Uncertainties in carbon dioxide radiative forcing in atmospheric general circulation models   总被引：1，自引：0，他引：1  

Cess RD  Zhang MH  Potter GL  Barker HW  Colman RA  Dazlich DA  Del Genio AD  Esch M  Fraser JR  Galin V  Gates WL  Hack JJ  Ingram WJ  Kiehl JT  Lacis AA  Le Treut H  Li ZX  Liang XZ  Mahfouf JF  McAvaney BJ  Meleshko VP  Morcrette JJ  Randall DA  Roeckner E  Royer JF  Sokolov AP  Sporyshev PV  Taylor KE  Wang WC  Wetherald RT 《Science (New York, N.Y.)》1993,262(5137):1252-1255

Global warming caused by an increase in the concentrations of greenhouse gases, is the direct result of greenhouse gas-induced radiative forcing. When a doubling of atmospheric carbon dioxide is considered, this forcing differed substantially among 15 atmospheric general circulation models. Although there are several potential causes, the largest contributor was the carbon dioxide radiation parameterizations of the models.  相似文献   

Immunoglobulin structure: amino terminal sequences of mouse myeloma proteins that bind phosphorylcholine   总被引：26，自引：0，他引：26  

P Barstad  S Rudikoff  M Potter  M Cohn  W Konigsberg  L Hood 《Science (New York, N.Y.)》1974,183(128):962-966

The amino terminal sequences of five light and heavy immunoglobulin chains from myeloma proteins of the BALB/c mouse with binding activity to phosphorylcholine are presented. Except for a single substitution in position 4, all five heavy chains have identical amino terminal sequences through the first hypervariable region. Proteins which share unique (idiotypic) antigenic determinants are identical through the first hypervariable region of their light and heavy chains. Proteins with differing idiotypic determinants have light chains of differing amino acid sequence. These observations suggest that the heavy chain plays a more important role than the light chain in determining the phosphorylcholine binding site.  相似文献   

Manganese oxide octahedral molecular sieves: preparation, characterization, and applications     

Shen YF  Zerger RP  Deguzman RN  Suib SL  McCurdy L  Potter DI  O'young CL 《Science (New York, N.Y.)》1993,260(5107):511-515

A thermally stable 3 x 3 octahedral molecular sieve corresponding to natural todorokite (OMS-1) has been synthesized by autoclaving layer-structure manganese oxides, which are prepared by reactions of MnO(4)(-) and Mn(2+) under markedly alkaline conditions. The nature and thermal stability of products depend strongly on preparation parameters, such as the MnO(4)(-)/Mn(2+) ratio, pH, aging, and autoclave conditions. The purest and the most thermally stable todorokite is obtained at a ratio of 0.30 to 0.40. Autoclave treatments at about 150 degrees to 180 degrees C for more than 2 days yield OMS-1, which is as thermally stable (500 degrees C) as natural todorokite minerals. Adsorption data give a tunnel size of 6.9 angstroms and an increase of cyclohexane or carbon tetrachloride uptake with dehydration temperature up to 500 degrees C. At 600 degrees C, the tunnel structure collapses. Both Lewis and Br?nsted acid sites have been observed in OMS-1. Particular applications of these materials include adsorption, electrochemical sensors, and oxidation catalysis.  相似文献   

Reconstruction of Current Flow and Imaging of Current-Limiting Defects in Polycrystalline Superconducting Films     

AE Pashitski  A Gurevich  AA Polyanskii  DC Larbalestier  A Goyal  ED Specht  DM Kroeger  JA DeLuca  JE Tkaczyk 《Science (New York, N.Y.)》1997,275(5298):367-369

Magneto-optical imaging was used to visualize the inhomogeneous penetration of magnetic flux into polycrystalline TlBa2Ca2Cu3Ox films with high critical current densities, to reconstruct the local two-dimensional supercurrent flow patterns and to correlate inhomogeneities in this flow with the local crystallographic misorientation. The films have almost perfect c-axis alignment and considerable local a- and b-axis texture because the grains tend to form colonies with only slightly misaligned a and b axes. Current flows freely over these low-angle grain boundaries but is strongly reduced at intermittent colony boundaries of high misorientation. The local (<10-micrometer scale) critical current density Jc varies widely, being up to 10 times as great as the transport Jc (scale of approximately 1 millimeter), which itself varies by a factor of about 5 in different sections of the film. The combined experiments show that the magnitude of the transport Jc is largely determined by a few high-angle boundaries.  相似文献   

