bluuebunny/crossref_metadata_2025 huggingface dataset:
Why People Do Not Vote
Authors: Caprara Gian Vittorio , Vecchione Michele , Schwartz Shalom H.
Published: December 2011

Falling levels of electoral participation in established democracies have raised serious concern. We investigate the role of basic personal values in identifying those who do not vote. We argue that voting in specific elections offers non-voters less opportunity to affirm, protect, or attain the values they cherish than it offers to voters. We hypothesize that people who do not vote attribute less importance than voters to those values that the contesting parties actually endorse (actual value congruence) and that the parties are perceived as endorsing (perceived value congruence). Study 1 (Italian national elections of 2001, n = 1,782) confirmed the hypothesis for actual congruence between own and coalition endorsed values. Study 2 (2008 elections, n = 543) confirmed the hypothesis both for actual and perceived value congruence. In both studies, value congruence explained substantial variance in voter abstention beyond the effects of socio-demographic variables.
Grandiose and Vulnerable Narcissism
Authors: Rohmann Elke , Neumann Eva , Herner Michael Jürgen , Bierhoff Hans-Werner
Published: December 2011

It is suggested that the two factors of narcissism identified by Wink (1991) – grandiose (overt) and vulnerable (covert) narcissism – represent different conceptualizations of narcissism, which are measured by the Narcissistic Personality Inventory and the Narcissism Inventory, respectively. The focus of this research is on the divergent interpersonal consequences of both factors of narcissism. Results of two studies indicate that the nomological networks of grandiose and vulnerable narcissism in terms of self-construal on the one hand and attachment and love on the other hand differ substantially. As predicted, grandiose narcissism was linked to high self-esteem and independent self-construal, whereas vulnerable narcissism was linked to low self-esteem and interdependent self-construal. In addition, high vulnerable narcissism implied higher attachment anxiety than low vulnerable narcissism, whereas high grandiose narcissism implied less attachment avoidance than low grandiose narcissism. In partial support of the hypotheses, Eros, Ludus, and Pragma correlated positively with the measure of grandiose narcissism, whereas Eros, Ludus, Pragma, Mania, and Agape were positively related to the measure of vulnerable narcissism. An intriguing pattern of results emerged because vulnerable narcissism turned out to be the more powerful predictor for love styles than grandiose narcissism.
The Identification of Negative Emotions Through a Go/No-Go Task
Authors: Iria Catarina , Barbosa Fernando , Paixão Rui
Published: December 2011

This study compares the performance, when identifying negative emotions on facial expression, of male offenders (n = 62) with a high level of psychopathy (n = 25) with other criminals with a low level of psychopathy (n = 37), as well as other “successful psychopaths” (n = 12) and non-criminals with a low level of psychopathy (n = 39) in order to clarify the negative emotional processing of offenders and non-offenders that are either high or low in psychopathy. The participants were assessed on a Go/No-Go paradigm in which subjects had to respond to the facial expressions of fear, sadness, and anger. The psychopathy level was obtained by Factor 1 of Hare’s PCL:SV. Both psychopathic groups, criminal and non-criminal, showed worse performance than their non-psychopathic counterparts on the identification of fear and sadness. An overresponsivity to both anger and fear was common to criminals, psychopaths, and non-psychopaths. These results reinforce the idea that psychopathy is related to a poor ability to identify fear and sadness in facial expressions independently of its manifestation in criminal behavior. In turn, a misidentified response pattern, characterized by an overresponsiveness for fear and anger, is common to both psychopaths and the criminal groups, and it appears to be the characteristic that distinguishes the three groups under study from non-criminal non-psychopath controls.
Testing Practices in the 21st Century
Authors: Evers Arne , Muñiz José , Bartram Dave , Boben Dusica , Egeland Jens , Fernández-Hermida José R. , Frans Örjan , Gintiliené Grazina , Hagemeister Carmen , Halama Peter , Iliescu Dragos , Jaworowska Aleksandra , Jiménez Paul , Manthouli Marina , Matesic Krunoslav , Schittekatte Mark , Sümer H. Canan , Urbánek Tomáš
Published: December 2011

The main goal of the European Federation of Psychologists’Associations (EFPA) Standing Committee on Tests and Testing (SCTT) is the improvement of testing practices in European countries. In order to reach this goal, the SCTT carries out various actions and projects, some of which are described in this paper. To better inform its work, it decided to survey the opinions of professional psychologists on testing practices. A questionnaire of 33 items was administered to a sample of 12,606 professional psychologists from 17 European countries. The questionnaire was based on, but not identical to, one used in 2000. The new data show that the positive attitude of the respondents toward the use of tests that was obtained in 2000 has increased in most countries, with a high percentage of the surveyed psychologists using tests regularly. Five main dimensions explained 43% of the total item variance. The dimensions involve items relating to: Concern over incorrect test use, regulations on tests and testing, Internet testing, appreciation of tests, and knowledge and training relating to tests and test use. Important differences between countries were found on these five dimensions. Differences were found according to gender for four of the five dimensions and in relation to field of specialization for all five dimensions. The most commonly used tests are the classic psychometric tests of intelligence and personality: WISC, WAIS, MMPI, RAVEN, 16PF, NEO-PI-R, BDI, SCL-90. Finally, some future perspectives are discussed.
Macondo‐1 well oil‐derived polycyclic aromatic hydrocarbons in mesozooplankton from the northern Gulf of Mexico
Authors: Mitra Siddhartha , Kimmel David G. , Snyder Jessica , Scalise Kimberly , McGlaughon Benjamin D. , Roman Michael R. , Jahn Ginger L. , Pierson James J. , Brandt Stephen B. , Montoya Joseph P. , Rosenbauer Robert J. , Lorenson Thomas D. , Wong Florence L. , Campbell Pamela L.
Published: December 2011

