Isolate, definition

Today Vieille s formulae are regarded as purely conventional though useful in arranging various types of nitrocellulose into classes. Nevertheless, many authors have tried to isolate definite substances corresponding to Vieille s compounds. Thus de Bruin [6] claimed that he had isolated definite compounds containing 11.97 and 12.76% of nitrogen, corresponding to the enneanitrocellulose and deca-nitrocellulose of Vieille. 

Different authors have isolated definite compounds from the products of alkaline hydrolysis of nitrocotton. Wolfrom et al. [42] enumerate the compounds that are produced by hydrolysis of nitrocellulose in the presence of acids and bases inorganic nitrates and nitrites, cyanides,... 

Chesebro, B., Wehrly, K., Nishio, J., and Perryman, S. (1992) Macrophage-tropic HIV isolates from different patients exhibit unusual V3 envelope sequence homogeneity in comparison with T-cell-tropic isolates definition of critical amino acids involved in cell tropism. J. Virol. 66, 6547-6554. 

In summary, it appears that the adsorption of proteins at fluid/fluid interfaces is very complex and involves several steps that are not encountered in classical surfactants or even polymeric surfactants. All the parameters that are controlling the surface activity may be changed by chemical or physicochemical modifications, such as covalent attachment of various groups, breaking of disulfide bonds, de-naturation by heat, etc. It is important to note that while changing one parameter, one may change the others as well, and therefore it would be difficult to isolate definite parameters. 

Is it possible to isolate definite carbonyl, phosphane, or olefinic complexes of the zerovalent lanthanoides ... 

When it comes to the heaviest of petroieum fractions, modern analytical methods are not able to isolate and characterize the molecules completely. In the absence of something better, the analyst separates the heavy fractions into different categories, which leads merely to definitions that are workable but are no longer in terms of exact structure. 

La sensibilite aux defauts et autres parametres de controle peut etre amelioree par le choix optimal de la sonde. II apparait, apres etudes des differents types de sondes (ferritiques, acier doux, isolant) avec des geometries differentes (plate, conique,. ..), necessaires de souligner que le succes d une recherche de faisabilite depend en grande partie de la bonne definition des capteurs de mesure, de telle sorte que ceux-ci soient adaptes au probleme considere. 

Snch a generalization is consistent with the Second Law of Thennodynamics, since the //theorem and the generalized definition of entropy together lead to the conchision that the entropy of an isolated non-eqnilibrium system increases monotonically, as it approaches equilibrium. 

The slopes of the fimctions shown provide the reaction rates according to the various definitions under the reaction conditions specified in the figure caption. These slopes are similar, but not identical (nor exactly proportional), in this simple case. In more complex cases, such as oscillatory reactions (chapter A3.14 and chapter C3.6). the simple definition of an overall rate law tluough equation (A3.4.6) loses its usefiilness, whereas equation (A3.4.1) could still be used for an isolated system. 

This is the situation exploited by the so-called isolation method to detennine the order of the reaction with respect to each species (see chapter B2.1). It should be stressed that the rate coefficient k in (A3,4,10) depends upon the definition of the in the stoichiometric equation. It is a conventionally defined quantity to within multiplication of the stoichiometric equation by an arbitrary factor (similar to reaction enthalpy). 

For tire purjDoses of tliis review, a nanocrystal is defined as a crystalline solid, witli feature sizes less tlian 50 nm, recovered as a purified powder from a chemical syntliesis and subsequently dissolved as isolated particles in an appropriate solvent. In many ways, tliis definition shares many features witli tliat of colloids , defined broadly as a particle tliat has some linear dimension between 1 and 1000 nm [1] tire study of nanocrystals may be drought of as a new kind of colloid science [2]. Much of die early work on colloidal metal and semiconductor particles stemmed from die photophysics and applications to electrochemistry. (See, for example, die excellent review by Henglein [3].) However, the definition of a colloid does not include any specification of die internal stmcture of die particle. Therein lies die cmcial distinction in nanocrystals, die interior crystalline stmcture is of overwhelming importance. Nanocrystals must tmly be little solids (figure C2.17.1), widi internal stmctures equivalent (or nearly equivalent) to drat of bulk materials. This is a necessary condition if size-dependent studies of nanometre-sized objects are to offer any insight into die behaviour of bulk solids. 

The definition above is a particularly restrictive description of a nanocrystal, and necessarily limits die focus of diis brief review to studies of nanocrystals which are of relevance to chemical physics. Many nanoparticles, particularly oxides, prepared dirough die sol-gel niediod are not included in diis discussion as dieir internal stmcture is amorjihous and hydrated. Neverdieless, diey are important nanoniaterials several textbooks deal widi dieir syndiesis and properties [4, 5]. The material science community has also contributed to die general area of nanocrystals however, for most of dieir applications it is not necessary to prepare fully isolated nanocrystals widi well defined surface chemistry. A good discussion of die goals and progress can be found in references [6, 7, 8 and 9]. Finally, diere is a rich history in gas-phase chemical physics of die study of clusters and size-dependent evaluations of dieir behaviour. This topic is not addressed here, but covered instead in chapter C1.1, Clusters and nanoscale stmctures, in diis same volume. 

