X射线扫描技术对原木内部缺陷的识别方法

对X射线的吸收能力,原木木质部分与内部缺陷部分存在不同,因此在X射线底片上形成的影像也不一样,根据一定的处理识别分析,可以对原木内部缺陷的参数进行测定。利用X射线的扫描图像,提出一种原木缺陷的识别方法。     

The use of micro-beam X-ray diffraction for the characterization of starch crystal structure in rice mutant kernels of waxy, amylose extender, and sugary1

Micro-beam X-ray diffraction analyses were carried out on slices from wild-type rice and mutants. The method permitted the crystalline structure to be analyzed with less destruction of cells and fewer artificial effects that occur during the purification of starch from tissue and provided information concerning the localization and crystalline structure of starches distributed in the endosperm. The starch on kernel slices from the wild-type and waxy mutant, carrying a defect for the Granule-bound starch synthase I (GBSSI) gene, displayed an A-type of diffraction pattern; no difference in the crystalline patterns between starches located in the inner and outer region in a kernel were observed. A double mutant of the waxy and amylose extender (ae) mutant carrying a defect for the Starch branching enzyme IIb gene accumulated amylose-free B-type starches. The kernel slice from the double mutant of waxy and sugary1, mutated on the Isoamylase I locus, displayed an A-type diffraction pattern in the outer region and was amorphous in the inner region. A chain-length distribution analysis of polyglucans in kernels from wild-type and mutants showed that ae amylopectin had more long chains and less short chains than the wild-type and waxy amylopectin. On the other hand, the water-soluble polysaccharide in the inner region of the sugary1 endosperm had more short chains than the amylopectin in the outer region counterparts. These results indicate that branch chain length in amylopectin is crucial in determining the formation of A- and B-type starches.     

Use of geochemical fingerprints to trace sediment sources in an agricultural catchment of Argentina

Soil erosion and associated sediment redistribution are key environmental problems in Central Argentina. Specific land uses and management practices, such as intensive grazing and crop cultivation, are considered to be significantly driving and accelerating these processes. This research focuses on the identification of suitable soil tracers from hot spots of land degradation and sediment fate in an agricultural catchment of central Argentina with erodible loess soils. Using Energy Dispersive X-Ray Fluorescence (EDXRF), elemental concentrations were determined and later used as soil tracers for geochemical characterization. The best set of tracers were identified using two artificial mixtures composed of known proportions of soil sources collected from different lands having contrasting soil uses. Barium, calcium, iron, phosphorus, and titanium were identified for obtaining the best suitable reconstruction of source proportions in the laboratory-prepared artificial mixtures. Then, these elements, as well as the total organic carbon, were applied for pinpointing critical hot spots of erosion within the studied catchment. Feedlots were identified to be the main source of sediments, river banks and dirt roads together are the second most important source. This investigation provides key information for optimizing soil conservation strategies and selecting land management practices and land uses which do not generate great contribution of sediment, preventing pollution of the waterways of the region.     

应用三维图像和数学模型对土壤团聚体内外溶质的交换速率的研究

受土壤有机质和微生物的影响,大部分农业土壤都有团聚体结构。团聚体内部的孔隙一般很小,与团聚体之间的水流相比,团聚体内部的水可以视为不动的。但受质量浓度梯度和分子扩散的影响,2个水体内的溶质可以相互交换。模拟溶质在具有团聚体结构土壤中运移时,溶质在以上2个水体间的交换过程常用可动-不可动水体模型来描述。土壤溶质运移涉及的参数较多,很多参数不能直接测定,要靠观测值拟合才能获得。由于不同的参数组合可以得出相同溶质质量浓度分布,因此,即使模拟结果和实验结果吻合也不能确保该模型正确描述了2个水体之间的溶质交换过程。为了深入研究这一问题,利用三维图像技术和数学模型,计算了团聚体内外溶质交换速率。结果表明,Coats-Smith模型误差很大,2个水体之间的溶质交换速率并非与其质量浓度差成正比。作为改进,提出并证明广义γ分布函数可以准确地描述团聚体内外溶质交换过程。     

香菇栽培前后基质中纤维素结构的变化

为了探讨食用菌栽培料和菌糠纤维素微观结构的差异,本研究以黑龙江省常见的香菇栽培料和香菇菌糠为实验材料,利用扫描电子显微镜(SEM)观察香菇栽培前后纤维素微观表面的变化,利用光衍射(XRD)和红外光谱(FT-IR)研究了香菇栽培前后纤维素结晶度和微观结构分子基团的改变。扫描电镜观察到栽培食用菌后,纤维素微观结构整体变化不大,但纤维素表面出现了更多的细小洞穴;XRD和FT-IR测定的香菇菌糠纤维素结晶区的结晶度和纤维素特征吸收峰的吸收强度都明显低于香菇栽培料,表明纤维素晶体结构遭到破坏,这正好和SEM观察到的图像吻合。栽培香菇后纤维素结构分子间和分子内氢键发生重排,这也是纤维素降解困难的原因。     

