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971.
972.
A. De Roeck J. Ellis F. Gianotti F. Moortgat K.A. Olive L. Pape 《The European Physical Journal C - Particles and Fields》2007,49(4):1041-1066
We motivate, propose and examine a new set of benchmark supersymmetric scenarios, some of which have non-universal Higgs scalar
masses (NUHM) and others have gravitino dark matter (GDM). The scalar masses in these proposed models are either considerably
larger or smaller than the narrow range allowed for the same gaugino mass m1/2 in the constrained MSSM (CMSSM) with universal scalar masses m0 and neutralino dark matter. Unlike the CMSSM, the proposed NUHM and GDM models with larger m0 may have large branching ratios for Higgs and/or Z production in the cascade decays of heavier sparticles, whose detection
we discuss. The novel phenomenology of the GDM models depends on the nature of the next-to-lightest supersymmetric particle
(NLSP), which has a lifetime exceeding 104 s in the proposed benchmark scenarios. In one GDM scenario the NLSP is the lightest neutralino χ, and the supersymmetric
collider signatures are similar to those in previous CMSSM benchmarks, but with a distinctive spectrum that would be challenging
for the LHC and ILC. In the other GDM scenarios based on minimal supergravity (mSUGRA), the NLSP is the lighter stau slepton
, with a lifetime between ∼104 and 3×106 s. Every supersymmetric cascade would end in a , which would have a distinctive time-of-flight signature. Slow-moving ’s might be trapped in a collider detector or outside it, and the preferred detection strategy would depend on the lifetime. We discuss the extent to which these mSUGRA GDM scenarios could be distinguished from gauge-mediated models. 相似文献
973.
Donald Alan Krogstad Gordon S. Ellis Andrew K. Gunderson Alyssa J. Hammrich Joseph W. Rudolf Jason A. Halfen 《Polyhedron》2007
Two water-soluble phosphines, 3,7-diformyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (1, DFPTA) and 1-pyridylmethyl-3,5-diaza-1-azonia-7-phosphatricyclo[3.3.1.1]decane bromide (2, [pymePTA]Br), have been respectively, prepared by reacting 1,3,5-triaza-7-phosphaadamantane (PTA) with formic anhydride and bromomethylpyridine. Compound 1 is only the second acyl derivative of PTA to be prepared while 2 is only the second derivative of PTA reported that contains an aromatic appendage. Both compounds were characterized by elemental analysis, FAB-MS, 1H, 13C, and 31P NMR spectroscopy, and single crystal X-ray diffraction. This analysis showed that the formamide groups of 1 were in an anti confirmation in solution but in a syn confirmation in the solid state. The solubilities of 1 and 2 were examined in common organic solvents and water. It was found that 1.1 M aqueous solutions of 1 could be prepared while 2.4 M solutions of 2 were produced. The greater solubility of 2 was likely due to its ionic nature. 相似文献
974.
Spectra of clusters formed between lithium atoms and methylamine molecules are reported for the first time. Mass-selective infrared spectra of Li(NH(2)CH(3))(n) have been recorded in both the N-H and C-H stretching fundamental regions. The infrared spectra are broadly in agreement with ab initio predictions, showing redshifted N-H stretching bands relative to free methylamine and a strong enhancement of the N-H stretching fundamentals relative to the C-H stretching fundamentals. The ab initio calculations suggest that, for n=3, the methylamine molecules bunch together on one side of the lithium atom to minimize repulsive interactions with the unpaired electron density. The addition of a fourth methylamine molecule results in closure of the inner solvation shell and, thus, Li(NH(2)CH(3))(5) is forced to adopt a two-shell coordination structure. This is consistent with neutron diffraction studies of concentrated lithium/methylamine solutions, which also suggest that the first solvation shell around the lithium atom can contain a maximum of four methylamine molecules. 相似文献
975.
Barybin MV Brennessel WW Kucera BE Minyaev ME Sussman VJ Young VG Ellis JE 《Journal of the American Chemical Society》2007,129(5):1141-1150
Treatment of [M(CO)(6)](-), M = Nb, Ta, with Ag(+), I(2) or NO(+) in the presence of CNXyl provided [M(CNXyl)(7)](+), M(CNXyl)(6)I, or cis-[M(CNXyl)(4)(NO)(2)](+), which are isocyanide analogues of the unknown carbonyl complexes [M(CO)(7)](+), M(CO)(6)I, or cis-[M(CO)(4)(NO)(2)](+), respectively. Reduction of M(CNXyl)(6)I by cesium graphite gave the respective Cs[M(CNXyl)(6)], which have been structurally characterized and represent the first isolable homoleptic isocyanidemetalates for second or third row transition metals. Nitrosylation of [Ta(CNXyl)(6)](-) affords a rare example of a mononitrosyl tantalum complex, Ta(CNXyl)(5)NO, which is an isocyanide analogue of the unknown Ta(CO)(5)NO. This study emphasizes, inter alia, the remarkable versatility of the CNXyl ligand compared to CO in stabilizing various electronic environments at heavier group 5 metal centers. 相似文献
976.
