bluuebunny/crossref_metadata_2025 huggingface dataset:
Asymptotic decay to relaxation shock fronts in two dimensions
Authors: Liu Hailiang
Published: July 2007

We prove nonlinear stability of planar shock fronts for certain relaxation systems in two spatial dimensions. If the subcharacteristic condition is assumed and the initial perturbation is sufficiently small and the mass carried by the perturbations is not necessarily finite, then the solution converges to a shifted planar shock front solution as time t ↑ ∞. The asymptotic phase shift of shock fronts is, in general, non-zero and governed by a similarity solution to the heat equation. The asymptotic decay rate to the shock front is proved to be t−1/4 in L∞(R2) without imposing extra decay rates in space for the initial perturbations. The proofs are based on an elementary weighted energy analysis to the error equation.
Uniqueness and critical spectrum of boundary spike solutions
Authors: Wei Juncheng
Published: July 2007

We study the properties of single boundary spike solutions for the following singularly perturbed problem

It is known that at a non-degenerate critical point of the mean curvature function H(P), there exists a single boundary spike solution. In this paper, we show that the single boundary spike solution is unique and moreover it has exactly (N − 1) small eigenvalues. We obtain the exact asymptotics of the small eigenvalues in terms of H(P).
Some results for semilinear elliptic equations with critical potential
Authors: Abdellaoui B. , Peral I.
Published: July 2007

This paper is devoted to the study of the elliptic problems with a critical potential,

where N ≥ 3, λ ≥ 0 and 0 < q < 1 < p ≤ (N + 2)/(N − 2). Existence, multiplicity, behaviour in x = 0 and bifurcation are considered under some hypotheses in h and g.
Explicit Wiener–Hopf factorization and nonlinear Riemann–Hilbert problems
Authors: Câmara M. C. , dos Santos A. F. , Carpentier M. P.
Published: July 2007

A method for explicit Wiener–Hopf factorization of 2 × 2 matrix-valued functions is presented together with an abstract definition of a class of functions, C(Q1, Q2), to which it applies. The method involves the reduction of the original factorization problem to certain nonlinear scalar Riemann–Hilbert problems, which are easier to solve. The class C(Q1, Q2) contains a wide range of classes dealt with in the literature, including the well-known Daniele–Khrapkov class. The structure of the factors in the factorization of any element of the class C(Q1, Q2) is studied and a relation between the two columns of the factors, which gives one of the columns in terms of the other through a linear transformation, is established. This greatly simplifies the complete determination of the factors and gives relevant information on the nature of the factorization. Two examples suggested by applications are completely worked out.
Sharp estimates for iterated Green functions
Authors: Grunau H.-Ch. , Sweers G.
Published: July 2007

Optimal pointwise estimates from above and below are obtained for iterated (poly)harmonic Green functions corresponding to zero Dirichlet boundary conditions. For second-order elliptic operators, these estimates hold true on bounded C1,1 domains. For higher-order elliptic operators we have to restrict ourselves to the polyharmonic operator on balls. We will also consider applications to non-cooperatively coupled elliptic systems and to the lifetime of conditioned Brownian motion.
On Korn's first inequality with non-constant coefficients
Authors: Neff Patrizio
Published: July 2007

In this paper we prove a Korn-type inequality with non-constant coefficients which arises from applications in elasto-plasticity at large deformations. More precisely, let Ω ⊂ R3 be a bounded Lipschitz domain and let Γ ⊂ ∂Ω be a smooth part of the boundary with non-vanishing two-dimensional Lebesgue measure. Define and let be given with det Fp(x) ≥ μ+ > 0. Moreover, suppose that Rot . Then Clearly, this result generalizes the classical Korn's first inequality

which is just our result with Fp = 11. With slight modifications, we are also able to treat forms of the type
Relaxation of rate-independent evolution problems
Authors: Theil Florian
Published: July 2007

The relaxation of certain time-evolution problems is investigated. As a conceptually simple example, we study elastically deformable bodies that undergo martensitic phase transformations. The movement of the phase boundaries is hindered by dry friction. The fundamental problem is that the phase distribution forms a highly oscillatory microstructure in space. Therefore, it is desirable to derive a coarse-grained system that describes the effective properties. We introduce a concept of relaxation of the evolution system and apply it to the case where only two phases occur and the elastic energy is quadratic. Finally, we present a candidate for the relaxation in the general case.
Adjacency preserving maps on matrices and operators
Authors: Petek Tatjana , Šemrl Peter
Published: July 2007

We characterize injective continuous maps on the space of real or complex rectangular matrices preserving adjacent pairs of matrices. We also extend Hua's fundamental theorem of the geometry of rectangular matrices to the infinite-dimensional case. An application in the theory of local automorphisms is presented.
A priori estimates for solutions to elliptic equations on non-smooth domains
Authors: Daners Daniel
Published: July 2007

It is proved that elliptic boundary-value problems have a global smoothing property in Lebesgue spaces, provided the underlying space of weak solutions admits a Sobolev-type inequality. The results apply to all standard boundary conditions, and a wide range of non-smooth domains, even if the classical estimates fail. The dependence on the data is explicit. In particular, this provides good control over the domain dependence, which is important for applications involving varying domains.
Large-time behaviour of solutions of Burgers' equation
Authors: Dix Daniel B.
Published: July 2007