Cellular structure and rheological properties of shaped fermented wheat flour dough

Among the various operations of the breadmaking chain, the impact of shaping on dough cellular structure has scarcely been studied. In this work, wheat flour dough has been laminated under different roll gap conditions δ(mm)= (2,5, 10, 20, ∞). Rheological properties were measured under large and small strains, by lubricated squeezing flow test and dynamic thermomechanical analysis, respectively. Laminating has a limited effect on the elongational viscosity of the dough. However, the minimum value of the ratio of storage modulus reached for gap δ = 5 mm suggests that gluten network structuration is improved in this case. The kinetics of porosity and shape ratio of fermenting laminated doughs were calculated from image analysis of dough follow-up during proofing. They showed that stability is improved for δ = 5 mm. Finally, Xray tomography experiments, performed on laminated rolled dough during proofing, confirmed that the main changes can be attributed to an increase of cellular homogeneity at δ = 5 mm, reflected by lower median gas cell size and less spread size distributions.     

Automatic grading of sawlogs: A comparison between X-ray scanning,optical three-dimensional scanning and combinations of both methods

As sawmills become increasingly efficient, the importance of focusing on value recovery becomes obvious. To maximize value recovery, sawmills require the ability to sort logs according to quality. This study compares four different combinations of three-dimensional (3D) and X-ray scanning that can be used to grade logs automatically. The study was based on 135 Scots pine (Pinus sylvestris L.) logs that had been scanned with both a 3D scanner and an X-ray scanner with two X-ray sources. The percentage of boards with correct grade sawn from automatically graded logs varied from 57% when using only 3D scanning to 66% when using a combination of 3D scanning and X-ray scanning in two directions. The highest possible result, with ideal log grading, was 81%. The result also shows that the combination of a 3D scanner and one X-ray direction results in higher accuracy than a scanner based on two X-ray directions.     

The Involvement of Silicon Deposition in Salinity-Induced White Head in Rice (Oryza sativa L.)

Abstract

White heads and silicon deposition in spikelets were observed in three rice varieties (IR28, IR4595-4-1-13 and Mangasa), which were different in vulnerability to white heads under salinity conditions. Plants were grown in three-liter pots with two nitrogen fertilizer levels (HN : high nitrogen and LN : low nitrogen) and subjected to salinity by submerging the soil in a lOOmM sodium chloride solution from booting to seven days after panicle emergence. White heads occurred in IR4595-4-1-13 and Mangasa but not in IR28 under the salinity condition, and the vulnerability to white heads was higher with the HN treatment than the LN treatment. Silicon deposition in spikelets, measured by energy-dispersive X-ray analysis with a scanning electron microscope, was correlated to the vulnerability to white heads. White heads inhibited flower opening and thus induced high sterility. It was concluded that low silicon deposition in spikelets was responsible for the occurrence of white heads under salinity conditions in rice.     

Improving strength grading of timber by grain angle measurement and mechanical modeling

Abstract

Timber strength grading has become a major issue in the European Union during the last years, due to the introduction of the Eurocode 5 and all its related standards. Currently, the most performing strength grading machines are able to locally detect the boards’ knots sizes and positions and interpret this information through adapted grading models. The best lead to improve their accuracy seems to be the introduction of new information about the boards and adapt the mechanical model to take them in account. Small grain angle causes high reduction of clear wood's mechanical properties; local value of slope of grain appears to be of high interest. The aim of this study is to quantify the additional accuracy that grain angle information can bring to an optical scanner used as a strength grading machine. A specific grading model has been developed accordingly, and the results obtained for different machine/model/loading combinations are presented. These results show that slope of grain measurement can significantly improve the accuracy of the optical scanner, for both modulus of elasticity and modulus of rupture estimations.     

Effects of artificial environmental conditions on anatomical and physiological ripening of Pinus sylvestris L. seeds

To determine suitable conditions for artificial ripening of Scots pine seeds, cones collected on seven occasions between August 6 and November 26, 1990, in northern Sweden, were subjected to artificial ripening at different temperatures (+5°–+15°C) and cone moisture contents for 3–9 weeks. Complete physiological ripening and improved seed vigour were attained after artificial ripening if collection occurred no earlier than the beginning of September. The highest germination percentage after artificial ripening, ca 90%, was achieved for seeds collected after the anatomical ripening in nature had ceased and was at least as high as for seeds ripened in nature. Temperature did not influence ripening, whereas a low cone moisture content impaired ripening of those seeds collected earliest. The germination percentage was not influenced by 2–6 months of cone storage subsequent to artificial ripening, but seed vigour was impaired. Anatomical ripening during artificial ripening was very limited.