bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neo‐Fused Hexaphyrin: A Molecular Puzzle Containing an N‐Linked Pentaphyrin
Authors: Wei Pingchun , Zhang Kai , Li Xin , Meng Deying , Ågren Hans , Ou Zhongping , Ng Seikweng , Furuta Hiroyuki , Xie Yongshu 
Published: October 2014

AbstractThe first neo‐confused hexaphyrin(1.1.1.1.1.0) was synthesized by oxidative ring closure of a hexapyrrane bearing two terminal “confused” pyrroles. The new compound displays a folded conformation with a short interpyrrolic C⋅⋅⋅N distance of 3.102 Å, and thus it readily underwent ring fusion to afford a neo‐fused hexaphyrin with an unprecedented 5,5,5,7‐tetracyclic ring structure. Furthermore, coordination of CuII triggered a ring opening/contracting reaction to afford a CuII complex of an N‐linked pentaphyrin derivative. The roles of reactive NC bonds in the porphyrinoid macrocycles were demonstrated.
Iron(III) Located in the Dinuclear Metallo‐β‐Lactamase IMP‐1 by Pseudocontact Shifts
Authors: Carruthers Thomas J. , Carr Paul D. , Loh Choy‐Theng , Jackson Colin J. , Otting Gottfried 
Published: October 2014

AbstractHeterodinuclear metalloenzymes are an important class of metalloproteins, but determining the location of the different metal ions can be difficult. Herein we present a new NMR spectroscopy method that uses pseudocontact shifts (PCS) to achieve this without assumptions about the coordinating ligands. The approach is illustrated with the dinuclear [FeZn] complex of IMP‐1, which is a prototypical metallo‐β‐lactamase (MβL) that confers resistance to β‐lactam antibiotics. Results from single‐crystal X‐ray diffraction were compromised by degradation during crystallization. With [GaZn]‐IMP‐1 as diamagnetic reference, the PCSs unambiguously identified the iron binding site in fresh samples of [FeZn]‐IMP‐1, even though the two metal centers are less than 3.8 Å apart and the iron is high‐spin Fe3+, which produces only small PCSs. [FeZn]‐MβLs may be important drug targets, as [FeZn]‐IMP‐1 is enzymatically active and readily produced in the presence of small amounts of Fe3+.
C60‐Mediated Molecular Shape Sorting: Separation and Purification of Geometrical Isomers
Authors: Rana Moumita , Reddy R. Bharathanatha , Rath Bibhuti Bhusan , Gautam Ujjal K. 
Published: October 2014

AbstractA supramolecular crystallization‐based approach has been developed for the shape‐dependent separation of geometrical isomers under near‐ambient conditions. Difficulties to separate such isomers arise because of their very similar physical properties. The present approach relies on the ability of C60 to preferentially form solvate crystals with molecules of a specific geometry. Subsequently, these molecules are released upon mild heating to regenerate pure C60. By taking isomers of xylene and trimethylbenzene (TMB) as examples, we show that one of the isomers can be extracted from the rest with very high purity. To separate TMB isomers, a new C60–1,3,5‐TMB solvate was developed, which led to the isolation of isomer purities greater than 99.6 %. Versatility, a low operating temperature of approximately 100 °C, a separation efficiency of more than 10 weight % of C60 per cycle, and reagent recyclability makes this a promising molecular shape‐sorting approach.
Study of resonances for the restricted 3‐body problem
Authors: Quarles B. , Musielak Z.E. , Cuntz M. 
Published: October 2014

