bluuebunny/crossref_metadata_2025 huggingface dataset:
Pseudo Market Timing: A Reappraisal
Authors: Dahlquist Magnus , de Jong Frank
Published: April 2009

The average firm going public or issuing new equity underperforms the market in the long run. This underperformance could be related to the endogeneity of the number of new issues if new issues cluster after periods of high abnormal returns on new issues. In such a case, ex post measures of new issue abnormal returns may be negative on average, despite the absence of ex ante abnormal returns. We evaluate this endogeneity problem in event studies of long-run performance. We argue that it is unlikely that the endogeneity of the number of new issues explains the long-run underperformance of equity issues.
The Cost to Firms of Cooking the Books
Authors: Karpoff Jonathan M. , Lee D. Scott , Martin Gerald S.
Published: April 2009

We examine the penalties imposed on the 585 firms targeted by SEC enforcement actions for financial misrepresentation from 1978–2002, which we track through November 15, 2005. The penalties imposed on firms through the legal system average only $23.5 million per firm. The penalties imposed by the market, in contrast, are huge. Our point estimate of the reputational penalty—which we define as the expected loss in the present value of future cash flows due to lower sales and higher contracting and financing costs—is over 7.5 times the sum of all penalties imposed through the legal and regulatory system. For each dollar that a firm misleadingly inflates its market value, on average, it loses this dollar when its misconduct is revealed, plus an additional $3.08. Of this additional loss, $0.36 is due to expected legal penalties and $2.71 is due to lost reputation. In firms that survive the enforcement process, lost reputation is even greater at $3.83. In the cross section, the reputation loss is positively related to measures of the firm's reliance on implicit contracts. This evidence belies a widespread belief that financial misrepresentation is disciplined lightly. To the contrary, reputation losses impose substantial penalties for cooking the books.
Aggregate Earnings, Firm-Level Earnings, and Expected Stock Returns
Authors: Bali Turan G. , Demirtas K. Ozgur , Tehranian Hassan
Published: April 2009

This paper provides an analysis of the predictability of stock returns using market-, industry-, and firm-level earnings. Contrary to Lamont (1998), we find that neither dividend payout ratio nor the level of aggregate earnings can forecast the excess market return. We show that these variables do not have robust predictive power across different stock portfolios and sample periods. In contrast to the aggregate-level findings, earnings yield has significant explanatory power for the time-series and cross-sectional variation in firmlevel stock returns and the 48 industry portfolio returns. The mean reversion of stock prices as well as the earnings' correlation with expected stock returns are responsible for the forecasting power of earnings yield. These results are robust after controlling for bookto-market, size, price momentum, and post-earnings announcement drift. At the aggregate level, the information content of firm-level earnings about future cash flows is diversified away and higher aggregate earnings do not forecast higher returns.
Home-Biased Analysts in Emerging Markets
Authors: Lai Sandy , Teo Melvyn
Published: April 2009

We find that local analyst recommendations are systematically more optimistic than foreign analyst recommendations in emerging markets. The effects of this novel “home bias” among local analysts overwhelm any information asymmetry between foreign and local analysts. Consequently, local analyst upgrades underperform foreign analyst upgrades, while local analyst downgrades outperform foreign analyst downgrades. Neither foreign investors, local institutions, nor retail investors appear to be fully cognizant of this bias. Trade reactions suggest that foreign investors overestimate the bias in foreign analyst recommendations while local institutions underestimate the bias in local analyst recommendations. These results are pervasive across countries, time periods, and stock groupings, and can be traced to investment banking pressure.
The Costs of Owning Employer Stocks: Lessons from Taiwan
Authors: Lee Yi-Tsung , Liu Yu-Jane , Zhu Ning
Published: April 2009

Using data on all employees at listed companies in Taiwan, we find that the bias toward employer stocks is generic to individual investor decision making, but not limited to retirement plans. Seventy-one percent of the sample employees invest in employer stocks and employer stocks make up on average 47% of employee equity portfolios. The underdiversification resulting from the bias toward employer stocks is very costly. Holding current portfolio risk constant, employees forego 4.89% per annum in raw returns by investing in employer stocks, which represents 39.74% of their average 1998 salary income. Our findings have important implications for social security reform and retirement account management.
Investment Banking and Analyst Objectivity: Evidence from Analysts Affiliated with Mergers and Acquisitions Advisors
Authors: Kolasinski Adam C. , Kothari S. P.
Published: April 2009

We find evidence that conflicts of interest arising from mergers and acquisitions (M&A) relations influence analysts' recommendations, corroborating regulators' and practitioners' suspicions in a setting, i.e., M&A relations, not previously examined in research on analyst conflicts. In addition, the M&A context allows us to disentangle the conflict of interest effect from selection bias. We find that analysts affiliated with acquirer advisors upgrade acquirer stocks around M&A deals, even around all-cash deals, in which selection bias is unlikely. Also consistent with conflict of interest but not selection bias, target-affiliated analysts publish optimistic reports about acquirers after, but not before, the exchange ratio of an all-stock deal is set.
Generation of magnetic fields by the ponderomotive force of electromagnetic waves in dense plasmas
Authors: SHUKLA P. K. , SHUKLA NITIN , STENFLO L.
Published: April 2009

