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121.
We discuss and formulate the correct equivariant generalization of the strong Novikov conjecture. This will be the statement that certain G-equivariant higher signatures (living in suitable equivariant K-groups) are invariant under G-maps of manifolds which, nonequivariantly, are homotopy equivalences preserving orientation. We prove this conjecture for manifolds modeled on a complete Riemannian manifold of nonpositive curvature on which G (a compact Lie group) acts by isometries. We also use the theory of harmonic maps to construct (in some cases) G-maps into such model spaces.Dedicated to Alexander GrothendieckPartially supported by NSF Grants DMS 84-00900 and 87-00551.Partially supported by NSF Grant DMS 86-02980, a Presidential Young Investigator Award, and a Sloan Foundation Fellowship. 相似文献
122.
R. J. Rosenberg A. -M. Forsbacka N. Gras 《Journal of Radioanalytical and Nuclear Chemistry》1991,152(1):117-126
The separation of metallic impurities from uranium by anion exchange with a Dowex 1×8 resin has been investigated. The following elements can be quantitatively separated from 400 mg uranium using a 1 cm diameter 15 or 30 cm long column. The elements Ag, Al, Ba, Ca, Cr, Cs, K, Mg, Mn, Na, Ni, Rb, REE, Sc, Th, Ti and Y can be separated by eluting the elements with conc. HCl. Uranium is retained by the resin. Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Na, REE and V can be separated by eluting with 0.01 N H2SO4. Uranium is retained by the resin. Cd and Zn can be separated by first eluting uranium with 0.5 N HCl and then eluting Cd and Zn with 1 N NH3. Hf, Zr and V can be separated by eluting with 5 N HCl but some uranium contamination is unavoidable. 相似文献
123.
Tahmina Akter Daniel T. Haworth Shariff E. Kabir Nitai C. Sarker Edward Rosenberg 《Journal of organometallic chemistry》2004,689(16):2571-2580
Treatment of [Os3(CO)7(μ3-S)2(μ-dppm)] (1) with Me3NO in toluene at 80 °C affords the trinuclear cluster [Os3(CO)6(μ3-S)2(NMe3)(μ-dppm)] (2) and the hexanuclear cluster [Os6(CO)12(μ3-S)4(μ-dppm)2] (3) in 30% and 51% yields, respectively. The reaction of 1 with [Os3(CO)10(MeCN)2] in refluxing benzene at 80 °C gives the hexanuclear cluster [Os6(CO)14(μ3-S)2(μ-dppm)] (4) in 15% yield. Compound 2 reacts with CO, PPh3 and P(OMe)3 at room temperature to give 1, [Os3(CO)6(μ3-S)2(μ-dppm)(PPh3)] (5) and [Os3(CO)6(μ3-S)2(μ-dppm){P(OMe)3}] (6), respectively; in high yields indicating that the NMe3 ligand is weakly bound. Compound 1 reacts with PPh3 in presence of Me3NO to afford 5, 2 and 3 in 53%, 6% and 18% yields, respectively, whereas with P(OMe)31 gives only 6 in 84% yield. Compound 3 reacts with CO at 98 °C to regenerate 1 by the cleavage of the three unsupported osmium-osmium bonds. The molecular structures of 4 and 6 have been unambiguously determined by single crystal X-ray diffraction studies. The hexanuclear compound 3 appears to be a64-electron butterfly core with four triply bridging sulfido ligands and two bridging dppm ligands based on the spectroscopic and analytical data. The metal core of 4 can be described as a central tetrahedral array capped on two faces with two additional osmium atoms. The triply bridging sulfido ligands face cap the two tetrahedral arrays formed by metal capping of the two faces of the central tetrahedron. The dppm ligand bridges one edge of one of the external tetrahedral arrays. Compounds 5 and 6 are formed by the displacement of equatorial carbonyl group of 1 by a PPh3 and P(OMe)3 ligand respectively and their structures are comparable to that of 1. 相似文献
124.
The reason for the compound-dependent over-estimation of the recoveries of several volatile organic sulfur compounds when using a Silcosteel cylinder for sample storage as reported earlier was examined. From the different possible sources of errors that were taken into consideration, the silicone tubing, which was used to fill a standard Tedlar sample bag for calibration, was identified as the cause of the artefact. The comparison of different tubing materials showed that PTFE is the best choice since it causes only minor losses (<10%) of propyl- and butylmercaptans. 相似文献
125.
