Use of Cu isotopes to distinguish primary and secondary Cu mineralization in the Ca?ariaco Norte porphyry copper deposit, Northern Peru     

Ryan Mathur  Joaquin Ruiz  Michael J. Casselman  Peter Megaw  Robert van Egmond 《Mineralium Deposita》2012,47(7):755-762

A significant proportion of the copper in the Ca?ariaco Norte porphyry copper deposit in northern Peru occurs in chalcocite and covellite-rich veins and disseminations that exist from the surface to depths greater than 1?km. The overall range of Cu isotopic ratios of 42 mineral separates from Ca?ariaco varies from ?8.42 to 0.61?‰, with near-surface chalcocite and Fe oxides having isotopically depleted values compared to chalcocite, covellite, and chalcopyrite from deeper levels. The majority (34 of 36) of measured Cu sulfides have a typical hypogene copper isotope composition of δ⁶⁵Cu?=?0.18?±?0.38?‰, with no enriched isotopic signature existing in the Ca?ariaco Norte sulfide data. Thus, the copper isotope data indicate that most of the chalcocite and covellite formed from high-temperature hypogene mineralization processes and that only a minor portion of the deposit is enriched by supergene processes. The nonexistence of an enriched δ⁶⁵Cu reservoir suggest the presence of an undiscovered lateral/exotic Cu occurrence that enriched ⁶⁵Cu that remained in solution during weathering. Regardless of the cause, the comparative analysis of the Cu isotope dataset reveals that little exploration potential for an extensive supergene enrichment blanket exists because the weathering history at Ca?ariaco Norte was not conducive to preservation of enriched Cu at depth beneath the leach cap.  相似文献   

Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301     

Mathur S  Green PJ  Arav N  Brotherton M  Crenshaw M  deKool M  Elvis M  Goodrich RW  Hamann F  Hines DC  Kashyap V  Korista K  Peterson BM  Shields JC  Shlosman I  van Breugel W  Voit M 《The Astrophysical journal》2000,535(2):L79-L82

We present results of new ASCA observations of the low-luminosity active galactic nucleus (LLAGN) NGC 4579 obtained on 1998 December 18 and 28, and we report on the detection of variability of an iron K emission line. The X-ray luminosities in the 2-10 keV band for the two observations are nearly identical (LX approximately 2x1041 ergs s(-1)), but they are approximately 35% larger than that measured in 1995 July by Terashima et al. An Fe K emission line is detected at 6.39+/-0.09 keV (source rest frame), which is lower than the line energy 6.73+0.13-0.12 keV in the 1995 observation. If we fit the Fe lines with a blend of two Gaussians centered at 6.39 and 6.73 keV, the intensity of the 6.7 keV line decreases, while the intensity of the 6.4 keV line increases, within an interval of 3.5 yr. This variability rules out thermal plasmas in the host galaxy as the origin of the ionized Fe line in this LLAGN. The detection and variability of the 6.4 keV line indicates that cold matter subtends a large solid angle viewed from the nucleus and that it is located within approximately 1 pc from the nucleus. It could be identified with an optically thick standard accretion disk. If this is the case, a standard accretion disk is present at the Eddington ratio of Lbol/LEdd approximately 2x10-3. A broad disk-line profile is not clearly seen, and the structure of the innermost part of accretion disk remains unclear.  相似文献   

Shallow groundwater in a middle mountain catchment of Nepal: quantity and quality issues   总被引：1，自引：0，他引：1  

Bhawani S. Dongol  Juerg Merz  Monika Schaffner  Gopal Nakarmi  Pravakar B. Shah  Smita K. Shrestha  Pradeep M. Dangol  Madhav P. Dhakal 《Environmental Geology》2005,49(2):219-229

The use of shallow groundwater in middle mountain catchments of Nepal is a recent development. It was only in early 1998 that a number of dug wells had been constructed in the Jhikhu Khola catchment. But their numbers are rapidly increasing. While it seems to be a good way of accessing additional water resources both for domestic (current) and agricultural purposes (future), it is very important that the groundwater resources are not overexploited. Current dug wells are used to abstract groundwater, which is seasonally being recharged by the abundant monsoon rainfall. The water levels responded rapidly to the rainfall and differed according to the location of the well. The water quality parameters indicated that the water of most of the wells was not suitable for drinking purposes without prior treatment. Microbiological contamination is of particular concern, in addition to the high nitrate and phosphate levels. Some wells show elevated turbidity levels, indicating that there is an interaction between the muddy surface water and the water in the well.  相似文献   

Late Archean Cu-Au-Mo mineralization at Gameleira and Serra Verde, Carajàs Mineral Province, Brazil: constraints from Re-Os molybdenite ages     

Robert Marschik  Ryan Mathur  Joaquin Ruiz  Richard A. Leveille  Antonio-José de Almeida 《Mineralium Deposita》2005,39(8):983-991

