bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric forcing on the drift of Arctic sea ice in 1989–2009
Authors: Vihma Timo , Tisler Priit , Uotila Petteri
Published: December 2011

Inter‐annual variations in Arctic sea ice drift speed (Vi) in 1989–2009 were analyzed on the basis of buoy data and atmospheric circulation indices. In the circumpolar and eastern Arctic and the Fram Strait, the annual mean Vi was best explained by the sea level pressure (SLP) difference across the Arctic Ocean along meridians 270°E and 90°E, called as the Central Arctic Index (CAI). In general, Vi was more strongly related to CAI than to the Dipole Anomaly (DA). This was because CAI is calculated across the Transpolar Drift Stream (TDS), whereas the pressure patterns affecting DA sometimes move far from TDS. CAI also has the benefit of being a simple index, insensitive to the calculation method applied, whereas DA, as the second mode of a principal component analysis, is sensitive both to the time period and area of calculations. In summer, the circulation index most important for the circumpolar mean Vi was the SLP gradient across the Fram Strait. In the Canadian Basin in winter, the Arctic Oscillation index was most important. Circulation indices explained 48% of the variance of the annual mean Viin the circumpolar Arctic, 38% in the eastern Arctic, and 25% in the Canadian Basin. The local air‐ice momentum flux (τ) was always better than the 10 m wind speed in explaining Vi, but τ outperformed the circulation indices only in the Fram Strait. Atmospheric forcing did not explain the increasing trend in Vi in the period 1989–2009.
A Rayleigh wave back‐projection method applied to the 2011 Tohoku earthquake
Authors: Roten Daniel , Miyake Hiroe , Koketsu Kazuki
Published: December 2011

We study the rupture process of the 2011 Tohoku megathrust by analyzing 384 regional strong‐motion records using a novel back‐projection method for Rayleigh waves with periods between 13 and 100 s. The proposed approach is based on isolating the signal at the selected period with a continuous wavelet transform, and generating the stack using arrival times predicted from detailed fundamental mode Rayleigh wave group velocity maps. We verify the method by back‐projecting synthetic time series representing a point source off the coast of Tohoku, which we generate with a 3D finite difference method and a mesh based on the Japan Integrated Velocity Structure Model. Application of the method to K‐NET/KiK‐net records of theMw9.1 Tohoku earthquake reveals several Rayleigh wave emitters, which we attribute to different stages of rupture. Stage 1 is characterized by slow rupture down‐dip from the hypocenter. The onset of stage 2 is marked by energetic Rayleigh waves emitted from the region between the JMA hypocenter and the trench within 60 s after hypocentral time. During stage 3 the rupture propagates bilaterally towards the north and south at rupture velocities between 3 and 3.5 km · s−1, reaching Iwate‐oki 65 s and Ibaraki‐oki 105 s after nucleation. In contrast to short‐period back‐projections from teleseismic P‐waves, which place radiation sources below the Honshu coastline, Rayleigh wave emitters identified from our long‐period back‐projection are located 50–100 km west of the trench. This result supports the interpretation of frequency‐dependent seismic wave radiation as suggested in previous studies.
A recent and abrupt decline in the East African long rains
Authors: Lyon Bradfield , DeWitt David G.
Published: December 2011

The successive failure of the East African short rains (typically October‐December) and subsequent long rains (March‐May) in 2010–11 plunged much of the region into severe drought, impacting millions of people and triggering a humanitarian crisis. While poor short rains in 2010 were generally anticipated given linkages with La Niña, the subsequent long rains do not exhibit similar predictability. Here we show the long rains failure in boreal spring of 2011 is consistent with a recurrent large‐scale precipitation pattern that followed their abrupt decline around 1999. Using observations and climate model simulations, we show the abrupt decline in long rains precipitation is linked to similarly abrupt changes in sea surface temperatures, predominately in the tropical Pacific basin.
Gravity waves, cold pockets and CO2 clouds in the Martian mesosphere
Authors: Spiga A. , González‐Galindo F. , López‐Valverde M.‐Á. , Forget F.
Published: December 2011

Many independent measurements have shown that extremely cold temperatures are found in the Martian mesosphere. These mesospheric “cold pockets” may result from the propagation of atmospheric waves. Recent observational achievements also hint at such cold pockets by revealing mesospheric clouds formed through the condensation of CO2, the major component of the Martian atmosphere. Thus far, modeling studies addressing the presence of cold pockets in the Martian mesosphere have explored the influence of large‐scale circulations. Mesoscale phenomena, such as gravity waves, have received less attention. Here we show through multiscale meteorological modeling that mesoscale gravity waves could play a key role in the formation of mesospheric cold pockets propitious to CO2 condensation.
Association of U.S. tornado occurrence with monthly environmental parameters
Authors: Tippett Michael K. , Sobel Adam H. , Camargo Suzana J.
Published: December 2011

Monthly U.S. tornado numbers are here related to observation‐based monthly averaged atmospheric parameters. Poisson regression is used to form an index which captures the climatological spatial distribution and seasonal variation of tornado occurrence, as well as year‐to‐year variability, and provides a framework for extended range forecasts of tornado activity. Computing the same index with predicted atmospheric parameters from a comprehensive forecast model gives some evidence of the predictability of monthly tornado activity.
Nonmigrating tidal characteristics in thermospheric neutral mass density
Authors: Kwak Young‐Sil , Kil Hyosub , Lee Woo Kyoung , Oh Seung‐Jun , Ren Zhipeng
Published: December 2011

