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Observation of

In this section, to satisfy the disproof of Henry s law several instances of the observed are presented. This has indeed been reported in the literature by others. With the adsorption of water on NaCl reported by Peters and Ewing [18,19] the threshold pressure is very clear, confirmed by both the isotherm and by infrared. In their investigation of the microporosity of Y-zeolites for which very low-pressure measurements were needed Guo et al. [20] reveal threshold pressures along with the reported oscillating adsorption. The oscillations are undoubtedly due to a variety of effect but one of these could be change in E.  [Pg.143]

Gil et al. [21] present data which seem to evidence a threshold pressure for N2 adsorption. This observation was for nitrogen adsorption on microporous carbon. What is important about this data is that the threshold pressure is obvious even when looking at the data from the point of view of Henry s law. Fig. 77 illustrates this quite well. This plot illustrates that the threshold pressure is not an artifact of the transformation to the x plot. In this figure the threshold pressure appears to be at about 1.0X10 whereas, a x plot indicates it to be about 1.2X 10 P/Ps- [Pg.143]

In an attempt to observe the threshold pressure, Thompson selected a material that one would believe to have a low energy of adsorption. The direct observation of the threshold pressure is possible, if the interaction energy between the surface and the adsorbed molecules is small. This can be easily illustrated with adsorption of N2 or Ar on polytetrafluoroethylene (Teflon ) obtained by Thompson [22], which according to theory should have a very high threshold pressure. The threshold pressure may clearly be seen at a pressure of about 0.01 atm (about 8 Torr), well within (by a factor of at least 10 ) the capability of the most modem instrumentation. Direct observations of threshold pressures, which are lower, require the use of more sensitive gravimetric techniques. This was also found experimentally by Thompson with adsorption data on diamond and alumina that had an ultrahigh vacuum surface cleaning. Since the results of Thompson s polytetrafluoroethylene experiments have not been reported in the open literature, these will be discussed in some detail. [Pg.144]

The powder used was a Teflon Dupont resin obtained from Aldrich Chemical Company (polytetrafluoroethylene lot 6). The measurements on this material were performed over an extended period of time in both the adsorption and desorption mode. There was absolutely no indication that the isotherms exhibited any type of metastable condition or that the phenomenon reported herein is related to kinetics. The kinetics of both adsorption and desorption were indeed measured. The adsorption measurements [Pg.144]

The results of the adsorption Ar on Teflon shown in Fig. 78 are in the untransformed form to illustrate the shape of the isotherm. The data for this figure are given in Table 24 to show the precision and accuracy that is obtainable with the instrumentation described. In this form, even with a high threshold pressure, the presence of a threshold pressure for most experiments, especially the volumetric type, would be missed. The zero pressure recording, however, is very obvious with the instruments described. This value is well within any conceivable error by a factor of 10 The flat portion of the pressure curve is more evident in the x plot. This plot is shown [Pg.145]


For Jet Al, the pressure drop should be less than 33 mbar, and the visual observation of the tube should correspond to a minimum of three on the scale of reference. [Pg.229]

Corrosive sulfur NFT 60-131 ISO 5662 ASTM D 1275 Observation of copper strip after immersion for 19 h at HOT... [Pg.447]

The diagram (Fig. 5.21) shows that as the pressure is reduced below the dew point, the volume of liquid in the two phase mixture initially increases. This contradicts the common observation of the fraction of liquids in a volatile mixture reducing as the pressure is dropped (vaporisation), and explains why the fluids are sometimes referred to as retrograde gas condensates. [Pg.103]

Here presented results were acquainted predominantly by one-channel ten-level AE analyser IOC of the AED Laboratory Brno firm. This device is equipped by ten window threshold levels, defined fi-om top and bottom, the tenth level has not limitation fi-om top. Total dynamic range is 40 dB. The analyser enables continuous observation of total number of counts Nc, or number of counts per time unit and similar. Everything may be observed both in lull measured range and in individual levels. Range of measuring interval is SO ms up to 2500 ms. [Pg.62]

MAZAL,P.-DVOftACEK,J.- KOLAft,D. AET Utilisation for Pitting Observation of Grey Cast Iron with Heat Treated Sur ce. Surface Modif. Technologies XI, will be published 1998. [Pg.66]

The estimated VSS and EPD allow for the observation of the tip diffraction effects (phase inversion - Atp = 180° - for the direct and mirror diffraction echoes) for all selected Ascan signals. This proves the plane nature of the OSD and confirm our initial hypothesis. [Pg.178]

