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  • 1
    Publication Date: 2014-01-25
    Description: Opportunity has investigated in detail rocks on the rim of the Noachian age Endeavour crater, where orbital spectral reflectance signatures indicate the presence of Fe(+3)-rich smectites. The signatures are associated with fine-grained, layered rocks containing spherules of diagenetic or impact origin. The layered rocks are overlain by breccias, and both units are cut by calcium sulfate veins precipitated from fluids that circulated after the Endeavour impact. Compositional data for fractures in the layered rocks suggest formation of Al-rich smectites by aqueous leaching. Evidence is thus preserved for water-rock interactions before and after the impact, with aqueous environments of slightly acidic to circum-neutral pH that would have been more favorable for prebiotic chemistry and microorganisms than those recorded by younger sulfate-rich rocks at Meridiani Planum.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arvidson, R E -- Squyres, S W -- Bell, J F 3rd -- Catalano, J G -- Clark, B C -- Crumpler, L S -- de Souza, P A Jr -- Fairen, A G -- Farrand, W H -- Fox, V K -- Gellert, R -- Ghosh, A -- Golombek, M P -- Grotzinger, J P -- Guinness, E A -- Herkenhoff, K E -- Jolliff, B L -- Knoll, A H -- Li, R -- McLennan, S M -- Ming, D W -- Mittlefehldt, D W -- Moore, J M -- Morris, R V -- Murchie, S L -- Parker, T J -- Paulsen, G -- Rice, J W -- Ruff, S W -- Smith, M D -- Wolff, M J -- New York, N.Y. -- Science. 2014 Jan 24;343(6169):1248097. doi: 10.1126/science.1248097.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Planetary Sciences, Washington University in Saint Louis, St. Louis, MO 63130, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24458648" target="_blank"〉PubMed〈/a〉
    Keywords: Bacteria ; *Exobiology ; Extraterrestrial Environment/*chemistry ; Geologic Sediments ; Hydrogen-Ion Concentration ; *Mars ; Silicates/analysis/chemistry ; Spacecraft ; Sulfates/chemistry ; *Water
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2015-10-17
    Description: The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stern, S A -- Bagenal, F -- Ennico, K -- Gladstone, G R -- Grundy, W M -- McKinnon, W B -- Moore, J M -- Olkin, C B -- Spencer, J R -- Weaver, H A -- Young, L A -- Andert, T -- Andrews, J -- Banks, M -- Bauer, B -- Bauman, J -- Barnouin, O S -- Bedini, P -- Beisser, K -- Beyer, R A -- Bhaskaran, S -- Binzel, R P -- Birath, E -- Bird, M -- Bogan, D J -- Bowman, A -- Bray, V J -- Brozovic, M -- Bryan, C -- Buckley, M R -- Buie, M W -- Buratti, B J -- Bushman, S S -- Calloway, A -- Carcich, B -- Cheng, A F -- Conard, S -- Conrad, C A -- Cook, J C -- Cruikshank, D P -- Custodio, O S -- Dalle Ore, C M -- Deboy, C -- Dischner, Z J B -- Dumont, P -- Earle, A M -- Elliott, H A -- Ercol, J -- Ernst, C M -- Finley, T -- Flanigan, S H -- Fountain, G -- Freeze, M J -- Greathouse, T -- Green, J L -- Guo, Y -- Hahn, M -- Hamilton, D P -- Hamilton, S A -- Hanley, J -- Harch, A -- Hart, H M -- Hersman, C B -- Hill, A -- Hill, M E -- Hinson, D P -- Holdridge, M E -- Horanyi, M -- Howard, A D -- Howett, C J A -- Jackman, C -- Jacobson, R A -- Jennings, D E -- Kammer, J A -- Kang, H K -- Kaufmann, D E -- Kollmann, P -- Krimigis, S M -- Kusnierkiewicz, D -- Lauer, T R -- Lee, J E -- Lindstrom, K L -- Linscott, I R -- Lisse, C M -- Lunsford, A W -- Mallder, V A -- Martin, N -- McComas, D J -- McNutt, R L Jr -- Mehoke, D -- Mehoke, T -- Melin, E D -- Mutchler, M -- Nelson, D -- Nimmo, F -- Nunez, J I -- Ocampo, A -- Owen, W M -- Paetzold, M -- Page, B -- Parker, A H -- Parker, J W -- Pelletier, F -- Peterson, J -- Pinkine, N -- Piquette, M -- Porter, S B -- Protopapa, S -- Redfern, J -- Reitsema, H J -- Reuter, D C -- Roberts, J H -- Robbins, S J -- Rogers, G -- Rose, D -- Runyon, K -- Retherford, K D -- Ryschkewitsch, M G -- Schenk, P -- Schindhelm, E -- Sepan, B -- Showalter, M R -- Singer, K N -- Soluri, M -- Stanbridge, D -- Steffl, A J -- Strobel, D F -- Stryk, T -- Summers, M E -- Szalay, J R -- Tapley, M -- Taylor, A -- Taylor, H -- Throop, H B -- Tsang, C C C -- Tyler, G L -- Umurhan, O M -- Verbiscer, A J -- Versteeg, M H -- Vincent, M -- Webbert, R -- Weidner, S -- Weigle, G E 2nd -- White, O L -- Whittenburg, K -- Williams, B G -- Williams, K -- Williams, S -- Woods, W W -- Zangari, A M -- Zirnstein, E -- New York, N.Y. -- Science. 2015 Oct 16;350(6258):aad1815. doi: 10.1126/science.aad1815.