Later Developments

Some of the newer phosphate glasses which have been developed include [76] 

Ultra-low-melting-point glasses based on Snp2/Sn0/P205 systems (T 100°C) 

Chemically durable glasses based on M20/Zr0/P205 systems 

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Barbituric acid was first pre pared in 1864 by Adolf von Baeyer (page 112) A histori cal account of his work and the later development of barbiturates as sedative-hypnotics appeared in the October 1951 issue of the Journal of Chemical Education (pp 524-526)... 

Deviation from the standard isotherm in the high-pressure region offers a means of detecting the occurrence of capillary condensation in the crevices l>etween the particles of a solid and in any mesopores present within the particles themselves. A convenient device for detecting deviations from the standard is the t-plot . In the next section the nature and uses of t-plots will be discussed, together with a,-plots, a later development from them. As will l>e shown, both of these plots may l>e used not only for the detection of capillary condensation in mesopores, but also for showing up the presence of micropores and evaluating their volume. 

The first HFIP-based polycarbonate was synthesi2ed from bisphenol AF with a nonfluorkiated aromatic diol (bisphenol A) and phosgene (121,122). Incorporation of about 2—6% of bisphenol AF and bisphenol A polycarbonate improved the dimensional stabkity and heat-distortion properties over bisphenol A homopolycarbonate. Later developments in this area concern the flame-retardant properties of these polymers (123,124). 

Different combinations of stable xenon isotopes have been sealed into each of the fuel elements in fission reactors as tags so that should one of the elements later develop a leak, it could be identified by analyzing the xenon isotope pattern in the reactor s cover gas (4). Historically, the sensitive helium mass spectrometer devices for leak detection were developed as a cmcial part of building the gas-diffusion plant for uranium isotope separation at Oak Ridge, Tennessee (129), and heHum leak detection equipment is stiU an essential tool ia auclear technology (see Diffusion separation methods). 

Riboflavin can be assayed by chemical, en2ymatic, and microbiological methods. The most commonly used chemical method is fluorometry, which involves the measurement of intense yeUow-green fluorescence with a maximum at 565 nm in neutral aqueous solutions. The fluorometric deterrninations of flavins can be carried out by measuring the intensity of either the natural fluorescence of flavins or the fluorescence of lumiflavin formed by the irradiation of flavin in alkaline solution (68). The later development of a laser—fluorescence technique has extended the limits of detection for riboflavin by two orders of magnitude (69,70). 

The Copyright Act specifies that copyright extends to "original works of authorship fixed in any tangible medium of expression, now known or later developed, from which they can be perceived, reproduced, or otherwise communicated, either dkecdy or with the aid of a machine or device" (3). Many of the requkements for copyrightabiUty may be gleaned from this provision. 

During World War II, production of butadiene (qv) from ethanol was of great importance. About 60% of the butadiene produced in the United States during that time was obtained by a two-step process utilizing a 3 1 mixture of ethanol and acetaldehyde at atmospheric pressure and a catalyst of tantalum oxide and siHca gel at 325—350°C (393—397). Extensive catalytic studies were reported (398—401) including a fluidized process (402). However, because of later developments in the manufacture of butadiene by the dehydrogenation of butane and butenes, and by naphtha cracking, the use of ethanol as a raw material for this purpose has all but disappeared. 

A very practical way to infer the contact area was later developed by Carpick et al. [65] and Lantz et al. [66]. In these experiments, a small (up to nanometer) lateral modulation, djc, is applied to the sample, and torsion of the cantilever is monitored with a lock-in amplifier to detect the lateral force response, dF (Fig. 5). In this way, the lateral stiffness, [51], given by... 

The use of drugs to treat disease antedates modem science ly 21 good many millenia. Every culture sooner or later developed I i own pharmacopeia. These compendia of natural products and... 

In 1939 Einstein wrote to Roosevelt to draw his attention to possible military use of atomic energy. His influence on these later developments was marginal, however. In 1943 he became consultant to the U.S. Navy Bureau of Ordnance but was never involved in atomic bomb work. In 1944 a copy of his 1905 paper on special relativity, handwritten by him for this purpose, was auctioned for six million dollars as a contribution to the war effort. (It is now in the Library of Congress.)... 

The Voltaie battery eoneeived and built toward the end of 1799 in Como, was the first deviee to produee a steady flow of eleetrieity, or eleetrie eurrent. The instrument enabled other natural philosophers, notably Humphry Davy, to develop eleetroehemistry as a new braneh of seienee, and still others, notably Hans Christian Oersted and Georg Simon Ohm, to explore eleetromagnetism. Beeause of these later developments—showing that ehemieal, eleetrieal... 

To achieve higher energy in solid proplnts the most notable advances were achieved with the addition of aluminum and beryllium to both double-base and composite proplnts. Energy in this case is commonly equated to high specific impulse. Later developments added aluminum hydride and beryllium hydride to this list. In Table 16, the specific impulse performance of proplnts using AP with various metals and hydrides is compared to those systems without these additives (Ref 43)... 

Partial aromatic PAs have also been well studied and are of industrial importance. The later developed, wholly aromatic PAs poly(m-phe-nyleneisophthalamide) in (3.3) and poly (p-phenyleneterephthalamide) in (3.4) are interesting fiber-forming materials witii high maximum-use temperature7 914. 

The commercial production of stabilized liquid sulfur trioxide and the assessment of its advantages led to increased use [47-49]. Later development of specialized sulfur burners with catalytic conversion of sulfur dioxide to sulfur trioxide in air by vanadium pentoxide has established this method as an alternative to liquid sulfur trioxide. 

The discoveries of Becquerel, Curie, and Rutherford and Rutherford s later development of the nuclear model of the atom (Section B) showed that radioactivity is produced by nuclear decay, the partial breakup of a nucleus. The change in the composition of a nucleus is called a nuclear reaction. Recall from Section B that nuclei are composed of protons and neutrons that are collectively called nucleons a specific nucleus with a given atomic number and mass number is called a nuclide. Thus, H, 2H, and lhO are three different nuclides the first two being isotopes of the same element. Nuclei that change their structure spontaneously and emit radiation are called radioactive. Often the result is a different nuclide. 

Among the later developments noteworthy is an isomerization in the reaction... 

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