bluuebunny/crossref_metadata_2025 huggingface dataset:
Regulation of antigen‐receptor gene assembly in hagfish
Authors: Kishishita Natsuko , Matsuno Tatsuya , Takahashi Yoshimasa , Takaba Hiroyuki , Nishizumi Hirofumi , Nagawa Fumikiyo
Published: January 2010

Variable lymphocyte receptors (VLRs) are antigen receptors in the jawless vertebrates lamprey and hagfish. VLR genes are classified into VLRA and VLRB, and lymphocytes expressing VLRA are T‐cell‐like, whereas those expressing VLRB are B‐cell‐like in the sea lamprey. Diverse VLR genes are assembled somatically in lymphocytes; however, how the assembly is regulated is still largely unknown. Here, we analyse VLR gene assembly at the single‐cell level in the inshore hagfish (Eptatretus burgeri). Each lymphocyte assembles and transcribes only one type of VLR gene, either VLRA or VLRB. In general, monoallelic assembly of VLR was observed, but diallelic assembly was found in some cases—in many of which, one allele was functional and the other was defective. In fact, all VLR‐assembled lymphocytes contained at least one functional VLR gene. Together, these results indicate a feedback inhibition of VLR assembly and selection of VLR‐positive lymphocytes.
Integrin–TGF‐β crosstalk in fibrosis, cancer and wound healing
Authors: Margadant Coert , Sonnenberg Arnoud
Published: January 2010

Accumulating evidence indicates that there is extensive crosstalk between integrins and TGF‐β signalling. TGF‐β affects integrin‐mediated cell adhesion and migration by regulating the expression of integrins, their ligands and integrin‐associated proteins. Conversely, several integrins directly control TGF‐β activation. In addition, a number of integrins can interfere with both Smad‐dependent and Smad‐independent TGF‐β signalling in different ways, including the regulation of the expression of TGF‐β signalling pathway components, the physical association of integrins with TGF‐β receptors and the modulation of downstream effectors. Reciprocal TGF‐β–integrin signalling is implicated in normal physiology, as well as in a variety of pathological processes including systemic sclerosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease and cancer; thus, integrins could provide attractive therapeutic targets to interfere with TGF‐β signalling in these processes.
Precise stress measurements with white synchrotron x rays
Authors: Weidner Donald J. , Vaughan Michael T. , Wang Liping , Long Hongbo , Li Li , Dixon Nathaniel A. , Durham William B.
Published: January 2010

In situ measurement of stress in polycrystalline samples forms the basis for studies of the mechanical properties of materials with very broad earth science and materials science applications. Synchrotron x rays have been used to define the local elastic strain in these samples, which in turn define stress. Experimental work to date has been carried out on a prototype detection system that provided a strain measurement precision >10−4, which corresponds to a stress resolution >50 MPa for silicate minerals. Here we report operation of a new, permanent, energy dispersive detection system for white radiation, which has been developed at the National Synchrotron Light Source. The new system provides differential strain measurements with a precision of 3×10−5 for volumes that are 50×50×500 μm3. This gives a stress precision of about 10 MPa for silicate minerals.
Reaction-in-flight neutrons as a signature for shell mixing in National Ignition Facility capsules
Authors: Hayes A. C. , Bradley P. A. , Grim G. P. , Jungman Gerard , Wilhelmy J. B.
Published: January 2010

Analytic calculations and results from computational simulations are presented that suggest that reaction-in-flight (RIF) neutrons can be used to diagnose mixing of the ablator shell material into the fuel in deuterium-tritium (DT) capsules designed for the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)]. Such mixing processes in NIF capsules are of fundamental physical interest and can have important effects on capsule performance, quenching the total thermonuclear yield. The sensitivity of RIF neutrons to hydrodynamical mixing arises through the dependence of RIF production on charged-particle stopping lengths in the mixture of DT fuel and ablator material. Since the stopping power in the plasma is a sensitive function of the electron temperature and density, it is also sensitive to mix. RIF production scales approximately inversely with the degree of mixing taking place, and the ratio of RIF to down-scattered neutrons provides a measure of the mix fraction and/or the mixing length. For sufficiently high-yield capsules, where spatially resolved RIF images may be possible, neutron imaging could be used to map RIF images into detailed mix images.
The stability of adaptive synchronization of chaotic systems
Authors: Sorrentino Francesco , Barlev Gilad , Cohen Adam B. , Ott Edward
Published: January 2010

In past works, various schemes for adaptive synchronization of chaotic systems have been proposed. The stability of such schemes is central to their utilization. As an example addressing this issue, we consider a recently proposed adaptive scheme for maintaining the synchronized state of identical coupled chaotic systems in the presence of a priori unknown slow temporal drift in the couplings. For this illustrative example, we develop an extension of the master stability function technique to study synchronization stability with adaptive coupling. Using this formulation, we examine the local stability of synchronization for typical chaotic orbits and for unstable periodic orbits within the synchronized chaotic attractor (bubbling). Numerical experiments illustrating the results are presented. We observe that the stable range of synchronism can be sensitively dependent on the adaptation parameters, and we discuss the strong implication of bubbling for practically achievable adaptive synchronization. We also find that for our coupled systems with adaptation, bubbling can be caused by a slow temporal drift in the coupling strength.
Recurrence quantification analysis of turbulent fluctuations in the plasma edge of Tokamak Chauffage Alfvén Brésilien tokamak
Authors: Guimarães-Filho Z. O. , Caldas I. L. , Viana R. L. , Nascimento I. C. , Kuznetsov Yu. K. , Kurths J.
Published: January 2010

