Large-sample pairwise comparisons among multinomial proportions with an application to analysis of mutant spectra     

Walter W. Piegorsch  Kelly A. Richwine 《Journal of Agricultural, Biological & Environmental Statistics》2001,6(3):305-325

In studies examining patterns of mutational damage, the primary variables of interest are expressed typically as discrete counts within defined categories of damage. The multinomial distribution is a common model for such data settings. Of interest is statistical comparison of the pattern, or spectrum, of mutation among the various mutant categories. A specific question in such instances is the identification of differences among the spectral categories, identified, e.g., via simultaneous confidence intervals for pairwise differences in or ratios of the multinomial response probabilities. Herein, a selection of possible methods for constructing such intervals is described and compared via computer simulations to determine which are most appropriate for practical use in the evaluation of mutant spectra.  相似文献   

Die Interpretation von K/Ca-Austauschkurven mit Hilfe einer einfachen GAPON-Gleichung     

Walter R. Fischer 《植物养料与土壤学杂志》1990,153(2):93-95

The interpretation of K/Ca exchange isotherms by a simple GAPON equation K/Ca exchange isotherms of various soils can be described by a GAPON equation, where the coefficients being fitted to the measured values by iteration. The resulting values for the “labile potassium” are very similar to those of exchangeable K, whereas only 5–25% of the cec is involved in the short-term K/Ca exchange.  相似文献   

Antioxidant capacity of oat (Avena sativa L.) extracts. 1. Inhibition of low-density lipoprotein oxidation and oxygen radical absorbance capacity     

Handelman GJ  Cao G  Walter MF  Nightingale ZD  Paul GL  Prior RL  Blumberg JB 《Journal of agricultural and food chemistry》1999,47(12):4888-4893

Milled oat groat pearlings, trichomes, flour, and bran were extracted with methanol and the fractions tested in vitro for antioxidant capacity against low-density lipoprotein (LDL) oxidation and R-phycoerythrin protein oxidation in the oxygen radical absorbance capacity (ORAC) assay. The oxidative reactions were generated by 2,2'-azobis(2-amidinopropane) HCl (AAPH) or Cu(2+) in the LDL assay and by AAPH or Cu(2+) + H(2)O(2) in the ORAC assay and calibrated against a Trolox standard to calculate Trolox equivalents (1 Trolox equivalent = 1 TE = activity of 1 micromol of Trolox). The antioxidant capacity of the oat fractions was generally consistent with a potency rank of pearlings (2.89-8.58 TE/g) > flour (1.00-3.54 TE/g) > trichome (1.74 TE/g) = bran (1.02-1.62 TE/g) in both LDL and ORAC assays regardless of the free radical generator employed. A portion of the oat antioxidant constituents may be heat labile as the greatest activity was found among non-steam-treated pearlings. The contribution of oat tocols from the fractions accounted for <5% of the measured antioxidant capacity. AAPH-initiated oxidation of LDL was inhibited by the oat fractions in a dose-dependent manner, although complete suppression was not achieved with the highest doses tested. In contrast, Cu(2+)-initiated oxidation of LDL stimulated peroxide formation with low oat concentrations but completely inhibited oxidation with higher doses. Thus, oats possess antioxidant capacity most of which is likely derived from polar phenolic compounds in the aleurone.  相似文献   

Thermokarst lakes as a source of atmospheric CH4 during the last deglaciation   总被引：2，自引：0，他引：2  

Walter KM  Edwards ME  Grosse G  Zimov SA  Chapin FS 《Science (New York, N.Y.)》2007,318(5850):633-636

Polar ice-core records suggest that an arctic or boreal source was responsible for more than 30% of the large increase in global atmospheric methane (CH4) concentration during deglacial climate warming; however, specific sources of that CH4 are still debated. Here we present an estimate of past CH4 flux during deglaciation from bubbling from thermokarst (thaw) lakes. Based on high rates of CH4 bubbling from contemporary arctic thermokarst lakes, high CH4 production potentials of organic matter from Pleistocene-aged frozen sediments, and estimates of the changing extent of these deposits as thermokarst lakes developed during deglaciation, we find that CH4 bubbling from newly forming thermokarst lakes comprised 33 to 87% of the high-latitude increase in atmospheric methane concentration and, in turn, contributed to the climate warming at the Pleistocene-Holocene transition.  相似文献   