New Re-Os molybdenite ages provide constraints on the timing of Late Archean Cu-Au-Mo mineralization in the northern Carajás Mineral Province. Molybdenite from the Gameleira iron oxide Cu-Au-Mo deposit yielded an age of 2,614±14 Ma. This age overlaps within its analytical error with Re-Os ages of molybdenite from the Serra Verde Cu-Au-Mo vein deposit (2,609±13 Ma) and from the nearby small Garimpo Fernando gold mining operation (2,592±13 and 2,602±13 Ma), which is probably related to the latter. The geochronological data imply that the hydrothermal Cu-Au-Mo mineralization in these three deposits was epigenetic and coincides with a regional tectonic regime changing from dextral transtension and clastic sedimentation at 2.7–2.6 Ga to sinistral transpression and inversion at 2.6 Ga. Previously reported stable isotope and microthermometric data are compatible with a magmatic affiliation of the Cu-Au-Mo ores at Gameleira and Serra Verde. A genetic relationship of mineralization may therefore exist with 2.56–2.76 Ga Archean alkaline granitoids or with 2.6–2.7 calc-alkaline to tholeiitic volcanic-arc type magmatism.Editorial handling: F. Tornos  相似文献   

Care and Global Migration in the Nursing Profession: a north Indian perspective     

Margaret Walton-Roberts  Smita Bhutani  Amandeep Kaur 《The Australian geographer》2017,48(1):59-77

ABSTRACT

Globalisation, supply–demand dynamics, uneven development, enhanced connectivity including the better flow of information, communication and the reduced cost of travel have encouraged the global integration of nursing labour markets. Developed regions of the world have attracted internationally educated nurses (IENs) because of growing healthcare needs. India, along with the Philippines, has become a key supplier of nurses in the global economy. Traditionally the supply of nurses was heavily regionalised in south India, especially Kerala, but of late Punjab, in north India, has played an increasing role in nurse training and migration as the profession has become more respected and more international. This paper uses survey and interview data to detail the recent interest in nursing as a channel for independent female international migration from Punjab, and to examine how migratory ambitions have developed over the last decade in parallel with the changing status of nursing as an internationally respected profession. We identify growing interest in international migration for nursing students and their increased intention to pursue employment opportunities in Australia and New Zealand. This research highlights how nursing and care migration are increasingly structured by international circuits of training and employment, and how such circuits alter migrant and occupational geographies on the ground in sending regions.  相似文献   

Simulation of extreme water levels in response to tropical cyclones along the Indian coast: a climate change perspective     

Rao  A. D.  Upadhaya  Puja  Pandey  Smita  Poulose  Jismy 《Natural Hazards》2020,100(1):151-172

Natural Hazards - Indian coasts are often influenced by life-threatening water levels caused by tropical cyclones. To have a better long-term planning for the coastal districts due to tropical...  相似文献   

The transition region and coronal explorer   总被引：5，自引：0，他引：5  

Handy  B.N.  Acton  L.W.  Kankelborg  C.C.  Wolfson  C.J.  Akin  D.J.  Bruner  M.E.  Caravalho  R.  Catura  R.C.  Chevalier  R.  Duncan  D.W.  Edwards  C.G.  Feinstein  C.N.  Freeland  S.L.  Friedlaender  F.M.  Hoffmann  C.H.  Hurlburt  N.E.  Jurcevich  B.K.  Katz  N.L.  Kelly  G.A.  Lemen  J.R.  Levay  M.  Lindgren  R.W.  Mathur  D.P.  Meyer  S.B.  Morrison  S.J.  Morrison  M.D.  Nightingale  R.W.  Pope  T.P.  Rehse  R.A.  Schrijver  C.J.  Shine  R.A.  Shing  L.  Strong  K.T.  Tarbell  T.D.  Title  A.M.  Torgerson  D.D.  Golub  L.  Bookbinder  J.A.  Caldwell  D.  Cheimets  P.N.  Davis  W.N.  Deluca  E.E.  McMullen  R.A.  Warren  H.P.  Amato  D.  Fisher  R.  Maldonado  H.  Parkinson  C. 《Solar physics》1999,187(2):229-260

The Transition Region and Coronal Explorer (TRACE) satellite, launched 2 April 1998, is a NASA Small Explorer (SMEX) that images the solar photosphere, transition region and corona with unprecedented spatial resolution and temporal continuity. To provide continuous coverage of solar phenomena, TRACE is located in a sun-synchronous polar orbit. The ∼700 Mbytes of data which are collected daily are made available for unrestricted use within a few days of observation. The instrument features a 30-cm Cassegrain telescope with a field of view of 8.5×.5 arc min and a spatial resolution of 1 arc sec (0.5 arc sec pixels). TRACE contains multilayer optics and a lumogen-coated CCD detector to record three EUV wavelengths and several UV wavelengths. It observes plasmas at selected temperatures from 6000 K to 10 MK with a typical temporal resolution of less than 1 min.  相似文献   

