Showing papers by "University of Warsaw published in 1999"
TL;DR: Modifications to the Cornell et al. force field are tested in molecular dynamics simulations of mononucleosides and double helices of DNA and RNA (to assess helical and sequence specific structural properties) and lead to improved agreement with experimental data.
Abstract: We have examined some subtle parameter modifications to the Cornell et al. force field, which has proven quite successful in reproducing nucleic acid properties, but whose C2'-endo sugar pucker phase and helical repeat for B DNA appear to be somewhat underestimated. Encouragingly, the addition of a single V2 term involving the atoms C(sp3)-O-(sp3)-C(sp3)-N(sp2), which can be nicely rationalized because of the anomeric effect (lone pairs on oxygen are preferentially oriented relative to the electron withdrawing N), brings the sugar pucker phase of C2'-endo sugars to near perfect agreement with ab initio calculations (W near 162 degrees). Secondly, the use of high level ab initio calculations on entire nucleosides (in contrast to smaller model systems necessitated in 1994-95 by computer limitations) lets one improve the chi torsional potential for nucleic acids. Finally, the O(sp3)-C(sp3)- C(sp3)-O(sp3) V2 torsional potential has been empirically adjusted to reproduce the ab initio calculated relative energy of C2'-endo and C3'-endo nucleosides. These modifications are tested in molecular dynamics simulations of mononucleosides (to assess sugar pucker percentages) and double helices of DNA and RNA (to assess helical and sequence specific structural properties). In both areas, the modified force field leads to improved agreement with experimental data.
915 citations
TL;DR: It is shown that the standard semideviation (square root of the semivariance) as the risk measure makes the mean-risk model consistent with the second degree stochastic dominance, provided that the trade-off coefficient is bounded by a certain constant.
559 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, Stony Brook University13, Niigata University14, Osaka University15, Seoul National University16, Tohoku University17, Tokai University18, Tokyo Institute of Technology19, University of Warsaw20, University of Washington21, California Institute of Technology22, Stanford University23
TL;DR: A total of 614 upward throughgoing muons were observed by Super-Kamiokande during 537 detector live days and the measured muon flux is [1.74{plus_minus} 0.02(sys)]{times} 10{sup {minus}13} cm{sup 2}thinsp2{theta} {gt}0.
Abstract: A total of 614 upward throughgoing muons of minimum energy 1.6thinspthinspGeV are observed by Super-Kamiokande during 537 detector live days. The measured muon flux is [1.74{plus_minus}0.07(stat){plus_minus} 0.02(sys)]{times}10{sup {minus}13} cm{sup {minus}2}thinsps{sup {minus}1}thinspsr{sup {minus}1} compared to an expected flux of [1.97{plus_minus}0.44(theor)]{times} 10{sup {minus}13} cm{sup {minus}2}thinsps{sup {minus}1}thinspsr{sup {minus}1} . The absolute measured flux is in agreement with the prediction within the errors. However, the zenith-angle dependence of the observed upward throughgoing muon flux does not agree with no-oscillation predictions. The observed distortion in shape is consistent with the {nu}{sub {mu}}{leftrightarrow}{nu}{sub {tau}} oscillation hypothesis with sin{sup 2}thinsp2{theta} {gt}0.4 and 1{times}10{sup {minus}3}{lt}{Delta}m{sup 2}{lt}1{times}1 0{sup {minus}1} eV{sup 2} at 90{percent} confidence level. {copyright} {ital 1999} {ital The American Physical Society}
429 citations
TL;DR: In this article, a universal technique for quantum-state estimation based on the maximum-likelihood method is presented, which provides a positive-definite estimate for the density matrix from a sequence of measurements performed on identically prepared copies of the system.