The wave number 4 (wave 4) and wave number 3 (wave 3) longitudinal structures in the thermospheric neutral mass density are understood as tidal structures driven by diurnal eastward propagating zonal wave number 3 (DE3) and wave number 2 (DE2) tides, respectively. However, those structures have been identified using data from limited time periods, and the consistency and recurrence of those structures have not yet been examined using long‐term observation data. We examine the persistence of those structures by analyzing the neutral mass density data for the years 2001–2008 taken by the Challenging Minisatellite Payload (CHAMP) satellite. During years of low solar activity the amplitude of the wave 4 structure is pronounced during August and September, and the wave 4 phase shows a consistent eastward phase progression of 90° within 24 h local time in different months and years. During years of high solar activity the wave 4 amplitude is small and does not show a distinctive annual pattern, but the tendency of the eastward phase shift at a rate of 90°/24 h exists. Thus the DE3 signature in the wave 4 structure is considered as a persistent feature. The wave 3 structure is a weak feature in most months and years. The amplitude and phase of the wave 3 structure do not show a notable solar cycle dependence. Among the contributing tidal modes to the wave 3 structure, the DE2 amplitude is most pronounced. This result may suggest that the DE2 signature, although it is a weak signature, is a perceivable persistent feature in the thermosphere.
Seasonal thermocline in the China Seas and northwestern Pacific Ocean
Authors: Hao Jiajia , Chen Yongli , Wang Fan , Lin Pengfei
Published: December 2011

Climatological seasonal variations of the thermocline in the China Seas and northwestern Pacific Ocean were studied using historical data from 1930 through 2001 (707,624 profiles). The quantitative roles of surface thermal buoyancy (Bq), haline buoyancy flux (Bp), and total buoyancy flux (B) against the wind‐induced mixing (τ) in different seasons and regions were also explored using the buoyancy ratio (R = ∣Bq/Bp∣) and the Monin‐Obukhov depth ratio (δ), respectively. The thermocline has obvious seasonal variations in the study area north of 20°N. There is no thermocline along the west coast of the Bohai Sea (BS), Yellow Sea (YS), and northern East China Sea from December to March resulting from surface cooling and wind mixing. The significantly different variation of the thermocline strength on and off the Chinese shelf is mainly caused by the fact that the thermal stratification is enhanced by bottom tidal mixing on the shelf. The δ indicates that the thermocline depth on the Chinese shelf is mainly dominated by B in summer, while it is dominated by τ in winter. It reveals an opposite feature in the Kuroshio region; the dominating factor is B in winter, associated with the large heat buoyancy loss there. South of 20°N, the dominating factor is similar to that on the shelf, with the more obvious B dominant characteristic during the monsoon transition periods. The R demonstrates that B is mainly controlled by Bq all year round, with some sporadically Bp‐dominated regions in the tropical area in winter and in the BS and eastern YS in September.
Hygroscopicity frequency distributions of secondary organic aerosols
Authors: Suda S. R. , Petters M. D. , Matsunaga A. , Sullivan R. C. , Ziemann P. J. , Kreidenweis S. M.
Published: December 2011

Secondary organic compounds are an important component of ambient aerosol and potentially lower the supersaturation that is required for individual particles to serve as cloud condensation nuclei (CCN). Secondary organic aerosol (SOA) formed from the oxidation of a single precursor can be composed of many different compounds and their overall CCN efficiency has been reported for many different SOA systems. An aerosol's CCN efficiency can be described by a single hygroscopicity parameter, κ. However, this κ comprises an unknown distribution of underlying κ‐values resulting from each individual compound in the SOA mixture. Here we report on a new technique for characterizing this distribution ofκ. Precursor hydrocarbons were oxidized in an environmental chamber to form SOA, which was collected on filters and extracted using ethyl acetate. Extracts were then fractionated by reversed‐phase high‐performance liquid chromatography using gradient elution with acetonitrile and water. The eluate was atomized, the solvent was removed by evaporation, and the residual aerosol particles were analyzed as a function of retention time using scanning flow CCN analysis. Kappa‐values generally decreased with component retention time, consistent with expected decreasing polarity. Averaged SOAκ‐values reconstructed by integrating over the chromatogram agreed well with values measured for SOA sampled directly from the environmental chamber, suggesting thatκfor SOA represents the volume‐weighted average of the constituent compounds'κ‐values. We anticipate that our measured hygroscopicity distributions will serve as validation points for mechanistic models that seek to predict the generation and evolution of organic aerosol composition and properties in the atmosphere.
Morphometric analysis of small‐scale lobate scarps on the Moon using data from the Lunar Reconnaissance Orbiter
Authors: Banks M. E. , Watters T. R. , Robinson M. S. , Tornabene L. L. , Tran T. , Ojha L. , Williams N. R.
Published: December 2011

