bluuebunny/crossref_metadata_2025 huggingface dataset:
Biomagnetic of Apatite-Coated Cobalt Ferrite: A Core–Shell Particle for Protein Adsorption and pH-Controlled Release
Authors: Tang I-Ming , Krishnamra Nateetip , Charoenphandhu Narattaphol , Hoonsawat Rassmidara , Pon-On Weeraphat
Published: August 2010

Magnetic nanoparticle composite with a cobalt ferrite (CoFe2O4, (CF)) core and an apatite (Ap) coating was synthesized using a biomineralization process in which a modified simulated body fluid (1.5SBF) solution is the source of the calcium phosphate for the apatite formation. The core–shell structure formed after the citric acid–stabilized cobalt ferrite (CFCA) particles were incubated in the 1.5 SBF solution for 1 week. The mean particle size of CFCA-Ap is about 750 nm. A saturation magnetization of 15.56 emug-1 and a coercivity of 1808.5 Oe were observed for the CFCA-Ap obtained. Bovine serum albumin (BSA) was used as the model protein to study the adsorption and release of the proteins by the CFCA-Ap particles. The protein adsorption by the CFCA-Ap particles followed a more typical Freundlich than Langmuir adsorption isotherm. The BSA release as a function of time became less rapid as the CFCA-Ap particles were immersed in higher pH solution, thus indicating that the BSA release is dependent on the local pH.
Hautkrebsvorsorge
Authors: Kolm Isabell , Hofbauer Günther , Braun Ralph P.
Published: August 2010

Die Haut ist das Organ, das am häufigsten von malignen Erkrankungen befallen wird. In den letzten Jahren wurden neue nicht invasive Techniken zur Frühdiagnose des Melanoms immer populärer. Dermatoskopie, Ganzkörperübersichtsphotographie, digitale Dermatoskopie werden immer häufiger von Dermatologen eingesetzt um Muttermale frühzeitig von Melanomen unterscheiden zu können. Einen neuen, vielversprechenden Ansatz der nicht invasiven Diagnostik des Melanoms stellt die konfokale Mikroskopie dar. Der epitheliale oder „weißer“ Hautkrebs (Basalzellkarzinom und spinozelluläres Karzinom) ist die häufigste Krebsform beim Menschen überhaupt. Beide Karzinomarten können mit konsequentem Sonnenschutz verhindert werden. Früh erkannt, ist weißer Hautkrebs durch invasive und nicht-invasive Verfahren gut heilbar.
Aktuelle Therapie des Melanoms der Haut
Authors: Dummer Reinhard , Goldinger Simone M. , Sailer Eva , French Lars E.
Published: August 2010

Große Metaanalysen der verfügbaren Daten zu Interferon-alpha zeigen, dass die Substanz in der adjuvanten Situation einen positiven Einfluss auf rezidivfreies und fernmetastasenfreies Überleben ausübt. Entsprechend der Ergebnisse großer, prospektiv randomisierter Studien, die weltweit durchgeführt werden, ergeben sich heute klare Hinweise dafür, dass eine langfristige, eher niedrig dosierte Interferon-Therapie bei Patienten mit Mikrometastasen zu erwägen ist. Bei Patienten mit Fernmetastasierung wird eine systemische Therapie angestrebt. Bis anhin gibt es keine Behandlung, die das Gesamtüberleben im fortgeschrittenen Stadium der Fernmetastasierung verlängern kann. Deshalb wird gemäß den aktuellen internationalen Richtlinien eine Therapie im Rahmen einer klinischen Studie an einem Referenzzentrum empfohlen [1].
Sudden and gradual compaction of shallow brittle porous rocks
Authors: Sleep Norman H.
Published: August 2010

Porous brittle rocks fail in shear and compaction. Rate and state friction describes such failure on a planar surface, while end‐cap failure describes the failure of a continuum. Both formalisms include Coulomb failure in shear at low normal tractions. Rate and state friction includes slow compaction of gouge by normal traction when shearing is not occurring. Rate and state friction also represents slow compaction of porous sandstone. End‐cap failure includes both grain crushing and shear. Micromechanically, all these mechanisms involve exponential creep at stresses of a few gigapascals. Rate and state friction is modeled by tabular real contacts where shear and extrusion occur. The observed compaction rate depends on the normal traction to a modest power of ∼27 for gouge and ∼10 for sandstone. End‐cap failure involves grain cracking in the neighborhood of the grain‐grain contact. Its rate should depend on the normal traction raised to a power of ∼100. This strong rate dependence is not measurable in practice as a failure cascade commences once some grains crack. Materials with pointy contacts including unwelded tuff and “regolith” in the uppermost tens of meters that has repeatedly been damaged by strong seismic waves compact in this manner at dynamic stresses modestly above their ambient lithostatic stress. This failure produces significant nonlinear attenuation of compressional P waves with sustained dynamic accelerations that are a modest fraction of the ambient acceleration of gravity.
Radiated seismic energy from coda measurements and no scaling in apparent stress with seismic moment
Authors: Baltay Annemarie , Prieto German , Beroza Gregory C.
Published: August 2010

