bluuebunny/crossref_metadata_2025 huggingface dataset:
Creep events slip less than ordinary earthquakes
Authors: Brodsky Emily E. , Mori James
Published: August 2007

We find that slow seismic events have smaller fault slips compared to ordinary earthquakes with similar dimensions. For ordinary earthquakes, the ratio of slip to fault length is largely consistent, yet the physical controls on this ratio are unknown. Recently discovered slow slip or creep events in which faults move quasi‐statically over periods of days to years shed new light on this old conundrum. For example, large slow events that extend over 100 km have slips of centimeters, while ordinary earthquakes that rupture a comparable length of fault typically slip meters. The small slips of quasi‐static events compared to the large slips of earthquakes show that dynamic processes significantly control the rupture growth of ordinary earthquakes. We propose a model where slip on a heterogeneous fault accounts for the difference. Inertial overshoot may result in larger final slips for earthquakes than comparable creep events.
Theoretical study of the two-photon absorption properties of several asymmetrically substituted stilbenoid molecules
Authors: Ohta Koji , Antonov Liudmil , Yamada Satoru , Kamada Kenji
Published: August 2007

Two-photon absorption (TPA) properties of noncentrosymmetric π-conjugated stilbenoid molecules with D-π-A structures, TPA spectra of which have been reported [L. Antonov et al., Phys. Chem. Chem. Phys. 5, 1193 (2003)], have been investigated theoretically by ab initio molecular orbital methods. The difference in the observed one-photon absorption and TPA spectra among compounds with the same donor (D) and acceptor (A) units is well reproduced by the present calculations, although the calculated excitation energies are overestimated by the configuration interaction with single excitation method used. It was found that the spectral differences among the compounds were mainly due to the deviation from the planar structure by intramolecular rotation around the NC (phenyl) bond of the N-benzilideneanilines having the CN linkage as the central π bridge. Substitution of the end donor or acceptor groups with weaker ones leads to a decrease in the TPA intensity of the lowest π-π* TPA states, resulting mainly from the decrease in the dipole moment of the excited states. The total TPA cross section spectra have been separated into contributions of the dipolar term, which appear only in noncentrosymmetric systems, and the three-state term, which appear in any systems irrespective of symmetry. The dipolar term predominates only for the lowest π-π* state, while for the higher excited states the three-state terms become predominant. An analysis employing the index Rf defined with the transition polarizability shows that the TPA properties of the higher excited states are well described by the three-state approximation mediated by the lowest π-π* state. The differences found between the centrosymmetric and dipolar molecules in the enhancement mechanism of the TPA intensity by substituting the end groups with strong donors are discussed by comparison with the TPA properties of azobenzenes symmetrically substituted with the same donors.
Application of the level-set method to the implicit solvation of nonpolar molecules
Authors: Cheng Li-Tien , Dzubiella Joachim , McCammon J. Andrew , Li Bo
Published: August 2007

A level-set method is developed for numerically capturing the equilibrium solute-solvent interface that is defined by the recently proposed variational implicit solvent model [Dzubiella, Swanson, and McCammon, Phys. Rev. Lett. 104, 527 (2006); J. Chem. Phys. 124, 084905 (2006)]. In the level-set method, a possible solute-solvent interface is represented by the zero level set (i.e., the zero level surface) of a level-set function and is eventually evolved into the equilibrium solute-solvent interface. The evolution law is determined by minimization of a solvation free energy functional that couples both the interfacial energy and the van der Waals type solute-solvent interaction energy. The surface evolution is thus an energy minimizing process, and the equilibrium solute-solvent interface is an output of this process. The method is implemented and applied to the solvation of nonpolar molecules such as two xenon atoms, two parallel paraffin plates, helical alkane chains, and a single fullerence C60. The level-set solutions show good agreement for the solvation energies when compared to available molecular dynamics simulations. In particular, the method captures solvent dewetting (nanobubble formation) and quantitatively describes the interaction in the strongly hydrophobic plate system.
Quantum chemical study and infrared spectroscopy of hydrogen-bonded CHCl3–NH3 in the gas phase
Authors: Hippler Michael
Published: August 2007

Molecular association of chloroform with ammonia is studied by high-level quantum chemical calculations including correlated MP2 and CCSD(T) calculations with basis sets up to6-311++G(d,p) and counterpoise corrected energies, geometries, and frequencies. The calculations predict an eclipsed hydrogen-bonded complex of C3v symmetry (ΔE0=−15.07kJmol−1) with 225.4pm intermolecular CH⋯N distance. Intermolecular interactions are analysed by Kitaura-Morokuma [Int. J. Quantum Chem. 10, 325 (1976)] interaction energy decomposition. Compared to the monomer, the C–H bond is elongated, and the CH-stretching fundamental shifts to lower wave numbers and has a marked ∼340-fold increase of its intensity. Based on these predictions, the complex is observed by infrared spectroscopy in the gas phase at room temperature. A subtraction procedure isolates its spectrum, and a dilution series confirms the presence of a 1:1 complex. The CHCl3⋯NH3 complex has an experimental −17.5cm−1 shift of its CH-stretching vibration, and CDCl3⋯NH3 a −12.5cm−1 shift of the CD-stretching vibration. After a deperturbation of the CH-stretching/bending mode Fermi resonance system, this indicates a “redshifting” or more appropriately, a “C–H elongating” hydrogen bond in agreement with the ab initio calculations. An estimate of the complex concentration gives the equilibrium constant Kp=0.024 (pθ=105Pa) at 295K for the dimerization, providing one of the few examples where a hydrogen-bonded gas phase complex at room temperature could be quantitatively studied by infrared spectroscopy.
Photodissociation dynamics of OCS at 248nm: The S(D21) atomic angular momentum polarization
Authors: Brouard M. , Green A. V. , Quadrini F. , Vallance C.
Published: August 2007

