大型贯流式泵站快速门加速启动过渡过程

为研究大型贯流式泵站机组闸门加速启动过程中的外特性参数变化及流态变化,对灯泡贯流泵机组进行三维建模,采用Fluent软件中的UDF来控制闸门的启动过程,使用铺层法动网格技术来控制闸门处网格生成与消灭,并设定S-A模型作为湍流模型,对灯泡贯流泵机组启动过程进行瞬态数值模拟.计算结果表明:当贯流泵机组快速门以10倍设计速度启动时,机组的转速与流量将以更快的速度达到额定转速与额定流量,同时瞬间最大倒灌流量相比未加速启动时增加了30%.当贯流泵机组处于倒流状态时,靠近轮毂处叶轮叶道压力面的压强呈现出从叶轮进水边向出水边逐渐递增的分布规律.当机组处于零流量的临界状态时,混乱的流态导致压力集中及脱流现象加重,叶轮进水边负压区范围扩大且程度加深.     

干湿交替灌溉对抗旱性不同水稻品种产量的影响及其生理原因分析

【目的】旨在阐明全生育期干湿交替灌溉对抗旱性不同水稻品种产量的影响。【方法】以抗旱性差异显著的4个水稻品种(籼稻扬稻6号和两优培九,粳稻旱优8号和镇稻88)为材料,以常规水层灌溉(CI)为对照,在盆栽条件下研究了轻干湿交替灌溉(WMD)和重干湿交替灌溉(WSD)对水稻产量、根系、叶片及籽粒部分生理特性的影响。【结果】与CI相比,WMD处理下抗旱性较强品种扬稻6号和旱优8号产量分别提高6.90%和7.45%,抗旱性较弱品种两优培九和镇稻88产量分别降低7.28%和8.10%。WSD处理下,4个水稻品种的产量均显著下降,抗旱性较弱的品种产量降幅远高于抗旱性较强的水稻品种。WMD处理下,扬稻6号和旱优8号复水后根系氧化力、根系与叶片细胞分裂素(玉米素+玉米素核苷)含量、叶片光合速率和籽粒中蔗糖-淀粉代谢途径关键酶的活性均较CI有不同程度提高,而两优培九和镇稻88上述指标则与CI持平或有不同程度降低。WSD处理下,4个品种上述指标均较CI不同程度降低。【结论】轻干湿交替灌溉条件下,根系活性强、叶片细胞分裂素含量和光合速率高、籽粒中蔗糖-淀粉代谢途径关键酶活性强是抗旱性较强水稻品种的基本生理特征。     

Polymerisation of gluten proteins in developing wheat grain as affected by desiccation

The breadmaking quality of wheat is affected by the composition of gluten proteins and the polymerisation of subunits that are synthesised and accumulated in developing wheat grain. The biological mechanisms and time course of these events during grain development are documented, but not widely confirmed. Therefore, the aim of this study was to monitor the accumulation of gluten protein subunits and the size distribution of protein aggregates during grain development. The effect of desiccation on the polymerisation of gluten proteins and the functional properties of gluten were also studied. The results showed that the size of glutenin polymers remained consistently low until yellow ripeness (YR), while it increased during grain desiccation after YR. Hence, this polymerisation process was presumed to be initiated by desiccation. A similar polymerisation event was also observed when premature grains were dried artificially. The composition of gluten proteins, the ratios of glutenin to gliadin and high molecular weight-glutenin subunits to low molecular weight-glutenin subunits, in premature grain after artificial desiccation showed close association with the size of glutenin polymers in artificially dried grain. Functional properties of gluten in these samples were also associated with polymer size after artificial desiccation.     

Mycobacteriosis caused by Mycobacterium marinum in reared mullets: first evidence from Sardinia (Italy)

Mycobacterium marinum is a slow‐growing non‐tuberculous mycobacterium, and it is considered the most common aetiologic agent of mycobacteriosis in wild and cultured fish. The diagnosis is principally made by histology when positive Ziehl–Neelsen stain granulomas are detected. The aim of this study was to investigate the occurrence of mycobacteriosis in extensively cultured Mugilidae of two lagoons (Cabras and San Teodoro) from Sardinia by the use of histology, microbiology, PCR and DNA sequencing. Nine of 106 mullets examined were affected by mycobacteriosis, and the spleen was the most affected organ. The histology detected higher rate (100%) of infection in spleen than the culture and PCR (75% and 62.5%, respectively). The sequencing of hsp65 gene identified M. marinum as the primary cause of mycobacteriosis in the mullets examined. Mullets affected by mycobacteriosis were mainly fished in the San Teodoro lagoon characterized by critical environmental conditions. Histology remains the most common method in detecting fish affected by mycobacteriosis, and PCR‐based methods are essential for species identification. Our finding are worthy of attention because mycobacteriosis caused by M. marinum in reared mullets was evidenced for the first time in Sardinia, suggesting that this disease may be underestimated also in other cultured fish species.     

