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Sökning: WFRF:(Sanchez L) > (2000-2004)

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1.
  • Abt, I, et al. (författare)
  • Measurement of the b(b)over-bar production cross section in 920 GeV fixed-target proton-nucleus collisions
  • 2003
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 26:3, s. 345-355
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the HERA-B detector, the b (b) over bar production cross section has been measured in 920 GeV proton collisions on carbon and titanium targets. The b (b) over bar production was tagged via inclusive bottom quark decays into J/psi by exploiting the longitudinal separation of J/psi --> l(+)l(-) decay vertices from the primary proton-nucleus interaction. Both e(+)e(-) and mu(+)mu(-) channels have been reconstructed and the combined analysis yields the cross section sigma(b (b) over bar) = 32(-12)(+14)(stat) (+6)(-7)(sys) nb/nucleon.
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2.
  • Abt, I, et al. (författare)
  • Inclusive V-0 production cross sections from 920 GeV fixed target proton-nucleus collisions
  • 2003
  • Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 29:2, s. 181-190
  • Tidskriftsartikel (refereegranskat)abstract
    • Inclusive differential cross sections dsigma(pA)/dx(F) and dsigma(pA)/dp(t)(2) for the production of K-S(0), Lambda, and (&ULambda;) over bar particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to roots = 41.6 GeV in the proton-nucleon system. The ratios of differential cross sections dsigma(pA)(K-S(0))/dsigma(pA)(Lambda) and dsigma(pA)((&ULambda;) over bar)/dsigma(pA) (Lambda) are measured to be 6.2 +/- 0.5 and 0.66 +/- 0.07, respectively, for x(F) approximate to -0.06. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions da,Ald t also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections sigma(pA) on the atomic mass A of the target material is discussed, and the deduced cross sections per nucleon sigma(pN) are compared with results obtained at other energies.
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  • Björk, Gunnar, et al. (författare)
  • Entangled-state lithography : Tailoring any pattern with a single state
  • 2001
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 86:20, s. 4516-4519
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate a systematic approach to Heisenberg-Limited lithographic image formation using four-mode reciprocal binomial states. By controlling the exposure pattern with a simple bank of birefringent plates, any pixel pattern on a (N + 1) X (N + 1) grid, occupying a square with the side half a wavelength long, can be generated from a 2N-photon state.
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  • Björk, Gunnar, et al. (författare)
  • Single-particle nonlocality and entanglement with the vacuum
  • 2001
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 6404:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose a single-particle experiment that is equivalent to the conventional two-particle experiment used to demonstrate a violation of Bell's inequalities. Hence, we argue that quantum mechanical nonlocality can be demonstrated by single-particle states. The validity of such a claim has been discussed in the literature, but without reaching a clear consensus. We show that the disagreement can be traced to what part of the total state of the experiment one assigns to the (macroscopic) measurement apparatus. However, with a conventional and legitimate interpretation of the measurement process one is led to the conclusion that even a single particle can show nonlocal properties.
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8.
  • Björk, Gunnar, et al. (författare)
  • Subwavelength lithography over extended areas
  • 2001
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 6401:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate a systematic approach to subwavelength resolution Lithographic image formation on films covering areas larger than a wavelength squared. For example, it is possible to make a lithographic pattern with a feature size resolution of lambda/[2(N+1)] by using a particular 2M-photon, multimode entangled state, where N less than or equal toM, and banks of birefringent plates. By preparing such a statistically mixed state, one can form any pixel pattern on a 2(M-N)(N+1) x 2(M-N)(N+1) pixel grid occupying a square with side L = 2(M-N-1)lambda. Hence, there is a trade off between the exposed area, the minimum lithographic feature size resolution, and the number of photons used for the exposure. We also show that the proposed method will work even under nonideal conditions, albeit with somewhat poorer performance.
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  • Björk, Gunnar, et al. (författare)
  • Two-photon imaging and quantum holography
  • 2004
  • Ingår i: Journal of Optics B-Quantum and Semiclassical Optics. - : IOP Publishing. - 1464-4266 .- 1741-3575. ; 6:6, s. S478-S482
  • Tidskriftsartikel (refereegranskat)abstract
    • We discuss when the use of entangled photon pairs in an imaging system can be simulated with a classically correlated source. In particular, we consider two recently proposed schemes with 'bucket detection' of one of the photons. We argue that these schemes give identical results for entangled states as for appropriately prepared classically correlated states.
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10.
