New source of decoupling of E1 strength from the GDR: boundary condition mixing for s- and p-wave neutron states near threshold

Non-statistical effects in neutron capture reveal that E1 strength of neutron orbits of low l-value is partially decoupled from the GDR. Particle-hole diagonalisations with realistic forces do not show this effect. We show that it can arise from a new source, boundary condition mixing, which operates when fine-structure states are introduced. This may also explain the ‘pygmy dip’ in E1 strength reported for masses ～ 195.     

A singularity in E1 matrix elements at the neutron threshold: Evidence from (d,p)-(n, γ) correlations

There are several independent effects which tend to suppres correlations of (d, p)-(n, γ) type. When a near-perfect correlation is found, as in the case ³⁷Cl with thermal capture, it follows that all the effects are small. This has important implications, such as showing that the dominant thermal capture process can be ‘direct’, thereby settling a long debate. Further, the data establishes the E_γ^?1 singularity in E1 matrix elements for thermal capture that was derived theoretically in 1960.     

Generalized Vaidya metrics

We investigate criteria under which one may construct the energy tensor of a null radiation field from an algebraically special vacuum metric. The field bears the same relationship to the original metric as does Vaidya's to Schwarzschild's. As an example we generate a class of null radiation fields from a class of vacuum metrics without symmetry discovered by Robinson and Robinson.Supported in part by the National Science Foundation (GP-8868, GP-20033, and GU-1598), Air Force Office of Scientific Research under Grant AF-AFOSR-903-67 and by the National Aeronautics and Space Administration under NASA Grant No. NGL 44-004-001.     

Evidence for assignment of 14.0 MeV state in 11B from 10B(n,n)10B

The differential cross section and polarization for neutrons scattered from ¹⁰B have been measured at E_n = 2.63 MeV (E_x = 13.85 MeV). The results of this experiment and other available neutron scattering data in the range 1 < E_n < 4 MeV are interpreted through a single-level R-matrix calculation over the region 12 < E_x < 15 MeV. Based on this analysis the most probable J^π assignment for the 14.0 MeV level in ¹¹B is $\text{11}\text{2}{}^{\mathrm{+}}$. The anomaly near E_x = 13.1 MeV can only be explained in terms of two overlapping levels having assignments of ($\text{5}\text{2}$, $\text{7}\text{2}$)^? and ($\text{3}\text{2}$, $\text{5}\text{2}$, $\text{7}\text{2}$)⁺.     

The Operational Audit: A Business Appraisal Approach to Improved Operations and Profitability

The operational audit is concerned with the appraisal of company effectiveness, identifying operations which are open to improvement. This paper looks at the history of the operational audit and its relationship to other types of audit. The scope of the operational audit is discussed and so also is the manner in which assignments are typically conducted. Two case studies, one in a sales company and the other in a production company, are presented, and details are provided of the results obtained. The relationship of operational research to operational audit is reviewed, and the benefits of including operational researchers in audit teams are pointed out.     

OH-stretch vibrational spectroscopy of hydroxymethyl hydroperoxide

We report measurement and analysis of the photodissociation spectrum of hydroxymethyl hydroperoxide (HOCH(2)OOH) and its partially deuterated analogue, HOCD(2)OOH, in the OH-stretching region. Spectra are obtained by Fourier transform infrared spectroscopy in the 1nu(OH) and 2nu(OH) regions, and by laser induced fluorescence detection of the OH fragment produced from dissociation of HOCH(2)OOH initiated by excitation of the 4nu(OH) and 5nu(OH) overtone regions (action spectroscopy). A one-dimensional local-mode model of each OH chromophore is used with ab initio calculated OH-stretching potential energy and dipole moment curves at the coupled-cluster level of theory. Major features in the observed absorption and photodissociation spectra are explained by our local-mode model. In the 4nu(OH) region, explanation of the photodissocation spectrum requires a nonuniform quantum yield, which is estimated by assuming statistical energy distribution in the excited state. Based on the estimated dissociation threshold, overtone photodissociation is not expected to significantly influence the atmospheric lifetime of hydroxymethyl hydroperoxide.     

Raman and surface‐enhanced Raman spectroscopic studies of the 15‐mer DNA thrombin‐binding aptamer

Aptamers are single‐stranded oligonucleotides that selectively bind to their target molecules owing to their ability to form secondary structures and shapes. The 15‐mer (5′‐GGTTGGTGTGGTTGG‐3′) DNA thrombin‐binding aptamer (TBA) binds to thrombin following the formation of a quadruplex structure via the Hoogsten‐type G–G interactions. In the present study, Raman and SERS spectra of TBA and thiolated TBA (used to facilitate covalent bonding to metal nanoparticle) in different conditions are investigated. The spectra of the two analogs exhibit vibrations, such as the C8N7 H2 deformation band at ∼1480 cm⁻¹ of the guanine tetrad, that are characteristic of the quadruplex structure in the presence of K⁺ ions or at low temperature. Interestingly, SERS spectra of the two analogs differ markedly from their respective normal Raman spectra, possibly due to changes in the conformation of the aptamer upon binding, as well as to the specific interaction of individual vibrational modes with the metal surface. In addition, the SERS spectra of the thiolated aptamer show significant changes with different concentrations, which may be due to different orientation of the molecule with respect to the metal surface. This study provides useful information for the development of label‐free aptamer‐based SERS sensors and assays. Copyright © 2009 John Wiley & Sons, Ltd.     

DICE: exploiting <Emphasis Type="Italic">all</Emphasis> bivariate dependencies in binary and multary search spaces

Although some of the earliest Estimation of Distribution Algorithms (EDAs) utilized bivariate marginal distribution models, up to now, all discrete bivariate EDAs had one serious limitation: they were constrained to exploiting only a limited O(d) subset out of all possible \(O(d^{2})\) bivariate dependencies. As a first we present a family of discrete bivariate EDAs that can learn and exploit all \(O(d^{2})\) dependencies between variables, and yet have the same run-time complexity as their more limited counterparts. This family of algorithms, which we label DICE (DIscrete Correlated Estimation of distribution algorithms), is rigorously based on sound statistical principles, and particularly on a modelling technique from statistical physics: dichotomised multivariate Gaussian distributions. Initially (Lane et al. in European Conference on the Applications of Evolutionary Computation, Springer, 1999), DICE was trialled on a suite of combinatorial optimization problems over binary search spaces. Our proposed dichotomised Gaussian (DG) model in DICE significantly outperformed existing discrete bivariate EDAs; crucially, the performance gap increasingly widened as dimensionality of the problems increased. In this comprehensive treatment, we generalise DICE by successfully extending it to multary search spaces that also allow for categorical variables. Because correlation is not wholly meaningful for categorical variables, interactions between such variables cannot be fully modelled by correlation-based approaches such as in the original formulation of DICE. Therefore, here we extend our original DG model to deal with such situations. We test DICE on a challenging test suite of combinatorial optimization problems, which are defined mostly on multary search spaces. While the two versions of DICE outperform each other on different problem instances, they both outperform all the state-of-the-art bivariate EDAs on almost all of the problem instances. This further illustrates that these innovative DICE methods constitute a significant step change in the domain of discrete bivariate EDAs.