The large-time asymptotic behaviour of real-valued solutions of the pure initial-value problem for Burgers' equation ut + uuxuxx = 0, is studied. The initial data satisfy u0(x) ~ nx as |x| , where n R. There are two constants of the motion that affect the large-time behaviour:

Hopf considered the case n = 0 (i.e. u0L1(R)), and the case

sufficiently small was considered by Dix. Here we completely remove that smallness condition. When n < 1, we find an explicit function U(), depending only on and n, such that

uniformly in . When n 1, there are two different functions U() that simultaneously attract the quantity t12u(t12, t), and each one wins in its own range of . Thus we give an asymptotic description of the solution in different regions and compute its decay rate in L. Sharp error estimates are proved.
A construction of infinitely many singular weak solutions to the equations of nonlinear elasticity
Authors: Sivaloganathan J. , Spector S. J.
Published: July 2007

Radial deformations of a ball composed of a nonlinear elastic material and corresponding to cavitation have been much studied. In this paper we use rescalings to show that each such deformation can be used to construct infinitely many non-symmetric singular weak solutions of the equations of nonlinear elasticity for the same displacement boundary-value problem. Surprisingly, this property appears to have been unnoticed in the literature to date.
Generic types and transitions in hyperbolic initial–boundary-value problems
Authors: Benzoni-Gavage Sylvie , Rousset Frédéric , Serre Denis , Zumbrun K.
Published: July 2007

The stability of linear initial–boundary-value problems for hyperbolic systems (with constant coefficients) is linked to the zeros of the so-called Lopatinskii determinant. Depending on the location of these zeros, problems may be either unstable, strongly stable or weakly stable. The first two classes are known to be ‘open’, in the sense that the instability or the strong stability persists under a small change of coefficients in the differential operator and/or in the boundary condition.

Here we show that a third open class exists, which we call ‘weakly stable of real type’. Many examples of physical or mathematical interest depend on one or more parameters, and the determination of the stability class as a function of these parameters usually needs an involved computation. We simplify it by characterizing the transitions from one open class to another one. These boundaries are easier to determine since they must solve some overdetermined algebraic system.

Applications to the wave equation, linear elasticity, shock waves and phase boundaries in fluid mechanics are given.
Quasilinear diffusion problems with singular coefficients with respect to the unknown
Authors: Blanchard Dominique , Redwane Hicham
Published: July 2007

We study a class of quasilinear elliptic problems with diffusion matrices that have at least one diagonal coefficient that blows up for a finite value of the unknown; the other coefficients being continuous with respect to the unknown (without any growth assumption). We introduce two equivalent notions of solutions for such problems and we prove an existence result in these frameworks. Under additional local assumptions on the coefficients, we also establish the uniqueness of the solution. In that case, and when the non-diagonal coefficients are bounded, this unique (generalized) solution is also the unique weak solution strictly less than the value where the diagonal coefficient blows up.
Totally multiplicatively prime algebras
Authors: Cabrera M. , Mohammed Amir A.
Published: July 2007

We introduce the totally multiplicatively prime algebras as those normed algebras for which there exists a positive number K such that K‖F‖‖a‖ ≤ ‖WF,a‖ for all F in M(A) (the multiplication algebra of A) and a in A, where WF,a denotes the operator from M(A) into A defined by WF,a(T) = FT(a) for all T in M(A). These algebras are totally prime and their multiplication algebra is ultraprime. We get the stability of the class of totally multiplicatively prime algebras by taking central closure. We prove that prime H*-algebras are totally multiplicatively prime and that the ℓ1-norm is the only classical norm on the free non-associative algebras for which these are totally multiplicatively prime.
From the discrete to the continuous coagulation–fragmentation equations
Authors: Laurençot Philippe , Mischler Stéphane
Published: July 2007

The connection between the discrete and the continuous coagulation–fragmentation models is investigated. A weak stability principle relying on a priori estimates and weak compactness in L1 is developed for the continuous model. We approximate the continuous model by a sequence of discrete models and, writing the discrete models as modified continuous ones, we prove the convergence of the latter towards the former with the help of the above-mentioned stability principle. Another application of this stability principle is the convergence of an explicit time and size discretization of the continuous coagulation-fragmentation model.
On a class of two-dimensional singular elliptic problems
Authors: Caldiroli Paolo , Musina Roberta
Published: July 2007

We consider Dirichlet problems of the form −|x|αΔu = λu + g(u) in Ω, u = 0 on ∂Ω, where α, λ ∈ ℝ, g ∈ C(ℝ) is a superlinear and subcritical function, and Ω is a domain in ℝ2. We study the existence of positive solutions with respect to the values of the parameters α and λ, and according that 0 ∈ Ω or 0 ∈ ∂Ω, and that Ω is an exterior domain or not.
Global structure of solutions for equations of Brezis-Nirenberg type on the unit ball
Authors: Kabeya Yoshitsugu , Yanagida Eiji , Yotsutani Shoji
Published: July 2007

The Brezis-Nirenberg equation and the scalar field equation on the three-dimensional unit ball are studied. Under the Robin condition, we show the existence and uniqueness of radial solutions in a unified way. In particular, it is shown that the global structure of solutions changes qualitatively when a parameter in the boundary condition exceeds a certain critical value.
Imbeddings of Brezis-Wainger type. The case of missing derivatives
Authors: Krbec M. , Schmeisser Hans-Jürgen
Published: July 2007

We prove limiting imbeddings of spaces with dominating mixed derivatives into the spaces of almost Lipschitz continuous functions.
Welcoming Address
Authors: Harmanec Petr
Published: July 2007

It is great privilege for me to welcome so many of you to Prague, or Praha as we call our capital in Czech.