The seismic coda consists of scattered waves that leave the earthquake source in a variety of directions. The averaging of source radiation that results leads to stable ground motion spectra that we use as the basis for a robust measurement of radiated wave energy. We apply an empirical Green's function (EGF) method to the seismic coda in order to investigate scaling of the radiated seismic energy. We correct for path effects in the spectra of earthquakes by using a stack of closely located, small earthquakes as an EGF. We apply this approach to four earthquake sequences in western North America that span a magnitude range from Mw 3.0–Mw 7.1. Our estimates of scaled energy are consistent with independent measurements, where available. We find no dependence in individual seismic energy estimates on source‐station distance, which validates the EGF approximation. We find that a constant scaled energy of 3.5 × 10−5 provides a reasonable fit to the data, with no dependence of the scaled energy on seismic moment.
Gravity anomalies of the Northern Hawaiian Islands: Implications on the shield evolutions of Kauai and Niihau
Authors: Flinders Ashton F. , Ito Garrett , Garcia Michael O.
Published: August 2010

New land and marine gravity data reveal two positive residual gravity anomalies in the Northern Hawaiian Islands: one over Kaua'i, the other between the islands of Kaua'i and Ni'ihau. These gravitational highs are similar in size and magnitude to those of other Hawaiian volcanoes, indicating local zones of high‐density crust, attributed to olivine cumulates in solidified magma reservoirs. The residual gravity high over Kaua'i is located in the Līhu'e Basin, offset 8‐12 km east of Kaua'i's geologically mapped caldera. This offset suggests that the mapped caldera is a collapsed feature later filled in with lava and not the long‐term center of Kaua'i shield volcanism. A second residual gravity high, in the submarine channel between Kaua'i and Ni'ihau, marks the volcanic center of the Ni'ihau shield volcano. This second residual gravity anomaly implies that Ni'ihau's eastern boundary extended ∼20 km east of its present location. Through inversion, the residual gravity anomalies were modeled as being produced by two solidified magma reservoirs with average densities of 3100 kg/m3 and volumes between 2470 and 2540 km3. Considering the locations and sizes of the residual gravity anomalies/magma reservoirs, the extent of the two islands' paleoshorelines and potassium‐argon dating of shield‐stage lavas, we conclude that the two islands were not connected subaerially during their respective shield stages and that Ni'ihau's topographic summit was removed by an eastern flank collapse between 4.3 and 5.6 Ma. Continued constructional volcanism on western Kaua'i likely covered much of the submerged remains of eastern Ni'ihau.
Global canopy interception from satellite observations
Authors: Miralles Diego G. , Gash John H. , Holmes Thomas R. H. , de Jeu Richard A. M. , Dolman A. J.
Published: August 2010

A new methodology for estimating forest rainfall interception from multisatellite observations is presented. The Climate Prediction Center morphing technique (CMORPH) precipitation product is used as driving data and is applied to Gash's analytical model to derive daily interception rates at global scale. Results compare well with field observations of rainfall interception (R = 0.86, n = 42). Global estimates are presented and spatial differences in the distribution of interception over different ecosystems analyzed. According to our findings, interception loss is responsible for the evaporation of approximately 13% of the total incoming rainfall over broadleaf evergreen forests, 19% in broadleaf deciduous forests, and 22% in needleleaf forests. The product is sensitive to the volume of rainfall, rain intensity, and forest cover. In combination with separate estimates of transpiration it offers the potential to study the impact of climate change and deforestation on the dynamics of the global hydrological cycle.
Reservoir theory for studying the geochemical evolution of soils
Authors: Mudd Simon Marius , Yoo Kyungsoo
Published: August 2010

Linking mineral weathering rates measured in the laboratory to those measured at the landscape scale is problematic. In laboratory studies, collections of minerals are exposed to the same weathering environment over a fixed amount of time. In natural soils, minerals enter, are mixed within, and leave the soil via erosion and dissolution/leaching over the course of soil formation. The key to correctly comparing mineral weathering studies from laboratory experiments and field soils is to consistently define time. To do so, we have used reservoir theory. Residence time of a mineral, as defined by reservoir theory, describes the time length between the moment that a mineral enters (via soil production) and leaves (via erosion and dissolution/leaching) the soil. Age of a mineral in a soil describes how long the mineral has been present in the soil. Turnover time describes the time needed to deplete a species of minerals in the soil by sediment efflux from the soil. These measures of time are found to be sensitive to not only sediment flux, which controls the mineral fluxes in and out of a soil, but also internal soil mixing that controls the probability that a mineral survives erosion. When these measures of time are combined with published data suggesting that a mineral's dissolution reaction rate decreases during the course of weathering, we find that internal soil mixing, by partially controlling the age distribution of minerals within a soil, might significantly alter the soil's mass loss rate via chemical weathering.
Distribution of dissolved iron in Antarctic sea ice: Spatial, seasonal, and inter‐annual variability
Authors: Lannuzel Delphine , Schoemann Véronique , de Jong Jeroen , Pasquer Bénédicte , van der Merwe Pier , Masson Florence , Tison Jean‐Louis , Bowie Andrew
Published: August 2010

