Nanoadhesion of a Power-Law Graded Elastic Material

The Dugdale-Barenblatt model is used to analyze the adhesion of graded elastic materials at the nanoscale with Young's modulus E varying with depth z according to a power law E = E-0(z/c(0))(k) (0 < k < 1) while Poisson's ratio v remains a constant, where E-0 is a referenced Young's modulus, k is the gradient exponent and c(0) is a characteristic length describing the variation rate of Young's modulus. We show that, when the size of a rigid punch becomes smaller than a critical length, the adhesive interface between the punch and the graded material detaches due to rupture with uniform stresses, rather than by crack propagation with stress concentration. The critical length can be reduced to the one for isotropic elastic materials only if the gradient exponent k vanishes.

捷安肽素对采后柑桔青绿霉菌抑制效果及作用机理研究

捷安肽素是一种由枯草芽孢杆菌（Bacillus subtilis）ZK 产生的抗真菌多肽。本文以柑桔青霉菌（Penicillium italicum）和绿霉菌（Penicillium digitaum）为供试真菌，研究了捷安肽素的抑菌性能及作用机理，为捷安肽素开发为有效的生物杀菌剂提供理论依据。全文共分两部分：第一部分：捷安肽素对柑桔青霉菌和绿霉菌抑制效果研究。采用琼脂扩散法测定捷安肽素对柑桔青霉菌和绿霉菌的抑菌活性。53.9 µg/mL 捷安肽素对绿霉菌和青霉菌的抑菌圈直径分别为26.7mm 和24.1mm。结果表明捷安肽素能够抑制柑桔青绿霉菌的生长，柑桔绿霉菌比青霉菌对捷安肽素敏感。在柑桔果实上，研究了不同浓度、不同接入时间的捷安肽素对柑桔青霉病和绿霉病的防治效果，并与常用化学杀菌剂抑霉唑、咪鲜胺、甲基硫菌灵和多菌灵作比较。53.9 µg/mL捷安肽素处理柑桔果实，柑桔青霉病和绿霉病发病率分别为5.0 %和5.3 %,比对照低95.0 %和94.7 %；柑桔青霉病和绿霉病的病情指数分别为1.87 和2.18，比对照低73.73 和97.82。结果表明，捷安肽素能够有效地防治柑桔青绿霉病。与对照相比，捷安肽素先于或后于柑桔青绿霉菌接入时，对柑桔青绿霉菌均有抑制作用，但抑制效果随接入间隔时间的增长而降低。第二部分：捷安肽素对绿霉菌作用机理研究。首先在光学显微镜和透射电镜下观察捷安肽素处理后绿霉菌菌丝表面形态结构与菌丝体内超微结构的变化。形态观察发现，捷安肽素处理24h以内，绿霉菌菌丝结构无变化。捷安肽素作用36h后，绿霉菌菌丝不规则缢缩和膨大。48h后，在绿霉菌菌丝顶端、中部、末端的多处细胞均可发生畸形的球状结构，这种畸变结构随处理的延长而增加，致使细胞成为捻珠状。处理72 h后，畸变球形细胞开始断裂离解。处理96h后，镜下几乎无完整菌丝，成单个的球状细胞，部分细胞出现破裂。而对照菌丝表面光滑，结构完整。通过透射电镜观察发现，与对照相比，捷安肽素处理后，绿霉菌细胞壁、细胞膜轮廓模糊不清，细胞质外泄。推测捷安肽素能够使绿霉菌细胞膜通透性发生改变。进一步实验利用紫外-可见分光光度计检测捷安肽素作用后绿霉菌胞外液紫外吸光度的变化，表明捷安肽素作用于绿霉菌菌丝后，细胞内蛋白质、核酸缓慢泄漏。通过Atomscan Advantage单道扫描等离子体发射光谱仪(ICP)测定捷安肽素作用后菌丝体内K+浓度的改变，结果表明捷安肽素作用于柑桔绿霉菌1h内，菌丝体内K+含量迅速下降，为对照绿霉菌K+含量的37.53 %，1 h后菌丝体内K+含量变化趋于平缓。K+的迅速泄漏，以及蛋白质、核酸的泄漏表明捷安肽素通过迅速改变绿霉菌细胞膜通透性，使绿霉菌菌丝生长受到抑制。Jiean-peptide produced by Bacillus subtilis ZK has broad-spectrumresistance to plant pathogens. In this study, we investigated the antifungal propertyand the possible antifungal mechanism of jiean-peptide against two commonphytopathogenic fungi of citrus fruits: blue molds (P. italicum) and green molds (P.digitatum).The paper involved two parts:Part 1 is the study of the antifungal property of jiean-peptide against blue moldsand green molds of citrus fruits. The in vitro inhibition effect of jiean-peptide againstblue molds and green molds was detected by agar diffusion method. The diameters ofinhibition zones of green molds and blue molds are 26.7mm and 24.1mm respectivelyby treating with 53.9 µg/mL jiean-peptide. It shows that jiean-peptide effectivelyinhibits the both phytopathogenic fungi, and it is more effective for inhibiting greenmolds than blue molds. The effectiveness of jiean-peptde to inhibit green molds andblue molds in vivo was investigated compared with four conventional fungicides thatare imazalil, prochloraz, carbendazin and methylthiophanate. The result is that the incidences of the blue mold disease and green mold disease are 5.0 % and 5.3 %, thedisease severities are 1.87 and 2.18 respectively when citrus are inoculated with 53.9µg/ml jiean-peptide. The decay incidences and disease severities were significantlyreduced by treating with jiean-peptide compared with the control. The results indicateJiean-peptide is effective for controlling blue molds and green molds on citrus. Theoptimized inoculation time was also investigated. When inoculated with jiean-peptideat 0 h, 6 h, 12 h, 24 h and 48 h before or after pathogens’ inoculation, Jiean-peptidecan suppress the occurrence of blue molds and green molds compared with the control, but the effect of later inoculation decreases compared with the inoculation at the sametime.In Part 2, we investigated the possible antifungal mechanism against greenmolds of citrus. At first, we observed the exterior morphological changes andultrastructural changes of blue molds under light microscopy (LM) and transmissionelectron microscopy (TEM). Compared with untreated control cells which aregenerally uniform in shape, the appearances of treated hyphae change obviously. Itshows that some cells of hyphae irregularly shrink or enlarge when cultured for 36h.When the treating time of jiean-peptide increases, the aberrance of the hyphaebecomes more obvious, and hyphae exhibit the moniliform appearances. Finally, thereis no intact hypha leaved except only single cells, and some of which appear fractured.By transmission electron microscopy (TEM) observation, we find that the outline ofthe cell wall and the cell membrane of hyphae are blurry, and the cytoplasma oozesout. The observation result under LM and TEM suggests that jiean-peptide mightchange the permeability of the cell membrane. So we conducted further experiment todetect the change of permeability when the cells of blue molds were treated withjiean-peptide. And the effect of jiean-peptide on non-growing cells of blue molds wastested. By the spectrophotometer measurement, we found that compounds with lightabsorption at 260 nm and 280 nm were released and amounts increased within 12 hcompared with the control. Moreover, by the ICP measurement, the leakage of K+occurred immediately in the presence of jiean-peptide within 1 h, but with nearly nofurther change after 1 h. All these results indicate that jiean-peptide could change themembrane permeability of blue molds immediately and result in leaking nucleotides,proteins and K+ from cells.

