310 research outputs found
Broad ion energy distributions in helicon wave-coupled helium plasma
Helium ion energy distributions were measured in helicon wave-coupled plasmas of the dynamics of ion implantation and sputtering of surface experiment using a retarding field energy analyzer. The shape of the energy distribution is a double-peak, characteristic of radiofrequency plasma potential modulation. The broad distribution is located within a radius of 0.8 cm, while the quartz tube of the plasma source has an inner radius of 2.2 cm. The ion energy distribution rapidly changes from a double-peak to a single peak in the radius range of 0.7-0.9 cm. The average ion energy is approximately uniform across the plasma column including the double-peak and single peak regions. The widths of the broad distribution, ÎE, in the wave-coupled mode are large compared to the time-averaged ion energy, ăEă. On the axis (r = 0), ÎE/ ăEă âČ 3.4, and at a radius near the edge of the plasma column (r = 2.2 cm), ÎE/ ăEă ⌠1.2. The discharge parameter space is scanned to investigate the effects of the magnetic field, input power, and chamber fill pressure on the wave-coupled mode that exhibits the sharp radial variation in the ion energy distribution.United States. Department of Energy (Award DESC00-02060)United States. Department of Energy (Award DE-FC02-99ER54512
Isolated nano-tendril bundles on tungsten surfaces exposed to radiofrequency helium plasma
The DIONISOS experiment is used to study the impact of RF helium (He) plasma on the surface morphology of tungsten (W) at a frequency of 13.56 MHz. Helium ion energy distributions with a span of 70â75 eV, while still below the sputtering threshold result in nano-tendril bundles (NTBs) and free-standing W whiskers on surfaces at 1020 K. The NTBs are distributed intragranularly with coverage of less than 10% while reaching up to 30 ”m normal to the surface for He ion fluence of 7.6 Ă 10ÂČâ”mâ»ÂČ and flux density of 10ÂČÂČmâ»ÂČsâ»Âč. Analysis of the NTB interior and sub-surface structure is provided through focused ion beam cross section. Keywords: Tungsten fuzz; Helium; Nano-tendril; RF sheathUnited States. Department of Energy (Award DE-SC00-02060)United States. Department of Energy (Grant DE-FC02-99ER54512
Characterizing the recovery of a solid surface after tungsten nano-tendril formation
Recovery of a flat tungsten surface from a nano-tendril surface is attempted through three techniques; a mechanical wipe, a 1673 K annealing, and laser-induced thermal transients. Results were determined through SEM imaging and elastic recoil detection to assess the helium content in the surface. The mechanical wipe leaves a âŒ0.5 ÎŒm deep layer of nano-tendrils on the surface post-wipe regardless of the initial nano-tendril layer depth. Laser-induced thermal transients only significantly impact the surface morphology at heat loads of 35.2 MJ/m2 s1/2 or above, however a fully flat or recovered surface was not achieved for 100 transients at this heat load despite reducing the helium content by a factor of âŒ7. A 1673 K annealing removes all detectable levels of helium but sub-surface voids/bubbles remain intact. The surface is recovered to a nearly flat state with only some remnants of nano-tendrils re-integrating into the surface remaining.</p
Soft-Surface DNA Nanotechnology: DNA Constructs Anchored and Aligned to Lipid Membrane**
No strings attached: At least three attachment points are needed to align a two-dimensional DNA nanoconstruct to a soft lipid membrane surface with a porphyrin nucleoside as membrane anchor (see picture). The resulting freely diffusing DNA constructs can be reversibly assembled on the surface thus enabling the possibility of a self-repairing system. \ua9 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Predicting postoperative troponin in patients undergoing elective hip or knee arthroplasty: A comparison of five cardiac risk prediction tools
BACKGROUND: Elderly patients undergoing hip or knee arthroplasty are at a risk for myocardial injury after noncardiac surgery (MINS). We evaluated the ability of five common cardiac risk scores, alone or combined with baseline high-sensitivity cardiac troponin I (hs-cTnI), in predicting MINS and postoperative day 2 (POD2) hs-cTnI levels in patients undergoing elective total hip or knee arthroplasty.
METHODS: This study is ancillary to the Genetics-InFormatics Trial (GIFT) of Warfarin Therapy to Prevent Deep Venous Thrombosis, which enrolled patients 65 years and older undergoing elective total hip or knee arthroplasty. The five cardiac risk scores evaluated were the atherosclerotic cardiovascular disease calculator (ASCVD), the Framingham risk score (FRS), the American College of Surgeon\u27s National Surgical Quality Improvement Program (ACS-NSQIP) calculator, the revised cardiac risk index (RCRI), and the reconstructed RCRI (R-RCRI).