Abstract: We present a universal technique for quantum-state estimation based on the maximum-likelihood method. This approach provides a positive-definite estimate for the density matrix from a sequence of measurements performed on identically prepared copies of the system. The method is versatile and can be applied to multimode radiation fields as well as to spin systems. The incorporation of physical constraints, which is natural in the maximum-likelihood strategy, leads to a substantial reduction of statistical errors. Numerical implementation of the method is based on a particular form of the Gauss decomposition for positive-definite Hermitian matrices. PACS number~s!: 03.67.2a, 03.65.Bz In quantum mechanics, the achievable information on a physical system is encoded into the density matrix % ˆ , which allows one to evaluate all possible expectation values through the Born statistical rule ^O ˆ &5Tr(% ˆO ˆ). In order to obtain full information on a quantum system we need to estimate its density matrix. In principle, this can be accomplished by successive measurements on repeated identical preparations of the same system. With a proper choice of the measurements, and after collecting a suitably large number of data, we can arrive at a reliable knowledge of the quantum state of the system.
321 citations
TL;DR: In this article, a strong correlation between the intrinsic spectral slope in X-rays and the amount of Compton reflection from a cold medium in Seyfert AGNs and in the hard state of X-ray binaries with either black holes or weakly magnetized neutron stars was found.
Abstract: We find a very strong correlation between the intrinsic spectral slope in X-rays and the amount of Compton reflection from a cold medium in Seyfert AGNs and in the hard state of X-ray binaries with either black holes or weakly magnetized neutron stars. Objects with soft intrinsic spectra show much stronger reflection than those with hard spectra. We find that, at a given spectral slope, black hole binaries have similar reflection to or more reflection than Seyferts, whereas neutron star binaries in our sample have reflection consistent with that in Seyferts. The existence of the correlation implies a dominant role of the reflecting medium as a source of seed soft photons for thermal Comptonization in the primary X-ray source.
293 citations
TL;DR: In this article, a single photon incident on a beam splitter was used to demonstrate the non-locality of a quantum singlet-like state generated from an optical quantum state.
Abstract: We propose an experiment demonstrating the nonlocality of a quantum singlet-like state generated from a single photon incident on a beam splitter Each of the two spatially separated apparatuses in the setup performs a strongly unbalanced homodyning, employing a single photon counting detector We show that the correlation functions violating the Bell inequalities in the proposed experiment are given by the joint two-mode Q-function and the Wigner function of the optical singlet-like state This establishes a direct relationship between two intriguing aspects of quantum mechanics: the nonlocality of entangled states and the noncommutativity of quantum observables, which underlies the nonclassical structure of phase space quasidistribution functions
291 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, University of Chicago13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22, Stanford University23
TL;DR: In this article, a search for day-night variations in the solar neutrino flux resulting from neutrinos oscillations has been carried out using the 504 day sample of solar NE data obtained at Super-Kamiokande.
Abstract: A search for day-night variations in the solar neutrino flux resulting from neutrino oscillations has been carried out using the 504 day sample of solar neutrino data obtained at Super-Kamiokande. The absence of a significant day-night variation has set an absolute flux independent exclusion region in the two neutrino oscillation parameter space.
287 citations
01 Jul 1999-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The NA49 detector as mentioned in this paper is a wide acceptance spectrometer for the study of hadron production in p+p, p+A, and A+A collisions at the CERN SPS.
Abstract: The NA49 detector is a wide acceptance spectrometer for the study of hadron production in p+p, p+A, and A+A collisions at the CERN SPS. The main components are 4 large-volume TPCs for tracking and particle identification via dE/dx. TOF scintillator arrays complement particle identification. Calorimeters for transverse energy determination and triggering, a detector for centrality selection in p+A collisions, and beam definition detectors complete the set-up. A description of all detector components is given with emphasis on new technical realizations. Performance and operational experience are discussed in particular with respect to the high track density environment of central Pb+Pb collisions.
269 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, University of Chicago13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22, California Institute of Technology23, Stanford University24
TL;DR: In this article, a measurement of the energy spectrum of recoil electrons from solar neutrino scattering in the Super-Kamiokande detector is presented, where the shape of the measured spectrum is compared with the expectation for solar {sup 8}B neutrinos.
Abstract: A measurement of the energy spectrum of recoil electrons from solar neutrino scattering in the Super-Kamiokande detector is presented. The results shown here were obtained from 504 days of data taken between 31 May 1996 and 25 March 1998. The shape of the measured spectrum is compared with the expectation for solar {sup 8}B neutrinos. The comparison takes into account both kinematic and detector related effects in the measurement process. The spectral shape comparison between the observation and the expectation gives a {chi}{sup 2} of 25.3 with 15 degrees of freedom, corresponding to a 4.6{percent} confidence level. {copyright} {ital 1999} {ital The American Physical Society}
253 citations
TL;DR: Experimental evidence for the existence of the two types of alpha rhythm and the bifurcation predicted by the model is found, apparently, during these epochs the activity of the brain has such a high complexity that it cannot be distinguished from a random process.
