bluuebunny/crossref_metadata_2025 huggingface dataset:
Grain boundary‐modified dielectric spectra of electroceramics: the occurrence of ‘unexpected' thermal dielectric loss peaks
Authors: Antonelli Eduardo , M'Peko Jean‐Claude , Hernandes Antonio Carlos
Published: April 2007

Manifestation of dielectric/magnetic anomalies is often used to postulate or corroborate occurrence of structural phase transitions in both single‐crystal and polycrystalline materials. In the latter case, furthermore, some important aspects of grain‐boundary influence on the overall electrical response of materials have been more or less extensively characterized elsewhere. Nevertheless, the possible occurrence of ‘anomalous' thermal dielectric loss peaks, not associated with phase transitions or any other potential source, but still arising from grain boundary‐induced effects, has been less considered and explored. Here, BaZrO3 ceramics, commonly proposed to be attractive in the capacitor industry, are found to qualitatively and quantitatively help discussing and approaching this question by measuring, deeply treating and analyzing fixed‐frequency and frequency‐dependent impedance data. The overall work shows that grain boundary‐induced thermal dielectric peaks may occur, with temperature locations that may also be reasonably predicted. © 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim
Bound electron pairs on a triangular lattice in an extended Hubbard model
Authors: Bak M.
Published: April 2007

The properties of the bound states on a lattice is an interesting problem related to the properties of superconductivity and Bose–Einstein condensation in a given model. By means of the exact solution of the Schrödinger equation the properties of the bound pairs on a frustrated, triangular lattice are examined within extended Hubbard model. Dispersion curves and mobilities are calculated for both positive and negative sign of the hopping integral. The possibility of increasing the mobility with increasing intersite Coulomb interaction is found. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Field tunable spin/orbital correlations in Ca‐based ruthenates
Authors: Cuoco Mario , Forte Filomena , Noce Canio
Published: April 2007

We consider the field response of correlated t2g electrons within the layered Ca‐based ruthenates. Our analysis shows that, as a consequence of a fine interplay between the spin–orbit interaction and the octahedral distortions, the application of the field along different directions can bring to polarized configurations with inequivalent spin and orbital character. In particular, we underline how such behavior manifests at the boundary between an antiferromagnetic state with ferro‐type orbital correlations, and a ferromagnetic configuration with an antiferro‐type orbital character. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spin‐charge rotating local reference frames: a unified U(2) = U(1) ⊗ SU(2) approach to the interacting electrons
Authors: Kopeć T. K.
Published: April 2007

A spin‐charge unifying description for the Hubbard model based on the time dependent local gauge transformations is developed. The collective variables for charge and spin are isolated in the form of the space‐time fluctuating U(1) phase field and rotating spin quantization axis governed by the SU(2) symmetry, respectively. As a result interacting electrons appear as a composite objects consisting of bare fermions with attached U(1) and SU(2) gauge fields. We elaborate on the microscopic origins of the effective action with the Coulomb interaction that contain topological theta terms. Furthermore, we unravel the link between non‐trivial multiply‐connected topological structure of the U(2) = U(1) ⊗ SU(2) configurational space for gauge fields and the instanton contribution to the statistical sum. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improved electroluminescence on nonpolar m ‐plane InGaN/GaN quantum wells LEDs
Authors: Kim Kwang‐Choong , Schmidt Mathew C. , Sato Hitoshi , Wu Feng , Fellows Natalie , Saito Makoto , Fujito Kenji , Speck James S. , Nakamura Shuji , DenBaars Steven P.
Published: April 2007

Improved nonpolar m ‐plane $\bar 1$ light emitting diodes (LEDs) with a thick InGaN multi‐quantum‐well (MQW) structure have been fabricated on low extended defect bulk m ‐plane GaN substrates using metal organic chemical vapor deposition (MOCVD). The peak wavelength of the electroluminescence emission from the packaged LEDs was 402 nm, which is in the blue‐violet region. The output power and EQE were 28 mW and 45.4%, respectively, at a pulsed driving current of 20 mA. With increasing current, the output power increased linearly, and fairly flat EQE was observed with increasing drive current. At 200 mA, the power and EQE were 250 mW and 41%, respectively. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
H∞ filtering for a class of stochastic Markovian jump systems with impulsive effects
Authors: Dong Yuewu , Sun Jitao , Wu Qidi
Published: April 2007

In this paper, we discuss the problem of H∞ filtering for a class of stochastic Markovian jump systems with impulsive effects. The aim is to design a stochastically stable filter, using the locally sampled measurements, which guarantee both the stochastic stability and a prescribed level of H∞ performance for the filtering error dynamics. A sufficient condition for the existence of such a filter is given in terms of certain linear matrix inequalities (LMIs). When these LMIs are feasible, an explicit expression of a desired filter is obtained. A numerical example is provided to show the effectiveness of the proposed results. Copyright © 2007 John Wiley & Sons, Ltd.
An extended age period cohort model for analysing (age, period)‐tabulated data
Authors: Hanayama Nobutane
Published: April 2007

A model of an extended version of the age period cohort (APC) model is proposed for analysing (age, period)‐tabulated data on mortality of some chronic diseases. Estimable functions of the parameters in the proposed model for ML estimation are elucidated, and the result of fitting the proposed model to the data on breast cancer mortality for females in the U.S. is shown, where it is seen that the proposed model provides a better fit to the data than APC model in terms of AIC. Copyright © 2007 John Wiley & Sons, Ltd.
Blade load mitigation control design for a wind turbine operating in the path of vortices
Authors: Hand M. Maureen , Balas Mark J.
Published: April 2007

