bluuebunny/crossref_metadata_2025 huggingface dataset:
Turbulence modification by stable stratification in channel flow
Authors: García-Villalba Manuel , del Álamo Juan C.
Published: April 2011

Direct numerical simulations of stably stratified, turbulent channel flow at low to moderate Reynolds number have been performed using large computational boxes and considering a wide range of stratification levels. For weak stratification or high Reynolds number, the turbulence is affected by buoyancy in the core of the channel, but the near-wall region differs little from the neutral case. With strong stratification, large laminar patches appear in the near-wall region and turbulent momentum and buoyancy fluxes vanish in the core of the channel. With increasing stratification, the near-wall streaks remain essentially unmodified, while large-scale global modes are damped. In the central region, internal gravity waves are dominant. In addition, there is an intermediate outer layer where the dynamics of the turbulent structures is governed by local fluxes. In this region, energy spectra collapse when using local Obukhov scaling.
Epitaxial germanidation of full-Heusler Co2FeGe alloy thin films formed by rapid thermal annealing
Authors: Takamura Yota , Sakurai Takuya , Nakane Ryosho , Shuto Yusuke , Sugahara Satoshi
Published: April 2011

The authors demonstrated that a full-Heusler Co2FeGe (CFG) alloy thin film was epitaxially grown by rapid-thermal-annealing-induced germanidation of an Fe/Co/pseudo-Ge(001)-on-insulator (GOI) multilayer formed on a Si-on-insulator (SOI) substrate. X-ray diffraction (XRD) measurements with out-of-plane and in-plane configurations revealed that the CFG film was epitaxially grown along the [001] direction with the in-plane epitaxial relation of CFG[100]‖GOI[100], although the film slightly contained a non-epitaxial component. The strong (111) and (200) superlattice diffraction intensities indicated that the CFG film had a high degree of order for the L21 structure. Cross-sectional high-resolution transmission electron microscopy images of the film revealed that the film had dominant epitaxial and slight non-epitaxial components, which was consistent with the XRD measurements. The epitaxial component was grown directly on the buried oxide layer of the SOI substrate without formation of any interfacial layer.
Micromagnetic method of s-parameter characterization of magnonic devices
Authors: Dvornik M. , Kuchko A. N. , Kruglyak V. V.
Published: April 2011

Designers of nano-scale magnonic devices would benefit from methods of their evaluation that do not require one to access the microscopic level of description or to construct device prototypes. Here, we propose a numerical micromagnetics version of such a method, in which magnonic devices are considered as two-port linear networks and can therefore be described in terms of their s-parameters (i.e., reflection and transmission characteristics). In the micromagnetic model, the sample is composed from a magnonic device-under-test situated between input and output magnonic waveguides. First, dispersion relations and amplitudes of spin waves in the input and output waveguides are calculated from the simulations. The results are then compared to derive the s-parameters of the device-under-test. We use a simple rectangular magnetic nonuniformity, for which analytical results are readily obtained, to evaluate the efficiency and limitations of the technique in the sub-terahertz band.
Synthesis of CoFe/Al2O3 composite nanoparticles as the impedance matching layer of wideband multilayer absorber
Authors: Zhen L. , Gong Y. X. , Jiang J. T. , Xu C. Y. , Shao W. Z. , Liu P. , Tang J.
Published: April 2011

CoFe/Al2O3 composite nanoparticles were successfully prepared by hydrogen-thermally reducing cobalt aluminum ferrite. Compared with CoFe alloy nanoparticles, the permeability of CoFe/Al2O3 composite nanoparticles was remarkably enhanced and an improved impedance characteristic was achieved due to the introduction of insulated Al2O3. A multilayer absorber with CoFe/Al2O3 composite nanoparticles as the impedance matching layer and CoFe nanoflake as the dissipation layer was designed by using genetic algorithm, in which an ultrawide operation frequency bandwidth over 2.5–18 GHz was obtained. The microwave absorption performance in both normal and oblique incident case was evaluated by using electromagnetic simulator. The backward radar cross-section (RCS) was decreased at least 10 dB over a wide frequency range by covering the multilayer absorber on the surface of perfect electrical conductive plate.
Path reweighting technique with scaling factor for stochastic dynamics and its application to the magnetization reversal process
Authors: Cheng X. Z. , Jalil M. B. A.
Published: April 2011

Reweighting of trajectories in stochastic dynamical processes leads to significant reduction in simulation effort as it allows stochastic dynamical result corresponding to one temperature to be ported to another temperature. In this paper, we propose an improved reweighting technique which incorporates a time scaling factor. This results in an improved distribution in the trajectory’s weight space, and broadens the range of temperature over which the reweighting technique can be applied. The technique is employed in numerical simulation of an exemplary stochastic process, i.e., the thermally activated magnetization reversal process of an Ising system.
Improved methods for calculating thermodynamic properties of magnetic systems using Wang-Landau density of states
Authors: Brown G. , Rusanu A. , Daene M. , Nicholson D. M. , Eisenbach M. , Fidler J.
Published: April 2011

