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Katja Laufer, Annika Niemeyer, Verena Nikeleit, Maximilian Halama, James M Byrne, Andreas Kappler
Anoxygenic photoautotrophic bacteria which use light energy and electrons from Fe(II) for growth, so-called photoferrotrophs, are suggested to have been amongst the first phototrophic microorganisms on Earth and to have contributed to the deposition of sedimentary iron mineral deposits, i.e. banded iron formations. To date only two isolates of marine photoferrotrophic bacteria exist, both of which are closely related purple non-sulfur bacteria. Here we present a novel green-sulfur photoautotrophic Fe(II)-oxidizer isolated from a marine coastal sediment, Chlorobium sp...
April 18, 2017: FEMS Microbiology Ecology
Maosheng Miao
No abstract text is available yet for this article.
April 21, 2017: Nature Chemistry
Xiao Dong, Artem R Oganov, Alexander F Goncharov, Elissaios Stavrou, Sergey Lobanov, Gabriele Saleh, Guang-Rui Qian, Qiang Zhu, Carlo Gatti, Volker L Deringer, Richard Dronskowski, Xiang-Feng Zhou, Vitali B Prakapenka, Zuzana Konôpková, Ivan A Popov, Alexander I Boldyrev, Hui-Tian Wang
Helium is generally understood to be chemically inert and this is due to its extremely stable closed-shell electronic configuration, zero electron affinity and an unsurpassed ionization potential. It is not known to form thermodynamically stable compounds, except a few inclusion compounds. Here, using the ab initio evolutionary algorithm USPEX and subsequent high-pressure synthesis in a diamond anvil cell, we report the discovery of a thermodynamically stable compound of helium and sodium, Na2He, which has a fluorite-type structure and is stable at pressures >113 GPa...
May 2017: Nature Chemistry
Z C Kennedy, J F Christ, K A Evans, B W Arey, L E Sweet, M G Warner, R L Erikson, C A Barrett
We report the production of flexible, highly-conductive poly(vinylidene fluoride) (PVDF) and multi-walled carbon nanotube (MWCNT) composites as filament feedstock for 3D printing. This account further describes, for the first time, fused deposition modelling (FDM) derived 3D-printed objects with chemiresistive properties in response to volatile organic compounds. The typically prohibitive thermal expansion and die swell characteristics of PVDF were minimized by the presence of MWCNTs in the composites enabling straightforward processing and printing...
April 19, 2017: Nanoscale
G W Stagg, N G Parker, C F Barenghi
We model the superfluid flow of liquid helium over the rough surface of a wire (used to experimentally generate turbulence) profiled by atomic force microscopy. Numerical simulations of the Gross-Pitaevskii equation reveal that the sharpest features in the surface induce vortex nucleation both intrinsically (due to the raised local fluid velocity) and extrinsically (providing pinning sites to vortex lines aligned with the flow). Vortex interactions and reconnections contribute to form a dense turbulent layer of vortices with a nonclassical average velocity profile which continually sheds small vortex rings into the bulk...
March 31, 2017: Physical Review Letters
T Tessonnier, A Mairani, S Brons, T Haberer, J Debus, K Parodi
At the Heidelberg Ion Beam Therapy Center, scanned helium and oxygen ion beams are available in addition to the clinically used protons and carbon ions for physical and biological experiments. In this work, a study of the basic dosimetric features of the different ions is performed in the entire therapeutic energy range. Depth dose distributions are investigated for pencil-like beam irradiation, with and without a modulating ripple filter, focusing on the extraction of key Bragg curve parameters, such as the range, the peak-width and the distal 80%-20% fall-off...
April 13, 2017: Physics in Medicine and Biology
Jingwei Yin, Zhongjun Zhao, Xuefang Zhan, Yixiang Duan
RATIONALE: Microwave-induced plasma (MIP) with different discharge gases of argon or helium provides significant plasma-based ambient desorption/ionization sources, which have potential applicability in direct analysis of complex samples without any sample pre-treatment. In this study, experiments were conducted to better understand microwave-induced plasma desorption/ionization (MIPDI) sources and the corresponding ionization mechanisms. METHODS: Emission spectra of microwave-induced argon (MIP-Ar) and helium (MIP-He) plasmas were obtained from the plasma tail flame of a MIP source...