Pesticide occurrence in selected South Florida canals and Biscayne Bay during high agricultural activity     

Harman-Fetcho JA  Hapeman CJ  McConnell LL  Potter TL  Rice CP  Sadeghi AM  Smith RD  Bialek K  Sefton KA  Schaffer BA  Curry R 《Journal of agricultural and food chemistry》2005,53(15):6040-6048

Climate and soil conditions in South Florida along with an extensive canal system facilitate movement of agricultural pesticides into surface waters. In a two-year study (2002-2004) of the currently used pesticides in South Florida, atrazine, endosulfan, metolachlor, chlorpyrifos, and chlorothalonil were the most frequently detected in the canals and in Biscayne Bay, with average concentrations of 16, 11, 9.0, 2.6, and 6.0 ng/L, respectively. Concentrations of atrazine and chlorpyrifos were highest near corn production. Chlorothalonil and endosulfan concentrations were highest near vegetable production, with no clear trend for metolachlor, which is used on multiple crops. Concentration data were used to calculate an aquatic life hazard potential for the planting period (November) versus the harvest period (March). This analysis indicated that a higher hazard potential occurs during harvest, primarily from the use of endosulfan. These data will also serve to document canal conditions prior to implementation of the Comprehensive Everglades Restoration Plan (CERP).  相似文献   

An increase in the concentration of hepatic iron during the metamorphosis of the lamprey Geotria australis is accompanied by increased superoxide dismutase activity     

L. R. Harris  M. H. Cake  D. J. Macey  I. C. Potter 《Fish physiology and biochemistry》1990,8(6):451-457

The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase (SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1–7) and recently metamorphosed downstream migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15–0.55 μg.mg wet weight⁻¹ in ammocoetes and metamorphosing stages 1–3 to 2.2–2.9 μg.mg⁻¹ in stages 5–7 and to 8.8 μg.mg⁻¹ in downstream migrants. The comparable values for ferritin iron were 0.06–0.26, 1.4–2.0, and 5.3 μg.mg⁻¹. Superoxide dismutase activity fell sharply from 0.39 μg.mg⁻¹ in large ammocoetes to between 0.07 μg.mg⁻¹ in stage 1 and 0.15 μg.mg⁻¹ in stage 6, before rising significantly to 0.26 μg.mg⁻¹ in stage 7 and 0.35 μg.mg⁻¹ in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity in the liver of non-trophic animals.  相似文献   

Dutch elm disease revisited: past,present and future management in Great Britain     

T. D. Harwood  I. Tomlinson  C. A. Potter  J. D. Knight 《Plant pathology》2011,60(3):545-555

The arrival of a new species of the fungus which causes Dutch elm disease into Great Britain in the 1960s caused widespread elm death and continues to be problematic following elm regeneration. Attempts at managing the disease have been largely unsuccessful. Forty years after the outbreak, however, researchers continue to be interested in both the underlying biology of such a severe and dramatic disease event and in the policy lessons that can be drawn from it. We develop a spatial model at a 1 km² resolution. Following parameterization to replay the historical epidemic, the model is used to explore previously proposed counterfactual management strategies. A new introduction date of late 1962 is estimated. We show that, even had there been high intervention at a national level in terms of disease management early in the epidemic, there would have been little long‐term effect on elm numbers. In Brighton, a local pocket of elm which survived the peak of the initial epidemic has been successfully managed. However, Brighton and similar locations are subject to repeated waves of the disease at a 15‐ to 20‐year intervals following regeneration and reinfection of the surrounding areas, during which much more intensive management is required.  相似文献   

Tree crop smallholders,capitalism, and adat: Studies in Riau Province1, Indonesia     

Lesley Potter  Simon Badcock 《Asia Pacific viewpoint》2004,45(3):341-356

Abstract: This paper examines the extent to which traditional techniques and practices remain current among a sub‐set of Indonesian tree crop smallholders. Village‐based studies of independent oil palm and rubber smallholders in Riau (Sumatra) indicate that bio‐diverse ‘jungle rubber’ and multi‐cropping techniques still exist, but primarily as components of farmers’ coping strategies under low commodity prices. A further strategy, seeking income from non‐agrarian sources, notably ‘illegal’ logging and land sales to migrants, partially fits Rigg's ‘deagrarianisation’ thesis, though his suggestion that the farm household has become a mere ‘shell’ is not substantiated. The lack of full legalisation of tenure constrains full capitalist development but does not impede land sales. Land seizures during the Suharto period reduced belief in the efficacy of customary (adat) law, though adat has retained importance in dispute resolution and as a cultural framework. New structures of village governance following decentralisation have so far had minimal impact in either empowering villagers or dispossessing elites.  相似文献   

