不同处理方式对蔬菜种传病毒病的消毒效果评价

为了研究不同种子处理对种子传播病毒的灭活效果,试验以番茄、辣椒、甜瓜、南瓜种子样本中被番茄花叶病毒(ToMV)、烟草花叶病毒(TMV)、黄瓜花叶瓜病毒(CMV)感染的种子为研究对象,经过酶联免疫吸附测定(ELISA)和逆转录聚合酶链反应(RT-PCR)测试选择出研究材料,采用7种病毒失活处理方法,分别为醋酸、过氧化氢、盐酸、次氯酸钠浸种,干热处理,温汤浸种和臭氧熏蒸处理。结果发现,能有效减少病毒浓度的处理为盐酸浸种、干热处理、温汤浸种(65℃)和臭氧(10 g/m3)处理,分别能将种子传播病毒的浓度平均降低51%、50%、42%和32%。其他灭活方法治疗效果较差,病毒浓度平均降低了12%~27%。盐酸浸种和干热处理是最有效的方法,对种子出芽率和活力没有影响。     

基于树莓派的代理机器人系统

为了弥补家庭服务从业人员的不足，解决中国的老龄化问题，本文提出了基于树莓派的代理机器人系统。该系统实现了对家居环境参数的采集，建立代理机器人与远程用户的连接，实现信息反馈和控制。     

棉花花铃期低温对叶片PSI和PSII光抑制的影响

选用陆地棉(Gossypium hirsutum L.)品种新陆早45号,在室外盆栽至开花结铃期后,移至人工气候室,模拟新疆棉花花铃期易出现的低温逆境条件,设置处理T(16℃/10℃,昼/夜),以常温(30℃/18℃,昼/夜)处理作为对照,采用叶绿素荧光和P700同步测定技术,研究低温对棉花花铃期叶片光合机构PSII能量分配、PSI氧化还原状态及环式电子传递流的影响。结果表明,与对照相比,低温处理显著降低了棉花叶片PSII光适应状态下最大光化学量子产量(F_v'/F_m')、光化学猝灭系数(qP)和PSII有效光化学量子产量[Y(II)],并使PSII非调节性能量耗散[Y(NO)]和调节性能量耗散[Y(NPQ)]量子产量显著升高,诱导PSII发生光抑制。低温引起棉花叶片光合机构PSI受体侧限制[Y(NA)]显著下降和供体侧限制[Y(ND)]显著升高,但未引起有效的PSI复合体含量(P_m)显著降低,表明与PSII相比,棉花叶片PSI对低温不敏感。此外,低温引起环式电子传递量子产量[Y(CEF)]以及与PSII实际量子产量比率的[Y(CEF)/Y(II)]显著升高,进一步表明在低温下,光破坏防御机制中环式电子传递流对棉花PSI、PSII起着重要的保护作用,是主要的光破坏防御机制。非光化学热耗散(NPQ)和调节性非光化学热耗散[Y(NPQ)]与[Y(CEF)]具有显著的正相关关系,表明低温引起棉花花铃期叶片PSII反应中心过度关闭产生过剩的激发能,造成了PSII可逆的光抑制,环式电子传递流的响应及较高的调节性能量耗散共同保护了棉花叶片PSI和PSII免受光抑制的损伤,这可能是棉花叶片PSI对低温不敏感的重要原因。     

红素氧还蛋白研究进展

自然界中大多数的红素氧还蛋白(rubredoxin)集中来自严格厌氧菌,包括细菌、古菌和少数微需氧细菌,而植物中该类蛋白相对较少,它的功能主要表现在作为辅因子或电子供体参与多个生化途径。也有研究显示,无论是植物中还是微生物中的红素氧还蛋白基因在协助生物抵御氧化胁迫方面均发挥着重要的作用。本文全面介绍自然界中的红素氧还蛋白基因的分布、结构以及在微生物、植物中所发挥的作用等,希望能为今后的进一步研究提供参考。     

