bluuebunny/crossref_metadata_2025 huggingface dataset:
14-3-3 binding to LRRK2 is disrupted by multiple Parkinson's disease-associated mutations and regulates cytoplasmic localization
Authors: Nichols R. Jeremy , Dzamko Nicolas , Morrice Nicholas A. , Campbell David G. , Deak Maria , Ordureau Alban , Macartney Thomas , Tong Youren , Shen Jie , Prescott Alan R. , Alessi Dario R.
Published: July 2010

LRRK2 (leucine-rich repeat protein kinase 2) is mutated in a significant number of Parkinson's disease patients, but still little is understood about how it is regulated or functions. In the present study we have demonstrated that 14-3-3 protein isoforms interact with LRRK2. Consistent with this, endogenous LRRK2 isolated from Swiss 3T3 cells or various mouse tissues is associated with endogenous 14-3-3 isoforms. We have established that 14-3-3 binding is mediated by phosphorylation of LRRK2 at two conserved residues (Ser910 and Ser935) located before the leucine-rich repeat domain. Our results suggests that mutation of Ser910 and/or Ser935 to disrupt 14-3-3 binding does not affect intrinsic protein kinase activity, but induces LRRK2 to accumulate within discrete cytoplasmic pools, perhaps resembling inclusion bodies. To investigate links between 14-3-3 binding and Parkinson's disease, we studied how 41 reported mutations of LRRK2 affected 14-3-3 binding and cellular localization. Strikingly, we found that five of the six most common pathogenic mutations (R1441C, R1441G, R1441H, Y1699C and I2020T) display markedly reduced phosphorylation of Ser910/Ser935 thereby disrupting interaction with 14-3-3. We have also demonstrated that Ser910/Ser935 phosphorylation and 14-3-3 binding to endogenous LRRK2 is significantly reduced in tissues of homozygous LRRK2(R1441C) knock-in mice. Consistent with 14-3-3 regulating localization, all of the common pathogenic mutations displaying reduced 14-3-3-binding accumulated within inclusion bodies. We also found that three of the 41 LRRK2 mutations analysed displayed elevated protein kinase activity (R1728H, ~2-fold; G2019S, ~3-fold; and T2031S, ~4-fold). These results provide the first evidence suggesting that 14-3-3 regulates LRRK2 and that disruption of the interaction of LRRK2 with 14-3-3 may be linked to Parkinson's disease.
Crystal structure of the ALK (anaplastic lymphoma kinase) catalytic domain
Authors: Lee Christian C. , Jia Yong , Li Nanxin , Sun Xiuying , Ng Kenneth , Ambing Eileen , Gao Mu-Yun , Hua Su , Chen Connie , Kim Sungjoon , Michellys Pierre-Yves , Lesley Scott A. , Harris Jennifer L. , Spraggon Glen
Published: July 2010

ALK (anaplastic lymphoma kinase) is an RTK (receptor tyrosine kinase) of the IRK (insulin receptor kinase) superfamily, which share an YXXXYY autophosphorylation motif within their A-loops (activation loops). A common activation and regulatory mechanism is believed to exist for members of this superfamily typified by IRK and IGF1RK (insulin-like growth factor receptor kinase-1). Chromosomal translocations involving ALK were first identified in anaplastic large-cell lymphoma, a subtype of non-Hodgkin's lymphoma, where aberrant fusion of the ALK kinase domain with the NPM (nucleophosmin) dimerization domain results in autophosphosphorylation and ligand-independent activation. Activating mutations within the full-length ALK kinase domain, most commonly R1275Q and F1174L, which play a major role in neuroblastoma, were recently identified. To provide a structural framework for understanding these mutations and to guide structure-assisted drug discovery efforts, the X-ray crystal structure of the unphosphorylated ALK catalytic domain was determined in the apo, ADP- and staurosporine-bound forms. The structures reveal a partially inactive protein kinase conformation distinct from, and lacking, many of the negative regulatory features observed in inactive IGF1RK/IRK structures in their unphosphorylated forms. The A-loop adopts an inhibitory pose where a short proximal A-loop helix (αAL) packs against the αC helix and a novel N-terminal β-turn motif, whereas the distal portion obstructs part of the predicted peptide-binding region. The structure helps explain the reported unique peptide substrate specificity and the importance of phosphorylation of the first A-loop Tyr1278 for kinase activity and NPM–ALK transforming potential. A single amino acid difference in the ALK substrate peptide binding P−1 site (where the P-site is the phosphoacceptor site) was identified that, in conjunction with A-loop sequence variation including the RAS (Arg-Ala-Ser)-motif, rationalizes the difference in the A-loop tyrosine autophosphorylation preference between ALK and IGF1RK/IRK. Enzymatic analysis of recombinant R1275Q and F1174L ALK mutant catalytic domains confirms the enhanced activity and transforming potential of these mutants. The transforming ability of the full-length ALK mutants in soft agar colony growth assays corroborates these findings. The availability of a three-dimensional structure for ALK will facilitate future structure–function and rational drug design efforts targeting this receptor tyrosine kinase.
Rab11 regulates JNK and Raf/MAPK‐ERK signalling pathways during Drosophila wing development
Authors: Bhuin Tanmay , Roy Jagat K.
Published: July 2010

