一种新的快速石蜡制片法——电热恒温石蜡制片法

为缩短传统石蜡制片法的制片时间,将电热恒温干燥箱应用于石蜡制片过程中,观察电热恒温石蜡制片法制片效果。结果表明:此法试验周期缩短为1 d内,获得了染色清晰,组织完整的解剖结构,与传统石蜡制片法的效果相同。     

Intestinal metabolism and absorption of carbaryl studied with a portal fistula

These data were obtained by use of a total and continuous portal vein fistula which virtually eliminated vascular redistribution of compounds absorbed from the gastrointestinal tract to nondigestive tissues (i.e., liver). The method allows direct measurement of the compounds absorbed, which is especially important in metabolism studies of ingested toxic compounds. These studies demonstrated that in vivo metabolism did occur within the intestine during the process of absorption of the pesticide carbaryl (naphthyl N-methylcarbamate) and naphthol, the hydrolysis product of the pesticide. Portal absorption of naphthol from a liquid diet (46 ± 4% of dose/120 min) was slower than from Ringer medium (75 ± 1%/120 min); portal absorption accounted for 82 ± 8 and 83 ± 4%, respectively, of the ¹⁴C absorbed from the intestine. The proportion of hydrophilic ¹⁴C-metabolites (water soluble) in portal blood varied from 6 to 89% and was a function of the substrate, dose vehicle (liquid diet vs Ringer), and time of portal fluid collection. Metabolism in the small intestine before absorption was confirmed for both substrates. The principal lipophilic constituent in portal fluid was the unmetabolized substrate for both carbaryl and naphthol; the principal ampholyte metabolite was naphthyl glucuronide. Although these in vivo data are qualitatively similar to evidence from previous in vitro studies, this in vivo evidence demonstrated that the extent of metabolism (and possibly detoxication) was considerably less than would be predicted from in vitro studies and indicates that the hazard of ingestion of carbaryl and other lipophilic toxic agents may be greater than realized.     

The effect of defoliation on bulb production of tulip cultivar ‘Apeldoorn’

The distribution of dry matter between the different bulblets of tulip is not markedly influenced by either changes in leaf area or the position of the leaf. On the contrary, total bulb yield is strongly affected.A reduction factor, S_c, for incomplete soil coverage, when the leaf area index (LAI) is less than 4, normally used for evaluation of planting density effects, can also be used for the effects of defoliation on dry matter increase. This LAI-dependent factor shows a distinctly asymptotic pathway closely resembling

$\text{S}{}_{\mathrm{c}}\text{=}\text{P}{}_{\mathrm{act}}\text{P}{}_{\mathrm{pot}}\text{=1?e}{}^{\mathrm{?k1LAI}}$

where k ～ 0.6 and in which P_act is the actual measured dry weight increase and $\text{P}\text{?}{}_{\mathrm{<mtext>pot</mtext>}}$ the potential net dry weight increase for a closed canopy.     

Nitrogen transfer from a legume tree to the associated grass estimated by the isotopic signature of tree root exudates: A comparison of the N leaf feeding and natural N abundance methods

Nitrogen (N) transfer from legume trees to associated crops is a key factor for the N economy of low-input agroforestry systems. In this work, we presented a new approach to estimate N transfer based on the ¹⁵N content of root exudates and N released by root turnover of the donor plant (Gliricidia sepium) and the temporal change of the ¹⁵N content of the receiver plant (Dichanthium aristatum). The study was carried out in greenhouse using two isotopic methods: ¹⁵N leaf feeding (LF) and the natural ¹⁵N abundance (NA). Measurements of exudate ¹⁵N were made at several dates before and after tree pruning. A time-dependent box model was devised to quantify N transfer in time and to make comparisons between the isotopic methods. In NA, although tree roots and exudates presented a similar ¹⁵N signature before tree pruning, exudates were strongly depleted in ¹⁵N after pruning. In LF, exudates were always depleted in ¹⁵N in relation to tree roots. Hence, the current assumption used in N transfer studies concerning the equal ¹⁵N/¹⁴N distribution in tissues of the donor plant and in its excreted N was not confirmed in our study. Before pruning, N transfer functioned as a two-N-source system (soil N and exudates N) and both isotopic methods provided similar estimates: 11–12% for LF and 10–15% for NA. Calculations performed with the model indicated that N transfer occurred with small or nil fractionation of ¹⁵N in exudates. After pruning, there was a third N source associated with N released from tree root turnover. During this period, the isotopic signature of the receiver plant showed a transient state due to the progressive decrease of ¹⁵N content of that N source. The amount of N derived from the tree represented 65% of the total N content of the grass at the end of the experiments.     

WTO"绿箱"措施在中国的运用

WTO“绿箱”措施是规范员方农林业财政补贴政策的国际规则。目前,员方纷纷将本国的农林业财政补贴政策“绿箱”化,我国也应考虑如何利用“绿箱”措施来完善我国的林业财政补贴政策,以促进我国林业的可持续发展。文章回顾了现有农林业文献中与WTO“绿箱”措施密切相关的主要观点,在此基础上做出了综合评论,并指出了今后的研究方向。     

下拉式夹具在箱体类零件加工中的应用研究

采用拉紧式结构可以简化箱体加工夹具,实现全方位无障碍加工。这种下拉式夹具利用零件定位面上螺纹孔产生的拉紧力使加工件紧贴定位面,保证加工时可靠夹紧,同时克服了压板式夹具压紧变形问题,还可以避免平面度超差、销子孔椭圆等由于零件变形产生的加工误差。     

象山港多品种养殖与富营养化状况的数值模拟

建立了基于氮通量物质平衡的象山港海湾养殖生态系统箱式模型。模型模拟的象山港主要生态变量的变化动态与实测数据资料相吻合。模型计算结果表明,生物生产过程的季节变化导致了营养要素(如氮)在可溶性无机状态和有机碎屑状态中的相互转化并呈现周年振荡。象山港总氮输入约2182tonN/a,其中养殖输入和排污输入约各占一半;氮输出途径按比例依次为水交换扩散、养殖业收获和渔业捕捞收获。目前象山港氮输入大于氮输出(约11%),造成海湾无机氮浓度年均升高约42μgN/L。利用模型对不同多品种养殖模式下无机氮浓度的长期变化趋势进行了预测。当前养殖模式下,象山港内无机氮浓度增长幅度较小且逐渐趋于输入输出平衡,而要使象山港海水水质达到国家Ⅲ类标准则需要减少鱼类养殖规模至当前规模的约40%或增加藻类养殖规模至当前养殖规模的20倍。     

液压式棉田地膜回收压捆机设计与参数优化

针对棉田地膜收储运困难、易造成二次污染等问题，设计一种液压式棉田地膜回收压捆机，可一次性完成棉田地膜的回收和液压压捆作业。根据机具初步试验结果，将挑膜滚筒转速、机具前进速度、切刀线速度、地膜喂入量、地膜厚度作为试验因素，将地膜回收率、压缩密度和缠膜率作为目标值，进行5因素3水平的Box Behnken试验，采用Design Expert软件进行响应面分析，建立相关的数学模型和目标函数，进行样机作业参数组合优化计算，并对优化结果进行试验验证，最终确定样机的最优作业参数组合。结果表明：样机进行地膜回收压捆作业时的最优作业参数组合为挑膜滚筒转速4800 r/min，机具前进速度0.80 m/s，切刀线速度2.47 m/s，地膜喂入量0.52 kg/次，地膜厚度0.012 mm，地膜回收率95.09%，压缩密度137.68 kg/m3，缠膜率8.91%。