We have been witnessing a very rapid development of observational techniques over the past few decades, leading to many exciting discoveries, quite often in the field of extragalactic research. I sometimes sense the tendency to consider the studies of binaries and stars in general as exhausted topics. However, we all know that the better our real and deep understanding of the principal sources of radiative energy in the Universe becomes, the safer will be the ground for studies of all higher hierarchical systems.
Charles Edmund Worley (1935–1997)
Authors: Mason Brian D. , Hartkopf William I. , Corbin Thomas E. , Douglass Geoffrey G.
Published: July 2007

In keeping with its co-sponsorship by members of both the “close” and “wide” binary star communities, IAU Symposium 240 has been jointly dedicated to the honor of Czech astronomer Mirek J. Plavec and the memory of U.S. astronomer Charles E. Worley.

Charles Worley, long-time astronomer at the U.S. Naval Observatory, was born on May 22, 1935, in Iowa City, Iowa, and grew up in Des Moines the son of an M.D., Charles L. Worley, and his wife Iona Cooney Worley, a homemaker. He became interested in astronomy at age nine. His first observational work as an amateur astronomer was plotting and recording more than 10,000 meteors for the American Meteor Society. Continuing his love for astronomy he attended Swarthmore College, where he took part in the parallax program as an Observing Assistant. He also met the other love of his life, his wife, Jane Piper. They were married in 1956 next to Sproul Observatory on the Swarthmore campus. He obtained a B.A. in mathematics from San Jose State College in 1959. He worked for the Lick Observatory in California (1959–1961) as a Senior Assistant and Research Astronomer under a Naval Research grant to observe double stars. After arriving at the U.S. Naval Observatory in 1961, he was the motive force behind an extensive program of double star observation (being himself, a prolific observer), instrumental innovation, and double star cataloging. He quickly gained recognition as one of the world's leading experts in the field of double star astronomy. Charles died on New Year's Eve, 1997, two days before his scheduled retirement.
Analysis of the Eclipsing Binaries in the LMC Discovered by OGLE: Period Distribution and Frequency of the Short–Period Binaries
Authors: Mazeh Tsevi , Tamuz Omer , North Pierre
Published: July 2007

We review the results of our analysis of the OGLE LMC eclipsing binaries (Mazeh, Tamuz & North 2006), using EBAS — Eclipsing Binary Automated Solver, an automated algorithm to fit lightcurves of eclipsing binaries (Tamuz, Mazeh & North 2006). After being corrected for observational selection effects, the set of detected eclipsing binaries yielded the period distribution and the frequency of all LMC short-period binaries, and not just the eclipsing systems. Somewhat surprisingly, the period distribution is consistent with a flat distribution in logP between 2 and 10 days. The total number of binaries with periods shorter than 10 days in the LMC was estimated to be about 5000. This figure led us to suggest that (0.7± 0.4)% of the main-sequence A- and B-type stars are found in binaries with periods shorter than 10 days. This frequency is substantially smaller than the fraction of binaries found by smaller radial-velocity surveys of Galactic B stars.
A Survey of Stellar Families: Multiplicity Among Solar-type Stars
Authors: Raghavan Deepak , McAlister H. A. , Henry T. J. , Mason B. D.
Published: July 2007

Stellar multiplicity is a fundamental astrophysical property. In addition to being the only physical basis for accurate mass determination, this parameter is believed to influence important aspects such as planet formation and stability. Contrary to earlier expectations, recent studies have shown that even against selection biases, as many as 23% of the planetary systems reside in multiple star systems (Raghavan et al. 2006)). Leveraging recent efforts in identifying stellar and substellar companions to solar-type stars, and augmenting them with targeted observations, we are conducting a comprehensive survey, aimed at providing a modern update to the seminal work of Duquennoy & Mayor (1991). The details of our sample, survey methods, and some preliminary results are presented here.
Close Binaries in the CoRoT Space Experiment
Authors: Maceroni Carla , Ribas Ignasi
Published: July 2007

We discuss the impact that the space experiment CoRoT, whose launch is scheduled for late 2006, will have on the field of close binary.
Interferometric Constraints on Gravity Darkening with Application to the Modeling of Spica A & B
Authors: Aufdenberg J.P. , Ireland M. J. , Mérand A. , du Foresto V. Coudé , Absil O. , Folco E. Di , Kervella P. , Bagnuolo W. G. , Gies D. R. , Ridgway S. T. , Berger D. H. , ten Brummelaar T. A. , McAlister H. A. , Sturmann J. , Sturmann L. , Turner N. H. , Jacob A. P.
Published: July 2007

