The production of low-energy neutral oxygen beams by grazing-incidence neutralization

The Vanderbilt University neutral oxygen facility produces beams of low-energy neutral oxygen atoms by means of grazing-incidence collisions between ion beams and metal surfaces. Residual ions are reflected by applied electric fields. This method can utilize initial ion beams of either O(+) or O2(+) since a very large percentage of molecular oxygen ions are dissociated when they undergo grazing-incidence neutralization. The method of neutralization is applicable to low-energy beams and to all ions. Particular emphasis is on O and N2 beams for simulation of the low Earth orbit space environment. Since the beam is a pure O-neutral beam and since measurements of the interaction of the beam with solid surfaces are made spectroscopically, absolute reaction rates can be determined. The technique permits the beams to be used in conjunction with electron and photon irradiation for studies of synergistic effects. Comparisons of optical spectra of Kapton excited by 2.5-keV O, O(+), and O2(+) show significant differences. Optical spectra of Kapton excited by neutral oxygen beams of less than 1 keV have been recorded

Hybrid Models as Transdisciplinary Research Enablers

This is the final version. Available on open access from Elsevier via the DOI in this recordModelling and simulation (M&S) techniques are frequently used in Operations Research (OR) to aid decision-making. With growing complexity of systems to be modelled, an increasing number of studies now apply multiple M&S techniques or hybrid simulation (HS) to represent the underlying system of interest. A parallel but related theme of research is extending the HS approach to include the development of hybrid models (HM). HM extends the M&S discipline by combining theories, methods and tools from across disciplines and applying multidisciplinary, interdisciplinary and transdisciplinary solutions to practice. In the broader OR literature, there are numerous examples of cross-disciplinary approaches in model development. However, within M&S, there is limited evidence of the application of conjoined methods for building HM. Where a stream of such research does exist, the integration of approaches is mostly at a technical level. In this paper, we argue that HM requires cross-disciplinary research engagement and a conceptual framework. The framework will enable the synthesis of discipline-specific methods and techniques, further cross-disciplinary research within the M&S community, and will serve as a transcending framework for the transdisciplinary alignment of M&S research with domain knowledge, hypotheses and theories from diverse disciplines. The framework will support the development of new composable HM methods, tools and applications. Although our framework is built around M&S literature, it is generally applicable to other disciplines, especially those with a computational element. The objective is to motivate a transdisciplinarity-enabling framework that supports the collaboration of research efforts from multiple disciplines, allowing them to grow into transdisciplinary research

Near-bandgap wavelength-dependent studies of long-lived traveling coherent longitudinal acoustic phonon oscillations in GaSb/GaAs systems

We report first studies of long-lived oscillations in optical pump-probe measurements on GaSb-GaAs heterostructures. The oscillations arise from a photogenerated coherent longitudinal acoustic phonon wave, which travels from the top surface of GaSb across the interface into the GaAs substrate, providing information on the optical properties of the material as a function of time/depth. Wavelength-dependent studies of the oscillations near the bandgap of GaAs indicate strong correlations to the optical properties of GaAs.Comment: 11 pages, 4 figure

Purpose and benefits of hybrid simulation: Contributing to the convergence of its definition

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Point defect formation in optical materials expos ed to the space environment

Point defect formation associated with early stages of optical damage was observed unexpectedly in two, and possibly three, different optical materials subjected to short-duration space exposure. Three calcium fluoride, two lithium fluoride, and three magnesium fluoride samples were flown on Space Shuttle flight STS-46 as part of the Evaluation of Oxygen Interactions with Materials - Third Phase experiment. One each of the calcium and magnesium fluoride samples was held at a fixed temperature of 60 C during the space exposure, while the temperatures of the other samples were allowed to vary with the ambient temperature of the shuttle cargo bay. Pre-flight and post-flight optical absorption measurements were performed on all of the samples. With the possible exception of the magnesium fluoride samples, every sample clearly showed the formation of F-centers in that section of the sample that was exposed to the low earth orbit environment. Solar vacuum ultraviolet radiation is the most probable primary cause of the defect formation; however, the resulting surface metallization may be synergistically altered by the atomic oxygen environment

Time-resolved second harmonic generation study of buried semiconductor heterointerfaces using soliton-induced transparency

The transient second harmonic generation and linear optical reflectivity signals measured simultaneously in reflection from GaAs/GaSb/InAs and GaAs/GaSb heterostructures revealed a new mechanism for creating self-induced transparency in narrow bandgap semiconductors at low temperatures, which is based on the dual-frequency electro-optic soliton propagation. This allows the ultrafast carrier dynamics at buried semiconductor heterointerfaces to be studied

Improved performance of the LHCb Outer Tracker in LHC Run 2

The LHCb Outer Tracker is a gaseous detector covering an area of $5\times 6 m^2$ with 12 double layers of straw tubes. The performance of the detector is presented based on data of the LHC Run 2 running period from 2015 and 2016. Occupancies and operational experience for data collected in $p p$, pPb and PbPb collisions are described. An updated study of the ageing effects is presented showing no signs of gain deterioration or other radiation damage effects. In addition several improvements with respect to LHC Run 1 data taking are introduced. A novel real-time calibration of the time-alignment of the detector and the alignment of the single monolayers composing detector modules are presented, improving the drift-time and position resolution of the detector by 20\%. Finally, a potential use of the improved resolution for the timing of charged tracks is described, showing the possibility to identify low-momentum hadrons with their time-of-flight.Comment: 29 pages, 20 figures, minor changes to match the published versio

