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排序方式: 共有986条查询结果,搜索用时 15 毫秒
961.
Mixing and transport in turbulent flows-which have strong local concentration fluctuations-are essential in many natural and industrial systems including reactions in chemical mixers, combustion in engines and burners, droplet formation in warm clouds, and biological odor detection and chemotaxis. Local concentration fluctuations, in turn, are intimately tied to the problem of the separation of pairs of fluid elements. We have measured this separation rate in an intensely turbulent laboratory flow and have found, in quantitative agreement with the seminal predictions of Batchelor, that the initial separation of the pair plays an important role in the subsequent spreading of the fluid elements. These results have surprising consequences for the decay of concentration fluctuations and have applications to biological and chemical systems. 相似文献
962.
Achard P Cheng H De Grauwe L Decat J Schoutteten H Moritz T Van Der Straeten D Peng J Harberd NP 《Science (New York, N.Y.)》2006,311(5757):91-94
Plants live in fixed locations and survive adversity by integrating growth responses to diverse environmental signals. Here, we show that the nuclear-localized growth-repressing DELLA proteins of Arabidopsis integrate responses to independent hormonal and environmental signals of adverse conditions. The growth restraint conferred by DELLA proteins is beneficial and promotes survival. We propose that DELLAs permit flexible and appropriate modulation of plant growth in response to changes in natural environments. 相似文献
963.
Ledbetter EC Riis RC Kern TJ Haley NJ Schatzberg SJ 《Journal of the American Veterinary Medical Association》2006,229(3):376-384
CASE DESCRIPTION: An 8-year-old Labrador Retriever with diabetes mellitus in which bilateral phacoemulsification had been performed 3 weeks earlier was evaluated for acute onset of blepharospasm, and a 7-year-old Miniature Schnauzer with chronic immune-mediated thrombocytopenia was reevaluated for keratoconjunctivitis sicca that had been diagnosed 4 weeks earlier. CLINICAL FINDINGS: Dendritic corneal ulcerations were detected in both dogs. Canine herpesvirus-1 (CHV-1) was isolated from corneal swab specimens obtained during the initial evaluation of each dog and during recheck examinations performed until the ulcerations were healed. Canine herpesvirus-1 serum neutralization titers were detected in both dogs. Results of virus isolation from oropharyngeal and genital swab specimens were negative for both dogs. The isolated viruses were identified as CHV-1 via immunofluorescence, transmission electron microscopy, PCR assay, and gene sequencing. Negative controls for PCR assay and virus isolation included conjunctival swab specimens from 50 dogs without extraocular disease and corneal swab specimens from 50 dogs with corneal ulcers, respectively. TREATMENT AND OUTCOME: Lesions resolved in both dogs after topical administration of idoxuridine or trifluridine and discontinuation of topically administered immunosuppressive medications. CLINICAL RELEVANCE: To the authors' knowledge, this is the first report of corneal ulcerations associated with naturally occurring CHV-1 infection and may represent local ocular recrudescence of latent CHV-1 infection. The viruses isolated were identified as CHV-1, and the morphology, antigenicity, and genotype were similar to those for CHV-1 isolates obtained from a puppy that died from systemic CHV-1 infection. 相似文献
964.
Frank N Elliott SB Brandt LE Keisler DH 《Journal of the American Veterinary Medical Association》2006,228(9):1383-1390
OBJECTIVE: To compare obese horses with insulin resistance (IR) with nonobese horses and determine whether blood resting glucose, insulin, leptin, and lipid concentrations differed between groups and were correlated with combined glucose-insulin test (CGIT) results. ANIMALS: 7 obese adult horses with IR (OB-IR group) and 5 nonobese mares. PROCEDURES: Physical measurements were taken, and blood samples were collected after horses had acclimated to the hospital for 3 days. Response to insulin was assessed by use of the CGIT, and maintenance of plasma glucose concentrations greater than the preinjection value for > or = 45 minutes was used to define IR. Area under the curve values for glucose (AUC(g)) and insulin (AUC(i)) concentrations were calculated. RESULTS: Morgan, Paso Fino, Quarter Horse, and Tennessee Walking Horse breeds were represented in the OB-IR group. Mean neck circumference and BCS differed significantly between groups and were positively correlated with AUC values. Resting insulin and leptin concentrations were 6 and 14 times as high, respectively, in the OB-IR group, compared with the nonobese group, and were significantly correlated with AUC(g) and AUC(i). Plasma nonesterified fatty acid, very low-density lipoprotein, and high-density lipoprotein-cholesterol (HDL-C) concentrations were significantly higher (86%, 104%, and 29%, respectively) in OB-IR horses, and HDL-C concentrations were positively correlated with AUC values. CONCLUSIONS AND CLINICAL RELEVANCE: Measurements of neck circumference and resting insulin and leptin concentrations can be used to screen obese horses for IR. Dyslipidemia is associated with IR in obese horses. 相似文献
965.
The heartbeat of the Oligocene climate system 总被引:2,自引:0,他引:2
Pälike H Norris RD Herrle JO Wilson PA Coxall HK Lear CH Shackleton NJ Tripati AK Wade BS 《Science (New York, N.Y.)》2006,314(5807):1894-1898
A 13-million-year continuous record of Oligocene climate from the equatorial Pacific reveals a pronounced "heartbeat" in the global carbon cycle and periodicity of glaciations. This heartbeat consists of 405,000-, 127,000-, and 96,000-year eccentricity cycles and 1.2-million-year obliquity cycles in periodically recurring glacial and carbon cycle events. That climate system response to intricate orbital variations suggests a fundamental interaction of the carbon cycle, solar forcing, and glacial events. Box modeling shows that the interaction of the carbon cycle and solar forcing modulates deep ocean acidity as well as the production and burial of global biomass. The pronounced 405,000-year eccentricity cycle is amplified by the long residence time of carbon in the oceans. 相似文献
966.
