bluuebunny/crossref_metadata_2025 huggingface dataset:
Alkaline dyeing of polyester and polyester/cotton blend fabrics using sodium edetate
Authors: Youssef Y. A. , Ahmed Nahed S. E. , Mousa A. A. , El‐Shishtawy Reda M.
Published: December 2007

An alkaline dyeing of polyester with an alkali‐stable disperse dye, Dianix® Scarlet AD‐RG, was developed using sodium edetate as an alkaline buffering agent. The results obtained indicate the suitability of using sodium edetate for alkaline dyeing of polyester when compared with the control alkaline dyeing using Dianix AD system. Selected mono and bifunctional reactive dyes were used in combination with the alkali‐stable disperse dye for dyeing of polyester/cotton blend. Different dyeing methods for cotton and polyester/cotton blend fabrics using sodium edetate were evaluated in comparison with their respective control alkaline dyeing methods. The results of using sodium edetate in one‐bath two‐stage and two‐bath dyeing of polyester/cotton blend were comparable with that of the control dyeing method. Particularly, no change in the leveling and fastness properties was evaluated for all samples irrespective of the dyeing method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Fe(acac)3‐bis(imino)pyridine/MAO: A new catalytic system for ethylene polymerization
Authors: Wang Lincai , Ren Hua , Sun Junquan
Published: December 2007

New catalytic systems, composed of bis(imino)pyridine (2,6‐bis[1‐(2,6‐diisopropylphenylimino)ethyl]pyridine (A1), methylene‐bridged bis(imino)pyridine (A2)), iron (III) acetylacetonate (Fe(acac)3), and methylaluminoxane (MAO), are highly active for ethylene polymerization. The performance of this new catalytic system was evaluated with respect to catalytic activity and polymer properties. The highest catalytic activity of Fe(acac)3‐A1/MAO (catA) system and Fe(acac)3‐A2/MAO (catB) system at optimum condition reaches 10.5 × 106 g PE·(mol Fe h)−1 and 17.3 × 106 g PE·(mol Fe h)−1, respectively. The product viscosity‐average molecular weight (Mη) of two catalytic systems range from 0.40 to 8.7 × 105. GPC characterizations of PE obtained show that the PE has bimodal molecular weight distribution (MWD). 13C NMR and DSC analysis of PE sample indicates that the PE is highly linear and crystalline. Analysis of UV–vis absorption spectra, ethylene polymerization results, and prepared polyethylene structures indicate that Fe(acac)3‐bis(imino)pyridine/MAO catalytic system could generate same active species as bis(imino)pyridyliron catalytic systems. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Lanthanide Coordination Polymers Constructed from Infinite Rod‐Shaped Secondary Building Units and Flexible Ligands
Authors: Lü Jian , Bi Wen‐Hua , Xiao Fu‐Xian , Batten Stuart R. , Cao Rong
Published: December 2007

Three lanthanide coordination polymers constructed from infinite rod‐shaped secondary building units (SBUs), [Nd2(H2O)2(cis‐chdc)2(trans‐chdc)]⋅2H2O (1), Nd2(H2O)4(trans‐chdc)3 (2), and [Sm2(H2O)2(cis‐chdc)(trans‐chdc)2]⋅4H2O (3) (chdcH2=1,4‐cyclohexanedicarboxylic acid), were hydrothermally synthesized and structurally characterized. The structures of 1–3 are modulated by different ratios of the cis and trans configurations of chdc2− ligands, which was achieved by temperature control in the hydrothermal reactions. Crystal‐structure analysis revealed that 1 is a four‐connected pcu‐type rod packing network built from cross‐linking of rod‐shaped neodymium–oxygen SBUs by cis‐ and trans‐chdc2− ligands in a 2:1 ratio, 2 displays a complicated six‐connected hex‐type rod packing structure built by connection of rod‐shaped neodymium–oxygen SBUs and trans‐chdc2− ligands, and 3 features an unprecedented five‐connected rod packing pattern constructed from rod‐shaped samarium–oxygen SBUs and cis‐ and trans‐chdc2− ligands in a 1:2 ratio.
Are solar cycles predictable?
Authors: Schüssler M.
Published: December 2007

Various methods (or recipes) have been proposed to predict future solar activity levels – with mixed success. Among these, some precursor methods based upon quantities determined around or a few years before solar minimum have provided rather high correlations with the strength of the following cycles. Recently, data assimilation with an advection‐dominated (flux‐transport) dynamo model has been proposed as a predictive tool, yielding remarkably high correlation coefficients. After discussing the potential implications of these results and the criticism that has been raised, we study the possible physical origin(s) of the predictive skill provided by precursor and other methods. It is found that the combination of the overlap of solar cycles and their amplitude‐dependent rise time (Waldmeier's rule) introduces correlations in the sunspot number (or area) record, which account for the predictive skill of many precursor methods. This explanation requires no direct physical relation between the precursor quantity and the dynamo mechanism (in the sense of the Babcock‐Leighton scheme or otherwise). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rotating convection in f‐boxes: Faster rotation
Authors: Chan K. L.
Published: December 2007

Results based on 36 cases of f‐box computations for different latitudes and rotation rates are summarized. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Changing stellar activity cycles
Authors: Oláh K. , Strassmeier K.G. , Granzer T. , Soon W. , Baliunas S.L.
Published: December 2007

