bluuebunny/crossref_metadata_2025 huggingface dataset:
Connecteurs de causalité, implication du locuteur et profils prosodiques: le cas de car et de parce que
Authors: SIMON ANNE CATHERINE , DEGAND LIESBETH
Published: October 2007

Nous comparons l'usage de deux connecteurs de causalité, car et parce que, en fonction de leur fréquence dans différents types de corpus en français (écrits et oraux). Sur la base d'une analyse sémantique et cognitive, nous décrivons quel degré d'Implication du Locuteur chaque connecteur est susceptible d'encoder dans la construction des relations de discours, à l'écrit et à l'oral (où car est nettement moins fréquent, ce qui produit une réorganisation des types de relations causales couvertes par chaque connecteur). Enfin, sur la base de l'analyse de 50 occurrences de chaque connecteur à l'oral (extraites de la banque de données VALIBEL), nous décrivons les différents types d'empaquetages prosodiques et leur corrélation avec les relations causales plus ou moins objectives.
Le verbe ALLER: L'affranchissement du contexte d'énonciation immédiat
Authors: VANDELOISE CLAUDE
Published: October 2007

Le verbe aller s'utilise comme verbe de manière de déplacement (aller vite) ou verbe de déplacement suivi d'un syntagme prépositionnel de lieu (aller devant l'église) ou d'un infinitif (aller manger). Dans le premier cas, la préposition introduit le terme anticipé du mouvement (règle R1); dans le second, l'infinitif désigne une action anticipée (règle R2). Yvan va manger est ambigu et peut également introduire un futur proche qui sera justifié par une extension de la règle R2. L'originalité du verbe aller est d'obliger l'interlocuteur à se détacher du contexte d'énonciation, même s'il est énoncé au moment de l'action. D'autres termes comme hier ont cette propriété mais, en ce cas, toute la proposition est transférée au passé. Au contraire, le verbe aller établit un lien entre le contexte d'énonciation immédiat et son au-delà. Il constitue ainsi une charnière importante entre un langage primitif tributaire de la référence et un langage capable de créer des contextes discursifs fondés sur l'imagination. Une règle unique R définit le verbe aller par son rôle dans l'évolution du langage. Elle constitue une alternative aux règles R1 et R2 qui rendent mieux compte de la connaissance consciente que le locuteur a du verbe aller
INSULIN-LIKE GROWTH FACTORS AND PLACENTAL FUNCTION
Authors: SCHLABRITZ-LOUTSEVITCH NATALIA , LI CUN , NATHANIELSZ PETER W
Published: October 2007

Placentas from different species differ not only in their cellular structure and normal trajectory of growth but also in the architecture of their placental vasculature and the transport and exchange mechanisms that determine nutritional transfer from mother to fetus and waste disposal from fetus to mother.1Many maternal and fetal hormonal and nutritional factors, as well as placental paracrine and autocrine systems affect placental growth and development throughout gestation.2Nutrients delivered from the maternal circulation are as important for placental growth as they are for fetal growth. In addition to passing across the placenta to provide the building blocks for fetal growth, amino acids, carbohydrate and lipids are incorporated into the placenta.
Bacterial adhesion to stainless steel is reduced by aqueous fish extract coatings
Authors: Bernbom N. , Jørgensen R. L. , Ng Y. Y. , Meyer R. L. , Kingshott P. , Vejborg R. M. , Klemm P. , Besenbacher F. , Gram L.
Published: October 2007

Microbial adhesion and biofilm formation on surfaces pose major problems and risks to human health. One way to circumvent this problem is to coat surfaces (in this report stainless steel) with a non-toxic fish extract that generates an abiotic surface with less bacterial attachment than uncoated surfaces or surfaces coated with, for example, tryptone soy broth. The bacteria grow well in the fish extract; hence a general bacteriocidal effect is not the reason for the antifouling effect. Bacterial attachment was quantified by different methods including (a) direct fluorescence microscopy, (b) removal by ultrasound and subsequent quantification of the adhered bacteria, and (c) regrowth of the adhered bacteria measured by indirect conductometry. Surprisingly, the bacterial counts on surfaces coated with aqueous fish extract were 10–100 times lower than on surfaces coated with laboratory broths when surfaces were submerged in bacterial suspensions. The effect was seen forPseudomonas fluorescensAH2,Pseudomonas aeruginosaPAO1,Escherichia coliMG1655,Vibrio anguillarum90-11-287 andAeromonas salmonicidaJno 3175/88. It lasted for at least 7 days. Atomic force microscopy showed that steel surfaces conditioned with fish extract were covered by a thin layer of spherical, nanosized particles. Chemical analysis of the surfaces coated with adsorbed fish extract using X-ray photoelectron spectroscopy revealed that the layer was proteinaceous and had a thickness less than 2 nm. Numerous protein bands/peaks were also detected by sodium dodecyl sulphate–polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry techniques. We conclude that coating the stainless steel surface with fish extract results in a thin protein layer that reduces bacterial adhesion significantly.
Effects of smectite clay on biofilm formation by microorganisms
Authors: Alimova A. , Roberts M. , Katz A. , Rudolph E. , Steiner J. C. , Alfano R. R. , Gottlieb P.
Published: October 2007