Recurrences are close returns of a given state in a time series, and can be used to identify different dynamical regimes and other related phenomena, being particularly suited for analyzing experimental data. In this work, we use recurrence quantification analysis to investigate dynamical patterns in scalar data series obtained from measurements of floating potential and ion saturation current at the plasma edge of the Tokamak Chauffage Alfvén Brésilien [R. M. O. Galvão et al., Plasma Phys. Controlled Fusion 43, 1181 (2001)]. We consider plasma discharges with and without the application of radial electric bias, and also with two different regimes of current ramp. Our results indicate that biasing improves confinement through destroying highly recurrent regions within the plasma column that enhance particle and heat transport.
Efficient computation of parameter sensitivities of discrete stochastic chemical reaction networks
Authors: Rathinam Muruhan , Sheppard Patrick W. , Khammash Mustafa
Published: January 2010

Parametric sensitivity of biochemical networks is an indispensable tool for studying system robustness properties, estimating network parameters, and identifying targets for drug therapy. For discrete stochastic representations of biochemical networks where Monte Carlo methods are commonly used, sensitivity analysis can be particularly challenging, as accurate finite difference computations of sensitivity require a large number of simulations for both nominal and perturbed values of the parameters. In this paper we introduce the common random number (CRN) method in conjunction with Gillespie’s stochastic simulation algorithm, which exploits positive correlations obtained by using CRNs for nominal and perturbed parameters. We also propose a new method called the common reaction path (CRP) method, which uses CRNs together with the random time change representation of discrete state Markov processes due to Kurtz to estimate the sensitivity via a finite difference approximation applied to coupled reaction paths that emerge naturally in this representation. While both methods reduce the variance of the estimator significantly compared to independent random number finite difference implementations, numerical evidence suggests that the CRP method achieves a greater variance reduction. We also provide some theoretical basis for the superior performance of CRP. The improved accuracy of these methods allows for much more efficient sensitivity estimation. In two example systems reported in this work, speedup factors greater than 300 and 10 000 are demonstrated.
Note: Interference technique for minimally invasive, subnanometer, microsecond measurements of displacements
Authors: Dujovne Irene , Kerssemakers Jacob , Cappello G. , Dekker Cees
Published: January 2010

We present a novel high-resolution technique for single-molecule experiments, viz., differential traveling wave tracking. This is an interference-based scattering technique where we use gold nanoparticles for high scattering intensities and incorporate differential measurements along one in-plane direction to subtract mechanical noise and drift of the system. In addition, out-of-plane distances are measured via scattered light intensity in a total internal reflectance illumination field. In plane, we demonstrate a rms noise level of only 0.10 nm at 10 kHz and less than 0.5 nm at 600 kHz.
In situ impedance measurements in diamond anvil cell under high pressure
Authors: Wang Yue , Han Yonghao , Gao Chunxiao , Ma Yanzhang , Liu Cailong , Peng Gang , Wu Baojia , Liu Bao , Hu Tingjing , Cui Xiaoyan , Ren Wanbin , Li Yan , Su Ningning , Liu Hongwu , Zou Guangtian
Published: January 2010

Two-electrode configuration was developed for in situ electrical impedance detecting on diamond anvil cell under high pressure. The metal gasket was used as one electrode and the risk coming from electrical short between sample and interside wall of the gasket was eliminated. The configuration was evaluated and proved to be effective by measuring the electric impedance of nanocrystalline ZnS under high pressure.
Probe molecules in polymer melts near the glass transition: A molecular dynamics study of chain length effects
Authors: Vallée R. A. L. , Paul W. , Binder K.
Published: January 2010

Molecular dynamics simulations of a dense melt of short bead-spring polymer chains containing N=5, 10, or 25 effective monomers are presented and analyzed. Parts of our simulations include also a single dumbbell (N=2) of the same type, which is interpreted to represent a coarse-grained model for a fluorescent probe molecule as used in corresponding experiments. We obtain the mean-square displacements of monomers and chains center of mass, and intermediate incoherent scattering functions of both monomers in the chains and particles in the dumbbells as function of time for a broad regime of temperatures above the critical temperature Tc of mode-coupling theory. For both the chains and the dumbbell, also orientational autocorrelation functions are calculated and for the dumbbell time series for the time evolution of linear dichroism and its autocorrelation function are studied. From both sets of data we find that both the mode-coupling critical temperature Tc (representing the “cage effect”) and the Vogel–Fulcher temperature T0 (representing the caloric glass transition temperature) systematically increase with chain length. Furthermore, the dumbbell dynamics yields detailed information on the differences in the matrix dynamics that are caused by the chain length variation. Deviations from the Stokes–Einstein relation are discussed, and an outlook to related experiments is given.
Microcontroller-driven fluid-injection system for atomic force microscopy
Authors: Kasas S. , Alonso L. , Jacquet P. , Adamcik J. , Haeberli C. , Dietler G.
Published: January 2010