We investigated continuous long‐term photometric datasets of thirteen active stars, Ca II variability of one single mainsequence star, and 10.7 cm radio data of the Sun, with simple Fourier‐ and time‐frequency analysis. The data reflect the strength of the activity manifested in magnetic spots. All studied stars show multiple (2 to 4) cycles of different lengths. The time‐frequency analysis reveals, that in several cases of the sample one or two of the cycles exhibit continuous changes (increase or decrease). For four stars (V711 Tau, IL Hya, HK Lac, HD 100180) and for the Sun we find that the cycle length changes are strong, amounting to 10–50% during the observed time intervals. The cycle lengths are generally longer for stars with longer rotational periods. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Meridional circulation in the radiation zones of rotating stars: Origins, behaviors and consequences on stellar evolution
Authors: Mathis S. , Decressin T. , Palacios A. , Eggenberger P. , Siess L. , Talon S. , Charbonnel C. , Turck‐Chièze S. , Zahn J.‐P.
Published: December 2007

Stellar radiation zones are the seat of meridional currents. This circulation has a strong impact on the transport of angular momentum and the mixing of chemicals that modify the evolution of stars. First, we recall in details the dynamical processes that are taking place in differentially rotating stellar radiation zones and the assumptions which are adopted for their modelling in stellar evolution. Then, we present our new results of numerical simulations which allow us to follow in 2D the secular hydrodynamics of rotating stars, assuming that anisotropic turbulence enforces a shellular rotation law and taking into account the transport of angular momentum by internal gravity waves. The different behaviors of the meridional circulation in function of the type of stars which is studied are discussed with their physical origin and their consequences on the transport of angular momentum and of chemicals. Finally, we show how this work is leading to a dynamical vision of the evolution of rotating stars from their birth to their death. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rapid rotation, active nests of convection and global‐scale flows in solar‐likestars
Authors: Brown B.P. , Browning M.K. , Brun A.S. , Miesch M.S. , Toomre J.
Published: December 2007

In the solar convection zone, rotation couples with intensely turbulent convection to build global‐scale flows of differential rotation and meridional circulation. Our sun must have rotated more rapidly in its past, as is suggested by observations of many rapidly rotating young solar‐type stars. Here we explore the effects of more rapid rotation on the patterns of convection in such stars and the global‐scale flows which are self‐consistently established. The convection in these systems is richly time dependent and in our most rapidly rotating suns a striking pattern of spatially localized convection emerges. Convection near the equator in these systems is dominated by one or two patches of locally enhanced convection, with nearly quiescent streaming flow in between at the highest rotation rates. These active nests of convection maintain a strong differential rotation despite their small size. The structure of differential rotation is similar in all of our more rapidly rotating suns, with fast equators and slower poles. We find that the total shear in differential rotation, as measured by latitudinal angular velocity contrast, ΔΩ, increases with more rapid rotation while the relative shear, ΔΩ/Ω, decreases. In contrast, at more rapid rotation the meridional circulations decrease in both energy and peak velocities and break into multiple cells of circulation in both radius and latitude. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rotating ‘star‐in‐a‐box’ experiments
Authors: Steffen M. , Freytag B.
Published: December 2007

Using the radiation hydrodynamics code CO5BOLD in its ‘star‐in‐a‐box’ setup, we have performed exploratory simulations of global convection in a rotating reference frame. The goal is to study the interaction of convection and rotation by direct numerical simulation. For these first experiments, we chose an idealized configuration (a scaled‐down, fast rotating Sun) whose properties resemble those of red supergiants in some respect. We describe the setup and time evolution of these models, and discuss the particular problems we have encountered. Finally, we derive the resulting differential rotation pattern and meridional flow field by temporal and azimuthal averaging of the simulation data. We find anti‐solar differential rotation for all cases studied so far. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Does the Sun have a face?
Authors: Tuominen I. , Pelt J. , Brooke J. , Korpi M.
Published: December 2007

We analyse the Greenwich sunspot data with methods using kinematic frames, which allow to detect and filter off any systematic motion, such as differential rotation, of the longitudinal activity traces. The aim is to check the recent claim of the existence of century‐scale persistent solar active longitudes exhibiting antisolar differential rotation. As a result, we find no evidence for such features. Nevertheless, as is well known, the sunspot distribution is highly clustered in longitude (activity nests); the simple cell‐counting statistics allows us to estimate the coherence time of these features, giving roughly10 Carrington rotations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear simulations of magnetic instabilities in stellar radiation zones: The role of rotation and shear
Authors: Brun A.S.
Published: December 2007

Using the 3‐dimensional ASH code, we have studied numerically the instabilities that occur in stellar radiation zones in presence of large‐scale magnetic fields, rotation and large‐scale shear. We confirm that some configurations are linearly unstable, as predicted by Tayler and collaborators, and we determine the saturation level of the instability. We find that rotation modifies the peak of the most unstable wave number of the poloidal instability but not its growth rate as much as in the case of the m = 1 toroidal instability for which it is changed to σ = $ \sigma^2_{\rm A} $/Ω. Further in the case with rotation and shear, we found no sign of the dynamo mechanism suggested recently by Spruit even though we possess the essential ingredients (Tayler's m = 1 instability and a large scale shear) supposedly at work. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐kinematic flux‐transport dynamos with variable meridional flow
Authors: Rempel M.
Published: December 2007

