常见生物显微制片方法的比较研究

对常见生物材料进行切片法和非切片法制片技术的比较,结果表明:不同的生物材料、不同的组织、选择不同的制片方法,可以提高生物显微制片的质量和效率,为生物显微制片技术的研究提供参考。     

螺旋焊缝管道的开裂原因

采用光学显微镜、扫描电子显微镜、能谱仪、维氏硬度仪及金相观察等分析手段,对开裂螺旋焊缝管进行取样分析,利用冲击试验测试了管道母材的抗开裂能力。结果表明：该管道焊缝存在明显缺陷,缺陷类型包括存在于焊缝中的焊缝金属裂纹和夹杂,存在于热影响区中的焊趾裂纹和焊接裂纹,同时在热影响区及母材中存在夹杂。在高外载作用下,由于焊缝区硬度高于热影响区及母材的硬度,使得焊趾裂纹先于焊缝金属裂纹向热影响区扩展。热影响区中沿轧制方向排列的层状夹杂的存在促进了裂纹的扩展,形成层状撕裂,最终导致管道沿热影响区开裂直至母材。     

The variation of the basic density within the juvenile wood of Sitka spruce (Picea sitchensis)

The variation in the basic‐density level of 45 stems of Sitka spruce from two Danish sites has been examined. It is shown that the basic‐density level, i.e. the basic density as a function of ring width, within the juvenile wood decreases with (1) increasing distance from the pith and (2) increasing height in the stem (same ring number from pith provided). Furthermore, the basic‐density level seems to decrease with increasing stand quality, which may affect the pattern of variation in basic‐density level if the stand quality class varies with age. The basic density of the juvenile wood is markedly higher in Sitka spruce than in Norway spruce, whereby the risk of stem cracks probably is reduced.     

微生态营养素对鱼苗池浮游生物的影响

通过在鱼苗培育过程中使用微生态营养素和传统养殖模式进行对比,分析测定养殖环境中的浮游生物种类、数量和生物量以及透明度等理化因子,研究微生态营养素在苗种培育中的使用效果。研究结果表明:微生态营养素能有效促进浮游生物的生长,施放微生态营养素的水体中鱼类喜食且易消化的浮游植物及浮游动物的种类和数量显著增加,总生物量提高了20%~58%,水体透明度降低了30%～52%,培育出来的苗种,较常规培育的个体更大、成活率更高。     

Microcracking and Chloride Penetration of Concrete under Uniaxial Compression

A non-destructive method of evaluation of specific crack area was used to characterise microcracking in concrete prisms during uniaxial compression loading and unloading. Chloride profiles were also measured after the same concretes were exposed to chloride environment. The relation among microcracking, stress-strength ratio and chloride penetration of concrete were analysed based on the experimental results. Under compressive load, the apparent chloride diffusion coefficient decreases until about one third of the ultimate load. Further increase of compressive load improves the chloride diffusion coefficient again. There is a close link between microcracking and stress-strength ratio. The index of specific crack area can be used to indicate the microcracking and study chloride transport behaviour into concrete under the influence of microcracking.     

Effect of lamellas annual-ring orientation on cracking of glulam beams investigated with computer tomography and image processing

Abstract

Cracks in glulam beams can reduce their strength, depending on the crack's depth, length, and location and can also be a passage for the accumulation of water and dirt. To avoid cracks, the relationship between cracks (area of cracks, mm²) and annual-ring orientation in glulam beams of spruce (Picea abies), and pine (Pinus sylvestris) with different dimensions and surface treatments was investigated using RGB images of the surface and tomography images of the cross-sections. Image processing was used to measure characteristics visible in the photos such as crack area and lamella position in the beam. Combination of lamellas in lay up was measured from computer tomography images. Four types of combinations were defined; type 1 (pith side facing outward), types 2 and 3 (pith to the same side), and type 4 (pith sides meet pith side). It was found that the area close to the glue line in the lamellas in combination type 4 is the most subject to cracking, whereas combinations of type 1 show the highest resistance to cracking. This means that type 4 should not be used in glulam beams, because the lamellas shrink apart from each other causing stresses and resulting cracks.     

