bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation, spectral characterization, electrochemistry, EXAFS, antibacterial and catalytic activity of new ruthenium (III) complexes containing ONS donor ligands with triphenylphosphine/arsine
Authors: Prabhakaran R. , Krishnan V. , Pasumpon K. , Sukanya D. , Wendel E. , Jayabalakrishnan C. , Bertagnolli H. , Natarajan K.
Published: December 2005

New hexa‐coordinated ruthenium (III) complexes of the type [RuX(EPh3)2(L)] (X = Cl or Br; L = dibasic tridentate Schiff base ligand; E = P or As) have been synthesized by the reactions of [RuCl3(PPh3)3], [RuCl3(AsPh3)3] or [RuBr3(AsPh3)3] with the appropriate Schiff base ligands derived by the condensation of salicylaldehyde and 2‐hydroxy‐1‐naphthaldehyde with N(4) substituted thiosemicarbazones. All the new complexes were characterized using various physico‐chemical methods such as elemental analyses, infrared, electron paramagnetic resonance (EPR) spectroscopy, magnetic moment and cyclic voltammetry. Based on the extended X‐ray absorption fine structure (EXAFS) analysis, an octahedral structure has been confirmed for the complexes. The new complexes have been subjected to the catalytic activity and antibacterial studies. Copyright © 2005 John Wiley & Sons, Ltd.
Synthesis, structure and ethylene polymerization of group 4 complexes with phosphinoamide ligands
Authors: Qi Changhe , Zhang Suobo , Sun Jinghun
Published: December 2005

Group 4 complexes containing diphosphinoamide ligands [Ph2PNR]2MCl2 (3: R = tBu, M = Ti; 4: R = tBu, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction of MCl4 (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [Ph2PNtBu]2TiCl2 (3) was determined by X‐ray crystallography. The phosphinoamides functioned as η2‐coordination ligands in the solid state and the TiN bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i‐Bu3Al/Ph3BC(C6F5)4, catalytic activity of up to 59.5 kg PE/mol cat h bar was observed. Copyright © 2005 John Wiley & Sons, Ltd.
Morphology and DNA degeneration during autoschizic cell death in bladder carcinoma T24 cells induced by ascorbate and menadione treatment
Authors: Gilloteaux Jacques , Jamison James M. , Arnold David , Neal Deborah R. , Summers Jack L.
Published: December 2005

Feulgen and actin‐phalloidin staining as well as gel electrophoresis have been employed in conjunction with cell ultrastructure to describe the effects of 1‐, 2‐, and 4‐hr ascorbate (VC), menadione (VK3), and ascorbate:menadione (VC:VK3) treatments on the T24 human bladder carcinoma cell line. T24 cells exposed to VC alone display blebs and other superficial membrane defects related to membrane alterations and to superficial cytoskeleton changes. VK3 treatment damages the cell nucleus and organelles, leads to the redistribution of the organelles in the perikaryon as a consequence of cytoskeletal damage, and results in cytoplasmic self‐excisions. After VC:VK3 treatment, the cells show exaggerated alterations characteristic of each vitamin treatment alone, including damaged mitochondria, self‐excision of organelle‐free pieces of cytoplasm, and extrusion of the perikaryon containing a nucleus surrounded by the damaged organelles. The nuclear envelope appears intact and contains chromatin that decondenses and dissipates. During the cellular demise that concludes with apparent karyolysis, the cells significantly decrease their size and alter their shape. However, the cisterns of rough endoplasmic reticulum are undamaged, but may become dilated. Since the cellular phenomena leading to cell death differ morphologically from apoptosis and necrosis, but entail self‐cutting without nuclear bodies, this new form of cell death was called autoschizis. In addition, gel electrophoresis and Feulgen staining demonstrate that autoschizis is accompanied by random DNA degeneration. © 2005 Wiley‐Liss, Inc.
L and T brown dwarfs in the Ursa Major moving group
Authors: Bannister N. P. , Jameson R. F.
Published: December 2005

We have applied the “moving cluster” method to an archive of L and T brown dwarf stars to identify those stars which are members of the Ursa Major moving group.We show that five stars have proper motion directions which agree with the direction of motion expected for a cluster member, and which have proper motion distances in agreement with distances determined by trigonometrical parallax observations. We then use 2MASS data to produce an M K versus J ‐ K S colour magnitude diagram. The group members define an empirical 400 Myr isochrone, which is compared to theoretical models. This is the first cluster/group to have a known T dwarf member. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Widely separated binary systems of very low‐mass stars
Authors: Phan‐Bao N. , Martín E. L. , Reylé C. , Forveille T. , Lim J.
Published: December 2005

In this paper we review some recent detections of wide binary brown dwarf systems and discuss them in the context of the multiplicity properties of very low‐mass stars and brown dwarfs. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Calibrating models of ultralow‐mass stars
Authors: Reiners A.
Published: December 2005