牛结节性皮肤病的生物安全防控

牛结节性皮肤病（LSD）是《中华人民共和国进境动物检疫疫病名录》中的一类传染病,在新疆出现之后迅速在全国范围扩散,对我国的奶牛和肉牛养殖业造成严重经济损失。LSD主要通过在边境地区的动物贸易或虫媒活动传入未发生疫情的国家,疫苗接种被认为是防控 LSD疫情最有效的方法之一。各国根据本土疫情的传播情况,制定了不同的疫苗接种计划,目前用来预防LSD的疫苗主要为针对不同病原的减毒活疫苗。但是,在防控LSD的同时也造成了生物安全风险,导致重组疫苗样毒株引发的疫情从中亚向东亚迅速蔓延。只有将切断传播途径、保护易感动物和管控生物安全相结合,才能有效预防LSD疫情爆发,促进养殖业的繁荣发展。     

Modelling the introduction and transmission of Campylobacter in a North American chicken flock

Campylobacter is the second leading cause of foodborne illness in the United States. Although many food production animals carry Campylobacter as commensal bacteria, consumption of poultry is the main source of human infection. Previous research suggests that the biology of Campylobacter results in complete flock colonization within days. However, a recent systematic review found that the on-farm prevalence of Campylobacter varies widely, with some flocks reporting low prevalence. We hypothesized that the low prevalence of Campylobacter in some flocks may be driven by a delayed introduction of the pathogen. The objectives of this study were to (a) develop a deterministic compartmental model that represents the biology of Campylobacter, (b) identify the parameter values that best represent the natural history of the pathogen in poultry flocks and (c) examine the possibility that a delayed introduction of the pathogen is sufficient to replicate the observed low prevalence examples documented in the literature. A deterministic compartmental model was developed to examine the dynamics of Campylobacter in chicken flocks over a 56-day time period prior to movement to the abattoir. The model outcome of interest was the final population prevalence of Campylobacter at day 56. The resulting model that incorporated a high transmission rate (β = 1.04) was able to reproduce the wide range of prevalence estimates observed in the literature when pathogen introduction time is varied. Overall, we established that the on-farm transmission rate of Campylobacter in chickens is likely high and can result in complete colonization of a flock when introduced early. However, delaying the time at which the pathogen enters the flock can reduce the prevalence observed at 56 days. These results highlight the importance of enforcing strict biosecurity measures to prevent or delay the introduction of the bacteria to a flock.     

带幅设计对玉米/苜蓿间作群体光环境特征及光能利用效率的影响北大核心CSCD

探究间作带幅设计对玉米/苜蓿间作群体光环境特征、产量及光能利用效率(LUE)的影响,提出黄土高原旱作条件下玉米/苜蓿间作群体最佳带幅比例。研究设置了玉米单作(SM)、紫花苜蓿单作(SA)以及玉米/紫花苜蓿1∶2(I_(12))、2∶2(I_(22))和2∶4(I_(24))间作5种种植模式,并采用田间试验和数学模拟相结合的方法,分别测定了玉米和苜蓿的干物质产量及作物冠层光合有效辐射(PAR)等指标;建立了考虑光线入射角度和群体冠层结构几何关系的玉米/苜蓿间作群体辐射传输模型,并用实测值对其进行了验证。试验结果表明,在2018年,单作处理的苜蓿干物质产量显著高于间作处理(P<0.05),而在2019年各间作处理苜蓿的干物质分别比单作高197.8、180.3和197.0 g·m^(-2);处理I_(12)、I_(22)和I_(24)两年总的玉米生物量比SM处理高12.1%、0.9%和23.9%。所有间作处理的土地当量比在2019年均大于1.0,表现出间作优势。辐射传输模型可准确模拟玉米/苜蓿间作群体冠层底部的光合有效辐射,间作群体光合有效辐射模拟值与实测值的平均绝对误差和均方根误差分别为59.0和66.6μmol·m^(-2)·s^(-1)。除玉米和苜蓿生育前期及玉米收获后,不同间作处理苜蓿群体冠层上方的PAR均低于单作苜蓿。2018和2019年I_(12)、I_(22)和I_(24)间作处理玉米的光能利用效率分别比单作处理高52.5%、9.3%、51.7%和28.5%、9.6%、21.0%,而间作苜蓿的LUE仅在2019年显著高于单作19.2%、32.4%和20.9%(P<0.05)。因此,合理的玉米/苜蓿间作带幅搭配可改善苜蓿的光照环境,提高其光能利用效率,尤其是玉米/紫花苜蓿2∶4间作群体光能利用效率和产量优势显著,建议在具有类似气候的地区推广种植。     