Results from recent field studies in Antarctic sea ice show no clear differences in dissolved iron (dFe) concentrations between pack ice sampled in East Antarctica (2.6–20.5 nmol/L), in the Weddell Sea (0.7–36.8 nmol/L), and in the Bellingshausen Sea (1.1–30.2 nmol/L). Dissolved Fe concentrations were also similar in land‐fast ice collected in East Antarctica (0.7–4.3 nmol/L) and in the Ross Sea (1.1–6.0 nmol/L). In contrast, we observed a remarkable seasonal drawdown of dFe in sea ice for all reported studies. Furthermore, large inter‐annual variations in depth‐averaged dFe and organic matter concentrations were observed in sea ice collected in the East Antarctic sector between expeditions in late austral winter‐spring of 2003 and 2007. Variability in the water column productivity and in the magnitude of the “new” Fe supply (e.g., upwelling, resuspended shelf sediments) at the time of sea ice formation could explain such differences.
An enhanced nonparametric streamflow disaggregation model with genetic algorithm
Authors: Lee T. , Salas J. D. , Prairie J.
Published: August 2010

Stochastic streamflow generation is generally utilized for planning and management of water resources systems. For this purpose, a number of parametric and nonparametric models have been suggested in literature. Among them, temporal and spatial disaggregation approaches play an important role particularly to make sure that historical variance‐covariance properties are preserved at various temporal and spatial scales. In this paper, we review the underlying features of existing nonparametric disaggregation methods, identify some of their pros and cons, and propose a disaggregation algorithm that is capable of surmounting some of the shortcomings of the current models. The proposed models hinge on k‐nearest neighbor resampling, the accurate adjusting procedure, and a genetic algorithm. The models have been tested and compared to an existing nonparametric disaggregation approach using data of the Colorado River system. It has been shown that the model is capable of (1) reproducing the season‐to‐season correlations including the correlation between the last season of the previous year and the first season of the current year, (2) minimizing or avoiding the generation of flow patterns across the year that are literally the same as those of the historical records, and (3) minimizing or avoiding the generation of negative flows. In addition, it is applicable to intermittent river regimes.
Downscaling soil moisture in the southern Great Plains through a calibrated multifractal model for land surface modeling applications
Authors: Mascaro Giuseppe , Vivoni Enrique R. , Deidda Roberto
Published: August 2010

Accounting for small‐scale spatial heterogeneity of soil moisture (θ) is required to enhance the predictive skill of land surface models. In this paper, we present the results of the development, calibration, and performance evaluation of a downscaling model based on multifractal theory using aircraft‐based (800 m) θ estimates collected during the southern Great Plains experiment in 1997 (SGP97). We first demonstrate the presence of scale invariance and multifractality in θ fields of nine square domains of size 25.6 × 25.6 km2, approximately a satellite footprint. Then, we estimate the downscaling model parameters and evaluate the model performance using a set of different calibration approaches. Results reveal that small‐scale θ distributions are adequately reproduced across the entire region when coarse predictors include a dynamic component (i.e., the spatial mean soil moisture 〈θ〉) and a stationary contribution accounting for static features (i.e., topography, soil texture, vegetation). For wet conditions, we found similar multifractal properties of soil moisture across all domains, which we ascribe to the signature of rainfall spatial variability. For drier states, the θ fields in the northern domains are more intermittent than in southern domains, likely because of differences in the distribution of vegetation coverage. Through our analyses, we propose a regional downscaling relation for coarse, satellite‐based soil moisture estimates, based on ancillary information (static and dynamic landscape features), which can be used in the study area to characterize statistical properties of small‐scale θ distribution required by land surface models and data assimilation systems.
Paving the seafloor: Volcanic emplacement processes during the 2005–2006 eruptions at the fast spreading East Pacific Rise, 9°50′N
Authors: Fundis A. T. , Soule S. A. , Fornari D. J. , Perfit M. R.
Published: August 2010

The 2005–2006 eruptions near 9°50′N at the East Pacific Rise (EPR) marked the first observed repeat eruption at a mid‐ocean ridge and provided a unique opportunity to deduce the emplacement dynamics of submarine lava flows. Since these new flows were documented in April 2006, a total of 40 deep‐towed imaging surveys have been conducted with the Woods Hole Oceanographic Institution's (WHOI) TowCam system. More than 60,000 digital color images and high‐resolution bathymetric profiles of the 2005–2006 flows from the TowCam surveys were analyzed for lava flow morphology and for the presence of kipukas, collapse features, faults and fissures. We use these data to quantify the spatial distributions of lava flow surface morphologies and to investigate how they relate to the physical characteristics of the ridge crest, such as seafloor slope, and inferred dynamics of flow emplacement. We conclude that lava effusion rate was the dominant factor controlling the observed morphological variations in the 2005–2006 flows. We also show that effusion rates were higher than in previously studied eruptions at this site and varied systematically along the length of the eruptive fissure. This is the first well‐documented study in which variations in seafloor lava morphology can be directly related to a well documented ridge‐crest eruption where effusion rate varied significantly.
A Theory of Limited Metabolic Energy and Premenstrual Syndrome Symptoms: Increased Metabolic Demands during the Luteal Phase Divert Metabolic Resources from and Impair Self-Control
Authors: Gailliot Matthew T. , Hildebrandt Britny , Eckel Lisa A. , Baumeister Roy F.
Published: August 2010