Luminosity determination for the dd→αK+K-experiment atANKE/COSY

High resolution studies of a0/f0(980) decays into channels involving open strangeness are currently being performed at COSY-Jülich. As a “filter” for isospin-zero intermediate states, i.e. to selectively produce the f0(980) resonance, the dd→αK+K− reaction was measured with the magnetic ANKE spectrometer. In order to determine the luminosity of this experiment, the elastically and quasi-elastically scattered deuterons were recorded simultaneously with the αK+K− events. Here we report about the luminosity determination via investigating the (quasi-) elastic deuterons at ANKE.

Measurement of the isospin-filtering dd → 4He K+K- reaction at Q = 39 MeV

The total cross-section for the dd → 4HeK+K− reaction has been measured at a beam momentum of 3.7GeV/c, corresponding to an excess energy of 39MeV, which is the maximum possible atthe Cooler Synchrotron COSY-Jülich. A deuterium cluster-jet target and the ANKE forward magnetic spectrometer, placed inside the storage ring, have been employed in this investigation. We find a total cross-section of σtot < 14 pb, which brings into question the viability of investigating the dd → 4He a0(980)reaction as a means of studying isospin violation.

84.5MeV~(12)C~(4+)离子诱发金属靶原子发射的Kβ与Kα-X射线强度比值的研究

本实验是在中国科学院兰州近代物理研究所,国家实验室的重离子加速器上完成的.实验用OR-TEC公司生产的HPGe X射线探测器测量了84.5 MeV的12C4+离子轰击Cu,Mo,Ag,Cd,In,Sn,W和Au金属靶产生的K壳层特征X射线谱,计算了Kβ与Kα-X射线强度的比值,并将结果与Scofield用Hartree-Fock-Slater模型计算出的理论值与用其它方法(如:衰变幅射,用光子,电子,质子等粒子与靶相互作用)得到的实验值进行了比较.比较结果表明用84.5 MeV的12C4+离子轰击Cu,Mo,Ag,Cd,In,Sn,W和Au金属靶产生的Kβ与K-αX射线强度比值比理论值和其它实验值要大许多.

