近三十年农田土壤磷分子形态的研究进展

农田土壤磷的赋存形态决定迁移、转化及归趋过程,单单通过全磷或有效磷含量并不能全面、准确、长效地评估土壤磷的养分供应能力和生态环境风险,探索可持续的农田磷素管理措施迫切需要能够科学表征、准确认识土壤磷形态。随着分析测试技术发展,农田土壤磷形态领域经历了以传统连续提取法为主的分级组分研究,到目前基于先进光谱技术的分子形态研究的发展历程。液相磷-31核磁共振技术(P-NMR)、基于同步辐射的X射线吸收近边结构谱技术(P-XANES)是当今土壤磷分子形态表征的主流技术,分别促进土壤多种有机磷和无机磷(铁磷/钙磷/铝磷)分子形态的有效识别。借助Histcite软件进行引文网络分析,梳理了近三十年(1990—2019年)土壤磷分子形态研究发展历程中具有重大借鉴意义的关键性成果,基于此综述了该领域的发展脉络,归纳发现农田土壤磷分子形态研究最初主要借助P-NMR技术侧重有机磷分子形态表征,而后过渡至与同步辐射XANES以及X射线微探针技术相结合,实现了土壤磷分子形态的全面认识。最后,对多谱学技术联用推动土壤磷分子形态研究的发展趋势进行了展望。     

基于NB-IoT技术的土壤重金属检测仪设计与验证

为解决土壤重金属检测准确度较低、实时性差以及数据分散的问题,该研究设计了一种基于窄带物联网(NarrowBand Internet of Things,NB-IoT)技术的土壤重金属检测仪.自主研发高准确度能量色散X射线荧光光谱仪,将测量得到的数据通过NB-IoT实时上传到数据集成云平台.设计试验探究了该设备的最佳测试...     

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.     

Evolution of burrow systems after the accidental introduction of a new earthworm species into a Swiss pre-alpine meadow

 The unintentional introduction of a new earthworm species (Aporrectodea nocturna) into a Swiss pre-alpine meadow resulted in a great increase in earthworm density in the newly colonized area (386 m^–2) compared with the density observed in the natural area (273 m^–2) where an earthworm community was already present. To investigate the impact of this introduction on the burrow systems, eight soil cores (length 25 cm, diameter 16 cm) were taken (four in the colonized area and four in the natural area) and analysed with computer-assisted X-ray tomography. The resulting images were processed to obtain the 3D-skeleton reconstructions of the earthworm burrow systems. Due to high variability in these burrow systems, only slight differences were observed between the two areas. The total burrow length and the mean burrow lengths tended to be greater in the colonized area. Moreover, the distribution of pore numbers with depth showed different patterns with a maximum for depths between 10 cm and 15 cm in the colonized area and a maximum for depths between 20 cm and 25 cm in the natural area. These differences may have been related to: (1) the particular behaviour of A. nocturna, which was observed to cast at the surface in this site, and (2) the predominance of juvenile earthworms around the colonization front. These differences were sufficient to create significant effects on the continuity of the burrow systems (assessed by the number of different pathways between virtual horizontal planes) for the two areas. The colonized area was characterized by a greater pore continuity, which could have resulted in enhanced transfer properties. Received: 2 July 1999     

常见坚果壳的元素组成·纤维素含量和结晶度分析

[目的]对5种常见坚果壳的元素组成、纤维素含量和结晶度进行分析。[方法]采用X射线衍射技术按照高度法、切线法、分峰面积法3种方法对坚果壳中的纤维素的结晶度进行了分析,采用X射线光电子能谱技术对坚果壳的成分和原子比进行了分析。[结果]X射线衍射测试结果表明,板栗、花生、瓜子、夏威夷果和核桃皮层纤维素的结晶度不同,结晶度变化趋势相同;X射线光电子能谱测试结果表明,这5种坚果壳主要是由C、O、N、Si元素组成,成分含量有差异。夏威夷果壳的结晶度最大,板栗壳原料纤维素结晶度最小;花生中的氮元素含量最高,原子百分比达到3.78%,花生中的O/C和N/C比值最大,分别达到0.29和0.05,Si/C原子比最高的是花生壳。[结论]该研究结果可为硬果壳的综合开发利用提供依据。     

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.     

