bluuebunny/crossref_metadata_2025 huggingface dataset:
The Contributions of Lattice Anharmonicity to the Zero‐Phonon Linewidth
Authors: Chow H. C.
Published: July 2007

The influence of the host lattice anharmonicity on the optical absorption and emission by an impurity center or a defect in a solid is studied theoretically. Lattice anharmonicity is shown to contribute to the width of the zero‐phonon line via two mechanisms: the finite lifetimes of phonon states and those impurity (defect)‐phonon collisions which are mediated by another phonon.
Dynamical theory of X‐ray diffraction by elastically bent crystals with microdefects. II. Diffraction intensity
Authors: Molodkin V. B. , Olikhovskii S. I. , Kostyuk A. N.
Published: July 2007

The amplitudes of wave fields inside a macroscopically deformed crystal with defects are obtained in the two‐beam approximation. The amplitudes of coherent (strong Bragg and “quasidiffuse”) and diffuse waves emerging from the crystal are determined by taking account of boundary conditions for both Bragg and Laue cases of diffraction. The general expressions for coherent and diffuse components of the differential reflection power of bent crystals with microdefects are obtained.
Hamiltonian dynamics of the landau model of ferroelectric liquid crystals (II)
Authors: Pitanga P. , Filho A. Ribeiro , Mundim K. C.
Published: July 2007

Ferroelectric liquid crystals are presented as a simple non‐integrable Hamiltonian system. The smectic A‐smectic C* phase transition undergoes a Hopf bifurcation. The Poincaré sections of the solutions in the smectic C* phase shows the existence of spatially chaotic behavior of the molecular structure depending on temperature and external magnetic field. The smectic C‐smectic C* phase transition is also studied as second‐order derivative Hamiltonian theory.
Vacuum ultraviolet optical analysis of spin‐cast chitosan films modified by succinic anhydride and glycidyl phenyl ether
Authors: Nosal W. H. , Thompson D. W. , Tiwald T. E. , Sarkar S. , Subramanian A. , Woollam J. A.
Published: July 2007

Optical properties of spin‐cast chitosan films were determined in the vacuum ultraviolet (VUV) through visible regions of the spectrum using spectroscopic ellipsometry. The onset of absorption in the ultraviolet was determined for chitosan films modified with succinic anhydride (SA) and glycidyl phenyl ether (GPE). This absorption was accounted for by including Gaussian and Tauc–Lorentz shaped oscillators in the optical model. VUV through visible optical constants were determined for these modified films, as well as for immunoglobulin G (IgG) attached to GPE‐modified samples. Several resonant oscillator structures exhibit greatly differing oscillator parameters for the as‐deposited, as well as SA‐ and GPE‐modified films. These in‐plane and out‐of‐plane oscillator strengths, energy positions, and broadening were determined and tabulated, and their chemical origins identified. A phenyl resonant π‐bond at approximately 6.3 eV was observed for the GPE‐modified sample. This was not present in the bare chitosan data. GPE contains a phenyl group in the molecule and absorption due to it is clearly identified. Clarity of data after surface chemical modification is due to the high surface sensitivity of VUV ellipsometry. Copyright © 2007 John Wiley & Sons, Ltd.
The general rescue subsystem‐adaptation and structure at sea
Authors: Skyttner Lars
Published: July 2007

The existence of a general rescue subsystem in higher organisms, as part of the GLS theory and the GAS syndrome, is asserted. Working principles for the system and its existence throughout higher system levels are presented. Among important processes demonstrated are the adaptation of the system to special threats at sea and the storage of the system's knowledge and organization in the sea‐safety convention. Recursiveness of the rescue subsystem within all higher system levels was found to be a basic requisite for individual survival, especially at sea. Finally, the most serious threat to lives on board ships at sea, was found to be system morality failures.
A systems‐based conceptual framework for auditing
Authors: Swanson G. A. , Marsh Hugh L.
Published: July 2007

Since the stock market crash of 1929, the auditing profession has rapidly emerged in advanced economies. The procedures of the profession have generally evolved out of political processes without the systematic guidance of a cohesive conceptual framework. That eclectic approach has produced generally accepted accounting principles that encourage publication of global organizational performance assessments such as net income that have little obvious connection to the concrete processes they purport to describe. The approach, furthermore, allows fragmented and disconnected auditing procedures. This paper presents an interpretive and analytical study of auditing in organizations and societies. A systematic conceptual framework of auditing based on observable, measurable entities is developed through living systems theory. This approach provides a means of applying to auditing the well developed investigation methods and procedures of the sciences.
System life cycle ‐ system life: The model ‐ based technical diagnostics ‐ A view on holistic modelling
Authors: Cempel C. , Natke H. G.
Published: July 2007

Man‐made systems are becoming more and more complex, so there is a necessity to analyse and simulate their dynamic behaviour over their whole life. To deal with these problems we require a holistic model of the operating system which includes the concept of life. This is defined on the basis of energy internally dissipated in the system, when it is treated as open and energy‐transforming. The holistic model of a system can be very useful for the space‐time‐life simulation of its condition at the design stage and for a model‐based diagnosis at the life stage. This procedure will substantially increase the reliability of operating systems and reduce the total life cycle costs.
Methodology for Design of Mis Architecture (INFLOS)
Authors: Gupta M. P. , Sushil
Published: July 2007