Prior to Lunar Reconnaissance Orbiter (LRO), the morphology and dimensions of only a limited number of lobate scarps, all located near the equator (within 21°), had been characterized. Topography derived from LRO Camera stereo images and Lunar Orbiter Laser Altimeter (LOLA) ranging is used to measure the relief and analyze the morphology of previously known and newly detected low and high latitude lobate scarps. The asymmetric profiles and maximum slopes on scarp faces (∼5° to 29°) of lunar lobate scarps are similar to those of lobate scarps observed on Mars and Mercury. Scarp lengths range from ∼0.6 to 21.6 km (mean = ∼6.0 km, median = ∼4.4 km, n = 79), and measured relief ranges from ∼5 to 150 m (mean = ∼35 m, median = ∼20 m, n = 26). Assuming a range of 20° to 40° for the fault plane dip, estimated lower limits for the horizontal shortening (S) expressed by the lobate scarp thrust faults range from ∼10 to 410 m. The range in S estimated for the lunar scarps is roughly an order of magnitude lower than estimates of S for lobate scarp thrust faults on Mars and Mercury. The relatively small range of S estimated for the growing number of well‐characterized lunar scarps is consistent with a small amount of global contraction.
How old are young lunar craters?
Authors: Hiesinger H. , van der Bogert C. H. , Pasckert J. H. , Funcke L. , Giacomini L. , Ostrach L. R. , Robinson M. S.
Published: December 2011

The accurate definition of the lunar cratering chronology is important for deriving absolute model ages across the lunar surface and throughout the Solar System. Images from the Lunar Reconnaissance Orbiter Narrow Angle Cameras and Wide‐Angle Camera and the SELENE/Kaguya Terrain Camera provide new opportunities to investigate crater size‐frequency distributions (CSFDs) on individual geological units at lunar impact craters. We report new CSFD measurements for the Copernican‐aged craters North Ray, Tycho, and Copernicus, which are crucial anchor points for the lunar cratering chronology. We also discuss possible reasons for an age discrepancy observed between the impact melt and ejecta units. Our CSFDs for North Ray and Tycho crater ejecta deposits are consistent with earlier measurements. However, for Copernicus crater and one of its rays, we find significantly lower cumulative crater frequencies than previous studies. Our new results for Copernicus crater fit the existing lunar absolute chronologies significantly better than the previous counts. Our derived model ages of the ejecta blankets of North Ray, Tycho, and Copernicus agree well with radiometric and exposure ages of the Apollo 16, 17, and 12 landing sites, respectively, and are generally consistent with a constant impact rate over the last 3 Ga. However, small variations of the impact rate cannot be resolved in our data and require further investigations.
Correlations of fluvial knickzones with landslide dams, lithologic contacts, and faults in the southwestern Annapurna Range, central Nepalese Himalaya
Authors: Walsh Lisa S. , Martin Aaron J. , Ojha Tank P. , Fedenczuk Tom
Published: December 2011

We investigate the role of landslide dams, spatial changes in lithology, and rock uplift on faults in the formation of knickzones on bedrock rivers. We focus our analysis in the southwestern Annapurna Range of the central Nepalese Himalaya where detailed geologic maps, topographic data, field observations, and aerial photographs are available. We identified knickzones in our study area from normalized river steepness indices (ksn values) extracted from river longitudinal profiles derived from a 25 m digital elevation model we interpolated from digitized topographic map contours. We compared the location of these knickzones with (1) lithologic contacts and faults from a detailed geologic map of the Modi Khola valley and (2) inferred ancient landslide dam features mapped from field observations and aerial photographs. The steepest location on the Modi Khola occurs near the same latitude as the steepest reach on the Mardi Khola located directly to the east, potentially highlighting a major topographic transition across the Annapurna. However, we find that landslide dams once blocked the flow of the Modi Khola, and damming followed by incision after landslide breaching can explain the location of these knickzones without the need for active faulting near the Main Central thrust. We also conclude that (1) knickzones do not correlate with any spatial changes in lithology and (2) knickzones generated by rock uplift on unmapped faults cannot be ruled out. We emphasize that disentangling the processes responsible for knickzone formation remains challenging even when high‐resolution geologic and topographic data are available.
The role of lithospheric heterogeneities in the location of the Cenozoic intraplate deformation of Iberia from finite element modeling
Authors: Martín‐Velázquez S. , de Vicente G.
Published: December 2011

The Cenozoic evolution of the Central System basement uplift and of the continental Duero and Madrid basins on the Iberian Peninsula occurred in a compressive context triggered by the Alpine orogeny. Although several models of deformation have been suggested, the factors that led to the development of these have not been analyzed to date. We present here finite element modeling of the intraplate deformation of the Iberian lithosphere during the Cenozoic. This modeling has taken into account the role played by (1) the tectonic shortening originating from the Pyrenean and Betic collisions, (2) the weight of Tertiary continental sediments, and (3) thermomechanical heterogeneities present in the lithosphere. The numerical model represents a lithospheric section, with a creep‐type mechanical behavior, perpendicular to the Central System, and the two sedimentary basins. Both initial conditions and the results obtained have been specified based on the available geophysical and geological data. This study has enabled us to simulate the present lithospheric structure of the central Iberian peninsula: (a) the formation of the Central System relief and its horizontal shortening, (b) the basement folding in the Duero and Madrid basins, (c) the development of the root of the mountain range, and (d) the depth of the lithosphere‐asthenosphere border in the interior of Iberia. The deformations occurred through a large‐scale folding and thickening mechanism, by the shortening of a lithosphere that was initially thinner, and with lateral contrasts in temperatures and composition.
Identifying effective forecast horizon for real‐time reservoir operation under a limited inflow forecast
Authors: Zhao Tongtiegang , Yang Dawen , Cai Ximing , Zhao Jianshi , Wang Hao
Published: December 2011

