Analysis of small signal stability margins using genetic optimization

Power system small signal stability analysis aims to explore different small signal stability conditions and controls, namely: (1) exploring the power system security domains and boundaries in the space of power system parameters of interest, including load flow feasibility, saddle node and Hopf bifurcation ones; (2) finding the maximum and minimum damping conditions; and (3) determining control actions to provide and increase small signal stability. These problems are presented in this paper as different modifications of a general optimization to a minimum/maximum, depending on the initial guesses of variables and numerical methods used. In the considered problems, all the extreme points are of interest. Additionally, there are difficulties with finding the derivatives of the objective functions with respect to parameters. Numerical computations of derivatives in traditional optimization procedures are time consuming. In this paper, we propose a new black-box genetic optimization technique for comprehensive small signal stability analysis, which can effectively cope with highly nonlinear objective functions with multiple minima and maxima, and derivatives that can not be expressed analytically. The optimization result can then be used to provide such important information such as system optimal control decision making, assessment of the maximum network's transmission capacity, etc. (C) 1998 Elsevier Science S.A. All rights reserved.

Single-spin measurement using single-electron transistors to probe two-electron systems

We present a method for measuring single spins embedded in a solid by probing two-electron systems with a single-electron transistor (SET). Restrictions imposed by the Pauli principle on allowed two-electron states mean that the spin state of such systems has a profound impact on the orbital states (positions) of the electrons, a parameter which SET's are extremely well suited to measure. We focus on a particular system capable of being fabricated with current technology: a Te double donor in Si adjacent to a Si/SiO2, interface and lying directly beneath the SET island electrode, and we outline a measurement strategy capable of resolving single-electron and nuclear spins in this system. We discuss the limitations of the measurement imposed by spin scattering arising from fluctuations emanating from the SET and from lattice phonons. We conclude that measurement of single spins, a necessary requirement for several proposed quantum computer architectures, is feasible in Si using this strategy.

Using biplots to interpret gene expression patterns in plants

Sum: Plant biologists in fields of ecology, evolution, genetics and breeding frequently use multivariate methods. This paper illustrates Principal Component Analysis (PCA) and Gabriel's biplot as applied to microarray expression data from plant pathology experiments. Availability: An example program in the publicly distributed statistical language R is available from the web site (www.tpp.uq.edu.au) and by e-mail from the contact. Contact: scott.chapman@csiro.au.

The incidence of schizophrenia: A systematic review

There has been a debate on whether or not the incidence of schizophrenia varies across time and place. In order to optimise the evidence upon which this debate is based, we have undertaken a systematicsystematic review of the literature. In this paper we provide an overview of the methods of the review and a preliminary analysis of the studies identified to date. Electronic databases (Medline, Psychlnfo, Embase, LILAC) were systematically searched for articles published between January 1965 and December 2001. The search terms were: (schizo* OR psycho*)AND (incidence OR prevalence). References were also identified from review articles, reference list and by writing to authors. To date we have identified 137 papers drawn from 33 nations. 37 papers in language other than English await translation. The currently included papers have generated 1413 different items of rate information data. In order to analyze these data we have undertaken several sequential filters in order to identify (a) non-overlapping data, (b) birth cohort study versus noncohort studies, (c) overall and sex-specific rates, (d) diagnostic criteria, (e) age ranges, (f) epoch of study, and (g) data on migrant or other special interest groups. In addition, we will examine the impact of urbanicity of site, age and/or sex standardization, and quality score on the incidence rates. The various discrete incidence rates will be presented graphically and the impact of various filters on these rates will be inspected using meta-analytic techniques. The use of meta-analysis may help elucidate the epidemiological landscape with respect to the incidence of schizophrenia and aid in the generation of new hypothesis. Acknowledgements: The Stanley Medical Research Institute supported project

Integrability and exact solution of an electronic model with long range interactions

We present an electronic model with long range interactions. Through the quantum inverse scattering method, integrability of the model is established using a one-parameter family of typical irreducible representations of gl(211). The eigenvalues of the conserved operators are derived in terms of the Bethe ansatz, from which the energy eigenvalues of the Hamiltonian are obtained.