We show that the non-stationary ponderomotive force of a large-amplitude electromagnetic wave in a very dense quantum plasma with streaming degenerate electrons can spontaneously create d.c. magnetic fields. The present result can account for the seed magnetic fields in compact astrophysical objects and in the next-generation intense laser–solid density plasma interaction experiments.
Back to the Future: Today's and Tomorrow's Politics of Degrowth Economics (Décroissance) in Light of the Debate over Luxury among Eighteenth and Early Nineteenth Century Utopists
Authors: Sippel Alexandra
Published: April 2009

French Socialists currently appear less and less convinced of the relevance of rejecting today's consumption-oriented society and turn increasingly to more center-left models in order to refound their party. (Refoundation is one of the most frequently used terms within the party.) Therefore, it is instructive to go back to the eighteenth-century roots of socialism and note the way many of its founding theorists promoted the establishment of truly social communities set in a perfectly harmonious relationship to the natural environment.

As the intellectual debate was not confined within French borders at the time of the Enlightenment, this study will create a dialogue between those who argued that luxury was absolutely essential in a modern society (Mandeville, and later Malthus, whose views are echoed in the voices of contemporary right-wing politicians) and those who, on the contrary, advocated a return to a voluntary state of nature, which implied the rejection of material accumulation and social inequality (such as Rousseau and later William Godwin, whose concerns are nowadays echoed by the defenders of décroissance). This article also explores the most utopian propositions coming from objecteurs de croissance, individuals who side with the far left while adding their concern for the environment and emphasis on humane values.
Class, Nation, and Political Organization: The Anti-Zionist Left in Israel/Palestine
Authors: Greenstein Ran
Published: April 2009

The paper discusses historical lessons offered by the experience of two leftwing movements, the pre-1948 Palestinian Communist Party, and the post-1948 Israeli Socialist Organization (Matzpen). The focus of discussion is the relationship between class and nation as principles of organization.

The Palestinian Communist Party was shaped by forces that shaped the Israeli-Palestinian conflict: British rule, Zionist ideology and settlement practices, and Arab nationalism. At intensified conflict periods it was torn apart by the pressures of competing nationalisms. By the end of the period, its factions agreed on one principle: the need to treat members of both national groups equally, whether as individuals or as groups entitled to self-determination. This position was rejected by both national movements as incompatible with their quest for control.

In the post-1948 period, Matzpen epitomized the radical critique of Zionism. It was the clearest voice speaking against the 1967 occupation and for restoration of Palestinian rights. However, it never moved beyond the political margins, and its organization failed to provide members with a sustainable mode of activism. It was replaced by a new mode, mobilizing people around specific issues instead of presenting an overall program.

The paper concludes with suggestions on how the Left may use these lessons to develop a strategy to focus on the quest for social justice and human rights.
In Search of a Post-Neoliberal Paradigm: The Brazilian Left and Lula's Government
Authors: Fortes Alexandre
Published: April 2009

The first decade of the twenty-first century has seen extraordinary political developments in the Latin American left. Indeed, there is no historical precedent for the simultaneous election across the region of governments that can be identified with the political left. From Tabaré Vasquez in Uruguay to Martín Torrijos in Panama; from Néstor and Cristina Kirchner in Argentina to Daniel Ortega in Nicaragua; from Michelle Bachelet in Chile to Hugo Chavez in Venezuela; from Evo Morales in Bolivia to Rafael Correa no Ecuador—as well as Luis Inácio Lula da Silva in Brazil and, more recently, Fernando Lugo in Paraguay—representatives of practically all of the region's formative leftist currents have taken over the governments of large, medium, and small countries.

This article takes Brazil under Lula's government as a case study in order to explore the relationship between the various dimensions of the region's lefts: the social and the institutional, civil society and the state, the national and the international, and stability and transformation. Indeed, the election to the presidency of a survivor of the extreme poverty and harsh droughts of northeastern Brazil, a one-time metalworker with little access to formal education, had a profound impact on both the country's social movements and the political party that he founded and led. By examining the hopes and frustrations, dilemmas, and accomplishments of Lula's government, we can better achieve a more dense and nuanced understanding of the larger historical process through which the Latin American Left has reached power.
Is Labor Dead?
Authors: Friedman Gerald
Published: April 2009

The Labor Movement has entered a crisis. Declining support for unions and for socialist political movements reflects the exhaustion of a reformist growth strategy where capitalists and state officials accepted unions in exchange for labor peace. While winning real gains for workers, this strategy undermined labor and its broader democratic aspirations by establishing unions and union and party leaders as authoritiesoverthe workers themselves. In the upheavals of the late-1960s and the 1970s, dissident movements, directed as much against reformist leaders as against employers and state officials, pushed protest beyond traditional limits toward demands for popular empowerment and democracy. Union decline began then, not because workers had lost interest in collective action but because employers and state officials abandoned collective bargaining to find alternative means of controlling unrest. Capitalism entered a new post-union era, when national leaders like Margaret Thatcher and Ronald Reagan used policies of open trade and capital flows and high unemployment to discipline labor. Abandoned by their capitalist bargaining partners, reformist unions and political parties have withered. Now, without social space for reformist movements, the labor movement can only advance by openly avowing its original goals of popular empowerment and the establishment of economic democracy.
Tunes That Bind: Paul J. Seelig, Eva Gauthier, Charles T. Griffes, and the Javanese Other
Authors: SPILLER HENRY
Published: April 2009