As wind turbine rotor size continues to increase, load mitigation becomes an important control objective. Turbines with hub heights of nearly 100m operate in the stable, nocturnal boundary layer where coherent turbulence can be generated by atmospheric phenomena outside the surface layer. These coherent turbulent structures may contribute to blade fatigue loads that can be mitigated with advanced control algorithms. Disturbance accommodating control (DAC) methods were implemented in a wind turbine structural dynamics simulation code to mitigate transient blade load response induced by a simple, Rankine vortex in the inflow. As a best‐case scenario, a full‐state feedback controller (which included a very detailed disturbance model) showed that blade flap damage equivalent load caused by the vortex passing through the rotor could be reduced by 30% compared to one that resulted from simulation of a typical proportional‐integral (PI) controller. A realizable DAC controller that incorporates only the vertical shear component of the vortex reduced loads by 9% compared to that resulting from simulation of a PI controller. The load reduction was even greater when the vortex was superimposed over full‐field, homogeneous turbulence. DAC methods have the flexibility to incorporate properties of coherent turbulent inflow structures in the controller design to mitigate blade fatigue loads. Further work must be done to develop disturbance models as more details about the turbulent structures are identified. Copyright © 2007 John Wiley & Sons, Ltd.
The use of a European coinage alloy to compare the detection limits of mobile XRF systems. A feasibility study
Authors: Cesareo R. , Ferretti M. , Gigante G. E. , Guida G. , Moioli P. , Ridolfi S. , Roldán Garcia C.
Published: April 2007

The investigation of archaeological and historical materials makes use of techniques that, though borrowed from other fields of research and industrial production, frequently have to be ‘re‐invented’ because of peculiar characteristics of the analysed objects. Artistic relevance, limited movability, compositional and structural heterogeneity radically change the experimental approach and often require ad hoc designed equipment. These considerations also apply to x‐ray fluorescence, especially regarding mobile systems. The extensive development and use of mobile spectrometers has produced an extremely diversified context and created the need for common criteria to evaluate their performances as well as the advisability of a survey on the existing equipment.

This paper shows the feasibility of such an idea through a demonstrative survey that was carried out among users of different mobile x‐ray fluorescence spectrometry (XRF) systems in the areas of Rome, Italy and Valencia, Spain. The experimental protocol was based on measuring spectrometer detection limits with the single standard method. The standard was the 50 eurocent coin, whose alloy is made of 89% Cu, 5% Al, 5% Zn, 1% Sn; the large spread of the European currency guarantees maximum availability. The experimental data show that the use of different x‐ray tubes and detectors results in detection limits that may differ from each other by a factor of 6 for Zn and almost 100 for Sn; despite the large number of variables that in principle affect the performance, it was observed that the high voltage of the x‐ray tube is the most important parameter. Copyright © 2007 John Wiley & Sons, Ltd.
Accurate efficiency calibration of a low‐energy HPGe detector using a monochromatic x‐ray source
Authors: Plagnard Johann , Bobin Christophe , Lépy Marie‐Christine
Published: April 2007

HPGe detector efficiency has been calibrated using complementary methods involving radioactive x‐ray standards, reference synchrotron flux (Super ACO, LURE, France) and a monochromatic x‐ray source (SOLEX), combined with Monte Carlo simulation. In the study described here, SOLEX was used to determine the thickness of detector components that create absorption sites in front of the active zone of the detector, by energy scanning in the vicinity of their K and L binding energies. The layers of aluminium (infrared shielding), nickel (electrical contact) and germanium (dead layer) have been measured. This approach ensures accurate determination of the thickness of each component and enables the detector efficiency calculation by Monte Carlo simulation. Differences between simulated data and experimental efficiency values are about 1–5% at energies above 1400 eV and reach 20% at lower energies. Copyright © 2007 John Wiley & Sons, Ltd.
Capital shocks, bank asset allocation, and the revised Basel Accord
Authors: Jacques Kevin T.
Published: April 2007

In contrast to the 1988 Basel Accord (Basel I), the revised risk‐based capital standards (Basel II) propose regulatory capital requirements based on credit ratings. This paper develops a theoretical model to analyze how banks will adjust their low and high credit risk commercial loans under the proposed newer standard. Capital‐constrained banks respond to an adverse capital shock by reducing high credit risk loans, while under certain circumstances, low credit risk loans may actually increase. When compared to Basel I, it is shown that high‐risk loans are reduced more under Basel II, but whether a bank reduces total lending more under Basel I or under the revised standards depends on a complex interaction of factors.
ON THE STRUCTURE OF GROUPS WITH POLYNOMIAL GROWTH II
Authors: LOSERT V.
Published: April 2007

The relation between compactly generated groups of polynomial growth and FC−-groups
is clarified. It follows that L1(G) is symmetric for G compactly
generated and of polynomial growth.
GEOMETRY OF CRITICAL LOCI
Authors: TRÁNG LÊ DŨNG , MAUGENDRE HÉLÈNE , WEBER CLAUDE
Published: April 2007

Let

(formula here)

be the germ of a finite (that is, proper with finite fibres) complex analytic morphism
from a complex analytic normal surface onto an open neighbourhood U of the origin
0 in the complex plane C2. Let u and v be coordinates of C2
defined on U. We shall call the triple (π, u, v) the initial data.

Let Δ stand for the discriminant locus of the germ π, that is, the image by π of the
critical locus Γ of π.

Let (Δα)α∈A be the branches of the discriminant locus
Δ at O which are not the coordinate axes.

