中国大学英语学习者中介语动词结构陋用之管窥

对二语/外语动词习得的研究通常围绕动词形态的习得顺序来进行,但本文主要从动词和其它词的搭配着手研究中国大学英语学习者英语动词结构的习得。利用两个大型语料库定量对比了cost、survive和adapt三个常用动词在本族语英语和中国大学英语学习者中介语中的使用情况,发现后者中有较严重的滥用、少用和误用现象,以此我们可以管窥大学英语学习者中介语中动词结构的使用特征。导致这一情况的两个主要原因是培训迁移和母语迁移。     

硫酸化酵母葡聚糖对鸡球虫病的防治效果

旨在探讨硫酸化酵母葡聚糖（sGSC）对人工感染鸡柔嫩艾美耳球虫（Eimeria tenella）病的防治效果。采用笼饲法，将200只鸡随机分为A组（4 mg·kg^-1）、B组（16 mg·kg^-1）、C组（64 mg·kg^-1）、D组（感染对照组）和E组（健康对照组）。感染球虫前3 d开始，给A、B、C组鸡每天按体重饮水喂上述各浓度的sGSC，给D、E组的鸡喂纯水（RO水），持续至试验结束。试验过程中观察各组鸡的临床症状、血便情况并记录，收集感染后5～6 d的粪便，检测每克粪便中的卵囊数，感染后第7天剖杀所有鸡，计算脏器指数；并通过Illumina测序平台研究鸡盲肠内微生物群落多样性。结果显示：1）与D组比较，各给糖组鸡的盲肠肿胀明显减轻，肠内容物和出血明显减少，与E组鸡体重相比，A、D组体重明显降低（P<0.05），但B组和C组鸡的体重升高至接近E组水平，体重与E组鸡无显著差异（P>0.05）；B组和C组鸡排出的卵囊数与D组相比，出现了明显的减少，但无统计学差异（P>0.05）；A组鸡的胸腺指数明显增加（P<0.05），肝指数也出现显著改善（P<0.05）；2）对盲肠内菌群分析发现，sGSC能提高盲肠内韦荣氏菌科（Veillonellaceae）和乳酸杆菌科（Lactobacillaceae）的相对丰度，降低肠球菌科（Enterococcaceae）的相对丰度。sGSC能减轻柔嫩艾美尔球虫感染对鸡造成的危害，且随着sGSC剂量的增加，效果越明显。综上表明，sGSC具有一定的抗球虫效果，并且对感染球虫鸡肠道内的菌群具有有益的调节作用。     

Imported ornamental fish are colonized with antibiotic‐resistant bacteria

There has been growing concern about the overuse of antibiotics in the ornamental fish industry and its possible effect on the increasing drug resistance in both commensal and pathogenic organisms in these fish. The aim of this study was to carry out an assessment of the diversity of bacteria, including pathogens, in ornamental fish species imported into North America and to assess their antibiotic resistance. Kidney samples were collected from 32 freshwater ornamental fish of various species, which arrived to an importing facility in Portland, Oregon from Colombia, Singapore and Florida. Sixty‐four unique bacterial colonies were isolated and identified by PCR using bacterial 16S primers and DNA sequencing. Multiple isolates were identified as bacteria with potential to cause disease in both fish and humans. The antibiotic resistance profile of each isolate was performed for nine different antibiotics. Among them, cefotaxime (16% resistance among isolates) was the antibiotic associated with more activity, while the least active was tetracycline (77% resistant). Knowing information about the diversity of bacteria in imported ornamental fish, as well as the resistance profiles for the bacteria will be useful in more effectively treating clinical infected fish, and also potential zoonoses in the future.     

