3,025 research outputs found
Measurement of stimulated Hawking emission in an analogue system
There is a mathematical analogy between the propagation of fields in a
general relativistic space-time and long (shallow water) surface waves on
moving water. Hawking argued that black holes emit thermal radiation via a
quantum spontaneous emission. Similar arguments predict the same effect near
wave horizons in fluid flow. By placing a streamlined obstacle into an open
channel flow we create a region of high velocity over the obstacle that can
include wave horizons. Long waves propagating upstream towards this region are
blocked and converted into short (deep water) waves. This is the analogue of
the stimulated emission by a white hole (the time inverse of a black hole), and
our measurements of the amplitudes of the converted waves demonstrate the
thermal nature of the conversion process for this system. Given the close
relationship between stimulated and spontaneous emission, our findings attest
to the generality of the Hawking process.Comment: 7 pages, 5 figures. This version corrects a processing error in the
final graph 5b which multiplied the vertical axis by 2. The graph, and the
data used from it, have been corrected. Some minor typos have also been
corrected. This version also uses TeX rather than Wor
Aircraft engine with inter-turbine engine frame supported counter rotating low pressure turbine rotors
An aircraft gas turbine engine assembly includes an inter-turbine frame axially located between high and low pressure turbines. Low pressure turbine has counter rotating low pressure inner and outer rotors with low pressure inner and outer shafts which are at least in part rotatably disposed co-axially within a high pressure rotor. Inter-turbine frame includes radially spaced apart radially outer first and inner second structural rings disposed co-axially about a centerline and connected by a plurality of circumferentially spaced apart struts. Forward and aft sump members having forward and aft central bores are fixedly joined to axially spaced apart forward and aft portions of the inter-turbine frame. Low pressure inner and outer rotors are rotatably supported by a second turbine frame bearing mounted in aft central bore of aft sump member. A mount for connecting the engine to an aircraft is located on first structural ring
Enantioselective Decarboxylative Arylation of α-Amino Acids via the Merger of Photoredox and Nickel Catalysis
An asymmetric decarboxylative C_(sp)^3âC_(sp)^2 cross-coupling has been achieved via the synergistic merger of photoredox and nickel catalysis. This mild, operationally simple protocol transforms a wide variety of naturally abundant α-amino acids and readily available aryl halides into valuable chiral benzylic amines in high enantiomeric excess, thereby producing motifs found in pharmacologically active agents
802.16e System Profile for NASA Extra-Vehicular Activities
This report identifies an 802.16e system profile that is applicable to a lunar surface wireless network, and specifically for meeting extra-vehicular activity (EVA) data flow requirements. EVA suit communication needs are addressed. Design-driving operational scenarios are considered. These scenarios are then used to identify a configuration of the 802.16e system (system profile) that meets EVA requirements, but also aim to make the radio realizable within EVA constraints. Limitations of this system configuration are highlighted. An overview and development status is presented by Toyon Research Corporation concerning the development of an 802.16e compatible modem under NASA s Small Business Innovative Research (SBIR) Program. This modem is based on the recommended system profile developed as part of this report. Last, a path forward is outlined that presents an evolvable solution for the EVA radio system and lunar surface radio networks. This solution is based on a custom link layer, and 802.16e compliant physical layer compliant to the identified system profile, and a later progression to a fully interoperable 802.16e system
Acceptance and Commitment Therapy for Symptom Interference in Advanced Lung Cancer and Caregiver Distress: A Pilot Randomized Trial
Context
Advanced lung cancer patients typically have a poor prognosis and many symptoms that interfere with functioning, contributing to high rates of emotional distress in both patients and family caregivers. There remains a need for evidence-based interventions to improve functional outcomes and distress in this population.
Objectives
This pilot trial examined the feasibility and preliminary efficacy of telephone-based Acceptance and Commitment Therapy (ACT) for symptomatic, advanced lung cancer patients and their distressed family caregivers. Primary outcomes were patient symptom interference with functioning and patient and caregiver distress.
Methods
Symptomatic, advanced lung cancer patients and distressed caregivers (n = 50 dyads) were randomly assigned to six sessions of ACT or an education/support condition. Patients completed measures of symptom interference and measures assessing the severity of fatigue, pain, sleep disturbance, and breathlessness. Patients and caregivers completed measures of distress and illness acceptance and struggle.
Results
The eligibility screening rate (51%) and retention rate (76% at six weeks postintervention) demonstrated feasibility. No group differences were found with respect to patient and caregiver outcomes. Both groups showed a small, significant decrease in struggle with the illness over the study period, but did not show meaningful change in other outcomes.
