828 research outputs found
Diminiode thermionic conversion with 111-iridium electrodes
Preliminary data indicating thermionic-conversion potentialities for a 111-iridium emitter and collector spaced 0.2 mm apart are presented. These results comprise output densities of current and of power as functions of voltage for three sets of emitter, collector, and reservoir temperatures: 1553, 944, 561 K; 1605, 898, 533 K; and 1656, 1028, 586 K. For the 1605 K evaluation, estimates produced work-function values of 2.22 eV for the emitter and 1.63 eV for the collector with a 2.0-eV barrier index (collector work function plus interelectrode voltage drop) corresponding to the maximum output of 5.5 W/sq cm at 0.24 volt. The current, voltage curve for the 1656 K 111-iridium diminiode yields a 6.2 W/sq cm maximum at 0.25 volt and is comparable with the 1700 K envelope for a diode with an etched-rhenium emitter and a 0.025-mm electrode gap made by TECO and evaluated by NASA
Diminiode thermionic energy conversion with lanthanum-hexaboride electrodes
Thermionic conversion data obtained from a variable gap cesium diminiode with a hot pressed, sintered lanthanum hexaboride emitter and an arc melted lanthanum hexaboride collector are presented. Performance curves cover a range of temperatures: emitter 1500 to 1700 K, collector 750 to 1000 K, and cesium reservoir 370 to 510 K. Calculated values of emitter and collector work functions and barrier index are also given
Impact of intrinsic biophysical diversity on the activity of spiking neurons
We study the effect of intrinsic heterogeneity on the activity of a
population of leaky integrate-and-fire neurons. By rescaling the dynamical
equation, we derive mathematical relations between multiple neuronal parameters
and a fluctuating input noise. To this end, common input to heterogeneous
neurons is conceived as an identical noise with neuron-specific mean and
variance. As a consequence, the neuronal output rates can differ considerably,
and their relative spike timing becomes desynchronized. This theory can
quantitatively explain some recent experimental findings.Comment: 4 pages, 5 figure
Band offsets in Si/Si1–x–yGexCy heterojunctions measured by admittance spectroscopy
We have used admittance spectroscopy to measure conduction-band and valence-band offsets in Si/Si1–xGex and Si/Si1–x–yGexCy heterostructures grown by solid-source molecular-beam epitaxy. Valence-band offsets measured for Si/Si1–xGex heterojunctions were in excellent agreement with previously reported values. Incorporation of C into Si1–x–yGexCy lowers the valence- and conduction-band-edge energies compared to those in Si1–xGex with the same Ge concentration. Comparison of our measured band offsets with previously reported measurements of energy band gaps in Si1–x–yGexCy and Si1–yCy alloy layers indicate that the band alignment is Type I for the compositions we have studied and that our measured band offsets are in quantitative agreement with these previously reported results
Measurement of band offsets in Si/Si1–xGex and Si/Si1–x–yGexCy heterojunctions
Realization of group IV heterostructure devices requires the accurate measurement of the energy band offsets in Si/Si1–xGex and Si/Si1–x–yGexCy heterojunctions. Using admittance spectroscopy, we have measured valence-band offsets in Si/Si1–xGex heterostructures and conduction-band and valence-band offsets in Si/Si1–x–yGexCy heterostructures grown by solid-source molecular-beam epitaxy. Measured Si/Si1–xGex valence-band offsets were in excellent agreement with previously reported values. For Si/Si1–x–yGexCy our measurements yielded a conduction-band offset of 100 ± 11 meV for a n-type Si/Si0.82Ge0.169C0.011 heterojunction and valence-band offsets of 118 ± 12 meV for a p-type Si/Si0.79Ge0.206C0.004 heterojunction and 223 ± 20 meV for a p-type Si/Si0.595Ge0.394C0.011 heterojunction. Comparison of our measured band offsets with previously reported measurements of energy band gaps in Si1–x–yGexCy and Si1–yCy alloy layers indicates that the band alignment is type I for the compositions we have studied and that our measured band offsets are in quantitative agreement with these previously reported results
Pain Management for Primary Care Providers: A Narrative Review of High-Impact Studies, 2014-2016
Objective:
This manuscript reviews high-impact, peer-reviewed studies published from January 2014 to March 2016 that are relevant to pain management in primary care. Given the recent release of the US Centers for Disease Control and Prevention's "Guideline for Prescribing Opioids for Chronic Pain" emphasizing the primacy of nonopioid treatment, we focused our review on nonopioid pain management.
Design:
Narrative review of peer-reviewed literature.
Methods:
We searched three article summary services and queried expert contacts for high-impact, English-language studies related to the management of pain in adults in primary care. All authors reviewed 142 study titles to arrive at group consensus on article content domains. Within article domains, individual authors selected studies approved by the larger group according to their impact on primary care clinical practice, policy, and research, as well as quality of the study methods. Through iterative discussion, 12 articles were selected for detailed review, discussion, and presentation in this narrative review.
Results:
We present key articles addressing each of six domains of pain management: pharmacotherapy for acute pain; interventional treatments; medical cannabis; complementary and integrative medicine; care management in chronic pain; and prevention. Within each section, we conclude with implications for pain management in primary care.
Conclusions:
There is growing evidence for multiple nonopioid treatment modalities available to clinicians for the management of pain in primary care. The dissemination and implementation of these studies, including innovative care management interventions, warrant additional study and support from clinicians, educators, and policy-makers
Scaling of Horizontal and Vertical Fixational Eye Movements
Eye movements during fixation of a stationary target prevent the adaptation
of the photoreceptors to continuous illumination and inhibit fading of the
image. These random, involuntary, small, movements are restricted at long time
scales so as to keep the target at the center of the field of view. Here we use
the Detrended Fluctuation Analysis (DFA) in order to study the properties of
fixational eye movements at different time scales. Results show different
scaling behavior between horizontal and vertical movements. When the small
ballistics movements, i.e. micro-saccades, are removed, the scaling exponents
in both directions become similar. Our findings suggest that micro-saccades
enhance the persistence at short time scales mostly in the horizontal component
and much less in the vertical component. This difference may be due to the need
of continuously moving the eyes in the horizontal plane, in order to match the
stereoscopic image for different viewing distance.Comment: 5 pages, 4 figure
Does the 1/f frequency-scaling of brain signals reflect self-organized critical states?
Many complex systems display self-organized critical states characterized by
1/f frequency scaling of power spectra. Global variables such as the
electroencephalogram, scale as 1/f, which could be the sign of self-organized
critical states in neuronal activity. By analyzing simultaneous recordings of
global and neuronal activities, we confirm the 1/f scaling of global variables
for selected frequency bands, but show that neuronal activity is not consistent
with critical states. We propose a model of 1/f scaling which does not rely on
critical states, and which is testable experimentally.Comment: 3 figures, 6 page
Timescales of spike-train correlation for neural oscillators with common drive
We examine the effect of the phase-resetting curve (PRC) on the transfer of
correlated input signals into correlated output spikes in a class of neural
models receiving noisy, super-threshold stimulation. We use linear response
theory to approximate the spike correlation coefficient in terms of moments of
the associated exit time problem, and contrast the results for Type I vs. Type
II models and across the different timescales over which spike correlations can
be assessed. We find that, on long timescales, Type I oscillators transfer
correlations much more efficiently than Type II oscillators. On short
timescales this trend reverses, with the relative efficiency switching at a
timescale that depends on the mean and standard deviation of input currents.
This switch occurs over timescales that could be exploited by downstream
circuits
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