bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of (100)-oriented BiScO3–PbTiO3 thin films synthesized by a modified sol-gel method
Authors: Wen Hai , Wang Xiaohui , Deng Xiangyun , Li Longtu
Published: June 2006

The ferroelectric and piezoelectric properties of (100)-oriented BiScO3–PbTiO3 (BSPT) thin films were investigated. (100)-oriented 0.34BiScO3–0.66PbTiO3 thin films were synthesized on Pt(111)∕Ti∕SiO2∕Si(111) substrates using a modified sol-gel method. Saturated polarization hysteresis loops were observed, showing a remanent polarization of 33μC∕cm2. The dielectric constant and loss for the thin films were 1200 and 5%, respectively. The Curie temperature appeared at 435°C, over 80°C higher than that of the Pb(Zr,Ti)O3 (PZT) thin films. The local effective piezoelectric coefficient d33* was approximately 70pm∕V, which was comparable to that of the highly (100)-oriented PZT thin films.
Recording potential of bit-patterned media
Authors: Richter H. J. , Dobin A. Y. , Lynch R. T. , Weller D. , Brockie R. M. , Heinonen O. , Gao K. Z. , Xue J. , Veerdonk R. J. M. v. d. , Asselin P. , Erden M. F.
Published: June 2006

A comprehensive analysis of the areal density potential of bit-patterned media recording shows that the recording performance is dominated by written-in errors. The statistical fluctuations of the magnetic properties and the locations of the individual bits lead to error probabilities so that some dots are either not recorded at all or cannot be recorded in the time window necessary to ensure synchronized writing. The highest areal densities are obtained with a combination of a pole head, a soft magnetic underlayer, and a storage medium of the composite type. Areal density scenarios of up to 5Tbits∕in.2 are analyzed.
Low-resistivity, stable p-type ZnO thin films realized using a Li–N dual-acceptor doping method
Authors: Lu J. G. , Zhang Y. Z. , Ye Z. Z. , Zhu L. P. , Wang L. , Zhao B. H. , Liang Q. L.
Published: June 2006

A Li–N dual-acceptor doping method has been developed to prepare p-type ZnO thin films by pulsed laser deposition. The lowest room-temperature resistivity is found to be ∼0.93Ωcm, much lower than that of Li or N monodoped ZnO films. The p-type conductivity of ZnO:(Li,N) films is very reproducible and stable, with acceptable crystal quality. The acceptor activation energy in ZnO:(Li,N) is about 95meV. ZnO-based homostructural p-n junctions were fabricated by depositing an n-type ZnO:Al layer on a p-type ZnO:(Li,N) layer, confirmed by secondary ion mass spectroscopy. The current-voltage characteristics exhibit their inherent rectifying behaviors.
Fabrication of nanoscale gaps using a combination of self-assembled molecular and electron beam lithographic techniques
Authors: Negishi R. , Hasegawa T. , Terabe K. , Aono M. , Ebihara T. , Tanaka H. , Ogawa T.
Published: June 2006

We have developed and tested a new method of fabricating nanogaps using a combination of self-assembled molecular and electron beam lithographic techniques. The method enables us to control the gap size with an accuracy of approximately 2nm and designate the positions where the nanogaps should be formed with high-resolution patterning by using electron beam lithography. We have demonstrated the utility of the fabricated nanogaps by measuring a single electron tunneling phenomenon through dodecanethiol-coated Au nanoparticles placed in the fabricated nanogap.
Self-sustaining vortex perturbations in smooth shear flows
Authors: Kim J.-H. , Perez J. C. , Horton W. , Chagelishvili G. D. , Changishvili R. G. , Lominadze J. G. , Bowman John C.
Published: June 2006

The nonlinear dynamics of coherent circular/elliptical cyclonic and anticyclonic vortices in plane flow with constant shear is investigated numerically using a dealiased Fourier pseudospectral code. The flow is asymptotically linearly stable, but is highly non-normal, allowing perturbations to gain energy transiently from the background shear flow. This linear transient growth interplays with nonlinear processes. In certain cases it is shown that the nonlinear feedback is positive, leading to self-sustaining coherent vortices. Self-sustaining coherent vortices exist where the vorticity is parallel to the mean flow vorticity (cyclonic rotation). The required nonlinear feedback is absent for small amplitude anticyclonic vortices. However, elliptical anticyclonic vortices become self-sustaining if the amplitude exceeds a threshold value. The self-sustaining of coherent vortices is similar to the subcritical, so-called bypass, transition to turbulence in shear flows. The common features are: transient linear growth; positive nonlinear feedback; and anisotropy of the linear and nonlinear phenomena (in contrast to isotropic Kolmogorov turbulence). A plasma laboratory experiment is suggested based on the results of this investigation.
Physical origin of the quadrupole out-of-plane magnetic field in Hall-magnetohydrodynamic reconnection
Authors: Uzdensky Dmitri A. , Kulsrud Russell M.
Published: June 2006

A quadrupole pattern of the out-of-plane component of the magnetic field inside a reconnection region is seen as an important signature of the Hall-magnetohydrodynamic regime of reconnection. It has been first observed in numerical simulations and just recently confirmed in the Magnetic Reconnection Experiment [Y. Ren, M. Yamada, S. Gerhardt, H. Ji, R. Kulsrud, and A. Kuritsin, Phys. Rev. Lett. 95, 055003 (2005)] and also seen in spacecraft observations of Earth’s magnetosphere. In this study, the physical origin of the quadrupole field is analyzed and traced to a current of electrons that flows along the lines in and out of the inner reconnection region to maintain charge neutrality. The role of the quadrupole magnetic field in the overall dynamics of the reconnection process is discussed. In addition, the bipolar poloidal electric field is estimated and its effect on ion motions is emphasized.
Flowerlike ZnO nanocones and nanowires: Preparation, structure, and luminescence
Authors: Du G. H. , Xu F. , Yuan Z. Y. , Van Tendeloo G.
Published: June 2006

