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61.
McEwen AS Hansen CJ Delamere WA Eliason EM Herkenhoff KE Keszthelyi L Gulick VC Kirk RL Mellon MT Grant JA Thomas N Weitz CM Squyres SW Bridges NT Murchie SL Seelos F Seelos K Okubo CH Milazzo MP Tornabene LL Jaeger WL Byrne S Russell PS Griffes JL Martínez-Alonso S Davatzes A Chuang FC Thomson BJ Fishbaugh KE Dundas CM Kolb KJ Banks ME Wray JJ 《Science (New York, N.Y.)》2007,317(5845):1706-1709
Water has supposedly marked the surface of Mars and produced characteristic landforms. To understand the history of water on Mars, we take a close look at key locations with the High-Resolution Imaging Science Experiment on board the Mars Reconnaissance Orbiter, reaching fine spatial scales of 25 to 32 centimeters per pixel. Boulders ranging up to approximately 2 meters in diameter are ubiquitous in the middle to high latitudes, which include deposits previously interpreted as finegrained ocean sediments or dusty snow. Bright gully deposits identify six locations with very recent activity, but these lie on steep (20 degrees to 35 degrees) slopes where dry mass wasting could occur. Thus, we cannot confirm the reality of ancient oceans or water in active gullies but do see evidence of fluvial modification of geologically recent mid-latitude gullies and equatorial impact craters. 相似文献
62.
Anderson WA Amasino RM Ares M Banerjee U Bartel B Corces VG Drennan CL Elgin SC Epstein IR Fanning E Guillette LJ Handelsman J Hatfull GF Hoy RR Kelley D Leinwand LA Losick R Lu Y Lynn DG Neuhauser C O'Dowd DK Olivera T Pevzner P Richards-Kortum RR Rine J Sah RL Strobel SA Walker GC Walt DR Warner IM Wessler S Willard HF Zare RN 《Science (New York, N.Y.)》2011,334(6057):760-761
63.
Lynn H. Booth Vanessa J. Heppelthwaite Kathryn O’Halloran 《Journal of Soils and Sediments》2002,2(3):148-154
Objectives and Methods. The sensitivity of two biomarkers, the neutral red retention assay (NRRA) and cytochrome P450 were evaluated in the earthwormAporrectodea caliginosa for their potential to detect exposure to benzo[a]pyrene (BaP). Cytochrome P450 was also evaluated in the earthwormLumbricus rubellus, and measured using the substrate ethoxycoumarin. Optimal assay conditions (pH, and temperature) were determined, followed
by exposure of earthworms to 20 mg/kg BaP (a typical concentration at contaminated sites in New Zealand). Ethoxycoumarin-O-dealkylase
(ECOD) activity was measured after 7, 14, and 21 days exposure. The NRRA was evaluated in earthworms exposed to 0.2, 20, and
100 mg BaP/kg, and biomarker responses were compared with effects on body weight.
Results and Discussion Benzo[a]pyrene failed to induce ECOD activity in either earthworm species, and therefore it is not useful as a biomarker
of BaP exposure and was not evaluated further. In all cases, the NRRA was significantly affected in the absence of any effects
on earthworm body weight, indicating that this assay can detect exposure to BaP at a range of concentrations comparable to
those found at contaminated sites. The NRRA should be linked to reproductive endpoints, then it can be used as an early warning
indicator of adverse effects. Establishing biomarker stability under environmental conditions is an important step in biomarker
development. Therefore, the effects of soil type (sandy soil, silt loam, and a clay soil), moisture content (15–30%), and
temperature (5–20°) on the NRRA were determined. In all cases, there was no effect on the NRRA, indicating that this assay
is very stable under varying environmental conditions.
Conclusion and Outlook In conclusion, cytochrome P450 activity does not appear to be a useful indicator of PAH exposure in eitherA. caliginosa or L.rubellus, and due to the inherently low activity, it is not suitable as a routine biomarker for detecting environmental contamination
by these compounds. In contrast, the NRRA in the earthworm A.caliginosa is a promising indicator of PAH exposure at the concentrations likely to be found in contaminated sites in New Zealand, and
therefore has potential for evaluating these contaminated sites. If the NRRA can be linked to ecologically important life-cycle
endpoints, such as reproduction, then it could be used as an early warning indicator of adverse effects at contaminated sites,
i.e., by measuring biomarker responses in earthworms from a ‘contaminated area’ and comparing these with earthworms from a
matched control area. 相似文献
64.