Abstract Management Information System (MIS) architecture reveals the nexus of information‐decision elements and has been described as an important planning tool of MIS development. In this paper, it is considered as a key design issue and a methodology (INFLOS) is presented for the same. Salient features of INFLOS have been discussed. The methodology proceeds in two phases. This paper is restricted to discuss only the first phase.
Visionary Systems Thinking (VST) as a Support to Creativity in the Quality Management (TQM) Process
Authors: Filion Louis Jacques
Published: July 2007

Abstract ‐ Innovation, the introduction of new products/services and new ways of doing is one of the dimensions of quality. It is achieved by the integration of creativity. Visionary Systems Thinking (VST) based on Soft Systems Methodology (SSM) ‐ is identified as one of the concepts for supporting creativity in the quality management (TQM) process. This paper presents VST and proposes a model for effective integration of quality management within the managerial process. Learning, unlearning and anticipatory learning become basic means for making this possible.
Symbolic and subsymbolic models, and their use in systems research
Authors: Pessa Eliano
Published: July 2007

This paper contains a sketch of a generalized systems theory in order to deal with the so‐called “subsymbolic” models, whose implicit informational content cannot be made entirely explicit in a reasonable amount of time. To deal with such a situation, a new “genetic” approach has been proposed, in which the researcher manages a “population” of models, instead of a single one. The systemic modeling activity thus become equivalent to an evolutionary dynamics of this population, driven by suitable “genetic” rules and satisfying some fitness criteria. Some concrete examples are presented to this regard, so that a rigorous formalization of this new type of systems theory becomes possible, opening the way for a semi‐automatized application to the modeling of economic, social, and psychological systems, where we deal with organized complexity.
Discontinuous change in multilevel hierarchical systems
Authors: Rosser J. Barkley , Folke Carl , Günther Folke , Isomaki Heikki , Perrings Charles , Puu Tönu
Published: July 2007

We examine sources and dynamics of discontinuous changes in discrete multi‐level hierarchical ecological‐economic systems. We hypothesize the anagenetic moment, the creation of a new level of hierarchy, as arising from variable entrainment at some level. Bottom‐up as well as top‐down dynamics are studied and competing theories of the sources of such discontinuities are reviewed. Implications for the analysis of complex ecological‐economic systems are considered depending on whether they are characterized by single hierarchy, bi‐hierarchy, or matrix hierarchy relationships.
Gdss does not guarantee equal participation
Authors: Maris Jo‐Mae
Published: July 2007

Group decision support systems (GDSS) provide forums capable of reducing group process loss and of allowing equal participation. The design of GDSS provides conditions necessary to produce equal participation, but a forum does not ensure equal participation. Reducing group process loss increases the number of comments produced by groups using GDSS. Participants producing more comments did not lead to a uniform distribution of the number of comments. Our study, also, investigated quantity of comments produced by participants with some self‐reported measures of participation. We found participation was associated with “talkativeness”.
Values, science and the quest for demarcation
Authors: de Zeeuw Gerard
Published: July 2007

Although the study of human values is excluded by classical science, it is a major area of interest in systems science. Its difficulties challenge much of the field's creative force. This manifests itself in a strong tendency to propose what is ‘new’: directions of research, methodologies, paradigms. This variety poses problems of evaluation. A tool is described to solve these problems. It simplifies the process of comparing studies, and suggests how to improve on them.
Beyond the fads: Systems thinking for managers
Authors: Jackson Mike C.
Published: July 2007

This paper makes a comparison between research work going on in management science, particularly that taking a systems approach, and the research which underlies what is being offered to managers on the market in the form of the so‐called management ‘fads’—concentrating here on guru theory, total quality management, business process re‐engineering and the learning organization. This comparison proves favourable to the systems approach which, with its carefully crafted foundations, seems to offer much more to managers than the fads. Broadening the debate beyond management, a final section discusses the relationship between systems thinking and postmodernism—the latter usually associated with a pessimism about adopting any systemic or systematic approach.
Developing a family declaration of interdependence: A methodology for systems design within a small social unit
Authors: Dyer Gordon
Published: July 2007

The paper offers a possible approach to the development of a Family Declaration of Interdependence as a framework for future‐creating social system design. A methodology for its introduction, incorporation and further development within the social unit, together with a draft family Bill of Rights and Responsibilities, are suggested. The methodology is intended for those with lay appreciation of systems design in the hope that this will speed the diffusion of design competence. The word ‘family’ is interpreted broadly, and the methodology is seen as applicable to a wide range of small social units and cultural settings, e.g. club, association, learning or development group where a form of contract which recognizes members' interdependence, and which generates commitment, participation and sustainability, would be desirable. An adaptation of the Declaration currently evolving within the International Systems Institute is described.
Ethics and science
Authors: Churchman C. West
Published: July 2007

In this paper C. West Churchman explores a question that Kenneth Boulding asked repeatedly: ‘Is economics basically a study of ethical behaviour?’ In typical Churchman style, he has a conversation with Boulding about this question and discusses it in the context of his own primary concern: the relationships between ethics and science.
Perspectives from the Boulding files
Authors: Hammond Debora
Published: July 2007

