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91.
A new method for generating group 3 metal complexes containing radical-anionic 2,2'-bipyridyl (bipy) ligands is described that relies on hydrogen-atom abstraction from dearomatized biheterocyclic complexes. This method does not involve electron transfer to neutral 2,2'-bipyridyl or salt metathesis between the lithium salt of the 2,2'-bipyridyl radical anion and group 3 metal halides. The new metal complexes were characterized by single-crystal X-ray diffraction, electron paramagnetic resonance, and absorption spectroscopy. Density functional theory (DFT) calculations were used to probe the electronic structure of these compounds. All these methods support the radical-anionic character of bipy in all bipy compounds presented. 相似文献
92.
Weichert K Carlson B Reinke H Krempner C 《Dalton transactions (Cambridge, England : 2003)》2010,39(48):11513-11515
The synthesis and structure of a dimeric aluminium hydroxide complex containing the novel chelating 1,4-disiloxide ligand [CH(2){Me(Me(3)Si)(2)Si}(2)SiO](2)(2-) (2)-2H is reported. [CH(2){Me(Me(3)Si)(2)Si}(2)SiO](2)AlOH (4) was prepared by careful hydrolysis of [CH(2){Me(Me(3)Si)(2)Si}(2)SiO](2)AlMe·THF (3). 相似文献
93.
Biechele TL Camp ND Fass DM Kulikauskas RM Robin NC White BD Taraska CM Moore EC Muster J Karmacharya R Haggarty SJ Chien AJ Moon RT 《Chemistry & biology》2010,17(11):1177-1182
To identify new protein and pharmacological regulators of Wnt/β-catenin signaling, we used a cell-based reporter assay to screen a collection of 1857 human-experienced compounds for their ability to enhance activation of the β-catenin reporter by a low concentration of WNT3A. This identified 44 unique compounds, including the FDA-approved drug riluzole, which is presently in clinical trials for treating melanoma. We found that treating melanoma cells with riluzole in?vitro enhances the ability of WNT3A to regulate gene expression, to promote pigmentation, and to decrease cell proliferation. Furthermore riluzole, like WNT3A, decreases metastases in a mouse melanoma model. Interestingly, siRNAs targeting the metabotropic glutamate receptor, GRM1, a reported indirect target of riluzole, enhance β-catenin signaling. The unexpected regulation of β-catenin signaling by both riluzole and GRM1 has implications for the future uses of this drug. 相似文献
94.
Schmidt B Mahmud G Soh S Kim SH Page T O'Halloran TV Grzybowski BA Hoffman BM 《Applied magnetic resonance》2011,40(4):415-425
Abstract
Rapid freeze-quench (RFQ) trapping of short-lived reaction intermediates for spectroscopic study plays an important role in the characterization of biological reactions. Recently, there has been considerable effort to achieve sub-millisecond reaction deadtimes. We present here a new, robust, high-velocity microfluidic mixer that enables such rapid freeze-quenching. It is a based on the mixing method of two impinging jets commonly used in reaction injection molding of plastics. This method achieves efficient mixing by inducing chaotic flow at relatively low Reynolds numbers (Re = 140). We present the first mathematical simulation and microscopic visualization of mixing in such RFQ micromixers, the results of which show that the impinging solutions efficiently mix within the mixing chamber. These tests, along with a practical demonstration in an RFQ setup that involves copper wheels, show that this new mixer can in practice provide reaction deadtimes as low as 100 μs. 相似文献95.
Sally McClean Jennifer Gillespie Lalit Garg Maria Barton Bryan Scotney Ken Kullerton 《European Journal of Operational Research》2014
Stroke disease places a heavy burden on society, incurring long periods of time in hospital and community care, and associated costs. Also stroke is a highly complex disease with diverse outcomes and multiple strategies for therapy and care. Previously a modeling framework has been developed which clusters patients into classes with respect to their length of stay (LOS) in hospital. Phase-type models were then used to describe patient flows for each cluster. Also multiple outcomes, such as discharge to normal residence, nursing home, or death can be permitted. We here add costs to this model and obtain the Moment Generating Function for the total cost of a system consisting of multiple transient phase-type classes with multiple absorbing states. This system represents different classes of patients in different hospital and community services states. Based on stroke patients’ data from the Belfast City Hospital, various scenarios are explored with a focus on comparing the cost of thrombolysis treatment under different regimes. The overall modeling framework characterizes the behavior of stroke patient populations, with a focus on integrated system-wide costing and planning, encompassing hospital and community services. Within this general framework we have developed models which take account of patient heterogeneity and multiple care options. Such complex strategies depend crucially on developing a deep engagement with the health care professionals and underpinning the models with detailed patient-specific data. 相似文献
96.
97.
