bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear development of subsonic modes on compressible mixing layers: a unified strongly nonlinear critical-layer theory
Authors: SPARKS CLIFFORD A. , WU XUESONG
Published: October 2008

This paper is concerned with the nonlinear instability of compressible mixing layers in the regime of small to moderate values of Mach numberM, in which subsonic modes play a dominant role. At high Reynolds numbers of practical interest, previous studies have shown that the dominant nonlinear effect controlling the evolution of an instability wave comes from the so-called critical layer. In the incompressible limit (M= 0), the critical-layer dynamics are strongly nonlinear, with the nonlinearity being associated with the logarithmic singularity of the velocity fluctuation (Goldstein & Leib,J. Fluid Mech.vol. 191, 1988, p. 481). In contrast, in the fully compressible regime (M=O(1)), nonlinearity is associated with a simple-pole singularity in the temperature fluctuation and enters in a weakly nonlinear fashion (Goldstein & Leib,J. Fluid Mech.vol. 207, 1989, p. 73). In this paper, we first consider a weakly compressible regime, corresponding to the distinguished scalingM=O(ε1/4), for which the strongly nonlinear structure persists but is affected by compressibility at leading order (where ε ≪ 1 measures the magnitude of the instability mode). A strongly nonlinear system governing the development of the vorticity and temperature perturbation is derived. It is further noted that the strength of the pole singularity is controlled byT′c, the mean temperature gradient at the critical level, and for typical base-flow profilesT′cis small even whenM=O(1). By treatingT′cas an independent parameter ofO(ε1/2), we construct a composite strongly nonlinear theory, from which the weakly nonlinear result forM=O(1) can be derived as an appropriate limiting case. Thus the strongly nonlinear formulation is uniformly valid forO(1) Mach numbers. Numerical solutions show that this theory captures the vortex roll-up process, which remains the most prominent feature of compressible mixing-layer transition. The theory offers an effective tool for investigating the nonlinear instability of mixing layers at high Reynolds numbers.
Laminar-to-turbulent transition of pipe flows through puffs and slugs
Authors: NISHI MINA , ÜNSAL BÜLENT , DURST FRANZ , BISWAS GAUTAM
Published: October 2008

Laminar-to-turbulent transition of pipe flows occurs, for sufficiently high Reynolds numbers, in the form of slugs. These are initiated by disturbances in the entrance region of a pipe flow, and grow in length in the axial direction as they move downstream. Sequences of slugs merge at some distance from the pipe inlet to finally form the state of fully developed turbulent pipe flow. This formation process is generally known, but the randomness in time of naturally occurring slug formation does not permit detailed study of slug flows. For this reason, a special test facility was developed and built for detailed investigation of deterministically generated slugs in pipe flows. It is also employed to generate the puff flows at lower Reynolds numbers. The results reveal a high degree of reproducibility with which the triggering device is able to produce puffs. With increasing Reynolds number, ‘puff splitting’ is observed and the split puffs develop into slugs. Thereafter, the laminar-to-turbulent transition occurs in the same way as found for slug flows. The ring-type obstacle height, h, required to trigger fully developed laminar flows to form first slugs or puffs is determined to show its dependence on the Reynolds number, Re = DU/ν (where D is the pipe diameter, U is the mean velocity in the axial direction and ν is the kinematic viscosity of the fluid). When correctly normalized, h+ turns out to be independent of Reτ (where h+ = hUτ/ν, Reτ = DUτ/ν and $U_{\tau}\,{=}\,\sqrt{\tau_{w}/ \rho}$; τw is the wall shear stress and ρ is the density of the fluid).
The piecewise constant symmetric potential vorticity vortex in geophysical flows
Authors: VIÚDEZ ÁLVARO
Published: October 2008

The concept of piecewise constant symmetric vortex in the context of three-dimensional baroclinic balanced geophysical flows is explored. The pressure gradients generated by horizontal cylinders and spherical balls of uniform potential vorticity (PV), or uniform material invariants, are obtained either analytically or numerically, in the general case of Boussinesq andf-plane dynamics as well as under the quasi-geostrophic and semigeostrophic dynamical approximations. Based on the order of magnitude of the different terms in the PV inversion equation, approximated PV equations are deduced. In some of these cases, radial solutions are possible and the interior and exterior solutions are found analytically. In the case of non-radial dependence, exterior solutions can be found numerically. Linear, and upper and lower bound approximations to the full PV inversion equations, and their respective solutions, are also included. However, the general solution for the pressure gradient in the vortex exterior does not have spherical symmetry and remains as an important theoretical challenge. It is suggested that, in order to maintain everywhere the inertial and static stability of the balanced geophysical flows, small balls of finite radius, rather than PV singularities, could become, specially in numerical applications, useful mathematical objects.
The steady propagation of an air finger into a rectangular tube
Authors: DE LÓZAR ALBERTO , JUEL ANNE , HAZEL ANDREW L.
Published: October 2008

The steady propagation of an air finger into a fluid-filled tube of uniform rectangular cross-section is investigated. This paper is primarily focused on the influence of the aspect ratio, α, on the flow properties, but the effects of a transverse gravitational field are also considered. The three-dimensional interfacial problem is solved numerically using the object-oriented multi-physics finite-element library oomph-lib and the results agree with our previous experimental results (de Lózar et al. Phys. Rev. Lett. vol. 99, 2007, article 234501) to within the ±1% experimental error.