Mesozooplankton (>200 μm) collected in August and September of 2010 from the northern Gulf of Mexico show evidence of exposure to polycyclic aromatic hydrocarbons (PAHs). Multivariate statistical analysis revealed that distributions of PAHs extracted from mesozooplankton were related to the oil released from the ruptured British Petroleum Macondo‐1 (M‐1) well associated with the R/VDeepwater Horizon blowout. Mesozooplankton contained 0.03–97.9 ng g−1 of total PAHs and ratios of fluoranthene to fluoranthene + pyrene less than 0.44, indicating a liquid fossil fuel source. The distribution of PAHs isolated from mesozooplankton extracted in this study shows that the 2010 Deepwater Horizon spill may have contributed to contamination in the northern Gulf of Mexico ecosystem.
Multidecadal modulation of El Niño influence on the Euro‐Mediterranean rainfall
Authors: López‐Parages Jorge , Rodríguez‐Fonseca Belén
Published: December 2011

El Niño influence on the Euro‐Mediterranean Rainfall (EMedR) has changed along the 20th century, and the reasons for this lack of stationarity, which represents an important issue in the climate change context, are still unclear. Here, the causes of this changing relationship are studied at interannual timescales. To this aim the EMedR is analyzed using observations from 1900 to 2008. Results confirm the lack of stationarity, showing how the teleconnections with El Niño appear modulated by multidecadal oscillations of the anomalous Sea Surface Temperature (SST) over the Atlantic and Pacific basins. The study presents statistically significant evidences about how the Atlantic Multidecadal Oscillation (AMO) seems to modulate El Niño teleconnection for late winter‐spring, while modulation in fall could be controlled by the Pacific Decadal Oscillation (PDO). The results of this study have important implications in seasonal and decadal predictability, but they also represent a step forward in the understanding of the role of changes in the ocean mean state on the interannual teleconnections.
Deep intense vertical mixing in the Bussol' Strait
Authors: Yagi Masahiro , Yasuda Ichiro
Published: December 2011

To reveal the intensity of deep mixing in the Bussol' Strait, we performed the direct observations of turbulence for the first time. Vigorous vertical mixing with a turbulent energy dissipation rate ε above 10−6 W/kg and diapycnal diffusivity Kρ above 103 cm2/s were observed at depths of 600–1300 m (potential densities of 27.0–27.5 σθ) at the western gap of the Bussol' Strait, possibly affecting water‐mass transformation and thermohaline circulation. The strong vertical mixing with a diurnal period occurred when the diurnal tidal current flowed toward the Okhotsk Sea, corresponding to a period of enhanced shear consisting of the mean flow with a two‐layered structure and the large‐amplitude diurnal tidal current with a vertical structure explained by a low‐vertical mode topographically trapped wave. The empirical relationship ofε = 10−1.46±1.91 × S2.16±0.72 is obtained between ε and the shear Sreconstructed from the 50‐m‐scale mean, diurnal, and semi‐diurnal tidal currents.
Temporal variability of internal tides in the northeast South China Sea
Authors: Huan Lee I. , Wang Yu‐Huai , Yang Yih , Wang Dong‐Ping
Published: December 2011

The northeast South China Sea is perhaps the largest internal tide energy source in the world. The temporal variability of internal tides was investigated on the basis of 8‐month moored acoustic Doppler current profiler observations on the continental slope at the Dongsha Plateau. The daily amplitude and phase of diurnal and semidiurnal internal tides were determined from complex demodulation, and the dominant spatial and temporal patterns were extracted with empirical orthogonal function (EOF) analysis. The EOF modal structures showed good agreement with the normal mode solution, although vertical phase propagations were apparent. The first semidiurnal EOF mode corresponded to the first normal mode, and the first two diurnal EOF modes corresponded to the second and third normal modes, respectively. The modal structure and energy flux also were consistent with previous observations near the shelf break from the Asian Seas International Acoustic Experiment. On the other hand, the amplitudes of diurnal and semidiurnal EOF modes both indicated large irregular fortnightly variations that were not phase locked (incoherent) with astronomical forcing. The study highlighted the importance of incoherent internal tidal motion, which accounted for about three fourths of the observed tidal energy.
Arctic sea ice freeboard from IceBridge acquisitions in 2009: Estimates and comparisons with ICESat
Authors: Kwok R. , Cunningham G. F. , Manizade S. S. , Krabill W. B.
Published: December 2011

