The effect on model identifiability of allowing different relocation rates for live and dead animals in the combined analysis of telemetry and recapture data     

Marlina?D.?NasutionEmail author  Cavell?Brownie  Kenneth?H.?Pollock  Roger?A.?Powell 《Journal of Agricultural, Biological & Environmental Statistics》2004,9(1):27-41

Models are described for the joint analysis of live-trapping and radio telemetry data from a study on black bears (Ursus americanus) in which all animals received ear tags and a subset also received radio tags. Concerns about bias in survival estimates led to investigation of identifiability and estimator precision for a series of models that allowed differenttelemetry relocation rates for living and dead animals, in addition to emigration and seasonal variation in survival. Identifiability was determined by showing that the expected information matrix was nonsingular. Models with fidelity constant across time, and with the same degree of time specificity for survival rates and relocation rates for dead animals, were determined to be nonidentifiable. More general models, with a greater degree of time specificity for survival rates, were near-singular, and estimators under these near-singular models had poor precision. Analysis of data from the study on black bears illustrated that estimates of survival have poor precision when relocation rates are estimated separately for live and dead animals. It is recommended that the effort expended to relocate both living and dead animals be consistently high in each telemetry survey, so that relocation rates will be high and constant across time and mortality status.  相似文献   

Precipitation of sulfide ores and organic matter: sulfate reactions at pine point, Canada   总被引：1，自引：0，他引：1  

Powell TG  Macqueen RW 《Science (New York, N.Y.)》1984,224(4644):63-66

Bitumen is a common associate of carbonate-hosted lead-zinc deposits. On the Pine Point lead-zinc property, Northwest Territories, Canada, there are two forms of bitumen. Unaltered bitumens have atomic hydrogen/carbon ratios of about 1.4, sulfur contents of about 7.8 percent, and sulfur isotope ratios ( section sign(34)S) of approximately +4.6 per mil. Altered bitumens occur in proximity to sulfide ore bodies and white sparry dolomite. Their hydrogen/carbon ratios are about 1.02, the sulfur contents average 22 percent, and the section sign(34)S values are about +12.4 per mil. These data indicate that some bitumen has participated in the thermochemical reduction of sulfate to produce hydrogen sulfide required to precipitate the ores. Mass balance considerations show that the amount and degree of alteration of bitumen is more than adequate to account for the reduced sulfur species (lead, zinc, and iron sulfides) deposited at Pine Point. These reactions may provide an important means of generating the large volumes of sulfide necessary to precipitate ore bodies in carbonate rocks.  相似文献   

Microwave spectrum and structure of sulfur difluoride     

Johnson DR  Powell FX 《Science (New York, N.Y.)》1969,164(3882):950-951

Sulfur difluioride has been identified and characterized from its microwave spectrum. The analysis of rotational transitions for both sulfur difluoride-32 and sulfur difluoride-34 shows that this molecular species has C(2v) symmetry with a bond length of 1.589 angstroms, a bond angle of 98 degrees 16', and a dipole moment of 1.05 Debye.  相似文献   

Induction of HTLV-III/LAV from a nonvirus-producing T-cell line: implications for latency   总被引：42，自引：0，他引：42  

T Folks  D M Powell  M M Lightfoote  S Benn  M A Martin  A S Fauci 《Science (New York, N.Y.)》1986,231(4738):600-602

When the human T-cell line A3.01 is infected with HTLV-III/LAV, the virus associated with the acquired immune deficiency syndrome (AIDS), most of the cells are killed. However, a small number of cells that lack the Leu-3 surface marker survive. Under normal conditions these surviving cells do not produce virus, nor can they be infected by the virus, but they can be induced to produce virus by treatment with 5-iodo-2'-deoxyuridine. This response can be induced for as long as 3 months after the initial infection, suggesting that the cells may harbor a latent form of HTLV-III/LAV.  相似文献   

Catalytic hydrolysis of vasoactive intestinal peptide by human autoantibody   总被引：11，自引：0，他引：11  

S Paul  D J Volle  C M Beach  D R Johnson  M J Powell  R J Massey 《Science (New York, N.Y.)》1989,244(4909):1158-1162

Vasoactive intestinal peptide (VIP) labeled with 125I, [Tyr10-125I]VIP, can be hydrolyzed by immunoglobulin G (IgG) purified from a human subject, as judged by trichloroacetic acid precipitation and reversed-phase high-performance liquid chromatography (HPLC). The hydrolytic activity was precipitated by antibody to human IgG, it was bound by immobilized protein G and showed a molecular mass close to 150 kilodaltons by gel filtration chromatography, properties similar to those of authentic IgG. The Fab fragment, prepared from IgG by papain treatment, retained the VIP hydrolytic activity of the IgG. Peptide fragments produced by treatment of VIP with the antibody fraction were purified by reversed-phase HPLC and identified by fast atom bombardment-mass spectrometry and peptide sequencing. The scissile bond in VIP deduced from these experiments was Gln16-Met17. The antibody concentration (73.4 fmol per milligram of IgG) and the Kd (0.4 nM) were computed from analysis of VIP binding under conditions that did not result in peptide hydrolysis. Analysis of the antibody-mediated VIP hydrolysis at varying concentrations of substrate suggested conformity with Michaelis-Menton kinetics (Km). The values for Km (37.9 X 10(-9) M) and the turnover number kcat (15.6 min-1) suggested relatively tight VIP binding and a moderate catalytic efficiency of the antibody.  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   

First solvation shell of the Cu(II) aqua ion: evidence for fivefold coordination     

Pasquarello A  Petri I  Salmon PS  Parisel O  Car R  Toth E  Powell DH  Fischer HE  Helm L  Merbach A 《Science (New York, N.Y.)》2001,291(5505):856-859

We determined the structure of the hydrated Cu(II) complex by both neutron diffraction and first-principles molecular dynamics. In contrast with the generally accepted picture, which assumes an octahedrally solvated Cu(II) ion, our experimental and theoretical results favor fivefold coordination. The simulation reveals that the solvated complex undergoes frequent transformations between square pyramidal and trigonal bipyramidal configurations. We argue that this picture is also consistent with experimental data obtained previously by visible near-infrared absorption, x-ray absorption near-edge structure, and nuclear magnetic resonance methods. The preference of the Cu(II) ion for fivefold instead of sixfold coordination, which occurs for other cations of comparable charge and size, results from a Jahn-Teller destabilization of the octahedral complex.  相似文献   

ON THE FUNDAMENTAL THEORY OF DYNAMIC GEOLOGY     

Powell JW 《Science (New York, N.Y.)》1884,3(64):511-513

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THE WYANDOTTES     

Powell JW 《Science (New York, N.Y.)》1880,1(11):137-138

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THE WORK OF THE U. S. GEOLOGICAL SURVEY     

Powell JW 《Science (New York, N.Y.)》1893,21(519):15-17

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