Optical and magnetic properties of the exact PPP states of biphenyl

The low-lying singlets and triplets of biphenyl are obtained exactly within the PPP model using the diagrammatic valence bond method. The energy gaps within the singlet manifold as well as the lowest singlet-triplet gap are found to be in good agreement with experimental results. The two weak absorptions between 4·1 and 4·2 eV reported experimentally are attributed to the two states lying below the optical gap that become weakly allowed on breaking electron-hole and inversion symmetries. The observed blue shift of the spectral lines, attributed to a change in dihedral angle, on going from crystalline to solution to vapour phase is also well reproduced within the PPP model. The bond orders show that the ground singlet state is benzenoidal while the dipole excited state as well as the lowest triplet state are quinonoidal and planar. Comparison with the experimental spin densities and the fine structure constants D and E in the triplet state point to slightly weaker correlations than assumed by the PPP model. The introduction of a 1-8 bond to mimic poly(paraphenylene)s gives an optical gap that is in good agreement with experiment.

Bridging East and West : The Establishment of the International Institute for Applied Systems Analysis (IIASA) in the United States Foreign Policy of Bridge Building, 1964-1972.

The dissertation examines the foreign policies of the United States through the prism of science and technology. In the focal point of scrutiny is the policy establishing the International Institute for Applied Systems Analysis (IIASA) and the development of the multilateral part of bridge building in American foreign policy during the 1960s and early 1970s. After a long and arduous negotiation process, the institute was finally established by twelve national member organizations from the following countries: Bulgaria, Canada, Czechoslovakia, Federal Republic of Germany (FRG), France, German Democratic Republic (GDR), Great Britain, Italy, Japan, Poland, Soviet Union and United States; a few years later Sweden, Finland and the Netherlands also joined. It is said that the goal of the institute was to bring together researchers from East and West to solve pertinent problems caused by the modernization process experienced in industrialized world. It originates from President Lyndon B. Johnson s bridge building policies that were launched in 1964, and was set in a well-contested and crowded domain of other international organizations of environmental and social planning. Since the distinct need for yet another organization was not evident, the process of negotiations in this multinational environment enlightens the foreign policy ambitions of the United States on the road to the Cold War détente. The study places this project within its political era, and juxtaposes it with other international organizations, especially that of the OECD, ECE and NATO. Conventionally, Lyndon Johnson s bridge building policies have been seen as a means to normalize its international relations bilaterally with different East European countries, and the multilateral dimension of the policy has been ignored. This is why IIASA s establishment process in this multilateral environment brings forth new information on US foreign policy goals, the means to achieve these goals, as well as its relations to other advanced industrialized societies before the time of détente, during the 1960s and early 1970s. Furthermore, the substance of the institute applied systems analysis illuminates the differences between European and American methodological thinking in social planning. Systems analysis is closely associated with (American) science and technology policies of the 1960s, especially in its military administrative applications, thus analysis within the foreign policy environment of the United States proved particularly fruitful. In the 1960s the institutional structures of European continent with faltering, and the growing tendencies of integration were in flux. One example of this was the long, drawn-out process of British membership in the EEC, another is de Gaulle s withdrawal from NATO s military-political cooperation. On the other hand, however, economic cooperation in Europe between East and West, and especially with the Soviet Union was expanding rapidly. This American initiative to form a new institutional actor has to be seen in that structural context, showing that bridge building was needed not only to the East, but also to the West. The narrative amounts to an analysis of how the United States managed both cooperation and conflict in its hegemonic aspirations in the emerging modern world, and how it used its special relationship with the United Kingdom to achieve its goals. The research is based on the archives of the United States, Great Britain, Sweden, Finland, and IIASA. The primary sources have been complemented with both contemporary and present day research literature, periodicals, and interviews.

Spiral states in the square-lattice Hubbard model

We present a variety of physical implications of a mean-field theory for spiral spin-density-wave states in the square-lattice Hubbard model for small deviations from half filling. The phase diagram with the paramagnetic metal, two spiral (semimetallic) states, and ferromagnet is calculated. The momentum distribution function and the (quasiparticle) density of states are discussed. There is a significant broadening of the quasiparticle bands when the antiferromagnetic insulator is doped. The evolution of the Fermi surface and the variation of the plasma frequency and a charge-stiffness constant with U/t and δ are calculated. The connection to results based on the Schwinger-boson-slave-fermion formalism is made.

Public and private technical assistance programs for non-industrial private forest landowners in the southern United States.

XVIII IUFRO World Congress, Ljubljana 1986.