For each α ∈ A, we define a rational number dα by

(formula here)

where I(–, –) denotes the intersection number at 0 of complex analytic curves in
C2. The set of rational numbers dα, for α ∈ A,
is a finite subset D of the set of rational numbers Q. We shall call D the set of
discriminantal ratios of the initial data (π, u, v).
The interesting situation is when one of the two coordinates (u, v) is tangent to some
branch of Δ, otherwise D = {1}. The definition of D depends not only on the choice
of the two coordinates, but also on their ordering.

In this paper we prove that the set D is a topological invariant of the initial data
(π, u, v) (in a sense that we shall define below) and we give several ways to compute
it. These results are first steps in the understanding of the geometry of the
discriminant locus. We shall also see the relation with the geometry of the critical
locus.
THE AVERAGE DENSITY OF SELF-CONFORMAL MEASURES
Authors: ZÄHLE M.
Published: April 2007

The paper calculates the average density of the normalized Hausdorff measure on the fractal set
generated by a conformal iterated function system. It equals almost everywhere a positive constant given
by a truncated generalized s-energy integral, where s is the corresponding Hausdorff dimension. As a
main tool a conditional Gibbs measure is determined. The appendix proves an appropriate extension of
Birkhoff's ergodic theorem which is also of independent interest.
SCHEMES OF TORI AND THE STRUCTURE OF TAME RESTRICTED LIE ALGEBRAS
Authors: FARNSTEINER ROLF , VOIGT DETLEF
Published: April 2007

Much of the recent progress in the representation theory of infinitesimal group
schemes rests on the application of algebro-geometric techniques related to the notion
of cohomological support varieties (cf. [6, 8–10]). The noncohomological characterization
of these varieties via the so-called rank varieties (see [21, 22]) involves
schemes of additive subgroups that are the infinitesimal counterparts of the
elementary abelian groups. In this note we introduce another geometric tool by
considering schemes of tori of restricted Lie algebras. Our interest in these derives
from the study of infinitesimal groups of tame representation type, whose
determination [12] necessitates the results to be presented in §4 and §5 as well as
techniques from abstract representation theory.

In contrast to the classical case of complex Lie algebras, the information on the
structure of a restricted Lie algebra that can be extracted from its root systems is
highly sensitive to the choice of the underlying maximal torus. Schemes of tori obviate
this defect by allowing us to study algebraic families of root spaces. Accordingly,
these schemes may also shed new light on various aspects of the structure theory of
restricted Lie algebras. We intend to pursue these questions in a forthcoming paper
[13], and focus here on first applications within representation theory.
A DUALITY FOR SPIN VERLINDE SPACES AND PRYM THETA FUNCTIONS
Authors: PAULY C. , RAMANAN S.
Published: April 2007

The paper proves canonical isomorphisms between Spin Verlinde spaces, that is, spaces of global
sections of a determinant line bundle over the moduli space of semistable Spinn-bundles over a smooth
projective curve C, and the dual spaces of theta functions over Prym varieties of unramified double covers
of C.
PROJECTIVE PRIME IDEALS AND LOCALISATION IN PI-RINGS
Authors: CHATTERS A. W. , HAJARNAVIS C. R. , LISSAMAN R. M.
Published: April 2007

The results here generalise [2, Proposition 4.3] and [9, Theorem 5.11]. We shall
prove the following.

THEOREM A. Let R be a Noetherian PI-ring. Let P be a non-idempotent prime
ideal of R such that PRis projective. Then P is left localisable and RPis a prime principal
left and right ideal ring.

We also have the following theorem.

THEOREM B. Let R be a Noetherian PI-ring. Let M be a non-idempotent maximal
ideal of R such that MRis projective. Then M has the left AR-property and M contains
a right regular element of R.
ON SECOND-ORDER ALMOST-PERIODIC ELLIPTIC OPERATORS
Authors: DUNGEY N. , TER ELST A. F. M. , ROBINSON DEREK W.
Published: April 2007

The paper considers second-order, strongly elliptic, operators H with complex almost-periodic
coefficients in divergence form on Rd. First,
it is proved that the corresponding heat kernel is Hölder
continuous and Gaussian bounds are derived with the correct small and large time asymptotic behaviour
on the kernel and its Hölder derivatives. Secondly, it is established that the kernel has a variety of
properties of almost-periodicity. Thirdly, it is demonstrated that the kernel of the homogenization Ĥ of
H is the leading term in the asymptotic expansion of t [map ] Kt.
FIXED POINT INDEX IN HYPERSPACES: A CONLEY-TYPE INDEX FOR DISCRETE SEMIDYNAMICAL SYSTEMS
Authors: RUIZ DEL PORTAL F. R. , SALAZAR J. M.
Published: April 2007

Let X be a locally compact metric absolute neighbourhood retract for metric spaces, U ⊂ X be an open

subset and f: U → X be a continuous map. The aim of the paper is to study the fixed point index of the

map that f induces in the hyperspace of X. For any compact isolated invariant set, K ⊂ U, this fixed point

index produces, in a very natural way, a Conley-type (integer valued) index for K. This index is computed

and it is shown that it only depends on what is called the attracting part of K. The index is used to obtain

a characterization of isolating neighbourhoods of compact invariant sets with non-empty attracting part.