Copper and zinc balance in exercising horses fed 2 forms of mineral supplements     

Wagner EL  Potter GD  Gibbs PG  Eller EM  Scott BD  Vogelsang MM  Walzem RL 《Journal of animal science》2011,89(3):722-728

Studies comparing the absorption and retention of various forms of trace minerals in horses have yielded mixed results. The objective of this study was to compare Cu and Zn absorption and retention in exercising horses where the mineral was supplemented in the sulfate or organic chelate form. Nine mature horses were used in a modified switchback design experiment consisting of seven 28-d periods. Horses were fed a diet consisting of 50% concentrate and 50% hay that was balanced to meet the energy, protein, Ca, and P requirements for horses performing moderate-intensity exercise. Horses were subjected to a controlled mineral repletion-depletion diet sequence before feeding the experimental diet to standardize mineral status across horses. The experimental diet was designed to provide 90% of the 1989 NRC for Cu and Zn, with supplemental mineral provided in the inorganic sulfate form (CuSO(4) and ZnSO(4)) or the organic chelate form (Cu-Lys and Zn-Met). Feed, fecal, urine, and water samples collected during a total collection during the last 4 d of the experimental diet periods were analyzed to determine apparent absorption and retention of Cu and Zn from the 2 mineral forms. A formulation error caused horses receiving the organic chelate diet to consume about 3 times the amount of Cu and Zn compared with those fed the sulfate-supplemented diet. Copper and Zn intake and fecal excretion were greater (P < 0.05) for horses consuming the organic chelate-supplemented diet. Apparent absorption values for all horses were negative. Apparent Cu absorption and retention as a percentage of intake were greater for horses fed the organic chelate diet (P < 0.05). It is unknown why excretion of Cu and Zn by the horses during the total collection exceeded the mineral intake. Although Cu-Lys seemed to be better absorbed than CuSO(4) and absorption of Zn-Met and ZnSO(4) were not different, these results are tempered by the observation of abnormally high fecal and urinary excretion values for Cu and Zn in the present study.  相似文献   

Vaccination with type III secreted proteins leads to decreased shedding in calves after experimental infection with Escherichia coli O157     

Allen KJ  Rogan D  Finlay BB  Potter AA  Asper DJ 《Canadian journal of veterinary research》2011,75(2):98-105

Escherichia coli O157:H7 remains a threat to humans via cattle-derived fecal contamination of food and water. Preharvest intervention strategies represent a means of reducing the pathogen burden before harvest. In this study, the efficacy of a commercially produced type III secreted protein (TTSP) vaccine was evaluated with the use of a commingled experimental calf infection model (30 placebo-treated animals and 30 vaccinates). The calves were vaccinated on days 0, 21, and 42 and infected with 10(9) colony-forming units (CFU) of E. coli O157 by oral-gastric intubation on day 56. Fecal shedding was monitored daily for 14 d. Serologic assessment revealed a robust immune response to vaccination; the serum titers of antibodies against EspA, Tir, and total TTSPs were significantly higher in the vaccinates than in the placebo-treated animals on days 21, 42, 56, and 70. Significantly less (P = 0.011) of the challenge organism was shed by the vaccinates than by the placebo-treated animals on days 3 to 10. Peak shedding occurred in both groups on days 3 to 6; during this period the vaccinates showed a mean log reduction of 1.4 (P = 0.002) and a mitigated fraction of 51%. The number of animals shedding was significantly lower among the vaccinates compared with the placebo group on days 3 to 6 (P ≤ 0.05), with a mean prevented fraction of 21%. No differences in the duration of shedding were observed. Owing to the low challenge shedding in both groups on days 11 to 14 (mean CFU/g < 10; median = 0), no significant differences were observed. These data indicate that TTSP vaccination had protective effects through significant reductions in the number of animals shedding and the number of challenge organisms shed per animal and provides evidence that TTSP vaccination is an effective preharvest intervention strategy against E. coli O157.  相似文献