The use of a streamflow forecast for real‐time reservoir operation is constrained by forecast uncertainty (FU) and limited forecast horizon (FH). The effects of the two factors are complicating since increasing the FH usually provides more information for decision making in a longer time framework but with increasing uncertainty, which offsets the information gain from a longer FH. This paper illustrates the existence of an effective FH (EFH) with a given forecast, which balances the effects of the FH and FU and provides the maximum information for reservoir operation decision making. With the assumption of a concave objective function, a monotonic relationship between current operation decision and ending storage is derived. Metrics representing the error resulting from a limited forecast relative to a perfect forecast are defined to evaluate reservoir performance. Procedures to analyze the complicating effect of FU and FH and to identify EFH are proposed. Results show that: (1) when FH is short, FH is the dominating factor for determining reservoir operation, and reservoir performance exhibits a quick improvement as FH increases; (2) when FH is long, the inflow information may be too uncertain to guide reservoir operation decisions and FU becomes the dominating factor; and (3) at a medium FH, reservoir performance depends on the complicating effects of FU and FH and EFH locates with a certain balanced level of FU and FH. The statistical characteristics of EFH are illustrated with case studies with deterministic forecast and ensemble forecast. Moreover, the impacts of temporal correlation of FU, inflow variability, evaporation loss, and reservoir capacity on EFH are explored.
Asymmetric Catalysis in Ionic Liquids with ‘Unmodified’ Catalysts
Authors: Goodrich Peter , Paun Cristina , Hardacre Christopher
Published: December 2011

Since the late 1960s metal-catalysed enantioselective transformations have become one of the most studied fields in synthetic chemistry. This area has seen the advancement of a vast array of new catalysts based on various metals and ligands. More recently, due to environmental and toxicity constraints placed upon the chemical industry, the choice of solvent has also become important. Reaction engineering and recycling of the catalyst systems has become standard practice with the use of liquid-liquid biphasic systems or grafting of the catalysts onto solid supports two of the main techniques employed. In some cases this has resulted in poor catalyst performance or catalyst leaching. Recently, ionic liquids have provided the means to tune catalytic processes, and even more importantly, immobilize the catalyst and facilitate recycling. This chapter discusses the concept of homogeneous supported catalysis in ionic liquids for enantioselective reactions.
Metal Catalysts on Soluble Polymers
Authors: Bandini Marco
Published: December 2011

The creation of chemical diversity/complexity combined with excellent catalytic performances are some of the main features that arise with the use of chiral metal complexes supported on soluble polymers in asymmetric synthesis. The successful combination of high catalytic performance due to the homogenous catalysis with the productivity of the heterogeneous catalysis generates a reliable synthetic tool to face the current demanding request of sustainability in modern organic chemistry.
Fluorous Catalysts
Authors: Pozzi Gianluca
Published: December 2011

The presence of extended fluorocarbon domains in the structure of chiral catalysts and ligands can trigger unusual solubility properties, phase behaviour or interactions with solid supports, which can be used to achieve their efficient separation from organic products. In the last decade, the many reaction/separation/recycling options offered by the use of chiral fluorous catalysts, including their solubilization in supercritical or compressed CO2, have been explored in several fundamental asymmetric catalytic transformations. A broad overview of the achievements and problems connected with the application of fluorous chiral catalytic systems is presented in this chapter.
Aqueous Phase Asymmetric Catalysis
Authors: Buda Szymon , Pasternak Monika , Mlynarski Jacek
Published: December 2011

Although stereoselective transformations in living systems occur in an aqueous environment, it was only recently that a breakthrough was achieved in the use of water as a solvent or co-solvent in asymmetric synthesis. While few years ago, only a few practitioners studied the subject, now organic reactions in water have become one of the most exciting research areas, not only because of green chemistry perspectives. Both organometallic and organocatalytic processes in aqueous systems are of great interest and are under intensive investigation. This chapter will focus on recent advances in performing enantioselective reactions in aqueous media. The quest to identify water-compatible catalysts has evoked an intense search for new exciting possibilities. Here, we summarize recent efforts towards asymmetric transformations performed in water or in the presenceof water, with a focus on homogeneous solutions.
Non-covalent Immobilization
Authors: Fraile J. M. , García J. I. , Herrerias C. I. , Mayoral J. A. , Pires E.
Published: December 2011

This chapter will focus on the use of non-covalent strategies to support enantioselective catalysts. Although most frequently used, covalent bonding to insoluble supports requires a noticeable synthetic effort to introduce a function allowing the catalyst–support bonding. In general, non-covalent immobilization does not require this modification and is simpler to use. The strategies to avoid leaching and the possibility to modify the stereochemical results by controlling catalyst–support interactions will be reviewed.
Similarities and Differences Between Perseverative and Non-Perseverative Errors in Aphasia: Theoretical and Clinical Implications
Authors: Martin Nadine
Published: December 2011