253 citations
TL;DR: In this article, the authors discussed the phenomenon of shape coexistence within the self-consistent Hartree-Fock method and the nuclear shell model and traced the occurrence of the coexisting configurations with different intrinsic shapes back to the properties of the effective Hamiltonian.
Abstract: The phenomenon of shape coexistence is discussed within the self-consistent Hartree-Fock method and the nuclear shell model. The occurrence of the coexisting configurations with different intrinsic shapes is traced back to the properties of the effective Hamiltonian.
TL;DR: The NA48 experiment at CERN has performed a new measurement of direct CP violation, based on data taken in 1997 by simultaneously collecting KL and KS decays into π0π0 and π+π− as discussed by the authors.
TL;DR: The fact that the same mathematical model described the behavior of individuals of different ages suggests that age and individual differences in the discounting of delayed rewards are primarily quantitative in nature and reflect variations on fundamentally similar choice processes.
Heidelberg University1, GSI Helmholtz Centre for Heavy Ion Research2, CERN3, University of Washington4, University of Birmingham5, Polish Academy of Sciences6, Goethe University Frankfurt7, University of California, Davis8, University of California, Berkeley9, Hungarian Academy of Sciences10, Max Planck Society11, University of Marburg12, Eötvös Loránd University13, University of Warsaw14, Yale University15, University of California, Los Angeles16, Joint Institute for Nuclear Research17, Kent State University18, National and Kapodistrian University of Athens19
TL;DR: In this paper, the spectra for central Pb+Pb collisions at the CERN Super Proton Synchrotron were measured and compared to spectra from lighter systems.
Abstract: Net proton and negative hadron spectra for central Pb+Pb collisions at 158thinspthinspGeV per nucleon at the CERN Super Proton Synchrotron were measured and compared to spectra from lighter systems. Net baryon distributions were derived from those of net protons. Stopping (rapidity shift with respect to the beam) and mean transverse momentum {l_angle}p{sub T}{r_angle} of net baryons increase with system size. The rapidity density of negative hadrons scales with the number of participant nucleons for nuclear collisions, whereas their {l_angle}p{sub T}{r_angle} is independent of system size. The {l_angle}p{sub T}{r_angle} dependence upon particle mass and system size is consistent with larger transverse flow velocity at midrapidity for Pb+Pb compared to S+S central collisions. {copyright} {ital 1999} {ital The American Physical Society}
TL;DR: In this paper, the optical counterpart of the gamma-ray burst (GRB) was observed with the Las Campanas 1.0 m telescope between 15 and 48 hours after the burst and the temporal analysis of the data indicates steepening decay, independent of wavelength, approaching asymptotically t-0.76±0.62.
Abstract: We present BVRI observations of the optical counterpart to GRB 990510 obtained with the Las Campanas 1.0 m telescope between 15 and 48 hr after the burst. The temporal analysis of the data indicates steepening decay, independent of wavelength, approaching asymptotically t-0.76±0.01 at early times (t 1 day) and t-2.40±0.02 at late times, with the break time at t0 = 1.57 ± 0.03 days. GRB 990510 is the most rapidly fading of the well-documented gamma-ray burst (GRB) afterglows. It is also the first well-observed example of a broadband break for a GRB optical counterpart. The optical spectral energy distribution, corrected for significant Galactic reddening, is well fitted by a single power law with ν-0.61±0.12. However, when the B-band point is dropped from the fit, the power law becomes ν-0.46±0.08, indicating a possible deviation from the power law in the spectrum, either intrinsic or due to additional extinction near the source or from an intervening galaxy at z = 1.62. Broadband break behavior broadly similar to that observed in GRB 990510 has been predicted in some jet models of GRB afterglows, thus supporting the idea that the GRB energy is beamed, at least in some cases.