Flowerlike ZnO nanocone and nanowire arrays have been grown on a Zn foil via a solution-phase approach at low temperature. The tips of the nanocones are about 70–160nm in diameter and their roots are as thick as 350nm; the diameters of the nanowires are around 70–110nm. Both the nanocones and nanowires grow preferentially along the [0001] direction. Transmission electron microscopy analysis reveals that the surface of the ZnO nanocones is corrugated or protuberant while the nanowires have a smooth surface. Both shapes demonstrate a strong UV luminescence band around 385nm, and the nanocones also show three weak bands at 421, 484.6, and 532nm in the blue-green range.
Anomalous blueshift in emission spectra of ZnO nanorods with sizes beyond quantum confinement regime
Authors: Chen Chun-Wei , Chen Kuei-Hsien , Shen Ching-Hsing , Ganguly Abhijit , Chen Li-Chyong , Wu Jih-Jen , Wen Hui-I , Pong Way-Faung
Published: June 2006

Cathodoluminescence (CL) spectroscopy has been employed to study the electronic and optical properties of well-aligned ZnO nanorods with diameters ranging from 50to180nm. Single-nanorod CL studies reveal that the emission peak moves toward higher energy as the diameter of the ZnO nanorod decreases, despite that their sizes are far beyond the quantum confinement regime. Blueshift of several tens of meV in the CL peak of these nanorods has been observed. Moreover, this anomalous energy shift shows a linear relation with the inverse of the rod diameter. Possible existence of a surface resonance band is suggested and an empirical formula for this surface effect is proposed to explain the size dependence of the CL data.
Thickness dependence of the efficiency of polymer:fullerene bulk heterojunction solar cells
Authors: Lenes M. , Koster L. J. A. , Mihailetchi V. D. , Blom P. W. M.
Published: June 2006

We study the thickness dependence of the performance of bulk heterojunction solar cells based on poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] as electron donor and [6,6]-phenyl C61 butyric acid methyl ester as electron acceptor. Typically, these devices have an active layer thickness of 100nm at which only 60% of the incoming light is absorbed. Increasing device thickness results in a lower overall power conversion efficiency, mainly due to a lowering of the fill factor. We demonstrate that the decrease in fill factor and hence device efficiency is due to a combination of charge recombination and space-charge effects.
A crossed-beam study of the F+HD→DF+H reaction: The direct scattering channel
Authors: Dong Feng , Lee Shih-Huang , Liu Kopin
Published: June 2006

State-to-state differential cross sections of the title reaction are presented at four collision energies, ranging from 1.18to4.0kcal∕mol. Product angular distributions are predominantly backscattered at low energies and shift toward sideways (peaking near 150°) at higher energies. Experimental evidence for contributions from migratory trajectories was found in the more detailed angle-specific internal state distributions. The dynamics of this reaction is mostly governed by classical mechanics, and several major findings can qualitatively be rationalized. These “classical” behaviors serve as “references” and are to be contrasted to the attributes observed for the other isotopic product channel, HF+D, in a forthcoming paper.
Strong sub-band-gap infrared absorption in silicon supersaturated with sulfur
Authors: Kim T. G. , Warrender Jeffrey M. , Aziz Michael J.
Published: June 2006

Silicon supersaturated with up to 0.6at.% sulfur in solid solution was fabricated by ion implantation and pulsed-laser-melting-induced rapid solidification. The optical absorption coefficient over the range of 1200–2500nm is uniformly high at ∼2.5×104∕cm, which is at least an order of magnitude greater than the maximum value attributable to free carriers. High crystal quality was confirmed by transmission electron microscopy and ion channeling. The absorption coefficient decreases markedly with subsequent furnace annealing over the range of 200–600°C. We propose that the high absorptivity is due to a broad distribution of sulfur-related localized states within the band gap.
Atomic scale characterization of shear bands in an amorphous metal
Authors: Li Qi-Kai , Li Mo
Published: June 2006

The shear bands in a model amorphous CuZr metallic glass are examined using atomistic simulations. The localized shear zones are characterized at atomic scales by the nearest-neighbor atomic bond rotation angle, the nearest-neighbor atomic bond length, the atomic volume, and the potential energy. It is shown that the shear band is indeed a region with a liquidlike structure and different thermomechanical properties. Shear band formation could be a result from both local heating and free volume generation. The variation of shear band properties with temperature and strain rate is also briefly reported.
Structural evolution of carbon nanotubes in composites under contact sliding stresses
Authors: Zarudi I. , Zhang L. C.
Published: June 2006

We discovered a new structural evolution of carbon nanotubes (CNTs) in epoxy composites subjected to contact sliding stresses. Our analysis under high resolution transmission electron microscopy showed that the evolution has three stages which are (a) the bonding breakage of the CNTs, (b) the formation of sinusoidal shells, and (c) the consolidation of nanoparticles. We then explored the evolution mechanisms theoretically.
Excitation and spin-transport of hot holes in ballistic hole magnetic microscopy
Authors: Haq E. , Banerjee T. , Siekman M. H. , Lodder J. C. , Jansen R.
Published: June 2006

A hybrid structure of a ferromagnetic Co∕Au∕Ni81Fe19 trilayer on p-type silicon is used to probe the excitation of electron-hole pairs in a ferromagnet during inelastic decay of hot electrons and the subsequent spin-dependent transport of the excited holes into the valence band of the p-type Si collector. The hole current is remarkably sensitive to magnetic fields, with a magnetocurrent of up to 250% and, unexpectedly, with a positive sign. We determine effective attenuation lengths and their magnetic field and bias voltage dependence.
Rear emitter n-type passivated emitter, rear totally diffused silicon solar cell Structure
Authors: Zhao Jianhua , Wang Aihua
Published: June 2006

