bluuebunny/crossref_metadata_2025 huggingface dataset:
Properties of zero-lag long-range synchronization via dynamical relaying
Authors: de Sousa Vieira Maria
Published: April 2010

In 2006 Fischer et al. reported the phenomenon of zero-lag long-range isochronous synchronization via dynamical relaying in systems with delay [Phys. Rev. Lett. 97, 123902 (2006)]. They reported that when one has two coupled systems A and C, with delay between them, then the introduction of a third coupled element B between A and C will allow them to synchronize even in regions of the parameter space where this was not possible without the presence of B. Here we studied this phenomenon in detail in coupled Rössler oscillators and found that this happens in three different ways, that is, we verified that when there is feedback between A and B this kind of synchronization can happen via antiphase or in-phase synchronization depending on the delay value. The third case occurs via anticipating synchronization and is found when B drives A and C without getting feedback from them. We found similar phenomena in coupled Kuramoto oscillators, which present periodic orbits only and this allowed us to perform analytical calculations. Finally, we studied coupled logistic maps and identify the region where zero-lag long-range synchronization is possible as the region characterized by a negative transversal Lyapunov exponent.
Controllable graphene N-doping with ammonia plasma
Authors: Lin Yung-Chang , Lin Chih-Yueh , Chiu Po-Wen
Published: April 2010

Here we show that gas-phase doping by means of NH3 plasma exposure is a highly flexible and manufacturable process for graphene electronics. The nitrogen-containing radicals can readily form covalent bonds with the carbon lattice and keep stable in the postannealing for damage restoration. The amount of charge transfer can be fine tuned by controlling the exposure time and monitored by the systematic shift in the Raman G mode and the Gds−Vg curves in transport measurements. The maximum doping level can reach 1.5×1013 cm−2.
Characteristics of extreme ultraviolet emission from a discharge-produced potassium plasma for surface morphology application
Authors: Higashiguchi Takeshi , Terauchi Hiromitsu , Yugami Noboru , Yatagai Toyohiko , Sasaki Wataru , D’Arcy Rebekah , Dunne Padraig , O’Sullivan Gerry
Published: April 2010

We have demonstrated a discharge-produced microplasma extreme ultraviolet source based on a pure potassium vapor. Potassium ions produced strong broadband emission around 40 nm with a bandwidth of 8 nm (full width at half-maximum). The current-voltage characteristics of microdischarge suggest that the source operates in a hollow cathode mode. By comparison with atomic structure calculations, the broadband emission is found to be primarily due to 3d−3p transitions in potassium ions ranging from K2+ to K4+.
A theory for the arrangement of sensory organs in Drosophila
Authors: Zhu Huifeng , Gunaratne Preethi H. , Roman Gregg W. , Gunaratne Gemunu H.
Published: April 2010

We study the arrangements of recurved bristles on the anterior wing margin of wild-type and mutant Drosophila. The epidermal or neural fate of a proneural cell depends on the concentrations of proteins of the achaete-scute complex. At puparium formation, concentrations of proteins are nearly identical in all cells of the anterior wing and each cell has the potential for neural fate. In wild-type flies, the action of regulatory networks drives the initial state to one where a bristle grows out of every fifth cell. Recent experiments have shown that the frequency of recurved bristles can be made to change by adjusting the mean concentrations of the zinc-finger transcription factor Senseless and the micro-RNA miR-9a. Specifically, mutant flies with reduced levels of miR-9a exhibit ectopic bristles, and those with lower levels of both miR-9a and Senseless show regular organization of recurved bristles, but with a lower periodicity of 4. We argue that these characteristics can be explained assuming an underlying Turing-type bifurcation whereby a periodic pattern spontaneously emerges from a uniform background. However, bristle patterns occur in a discrete array of cells, and are not mediated by diffusion. We argue that intracellular actions of transmembrane proteins such as Delta and Notch can play a role of diffusion in destabilizing the homogeneous state. In contrast to diffusion, intercellular actions can be activating or inhibiting; further, there can be lateral cross-species interactions. We introduce a phenomenological model to study bristle arrangements and make several model-independent predictions that can be tested in experiments. In our theory, miRNA-9a is one of the components of the underlying network and has no special regulatory role. The loss of periodicity in its absence is due to the transfer of the system to a bistable state.
Electron collisions with α-D-glucose and β-D-glucose monomers
Authors: da Costa Romarly F. , Bettega Márcio H. F. , Varella Márcio T. do N. , Lima Marco A. P.
Published: April 2010

The development of new alternative routes for production of second generation ethanol from sugarcane biomass poses a challenge to the scientific community. Current research in this field addresses the use of a plasma-based pretreatment of the lignocellulosic raw material. With the aim to provide a theoretical background for this experimental technique we investigate the role of low-energy electrons from the plasma in the rupture of the matrix of cellulosic chains. In this paper, we report calculated cross sections for elastic scattering of low-energy electrons by the α- and β-D-glucose monomers. The calculations employed the Schwinger multichannel method with pseudopotentials and were carried out at the static-exchange and static-exchange plus polarization levels of approximation. Through the comparison of the results obtained with inclusion of polarization effects we discuss the influence of the different conformations of the hydroxyl group linked to the anomeric carbon on the resonance spectra of these molecules. Resonant structures appearing at different energies for α- and β-glucose at the low-energy regime of impact energies can be understood as a fingerprint of an “isomeric effect” and suggest that distinct fragmentation mechanisms proceeding via σ∗ shape resonances may become operative depending on the glucose anomer under consideration. For energies above 15 eV the integral elastic cross sections are very similar for both monomers. Differential cross sections for the glucopyranose anomers considered in this work are typically dominated by a strong forward scattering due to the molecules’ large electric dipole moments and, for energies close to the resonances’ positions, they display particular features at the intermediate angular region, notably a pronounced f-wave scattering pattern, that are probably associated with the presence of those structures.
Driven dust acoustic waves with thermal effects: Comparison of experiment to fluid theory
Authors: Thomas Edward
Published: April 2010