Magnesium interaction with the surface of calcite in seawater     

Morse JW  Mucci A  Walter LM  Kaminsky MS 《Science (New York, N.Y.)》1979,205(4409):904-905

Magnesian calcite overgrowth containing 4 (+/- 2) mole percent magnesium carbonate forms on calcite exposed to natural seawater near the ocean surface. This magnesian calcite is approximately 30 percent less soluble in seawater than pure calcite. The formation of the magnesian calcite of reduced solubility may have a major influence on calcite accumulation in deep sea sediments.  相似文献   

The fish communities and fisheries of the Sundarbans: Development assistance and dilemmas of the aquatic commons     

Walter J. Rainboth 《Agriculture and Human Values》1990,7(2):61-72

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Brain dopamine and serotonin receptor sites revealed by digital subtraction autoradiography   总被引：5，自引：0，他引：5  

C A Altar  S O'Neil  R J Walter  J F Marshall 《Science (New York, N.Y.)》1985,228(4699):597-600

Autoradiography combined with image analysis permitted quantitative visualization of dopamine (D2) and serotonin (S2) binding sites in rat brain. Forebrain sections were incubated with tritiated spiroperidol alone or with tritiated spiroperidol plus unlabeled compounds that saturated the D2 or S2 sites. By subtracting the digitized image of an autoradiograph derived from the latter sections from that of the former, the D2 or S2 sites were specifically revealed. The resulting quantitative images demonstrate the differing anatomical distributions of these sites. The D2 site is largely restricted to the striatal complex (caudate-putamen, nucleus accumbens septi, and olfactory tubercle), whereas the S2 site is enriched in layer 5 of motor cortex, the perirhinal and cingulate cortices, and the claustrum.  相似文献   

8-Arginine]-vasopressinoic acid: an inhibitor of rabbit kidney adenyl cyclase   总被引：6，自引：0，他引：6  

T Dousa  O Hechter  R Walter  I L Schwartz 《Science (New York, N.Y.)》1970,167(921):1134-1135

Neurohypophyseal hormnones and several synthetic analogs stimulate adenyl cyclase prepared from rabbit kidney medullary tissue. [8-Arginine]-vasopressinoic acid inhibits the stimulation of medullary adenyl cyclase by neurohypophyseal peptides but does not influence the action of parathyroid hormone on adenyl cyclase from kidiney cortex.  相似文献   

A homolog of Drosophila grainy head is essential for epidermal integrity in mice   总被引：1，自引：0，他引：1  

Ting SB  Caddy J  Hislop N  Wilanowski T  Auden A  Zhao LL  Ellis S  Kaur P  Uchida Y  Holleran WM  Elias PM  Cunningham JM  Jane SM 《Science (New York, N.Y.)》2005,308(5720):411-413

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Deep mantle cycling of oceanic crust: evidence from diamonds and their mineral inclusions   总被引：6，自引：0，他引：6  

Walter MJ  Kohn SC  Araujo D  Bulanova GP  Smith CB  Gaillou E  Wang J  Steele A  Shirey SB 《Science (New York, N.Y.)》2011,334(6052):54-57

A primary consequence of plate tectonics is that basaltic oceanic crust subducts with lithospheric slabs into the mantle. Seismological studies extend this process to the lower mantle, and geochemical observations indicate return of oceanic crust to the upper mantle in plumes. There has been no direct petrologic evidence, however, of the return of subducted oceanic crustal components from the lower mantle. We analyzed superdeep diamonds from Juina-5 kimberlite, Brazil, which host inclusions with compositions comprising the entire phase assemblage expected to crystallize from basalt under lower-mantle conditions. The inclusion mineralogies require exhumation from the lower to upper mantle. Because the diamond hosts have carbon isotope signatures consistent with surface-derived carbon, we conclude that the deep carbon cycle extends into the lower mantle.  相似文献