bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stellar ages from stellar rotation
Authors: Meibom Søren 
Published: June 2009

AbstractOur ability to determine stellar ages from measurements of stellar rotation, hinges on how well we can measure the dependence of rotation on age for stars of different masses. Rotation periods for stars in open clusters are essential to determine the relations between stellar age, rotation, and mass. Until recently, ambiguities in vsini data and lack of cluster membership information, prevented a clear empirical definition of the dependence of rotation on color. Direct measurements of stellar rotation periods for members in young clusters have now revealed a well-defined period-color relation. We show new results for the open clusters M35 and M34. However, rotation periods based on ground-based observations are limited to young clusters. The Hyades represent the oldest coeval population of stars with measured rotation periods. Measurements of rotation periods for older stars are needed to properly constrain the dependence of stellar rotation on age. We present our plans to use the Kepler space telescope to measure rotation periods in clusters as old as and older than the Sun.
The rotational evolution of low-mass stars
Authors: Irwin Jonathan , Bouvier Jerome 
Published: June 2009

AbstractWe summarise recent progress in the understanding of the rotational evolution of low-mass stars (here defined as solar mass down to the hydrogen burning limit) both in terms of observations and modelling. Wide-field imaging surveys on moderate-size telescopes can now efficiently derive rotation periods for hundreds to thousands of open cluster members, providing unprecedented sample sizes which are ripe for exploration. We summarise the available measurements, and provide simple phenomenological and model-based interpretations of the presently-available data, while highlighting regions of parameter space where more observations are required, particularly at the lowest masses and ages ≳500 Myr.
How accurately can we age-date solar-type dwarfs using activity/rotation diagnostics?
Authors: Mamajek Eric E. 
Published: June 2009

AbstractIt is well established that activity and rotation diminishes during the life of sun-like main sequence (~F7-K2V) stars. Indeed, the evolution of rotation and activity among these stars appears to be so deterministic that their rotation/activity diagnostics are often utilized as estimators of stellar age. A primary motivation for the recent interest in improving the ages of solar-type field dwarfs is in understanding the evolution of debris disks and planetary systems. Reliable isochronal age-dating for field, solar-type main sequence stars is very difficult given the observational uncertainties and multi-Gyr timescales for significant structural evolution. Observationally, significant databases of activity/rotation diagnostics exist for field solar-type field dwarfs (mainly from chromospheric and X-ray activity surveys).But how well can we empirically age-date solar-type field stars using activity/rotation diagnostics?Here I summarize some recent results for F7-K2 dwarfs from an analysis by Mamajek & Hillenbrand (2008), including an improved “gyrochronology” [Period(color, age)] calibration, improved chromospheric (R′HK) and X-ray (log(LX/Lbol)) activity vs. rotation (via Rossby number) relations, and a chromospheric vs. X-ray activity relation that spans four orders of magnitude in log(LX/Lbol). Combining these relations, one can produce predicted chromospheric and X-ray activity isochrones as a function of color and age for solar type dwarfs.
Isochrones for late-type stars
Authors: Demarque Pierre 
Published: June 2009

AbstractA brief summary of the history of stellar evolution theory and the use of isochrones is given. The present state of the subject is summarized. The major uncertainties in isochrone construction are considered: chemical abundances and color calibrations, and the treatment of turbulent convection in stellar interior and atmosphere models. The treatment of convection affects the modeling of stellar interiors principally in two ways: convective core overshoot which increases evolutionary lifetimes, and the depth of convection zones which determines theoretical radii. Turbulence also modifies atmospheric structure and dynamics, and the derivation of stellar abundances. The symbiosis of seismic techniques with increasingly more realistic three-dimensional radiation hydrodynamics simulations is transforming the study of late-type stars. The important case of very low mass stars, which are fully convective, is briefly visited.
The Sun in time: age, rotation, and magnetic activity of the Sun and solar-type stars and effects on hosted planets
Authors: Guinan Edward F. , Engle Scott G. 
Published: June 2009

