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https://www.readbyqxmd.com/read/29154504/comparative-study-of-image-contrast-in-scanning-electron-microscope-and-helium-ion-microscope
#1
R O'Connell, Y Chen, H Zhang, Y Zhou, D Fox, P Maguire, J J Wang, C Rodenburg
Images of Ga(+) -implanted amorphous silicon layers in a 110 n-type silicon substrate have been collected by a range of detectors in a scanning electron microscope and a helium ion microscope. The effects of the implantation dose and imaging parameters (beam energy, dwell time, etc.) on the image contrast were investigated. We demonstrate a similar relationship for both the helium ion microscope Everhart-Thornley and scanning electron microscope Inlens detectors between the contrast of the images and the Ga(+) density and imaging parameters...
December 2017: Journal of Microscopy
https://www.readbyqxmd.com/read/29152573/self-organization-of-helium-precipitates-into-elongated-channels-within-metal-nanolayers
#2
Di Chen, Nan Li, Dina Yuryev, J Kevin Baldwin, Yongqiang Wang, Michael J Demkowicz
Material degradation due to precipitation of implanted helium (He) is a key concern in nuclear energy. Decades of research have mapped out the fate of He precipitates in metals, from nucleation and growth of equiaxed bubbles and voids to formation and bursting of surface blisters. By contrast, we show that He precipitates confined within nanoscale metal layers depart from their classical growth trajectories: They self-organize into elongated channels. These channels form via templated nucleation of He precipitates along layer surfaces followed by their growth and spontaneous coalescence into stable precipitate lines...
November 2017: Science Advances
https://www.readbyqxmd.com/read/29152211/xenon-helium-gas-mixture-at-equimolar-concentration-of-37-5-protects-against-oxygen-and-glucose-deprivation-induced-injury-and-inhibits-tissue-plasminogen-activator
#3
Hélène N David, Benoit Haelewyn, Jean-Éric Blatteau, Jean-Jacques Risso, Nicolas Vallée, Jacques H Abraini
Xenon (Xe) is considered to be the golden standard neuroprotective gas. However, Xe has a higher molecular weight and lower thermal conductivity and specific heat than those of nitrogen, the main diluent of oxygen in air. These physical characteristics could impair or at least reduce the intrinsic neuroprotective action of Xe by increasing the patient's respiratory workload and body temperature. In contrast, helium (He) is a cost-efficient gas with a lower molecular weight and higher thermal conductivity and specific heat than those of nitrogen, but is far less potent than Xe...
July 2017: Medical Gas Research
https://www.readbyqxmd.com/read/29152210/a-method-for-calculating-the-gas-volume-proportions-and-inhalation-temperature-of-inert-gas-mixtures-allowing-reaching-normothermic-or-hypothermic-target-body-temperature-in-the-awake-rat
#4
Jacques H Abraini, Hélène N David, Jean-Éric Blatteau, Jean Jacques Risso, Nicolas Vallée
The noble gases xenon (Xe) and helium (He) are known to possess neuroprotective properties. Xe is considered the golden standard neuroprotective gas. However, Xe has a higher molecular weight and lower thermal conductivity and specific heat than those of nitrogen, the main diluent of oxygen (O2) in air, conditions that could impair or at least reduce the intrinsic neuroprotective properties of Xe by increasing the critical care patient's respiratory workload and body temperature. In contrast, He has a lower molecular weight and higher thermal conductivity and specific heat than those of nitrogen, but is unfortunately far less potent than Xe at providing neuroprotection...
July 2017: Medical Gas Research
https://www.readbyqxmd.com/read/29148776/coagulation-of-metals-in-superfluid-and-normal-liquid-helium
#5
Eugene B Gordon, Alexander Vladimirovich Karabulin, Mikhail I Kulish, Vladimir Igorevich Matyushenko, Maxim E Stepanov
The thermal emission study in this work has shown that coagulation of metals in liquid helium is accompanied by enormous local overheating of several thousand degrees. Direct experiments demonstrated, for the first time, that condensation of metals in superfluid helium occurs via the specific mechanism which is substantially faster than that in normal liquid helium. It has been stated that coagulation of metals in superfluid helium indeed occurs in two stages - a "hot" one of nanoparticles coalescence with the formation of molten nanospheres and the subsequent stage of their sticking together into nanowires...
