Shading effects on spatial growth and biomass partitioning of Cynodon dactylon

Cynodon dactylon is a low-growing C4 weed that is highly sensitive to shading. This species shows severe biomass reductions and highly plastic morphological changes in response to resource availability. The objective of this study was to analyse the effect of shading on the spatial and biomass growth of C. dactylon . Two experiments were carried out exploring different environmental conditions. Six treatments were applied on C. dactylon patches. Daylight and 18%, 41%, 48%, 69% and 85% shading of daylight photosynthetic active radiation (PAR) were imposed in Expt 1 and 0%, 22%, 44%, 50%, 74% and 87% shading of daylight PAR in Expt 2. Patches were slightly elliptical in shape and grew 3.2 and 1.5 cm d⁻¹ with 0% shading, on average, during the whole studied periods in Expts 1 and 2 respectively. Biomass was significantly reduced from 41% shading onwards in Expt 1 and from 50% shading in Expt 2. However, patch extension rate was only significantly reduced from 85% and 74% shading in Expts 1 and 2 respectively. Biomass partitioning was modified by shading in both experiments. A functional analysis of C. dactylon patches showed that the patch extension rate diminished linearly when patch biomass growth rate was lower than 1.66 g d⁻¹; above this value, the extension rate remained constant.     

差量法测定猪回肠AA的真消化率及内源AA的排泄量

本文探讨了采用差量法测定猪对豆粕氨基酸(AA)的消化率和内源氨基酸排泄量的可行性.试验测得豆粕在16%、10%日粮蛋白水平上的表观氨基酸消化率分别为81.84%、78.59%,以差量法求得真消化率为87.87%.研究结果表明,差量法可以作为测定猪氨基酸真消化率和内源氨基酸排泄量的新方法.     

液液系统中荷电射流不稳定性

针对生物柴油液液静电雾化乳化过程,建立了色散方程并应用Matlab进行数值计算,分析了水射流速度、荷电电压、水与生物柴油各自的黏度、表面张力对生物柴油中水射流不稳定性的影响.研究结果表明,在水-生物柴油系统中,提高水射流的速度或荷电电压,均能使界面波最大增长率增大,对应的最优波数也随之增加.水的黏度阻碍水射流的破碎雾化,而生物柴油黏度对水射流的破碎雾化却起着促进作用.水-生物柴油的界面张力越小,对液液静电雾化乳化过程越有利.在水-生物柴油液液静电雾化乳化实际应用过程中,除提高水射流速度和荷电电压外,提高水的温度同时尽可能地降低生物柴油的温度,可以形成粒径细小均匀离散相液滴,获得优质的生物柴油乳化燃油.     

Effects of remifentanil on monophasic action potential and transmural dispersion of repolarization in rabbit myocardium

AIM: To study the effect of remifentanil on monophasic action potential and transmural dispersion of repolarization (TDR) in the 3-layer myocardium of isolated rabbit hearts. METHODS: Adult rabbits (n=18, 2.0 ~ 2.5 kg) were used to isolate the hearts for preparing Langendorff perfusion model. The hearts were randomly divided into 3 groups after perfusion with K-H solution for 15 min: the perfusion in control group (C group) continued for 60 min; the hearts in remifentanil group (R group) were perfused with 12 μg/L remifentanil K-H solution for 60 min; the hearts in remifentanil+aminophylline group (RA group) were given 60-min perfusion of 12 μg/L K-H remifentanil+30 mg/L aminophylline. The HR and 3 layers of myocardial monophasic action potential (MAP) in the left ventricular anterior wall were recorded at time points after balanced infusion for 15 min (T₀), and continued perfusion for 15 min (T₁), 30 min (T₂) and 60 min (T₃). The monophasic action potential duration of repolarization at 90% (MAPD₉₀) and the transmural dispersion of repolarization (TDR) were calculated. The early afterdepolarization, delay afterdepolarization and arrhythmia were also observed. RESULTS: In R group, slower HR and prolonger MAPD₉₀ and TDR at T₁~T₃ were observed as compared with those at T₀ (P<0.05). R group showed slower HR and longer MAPD₉₀ and TDR than C group and RA group (P<0.05). CONCLUSION: Remifentanil slows the HR, extends the MAPD₉₀ and increases the TDR, thus being prone to induce reentry. Aminophylline makes HR faster and MAPD₉₀ shorter, thereby reducing the TDR.     

不同增稠剂对农药可分散油悬浮剂稳定性的影响

为明确不同增稠剂对以矿物油为分散介质的油悬浮体系稳定性的影响,以12.5%丙炔·吡嘧(丙炔噁草酮·吡嘧磺隆)可分散油悬浮剂为对象,通过流变学和多重光散射方法,研究了有机膨润土、有机高分子和气相二氧化硅3类增稠剂单独使用及有机膨润土和其他两类增稠剂分别搭配使用对可分散油悬浮剂物理稳定性的影响。结果表明:所有样品的流动特性指数(n)均小于1,为假塑性流体,具有触变性。除有机膨润土和高分子增稠剂Atlox Rheostrux100组合使用时体系更符合Casson方程外,其余样品均更符合Herschel-Bulkley方程。单独使用时,有机膨润土对保证体系稳定的效果相对较好;Atlox Rheostrux 100和Atlox Rheostrux200两种高分子增稠剂的效果差别较大,其中Atlox Rheostrux 100效果更好,这可能是由分子结构差异造成;两种气相二氧化硅类增稠剂由于不能有效形成氢键,效果较差。将有机膨润土和有机高分子增稠剂组合使用时,体系的稳定性有所提升,其中有机膨润土869和Atlox Rheostrux 100组合使用效果更好,体系具有较高的黏度,且具有良好的触变性,物理稳定性优异;有机膨润土869和疏水气相二氧化硅R974组合使用时则效果没有明显的提升。研究表明,流变学和多重光散射两种方法均能较好地表征可分散油悬浮剂的物理稳定性;新型高分子增稠剂和有机膨润土具有协同作用,将二者合理组合添加能大幅提升可分散油悬浮剂的稳定性。     