The Wang-Landau method [F. Wang and D. P. Landau, Phys. Rev. E 64, 056101 (2001)] is an efficient way to calculate the density of states (DOS) for magnetic systems, and the DOS can then be used to rapidly calculate the thermodynamic properties of the system. A technique is presented that uses the DOS for a simple Hamiltonian to create a stratified sample of configurations which are then used calculate a “warped’’ DOS for more realistic Hamiltonians. This technique is validated for classical models of bcc Fe with exchange interactions of increasing range, but its real value is using the DOS for a model Hamiltonian calculated on a workstation to select the stratified set of configurations whose energies can then be calculated for a density-functional Hamiltonian. The result is an efficient first-principles calculation of thermodynamic properties such as the specific heat and magnetic susceptibility. Another technique uses the sample configurations to calculate the parameters of a model exchange interaction using a least-squares approach. The thermodynamic properties can be subsequently evaluated using traditional Monte Carlo techniques for the model exchange interaction. Finally, a technique that uses the configurations to train a neural network to estimate the configuration energy is also discussed. This technique could potentially be useful in identifying the configurations most important in calculating the “warped’’ DOS.
Structure and magnetic properties of L1-FePt thin films on TiN/RuAl underlayers
Authors: Yang En , Ratanaphan Sutatch , Zhu Jian-Gang , Laughlin David E.
Published: April 2011

Highly ordered L10 FePt-oxide thin films with small grains were prepared by using a RuAl layer as a grain size defining seed layer along with a TiN barrier layer. Different HAMR (Heat Assisted Magnetic Recording) favorable underlayers were studied to encourage perpendicular texture and preferred microstructure. It was found that the epitaxial and small grain growth from the RuAl/TiN underlayer results in small and uniform grains in the FePt layer with perpendicular texture. By introducing the grain size defining underlayers, the FePt grain size can be reduced from 30 to 6 nm with the same volume fraction (9%) of SiO2 in the film, excellent perpendicular texture, and very high order parameter at 520 °C.
Switching field distribution of planar-patterned CrPt3 nanodots fabricated by ion irradiation
Authors: Suharyadi E. , Oshima D. , Kato T. , Iwata S.
Published: April 2011

Planar-patterned CrPt3 ordered L12 nanodots with various bit sizes (D) from 220 to 55 nm were fabricated by the local irradiation of 30 keV of Kr+ ions not by conventional physical etching. Patterned nanodots with bit size ≤ 65 nm show either dark or bright contrast, suggesting that they have single domain structure. Switching field distribution of nanodots was studied by taking magnetic force microcopy images, in the progress of the magnetization reversal. As-prepared CrPt3 film exhibited perpendicular hysteresis loop with the coercivity of 5.5 kOe. Compared with the as-prepared film, the average switching field (Hsf) of the CrPt3 nanodots increased as 6.5, 8.5, and 9.2 kOe while the switching field distribution (ΔHsf) decreased as 6.8, 3.6, and 2.8 kOe, for the patterned nanodots with bit sizes of 220, 150, 65 nm, respectively. We found that the small ΔHsf/Hsf is possible in the high density planar bit patterned media fabricated by ion irradiation.
Micromagnetic simulations of magnetoelectric materials
Authors: Fischbacher Thomas , Franchin Matteo , Fangohr Hans
Published: April 2011

Some magnetic materials show a magnetoelectric coupling between inhomogeneous magnetization patterns and electric polarization that is sufficiently strong to allow external control of magnetization structure by electric fields. Numerical simulations of “magnetoelectric” materials of this type require an extension of the standard micromagnetic model which conceptually parallels the introduction of spin-current interaction terms. We show how the micromagnetic simulator “Nmag” can be extended to support the inhomogeneous magnetoelectric interaction term and also give a simple self-contained example for simulating the micromagnetic dynamics of a magnetoelectric system in the presence of an external electric field.
Particle size dependence of magnetization and noncentrosymmetry in nanoscale BiFeO3
Authors: Goswami Sudipta , Bhattacharya Dipten , Choudhury P.
Published: April 2011

The saturation magnetization (MS), antiferromagnetic transition point (TN), and the off-center displacements of Bi and Fe ions have been measured as a function of particle size in nanoscale BiFeO3. TN decreases down to ∼550 K for particles of size ∼5 nm from ∼653 K in bulk, while MS rises by more than an order of magnitude. Analysis of crystallographic structure from Rietveld refinement of x-ray diffraction patterns shows significant rise in off-center displacements of Bi (δBi) and Fe (δFe) ions within a unit cell with the decrease in particle size. The net unit-cell polarization PS too, is found to be larger in nanoscale regime.
Relaxation of the shear modulus of a metallic glass near the glass transition
Authors: Mitrofanov Yu. P. , Khonik V. A. , Granato A. V. , Joncich D. M. , Khonik S. V.
Published: April 2011

Precise in situ measurements of the high-frequency (f≈560 kHz) shear modulus G of Pd40Cu30Ni10P20 bulk metallic glass at heating rates 0.38≤T·≤7.5 K/min have been performed. It has been found that structural relaxation leads to an increase of G below the glass transition temperature Tg while decreasing it at T>Tg. A quantitative analysis of this phenomenon within the framework of the interstitialcy theory has shown that structural relaxation below Tg can be understood as a decrease of the concentration of interstitialcy-like defects frozen-in upon glass production. The relaxation turns into defect multiplication on continued heating above Tg. The beginning of defect multiplication represents the glass transition temperature. An excellent agreement between calculated and experimental Tg ’s as a function of the heating rate has been found.
Extensional rheometer for in situ x-ray scattering study on flow-induced crystallization of polymer
Authors: Liu Yanping , Zhou Weiqing , Cui Kunpeng , Tian Nan , Wang Xiao , Liu Liangbao , Li Liangbin , Zhou Yingui
Published: April 2011