The powerful concept of orientalism has undergone considerable refinement since Edward Said popularized the term with his eponymous book in 1978. Orientalism typically is presented as a totalizing process that creates polar oppositions between a dominating West and a subordinate East. U.S. orientalisms, however, reflect uniquely North American approaches to identity formation that include assimilating characteristics usually associated with the Other. This article explores the complex relationship among three individuals—U.S. composer Charles T. Griffes, Canadian singer Eva Gauthier, and German-trained Dutch East Indies composer Paul J. Seelig—and how they exploited the same Javanese songs to lend legitimacy to their individual artistic projects. A comparison of Griffes's and Seelig's settings of a West Javanese tune (“Kinanti”) provides an especially clear example of how contrasting approaches manifest different orientalisms. Whereas Griffes accompanied the melody with stock orientalist gestures to express his own fascination with the exotic, Seelig used chromatic harmonies and a chorale-like texture to ground the melody in the familiar, translating rather than representing its Otherness. The tunes that bind Griffes, Gauthier, and Seelig are only the raw materials from which they created their own unique orientalisms, each with its own sense of self and its own Javanese others.
Tejano Music in the Urbanizing Midwest: The Musical Story ofConjuntoMaster Jesse Ponce
Authors: HARNISH DAVID
Published: April 2009

This article explores the story and agency ofconjuntomaster musician Jesse Ponce from his early life in San Antonio to his migration to northwest Ohio as an “authentic” Tejano (Texas-Mexican) musician. Although Ponce used this status as a form of cultural capital to construct his identity, integrate into local Latino communities, and interface with Latino cultural institutions, three outside agents, including the author, worked to publicize his expertise in Ohio, which, in turn, led to new acknowledgment and self-identification. The recent history of the “traditional” conjunto style is revealed as paralleling Ponce's career and aesthetic preferences. Both are in slight decline: Ponce, because of his failing health and resulting fewer performance opportunities; traditionalconjunto, because of the rise of a more virtuosic “progressive” style

Bourdieu's notion of cultural capital and Loza's concept of enculturation are utilized to explicate Ponce's experience and self-construction in urbanizing northwest Ohio. The author's experiences with Ponce (as promoter and musician) are included to demonstrate the constant negotiations between Ponce, his musical identity and authority, and the outside world
Spring and summertime diurnal surface ozone fluxes over the polar snow at Summit, Greenland
Authors: Helmig Detlev , Cohen Lana D. , Bocquet Florence , Oltmans Samuel , Grachev Andrey , Neff William
Published: April 2009

Continuous surface‐layer ozone flux measurements over the polar, year‐round snowpack at Summit, Greenland, resulted in deposition velocities (vd) that were smaller than most previous assumptions and model inputs. Substantial seasonal differences were seen in the ozone vd behavior. Spring, daytime ozone vd values showed low variability and were consistently ≤0.01 cm s−1. During summer, ozone fluxes displayed distinct diurnal cycles, and evidence for regular occurrences of bi‐directional behavior. Summer, daytime vd ranged between ∼0.01 to 0.07 cm s−1. Maximum summertime downward fluxes (ozone deposition) coincided with the hours of maximum solar radiation, i.e., noon–afternoon. During summer nighttime hours upward ozone fluxes were observed. These upward fluxes were interpreted as ozone production in a shallow layer near and above the snow surface with resulting upward ozone fluxes out of the shallow surface layer. Comparisons with published observations from temperate, midlatitude sites suggest different controls and behavior of ozone fluxes, and that ozone fluxes over snow depend on a myriad of parameters, including solar irradiance, snow chemical and physical properties, snowpack depth, and the type of substrate underneath the snow.
Identification of plasma instability from wavelet spectra in a current disruption event
Authors: Yoon P. H. , Lui A. T. Y. , Bonnell J. W.
Published: April 2009

We investigate the plasma instability of a current disruption event that shows an inverse cascade of waves starting at frequencies slightly below the ion cyclotron frequency to waves at low frequencies that correspond to the time scale of dipolarization. The electric and magnetic perturbations in the initial wave excited are extracted to check their agreement with two alternative theoretically predicted instability mechanisms. The first mechanism involves the electromagnetic ion cyclotron instability propagating along the magnetic field driven by the relative cross‐field drift, while the second corresponds to the Alfvén ion cyclotron instability propagating in quasi‐perpendicular direction with respect to the local magnetic field. It is found that the observed electric and magnetic perturbations are incompatible with the quasi‐parallel electromagnetic ion cyclotron instability, but they are found to be consistent with nearly perpendicular propagating waves generated by the Alfvén ion cyclotron instability.
Molecular discrimination of structurally equivalent Lys 63‐linked and linear polyubiquitin chains
Authors: Komander David , Reyes‐Turcu Francisca , Licchesi Julien D F , Odenwaelder Peter , Wilkinson Keith D , Barford David
Published: April 2009