In vitro photodynamic therapy on human oral keratinocytes using chloroaluminum-phthalocyanine

In this study, oral carcinoma cells were used to evaluate chloroaluminum-phthalocyanine encapsulated in liposomes as the photosensitizer agent in support of photodynamic therapy (PDT). The genotoxicity and cytotoxicity behavior of the encapsulated photosensitizer in both dark and under irradiation using the 670-nm laser were investigated with the classical trypan blue cell viability test, the acridine orange/ethidium bromide staining organelles test, micronucleus formation frequency, DNA fragmentation, and cell morphology. The cell morphology investigation was carried out using light and electronic microscopes. Our findings after PDT include reduction in cell viability (95%) associated with morphologic alterations. The neoplastic cell destruction was predominantly started by a necrotic process, according to the assay with acridine orange and ethidium bromide, and this was confirmed by electronic microscopy analysis. Neither the PDT agent nor laser irradiation alone showed cytotoxicity, genotoxicity, or even morphologic alterations. Our results reinforce the efficiency of tight-irradiated chloroaluminum-phthalocyanine in inducing a positive effect of PDT. (C) 2008 Elsevier Ltd. All rights reserved.

Biochemical properties of an extracellular beta-D-fructofuranosidase II produced by Aspergillus phoenicis under Solid-Sate Fermentation using soy bran as substrate

The filamentous fungus A. phoenicis produced high levels of beta-D-fructofuranosidase (FFase) when grown for 72 hrs under Solid-State Fermentation (SSF), using soy bran moistened with tap water (1:0.5 w/v) as substrate/carbon source. Two isoforms (I and II) were obtained, and FFase II was purified 18-fold to apparent homogeneity with 14% recovery. The native molecular mass of the glycoprotein (12% of carbohydrate content) was 158.5 kDa with two subunits of 85 kDa estimated by SDS-PAGE. Optima of temperature and pH were 55 degrees C and 4.5. The enzyme was stable for more than 1 hr at 50 degrees C and was also stable in a pH range from 7.0 to 8.0. FFase II retained 80% of activity after storage at 4 degrees C by 200 hrs. Dichroism analysis showed the presence of random and beta-sheet structure. A. phoenicis FFase II was activated by Mn(2+), Mg(2+) and Co(2+), and inhibited by Cu(2+), Hg(2+) and EDTA. The enzyme hydrolyzed sucrose, inulin and raffinose. K(d) and V(max) values were 18 mM and 189 U/mg protein using sucrose as substrate.

Electronic medical records may be inadequate for improving population health status through general practice: cervical smears as a case study

Objective: To determine whether routine electronic records are an accurate source of population health data in general practice through reviewing cervical smears rates in four South Australian practices. Methods: The cervical screening rate in a purposive sample of four general practices (three rural and one urban) was obtained using an audit of medical records and a telephone follow-up. Results: The cervical screening rate using only immediately available electronic medical records indicated an overall low rate for the participating practices (44.9%). However, telephone follow-up and adjustments to the denominator indicated the real rate to be 85.7%. The offer of appointments during the telephone follow-up further improved this rate for eligible women (93.8%). Conclusions and implications: Electronic medical records may be inadequate in preventive screening in general practice, without ensuring their accuracy. Updating records by telephone or personal follow-up produces a much more accurate denominator.

Children`s oral production of narratives and constructive memory using prior reading of pictures

With the purpose of approximating two issues, oral narrative and constructive memory, we assume that children, as well as adults, have a constructive memory. Accordingly, researchers of the constructive memory share with piagetians the vision that memory is an applied cognition. Under this perspective, understanding and coding into memory constitute a process which is considered similar to the piagetian assimilation of building an internal conceptual representation of the information (hence the term constructive memory. The objective of this study is to examine and illustrate, through examples drawn from a research about oral narrative with 5, 8 and 10 years old children, the extent to which the constructive memory is stimulated by the acquisition of the structures of knowledge or ""mental models"" (schemes of stories and scenes, scripts), and if they automatically employ them to process constructively the information in storage and rebuild them in the recovery. A sequence of five pictures from a book without text was transformed into computerized program, and the pictures were thus presented to the children. The story focuses on a misunderstanding of two characters on a different assessment about a key event. In data collection, the demands of memory were preserved, since children narrate their stories when the images were no longer viewed on the computer screen. Each narrative was produced as a monologue. The results show that this story can be told either in a descriptive level or in a more elaborated level, where intentions and beliefs are attributed to the characters. Although this study allows an assessment of the development of children`s capabilities (both cognitive and linguistic) to narrate a story, there are for sure other issues that could be exploited.

