bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature responses to spectral solar variability on decadal time scales
Authors: Cahalan Robert F. , Wen Guoyong , Harder Jerald W. , Pilewskie Peter
Published: April 2010

Two scenarios of spectral solar forcing, namely Spectral Irradiance Monitor (SIM)‐based out‐of‐phase variations and conventional in‐phase variations, are input to a time‐dependent radiative‐convective model (RCM), and to the GISS modelE. Both scenarios and models give maximum temperature responses in the upper stratosphere, decreasing to the surface. Upper stratospheric peak‐to‐peak responses to out‐of‐phase forcing are ∼0.6 K and ∼0.9 K in RCM and modelE, ∼5 times larger than responses to in‐phase forcing. Stratospheric responses are in‐phase with TSI and UV variations, and resemble HALOE observed 11‐year temperature variations. For in‐phase forcing, ocean mixed layer response lags surface air response by ∼2 years, and is ∼0.06 K compared to ∼0.14 K for atmosphere. For out‐of‐phase forcing, lags are similar, but surface responses are significantly smaller. For both scenarios, modelE surface responses are less than 0.1 K in the tropics, and display similar patterns over oceanic regions, but complex responses over land.
Turbulence characteristics over tropical station Gadanki (13.5°N, 79.2°E) estimated using high‐resolution GPS radiosonde data
Authors: Nath Debashis , Venkat Ratnam M. , Patra A. K. , Krishna Murthy B. V. , Bhaskar Rao S. Vijaya
Published: April 2010

Seasonal variation of the turbulence parameters, refractivity structure constant Cn2, eddy dissipation rate ɛ, and eddy diffusivity K, is presented using 3 years (April 2006 to March 2009) of high vertical resolution GPS radiosonde measurements over the tropical station Gadanki (13.5°N, 79.2°E). First, a correlation analysis was done in order to study the relative contributions of temperature (T) and relative humidity (RH) to the refractive index gradient (M). A strong positive (negative) correlation between M and RH (T) gradients is noticed up to 10 km. Above 10 km, a strong positive correlation between M and T gradients is seen, except at altitudes near the tropopause. In the present study we flag the turbulent layers using the Thorpe sorting method and estimate the structure constant Cn2 for the turbulent layers. The probability of occurrence of Cn2 is derived from the cumulative distribution at each height and is found to decrease from 10−7 to 10−17 m−2/3 with height. The probability of the occurrence of Cn2 conditioned to the occurrence of turbulence as a function of height is derived, and it is found that only the mean and the 90th percentile profile reach an altitude of ∼27 km. The demarcation between the boundary layer and the free atmosphere as well as between the troposphere and the stratosphere are quite clear from the turbulence profile, which allows us to identify the boundary layer and tropopause heights from turbulence profiles. Thus, the present analysis introduces an alternative approach to identify the height of the boundary layer as well as the tropopause and also to characterize the probability of turbulence and thickness of turbulent eddies in the atmosphere with a finer scale size (down to 5 m) for the first time from a tropical latitude.
Plot‐scale effects on runoff and erosion along a slope degradation gradient
Authors: Moreno‐de las Heras Mariano , Nicolau José M. , Merino‐Martín Luis , Wilcox Bradford P.
Published: April 2010

In Earth and ecological sciences, an important, crosscutting issue is the relationship between scale and the processes of runoff and erosion. In drylands, understanding this relationship is critical for understanding ecosystem functionality and degradation processes. Recent work has suggested that the effects of scale may differ depending on the extent of degradation. To test this hypothesis, runoff and sediment yield were monitored during a hydrological year on 20 plots of various lengths (1–15 m). These plots were located on a series of five reclaimed mining slopes in a Mediterranean‐dry environment. The five slopes exhibited various degrees of vegetative cover and surface erosion. A general decrease of unit area runoff was observed with increasing plot scale for all slopes. Nevertheless, the amount of reinfiltrated runoff along each slope varied with the extent of degradation, being highest at the least degraded slope and vice versa. In other words, unit area runoff decreased the least on the most disturbed site as plot length increased. Unit area sediment yield declined with increasing plot length for the undisturbed and moderately disturbed sites, but it actually increased for the highly disturbed sites. The different scaling behavior of the most degraded slopes was especially clear under high‐intensity rainfall conditions, when flow concentration favored rill erosion. Our results confirm that in drylands, the effects of scale on runoff and erosion change with the extent of degradation, resulting in a substantial loss of soil and water from disturbed systems, which could reinforce the degradation process through feedback mechanisms with vegetation.
Superposed epoch study of PV5/3 during substorms, pseudobreakups and convection bays
Authors: Yang J. , Toffoletto F. R. , Erickson G. M. , Wolf R. A.
Published: April 2010

We present a superposed epoch study to examine the entropy parameter PV5/3, for isolated substorms, pseudobreakups and convection bays observed by Geotail in the near‐Earth plasma sheet, by using a flux‐tube‐volume formula with coefficients adjusted to fit magnetic field models for a variety of conditions. It is found that the changes of PV5/3 for these three types of events are distinct: (1) for substorms, PV5/3 increases continuously during the growth phase, decreases after dipolarization, and maintains a low value of ∼0.08 nPa(RE/nT)5/3; (2) for pseudobreakups, PV5/3 changes in a way similar to substorms, but decreases more moderately and then gradually increases; (3) for convection bays, PV5/3 takes a nearly constant value of 0.06 nPa(RE/nT)5/3. These results suggest that the characteristics of the processes that violate conservation of PV5/3 play a central role in the temporal and spatial reduction of PV5/3 and thus determine the earthward plasma transport during active times.
Reproduction of Inflectional Markers in French-Speaking Children With Reading Impairment
Authors: St-Pierre Marie-Catherine , Béland Renée
Published: April 2010

Purpose

Children with reading impairment (RI) experience difficulties in oral and written production of inflectional markers. The origin of these difficulties is not well documented in French. According to some authors, acquisition of irregular items by typically developing children is predicted by token frequency, whereas acquisition of regular items is predicted by type frequency. The authors hypothesized that acquisition of inflectional markers in French depends on the distribution of irregular, invariable, and regular (transparent) items within a grammatical category.