We have investigated the role of smectite clay particles in biofilm formation by several different species of bacteria (Pseudomonas syringae, Escherichia coli,Staphylococcus aureusandBacillus subtilis). We observed that the presence of clay particles enhances the formation of biofilms and, after 24 h, the bacterial populations in the clay mixtures were greater than the respective populations in media without clay. Smectite-bearing clay slurries uniformly develop bacteria–clay aggregates with a substantial biofilm component within 24 h, while the exclusively bacterial suspensions do not develop any observable biofilm component. The biofilm–clay aggregates vary in size from tens of micrometers to several millimeters. Biofilm formation was evaluated by phase contrast microscopy and fluorescence staining. Biofilm promotion by smectite clays may indicate the importance of transport of bacteria by aerosol dust particles.
Adsorption‐induced coal swelling and stress: Implications for methane production and acid gas sequestration into coal seams
Authors: Cui Xiaojun , Bustin R. Marc , Chikatamarla Laxmi
Published: October 2007

Sequestration of CO2 and H2S into deep unminable coal seams is an attractive option to reduce their emission into atmosphere and at the same time displace preadsorbed CH4 which is a clean energy resource. High coal seam permeability is required for efficient and practical sequestration of CO2 and H2S and recovery of CH4. However, adsorption of CO2 and H2S into coals induces strong swelling of the coal matrix (volumetric strain) and thus reduces significantly coal permeability by narrowing and even closing fracture apertures. Our experimental data on three western Canadian coals show that the adsorption‐induced volumetric strain is approximately linearly proportional to the volume of adsorbed gas, and for the same gas, different coals have very similar volumetric strain coefficient. Impacts of adsorption‐induced swelling on stress and permeability around wellbores were analytically investigated using our developed stress and permeability models. Our model results indicate that adsorption‐induced volumetric strain has significant controls on stress and permeability of producing and sequestrating coal seams and consequently the potential of acid gas sequestration. Coal seams may undergo >10 times enhancement of permeability around CH4‐producing wellbores due to a reduction in effective stress as a result of coal shrinking caused by methane desorption accompanying a reduction in reservoir pressure. Injection of H2S and CO2 on the other hand results in strong sorption‐induced swelling and a marked increase in effective stress which in turn leads to a reduction of coal seam permeability of up to several orders of magnitude. Injection of mixtures of N2 and CO2 such as found in flue gas results in weaker swelling, the amount of which varies with gas composition, and provides the greatest opportunity of sequestering CO2 and secondary recovery of CH4 for most coals. Because of the marked swelling of coal in the presence of H2S, even minor amounts of H2S result in a marked reduction in permeability, and hence sequestration of H2S in deep coals will be likely impractical. Furthermore, high stresses resulting from sorption of acid gases will potentially cause the coal to yield, fracture or slip, and produce fine particles, which further affect permeability and thus methane production and acid gas sequestration.
Possible role of midcrustal igneous sheet intrusions in cratonic arch formation
Authors: Welford J. K. , Hearn E. H. , Clowes R. M.
Published: October 2007

Factors controlling widespread cratonic arch formation across western North America from the Early Paleozoic to the Middle Mesozoic remain poorly understood. While a number of causes, such as mantle hot spots, lithospheric contraction, mantle flow, and lithospheric flexure due to surface loading, have been suggested to explain the localized uplift of basement blocks on otherwise tectonically quiescent margins, a variety of mechanisms may be at work. Here, we test the hypothesis that seismically detected packages of discrete midcrustal igneous sheet intrusions impart rheological contrasts within the crust, which act as seeds for cratonic arch formation in the presence of weak intraplate compression, using finite element modeling of intraplate deformation. We find that the seismically resolved sills can generate significant surface uplift in the presence of modest strain rates over reasonable orogenic timescales. Cratonic arch formation would be enhanced in the presence of additional thin, seismically unresolvable sills. While midcrustal sheet intrusions may be just one of many factors influencing cratonic arch formation, their presence in northern Alberta, Canada, can help explain the asymmetric configuration of the well‐studied Peace River Arch.
Climatology of extreme rainfall and flooding from orographic thunderstorm systems in the upper Arkansas River basin
Authors: Javier Julie Rose N. , Smith James A. , England John , Baeck Mary Lynn , Steiner Matthias , Ntelekos Alexandros A.
Published: October 2007

Analyses of the spatial and temporal distribution of extreme rainfall in the Arkansas River basin above Pueblo, Colorado, are based on volume scan reflectivity observations from the Pueblo WSR‐88D radar during the period 1995–2003. A storm catalog of 66 rainfall events during the 9‐year period has been developed. Climatological analyses of extreme rainfall are carried out both from an Eulerian perspective, in which distributional aspects of rainfall at fixed locations are examined, and from a Lagrangian perspective, in which distributional aspects of rainfall are based on storm‐tracking algorithms. Of particular interest is the spatial heterogeneity of extreme rainfall in the complex terrain of the upper Arkansas River basin. Lagrangian analyses are used to characterize the spatially varying distribution of storm initiation, storm motion, and storm structure. Climatological analyses indicate that convective rainfall in the Arkansas River basin above Canon City (drainage area of 8070 km2) does not contribute to the extreme flood response of the Arkansas River at Pueblo (drainage area of 12,140 km2). There is pronounced diurnal variation in warm season rainfall in the Arkansas River basin, and this feature of extreme rainfall is a key element of flood response in the upper Arkansas River basin. Climatological analyses of extreme rainfall in the upper Arkansas River basin are examined relative to the spatial and temporal properties of rainfall for extreme flood events that have occurred in the basin, including major flood episodes in June 1921 and June 1965.
A map of relative P wave delay times across southern California
Authors: Polet Jascha
Published: October 2007