Developmental signalling pathways are regulated by intracellular vesicle trafficking in multicellular organisms. In our earlier communication, we have shown that mutation in Rab11 (a subfamily of the Ypt/Rab gene family) results in the activation of JNK signalling pathways in Drosophila eye. Here, we report that Rab11 regulates JNK and Raf/MAPK‐ERK signalling pathways during Drosophila wing development. Using immunofluorescence and immunohistochemical analyses, we show that overexpression of Rab11 in mutant wing imaginal disc cells triggers the induction of apoptosis and activation of JNK and ERK. Further, using a genetic approach it has been shown that Rab11 interacts with the components of these pathways during Drosophila wing development. In addition to this, in Rab11 mutant wing imaginal discs JNK activity was monitored using pucE69, a P‐lacZ enhancer‐trap line inserted in puckered (puc). A strong induction of puc in Rab11 mutant wing imaginal disc cells provided a strong support that Rab11 regulates the JNK signalling pathway during Drosophila wing development.
Attentional Regulation in Young Twins With Probable Stuttering, High Nonfluency, and Typical Fluency
Authors: Felsenfeld Susan , van Beijsterveldt Catharina Eugenie Maria , Boomsma Dorret Irene
Published: July 2010

Purpose

Using a sample of 20,445 Dutch twins, this study examined the relationship between speech fluency and attentional regulation in children. A secondary objective was to identify etiological overlap between nonfluency and poor attention using fluency-discordant twin pairs.

Method

Three fluency groups were created at age 5 using a parent questionnaire: (a) probable stuttering (PS;
N
= 826; 4.0%), highly nonfluent (HNF;
N
= 547; 2.7%), and typically fluent (TF;
N
= 19,072; 93%). Multiple scales assessing attention, primarily self-regulation/inhibition, were obtained from both parents when children were ages 5 and 7 and from teachers when children were age 7.

Results

When compared with the TF controls, both the PS and HNF children received higher (i.e., more problematic) scores on parental attention ratings at both ages (
p
< .002). Effect sizes were moderate for both groups. Teacher and parent ratings were generally comparable. The discordant co-twin analyses suggested that nonfluency and attention were influenced by potentially overlapping genetic and shared environmental factors.

Conclusions

The liability to express both high nonfluency and problems with self-regulation/inhibition may arise from a common set of pathogenic mechanisms. This supports emerging models of stuttering, which propose that poor fluency may be part of a broader network of impaired self-regulatory processes.
Classification of Speech and Language Profiles in 4-Year-Old Children With Cerebral Palsy: A Prospective Preliminary Study
Authors: Hustad Katherine C. , Gorton Kristin , Lee Jimin
Published: July 2010

Purpose

In this study, the authors proposed and tested a preliminary speech and language classification system for children with cerebral palsy.

Method

Speech and language assessment data were collected in a laboratory setting from 34 children with cerebral palsy (CP; 18 male, 16 female) with a mean age of 54 months (SD= 1.8). Measures of interest were vowel area, speech rate, language comprehension scores, and speech intelligibility ratings.

Results

Canonical discriminant function analysis showed that 3 functions accounted for 100% of the variance among profile groups, with speech variables accounting for 93% of the variance. Classification agreement varied from 74% to 97% based on 4 different classification paradigms.

Conclusions

The results of this study provide preliminary support for the classification of speech and language abilities of children with CP into 4 initial profile groups. Further research is necessary to validate the full classification system.
Delineating ‘Pervasiveness’ in Pervasive Information Systems: A Taxonomical Framework and Design Implications
Authors: Kourouthanassis Panos E , Giaglis George M , Karaiskos Dimitrios C
Published: July 2010

Pervasive Information Systems (IS) exemplify a paradigm where Information Technology is embedded in the physical environment, capable of accommodating user needs and wants when desired. Pervasive IS differ from IS that are based on the desktop paradigm In that they encompass a complex, dynamic environment composed of multiple artifacts, capable of perceiving contextual information and supporting user mobility. Building on the novel properties of pervasive IS, we propose a taxonomical framework assessing the level of ‘pervasiveness’ in a given information system. The framework consists of three interweaving dimensions, namely ubiquity (encompassing mobility and heterogeneity), diffusion (encompassing invisibility and interactivity) and contextual awareness. The framework may be employed either to prospectively inform the design of pervasive IS (by pointing towards pertinent design considerations) or to retrospectively assess the pervasiveness of a system and identify improvement opportunities. We demonstrate both uses, firstly by discussing design priorities for ex ante IS evaluation and secondly by showcasing ex post assessments of a domestic and a corporate pervasive IS.
In situ laser crystallization of amorphous silicon: Controlled nanosecond studies in the dynamic transmission electron microscope
Authors: Taheri M. L. , McGowan S. , Nikolova L. , Evans J. E. , Teslich N. , Lu J. P. , LaGrange T. , Rosei F. , Siwick B. J. , Browning N. D.
Published: July 2010

We describe an in situ method for studying the influence of deposited laser energy on microstructural evolution during nanosecond laser driven crystallization of amorphous Si. By monitoring microstructural evolution as a function of deposited energy in a dynamic transmission electron microscope (DTEM), information on grain size and defect concentration can be correlated directly with processing conditions. This work demonstrates that DTEM studies are a promising approach for obtaining fundamental information on nucleation and growth processes that have technological importance for the development of thin film transistors.
Piezoelectric thin-film superlattices without using piezoelectric materials
Authors: Sharma N. D. , Landis C. M. , Sharma P.
Published: July 2010