Evolutionary and atmospheric models have become available for young ultralow‐mass objects. These models are being used to determine fundamental parameters from observational properties. TiO bands are used to determine effective temperatures in ultralow‐mass objects, and together with Na‐ and K‐lines to derive gravities at the substellar boundary. Unfortunately, model calibrations in (young) ultralow‐mass objects are rare. As a first step towards a calibration of synthetic spectral features, I show molecular bands of TiO, which is a main opacity source in late M‐dwarfs. The TiO ε ‐band at 8450 Å is systematically too weak. This implies that temperatures determined from that band are underestimated, and I discuss implications for determining fundamental parameters from high resolution spectra. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low mass companions to white dwarfs
Authors: Farihi J. , Zuckerman B. , Becklin E. E.
Published: December 2005

This paper summarizes the results of over 17 years of work searching for low mass stellar and substellar companions to more than 370 nearby white dwarfs. Roughly 60 low mass, unevolved companions were found and studied all together, with over 20 discovered in the last few years, including the first unambiguous brown dwarf companion to a white dwarf, GD 1400B. The resulting spectral type distributions for companions to white dwarfs and nearby cool field dwarfs are compared, and the implications for binary star formation are discussed. A brief analysis of GD 1400B, including new data, is also presented. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interactions between hot Jupiters and their host stars
Authors: Gu Pin‐Gao , Shkolnik E. , Li Shu‐Lin , Liu Xiao‐Wei
Published: December 2005

A young hot Jupiter might have been tidally inflated beyond its Roche radius when its orbit was being circularized. This scenario has the potential to explain a couple of solid or tentative observations such as a pile‐up of hot Jupiters around 0.04‐0.05 AU, the mass‐period correlation of transiting planets, as well as the existence of hot Neptunes. Other scenarios such as tidal dissipation in a planet‐host star as well as the magnetic interaction will be also discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
VISIR/VLT observations of brown dwarfs in Upper Scorpius
Authors: Huélamo N. , Bouy H. , Sterzik M. , Pantin E. , MartÍn E.L.
Published: December 2005

We present mid‐IR observations of a sample of very low‐mass stars and brown dwarfs in the Upper Scorpius association. The main goal of these observations is to derive the disk frequency and the disk properties of the sample in order to shed light on brown dwarf formation theories. The observations have been performed with VISIR at the Very Large Telescope (VLT, Paranal). A total of ten targets were observed and six were detected. In this paper we show preliminary results for two of them: DENIS‐PJ160334 and DENIS‐PJ161939. While the former shows mid‐IR fluxes consistent with pure photospheric emission, the latter displays strong mid‐IR excesses which are probably related with a circumstellar disk. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AB Doradus C: age, spectral type, orbit, and comparison to evolutionary models
Authors: Nielsen E. L. , Close L. M. , Guirado J. C. , Biller B. A. , Lenzen R. , Brandner W. , Hartung M. , Lidman C.
Published: December 2005

We expand upon the results of Close et al. (2005) regarding the young, low‐mass object AB Dor C and its role as a calibration point for theoretical tracks. We present an improved spectral reduction and a new orbital solution with two additional epochs. Our improved analysis confirms our spectral type of M8 (±1) and mass of 0.090 ± 0.003 M⊙ for AB Dor C. Comparing the results for AB Dor C with other young, low‐mass objects with dynamical masses we find a general trend where current evolutionary models tend to over‐predict the temperature (or under‐predict the mass) for low‐mass stars and brown dwarfs. Given our precision, there is a ∼99% chance that the mass of AB Dor C is underestimated by the DUSTY tracks in the HR diagram. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variability in the Lambda Orionis cluster substellar domain
Authors: Barrado Y Navascués D. , Huélamo N. , Morales Calderón M.
Published: December 2005

We present the first results on variability of very low mass stars and brown dwarfs belonging to the ∼5 Myr Lambda Orionis cluster (Collinder 69). We have monitored almost continuously in the J filter a small area of the cluster which includes 12 possible members of the cluster during one night. Some members have turned to be short‐term variables. One of them, LOri167, has a mass close to the planetary mass limit and its variability might be due to instabilities produced by the deuterium burning, although other mechanism cannot be ruled out. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A coronagraphic search for brown dwarfs and planets around nearby stars
Authors: Nakajima T. , Morino J.‐I. , Tsuji T. , Suto H. , Ishii M. , Tamura M. , Fukagawa M. , Murakawa K. , Miyama S. , Takami H. , Takato N. , Oya S. , Hayashi S. , Kudo T. , Itoh Y. , Oasa Y. , Oppenheimer B. R.
Published: December 2005

We have started a corongraphic search for brown dwarfs and planets around young nearby stars within 20 pc of the Sun, using the adaptive optics coronagraph, CIAO, on Subaru. The dynamic range we have achieved is ΔK = 13 at 2.5″ from the central star. For a typical target with K = 7 at 10 pc, the limiting absolute magnitude is MK = 20. We apply two kinematical age criteria to select M and K dwarfs statistically younger than 350Myr. The first criterion is a small velocity deviation from the velocity of LSR. The second is a (U, V,W ) velocity vector similar to a particular young moving group. The combination of the age and magnitude limits implies that the mass limit for giant planet detection is about 2 MJ. We show a sample image of a target field at 3 pc of the Sun with faint companion candidates, to be followed up for the common proper motion test. We give a brief description of our procedures for data acquisition, reduction, and analysis. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The formation of brown dwarfs
Authors: Whitworth A. P. , Goodwin S.P.
Published: December 2005