AbstractMulti-wavelength studies of solar analogs (G0–5 V stars) with ages from ~50 Myr to 9 Gyr have been carried out as part of the “Sun in Time” program for nearly 20 yrs. From these studies it is inferred that the young (ZAMS) Sun was rotating more than 10× faster than today. As a consequence, young solar-type stars and the early Sun have vigorous magnetohydrodynamic (MHD) dynamos and correspondingly strong coronal X-ray and transition region/chromospheric FUV–UV emissions (up to several hundred times stronger than the present Sun). Also, rotational modulated, low amplitude light variations of young solar analogs indicate the presence of large starspot regions covering ~5–30% of their surfaces. To ensure continuity and homogeneity for this program, we use a restricted sample of G0–5 V stars with masses, radii, Teff, and internal structure (i.e. outer convective zones) closely matching those of the Sun. From these analogs we have determined reliable rotation-age-activity relations and X-ray–UV (XUV) spectral irradiances for the Sun (or any solar-type star) over time. These XUV irradiance measures serve as input data for investigating the photo-ionization and photo-chemical effects of the young, active Sun on the paleo-planetary atmospheres and environments of solar system planets. These measures are also important to study the effects of these high energy emissions on the numerous exoplanets hosted by solar-type stars of different ages. Recently we have extended the study to include lower mass, main-sequence (dwarf) dK and dM stars to determine relationships among their rotation spin-down rates and coronal and chromospheric emissions as a function of mass and age. From rotation-age-activity relations we can determine reliable ages for main-sequence G, K, M field stars and, subsequently, their hosted planets. Also inferred are the present and the past XUV irradiance and plasma flux exposures that these planets have endured and the suitability of the hosted planets to develop and sustain life.
The promise of Gaia and how it will influence stellar ages
Authors: Cacciari Carla 
Published: June 2009

AbstractThe Gaia space project, planned for launch in 2011, is one of the ESA cornerstone missions, and will provide astrometric, photometric and spectroscopic data of very high quality for about one billion stars brighter than V = 20. This will allow to reach an unprecedented level of information and knowledge on several of the most fundamental astrophysical issues, such as mapping of the Milky Way, stellar physics (classification and parameterization), Galactic kinematics and dynamics, study of the resolved stellar populations in the Local Group, distance scale and age of the Universe, dark matter distribution (potential tracers), reference frame (quasars, astrometry), planet detection, fundamental physics, Solar physics, Solar system science.I will present a description of the instrument and its main characteristics, and discuss a few specific science cases where Gaia data promise to contribute fundamental improvement within the scope of this Symposium.
Stellar ages from asteroseismology
Authors: Lebreton Yveline , Montalbán Josefina 
Published: June 2009

AbstractAsteroseismology has been recognized for a long time as a very powerful mean to probe stellar interiors. The oscillations frequencies are closely related to stellar internal structure properties via the density and the sound speed profiles. Since these properties are in turn tightly linked with the mass and evolutionary state, we can expect to determine the age and mass of a star from the comparison of its oscillation spectrum with the predictions of stellar models. Such a comparison will of course suffer both from the problems we face when modeling a particular star (for instance the uncertainties on its global parameters and chemical composition) and from our general misunderstanding of the physical processes at work in stellar interiors (for instance the various transport processes that may lead to core mixing and affect the ages predicted by models). However for stars where observations have provided very precise and numerous oscillation frequencies together with accurate global parameters and additional information (as the radius or the mass of the star if it is member of a binary system, the radius if it observable in interferometry or the mean density if the star is an exoplanet host), we can also expect to better constrain the physical description of the stellar structure and transport processes and to finally get a more reliable age estimation.After a brief survey of stellar pulsations, we present some general seismic diagnostics that can be used to infer the age of a pulsating star as well as their limitations. We then illustrate the ability of asteroseismology to scrutinize stellar interiors on the basis of a few examples. In the years to come, extended very precise asteroseismic observations are expected, either in photometry or in spectroscopy, from present and future ground-based (HARPS, CORALIE, ELODIE, UVES, UCLES, SIAMOIS, SONG) or spatial devices (MOST, CoRoT, WIRE, Kepler, PLATO). This will considerably enlarge the sample of stars eligible to asteroseismic age determination and should allow to estimate the age of individual stars with a 10-20% accuracy.
Stellar ages from asteroseismology: a few examples
Authors: Vauclair Sylvie 
Published: June 2009

