Anomalous Raman scattering from phonons and electrons of superconducting FeSe0.82

We report interesting anomalies in the temperature dependent Raman spectra of FeSe0.82 measured from 3 K to 300 K in the spectral range from 60 to 1800 cm(-1) and determine their origin using complementary first-principles density functional calculations. A phonon mode near 100 cm-1 exhibits a sharp increase by similar to 5% in the frequency below a temperature T-s (similar to 100 K) attributed to strong spin-phonon coupling and onset of short-range antiferromagnetic order. In addition, two high frequency modes are observed at 1350 cm-1 and 1600 cm-1, attributed to electronic Raman scattering from (x(2)-y(2)) to xz/yz d-orbitals of Fe. (C) 2010 Elsevier Ltd. All rights reserved.

Joseph A. Schumpeter's Theory of Social and Economic Evolution : a Reconstruction and Critique

The book presents a reconstruction, interpretation and critical evaluation of the Schumpeterian theoretical approach to socio-economic change. The analysis focuses on the problem of social evolution, on the interpretation of the innovation process and business cycles and, finally, on Schumpeter s optimistic neglect of ecological-environmental conditions as possible factors influencing social-economic change. The author investigates how the Schumpeterian approach describes the process of social and economic evolution, and how the logic of transformations is described, explained and understood in the Schumpeterian theory. The material of the study includes Schumpeter s works written after 1925, a related part of the commentary literature on these works, and a selected part of the related literature on the innovation process, technological transformations and the problem of long waves. Concerning the period after 1925, the Schumpeterian oeuvre is conceived and analysed as a more or less homogenous corpus of texts. The book is divided into 9 chapters. Chapters 1-2 describe the research problems and methods. Chapter 3 is an effort to provide a systematic reconstruction of Schumpeter's ideas concerning social and economic evolution. Chapters 4 and 5 focus their analysis on the innovation process. In Chapters 6 and 7 Schumpeter's theory of business cycles is examined. Chapter 8 evaluates Schumpeter's views concerning his relative neglect of ecological-environmental conditions as possible factors influencing social-economic change. Finally, chapter 9 draws the main conclusions.

Conformal Field Theory Methods for Variants of Schramm-Loewner Evolutions

This thesis consists of an introduction, four research articles and an appendix. The thesis studies relations between two different approaches to continuum limit of models of two dimensional statistical mechanics at criticality. The approach of conformal field theory (CFT) could be thought of as the algebraic classification of some basic objects in these models. It has been succesfully used by physicists since 1980's. The other approach, Schramm-Loewner evolutions (SLEs), is a recently introduced set of mathematical methods to study random curves or interfaces occurring in the continuum limit of the models. The first and second included articles argue on basis of statistical mechanics what would be a plausible relation between SLEs and conformal field theory. The first article studies multiple SLEs, several random curves simultaneously in a domain. The proposed definition is compatible with a natural commutation requirement suggested by Dubédat. The curves of multiple SLE may form different topological configurations, ``pure geometries''. We conjecture a relation between the topological configurations and CFT concepts of conformal blocks and operator product expansions. Example applications of multiple SLEs include crossing probabilities for percolation and Ising model. The second article studies SLE variants that represent models with boundary conditions implemented by primary fields. The most well known of these, SLE(kappa, rho), is shown to be simple in terms of the Coulomb gas formalism of CFT. In the third article the space of local martingales for variants of SLE is shown to carry a representation of Virasoro algebra. Finding this structure is guided by the relation of SLEs and CFTs in general, but the result is established in a straightforward fashion. This article, too, emphasizes multiple SLEs and proposes a possible way of treating pure geometries in terms of Coulomb gas. The fourth article states results of applications of the Virasoro structure to the open questions of SLE reversibility and duality. Proofs of the stated results are provided in the appendix. The objective is an indirect computation of certain polynomial expected values. Provided that these expected values exist, in generic cases they are shown to possess the desired properties, thus giving support for both reversibility and duality.