At a fixed capillary number Ca (ratio of viscous to surface-tension forces) the pressure drops across the finger tip and relative finger widths decrease with increasing α. The dependence of the wet fraction m (the relative quantity of liquid that remains on the tube walls after the propagation of the finger) is more complicated: m decreases with increasing α for low Ca but it increases with α at high Ca. Our results also indicate that the system is approximately quasi-two-dimensional for α ≥ 8, when we obtain quantitative agreement with McLean & Saffman's two-dimensional model for the relative finger width as a function of the governing parameter 1/B = 12α2Ca. The action of gravity causes an increase in the pressure drops, finger widths and wet fractions at fixed capillary number. In particular, when the Bond number (ratio of gravitational to surface-tension forces) is greater than one the finger lifts off the bottom wall of the tube leading to dramatic increases in the finger width and wet fraction at a given Ca.

For α ≥ 3 a previously unobserved flow regime has been identified in which a small recirculation flow is situated in front of the finger tip, shielding it from any contaminants in the flow. In addition, for α ≳ 2 the capillary number, Cac, above which global recirculation flows disappear has been observed to follow the simple empirical law: Cac2/3α = 1.21.
Vertical dispersion by stratified turbulence
Authors: LINDBORG E. , BRETHOUWER G.
Published: October 2008

We derive a relation for the growth of the mean square of vertical displacements, δz, of fluid particles of stratified turbulence. In the case of freely decaying turbulence, we find that for large times 〈δz2〉 goes to a constant value 2(EP(0) +aE(0))/N2, whereEP(0) andE(0) are the initial mean potential and total turbulent energy per unit mass, respectively,a< 1 andNis the Brunt–Väisälä frequency. In the case of stationary turbulence, we find that 〈δz2〉 = 〈δb2〉/N2+ 2εPt/N2, where εPis the mean dissipation of turbulent potential energy per unit mass and 〈δb2〉 is the Lagrangian structure function of normalized buoyancy fluctuations. The first term is the same as that obtained in the case of adiabatic fluid particle dispersion. This term goes to the finite limit 4EP/N2ast→ ∞. Assuming that the second term represents irreversible mixing, we show that the Osborn & Cox model for vertical diffusion is retained. In the case where the motion is dominated by a turbulent cascade with an eddy turnover timeT≫N−1, rather than linear gravity waves, we suggest that there is a range of time scales,t, betweenN−1andT, where 〈δb2〉 = 2πCPLεPt, whereCPLis a constant of the order of unity. This means that for such motion the ratio between the adiabatic and the diabatic mean-square displacement is universal and equal to πCPLin this range. Comparing this result with observations, we make the estimateCPL≈ 3.
Host choice and penetration bySchistosoma haematobiummiracidia
Authors: Allan F. , Rollinson D. , Smith J.E. , Dunn A.M.
Published: October 2008

Schistosome parasites commonly show specificity to their intermediate mollusc hosts and the degree of specificity can vary between parasite strains and geographical location. Here the role of miracidial behaviour in host specificity ofSchistosoma haematobiumon the islands of Zanzibar is investigated. In choice-chamber experiments,S. haematobiummiracidia moved towardsBulinus globosussnail hosts in preference to empty chambers. In addition, miracidia preferred uninfected over patentB. globosus. This preference should benefit the parasite as patent snails are likely to have mounted an immune response toS. haematobiumas well as providing poorer resources than uninfected snails. Miracidia also discriminated between the hostB. globosusand the sympatric, non-host speciesCleopatra ferruginea. In contrast,S. haematobiumdid not discriminate against the allopatricBulinus nasutus. Penetration of the host by miracidia was investigated by screening snails 24 h after exposure using polymerase chain reaction (PCR) withS. haematobiumspecificDraI repeat primers. There was no difference in the frequency of penetration ofB. globosusversusB. nasutus. These responses to different snail species may reflect selection pressure to avoid sympatric non-hosts which represent a transmission dead end. The distribution ofB. nasutuson Unguja is outside the endemic zone and so there is less chance of exposure toS. haematobium, hence there will be little selection pressure to avoid this non-host snail.
The effect of abiotic factors on the toxicity of cypermethrin against the snailLymnaea acuminatain the control of fascioliasis
Authors: Singh V. , Singh D.K.
Published: October 2008

