Influence of the geometry on the pressure distribution of granular heaps

We investigate the effect of the geometry of granular heaps on the pressure distribution. For given pressure distributions under cones we compute the pressure distribution under wedges using linear superposition. For cones with a pressure minimum, the pressure minimum for the corresponding wedge vanishes. Comparisons with experimental data gives good qualitative aggreement, but the total pressure is overestimated.     

drupa 2004展示印刷的前景

被誉为全球印刷业界“奥林匹克”盛会的drupa 2004国际印刷媒体、出版和纸品加工展览会将于今年5月6日在德国杜塞尔多夫展览中心拉开帷幕。据有关方面预计,届时我国印刷及设备器材行业将有5000余人前往参观。即使是没有机会亲临现场的业内人士,也无疑会对这一盛会给予极大的关注。为了使国内印刷业同仁能够在展会开幕前就对本届drupa展会有更好的了解,本刊于本期推出了“drupa观展指南”专题。本专题由二部分组成,前一部分是10篇国外印刷界专家撰写的文章,从各不同角度介绍和分析了当前印刷业各相关技术的发展趋势,也提示参观者在展会上看什么,怎么看?本专题的后一部分是国内外的一些知名参展商将在展会上推出的热点产品;穿插在专题当中的还有与本届展览相关的各种信息,可供参观人员参考。愿本专题能为即将赴德参观drupa2004的人士以及虽然不能亲临展会现场但密切关注drupa2004的本刊广大读者提供有益的帮助。这即是本刊编辑这一专题的初衷。     

Compatibility and molecular structure of rubbers

Compatibility of 17 pairs of rubbers has been investigated by means of phase separation, glass transition measurements and electron microscopy. Influence of structural details like side chains, configuration of monomer units and distance between double bonds in the chain on the compatibility of polymers has been elucidated. Experimental data lead to following results: Side chains have the strongest influence on compatibility; poly(isobutene) and poly(pentenamer), e.g., are highly incompatible. With decreasing influence on compatibility follows the configuration of the double bond in the polymer chain. Polymers with equal configuration are more compatible than polymers with different configuration. The structural detail with the weakest influence on compatibility is the distance between double bonds along the polymer chain. Poly(octenamer) and poly(pentenamer), e.g., with 6 and 3 methylene groups between the double bonds are less compatible than poly(butadiene) and poly(pentenamer) with a distance of 2 and 3 methylene groups. Cis-poly(pentenamer) and natural rubber were found to be highly compatible although electron micrographs show domains with an average diameter of 50 Å.     

Expression of the retinoblastoma tumor suppressor gene (RB-1) in acute leukemia

In this report we review current studies concerning the RB-1 gene expression in acute leukemias. The RB-1 gene was analyzed in several studies by protein-, RNA and DNA-techniques in acute lymphoblastic leukemia (ALL) as well as in acute myelogenous leukemia (AML). The frequency of RB-1 inactivation in ALL-patients ranged between 30% and 64% in several studies. Structural abnormalities of the RB-1 gene were reported in 18% of ALL-patients and in 27% of Philadelphia chromosome-positive ALL, respectively. The proportion of AML-patients with absent RB-1 protein expression ranged between 19% and 55%. Structural RB-1-abnormalities in AML were predominantly reported in leukemias with monocytic differentiation. Furthermore, the prognostic value of an abnormal RB-1 gene expression was also estimated in some studies. In childhood ALL RB-1 inactivation was reported to have prognostic significance while in contrast, in another study on adults no prognostic value of RB-1 was found. In 4 out of 5 documented studies AML-patients with RB-1 inactivation generally had a poorer prognosis. In conclusion, RB-1 inactivation is frequently observed in acute leukemia. The prognostic value of low RB-1 expression is controversial but the majority of published studies found low RB-1 expression to be a negative prognostic predictor, in acute leukemia.     

Carnocin U149, a potential biopreservative produced by Carnobacterium piscicola: large scale purification and activity against various Gram-positive bacteria including Listeria sp.

This paper describes a simple purification method for the purification of carnocin U149, a potential biopreservative produced by Carnobacterium piscicola U149. The protocol was also applicable for the isolation of nisin Z, which is a biopreservative produced by Lactococcus lactis SIK-83. The protocol consists of only two purification steps, XAD chromatography and cation exhange chromatography. It is quick, easy, and can be used for large scale purification of these lantibiotics. The bactericidal activity of carnocin U149 against carnobacteria, lactococci and Listeria was compared with that of nisin Z. The carnobacteria showed similar sensitivity towards carnocin U149 and nisin. The nisin producing L. lactis strains were very sensitive towards carnocin U149, while the non-producing L. lactis strains were more sensitive to nisin. The Listeria strains were weakly sensitive to carnocin U149, lower concentrations of nisin were needed to inhibit growth.     

On the simulation of molded micro components and systems

Regarding micro components and systems, experimental work for characterizing materials’ properties as well as components’ and systems’ behaviors have to be supplemented by numerical analyses. These analyses should cover component and system issues. On a component level, macroscopic approaches are extended by methods allowing consideration of the influence of components’ grain structures including possible defects. On a system level, the high tolerances accepted for the individual components due to production inaccuracy and their effects on the expected load distribution capability of the system are taken into account. This paper presents approaches for simulation of micro components and systems using the finite element method and multi body simulation. Methods to overcome the abovementioned issues will be shown, as well as the effects of grain structure on the stress distribution in the individual components.