Singly, doubly and triply resonant multiphoton processes involving autoionizing states in magnesium

Using the R-matrix Floquet theory we have carried out non-perturbative, ab initio one- and two-colour calculations of the multiphoton ionization of magnesium with the laser frequencies chosen such that the initial state of the atom is resonantly coupled with autoionizing resonances of the atom. Good agreement is obtained with previous calculations in the low-intensity regimes. The single-photon ionization from the 3s3p P excited state of magnesium has been studied in the vicinity of the 3p S autoionizing resonance at non-perturbative laser intensities. Laser-induced degenerate states (LIDS) are observed for modest laser intensities. By adding a second laser which resonantly couples the 3p S = and 3p3d P autoionizing levels, we show that, due to the small width of the 3p3d P state, LIDS occur between this state and the 3s3p P state at intensities of the first laser below 10 W cm . We next investigate the case in which the first laser induces a resonant two-photon coupling between the ground state and the 3p S autoionizing state, while the second laser again resonantly couples the respective 3p S and 3p3d P autoionizing states. At weak intensities, our calculations compare favourably with recent experimental data and calculations. We show that when the intensity of the first laser is increased, the effect of an additional autoionizing state, the 4s5s S state, becomes significant. This state is coupled to the 3p3d P autoionizing level by one photon, inducing a triply resonant processes. We show that LIDS occur among the three autoionizing levels and we discuss their effect on the decay rate of the ground state. We consider dressed two- and three-level atoms which can be used to model the results of our calculations.

2DRMP-G: Migrating a large-scale numerical mathematical application to a grid environment

We report on the migration of a traditional, single architecture application to a grid application using heterogeneous resources. We focus on the use of the UK e-Science Level 2 grid (UKL2G) which provides a heterogeneous collection of resources distributed within the UK. We discuss the solution architecture, the performance of our application, its future development as a grid-based application and comment on the lessons we have learned in using a grid infrastructure for large-scale numerical problems.

An Integration Methodology for Automated Recurring Cost Prediction using Digital Manufacturing Technology

The need to account for the effect of design decisions on manufacture and the impact of manufacturing cost on the life cycle cost of any product are well established. In this context, digital design and manufacturing solutions have to be further developed to facilitate and automate the integration of cost as one of the major driver in the product life cycle management. This article is to present an integration methodology for implementing cost estimation capability within a digital manufacturing environment. A digital manufacturing structure of knowledge databases are set out and the ontology of assembly and part costing that is consistent with the structure is provided. Although the methodology is currently used for recurring cost prediction, it can be well applied to other functional developments, such as process planning. A prototype tool is developed to integrate both assembly time cost and parts manufacturing costs within the same digital environment. An industrial example is used to validate this approach.

MIXED-MODEL PRODUCTION SYSTEM DESIGN FOR AIRCRAFT ASSEMBLY

With the advancement of flexible fixture and flexible tooling, mixed production has become possible for aircraft assembly as the manufacturing processes of different aircraft/sub-assembly models are similar. However, it is a great challenge to model the problem and provide a practical solution due to the low volume and complex constraints of aircraft assemblies. To tackle this problem, this work proposes a methodology for designing the mixed production system, and a new scheduling approach is proposed by combined backward and forward scheduling methods. These methods are validated through a real-life industrial case study. Simulation results show that the number of workstations and the cycle time for making a fuselage can be reduced by 50% and 39% respectively with the newly designed mixed-model system.

Exclusion of linkage between schizophrenia and the D2 dopamine receptor gene region of chromosome 11q in 112 Irish multiplex families

A leading theory hypothesizes that schizophrenia arises from dysregulation of the dopamine system in certain brain regions. As this dysregulation could arise from abnormal expression of D2 dopamine receptors, the D2 receptor gene (DRD2) on chromosome 11q is a candidate locus for schizophrenia. We tested whether allelic variation at DRD2 and five surrounding loci cosegregated with schizophrenia in 112 small- to moderate-size Irish families containing two or more members affected with schizophrenia or schizoaffective disorder, defined by DSM-III-R. Evidence of linkage was assessed using varying definitions of illness and modes of transmission. Assuming genetic homogeneity, linkage between schizophrenia and large regions of 11q around DRD2 could be strongly excluded. Assuming genetic heterogeneity, variation at the DRD2 locus could be rejected as a major risk factor for schizophrenia in more than 50% of these families for all models tested and in as few as 25% of the families for certain models. The DRD2 linkage in fewer than 25% of these families could not be excluded under any of the models tested. Our results suggest that the major component of genetic susceptibility to schizophrenia is not due to allelic variation at the DRD2 locus or other genes in the surrounding chromosomal region.

