Modeling of non-stationary ground motion using the mean reverting stochastic process

This paper presents a new method for modeling amplitude and frequency non-stationary earthquake ground motions using a scalar first order dynamic mean reverting stochastic differential equation driven by Brownian motion with parametric time varying coefficients. It determines the proper relationship between these time varying parametric coefficients and presents the statistical and probability distribution characteristics of the response solution. It demonstrates the applicability of the method by presenting some simulations of amplitude and frequency non-stationary earthquake ground motions. The verification of the amplitude and frequency non-stationary contents of the mean reverting stochastic ground motions is demonstrated using the Hilbert–Huang transform method. Also a corresponding interpretation between the coefficients of the proposed model and the coefficients of the usual oscillatory second order differential equation driven by white Gaussian noise is presented along with some comments how it can be applied to simulate ground motions consistent with acceleration target records such as boxcar, trapezoidal, other exponential functions, or compound and target records at source, near field, and far field distances.     

A computer-controlled direct sample insertion device for inductively coupled plasma-mass spectrometry

A direct sample insertion (DSI) device has been developed for application to inductively coupled plasma-mass spectrometry (ICP-MS). In a DSI device for use with ICPs, the sample is placed into or onto a probe with subsequent introduction of the sample carrying probe, via the central tube of the ICP torch, into the plasma. A mechanical, stepper-motor driven, computer controlled DSI device and software support system has been designed and developed that can easily be attached to a commercial ICP-MS system (Perkin-Elmer/SClEX Elan). This system allows the direct introduction of microliter volumes of liquids and milligram quantities of powdered/solid samples into the ICP-MS with little or no sample pre-treatment.     

1-D coordination polymers consisting of a high-spin Mn17 octahedral unit

The reaction of [Mn(O₂CMe)₂] · 4H₂O with pdH₂ (1,3-propanediol) or mpdH₂ (2-methyl-1,3-propanediol) in the presence of NaN₃ in MeCN/py (py = pyridine) results in the formation of two new one-dimensional coordination polymers composed of a [Mn^III₆Mn^II₁₁(μ₄-O)₈(μ₃-N₃)₄]²⁵⁺ octahedral unit. The peripheral ligation is completed by pd^2? (or mpd^2?), acetate, pyridine and μ-1,3-N₃^? ligands. The latter bridges each Mn₁₇ unit to its neighboring one, resulting in the formation of the two 1-D coordination polymers. Variable-temperature dc magnetic susceptibility studies indicate the existence of predominantly ferromagnetic interactions and a resulting giant ground state spin within the Mn₁₇ units and intermolecular antiferromagnetic exchange interactions between the neighboring Mn₁₇ units that result in diamagnetic ground spin states for both polymeric compounds.     

Development of an egg-white bioassay for monitoring biotin levels in urine and serum.

This article reports on the development of a simple and cost-effective bioassay for the detection of biotin in urine and serum, based on the very selective binding of avidin and biotin. Avidin was allowed to react without isolating it from egg white. Egg white was treated with the dye HABA, which binds to avidin. Upon subsequent treatment with biotin, HABA is released due to the high affinity of biotin to avidin. The amount of HABA released is proportional to the amount of biotin used.     

Synthesis of enantiopure (S)-7-hydroxy-3-amino-3,4-dihydro-2H-1-benzopyran en route to (+)-scyphostatin

(S)-7-Hydroxy-3-amino-3,4-dihydro-2H-1-benzopyran, a key synthetic intermediate towards the total synthesis of (+)-scyphostatin, has been prepared in >98% ee. Key synthetic steps were (i) the oxidative dearomatization of an l-tyrosine derived phenol, (ii) the transformation of the resulting p-quinol acetate to the corresponding resorcinol upon exposure to Thiele reaction conditions and, (iii) the direct formation of the benzopyran ring upon treatment of an N-Boc protected 4-(2-acetoxybenzyl)oxazolidin-2-one with sodium methoxide.     

Hybridization of optical phonons with double quantum-wire plasmons including drift instabilities

We examine the collective mode spectrum for a double quantum-wire system embedded in semi-infinite polar medium, taking account of the role of optical phonons in interaction with the double quantum-wire plasmons and bulk/surface plasmons. The collective mode frequencies are exhibited as functions of q_x (wavenumber parallel to the wires) and as functions of z₀ (distance of first wire from the interface). We also find that the region of drift instability of the collective modes is split into two disjoint regions of instability by the optical phonons, with a region of stability between them.     

3D elastic scattering theorems for point-generated dyadic fields

The problem of scattering of elastic spherical waves by a rigid body, cavity or a penetrable obstacle in 3D linear elasticity is considered. For two point sources, dyadic far-field pattern generators are defined, which are used for the formulation of a general scattering theorem. The main reciprocity principle and mixed scattering relations are also established. We provide the necessary energy considerations, presenting relative energy functionals and expressions for the differential and the scattering cross section due to point-source dyadic incidence. Finally, an application of the general scattering theorem for appropriate locations of the point source leads to an optical theorem. Copyright © 2007 John Wiley & Sons, Ltd.     

Structure determination of oligomeric alkannin and shikonin derivatives

Monomeric alkannin and shikonin (A/S) are potent pharmaceutical substances with a wide spectrum of biological activity and comprise the active ingredients for several pharmaceutical preparations. Therefore, the determination of the impurities, degradation products or byproducts in alkannin and shikonin samples is of great importance. Oligomeric alkannin and shikonin are formed during biosynthesis of these bioactive secondary metabolites in Boraginaceaous root plants, during tissue culture production of A/S, during alkaline hydrolysis of A/S esters and also thermal treatment of A/S. In the present study, a dimeric alkannin/shikonin compound was isolated by size exclusion chromatography from alkannin and shikonin commercial samples and its structure was determined by one- and two-dimensional NMR spectroscopy. The structure of the most abundant oligomeric species in these samples, a dimeric naphthoquinone, was established for the fi rst time, indicating that coupling of the side chain of one naphthoquinone unit with the aromatic ring of a second naphthoquinone leads to dimer formation. This type of coupling allows further oligomerization by leaving one isohexenyl side chain available at the second monomer unit.     

The homogeneous projective transformation of general quadratic matrix equations

^** Email: vassilios.tsachouridis{at}ieee.org^*** Email: basil.kouvaritakis{at}eng.ox.ac.uk Algebraic quadratic equations are a special case of a singlegeneralized algebraic quadratic matrix equation (GQME). Hence,the importance of that equation in science and engineering isevident. This paper focus on the study of solutions of thatGQME and a unified framework for the characterization and identificationof solutions at infinity and of finite solutions of generalquadratic algebraic matrix equations is presented. The analysisis based on the concept of homogeneous projective transformationfor general polynomial systems (Morgan, 1986). In addition,a numerical error analysis for the computed solutions is providedfor the assessment of numerical accuracy, stability and conditioningof the computed solutions. The proposed framework is independentof any numerical method and therefore it can be used along withvarious possible numerical methods for the GQME solution, especiallymatrix flow-based algorithms (Chu, 1994) (e.g. continuation/homotopy,Morgan, 1989).