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Southwest Research Institute, Boulder, CO 80302, USA. astern@boulder.swri.edu. ; Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303, USA. ; National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA. ; Southwest Research Institute, San Antonio, TX 28510, USA. ; Lowell Observatory, Flagstaff, AZ 86001, USA. ; Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA. ; Southwest Research Institute, Boulder, CO 80302, USA. ; Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. ; Universitat der Bundeswehr Munchen, Neubiberg 85577, Germany. ; Planetary Science Institute, Tucson, AZ 85719, USA. ; KinetX Aerospace, Tempe, AZ 85284, USA. ; NASA Jet Propulsion Laboratory, La Canada Flintridge, CA 91011, USA. ; Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ; University of Bonn, Bonn D-53113, Germany. ; NASA Headquarters (retired), Washington, DC 20546, USA. ; University of Arizona, Tucson, AZ 85721, USA. ; Cornell University, Ithaca, NY 14853, USA. ; NASA Headquarters, Washington, DC 20546, USA. ; Rheinisches Institut fur Umweltforschung an der Universitat zu Koln, Cologne 50931, Germany. ; Department of Astronomy, University of Maryland, College Park, MD 20742, USA. ; Search for Extraterrestrial Intelligence Institute, Mountain View, CA 94043, USA. ; Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, USA. ; NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. ; National Optical Astronomy Observatory, Tucson, AZ 26732, USA. ; NASA Marshall Space Flight Center, Huntsville, AL 35812, USA. ; Stanford University, Stanford, CA 94305, USA. ; Space Telescope Science Institute, Baltimore, MD 21218, USA. ; University of California, Santa Cruz, CA 95064, USA. ; Lunar and Planetary Institute, Houston, TX 77058, USA. ; Michael Soluri Photography, New York, NY 10014, USA. ; Johns Hopkins University, Baltimore, MD 21218, USA. ; Roane State Community College, Jamestown, TN 38556, USA. ; George Mason University, Fairfax, VA 22030, USA. ; Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26472913" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2016-03-19
    Description: NASA's New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto's encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection, with a crater retention age no greater than ~10 million years. Surrounding terrains show active glacial flow, apparent transport and rotation of large buoyant water-ice crustal blocks, and pitting, the latter likely caused by sublimation erosion and/or collapse. More enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic and ridges with complex bladed textures. Pluto also has ancient cratered terrains up to ~4 billion years old that are extensionally faulted and extensively mantled and perhaps eroded by glacial or other processes. Charon does not appear to be currently active, but experienced major extensional tectonism and resurfacing (probably cryovolcanic) nearly 4 billion years ago. Impact crater populations on Pluto and Charon are not consistent with the steepest impactor size-frequency distributions proposed for the Kuiper belt.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Moore, Jeffrey M -- McKinnon, William B -- Spencer, John R -- Howard, Alan D -- Schenk, Paul M -- Beyer, Ross A -- Nimmo, Francis -- Singer, Kelsi N -- Umurhan, Orkan M -- White, Oliver L -- Stern, S Alan -- Ennico, Kimberly -- Olkin, Cathy B -- Weaver, Harold A -- Young, Leslie A -- Binzel, Richard P -- Buie, Marc W -- Buratti, Bonnie J -- Cheng, Andrew F -- Cruikshank, Dale P -- Grundy, Will M -- Linscott, Ivan R -- Reitsema, Harold J -- Reuter, Dennis C -- Showalter, Mark R -- Bray, Veronica J -- Chavez, Carrie L -- Howett, Carly J A -- Lauer, Tod R -- Lisse, Carey M -- Parker, Alex Harrison -- Porter, S B -- Robbins, Stuart J -- Runyon, Kirby -- Stryk, Ted -- Throop, Henry B -- Tsang, Constantine C C -- Verbiscer, Anne J -- Zangari, Amanda M -- Chaikin, Andrew L -- Wilhelms, Don E -- New Horizons Science Team -- New York, N.Y. -- Science. 2016 Mar 18;351(6279):1284-93. doi: 10.1126/science.aad7055.