Persistence of nonprotein seed amino acid s-(β-carboxyethyl)-cysteine in young leaves ofCalliandra rubescens Ecological implications

The insecticidal nonprotein amino acid S-(-carboxyethyl)-cysteine (S-CEC) is the major free amino acid in the seeds of severalCalliandra spp. where it accounts for up to 2.9 % of dry weight. Lesser amounts of other related S-containing amino acids and an array of nonprotein imino acids derived from pipecolic acid are other constituents. High concentrations of imino acids, which also show insecticidal activity, are maintained in the mature leaves, but sulfur compounds are lacking. In this study the disappearance of S-CEC from the germinating seeds and young seedlings ofC. rubescens was monitored over time. After 10 weeks, S-CEC continues to be found in high concentrations in the stems and new leaves. As young leaves mature, sulfur compounds quickly decrease in concentration. Traces of S-CEC are found in new leaves of plants up to nine months after germination. Whether high concentration of S-CEC in young leaves is due to transportation from the seed or de novo synthesis is unclear. The ecological implications are discussed.     

基于深度学习的恶意文档可视化检测

为了更加准确、快速地检测恶意PDF与DOCX格式文档,提出一种基于深度学习的恶意文档可视化检测方法。该方法通过马尔可夫模型将文档的字节序列转化为三通道的彩色图,从而获取更能区分恶意文档和良性文档的视觉表征,并采用当前主流的EfficientNet-B0模型对提取的可视化特征进行分类。结合迁移学习领域中的微调技术,将ImageNet上的分类权重应用到EfficientNet-B0模型的训练中,加快检测模型的收敛速度,缩短模型的训练时间。实验证明,在两个数据集上,模型的收敛速度快于随机初始化权重的预训练,且模型对恶意PDF文档和恶意DOCX文档的检测准确率分别达到了99.80%和98.14%,优于ResNet34、MobileNetV2等模型。与主流的恶意文档检测工具Wepawet和PJScan相比,所提出的方法具有更优的综合检测性能,进一步验证了所提出方法对恶意文档检测的有效性。     

Effects of allelochemicals on plant respiration and oxygen isotope fractionation by the alternative oxidase

The goal of this investigation was to determine the effects of allelochemicals on plant respiration that thereby may be responsible for their role in growth inhibition. We have tested the effects of juglone, quercetin, cinnamic acid, and-pinene on respiration rates, and electron partitioning through the cytochrome and alternative respiratory pathways, by measuring on-line oxygen consumption and oxygen isotope fractionation in soybean cotyledon tissue. Cinnamic acid and-pinene decreased the oxygen consumption rate and increased the relative partitioning of electron transport to the alternative pathway. Possible biochemical mechanisms of these effects are discussed.     

Al ionic radius influence on molecular dynamics simulations ofγ-Al2O3

Molecular dynamics (MD) simulations of-Al₂O₃, using a pairwise additive interaction potential of Pauling's type with four different radii for aluminum atoms, were analysed in order to determine the influence of the radius on the modification of coordination numbers of A1 relative to the ideal structure, at two different temperatures of 300 and 1500 K. It is found that the best choice is the radius of penta-coordinated aluminum, reproducing structural and vibrational properties of the compound in excellent agreement with experimentally observed properties.     