It can be observed from the Figure 1 that the sensitivity of I.I. system is quite low at lower thicknesses and improves as the thicknesses increase. Further the sensitivity is low in case of as observed images compared to processed images. This can be attributed to the quantum fluctuations in the number of photons received and also to the electronic and screen noise. Integration of the images reduces this noise by a factor of N where N is the number of frames. Another observation of interest from the experiment was that if the orientation of the wires was horizontal there was a decrease in the observed sensitivity. It can be observed from the contrast response curves that the response for defect detection is better in magnified modes compared to normal mode of the II tube. Further, it can be observed that the vertical resolution is better compared to horizontal which is in line with prediction by the sensitivity curves. [Pg.446]

Special demands are made to the laboratories that perform radiographic testing. They must observe sanitary norms and rules of radiation safety in their activities. Transportation of the equipment for implement works on site has to ensure observance of the requirements of the radiation safety. [Pg.957]

There are a number of complications in the experimental measurement of the electrophoretic mobility of colloidal particles and its interpretation see Section V-6F. TTie experiment itself may involve a moving boundary type of apparatus, direct microscopic observation of the velocity of a particle in an applied field (the zeta-meter), or measurement of the conductivity of a colloidal suspension. [Pg.184]

Relaxations in the double layers between two interacting particles can retard aggregation rates and cause them to be independent of particle size [101-103]. Discrepancies between theoretical predictions and experimental observations of heterocoagulation between polymer latices, silica particles, and ceria particles [104] have promptetl Mati-jevic and co-workers to propose that the charge on these particles may not be uniformly distributed over the surface [105, 106]. Similar behavior has been seen in the heterocoagulation of cationic and anionic polymer latices [107]. [Pg.192]

Plot the shape of the contact line pinned to a defect using Eq. X-30 for water on polyethylene, stearic acid, and platinum. Assume that the upper cutoff length is 2 mm. How does the shape of the pinned contact line compare with your observations of raindrops on dirty windows ... [Pg.382]

The traditional association colloid is of the M R" type where R" is the surfactant ion, studied in aqueous solution. Such salts also form micelles in nonaqueous and nonpolar solvents. These structures, termed inverse micelles, have the polar groups inward if some water is present [198] however, the presence of water may prevent the observation of a well-deflned CMC [198,199]. Very complex structures may be formed in nearly anhydrous media (see Ref. 200). [Pg.483]

In conclusion, any observation of slowness in attainment of physical adsorption equilibrium should be analyzed with caution and in detail. When this has been done, the phenomenon has either been found to be due to trivial causes or else some unsuspected and interesting other effects were operative. [Pg.662]

Sing (see Ref. 207 and earlier papers) developed a modification of the de Boer r-plot idea. The latter rests on the observation of a characteristic isotherm (Section XVII-9), that is, on the conclusion that the adsorption isotherm is independent of the adsorbent in the multilayer region. Sing recognized that there were differences for different adsorbents, and used an appropriate standard isotherm for each system, the standard isotherm being for a nonporous adsorbent of composition similar to that of the porous one being studied. He then defined a quantity = n/nx)s where nx is the amount adsorbed by the nonporous reference material at the selected P/P. The values are used to correct pore radii for multilayer adsorption in much the same manner as with de Boer. Lecloux and Pirard [208] have discussed further the use of standard isotherms. [Pg.667]

It has also been shown that sufiBcient surface self-diflfiision can occur so that entire step edges move in a concerted maimer. Although it does not achieve atomic resolution, the low-energy electron microscopy (LEEM) technique allows for the observation of the movement of step edges in real time [H]. LEEM has also been usefiil for studies of epitaxial growth and surface modifications due to chemical reactions. [Pg.293]

Kitamura N, Lagaiiy M G and Webb M B 1993 Reai-time observations of vacancy diffusion on Si(100)-(2 1) by scanning tunneiing microscopy Phys. Rev. Lett. 71 2082... [Pg.317]

Jungst S, Knuth B and Hensel F 1985 Observation of singular diameters in the coexistence curves of metals Phys. Rev. Lett. 55 2160-3... [Pg.662]

Versa V, Campagnoia P J, Nandi S, Larsson M and Lineberger W C 1996 Protofragements of ir-Ar ciusters observation of metastabie isomeric ionic fragments J. Ghem. Phys. 105 2298-308... [Pg.827]

The observation of a bend progression is particularly significant. In photoelectron spectroscopy, just as in electronic absorption or emission spectroscopy, the extent of vibrational progressions is governed by Franck-Condon factors between the initial and final states, i.e. the transition between the anion vibrational level u" and neutral level u is given by... [Pg.879]

Hurst J E, Becker C A, Cowin J P, Janda K C, Auerbach D J and Wharton LI 979 Observation of direct ineiastic scattering in the presence of trapping-desorption scattering Xe on Pt(111) Phys. Rev. Lett. 43 1175... [Pg.916]

