Nominal resolution

The number of accumulated scans and nominal resolution have been tested in order to ensure a compromise between sensitivity and sampling frequency. 

In order to select the instmmental conditions for carrying out the ATR measurements several parameters including the number of accumulated scans per spectra or nominal resolution were tested. To avoid the crosscontamination and to establish an appropriate strategy for cleaning the ATR cell between samples, several procedures were tested using background and blank controls. Moreover, the possible sample sedimentation on the ATR plate cell due to the complexity of the sample matrix during the spectra acquisition was also checked. 

Fig. 3.4.12 Three-dimensional rendered spin-echo image of water filled cracks in a cement paste specimen [13]. Three cracks are visible in the image a large triangular crack in the forefront, a smaller crack in the bottom left corner and a sheet-like structure at the top of the image. Water droplets can also be observed condensing on the cement paste surfaces. The measurement parameters were FOV 20 x 20 x 20 mm, acquisition points 128 x 128 x 64, nominal resolution 156 x 156 x 312 pm, echo time 2.7 ms, repetition time 500 ms and acquisition time 270 min.

The spin-echo successfully imaged water held in the cracks of cement paste. This technique can be used to resolve cracks much smaller than the nominal resolution by relying on water saturation of the crack, the connectivity of the crack structure and the fact that it is relatively easy to detect a high intensity structure on a low intensity background. 

Extensive biochemical and spectroscopic studies have been undertaken on hCP in order to investigate the nature of the copper centers and their role in structure-function relationships. However, the protein is very susceptible to aggregation, proteolysis, loss of copper, and other chemical degradations and requires careful preparation and handling in these circumstances it is difficult to review all the literature objectively and comprehensively. A three-dimensional crystal structure of hCP has been reported at a nominal resolution of 3.1A [7], but this resolution has been extended to just beyond 3.0 A. This chapter will summarize some of the more important biochemical and spectroscopic studies of the protein. It will then focus on the structural results recently obtained by X-ray crystallographic methods and attempt to explain putative functions of the protein in terms of its molecular structure. 

Fig. 26 Fourier transform spectrum of v2 of ammonia. Trace (a) is a section of the infrared absorption spectrum of ammonia recorded on a Digilab Fourier transform spectrometer at a nominal resolution of 0.125 cm-1. In this section of the spectrum near 848 cm-1 the sidelobes of the sine response function partially cancel, but the spectrum exhibits negative absorption and some sidelobes. Trace (b) is the same section of the ammonia spectrum using triangular apodiza-tion to produce a sine-squared transfer function. Trace (c) is the deconvolution of the sine-squared data using a Jansson-type weight constraint.

Balcom et al. developed a novel diagnostic technique suitable for a thin-film by MRI.42 The authors obtained one-dimensional water content profiles with nominal resolution of 6 p,m using a prototype resonator and double half k-space spin echo single-point imaging (SPI) technique.15 Even at room temperature, partial dehydration of the membrane in the anode side was captured clearly with high spatial resolution. 

All of the infrared experiments were performed on a Digilab FTS-40 Fourier transform infrared (FT-IR) spectrometer equipped with a narrow-band liquid-nitrogen-cooled mercury-cadmium-telluride (MCT) detector. The spectrometer was operated at a nominal resolution of 4 cm-1 using a mirror velocity of 1.28 cm/s. The data collected using the gas chromatography (GC) IR software were measured at 8 cm-1 resolution. Protein assays for all the experiments were measured on a Beckman DU-70 UV-visible spectrophotometer. 

Rapid-scanning Spectrophotometers. These en loy multi-channel detectors. The most commonly encountered detector of diis t e is tlie linear photodiode array. The reversed-optics mode is employed, so that radiation is passed throu tiie sample or reference cell, tiien dispersed by a dif action grating polychiomator integrated intensity of radiation incident on it which is determined by tiie spectial dispersion photo ode ratio. If, for example, a 200-nm txmdwidtii of radiation were dispersed across 256 photodiodes, tiie nominal resolution per photodiode woitid be 0.78 nm. 

The choice of GC conditions employed was left to the discretion of the seven participating laboratories. Instrument types used in this study included three quadrupole systems and four magnetic sector instruments. One of the laboratories performed the analyses using both electron capture and mass spectral detection. Two laboratories performed the analysis at a high resolving power (RP > 10,000) while others used the mass spectrometer operating at nominal resolution. All laboratories performed the analysis under ECNI conditions... 

At this stage, assuming that the nominal resolution is 4 A or better, the electron density map should be of sufficient quality to interpret readily the course of the polypeptide chain and rapidly build a model, usually for the icosahederal asymmetric unit. Conventional crystallographic refinement techniques are then employed to refine the model against the observed data. 