Determination of occupational exposure to toluene diisocyanate by biological monitoring 总被引:2,自引:0,他引:2
Exposure of workers to toluene diisocyanate monomer in a factory producing flexible polyurethane was measured using impinger and reagent-impregnated filter sampling. These techniques yielded highly concordant results so that the facile filter techniques can be recommended. The personal exposures were compared with the individual excretion of amine metabolites from the parent toluene diisocyanates. The excretion was linearly related to the product of sampling time and concentration. The biological half-lives of the amines proved to be short so that urine should be sampled 2 h after the exposure. The percutaneous absorption of the monomers could also be controlled. 相似文献
126.
Shariff E. Kabir Tasneem A. Siddiquee Edward Rosenberg Ryan Smith Michael B. Hursthouse K. M. Abdul Malik Kenneth I. Hardcastle Mandana Visi 《Journal of Cluster Science》1998,9(2):185-199
The reactions of [Ru3(CO)10(μ-dppm)] 4 with quinolines afforded [Ru3 (μ-CO)(CO)7{μ3-η2-P(C6H5)CH2P(C6H5)2)}{μ-η2-C9H5(R)N}] (8, R = 4-Me; 9, R = H) as the major products along with small amounts of known compound [Ru3(CO)9{μ3-η3-P(C6H5)CH2P(C6H5)(C6H4)}] 5. The molecular structure of 8 has been determined by single crystal X-ray studies. The reaction of 5 with 4-methylquinoline in refluxing cyclohexane afforded 8 and two known dinuclear compounds, [Ru2(CO)6{μ-CH2P(C6H5)(C6H4)P(C6H5}] 10 and [Ru2(CO)6 {μ-(C6H4)P(C6H5)(CH2)P(C6H5}] 11, in 40, 12, and 10% yields, respectively. The compounds 10 and 11 are also formed from the thermolysis of 4 in addition to the major compound 5. The solid state structure of the previously reported [Ru3(CO)10(η-H){μ-η2-C9H6N}] 2a is also reported for comparison. 相似文献
127.
E. Rosenberg 《Mathematical Methods of Operations Research》1989,33(2):131-143
Floorplanning is the VLSI design problem of deciding the position and shapes of all modules (e.g., memory or random logic) in order to minimize the chip area and satisfy all constraints. The modules may not be fixed in shape — the ratio of height to width may be modified in order to achieve minimal chip area. In the CADRE (AT&T) and Planar Package Planner (IBM) floorplanning systems, relative positions of the modules are specified by a relative position graph. Given the relative positions, a heuristic attempts to determine the optimal shape of each module, subject to the relative orientations dictated by the graph and also interconnection requirements, to minimize the chip area. In CADRE, the heuristics iterate between improving horizontal and vertical module dimensions; the IBM system uses a Simplex-method based heuristic. These heuristics are not guaranteed to solve the problem exactly. Consequently, it is not known how far the heuristic solution is from optimal, and it is not obvious when to terminate the heuristic. In this paper we show that, given the relative positions, we can compute theprovably optimal shape of each module, by transforming the problem into a convex nonlinear programming problem. Each local minimum of such a problem must also be a global minimum. We illustrate the method by applying it to an example solved by IBM. 相似文献
128.
129.
Ford WT Qi N Read AL Smith JG Camporesi T De Sangro R Peruzzi I Piccolo M Hurst RB Pyrlik J Venuti JP Weinstein R Gettner MW Goderre GP Sleeman JC von Goeler E Chadwick GB Leedy RE Messner RL Moss LJ Muller F Nelson HN Ritson DM Rosenberg LJ Wiser DE Zdarko RW Groom DE Verdini PG Band HR Delfino MC Johnson JR Lavine TL Maruyama T Prepost R 《Physical review D: Particles and fields》1989,40(5):1385-1396
130.
Schubert P Rosenberg E Grasserbauer M 《Fresenius' Journal of Analytical Chemistry》2000,366(4):356-360
The influence of pH on the propylation with sodium tetra(n-propyl)borate of butyl- and phenyltins as well as for trimethyl- and triethyllead was investigated. Ethylation and propylation with tetraalkylborates were compared with regard to derivatization yields and figures of merit for organotin compounds in real water samples. Similar results for limit of detection (3-12 ng/L as tin), derivatization yield (40-100%) and relative standard deviation of the method (3-10%) were achieved for derivatization with the two tetraalkylborates. Propylation is thus the preferred method for the simultaneous determination of environmentally relevant organotin and organolead compounds. The handling of the hygroscopic and air sensitive reagents NaBEt4 and NaBPr4 was simplified by dissolving them in tetrahydrofurane. The reagent solutions in tetrahydrofurane can be stored for at least one month at 4 degrees C in the dark without observing any decrease in the derivatization efficiency. 相似文献