Method

Fifteen children with RI age matched with 15 children with typical reading development repeated and read aloud sentences containing adjectives inflected for gender and verbs inflected for number. Inflected adjectives and verbs were matched for token frequency and phonological complexity, whereas distribution of invariable, transparent, and irregular items differed within each grammatical category.

Results

Results show higher error rates in the RI group, who produced more errors in reading than repetition, and more errors on inflected verbs than adjectives. Error distribution varied with the proportion of invariable, irregular, and transparent items within each grammatical category, confirming the authors' hypothesis.

Conclusion

The authors concluded that morphological difficulties of children with RI group originated from a delay in extracting systematicity in verb and adjective inflectional marking.
Multitime response functions and nonlinear spectra for model quantum dissipative systems
Authors: Sahrapour Mohammad M. , Makri Nancy
Published: April 2010

Using iterative evaluation of the real-time path integral expression, we calculate four-time correlation functions for one-dimensional systems coupled to model dissipative environments. We use these correlation functions to calculate response functions relevant to third order infrared or seventh order Raman experiments for harmonic, Morse, and quadratic-quartic potentials interacting with harmonic and two-level-system dissipative baths. Our calculations reveal the role of potential features (anharmonicity and eigenvalue spectrum), both on short and long time scales, on the response function. Further, thermal excitation causes dramatic changes in the appearance of the response function, introducing symmetry with respect to the main diagonal. Finally, coupling to harmonic dissipative baths leads to decay of the response function (primarily along the τ3 direction) and a broadening of the peaks in its Fourier transform. At high temperatures two-level-system baths are less efficient in destroying coherence than harmonic baths of similar parameters.
DNA-protein binding rates: Bending fluctuation and hydrodynamic coupling effects
Authors: von Hansen Yann , Netz Roland R. , Hinczewski Michael
Published: April 2010

We investigate diffusion-limited reactions between a diffusing particle and a target site on a semiflexible polymer, a key factor determining the kinetics of DNA-protein binding and polymerization of cytoskeletal filaments. Our theory focuses on two competing effects: polymer shape fluctuations, which speed up association, and the hydrodynamic coupling between the diffusing particle and the chain, which slows down association. Polymer bending fluctuations are described using a mean field dynamical theory, while the hydrodynamic coupling between polymer and particle is incorporated through a simple heuristic approximation. We validate both of these through comparison to Brownian dynamics simulations. Neither of the effects has been fully considered before in the biophysical context and we show they are necessary to form accurate estimates of reaction processes. The association rate depends on the stiffness of the polymer and the particle size, exhibiting a maximum for intermediate persistence length and a minimum for intermediate particle radius. In the parameter range relevant to DNA-protein binding, the rate increase is up to 100% compared with the Smoluchowski result for simple center-of-mass motion. The quantitative predictions made by the theory can be tested experimentally.
Metamaterial electro-optic switch of nanoscale thickness
Authors: Sámson Z. L. , MacDonald K. F. , De Angelis F. , Gholipour B. , Knight K. , Huang C. C. , Di Fabrizio E. , Hewak D. W. , Zheludev N. I.
Published: April 2010

We demonstrate an innovative concept for nanoscale electro-optic switching. It exploits the frequency shift of a narrow-band Fano resonance mode in a plasmonic planar metamaterial induced by a change in the dielectric properties of an adjacent chalcogenide glass layer. An electrically stimulated transition between amorphous and crystalline forms of the glass brings about a 150 nm shift in the near-infrared resonance providing transmission modulation with a contrast ratio of 4:1 in a device of subwavelength thickness.
Time periodic electro-osmotic flow through a microannulus
Authors: Jian Yongjun , Yang Liangui , Liu Quansheng
Published: April 2010

Flow behavior of time periodic electro-osmosis in a cylindrical microannulus is investigated based on a linearized Poisson–Boltzmann equation and Navier–Stokes equation. An analytical solution of electro-osmotic flow (EOF) velocity distribution as functions of radial distance, periodic time and relevant parameters is derived. By numerical computations, the influences of the electrokinetic width K denoting the characteristic scale of the microannulus to Debye length, the wall zeta potential ratio β denoting the inner cylinder to the outer cylinder, the ratio α denoting of the annular inner radius to outer radius and the periodical EOF electric oscillating Reynolds number Re on velocity profiles are presented. Results show that when electric oscillating Reynolds number is low and the electrokinetic width K is large, the electro-osmotic velocity amplitude shows a square pluglike profile. When the Reynolds number is high, the driving effect of the electric force decreases immediately away from the two cylindrical walls. The parameter β affects the dimension and direction of the EOF velocity profiles within the electric double layer near the two cylindrical walls in a microannulus. Two limiting cases are discussed, i.e., the time periodical EOF approximately in parallel plate microchannel and circular microtube. These results are agreed qualitatively with those obtained by previously related researches. Furthermore, the instantaneous EOF velocity profiles within a period of a time cycle for different applied electric frequency f, electrokinetic width K, and zeta potential ratio β are illustrated.
Numerical simulation of the magnetron operation with resonance load
Authors: Sayapin A. , Krasik Y. E.
Published: April 2010

