Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree–Fock, Kohn–Sham, multiconfigurational self-consistent-field, Møller–Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from http://www.daltonprogram.org for a number of UNIX platforms.

Both MMI/CMZ and PTU were associated with birth defects, but the spectrum of malformations differed. More studies are needed to corroborate results in regard to early pregnancy shift from MMI/CMZ to PTU. New ATD with fewer side effects should be developed.

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Background: Previous studies have suggested that psychological stress may play a role in the risk of multiple sclerosis (MS), but the evidence is very limited. Objective: To examine the association between MS and a well-defined major stressful life event: the death of a child. Methods: In this follow-up study based on nationwide and population-based registers, all 21,062 parents who lost a child younger than 18 years from 1980 to 1996 in Denmark were included in the exposed cohort and 293,745 matched parents who did not lose a child in the unexposed cohort. The two cohorts were followed for incident MS from 1980 to 1997. Hazard ratios (HR) with 95% CI were calculated as the measure of association between the exposure and MS, using the Cox proportional hazards regression model. Results: Two hundred fifty-eight MS patients were identified (28 in the exposed cohort and 230 in the unexposed cohort). The exposed parents had an increased risk of MS (HR 1.56, 95% CI 1.05 to 2.31), which is significant only when follow-up was at least 8 years. The HR for definite/probable MS was 1.42 (95% CI 0.90 to 2.24). Parents who lost a child unexpectedly had an HR of 2.13 (95% CI 1.13 to 4.03) for all MS, which is higher than that for other bereaved parents (HR 1.33; 95% CI 0.81 to 2.16). Conclusion: Psychological stress may play a role in the development of MS.

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We found RC to be a safe and feasible alternative to LC for colonic cancer. We found that for RC surgical time was shorter and overall procedure time was comparable to that for LC; however, these results should be confirmed in future randomized clinical trials.

The conjugate residual with optimal trial vectors CROP algorithm is developed. In this algorithm, the optimal trial vectors of the iterations are used as basis vectors in the iterative subspace. For linear equations and nonlinear equations with a small-to-medium nonlinearity, the iterative subspace may be truncated to a three-dimensional subspace with no or little loss of convergence rate, and the norm of the residual decreases in each iteration. The efficiency of the algorithm is demonstrated by solving the equations of coupled-cluster theory with single and double excitations in the atomic orbital basis. By performing calculations on H 2 O with various bond lengths, the algorithm is tested for varying degrees of nonlinearity. In general, the CROP algorithm with a three-dimensional subspace exhibits fast and stable convergence and outperforms the standard direct inversion in iterative subspace method.

It is shown that the isotropic hyperfine coupling constant Aiso associated with the Fermi contact interaction can be accurately calculated from conventional multiconfiguration self-consistent-field wave functions if, in addition to the expectation value of the contact operator, one also includes the terms originating from the response of the wave function. These response terms are nonvanishing only for perturbation operators that are nonsymmetric in spin space. Calculations of Aiso for N and BH2 illustrate the importance of the response terms and also indicate that a good estimate of the spin polarization of the core orbitals may be obtained from the response terms without correlating the core.