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https://www.readbyqxmd.com/read/28106422/circular-dichroism-in-multiphoton-ionization-of-resonantly-excited-he-ions
#1
M Ilchen, N Douguet, T Mazza, A J Rafipoor, C Callegari, P Finetti, O Plekan, K C Prince, A Demidovich, C Grazioli, L Avaldi, P Bolognesi, M Coreno, M Di Fraia, M Devetta, Y Ovcharenko, S Düsterer, K Ueda, K Bartschat, A N Grum-Grzhimailo, A V Bozhevolnov, A K Kazansky, N M Kabachnik, M Meyer
Intense, circularly polarized extreme-ultraviolet and near-infrared (NIR) laser pulses are combined to double ionize atomic helium via the oriented intermediate He^{+}(3p) resonance state. Applying angle-resolved electron spectroscopy, we find a large photon helicity dependence of the spectrum and the angular distribution of the electrons ejected from the resonance by NIR multiphoton absorption. The measured circular dichroism is unexpectedly found to vary strongly as a function of the NIR intensity. The experimental data are well described by theoretical modeling and possible mechanisms are discussed...
January 6, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/28106005/modification-of-the-saturation-magnetization-of-exchange-bias-thin-film-systems-upon-light-ion-bombardment
#2
Henning Huckfeldt, Alexander Gaul, Nicolas Müglich, Dennis Holzinger, Dennis Nissen, Manfred Albrecht, Daniel Emmrich, Andre Beyer, A Goelzhaeuser, Arno Ehresmann
The magnetic modification of exchange bias materials by ���ion bombardment induced magnetic patterning��� has been established more than a decade ago. To understand these experimental findings several theoretical models were introduced. Few investigations, however, did focus on magnetic property modifications caused by effects of ion bombardment in the ferromagnetic layer. In the present study, the structural changes occurring under ion bombardment were investigated by Monte-Carlo simulations and in experiments...
January 20, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28105165/the-value-of-64-slice-spiral-ct-perfusion-imaging-in-the-treatment-of-liver-cancer-with-argon-helium-cryoablation
#3
Yinggang Lv, Yurong Jin, Qiaohuan Yan, Dingling Yuan, Yanling Wang, Xianping Li, Yanfeng Shen
We analyzed the effectiveness of using 64-slice spiral computed tomography (CT) and perfusion imaging to guide argon-helium cryoablation treatment of liver cancer. In total, 60 cases of advanced hepatocellular carcinoma before surgery treated with argon-helium cryoablation were inlcuded in the present study. Retrospective summary of the 60 cases of metaphase and advanced liver cancer were used as the control group. The control group were treated using cryoablation with argon-helium knife. We used enhanced scanning with 64-slice spiral CT to define the extent of their lesions and prepared a plan of percutaneous cryoablation for the treatment...
December 2016: Oncology Letters
https://www.readbyqxmd.com/read/28100048/unanticipated-stickiness-of-%C3%AE-pinene
#4
Hilary M Chase, Junming Ho, Mary Alice Upshur, Regan J Thomson, Victor S Batista, Franz M Geiger
Hilary M. Chase1#, Junming Ho2#, Mary Alice Upshur1, Regan J. Thomson1, Victor S. Batista3, Franz M. Geiger1* 1Department of Chemistry, Northwestern University, Evanston, IL. 60208, United States; 2 Agency for Science, Technology and Research, Institute of High Performance Computing, 1 Fusionopolis Way #16-16 Connexis North, Singapore 138632; 3Department of Chemistry, Yale University, P.O. Box 208107, New Haven, CT. 06520, United States # These authors contributed equally to this work. *corresponding author: geigerf@chem...
January 19, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28098214/clinical-roles-of-lung-volumes-detected-by-body-plethysmography-and-helium-dilution-in-asthmatic-patients-a-correlation-and-diagnosis-analysis
#5
Jian Luo, Dan Liu, Guo Chen, Binmiao Liang, Chuntao Liu
Roles of lung volumes in asthma remain controversial. We aimed to evaluate the efficacy of lung volumes in differentiating asthma severity levels. Consecutive outpatients with chronic persistent asthma were enrolled, and body plethysmography (BP) and helium dilution (HD) were performed simultaneously to extract RV%pred, TLC%pred, and RV/TLC. Significant negative correlations were found between FEV1%pred and RV%pred (r = -0.557, P < 0.001), TLC%pred (r = -0.387, P < 0.001), and RV/TLC (r = -0...
