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171.
The effects of nitrogen and alkene substitution on the cycloisomerization of N-tethered 1,6-enynes into 3-azabicyclo[4.1.0]heptene precursors to the triple reuptake inhibitor GSK1360707 are described. In general, electron donating substituents proved beneficial both in terms of the reaction rate and chemoselectivity. 相似文献
172.
Syed R. HaiderBarry L. Sharp Helen J. Reid 《Trends in analytical chemistry : TRAC》2011,30(11):1793-1808
The on-line coupling of gel electrophoresis with inductively coupled plasma-mass spectrometry (GE-ICP-MS) is a powerful tool for simultaneous separation, detection and quantification of bio-molecules, and has been applied to the determination of phosphorus in DNA, phosphoproteins, and phosphopeptides, gold in nano-particles, iron in metalloproteins, and iodine in aerosols, and cisplatin-oligonucleotide interactions. However, since the first report in 2005, relatively few papers have been published, perhaps reflecting the lack of familiarity with the benefits of this promising methodology. So, here for the first time, we critically review the applications of GE-ICP-MS, and explore the advantages and the limitations of the technique for various applications. Such scrutiny may be useful in not only the development of the technique but also highlighting its potential in proteomics, genomics and metallomics. 相似文献
173.
Numerical modeling of surge overtopping of a levee 总被引:1,自引:0,他引:1
Levee protection/armoring is critical in flood fighting, and understanding the flow characteristics involved requires the evaluation of the overtopping processes with a variety of tools. The Adaptive Hydraulics Model (AdH) is used to calculate velocity and depth during an overtopping event. Using these values, the work explores the application of AdH for the estimation of associated shear stresses, so that appropriate measures are applied for protection to ultimately reduce the probability of levee failure during an overtopping event. Four different depths and three Manning’s n values were used for a total of twelve different test cases. Results show mean shear stress increases with increased surge depth and roughness. Additionally, the area of greatest shear stress is shown to be at the slope transitions from levee to berm. Values calculated in this effort should be considered in the design and implementation of levee protection. 相似文献
174.
Nathan D. Lowhorn W. Wong-Ng Z. Q. Lu E. Thomas M. Otani M. Green N. Dilley J. Sharp T. N. Tran 《Applied Physics A: Materials Science & Processing》2009,96(2):511-514
We have successfully developed a Seebeck coefficient Standard Reference Material (SRM™), Bi2Te3, that is crucial for inter-laboratory data comparison and for instrument calibration. Certification measurements were performed
using two different techniques on 10 samples randomly selected from a batch of 390 bars. The certified Seebeck coefficient
values are provided from 10 to 390 K. The availability of this SRM will validate the measurement accuracy, leading to a better
understanding of the structure/property relationships, and the underlying physics of new and improved thermoelectric materials.
An overview of the measurement techniques and data analysis is given. 相似文献
175.
N. G. Semaltianos S. Logothetidis W. Perrie S. Romani R. J. Potter M. Sharp P. French G. Dearden K. G. Watkins 《Applied Physics A: Materials Science & Processing》2009,94(3):641-647
Nanoparticles of the II–VI semiconductors CdTe, CdSe and ZnTe were synthesized by laser ablation (387 nm, 180 fs, 1 kHz, pulse
energy of 7 μJ (fluence of 2 J/cm2)) of the target materials in methanol, de-ionized water and acetone. The nanoparticles size distributions follow log-normal
functions with median diameters between about 6 and 11 nm for the several materials. The nanoparticles have the same crystalline
structure as that of the corresponding bulk material and under the present conditions of ablation are rich in the higher volatility
element of the two in the binary alloy and oxidized. Photoluminescence emission in the green-yellow (∼570 nm) was detected
from CdSe nanoparticles. 相似文献
176.
V. K. Ivanov G. P. Kopitsa A. Ye. Baranchikov M. Sharp K. Pranzas S. V. Grigoriev 《Russian Journal of Inorganic Chemistry》2009,54(14):2091-2106
By use of small angle and ultra small angle neutron scattering techniques it was established that amorphous xerogels of hydrous
zirconia and hafnia possess fractal properties in a wide range of scales, and the fractal dimension of these materials can
be intentionally modified by changing their precipitation pH. It was found that the changes in fractal dimension and specific
surface area of hydrous zirconia and hafnia xerogels are governed by the changes in the adsorption of anions onto their surface.
It was demonstrated that particle size and specific surface area of ZrO2 and HfO2 nanopowders prepared by thermal decomposition of hydrous zirconia and hafnia xerogels depends strongly on the mesostructure
and synthesis conditions of these xerogels. 相似文献
177.
