169,992 research outputs found
Cordelia C. Nevers, Les idées communes des hommes et des femmes d'après Jastrow
No full textBinet Alfred. Cordelia C. Nevers, Les idées communes des hommes et des femmes d'après Jastrow. In: L'année psychologique. 1895 vol. 2. pp. 699-700
Assessing the accuracy of the Jastrow antisymmetrized geminal power in the H 4 model system
No full textWe report a quantum Monte Carlo study, on a very simple but nevertheless very instructive model system of four hydrogen atoms, recently proposed in Gasperich et al. [J. Chem. Phys. 147, 074106 (2017)]. We find that the Jastrow correlated Antisymmetrized Geminal Power (JAGP) is able to recover most of the correlation energy even when the geometry is symmetric and the hydrogens lie on the edges of a perfect square. Under such conditions, the diradical character of the molecule ground state prevents a single determinant Ansatz to achieve an acceptable accuracy, whereas the JAGP performs very well for all geometries. Remarkably, this is obtained with a similar computational effort. Moreover, we find that the Jastrow factor is fundamental in promoting the correct resonances among several configurations in the JAGP, which cannot show up in the pure Antisymmetrized Geminal Power (AGP). We also show the extremely fast convergence of this approach in the extension of the basis set. Remarkably, only the simultaneous optimization of the Jastrow and the AGP part of our variational Ansatz is able to recover an almost perfect nodal surface, yielding therefore state of the art energies, almost converged in the complete basis set limit, when the so called diffusion Monte Carlo is applied
Quantum Monte Carlo with Jastrow-valence-bond wave functions
No full textInternational audienceWe consider the use in quantum Monte Carlo calculations of two types of valence bond wave functions based on strictly localized active orbitals, namely valence bond self-consistent-field (VBSCF) and breathing-orbital valence bond (BOVB) wave functions. Complemented by a Jastrow factor, these Jastrow-Valence-Bond wave functions are tested by computing the equilibrium well depths of the four diatomic molecules C, N, O, and F in both variational Monte Carlo (VMC) and diffusion Monte Carlo (DMC). We show that it is possible to design compact wave functions based on chemical grounds that are capable of describing both static and dynamic electron correlation. These wave functions can be systematically improved by inclusion of valence bond structures corresponding to additional bonding patterns
Implementing Jastrow--Gutzwiller operators on a quantum computer using the cascaded variational quantum eigensolver algorithm
No full textA Jastrow--Gutzwiller operator adds many-body correlations to a quantum
state. However, the operator is non-unitary, making it difficult to implement
directly on a quantum computer. We present a novel implementation of the
Jastrow--Gutzwiller operator using the cascaded variational quantum eigensolver
algorithm. We demonstrate the method on IBM Q Lagos for a Hubbard model
Jastrow-Type Calculations of One-Nucleon Removal Reactions in Open s-d Shell Nuclei
No full textSingle-particle overlap functions and spectroscopic factors are calculated on the basis of Jastrow-type onebody density matrices of open-shell nuclei constructed by using a factor cluster expansion. The calculations use
the relationship between the overlap functions corresponding to bound states of the (A-1)-particle system and the one-body density matrix for the ground state of the A-particle system. In this work, we extend our previous
analyses of reactions on closed-shell nuclei by using the resulting overlap functions for the description of the
cross sections of (p,d) reactions on the open s-d shell nuclei 24Mg, 28Si, and 32S and of 32S(e,e'p) reaction.
The relative role of both shell structure and short-range correlations incorporated in the correlation approach onthe spectroscopic factors and the reaction cross sections is pointed out
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
Full optimization of Jastrow–Slater wave functions with application to the first-row atoms and homonuclear diatomic molecules
No full textInternational audienceWe pursue the development and application of the recently introduced linear optimization method for determining the optimal linear and nonlinear parameters of Jastrow-Slater wave functions in a variational Monte Carlo framework. In this approach, the optimal parameters are found iteratively by diagonalizing the Hamiltonian matrix in the space spanned by the wave function and its first-order derivatives, making use of a strong zero-variance principle. We extend the method to optimize the exponents of the basis functions, simultaneously with all the other parameters, namely, the Jastrow, configuration state function, and orbital parameters. We show that the linear optimization method can be thought of as a so-called augmented Hessian approach, which helps explain the robustness of the method and permits us to extend it to minimize a linear combination of the energy and the energy variance. We apply the linear optimization method to obtain the complete ground-state potential energy curve of the C2 molecule up to the dissociation limit and discuss size consistency and broken spin-symmetry issues in quantum Monte Carlo calculations.We perform calculations for the first-row atoms and homonuclear diatomic molecules with fully optimized Jastrow-Slater wave functions, and we demonstrate that molecular well depths can be obtained with near chemical accuracy quite systematically at the diffusion Monte Carlo level for these systems
Geminal wave functions with Jastrow correlation: A first application to atoms
No full textWe introduce a simple generalization of the well-known geminal wave function already applied in quantum chemistry to atoms and small molecules. The main feature of the proposed wave function is the presence of the antisymmetric geminal part together with a Jastrow factor. Both the geminal and the Jastrow play a crucial role in determining the remarkable accuracy of the many-body state: the former permits the correct treatment of the nondynamic correlation effects; the latter allows the wave function to fulfill the cusp conditions and makes the geminal expansion rapidly converge to the lowest possible variational energies. This ansatz is expected to provide a substantial part of the correlation energy for general complex atomic and molecular systems. The antisymmetric geminal term can be written as a single determinant even in the polarized cases. In general, therefore, the computational effort to sample this correlated wave function is not very demanding, the scaling of the algorithm with the number of atoms being comparable with the simplest Hartree-Fock calculation. We applied this Jastrow-geminal approach to atoms up to Z=14, always getting good variational energies, by particularly improving those with a strong multiconfigurational nature. Our wave function is very useful for Monte Carlo techniques, such as fixed node. Indeed, the nodal surface obtained within this approach can be substantially improved through the geminal expansion. (C) 2003 American Institute of Physics
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
The Jastrow cluster expansion method for finite nuclei
No full textThe binding energies and RMS radii of nuclei in the mass region 16<or=A<or=208 are calculated in the Jastrow cluster expansion method by including the second-order correction to the energy. The Reid soft-core NN interaction has been employed in the calculations. The binding energies are predicted reasonably well for the nuclei in the mass region A approximately 90 whereas they are underestimated in nuclei with A<56 and overestimated in nuclei with A>120. The calculated RMS radii are in good agreement with the experimental data for nuclei with A<or=56 but nor for heavy nuclei where considerable compression is predicted. The contribution of the three-body cluster correction to the two-body correlation energy is estimated to be at the most 9% thereby indicating a good convergence of the cluster expansion. Results are compared with those recently obtained from the Brueckner-Bethe-Goldstone method using the same NN interaction
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