS-1 satellite: A simulation study

The first ERS-1 satellite launched in May 1991 promises to make a substantial contribution towards the cloud stereoscopy. One of its payload, Along Track Scanning Radiometer (hereafter ATSR) has IR split window channels and scans the earth conically leading to earth views at two view angles (0° and 55°) in two curved swaths registered with respect to each other in image frame. This enables us to construct stereoscopic image of a cloud thereby determining its height geometrically. The present paper describes the utility of ATSR onboard ERS-1 in retrieving cloud height by synthetic stereo imaging over NOAA-AVHRR visible and thermal band observations.     

Comparative Toxicity of Heavy Metals and Interaction of Metals on a Freshwater Pulmonate Snail Lymnaea acuminata (Lamarck)

In static bioassays the toxicity of heavy metal ions against Lymnaea acuminata over 24 … 96 h is tested. The values of the LC_50,96h for the metals tested are, in mg/l: Hg²⁺ ?0.023; Cu²⁺-0.034, Cd²⁺ ?0.872, Ni²⁺ ?2.78, Cr⁶⁺ ?5.97 and Zn²⁺ ?10.49. In the combined solutions of Cu²⁺, Ni²⁺ and Zn²⁺ at least an additive effect of toxicity occurs in the presence of two metals. The same holds for the presence of the three metals; in this case, the relative toxicity against the mixture of two metallic salt solutions appears to be slightly reduced. The acute manifestation of the toxic effect occurs within 48 h, subsequently the relative mortality decreases especially in the mixed solutions.     

Field based spectral reflectance studies to develop NDSI method for snow cover monitoring

Snow is highly reflective in the visible region of the electromagnetic spectrum making it possible to easily distinguish on a satellite image. However, cloud cover and mountain shadows pose a serious problem in the identification of snow in a mountainous region. Therefore, to identify snow in such an environment, a Normalized Difference Snow Index (NDSI) has been applied. The NDSI is based on the high reflectance of snow in the visible region and its low reflectance in the SWIR region, whereas, reflectance of cloud remains high compared to snow in the SWIR region. Efforts have been made to carry out field observations on reflectance of various land features near Manali in Himachal Pradesh (HP) to develop NDSI values for identifying snow. Field data have been collected using three field radiometers, viz., Multi-band Ground Truth Radiometer (GTR) operating in the 12 spectral bands ranging from visible to near-infrared wavelengths, Near-Infrared Ground Truth Radiometer (NIGTR) operating in the SWIR range, and Ratio-Radiometer (RR) operating in two spectral bands, one in the visible range, and another band in the SWIR range. All these three field radiometers have been designed and developed indigenously at the Space Applications Centre (ISRO), Ahmedabad. NDSI values for all types of snow, such as, fresh, clear, patchy and wet, have been found to be in the range 0.9 to 0.96. In addition, the NDSI value for snow under mountain shadow is found to be more than 0.9. This suggests the use of NDSI method for snow cover monitoring under mountain shadow. NDSI values for other land features such as soil, vegetation, and rock were substantially different than snow. However, water bodies have NDSI values close to snow and they need to be masked during snow cover delineation using NIR band.