During the spring of 2009, the Airborne Topographic Mapper (ATM) system on the IceBridge mission acquired cross‐basin surveys of surface elevations of Arctic sea ice. In this paper, the total freeboard derived from four ∼2000 km transects are examined and compared with those from the 2009 ICESat campaign. Total freeboard, the sum of the snow and ice freeboards, is the elevation of the air‐snow interface above the local sea surface. Prior to freeboard retrieval, signal dependent range biases are corrected. With data from a near co‐incident outbound and return track on 21 April, we show that our estimates of the freeboard are repeatable to within ∼4 cm but dependent locally on the density and quality of sea surface references. Overall difference between the ATM and ICESat freeboards for the four transects is 0.7 (8.5) cm (quantity in bracket is standard deviation), with a correlation of 0.78 between the data sets of one hundred seventy‐eight 50 km averages. This establishes a level of confidence in the use of ATM freeboards to provide regional samplings that are consistent with ICESat. In early April, mean freeboards are 41 cm and 55 cm over first year and multiyear sea ice (MYI), respectively. Regionally, the lowest mean ice freeboard (28 cm) is seen on 5 April where the flight track sampled the large expanse of seasonal ice in the western Arctic. The highest mean freeboard (71 cm) is seen in the multiyear ice just west of Ellesmere Island from 21 April. The relatively large unmodeled variability of the residual sea surface resolved by ATM elevations is discussed.
Seasonal variation in the temperature sensitivity of proteolytic enzyme activity in temperate forest soils
Authors: Brzostek Edward R. , Finzi Adrien C.
Published: December 2011

Increasing soil temperature has the potential to alter the activity of the extracellular enzymes that mobilize nitrogen (N) from soil organic matter (SOM) and ultimately the availability of N for primary production. Proteolytic enzymes depolymerize N from proteinaceous components of SOM into amino acids, and their activity is a principal driver of the within‐system cycle of soil N. The objectives of this study were to investigate whether the soils of temperate forest tree species differ in the temperature sensitivity of proteolytic enzyme activity over the growing season and the role of substrate limitation in regulating temperature sensitivity. Across species and sampling dates, proteolytic enzyme activity had relatively low sensitivity to temperature with a mean activation energy (Ea) of 33.5 kJ mol−1. Ea declined in white ash, American beech, and eastern hemlock soils across the growing season as soils warmed. By contrast, Eain sugar maple soil increased across the growing season. We used these data to develop a species‐specific empirical model of proteolytic enzyme activity for the 2009 calendar year and studied the interactive effects of soil temperature (ambient or +5°C) and substrate limitation (ambient or elevated protein) on enzyme activity. Declines in substrate limitation had a larger single‐factor effect on proteolytic enzyme activity than temperature, particularly in the spring. There was, however, a large synergistic effect of increasing temperature and substrate supply on proteolytic enzyme activity. Our results suggest limited increases in N availability with climate warming unless there is a parallel increase in the availability of protein substrates.
Predicting the arrival of high‐speed solar wind streams at Earth using the STEREO Heliospheric Imagers
Authors: Davis C. J. , Davies J. A. , Owens M. J. , Lockwood M.
Published: December 2011

High‐speed solar wind streams modify the Earth's geomagnetic environment, perturbing the ionosphere, modulating the flux of cosmic rays into the Earth atmosphere, and triggering substorms. Such activity can affect modern technological systems. To investigate the potential for predicting the arrival of such streams at Earth, images taken by the Heliospheric Imager (HI) on the STEREO‐A spacecraft have been used to identify the onsets of high‐speed solar wind streams from observations of regions of increased plasma concentrations associated with corotating interaction regions, or CIRs. In order to confirm that these transients were indeed associated with CIRs and to study their average properties, arrival times predicted from the HI images were used in a superposed epoch analysis to confirm their identity in near‐Earth solar wind data obtained by the Advanced Composition Explorer (ACE) spacecraft and to observe their influence on a number of salient geophysical parameters. The results are almost identical to those of a parallel superposed epoch analysis that used the onset times of the high‐speed streams derived from east/west deflections in the ACE measurements of solar wind speed to predict the arrival of such streams at Earth, assuming they corotated with the Sun with a period of 27 days. Repeating the superposed epoch analysis using restricted data sets demonstrates that this technique can provide a timely prediction of the arrival of CIRs at least 1 day ahead of their arrival at Earth and that such advanced warning can be provided from a spacecraft placed 40° ahead of Earth in its orbit.
Quantification of experimental subsurface fluid saturations from high‐resolution source zone images
Authors: Christ John A. , Pennell Kurt D. , Abriola Linda M.
Published: December 2011