At least eight types of ubiquitin chain exist, and individual linkages affect distinct cellular processes. The only distinguishing feature of differently linked ubiquitin chains is their structure, as polymers of the same unit are chemically identical. Here, we have crystallized Lys 63‐linked and linear ubiquitin dimers, revealing that both adopt equivalent open conformations, forming no contacts between ubiquitin molecules and thereby differing significantly from Lys 48‐linked ubiquitin chains. We also examined the specificity of various deubiquitinases (DUBs) and ubiquitin‐binding domains (UBDs). All analysed DUBs, except CYLD, cleave linear chains less efficiently compared with other chain types, or not at all. Likewise, UBDs can show chain specificity, and are able to select distinct linkages from a ubiquitin chain mixture. We found that the UBAN (ubiquitin binding in ABIN and NEMO) motif of NEMO (NF‐κB essential modifier) binds to linear chains exclusively, whereas the NZF (Npl4 zinc finger) domain of TAB2 (TAK1 binding protein 2) is Lys 63 specific. Our results highlight remarkable specificity determinants within the ubiquitin system.
Relationship between the surface chemical states and magnetic properties of CeO2 nanoparticles
Authors: Li Mingjie , Ge Shihui , Qiao Wen , Zhang Li , Zuo Yalu , Yan Shiming
Published: April 2009

Hydrogen reduction treatments with variations in isothermal reduction temperature, duration, and partial pressure of hydrogen (PH2) are carried out on CeO2 nanoparticles (NPs) to investigate the relationship between the surface chemical states and magnetic properties of the samples. The phenomenon of surface reduction degree dependence of the ferromagnetism of CeO2 NPs is observed. Semiquantitative calculated concentrations of surface Ce3+ ions from x-ray photoelectron spectroscopy data demonstrate that ferromagnetism does not relate to the surface oxygen vacancies but to the surface Ce3+/Ce4+ pairs. The higher the number of surface Ce3+/Ce4+ pairs, the more robust the ferromagnetism appears.
Application of the high-resolution grazing-emission x-ray fluorescence method for impurities control in semiconductor nanotechnology
Authors: Szlachetko J. , Banaś D. , Kubala-Kukuś A. , Pajek M. , Cao W. , Dousse J.-Cl. , Hoszowska J. , Kayser Y. , Szlachetko M. , Kavčič M. , Salome M. , Susini J.
Published: April 2009

We report on the application of synchrotron radiation based high-resolution grazing-emission x-ray fluorescence (GEXRF) method to measure low-level impurities on silicon wafers. The presented high-resolution GEXRF technique leads to direct detection limits of about 1012 atoms/cm2. The latter can be presumably further improved down to 107 atoms/cm2 by combining the synchrotron radiation-based GEXRF method with the vapor phase decomposition preconcentration technique. The capability of the high-resolution GEXRF method to perform surface-sensitive elemental mappings with a lateral resolution of several tens of micrometers was probed.
Time-decaying magnetoelectric effects in multiferroic fibrous composites with a viscous interface
Authors: Pan E. , Wang X. , Albrecht J. D.
Published: April 2009

This paper addresses the time-dependent magnetoelectroelastic responses of multiferroic fibrous composites with a viscous interface. First, the problem of an isolated multiferroic fiber embedded in an infinite multiferroic matrix is rigorously solved. It is observed that the internal magnetoelectroelastic field such as stresses, electric displacements, and magnetic inductions inside an isolated multiferroic fiber is uniform but time dependent. The Mori–Tanaka mean-field method is then utilized to derive an extremely concise expression of the time-dependent effective moduli of the multiferroic fibrous composite. The numerical results demonstrate that the viscosity of the interface will cause a time-decaying magnetoelectric effect of the BaTiO3–CoFe2O4 fibrous composite. As the time approaches infinity the magnetoelectric effect will approach zero due to the fact that a viscous interface will finally evolve into a free-sliding one which does not sustain shear stress. This interesting feature should be particularly important to the analysis and design of multiferroic composites where the interface is utilized to enhance the magnetoelectric effect.
Enhancement of the electromechanical response in ferroelectric ceramics by design
Authors: Jayachandran K. P. , Guedes J. M. , Rodrigues H. C.
Published: April 2009

It is demonstrated based on continuum mechanics modeling and simulation that it is possible to obtain polycrystalline ceramic ferroelectric (FE) materials which beggar single crystals in electromechanical properties. The local inhomogeneities at the FE domain-scale level due to spontaneous polarization and the underlying anisotropy are taken into consideration in the framework of mathematical homogenization of physical properties in FE materials. The intrinsic randomness of the spatial distribution of polarization is shown to be judiciously employed for the design of better polycrystalline FEs. The noncollinear rotation of the net polarization vectors embedded in crystallites of the ceramic FEs is demonstrated to play the key role in the enhancement of physical properties.
Epitaxial 3C-SiC nanocrystal formation at the SiO2/Si interface by combined carbon implantation and annealing in CO atmosphere
Authors: Pécz B. , Stoemenos J. , Voelskow M. , Skorupa W. , Dobos L. , Pongrácz A. , Battistig G.
Published: April 2009