The group of states, for which Eq. (137) is expected to be valid, fomis a sub-Hilbert space that is isolated with respect to other portions of the Hilbert space following the definition in Eqs. (40). 

At first, the dimeric nature of the base isolated from 3-ethyl-2-methyl-4-phenylthiazolium was postulated via a chemical route. Indeed the adduct of ICH, on a similar 2-ethylidene base is a 2-isopropylthiazolium salt in the case of methylene base it is an anilinovinyl compound identified by its absorption spectrum and chemical reactivity (45-47). This dimeric structure of the molecule has been definitively established by its NMR spectrum. It is very similar to the base issued from 2.3-dimethyl-benzo thiazolium (48). It corresponds to 2-(3 -ethyl-4 -phenyl-2 -methylenethiazolinilydene)2-methyl-3-ethyl-4-phenylthiazoline (13). There is only one methyl signal (62 = 2.59), and two series of signals (63= 1.36-3.90, 63= 1.12-3.78) correspond to ethyl groups. Three protons attributed to positions T,5,5 are shifted to a lower field 5.93, 6.58, and 8.36 ppm. The bulk of the ten phenyl protons is at 7.3 ppm (Scheme 22). 

The term feedstock in this article refers not only to coal, but also to products and coproducts of coal conversion processes used to meet the raw material needs of the chemical industry. This definition distinguishes between use of coal-derived products for fuels and for chemicals, but this distinction is somewhat arbitrary because the products involved in fuel and chemical appHcations are often identical or related by simple transformations. For example, methanol has been widely promoted and used as a component of motor fuel, but it is also used heavily in the chemical industry. Frequendy, some or all of the chemical products of a coal conversion process are not isolated but used as process fuel. This practice is common in the many coke plants that are now burning coal tar and naphtha in the ovens. 

These are the definitions of the two characteristic dissociation constants normally expressed in terms of p K. When three dissociating groups are present in a molecule there are three piC values, ie, pfC, P 3- knowledge of these piC values is important in the separation or isolation of each amino acid by ion-exchange chromatography. 

An especially interesting case of oxygen addition to quinonoid systems involves acidic treatment with acetic anhydride, which produces both addition and esterification (eq. 3). This Thiele-Winter acetoxylation has been used extensively for synthesis, stmcture proof, isolation, and purification (54). The kinetics and mechanism of acetoxylation have been described (55). Although the acetyhum ion is an electrophile, extensive studies of electronic effects show a definite relationship to nucleophilic addition chemistry (56). 

Bismuth Oxides and Bismuthates. The only oxide of bismuth that has been definitely isolated in a pure state is bismuth trioxide. An acidic oxide that approximates the composition Bi20 certainly exists. However, there is considerable question as to the exact nature of this material and the species involved. A number of other oxides have been reported, eg, bismuth oxide (1 1) [1332-64-5], bismuth oxide (1 2), bismuth oxide (2 4)... 

Bismuth trioxide may be prepared by the following methods (/) the oxidation of bismuth metal by oxygen at temperatures between 750 and 800°C (2) the thermal decomposition of compounds such as the basic carbonate, the carbonate, or the nitrate (700—800°C) (J) precipitation of hydrated bismuth trioxide upon addition of an alkah metal hydroxide to a solution of a bismuth salt and removal of the water by ignition. The gelatinous precipitate initially formed becomes crystalline on standing it has been represented by the formula Bi(OH)2 and called bismuth hydroxide [10361 -43-0]. However, no definite compound has been isolated. 

The first definitive studies of boron hydrides were carried out by Alfred Stock in Germany starting about 1912 (1). Through extensive and now classic synthetic studies, the field of boron hydride chemistry was founded with the isolation of a series of highly reactive, air-sensitive, and volatile compounds of general composition and This accomplishment required the development of basic vacuum line techniques for the... 

Switches and switch isolators for voltages above lOOOV General and definitions 9920-1 10 4/1992 BSEN 60265 1/1998 ... 

A most successful paradigm for isolating reaction pathways in complex systems begins with a definition of the reaction pathway as a continuous line l(r) that connects known reactant Tr and product rp configurations. We then define an integrated cost functional... 

Coniine, CgH jN. The alkaloid was first isolated by Giesecke. but the formula was suggested by Blyth and definitely established by Hofmann. 

Comparison of these results indicates identity of the two substances isolated independently by Orekhov and Ehrenstein, but Spiith and Kesztler have suggested that Pictet s nicoteine and Ehrenstein s base, consisted of impure Z-anatabine (p. 46). In this connection it may be noted that Ehrenstein s base was laevorotatory in acid solution, whereas Salts of anabasine are dextrorotatory. These authors have themselves isolated Z-anabasine from tobacco. The identity of synthetic 2-(3 -Pyridyl)piperidine with dZ-anabasine seems to have been definitely established. Anabasis aphylla is the source of the anabasine raanufac-... 

In addition to the foregoing five phthalideisoquinoline alkaloids obtained from opium, Manske has isolated from genera of the Rhceadales six more alkaloids definitely assigned to, and three, including base F38 (p. 173), which he considers may belong to this group. Hydrastine, already dealt with (p. 162), is also a phthalidcMoquinoline derivative. 

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