Laboratory‐scale aquifer cells are commonly used to investigate processes governing contaminant fate and transport in heterogeneous subsurface systems. In recent years, dramatic improvements in image processing methods have led to increasingly refined image resolution in these experiments. With these enhanced imagining methodologies, system parameters, such as nonaqueous phase liquid (NAPL) saturation, can now be quantified at the submillimeter scale. This fine level of resolution, however, is generally inconsistent with the typical scale of a representative elementary volume (REV), the averaging volume associated with property evaluation in continuum‐based flow and transport models. Such inconsistency of scales calls into question the practice of directly comparing laboratory observations with continuum‐based model simulations. This work explores the application of alternative approaches to image data processing for characterization of NAPL source zone architecture in aquifer cells and examines the implications of data processing on the interpretation of experimental‐model comparisons. The utility of two alternative upscaling methods, a continuity‐equation based (CB) and discrete‐block based (DBB) approach are considered. Examination of the stability of point averages of saturation demonstrates that a REV length scale can be defined as ∼30 × d50 for the thickness‐averaged, two‐dimensional aquifer cell experiments examined. Quantification of upscaled source zone metrics, including the average saturation, the second spatial moment in the vertical direction, and the ganglia‐to‐pool (GTP) mass ratio reveals that the GTP is strongly sensitive to observation scale. Use of GTP values computed from upscaled images is shown to improve mathematical model predictions of experimental effluent concentrations by nearly 50%.
Taking shortcuts with OWL using safe macros
Authors: Mungall Christopher , Ruttenberg Alan , Osumi-Sutherland David
Published: December 2011

Accurate representation of complex domains such as biology demands powerful and expressive ontology languages such as OWL. However, the complex nested class expressions required for modeling can be a hindrance to ontology authoring and adoption. These class expressions can appear opaque to domain experts, and even users proficient in OWL can benefit from some kind of syntactic sugar or "short-cut" strategy, especially when authoring large ontologies.One solution is to have domain experts fill in simple templates (for example, in Excel) and translate the results into more complex axioms, but this has the disadvantage of being disconnected from full ontology authoring and reasoning environment.We present here a method of specifying shortcut properties directly in OWL. These shortcut properties can be used in similar ways as object properties within the OWL environment, with the resulting simple axioms translated automatically to more complex axioms via macro expansion. We describe some example scenarios where this is of use in authoring existing bio-ontologies.One of the main implications of this work is a way to simplify the translation between OBO format and OWL, and the use of RDF triple-stores with complex OWL ontologies.
Two-photon absorption yields Doppler-free spectroscopy
Authors: Lubkin Gloria B.
Published: December 2011

In one of those events so typical of research, three groups have independently and almost simultaneously demonstrated two-photon absorption in sodium vapor without blurring from Doppler broadening. The technique appears to open up a new way of achieving high-resolution spectroscopy with tunable lasers. And it can be applied, for example, to induce photochemical reactions selectively, to separate isotopes, or to provide more precise values for the Rydberg constant and Lamb shifts.
Synchrotron radiation—light fantastic
Authors: Perlman M. L. , Watson R. E. , Rowe E. M.
Published: December 2011

“Wouldn't it be interesting if these beautiful and sophisticated machines made their greatest contributions to science as light bulbs?” So queried Donald Kerst, inventor of the betatron, in speaking recently about the current generation of electron accelerators. Indeed, in the past ten years, many synchrotrons and storage rings have been very successfully used as light bulbs—to illumine the electronic and optical properties of gases, liquids and solids. Why have researchers gone to the trouble and expense of using synchrotron radiation from these facilities rather than staying at home with discharge lamps and x-ray tubes? Because the synchrotron radiation has special characteristics that enable investigations to be done that would otherwise be impossible. It produces a highly collimated, continuous spectrum, which includes wavelengths not available from other sources, and it provides a narrow spectral slice of high intensity through monochromatization. These characteristics are obviously desirable for experiments that demand high resolution in space and in energy simultaneously. The wide range and high value of research done with synchrotron radiation to date would support an argument for the construction of a national facility intended especially as a radiation source and invite speculation about the design of such a facility.
A scheme to interpolate potential energy surfaces and derivative coupling vectors without performing a global diabatization
Authors: Evenhuis Christian , Martínez Todd J.
Published: December 2011

Simulation of non-adiabatic molecular dynamics requires the description of multiple electronic state potential energy surfaces and their couplings. Ab initio molecular dynamics approaches provide an attractive avenue to accomplish this, but at great computational expense. Interpolation approaches provide a possible route to achieve flexible descriptions of the potential energy surfaces and their couplings at reduced expense. A previously developed approach based on modified Shepard interpolation required global diabatization, which can be problematic. Here, we extensively revise this previous approach, avoiding the need for global diabatization. The resulting interpolated potentials provide only adiabatic energies, gradients, and derivative couplings. This new interpolation approach has been integrated with the ab initio multiple spawning method and it has been rigorously validated against direct dynamics. It is shown that, at least for small molecules, constructing an interpolated PES can be more efficient than performing direct dynamics as measured by the total number of ab initio calculations that are required for a given accuracy.
Structural properties of fluorozirconate-based glass ceramics doped with multivalent europium
Authors: Paßlick C. , Müller O. , Lützenkirchen-Hecht D. , Frahm R. , Johnson J. A. , Schweizer S.
Published: December 2011