We present a programmable microcontroller-driven injection system for the exchange of imaging medium during atomic force microscopy. Using this low-noise system, high-resolution imaging can be performed during this process of injection without disturbance. This latter circumstance was exemplified by the online imaging of conformational changes in DNA molecules during the injection of anticancer drug into the fluid chamber.
Communications: On artificial frequency shifts in infrared spectra obtained from centroid molecular dynamics: Quantum liquid water
Authors: Ivanov Sergei D. , Witt Alexander , Shiga Motoyuki , Marx Dominik
Published: January 2010

Centroid molecular dynamics (CMD) is a popular method to extract approximate quantum dynamics from path integral simulations. Very recently we have shown that CMD gas phase infrared spectra exhibit significant artificial redshifts of stretching peaks, due to the so-called “curvature problem” imprinted by the effective centroid potential. Here we provide evidence that for condensed phases, and in particular for liquid water, CMD produces pronounced artificial redshifts for high-frequency vibrations such as the OH stretching band. This peculiar behavior intrinsic to the CMD method explains part of the unexpectedly large quantum redshifts of the stretching band of liquid water compared to classical frequencies, which is improved after applying a simple and rough “harmonic curvature correction.”
A modulated gradient model for large-eddy simulation: Application to a neutral atmospheric boundary layer
Authors: Lu Hao , Porté-Agel Fernando
Published: January 2010

The subgrid-scale (SGS) parametrization represents a critical component of a successful large-eddy simulation (LES). It is known that in LES of high-Reynolds-number atmospheric boundary layer turbulence, standard eddy-viscosity models poorly predict mean shear in the near-wall region and yield erroneous velocity profiles. In this paper, a modulated gradient model is proposed. This approach is based on the Taylor expansion of the SGS stress and uses local equilibrium hypothesis to evaluate the SGS kinetic energy. To ensure numerical stability, a clipping procedure is used to avoid local kinetic energy transfer from unresolved to resolved scales. Two approaches are considered to specify the model coefficient: a constant value of 1 and a simple correction to account for the effects of the clipping procedure on the SGS energy production rate. The model is assessed through a systematic comparison with well-established empirical formulations and theoretical predictions of a variety of flow statistics in a neutral atmospheric boundary layer. Overall, the statistics of the simulated velocity field obtained with the new model show good agreement with reference results and a significant improvement compared to simulations with standard eddy-viscosity models. For instance, the new model is capable of reproducing the expected log-law mean velocity profile and power-law energy spectra. Simulations also yield streaky structures and near-Gaussian probability density functions of velocity in the near-wall region. It is found that using a constant coefficient of 1 yields a slightly excessive SGS dissipation, which is corrected when the coefficient is modified using the above mentioned correction.
Vertical dispersion of light inertial particles in stably stratified turbulence: The influence of the Basset force
Authors: van Aartrijk M. , Clercx H. J. H.
Published: January 2010

The dispersion of light inertial particles [ρp/ρf=O(1)] in statistically stationary stably stratified turbulence is studied by means of direct numerical simulations. The light particle dispersion behavior is found to be comparable to that of heavy particles when displayed as a function of the Stokes number. Deviations from fluid particle dispersion are found already for small Stokes numbers; the length of the typical plateau for vertical dispersion is shorter for the light inertial particles. All the forces in the Maxey–Riley equation are taken into account and they are found to be of similar magnitude as the Stokes drag for particles with ρp/ρf=O(1). However, not all forces directly influence the particle dispersion. It is shown that especially the often neglected Basset force plays a considerable role in the vertical dispersion of light particles in stratified turbulence. Neglecting this force results in an overprediction of the vertical dispersion by about 15%–20%.
Sensitivity analysis of a streamwise corner flow
Authors: Alizard Frédéric , Robinet Jean-Christophe , Rist Ulrich
Published: January 2010

The stability of the flow formed by the intersection of two perpendicular flat plates is revisited through a study of the sensitivity to base-flow variations. After a brief presentation of the asymptotic regime, sensitivity functions underlying corner mode (concentrated close to the intersection) and Tollmien–Schlichting modes, with different obliqueness angles, are computed. Taking this into consideration, associated mechanisms as well as active regions are identified, which further confirm the sensitivity area of the corner mode along the intersection of two flat plates. Furthermore, the concept of ΔU-pseudospectra indicates that under a small base-flow modification, a certain range of frequencies underlying the corner mode could become unstable. Then, an optimization technique tracking the worst-case scenario, i.e., the deviation leading to a maximum temporal amplification rate, shows that a small variation in the reference field in the area of uncertainty leads to a significant decrease in the critical Reynolds number as observed in experiments. A hypothesis based on the onset of an inflectional mechanism is thus proposed to explain the experimental results.
Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma
Authors: Clayton D. J. , Chapman B. E. , O’Connell R. , Almagri A. F. , Burke D. R. , Forest C. B. , Goetz J. A. , Kaufman M. C. , Bonomo F. , Franz P. , Gobbin M. , Piovesan P.
Published: January 2010