We designed and constructed an extensional rheometer for in situ small and wide angle x-ray study on flow-induced crystallization of polymer. Two rotating drums with an axis distance of 20 mm are employed to impose extensional deformation on the samples. With a constant angular velocity, the two drums generate a constant Henkcy strain rate as sample length for testing keeps constant during deformation. An ionic liquid is used as heating medium to prevent polymer melt from bending downward due to gravity, which is excellent in terms of high thermal stability, low viscosity, and relative low adsorption on x-ray. Flow-induced crystallization experiments are conducted with this apparatus on x-ray scattering station in Shanghai Synchrotron Radiation Facility (SSRF), which allows us to collect rheological and structural data simultaneously and may lead to a better understanding on flow-induced crystallization of polymer.
Transient dynamics around unstable periodic orbits in the generalized repressilator model
Authors: Strelkowa Natalja , Barahona Mauricio
Published: April 2011

We study the temporal dynamics of the generalized repressilator, a network of coupled repressing genes arranged in a directed ring topology, and give analytical conditions for the emergence of a finite sequence of unstable periodic orbits that lead to reachable long-lived oscillating transients. Such transients dominate the finite time horizon dynamics that is relevant in confined, noisy environments such as bacterial cells (see our previous work [Strelkowa and Barahona, J. R. Soc. Interface 7, 1071 (2010)]), and are therefore of interest for bioengineering and synthetic biology. We show that the family of unstable orbits possesses spatial symmetries and can also be understood in terms of traveling wave solutions of kink-like topological defects. The long-lived oscillatory transients correspond to the propagation of quasistable two-kink configurations that unravel over a long time. We also assess the similarities between the generalized repressilator model and other unidirectionally coupled electronic systems, such as magnetic flux gates, which have been implemented experimentally.
Experimental observation of contact mode cantilever dynamics with nanosecond resolution
Authors: Payton O. D. , Picco L. , Champneys A. R. , Homer M. E. , Miles M. J. , Raman A.
Published: April 2011

We report the use of a laser Doppler vibrometer to measure the motion of an atomic force microscope contact mode cantilever during continuous line scans of a mica surface. With a sufficiently high density of measurement points the dynamics of the entire cantilever beam, from the apex to the base, can be reconstructed. We demonstrate nanosecond resolution of both rectangular and triangular cantilevers. This technique permits visualization and quantitative measurements of both the normal and lateral tip sample interactions for the first and higher order eigenmodes. The ability to derive quantitative lateral force measurements is of interest to the field of microtribology/nanotribology while the comprehensive understanding of the cantilever's dynamics also aids new cantilever designs and simulations.
Comment on “Heat capacity, enthalpy fluctuations, and configurational entropy in broken ergodic systems” [J. Chem. Phys. 133, 164503 (2010)]
Authors: Johari G. P.
Published: April 2011

A critical examination shows that the specific heat and shear modulus relaxation spectra do not support the notions of continuously broken ergodicity and loss of configurational contribution on isothermal glass transition, nor does the long-known result that Cp → 0 as T → 0 K prove that Sconf → 0. Spectra show variation of the real and imaginary components due to phase lag and not due to loss of configurational degrees of freedom. The high-frequency shear modulus, G∞, of glass increases with time as its fictive temperature decreases and dG∞/dT decreases when a glass forms.
A half wave retarder made of bilayer subwavelength metallic apertures
Authors: Marcet Z. , Chan H. B. , Carr D. W. , Bower J. E. , Cirelli R. A. , Klemens F. , Mansfield W. M. , Miner J. F. , Pai C. S. , Kravchenko I. I.
Published: April 2011

We demonstrate a half wave plate whose principle of operation is based on the strong evanescent field coupling between two metal layers with arrays of subwavelength slits. The device is divided into two kinds of pixels in which the slits are oriented in orthogonal directions. By tuning the phase delay of the transmitted light through the lateral displacement between the top and bottom layers, the polarization of linearly polarized light at 1.55 μm can be rotated by up to 90°. The polarization extinction ratio of the transmitted light exceeds 22 dB.
High sensitivity plasmonic index sensor using slablike gold nanoring arrays
Authors: Tsai Chia-Yang , Lu Shao-Ping , Lin Jyun-Wei , Lee Po-Tsung
Published: April 2011

We investigate the index sensing characteristics of plasmonic arrays based on square lattice slablike gold nanorings (NRs) with different ring widths. The gold NR arrays exhibit two extinction peaks in the visible and near-infrared corresponding to antibonding and bonding modes. Redshift and blueshift in antibonding and bonding modes when broadening the average ring width are observed. We experimentally demonstrate the sensitivity of bonding mode can be tuned by varying the average ring width. High sensitivity of 691 nm per refractive index unit is obtained for NRs with 199 nm average ring width.
Electric-field-control of resistance and magnetization switching in multiferroic Zn0.4Fe2.6O4/0.7Pb(Mg2/3Nb1/3)O3–0.3PbTiO3 epitaxial heterostructures
Authors: Yang Yuanjun , Luo Z. L. , Huang Haoliang , Gao Yachun , Bao J. , Li X. G. , Zhang Sen , Zhao Y. G. , Chen Xiangcun , Pan Guoqiang , Gao C.
Published: April 2011

