Fe‐bearing phases in a ureilite fragment from the asteroid 2008 TC3 (= Almahata Sitta meteorites): A combined Mössbauer spectroscopy and X‐ray diffraction study     

Abbasher M. Gismelseed  Yassir A. Abdu  Muawia H. Shaddad  Harish C. Verma  Peter Jenniskens 《Meteoritics & planetary science》2014,49(8):1485-1493

The iron‐bearing phases in a ureilite fragment (AS#051) from the Almahata Sitta meteorite are studied using Mössbauer spectroscopy, X‐ray diffraction (XRD), and electron microprobe analysis (EMPA). AS#051 has a typical ureilite texture of medium‐ to coarse‐grained silicates (olivine, orthopyroxene, and pigeonite) with minor opaques (Fe‐Ni metal, troilite, and graphite). The silicate compositions, determined by EMPA, are homogeneous: olivine (Fo_90.2), orthopyroxene (En_86.3Fs_8.6Wo_5.1), and pigeonite (En_81.6Fs_8.9Wo_9.5), and are similar to those of magnesian ureilites. The modal abundance of mineral phases was determined by Rietveld refinement of the powder XRD data. The Mössbauer spectra at 295 K and 78 K are composed of two sharp well‐defined paramagnetic doublets superimposed on a well‐resolved magnetic sextet and other weak absorption features. The two paramagnetic doublets are assigned to olivine and pyroxene (orthopyroxene and pigeonite), and the ferromagnetic sextet to kamacite (magnetic hyperfine field ≈ 33.2 T), in agreement with the XRD characterization. The Mössbauer results also show the presence of small amounts of troilite (FeS) and cohenite ([Fe,Ni,Co]₃C). Using the Mössbauer data, the relative abundance of each Fe‐bearing phase is determined and compared with the results obtained by XRD.  相似文献   

Observations of the Hubble Deep Field South with the Infrared Space Observatory– II. Associations and star formation rates     

Robert G. Mann  Seb Oliver  Ruth Carballo  Alberto Franceschini  Michael Rowan-Robinson  Alan F. Heavens  Maria Kontizas  David Elbaz  Anastasios Dapergolas  Evanghelos Kontizas  Gian Luigi Granato  Laura Silva  Dimitra Rigopoulou  J. Ignacio Gonzalez-Serrano  Aprajita Verma  Steve Serjeant  reas Efstathiou  Paul P. van der Werf 《Monthly notices of the Royal Astronomical Society》2002,332(3):549-574

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Simultaneous infrared and H-alpha measurements of Be stars     

Krishna M. V. Apparao  S. P. Tarafdar  R. P. Verma  K. V. K. Iyengar  K. K. Ghosh 《Journal of Astrophysics and Astronomy》1993,14(3-4):131-134

The observed infrared excess in Be stars is usually interpreted as free-free and free-bound emission from a hot gas envelope around the Be star. This hot gas should also emit H-alpha line radiation. Earlier observations had suggested that the infrared excess and Hα radiation were not consistent with models in which they arise from the same ionized region; however the observations were made at different times. We have made simultaneous observation of infrared and H-alpha line radiation. Our observations imply that either both these radiations cannot arise from the same hot gas or additional processes have to be invoked to account for the observed excess infrared radiation.  相似文献   

The European Large Area ISO Survey – VIII. 90-μm final analysis and source counts     

Ph. Héraudeau  S. Oliver  C. del Burgo  C. Kiss  M. Stickel  T. Mueller  M. Rowan-Robinson  A. Efstathiou  C. Surace  L. V. Tóth  S. Serjeant  D. M. Alexander  A. Franceschini  D. Lemke  T. Morel  I. Pérez-Fournon  J.-L. Puget  D. Rigopoulou  B. Rocca-Volmerange  A. Verma 《Monthly notices of the Royal Astronomical Society》2004,354(3):924-934

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Strike-slip and tectonics granitoid emplacement: an AMS fabric study from the Odenwald Crystalline Complex, SW Germany     

R. O. Greiling  P. K. Verma 《Mineralogy and Petrology》2001,72(1-3):165-184

Summary AMS fabric studies supported by field and microscopic work were applied to identify the internal structure and possible emplacement processes of the Variscan late-tectonic granodiorite-granite intrusions of the Unit III in the Odenwald Crystalline Complex. This Unit is bounded towards NW and NNE by steeply inclined shear zones, the southern part is unexposed. The magnetic susceptibility ranges between 10⁻³ and 10⁻⁶ SI units and is caused by paramagnetic and subordinately by ferromagnetic components. AMS ellipsoids are typically oblate with gently plunging long axes (lineations). AMS foliations and lineations trend mainly WSW-ENE and NNW-SSE, parallel with the NNW and ENE trending marginal shear zones of Unit III, respectively. As revealed by microstructural studies, a penetrative foliation in the plutons is related to emplacement processes. Therefore the observed AMS foliation and lineation are also interpreted as the result of syn-emplacement deformation which is dominantly strike-slip. Weakly inclined foliations around pluton roof xenoliths point to a component of buoyant rise of magma. It is suggested that the granitoid magma was generated in a low level anatectic zone along a left-lateral transpressive shear zone during local extension at releasing bends. During successive fault movements magma ascended through extensional parts of the shear zone. Local normal faults and the Otzberg zone at the eastern margin of Unit III document mostly brittle extension, which overprinted the strike-slip fabrics after the emplacement of the plutons.