The results of numerical simulations and a comparison with experimental data obtained in recent experiments with the relativistic S-band magnetron by Sayapin et al. [Appl. Phys. Lett. 95, 074101 (2009)], having a resonance load and without special measures being taken to suppress the microwaves reflected from the load, are presented. The numerical simulations were based on the model which considers a magnetron as a traveling wave resonator coupled with external resonator. In these simulations, experimentally determined parameters of the magnetron and resonator and their coupling coefficient were used. It was found that, under certain conditions, the electromagnetic wave reflected from the resonator leads to an increase in the efficiency of the magnetron operation. Taking into account microwave energy compression in the resonator, one obtains a microwave power comparable with the power of the electron beam in the magnetron. Also, it was shown that the magnetron traveling wave acquires a phase shift due to its interaction with the amplified wave of the resonator. This phase shift can be comparable with the phase of the electron spoke with respect to the maximum of the decelerating phase of the microwave electric field. The latter could be a reason for the quenching of the microwave generation and the fast decay of the microwave power in the resonator found in experiments.
An imaging technique for detection and absolute calibration of scintillation light
Authors: Pappalardo Alfio , Cosentino Luigi , Finocchiaro Paolo
Published: April 2010

Triggered by the need of a detection system to be used in experiments of nuclear fusion in laser-generated plasmas, we developed an imaging technique for the measurement and calibration of the scintillation light yield of scintillating materials. As in such experiments, all the reaction products are generated in an ultrashort time frame, the event-by-event data acquisition scheme is not feasible. As an alternative to the emulsion technique (or the equivalent CR39 sheets) we propose a scintillating screen readout by means of a high performance charge coupled device camera. Even though it is not strictly required in the particular application, this technique allows the absolute calibration of the scintillation light yield.
Shear-induced reaction-limited aggregation kinetics of Brownian particles at arbitrary concentrations
Authors: Zaccone Alessio , Gentili Daniele , Wu Hua , Morbidelli Massimo
Published: April 2010

The aggregation of interacting Brownian particles in sheared concentrated suspensions is an important issue in colloid and soft matter science per se. Also, it serves as a model to understand biochemical reactions occurring in vivo where both crowding and shear play an important role. We present an effective medium approach within the Smoluchowski equation with shear which allows one to calculate the encounter kinetics through a potential barrier under shear at arbitrary colloid concentrations. Experiments on a model colloidal system in simple shear flow support the validity of the model in the concentration range considered. By generalizing Kramers’ rate theory to the presence of shear and collective hydrodynamics, our model explains the significant increase in the shear-induced reaction-limited aggregation kinetics upon increasing the colloid concentration.
Fabrication of conductive interconnects by Ag migration in Cu–Ag core-shell nanoparticles
Authors: Kim Suk Jun , Stach Eric A. , Handwerker Carol A.
Published: April 2010

Fabrication of conductive nanoparticle films is observed in Cu–Ag core-shell nanoparticles by fast diffusion of Ag at 220 °C from particle surfaces, leading to the formation of sintered necks of Ag at the initial particle-particle contacts. Transmission electron microscopy showed that the necks were pure Ag and that particle surfaces away from the contacts were nearly Ag-free. The extent of neck formation is controllable by the choice of initial Ag thickness. Analysis of the thermodynamics of the Ag–Cu system and the relative diffusivities of Ag and Cu provide criteria for fabrication of other core-shell two-phase systems by the same mechanism.
Master equation approach to single oligomeric enzyme catalysis: Mechanically controlled further catalysis
Authors: Das Biswajit , Gangopadhyay Gautam
Published: April 2010

Motivated by the single molecule enzymatic experiments, we have provided a master equation description of enzyme catalysis in a chemiostatic condition for an immobilized oligomeric molecule with many equivalent active sites. The random attachment and detachment of substrate molecules on the various active sites of the oligomeric enzyme is studied in terms of the classical parameters of the Michaelis–Menten type process. In the limit of single molecule process, the master equation approach gives the result of waiting time distribution. On the other hand, for a large number of equivalent active sites or a few numbers of active sites with large Michaelis constant, the master equation gives a Poisson distribution in the nonequilibrium steady state. For the oligomeric enzyme, the net rate of the reaction in the nonequilibrium steady state is multiplied by the number of active sites which is further enhanced by more than two orders of magnitude with the application of external force of 10–100 pN through the techniques of atomic force microscopy. Substrate flux and reaction rate constants have interesting consequences on the dynamics and at nonequilibrium steady state which can be the controlling factors for macroscopic biochemical processes.
Compressible laminar flow in a channel
Authors: Venerus D. C. , Bugajsky D. J.
Published: April 2010