In a rear emitter n-type passivated emitter, rear totally diffused cell design, the boron diffused emitters are placed at the rear surface of n-type silicon substrates. This has significantly improved the cell efficiency up to 22.7%. A 170μm thin float zone substrate and a 1.5Ωcm modest substrate resistivity helped these cells to achieve highly efficient carrier transportation to the rear emitter. These 22cm2 large cells are scribed off from the silicon wafer, representing efficiencies for applicable devices. These rear emitter cells also demonstrated stable performances both under one-sun illumination and after a few months storage in nitrogen.
Schottky barrier between 6H-SiC and graphite: Implications for metal/SiC contact formation
Authors: Seyller Th. , Emtsev K. V. , Speck F. , Gao K.-Y. , Ley L.
Published: June 2006

Using photoelectron spectroscopy we have determined the Schottky barrier between 6H-SiC(0001) and graphite layers grown by solid state graphitization. For n-type 6H-SiC(0001) we find a low Schottky barrier of ϕbn=0.3±0.1eV. For p-type SiC(0001) a rather large value of ϕbp=2.7±0.1eV was determined. It is proposed that these extreme values are likely to have an impact on the electrical behavior of metal/SiC contacts subjected to postdeposition anneals.
Room-temperature ferromagnetism in (Mn, N)-codoped ZnO thin films prepared by reactive magnetron cosputtering
Authors: Xu H. Y. , Liu Y. C. , Xu C. S. , Liu Y. X. , Shao C. L. , Mu R.
Published: June 2006

(Mn, N)-codoped ZnO films were grown on fused silica substrates by reactive magnetron cosputtering. X-ray diffraction measurements reveal that the films have the single-phase wurtzite structure with c-axis preferred orientation. X-ray photoelectron spectroscopy studies indicate the incorporation of both divalent Mn2+ and trivalent N3− ions into ZnO lattice. Acceptor doping with nitrogen partly compensates the “native donors,” which results in a low electron concentration of 3.16×1016cm−3 though p-type conductivity is not achieved. (Mn, N)-codoped ZnO films show significant ferromagnetism with Curie temperature above 300K. The mechanism of ferromagnetic coupling in codoped ZnO is discussed based on a bound magnetic polaron model.
Effect of oxygen annealing on Mn doped ZnO diluted magnetic semiconductors
Authors: Ramachandran S. , Narayan J. , Prater J. T.
Published: June 2006

We have investigated the properties of Zn1−xMnxO (x=0.01–0.1) thin films grown on c-plane sapphire single crystals by pulsed laser deposition. The electrical, magnetic, optical, and microstructural properties of these thin films have been characterized systematically, with a primary focus on establishing a correlation between magnetic properties and electrical conductivity. We have shown that this system exhibits ferromagnetism at room temperature when in the conducting as-deposited state. However, upon high temperature annealing in excess oxygen, the samples become insulating and exhibit nonferromagnetic behavior at room temperature. Thus, it is possible to tune ferromagnetism in Zn1−xMnxO diluted magnetic semiconductors by controlling the concentrations of oxygen vacancies and substitutional Mn dopants.
Nonvolatile Cu∕CuTCNQ∕Al memory prepared by current controlled oxidation of a Cu anode in LiTCNQ saturated acetonitrile
Authors: Müller R. , Genoe J. , Heremans P.
Published: June 2006

In this letter we propose a preparation method of the metal organic charge transfer complex Cu-tetracyanoquinodimethane (CuTCNQ) for use in nonvolatile organic memories. The method, consisting in current controlled oxidation of a Cu electrode in LiTCNQ saturated acetonitrile, is attractive because CuTCNQ growth is limited strictly to anodically polarized Cu metal, and because of material and solvent compatibilities with the requirements of the complementary metal-oxide-semiconductor (CMOS) copper back end-of-line process. Crossbar memories of this CuTCNQ exhibit superior performance compared to corresponding devices prepared by the standard method, which we attribute to a higher compactness of the CuTCNQ layer.
Low field driven latching-type Bi3Fe5O12∕Gd3Ga5O12 magneto-optical display
Authors: Grishin A. M. , Khartsev S. I. , Bonetti S.
Published: June 2006

Series of heteroepitaxial all-garnet magneto-optical (MO) Bi3Fe5O12n∕Gd3Ga5O12m (BIGn∕GGGm, n=1, 2, 3, 4, 5 and m=1 and 2 are the numbers of unit cells) nanostructured multilayers have been sintered by pulsed laser deposition technique. Processing parameters and structure of grown films have been optimized to obtain perpendicular magnetic anisotropy and square hysteresis loop with low coercive and saturation magnetic fields. Regular alternating of lattice mismatched BIG and GGG atomic layers inhibited nucleation of misfit dislocations; thus a long range coherent compressive strain was preserved through the whole thickness of BIGn∕GGGm multilayer stack. 2.5μm thick BIG3∕GGG2 sample (1200 BIG and 800 GGG unit cells) at λ=678nm shows MO Faraday rotation ΘF=±1.4°, transmittance of 82%, attenuation α=3400dB∕cm, squareness of magnetization loop (remnant-to-saturation magnetizations ratio) as high as 92%, and saturation and coercive fields as low as 56 and 25Oe, respectively. MO remanence (latching capability) enables application of nanostructured garnet as a magnetic relief replicator/visualizer and as a material for low power consuming displays.
Femtogram mass sensing platform based on lateral extensional mode piezoelectric resonator
Authors: Pang Wei , Yan Le , Zhang Hao , Yu Hongyu , Kim Eun Sok , Tang William C.
Published: June 2006