Every month during the year 2006–2007, the 24, 48, 72 and 96 h LC50values of a molluscicide, cypermethrin, were determined for a snailLymnaea acuminata, with concomitant estimation of levels of temperature, pH, dissolved oxygen and carbon dioxide and electrical conductivity, both in control and test water. On the basis of a 24 h toxicity assay, it was noted that LC50values of 10.39, 10.90 and 11.19 mg l− 1during the months of May, June and July, respectively, were most effective in killing the snails, while the molluscicide was least effective in the month of January, when its 24 h LC50was 65.84 mg l− 1.There was a significant positive correlation between LC50of cypermethrin and levels of dissolved O2/pH of water in corresponding months. On the contrary, a negative correlation was observed between LC50and dissolved CO2/temperature of test water in the same months. In order to ascertain that such a relationship between toxicity and abiotic factors is not coincidental, the nervous tissue of the snail was assayed for the activity of acetylcholinesterase (AChE), acid phosphatase (ACP) and alkaline phosphatase (ALP) to sublethal concentrations (40% and 80%) of 24 h LC50during each of the 12 months of the same year. The findings confirmed that abiotic factors indeed influence toxicity of cypermethrin in the snail. A significant positive rank correlation between AChE, ACP and ALP activity did exist following exposure to the corresponding sublethal concentrations. Moreover, there was a maximum inhibition of 61.29 and 76.16% of AChE and ACP, respectively, in snails exposed to 80% of the 24 h LC50in the month of May. A similar treatment caused a maximum inhibition of 70.53% of ALP activity in the month of June. This work shows conclusively that the best time to control the snail population with cypermethrin is during the months of May and June.
Fish assemblages composition and structure in three shallow habitats in north Australian tropical bay, Garig Gunak Barlu National Park, Northern Territory, Australia
Authors: Gomelyuk Victor E.
Published: October 2008

The baited remote underwater video technique (BRUVS) was used to compare fish assemblages at three sites with different habitat characteristics: sandy bank (SB), rock reef (RR) and degraded coral reef (DCR) in Port Essington, Garig Gunak Barlu National Park, Northern Territory, Australia. The Carangidae family dominated, representing 35% of all recorded fish. The highest species number was recorded at RR followed by DCR and SB. The highest total fish number was recorded at DCR followed by SB and RR. Fish assemblages from all three sites are clearly different at high confidence level, but still overlapping and higher overlapping was found between SB and RR. Fish assemblages at all three studied sites contained some coral-associated species, fish fauna was less rich compared to coral reefs in the mouth of the bay and fish assemblages were noticeably different from typical coral fish communities. None of the fish assemblages at studied sites were presented by the ‘pure’, single habitat-associated association of species—at all three sites fish communities were a mixture of fish with various habitat preferences. Reef-associated species have a larger proportion at DCR and at RR their habitat complexity was higher; still soft-bottom habitat fish make substantial fractions in fish assemblages at both DCR and RR. Similarly, fish usually identified as ‘reef associated’ were found in notable proportions on SB. Fish with wide distribution and low selectivity in habitat preferences comprised a significant part in fish assemblages at all studied sites. In this study the BRUVS technique worked well in the area where diving visual surveys were impossible to implement because of high water turbidity. Another advantage of this method is the non-impact nature of visual survey; they can be used in long-term monitoring of fish assemblages at reference sites.
Illustrated key for the identification of brachyuran zoeal stages (Crustacea: Decapoda) in the plankton of Peter the Great Bay (Sea of Japan)
Authors: Kornienko Elena S. , Korn Olga M.
Published: October 2008

A dichotomous identification key for brachyuran zoeal stages from Peter the Great Bay (Russian waters of the Sea of Japan) is provided for the first time. The key covers 16 taxa identified to species level and uses only the most conspicuous external characters of larvae that are easy to observe under a stereomicroscope without specimens dissection. The key is based on the accounts by various authors and new original descriptions of larvae obtained both from plankton samples and from laboratory culture. Brief descriptions of larvae of 16 brachyuran species are also included.
Designing care environments for persons with Alzheimer's disease: visuoperceptual considerations
Authors: Jones Gemma MM , van der Eerden William J
Published: October 2008

This article provides information about the projected need for specialist dementia care environments in the United Kingdom. It summarizes the adverse effects of poorly designed environments and acknowledges that, despite a range of residential models, none has been shown or agreed to be the best. It considers current efforts in the UK that might influence future care environments positively.
Why There are No Ready-Made Phenomena: What Philosophers of Science Should Learn From Kant
Authors: Massimi Michela
Published: October 2008

The debate on scientific realism has raged among philosophers of science for decades. The scientific realist's claim that science aims to give us a literally true description of the way things are, has come under severe scrutiny and attack by Bas van Fraassen's constructive empiricism. All science aims at is to save the observable phenomena, according to van Fraassen. Scientific realists have faced since a main sceptical challenge: the burden is on them to prove that the entities postulated by our scientific theories are real and that science is still in the ‘truth’ business.
Arithmetic from Kant to Frege: Numbers, Pure Units, and the Limits of Conceptual Representation
Authors: Sutherland Daniel
Published: October 2008

There is evidence in Kant of the idea that concepts of particular numbers, such as the number 5, are derived from the representation of units, and in particular pure units, that is, units that are qualitatively indistinguishable. Frege, in contrast, rejects any attempt to derive concepts of number from the representation of units. In the Foundations of Arithmetic, he softens up his reader for his groundbreaking and unintuitive analysis of number by attacking alternative views, and he devotes the majority of this attack to the units view, with particular attention to pure units. Since Frege, the units view has been all but abandoned. Nevertheless, the idea that concepts of number are derived from the representation of units has a long history, beginning with the ancient Greeks, and was prevalent among Frege's contemporaries. I am not interested in resurrecting the units view or in righting wrongs in Frege's criticisms of his contemporaries. Rather, I am interested in the program of deriving concepts of number from pure units and its history from Kant to Frege. An examination of that history helps us understand the units view in a way that Frege's criticisms do not, and in the process uncovers important features of both Kant's and Frege's views. I will argue that, although they had deep differences, Kant and Frege share assumptions about what such a view would require and about the limits of conceptual representation. I will also argue that they would have rejected the accounts given by some of Frege's contemporaries for the same reasons. Despite these agreements, however, there is evidence that Kant thinks that space and time play a role in overcoming the limitations of conceptual representation, while Frege argues that they do not.
Intuition and Infinity: A Kantian Theme with Echoes in the Foundations of Mathematics
Authors: Posy Carl
Published: October 2008