November 17, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29141430/lithium-atoms-on-helium-nanodroplets-rydberg-series-and-ionization-dynamics
#6
Florian Lackner, Günter Krois, Wolfgang E Ernst
The electronic excitation spectrum of lithium atoms residing on the surface of helium nanodroplets is presented and analyzed employing a Rydberg-Ritz approach. Utilizing resonant two-photon ionization spectroscopy, two different Rydberg series have been identified: one assigned to the nS(Σ) series and the other with predominantly nP(Π) character. For high Rydberg states, which have been resolved up to n = 13, the surrounding helium effectively screens the valence electron from the Li ion core, as indicated by the apparent red-shift of Li transitions and lowered quantum defects on the droplet with respect to their free atom counterparts...
November 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29140329/demonstration-of-a-cw-diode-pumped-ar-metastable-laser-operating-at-4%C3%A2-%C3%A2-w
#7
J Han, M C Heaven, P J Moran, G A Pitz, E M Guild, C R Sanderson, B Hokr
Optically pumped rare gas lasers are being investigated as potential high-energy, high beam quality systems. The lasing medium consists of rare gas atoms (Rg=Ne, Ar, Kr, or Xe) that have been electric discharge excited to the metastable np(5)(n+1)s P32 state. Following optical excitation, helium (He) at pressures of 200-1000 Torr is used as the energy transfer agent to create a population inversion. The primary technical difficulty for this scheme is the discharge production of sufficient Rg* metastables in the presence of >200  Torr of He...
November 15, 2017: Optics Letters
https://www.readbyqxmd.com/read/29136898/aerosol-dilution-as-a-simple-strategy-for-analysis-of-complex-samples-by-icp-ms
#8
Ariane I Barros, Fernanda C Pinheiro, Clarice D B Amaral, Rodolfo Lorençatto, Joaquim A Nóbrega
This study investigated the capability of High Matrix Introduction (HMI) strategy for analysis of dialysis solution and urine samples using inductively coupled plasma mass spectrometry. The use of HMI enables the direct introduction of urine samples and dialysis solutions 2-fold diluted with 0.14molL(-1) HNO3. Bismuth, Ge, Ir, Li, Pt, Rh, Sc and Tl were evaluated as internal standards for Al, Ag, As, Be, Cd, Cr, Pb, Sb, Se, Tl, and Hg determination in dialysis solution and As, Cd, Hg and Pb determination in urine samples...
February 1, 2018: Talanta
https://www.readbyqxmd.com/read/29134743/rapid-determination-of-ginkgolic-acids-in-ginkgo-biloba-kernels-and-leaves-by-direct-analysis-in-real-time-mass-spectrometry
#9
Zhongping Huang, Yueting Xu, Yilei Huang, Charles Liu, Kezhi Jiang, Lili Wang
A novel method on basis of direct analysis in real time integrated with mass spectrometry was established and applied into rapid determination of ginkgolic acids in Ginkgo biloba kernels and leaves. Instrument parameter settings were optimized to obtain the sensitive and accurate determination of ginkgolic acids. At the sample introduction speed of 0.2 mm/s, high intensity of [M-H](-) ions for ginkgolic acids were observed in the negative ion mode by utilization of high purity helium gas at 450°C. 2 μL methanol extract of Ginkgo biloba kernels or leaves dropped on the surface of Quick-Strip module was analyzed after solvent evaporated to dryness...
November 14, 2017: Journal of Separation Science
https://www.readbyqxmd.com/read/29129582/ventilation-defect-percent-in-helium-3-mri-as-a-biomarker-of-severe-outcomes-in-asthma
#10
David G Mummy, Stanley J Kruger, Wei Zha, Ronald L Sorkness, Nizar N Jarjour, Mark L Schiebler, Loren C Denlinger, Michael D Evans, Sean B Fain
Ventilation defect percent (VDP) measured in asthmatics with hyperpolarized helium-3 MRI was more strongly associated with ED visits and hospitalizations due to asthma exacerbation than were conventional biomarkers of lung function and inflammation.