Numerous studies suggest that premenstrual syndrome (PMS) may be linked to impaired self-control since many of the symptoms of PMS are indicative of impaired self-control. Evidence links PMS to increased difficulty controlling emotions, attention, and fine motor movements; increased intake of alcohol, drugs, nicotine, caffeine, and food; impaired work performance, and increased stress, aggression, criminal behavior, interpersonal conflicts, and passivity. Empirical research demonstrates that self-control is metabolically expensive and, as such, can be impaired when metabolic energy (i.e., glucose) is low or processed ineffectively. The expression of PMS is tightly linked to the luteal phase of the menstrual cycle, a time in which considerable metabolic energy is allocated to the ovaries. This increased ovarian metabolic demand could, therefore, divert energy away from, and thereby impair, other processes during this phase of the menstrual cycle. Here, we propose a novel theory in which PMS symptoms are partly attributable to the diversion of metabolic energy to the ovaries and away from processes that benefit self-control.
Birth Cohort Differences in Self-Esteem, 1988–2008: A Cross-Temporal Meta-Analysis
Authors: Gentile Brittany , Twenge Jean M. , Campbell W. Keith
Published: August 2010

Three meta-analyses find increases over the generations in Rosenberg Self-Esteem scale (RSE) scores between 1988 and 2008 among American middle school ( d = 0.78, n = 10,119), high school ( d = 0.39, n = 16,669), and college students ( d = 0.30, n = 28,918). The changes are consistent with an increasing emphasis on self-worth in American culture and, for high school students, with small increases in academic competence over time. College students’ scores change only when the RSE is administered with a 4-point Likert scale with no midpoint. By 2008, a score of 40 (perfect self-esteem) was the modal response of college students, chosen by 18% of participants; 51% scored 35 or over. Given these shifts in responses, the possibility of revising the RSE is discussed.
The Science of Sex Appeal: An Evolutionary Perspective
Authors: Gallup Gordon G. , Frederick David A.
Published: August 2010

Growing evidence shows that features we find attractive in members of the opposite sex signal important underlying dimensions of health and reproductive viability. It has been discovered that men with attractive faces have higher quality sperm, women with attractive bodies are more fertile, men and women with attractive voices lose their virginity sooner, men who spend more money than they earn have more sex partners, and lap dancers make more tips when they are in the fertile phase of their menstrual cycle. This paper highlights recent evidence showing that the way we perceive other people has been shaped by our evolutionary history. An evolutionary approach provides a powerful tool for understanding the consistency and diversity of mating preferences and behaviors across individuals and cultures.
Dynamical typicality: Convergence of time evolved macro-observables to their mean values in random matrix models
Authors: Vidal Miranda P. A. , Mahler G.
Published: August 2010

Here we analyze the notion of dynamical typicality in large quantum random matrix models. By dynamical typicality we mean that different Hamiltonian systems evolve in time in a practically indistinguishable manner. We prove dynamical typicality for a Hamiltonian belonging to the Gaussian unitary ensemble (GUE) ensemble and argue in the conclusion why the same result is valid for more general Hamiltonians.
A connection between spin and statistics based on Galilean invariant delta functions
Authors: Kobayashi Masanori , de Montigny Marc , Khanna Faqir C.
Published: August 2010

We define Galilean invariant delta functions by using the Takahashi formulation, which describes particles with arbitrary spin. The direct calculation of the Galilean invariant delta functions in the (N+1)-dimensional Galilean covariant extended manifolds reveals that, for N odd, there exists a surface on which these delta functions vanish. This feature corresponds to the spacelike separation in the relativistic quantum field theory, and it enables us to discuss a connection between spin and statistics in the Galilean covariant theories. These results show that a spin-statistics connection holds for even-dimensional Galilean covariant extended manifolds; that is, for N-dimensional space-times with odd N≥5. Likewise, we observe that there is no such connection for odd-dimensional Galilean covariant extended manifolds; that is, for N-dimensional space-times with even N≥4. Thus, our results support the claim that there is no connection between spin and statistics in the usual nonrelativistic theory, for which N=4.
Ergodic theory and visualization. I. Mesochronic plots for visualization of ergodic partition and invariant sets
Authors: Levnajić Zoran , Mezić Igor
Published: August 2010

We present a computational study of a visualization method for invariant sets based on ergodic partition theory, first proposed by Mezić (Ph.D. thesis, Caltech, 1994) and Mezić and Wiggins [Chaos 9, 213 (1999)]. The algorithms for computation of the time averages of observables on phase space are developed and used to provide an approximation of the ergodic partition of the phase space. We term the graphical representation of this approximation—based on time averages of observables—a mesochronic plot (from Greek: meso—mean, chronos—time). The method is useful for identifying low-dimensional projections (e.g., two-dimensional slices) of invariant structures in phase spaces of dimensionality bigger than two. We also introduce the concept of the ergodic quotient space, obtained by assigning a point to every ergodic set, and provide an embedding method whose graphical representation we call the mesochronic scatter plot. We use the Chirikov standard map as a well-known and dynamically rich example in order to illustrate the implementation of our methods. In addition, we expose applications to other higher dimensional maps such as the Froéschle map for which we utilize our methods to analyze merging of resonances and, the three-dimensional extended standard map for which we study the conjecture on its ergodicity [I. Mezić, Physica D 154, 51 (2001)]. We extend the study in our next paper [Z. Levnajić and I. Mezić, e-print arXiv:0808.2182] by investigating the visualization of periodic sets using harmonic time averages. Both of these methods are related to eigenspace structure of the Koopman operator [I. Mezić and A. Banaszuk, Physica D 197, 101 (2004)].
Upper bounds on the number of eigenvalues of stationary Schrödinger operators
Authors: Shi Dai
Published: August 2010