Using cross correlation of band‐pass‐filtered waveforms, we have determined relative teleseismic P wave arrival times for the broadband stations in the Southern California Seismic Network (formerly known as TriNet). To remove as much as possible contamination of the direct P wave by near surface reflections and refractions, visible for arrivals at several stations located directly above complex three‐dimensional structures, we carried out this cross correlation over only the first quarter wavelength of the P waveform, after applying a 1–2 Hz Butterworth band‐pass filter. We subsequently completed a thorough visual and numerical quality control of the resulting traveltimes and were left with 12320 measurements for 144 events spanning a time period of almost 4 years, from 2000 to 2004. We present this complete data set on a topographic map of southern California (including a detailed inset map of the more densely covered LA basin area), enabling a direct investigation of data patterns. This visualization helps to develop an understanding of expected features of a future tomographic inversion of this data set.
Impact of Argo, SST, and altimeter data on an eddy‐resolving ocean reanalysis
Authors: Oke Peter R. , Schiller Andreas
Published: October 2007

We perform a series of Observing System Experiments (OSEs), where components of the Global Ocean Observing System (GOOS) are systematically withheld from a data assimilating ocean reanalysis. We assess the relative importance of Argo temperature (T) and salinity (S) profiles, sea‐surface temperature (SST) and altimetric sea‐level anomalies (SLA) for constraining upper‐ocean T and S properties and mesoscale variability of SLA in an eddy resolving ocean reanalysis in the Australian region. Each OSE is assessed by comparing modelled fields with assimilated and withheld observations. We show that each observation type brings complementary information to the GOOS, and demonstrate that while there is some redundancy for representing broad‐scale circulation, mesoscale circulation requires all observation types to be assimilated.
Influence of runoff parameterization on continental hydrology: Comparison between the Noah and the ISBA land surface models
Authors: Decharme B.
Published: October 2007

A comprehensive set of hydrological parameterizations without any basin‐scale calibration was recently introduced into the global ISBA land surface model in order to improve the simulation of the hydrological impacts of both seasonal climate anomalies and global warming. In this study, the same approach is introduced into the Noah land surface model, in order to improve the representation of surface runoff. The Dunne runoff is computed using topographic information via a TOPMODEL approach and the Horton runoff using an explicit distinction between frozen and unfrozen soils, while land surface heterogeneities are introduced via a tile approach. The validation is conducted at a 1° by 1° horizontal resolution using global off line simulations that were driven by Global Soil Wetness Project atmospheric forcing. The simulated runoff is converted into discharges using the TRIP river routing model and compared to observations from a dense network of gauging stations distributed over the world's largest river basins. Results confirm that the relationships between the Dunne runoff and the topography, as well as between the Horton runoff and the frozen soils, are among the main hydrological processes to simulate realistic global river discharges. The comparison between the old and the new versions of Noah and ISBA reveal that the model disparity, in term of water flux production, is globally reduced due to the use of similar surface hydrology that lead to comparable improvements of discharge scores. This confirms the relevance of these surface hydrological processes for regional and global applications.
On the variability of mesospheric OH emission profiles
Authors: Nikoukar Romina , Swenson Gary R. , Liu Alan Z. , Kamalabadi Farzad
Published: October 2007

Mesospheric OH radiance limb profiles measured by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) spacecraft were inverted to yield altitude profiles of OH volume emission rates. The Abel inversion results of two months of data (from 1 June to 31 July 2004) were analyzed for the layer mean and standard deviation as a function of latitude and local time. Statistical analysis of SABER data shows that the global difference between the mean and standard deviation profiles for the OH(vu = 7, 8, 9; Δv = 2) emission (at 2.0 μm) is approximately 2.8 km, very similar to the theoretical model prediction by Liu and Swenson (2003). This agreement is an indication that these variations from the mean are likely caused by atmospheric tides and gravity waves.
Water‐soluble species in the marine aerosol from the northern South China Sea: High chloride depletion related to air pollution
Authors: Hsu Shih‐Chieh , Liu Shaw Chen , Kao Shuh‐Ji , Jeng Woei‐Lih , Huang Yi‐Tang , Tseng Chun‐Mao , Tsai Fujung , Tu Jien‐Yi , Yang Yih
Published: October 2007

