First record of metazoan eggs and embryos from early Cambrian Chert Member of Deo ka Tibba Formation,Tal Group,Uttarakhand Lesser Himalaya

The phosphatized globular to sub-oval metazoan eggs with distinctively ornamented covering and phosphatized polar lobe forming embryos are recorded for the first time from the black phosphatic chert lenticles and bands of early Cambrian Chert Member of Deo ka Tibba Formation, Tal Group, Uttarakhand Lesser Himalaya. Similar metazoan eggs have been recorded earlier from early Cambrian rocks of Shaanxi Province, China, northwestern Canada, Australia, Mongolia, Siberia and Kazakhstan. These eggs are found in association with Small Shelly Fossils (SSF) and may belong to them. However, polar lobe forming embryos have been earlier recorded from Neoproterozoic rocks of southwestern China only. Similar embryos are common in modern molluscs and bilaterians.     

Examining the Effect of Ancillary and Derived Geographical Data on Improvement of Per-Pixel Classification Accuracy of Different Landscapes

Effective conservation and management of natural resources requires up-to-date information of the land cover (LC) types and their dynamics. Multi-resolution remote sensing (RS) data coupled with additional ancillary topographical layers (both remotely acquired or derived from ground measurements) with appropriate classification strategies would be more effective in capturing LC dynamics and changes associated with the natural resources. Ancillary information would make the decision boundaries between the LC classes more widely separable, enabling classification with higher accuracy compared to conventional methods of RS data classification. In this work, we ascertain the possibility of improvement in classification accuracy of RS data with the addition of ancillary and derived geographical layers such as vegetation indices, temperature, digital elevation model, aspect, slope and texture, implemented in three different terrains of varying topography—urbanised landscape (Greater Bangalore), forested landscape (Western Ghats) and rugged terrain (Western Himalaya). The study showed that use of additional spatial ancillary and derived information significantly improved the classification accuracy compared to the classification of only original spectral bands. The analysis revealed that in a highly urbanised area with less vegetation cover and contrasting features, inclusion of elevation and texture increased the overall accuracy of IKONOS data classification to 88.72% (3.5% improvement), and inclusion of temperature, NDVI, EVI, elevation, slope, aspect, Panchromatic band along with texture measures, significantly increased the overall accuracy of Landsat ETM+ data classification to 83.15% (7.6% improvement). In a forested landscape with moderate elevation, temperature was useful in improving the overall accuracy by 6.7 to 88.26%, and in a rugged terrain with temperate climate, temperature, EVI, elevation, slope, aspect and Panchromatic band significantly improved the classification accuracy to 89.97% (10.84% improvement) compared to the classification of only original spectral bands, suggesting selection of appropriate ancillary data depending on the terrain.     

Inverted metamorphic sequence in the Sikkim Himalayas: crystallization history, P–T gradient and implications

The metapelitic rocks of the Sikkim Himalayas show an inverted metamorphic sequence (IMS) of the complete Barrovian zones from chlorite to sillimanite + K‐feldspar, with the higher grade rocks appearing at progressively higher structural levels. Within the IMS, four groups of major planar structures, S₁, S₂ and S₃ were recognised. The S₂ structures are pervasive throughout the Barrovian sequence, and are sub‐parallel to the metamorphic isograds. The mineral growth in all zones is dominantly syn‐S₂. The disposition of the metamorphic zones and structural features show that the zones were folded as a northerly plunging antiform. Significant bulk compositional variation, with consequent changes of mineralogy, occurs even at the scale of a thin section in some garnet zone rocks. The results of detailed petrographic and thermobarometric studies of the metapelites along a roughly E–W transect show progressive increase of both pressure and temperature with increasing structural levels in the entire IMS. This is contrary to all models that call for thermal inversion as a possible reason for the origin of the IMS. Also, the observation of the temporal relation between crystallization and S₂ structures is problematic for models of post‐/late‐metamorphic tectonic inversion by recumbent folding or thrusting. A successful model of the IMS should explain the petrological coherence of the Barrovian zones and the close relationship of crystallization in each zone with S₂ planar structures along with the observed trend(s) of P–T variation in Sikkim and in other sections. A discussion is presented of some of the available models that, with some modifications, seem to be capable of explaining these observations.     