High quality 3C-SiC nanocrystallites were epitaxially formed on (100) Si wafers covered by a 150 nm thick SiO2 capping layer after low dose carbon implantation and high temperature annealing in CO atmosphere. Carbon implantation is used to introduce nucleation sites by forming silicon-carbon clusters at the SiO2/Si interface acting as nucleation sites for the growth of 3C-SiC nanocrystallites. The formation of the nucleation clusters as well as the morphology, the size, and the density of the nanocrystals were systematically studied by conventional and high resolution transmission electron microscopy. The nanocrystallites were developed following two different modes of growth: The first develops facets along the ⟨100⟩ crystallographic direction giving tetragonal grains and the second facets along the ⟨110⟩ direction resulting in elongated nanocrystallites. The formation mechanism of the nanocrystallites and the strain related with them are also discussed.
Defects in hydrogenated microcrystalline silicon prepared by plasma-enhanced chemical vapour deposition
Authors: Morigaki K. , Niikura C. , Hikita H. , Yamaguchi M.
Published: April 2009

Defects in hydrogenated microcrystalline silicon (μc-Si:H) prepared by plasma-enhanced chemical vapor deposition at 100°C have been investigated as a function of crystalline volume fraction (Xc) from electron spin resonance (ESR) measurements. Magnetic centers responsible for ESR are suggested from g-value considerations to be dangling bonds on the surface of crystalline grains for Xc of less than 50% and positively charged single vacancies with positive correlation energy inside the crystalline grain for Xc of more than 50%. For the latter Xc range, it is suggested from correlation of these defects with photoluminescence (PL) and its light-induced effect and optically detected magnetic resonance that they are nonradiative centers. Further, the low-energy PL associated with the microcrystalline phase in μc-Si:H is concluded to arise from radiative recombination between trapped electrons in the conduction-band tail and trapped holes in the valence-band tail arising from disordered potentials around the grain boundary.
Comparison of the x-ray spectroscopy response and charge transport properties of semi-insulating In/Al doped CdZnTe crystals
Authors: Xu Y. , Sellin P. J. , Lohstroh A. , Jie W. , Wang T. , Mills C. , Veeramani P. , Veale M.
Published: April 2009

The x-ray spectroscopy performance of In/Al doped CdZnTe planar detectors based on as-grown crystals were investigated at room temperature, using a Tb x-ray source with a principle energy of 44.2 keV. The observed broadening in the photopeak resolution was attributed to incomplete charge carrier collection due to carrier trapping and scattering by the defects in the crystal. Alpha particle spectroscopy and pulse shape rise time analysis were used to measure the electron mobility lifetime product (μτ), as well as the mobility (μ) of the CdZnTe material grown with different dopant concentrations. To further clarify the role of the dopant and associated trapping states, temperature dependent alpha particle spectroscopy and pulse shapes were investigated at various applied bias fields over a temperature range from 200 to 300 K. CdZnTe doped with 1.5 ppm In exhibits excellent x-ray spectral resolution and charge transport properties, which implies a lower density of trapping centers in the crystal. The deep levels associated with Cdi2+ have been tentatively recognized as electron trapping centers and this is confirmed by the observed reduction in electron lifetime in CdZnTe crystal with 15 ppm In. Additionally, a shallower electron detrapping defect, with an activation energy of 0.14±0.02 eV, was also discovered to be simultaneously present in the crystal. In 30 ppm Al doped CdZnTe, however, the carrier mobility was significantly degraded due to scattering of the ionized centers attributed to the aluminum interstitial Ali.
A radiative transport model for heating paints using high density plasma arc lamps
Authors: Sabau Adrian S. , Duty Chad E. , Dinwiddie Ralph B. , Nichols Mark , Blue Craig A. , Ott Ronald D.
Published: April 2009

The energy distribution and temperature evolution within paintlike systems that are exposed to spectral radiant energy were studied. A complete set of material properties was derived and discussed. Infrared measurements were conducted to obtain experimental data for the temperature in the paint film. The heat flux due to the incident radiation from the plasma arc lamp was measured using a heat flux sensor with a very short response time. A radiative transport model based on spectral four-flux radiation transport equations has been developed for multilayered and semitransparent material systems. Comparisons between the computed and experimental results for temperature show that the energy transport model yields accurate results for a black painted substrate.
Diffusion, convection, and solidification in cw-mode free electron laser nitrided titanium
Authors: Höche Daniel , Shinn Michelle , Müller Sven , Schaaf Peter
Published: April 2009

Titanium sheets were irradiated by free electron laser radiation in cw mode in pure nitrogen. Due to the interaction, nitrogen diffusion occurs and titanium nitride was synthesized in the tracks. Overlapping tracks have been utilized to create coatings in order to improve the tribological properties of the sheets. Caused by the local heating and the spatial dimension of the melt pool, convection effects were observed and related to the track properties. Stress, hardness, and nitrogen content were investigated with x-ray diffraction, nanoindention, and resonant nuclear reaction analysis. The measured results were correlated with the scan parameters, especially to the lateral track shift. Cross section micrographs were prepared and investigated by means of scanning electron microscopy. They show the solidification behavior, phase formation, and the nitrogen distribution. The experiments give an insight into the possibilities of materials processing using such a unique heat source.
Direct and indirect photoluminescence excitation and ultraviolet emission from Tm-doped AlxGa1−xN
Authors: Glinka Yuri D. , Foreman John V. , Everitt Henry O. , Lee Don S. , Steckl Andrew J.
Published: April 2009

