Py structure

Fig. 10 Glass form factors fq as function of wavevector q in a colloidal glass of hard spheres for packing fractions as labeled. Data obtained by van Megen and coworkers by dynamic light scattering are qualitatively compared to MCT computations using the PY-5j at values chosen ad hoc to match the experimental data from [12]. The PY structure factor at the glass transition density = 0.58 is shown as broken line, rescaled by a factor 1/10...

A monomeric Py is not possible, but the dimeric Ph is known from the solvated Na4(en)6Pi4. EuPy is a Eu compound with a polymeric Py structure of two-dimensional puckered layers resulting from a network of six-membered rings (chair conformation axial and equatorial linkage). For a description of Py in Cu2Py, see Section 6.5.6. 

The same Py structural unit functionalized with the Os complex (Fig. 3.22) has also been co-polymerized with Th and used in the frame of amperometric biosensing for pyruvate determination [107], taking advantage of the mediation... 

It may be pointed out that dehydration of p hydroxy esters with fused potassium hydrogen sulphate, acetic anhydride, phosphoric oxide or with tliionyl chloride in benzeue solution leads to ap unsiiturated esters containing some PY-unsaturated ester the proportion of the latter depends not only upon the structure of the ester but also upon the dehydrating agent used. Elehydration occasionally occurs during the reaction itself or upon attempted distillation. 

Pyrano[3,2-c]benzopyran-2,5-diones synthesis, 3, 808 Pyranobenzopyranones crystal structures, 3, 623 Py rano[3,2-c][ 1 ]benzopyran-2-ones synthesis, 3, 797 Pyranobenzothiazoles mass spectra, 3, 615 Pyrano[2,3-y]benzoxazine synthesis, 3, 714... 

Pyrimido[4,5-d]pyrimidine-5,7-diones synthesis, 3, 363 Pyrimidopyrimi dines synthesis, 4, 507 Pyrimido[ 1,2-a]pyrimidines reaetivity, 3, 348 strueture, 3, 337-338 synthesis, 3, 360 Pyrimido[ 1,6-a]pyrimidines reaetivity, 3, 349 structure, 3, 338 synthesis, 3, 362 Pyrimido[l, 6-c]pyrimidines reaetivity, 3, 349 strueture, 3, 338 synthesis, 3, 362 Py rimi do[4,5-djpyri midi nes applieations, 3, 368 eleavage, 3, 350 reaetions... 

PY Chou, CD Easman. Prediction of the secondary structure of proteins from their ammo acid sequence. Adv Enzymol Relat Areas Mol Biol 47 45-148, 1978. 

To solve the replica OZ equations, they must be completed by closure relations. Several closures have been tested against computer simulations for various models of fluids adsorbed in disordered porous media. In particular, common Percus-Yevick (PY) and hypernetted chain approximations have been applied [20]. Eq. (21) for the matrix correlations can be solved using any approximation. However, it has been shown by Given and Stell [17-19] that the PY closure for the fluid-fluid correlations simplifies the ROZ equation, the blocking effects of the matrix structure are neglected in this... 

However, before proceeding with the description of simulation data, we would like to comment the theoretical background. Similarly to the previous example, in order to obtain the pair correlation function of matrix spheres we solve the common Ornstein-Zernike equation complemented by the PY closure. Next, we would like to consider the adsorption of a hard sphere fluid in a microporous environment provided by a disordered matrix of permeable species. The fluid to be adsorbed is considered at density pj = pj-Of. The equilibrium between an adsorbed fluid and its bulk counterpart (i.e., in the absence of the matrix) occurs at constant chemical potential. However, in the theoretical procedure we need to choose the value for the fluid density first, and calculate the chemical potential afterwards. The ROZ equations, (22) and (23), are applied to decribe the fluid-matrix and fluid-fluid correlations. These correlations are considered by using the PY closure, such that the ROZ equations take the Madden-Glandt form as in the previous example. The structural properties in terms of the pair correlation functions (the fluid-matrix function is of special interest for models with permeabihty) cannot represent the only issue to investigate. Moreover, to perform comparisons of the structure under different conditions we need to calculate the adsorption isotherms pf jSpf). The chemical potential of a... 