奇异核物质中K介子有效质量

在Schaffner相对论平均场模型的框架基础上,考虑同位旋矢量介子δ,扩展了强子动力学模型和单玻色子交换K介子-模型,重新讨论了介子与重子和介子与K介子相互作用的耦合常数,研究了奇异核物质中K介子的有效质量,发现在奇异核物质中K介子的有效质量随密度的变化比在纯核子物质中的变化小.同位旋矢量介子δ对在奇异核物质中K介子有效质量随密度变化有明显的影响,但对不同的参数组,其影响的大小不同.

在pA碰撞中K~±,η和ф介子的阈下产生

简要评述了在pA碰撞过程中K±,η和ф介子的阈下产生及其对应的物理含义。这些介子的阈下产生都可以在兰州CSR上实现,特别是通过pA碰撞实现ф介子的阈下产生还没有看到实验数据的报道。

中子星物质中的K介子凝聚与三体核力效应

利用BruecknerHartreeFock方法,计算了β稳定中子星物质的状态方程以及三体核力的影响,特别是研究了三体核力对中子星物质中K介子凝聚的影响.结果表明三体核力对β稳定中子星物质中出现K介子凝聚的临界密度以及中子星物质中各种粒子所占的比例均有重要影响.三体核力的主要作用是降低了中子星物质中出现K介子凝聚的临界密度并使K凝聚相中的核物质更加接近于对称核物质.

空心原子的K-x射线谱

报道了利用兰州重离子加速器国家实验室ECR离子源首次引出的全裸Ar离子和类氢、类氦、类锂Ar离子与Be固体表面相互作用形成的空心原子x射线实验测量结果 .结果发现 ,同样条件下 ,由于K壳层电子的剥离 ,Ar的K_x射线单离子发射产额增加了 5个量级 ,约为 3 6× 10 - 3每原子 ;而当L壳层存在电子时 ,Ar的K_x射线几乎观测不到

δ介子对确定K介子有效质量的影响

运用密度相关的平均场理论 ,分析了耦合常数随密度的变化及其对核子有效质量的影响 .尤其引入δ介子后 ,质子和中子的同位旋效应得到体现 ,使非对称核物质中质子和中子的有效质量出现差别 ,从而对标量密度产生影响 .利用含δ介子密度相关的相对论平均场理论 ,计算了在对称和非对称核物质中标量密度 ρS 和矢量密度 ρB 的关系 ,并由此研究了K介子有效质量随核物质密度的变化 ,分析了密度相关的耦合常数以及核物质非对称参数对K介子有效质量产生影响的大小 ,并与在耦合常数不依赖于核物质密度的情况下进行了比较 .

核物质中K介子有效质量与非线性效应

分析了核物质标量密度和矢量密度对K介子有效质量的影响.使用非线性σ ω ρ模型和相对论平均场理论,给出了核物质标量密度和矢量密度的近似关系曲线,并与线性σ ω模型的情况进行了比较.利用这一关系,改进了K介子有效质量和核物质密度之间存在的依赖关系,比较不同模型对K介子有效质量的影响.同时也计算了纯中子物质中K介子在不同模型下的有效质量曲线,并与在对称核物质中的情况进行了比较.

模型及其参数对确定K介子有效质量的影响

分别使用线性和非线性Walecka模型 ,讨论了重子标量密度 ρS 和矢量密度 ρB 的关系 .运用相对论平均场理论给出了不同模型下 ρS ρB 关系曲线 .利用这些结果 ,分析了模型和参数组对核物质中K介子有效质量影响的大小 ,得到了不同参数组下K介子有效质量随核物质密度的变化关系曲线 .同时计算了非对称核物质中K介子有效质量在不同模型和不同参数下的有效质量的曲线 ,并与对称核物质中的情况进行了比较 .

K-600中子发生器辐射防护的改进

目的　对K -60 0中子发生器原有的辐射防护做出评价 ,提出改进措施。方法　使用高灵敏度中子探测器和γ监测器 ,对中子发生器运行时n、γ辐射进行了全面的测量并对辐射场围周的防护设施进行改造。结果　改造前在中子厅西、南屏蔽墙外表面有贯穿辐射 ,特别是中子发生器建筑物项部表面有明显的贯穿辐射 ,并且在距离辐射源 3 0～ 40m处呈现峰值 ,显示出天空反射的效果。改造后辐射场外部周围贯穿辐射大为减弱。结论　通过改进措施达到了降低贯穿辐射的目的

核物质中K介子有效质量

分析了K介子在核物质中有效质量的变化受到核物质标量密度和矢量密度的双重影响,使用Walecka模型和相对论平均场理论,讨论了核物质标量密度与矢量密度的关系,利用这一关系改进了K介子有效质量和核物质密度之间存在的依赖关系。