THIELE

The filtrate from hydra/odic rbonaniicle, prepared in the manner described above, is cautiously made alka line and shaken uilh acrbinc, the aictone scmicarba zone, vvlmh is deposited, is mixed with alcohol, and treated with the calculated quantity of sulphuric acid  

Semicarbazine hydrochloride, dissolved in the minimum quantity of water, is mixed with the calculated amount of potassium acetate in alcoholic solution, knd the ketone added, together with water and aleohol sufficient to give a clear homogeneous liquid. This is 

The production of stereoisomeric semicarbazones of cyclic ketones has been investigated. 

Nitroguinadine (208 grams) is mixed with zinc-dust (700 grams), and sufficient ice and water to form a stiff paste to this commercial glacial acetic acid (124 

The liquid obtained by the reduction of nitroguina-dine with zinc-dust and acetic acid is maintained 

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H. Thiele, A. Hecht, U. Steinhofif DGZfP Jahrestagung, Aachen (1995)... 

For hard spheres of diameter a, the PY approximation is equivalent to c(r) = 0 for r > o supplemented by the core condition g(r) = 0 for r < o. The analytic solution to the PY approximation for hard spheres was obtained independently by Wertheim [32] and Thiele [33]. Solutions for other potentials (e.g. Leimard-Jones) are... 

Thiele E 1963 Equation of state for hard spheres J. Chem. Phys. 39 474... 

Nellis W J, Holmes N C, Mitchell A C and Van Thiel M 1984 Phase transition in fluid nitrogen at high densities and temperatures Phys. Rev. Lett. 53 1661... 

Thiel W 1996 Perspectives on semiempirical molecular orbital theory New Methods in Computationai Quantum Meohanios (Adv. Chem. Phys. XCiti) ed I Prigogine I and S A Rice (New York Wiley) pp 703-57 Earlier texts dealing with semi-empirical methods include ... 

As ab initio MD for all valence electrons [27] is not feasible for very large systems, QM calculations of an embedded quantum subsystem axe required. Since reviews of the various approaches that rely on the Born-Oppenheimer approximation and that are now in use or in development, are available (see Field [87], Merz ]88], Aqvist and Warshel [89], and Bakowies and Thiel [90] and references therein), only some summarizing opinions will be given here. 

Bakowies, D., Thiel, W. Hybrid models for combined quantum mechanical and molecular mechanical approaches. J. Phys. Chem. 100 (1996) 10580-10594. 

The first quantum mechanical improvement to MNDO was made by Thiel and Voityuk [19] when they introduced the formalism for adding d-orbitals to the basis set in MNDO/d. This formalism has since been used to add d-orbitals to PM3 to give PM3-tm and to PM3 and AMI to give PM3(d) and AMl(d), respectively (aU three are available commercially but have not been published at the time of writing). Voityuk and Rosch have published parameters for molybdenum for AMl(d) [20] and AMI has been extended to use d-orbitals for Si, P, S and Q. in AMI [21]. Although PM3, for instance, was parameterized with special emphasis on hypervalent compounds but with only an s,p-basis set, methods such as MNDO/d or AMI, that use d-orbitals for the elements Si-Cl are generally more reliable. 

For many applications, especially studies on enzyme reaction mechanisms, we do not need to treat the entire system quantum mechanically. It is often sufficient to treat the center of interest (e.g., the active site and the reacting molecules) quantum mechanically. The rest of the molecule can be treated using classical molecular mechanics (MM see Section 7.2). The quantum mechanical technique can be ab-initio, DFT or semi-empirical. Many such techniques have been proposed and have been reviewed and classified by Thiel and co-workers [50] Two effects of the MM environment must be incorporated into the quantum mechanical system. 

As a simple example, the Thiele modulus is the only parameter in... 

Table II.1 which depends on the pellet size, so the familiar plot of effectiveness factor versus Thiele modulus shows how t varies with pellet radius. A slightly more interesting case arises if it is desired to exhibit the variation of the effectiveness factor with pressure as the mechanism of diffusion changes from Knudsen streaming to bulk diffusion control [66,...

Thiel W and A A Voityuk 1994. Extension of MNDO to d Orbitals Parameters and Results for Silicon. 

Semiempirical molecular orbital calculations have gone through many stages of refinement and elaboration since Pople s 1965 papers on CNDO. Programs like PM3, which is widely used in contemporary research, are the cumulative achievement of numerous authors including Michael Dewar (1977), Walter Thiel (1998), James Stewart (1990), and their coworkers. 

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