The dissociation of OCS has been investigated subsequent to excitation at 248nm. Speed distributions, speed dependent translational anisotropy parameters, angular momentum alignment, and orientation are reported for the channel leading to S(D21). In agreement with previous experiments, two product speed regimes have been identified, correlating with differing degrees of rotational excitation in the CO coproducts. The velocity dependence of the translational anisotropy is also shown to be in agreement with previous work. However, contrary to previous interpretations, the speed dependence is shown to primarily reflect the effects of nonaxial recoil and to be consistent with predominant excitation to the 2A′1 electronic state. It is proposed that the associated electronic transition moment is polarized in the molecular plane, at an angle greater than ∼60° to the initial linear OCS axis. The atomic angular momentum polarization data are interpreted in terms of a simple long-range interaction model to help identify likely surfaces populated during dissociation. Although the model neglects coherence between surfaces, the polarization data are shown to be consistent with the proposed dissociation mechanisms for the two product speed regimes. Large values for the low and high rank in-plane orientation parameters are reported. These are believed to be the first example of a polyatomic system where these effects are found to be of the same order of magnitude as the angular momentum alignment.
Effect of polydispersity on the crystallization kinetics of suspensions of colloidal hard spheres when approaching the glass transition
Authors: Schöpe Hans Joachim , Bryant Gary , van Megen William
Published: August 2007

We present a comprehensive study of the solidification scenario in suspensions of colloidal hard spheres for three polydispersities between 4.8% and 5.8%, over a range of volume fractions from near freezing to near the glass transition. From these results, we identify four stages in the crystallization process: (i) an induction stage where large numbers of precursor structures are observed, (ii) a conversion stage as precursors are converted to close packed structures, (iii) a nucleation stage, and (iv) a ripening stage. It is found that the behavior is qualitatively different for volume fractions below or above the melting volume fraction. The main effect of increasing polydispersity is to increase the duration of the induction stage, due to the requirement for local fractionation of particles of larger or smaller than average size. Near the glass transition, the nucleation process is entirely frustrated, and the sample is locked into a compressed crystal precursor structure. Interestingly, neither polydispersity nor volume fraction significantly influences the precursor stage, suggesting that the crystal precursors are present in all solidifying samples. We speculate that these precursors are related to the dynamical heterogeneities observed in a number of dynamical studies.
Assessment of time-dependent density functional schemes for computing the oscillator strengths of benzene, phenol, aniline, and fluorobenzene
Authors: Miura Masanori , Aoki Yuriko , Champagne Benoît
Published: August 2007

In present study the relevance of using the time-dependent density functional theory (DFT) within the adiabatic approximation for computing oscillator strengths (f) is assessed using different LDA, GGA, and hybrid exchange-correlation (XC) functionals. In particular, we focus on the lowest-energy valence excitations, dominating the UV/visible absorption spectra and originating from benzenelike HOMO(π)→LUMO(π*) transitions, of several aromatic molecules: benzene, phenol, aniline, and fluorobenzene. The TDDFT values are compared to both experimental results obtained from gas phase measurements and to results determined using several ab initio schemes: random phase approximation (RPA), configuration interaction single (CIS), and a series of linear response coupled-cluster calculations, CCS, CC2, and CCSD. In particular, the effect of the amount of Hartree-Fock (HF) exchange in the functional is highlighted, whereas a basis set investigation demonstrates the need of including diffuse functions. So, the hybrid XC functionals—and particularly BHandHLYP—provide f values in good agreement with the highly correlated CCSD scheme while these can be strongly underestimated using pure DFT functionals. These results also display systematic behaviors: (i) larger f and squares of the transition dipole moments (∣μ∣2) are associated with larger excitation energies (ΔE); (ii) these relationships present generally a linear character with R>0.9 in least-squares fit procedures; (iii) larger amounts of HF exchange in the XC functional lead to larger f, ∣μ∣2, as well as ΔE values; (iv) these increases in f, ∣μ∣2, and ΔE are related to increased HOMO-LUMO character; and (v) these relationships are, however, not universal since the linear regression parameters (the slopes and the intercepts at the origin) depend on the system under investigation as well as on the nature of the excited state.
Polarization hysteresis and piezoelectricity in open-porous fluoropolymer sandwiches
Authors: Zhukov S. , von Seggern H.
Published: August 2007

