bluuebunny/crossref_metadata_2025 huggingface dataset:
A Cauchy problem for the Tartar equation
Authors: Sazhenkov Sergey
Published: July 2007

In order to study weak limits of quadratic expressions of oscillatory solutions of partial differential equations, there was proposed a construction of H-measures defined on the space of positions and frequencies. The present paper is devoted to the investigation of the Tartar equation
which describes the evolution of the H-measure μt associated with a sequence of oscillatory solutions of the linear transport equation

in cases when a given solenoidal velocity field v(x, t) is sufficiently smooth. Here, (t, x, y) ∈ (0, T) × Ω × S1, 0 < T < +∞, Ω is a bounded open subset of R2 and S1 is the unit circle in R2, given coefficients Yij = Yij(y) are infinitely smooth.

Assuming that v belongs to , we establish the well posedness of Cauchy problem for the Tartar equation in the same measure class as the H-measures are in. For this purpose, we develop and use an extension of the theory of Lagrange coordinates for a case of non-smooth solenoidal velocity fields.
Monotonicity of rotationally invariant convex and rank 1 convex functions
Authors: Šilhavý M.
Published: July 2007

Let f : Mn×n → R ∪ {∞} be a function on the space Mn×n of n by n matrices that is invariant with respect to the left and right multiplication by proper orthogonal tensors. It is shown that f(A) ≤ f(Ā) if f is convex and the partial sums of the singular values of A, Ā ∈ Mn×n satisfy certain ordering inequalities. The same holds if f is rank 1 convex and the partial products of the singular values satisfy analogous inequalities. The proofs emphasize the roles of the ordered-forces inequalities and the Baker-Ericksen inequalities for invariant convex and rank 1 convex functions. As an application, the evaluation of the convex and lamination convex hulls of fully rotationally invariant sets by Dacorogna and Tanteri is simplified and similar results are given for sets invariant only with respect to the proper orthogonal group.
Homogenization of a neutronic critical diffusion problem with drift
Authors: Capdeboscq Yves
Published: July 2007

In this paper we study the homogenization of an eigenvalue problem for a cooperative system of weakly coupled elliptic partial differential equations, called the neutronic multigroup diffusion model, in a periodic heterogeneous domain. Such a model is used for studying the criticality of nuclear reactor cores. In a recent work in collaboration with Grégoire Allaire, it is proved that, under a symmetry assumption, the first eigenvector of the multigroup system in the periodicity cell controls the oscillatory behaviour of the solutions, whereas the global trend is asymptotically given by a homogenized diffusion eigenvalue problem. It is shown here that when this symmetry condition is not fulfilled, the asymptotic behaviour of the neutron flux, corresponding to the first eigenvector of the multigroup system, is dramatically different. This result enables to consider new types of geometrical configurations in practical nuclear reactor core computations.
Normal modes for a stratified viscous fluid layer
Authors: Gurski K. F. , Pego R. L.
Published: July 2007

We consider internal gravity waves in a stratified fluid layer with rigid horizontal boundaries and periodic boundary conditions on the sides at constant temperature with a small constant viscosity, modelled using the incompressible Navier-Stokes equations. Using operator-theoretic methods to study the damping rates of internal waves we prove there are non-oscillatory wave modes with arbitrarily small damping rates. We provide an asymptotic approximation for these non-oscillatory modes. Additionally, we find that the eigenvalues for damped oscillations are in an explicitly describable half-ring.
Remarks on the asymptotic behaviour of solutions to the compressible Navier–Stokes equations in the half-line
Authors: Jiang Song
Published: July 2007

We study the time-asymptotic behaviour of solutions to the Navier-Stokes equations for a one-dimensional viscous polytropic ideal gas in the half-line. Using a local representation for the specific volume, which is obtained by using a special cut-off function to localize the problem, and the weighted energy estimates, we prove that the specific volume is pointwise bounded from below and above for all x, t and that for all t the temperature is bounded from below and above locally in x. Moreover, global solutions are convergent as time goes to infinity. The large-time behaviour of solutions to the Cauchy problem is also examined.
Universal attractors for a nonlinear one-dimensional heat-conductive viscous real gas
Authors: Qin Yuming , Muñoz Rivera Jaime E.
Published: July 2007

In this paper we employ some new ideas and more delicate estimates, as well as some ideas from previous works, to establish the existence of universal attractors for a nonlinear one-dimensional heat-conductive viscous real gas in the bounded domain Ω = (0,1).
On convergence, admissibility and attractors for damped wave equations on squeezed domains
Authors: Carbinatto M. C. , Rybakowski K. P.
Published: July 2007

Let be an arbitrary non-empty bounded Lipschitz domain in RM RN. Given > 0, squeeze by the factor in the y-direction to obtain the squeezed domain := {(x, y) | (x, y) }. Let and be positive constants. Consider the following semilinear damped wave equation on ,

where is the exterior normal vector field on and G is an appropriate nonlinearity, which ensures that (W) generates a (local) flow ̃ on X := H1() L2(). We show that there is a closed subspace X0 of X and a flow ̃0 on X0 that is the limit flow of the family ̃, > 0. We show that, as 0, the family ̃ converges in some singular sense to ̃ and establish a technical singular asymptotic compactness property. As a corollary, we obtain an upper-semicontinuity result for global attractors of the family ̃, 0, generalizing results obtained previously by Hale and Raugel for domains that are ordinate sets of a positive function.