AbstractOur aim is to identify and classify mean‐motion resonances (MMRs) for the coplanar circular restricted three‐body problem (CR3BP) for mass ratios between 0.10 and 0.50. Our methods include the maximum Lyapunov exponent, which is used as an indicator for the location of the resonances, the Fast Fourier Transform (FFT) used for determining what kind of resonances are present, and the inspection of the orbital elements to classify the periodicity. We show that the 2:1 resonance occurs the most frequently. Among other resonances, the 3:1 resonance is the second most common, and furthermore both 3:2 and 5:3 resonances occur more often than the 4:1 resonance. Moreover, the resonances in the coplanar CR3BP are classified based on the behaviour of the orbits. We show that orbital stability is ensured for high values of resonance (i.e., high ratios) where only a single resonance is present. The resonances attained are consistent with the previously established resonances for the solar system, i.e., specifically, in regards to the asteroid belt. Previous work employed digital filtering and Lyapunov characteristic exponents to determine stochasticity of the eccentricity, which is found to be consistent with our usage of Lyapunov exponents as an alternate approach based on varying the mass ratio instead of the eccentricity. Our results are expected to be of principal interest to future studies, including augmentations to observed or proposed resonances, of extra‐solar planets in binary stellar systems (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Simultaneous UBVRI observations of the cataclysmic variable AE Aquarii: Temperatures and masses of fireballs
Authors: Zamanov R.K. , Latev G.Y. , Stoyanov K.A. , Boeva S. , Spassov B. , Tsvetkov S.V. 
Published: October 2014

AbstractWe report simultaneous multicolour observations in 5 bands (UBVRI) of the flickering variability of the cataclysmic variable AE Aqr. Our aim is to estimate the parameters (colours, temperature, size) of the fireballs that produce the optical flares. The observed rise times of the optical flares are in the interval 220‐440 s. We estimate the dereddened colours of the fireballs as (U ‐B)0∼0.8‐1.4, (B ‐V)0∼0.03‐0.24, and (V ‐I)0∼0.26‐0.78. We find for the fireballs temperatures of 10000‐25000 K, masses of (7‐90)x1019 g, and sizes of (3‐7)x109 cm (using a distance of d = 86 pc). These values refer to the peak of the flares observed in the UBVRI bands. The data are available upon request from the authors (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
No evidence for an early seventeenth‐century Indian sighting of Kepler's supernova (SN1604)
Authors: van Gent R.H. 
Published: October 2014

AbstractIn a recent paper in this journal, Sule et al. (2011) argued that an early 17th‐century Indian mural of the constellation Sagittarius with a dragon‐headed tail indicated that the bright supernova of 1604 was also sighted by Indian astronomers. In this paper it will be shown that this identification is based on a misunderstanding of traditional Islamic astrological iconography and that the claim that the mural represents an early 17th‐century Indian sighting of the supernova of 1604 has to be rejected. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The 1.5 meter solar telescope GREGOR
Authors: Schmidt W. , von der Lühe O. , Volkmer R. , Denker C. , Solanki S.K. , Balthasar H. , Bello González N. , Berkefeld Th. , Collados M. , Fischer A. , Halbgewachs C. , Heidecke F. , Hofmann A. , Kneer F. , Lagg A. , Nicklas H. , Popow E. , Puschmann K.G. , Schmidt D. , Sigwarth M. , Sobotka M. , Soltau D. , Staude J. , Strassmeier K.G. , Waldmann T.A. 
Published: October 2014

AbstractThe 1.5 m telescope GREGOR opens a new window to the understanding of solar small‐scale magnetism. The first light instrumentation includes the Gregor Fabry Pérot Interferometer (GFPI), a filter spectro‐polarimeter for the visible wavelength range, the GRating Infrared Spectro‐polarimeter (GRIS) and the Broad‐Band Imager (BBI). The excellent performance of the first two instruments has already been demonstrated at the Vacuum Tower Telescope. GREGOR is Europe’s largest solar telescope and number 3 in the world. Its all‐reflective Gregory design provides a large wavelength coverage from the near UV up to at least 5 microns. The field of view has a diameter of 150″. GREGOR is equipped with a high‐order adaptive optics system, with a subaperture size of 10 cm, and a deformable mirror with 256 actuators. The science goals are focused on, but not limited to, solar magnetism. GREGOR allows us to measure the emergence and disappearance of magnetic flux at the solar surface at spatial scales well below 100 km. Thanks to its spectro‐polarimetric capabilities, GREGOR will measure the interaction between the plasma flows, different kinds of waves, and the magnetic field. This will foster our understanding of the processes that heat the chromosphere and the outer layers of the solar atmosphere. Observations of the surface magnetic field at very small spatial scales will shed light on the variability of the solar brightness (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The GREGOR Fabry‐Pérot Interferometer
Authors: Puschmann K.G. , Denker C. , Kneer F. , Al Erdogan N. , Balthasar H. , Bauer S.M. , Beck C. , Bello González N. , Collados M. , Hahn T. , Hirzberger J. , Hofmann A. , Louis R.E. , Nicklas H. , Okunev O. , Martínez Pillet V. , Popow E. , Seelemann T. , Volkmer R. , Wittmann A.D. , Woche M. 
Published: October 2014