Researchers have learned much about the cognitive organization of the language system by studying speech errors made by speakers with and without aphasia. Some aspects of errors made in language production reflect linguistic properties of language (e.g., linguistic similarities between an intended word and the word that was produced in error). Other aspects reflect processes that enable production of language (e.g., substitutions or sequencing errors). A particularly intriguing class of error is perseveration, the unintended retrieval of words or sounds after they have been recently produced. Although the occurrence of perseverations is influenced by both linguistic and processing aspects of language production, these errors have been particularly instructive about the latter aspect. Martin and Dell (2007) proposed that word and sound perseverations result from the same mechanisms as non-perseverative substitutions: slowed activation of the intended utterance and linguistic similarity between the target and error. They differ from non-perseverative substitutions in their probability of occurrence, which is increased by residual activation following their recent production. In this article, I will review this account of perseverations and discuss its implications for treatment approaches to reduce perseverations.
Reducing Aphasic Perseverations: A Case Study
Authors: Muñoz Maria L.
Published: December 2011

The purpose of this study was to measure outcomes resulting from a treatment designed to reduce aphasic perseverations by decreasing activation of the perseverative response and increasing activation of the target response. A single-subject design was used. A Spanish-speaking male with moderate-to-severe receptive-expressive aphasia participated in this study. Treatment involved the use of systematic reduction of interstimulus interval paired with semantic feature analysis. The treatment resulted in a decrease in perseveration, but only minor increases in naming accuracy on trained and untrained stimuli. In addition, an increase in overall verbal output was observed. Decreased perseveration was maintained during follow-up. Outcomes suggest the treatment successfully reduces perseveration and increases verbal output. Additional research is needed to evaluate the effectiveness of this treatment.
Complete Basilar Artery Assessment by Transcranial Color-Coded Duplex Sonography Using the Combined Transforaminal and Transtemporal Approach
Authors: Pade O. , Eggers J. , Schreiber S. , Valdueza J.
Published: December 2011

Purpose: Visualization of the basilar artery (BA) by transcranial color-coded duplex sonography (TCCD) can be challenging. The detection of stenosis or occlusion of the BA often has to rely on indirect signs like a highly pulsatile flow in the vertebral arteries. In case of a distal BA occlusion, however, the flow of the VAs can even be normal. The aim of our TCCD study was to visualize a maximum length of the BA combining the customarily used transforaminal appraoch for the proximal part and the less well known transtemporal coronal approach for the distal BA segment.

Materials and Methods: TCCD was performed in 60 subjects with a good temporal bone window. Detectable extracranial or intracranial pathology was previously excluded. The BA was insonated using the transforaminal and transtemporal insonation plane and the visible length was measured. In one subject MRA was performed to substantiate our findings.

Results: The BA was visualized in all subjects via both approaches. The maximal detectable BA length via the transforaminal and transtemporal approach was 26 ± 8 mm and 18 ± 5 mm, respectively. Assuming a previously reported average anatomical total BA length of 33 ± 6 mm, we supposed complete vessel visualization in 44 subjects (73 %).

Conclusion: The combined transforaminal and transtemporal insonation approach may permit total BA insonation, thus facilitating the evaluation of BA pathology.
Accurate partition function for acetylene, 12C2H2, and related thermodynamical quantities
Authors: Amyay B. , Fayt A. , Herman M.
Published: December 2011

The internal partition function (Qint) of ethyne (acetylene), 12C2H2, is calculated by explicit summation of the contribution of all individual vibration-rotation energy levels up to 15 000 cm−1. The corresponding energies are predicted from a global model and constants reproducing within 3σ all 18 415 published vibration-rotation lines in the literature involving vibrational states up to 8900 cm−1, as produced by Amyay et al. [J. Mol. Spectrosc. 267, 80 (2011)]. Values of Qint, with distinct calculations for para and ortho species are provided from 1 to 2000 K, in step of 1 K. The total internal partition function at 298.15 K is 104.224387(47) or 416.89755(19), with the nuclear degeneracy spin factors taken as 1/4: 3/4 (astronomer convention) or 1:3 (atmospheric convention), respectively, for para:ortho species. The Helmholtz function, Gibbs enthalpy function, entropy, and specific heat at constant pressure are also calculated over the same temperature range. Accuracies as well as the missing contribution of the vinylidene isomer of acetylene in the calculations are discussed.
An ab initio quasi-diabatic potential energy matrix for OH(2Σ) + H2
Authors: Collins Michael A. , Godsi Oded , Liu Shu , Zhang Dong H.
Published: December 2011

A diabatic potential energy matrix for three electronic states of OH3 has been constructed by interpolation of multi-reference configuration interaction electronic structure data. The reactive, exchange and non-reactive quenching dynamics are investigated using surface hopping classical trajectories. Classical trajectory simulations show good agreement with cross molecular beam data for the OH(2Σ) + D2 → HOD + D reaction.
Solvent and conformation dependence of amide I vibrations in peptides and proteins containing proline
Authors: Roy Santanu , Lessing Joshua , Meisl Georg , Ganim Ziad , Tokmakoff Andrei , Knoester Jasper , Jansen Thomas L. C.
Published: December 2011