In 2005 we obtained very precise interferometric measurements of the pole-on rapid rotator Vega (A0 V) with the longest baselines of the Center for High Angular Angular Resolution (CHARA) Array and the Fiber Linked Unit for Optical Recombination (FLUOR). For the analysis of these data, we developed a code for mapping sophisticated PHOENIX model atmospheres on to the surface of rotationally distorted stars described by a Roche-von Zeipel formalism. Given a set of input parameters for a star or binary pair, this code predicts the interferometric visibility, spectral energy distribution and high-resolution line spectrum expected for the system. For the gravity-darkened Vega, our model provides a very good match to theK-band interferometric data, a good match to the spectral energy distribution – except below 160 nm – and a rather poor match to weak lines in the high dispersion spectrum where the model appears overly gravity darkened. In 2006, we used the CHARA Array and FLUOR to obtain high precision measurements of the massive, non-eclipsing, double-line spectroscopic binary Spica, a 4-day period system where both components are gravity darkened rapid rotators. These data supplement recent data obtained with the Sydney University Stellar Interferometer (SUSI). Our study follows the classic 1971 study by Herbison-Evanset al. who resolved Spica as a binary with the Narrabri Stellar Intensity Interferometer (NSII). We will report on our progress modeling the new interferometric and archival spectroscopic data, with the goal towards better constraining the apsidal constant.
The Formation of Binary Stars
Authors: Clarke C.J.
Published: July 2007

I argue that binary star statistics offer the best observational constraints on current hydrodynamical simulations of star forming clusters. In these simulations, clusters form hierarchically from the bottom up, and dynamical interactions, mediated by the presence of circumstellar material, play a vital role at the lowest (few body) level of the hierarchy. Such a scenario produces a rich array of complex multiple systems whose properties are in many respects consistent with observations. I however highlight two areas of current disagreement: the simulations over-produce low mass single stars and under-produce binaries with low mass ratios. It is currently unclear to what extent these shortcomings reflect numerical issues and to what extent the omission of relevant physical processes. I conclude with a theorist's wish list for observational diagnostics that would most meaningfully constrain future modeling efforts.
Active Longitudes and Flip-Flops in Binary Stars
Authors: Korhonen Heidi , Järvinen Silva P.
Published: July 2007

We present results from an investigation where the long-term photometry of several magnetically active RS CVn binaries is studied to see whether or not they show permanent active longitudes and the flip-flop phenomenon. We confirm that it is very common for the active regions to occur on permanent active longitudes. Many of our target stars also show clear flip-flop phenomenon, but often the data set is not long enough for reliable determination of the flip-flop period.
Global aerosol optical properties and application to Moderate Resolution Imaging Spectroradiometer aerosol retrieval over land
Authors: Levy Robert C. , Remer Lorraine A. , Dubovik Oleg
Published: July 2007

As more information about global aerosol properties has become available from remotely sensed retrievals and in situ measurements, it is prudent to evaluate this new information, both on its own and in the context of satellite retrieval algorithms. Using the climatology of almucantur retrievals from global Aerosol Robotic Network (AERONET) Sun photometer sites, we perform cluster analysis to determine aerosol type as a function of location and season. We find that three spherical‐derived types (describing fine‐sized dominated aerosol) and one spheroid‐derived types (describing coarse‐sized dominated aerosol, presumably dust) generally describe the range of AERONET observed global aerosol properties. The fine‐dominated types are separated mainly by their single scattering albedo (ω0), ranging from nonabsorbing aerosol (ω0 ∼ 0.95) in developed urban/industrial regions, to moderately absorbing aerosol (ω0 ∼ 0.90) in forest fire burning and developing industrial regions, to absorbing aerosol (ω0 ∼ 0.85) in regions of savanna/grassland burning. We identify the dominant aerosol type at each site, and extrapolate to create seasonal 1° × 1° maps of expected aerosol types. Each aerosol type is bilognormal, with dynamic (function of optical depth) size parameters (radius, standard deviation, volume distribution) and complex refractive index. Not only are these parameters interesting in their own right, they can also be applied to aerosol retrieval algorithms, such as to aerosol retrieval over land from Moderate Resolution Imaging Spectroradiometer. Independent direct‐Sun AERONET observations of spectral aerosol optical depth (τ) are consistent the spectral dependence of the models, indicating that our derived aerosol models are relevant.
Scattering matrix of large Saharan dust particles: Experiments and computations
Authors: Muñoz O. , Volten H. , Hovenier J. W. , Nousiainen T. , Muinonen K. , Guirado D. , Moreno F. , Waters L. B. F. M.
Published: July 2007