Runaway electrons with energies >100 keV are observed with the appearance of an m=1 magnetic island in the core of otherwise stochastic Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field-pinch plasmas. The island is associated with the innermost resonant tearing mode, which is usually the largest in the m=1 spectrum. The island appears over a range of mode spectra, from those with a weakly dominant mode to those, referred to as quasi single helicity, with a strongly dominant mode. In a stochastic field, the rate of electron loss increases with electron parallel velocity. Hence, high-energy electrons imply a region of reduced stochasticity. The global energy confinement time is about the same as in plasmas without high-energy electrons or an island in the core. Hence, the region of reduced stochasticity must be localized. Within a numerical reconstruction of the magnetic field topology, high-energy electrons are substantially better confined inside the island, relative to the external region. Therefore, it is deduced that the island provides a region of reduced stochasticity and that the high-energy electrons are generated and well confined within this region.
Modulational instability of ion-acoustic wave envelopes in magnetized quantum electron-positron-ion plasmas
Authors: Bains A. S. , Misra A. P. , Saini N. S. , Gill T. S.
Published: January 2010

The amplitude modulation of quantum ion-acoustic waves (QIAWs) along an external magnetic field is studied in a quantum electron-positron-ion (e-p-i) magnetoplasma. Reductive perturbation technique is used to derive the three-dimensional nonlinear Schrödinger equation which governs the slow modulation of QIAW packets. Accounting for the effects of the electron to ion number density ratio (μ), the normalized ion-cyclotron frequency (ωc) as well as the ratio (H) of the “plasmonic energy density” to the Fermi energy, new regimes for the modulational instability of QIAWs are obtained and analyzed. In contrast to one-dimensional unmagnetized e-p-i plasmas, the instability growth rate is shown to suppress with increasing μ or decreasing the values of H. The predicted results could be important for understanding the salient features of modulated QIAW packets in dense astrophysical plasmas as well as to the next generation intense laser solid density plasma experiments.
Chemiluminescence from the Ba(P3)+N2O→BaO(A Σ1+)+N2 reaction: Collision energy effects on the product rotational alignment and energy release
Authors: Rossa Maximiliano , Rinaldi Carlos A. , Ferrero Juan C.
Published: January 2010

Both fully dispersed unpolarized and polarized chemiluminescence spectra from the Ba(P3)+N2O reaction have been recorded under hyperthermal laser-ablated atomic beam-Maxwellian gas conditions at three specific average collision energies ⟨Ec⟩ in the range of 4.82–7.47 eV. A comprehensive analysis of the whole data series suggests that the A Σ1+→X Σ1+ band system dominates the chemiluminescence. The polarization results revealed that the BaO(A Σ1+) product rotational alignment is insensitive to its vibrational state υ′ at ⟨Ec⟩=4.82 eV but develops into an strong negative correlation between product rotational alignment and υ′ at 7.47 eV. The results are interpreted in terms of a direct mechanism involving a short-range, partial electron transfer from Ba(P3) to N2O which is constrained by the duration of the collision, so that the reaction has a larger probability to occur when the collision time is larger than the time needed for N2O bending. The latter in turn determines that, at any given ⟨Ec⟩, collinear reactive intermediates are preferentially involved when the highest velocity components of the corresponding collision energy distributions are sampled. Moreover, the data at 4.82 eV suggest that a potential barrier to reaction which favors charge transfer to bent N2O at chiefly coplanar geometries is operative for most of the reactive trajectories that sample the lowest velocity components. Such a barrier would arise from the relevant ionic-covalent curve crossings occurring in the repulsive region of the covalent potential Ba(P3)⋯N2O(Σ1+); from this crossing the BaO(A Σ1+) product may be reached through mixings in the exit channel with potential energy surfaces leading most likely to the spin-allowed b Π3 and a Σ3+ products. The variation with increasing ⟨Ec⟩ of both the magnitude of the average BaO(A Σ1+) rotational alignment and the BaO(A Σ1+) rovibrational excitation, as obtained from spectral simulations of the unpolarized chemiluminescence spectra, consistently points to additional dynamic factors, most likely the development of induced repulsive energy release as the major responsible for the angular momentum and energy disposal at the two higher ⟨Ec⟩ studied. The results of a simplified version of the direct interaction with product repulsion-distributed as in photodissociation model do not agree with the observed average product rotational alignments, showing that a more realistic potential energy surface model will be necessary to explain the present results.
Equation of State in the σ – ω – ρ Model Supported by the Observational Data of 4U 1608–52 Neutron Star
Authors: Wen De-Hua
Published: January 2010

The properties of the neutron star rotating at 619Hz (which is the spin frequency of 4U 1608–52 neutron star) are investigated by using an equation of state (EOS) of the nuclear matter in the relativistic σ-ω-ρ model. It is shown that the EOS in the relativistic σ-ω-ρ model is supported by the observational mass and radius of the 4U 1608–52 neutron star. Moreover, a strict constraint on the polar redshift of 4U 1608–52 neutron star is obtained.
Decay estimates for wave equations with variable coefficients
Authors: Radu Petronela , Todorova Grozdena , Yordanov Borislav
Published: January 2010

We establish weighted

L
2

−

L^2-

estimates for dissipative wave equations with variable coefficients that exhibit a dissipative term with a space dependent potential. These results yield decay estimates for the energy and the

L
2

−

L^2-

norm of solutions. The proof is based on the multiplier method where multipliers are specially engineered from asymptotic profiles of related parabolic equations.
Conductivity interface problems. Part I: Small perturbations of an interface
Authors: Ammari Habib , Kang Hyeonbae , Lim Mikyoung , Zribi Habib
Published: January 2010

We derive high-order terms in the asymptotic expansions of boundary perturbations of steady-state voltage potentials resulting from small perturbations of the shape of a conductivity inclusion with

