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71.
72.
This paper describes the development of a model for making project funding decisions at The National Cancer Institute (NCI). The American Stop Smoking Intervention Study (ASSIST) is a multiple-year, multiple-site demonstration project, aimed at reducing smoking prevalence. The initial request for ASSIST proposals was answered by about twice as many states as could be funded. Scientific peer review of the proposals was the primary criterion used for funding decisions. However, a modified Delphi process made explicit several criteria of secondary importance. A structured questionnaire identified the relative importance of these secondary criteria, some of which we incorporated into a composite preference function. We modeled the proposal funding decision as a zero-one program, and adjusted the preference function and available budget parametrically to generate many suitable outcomes. The actual funding decision, identified by our model, offers significant advantages over manually generated solutions found by experts at NCI. 相似文献
73.
Smoothed cross-validation 总被引:3,自引:0,他引:3
Summary For bandwidth selection of a kernel density estimator, a generalization of the widely studied least squares cross-validation method is considered. The essential idea is to do a particular type of presmoothing of the data. This is seen to be essentially the same as using the smoothed bootstrap estimate of the mean integrated squared error. Analysis reveals that a rather large amount of presmoothing yields excellent asymptotic performance. The rate of convergence to the optimum is known to be best possible under a wide range of smoothness conditions. The method is more appealing than other selectors with this property, because its motivation is not heavily dependent on precise asymptotic analysis, and because its form is simple and intuitive. Theory is also given for choice of the amount of presmoothing, and this is used to derive a data-based method for this choice.Research of the second author was done while on leave from the University of North Carolina. That of both the second and third was partially supported by National Science Foundation Grants DMS-8701201 and DMS-8902973 相似文献
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75.
Adams RD Miao S Smith MD Farach H Webster CE Manson J Hall MB 《Inorganic chemistry》2004,43(8):2515-2525
The reaction of Mn(2)(CO)(7)(mu-S(2)) with [CpNi(CO)](2) yielded the paramagnetic new compound Cp(2)Ni(2)Mn(CO)(3)(mu(3)-S)(2) (1) and a new hexanuclear metal product Cp(2)Ni(2)Mn(4)(CO)(14)(mu(6)-S(2))(mu(3)-S)(2) (2). Structurally, compound 1 contains two triply bridging sulfido ligands on opposite sides of an open Ni(2)Mn triangular cluster. EPR and temperature-dependent magnetic susceptibility measurements of 1 show that it contains one unpaired electron. The electronic structure of 1 was determined by Fenske-Hall molecular orbital calculations which show that the unpaired electron occupies a low lying antibonding orbital delocalized unequally across the three metal atoms. The selenium homologue Cp(2)Ni(2)Mn(CO)(3)(mu(3)-Se)(2) (3) was obtained from the reaction of a mixture of Mn(2)(CO)(10) and [CpNi(CO)](2) with elemental selenium and Me(3)NO.2H(2)O. It also has one unpaired electron. Compound 1 reacted with elemental sulfur to yield the dinickeldimanganese compound, Cp(2)Ni(2)Mn(2)(CO)(6)(mu(4)-S(2))(mu(4)-S(5)), 4, which can also be made from the reaction of Mn(2)(CO)(7)(mu-S(2)) with [CpNi(CO)](2) and sulfur. Compound 4 was converted back to 1 by sulfur abstraction using PPh(3). The reaction of Mn(2)(CO)(10) with [CpNi(CO)](2) in the presence of thiirane yielded the ethanedithiolato compound CpNiMn(CO)(3)(mu-SCH(2)CH(2)S) (5), which was also obtained from the reaction of Mn(4)(CO)(15)(mu(3)-S(2))(mu(4)-S(2)) with [CpNi(CO)](2) in the presence of thiirane. Compound 5 reacted with additional quantities of thiirane to yield the new compound CpNiMn(CO)(3)[mu-S(CH(2)CH(2)S)(2)], 6, which contains a 3-thiapentanedithiolato ligand that bridges the two metal atoms. Compound 6 was also obtained from the reaction of Mn(2)(CO)(10) with [CpNi(CO)](2) and thiirane. The molecular structures of the new compounds 1-6 were established by single-crystal X-ray diffraction analyses. 相似文献
76.
Hall RW 《The Journal of chemical physics》2005,122(16):164112
A kink-based path integral method, previously applied to atomic systems, is modified and used to study molecular systems. The method allows the simultaneous evolution of atomic and electronic degrees of freedom. The results for CH4, NH3, and H2O demonstrate this method to be accurate for both geometries and energies. A comparison with density functional theory (DFT) and second-order Moller-Plesset (MP2) level calculations show the path integral approach to produce energies in close agreement with MP2 energies and geometries in close agreement with both DFT and MP2 results. 相似文献
77.
Papadakis NG Xing D Huang CL Hall LD Carpenter TA 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,137(1):67-82
This study has investigated the effects of the selection of the diffusion-weighted (DW) gradient directions on the precision of a diffusion tensor imaging (DTI) experiment. The theoretical analysis provided a quantitative framework in which the noise performance of DTI schemes could be assessed objectively and for the development of novel DTI schemes, which employ multiple DW gradient directions. This generic framework was first applied to the examination of two commonly used DTI schemes, which employed 6 DW gradient directions and hitherto were used indiscriminately under the sole condition of noncollinearity. It was then used to design and assess a novel 12-DW-gradient-direction DTI protocol, which employed the same total number of DW acquisitions as the two conventional schemes (12). This theoretical investigation was then corroborated using rigorous simulation and DTI experiments on both an isotropic phantom and a healthy human brain. Both the theoretical and the experimental analysis demonstrated that the two conventional schemes showed a significantly different noise performance and that use of the new multiple-DW-gradient-direction scheme clearly improved the precision of the DTI measurements. 相似文献
78.
79.
Charles M. Hall 《合成通讯》2013,43(3):121-124
It has been known for many years that dihalocarbenes may be generated by the reaction of strong bases with haloforms and that the resulting dihalocarbenes react rapidly with alkenes to produce dihalocyclopropane derivatives.1 The procedures reported to date suffer from two disadvantages in that they require: 1) the use of a date solvent or the necessity of a two-phase system when a hydrocarbon solvent is used, and 2) the use of covalent nature and unique solubility properties of thallium (I) ethoxide suggested that its use might eliminate, or at least minimize, these diffculties in the generation of dichalocarbenes. 相似文献
80.
Hong Zhang Zuoquan Wang Ion Ghiviriga Girinath G. Pillai Farukh Jabeen Justin A. Arami Wenfeng Zhou Peter J. Steel C. Dennis Hall Alan R. Katritzky 《Tetrahedron letters》2017,58(12):1079-1085
Synthesis, characterization and energetic properties of novel, nitrogen-rich 1-methyl-1,2,4-triazolium N-aryl/N-pyridinyl ylids 3a–m are reported. 相似文献