Laminar flow of a compressible Newtonian fluid in a channel is analyzed. An analytic solution to the vorticity-stream function form of the hydrodynamics equations is found for weakly compressible flow using a regular perturbation method. In contrast with previous studies, the present analysis does not invoke the lubrication approximation and, consequently, predicts both a nonzero transverse velocity and a nonzero transverse pressure gradient. Predicted velocity and pressure fields from the perturbation solution are compared with previously published analytical and numerical solutions. Expressions for pressure drop are also given for compressible laminar flow in a channel that display significant deviations from the incompressible case. In addition, experimental data from the literature for the flow of gases in microchannels are analyzed and compared with predictions from the analytical solution. We find that a commonly used method for analyzing microchannel flow experiments obscures a rather simple dependence of pressure drop on the same dimensionless parameter used in the perturbation solution.
Room temperature ferromagnetism in vacuum annealed ZnFe2O4 nanoparticles
Authors: Ayyappan S. , Raja S. Philip , Venkateswaran C. , Philip John , Raj Baldev
Published: April 2010

We report room temperature ferromagnetism in vacuum annealed ZnFe2O4 (ZFO) nanoparticles. Upon vacuum and air annealing, ZFO nanoparticles show ferro and paramagnetic behavior, respectively. The well defined sextets along with doublet seen in the Mossbauer spectra confirms ferromagnetic coupling in vacuum annealed ZFO. After reannealing in air, the magnetization of vacuum annealed sample reduces from 62 to 1.5 emu/g. Both Mossbauer and micro-Raman results suggest that oxygen vacancies generated during vacuum annealing causes cation redistribution between the interstitial sites resulting in magnetic ordering. Our results show a unique possibility of switching the magnetic properties of ZFO between paramagnetic to ferromagnetic.
Improved stability of a phase change memory device using Ge-doped SbTe at varying ambient temperature
Authors: Wu Zhe , Lee Suyoun , Park Young-Wook , Ahn Hyung-Woo , Jeong Doo Seok , Jeong Jeung-hyun , No Kwangsoo , Cheong Byung-ki
Published: April 2010

Ge-doped SbTe (Ge–ST) was compared with Ge2Sb2Te5 (GST) for its potential use in the phase-change memory with improved stability at varying ambient temperature (TA). Device characteristics such as RESET current, RESET resistance, and SET resistance of Ge–ST devices were found to vary significantly less with TA than those of GST devices. From measured carrier density, mobility, and optical band gaps, these findings are interpreted to derive from a metallic nature of the crystalline Ge–ST in contrast with a semiconducting nature of the crystalline GST as well as a relatively weaker covalent bonding in amorphous Ge–ST.
A cusp electron gun for millimeter wave gyrodevices
Authors: Donaldson C. R. , He W. , Cross A. W. , Li F. , Phelps A. D. R. , Zhang L. , Ronald K. , Robertson C. W. , Whyte C. G. , Young A. R.
Published: April 2010

The experimental results of a thermionic cusp electron gun, to drive millimeter and submillimeter wave harmonic gyrodevices, are reported in this paper. Using a “smooth” magnetic field reversal formed by two coils this gun generated an annular-shaped, axis-encircling electron beam with 1.5 A current, and an adjustable velocity ratio α of up to 1.56 at a beam voltage of 40 kV. The beam cross-sectional shape and transported beam current were measured by a witness plate technique and Faraday cup, respectively. These measured results were found to be in excellent agreement with the simulated results using the three-dimensional code MAGIC.
Metastable bound D1,3o states below N=3 ionization threshold of He+
Authors: Saha Jayanta K. , Bhattacharyya S. , Mukherjee Tapan K.
Published: April 2010

The applicability of Ritz-variational principle for 3dnf (D1,3o) states lying between N=2 and N=3 ionization threshold of singly ionized helium is discussed in this communication. Probable existence of such a state for O6+ within the planetary atmosphere in the polar regions of Jupiter is discussed.
Charge transport in flat and nanorod structured ruthenium thin films
Authors: Steeves M. M. , Deniz D. , Lad R. J.
Published: April 2010

Resistivities and Hall coefficients of flat and nanorod-structured Ru thin films were investigated from 295 to 600 K. Resistivities decreased upon first heating due to defect annealing, but Hall coefficients were found to be independent of temperature and defect content. The error in the Hall coefficient due to the Ettingshausen effect is shown to be negligible. Although resistivities and Hall coefficients of flat films are determined by a nominal film thickness, resistivities of nanorod-structured films are dominated by an ultrathin polycrystalline layer at the film-substrate interface and Hall coefficients appear to depend on an effective thickness determined by nanorod size and spacing.
Electrically tunable, high performance quantum cascade laser
Authors: Bismuto A. , Terazzi R , Beck M. , Faist Jerome
Published: April 2010

A quantum cascade laser design for wide voltage-tuning, emitting at ∼8.5 μm, is presented based on a diagonal bound-to-continuum design. The relatively short period length and the diagonal nature of the laser transition guarantees a wide tuning of the emission due to the linear Stark shift effect. Tuning of both the spontaneous and stimulated emission is presented over almost 100 cm−1. In spite of the large tuning, laser performance are comparable with the best results present in literature in this spectral range. In particular, continuous wave operation up to 450 mW and pulsed wall plug efficiencies up to 11.5% were measured at 300 K. A transport model, based on the density matrix formalism, was used to simulate spontaneous and stimulated emission as function of the applied field. Same model was also used to predict light-current-voltage characteristics of the lasers.
Dielectrophoresis of Janus particles under high frequency ac-electric fields
Authors: Zhang Lu , Zhu Yingxi
Published: April 2010