This index also provides a characterization of compact isolated minimal sets that are attractors.
ASYMPTOTIC VALUES OF HYPERBOLIC MONOPOLES
Authors: NORBURY PAUL
Published: April 2007

It is shown that many hyperbolic monopoles can be distinguished from each other via their asymptotic
values in contrast to the case of Euclidean monopoles.
ISOTROPY REPRESENTATIONS, EIGENVALUES OF A CASIMIR ELEMENT, AND COMMUTATIVE LIE SUBALGEBRAS
Authors: PANYUSHEV DMITRI I.
Published: April 2007

Let [hfr ] be a reductive subalgebra of a semisimple Lie algebra [gfr ] and C[hfr ] ∈ U([hfr ]) be the Casimir element
determined by the restriction of the Killing form on [gfr ] to [hfr ]. The paper studies eigenvalues of C[hfr ] on the
isotropy representation [mfr ]≃[gfr ]/[hfr ]. Some general estimates connecting the eigenvalues and the Dynkin
indices of [mfr ] are given. If [hfr ] is a symmetric subalgebra, it is shown that describing the maximal eigenvalue
of C[hfr ] on exterior powers of [mfr ] is connected with possible dimensions of commutative Lie subalgebras in
[mfr ], thereby extending a result of Kostant. In this situation, a formula is also given for the maximal
eigenvalue of C[hfr ] on ∧ [mfr ]. More generally, a similar picture arises if [hfr ] = [gfr ]Θ, where Θ is an automorphism
of finite order m and [mfr ] is replaced by the eigenspace of Θ corresponding to a primitive mth root of unity.
The anti-schistosomal drug praziquantel is an adenosine antagonist
Authors: ANGELUCCI F. , BASSO A. , BELLELLI A. , BRUNORI M. , PICA MATTOCCIA L. , VALLE C.
Published: April 2007

The mechanism of action of praziquantel (PZQ), the drug of choice against schistosomiasis, is still unclear. Since exposure of schistosomes to the drug is associated with calcium influx and muscular contraction, calcium channels have been suggested as the target, although direct combination of PZQ with their subunits was never demonstrated. We report a hitherto unknown effect of PZQ, namely the inhibition of nucleoside uptake, as observed in living worms using radio-isotope labelled adenosine and uridine. This effect is clearly seen in schistosomes but is absent in mammalian cells in culture. Moreover it is a specific pharmacological effect seen exclusively with the active levo-R(−)stereo isomer of the drug, and is shared by at least one benzodiazepine having antischistosomal activity. This novel effect acquires significance given that schistosomes cannot synthesize purine nucleosidesde novo. A possible relationship between this novel effect and the known action of PZQ on calcium channels is discussed, since adenosine is known to bind to specific receptors and to behave as an indirect antagonist of calcium release in mammalian cells. If calcium channels were correlated with adenosine receptors also in schistosomes, as they are in mammals, this would support the hypothesis that PZQ-induced calcium influx may be correlated to adenosine receptor blockade.
Neuronal response to texture- and contrast-defined boundaries in early visual cortex
Authors: SONG YUNING , BAKER CURTIS L.
Published: April 2007

Natural scenes contain a variety of visual cues that facilitate boundary perception (e.g., luminance, contrast, and texture). Here we explore whether single neurons in early visual cortex can process both contrast and texture cues. We recorded neural responses in cat A18 to both illusory contours formed by abutting gratings (ICs, texture-defined) and contrast-modulated gratings (CMs, contrast-defined). We found that if a neuron responded to one of the two stimuli, it also responded to the other. These neurons signaled similar contour orientation, spatial frequency, and movement direction of the two stimuli. A given neuron also exhibited similar selectivity for spatial frequency of the fine, stationary grating components (carriers) of the stimuli. These results suggest that the cue-invariance of early cortical neurons extends to different kinds of texture or contrast cues, and might arise from a common nonlinear mechanism.
Evidence that L-AP5 and D,L-AP4 can preferentially block cone signals in the rat retina
Authors: GREEN DANIEL G. , KAPOUSTA-BRUNEAU NATALIA V.
Published: April 2007

Several lines of evidence suggest that, as concentrations of two agonists of group III metabotropic glutamate receptors are increased, cone contributions to the b-wave are blocked before rod contributions. Application of L-AP5 (L-2-amino-5-phosphonobutyric acid) at concentrations of 50 μM and D,L-AP4 (D,L-2-amino-4-phosphonobutyric acid) at concentrations 2 μM had a greater effect in reducing the amplitude of the rat ERG b-wave at high light intensities than at low light intensities. The amplitude reduction occurs at flash intensities that saturate rod photoreceptor responses. When steady backgrounds are used to saturate rod photoreceptors, the b-wave responses show increased long-wavelength sensitivity. Responses on a rod saturating background are blocked by adding L-AP5 or AP4 at the above concentrations to the perfusate. Further evidence for metabotrophic receptors being involved comes from the observation that even when ionotropic glutamate receptors are pharmacologically blocked with MK801 and DNQX, AP4 selectively blocks cone contributions to the b-wave. Thus we suggest that the type III metabotrophic receptors on depolarizing cone bipolar cells or cone synaptic terminals are affected by concentrations of L-AP5 and D,L-AP4 that have minimal effects on rod bipolar cells or rod synaptic terminals.
Influence of gravity waves on fog structure revealed by a millimeter‐wave scanning Doppler radar
Authors: Uematsu Akihisa , Hashiguchi Hiroyuki , Yamamoto Masayuki K. , Dhaka Surendra K. , Fukao Shoichiro
Published: April 2007