This paper describes the results of a recent study of thermal effects on the fluid dispersion relation of dust acoustic waves. In this study, different comparisons are made of the dispersion relation, e.g., wave frequency versus wave number and wave number versus dust number density, which show that dust kinetic temperature is in the range 200–400 eV. An independent measurement of the dust kinetic temperature using stereoscopic particle image velocimetry techniques confirms this range of dust kinetic temperatures.
Multiorder boundaries among discrete domains: Relative fractal dimension and others
Authors: Xuan Qi , Du Fang , Wu Tie-Jun
Published: April 2010

In nature and society, most of competitions take place on the boundaries among a group of domains where different individuals or colonies share common resources; therefore, it is widely believed that domain boundaries play important roles in the evolution of many complex systems. Here, we first give a definition for multiorder boundaries among discrete domains and then propose a general method to calculate their relative fractal dimension, i.e., the ratio of the fractal dimension of the boundaries versus that of the domains themselves. Through analyzing three types of real-world discrete domains, several interesting results are revealed. For example, the limitation on the number of domains that an individual can join in may produce longer boundaries indicating more cruel competitions among the domains. Besides, the individuals with more social links are always considered more important in social networks, and it is found that these individuals as valuable resources of social domains are always centralized on the boundaries of higher order.
Open channel flow through a linear contraction
Authors: Defina Andrea , Viero Daniele Pietro
Published: April 2010

In this work we study the open channel flow through a linear contraction. We focus on the flow configuration with a two-dimensional jump in the contraction discussed by Akers and Bokhove [Phys. Fluids 20, 056601 (2008)] and propose a simple quasi-two-dimensional model to assess equilibrium conditions and explore their stability. We show that both bed friction and bed slope contribute to the stability of this flow configuration, which otherwise would be unstable. Results of the theoretical model are compared to both experimental data and the results of numerical simulations, and the comparison confirms the reliability of the proposed model. We also show that channel flow through a linear contraction can experience two different nested hysteretic loops.
In situ observation of ZnO nanowire growth on zinc film in environmental scanning electron microscope
Authors: Sun Yanghui , Gao Jingyun , Zhu Rui , Xu Jun , Chen Li , Zhang Jingmin , Zhao Qing , Yu Dapeng
Published: April 2010

In situ uniform growth of ZnO nanowires was realized and monitored at real time by heating zinc film in an environmental scanning electron microscope. Better controllability and repeatability were obtained by using zinc film as source material compared to traditionally used zinc powder. Morphology of the as-grown ZnO nanowires was found to depend on both the growth temperature and holding time. Low temperature (500 °C) and short growth time (∼20 min) favor one-dimensional nanowire growth, whereas longer holding time (>40 min) or higher temperature (700 °C) lead to nanosheet growth. The results suggest that the zinc vapor partial pressure is vital in determining the final morphology. These results help to give more insights into the mechanism of ZnO nanowire synthesis.
Silicon nanowires: Diameter dependence of growth rate and delay in growth
Authors: Dhalluin F. , Baron T. , Ferret P. , Salem B. , Gentile P. , Harmand J.-C.
Published: April 2010

We grew Si nanowires by chemical vapor deposition, via the vapor liquid solid growth, using silane as gaseous precursor and gold as catalyst. The results show that the nanowire length depends on their diameter. For nanowires with diameter under 100 nm, the length increases when diameter increases, because of an increase in the growth velocity. For the thicker diameter (d>100 nm), length decreases when diameter increases, due to an apparent incubation time which is all the higher as the diameter is high. We propose a semiempirical model combining Gibbs–Thomson effect and incubation time, which shows good agreement with the experimental data.
Twin microstructure dependent mechanical response in Ni–Mn–Ga single crystals
Authors: Straka Ladislav , Lanska Natalyia , Ullakko Kari , Sozinov Alexei
Published: April 2010

Ni–Mn–Ga single crystals with a twinning stress of about 0.1 MPa were studied. They showed a tendency to stay in a single variant state and to retain only one or very few twin boundaries during martensite reorientation induced by an external stress or magnetic field. This makes the crystals problematic for application in a magnetic actuator. To solve the issue, we introduced many parallel twin boundaries into the crystals by bending. However, this twin microstructure was not stable under cycling load. Additionally, it exhibited a twinning stress of 0.8 MPa—about ten times higher than a crystal with a single boundary.
A frequency-controlled magnetic vortex memory
Authors: Pigeau B. , de Loubens G. , Klein O. , Riegler A. , Lochner F. , Schmidt G. , Molenkamp L. W. , Tiberkevich V. S. , Slavin A. N.
Published: April 2010