A single counter clockwise flow cell is the assumption underlying most flux‐transport dynamo models to date. On the other hand, global 3D simulations of the solar convection zone byMiesch et al. indicate that the meridional flow is strongly variable and shows at a given time a multi‐cellular flow structure, with only the long term average reflecting a more regular flow field. We investigate the influence of such a highly time variable meridional flow on a flux‐transport dynamo model. In our model the differential rotation and meridional flow are driven self‐consistently through a parameterization of the Reynolds‐stress (Λ‐effect) and also macroscopic Lorentz‐force feedback is considered. We achieve the time variable flow by adding random fluctuations with a given correlation time and length scale to both components of the turbulent angular momentum flux. We find that a significant amount of random fluctuations can be tolerated before the dynamo loses its coherence, provided that the correlation time scale of the random component is significantly shorter than the cycle length. Stronger constraints on the amplitude of random fluctuations come from helioseismic constraints on the variability of differential rotation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling the differential rotation of F stars
Authors: Küker M. , Rüdiger G.
Published: December 2007

We model stellar differential rotation based on the mean‐field theory of fluid dynamics. DR is mainly driven by Reynolds stress, which is anisotropic and has a non‐diffusive component because the Coriolis force affects the convection pattern. Likewise, the convective heat transport is not strictly radial but slightly tilted towards the rotation axis, causing the polar caps to be slightly warmer than the equator. This drives a flow opposite to that caused by differential rotation and so allows the system to avoid the Taylor‐Proudman state. Our model reproduces the rotation pattern in the solar convection zone and allows predictions for other stars with outer convection zones. The surface shear turns out to depend mainly on the spectral type and only weakly on the rotation rate. We present results for stars of spectral type F which show signs of very strong differential rotation in some cases. Stars just below the mass limit for outer convection zones have shallow convection zones with short convective turnover times. We find solar‐type rotation and meridional flow patterns at much shorter rotation periods and horizontal shear much larger than on the solar surface, in agreement with recent observations. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simulation of turbulent convection in a slowly rotating red giant star
Authors: Palacios A. , Brun A.S.
Published: December 2007

The first 3‐D non‐linear hydrodynamical simulation of the inner convective envelope of a rotating low mass red giant star is presented. This simulation, computed with the ASH code, aims at understanding the redistribution of angular momentum and heat in extended convection zones. The convection patterns achieved in the simulation consist of few broad and warm upflows surrounded by a network of cool downflows. This asymmetry between up and downflows leads to a strong downward kinetic energy flux, that must be compensated by an overluminous enthalpy flux in order to carry outward the total luminosity of the star. The influence of rotation on turbulent convection results in the establishment of largescale mean flows: a strong radial differential rotation and a single cell poleward meridional circulation per hemisphere. A detailed analysis of angular momentum redistribution reveals that the meridional circulation transports angular momentum outward in the radial direction and poleward in the latitudinal direction, with the Reynolds stresses acting in the opposite direction. This simulation indicates that the classical hypothesis of mixing length theory and solid‐body rotation in the envelope of red giants assumed in 1‐D stellar evolution models are unlikely to be realized and thus should be reconsidered. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Force‐free magnetic fields in the solar atmosphere
Authors: Seehafer N. , Fuhrmann M. , Valori G. , Kliem B.
Published: December 2007

Reliable measurements of the solar magnetic field are restricted to the level of the photosphere. For about half a century attempts have been made to calculate the field in the layers above the photosphere, i.e. in the chromosphere and in the corona, from the measured photospheric field. The procedure is known as magnetic field extrapolation. In the superphotospheric parts of active regions the magnetic field is approximately force‐free, i.e. electric currents are aligned with the magnetic field. The practical application to solar active regions has been largely confined to constant‐αor linear force‐free fields, with a spatially constant ratio,α, between the electric current and the magnetic field. We review results obtained from extrapolations with constant‐αforce‐free fields, in particular on magnetic topologies favourable for flares and on magnetic and current helicities. Presently, different methods are being developed to calculate non‐constant‐αor nonlinear force‐free fields from photospheric vector magnetograms. We also briefly discuss these methods and present a comparison of a linear and a nonlinear force‐free magnetic field extrapolation applied to the same photospheric boundary data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stability of toroidal magnetic fields in the solar tachocline and beneath
Authors: Kitchatinov L.L. , Rüdiger G.
Published: December 2007

Stability of toroidal magnetic field in a stellar radiation zone is considered for the cases of uniform and differential rotation. In the rigidly rotating radiative core shortly below the tachocline, the critical magnetic field for instability is about 600 G. The unstable disturbances for slightly supercritical fields have short radial scales ∼1 Mm. Radial mixing produced by the instability is estimated to conclude that the internal field of the sun can exceed the critical value of 600 G only marginally. Otherwise, the mixing is too strong and not compatible with the observed lithium abundance. Analysis of joint instability of differential rotation and toroidal field leads to the conclusion that axisymmetric models of the laminar solar tachocline are stable to nonaxisymmetric disturbances. The question of whether sun‐like stars can posses tachoclines is addressed with positive answer for stars with rotation periods shorter than about two months. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analytical theory of tachocline transport at mid latitudes
Authors: Leprovost N. , Kim E.‐J.
Published: December 2007