  • Casellas, D., et al. (författare)
  • On the transformation toughening of Y-ZrO2 ceramics with mixed Y-TZP/PSZ microstructures
  • 2001
  • Ingår i: Journal of the European Ceramic Society. - 0955-2219 .- 1873-619X. ; 21:6, s. 765-777
  • Tidskriftsartikel (refereegranskat)abstract
    • Heat treatment of Y-TZP at high temperatures produces materials with a mixed Y-TZP/PSZ phase assemblage, which exhibit a unique combination of high mechanical strength and fracture toughness, uncommon in zirconia ceramics. The microstructure and crack growth resistance of the Y-TZP/PSZ materials developed by treating at 1650°C in air a fine-grained Y-TZP was studied. XRD as well as Raman spectroscopy results indicate that the obtained microstructure allow the retention of large tetragonal grains (up to ˜4 μm), resulting in both phase transformability enhancement and pronounced R-curve behavior. The large transformation zone, discerned from accurate measurements with Raman microprobe spectroscopy, sustains the above assessment and points out tetragonal to monoclinic phase transformation as the main toughening mechanism in the investigated Y-TZP/PSZ microstructures. This was confirmed by satisfactory agreement between the transformation toughening estimated from numerical analysis and the crack shielding experimentally determined from the R-curve measurements.
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  • Heydari, H., et al. (författare)
  • Measurable entanglement criterion for two qubits
  • 2003
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 68:6
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose a directly measurable criterion for the entanglement of two qubits. We compare the criterion with other criteria, and we find that for pure states, and some mixed states, it coincides with the state's concurrence. The measure can be obtained with a Bell-state analyzer and the ability to make general local unitary transformations. However, the procedure fails to measure the entanglement of a general mixed two-qubit state.
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15.
  • Klimov, A. B., et al. (författare)
  • Quantum phases of a qutrit
  • 2004
  • Ingår i: Journal of Physics A. - : IOP Publishing. - 0305-4470 .- 1361-6447. ; 37:13, s. 4097-4106
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider various approaches to treat the phases of a qutrit. Although it is possible to represent qutrits in a convenient geometrical manner by resorting to a generalization of the Poincare sphere, we argue that the appropriate way of dealing with this problem is through phase operators associated with the algebra su(3). The rather unusual properties of these phases are caused by the small dimension of the system and are explored in detail. We also examine the positive operator-valued measures that can describe the qutrit phase properties.
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16.
  • Sanchez-Soto, L. L., et al. (författare)
  • Description of entanglement in terms of quantum phase
  • 2002
  • Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 66:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We explore the role played by the phase in an accurate description of the entanglement of bipartite systems. We first present an appropriate polar decomposition that leads to a truly Hermitian operator for the phase of a single qubit. We also examine the positive operator-valued measures that can describe the qubit phase properties. When dealing with two qubits, the relative phase seems to be a natural variable to understand entanglement. In this spirit, we propose a measure of entanglement based on this variable.
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17.
  • Sanchez-Soto, L. L., et al. (författare)
  • Quantum lithography : Toward entangled-photon optics
  • 2003
  • Ingår i: Optics and Spectroscopy. - : Pleiades Publishing Ltd. - 0030-400X .- 1562-6911. ; 94:5, s. 666-674
  • Tidskriftsartikel (refereegranskat)abstract
    • The advantages of using nonclassical states of light for optical imaging are discussed, with special emphasis on the new field of quantum optical lithography. The classical resolution limit given by the Rayleigh criterion is approximately half of the optical wavelength. However, it has been argued that, by using special quantum states of light and a multiphoton-sensitive material or detector, this limit can be broken. Here, a brief and rigorous overview of this problem is provided, some particularly widespread misconceptions are addressed, and quantum lithography into a practical technology is discussed.
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  • Dupuy, E., et al. (författare)
  • Strato-mesospheric Measurements of Carbon Monoxide with the Odin Sub-millimetre Radiometer: Retrieval and First Results
  • 2004
  • Ingår i: Geophysical Research Letters. - 1944-8007 .- 0094-8276. ; 31:20
  • Tidskriftsartikel (refereegranskat)abstract
    • The Sub-Millimetre Radiometer (SMR) aboard the Odin satellite has been measuring vertical profiles of atmospheric trace gases since August 2001. We present the inversion methodology developed for CO measurements and the first retrieval results. CO can be retrieved from a single scan measurement throughout the middle atmosphere, with a typical resolution of similar to3 km and a relative error of similar to10% to similar to25%. Retrieval results are evaluated through comparison with data from the Whole Atmosphere Community Climate Model (WACCM) and observations of the Improved Stratospheric and Mesospheric Sounder (ISAMS) on board the Upper Atmospheric Research Satellite (UARS). Considering the large natural variability of CO, the SMR retrievals give good confirmation of the WACCM results, with an overall agreement within a factor of 2. ISAMS abundances are higher than SMR mixing ratios by a factor of 5-10 above 0.5 hPa from similar to80degreesS to similar to50degreesN.