We present a mixed quantum-classical model for studying the amide I vibrational dynamics (predominantly CO stretching) in peptides and proteins containing proline. There are existing models developed for determining frequencies of and couplings between the secondary amide units. However, these are not applicable to proline because this amino acid has a tertiary amide unit. Therefore, a new parametrization is required for infrared-spectroscopic studies of proteins that contain proline, such as collagen, the most abundant protein in humans and animals. Here, we construct the electrostatic and dihedral maps accounting for solvent and conformation effects on frequency and coupling for the proline unit. We examine the quality and the applicability of these maps by carrying out spectral simulations of a number of peptides with proline in D2O and compare with experimental observations.
Dopant optimization for triplet harvesting in polymer photovoltaics
Authors: Winroth Gustaf , Podobinski Daniel , Cacialli Franco
Published: December 2011

We investigate the dependence of the characteristics of polymer photovoltaic cells on the concentration of doping of the active layers by heavy-metal complexes. We wish to exploit the strong spin-orbit coupling of such complexes to induce a relatively fast exciton intersystem crossing from the singlet to the longer-lived triplet manifold, to increase in turn the lifetime of the exciton, its diffusion length, and thus the probability of dissociation and the overall device conversion efficiency. We combine current–voltage curves, photocurrent spectra, and atomic force micrographs to show that there is an optimum doping load above which the device performance severely deteriorates. We find, for an Ir-pyridine dopant, a maximum load of approximately 5%.
Modeling intermolecular interactions of physisorbed organic molecules using pair potential calculations
Authors: Kröger Ingo , Stadtmüller Benjamin , Wagner Christian , Weiss Christian , Temirov Ruslan , Tautz F. Stefan , Kumpf Christian
Published: December 2011

The understanding and control of epitaxial growth of organic thin films is of crucial importance in order to optimize the performance of future electronic devices. In particular, the start of the submonolayer growth plays an important role since it often determines the structure of the first layer and subsequently of the entire molecular film. We have investigated the structure formation of 3,4,9,10-perylene-tetracarboxylic dianhydride and copper-phthalocyanine molecules on Au(111) using pair-potential calculations based on van der Waals and electrostatic intermolecular interactions. The results are compared with the fundamental lateral structures known from experiment and an excellent agreement was found for these weakly interacting systems. Furthermore, the calculations are even suitable for chemisorptive adsorption as demonstrated for copper-phthalocyanine/Cu(111), if the influence of charge transfer between substrate and molecules is known and the corresponding charge redistribution in the molecules can be estimated. The calculations are of general applicability for molecular adsorbate systems which are dominated by electrostatic and van der Waals interaction.
Dielectric barrier discharge plasma in Ar/O2 promoting apoptosis behavior in A549 cancer cells
Authors: Huang Jun , Li Hui , Chen Wei , Lv Guo-Hua , Wang Xing-Quan , Zhang Guo-Ping , Ostrikov Kostya , Wang Peng-Ye , Yang Si-Ze
Published: December 2011

The Ar/O2 plasma needle in the induction of A549 cancer cells apoptosis process is studied by means of real-time observation. The entire process of programmed cell death is observed. The typical morphological changes of A549 apoptosis are detected by 4′, 6-diamidino-2-phenylindole staining, for example, chromatin condensation and nuclear fragmentation. Cell viability is determined and quantified by neutral red uptake assay, and the survival rate of A549 from Ar/O2 plasmas is presented. Further spectral analysis indicates the reactive species, including O and OH play crucial roles in the cell inactivation.
Equilibrium compositional distribution in freestanding ternary semiconductor quantum dots: The case of InxGa1−xAs
Authors: Pandey Sumeet C. , Maroudas Dimitrios
Published: December 2011

We report the findings of a systematic computational study that addresses the effects of surface segregation on the atomic distribution at equilibrium of constituent group-III atoms in freestanding ternary semiconductor InxGa1−xAs nanocrystals. Our analysis is based on density functional theory calculations in conjunction with Monte Carlo simulations of the freestanding nanocrystals using a DFT-re-parameterized valence force field description of interatomic interactions. We have determined the equilibrium concentration profiles as a function of nanocrystal size (d), composition (x), and temperature (T). The ranges of d, x, and T are explored and demonstrate surface segregation and phase separation that leads to different extents of alloying in the nanocrystal core and in the near-surface regions. We find that formation of core/shell-like quantum dots characterized by an In-deficient core and an In-rich shell with a diffuse interface is favored at equilibrium. The analysis elucidates the relationship between the constituent species distribution in the nanocrystal and the parameters that can be tuned experimentally to design synthesis routes for tailoring the properties of ternary quantum dots.
Charge transport properties in CdZnTe detectors grown by the vertical Bridgman technique
Authors: Auricchio N. , Marchini L. , Caroli E. , Zappettini A. , Abbene L. , Honkimaki V.
Published: December 2011