Kant says patently conflicting things about infinity and our grasp of it. Infinite space is a good case in point. In his solution to the First Antinomy, he denies that we can grasp the spatial universe as infinite, and therefore that this universe can be infinite; while in the Aesthetic he says just the opposite: ‘Space is represented as a given infinite magnitude’(A25/B39). And he rests these upon consistently opposite grounds. In the Antinomy we are told that we can have no intuitive grasp of an infinite space, and in the Aesthetic he says that our grasp of infinite space is precisely intuitive.
Order out of chaos? The English gender change in the Southwest Midlands as a process of semantically based reorganization
Authors: STENROOS MERJA
Published: October 2008

The article presents a study of the process of gender change in the thirteenth-century Southwest Midlands, based on twenty texts localized in this area. The assumption is that a study limited to a single text community would give a better view of the patterns of change than studies spanning a wide chronological and/or geographical range. It is suggested that the system of pronominal gender assignment went through a process of semantically based reorganization during this period, and that the resulting patterns are most usefully described using the model of a hierarchy or continuum of individuation (Dahl 1999a: 99; Siemund 2008: 140). The gender assignment of individual nouns is found to be remarkably regular, and the material seems to give no reason to assume a period of confusion between the Old and postmedieval English systems of gender assignment.
A Two-Level Approach to Morphological Structure
Authors: Wiese Richard
Published: October 2008

In morphological theory, various models have been developed with respect to the appropriate levels of abstraction for stating morphological generalizations. This paper addresses a class of seemingly marginal and/or problematic phenomena in morphology and proposes that morphological descriptions regularly refer to two distinct levels of description. One is the level of “morphosyntax,” and one is the level of “morphophonology.” Furthermore, morphology is considered to be marginal if and only if the degree of isomorphy between representations on these two levels is reduced. This basic proposal is illustrated and tested with several central phenomena of morphology found in German: synthetic compounds, conversion, empty morphs, and trun-cation. The analysis proposed here argues for the necessity of a two-level model of morphology as an approach in which both abstract morphosyntax as well as more concrete morphophonology have a place.*
Sur les collapses de corps différentiels colorés en caractéristique nulle décrits par Poizat à l'aide des amalgames à la Hrushovski
Authors: Blossier T. , Martin-Pizarro A.
Published: October 2008

Nous collapsons le corps différentielrougede Poizat en des corps différentiellement clos de rang de Morley ω·2, chacun muni d'un sous-groupe additif définissable de rang ω. En utilisant la dérivée logarithmique, on obtient un corpsvertde rang ω·2 avec un sous-groupe multiplicatif définissable divisible contenant le corps des constantes, qui reste définissable dans le réduit à la structure de corps vert.
Changing Abundances, Changing Opacities
Authors: Ferguson Jason W. , Dotter Aaron
Published: October 2008

With ever changing solar abundances being reported the equation of state and opacities needed for stellar evolution models also change. A discussion of those changes in mean molecular opacities will be presented with a discussion on the effect on evolution models. Aside from changing the abundances of the base mixture the enrichment changes too. Traditionally mean opacity tables are produced for oxygen-rich mixtures, however stars will often become carbon-rich. A discussion of carbon-rich opacities tables will also be presented.
Some discussion of the nonlocal treatment of the dissipation in the Reynolds stress models
Authors: Cai Tao
Published: October 2008

We investigate the weakness of the present turbulence model with the nonlocal treatment of dissipation rate. A revised version is well tested for the solar convection. The suggestion of constant mixing length parameter of MLT could not hold any more if we refer to the nonlocal description of the dissipation rate, especially in the region of overshooting zone.
Thermohaline Convection in Main Sequence Stars
Authors: Vauclair S.
Published: October 2008

Thermohaline convection is a well known subject in oceanography, which has long been put aside in stellar physics. In the ocean, it occurs when warm salted layers sit on top of cool and less salted ones. Then the salted water rapidly diffuses downwards even in the presence of stabilizing temperature gradients, due to double diffusion between the falling blobs and their surroundings. A similar process may occur in stars in case of inverse μ-gradients in a thermally stabilized medium. Here we describe this process and some of its stellar applications.
Observations of clusters with ages from 0.01 to 1.0 Gyr in the Large Magellanic Cloud
Authors: Liu Q. , de Grijs R. , Deng L. C. , Hu Y. , Baraffe I.
Published: October 2008

