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81.
Weiss NG Hayes MA Garcia AA Ansari RR 《Langmuir : the ACS journal of surfaces and colloids》2011,27(1):494-498
A novel approach to molecular separations is investigated using a technique termed droplet-based isoelectric focusing. Drops are manipulated discretely on a superhydrophobic surface, subjected to low voltages for isoelectric focusing, and split-resulting in a preparative separation. A universal indicator dye demonstrates the generation of stable, reversible pH gradients (3-10) in ampholyte buffers, and these gradients lead to protein focusing within the drop length. Focusing was visually characterized, spectroscopically verified, and assessed quantitatively by noninvasive light scattering measurements. It was found to correlate with a quantitative model based on 1D steady-state theory. This work illustrates that molecular separations can be deployed within a single open drop, and the differential fractions can be separated into new discrete liquid elements. 相似文献
82.
Challinor VL Hayes PY Bernhardt PV Kitching W Lehmann RP De Voss JJ 《The Journal of organic chemistry》2011,76(17):7275-7280
The absolute stereochemistry of the steroidal saponins bethosides B and C was previously assigned as (22R,25R) on the basis of work that employed Horeau's method. Our studies of helosides A and B created doubt about both the original assignment and consequently our conclusion that relied upon it. The absolute configurations of bethosides B and C are revised to (22S,25R) following X-ray crystallographic analysis of their aglycone. Synthesis and full spectral characterization of both the 22R and 22S aglycones is reported to facilitate future stereochemical assignments in this series of saponins. 相似文献
83.
The bulk structure of the two oldest ionic liquids (ILs), ethylammonium nitrate (EAN) and ethanolammonium nitrate (EtAN), is elucidated using neutron diffraction. The spectra were modelled using empirical potential structure refinement (EPSR). The results demonstrate that EAN exhibits a long-range structure of solvophobic origin, similar to a bicontinuous microemulsion or disordered L(3)-sponge phase, but with a domain size of only 1 nm. The alcohol (-OH) moiety in EtAN interferes with solvophobic association between cation alkyl chains resulting in small clusters of ions, rather than an extended network. 相似文献
84.
Atkin R Borisenko N Drüschler M el-Abedin SZ Endres F Hayes R Huber B Roling B 《Physical chemistry chemical physics : PCCP》2011,13(15):6849-6857
The structure and dynamics of the interfacial layers between the extremely pure air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate and Au(111) has been investigated using in situ scanning tunneling microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and atomic force microscopy measurements. The in situ scanning tunnelling microscopy measurements reveal that the Au(111) surface undergoes a reconstruction, and at -1.2 V versus Pt quasi-reference the famous (22 × √3) herringbone superstructure is probed. Atomic force microscopy measurements show that multiple ion pair layers are present at the ionic liquid/Au interface which are dependent on the electrode potential. Upon applying cathodic electrode potentials, stronger ionic liquid near surface structure is detected: both the number of near surface layers and the force required to rupture these layers increases. The electrochemical impedance spectroscopy results reveal that three distinct processes take place at the interface. The fastest process is capacitive in its low-frequency limit and is identified with electrochemical double layer formation. The differential electrochemical double layer capacitance exhibits a local maximum at -0.2 V versus Pt quasi-reference, which is most likely caused by changes in the orientation of cations in the innermost layer. In the potential range between -0.84 V and -1.04 V, a second capacitive process is observed which is slower than electrochemical double layer formation. This process seems to be related to the herringbone reconstruction. In the frequency range below 1 Hz, the onset of an ultraslow faradaic process is found. This process becomes faster when the electrode potential is shifted to more negative potentials. 相似文献
85.
M. Hayes 《Journal of Elasticity》1997,49(3):285-288
A simple direct proof is given of the known result that in any deformation x = x(X), the planes of the central circular sections
of the material strain-ellipsoid at X are deformed into the planes of the spatial strain-ellipsoid at x.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
86.
87.
K.H. Chow Th. Jestädt S.J. Blundell S.R. Dunsiger W. Hayes B. Hitti M.A. Green R.F. Kiefl J.E. Millburn P.A. Pattenden F.L. Pratt M.J. Rosseinsky 《Hyperfine Interactions》1997,104(1-4):55-60
We report μSR measurements on a series of compounds with composition La2-xSrxNiO4+\delta where the net hole concentration x+2\delta is greater than 0.4. A magnetic transition is found in all the samples studied
which occurs at a composition‐dependent temperature TM. Below TM, clear precession signals are observed in zero applied magnetic field. The possible muon sites are discussed within the context
of dipole‐field calculations.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
89.
David R. Hayes 《Inventiones Mathematicae》1988,94(3):505-527
Partially supported by NSF grant DMS-8702716 相似文献
90.