A potential vulnerability locus for schizophrenia on chromosome 6p24-22:evidence for genetic heterogeneity

In 265 Irish pedigrees, with linkage analysis we find evidence for a vulnerability locus for schizophrenia in region 6p24-22. The greatest lod score, assuming locus heterogeneity, is 3.51 (P = 0.0002) with D6S296. Another test, the C test, also supported linkage, the strongest results being obtained with D6S296 (P = 0.00001), D6S274 (P = 0.004) and D6S285 (P = 0.006). Non-parametric analysis yielded suggestive, but substantially weaker, findings. This locus appears to influence the vulnerability to schizophrenia in roughly 15 to 30% of our pedigrees. Evidence for linkage was maximal using an intermediate phenotypic definition and declined when this definition was narrowed or was broadened to include other psychiatric disorders.

Irish study on high-density schizophrenia families:field methods and power to detect linkage

Large samples of multiplex pedigrees will probably be needed to detect susceptibility loci for schizophrenia by linkage analysis. Standardized ascertainment of such pedigrees from culturally and ethnically homogeneous populations may improve the probability of detection and replication of linkage. The Irish Study of High-Density Schizophrenia Families (ISHDSF) was formed from standardized ascertainment of multiplex schizophrenia families in 39 psychiatric facilities covering over 90% of the population in Ireland and Northern Ireland. We here describe a phenotypic sample and a subset thereof, the linkage sample. Individuals were included in the phenotypic sample if adequate diagnostic information, based on personal interview and/or hospital record, was available. Only individuals with available DNA were included in the linkage sample. Inclusion of a pedigree into the phenotypic sample required at least two first, second, or third degree relatives with non-affective psychosis (NAP), one whom had schizophrenia (S) or poor-outcome schizo-affective disorder (PO-SAD). Entry into the linkage sample required DNA samples on at least two individuals with NAP, of whom at least one had S or PO-SAD. Affection was defined by narrow, intermediate, and broad criteria. The phenotypic sample contained 277 pedigrees and 1,770 individuals and the linkage sample 265 pedigrees and 1,408 individuals. Using the intermediate definition of affection, the phenotypic sample contained 837 affected individuals and 526 affected sibling pairs. Parallel figures for the linkage sample were 700 and 420. Individuals with schizophrenia from these multiplex pedigrees resembled epidemiologically sampled cases with respect to age at onset, gender distribution, and most clinical symptoms, although they were more thought-disordered and had a poorer outcome. Power analyses based on the model of linkage heterogeneity indicated that the ISHDSF should be able to detect a major locus that influences susceptibility to schizophrenia in as few as 20% of families. Compared to first-degree relatives of epidemiologically sampled schizophrenic probands, first-degree relatives of schizophrenic members from the ISHDSF had a similar risk for schizotypal personality disorder, affective illness, alcoholism, and anxiety disorder. With sufficient resources, large-scale ascertainment of multiplex schizophrenia pedigrees is feasible, especially in countries with catchmented psychiatric care and stable populations. Although somewhat more severely ill, schizophrenic members of such pedigrees appear to clinically resemble typical schizophrenic patients. Our ascertainment process for multiplex schizophrenia families did not select for excess familial risk for affective illness or alcoholism. With its large sample ascertained in a standardized manner from a relatively homogeneous population, the ISHDSF provides considerable power to detect susceptibility loci for schizophrenia.

Evidence for a schizophrenia vulnerability locus on chromosome 8p in the Irish Study of High-Density Schizophrenia Families

This study was an attempt to replicate evidence for a vulnerability locus for schizophrenia and associated disorders in the 8p22-21 region reported by Pulver and colleagues.

The Role of Growth Trajectories in Classifying Fetal Growth Restriction

OBJECTIVE: To examine the validity of a growth trajectory method to discriminate between pathologically and constitutionally undergrown fetuses using repeated measures of estimated fetal weight.