This letter introduces a resonant mass sensor that is based on a lateral extensional mode piezoelectric resonator and has a minimum detectable mass of 10−15g at room temperature and atmospheric pressure. The resonator with size of about 200×50×1μm3 has a quality factor (Q) of >1400 at 60MHz, and as small as 0.1ppm shift of its resonant frequency can be detected. The 0.1ppm detection capability corresponds to a mass uncertainty of only about 4.6fg. We have experimentally demonstrated a minimum detectable frequency shift of ∼1.6ppm due to absorption of isopropanol vapor (73fg) on the sidewalls of the parylene-coated lateral extensional mode piezoelectric resonator.
Task Switching: The Effect of Task Recency with Dual- and Single-Affordance Stimuli
Authors: Sumner Petroc , Ahmed Lubna
Published: June 2006

When we switch to a new task, performance is transiently relatively poor, but improves dramatically after one trial. Such a “switch cost” may result from the preceding task being highly primed while the new task is not yet primed. This predicts that it should become more difficult to switch back to Task A when more trials of Task B have intervened. Such a lag effect has been found in some but not in most previous experiments, and to resolve this discrepancy we examined the effects of task lag with different stimuli. We found that when stimuli uniquely and clearly cued the task—minimizing the need for control—switch reaction time increased with task lag. However, when the need for control was increased by using similar or identical stimuli in the two tasks, this lag effect was abolished or reversed. Thus only when control processes are minimized can priming explain the difficulty of switching back from Task B to Task A. Second, we asked how the impact of control is mediated in conditions where it is not minimized. If it is mediated through altering the relative activation states of competing tasks, then as it becomes easier to do one task—the relative task-set activation state is tipped in that task's favour—it should always become harder to do the other task. On the other hand, if control bias affects switch performance directly, this relationship need not hold. We found that as it becomes easier to perform one task it can become easier, not harder, to switch to the competing task. Thus control bias must act directly on switch performance, rather than only through its influence on relative task-set activation.
Short Article: Limiting the use of Verbal Coding in the Visual Patterns Test
Authors: Brown Louise A. , Forbes Douglas , McConnell Jean
Published: June 2006

The aims of the study were to assess the availability of verbal coding and its effect on performance in a standard visual matrix task, the Visual Patterns Test (VPT). In a pilot study, participants were presented with the patterns from the VPT and were asked to name the shapes within them. Availability of verbal codes was low overall; however, some patterns resulted in a higher mean number of labels than others. A modified version of the test was created from those patterns that had produced the lowest mean number of labels. A total of 60 participants then took part in an experimental study, which was carried out to assess whether or not the availability of verbal coding affects task performance. It was found that the modified version resulted in a lower visual working-memory span than that of another version in which the availability of verbal coding was higher. The study confirmed that verbal coding does influence visual matrix task performance; however, the modified version now offers a selection of patterns from the VPT where verbal coding has been limited.
Bringing order to early B cell chaos
Authors: Van Epps Heather L.
Published: June 2006

In the early 1990s, Richard (Randy) Hardy and colleagues divided B cell precursors into subpopulations—the Hardy fractions—based on the cells' expression of various cell surface proteins. This classification helped lay the groundwork for our present-day understanding of the molecular events that control early B cell development.
A theorem on reflexive large rank operator spaces
Authors: Ding Lifeng
Published: June 2006

If every nonzero operator in an

n
n

-dimensional operator space

S

\mathbb {S}

has rank

⩾
2
n

\geqslant 2n

, then

S

\mathbb {S}

is reflexive.
The proof of Tchakaloff’s Theorem
Authors: Bayer Christian , Teichmann Josef
Published: June 2006

We provide a simple proof of Tchakaloff’s Theorem on the existence of cubature formulas of degree

m
m

for Borel measures with moments up to order

m
m

. The result improves known results for non-compact support, since we do not need conditions on

(
m
+
1
)

(m+1)

st moments. In fact, we reduce the classical assertion of Tchakaloff’s Theorem to a well-known statement going back to F. Riesz.
On some dyadic models of the Euler equations
Authors: Waleffe Fabian
Published: June 2006

Katz and Pavlovic recently proposed a dyadic model of the Euler equations for which they proved finite time blow-up in the

H

3

/

2
+
ϵ

H^{3/2+\epsilon }

Sobolev norm. It is shown that their model can be reduced to a dyadic model of the inviscid Burgers equation. The inviscid Burgers equation exhibits finite time blow-up in

H

α

H^{\alpha }

, for

α
≥
1

/

2

\alpha \ge 1/2

, but its dyadic restriction is even more singular, exhibiting blow-up for any

α
>
0

\alpha >0

. Friedlander and Pavlovic developed a closely related model for which they also prove finite time blow-up in

H

3

/

2
+
ϵ

H^{3/2+\epsilon }

. Some inconsistent assumptions in the construction of their model are outlined. Finite time blow-up in the

H

α

H^{\alpha }

norm, for any

α
>
0

\alpha >0

, is proven for a class of models that includes all those models. An alternative shell model of the Navier-Stokes equations is discussed.
A class of Nevanlinna functions related to singular Sturm-Liouville problems
Authors: Hassi Seppo , Möller Manfred , de Snoo Henk
Published: June 2006

The class of Nevanlinna functions consists of functions which are holomorphic off the real axis, which are symmetric with respect to the real axis, and whose imaginary part is nonnegative in the upper halfplane. The Kac subclass of Nevanlinna functions is defined by an integrability condition on the imaginary part. In this note a further subclass of these Kac functions is introduced. It involves an integrability condition on the modulus of the Nevanlinna functions (instead of the imaginary part). The characteristic properties of this class are investigated. The definition of the new class is motivated by the fact that the Titchmarsh-Weyl coefficients of various classes of Sturm-Liouville problems (under mild conditions on the coefficients) actually belong to this class.
Entropy for automorphisms of free groups
Authors: Choda Marie
Published: June 2006

Let

σ
\sigma

be the automorphism of the free group

F
∞

F_\infty

which is arising from a permutation of the free generators of

F
∞

.