In this article we provide several upper bounds on the number of eigenvalues, respectively, for Schrödinger operators of one-dimensional case, central potential case, and the case with point-interactions. Compared with Bargman’s and Calogero’s results, the new bounds can give finite estimates when the potential function has a heavy tail. Besides, a generalization of Calogero’s bound is given, which can be applied to bell shaped potential functions rather than merely monotonous ones. With respect to Schrödinger operators containing Dirac functions, some bounds are also established.
Dynamics of the plumes produced by ultrafast laser ablation of metals
Authors: Donnelly T. , Lunney J. G. , Amoruso S. , Bruzzese R. , Wang X. , Ni X.
Published: August 2010

We have analyzed ultrafast laser ablation of a metallic target (Nickel) in high vacuum addressing both expansion dynamics of the various plume components (ionic and nanoparticle) and basic properties of the ultrafast laser ablation process. While the ion temporal profile and ion angular distribution were analyzed by means of Langmuir ion probe technique, the angular distribution of the nanoparticulate component was characterized by measuring the thickness map of deposition on a transparent substrate. The amount of ablated material per pulse was found by applying scanning white light interferometry to craters produced on a stationary target. We have also compared the angular distribution of both the ionic and nanoparticle components with the Anisimov model. While the agreement for the ion angular distribution is very good at any laser fluence (from ablation threshold up to ≈1 J/cm2), some discrepancies of nanoparticle plume angular distribution at fluencies above ≈0.4 J/cm2 are interpreted in terms of the influence of the pressure exerted by the nascent atomic plasma plume on the initial hydrodynamic evolution of the nanoparticle component. Finally, analyses of the fluence threshold and maximum ablation depth were also carried out, and compared to predictions of theoretical models. Our results indicate that the absorbed energy is spread over a length comparable with the electron diffusion depth Lc (≈30 nm) of Ni on the timescale of electron-phonon equilibration and that a logarithmic dependence is well-suited for the description of the variation in the ablation depth on laser fluence in the investigated range.
Vector and axial anomaly in the Thirring–Wess model
Authors: Falco Pierluigi
Published: August 2010

We study the two dimensional vector meson model introduced by Thirring and Wess, that is to say the Schwinger model with massive photon and massless fermion. We prove, with a renormalization group approach, that the vector and axial Ward identities are broken by the Adler–Bell–Jackiw anomaly; and we rigorously establish three widely believed consequences: (a) the interacting meson-meson correlation equals a free boson propagator, although the mass is additively renormalized by the anomaly; (b) the anomaly is quadratic in the charge, in agreement with the Adler–Bardeen formula; (c) the fermion-fermion correlation has an anomalous long-distance decay.
Design of a standalone-type beryllium vessel for high-pressure protein crystallography
Authors: Suzuki Yoshihisa , Tsukamoto Masayuki , Sakuraba Haruhiko , Matsumoto Masamitsu , Nagasawa Makoto , Tamura Katsuhiro
Published: August 2010

A standalone-type beryllium (Be) high-pressure crystallography vessel has been developed. Using a coupler-joint unit and a pressure valve, we could keep the pressure in the vessel constant at 100±1 MPa for more than 24 h without connecting to a pressure-generating apparatus. Diffraction spots of a glucose isomerase (GI) crystal under 100 MPa were collected using the vessel and a rotating copper-anode in-house x-ray generator (0.8 kW). We successfully collected a 2.0 Å resolution data set of a 0.5 mm size GI crystal in an aqueous solution at 100 MPa.
Annealing induced anomalous electrical transport behavior in SnO2 thin films prepared by pulsed laser deposition
Authors: Ke C. , Yang Z. , Pan J. S. , Zhu W. , Wang L.
Published: August 2010

SnO 2 thin films were deposited on quartz substrates by pulsed laser deposition and postannealed at different temperatures in oxygen ambience. X-ray diffraction, Hall measurement, and x-ray photoelectron spectroscopy were employed to investigate the properties of the annealed SnO2 thin films. An anomalous electrical transport behavior as a function of the annealing temperature was observed. Both the growth of the crystal grain and oxygen vacancy density variation in the annealing process have been identified to be responsible for the transition of electrical transport properties.
The role of stochasticity on compactness of the native state of protein peptide backbone
Authors: Figueirêdo P. H. , Moret M. A. , Coutinho S. , Nogueira E.
Published: August 2010