Multiscale band structure in fog influenced by gravity waves and Kelvin‐Helmholtz instability (KHI) is studied based on observations with a millimeter‐wave scanning Doppler radar on 1 August 2000 in Kushiro District, Hokkaido Prefecture, Japan. Band structure in fog having radar reflectivity >−20 dBZ and a scale of ∼1.5 km was observed around 50 m altitude. The band structure was also observed in Doppler velocity. The band structure in both radar reflectivity and Doppler velocity propagated northwestward with a speed of 4.17 m s−1. From linear gravity wave theory it is estimated that the observed gravity waves had a horizontal wavelength of 1.5 km and period of 6 min. The updraft induced by gravity waves is estimated to be 7.8 cm s−1. The increase in liquid water content (LWC) caused by the updraft is 0.035 g m−1, and the increase of radar reflectivity is 2 dBZ. Within the band structure induced by the gravity waves (horizontal scale ∼1.5 km), roll structure with a smaller horizontal scale (∼300–600 m) was also observed in radar reflectivity. A previous study has shown that this smaller‐scale roll structure is caused by shear‐induced KHI. This study shows that both gravity waves and KHI modulated the structure of fog and resulted in the existence of multiscale (1.5 km and 300–600 m scale) fog structure.
Altitude resolved sprite spectra with 3 ms temporal resolution
Authors: Kanmae T. , Stenbaek‐Nielsen H. C. , McHarg M. G.
Published: April 2007

Altitude resolved sprite spectra have been obtained with an imaging slit spectrograph with 3 ms temporal and ∼3 nm spectral resolution. Spectral coverage is from 640 to 820 nm. The slit was vertical to provide altitude resolution. The observed spectra are exclusively composed of emissions from the N2 first positive (1PG) bands. There are no obvious N2+ Meinel emissions, probably due to a combination of quenching and rapid motion of the streamer heads in which ionization is assumed to take place. The spectral analysis shows that the vibrational population in the upper state of the 1PG bands, N2 B 3Πg state, varies with altitude and is similar to that of laboratory afterglow at high pressure. This result suggests that secondary interactions among excited states created by electron impact may also play a role in exciting the B 3Πg state.
Implementation and evaluation of cloud analysis with WSR‐88D reflectivity data for GSI and WRF‐ARW
Authors: Hu Ming , Xue Ming
Published: April 2007

The cloud analysis procedure of the Advanced Regional Prediction System (ARPS) is implemented in a proposed operational numerical forecast system composed of the Grid‐point Statistical Interpolation (GSI) and the Advanced Research WRF (WRF‐ARW). The case of 23 May 2005 Central Plains storm cluster is used to assess the impact of the cloud analysis using reflectivity data from six operational WSR‐88D radars within the proposed operational configuration on 6‐h forecast of the storm cluster. The cloud analysis is shown to significantly reduce the spin‐up problem and improve the short‐range forecast for the storm cluster, even at the relatively coarse 9 km resolution.
A link between variability of the semidiurnal tide and planetary waves in the opposite hemisphere
Authors: Smith Anne K. , Pancheva Dora V. , Mitchell Nicholas J. , Marsh Daniel R. , Russell James M. , Mlynczak Martin G.
Published: April 2007

Horizontal wind observations over four years from the meteor radar at Esrange (68°N, 21°E) are analyzed to determine the variability of the semidiurnal tide. Simultaneous global observations of temperature and geopotential from the SABER satellite instrument are used to construct time series of planetary wave amplitudes and geostrophic mean zonal wind. During Northern Hemisphere summer and fall, the temporal variability of the semidiurnal tide at Esrange is found to be well correlated with the amplitude of planetary wavenumber 1 in the stratosphere in high southern latitudes (i.e. in the opposite hemisphere). The correlations indicate that a significant part of the tidal variation at Esrange is due to dynamical interactions in the Southern Hemisphere. A corresponding robust correlation pattern for the Esrange tides is not apparent at other times of the multiple years analyzed.
Timescales for radiation belt electron acceleration and loss due to resonant wave‐particle interactions: 2. Evaluation for VLF chorus, ELF hiss, and electromagnetic ion cyclotron waves
Authors: Summers Danny , Ni Binbin , Meredith Nigel P.
Published: April 2007

Outer zone radiation belt electrons can undergo gyroresonant interaction with various magnetospheric wave modes including whistler‐mode chorus outside the plasmasphere and both whistler‐mode hiss and electromagnetic ion cyclotron (EMIC) waves inside the plasmasphere. To evaluate timescales for electron momentum diffusion and pitch angle diffusion, we utilize bounce‐averaged quasi‐linear diffusion coefficients for field‐aligned waves with a Gaussian frequency spectrum in a dipole magnetic field. Timescales for momentum diffusion of MeV electrons due to VLF chorus can be less than a day in the outer radiation belt. Equatorial chorus waves (∣λW∣ < 15 deg) can effectively accelerate MeV electrons. Efficiency of the chorus acceleration mechanism is increased if high‐latitude waves (∣λW∣ > 15 deg) are also present. Our calculations confirm that chorus diffusion is a viable mechanism for generating relativistic (MeV) electrons in the outer zone during the recovery phase of a storm or during periods of prolonged substorm activity when chorus amplitudes are enhanced. Radiation belt electrons are subject to precipitation loss to the atmosphere due to resonant pitch angle scattering by plasma waves. The electron precipitation loss timescale due to scattering by each of the wave modes, chorus, hiss, and EMIC waves, can be 1 day or less. These wave modes can separately, or in combination, contribute significantly to the depletion of relativistic (MeV) electrons from the outer zone over the course of a magnetic storm. Efficient pitch angle scattering by whistler‐mode chorus or hiss typically requires high latitude waves (∣λW∣ > 30 deg). Timescales for electron acceleration and loss generally depend on the spectral properties of the waves, as well as the background electron number density and magnetic field. Loss timescales due to EMIC wave scattering also depend on the ion (H+, He+, O+) composition of the plasma. Complete models of radiation belt electron transport, acceleration and loss should include, in addition to radial (cross‐L) diffusion, resonant diffusion due to gyroresonance with VLF chorus, plasmaspheric hiss, and EMIC waves. Comprehensive observational data on the spectral properties of these waves are required as a function of spatial location (L, MLT, MLAT) and magnetic activity.
Remote sensing of upper canopy leaf area index and forest floor vegetation cover as indicators of net primary productivity in a Siberian larch forest
Authors: Kushida Keiji , Isaev Alexander P. , Maximov Trofim C. , Takao Gen , Fukuda Masami
Published: April 2007