The stellar initial mass function (IMF) is a very important question in modern astrophysics. Globular clusters (GCs) are good samples for studying the IMF, but the Galactic GCs can provide only one time-scale evolutionary stage. The Large Magellanic Cloud (LMC) is an ideal environment for studying the IMF because it contains compact clusters at different evolutionary stages. By studying the IMF at different evolutionary stages, we can see how the mass function evolves with time.
Low-Mass Extremely Metal-Poor Stellar Models: Yields, Uncertainties and the Galactic Halo Stars
Authors: Campbell Simon W. , Lattanzio J. C.
Published: October 2008

We have calculated a set of low-mass (0.85 M⊙ ≤ M ≤ 3.0 M⊙) zero metallicity and extremely metal-poor (−6.5 ≤ [Fe/H] ≤ −3.0) stellar models, including nucleosynthetic yields for 74 species. As far as we are aware these are the first detailed yields in the mass and metallicity range considered. Due to the difficulty in modelling such stars the yields naturally contain numerous uncertainties, and thus present interesting challenges for future stellar modelling. We briefly present some results in the context of the Galactic Halo star observations, and also discuss qualitatively some of the uncertainties in the modelling. We conclude by suggesting that much work is still necessary in this research area. For example, multidimensional fluid dynamics models are needed to simulate the violent proton ingestion events that occur during the core He flash and early TPAGB, observations and theory of mass loss at low metallicities are needed, the effects of reaction rate uncertainties need to be quantified, and low temperature opacities variable in carbon (and nitrogen) need to be included in the models.
A New, Efficient Stellar Evolution Code for Calculating Complete Evolutionary Tracks
Authors: Kovetz A. , Yaron O. , Prialnik D.
Published: October 2008

We report on the development of a new stellar evolution code, and provide a taste of results, showing its capability to calculate full evolutionary tracks for a wide range of masses and metalicities. The code is fast and efficient, and is capable of following through all evolutionary phases, including core/shell flashes and thermal pulses, without any interruption or intervention. It is meant to be used also in the context of modeling the evolution of dense stellar systems, for performing live calculations for both ‘normal’ ZAMS/PRE-MS models, but mainly for ‘non-canonical’ stellar configurations (i.e. merger-products). We show a few examples of evolutionary calculations for stellar populations I and II, and for masses in the range 0.25–64 M⊙.
Surface convection in Population II stars
Authors: Piau Laurent , Stein Robert F.
Published: October 2008

The initial surface abundances of Population II stars have been altered by the interplay between convection, rotational mixing and diffusion. In particular the shallower the outer convection zone the stronger the diffusion impact. We present preliminary results on constraining the extension of the convection zones of Population II stars thanks to 3D hydrodynamical simulations.
The Rotation of the Solar Radiative zone
Authors: Turck-Chieze S.
Published: October 2008

Dynamical processes are progressively introduced in stellar evolution. In this framework, the Sun is a very specific case where both models and observations have been developed in parallel during the last decade in order to progress on our present insight of solar like stars. In this poster I show the recent progress done on both sides for the rotation of the radiative zone. The present knowledge of the solar rotation profile comes from the detection of acoustic and gravity modes with the instruments GOLF and MDI aboard SoHO. In parallel we study the sensitivity of the theoretical rotation profiles obtained with the CESAM code using different rotation history in the premainsequence.
Mass loss and evolution of hot massive stars
Authors: Vink Jorick S.
Published: October 2008

We discuss the role of mass loss for the evolution of the most massive stars, highlighting the role of the predicted bi-stability jump that might be relevant for the evolution of rotational velocities during or just after the main sequence. This mechanism is also proposed as an explanation for the mass-loss variations seen in the winds from Luminous Blue Variables (LBVs). These might be relevant for the quasi-sinusoidal modulations seen in a number of recent transitional supernovae (SNe), as well as for the double-throughed absorption profile recently discovered in the Hα line of SN 2005gj. Finally, we discuss the role of metallicity via the Z-dependent character of their winds, during both the initial and final (Wolf-Rayet) phases of evolution, with implications for the angular momentum evolution of the progenitor stars of long gamma-ray bursts (GRBs).
Stellar evolution models with mass loss and turbulence
Authors: Vick M. , Michaud G. , Richard O.
Published: October 2008

Although chemical separation is generally accepted as the main physical process responsible for the anomalous surface abundances of AmFm stars, its exact behavior within the interior of these stars is still uncertain. We will explore two hydrodynamical processes which could compete with atomic diffusion: mass loss and turbulence. We will also discuss the extent to which separation occurs immediately below the surface convection zone as well as the extent to which separation occurs below 200,000 K. To do so, self-consistent stellar models with mass loss and turbulence where calculated using the Montreal stellar evolution code and compared to observations of A and F stars. It is shown that to the precision of observations available for F stars, a mass loss rate of 2×10−14M⊙· yr−1, is compatible with observations and that no turbulence is then required.
The most massive AGB stars
Authors: Siess Lionel
Published: October 2008

The general properties of stars in the mass range 7–12M⊙, also referred to assuper-AGBstars, are reviewed and special attention is paid to determine how their mass range depends on the initial metallicity and what fraction of these stars end their life as ONe white dwarfs or explode as electron-capture supernova.
Around the Pair Instability Valley – Massive SN Progenitors
Authors: Waldman Roni
Published: October 2008