Turf-banked terrace treads and risers, turf exfoliation and possible relationships with advancing treeline 总被引:4,自引:0,他引:4
Fine-scale geomorphic/pedogenic processes at alpine treeline may facilitate the initial stages of conifer invasion of alpine tundra. Turf-banked terraces and turf exfoliation associated with solifluction may provide both the topographic protection and the seedbed necessary for conifer establishment above treeline. The morphometry, stoniness and surface penetrability of turf-banked terraces were recorded. Whereas differences among sites exist due to topographic constraints, differences in soil penetrability depend on turf exfoliation. Exfoliated turf risers are significantly more penetrable than non-exfoliated solifluction risers and adjacent treads. These penetrable microsites provide favorable conditions for seed germination. The process of turf exfoliation may play a role in conifer advance into tundra during climatic change. 相似文献
65.
Rose NL Sporns P Dodd HM Gasson MJ Mellon FA McMullen LM 《Journal of agricultural and food chemistry》2003,51(10):3174-3178
Nisin variants and fragments were reacted with glutathione, and the products of the reactions were analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and liquid chromatography/mass spectrometry (LC-MS). Reactions between glutathione and either [Ala5]nisin or [Ala33]nisin resulted in products with two glutathione molecules conjugated to one nisin variant molecule. Only one glutathione molecule was added to [Ala5,Ala33]nisin. Fragmentation of the nisin molecule resulted in nisin 1-12, nisin 1-20, and nisin 1-32 fragments. Each fragment retained two dehydro residues, which subsequently underwent reaction with glutathione. The data indicated that the dehydroalanine residues of nisin are sites of addition for glutathione. Such addition renders the nisin molecule inactive. 相似文献
66.
Garrossian M Gardner DR Panter KE James LF 《Journal of agricultural and food chemistry》2002,50(8):2235-2240
Isocupressic acid (1) was used to synthetically prepare a mixture of (8S,13R,S)-labda-15,19-dioic acid (tetrahydroagathic acid) (5) via a two-step oxidation procedure followed by hydrogenation of the double bonds at C13 and C8. Reduction of the C8,17 double bond was stereospecific producing only the 8S isomer and confirmed by the nOe interaction between the resulting C17 and C20 methyl groups. The 13R and 13S isomers of 5 were separated and analyzed by HPLC/MS, and (13S)-tetrahydroagathic acid was isolated and identified by comparison to a standard prepared by hydrogenation of naturally occurring (13S)-dihydroagathic acid (4). (13R,S)-dihydroagathic acid was prepared by selective sodium metal-catalyzed hydrogenation of the C13,14 allylic double bond of agathic acid (3). The prepared compounds were then used as standards to confirm the presence of 4 and 5 and their respective 13R and 13S isomers in bovine serum samples. Tetrahydroagathic acid was shown to be the only metabolite detected in serum samples taken from a suspected cattle abortion case submitted for diagnosis; and, thus, 5 could be a valuable diagnostic marker for pine needle-induced abortions. 相似文献
67.
Henry Lynn Charles L. Mohler Stephen D. DeGloria Charles E. McCulloch 《Landscape Ecology》1995,10(6):323-335
Methods were developed to evaluate the performance of a decision-tree model used to predict landscape-level patterns of potential forest vegetation in central New York State. The model integrated environmental databases and knowledge on distribution of vegetation. Soil and terrain decision-tree variables were derived by processing state-wide soil geographic databases and digital terrain data. Variables used as model inputs were soil parent material, soil drainage, soil acidity, slope position, slope gradient, and slope azimuth. Landscapescale maps of potential vegetation were derived through sequential map overlay operations using a geographic information system (GIS). A verification sample of 276 field plots was analyzed to determine: (1) agreement between GIS-derived estimates of decision-tree variables and direct field measurements, (2) agreement between vegetation distributions predicted using GIS-derived estimates and using field observations, (3) effect of misclassification costs on prediction agreement, (4) influence of particular environmental variables on model predictions, and (5) misclassification rates of the decision-tree model. Results indicate that the prediction model was most sensitive to drainage and slope gradient, and that the imprecision of the input data led to a high frequency of incorrect predictions of vegetation. However, in many cases of misclassification the predicted vegetation was similar to that of the field plots so that the cost of errors was less than expected from the misclassification rate alone. Moreover, since common vegetation types were more accurately predicted than rare types, the model appears to be reasonably good at predicting vegetation for a randomly selected plot in the landscape. The error assessment methodology developed for this study provides a useful approach for determining the accuracy and sensitivity of landscape-scale environmental models, and indicates the need to develop appropriate field sampling procedures for verifying the predictions of such models. 相似文献
68.