We review four mechanisms for forming brown dwarfs: (i) turbulent fragmentation (producing very low‐mass prestellar cores); (ii) gravitational instabilities in discs; (iii) dynamical ejection of stellar embryos from their placental cores; and (iv) photo‐erosion of pre‐existing cores in HII regions. We argue (a) that these are simply the mechanisms of low‐mass star formation , and (b) that they are not mutually exclusive. If, as seems possible, all four mechanisms operate in nature, their relative importance may eventually be constrained by their ability to reproduce the binary statistics of brown dwarfs, but this will require fully 3‐D radiative magneto‐hydrodynamic simulations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Using near‐IR spectroscopy to classify substellar candidates in the Trapezium Cluster
Authors: Meeus G. , McCaughrean M. J.
Published: December 2005

We discuss the use of near‐IR spectroscopy to confirm young substellar candidates that were selected by photometry. We first review near‐IR spectroscopic methods used to classify young brown dwarf candidates. In a subsequent part, we present ISAAC/VLT photometric and spectroscopic data of substellar candidates in the Trapezium Cluster. These data will be used to derive the effective temperature and reddening of the objects. We create a grid of synthetic spectra from Allard et al. (2000) with different degrees of reddening and compare those with our spectra, assuming a gravity of log g = [3.5, 4.0], which is typical for young objects. The best fitting reddened synthetic spectrum gives us the most likely effective temperature and extinction for our sources. Next, we compare the temperature derived from dereddening the objects towards a 1 Myr isochrone in a colour‐magnitude diagram with the one obtained by fitting synthetic atmosphere models to the spectra, and show what extend the differences have when deriving the masses of the objects (under the assumption of an age of 1 Myr). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Convective radiation fluid‐dynamics: formation and early evolution of ultra low‐mass objects
Authors: Wuchterl G.
Published: December 2005

The formation process of ultra low‐mass objects is some kind of extension of the star formation process. The physical changes towards lower mass are discussed by investigating the collapse of cloud cores that are modelled as Bonnor‐Ebert spheres. Their collapse is followed by solving the equations of fluid dynamics with radiation and a model of time‐dependent convection that has been calibrated to the Sun. For a sequence of cloud‐cores with 1 to 0.01 solar masses, evolutionary tracks and isochrones are shown in the mass‐radius diagram, the Hertzsprung‐Russel diagram and the effective temperaturesurface gravity or Kiel diagram. The collapse and the early hydrostatic evolution to ages of few Ma are briefly discussed and compared to observations of objects in Upper Scorpius and the low‐mass components of GG Tau. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Accretion in brown dwarfs down to nearly planetary masses
Authors: Mohanty S. , Basri G. , Jayawardhana R.
Published: December 2005

We show that in accreting ultra low‐mass stars and brown dwarfs, the CaII λ 8662 emission line flux correlates remarkably well with the mass accretion rate ($ \dot M $), just as it does in higher mass classical T Tauri stars (CTTs). A straightforward measurement of the CaII flux thus provides an easier $ \dot M $ determination technique than detailed modeling of the Hα emission line profile (except at the very lowest accretion rates, where CaII does not appear to be in emission for ultra low‐mass objects, and Hα modeling is required). Using optical high‐resolution spectra, we infer $ \dot M $ from CaII emission for young ultra low‐mass objects down to nearly the deuterium‐burning (planetary‐mass) limit. Our results, in combination with previous determinations of $ \dot M $ in CTTs, illustrate that the accretion rate declines steeply with mass, roughly as $ \dot M $ ∝ M*2 (albeit with considerable scatter). A similar relationship has been suggested by previous studies; we extend it down to nearly the planetary regime. The physical reason for this phenomenon is not yet clear; we discuss various possible mechanisms. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A search for brown dwarfs in Collinder 70 and Collinder 121
Authors: Pérez‐Garrido A. , Díaz‐Sánchez A. , Villo I.
Published: December 2005

We present a study of the brown dwarf population in Collinder 70 and 121 open star clusters. Using photometric data from several catalogues we select several candidates in both clusters. We cover a circular area of radius equal to 1 degree around the cluster centers. We found candidates with photometry compatible with theoretical evolutionary models for the age and distance of these clusters. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Observational characteristics of dense cores with deeply embedded young protostars
Authors: Stamatellos D. , Whitworth A. P. , Goodwin S. P.
Published: December 2005

Class 0 objects, which are thought to be the youngest protostars, are identified in terms of NIR or radio emission and/or the presence of molecular outflows. We present combined hydrodynamic and radiative transfer simulations of the collapse of a star‐forming molecular core, which suggest two criteria for identifying dense cores with deeply embedded very young protostars that may not be observable in the NIR or radio with current telescopes. We find that cores with protostars are relatively warm (T > 15 K) with their SEDs peaking at wavelengths <170 µm, and they tend to appear circular. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ULMSF conference summary
Authors: Jameson R. F.
Published: December 2005