F_\infty .

The

σ
\sigma

naturally induces the automorphism

σ
^

\hat \sigma

of the reduced

C
∗

C^*

-algebra

C
r
∗

(

F
∞

)
,

C^*_r(F_\infty ),

and also the automorphism

σ
^

¯

\bar {\hat \sigma }

of the group factor

L
(

F
∞

)
.

L(F_\infty ).

We show that the Brown-Germain entropy

h
a
(
σ
)

ha(\sigma )

is zero. This implies that the Brown-Voiculescu topological entropy

h
t
(

σ
^

)
,

ht(\hat \sigma ),

the Connes-Narnhofer-Thirring dynamical entropy

h
ϕ

(

σ
^

)

h_\phi (\hat \sigma )

and the Connes-Størmer entropy

H
(

σ
^

¯

)

H(\bar {\hat \sigma } )

are all zero.
On positive periodic solutions of Lotka-Volterra competition systems with deviating arguments
Authors: Tang Xianhua , Zou Xingfu
Published: June 2006

By using Krasnoselskii’s fixed point theorem, we prove that the following periodicn−n-species Lotka-Volterra competition system with multiple deviating arguments<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-parenthesis asterisk right-parenthesis ModifyingAbove x With dot Subscript i Baseline left-parenthesis t right-parenthesis equals x Subscript i Baseline left-parenthesis t right-parenthesis left-bracket r Subscript i Baseline left-parenthesis t right-parenthesis minus sigma-summation Underscript j equals 1 Overscript n Endscripts a Subscript i j Baseline left-parenthesis t right-parenthesis x Subscript j Baseline left-parenthesis t minus tau Subscript i j Baseline left-parenthesis t right-parenthesis right-parenthesis right-bracket comma i equals 1 comma 2 comma ellipsis comma n comma">(∗)x˙i(t)=xi(t)[ri(t)−∑j=1naij(t)xj(t−τij(t))],i=1,2,…,n,\begin{equation*} (\ast )\quad \quad \dot {x}_i(t)=x_i(t)\left [r_i(t)-\sum _{j=1}^{n}a_{ij}(t)x_j(t-\tau _{ij}(t)) \right ],\quad i=1, 2, \ldots , n,\qquad \quad \end{equation*}has at least one positiveω−\omega -periodic solution provided that the corresponding system of linear equations<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="left-parenthesis asterisk asterisk right-parenthesis sigma-summation Underscript j equals 1 Overscript n Endscripts a overbar Subscript i j Baseline x Subscript j Baseline equals r overbar Subscript i Baseline comma i equals 1 comma 2 comma ellipsis comma n comma">(∗∗)∑j=1na¯ij xj=r¯i,i=1,2,…,n,\begin{equation*} (\ast \ast )\qquad \qquad \qquad \qquad \quad \sum _{j=1}^{n}\bar {a}_{ij}\ x_j= \bar {r}_i, \quad i=1, 2, \ldots , n,\qquad \qquad \qquad \qquad \quad \end{equation*}has a positive solution, whereri,aij∈C(R,[0,∞))r_i, a_{ij}\in C({\mathbf {R}}, [0, \infty ))andτij∈C(R,R)\tau _{ij}\in C({\mathbf {R}}, {\mathbf {R}})areω−\omega -periodic functions with\[<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="r overbar Subscript i Baseline equals StartFraction 1 Over omega EndFraction integral Subscript 0 Superscript omega Baseline r Subscript i Baseline left-parenthesis s right-parenthesis d s greater-than 0 semicolon a overbar Subscript i j Baseline equals StartFraction 1 Over omega EndFraction integral Subscript 0 Superscript omega Baseline a Subscript i j Baseline left-parenthesis s right-parenthesis d s greater-than-or-equal-to 0 comma i comma j equals 1 comma 2 comma ellipsis comma n period">r¯i=1ω∫0ωri(s)ds>0;   a¯ij=1ω∫0ωaij(s)ds≥0,i,j=1,2,…,n.\bar {r}_i=\frac {1}{\omega }\int _{0}^{\omega }r_i(s)ds >0;\ \ \ \bar {a}_{ij}=\frac {1}{\omega }\int _{0}^{\omega }a_{ij}(s)ds \ge 0, \quad i, j=1, 2, \ldots , n.\]Furthermore, whenaij(t)≡aija_{ij}(t)\equiv a_{ij}andτij(t)≡τij\tau _{ij}(t)\equiv \tau _{ij},i,j=1,…,ni,j =1,\ldots ,n, are constants butri(t), i=1,…,nr_i(t),\ i=1, \ldots ,n, remainω\omega-periodic, we show that the condition on(∗∗)(\ast \ast )is also necessary for(∗)(\ast )to have at least one positiveω−\omega -periodic solution.
The Furstenberg lemma characterizes amenability
Authors: Hjorth Greg
Published: June 2006

We characterize amenability in terms of the existence of equivariant assignments of measures for cocycles into the homeomorphism group of a single compact metric space.
Beurling-Nevanlinna inequality for subfunctions of the stationary Schrödinger operator
Authors: Kheyfits Alexander
Published: June 2006

The classical Beurling-Nevanlinna upper bound for subharmonic functions is extended to subsolutions of the stationary Schrödinger equation.
The real rank zero property of crossed product
Authors: Fang Xiaochun
Published: June 2006