Dichotomous (PM2.5–10 and PM2.5 modes) and size‐resolved marine aerosols collected during the northeastern monsoon on two wintertime cruises in the subtropical South China Sea (SCS) were analyzed for water‐soluble ions. During the sampling periods the study region was under the influence of strong pollution originating primarily from the Asian continent. Elevated levels of non‐sea‐salt sulfate and ammonium ions of up to 4.5 and 1.2 μg/m3, respectively, were observed, indicating that the SCS is now substantially contaminated by massive amounts of air pollutants most likely from China and South/Southeast Asia. The non‐sea‐salt sulfate to nitrate mass ratios reaching 3.8 ± 1.9 are much larger than those (approximately 2) in and around East Asia and the western Pacific Ocean, suggesting that the Asian outflow aerosols measured in the SCS experienced different traveling history from those in the vicinity of source regions. High chloride depletion (Cl‐depletion) measured in the SCS marine aerosols was, on average, 30% for coarse‐mode particles and nearly 90% for fine‐mode particles. Cl‐depletion is size‐dependent, and maximizes in submicrometer particles (i.e., Cl has almost been completely lost). Acid displacement is responsible for the observed high Cl‐depletion: nitrate substitution accounts for the coarse‐mode depletion, whereas sulfate substitution accounts for the fine‐mode depletion. The acid displacement of sea salt aerosols may be related to a variety of factors, especially the substantial air pollution, which is discussed in detail in this paper. On cloudy/rainy days, fine‐mode aerosol samples have moderate Cl‐depletion (i.e., ∼40–50%), in contrast to nearly complete Cl loss on sunny days, presumably indicating that photochemical reactions would play a key role in the Cl‐deficit; however, it merits further investigation as the available samples were limited.
Agonist‐dependent cannabinoid receptor signalling in human trabecular meshwork cells
Authors: McIntosh B T , Hudson B , Yegorova S , Jollimore C A B , Kelly M E M
Published: October 2007

Background and purpose:

Trabecular meshwork (TM) is an ocular tissue involved in the regulation of aqueous humour outflow and intraocular pressure (IOP). CB1receptors (CB1) are present in TM and cannabinoid administration decreases IOP. CB1signalling was investigated in a cell line derived from human TM (hTM).

Experimental approach:

CB1signalling was investigated using ratiometric Ca2+imaging, western blotting and infrared In‐Cell Western analysis.

Key results:

WIN55212‐2, a synthetic aminoalkylindole cannabinoid receptor agonist (10–100 μM) increased intracellular Ca2+in hTM cells. WIN55,212‐2‐mediated Ca2+increases were blocked by AM251, a CB1antagonist, but were unaffected by the CB2antagonist, AM630. The WIN55,212‐2‐mediated increase in [Ca2+]iwas pertussis toxin (PTX)‐insensitive, therefore, independent of Gi/ocoupling, but was attenuated by a dominant negative Gαq/11subunit, implicating a Gq/11signalling pathway. The increase in [Ca2+]iwas dependent upon PLC activation and mobilization of intracellular Ca2+stores. A PTX‐sensitive increase in extracellular signal‐regulated kinase (ERK1/2) phosphorylation was also observed in response to WIN55,212‐2, indicative of a Gi/osignalling pathway. CB1‐Gq/11coupling to activate PLC‐dependent increases in Ca2+appeared to be specific to WIN55,212‐2 and were not observed with other CB1agonists, including CP55,940 and methanandamide. CP55940 produced PTX‐sensitive increases in [Ca2+]iat concentrations ≥15 μM, and PTX‐sensitive increases in ERK1/2 phosphorylation.

Conclusions and implications:

This study demonstrates that endogenous CB1couples to both Gq/11and Gi/oin hTM cells in an agonist‐dependent manner. Cannabinoid activation of multiple CB1signalling pathways in TM tissue could lead to differential changes in aqueous humour outflow and IOP.

British Journal of Pharmacology(2007)152, 1111–1120; doi:10.1038/sj.bjp.0707495; published online 8 October 2007
Flow‐induced enhancement of vasoconstriction and blockade of endothelium‐derived hyperpolarizing factor (EDHF) by ascorbate in the rat mesentery
Authors: Stirrat A , Nelli S , Dowell F J , Martin W
Published: October 2007

Background and purpose:

We previously reported that ascorbate inhibits flow‐ and agonist‐induced, EDHF‐mediated vasodilatation in the bovine ciliary circulation. This study examined whether ascorbate had similar actions in the rat mesenteric vasculature.

Experimental approach:

The effects of ascorbate were examined both in rat second order mesenteric arterial rings suspended in a static wire myograph and the rat mesentery perfused at different rates of flow.

Key results:

Ascorbate (50 μM) had no effect on U46619‐induced tone or acetylcholine‐induced, EDHF‐mediated vasodilatation in either rings of mesenteric artery or the perfused mesentery at rates of flow below 10 ml min−1. At higher rates of flow, ascorbate produced two distinct effects in the rat mesentery: a rapid and maintained enhancement of vasoconstrictor tone and a slow (max at 3 h) inhibition of acetylcholine‐induced, EDHF‐mediated vasodilatation. The enhancement of vasoconstrictor tone appeared to be due to inhibition of flow‐induced EDHF‐like activity, since it was endothelium‐dependent, but could be elicited during blockade of nitric oxide synthase and cyclooxygenase. Despite this, the classical inhibitors of EDHF, apamin and charybdotoxin, failed to affect the ascorbate‐induced enhancement of tone, although they inhibited acetylcholine‐induced vasodilatation.

Conclusions and implications:

Ascorbate inhibits both flow‐ and agonist‐induced EDHF in the rat mesentery. The strikingly different timecourses of these two effects, together with their differential sensitivity to apamin and charybdotoxin, suggest that the flow‐ and agonist‐induced EDHFs in the rat mesenteric vasculature may either be different entities or operate by different mechanisms.

