银鲑不同部位肌肉的营养评价与特征风味分析

为科学评价银鲑不同部位肌肉的营养品质及风味差异,本试验以银鲑背部和腹部肌肉为原料,通过测定银鲑不同部位肌肉的基本营养成分、氨基酸和脂肪酸组成,分析其营养学特征;采用气相离子迁移谱仪(GC-IMS)分析不同部位肌肉的特征风味.结果表明,除灰分外,银鲑背部和腹部肌肉的营养组成存在显著差异,腹部肌肉粗脂肪含量高达10.93 ...     

银中杨不同根幅造林试验

采用拉丁方设计方法,较系统地研究了不同根幅银中杨大苗造林成活率及当年高、径生长量的关系。结果表明:根幅35 cm和25 cm的较15 cm的造林成活率分别提高28和21个百分点;根幅35 cm和25 cm的较15 cm的当年高生长量分别提高246%和65%,当年径生长量分别提高83%和37%;在黑龙江省西部半干旱地区,采用二根一干或二根二干的银中杨大苗造林,根幅以35 cm左右为宜。     

Influence on new tunnel mechanics behaviorinduced by construction about adjacent spacing

This paper takes Chongqing Two-River Tunnel as the research background, based on the system for structure and surrounding rockmass of the highway tunnel, conducts a three-dimension model test about forked tunnel with different altitude to study new tunnel’s mechanics behavior induced by construction, and uses numerical simulation to analyze model domain. The results show that the displacement on new tunnel’s left hance is larger than the displacement on its right hance. Left hance displacement is larger than hance displacement of the single tunnel, and the right hance displacement is less than hance displacement of the single tunnel. The trend of hance displacement and crown settlement with different adjacent spacing is got. Normalizing hance displacement and crown settlement of model test, the relation between displacement and adjacent spacing is disclosed. The hance displacement and crown settlement gained by numerical simulation is close to the converted result of model test, which indicates that the model test data is consistent with the result of numerical simulation.     

不同棱型大麦品种混种增产效果初探

为了探索不同棱型大麦品种混种的增产机理及效果,以保山市大面积推广的多棱品种保大麦14号、二棱品种82-1为材料,设5个处理,进行单种和混种比较试验,结果表明,混种能充分利用空间、利用光能,从而提高产量,产量比单种二棱矮秆品种增加139.5～719㎏/hm2,比单种多棱高秆品种增40.5～720㎏/hm2;产量构成因素中,有效穗与单种二棱品种(单种中有效穗最多)相近,穗实粒数比单种二棱矮秆品种增7.8～10.7粒,千粒重比单种多棱高秆品种增1.2～5.5g,同时,混种还能减轻倒伏;二棱品种82-1与多棱品种保大麦14号混种基本苗最佳比例为6:4(折合种子重量≈7:3)。     

不同海拔野生金露梅叶的成分分析

金露梅灌木林是青海最大的灌木林区之一。目前对金露梅叶片的研究仅限于解剖结构、灌丛地上部分生物量和黄酮类物质的研究,对青海野生金露梅叶成分整体研究少。2005年7月在海拔2840m和2510m处采野生金露梅叶作为样品进行成分分析,结果表明:样品在海拔2840m处黄酮的含量高于样品在海拔2510m处的含量;单宁的含量相当;样品在海拔2840m处还原糖的含量高于样品在海拔2510m处的含量,粗蛋白的含量低于样品2510m处的含量。     

Influence of different agricultural management systems on nitrogen leaching: results of lysimeter studies

The objective was to estimate the potential risk of N leaching into the groundwater under various types of agriculture by using lysimeter experiments on the nitrogen(N)‐cycle of various soil types. Results were obtained with 12 weighable, monolithic lysimeters with a surface area of 1 m², a total depth of 3 m, and free drainage. Mean annual N‐leaching losses of 5 to 44 kg ha^—1 and nitrate concentrations of the seepage water (leachate) between 80 and 200 mg l^—1 were measured during the period of intensive agricultural use. On fallow land with a well‐established grass vegetation, some nitrate was removed by the plants. As a result, the nitrate concentrations in the leachate were reduced significantly. Ecological farming measures generally reduced N leaching losses and kept the N‐concentration in the leachate below the German threshold value for drinking water with 50 mg l^—1 nitrate. However, ploughing in of clover or leguminous vegetation and the application of farmyard manure in autumn caused the nitrate concentration in the leachate to rise significantly above the mentioned threshold value.<?show $6#>     