April 12, 2017: Rapid Communications in Mass Spectrometry: RCM
Ken Kakegawa, Ryoto Harigane, Mari Aida, Hidekazu Miyahara, Shoji Maruo, Akitoshi Okino
To achieve a highly sensitive and onsite analysis of a small amount samples, a microplasma-based micro total analysis systems (μ-TAS) device was developed. A dielectric barrier discharge (DBD) that can generate a stable plasma at atmospheric pressure was generated in a microchip and used as the plasma source. The use of DBD suppresses the temperature rise of the electrodes and enables operation for long times because of a reduction of the electrode damage due to suppression of the current via dielectric interposing between the electrodes...
2017: Analytical Sciences: the International Journal of the Japan Society for Analytical Chemistry
Yu-Hsin Chen, Sheng D Chao
We have used the recently developed kinetic energy partition (KEP) method to solve the quantum eigenvalue problems for helium-like atoms and obtain precise ground state energies and wave-functions. The key to treating properly the electron-electron (repulsive) Coulomb potential energies for the KEP method to be applied is to introduce a "negative mass" term into the partitioned kinetic energy. A Hartree-like product wave-function from the subsystem wave-functions is used to form the initial trial function, and the variational search for the optimized adiabatic parameters leads to a precise ground state energy...
March 28, 2017: Journal of Chemical Physics
Yaroslav Lutsyshyn
We consider the Jastrow pair-product wavefunction for strongly correlated Bose systems, in our case liquid helium-4. An ansatz is proposed for the pair factors which consist of a numeric solution to a modified and parametrized pair scattering equation. We consider a number of such simple one-variable parametrizations. Additionally, we allow for a parametrizeable cutoff of the pair factors and for the addition of a long-range phonon tail. This approach results in many-body wavefunctions that have between just one and three variational parameters...
March 28, 2017: Journal of Chemical Physics
Erin Adamson, Kai Ludwig, David Mummy, Sean B Fain
In the past decade, hyperpolarized (HP) contrast agents have been under active development for MRI applications to address the twin challenges of functional and quantitative imaging. Both HP helium (<sup>3</sup>He) and xenon (<sup>129</sup>Xe) gases have reached the stage where they are under study in clinical research. HP <sup>129</sup>Xe, in particular, is poised for larger scale clinical research to investigate asthma, chronic obstructive pulmonary disease, and fibrotic lung diseases...
April 6, 2017: Physics in Medicine and Biology
Massimiliano Lucci, Ivano Ottaviani, Matteo Cirillo, Fabio De Matteis, Roberto Francini, Vittorio Merlo, Ivan Davoli
We studied the growth and oxidation of niobium nitride (NbN) films that we used to fabricate superconductive tunnel junctions. The thin films were deposited by dc reactive magnetron sputtering using a mixture of argon and nitrogen. The process parameters were optimized by monitoring the plasma with an optical spectroscopy technique. This technique allowed us to obtain NbN as well as good quality AlN films and both were used to obtain NbN/AlN/NbN trilayers. Lift-off lithography and selective anodization of the NbN films were used, respectively, to define the main trilayer geometry and/or to separate electrically, different areas of the trilayers...
2017: Beilstein Journal of Nanotechnology
Andrey Lomov, Kirill Shcherbachev, Yurii Chesnokov, Dmitry Kiselev
The structural changes in the surface layer of p-type Cz-Si(001) samples after high-dose low-energy (2 keV) He(+) plasma-immersion ion implantation and subsequent thermal annealing were studied using a set of complementary methods: high-resolution X-ray reflectometry, high-resolution X-ray diffraction, transmission electron microscopy and atomic force microscopy. The formation of a three-layer structure was observed (an amorphous a-SiO x layer at the surface, an amorphous a-Si layer and a heavily damaged tensile-strained crystalline c-Si layer), which remained after annealing...
April 1, 2017: Journal of Applied Crystallography
Haiwen Zhao, Candong Liu, Yinghui Zheng, Zhinan Zeng, Ruxin Li
We theoretically investigate the attosecond transient absorption spectrum of helium atom in the presence of an infrared-dressed laser pulse upon scanning their relative delay, with the particular emphasis on the chirp effect of the attosecond pulse. By numerically solving the fully three-dimensional time-dependent Schrödinger equation, we identify the attoscecond chirp can induce the temporal shift of the absorption spectrogram along the delay axis. Additionally, it is found that the extent of the temporal shift is dependent on both the position of the absorption line and the infrared pulse wavelength, which is well confirmed and reproduced by a three-level model...