January 18, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28097537/optimization-of-a-new-aerodynamic-cylindrical-faims-device-for-small-molecule-analysis
#6
Randy W Purves, Satendra Prasad, Michael Belford, Albert Vandenberg, Jean-Jacques Dunyach
The implementation of an aerodynamic mechanism to improve ion sampling between nanoelectrospray (n-ESI) and FAIMS was recently reported for proteomic analyses. This investigation explores the new FAIMS interface for small molecule analysis at high liquid flow rates and includes an examination of key differences in ionization between heated-ESI (HESI) and n-ESI. The sheath gas, critical for desolvation with HESI, affects FAIMS operation as higher FAIMS gas flow rates are required to achieve sufficient desolvation...
January 17, 2017: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/28091811/charge-transfer-dissociation-ctd-mass-spectrometry-of-peptide-cations-study-of-charge-state-effects-and-side-chain-losses
#7
Pengfei Li, Glen P Jackson
1+, 2+, and 3+ precursors of substance P and bradykinin were subjected to helium cation irradiation in a 3D ion trap mass spectrometer. Charge exchange with the helium cations produces a variety of fragment ions, the number and type of which are dependent on the charge state of the precursor ions. For 1+ peptide precursors, fragmentation is generally restricted to C-CO backbone bonds (a and x ions), whereas for 2+ and 3+ peptide precursors, all three backbone bonds (C-CO, C-N, and N-Cα) are cleaved. The type of backbone bond cleavage is indicative of possible dissociation channels involved in CTD process, including high-energy, kinetic-based, and ETD-like pathways...
January 13, 2017: Journal of the American Society for Mass Spectrometry
https://www.readbyqxmd.com/read/28089069/a-sensitive-gas-chromatography-detector-based-on-atmospheric-pressure-chemical-ionization-by-a-dielectric-barrier-discharge
#8
Ansgar T Kirk, Torben Last, Stefan Zimmermann
In this work, we present a novel concept for a gas chromatography detector utilizing an atmospheric pressure chemical ionization which is initialized by a dielectric barrier discharge. In general, such a detector can be simple and low-cost, while achieving extremely good limits of detection. However, it is non-selective apart from the use of chemical dopants. Here, a demonstrator manufactured entirely from fused silica capillaries and printed circuit boards is shown. It has a size of 75×60×25mm(3) and utilizes only 2W of power in total...
December 24, 2016: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28088866/a-combined-experimental-and-computational-study-on-the-unimolecular-decomposition-of-jp-8-jet-fuel-surrogates-ii-n-dodecane-n-c12h26
#9
Long Zhao, Tao Yang, Ralf I Kaiser, Tyler Patrick Troy, Musahid Ahmed, Joao Marcelo Ribeiro, Daniel Belisario-Lara, Alexander Moiseevich Mebel
We investigated temperature-dependent products in the pyrolysis of helium-seeded n-dodecane, which represents a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) aviation fuel. The experiments were performed in a high temperature chemical reactor over a temperature range of 1,200 K to 1,600 K at a pressure of 600 Torr, with in situ identification of the nascent products in a supersonic molecular beam using single photon vacuum ultraviolet (VUV) photoionization coupled with the analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF)...