We present measurements of the complete scattering matrix as a function of the scattering angle of a sample of Sahara sand particles collected from a dune in Libya. The measurements were performed at a wavelength of 632.8 nm in the scattering angle range from 4° to 174°. To facilitate the use of the experimental data for multiple‐scattering calculations with polarization included, we present a synthetic scattering matrix based on the measurements and defined in the full angle range from 0° to 180°. The Libyan sample consists of large particles distributed over a narrow size distribution which makes it an interesting test case for the Ray Optics Approximation (ROA) that provides accurate results for particles with curvature radii much larger than the wavelength. Numerical simulations using the ROA are compared with the experimental data. Moreover, the traditional ROA was modified with ad hoc simple schemes of Lambertian surface elements and internal screens to study the effects of small‐scale surface roughness and internal structures, respectively. Model particle shapes used in the simulations are based on a shape analysis of our sample. The traditional ray optics approximation does not reproduce the experimental data although a significant improvement is obtained if unrealistically spiky particle shapes are used. When the Lambertian schemes are applied the agreement with the experimental data improves. Still, to get a good agreement with the experimental data we need unrealistic spiky particles together with the inclusion of external Lambertian reflections. This seems to indicate that a more refined treatment is needed to reproduce the scattering effects of the small‐scale surface roughness of the Libyan sand particles.
Rainfall‐runoff modeling through hybrid intelligent system
Authors: Nayak P. C. , Sudheer K. P. , Jain S. K.
Published: July 2007

This study explores the potential of integrating two different artificial intelligence techniques, namely neural network and fuzzy logic, effectively to model the rainfall‐runoff process from rainfall and runoff information. The integration is achieved through representing fuzzy system computations in a generic artificial neural network (ANN) architecture, which is functionally equivalent to a fuzzy inference system. The model is initialized by a hyperellipsoidal fuzzy clustering (HEC) procedure, which identifies suitable numbers of fuzzy if‐then rules through proper partition of the input space. The parameters of the membership functions are optimized using a nonlinear optimization procedure. The consequent functions are chosen to be linear in their parameters, and a standard least squares error method is employed for parameter estimation. The proposed model is tested on two case studies: Narmada basin in India and Kentucky basin in the United States. The results are highly encouraging as the model is able to explain more than 92% of the variance. The performance of the proposed model is found to be comparable to that of an adaptive neural based fuzzy inference system (ANFIS) developed for both the basins. The number of parameters in the proposed model is fewer compared to ANFIS, and the former can be trained in lesser time. It is also observed that the proposed model simulates the peak flow better than ANFIS. Overall, the study suggests that the proposed model can potentially be a viable alternative to ANFIS for use as an operational tool for rainfall runoff modeling purposes.
Exploring the relationship between hydroclimatic stationarity and rainfall‐runoff model parameter stability: A case study in West Africa
Authors: Le Lay M. , Galle S. , Saulnier G. M. , Braud I.
Published: July 2007

Forecasting the hydrological impacts of climatic and anthropic changes assumes that the evolution of model parameters under changing conditions can be predicted. Hence it is necessary to study the relationship between hydroclimatic variability and model parameter values. In this paper, we explore this issue by implementing a daily lumped hydrological model (GR4J, Perrin et al. (2003)) on the Upper Ouémé watershed (10,050 km2, Benin). West Africa was subjected to changing climatic and hydrological conditions during the second half of the last century, and changes in the water balance can be evidenced on this watershed. Contrasted periods are extracted from the available 1954–2002 data set, so that hydrological and pluviometric extreme periods can be defined. First, the magnitude of changes in model parameter values under changing conditions are analyzed, using a resampling method (first approach) and within an equifinality context (second approach). It is shown that significant changes in the rainfall‐runoff relationship do not induce significant changes in the model's parameter values. A third original approach analyzes the signature of hydroclimatic variability in model performance. Hence a test is defined that uses interannual model efficiency variances to measure performance homogeneity and a resampling test to statistically characterize the calculated results. This test demonstrates the hydrological relevance of the calibrated parameter sets because the more stationary the rainfall‐runoff relationship, the more homogeneous the model's performance.
Matrix diffusion rates in fractured volcanic rocks at the Nevada Test Site: Evidence for a dominant influence of effective fracture apertures
Authors: Reimus Paul W. , Callahan Timothy J.
Published: July 2007

Solute matrix diffusion in saturated, fractured volcanic rock at the Nevada Test Site was evaluated from field tracer tests conducted at two different locations and from laboratory‐scale transport experiments using core samples from the two locations. The laboratory tests included 15 separate tracer transport experiments conducted in 8 fractured cores (4 from each location) and 17 diffusion cell experiments conducted in matrix material adjacent to the fractures. All of the experiments featured two nonsorbing tracers with free diffusion coefficients differing by a factor of approximately 3 to allow the effects of diffusion to be distinguished from the effects of advection, dispersion, and source‐term tailing in the experiments. When considering all the laboratory and field transport experiments collectively, the lumped mass transfer parameter that characterizes matrix diffusion rates, (sec−1/2) (where ϕm is the matrix porosity, b is the effective fracture half‐aperture, and Dm is the matrix diffusion coefficient), appears to decrease as time and length scales of observation increase. However, these decreasing trends largely disappear when the laboratory and field data are considered separately, and there is little difference in Dm values measured at different timescales in laboratory experiments using the same rocks. Also, the overall variability in ϕm and Dm in the laboratory experiments is not large enough to account for the order‐of‐magnitude smaller field‐scale values of compared to lab‐scale values. We conclude that experimentally observed trends of versus time or distance scale in saturated fractured rocks at the Nevada Test Site are dominated by differences in effective fracture apertures in the various experiments, with a tendency toward larger apertures in the field experiments. These results underscore the importance of acquiring a better understanding of the factors that control effective fracture apertures as a function of distance scale in fractured media if values of from laboratory and field tracer experiments are to be reliably extrapolated to time and distance scales in risk assessment models.
Magnetic character of a large continental transform: An aeromagnetic survey of the Dead Sea Fault
Authors: ten Brink Uri S. , Rybakov Michael , Al‐Zoubi Abdallah S. , Rotstein Yair
Published: July 2007

