An Alternative Approach towards C-12 Functionalized Scalaranic Sesterterpenoids Synthesis of 17-Oxo-20-norscalaran-12α,19-O-lactone

Scalarane sesterterpenoids emerged as interesting bioactive natural products which were isolated extensively from marine sponges and shell-less mollusks. Some representatives were also reported recently from superior plants. Many scalarane sesterterpenoids displayed a wide spectrum of valuable properties, such as antifeedant, antimicrobial, antifungal, antitubercular, antitumor, anti-HIV properties, cytotoxicity and stimulation of nerve growth factor synthesis, as well as anti-inflammatory activity. Due to their important biological properties, many efforts have been undertaken towards the chemical synthesis of natural scalaranes. The main synthetic challenges are connected to their complex polycyclic framework, chiral centers and different functional groups, in particular the oxygenated functional groups at the C-12 position, which are prerequisites of the biological activity of many investigated scalaranes. The current work addresses this problem and the synthesis of 17-oxo-20-norscalaran-12α,19-O-lactone is described. It was performed via the 12α-hydroxy-ent-isocopal-13(14)-en-15-al obtained from (-)-sclareol as an accessible starting material. The tetracyclic lactone framework was built following an addition strategy, which includes the intramolecular Michael addition of a diterpenic acetoacetic ester and an intramolecular aldol condensation reaction as key synthetic steps. The structure and stereochemistry of the target compound have been proven by X-Ray diffraction method.     

Clonal and Within-tree Variation in Microfibril Angle in Poplar Clones

The microfibril angle (MFA) of seven poplar clones was determined using X-ray diffraction technique. MFA was measured for every growth ring at breast height (1.3 m) for all sample trees, and at 0 (butt), 5.6, 9.6, 13.6, 17.6, 19.6 and 21.6 m for clone I-69, Nanlin-95 and Nanlin-895. A total of 900 samples (chips) were assessed. Significant variation was observed among poplar clones and growth rings. Mean clonal MFAs at the breast height ranged from 15.2° to 21.0°. MFA at breast height varied from 7.8° to 28° between growth rings and showed a consistent pith-to-bark trend of declining angles. Disc-average microfibril angle in poplar clones declines rapidly from 0 to 5.6 m height, after which, it is near constant within tree height. Significant variation was also observed in disc-average MFA among tree heights. Correlation analysis showed that the correlation between MFAs from rings 5 to 11 at breast height was significant, while whole-tree values of each growth ring were significantly correlated with the corresponding MFA at breast height. The results of this study provide some basis for genetic selection of poplar trees based on wood-quality criteria and for devising appropriate sampling strategies for MFA measurement.     

基于软X射线成像技术的柑橘内部浮皮和枯水检测

针对传统方法无法高效、无损地对柑橘浮皮和枯水进行检测的问题,本研究自制了一套软X射线成像系统,包括载物传送装置、软X射线成像装置、触发装置和软X射线防护装置.本研究根据宽皮柑橘物理特性确定检测参数,以柑橘图像的清晰度、对比度、畸变率为评判标准,通过调节成像装置参数,确定了最佳的成像参数为:X射线源的管电压60 kV,管...     

基于软X射线成像的储粮害虫米象生长阶段检测

为了准确检测单粒小麦内部是否感染米象（Sitophilus oryzae）,利用软X射线成像检测技术对感染不同生长阶段米象的小麦颗粒进行成像,试图通过图像分析来确定小麦内部米象的幼虫、蛹和成虫等不同生长阶段,并利用随机重复来评价结果可靠性。通过对被感染米象虫卵不同天数小麦的图像分析发现,图像灰度分布直方图随感染天数变化明显,低灰度值区域（灰度值为10～102）的灰度区域像素点随感染天数增加而减少,中灰度（灰度值为103～162）和高灰度区域（灰度值为163～232)则随感染天数增加而增多。使用包括图像灰度分布和纹理特征等47个特征值,利用线性判别分析（Linear Discriminant Analysis,LDA）与二次判别分析（Quadratic Discriminant Analysis,QDA）建立判别模型,并通过多次随机重复抽样（1 000次）对模型预测效果进行评估分析。结果表明：在95% 置信区间下,在感染与未感染小麦的分类判别中,LDA的判别准确率都在76%以上,除幼虫外生长阶段判别正确率达到95%以上;而QDA的平均判别准确率较低且判别误差也相对较高。因此,该研究使用基于随机重复的LDA判别小麦是否受到米象感染和区分不同生长阶段是准确可靠的。     

基于邻差和的农产品X射线图像分割算法

针对图像阈值分割中二维灰度直方图和模态法的不足,提出了一种基于邻域差值之和与直方图凹面相结合的图像分割算法,并将此方法与二维直方图方法在板栗、苹果和猕猴桃的X射线图像分割中的效果进行了对比试验.试验结果表明,本方法的图像分割误差小于2.1％,最大分割误差仅是二维直方图简便算法分割误差的23.7％,能够更精确地提取果品的图像.     