Conclusion
Findings suggest that telephone-based ACT is feasible for many advanced lung cancer patients and caregivers, but may not substantially reduce symptom interference and distress. Low baseline levels of certain symptoms may have contributed to null findings. Next steps include applying ACT to specific, clinically meaningful symptom interference and varying intervention dose and modality
CMBPol Mission Concept Study: Foreground Science Knowledge and Prospects
We report on our knowledge of Galactic foregrounds, as well as on how a CMB
satellite mission aiming at detecting a primordial B-mode signal (CMBPol) will
contribute to improving it. We review the observational and analysis techniques
used to constrain the structure of the Galactic magnetic field, whose presence
is responsible for the polarization of Galactic emissions. Although our current
understanding of the magnetized interstellar medium is somewhat limited,
dramatic improvements in our knowledge of its properties are expected by the
time CMBPol flies. Thanks to high resolution and high sensitivity instruments
observing the whole sky at frequencies between 30 GHz and 850 GHz, CMBPol will
not only improve this picture by observing the synchrotron emission from our
galaxy, but also help constrain dust models. Polarized emission from
interstellar dust indeed dominates over any other signal in CMBPol's highest
frequency channels. Observations at these wavelengths, combined with
ground-based studies of starlight polarization, will therefore enable us to
improve our understanding of dust properties and of the mechanism(s)
responsible for the alignment of dust grains with the Galactic magnetic field.
CMBPol will also shed new light on observations that are presently not well
understood. Morphological studies of anomalous dust and synchrotron emissions
will indeed constrain their natures and properties, while searching for
fluctuations in the emission from heliospheric dust will test our understanding
of the circumheliospheric interstellar medium. Finally, acquiring more
information on the properties of extra-Galactic sources will be necessary in
order to maximize the cosmological constraints extracted from CMBPol's
observations of CMB lensing. (abridged)Comment: 43 pages, 7 figures, 2 table
Genome landscapes and bacteriophage codon usage
Across all kingdoms of biological life, protein-coding genes exhibit unequal
usage of synonmous codons. Although alternative theories abound, translational
selection has been accepted as an important mechanism that shapes the patterns
of codon usage in prokaryotes and simple eukaryotes. Here we analyze patterns
of codon usage across 74 diverse bacteriophages that infect E. coli, P.
aeruginosa and L. lactis as their primary host. We introduce the concept of a
`genome landscape,' which helps reveal non-trivial, long-range patterns in
codon usage across a genome. We develop a series of randomization tests that
allow us to interrogate the significance of one aspect of codon usage, such a
GC content, while controlling for another aspect, such as adaptation to
host-preferred codons. We find that 33 phage genomes exhibit highly non-random
patterns in their GC3-content, use of host-preferred codons, or both. We show
that the head and tail proteins of these phages exhibit significant bias
towards host-preferred codons, relative to the non-structural phage proteins.
Our results support the hypothesis of translational selection on viral genes
for host-preferred codons, over a broad range of bacteriophages.Comment: 9 Color Figures, 5 Tables, 53 Reference
One-Year Risk of Stroke after Transient Ischemic Attack or Minor Stroke
BACKGROUND Previous studies conducted between 1997 and 2003 estimated that the risk of stroke or an acute coronary syndrome was 12 to 20% during the first 3 months after a transient ischemic attack (TIA) or minor stroke. The TIAregistry.org project was designed to describe the contemporary profile, etiologic factors, and outcomes in patients with a TIA or minor ischemic stroke who receive care in health systems that now offer urgent evaluation by stroke specialists.
METHODS We recruited patients who had had a TIA or minor stroke within the previous 7 days. Sites were selected if they had systems dedicated to urgent evaluation of patients with TIA. We estimated the 1-year risk of stroke and of the composite outcome of stroke, an acute coronary syndrome, or death from cardiovascular causes. We also examined the association of the ABCD2 score for the risk of stroke (range, 0 [lowest risk] to 7 [highest risk]), findings on brain imaging, and cause of TIA or minor stroke with the risk of recurrent stroke over a period of 1 year.
RESULTS From 2009 through 2011, we enrolled 4789 patients at 61 sites in 21 countries. A total of 78.4% of the patients were evaluated by stroke specialists within 24 hours after symptom onset. A total of 33.4% of the patients had an acute brain infarction, 23.2% had at least one extracranial or intracranial stenosis of 50% or more, and 10.4% had atrial fibrillation. The KaplanâMeier estimate of the 1-year event rate of the composite cardiovascular outcome was 6.2% (95% confidence interval, 5.5 to 7.0). KaplanâMeier estimates of the stroke rate at days 2, 7, 30, 90, and 365 were 1.5%, 2.1%, 2.8%, 3.7%, and 5.1%, respectively. In multivariable analyses, multiple infarctions on brain imaging, large-artery atherosclerosis, and an ABCD2 score of 6 or 7 were each associated with more than a doubling of the risk of stroke.
CONCLUSIONS We observed a lower risk of cardiovascular events after TIA than previously reported. The ABCD2 score, findings on brain imaging, and status with respect to large-artery atherosclerosis helped stratify the risk of recurrent stroke within 1 year after a TIA or minor stroke. (Funded by Sanofi and Bristol-Myers Squibb.)Supported by an unrestricted grant from Sanofi and Bristol-Myers Squibb
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