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA. jeff.moore@nasa.gov. ; Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA. ; Southwest Research Institute, Boulder, CO 80302, USA. ; Department of Environmental Sciences, University of Virginia, Charlottesville, VA 22904, USA. ; Lunar and Planetary Institute, Houston, TX 77058, USA. ; The SETI Institute, Mountain View, CA 94043, USA. National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA. ; University of California, Santa Cruz, CA 95064, USA. ; National Aeronautics and Space Administration (NASA) Ames Research Center, Space Science Division, Moffett Field, CA 94035, USA. ; Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. ; Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ; NASA Jet Propulsion Laboratory, Pasadena, CA 91019, USA. ; Lowell Observatory, Flagstaff, AZ 86001, USA. ; Stanford University, Stanford, CA 94305, USA. ; NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. ; The SETI Institute, Mountain View, CA 94043, USA. ; University of Arizona, Tucson, AZ 85721, USA. ; National Optical Astronomy Observatory, Tucson, AZ 85719, USA. ; Roane State Community College, Oak Ridge, TN 37830, USA. ; Planetary Science Institute, Tucson, AZ 85719, USA. ; Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA. ; Independent Science Writer, Arlington, VT 05250, USA. ; U.S. Geological Survey, Retired, Menlo Park, CA 94025, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26989245" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
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  • 4
    Publication Date: 2016-03-19
    Description: The New Horizons mission has provided resolved measurements of Pluto's moons Styx, Nix, Kerberos, and Hydra. All four are small, with equivalent spherical diameters of ~40 kilometers for Nix and Hydra and ~10 kilometers for Styx and Kerberos. They are also highly elongated, with maximum to minimum axis ratios of ~2. All four moons have high albedos (~50 to 90%) suggestive of a water-ice surface composition. Crater densities on Nix and Hydra imply surface ages of at least 4 billion years. The small moons rotate much faster than synchronous, with rotational poles clustered nearly orthogonal to the common pole directions of Pluto and Charon. These results reinforce the hypothesis that the small moons formed in the aftermath of a collision that produced the Pluto-Charon binary.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Weaver, H A -- Buie, M W -- Buratti, B J -- Grundy, W M -- Lauer, T R -- Olkin, C B -- Parker, A H -- Porter, S B -- Showalter, M R -- Spencer, J R -- Stern, S A -- Verbiscer, A J -- McKinnon, W B -- Moore, J M -- Robbins, S J -- Schenk, P -- Singer, K N -- Barnouin, O S -- Cheng, A F -- Ernst, C M -- Lisse, C M -- Jennings, D E -- Lunsford, A W -- Reuter, D C -- Hamilton, D P -- Kaufmann, D E -- Ennico, K -- Young, L A -- Beyer, R A -- Binzel, R P -- Bray, V J -- Chaikin, A L -- Cook, J C -- Cruikshank, D P -- Dalle Ore, C M -- Earle, A M -- Gladstone, G R -- Howett, C J A -- Linscott, I R -- Nimmo, F -- Parker, J Wm -- Philippe, S -- Protopapa, S -- Reitsema, H J -- Schmitt, B -- Stryk, T -- Summers, M E -- Tsang, C C C -- Throop, H H B -- White, O L -- Zangari, A M -- New York, N.Y. -- Science. 2016 Mar 18;351(6279):aae0030. doi: 10.1126/science.aae0030.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. hal.weaver@jhuapl.edu. ; Southwest Research Institute, Boulder, CO 80302, USA. ; NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA. ; Lowell Observatory, Flagstaff, AZ 86001, USA. ; National Optical Astronomy Observatory, Tucson, AZ 26732, USA. ; SETI Institute, Mountain View, CA 94043, USA. ; Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA. ; Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130, USA. ; Space Science Division, NASA Ames Research Center, Moffett Field, CA 94035, USA. ; Lunar and Planetary Institute, Houston, TX 77058, USA. ; Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA. ; NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA. ; Department of Astronomy, University of Maryland, College Park, MD 20742, USA. ; SETI Institute, Mountain View, CA 94043, USA. Space Science Division, NASA Ames Research Center, Moffett Field, CA 94035, USA. ; Massachusetts Institute of Technology, Cambridge, MA 02139, USA. ; University of Arizona, Tucson, AZ 85721, USA. ; Independent science writer, Arlington, VT, USA. ; Southwest Research Institute, San Antonio, TX 78238, USA. ; Stanford University, Stanford, CA 94305, USA. ; University of California, Santa Cruz, CA 95064, USA. ; Universite Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France. ; Roane State Community College, Oak Ridge, TN 37830, USA. ; George Mason University, Fairfax, VA 22030, USA. ; Planetary Science Institute, Tucson, AZ 85719, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26989256" target="_blank"〉PubMed〈/a〉