We provide experimental evidence for direct and indirect excitations of photoluminescence (PL) from Tm-doped AlxGa1−xN of varying Al content. Direct excitation of Tm3+ ions is observed primarily at 85K through transitions H63→I61, P03, P13, and P23 when these levels are below the absorption edge of the AlxGa1−xN for a given Al content. Strong ultraviolet emission at 298nm (I61→H63), 355nm (I61→F43), and 371nm (D21→H63), as well as the familiar blue emission at 463nm (D21→F43), and 479nm (G41→H63), is found to depend sensitively on the Al content, excitation wavelength (i.e., direct or indirect), excitation type (continuous wave versus pulsed), and upper state of the transition. PL excitation spectroscopy and time-integrated and time-resolved PL spectra are compared to elucidate the complex energy transfer pathways.
Ab initio calculation of the electronic structures of the ∑7+ ground and A Π7 and a ∑5+ excited states of MnH
Authors: Tomonari Mutsumi , Nagashima Umpei , Hirano Tsuneo
Published: April 2009

Electronic structures and molecular constants of the ground ∑7+ and low-lying A 7Π and a ∑5+ electronic excited states of the MnH molecule were studied by multireference single and double excitation configuration interaction (MR-SDCI) with Davidson’s correction (+Q) calculations under exact C∞v symmetry using Slater-type basis sets. To correctly describe the ∑7+ electronic ground state, X ∑7+, at the MR-SDCI+Q calculation, we employed a large number of reference configurations in terms of the state-averaged complete active space self-consistent field (CASSCF) orbitals, taking into account the contribution from the B ∑7+ excited state. The A 7Π and a ∑5+ states can well be described by the MR-SDCI wave functions based on the CASSCF orbitals obtained for the lowest state only. In the MR-SDCI+Q, calculations of the X ∑7+, A 7Π, and a ∑5+ states required 16, 7, and 17 reference configurations, respectively. Molecular constants, i.e., re and ωe of these states and excitation energy from the X ∑7+ state, obtained at the MR-SDCI+Q level, showed a good agreement with experimental values. The small remaining differences may be accounted for by taking relativistic effects into account.
Bicoherence in electrostatic turbulence driven by high magnetohydrodynamic activity in Tokamak Chauffage Alfvén Brésilien
Authors: dos Santos Lima G. Z. , Guimarães-Filho Z. O. , Batista A. M. , Caldas I. L. , Lopes S. R. , Viana R. L. , Nascimento I. C. , Kuznetsov Yu. K.
Published: April 2009

During some discharges in Tokamak Chauffage Alfvén Brésilien [R. M. O. Galvão et al., Plasma Phys. Controlled Fusion 43, 1181 (2001)] high magnetohydrodynamic activity may appear with a peaked frequency spectrum. Whenever this peak occurs, the ambient broadband electrostatic turbulence is remarkably modified, synchronizing into the dominant magnetic fluctuation frequency and presenting high bicoherence in the whole plasma edge with a maximum bicoherence inside the plasma. A phenomenological model is introduced to investigate this driven turbulence bicoherence, consisting of nonlinearly coupled phase-randomized drift modes with time-periodic external driving at the dominant magnetic fluctuation frequency. The bicoherence spectrum of this model can mimic features of the experimental results.
Escort mean values and the characterization of power-law-decaying probability densities
Authors: Tsallis C. , Plastino A. R. , Alvarez-Estrada R. F.
Published: April 2009

Escort mean values (or q-moments) constitute useful theoretical tools for describing basic features of some probability densities such as those which asymptotically decay like power laws. They naturally appear in the study of many complex dynamical systems, particularly those obeying nonextensive statistical mechanics, a current generalization of the Boltzmann–Gibbs theory. They recover standard mean values (or moments) for q=1. Here we discuss the characterization of a (non-negative) probability density by a suitable set of all its escort mean values together with the set of all associated normalizing quantities, provided that all of them converge. This opens the door to a natural extension of the well-known characterization, for the q=1 instance, of a distribution in terms of the standard moments, provided that all of them have finite values. This question would be specially relevant in connection with probability densities having divergent values for all nonvanishing standard moments higher than a given one (e.g., probability densities asymptotically decaying as power laws), for which the standard approach is not applicable. The Cauchy–Lorentz distribution, whose second and higher even order moments diverge, constitutes a simple illustration of the interest of this investigation. In this context, we also address some mathematical subtleties with the aim of clarifying some aspects of an interesting nonlinear generalization of the Fourier transform, namely, the so-called q-Fourier transform.
Two-dimensional transient simulations of drain lag and current collapse in GaN-based high-electron-mobility transistors
Authors: Hu W. D. , Chen X. S. , Yin F. , Zhang J. B. , Lu W.
Published: April 2009