The results obtained here are also applied in our paper On a general Conley index continuation principle for singular perturbation problems to establish a singular Conley index continuation principle for damped wave equations on thin domains.
Some fine properties of currents and applications to distributional Jacobians
Authors: De Lellis Camillo
Published: July 2007

We study fine properties of currents in the framework of geometric measure theory on metric spaces developed by Ambrosio and Kirchheim, and we prove a rectifiability criterion for flat currents of finite mass. We apply these tools to study the structure of the distributional Jacobians of functions in the space BnV, defined by Jerrard and Soner. We define the subspace of special functions of bounded higher variation and we prove a closure theorem.
On growth of holomorphic embeddings into C2
Authors: Globevnik Josip
Published: July 2007

Let be the open unit disc in C. It is proved that a holomorphic embedding f : C2 can grow arbitrarily fast near b. It is also proved that a holomorphic embedding f : C C2 can grow arbitrarily fast near infinity.
Existence and non-existence of the first eigenvalue of the perturbed Hardy–Sobolev operator
Authors: Adimurthi  , Sandeep K.
Published: July 2007

In this paper we study the existence, non-existence and simplicity of the first eigenvalue of the perturbed Hardy-Sobolev operator under various assumptions on the perturbation q. We study the asymptotic behaviour of the first eigenfunction near the origin when the perturbation q is q = s, 0 < s < 1. We will also establish the best constant in a Hardy-Sobolev inequality proved by Adimurthi et al.
Stability of the two-dimensional Brown–Ravenhall operator
Authors: Bouzouina A.
Published: July 2007

We prove that the two-dimensional Brown–Ravenhall operator is bounded from below when the coupling constant is below a specified critical value—a property also referred to as stability. As a consequence, the operator is then self-adjoint. The proof is based on the strategy followed by Evans et al. and Lieb and Yau, with some relevant changes characteristic of the dimension. Our analysis also yields a sharp Kato inequality.
Dn-forced symmetry breaking of O(2)-equivariant problems
Authors: Furter Jacques-Elie , Sitta Angela Maria
Published: July 2007

We use singularity theory to classify forced symmetry-breaking bifurcation problems

where f1 is O(2)-equivariant and f2 is Dn-equivariant with the orthogonal group actions on z ∈ R2. Forced symmetry breaking occurs when the symmetry of the equation changes when parameters are varied. We explicitly apply our results to the branching of subharmonic solutions in a model periodic perturbation of an autonomous equation and sketch further applications.
Resonances of a λ-rational Sturm–Liouville problem
Authors: Langer Matthias
Published: July 2007

We consider a family of self-adjoint 2 × 2-block operator matrices Ãϑ in the space L2(0, 1) ⊕ L2(0, 1), depending on the real parameter ϑ. If Ã0 has an eigenvalue that is embedded in the essential spectrum, then it is shown that for ϑ ≠ 0 this eigenvalue in general disappears, but the resolvent of Ãϑ has a pole on the unphysical sheet of the Riemann surface. Such a pole is called a resonance pole. The unphysical sheet arises from analytic continuation from the upper half-plane ℂ+ across the essential spectrum. Furthermore, the asymptotic behaviour of this resonance pole for small ϑ is investigated. The results are proved by considering a certain λ-rational Sturm-Liouville problem and its Titchmarsh–Weyl coefficient.
Computation of critical groups in elliptic boundary-value problems where the asymptotic limits may not exist
Authors: Li Shujie , Perera Kanishka , Su Jiabao
Published: July 2007

We compute critical groups in semilinear elliptic boundary-value problems in which the nonlinear term may fail to have asymptotic limits at zero and at infinity. As applications, we prove several new existence results.
Variation in English syntax: theoretical implications
Authors: ADGER DAVID , TROUSDALE GRAEME
Published: July 2007

This article provides an overview of the relationship between studies of syntactic variation in dialects of English and theoretical accounts of language structure. In the first section of the article, we provide a discussion of the place of syntactic variation within various subdisciplines of linguistic enquiry: we address issues such as I- and E-language, the place of Standard English in linguistic theory, and interfaces between traditional dialectology, variationist sociolinguistics, and theoretical linguistics. These interfaces suggest the need for a clarification of the nature and status of the (morpho)syntactic variable, which we provide in section 3; and in section 4, we examine the way in which (morpho)syntactic variation is treated within a number of theoretical models – for instance, Principles and Parameters theory, HPSG, OT, and cognitive linguistics (including Word Grammar and Construction Grammar) – all of which feature in the other articles in this special issue.
Typology in variation: a probabilistic approach to be and n't in the Survey of English Dialects
Authors: BRESNAN JOAN , DEO ASHWINI , SHARMA DEVYANI
Published: July 2007