TL;DR: In this article, the spectral and scattering theory of massive Pauli-Fierz Hamiltonians is studied and geometric asymptotic completeness of these Hamiltonians are shown.
Abstract: Spectral and scattering theory of massive Pauli–Fierz Hamiltonians is studied. Asymptotic completeness of these Hamiltonians is shown. The proof consists of three parts. The first is a construction of asymptotic fields and a proof of their Fock property. The second part is a geometric analysis of observables. Its main result is what we call geometric asymptotic completeness. Finally, the last part is a proof of asymptotic completeness itself.
TL;DR: In this paper, decay rates for spherical neutron-rich r-process waiting-point nuclei are calculated within a self-consistent quasiparticle random-phase approximation, formulated in the Hartree-Fock-Bogoliubov canonical single-particle basis.
Abstract: \ensuremath{\beta} decay rates for spherical neutron-rich r-process waiting-point nuclei are calculated within a fully self-consistent quasiparticle random-phase approximation, formulated in the Hartree-Fock-Bogoliubov canonical single-particle basis. The same Skyrme force is used everywhere in the calculation except in the proton-neutron particle-particle channel, where a finite-range force is consistently employed. In all but the heaviest nuclei, the resulting half-lives are usually shorter by factors of 2 to 5 than those of calculations that ignore the proton-neutron particle-particle interaction. The shorter half-lives alter predictions for the abundance distribution of r-process elements and for the time it takes to synthesize them.
TL;DR: In this paper, a direct measurement of the Wigner function characterizing the quantum state of a light mode is reported, which is based on the representation of the function as an expectation value of a displaced photon number parity operator.
Abstract: We report a direct measurement of the Wigner function characterizing the quantum state of a light mode. The experimental scheme is based on the representation of the Wigner function as an expectation value of a displaced photon number parity operator. This allowed us to scan the phase space point-by-point, and obtain the complete Wigner function without using any numerical reconstruction algorithms.
TL;DR: In this paper, the structure of the odd-N superheavy elements with Z{approx_lt}118 and N {approx}175 was investigated using the self-consistent Skyrme-Hartree-Fock-Bogoliubov method with pairing.
Abstract: Structure of the odd-N superheavy elements with Z{approx_lt}118 and N{approx_lt}175 is investigated using the self-consistent Skyrme-Hartree-Fock-Bogoliubov method with pairing. Microscopic analysis of one-quasiparticle neutron states, alpha-decay energies, and deformations is performed. Good agreement was obtained with the recently reported {alpha} -decay chains of {sup 289} 114 and {sup 293} 118 . {copyright} {ital 1999} {ital The American Physical Society}
TL;DR: A filling transition is found at which the height of the meniscus becomes macroscopically large while the planar walls of the wedge far away from its center remain nonwet up to the wetting transition occurring at Tw>Tphi.
Abstract: We study the formation and the shape of a liquid meniscus in a wedge with opening angle 2\ensuremath{\varphi} which is exposed to a vapor phase. By applying a suitable effective interface model, at liquid-vapor coexistence and at a temperature ${T}_{\ensuremath{\varphi}}$ we find a filling transition at which the height of the meniscus becomes macroscopically large while the planar walls of the wedge far away from its center remain nonwet up to the wetting transition occurring at ${T}_{w}g{T}_{\ensuremath{\varphi}}.$ Depending on the fluid and the substrate potential the filling transition can be either continuous or discontinuous. In the latter case it is accompanied by a prefilling line extending into the vapor phase of the bulk phase diagram and describing a transition from a small to a large, but finite, meniscus height. The filling and the prefilling transitions correspond to nonanalyticities in the surface and line contributions to the free energy of the fluid, respectively.
TL;DR: The results of this study suggest that processes of generation of both types of sleep spindles are weakly coupled.
TL;DR: In this article, the optimal structures, interaction energies, and OH stretch frequencies of water cage clusters, (H2O)n, n = 7−10, were investigated theoretically.
Abstract: The optimal structures, interaction energies, and OH stretch frequencies of water cage clusters, (H2O)n, n = 7−10, have been investigated theoretically. The study consisted of MP2 level ab initio c...