AbstractAsteroseismology is a powerful tool to derive stellar ages, masses, gravities, radii, etc. Precise determinations of these parameters need deep analyses for each individual stars. Approximate theories are not efficient enough. Here I present results for two stars, μ Arae and ι Hor, which have both been observed during eight nights with the HARPS spectrograph in La Silla. I also show that important constraints can be obtained on core overshooting using the same techniques.
Stellar age dating with thorium, uranium and lead
Authors: Frebel Anna , Kratz Karl-Ludwig 
Published: June 2009

AbstractWe present HE 1523-0901, a metal-poor star in which the radioactive elements Th and U could be detected. Only three stars have measured U abundances, of which HE 1523-0901 has the most confidently determined value. From comparing the stable Eu, Os, and Ir abundances with measurements of Th and U, stellar ages can be derived. Based on seven such chronometer abundance ratios, the age of HE 1523-0901 was found to be ~13 Gyr. Only an upper limit for Pb could be measured so far. Knowing all three abundances of Th, U, and Pb would provide a self-consistent test for r-process calculations. Pb is the beta- plus alpha-decay end-product of all decay chains in the mass region between Pb and the onset of dominant spontaneous fission above Th and U. Hence, in addition to Th/U also Th, U/Pb should be used to obtain a consistent picture for actinide chronometry. From recent r-process calculations within the classical “waiting-point” model, for a 13 Gyr old star we predict the respective abundance ratios of logϵ(Th/U) = 0.84, logϵ(Th/Pb) = −1.32 and logϵ(U/Pb) = −2.16. We compare these values with the measured abundance ratios in HE 1523-0901 of logϵ(Th/U) = 0.86, logϵ(Th/Pb) > −1.0 and logϵ(U/Pb) > −1.9. With this good level of agreement, HE 1523-0901 is already a vital probe for observational “near-field” cosmology by providing an independent lower limit for the age of the Universe.
A comparative assessment of octanol-water partitioning and distribution constant estimation methods for perfluoroalkyl carboxylates and sulfonates
Authors: Rayne Sierra , Forest Kaya 
Published: June 2009

AbstractNew experimental data is available in the literature regarding the octanol-water distribution behavior of representative straight chain perfluoroalkyl carboxylate (PFCA) and sulfonate (PFSA) congeners. The current study provides the first investigation into the predictive ability of various software programs for estimating the corresponding octanol-water partitioning (log P) and distribution (log D) constants of PFCAs and PFSAs. Wide predictive variation was found within and between the various methods. Several programs were able to accurately estimate the log P/D fragmental contributions of a -CF~2~- group for PFCAs, as well as the associated Gibbs free energies for partitioning into octanol from water due to the hydrophobic character of the perfluoroalkyl chain (Δ~hydrophobic~G~ow~). Only the SPARC log D method accurately predicted the electrostatic contributions of the carboxylate head group (Δ~electrostatic~G~ow~) towards octanol-water partitioning for PFCAs. Similar log D values and organic carbon normalized sediment-water partitioning coefficients (K~oc~) for PFCAs and PFSAs having equivalent perfluoroalkyl chain lengths suggests potentially equivalent Δ~electrostatic~G~ow~ and Δ~hydrophobic~G~ow~ contributions towards lipophilic partitioning for these two contaminant classes at near neutral pH values, regardless of head group identity. In contrast, there are potentially different Δ~electrostatic~G~ow~ and Δ~hydrophobic~G~ow~ contributions towards proteinophilic partitioning under biologically relevant conditions.
Subjective Improvement in Proprioception in 2 Patients With Atypical Friedreich Ataxia Treated With Varenicline (Chantix)
Authors: Zesiewicz Theresa A , Sullivan Kelly L , Gooch Clifton L , Lynch David R 
Published: June 2009

Abstract

Two patients with atypical Friedreich ataxia (heterozygotes for a GAA expansion and a G130V point mutation) experienced modest proprioceptive improvements in their extremities within a month of taking varenicline (Chantix), a drug approved for smoking cessation.
Demyelinating Findings in Typical and Atypical Chronic Inflammatory Demyelinating Polyneuropathy: Sensitivity and Specificity
Authors: De Sousa Eduardo A , Chin Russell L , Sander Howard W , Latov Norman , Brannagan Thomas H 
Published: June 2009

Objective:
The objective of this study was to evaluate how the number of demyelinating findings (DF) on nerve conductions affects sensitivity and specificity of electrodiagnostic criteria for chronic inflammatory demyelinating polyneuropathy (CIDP).