January 16, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28088860/a-combined-experimental-and-computational-study-on-the-unimolecular-decomposition-of-jp-8-jet-fuel-surrogates-i-n-decane-n-c10h22
#10
Long Zhao, Tao Yang, Ralf I Kaiser, Tyler Patrick Troy, Musahid Ahmed, Daniel Belisario-Lara, Joao Marcelo Ribeiro, Alexander Moiseevich Mebel
Exploiting a high temperature chemical reactor, we explored the pyrolysis of helium-seeded n-decane as a surrogate of the n-alkane fraction of Jet Propellant-8 (JP-8) over a temperature range of 1,100 K to 1,600 K at a pressure of 600 Torr. The nascent products were identified in situ in a supersonic molecular beam via single photon vacuum ultraviolet (VUV) photoionization coupled with a mass spectroscopic analysis of the ions in a reflectron time-of-flight mass spectrometer (ReTOF). Our studies probe, for the first time, the initial reaction products formed in the decomposition of n-decane - including radicals and thermally labile closed-shell species effectively excluding mass growth processes...
January 16, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28088134/dirac-bubble-potential-for-he-he-and-inadequacies-in-the-continuum-comparing-an-analytic-model-with-elastic-collision-experiments
#11
Michael Chrysos
We focus on the long-pending issue of the inadequacy of the Dirac bubble potential model in the description of He-He interactions in the continuum [L. L. Lohr and S. M. Blinder, Int. J. Quantum Chem. 53, 413 (1995)]. We attribute this failure to the lack of a potential wall to mimic the onset of the repulsive interaction at close range separations. This observation offers the explanation to why this excessively simple model proves incapable of quantitatively reproducing previous experimental findings of glory scattering in He-He, although being notorious for its capability of reproducing several distinctive features of the atomic and isotopic helium dimers and trimers [L...
January 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28079191/enhanced-radiation-tolerant-oxide-dispersion-strengthened-steel-and-its-microstructure-evolution-under-helium-implantation-and-heavy-ion-irradiation
#12
Chenyang Lu, Zheng Lu, Xu Wang, Rui Xie, Zhengyuan Li, Michael Higgins, Chunming Liu, Fei Gao, Lumin Wang
The world eagerly needs cleanly-generated electricity in the future. Fusion reactor is one of the most ideal energy resources to defeat the environmental degradation caused by the consumption of traditional fossil energy. To meet the design requirements of fusion reactor, the development of the structural materials which can sustain the elevated temperature, high helium concentration and extreme radiation environments is the biggest challenge for the entire material society. Oxide dispersion strengthened steel is one of the most popular candidate materials for the first wall/blanket applications in fusion reactor...
January 12, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28076336/a-theoretical-framework-to-predict-the-most-likely-ion-path-in-particle-imaging
#13
Charles-Antoine Collins-Fekete, Lennart Volz, Stephen Portillo, Luc Beaulieu, Joao Seco
In this work, a generic rigorous Bayesian formalism is introduced to predict the most likely path of any ion crossing a medium between two detection points. The path is predicted based on a combination of the particle scattering in the material and measurements of its initial and final position, direction and energy. The path estimate's precision is compared to the Monte Carlo simulated path. Every ion from hydrogen to carbon is simulated in two scenarios, 1) where the range is fixed and 2) where the initial velocity is fixed...
January 11, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28070559/the-mechanics-and-design-of-a-lightweight-three-dimensional-graphene-assembly
#14
Zhao Qin, Gang Seob Jung, Min Jeong Kang, Markus J Buehler
Recent advances in three-dimensional (3D) graphene assembly have shown how we can make solid porous materials that are lighter than air. It is plausible that these solid materials can be mechanically strong enough for applications under extreme conditions, such as being a substitute for helium in filling up an unpowered flight balloon. However, knowledge of the elastic modulus and strength of the porous graphene assembly as functions of its structure has not been available, preventing evaluation of its feasibility...
January 2017: Science Advances
https://www.readbyqxmd.com/read/28069170/a-sensitive-gas-chromatography-detector-based-on-atmospheric-pressure-chemical-ionization-by-a-dielectric-barrier-discharge
#15
Ansgar T Kirk, Torben Last, Stefan Zimmermann
In this work, we present a novel concept for a gas chromatography detector utilizing an atmospheric pressure chemical ionization which is initialized by a dielectric barrier discharge. In general, such a detector can be simple and low-cost, while achieving extremely good limits of detection. However, it is non-selective apart from the use of chemical dopants. Here, a demonstrator manufactured entirely from fused silica capillaries and printed circuit boards is shown. It has a size of 75×60×25mm(3) and utilizes only 2W of power in total...