C

2

{\mathcal C}^2

-boundary. Our derivation is rigorous and based on layer potential techniques. The asymptotic expansion in this paper is valid for

C

1

{\mathcal C}^1

-perturbations and inclusions with extreme conductivities. It extends those already derived for small volume conductivity inclusions and leads us to very effective algorithms for determining lower-order Fourier coefficients of the shape perturbation of the inclusion based on boundary measurements. We perform some numerical experiments using the algorithm to test its effectiveness.
Involutive Yang-Baxter groups
Authors: Cedó Ferran , Jespers Eric , del Río Ángel
Published: January 2010

In 1992 Drinfeld posed the question of finding the set-theoretic solutions of the Yang-Baxter equation. Recently, Gateva-Ivanova and Van den Bergh and Etingof, Schedler and Soloviev have shown a group-theoretical interpretation of involutive non-degenerate solutions. Namely, there is a one-to-one correspondence between involutive non-degenerate solutions on finite sets and groups ofII-type. A groupG\mathcal {G}ofII-type is a group isomorphic to a subgroup ofFan⋊Symn\mathrm {Fa}_n\rtimes \mathrm {Sym}_nso that the projection onto the first component is a bijective map, whereFan\mathrm {Fa}_nis the free abelian group of ranknnandSymn\mathrm {Sym}_{n}is the symmetric group of degreenn. The projection ofG\mathcal {G}onto the second componentSymn\mathrm {Sym}_nwe call an involutive Yang-Baxter group (IYB group). This suggests the following strategy to attack Drinfeld’s problem for involutive non-degenerate set-theoretic solutions. First classify the IYB groups and second, for a given IYB groupGG, classify the groups ofII-type withGGas associated IYB group. It is known that every IYB group is solvable. In this paper some results supporting the converse of this property are obtained. More precisely, we show that some classes of groups are IYB groups. We also give a non-obvious method to construct infinitely many groups ofII-type (and hence infinitely many involutive non-degenerate set-theoretic solutions of the Yang-Baxter equation) with a prescribed associated IYB group.
Positive polynomials and sequential closures of quadratic modules
Authors: Netzer Tim
Published: January 2010

Let
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="script upper S equals StartSet x element-of double-struck upper R Superscript n Baseline bar f 1 left-parenthesis x right-parenthesis greater-than-or-equal-to 0 comma ellipsis comma f Subscript s Baseline left-parenthesis x right-parenthesis greater-than-or-equal-to 0 EndSet">

S

=
{
x
∈

R

n

∣

f
1

(
x
)
≥
0
,
…
,

f
s

(
x
)
≥
0
}

\mathcal {S}=\{x\in \mathbb {R}^n\mid f_1(x)\geq 0,\ldots ,f_s(x)\geq 0\}

be a basic closed semi-algebraic set in

R

n

\mathbb {R}^n

and let

P
O

(

f
1

,
…
,

f
s

)

\mathrm {PO}(f_1,\ldots ,f_s)

be the corresponding preordering in

R

[

X
1

,
…
,

X
n

]

\mathbb {R}[X_1,\ldots ,X_n]

. We examine for which polynomials

f
f

there exist identities
\[

f
+
ε
q
∈

P
O

(

f
1

,
…
,

f
s

)

 for all 

ε
>
0.

f+\varepsilon q\in \mathrm {PO}(f_1,\ldots ,f_s) \mbox { for all } \varepsilon >0.

\]
These are precisely the elements of the sequential closure of

P
O

(

f
1

,
…
,

f
s

)

\mathrm {PO}(f_1,\ldots ,f_s)

with respect to the finest locally convex topology. We solve the open problem from Kuhlmann, Marshall, and Schwartz (2002, 2005), whether this equals the double dual cone
\[

P
O

(

f
1

,
…
,

f
s

)

∨
∨

,

\mathrm {PO}(f_1,\ldots ,f_s)^{\vee \vee },

\]
by providing a counterexample. We then prove a theorem that allows us to obtain identities for polynomials as above, by looking at a family of fibre-preorderings, constructed from bounded polynomials. These fibre-preorderings are easier to deal with than the original preordering in general. For a large class of examples we are thus able to show that either every polynomial

f
f

that is nonnegative on

S

\mathcal {S}

admits such representations, or at least the polynomials from

P
O

(

f
1

,
…
,

f
s

)

∨
∨

\mathrm {PO}(f_1,\ldots ,f_s)^{\vee \vee }

do. The results also hold in the more general setup of arbitrary commutative algebras and quadratic modules instead of preorderings.
Mann pairs
Authors: van den Dries Lou , Günaydın Ayhan
Published: January 2010

Mann proved in the 1960s that for any

n
≥
1

n\ge 1

there is a finite set

E
E

of

n
n

-tuples

(

η
1

,
…
,

η
n

)