Ten years on from the discovery of the first brown dwarf and the first exoplanet, how well have we progressed in our understanding of these low‐mass objects? In particular how well do we understand their formation? The strong impression from this conference was that the formation of brown dwarfs was just a continuation of the star formation process, no special additional mechanism is indicated. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New brown dwarf companions to dM(e) stars
Authors: Seifahrt A. , Mugrauer M. , Wiese M. , Neuhäuser R. , Guenther E. W.
Published: December 2005

We present new astrometric and spectroscopic data to confirm two new M/L dwarf systems, G124‐62 and LHS5166, and discuss the nature of a third system (LP261‐75). Age and thus mass determinations of the L dwarf companions are discussed based on various activity‐age relationships of the M dwarf primaries. This publication will update the list of widely separated substellar companions to nearby stars. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The IAC online catalog for M‐, L‐ and T‐type dwarfs
Authors: Martín E. L. , Cabrera J. , Cenizo E.
Published: December 2005

We present an online catalog for dwarfs with spectral types M, L and T. The catalog currently contains 893 objects listed in order of right ascension. For most of them the spectra can be downloaded from the catalog in ASCII or FITS formats. The web address is http://www.iac.es/galeria/ege/catalogo spectral/.
NAHUAL: a near‐infrared high‐resolution spectrograph for the GTC optimized for studies of ultracool dwarfs
Authors: Martín E. L. , Guenther E. , Barrado y Navascués D. , Esparza P. , Manescau A. , Laux U.
Published: December 2005

We present the status of an ongoing study for a high‐resolution near‐infrared echelle spectrograph for the 10.4‐m GTC (Gran Telescopio de Canarias) which will soon start operating at the Observatorio del Roque de los Muchachos on the island of La Palma. The main science driver of this instrument, which we have baptized NAHUAL, is to carry out a high precision radial velocity survey of exoplanets around ultracool dwarfs. NAHUAL is being especially designed to achieve the highest possible accuracy for radial velocity measurements. The goal is to reach an accuracy of a few m/s. It is thus required that the instrument is cross‐dispersed and that it covers simultaneously a wide wavelength range. Absorption cells will be placed in front of the slit which will allow a simultaneous self‐reference similar to an iodine‐cell in the optical regime. It is planned to place the instrument at one of the Nasmyth platform of the GTC behind the Adaptive Optics system. Our current design reaches a maximum spectral resolution of λ/Δλ = 50000 with a slit width of 0.175 arcsec, and gives nearly complete spectral coverage from 900 to 2400 nm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Searching for proto‐brown dwarfs: Extending near IR spectroscopy of protostars below the hydrogen burning limit
Authors: Covey K. R. , Greene T. P. , Doppmann G. W. , Lada C. J. , Wilking B. A.
Published: December 2005

Recent observations of nearby star forming regions have offered evidence that young brown dwarfs undergo a period of mass accretion analogous to the T Tauri phase observed in young stars. Brown dwarf analogs to stellar protostars, however, have yet to be definitively observed. These young, accreting objects would shed light on the nature of the dominant brown dwarf formation process, as well as provide ideal laboratories to investigate the dependence of the accretion mechanism on protostellar mass. Recent near infrared surveys have identified candidate proto‐brown dwarfs and characterized low mass protostars in nearby star forming regions. These techniques allow near infrared spectra to diagnose the effective temperature, accretion luminosity, magnetic field strength and rotation velocity of young low mass stars across the stellar/substellar boundary. The lowest mass proto‐brown dwarfs (M < 40 MJup), however, will prove challenging to observe given current near IR observational capabilities. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The lower mass function of young open clusters: clues to (sub)stellar formation
Authors: Moraux E. , Bouvier J. , Clarke C.
Published: December 2005

We report the present day mass functions (PDMFs) of 4 young open clusters over a mass range from 30 Jupiter masses to 3M_ . Three of these clusters have been chosen to have a similar age of ∼100 Myr. Their PDMFs are remarkably similar and are comparable to the field mass function. This suggests little impact of initial conditions (stellar density, metallicity) on the mass distribution and raises some issues concerning the currently debated star and brown dwarf formation theories. The fourth cluster is older (600 Myr) which allow us to investigate the effect of the cluster dynamical evolution on the shape of the mass function. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies of the substellar population in the Taurus cloud
Authors: Monin J.‐L. , Dougados C. , Guieu S.
Published: December 2005

The currently known substellar population of the Taurus cloud now approaches three dozen; two third of this population has been published in the literature before 2005, while a remaining 12 were recently found by Guieu et al. (2005a, b). With such a large number of brown dwarfs at hand, a series of statistical studies can be tackled. In this paper, we examine the state of the art of the current studies for brown dwarfs in Taurus and present some general properties of this population. We discuss the number of substellar objects with respect to stars, as well as some preliminary implications for substellar formation models in Taurus. We find that the embryo‐ejection model seems to reproduce both qualitatively and quantitatively the spatial distribution of stars and BDs in Taurus as well as the evolution of the brown dwarfs to stars ratio RSS , and does not appear incompatible with the accretion properties of the Taurus substellar population. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultracool dwarf binaries
Authors: Bouy H. , Martín E. , Brandner W. , Bouvier J.
Published: December 2005

