131,431 research outputs found
Synthetic spectra of BeH, BeD and BeT for emission modeling in JET plasmas
No full textA theoretical model for isotopologues of beryllium monohydride, BeH, BeD and BeT, A to X visible and X to X infrared rovibronic spectra is presented. The MARVEL procedure is used to compute empirical rovibronic energy levels for BeH, BeD and BeT, using experimental transition data for the X , A , and C states. The energy levels from these calculations are then used in the program Duo to produce a potential energy curve for the ground state, X , and to fit an improved potential energy curve for the first excited state, A , including a spin–orbit coupling term, a Λ-doubling state to state (A–X states) coupling term, and Born–Oppenheimer breakdown terms for both curves. These, along with a previously computed ab initio dipole curve for the X and A states are used to generate vibrational-rotational wavefunctions, transition energies and A-values. From the transition energies and Einstein coefficients, accurate assigned synthetic spectra for BeH and its isotopologues are obtained at given rotational and vibrational temperatures. The BeH spectrum is compared with a high resolution hollow-cathode lamp spectrum and the BeD spectrum with high resolution spectra from JET giving effective vibrational and rotational temperatures. Full A–X and X–X line lists are given for BeH, BeD and BeT and provided as supplementary data on the ExoMol website
Formation of the BeH+ and BeD+ Molecules in Be+ + H/D Collisions Through Radiative Association
No full textCross sections and rate coefficients for the formation of BeH+ and BeD+ molecules in Be+ + H/D collisions through radiative association are calculated using quantum mechanical perturbation theory and Breit-Wigner theory. The local thermodynamic equilibrium limit of the molecule formation is also studied, since the process is also relevant in environments with high-density and/or strong radiation fields. The obtained rate coefficients may facilitate the kinetic modelling of BeH+/BeD+ production in astrochemical environments as well as the corrosion chemistry of thermonuclear fusion reactors
Synthetic spectra of BeH, BeD and BeT for emission modeling in JET plasmas
No full textA theoretical model for isotopologues of beryllium monohydride, BeH, BeD and BeT, A 2P to X 2Σ+ visible and X 2Σ+ to X 2Σ+ infrared rovibronic spectra is presented. The MARVEL procedure is used to compute empirical rovibronic energy levels for BeH, BeD and BeT, using experimental transition data for the X 2Σ+, A 2P, and C 2Σ+ states. The energy levels from these calculations are then used in the program Duo to produce a potential energy curve for the ground state, X 2S, and to fit an improved potential energy curve for the first excited state, A 2P, including a spin-orbit coupling term, a λ-doubling state to state (A-X states) coupling term, and Born-Oppenheimer breakdown terms for both curves. These, along with a previously computed ab initio dipole curve for the X and A states are used to generate vibrational-rotational wavefunctions, transition energies and A-values. From the transition energies and Einstein coefficients, accurate assigned synthetic spectra for BeH and its isotopologues are obtained at given rotational and vibrational temperatures. The BeH spectrum is compared with a high resolution hollow-cathode lamp spectrum and the BeD spectrum with high resolution spectra from JET giving effective vibrational and rotational temperatures. Full A-X and X-X line lists are given for BeH, BeD and BeT and provided as supplementary data on the ExoMol website
Distribution en masse du boson BEH avec le detecteur ATLAS au LHC : Etalonnage, masse, largeur et interferences
No full textSince the data collected during the first run of the LHC by the ATLAS and CMS collab- orations allowed for the discovery of the BEH boson, a huge effort has been done toward the detailed studies of its properties. This thesis is particularly oriented toward the un- derstanding of the BEH boson lineshape in its diphoton decay channel, using the data collected by the ATLAS detector in 2011 and 2012. The electromagnetic calibration of the ATLAS detector is described in details, and the precise measurement of the BEH boson mass it allowed for, at mh = 125.98 ± 0.50 GeV, is summarized. A first upper limit on the BEH boson decay width, that gave a limit at Γh < 5.3 GeV at 95% C.L., is presented in details). The last part of this thesis presents a study of quantum interferences between signal and background processes in the gg → γγ channel, which are expected to distord the diphoton lineshape and create a shift of the measured BEH boson mass, that is estimated to be of 35 MeV, which is small but not negligible.Depuis que les donn ́ees collect ́ees par