A generalization of second variation

f p- , l p . p=1 . . p - , f -.     

Thermal stability and electronic structure of atomically uniform Pb films on Si(111)

Atomically uniform Pb films are successfully prepared on Si(111), despite a large lattice mismatch. Angle-resolved photoemission measurements of the electronic structure show layer-resolved quantum well states which can be correlated with dramatic variations in thermal stability. The odd film thicknesses N = 5, 7, and 9 monolayers show sharp quantum well states. The even film thicknesses N = 6 and 8 do not, but are much more stable than the odd film thicknesses. This correlation is discussed in terms of a total energy calculation and Friedel-like oscillations in properties.     

SOME NEW CLASSES OF ALMOST PERIODIC FUNCTIONS

In this paper classes of almost periodic functions are formed whlch lie between those established by W. Stepanoff and by H. Burkill.     

Use of high-performance thin layer chromatography by the American Herbal Pharmacopoeia

TLC characterizations are among the key identity tests in most pharmacopoeial monographs. Pharmacopoeial standards are typically used by industry as a basis for meeting QC requirements and current good manufacturing practices (cGMPs). TLC is a relatively low-cost, highly versatile tool for developing specifications for raw materials, as well as for the various preparations for which pharmacopoeial standards are created. In addition to its use in the development of identity tests, TLC is a valuable tool for screening plant samples that pharmacopoeias must review in the development of monographs and botanical reference materials (BRMs). Specifically, HPTLC is the ideal TLC technique for these purposes because of its increased accuracy, reproducibility, and ability to document the results, compared with standard TLC. Because of this, HPTLC technologies are also the most appropriate TLC technique for conformity with GMPs. This article highlights the manner in which HPTLC is used by the American Herbal Pharmacopoeia (AHP) in the development of AHP monograph identity standards, the identification of adulterating species, and the development of AHP-verified BRMs.     

α-Azido bisphosphonates: synthesis and nucleotide analogues

The first examples of α-azido bisphosphonates [(RO)(2)P(O)](2)CXN(3) (1, R = i-Pr, X = Me; 2, R = i-Pr, X = H; 3, R = H, X = Me; 4, R = H, X = H) and corresponding β,γ-CXN(3) dGTP (5-6) and α,β-CXN(3) dATP (7-8) analogues are described. The individual diastereomers of 7 (7a/b) were obtained by HPLC separation of the dADP synthetic precursor (14a/b).     

Off-critical Casimir effect in Ising slabs with symmetric boundary conditions in d=3

Extended de Gennes-Fisher (EdGF) local-functional method has been applied to the thermodynamic Casimir effect away from the critical point for systems in the Ising universality class confined between parallel plane plates with symmetric boundary conditions [denoted (ab)=(++)]. Results on the universal scaling functions of the Casimir force W++(y) (y is a temperature-dependent scaling variable) and Gibbs adsorption G[over ](y) are presented in spatial dimension d=3. Also, the mean-field form of the universal scaling function of the Gibbs adsorption G[over ](y) is derived within the local functional theory. Asymptotic behavior of W++(y) for large values of the scaling variable y is analyzed in general dimension d.     

Poissonian Behavior of Ising Spin Systems in an External Field

We apply the Stein–Chen method for Poisson approximation to spin-half Ising-type models in positive external field which satisfy the FKG inequality. In particular, we show that, provided the density of minus spins is low and can be expanded as a convergent power series in the activity (fugacity) variable, the distribution of minus spins is approximately Poisson. The error of the approximation is inversely proportional to the number of lattice sites (we obtain upper and lower bounds on the total variation distance between the exact distribution and its Poisson approximation). We illustrate these results by application to specific models, including the mean-field and nearest neighbor ferromagnetic Ising models.