This paper draws upon research for my dissertation, which is a history of the general systems movement, focusing specifically on the Society for General Systems Research. In the dissertation I examine the backgrounds of the individual founders of the Society in order to understand the influences that led them to establish the Society and to clarify their intentions in doing so. In this paper I discuss Kenneth Boulding's interdisciplinary social science seminars at the University of Michigan as background for his work at the Center for Advanced Study in the Behavioral Sciences at Stanford during its opening year (1954–55), where the idea for the Society was developed and realized. I also discuss the role of the Ford Foundation in establishing the Center and promoting interdisciplinary work in the behavioral sciences during the postwar era. An understanding of this context may enhance appreciation for the significance of Boulding's contribution to the systems movement.
Yeast genome evolution—the origin of the species
Authors: Scannell Devin R. , Butler Geraldine , Wolfe Kenneth H.
Published: July 2007

With almost 20 genomes sequenced from unicellular ascomycetes (Saccharomycotina), and the prospect of many more in the pipeline, we review the patterns and processes of yeast genome evolution. A central core of about 4000 genes is shared by all the sequenced yeast genomes. Gains of genes by horizontal gene transfer seem to be very rare. Gene losses are more frequent, and losses of whole sets of genes in some pathways in some species can be understood in terms of species‐specific differences in biology. The wholesale loss of redundant copies of duplicated genes after whole‐genome duplication in the ancestor of one clade of yeasts is likely to have caused the emergence of many reproductively isolated lineages of yeasts at that time, but other processes are responsible for species barriers that arose more recently among close relatives ofSaccharomyces cerevisiae. Copyright © 2007 John Wiley & Sons, Ltd.
What I Learned (and Re-Learned) When I Ran for Local
Office
Authors: Andersen Kristi
Published: July 2007

As political scientists, many of us encourage our students to get
involved in community activities and local politics; and in fact
many of our political science colleagues have run for state and
local (and, less frequently, national) office. While the literature
on parties, elections, and voting behavior may help provide us with
some context when we (or our students) enter the political arena,
there is a striking dearth of literature on voting behavior (and
candidate behavior) in local elections. What Herson (1957) referred to as “the lost world of
municipal government” can still be so characterized today, though a
few recent studies have attempted to predict winners of municipal
races (for example, McGleneghan and Ragland 2002; Lieske 1989). This
article analyzes my own education in local politics, which resulted
from my candidacy for the Town Council of Cazenovia, New York in
November, 2005. I came to the experience of participating in a local
campaign with expectations shaped by my teaching and research in
American politics at the national level, and found that these
expectations often gave way to the specifics of context. Jennifer
Lawless, a political scientist running for Congress in 2006,
expressed this sentiment as: “Political science is all generalities.
Politics is all individual circumstances” (Fischer 2006).
Market Principles, Philanthropic Ideals, and Public
Service Values in International Public Policy
Programs
Authors: Stone Diane
Published: July 2007

Just as there was a boom in the establishment of Master's of Business
Administration programs over the past 30 or more years, today there
is an equivalent boom in graduate programs in the field of public
policy. This is so for the transition states of Central and Eastern
Europe (CEE) and the former Soviet Union where the dynamics of
globalization and “Europeanization” are apparent and the pressures
for reform pronounced (Verheijen and Connaughton 2003, 843). Appointing personnel with the educational
prerequisites necessary for managing reform and meeting the
challenges of globalization has been problematic for both official
actors such as national education ministries, international
organizations, and bilateral development agencies, as well as for
non-state actors such as the business sector, philanthropic
foundations, and non-governmental organizations (NGOs). The need for
graduates who can function in international and cross-cultural
contexts is prompting institutions to create new courses and
professional degree programs (Mallea 1998,
16).
Timothy Cook
Authors: Garand James C. , Schafer Mark
Published: July 2007

It is with indescribable sorrow that we write with news of the death
of our dear friend and colleague, Timothy Cook. Tim passed away from
complications associated with brain cancer on August 5, 2006, in
Baton Rouge, Louisiana. He was only 51. Tim held the Kevin P.
Reilly, Sr. Chair in Political Communication at Louisiana State
University.
Things Students and Political Scientists Might Consider
about our Military
Authors: Stiehm Judith Hicks
Published: July 2007

The October, 2006 issue of PS (923–4) published a
quiz on the U.S. Military alongside a call for submissions on what
we should be teaching students about our military. The essays here
represent a fraction of the response. Other proposals have been
incorporated in several panels that will be presented at the APSA
Annual Meeting in Chicago this fall. Still others have been
incorporated in a volume contracted to Palgrave Press and
provisionally titled Inside Defense.
Suicide and Alcohol Psychoses in Belarus 1970-2005
Authors: Razvodovsky Yury E.
Published: July 2007