(\eta _1,\dots , \eta _n)

of complex roots of unity with the following property: if

a
1

,
…
,

a
n

a_1,\dots ,a_n

are any rational numbers and

ζ
1

,
…
,

ζ
n

\zeta _1,\dots ,\zeta _n

are any complex roots of unity such that

∑

i
=
1

n

a
i

ζ
i

=
1

\sum _{i=1}^n a_i\zeta _i=1

and

∑

i
∈
I

a
i

ζ
i

≠
0

\sum _{i\in I} a_i \zeta _i\ne 0

for all nonempty

I
⊆
{
1
,
…
,
n
}

I\subseteq \{1,\dots ,n\}

, then

(

ζ
1

,
…
,

ζ
n

)
∈
E

(\zeta _1,\dots ,\zeta _n)\in E

. Taking an arbitrary field

k

\mathbf {k}

instead of

Q

\mathbb {Q}

and any multiplicative group in an extension field of

k

\mathbf {k}

instead of the group of roots of unity, this property defines what we call a Mann pair

(

k

,
Γ
)

(\mathbf {k}, \Gamma )

. We show that Mann pairs are robust in certain ways, construct various kinds of Mann pairs, and characterize them model-theoretically.
On abstract Strichartz estimates and the Strauss conjecture for nontrapping obstacles
Authors: Hidano Kunio , Metcalfe Jason , Smith Hart , Sogge Christopher , Zhou Yi
Published: January 2010

We establish the Strauss conjecture concerning small-data global existence for nonlinear wave equations, in the setting of exterior domains to compact obstacles, for space dimensions

n
=
3

n=3

and

4
4

. The obstacle is assumed to be nontrapping, and the solution is assumed to satisfy either Dirichlet or Neumann conditions along the boundary of the obstacle. The key step in the proof is establishing certain “abstract Strichartz estimates” for the linear wave equation on exterior domains.
The hitting distributions of a line for two dimensional random walks
Authors: Uchiyama Kôhei
Published: January 2010

For every irreducible random walk on

Z

2

\mathbf {Z}^2

with zero mean and finite

2
+
δ

2+\delta

absolute moment (

0
≤
δ
>
1

0\leq \delta >1

) we obtain fine asymptotic estimates of the probability that the first visit of the walk to the horizontal axis takes place at a specified site of it.
Noncommutative Poisson structures on orbifolds
Authors: Halbout Gilles , Tang Xiang
Published: January 2010

In this paper, we compute the Gerstenhaber bracket on the Hoch-schild cohomology of

C
∞

(
M
)
⋊
G

C^\infty (M)\rtimes G

for a finite group

G
G

acting on a compact manifold

M
M

. Using this computation, we obtain geometric descriptions for all noncommutative Poisson structures on

C
∞

(
M
)
⋊
G

C^\infty (M)\rtimes G

when

M
M

is a symplectic manifold. We also discuss examples of deformation quantizations of these noncommutative Poisson structures.
New enterovirulent Escherichia coli serogroup 64474 showingantigenic and genotypic relationships to Shigella boydii 16
Authors: Navarro Armando , Eslava Carlos , Perea Luis Manuel , Inzunza Alma , Delgado Gabriela , Morales-Espinosa Rosario , Cheasty Thomas , Cravioto Alejandro
Published: January 2010

Studies based on the analysis of housekeeping genes indicate thatEscherichia coliand allShigellaspecies, except forShigellaboydiitype 13, belong to a single species. This study analysed the phenotypicand genotypic characteristics of 23E.colistrains isolatedin different countries from faecal specimens taken from children with diarrhoea.Strains were identified using the VITEK system and typed with rabbit seraobtained against 186 somatic and 53 flagellarE. coliantigens andagainst 45Shigellasomatic antigens. Biochemical analysis of thesestrains showed a typicalE. coliprofile with a defined reactionagainst bothE.coliO179 andS.boydii16 somatic antisera. Agglutination assays for flagellar antigens showed aresponse against H2 in 7 (30 %) strains, H10 in 2 (9 %)strains, H32 in 12 (52 %) strains and H34 in 2 (9 %)strains, demonstrating 4 serotypes associated with this new somatic antigen64474. A serum against one of theseE.colistrains (64474)was prepared. Absorption assays ofS.boydii16 andE.coli64474 antisera withE. coliO179 antigen removedthe agglutination response against this O179 antigen completely, while theagglutination titres against bothS.boydii16 andE. coli64474 remained the same. Four (17 %)E.colistrains showed antimicrobial resistance to piperacillinonly, one (4 %) to piperacillin and trimethoprim/sulfamethoxazole,one (4 %) to ciprofloxacin, nitrofurantoin and piperacillin,and two (9 %) strains were resistant to ciprofloxacin,norfloxacin, ofloxacin, piperacillin and trimethoprim/sulfamethoxazole.With regards to PCR assays, one (4 %) of the strainswas positive forShigellageneipaH, one (4 %)foripaA, two (9 %) foripaB, one (4 %)foripaD, two (9 %) forsepAandthree (13 %) forospF. Therfbgenecluster in theE. colistrains was analysed by RFLP and comparedwith the gene cluster obtained fromS. boydii16. Therfb-RFLPpatterns for all 23E.colistrains were similar to thoseobtained forS.boydii16. The results from PCR tests todetectrfbgeneswzx(encoding O unit flippase)andwzy(encoding polymerase) belonging to a cluster relatedto the biosynthesis of theS. boydii16-specific O antigen were positivein 21 (91 %) and 22 (96 %)of the strains, respectively. PCR assays to detectE.colivirulence genes were also performed. These assays detected enterotoxigenicE.coligenesltA1in 12 of the strains (52 %),st1ain 4 (17 %),cfa1 in 6 (26 %),cs1 in 1 (4 %),cs3 in 3 (13 %),cs13 in 9 (39 %) andcs14 in 5 (22 %)of the strains. Results from the PFGE analyses confirmed the wide geographicaldistribution of these strains suggesting that 64474 : H2, 64474 : H10,64474 : H32 and 64474 : H34 are new serotypesofE.colistrains with a defined virulence capacity, andshare a common O antigen withS. boydii16.
A vertebrate gene, ticrr, is an essential checkpoint and replication regulator
Authors: Sansam Christopher L. , Cruz Nelly M. , Danielian Paul S. , Amsterdam Adam , Lau Melissa L. , Hopkins Nancy , Lees Jacqueline A.
Published: January 2010