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22.
  • Gomez, B., et al. (författare)
  • Levels and risk assessment for humans and ecosystems of platinum group elements in the airborne particles of some European cities
  • 2002
  • Ingår i: The Science of the Total Environment. ; 299, s. 1-19
  • Tidskriftsartikel (refereegranskat)abstract
    • Traffic is the main source of platinum-group element (PGE) contamination in populated urban areas. There is increasing concern about the hazardous effects of these new pollutants for people and for other living organisms in these areas. Airborne and road dusts, as well as tree bark and grass samples were collected at locations in the European cities of Göteborg (Sweden), Madrid (Spain), Rome (Italy), Munich (Germany), Sheffield and London (UK). Today, in spite of the large number of parameters that can influence the airborne PGE content, the results obtained so far indicate significantly higher PGE levels at traffic sites compared with the rural or non-polluted zones that have been investigated (background levels). The average Pt content in airborne particles found in downtown Madrid, Göteborg and Rome is in the range 7.313.1 pg m−3. The ring roads of these cities have values in the range 4.117.7 pg m−3. In Munich, a lower Pt content was found in airborne particles (4.1 pg m−3). The same tendency has been noted for downtown Rh, with contents in the range 2.22.8 pg m−3, and in the range 0.83.0 and 0.3 pg m−3 for motorway margins in Munich. The combined results obtained using a wide-range airborne classifier (WRAC) collector and a PM-10 or virtual impactor show that Pt is associated with particles for a wide range of diameters. The smaller the particle size, the lower the Pt concentration. However, in particles
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23.
  • Jersblad, J., et al. (författare)
  • Anisotropic velocity distributions in 3D dissipative optical lattices
  • 2003
  • Ingår i: European Physical Journal D. - : EDP Sciences. - 1434-6060 .- 1434-6079. ; 22:3, s. 333-339
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a direct measurement of velocity distributions in two dimensions by using an absorption imaging technique in a 3D near resonant optical lattice. The results show a clear difference in the velocity distributions for the different directions. The experimental results are compared with a numerical 3D semi-classical Monte-Carlo simulation. The numerical simulations are in good qualitative agreement with the experimental results.
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  • Jiang, J. Z., et al. (författare)
  • Compressibility and thermal expansion of cubic silicon nitride
  • 2002
  • Ingår i: Physical Review B (Condensed Matter). - 0163-1829. ; 65:16, s. 1612021-1612024
  • Tidskriftsartikel (refereegranskat)abstract
    • The compressibility and thermal expansion of the cubic silicon nitride (c-Si3N4) phase have been investigated by performing in situ x-ray powder-diffraction measurements using synchrotron radiation, complemented with computer simulations by means of first-principles calculations. The bulk compressibility of the c-Si3N4 phase originates from the average of both Si-N tetrahedral and octahedral compressibilities where the octahedral polyhedra are less compressible than the tetrahedral ones. The origin of the unit cell expansion is revealed to be due to the increase of the octahedral Si-N and N-N bond lengths with temperature, while the lengths for the tetrahedral Si-N and N-N bonds remain almost unchanged in the temperature range 295-1075 K.
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26.