Janus polystyrene particles with gold and dielectric multilayer coatings on one hemisphere are shown to drastically alter the dielectrophoresis (DEP) behavior of homogeneous precursor particles under ac-electric fields. Alkanethiol coatings on the gold-coated hemisphere can effectively modify the DEP crossover frequency (ωc) with a negative (n) to positive (p) (p→n) DEP transition as increasing ac-frequency, in contrast to p→n DEP transition observed with precursor particles. All measured n→p DEP crossover frequencies with dependence on particle size, alkanethiol thickness, and medium conductivity are collapsed to yield a scaling with the resistance-capacitance (RC) time of the alkanethiol layer capacitance and the conductive medium resistance.
High resolution magnetic imaging of perpendicular magnetic recording head using frequency-modulated magnetic force microscopy with a hard magnetic tip
Authors: Lu Wei , Li Zhenghua , Hatakeyama Kodai , Egawa Genta , Yoshimura Satoru , Saito Hitoshi
Published: April 2010

High resolution imaging of ac magnetic field from a trailing-edge shielded perpendicular magnetic writing head was demonstrated by using frequency-modulated magnetic force microscopy (FM-MFM) with a high-coercivity FePt MFM tip. The distribution of perpendicular magnetic field gradient of the recording head is presented and can be used to evaluate the recording performance of the head. A Fourier analysis of the images suggests that magnetic spectral features as small as 15 nm should be detectable by using the FM-MFM technique with a high coercivity tip. The enhancement in spatial resolution of FM-MFM is very crucial for the analysis of nanoscale magnetic features and to shed light on the development of next generation magnetic recording heads.
Application of microplasma discharge in a spark gap for high repetitive switching
Authors: Rahaman Hasibur , Nam Sang Hoon , Nam Jong Woo , Lee Byung-Joon , Frank Klaus
Published: April 2010

The electrical breakdown in a spark gap for repetitive switching has been a long research interest. For this purpose, microplasma discharge is implemented in the spark gap which is further integrated inside a coaxial transmission line. This work addresses important physical properties and insights of the microplasma discharge, to be optimized, such as plasma generation in a spark channel, dielectric recovery process, and residual plasma in the postspark discharge period. Although understanding the microplasma discharge is the primary goal, considerable attention has been focused on an external circuit scheme to drive the discharge system at a high repetition rate.
The controlling role of envelope mismatches in intense inhomogeneous charged beams
Authors: Souza E. G. , Endler A. , Pakter R. , Rizzato F. B. , Nunes R. P.
Published: April 2010

Inhomogeneous cold beams undergo wave breaking as they move along the axis of a magnetic focusing system. All the remaining control parameters fixed, the earliest wave breaking is a sensitive function of the inhomogeneity parameter: the larger the inhomogeneity, the sooner the breaking. The present work analyzes the role of envelope size mismatches in the wave breaking process. The analysis reveals that the wave breaking time is also very susceptible to the mismatch; judiciously chosen mismatches can largely extend beam lifetimes. The work is extended to include recently discussed issues on the presences of fast and slow regimes of wave breaking, and the theory is shown to be accurate against simulations.
N-terminal regions of Mps1 kinase determine functional bifurcation
Authors: Araki Yasuhiro , Gombos Linda , Migueleti Suellen P.S. , Sivashanmugam Lavanya , Antony Claude , Schiebel Elmar
Published: April 2010

Mps1 is a conserved kinase that in budding yeast functions in duplication of the spindle pole body (SPB), spindle checkpoint activation, and kinetochore biorientation. The identity of Mps1 targets and the subdomains that convey specificity remain largely unexplored. Using a novel combination of systematic deletion analysis and chemical biology, we identified two regions within the N terminus of Mps1 that are essential for either SPB duplication or kinetochore biorientation. Suppression analysis of the MPS1 mutants defective in SPB duplication and biochemical enrichment of Mps1 identified the essential SPB components Spc29 and the yeast centrin Cdc31 as Mps1 targets in SPB duplication. Our data suggest that phosphorylation of Spc29 by Mps1 in G1/S recruits the Mps2–Bbp1 complex to the newly formed SPB to facilitate its insertion into the nuclear envelope. Mps1 phosphorylation of Cdc31 at the conserved T110 residue controls substrate binding to Kar1 protein. These findings explain the multiple SPB duplication defects of mps1 mutants on a molecular level.
Intraflagellar transport molecules in ciliary and nonciliary cells of the retina
Authors: Sedmak Tina , Wolfrum Uwe
Published: April 2010

The assembly and maintenance of cilia require intraflagellar transport (IFT), a process mediated by molecular motors and IFT particles. Although IFT is a focus of current intense research, the spatial distribution of individual IFT proteins remains elusive. In this study, we analyzed the subcellular localization of IFT proteins in retinal cells by high resolution immunofluorescence and immunoelectron microscopy. We report that IFT proteins are differentially localized in subcompartments of photoreceptor cilia and in defined periciliary target domains for cytoplasmic transport, where they are associated with transport vesicles. IFT20 is not in the IFT core complex in photoreceptor cilia but accompanies Golgi-based sorting and vesicle trafficking of ciliary cargo. Moreover, we identify a nonciliary IFT system containing a subset of IFT proteins in dendrites of retinal neurons. Collectively, we provide evidence to implicate the differential composition of IFT systems in cells with and without primary cilia, thereby supporting new functions for IFT beyond its well-established role in cilia.
CDK5RAP2 functions in centrosome to spindle pole attachment and DNA damage response
Authors: Barr Alexis R. , Kilmartin John V. , Gergely Fanni
Published: April 2010

