农业拖拉机发动机变速器控制系统的计算机模拟

对手动换档、自动负载换档、自动无级变速等各类传动系,以固定作业速度运行模式进行模拟比较表明,负载换档变速器自动运行模式有较好节能效果。该文对负载换档变速器全油门变速作业的运行模式进行模拟结果表明,这种操用模式在节油及提高生产率方面有更明显的效果。     

太行山干旱低山丘陵区林草复合系统能量环境特征研究

研究了太行山干旱低山丘陵区林草复合系统能量环境特征,结果表明复合系统年太阳总辐射量为49868.65GJ.hm-2.a-1,光合有效辐射为24244.67GJ.hm-2.a-1,复合系统的平均反射率为22.5%,高于单作苹果系统,平均透射率为18.0%,低于单作苹果系统,说明林草复合系统可以截获和利用更多的光能。     

A preliminary study of the role of ducks in the transmission of Newcastle disease virus to in-contact rural free-range chickens

The role of ducks in the transmission of Newcastle disease virus (NDV) to free-range village chicken was investigated experimentally. Newcastle disease (ND) seronegative ducklings reared in a pen were infected oronasally with velogenic NDV of intracerebral pathogenicity index (ICPI) 1.8 isolated from outbreaks in village chickens in Uganda. A first group of 3-week-old ND seronegative chicks was mixed with the ducks and they were kept together for 7 days. Both ducks and chicks were observed for ND clinical signs and any mortality, and they were bled and their sera were tested for ND antibodies by haemagglutination inhibition (HI) test. The chicks were removed, euthanized and examined for any ND lesions, while the ducks were transferred to a fresh pen and a second group of chicks was introduced and observed and treated as above. The ducks and the chicks tested positive for ND antibodies 7 days post infection and contact, respectively, but showed no clinical signs, post-mortem lesions or mortality. The mean ND antibody titre of the second group of chicks was lower than for the first group. This study has shown that although ducks can be infected with velogenic NDV, they do not show clinical signs but are able to transmit NDV to in-contact chicks. Further investigations are needed of the lack of clinical signs in the in-contact chicks and how long the ducks remain infective.     

输气站场自控系统夜间无人值守功能的实现

基于西气东输管道系统的实际运行情况,给出了实现夜间无人值守功能所需的功能逻辑。根据西气东输站场自动化控制系统的构架,对现有系统程序进行编辑与修改,加入了流量计算机的故障报警逻辑、压力调节自动分输逻辑和流量调节自动分输逻辑,提出了实现夜间无人值守功能的自动化控制系统改造方法,包括:PLC逻辑设置、RCI文件修改、增加站控画面及数据库建点。西气东输分输站夜间无人值守功能的实现,在保证管道安全生产的同时,提高了自动控制水平和管理水平。     

Potentiation of triclabendazole action in vivo against a triclabendazole-resistant isolate of Fasciola hepatica following its co-administration with the metabolic inhibitor, ketoconazole

An in vivo study in the laboratory rat model has been carried out to monitor morphological changes in adult Fasciola hepatica over a 4-day period resulting from co-treatment with triclabendazole (TCBZ) and ketoconazole (KTZ), a cytochrome P450 inhibitor. Rats were infected with the triclabendazole-resistant Oberon isolate of F. hepatica, dosed orally with triclabendazole at a dosage of 10 mg/kg live weight and ketoconazole at a dosage of 10 mg/kg live weight. Flukes were recovered at 24, 48, 72 and 96 h post-treatment (p.t.) and changes to fluke ultrastructure were assessed using transmission electron microscopy (TEM). Results showed an increase in the severity of changes to the fluke ultrastructure with time p.t. Swelling of the basal infolds and the associated mucopolysaccharide masses became more severe with time. Golgi complexes, if present, were greatly reduced in size and number by 96 h p.t., and sub-tegumental flooding was seen from the 72 h time-period onwards. Some sloughing of the tegumental covering over the spines was observed at 96 h p.t. The results demonstrated that the Oberon isolate is more sensitive to TCBZ action in the presence of KTZ than to TCBZ alone, reinforcing the idea that altered drug metabolism is involved in the resistance mechanism. Moreover, they support the concept that TCBZ + inhibitor combinations (aimed at altering drug pharmacokinetics and potentiating the action of TCBZ) could be used in the treatment of TCBZ-R populations of F. hepatica.     

Inhibitory action of intravenously administered ammonium acetate on the motility of the rumen in sheep

Summary

The effect of 60 minutes’ intravenous infusions, before morning feeding, of ammonium acetate (18.6 micromole/min/kg of body weight) and ammonium acetate with propranolol (11 μg/min/kg of body weight) on the ruminal motility of sheep was examined. Ammonia has an adrenaline‐like action therefore propranolol, a beta‐receptor blocking agent, was administered in order to eliminate the possible effect of adrenaline on ruminal motility. The contractions of the dorsal sack of the rumen were registered by means of the balloon method, with the gauge inserted through the rumen fistula. The infusion of ammonium acetate caused an increase of the ammonia concentration in the blood to 0.6 mmolel/at the end of 60 minutes’ infusion. Already during the first 5 minutes of the intravenous infusion of ammonium acetate there was a decreased frequency of ruminal contractions, which was observed throughout the infusion. After the infusion there was a radical decrease of the concentration of ammonia in the blood, and at the same time an increase in the frequency of rumen contraction was observed.

Blocking of the beta‐adrenergic receptors by propranolol did not eliminate the inhibiting action of ammonium ion on rumen motility. The infusion of the ammonium acetate caused an increase of adrenaline and glucose concentration. This response was eliminated by propranolol in the case of adrenaline but not glucose. It is assumed that the action of ammonium ion on the rumen motility is derived primarily by the central nervous system.     

Evaluation of Praziquantel effects on Echinostoma paraensei ultrastructure

Echinostomiasis is a food-borne, intestinal, zoonotic, snail-mediated helminthiasis caused by digenean trematodes of the family Echinostomatidae with seven species of the genus Echinostoma infecting humans or domestic and wildlife animals. Echinostoma paraensei is a peristomic 37-collar-spined echinostome belonging to the “revolutum group”.     

Effects of Salinity Stress on the Seminal Root Tip Ultrastructures of Rice Seedlings (Oryza sativa L.)

Abstract

Growth and structural changes in the seminal root tip of rice seedlings (Oryza sativa L. cv. Nipponbare) in response to NaCl salinity were studied. Seedlings were grown in agar medium with 0, 0.1, 0.3, 1.0, 2.0 and 3.0% NaCl(agar culture), and in water with 0, 0.01, 0.03, 0.06 and 0.1% NaCl (water culture). Seedling growth was significantly suppressed by higher concentrations of NaCl. The effect of NaCl appeared faster in water culture than in agar culture. In both agar and water cultures, root growth was markedly suppressed over shoot growth. Under saline conditions, epidermis, cortex and root cap cells appear to be damaged to a greater extent than the meristem and stelar cells. The most notable ultrastructural change in response to salinity was the development and increment of vacuoles, which seem to provide a space for accumulation of excess ions. Many electron dense deposits were observed in the larger vacuoles of the epidermal and cortical cells. Under saline conditions, cell wall thickening of the epidermis, an increase in endoplasmic reticulum, myelin figures, less compact Golgi bodies and inhibited production of Golgi vesicles were also observed.     

拖拉机传动系密封性设计改进

介绍几种拖拉机传动系密封性设计改进方案。