Methods:
Electrodiagnostic findings of 26 consecutive patients with CIDP were compared with amyotrophic lateral sclerosis (ALS) and diabetic polyneuropathy controls. Patients with CIDP were divided into typical and atypical CIDP, as defined elsewhere.

Results:
Depending on the minimal required number (MRN) of DF on nerve conductions, sensitivities decreased from an arbitrary 100% to 58% and 54%, for an MRN of 1, 2, and 3, respectively, as specificities increased, from 48% to 81% and 95%, respectively. The number of DF per patient was higher in typical CIDP than in atypical CIDP.

Conclusions:
The considerable gap between specificity and sensitivity is the reason for controversy regarding the MRN for the diagnosis of CIDP. Requiring 2 or more DFs to identify CIDP increases specificity from 48% to 81% but lowers sensitivity from 100% to 58%. For patients with other potential causes of neuropathy, the requirement of 2 or more DFs could further increase specificity.
Rituximab for the Treatment of Thymoma-Associated and De Novo Myasthenia Gravis: 3 Cases and Review
Authors: Nelson Robert P , Pascuzzi Robert M , Kessler Kenneth , Walsh Laurence E , Faught Phillip P , Ramanuja Srinivasan , Pescovitz Mark D , Loehrer Patrick J 
Published: June 2009

Abstract

Objectives:
Myasthenia gravis (MG) is an immune-mediated disorder associated with autoantibodies against postsynaptic nicotinic acetylcholine receptors at neuromuscular junctions. Rituximab, a monoclonal antibody specific for CD20, is used primarily to treat B-cell non-Hodgkin lymphoma. Although it has been used for treatment of a number of autoimmune diseases, there is limited experience in MG.

Methods:
Three patients with refractory MG (2 with concurrent thymoma) were given rituximab.

Results:
Symptoms stabilized and reductions in immunosuppressive medications were tolerated for extended periods, without adverse effects or infectious complications.

Conclusions:
These observations support the concept that rituximab may be helpful for the treatment of MG. Remissions in patients with or without thymoma are achievable with rituximab given in combination with commonly used modalities. Furthermore, rituximab is not necessarily contraindicated for the treatment of MG in patients being treated for thymoma. Controlled studies are called for to define its role in the treatment of refractory MG.
Facial and Trigeminal Neuropathies as the Initial Manifestation of Chronic Inflammatory Demyelinating Polyradiculopathy
Authors: Varela Heber , Rubin Devon I 
Published: June 2009

Abstract

Objective:
To report the clinical and electrophysiological features of a patient who presented with facial weakness and numbness as the initial manifestation of Chronic inflammatory demyelinating polyradiculopathy (CIDP).

Case Report:
An 83-year-old woman presented with facial numbness and weakness. Examination demonstrated mild facial weakness with no other cranial abnormalities. Blink and jaw-jerk reflex latencies were prolonged bilaterally; myokymic discharges were seen in the right frontalis. Cerebrospinal fluid demonstrated an elevated protein. After 3 weeks of intravenous immunoglobulin treatment, the symptoms and electrophysiological findings improved but the symptoms recurred and became more generalized after cessation of intravenous immunoglobulin.

Conclusions:
This case represents a patient with an unusual initial presentation of cranial nerve involvement in CIDP. Blink reflexes may be a useful electrophysiological technique to assess for peripheral nerve demyelination in patients with suspected CIDP.
Improvement in Aerobic Capacity After an Exercise Program in Sporadic Inclusion Body Myositis
Authors: Johnson Liam G , Collier Kelly E , Edwards Dylan J , Philippe Danielle L , Eastwood Peter R , Walters Susan E , Thickbroom Gary W , Mastaglia Frank L 
Published: June 2009

Abstract

Objectives:
The study aimed to investigate the effects of a combined functional and aerobic exercise program on aerobic capacity, muscle strength, and functional mobility in a group of patients with sporadic inclusion body myositis (IBM).