We review here the multiplicity properties of ultracool dwarfs (spectral type later than M6) observed in three different environments and at three different ages: in the field, where the objects are relatively old (1–5 Gyrs) and isolated, in the Pleiades young (∼120 Myr) open cluster, and in the young (∼5 Myr) Upper Scorpius OB association (USco). While the field and Pleiades populations seem to have very similar properties, the preliminary results obtained in USco might show significant differences. If confirmed, it would mean that the phenomena responsible for the “final” properties of ultracool dwarfs multiplicity are still at work at the age of USco, but are already over at the age of the Pleiades. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultra low‐mass star and substellar formation in σ Orionis
Authors: Caballero J. A.
Published: December 2005

The nearby young σ Orionis cluster (∼360 pc, ∼3 Myr) is becoming one of the most important regions for the study of ultra low‐mass star formation and its extension down to the mass regimes of the brown dwarfs and planetarymass objects. Here, I introduce the σ Orionis cluster and present three studies that the JOVIAN group is developing: a pilot programme of near‐infrared adaptive‐optics imaging of stars of the cluster, intermediate‐resolution optical spectroscopy of a large sample of stars of the cluster and a study of the mass function down to the planetary‐mass domain. This paper is a summary of the content of four posters that I presented in the Ultra low‐mass star formation and evolution Workshop, as single author or on behalf of different collaborations. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The distribution of ejected brown dwarfs in clusters
Authors: Goodwin S. P. , Huber D. A. , Moreaux E. , Whitworth A. P.
Published: December 2005

We examine the spatial distribution of brown dwarfs produced by the decay of small‐N stellar systems as expected from the embryo ejection scenario. We model a cluster of several hundred stars grouped into ‘cores’ of a few stars/brown dwarfs. These cores decay, preferentially ejecting their lowest‐mass members. Brown dwarfs are found to have a wider spatial distribution than stars, however once the effects of limited survey areas and unresolved binaries are taken into account it can be difficult to distinguish between clusters with many or no ejections. A large difference between the distributions probably indicates that ejections have occurred, however similar distributions sometimes arise even with ejections. Thus the spatial distribution of brown dwarfs is not necessarily a good discriminator between ejection and non‐ejection scenarios. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Submillimetre observations of low‐mass cloud cores: forming tiny objects in situ
Authors: Greaves J. S.
Published: December 2005

The origin of very low‐mass objects such as brown dwarfs and ‘isolated planets’ is unclear: can they form in‐situ from very low‐mass cloud cores in a scaled‐down version of star formation? Here I discuss methods of detecting and characterising such faint cores using submillimetre‐wavelength observations. Some data are presented for the Ophiuchus clouds that strongly suggest there is little division between stars and ultra low‐mass objects at the earliest evolutionary stages. Some challenging results have emerged (in the context of current theory), including finding cores of only a few Jupiter masses and a core mass function still rising at the mass detection limit: the implications are briefly discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Triggered planet formation in young stellar clusters
Authors: Thies I. , Kroupa P. , Theis C.
Published: December 2005

Conventional planet formation models via coagulation of planetesimals require timescales in the range of several 10 or even 100 Myr in the outer regions of a protoplanetary disk. But according to observational data, the lifetime of a protoplanetary disk is limited to about 6 Myr. Therefore the existence of Uranus and Neptune poses a problem. Planet formation via gravitational instability may be a solution for this discrepancy. We present a parameter study of the possibility of gravitationally triggered disk instability. Using a restricted N‐body model which allows for a survey of an extended parameter space, we show that a passing dwarf star with a mass between 0.1 and 1 M⊙ can probably induce gravitational instabilities in the pre‐planetary solar disk for prograde passages with minimum separations below 80‐170 AU. Inclined and retrograde encounters lead to similar results but require slightly closer passages. Such encounter distances are quite likely in young moderately massive star clusters. The induced gravitational instabilities may lead to enhanced planetesimal formation in the outer regions of the protoplanetary disk, and could therefore be relevant for the formation of Uranus and Neptune. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The chemical composition of stars with extrasolar planetary systems
Authors: Israelian G.
Published: December 2005

Spectroscopic studies of stars with and without planetary systems have concluded that planet hosts are more metal‐rich. This enrichment is also seen in the other chemical elements studied and is likely to be primordial in nature. Interesting trends of different chemical elements begin to appear as the number of extrasolar planets continues to grow. I present our current knowledge concerning the observed abundance trends of chemical elements in planet hosts and their possible implications. In most cases the abundance trends of planet host stars are identical to those of the comparison sample. However, some exceptions (such as Li) have been reported too. No clear correlation was found between orbital parameters of planets and host star metallicity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proper motion Pleiades candidate L‐type brown dwarfs
Authors: Bihain G. , Rebolo R. , Béjar V. J. S. , Caballero J. A. , Bailer‐Jones C. A. L. , Mundt R.
Published: December 2005