The intrinsic mechanisms of drain lag and current collapse in GaN-based high-electron-mobility transistors are studied by using two-dimensional numerical simulations. Simulated drain lag characteristics are in good agreement with reported experimental data. The dynamic pictures of trapping of hot electrons under drain-pulse voltages are discussed in detail. Hot-electron buffer-trapping effect plays an instrumental role in the current collapse mechanism. Polarization-induced interface charges have significant effect on the hot-electron buffer trapping and the current collapse can be weakened by increasing the interface charges. The trapped charges can accumulate at the drain-side gate edge, where the electric field significantly changes and gate-to-drain-voltage-dependent strain is induced, causing a notable current collapse. The simulation results show that the drain voltage range, beyond 5 V, is already in the field of the well-developed hot electron regime. The hot electrons can occupy a great number of traps at the drain-side gate edge leading to the current collapse at high drain bias (around 10 V), where the hot-electron trapping effect dominates. By considering quantum-well high-electron-mobility transistors, we find that better electron localization can reduce the current collapse.
High efficiency blue light emitting unipolar transistor incorporating multifunctional electrodes
Authors: Ke Tung-Huei , Gehlhaar Robert , Chen Chih-Hsin , Lin Jiann-T , Wu Chung-Chih , Adachi Chihaya
Published: April 2009

The authors report on blue light emitting unipolar organic light emitting transistors (OLETs) with external quantum efficiency up to 0.2% by using multifunctional Mg/Au electrodes formed in combination with an efficient light emitting fluorene derivative. A mobility up to 6×10−6 cm2 V−1 s−1 has been achieved, which is comparable to previous results from time of flight mobility measurements. An anomalous light emission behavior is observed in unipolar OLETs. The phenomenon is discussed in light of the effects of electron injection and outcoupling efficiency, respectively. Our results show that the multifunctional electrodes are useful for implementing highly efficient unipolar OLETs.
A Kalman filter for feedback control of rotating external kink instabilities in the presence of noise
Authors: Hanson Jeremy M. , De Bono Bryan , Levesque Jeffrey P. , Mauel Michael E. , Maurer David A. , Navratil Gerald A. , Pedersen Thomas Sunn , Shiraki Daisuke , James Royce W.
Published: April 2009

The simulation and experimental optimization of a Kalman filter feedback control algorithm for n=1 tokamak external kink modes are reported. In order to achieve the highest plasma pressure limits in ITER, resistive wall mode stabilization is required [T. C. Hender et al., Nucl. Fusion 47, S128 (2007)] and feedback algorithms will need to distinguish the mode from noise due to other magnetohydrodynamic activity. The Kalman filter contains an internal model that captures the dynamics of a rotating, growing n=1 mode. This model is actively compared with real-time measurements to produce an optimal estimate for the mode’s amplitude and phase. On the High Beta Tokamak-Extended Pulse experiment [T. H. Ivers et al., Phys. Plasmas 3, 1926 (1996)], the Kalman filter algorithm is implemented using a set of digital, field-programmable gate array controllers with 10 μs latencies. Signals from an array of 20 poloidal sensor coils are used to measure the n=1 mode, and the feedback control is applied using 40 poloidally and toroidally localized control coils. The feedback system with the Kalman filter is able to suppress the external kink mode over a broad range of phase angles between the sensed mode and applied control field. Scans of filter parameters show good agreement between simulation and experiment, and feedback suppression and excitation of the kink mode are enhanced in experiments when a filter made using optimal parameters from the scans is used.
Super-X divertors and high power density fusion devices
Authors: Valanju P. M. , Kotschenreuther M. , Mahajan S. M. , Canik J.
Published: April 2009

The Super-X Divertor (SXD), a robust axisymmetric redesign of the divertor magnetic geometry that can allow a fivefold increase in the core power density of toroidal fusion devices, is presented. With small changes in poloidal coils and currents for standard divertors, the SXD allows the largest divertor plate radius inside toroidal field coils. This increases the plasma-wetted area by 2–3 times over all flux-expansion-only methods (e.g., plate near main X point, plate tilting, X divertor, and snowflake), decreases parallel heat flux and hence plasma temperature at plate, and increases connection length by 2–5 times. Examples of high-power-density fusion devices enabled by SXD are discussed; the most promising near-term device is a 100 MW modular compact fusion neutron source “battery” small enough to fit inside a conventional fission blanket.
Observation of an impurity hole in a plasma with an ion internal transport barrier in the Large Helical Device
Authors: Ida K. , Yoshinuma M. , Osakabe M. , Nagaoka K. , Yokoyama M. , Funaba H. , Suzuki C. , Ido T. , Shimizu A. , Murakami I. , Tamura N. , Kasahara H. , Takeiri Y. , Ikeda K. , Tsumori K. , Kaneko O. , Morita S. , Goto M. , Tanaka K. , Narihara K. , Minami T. , Yamada I. ,   LHD Experimental Group
Published: April 2009

Extremely hollow profiles of impurities (denoted as “impurity hole”) are observed in the plasma with a steep gradient of the ion temperature after the formation of an internal transport barrier (ITB) in the ion temperature transport in the Large Helical Device [A. Iiyoshi et al., Nucl. Fusion 39, 1245 (1999)]. The radial profile of carbon becomes hollow during the ITB phase and the central carbon density keeps dropping and reaches 0.1%–0.3% of plasma density at the end of the ion ITB phase. The diffusion coefficient and the convective velocity of impurities are evaluated from the time evolution of carbon profiles assuming the diffusion and the convection velocity are constant in time after the formation of the ITB. The transport analysis gives a low diffusion of 0.1–0.2 m2/s and the outward convection velocity of ∼1 m/s at half of the minor radius, which is in contrast to the tendency in tokamak plasmas for the impurity density to increase due to an inward convection and low diffusion in the ITB region. The outward convection is considered to be driven by turbulence because the sign of the convection velocity contradicts the neoclassical theory where a negative electric field and an inward convection are predicted.
Gigahertz-range synchronization at room temperature and other features of charge-density wave transport in the quasi-one-dimensional conductor NbS3
Authors: Zybtsev S. G. , Pokrovskii V. Ya. , Nasretdinova V. F. , Zaitsev-Zotov S. V.
Published: April 2009