Multiferroic (001)–Zn0.4Fe2.6O4/0.7Pb(Mg2/3Nb1/3)O3–0.3PbTiO3 (ZFO/PMN–PT) epitaxial heterostructures have been investigated to demonstrate the electric-field-controlled resistance and magnetization switching. The tunabilitiy of resistance of the ZFO film is about −0.1% under the in-plane strain −0.02% at 296 K and 0.2% for the electric field 1.0 kV/cm at 80 K, respectively, and the tunabilitiy of magnetization is about 1.1% under the in-plane strain −0.11% at 296 K, which is attributed to the controllable strain transferred into the ZFO film from the piezoelectric PMN–PT substrate. A possible microscopic mechanism of the manipulation of resistance and magnetization is the enhancement of hopping amplitude of electrons between mixed-valent Fe2+ and Fe3+ ions under the electric-field-induced in-plane compressive strain.
First-principles time-dependent simulation of laser assisted desorption of hydrogen atoms from H–Si(111) surface
Authors: Bubin Sergiy , Varga Kálmán
Published: April 2011

The dynamics of hydrogen desorption from H-terminated silicon surface clusters has been simulated in the framework of real space time-dependent density functional theory complemented with molecular dynamics for ions. It has been demonstrated that by choosing an appropriate frequency and intensity of the laser it is possible to remove the hydrogen layer from the surface without destroying the structure of underlying silicon. At the laser field intensities used in the current study (0.5–2.0 V/Å) the desorption process is notably nonlinear.
Electrical reliability and leakage mechanisms in highly resistive multiferroic La0.1Bi0.9FeO3 ceramics
Authors: Wang S. Y. , Qiu Xue , Gao J. , Feng Yu , Su W. N. , Zheng J. X. , Yu D. S. , Li D. J.
Published: April 2011

Multiferroic La0.1Bi0.9FeO3 (LBFO) ceramics with high resistivity were synthesized by using a modified rapid thermal process. The LBFO ceramics show very low leakage and low dielectric loss. Well saturated ferroelectric hysteresis loops and polarization switching currents have been observed. For a maximum applied electric field of 145 kV/cm, the remanent polarization is 17.8 μC/cm2 and the coercive filed is 75 kV/cm. The dominant conduction mechanism in the LBFO ceramics has been found to be the space-charge-limited current mechanism rather than the thermal excitation mechanism. Electrical reliability related to the fatigue and polarization retention of the LBFO ceramics has also been discussed with the leakage mechanisms.
Correlation between internal states and plasticity in bulk metallic glass
Authors: Tan J. , Zhang Y. , Sun B. A. , Stoica M. , Li C. J. , Song K. K. , Kühn U. , Pan F. S. , Eckert J.
Published: April 2011

We report a close correlation between the internal states and plasticity in a bulk metallic glass (BMG) and discover that the optimization of copper-mold casting current can induce large plasticity stably in an otherwise brittle BMG. It is possible to confirm that larger plasticity corresponds to the internal states with more average free volume (FV) as revealed by lower density, higher enthalpy change, and higher Poisson’s ratio. The enhanced plastic deformation mechanism is interpreted based on the FV model of BMGs, and our results may have some implications for understanding the role of the FV during plastic deformation of BMGs.
A mathematical model for adaptive prediction of environmental changes by microorganisms
Authors: Mitchell Amir , Pilpel Yitzhak
Published: April 2011

Survival in natural habitats selects for microorganisms that are well-adapted to a wide range of conditions. Recent studies revealed that cells evolved innovative response strategies that extend beyond merely sensing a given stimulus and responding to it on encounter. A diversity of microorganisms, including
Escherichia coli
,
Vibrio cholerae
, and several yeast species, were shown to use a predictive regulation strategy that uses the appearance of one stimulus as a cue for the likely arrival of a subsequent one. A better understanding of such a predictive strategy requires elucidating the interplay between key biological and environmental forces. Here, we describe a mathematical framework to address this challenge. We base this framework on experimental systems featuring early preparation to either a stress or an exposure to improvement in the growth medium. Our model calculates the fitness advantage originating under each regulation strategy in a given habitat. We conclude that, although a predictive response strategy might by advantageous under some ecologies, its costs might exceed the benefit in others. The combined theoretical–experimental treatment presented here helps assess the potential of natural ecologies to support a predictive behavior.
Can young children learn words from a robot?
Authors: Moriguchi Yusuke , Kanda Takayuki , Ishiguro Hiroshi , Shimada Yoko , Itakura Shoji
Published: April 2011

Young children generally learn words from other people. Recent research has shown that children can learn new actions and skills from nonhuman agents. This study examines whether young children could learn words from a robot. Preschool children were shown a video in which either a woman (human condition) or a mechanical robot (robot condition) labeled novel objects. Then the children were asked to select the objects according to the names used in the video. The results revealed that children in the human condition were more likely to select the correct objects than those in the robot condition. Nevertheless, the five-year-old children in the robot condition performed significantly better than chance level, while the four-year olds did not. Thus there is a developmental difference in children’s potential to learn words from a robot. The results contribute to our understanding of how children interact with non-human agents. Keywords: developmental cybernetics; word learning; social cognition; cognitive development
Mindful tutors
Authors: Fischer Kerstin , Foth Kilian , Rohlfing Katharina J. , Wrede Britta
Published: April 2011