Eukaryotes have numerous checkpoint pathways to protect genome fidelity during normal cell division and in response to DNA damage. Through a screen for G2/M checkpoint regulators in zebrafish, we identified ticrr (for TopBP1-interacting, checkpoint, and replication regulator), a previously uncharacterized gene that is required to prevent mitotic entry after treatment with ionizing radiation. Ticrr deficiency is embryonic-lethal in the absence of exogenous DNA damage because it is essential for normal cell cycle progression. Specifically, the loss of ticrr impairs DNA replication and disrupts the S/M checkpoint, leading to premature mitotic entry and mitotic catastrophe. We show that the human TICRR ortholog associates with TopBP1, a known checkpoint protein and a core component of the DNA replication preinitiation complex (pre-IC), and that the TICRR–TopBP1 interaction is stable without chromatin and requires BRCT motifs essential for TopBP1's replication and checkpoint functions. Most importantly, we find that ticrr deficiency disrupts chromatin binding of pre-IC, but not prereplication complex, components. Taken together, our data show that TICRR acts in association with TopBP1 and plays an essential role in pre-IC formation. It remains to be determined whether Ticrr represents the vertebrate ortholog of the yeast pre-IC component Sld3, or a hitherto unknown metazoan replication and checkpoint regulator.
Swedish managers in TWA act as boundary spanners
Authors: Augustsson Gunnar , Olofsdotter Gunilla , Wolvén Lars‐Erik
Published: January 2010

Purpose

The purpose of this paper is to highlight the complexity of manpower management in temporary work agencies (TWA). The aim is to investigate to which extent the managers reflects the features of boundary spanners.

Design/methodology/approach

The results come from a case study where manpower managers at one of the biggest TWAs in Sweden are interviewed.

Findings

TWAs' boundary‐spanning managers mediate between the opinions of the clients, the TWAs, and the individual temps as well as balancing between trust and risk. The findings reveal the relevance of the managers' application of a flexible and a dialectical approach when delivering service to clients, the TWA and the temps. This flexible approach means being able to simultaneously embrace these three perspectives of interests. A dialectical approach involves being able to: systematically balance between the opposing pair of trust and risk and search for the most functional option and not relate others' opinions to one's own personal values.

Research limitations/implications

The interview data come from a case study at only one TWA and it is collected in a limited number of interview subjects.

Practical implications

The results can provide useful information for recruiters of manpower managers in a TWA when choosing staff members that can enhance strategic management of temps. The results can also be of assistance for managers when interacting with both customers and temps.

Originality/value

The paper contributes to the literature by an analysis of the complex working conditions under which manpower managers in TWAs work.
Mapping the intellectual structure of modern leadership studies
Authors: Tseng Hsing‐Chau , Tung Hui‐Lien , Duan Chi‐Hsiang
Published: January 2010

Purpose

The purpose of this paper is to explore and map the intellectual structure of leadership studies during 1997‐2006. This paper also attempts to help researchers identify the important publications and the influential scholars as well as the correlations among these publications using citation and co‐citation.

Design/methodology/approach

In this paper, co‐citation analysis and social network analysis techniques are used to research knowledge network of the leadership literature by analyzing 31,232 cited references of 2,322 articles from two leadership related journals in social science citation index and science citation index databases.

Findings

Four factors emerged in this paper: effectiveness of leadership style, leadership theory and development, leadership categorization, and current issues of leadership research.

Originality/value

This paper provides management researchers a tool for evaluating leadership publications and provides a systematic and objective means of determining the relative importance of different knowledge nodes in the development of the leadership research.
Financial market development and corporate financing: evidence from emerging market economies
Authors: Bokpin Godfred A.
Published: January 2010

Purpose

The purpose of this paper is to examine the effects of financial market development on corporate financing of emerging market firms to ascertain whether or not interactions in the financial market has any impact on the available choice of financing of firms.

Design/methodology/approach

Panel data covering the period 1990‐2006 for 34 emerging market economies were analyzed within the framework of Pesaran's dynamic fixed effect model and the pooled mean group estimator to capture the short‐ and long‐run effects of the covariates on the endogenous variables.

Findings

The findings of the research indicate significantly that the direction and magnitude of the impact of financial market development and macroeconomic variables on capital structure vary with the maturities of the security issue. It is also documented that firm level variables such as profitability, investment opportunity, asset tangibility and risk are equally important in predicting firms' capital structure decisions. The findings also indicate that economy wide variables such as gross domestic product per capita are significant predictors of financing choices of firms. The results of the study generally support existing literature on the impact of financial market development, macroeconomic variables and certain firm level factors on capital structure.