A restricted angular random-walk model to build up polypeptide structures, which encompasses properties of the dihedral-angle Ramachandran map of folded proteins, is proposed to study the role of stochasticity on the compactness of the native state of proteins. Sample structures will be built with lengths ranging from 125 up to 400 amino acids for the different fractions of secondary structure motifs, from which dihedral angles were randomly chosen according to narrow Gaussian probability distributions. Physical properties of these polypeptide protein backbones such as the radius of gyration, the compactness parameter, the number of contacts, and the associated energy were computed and analyzed from an ensemble of thousands of realizations of protein peptide chains built with different rates of α-helix or β-strand motifs. Such geometric and physical parameters are compared to data from several globular proteins extracted from the Protein Data Bank indicating that a certain (small fraction) randomness is an essential ingredient for achieving the folded state of proteins, suggesting that they are neither driven by deterministic nor random-walk processes.
Experimental validation of the theory of wall effect on dielectrophoresis
Authors: Lo Y. J. , Lei U.
Published: August 2010

Many dielectrophoretic manipulations of particles are performed near walls. The theory of wall effect on dielectrophoresis was recently reported but not experimentally validated. Two experiments with polystyrene particles in deionized water were performed. The dielectrophoretic force normal to an insulated wall is validated by balancing it with buoyancy in an inclined rectangular channel subject to a uniform electric field. The dielectrophoretic force parallel to the wall is validated by balancing it with fluid drag in a diverging channel subject to a radial field. The measurements agree with theory within 7.4% and 8.1% discrepancies, for the normal and parallel forces, respectively.
A frequency-addressed plasmonic switch based on dual-frequency liquid crystals
Authors: Liu Yan Jun , Hao Qingzhen , Smalley Joseph S. T. , Liou Justin , Khoo Iam Choon , Huang Tony Jun
Published: August 2010

A frequency-addressed plasmonic switch was demonstrated by embedding a uniform gold nanodisk array into dual-frequency liquid crystals (DFLCs). The optical properties of the hybrid system were characterized by extinction spectra of localized surface plasmon resonances (LSPRs). The LSPR peak was tuned using a frequency-dependent electric field. A ∼4 nm blueshift was observed for frequencies below 15 kHz, and a 23 nm redshift was observed for frequencies above 15 kHz. The switching time for the system was ∼40 ms. This DFLC-based active plasmonic system demonstrates an excellent, reversible, frequency-dependent switching behavior and could be used in future integrated nanophotonic circuits.
One-dimensional Si-in-Si(001) template for single-atom wire growth
Authors: Owen J. H. G. , Bianco F. , Köster S. A. , Mazur D. , Bowler D. R. , Renner Ch.
Published: August 2010

Single atom metallic wires of arbitrary length are of immense technological and scientific interest. We present atomic-resolution scanning tunneling microscope data of a silicon-only template, which modeling predicts to enable the self-organized growth of isolated micrometer long surface and subsurface single-atom chains. It consists of a one-dimensional, defect-free Si reconstruction four dimers wide—the Haiku core—formed by hydrogenation of self-assembled Bi-nanolines on Si(001) terraces, independent of any step edges. We discuss the potential of this Si-in-Si template as an appealing alternative to vicinal surfaces for nanoscale patterning.
Viscous spreading of an inertial wave beam in a rotating fluid
Authors: Cortet Pierre-Philippe , Lamriben Cyril , Moisy Frédéric
Published: August 2010

We report experimental measurements of inertial waves generated by an oscillating cylinder in a rotating fluid. The two-dimensional wave takes place in a stationary cross-shaped wavepacket. Velocity and vorticity fields in a vertical plane normal to the wavemaker are measured by a corotating particle image velocimetry system. The viscous spreading of the wave beam and the associated decay of the velocity and vorticity envelopes are characterized. They are found in good agreement with the similarity solution of a linear viscous theory, derived under a quasiparallel assumption similar to the classical analysis of Thomas and Stevenson [“A similarity solution for viscous internal waves,” J. Fluid Mech. 54, 495 (1972)] for internal waves.
Dynamics of the triple contact line on a nonisothermal heater at partial wetting
Authors: Nikolayev Vadim S.
Published: August 2010

The dynamics of the triple gas-liquid-solid contact line is analyzed for the case where the gas is the saturated vapor corresponding to the liquid. For partial wetting conditions, a nonstationary contact line problem where the contact line motion is caused by evaporation or condensation is treated. It is shown that the Navier slip condition alone is not sufficient to relax the hydrodynamic contact line singularity: the Marangoni term is equally important when the heat transfer is involved. The transient heat conduction inside the heater is accounted for. A multiscale problem of drop evaporation with freely moving contact line is solved in the lubrication approximation as an illustration of the proposed approach.
Millimeter-wave generation via frequency multiplication in graphene
Authors: Dragoman M. , Neculoiu D. , Deligeorgis G. , Konstantinidis G. , Dragoman D. , Cismaru A. , Muller A. A. , Plana R.
Published: August 2010

In this letter, we demonstrate that a graphene monolayer, over which three metallic electrodes forming a coplanar waveguide are patterned, acts as a frequency multiplier and generates frequencies at least up to 40 GHz. These results show that monolayer graphene is a natural frequency multiplier.
Compression of complicated rf pulses produced from the super-radiant backward-wave oscillator
Authors: Savilov A. V.
Published: August 2010

Theory of a backward-wave electron oscillator, which operates in the nonstationary regime of the super-radiation of short powerful rf pulses, is developed. In some regimes of this auto-oscillator, complicated two-peak rf pulses are produced. It is shown that such rf pulses can be easily compressed into single-peak pulses. This provides a significant enhancement of the peak rf power.
Structural origin of the high glass-forming ability in Gd doped bulk metallic glasses
Authors: Yang Liang , Guo Gu-Qing
Published: August 2010

