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排序方式: 共有73条查询结果,搜索用时 234 毫秒
31.
Triblock copolymer syntheses of mesoporous silica with periodic 50 to 300 angstrom pores 总被引:32,自引:0,他引:32
D Zhao J Feng Q Huo N Melosh GH Fredrickson BF Chmelka GD Stucky 《Science (New York, N.Y.)》1998,279(5350):548-552
Use of amphiphilic triblock copolymers to direct the organization of polymerizing silica species has resulted in the preparation of well-ordered hexagonal mesoporous silica structures (SBA-15) with uniform pore sizes up to approximately 300 angstroms. The SBA-15 materials are synthesized in acidic media to produce highly ordered, two-dimensional hexagonal (space group p6mm) silica-block copolymer mesophases. Calcination at 500 degrees C gives porous structures with unusually large interlattice d spacings of 74.5 to 320 angstroms between the (100) planes, pore sizes from 46 to 300 angstroms, pore volume fractions up to 0.85, and silica wall thicknesses of 31 to 64 angstroms. SBA-15 can be readily prepared over a wide range of uniform pore sizes and pore wall thicknesses at low temperature (35 degrees to 80 degrees C), using a variety of poly(alkylene oxide) triblock copolymers and by the addition of cosolvent organic molecules. The block copolymer species can be recovered for reuse by solvent extraction with ethanol or removed by heating at 140 degrees C for 3 hours, in both cases, yielding a product that is thermally stable in boiling water. 相似文献
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B L Coomber J Denton A Sylvestre S Kruth 《Canadian journal of veterinary research》1998,62(3):199-204
Canine osteosarcoma is a prevalent bone neoplasm which has similarities to the human disease. We used a retrospective study to investigate the possibility that tumor vascularity may provide useful prognostic information, indicative of the role of this parameter in progression of this cancer. We quantified microvessel density in 52 histological specimens of primary tumor, immunostained for von Willebrand's Factor to identify vascular endothelium. For the 20 cases not euthanized at presentation or lost to follow-up, we found significantly higher tumor microvascular densities in animals presenting with detectable pulmonary metastases (5 of 20), and significantly lower densities in animals without metastatic disease at presentation, but later surviving to develop pulmonary metastases (7 of 20; P < 0.05). Animals with no evidence of pulmonary metastases at time of death (8 of 20) had intermediate vascular densities in their tumors. The results of this preliminary study suggest that vascularity of the primary tumor may be an indication of tumor progression. Future studies with a larger number of cases should establish whether vascular density can be a useful prognostic parameter for canine osteosarcoma. 相似文献
34.
Todd R. Bennett Phil Roni Keith Denton Michael McHenry Raymond Moses 《Ecology of Freshwater Fish》2015,24(2):264-275
The downstream movement of coho salmon fry and parr in the fall, as distinct from the spring migration of smolts, has been well documented across the range of the species. In many cases, these fish overwinter in freshwater, but they sometimes enter marine waters. It has long been assumed that these latter fish did not survive to return as adults and were ‘surplus’ to the stream's carrying capacity. From 2004 to 2010, we passive integrated transponder tagged 25,981 juvenile coho salmon in three streams in Washington State to determine their movement, survival and the contribution of various juvenile life histories to the adult escapement. We detected 86 returning adults, of which 32 originated from fall/winter migrants. Half of these fall/winter migrants spent ~1 year in the marine environment, while the other half spent ~2 years. In addition, the median return date for fall/winter migrants was 16 days later than spring migrants. Our results indicated that traditional methods of spring‐only smolt enumeration may underestimate juvenile survival and total smolt production, and also overestimate spring smolt‐to‐adult return (SAR). These are important considerations for coho salmon life cycle models that assume juvenile coho salmon have a fixed life history or use traditional parr‐to‐smolt and SAR rates. 相似文献
35.
An experiment was conducted to determine chemical composition of raw and treated bitter vetch seed for use in poultry diets.
Processing methods were: soaked in water for 12 h, then autoclaved and dried (SA); coarsely ground, soaked in water for 24 h,
autoclaved and dried (GSA); coarsely ground, soaked in water for 47 h with exchange of water every 12 h, cooked and dried
(GSC); coarsely ground, soaked in solution of 1% acetic acid for 24 h at 60°C and dried (GAA). Raw bitter vetch seed was contained
94.52, 26.56, 0.4, 58.86, 3.38, 5.32, 12.28 and 14.20 percent DM, CP, EE, NFE, Ash, CF, ADF and NDF, respectively. Its GE,
AME, AMEn, TME and TMEn values were 18.10, 13.15, 14.38, 14.10 and 14.69 MJ/kg, respectively. Results indicated that bitter
vetch is a good source of Fe (340 ppm) and Cu (46.7 ppm). It s amino acid profile was suitable and methionine was the first
limiting amino acid when compared with broiler and layer chicks requirements. Its canavanine and tannin content were 0.78
and 6.7 mg/kgDM, respectively. Processing methods improved CP and in some cases AMEn. All processing methods especially GSC
resulted in a significant (P < 0.05) reduction in canavanine and tannin. 相似文献
36.