In this paper we show that experimentally realizable apparently piezoelectric thin-film superlattices can be created from nonpiezoelectric materials provided an odd-order (e.g., trilayer) stacking sequence is used. The size-dependent mechanism of flexoelectricity, which couples gradients of strain to polarization, allows such a possibility. We present closed-form analytical expressions for the response of various thin-film and superlattice configurations. We also clarify some of the subtleties that arise in considering interface boundary conditions in the theory of flexoelectricity as well as the relationship of flexoelectricity to the frequently used polarization gradient terms used in modeling ferroelectrics. We find that for certain (optimum) material combinations and length scales, thin-film superlattices yielding apparent piezoelectricity close to 75% of ferroelectric barium titanate may be achievable.
Comment on “Investigating hydration dependence of dynamics of confined water: Monolayer, hydration water, and Maxwell–Wagner processes” [J. Chem. Phys. 128, 154503 (2008)]
Authors: Ryabov Yaroslav , Gutina Anna , Feldman Yuri , Frunza Stefan , Frunza Ligia , Schönhals Andreas
Published: July 2010

This comment on the experimental methods and the conclusions of the paper “Investigating hydration dependence of dynamics of confined water: Monolayer, hydration water, and Maxwell–Wagner processes” [J. Sjöström et al., J. Chem. Phys.128, 154503 (2008)] exposes serious shortcomings in the understanding and the interpretation of the observed relaxation behavior of confined water presented in the article. There are contradictions between the suggested theory and the experimental observations that mislead the reader. In this comment we prove that the Maxwell–Wagner relaxation cannot explain the nonmonotonous temperature dependence for the process observed in confined water.
Adsorption of a wormlike polymer in a potential well near a hard wall: Crossover between two scaling regimes
Authors: Deng Mingge , Jiang Ying , Liang Haojun , Chen Jeff Z. Y.
Published: July 2010

We consider the adsorption of a semiflexible wormlike polymer to the surface of a flat wall by a square potential well of width W and depth v. Using a wormlike chain formalism that couples the orientational and positional degrees of freedom, for a wormlike chain much longer than the persistence length, we numerically calculate the adsorption phase diagram and analyze the scaling behavior near the phase transition. Our numerical results over a wide range of W can be used to identify scaling behaviors valid in the large and small width-to-persistence-length ratio as well as near the adsorption phase transition.
Symmetry and magnetoelectric interactions in BaMnF4
Authors: Zvezdin A. K. , Pyatakov A. P.
Published: July 2010

Symmetry analysis is used to study magnetic anisotropy and magnetoelectric interactions in the ferroelectric antiferromagnet BaMnF4 theoretically. It is shown that symmetry admits the existence in this material of a nonuniform magnetoelectric interaction (flexomagnetoelectric type) with a specific dependence on the magnitude and orientation of the external magnetic field. With increasing magnetic field this interaction can cause a phase transition into a magnetic incommensurate phase with a characteristic jump of the electric polarization. The linear and quadratic magnetoelectric effects and the question of the relativistic canting of the sublattices, which is due to the magnetoelectric interaction, are examined. The proposed approach is a natural generalization of the method of constructing invariants from the magnetic modes of the crystal to the case of phase transitions with a doubled unit cell of the crystal and can be used for symmetry analysis of other ferroelectric magnetic compounds.
Magnetoelectricity in the ferrimagnetic Cu2OSeO3: symmetry analysis and Raman scattering study
Authors: Gnezdilov V. P. , Lamonova K. V. , Pashkevich Yu. G. , Lemmens P. , Berger H. , Bussy F. , Gnatchenko S. L.
Published: July 2010

sublattices ferrimagnet Cu2OSeO3 with a cubic symmetry and a linear magnetoelectric effect. There is no spectroscopic evidence for structural lattice distortions below TC=60K, which are expected due to magnetoelectric coupling. Using symmetry arguments we explain this observation by considering a special type of ferrimagnetic ground state which does not generate a spontaneous electric polarization. Interestingly, Raman scattering shows a strong increase of electric polarization of media through a dynamic magnetoelectric effect as a remarkable enhancement of the scattering intensity below TC. New lines of purely magnetic origin have been detected in the magnetically ordered state. A part of them are attributed as scattering on exchange magnons. Using this observation and further symmetry considerations we argue for strong Dzyaloshinskii–Moriya interaction existing in the Cu2OSeO3.
Emergence of equilibrium thermodynamic properties in quantum pure states. I. Theory
Authors: Fresch Barbara , Moro Giorgio J.
Published: July 2010

