bluuebunny/crossref_metadata_2025_split huggingface dataset:
The kinematic characteristics of magnetic O‐type stars
Authors: Hubrig S. , Kharchenko N.V. , Schöller M. 
Published: January 2011

AbstractAlthough magnetic fields have been discovered in ten massive O‐type stars during the last years, the origin of their magnetic fields remains unknown. Among the magnetic O‐type stars, two stars, HD 36879 and HD 57682, were identified as candidate runaway stars in the past, and θ1 Ori C was reported to move rapidly away from its host cluster. We search for an explanation for the occurrence of magnetic fields in O‐type stars by examining the assumption of their runaway status. We use the currently best available astrometric, spectroscopic, and photometric data to calculate the kinematical status of seven magnetic O‐type stars with previously unknown space velocities. The results of the calculations of space velocities suggest that five out of the seven magnetic O‐type stars can be considered as candidate runaway stars. Only two stars, HD 155806 and HD 164794, with the lowest space velocities, are likely members of Sco OB4 and NGC 6530, respectively. However, the non‐thermal radio emitter HD 164794 is a binary system with colliding winds, for which the detected magnetic field has probably a different origin in comparison to other magnetic O‐type stars (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic fields of Ap stars as a result of the Tayler instability
Authors: Arlt R. , Rüdiger G. 
Published: January 2011

AbstractAp star magnetism is often attributed to fossil magnetic fields which have not changed much since the pre‐main‐sequence epoch of the stars. Stable magnetic field configurations are known which could persist probably for the entire mainsequence life of the star, but they may not show the complexity and diversity exhibited by the Ap stars observed. We suggest that the Ap star magnetism is not a result of stable configurations, but is the result of an instability based on strong toroidal magnetic fields buried in the stars. The highly nonaxisymmetric remainders of the instability are reminiscent of the diversity of fields seen on Ap stars. The strengths of these remnant magnetic fields are actually between a few per cent up to considerable fractions of the internal toroidal field; this means field strengths of the order of kGauss being compatible with what is observed. The magnetic fields emerge at the surface rather quickly; rough estimates deliver time‐scales of the order of a few years. Since rotation stabilizes the instability, normal A stars may still host considerable, invisible toroidal magnetic fields (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Tayler instability of toroidal magnetic fields in a columnar gallium experiment
Authors: Rüdiger G. , Schultz M. , Gellert M. 
Published: January 2011

AbstractThe nonaxisymmetric Tayler instability of toroidal magnetic fields due to axial electric currents is studied for conducting incompressible fluids between two coaxial cylinders without endplates. The inner cylinder is considered as so thin that the limit of Rin → 0 can be computed. The magnetic Prandtl number is varied over many orders of magnitudes but the azimuthal mode number of the perturbations is fixed to m = 1. In the linear approximation the critical magnetic field amplitudes and the growth rates of the instability are determined for both resting and rotating cylinders. Without rotation the critical Hartmann numbers do not depend on the magnetic Prandtl number but this is not true for the corresponding growth rates. For given product of viscosity and magnetic diffusivity the growth rates for small and large magnetic Prandtl number are much smaller than those for Pm = 1. For gallium under the influence of a magnetic field at the outer cylinder of 1 kG the resulting growth time is 5 s. The minimum electric current through a container of 10 cm diameter to excite the instability is 3.20 kA. For a rotating container both the critical magnetic field and the related growth times are larger than for the resting column (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Long‐term photometry of the ultra‐fast rotator LO Peg
Authors: Taş G. 
Published: January 2011

AbstractLO Peg is a young main‐sequence star of spectral type K3. With its equatorial rotation velocity of 65 km s–1 it is amongst the ultra‐fast rotators. Its high equatorial rotation velocity and rapidly changing surface activity features make it an important object in terms of both stellar activity and the evolution of stellar rotation and angular momentum. Since its discovery as a variable star, it has mostly been subject to spectral surface mapping studies such as Doppler Imaging, while there have been very few photometric studies on it. This paper aims to present the first long‐term photometric observations and its results covering the years between 2003 and 2009. The UBVR Johnson wide band photometric data showed that the surface activity structures of LO Peg vary in timescales changing between days and months, and parallel to this, the mean, maximum and minimum brightness and amplitudes change dramatically between years and sometimes even within the same observation season. Long‐term changes in system brightness and colours, both characteristic features of active stars, were also seen in this ultra‐fast young star. The active longitudes, which has a life time of ∼1.3 years and an activity cycle period of ∼4.8 years for LO Peg were estimated (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Metric study of Egyptian sacrum for lumbo‐sacral fixation procedures
Authors: El‐Sayed Hassanein Gamal Hamed 
Published: January 2011