Variation within grammars is a reflection of variation between grammars.
Subject agreement and synthetic negation for the verb be show extraordinary local variation in the Survey of English Dialects (Orton et al., 1962–71). Extracting partial grammars of individuals, we confirm leveling patterns across person, number, and negation (Ihalainen, 1991; Cheshire, Edwards & Whittle, 1993; Cheshire, 1996). We find that individual variation bears striking structural resemblances to invariant dialect paradigms, and also reflects typologically observed markedness properties (Aissen, 1999). In the framework of Stochastic Optimality Theory (Boersma & Hayes, 2001), variable outputs of individual speakers are expected to be constrained by the same typological and markedness generalizations found crosslinguistically. The stochastic evaluation of candidate outputs in individual grammars reranks individual constraints by perturbing their ranking values, with the potential for stable variation between two near-identical rankings. The stochastic learning mechanism is sensitive to variable frequencies encountered in the linguistic environment, whether in geographical or social space. In addition to relating individual and group dialectal variation to typological variation (Kortmann, 1999; Anderwald, 2003), the findings suggest that an individual grammar is sensitively tuned to frequencies in the linguistic environment, leading to isolated loci of variability in the grammar rather than complete alternations of paradigms.
A characteristic of linguistic variation that has emerged in distinct fields of enquiry is that variation within a single grammar bears a close resemblance to variation across grammars. Sociolinguistic studies, for instance, have long observed that ‘variation within the speech of a single speaker derives from the variation which exists between speakers’ (Bell, 1984: 151). In the present study, individual patterns of variation in subject–verb agreement with affirmative and negative be extracted from the Survey of English Dialects(SED, Orton et al., 1962–71) show striking structural resemblances to patterns of interdialectal, or categorical, variation.
A construction grammar account of possessive constructions in Lancashire dialect: some advantages and challenges
Authors: HOLLMANN WILLEM , SIEWIERSKA ANNA
Published: July 2007

This study investigates reduction of 1SG possessives in possessive–noun constructions in Lancashire dialect. On the basis of a corpus of twenty-six interviews we show that reduction patterns according to (in)alienability. This dialectal evidence runs counter to the normal assumption about English, i.e. that there is no such effect. Following work by Haspelmath (2006b) that reinterprets iconicity effects in terms of frequency, we proceed to show that frequency may indeed underlie alienability/iconicity in our data as well. Relative frequency seems more useful in capturing the correlation with reduction than absolute frequency. For a few [1SGPOSS-N] combinations the reduction facts are problematic for the frequency-based account we offer. These difficulties might seem to disappear in the light of the construction grammar notion of schemas, but we point out that this notion itself has serious theoretical problems associated with it. Future theory-driven work on dialect grammar may help resolve these issues.
n–3 Fatty acids,
hypertension and risk of cognitive decline among older adults in the
Atherosclerosis Risk in Communities (ARIC) study
Authors: Beydoun May A , Kaufman Jay S , Sloane Philip D , Heiss Gerardo , Ibrahim Joseph
Published: July 2007

Objective

Recent research indicates that n–3 fatty acids can inhibit cognitive decline,
perhaps differentially by hypertensive status.

Design

We tested these hypotheses in a prospective cohort study (the Atherosclerosis
Risk in Communities). Dietary assessment using a food-frequency
questionnaire and plasma fatty acid exposure by gas chromatography were
completed in 1987–1989 (visit 1), while cognitive assessment with
three screening tools – the Delayed Word Recall Test, the Digit
Symbol Substitution Test of the Wechsler Adult Intelligence
Scale–Revised and the Word Fluency Test (WFT) – was
completed in 1990–1992 (visit 2) and 1996–1998 (visit
4). Regression calibration and simulation extrapolation were used to control
for measurement error in dietary exposures.

Setting

Four US communities – Forsyth County (North Carolina), Jackson
(Mississippi), suburbs of Minneapolis (Minnesota) and Washington County
(Maryland).

Subjects

Men and women aged 50–65 years at visit 1 with complete dietary
data (n = 7814); white men and women in
same age group in the Minnesota field centre with complete plasma fatty acid
data (n = 2251).

Results

Findings indicated that an increase of one standard deviation in dietary
long-chain n–3 fatty acids (%
of energy intake) and balancing long-chain n−3/n–6 decreased the risk of 6-year cognitive decline in
verbal fluency with an odds ratio (95% confidence interval) of 0.79
(0.66–0.95) and 0.81 (0.68–0.96), respectively, among
hypertensives. An interaction with hypertensive status was found for dietary
long-chain n–3 fatty acids (g
day−1) and WFT decline (likelihood ratio test,
P = 0.06). This exposure in plasma
cholesteryl esters was also protective against WFT decline, particularly
among hypertensives (OR = 0.51, P
< 0.05).

Conclusion

One implication from our study is that diets rich in fatty acids of marine
origin should be considered for middle-aged hypertensive subjects. To this
end, randomised clinical trials are needed.
Obesity and associated lifestyle behaviours in Iran: findings from the First National Non-communicable Disease Risk Factor Surveillance Survey
Authors: Kelishadi Roya , Alikhani Siamak , Delavari Alireza , Alaedini Farshid , Safaie Afshin , Hojatzadeh Eliyeh
Published: July 2007

Objective

To assess the national prevalence of overweight and obesity, as well as some associated lifestyle behaviours, for the first time in Iran.