RESULTS: None of the scores predicted MINS in women. Among men, the ASCVD (
CONCLUSION: In elderly patients undergoing elective hip or knee arthroplasty, several of the scores modestly predicted MINS in men and correlated with POD2 hs-cTnI
OGLE-2005-BLG-018: Characterization of Full Physical and Orbital Parameters of a Gravitational Binary Lens
We present the analysis result of a gravitational binary-lensing event
OGLE-2005-BLG-018. The light curve of the event is characterized by 2 adjacent
strong features and a single weak feature separated from the strong features.
The light curve exhibits noticeable deviations from the best-fit model based on
standard binary parameters. To explain the deviation, we test models including
various higher-order effects of the motions of the observer, source, and lens.
From this, we find that it is necessary to account for the orbital motion of
the lens in describing the light curve. From modeling of the light curve
considering the parallax effect and Keplerian orbital motion, we are able to
measure not only the physical parameters but also a complete orbital solution
of the lens system. It is found that the event was produced by a binary lens
located in the Galactic bulge with a distance kpc from the Earth.
The individual lens components with masses and are separated with a semi-major axis of AU and
orbiting each other with a period yr. The event demonstrates
that it is possible to extract detailed information about binary lens systems
from well-resolved lensing light curves.Comment: 19 pages, 6 figure
Deriving the number of jobs in proximity services from the number of inhabitants in French rural municipalities
We use a minimum requirement approach to derive the number of jobs in
proximity services per inhabitant in French rural municipalities. We first
classify the municipalities according to their time distance to the
municipality where the inhabitants go the most frequently to get services
(called MFM). For each set corresponding to a range of time distance to MFM, we
perform a quantile regression estimating the minimum number of service jobs per
inhabitant, that we interpret as an estimation of the number of proximity jobs
per inhabitant. We observe that the minimum number of service jobs per
inhabitant is smaller in small municipalities. Moreover, for municipalities of
similar sizes, when the distance to the MFM increases, we find that the number
of jobs of proximity services per inhabitant increases.Comment: 6 pages, 5 figure
Limits on additional planetary companions to OGLE-2005-BLG-390L
We investigate constraints on additional planets orbiting the distant M-dwarf
star OGLE-2005-BLG-390L, around which photometric microlensing data has
revealed the existence of the sub-Neptune-mass planet OGLE-2005-BLG-390Lb. We
specifically aim to study potential Jovian companions and compare our findings
with predictions from core-accretion and disc-instability models of planet
formation. We also obtain an estimate of the detection probability for
sub-Neptune mass planets similar to OGLE-2005-BLG-390Lb using a simplified
simulation of a microlensing experiment. We compute the efficiency of our
photometric data for detecting additional planets around OGLE-2005-BLG-390L, as
a function of the microlensing model parameters and convert it into a function
of the orbital axis and planet mass by means of an adopted model of the Milky
Way. We find that more than 50 % of potential planets with a mass in excess of
1 M_J between 1.1 and 2.3 AU around OGLE-2005-BLG-390L would have revealed
their existence, whereas for gas giants above 3 M_J in orbits between 1.5 and
2.2 AU, the detection efficiency reaches 70 %; however, no such companion was
observed. Our photometric microlensing data therefore do not contradict the
existence of gas giant planets at any separation orbiting OGLE-2005-BLG-390L.
Furthermore we find a detection probability for an OGLE-2005-BLG-390Lb-like
planet of around 2-5 %. In agreement with current planet formation theories,
this quantitatively supports the prediction that sub-Neptune mass planets are
common around low-mass stars.Comment: 10 pages, 4 figures, accepted by A&
OGLE-2005-BLG-153: Microlensing Discovery and Characterization of A Very Low Mass Binary
The mass function and statistics of binaries provide important diagnostics of
the star formation process. Despite this importance, the mass function at low
masses remains poorly known due to observational difficulties caused by the
faintness of the objects. Here we report the microlensing discovery and
characterization of a binary lens composed of very low-mass stars just above
the hydrogen-burning limit. From the combined measurements of the Einstein
radius and microlens parallax, we measure the masses of the binary components
of and . This discovery
demonstrates that microlensing will provide a method to measure the mass
function of all Galactic populations of very low mass binaries that is
independent of the biases caused by the luminosity of the population.Comment: 6 pages, 3 figures, 1 tabl
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