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196 results on '"Papanastasiou, D."'

1. Chemically Aware Unitary Coupled Cluster with ab initio Calculations on System Model H1: A Refrigerant Chemicals Application

Author

Khan, I. T., Tudorovskaya, M., Kirsopp, J. J. M., Ramo, D. Muñoz, Warrier, P. W., Papanastasiou, D. K., and Singh, R.

Subjects
Quantum Physics, Condensed Matter - Materials Science
Abstract

Circuit depth reduction is of critical importance for quantum chemistry simulations on current and near term quantum computers. This issue is tackled by introducing a chemically aware strategy for the Unitary Coupled Cluster ansatz. The objective is to use the chemical description of a system to aid in the synthesis of a quantum circuit. We combine this approach with two flavours of Symmetry Verification for the reduction of experimental noise. These method enable the use of System Model H1 for a 6-qubit QSE (Quantum Subspace Expansion). We present (i) calculations to obtain CH4 optical spectra; (ii) an atmospheric gas reaction simulation involving $[$CH$^{\cdot}_3$--H--OH$^{\cdot}]^{\ddagger}$. Using our chemically aware UCC state-preparation strategy in tandem with state of the art symmetry verification methods, we improve device yield for CH4 at 6-qubits. This is demonstrated by a 90% improvement in two-qubit gate count and reduction in relative error to 0.2% for electronic energy calculated on System Model H1.

Published
2022
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2. Chemically aware unitary coupled cluster with ab initio calculations on an ion trap quantum computer: A refrigerant chemicals' application.

Author

Khan, I. T., Tudorovskaya, M., Kirsopp, J. J. M., Muñoz Ramo, D., Warrier, P., Papanastasiou, D. K., and Singh, R.

Subjects
QUANTUM computers, AB-initio calculations, ION traps, REFRIGERANTS, CIRCUIT complexity, QUANTUM chemistry
Abstract

Circuit depth reduction is of critical importance for quantum chemistry simulations on current and near term quantum computers. This issue is tackled by introducing a chemically aware strategy for the unitary coupled cluster ansatz. The objective is to use the chemical description of a system to aid in the synthesis of a quantum circuit. We combine this approach with two flavors of symmetry verification for the reduction of experimental noise. These methods enable the use of Quantinuum's System Model H1 ion trap quantum computer for a 6-qubit quantum subspace expansion calculation. We present (i) calculations to obtain methane's optical spectra; (ii) an atmospheric gas reaction simulation involving [ C H 3 ⋅ —H—OH]‡. Using our chemically aware unitary coupled cluster state-preparation strategy in tandem with state of the art symmetry verification methods, we improve device yield for CH4 at 6 qubits. This is demonstrated by a 90% improvement in two-qubit gate count and a reduction in relative error to 0.2% for electronic energy calculated on System Model H1. [ABSTRACT FROM AUTHOR]

Published
2023
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11. A mass-selective ion transfer line coupled with a uniform supersonic flow for studying ion–molecule reactions at low temperatures.

Author

Joalland, B., Jamal-Eddine, N., Papanastasiou, D., Lekkas, A., Carles, S., and Biennier, L.

Subjects
ION-molecule collisions, SUPERSONIC flow, RADIATION trapping, LOW temperatures, COMPLEX ions, ION traps
Abstract

A new approach based on the uniform supersonic flow technique—a cold, thermalized de Laval expansion offering the advantage of performing experiments with condensable species—has been developed to study ion–molecule reactions at low temperatures. It employs a mass-selective radio frequency transfer line to capture and select ions from an adaptable ionization source and to inject the selected ions in the core of the supersonic expansion where rate coefficients and product branching can be measured from room temperature down to ∼15 K. The transfer line incorporates segmented ion guides combining quadrupolar and octapolar field orders to maximize transmission through the differential apertures and the large pressure gradients encountered between the ionization source (∼mbar), the quadrupole mass filter (∼10−5 mbar), and the de Laval expansion (∼mbar). All components were designed to enable the injection of cations and anions of virtually any m/z ratio up to 200 at near ground potential, allowing for a precise control over the momentum and thermalization of the ions in the flow. The kinetics and branching ratios of a selection of reactions have been examined to validate the approach. The technique will be instrumental in providing new insight on the reactivity of polyatomic ions and molecular cluster ions in astrophysical and planetary environments. [ABSTRACT FROM AUTHOR]

Published
2019
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24. Réactivité Des Ions Dans Les Environnements Astrophysiques Froids : Nouveau Dispositif Expérimental CRESU-SIS

