3,622 research outputs found
REIT Stock Repurchases: Completion Rates, Long - Run Returns, and the Straddle Hypothesis
This study of real estate investment trusts (REITs) analyzes three possible explanations for the stock price reaction to a repurchase announcement and the subsequent repurchase behavior of managers under each hypothesis. Two of the hypotheses, the signaling hypothesis and the exchange option hypothesis, are established in the existing literature; the third hypothesis is a modification of the exchange option hypothesis. The exchange option hypothesis is extended to allow for additional flexibility in management decisions. This extended exchange option hypothesis is termed the ââstraddleââ hypothesis because it provides management with both a call and put option. The empirical analyses show the straddle hypothesis is a more robust explanation of changes in shares outstanding in the postannouncement period than the alternative explanations.
Constraints on the Intergalactic Transport of Cosmic Rays
Motivated by recent experimental proposals to search for extragalactic cosmic
rays (including anti-matter from distant galaxies), we study particle
propagation through the intergalactic medium (IGM). We first use estimates of
the magnetic field strength between galaxies to constrain the mean free path
for diffusion of particles through the IGM. We then develop a simple analytic
model to describe the diffusion of cosmic rays. Given the current age of
galaxies, our results indicate that, in reasonable models, a completely
negligible number of particles can enter our Galaxy from distances greater than
Mpc for relatively low energies ( GeV/n). We also find
that particle destruction in galaxies along the diffusion path produces an
exponential suppression of the possible flux of extragalactic cosmic rays.
Finally, we use gamma ray constraints to argue that the distance to any
hypothetical domains of anti-matter must be roughly comparable to the horizon
scale.Comment: 24 pages, AAS LaTex, 1 figure, accepted to Ap
Assessment of an Innovative Medication Adherence Training Exercise in an Interprofessional Training Program
OBJECTIVE To assess the effect of an innovative training exercise on post-graduate healthcare traineesâ knowledge and perspectives of medication adherence and skills gained within an interprofessional training program.
METHODS Postgraduate trainees (medicine, pharmacy, advanced practice nursing, and mental health) at the Michael E. DeBakey VA Medical Centerâs Center of Excellence in Primary Care Education interprofessional training program participated in a medication adherence exercise and training session. The session included a formal PowerPoint presentation, an innovative medication adherence simulation exercise, clinical scenarios, and a journal club. Verbal feedback during the debriefing session occurred after the medication adherence simulation exercise and throughout the session.
RESULTS
Six trainees participated in the exercise and training session (2 medical residents, 2 nurse practitioner residents, 1 pharmacy resident, and 1 clinical psychology fellow). Trainees reported developing a greater understanding for barriers patients face with medication adherence, empathy, and strategies to manage patientsâ medication adherence.
CONCLUSIONS
The medication adherence exercise and training session provided an opportunity for healthcare professionals from different professions to discuss medication adherence and share their educational training and previous clinical experiences within an interprofessional training program
Photoevaporation of Circumstellar Disks due to External FUV Radiation in Stellar Aggregates
When stars form in small groups (N = 100 - 500 members), their circumstellar
disks are exposed to little EUV radiation but a great deal of FUV radiation
from massive stars in the group. This paper calculates mass loss rates for
circumstellar disks exposed to external FUV radiation. Previous work treated
large disks and/or intense radiation fields in which the disk radius exceeds
the critical radius (supercritical disks) where the sound speed in the FUV
heated layer exceeds the escape speed. This paper shows that significant mass
loss still takes place for subcritical systems. Some of the gas extends beyond
the disk edge (above the disk surface) to larger distances where the
temperature is higher, the escape speed is lower, and an outflow develops. The
evaporation rate is a sensitive function of the stellar mass and disk radius,
which determine the escape speed, and the external FUV flux, which determines
the temperature structure of the flow. Disks around red dwarfs are readily
evaporated and shrink to disk radii of 15 AU on short time scales (10 Myr) when
exposed to moderate FUV fields with = 3000. Although disks around solar
type stars are more durable, these disks shrink to 15 AU in 10 Myr for intense
FUV radiation fields with = 30,000; such fields exist in the central 0.7
pc of a cluster with N = 4000 stars. If our solar system formed in the presence