We provide a theory of magnetic diffusion, momentum transport, and mixing in the solar tachocline by considering magnetohydrodynamics (MHD) turbulence on a β plane subject to a large scale shear (provided by the latitudinal differential rotation). In the strong magnetic field regime, we find that the turbulent viscosity and diffusivity are reduced by magnetic fields only, similarly to the two‐dimensional MHD case (without Rossby waves). In the weak magnetic field regime, we find a crossover scale (LR) from a Alfvén dominated regime (on small scales) to a Rossby dominated regime (on large scales). For parameter values typical of the tachocline, LR is larger than the solar radius so that Rossby waves are unlikely to play an important role in the transport of magnetic field and angular momentum. This is mainly due to the enhancement of magnetic back‐reaction by shearing which efficiently generates small scales, thus strong currents. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy distribution in nonaxisymmetric magnetic Taylor‐Couette flow
Authors: Gellert M. , Rüdiger G. , Fournier A.
Published: December 2007

Azimuthal magnetorotational instability is a mechanism that generates nonaxisymmetric field pattern. Nonlinear simulations in an infinite Taylor‐Couette system with current‐free external field show, that not only the linearly unstable mode m = 1 appears, but also an inverse cascade transporting energy into the axisymmetric field is possible. By varying the Reynolds number of the flow and the Hartmann number for the magnetic field, we find that the ratio between axisymmetric (m = 0) and dominating nonaxisymmetric mode (m = 1) can be nearly free chosen. On the surface of the outer cylinder this mode distribution appears similarly, but with weaker axisymmetric fields.We do not find significant differences in the case that a constant current within the flow is added. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rotation of the magnetic elements in polar regions on the Sun
Authors: Benevolenskaya E.E.
Published: December 2007

Using the Michelson Doppler Imager (MDI) data from Solar and Heliospheric Observatory (SOHO), the rotation rate of the unipolar magnetic regions in North high‐latitude regions of the Sun is estimated by tracking individual magnetic elements. The analysis reveals a strong spin down near the pole, which is greater than the Doppler and magnetic rotation rates estimated by Snodgrass & Ulrich (1990), and rotation rate inferred from helioseismology (Birch & Kosovichev 1998), and is probably related to variation of velocity gradient in the subsurface shear layer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Looking inside the butterfly diagram
Authors: Ternullo M.
Published: December 2007

The suitability of Maunder's butterfly diagram to give a realistic picture of the photospheric magnetic flux large scale distribution is discussed. The evolution of the sunspot zone in cycle 20 through 23 is described. To reduce the noise which covers any structure in the diagram, a smoothing algorithm has been applied to the sunspot data. This operation has eliminated any short period fluctuation, and given visibility to long duration phenomena. One of these phenomena is the fact that the equatorward drift of the spot zone center of mass results from the alternation of several prograde (namely, equatorward) segments with other stationary or poleward segments. The long duration of the stationary/retrograde phases as well as the similarities among the spot zone alternating paths in the cycles under examination prevent us from considering these features as meaningless fluctuations, randomly superimposed on the continuous equatorward migration. On the contrary, these features should be considered physically meaningful phenomena, requiring adequate explanations. Moreover, even the smoothed spotted area markedly oscillates. The compared examination of area and spot zone evolution allows us to infer details about the spotted area distribution inside the butterfly diagram. Links between the changing structure of the spot zone and the tachocline rotation rate oscillations are proposed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Differential rotation of giant stars
Authors: Weber M.
Published: December 2007

From a set of high‐resolution spectral observations of late type giant stars we used Doppler imaging to derive time‐series temperature maps of the stellar surfaces. Using these temperature maps, it is possible to track the temporal changes of the spot features and derive estimates of the strength and sign of the differential surface rotation of these stars. Looking into the latitudinal changes of the surface maps, it is also possible to derive meridional flows on these stars. But due to the lower accuracy of the latitudes of the reconstructed spot features, the data requirements are higher than for the detection of differential rotation. Nevertheless, a correlation between the differential rotation and meridional flow estimates is suggested. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Rapid differential rotation in intermediate mass stars
Authors: Toque N. , Deupree R.G. , Gillich A. , Lovekin C.C.
Published: December 2007

ZAMS models with internal differential rotation are computed for 6.5 M⊙ and 10 M⊙ models with the 2D evolution code ROTORC. Two applications of these models, their pulsational frequencies and deduced locations in the HR diagram, are discussed in order to show how the internal differential rotation could be investigated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultra‐cool and extra‐vigorous: Rotation and activity in Mand L dwarfs
Authors: Reiners A.
Published: December 2007

The study of rotation and activity in low‐mass stars or brown dwarfs of spectral classes M and L has seen enormous progress during the last years. I summarize the results from different works that measured activity, rotation, and sometimes magnetic fields. The generation of magnetic activity seems to be unchanged at the threshold to completely convective stars, i.e. no change in the efficiency of the magnetic dynamos is observed. On the other hand, a sudden change in the strength of rotational braking appears at the threshold mass to full convection, and strong evidence exists for rotational braking weakening with lower mass. A probable explanation is that the field topology changes from dipolar to small scale structure as the objects become fully convective. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Starspots and relativity: Applied Doppler imaging for the Gravity Probe B mission
Authors: Marsden S.C. , Berdyugina S.V. , Donati J.‐F. , Eaton J.A. , Williamson M.H.
Published: December 2007