Let

A
A

be a unital

C
∗

C^*

-algebra, and let

(
A
,
G
,
α
)

(A, G, \alpha )

be a

C
∗

C^*

-dynamical system with

G
G

abelian and discrete. In this paper, we introduce the continuous affine map

R
R

from the trace state space

T
(
A

×

α

G
)

T(A\times _{\alpha }G)

of the crossed product

A

×

α

G

A\times _{\alpha }G

to the

α
\alpha

-invariant trace state space

T
(
A

)

α
∗

T(A)_{\alpha ^*}

of

A
A

. If

A

×

α

G

A\times _{\alpha }G

is of real rank zero and

G
^

\hat {G}

is connected, we have proved that

R
R

is homeomorphic. Conversely, if

R
R

is homeomorphic, we also get some properties and real rank zero characterization of

A

×

α

G

A\times _{\alpha }G

. In particular, in that case,

A

×

α

G

A\times _{\alpha }G

is of real rank zero if and only if each unitary element in

A

×

α

G

A\times _{\alpha }G

with the form

u

A

∏

i
=
1

n

x
i
∗

y
i
∗

x
i

y
i

u_{_A}\prod _{i=1}^n x_i^*y_i^*x_iy_i

can be approximated by the unitary elements in

A

×

α

G

A\times _{\alpha }G

with finite spectrum, where

u

A

∈

U
0

(
A
)

u_{_A}\in U_0(A)

,
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="x Subscript i Baseline comma y Subscript i Baseline element-of upper C Subscript c Baseline left-parenthesis upper G comma upper A right-parenthesis intersection upper U 0 left-parenthesis upper A times Subscript alpha Baseline upper G right-parenthesis">

x
i

,

y
i

∈

C
c

(
G
,
A
)
∩

U
0

(
A

×

α

G
)

x_i,y_i\in C_c(G,A)\cap U_0(A\times _{\alpha }G)

, and if moreover

A
A

is a unital inductive limit of the direct sums of non-elementary simple

C
∗

C^*

-algebras of real rank zero, then the

u

A

u_{_A}

above can be cancelled.
Dualized and scaled Fitzpatrick functions
Authors: Simons Stephen
Published: June 2006

In this paper, we obtain an explicit formula for the interior of the domain of a maximal monotone multifunction in terms of its Fitzpatrick function.
On chaotic 𝐶₀-semigroups and infinitely regular hypercyclic vectors
Authors: Kalmes T.
Published: June 2006

A

C
0

C_0

-semigroup

T

=
(
T
(
t
)

)

t
≥
0

\mathcal {T}=(T(t))_{t\geq 0}

on a Banach space

X
X

is called hypercyclic if there exists an element

x
∈
X

x\in X

such that

{
T
(
t
)
x
;

t
≥
0
}

\{T(t)x;\,t\geq 0\}

is dense in

X
X

.

T

\mathcal {T}

is called chaotic if

T

\mathcal {T}

is hypercyclic and the set of its periodic vectors is dense in

X
X

as well. We show that a spectral condition introduced by Desch, Schappacher and Webb requiring many eigenvectors of the generator which depend analytically on the eigenvalues not only implies the chaoticity of the semigroup but the chaoticity of every

T
(
t
)
,

t
>
0

T(t),\,t>0

. Furthermore, we show that semigroups whose generators have compact resolvent are never chaotic. In a second part we prove the existence of hypercyclic vectors in

D
(

A
∞

)

D(A^\infty )

for a hypercyclic semigroup

T

\mathcal {T}

, where

A
A

is its generator.
On generalized hyperinterpolation on the sphere
Authors: Dai Feng
Published: June 2006

It is shown that second-order results can be attained by the generalized hyperinterpolation operators on the sphere, which gives an affirmative answer to a question raised by Reimer in Constr. Approx. 18(2002), no. 2, 183–203.
Uniqueness problem of meromorphic functions sharing small functions
Authors: Chen Zhihua , Yan Qiming
Published: June 2006

In this paper, a uniqueness theorem of meromorphic functions which share four small functions is given.
Stable degenerations of surfaces isogenous to a product of curves
Authors: van Opstall Michael
Published: June 2006

We show that an example of Catanese yields nonrigid surfaces that are diffeomorphic, yet lie on different connected components of the moduli space of stable surfaces.
The sufficiency of arithmetic progressions for the 3𝑥+1 Conjecture
Authors: Monks Kenneth
Published: June 2006

DefineT:Z+→Z+T:\mathbb {Z} ^{+}\rightarrow \mathbb {Z} ^{+}byT(x)=(3x+1)/2T\left ( x\right ) =\left ( 3x+1\right ) /2ifxxis odd andT(x)=x/2T\left ( x\right ) =x/2ifxxis even. The3x+13x+1Conjecture states that theTT-orbit of every positive integer contains11. A set of positive integers is said to besufficientif theTT-orbit of every positive integer intersects theTT-orbit of an element of that set. Thus to prove the3x+13x+1Conjecture it suffices to prove it on some sufficient set. Andaloro proved that the sets1+2nN1+2^{n} \mathbb {N}are sufficient forn≤4n\leq 4and asked if1+2nN1+2^{n}\mathbb {N}is also sufficient for larger values ofnn. We answer this question in the affirmative by proving the stronger result thatA+BNA+B\mathbb {N}is sufficient for any nonnegative integersAAandBBwithB≠0,B\neq 0,i.e. every nonconstant arithmetic sequence forms a sufficient set. We then prove analagous results for the Divergent Orbits Conjecture and Nontrivial Cycles Conjecture.
Human impacts and the global distribution of extinction risk
Authors: Davies Richard G , Orme C. David L , Olson Valerie , Thomas Gavin H , Ross Simon G , Ding Tzung-Su , Rasmussen Pamela C , Stattersfield Ali J , Bennett Peter M , Blackburn Tim M , Owens Ian P.F , Gaston Kevin J
Published: June 2006