生物炭对黑土区土壤水分扩散与溶质弥散持续效应研究

为探究施用生物炭对黑土区坡耕地土壤水分扩散和溶质弥散的持续效应，于2016—2019年在1.5°、3°、5°的径流小区开展了生物炭持续效应试验，分析了单次施加生物炭对土壤容重、孔隙度、有机质含量、Boltzmann变换参数ξ、非饱和土壤水分扩散率D(θ)、非饱和土壤水动力弥散系数Dsh(θ)的持续作用。结果表明：土壤中单次添加生物炭后的4年内均可显著降低土壤容重、提高土壤孔隙度、增加土壤中有机质含量，且各指标变化率均随坡度增大、施炭年限延长而减小；坡度、年份、是否施用生物炭3个因素中，对土壤容重、孔隙度、有机质含量影响程度最大的均为是否施用生物炭；施用生物炭增大了ξ，且ξ随坡度增加、施炭后年限延长逐年减小。2016—2019年D(θ)与Dsh(θ)均随土壤含水率的增加而迅速增加。当土壤含水率小于等于042cm3/cm3时，生物炭抑制土壤水分扩散；当土壤含水率大于0.42cm3/cm3时，生物炭促进土壤水分扩散。当土壤含水率小于等于0.36cm3/cm3时，生物炭抑制土壤中NaCl溶液的弥散；当土壤含水率大于0.36cm3/cm3时，生物炭可以促进土壤中NaCl溶液的弥散。试验区θ处于0.20~0.35cm3/cm3，故施用生物炭对水分扩散、NaCl溶液弥散均具有抑制效果，且生物炭对水分扩散和溶液弥散抑制效果均随坡度增加、施炭后年限延长而减弱。     

Evaluation of the pattern of spray released from a moving multicopter

BACKGROUND

Multicopters are used for releasing particulates seeds, fertilizer and spray. Their low cost and high manoeuvrability make them attractive for spraying in steep terrain and areas where overspray is undesirable. This article describes a model of multicopter wake and its influence on particulate dispersion, which is computationally economical compared to many computational fluid dynamics (CFD) approaches, yet retains reasonable accuracy.

RESULTS

A model was successfully implemented in OpenFOAM . It features source terms for the rotor wash, Lagrangian particle tracking, an evaporation model, and a porous medium approach to model the effect of the ground vegetation. Predictions were validated against the field tests of Richardson et al. which used a DJI Agras MG-1 multicopter in three different flights with airspeeds of 3.2–4.9 m s⁻¹, ground speeds of 2.1–2.9 m s⁻¹ and cross-wind speeds of 0.04–2.2 m s⁻¹. The effective swath width (30% line separation) was predicted to within one standard deviation. Sensitivity to a rotor rotational speed, flight height, flight velocity, multicopter roll and yaw angles, surface roughness length, plant height and leaf density was checked.

CONCLUSION

In all flight trials, the modelled swath was closest to the experimentally obtained swath when the surface roughness of the fetch was equal to 0.5 m (bushes) and the rotational speed of all rotors was equal to 2475 rpm with 0.75R (0.2 m) tall plant canopy (grass) introduced to the model. The model showed acceptable validity for flight velocities of ≤2.8–5 m s⁻¹ when flight parameters can be approximately estimated. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

抗球虫药新剂型的制备与研究

采用固体分散技术,利用溶剂法,以处方比例马度米星铵:聚维酮(聚乙烯吡咯烷酮,PVPk30)分别为1:1、1:2、1:3制备了3个马度米星铵固体分散体,通过差示扫描量热法(DSC)分析鉴定,当马度米星铵与PVP k30的比例为1:3时马度米星铵的药物特征吸热峰消失,说明固体分散体制备成功。对药物进行体外累积溶出度研究,结果马度米星铵固体分散体在60 min内体外累积溶出度可达98.46%,比马度米星铵预混剂的2.57%提高了38倍多。抗球虫效果研究表明,马度米星铵固体分散体的抗球虫指数(ACI)为197.7,明显高于ACI为191.8的马度米星铵预混剂。     

球磨-酶解法制备纳米竹纤维的结构表征

采用机械球磨对竹纤维进行预处理,再经纤维素酶水解制备纳米竹纤维。通过光学显微镜(OM)、透射电子显微镜(TEM)、傅立叶红外光谱仪(FTIR)和X射线衍射仪(XRD)对竹纤维的形貌、组成、光谱学性能以及晶体特性进行了表征。实验结果表明:球磨法和酶解法在一定程度上都可以细化竹纤维;球磨预处理有助于竹纤维的酶解过程,且球磨-酶解法制备的纳米竹纤维粒径在100 nm左右;所制备的纳米竹纤维仍然保持竹纤维的基本化学结构,但球磨处理破坏了纤维素的结晶结构,其结晶度由64.15%降低到了38.55%。