Herschel

It was known in the sixteenth century that silver salts were photosensitive, but it was not until the beginning of the nineteenth century, when Herschel found that silver chloride was soluble in sodium thiosulphate, that photography became possible. 

Bingham plastics are fluids which remain rigid under the application of shear stresses less than a yield stress, Ty, but flow like a. simple Newtonian fluid once the applied shear exceeds this value. Different constitutive models representing this type of fluids were developed by Herschel and Bulkley (1926), Oldroyd (1947) and Casson (1959). 

Herschel, W.H. and Bulkley, R., 1927. See Rudraiah, N, and Kaloni, P.N. 1990. Flow of non-Newtonian fluids. In Encyclopaedia of Fluid Mechanics, Vol. 9, Chapter 1, Gulf Publishers, Houston. 

The power law model can be extended by including the yield value r — Tq = / 7 , which is called the Herschel-BulMey model, or by adding the Newtonian limiting viscosity,. The latter is done in the Sisko model, 77 +. These two models, along with the Newtonian, Bingham, and Casson... 

The concept of a contact lens device for modifying the optical power of the eye was described by Leonardo da Vinci and later by Rene Descartes and Thomas Young. In 1823, Sir John Herschel described the appHcation of a contact lens device specifically for the purpose of correcting vision. The first contact lens was fitted to a human eye for correction of vision in 1888. The early lenses were made of blown or molded glass and were difficult to wear. 

Hydrogels, ie, gelatin and agar, have been known for a long time. In the late nineteenth century, Herschel proposed the use of jelly materials on the cornea for the correction of vision (108). In 1960, the use of synthetic hydrogels for contact lenses was proposed and several U.S. patents were obtained for the invention of cross-linked hydrophilic polymers, eg, systems based on 2-hydroxethyl methacrylate [868-77-9] (HEMA) (5) (109—112). 

Venturi Meters The standard Herschel-type venturi meter consists of a short length of straight tubing connected at either end to the pipe line by conic sections (see Fig. 10-15). Recommended proportions (ASME PTC, op. cit., p. 17) are entrance cone angle Oti = 21 2°, exit cone angle Cto = 5 to 15°, throat length = one throat diameter, and upstream tap located 0.25 to 0.5 pipe diameter upstream of the entrance cone. The straight and conical sections should be joined by smooth cui ved surfaces for best results. 

Value of the discharge coefficient C for a Herschel-type venturi meter depends upon the Reynolds number and to a minor extent upon the size of the venturi, increasing with diameter. A plot of C versus pipe Reynolds number is given in ASME PTC, op. cit., p. 19. A value of 0.984 can be used for pipe Reynolds numbers larger than 200,000. 

For flow measurement of steam and water mixtures with a Herschel-type venturi in 2V2-in- and 3-in-diameter pipes, see Collins and Gacesa, y. Basic Eng., 93, 11-21 (1971). 

Flow Nozzles A simple form of flow nozzle is shown in Fig. 10-17. It consists essentially of a short cylinder with a flared approach section. The approach cross section is preferably elliptical in shape but may be conical. Recommended contours for long-radius flow nozzles are given in ASME PTC, op. cit., p. 13. In general, the length of the straight portion of the throat is about one-h f throat diameter, the upstream pressure tap is located about one pipe diameter from the nozzle inlet face, and the downstream pressure tap about one-half pipe diameter from the inlet face. For subsonic flow, the pressures at points 2 and 3 will be practically identical. If a conical inlet is preferred, the inlet and throat geometry specified for a Herschel-type venturi meter can be used, omitting the expansion section. 

The p, p, K and n are usually determined with the Fann rotational viscosimeter. The Herschel and Buckley model is not considered in this manual. 

Thus, equation 3.127, which includes three parameters, is effectively a combination of equations 3.121 and 3.125. It is sometimes called the generalised Bingham equation or Herschel -Bulkley equation, and the fluids are sometimes referred to as having/n/re body. Figures 3.30 and 3.31 show shear stress and apparent viscosity, respectively, for Bingham plastic and false body fluids, using linear coordinates. 

Reflecting telescopes would, however, still compete with refracting ones, mostly for their feasibility in much larger diameters. Herschel s telescopes,... 

The first example is the 4-m class William Herschel telescope, at la Pakna, whose optical specifications, drafted by D. Brown, were expressed in terms of allowable wavefront error as a function of spatial frequencies matching those of atmospheric turbulence. 

Figure 2 (a) The optimized electric field as a function of time for the H2(v = 0,) = 0) — H2 (v = 0,7 = 2) rotational excitation process, (b) Absolute value of the Fourier transform of the optimized electric field, (c) The change in populations of the ground-and target excited-state shown as a function of time. Taken from Ref [24] with permission from Qinghua Ren, Gabriel G. Balint-Kurti, Frederick R. Manby, Maxim Artamonov, Tak-San Ho, and Herschel Rabitz, 7. Chem. Phys. 124, 014111 (2006). Copyright 2006, American Institute of Physics. 

Herschel has worked 40% of his 8-hour shift at the widget factory. How many hours has he worked ... 

On the last three decades, several space experiments with parts at very low temperatures have been flown. Among these, we mention IRAS (Infrared Astronomical Satellite) launched in 1983 (see Fig. 14.1), COBE (Cosmic Background Explorer) launched in 1989, ISO (Infrared Space Observatory) launched in 1995 and Astro-E (X-ray Observatory), launched in 2000 with instrumentation at 65 mK [35], Some cryogenic space missions are in the preparation or in final phase in Europe, USA and Japan. For example, ESA is going to fly Planck (for the mapping of the cosmic background radiation) and Herschel (called before FIRST Far Infrared and Submillimetre Telescope ) [36], These missions will carry experiments at 0.1 and 0.3 K respectively. 

Infrared radiation was discovered by Herschel [58] in 1800, using a mercury thermometer to detect sunlight dispersed by a prism. However, the Latin poet Lucretius in his De rerum Natura (On the Nature of Things, about 50 BC) clearly showed a clear feeling of the infrared radiation. Of course Lucretius s terminology was far from the modern one, and he had no thermometer at his disposal ... 

Planck/Herschel [1-5], a space experiment which should be launched in 2007 by an Arianne 5G vector. 

Herschel, a far infrared and submillimetre instrument (60-670 xm), has the following main goals ... 

William Herschel, On the Construction of the Heavens , Phil. Trans., LXXV (1785), 213.1... 

William Herschel, Catalogue of500 new Nebulae, nebulous stars, planetary Nebulae, and Clusters of Stars with Remarks on the... 

Fig. 12.5. Parts of the spectra of two QSOs (with emission redshifts 2.9 and 3.3 respectively) taken with the 4-m William Herschel Telescope on La Palma with a resolution of about 50kms 1 showing Lyman-a lines with damping wings (column densities N(H i) 2 x 1021 cm 2 or 6M0pc-2 and 8 x 1020 cm-2 or 2.4 Mq pc-2 respectively). After Pettini et al. (1997).

John Dalton s Atomic hypothesis. J. Fraunhofer locates and names Fraunhofer lines A...L in solar spectrum. About the same time, Herschel discovers infrared radiation from the Sun. 

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