British Journal of Pharmacology (2008) 153, 1162–1168; doi:10.1038/sj.bjp.0707499; published online 8 October 2007
Phosphatase and tensin homologue deleted on chromosome ten (PTEN) as a molecular target in lung epithelial wound repair
Authors: Lai J‐P , Dalton J T , Knoell D L
Published: October 2007

Background and purpose:

Epithelial injury contributes to lung pathogenesis. Our work and that of others have identified the phosphoinositide‐3 kinase (PI3K)/Akt pathway as a vital component of survival in lung epithelia. Therefore, we hypothesized that pharmacological inhibition of PTEN, a major suppressor of this pathway, would enhance wound closure and restore lung epithelial monolayer integrity following injury.

Experimental approach:

We evaluated the ability of two bisperoxovanadium derivatives, bpV(phen) and bpV(pic), in differentiated primary human airway epithelia and BEAS2B cultures for their ability to inhibit PTEN, activate the PI3K/Akt pathway and restore epithelial monolayer integrity following mechanical injury.

Key results:

BpV(phen) and bpV(pic) induced Akt phosphorylation in primary and BEAS2B cells in a dose and time dependent manner. Minimal toxicity was observed as measured by lactate dehydrogenase (LDH) release. To verify that Akt phosphorylation is specifically induced by PTEN inhibition, the PTEN positive cell line, DU145, and two PTEN negative cell lines, LNCaP and PC3, were examined. PTEN positive cells demonstrated a dose responsive increase in Akt phosphorylation whereas PTEN negative cells showed no response indicating that bpV(phen) directly suppresses PTEN without affecting auxiliary pathways. Next, we observed that exposure to either compound resulted in accelerated wound closure following mechanical injury. Similar effects were observed after transfection with a dominant negative isoform of PTEN and PTEN specific siRNA.

Conclusions and implications:

From these studies, we conclude that PTEN is a valid target for future studies directed at restoring epithelial barrier function after lung injury.

British Journal of Pharmacology (2007) 152, 1172–1184; doi:10.1038/sj.bjp.0707501; published online 8 October 2007
Luxationen und Luxationsfrakturen des Lisfranc-Gelenks
Authors: Richter Martinus
Published: October 2007

Verletzungen des Lisfranc-Gelenks umfassen Frakturen, Luxationen und/oder Luxationsfrakturen. Insbesondere die Verrenkungsbrüche sind folgenschwere Verletzungen, die sich erheblich auf die Funktion des gesamten Fußes auswirken. Da nach wie vor eine hohe Zahl von Kombinationsverletzungen primär nicht erkannt wird, kommt der korrekten Diagnostik als Grundlage der Behandlungsplanung entscheidende Bedeutung zu. Hierzu gehören Standardröntgenaufnahmen des Fußes in drei Ebenen (dorsoplantar, exakt seitlich und 45°-Schrägaufnahme); bei entsprechenden Verdachtsmomenten ist die Indikation für die Computertomografie inklusive multiplanarer Rekonstruktion notwendig. Die Grundprinzipien der adäquaten Behandlung sind die anatomiegerechte Rekonstruktion der Gelenkstrukturen und der geometrischen Beziehungen der medialen zur lateralen Fußsäule sowie die Erfassung und Therapie der ligamentären Instabilitäten. Werden diese Ziele nicht erreicht oder treten Komplikationen auf, sind oftmals Korrekturarthrodesen unvermeidlich.
Fluids in porous media. II. A new model of templated matrices
Authors: Zhao S. L. , Dong W. , Liu Q. H.
Published: October 2007

With the help of different templates, experimental techniques allow now for synthesizing a variety of porous materials with hierarchical pore structure, i.e., pores with multiple characteristic sizes. Despite their importance and the numerous experimental investigations devoted to porous materials with hierarchical pore structure, there are still few theoretical approaches available for describing such materials. We propose a new templated matrix model here. A primitive matrix is first prepared by quenching an equilibrium one-component fluid then the templated matrix is obtained by digging some cavities in the primitive matrix. The pore-space architecture of this model is similar to that of Van Tassel’s model [Phys. Rev. E 60, R25 (1999)]. We derived the diagrammatic expansions of various distribution functions and free energy as well as the Ornstein-Zernike equations. The new model we propose here possesses several attractive features. First, in some cases, the description of structure of the templated matrix can be considerably simplified which is determined exactly and entirely analytically. Moreover, many closed analytical results can be obtained for an ideal gas adsorbed in a simple case of our model while none of such results can be obtained from Van Tassel’s model under the similar conditions.
Fluid dynamics of rivulet flow between plates
Authors: Drenckhan W. , Ritacco H. , Saint-Jalmes A. , Saugey A. , McGuinness P. , van der Net A. , Langevin D. , Weaire D.
Published: October 2007

We present computational and experimental investigations into the fluid dynamics of a narrow stream of surfactant solutions, which descends under gravity between two narrowly spaced, vertical glass plates. Such a “rivulet” is bounded by two liquid/solid and two mobile liquid/gas interfaces, posing fluid dynamic problems of direct relevance to local fluid flow in liquid foams and recently reported meandering phenomena. The rivulet presents a system in which the coupling between the bulk flow and the rheological properties of the gas/liquid interface can be systematically investigated. In particular, it carries the promise of providing an alternative measuring technique for interfacial shear viscosities. We present finite element simulations in conjunction with experiments in order to describe the relationship between the rivulet geometry, the flow field, and the interfacial shear viscosities. We also report on the role of the boundary condition between the liquid-carrying channels (surface Plateau borders) and the thin soap film, which spans the two plates at low flow rates.
On the spin gaps of conjugated hydrocarbon polymers
Authors: Al Hajj Mohamad , Malrieu Jean-Paul
Published: October 2007