AbstractThe GREGOR Fabry‐Pérot Interferometer (GFPI) is one of three first‐light instruments of the German 1.5‐meter GREGOR solar telescope at the Observatorio del Teide, Tenerife, Spain. The GFPI uses two tunable etalons in collimated mounting. Thanks to its large‐format, high‐cadence CCD detectors with sophisticated computer hard‐ and software it is capable of scanning spectral lines with a cadence that is sufficient to capture the dynamic evolution of the solar atmosphere. The field‐of‐view (FOV) of 50″×38″is well suited for quiet Sun and sunspot observations. However, in the vector spectropolarimetric mode the FOV reduces to 25″×38″. The spectral coverage in the spectroscopic mode extends from 530–860 nm with a theoretical spectral resolution of R ≈250 000, whereas in the vector spectropolarimetric mode the wavelength range is at present limited to 580–660 nm. The combination of fast narrow‐band imaging and post‐factum image restoration has the potential for discovery science concerning the dynamic Sun and its magnetic field at spatial scales down to ∼50 km on the solar surface (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The return of the mummy: Evidence for starlight reflected from the massive hot Jupiter τ Boo b?
Authors: Rodler F. , Kürster M. , López‐Morales M. , Ribas I. 
Published: October 2014

AbstractVery recently, we were able to measure CO absorption features in the atmosphere of the non‐transiting planet τ Boo b for the very first time. This allowed us to unravel a long‐term mystery in planet atmosphere studies, the determination of the orbital inclination of a non‐transiting planet and the exact planetary mass, respectively being 46° and 5.7 MJup. In light of these new results, we reanalyzed a UVES/VLT data set taken by us with the goal to detect starlight reflected from this hot Jupiter. In the previous analysis of these data, we found a candidate signal of low confidence (2σ), indicating a geometric albedo of the planetary atmosphere lower than 0.4 and an orbital inclination of 41°, which is close to the recently measured value. We reanalyzed these data by adopting updated orbital parameters and find as result that the candidate signal of marginal significance now appears at an orbital inclination of 43°. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Advanced Spectral Library (ASTRAL): Cool stars edition
Authors: Ayres T.R. 
Published: October 2014

AbstractASTRAL is a project to create high‐resolution, high‐S/N UV (1150–3200 Å) atlases of bright stars utilizing HST/STIS. During Cycle 18 (2010–2011), eight cool star targets were observed, including key objects like Procyon and Betelgeuse, churning through 146 orbits in the process. The new spectral atlases are publically available through the project website. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear time series analysis of Kepler Space Telescope data: Mutually beneficial progress
Authors: Jevtić N. , Stine P. , Schweitzer J.S. 
Published: October 2014

AbstractNonlinear time series analysis, though a powerful tool, has not been used widely in astronomy and astro‐physics because the principle requirements that the data be sampled uniformly and continuous are rarely met. Kepler Space Telescope variable‐star light curves satisfy these and almost all other requirements. These data have allowed a more systematic study of the methodology and yielded new information. Nonlinear noise reduction is the aspect we focus on here. Nonlinear time series power spectra often have relevant information across all the frequencies in a spectrum. As opposed to traditional filtering that results in a loss of information at the high frequencies, nonlinear local projective noise reduction allows us to significantly reduce noise while keeping high‐frequency information. Nonlinear noise reduction is discussed for a number of Kepler Space Telescope targets with different power‐spectral characteristics. The extremely high quality of the Kepler data has also allowed us to explore the novel use of average mutual information (AMI) for distinguishing signal from noise in broadband spectra. We report on noise reduction for targets with power spectra that contain a fundamental and harmonics, power spectra with no such lines and spectra with high‐frequency lines (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
SONG‐OT: The prototype SONG node at Tenerife
Authors: Uytterhoeven K. , Pallé P.L. , Grundahl F. , Frandsen S. , Christensen‐Dalsgaard J. , Triviño Hage A. , the SONG team  
Published: October 2014