We present results of an optical and near‐infrared (IR) 1.8 deg2 survey in the Pleiades open cluster to search for substellar objects. From optical I ‐band images from the CFHT and J ‐band images from the 3.5m CAHA Telescope, we identify 18 faint and very red L brown dwarf candidates, with I > 20.9 and I – J > 3.2. The follow‐up observations of nine objects in the H ‐ and K s‐bands confirm that eight belong to the IR sequence of the cluster and the proper motion measurements of seven candidates confirm that they are Pleiades members. A preliminary estimation of the substellar mass spectrum dN/ dM in the form of a power law M c–α provides α = +0.57 ± 0.14. We extrapolate this function to estimate the number of planetary mass objects that could be present in the cluster down to 1 MJup. Sensitive searches combining far red and near‐IR observations may unveal these objects in a near future. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultra‐cool dwarf variability
Authors: Goldman B.
Published: December 2005

Ultra‐cool dwarf variability studies have matured into a multi‐wavelength, multi‐method probe of ultra‐cool atmospheres. They have the unique potential to address the question of heterogeneity on the ultra‐cool dwarf surface. The constraints on the models that we can gain though time‐sensitive observations are however hampered by the weak signal detected so far, and the limitations of current atmospheric models, otherwise quite successful, to predict dynamical, or even static 2‐D atmosphere characteristics. Here I review the situation of the ultra‐cool dwarf variability studies: possible sources of variability; methods, their limitations and their results; tentative interpretation and prospects. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Brown dwarfs and very low‐mass stars: variability in the Pleiades
Authors: Morales‐Calderón M. , Barrado y Navascués D. , Caballero J. A. , Martín E. L.
Published: December 2005

We present the results of the optical photometric observations of the Pleiades (125 Myr) cluster. The aim of this research is to look for variability, both due to rotation of single stars and the presence of eclipsing binaries. We have used differential photometry and two different methods of statistical analysis of the data.We have found variability in the Pleiades cluster with amplitudes of about 50 mmag and uncertainties of 5 mmag until I=17.9, well within the brown dwarf regime. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Twelve new substellar members in Taurus. Clues for substellar formation models
Authors: Guieu S. , Monin J.‐L. , Dougados C. , Magnier E. , Martín E. L.
Published: December 2005

Recent studies of the substellar population in the Taurus cloud have revealed a deficit of brown dwarfs compared to the Trapezium cluster population (Briceño et al. 1998; Luhman 2000; Luhman et al. 2003a; Luhman 2004) However, these works have concentrated on the highest stellar density regions of the Taurus cloud. We have performed a large scale optical survey of this region, covering a total area of ≃ 28 deg2, and encompassing the densest parts of the cloud as well as their surroundings. In this paper, we present optical spectroscopic follow‐up observations of 97 photometrically selected potential new low‐mass Taurus members. We derive spectral types, visual absorption and luminosity class estimates and discuss our criteria to assess Taurus membership. These observations reveal 5 new very low‐mass stars (VLMs) and 12 new Brown Dwarfs (BDs) on the Taurus cloud. We derive a new substellar to stellar ratio in Taurus of ℛss = 0.23 ± 0.05. This revisited ratio appears consistent with the value of 0.26 ± 0.04 previously derived in the Trapezium cluster under similar assumptions. We find indications that the relative numbers of BDs with respect to stars is decreased by a factor 2 in the central regions of the aggregates with respect to the more distributed population. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure–function correlation of outer membrane protein porin from Paracoccus denitrificans
Authors: Sukumaran S. , Hauser K. , Maier E. , Benz R. , Mäntele W.
Published: December 2005

Porins from outer membrane of Gram‐negative bacteria have a highly stable structure. Our previous studies on porin from Paracoccus denitrificans showed that the outer membrane protein porin is extremely stable toward heat, pH, and chemical denaturants. The major question we have addressed in this paper is whether the high stability of porin is a consequence of the β‐barrel structure and whether it is required for its function. To explain this we have analyzed two cases: first, we used porin wild‐type and mutants and compared their structure and function; second, we compared the activity of porin preheated to different temperatures. Structural changes were monitored by infrared spectroscopy. We observed that the structural stability of porin is not equivalent to functional activity as minor alteration in the structure can result in drastic differences in the activity of porins. © 2005 Wiley Periodicals, Inc. Biopolymers 82: 344–348, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Low versus high molecular weight poly(ethylene glycol)‐induced states of stem bromelain at low pH: Stabilization of molten globule and unfolded states
Authors: Ahmad Basir , Ansari Mairaj A. , Sen Priyankar , Khan Rizwan Hasan
Published: December 2005

