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71.
刘洪武 《吉林农业科技学院学报》2014,(2):108-110
随着国际间的频繁交往以及中国政治经济地位的不断提升,对具备英语口语表达能力的人才也提出了更高的要求,大学毕业生应能和外国人进行英语交流、用英语完成求职面试、出国旅游等.因此,提高大学生英语口语水平尤为重要,教育者应尝试新的教学模式,用一种新的理论来指导大学英语口语教学,本文从系统功能语法这个纯理论角度探讨了如何以一种新的模式来提高口语能力. 相似文献
72.
Hannah J. Munro Lesley Berghuis Andrew S. Lang Laura Rogers Hugh Whitney 《Canadian journal of veterinary research》2014,78(2):140-144
Feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) are retroviruses found within domestic and wild cat populations. These viruses cause severe illnesses that eventually lead to death. Housing cats communally for long periods of time makes shelters at high risk for virus transmission among cats. We tested 548 cats from 5 different sites across the island of Newfoundland for FIV and FeLV. The overall seroprevalence was 2.2% and 6.2% for FIV and FeLV, respectively. Two sites had significantly higher seroprevalence of FeLV infection than the other 3 sites. Analysis of sequences from the FeLV env gene (envelope gene) from 6 positive cats showed that 4 fell within the FeLV subtype-A, while 2 sequences were most closely related to FeLV subtype-B and endogenous feline leukemia virus (en FeLV). Varying seroprevalence and the variation in sequences at different sites demonstrate that some shelters are at greater risk of FeLV infections and recombination can occur at sites of high seroprevalence. 相似文献
73.
K. Merhof J. Lang S. Dürr C. Stahl D. Gorgas 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2014,28(4):1263-1267
Background
The diagnostic value of a contrast‐enhanced T2‐weighted FLAIR sequence (ceFLAIR) in brain imaging is unclear.Hypothesis/Objectives
That the number of brain lesions detected with ceFLAIR would be no greater than the sum of lesions detected with nFLAIR and ceT1W sequence.Animals
One hundred and twenty‐nine animals (108 dogs and 21 cats) undergoing magnetic resonance imaging (MRI) of the head between July 2010 and October 2011 were included in the study.Methods
A transverse ceFLAIR was added to a standard brain MRI protocol. Presence and number of lesions were determined based on all available MRI sequences by 3 examiners in consensus and lesion visibility was evaluated for nFLAIR, ceFLAIR, and ceT1W sequences.Results
Eighty‐three lesions (58 intra‐axial and 25 extra‐axial) were identified in 51 patients. Five lesions were detected with nFLAIR alone, 2 with ceT1W alone, and 1 with ceFLAIR alone. Significantly higher numbers of lesions were detected using ceFLAIR than nFLAIR (76 versus 67 lesions; P = 0.04), in particular for lesions also detected with ceT1W images (53 versus 40; P =.01). There was no significant difference between the number of lesions detected with combined nFLAIR and ceT1W sequences compared to those detected with ceFLAIR (82 versus 76; P =.25).Conclusion and Clinical Importance
Use of ceFLAIR as a complementary sequence to nFLAIR and ceT1W sequences did not improve the detection of brain lesions and cannot be recommended as part of a routine brain MRI protocol in dogs and cats with suspected brain lesions. 相似文献74.
75.
对喜马拉雅紫茉莉(Mirabilis himalaica)正丁醇提取物进行研究,利用反相硅胶柱色谱、Sephedex LH-20、半制备HPLC进行分离,通过理化性质和UV、IR、MS、1 H-NMR和13 C-NMR等方法进行结构鉴定,分离鉴定5个化合物,分别为:腺苷(1),色氨酸(2),1-甲基-1,2,3,4-四氢-β-咔啉-3-羧酸(3),6′-O-(E)-feruloylsucrose(4),丁香树脂酚单-β-D-葡萄糖苷(5),化合物1~4均为首次从该植物中得到,通过还原力和DPPH自由基清除能力试验表明,化合物2、4、5仅有较弱的抗氧化能力。 相似文献
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79.
Steven G. Hall James Finney R. Paul Lang Terrence R. Tiersch 《Aquacultural Engineering》2002,26(4):277-289
A control system was designed to raise and maintain water temperatures within 0.03-ha earthen ponds to a range conducive for spawning (24–30 °C) channel catfish Ictalurus punctatus. Heating was done during February 2001 to April 2001, when temperatures would have otherwise prohibited spawning (<24 °C). Temperature was increased from 10 °C (ambient) by 2 °C per day, and maintained at 27 °C, by the addition of geothermally warmed water (36 °C). The control system substantially increased the controllability and precision of heating ponds compared to manual operation. Systems were designed to control sets of four ponds. In designing this control system, consideration of biological constraints was essential. Reproduction in channel catfish is most strongly influenced by temperature. Because cold fronts are common during the winter and early spring (January–March), it was essential to ensure that pond temperatures did not fall below the range for spawning. Constraints on the heating rate and temperature variability to maintain fish health and stimulate spawning behavior were considered. Components of the control system included temperature measurement devices (type-T thermocouples), a central electronic control unit, electronic switches and electrically actuated ball valves. In response to the temperature sensed by each thermocouple, the controller sent a message to close or open the valve. When the valve was opened, warm water was added to the pond to increase the average pond temperature. Hardware and algorithm design and initial system testing were the major components of this project. The final design incorporated information on relevant biological parameters and safety features including peak pond temperature, independent aeration and water pressure control mechanisms. Initial results indicate successful control of this biological system, and ongoing studies suggest similar mechanisms may be used for additional control objectives. In particular, this system could be used to vary pond temperatures to study biological responses and to cool ponds by addition of well water during summer months. 相似文献
80.
为探究贵州省植被生长变化趋势对多时间尺度气象干旱的响应,基于2001—2020年的逐月MODIS-NDVI、EVI影像和气象数据,利用皮尔森相关系数、slope趋势性分析等方法,对贵州省20 a的植被生长状况及气象干旱时空变化特征进行了分析。结果表明:(1)贵州省不同时间尺度下的SPEI在整体上呈现出缓慢增加趋势,表明干旱程度有所降低; 空间分布上干旱化趋势表现在北部的遵义、铜仁及黔西南地区。(2)贵州省植被生长状况整体呈现出增加趋势,空间分布上的黔东南地区以降低趋势为主,毕节西部地区以增长趋势为主;(3)贵州省植被生长状况与不同时间尺度的气象干旱呈现出不同程度的正相关性,以贵州省植被在黔西南和北部地区对干旱的响应最强,其次为贵阳和毕节东部; 不同的土地利用类型中,草地对SPEI3的响应最强,其次为耕地和林地; 生长季内的不同植被类型对SPEI3和SPEI12的响应较强。综上,贵州省植被和气象干旱时空分布特征存在一定的差异性,且不同植被类型对不同时间尺度气象干旱的响应情况也有所差别。 相似文献