AbstractLumbo‐sacral fixation for the management of lumbo‐sacral instability includes insertion of screws to the sacrum, most commonly into the posterior aspect of the pedicles of the first sacralvertebra. This study was carried out to determine the normal anatomical parameters of the Egyptian sacrum, particularly of the first sacral vertebra and its pedicles, to find the safest approach for sacral screw placement in lumbo‐sacral fixation procedures, and to describe racial characteristics, if any. In this study, 45 adult Egyptian dry sacra of unknown sex were used. Eleven sacral parameters were measured using the Vernier sliding caliper which is accurate to 0.1 millimeter. In this study, the sacrum showed a mean height of 11.43 ± 0.88 centimeters a mean width of 10.39 ± 0.91 centimeters with a mean sacral index of 90.82 ± 1.80 %. The first sacral pedicle had a mean anterior height of 1.83 ± 0.49 centimeters, a mean depth of 2.99 ± 0.53 centimeters and a mean posterior height of 2.38 ± 0.50 centimeters. A medialtrajectory path (representing an anteromedially‐oriented first sacral pedicle screw) starting from the infero‐lateral border of the S1 facet to the sacral promontory in the middle line was 5.23 ± 0.52 cm. The findings of the present study could provide accurate and specific parameters of the sacrum among Egyptians that could enhance the safety of insertion of sacral screws during lumbo‐sacral fixation procedures upon Egyptian patients. Clin. Anat. 24:218–224, 2011. © 2011 Wiley‐Liss, Inc.
Microstructure of the vocal fold in elderly humans
Authors: Roberts T. , Morton R. , Al‐Ali S. 
Published: January 2011

AbstractSignificant changes in the voice occur after the age of 50 years. Changes in the structure of the vocal fold (VF) can interfere with the voice. The aim of this study is to investigate the structure of the VF of elderly people that may contribute to the tendency of the human voice to deteriorate. Larynges were obtained from eight embalmed cadavers aged 72–98 years. The middle portion of each vocal fold was removed and placed in 4% buffered formalin. Tissue blocks were then processed and embedded in wax. Four to six micron coronal sections were cut and stained with Haematoxylin and Eosin (H&E), Masson's Trichrome (MTS), Elastin van Gieson (EVG), Herovici (HERO), picrosirius and CD31 immunohistochemical marker in order to study the collagen fibers, elastic fibers and microvasculature of the VF. The maturity of collagen fibers within the VF were noted to increase from the superficial to the deep layer of the lamina propria (LP). Contrary to current literature, the amount of elastic fibers was sparse in the superficial layer of the LP in the vocal tissue of elderly cadavers. Numerous cross‐sectioned blood vessels were seen in the lamina propria near the free edge, and near the superior and inferior surfaces of the VF. The presence of lymphatic vessels was confirmed in the VF of elderly subjects. This study revealed that the collagenous component of the deep layer of the VF LP was made up of mature fibers whilst immature collagen fibers made up the superficial layer of the LP. There was a notable scarcity of elastic fibers in the superficial layer of the LP. Lymphatics were seen and were orientated differently in the geriatric vocal folds. Clin. Anat. 24:544–551, 2011. © 2011 Wiley‐Liss, Inc.
A comprehensive analysis of muscle recruitment patterns during shoulder flexion: An electromyographic study
Authors: Wattanaprakornkul Duangjai , Halaki Mark , Boettcher Craig , Cathers Ian , Ginn Karen A. 
Published: January 2011

AbstractAlthough flexion is a common component of the routine clinical assessment of the shoulder the muscle recruitment patterns during this movement are not clearly understood making valid interpretation of potential muscle dysfunction problematic. The purpose of this study was to comprehensively examine shoulder muscle activity during flexion in order to compare the activity levels and recruitment patterns of shoulder flexor, scapular lateral rotator and rotator cuff muscles. Electromyographic (EMG) data were recorded from 12 shoulder muscles sites in 15 volunteers. Flexion was performed in standing in the sagittal plane at no load, 20%, and 60% of each subject's maximum load. EMG data were normalized to maximum values obtained during maximum voluntary contractions. Results indicated that anterior deltoid, pectoralis major, supraspinatus, infraspinatus, serratus anterior, upper, and lower trapezius were activated at similar moderate levels. However, subscapularis was activated at low levels and significantly lower than supraspinatus and infraspinatus. Similar activity patterns across time were demonstrated in the muscles that produce flexion torque, laterally rotate the scapula, as well as supraspinatus and infraspinatus, and did not change as flexion load increased. The onset of activity in supraspinatus and anterior deltoid occurred at the same time and prior to movement of the limb at all loads with infraspinatus activity also occurring prior to movement onset at the medium and high load conditions only. Posterior rotator cuff muscles appear to be counterbalancing anterior translational forces produced during flexion and it would appear that supraspinatus is one of the muscles that consistently “initiates” flexion. Clin. Anat. 24:619–626, 2011. © 2011 Wiley‐Liss, Inc.
High spatial and temporal resolution imaging of the arterial vasculature of the lower extremity with contrast enhanced mr angiography
Authors: Mostardi Petrice M. , Haider Clifton R. , Glockner James F. , Young Phillip M. , Riederer Stephen J. 
Published: January 2011