of such strong FUV radiation fields, this mechanism could explain why Neptune
and Uranus in our solar system are gas poor, whereas Jupiter and Saturn are gas
rich. This mechanism for photoevaporation can also limit the production of
Kuiper belt objects and can suppress giant planet formation in sufficiently
large clusters, such as the Hyades, especially for disks associated with low
mass stars.Comment: 49 pages including 12 figures; accepted to Ap
HIghMass - High HI Mass, HI-Rich Galaxies at : Combined HI and H Observations
We present resolved HI and CO observations of three galaxies from the
HIghMass sample, a sample of HI-massive (), gas-rich
( in top for their ) galaxies identified in the ALFALFA
survey. Despite their high gas fractions, these are not low surface brightness
galaxies, and have typical specific star formation rates (SFR) for their
stellar masses. The three galaxies have normal star formation rates for their
HI masses, but unusually short star formation efficiency scale lengths,
indicating that the star formation bottleneck in these galaxies is in the
conversion of HI to H, not in converting H to stars. In addition, their
dark matter spin parameters () are above average, but not
exceptionally high, suggesting that their star formation has been suppressed
over cosmic time but are now becoming active, in agreement with prior H
observations.Comment: 20 pages, 13 figure
Diversity and Keratin Degrading Ability of Fungi Isolated from Canadian Arctic Marine Bird Feathers
We present the first records of fungi associated with feathers from seabirds and sea ducks in the Canadian Arctic and sub-Arctic. Birds sampled in Nunavut and Newfoundland (Canada) included the Common Eider (Somateria mollissima), King Eider (S. spectabilis), Black-legged Kittiwake (Rissa tridactyla), Northern Fulmar (Fulmarus glacialis), Glaucous Gull (Larus hyperboreus), Black Guillemot (Cepphus grylle), and Thick-billed Murre (Uria lomvia). In total 19 fungal species were cultured from feathers, identified using ITS rDNA barcoding, and screened for their ability to degrade keratin using a keratin azure assay. Our results indicate that 1) of the 19 isolates, 74% were ascomycetes, while the remaining 26% were basidiomycetes (yeasts); 2) 21% of the ascomycete isolates demonstrated keratinolytic activity (a known pathogenicity factor for fungi that may potentially be harmful to birds); 3) the largest number of fungi were cultured from the sampled Thick-billed Murre; and 4) based on a multiple correspondence analysis, there is some indication that both the King Eider and the Thick-billed Murre collected in the low Arctic had distinct fungal communities that were different from each other and from the other birds sampled. Although our sample sizes were small, initial trends in point (4) do demonstrate that additional study is merited to assess whether the fungal community differences are influenced by variation in the known ecologies of the avian hosts and fungi identified.Nous prĂ©sentons les premiers enregistrements de champignons se rapportant aux plumes dâoiseaux et de canards de mer dans lâArctique et la rĂ©gion subarctique du Canada. Parmi les oiseaux Ă©chantillonnĂ©s au Nunavut et Ă Terre-Neuve (Canada), notons lâeider Ă duvet (Somateria mollissima), lâeider Ă tĂȘte grise (S. spectabilis), la mouette tridactyle (Rissa tridactyla), le fulmar borĂ©al (Fulmarus glacialis), le goĂ©land bourgmestre (Larus hyperboreus), le guillemot Ă miroir (Cepphus grylle) et le guillemot de BrĂŒnnich (Uria lomvia). En tout, 19 espĂšces de champignons ont Ă©tĂ© prĂ©levĂ©es Ă partir de plumes. Elles ont Ă©tĂ© identifiĂ©es au moyen de codes Ă barres ITS ADNr et examinĂ©es afin de dĂ©terminer si elles sont capables de dĂ©grader la kĂ©ratine, et ce, Ă lâaide dâune Ă©preuve de dĂ©gradation de la kĂ©ratine au bleu azur. Nos rĂ©sultats indiquent : 1) que parmi les 19 isolats, 74 % Ă©taient des ascomycĂštes et que les 26 % restants Ă©taient des basidiomycĂštes (levures); 2) que 21 % des isolats dâascomycĂštes ont affichĂ© une activitĂ© kĂ©ratinolytique (un facteur de pathogĂ©nicitĂ© pour les champignons, facteur susceptible de nuire aux oiseaux); 3) que le plus grand nombre de cultures de champignons a Ă©tĂ© prĂ©levĂ© chez le guillemot de BrĂŒnnich; et 4) que dâaprĂšs une analyse de correspondance multiple, il y a une certaine indication que les Ă©chantillons de lâeider Ă tĂȘte grise et du guillemot de BrĂŒnnich recueillis dans le Bas-Arctique comprenaient des communautĂ©s fongiques distinctes qui diffĂ©raient les unes des autres ainsi que des autres oiseaux Ă©chantillonnĂ©s. MĂȘme si la taille de nos Ă©chantillons Ă©tait petite, les premiĂšres tendances ressortant du point (4) dĂ©montrent quâil y a lieu de faire des Ă©tudes plus poussĂ©es afin de dĂ©terminer si les diffĂ©rences entre les communautĂ©s fongiques sont influencĂ©es par la variation des Ă©cologies connues des hĂŽtes aviaires et des champignons identifiĂ©s
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