Rapid optical variability of the gamma-ray burst grb 080319b and its central engine

The results of observations of the optical emission that accompanied the gamma-ray burst GRB 080319B are reported. Observations were made using the TORTORA fast wide-field camera mounted on the REM robotic telescope in Chile. The behavior of the light curve before, during, and after the gamma-ray burst is described. The light curve consists of four, possibly periodic, 5–7 s long peaks 8–9 s apart. The behavior of the burst in the gamma and optical energy ranges are compared and the results of the theoretical interpretation of this comparison are reported.     

New CCRMP Reference Uranium ore BL-5 And Sulphide Concentrates CCU-I, CPB-1 and CZN-1

Under the Canadian Certified Reference Mate-vials Project (CCRMP), four new ore reference materials, one uranium ore BL-5 and three sulphide concentrates (CCV-1, CPB-1 and CZN-1) have been recently issued. The preparation, characterization and certification of these samples are briefly presented.     

Effects of hillslope geometry on surface and subsurface flows

Dividing a catchment to subcatchment or hillslope scales allows for better scrutiny of the changes in spatial distribution of rainfall, soil attributes and plant cover across the catchment. An instantaneous unit hydrograph model is suggested for simulating runoff hydrographs for complex hillslopes. This model is able to estimate surface and subsurface flows of the catchment based on the Dunne-Black mechanism. For this purpose, a saturation model is used to separate the saturated and unsaturated zones in complex hillslopes. The profile curvatures (concave, straight and convex) and plan shapes (convergent, parallel and divergent) of complex hillslopes are considered, in order to compute the travel time of surface and subsurface flows. The model was used for prediction of the direct runoff hydrograph and subsurface flow hydrograph of Walnut Gulch No. 125 catchment in Arizona (USA). Based on results, the geometry of hillslopes can change the peak of the direct runoff hydrograph up to two-fold, either higher or lower. The divergent hillslopes show higher peaks in comparison with the parallel and convergent hillslopes. The highest and lowest peak flows correspond to divergent-concave and convergent-straight hillslopes, respectively.     

Morphostratigraphy and fan morphology of doon valley

In the present study analysis of Landsat MSS, TM and SPOT imagery and digital analysis of IRS LISS-1 data of Doon Valley was carried out. Various geomorphic features were identified and classified, morphostratigraphy of the area has been established. Main geomorphic units of the area are Mussoorie Hill Range (Denudational), Siwalik Hills (Structural), Remnant Hills (Residual). Siwalik Piedmont. Doon Piedmont, River Terraces and Flood Plain. Three large fan lobes are identified on Doon Piedmont deposits, viz., Western fan lobe, Central fan lobe and Eastern fan lobe. Average slope of these three fan lobes are 2°21′, 2°3′, and 1°24′ for the western, central and eastern fan lobes respectively. Western and central fan lobes have been affected by neotectonic activity which is reflected in transverse profiles.     

Young eclogite from the Greater Himalayan Sequence,Arun Valley,eastern Nepal: P–T–t path and tectonic implications