Open-porous polymers form an attractive class of piezoelectric materials. Up to now it has been demonstrated that fibrous polyterafluoroethylene films after proper polarizing are responsible for the high piezoelectric response if confined between two electrically blocking polyfluoroethylene propylene layers. The sandwich structures reveal large quasistatic piezoelectric coefficients of up to 1500 pC/N. Here a theoretical model is proposed for a three-layer sandwich which quantitatively explains the experimentally obtainable polarization and its hysteresis behavior for different poling voltages. It will be reported that each sandwich structure exhibits a limit for the remanent polarization induced by polarization backswitching due to insufficient charge compensation. The correlation of the remanent polarization to the device geometry and the dielectric constants will be highlighted and suggestions for optimization will be given. It will be reported that the limitation of the remanent polarization also limits the obtainable piezoelectric coefficient of the sandwich structures.
Designing synthetic vesicles that engulf nanoscopic particles
Authors: Smith Kurt A. , Jasnow David , Balazs Anna C.
Published: August 2007

We examine the interaction of a lipid bilayer membrane with a spherical particle in solution using dissipative particle dynamics, with the aim of controlling the passage of foreign objects into and out of vesicles. Parameters are chosen such that there is a favorable adhesive interaction between the membrane and the particle. Under these conditions, the membrane wraps the particle in a process resembling phagocytosis in biological cells. We find that, for a homogeneous membrane with a uniform attraction to the particle, the membrane is unable to fully wrap the particle when the adhesion strength is below a certain value. This is observed even in the limit of zero membrane tension. When the adhesion strength is increased above the threshold value, the membrane fully wraps the particle. However, the wrapped particle remains tethered to the larger membrane. We next consider an adhesive domain, or raft, in an otherwise nonadhesive membrane. We find that, when the particle is wrapped by the raft, the line tension at the raft interface promotes fission, allowing the wrapped particle to detach from the larger membrane. This mechanism could be used to allow particles to cross a vesicle membrane.
Microstructure and electrical properties of (120)O-oriented and of (001)O-oriented epitaxial antiferroelectric PbZrO3 thin films on (100) SrTiO3 substrates covered with different oxide bottom electrodes
Authors: Boldyreva Ksenia , Bao Dinghua , Le Rhun Gwenael , Pintilie Lucian , Alexe Marin , Hesse Dietrich
Published: August 2007

Epitaxial antiferroelectric PbZrO3 (PZO) thin films of two different crystallographic orientations were grown by pulsed laser deposition on (100)-oriented SrTiO3 single crystal substrates. The latter were covered either with SrRuO3 epitaxial bottom electrodes, or with an epitaxial BaZrO3 buffer layer and an epitaxial BaPbO3 bottom electrode, respectively. Their crystal orientation and microstructure were characterized by x-ray diffraction, transmission electron microscopy, and electron diffraction. The orthorhombic (index O) PZO films on SrRuO3∕SrTiO3 were predominantly (120)O oriented and consisted of four azimuthal domains forming 90° and 60° boundaries, whereas those grown on BaPbO3∕BaZrO3∕SrTiO3 were (001)O oriented. All films showed well-defined double P-E hysteresis loops, four distinct switching peaks in the current-voltage characteristics, and piezoelectric double loops recorded by piezoresponse scanning force microscopy. The values of the saturation polarization PS and the critical field EC of the (120)O-oriented PZO films (PS=41μC∕cm2; EC=445kV∕cm) are different from those of the (001)O-oriented films (PS=24μC∕cm2; EC=500kV∕cm). A transition temperature to the paraelectric phase of 260°C has been found, which is 30K higher than the bulk value, probably indicating a stabilization of the antiferroelectric phase by substrate-induced strain.
Electrical properties of Cr-doped BiFeO3 thin films fabricated on the p-type Si (100) substrate by chemical solution deposition
Authors: Lee Seung U , Kim Sang Su , Jo Hyeun Kyung , Park Mun Heum , Kim Jin Won , Bhalla Amar S.
Published: August 2007

Ferroelectric Cr-doped BiFeO3 (BFCr) thin films having a rhombohedrally distorted simple perovskite structure were fabricated on the p-type Si (100) substrate by the chemical solution deposition technique. The microstructures and the surface morphologies of BFCr thin films on the p-type Si (100) annealed at 550 °C for 30 min in nitrogen atmosphere were examined by an x-ray diffractometer and a scanning electron microscope, respectively. The capacitance-voltage (C−V) curves for BFCr thin film as the clockwise ferroelectric hysteresis loop were observed. Furthermore, the C−V characteristics for the metal-ferroelectrics-semiconductor structured BFCr thin films were measured as functions of the voltage and the frequency. From these results, the fixed charge density Nfc was calculated as 5.3×1011 cm−2. The leakage current characteristics of BFCr thin films were also measured by a thermally stimulated current measurement. Using the current-voltage curves, the current conduction mechanism of BFCr thin films on the p-type Si (100) capacitor was found to be dominated by the ferroelectric Schottky emission with a barrier height ϕB of 0.45±0.02 eV.
Hydrogen trapping in oxygen-deficient hafnium silicates
Authors: Fonseca L. R. C. , Xavier A. L. , Ribeiro M. , Driemeier C. , Baumvol I. J. R.
Published: August 2007