The centrosomal protein, CDK5RAP2, is mutated in primary microcephaly, a neurodevelopmental disorder characterized by reduced brain size. The Drosophila melanogaster homologue of CDK5RAP2, centrosomin (Cnn), maintains the pericentriolar matrix (PCM) around centrioles during mitosis. In this study, we demonstrate a similar role for CDK5RAP2 in vertebrate cells. By disrupting two evolutionarily conserved domains of CDK5RAP2, CNN1 and CNN2, in the avian B cell line DT40, we find that both domains are essential for linking centrosomes to mitotic spindle poles. Although structurally intact, centrosomes lacking the CNN1 domain fail to recruit specific PCM components that mediate attachment to spindle poles. Furthermore, we show that the CNN1 domain enforces cohesion between parental centrioles during interphase and promotes efficient DNA damage–induced G2 cell cycle arrest. Because mitotic spindle positioning, asymmetric centrosome inheritance, and DNA damage signaling have all been implicated in cell fate determination during neurogenesis, our findings provide novel insight into how impaired CDK5RAP2 function could cause premature depletion of neural stem cells and thereby microcephaly.
A ribosome-anchored chaperone network that facilitates eukaryotic ribosome biogenesis
Authors: Albanèse Véronique , Reissmann Stefanie , Frydman Judith
Published: April 2010

Molecular chaperones assist cellular protein folding as well as oligomeric complex assembly. In eukaryotic cells, several chaperones termed chaperones linked to protein synthesis (CLIPS) are transcriptionally and physically linked to ribosomes and are implicated in protein biosynthesis. In this study, we show that a CLIPS network comprising two ribosome-anchored J-proteins, Jjj1 and Zuo1, function together with their partner Hsp70 proteins to mediate the biogenesis of ribosomes themselves. Jjj1 and Zuo1 have overlapping but distinct functions in this complex process involving the coordinated assembly and remodeling of dozens of proteins on the ribosomal RNA (rRNA). Both Jjj1 and Zuo1 associate with nuclear 60S ribosomal biogenesis intermediates and play an important role in nuclear rRNA processing, leading to mature 25S rRNA. In addition, Zuo1, acting together with its Hsp70 partner, SSB (stress 70 B), also participates in maturation of the 35S rRNA. Our results demonstrate that, in addition to their known cytoplasmic roles in de novo protein folding, some ribosome-anchored CLIPS chaperones play a critical role in nuclear steps of ribosome biogenesis.
Emerging Viral Diseases of Tomato Crops
Authors: Hanssen Inge M. , Lapidot Moshe , Thomma Bart P. H. J.
Published: April 2010

Viral diseases are an important limiting factor in many crop production systems. Because antiviral products are not available, control strategies rely on genetic resistance or hygienic measures to prevent viral diseases, or on eradication of diseased crops to control such diseases. Increasing international travel and trade of plant materials enhances the risk of introducing new viruses and their vectors into production systems. In addition, changing climate conditions can contribute to a successful spread of newly introduced viruses or their vectors and establishment of these organisms in areas that were previously unfavorable. Tomato is economically the most important vegetable crop worldwide and many viruses infecting tomato have been described, while new viral diseases keep emerging. Pepino mosaic virus is a rapidly emerging virus which has established itself as one of the most important viral diseases in tomato production worldwide over recent years. Begomovirus species and other whitefly-transmitted viruses are invading into new areas, and several recently described new viruses such as Tomato torrado virus and new Tospovirus species are rapidly spreading over large geographic areas. In this article, emerging viruses of tomato crops are discussed.
Wounding-Induced WRKY8 Is Involved in Basal Defense in Arabidopsis
Authors: Chen Ligang , Zhang Liping , Yu Diqiu
Published: April 2010

The WRKY family of plant transcription factors controls several types of plant stress responses. Arabidopsis WRKY8, localized to the nucleus, is mainly induced by abscissic acid, H2O2, wounding, Pseudomonas syringae and Botrytis cinerea infection, and aphid and maggot feeding. To determine its biological functions, we isolated loss-of-function T-DNA insertion mutants and generated gain-of-function overexpressing WRKY8 transgenic plants in Arabidopsis. Plants expressing the mutated WRKY8 gene showed increased resistance to P. syringae but slightly decreased resistance to B. cinerea. In contrast, transgenic plants overexpressing WRKY8 were more susceptible to P. syringae infection but more resistant to B. cinerea infection. The contrasting responses to the two pathogens were correlated with opposite effects on pathogen-induced expression of two genes; salicylic acid-regulated PATHOGENESIS-RELATED1 (PR1) and jasmonic acid-regulated PDF1.2. Therefore, our results suggest that WRKY8 is a negative regulator of basal resistance to P. syringae and positive regulator to B. cinerea.
Synergistic Activation of Defense Responses in Arabidopsis by Simultaneous Loss of the GSL5 Callose Synthase and the EDR1 Protein Kinase
Authors: Wawrzynska Anna , Rodibaugh Natalie L. , Innes Roger W.
Published: April 2010