Structure of Relativistic States

QCD factorization in the Bjorken limit allows to separate the long-distance physics from the hard subprocess. At leading twist, only one parton in each hadron is coherent with the hard subprocess. Higher twist effects increase as one of the active partons carries most of the longitudinal momentum of the hadron, x -> 1. In the Drell-Yan process \pi N -> \mu^- mu^+ + X, the polarization of the virtual photon is observed to change to longitudinal when the photon carries x_F > 0.6 of the pion. I define and study the Berger-Brodsky limit of Q^2 -> \infty with Q^2(1-x) fixed. A new kind of factorization holds in the Drell-Yan process in this limit, in which both pion valence quarks are coherent with the hard subprocess, the virtual photon is longitudinal rather than transverse, and the cross section is proportional to a multiparton distribution. Generalized parton distributions contain information on the longitudinal momentum and transverse position densities of partons in a hadron. Transverse charge densities are Fourier transforms of the electromagnetic form factors. I discuss the application of these methods to the QED electron, studying the form factors, charge densities and spin distributions of the leading order |e\gamma> Fock state in impact parameter and longitudinal momentum space. I show how the transverse shape of any virtual photon induced process, \gamma^*(q)+i -> f, may be measured. Qualitative arguments concerning the size of such transitions have been previously made in the literature, but without a precise analysis. Properly defined, the amplitudes and the cross section in impact parameter space provide information on the transverse shape of the transition process.

From ‘Afflicted’ to Activists: Structural Violence and Climate Change Discourse in the States of Pernambuco and Paraíba in Northeast Brazil

This study approaches the problem of poverty in the hinterlands of Northeast Brazil through the concept of structural violence, linking the environmental threats posed by climate change, especially those related to droughts, to the broader social struggles in the region. When discussions about potentials and rights are incorporated into the problematic of poverty, a deeper insight is obtained regarding the various factors behind the phenomenon. It is generally believed that climate change is affecting the already marginalized and poor more than those of higher social standing, and will increasingly do so in the future. The data for this study was collected during a three month field work in the states of Pernambuco and Paraíba in Northeast Brazil. The main methods used were semi-structured interviews and participant observation, including attending seminars concerning climate change on the field. The focus of the work is to compare both layman and expert perceptions on what climate change is about, and question the assumptions about its effects in the future, mainly that of increased numbers of ‘climate refugees’ or people forced to migrate due to changes in climate. The focus on droughts, as opposed to other manifestations of climate change, arises from the fact that droughts are not only phenomena that develop over a longer time span than floods or hurricanes, but is also due to the historical persistence of droughts in the region, and both the institutional and cultural linkages that have evolved around it. The instances of structural violence that are highlighted in this study; the drought industry, land use, and the social and power relations present in the region, including those between the civil society, the state and the private agribusiness sector, all work against a backdrop of symbolic and moral realms of value production, where relations between the different actors are being negotiated anew with the rise of the climate change discourse. The main theoretical framework of the study consists of Johan Galtung’s and Paul Farmer’s theory of structural violence, Ulrich Beck’s theory of the risk society, and James Scott’s theory of everyday peasant resistance.

Electronic states in a disordered metal: Magnetotransport in doped germanium

We observe a sharp feature in the ultra-low-temperature magnetoconductivity of degenerately doped Ge:Sb at H∼25 kOe, which is robust up to at least three times the critical density for the insulator-metal transition. This field corresponds to a low-energy scale characteristic of the special nature of antimony donors in germanium. Its presence and sensitivity to uniaxial stress confirm the notion of metallic impurity bands in doped germanium.

Interaction of C60 and C70 with aromatic amines in the ground and excited states. Evindence for fullerene—benzene interaction in the ground state

While C60 interacts with aromatic amines such as dimethylaniline in the ground state, C70 does not. Fluorescence spectroscopic studies, including lifetime measurements, show the formation of exciplexes of both C60 and C70 with aromatic amines in nonaromatic solvents such as methylcyclohexane. Exciplexes are however not formed in benzene solvent, due to π—π interaction between benzene and the fullerene. Based on spectroscopic absorption measurements, it is shown that both C60 and C70 do indeed interact with benzene in the ground state.

