596 research outputs found
Baseline shifts in coral skeletal oxygen isotopic composition: a signature of symbiont shuffling?
Decades-long records of the stable isotopic composition of coral skeletal cores were analyzed from four sites on the Mesoamerican Reef. Two of the sites exhibited baseline shifts in oxygen isotopic composition after known coral bleaching events. Changes in pH at the calcification site caused by a change in the associated symbiont community are invoked to explain the observed shift in the isotopic composition. To test the hypothesis that changes in symbiont clade could affect skeletal chemistry, additional coral samples were collected from Belize for paired Symbiodinium identification and skeletal stable isotopic analysis. We found some evidence that skeletal stable isotopic composition may be affected by symbiont clade and suggest this is an important topic for future investigation. If different Symbiodinium clades leave consistent signatures in skeletal geochemical composition, the signature will provide a method to quantify past symbiont shuffling events, important for understanding how corals are likely to respond to climate change
Starlight Demonstration of the Dragonfly Instrument: an Integrated Photonic Pupil Remapping Interferometer for High Contrast Imaging
In the two decades since the first extra-solar planet was discovered, the
detection and characterization of extra-solar planets has become one of the key
endeavors in all of modern science. Recently direct detection techniques such
as interferometry or coronography have received growing attention because they
reveal the population of exoplanets inaccessible to Doppler or transit
techniques, and moreover they allow the faint signal from the planet itself to
be investigated. Next-generation stellar interferometers are increasingly
incorporating photonic technologies due to the increase in fidelity of the data
generated. Here, we report the design, construction and commissioning of a new
high contrast imager; the integrated pupil-remapping interferometer; an
instrument we expect will find application in the detection of young faint
companions in the nearest star-forming regions. The laboratory characterisation
of the instrument demonstrated high visibility fringes on all interferometer
baselines in addition to stable closure phase signals. We also report the first
successful on-sky experiments with the prototype instrument at the 3.9-m
Anglo-Australian Telescope. Performance metrics recovered were consistent with
ideal device behaviour after accounting for expected levels of decoherence and
signal loss from the uncompensated seeing. The prospect of complete
Fourier-coverage coupled with the current performance metrics means that this
photonically-enhanced instrument is well positioned to contribute to the
science of high contrast companions.Comment: 10 pages, 7 figures, accepted to Mon. Not. of Roy. Ast. Soc., 201
Treatment of Small-Cell Lung Cancer: American Society of Clinical Oncology Endorsement of the American College of Chest Physicians Guideline
PURPOSE: The American College of Chest Physicians (ACCP) produced an evidence-based guideline on treatment of patients with small-cell lung cancer (SCLC). Because of the relevance of this guideline to American Society of Clinical Oncology (ASCO) membership, ASCO reviewed the guideline, applying a set of procedures and policies used to critically examine guidelines developed by other organizations.
METHODS: The ACCP guideline on the treatment of SCLC was reviewed for developmental rigor by methodologists. An ASCO Endorsement Panel updated the literature search, reviewed the content, and considered additional recommendations.
RESULTS: The ASCO Endorsement Panel determined that the recommendations from the ACCP guideline, published in 2013, are clear, thorough, and based on current scientific evidence. ASCO endorses the ACCP guideline on the treatment of SCLC, with the addition of qualifying statements.
RECOMMENDATIONS: Surgery is indicated for selected stage I SCLC. Limited-stage disease should be treated with concurrent chemoradiotherapy in patients with good performance status. Thoracic radiotherapy should be administered early in the course of treatment, preferably beginning with cycle one or two of chemotherapy. Chemotherapy should consist of four cycles of a platinum agent and etoposide. Extensive-stage disease should be treated primarily with chemotherapy consisting of a platinum agent plus etoposide or irinotecan. Prophylactic cranial irradiation prolongs survival in patients with limited-stage disease who achieve a complete or partial response to initial therapy and may do so in similarly responding patients with extensive-stage disease as well. Additional information is available at http://www.asco.org/endorsements/sclc and http://www.asco.org/guidelineswiki
Time-Resolved Spectroscopy of the 3 Brightest and Hardest Short Gamma-Ray Bursts Observed with the FGST Gamma-Ray Burst Monitor
From July 2008 to October 2009, the Gamma-ray Burst Monitor (GBM) on board
the Fermi Gamma-ray Space Telescope (FGST) has detected 320 Gamma-Ray Bursts
(GRBs). About 20% of these events are classified as short based on their T90
duration below 2 s. We present here for the first time time-resolved
spectroscopy at timescales as short as 2 ms for the three brightest short GRBs
observed with GBM. The time-integrated spectra of the events deviate from the
Band function, indicating the existence of an additional spectral component,
which can be fit by a power-law with index ~-1.5. The time-integrated Epeak
values exceed 2 MeV for two of the bursts, and are well above the values
observed in the brightest long GRBs. Their Epeak values and their low-energy
power-law indices ({\alpha}) confirm that short GRBs are harder than long ones.