It has been proposed that the design of robots might benefit from interactions that are similar to caregiver–child interactions, which is tailored to children’s respective capacities to a high degree. However, so far little is known about how people adapt their tutoring behaviour to robots and whether robots can evoke input that is similar to child-directed interaction. The paper presents detailed analyses of speakers’ linguistic behaviour and non-linguistic behaviour, such as action demonstration, in two comparable situations: In one experiment, parents described and explained to their nonverbal infants the use of certain everyday objects; in the other experiment, participants tutored a simulated robot on the same objects. The results, which show considerable differences between the two situations on almost all measures, are discussed in the light of the computer-as-social-actor paradigm and the register hypothesis. Keywords: child-directed speech (CDS); motherese; robotese; motionese; register theory; social communication; human–robot interaction (HRI); computers-as-social-actors; mindless transfer
Boundedness and relativity
Authors: Tribushinina Elena
Published: April 2011

It is often assumed that relative adjectives (e.g. ‘long’, ‘old’) evoke unbounded scales and are, therefore, incompatible with maximizers (e.g. ‘completely’) and approximators (e.g. ‘almost’). In contrast, absolute adjectives which are felicitous with maximizers (e.g. ‘completely full’) and approximators (e.g. ‘almost full’) are argued to trigger bounded scales. This paper investigates whether the semantic typology of gradable adjectives developed for Germanic languages can be extended to non-Germanic languages by comparing the distribution of relative adjectives with totality modifiers in English and Russian corpora. In line with previous research, the corpus analysis shows that English relative adjectives are associated with fully unbounded scales and are very infrequent in combination with maximizers and approximators. In contrast, Russian relative adjectives evoke half-bounded scales. Therefore, relative adjectives denoting less of a property (e.g. korotkij “short”, dešëvyj “cheap”) are quite frequently modified by maximizing adverbs in Russian. However, unlike maximum-standard absolute adjectives, Russian relative adjectives are incompatible with approximators. It is concluded that there is no universal one-to-one relationship between adjective types and scale types.
Order reduction method for linear difference equations
Authors: Korhonen R. , Ronkainen O.
Published: April 2011

An order reduction method for homogeneous linear difference equations, analogous to the standard order reduction of linear differential equations, is introduced, and this method is applied to study the Nevanlinna growth relations between meromorphic coefficients and solutions of linear difference equations.
Evaluating Whittaker functions and Maass forms for 𝑆𝐿(3,ℤ)
Authors: Mezhericher Borislav
Published: April 2011

We present and compare several algorithms for evaluating Jacquet’s Whittaker functions for

S
L
(
3
,

Z

)

SL(3,\mathbb {Z})

. The most suitable algorithm is then applied to the problem of evaluating a Maass form for

S
L
(
3
,

Z

)

SL(3,\mathbb {Z})

with known eigenvalues and Fourier coefficients.
Cobweb: a Java applet for network exploration and visualisation
Authors: von Eichborn Joachim , Bourne Philip E. , Preissner Robert
Published: April 2011

Summary: Cobweb is a Java applet for real-time network visualization; its strength lies in enabling the interactive exploration of networks. Therefore, it allows new nodes to be interactively added to a network by querying a database on a server. The network constantly rearranges to provide the most meaningful topological view.

Availability: Cobweb is available under the GPLv3 and may be freely downloaded at http://bioinformatics.charite.de/cobweb.

Contact:  joachim.eichborn@charite.de

Supplementary Information:  Supplementary data are available at Bioinformatics online.
Perioperative Stroke and Associated Mortality after Noncardiac, Nonneurologic Surgery
Authors: Mashour George A. , Shanks Amy M. , Kheterpal Sachin
Published: April 2011

Background

Stroke is a leading cause of morbidity and mortality in the United States and occurs in the perioperative period. The authors studied the incidence, predictors, and outcomes of perioperative stroke using the American College of Surgeons National Surgical Quality Improvement Program.

Methods

Data on 523,059 noncardiac, nonneurologic patients in the American College of Surgeons National Surgical Quality Improvement Program database were analyzed for the current study. The incidence of perioperative stroke was identified. Logistic regression was applied to a derivation cohort of 350,031 patients to generate independent predictors of stroke and develop a risk model. The risk model was subsequently applied to a validation cohort of 173,028 patients. The role of perioperative stroke in 30-day mortality was also assessed.

Results

The incidence of perioperative stroke in both the derivation and validation cohorts was 0.1%. Multivariate analysis revealed the following independent predictors of stroke in the derivation cohort: age ≥ 62 yr, history of myocardial infarction within 6 months before surgery, acute renal failure, history of stroke, dialysis, hypertension, history of transient ischemic attack, chronic obstructive pulmonary disease, current tobacco use, and body mass index 35-40 kg/m² (protective). These risk factors were confirmed in the validation cohort. Surgical procedure also influenced the incidence of stroke. Perioperative stroke was associated with an 8-fold increase in perioperative mortality within 30 days (95% CI, 4.6-12.6).