Finally, let us discuss the adsorption isotherms. The chemical potential is more difficult to evaluate adequately from integral equations than the structural properties. It appears, however, that the ROZ-PY theory reflects trends observed in simulation perfectly well. The results for the adsorption isotherms for a hard sphere fluid in permeable multiple membranes, following from the ROZ-PY theory and simulations for a matrix at p = 0.6, are shown in Fig. 4. The agreement between the theoretical results and compu-... 

Let us describe the results for the case of a matrix made of chains with four beads, i.e., m = M = 4. We observe that both the PY and the HNC approximation quite accurately describe the adsorption isotherms in matrices of different microporosity (Fig. 5). However, a discrepancy between the HNC results and simulation data increases with increasing chemical potential, especially at higher matrix densities. The structural... 

Benzodiazepinones also undergo rearrangement to isoindoles when treated with acetic anhydride and pyridine (Py). The diazepinone (81), for instance, gives l-phenyl-3-acetylisoindole (82) under these conditions. The structure of the product was established in this case by comparison with (82) prepared by acetylation of 1-phenyl-isoindole. The rearrangement may be formally represented by a... 

In the perfect lattice the dominant feature of the electron distribution is the formation of the covalent, directional bond between Ti atoms produced by the electrons associated with d-orbitals. The concentration of charge between adjacent A1 atoms corresponds to p and py electrons, but these electrons are spatially more dispersed than the d-electrons between titanium atoms. Significantly, there is no indication of a localized charge build-up between adjacent Ti and A1 atoms (Fu and Yoo 1990 Woodward, et al. 1991 Song, et al. 1994). The charge densities in (110) planes are shown in Fig. 7a and b for the structures relaxed using the Finnis-Sinclair type potentials and the full-potential LMTO method, respectively. 

Figure 1.72 The structure of (C60)OsO4(Bu py)2. (Reprinted with permission from Science, 1991, 252, 312.) Copyright (1991) American Association for the Advancement of Science.)...

The soft Au+ forms relatively few complexes compared with those of phosphines. Complexes with ammines, nitriles and diazoles like Au(NH3)2 and Au(RCN)2 are known but little studied. In linear Au(NH3)2, Au-N is 2.01-2.03 A [70a], [Au(NCPh)2]+ has been used as a labile source of other gold complexes [70b]. AuCl(piperidine) is a monomer with weak tetra-meric association in contrast AuX(py) (X = Cl, Br, I) are [Aupy2]+[AuX2] with a chain structure in the solid state (and Au-Au interactions), suggesting a close balance between factors for molecular and ionic structures [70c] (note also the tetrahydrothiophene complexes in section 4.10.6). 

The photographs obtained for pyridine and py-razine are so closely similar to those of benzene as to leave no doubt that the three molecules have nearly identical structures. The radial distribution curve for pyridine (Fig. 1) calculated from the data given in Table II has well-defined peaks at 1.38, 2.39 (= V3 X 1.38), and 2.76 (= 2 X 1.38) A. The sharpness of the 2.39 peak indicates that the six meta distances in the ring are nearly equal. The calculated intensity curve for the model with C-C = 1.39 A., C-N = 1.33 A., C-H = 1.08 A., the angle C-N-C = 119° and the angles C-C-C = 121°, and having nearly equal meta and para distances, is shown in Fig. 3. The comparison of s0 and s values for this model (Table II) leads to the values C-H =... 

The role of steric influences on the formation of various vanadium amidinate complexes in the oxidation states +2 and +3 has been studied in detail. The reaction of VCl2(TMEDA)2 and of VCl3(THF)3 with 2 equivalents of formamidinate salts afforded dimeric V2[HC(NCy)2l4 (cf. Section IV.E) with a very short V-V multiple bond and [ [HC(NCy)2 V(/i-Cl)l2 which is also dimeric (Scheme 107). The formation of V2[HC(NCy)2l4 was shown to proceed through the intermediate monomeric [HC(NCy)2l2V(TMEDA), which was isolated and fully characterized. The dinuclear structure was reversibly cleaved by treatment with pyridine forming the monomeric [HC(NCy)2l2V(py)2. ... 

---