Design and Settings

This population-based study was performed in early 2005 as part of the World Health Organization (WHO) STEPwise approach to non-communicable diseases’ risk factor surveillance. Dietary and physical activity habits were assessed by WHO questionnaires.

Subjects

The study population comprised 89 532 subjects aged over 15 years living in the 28 provinces of Iran.

Results

Overall, 50.4% (n= 45 113) of the participants were male and 64.6% (n= 57 866) were from the urban areas. The national estimates of overweight, obesity and morbid obesity were 28.6%, 10.8% and 3.4%, respectively. Body mass index (BMI) ≥ 25 kg m−2in men, women, urban residents and rural residents were found in 37%, 48%, 46.7% and 35.5%, respectively. Abdominal obesity was present in 43.4% of women, 9.7% of men, 28.5% of the urban residents and 23% of the rural residents. Overweight as well as generalised and abdominal obesity were more prevalent in the 45–64-year age group. Although there was no significant difference in frequency of consumption of the food groups in subjects with different BMI categories, various kinds of physical activities showed a steady decline with increasing BMI.

Conclusions

The findings of the present study provide alarming evidence for health professionals and policy makers about the very high prevalence of generalised and abdominal obesity in Iran. The unhealthy lifestyle habits, notably sedentary lifestyles in our community, are the major contributing factors for this emerging public health problem.
Professor Mirek J. Plavec
Authors: Harmanec Petr , Grygar Jiří , Batten Alan H. , Peters Geraldine J. , Linnell Albert P. , Hubeny Ivan , Guinan Edward F.
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.
Overview of Multiple–Aperture Interferometry Binary Star Results from the Southern Hemisphere
Authors: Davis John
Published: July 2007

The first multiple-aperture interferometric study of a binary system, in which the power of combining interferometric and spectroscopic data was demonstrated, was made from the Southern Hemisphere. The observations of α Vir with the Narrabri Stellar Intensity Interferometer (NSII) were combined with spectroscopic and photometric data to yield the mass, radius and luminosity of the primary as well as an accurate distance to the system. The NSII also revealed a number of stars, previously thought to be single, to be binary systems. Several of these systems have subsequently been shown to be spectroscopic binaries.

The Sydney University Stellar Interferometer (SUSI) and the European Southern Observatory's Very Large Telescope Interferometer (VLTI) are the two current Southern Hemisphere multiple aperture interferometers. SUSI is being used to determine interferometric orbits for some of the binary systems discovered with the NSII including β Cen and λ Sco and, in combination with spectroscopy, to determine accurate masses for early-type stars and accurate dynamical parallaxes for the systems.

The VLTI has operated with three beam-combining instruments, namely VINCI, MIDI and AMBER. The few observations of binary systems that have been made so far are summarised and, while in general they are of a preliminary nature, they demonstrate the potential of the VLTI for binary star studies.

One double-lined spectroscopic binary that has been observed with all three Southern Hemisphere instruments is γ2Vel, which has the brightest Wolf-Rayet star in the sky as its secondary. The observations and preliminary results for the masses of the O-type primary and WC8 secondary and for the distance to the system are summarised.
Spectroscopic Binary Candidates for Interferometers
Authors: Fekel Francis C. , Tomkin Jocelyn
Published: July 2007

We present a progress report on a program to improve the orbits of known spectroscopic binaries that are potential targets for ground-based optical interferometers, such as the CHARA array and PTI. The combination of such observations results in three-dimensional orbits that produce very accurate masses (uncertainties of less than 0.5%) as well as orbital parallaxes that are generally more precise than those from Hipparcos. After additional analyses determine other basic parameters of the stars, the components can be compared with theoretical evolutionary tracks. We are currently using three observatories to obtain high-resolution, red-wavelength spectra of 44 systems. Results from four years of observation are highlighted. Interferometric observations of some systems are in progress.
DE CVn: A Bright, Eclipsing Red Dwarf – White Dwarf Binary
Authors: van den Besselaar E. J. M. , Greimel R. , Morales-Rueda L. , Nelemans G. , Thorstensen J. R. , Marsh T. R. , Dhillon V. S. , Robb R. M. , Balam D. D. , Guenther E. W. , Kemp J. , Augusteijn T. , Groot P. J.
Published: July 2007

DE CVn is a relatively unstudied eclipsing binary where one of the components is an M dwarf and the other is a white dwarf. Its brightness makes it an ideal system for a detailed study in the context of common-envelope evolution of a detached white dwarf – red dwarf binary with a relatively short orbital period (∼8.7 hours). We present a detailed study of the basic parameters (e.g. orbital period, components' masses and spectral types) for this system from photometric and spectroscopic studies. The eclipses observed during several photometric observing runs were used to derive the ephemeris. We have used spectroscopic data to derive the radial velocity variations of the emission lines and these are used to determine the components' masses and the orbital separation. The secondary component in DE CVn is an M3 main-sequence star and the primary star, which only contributes to the blue continuum, is a cool white dwarf with a temperature of ∼8000 K. From the photometry and spectroscopy together, we have set a limit on the binary inclination. This system is a post-common-envelope system where the progenitor of the present day white dwarf was a low-mass star (M≤2M⊙). The time before DE CVn becomes a semi-detached system is longer than the Hubble time.
The Eclipsing Triple System U Ophiuchi Revisited
Authors: Vaz Luiz Paulo R. , Andersen Johannes , Claret Antônio
Published: July 2007

