5,169 research outputs found
Molecular Applications of a State-Specific Multireference Coupled Electron-Pair Approximation (SS-MRCEPA)-like Method
No full textIn this paper, we present a coupled electron-pair (CEPA) type variant of the state-specific multireference coupled cluster (SS-MRCC) method [Mahapatra, U. S., et al. J. Chem. Phys. 1999, 110, 6171]. The method termed as SS-MRCEPA based on complete active space (CAS) can handle quasi-degeneracy of varying degrees over a wide range of potential energy curves (PECs), including regions of real or avoided curve-crossing. The method is size-extensive and avoids the intruder problem in a natural manner. Exploiting a two-dimensional CAS-based SS-MRCEPA method, we consider, in this paper, several demanding molecular systems that benefit from multireference description. The reliability of computational results of the method for PECs of the ground state of P4, H4, H8, perpendicular insertion of Be into H2, Li2, and ground-state energy at the equilibrium point of CH2 will be discussed with respect to the parent SS-MRCC and full CI/large scale CI results. We have also reported the excitation energies corresponding to the ground states of H8 and CH2 systems. The method has also been applied to study the bond breaking in the F2 molecule which is a challenging task for any ab initio method. In all cases, the comparison is also made with the results obtained from other CC- and CEPA-type methods wherever available
RDLS-SS-DWT v. 0.9
No full textThis fileset contains the implementation of RDLS-DWT and SS-DWT in JPEG 2000 (RDLS-SS-DWT v. 0.9), which was used in a research described in: R. Starosolski, “Application of reversible denoising and lifting steps to DWT in lossless JPEG 2000 for improved bitrates,” Signal Processing: Image Communication, Vol. 39, Part A, pp. 249-63, DOI: 10.1016/j.image.2015.09.013, 2015 and R. Starosolski, “Skipping selected steps of DWT computation in lossless JPEG 2000 for improved bitrates,” submitted. This software is intended for research purposes only; it is provided "as is"; author makes no warranty of any kind, either express or implied, with respect to this software. <br
Applications of size-consistent state-specific multi-reference coupled cluster (SS-MRCC) theory to study the potential energy curves of some interesting molecular systems
No full textIn this paper we apply the state-specific multi-reference coupled cluster method (SS-MRCC) (Mahapatra et al 1999 J. Chem. Phys. 110 6171) to compute the potential energy curves (PECs) of some interesting diatomic molecular systems. The theory is built on complete active space (CAS) reference functions. This formulation relies upon a small CAS, but is capable of producing energies to a high degree of accuracy. In the SS-MRCC method, depending upon the method of iteration, we may determine cluster amplitudes and consequently the effective Hamiltonian either with the frozen (unrelaxed scheme) or with the converged coefficients (relaxed scheme) which are the model space coefficients in the final wavefunction. Thus the energy can be obtained either as an expectation value with respect to the unrelaxed function or by diagonalizing within the CAS. The SS-MRCC method is rigorously size-extensive and size-consistent. The method bypasses the intruders by focusing on a single state of interest in a natural manner. The method could thus serve as a reliable choice for PEC studies over a wide range of geometries. We will also compare the relative performances of the description of 'unrelaxed' versus 'relaxed' coefficients. We also evaluate certain spectroscopic constants and compare them with experimental results
Prediction of welding responses using AI approach: adaptive neuro-fuzzy inference system and genetic programming
No full textSS Northland Echo
No full textPhotograph - A view of the steamboat, SS Northland Echo on the Athabasca River. Athabasca, Albert
SS Athabasca River - 02
No full textPhotograph - A view of the SS Athabasca River paddle steamer on the river, Athabasca, Albert
RIC-HSCT for MF/SS
No full textAdvanced-stage mycosis fungoides and Sezary syndrome (MF/SS) have a poor prognosis. Allogeneic hematopoietic stem cell transplantation (HSCT), particularly using a reduced-intensity conditioning (RIC) regimen, is a promising treatment for advanced-stage MF/SS. We performed RIC-HSCT in nine patients with advanced MF/SS. With a median follow-up period of 954days after HSCT, the estimated 3-year overall survival was 85.7% (95% confidence interval, 33.4-97.9%) with no non-relapse mortality. Five patients relapsed after RIC-HSCT; however, in four patients whose relapse was detected only from the skin, persistent complete response was achieved in one patient, and the disease was manageable in other three patients by the tapering of immunosuppressants and donor lymphocyte infusion, suggesting that graft-versus-lymphoma effect and "down-staging" effect from advanced stage to early stage by HSCT improve the prognosis of advanced-stage MF/SS. These results suggest that RIC-HSCT is an effective treatment for advanced MF/SS
SS Northland Sun at Mirror Landing, AB
No full textPhotograph - The paddle-wheeler, SS Northland Sun, docked at shore in Mirror Landing, Albert
SS Northland Light at Sawridge, AB
No full textPhotograph - Paddle-wheeler, SS Northland Light, docked at the shore. Sawridge, A
A state-specific approach to multireference coupled electron-pair approximation like methods: development and applications
No full textThe traditional multireference (MR) coupled-cluster (CC) methods based on the effective Hamiltonian are often beset by the problem of intruder states, and are not suitable for studying potential energy surface (PES) involving real or avoided curve crossing. State-specific MR-based approaches obviate this limitation. The state-specific MRCC (SS-MRCC) method developed some years ago [Mahapatra et al., J. Chem. Phys. 110, 6171 (1999)] can handle quasidegeneracy of varying degrees over a wide range of PES, including regions of real or avoided curve-crossing. Motivated by its success, we have suggested and explored in this paper a suite of physically motivated coupled electron-pair approximations (SS-MRCEPA) like methods, which are designed to capture the essential strength of the parent SS-MRCC method without significant sacrificing its accuracy. These SS-MRCEPA theories, like their CC counterparts, are based on complete active space, treat all the reference functions on the same footing and provide a description of potentially uniform precision of PES of states with varying MR character. The combining coefficients of the reference functions are self-consistently determined along with the cluster amplitudes themselves. The newly developed SS-MRCEPA methods are size-extensive, and are also size-consistent with localized orbitals. Among the various versions, there are two which are invariant with respect to the restricted rotations among doubly occupied and active orbitals separately. Similarity of performance of this latter and the noninvariant versions at the crossing points of the degenerate orbitals imply that the all the methods presented are rather robust with respect to the rotations among degenerate orbitals. Illustrative numerical applications are presented for PES of the ground state of a number of difficult test cases such as the model H4, H8 problems, the insertion of Be into H2, and Li2, where intruders exist and for a state of a molecule such as CH2, with pronounced MR character. Results obtained with SS-MRCEPA methods are found to be comparable in accuracy to the parent SS-MRCC and FCI/large scale CI results throughout the PES, which indicates the efficacy of our SS-MRCEPA methods over a wide range of geometries, despite their neglect of a host of complicated nonlinear terms, even when the traditional MR-based methods based on effective Hamiltonians fail due to intruders
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