Direct and Inverse Scattering for Beltrami Fields

We consider an obstacle scattering problem for linear Beltrami fields. A vector field is a linear Beltrami field if the curl of the field is a constant times itself. We study the obstacles that are of Neumann type, that is, the normal component of the total field vanishes on the boundary of the obstacle. We prove the unique solvability for the corresponding exterior boundary value problem, in other words, the direct obstacle scattering model. For the inverse obstacle scattering problem, we deduce the formulas that are needed to apply the singular sources method. The numerical examples are computed for the direct scattering problem and for the inverse scattering problem.

Simplified theory of optical nonlinearities in spin-polarized bulk GaAs

Apart from their intrinsic physical interest, spin-polarized many-body effects are expected to be important to the working of spintronic devices. A vast literature exists on the effects of a spin-unpolarized electron-hole plasma on the optical properties of a semiconductor. Here, we include the spin degree of freedom to model optical absorption of circularly polarized light by spin-polarized bulk GaAs. Our model is easy to implement and does not require elaborate numerics, since it is based on the closed-form analytical pair-equation formula that is valid in 3d. The efficacy of our approach is demonstrated by a comparison with recent experimental data.

Non-Fermi liquid theory of quantum hall effects

Within the Grassmannian U(2N)/U(N) x U(N) nonlinear sigma-model representation of localization, one can study the low-energy dynamics of both a free and interacting electron gas. We study the crossover between these two fundamentally different physical problems. We show how the topological arguments for the exact quantization of the Hall conductance are extended to include the Coulomb interaction problem. We discuss dynamical scaling and make contact with the theory of variable range hopping. (C) 2005 Pleiades Publishing, Inc.

Surface instability of confined elastic bilayers: Theory and simulations

The surface of a soft elastic film becomes unstable and forms a self-organized undulating pattern because of adhesive interactions when it comes in contact proximity with a rigid surface. For a single film, the pattern length scale lambda, which is governed by the minimization of the elastic stored energy, gives lambda similar to 3h, where h is the film thickness. Based on a linear stability analysis and simulations of adhesion and debonding, we consider the contact instability of an elastic bilayer, which provides greater flexibility in the morphological control of interfacial instability. Unlike the case of a single film, the morphology of the contact instability patterns, debonding distance, and debonding force in a bilayer can be controlled in a nonlinear way by varying the thicknesses and shear moduli of the films. Interestingly, the pattern wavelength in a bilayer can be greatly increased or decreased compared to a single film when the adhesive contact is formed by the stiffer or the softer of the two films, respectively. In particular, lambda as small as 0.5h can be obtained. This indicates a new strategy for pattern miniaturization in elastic contact lithography.

Theory of laminar flame propagation with non-normal diffusion.

A study has been made of the problem of steady, one-dimensional, laminar flame propagation in premixed gases, with the Lewis number differing from (and equal to) unity. Analytical solutions, using the method of matched asymptotic expansions, have been obtained for large activation energies. Numerical solutions have been obtained for a wide range of the reduced activation temperature parameter (n {geometrically equal to} E/RTb), and the Lewis number δ. The studies reveal that the flame speed eigenvalue is linear in Lewis number for first order and quadratic in Lewis number for second order reactions. For a quick determination of flame speeds, with reasonable accuracy, a simple rule, expressing the flame speed eigenvalue as a function of the Lewis number and the centroid of the reaction rate function, is proposed. Comparisons have been made with some of the earlier works, for both first and second order reactions.

Interculturality in Theory and Practice in the Master's Programme of Intercultural Bilingual Education in Bolivia