We have redetermined the absolute dimensions of the mid B-type eclipsing binary U Oph from new light and radial-velocity curves, accounting for both the apsidal motion and the light-time orbit around the third star. The stars in U Oph have masses of 5.27 and 4.74 M⊙(±1.5%) and are located in the middle of the main-sequence band for an an age of ∼50 Myr. U Oph and three other systems (V760 Sco, MU, Cas and DI Her) all have components within 10% of 5M⊙ and ages below 100 Myr; we find significant heavy-element abundance differences between these young nearby stars.
Doppler Imaging of Close Binaries
Authors: Strassmeier Klaus G.
Published: July 2007

Many of the interesting spotted stars are in close binaries where one can find almost any rotational period due to the rotational synchronization with the orbital motion. Binaries are thus good laboratories to study the impact of particular astrophysical parameters that nature usually does not make easily observable. On rapidly-rotating stars, we can indirectly resolve the surface by tomographic imaging techniques and map the surface temperature distribution as a proxy of the (predominantly radial) magnetic field. Binaries are not as straightforward to map as single stars and I will show some examples where it was successful and some where it failed. Eclipses may give some clues on the amount of unresolved features in the images. I present one case of a bright giant of 100L⊙ in a close binary with even a deformed surface geometry but otherwise solar-type behavior. One of the basic goals is to learn about the impact of inter-binary magnetic fields on the evolution of its components in general and to eventually provide conclusive constraints for numerical MHD models on the other hand.
Evidence for a Precessing Disk in the Extreme Binary ϵ Aurigae
Authors: Stencel Robert E.
Published: July 2007

Among the longest known eclipse durations and binary periods is that of the star ϵ Aurigae, which exhibits 2-year long eclipses every 27.1 years. Oddly, the nature of the secondary in the system continues to elude ready identification. In 1965, Huang proposed a massive disk as the eclipsing body, and study of the 1984 eclipse led Lissauer and Backman to suggest an embedded B star binary in the disk to maintain it. A collaboration of observers allows me to present recent optical photometry and spectroscopy, near-IR spectroscopy and Spitzer space telescope IRS and MIPS observations of ϵ Aurigae as it approaches its next eclipse. These data argue for current detectability of the embedded binary, and precession of the disk axis, suggesting a radical change is possible for the next mid-eclipse brightening. An international monitoring campaign for the 2009-2011 is being organized, and participation invited via website http://www.du.edu/~rstencel/epsaur.htm.
New Findings Supporting the Presence of Several Distinct Structures of Circumstellar Matter in β Lyræ
Authors: Chadima P. , Harmanec P. , Ak H , Demirçan O. , Yang S. , Koubský P. , Škoda P. , Šlechta M. , Wolf M. , Božić H. , Ruždjak D. , Sudar D.
Published: July 2007

(1) 52 photographic and 651 electronic spectra were disentangled using the program KOREL. This led to the detection of a number of weak absorption lines originating in the atmosphere of the accretion disk. So far, the detection of this disk spectrum was only reported for the Si 6347 and 6371 Å doublet. (2) The basic spectrophotometric quantities of 15 absorption lines of the primary were measured and corrected for the orbital light changes in order to eliminate the contribution of the secondary light to the observed continuum level. After the correction, a significant phase dependency of the spectral-line characteristics near the primary eclipse was detected. In all probability, another so far unknown absorption-line spectrum was thus found. This spectrum may be due to additional absorption of light of the primary in one of the jet-like structures and in the spherical gas envelope surrounding the accretion disk. Both these structures are seen projected against the primary during its eclipse.
TheKepler Missionand Eclipsing Binaries
Authors: Koch David , Borucki William , Basri Gibor , Brown Timothy , Caldwell Douglas , Christensen-Dalsgaard Jorgen , Cochran William , DeVore Edna , Dunham Edward , Gautier Thomas N. , Geary John , Gilliland Ronald , Gould Alan , Jenkins Jon , Kondo Yoji , Latham David , Lissauer Jack , Monet David
Published: July 2007

TheKepler Missionis a space-based photometric mission with a differential photometric precision of 14 ppm (atV= 12 for a 6.5 hour transit). It is designed to continuously observe a single field of view (FOV) of greater then 100 square degrees in the Cygnus-Lyra region for four or more years. The primary goal of the mission is to monitor more than one-hundred thousand stars for transits of Earth-size and smaller planets in the habitable zone of solar-like stars. In the process, many eclipsing binaries (EB) will also be detected and light curves produced. To enhance and optimize the mission results, the stellar characteristics for all the stars in theKeplerFOV withV< 16 will have been determined prior to launch. As part of the verification process, stars with transit candidates will have radial-velocity follow-up observations performed to determine the component masses and thereby separate eclipses caused by stellar companions from transits caused by planets. The result will be a rich database on EBs. The community will have access to the archive for further analysis, such as, for EB modeling of the high-precision light curves. A guest observer program is also planned to allow for photometric observations of objects not on the target list but within the FOV.
Multiplicity of Herbig Ae/Be Stars
Authors: Thomas Sandrine J. , van der Bliek Nicole S. , Rodgers Bernadette , Doppmann Greg , Bouvier Jérôme
Published: July 2007