Using the ultralow damping NiMnSb half-Heusler alloy patterned into vortex-state magnetic nanodots, we demonstrate a concept of nonvolatile memory controlled by the frequency. A perpendicular bias magnetic field is used to split the frequency of the vortex core gyrotropic rotation into two distinct frequencies, depending on the sign of the vortex core polarity p=±1 inside the dot. A magnetic resonance force microscope and microwave pulses applied at one of these two resonant frequencies allow for local and deterministic addressing of binary information (core polarity).
Physical origins of mobility degradation in extremely scaled SiO2/HfO2 gate stacks with La and Al induced dipoles
Authors: Ando Takashi , Copel Matt , Bruley John , Frank Martin M. , Watanabe Heiji , Narayanan Vijay
Published: April 2010

We demonstrate metal-gate-induced interfacial layer (IL) scaling using a HfO2 dielectric and clarify the kinetics underlying this process. The intrinsic IL scaling effect on electron mobility is separated from La and Al-induced dipole effects. We find that the mobility degradation for La-containing high-κ dielectrics is not due to the La-induced dipole but due to the intrinsic IL scaling effect, whereas the Al-induced dipole brings about additional mobility degradation. This unique nature of the La-induced dipole enables aggressive equivalent oxide thickness scaling down to 0.42 nm without extrinsic mobility degradation when combined with IL scaling.
Probing the relationship between structural and optical properties of Si-doped AlN
Authors: Pantha B. N. , Sedhain A. , Li J. , Lin J. Y. , Jiang H. X.
Published: April 2010

Much efforts have been devoted to achieve conductivity control in the ultrahigh band gap (∼6.1 eV) AlN by Si doping. The effects of Si-doping on the structural and optical properties of AlN epilayers have been investigated. X-ray diffraction studies revealed that accumulation of tensile stress in Si-doped AlN is a reason for the formation of additional edge dislocations. Photoluminescence (PL) studies revealed that the linewidths of both band-edge and impurity related transitions are directly correlated with the density of screw dislocations, Nscrew, which increases with the Si doping concentration (NSi). Furthermore, it was formulated that the band-edge (impurity) PL emission linewidth increases linearly with increasing Nscrew at a rate of ∼3.3±0.7 meV/108 cm−2 (26.5±4 meV/108 cm−2), thereby establishing PL measurement as a simple and effective method to estimate screw dislocation density in AlN epilayers.
Josephson supercurrent in Nb/InN-nanowire/Nb junctions
Authors: Frielinghaus R. , Batov I. E. , Weides M. , Kohlstedt H. , Calarco R. , Schäpers Th.
Published: April 2010

We experimentally studied the Josephson supercurrent in Nb/InN-nanowire/Nb junctions. Large critical currents up to 5.7 μA have been achieved, which proves the good coupling of the nanowire to the superconductor. The effect of a magnetic field perpendicular to the plane of the Josephson junction on the critical current has been studied. The observed monotonous decrease in the critical current with magnetic field is explained by the magnetic pair-breaking effect in planar Josephson junctions of ultra-narrow width [J. C. Cuevas and F. S. Bergeret, Phys. Rev. Lett. 99, 217002 (2007)].
Microstructural evolution of Mn-rich antiferromagnetic Mn–Cu alloy under temperature field
Authors: Man J. , Zhang J. H. , Rong Y. H.
Published: April 2010

This paper reports the microstructural evolution during forward and reverse martensitic transformations as temperature changes in Mn-rich Mn–Cu alloy. The driving force of martensitic transformation and transformation strain in time-dependent Ginzburg–Laudau kinetic equation is considered as functions of temperature. The computer simulation by using a three-dimensional phase-field theory shows that fct (011) twin martensites grow up with decreasing temperature and shrink with increasing temperature under martensitic transformation temperature, Ms. The forward and reverse processes are entirely reversible and show a very small hysteresis. It is proved that the relaxation of stored strain energy during the forward martensitic transformation plays a key role when reverse martensitic transformation takes place. The simulated results are consistent with experiments.
High-contrast all optical bistable switching in coupled nonlinear photonic crystal microcavities
Authors: Li Shaohui , Cai Xuhong
Published: April 2010

We present a photonic crystal configuration consisting of a waveguide directly coupled to two microcavities with instantaneous Kerr nonlinearity. We prove that such a configuration can function as a high contrast all optical switch with properly misaligning the resonant frequencies of the constitutional photonic crystal microcavities.
Analysis of periodic dislocation networks using x-ray diffraction and extended finite element modeling
Authors: Wintersberger E. , Hrauda N. , Kriegner D. , Keplinger M. , Springholz G. , Stangl J. , Bauer G. , Oswald J. , Belytschko T. , Deiter C. , Bertram F. , Seeck O. H.
Published: April 2010

We combine the extended finite element method with simulations of diffracted x-ray intensities to investigate the diffusely scattered intensity due to dislocations. As a model system a thin PbSe epitaxial layer grown on top of a PbTe buffer on a CdTe substrate was chosen. The PbSe film shows a periodic dislocation network where the dislocations run along the orthogonal ⟨110⟩ directions. The array of dislocations within this layer can be described by a short range order model with a narrow distribution.
Characterizing a strain-driven phase transition in VO2
Authors: Kikuzuki T. , Lippmaa M.
Published: April 2010