April 3, 2017: Optics Express
Spela Kos, Tanja Blagus, Maja Cemazar, Gregor Filipic, Gregor Sersa, Uros Cvelbar
Biomedical applications of plasma require its efficacy for specific purposes and equally importantly its safety. Herein the safety aspects of cold plasma created with simple atmospheric pressure plasma jet produced with helium gas and electrode discharge are evaluated in skin damage on mouse, at different duration of exposure and gas flow rates. The extent of skin damage and treatments are systematically evaluated using stereomicroscope, labelling with fluorescent dyes, histology, infrared imaging and optical emission spectroscopy...
2017: PloS One
Oleg Lunov, Vitalii Zablotskii, Olexander Churpita, Mariia Lunova, Milan Jirsa, Alexandr Dejneka, Šárka Kubinová
A rigorous biochemical analysis of interactions between non-thermal plasmas (NTPs) and living cells has become an important research topic, due to recent developments in biomedical applications of non-thermal plasmas. Here, we decouple distinct cell death pathways targeted by chemically different NTPs. We show that helium NTP cells treatment, results in necrosome formation and necroptosis execution, whereas air NTP leads to mTOR activation and autophagy inhibition, that induces mTOR-related necrosis. On the contrary, ozone (abundant component of air NTP) treatment alone, exhibited the highest levels of reactive oxygen species production leading to CypD-related necrosis via the mitochondrial permeability transition...
April 4, 2017: Scientific Reports
Pragya Punj, Premkumar Nattanmai, Pravin George, Christopher R Newey
Postextubation stridor is associated with significant morbidity. It commonly results in extubation failure after established medical treatment fails, such as nebulized epinephrine and/or intravenous steroids. The role of heliox (i.e., combination of helium and oxygen) in managing patients with postextubation stridor has not been fully established. We report two cases of postextubation stridor successfully treated with heliox delivered with bilevel positive airway pressure (BiPAP) after failure of standard medical therapy...
2017: Case Reports in Pulmonology
Sofia M Johansson, Xiangrui Kong, Panos Papagiannakopoulos, Erik S Thomson, Jan B C Pettersson
Molecular beam techniques are commonly used to obtain detailed information about reaction dynamics and kinetics of gas-surface interactions. These experiments are traditionally performed in vacuum and the dynamic state of surfaces under ambient conditions is thereby excluded from detailed studies. Herein we describe the development and demonstration of a new vacuum-gas interface that increases the accessible pressure range in environmental molecular beam (EMB) experiments. The interface consists of a grating close to a macroscopically flat surface, which allows for experiments at pressures above 1 Pa including angularly resolved measurements of the emitted flux...
March 2017: Review of Scientific Instruments
M Griener, O Schmitz, K Bald, D Bösser, M Cavedon, P De Marné, T Eich, G Fuchert, A Herrmann, A Kappatou, T Lunt, V Rohde, B Schweer, M Sochor, U Stroth, A Terra, E Wolfrum
In magnetically confined fusion plasmas controlled gas injection is crucial for plasma fuelling as well as for various diagnostic applications such as active spectroscopy. We present a new, versatile system for the injection of collimated thermal gas beams into a vacuum chamber. This system consists of a gas pressure chamber, sealed by a custom made piezo valve towards a small capillary for gas injection. The setup can directly be placed inside of the vacuum chamber of fusion devices as it is small and immune against high magnetic fields...
March 2017: Review of Scientific Instruments
Kent B Pfeifer, Komandoor E Achyuthan, Matthew Allen, Michele L B Denton, Michael P Siegal, Ronald P Manginell
Neutron sensing is critical in civilian and military applications. Conventional neutron sensors are limited by size, weight, cost, portability and helium supply. Here the microfabrication of gadolinium (Gd) conversion material-based heterojunction diodes for detecting thermal neutrons using electrical signals produced by internal conversion electrons (ICEs) is described. Films with negligible stress were produced at the tensile-compressive crossover point, enabling Gd coatings of any desired thickness by controlling the radiofrequency sputtering power and using the zero-point near p(Ar) of 50 mTorr at 100 W...
March 25, 2017: Journal of Radiation Research
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