LOW-ENERGY 4He+ SCATTERING FROM DEUTERIUM ADSORBED ON STEPPED Pd(331)

1997 ◽  
Vol 04 (06) ◽  
pp. 1305-1308 ◽  
Author(s):  
W. P. ELLIS ◽  
R. BASTASZ
Keyword(s):  
Incidence Angle ◽  
Forward Scattering ◽  
Low Energy ◽  
Quasielastic Scattering ◽  
Scattering Angle ◽  
Octahedral Void ◽  
Scattering Study ◽  
Adsorption Geometry ◽  
The Impact ◽  
Scattering Signal

We have taken angle-resolved data for the scattering of low-energy (<1 keV) 4 He + from deuterium adsorbed on a stepped Pd (331) surface. The impact geometry was "up the staircase," i.e. the 4 He + beam was perpendicular to and directly incident onto the unshadowed <011> Pd ledge atoms. A strong quasielastic scattering signal of 4 He + from D (4 He +/D) was observed at a forward-scattering angle of θ= 25° and an incidence angle of α= 76° from the (331) normal. The results agree with shadow-cone calculations of scattering first from Pd ledge atoms followed by a second event, 4 He +/D. The resultant adsorption geometry shows D to reside in the quasi-threefold ledge site on the surface directly above the bulk fcc octahedral void. These results are consistent with the previous 4 He + scattering study of the geometrically related Pd(110)-D(ads) system.

scholarly journals Towards Including Dynamic Vegetation Parameters in the EUMETSAT H SAF ASCAT Soil Moisture Products

2021 ◽  
Vol 13 (8) ◽  
pp. 1463
Author(s):  
Susan C. Steele-Dunne ◽  
Sebastian Hahn ◽  
Wolfgang Wagner ◽  
Mariette Vreugdenhil
Keyword(s):  
Soil Moisture ◽  
Interannual Variability ◽  
Incidence Angle ◽  
Pearson Correlation ◽  
The United States ◽  
Research Network ◽  
Window Width ◽  
High Frequency Variability ◽  
Vegetation Parameters ◽  
The Impact

The TU Wien Soil Moisture Retrieval (TUW SMR) approach is used to produce several operational soil moisture products from the Advanced Scatterometer (ASCAT) on the Metop series of satellites as part of the EUMETSAT Satellite Application Facility on Support to Operational Hydrology and Water Management (H SAF). The incidence angle dependence of backscatter is described by a second-order Taylor polynomial, the coefficients of which are used to normalize ASCAT observations to the reference incidence angle of 40∘ and for correcting vegetation effects. Recently, a kernel smoother was developed to estimate the coefficients dynamically, in order to account for interannual variability. In this study, we used the kernel smoother for estimating these coefficients, where we distinguished for the first time between their two uses, meaning that we used a short and fixed window width for the backscatter normalisation while we tested different window widths for optimizing the vegetation correction. In particular, we investigated the impact of using the dynamic vegetation parameters on soil moisture retrieval. We compared soil moisture retrievals based on the dynamic vegetation parameters to those estimated using the current operational approach by examining their agreement, in terms of the Pearson correlation coefficient, unbiased RMSE and bias with respect to in situ soil moisture. Data from the United States Climate Research Network were used to study the influence of climate class and land cover type on performance. The sensitivity to the kernel smoother half-width was also investigated. Results show that estimating the vegetation parameters with the kernel smoother can yield an improvement when there is interannual variability in vegetation due to a trend or a change in the amplitude or timing of the seasonal cycle. However, using the kernel smoother introduces high-frequency variability in the dynamic vegetation parameters, particularly for shorter kernel half-widths.

scholarly journals Towards Transabdominal Functional Photoacoustic Imaging of the Placenta: Improvement in Imaging Depth Through Optimization of Light Delivery

2021 ◽  
Author(s):  
Kristie Huda ◽  
Kenneth F. Swan ◽  
Cecilia T. Gambala ◽  
Gabriella C. Pridjian ◽  
Carolyn L. Bayer
Keyword(s):  
Delivery System ◽  
Light Propagation ◽  
Ex Vivo ◽  
Photoacoustic Imaging ◽  
Incidence Angle ◽  
Incident Angle ◽  
Placental Tissue ◽  
Light Delivery ◽  
Imaging Depth ◽  
The Impact

AbstractFunctional photoacoustic imaging of the placenta could provide an innovative tool to diagnose preeclampsia, monitor fetal growth restriction, and determine the developmental impacts of gestational diabetes. However, transabdominal photoacoustic imaging is limited in imaging depth due to the tissue’s scattering and absorption of light. The aim of this paper was to investigate the impact of geometry and wavelength on transabdominal light delivery. Our methods included the development of a multilayer model of the abdominal tissue and simulation of the light propagation using Monte Carlo methods. A bifurcated light source with varying incident angle of light, distance between light beams, and beam area was simulated to analyze the effect of light delivery geometry on the fluence distribution at depth. The impact of wavelength and the effects of variable thicknesses of adipose tissue and muscle were also studied. Our results showed that the beam area plays a major role in improving the delivery of light to deep tissue, in comparison to light incidence angle or distance between the bifurcated fibers. Longer wavelengths, with incident fluence at the maximum permissible exposure limit, also increases fluence within deeper tissue. We validated our simulations using a commercially available light delivery system and ex vivo human placental tissue. Additionally, we compared our optimized light delivery to a commercially available light delivery system, and conclude that our optimized geometry could improve imaging depth more than 1.6×, bringing the imaging depth to within the needed range for transabdominal imaging of the human placenta.