We present Doppler images and surface differential rotation measurements for the primary of the RS CVn binary IM Pegasi, the guide star for the Gravity Probe B experiment. The data used is a subset of that taken during optical support of the mission and was obtained almost nightly over a near three year period from the Automatic Spectroscopic Telescope operated by Tennessee State University. Using the technique of least‐squares deconvolution to increase the signal‐to‐noise ratio of the data, we have reconstructed 31 maximum entropy Doppler images of the star. The images show that the spot features are relatively stable for over a year (and possibly longer) with both a polar spot and lower latitude features. The most intense features are located on the side facing the secondary. In addition, we have incorporated a solar‐like differential rotation law into the imaging process to determine the level of surface differential rotation for IM Peg for 22 epochs. A weighted least‐squares average of the measurements gives a surface shear of 0.0142 ± 0.0007 rad/d, meaning that the equator takes ∼440 ± 20 days to lap the poles. Although the level of surface differential rotation was shown to vary over the period of the observations, this may indicate an underestimate in the errors of the method rather than any temporal evolution in the differential rotation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface velocity network with anti‐solar differential rotation on the activeK‐giant σ Geminorum
Authors: Kőovári Zs. , Bartus J. , Švanda M. , Vida K. , Strassmeier K.G. , Oláh K. , Forgács‐Dajka E.
Published: December 2007

We demonstrate the power of the local correlation tracking technique on stellar data for the first time. We recover the spot migration pattern of the long‐period RS CVn‐type binary σ Gem from a set of six Doppler images from 3.6 consecutive rotation cycles. The resulting surface flow map suggests a weak anti‐solar differential rotation with α ≈ –0.0022 ± 0.0016, and a coherent poleward spot migration with an average velocity of 220 ± 10ms‐1. This result agrees with our recent findings from another study and could also be confirmed theoretically. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Flux‐dominated solar dynamo model with a thin shear layer
Authors: Guerrero G. A. , de Gouveia Dal Pino E. M.
Published: December 2007

Flux‐dominated solar dynamo models have demonstrated to reproduce the main features of the large scale solar magnetic cycle, however the use of a solar like differential rotation profile implies in the the formation of strong toroidal magnetic fields at high latitudes where they are not observed. In this work, we invoke the hypothesis of a thin‐width tachocline in order to confine the high‐latitude toroidal magnetic fields to a small area below the overshoot layer, thus avoiding its influence on a Babcock‐Leighton type dynamo process. Our results favor a dynamo operating inside the convection zone with a tachocline that essentially works as a storage region when it coincides with the overshoot layer. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evidence for weak magnetic fields in early‐type emission stars
Authors: Hubrig S. , Yudin R. V. , Pogodin M. , Schöller M. , Peters G. J.
Published: December 2007

We report the results of our study of magnetic fields in a sample of 15 Be stars using spectropolarimetric data obtained at the European Southern Observatory with the multi‐mode instrument FORS 1 installed at the 8m Kueyen telescope. We detect weak photospheric magnetic fields in four stars, HD56014, HD148184, HD155806, and HD181615. We note that for HD181615 the evolutionary status is not obvious due to the fact that it is a binary system currently observed in the initial rapid phase of mass exchange between the two components. Further, we notify the possible presence of distinct circular polarisation features in the circumstellar components of Ca II H&K in three stars, HD58011, HD117357, and HD181615, hinting at a probable presence of magnetic fields in the circumstellar mass loss disks of these stars. We emphasize the need for future spectropolarimetric observations of Be stars with detected magnetic fields to study the temporal evolution of their magnetic fields and the correlation of magnetic field properties with dynamical phenomena taking place in the gaseous circumstellar disks of these stars. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Line profile variability of OB stars: Pulsation, rotation, clumps and magnetic fields
Authors: Kholtygin A.F. , Fabrika S.N. , Chountonov G.A. , Burlakova T.E. , Valyavin G.G. , Kang Dong‐il
Published: December 2007

The variability of line profiles in spectra of bright OB stars has been studied.We obtain more than 1000 high quality spectra of δ Ori A, λ Ori A, α Cam, 19 Cep, ι Her, ρ Leo and other target stars. We revealed the line profile microvariability of small amplitude (0.5–3% in the adjacent continuum units) for all observed stars. For most stars only cyclic components of the line profile variability (LPV) at the time scales from hours to days were detected. These components seem to be connected with both the non‐radial pulsations (NRP) and rotation line profile modulation. In the spectra of δ Ori A and λ Ori A we found the evidences of the stochastic LPV in spectra, probably connected with the small clumps in the stellar wind. On the basis of recent observations we discuss the origin of the magnetic field of early‐type stars. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Differential rotation on rapidly rotating stars
Authors: Collier Cameron A.
Published: December 2007

Theories of meridional circulation and differential rotation in stellar convective zones predict trends in surface flow patterns on main‐sequence stars that are amenable to direct observational testing. Here I summarise progress made in the last few years in determining surface differential rotation patterns on rapidly‐rotating young main‐sequence stars of spectral types F, G, K and M. Differential rotation increases strongly with increasing effective temperature along the main sequence. The shear rate appears to increase with depth in the sub‐photospheric layers. Tidal locking in close binaries appears to suppress differential rotation, but better statistics are needed before this conclusion can be trusted. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The helicity constraint in spherical shell dynamos
Authors: Brandenburg A. , Käpylä P. J. , Mitra D. , Moss D. , Tavakol R.
Published: December 2007