Many of the (ideal) infinite conjugated hydrocarbon polymers do not present a gap at the Fermi level in tight-binding calculations. However, due to the bielectronic interaction the excitation energy from the ground state to the lowest triplet state may be nonzero for some lattices (called spin gapped), while other lattices will keep a singlet-triplet degeneracy (spin-gapless lattices). This difference results in qualitative differences in their magnetic properties. Making use of the relevance of Heisenberg Hamiltonians for the study of the lowest states of conjugated hydrocarbons, this paper presents some qualitative arguments to predict the spin-gap character of various classes of such polymers. The arguments are based on real space renormalization group procedures, which considers fragments of the polymers as effective spins. Numerical evaluations, based on a renormalized excitonic method, confirm the qualitative predictions.
On the properties of microsolvated molecules in the ground (S) and excited (S1) states: The anisole-ammonia 1:1 complex
Authors: Biczysko Malgorzata , Piani Giovanni , Pasquini Massimiliano , Schiccheri Nicola , Pietraperzia Giangaetano , Becucci Maurizio , Pavone Michele , Barone Vincenzo
Published: October 2007

State-of-the-art spectroscopic and theoretical methods have been exploited in a joint effort to elucidate the subtle features of the structure and the energetics of the anisole-ammonia 1:1 complex, a prototype of microsolvation processes. Resonance enhanced multiphoton ionization and laser-induced fluorescence spectra are discussed and compared to high-level first-principles theoretical models, based on density functional, many body second order perturbation, and coupled cluster theories. In the most stable nonplanar structure of the complex, the ammonia interacts with the delocalized π electron density of the anisole ring: hydrogen bonding and dispersive forces provide a comparable stabilization energy in the ground state, whereas in the excited state the dispersion term is negligible because of electron density transfer from the oxygen to the aromatic ring. Ground and excited state geometrical parameters deduced from experimental data and computed by quantum mechanical methods are in very good agreement and allow us to unambiguously determine the molecular structure of the anisole-ammonia complex.
On the use of multiple interpolation functions in scaled particle theory to improve the predictions of the properties of the hard-sphere fluid
Authors: Siderius Daniel W. , Corti David S.
Published: October 2007

We present a modification to a previously proposed method of adapting scaled particle theory (SPT) to an arbitrary hard-sphere equation of state that satisfies a large number of exact SPT conditions, including thermodynamic consistency. By introducing a set of functions to interpolate the density of hard-spheres centers at the cavity surface, a broad range of hard-sphere properties, in particular the planar surface tension and related properties, are predicted with high accuracy as compared to simulation data. Similarly accurate results are obtained when this modified interpolation scheme is incorporated into a self-consistent version of SPT, i.e., an equation of state is a predicted output of the method. Hence, SPT is now able to closely match the surface thermodynamic properties of the hard-sphere fluid either without using any adjustable parameters or by simply setting the pressure and chemical potential via a reliable equation of state. We also consider other interpolation schemes, some of which better represent certain exact relations that can be derived within SPT. The limited success of these more rigorous approaches provides insights into the various trade-offs between the simplicity and rigor of the chosen interpolation method, as well as the accuracy of the results, that arise in any (inexact) version of SPT.
Multiple steady flows in confined gaseous double diffusion with discrete thermosolutal sources
Authors: Zhao Fu-Yun , Liu Di , Tang Guang-Fa
Published: October 2007

A detailed numerical study has been conducted to investigate the steady natural convection in a binary mixture in rectangular enclosures with the simultaneous presence of discrete heat and moisture sources. The Prandtl number and Lewis number used are 0.7 and 0.8, respectively. The heat and mass transfer characteristics of the horizontal enclosure are analyzed using the heat lines and mass lines, and the heat and moisture transfer potentials are also explained by the variations of overall Nusselt and Sherwood numbers. Numerical results are particularly presented to illustrate the effects of the buoyancy ratio, thermal Rayleigh number, and strip pitch on the multiple steady flow patterns and the associated heat and mass transfer, for both destabilizing and stabilizing solutal buoyancy forces. The effects of the buoyancy ratio are found to be rather significant on the flow pattern and heat and mass transfer especially for the destabilizing solutal forces. Additionally, in the regime that both thermal and concentration buoyancy forces are destabilizing, the heat and mass transfer potential can be promoted or inhibited, depending strongly on the thermal Rayleigh number and strip pitch.
Proton transfer reactions in model condensed-phase environments: Accurate quantum dynamics using the multilayer multiconfiguration time-dependent Hartree approach
Authors: Craig Ian R. , Thoss Michael , Wang Haobin
Published: October 2007

The recently proposed multilayer multiconfiguration time-dependent Hartree (ML-MCTDH) approach to evaluating reactive quantum dynamics is applied to two model condensed-phase proton transfer reactions. The models consist of a one-dimensional double-well “system” that is bilinearly coupled to a “bath” of harmonic oscillators parameterized to represent a condensed-phase environment. Numerically exact quantum-mechanical flux correlation functions and thermal rate constants are obtained for a broad range of temperatures and system-bath coupling strengths, thus demonstrating the efficacy of the ML-MCTDH approach. Particular attention is focused on the regime where low temperatures are combined with weak system-bath coupling. Under such conditions it is found that long propagation times are often required and that quantum coherence effects may prevent a rigorous determination of the rate constant.
Generating topological chaos in lid-driven cavity flow
Authors: Stremler Mark A. , Chen Jie
Published: October 2007