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Zusammenfassung Horizontalverschiebungen und Granitoidintrusion: AMS Gefüge am Beispiel des SW Odenwaldes Durch AMS Gefügestudien und Gel?nde- und mikroskopische Arbeiten werden die Internstruktur und m?gliche Aufstiegsmechanismen des Granit-Granodiorit-Plutons der Einheit III des SW Odenwaldes erfasst. Dieser sp?t-tektonische, variscische Plutonkomplex ist nach NW und NNE durch steile Scherzonen begrenzt, das südliche Ende ist nicht aufgeschlossen. Die magnetische Suszeptibilit?t variiert von 10⁻³ bis 10⁻⁶ SI Einheiten und wird vor allem durch paramagnetische, untergeordnet auch durch ferromagnetische Komponenten verursacht. Die AMS Ellipsoide sind überwiegend oblat mit flachen langen Achsen (Lineationen). AMS Foliationen und Lineationen verlaufen haupts?chlich WSW-ENE und NNW-SSE, jeweils parallel mit den NNW und ENE orientierten Scherzonen am Rand der Einheit III. Nach mikrostrukturellen Ergebnissen entstand die penetrative Foliation der Plutone w?hrend ihrer Platznahme. Dabei entstand auch das beobachtete AMS Gefüge, das durch flache Lineationen und Horizontal-verschiebungen bestimmt ist. Flache Foliationen im Bereich der Xenolithe des Pluton-Daches sprechen für eine Komponente des gravitativen Aufstiegs des Magmas. Die granitoiden Magmen entstanden offenbar w?hrend einer Transpression mit sinistralen Horizontalverschiebungen in NNE-SSW-Richtung, in denen lokal auch Dehnung erfolgte. Dabei stieg das in der Tiefe gebildete Magma durch die Bereiche der Dehnung in der aktiven St?rungszone auf. Lokale Abschiebungen und die Otzberg Zone am Ostrand der Einheit III belegen überwiegend spr?de Deformation, die nach der Platznahme der Plutone die Gefüge der Horizontalverschiebungen überpr?gte.

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Received June 21, 1999; revised version December 24, 1999  相似文献   

Propagation of sonic waves in an optically thick medium in the presence of magnetic field     

B. G. Verma  R. C. Srivastava  M. A. Khan 《Astrophysics and Space Science》1983,92(2):325-333

This paper studies sonic waves in an optically thick medium under the influence of a magnetic field. The conductivity of the medium has been taken to be infinite. The effects of radiation, radiation energy density, radiative heat transfer and magnetic field have been taken into account. It has been obtained that the magnetic field has significant effect on sonic velocity. The fundamental differential equations governing the growth and decay of sonic waves are determined and solved.  相似文献   

Propagation of blast waves in Roche model     

B. G. Verma  R. C. Srivastava  A. H. Khan 《Astrophysics and Space Science》1982,85(1-2):465-476

A non-similarity solution for propagation of magnetogasdynamic blast waves in Roche model is obtained. The density outside the central core varies according to some inverse power of distance from the centre of explosion. The strength of the shock surface heading the disturbance as well as the total energy of the wave vary with time.  相似文献   

Correction to: Stress shadow,stress triggering,and recent earthquake activity in the Kashmir Himalaya,India     

Prasath  R. Arun  Verma  Mithila  Bansal  Brijesh K. 《Journal of Seismology》2022,26(2):415-415

Journal of Seismology -  相似文献   

Flood Frequency Analysis of Betwa River,Madhya Pradesh India     

H. K. Pandey  Shivam Dwivedi  Kamlesh Kumar 《Journal of the Geological Society of India》2018,92(3):286-290

Flood is common phenomena worldwide since time immemorial. Recently the change in climatic parameters has drastically affected the pattern and magnitude of flood. India being one of the tropical country face flood and drought situations every year, therefore it needs accurate assessment and forecast of flood for proper management of natural resources.An attempt has been made through the present study which consists frequency analysis on maximum daily discharge data in Betwa river at Basoda, Mohana and Shahijina gauging stations in Madhya Pradesh state using Gumbel’s Extreme value distribution and Log Pearson Type-3 distribution for 20 years period (1993-2012).The result shows that Log Pearson Type-3 distribution is better suited for Betwa basin. The results can be used by civil engineers for deciding the dimensions of hydraulic structures such as spillways, dams, bridges etc. Floods are forecasted for the different return periods for Betwa river.  相似文献   

Assessment of Groundwater Quality of the Central Gangetic Plain Area of India Using Geospatial and WQI Techniques     

Dharmendra Kumar Verma  Gouri Sankar Bhunia  Pravat Kumar Shit  Ashwani Kumar Tiwari 《Journal of the Geological Society of India》2018,91(6):743-748

The paper presents results of research to determine the health risk of potentially toxic elements (PTEs) in soils of gold mining area in Ilesha, Southwestern Nigeria. Eighteen top soil samples were collected and analysed for PTEs using ICPMS. The pollution level in soils were assessed using pollution load index (PLI) and potential ecological risk index (PERI). The human health risk was assessed using hazard index (HI), non-carcinogenic risk index and carcinogenic risk index. All the PTEs were higher than crustal average values except Fe and follow the order Mn > Ba > Cr > Zn > Cu > Ni > Pb > Co >Fe > As > Cd. The soil samples can be classified as unpolluted to moderately polluted (0.18-1.23) and low risk (15.28-94.24) based on PLI and PERI respectively. The values of hazard Index (HI) calculated for child and adult population for all the pathways were <1 and pose no obvious non carcinogenic risk to the population except for ingestion pathway where 33% of the samples showed value >1 in child population. As, Co, Cd and Pb constituted high cancer risk in the study area with child at higher risk than adult. The Total Cancer Risk (TCR) in the study area based on all the pathways ranges between 0.19 -3.86 and 0.18-3.58 for child and adult respectively and the ingestion route seems to be the major contributor to excess lifetime cancer risk followed by the dermal pathway.  相似文献