The structure/property relationships of fluorochlorozirconate glass ceramics as a function of divalent and trivalent europium (Eu) co-doping and thermal processing have been investigated; the influence of doping ratio on the formation of barium chloride (BaCl2) nanocrystals therein was elucidated. X-ray absorption near-edge structure spectroscopy shows that the post-thermal annealing changes the Eu valence of the as-poured glass slightly, but during the melting process Eu3+ is more strongly reduced to Eu2+, in particular, when doped as a chloride instead of fluoride compound. The Eu2+-to-Eu3+ doping ratio also plays a significant role in chemical equilibrium in the melt. X-ray diffraction measurements indicate that a higher Eu2+ fraction leads to a BaCl2 phase transition from hexagonal to orthorhombic structure at a lower temperature.
Compact ultra-fast vertical nanopositioner for improving scanning probe microscope scan speed
Authors: Kenton Brian J. , Fleming Andrew J. , Leang Kam K.
Published: December 2011

The mechanical design of a high-bandwidth, short-range vertical positioning stage is described for integration with a commercial scanning probe microscope (SPM) for dual-stage actuation to significantly improve scanning performance. The vertical motion of the sample platform is driven by a stiff and compact piezo-stack actuator and guided by a novel circular flexure to minimize undesirable mechanical resonances that can limit the performance of the vertical feedback control loop. Finite element analysis is performed to study the key issues that affect performance. To relax the need for properly securing the stage to a working surface, such as a laboratory workbench, an inertial cancellation scheme is utilized. The measured dominant unloaded mechanical resonance of a prototype stage is above 150 kHz and the travel range is approximately 1.56 μm. The high-bandwidth stage is experimentally evaluated with a basic commercial SPM, and results show over 25-times improvement in the scanning performance.
Electronic structure of lithium battery interphase compounds: Comparison between inelastic x-ray scattering measurements and theory
Authors: Fister Tim T. , Schmidt Moritz , Fenter Paul , Johnson Chris S. , Slater Michael D. , Chan Maria K. Y. , Shirley Eric L.
Published: December 2011

In lithium ion batteries, decomposition of the electrolyte and its associated passivation of the electrode surface occurs at low potentials, resulting in an electronically insulating, but Li-ion conducting, solid electrolyte interphase (SEI). The products of the SEI and their chemical constituents/properties play an important role in the long-term stability and performance of the battery. Reactivity and the sub-keV core binding energies of lithium, carbon, oxygen, and fluorine species in the SEI present technical challenges in the spectroscopy of these compounds. Using an alternative approach, nonresonant inelastic x-ray scattering, we examine the near-edge spectra of bulk specimens of common SEI compounds, including LiF, Li2CO3, LiOH, LiOH·H2O, and Li2O. By working at hard x-ray energies, we also experimentally differentiate the s- and p-symmetry components of lithium's unoccupied states using the evolution of its K edge with momentum transfer. We find good agreement with theoretical spectra calculated using a Bethe-Salpeter approach in all cases. These results provide an analytical and diagnostic foundation for better understanding of the makeup of SEIs and the mechanism of their formation.
Efficient exploration of reaction paths via a freezing string method
Authors: Behn Andrew , Zimmerman Paul M. , Bell Alexis T. , Head-Gordon Martin
Published: December 2011

The ability to efficiently locate transition states is critically important to the widespread adoption of theoretical chemistry techniques for their ability to accurately predict kinetic constants. Existing surface walking techniques to locate such transition states typically require an extremely good initial guess that is often beyond human intuition to estimate. To alleviate this problem, automated techniques to locate transition state guesses have been created that take the known reactant and product endpoint structures as inputs. In this work, we present a simple method to build an approximate reaction path through a combination of interpolation and optimization. Starting from the known reactant and product structures, new nodes are interpolated inwards towards the transition state, partially optimized orthogonally to the reaction path, and then frozen before a new pair of nodes is added. The algorithm is stopped once the string ends connect. For the practical user, this method provides a quick and convenient way to generate transition state structure guesses. Tests on three reactions (cyclization of cis,cis-2,4-hexadiene, alanine dipeptide conformation transition, and ethylene dimerization in a Ni-exchanged zeolite) show that this “freezing string” method is an efficient way to identify complex transition states with significant cost savings over existing methods, particularly when high quality linear synchronous transit interpolation is employed.
Improved measurement for volatile particles: Vapor-particle separator design and laboratory tests
Authors: Cheng Meng-Dawn , Allman Steve E.
Published: December 2011