Abstract. Background: The relationship between alcohol and suicide is well documented. The research evidence suggests an important role for a cultural and social context in the alcohol-suicide association. Purpose: To estimate the aggregate level effect of alcohol consumption on the suicide rate in Slavic culture. Method: Trends in the suicide and alcohol-psychoses morbidity rate in the former Soviet Slavic republic of Belarus from 1970 to 2005 were analyzed employing an ARIMA time-series analysis. Results: The results of the analysis suggest a close association between the suicide and alcohol-psychoses morbidity rate. Conclusion: This study replicates previous findings that highlighted a close link between alcohol and suicide at the aggregate level. The results of this study also suggest that alcohol is responsible for the fluctuation of the suicide rate in the former Soviet republic of Belarus during the last decades.
Stochastic analysis of exit fluid temperature records from the active TAG hydrothermal mound (Mid‐Atlantic Ridge, 26°N): 1. Modes of variability and implications for subsurface flow
Authors: Sohn R. A.
Published: July 2007

Yearlong time series records of exit fluid temperature from the active TAG hydrothermal mound (Mid‐Atlantic Ridge, 26°N) reveal a complex space‐time pattern of flow variability within the mineral deposit. Exit fluid temperatures were measured every 8–10 min from 17 sites distributed across the upper terrace of the mound from June 2003 to June 2004. High‐temperature records were obtained using Deep Sea Power and Light SeaLogger® probes deployed in fractures discharging ∼360°C black smoker fluids, and low‐temperature records were obtained using VEMCO Ltd. Minilog probes deployed in cracks discharging ∼20°C diffuse flow fluids. The temperature records are considerably more variable than those acquired from vent fields on the fast spreading East Pacific Rise and exhibit a complex mix of both episodic and periodic variability. The diffuse flow records alternate between periods of discharge and periods of what I infer to be recharge when fluid temperatures are equal to background water column levels (∼2.7°C) as ambient seawater is drawn into the seafloor. The space‐time patterns of these episodic variations suggest that they represent reorganizations of the secondary circulation system driving diffuse discharge on the upper terrace of the mound on timescales from a few hours to a few days, most likely in response to permeability perturbations. Harmonic temperature oscillations were observed over a range of periods, with the principal lunar semidiurnal tidal period (M2) being most dominant. During certain times, exit fluid temperatures at diffuse sites pulse at diurnal and semidiurnal tidal periods when they are hovering near background water column levels, which I interpret as flow reversals associated with the vertical displacement of a fluid boundary layer at the seafloor interface when the local net flux is near zero. The pulsing behavior is predicted by poroelastic models of tidal loading but is not consistent with effects from tidal currents, which demonstrates that poroelastic effects from tidal loading modulate shallow subsurface flow at the active TAG mound.
Hydrometeor charges observed below an electrified cloud using a new instrument
Authors: Mo Qixu , Detwiler Andrew G. , Helsdon John , Winn W. P. , Aulich G. , Murray W. Clifton
Published: July 2007

Investigation of charges on particles in thunderstorms was conducted during the Severe Thunderstorm Electrification and Precipitation Study. In the case presented here, aircraft measurements of the electric field, and hydrometeor size and charge, were made in a precipitation shaft beneath the base of a small convective cloud which was electrified, but which produced no lightning. A newly designed instrument was used to obtain particle image and charge measurements for particles larger than 0.2 mm in size. Laboratory tests and calculations suggest that under optimum conditions particle charge can be determined with this instrument to within 13% for particles carrying more than a few pC of charge. Uncertainty in charge magnitude increases to 24% in less optimum conditions. It was found in this shower of melting graupel with a peak concentration of ∼80 particles m−3 that 70% of the particles were charged, with 98% of the charged particles having positive charge. Peak particle sizes were 2 mm, and peak charges were 25 pC. The magnitude of charge varied widely for particles of a given size, but minimum, average, and maximum charge generally increased as particle size increased. The hydrometeors in this region constituted a lower positive charge center. This center must have developed through microphysical interactions and not charge transferred by lightning discharges.
Effect of geomagnetic activity on the channel scattering functions of HF signals propagating in the region of the midlatitude trough and the auroral zone
Authors: Zaalov N. Y. , Warrington E. M. , Stocker A. J.
Published: July 2007

The morphology of the auroral and subauroral ionosphere is strongly dependent on the interplanetary magnetic field and the level of geomagnetic activity. This change in the morphology impacts on the characteristics of signals received after propagation through these regions of the ionosphere. In order to develop a better understanding of these effects, a number of experiments have recently been undertaken in which the time of flight, Doppler frequency, and direction of arrival of HF signals have been measured over several northerly paths. In this paper, parameters derived from the observations of the channel scattering functions and direction of arrival for HF signals propagating over two paths (one in the auroral zone, and one at latitudes affected by the midlatitude trough) are presented.
The stabilizing effect of streaks on Tollmien-Schlichting and oblique waves: A parametric study
Authors: Bagheri Shervin , Hanifi Ardeshir
Published: July 2007

The stabilizing effect of finite amplitude streaks on the linear growth of unstable perturbations [Tollmien-Schlichting (TS) and oblique waves] is numerically investigated by means of the nonlinear parabolized stability equations. We have found that for stabilization of a TS-wave, there exists an “optimal” spanwise spacing of the streaks. These streaks reach their maximum amplitudes close to the first neutral point of the TS-wave and induce the largest distortion of the mean flow in the unstable region of the TS-wave. For such a distribution, the required streak amplitude for complete stabilization of a given TS-wave is considerably lower than for β=0.45, which is the optimal for streak growth and used in previous studies. We have also observed a damping effect of streaks on the growth rate of oblique waves in Blasius boundary layer and for TS-waves in Falkner-Skan boundary layers.
Gate-induced switching and negative differential resistance in a single-molecule transistor: Emergence of fixed and shifting states with molecular length
Authors: Farajian A. A. , Belosludov R. V. , Mizuseki H. , Kawazoe Y. , Hashizume T. , Yakobson B. I.
Published: July 2007