Whiskers of the quasi-one-dimensional conductor NbS3, phase II, have been synthesized. The samples show two charge-density wave (CDW) states: below 360 and below 150 K. Both CDWs show sharp threshold fields and coherent transport revealed by ac-dc coupling, i.e., Shapiro steps. The thinnest samples (cross sections below 104 nm2) exhibit Shapiro steps for frequencies at least as high as 4 GHz at room temperature. The results indicate that, for each of the CDW states, only one Nb chain per unit cell participates in the CDW transport.
Optical feedback instabilities in a monolithic InAs/GaAs quantum dot passively mode-locked laser
Authors: Grillot F. , Lin C.-Y. , Naderi N. A. , Pochet M. , Lester L. F.
Published: April 2009

The impact of optical feedback on the direct performance of a monolithic InAs/GaAs quantum dot passively mode-locked laser intended for applications such as multigigahertz interchip/intrachip clock distribution is experimentally investigated. Evaluation of the feedback resistance is an important feature, as the laser is to be monolithically integrated on chip with other devices, in which case optical isolation is difficult. This work shows that a feedback level on the order of −24 dB is detrimental for mode-locking operation, enhancing noise in the rf electrical signal, strongly narrowing the useful mode-locking region as well as causing central frequency shift, and severe instabilities.
Simple models for two-dimensional tunable colloidal crystals in rotating ac electric fields
Authors: Elsner Nils , Royall C. Patrick , Vincent Brian , Snoswell David R. E.
Published: April 2009

We compare the behavior of a new two-dimensional aqueous colloidal model system with a simple numerical treatment. To the first order the attractive interaction between the colloids induced by an in-plane rotating ac electric field is dipolar, while the charge stabilization leads to a shorter ranged, Yukawa-like repulsion. In the crystal-like “rafts” formed at sufficient field strengths, we find quantitative agreement between experiment and Monte Carlo simulation, except in the case of strongly interacting systems, where the well depth of the effective potential exceeds 250 times the thermal energy. The “lattice constant” of the crystal-like raft is located approximately at the minimum of the effective potential, resulting from the sum of the Yukawa and dipolar interactions. The experimental system has display applications, owing to the possibility of tuning the lattice spacing with the external electric field. Limitations in the applied field strength and relative range of the electrostatic interactions of the particles result in a reduction in tunable lattice spacing for small and large particles, respectively. The optimal particle size for maximizing the lattice spacing tunability was found to be around 1000 nm.
High performance organic thin film transistor with phenyltrimethoxysilane-modified dielectrics
Authors: Yuan Guang Cai , Xu Zheng , Gong Cheng , Cai Qin Jia , Lu Zhi Song , Shi Jing Sheng , Zhang Fu Jun , Zhao Su Ling , Xu Na , Li Chang Ming
Published: April 2009

In this work, fabrication of organic thin film transistors (OTFTs) using a phenyltrimethoxysilane (PhTMS) modified SiO2 insulator greatly improves the device electrical properties over those with plain or octadecyltrichlorosilane (OTS) modified SiO2, particularly improves the carrier mobility, the subthreshold slope, and channel resistance resulted from reduced density of charge trapping states at the semiconductor/insulator interface. The pentacene OTFTs with modification from PhTMS (3.5‰ v/v) achieves carrier mobility of 1.03 cm2/V s, on/off current ratio of 1.98×105, and subthreshold slope of 0.20 V/decade. This work renders a new, simple approach to significantly improve the OTFT performance.
Invited Article: Data analysis of the Floating Potential Measurement Unit aboard the International Space Station
Authors: Barjatya Aroh , Swenson Charles M. , Thompson Donald C. , Wright Kenneth H.
Published: April 2009

We present data from the Floating Potential Measurement Unit (FPMU) that is deployed on the starboard truss of the International Space Station. The FPMU is a suite of instruments capable of redundant measurements of various plasma parameters. The instrument suite consists of a floating potential probe, a wide-sweeping spherical Langmuir probe, a narrow-sweeping cylindrical Langmuir probe, and a plasma impedance probe. This paper gives a brief overview of the instrumentation and the received data quality, and then presents the algorithm used to reduce I-V curves to plasma parameters. Several hours of data are presented from August 5, 2006 and March 3, 2007. The FPMU derived plasma density and temperatures are compared with the International Reference Ionosphere (IRI) and Utah State University-Global Assimilation of Ionospheric Measurement (USU-GAIM) models. Our results show that the derived in situ density matches the USU-GAIM model better than the IRI, and the derived in situ temperatures are comparable to the average temperatures given by the IRI.