The effect of low, medium, and high molecular weight poly(ethylene glycol) (e.g., PEG‐400, ‐6000, and ‐20,000) on the structure of the acid unfolded state of unmodified stem bromelain (SB) obtained at pH 2.0 has been studied by various spectroscopic methods. The conformation of stem bromelain at pH 2.0 exhibits substantial loss of secondary structure and almost complete loss of native tertiary contacts and has been termed the acid unfolded state (AU). Addition of PEG‐400 to AU led to an increase in the mean residue ellipticity (MRE) value at 222 nm, indicating formation of α‐helical structure. On the other hand, PEG‐6000 and 20,000 led to a decrease in the MRE value at 222 nm, indicating unfolding of the AU state. Interestingly, at 70% (w/v) PEG‐400 and 40% (w/v) PEG‐20,000, MRE values at 222 nm almost approach the native state at pH 7.0 and the unfolded state (6 M GnHCl) of stem bromelain, respectively. The probes for tertiary structure showed formation of nonnative tertiary contacts in the presence of 70% (w/v) PEG‐400, while 40% (w/v) PEG‐6000 and 20,000 were found to stabilize the unfolded state of SB. An increase in binding of 1‐anilino 8‐naphthalene sulfonic acid and a decrease in fractional accessibility of tryptophan residues (fa) compared to AU in the presence of 70% PEG‐400 indicate that the PEG‐400–induced state has a significant amount of exposed hydrophobic patches and is more compact than AU. The results imply that the PEG‐400–induced state has characteristics of molten globule, and higher molecular weight PEGs led to the unfolding of the AU state. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 350–359, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Studies of DNA dumbbells VIII. Melting analysis of DNA dumbbells with dinucleotide repeat stem sequences
Authors: Mandell Kathleen E. , Vallone Peter M. , Owczarzy Richard , Riccelli Peter V. , Benight Albert S.
Published: December 2005

Melting curves and circular dichroism spectra were measured for a number of DNA dumbbell and linear molecules containing dinucleotide repeat sequences of different lengths. To study effects of different sequences on the melting and spectroscopic properties, six DNA dumbbells whose stems contain the central sequences (AA)10, (AC)10, (AG)10, (AT)10, (GC)10, and (GG)10 were prepared. These represent the minimal set of 10 possible dinucleotide repeats. To study effects of dinucleotide repeat length, dumbbells with the central sequences (AG)n, n = 5 and 20, were prepared. Control molecules, dumbbells with a random central sequence, (RN)n, n = 5, 10, and 20, were also prepared. The central sequence of each dumbbell was flanked on both sides by the same 12 base pairs and T4 end‐loops. Melting curves were measured by optical absorbance and differential scanning calorimetry in solvents containing 25, 55, 85, and 115 mM Na+. CD spectra were collected from 20 to 45°C and [Na+] from 25 to 115 mM. The spectral database did not reveal any apparent temperature dependence in the pretransition region. Analysis of the melting thermodynamics evaluated as a function of Na+ provided a means for quantitatively estimating the counterion release with melting for the different sequences. Results show a very definite sequence dependence, indicating the salt‐dependent properties of duplex DNA are also sequence dependent. Linear DNA molecules containing the (AG)n and (RN)n, sequences, n = 5, 10, 20, and 30, were also prepared and studied. The linear DNA molecules had the exact sequences of the dumbbell stems. That is, the central repeat sequence in each linear duplex was flanked on both sides by the same 12‐bp sequence. Melting and CD studies were also performed on the linear DNA molecules. Comparison of results obtained for the same sequences in dumbbell and linear molecular environments reveals several interesting features of the interplay between sequence‐dependent structural variability, sequence length, and the unconstrained (linear) or constrained (dumbbell) molecular environments. © 2005 Wiley Periodicals, Inc. Biopolymers 82: 199–221, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Characterization of human islet‐like structures generated from pancreatic precursor cells in culture
Authors: Bodnar Cheryl A. , Sen Arindom , Kallos Michael S. , Behie Leo A. , Petropavlovskaia Maria , Rosenberg Lawrence
Published: December 2005

This study addresses the characterization of human islet‐like structures generated from a newly discovered sparse population of precursor cells (Petropavlovskaia and Rosenberg, 2002) in the human pancreas. These cells may be progenitor cells capable of producing pancreatic cells suitable for the treatment of type 1 diabetes. The cells were cultured successfully in non‐adherent stationary cultures and yielded, as an important first step, a 1.9‐fold expansion in a serum‐free medium developed specifically for this cell type. This expanded population grew as pancreatic cell aggregates, which were analyzed for islet‐like characteristics. Specifically, through RT‐PCR analyses and functionality assays, we show that cells within the population expressed all four of the endocrine hormone genes and proteins (insulin, glucagon, somatostatin, pancreatic polypeptide). As well, the expanded pancreatic precursor cell population exhibited glucose responsiveness although the produced cells appeared to be still primitive in nature. © 2005 Wiley Periodicals, Inc.
Protein Function Microarrays Based on Self‐Immobilizing and Self‐Labeling Fusion Proteins
Authors: Sielaff India , Arnold Anke , Godin Guillaume , Tugulu Stefano , Klok Harm‐Anton , Johnsson Kai
Published: December 2005

Protein microarrays are an attractive approach for the high‐throughput analysis of protein function, but their impact on proteomics has been limited by the technical difficulties associated with their generation. Here we demonstrate that fusion proteins of O6‐alkylguanine‐DNA alkyltransferase (AGT) can be used for the simple and reliable generation of protein microarrays for the analysis of protein function. Important features of the approach are the selectivity of the covalent immobilization; this allows for direct immobilization of proteins out of cell extracts, and the option both to label and to immobilize AGT fusion proteins, which allows for direct screening for protein–protein interactions between different AGT fusion proteins. In addition to the identification of protein–protein interactions, AGT‐based protein microarrays can be used for the characterization of small molecule–protein interactions or post‐translational modifications. The potential of the approach was demonstrated by investigating the post‐translational modification of acyl carrier protein (ACP) from E. coli by different phosphopantetheine transferases (PPTases), yielding insights into the role of selected ACP amino acids in the ACP–PPTase interaction.
Optimization of Xenon Biosensors for Detection of Protein Interactions
Authors: Lowery Thomas J. , Garcia Sandra , Chavez Lana , Ruiz E. Janette , Wu Tom , Brotin Thierry , Dutasta Jean‐Pierre , King David S. , Schultz Peter G. , Pines Alex , Wemmer David E.
Published: December 2005