Productivity effect and overuse of pesticide in crop production in China

Chinese farmers are often accused of overusing pesticides that play a crucial role in enhancing crop yield by reducing losses to crop pests. Pesticide overuse has caused a series of negative health and environmental externalities. This paper quantifies the productivity effect and the optimal amount of pesticides in rice, cotton and maize production in China from the economic perspective. Using survey data collected in 2012 and 2013, both Cobb-Douglas and Weibull damage control specifications are used to estimate the production function. Results show that pesticides have statistically significant productivity effect on crop yield. On the condition of Weibull damage control specifications, the marginal products of 1 kg of the active ingredients of pesticides for rice, cotton and maize are 71.06, 22.73 and 98.45 kg, respectively. However, 57, 64 and 17% of the actual amount of pesticides are overused for rice, cotton and maize, respectively. Moreover, the productivity effect of pesticides would be overestimated using Cobb-Douglas specification without incorporating a damage control agent.     

钾通道ZmK2;1在水稻中超表达提升水稻氮素利用潜力

气孔运动与光合同化效率密切相关,通过影响叶片对碳源的获取能力对植株生长发育和籽粒生产发挥作用。针对稻田过量施氮导致的环境风险和氮素利用效率趋缓的现状,研究高氮投入时促进氮素吸收利用的调控策略非常必要。本研究利用气孔钾通道基因ZmK2;1超表达水稻遗传材料,设置N 缺乏(LN, 不施氮)、中量或减少氮投入(MN, 200 kg hm_^-2)和过量施氮(HN, 350 kg hm_^-2)三个施氮水平的田间试验,对ZmK2;1超表达植株在生育后期的氮素营养特征和生产特性进行研究。结果表明：ZmK2;1超表达能改善水稻植株在各氮肥施用水平下的产量形成特征,提升植株氮钾含量和生物量,改善植株的氮素营养特征,其剑叶在生育后期保持较高的光合效率和气孔导度。另外,ZmK2;1基因超表达能促进水稻氮素利用效率的提升,尤其在过量施氮(HN)条件下,该基因过表达仍能够改善其氮素利用。利用气孔钾通道ZmK2;1在水稻中超表达可以调节植株和关键功能叶氮钾比,促进各施氮水平下的光合效率的同时提升了水稻产量；在过量施氮时,依然能保持较高的光合同化能力,提升水稻氮素利用率和增产潜力。     

水稻OsAMT1;1过表达提升氮肥减施情境下的氮素利用效率

水稻铵转运蛋白AMT1;1是根系获取土壤氮素(铵态氮)的重要组分,同时参与氮素向地上部的转运。针对稻田施氮过量导致的环境风险和氮素利用效率趋缓的现状,亟需探究既能减少氮肥投入又能维持现有生产水平的调控策略。本研究利用OsAMT1;1过表达水稻材料,设置氮缺乏(LN, 不施氮)、减氮投入(MN, 200 kg hm_^-2)和过量施氮(HN, 350 kg hm_^-2)三个处理水平的田间试验,用以评估OsAMT1;1过表达株系在关键生育期的氮素生产特性。结果表明：在LN条件下,OsAMT1;1过表达相比野生型能够明显改善植株和剑叶氮素营养状态,有利于植株生物量的积累和产量形成。在MN条件下,促进植株在齐穗期至完熟期的生长速率和生物量积累；灌浆期,过表达单株和剑叶含氮量相比野生型分别增加22.95%和29.53%,光合效率(Pn)和气孔导度(g_s)分别增加40.71%和19.39%,千粒重和产量平均增加10.26%和27.36%,氮肥吸收效率(RE_N)和氮素干物质生产效率(NUEb)显著提升,对氮素生理效率(PE_N)和氮肥农学效率(AE_N)有促进作用但并不显著。在HN条件下,该基因过表达在灌浆期的植株含氮量较野生型平均高出22.64%,提升了RE_N,灌浆阶段植株生物量的增加和Pn趋于饱和,PE_N和AE_N均显著降低。可见,与过量施氮(当前施氮习惯)相比,OsAMT1;1过表达在减少氮投入时更有利于协同植株高氮的内部环境实现相当的产量水平,提高水稻氮素利用效率。