Author

Carles, Sophie, Mortada, Ahmad, Joalland, Baptiste, Jamal-Eddine, Nour, Papanastasiou, D., Lekkas, A., Biennier, Ludovic, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), Wayne State University [Detroit], National Center for Scientific Research 'Demokritos' (NCSR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), and Carles, Sophie

Subjects
[PHYS]Physics [physics], [PHYS.ASTR.IM]Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], [PHYS.ASTR.IM] Physics [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Molecular physics, ComputingMilieux_MISCELLANEOUS, [PHYS.PHYS.PHYS-CHEM-PH] Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], [PHYS] Physics [physics]
Abstract

National audience

Published
2019

25. VIRUSCAN: identification and characterization of viruses from their nano-mechanical properties

Author

Heiden, M.S. van der, Harmsma, P.J., Altmann, R.K., Lucas, P., Thuaire, A., Papanastasiou, D., Favero, I., Sbarra, S., and Tamayo, J.

Subjects
Industrial Innovation, VIRUSCAN, ERP 3D Nanomanufacturing Instruments, viruses, Nano-mechanical properties, ERP Early Research Program, Viruses, High Tech Systems & Materials
Abstract

Measuring the nano-mechanical properties of viruses opens a new route to identify viruses and to assess their infectiveness. Current targeted techniques, like PCR, are only suitable for confirmation and have a high false positive rate due to cross contamination and DNA strands presents in the blood sample after former infection. The VIRUSCANproject aims to detect and identify individual viruses and assess their infectiveness based on measuring the mass and stiffness of individual viruses in a blood sample. This non-targeted method enables identification of mixtures of multiple viruses and unknown viruses together with the ability to measure their infectiveness.

Published
2019

33. Characterization of carbon fractal-like aggregates by size distribution measurements and theoretical calculations

Author

Gini, M.I. Helmis, C. Melas, A.D. Papanastasiou, D. Orfanopoulos, G. Giannakopoulos, K.P. Drossinos, Y. Eleftheriadis, K.

Abstract

The structural characteristics of carbon nanoparticles synthesized by a spark discharge source were investigated by combined measurements of polydisperse number and Fuchs surface-area distributions against equivalent particle mobility and aerodynamic diameters. The number and Fuchs surface area distribution measurements were conducted by a scanning mobility particle sizer (SMPS) and a cascade epiphaniometer (CEPI), respectively. The CEPI-measured total Fuchs surface area and the Fuchs surface area calculated from SMPS number distributions were found to be in reasonable agreement (average absolute difference 28%), suggesting that the momentum-transfer diameter may be approximated by the mass-transfer diameter. The measured total Fuchs surface area of polydisperse distributions was reasonably reproduced by the Fuchs surface area of a monodisperse distribution (average absolute difference 26%). A fitting procedure was used to obtain the effective density mobility diameter relationship. The generated carbon aggregates, composed of primary particles of average diameter of 12.7 ± 2.5 nm, were determined to obey a fractal-like power law with a mass mobility fractal dimension Dm = 2:14 and a prefactor km = 1:06, in good agreement with theoretical calculations. Experimental measurements were compared to various theoretical models for the number of primary particles, the dynamic shape factors, and the effective density. © 2016 American Association for Aerosol Research.

Published
2016

34. Differential mobility separation of ions using a rectangular asymmetric waveform

Author

Papanastasiou, D., Wollnik, H., Rico, G., Tadjimukhamedov, F., Mueller, W., and Eiceman, G.A.

Subjects
Waveforms -- Analysis, Electric fields -- Research, Ionic mobility -- Research, Chemicals, plastics and rubber industries
Abstract

The article discusses the performance of a differential mobility spectrometer (DMS), which uses a rectangular asymmetric waveform for the separation of ions. The ion mobility is shown to be highly dependent on the magnitude of the electric field.

Published
2008

40. Bending stability of Cu0.4CrO2—A transparent p-type conducting oxide for large area flexible electronics.

Author

Norton, E., Farrell, L., Zhussupbekova, A., Mullarkey, D., Caffrey, D., Papanastasiou, D. T., Oser, D., Bellet, D., Shvets, I. V., and Fleischer, K.