Investigation on foundational aspects of quantum statistical mechanics recently entered a renaissance period due to novel intuitions from quantum information theory and to increasing attention on the dynamical aspects of single quantum systems. In the present contribution a simple but effective theoretical framework is introduced to clarify the connections between a purely mechanical description and the thermodynamic characterization of the equilibrium state of an isolated quantum system. A salient feature of our approach is the very transparent distinction between the statistical aspects and the dynamical aspects in the description of isolated quantum systems. Like in the classical statistical mechanics, the equilibrium distribution of any property is identified on the basis of the time evolution of the considered system. As a consequence equilibrium properties of quantum system appear to depend on the details of the initial state due to the abundance of constants of the motion in the Schrödinger dynamics. On the other hand the study of the probability distributions of some functions, such as the entropy or the equilibrium state of a subsystem, in statistical ensembles of pure states reveals the crucial role of typicality as the bridge between macroscopic thermodynamics and microscopic quantum dynamics. We shall consider two particular ensembles: the random pure state ensemble and the fixed expectation energy ensemble. The relation between the introduced ensembles, the properties of a given isolated system, and the standard quantum statistical description are discussed throughout the presentation. Finally we point out the conditions which should be satisfied by an ensemble in order to get meaningful thermodynamical characterization of an isolated quantum system.
Magnetic field induced spin reorientation in the strongly anisotropic antiferromagnetic crystal LiCoPO4
Authors: Kharchenko N. F. , Khrustalev V. M. , Savitskiĭ V. N.
Published: July 2010

It has been found experimentally that in the strongly anisotropic orthorhombic antiferromagnetic crystal LiCoPO4 (TN=21.7K) the destruction of antiferromagnetic order by a magnetic field directed along the antiferromagnetism axis H∥b occurs in steps by means of three phase transitions: two first-order transitions in the fields H1=118kOe, H2=224Oe and one second-order phase transition in the field H3=283kOe (T=1.7K). A section of magnetic fields (H2, H3) where the magnetization of the crystal varies almost linearly with the field was found. Possible magnetic structures formed in a magnetic field are discussed. The values of the exchange parameters are estimated.
No evidence for Evans’ holes in the A, B, C vibrational structure of potassium dihydrogen arsenate
Authors: Tomkinson John , Parker Stewart F. , Lennon David
Published: July 2010

We have used inelastic neutron scattering (INS) spectroscopy to study the “A, B, C” region of the hydrogen bond in potassium dihydrogen arsenate. The broad spectral feature observed in infrared spectroscopy is shown to be associated with a ridge of constant intensity in the INS, which follows the recoil line for a unit-mass particle. The onset energy of the ridge is unclear but, we believe, is associated with the optical “C” feature at 1610 cm−1, and which we assign to ν(O–H). The “B” and “A” optical bands were both demonstrated to be two-quantum events and are, thus, not associated with the fundamental ν(O–H). They are readily assigned to the harmonic overtone δ(OH)(0-2) and the combination γ(OH)(0-1)+δ(OH)(0-1), which both sit astride the ridge and there is no evidence for Evans’ holes. The other overtone, γ(OH)(0-2), has been assigned to a very weak feature, observed for the first time at 1900 cm−1. A simple model was used to describe the intensity distributions.
An extended noncommutative KP hierarchy
Authors: Ma Wen-Xiu
Published: July 2010

Introducing squared eigenfunctions in the Moyal-deformed Lax equations generates an extended noncommutative KP (ncKP) hierarchy. The compatibility equations between the ncKP flows and the extended ncKP flows and the compatibility equations among the extended ncKP flows themselves are constructed. The n-reductions and the k-constraints are analyzed, and thus, the ncKP hierarchy with self-consistent sources, the constrained ncKP hierarchy, and the constrained ncKP hierarchy with self-consistent sources are presented. Various illustrative examples are worked out, together with their Lax representations involving pseudodifferential Lax operators.
A decay result to a viscoelastic problem in Rn with an oscillating kernel
Authors: Kafini Mohammad , Tatar Nasser-eddine
Published: July 2010

In this paper we consider a linear Cauchy viscoelastic problem. We show that, for compactly supported initial data and for not necessarily decreasing (oscillating) relaxation function, the decay of the first energy of solutions is polynomial. The proof relies on some appropriately chosen functionals. The combination of which satisfies a certain integral inequality.
Dynamic global model for large eddy simulation of transient flow
Authors: Lee Jungil , Choi Haecheon , Park Noma
Published: July 2010

In the present study, the dynamic subgrid-scale eddy viscosity models with a global model coefficient by Park et al. [Phys. Fluids 18, 125109 (2006)] (called dynamic global models hereafter) are applied to large eddy simulation of decaying isotropic turbulence to examine their performances in transient flow. The dynamic global model based on the global equilibrium between the subgrid-scale dissipation and the viscous dissipation fails to predict the temporal behavior of decaying isotropic turbulence. On the other hand, the dynamic global model based on the Germano identity shows an excellent agreement with the experimental data of decaying isotropic turbulence.
On a variational principle for Beltrami flows
Authors: González Rafael , Costa Andrea , Santini E. Sergio
Published: July 2010