一个新的不耐热的伤寒沙门氏菌特异性抗原(θ)的发现

我们在研究伤寒沙门氏菌保护性抗原期间,发现了一个新的不耐热的伤寒沙门氏菌特异性抗原,暂时命名为θ抗原。这个抗原存在于各种类型的伤寒沙门氏菌中,并能从Ty2菌苗株细胞提取。以不吸收的抗θ兔血清作试管凝集时,与O90l和H901菌株的凝集效价分别为1:640和1:320。但与Ty2或9,12,Vi:d:-菌株不发生凝集,这一现象以后证实是由于Vi抗原的存在。θ抗原形成凝集较幔(31℃18～24小时),其所形成的凝集块疏松,易摇散、呈半絮状。菌体经100℃30分钟加热后与θ血清不发生凝集。玻片凝集试验显示θ血清与W和V型伤寒沙门氏菌(后者须培养在含酚培养基上)在1分钟内产生明显凝集。而与大多数D群(包括D_1和D_2)沙门氏菌和其他沙门氏菌不凝集,并与下列肠杆菌科细菌亦不凝集,包括志贺氏菌属A、B、C、D群,大肠艾希氏菌O:1～25和致病性大肠艾希氏菌12个不同的血清型,3株变形杆菌以及含有α抗原的Wakefield茵。化学分析显示,粗制θ提取物含有核酸(491μg/ml)。蛋白质(39μg/ml)和KDO(23μg/ml),但不含有O-乙酰基,表明θ抗原不同于Vi抗原。作者建议以θ血清替代现用的O:9,Vi和d因子血清作为伤寒沙门氏菌的血清学诊断。并需继续查明θ抗原的化学本质。     

月桂氮草酮研究进展

介绍了月桂氮草酮作为高效皮肤促渗剂的发展概况、合成工艺、研究进展及其应用前景。     

Nanocomposite route to the stabilization of porous ϑ-alumina

Stabilization of -alumina phase by silica was studied in nanocomposite (diphasic) alumina-silica gels by XRD and BET surface areas measurements. Five wt.% of silica (22 nm particles) increased the crystallization temperature of to -alumina by about 100°C from boehmite (10 nm particles) derived alumina. Stabilization of -alumina was caused by the formation of intimate contact (Al-O-Si) between components by diffusion of silica into the defect alumina structure.Also with the Department of Agronomy.     

Allelopathic Effects of Volatile Monoterpenoids Produced by <Emphasis Type="Italic">Salvia leucophylla</Emphasis>: Inhibition of Cell Proliferation and DNA Synthesis in the Root Apical Meristem of <Emphasis Type="Italic">Brassica campestris</Emphasis> Seedlings

Salvia leucophylla, a shrub observed in coastal south California, produces several volatile monoterpenoids (camphor, 1,8-cineole, -pinene, -pinene, and camphene) that potentially act as allelochemicals. The effects of these were examined using Brassica campestris as the test plant. Camphor, 1,8-cineole, and -pinene inhibited germination of B. campestris seeds at high concentrations, whereas -pinene and camphene did not. Root growth was inhibited by all five monoterpenoids in a dose-dependent manner, but hypocotyl growth was largely unaffected. The monoterpenoids did not alter the sizes of matured cells in either hypocotyls or roots, indicating that cell expansion is relatively insensitive to these compounds. They did not decrease the mitotic index in the shoot apical region, but specifically lowered mitotic index in the root apical meristem. Moreover, morphological and biochemical analyses on the incorporation of 5-bromo-2-deoxyuridine into DNA demonstrated that the monoterpenoids inhibit both cell-nuclear and organelle DNA synthesis in the root apical meristem. These results suggest that the monoterpenoids produced by S. leucophylla could interfere with the growth of other plants in its vicinity through inhibition of cell proliferation in the root apical meristem.     

“LOGO”在塑料机械中的应用

把可编程控制器“PLC”中“LOGO”集成块应用于塑料机械中,把可编程序输入到“LOGO”,来表达电器线路对塑料制品的记数和裁刀部分进行自动控制。     

Heterogeneous asymmetric reactions. 23. Enantioselective hydrogenation of ethyl pyruvate over cinchonine- and α-isocinchonine-modified platinum catalysts

The enantioselective hydrogenation of ethyl pyruvate to (S)-ethyl lactate over cinchonine- and -isocinchonine-modified Pt/Al₂O₃ catalysts was studied as a function of modifier concentration and reaction temperature. The maximum enantioselectivities obtained under the applied mild conditions were 89% ee using cinchonine (0.014 mmoldm^–3, 1 bar H₂, 23°C, 6% AcOH in toluene), and 76% ee in the case of -isocinchonine (0.14 mmoldm^–3, 1 bar H₂, –10°C, 6% AcOH in toluene). Since -isocinchonine of rigid structure exists only in anti-open conformation these data provide additional experimental evidence to support the former suggestion concerning the dominating role of anti-open conformation in these cinchona-modified enantioselective hydrogenations.