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PubMed2006

Spin-spin contributions to the zero-field splitting tensor in organic triplets, carbenes and biradicals-a density functional and ab initio study.

An evaluation study for the direct dipolar electron spin-spin (SS) contribution to the zero-field splitting (ZFS) tensor in electron paramagnetic resonance (EPR) spectroscopy is presented. Calculations were performed on a wide variety of organic systems where the SS contribution to the ZFS dominates over the second-order spin-orbit coupling (SOC) contribution. Calculations were performed using (hybrid) density functional theory (DFT), as well as complete active space self-consistent field (CASSCF) wave functions. In the former case, our implementation is an approximation, because we use the two-particle reduced spin-density matrix of the noninteracting reference system. In the latter case, the SS contribution is approximated by a mean-field method which, nevertheless, gives accurate results, compared to the approximation free computation of the SS part in a CASSCF framework. For the case of the triplet dioxygen molecule, it was shown that restricted open-shell density functional theory (RODFT), as well as CASSCF, can provide accurate spin-spin couplings while spin-unrestricted DFT leads to much larger errors. Furthermore, 15 organic radicals, including several 1,3 and 1,5 diradicals, dinitroxide biradicals, and even a chlorophyll a model system, were examined as test cases to demonstrate the accuracy and efficiency of our approach within a DFT framework. Accurate D values with root-mean-square deviations of 0.0035 cm(-1) were obtained. Furthermore, all trends, including those due to substituent effects, were correctly reproduced. In a different set of calculations, the polyacenes benzene, naphthalene, anthracene, and tetracene were studied. Applying DFT, the absolute D values were noticeably underestimated, but it was possible to correctly reproduce the trend to smaller D values with larger size of the systems. Finally, it was demonstrated that our approach is also well-suited for the study of carbenes. The smaller organic radicals of this work were also studied, through the use of CASSCF wave functions. This was a special advantage in the case of the triplet polyacenes, where the CASSCF approach gave better results than the DFT method. In comparing spin-restricted and spin-unrestricted results, it was shown through a natural orbital analysis and comparison to high-level ab initio calculations that even small amounts of spin polarization introduced by the unrestricted calculations lead to large deviations between the unrestricted Kohn-Sham (UKS) and restricted open-shell Kohn-Sham (ROKS) approaches. It is challenging to understand why the ROKS results show much better correlation with the experimental data.

Algorithms↗
PubMed1993

[The determination of cerebral speech dominance with the intracarotid amobarbital test].

In neuropsychological diagnostics of lateralisation of cognitive functions, the intracarotid amobarbital procedure (IAP) is a well established method for the determination of cerebral language dominance. In this review, different frameworks of classification of dominance patterns are discussed, ranging from the simple left/right/bilateral-dominance framework to a quantitative analysis according to a computed lateralisation index. Evidence from IAP studies concerning the cerebral organisation of linguistic subfunctions like naming and reading are discussed. A critical evaluation of rivalling approaches like electrical stimulation mapping or visual hemifield studies suggests that these methods mainly yield results complementary to IAP data and hence should not be taken as substitutes of that procedure.

Amobarbital↗
PubMed2002

Likelihood and Bayes estimation of ancestral population sizes in hominoids using data from multiple loci.

Polymorphisms in an ancestral population can cause conflicts between gene trees and the species tree. Such conflicts can be used to estimate ancestral population sizes when data from multiple loci are available. In this article I extend previous work for estimating ancestral population sizes to analyze sequence data from three species under a finite-site nucleotide substitution model. Both maximum-likelihood (ML) and Bayes methods are implemented for joint estimation of the two speciation dates and the two population size parameters. Both methods account for uncertainties in the gene tree due to few informative sites at each locus and make an efficient use of information in the data. The Bayes algorithm using Markov chain Monte Carlo (MCMC) enjoys a computational advantage over ML and also provides a framework for incorporating prior information about the parameters. The methods are applied to a data set of 53 nuclear noncoding contigs from human, chimpanzee, and gorilla published by Chen and Li. Estimates of the effective population size for the common ancestor of humans and chimpanzees by both ML and Bayes methods are approximately 12,000-21,000, comparable to estimates for modern humans, and do not support the notion of a dramatic size reduction in early human populations. Estimates published previously from the same data are several times larger and appear to be biased due to methodological deficiency. The divergence between humans and chimpanzees is dated at approximately 5.2 million years ago and the gorilla divergence 1.1-1.7 million years earlier. The analysis suggests that typical data sets contain useful information about the ancestral population sizes and that it is advantageous to analyze data of several species simultaneously.

Algorithms↗
PubMed2026

Comparative and Subtractive Genomics Analysis of Multidrug-Resistant Klebsiella pneumoniae Strains for Novel Target Identification and Drug Repurposing Strategies.

The rapid rise of multidrug-resistant (MDR) Klebsiella pneumoniae has created a major global health challenge due to the limited availability of conserved therapeutic targets effective across diverse resistant strains. In this study, an integrative computational target-discovery and drug-repurposing framework was applied to six clinically relevant K. pneumoniae strains. Comparative genomic analysis identified 3012 conserved genes, which were subsequently filtered to nine essential, non-host homologous proteins. Among these, three conserved cytoplasmic proteins (accD, cpxR, and mraZ) were prioritized for functional analysis, with acetyl-CoA carboxylase subunit beta (accD) emerging as the most promising therapeutic target based on sequence conservation, predicted essentiality, subcellular localization, and pathway association. Structural assessment supported the reliability of the predicted accD model, whereas consensus binding-site analysis identified key residues suitable for ligand interaction. Virtual screening of FDA-approved drugs followed by molecular docking identified several compounds with favorable binding profiles toward accD. Subsequent molecular dynamics simulations, including root mean square deviation (RMSD), root mean square fluctuation (RMSF), radius of gyration (Rg), hydrogen-bond occupancy, principal component analysis (PCA), and PCA-based free energy landscape (FEL) analyses, consistently identified tenapanor, micafungin, deferoxamine, and cobicistat as the most stable protein-ligand complexes, with tenapanor exhibiting the most favorable overall structural and thermodynamic stability profile. These findings identify accD as a promising therapeutic target in MDR K. pneumoniae and suggest several FDA-approved compounds as potential candidates for drug repurposing. Although experimental validation is needed to confirm their biological activity and therapeutic potential, this study demonstrates the potential of integrating comparative genomics with molecular dynamics analyses to support antimicrobial target identification and drug repurposing against MDR bacterial pathogens.