The discovery of the extremely luminous supernova SN 2006gy, possibly interpreted as a pair instability supernova, renewed the interest in very massive stars. We explore the evolution of these objects, which end their life as pair instability supernovae or as core collapse supernovae with relatively massive iron cores, up to about 3 M⊙.
Stellar radii from long-baseline interferometry
Authors: Kervella Pierre
Published: October 2008

Long baseline interferometers now measure the angular diameters of nearby stars with sub-percent accuracy. They can be translated in photospheric radii when the parallax is known, thus creating a novel and powerful constraint for stellar models. I present applications of interferometric radius measurements to the modeling of main sequence stars. Over the last few years, we obtained accurate measurements of the linear radius of many of the nearest stars: Procyon A, 61 Cyg A & B, α Cen A & B, Sirius A, Proxima. . . Firstly, I describe the example of our modeling of Procyon A (F5IV-V) with the CESAM code, constrained using spectrophotometry, the linear radius, and asteroseismic frequencies. I also present our recent results on the low-mass 61 Cyg system (K5V+K7V), for which asteroseismic frequencies have not been detected yet.
SONG – Stellar Observations Network Group
Authors: Grundahl Frank , Christensen-Dalsgaard J. , Kjeldsen H. , Frandsen S. , Arentoft T. , Kjaergaard P. , Jørgensen U. G.
Published: October 2008

Several areas of stellar observations depend critically on nearly continuous observations of individual objects over very extended periods. Important examples are investigations of stellar oscillations to carry out asteroseismology, and the search for extra-solar planets. To meet this requirement we are establishing the SONG network, consisting of 8 sites with a 1-meter-class telescope with a suitable geographical distribution. These will be optimized for asteroseismology based on Doppler-velocity observations and the characterization of extra-solar planets with photometry, using gravitational microlensing. Funding has been obtained towards the construction of the prototype SONG telescope which will be set up on Tenerife, with first light expected in 2011. The full network will be established in parallel with the tests of the prototype and is planned to be operational in 2014.
Linkages within institutional structure: an empirical analysis of water institutions
Authors: SALETH R. MARIA , DINAR ARIEL
Published: October 2008

Taking water institutions as an illustrative context, this paper attempts a quantitative analysis of the structural and functional linkages within institutional structure and indicates their performance implications and strategic importance for promoting institutional reforms. Against an overview of existing empirical works on institutions in general and water institutions in particular, the paper develops an analytical framework for specifying alternative models of institution–performance interaction within the water sector under different assumptions concerning institutional linkages and their structural properties. These models are, then, empirically estimated using the perception-based information provided by an international panel of 127 water experts from 43 countries and regions around the world. Based on the model results, the paper offers quantitative evidences for institutional linkages and their performance implications, and concludes by indicating their policy roles, especially in developing some reform design and implementation principles useful to overcome the technical and political economy constraints for institutional reforms.
Nasir ad-Din Tusi on social cooperation and the division of labor: Fragment from The Nasirean Ethics
Authors: SUN GUANG-ZHEN
Published: October 2008

Nasir ad-Din Tusi's (born 1201 in Tus in northeastern Persia; died 1274 in Baghdad), has been far more influential for his various contributions to astronomy and mathematics, including founding the Maraghah observatory (in Iranian Azerbaijan) and his brilliant reformulations of the Ptolemaic planetary model, which served as an important inspiration for Nicolaus Copernicus (1473–1543) revolutionary work than for anything else. Nonetheless, he also stands as one major figure in the medieval Islamic philosophical ethics and a profound thinker on socio-economic matters, as is attested by his masterpiece Akhlāq-i Nāsirī (The Nasirean Ethics – titled after his first name), from which the following Fragment is taken. He may be deservingly credited as an important pioneer of the science of political economy.
Awards
Authors: Frey Bruno S. , Neckermann Susanne
Published: October 2008

Awards in the form of orders, decorations, prizes, and titles are ubiquitous in monarchies and republics, private organizations, not-for-profit, and profit-oriented firms. This paper argues that awards present a unique combination of different stimuli and that they are distinct and unlike other monetary and nonmonetary rewards. Despite their relevance in all areas of life, awards have not received much scientific attention. Employing a unique data set, we demonstrate that there are substantial differences in the frequency of awards across countries. Moreover, we present the results of a vignette experiment that quantifies and isolates the effects of different award characteristics such as the publicity associated with winning an award.
Image Effects of Newspapers
Authors: Fichter Christian , Jonas Klaus
Published: October 2008

Brand image is supposed to influence consumers’ product evaluations. The goal of this study was to enlighten this phenomenon. A total of 220 participants rated fictitious but realistic articles from newspapers that have different images: Blick, a popular tabloid newspaper and NZZ, a traditional quality newspaper. Articles were created that appeared as if they were copied from Blick or NZZ but, in fact, both contained the same text. The main hypothesis that product ratings would differ as a result of the manipulation of image was confirmed. Participants evaluated the fictitious articles completely differently. As expected, product ratings were in line with the related brand images. Also, more salient stimuli elicited stronger image effects. The effect persisted at general as well as detailed product-rating levels. Next to product ratings, image effects also influenced participants’ consumption experiences. Involvement, knowledge, and usage did not moderate the image effect.
Anxiety, Inhibition, Efficiency, and Effectiveness
Authors: Derakshan Nazanin , Ansari Tahereh L. , Hansard Miles , Shoker Leor , Eysenck Michael W.
Published: October 2008