  • Linseisen, J, et al. (författare)
  • Consumption of added fats and oils in the European Prospective Investigation into Cancer and Nutrition (EPIC) centres across 10 European countries as assessed by 24-hour dietary recalls
  • 2002
  • Ingår i: Public Health Nutrition. - 1475-2727. ; 5:6B, s. 1227-1242
  • Tidskriftsartikel (refereegranskat)abstract
    • Objective: To evaluate the consumption of added fats and oils across the European centres and countries participating in the European Prospective Investigation into Cancer and Nutrition (EPIC). Design and setting: 24-Hour dietary recalls were collected by means of standardised computer-guided interviews in 27 redefined EPIC centres across 10 European countries. Subjects: From an initial number of 36 900 subjects, single dietary recalls from 22 924 women and 13 031 men in the age range of 35-74 years were included. Results: Mean daily intake of added fats and oils varied between 16.2 g (Varese, Italy) and 41.1 g (Malmo, Sweden) in women and between 24.7 g (Ragusa, Italy) and 66.0 g (Potsdam, Germany) in men. Total mean lipid intake by consumption of added fats and oils, including those used for sauce preparation, ranged between 18.3 (Norway) and 37.2 g day(-1) (Greece) in women and 28.4 (Heidelberg, Germany) and 51.2 g day(-1) (Greece) in men. The Mediterranean EPIC centres with high olive oil consumption combined with low animal fat intake contrasted with the central and northern European centres where fewer vegetable oils, more animal fats and a high proportion of margarine were consumed. The consumption of added fats and oils of animal origin was highest in the German EPIC centres, followed by the French. The contribution of added fats and oils to total energy intake ranged from 8% in Norway to 22% in Greece. Conclusions: The results demonstrate a high variation in dietary intake of added fats Oil and oils in EPIC, providing a good opportunity to elucidate the role of dietary fats in cancer aetiology.
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  • Pedersen, Thomas, et al. (författare)
  • Origin invariant calculation of optical rotation without recourse to London orbitals
  • 2004
  • Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614. ; 393:4-6, s. 319-326
  • Tidskriftsartikel (refereegranskat)abstract
    • We propose an inherently origin invariant formulation of specific optical rotation obtained from the conventional velocity gauge expression by subtracting the static limit from the electric dipole-magnetic dipole polarizability: <<(p) over right arrow, (L) over right arrow >>(omega) --> <<(p) over right arrow, (L) over right arrow >>(omega) - <<(p) over right arrow, (L) over right arrow >>(0). London (gauge including) atomic orbitals are therefore not needed to ensure origin invariance and, consequently, this modified velocity gauge formulation may be employed in conjunction with variational and non-variational quantum chemical methods alike. Sample calculations on S-propylene oxide and 3,4-methylenedioxymethamphetamine using self-consistent field and coupled cluster wave functions underline this point and show that the basis set convergence of the modified velocity gauge formulation is similar to the conventional length gauge and London expressions. (C) 2004 Elsevier B.V. All rights reserved.
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  • Sanchez-Agudo, M, et al. (författare)
  • 3p -> 3d resonant photoemission spectroscopy of a TiO2 sub-monolayer grown on Al2O3
  • 2004
  • Ingår i: Proceedings of the 22nd European Conference on Surface Science (Surface Science). - : Elsevier BV. - 0039-6028. ; 566-68:Part 1, s. 515-519
  • Konferensbidrag (refereegranskat)abstract
    • The valence band resonant photoemission spectra of a TiO2 sub-monolayer grown on an Al2O3 substrate have been measured throughout the Ti 3p absorption edge, i.e. at photon energies between 40 and 60 eV. The resonance process has been analysed in terms of constant initial state (CIS) curves, showing a peak at 49.5 eV photon energy, corresponding to a Fano-like resonant process. The Ti 3d contribution to the valence band shows a significant energy shift with respect to bulk TiO2. These results are compared to cluster model calculations for a TiO6 cluster. (C) 2004 Elsevier B.V. All rights reserved.
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  • Sanpera, A., et al. (författare)
  • Atomic Fermi-Bose Mixtures in Inhomogeneous and Random Lattices : From Fermi Glass to Quantum Spin Glass and Quantum Percolation
  • 2004
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:4
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate strongly interacting atomic Fermi-Bose mixtures in inhomogeneous and random optical lattices. We derive an effective Hamiltonian for the system and discuss its low temperature physics. We demonstrate the possibility of controlling the interactions at local level in inhomogeneous but regular lattices. Such a control leads to the achievement of Fermi glass, quantum Fermi spin-glass, and quantum percolation regimes involving bare and/or composite fermions in random lattices.
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  • Sipos, A., et al. (författare)
  • Visualization of neutron and proton induced particle production in a CMOS image sensor
  • 2003
  • Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - 0168-9002 .- 1872-9576. ; 509:03-jan, s. 328-332
  • Tidskriftsartikel (refereegranskat)abstract
    • A commercially available off the shelf CMOS Image Sensor was irradiated with neutron and proton beams. The Image Sensor is equipped with standard video output. The data were collected on VHS videotapes and analyzed off-line after digitization. The camera chip with 110 000 pixels each having 12 x 12 mum(2) size, shows the nuclear reactions occurring in the sensitive layer as bright spots or tracks. Several applications are suggested based on the inexpensive CMOS Image Sensor.
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