TL;DR: A large seismic experiment, the POLONAISE'97 project, was conducted in Poland during May of 1997 and targeted the deep structure of the Trans-European Suture Zone (TESZ) and the complex series of upper crustal features associated with it as discussed by the authors.
TL;DR: Chrzanowski et al. as mentioned in this paper showed that at a typical potential of interest to methanol fuel cell technology (ca. 0.3 V vs. RHE), methanoline oxidation reaction occurs at the surface which is covered by the chemisorbed CO at high coverage.
TL;DR: Overall, these results indicate that some progress has been made on the ab initio protein folding problem, and the current method still fails on some beta proteins, proteins over the 110‐residue threshold, and sequences in which only a poor multiple sequence alignment can be built.
Abstract: We present our predictions in the ab initio structure prediction category of CASP3. Eleven targets were folded, using a method based on a Monte Carlo search driven by secondary and tertiary restraints derived from multiple sequence alignments. Our results can be qualitatively summa- rized as follows: The global fold can be considered ''correct'' for targets 65 and 74, ''almost correct'' for targets 64, 75, and 77, ''half-correct'' for target 79, and ''wrong'' for targets 52, 56, 59, and 63. Target 72 has not yet been solved experimentally. On average, for small helical and alpha/beta proteins (on the order of 110 residues or smaller), the method pre- dicted low resolution structures with a reasonably good prediction of the global topology. Most encour- aging is that in some situations, such as with target 75 and, particularly, target 77, the method can pre- dict a substantial portion of a rare or even a novel fold. However, the current method still fails on some beta proteins, proteins over the 110-residue thresh- old, and sequences in which only a poor multiple sequence alignment can be built. On the other hand, for small proteins, the method gives results of qual- ity at least similar to that of threading, with the advantage of not being restricted to known folds in the protein database. Overall, these results indicate that some progress has been made on the ab initio protein folding problem. Detailed information about our results can be obtained by connecting to http://www.bioinformatics.danforthcenter.org/CASP3. Proteins Suppl 1999;3:177-185. r 1999 Wiley-Liss, Inc.
09 Nov 1999
TL;DR: NP-hardness of the problem of finding optimal approximate association rules is shown, which makes the results enabling the usage of rough sets algorithms to the search of association rules extremely important in view of applications.
Abstract: We consider approximate versions of fundamental notions of theories of rough sets and association rules. We analyze the complexity of searching for α-reducts, understood as subsets discerning “α-almost” objects from different decision classes, in decision tables. We present how optimal approximate association rules can be derived from data by using heuristics for searching for minimal α-reducts. NP-hardness of the problem of finding optimal approximate association rules is shown as well. It makes the results enabling the usage of rough sets algorithms to the search of association rules extremely important in view of applications.
TL;DR: In this paper, the convergence of solutions to the cahn-hilliard equation is discussed and discussed in the context of Partial Differential Equations (PDE) and partial differential equations.
Abstract: (1999). Convergence of solutions to cahn-hilliard equation. Communications in Partial Differential Equations: Vol. 24, No. 5-6, pp. 1055-1077.
TL;DR: In this paper, the authors investigated the $s,p\ensuremath{-}d$ exchange interaction of p-type epilayers by means of magnetoabsorption.
Abstract: The $s,p\ensuremath{-}d$ exchange interaction of p-type ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As} (xl0.05)$ epilayers is investigated by means of magnetoabsorption. The observed ferromagnetic-type splitting of fundamental absorption edge is explained by antiferromagnetic $p\ensuremath{-}d$ exchange interaction, taking into account the Moss-Burstein effect, resulting from high hole concentration.
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University, Dominguez Hills5, George Mason University6, Gifu University7, Kobe University8, Kyoto University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, Stony Brook University13, Niigata University14, Osaka University15, Seoul National University16, Tohoku University17, Tokai University18, Tokyo Institute of Technology19, University of Warsaw20, University of Washington21, California Institute of Technology22
TL;DR: In this paper, the authors measured the upward through-going muon flux and calculated the stopping/through-going flux ratio R, which has less theoretical uncertainty than the expected values.
TL;DR: The lesson contained in the review is that even with just twelve papers more or less explicitly oriented towards ecological theory, elements of a theory that might emerge from individual-based modelling in the future can already be identified.