In this study, we demonstrated that the leaf area index (LAI) and forest floor vegetation cover (FVC) are indicators of net primary productivity (NPP) in Siberian larch forest by considering forest biometric and CO2 budget parameters. Further, we estimated the distributions of these indicators and the corresponding NPP using Landsat ETM+ imagery. This estimation was based on the spectral measurements of larch leaves and the forest floor and on radiative transfer modeling studies. The results revealed that the estimated and observed values of larch LAI and FVC were similar; however, the estimated NPP (222 ± 24 gC m−2 yr−1) was greater than that obtained from observations from meteorological towers and soil heterotrophic respiration values (130–180 gC m−2 yr−1) at the study site. We present the geographical distributions of larch LAI, FVC, and annual NPP that are associated with the components of the CO2 budget and spectral parameters, which will be used to conduct intercomparison studies in the future.
What is the role of non-invasive measurements of atherosclerosis in individual cardiovascular risk prediction?
Authors: ter Avest Ewoud , Stalenhoef Anton F. H. , de Graaf Jacqueline
Published: April 2007

Primary prevention of CVD (cardiovascular disease) is mainly based on the assessment of individual cardiovascular risk factors. However, often, only the most important (conventional) cardiovascular risk factors are determined, and every level of risk factor exposure is associated with a substantial variation in the amount of atherosclerosis. Measuring the effect of risk factor exposure over time directly in the vessel might (partially) overcome these shortcomings. Several non-invasive imaging techniques have the potential to accomplish this, each of these techniques focusing on a different stage of the atherosclerotic process. In this review, we aim to define the current role of various of these non-invasive measurements of atherosclerosis in individual cardiovascular risk prediction, taking into account the most recent insights about validity and reproducibility of these techniques and the results of recent prospective outcome trials. We conclude that, although the clinical application of FMD (flow-mediated dilation) and PWA (pulse wave analysis) in individual cardiovascular risk prediction seems far away, there may be a role for PWV (pulse wave velocity) and IMT (intima-media thickness) measurements in the near future.
Presence of tumour inhibits the normal post-operative response in arginine and NO production in non-cachectic mice
Authors: Vissers Yvonne L. J. , von Meyenfeldt Maarten F. , Luiking Yvette C. , Dejong Cornelis H. C. , Buurman Wim A. , Deutz Nicolaas E. P.
Published: April 2007

We have described recently that cancer patients have low plasma arginine concentrations, even without weight loss being present, suggesting that decreased arginine availability may be a specific feature of the presence of tumour. As arginine is important in post-operative repair, we hypothesized that abnormalities in arginine metabolism in cancer lead to an aberrant post-operative response in arginine and NO metabolism. To investigate this, we studied post-operative alterations in arginine and NO production and the acute-phase response in MCA (methylcholanthrene) sarcoma-bearing mice. Controls, mice with small MCA tumours (<15% of carcass weight) and large MCA tumours (>15% of carcass weight) were studied, either with or without undergoing laparotomy. The stable isotopes L-[guanidino-15N2-2H2]arginine and L-[ureido-15N]citrulline were used to study whole-body arginine and NO production rates. SAP (serum amyloid P component) concentrations were measured to assess the acute-phase response. Significance was tested using Mann–Whitney U test. In healthy FVB mice, laparotomy significantly increased whole-body arginine production (from 42±3 to 54±3 nmol·10 g−1 of carcass weight·min−1), NO production (from 1.1±0.1 to 1.4±0.2 nmol·10 g−1 of carcass weight·min−1) and levels of SAP (from 4±1 to 115±23 ng/ml), whereas in all MCA tumour-bearing mice baseline values of arginine metabolism and SAP concentration were already elevated and the response to laparotomy was absent. In conclusion, MCA tumour-bearing mice had a disturbed post-operative metabolic response, as evidenced by attenuated post-operative arginine and NO production, concomitant with an attenuated acute-phase response. This indicates that altered arginine metabolism may be an important characteristic of the metabolic changes in cancer.
Rechnergestützte, weniger invasive Verfahren bei Osteosynthesen am Becken*
Authors: Grützner Paul Alfred , Franke Jochen , Vock Bernd , Wentzensen Andreas
Published: April 2007

Durch die dreidimensionale Bildgebung mit einem speziellen Bildverstärker lässt sich im Bereich der anatomisch komplexen Region des Beckens eine verbesserte intraoperative Kontrolle des Repositionsergebnisses und der Qualität der Osteosynthese erzielen. Dies ist eine wesentliche Voraussetzung, auch bei reduzierter Invasivität ohne direkte Darstellung der Fraktur die Qualität der Versorgung zu gewährleisten. In Kombination mit der registrierungsfreien Navigation können die Abläufe optimiert werden und versprechen einen weiteren Gewinn an Sicherheit und Qualität bei der Versorgung von Verletzungen am Becken.
Navigationssystem und Bildgebung, Setup, Wartung und Bedienung
Authors: Grützner Paul Alfred , Wentzensen Andreas
Published: April 2007