含岩屑紫色土水分扩散规律

紫色土中存在的岩屑显著影响土壤水分扩散。以往研究主要集中在> 2 mm岩屑上而忽视了<2 mm岩屑的作用。因此,探讨>2 mm岩屑对紫色土水分扩散的影响基础上,明确<2 mm岩屑的作用对完善含岩屑紫色土水分扩散规律的研究具有重要的意义,从而为土壤水动力学模型的构建提供理论依据。以四川盆地紫色页岩发育的暗棕紫泥土和泥岩发育的红棕紫泥土为研究对象,设置3种岩屑粒径(0.25~2,2~5,5~10 mm)和4种岩屑含量(0,30%,50%,70%),利用水平土柱吸渗法测定含岩屑土壤湿润锋变化特征、水分扩散率D(θ)和土壤含水率θ,并拟合D(θ)、Boltzmann参数λ与θ之间的关系。结果表明:对于暗棕紫泥土,岩屑粒径为2~5 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加呈先增加后降低再增加的趋势;岩屑粒径为0.25~2,5~10 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加逐渐增加。对于红棕紫泥土,岩屑粒径为2~5,5~10 mm,随岩屑含量增加,70%岩屑含量的土壤D(θ)明显大于其余3个岩屑含量的土壤,而30%岩屑含量和50%岩屑含量土壤之间的D(θ)无显著差异,且土壤湿润锋前进速率均呈先增加后降低再增加的趋势;岩屑粒径为0.25~2 mm时,土壤湿润锋前进速率和D(θ)随岩屑含量增加逐渐增加。因此,随岩屑含量提高,土壤水分扩散速率整体呈现增加趋势;且泥岩发育的土壤水分扩散速率高于页岩发育的土壤。     

滴灌条件下水土温度对覆砂土壤水热运移影响的数值模拟

为探究滴灌条件下水温与土温对覆砂土壤水热运移规律的影响,基于HYDRUS-2D构建了不同水土温度土壤水热运移数值模型,模拟分析了不同水土温度对覆砂土壤水分、温度动态变化的影响。结果表明:灌溉水温对土壤水热分布影响显著,随着温度升高,土壤湿润体内含水率减小,表现为35℃水温20℃水温5℃水温,灌溉水温对土壤剖面温度分布也有较大影响,表层0—15 cm范围内温度变化了5～10℃。相同水温条件下,随着土壤温度升高,土壤饱和导水率增大,湿润土体内体积含水率减小,表现为30℃土壤温度15℃土壤温度5℃土壤温度。滴灌水平和垂直湿润锋运移距离随温度升高而增大,湿润锋运移距离与时间符合幂函数F=at~b,决定系数R~2介于0.977 4～0.999 6,并建立了水平和垂直湿润锋运移距离与入渗时间和温度的关系模型。以期为西北干旱地区砂石覆盖生态农业的合理补灌提供理论指导。     

Growth,yield and water productivity of dry direct seeded rice and transplanted aromatic rice under different irrigation management regimes