Subjects
FLEXIBLE electronics, OXIDES
Abstract

The current best performing p-type transparent conducting oxides are typically highly crystalline materials, deposited at high temperatures, and hence incompatible with the drive to low cost flexible electronics. We investigated a nanocrystalline, copper deficient CuxCrO2, deposited at low temperatures upon a flexible polyimide substrate. The as-deposited film without post annealing has an electrical conductivity of 6Scm−1. We demonstrate that this p-type transparent oxide retains its excellent electrical conductivity under tensile strain, withstanding more than one thousand bending cycles without visible cracks or degradation in electrical properties. In contrast, compressive strain is shown to lead to an immediate reduction in conductivity which we attribute to a de-lamination of the thin film from the substrate. [ABSTRACT FROM AUTHOR]

Published
2018
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41. Stratospheric Ozone and Surface Ultraviolet Radiation

Author

Douglass, A., Fioletov, V., Godin-Beekmann, S., Müller, R., Stolarski, R. S., Webb, A., Arola, A., Burkholder, J. B., Burrows, J. P., Chipperfield, M. P., Cordero, R., David, C., den Outer, P. N., Diaz, S. B., Flynn, L. E., Hegglin, M., Herman, J. R., Huck, P., Janjai, s., Janosi, I. M., Kryscin, J. W., Liu, Y., Logan, J., Matthes, Katja, McKenzie, R. L., Muthama, N. J., Petropavlovskikh, I., Pitts, M., Ramachandran, S., Rex, M., Salawitch, R. J., Sinnhuber, B.-M., Staehelin, J., Strahan, S., Tourpali, K., Valverde-Canossa, J., Vigouroux, C., Bodeker, G. E., Canty, T., De Backer, H., Demoulin, P., Feister, U., Frith, S. M., Grooß, J.-U., Hase, F., Klyft, J., Koide, T., Kurylo, M. J., Loyola, D., McLinden, C. A., Megretskaia, I. A., Nair, P. J., Palm, M., Papanastasiou, D., Poole, L. R., Schneider, M., Schofield, R., Slaper, H., Steinbrecht, W., Tegtmeier, Susann, Terao, Y., Tilmes, S., Vyushin, D. I., Weber, M., and Yang, E.-S.

Published
2011

42. Present climate trend analysis of the Etesian winds in the Aegean Sea

Author

Poupkou, A. Zanis, P. Nastos, P. Papanastasiou, D. Melas, D. Tourpali, K. Zerefos, C.

Abstract

The main objective of the present study is to perform a trend analysis and investigate the possible changes in the frequency and wind intensity of the Etesians during June to September of the years 1979 to 2009. The analysis is based mainly on the use of Reanalysis-1 data from the National Centers for Environmental Prediction/National Center for Atmospheric Research. The results are indicative of negative trends in the frequency and wind speed (WS) of the Etesians. During the 31-year period studied, the total number of Etesian days from June to September decreased by about 4.6 days, while the monthly maximum intensity of the daily WS was reduced by almost 1 m s-1. The above indications are strengthened by similar results derived from the trend analysis of observational wind data in the central Aegean for the years 1955 to 2002. The negative trend in the frequency of the Etesian days could be explained by a decreasing trend in the pressure gradient between the central and southern Europe high-pressure center and the Middle East low-pressure center, which cause the Etesians system. In the study, a possible association between the Southern Oscillation and the Etesian winds is also revealed. The negative trend in the frequency and WS of the Etesian winds could imply a reduced cooling mechanism in the eastern Mediterranean in the summer period due to climate change. © 2011 Springer-Verlag.

Published
2011

46. Double-Blind Ureteral Duplication: A Rare Urologic Anomaly

Author

Salakos, C. Tyritzis, S. I. Papanastasiou, D. Geropoulou, E. and Constantinides, C. A.

Subjects
urologic and male genital diseases
Abstract

We present an extremely infrequent Urologic entity of asymptomatic. double-blind ureteral duplication in an 8-year-old girl. Contemporary imaging modalities provided major assistance in the diagnosis. Surgical management is advocated because of the potential for future complications, such as lithiasis, obstruction of the collecting system, and renal failure. UROLOGY 73: 210.e1-210.e2, 2009. (C) 2009 Elsevier Inc.

Published
2009

50. Antigenic structure of the muscle nicotinic acetylcholine receptor

Author

Tzartos, S. J., Cung, M. T., Mamalaki, A., Marraud, M., Papanastasiou, D., Sakarellos, C., Sakarellos-Daitsiotis, M., and Tsantili, P.

Subjects
alpha-subunit, myasthenia gravis, modulation, epitope, phosphorylation, racetylcholine receptor, main immunogenic region, monoclonal-antibodies, expression, autoimmune myasthenia-gravis, site-specific probes, tyrosine
Abstract

Ann Med Interne (Paris)

Published
1996

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