The quantum transport of a gated polythiophene nanodevice is analyzed using density functional theory and nonequilibrium Green’s function approach. For this typical molecular field effect transistor, we prove the existence of two main features of electronic components, i.e., negative differential resistance and good switching. Ab initio based explanations of these features are provided by distinguishing fixed and shifting conducting states, which are shown to arise from the interface and functional molecule, respectively. The results show that proper functional molecules can be used in conjunction with metallic electrodes to achieve basic electronics functionality at molecular length scales.
Spin-orbit coupling in complexes of toluene with rare gas atoms
Authors: Oliver Thomas A. A. , Taylor Peter R. , Doyle Richard J. , Mackenzie Stuart R.
Published: July 2007

The potential energy surfaces (PESs) and S1-T1 spin-orbit coupling matrix element (SOCME) surfaces are investigated for the toluene–X weakly bound clusters (X=Ne, Ar, and Kr). Calculations of the vibrational wave functions using a one-dimensional stretch model are presented and used to determine vibrationally averaged values of the SOCMEs. Our ab initio theoretical results compare well with intersystem crossing rates derived from recent experimental fluorescence lifetime data [Doyle et al., J. Chem. Phys. 122, 194315 (2005)]. Vibrational averaging is shown to change the absolute magnitude of the calculated SOCMEs, but the ratio between them remains very similar to that of the single-point values calculated at the minima of the PESs.
Water absorption in polyethylene under external electric fields
Authors: Johansson E. , Bolton K. , Ahlström P.
Published: July 2007

Monte Carlo simulations of the solubility and structure of water in polyethylene in thermodynamic equilibrium with liquid water were performed in external fields ranging from 2×105to4×109V∕m. For a given equilibrium temperature and pressure, the water solubility decreases at higher fields. This occurs since it is energetically favorable for water molecules to be in the pure water phase than in the polyethylene matrix at high field strengths, and results in an increased density in the water phase. However, fields relevant to high voltage conduction (in the absence of defects that can lead to large local field strengths) do not change the solubility. In addition, at large fields the number of water clusters decreases for all cluster sizes. The rate of decrease is highest for large clusters, and a larger fraction of water molecules exist as monomers in the polyethylene matrix at high fields. Large fields also cause alignment of the water molecules, which leads to more clusters with linear topologies and hence an increase in the cluster radius of gyration.
Geometric and electronic structures of NO dimer layers on Rh(111) studied with near edge x-ray absorption fine structure spectroscopy: Experiment and theory
Authors: Nakai Ikuyo , Kondoh Hiroshi , Shimada Toru , Yokota Reona , Katayama Tetsuo , Ohta Toshiaki , Kosugi Nobuhiro
Published: July 2007

Adsorption of NO on the Rh(111) surface has been studied in the monolayer, bilayer, and multilayer regimes with near edge x-ray absorption fine structure (NEXAFS) spectroscopy. NO dimer layers are formed on a chemisorbed monomer layer. The polarization dependence in the NEXAFS spectra of the dimer components has contradicted the previous assignments. To determine the structure of the NO dimer layers from the polarization analysis of the NEXAFS spectra, ab initio configuration interaction calculations have been carried out for some low-lying core excited states of the weakly bound NO dimer with cis-ONNO planar geometry. It is revealed that the NO dimers in the multilayer are standing with the N–N bond perpendicular to the surface, while in the second layer they are rather lying on the first monomer layer.
Structural and magnetic properties of Mn-ion implanted ZnO films
Authors: Venkataraj Selvaraj , Ohashi Naoki , Sakaguchi Isao , Adachi Yutaka , Ohgaki Takeshi , Ryoken Haruki , Haneda Hajime
Published: July 2007

Zinc oxide films doped with Mn (Mn:ZnO) were prepared by implanting Mn+ ions into ZnO films deposited by pulsed laser deposition, and their structure and magnetic properties were studied. The Raman spectra of the films indicated that Mn ions occupied the Zn site of ZnO after annealing, while the as-implanted films were amorphous like the ones with very low crystallinity. Magnetic measurements revealed that neither as-implanted nor annealed Mn:ZnO films showed ferromagnetism. The Mn:ZnO films demonstrated paramagnetism that was likely due to Mn2+ ions at the substitutional Zn site.
Modeling the effect of the structure of polymer photocells on their absorption spectrum
Authors: Shikler Rafi , Friend Richard H.
Published: July 2007