Tang JA Ellis BD Warren TH Hanna JV Macdonald CL Schurko RW 《Journal of the American Chemical Society》2007,129(43):13049-13065
Solid-state 63Cu and 65Cu NMR experiments have been conducted on a series of inorganic and organometallic copper(I) complexes possessing a variety of spherically asymmetric two-, three-, and four-coordinate Cu coordination environments. Variations in structure and symmetry, and corresponding changes in the electric field gradient (EFG) tensors, yield 63/65Cu quadrupolar coupling constants (CQ) ranging from 22.0 to 71.0 MHz for spherically asymmetric Cu sites. These large quadrupolar interactions result in spectra featuring quadrupolar-dominated central transition patterns with breadths ranging from 760 kHz to 6.7 MHz. Accordingly, Hahn-echo and/or QCPMG pulse sequences were applied in a frequency-stepped manner to rapidly acquire high S/N powder patterns. Significant copper chemical shielding anisotropies (CSAs) are also observed in some cases, ranging from 1000 to 1500 ppm. 31P CP/MAS NMR spectra for complexes featuring 63/65Cu-31P spin pairs exhibit residual dipolar coupling and are simulated to determine both the sign of CQ and the EFG tensor orientations relative to the Cu-P bond axes. X-ray crystallographic data and theoretical (Hartree-Fock and density functional theory) calculations of 63/65Cu EFG and CS tensors are utilized to examine the relationships between NMR interaction tensor parameters, the magnitudes and orientations of the principal components, and molecular structure and symmetry. 相似文献
977.
Cheran LE Cheung S Al Chawaf A Ellis JS Belsham DD MacKay WA Lovejoy D Thompson M 《The Analyst》2007,132(3):242-255
Kelvin and acoustic fields of high-frequency have been employed in the non-invasive investigation of immortalized hypothalamic neurons, in order to assess their response to different concentrations of specific drugs, toxins, a stress-reducing hormone and neurotrophic factors. In an analytical systems biology approach, this work constitutes a first study of living neuron cultures by scanning Kelvin nanoprobe (SKN) and thickness shear mode (TSM) acoustic wave techniques. N-38 hypothalamic mouse neurons were immobilized on the gold electrode of 9 MHz TSM acoustic wave devices and gold-coated slides for study by SKN. The neurons were exposed to the neurochemicals betaseron, forskolin, TCAP, and cerebrolysin. Signals were collected with the TSM in real-time mode, and with the SKN in scanning and real-time modes, as the drugs were applied at biologically significant concentrations. With the TSM, for all drugs, some frequency and resistance shifts were in the same direction, contrary to normal functioning for this type of instrument. Possible mechanisms are presented to explain this behaviour. An oscillatory signal with periodicity of approximately 2 min was observed for some neuron-coated surfaces, where the amplitude of these oscillations was altered upon application of certain neurotrophic factors. These two new techniques present novel and non-invasive electrodeless methods for detecting changes at the cellular level caused by a variety of neuroactive compounds, without killing or destroying the neurons. 相似文献
978.
Lopez ME Edie MJ Ellis D Horneber A Macgregor SA Rosair GM Welch AJ 《Chemical communications (Cambridge, England)》2007,(22):2243-2245
Symmetric 4,5,2,3-M(2)C(2)B(9) 13-vertex bimetallacarboranes of cobalt and ruthenium with 14 skeletal electron pairs are afforded by reduction and metallation of 3,1,2-MC(2)B(9) icosahedra; the symmetric species can be converted to their asymmetric 4,5,1,6-M(2)C(2)B(9) isomers by heat, but an easier route is by thermolysis of the reduced species before metallation. 相似文献
979.
Bailey KR Ellis AJ Reiss R Snape TJ Turner NJ 《Chemical communications (Cambridge, England)》2007,(35):3640-3642
A template-based mnemonic has been developed for the enzyme monoamine oxidase from Aspergillus niger and has been used to successfully identify the alkaloid (+/-)-crispine A as a target for chemo-enzymatic deracemisation yielding the biologically active (R)-enantiomer in 97% e.e. 相似文献
980.
Laser desorption/ionization mass spectrometry on porous silicon for metabolome analyses: influence of surface oxidation 总被引:1,自引:0,他引:1
Vaidyanathan S Jones D Ellis J Jenkins T Chong C Anderson M Goodacre R 《Rapid communications in mass spectrometry : RCM》2007,21(13):2157-2166
Laser desorption/ionization mass spectrometry (LDI-MS) on porous silicon is a promising analytical strategy for the rapid detection of metabolites in biological matrices. We show that both oxidized and unoxidized porous silicon surfaces are useful in detecting protonated/deprotonated molecules from compounds when analyzed in mixtures. We demonstrate the feasibility of using this technique for the simultaneous detection of multiple analytes using a synthetic cocktail of 30 compounds commonly associated with prokaryotic and eukaryotic primary metabolism. The predominantly detected species were the protonated molecules or their sodium/potassium adducts in the positive-ion mode and the deprotonated molecules in the negative-ion mode, as opposed to fragments or other adducts. Surface oxidation appears to influence mass spectral responses; in particular, in the mixture we studied, the signal intensities of the hydrophobic amino acids were noticeably reduced. We show that whilst quantitative changes in individual analytes can be detected, ion suppression effects interfere when analyte levels are altered significantly. However, the response of most analytes was relatively unaffected by changes in the concentration of one of the analytes, so long as it was not allowed to dominate the mixture, which may limit the dynamic range of this approach. The differences in the response of the analytes when analyzed in mixtures could not be accounted for by considering their gas-phase and aqueous basicities alone. The implications of these findings in using the technique for metabolome analyses are discussed. 相似文献