Conclusions

Noncardiac, nonneurologic surgery carries a risk of perioperative stroke, which is associated with higher mortality. The models developed in this study may be informative for clinicians and patients regarding risk and prevention of this complication.
Not whale-fall specialists,
Osedax
worms also consume fishbones
Authors: Rouse Greg W. , Goffredi Shana K. , Johnson Shannon B. , Vrijenhoek Robert C.
Published: April 2011

Marine annelid worms of the genus
Osedax
exploit sunken vertebrate bones for food. To date, the named species occur on whale or other mammalian bones, and it is argued that
Osedax
is a whale-fall specialist. To assess whether extant
Osedax
species could obtain nutrition from non-mammalian resources, we deployed teleost bones and calcified shark cartilage at approximately 1000 m depth for five months. Although the evidence from shark cartilage was inconclusive, the teleost bones hosted three species of
Osedax
, each of which also lives off whalebones. This suggests that rather than being a whale-fall specialist,
Osedax
has exploited and continues to exploit a variety of food sources. The ability of
Osedax
to colonize and to grow on fishbone lends credibility to a hypothesis that it might have split from its siboglinid relatives to assume the bone-eating lifestyle during the Cretaceous, well before the origin of marine mammals.
Species differences in the winner effect disappear in response to post-victory testosterone manipulations
Authors: Fuxjager Matthew J. , Montgomery Jon L. , Marler Catherine A.
Published: April 2011

Evolutionary processes can interact with the mechanisms of steroid hormone action to drive interspecific variation in behavioural output, yet the exact nature of these interactions is poorly understood. To investigate this issue, we compare the endocrine machinery underlying the winner effect (an ability to increase winning behaviour in response to past victories) in two closely related species of
Peromyscus
mice. Typically, after winning a fight, California mice (
Peromyscus californicus
) experience a testosterone (T) surge that helps enhance their future winning behaviour, whereas white-footed mice (
Peromyscus leucopus
) experience neither a T surge nor a change in subsequent winning behaviour. However, our results indicate that when the post-victory T response of male white-footed mice is phenotypically engineered to resemble that of California mice, individuals are capable of developing a strong and lasting winner effect. Moreover, this ‘induced’ winner effect in white-footed mice qualitatively matches the winner effect that develops naturally in California mice. Taken together, these findings suggest that white-footed mice have the physiological machinery necessary to form a robust winner effect comparable to that formed by California mice, but are unable to endogenously activate this machinery after achieving winning experiences. We speculate that evolutionary processes, like selection, operate on the physiological substrates that govern post-victory T release to guide divergence in the winner effect between these two species.
How to evade a coevolving brood parasite: egg discrimination versus egg variability as host defences
Authors: Spottiswoode Claire N. , Stevens Martin
Published: April 2011

Arms races between avian brood parasites and their hosts often result in parasitic mimicry of host eggs, to evade rejection. Once egg mimicry has evolved, host defences could escalate in two ways: (i) hosts could improve their level of egg discrimination; and (ii) negative frequency-dependent selection could generate increased variation in egg appearance (polymorphism) among individuals. Proficiency in one defence might reduce selection on the other, while a combination of the two should enable successful rejection of parasitic eggs. We compared three highly variable host species of the Afrotropical cuckoo finch
Anomalospiza imberbis
, using egg rejection experiments and modelling of avian colour and pattern vision. We show that each differed in their level of polymorphism, in the visual cues they used to reject foreign eggs, and in their degree of discrimination. The most polymorphic host had the crudest discrimination, whereas the least polymorphic was most discriminating. The third species, not currently parasitized, was intermediate for both defences. A model simulating parasitic laying and host rejection behaviour based on the field experiments showed that the two host strategies result in approximately the same fitness advantage to hosts. Thus, neither strategy is superior, but rather they reflect alternative potential evolutionary trajectories.
Experiments with humans indicate that decision accuracy drives the evolution of niche width
Authors: Tosh Colin R. , Ruxton Graeme D. , Krause Jens , Franks Daniel W.
Published: April 2011

One theory to explain the high incidence of niche specialization in many animals is that it reduces attentional load during resource-seeking behaviour and thus leads to more accurate resource selection. A recent neural network model refined the predictions of this theory, indicating that a cognitive advantage in specialists is likely to occur under realistic ecological conditions, namely when ‘mistakes’ (i.e. selection of non-host resources) contribute moderately but positively to fitness. Here, we present a formal empirical test of the predictions of this model. Using a human–computer interactive, we demonstrate that the central prediction of the model is supported: specialist humans are more accurate decision-makers than generalists when their mistakes are rewarded, but not when mistakes are punished. The idea that increased decision accuracy drives the evolution of niche width in animals has been supported in almost all empirical systems in which it has been investigated. Theoretical work supports the idea, and now the predictions of a key theoretical model have been demonstrated in a real biological information-processing system. Considering these interlocking pieces of evidence, we argue that specialization through increased decision accuracy may contribute significantly, along with other mechanisms, to promote niche specialization in animals.
Intronic T-DNA Insertion Renders Arabidopsisopr3a Conditional Jasmonic Acid-Producing Mutant
Authors: Chehab E. Wassim , Kim Se , Savchenko Tatyana , Kliebenstein Daniel , Dehesh Katayoon , Braam Janet
Published: April 2011