Sustainability of traditionally cultivated rice in the rice-wheat cropping zone (RWCZ) of Pakistan is dwindling due to the high cost of production, declining water resources and escalating labour availability. Thus, farmers and researchers are compelled to find promising alternatives to traditional transplanted rice (TPR). A field study was conducted in Punjab, Pakistan, in 2017 and 2018 to explore the trade-offs between water saving and paddy yield, water productivity and economics of two aromatic rice varieties under dry direct seeded rice (DDSR) and TPR. The experiment was comprised of three irrigation regimes on the basis of soil moisture tension (SMT) viz., continuous flooded (>−10 kPa SMT), alternate wetting and drying (AWD) (−20 kPa SMT) and aerobic rice (−40 kPa SMT), maintained under TPR and DDSR systems. Two aromatic rice verities: Basmati-515 and Chenab Basmati-2016 were used during both years of study. In both years, DDSR produced higher yields (13–18%) and reduced the total water inputs (8–12%) in comparison to TPR. In comparison to traditional continuous flooded (CF), AWD under DDSR reduced total water input by 27–29% and improved the leaf area index (LAI), tillering, yield (7–9%), and water productivity (44–50%). The performance of AWD with regard to water savings and increased productivity was much higher in DDSR system as compared to AWD in TPR system. Cultivation of DDSR with aerobic irrigation improved water savings (49–55%) and water productivity (22–30%) at the expense of paddy yield reduction (36–39%) and spikelet sterility. With regard to variety, the highest paddy yield (6.6 and 6.7 t ha⁻¹) was recorded in DDSR using Chenab Basmati-2016 under AWD irrigation threshold that attributed to high tiller density and LAI. The economic analysis showed DDSR as more beneficial rice establishment method than TPR with a high benefit-cost ratio (BCR) when the crop was irrigated with AWD irrigation threshold. Our results highlighted that with the use of short duration varieties, DDSR cultivation in conjunction with AWD irrigation can be more beneficial for higher productivity and crop yield.     

Rapid brain MRI protocols result in comparable differential diagnoses versus a full brain protocol in most canine and feline cases

Evaluation of brain disease in veterinary patients uses a wide variety of MRI sequences. A shortened protocol that maintains consistency of interpretation would reduce radiologist reporting time, patient anesthetic time, and client cost. The aims of this retrospective, methods comparison, observer agreement study were to evaluate whether abbreviated MRI protocols alter differential diagnoses and recommendations compared to our institution's standard protocol; evaluate interobserver agreement on standard brain MRIs; and assess whether differential diagnoses change after postcontrast images. Normal and pathologic canine and feline brain MRIs were retrieved from hospital archives. Three protocols were created from each: a 5-sequence noncontrast enhanced Fast Brain Protocol 1 (FBP1); a 6-sequence contrast-enhanced Fast Brain Protocol 2 (FBP2); and an 11-sequence standard brain protocol (SBP). Three blinded veterinary radiologists interpreted FBP images for 98 cases (1 reader/case) and SBP images for 20 cases (3 readers/case). A fourth observer compared these interpretations to the original MRI reports (OMR). Overall agreement between FBPs and OMR was good (k = 0.75) and comparable to interobserver agreement for multiple reviews of SBP cases. Postcontrast images substantially altered conclusions in 17/97 cases (17.5%), as well as improved interobserver agreement compared to noncontrast studies. The conclusions reached with shortened brain protocols were comparable to those of a full brain study. The findings supported the use of a 6-sequence brain MRI protocol (sagittal T2-weighted [T2w] TSE; transverse T2w turbo spin echo fluid-attenuated inversion recovery, T2*-weighted gradient recalled echo, T1-weighted spin echo, and diffusion weighted imaging/apparent diffusion coefficient; and postcontrast transverse T1-weighted spin echo) for dogs and cats with suspected intracranial disease.     

余甘子丛生芽诱导和快速繁殖研究

本试验以余甘子嫩芽和嫩枝茎段为外植体 ,在 MS培养基中进行离体繁殖和培养试验。结果表明 ,添加细胞分裂素 BA对丛生芽诱导有明显促进作用 ,激素组合以 BA与 NAA为最好 ,嫩芽外植体诱导丛生芽的最适培养基为 MS BA0 .5 mg/ L NAA 0 .1mg/ L,分化率达 90 %以上 ;嫩枝茎段旅导丛生芽所需的 BA浓度相对高些 ,最适培养基为 MS BA 2 .0 mg/ L NAA 0 .1mg/ L,分化率达 5 6 .7% ,丛生芽增殖生长培养基为 MS BA 0 .1mg/ L NAA 0 .1mg/ L Na H2 PO45 0 mg/ L。生根培养基为 1/ 2MS NAA 0 .2 5 mg/ L IBA 0 .2 5 mg/ L ,生根率在 30 %左右     

多功能园林机械快速接口技术的研究

通过对加工中心刀具布局及多功能车整体布局的分析,提出了可行的作业头布局方式.结合作业头布局特点,分析了快速接口的设计要求,提出了可行的快速接口结构形式.