A crystal bending stage was developed for measuring the transport properties of a VO2 thin film under low-frequency dynamic strain. A compressive stress of ∼20 MPa, applied along the VO2 c-axis at frequencies of up to 1 kHz, resulted in a 25% resistance change in the film. It was found that the activation energy of the strain-driven metal-insulator transition scales with the width of resistance hysteresis as 0.030 eV/K. The effect of normalized strain on resistance was nearly two times larger than the effect of normalized temperature at the transition point.
A single-component organic crystal is ferroelectric at room temperature
Authors: Day Charles
Published: April 2010

Hydrogen bonds that hold croconic acid crystals together are responsible for the material’s high spontaneous polarization and strong ferroelectric effect.
National Science Board warns of slide in US competitiveness
Authors: Kramer David
Published: April 2010

Board instructs NSF to select “truly transformational” research proposals and advises White House to ensure that US retains international leadership in key fields.
Laboratory architecture: Building for an uncertain future
Authors: Leslie Stuart W.
Published: April 2010

Three iconic laboratories constructed in 1966 reveal how architectural design and scientific culture can help—or hinder—a building’s ability to adapt to the changing discipline it serves.
Frontiers in spin-polarized tunneling
Authors: Moodera Jagadeesh S. , Miao Guo-Xing , Santos Tiffany S.
Published: April 2010

Thanks to recent advances in materials research, magnetic tunnel junctions that control the flow of polarized electrons are poised to revolutionize information technology.
Neutrino mass and the origin of matter
Authors: Mohapatra Rabindra N.
Published: April 2010

Astronomical observations have established that the universe consists almost exclusively of matter, with just a tiny amount of antimatter. A key problem in particle physics and cosmology is to understand that asymmetry.
The Right Path: A Post-Mongol Persian Ismaili Treatise
Authors: Virani Shafique N.
Published: April 2010

The Epistle of the Right Path (Risāla-yi Ṣirāṭ al-Mustaqīm) is an anonymous treatise, possibly dating to the late fourteenth or early fifteenth century. It may be the earliest Persian Ismaili prose work of the post-Mongol period to come to light, and is here introduced, discussed, edited and translated. A clearly articulated, philosophically inclined treatment of numerous themes in Ismaili thought, the text draws frequently from Nasir al-Din Tusi's spiritual autobiography, The Voyage (Sayr wa-Sulūk). Its subject matter includes the correspondence between the exoteric and esoteric worlds, the concept of the divine command through which creation attains perfection, the role of the Imam and the esoteric hierarchy, and the fact that esoteric exegesis (ta 'wīl) of divine revelation must be compatible with the principles of the intellect.
Iranian Women's Participation in the Academic World
Authors: Khosrokhavar Farhad , Ghaneirad Mohammad Amin
Published: April 2010

This article intends to give a comprehensive picture of women's participation in the scientific field in Iran in the last four decades, among students and members of academia. One major fact is that despite the legal and cultural impediments the proportion of young women in the universities has risen above 50 percent. Another is that this increase has occurred much more at the undergraduate level than at the graduate and post-graduate levels. In the academic world, women are still far outnumbered by men, particularly at the higher levels of the hierarchy. We intend to show how the discrepancies are structured between the undergraduate and the graduate levels on the one hand, and between the lower and higher levels of academic hierarchy on the other, and propose an interpretation of these two major tendencies.
Jews in the Pre-Constitutional Years: The Shiraz Incident of 1905
Authors: Tsadik Daniel
Published: April 2010

During the Constitutional years (1906–11) the legal status of the Jews and some other religious minorities improved, even if only to a limited extent. Can one assume that this change in the legal status of the Jews reflected changes in the public's actual treatment toward the Jews in reality during the days leading up to the Constitutional Revolution in 1906? To an extent, the answer is in the affirmative. The present article argues, however, that the real life situation of the Jews in the years leading up to the Constitutional Revolution was still often one of abuse and occasional persecution. To prove this contention, section I of the article presents some such cases. Section II establishes some of the reasons for the attacks on the Jews—not only religious, but also economic and socio-political ones, as well as briefly suggesting certain recurring paradigms surrounding it. Section III looks at one case study from November 1905 in the city of Shiraz. Finally, this preliminary research ends with some concluding remarks.

Be-karestan-e Sane‘ kas cheh danad,

kherad dar kar-e U hayran bemanad.1
A dialogue model of belief
Authors: Walton Douglas
Published: April 2010

This paper offers a new model of belief by embedding the Peircean account of belief into a formal dialogue system that uses argumentation schemes for practical reasoning and abductive reasoning. A belief is characterised as a stable proposition that is derived abductively by one agent in a dialogue from the commitment set (including commitments derived from actions and goals) of another agent. On the model (to give a rough summary), a belief is defined as a proposition held by an agent that (1) is not easily changed (stable), (2) is a matter of degree (held more or less weakly or strongly), (3) guides the goals and actions of the agent, and (4) is habitually or tenaciously held in a manner that indicates a strong commitment to defend it. It is argued that the new model overcomes the pervasive conflict in artificial intelligence between the belief-desire-intention model of reasoning and the commitment model.
Persistence of the non-twist torus in nearly integrable hamiltonian systems
Authors: Xu Junxiang , You Jiangong
Published: April 2010

In this paper we consider analytic nearly integrable hamiltonian systems, and prove that if the frequency mapping has nonzero Brouwer topological degree at some Diophantine frequency, then the invariant torus with this frequency persists under small perturbations.
Subsystems of Fock need not be Fock: Spatial CP-semigroups
Authors: Bhat B. , Liebscher Volkmar , Skeide Michael
Published: April 2010