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  • 5
    Publication Date: 2018-03-16
    Description: Purpose: To perform real-time whole genome sequencing (WGS) and RNA sequencing (RNASeq) of advanced pancreatic ductal adenocarcinoma (PDAC) to identify predictive mutational and transcriptional features for better treatment selection. Experimental Design: Patients with advanced PDAC were prospectively recruited prior to first-line combination chemotherapy. Fresh tumor tissue was acquired by image-guided percutaneous core biopsy for WGS and RNASeq. Laser capture microdissection was performed for all cases. Primary endpoint was feasibility to report WGS results prior to first disease assessment CT scan at 8 weeks. The main secondary endpoint was discovery of patient subsets with predictive mutational and transcriptional signatures. Results: Sixty-three patients underwent a tumor biopsy between December 2015 and June 2017. WGS and RNASeq were successful in 62 (98%) and 60 (95%), respectively. Genomic results were reported at a median of 35 days (range, 19–52 days) from biopsy, meeting the primary feasibility endpoint. Objective responses to first-line chemotherapy were significantly better in patients with the classical PDAC RNA subtype compared with those with the basal-like subtype ( P = 0.004). The best progression-free survival was observed in those with classical subtype treated with m-FOLFIRINOX. GATA6 expression in tumor measured by RNA in situ hybridization was found to be a robust surrogate biomarker for differentiating classical and basal-like PDAC subtypes. Potentially actionable genetic alterations were found in 30% of patients. Conclusions: Prospective genomic profiling of advanced PDAC is feasible, and our early data indicate that chemotherapy response differs among patients with different genomic/transcriptomic subtypes. Clin Cancer Res; 24(6); 1344–54. ©2017 AACR .
    Print ISSN: 1078-0432
    Electronic ISSN: 1557-3265
    Topics: Medicine
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  • 6
    Publication Date: 2018-06-01
    Description: The surface of Pluto is more geologically diverse and dynamic than had been expected, but the role of its tenuous atmosphere in shaping the landscape remains unclear. We describe observations from the New Horizons spacecraft of regularly spaced, linear ridges whose morphology, distribution, and orientation are consistent with being transverse dunes. These are located close to mountainous regions and are orthogonal to nearby wind streaks. We demonstrate that the wavelength of the dunes (~0.4 to 1 kilometer) is best explained by the deposition of sand-sized (~200 to ~300 micrometer) particles of methane ice in moderate winds (〈10 meters per second). The undisturbed morphology of the dunes, and relationships with the underlying convective glacial ice, imply that the dunes have formed in the very recent geological past.
    Keywords: Geochemistry, Geophysics, Planetary Science
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    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    ISSN: 1432-0789
    Keywords: Key words Biomass carbon ; Biomass nitrogen ; Cropping systems ; Nitrogen mineralization constants ; Active nitrogen pools
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Studies were conducted to evaluate the relationships among different active N pools of organic matter in soils at two long-term cropping systems in Iowa. Results indicated that multi-cropping systems, particularly meadow-based systems, enhanced bioactivities of soils. Mono-cropping systems, particularly soybean, reduced soil microbial biomass and enzyme activities. The mineralizable N pool (potential N mineralization;N o) was more sensitive to changes in the size of the microbial biomass N (Nmic) than to changes in organic N. One unit change in organic N did not lead to substantial changes in N o, but 1 unit change in Nmic resulted in three or more units change in N o. The active N pools and turnover rate were more sensitive to changes in organic C than to changes in microbial biomass C (Cmic). A unit change in organic C resulted in 10.6 units change in N o, but a unit change in Cmic resulted in only 0.8 unit change in N o. Cmic or Nmic are better indexes than organic C or N for the estimation of N o or N availability, because biomass values are more highly correlated with cumulative N mineralized during 24 weeks of incubation, with r values ranging from 0.57 (P〈0.001) to 0.88 (P〈0.001).