The structural origin of the high glass-forming ability (GFA) in Gd-doped CuZrAl bulk metallic glasses was investigated via synchrotron radiation techniques combined with simulations. It is found that 2 at. % Gd addition increases and stabilizes the solute-centered clusters, which leads to the relatively high atomic- and cluster-level packing efficiency and GFA in Cu46Zr45Al7Gd2 alloy. However, the presence of Al–Gd solute-solute bonding in Cu46Zr42Al7Gd5 decreases the packing efficiency, deteriorating the GFA of this alloy. These findings may extend our understanding on the sensitive dependence of GFA on the concentration of doping atoms in a number of multicomponent bulk metallic glasses.
Perssoniella and the genera of Schistochilaceae: a new classification based on molecular phylogenies
Authors: He Xiaolan , Glenny David
Published: August 2010

The monotypic genus Perssoniella with P. vitreocincta Herzog, endemic to New Caledonia, possesses a series of unique morphological characters and it has been assumed that the genus, assigned to the family Perssoniellaceae and suborder Perssoniellineae, is very isolated but sister to the family Schistochilaceae. The systematic identity of Perssoniella vitreocincta was studied using DNA sequence data for the chloroplast rbcL, rps4 and trnL-F regions. Our analyses placed Perssoniella vitreocincta within the family Schistochilaceae, and within Schistochila itself, with strong support. It suggests that retaining Perssoniella as an independent genus is untenable and we transfer it to the genus Schistochila. Our results indicate that Perssoniella vitreocincta is not an archaic species, as presupposed earlier. The differentiating characters in Perssoniella are mostly probably later derived, rather than ancestral. Our analyses also placed Pachyschistochila and Paraschistochila within Schistochila, again with strong support. We also transfer these two genera to Schistochila.
Find-me and eat-me signals in apoptotic cell clearance: progress and conundrums
Authors: Ravichandran Kodi S.
Published: August 2010

Everyday we turnover billions of cells. The quick, efficient, and immunologically silent disposal of the dying cells requires a coordinated orchestration of multiple steps, through which phagocytes selectively recognize and engulf apoptotic cells. Recent studies have suggested an important role for soluble mediators released by apoptotic cells that attract phagocytes (“find-me” signals). New information has also emerged on multiple receptors that can recognize phosphatidylserine, the key “eat-me” signal exposed on the surface of apoptotic cells. This perspective discusses recent exciting progress, gaps in our understanding, and the conflicting issues that arise from the newly acquired knowledge.
Sliding set-points of immune responses for therapy of autoimmunity
Authors: Hsieh Chyi-Song , Bautista Jhoanne Lynne
Published: August 2010

Although recent developments in the treatment of autoimmune disease have dramatically improved patient outcomes, these medications are not curative. Two studies in this issue demonstrate the feasibility of curing spontaneous autoimmunity in animal models via short-term enhancement of naturally arising regulatory T (T reg) cells, a subset of CD4+ T cells needed for maintaining self-tolerance. Importantly, these therapies seemed to generate a new equilibrium, or “set-point,” at which self-tissue damage no longer occurred long after the drug was eliminated from the body.
Post-tetanic increase in the fast-releasing synaptic vesicle pool at the expense of the slowly releasing pool
Authors: Lee Jae Sung , Ho Won-Kyung , Lee Suk-Ho
Published: August 2010

Post-tetanic potentiation (PTP) at the calyx of Held synapse is caused by increases not only in release probability (Pr) but also in the readily releasable pool size estimated from a cumulative plot of excitatory post-synaptic current amplitudes (RRPcum), which contribute to the augmentation phase and the late phase of PTP, respectively. The vesicle pool dynamics underlying the latter has not been investigated, because PTP is abolished by presynaptic whole-cell patch clamp. We found that supplement of recombinant calmodulin to the presynaptic pipette solution rescued the increase in the RRPcum after high-frequency stimulation (100 Hz for 4-s duration, HFS), but not the increase in Pr. Release-competent synaptic vesicles (SVs) are heterogeneous in their releasing kinetics. To investigate post-tetanic changes of fast and slowly releasing SV pool (FRP and SRP) sizes, we estimated quantal release rates before and 40 s after HFS using the deconvolution method. After HFS, the FRP size increased by 19.1% and the SRP size decreased by 25.4%, whereas the sum of FRP and SRP sizes did not increase. Similar changes in the RRP were induced by a single long depolarizing pulse (100 ms). The post-tetanic complementary changes of FRP and SRP sizes were abolished by inhibitors of myosin II or myosin light chain kinase. The post-tetanic increase in the FRP size coupled to a decrease in the SRP size provides the first line of evidence for the idea that a slowly releasing SV can be converted to a fast releasing one.
Fatty acid modulation and polyamine block of GluK2 kainate receptors analyzed by scanning mutagenesis
Authors: Wilding Timothy J. , Chen Kevin , Huettner James E.
Published: August 2010