Understanding the global geographical distribution of extinction risk is a key challenge in conservation biology. It remains controversial, however, to what extent areas become threat hotspots simply because of high human impacts or due to predisposing ecological conditions. Limits to the taxonomic and geographical extent, resolution and quality of previously available data have precluded a full global assessment of the relative roles of these factors. Here, we use a new global database on the geographical distributions of birds on continents and continental islands to show that, after controlling for species richness, the best predictors of the global pattern of extinction risk are measures of human impact. Ecological gradients are of secondary importance at a global scale. The converse is true for individual biogeographic realms, within which variation in human impact is reduced and its influence on extinction risk globally is therefore underestimated. These results underline the importance of a global perspective on the mechanisms driving spatial patterns of extinction risk, and the key role of anthropogenic factors in driving the current extinction crisis.
The role of zooxanthellae in the thermal tolerance of corals: a ‘nugget of hope’ for coral reefs in an era of climate change
Authors: Berkelmans Ray , van Oppen Madeleine J.H
Published: June 2006

The ability of coral reefs to survive the projected increases in temperature due to global warming will depend largely on the ability of corals to adapt or acclimatize to increased temperature extremes over the next few decades. Many coral species are highly sensitive to temperature stress and the number of stress (bleaching) episodes has increased in recent decades. We investigated the acclimatization potential of
Acropora millepora
, a common and widespread Indo-Pacific hard coral species, through transplantation and experimental manipulation. We show that adult corals, at least in some circumstances, are capable of acquiring increased thermal tolerance and that the increased tolerance is a direct result of a change in the symbiont type dominating their tissues from
Symbiodinium
type C to D. Our data suggest that the change in symbiont type in our experiment was due to a shuffling of existing types already present in coral tissues, not through exogenous uptake from the environment. The level of increased tolerance gained by the corals changing their dominant symbiont type to D (the most thermally resistant type known) is around 1–1.5 °C. This is the first study to show that thermal acclimatization is causally related to symbiont type and provides new insight into the ecological advantage of corals harbouring mixed algal populations. While this increase is of huge ecological significance for many coral species, in the absence of other mechanisms of thermal acclimatization/adaptation, it may not be sufficient to survive climate change under predicted sea surface temperature scenarios over the next 100 years. However, it may be enough to ‘buy time’ while greenhouse reduction measures are put in place.
The anti‐CD20 antibody rituximab augments the immunospecific therapeutic effectiveness of an anti‐CD19 immunotoxin directed against human B‐cell lymphoma
Authors: Flavell David J. , Warnes Sarah L. , Bryson Christine J. , Field Sarah A. , Noss Armorel L. , Packham Graham , Flavell Sopsamorn U.
Published: June 2006

The chimaeric anti‐CD20 antibody rituximab (Rituxan) sensitises lymphoma cells to small molecule cytotoxic drugs and to protein toxins. We have explored the augmentive effect of rituximab on the anti‐CD19 immunotoxin BU12‐SAPORIN in a model of human lymphoma. Intact rituximab and its F(ab)2 derivative both augmented the immunospecific protein synthesis inhibitory effects of BU12‐SAPORIN in a complement‐independent manner. A combination of rituximab + BU12‐SAPORIN completely abolished the proliferation of Ramos cells in vitro and also induced a significantly greater degree of apoptosis in these cells. Treatment with rituximab, BU12‐SAPORIN or a combination of both induced poly(ADPribose) polymerase and caspase 3 cleavage, although this was always consistently greater in combination‐treated cells. zVAD almost completely inhibited apoptosis in rituximab‐ or BU12‐SAPORIN‐treated cells but only partially in combination‐treated cells. In severe combined immunodeficient (SCID)‐Ramos mice the combination of rituximab + BU12‐SAPORIN was significantly better therapeutically than either single agent. The immunological fidelity of the therapeutic effect because of combination treatment was demonstrated through the failure of rituximab to augment an irrelevant anti‐CD7 immunotoxin. The therapeutic efficacy of rituximab and combination treatment was reduced in SCID‐Ramos mice depleted of serum complement while natural killer cell depletion failed to show any convincing role for antibody‐dependent cellular cytotoxicity. This study shows a clear therapeutic advantage from using rituximab to immunospecifically augment immunotoxin cytotoxicity warranting further investigation.
Effects of storage‐induced platelet microparticles on the initiation and propagation phase of blood coagulation
Authors: Keuren Jeffery F.W. , Magdeleyns Elke J.P. , Govers‐Riemslag José W.P. , Lindhout Theo , Curvers Joyce
Published: June 2006

Platelets shed microparticles, which support haemostasis via adherence to the damaged vasculature and by promoting blood coagulation. We investigated mechanisms through which storage‐induced microparticles might support blood coagulation. Flow cytometry was used to determine microparticle number, cellular origin and surface expression of tissue factor (TF), procoagulant phosphatidylserine (PtdSer) and glycoprotein (GP) Ib‐α. The influence of microparticles on initiation and propagation of coagulation were examined in activated factor X (factor Xa; FXa) and thrombin generation assays and compared with that of synthetic phospholipids. About 75% of microparticles were platelet derived and their number significantly increased during storage of platelet concentrates. About 10% of the microparticles expressed functionally active TF, as measured in a FXa generation assay. However, TF‐driven thrombin generation was only found in plasma in which tissue factor pathway inhibitor (TFPI) was neutralised, suggesting that microparticle‐associated TF in platelet concentrates is of minor importance. Furthermore, 60% of all microparticles expressed PtdSer. In comparison with synthetic procoagulant phospholipids, the maximal rate of thrombin formation in TF‐activated plasma was 15‐fold higher when platelet‐free plasma was titrated with microparticles. This difference could be attributed to the ability of microparticles to propagate thrombin generation by thrombin‐activated FXI. Collectively, our findings indicate a role of microparticles in supporting haemostasis by enhancement of the propagation phase of blood coagulation.
The abundance of juvenile yellowtail (Seriola quinqueradiata) near the Kuroshio: the roles of drifting seaweed and regional hydrography
Authors: UEHARA SHINJI , TAGGART CHRISTOPHER T. , MITANI TAKUMI , SUTHERS IAIN M.
Published: June 2006