Twisted quantum affine superalgebra U-q[sl(2/2)((2))], U-q[osp(2/2)] invariant R-matrices and a new integrable electronic model

We describe the twisted affine superalgebra sl(2\2)((2)) and its quantized version U-q[sl(2\2)((2))]. We investigate the tensor product representation of the four-dimensional grade star representation for the fixed-point sub superalgebra U-q[osp(2\2)]. We work out the tensor product decomposition explicitly and find that the decomposition is not completely reducible. Associated with this four-dimensional grade star representation we derive two U-q[osp(2\2)] invariant R-matrices: one of them corresponds to U-q [sl(2\2)(2)] and the other to U-q [osp(2\2)((1))]. Using the R-matrix for U-q[sl(2\2)((2))], we construct a new U-q[osp(2\2)] invariant strongly correlated electronic model, which is integrable in one dimension. Interestingly this model reduces in the q = 1 limit, to the one proposed by Essler et al which has a larger sl(2\2) symmetry.

Spin-orbit mixing and nephelauxetic effects in the electronic spectra of nickel(II)-encapsulating complexes involving nitrogen and sulfur donors

A study of spin-orbit mixing and nephelauxetic effects in the electronic spectra of nickel(II)-encapsulating complexes involving mixed nitrogen and sulfur donors is reported. As the number of sulfur donors is systematically varied through the series [Ni(N6-xSx)](2+) (x = 0-6), the spin-forbidden (3)A(2)g --> E-1(g) and (3)A(2g) --> (1)A(1g) transitions undergo a considerable reduction in energy whereas the spin-allowed transitions are relatively unchanged. The [Ni(diAMN(6)sar)](2+) and [Ni(AMN(5)Ssar)](2+) complexes exhibit an unusual band shape for the (3)A(2g) --> T-3(2g) transition which is shown to arise from spin-orbit mixing of the E spin-orbit levels associated with the E-1(g) and T-3(2g) states. A significant differential nephelauxetic effect also arises from the covalency differences between the t(2g) and e(g) orbitals with the result that no single set of Racah B and C interelectron repulsion parameters adequately fit the observed spectra. Using a differential covalency ligand-field model, the spectral transitions are successfully reproduced with three independent variables corresponding to 10Dq and the covalency parameters f(t) and f(e), associated with the t(2g) and e(g) orbitals, respectively. The small decrease in f(t) from unity is largely attributed to central-field covalency effects whereas the dramatic reduction in f(e) with increasing number of sulfur donors is a direct consequence of the increased metal-ligand covalency associated with the sulfur donors. Covalency differences between the t(2g) and e(g) orbitals also result in larger 10Dq values than those obtained simply from the energy of the (3)A(2g) --> T-3(2g) spin-allowed transition.

Geometric and electronic information from the spectroscopy of six-coordinate copper(II) compounds

The ground and excited state geometry of the six-coordinate copper(II) ion is examined in detail using the CuF64- and Cu(H2O)(6)(2+) complexes as examples. A variety of spectroscopic techniques are used to illustrate the relations between the geometric and electronic properties of these complexes through the characterization of their potential energy surfaces.

Comparison of language impairment in late-onset depression and Alzheimer`s disease

Objectives: Depression and dementia are highly prevalent in the elderly. Language impairment is an inherent component of Alzheimer`s disease (AD), which can also be encountered in depressed patients. The aim of this study wasto compare the profiles of language abilities in late-onset depression and mild AD groups. Methods: We studied 25 patients with late-onset depression (mean age 73.6 +/- 6.6 years; schooling 9.1 +/- 5.7 years) and 30 patients with mild AD (77.6 +/- 5.4 years; 7.5 +/- 7.1 years) using the Arizona Battery for Communication Disorders of Dementia (ABCD), compared to a group of 30 controls (73.8 +/- 5.8 years; 9.1 +/- 5.4 years). Cut-off scores to discriminate between Controls x Depression and Depression x AD were determined. Results: Depressed patients` scores were similar to AD in confrontation naming, concept definition, following commands, repetition and reading comprehension (sentence). Episodic memory and mental status subtests were useful in differentiating depressed patients from AD, a result that was reproduced when using analysis of covariance to control for the effect of age in the same subtests (p = 0.01 and 0.04, respectively). Conclusion: Language impairment resembling AD was found in the aforementioned language subtests of the ABCD in elderly depressed patients; the mental status and episodic memory subtests were useful to discriminate between AD and depression. The ABCD has proven to be a suitable tool for language evaluation in this population and should aid in the differentiation of AD and pseudodementia (as that of depression).