水稻田间育秧水肥药变量喷灌装置设计与试验

为解决南方水稻工厂化田间育秧水肥药人工管理作业中存在的灌溉均匀性差、化肥和农药浪费以及劳动强度大等问题,该研究设计了一种水稻田间育秧水肥药变量喷灌装置,阐述了水肥药变量喷灌装置总体结构和工作原理,进行了关键部件设计与试验;以可编程逻辑控制器（programmable logic controller,PLC）为控制核心,构建了注肥量在线调控及整机变量喷灌控制系统。采用Box-Behnken试验设计方法,对装置喷灌均匀性与主要影响因素进行试验研究,应用单目标优化方法对喷灌关键参数进行优化,并通过验证试验,得到最优参数组合为：干管入口水压0.20 MPa、球阀开度90°、喷头喷角80°,此时装置的喷灌均匀性为92.69%;构建了氯化钾肥液质量浓度与电导率（electrical conductance,EC）值的线性模型,开展了装置变量灌溉施肥性能试验,3种喷灌等级下各作业区的肥液EC值分别为1.65、1.66和1.68 mS/cm,平均喷灌强度分别为900.85、1092.04和1263.67 mm/h,施肥均匀系数分别为85.21%、87.86%和91.62%。采用水肥药变量喷灌装置开展水稻育秧田间管理试验,华航51常规稻和广8优165杂交稻的秧苗长势均匀度均高于95%,成毯性良好,各项素质指标满足机插作业要求。所设计的水肥药变量喷灌装置能够满足水稻田间育秧水肥药变量喷灌作业要求,对提高水稻工厂化田间育秧机械化水平、保证秧苗质量具有实际应用价值。     

稀燃汽油机瞬态空燃比的滑模-神经网络控制

提出了稀燃汽油机空燃比滑模-神经网络控制方案,采用滑模变结构控制对稀燃工况的空燃比进行反馈控制,采用神经网络实现对进气量的精确预测和油膜动态特性的前馈补偿,进而实现对稀燃发动机瞬态空燃比的精确控制。采用自行开发的电控系统,在一台稀燃发动机上进行了瞬态空燃比实验。实验结果表明:节气门急速变化时空燃比超调可以控制在1个空燃比单位以内,调整时间不超过3s;转速越低,节气门变化越剧烈;空燃比超调越大,调整时间越长。     

MAGNETIC RESONANCE IMAGING FEATURES OF CERVICAL SPINAL CORD MENINGIOMAS

The records of four dogs with cervical spinal cord meningiomas were retrospectively reviewed. Signalment, history, laboratory findings, neurological examination, and histopathological findings were evaluated. Magnetic resonance imaging (MRI) was performed using a 1.0-T superconducting magnet and T2-weighted (W) and noncontrast and postcontrast T1-W spin echo pulse sequences. Meningiomas were located at the level of the second, third, and fifth cervical vertebrae and the C2-3 intervertebral space. All meningiomas appeared as focal masses that were hyperintense to the spinal cord on T2-W images and iso- to hypointense on the T1-W images. They could be identified as intradural and extramedullary in origin based on a broad-based dural margin seen on at least one of the imaging planes and a gradual expansion of the subarachnoid space cranial and caudal to the mass, best noted on the transverse and dorsal plane images. On dorsal plane T2-W images in three dogs, expansion of the subarachnoid space adjacent to the mass appeared similar to the myelographic "golf tee" sign. All meningiomas exhibited moderate, well-defined contrast enhancement with dural tails seen in three of the four dogs. One dog had extension into the intervertebral foramen along the nerve and ipsilateral atrophy of the muscles of the neck. By differentiating the meningiomas from intramedullary tumors and by clearly depicting the extent of the masses, MRI provided valuable information about treatment options and prognosis.     

Genetic diversity,anti‐microbial resistance,plasmid profile and frequency of the Vi antigen in Salmonella Dublin strains isolated in Brazil

Salmonella Dublin is strongly adapted to cattle causing enteritis and/or systemic disease with high rates of mortality. However, it can be sporadically isolated from humans, usually causing serious disease, especially in patients with underlying chronic diseases. The aim of this study was to molecularly type S. Dublin strains isolated from humans and animals in Brazil to verify the diversity of these strains as well as to ascertain possible differences between strains isolated from humans and animals. Moreover, the presence of the capsular antigen Vi and the plasmid profile was characterized in addition to the anti‐microbial resistance against 15 drugs. For this reason, 113 S. Dublin strains isolated between 1983 and 2016 from humans (83) and animals (30) in Brazil were typed by PFGE and MLVA. The presence of the capsular antigen Vi was verified by PCR, and the phenotypic expression of the capsular antigen was determined serologically. Also, a plasmid analysis for each strain was carried out. The strains studied were divided into 35 different PFGE types and 89 MLVA‐types with a similarity of ≥80% and ≥17.5%, respectively. The plasmid sizes found ranged from 2 to >150 kb and none of the strains studied presented the capsular antigen Vi. Resistance or intermediate resistance was found in 23 strains (20.3%) that were resistant to ampicillin, ciprofloxacin, chloramphenicol, imipenem, nalidixic acid, piperacillin, streptomycin and/or tetracycline. The majority of the S. Dublin strains studied and isolated over a 33‐year period may descend from a common subtype that has been contaminating humans and animals in Brazil and able to cause invasive disease even in the absence of the capsular antigen. The higher diversity of resistance phenotypes in human isolates, as compared with animal strains, may be a reflection of the different anti‐microbial treatments used to control S. Dublin infections in humans in Brazil.     

沙生针茅种子萌发特性及其影响因素

利用控制试验研究了不同温度蒸馏水水分、盐分胁迫等生态因子对沙生针茅种子萌发的影响,探索了沙生针茅种子对各种生态因子的适应性。结果表明:(1)蒸馏水浸泡种子,以60℃温水浸泡、自然降温至常温12h最好;(2)低温处理与未经低温处理的种子发芽率差异不显著(P0.05),说明沙生针茅种子不存在生理后熟因素影响;(3)随着PEG-6000浓度的增加,沙生针茅种子的发芽率、发芽势、发芽指数呈下降趋势,种子发芽率的PEG-6000浓度的临界值和极限值分别为15.9%和26.3%;(4)沙生针茅种子的发芽率、发芽势、发芽指数随着盐分浓度的增加呈下降趋势,其中Na2CO3处理下的沙生针茅种子萌发率下降幅度明显大于NaCl,表明沙生针茅种子对相同质量浓度的Na2CO3的耐受能力显著低于对NaCl的耐受能力。     

IMAGING DIAGNOSIS—USE OF MULTIPHASIC CONTRAST‐ENHANCED COMPUTED TOMOGRAPHY FOR DIAGNOSIS OF MESENTERIC VOLVULUS IN A DOG

A 4‐year‐old German shorthaired pointer presented with collapse and hematochezia. Radiographs showed gas and fluid‐distended small intestines and loss of serosal detail. Ultrasound examination showed hypomotile, fluid‐distended small intestines, and thrombosed jejunal veins. Multiphasic contrast‐enhanced computed tomography was performed and showed a CT “whirl sign,” an important but nonspecific sign of intestinal volvulus in human patients. At surgery, the majority of the small intestine was entangled in the volvulus and showed black discoloration. The patient was euthanized. Postmortem evaluation yielded a diagnosis of jejunoileal mesenteric volvulus secondary to a congenital omphalomesenteric duct remnant.