We find that short GRBs are very similar to long ones, but with light curves
contracted in time and with harder spectra stretched towards higher energies.
In our time-resolved spectroscopy analysis, we find that the Epeak values range
from a few tens of keV up to more than 6 MeV. In general, the hardness
evolutions during the bursts follows their flux/intensity variations, similar
to long bursts. However, we do not always see the Epeak leading the light-curve
rises, and we confirm the zero/short average light-curve spectral lag below 1
MeV, already established for short GRBs. We also find that the time-resolved
low-energy power-law indices of the Band function mostly violate the limits
imposed by the synchrotron models for both slow and fast electron cooling and
may require additional emission processes to explain the data. Finally, we
interpreted these observations in the context of the current existing models
and emission mechanisms for the prompt emission of GRBs.Comment: 14 pages, 10 figures, 9 tables, Accepted for publication in the
Astrophysical Journal September, 23 2010 (Submitted May, 16 2010)
Corrections: 1 reference updated, figure 10 captio
A mutation affecting the sodium/proton exchanger, SLC9A6, causes mental retardation with tau deposition
We have studied a family with severe mental retardation characterized by the virtual absence of speech, autism spectrum disorder, epilepsy, late-onset ataxia, weakness and dystonia. Post-mortem examination of two males revealed widespread neuronal loss, with the most striking finding being neuronal and glial tau deposition in a pattern reminiscent of corticobasal degeneration. Electron microscopic examination of isolated tau filaments demonstrated paired helical filaments and ribbon-like structures. Biochemical studies of tau demonstrated a preponderance of 4R tau isoforms. The phenotype was linked to Xq26.3, and further analysis identified an in-frame 9 base pair deletion in the solute carrier family 9, isoform A6 (SLC9A6 gene), which encodes sodium/hydrogen exchanger-6 localized to endosomal vesicles. Sodium/hydrogen exchanger-6 is thought to participate in the targeting of intracellular vesicles and may be involved in recycling synaptic vesicles. The striking tau deposition in our subjects reveals a probable interaction between sodium/proton exchangers and cytoskeletal elements involved in vesicular transport, and raises the possibility that abnormalities of vesicular targeting may play an important role in more common disorders such as Alzheimer's disease and autism spectrum disorder
Population Health Solutions for Assessing Cognitive Impairment in Geriatric Patients.
In December 2017, the National Academy of Neuropsychology convened an interorganizational Summit on Population Health Solutions for Assessing Cognitive Impairment in Geriatric Patients in Denver, Colorado. The Summit brought together representatives of a broad range of stakeholders invested in the care of older adults to focus on the topic of cognitive health and aging. Summit participants specifically examined questions of who should be screened for cognitive impairment and how they should be screened in medical settings. This is important in the context of an acute illness given that the presence of cognitive impairment can have significant implications for care and for the management of concomitant diseases as well as pose a major risk factor for dementia. Participants arrived at general principles to guide future screening approaches in medical populations and identified knowledge gaps to direct future research. Key learning points of the summit included: recognizing the importance of educating patients and healthcare providers about the value of assessing current and baseline cognition;emphasizing that any screening tool must be appropriately normalized and validated in the population in which it is used to obtain accurate information, including considerations of language, cultural factors, and education; andrecognizing the great potential, with appropriate caveats, of electronic health records to augment cognitive screening and tracking of changes in cognitive health over time
Vascular complications of prosthetic inter-vertebral discs
Five consecutive cases of prosthetic inter-vertebral disc displacement with severe vascular complications on revisional surgery are described. The objective of this case report is to warn spinal surgeons that major vascular complications are likely with anterior displacement of inter-vertebral discs. We have not been able to find a previous report on vascular complications associated with anterior displacement of prosthetic inter-vertebral discs. In all five patients the prosthetic disc had eroded into the bifurcation of the inferior vena cava and the left common iliac vein. In three cases the aortic bifurcation was also involved. The fibrosis was so severe that dissecting out the arteries and veins to provide access to the relevant disc proved impossible. Formal division of the left common iliac vein and artery with subsequent repair was our solution. Anterior inter-vertebral disc displacement was associated with severe vascular injury. Preventing anterior disc displacement is essential in disc design. In the event of anterior displacement, disc removal should be planned with a Vascular Surgeon
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