Sampling and measurement of volatile particles is a challenging task. It has been hampered by lack of a reliable technique capable of accurately capturing the phase-partition process of the pollutants without generating bias and artifacts in the data. The objective of this research is to design a new vapor-particle separation technique for performing the phase separation on-line (the sampling aspect), which, simultaneously, enables characterization of the vapors and particles. The new vapor-particle separator (VPS) consists of a thin metallic microporous membrane for (1) extraction of vapor molecules that are thermally desorbed from the condensed particulate phases and (2) collection of the vapors for subsequent chemical analysis. We evaluated this new separator using synthetic particles made of nonvolatile and or semi-volatile chemicals, and reported the laboratory test results in this paper. The laboratory particle test results showed reasonably high particle transmission efficiency across all particle sizes. The thermal dynamics of nanoparticles was succinctly observed on-line. The results successfully demonstrated the ability of VPS to separate particles and vapors thus enabling a faithful observation of the thermal behavior. We believe the new technology will make a great contribution to the measurement of volatile particles.
Sound absorption characteristics of aluminum foam with spherical cells
Authors: Li Yunjie , Wang Xinfu , Wang Xingfu , Ren Yuelu , Han Fusheng , Wen Cuie
Published: December 2011

Aluminum foams were fabricated by an infiltration process. The foams possess spherical cells with a fixed porosity of 65% and varied pore sizes which ranged from 1.3 to 1.9 mm. The spherical cells are interconnected by small pores or pore openings on the cell walls that cause the foams show a characteristic of open cell structures. The sound absorption coefficient of the aluminum foams was measured by a standing wave tube and calculated by a transfer function method. It is shown that the sound absorption coefficient increases with an increase in the number of pore openings in the unit area or with a decrease of the diameter of the pore openings in the range of 0.3 to 0.4 mm. If backed with an air cavity, the resonant absorption peaks in the sound absorption coefficient versus frequency curves will be shifted toward lower frequencies as the cavity depth is increased. The samples with the same pore opening size but different pore size show almost the same absorption behavior, especially in the low frequency range. The present results are in good agreement with some theoretical predictions based on the acoustic impedance measurements of metal foams with circular apertures and cylindrical cavities and the principle of electroacoustic analogy.
Intrinsic evolutions of optical functions, band gap, and higher-energy electronic transitions in VO2 film near the metal-insulator transition region
Authors: Li W. W. , Yu Q. , Liang J. R. , Jiang K. , Hu Z. G. , Liu J. , Chen H. D. , Chu J. H.
Published: December 2011

Transmittance spectra of (011) vanadium dioxide (VO2) film have been studied in the temperature range of 45–80 °C. Owing to increasing carrier concentration, the near-infrared extinction coefficient and optical conductivity around metal-insulator transition (MIT) rapidly increase with the temperature. Moreover, three electronic transitions can be uniquely assigned and show the hysteresis behavior near the MIT region. It was found that the optical band gap decreases from 0.457 to 0.042 eV before the MIT, then reduces to zero for the metal state. This confirms the fact that the a1g and egπ bands are moved close and finally overlap with the temperature.
Organization of flux line system and voltage oscillations in superconducting MgB2
Authors: Kiliç A. , Olutaş M. , Kiliç K. , Altinkok A.
Published: December 2011

The influence of bidirectional square wave (BSW) current on the evolution of the V–t curves was studied in a polycrystalline sample of MgB2. Regular sinusoidal-like voltage oscillations were observed at well-defined values of the amplitude (IBSW) and period (PI) of the BSW current, temperature, and external magnetic field. The voltage oscillations were interpreted mainly in terms of short- and long-range spatial correlations in a flux line system, relaxation effects, and the dynamic competition between pinning and depinning. The oscillating mode was also discussed in terms of sliding charge density waves associated with density fluctuations. Alternatively, the coupling between conventional thermally activated flux creep theory and annealing of the disordered states was considered as another possible mechanism in describing the voltage oscillations. Due to the complex interplay of pinning and driving forces, the oscillating mode is correlated to the drifting of flux lines, which are in motion, and it is assumed that the majority of flux lines try to traverse the sample, but do not leave it entirely. The symmetry in voltage oscillations was attributed to the equality between flux exit and entry along the sample edges. In this process, the majority of flux lines leave the sample and the direction of motion of flux lines reverses. During the oscillatory motion, we suggest that the interaction between flux lines and pinning centers may be elastic coupling in nature, because of rigidity of the flux line lattice in MgB2. Non-oscillatory behavior of V-t curves measured for BSW drive with low PI was attributed pre-dominantly to the effect of pinning on the distribution of the flux lines. The vortex capacitor model could be applied to explain the voltage decays in these V-t curves. However, the voltage decays associated with switching of IBSW to dc current (Idc) were correlated to current-induced quenched disorder and to the glassy state relaxation. Further, angular dependence of voltage oscillations reveals that the anisotropic effects are nearly negligible on the evolution of V-t curves. It was shown that the voltage oscillations can be described well by an empirical expression V(t) ∼ sin(wt + φ), where w is the frequency and φ is the phase angle. Finally, at well-defined values of IBSW and PI of BSW current, H, and T, it was argued that the MgB2 sample behaves like a double-integrator.
Magnetic relaxation of a system of superparamagnetic particles weakly coupled by dipole-dipole interactions
Authors: Déjardin Pierre-Michel
Published: December 2011