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  • 8
    ISSN: 1432-0789
    Keywords: Key words Arylsulfatase activity ; Chloroform-fumigation method ; Biomass enzymes ; Crop rotations ; N fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The impacts of crop rotations and N fertilization on different pools of arylsulfatase activity (total, intracellular, and extracellular) were studied in soils of two long-term field experiments in Iowa to assess the contibution of the microbial biomass to the activity of this enzyme. Surface-soil samples were taken in 1996 and 1997 in corn, soybeans, oats, or meadow (alfalfa) plots that received 0 or 180 kg N ha–1 before corn, and an annual application of 20 kg P ha–1 and 56 kg K ha–1. The arylsulfatase activity in the soils was assayed at optimal pH (acetate buffer, pH 5.8) before and after chloroform fumigation; microbial biomass C (Cmic) and N (Nmic) were determined by chloroform-fumigation methods. All pools of arylsulfatase activity in soils were significantly affected by crop rotation and plant cover at sampling time, but not by N fertilization. Generally, the highest total, intracellular, and extracellular arylsulfatase activities were obtained in soils under cereal-meadow rotations, taken under oats or meadow, and the lowest under continuous cropping systems.Total, intracellular, and extracellular arylsulfatase activities were significantly correlated with Cmic (r〉0.41, P〈0.01) and Nmic (r〉0.38, P〈0.01) in soils. The averages of specific activity values, i.e., of arylsulfatase activity of the microbial biomass, expressed per milligram Cmic, ranged from 315 to 407 μg p-nitrophenol h–1. The total arylsulfatase activity was significantly correlated with the intracellular activity, with r values 〉0.79 (P〈0.001). In general, about 45% of the total arylsulfatase activity was extracellular, and 55% was associated with the microbial biomass in soils, indicating the importance of the microflora as an enzyme source in soils.
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  • 9
    ISSN: 1432-0789
    Keywords: Key words Crop rotation ; Organic carbon ; Organic nitrogen ; Long-term cropping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The impacts of crop rotations and N fertilization on microbial biomass C (Cmic) and N (Nmic) were studied in soils of two long-term field experiments initiated in 1978 at the Northeast Research Center (NERC) and in 1954 at the Clarion-Webster Research Center (CWRC), both in Iowa. Surface soil samples were taken in 1996 and 1997 from plots of corn (Zea mays L.), soybeans (Glycine max (L.) Merr.), oats (Avena sativa L.), or meadow (alfalfa) (Medicago sativa L.) that had received 0 or 180 kg N ha–1 before corn and an annual application of 20 kg P and 56 kg K ha–1. The Cmic and Nmic values were determined by the chloroform-fumigation-extraction method and the chloroform-fumigation-incubation method, respectively. The Cmic and Nmic values were significantly affected (P〈0.05) by crop rotation and plant cover at time of sampling, but not by N fertilization. In general, the highest Cmic and Nmic contents were found in the multicropping systems (4-year rotations) taken in oats or meadow plots, and the lowest values were found in continuous corn and soybean systems. On average, Cmic made up about 1.0% of the organic C (Corg), and Nmic contributed about 2.4% of the total N (Ntot) in soils at both sites and years of sampling. The Cmic values were significantly correlated with Corg contents (r≥0.41**), whereas the relationship between Cmic and Ntot was significant (r≤0.53***) only for the samples taken in 1996 at the NERC site. The Cmic : Nmic ratios were, on average, 4.3 and 6.4 in 1996, and 7.6 and 11.4 in 1997 at the NERC and CWRC sites, respectively. Crop rotation significantly (P〈0.05) affected this ratio only at the NERC site, and N fertilization showed no effect at either site. In general, multicropping systems resulted in greater Cmic : Corg (1.1%) and Nmic : Ntot (2.6%) ratios than monocropping systems (0.8% and 2.1%, respectively).
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  • 10
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The ice-rich surface of the jovian satellite Europa is sparsely cratered, suggesting that this moon might be geologically active today. Moreover, models of the satellite's interior indicate that tidal interactions with Jupiter might produce enough heat to maintain a subsurface liquid water ...
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