New high‐resolution airborne magnetic (HRAM) data along a 120‐km‐long section of the Dead Sea Transform in southern Jordan and Israel shed light on the shallow structure of the fault zone and on the kinematics of the plate boundary. Despite infrequent seismic activity and only intermittent surface exposure, the fault is delineated clearly on a map of the first vertical derivative of the magnetic intensity, indicating that the source of the magnetic anomaly is shallow. The fault is manifested by a 10–20 nT negative anomaly in areas where the fault cuts through magnetic basement and by a <5 nT positive anomaly in other areas. Modeling suggests that the shallow fault is several hundred meters wide, in agreement with other geophysical and geological observations. A magnetic expression is observed only along the active trace of the fault and may reflect alteration of magnetic minerals due to fault zone processes or groundwater flow. The general lack of surface expression of the fault may reflect the absence of surface rupture during earthquakes. The magnetic data also indicate that unlike the San Andreas Fault, the location of this part of the plate boundary was stable throughout its history. Magnetic anomalies also support a total left‐lateral offset of 105–110 km along the plate boundary, as suggested by others. Finally, despite previous suggestions of transtensional motion along the Dead Sea Transform, we did not identify any igneous intrusions related to the activity of this fault segment.
Impact of altimetry data on ENSO ensemble initializations and predictions
Authors: Zheng Fei , Zhu Jiang , Zhang Rong‐Hua
Published: July 2007

The El Niño/Southern Oscillation (ENSO) predictions strongly depend on the accuracy and dynamical consistency of the coupled initial conditions. Based on the proposed ensemble Kalman filter (EnKF), a new initialization scheme for the ENSO ensemble prediction system (EPS) was designed and tested in an intermediate coupled model (ICM). The inclusion of this scheme in the ICM leads to substantial improvements in ENSO prediction skill via the successful assimilation of both observed sea surface temperature (SST) and TOPEX/Poseidon/Jason‐1 (T/P/J) altimeter data into the initial ensemble conditions. Comparisons with the original ensemble hindcast experiment show that the ensemble prediction skills were significantly improved out to a 12‐month lead time by improving sea level (SL) initial conditions for better parameterization of subsurface thermal effects. It is clearly demonstrated that improvement in forecast skill can result from the multivariate and multi‐observational ensemble data assimilation.
Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes
Authors: Liu Libo , Zhao Biqiang , Wan Weixing , Venkartraman S. , Zhang Man‐Lian , Yue X.
Published: July 2007

In this paper, the 10‐year (1996–2005) measurements of total ion density (Ni) from the Defense Meteorological Satellite Program (DMSP) spacecraft at 0930 and 2130 LT have been analyzed to investigate the yearly variations of global plasma densities in the topside ionosphere at magnetic latitudes from 60°S to 60°N. Results indicate that there are strong yearly variations in the DMSP Ni at 840 km. The annual components of longitude‐averaged Ni dominate at most latitudes with maxima around the June solstices in the Northern Hemisphere and the December solstice in the Southern Hemisphere. In contrast, seasonal anomaly (maxima Ni around the December solstice) exists in the northern equatorial zone. Moreover, the differences in Ni at the two solstices are not symmetrical about the magnetic equator, being generally higher in the Southern Hemisphere than in the Northern Hemisphere. Conjugate‐averaged Ni is substantially greater at the December solstice than at the June solstice. This annual asymmetry is modulated by solar activity effect and has latitudinal and longitudinal structures. The longitude effects of the annual asymmetry depend on local time, being stronger in the evening sector than in the morning sector. The solstice differences and annual asymmetry are more marked with increasing solar activity. The annual asymmetry appears not only in the rising phase of the solar cycle but also in the declining phase. Thus the solar condition differences between the two solstices do not account for the Ni asymmetry. The concentration of neutral oxygen [O], provided from the NRLMSIS model, shows a similar pattern of annual and hemispheric asymmetries. Moreover, effects of the HWM model neutral winds are also constituent with the change patterns of Ni. Therefore, considering the principal processes in the topside ionosphere, the changes of [O] and the rates of thermospheric winds should contribute to the annual asymmetry in Ni at 840‐km altitude.
Labile associations between fungus-growing ant cultivars and their garden pathogens
Authors: Gerardo Nicole M , Caldera Eric J
Published: July 2007

