In nongravitational physics the local density of energy is often regarded as merely a bookkeeping device; only total energy has an experimental meaning—and it is only modulo a constant term. But in general relativity the local stress–energy tensor is the source term in Einstein's equation. In closed universes, and those with Kaluza–Klein dimensions, theoretical consistency demands that quantum vacuum energy should exist and have gravitational effects, although there are no boundary materials giving rise to that energy by van der Waals interactions. In the lab there are boundaries, and in general the energy density has a nonintegrable singularity as a boundary is approached (for idealized boundary conditions). As pointed out long ago by Candelas and Deutsch, in this situation there is doubt about the viability of the semiclassical Einstein equation. Our goal is to show that the divergences in the linearized Einstein equation can be renormalized to yield a plausible approximation to the finite theory that presumably exists for realistic boundary conditions. For a scalar field with Dirichlet or Neumann boundary conditions inside a rectangular parallelepiped, we have calculated by the method of images all components of the stress tensor, for all values of the conformal coupling parameter and an exponential ultraviolet cutoff parameter. The qualitative features of contributions from various classes of closed classical paths are noted. Then the Estrada–Kanwal distributional theory of asymptotics, particularly the moment expansion, is used to show that the linearized Einstein equation with the stress–energy near a plane boundary as source converges to a consistent theory when the cutoff is removed.

探讨SIOC-AA-005抗肿瘤的作用机制.采用测定HT-29 细胞线粒体膜流动性、线粒体ATP含量、线粒体ATP酶活性及NADH-CoQ氧化还原酶活性、细胞质膜NADH氧化酶活性的方法,对其作用机制进行了深入探讨;SIOC-AA-005在10 nmol/L剂量下可明显降低线粒体膜的流动性,并使线粒体膜电位显著升高;在此浓度下,SIOC-AA-005还可使HT-29细胞内的ATP耗竭,ATP酶活性受到抑制,线粒体中能量产生过程受阻.在胞外反应体系中,SIOC-AA-005对NADH-CoQ氧化还原酶有强烈的抑制作用,对细胞质膜NADH氧化酶也具有较强的抑制作用.SIOC-AA-005可能是通过抑制线粒体NADH-CoQ氧化还原酶、抑制细胞质膜NADH氧化酶以及线粒体ATP酶活性,从而使线粒体膜流动性下降,膜电位升高,细胞内ATP耗竭,最终使肿瘤细胞死亡.

A class of structurally simplified analogues of the naturally occurring annonaceous acetogenins were developed, amongst which some non-THF analogues showed remarkable cytotoxicities against tumor cell lines, as well as good selectivity between human tumor cells and normal cells. The synthetic routes were significantly shortened because of the removal of the chiral centers bearing the THF rings on the natural templates. This simplification also provides access to the parallel synthesis of these mimics by a combinatorial strategy. The remaining stereogenic centers at the positions alpha to the ethereal links were introduced by the Chiron approach from the easily accessible chiral building blocks 6a and/or 6b, made in turn from L-ascorbic acid or D-mannitol, while the one in the butenolide segment was taken from L-lactate. All four diastereomeric non-THF analogues 2a-2d showed remarkable activity against the HCT-8 cell line, and better differentiation was found when testing against the HT-29 cell line. It was also discovered that both the butenolide and ethylene glycol subunits play essential roles in the cytotoxicities against tumor cell lines, while the 10-substituted hydroxy group and the absolute configuration of methyl group at the butenolide moiety are less important for their activity.

AIMTo investigate the inhibitory effect of recombinant human endostatin (rhEndostatin) on endothelia cell proliferation and tumor growth.METHODSMTT assay was applied to examine the anti-proliferation of rhEndostatin on human embryo umbilical cord vascular endothelial cell ECV304 and human cancer cell HCT-8, BGC803 and EJ. Xenotrasplanted nude mice models with human cancer and experimental implanted tumor mice model were used to evaluate rhEndostatin's antitumor activity.RESULTSrhEndostatin was shown to inhibit the proliferation of ECV304 cells and the IC50 is about 7 x 10(-6) g.L-1. No inhibition was observed in HCT-8, BGC803 and EJ cells at 1 x 10(-4) g.L-1 rhEndostatin. rhEndostatin was shown to inhibit human xenograft in nude mice with human gastric cancer BGC803 and breast cancer B37 when administered subcutaneously at 5, 10, 20 mg.kg-1.d-1 for 24 days in a dose-dependent manner. Mouse hepatoma H22 was also suppressed when given rhEndostatin subcutaneously 20 mg.kg-1.d-1 for 9 days, but it showed no inhibitory effect on Lewis lung carcinoma and B16 melanoma.CONCLUSIONThese results indicate that rhEndostatin can inhibit the growth of xenotransplanted human tumors in nude mice and certain murine tumor. The action mechanisms may be that it can inhibit endothelial cell proliferation, thereby inhibiting the formation of new blood vessel in tumor, leading the tumor to stop grow.

The (4R)-hydroxylated analogues of annonaceous acetogenin mimicking compound 2 were designed and synthesized structurally on the basis of the naturally occurring annonaceous acetogenin bullatacin, which was discovered as a typical member of the novel family of polyketides with potent cytotoxicity, antitumoral, and other biological activities. The preliminary screenings show that the IC50 values of 2 were 1.6 x 10(-3) and 8 x 10(-2) mug/mL against HT-29 and HCT-8, respectively. A remarkable enhancement effect was observed by the activity comparison of 1c and its (4R)hydroxylated analogue 2.

Much work has been done in the last few years on various aspects of automated map generalization. However, many of these efforts have been directed to the generalization of individual objects - houses, roads, etc. - while ignoring the spatial relationships between the objects themselves. This problem is particularly apparent where map generalization includes the simplification of contour lines (which may overlap as a result, if no spatial relationships are preserved), or the question of preserving the relationships between different linear features (roads, rivers, railways) that must be cartographically displayed (even if displaced) in the smaller-scale maps after generalization. We here propose a new generalization method based on the medial axis transform, or skeleton. This new technique, as opposed to other traditional generalization methods, has the advantage of preserving the topological structure of the object, which eliminates any risk of overlapping of neighbouring objects. It is thus especially appropriate for the generalization of contour lines, among other things, where there may be high density and proximity of linear elements.