微喷周期对葡萄叶片SPAD值和叶绿素含量与产量的影响分析

为研究极端干旱区微喷灌水技术对葡萄生理和产量的影响,通过对葡萄不同生育期叶片SPAD值、叶绿素含量和产量的测定,分析不同微喷周期条件下各处理的叶片SPAD值、叶绿素含量的变化特征和相互关系及对产量的影响。结果显示:在不同喷水周期条件下,各处理的SPAD值呈先减小后增大的变化趋势,日变化值为38.31~43.8。其中,每天喷水1h处理的SPAD值日平均值最高,为42.0,之后是对照处理和每隔1d喷水2h处理,分别为41.2和40.3,每隔2d喷水3h处理的SPAD值最低,为39.3。葡萄SPAD值与叶绿素a、叶绿素b以及总叶绿素含量间相关关系显著,回归方程分别为Ca=0.1028VSPAD-2.2266、Cb=0.0796VSPAD-2.3749、Ct=0.1824VSPAD-4.4602。在葡萄品质指标和产量上,采用微喷可以提高VC含量、多酚含量和单宁含量等多项品质指标,并使葡萄平均增产5.4%,表明合理的微喷周期处理有利于提高葡萄叶片叶绿素含量,并使产量增加,而叶绿素仅是葡萄生理生长的指标之一,如光合、叶绿素荧光等指标对葡萄生理的影响仍需作更深入的研究,以期能更进一步揭示微喷条件下的葡萄增产作用机理。     

Nutrient release pattern of organic and inorganic resources used in cassava production (Manihot esculenta Crantz)

The major constraint in the promotion of organic farming, a safe and sustainable alternative, is lack of availability of quality organic resources in sufficient quantities. The quality of resources can be ascertained by monitoring its nutrient release pattern, which has not yet been attempted. A controlled condition pot experiment was conducted at ICAR-Central Tuber Crops Research Institute, Thiruvananthapuram, India, in completely randomized design to study the nutrient dynamics of various organic and inorganic resources, commonly used in cassava production, at monthly intervals up to six months. The release of almost all nutrients and activity of soil enzymes were higher at the middle (3 or 4?months) of the incubation period. The pH showed an increasing trend and electrical conductivity, organic C and Fe content declined from initial. Averaging over stages, organic practice favored the activity of soil enzymes and release of almost all nutrients over conventional system significantly, except N.     

Physical carbon‐sequestration mechanisms under special consideration of soil wettability

The protective impact of aggregation on microbial degradation through separation has been described frequently, especially for biotically formed aggregates. However, to date little information exists on the effects of organic‐matter (OM) quantity and OM quality on physical protection, i.e., reduced degradability by microorganisms caused by physical factors. In the present paper, we hypothesize that soil wettability, which is significantly influenced by OM, may act as a key factor for OM stabilization as it controls the microbial accessibility for water, nutrients, and oxygen in three‐phase systems like soil. Based on this hypothesis, the first objective is to evaluate new findings on the organization of organo‐mineral complexes at the nanoscale as one of the processes creating water‐repellent coatings on mineral surfaces. The second objective is to quantify the degree of alteration of coated surfaces with regard to water repellence. We introduce a recently developed trial that combines FTIR spectra with contact‐angle data as the link between chemical composition of OM and the physical wetting behavior of soil particles. In addition to characterizing the wetting properties of OM coatings, we discuss the implications of water‐repellent surfaces for different physical protection mechanisms of OM. For typical minerals, the OM loading on mineral surfaces is patchy, whereas OM forms nanoscaled micro‐aggregates together with metal oxides and hydroxides and with layered clay minerals. Such small aggregates may efficiently stabilize OM against microbial decomposition. However, despite the patchy structure of OM coating, we observed a relation between the chemical composition of OM and wettability. A higher hydrophobicity of the OM appears to stabilize the organic C in soil, either caused by a specific reduced biodegradability of OM or indirectly caused by increased aggregate stability. In partly saturated nonaggregated soil, the specific distribution of the pore water appears to further affect the mineralization of OM as a function of wettability. We conclude that the wettability of OM, quantified by the contact angle, links the chemical structure of OM with a bundle of physical soil properties and that reduced wettability results in the stabilization of OM in soils.     

微域尺度苏打碱土的特征与植被的分布规律

探讨了微域尺度(32 m长的横剖面)苏打碱土的特征以及植被分布规律.结果表明,沿洼地向高平地土壤表现为盐化草甸土-浅位柱状苏打碱土-白盖苏打碱土-中位柱状苏打碱土的分布格局.植被为圆叶碱毛茛/蔚蓄蓼群落、鹅绒委陵菜群落、羊草/寸草苔群落、裸地以及羊草/星星草/虎尾草群落,其中委陵菜/篇蓄蓼群落、羊草/苔草群落沿洼地呈环状分布,裸地以及碱茅/虎尾草/羊草群落呈斑状分布.洼地边缘的植被具有最高的物种丰富度和覆盖度,生物量也最高;高平地的植被矮小,生物量较少.裸地的盐分含量较高(可达3.38%),土体紧实,限制了植被生长.