Garnet geochronology was used to provide the first direct measurement of the timing of eclogitization in the central Himalaya. Lu–Hf dates from garnet separates in one relict eclogite from the Arun River Valley in eastern Nepal indicate an age of 20.7 ± 0.4 Ma, significantly younger than ultra-high pressure eclogites from the western Himalaya, reflecting either different origins or substantial time lags in tectonics along strike. Four proximal garnet amphibolites from structurally lower horizons are 14–15 Ma, similar to post-eclogitization ages published for rocks along strike in southern Tibet. P–T calculations indicate three metamorphic episodes for the eclogite: i) eclogite-facies metamorphism at ～ 670 °C and ≥ 15 kbar at 23–16 Ma; ii) a peak-T granulite event at ～ 780 °C and 12 kbar; and iii) late-stage amphibolite-facies metamorphism at ～ 675 °C and 6 kbar at ～ 14 Ma. The garnet amphibolites were metamorphosed at ～ 660 °C. Three models are considered to explain the observed P–T–t evolution. The first assumes that the Main Himalayan Thrust (basal thrust of the Himalayan thrust system) cuts deeper at Arun than elsewhere. While conceptually the simplest, this model has difficulty explaining both the granulite-facies overprint and the pulse of exhumation between 25 and 14 Ma. A second model assumes that (aborted) subduction, slab breakoff, and ascent of India's leading edge occurred diachronously: ～ 50 Ma in the western Himalaya, ～ 25 Ma in the central Himalaya of Nepal, and presumably later in the eastern Himalaya. This model explains the P–T–t path, particularly heating during initial exhumation, but implies significant along-strike diachroneity, which is generally lacking in other features of the Himalaya. A third model assumes repeated loss of mantle lithosphere, first by slab breakoff at ～ 50 Ma, and again by delamination at ～ 25 Ma; this model explains the P–T–t path, but requires geographically restricted tectonic behavior at Arun. The P–T–t history of the Arun eclogites may imply a change in the physical state of the Himalayan metamorphic wedge at 16–25 Ma, ultimately giving rise to the Main Central Thrust by 15–16 Ma.     

THE PRESENT STATUS OF ZIRCON

The present writer (SAXENA, 1966) does not propose that the use of zircons in problems of stratigraphy, pedogenesis and petrology should be discarded. His conclusions (pp.30–31) make a plea for caution in such use. The writer suggests several possible modes of the origin of Lircons and by no means the authigenic mode of origin is more important than any other. Igneous or detrital zircons could certainly be used provided due consideration is given to other possible modes of origin. The solution does not lie in abandoning the use of zircons but an individual case is to be judged according to the local geologic evidence. It may be possible to find the genctic history imprinted on the morphological features of Zircons. Most of MARSHALL'S (1967) criticism is because of his failure to realize the broader genetic aspects of zircons.     

Carbon cycling in a shallow turbid estuary of southeast Texas: The use of plant pigment biomarkers and water quality parameters

Particulate organic carbon (POC), dissolved organic carbon (DOC), and plant pigments (chlorophylls and carotenoids) were measured approximately bimonthly from March 1992 to October 1993 in the Sabine-Neches estuary (Sabine Lake region), located on the Texas-Louisiana border. High freshwater inflow into this shallow turbid estuary results in the shortest hydraulic residence time (ca. 7 d) of all Texas estuaries (Baskaran et al. in press). Annual averages of chlorophyll-a (3.0 μg l^?1) and particulate organic carbon (1.1 mg l^?1) in the water column were extremely low in comparison to other shallow estuaries. The highest chlorophyll-a concentrations were observed in October 1993, in the mid and lower regions of the estuary, during the lowest river discharge. Zeaxanthin and fucoxanthin concentrations suggested that much of the chlorophyll-a during this low flow period was represented by cyanobacteria and diatoms that entered from the Gulf of Mexico. The range of DOC concentrations was generally high (4.4–20.9 mg l^?1) and were significantly correlated with POC, but not with chlorophyll-a concentrations. When total suspended particulate (TSP) concentrations were below 20 to 30 mg l^?1, there were significant increases in %POC and %PON of the TSP. The unusually high POC: chlorophyll-a ratios (highest value of 1423) suggested that much of the POC contained low concentrations of chlorophyll-a that had degraded during transport from wetlands in the Sabine and Neches rivers. Based on these data, this estuary can be characterized as a predominantly heterotrophic system, with low light penetrance, short particle-residence times, high DOC, and low inputs from autochthonous carbon sources.     

The IGS VTEC maps: a reliable source of ionospheric information since 1998

The International GNSS Service (IGS) Working Group on Ionosphere was created in 1998. Since then, the Scientific community behind IGS, in particular CODE, ESA, JPL and UPC, have been continuosly contributing to reliable IGS combined vertical total electron content (VTEC) maps in both rapid and final schedules. The details on how these products are being generated, performance numbers, proposed improvement as far as VTEC evolution trends during near one Solar Cycle, are summarized in this paper. The confirmation of (1) the good performance of the IGS combined VTEC maps, and (2) the characteristic VTEC variability periods, are two main results of this work.