Hyperpolarized 129Xe NMR spectroscopy can detect the presence of specific low‐concentration biomolecular analytes by means of a xenon biosensor that consists of a water‐soluble, targeted cryptophane‐A cage that encapsulates the xenon. In this work, we use the prototypical biotinylated xenon biosensor to determine the relationship between the molecular composition of the xenon biosensor and the characteristics of protein‐bound resonances. The effects of diastereomer overlap, dipole–dipole coupling, chemical‐shift anisotropy, xenon exchange, and biosensor conformational exchange on the protein‐bound biosensor signal were assessed. It was found that an optimal protein‐bound biosensor signal can be obtained by minimizing the number of biosensor diastereomers and using a flexible linker of appropriate length. Both the line width and sensitivity of chemical shift to protein binding of the xenon biosensor were found to be inversely proportional to linker length.
Magnetic resonance assessment of myocardial perfusion via catheter‐based ventricle–coronary vein bypass in porcine myocardial infarction model
Authors: Yoneyama Ryuichi , Kawase Yoshiaki , Hoshino Kozo , McGregor Jennifer , Mac Neill Briain D. , Lowe Harry C. , Burkhoff Daniel , Boekstegers Peter , Hajjar Roger J. , Hayase Motoya
Published: December 2005

Objective: The goal of this study was to investigate the efficacy of VPASS with physiological measurements, magnetic resonance imaging (MRI), and histology in a porcine model of myocardial infarction. Background: A catheter‐based ventricle‐to‐coronary vein bypass (VPASS™) has been proposed as a potential treatment strategy for refractory coronary artery disease patients. Methods: In an acute setting, the VPASS implant was deployed percutaneously in three swine. The partial pressure of oxygen (PO2) in the anterior interventricular vein (AIV) and left ventricle (LV) were measured before and after VPASS implant with various combinations of balloon occlusion in the AIV and left anterior descending artery (LAD). In a separate chronic study, the VPASS procedure was completed on three swine with a mid‐LAD occlusion. Thirty days post‐VPASS procedure, angiography, contrast‐enhanced MRI, and histology were performed to assess myocardial viability. Perfusion was analyzed using the average percent signal intensity change (APSIC) in the anterior walls (AW) and inferior walls (IW). Results: The VPASS implant was performed without complication. Post‐VPASS implantation, the distal AIV PO2 increased up to the LV PO2 level during simultaneous AIV and LAD blockage (432 ± 24 mmHg). At day 30, quantitative perfusion analysis demonstrated no difference in APSIC between AW and IW (125 ± 26% vs. 137 ± 38%, P = 0.46). Delayed enhancement and histology showed focal subendomyocardial infarction. Conclusions: VPASS implant with simultaneous AIV and LAD occlusion allows perfusion of oxygenated blood to the distal AIV, which in the setting of an acute myocardial infarction model was capable of rescuing most of the myocardium at risk. © 2005 Wiley‐Liss, Inc.
Percutaneous closure of an aorta to left atrium fistula with an Amplatzer duct occluder
Authors: Feldman Ted , Salinger Michael H. , Das Sundeep , Hamilton Andrew J.
Published: December 2005

We describe percutaneous closure of an unusual paravalvular leak, with a communication from the noncoronary cusp of the aortic valve to the left atrium adjacent to a St. Jude mitral valve prosthesis, in the absence of an infection. The patient presented with worsening dyspnea and edema. The anatomic location of the valve annulus adjacent to the noncoronary cusp underlies the etiology of this communication. Outcomes from surgical repair are associated with high mortality. We performed percutaneous closure of the defect, using general anesthesia and transesophageal echo guidance. An Amplatzer duct occluder was placed in the fistula, with immediate and complete closure of the shunt. While no devices specific for closure of paravalvular leaks have been designed, growing experience with a variety of devices and the use of echo guidance have allowed successful therapy in many complex cases. © 2005 Wiley‐Liss, Inc.
Influence properties of trilinear partial least squares regression
Authors: Serneels Sven , Geladi Paul , Moens Maarten , Blockhuys Frank , Van Espen Pierre J.
Published: December 2005

In this article we derive an algorithm to compute the influence function for tri‐PLS1 regression. Based on the influence function, we propose the squared influence diagnostic plot to assess the influence of individual samples on calibration and prediction. We illustrate the applicability of the squared influence diagnostic plot for tri‐PLS1 to two different data sets which have previously been reported in literature. Finally we note that from the influence function, a new estimate of prediction variance can be obtained. Copyright © 2005 John Wiley & Sons, Ltd.