RNA editing of kainate receptor subunits at the Q/R site determines their susceptibility to inhibition by cis-unsaturated fatty acids as well as block by cytoplasmic polyamines. Channels comprised of unedited (Q) subunits are strongly blocked by polyamines, but insensitive to fatty acids, such as arachidonic acid (AA) and docosahexaenoic acid (DHA), whereas homomeric edited (R) channels resist polyamine block but are inhibited by AA and DHA. In the present study, we have analyzed fatty acid modulation of whole-cell currents mediated by homomeric recombinant GluK2 (formerly GluR6) channels with individual residues in the pore-loop, M1 and M3 transmembrane helices replaced by scanning mutagenesis. Our results define three abutting surfaces along the M1, M2, and M3 helices where gain-of-function substitutions render GluK2(Q) channels susceptible to fatty acid inhibition. In addition, we identify four locations in the M3 helix (F611, L614, S618, and T621) at the level of the central cavity where Arg substitution increases relative permeability to chloride and eliminates polyamine block. Remarkably, for two of these positions, L614R and S618R, exposure to fatty acids reduces the apparent chloride permeability and potentiates whole-cell currents ∼5 and 2.5-fold, respectively. Together, our results suggest that AA and DHA alter the orientation of M3 in the open state, depending on contacts at the interface between M1, M2, and M3. Moreover, our results demonstrate the importance of side chains within the central cavity in determining ionic selectivity and block by cytoplasmic polyamines despite the inverted orientation of GluK2 as compared with potassium channels and other pore-loop family members.
A regulatory calcium-binding site at the subunit interface of CLC-K kidney chloride channels
Authors: Gradogna Antonella , Babini Elena , Picollo Alessandra , Pusch Michael
Published: August 2010

The two human CLC Cl− channels, ClC-Ka and ClC-Kb, are almost exclusively expressed in kidney and inner ear epithelia. Mutations in the genes coding for ClC-Kb and barttin, an essential CLC-K channel β subunit, lead to Bartter syndrome. We performed a biophysical analysis of the modulatory effect of extracellular Ca2+ and H+ on ClC-Ka and ClC-Kb in Xenopus oocytes. Currents increased with increasing [Ca2+]ext without full saturation up to 50 mM. However, in the absence of Ca2+, ClC-Ka currents were still 20% of currents in 10 mM [Ca2+]ext, demonstrating that Ca2+ is not strictly essential for opening. Vice versa, ClC-Ka and ClC-Kb were blocked by increasing [H+]ext with a practically complete block at pH 6. Ca2+ and H+ act as gating modifiers without changing the single-channel conductance. Dose–response analysis suggested that two protons are necessary to induce block with an apparent pK of ∼7.1. A simple four-state allosteric model described the modulation by Ca2+ assuming a 13-fold higher Ca2+ affinity of the open state compared with the closed state. The quantitative analysis suggested separate binding sites for Ca2+ and H+.

A mutagenic screen of a large number of extracellularly accessible amino acids identified a pair of acidic residues (E261 and D278 on the loop connecting helices I and J), which are close to each other but positioned on different subunits of the channel, as a likely candidate for forming an intersubunit Ca2+-binding site. Single mutants E261Q and D278N greatly diminished and the double mutant E261Q/D278N completely abolished modulation by Ca2+. Several mutations of a histidine residue (H497) that is homologous to a histidine that is responsible for H+ block in ClC-2 did not yield functional channels. However, the triple mutant E261Q/D278N/H497M completely eliminated H+ -induced current block. We have thus identified a protein region that is involved in binding these physiologically important ligands and that is likely undergoing conformational changes underlying the complex gating of CLC-K channels.
Dual roles of the sixth transmembrane segment of the CFTR chloride channel in gating and permeation
Authors: Bai Yonghong , Li Min , Hwang Tzyh-Chang
Published: August 2010

Cystic fibrosis transmembrane conductance regulator (CFTR) is the only member of the adenosine triphosphate–binding cassette (ABC) transporter superfamily that functions as a chloride channel. Previous work has suggested that the external side of the sixth transmembrane segment (TM6) plays an important role in governing chloride permeation, but the function of the internal side remains relatively obscure. Here, on a cysless background, we performed cysteine-scanning mutagenesis and modification to screen the entire TM6 with intracellularly applied thiol-specific methanethiosulfonate reagents. Single-channel amplitude was reduced in seven cysteine-substituted mutants, suggesting a role of these residues in maintaining the pore structure for normal ion permeation. The reactivity pattern of differently charged reagents suggests that the cytoplasmic part of TM6 assumes a secondary structure of an α helix, and that reactive sites (341, 344, 345, 348, 352, and 353) reside in two neighboring faces of the helix. Although, as expected, modification by negatively charged reagents inhibits anion permeation, interestingly, modification by positively charged reagents of cysteine thiolates on one face (344, 348, and 352) of the helix affects gating. For I344C and M348C, the open time was prolonged and the closed time was shortened after modification, suggesting that depositions of positive charges at these positions stabilize the open state but destabilize the closed state. For R352C, which exhibited reduced single-channel amplitude, modifications by two positively charged reagents with different chemical properties completely restored the single-channel amplitude but had distinct effects on both the open time and the closed time. These results corroborate the idea that a helix rotation of TM6, which has been proposed to be part of the molecular motions during transport cycles in other ABC transporters, is associated with gating of the CFTR pore.