High resolution neutron scattering study of low-energy magnetic excitations in Nd2-xCexCuO4

2010 ◽  
Vol 508 (2) ◽  
pp. 197-202
Author(s):  
M. Loewenhaupt ◽  
A. Metz ◽  
N. M. Pyka ◽  
D. McK. Paul ◽  
J. Martin ◽  
...  
Keyword(s):  
High Resolution ◽  
Neutron Scattering ◽  
Low Energy ◽  
Magnetic Excitations ◽  
Scattering Study ◽  
Neutron Scattering Study

Evaluation and defense of light commands attacks against voice controllable systems in smart cars

2021 ◽  
pp. 095745652110015
Author(s):  
Zhijian Xu ◽  
Guoming Zhang ◽  
Xiaoyu Ji ◽  
Wenyuan Xu
Keyword(s):  
Laser Beam ◽  
Success Rate ◽  
Incidence Angle ◽  
Attack Angle ◽  
Light Transmittance ◽  
Controllable System ◽  
Lower Light ◽  
Controllable Systems ◽  
Smart Cars ◽  
The Impact

The in-car voice controllable system has become an almost standard feature in smart cars. Prior work shows that the voice controllable system is vulnerable to light commands attack which uses the laser as the medium to inject voice commands. In this article, we first reproduced the light commands attack on acoustic isolated in-car voice controllable system under several scenarios with a lightweight solution. We validate the feasibility of injecting the malicious voice command through a window into the microphone by modulating a laser beam. Then, we tested a variety of mainstream countermeasures such as placing sunscreen film on the glass panel to see whether it can protect the microphone from being attacked. Surprisingly, we find that the lower light transmittance of sunscreen film is the lower the success rate of the attack. Experiment results also show that when the transmittance rate of sun film is 50% which is the darkest sunscreen film that can be applied, the attacking success rate decreased by up to 0.4. We also explore the impact of attack angle by changing the incidence angle of the laser beam and the results demonstrate that light commands is sensitive to attack angle and the successful angle range is ± 15°. Finally, we propose a series of hardware-based protection schemes against light commands attacks.

scholarly journals From micro to macro-contaminants: The impact of low-energy titanium dioxide photocatalysis followed by filtration on the mitigation of drinking water organics

Chemosphere ◽  
2019 ◽  
Vol 217 ◽  
pp. 111-121 ◽  
Author(s):  
Brooke K. Mayer ◽  
Carlan Johnson ◽  
Yu Yang ◽  
Nicole Wellenstein ◽  
Emily Maher ◽  
...  
Keyword(s):  
Drinking Water ◽  
Titanium Dioxide ◽  
Low Energy ◽  
Titanium Dioxide Photocatalysis ◽  
The Impact

Low-Energy Ion Scattering Measurements from an Al-Pd-Mn Quasicrystal

2000 ◽  
Vol 643 ◽  
Author(s):  
R. Bastasz ◽  
C. J. Jenks ◽  
T. A. Lograsso ◽  
A. R. Ross ◽  
P. A. Thiel ◽  
...  
Keyword(s):  
Signal Intensity ◽  
Surface Composition ◽  
Incidence Angle ◽  
Local Environment ◽  
Forward Direction ◽  
Low Energy ◽  
Angle Of Incidence ◽  
Fold Axis ◽  
Ion Scattering ◽  
Low Energy Ion Scattering

AbstractEnergy-angle distributions of low-energy inert-gas ions scattered from surfaces provide information about surface composition and structure. We have measured energy spectra of He+ scattered from an Al71Pd20Mn9 quasicrystal, which was oriented perpendicular to the 5-fold axis, along various azimuthal directions. Strong scattering signals are seen from Al and Pd, but only a weak Mn signal is observed. From measurements made of He+ at an oblique angle of incidence scattered in the forward direction, we observe a 72° periodicity in the azimuthal dependence of the scattering signal intensity from Al surface atoms. The effect arises from shadowing effects involving neighboring surface atoms and provides direct evidence that Al surface atoms exist in a local environment with 5-fold symmetry. In addition, measuring the variation of the signal intensity with incidence angle provides information about neighboring atom distances, which compare favorably with a model of the quasicrystal surface derived from the bulk structure.

scholarly journals Radon daughter removal from PTFE surfaces and its application in liquid xenon detectors

2021 ◽  
Vol 81 (4) ◽  
Author(s):  
S. Bruenner ◽  
D. Cichon ◽  
G. Eurin ◽  
P. Herrero Gómez ◽  
F. Jörg ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Lead Isotopes ◽  
Ambient Air ◽  
Low Energy ◽  
Small Scale ◽  
Liquid Xenon ◽  
Radon Daughters ◽  
Radon Daughter ◽  
Cleaning Procedures ◽  
The Impact

AbstractLong-lived radon daughters are a critical background source in experiments searching for low-energy rare events. Originating from radon in ambient air, radioactive polonium, bismuth and lead isotopes plate-out on materials that are later employed in the experiment. In this paper, we examine cleaning procedures for their capability to remove radon daughters from PTFE surfaces, a material often used in liquid xenon TPCs. We find a large difference between the removal efficiency obtained for the decay chains of $$^{222}$$ 222 Rn and $$^{220}$$ 220 Rn. This indicates that the plate-out mechanism has an effect on the cleaning success. While the long-lived $$^{222}$$ 222 Rn daughters can be reduced by a factor of  2, the removal of $$^{220}$$ 220 Rn daughters is up to 10 times more efficient depending on the treatment. Furthermore, the impact of a nitric acid based PTFE cleaning on the liquid xenon purity is investigated in a small-scale liquid xenon TPC.

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