Resolution of a Left Ureteral Stone Using Electrohydraulic Lithotripsy in a Thoroughbred Colt 总被引:1,自引:0,他引:1
Lynn D. Rodger Gary P. Carlson Michael E. Moran Tom B. Yarbrough John R. Pascoe Jay A. Reynolds 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1995,9(4):280-282
A 3-year-old Thoroughbred colt was presented for evaluation of azotemia and anorexia. Physical examination revealed a ureterolith in the left ureter, approximately 10 cm from the bladder, which was thought to obstruct urine flow by approximately 90% when viewed cystoscopically. Ultrasonographic examination of both kidneys revealed indistinct corticomedullary junctions, and the right kidney was more hyperechoic. A percutaneous biopsy of the right kidney revealed chronic interstitial nephritis with marked interstitial medullary fibrosis. Medical therapy consisting of IV fluids, sodium chloride PO, and ammonium chloride PO was initiated. Ureteroscopic electrohydraulic lithotripsy via a perineal urethrostomy was used to successfully remove the stone. Klebsiella oxytoca , which responded to oral enrofloxacin therapy, was cultured from the urine after surgery. Azotemia resolved and the horse resumed training. 相似文献
69.
Changes in landscape patterns in Georgia,USA 总被引:39,自引:0,他引:39
The objectives of this study were to determine how landscape patterns in Georgia, USA have changed through time and whether the spatial patterns varied by physiographic region. Historical aerial photography was used to analyze spatial patterns of land use from the 1930's to the 1980's. Land use patterns were quantified by: (1) mean number and size of patches; (2) fractal dimension of patches; (3) amount of edge between land uses; and (4) indices of diversity, dominance, and contagion. Forest cover increased in aerial extent and in mean patch size. The mean size of agricultural patches increased in the coastal plain and decreased in the mountains and piedmont. Edges between land uses decreased through time, indicating less dissection of the landscape. Fractal dimensions also decreased, indicating simpler patch shapes. Indices of diversity and dominance differed through time but not among regions; the contagion index differed among regions but not through time. A geographic trend of decreasing diversity and increasing dominance and contagion was observed from the mountains to the lower coastal plain. Landscape patterns exhibited the greatest changes in the piedmont region. Overall, the Georgia landscape has become less fragmented and more connected during the past 50 years. Changing patterns in the landscape may have implications for many ecological processes and resources. 相似文献
70.
Harland W. Renshaw John W. Gessner Lynn F. Woodard Dale O. Everson 《Veterinary microbiology》1983,8(3):281-291
Miniature swine (n = 5 per group) were inoculated intradermally with mineral oil-in-water emulsions containing either 150 μg of mycobacterial immunopotentiating glyco-lipid P3 (EP3), 150 μg of lyophilized Mycobacterium avium (serotype 8) cell walls (E-MaCW), or 150 μg P3 and 150 μg M. avium cell walls (EP3-MaCW). Swine vaccinated with E-MaCW and EP3-MaCW developed antigen-sensitive lymphocytes detectable with delayed-type hypersensitivity (DTH) skin tests and lymphocyte transformation assay. Swine injected with EP3 were not sensitized. In general EP3-MaCW evoked a more pronounced in vivo DTH tuberculin skin test and in vitro lymphocyte transformation responses than E-MaCW. Time-course studies indicated a more persistent response in swine injected with EP3-MaCW than in those given E-MaCW. Commercial type Yorkshire swine (n = 5) inoculated intradermally with EP3-MaCW developed cell-mediated immune (CMI) responses to avian tuberculin detectable in vivo with delayed-type skin hypersensitivity and in vitro with lymphocyte immunostimulation responses. 相似文献