Bovine blood components: fractionation, composition, and nutritive value   总被引：2，自引：0，他引：2  

Duarte RT  Carvalho Simões MC  Sgarbieri VC 《Journal of agricultural and food chemistry》1999,47(1):231-236

The objective of this research work was to fractionate bovine blood, collected hygienically in a slaughterhouse, into blood plasma protein concentrate, red blood cell concentrate, globin isolate, and a carboxymethylcellulose-heme iron (CMC-heme) complex. All four fractions were studied for proximate composition and amino acid and mineral contents. The nutritive value of plasma protein concentrate and globin isolate was comparatively studied using rat bioassays. The amino acid content in plasma protein concentrate is well balanced and produced net protein utilization and net protein ratio equivalent to 95% those of casein. Globin isolate ( approximately 91% protein) is deficient in isoleucine and S-containing amino acids and was unable to support rat growth at 10% concentration in the diet. Red blood cell concentrate and the isolated CMC-heme complex were good sources of bioavailable iron. Iron availabilities for CMC-heme and whole blood cell concentrate, related to ferrous sulfate as 100%, were 64 and 70%, respectively.  相似文献   

Determination of Organic Mercury in Biota, Plants and Contaminated Sediments Using a Thermal Atomic Absorption Spectrometry Technique   总被引：1，自引：0，他引：1  

M. Válega  S. Abreu  P. Pato  L. Rocha  A. R. Gomes  M. E. Pereira  A. C. Duarte 《Water, air, and soil pollution》2006,174(1-4):223-234

A simple, rapid procedure for the determination of organic mercury in sediments, plants and fish tissues has been developed and validated. Extraction and separation of organic mercury compounds from the sample matrix was achieved by an established procedure based on an acid leaching of the sample (H₂SO₄/KBr/CuSO₄), followed by extraction of the organic mercury halide with toluene and back-extraction with an aqueous solution of thiosulphate. Detection and quantification of mercury, in the liquid extracts, was made by atomic absorption spectrometry (AAS), following thermal decomposition of the sample. The method was evaluated using Certified Reference Material (CRM) BCR 463 (tuna fish), BCR 580 (estuarine sediment), IAEA-140TM (sea plant homogenate) and NRCC TORT-2 (lobster hepathopancreas). The recovery factors for organic mercury in all tested CRM were between 81–107%. The precision of the method has relative standard deviations of less than 10% for sediments and fish tissues and of less than 16% for plant material. The method was successfully applied to natural samples of sediments, plants, macroalgae and fish tissues collected from an estuarine ecosystem and could, therefore, be used for routine analyses.  相似文献   

Wetting rate and sodicity effects on interrill erosion from semi-arid Israeli soils   总被引：4，自引：0，他引：4  

A. I. Mamedov  I. Shainberg  G. J. Levy   《Soil & Tillage Research》2002,68(2):121-132

Interrill erosion depends on soil detachment and sediment transport, which are affected by seal formation and runoff. The objective of this study was to investigate the effect of wetting rate (WR) on runoff and soil erosion in semi-arid Israeli soils varying in clay content and exchangeable sodium percentage (ESP). Six soils, ranging in clay content between 90 and 680 g kg⁻¹ and ESP between 0.9 and 20, were packed in 0.2 m×0.4 m trays, wetted at 3 WRs (2, 8, or 64 mm h⁻¹), and thereafter exposed to 60 mm of distilled water rain in a laboratory rainfall simulator. Under non-sodic conditions (ESP<2), highest runoff and erosion were obtained from loam (220 g kg⁻¹ clay and 350 g kg⁻¹ silt) which was ascribed to its high susceptibility to seal formation, runoff and detachability. Runoff and erosion increased with an increase in ESP and WR. The effect of WR on runoff and erosion was negligible in loamy sand and generally increased with an increase in clay content. In clay soils (>600 g kg⁻¹ clay), WR played a greater role in determining runoff and erosion compared with raindrop impact. A linear type dependence existed between erosion and runoff for soils with ESP<5 or when slow WR was used. For high ESP soils, or when medium or fast WR were used, an exponential type relation described better the dependence of erosion on runoff. It is suggested that for sodic soils or for conditions favoring aggregate slaking, runoff level and its velocity were high enough to initiate rill erosion that supplemented raindrop detachment in markedly increasing erosion.  相似文献   

Magnetic dynamo in the moon: a comparison with the Earth     

Levy EH 《Science (New York, N.Y.)》1972,178(4056):52-53

The assumption that the moon had an internal magnetic field produced in the same way as the geomagnetic field requires that the moon rotated faster than the angular velocity at which it would break up. This suggests that a lunar dynamo is not a tenable explanation for the magnetic remanence observed on the moon.  相似文献   

Pre-mesozoic palinspastic reconstruction of the eastern great basin (Western United States)     