Presently, a great amount of effort is being devoted to the development of CdTe and CdZnTe (CZT) detectors for a large variety of applications such as medical, industrial, and space research. We present the spectroscopic properties of some CZT crystals grown by the standard vertical Bridgman method and by the boron oxide encapsulated vertical Bridgman method, which has been recently implemented at IMEM-CNR (Parma, Italy). In this technique, the crystal is grown in an open quartz crucible fully encapsulated by a thin layer of liquid boron oxide. This method prevents contact between the crystal and the crucible, thereby allowing larger single grains with a lower dislocation density to be obtained. Several mono-electrode detectors were realized, with each having two planar gold contacts. The samples are characterized by an active area of about 7 mm × 7 mm and thicknesses ranging from 1 to 2 mm. The charge transport properties of the detectors have been studied by mobility-lifetime (μ × τ) product measurements, carried out at the European Synchrotron Radiation Facility (Grenoble, France) in the planar transverse field configuration, where the impinging beam direction is orthogonal to the collecting electric field. We have performed several fine scans between the electrodes with a beam spot of 10 μm × 10 μm at various energies from 60  to 400 keV. In this work, we present the test results in terms of the (μ × τ) product of both charge carriers.
Nonequilibrium Fermi golden rule for electronic transitions through conical intersections
Authors: Izmaylov Artur F. , Mendive–Tapia David , Bearpark Michael J. , Robb Michael A. , Tully John C. , Frisch Michael J.
Published: December 2011

We consider photoinduced electronic transitions through conical intersections in large molecules. Starting from the linear vibronic model Hamiltonian and treating linear diabatic couplings within the second order cumulant expansion, we have developed a simple analytical expression for the time evolution of electronic populations at finite temperature. The derived expression can be seen as a nonequilibrium generalization of the Fermi golden rule due to a nonequilibrium character of the initial photoinduced nuclear distribution. All parameters in our model are obtained from electronic structure calculations followed by a diabatization procedure. The results of our model are found to agree well with those of quantum dynamics for a test set of systems: fulvene molecule, 2,6-bis(methylene) adamantyl cation, and its dimethyl derivative.
Primitive models of ions in solution from molecular descriptions: A perturbation approach
Authors: Molina John J. , Dufrêche Jean-François , Salanne Mathieu , Bernard Olivier , Turq Pierre
Published: December 2011

The development of simple, primitive model descriptions for electrolyte solutions is usually carried out by fitting the system parameters to reproduce some experimental data. We propose an alternative method, that allows one to derive implicit solvent models of electrolyte solutions from all-atom descriptions. We obtain analytic expressions for the thermodynamic and structural properties of the ions, which are in good agreement with the underlying explicit solvent representation, provided that ion association is taken into account. Effective ion-ion potentials are derived from molecular dynamics simulations and are used within a first-order perturbation theory to derive the best possible description in terms of charged hard-spheres. We show that our model provides a valid description for a series of 1–1 electrolytes.
Ultrafast laser ablation of gold thin film targets
Authors: Amoruso S. , Nedyalkov N. N. , Wang X. , Ausanio G. , Bruzzese R. , Atanasov P. A.
Published: December 2011

Ultrafast laser ablation of a gold thin film is studied and compared with that of a bulk target, with particular emphasis given to the process of nanoparticles generation. The process is carried out in a condition where a single laser shot removes all the irradiated film spot. The experimental results evidence interesting differences and, in particular, a reduction of the nanoparticles size, and a narrowing of a factor two of their size distribution in the case of ablation of a thin film target, a feature which we relate to a more uniform heating of the target material. We thus show that ultrashort laser ablation of thin films provides a promising way of controlling plume features and nanoparticles size.
Effects of cell cycle on the uptake of water soluble quantum dots by cells
Authors: Zheng Shen , Chen Ji-Yao , Wang Jun-Yong , Zhou Lu-Wei , Peng Qian
Published: December 2011

Quantum dots (QDs) with excellent optical properties have become powerful candidates for cell imaging. Although numerous reports have studied the uptake of QDs by cells, little information exists on the effects of cell cycle on the cellular QD uptake. In this report, the effects of cell cycle on the uptake of water soluble thiol-capped CdTe QDs by the human cervical carcinoma Hela cell line, human hepatocellular carcinoma QGY7701 cell line, and human embryonic kidney 293T cell line were studied by means of laser scanning confocal microscopy and flow cytometry. All three cell lines show to take up CdTe QDs via endocytosis. After arresting cells at specific phases with pharmacological agents, the cells in G2/M phase take up the most CdTe QDs, probably due to an increased membrane expansion during mitosis; whereas the cells in G1 phase do the least. A mathematical physics model was built to calculate the relative uptake rates of CdTe QDs by cells in different phases of the cell cycle, with the result as the uptake rate in G2/M phase is 2-4 times higher than that in G1 phase for these three cell lines. The results obtained from this study may provide the information useful for intracellular delivery of QDs.
Impact of firing on surface passivation of p-Si by SiO2/Al and SiO2/SiNx/Al stacks
Authors: Chen J. , Cornagliotti E. , Loozen X. , Simoen E. , Vanhellemont J. , Lauwaert J. , Vrielinck H. , Poortmans J.
Published: December 2011