AbstractThe prototype SONG node, SONG‐OT, is currently being installed and tested at Observatory del Teide on Tenerife. SONG will be a global network of 1‐m robotic telescopes, equipped with a high‐resolution échelle spectrograph and dual‐colour lucky imaging cameras. The network will be devoted to the seismic study of bright stars and characterisation of low‐mass planets. We present the current status of the network in general and the SONG‐OT node in particular (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High precision pointing with a multiline spectrometer at the VTT
Authors: Staiger J. 
Published: October 2014

AbstractWe are investigating the pointing quality of the VTT, Tenerife under the aspect of suitability for long‐term heliosesimological observations. Tests have shown that thermal and mechanical loads within the telescope may create spurious image drifts with shift rates of up to 5″ per hour. During daylong recordings this will reduce significantly the effective size of the field‐of‐view and may infer artificial lateral movements into the data. The underlying problem that not all image position offsets developing during a measurement may be compensated for is common to most high‐resolution solar telescopes independently of the type of pointing system used. We are developing new approaches to address this problem which are to be tested in the near future at the VTT. The simulations established so far show that the problem may be reduced by more than 90% (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Differential rotation and meridional flows of K giants: Predictions from mean field theory
Authors: Küker M. , Rüdiger G. 
Published: October 2014

AbstractWe present a mean field model of the differential rotation and meridional flow of the giant star KIC 8366239. The model predicts a solar‐type surface differential rotation with a total shear of 0.03 rad/d. The horizontal shear decreases with depth and vanishes at the lower boundary. No drastic increase of the rotation rate towards the core is found. The surface meridional flow is directed towards the poles and has amplitude of 26 m/s. The return flow at the bottom of the convective envelope has an amplitude of 16 m/s. The results are compared with those for the K giant Arcturus and the Sun (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stellar characterization of large spectroscopic datasets: A Bayesian approach
Authors: Kaiser A. , Weiss W.W. 
Published: October 2014

AbstractThe task of accurately determining the fundamental parameters of a star from medium or low resolution spectra is time consuming and requires substantial experience. Since the first large‐scale space missions such as CoRoT or Kepler came along, the need for a fast and statistically sound method emerged to cope with the large amount of ground based support data. We present here a fully automated approach for the determination of stellar parameters from low‐resolution stellar spectra using a Bayesian approach and discuss the reliability and limits of the method (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variability survey in the young open cluster IC 1805
Authors: Moidzierski D. 
Published: October 2014

AbstractWe present preliminary results of the photometric variability survey in the very young open cluster IC 1805. We found more than 70 variable stars in the field, including pulsating stars and a large sample of most likely pre‐main sequence stars (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acoustic glitches in solar‐type stars from Kepler
Authors: Mazumdar A. , Monteiro M.J.P.F.G. , Ballot J. , Antia H.M. , Basu S. , Houdek G. , Mathur S. , Cunha M.S. , Silva Aguirre V. , García R.A. , Salabert D. , Verner G.A. , Christensen‐Dalsgaard J. , Metcalfe T.S. , Chaplin W.J. 
Published: October 2014

AbstractWe report the measurement of the acoustic locations of layers of sharp variation in sound speed in the interiors of 19 solar‐type stars observed by the Kepler mission. The oscillatory signal in the frequencies arising due to the acoustic glitches at the base of the convection zone and the second helium ionisation zone was utilised to determine their location by four independent methods. Despite the significantly different methods of analysis, remarkable agreement was found between the results of these four methods. Further, the extracted locations of these layers were found to be consistent with representative models of the stars (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excitation of pulsation modes in B‐type supergiant stars
Authors: Ostrowski J. , Daszyńska‐Daszkiewicz J. , Pamyatnykh A.A. 
Published: October 2014

AbstractWe present results on the instability analysis of the post main sequence massive star models against radial and nonradial pulsations. Both p‐ and g‐modes can be excited by the κ‐mechanism operating in the metal opacity bump. However, as opposed to the previous published results, an intermediate convective zone (ICZ) related to the hydrogen burning shell is not necessary for excitation of g‐modes. Such modes can be reflected at the chemical composition gradient region surrounding the radiative helium core. We investigate properties of instability parameter, kinetic energy density and work integrals of pulsational modes excited in B‐type supergiant models (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the possibility of using seismic probes to study the core composition in pulsating white dwarfs
Authors: Faria J.P. , Monteiro M.J.P.F.G. 
Published: October 2014