We show that a product subsystem of a time ordered system (that is, a product system of time ordered Fock modules), even one of type I, need not be isomorphic to a time ordered product system. In this way, we answer an open problem in the classification of CP-semigroups by product systems. We define spatial strongly continuous CP-semigroups on a unital

C
∗

C^*

-algebra and characterize them as those CP-semigroups that have a Christensen-Evans generator.
Burkholder’s inequalities in noncommutative Lorentz spaces
Authors: Jiao Yong
Published: April 2010

We prove Burkholder’s inequalities in noncommutative Lorentz spaces

L

p
,
q

(

M

)
,
1
>
p
>
∞
,

L^{p,q}(\mathcal {M}), 1>p>\infty ,

1
≤
q
>
∞

1\leq q>\infty

, associated with a von Neumann algebra

M

\mathcal {M}

equipped with a faithful normal tracial state. These estimates generalize the classical inequalities in the commutative case.
Discontinuity of the Lempert function of the spectral ball
Authors: Thomas Pascal , Trao Nguyen
Published: April 2010

We give some further criteria for continuity or discontinuity of the Lempert function of the spectral ball

Ω
n

\Omega _n

, with respect to one or both of its arguments, in terms of cyclicity of the matrices involved.
Integral conditions on the uniform asymptotic stability for two-dimensional linear systems with time-varying coefficients
Authors: Sugie Jitsuro , Onitsuka Masakazu
Published: April 2010

This paper is concerned with the uniform asymptotic stability of the zero solution of the linear systemx′=A(t)x\mathbf {x}’ = A(t)\mathbf {x}withA(t)A(t)being a2×22\times 2matrix. Our result can be used without knowledge about a fundamental matrix of the system.
Stochastic completeness and volume growth
Authors: Bär Christian , Bessa G.
Published: April 2010

It was suggested in 1999 that a certain volume growth condition for geodesically complete Riemannian manifolds might imply that the manifold is stochastically complete. This is motivated by a large class of examples and by a known analogous criterion for recurrence of Brownian motion. We show that the suggested implication is not true in general. We also give counterexamples to a converse implication.
Essential norms of composition operators between Bloch type spaces
Authors: Zhao Ruhan
Published: April 2010

For

α
>
0

\alpha >0

, the

α
\alpha

-Bloch space is the space of all analytic functions

f
f

on the unit disk

D
D

satisfying
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-vertical-bar f double-vertical-bar Subscript upper B Sub Superscript alpha Subscript Baseline equals sup Underscript z element-of upper D Endscripts StartAbsoluteValue f prime left-parenthesis z right-parenthesis EndAbsoluteValue left-parenthesis 1 minus StartAbsoluteValue z EndAbsoluteValue squared right-parenthesis Superscript alpha Baseline greater-than normal infinity period">

‖
f

‖

B

α

=

sup

z
∈
D

|

f
′

(
z
)

|

(
1
−

|

z

|

2

)

α

>
∞
.

\|f\|_{B^{\alpha }}=\sup _{z\in D}|f’(z)|(1-|z|^2)^{\alpha }>\infty .

\]
Let

φ
\varphi

be an analytic self-map of

D
D

. We show that for

0
>
α
,
β
>
∞

0>\alpha ,\beta >\infty

, the essential norm of the composition operator

C

φ

C_{\varphi }

mapping from

B

α

B^{\alpha }

to

B

β

B^{\beta }

can be given by the following formula:
\[
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-vertical-bar upper C Subscript phi Baseline double-vertical-bar Subscript e Baseline equals left-parenthesis StartFraction e Over 2 alpha EndFraction right-parenthesis Superscript alpha Baseline limit sup Underscript n right-arrow normal infinity Endscripts n Superscript alpha minus 1 Baseline double-vertical-bar phi Superscript n Baseline double-vertical-bar Subscript upper B Sub Superscript beta Subscript Baseline period">

‖

C

φ

‖
e

=

(

e

2
α

)

α

lim sup

n
→
∞

n

α
−
1

‖

φ
n

‖

B

β

.

\|C_{\varphi }\|_e=\left (\frac {e}{2\alpha }\right )^{\alpha }\limsup _{n\to \infty } n^{\alpha -1}\|\varphi ^n\|_{B^{\beta }}.

\]
Zeros of the Eisenstein series 𝐸₂
Authors: El Basraoui Abdelkrim , Sebbar Abdellah
Published: April 2010

In this paper we investigate the zeros of the Eisenstein series

E
2

E_2

. In particular, we prove that

E
2

E_2

has infinitely many

SL
2

⁡
(

Z

)

\operatorname {SL}_2(\mathbb {Z})

-inequivalent zeros in the upper half-plane

H

\mathfrak {H}

, yet none in the standard fundamental

F

\mathfrak {F}

. Furthermore, we go on to investigate other fundamental regions in the upper half-plane

H

\mathfrak {H}

for which there do or do not exist zeros of

E
2

E_2

. We establish infinitely many such regions containing a zero of

E
2

E_2

and infinitely many which do not.
A Barban-Davenport-Halberstam asymptotic for number fields
Authors: Smith Ethan
Published: April 2010