November 9, 2017: Journal of Allergy and Clinical Immunology
https://www.readbyqxmd.com/read/29116014/quantitative-assessment-of-radiation-dose-and-fractionation-effects-on-normal-tissue-by-utilizing-a-novel-lung-fibrosis-index-model
#11
Cheng Zhou, Bleddyn Jones, Mahmoud Moustafa, Christian Schwager, Julia Bauer, Bing Yang, Liji Cao, Min Jia, Andrea Mairani, Ming Chen, Longhua Chen, Juergen Debus, Amir Abdollahi
BACKGROUND: Normal lung tissue tolerance constitutes a limiting factor in delivering the required dose of radiotherapy to cure thoracic and chest wall malignancies. Radiation-induced lung fibrosis (RILF) is considered a critical determinant for late normal tissue complications. While RILF mouse models are frequently approached e.g., as a single high dose thoracic irradiation to investigate lung fibrosis and candidate modulators, a systematic radiobiological characterization of RILF mouse model is urgently needed to compare relative biological effectiveness (RBE) of particle irradiation with protons, helium-, carbon and oxygen ions now available at HIT...
November 7, 2017: Radiation Oncology
https://www.readbyqxmd.com/read/29110006/porous-germanene-as-a-highly-efficient-gas-separation-membrane
#12
Ang Bian, Yafei Dai, Jinlong Yang
Using a gas separation membrane as a simple gas separation device has an obvious advantage because of the low energy consumption and pollution-free manufacturing. The first-principles calculations used in this work show that germanene with its divacancy is an excellent material for use as a hydrogen (H2) and helium (He) separation membrane, and that it displays an even better competitive advantage than porous graphene and porous silicene. Porous germanene with its divacancy is chemically inert to gas molecules, because it lacks additional atoms to protect the edged dangling germanium atoms in defects, and thus shows great advantages for gas separation over previously prepared graphene...
November 16, 2017: Nanoscale
https://www.readbyqxmd.com/read/29107732/the-rapid-determination-of-bromadiolone-in-liver-and-blood-plasma-by-in-injector-pyrolysis-gas-chromatography-ion-trap-tandem-mass-spectrometry
#13
Veronika Doubková, Petr Maršálek, Vladimír Večerek
The unintentional poisoning of off-target animals by bromadiolone, a second generation anticoagulant rodenticide, is an undesirable outcome requiring sensitive analytical methods. In this study, a rapid and sensitive method for the determination of bromadiolone in liver and blood plasma by means of gas chromatography coupled with tandem mass spectrometry without need for derivatization was developed. The method is based on the in-injector pyrolysis of bromadiolone and subsequent gas chromatography coupled with ion trap tandem mass spectrometry with electron ionization...
October 14, 2017: Journal of Chromatography. B, Analytical Technologies in the Biomedical and Life Sciences
https://www.readbyqxmd.com/read/29099133/sub-doppler-infrared-spectroscopy-of-resonance-stabilized-hydrocarbon-intermediates-%C3%AE-3-%C3%AE-4-ch-stretch-modes-and-ch2-internal-rotor-dynamics-of-benzyl-radical
#14
A Kortyna, A J Samin, T A Miller, D J Nesbitt
Highly reactive benzyl radicals are generated by electron dissociative attachment to benzyl chloride doped into a neon-hydrogen-helium discharge and immediately cooled to Trot = 15 K in a high density, supersonic slit expansion environment. The sub-Doppler spectra are fit to an asymmetric-top rotational Hamiltonian, thereby yielding spectroscopic constants for the ground (v = 0) and first excited (v = 1, ν3, ν4) vibrational levels of the ground electronic state. The rotational constants obtained for the ground state are in good agreement with previous laser induced fluorescence measurements (LIF), with vibrational band origins (ν3 = 3073...
November 3, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29096458/exact-exchange-correlation-potentials-of-singlet-two-electron-systems
#15
Ilya G Ryabinkin, Egor Ospadov, Viktor N Staroverov
We suggest a non-iterative analytic method for constructing the exchange-correlation potential, vXC(r), of any singlet ground-state two-electron system. The method is based on a convenient formula for vXC(r) in terms of quantities determined only by the system's electronic wave function, exact or approximate, and is essentially different from the Kohn-Sham inversion technique. When applied to Gaussian-basis-set wave functions, the method yields finite-basis-set approximations to the corresponding basis-set-limit vXC(r), whereas the Kohn-Sham inversion produces physically inappropriate (oscillatory and divergent) potentials...
