Pollutant loadings from solvay waste beds to lower Ninemile Creek,New York     

Steven W. Effler  Carol M. Brooks  Jeffrey M. Addess  Susan M. Doerr  Michelle L. Storey  Bruce A. Wagner 《Water, air, and soil pollution》1991,55(3-4):427-444

Concentrations of Cl, total ammonia (TNH₃), NO₃ plus NO₂, total P (TP), and soluble reactive P (SRP) were measured at two sites, located 5 km apart, on Ninemile Creek, New York, for a period of more than 8 mo. The sites bound the most recently formed Solvay waste beds, associated with the production of soda ash, that adjoin the creek. Concentrations of Cl and T-NH₃ increased on average by factors of 16.1 and 7.6, respectively, over the monitored stream reach. The estimated average loadings of these materials to the stream over this reach were 2.3 × 10⁵ and 1.2 × 102 kg d^?1, respectively. These inputs are attributable to the Solvay waste beds. The loading of Cl from this source has not changed significantly over a 4 yr period since the closure of the soda ash manufacturing facility. This is the single largest source of Cl, and the second largest source of T-NH₃, to polluted Onondaga Lake. Profiles of Cl in the lake indicated that at times the creek inflow plunges to subsurface layers as a result of its elevated density. This is at least in part a result of the creek's ionic enrichment. The concentration of SRP decreased by a factor of 2.0 on average over the study reach, probably due to adsorption to the CaCO₃ deposits that cover the stream bed in this area. However, the TP load from the creek to the lake is not significantly affected by this phenomenon.  相似文献   

Influence of climate on the tocopherol content of shea butter     

Maranz S  Wiesman Z 《Journal of agricultural and food chemistry》2004,52(10):2934-2937

The shea tree, Vitellaria paradoxa Gaertner, is the source of a commercial seed fat known as shea butter. High-performance liquid chromatography (HPLC) analysis of the tocopherol content of shea butters from different regions of Africa showed high variability between provenances and a significant effect of climate on alpha-tocopherol levels. The total tocopherol content (alpha, beta, gamma, and delta) in 102 shea butter samples from 11 countries ranged from 29 to 805 microg/g of shea butter, with a mean of 220 microg/g. alpha-Tocopherol, the principal form detected, averaged 64% of the total tocopherol content. Shea butters from Vitellaria populations situated in hot, dry climates had the highest levels of alpha-tocopherol (for example, a mean of 414 microg/g in samples from N'Djamena, Chad). The lowest concentrations of alpha-tocopherol were found in samples from cool highland areas, especially in northern Uganda (a mean of 29 microg/g).  相似文献   

Glucosinolates in the new oilseed crop meadowfoam: natural variation in Section Inflexae of Limnanthes,a new glucosinolate in L. floccosa,and QTL analysis in L. alba     

Pablo Velasco  Mary B. Slabaugh  Ralph Reed  Jennifer Kling  Venkata K. Kishore  Jan F. Stevens  Steven J. Knapp 《Plant Breeding》2011,130(3):352-359

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Host resistance to lung infection mediated by major vault protein in epithelial cells     

Kowalski MP  Dubouix-Bourandy A  Bajmoczi M  Golan DE  Zaidi T  Coutinho-Sledge YS  Gygi MP  Gygi SP  Wiemer EA  Pier GB 《Science (New York, N.Y.)》2007,317(5834):130-132

The airway epithelium plays an essential role in innate immunity to lung pathogens. Ribonucleoprotein particles primarily composed of major vault protein (MVP) are highly expressed in cells that encounter xenobiotics. However, a clear biologic function for MVP is not established. We report here that MVP is rapidly recruited to lipid rafts when human lung epithelial cells are infected with Pseudomonas aeruginosa, and maximal recruitment is dependent on bacterial binding to the cystic fibrosis transmembrane conductance regulator. MVP was also essential for optimal epithelial cell internalization and clearance of P. aeruginosa. These results suggest that MVP makes a substantial contribution to epithelial cell-mediated resistance to infection.  相似文献   

Small interfering RNA-induced transcriptional gene silencing in human cells   总被引：1，自引：0，他引：1  

Morris KV  Chan SW  Jacobsen SE  Looney DJ 《Science (New York, N.Y.)》2004,305(5688):1289-1292

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Diamond genesis,seismic structure,and evolution of the Kaapvaal-Zimbabwe craton     

Shirey SB  Harris JW  Richardson SH  Fouch MJ  James DE  Cartigny P  Deines P  Viljoen F 《Science (New York, N.Y.)》2002,297(5587):1683-1686