AbstractVascular imaging can be essential in the diagnosis, monitoring, and planning and assessment of treatment of patients with peripheral vascular disease. The purpose of this work is to describe a recently developed three‐dimensional (3D) time‐resolved contrast‐enhanced MR angiography (CE‐MRA) technique, Cartesian Acquisition with Projection Reconstruction‐like sampling (CAPR), and its application to imaging of the vasculature of the lower legs and feet. CAPR implements accelerated imaging techniques and uses specialized multielement imaging coil arrays to achieve high temporal and high spatial resolution imaging. Volunteer and patient studies of the vasculature of the lower legs and feet have been performed. Temporal resolution of 4.9–6.5 sec and spatial resolution less than or equal to 1 mm in all directions allow for the depiction of progressive arterial filling and complex flow patterns as well as sharp visualization of vascular structure as small as the fine muscular branches. High‐quality diagnostic imaging is made possible with CAPR's advanced acquisition and reconstruction techniques and the use of specialized coil arrays. Clin. Anat. 24:478–488, 2011. © 2011 Wiley‐Liss, Inc.
Structure, Bioactivity and Synthesis of Natural Products with Hexahydropyrrolo[2,3‐b]indole
Authors: Ruiz‐Sanchis Pau , Savina Svetlana A. , Albericio Fernando , Álvarez Mercedes 
Published: January 2011

AbstractResearch on natural products containing hexahydropyrrolo[2,3‐b]indole (HPI) has dramatically increased during the past few years. Newly discovered natural products with complex structures and important biological activities have recently been isolated and synthesized. This review summarizes the structures, biological activities, and synthetic routes for natural compounds containing HPI, emphasizing the different strategies for assembling this motif. It covers a broad range of molecules, from small alkaloids to complex peptides.
Isocyanide in Biochemistry? A Theoretical Investigation of the Electronic Effects and Energetics of Cyanide Ligand Protonation in [FeFe]‐Hydrogenases
Authors: Greco Claudio , Bruschi Maurizio , Fantucci Piercarlo , Ryde Ulf , De Gioia Luca 
Published: January 2011

AbstractThe presence of Fe‐bound cyanide ligands in the active site of the proton‐reducing enzymes [FeFe]‐hydrogenases has led to the hypothesis that such Brønsted–Lowry bases could be protonated during the catalytic cycle, thus implying that hydrogen isocyanide (HNC) might have a relevant role in such crucial microbial metabolic paths. We present a hybrid quantum mechanical/molecular mechanical (QM/MM) study of the energetics of CN− protonation in the enzyme, and of the effects that cyanide protonation can have on [FeFe]‐hydrogenase active sites. A detailed analysis of the electronic properties of the models and of the energy profile associated with H2 evolution clearly shows that such protonation is dysfunctional for the catalytic process. However, the inclusion of the protein matrix surrounding the active site in our QM/MM models allowed us to demonstrate that the amino acid environment was finely selected through evolution, specifically to lower the Brønsted–Lowry basicity of the cyanide ligands. In fact, the conserved hydrogen‐bonding network formed by these ligands and the neighboring amino acid residues is able to impede CN− protonation, as shown by the fact that the isocyanide forms of [FeFe]‐hydrogenases do not correspond to stationary points on the enzyme QM/MM potential‐energy surface.
Elucidating Gating Effects for Hydrogen Sorption in MFU‐4‐Type Triazolate‐Based Metal–Organic Frameworks Featuring Different Pore Sizes
Authors: Denysenko Dmytro , Grzywa Maciej , Tonigold Markus , Streppel Barbara , Krkljus Ivana , Hirscher Michael , Mugnaioli Enrico , Kolb Ute , Hanss Jan , Volkmer Dirk 
Published: January 2011