Let

K
K

be a fixed number field, and assume that

K
K

is Galois over

Q

\mathbb {Q}

. Previously, the author showed that when estimating the number of prime ideals with norm congruent to

a
a

modulo

q
q

via the Chebotarëv Density Theorem, the mean square error in the approximation is small when averaging over all

q
≤
Q

q\le Q

and all appropriate

a
a

. In this article, we replace the upper bound by an asymptotic formula. The result is related to the classical Barban-Davenport-Halberstam Theorem in the case

K
=

Q

K=\mathbb {Q}

.
On the Gauss curvature of compact surfaces in homogeneous 3-manifolds
Authors: Torralbo Francisco , Urbano Francisco
Published: April 2010

Compact flat surfaces of homogeneous Riemannian 3-manifolds with isometry group of dimension 4 are classified. Nonexistence results for compact constant Gauss curvature surfaces in these 3-manifolds are established.
New thoughts on the vector-valued Mihlin–Hörmander multiplier theorem
Authors: Hytönen Tuomas
Published: April 2010

Let

X
X

be a UMD space with type

t
t

and cotype

q
q

, and let

T
m

T_m

be a Fourier multiplier operator with a scalar-valued symbol

m
m

. If
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="StartAbsoluteValue partial-differential Superscript alpha Baseline m left-parenthesis xi right-parenthesis EndAbsoluteValue less-than-or-equivalent-to StartAbsoluteValue xi EndAbsoluteValue Superscript minus StartAbsoluteValue alpha EndAbsoluteValue">

|

∂

α

m
(
ξ
)

|

≲

|

ξ

|

−

|

α

|

|\partial ^{\alpha }m(\xi )|\lesssim |{\xi }|^{-|\alpha |}

for all

|

α

|

≤
⌊

n

/

max
(
t
,

q
′

)
⌋

+
1

|\alpha |\leq \lfloor {n/\max (t,q’)\rfloor }+1

, then

T
m

T_m

is bounded on

L
p

(

R

n

;
X
)

L^p(\mathbb {R}^n;X)

for all

p
∈
(
1
,
∞
)

p\in (1,\infty )

. For scalar-valued multipliers, this improves the theorem of Girardi and Weis (J. Funct. Anal., 2003), who required similar assumptions for derivatives up to the order

⌊

n

/

r

⌋
+
1

\lfloor {n/r}\rfloor +1

, where

r
≤
min
(
t
,

q
′

)

r\leq \min (t,q’)

is a Fourier-type of

X
X

. However, the present method does not apply to operator-valued multipliers, which are also covered by the Girardi–Weis theorem.
A note on values of noncommutative polynomials
Authors: Brešar Matej , Klep Igor
Published: April 2010

We find a class of algebras

A

\mathcal {A}

satisfying the following property: for every nontrivial noncommutative polynomial

f
(

X
1

,
…
,

X
n

)

f(X_1,\ldots ,X_n)

, the linear span of all its values

f
(

a
1

,
…
,

a
n

)

f(a_1,\ldots ,a_n)

,

a
i

∈

A

a_i\in \mathcal {A}

, equals

A

\mathcal {A}

. This class includes the algebras of all bounded and all compact operators on an infinite dimensional Hilbert space.
A non-finitely generated algebra of Frobenius maps
Authors: Katzman Mordechai
Published: April 2010

This paper describes an Artinian module over a ring of prime characteristic whose algebra of Frobenius maps is not finitely generated. This settles a question raised by Lyubeznik and Smith.
Invariant subspaces in Bergman space over the bidisc
Authors: Redett David , Tung James
Published: April 2010

In this paper, we investigate the doubly commuting condition restricted to invariant subspaces of the Bergman space over the bidisc. This condition was first introduced by V. Mandrekar in the setting of the Hardy space over the bidisc.
The Hydrophobic Core of the Sec61 Translocon Defines the Hydrophobicity Threshold for Membrane Integration
Authors: Junne Tina , Kocik Lucyna , Spiess Martin
Published: April 2010

The Sec61 translocon mediates the translocation of proteins across the endoplasmic reticulum membrane and the lateral integration of transmembrane segments into the lipid bilayer. The structure of the idle translocon is closed by a lumenal plug domain and a hydrophobic constriction ring. To test the function of the apolar constriction, we have mutated all six ring residues of yeast Sec61p to more hydrophilic, bulky, or even charged amino acids (alanines, glycines, serines, tryptophans, lysines, or aspartates). The translocon was found to be surprisingly tolerant even to the charge mutations in the constriction ring, because growth and translocation efficiency were not drastically affected. Most interestingly, ring mutants were found to affect the integration of hydrophobic sequences into the lipid bilayer, indicating that the translocon does not simply catalyze the partitioning of potential transmembrane segments between an aqueous environment and the lipid bilayer but that it also plays an active role in setting the hydrophobicity threshold for membrane integration.
Streamlining the construction of large-scale dynamic models using generic kinetic equations
Authors: Adiamah Delali A. , Handl Julia , Schwartz Jean-Marc
Published: April 2010

Motivation: Studying biological systems, not just at an individual component level but at a system-wide level, gives us great potential to understand fundamental functions and essential biological properties. Despite considerable advances in the topological analysis of metabolic networks, inadequate knowledge of the enzyme kinetic rate laws and their associated parameter values still hampers large-scale kinetic modelling. Furthermore, the integration of gene expression and protein levels into kinetic models is not straightforward.