Biofiltration of Pyridine by Shewanella putrefaciens in a Corn‐Cob Packed Biotrickling Filter     

Anil Kumar Mathur  C. B. Majumder 《洁净——土壤、空气、水》2008,36(2):180-186

In this study, a new strain of microorganism Shewanella putrefaciens was used for biofiltration of a pyridine laden air stream in a corn‐cob packed biotrickling filter. In the biotrickling filter tested with S. putrefaciens, the maximum removal of pyridine is determined to be 100% at less than the average inlet concentration of 0.653 g m^–3 and more than 93% at a higher average inlet concentration of 1.748 g m^–3 (phase VIII) with an empty bed residence time (EBRT) of 106 s. However, when the biotrickling filter was operated at a low EBRT of 53 s and almost the same average inlet concentration of 1.752 g m^–3 (phase VII), the removal level attained was not greater than 85%. The maximum elimination capacity (EC) of the biotrickling filter was 102.34 g m^–3h^–1 at an inlet pyridine load of 119.62 g m^–3h^–1 with an EBRT of 53 s in phase VII. The maximum deviation of the EC from the 100% conversion line varied from 0.257 to 10.166% when going from phase I to VIII. Kinetic analysis showed that the maximum removal rate, r_max, and saturation constant, K_s, values for pyridine were calculated as 0.24 g m^–3h^–1 and 6.44 g m^–3, respectively, with a correlation coefficient, R², of 0.9939 and a standard deviation of error of 23.94%. The information contained herein indicates that the corn‐cob packed biotrickling filter inoculated by S. putrefaciens should provide excellent performance in the removal of gaseous pyridine.  相似文献   

Image quality characterization of fine resolution RISAT-1 data using impulse response function     

Gautam Dadhich  Shweta Sharma  Mihir Rambhia  Aloke K. Mathur  P. R. Patel  Alpana Shukla 《国际地球制图》2019,34(6):586-596

This study presents the results obtained from image quality assessment of Radar Imaging SATellite (RISAT-1). Image quality parameters such as spatial resolution, peak to sidelobe ratio (PSLR) and integrated sidelobe ratio (ISLR) are calculated by the analysis of impulse response function (IRF) of the point target. The study is carried out to assess temporal stability and consistency of image quality parameters obtained from analysis of IRF of 44 point targets. The results obtained from this study show that the mean values of the range and azimuth resolution are 2.048 ± 0.081 m and 3.383 ± 0.097 m for RH and 1.981 ± 0.081 m and 3.348 ± 0.076 m for RV, respectively. PSLR/ISLR values for RH channel are obtained as ?26.492 dB/?26.823 dB for azimuth and ?19.209 dB/?19.921 dB for the range. For RV channel, PSLR/ISLR values are ?26.300 dB/?27.572 dB for azimuth and ?19.146 dB/?19.827 dB for range.  相似文献   

Role of environment and hydrography in determining the picoplankton community structure of Sagami Bay,Japan   总被引：1，自引：0，他引：1  

Smita Mitbavkar  Toshiro Saino  Naho Horimoto  Jota Kanda  Takashi Ishimaru 《Journal of Oceanography》2009,65(2):195-208

Seasonal variations in the picoplankton community were investigated from June 2002 to March 2004 within the photic zone of Sagami Bay, Japan. The study area was mostly dominated by coastal waters during the warm period (mixed layer water temperature ≥ 18°C). During the cold period (mixed layer water temperature ≤ 18°C), the water mass was characterized by low temperature and high saline waters indicative of the North Pacific Subtropical Mode Water (NPSTMW). Occasionally, a third type of water mass characterized by high temperature and low saline properties was observed, which could be evidence of the intrusion of warm Kuroshio waters. Synechococcus was the dominant picophytoplankton (5−28 × 10¹¹ cells m⁻²) followed by Prochlorococcus (1−5 × 10¹¹ cells m⁻²) and picoeukaryotes during the warm period. Heterotrophic bacteria dominated the picoplankton community throughout the year, especially in the warm period. During the Kuroshio Current advection, cyanobacterial abundance was high whereas that of picoeukaryotes and heterotrophic bacteria was low. During the cold period, homogeneously distributed, lower picophytoplankton cell densities were observed. The dominance of Synechococcus in the warm period reflects the importance of high temperature, low salinity and high Photosynthetically Active Radiation (PAR) on its distribution. Cyanobacterial and heterotrophic bacterial abundance showed a positive correlation with temperature. Prochlorococcus and picoeukaryotes showed a positive correlation with nutrients. Picoeukaryotes were the major contributors to the picophytoplankton carbon biomass. The annual picophytoplankton contribution to the photosynthetic biomass was 32 ± 4%. These observations suggest that the environmental conditions, combined with the seasonal variability in the source of the water mass, determines the community structure of picoplankton, which contributes substantially to the phytoplankton biomass and can play a very important role in the food web dynamics of Sagami Bay.  相似文献