les collaborations ATLAS et CMS au cours de la premiere periode de fonctionnement du LHC ont permis la d ́ecouverte du boson BEH, un effort important a ́et ́e investi dans l’ ́etude d ́etaill ́ee de ses propri ́et ́es. Cette th`ese est orient ́ee en particulier vers la compr ́ehension de la distribution en masse du boson BEH dans son canal de d ́esint ́egration en deux photons, en utilisant les donn ́ees collect ́ees par le d ́etecteur ATLAS en 2011 et 2012. L’ ́etalonnage en ́energie des ́electrons et les photons est d ́ecrit en d ́etail, et la mesure pr ́ecise de la masse qu’il a permis, a` mh = 125.98 ± 0.50 GeV, est r ́esum ́e. Une premiere limite sur la largeur de d ́esint ́egration du boson BEH est aussi pr ́esent ́ee en d ́etail, et donne une limite a` Γh < 5.3 GeV `a 95% C.L. . La derni`ere partie de cette th`ese est d ́edi ́ee `a une ́etude de l’impact des interferences quantiques entre les processus de signal et de bruit de fond dans le canal gg → γγ, dont l’effet d ́eforme le spectre en masse et cr ́ee un biais pour la mesure de masse dans ce canal, qui a ́et ́e estim ́e a 35 MeV, ce qui est petit mais non-n ́egligeable
Distribution en masse du boson BEH avec le detecteur ATLAS au LHC : Etalonnage, masse, largeur et interferences
No full textSince the data collected during the first run of the LHC by the ATLAS and CMS collab- orations allowed for the discovery of the BEH boson, a huge effort has been done toward the detailed studies of its properties. This thesis is particularly oriented toward the un- derstanding of the BEH boson lineshape in its diphoton decay channel, using the data collected by the ATLAS detector in 2011 and 2012. The electromagnetic calibration of the ATLAS detector is described in details, and the precise measurement of the BEH boson mass it allowed for, at mh = 125.98 ± 0.50 GeV, is summarized. A first upper limit on the BEH boson decay width, that gave a limit at Γh < 5.3 GeV at 95% C.L., is presented in details). The last part of this thesis presents a study of quantum interferences between signal and background processes in the gg → γγ channel, which are expected to distord the diphoton lineshape and create a shift of the measured BEH boson mass, that is estimated to be of 35 MeV, which is small but not negligible.Depuis que les donn ́ees collect ́ees par les collaborations ATLAS et CMS au cours de la premiere periode de fonctionnement du LHC ont permis la d ́ecouverte du boson BEH, un effort important a ́et ́e investi dans l’ ́etude d ́etaill ́ee de ses propri ́et ́es. Cette th`ese est orient ́ee en particulier vers la compr ́ehension de la distribution en masse du boson BEH dans son canal de d ́esint ́egration en deux photons, en utilisant les donn ́ees collect ́ees par le d ́etecteur ATLAS en 2011 et 2012. L’ ́etalonnage en ́energie des ́electrons et les photons est d ́ecrit en d ́etail, et la mesure pr ́ecise de la masse qu’il a permis, a` mh = 125.98 ± 0.50 GeV, est r ́esum ́e. Une premiere limite sur la largeur de d ́esint ́egration du boson BEH est aussi pr ́esent ́ee en d ́etail, et donne une limite a` Γh < 5.3 GeV `a 95% C.L. . La derni`ere partie de cette th`ese est d ́edi ́ee `a une ́etude de l’impact des interferences quantiques entre les processus de signal et de bruit de fond dans le canal gg → γγ, dont l’effet d ́eforme le spectre en masse et cr ́ee un biais pour la mesure de masse dans ce canal, qui a ́et ́e estim ́e a 35 MeV, ce qui est petit mais non-n ́egligeable
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
State-to-state electron impact cross sections for BeH+ molecular ions in ITER-like fusion edge plasmas with Be walls
No full textBeH+ molecules will be an important intermediary species present in fusion plasmas with Be walls (e.g. JET, ITER), both for impurity transport and spectroscopic studies. To enable such analyses the electron-impact-induced excitations X (1)Sigma(+)(v(i)) -> A (1)Sigma(+)(v(f)) and X (1)Sigma(+)(v(i)) -> B (1)Pi (v(f)) in BeH+(v(i)) molecular ion, occurring between the v(i) and v(f) vibrational levels of different electronic states (vibro-electronic transitions), have been studied using the Coulomb-Born approximation. The cross sections and rate coefficients for these transitions have been calculated in a broad energy and temperature range, respectively. Accurate analytic fit expressions have been derived for the cross sections and rate coefficients for the v(i) = v(f) = 0 case of considered electronic transitions that have correct asymptotic limits. It has been demonstrated that the cross sections and rate coefficients for v(i), v(f) > 0 transitions satisfy approximate (to within 10%) scaling relationships that involve the transition energies and matrix elements of dipole transition moments only
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