Die Bedeutung der computerassistierten Chirurgie wird in den nächsten Jahren noch zunehmen. Schon jetzt haben die intraoperative Navigation, die präoperative Planung und die intraoperative 3D-Bildgebung ihr Potenzial zur Erhöhung der Sicherheit und Präzision bei der Ausführung von chirurgischen Eingriffen bewiesen. Die Eingriffe in den Operationsablauf sind jedoch erheblich. Dies setzt hohe Anforderungen an die Schulung des Personals, aber auch an die Weiterentwicklung der Systeme in Richtung verbesserte intraoperative Ergonomie. Gerade in diese Richtung sollten zukünftige Entwicklungen vorangetrieben werden und nicht nur in die reine Machbarkeit von Vorgehensweisen. Die Navigation wird in Zukunft auch einen deutlichen Stellenwert in der Aus- und Weiterbildung von Chirurgen erlangen. Diese Verfahren sind längst nicht mehr schöne Spielereien für Computerfreaks, sondern gehören in vielen Operationssälen bereits zur Standardausrüstung, wie Bildverstärker und Endoskopieturm.
Topological and energetic aspects of the random-field Ising model
Authors: Bertotti G. , Bortolotti P. , Magni A. , Basso V.
Published: April 2007

We show that random-field Ising model spin states are organized in equivalence classes (basins), each class containing the states that can be mutually reached from one another by some field history. Of these basins, only one contains the field-reachable states which can be generated by applying a suitable field history to one of the saturation states. We show that the basins form an oriented graph of which the basin of field-reachable states represents the bottom. The graph exhibits a hierarchical structure which reflects the organization in real space of the spin blocks that can be reversed back and forth by the field in some appropriate field interval without affecting the state of surrounding spins.
Field cooling induced perpendicular exchange bias in FeMn∕(FeNi∕FeMn)n multilayers
Authors: Xing H. , Keshoju K. , Zhou S. M. , Sun L.
Published: April 2007

Based on two-dimensional magnetization vector measurements, it is confirmed that perpendicular exchange bias can be established in conventional ferromagnetic/antiferromagnetic multilayers when the samples are field-cooled along the surface normal direction. Here we report on the experimental observations from a systematic study of the perpendicular exchange bias in FeMn∕(FeNi∕FeMn)15 multilayers and the comparison with corresponding longitudinal field cooling results. For the two field cooling geometries, both the exchange field and the coercive field exhibit similar constituent layer thickness and temperature dependences when measuring along the cooling field direction. These observations indicate the same interfacial nature of the induced anisotropy for both perpendicular and longitudinal exchange biases. The establishment of perpendicular exchange bias and anisotropy through field cooling can have potential applications in perpendicular magnetic recording media development.
Uncompensated antiferromagnetic spins at the interface in Mn–Ir based exchange biased bilayers
Authors: Tsunoda M. , Yoshitaki S. , Ashizawa Y. , Mitsumata C. , Nakamura T. , Osawa H. , Hirono T. , Kim D. Y. , Takahashi M.
Published: April 2007

The microscopic origin of the uncompensated antiferromagnetic (AFM) spins was investigated by means of the x-ray magnetic circular dichroism (XMCD) spectroscopy with transmission mode for Mn–Ir/ferromagnetic (FM) bilayers. As the AFM layer thickness increases, resonant absorption magnitude of Mn L edge naturally increases, but the XMCD magnitude does not change so much. When the FM layer material is modified, the XMCD signal of Mn L edge drastically changes not only in its magnitude but also in its sign. The XMCD signal vanishes without the FM layer. These facts clearly mean that the uncompensated Mn components are induced through the exchange interaction between the FM and the AFM layers and are localized at the very interface. Micromagnetic simulation within the framework of the classical Heisenberg model well supported the above conclusion.
Model of grain charging in collisional plasmas accounting for collisionless layer
Authors: D’yachkov L. G. , Khrapak A. G. , Khrapak S. A. , Morfill G. E.
Published: April 2007

Grain charging in collision dominated plasmas is investigated. The transition from a thin collisionless region around the grain, ℓi(e)≪a, to a thick one, ℓi(e)≫a, is studied under the assumptions ℓi(e)≪λD and a≪λD, where ℓi(e) is the ion (electron) mean free path, a is the grain radius, and λD is the plasma screening length. It is also assumed that no ionization and recombination occur in the vicinity of the grain. With these assumptions, the analytical model of grain charging is constructed, the expressions for the ion and electron fluxes to the grain surface are derived, and the grain charge is obtained from their balance. The analytical results are then compared with the available experimental results. The behavior of ion and electron number densities in the vicinity of the grain is briefly discussed.
Structure and electrical properties of K0.5Na0.5NbO3–LiSbO3 lead-free piezoelectric ceramics
Authors: Lin Dunmin , Kwok K. W. , Lam K. H. , Chan H. L. W.
Published: April 2007