In a previous paper [R. González, L. G. Sarasua, and A. Costa, “Kelvin waves with helical Beltrami flow structure,” Phys. Fluids 20, 024106 (2008)] we analyzed the formation of Kelvin waves with a Beltrami flow structure in an ideal fluid. Here, taking into account the results of this paper, the topological analogy between the role of the magnetic field in Woltjer’s theorem [L. Woltjer, “A theorem on force-free magnetic fields,” Proc. Natl. Acad. Sci. U.S.A. 44, 489 (1958)] and the role of the vorticity in the equivalent theorem is revisited. Via this analogy we identify the force-free equilibrium of the magnetohydrodynamics with the Beltrami flow equilibrium of the hydrodynamic. The stability of the last one is studied applying Arnold’s theorem. We analyze the role of the enstrophy in the determination of the equilibrium and its stability. We show examples where the Beltrami flow equilibrium is stable under perturbations of the Beltrami flow type with the same eigenvalue as the basic flow one. The enstrophy variation results invariant with respect to a uniform rotating and translational frame and the stability is conserved when the flow experiences a transition from a Beltrami axisymmetric flow to a helical one of the same eigenvalue. These results are discussed in comparison with that given by Moffatt in 1986 [H. K. Moffatt, “Magnetostatic equilibria and analogous Euler flows of arbitrarily complex topology. Part 2. Stability considerations,” J. Fluid Mech. 166, 359 (1986)].
A new basis set for molecular bending degrees of freedom
Authors: Jutier Laurent
Published: July 2010

We present a new basis set as an alternative to Legendre polynomials for the variational treatment of bending vibrational degrees of freedom in order to highly reduce the number of basis functions. This basis set is inspired from the harmonic oscillator eigenfunctions but is defined for a bending angle in the range θ∊[0:π]. The aim is to bring the basis functions closer to the final (ro)vibronic wave functions nature. Our methodology is extended to complicated potential energy surfaces, such as quasilinearity or multiequilibrium geometries, by using several free parameters in the basis functions. These parameters allow several density maxima, linear or not, around which the basis functions will be mainly located. Divergences at linearity in integral computations are resolved as generalized Legendre polynomials. All integral computations required for the evaluation of molecular Hamiltonian matrix elements are given for both discrete variable representation and finite basis representation. Convergence tests for the low energy vibronic states of HCCH++, HCCH+, and HCCS are presented.
Progress in studying ferroelectromagnetic crystals
Authors: Chupis I. E.
Published: July 2010

A brief review of research performed on ferroelectromagnetic crystals over the 50years following the discovery of these materials by G. A. Smolenskiĭ and his colleagues is given. During the first decades single crystals and solid solutions of ferrloelectromagnetic substances were synthesized and the first evidence of an interaction between the ferroelectric and magnetic subsystems was obtained. The first two colossal magnetoelectric (ME) effects in nickel-iodine boracite were discovered. The theory explained qualitatively the observed and predicted new ME phenomena. Subsequently, the class of ferroelectromagnets grew, and compounds in which the electric polarization was induced by a spiral magnetic structure appeared. Measuring techniques improved. The discovery at the end of the 20th century of a new optical method of second-harmonic generation set the conditions for a new renaissance in ME studies. An entire series of new colossal ME effects attesting to the realization of cross ME control of the electric (magnetic) properties of a crystal by a magnetic (electric) field has now been discovered. The ME effects of greatest significance which have been discovered in the last few years are described. It is noted that ferroelectromagnets with electric polarization of an electronic nature (compounds with mixed valence, semiconductors) are promising materials.
Influence of polarization fields on carrier lifetime and recombination rates in InGaN-based light-emitting diodes
Authors: David Aurélien , Grundmann Michael J.
Published: July 2010

We study differential carrier lifetimes in InGaN light-emitting diodes (LEDs) of varying wavelengths. Increase in wavelength is correlated with an increase in lifetime, due to the impact of the polarization fields on carrier overlap. This effect explains the early onset of droop in longer-wavelength LEDs.
Molecular dynamics simulations of polymer crystallization in highly supercooled melt: Primary nucleation and cold crystallization
Authors: Yamamoto Takashi
Published: July 2010

Molecular mechanisms of crystallization at large supercooling and structure of supercooled melt are investigated in our polyethylenelike polymer through molecular dynamics simulations. Three representative crystallization processes are here considered: (1) isothermal homogeneous nucleation in the melt, (2) crystallization by rapid cooling of the melt, and (3) cold crystallization during slow heating of an amorphous state. Molecular level structures of the melt and the emerging crystallites are characterized by the use of the specific parameters, the effective segment length Lp and the radius of gyration Rg of the molecules, together with the overall crystallinity χc. In quasiequilibrium melt of moderate supercooling, the chains have random-coil conformations. However, the temperature dependence of the averaged Lp in the melt is found to show quite unexpected transition around the bulk melting temperature. At larger supercooling of 330 K, the homogeneous nucleation takes place after an induction period of about 4 ns. Characteristic conformational changes are here described by multimodal distributions of Rg, the main components of which correspond to relaxed random-coil chains in the melt and once-folded chains in the crystallites; the former chains transform continuously into the latter, having similar chain extension Rg. Rapid cooling of the melt is found to give poorly crystallized states having fringed-micellar organization. The effective segment length Lp shows considerably faster increase than Rg, resulting in peculiar conformational frustration. Nearly amorphous samples obtained by very rapid cooling show pronounced cold crystallization by slow heating over the glass transition temperature, where crystallites of random orientations form a granular texture due to steric collisions of the growing lamellae. The generated crystal texture is only metastable and readily reorganizes by annealing at high temperatures, where the chains are found to make large conformational transformations, the refolding from the twice-folded conformation into the once-folded.
Ferromagnetism in water-doped vanadium oxide nanotubes
Authors: Kweon Hyocheon , Lee Kyu Won , Lee Cheol Eui
Published: July 2010