One of the most interesting constraints on star formation models comes from the study of multiplicity of young stars as a function of mass. While multiplicity studies of low-mass T Tauri stars have been quite exhaustive, an unbiased and systematic investigation of multiplicity among intermediate-mass Herbig Ae/Be (HAEBE) stars is still lacking. We are therefore conducting a photometric and spectroscopic survey of HAEBE stars to detect companions, establish their physical association with the primary and investigate their properties. The frequency and degree of multiplicity of HAEBE systems will provide new constraints on their formation mechanisms. In this paper we present preliminary results of the high resolution imaging part of the survey, carried out with the adaptive optics system Altair-NIRI on Gemini North. Of 72 stars observed, we find 44 possible binaries or multiples, including at least 25 not previously known.
The Distance to the Pleiades Revisited
Authors: Valls-Gabaud David
Published: July 2007

The parallax of the Pleiades has been mired in controversy ever since the very first astrometric measures in the late 1880s. Over a century later, the measures from the HIPPARCOS catalogue gave results which were inconsistent with the distance inferred from the fitting of the colour-magnitude diagram. We briefly review here the debate and focus on the various attempts made at solving the problem, and especially those using binary stars. The only double-lined eclipsing binary found so far in the Pleiades, HD 23642, provides not only the final answer to the problem but also, through detailed state-of-the-art analyses, the fundamental calibration for binaries in more distant clusters and hence in the Local Group. We discuss some of the various sources of systematic uncertainties that limit, so far, the accuracy of the measured stellar parameters to about 1% and the progress that is required to break this barrier.
Young Binaries as a Test for Pre-Main Sequence Evolutionary Tracks
Authors: Zinnecker Hans
Published: July 2007

Observations of young low-mass binaries (t ≲ 107 yr, M ≲ 3 M_⊙) can be used to calibrate pre-Main Sequence (pre-MS) evolutionary tracks. Recent high angular resolution HST/FGS, speckle, and long-baseline interferometry have resolved the astrometric orbits of a few SB2 pre-MS binaries and have provided the individual dynamical masses of their components as well as the system orbital parallaxes. Spectroscopic fits and filter photometry have permitted to determine SpT (temperatures) and a good estimate of the absolute magnitude (bolometric luminosity) of the components, which in turn allows one to place the components on a theoretical HR-diagram. In this way, one can check (a) whether the measured dynamical masses agree with the predicted masses on the tracks and (b) whether both components lie on an isochrone, as they should for a coeval physical pair of stars.

With a sufficiently large sample of different masses and ages of resolved SB2 systems, most of the parameter space of pre-MS tracks can be tested, even for very low stellar masses (M < 0.5 M_⊙) and very young ages (< 2 Myr). This is a prerequisite in order to derive the IMF and star formation history in very young clusters and associations.
The Initial–Final Mass Relationship of White Dwarfs in Common Proper Motion Pairs and Open Clusters
Authors: Catalán S. , Ribas I. , Isern J. , García–Berro E. , Prieto C. Allende
Published: July 2007

We have studied white dwarfs in common proper motion pairs (CPMPs) to improve the semi-empirical initial–final mass relationship of white dwarfs. In this contribution, we report new results obtained from spectroscopic observations of both members of several CPMPs composed of an F, G or K type star and a DA white dwarf.
Closing Comments
Authors: Hartkopf William I.
Published: July 2007

So at last we come to the end of our meeting! I have the honor of being the last speaker at Symposium 240, and apparently the last speaker of the GA itself! I will keep my comments very brief, so that you all may experience a few more minutes of sightseeing or perhaps another fine Czech beer before beginning your travels home.
Modeling of very low frequency motions during RIPEX
Authors: Reniers A. J. H. M. , MacMahan J. H. , Thornton E. B. , Stanton T. P.
Published: July 2007

Numerical computations are used to explain the presence of very low frequency motions (VLFs), with frequencies less than 0.004 Hz, in the rip current velocity signals observed during the Rip‐current field Experiment (RIPEX) field experiment. Observations show that the VLF motions are most intense within the surfzone and then quickly taper off in the offshore direction. By comparing computed VLF intensity (URMS,vlf) distributions in both the cross‐shore and alongshore direction with observations in a qualitative sense, the most important contributions to the VLF dynamics are established. VLF motions at neighboring rip‐channels are seen to interact in the computations, with stronger surfzone intensity for increasing bathymetric variation. The intermittent forcing by spatially varying wave groups is essential in obtaining the correctURMS,vlfdistribution in the cross‐shore direction, suggesting this is the predominant mechanism responsible for the generation of the VLF motions observed during RIPEX. Computations also suggest that VLF motions can occasionally propagate offshore but are mostly confined to the surfzone corresponding to surfzone eddies. A quantitative comparison shows good correspondence between model computations and measurements ofURMS,vlfwith a model skill ofO(0.7), with generally increased (decreased)URMS,vlfduring mean low (high) water levels.
A systematic study of source time functions and moment tensors of intermediate and deep earthquakes
Authors: Tocheport A. , Rivera L. , Chevrot S.
Published: July 2007