The distribution of genetic and phenotypic variation in both hosts and parasites over their geographic ranges shapes coevolutionary dynamics. Specifically, concordant host and parasite distributions facilitate localized adaptation and further specialization of parasite genotypes on particular host genotypes. We here compare genetic population structure of the cultivated fungi of the fungus-growing ant Apterostigma dentigerum and of the cultivar-attacking fungus, Escovopsis, to determine whether these microbial associations have evolved or are likely to evolve genotype–genotype specialization. Analyses based on amplified fragment length polymorphism (AFLP) genotyping of host cultivars and pathogenic Escovopsis from 77 A. dentigerum colonies reveal that populations of hosts and pathogens are not similarly diverged and that host and pathogen genetic distances are uncorrelated, indicating that genetically similar parasites are not infecting genetically similar hosts. Microbial bioassays between pathogens and cultivars of different genotypes and from different populations show little pairwise specificity; most Escovopsis strains tested can successfully infect all cultivar strains with which they are paired. These molecular and experimental data suggest that Escovopsis genotypes are not tightly tracking cultivar genotypes within the A. dentigerum system. The diffuse nature of this host–pathogen association, in which pathogen genotypes are not interacting with a single host genotype but instead with many different hosts, will influence evolutionary and ecological disease dynamics of the fungus-growing ant–microbe symbiosis.
Effects of Visual Stimuli and a Stressor on Head Pain
Authors: Martin Paul R. , Teoh Hsien‐Jin
Published: July 2007

This study sought to experimentally validate two reported precipitants of chronic headaches, namely, negative affect (anxiety, anger, depression) and visual disturbance (flicker, glare, eyestrain), and to investigate whether they triggered common or different physiological mechanisms. Twenty‐two male and 68 female subjects (46 with migraine, 29 with tension‐type headache, and 15 controls) were submitted to antecedent challenges in the laboratory which induced negative affect or visual disturbance and to a control challenge. The results demonstrated that negative affect and visual disturbance can indeed precipitate headaches, and that the physiological responses associated with these antecedents differ, but the findings were not conclusive as to whether one or more physiological mechanisms are operative. Follow‐up revealed that the antecedent challenges had significant effects on headache activity 48 to 72 hours after termination.
Fluoxetine for Migraine Prophylaxis: A Double‐Blind Trial
Authors: D'Amato Cesare Colucci , Pizza Vincenzo , Marmolo Teresa , Giordano Edoardo , Alfano Vincenza , Nasta Antonio
Published: July 2007

Selective serotonin reuptake inhibitors have recently been used in the treatment of migraine.

Objective.—We studied the safety and efficacy of fluoxetine in the prevention of migraine.

Patients.—Between February 1997 and December 1997, we examined 52 patients (33 women) at the Headache Diagnosis and Therapy Service of the Second University of Naples. Ages ranged from 18 to 65 years, and all patients suffered from migraine without aura according to IHS 1988 criteria. The sample was divided into two groups: group A included 32 patients (19 women; mean age, 36.8 years [SD 12.4]) who received fluoxetine at a dosage of 20 mg per day; group B included 20 patients (14 women; mean age, 38.8 years [SD 15.6]) who received placebo.

Methods.—Our study was a single‐center, randomized, double‐blind, parallel study of fluoxetine for the prophylactic control of migraine and consisted of two phases: 30 days of pharmacological wash out and 6 months of therapy with monthly follow‐up. Patients were randomly assigned to two groups: A, fluoxetine or B, placebo.

At the first visit, patients provided a detailed history and underwent neurological evaluation and a Zung test for depression. No pathological values were revealed.

In order to monitor symptomatology, all patients received a form for the calculation of the total pain index at monthly follow‐up.

Results.—A comparison of the total pain index between basal values (calculated during the period of wash out) and monthly follow‐up (calculated monthly during the period of 6 months of the therapy) showed significant reduction (P<.05) beginning from the third month of treatment in the fluoxetine group and no significant reduction in the placebo group.

Conclusion.—Even if preliminary and to be confirmed, these data seem to support the use of fluoxetine in the treatment of migraine.
An Examination of the Validity of the IHS Classification System for Migraine and Tension‐Type Headache in the College Student Population
Authors: Rokicki Lori A. , Semenchuk Elizabeth M. , Bruehl Stephen , Lofland Kenneth R. , Houle Timothy T.
Published: July 2007

The validity of the International Headache Society (IHS) classification system for college‐aged students with headache was examined using cluster analysis. Undergraduate college student volunteers (N=369) underwent a structured diagnostic interview for headaches, and the sample was divided into two subsamples for purposes of replication. A hierarchical cluster analysis (Ward's method) of the headache characteristics reported by the first subsample suggested a statistically distinct three‐cluster solution, and the solution was replicated using the second subsample. It appeared that one cluster was tensionlike, while the other two were migrainelike. Nonhierarchical cluster analyses (K‐means) of the cases from each subsample revealed a similar pattern of a tensionlike and two migrainelike clusters. Identical three‐cluster solutions were found for the second subsample both by using cluster centers from the first subsample and by clustering the cases independently, suggesting that the cluster solution was not a random finding. The IHS classification system appears to lack adequate specificity and sensitivity for college‐aged students with headache who report migrainelike symptoms. Thus, the generalizability of research results using college‐aged students with headache to the adult population may be questionable.
Prevalence of Migraine in Schoolchildren and Some Clinical Comparisons Between Migraine With and Without Aura
Authors: Mavromichalis Ioannis , Anagnostopoulos Demetrios , Metaxas Nickolas , Papanastassiou Emanuel
Published: July 2007

Objectives.—To determine the prevalence of migraine and its association with age, gender, and social class and to find out whether or not the headache and nonheadache characteristics differ between children with migraine, with and without aura, using the diagnostic criteria of the International Headache Society for childhood migraine.