Isotopic substitution, nuclear reaction analysis, and x-ray photoelectron spectroscopy were employed to show that oxygen-deficient hafnium (Hf) silicates trap hydrogen atoms. Based on this experimental observation, we used first-principles calculations to investigate the structure, energetics, and electronic properties of H interacting with O vacancies in a hafnium silicate model. We found that O vacancies close to a Si atom are energetically favored when compared to vacancies in HfO2-like regions, implying that close-to-Si O vacancies are more likely to occur. Trapping of two H atoms at a close-to-Si O vacancy passivates the vacancy-induced gap states. The first H interacts with neighboring Hf atoms, whereas the second H binds to the Si atom.
Influence of the annealing temperature and silicon concentration on the absorption and emission properties of Si nanocrystals
Authors: Podhorodecki A. , Zatryb G. , Misiewicz J. , Wojcik J. , Mascher P.
Published: August 2007

Silicon nanocrystals embedded in a silicon-rich silicon-oxide matrix have been fabricated at different silicon contents (38%, 40%, and 49%) using plasma-enhanced chemical vapor deposition and annealing at different temperatures in the range from 900 °C to 1100 °C. Their optical properties have been investigated by photoluminescence and transmittance measurements. Strong, room-temperature emission bands at ∼1.6 eV have been observed for all samples, with intensities dependent on the annealing temperature and Si content of the samples. From transmittance measurements, a redshift of the absorption edge has been detected when increasing the annealing temperature or Si content.
Tensile behavior of bulk metallic glasses by in situ x-ray diffraction
Authors: Wang X. D. , Bednarcik J. , Saksl K. , Franz H. , Cao Q. P. , Jiang J. Z.
Published: August 2007

The authors report the use of in situ high-energy x-ray diffraction to detect the tensile behavior of two Zr- and La-based bulk metallic glasses (BMGs). Based on the diffraction data, the tensile elastic modulus and Poisson’s ratio can be accurately evaluated. No excess free volume appears in the fractured region. However, a drastic change in atomic-level strains is found in the La-based BMG along the tensile direction, while a tiny crystalline component is detected in the fracture region of Zr-based BMG, which may be the different factors leading to the catastrophic failure of them, respectively.
Phonon pressure coefficient as a probe of the strain status of self-assembled quantum dots
Authors: Reparaz J. S. , Bernardi A. , Goñi A. R. , Lacharmoise P. D. , Alonso M. I. , Garriga M. , Novák J. , Vávra I.
Published: August 2007

The built-in strain in self-assembled quantum dots has large impact on their physical properties, but both its average value and degree of anisotropy are often unknown. The authors demonstrate that the pressure coefficient of optical phonons might be used as probe for the strain status of the dots. This method was applied to the case of Ge dots capped with Si layers of different thicknesses. The authors observe a transition from a strictly biaxial stress situation for uncapped dots to a status of quasihydrostatic strain for cap-layer thicknesses larger than a critical value of the order of the dot height.
Enhanced luminescence of organic/metal nanostructure for grating coupler active long-range surface plasmonic device
Authors: Chiu Nan-Fu , Lin Chii-Wann , Lee Jiun-Haw , Kuan Chieh-Hsiung , Wu Kuang-Chong , Lee Chih-Kung
Published: August 2007

This letter is intended to demonstrate the effect of coupled active long-range surface plasmon polaritons (SPPs) on the plasmonics response of a lamellar grating nanostructure with organic material on the surface. The phenomenon of nano-optics gives rise to a selective spectral response and a local field enhancement. The authors’ fabricated device consists of coupled organic/metal nanostructure with specific width and symmetric dielectric structure. The interaction between organic/metal interface SPPs can allow specific directional emission rather than isotropic emission. The authors present recent experimental results and discuss potential applications of such an active plasmonic biosensor with enhanced resonance energy emission due to interactions on the organic/metal nanograting.
High temperature power performance of AlGaN∕GaN high-electron-mobility transistors on high-resistivity silicon
Authors: Arulkumaran S. , Ng G. I. , Liu Z. H. , Lee C. H.
Published: August 2007

High temperature power performance of AlGaN∕GaN high-electron-mobility transistor (HEMT) on high-resistivity-(HR) Si for different microwave frequencies of 3, 6, and 8GHz was studied. The device output power density (Pout) reduction with temperature for HR-Si-based AlGaN∕GaN HEMTs is almost equivalent to the Pout reduction with temperature for semi-insulating–SiC substrate based AlGaN∕GaN HEMTs. After high temperature stress, very small degradation was observed in the power performance at 3GHz. Moreover, the rate of Pout decrease with the temperature is not much affected by measurement frequencies. The conduction mechanism of trap assisted impact ionization and temperature assisted tunneling were identified on Si3N4 passivated AlGaN∕GaN HEMTs. The AlGaN∕GaN HEMTs on HR-Si can also be used for high-power and high-frequency applications at elevated temperatures.
Combining high mass resolution and velocity imaging in a time-of-flight ion spectrometer using pulsed fields and an electrostatic lens
Authors: Prümper G. , Fukuzawa H. , Lischke T. , Ueda K.
Published: August 2007

We describe a momentum resolving time-of-flight ion mass spectrometer that combines a high mass resolution, a velocity focusing condition for improved momentum resolution, and field-free conditions in the source region for high resolution electron detection. It is used in electron-ion coincidence experiments to record multiple ionic fragments produced in breakup reactions of small to medium sized molecules, such as F3SiCH2CH2Si(CH3)3. These breakup reactions are caused by soft x rays or intense laser fields. The ion spectrometer uses pulsed extraction fields, an electrostatic lens, and a delay line detector to resolve the position. Additionally, we describe a simple analytical method for calculating the momentum from the measured hit position and the time of flight of the ions.
Identification and characterization of a selenoprotein family containing a diselenide bond in a redox motif
Authors: Shchedrina Valentina A. , Novoselov Sergey V. , Malinouski Mikalai Yu. , Gladyshev Vadim N.
Published: August 2007