Results: The focus of our research is on streamlining the construction of large-scale kinetic models. A novel software tool was developed, which enables the generation of generic rate equations for all reactions in a model. It encompasses an algorithm for estimating the concentration of proteins for a reaction to reach a particular steady state when kinetic parameters are unknown, and two robust methods for parameter estimation. It also allows for the seamless integration of gene expression or protein levels into a reaction and can generate equations for both transcription and translation. We applied this methodology to model the yeast glycolysis pathway; our results show that the behaviour of the system can be accurately described using generic kinetic equations.

Availability and implementation: The software tool, together with its source code in Java, is available from our project web site at http://www.bioinf.manchester.ac.uk/schwartz/grape

Contact:  jean-marc.schwartz@manchester.ac.uk

Supplementary information:  Supplementary data are available at Bioinformatics online.
Combining sensitivity and uncertainty analysis to evaluate the impact of management measures with ISIS–Fish: marine protected areas for the Bay of Biscay anchovy (Engraulis encrasicolus) fishery
Authors: Lehuta Sigrid , Mahévas Stéphanie , Petitgas Pierre , Pelletier Dominique
Published: April 2010

Lehuta, S., Mahévas, S., Petitgas, P., and Pelletier, D. 2010. Combining sensitivity and uncertainty analysis to evaluate the impact of management measures with ISIS–Fish: marine protected areas for the Bay of Biscay anchovy (Engraulis encrasicolus) fishery. – ICES Journal of Marine Science, 67: 1063–1075. Spatio-seasonal explicit simulation models can predict the impact of spatial management measures on marine fish populations and fishing activities. As fisheries are complex systems, fisheries simulation models are often complex, with many uncertain parameters. Here, the methodology is provided to deliver fishery diagnostics within an uncertainty context using a complex simulation tool. A sensitivity analysis of the model is performed on model outputs using partial least-squares to identify the most sensitive parameters. The impact of several management measures is then simulated using a statistical simulation design taking into account the uncertainty of the selected sensitive parameters. This approach was applied to the Bay of Biscay anchovy stock using the ISIS-Fish (Integration of Spatial Information for Simulation of Fisheries) model to assess the impact of imposing marine protected areas (MPAs) conditionally on parameter uncertainty. The diagnostic appeared to be highly sensitive to the mortality of larvae and juveniles, growth, and reproduction. The uncertainty of the values of these parameters did not permit any of the simulated MPA designs to be proposed. However, according to anchovy catch and biomass, the simulations allowed the low impact of closure duration to be shown and underscored the utility of protecting such key processes as spawning.
Proximate determinants of telomere length in sand lizards (
Lacerta agilis
)
Authors: Olsson Mats , Pauliny Angela , Wapstra Erik , Blomqvist Donald
Published: April 2010

Telomeres are repeat sequences of non-coding DNA that cap the ends of chromosomes and contribute to their stability and the genomic integrity of cells. In evolutionary ecology, the main research target regarding these genomic structures has been their role in ageing and as a potential index of age. However, research on humans shows that a number of traits contribute to among-individual differences in telomere length, in particular traits enhancing cell division and genetic erosion, such as levels of free radicals and stress. In lizards, tail loss owing to predation attempts results in a stress-induced shift to a more cryptic lifestyle. In sand lizard (
Lacerta agilis
) males, telomere length was compromised by tail regrowth in a body size-related manner, so that small males, which already exhibit more cryptic mating tactics, were less affected than larger males. Tail regrowth just fell short of having a significant relationship with telomere length in females, and so did age in males. In females, there was a significant positive relationship between age and telomere length. We conclude that the proximate effect of compromised antipredation and its associated stress seems to have a more pronounced effect in males than in females and that age-associated telomere dynamics differ between the sexes.
Computational model of cell positioning: directed and collective migration in the intestinal crypt epithelium
Authors: Wong Shek Yoon , Chiam K.-H. , Lim Chwee Teck , Matsudaira Paul
Published: April 2010

The epithelium of the intestinal crypt is a dynamic tissue undergoing constant regeneration through cell growth, cell division, cell differentiation and apoptosis. How the epithelial cells maintain correct positioning and how they migrate in a directed and collective fashion are still not well understood. In this paper, we developed a computational model to elucidate these processes. We show that differential adhesion between epithelial cells, caused by the differential activation of EphB receptors and ephrinB ligands along the crypt axis, is necessary to regulate cell positioning. Differential cell adhesion has been proposed previously to guide cell movement and cause cell sorting in biological tissues. The proliferative cells and the differentiated post-mitotic cells do not intermingle as long as differential adhesion is maintained. We also show that, without differential adhesion, Paneth cells are randomly distributed throughout the intestinal crypt. In addition, our model suggests that, with differential adhesion, cells migrate more rapidly as they approach the top of the intestinal crypt. Finally, by calculating the spatial correlation function of the cell velocities, we observe that differential adhesion results in the differentiated epithelial cells moving in a coordinated manner, where correlated velocities are maintained at large distances, suggesting that differential adhesion regulates coordinated migration of cells in tissues.
Emergence of a prestressed eukaryotic nucleus during cellular differentiation and development
Authors: Mazumder Aprotim , Shivashankar G. V.
Published: April 2010