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.     

螺旋CT对大脑中动脉供血区超急性期脑梗死的诊断价值

目的探讨螺旋CT对大脑中动脉供血区超急性期脑梗死的诊断价值.方法对62例大脑中动脉供血区超急性期脑梗死（发病6 h内）的CT征象进行分析.结果大脑中动脉供血区脑梗死超急性期CT表现为MCA高密度征、点状征及豆状核边缘模糊,密度减低;岛叶密度减低,相应侧裂池变窄;颞叶灰质密度减低,脑沟变窄或消失,灰白质界限不清.结论螺旋CT对大脑中动脉供血区超急性期脑梗死有很高的诊断价值.     

Antioxidant profile of cataractous English Cocker Spaniels

Cataracts have been attributed to oxidative injury in proteins and lipids. Primary defenses that directly protect the lens against oxidative damage include small molecule antioxidants (vitamin C, vitamin E, glutathione and carotenoids) and antioxidant enzymes (superoxide dismutase, catalase, and the glutathione enzyme systems – glutathione peroxidase, glutathione reductase and glucose-6-phosphate dehydrogenase). In humans, low plasmatic levels of vitamin C, vitamin E and carotenoids have been associated with a high risk of senile cataracts. Dogs are more prone to develop cataracts. A decrease in antioxidant defenses could be responsible for increased lens oxidation and cataract development. In this study we report the levels of erythrocytic enzymatic antioxidants (superoxide dismutase, catalase, glutathione peroxidase and glucose-6-phosphate dehydrogenase) and plasma vitamin C as well as malondialdehyde, in normal and cataractous English Cocker Spaniel dogs. Plasma vitamin C levels were consistently lower in cataractous dogs (20.17 μ m  ± 8.2 μ m ) when compared with normal dogs (24.1 μ m  ± 9.4 μ m ). These results indicate a possibly decreased synthesis in vitamin C, leading to lower aqueous humor levels of this vitamin. Considering that vitamin C levels in the aqueous humor may be responsible for lens antioxidant maintenance, and that these levels are obtained from plasma secretion through the ciliary epithelium, decreased plasma levels may indicate a decrease in the antioxidant capacity of the aqueous humor.     

Immunohistochemical analysis of lens epithelial-derived membranes following cataract extraction in the dog

The objective of the study was to characterize the morphologic and immunohistochemical features of lens epithelial-derived proliferative membranes from the anterior segment of canine globes. These features were correlated with those previously identified for diseases resulting from lens epithelial cell (LEC) proliferation including posterior capsular opacification, traumatic subcapsular cataract, and subcapsular plaques associated with hypermature cataracts. Sixteen canine globes were removed as a result of glaucoma or other complications following cataract extraction. Light microscopic and immunohistochemical analysis was performed on sections from formalin-fixed, paraffin-embedded globes. The tissues were stained with a variety of antibodies for cellular markers for LECs, growth factors or other cellular constituents relevant to cellular metaplasia and proliferation. The membranes were composed of monolayers or multilayers of spindle-shaped cells on the external surfaces of the anterior and posterior lens capsule, ciliary processes, iris leaflets, and iridocorneal angle, and they could be seen extending from an obvious monolayer of LEC within the capsular sac. Variably, scattered pigment cells, presumably of uveal origin, were concurrently present. Cellular components of the membranes stained positive for vimentin, transforming growth factor-beta, basic fibroblast growth factor, and smooth muscle actin. An amorphous eosinophilic extracellular matrix consisting predominately of collagen was associated with the membranes. Proliferative anterior segment membranes following cataract surgery were morphologically and immunohistochemically similar to cellular and matrix components of posterior capsular opacification and capsular plaques seen with hypermature cataracts, both of which result from metaplasia and proliferation of LEC. The presence of these LEC-derived membranes in association with secondary glaucoma suggests that exuberant proliferation of LEC outside the confines of the lens capsular sac may cause pathologic alterations in the eye following cataract surgery in the dog.