We have investigated the magnetic properties of vanadium oxide nanotubes (VOx-NTs) of various V4+ concentrations. Ferromagnetic response was observed at ∼100 K only in the V4+-rich water-intercalated VOx-NTs, whose saturation moment is close to that of Li-doped VOx-NTs, a recently-reported room-temperature ferromagnet. The ferromagnetism may have to do with charge localization as well as the spin concentration giving rise to removal of spin frustration according to our previous study.
Influence of Co:Mn ratio on multiferroicity of Ca3Co2−xMnxO6 around x∼1
Authors: Ding P. , Li L. , Guo Y. J. , He Q. Y. , Gao X. S. , Liu J.-M.
Published: July 2010

A series of polycrystalline Ca3Co2−xMnxO6 with 0.93<x<1.07 are prepared in order to investigate the effect of Co:Mn ratio around x∼1.0 on the multiferroicity. It is found that the ferroelectric polarization P at low temperature shows significant dependence on the Co:Mn ratio, forming a V-shaped pattern with the lowest point at x∼0.99. It is proposed that the suppression of P with the Co:Mn ratio approaching to the best Co/Mn order originates from the disruption of the long range spin order.
Efficient photon number detection with silicon avalanche photodiodes
Authors: Thomas O. , Yuan Z. L. , Dynes J. F. , Sharpe A. W. , Shields A. J.
Published: July 2010

We demonstrate an efficient photon number detector for visible wavelengths using a silicon avalanche photodiode. Under subnanosecond gating, the device is able to resolve up to four photons in an incident optical pulse. The detection efficiency at 600 nm is measured to be 73.8%, corresponding to an avalanche probability of 91.1% of the absorbed photons, with a dark count probability below 1.1×10−6 per gate. With this performance and operation close to room temperature, fast-gated silicon avalanche photodiodes are ideal for optical quantum information processing that requires single-shot photon number detection.
Excitonic electroluminescence at room temperature in an (In,Ga)As multiple-quantum-well diode
Authors: Noriyasu M. , Fujiwara K.
Published: July 2010

Electroluminescence (EL) spectra of an In0.15Ga0.85As/Al0.15Ga0.85As multiple-quantum-well p-i-n diode measured at 15–300 K are dominated by the ground heavy-hole exciton transition, as assigned from coincidence to the leading exciton resonance absorption energy. Although most of excitons thermally dissociate into free carriers populated up to the first excited confinement states at room temperature, radiative recombination is strongly enhanced at the exciton states. Simulated EL spectra based on the excitonic absorption spectra rigorously reproduce all of the excitonic EL features superposed on the exponentially tailing emission at the continuum states, showing coexistence of excitons and free carriers at room temperature.
Magnetic memory based on La0.7Ca0.3MnO3/YBa2Cu3O7/La0.7Ca0.3MnO3 ferromagnet/superconductor hybrid structures
Authors: Nemes N. M. , Visani C. , Leon C. , Garcia-Hernandez M. , Simon F. , Fehér T. , te Velthuis S. G. E. , Hoffmann A. , Santamaria J.
Published: July 2010

We report a memory concept utilizing ferromagnet/superconductor/ferromagnet La0.7Ca0.3MnO3/YBa2Cu3O7/La0.7Ca0.3MnO3 thin film hybrid structures. The orientation of the magnetic field with respect to the ferromagnetic easy axis has a strong effect on superconductivity as indicated by a strong variation in the magnetoresistance (MR). MR can be controlled by rotating a small magnetic field applied in the plane of the film in a way that is determined by the in-plane biaxial magnetic anisotropy. The proposed memory device has the advantages of superconducting detection elements (fast response and low dissipation), small (100–150 Oe) writing fields, and resistance read-out without need for applied field.
High efficiency and low roll-off blue phosphorescent organic light-emitting devices using mixed host architecture
Authors: Chopra Neetu , Swensen James S. , Polikarpov Evgueni , Cosimbescu Lelia , So Franky , Padmaperuma Asanga B.
Published: July 2010

We report high efficiency and low roll-off for blue electrophosphorescent organic light emitting devices based on a mixed host layer architecture. The devices were fabricated using a mixed layer of di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane, a hole transport material, and 2,8-bis(diphenylphosphoryl)dibenzothiophene, an electron transport material, as the host layer doped with the blue phosphor iridium (III) bis[(4,6-difluorophenyl)-pyridinato-N,C2′]picolinate. Using a mixed layer as the host allowed us to achieve high power efficiency (59 lm/W at 100 cd/m2), low turn-on voltage (2.7 V for >10 cd/m2), and low roll-off in these devices.
Determination of edge purity in bilayer graphene using μ-Raman spectroscopy
Authors: Begliarbekov Milan , Sul Onejae , Kalliakos Sokratis , Yang Eui-Hyeok , Strauf Stefan
Published: July 2010

Polarization resolved μ-Raman spectroscopy was carried out at the edges of bilayer graphene. We find strong dependence of the intensity of the G band on the incident laser polarization, with its intensity dependence being 90° out of phase for the armchair and zigzag case, in accordance with theoretical predictions. For the case of mixed-state edges we demonstrate that the polarization contrast reflects the fractional composition of armchair and zigzag edges, providing a monitor of edge purity, which is an important parameter for the development of efficient nanoelectronic devices.
Pressure cycling of InN to 20 GPa: In situ transport properties and amorphization
Authors: Ovsyannikov Sergey V. , Shchennikov Vladimir V. , Karkin Alexander E. , Polian Alain , Briot Olivier , Ruffenach Sandra , Gil Bernard , Moret Matthieu
Published: July 2010

