Nanomechanics of a Hydrogen Molecule Suspended between Two Equally Charged Tips

Geometric configuration and energy of a hydrogen molecule centered between two point-shaped tips of equal charge are calculated with the variational quantum Monte-Carlo (QMC) method without the restriction of the Born-Oppenheimer (BO) approximation. Ground state nuclear distribution, stability, and low vibrational excitation are investigated. Ground state results predict significant deviations from the BO treatment that is based on a potential energy surface (PES) obtained with the same QMC accuracy. The quantum mechanical distribution of molecular axis direction and bond length at a sub-nanometer level is fundamental for understanding nanomechanical dynamics with embedded hydrogen. Because of the tips' arrangement, cylindrical symmetry yields a uniform azimuthal distribution of the molecular axis vector relative to the tip-tip axis. With approaching tips towards each other, the QMC sampling shows an increasing loss of spherical symmetry with the molecular axis still uniformly distributed over the azimuthal angle but peaked at the tip-tip direction for negative tip charge while peaked at the equatorial plane for positive charge. This directional behavior can be switched between both stable configurations by changing the sign of the tip charge and by controlling the tip-tip distance. This suggests an application in the field of molecular machines.Comment: 20 pages, 10 figure

Taraxacum gilliesii Hook. & Arn. (Asteraceae), nuevo registro para su área de distribución en Argentina

Taraxacum gilliesii Hook. & Arn. (Asteraceae) is reported for La Pampa province expanding its distribution area in Argentina. A key is supplied for distinguish from T. officinale F. H. Wigg. present too in this province.Se cita para la provincia de La Pampa Taraxacum gilliesii Hook. & Am. (Asteraceae). Se amplía su área de distribución en Argentina y se proporciona una clave para la diferenciación con la otra especie del género presente en la provincia, T. officinale F. H. Wigg

Contribuciones al conocimiento de la flora de Malargüe. Nuevas citas para la provincia de Mendoza (Argentina) Parte II.

During botanical explorations carried out in Malargüe, between 2003 and 2005, 940 specimens were collected, and 39 taxa are recorded for the first time for Mendoza province, Argentina. Characteristics of habitat and life form are given for each taxon. Common names of some of these taxa are given, based on the oral information obtained from the local people.Este trabajo es producto de exploraciones botánicas llevadas a cabo, entre los años 2003 y 2005. en el sur de la provincia de Mendoza, lo cual permitió la colección de 940 especímenes en el área en estudio, de los cuales, 39 taxones se citan por primera vez para la flora de la provincia. Se describen características de hábitat y forma de vida al que corresponde cada taxón, y asimismo se dan nombres vulgares sobre la base de la información oral obtenida de los pobladores de las áreas estudiadas

Contribuciones al conocimiento de Ia flora de Malargüe. Nuevas citas para la provincia de Mendoza (Argentina). Parte I

In botanical explorations carried out in Malargüe, 601 specific and infraespecifics taxa were collected, 76 of those are recorded for the first time for Mendoza province, Argentina, Herbarium specimens as a reference, characteristics of habitat and life form are given for each taxon. Common names of some of these taxa based on the oral information obtained from the residents in the studied areas are given.En exploraciones botánicas llevadas a cabo en el Departamento Malargüe, se colectaron 601 taxones específicos e infraespecíficos, 76 de Ios cuales se citan por primera vez para la provincia de Mendoza, Argentina. Se proporciona al menos un ejemplar de herbario como referencia para cada taxón y se informa sobre características de hábitat y forma de vida al que corresponda cada uno. asimismo, se dan nombres vulgares sobre la base de la información oral obtenida de los pobladores de las áreas estudiadas

Interactions of Ar(9+) and metastable Ar(8+) with a Si(100) surface at velocities near the image acceleration limit

Auger LMM spectra and preliminary model simulations of Ar(9+) and metastable Ar(8+) ions interacting with a clean monocrystalline n-doped Si(100) surface are presented. By varying the experimental parameters, several yet undiscovered spectroscopic features have been observed providing valuable hints for the development of an adequate interaction model. On our apparatus the ion beam energy can be lowered to almost mere image charge attraction. High data acquisition rates could still be maintained yielding an unprecedented statistical quality of the Auger spectra.Comment: 34 pages, 11 figures, http://pikp28.uni-muenster.de/~ducree

Nuevas citas botánicas para la provincia de La Pampa (Argentina)

Blackstonia perfoliata, Huds. (Gentianaceae) y Samolus valerandi L. (Primulaceae), new records for La Pampa province are reported with information about life forms, habitat and common names.Se cita por primera vez Blackslonia perfoliata, Huds. (Gentianaceae) y Samolus valerandi L. (Primulaceae) para la provincia de La Pampa. Se consignan sus formas de vida, ambientes y nombres vulgares

Measurement of the cross-section and charge asymmetry of WW bosons produced in proton-proton collisions at s=8\sqrt{s}=8 TeV with the ATLAS detector

This paper presents measurements of the $W^+ \rightarrow \mu^+\nu$ and $W^- \rightarrow \mu^-\nu$ cross-sections and the associated charge asymmetry as a function of the absolute pseudorapidity of the decay muon. The data were collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS experiment at the LHC and correspond to a total integrated luminosity of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the 1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured with an uncertainty between 0.002 and 0.003. The results are compared with predictions based on next-to-next-to-leading-order calculations with various parton distribution functions and have the sensitivity to discriminate between them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables, submitted to EPJC. All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal

Search for squarks and gluinos in events with isolated leptons, jets and missing transverse momentum at s√=8 TeV with the ATLAS detector

The results of a search for supersymmetry in final states containing at least one isolated lepton (electron or muon), jets and large missing transverse momentum with the ATLAS detector at the Large Hadron Collider are reported. The search is based on proton-proton collision data at a centre-of-mass energy s√=8 TeV collected in 2012, corresponding to an integrated luminosity of 20 fb−1. No significant excess above the Standard Model expectation is observed. Limits are set on supersymmetric particle masses for various supersymmetric models. Depending on the model, the search excludes gluino masses up to 1.32 TeV and squark masses up to 840 GeV. Limits are also set on the parameters of a minimal universal extra dimension model, excluding a compactification radius of 1/R c = 950 GeV for a cut-off scale times radius (ΛR c) of approximately 30

Measurements of fiducial and differential cross sections for Higgs boson production in the diphoton decay channel at s√=8 TeV with ATLAS

Measurements of fiducial and differential cross sections are presented for Higgs boson production in proton-proton collisions at a centre-of-mass energy of s√=8 TeV. The analysis is performed in the H → γγ decay channel using 20.3 fb−1 of data recorded by the ATLAS experiment at the CERN Large Hadron Collider. The signal is extracted using a fit to the diphoton invariant mass spectrum assuming that the width of the resonance is much smaller than the experimental resolution. The signal yields are corrected for the effects of detector inefficiency and resolution. The pp → H → γγ fiducial cross section is measured to be 43.2 ±9.4(stat.) − 2.9 + 3.2 (syst.) ±1.2(lumi)fb for a Higgs boson of mass 125.4GeV decaying to two isolated photons that have transverse momentum greater than 35% and 25% of the diphoton invariant mass and each with absolute pseudorapidity less than 2.37. Four additional fiducial cross sections and two cross-section limits are presented in phase space regions that test the theoretical modelling of different Higgs boson production mechanisms, or are sensitive to physics beyond the Standard Model. Differential cross sections are also presented, as a function of variables related to the diphoton kinematics and the jet activity produced in the Higgs boson events. The observed spectra are statistically limited but broadly in line with the theoretical expectations