Long range dipole-dipole interactions in the thermal fluctuations of the magnetization of an assembly of single-domain ferromagnetic particles are considered, ignoring orientational correlations between the particles, so that the evolution of the magnetization orientations may be described by a nonlinear Fokker-Planck equation (FPE) reducing to the usual linear one in the limit of infinite dilution [W. F. Brown Jr., Phys. Rev. 130, 1677 (1963)]. The thermally activated relaxation time scale of the assembly is estimated, leading to a simple and transparent modification of the axially symmetric asymptotes for the superparamagnetic relaxation time.
Efficient heating with a controlled microwave field
Authors: Chang T. H. , Chao H. W. , Syu F. H. , Chiang W. Y. , Fong S. C. , Chin T. S.
Published: December 2011

To uncover the intriguing non-thermal microwave effect, an experiment was conducted using an amplifier rather than an oscillator as the radiation source, which was injected into an applicator with strong electromagnetic field enhancement. The characteristics of the applicator are discussed and the enhancement of the microwave field is illustrated and explained. Thermal distribution is simulated based on the calculated microwave field profile. It was demonstrated that the proposed system heated a SiC susceptor to a temperature of 637 °C with the input power of 60 W. The reasons for such an efficient heating are discussed.
Ultra-sensitive high-precision spectroscopy of a fast molecular ion beam
Authors: Mills Andrew A. , Siller Brian M. , Porambo Michael W. , Perera Manori , Kreckel Holger , McCall Benjamin J.
Published: December 2011

Direct spectroscopy of a fast molecular ion beam offers many advantages over competing techniques, including the generality of the approach to any molecular ion, the complete elimination of spectral confusion due to neutral molecules, and the mass identification of individual spectral lines. The major challenge is the intrinsic weakness of absorption or dispersion signals resulting from the relatively low number density of ions in the beam. Direct spectroscopy of an ion beam was pioneered by Saykally and co-workers in the late 1980s, but has not been attempted since that time. Here, we present the design and construction of an ion beam spectrometer with several improvements over the Saykally design. The ion beam and its characterization have been improved by adopting recent advances in electrostatic optics, along with a time-of-flight mass spectrometer that can be used simultaneously with optical spectroscopy. As a proof of concept, a noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) setup with a noise equivalent absorption of ∼2 × 10−11 cm−1 Hz−1/2 has been used to observe several transitions of the Meinel 1–0 band of \documentclass[12pt]{minimal}\begin{document}${\rm N}_2^+$\end{document}N2+ with linewidths of ∼120 MHz. An optical frequency comb has been used for absolute frequency calibration of transition frequencies to within ∼8 MHz. This work represents the first direct spectroscopy of an electronic transition in an ion beam, and also represents a major step toward the development of routine infrared spectroscopy of rotationally cooled molecular ions.
Ferreting out correlations from trajectory data
Authors: Cukier Robert I.
Published: December 2011

Thermally driven materials characterized by complex energy landscapes, such as proteins, exhibit motions on a broad range of space and time scales. Principal component analysis (PCA) is often used to extract modes of motion from protein trajectory data that correspond to coherent, functional motions. In this work, two other methods, maximum covariance analysis (MCA) and canonical correlation analysis (CCA) are formulated in a way appropriate to analyze protein trajectory data. Both methods partition the coordinates used to describe the system into two sets (two measurement domains) and inquire as to the correlations that may exist between them. MCA and CCA provide rotations of the original coordinate system that successively maximize the covariance (MCA) or correlation (CCA) between modes of each measurement domain under suitable constraint conditions. We provide a common framework based on the singular value decomposition of appropriate matrices to derive MCA and CCA. The differences between and strengths and weaknesses of MCA and CCA are discussed and illustrated. The application presented here examines the correlation between the backbone and side chain of the peptide met-enkephalin as it fluctuates between open conformations, found in solution, to closed conformations appropriate to when it is bound to its receptor. Difficulties with PCA carried out in Cartesian coordinates are found and motivate a formulation in terms of dihedral angles for the backbone atoms and selected atom distances for the side chains. These internal coordinates are a more reliable basis for all the methods explored here. MCA uncovers a correlation between combinations of several backbone dihedral angles and selected side chain atom distances of met-enkephalin. It could be used to suggest residues and dihedral angles to focus on to favor specific side chain conformers. These methods could be applied to proteins with domains that, when they rearrange upon ligand binding, may have correlated functional motions or, for multi-subunit proteins, may exhibit correlated subunit motions.
The infrared spectrum of NN⋯CO+ trapped in solid neon
Authors: Thompson Warren E. , Jacox Marilyn E.
Published: December 2011

Codeposition of a Ne:N2:CO = 200:1:1 mixture at 4.3 K with a beam of very pure neon atoms excited to their energy levels between 16.6 and 16.85 eV leads to stabilization in the resulting solid of sufficient NNCO+ for detection of its NN- and CO-stretching vibration fundamentals. Detailed isotopic substitution studies and density functional calculations for the various isotopologues support the identification of NNCO+ and permit estimation of the positions of two of its low-frequency fundamentals. A sufficient concentration of NOCN is also stabilized in the neon matrix for detection of its NO-stretching vibrational fundamental
The significance of Debye length in disordered doped organic devices
Authors: Raja Munira , Eccleston Bill
Published: December 2011