Indium nitride was grown on Al2O3 substrate and characterized by x-ray diffraction, Raman, electrical resistivity, Hall, and magnetoresistance studies. Thermoelectric and electrical properties of free-standing films were measured in situ under high pressure (HP) cycling to 20 GPa, across a phase transformation to a rock-salt-structured lattice. HP-cycling-induced amorphization was established. The thermopower (Seebeck effect) data evidence that both crystalline and amorphous InN kept n-type conductivity to 20 GPa. Pressure effect on the carrier concentration and effective mass is analyzed. Two features that can be related to structural transitions in amorphous InN were found near 11 and 17 GPa.
Reproductive biology of Melaleuca alternifolia (Myrtaceae) 1. Floral biology
Authors: Baskorowati L. , Moncur M. W. , Doran J. C. , Kanowski P. J.
Published: July 2010

Melaleuca alternifolia (Maiden & Betche) Cheel is commercially important as the source of essential oil for the Australian tea tree-oil industry. Information on reproductive biology of M. alternifolia is important to the Australian breeding program directed at improving the quality and quantity of tea tree oil. Flowering in three geographically separated sites – two planted seed orchards and one managed natural population, all in NSW – was observed in the present study, with supporting data obtained from glasshouse-grown plants in Canberra. The majority of the work was conducted from 2004 to 2007, although the study also drew on some prior observations. M. alternifolia has spikes of flowers that open acropetally over a 6-day period. No strong separation of male and female phases was found in any individual flower; pollen was shed by 1.4 days after anthesis and the stigma reached peak receptivity 3–5 days after anthesis. Dichogamy and acropetal floral development may lead to geitonogamy. Flowering occurred during the months of October–November, with the peak in November, and was synchronous across all three sites. Flowering intensity and success in producing capsules appeared to be associated with total spring rainfall. Initiation of flowering in M. alternifolia appears to be correlated with daylength, or an environmental parameter closely correlated with daylength. Flowering intensity varied considerably among the years surveyed, sites and families, and appears to be promoted by a period of winter minimum temperatures below 5°C. In M. alternifolia, the morphological development of buds, flowers and fruit leading to the development of mature seed takes place over a period 16–18 months from flowering. M. alternifolia differed significantly in the number of viable seeds per capsule from individual trees, from 26 ± 3.8 to 57 ± 3.8 germinants.
Collective motion and density fluctuations in bacterial colonies
Authors: Zhang H. P. , Be’er Avraham , Florin E.-L. , Swinney Harry L.
Published: July 2010

Flocking birds, fish schools, and insect swarms are familiar examples of collective motion that plays a role in a range of problems, such as spreading of diseases. Models have provided a qualitative understanding of the collective motion, but progress has been hindered by the lack of detailed experimental data. Here we report simultaneous measurements of the positions, velocities, and orientations as a function of time for up to a thousand wild-type
Bacillus subtilis
bacteria in a colony. The bacteria spontaneously form closely packed dynamic clusters within which they move cooperatively. The number of bacteria in a cluster exhibits a power-law distribution truncated by an exponential tail. The probability of finding clusters with large numbers of bacteria grows markedly as the bacterial density increases. The number of bacteria per unit area exhibits fluctuations far larger than those for populations in thermal equilibrium. Such “giant number fluctuations” have been found in models and in experiments on inert systems but not observed previously in a biological system. Our results demonstrate that bacteria are an excellent system to study the general phenomenon of collective motion.
Coexistence of two adamantane binding sites in the influenza A M2 ion channel
Authors: Rosenberg Matthew R. , Casarotto Marco G.
Published: July 2010

The influenza A virus contains a proton-selective ion channel (M2) that is the target of the adamantane family of drug inhibitors. Two recently published studies relating to adamantane binding of the M2 ion channel using X-ray crystallography and solution NMR have reignited interest in the potential use of adamantanes in combating the spread of influenza A. However, these two studies propose different binding sites for the adamantane drugs with the X-ray M2/amantadine structure favoring an ion channel pore-binding model and the solution NMR M2/rimantadine structure suggesting the existence of a lipid-facing binding pocket. We conducted a series of surface plasmon resonance (SPR) experiments designed to accurately measure the affinity of amantadine and rimantadine to M2 ion channels embedded in 1,2-dimyristoyl-sn-glycero-phosphocholine (DMPC) liposomes. We find that this class of drug is capable of binding M2 with two different affinities in the order of 10
−4
and 10
−7
M, suggesting that both proposed binding sites are feasible. Furthermore, by examining drug binding to M2 mutant constructs (V27A, S31N, and D44A), it was possible to probe the location of the two binding sites. We show that a high-affinity binding site corresponds to the M2 ion channel pore whereas the secondary, low-affinity binding site can be attributed to the lipid face of the pore. These SPR results are in excellent agreement with the most recent solid-state NMR study of amantadine-bound M2 in lipid bilayers and provide independent support that the ion channel pore-binding site is responsible for the pharmacological activity elicited by the adamantane drugs.
Predicting resistance mutations using protein design algorithms
Authors: Frey Kathleen M. , Georgiev Ivelin , Donald Bruce R. , Anderson Amy C.
Published: July 2010