Selenocysteine (Sec, U) insertion into proteins is directed by translational recoding of specific UGA codons located upstream of a stem-loop structure known as Sec insertion sequence (SECIS) element. Selenoproteins with known functions are oxidoreductases containing a single redox-active Sec in their active sites. In this work, we identified a family of selenoproteins, designated SelL, containing two Sec separated by two other residues to form a UxxU motif. SelL proteins show an unusual occurrence, being present in diverse aquatic organisms, including fish, invertebrates, and marine bacteria. Both eukaryotic and bacterial SelL genes use single SECIS elements for insertion of two Sec. In eukaryotes, the SECIS is located in the 3′ UTR, whereas the bacterial SelL SECIS is within a coding region and positioned at a distance that supports the insertion of either of the two Sec or both of these residues. SelL proteins possess a thioredoxin-like fold wherein the UxxU motif corresponds to the catalytic CxxC motif in thioredoxins, suggesting a redox function of SelL proteins. Distantly related SelL-like proteins were also identified in a variety of organisms that had either one or both Sec replaced with Cys.
Danio rerio
SelL, transiently expressed in mammalian cells, incorporated two Sec and localized to the cytosol. In these cells, it occurred in an oxidized form and was not reducible by DTT. In a bacterial expression system, we directly demonstrated the formation of a diselenide bond between the two Sec, establishing it as the first diselenide bond found in a natural protein.
A self-similar isochoric implosion for fast ignition
Authors: Clark D.S. , Tabak M.
Published: August 2007

Various gain models have shown the potentially great advantages of fast ignition (FI) inertial confinement fusion (ICF) over its conventional hot spot ignition counterpart (e.g. Atzeni S. 1999Phys. Plasmas63316; Tabak M.et al2006Fusion Sci. Technol.49254). These gain models, however, all assume nearly uniform density fuel assemblies. In contrast, conventional ICF implosions yield hollowed fuel assemblies with a high-density shell of fuel surrounding a low-density, high-pressure hot spot. Hence, to realize fully the advantages of FI, an alternative implosion design must be found which yields nearly isochoric fuel assemblies without substantial hot spots. Here, it is shown that a self-similar spherical implosion of the type originally studied by Guderley (1942Luftfahrtforschung19302) may be employed to yield precisely such quasi-isochoric imploded states. The difficulty remains, however, of accessing these self-similarly imploding configurations from initial conditions representing an actual ICF target, namely a uniform, solid-density shell at rest. Furthermore, these specialized implosions must be realized for practicable drive parameters and at the scales and energies of interest in ICF. A direct-drive implosion scheme is presented which meets all of these requirements and reaches a nearly isochoric assembled density of 300 g cm−3and areal density of 2.4 g cm−2using 485 kJ of laser energy.
Enhanced ITER resistive wall mode feedback performance using optimal control techniques
Authors: Katsuro-Hopkins O. , Bialek J. , Maurer D.A. , Navratil G.A.
Published: August 2007

In order to achieve the highest plasma pressure limits in ITER, resistive wall kink mode stabilization is required. A novel resistive wall mode linear observer and feedback controller designed using model reduction and optimal control theory and employing only proportional gain are described here that allow operation of ITER up toCβ= 86% of the ideal wall limit using the present design external control coils. The full VALEN finite element ITER model containing ∼3000 modes was reduced to a minimum of 8 modes making real-time controller implementation possible. We find an order of magnitude reduction of the required control coil current and voltage in the presence of white noise from the no-wall limit to the optimal feedback system performance limit as compared with a traditional, classical controller.
Ultra-high beta in numerical simulations of a tearing-mode reduced reversed-field pinch
Authors: Dahlin Jon-Erik , Scheffel Jan
Published: August 2007

In the advanced reversed-field pinch (RFP), current profile control (CPC) enables energy confinement time and poloidal beta to increase substantially as compared with the conventional RFP due to reduced magnetic field stochasticity. Numerical simulations using the three-dimensional non-linear resistive MHD-code DEBSP are performed showing that the poloidal beta is not limited to them= 0 stability criterion βθ< 1/2. Instead, as tearing modes are diminished, it may approach unity. The beta criterion is theoretically analysed and a new, more general, criterion is derived. Analytic estimates of the resistive tearing andg-mode growth rates are derived form= 0, and it is shown that both tearing andg-mode growth rates decrease significantly as CPC is employed. Furthermore, quasi-steady state operation with increased confinement due to active control of the current profile is numerically demonstrated for the advanced RFP for a scenario with βθ< 1/2.
Experimental field study on the migratory behaviour of glass eels (Anguilla anguilla) at the interface of fresh and salt water
Authors: Bult Tammo P. , Dekker Willem
Published: August 2007

