Image pressure

An attempt has been made by Spiering et al. [39,40] to relate the magnitude of the interaction parameter F(x) as derived from experiment to the elastic interaction between HS and LS ions via an image pressure [47]. To this end, the metal atoms, inclusive of their immediate environments, in the HS and LS state are considered as incompressible spheres of radius /"h and Tl, respectively. The spheres are embedded in an homogeneous isotropic elastic medium, representing the crystal, which is characterized by specific values of the bulk modulus K and Poisson ratio a where 0 < a < 0.5. The change of molecular volume A Fas determined by X-ray diffraction may be related to the volume difference Ar = Ph — of the hard spheres by ... 

The dilution of the spin crossover system in a similar host lattice with bigger ions (e.g. an iron system in the corresponding zinc compound) will create a negative image pressure. The HS state becomes preferentially stabilised and consequently Tc decreases. Simultaneously the conversion curve xHs versus T becomes more gradual. Analogous behaviour is exhibited by [Fe M1 (2-pic)3]Cl2 EtOH systems (M = Co, Zn) and [Fe Mi (phen)2 (NCS)2] systems (M = Mn, Co, Zn). 

In service inspections of French nuclear Pressure Water Reactor (PWR) vessels are carried out automatically in complete immersion from the inside by means of ultrasonic focused probes working in the pulse echo mode. Concern has been expressed about the capabilities of performing non destructive evaluation of the Outer Surface Defects (OSD), i.e. defects located in the vicinity of the outer surface of the inspected components. OSD are insonified by both a "direct" field that passes through the inner surface (water/steel) of the component containing the defect and a "secondary" field reflected from the outer surface. Consequently, the Bscan images, containing the signatures of such defects, are complicated and their interpretation is a difficult task. 

Figure 6. Correlation images of manufactured pipe with defect, under pressure changes of (a) 20psi, (b) 30psi and (e) 40psi. The sealing rule lies to the left of the pipe and the defect zone is highlighted by the white arrow.

As a special development in recent years, SEMs have been designed which no longer necessitate high vacuum (enviromnental SEM, ESEM variable pressure SEM, VPSEM). This development is important for the imaging of samples with a residual vapour pressure, such as aqueous biological or medical samples, but also samples in materials science (wet rock) or organic chemistry (polymers). 

A group of aminoxanthenes, ie, pyra2oloxanthenes, is used as color formers ia pressure or heat-sensitive imaging papers (43). These compounds are colorless, but, upon contact with acidic electron-accepting material, are converted to resonance forms that are lightly colored. An example is stmcture [58294-05-6] (35), which forms upon the condensation of A[,A/-diethyl-y -aminophenol with phthalic anhydride, followed by addition of 6-hydroxyinda2ole ia 80% sulfuric acid (44). 

The development of active ceramic-polymer composites was undertaken for underwater hydrophones having hydrostatic piezoelectric coefficients larger than those of the commonly used lead zirconate titanate (PZT) ceramics (60—70). It has been demonstrated that certain composite hydrophone materials are two to three orders of magnitude more sensitive than PZT ceramics while satisfying such other requirements as pressure dependency of sensitivity. The idea of composite ferroelectrics has been extended to other appHcations such as ultrasonic transducers for acoustic imaging, thermistors having both negative and positive temperature coefficients of resistance, and active sound absorbers. 

Nickel salts and soaps have been used in electrosensitive copy paper for image development. Nickel bis-(3,5 di-Z fZ-butylsaHcylate) [68569-24-4] has been studied in pressure-sensitive color developer sheets (201). It has also been used for color stabili2ation of color copy paper (see Electroplating). 

Carbonless Copy Paper. In carbonless copy paper, also referred to as pressure-sensitive record sheet, an acid-sensitive dye precursor, such as crystal violet lactone or /V-hen2oy11eucomethy1ene blue, is microencapsulated with a high boiling solvent or oil within a cross-linked gelatin (76,83,84) or in synthetic mononuclear microcapsules. Microcapsules that have a starch binder are coated onto the back of the top sheet. This is referred to as a coated-back (CB) sheet. The sheet intended to receive the image is treated on the front (coated-front (CF)) with an acid. When the top sheet is mechanically impacted, the dye capsules mpture and the dye solution is transferred to the receiving sheet where the acid developer activates the dye. 

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