K DYNON A VARRASSO N FICORILLI SA HOLLOWAY GH REUBEL F LI CA HARTLEY MJ STUDDERT HE DRUMMER 《Australian veterinary journal》2001,79(10):695-702
OBJECTIVE: To develop rapid (< 8 hour) tests using polymerase chain reaction (PCR) for the diagnosis of equine herpesvirus 3 (EHV3; equine coital exanthema virus), equine gammaherpesviruses 2 (EHV2) and EHV5, equine adenovirus 1 (EAdV1), EAdV2, equine arteritis virus (EAV), equine rhinitis A virus (ERAV; formerly equine rhinovirus 1) DESIGN: Either single round or second round (seminested) PCRs were developed and validated. METHODS: Oligonucleotide primers were designed that were specific for each virus, PCR conditions were defined and the specificity and sensitivity of the assays were determined. The application of the tests was validated using a number of independent virus isolates for most of the viruses studied. The PCRs were applied directly to clinical samples where samples were available. RESULTS: We developed a single round PCR for the diagnosis of EHV3, a seminested PCR for EHV2 and single round PCRs for EHV5, EAdV1, EAdV2 and RT-PCRs for EAV and ERAV. The PCR primer sets for each virus were designed and shown to be highly specific (did not amplify any recognised non-target template) and sensitive (detection of minimal amounts of virus) and, where multiple virus isolates were available all isolates were detected. CONCLUSION: The development and validation of a comprehensive panel of PCR diagnostic tests, predominantly for viruses causing equine respiratory disease, that can be completed within 8 hours from receipt of clinical samples, provides a major advance in the rapid diagnosis or exclusion diagnosis of these endemic equine virus diseases in Australia. 相似文献
37.
Lowell TV Heusser CJ Andersen BG Moreno PI Hauser A Heusser LE Schlüchter C Marchant DR Denton GH 《Science (New York, N.Y.)》1995,269(5230):1541-1549
A radiocarbon chronology shows that piedmont glacier lobes in the Chilean Andes achieved maxima during the last glaciation at 13,900 to 14,890, 21,000, 23,060, 26,940, 29,600, and >/=33,500 carbon-14 years before present ((14)C yr B.P.) in a cold and wet Subantarctic Parkland environment. The last glaciation ended with massive collapse of ice lobes close to 14,000(14)C yr B.P., accompanied by an influx of North Patagonian Rain Forest species. In the Southern Alps of New Zealand, additional glacial maxima are registered at 17,720(14)C yr B.P., and at the beginning of the Younger Dryas at 11,050 (14)C yr B. P. These glacial maxima in mid-latitude mountains rimming the South Pacific were coeval with ice-rafting pulses in the North Atlantic Ocean. Furthermore, the last termination began suddenly and simultaneously in both polar hemispheres before the resumption of the modern mode of deep-water production in the Nordic Seas. Such interhemispheric coupling implies a global atmospheric signal rather than regional climatic changes caused by North Atlantic thermohaline switches or Laurentide ice surges. 相似文献
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Marc Koene Xavier Goupil Clemens Kampmann Peter D. Hanson Davida Denton Matthias G. Pollmeier 《Journal of Equine Veterinary Science》2010
The objective was to generate evidence for clinical efficacy and acceptability of a second generation coxib, firocoxib, administered orally for 14 days to lame horses under field conditions compared with a classic nonsteroidal anti-inflammatory drug, vedaprofen, in a prospective, randomized, controlled, double-blinded, multicenter field trial. Ninety-six client-owned horses with American Association of Equine Practitioners score of at least grade 3 lameness or grade 2 lameness plus at least a score of 2 for either pain on palpation, range of motion, or joint swelling were analyzed. Horses were administered 0.1 mg/kg firocoxib orally at 24 hour intervals (n = 48) or 1.0 mg/kg vedaprofen paste at 12 hour intervals for 14 days (single loading dose of 2.0 mg/kg vedaprofen) (n = 48). Physical examinations and lameness evaluations were conducted on Day 1 (V1, before treatment) and on Days 7 (V2) and 14 (V3). Blood chemistry and hematology profiles were also evaluated. With regard to the primary variable, clinical improvement, 83% of the firocoxib-treated horses improved at V3 compared with 65% of vedaprofen-treated horses improved meeting the criteria defined to demonstrate noninferiority of firocoxib to vedaprofen. Health and behavioral abnormalities for side effect detection occurred at the rate of 2% (1 horse) and 8% (4 horses) for firocoxib- and vedaprofen-treated horses, respectively. Changes in hematology and blood chemistry values from V1 to V3 were not significantly different between treatment groups. Firocoxib, formulated as an oral paste was highly effective, well tolerated, and acceptable for the control of pain and inflammation associated with lameness in horses under field conditions. 相似文献
40.