Bult, T. P., and Dekker, W. 2007. Experimental field study on the migratory behaviour of glass eels (Anguilla anguilla) at the interface of fresh and salt water. – ICES Journal of Marine Science, 64: 1396–1401. European eels (Anguilla anguilla) in the glass eel phase migrate using ocean currents and selective tidal stream transport. Conventional fish ladders installed at the interface of marine and fresh water, however, require the fish to swim upstream actively. We question the efficiency of these fish ladders for glass eel immigration, and propose a simple siphon over migration barriers, restoring the original selective tidal stream transport. A conventional trap and our siphon were tested concurrently at two sluice complexes in The Netherlands (Tholen, Nieuwe Statenzijl) in spring 2005. In all but one case, the siphon caught more glass eels than the trap, as well as more sticklebacks and other species. Clearly, the natural immigration process can be restored fairly easily and at low cost and with low intrusion levels of salt. Follow-up studies should focus on optimization, and the effect of a passage on the hinterland stock.
Autoinflammatory syndromes with a dermatological perspective
Authors: KANAZAWA Nobuo , FURUKAWA Fukumi
Published: August 2007

The term autoinflammatory syndromes describes a distinct group of systemic inflammatory diseases apparently different from infectious, autoimmune, allergic and immunodeficient ones. Originally, it was almost synonymous with clinically defined hereditary periodic fever syndromes, including familial Mediterranean fever, hyper immunoglobulin D syndrome with periodic fever and tumor necrosis factor receptor‐associated periodic syndrome. Similar but distinct periodic fever syndromes accompanied by urticarial rash, familial cold autoinflammatory syndrome, Muckle–Wells syndrome and chronic infantile neurological cutaneous articular syndrome, have all been reportedly associated with CIAS1 mutations and are collectively called cryopyrin‐associated periodic syndromes. Consequently, the concept of autoinflammatory syndromes has been spread to contain other systemic inflammatory diseases: rare hereditary diseases with or without periodic fevers, such as pyogenic sterile arthritis, pyoderma gangrenosum and acne syndrome, Blau syndrome and chronic recurrent multifocal osteomyelitis, and the more common collagen disease‐like diseases, such as Behcet's disease, Crohn's disease, sarcoidosis and psoriatic arthritis. These diseases are all caused by or associated with mutations of genes regulating innate immunity and have common clinical features accompanied with activation of neutrophils and/or monocytes/macrophages. In this review, major autoinflammatory syndromes are summarized and the pathophysiology of related skin disorders is discussed in association with dysregulated innate immune signaling.
Characteristics of acquired reactive perforating collagenosis
Authors: TSUBOI Hiromi , KATSUOKA Kensei
Published: August 2007

The status of the patient's associated disease can generally affect the onset or healing of acquired reactive perforating collagenosis (ARPC). We treated eight cases of ARPC and noted that the patients had similar findings. However, it was not clear why ARPC developed in the patients with these diseases. Nevertheless, several factors related to the diseases associated with ARPC could affect the degeneration of collagen fibers or the production of dermal products. Some patients had diseases that were characterized by fibrosis and an increased amount of reticular fibers. Factors related to tissue remodeling might act not only in diseases associated with ARPC but also in ARPC itself.
Elevated endogenous thrombin potential is associated with an increased risk of a first deep venous thrombosis but not with the risk of recurrence
Authors: Van Hylckama Vlieg A. , Christiansen S. C. , Luddington R. , Cannegieter S. C. , Rosendaal F. R. , Baglin T. P.
Published: August 2007

Measurement of the thrombin generating potential could provide a method for quantifying the composite effect of multiple risk factors. This study assessed the risk of a first as well as a recurrent venous thrombotic event associated with an increased endogenous thrombin potential (ETP). Analyses were performed in 360 patients and 404 control subjects of the Leiden Thrombophilia Study. The ETP was measured directly using a fluorogenic assay (ThrombinoscopeTM). Individuals with an increased ETP, i.e. above 90th percentile measured in control subjects (>2109·0 nM·min) had a 1·5‐fold [95% confidence interval (CI): 0·9–2·3] increased risk of a first deep venous thrombosis. The risk was more pronounced after the analysis was restricted to idiopathic thromboses, i.e. 1·7‐fold (95% CI: 1·0–2·8). Overall, the hazard ratio of a recurrent thrombotic event associated with a high ETP, adjusted for age, sex and oral anticoagulant use was 1·1 (95% CI: 0·5–2·2). Thus, a high ETP was not associated with an increased relative risk of recurrent venous thrombosis. At present, the clinical relevance of the thrombin generation assay in predicting recurrent venous thrombosis remains uncertain.
High expression of connective tissue growth factor in pre‐B acute lymphoblastic leukaemia
Authors: Boag Joanne M. , Beesley Alex H. , Firth Martin J. , Freitas Joseph R. , Ford Jette , Brigstock David R. , De Klerk Nicholas H. , Kees Ursula R.
Published: August 2007