We assess the effect of drifting seaweed (Sargassum sp.) biomass, geography and hydrography on juvenile yellowtail (Seriola quinqueradiata) abundance variation off the southeast coast of Japan, near the Kuroshio Current. The amount of drifting seaweed mats progressively increased northeastward into the cooler, coastal waters. Frontal structure indexed using a station‐to‐station ΔSST did not explain spatial variation in the seaweed mat distribution, although the western extent of the Kuroshio Current appeared to act as a boundary. Juvenile yellowtail constituted 51–62% of the fish collected in association with drifting seaweed mats in April 1996 and 1997 and 29% in June 1996. The abundance of juvenile yellowtail was positively correlated with seaweed biomass. The geographic distribution of juvenile yellowtail associated with drifting mats varied among sampling periods, being more southwesterly in April and more northeasterly in June. Simple multiple regression models based on seaweed biomass and geographic distribution (latitude) explained between 35% and 43% of the variation in juvenile yellowtail abundance in spring. Associations with spatial and temporal variations in hydrographic conditions did not contribute to explained variation in a meaningful manner. The results presented here indicate that, off the southeast coast of Japan during April, yellowtail juveniles are likely to be most abundant when seaweed biomass is high, occur offshore, and are bounded by the western extent of the Kuroshio Current near the 19–20°C SST isotherm.
Stock–environment–recruitment models for North Atlantic albacore (Thunnus alalunga)
Authors: ARREGUI IGOR , ARRIZABALAGA HARITZ , KIRBY DAVID S. , MARTÍN‐GONZÁLEZ JUAN MANUEL
Published: June 2006

Different stock–recruitment models were fitted to North Atlantic albacore (Thunnus alalunga) recruitment and spawning stock biomass data. A classical density dependence hypothesis, a recent environmental‐dependence hypothesis and a combination of both were considered. For the latter case, four stock–environment–recruitment models were used: Ricker, Beverton‐Holt, Deriso's General Model (modified to take into account environmental effects) and conditioned Neural Networks. Cross‐validation analysis showed that the modified Deriso model had the best predictive capability. It detected an inverse effect of the North Atlantic Oscillation (NAO) on recruitment, a Ricker‐type behaviour with density dependent overcompensation when environmental conditions are unfavourable and a Beverton–Holt‐type behaviour towards an asymptotic recruitment carrying capacity with favourable environmental conditions. The Neural Network model also detected that under favourable environmental conditions high spawning stock biomass does not necessarily have a depensatory effect on recruitment. Moreover, they suggest that under extremely favourable environmental conditions, albacore recruitment could increase well above the asymptotic carrying capacity predicted by Beverton–Holt‐type models. However, the general decrease in spawning stock biomass in recent years and increasing NAO trends suggest that there is low probability of exceptionally large recruitment in the future and instead there is a danger of recruitment overfishing.
What evidence exists for alternative ecological regimes in salinising wetlands?
Authors: SIM LIEN L. , DAVIS JENNY A. , CHAMBERS JANE M. , STREHLOW KARIN
Published: June 2006

1. Land clearing in Australia's southwest has led to widespread salinisation of aquatic ecosystems. Four different ecological regimes (clear, submerged macrophyte‐dominated; clear, benthic microbial community‐dominated; turbid, phytoplankton‐dominated; and turbid, sediment‐dominated) have previously been identified in the salinising wetlands of this region.

2. Monitoring data from seven saline wetlands over an 18‐month period were used to evaluate whether a continuum, simple threshold or alternative regimes conceptual model (sensu Hydrobiologia, 200/201, 1990, 367; Hydrobiologia, 200/201, 1990, 475) most appropriately represented transitions between these ecological regimes. We also aimed to identify whether factors other than salinity played a major role in defining ecological regimes or causing shifts between them.

3. Ordination of biological variables revealed a separation of benthic microbial community‐dominated from submerged macrophyte‐dominated sites and times. The mean salinities of these two groups were very similar, suggesting that a salinity threshold was not responsible for benthic microbial versus macrophyte dominance. No other environmental variable was found to have a strong, direct influence on the groupings.

4. The dynamics of regime change in saline wetlands appear not to be driven by any single variable, but by the combined effects of salinity and water regime on species life histories and competitive abilities. Macrophytes were powerful competitors, able to germinate and establish under a range of salinities, turbidities and water depths, and were favoured by seasonal drying.

5. Data from the seven wetlands indicated that the continuum, simple threshold and alternative regimes conceptual models did not appropriately represent transitions between ecological regimes in seasonally drying wetlands. Macrophyte and benthic microbial regimes occurred at overlapping salinity levels, excluding both the continuum and threshold models, and the regular occurrence of drying appeared to preclude the alternative regimes model. Drying prevented the development of strong positive feedback mechanisms, which might otherwise have maintained the benthic microbial community‐dominated regime. We hypothesise that an alternative regimes model might still be valid for salinising ecosystems holding permanent water.