Evaluation of Agronomic and Environmental Soil P Test Methods in a Network of Hungarian Long‐Term Field Trials

Abstract

Winter wheat shoot weight and phosphorus (P) concentrations, corn leaf weight and P concentrations, and soil AL, Olsen, H₂O, Bray 1, Pi (Fe-oxide impregnated paper strip) and AERM (anion exchange resin membrane) contents were determined in a network of uniform Hungarian national long‐term field trials. P application had a significant effect on soil P test values at different P levels and sites. The relationship between the different soil P test methods was studied separately for different soil groups (all, acid, and calcareous soils). Corn leaf weight was influenced by the sites much more than by soil P supply level, whereas corn leaf P percentage was influenced by both sites and P levels. For winter wheat, both sites and soil P levels had a positive effect on wheat shoot weight. Wheat shoot P percentage was influenced by the soil P supply much more than by the sites. Correlation between corn leaf P percentage and the Pi or AERM extractable P and between wheat shoot P percentage and the Pi and AERM P values was logarithmic.     

Porous tubing for use in monitoring soil CO2 concentrations

The composition of the soil atmosphere is an indicator of biological processes, and soil CO₂ gradients have been used to estimate CO₂ efflux from the surface. Soil atmosphere samplers, constructed with gas-permeable materials, have been used to quantify soil CO₂ concentrations. The type of material used can influence the perceived real-time concentrations of CO₂ in the soil. Previous works have not directly compared different types of materials under the same conditions. The objective of this study was to determine the diffusion coefficient (D) and time of 95% equilibrium (t_eq) of CO₂ through several materials, and to evaluate the effect of long-term soil burial (183 days) on diffusion characteristics. Materials tested included silicone, expanded Teflon (ePTFE), and ultra high molecular weight polyethylene (PE) tubing. The D of each material was determined using a closed-loop system consisting of a CO₂-enriched (7800 ppm) chamber, a CO₂ analyzer and an inner tube (experimental tubing) placed inside the chamber. Air was re-circulated through the inner tube, and as CO₂ diffused from the chamber into the tubing, the analyzer recorded the increase in concentration. The silicone tubes had values of D ranging from 8.64 to 5.80×10⁻⁶ cm² s⁻¹ with corresponding t_eq between 3.9 and 9.7 h. Diffusion coefficients of the ePTFE (1.25×10⁻⁴ cm² s⁻¹) and PE (7.70×10⁻⁴ cm² s⁻¹) materials were 2 orders of magnitude greater, with t_eq<6 min. Exposure to the soil environment for 183 days did not visibly deteriorate the materials or significantly affect the D or t_eq values. Use of the ePTFE or PE materials, over the silicone materials, may allow for better characterization of dynamic CO₂ concentrations in the soil based on the greater D and lesser t_eq values of these materials.     

Denitrification in intact subsoil cores

 Intact, unamended subsoil cores taken from two contrasting field sites were incubated in the laboratory at 12  °C under aerobic (21% O₂) and anaerobic (1.1–5.5% O₂) conditions. Denitrification of ¹⁵N-NO₃ ^– diffusing into the cores across a semi-permeable membrane was estimated by: (1) direct observation of ¹⁵N-labelled N₂ and N₂O, and (2) mass balance following sectioning at the end of the experiment. The in situ denitrification potential (rates where the supply of NO₃ ^– is not limited by diffusion) was estimated using a finite-difference approximation to a diffusion reaction equation based on comparison of time and depth profiles of NO₃ ^– and Br^– in the incubated cores. Potentials between 0.2 and 2.5 mg N kg^–1 day^–1 were obtained under low O₂ and natural C concentrations. These results indicate the potential for denitrification in glacial till subsoils to reduce NO₃ ^– leaching to ground or surface waters to levels unlikely to result in a pollution hazard. The major product of NO₃ ^– reduction in these subsoils was observed to be N₂, rather than the greenhouse gas and catalyst of stratospheric O₃ removal, N₂O. Received: 31 October 1997