Originality/value

The paper considers unique data from emerging market economies over a 17‐year period.
Struggles of managerial being and becoming
Authors: Andersson Thomas
Published: January 2010

Purpose

The purpose of this paper is to investigate the struggles of managerial identity in relation to the process of becoming/being a manager, and the personal conflicts involved within this process.

Design/methodology/approach

In a qualitative, longitudinal project, five managers were studied for two years using interviews and observations. This was undertaken before, during, and after their participation in personal development training. In total, 62 interviews and eight half‐day observations were conducted.

Findings

The study puts emphasis on the role of management training in providing templates for “how to be a manager”, but it also illustrates the double‐edged and complex role played by context in managerial being and becoming. On the one hand context shapes managerial identity; on the other hand, context might operate to dilute the identity an individual manager wishes to assume.

Research limitations/implications

The study focuses on only five managers in two organizations. This small sample limits the generalisabilty of the research.

Practical implications

Management training tends to be based on the idea that management concerns the acquisition of competencies, techniques and personal awareness, while managerial practice is more fluid and contextually based. There is a challenge for organizers of all types of management training to bridge the gap between a fixed idea of what it is to be a manager and how management is actually practised.

Originality/value

The longitudinal and in‐depth qualitative approach facilitates an important contribution to understanding issues in developing a managerial identity.
Study abroad education in New England higher education: a pilot survey
Authors: Niser John C.
Published: January 2010

Purpose

The purpose of this paper is to develop relevant questions for research by gaining an initial understanding of how the field of study abroad education is organizing itself within institutions of higher education. The context is the growing numbers of students, demands, and expectations made on study abroad programs.

Design/methodology/approach

The survey was carried out by analyzing publicly available data and information, as it would be available to students, of all the accredited institutions of higher education within the six states of New England.

Findings

The findings confirm that albeit for Community Colleges, the vast majority of institutions offer study abroad programs. However, this survey also reveals the important role providers are playing in offering generic programs to students from multiple institutions.

Research limitations/implications

The findings call for further investigation into institutional strategies concerning the choice of programs, particularly those involving providers who potentially imply losing tuition and control over educational outcomes. Limitations are discussed suggesting the need to widen the geographical area studied as well as analyzing in more detail the Community College offerings that are not easily accessible with the methodology that has been used in this paper. The findings also raise some questions and future avenues of research particularly in the area of examining the integration of generic study abroad programs within particular institutional and programmatic objectives. It is also suggested that further research is needed to better evaluate if/how study abroad programs are designed to capitalize on the employability advantage they offer to participating students when they enter the job market.

Originality/value

The number of US students participating in study abroad programs is expected to continue to grow and it seems these programs will become part of mainstream offerings in most institutions. Similar trends are observed in Europe between member states. Besides giving a broad overview of the current offerings, this pilot study principally reveals several important avenues for future research that should help institutions in their choices of programs and the orientation they give to study abroad.
Evaluation of the influence of Bi and Sb additions to Sn‐Ag‐Cu and Sn‐Zn alloys on their surface tension and wetting properties using analysis of variance – ANOVA
Authors: Bukat K. , Sitek J. , Kisiel R. , Moser Z. , Gasior W. , Kościelski M. , Pstruś J.
Published: January 2010

Purpose

The purpose of this paper is a comparable evaluation of the influence of a particular element (Bi and Sb) added to Sn‐Ag‐Cu and Sn‐Zn alloys on their surface and interfacial tensions, as well as the wetting properties on the Cu substrate expressed by the wetting angle.

Design/methodology/approach

The authors applied the L8 orthogonal Taguchi array to carry out the experiments and discussed the results using analysis of variance (ANOVA).

Findings

It was expected, on the base of previous studies, the decrease of the surface and interfacial tensions and thus improving wettability after the Bi and Sb addition to Sn‐Ag‐Cu and Sn‐Zn alloys. Unfortunately, the obtained results on the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys and the quaternary Sn‐Zn‐Bi‐Sb alloys do not confirm these trends. The performed analyses suggest that the compositions of the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys, as well as the quaternary Sn‐Zn‐Bi‐Sb alloys, do not have optimal compositions for practical application. The Cu, Bi and Sb elements in the case of the Sn‐Ag‐Cu‐Bi‐Sb alloys and the Zn, Bi and Sb elements in the case of the Sn‐Zn‐Bi‐Sb alloys show mutual interaction and, in consequence, there is no correlation between the tendency of the surface and interfacial tensions changes and the wettings of the Cu substrate.

Research limitations/implications

It is suggested that further studies are necessary for the purpose of the practical application, but they should be limited mainly to the Sn‐Ag‐Cu‐Bi and the Sn‐Zn‐Bi alloys with the optimal compositions.

Practical implications

The performed analysis suggests that none of the investigated compositions of the quinary Sn‐Ag‐Cu‐Bi‐Sb alloys, as well as the quaternary Sn‐Zn‐Bi‐Sb alloys, have the optimal compositions for practical application.

Originality/value

The quickest way to determine which element of the alloy composition influences the surface tension and the wetting properties, and how, is to apply orthogonal analysis. After choosing the orthogonal array, the experiments were performed and analysis of variance (ANOVA) was used to perform the quantifiable analysis of the measured and calculated results of surface and interfacial tensions, as well as the wetting properties on the Cu substrate.