Drug resistance resulting from mutations to the target is an unfortunate common phenomenon that limits the lifetime of many of the most successful drugs. In contrast to the investigation of mutations after clinical exposure, it would be powerful to be able to incorporate strategies early in the development process to predict and overcome the effects of possible resistance mutations. Here we present a unique prospective application of an ensemble-based protein design algorithm,
K
∗
, to predict potential resistance mutations in dihydrofolate reductase from
Staphylococcus aureus
using positive design to maintain catalytic function and negative design to interfere with binding of a lead inhibitor. Enzyme inhibition assays show that three of the four highly-ranked predicted mutants are active yet display lower affinity (18-, 9-, and 13-fold) for the inhibitor. A crystal structure of the top-ranked mutant enzyme validates the predicted conformations of the mutated residues and the structural basis of the loss of potency. The use of protein design algorithms to predict resistance mutations could be incorporated in a lead design strategy against any target that is susceptible to mutational resistance.
Automated vocal analysis of naturalistic recordings from children with autism, language delay, and typical development
Authors: Oller D. K. , Niyogi P. , Gray S. , Richards J. A. , Gilkerson J. , Xu D. , Yapanel U. , Warren S. F.
Published: July 2010

For generations the study of vocal development and its role in language has been conducted laboriously, with human transcribers and analysts coding and taking measurements from small recorded samples. Our research illustrates a method to obtain measures of early speech development through automated analysis of massive quantities of day-long audio recordings collected naturalistically in children's homes. A primary goal is to provide insights into the development of infant control over infrastructural characteristics of speech through large-scale statistical analysis of strategically selected acoustic parameters. In pursuit of this goal we have discovered that the first automated approach we implemented is not only able to track children's development on acoustic parameters known to play key roles in speech, but also is able to differentiate vocalizations from typically developing children and children with autism or language delay. The method is totally automated, with no human intervention, allowing efficient sampling and analysis at unprecedented scales. The work shows the potential to fundamentally enhance research in vocal development and to add a fully objective measure to the battery used to detect speech-related disorders in early childhood. Thus, automated analysis should soon be able to contribute to screening and diagnosis procedures for early disorders, and more generally, the findings suggest fundamental methods for the study of language in natural environments.
Leptin signaling maintains B-cell homeostasis via induction of Bcl-2 and Cyclin D1
Authors: Lam Queenie Lai Kwan , Wang Shengjun , Ko Otis King Hung , Kincade Paul W. , Lu Liwei
Published: July 2010

Regulation of apoptosis and cell cycle progression plays an essential role in the maintenance of B-cell homeostasis, because a fine balance of survival and expansion is critical for preventing lymphocytic disorders. Although remarkable progress in understanding B-cell development has been achieved, much less is known concerning niches that are critical to the maintenance of B-cell homeostasis. Leptin has recently been recognized to be important for modulating the immune responses, but it has remained unclear how leptin signaling influences B-cell physiology. A variety of lymphocytic malignancies have been reported to be linked to leptin, and therefore it is necessary to elucidate the mechanisms involved. Here we demonstrate that leptin promotes B-cell homeostasis by inhibiting apoptosis and by inducing cell cycle entry through the activation of expressions of B-cell CLL/lymphoma 2 (Bcl-2) and cyclin D1. We further show that leptin can induce Bcl-2 and cyclin D1 expression by two pathways, including the direct activation of their promoters and suppression of microRNAs (miRNAs) that target their putative 3′untranslated regions. Amplification of these leptin-modulated miRNAs inhibited B lymphoma cell growth. These findings provide insights into mechanisms for leptin regulation of the humoral immune system and suggest new therapeutic strategies for leptin receptor expressing malignancies.
Polyandry increases offspring viability and mother productivity but does not decrease mother survival in
Drosophila pseudoobscura
Authors: Gowaty Patricia Adair , Kim Yong-Kyu , Rawlings Jessica , Anderson W. W.
Published: July 2010

Polyandrous mating is common, but the benefits for females of polyandry remain controversial. To test whether mating with multiple males affects female fitness, we compared lifetime components of fitness of three experimental sets of
Drosophila pseudoobscura
females: monogamous females allowed to copulate one time (M
OC
); monogamous females held with a male over her entire life and experiencing many copulations (M
MC
); and polyandrous females with a different male over each day of their lives and also experiencing many copulations (P
MC
). Consistent with previous studies in this species, females in treatments in which multiple copulations occurred, M
MC
and P
MC
, had offspring with significantly higher egg-to-adult survival (i.e., offspring viability) and higher numbers of adult offspring (i.e., productivity) than M
OC
females, showing that multiple inseminations enhance offspring and mother fitness. In addition, although M
MC
females laid significantly more eggs than polyandrous (P
MC
) females, percent egg-to-adult survival and number of adult offspring were higher for P
MC
than M
MC
females, showing that polyandrous mating enhances the fitness of females more than multiply mating with only one male. Inconsistent with the cost of reproduction, lifespan was not significantly longer for M
OC
females than for M
MC
or P
MC
females. To our knowledge, this is the first study to examine simultaneously in outbred WT
Drosophila pseudoobscura
the lifetime costs and benefits to females of polyandry, monogamy with a single copulation, and monogamy with repeat copulations.