Firing impacts on surface passivation provided by a SiO2 and SiO2/SiNx stack with evaporated Al films are studied by capacitance-based techniques on MIS capacitors. For devices with insulator layers consisting solely of as-deposited SiO2, the densities of either interface states (Dit) or fixed charges (Qfc) are hardly influenced by firing. Capping the SiO2 layer with a SiNx layer results in a shift of the peak activation energy of Dit toward the valence band (Ev) of Si. Firing this SiO2/SiNx stack leads to an increase of Qfc, a reduction of Dit, and a moderate shift of peak activation energy of Dit toward Ev. Co-firing with the Al film on top significantly reduces the Qfc, Dit, and Dit peak activation energy, which is resulting from the atomic hydrogen passivation. These results are of particular interest for the development of solar cells with rear surface passivation and local contacts.
Electro-structural evolution and Schottky barrier height in annealed Au/Ni contacts onto p-GaN
Authors: Greco G. , Prystawko P. , Leszczyński M. , Lo Nigro R. , Raineri V. , Roccaforte F.
Published: December 2011

This paper reports on the evolution of the structural and electrical proprieties of Au/Ni contacts to p-type gallium nitride (GaN) upon thermal treatments. Annealing of the metals in an oxidizing atmosphere (N2/O2) led to better electrical characteristics, in terms of specific contact resistance (ρc), with respect to non-reacting ambient (Ar). The evolution of the metal structures and the formation of a NiO layer both at the sample surface and at the interface with p-GaN were monitored by several techniques such as transmission electron microscopy (TEM), x-ray diffraction (XRD), and atomic force microscopy (AFM). Furthermore, a reduction of the Schottky barrier height from 1.07 eV (Ar annealing) to 0.71 eV (N2/O2 annealing) was determined by the temperature dependence of the ρc. Local current maps by conductive AFM demonstrate the role of the interface in the conduction mechanism. These electrical results were correlated with the interfacial microstructure of the annealed contacts considering different transport models.
Steady-state hydrodynamics of a viscous incompressible fluid with spinning particles
Authors: Felderhof B. U.
Published: December 2011

The steady-state hydrodynamics of a viscous incompressible fluid with spinning particles is studied on the basis of extended Stokes equations. The profiles of flow velocity and spin velocity in simple flow situations may be used to determine the vortex viscosity and spin viscosity of the molecular liquid or fluid suspension. As an example, one situation studied is the flow generated by a uniform torque density in a planar layer of infinite fluid. The spinning particles drive a nearly uniform flow on either side of the layer, in opposite directions on the two sides. The Green function of the extended Stokes equations is derived. The translational and rotational friction coefficients of a sphere with no-slip boundary conditions, and the corresponding flow profiles, are calculated.
Cooperative effects in the oxidation of CO by palladium oxide cations
Authors: Reber Arthur C. , Khanna Shiv N. , Tyo Eric C. , Harmon Christopher L. , Castleman A. W.
Published: December 2011

Cooperative reactivity plays an important role in the oxidation of CO to CO2 by palladium oxide cations and offers insight into factors which influence catalysis. Comprehensive studies including guided-ion-beam mass spectrometry and theoretical investigations reveal the reaction products and profiles of PdO2+ and PdO3+ with CO through oxygen radical centers and dioxygen complexes bound to the Pd atom. O radical centers are more reactive than the dioxygen complexes, and experimental evidence of both direct and cooperative CO oxidation with the adsorption of two CO molecules are observed. The binding of multiple electron withdrawing CO molecules is found to increase the barrier heights for reactivity due to decreased binding of the secondary CO molecule, however, reactivity is enhanced by the increase in kinetic energy available to hurdle the barrier. We examine the effect of oxygen sites, cooperative ligands, and spin including two-state reactivity.
Potential and flux decomposition for dynamical systems and non-equilibrium thermodynamics: Curvature, gauge field, and generalized fluctuation-dissipation theorem
Authors: Feng Haidong , Wang Jin
Published: December 2011

The driving force of the dynamical system can be decomposed into the gradient of a potential landscape and curl flux (current). The fluctuation-dissipation theorem (FDT) is often applied to near equilibrium systems with detailed balance. The response due to a small perturbation can be expressed by a spontaneous fluctuation. For non-equilibrium systems, we derived a generalized FDT that the response function is composed of two parts: (1) a spontaneous correlation representing the relaxation which is present in the near equilibrium systems with detailed balance and (2) a correlation related to the persistence of the curl flux in steady state, which is also in part linked to a internal curvature of a gauge field. The generalized FDT is also related to the fluctuation theorem. In the equal time limit, the generalized FDT naturally leads to non-equilibrium thermodynamics where the entropy production rate can be decomposed into spontaneous relaxation driven by gradient force and house keeping contribution driven by the non-zero flux that sustains the non-equilibrium environment and breaks the detailed balance. On any particular path, the medium heat dissipation due to the non-zero curl flux is analogous to the Wilson lines of an Abelian gauge theory.
Tip-tilt mirror suspension: Beam steering for advanced laser interferometer gravitational wave observatory sensing and control signals
Authors: Slagmolen Bram J. J. , Mullavey Adam J. , Miller John , McClelland David E. , Fritschel Peter
Published: December 2011

We describe the design of a small optic suspension system, referred to as the tip-tilt mirror suspension, used to isolate selected small optics for the interferometer sensing and control beams in the advanced LIGO gravitational wave detectors. The suspended optics are isolated in all 6 degrees of freedom, with eigenmode frequencies between 1.3 Hz and 10 Hz. The suspended optic has voice-coil actuators which provide an angular range of ±4 mrad in the pitch and yaw degrees of freedom.