METHODS: In a prospective, observational, multicenter study in Ireland, 1,116 women with a growth-restricted fetus diagnosed participated with the objective of evaluating ultrasound findings as predictors of pediatric morbidity and mortality. Fetal growth trajectories were based on estimated fetal weight.

RESULTS: Between 22 weeks of gestation and term, two fetal growth trajectories were identified: normal (96.7%) and pathologic (3.3%). Compared with the normal trajectory, the pathologic trajectory was associated with an increased risk for preeclampsia (odds ratio [OR] 8.1, 95% confidence interval [CI] 2.6–23.4), increased umbilical artery resistance at 30 weeks of gestation (OR 12.6, 95% CI 4.6–34.1) or 34 weeks of gestation (OR 28.0, 95% CI 8.9–87.7), reduced middle cerebral artery resistance at 30 weeks of gestation (OR 0.33, 95% CI 0.12–0.96) or 34 weeks of gestation (OR 0.14, 95% CI 0.03–0.74), lower gestational age at delivery (mean 32.02 weeks of gestation compared with 38.02 weeks of gestation; P<.001), and higher perinatal complications (OR 21.5, 95% CI 10.5–44.2). In addition, 89.2% of newborns with pathologic fetal growth were admitted to neonatal intensive care units compared with 25.9% of those with normal growth.

CONCLUSIONS: Fetal growth trajectory analysis reliably differentiated fetuses with a pathologic growth pattern among a group of women with growth-restricted fetuses. With further development, this approach could provide clarity to how we define, identify, and ultimately manage pathologic fetal growth.

LEVEL OF EVIDENCE: II

Adaptive linear combination of heuristic orderings in constructing examination timetables

In this paper, we investigate adaptive linear combinations of graph coloring heuristics with a heuristic modifier to address the examination timetabling problem. We invoke a normalisation strategy for each parameter in order to generalise the specific problem data. Two graph coloring heuristics were used in this study (largest degree and saturation degree). A score for the difficulty of assigning each examination was obtained from an adaptive linear combination of these two heuristics and examinations in the list were ordered based on this value. The examinations with the score value representing the higher difficulty were chosen for scheduling based on two strategies. We tested for single and multiple heuristics with and without a heuristic modifier with different combinations of weight values for each parameter on the Toronto and ITC2007 benchmark data sets. We observed that the combination of multiple heuristics with a heuristic modifier offers an effective way to obtain good solution quality. Experimental results demonstrate that our approach delivers promising results. We conclude that this adaptive linear combination of heuristics is a highly effective method and simple to implement.

Liouville-space R-matrix-Floquet description of atomic radiative processes involving autoionizing states in the presence of intense electromagnetic fields

A reduced-density-operator description is developed for coherent optical phenomena in many-electron atomic systems, utilizing a Liouville-space, multiple-mode Floquet–Fourier representation. The Liouville-space formulation provides a natural generalization of the ordinary Hilbert-space (Hamiltonian) R-matrix-Floquet method, which has been developed for multi-photon transitions and laser-assisted electron–atom collision processes. In these applications, the R-matrix-Floquet method has been demonstrated to be capable of providing an accurate representation of the complex, multi-level structure of many-electron atomic systems in bound, continuum, and autoionizing states. The ordinary Hilbert-space (Hamiltonian) formulation of the R-matrix-Floquet method has been implemented in highly developed computer programs, which can provide a non-perturbative treatment of the interaction of a classical, multiple-mode electromagnetic field with a quantum system. This quantum system may correspond to a many-electron, bound atomic system and a single continuum electron. However, including pseudo-states in the expansion of the many-electron atomic wave function can provide a representation of multiple continuum electrons. The 'dressed' many-electron atomic states thereby obtained can be used in a realistic non-perturbative evaluation of the transition probabilities for an extensive class of atomic collision and radiation processes in the presence of intense electromagnetic fields. In order to incorporate environmental relaxation and decoherence phenomena, we propose to utilize the ordinary Hilbert-space (Hamiltonian) R-matrix-Floquet method as a starting-point for a Liouville-space (reduced-density-operator) formulation. To illustrate how the Liouville-space R-matrix-Floquet formulation can be implemented for coherent atomic radiative processes, we discuss applications to electromagnetically induced transparency, as well as to related pump–probe optical phenomena, and also to the unified description of radiative and dielectronic recombination in electron–ion beam interactions and high-temperature plasmas.