Nuclear shape and size are emerging as mechanistic regulators of genome function. Yet, the coupling between chromatin assembly and various nuclear and cytoplasmic scaffolds is poorly understood. The present work explores the structural organization of a prestressed nucleus in a variety of cellular systems ranging from cells in culture to those in an organism. A combination of laser ablation and cellular perturbations was used to decipher the dynamic nature of the nucleo-cytoplasmic contacts. In primary mouse embryonic fibroblasts, ablation of heterochromatin nodes caused an anisotropic shrinkage of the nucleus. Depolymerization of actin and microtubules, and inhibition of myosin motors, resulted in the differential stresses that these cytoplasmic systems exert on the nucleus. The onset of nuclear prestress was then mapped in two contexts—first, in the differentiation of embryonic stem cells, where signatures of prestress appeared with differentiation; second, at an organism level, where nuclear or cytoplasmic laser ablations of cells in the earlyDrosophilaembryo induced a collapse of the nucleus only after cellularization. We thus show that the interplay of physical connections bridging the nucleus with the cytoplasm governs the size and shape of a prestressed eukaryotic nucleus.
Live cell imaging of mechanotransduction
Authors: Liu Bo , Kim Tae-Jin , Wang Yingxiao
Published: April 2010

Mechanical forces play important roles in the regulation of cellular functions, including polarization, migration and stem cell differentiation. Tremendous advancement in our understanding of mechanotransduction has been achieved with the recent development of imaging technologies and molecular biosensors. In particular, genetically encoded biosensors based on fluorescence resonance energy transfer (FRET) technology have been widely developed and applied in the field of mechanobiology. In this article, we will provide an overview of the recent progress of FRET application in mechanobiology, specifically mechanotransduction. We first introduce fluorescent proteins and FRET technology. We then discuss the mechanotranduction processes in different cells including stem cells, with a special emphasis on the important signalling molecules involved in mechanotransduction. Finally, we discuss methods that can allow the integration of simultaneous FRET imaging and mechanical stimulation to trigger signalling transduction. In summary, FRET technology has provided a powerful tool for the study of mechanotransduction to advance our systematic understanding of the molecular mechanisms by which cells respond to mechanical stimulation.
A theoretical study of diffusional transport over the alveolar surfactant layer
Authors: Åberg Christoffer , Sparr Emma , Larsson Marcus , Wennerström Håkan
Published: April 2010

In this communication, we analyse the passage of oxygen and carbon dioxide over the respiratory membrane. The lung surfactant membrane at the alveolar interface can have a very special arrangement, which affects the diffusional transport. We present a theoretical model for the diffusion of small molecules in membranes with a complex structure, and we specifically compare a membrane composed of a tubular bilayer network with a membrane consisting of a stack of bilayers. Oxygen and carbon dioxide differ in terms of their solubility in the aqueous and the lipid regions of the membrane, and we show that this difference clearly influences their transport properties in the different membrane structures. During normal respiration, the rate-limiting step for carbon dioxide transport is in the gas phase of the different compartments in the lung. For oxygen, on the other hand, the rate is limited by the transport between alveoli and the capillary blood vessels, including the lung surfactant membrane. In a membrane with a structure of a continuous tubular lipid network, oxygen transport is facilitated to a significant extent compared with the structure of aligned lipid bilayers. The model calculations in the present study show that transport of oxygen through the tubular structure is indeed
ca
30 per cent faster than transport through a membrane composed of stacked bilayers. The tubular network will also facilitate the transport of apolar substances between the gas phase and the blood. Important examples are ethanol and other volatile liquids that can leave the blood through the lungs, and gaseous anaesthetics or volatile solvents that are inhaled. This exemplifies a new physiological role of a tubular lipid network in the lung surfactant membrane.
Mechanosensitivity of ion channels based on protein–lipid interactions
Authors: Yoshimura Kenjiro , Sokabe Masahiro
Published: April 2010

Ion channels form a group of membrane proteins that pass ions through a pore beyond the energy barrier of the lipid bilayer. The structure of the transmembrane segment of membrane proteins is influenced by the charges and the hydrophobicity of the surrounding lipids and the pressure on its surface. A mechanosensitive channel is specifically designed to change its conformation in response to changes in the membrane pressure (tension). However, mechanosensitive channels are not the only group that is sensitive to the physical environment of the membrane: voltage-gated channels are also amenable to the lipid environment. In this article, we review the structure and gating mechanisms of the mechanosensitive channels and voltage-gated channels and discuss how their functions are affected by the physical properties of the lipid bilayer.
Laminar flow around corners triggers the formation of biofilm streamers
Authors: Rusconi Roberto , Lecuyer Sigolene , Guglielmini Laura , Stone Howard A.
Published: April 2010

Bacterial biofilms have an enormous impact on medicine, industry and ecology. These microbial communities are generally considered to adhere to surfaces or interfaces. Nevertheless, suspended filamentous biofilms, or streamers, are frequently observed in natural ecosystems where they play crucial roles by enhancing transport of nutrients and retention of suspended particles. Recent studies in streamside flumes and laboratory flow cells have hypothesized a link with a turbulent flow environment. However, the coupling between the hydrodynamics and complex biofilm structures remains poorly understood. Here, we report the formation of biofilm streamers suspended in the middle plane of curved microchannels under conditions of laminar flow. Experiments with different mutant strains allow us to identify a link between the accumulation of extracellular matrix and the development of these structures. Numerical simulations of the flow in curved channels highlight the presence of a secondary vortical motion in the proximity of the corners, which suggests an underlying hydrodynamic mechanism responsible for the formation of the streamers. Our findings should be relevant to the design of all liquid-carrying systems where biofilms are potentially present and provide new insights on the origins of microbial streamers in natural and industrial environments.