The need for thin isolated active layers in organic electronic devices is becoming a critical issue for enhanced performance. Scaling-down the thickness of the layers causes a significant reduction in off-currents, however, also lowers on-currents with consequent effects on the drive capability. The Debye length is a fundamental material parameter of importance in understanding such scaling issues in devices. Here, we develop Debye length models for disordered doped organic devices operating under both accumulation and depletion regimes. The models are expressed in terms of the characteristic temperature associated with the distribution of the density of states. We show that for the same doping level, the Debye length of an organic semiconductor is smaller than that of silicon, which is most likely due to its low relative permittivity. This consequently also results in a higher ratio of the depletion width over the Debye length, suggesting the deployment of the abrupt depletion edge approximation in organics to be appropriate. Good agreement of the theory is demonstrated with the experimental data of the reverse current-voltage characteristics of P3HT Schottky diodes.
Milestoning with transition memory
Authors: Hawk Alexander T. , Makarov Dmitrii E.
Published: December 2011

Milestoning is a method used to calculate the kinetics and thermodynamics of molecular processes occurring on time scales that are not accessible to brute force molecular dynamics (MD). In milestoning, the conformation space of the system is sectioned by hypersurfaces (milestones), an ensemble of trajectories is initialized on each milestone, and MD simulations are performed to calculate transitions between milestones. The transition probabilities and transition time distributions are then used to model the dynamics of the system with a Markov renewal process, wherein a long trajectory of the system is approximated as a succession of independent transitions between milestones. This approximation is justified if the transition probabilities and transition times are statistically independent. In practice, this amounts to a requirement that milestones are spaced such that trajectories lose position and velocity memory between subsequent transitions. Unfortunately, limiting the number of milestones limits both the resolution at which a system's properties can be analyzed, and the computational speedup achieved by the method. We propose a generalized milestoning procedure, milestoning with transition memory (MTM), which accounts for memory of previous transitions made by the system. When a reaction coordinate is used to define the milestones, the MTM procedure can be carried out at no significant additional expense as compared to conventional milestoning. To test MTM, we have applied its version that allows for the memory of the previous step to the toy model of a polymer chain undergoing Langevin dynamics in solution. We have computed the mean first passage time for the chain to attain a cyclic conformation and found that the number of milestones that can be used, without incurring significant errors in the first passage time is at least 8 times that permitted by conventional milestoning. We further demonstrate that, unlike conventional milestoning, MTM permits milestones to be spaced such that trajectories do not have enough time to lose their velocity memory between successively crossed milestones.
Photoacoustic technique for simultaneous measurements of thermal effusivity and absorptivity of pigments in liquid solution
Authors: Balderas-López J. A. , Díaz-Reyes J. , Zelaya-Angel O.
Published: December 2011

A photoacoustic (PA) methodology, in the transmission configuration, for simultaneous measurements of thermal effusivity and molar absorption coefficient (absorptivity) for pigments in liquid solution is introduced. The analytical treatment involves a self-normalization procedure for the PA signal, as a function of the modulation frequency, for a strong absorbing material in the thermally thin regime, when the light travels across the sample under study. Two fitted parameters are obtained from the analysis of the self-normalized PA amplitude and phase, one of them proportional to the sample's optical absorption coefficient and from which, taking it for a series of samples at different concentrations, the pigment's absorptivity in liquid solution can be measured, the other one yields the sample's thermal effusivity. Methylene blue's absorptivity in distilled water was measured with this methodology at 658 nm, finding good agreement with the corresponding one reported in the literature.
Structure and morphology of an organic/inorganic multilayer stack: An x-ray reflectivity study
Authors: Neuhold Alfred , Fladischer Stefanie , Mitsche Stefan , Flesch Heinz-Georg , Moser Armin , Novak Jiri , Smilgies Detlef M. , Kraker Elke , Lamprecht Bernhard , Haase Anja , Grogger Werner , Resel Roland
Published: December 2011

The internal morphology and crystallographic properties of a complete organic thin film multilayer stack are characterized via x-ray scattering techniques, atomic force microscopy (AFM), and scanning electron microscopy. The stack consists of the three organic layers – copper(II)phthalocyanine (CuPc), perylene tetracarboxylic bisbenzimidazole (PTCBI), and aluminum-tris(8-hydroxychinolin) (Alq3) – sandwiched between an optically semitransparent gold layer and a top silver electrode. The interface roughness progress is determined by the x-ray reflectivity, which is confirmed by the surface roughness determination via AFM. The crystallographic properties are characterized via x-ray diffraction. The CuPc layer is highly crystalline with preferentially oriented crystallites but forms a rough interface (σRMS = 5.5 nm) toward the PTCBI layer. The PTCBI layer grows with randomly distributed crystallites in a worm-like morphology with an interface roughness of σRMS = 6.4 nm toward the Alq3 layer. The amorphous Alq3 layer acts as smoothing layer and reduces the roughness σRMS to 5.8 nm. Within this study we demonstrate the applicability of x-ray reflectivity in characterizing the interface morphology of an organic multilayer stack device.