Loss-of-function mutations in the EDR1 gene of Arabidopsis confer enhanced resistance to Golovinomyces cichoracearum (powdery mildew). Disease resistance mediated by the edr1 mutation is dependent on an intact salicylic acid (SA) signaling pathway, but edr1 mutant plants do not constitutively express the SA-inducible gene PR-1 and are not dwarfed. To identify other components of the EDR1 signaling network, we screened for mutations that enhanced the edr1 mutant phenotype. Here, we describe an enhancer of edr1 mutant, eed3, which forms spontaneous lesions in the absence of pathogen infection, constitutively expresses both SA- and methyl jasmonate (JA)–inducible defense genes, and is dwarfed. Positional cloning of eed3 revealed that the mutation causes a premature stop codon in GLUCAN SYNTHASE-LIKE 5 (GSL5, also known as POWDERY MILDEW RESISTANT 4), which encodes a callose synthase required for pathogen-induced callose production. Significantly, gsl5 single mutants do not constitutively express PR-1 or AtERF1 (a JA-inducible gene) and are not dwarfed. Thus, loss of both EDR1 and GSL5 function has a synergistic effect. Our data suggest that EDR1 and GSL5 negatively regulate SA and JA production or signaling by independent mechanisms and that negative regulation of defense signaling by GSL5 may be independent of callose production.
TheFrankia alniSymbiotic Transcriptome
Authors: Alloisio Nicole , Queiroux Clothilde , Fournier Pascale , Pujic Petar , Normand Philippe , Vallenet David , Médigue Claudine , Yamaura Masatoshi , Kakoi Kentaro , Kucho Ken-ichi
Published: April 2010

The actinobacteria Frankia spp. are able to induce the formation of nodules on the roots of a large spectrum of actinorhizal plants, where they convert dinitrogen to ammonia in exchange for plant photosynthates. In the present study, transcriptional analyses were performed on nitrogen-replete free-living Frankia alni cells and on Alnus glutinosa nodule bacteria, using whole-genome microarrays. Distribution of nodule-induced genes on the genome was found to be mostly over regions with high synteny between three Frankia spp. genomes, while nodule-repressed genes, which were mostly hypothetical and not conserved, were spread around the genome. Genes known to be related to nitrogen fixation were highly induced, nif (nitrogenase), hup2 (hydrogenase uptake), suf (sulfur-iron cluster), and shc (hopanoids synthesis). The expression of genes involved in ammonium assimilation and transport was strongly modified, suggesting that bacteria ammonium assimilation was limited. Genes involved in particular in transcriptional regulation, signaling processes, protein drug export, protein secretion, lipopolysaccharide, and peptidoglycan biosynthesis that may play a role in symbiosis were also identified. We also showed that this Frankia symbiotic transcriptome was highly similar among phylogenetically distant plant families Betulaceae and Myricaceae. Finally, comparison with rhizobia transcriptome suggested that F. alni is metabolically more active in symbiosis than rhizobia.
Synchronization engineering: tuning the phase relationship between dissimilar oscillators using nonlinear feedback
Authors: Rusin Craig G. , Kori Hiroshi , Kiss István Z. , Hudson John L.
Published: April 2010

A mild, nonlinear, time-delayed feedback signal was applied to two heterogeneous oscillators in order to synchronize their frequencies with an arbitrary and controllable phase difference. The feedback was designed using phase models constructed from experimental measurements of the intrinsic dynamical properties of the oscillators. The feedback signal produced an interaction function that corresponds to the desired collective behaviour. The synchronized phase difference between the elements can be tuned to any value on the interval 0 and 2
π
by shifting the phase of the interaction function using the feedback delay. Numerical simulations were conducted and experiments carried out with electrochemical oscillators.
An experimental and theoretical study of the mixing characteristics of a periodically reoriented irrotational flow
Authors: Metcalfe Guy , Lester Daniel , Ord Alison , Kulkarni Pandurang , Rudman Murray , Trefry Mike , Hobbs Bruce , Regenaur-Lieb Klaus , Morris Jeffery
Published: April 2010

The minimum-energy method to generate chaotic advection should be to use an irrotational flow. However, irrotational flows have no saddle connections to perturb in order to generate chaotic orbits. To the early work of Jones & Aref (Jones & Aref 1988
Phys. Fluids
31
, 469–485 (
doi:10.1063/1.866828
)) on potential flow chaos, we add periodic reorientation to generate chaotic advection with irrotational experimental flows. Our experimental irrotational flow is a dipole potential flow in a disc-shaped Hele-Shaw cell called the
rotated potential mixing
flow; it leads to chaotic advection and transport in the disc. We derive an analytical map for the flow. This is a partially open flow, in which parts of the flow remain in the cell forever, and parts of it pass through with residence-time and exit-time distributions that have self-similar features in the control parameter space of the stirring. The theory compares well with the experiment.
The maximum entropy production principle: two basic questions
Authors: Martyushev Leonid M.
Published: April 2010

The overwhelming majority of maximum entropy production applications to ecological and environmental systems are based on thermodynamics and statistical physics. Here, we discuss briefly maximum entropy production principle and raises two questions: (i) can this principle be used as the basis for non-equilibrium thermodynamics and statistical mechanics and (ii) is it possible to ‘prove’ the principle? We adduce one more proof which is most concise today.
A new one-dimensional radiative equilibrium model for investigating atmospheric radiation entropy flux
Authors: Wu Wei , Liu Yangang
Published: April 2010