The motivation for considering distributed large scale dynamos in the solar context is reviewed in connection with the magnetic helicity constraint. Preliminary accounts of 3‐dimensional direct numerical simulations (in spherical shell segments) and simulations of 2‐dimensional mean field models (in spherical shells) are presented. Interesting similarities as well as some differences are noted. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Predicting solar ‘climate’ by assimilating magnetic data into a flux‐transport dynamo
Authors: Dikpati M.
Published: December 2007

Observational and theoretical knowledge about global‐scale solar dynamo ingredients have reached the stage that it is possible to calibrate a flux‐transport dynamo for the Sun by adjusting only a few tunable parameters. The important ingredients in this class of model are differential rotation (Omega‐effect), helical turbulence (alpha‐effect), meridional circulation and turbulent diffusion. The meridional circulation works as a conveyor belt and governs the dynamo cycle period. Meridional circulation and magnetic diffusivity together govern the memory of the Sun's past magnetic fields. After describing the physical processes involved in a flux‐transport dynamo, we will show that a predictive tool can be built from it to predict mean solar cycle features by assimilating magnetic field data from previous cycles. We will discuss the theoretical and observational connections among various predictors, such as dynamo‐generated toroidal flux integral, cross‐equatorial flux, polar fields and geomagnetic indices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamo action in the presence of an imposed magnetic field
Authors: Featherstone N.A. , Browning M.K. , Brun A.S. , Toomre J.
Published: December 2007

Dynamo action within the cores of Ap stars may offer intriguing possibilities for understanding the persistent magnetic fields observed on the surfaces of these stars. Deep within the cores of Ap stars, the coupling of convection with rotation likely yields magnetic dynamo action, generating strong magnetic fields. However, the surface fields of the magnetic Ap stars are generally thought to be of primordial origin. Recent numerical models suggest that a primordial field in the radiative envelope may possess a highly twisted toroidal shape. We have used detailed 3‐D simulations to study the interaction of such a twisted magnetic field in the radiative envelope with the core‐dynamo operating in the interior of a 2 solar mass A‐type star. The resulting dynamo action is much more vigorous than in the absence of such a fossil field, yielding magnetic field strengths (of order 100 kG) much higher than their equipartition values relative to the convective velocities. We examine the generation of these fields, as well as the growth of large‐scale magnetic structure that results from imposing a fossil magnetic field. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Raumakustische Gestaltung von Umgebungen zum Darbieten, Aufnehmen und Wiedergeben von Sprache und Musik
Authors: Fuchs Helmut V.
Published: December 2007

Es wird ein Konzept zur akustischen Gestaltung von Räumen für anspruchsvolle musikalische und verbale Nutzungen vorgestellt. Es sorgt dafür, dass die Klangergebnisse der akustisch Aktiven für diese gut durchhörbar werden. Dies ermöglicht ihnen eine beträchtliche Absenkung der mittleren Schalldruckpegel im Raum und damit eine Erweiterung der erreichbaren Dynamik alles Dargebotenen und somit eine Steigerung ihrer Darstellungskraft ohne besondere Anstrengungen. Musikern und Sängern, aber auch Dienstleistern in ihren Orchestern, Chören und Service‐Centern wird so ihre oft sehr schwere Arbeit erleichtert und ihr häufig unzulässig belastetes Gehör geschützt. Wenn aber die ergonomischen Umgebungsbedingungen aufgewertet werden, wachsen Wohlbefinden und Motivation und führen zu besserer Qualität der Arbeitsergebnisse, höherer Produktivität, langsamerer Ermüdung und weniger Krankmeldungen. Die elektroakustisch Aktiven finden in derart konditionierten Räumen ebenfalls beste Aufnahme‐ und Beschallungsbedingungen vor. Sie müssen dann nicht mit einer Vielzahl von Mikrofonen bzw. Lautsprechern die akustischen Unzulänglichkeiten des Raumes zu kompensieren versuchen. Aber auch die akustisch passiven Zuhörer und Konsumenten von Live‐Darbietungen bzw. von Klangkonserven können von einer verbesserten Akustik profitieren, indirekt von derjenigen des Aufnahme‐ und direkt von derjenigen des Wiedergaberaumes. Dazu bedarf es keiner neuen raumakustischen Kriterien oder besonderer baulicher Vorkehrungen: Der Schlüssel für eine nachhaltige Aufwertung der raumakustischen Bedingungen liegt vor Allem in einer zu tiefen Frequenzen hin möglichst nicht oder nur wenig ansteigenden Nachhallzeit. Auf dem Weg zu einer das gesamte Hörspektrum des Menschen erfassenden Akustik für alle kommunikationsintensiv genutzten Räume haben sich breitbandig hochwirksame Schallabsorber bewährt, die sich ohne weiteres in den zeitgemäßen Innenausbau integrieren lassen. Die Bedeutung aller anderen raumakustischen Parameter, die traditionell bevorzugt bei mittleren und hohen Frequenzen gemessen und beurteilt werden, bleibt dabei uneingeschränkt erhalten und kann erklären, warum große und berühmte Konzertsäle mit zu tiefen Frequenzen ansteigendem Nachhall das Auditorium im Saal und die Akteure auf der Bühne durch ihre außerordentliche “Akustik” überzeugen können. Der Autor ist aber überzeugt, dass eine (bisher nicht übliche) Bedämpfung des Bassbereiches die Schallübertragung zwischen mehreren Quellen und zu den Empfängern im Raum verbessert – eine durch praktische Erfahrung gewachsene These, die nicht durch die konventionelle Messung und Beurteilung nur bei höheren Frequenzen widerlegt wird.
Optimierung des Einflusses von Latentspeichermaterial auf das thermische Verhalten von Gebäuden
Authors: Hu Jingfang , Dreyer Jürgen
Published: December 2007