In recent years microarrays have been used extensively to characterize gene expression in acute lymphoblastic leukaemia (ALL). Few studies, however, have analysed normal haematopoietic cell populations to identify altered gene expression in ALL. We used oligonucleotide microarrays to compare the gene expression profile of paediatric precursor‐B (pre‐B) ALL specimens with two control cell populations, normal CD34+ and CD19+IgM− cells, to focus on genes linked to leukemogenesis. A set of eight genes was identified with a ninefold higher average expression in ALL specimens compared with control cells. All of these genes were significantly deregulated in an independent cohort of 101 ALL specimens. One gene, connective tissue growth factor (CTGF, also known as CCN2), had exceptionally high expression, which was confirmed in three independent leukaemia studies. Further analysis of CTGF expression in ALL revealed exclusive expression in B‐lineage, not T‐lineage, ALL. Within B‐lineage ALL approximately 75% of specimens were consistently positive for CTGF expression, however, specimens containing the E2A‐PBX1 translocation showed low or no expression. Protein studies using Western blot analysis demonstrated the presence of CTGF in ALL cell‐conditioned media. These findings indicate that CTGF is secreted by pre‐B ALL cells and may play a role in the pathophysiology of this disease.
Establishment and exploitation of hyperdiploid and non‐hyperdiploid human myeloma cell lines
Authors: Li Xin , Pennisi Angela , Zhan Fenghuang , Sawyer Jeffrey R. , Shaughnessy John D. , Yaccoby Shmuel
Published: August 2007

The establishment of clinically relevant human myeloma cell lines is central for our understanding of myeloma pathogenesis and development of novel therapies for the disease. Unfortunately, most available lines were generated from extramedullary sites, harbored multiple genetic abnormalities and categorized as non‐hyperdiploid. In contrast, hyperdiploid myeloma cell lines, which represent more than 50% of patients, are rare. We established procedures for establishment of stroma‐dependent myeloma lines by passaging primary myeloma cells, in severe combined immunodeficient‐human (SCID‐hu) or SCID‐rab mice followed by maintenance in co‐culture with stromal cells. We described the establishment and characterization of two hyperdiploid (LD and CF) and two non‐hyperdiploid (JB and BN) cell lines. Using our animal models, we also established bortezomib‐sensitive and ‐resistant BN lines. These cell lines were cellularly, phenotypically and molecularly characterized using flow cytometry immunophenotyping, DNA content, G‐band and multicolor spectral karyotyping (SKY) and global gene expression profiling. All four cell lines were infected with lentiviral‐expressing luciferase for detection of tumour cells at high sensitivity level and for monitoring myeloma growth in co‐cultures and in vivo by live animal imaging. These myeloma cell lines and the procedures used for their establishment provide essential tools for studying myeloma biology and therapy.
Horizontal and vertical movements of juvenile bluefin tuna (Thunnus orientalis) in relation to seasons and oceanographic conditions in the eastern Pacific Ocean
Authors: KITAGAWA TAKASHI , BOUSTANY ANDRE M. , FARWELL CHARLES J. , WILLIAMS THOMAS D. , CASTLETON MICHAEL R. , BLOCK BARBARA A.
Published: August 2007

Electronically tagged juvenile Pacific bluefin, Thunnus orientalis, were released off Baja California in the summer of 2002. Time‐series data were analyzed for 18 fish that provided a record of 380 ± 120 days (mean ± SD) of ambient water and peritoneal cavity temperatures at 120 s intervals. Geolocations of tagged fish were estimated based on light‐based longitude and sea surface temperature‐based latitude algorithms. The horizontal and vertical movement patterns of Pacific bluefin were examined in relation to oceanographic conditions and the occurrence of feeding events inferred from thermal fluctuations in the peritoneal cavity. In summer, fish were located primarily in the Southern California Bight and over the continental shelf of Baja California, where juvenile Pacific bluefin use the top of the water column, undertaking occasional, brief forays to depths below the thermocline. In autumn, bluefin migrated north to the waters off the Central California coast when thermal fronts form as the result of weakened equatorward wind stress. An examination of ambient and peritoneal temperatures revealed that bluefin tuna fed during this period along the frontal boundaries. In mid‐winter, the bluefin returned to the Southern California Bight possibly because of strong downwelling and depletion of prey species off the Central California waters. The elevation of the mean peritoneal cavity temperature above the mean ambient water temperature increased as ambient water temperature decreased. The ability of juvenile bluefin tuna to maintain a thermal excess of 10°C occurred at ambient temperatures of 11–14°C when the fish were off the Central California coast. This suggests that the bluefin maintain peritoneal temperature by increasing heat conservation and possibly by increasing internal heat production when in cooler waters. For all of the Pacific bluefin tuna, there was a significant correlation between their mean nighttime depth and the visible disk area of the moon.
Job satisfaction and importance for intensive care unit research coordinators: results from binational survey
Authors: Rickard Claire M , Roberts Brigit L , Foote Jonathon , McGrail Matthew R
Published: August 2007

Objective. To measure Intensive Care Unit Research coordinator job satisfaction and importance and to identify priorities for role development.

Background. Research coordinator numbers are growing internationally in response to increasing clinical research activity. In Australia, 1% of registered nurses work principally in research, many as Research coordinators. Internationally, the Association of Clinical Research Professionals currently has 6536 certified Research coordinators in 13 countries, with likely additional large numbers practicing without the voluntary certification. Research coordinators are almost always nurses, but little is know about this emerging specialty.

Design. Cross‐sectional study using anonymous self‐report questionnaire.

Methods. After ethics approval, the McCloskey–Mueller Satisfaction Scale and McCloskey–Mueller Importance Scale were administered via the Internet. The sample was 49 (response rate 71%) Research coordinators from the Australia and New Zealand Intensive Care Unit Research coordinators’ Interest Group.