We present a framework for the calculation of light absorption in multicomponent polymer photocells. We have modeled a periodic lateral structure of two polyfluorene conjugated polymers with complementary absorption spectra. We show how the coupling induced by scattering at the interfaces between different regions of the structure leads to enhanced absorption arising from energy flow from the less-absorbing to the more-absorbing material. We also show that a periodic structure can lead to resonance amplification of absorption in part of the absorption spectrum. These lead to an enhancement in the numerically calculated absorption spectrum by up to 2.6 times. We further show that a periodic lateral structure can show larger optical absorption than similar devices with a bilayer structure. This method is generally applicable to multicomponent heterojunction photovoltaic diodes.
Magnetodielectric effect in BaTiO3−LaMnO3 composites
Authors: Kim N. G. , Koo Y. S. , Won C. J. , Hur N. , Jung J. H. , Yoon J. , Jo Y. , Jung M. H.
Published: July 2007

The structural, dielectric, magnetic, and magnetodielectric properties were systematically investigated for (1−x)BaTiO3−(x)LaMnO3 composites in wide temperatures, frequencies, and mole percent (x). Dielectric anomaly around 410 K and magnetic hysteresis at 293 K were clearly observed, which might imply the coexistence of ferroelectricity and ferromagnetism at room temperature. The values of magnetodielectric effect were well scaled with M2, i.e., ([ε(H)−ε(0)]/ε(0))∼M2, and were increased with x. The observed magnetodielectric effect were discussed in conjunction with the formation of a magnetoresistive (La,Ba)MnO3 phase.
Small valence band offset in (010) InS∕CuI heterojunction diodes
Authors: Konovalov I. , Makhova L.
Published: July 2007

Heterojunctions between the (010) facet of an orthorhombic InS single crystal and evaporated CuI show a remarkably small valence band offset of 0.15eV (cliff). This minor band offset allows rather good injection conditions for holes. In accordance to this result, the current-voltage characteristics of the device are rectifying and show a large forward voltage.
Nanoscale analysis of interfaces in a metal/oxide/oxide trilayer obtained by pulsed laser deposition
Authors: Fix T. , Ulhaq-Bouillet C. , Colis S. , Dinia A. , Bertoni G. , Verbeeck J. , Van Tendeloo G.
Published: July 2007

Sr 2 Fe Mo O 6 ∕ Sr Ti O 3 ∕ Co Fe 2 trilayers grown by pulsed laser deposition on SrTiO3 (001) are investigated by transmission electron microscopy and electron energy loss spectroscopy. The stack is epitaxial, independent of whether the CoFe2 electrode is grown at 500 or at 50°C. Thus it is possible to obtain epitaxy near room temperature. The SrTiO3∕CoFe2 interface is quite sharp, while the Sr2FeMoO6∕SrTiO3 interface presents regions of Fe depletion. The chemical composition of the films is close to the nominal stoichiometries. These results could be useful for the growth of heteroepitaxial devices and magnetic tunnel junctions.
Grating induced micelle alignment of mesostructured silica films
Authors: Yan Minhao , Henderson Mark J. , Gibaud Alain
Published: July 2007

A two-dimensional hexagonal film was produced by the evaporation-induced self-assembly route using the triblock copolymer (EO20PO70EO20) as the structure directing agent. The film was deposited between the walls of a grating of 450nm period and 55nm average line depths by dip coating the substrate in the direction perpendicular to the lines of the grating. In the case where film thicknesses were less than the height of grating walls, the orientation of the micelles was directed by the walls of the grating. Observation of the mesostructured film using atomic force microscopy after chemical etching revealed the internal structure.
Giant enhancement of second harmonic generation in poled ferroelectric crystals
Authors: Li Jingjuan , Li Zhiyuan , Sheng Yan , Zhang Daozhong
Published: July 2007

The authors propose a simple one-dimensional inhomogeneous system composed of periodically alternating stacked air and poled LiNbO3 crystal layers. This structure combines the advantages of photonic band gap (PBG) structures and periodically poled ferroelectric crystals, so the high density of modes and quasiphase matching can be achieved simultaneously. They find that compared with simple quasiphase-matched and PBG structures, the conversion efficiency of second harmonic generation in this structure can be significantly enhanced when the pump and second harmonic fields are both tuned to the band edge.
Spectral dependence of the photoluminescence decay in disordered semiconductors
Authors: Rubel O. , Stolz W. , Baranovskii S. D.
Published: July 2007

Kinetics of the energy transfer and the corresponding photoluminescence decay at selected photon energies in disordered semiconductors are studied theoretically. The authors show a straightforward way to arrive analytically at the solutions for the spectral and time dependences of the photoluminescence decay within a model based on the interplay between the radiative recombination and hopping energy relaxation of localized excitons. The theory is supported by comparison with experimental data, which yields valuable information on major properties of disorder in the underlying structures.
GluR7 is an essential subunit of presynaptic kainate autoreceptors at hippocampal mossy fiber synapses
Authors: Pinheiro Paulo S. , Perrais David , Coussen Françoise , Barhanin Jacques , Bettler Bernhard , Mann Jeffrey R. , Malva João O. , Heinemann Stephen F. , Mulle Christophe
Published: July 2007