Methods:
Aerobic capacity, muscle strength, and functional capacity assessments were conducted on 7 participants with sporadic IBM before and after a 12-week exercise program, which included resistance exercises and aerobic stationary cycling 3 times per week on alternative days.

Results:
Aerobic capacity of the group increased significantly by 38%, and significant strength improvements were observed in 4 of the muscle groups tested (P < 0.05). The exercise program was well tolerated, and there was no significant change in the serum creatine kinase level after the exercise period.

Conclusions:
An aerobic exercise program can be safely tolerated by patients with sporadic IBM and can improve aerobic capacity and muscle strength when combined with resistance training. These findings indicate that aerobic and functional muscle strengthening exercise should be considered in the management of patients with IBM.
Multiple Cranial Neuropathy Associated With Herpes Simplex Virus Infection and Anti-GM2 Immunoglobulin M Antibodies
Authors: Santos-García Diego , Llaneza M , Macias M , Fuente-Fernández R de la 
Published: June 2009

Abstract

Antiganglioside antibodies can appear after several acute infections and are often associated with various clinical patterns of Guillain-Barré syndrome. Thus, for example, cytomegalovirus infection has been associated with anti-GM2 antibodies and Guillain-Barré syndrome variants with severe sensory loss and cranial nerve involvement. We report on a patient who developed multiple cranial neuropathy associated with herpes simplex virus infection and anti-GM2 immunoglobulin M antibodies.
Myasthenia Gravis With Presynaptic Electrophysiologic Abnormalities
Authors: Callaghan Brian , Moster Mark L , Bird Shawn J 
Published: June 2009

Abstract

Objectives:
To describe the clinical, serologic, and electrophysiologic features of 2 patients with myasthenia gravis (MG), who also had presynaptic electrophysiologic abnormalities.

Methods:
Case reports.

Results:
Two patients developed clinical symptoms consistent with MG. They lacked autonomic symptoms or signs, and their reflexes were not absent. Acetylcholine receptor antibody studies were positive, but assays for voltage-gated calcium channel antibodies were negative. Low-amplitude baseline compound muscle action potentials combined with large incremental responses immediately after exercise were consistent with a presynaptic disorder. Thymic pathology in 1 patient was characteristic of autoimmune MG showing lymphoid follicular hyperplasia. No underlying malignancy was found in either patient.

Conclusions:
Patients with MG may rarely have presynaptic electrophysiologic abnormalities. This may occur even in the absence of the typical clinical and serologic features of the Lambert-Eaton syndrome. It is possible that there is another antibody present that is modulating presynaptic acetylcholine release.
The Honeybee Apis mellifera
Authors: Dearden Peter K. , Duncan Elizabeth J. , Wilson Megan J. 
Published: June 2009

INTRODUCTIONHoneybees (Apis mellifera) are distributed throughout the world and have a critical role in the pollination of crops and pasture. Honeybees have an intricate social structure and display complex behavioral traits such as sociality, language, division of labor, and exceptional feats of learning and memory. Honeybees also exhibit polyphenism, whereby the females can either develop as workers or as morphologically distinct, reproductively active queens. Although historical studies of honeybee biology have been performed, the recent advent of the genome sequence and a number of other modern tools have made dissection of the molecular details of this remarkable insect possible.
Selection and Evaluation of Tag-SNPs Using Tagger and HapMap
Authors: de Bakker Paul I.W. 
Published: June 2009

INTRODUCTIONThe HapMap can guide the design and analysis of genome-wide association studies by documenting not only the location of these single-nucleotide polymorphisms (SNPs) but also the correlation structure between them. This article describes how to use the Tagger web server for tag-SNP selection and evaluation using HapMap data.
Counting Chromosomes in Embryonic Stem (ES) Cells
Authors: Nagy Andras , Gertsenstein Marina , Vintersten Kristina , Behringer Richard 
Published: June 2009

INTRODUCTIONAneuploidy in embryonic stem (ES) cells is the major cause of failure in obtaining contributions to all tissues of chimeras, including the germ line. This protocol describes a simple method for counting chromosomes from metaphase spreads in ES cells. ES cell clones showing euploidy on 70%-80% of spreads are used for chimera production.