Lead-free piezoelectric ceramics (1−x)K0.5Na0.5NbO3–xLiSbO3 have been fabricated by a conventional ceramic sintering technique. The results of x-ray diffraction suggest that Li+ and Sb5+ diffuse into the K0.5Na0.5NbO3 lattices to form a solid solution with a perovskite structure. The ceramics can be well sintered at 1070–1110°C. The introduction of LiSbO3 into the Na0.5K0.5NbO3 solid solution decreases slightly the paraelectric cubic-ferroelectric tetragonal phase transition temperature (Tc), but greatly shifts the ferroelectric tetragonal-ferroelectric orthorhombic phase transition (TO–F) to room temperature. Coexistence of the orthorhombic and tetragonal phases is formed at 0.05<x<0.07 at room temperature, leading to a significant enhancement of the piezoelectric properties. For the ceramic with x=0.06, the piezoelectric properties become optimum: piezoelectric constant d33=212pC∕N, planar and thickness electromechanical coupling factors kP=46% and kt=47%, respectively, remanent polarization Pr=15.0μC∕cm2, coercive field Ec=1.74kV∕mm, and Curie temperature TC=358°C.
Density functional theory fragment descriptors to quantify the reactivity of a molecular family: Application to amino acids
Authors: Senet P. , Aparicio F.
Published: April 2007

By using the exact density functional theory, one demonstrates that the value of the local electronic softness of a molecular fragment is directly related to the polarization charge (Coulomb hole) induced by a test electron removed (or added) from (at) the fragment. Our finding generalizes to a chemical group a formal relation between these molecular descriptors recently obtained for an atom in a molecule using an approximate atomistic model [P. Senet and M. Yang, J. Chem. Sci. 117, 411 (2005)]. In addition, a practical ab initio computational scheme of the Coulomb hole and related local descriptors of reactivity of a molecular family having in common a similar fragment is presented. As a blind test, the method is applied to the lateral chains of the 20 isolated amino acids. One demonstrates that the local softness of the lateral chain is a quantitative measure of the similarity of the amino acids. It predicts the separation of amino acids in different biochemical groups (aliphatic, basic, acidic, sulfur contained, and aromatic). The present approach may find applications in quantitative structure activity relationship methodology.
Boundary-integral method for drop deformation between parallel plates
Authors: Janssen P. J. A. , Anderson P. D.
Published: April 2007

A new boundary-integral method is proposed to study the deformation of drops between two parallel walls. The free-space Green’s functions are extended to obey the no-slip condition at the walls. The current formulation is limited to drops with viscosity equal to the matrix fluid, but can be extended to study the effect of nonunit viscosity ratio systems. With this method, the influence of the capillary number and the degree of confinement on drop deformation is investigated. Results for small capillary are compared with small-deformation theory and large capillary results with recent experiments. In both cases, an excellent match is observed. Drops undergoing shear flow deform stronger and align themselves more in the flow direction as the distance between the walls becomes smaller relative to the drop size. Furthermore, the shapes of the drops start to divert significantly from the normal ellipsoidal shapes found, as they show more pointed tips closer to the walls. The transient deformation behavior for more confined systems shows that the drops stretch out to a maximum value, and they slowly retract again to a steady situation. For larger capillary numbers even damped, oscillatory behavior is observed. Investigating the critical capillary number reveals that a minimum is found at a mediocre degree of confinement, after which the critical capillary number increases again to values even larger than the unconfined system. The breakup mode also makes a significant change as it goes from binary to ternary breakup, where the breakup occurs as the drop is retracting.
Tikekar superdense stars in electric fields
Authors: Komathiraj K. , Maharaj S. D.
Published: April 2007

We present exact solutions to the Einstein-Maxwell system of equations with a specified form of the electric field intensity by assuming that the hypersurface {t=constant} are spheroidal. The solution of the Einstein-Maxwell system is reduced to a recurrence relation with variable rational coefficients which can be solved in general using mathematical induction. New classes of solutions of linearly independent functions are obtained by restricting the spheroidal parameter K and the electric field intensity parameter α. Consequently, it is possible to find exact solutions in terms of elementary functions, namely, polynomials and algebraic functions. Our result contains models found previously including the superdense Tikekar neutron star model [J. Math. Phys. 31, 2454 (1990)] when K=−7 and α=0. Our class of charged spheroidal models generalize the uncharged isotropic Maharaj and Leach solutions [J. Math. Phys. 37, 430 (1996)]. In particular, we find an explicit relationship directly relating the spheroidal parameter K to the electromagnetic field.
Strain-induced splitting of the valence band in epitaxially lifted-off GaAs films
Authors: Mateo Cherry May N. , Garcia Alipio T. , Ramos Flo Rykiel M. , Manibog Kristine I. , Salvador Arnel A.
Published: April 2007

We report a detailed study on the valence band splitting in epitaxial lift-off (ELO) GaAs film bonded to silicon. The GaAs film used in this study was grown by molecular beam epitaxy on epiready GaAs (100) substrate. Variable temperature photoluminescence and reflectivity spectra were obtained for the as-grown film, the freestanding ELO film, and the ELO GaAs film bonded to silicon. The PL spectra for the GaAs film on Si showed the removal of the valence band degeneracy with the light hole and heavy hole transitions separated by 4.2meV at 10K and decreased monotonously to 1.6meV at 230K. No similar splitting was observed for the as-grown and freestanding films. The strain and stress were calculated at ε=(1.2±0.04)×10−3 and X=0.8±0.05kbar, respectively, at 10K and ε=(2.3±0.04)×10−4 and X=0.3±0.05kbar at 230K. The temperature dependence of the heavy hole–light hole separation energy indicated a strain-induced effect caused by the difference in the coefficient of thermal expansion between GaAs and Si. This shows the efficiency of using ELO techniques on dissimilar materials for strain related spectroscopy.