现代酸性矿山废水环境中的真核微生物:生物多样性、生理学、生物地球化学特征及其对古环境和早期生命演化的指示

现代酸性矿山废水(AMD)环境被认为是地球早期环境的理想对应物.AMD的水环境具有金属含量高、pH低的特点,这与太古代-早元古代时期海洋的某些环境条件十分类似.然而,尽管AMD的环境条件恶劣,但仍然栖息着非常丰富的原核和真核微生物,在这其中那些嗜酸的、营光合作用的真核微生物类群(特别是Euglena mutabilis)更是引起众多科学家极大的研究兴趣.本文全面概述了在AMD环境中发现的真核微生物Euglenids种群的生物化学、生理学和生物地球化学特征,以及这些特征对于理解生命演化和早期地球环境条件等方面的指示性作用.Euglenids的细胞具备区域化功能,因而具备需氧和厌氧的蜡酯和甾醇的双生物合成途径,同时它们还可以形成生物膜,所有这些均使得Euglenids能够在早期地球极端恶劣的环境条件下生存并持续演化.在AMD酸性环境中发育的富铁叠层石、嗜酸微生物的脂类化合物及其碳同位素比值以及它们独特的生理和生化特征可用于阐述真核生物的演化、地球早期大气中氧气的产生、条带状富铁建造的形成以及地球早期的环境演化等.     

Earthquake forerunner as probable precursor — an example from north burma subduction zone

The Burmese Arc seismic activity is not uniform for its ∼ 1100 km length; only the Northern Burmese Arc (NBA) is intensely active. Six large earthquakes in the magnitude range 6.1–7.4 have originated from the NBA Benioff zone between 1954–2011, within an area of 200 × 300 km² where the Indian plate subducts eastward to depths beyond 200 km below the Burma plate. An analysis on seismogenesis of this interplate region suggests that while the subducting lithosphere is characterized by profuse seismicity, seismicity in the overriding plate is rather few. Large earthquakes occurring in the overriding plate are associated with the backarc Shan-Sagaing Fault (SSF) further east. The forecasting performance of the Benioff zone earthquakes in NBA as forerunner is analysed here by: (i) spatial earthquake clustering, (ii) seismic cycles and their temporal quiescence and (iii) the characteristic temporal b-value changes. Three such clusters (C1–C3) are identified from NBA Benioff Zones I & II that are capable of generating earthquakes in the magnitude ranges of 7.38 to 7.93. Seismic cycles evidenced for the Zone I displayed distinct quiescence (Q₁, Q₂ and Q₃) prior to the 6^th August 1988 (M 6.6) earthquake. Similar cycles were used to forecast an earthquake (Dasgupta et al. 2010) to come from the Zone I (cluster C1); which, actually struck on 4 February 2011 (M 6.3). The preparatory activity for an event has already been set in the Zone II and we speculate its occurrence as a large event (M > 6.0) possibly within the year 2012, somewhere close to cluster C3. Temporal analysis of b-value indicates a rise before an ensuing large earthquake.     

Relativistic and non-relativistic dust grains

Charged dust grains of radiia≃3×10⁻⁶∼3×10⁻⁵ cm could be a help in understanding high energy particles in extensive air showers (EAS). It is suggested that the dust grains in the intergalactic medium may attain relatistic energy (≥10²⁰ eV), and may be responsible for the apparent ‘bump’ in the energy spectrum. The relativistic and non-relativistic dust grains may help to understand the anomalies in the energy spectrum as regards the slope and intensity.     

Exact solution of transport equation in finite multiplying media

One speed neutron transport equation in a finite multiplying medium is exactly and uniquely solved following the first author's new technique (Das Gupta, 1978b) based on Laplace transformation and Wiener-Hopf technique, to obtain the angular neutron density at any depth. Criticality condition is derived.     

Release of protons with energy >1018 eV from intergalactic magnetic field into interstellar magnetic field

Drift instabilities arising when accelerated protons are trapped in the intergalactic medium are examined. If α, the ratio of total (plasma + energetic particles) pressure and magnetic field pressure is larger than some value α?0.1 to 0.3, the magnetic trap is destroyed and protons are released into interstellar medium. If α<α^*, the trapped protons exhibit gradient instability due to magnetic drift resonance. This ‘universal’ instability results in rapid development of strong Alfvén wave turbulence with small wavelengths transverse to the magnetic field. Particle diffusion due to the waves has a rather complicated character and appears to be weak as compared to quasilinear diffusion.