The fundamental (Δv = 1 ← 0) and the first overtone (Δv = 2 ← 0) transitions of monolayer physisorbed CO on NaCl(100) single crystal surfaces at 5 K have been investigated using polarized Fourier transform infrared spectroscopy. Comparisons of the transition frequencies, bandwidths and absorbances for these two transitions together with those of dilute isotopes allow us to isolate the contribution of dynamic and static coupling effects of molecules within the monolayer. Homogeneous and heterogeneous effects can also be distinguished from band profiles of these various transitions. We conclude that the residual line broadening of 0.1 cm?1 at 5 K for the isolated CO isotopes arises from heterogeneous surface effects. We set an upper limit of 0.07 cm?1 for the linewidth of single CO molecules on NaCl(lOO) due to surface heterogeneity. A lower limit of × 10?8 cm?1 is provided by the vibrational lifetime of adsorbed CO molecules. Sharpness of the vibrational features shows that infrared spectroscopy of adsorbate is a sensitive method for probing surface and adlayer irregularities of adsorbed molecules on a single crystal. 相似文献
Capillary electrophoresis in 770 nanometer inner diameter capillaries coupled to electrochemical detection with an etched electrode matching an etched capillary (etched electrochemical detection) has been used with ultrasmall sampling to inject subcellular samples from intact single mammalian cells. Separations of cytoplasmic samples taken from rat pheochromocytoma cells have been achieved. As little as 8% of the total volume of a single cell has been sampled and analyzed. Dopamine has been identified and quantified in these PC12 cells using this technique. The average cytoplasmic level of dopamine in rat pheochromocytoma cells has been determined to be 240 ± 60 μM. The use of electrophoresis in 770 nanometer inner diameter capillaries with electrochemical detection to monitor cytoplasmic neurotransmitters at the single cell level can provide information about complex cellular functions such as neurotransmitter storage and synthesis. 相似文献
The combination of o-phenylenediamine and 3-methylglutaric anhydride in xylene as solvent produces a complex mixture of products. Isolation and characterization of four products from this reaction has shed some light on the mechanism by which 4-(2-benzimidazolyl)-3-methylbutyric acid ( 1 ) is formed under these reaction conditions. 相似文献
Structure behavior of actinide brannerites ThTi2O6, Y0.5U0.5Ti1.5Nb0.5O6 and their analog oxide CeTi2O6 was studied at high pressure by using in situ x-ray diffraction, Raman scattering and infra-red absorption techniques, respectively. Brannerite structure was found to be not stable and started to become amorphous at pressures above 20 GPa. Some minor crystalline phase(s) due to phase decomposition was observed in all the three samples during pressurization. In addition, the observed bulk modulus indicated that the actinide-bearing brannerites are more compressible than their analog compound CeTi2O6, which may be related to the asymmetric 5f electron orbits of actinide elements. 相似文献
A mild process for the conversion of pyridones to the corresponding pyridines by palladium catalyzed ammonium formate hydrogenolysis of their (1-phenyltetrazol-2-yl) ethers is described. 相似文献
We have amperometrically measured dopamine release from rat pheochromocytoma cells (PC12 cells) in high osmolarity conditions with and without L ‐3,4‐dihydroxyphenylalanine (L ‐DOPA) treatment. We observe an increase in the number of release events displaying a prespike feature or “foot” when the cells are stimulated in high osmolarity saline. We also see an increase in foot area and duration when cells are stimulated in high osmolarity saline, or high osmolarity saline subsequent to incubation with the dopamine precursor L ‐DOPA in isotonic saline, which serves to increase the vesicle size. The data suggest that membrane biophysics are an important component in defining the rate, duration and amount of neurotransmitter release via the fusion pore. 相似文献
It is well known that significant errors occur in the velocity derivative moments measured in turbulent flows when the measuring
transducer is too large or Taylor's hypothesis is used in high-turbulence-intensity flows. An additional error occurs when
velocity derivative moments are measured with hot wires in high-turbulence-intensity flows, because the wires cannot resolve
the individual velocity components in these flows. Estimates of the error this causes in the derivative moments measured with
single-, cross-, and parallel-wire probes are developed herein. The errors are significant in the derivative moments measured
with cross-wire probes, but are smaller in derivative moments measured with single- and parallel-wire probes. For example,
the relative errors in measured in the far field of the round jet are 30–50% smaller than predicted in previous analyses.
Received: 10 March 1995/Accepted: 07 December 1999 相似文献
A light touch is all that is required to cleave a maleimide C? N bond to effect a [5+2] photocycloaddition with a sterically encumbered C?N moiety (see scheme).