October 28, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/29092495/a-platform-for-exploding-wires-in-different-media
#16
Ruoyu Han, Jiawei Wu, Aici Qiu, Haibin Zhou, Yanan Wang, Jiaqi Yan, Weidong Ding
A platform SWE-2 used for single wire explosion experiments has been designed, established, and commissioned. This paper describes the design and initial experiments of SWE-2. In summary, two pulsed current sources based on pulse capacitors and spark gaps are adopted to drive sub-microsecond and microsecond time scale wire explosions in a gaseous/liquid medium, respectively. In the initial experiments, a single copper wire was exploded in air, helium, and argon with a 0.1-0.3 MPa ambient pressure as well as tap water with a 283-323 K temperature, 184-11 000 μS/cm conductivity, or 0...
October 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29092469/second-sound-tracking-system
#17
Jihee Yang, Gary G Ihas, Dan Ekdahl
It is common that a physical system resonates at a particular frequency, whose frequency depends on physical parameters which may change in time. Often, one would like to automatically track this signal as the frequency changes, measuring, for example, its amplitude. In scientific research, one would also like to utilize the standard methods, such as lock-in amplifiers, to improve the signal to noise ratio. We present a complete He ii second sound system that uses positive feedback to generate a sinusoidal signal of constant amplitude via automatic gain control...
October 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29092462/versatile-variable-temperature-and-magnetic-field-scanning-probe-microscope-for-advanced-material-research
#18
Jin-Oh Jung, Seokhwan Choi, Yeonghoon Lee, Jinwoo Kim, Donghyeon Son, Jhinhwan Lee
We have built a variable temperature scanning probe microscope (SPM) that covers 4.6 K-180 K and up to 7 T whose SPM head fits in a 52 mm bore magnet. It features a temperature-controlled sample stage thermally well isolated from the SPM body in good thermal contact with the liquid helium bath. It has a 7-sample-holder storage carousel at liquid helium temperature for systematic studies using multiple samples and field emission targets intended for spin-polarized spectroscopic-imaging scanning tunneling microscopy (STM) study on samples with various compositions and doping conditions...
October 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/29089932/cryptoendolithic-antarctic-black-fungus-cryomyces-antarcticus-irradiated-with-accelerated-helium-ions-survival-and-metabolic-activity-dna-and-ultrastructural-damage
#19
Claudia Pacelli, Laura Selbmann, Ralf Moeller, Laura Zucconi, Akira Fujimori, Silvano Onofri
Space represents an extremely harmful environment for life and survival of terrestrial organisms. In the last decades, a considerable deal of attention was paid to characterize the effects of spaceflight relevant radiation on various model organisms. The aim of this study was to test the survival capacity of the cryptoendolithic black fungus Cryomyces antarcticus CCFEE 515 to space relevant radiation, to outline its endurance to space conditions. In the frame of an international radiation campaign, dried fungal colonies were irradiated with accelerated Helium ion (150 MeV/n, LET 2...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/29089492/room-temperature-spontaneous-superradiance-from-single-diamond-nanocrystals
#20
Carlo Bradac, Mattias T Johnsson, Matthew van Breugel, Ben Q Baragiola, Rochelle Martin, Mathieu L Juan, Gavin K Brennen, Thomas Volz
Superradiance (SR) is a cooperative phenomenon which occurs when an ensemble of quantum emitters couples collectively to a mode of the electromagnetic field as a single, massive dipole that radiates photons at an enhanced rate. Previous studies on solid-state systems either reported SR from sizeable crystals with at least one spatial dimension much larger than the wavelength of the light and/or only close to liquid-helium temperatures. Here, we report the observation of room-temperature superradiance from single, highly luminescent diamond nanocrystals with spatial dimensions much smaller than the wavelength of light, and each containing a large number (~ 10(3)) of embedded nitrogen-vacancy (NV) centres...
October 31, 2017: Nature Communications
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