Ziel der vorliegenden Arbeit ist es, den Einsatz von Phase Change Materials (PCM) bezeichnet, in Gebäuden zu untersuchen. Im Rahmen der Arbeit wurde ein Simulationsprogramm für die Planung und Optimierung des Einsatzes von PCM im Gebäude entwickelt. Dieses Programm ermöglicht es, das thermische Verhalten eines Gebäudes unter Einsatz von Latentspeichermaterial zu bestimmen. Experimentelle Untersuchungen wurden am Messobjekt mit und ohne Einsatz von PCM durchgeführt, um einerseits die temperaturstabilisierende Wirkung durch den Einsatz von PCM festzustellen, und andererseits als Grundlage, um das entwickelte Rechenprogramm zu validieren. Die Ergebnisse aus der Messung und der Berechnung lassen den Schluss zu, dass das entwickelte Programm das thermische Verhalten eines Raumes genau beschreibt. Mit dem entwickelten Rechenmodell wurde die PCM‐Anwendung im Gebäude optimiert. Anhand eines Raummodells wurden wichtige Einflussparameter untersucht, wie die Einsatzmenge und die Phasenwechseltemperatur von PCM, die Luftwechselrate eines Raumes und die Lüftungsgeschwindigkeit der Hinterlüftung der PCM‐Schicht. Es stellt sich dabei heraus, dass die optimale Ausnutzung der PCM den optimalen Wert der untersuchten Einflussparameter entscheidet.
Schallschutz von Bauteilen aus mineralischen Baustoffen in Abhängigkeit von der Abbindezeit
Authors: Sälzer Elmar , Maack Jürgen , Kühn Herbert
Published: December 2007

Bei Bauteilen, die aus mineralischen Baustoffen hergestellt werden, z. B. Decken und Wände aus Mauerwerk oder Beton, Estriche, Hohlraumböden, ist zu vermuten, dass sich die schallschutztechnischen Eigenschaften sowohl bei der Trittschalldämmung als auch bei der Luftschalldämmung in Abhängigkeit vom Zeitraum nach der Erstellung verändern. Zum einen nimmt bekanntlich die Festigkeit durch den Abbindeprozess zu, während gleichzeitig aber die Masse durch den Austrocknungsprozess abnimmt. Im Beitrag wird beschrieben, wie sich die Schalldämmung exemplarisch untersuchter Bauteile in Abhängigkeit vom Abbindezeitraum/Austrocknungszeitraum verhält und welche Zeiträume ausreichend sind, um mit einer akzeptablen Genauigkeit den nach 28 Tagen erreichbaren Zustand zu erfassen.
Der Einfluss natürlich durchströmter Doppelfassaden auf die Strahlungsbelastung
Authors: Weier Hubert
Published: December 2007

Erkenntnisse über Strömungs‐ und Wärmetransportvorgänge in natürlich durchlüfteten zweischaligen Fassaden liegen bisher im wesentlichen als Erfahrungsberichte von ausgeführten Fassaden vor. Die zu beschreibenden Verhältnisse werden als so komplex und so kompliziert angesehen, dass man annimmt, ihre Berechnung führt nur auf dem Wege der Simulation zu vertretbaren Ergebnissen. Dabei ist eine analytische Betrachtung dieser Vorgänge analog zur Petzold schen Betrachtung durchströmter Außenbauwerksteile durchaus möglich. Das Verfahren setzt voraus, dass Transmissions‐, Reflexions‐ und Absorptionsgrade (Übertragungsgrade) der Gläser bekannt sind. Mit dem Gesamt‐Energiedurchlassgrad (g‐Wert) als Berechnungsgröße kann eine Näherungslösung bestimmt werden. Deren Ergebnisse liegen stets über den mit Übertragungsgraden berechneten und damit auf der sicheren Seite, wenn man sie als Grundlage für das Auslegen von Anlagen benötigt. Strömungs‐ und Temperaturverhältnisse in der Fassade stimmen dagegen nahezu mit den Werten überein, die mit Übertragungsgraden ermittelt werden.
Untersuchungen zur immissions‐ und geruchsreduzierenden Eigenschaft von zeolithehaltigen Gipsbaustoffen
Authors: Hummel Hans‐Ulrich , Krämer Georg , Scherer Christian , Mair Stefan , Breuer Klaus , Sedlbauer Klaus
Published: December 2007

Emissionen an flüchtigen organischen Stoffen (VOC) aus Bauprodukten werden zunehmend kritisch bewertet. In Deutschland wurde dazu das AgBB‐Schema entwickelt, das die Vorgehensweise bei der gesundheitlichen Bewertung der Emissionen von flüchtigen organischen Verbindungen aus Bauprodukten beschreibt und heute die wesentliche Basis für Anforderungen an die raumlufthygienischen Eigenschaften von Bauprodukten ist. Im Beitrag werden die Untersuchungen an Gipsplatten mit Zeolithe vorgestellt.
Prüfkörperabdichtung und der Wasserabsorptionskoeffizient von mit Polypropylenfasern modifizierten Zementmörteln
Authors: Garbalińska Halina , Wygocka Agata
Published: December 2007