Presynaptic ionotropic glutamate receptors are emerging as key players in the regulation of synaptic transmission. Here we identify GluR7, a kainate receptor (KAR) subunit with no known function in the brain, as an essential subunit of presynaptic autoreceptors that facilitate hippocampal mossy fiber synaptic transmission. GluR7
−/−
mice display markedly reduced short- and long-term synaptic potentiation. Our data suggest that presynaptic KARs are GluR6/GluR7 heteromers that coassemble and are localized within synapses. We show that recombinant GluR6/GluR7 KARs exhibit low sensitivity to glutamate, and we provide evidence that presynaptic KARs at mossy fiber synapses are likely activated by high concentrations of glutamate. Overall, from our data, we propose a model whereby presynaptic KARs are localized in the presynaptic active zone close to release sites, display low affinity for glutamate, are likely Ca
2+
-permeable, are activated by single release events, and operate within a short time window to facilitate the subsequent release of glutamate.
Temporal patterns of genes in scientific publications
Authors: Pfeiffer Thomas , Hoffmann Robert
Published: July 2007

Publications in scientific journals contain a considerable fraction of our scientific knowledge. Analyzing data from publication databases helps us understand how this knowledge is obtained and how it changes over time. In this study, we present a mathematical model for the temporal dynamics of data on the scientific content of publications. Our data set consists of references to thousands of genes in the >15 million publications listed in PubMed. We show that the observed dynamics may result from a simple process: Researchers predominantly publish on genes that already appear in many publications. This might be a rewarding strategy for researchers, because there is a positive correlation between the frequency of a gene in scientific publications and the journal impact of the publications. By comparing the empirical data with model predictions, we are able to detect unusual publication patterns that often correspond to major achievements in the field. We identify interactions between yeast genes from PubMed and show that the frequency differences of genes in publications lead to a biased picture of the resulting interaction network.
Vertebrate Ctr1 coordinates morphogenesis and progenitor cell fate and regulates embryonic stem cell differentiation
Authors: Haremaki Tomomi , Fraser Stuart T. , Kuo Yien-Ming , Baron Margaret H. , Weinstein Daniel C.
Published: July 2007

Embryogenesis involves two distinct processes. On the one hand, cells must specialize, acquiring fates appropriate to their positions (differentiation); on the other hand, they must physically construct the embryo through coordinated mechanical activity (morphogenesis). In early vertebrate development, fibroblast growth factor (FGF) regulates multiple embryonic events, including germ layer differentiation and morphogenesis; the cellular components that direct FGF signaling to evoke these different responses remain largely unknown. We show here that the copper transporter 1 (Ctr1) protein is a critical router of FGF signals during early embryogenesis. Ctr1 both promotes the differentiation and inhibits the morphogenesis of mesoderm and neurectoderm in embryos of the frog
Xenopus laevis
, thereby coordinating normal development. Signal sorting by Ctr1 involves the activation of the Ras–MAP kinase cascade and appears to be independent of its role in copper transport. Mouse embryonic stem (ES) cells deficient for Ctr1 (
Ctr1
−/−
) retain characteristics of pluripotency under conditions that favor differentiation in wild-type ES cells, indicating a conserved role for Ctr1 during amphibian and mammalian cell fate determination. Our studies support a model in which vertebrate Ctr1 functions as a key regulator of the differentiation capacity of both stem and progenitor cell populations.
Precolumbian use of chili peppers in the Valley of Oaxaca, Mexico
Authors: Perry Linda , Flannery Kent V.
Published: July 2007

Excavations at Guilá Naquitz and Silvia's Cave, two dry rockshelters near Mitla, Oaxaca, Mexico, yielded the remains of 122 chili peppers dating to the period A.D. 600–1521. The chilies can be assigned to at least 10 cultivars, all belonging to the species
Capsicum annuum
or
Capsicum frutescens
. The specimens are well enough preserved to permit an evaluation of the criteria used to separate wild and domestic chilies and to distinguish among cultivated races. In addition, they provide the opportunity to assess the reliability of starch grains for documenting the presence of chilies in archaeological sites where no macrobotanical remains are preserved.
Quaternary structures of tumor suppressor p53 and a specific p53–DNA complex
Authors: Tidow Henning , Melero Roberto , Mylonas Efstratios , Freund Stefan M. V. , Grossmann J. Guenter , Carazo José María , Svergun Dmitri I. , Valle Mikel , Fersht Alan R.
Published: July 2007

The homotetrameric tumor suppressor p53 consists of folded core and tetramerization domains, linked and flanked by intrinsically disordered segments that impede structure analysis by x-ray crystallography and NMR. Here, we solved the quaternary structure of human p53 in solution by a combination of small-angle x-ray scattering, which defined its shape, and NMR, which identified the core domain interfaces and showed that the folded domains had the same structure in the intact protein as in fragments. We combined the solution data with electron microscopy on immobilized samples that provided medium resolution 3D maps.
Ab initio
and rigid body modeling of scattering data revealed an elongated cross-shaped structure with a pair of loosely coupled core domain dimers at the ends, which are accessible for binding to DNA and partner proteins. The core domains in that open conformation closed around a specific DNA response element to form a compact complex whose structure was independently determined by electron microscopy. The structure of the DNA complex is consistent with that of the complex of four separate core domains and response element fragments solved by x-ray crystallography and contacts identified by NMR. Electron microscopy on the conformationally mobile, unbound p53 selected a minor compact conformation, which resembled the closed conformation, from the ensemble of predominantly open conformations. A multipronged structural approach could be generally useful for the structural characterization of the rapidly growing number of multidomain proteins with intrinsically disordered regions.
Dimerization of the class A G protein-coupled neurotensin receptor NTS1 alters G protein interaction
Authors: White Jim F. , Grodnitzky Justin , Louis John M. , Trinh Loc B. , Shiloach Joseph , Gutierrez Joanne , Northup John K. , Grisshammer Reinhard
Published: July 2007