AbstractA highly porous member of isoreticular MFU‐4‐type frameworks, [Zn5Cl4(BTDD)3] (MFU‐4l(arge)) (H2‐BTDD=bis(1H‐1,2,3‐triazolo[4,5‐b],[4′,5′‐i])dibenzo[1,4]dioxin), has been synthesized using ZnCl2 and H2‐BTDD in N,N‐dimethylformamide as a solvent. MFU‐4l represents the first example of MFU‐4‐type frameworks featuring large pore apertures of 9.1 Å. Here, MFU‐4l serves as a reference compound to evaluate the origin of unique and specific gas‐sorption properties of MFU‐4, reported previously. The latter framework features narrow‐sized pores of 2.5 Å that allow passage of sufficiently small molecules only (such as hydrogen or water), whereas molecules with larger kinetic diameters (e.g., argon or nitrogen) are excluded from uptake. The crystal structure of MFU‐4l has been solved ab initio by direct methods from 3D electron‐diffraction data acquired from a single nanosized crystal through automated electron diffraction tomography (ADT) in combination with electron‐beam precession. Independently, it has been solved using powder X‐ray diffraction. Thermogravimetric analysis (TGA) and variable‐temperature X‐ray powder diffraction (XRPD) experiments carried out on MFU‐4l indicate that it is stable up to 500 °C (N2 atmosphere) and up to 350 °C in air. The framework adsorbs 4 wt % hydrogen at 20 bar and 77 K, which is twice the amount compared to MFU‐4. The isosteric heat of adsorption starts for low surface coverage at 5 kJ mol−1 and decreases to 3.5 kJ mol−1 at higher H2 uptake. In contrast, MFU‐4 possesses a nearly constant isosteric heat of adsorption of ca. 7 kJ mol−1 over a wide range of surface coverage. Moreover, MFU‐4 exhibits a H2 desorption maximum at 71 K, which is the highest temperature ever measured for hydrogen physisorbed on metal–organic frameworks (MOFs).
Polymer‐Supported Ionic‐Liquid‐Like Phases (SILLPs): Transferring Ionic Liquid Properties to Polymeric Matrices
Authors: Sans Victor , Karbass Naima , Burguete M. Isabel , Compañ Vicente , García‐Verdugo Eduardo , Luis Santiago V. , Pawlak Milena 
Published: January 2011

AbstractThe physico‐chemical properties of polymers with ionic‐liquid‐like moieties covalently bound to their surfaces (SILLPs) have been studied by thermal and spectroscopic techniques, as well as by direct impedance and dielectric measurements, and compared to those of the corresponding bulk ionic liquids. The effective transfer of properties from ionic liquids in solution to the supported species has thereby been demonstrated. The effects of the chemical nature of these tunable “solid solvents” on their macroscopic swelling and microwave heating, as well as the stabilities and activities of different catalytic moieties immobilized on the SILLPs, have been studied. Finally, the experimental effect observed in microwave heating can be directly correlated with the values of tan δ derived from dielectric measurements.
Copper‐Catalyzed Azide–Alkyne Cycloaddition in the Synthesis of Polydiacetylene: “Click Glycoliposome” as Biosensors for the Specific Detection of Lectins
Authors: Leal Manuel Pernía , Assali Mohyeddin , Fernández Inmaculada , Khiar Noureddine 
Published: January 2011

AbstractSupramolecular self‐assembly of conjugated diacetylenic amphiphile‐tethered ligands photopolymerize to afford polydiacetylene (PDA) functional liposomes. Upon specific interaction with a variety of biological analytes in aqueous solution, PDA exhibits rapid colorimetric transitions. The PDA nanoassemblies, which are excellent membrane mimics, include an ene–yne polymeric reporter responsible for the chromatic transitions and the molecular recognition elements that are responsible for selective and specific binding to the biological target. A bottleneck in the fabrication of these colorimetric biosensors is the preparation of the diacetylenic monomer embedded with the recognition element of choice. In the present work, we make use of copper‐catalyzed azide–alkyne cycloaddition (CuAAC) as key step in the preparation of sugar‐coated liposome biosensors. The regioselective click ligation of the triacetylenic N‐(2‐propynyl)pentacosa‐10,12‐diynamide (NPPCDAM) with a variety of mannose‐ and lactose‐tethered azides afforded chemo‐ and regioselectively the corresponding 1,2,3‐triazole. The obtained diacetylenic monomers were incorporated efficiently into vesicles to afford functional mannose‐ and lactose‐coated glycoliposomes. The obtained PDA‐based click glycoliposomes have been characterized by using transmission electronic microscopy (TEM), dynamic light scattering (DLS), and UV/Vis spectroscopy. The efficiency of the reported approach was demonstrated by the rapid optimization of the hydrophilic spacer between the lipidic matrix and the mannose head group for the colorimetric detection of Concavalin A.
Bijvoet in Solution Reveals Unexpected Stereoselectivity in a Michael Addition
Authors: Sun Han , d'Auvergne Edward J. , Reinscheid Uwe M. , Carlos Dias Luiz , Kleber Z. Andrade Carlos , Oliveira Rocha Rafael , Griesinger Christian 
Published: January 2011