A new one-dimensional radiative equilibrium model is built to analytically evaluate the vertical profile of the Earth's atmospheric radiation entropy flux under the assumption that atmospheric longwave radiation emission behaves as a greybody and shortwave radiation as a diluted blackbody. Results show that both the atmospheric shortwave and net longwave radiation entropy fluxes increase with altitude, and the latter is about one order in magnitude greater than the former. The vertical profile of the atmospheric net radiation entropy flux follows approximately that of the atmospheric net longwave radiation entropy flux. Sensitivity study further reveals that a ‘darker’ atmosphere with a larger overall atmospheric longwave optical depth exhibits a smaller net radiation entropy flux at all altitudes, suggesting an intrinsic connection between the atmospheric net radiation entropy flux and the overall atmospheric longwave optical depth. These results indicate that the overall strength of the atmospheric irreversible processes at all altitudes as determined by the corresponding atmospheric net entropy flux is closely related to the amount of greenhouse gases in the atmosphere.
The nuclear hormone receptor Coup-TFII is required for the initiation and early maintenance of Prox1 expression in lymphatic endothelial cells
Authors: Srinivasan R. Sathish , Geng Xin , Yang Ying , Wang Yingdi , Mukatira Suraj , Studer Michèle , Porto Marianna P.R. , Lagutin Oleg , Oliver Guillermo
Published: April 2010

The homeobox gene Prox1 is crucial for mammalian lymphatic vascular development. In the absence of Prox1, lymphatic endothelial cells (LECs) are not specified. The maintenance of LEC identity also requires the constant expression of Prox1. However, the mechanisms controlling the expression of this gene in LECs remain poorly understood. The SRY-related gene Sox18 is required to induce Prox1 expression in venous LEC progenitors. Although Sox18 is also expressed in embryonic arteries, these vessels do not express Prox1, nor do they give rise to LECs. This finding suggests that some venous endothelial cell-specific factor is required for the activation of Prox1. Here we demonstrate that the nuclear hormone receptor Coup-TFII is necessary for the activation of Prox1 in embryonic veins by directly binding a conserved DNA domain in the regulatory region of Prox1. In addition, we show that the direct interaction between nuclear hormone receptors and Prox1 is also necessary for the maintenance of Prox1 expression during early stages of LEC specification and differentiation.
ArabidopsisHistidine Kinase CKI1 Acts Upstream of HISTIDINE PHOSPHOTRANSFER PROTEINS to Regulate Female Gametophyte Development and Vegetative Growth
Authors: Deng Yan , Dong Haili , Mu Jinye , Ren Bo , Zheng Binglian , Ji Zhendong , Yang Wei-Cai , Liang Yan , Zuo Jianru
Published: April 2010

Cytokinin signaling is mediated by a multiple-step phosphorelay. Key components of the phosphorelay consist of the histidine kinase (HK)-type receptors, histidine phosphotransfer proteins (HP), and response regulators (RRs). Whereas overexpression of a nonreceptor-type HK gene CYTOKININ-INDEPENDENT1 (CKI1) activates cytokinin signaling by an unknown mechanism, mutations in CKI1 cause female gametophytic lethality. However, the function of CKI1 in cytokinin signaling remains unclear. Here, we characterize a mutant allele, cki1-8, that can be transmitted through female gametophytes with low frequency (∼0.17%). We have recovered viable homozygous cki1-8 mutant plants that grow larger than wild-type plants, show defective megagametogenesis and rarely set enlarged seeds. We found that CKI1 acts upstream of AHP (Arabidopsis HP) genes, independently of cytokinin receptor genes. Consistently, an ahp1,2-2,3,4,5 quintuple mutant, which contains an ahp2-2 null mutant allele, exhibits severe defects in megagametogenesis, with a transmission efficiency of <3.45% through female gametophytes. Rarely recovered ahp1,2-2,3,4,5 quintuple mutants are seedling lethal. Finally, the female gametophytic lethal phenotype of cki1-5 (a null mutant) can be partially rescued by IPT8 or ARR1 (a type-B Arabidopsis RR) driven by a CKI1 promoter. These results define a genetic pathway consisting of CKI1, AHPs, and type-B ARRs in the regulation of female gametophyte development and vegetative growth.
Gene expression profiles of infant acute lymphoblastic leukaemia and its prognostically distinct subsets
Authors: Qazi Sanjive , Uckun Fatih M.
Published: April 2010

This study compared the gene expression profiles of primary leukaemic cells from infants versus children with acute lymphoblastic leukaemia (ALL). Our analyses provided unprecedented evidence that remarkably different pathognomonic transcriptomes dominate the biology of infant versus paediatric high risk ALL. The genetic signature of infant ALL is characterized by concomitant overexpression of mitogenic and anti‐apoptotic genes, some of which have been associated with early relapse in ALL. Our study demonstrated that primary leukaemia cells from infant ALL patients expressed significantly higher levels of genes for cytokines that mediate their biological effects through stimulation of the JAK‐STAT signal transduction pathway including interleukin 1a, interleukin 1b, interleukin 2, and interleukin 7. We further showed that the JAK/STAT signalling pathway is constitutively active in CD10− infant ALL cells and treatment with a JAK3 inhibitor or a pan‐JAK kinase inhibitor effectively triggered their apoptosis. These findings identified JAK3 as an attractive molecular target for disrupting the constitutively deregulated anti‐apoptotic STAT3 and STAT5 signalling pathways in infant ALL cells.