Phytoplankton and cloudiness in the Southern Ocean 总被引:1,自引:0,他引:1
The effect of ocean biological productivity on marine clouds is explored over a large phytoplankton bloom in the Southern Ocean with the use of remotely sensed data. Cloud droplet number concentration over the bloom was twice what it was away from the bloom, and cloud effective radius was reduced by 30%. The resulting change in the short-wave radiative flux at the top of the atmosphere was -15 watts per square meter, comparable to the aerosol indirect effect over highly polluted regions. This observed impact of phytoplankton on clouds is attributed to changes in the size distribution and chemical composition of cloud condensation nuclei. We propose that secondary organic aerosol, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine cloud condensation nuclei and influence cloud droplet number. Model simulations support this hypothesis, indicating that 100% of the observed changes in cloud properties can be attributed to the isoprene secondary organic aerosol. 相似文献
967.
Phytophthora genome sequences uncover evolutionary origins and mechanisms of pathogenesis 总被引:2,自引:0,他引:2
Tyler BM Tripathy S Zhang X Dehal P Jiang RH Aerts A Arredondo FD Baxter L Bensasson D Beynon JL Chapman J Damasceno CM Dorrance AE Dou D Dickerman AW Dubchak IL Garbelotto M Gijzen M Gordon SG Govers F Grunwald NJ Huang W Ivors KL Jones RW Kamoun S Krampis K Lamour KH Lee MK McDonald WH Medina M Meijer HJ Nordberg EK Maclean DJ Ospina-Giraldo MD Morris PF Phuntumart V Putnam NH Rash S Rose JK Sakihama Y Salamov AA Savidor A Scheuring CF Smith BM Sobral BW Terry A Torto-Alalibo TA Win J Xu Z 《Science (New York, N.Y.)》2006,313(5791):1261-1266
Draft genome sequences have been determined for the soybean pathogen Phytophthora sojae and the sudden oak death pathogen Phytophthora ramorum. O?mycetes such as these Phytophthora species share the kingdom Stramenopila with photosynthetic algae such as diatoms, and the presence of many Phytophthora genes of probable phototroph origin supports a photosynthetic ancestry for the stramenopiles. Comparison of the two species' genomes reveals a rapid expansion and diversification of many protein families associated with plant infection such as hydrolases, ABC transporters, protein toxins, proteinase inhibitors, and, in particular, a superfamily of 700 proteins with similarity to known o?mycete avirulence genes. 相似文献
968.
Morgan RA Dudley ME Wunderlich JR Hughes MS Yang JC Sherry RM Royal RE Topalian SL Kammula US Restifo NP Zheng Z Nahvi A de Vries CR Rogers-Freezer LJ Mavroukakis SA Rosenberg SA 《Science (New York, N.Y.)》2006,314(5796):126-129
Through the adoptive transfer of lymphocytes after host immunodepletion, it is possible to mediate objective cancer regression in human patients with metastatic melanoma. However, the generation of tumor-specific T cells in this mode of immunotherapy is often limiting. Here we report the ability to specifically confer tumor recognition by autologous lymphocytes from peripheral blood by using a retrovirus that encodes a T cell receptor. Adoptive transfer of these transduced cells in 15 patients resulted in durable engraftment at levels exceeding 10% of peripheral blood lymphocytes for at least 2 months after the infusion. We observed high sustained levels of circulating, engineered cells at 1 year after infusion in two patients who both demonstrated objective regression of metastatic melanoma lesions. This study suggests the therapeutic potential of genetically engineered cells for the biologic therapy of cancer. 相似文献
969.
Dohrenwend BP Turner JB Turse NA Adams BG Koenen KC Marshall R 《Science (New York, N.Y.)》2006,313(5789):979-982
In 1988, the National Vietnam Veterans Readjustment Study (NVVRS) of a representative sample of 1200 veterans estimated that 30.9% had developed posttraumatic stress disorder (PTSD) during their lifetimes and that 15.2% were currently suffering from PTSD. The study also found a strong dose-response relationship: As retrospective reports of combat exposure increased, PTSD occurrence increased. Skeptics have argued that these results are inflated by recall bias and other flaws. We used military records to construct a new exposure measure and to cross-check exposure reports in diagnoses of 260 NVVRS veterans. We found little evidence of falsification, an even stronger dose-response relationship, and psychological costs that were lower than previously estimated but still substantial. According to our fully adjusted PTSD rates, 18.7% of the veterans had developed war-related PTSD during their lifetimes and 9.1% were currently suffering from PTSD 11 to 12 years after the war; current PTSD was typically associated with moderate impairment. 相似文献
970.
Improving plant water use efficiency (WUE) has the potential to lower plant susceptibility to drought. Amending soils with biochar has been suggested as a way to improve WUE, as it has been shown to increase the water holding capacity of soils. Here, we investigated the influence of two different biochar soil amendments on WUE measured by gas exchange and carbon isotopes of pine-oak ecosystem species. We measured WUE of individuals grown in soils where either lignocellulose or hemicellulose biochar was applied (10% v/v). WUE increased under lignocellulose, but not hemicellulose, biochar amendment during both late spring and early fall measurement periods in a single year study. However, net photosynthesis and stomatal conductance decreased in plants grown with biochar amendments. Physiochemical and sorption data provide a partial explanation of how biochar mechanisms impact soil-water-plant relations. Our results demonstrated that lignocellulosic biochar may be added to forest soils to reduce drought stress in pine-oak systems, but amendments may not lead to increases in carbon uptake rates. 相似文献