Tämän tutkielman aiheena on kulttuurienvälisyys kulttuurienvälisessä kaksikielisessä opetuksessa (Educación Intercultural Bilingüe, EIB) Boliviassa ja erityisesti kulttuurienvälisen kaksikielisen koulutuksen maisteriohjelmassa (Maestría en Educación Intercultural Bilingüe), jota koordinoi PROEIB Andes -järjestö yhteistyössä Cochabamban Universidad Mayor de San Simónin kanssa. Tutkielman tarkoituksena on selvittää, miten kulttuurienvälisyys määritellään ja mitä se käytännössä merkitsee opetuksen eri osa-alueilla: sisällöissä, opetusmetodeissa ja -materiaaleissa sekä arvioinnissa. Koska kulttuurienvälisen kaksikielisen opetuksen toteutus ja tutkiminen eri Latinalaisen Amerikan maissa on tähän asti painottunut lähes yksinomaan perusopetukseen, pyrin työssäni keskittymään kulttuurienvälisyyden ilmentymiin nimenomaan bolivialaisessa korkeakoulukontekstissa. Tutkielman aineistona on käytetty kahdeksaa EIB -asiantuntijoiden teemahaastattelua, jotka FM Eila Isotalus on tehnyt Boliviassa vuonna 2004. Haastatteluaineisto analysoitiin teoriasidonnaista eli abduktiivista sisällönanalyysiä käyttäen. Tutkielman teoriatausta koostuu yhtäältä kulttuurienvälisyyteen ja monikulttuurisuuteen liittyvien käsitteiden määrittelystä, ja toisaalta kulttuurienväliseen opetukseen liittyvien mallien esittelystä. Aineiston analyysissä avuksi on ollut etenkin James A. Banksin teoria monikulttuurisen opetuksen viidestä ulottuvuudesta, joiden kautta on voitu pohtia kulttuurienvälisyyden toteutumista opetuksen eri osa-alueilla ja nostaa esille bolivialaisen kulttuurienvälisen opetuksen erityispiirteitä. Aineiston analyysissä ilmenee, että kulttuurienvälisyyden käsitteen määrittely on vahvasti kontekstisidonnainen ja jatkuva prosessi, johon vaikuttavat eri toimijoiden näkemykset ja vaatimukset. EIB -asiantuntijoiden esittämät määrittelyt voidaan jakaa makro- ja mikrososiaaliseen kategoriaan sen mukaan, nähdäänkö kulttuurienvälisyys ensisijaisesti yhteiskunnallisena vai yksilötason käsitteenä. Aineistossa korostuu ajatus latinalaisamerikkalaisesta kulttuurienvälisyydestä poliittisena käsitteenä, jonka keskiössä on vaatimus yhteiskunnallisten valtasuhteiden muutoksesta. Yksi suurimmista haasteista kulttuurienvälisyyden toteuttamisessa bolivialaisessa korkeakouluopetuksessa ovat akateemiseen kulttuuriin liittyvät perinteet, jotka vaikeuttavat uusien toimintatapojen omaksumista. Kulttuurienvälisyys opetuksessa on toistaiseksi tarkoittanut etupäässä sisältöjen monipuolistamista lisäämällä opetusohjelmiin elementtejä paikallisista kulttuureista. Tärkeänä askeleena EIB:n kehityksessä voidaan pitää painopisteen siirtymistä sisältökysymyksistä kulttuurienvälisten opetusmetodien luomiseen. Näiden opetusmenetelmien tulisi pohjautua ymmärrykseen oppimisesta kokonaisvaltaisena, yhteisöllisenä prosessina ja siten kuroa umpeen kuilua koulun ja yhteisöjen arkielämän välillä. Opetusmenetelmien ja -materiaalien suhteen keskeinen kulttuurienvälisyyteen liittyvä kysymys on intiaanikansojen suullisen kulttuurin ja tiedon jakamisen perinteiden hyödyntäminen opetuksessa. Maisteriohjelman opiskelijoiden arvioinnissa pyritään huomioimaan yksilön kokonaisvaltainen kehitys pelkkien opintosuoritusten sijasta, mutta arvosanoihin pohjautuvasta arvostelukäytännöstä ei ole toistaiseksi voitu luopua yliopiston vaatimusten vuoksi. Kaiken kaikkiaan kulttuurienvälisyyden toteuttaminen EIB:ssä ja maisteriohjelmassa on pitkän tähtäimen prosessi, joka vaatii perinteisten opetuskäytäntöjen kyseenalaistamista ja korkeakouluopetuksessa myös akateemisen kulttuurin haastamista. On oleellisen tärkeää, että prosessiin osallistuvat asiantuntijoiden ohella myös esimerkiksi opiskelijat, intiaaniyhteisöt ja -järjestöaktiivit.