工程机械新型传动系统的特性分析

介绍了静液压传动这一新型动力传动系统的特点.通过详细分析该系统液压元件类型的选择、排量与传动变速比关系及该类系统特性参数之间的关系,得出了在实际使用中,为了保证工程机械在大功率工况下,不降低经常工况的效率,提高传动变速比与其它传动形式的匹配方案.通过对匹配方案的分析为工程车辆的开发设计提供理论基础和方法.     

Simultaneous measurements of quantum yield and CO2 uptake for the assessment of non-assimilative electron flow in tree leaves

Using attached and detached leaves ofAcer palmatum Thunb. andRhaphiolepsis umbellata Makino, pulse-modulated chlorophyll fluorescence and CO₂ exchange were measured. Quantum yield of photosynthesis was determined from the fluorescence parameter(Fm′−Fs)/Fm′, where (Fm′−Fs) was defined as the difference between steady state chlorophyll fluorescence (Fs) and maximum fluorescence (Fm′) elicited by a saturating light pulse. The rate of electron transport through photosystem II (total electron flow) was calculated from the product of quantum yield andA (PFD), whereA is the rate of absorbed photons as given by leaf absorptance, and PFD is the photon flux density at the leaf surface. The rate of electron transport dependant on CO₂ uptake (assimilative electron flow) was calculated from the gross photosynthetic rate in a leaf. The difference between the rates of total and assimilative electron transport was denoted as the rate of non-assimilative electron transport which depends on photorespiration and oxygen reduction. Available data provided quantitative information on the rate of non-assimilative electron flow in intact leaves. When leaf photosynthesis ofA. palmatum was measured under sunlight, the rates of total and assimilative electron transport were determined to be approximately 900 and 150 μmol equiv. e/mg Chl·h, respectively. The difference (750 μmol equiv. e/mg Chl·h) was attributed to the activity of non-assimilative electron flow. The ratio of total to assimilative electron flow was found to increase gradually with rising in irradiance. The results suggest that non-assimilative electron flow occurred at much higher rate than assimilative electron flow at high irradiance. Implications of the results are briefly discussed in relation to photosynthesis limitation in tree leaves.     

Fibril angle variability in earlywood of Norway spruce using soft rot cavities and polarization confocal microscopy

The main purpose of this study was to investigate the variability of the fibril angle of tracheids in earlywood of Norway spruce (Picea abies L. Karst.). Polarization confocal microscopy was chosen and compared with the method utilizing the orientation of soft rot cavities. There was a significant correlation between the soft rot and polarization confocal microscopy methods, which showed the same trend of high fibril angles in the first part of the earlywood followed by a decrease toward the end of earlywood. This declining trend was less pronounced in annual rings containing compression wood. Moreover, large variations in fibril angle occurred between neighboring tracheids. The investigation also emphasized the differences between X-ray diffraction and microscopic methods, as the large variation seen by the latter methods is not seen by the X-ray diffraction approach because of its large area of measurement. No correlation was found between fiber morphology (i.e., average length, width, density) and the average fibril angle in the investigated annual rings.