In diesem Artikel werden die Ergebnisse von Untersuchungen zum kapillaren Aufsaugen von Wasser in Zementmörteln dargestellt, die nach 18 verschiedenen Rezepturen auf der Basis natürlichen Quarzsandes 0 bis 2 mm hergestellt wurden. Die einzelnen Mörtel unterschieden sich durch zwei verschiedene Zementarten und zwei verschiedene Wasser‐Zement‐Werte w/z. Es wurden reiner Portlandzement CEM I 42,5 R mit w/z = 0,55 und Portlandflugaschezement CEM II/B‐V 32,5 R mit w/z = 0,55 und mit w/z = 0,45 verwendet. Diese Mörtel wurden durch Zugabe von drei Arten von Polypropylenfasern mit fünf Faserlängen zwischen 3 und 38 mm modifiziert. Die Mantelflächen aller Prüfkörper wurden für die Dauer des Experimentes zur Gewährleistung einaxialen Wassertransportes feuchtigkeitsisoliert. Für jede Mörtelart wurden zwei Abdichtungsstoffe eingesetzt: Siliconbeschichtung und Polyethylenfolie. Die Vergleichsanalyse diente der Bewertung des Einflusses auf den Wasserabsorptionskoeffizienten A durch die Faktoren Zementart, Wasser‐Zement‐Wert, Art und Länge der Fasern sowie der Art der Feuchtigkeitsabdichtung. Es erwies sich, dass der letztgenannte Faktor einen dominierenden Einfluss auf den Verlauf des Prozesses und somit auf die Größe des ihn quantitativ beschreibenden Parameters A hatte.
The social science of sustainable bioenergy production in Southeast Asia Perspective
Authors: Bush Simon R.
Published: December 2007

The social sciences have made considerable inroads into exploring the politics of environment, land and resources throughout Southeast Asia, yet the social and political character of bioenergy development remains little understood. Current assumptions that bioenergy provides benefits to rural populations requires a much stronger empi‐rical basis that will only come through further research. The challenge for the social sciences is to provide a critical but realistic understanding of the wider socio‐political context of bioenergy production, giving attention to who is promoting bioenergy production, to what ends, and at whose cost. This article hopes to provoke a more con‐sidered policy dialogue over bioenergy development in regions such as Southeast Asia through a more grounded understanding of production and governance to unlock, wherever possible, the potential of the sector. © 2007 Society of Chemical Industry and John Wiley & Sons, Ltd
A classification system for faecal incontinence based on anorectal investigations
Authors: Thekkinkattil D K , Lim M , Stojkovic S G , Finan P J , Sagar P M , Burke D
Published: December 2007

Background

Faecal incontinence is a socially disabling condition that affects a heterogeneous population of patients. There is no standardization of investigations, and treatment outcomes are variable. The major limitation for comparing the results from different studies is the lack of a pretreatment classification of incontinence. The aim of this study was to review the anorectal investigation findings and propose a simple, repeatable classification for faecal incontinence.

Methods

Patients who had anorectal investigations for defaecatory disorders from February 2000 to September 2006 were analysed retrospectively. All patients had anorectal manometry, anal mucosal electrosensitivity testing and endoanal ultrasonography.

Results

Of a total of 1294 patients, 135 were excluded, leaving 1159 (460 continent and 699 incontinent) for analysis. The patients were divided into four groups: traumatic incontinence, neuropathic faecal incontinence, combined faecal incontinence and idiopathic faecal incontinence. The manometric variables and demographics were distinct in these groups.

Conclusion

Patients with faecal incontinence can be classified into different groups with distinct pathophysiological variables. Such a classification system will enable comparison and interpretation of the outcomes of different studies and also help in the selection of patients for appropriate treatments.
Microbubble-enriched lavage fluid for treatment of experimental peritonitis
Authors: Sharma P K , Rakhorst G , Engels E , van der Mei H C , Busscher H J , Ploeg R J
Published: December 2007

Background

Relaparotomies and closed postoperative peritoneal lavage (CPPL) are performed to treat persistent peritonitis. This experimental animal study compared open abdominal lavage with CPPL, and evaluated the potential of microbubble-enriched lavage fluids to improve the efficiency of CPPL and reduce clinical morbidity, mortality and cost.

Methods

Fluorescent polystyrene spheres were injected intraperitoneally into 22 male Wistar rats to simulate localized peritonitis. After 18 h the rats received open abdominal lavage and CPPL, with and without microbubbles. Microbubbles were obtained by adding ultrasound contrast agents to continuous ambulatory peritoneal dialysis fluid.

Results

Open abdominal lavage was 3·5 times more effective in particle removal than CPPL, owing to better fluid dynamics. The introduction of air–liquid interfaces in the form of microbubbles made CPPL up to 2·4 times more effective than lavage without bubbles. Best detachment results were obtained when microbubbles with a flexible surfactant shell and longer blood elimination half-life were used.

Conclusion

Open abdominal and CPPL lavage techniques are not efficient beyond a certain duration and volume as they do not cause bacterial detachment from the peritoneal membrane. Using surface tension forces from microbubbles significantly enhanced polystyrene particle detachment. These findings may have great consequences for the treatment of patients with peritonitis.