We developed an inversion algorithm to determine the Source Time Function and Moment Tensor of intermediate and deep earthquakes from a set of teleseismic body wave records. The method proceeds in two stages. First, a nonlinear inversion by simulated annealing is performed to simultaneously (a) align the waveforms in time, (b) determine a common source time function, and (c) measure a collection of observed station amplitudes. The station amplitudes are then used, in a second stage, as secondary observables to invert for the moment tensors. We perform three different inversions to estimate the complete moment tensor solution, the pure deviatoric solution, and the double‐couple solution. All the calculations are extremely simple and, in particular, it is not necessary to compute synthetic seismograms. The method requires well‐isolated phases at different stations, which restricts its application to intermediate and deep events. The algorithm is applied to the FDSN broadband records corresponding to the period 1990–2005 of worldwide intermediate and deep seismicity (depth100 km) of magnitude greater than 6.5. The source time functions are compared to those obtained from other studies of intermediate and deep events. The moment tensors are also systematically compared to the Harvard‐CMT and USGS solutions. Both show a very good agreement with previous studies.
Retracted: Dependence of climate states of gray atmosphere on solar constant: From the runaway greenhouse to the snowball states
Authors: Ishiwatari M. , Nakajima K. , Takehiro S. , Hayashi Y.‐Y.
Published: July 2007

Multiple equilibrium solutions of a gray atmosphere are investigated for various values of the solar constant. Two types of models are utilized in order to conduct a comparative study: a general circulation model with simplified physical processes (GCM) and a one‐dimensional energy balance model (EBM). For intermediate values of solar constant, both of the models indicate the existence of multiple solutions that include the runaway greenhouse state in addition to the globally ice‐covered state and the partially ice‐covered state. In the GCM results, there is no partially ice‐covered state with the ice line latitude lower than 22°. This indicates that the large ice cap instability discussed in previous EBM studies also occurs in GCM. Compared to the results of EBM, the ice line of the partially ice‐covered state of GCM reaches lower latitudes. The appearance of the large ice cap instability in our GCM is impeded by condensation heating at the ice lines. The efficient latitudinal heat transport in the Hadley cell is considered to be a contributing factor to this delay in ice cap expansion.
Second‐generation operational algorithm: Retrieval of aerosol properties over land from inversion of Moderate Resolution Imaging Spectroradiometer spectral reflectance
Authors: Levy Robert C. , Remer Lorraine A. , Mattoo Shana , Vermote Eric F. , Kaufman Yoram J.
Published: July 2007

Since first light in early 2000, operational global quantitative retrievals of aerosol properties over land have been made from Moderate Resolution Imaging Spectroradiometer (MODIS) observed spectral reflectance. These products have been continuously evaluated and validated, and opportunities for improvements have been noted. We have replaced the surface reflectance assumptions, the set of aerosol model optical properties, and the aerosol lookup table (LUT). This second‐generation operational algorithm performs a simultaneous inversion of two visible (0.47 and 0.66 μm) and one shortwave‐IR (2.12 μm) channel, making use of the coarse aerosol information content contained in the 2.12 μm channel. Inversion of the three channels yields three nearly independent parameters, the aerosol optical depth (τ) at 0.55 μm, the nondust or fine weighting (η), and the surface reflectance at 2.12 μm. Retrievals of small‐magnitude negative τ values (down to −0.05) are considered valid, thus balancing the statistics of τ in near zero τ conditions. Preliminary validation of this algorithm shows much improved retrievals of τ, where the MODIS/Aerosol Robotic Network τ (at 0.55 μm) regression has an equation of: y = 1.01x + 0.03, R = 0.90. Global mean τ for the test bed is reduced from ∼0.28 to ∼0.21.
Riparian hydroecology: A coupled model of the observed interactions between groundwater flow and meadow vegetation patterning
Authors: Loheide Steven P. , Gorelick Steven M.
Published: July 2007

Stream incision is altering the hydroecology of riparian areas worldwide. In the Last Chance watershed in the northern Sierra Nevada, California, logging, overgrazing, and road/railroad construction have caused stream incision, which resulted in drainage of riparian meadow sediments and a succession from native wet meadow vegetation to sagebrush and dryland grasses. Restoration efforts have been initiated to reestablish the ecosystem function of these systems. Original field data including stream stage records, water table hydrographs, sediment hydraulic properties, topographic transects, and aerial imagery of vegetation patterning were used to develop a model of an archetype meadow. Hydrologic behavior was simulated with a finite element model of variably saturated groundwater flow. This model was coupled to an empirical, time‐dependent, vegetation threshold relationship between vegetation type and depth to the water table. This was a two‐way coupling requiring an iterative approach because water table depth is a determinant of vegetation type, yet the vegetation regime influences water table depth through evapotranspiration. The hydrology and vegetation patterns were analyzed under pristine, degraded (incised), and restored conditions. For the case of deep streambed incision, our hydroecological model predicts the observed shift from mesic (wetter) to xeric (drier) vegetation communities and reproduces their imaged longitudinal zonation. This patterning is explained as a response to groundwater drainage to the stream, which creates dry zones with xeric vegetation adjacent to the stream, while preserving sufficient moisture at the margins of the meadow to support holdout populations of mesic vegetation. The model further predicts the reestablishment of meadow vegetation when the incised channel is filled and a new shallow channel is restored. The coupling of a near‐surface hydrologic model to a vegetation response model may be used to design stream restoration projects by predicting vegetation patterning.
Calculating bed load transport in steep boulder bed channels
Authors: Yager E. M. , Kirchner J. W. , Dietrich W. E.
Published: July 2007

