41 research outputs found
A Hubble Space Telescope Survey for Resolved Companions of Planetary-Nebula Nuclei
We report results of an HST "snapshot" survey aimed at finding resolved
binary companions of the central stars of Galactic planetary nebulae (PNe).
Using WF/PC and WFPC2, we searched the fields of 113 PNe for stars whose close
proximity to the central star suggests a physical association. We find 10
binary nuclei that are very likely to be physically associated, and another six
that are possible binary associations. By correcting for interstellar
extinction and placing the central stars' companions on the main sequence, we
derive distances to the objects, and thereby significantly increase the number
of PNe with reliable distances.
Comparison of our derived distances with those obtained from various
statistical methods shows that all of the latter have systematically
overestimated the distances, by factors ranging up to a factor of two or more.
We show that this error is most likely due to the fact that the properties of
our PNe with binary nuclei are systematically different from those of PNe used
heretofore to calibrate statistical methods. Specifically, our PNe tend to have
lower surface brightnesses at the same physical radius than the traditional
calibration objects. This difference may arise from a selection effect: the PNe
in our survey are typically nearby, old nebulae, whereas most of the objects
that calibrate statistical techniques are low-latitude,
high-surface-brightness, and more distant nebulae. As a result, the statistical
methods that seem to work well with samples of distant PNe, e.g., those in the
Galactic bulge or external galaxies, may not be applicable to the more diverse
population of local PNe.Comment: 37 text pages, 17 table pages, 9 figures. Accepted by Astronomical
Journal for June 1999 issu
Ways of preventing surgeon burnout.
In surgical practice, numerous sources of stress (stressors) are unpredictable, two examples being daily workload and postoperative complications. They may help to explain surgeon burnout, of which the prevalence (34 to 53%) has been the subject of many studies. That said, even though assessments are legion, recommended solutions have been few and far between, especially insofar as by nature and training, surgeons are disinclined to interest themselves in burnout, which they are prone to consider as something experienced by "others". The objective of this attempt at clarification is to identify in the literature the strategies put forward in view of avoiding surgeon burnout, and to assess the impact of this phenomenon not only on the surgeon's professional and personal entourage, but also on patient safety. Prevention-based strategies, many of them focused on modifiable stressors, will be detailed
Lâatteinte cognitive est associĂ©e Ă une rupture de la barriĂšre hĂ©mato-encĂ©phalique et aux concentrations dâindoxyl sulfate dans deux modĂšles de maladie rĂ©nale chronique chez le rat
Insuffisance rénale chronique aprÚs transplantation hépatique : tout se joue pendant la période périopératoire !
Foaming in Glass Melts Produced by Sodium Sulfate Decomposition under Ramp Heating Conditions
COMMENTS ON W. B. STERN AND Y. GERBER, 'POTASSIUM-CALCIUM GLASS: NEW DATA AND EXPERIMENTS', ARCHAEOMETRY, 46(1) (2004), 137-56*
Atomic force and electron microscopic-based study of sarcolemmal surface of living cardiomyocytes unveils unexpected mitochondrial shift in heart failure.
Loss of T-tubules (TT), sarcolemmal invaginations of cardiomyocytes (CMs), was recently identified as a general heart failure (HF) hallmark. However, whether TT per se or the overall sarcolemma is altered during HF process is still unknown. In this study, we directly examined sarcolemmal surface topography and physical properties using Atomic Force Microscopy (AFM) in living CMs from healthy and failing mice hearts. We confirmed the presence of highly organized crests and hollows along myofilaments in isolated healthy CMs. Sarcolemma topography was tightly correlated with elasticity, with crests stiffer than hollows and related to the presence of few packed subsarcolemmal mitochondria (SSM) as evidenced by electron microscopy. Three days after myocardial infarction (MI), CMs already exhibit an overall sarcolemma disorganization with general loss of crests topography thus becoming smooth and correlating with a decreased elasticity while interfibrillar mitochondria (IFM), myofilaments alignment and TT network were unaltered. End-stage post-ischemic condition (15days post-MI) exacerbates overall sarcolemma disorganization with, in addition to general loss of crest/hollow periodicity, a significant increase of cell surface stiffness. Strikingly, electron microscopy revealed the total depletion of SSM while some IFM heaps could be visualized beneath the membrane. Accordingly, mitochondrial Ca(2+) studies showed a heterogeneous pattern between SSM and IFM in healthy CMs which disappeared in HF. In vitro, formamide-induced sarcolemmal stress on healthy CMs phenocopied post-ischemic kinetics abnormalities and revealed initial SSM death and crest/hollow disorganization followed by IFM later disarray which moved toward the cell surface and structured heaps correlating with TT loss. This study demonstrates that the loss of crest/hollow organization of CM surface in HF occurs early and precedes disruption of the TT network. It also highlights a general stiffness increased of the CM surface most likely related to atypical IFM heaps while SSM died during HF process. Overall, these results indicate that initial sarcolemmal stress leading to SSM death could underlie subsequent TT disarray and HF setting