A third virus that is structurally similar to BTV is rice dwarf virus (RDV) for which a cryo-EM reconstruction at a nominal resolution of 6.8 A has been obtained (Zhou et al., 2001). Bioinformatics coupled with novel methods in electron density map analysis were used to define the organization of secondary structure elements within the density and identify the primary sequences that form them (Zhou et al., 2001). This involved identifying tubular density corresponding to helices in assigning structure de novo and comparing regions of the viral structural proteins with domains of known folds (Zhou et al, 2001). The organization of RDV revealed was similar to that of BTV. 

FTIR spectra of the carbon samples were obtained using a Perkin-Elmer FTIR Spectrum 2000 spectrometer. The active carbon-KBr mixtures in a ratio of 1 300 were ground in an agate mortar, desorbed under vacuum (10 - Pa), and finally pressed in a hydraulic press. Before the spectrum of a sample was recorded, the background line was obtained arbitrarily and subtracted. The spectra were recorded from 4000 to 450 cm at a. scan rate of 0.2 cm/s, and the number of interferograms at a nominal resolution of 4 cm" was fixed at 25. Figures 3 and 4 present the FTIR spectra obtained for the relevant carbon samples. The measurements applied here (KBr pellet technique) make it impossible to compare quantitatively the FTIR spectra obtained for different carbons, but they do indicate which individual chemical structures may or may not be present in the carbon [90,91,123]. 

ASAXS experiments were conducted on Beamline II-2 at the Stanford Synchrotron Radiation Laboratory (SSRL). X-ray energies 5 and 100 eV below the measured K edge for Ni in the ionomer (8333 eV in Ni metal) were selected by a double-crystal monochromator using planar Sl(lll) crystals with a nominal resolution of zH eV. The scattering apparatus has been described in detail else rtiere[35,36]. The data were corrected for transmittance of the sample and fluctuations in Incident beam Intensity and are shown herein on a consistent relative intensity scale. 

The sampling point spread function pixel resolution is 21% more coarse than the nominal resolution. While it is not possible in the SPRITE experiment to introduce slice selection with radiofrequency pulses, physical slice selection with good edge definition is possible by using a moveable, metallic radiofrequency shield to restrict excitation/detection to a defined region of the sample. ... 

The FTIR-experiments were performed with thin discs (approximately 15 mg/cm ) of catalyst in a reaction chamber with CaF2-windows [8]. Two different catalysts were used one with Pt/BaO/A Os (2% Pt, 20% BaO) and one with Pt/Al203 (2% Pt). The fresh catalysts were initially reduced in 30% H2 in N2 (total flow rate of 100 ml/min) at 450°C for 30 minutes, stabilised in a gas mixture with 5% O2, 1000 ppm NO and 3000 ppm C3H6 in N2 (total flow rate 1000 ml/min) for 30 minutes and finally degassed in N2 (1000 ml/min) at 550°C for 30 minutes. All FTIR-experiments were performed at 380°C, at a total flow rate of 1000 ml/min with a scan speed of 1 cm Vs and a nominal resolution of 4 cm. ... 

The X-ray difEraction analysis was performed on a Philips PW 1051 instrument using monochromated Fe K radiation and standard recording conditions. XRD phases present in the samples were identified with the help of ASTM powder data files. Infrared spectra were recorded on a Nicolet 740 FTIR spectrometer using KBr discs, with a nominal resolution of 4 cm and averaging 100 spectra. 

The emission spectra were collected at suitable intervals, mostly 50 °C or 25 °C, over the range 200 - 800 C. The time between scans (while the temperature was raised to the next hold point) was approximately 100 seconds. Initial experiments have shown that this was sufficient time for the heating block and the powdered sample to reach temperature equilibrium. The spectra were acquired by co-addition of 64 scans for the whole temperature range (approximate seaming time 45 seconds), with a nominal resolution of 4 cm. Good quality spectra can be obtained provided that the sample thickness is not too large. If too large a sample is used, then the spectra become difficult to... 

In all simulations each dynamic spectrum consisted of 13 spectra with 130 points equivalent to an amide I band in the region 1700-1600 cm with a nominal resolution of 2cm The changes were assumed to be linear. The maps were obtained assuming that one or two peaks were changing. 

In recent years, new schemes have been introduced in Raman studies, taking advantage of Fourier transform spectrometers and of lasers. For instance CARS techniques can now achieve nominal resolutions of 0.003 to 0.005 cm" with accuracies of 0.001 cm" or better. Unfortunately, these experiments are still limited to a small number of skilled laboratories. Nevertheless, joint works using both IR and Raman data are found now, Raman being especially usefnl for infrared inactive bands. 

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