Levitation effect in zeolites: Quasielastic neutron scattering and molecular dynamics study of pentane isomers in zeolite NaY

We report the quasielastic neutron scattering (QENS) and molecular dynamics (MD) investigations into diffusion of pentane isomers in zeolite NaY. The molecular cross section perpendicular to the long molecular axis varies for the three isomers while the mass and the isomer-zeolite interaction remains essentially unchanged. Both QENS and MD results show that the branched isomers neopentane and isopentane have higher self-diffusivities as compared with n-pentane at 300 K in NaY zeolite. This result provides direct experimental evidence for the existence of nonmonotonic, anomalous dependence of self-diffusivity on molecular diameter known as the levitation effect. The energetic barrier at the bottleneck derived from MD simulations exists for n-pentane which lies in the linear regime while no such barrier is seen for neopentane which is located clearly in the anomalous regime.Activation energy is in the order E-a(n-pentane)>E-a(isopentane)>E-a(neopentane) consistent with the predictions of the levitation effect. In the liquid phase, it is seen thatD(n pentane)>D(isopentane)>D(neopentane) and E-a(n-pentane)< E-a(isopentane)< E-a(neopentane). Intermediate scattering function for small wavenumbers obtained from MD follows a single exponential decay for neopentane and isopentane. For n-pentane, a single exponential fit provides a poor fit especially at short times. Cage residence time is largest for n-pentane and lowest for neopentane. For neopentane, the width of the self-part of the dynamic structure factor shows a near monotonic decrease with wavenumber. For n-pentane a minimum is seen near k=0.5 A degrees(-1) suggesting a slowing down of motion around the 12-ring window, the bottleneck for diffusion. Finally, the result that the branched isomer has a higher diffusivity as compared with the linear analog is at variation from what is normally seen.

Growth Mechanism of Cadmium Sulfide Nanocrystals

We investigate the growth kinetics of CdS nanocrystals in the quantum confinement regime using time-resolved small-angle X-ray scattering. In contrast to earlier reports for similar systems, we establish that the growth kinetics in this case follows the Lifshitz-Slyozov-Wagner theory, for not only growth of the average diameter of the nanocrystals but also the time dependence of the size distribution and the temperature dependence of the rate constant. This is the first rigorous example of the coarsening process in the quantum confinement (< 5 nm)regime. Ab initio studies for the reaction pathways provide a microscopic understanding of this finding.

A generalized mathematical theory and experimental verification of proportional notches

A theory and generalized synthesis procedure is advocated for the design of weir notches and orifice-notches having a base in any given shape, to a depth a, such that the discharge through it is proportional to any singular monotonically-increasing function of the depth of flow measured above a certain datum. The problem is reduced to finding an exact solution of a Volterra integral equation in Abel form. The maximization of the depth of the datum below the crest of the notch is investigated. Proof is given that for a weir notch made out of one continuous curve, and for a flow proportional to the mth power of the head, it is impossible to bring the datum lower than (2m − 1)a below the crest of the notch. A new concept of an orifice-notch, having discontinuity in the curve and a division of flow into two distinct portions, is presented. The division of flow is shown to have a beneficial effect in reducing the datum below (2m − 1)a from the crest of the weir and still maintaining the proportionality of the flow. Experimental proof with one such orifice-notch is found to have a constant coefficient of discharge of 0.625. The importance of this analysis in the design of grit chambers is emphasized.

Fine Structure of the Rayleigh Line in Amorphous Substances

As is well known, when monochromatic light scattered by a liquid is examined under high resolution it exhibits a fine structure: an undisplaced central line and two lines on either side with wavelengths slightly different from that of the incident light. The appearance of the displaced components was first predicted by Brillouin1. On the basis of his theory, the observed displacements of frequency are regarded as a Doppler effect arising from the reflexion of the light wave by the progressive sound waves of thermal origin in the scattering medium. The frequency shift of the so-called Brillouin components is given by the formula where nu and c are the velocities of sound and light in the medium and theta is the angle of scattering. That the effect contemplated by Brillouin does arise in liquids and crystals is now a well-established experimental fact.

Moment methods and "restricted variation" in kinetic theory

It is shown that there is a strict one-to-one correspondence between results obtained by the use of "restricted" variational principles and those obtained by a moment method of the Mott-Smith type for shock structure.