Periodic motion of three stirrers in a two-dimensional flow can lead to chaotic transport of the surrounding fluid. For certain stirrer motions, the generation of chaos is guaranteed solely by the topology of that motion and continuity of the fluid. Work in this area has focused largely on using physical rods as stirrers, but the theory also applies when the “stirrers” are passive fluid particles. We demonstrate the occurrence of topological chaos for Stokes flow in a two-dimensional lid-driven cavity without internal rods. This approach to stirring can enhance mixing relative to a “standard” chaos-generating lid-driven cavity flow.
Quasilinear theory of interchange modes in a closed field line configuration
Authors: Kouznetsov A. , Freidberg J. P. , Kesner J.
Published: October 2007

Two important issues for any magnetic fusion configuration are the maximum achievable values of β and energy confinement time when ideal magnetohydrodynamic (MHD) modes are excited. It is well known that the excitation of the MHD unstable modes typically can lead to violent restructuring of the plasma profiles. The particle and energy transport associated with these modes normally dominates all other transport mechanisms and can lead to plasma disruptions and a rapid loss of energy. This paper analytically investigates the transport of particle density, energy, and magnetic field due to the ideal MHD interchange mode in a closed-line system using the quasilinear approximation. The transport equations are derived for a static plasma in a hardcore Z-pinch configuration and generalized to an arbitrary axisymmetric toroidal closed poloidal field line configuration. It is shown that violation of the marginal stability criterion leads to rapid quasilinear transport that drives the pressure profile back to its marginal profile and forces the particle density to be inversely proportional to ∮dl∕B. The applicability of the quasilinear approximation is numerically tested for the hardcore Z-pinch magnetic configuration using a full nonlinear code.
Theoretical prediction of β and τE in a hard core Z pinch
Authors: Kouznetsov A. , Freidberg J. P. , Kesner J.
Published: October 2007

The energy confinement time and maximum achievable pressure are critical figures of merit for any proposed magnetic fusion concept. The present work focuses on these issues for a hard core Z pinch, which is the cylindrical limit of a large aspect ratio levitated dipole configuration. An analysis is presented that theoretically predicts both τE and β for this configuration. The model makes the optimistic assumption that transport is purely classical in the region of the profile that is magnetohydrodynamically (MHD) stable against interchange modes. In the interchange-unstable region use is made of the quasilinear theory described in the accompanying paper [A. Kouznetsov, J. Freidberg, and J. Kesner, Phys. Plasmas 14, 102501 (2007)] which shows that the plasma pressure relaxes to the MHD marginally stable profile while the density evolves to n∝[∮dl∕B]−1. Analytic and numerical calculations lead to explicit scaling relations for τE and β which can be tested in future LDX experiments.
Secondary decomposition of C3H5 radicals formed by the photodissociation of 2-bromopropene
Authors: Fan Haiyan , Pratt Stephen T. , Miller James A.
Published: October 2007

The photodissociation of 2-bromopropene at 193nm produces C3H5 radicals with a distribution of internal energies that spans the threshold for the secondary decomposition of the 2-propenyl radicals into C3H4+H. Just above this threshold, the decomposition rate is on the nanosecond time scale, and in the present study, time-resolved velocity-map ion imaging is used to gain insight into this process. The results provide information on the energy dependence of the secondary dissociation process. In addition, comparison of the results with theoretical predictions of the energy dependence of the dissociation rate provides information on the branching between fragment rotational and vibrational energies in the primary photodissociation process.
A criterion for the generation of turbulent anabatic flows
Authors: Princevac M. , Fernando H. J. S.
Published: October 2007

Turbulent convection over a heated infinite horizontal plane is ideally characterized by updrafts and downdrafts with no net mean motion, but a mean upslope (or anabatic) flow can be generated if the plane is even slightly inclined. A study on the mechanism responsible for the generation of upslope flow is described in this paper. When the heat flux is sufficiently large, the upslope flow becomes turbulent and is signified by thermals rising from the surface and deflected upslope to feed into the anabatic flow. It is argued theoretically and demonstrated experimentally that for a certain Prandtl number (Pr) range the tendency for heated thermals to deflect and follow the slope is inversely proportional to Pr and directly proportional to the inclination angle (β), and thus the critical angle above which the upslope flow can be sustained is given by βc=cPr, where c is a constant. This finding can explain the existence of well-developed atmospheric (Pr∼1) upslope flows above very gentle slopes in areas of complex topography.
Investigation of compound jet electrospray: Particle encapsulation
Authors: Mei Fan , Chen Da-Ren
Published: October 2007