Steep, rough channels occupy a large fraction of the total channel length in mountainous regions. Most sediment mobilized on hillslopes must pass through these streams before reaching lower‐gradient channels. Steep channels have wide grain size distributions that are composed of finer, more mobile sediment and large, rarely mobile grains. The large grains can bear a significant portion of the total shear stress and thereby reduce the stress available to move the finer sediment. Conventional bed load transport equations often overpredict the sediment flux in steep channels by several orders of magnitude. We hypothesize that sediment transport equations overpredict the sediment flux because they do not (1) account for the stress borne by rarely mobile grains, (2) differentiate between highly and rarely mobile sediment, and (3) account for the limited availability of mobile sediment. Here we modify a conventional bed load transport equation to include these three effects. We use measurements of the flow, bed properties, and sediment flux in a small, steep flume to test this equation. We supply gravel at a constant rate through fields of regularly spaced immobile spheres and measure the bed coverage by gravel and sphere protrusion (the percent of the sphere that protrudes above the gravel deposit). For a given sphere spacing, the proportion of the bed covered by gravel increases and the sphere protrusion decreases with greater sediment supply. Thus bed coverage and immobile grain protrusion may serve as proxies for sediment availability in steep, rough streams. Unlike most transport equations that we tested, our modified bed load equation predicts sediment fluxes to within an order of magnitude of the measured values. Our results demonstrate that accurately predicting bed load transport in steep, rough streams may require accounting for the effects of local sediment availability (coverage by mobile sediment) and drag due to rarely mobile particles.
The 2006 aseismic slow slip event in Guerrero, Mexico: New results from GPS
Authors: Larson Kristine M. , Kostoglodov Vladimir , Miyazaki Shin'ichi , Santiago Jose Antonio Santiago
Published: July 2007

Crustal deformation measurements from Guerrero, Mexico were made with continuous GPS instrumentation. This network spans 75 km along the coast and a 275 km transect from the coast to Mexico City, which is perpendicular to the Middle America trench. A large aseismic slip transient occurred from April to December 2006, yielding horizontal displacements of nearly 6 cm in the direction opposite to that recorded interseismically. This transient slip episode closely follows a series of ∼M5 deep intraplate events that occurred in the northwestern portion of the Guerrero region. Both horizontal and vertical displacements are inverted for the Guerrero GPS network to determine slip along the subduction interface. Using a simple fault model that accommodates changes in the subduction zone geometry, it is found that slip is concentrated on interior fault patches, and propagated to the southeast. This slip event has a minimum equivalent Mw of 7.5.
Culture independent analysis of ileal mucosa reveals a selective increase in invasive Escherichia coli of novel phylogeny relative to depletion of Clostridiales in Crohn's disease involving the ileum
Authors: Baumgart Martin , Dogan Belgin , Rishniw Mark , Weitzman Gil , Bosworth Brian , Yantiss Rhonda , Orsi Renato H , Wiedmann Martin , McDonough Patrick , Kim Sung Guk , Berg Douglas , Schukken Ynte , Scherl Ellen , Simpson Kenneth W
Published: July 2007

Intestinal bacteria are implicated increasingly as a pivotal factor in the development of Crohn's disease, but the specific components of the complex polymicrobial enteric environment driving the inflammatory response are unresolved. This study addresses the role of the ileal mucosa-associated microflora in Crohn's disease. A combination of culture-independent analysis of bacterial diversity (16S rDNA library analysis, quantitative PCR and fluorescence in situ hybridization) and molecular characterization of cultured bacteria was used to examine the ileal mucosa-associated flora of patients with Crohn's disease involving the ileum (13), Crohn's disease restricted to the colon (CCD) (8) and healthy individuals (7). Analysis of 16S rDNA libraries constructed from ileal mucosa yielded nine clades that segregated according to their origin (P<0.0001). 16S rDNA libraries of ileitis mucosa were enriched in sequences for Escherichia coli (P<0.001), but relatively depleted in a subset of Clostridiales (P<0.05). PCR of mucosal DNA was negative for Mycobacterium avium subspecies paratuberculosis, Shigella and Listeria. The number of E. coli in situ correlated with the severity of ileal disease (ρ 0.621, P<0.001) and invasive E. coli was restricted to inflamed mucosa. E. coli strains isolated from the ileum were predominantly novel in phylogeny, displayed pathogen-like behavior in vitro and harbored chromosomal and episomal elements similar to those described in extraintestinal pathogenic E. coli and pathogenic Enterobacteriaceae. These data establish that dysbiosis of the ileal mucosa-associated flora correlates with an ileal Crohn's disease (ICD) phenotype, and raise the possibility that a selective increase in a novel group of invasive E. coli is involved in the etiopathogenesis to Crohn's disease involving the ileum.