团聚体大小分布对孔隙结构和土壤有机碳矿化的影响

土壤团聚体在外部和内部因素影响下发生团聚和破碎过程,形成不同大小分布的团聚体。团聚体大小分布的变化会改变土壤孔隙结构,影响各种土壤物理、化学和生物学过程,进而影响土壤有机碳(SOC)的周转。选择三种长期施用不同量有机肥的红壤(不施肥,CK;施低量有机肥,LM;施高量有机肥,HM),过不同大小孔径筛(5 mm,S₅;2 mm,S₂;0.5 mm,S_0.5)改变团聚体的大小分布,然后填装土柱(直径2.9 cm、高度4 cm),填装容重为1.3 g·cm^-3。利用X射线显微CT(Computed Tomography)成像技术分析土壤的孔隙结构,采用室内培养法测定土壤有机碳矿化量。结果表明,团聚体大小对孔隙结构有极显著的影响。相较于S₅和S₂处理,S_0.5处理土壤的大孔隙度(>16μm)降低了83.0%～93.9%,孔隙连通性降低了95%以上。而S₅和S₂处理的大孔隙度和孔隙连通性只在HM土...     

黄土高原旱地苹果园油菜间作对土壤大孔隙结构的影响

采用X-ray computed tomography(CT)技术研究了果树行间不同油菜间作密度(CK:清耕;L:低密度间作;M:中密度间作;H:高密度间作)对土壤大孔隙特征参数的影响。结果表明:油菜间作改善了果树行间(0—60 cm)土壤大孔隙特征,各土层的土壤大孔隙数量、大孔隙面积、大孔隙度等参数分别较清耕显著提高(P<0.05);不同间作密度对土壤大孔隙的作用不同,除10—20 cm外,中密度间作对土壤大孔隙度的改善效果均显著好于其他处理;中密度处理下大孔隙(d>1 mm)在各土层间的数目多、差异小,并且在0—30 cm土壤剖面上的成圆率最高。中、高密度油菜间作的土壤大孔隙特征参数均优于清耕及低密度间作,而中密度间作的土壤大孔隙分布更均匀、形状更规则,是黄土高原旱地苹果园改善土壤结构的适宜间作密度。     

不同浓度硒处理对彩叶草铅胁迫的EDXS和XRD分析

以彩叶草(Coleus blumei Benth.)为材料,用营养液培养方法,研究了不同浓度硒(Se)处理对浓度为1.0 mmol·L-1 Pb2+胁迫下彩叶草根、叶的形貌变化及其组分形态等变化,从光谱学角度初步探讨了硒对重金属铅毒害的缓解机制。结果表明:铅胁迫下的彩叶草根系C、K、Ca含量减少,O、Mg、Al、Si、Fe、Pb含量增加,叶片中的C、Mg、Al、Si、K、Ca、Fe含量减少,O、Cl含量增加。铅胁迫下硒处理的彩叶草根元素种类及其元素含量均发生了明显变化;根中晶体情况及其晶相也发生了相应变化。     

储粮害虫检测新技术及应用现状

储粮害虫的检测是粮食储藏部门的研究热点。害虫种类的正确识别是粮食管理人员进行害虫综合防治的必要依据。文章扼要评述了几种储粮害虫检测的新方法：声测法、近红外光谱法、X射线法、电导法、微波雷达检测法、图像识别法和电子鼻法,并展望了未来的发展趋势,为更好地进行储粮害虫检测提供了新思路。     

高精度便携式X射线荧光光谱仪在污染农田土壤重金属速测中的应用研究

针对便携式X射线荧光光谱(PXRF)法中的高精度便携式X射线荧光光谱(HDXRF)法进行检出限(Cd元素)、稳定性和土壤标准物质准确性的测试,同时对农田土壤中主要重金属元素Cu、Zn、Pb、Cd和类金属As进行快速测定,并将测定结果分别与原子吸收光谱(AAS)法、原子荧光光谱(AFS)法及电感耦合等离子体发射光谱(ICP-AES)法的测定结果建立线性回归方程,以期分析土壤粒径、水分、有机质及土壤类型对测定结果的影响。结果表明:HDXRF法测定土壤中重金属的稳定性高、准确度高、检测限低,对Cd元素的检测下限为0.27 mg·kg-1。颗粒粒径对土壤重金属浓度测定结果有一定影响,样品过100目筛时的测定结果较理想;土壤含水量对HDXRF法的测定结果影响较大,应保证测试土壤样品干燥;有机质对HDXRF法的测定结果存在影响,但可通过调整方程的常数进行校准。HDXRF法测定值更接近实验室ICP-AES法的测定结果,Cu、Zn、Pb和Cd的决定系数分别为0.997 5、0.996 7、0.961 4和0.995 4;HDXRF法与实验室AFS法测定As的决定系数最高可达0.979 8。相比于实验室测定方法,HDXRF法只需简单的前处理,如风干、研磨等,且HDXRF法测定范围宽,适用于土壤中重金属Cu、Zn、Pb、Cd和类金属As的快速测定,是一种简单、快速、准确、可靠的分析方法。