Effects of anxiety on the antisaccade task were assessed. Performance effectiveness on this task (indexed by error rate) reflects a conflict between volitional and reflexive responses resolved by inhibitory processes (Hutton, S. B., & Ettinger, U. (2006). The antisaccade task as a research tool in psychopathology: A critical review. Psychophysiology, 43, 302–313). However, latency of the first correct saccade reflects processing efficiency (relationship between performance effectiveness and use of resources). In two experiments, high-anxious participants had longer correct antisaccade latencies than low-anxious participants and this effect was greater with threatening cues than positive or neutral ones. The high- and low-anxious groups did not differ in terms of error rate in the antisaccade task. No group differences were found in terms of latency or error rate in the prosaccade task. These results indicate that anxiety affects performance efficiency but not performance effectiveness. The findings are interpreted within the context of attentional control theory (Eysenck, M. W., Derakshan, N., Santos, R., & Calvo, M. G. (2007). Anxiety and cognitive performance: Attentional control theory. Emotion, 7 (2), 336–353).
Seasonal variability of the Labrador Current and shelf circulation off Newfoundland
Authors: Han Guoqi , Lu Zhaoshi , Wang Zeliang , Helbig James , Chen Nancy , de Young Brad
Published: October 2008

Three‐dimensional finite element models were established for the Newfoundland and Labrador Shelf to investigate climatological monthly mean wind‐ and density‐driven circulation. The model was forced using wind stresses from the National Center for Environmental Prediction‐National Center for Atmospheric Research reanalysis data prescribed at the sea surface, large‐scale remote forcing determined from a North Atlantic model, monthly mean temperature and salinity climatology, and M2 tide on the open boundary. The model results were examined against various in situ observations (moored current meter, tide gauge, and vessel‐mounted acoustic Doppler current profiler data) and satellite drift measurements and discussed together with literature information. The seasonal mean circulation solutions were investigated in terms of relative importance of wind to density forcing for the Labrador Current. The model results indicate significant seasonal and spatial variations, consistent generally with previous study results and in approximate agreement with observations for the major currents. The region is dominated by the equatorward flowing Labrador Current along the shelf edge and along the Labrador and Newfoundland coasts. The Labrador Current is strong in the fall/winter and weak in the spring/summer. The mean transport of the shelf edge Labrador Current is 7.5 Sv at the Seal Island transect and 5.5 Sv through the Flemish Pass. The seasonal ranges are 4.5 and 5.2 Sv at the two sections, respectively. Density‐ and wind‐driven components are both important in the inshore Labrador Current. The density‐driven component dominates the mean component of the shelf edge Labrador Current while the large‐scale wind‐forcing contributes significantly to its seasonal variability.
Detection of surface emission hot spots, trends, and seasonal cycle from satellite‐retrieved NO2 over India
Authors: Ghude Sachin D. , Fadnavis S. , Beig G. , Polade S. D. , van der A R. J.
Published: October 2008

Tropospheric NO2 concentrations derived from spaceborne measurements of Global Ozone Monitoring Experiment (GOME) on board ERS 2 and Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) on board Envisat, respectively, for the time period of 1996–2006 have been used to identify major NO2 emission hot spots, trends, and seasonal cycle over different regions of India. Emission hot spots are observed over the locations of thermal power plants and over major urban and industrial regions. A multifunctional regression model has been used to analyze the trends and seasonal cycle over these emission hot spots. Increasing trends of ∼1.65 ± 0.52% a−1 have been observed for NO2 over India. The fast growing industrial regions of Mumbai and Delhi show increasing trends of ∼2.1 ± 1.1 and ∼2.4 ± 1.2% a−1, respectively. Seasonal variations of tropospheric NO2 concentrations show a maximum during winter‐summer (December–May) and a minimum during the monsoon seasons (June–September). The observed seasonal cycle in satellite‐derived NO2 agrees well with the surface‐level observations of NOX.
Ten years of multiwavelength Raman lidar observations of free‐tropospheric aerosol layers over central Europe: Geometrical properties and annual cycle
Authors: Mattis I. , Müller D. , Ansmann A. , Wandinger U. , Preißler J. , Seifert P. , Tesche M.
Published: October 2008