Experiments were performed to investigate the effect of surface tension on the particle encapsulation formation in the compound jet electrospray process. The outer liquid used in this study were olive oil and mineral oil; and inner liquids were ethanol, tri-butyl phosphate, ethylene glycol, and triethylene glycol. It was found that the core-shell structured droplets are formed only when the ratio of charge relaxation lengths of the inner and outer jets [i.e., rO*∕rI*, where r*=(Qεε0∕K)1∕3, in which Q is the liquid feed flow rate, K is electrical conductivity, and ε is the dielectric constant of liquid] is less than 500, and the ratio of inertial breakup lengths of the inner and outer jets [i.e., RO*∕RI*, where R*=(ρQ2∕γ)1∕3, in which ρ and γ are the density and surface tension of liquid, respectively] is less than 0.015. In this work we further studied the effect of inner and outer liquid flow rates on the size of compound droplets using an Aerosizer (TSI model 3220). The parameters affecting the droplet size distribution were obtained. We also observed that the spray current emitted through the compound jet was merely a linear function of the inner jet flow rate. This observation implies that olive oil and mineral oil, as the outer liquids, serve as an electrically insulated layer during the spray process.
Bidirectional mapping between self-consistent field theory and molecular dynamics: Application to immiscible homopolymer blends
Authors: Sewell Thomas D. , Rasmussen Kim Ø. , Bedrov Dmitry , Smith Grant D. , Thompson Russell B.
Published: October 2007

A bidirectional mapping scheme that bridges particle-based and field-based descriptions for polymers is presented. Initial application is made to immiscible homopolymer blends. The forward mapping (upscaling) approach is based on the use of molecular dynamics simulations to calculate interfacial density profiles for polymer molecular weights that can be readily relaxed using standard simulation methods. These profiles are used to determine the optimal, effective interaction parameter that appears in the one-parameter self-consistent field theory treatment employed in the present work. Reverse mapping from a field representation to a particle-based description is accomplished by the application of a density-biased Monte Carlo method that generates representative chain configurations in the blend using statistical weights derived from fields obtained from self-consistent field theory.
Ferromagnetic CrxTi1−xN solid solution nitride thin films grown by pulsed laser deposition and their magnetoresistance
Authors: Inumaru Kei , Koyama Kunihiko , Miyaki Yuji , Tanaka Kazuma , Yamanaka Shoji
Published: October 2007

Epitaxial nitride films of CrxTi1−xN were grown on MgO (001) by pulsed laser deposition under nitrogen radical irradiation, and their magnetic and transport properties were investigated, which was motivated by calculations on magnetism pointing out similarities of CrN to LaMnO3, the parent compound of colossal magnetoresistance oxides. The films showed ferromagnetism for 0.28⩽x⩽0.5 and the TC showed a maximum (140K) at x=0.5. When x exceeded 0.5(x=0.58) ferromagnetism disappeared completely. At x=0.5, the nitride film showed a large magnetoresistance (6%–7% at 5T), which had a maximum at 130K.
Quantum dynamics of the CH3 fragment: A curvilinear coordinate system and kinetic energy operators
Authors: Evenhuis Chris , Nyman Gunnar , Manthe Uwe
Published: October 2007

A curvilinear coordinate system for AB3 fragments is given. The corresponding exact kinetic energy operator is derived and a series of simpler, progressively more approximate kinetic energy operators are suggested. The operators are tailored for quantum dynamics simulations using the multiconfigurational time-dependent Hartree approach. It is outlined how these fragment coordinates can be utilized to set up coordinate systems for larger systems such as AB3C or AB3CD. Calculations of the vibrational levels of CH3 and quantum dynamics studies investigate the accuracy of the different kinetic energy operators suggested.
Systematic investigation into the influence of growth conditions on InAs/GaAs quantum dot properties
Authors: Passow T. , Li S. , Feinäugle P. , Vallaitis T. , Leuthold J. , Litvinov D. , Gerthsen D. , Hetterich M.
Published: October 2007

The influence of the conditions during growth of InAs/GaAs quantum-dot structures on GaAs(001) by molecular-beam epitaxy was investigated systematically with respect to achieving quantum-dot photoluminescence in the 1 eV range. The growth temperature, As flux, growth rate, InAs deposit, and growth interruption time before cap layer growth were varied. Photoluminescence spectroscopy and transmission electron microscopy were used to study the optical and structural properties. Large InAs quantum dots with photoluminescence in the 1 eV range were obtained at a low growth rate of 0.0056 ML/s. Analyzing in particular the low-growth-rate regime, we found that an InAs deposition of at least 2.4 ML and a growth temperature of 500−510 °C were crucial to obtain large quantum dots with a high size uniformity. Composition analyses by transmission electron microscopy revealed a significantly higher In concentration in the quantum dots grown at low growth rate compared to high-growth-rate samples.
Generation of mesoscale convective structures in tokamak edge plasma
Authors: Krasheninnikov S. I. , Smolyakov A. I.
Published: October 2007

It is shown that the interplay of the interchange drive and nonlinear effects of Reynolds stress and inverse cascade of drift wave turbulence select a range of plasma parameters (plasma pressure), for which mesoscale perturbations of a certain transverse length scale become unstable. It is suggested that the blob formation is a result of these mesoscale instabilities.
Broken symmetries and magnetic dynamos
Authors: Shebalin John V.
Published: October 2007

Phase space symmetries inherent in the statistical theory of ideal magnetohydrodynamic (MHD) turbulence are known to be broken dynamically to produce large-scale coherent magnetic structure. Here, results of a numerical study of decaying MHD turbulence are presented that show large-scale coherent structure also arises and persists in the presence of dissipation. Dynamically broken symmetries in MHD turbulence may thus play a fundamental role in the dynamo process.