NDDO-based CI methods for the prediction of electronic spectra and sum-over-states molecular hyperpolarization

NDDO-based (AM1) configuration interaction (CI) calculations have been used to calculate the wavelength and oscillator strengths of electronic absorptions in organic molecules and the results used in a sum-over-states treatment to calculate second-order-hyperpolarizabilities. The results for both spectra and hyperpolarizabilities are of acceptable quality as long as a suitable CI-expansion is used. We have found that using an active space of eight electrons in eight orbitals and including all single and pair-double excitations in the CI leads to results that agree well with experiment and that do not change significantly with increasing active space for most organic molecules. Calculated second-order hyperpolarizabilities using this type of CI within a sum-over-states calculation appear to be of useful accuracy.

Nonequilibrium stationary states of harmonic chains with bulk noises

We consider a chain composed of $N$ coupled harmonic oscillators in contact with heat baths at temperature $T_\ell$ and $T_r$ at sites 1 and $N$ respectively. The oscillators are also subjected to non-momentum conserving bulk stochastic noises. These make the heat conductivity satisfy Fourier's law. Here we describe some new results about the hydrodynamical equations for typical macroscopic energy and displacement profiles, as well as their fluctuations and large deviations, in two simple models of this type.

Role of molecular reorientation in the vitrification of molecular liquids: A Monte Carlo study of the liquid and glassy states of 2,2-dimethylbutane

The liquid and the glassy phases of 2,2-dimethylbutane have been investigated by isothermal isobaric ensemble Monte Carlo simulation. Thermodynamic Properties and radial distribution functions for both the liquid and the glass have been obtained. The radial distribution functions have been classified into three types based on the accessibility of the group. It has been shown that the structure of the Iiquid and the glass can be understood in terms of the above classification of the radial distribution functions. Molecular reorientation plays an important role in the structural rearrangement accompanying glass formation. As much as 35% of the contribution to the increase in the intermolecular interaction energy on vitrification is due to the reorientation of the neighbouring pairs of molecules. The observed changes in the dimerisation energy and the bonding energy distribution function are consistent with the observed structural changes.

Aspects of coherent states of nonlinear algebras

Various aspects of coherent states of nonlinear su(2) and su(1,1) algebras are studied. It is shown that the nonlinear su(1,1) Barut-Girardello and Perelomov coherent states are related by a Laplace transform. We then concentrate on the derivation and analysis of the statistical and geometrical properties of these states. The Berry's phase for the nonlinear coherent states is also derived. (C) 2010 American Institute of Physics. doi:10.1063/1.3514118]

Symmetry adaptation of correlated states in the valence bond basis

Symmetry?adapted linear combinations of valence?bond (VB) diagrams are constructed for arbitrary point groups and total spin S using diagrammatic VB methods. VB diagrams are related uniquely to invariant subspaces whose size reflects the number of group elements; their nonorthogonality leads to sparser matrices and is fully incorporated into a binary integer representation. Symmetry?adapated linear combinations of VB diagrams are constructed for the 1764 singlets of a half?filled cube of eight sites, the 2.8 million ??electron singlets of anthracene, and for illustrative S?0 systems.

Impedance peaks of sealed nickel/cadmium cells at low states-of-charge

The impedance of sealed nickel/cadmium cells is measured at low states-of-charge that correspond to a cell e.m.f. range of 0.0 to 1.3 V. The results show that the impedance exhibits a pronounced maximum between 0.3 and 0.45 V. It is concluded that the impedance maxima are due to physicochemical processes taking place at the nickel oxide electrode. The impedance of the nickel oxide electrode is dominated by three different phenomena: (i) a Ni(II)/Ni(III) reaction between 1.3 and 0.8 V; (ii) a double-layer impedance between 0.8 and 0.3 V; (iii) a hydrogen evolution reaction between 0.3 and 0.0 V.

Bound states of two spin-1/2 fermions in a synthetic non-Abelian gauge field

We study the bound states of two spin-1/2 fermions interacting via a contact attraction (characterized by a scattering length) in the singlet channel in three-dimensional space in presence of a uniform non-Abelian gauge field. The configuration of the gauge field that generates a Rashba-type spin-orbit interaction is described by three coupling parameters (lambda(x),lambda(y),lambda(z)). For a generic gauge field configuration, the critical scattering length required for the formation of a bound state is negative, i.e., shifts to the ``BCS side'' of the resonance. Interestingly, we find that there are special high-symmetry configurations (e.g., lambda(x) = lambda(y) = lambda(z)) for which there is a two-body bound state for any scattering length however small and negative. Remarkably, the bound-state wave functions obtained for such configurations have nematic spin structure similar to those found in liquid He-3. Our results show that the BCS-BEC (Bose-Einstein condensation) crossover is drastically affected by the presence of a non-Abelian gauge field. We discuss possible experimental signatures of our findings both at high and low temperatures.