December 24, 2016: Journal of Chromatography. A
https://www.readbyqxmd.com/read/28068106/cooperativity-and-dynamics-increase-the-performance-of-nife-dry-reforming-catalysts
#16
Sung Min Kim, Paula Macarena Abdala, Tigran Margossian, Davood Hosseini, Lucas Foppa, Andac Armutlulu, Wouter van Beek, Aleix Comas-Vives, Christophe Copéret, Christoph Mueller
The dry reforming of methane (DRM), i.e. the reaction of methane and CO2 to form a synthesis gas, converts two major greenhouse gases into a useful chemical feedstock. In this work, we probe in detail the effect and role of Fe in bimetallic NiFe dry reforming catalysts. To this end, monometallic Ni, Fe and bimetallic Ni-Fe catalysts supported on a MgxAlyOz-matrix derived via a hydrotalcite-like precursor were synthetized. Importantly, the textural features of the catalysts, i.e. the specific surface area (172-178 m2/gcat), pore volume (0...
January 9, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28063438/ground-state-properties-of-weakly-bound-helium-alkali-trimers
#17
P Stipanović, L Vranješ Markić, D Zarić, J Boronat
Weakly bound triatomic molecules consisting of two helium atoms and one alkali metal atom are studied by means of the diffusion Monte Carlo method. We determined the stability of (4)He2A, (4)He(3)HeA, and (3)He2A, where A is one of the alkali atoms Li, Na, K, Rb, or Cs. Some of the trimers with (3)He are predicted to be self-bound for the first time, but this is observed to be dependent on the He-A interaction potential model. In addition to the ground-state energy of the trimers, we determined their density, radial, and angular distributions...
January 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28060504/infrared-spectroscopy-of-methanol-and-methanol-water-clusters-in-helium-nanodroplets-the-oh-stretching-region
#18
Media I Sulaiman, Shengfu Yang, Andrew Michael Ellis
Infrared (IR) spectra of methanol clusters in helium nanodroplets are reported in the OH stretching region for the first time. A simple series of intense bands are seen which almost perfectly match previous gas phase studies of these clusters and which are consistent with cyclic structures for the trimer and larger clusters. This finding differs from an earlier report of (CH3OH)n clusters in helium nanodroplets, which focused on the CO stretching region and concluded that while the trimer was cyclic, the tetramer and pentamer adopted branched structures based on a cyclic trimer core...
January 6, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28059774/long-time-atomistic-dynamics-through-a-new-self-adaptive-accelerated-molecular-dynamics-method
#19
Ning Gao, Li Yang, Fei Gao, Richard Kurtz, Damien West, Shengbai Zhang
A self-adaptive accelerated molecular dynamics method is developed to model the infrequent atomic-scale events, especially for treating events that occur on a rugged free-energy surface. Key in the new development is the use of the total displacement of the system at a given temperature to construct a boost-potential, which is slowly increased to accelerate the dynamics. By allowing the system to evolve from one steady-state configuration to another by overcoming the transition state, this self-evolving approach makes it possible to explore the coupled motion of species that migrate on vastly different time scales...
January 6, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28058835/hybrid-basis-close-coupling-interface-to-quantum-chemistry-packages-for-the-treatment-of-ionization-problems
#20
Carlos Marante, Markus Klinker, Inés Corral, Jesús González-Vázquez, Luca Argenti, Fernando Martín
The theoretical description of observables in attosecond pump-probe experiments requires a good representation of the system's ionization continuum. For polyelectronic molecules, however, this is still a challenge, due to the complicated short-range structure of correlated electronic wave functions. Whereas quantum chemistry packages (QCP) implementing sophisticated methods to compute bound electronic molecular states are well-established, comparable tools for the continuum are not widely available yet. To tackle this problem, we have developed a new approach that, by means of a hybrid Gaussian-B-spline basis, interfaces existing QCPs with close-coupling scattering methods...
January 6, 2017: Journal of Chemical Theory and Computation
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