Musicians often claim to be able to discern differences in the playing properties of musical wind instruments that have been manufactured in exactly the same way. These differences are most likely due to disparities in bore profile or in the positioning and sealing of any valves or side holes. In this paper, the suitability of acoustic pulse reflectometry and a capillary-based impedance measurement technique for detecting differences between instruments of the same model is explored through measurements on two low-cost, mass-produced trumpets. Differences in the measured bore profiles of the two instruments are reported, with the largest deviation caused by the presence of a leak in the third valve of one of the trumpets. Differences in input impedance measurements made on the two instruments are also noted, with the main cause shown to be the leaky valve. Controlled playing tests are carried out using the same two trumpets in order to evaluate the effectiveness of psychophysical testing in establishing whether there are perceptible differences in the playing properties of nominally identical wind instruments. A semi-professional musician is proved to be able to discriminate between the trumpets whereas an amateur player is shown to be unable to do the same. 相似文献
178.
Polymer based photonic structures were produced by spin coating up to 50 alternating layers of polystyrene (PS) and poly(vinylpyrrolidone)
(PVP) from mutually exclusive (orthogonal) solvents. The resulting thin film multi-layer structures were studied using a simple
optical reflectivity apparatus and were shown to have narrow (10-20nm wide) reflectance bands in the visible region. The position
of the reflectance bands was controlled by varying the spin speed used during production of the multi-layers and peak reflectance
values of 55% were obtained for samples containing 50 layers. The results were shown to be in agreement with modified optical
transfer matrix method calculations which include the effects of diffuse polymer interfaces. This modelling approach revealed
that the width of the polymer/polymer interfaces formed by spin coating was in the range 15-20nm. Data and calculations were
also obtained for chirped polymer photonic structures. These results were also shown to be in good agreement. These experiments
demonstrate that simple processing methods such as spin coating can be used to produce organic photonic structures with tailored
optical properties. 相似文献
179.
Sohaib Z. Khan Yudie Yuan Amin Abdolvand Marc Schmidt Philip Crouse Lin Li Zhu Liu Martin Sharp K. G. Watkins 《Journal of nanoparticle research》2009,11(6):1421-1427
Pulsed laser ablation in liquid (PLAL) has been widely applied for the generation of nanoparticles (NPs). We report on the
generation of NiO NPs using a high-power, high-brightness continuous wave (CW) fiber laser source at a wavelength of 1,070 nm.
Characterization of such NPs in terms of size distribution, shape, chemical composition, and phase structure was carried out
by transmission electron microscopy (TEM), high-resolution TEM equipped with energy-dispersive X-ray (EDX), and X-ray diffraction
(XRD). The results revealed the formation of NiO NPs in water with an average size of 12.6 nm. The addition of anionic surfactant
sodium dodecyl sulfate (SDS) reduced the size of NiO NPs down to 10.4 nm. The shape of the NPs was also affected by the SDS,
showing the change of shapes from spherical domination in water to tetragonal with increased SDS concentrations. Furthermore,
the NiO NPs generated in water and SDS solutions were dual phase containing both cubic and rhombohedral structures. It was
also found that the NiO NPs were single crystalline in nature irrespective of the size and shape. 相似文献
180.
Kendra V. Sharp David Hill Daniel Troolin Geoffrey Walters Wing Lai 《Experiments in fluids》2010,48(1):167-183
Volumetric three-component velocimetry measurements have been taken of the flow field near a Rushton turbine in a stirred
tank reactor. This particular flow field is highly unsteady and three-dimensional, and is characterized by a strong radial
jet, large tank-scale ring vortices, and small-scale blade tip vortices. The experimental technique uses a single camera head
with three apertures to obtain approximately 15,000 three-dimensional vectors in a cubic volume. These velocity data offer
the most comprehensive view to date of this flow field, especially since they are acquired at three Reynolds numbers (15,000,
107,000, and 137,000). Mean velocity fields and turbulent kinetic energy quantities are calculated. The volumetric nature
of the data enables tip vortex identification, vortex trajectory analysis, and calculation of vortex strength. Three identification
methods for the vortices are compared based on: the calculation of circumferential vorticity; the calculation of local pressure
minima via an eigenvalue approach; and the calculation of swirling strength again via an eigenvalue approach. The use of two-dimensional
data and three-dimensional data is compared for vortex identification; a ‘swirl strength’ criterion is less sensitive to completeness
of the velocity gradient tensor and overall provides clearer identification of the tip vortices. The principal components
of the strain rate tensor are also calculated for one Reynolds number case as these measures of stretching and compression
have recently been associated with tip vortex characterization. Vortex trajectories and strength compare favorably with those
in the literature. No clear dependence of trajectory on Reynolds number is deduced. The visualization of tip vortices up to
140° past blade passage in the highest Reynolds number case is notable and has not previously been shown. 相似文献