AbstractThe absolute configuration of small crystallizable molecules can be determined with anomalous X‐ray diffraction as shown by Bijvoet in 1951. For the majority of compounds that can neither be crystallized nor easily be converted into crystallizable derivatives, stereocontrolled organic synthesis is still required to establish their absolute configuration. In this contribution, a new fundamental methodology for resolving the absolute configuration will be presented that does not require crystallization. With residual dipolar coupling enhanced NMR spectroscopy, ensembles of a limited number of structures are created reflecting the correct conformations and relative configuration. Subsequently, from these ensembles, optical rotation dispersion (ORD) spectra are predicted by DFT calculations and compared to experimental results. The combination of these two steps reveals the absolute configuration of a flexible molecule in solution, which is a big challenge to chiroptical methods and DFT in the absence of NMR spectroscopy. Here the absolute stereochemistry of the product of a new Michael addition, synthesized via a niobium(V) chiral enolate, will be elucidated by using the new methodology.
Scandium(III) Zeolites as New Heterogeneous Catalysts: [4+2]Cyclocondensation of in situ Generated Aryl Imines with Alkenes
Authors: Olmos Andrea , Sommer Jean , Pale Patrick 
Published: January 2011

AbstractScandium(III)‐exchanged zeolite was used as heterogeneous ligand‐free catalysts for the [4+2]cyclocondensation of amines and aldehydes with alkenes through the in situ formation of imines. Such catalysts offered a versatile, efficient, and highly regio‐ and stereoselective synthesis of tetrahydroquinoline derivatives. These catalysts exhibited a wide scope and compatibility with functional groups. They are very simple to use, easy to remove (by simple filtration), and they are recyclable (up to three times without loss of activity).
Theoretical Investigation of Carbon–Sulfur Triple Bonds
Authors: Denis Pablo A. , Iribarne Federico 
Published: January 2011

AbstractBy means of first principle calculations we have investigated a set of molecules that are presumed to contain carbon–sulfur triple bonds, namely HCSOH, H3SCH, cis‐FCSF, F3CCSF3, and F5SCSF3. For HCSOH, FCSF, and H3SCH we used the CCSD(T) methodology and the correlation‐consistent basis sets. On the other hand, F3CCSF3 and F5SCSF3 were studied at the B3LYP, M06‐2X, MP2, and G3 levels of theory. We found that none of these molecules display a carbon–sulfur adiabatic bond dissociation energy (ABDE) as strong as diatomic CS (170.5 kcal mol−1), or a diabatic bond dissociation energy (DBDE) larger than the one found in SCO (212.0 kcal mol−1), although the DBDE of FCSF comes quite close at 208.3 kcal mol−1. The CS ABDEs of F3CCSF3, F5SCSF3, and H3SCH are comparable to that of a single CS bond. In contrast with the experimental results, F3CCSF3 and F5SCSF3 are predicted to be linear with C3v and Cs symmetry, respectively, at the B3LYP/6‐311+G(3df,2p) level. MP2/6‐311+G(2df,2p) calculations support the C3v symmetry for F3CCSF3, despite F5SCSF3 not having a perfect linear structure; the CSC angle is 174.6°, which is nearly 20° larger than the experimental value. The analysis of the carbene structures of HCSOH and H3SCH revealed that they are not significant, because the triplet state is dissociative in these cases. However, for F3CCSF3 and F5SCSF3, the carbene triplet states lie 0.81 and 0.77 eV above the singlet state, respectively. In the same vein, our investigation supports the presence of a strong double bond for HCSOH. The conflicting evidence available for F3CCSF3 and F5SCSF3 makes it very difficult to determine the nature of the CS bonds. However, the bond dissociation energies and the singlet–triplet splittings clearly suggest that these compounds should be considered as masked sulfinylcarbenes. The analysis of the bond dissociation energies challenges the existence of a triple bond in these five molecules, but from a strictly thermodynamic standpoint, cis‐FCSF is found to be the candidate most likely to exhibit triple‐bond character.