Design.—Population‐based study in two stages comprising an initial screening questionnaire followed by telephone interviews of children with symptoms.

Setting.—Eighteen kindergarten and 39 primary and secondary schools in Thessaloniki and its semiurban areas.

Subjects.—Four thousand children, aged 4 to 15 years, representing a random sample of 5% of schoolchildren in Thessaloniki and its semiurban areas.

Main Outcome Measures.—(1) The prevalence of migraine, (2) the connection of migraine with social class, (3) differences in the occurrence of individual symptoms between migraine with and without aura.

Results.—The results of the present study show that migraine prevalence was 6.2% (95% confidence interval [CI], 5.4 to 7.0). The estimated prevalences of migraine with and without aura were 2.8% (95% CI, 2.3 to 3.4) and 3.4% (CI, 2.8 to 4.0), respectively. The prevalence of migraine increased with age and it was found to be almost equal in boys and girls aged 7 to 9 years or younger, but in older age groups the prevalence was higher in girls than in boys. The data showed no evidence that connected migraine with social class. It also showed that except for the aura, the headache (eg, frequency, duration, location, quality, and severity) and nonheadache (eg, nausea, vomiting, phonophobia, and photophobia) characteristics were no different between children with migraine, with and without aura. In conclusion, our findings indicate that migraine is a common underdiagnosed cause of severe recurrent headache in children. The findings show that childhood migraine is not connected with social class and varies with age and gender, and that except for the aura, both migraine with and without aura are so similar in their headache and nonheadache clinical characteristics that a common pathogenesis is plausible.
Demographics of Attendees at Public Education Seminars
Authors: Klapper Jack A. , Sheftell Fred D. , Seawell Marcia
Published: July 2007

Purpose.—The demographics of patients who attend public awareness seminars relating to headache have not been studied. In order to improve the presentations at these meetings, it was felt that the meeting planners should know as much as possible about the audience.

Methods.—Attendees at a public awareness seminar entitled Help for Headaches were asked to respond to a series of questions using an audience response system.

Results.—The majority of the 212 responders were women (90%) and were over the age of 50 (53%). Most felt that they had more than one type of headache (64%), were treated by a family practitioner or internist (58%), and had been denied important diagnostic or therapeutic modalities (42%). The majority were dissatisfied with current treatment (87%) and attended the meeting to find out more about new treatments (64%). Fifty‐eight percent felt their physicians did not know enough about headaches. Forty‐nine percent felt they had rebound headaches.

Conclusions.—Public awareness seminars for headache should be designed with the realization that most attendees will be women who have more than one type of headache. The majority will be interested in new and alternative therapies, and approximately half will have rebound headaches.
Fast ignition by laser driven particle beams of very high intensity
Authors: Hora H. , Badziak J. , Read M. N. , Li Yu-Tong , Liang Tian-Jiao , Cang Yu , Liu Hong , Sheng Zheng-Ming , Zhang Jie , Osman F. , Miley G. H. , Zhang Weiyan , He Xiantu , Peng Hansheng , Glowacz S. , Jablonski S. , Wolowski J. , Skladanowski Z. , Jungwirth K. , Rohlena K. , Ullschmied J.
Published: July 2007

Anomalous observations using the fast ignition for laser driven fusion energy are interpreted and experimental and theoretical results are reported which are in contrast to the very numerous effects usually observed at petawatt-picosecond laser interaction with plasmas. These anomalous mechanisms result in rather thin blocks (pistons) of these nonlinear (ponderomotive) force driven highly directed plasmas of modest temperatures. The blocks consist in space charge neutral plasmas with ion current densities above 1010A∕cm2. For the needs of applications in laser driven fusion energy, much thicker blocks are required. This may be reached by a spherical configuration where a conical propagation may lead to thick blocks for interaction with targets. First results are reported in view of applications for the proton fast igniter and other laser-fusion energy schemes.
Enhancement of the critical current density and the irreversibility field in maleic anhydride doped MgB2 based tapes
Authors: Gao Zhaoshun , Ma Yanwei , Zhang Xianping , Wang Dongliang , Yu Zhengguang , Yang Huan , Wen Haihu , Mossang E.
Published: July 2007

A significant enhancement of Jc, Hirr, and Hc2 in MgB2 tapes has been achieved by using maleic anhydride (C4H2O3) as dopants. MgB2 tape samples with 0 up to 30wt% C4H2O3 added were prepared by an in situ processed powder-in-tube method. Compared to the pure tapes, Jc for the 10wt% C4H2O3 doped samples was improved by more than an order of magnitude in high fields up to 18T. At 4.2K, the transport Jc for the 10wt% doped samples reached 1.08×104, 5.42×103, and 2.18×103A∕cm2 at 12, 14, and 16T, respectively, and were better than those of the best MgB2∕Fe tapes reported by far. Furthermore, the Hirr for the 10wt% doped sample reached 9.6T at 20K, which was comparable to that of NbTi at 4.2K. The improvement of the superconducting properties in doped tapes can be attributed to the increase of Hc2 and the grain size refinement by C4H2O3 doping.