Results. Research coordinators were satisfied with structural aspects of the position working business hours; flexibility of working hours; high levels of responsibility and control over their work. Dissatisfaction was expressed regarding: remuneration and recognition; compensation for weekend work; salary package; career advancement opportunities; and childcare facilities.

Conclusions. High priorities for role development are those rated highly important but with much lower satisfaction. These are: compensation for weekend call‐out work; salary and remuneration package; recognition by management and clinicians; career advancement opportunities; departmental research processes; encouragement and feedback; and number of working hours.

Relevance to clinical practice. Increasing numbers of nurses have been attracted to this clinically based research position. These data contribute to the understanding and development of the role.
Genetics and evolution of weedy Helianthus annuus populations: adaptation of an agricultural weed
Authors: KANE NOLAN C. , RIESEBERG LOREN H.
Published: August 2007

Agricultural weeds are a major cost to economies throughout the world, and have evolved from numerous plant species in many different plant families. Despite their ubiquity, we do not yet know how easily or often weeds evolve from their wild ancestors or the kinds of genes underlying their evolution. Here we report on the evolution of weedy populations of the common sunflower Helianthus annuus. We analysed 106 microsatellites in 48 individuals from each of six wild and four weed populations of the species. The statistical tests lnRV and lnRH were used to test for significant reductions in genetic variability at each locus in weedy populations compared to nearby wild populations. Between 1% and 6% of genes were significant outliers with reduced variation in weedy populations, implying that a small but not insignificant fraction of the genome may be under selection and involved in adaptation of weedy sunflowers. However, there did not appear to be a substantial reduction in variation across the genome, suggesting that effective population sizes have remained very large during the recent evolution of these weedy populations. Additional analyses showed that weedy populations are more closely related to nearby wild populations than to each other, implying that weediness likely evolved multiple times within the species, although a single origin followed by gene flow with local populations cannot be ruled out. Together, our results point to the relative ease with which weedy forms of this species can evolve and persist despite the potentially high levels of geneflow with nearby wild populations.
Experimental studies of evolution in guppies: a model for understanding the evolutionary consequences of predator removal in natural communities
Authors: REZNICK DAVID N. , GHALAMBOR CAMERON K. , CROOKS KEVIN
Published: August 2007

Guppies (Poecilia reticulata) in Trinidadian streams are found with a diversity of predators in the lower reaches of streams, but few predators in the headwaters. These differences have caused the adaptive evolution of guppy behaviour, morphology, male colouration and life history. Waterfalls often serve as barriers to the upstream distribution of predators and/or guppies. Such discontinuities make it possible to treat streams like giant test tubes by introducing guppies or predators to small segments of streams from which they were previously excluded. Such experiments enable us to document how fast evolution can occur and the fine spatial scales over which adaptation is possible. They also demonstrate that the role predators play in structuring this ecosystem resembles many others studied from a more purely ecological perspective; in these streams, as elsewhere, predators depress the numbers of individuals in prey species which in turn reduces the effects of the prey species on other trophic levels and hence the structure of the ecosystem. A focus on predators is important in conservation biology because predators are often the organisms that are most susceptible to local extinction. Their selective loss occurs because large predators have been deliberately exterminated and/or are more susceptible to environmental disturbances. Furthermore, we will argue that predator re‐introductions might be destabilizing if, in the absence of predators, their prey have evolved in a fashion that makes them highly susceptible to predation, even after time intervals as short as 50–100 years. A better understanding of the evolutionary impacts of top predators will be critical goal for the policy and practice of large carnivore restoration in the future.
Filaria/Wolbachia activation of dendritic cells and development of Th1‐associated responses is dependent on Toll‐like receptor 2 in a mouse model of ocular onchocerciasis (river blindness)
Authors: DAEHNEL K. , GILLETTE‐FERGUSON I. , HISE A. G. , DIACONU E. , HARLING M. J. , HEINZEL F. P. , PEARLMAN E.
Published: August 2007

Toll‐like receptors (TLRs) regulate dendritic cell function and activate signals that mediate the nature of the adaptive immune response. The current study examined the role of TLRs in dendritic cell activation and in regulating T cell and antibody responses to antigens from the filarial parasites Onchocerca volvulus and Brugia malayi, which cause river blindness and lymphatic filariasis, respectively. Bone‐marrow‐derived CD11c+ cells from C57BL/6 and TLR4−/– mice produced high levels of IL‐6 and RANTES, and showed elevated surface CD40 expression, whereas CD11c+ cells from myeloid differentiation factor 88−/– (MyD88−/–), TLR2−/– and TLR2/4−/– mice were not activated. Similarly, IFN‐γ production by splenocytes from immunized TLR2−/– mice was significantly impaired compared with splenocytes from C57BL/6 and TLR4−/– mice. In contrast, there was no difference among these strains in Th2‐associated responses including IL‐5 production by splenocytes from immunized animals, serum IgE and IgG1, or eosinophil infiltration into the corneal stroma. Neutrophil recruitment to the cornea and CXC chemokine production was inhibited in immunized TLR2−/– mice compared with C57BL/6 and TLR4−/– mice. Taken together, these findings demonstrate an essential role for TLR2 in filaria‐induced dendritic cell activation, IFN‐γ production and neutrophil migration to the cornea, but does not affect filaria‐induced Th2‐associated responses.