The lithospheric mantle beneath the Kaapvaal-Zimbabwe craton of southern Africa shows variations in seismic P-wave velocity at depths within the diamond stability field that correlate with differences in the composition of diamonds and their syngenetic inclusions. Middle Archean mantle depletion events initiated craton keel formation and early harzburgitic diamond formation. Late Archean accretionary events involving an oceanic lithosphere component stabilized the craton and contributed a younger Archean generation of eclogitic diamonds. Subsequent Proterozoic tectonic and magmatic events altered the composition of the continental lithosphere and added new lherzolitic and eclogitic diamonds to the Archean diamond suite.  相似文献   

Spin-liquid ground state of the S = 1/2 kagome Heisenberg antiferromagnet     

Yan S  Huse DA  White SR 《Science (New York, N.Y.)》2011,332(6034):1173-1176

We use the density matrix renormalization group to perform accurate calculations of the ground state of the nearest-neighbor quantum spin S = 1/2 Heisenberg antiferromagnet on the kagome lattice. We study this model on numerous long cylinders with circumferences up to 12 lattice spacings. Through a combination of very-low-energy and small finite-size effects, our results provide strong evidence that, for the infinite two-dimensional system, the ground state of this model is a fully gapped spin liquid.  相似文献   

Observation of polymer conformation hysteresis in extensional flow     

Schroeder CM  Babcock HP  Shaqfeh ES  Chu S 《Science (New York, N.Y.)》2003,301(5639):1515-1519

Highly extensible Escherichia coli DNA molecules in planar extensional flow were visualized in dilute solution by fluorescence microscopy. For a narrow range of flow strengths, the molecules were found in either a coiled or highly extended conformation, depending on the deformation history of the polymer. This conformation hysteresis persists for many polymer relaxation times and is due to conformation-dependent hydrodynamic forces. Polymer conformational free-energy landscapes were calculated from computer simulations and show two free-energy minima for flow strengths near the coil-stretch transition. Hysteresis cycles may directly influence bulk-solution stresses and the development of stress-strain relations for dilute polymer flows.  相似文献   

Mutational analysis of the tyrosine phosphatome in colorectal cancers   总被引：1，自引：0，他引：1  

Wang Z  Shen D  Parsons DW  Bardelli A  Sager J  Szabo S  Ptak J  Silliman N  Peters BA  van der Heijden MS  Parmigiani G  Yan H  Wang TL  Riggins G  Powell SM  Willson JK  Markowitz S  Kinzler KW  Vogelstein B  Velculescu VE 《Science (New York, N.Y.)》2004,304(5674):1164-1166

Tyrosine phosphorylation, regulated by protein tyrosine phosphatases (PTPs) and kinases (PTKs), is important in signaling pathways underlying tumorigenesis. A mutational analysis of the tyrosine phosphatase gene superfamily in human cancers identified 83 somatic mutations in six PTPs (PTPRF, PTPRG, PTPRT, PTPN3, PTPN13, PTPN14), affecting 26% of colorectal cancers and a smaller fraction of lung, breast, and gastric cancers. Fifteen mutations were nonsense, frameshift, or splice-site alterations predicted to result in truncated proteins lacking phosphatase activity. Five missense mutations in the most commonly altered PTP (PTPRT) were biochemically examined and found to reduce phosphatase activity. Expression of wild-type but not a mutant PTPRT in human cancer cells inhibited cell growth. These observations suggest that the mutated tyrosine phosphatases are tumor suppressor genes, regulating cellular pathways that may be amenable to therapeutic intervention.  相似文献   

Virus maturation involving large subunit rotations and local refolding     

Conway JF  Wikoff WR  Cheng N  Duda RL  Hendrix RW  Johnson JE  Steven AC 《Science (New York, N.Y.)》2001,292(5517):744-748

Large-scale conformational changes transform viral precursors into infectious virions. The structure of bacteriophage HK97 capsid, Head-II, was recently solved by crystallography, revealing a catenated cross-linked topology. We have visualized its precursor, Prohead-II, by cryoelectron microscopy and modeled the conformational change by appropriately adapting Head-II. Rigid-body rotations ( approximately 40 degrees) cause switching to an entirely different set of interactions; in addition, two motifs undergo refolding. These changes stabilize the capsid by increasing the surface area buried at interfaces and bringing the cross-link-forming residues, initially approximately 40 angstroms apart, close together. The inner surface of Prohead-II is negatively charged, suggesting that the transition is triggered electrostatically by DNA packaging.  相似文献