Jasmonic acid and its derived metabolites (JAs) orchestrate plant defense against insects and fungi. 12-Oxo-phytodienoic acid (OPDA), a JA precursor, has also been implicated in plant defense. We sought to define JAs and OPDA functions through comparative defense susceptibility characteristics of three Arabidopsis (Arabidopsis thaliana) genotypes: aos, lacking JAs and OPDA; opda reductase3 (opr3), deficient in JA production but can accumulate OPDA; and transgenics that overexpress OPR3. opr3, like aos, is susceptible to cabbage loopers (Trichoplusia ni) but, relative to aos, opr3 has enhanced resistance to a necrotrophic fungus. Gas chromatography-mass spectrometry reveals that opr3 produces OPDA but no detectable JAs following wounding and looper infestation; unexpectedly, substantial levels of JAs accumulate in opr3 upon fungal infection. Full-length OPR3 transcripts accumulate in fungal-infected opr3, potentially through splicing of the T-DNA containing intron. Fungal resistance correlates with levels of JAs not OPDA; therefore, opr3 resistance to some pests is likely due to JA accumulation, and signaling activities ascribed to OPDA should be reassessed because opr3 can produce JAs. Together these data (1) reinforce the primary role JAs play in plant defense against insects and necrotrophic fungi, (2) argue for a reassessment of signaling activities ascribed to OPDA, and (3) provide evidence that mutants with intron insertions can retain gene function.
Methylation silencing of angiopoietin‐like 4 in rat and human mammary carcinomas
Authors: Hattori Naoko , Okochi‐Takada Eriko , Kikuyama Mizuho , Wakabayashi Mika , Yamashita Satoshi , Ushijima Toshikazu
Published: April 2011

Aberrant DNA methylation is deeply involved in the development and progression of human breast cancers, but its inducers and molecular mechanisms are still unclear. To reveal such inducers and clarify the molecular mechanisms, animal models are indispensable. Here, to identify genes silenced by promoter DNA methylation in rat mammary carcinomas, we took a combined approach of methylated DNA immunoprecipitation (MeDIP)–CpG island (CGI) microarray analysis and expression microarray analysis after treatment with epigenetic drugs. MeDIP‐CGI microarray revealed that among 5031 genes with promoter CGI, 465 were methylated in a carcinoma cell line induced by 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP), but not in normal mammary epithelial cells. By treatment of the cell line with 5‐aza‐2′‐deoxycytidine and trichostatin A, 29 of the 465 genes were shown to be re‐expressed. In primary mammary carcinomas, five (Angptl4, Coro1a, RGD1304982, Tmem37 and Ndn) of the 29 genes were methylated in one or more of 25 samples. Quantitative expression analysis revealed that Angptl4 had high expression in normal mammary glands, but low expression in primary carcinomas. Also in humans, ANGPTL4 was unmethylated and expressed in normal mammary epithelial cells, but was methylated in 11 of 91 (12%) primary breast cancers. This is the first study to identify genes aberrantly methylated in rat mammary carcinomas, and Angptl4 is a novel methylation‐silenced gene both in rat and human mammary carcinomas. The combination of the MeDIP‐CGI microarray analysis and expression microarray analysis after treatment with epigenetic drugs was effective in reducing the number of methylated genes that are not methylation silenced. (Cancer Sci 2011; 102: 1337–1343)
Activation of coagulation in bullous pemphigoid and other eosinophil-related inflammatory skin diseases
Authors: Marzano A V , Tedeschi A , Berti E , Fanoni D , Crosti C , Cugno M
Published: April 2011

Bullous pemphigoid (BP) is a skin disease caused by autoantibodies to hemidesmosomal proteins BP180 and BP230, with eosinophils participating in blister formation. Tissue factor (TF), the initiator of coagulation, is embodied within the eosinophil granules and exposed upon activation. We evaluated the coagulation activation in patients with BP (63), chronic urticaria (CU; 20), atopic dermatitis (AD; 14), cutaneous drug reactions (CDRs; six), psoriasis (20), dermatitis herpetiformis (DH; four) and primary cutaneous T cell lymphoma (CTCL; five), and in 40 healthy controls. Prothrombin fragment F1+2 and d-dimer (coagulation markers) were measured by enzyme-linked immunosorbent assay (ELISA) in all plasma samples and BP blister fluid. Skin TF expression was evaluated immunohistochemically in the patients and 20 controls. F1+2 and d-dimer levels were higher in BP plasma than in control plasma (P = 0·0001 for both), and dramatically high in blister fluid; both correlated positively with disease severity, esinophil counts and anti-BP180 antibodies (P = 0·006–0·0001). Plasma F1+2 and d-dimer levels were higher in the CU, AD and CDR patients than in controls (P = 0·0001 for all), but normal in the psoriasis, DH and CTCL patients. Skin TF was expressed in the BP (P = 0·0001), CU (P = 0·0001), AD (P = 0·001) and CDR patients (P = 0·01), but not in the psoriasis, DH or CTCL patients. Co-localization confocal microscopy studies confirmed eosinophils as the source of TF in 10 BP patients. The coagulation cascade is activated in BP and other eosinophil-mediated skin disorders, but not in non-eosinophil driven conditions. This hypercoagulability may contribute to inflammation, tissue damage and, possibly, thrombotic risk.
CD46 in innate and adaptive immunity: an update
Authors: Cardone J , Le Friec G , Kemper C
Published: April 2011