Maturity Model for Interoperability Potential Measurement

Interoperability potential concerns the preparation level of an enterprise to establish an efficient collaboration with possible part- ners. In order to improve their interoperability, enterprises need to know witch level of maturity they have achieved. This article pro- poses a complete maturity model composed by a methodology and a reference set of parameters to measure interoperability potential. In order to clarify the proposal, an example of application in a real case is described.Campos, C.; Chalmeta, R.; Grangel, R.; Poler Escoto, R. (2013). Maturity Model for Interoperability Potential Measurement. Information Systems Management. 30(3):218-234. doi:10.1080/10580530.2013.794630S218234303Alfaro, J. J., Rodriguez-Rodriguez, R., Verdecho, M. J., & Ortiz, A. (2009). Business process interoperability and collaborative performance measurement. International Journal of Computer Integrated Manufacturing, 22(9), 877-889. doi:10.1080/09511920902866112Sabucedo, L. Á., & Rifón, L. A. (2010). Managing Citizen Profiles in the Domain of e-Government: The cPortfolio Project. Information Systems Management, 27(4), 309-319. doi:10.1080/10580530.2010.514181Berre, A.-J., Elvesæter, B., Figay, N., Guglielmina, C., Johnsen, S. G., Karlsen, D., … Lippe, S. (s. f.). The ATHENA Interoperability Framework. Enterprise Interoperability II, 569-580. doi:10.1007/978-1-84628-858-6_62Blanc, S., Ducq, Y., & Vallespir, B. (2007). Evolution management towards interoperable supply chains using performance measurement. Computers in Industry, 58(7), 720-732. doi:10.1016/j.compind.2007.05.011Campos, C., Martí, I., Grangel, R., Mascherpa, A. and Chalmeta, R. A methodological proposal for the development of an interoperability framework.Model Driven Interoperability for Sustainable Information Systems (MDISIS′08) (CAiSE′08). Vol. 340, pp.47–57. CEUR-WS. http://ceur-ws.org/Vol-340/paper04.pdfChalmeta, R., & Grangel, R. (2005). Performance measurement systems for virtual enterprise integration. International Journal of Computer Integrated Manufacturing, 18(1), 73-84. doi:10.1080/0951192042000213164Doumeingts, G. and Chen, D. Basic concepts and approaches to develop interoperability of enterprise applications.PRO-VE,IFIP Conference Proceedings. Edited by: Camarinha-Matos, L. M. and Afsarmanesh, H. Vol. 262, pp.323–330. Norwell, MA: Kluwer.Duque, A., Campos, C., Jimenez-Ruiz, E. and Chalmeta, R. An ontological solution to supprot interoperability in the textile industry.Second IFIP WG 5.8 International Workshop, IWEI 2009. Edited by: Poler, M. V. S. R. Vol. 38, pp.38–51. New York: Springer.Guédria, W., Naudet, Y., & Chen, D. (2008). Interoperability Maturity Models – Survey and Comparison –. Lecture Notes in Computer Science, 273-282. doi:10.1007/978-3-540-88875-8_48Hoving, R. (2007). Information Technology Leadership Challenges — Past, Present, and Future. Information Systems Management, 24(2), 147-153. doi:10.1080/10580530701221049Palomares, N., Campos, C., & Palomero, S. (2010). How to Develop a Questionnaire in Order to Measure Interoperability Levels in Enterprises. Enterprise Interoperability IV, 387-396. doi:10.1007/978-1-84996-257-5_36Walsham, G. (1995). Interpretive case studies in IS research: nature and method. European Journal of Information Systems, 4(2), 74-81. doi:10.1057/ejis.1995.

Observation of two new Ξb−\Xi_b^- baryon resonances

Two structures are observed close to the kinematic threshold in the $\Xi_b^0 \pi^-$ mass spectrum in a sample of proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb$^{-1}$ recorded by the LHCb experiment. In the quark model, two baryonic resonances with quark content $bds$ are expected in this mass region: the spin-parity $J^P = \frac{1}{2}^+$ and $J^P=\frac{3}{2}^+$ states, denoted $\Xi_b^{\prime -}$ and $\Xi_b^{*-}$. Interpreting the structures as these resonances, we measure the mass differences and the width of the heavier state to be $m(\Xi_b^{\prime -}) - m(\Xi_b^0) - m(\pi^{-}) = 3.653 \pm 0.018 \pm 0.006$ MeV$/c^2$, $m(\Xi_b^{*-}) - m(\Xi_b^0) - m(\pi^{-}) = 23.96 \pm 0.12 \pm 0.06$ MeV$/c^2$, $\Gamma(\Xi_b^{*-}) = 1.65 \pm 0.31 \pm 0.10$ MeV, where the first and second uncertainties are statistical and systematic, respectively. The width of the lighter state is consistent with zero, and we place an upper limit of $\Gamma(\Xi_b^{\prime -}) < 0.08$ MeV at 95% confidence level. Relative production rates of these states are also reported.Comment: 17 pages, 2 figure