Haiping Qi Manfred Gröning Tyler B. Coplen Bryan Buck Stanley J. Mroczkowski Willi A. Brand Heike Geilmann Matthias Gehre 《Rapid communications in mass spectrometry : RCM》2010,24(13):1821-1827
A new method to seal water in silver tubes for use in a TC/EA (thermal conversion/elemental analyzer) reduction unit using a semi‐automated sealing apparatus can yield reproducibilities (1 standard deviation) of δ2H and δ18O measurements of 1.0‰ and 0.06‰, respectively. These silver tubes containing reference waters may be preferred for the calibration of H‐ and O‐bearing materials analyzed with a TC/EA reduction unit. The new sealing apparatus employs a computer‐controlled stepping motor to produce silver tubes identical in length. The reproducibility of the mass of water sealed in tubes (in a range of 200–400 µg) can be as good as 1%. Approximately 99% of the sealed silver tubes are satisfactory (leak free). Although silver tubes sealed with reference waters are robust and can be shaken or heated to 110°C with no loss of integrity, they should not be frozen because the expansion during the phase transition of water to ice will break the cold seals and all the water will be lost. The tubes should be shipped in insulated containers. This new method eliminates air inclusions and isotopic fractionation of water associated with the loading of water into capsules using a syringe. The method is also more than an order of magnitude faster than preparing water samples in ordinary Ag capsules. Nevertheless, some laboratories may prefer loading water into silver capsules because expensive equipment is not needed, but users of this method are cautioned to apply the necessary corrections for evaporation, back exchange with laboratory atmospheric moisture, and blanks. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
98.
James Shaw-Stewart Bryan Chu Thomas Lippert Ylenia Maniglio Matthias Nagel Frank Nüesch Alexander Wokaun 《Applied Physics A: Materials Science & Processing》2011,105(3):713-722
Laser-induced forward transfer (LIFT) has been investigated for bilayer transfer material systems: silver/organic film (Alq3 or PFO). The LIFT process uses an intermediate dynamic release layer of a triazene polymer. This study focuses on the effect
of introducing a controlled donor–receiver substrate gap distance and the effect of doing the transfer at reduced air pressures,
whilst varying the fluence up to ∼200 mJ/cm2. The gap between ‘in-contact’ substrates has been measured to be a minimum of 2–3 μm. A linear variation in the gap width
from ‘in contact’ to 40 μm has been achieved by adding a spacer at one side of the substrate–substrate sandwich. At atmospheric
pressure, very little transfer is achieved for Alq3, although PFO shows some signs of successful doughnut transfer (with a large hole in the middle) in a narrow fluence range, at gaps greater than 20 μm. For the transfer of Ag/PFO
bilayers at atmospheric pressure, the addition of a PFO layer onto the receiver substrate improved the transfer enormously
at smaller gaps and higher fluences. However, the best transfer results were obtained at reduced pressures where a 100% transfer
success rate is obtained within a certain fluence window. The quality of the pixel morphology at less than 100 mbar is much
higher than at atmospheric pressure, particularly when the gap width is less than 20 μm. These results show the promise of
LIFT for industrial deposition processes where a gap between the substrates will improve the throughput. 相似文献
99.
Meng-Dawn Cheng Leslie KarrJohn Kornuc David StaatThomas Wainman Bryan HarreBarbara Sugiyama 《Microchemical Journal》2002,72(2):209-219
High levels of lead in some occupational environments still exist. These include lead paint abatement sites, smelting operations, small arms firing ranges, and other construction scenarios. New emerging technologies provide the capability to provide an on-site alternative to conventional laboratory methods for airborne lead. In this paper we describe the evaluation of two such technologies using laboratory prepared lead-laden super-micron aerosol particles. Size measurements by TSI Aerodynamic Particle Sizer™ indicated the fluctuation of the peak particle sizes varying less than 1% among different runs for a given solution concentration. The content of lead embedded in the particles varied from 14 to 18% between runs of three different lead solution concentrations. A commercially available instrument for airborne lead measurement, AeroLead™, showed promise of becoming fully validated with the addition of design enhancements, although not fully validated by the end of the research program. Some of these areas being reworked by the manufacturer include working electrode issues, such as a more uniform surface area. Once these have been addressed, the manufacturer plans to complete the field and laboratory validation procedures. In a subsequent study, the ABF-LIPS results shown in this paper indicated that the technology could be used to quantify lead in aerosol form with a signal-to-noise ratio of three or larger of approximately 100 μg m−3 or higher quantity in a few minutes of measurement interval. The estimated detection limit for Pb using the ABF-LIPS prototype was approximately 60 μg m−3. In comparison the Resource Conservation and Recovery Act (RCRA) limit for Pb emission is 250 μg m−3. 相似文献
100.
We discuss growth rates of Betti numbers in a family of coverings of a compact cell complex X, when the corresponding L2 Betti number of X is zero. We show that the Betti numbers are bounded by a function, sub-linear in the order of the covering. If the appropriate Novikov-Shubin invariant of X is positive, the rate bounds are improved. For well behaved families (such as congruence covers of symmetric spaces), if the L2 spectrum of X? has a gap at zero then the growth rate is bounded by the order of the covering raised to a power less than one. 相似文献