CD46 was discovered in 1986 during a search for novel C3b-binding proteins. CD46 is expressed ubiquitously and functions as a co-factor in the factor I-mediated proteolytic cleavage of C3b and C4b. Its vital role in preventing complement deposition on host tissue is underpinned by the fact that deficiency of CD46 is a predisposing factor for numerous disease conditions arising from complement-mediated ‘self-attack’. However, in the last 10 years, it has become apparent that CD46 is also heavily involved in a new and somewhat surprising functional aspect of the complement system: the down-modulation of adaptive T helper type 1 (Th1) immune responses by regulating the production of interferon (IFN)-γversus interleukin (IL)-10 within these cells. Specifically, this latter function of CD46 is a tantalizing discovery – it may not only have delivered the explanation as to why so many pathogens use and abuse CD46 as cell entry receptor but clearly has important clinical implications for the better understanding of Th1-mediated disease states and novel therapeutic approaches for their amelioration. Here, we summarize and discuss the current knowledge about CD46 and its expanding roles in the immune system.
Intrageneric variation in antipredator responses of coral reef fishes affected by ocean acidification: implications for climate change projections on marine communities
Authors: FERRARI MAUD C. O. , DIXSON DANIELLE L. , MUNDAY PHILIP L. , McCORMICK MARK I. , MEEKAN MARK G. , SIH ANDREW , CHIVERS DOUGLAS P.
Published: April 2011

Our planet is experiencing an increase in the concentration of atmospheric carbon dioxide (CO2) unprecedented in the past 800 000 years. About 30% of excess atmospheric CO2 is absorbed by the oceans, thus increasing the concentration of carbonic acid and reducing the ocean's pH. Species able to survive the physiological stress imposed by ocean acidification may still suffer strong indirect negative consequences. Comparing the tolerance of different species to dissolved CO2 is a necessary first step towards predicting the ecological impacts of rising CO2 levels on marine communities. While it is intuitive that not all aquatic species will be affected the same way by CO2, one could predict that closely related species, sharing similar life histories and ecology, may show similar tolerance levels to CO2. Our ability to create functional groups of species according to their CO2 tolerance may be crucial in our ability to predict community change in the future. Here, we tested the effects of CO2 exposure on the antipredator responses of four damselfish species (Pomacentrus chrysurus, Pomacentrus moluccensis, Pomacentrus amboinensis and Pomacentrus nagasakiensis). Although being sympatric and sharing the same ecology and life history, the four congeneric species showed striking and unexpected variation in CO2 tolerance, with CO2‐induced loss of response to predation risk ranging from 30% to 95%. Using P. chrysurus as a model species, we further tested if these behavioural differences translated into differential ability to survive predators under natural conditions. Our results indicate that P. chrysurus larvae raised under CO2 levels predicted by 2070 and 2100 showed decreased antipredator responses to risk, leading to a five‐ to sevenfold increase in predation‐related mortality in the first few hours of settlement. Examining ocean acidification, along with other environmental variables, will be a critical step in further evaluating ecological responses to predicted climatic change.
Postfire energy exchange in arctic tundra: the importance and climatic implications of burn severity
Authors: ROCHA ADRIAN V. , SHAVER GAIUS R.
Published: April 2011

Fires produce land cover changes that have consequences for surface energy balance and temperature. Three eddy covariance towers were setup along a burn severity gradient (i.e. Severely, Moderately, and Unburned tundra) to determine the effect of fire and burn severity on arctic tundra surface energy exchange and temperature for three growing seasons (2008–2010) following the 2007 Anaktuvuk River fire. The three sites were well matched before the fire, experienced similar weather, and had similar energy budget closure, indicating that the measured energy exchange differences between sites were largely attributable to burn severity. Increased burn severity resulted in decreased vegetation and moss cover, organic layer depth, and the rate of postfire vegetation recovery. Albedo and surface greenness steadily recovered with Moderately matching Unburned tundra by the third growing season. Decreased albedo increased net radiation and partly fueled increased latent and ground heat fluxes, soil temperatures, and thaw depth. Decreases in moss cover and the organic layer also influenced the ground thermal regime and increased latent heat fluxes. These changes either offset or decreased the surface warming effect from decreased albedo, resulting in a small surface warming in Severely and a small surface cooling in Moderately relative to Unburned tundra. These results indicate that fires have a significant impact on surface energy balance and highlight the importance of moss and permafrost thaw in regulating arctic surface energy exchange and temperature.
The effect of grazing management on plant species richness on the Qinghai‐Tibetan Plateau
Authors: Cao J. , Holden N. M. , Lü X‐T. , Du G.
Published: April 2011

In Maqu County, Gansu Province, China, there are two types of grazing management. Under multi‐household (MH) management, grassland is jointly managed by two or more households without fences between pastures. Under single‐household (SH) management, fenced‐off parcels of grassland are used. SH management was imposed in the belief that it would alleviate grassland degradation. Comparable land parcels with similar stocking rates subject to MH and SH management were identified and surveyed to determine the species present and species density (m−2). MH land had greater number values than SH but the differences were not significant. A further analysis indicated that the number of households using MH land influenced species richness. There was also evidence to suggest that the quality of the forage available deteriorated under SH management. It was concluded that MH grazing resulted in greater species richness than SH and is perhaps an important contributor to biodiversity conservation and grassland management for the region.