AbstractWhite dwarfs correspond to the final stages of stellar evolution of solar‐type stars. In these objects, production of energy by nuclear burning has ended which means that a white dwarf simply cools down over the course of the next billion years. It is now known that white dwarfs spend some of their cooling history in an instability strip. The pulsating white dwarfs with an hydrogen atmosphere (called DAV or ZZ Ceti stars) show non‐radial oscillation modes with periods in the range 100–1200 s. In this work we try to illustrate how the oscillation p‐mode frequencies of idealized white dwarf models change as the result of a different chemical composition in the core, with the ultimate goal of determining the chemical stratification from seismic observations. The presence of acoustic glitches in the internal structure results in a periodic signal in the frequencies. We find that this signal depends on the chemical stratification/composition of the core in a form that can be analytically modelled (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Is one month of observations enough? A case study on Kepler‐21
Authors: Valliappan S.P. , Karoff C. 
Published: October 2014

AbstractWe present the asteroseismic analysis of Kepler observations of the bright oscillating star Kepler‐21 (KIC 3632418, KOI 975, HD 179070). The pulsation modes exhibited by this star are similar to the acoustic p‐modes seen in our Sun. The analysis of observations covering a time period of 460 days has showed that the star hosts a small planet (Kepler‐21b), which has a mass of ∼10 MEarth, a radius of 1.64±0.04 REarth and a revolving period of 2.8 days (Howell et al. 2012). Our current work deals with the comparison of p‐mode frequency estimation using 1 and 10 months of observations (Quarter 2.3 and Quarters 5 through 7) of this F5 subgiant (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The non‐adiabatic high‐degree f‐mode
Authors: Zhugzhda Y.D. , Roth M. 
Published: October 2014

AbstractThe current theory of the high‐degree solar f‐mode based on an adiabatic approximation is in contradiction with obser‐vations, since the f‐mode is visible in intensity oscillations of the Sun. As a possible solution we present an universal analytical treatment for a non‐adiabatic f‐mode. This non‐adiabatic theory provides the explanation of brightness oscilla‐tions due to the f‐mode. We find that the non‐adiabatic effects do not lead to a damping of the f‐mode since the dispersion relation is the same as in the adiabatic approximation (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
UCAC4: Stellar kinematics with vector spherical functions
Authors: Vityazev V.V. , Tsvetkov A.S. 
Published: October 2014

AbstractWe present a method of kinematic analysis of proper motions by vector spherical functions, and the results of its application to astrometric data. The sets of vector spherical functions which are orthonormal on a full sphere as well as on a latitude zone are constructed. Decomposition of the proper motions into a set of such functions allows model‐independent study of stellar kinematics. If needed, the parameters of the standard (say, Ogorodnikov‐Milne) model may be derived from the coefficients of the decomposition. In contrast to the commonly used least squares estimation of the model's parameters, vector spherical functions identify all systematic components of the velocity field (no matter, whether they are incorporated into the model or not) and give us a possibility to test whether the data are compatible with the model. In this paper, we apply this technique for the first time to the proper motions from the UCAC4 catalog for stars in the 11 to 16 magnitude range. We derive all‐sky solutions and the solutions based on stars in the northern and southern Galactic hemispheres. The all‐sky solution provide evidence for noticeable magnitude‐dependent trends in the coordinates of the solar motion apex, Oort constants, angular speed of the local Galactic rotation, and the slope of the local rotation velocity curve as we go from bright to faint stars. Furthermore, our all‐sky vector spherical function analysis identified strong and reliable extramodel harmonics, whereas the solutions for the northern and southern hemisphere indicate sign reversals for some of the Ogorodnikov‐Milne parameters. We show that both effects appear simultaneously and can be explained by the slowdown of Galactic rotation with increasing distance from the main Galactic plane. We estimate the absolute value of the vertical gradient of the Galactic rotational velocity to be ∼40 km s–1 kpc–1. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)