We present geometrical properties and seasonal variations of appearance of aerosol particle pollution in the free troposphere over the central European lidar site at Leipzig, Germany. The data set has been acquired with Raman lidar in the past 10 years in the framework of the German Lidar Network (1997–2000) and since 2000 in the framework of the European Aerosol Research Lidar Network (EARLINET). In summary we analyzed 1028 measurements. Geometrical depth of the pollution layers was ≤1 km in 33% of all cases. Geometrical depths >5 km were found in 10% of all cases. Traces of particle pollution were detected up to the height of the tropopause. Forest‐fire burning in North America causes intrusion of particles into the stratosphere. Seven hundred seventeen of all observations were carried out on the basis of a regular measurement schedule which allows us to establish a statistic on the frequency of particle transport in the free troposphere. In 43% of the regular measurements we observed pollution above the continental boundary layer. The lofted particle layers largely result from intercontinental long‐range transport. We use backward trajectory analysis to identify the main source regions of the lofted pollution layers. In 19% of all regular measurements, free‐tropospheric pollution was advected from North America. Forest‐fire smoke from Canada and anthropogenic pollution from urban areas of the United States of America and Canada were the sources of the particle layers. We find a strong seasonal dependence of occurrence of these layers with a peak in June–August of each year. In a few cases we observed forest‐fire smoke advected from Siberia and east Asia with winds from westerly directions. Pollution advected from areas north of 70°N presents another transport channel. That pollution consists of Arctic haze or mixtures of haze with anthropogenic pollution. The main occurrence of such particle layers is around springtime of each year. Import of mineral dust from the Sahara represents another transport path. Most of such cases are observed during late springtime and summertime. Free‐tropospheric pollution advected from east and southeast Europe and Russia presents one transport channel from within the Euro‐Asian continent.
A global evaluation of the regional spatial variability of column integrated CO2 distributions
Authors: Alkhaled Alanood A. , Michalak Anna M. , Kawa S. Randolph , Olsen Seth C. , Wang Jih‐Wang
Published: October 2008

Satellites, such as the Orbiting Carbon Observatory (OCO), are expected to provide global measurements of column‐averaged carbon dioxide (CO2) dry‐air mole fraction (XCO2) with the potential of improving the scientific understanding of regional carbon cycle processes and budgets. The satellite data products, however, are expected to have large data gaps due to the satellite track and geophysical limitations (e.g., clouds and aerosols). The satellite data will also be representative of the XCO2 distribution at the spatial scale of satellite footprints, which is smaller than the resolution of typical transport or process models. Assessing the ability of the retrieved soundings to capture XCO2 variability over different regions and times, evaluating the representation error associated with using the retrieved XCO2 product to represent XCO2 at typical model resolutions, and filling data gaps while providing an estimate of the associated uncertainty all require the evaluation of the spatial variability of XCO2. In this study, the global spatial covariance structure of XCO2 is evaluated regionally using CO2 concentrations simulated using the MATCH/CASA model. Results show that regional and temporal changes in the XCO2 distribution caused by seasonal changes in surface fluxes and transport produce a spatially and temporally variable XCO2 covariance structure. The effects of model setup and the relatively low resolution of the MATCH/CASA model on the evaluated XCO2 covariance structure are assessed by comparing the MATCH/CASA results to the spatial variability inferred from the higher‐resolution PCTM/GEOS‐4 global model, the SiB‐RAMS regional model, and aircraft campaign point observations. The comparison with the higher‐resolution models and aircraft data shows good agreement with MATCH/CASA results, thus indicating that the presented results provide an adequate representation of XCO2 variability as will be measured by satellites such as OCO.
Photochemical production of hydroxyl radical and hydroperoxides in water extracts of nascent marine aerosols produced by bursting bubbles from Sargasso seawater
Authors: Zhou Xianliang , Davis Andrew J. , Kieber David J. , Keene William C. , Maben John R. , Maring Hal , Dahl Elizabeth E. , Izaguirre Miguel A. , Sander Rolf , Smoydzyn Linda
Published: October 2008

Marine aerosols produced by bursting bubbles at the ocean surface are highly enriched in organic matter (OM) relative to seawater. The importance of this OM in the photochemical evolution of marine aerosols, particularly as a source of reactive oxidants, is unknown but likely significant. To investigate oxidant production, nascent aerosols were generated by bubbling zero air through flowing Sargasso seawater and photochemical production of OH radical and hydroperoxide were quantified in aqueous aerosol extracts exposed to solar radiation. Extrapolation to ambient conditions indicates that OM photolysis was the primary in situ source for both OH (1.1 × 10−8 M s−1) and hydroperoxides (1.7 × 10−8 M s−1) in nascent aerosols; NO3− photolysis was the primary source in aged, acidified aerosols (1.4 × 10−7 and 4.1 × 10−8 M s−1, respectively). In situ OH photoproduction was comparable to gas‐phase uptake whereas H2O2 photoproduction was slower. Results provide important constraints for poorly quantified oxidant sources in marine aerosols.
Phase coherence analysis of a field line resonance and solar wind oscillation
Authors: Fenrich F. R. , Waters C. L.
Published: October 2008

Discrete field line resonances (FLRs) are a common occurrence in the magnetosphere. However, the source of the stable, discrete FLR frequencies is still an unresolved problem. Recent work has proposed that discrete, continuous oscillations in the solar wind directly drive magnetospheric FLRs. However, these studies have only concentrated on common frequency and amplitude comparisons. This paper presents a new technique which utilizes either Fast Fourier Transform or wavelet cross‐phase measurements to demonstrate a high degree of phase coherence between a 1.7 mHz FLR observed with the SuperDARN Kodiak radar and ACE SWE oscillations in solar wind plasma density. A statistical analysis which simulates the solar wind as red noise indicates with 99% confidence that the FLR oscillation is the same as the solar wind plasma density variation.