Rettner C T, Auerbaeh D J and Miehelsen H A 1992 Observation of direet vibrational-exeitation in eollisions of H2 and D2... [Pg.918]

Rettner C T, Fabre F, Kimman J and Auerbaeh D J 1985 Observation of direet vibrational-exeitation in gas-surfaee eollisions—NO on Ag(111) Phys. Rev. Lett. 55 1904... [Pg.918]

Ultraviolet photoelectron spectroscopy (UPS) results have provided detailed infomiation about CO adsorption on many surfaces. Figure A3.10.24 shows UPS results for CO adsorption on Pd(l 10) [58] that are representative of molecular CO adsorption on platinum surfaces. The difference result in (c) between the clean surface and the CO-covered surface shows a strong negative feature just below the Femii level ( p), and two positive features at 8 and 11 eV below E. The negative feature is due to suppression of emission from the metal d states as a result of an anti-resonance phenomenon. The positive features can be attributed to the 4a molecular orbital of CO and the overlap of tire 5a and 1 k molecular orbitals. The observation of features due to CO molecular orbitals clearly indicates that CO molecularly adsorbs. The overlap of the 5a and 1 ti levels is caused by a stabilization of the 5 a molecular orbital as a consequence of fomiing the surface-CO chemisorption bond. [Pg.951]

That is, rapid IVR in the long lived intennediate is an essential step. We shall treat this important process in the next section, but mention here in passing the observation of so-called supercollisions transferring large average amounts of energy (AE) m one collision [ ], even if intennediate complex fonnation may not be important. [Pg.1056]

Figure A3.14.12. The first experimental observation of a Turing pattern in a gel strip reactor. Solutions containing separate components of the CIMA/CDIMA reaction are flowed along each edge of the strip and a spatial pattern along the horizontal axis develops for a range of experimental conditions. (Reprinted with pennission from [38], The American Physical Society.)... Figure A3.14.12. The first experimental observation of a Turing pattern in a gel strip reactor. Solutions containing separate components of the CIMA/CDIMA reaction are flowed along each edge of the strip and a spatial pattern along the horizontal axis develops for a range of experimental conditions. (Reprinted with pennission from [38], The American Physical Society.)...
Lee K-J, MoCormiok W D, Pearson J E and Swinney H L 1994 Experimental observation of self-replioating spots in a reaotion-diffusion system Nature 369 215-8... [Pg.1118]


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Errors of observation—

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Experimental Observations of Rheology-Morphology Relationships in Immiscible Polymer Blends

Experimental Observations of Solid-State Sintering

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Experimental observation of Schottky and Frenkel defects

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Far Infrared Interferometry for the Observation of Disks

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Frequency Distribution of Observations

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In-situ Observation of Thin Film Growth

Independence of observations

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Interpretation of kinetic observations

Magic Angle Spinning Observation of Satellite Transitions

Methods of observation

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Multiplicity of observations

NMR observations of orientation in solid polymers

Nano-Scopic Observation of Biological Surfaces

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Observance of Equilibria Between Two Oligonucleotide Conformations

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Observation of Anion and Cation Radicals

Observation of Carbenes

Observation of Carbocations

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Observation of Fluctuations Using Light Scattering

Observation of Ices in Space

Observation of Intermediates by Transient Absorption

Observation of Internal States

Observation of Mixed-Valence Isomers

Observation of Multiple Steady States

Observation of Nuclear Motion during Ultrafast Intramolecular Proton Transfer

Observation of Performance

Observation of Primary Reaction Intermediates

Observation of Stable, Long-Lived Carbocations

Observation of Transient Effects

Observation of a Penetration Depth Gradient in ATR FT-IR Spectroscopic Imaging Applications

Observation of behavior

Observation of bound states by dissociative attachment

Observation of domain walls in pzt thin film using sndm

Observation of exciton surface polaritons at room temperature

Observation of nanoscale 180 stripe domains

Observation of others

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Observation of positronium slowing down

Observation of side effects

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Observation of the NMR Signal

Observation of the Oxidative Addition Reaction

Observation of water production, temperatures, and current density distributions

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Observing Properties of Acids and Bases

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Plane of observation

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Prediction of New Observations

Prediction of a Specific Observation

Proton Transfer to a Hydride Ligand in Solution Experimental Observation of Intermediates

Qualitative Observation of Labeled Cells

Qualitative observations of vacancy-induced surface diffusion

Real-Time Observations of Molecular Vibrations

Reduction of directly observed cycle numbers in subjects

Rejection of observations

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Reliability of observers

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Solid-state NMR observation of polymer blends and interphases

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Spectroscopic observations of alkylcarbonium ions in strong acid solutions

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Steps of the Observation Process

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Summary of Experimental Observations

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Systematic observation of behavior

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