Levy M  Christie-Blick N 《Science (New York, N.Y.)》1989,245(4925):1454-1462

The Great Basin of the western United States has proven important for studies of Proterozoic and Paleozoic geology [2500 to 245 million years ago (Ma)] and has been central to the development of ideas about the mechanics of crustal shortening and extension. An understanding of the deformational history of this region during Mesozoic and Cenozoic time (245 Ma to the present) is required for palinspastic reconstruction of now isolated exposures of older geology in order to place these in an appropriate regional geographic context. Considerable advances in unraveling both the crustal shortening that took place during Mesozoic to early Cenozoic time (especially from about 150 to 50 Ma) and the extension of the past 37 million years have shown that earlier reconstructions need to be revised significantly. A new reconstruction is developed for rocks of middle Proterozoic to Early Cambrian age based on evidence that total shortening by generally east-vergent thrusts and folds was at least 104 to 135 kilometers and that the Great Basin as a whole accommodated approximately 250 kilometers of extension in the direction 287 degrees +/- 12 degrees between the Colorado Plateau and the Sierra Nevada. Extension is assumed to be equivalent at all latitudes because available paleomagnetic evidence suggests that the Sierra Nevada experienced little or no rotation with respect to the extension direction since the late Mesozoic. An estimate of the uncertainty in the amount of extension obtained from geological and paleomagnetic uncertainties increases northward from +/-56 kilometers at 36 degrees 30N to (-87)(+108) kilometers at 40 degrees N. On the basis of the reconstruction, the original width of the preserved part of the late Proterozoic and Early Cambrian basin was about 150 to 300 kilometers, about 60 percent of the present width, and the basin was oriented slightly more north-south with respect to present-day coordinates.  相似文献   

Bone marrow-derived lymphoid cells (B cells): functional depletion with cobra factor and fresh serum   总被引：2，自引：0，他引：2  

N L Levy  D W Scott  R Snyderman 《Science (New York, N.Y.)》1972,178(63):866-867

Treatment of rat spleen cells with cobra factor and fresh rat serum provided a simple, rapid means of functionally eliminating complement receptor lymphocytes. Cells able to differentiate into plaque-forming cells in a syngeneic, irradiated host were diminished, but cells able to induce a graft-versus-host reaction were not diminished. There was no effect on plaque-forming cells from an immune spleen.  相似文献   

Similarity of synthetic peptide from human tumor to parathyroid hormone in vivo and in vitro   总被引：18，自引：0，他引：18  

N Horiuchi  M P Caulfield  J E Fisher  M E Goldman  R L McKee  J E Reagan  J J Levy  R F Nutt  S B Rodan  T L Schofield 《Science (New York, N.Y.)》1987,238(4833):1566-1568

One mechanism considered responsible for the hypercalcemia that frequently accompanies malignancy is secretion by the tumor of a circulating factor that alters calcium metabolism. The structure of a tumor-secreted peptide was recently determined and found to be partially homologous to parathyroid hormone (PTH). The amino-terminal 1-34 region of the factor was synthesized and evaluated biologically. In vivo it produced hypercalcemia, acted on bone and kidney, and stimulated 1,25-dihydroxy-vitamin D3 formation. In vitro it interacted with PTH receptors and, in some systems, was more potent than PTH. These studies support a long-standing hypothesis regarding pathogenesis of malignancy-associated hypercalcemia.  相似文献   

Observed diffraction pattern and proposed models of liquid water   总被引：1，自引：0，他引：1  

Narten AH  Levy HA 《Science (New York, N.Y.)》1969,165(3892):447-454

  相似文献   

Electronic origin of the inhomogeneous pairing interaction in the high-Tc superconductor Bi2Sr2CaCu2O8+delta     

Pasupathy AN  Pushp A  Gomes KK  Parker CV  Wen J  Xu Z  Gu G  Ono S  Ando Y  Yazdani A 《Science (New York, N.Y.)》2008,320(5873):196-201

Identifying the mechanism of superconductivity in the high-temperature cuprate superconductors is one of the major outstanding problems in physics. We report local measurements of the onset of superconducting pairing in the high-transition temperature (Tc) superconductor Bi2Sr2CaCu2O8+delta using a lattice-tracking spectroscopy technique with a scanning tunneling microscope. We can determine the temperature dependence of the pairing energy gaps, the electronic excitations in the absence of pairing, and the effect of the local coupling of electrons to bosonic excitations. Our measurements reveal that the strength of pairing is determined by the unusual electronic excitations of the normal state, suggesting that strong electron-electron interactions rather than low-energy (<0.1 volts) electron-boson interactions are responsible for superconductivity in the cuprates.  相似文献   

Design and chemical synthesis of a homogeneous polymer-modified erythropoiesis protein     

Kochendoerfer GG  Chen SY  Mao F  Cressman S  Traviglia S  Shao H  Hunter CL  Low DW  Cagle EN  Carnevali M  Gueriguian V  Keogh PJ  Porter H  Stratton SM  Wiedeke MC  Wilken J  Tang J  Levy JJ  Miranda LP  Crnogorac MM  Kalbag S  Botti P  Schindler-Horvat J  Savatski L  Adamson JW  Kung A  Kent SB  Bradburne JA 《Science (New York, N.Y.)》2003,299(5608):884-887

We report the design and total chemical synthesis of "synthetic erythropoiesis protein" (SEP), a 51-kilodalton protein-polymer construct consisting of a 166-amino-acid polypeptide chain and two covalently attached, branched, and monodisperse polymer moieties that are negatively charged. The ability to control the chemistry allowed us to synthesize a macromolecule of precisely defined covalent structure. SEP was homogeneous as shown by high-resolution analytical techniques, with a mass of 50,825 +/-10 daltons by electrospray mass spectrometry, and with a pI of 5.0. In cell and animal assays for erythropoiesis, SEP displayed potent biological activity and had significantly prolonged duration of action in vivo. These chemical methods are a powerful tool in the rational design of protein constructs with potential therapeutic applications.  相似文献