G protein-coupled receptors (GPCRs) have been found as monomers but also as dimers or higher-order oligomers in cells. The relevance of the monomeric or dimeric receptor state for G protein activation is currently under debate for class A rhodopsin-like GPCRs. Clarification of this issue requires the availability of well defined receptor preparations as monomers or dimers and an assessment of their ligand-binding and G protein-coupling properties. We show by pharmacological and hydrodynamic experiments that purified neurotensin receptor NTS1, a class A GPCR, dimerizes in detergent solution in a concentration-dependent manner, with an apparent affinity in the low nanomolar range. At low receptor concentrations, NTS1 binds the agonist neurotensin with a Hill slope of ≈1; at higher receptor concentrations, neurotensin binding displays positive cooperativity with a Hill slope of ≈2. NTS1 monomers activate Gαqβ1γ2, whereas receptor dimers catalyze nucleotide exchange with lower affinity. Our results demonstrate that NTS1 dimerizationper seis not a prerequisite for G protein activation.
Directed evolution can rapidly improve the activity of chimeric assembly-line enzymes
Authors: Fischbach Michael A. , Lai Jonathan R. , Roche Eric D. , Walsh Christopher T. , Liu David R.
Published: July 2007

Nonribosomal peptides (NRPs) are produced by NRP synthetase (NRPS) enzymes that function as molecular assembly lines. The modular architecture of NRPSs suggests that a domain responsible for activating a building block could be replaced with a domain from a foreign NRPS to create a chimeric assembly line that produces a new variant of a natural NRP. However, such chimeric NRPS modules are often heavily impaired, impeding efforts to create novel NRP variants by swapping domains from different modules or organisms. Here we show that impaired chimeric NRPSs can be functionally restored by directed evolution. Using rounds of mutagenesis coupled with
in vivo
screens for NRP production, we rapidly isolated variants of two different chimeric NRPSs with ≈10-fold improvements in enzyme activity and product yield, including one that produces new derivatives of the potent NRP/polyketide antibiotic andrimid. Because functional restoration in these examples required only modest library sizes (10
3
to 10
4
clones) and three or fewer rounds of screening, our approach may be widely applicable even for NRPSs from genetically challenging hosts.
Pharmacology of Opiates and Their Derivatives
Authors: Wing L.M.H.
Published: July 2007

Abstract: The opiates or opioids are exogenous substances which bind in a stereospecific and saturable manner to several subspecies of cell membrane receptors which are sites of action of endogenous ligands (enkephalins, B‐endorphine). The opiates, which have common structural features, are agonists or partial agonists, the potency of which generally correlates well with affinity for opiate receptors. Many of the actions of opiates are related to alteration of the release of endogenous neurotransmitters. Inhibition of intracelluar adenylate cyclase and altered transmembrane calcium fluxes also appear to be important consequences of opiate action. Most opiates share the pharmacological properties of morphine. The development of tolerance and physical dependence with chronic administration is a characteristic feature of all opiates limiting their clinical use and creating the liability for abuse. With established opiate tolerance, cessation of the drug is accompanied by a characteristic withdrawal syndrome which is suppressed by opiate administration and can also be precipitated by an opiate antagonist such as naloxone. Many of the differences between opiates are due to different pharmacokinetic properties, particularly oral bioavailability and elimination rate. The search for a non‐addictive opiate analgesic continues but is presently foiled by the inherent pharmacological properties of these drugs.
UXT is a novel and essential cofactor in the NF-κB transcriptional enhanceosome
Authors: Sun Shaogang , Tang Yujie , Lou Xiwen , Zhu Lianhui , Yang Kai , Zhang Bianhong , Shi Hexin , Wang Chen
Published: July 2007

As a latent transcription factor, nuclear factor κB (NF-κB) translocates from the cytoplasm into the nucleus upon stimulation and mediates the expression of genes that are important in immunity, inflammation, and development. However, little is known about how it is regulated inside the nucleus. By a two-hybrid approach, we identify a prefoldin-like protein, ubiquitously expressed transcript (UXT), that is expressed predominantly and interacts specifically with NF-κB inside the nucleus. RNA interference knockdown of UXT leads to impaired NF-κB activity and dramatically attenuates the expression of NF-κB–dependent genes. This interference also sensitizes cells to apoptosis by tumor necrosis factor-α. Furthermore, UXT forms a dynamic complex with NF-κB and is recruited to the NF-κB enhanceosome upon stimulation. Interestingly, the UXT protein level correlates with constitutive NF-κB activity in human prostate cancer cell lines. The presence of NF-κB within the nucleus of stimulated or constitutively active cells is considerably diminished with decreased endogenous UXT levels. Our results reveal that UXT is an integral component of the NF-κB enhanceosome and is essential for its nuclear function, which uncovers a new mechanism of NF-κB regulation.