Resolution determination

In addition to the surface/interface selectivity, IR-Visible SFG spectroscopy provides a number of attractive features since it is a coherent process (i) Detection efficiency is very high because the angle of emission of SFG light is strictly determined by the momentum conservation of the two incident beams, together with the fact that SFG can be detected by a photomultiplier (PMT) or CCD, which are the most efficient light detectors, because the SFG beam is in the visible region, (ii) The polarization feature that NLO intrinsically provides enables us to obtain information about a conformational and lateral order of adsorbed molecules on a flat surface, which cannot be obtained by traditional vibrational spectroscopy [29-32]. (iii) A pump and SFG probe measurement can be used for an ultra-fast dynamics study with a time-resolution determined by the incident laser pulses [33-37]. (iv) As a photon-in/photon-out method, SFG is applicable to essentially any system as long as one side of the interface is optically transparent. 

Rosenberg, M. F., Caliaghan, R., Ford, R. C., Higgins, C. F., Structure of the multidrug resistance P-glyco-protein to 2.5 nm resolution determined by electron microscopy and image analysis, J. Biol. Chem. 1997, 272, 10685-10694. 

The required level of resolution determines the extent of detail needed in a FMEA. The choices for the level of resolution range from the subcomponent level to the system level. To satisfy PSM Rule requirements, most FMEAs should be performed at the major component level. This level provides the best trade-off between the time necessary to perform the analysis and the usefulness of the information gained from it. 

Cullis, R., et al. (1961). The structure of haemoglobin, VIII. A three-dimensional Fourier synthesis at 5.5 A resolution determination of the phase angles. Proceed. Royal Soc. London Series A 265,15-38. 

It is of importance that expression (5.12) holds even when /(x) is known only in part of space, as is the case in a crystallography experiment at finite resolution determined by Hmax. Using the Fourier convolution theorem, we may write (Dunitz and Seiler 1973)... 

Straathof, A.J.J., Wolff, A. and Heijnen, J.J. (1998) Sohd-to-solid kinetic resolution— determination of the enantiomeric ratio. Journal of Molecular Catalysis B-Enzymatic, 5, 55-61. 

A time-of-flight spectrometer can be used as a mass analyzer, an ion kinetic energy analyzer, and an ion reaction time analyzer. We will consider here only what factors affect the resolution of the system in mass analysis.74 The same consideration can easily be extended to find the resolution in other analyses. There are at least two kinds of mass resolution. One refers to the ability of the system to separate two ion species of nearly equal masses in the same mass spectrum. This is related to the sharpness of the mass lines, or the full width at half maximum (FWHM) of the mass lines. The other refers to the ability of the system to distinguish two ion species of nearly identical masses, but not necessarily in the same mass spectrum. This latter mass resolution is related to the sharpness of reference points in the mass lines such as the onset flight times of the ion species, and the overall long-term stability of the system. This latter resolution determined also how accurately the instrument can measure the mass of ion species. Although this latter resolution is more closely related to ion kinetic energy analysis and is as important as the former one, we will consider here only the former kind, or the conventional kind, of mass resolution. 

Preparative-scale chromatography relies on a compromise between three variables (cf. Figure 1) (i) component resolution (determined by selectivity, efficiency and retention factor), (ii) speed of analysis and (iii) column sample capacity (Pescar, 1971). Any two of the desired goals may be realized only at the expense of the third. If a large amount of sample is required in a short time, resolution must be high. If resolution is insufficient, either the column load is limited or the time required for separation is long. 

Peroxide Sensitizers. Poly(methylmethacrylate), PMMA, is the first polymer reported to exhibit an increase in refractive index upon irradiation with uv light (41). Irradiation at either 325 nm (Cd laser) or 365 nm (Hg arc) was found to give an index increase of up to 0.3%, and the resolution, determined from gratings, was shown to be at least 5000 lines/mm. Applications to optical waveguides and holographic elements were suggested. This phenomenon was a serendipitous discovery. The PMMA had been intended for use as an inert matrix for reversible photodimerization when its own photosensitivity was uncovered. 

Zewail acknowledged early on that he was inspired to work in the dynamics area by amongst others, George Porter s development of fast reaction techniques, viz. Flash Photolysis which is reported elsewhere in this volume. In the early experiments outlined in the present paper, three detection techniques were employed time-correlated single photon counting, with 30-50 ps time resolution streak camera detection of fluorescence, with 10 ps resolution, and multiphoton ionisation with resolution determined by the pulse width of the laser, 1 or 15 ps. 

There is always a trade-off between the resolution (determined by the distance the moving mirror travels) and the time available for analysis. In off-line analysis of polymers. 

XPS enables the determination of the oxidation state of the Mn ions. The most precise evaluation rests on the measurement of the binding energy difference between the Mn 3s main peak and its shake-up satellite [2-4].The XPS analysis of the samples was performed on a SSI X-probe (SSX 100/206) spectrometer of FISONS equipped with a monochromatised microfocused A1 X-ray source (1486.6 eV). The angle between the sample surface and the electron detection axis was 55°. The analyser pass energy was set at 50 eV and the analyzed area was 1.4 mm. At these conditions, the energy resolution determined by the Au 4fj/2 full width at half maximum (FWHM) of gold was 1.1 eV. The XPS results are reported in Table 1. 

Anger, S., Mehnert, W., Caldwell, K.D. and Muller R.H. (1998) High resolution determination of adsorption layer mass on particles by sedimentation field-flow fractionation. Proc. Second World Meeting APGI/APV, Paris, 643-644. 

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