Klebsiella pneumoniae↗
PubMed2001

Partial versus full hospitalization for adults in psychiatric distress: a systematic review of the published literature (1957-1997).

OBJECTIVE: The authors reviewed published research that compared partial and full hospitalization as alternative programs for the care of mentally ill adults, with the goal of both systematizing the knowledge base and providing directions for future research. METHOD: Studies published since 1950 were obtained through manual and electronic searches. Results were stratified by outcome domain, type of measure used to report between-group differences (global, partial, or rate-based), and time of assessment. Effect sizes were computed and combined within a random-effects framework. RESULTS: Eighteen investigations published between 1957 and 1997 were systematically reviewed. Over half of eligible patients were excluded a priori; diagnostic severity of enrollees varied widely. On measures of psychopathology, social functioning, family burden, and service utilization, the authors found no evidence of differential outcome in the selected patient population admitted to the studies reviewed. Rates of satisfaction with services suggested an advantage for partial hospitalization within 1 year of discharge, with the gap being largest at 7-12 months. CONCLUSIONS: Although partial hospitalization is not an option for all patients requiring intensive services, outcomes of partial hospitalization patients in these studies were no different from those of inpatients. Further, patients and families were more satisfied with partial hospitalization in the short term. Weaknesses of the studies limited the scope of our inquiry and the generalizability of findings. Positive findings require replication under the present circumstances of mental health care, and more research is needed to identify predictors of differential outcome and successful partial hospitalization. A clearer definition of partial hospitalization will help consolidate its role in the continuum of mental health services.

Adult↗
PubMed1992

Cluster analysis and related techniques in medical research.

In this paper we review methods of cluster analysis in the context of classifying patients on the basis of clinical and/or laboratory type observations. Both hierarchical and non-hierarchical methods of clustering are considered, although the emphasis is on the latter type, with particular attention devoted to the mixture likelihood-based approach. For the purposes of dividing a given data set into g clusters, this approach fits a mixture model of g components, using the method of maximum likelihood. It thus provides a sound statistical basis for clustering. The important but difficult question of how many clusters are there in the data can be addressed within the framework of standard statistical theory, although theoretical and computational difficulties still remain. Two case studies, involving the cluster analysis of some haemophilia and diabetes data respectively, are reported to demonstrate the mixture likelihood-based approach to clustering.

Algorithms↗
PubMed1998

Aftereffects and sense of presence in virtual environments: formulation of a research and development agenda.

This report represents a committee summary of the current state of knowledge regarding aftereffects and sense of presence in virtual environments (VEs). The work presented in this article, and the proposed research agenda, are the result of a special session that was set up in the framework of the Seventh International Conference on Human Computer Interaction. Recommendations were made by the committee regarding research needs in aftereffects and sense of presence, and, where possible, priorities were suggested. The research needs were structured in terms of the short, medium, and long term and, if followed, should lead toward the effective use of VE technology. The 2 most critical research issues identified were (a) standardization and use of measurement approaches for aftereffects and (b) identification and prioritization of sensorimotor discordances that drive aftereffects. Identification of aftereffects countermeasures (i.e., techniques to assist users in readily transitioning between the real and virtual worlds), reduction of system response latencies, and improvements in tracking technology were also thought to be of critical importance.

Adaptation, Physiological↗
PubMed1982

Assessment of left ventricular function using an angiographic method.

Angiographic methods are by far the most frequently used for calculation of left ventricular volume, mass, forces acting within the ventricular wall or for analysis of contractile performance and diastolic property of the overall ventricle, as well as regional myocardial function in the presence of ischemia. A critical review of the theoretical basis and practical methods of calculation of these variables is presented. The left ventricular pressure-volume diagram is constructed which allows for an assessment of the inotropic state of the ventricle from the similar tension-length framework as obtained in the isolated papillary muscle. Computer technology of digital filtering and subtraction provides for an enhancement of the contrast of the ventricular image obtained with minimal doses of contrast medium. On-line methods for edge tracing and subsequent data processing are alleviating much of the tedious and laborious work of manual analysis of angiograms and accuracy of the calculation has been enhanced. Left ventriculography is most useful in diagnosing the presence of abnormal wall motion. Methods of assessing the magnitude and extent of the relative area of localized myocardial dysfunction are discussed. Quantitative information is crucial for evaluating prognosis and determining the application of therapeutic interventions.

Angiocardiography↗
PubMed2005

Improvement of mapping accuracy by unifying linkage and association analysis.

It is well known that pedigree/family data record information on the coexistence in founder haplotypes of alleles at nearby loci and the cotransmission from parent to offspring that reveal different, but complementary, profiles of the genetic architecture. Either conventional linkage analysis that assumes linkage equilibrium or family-based association tests (FBATs) capture only partial information, leading to inefficiency. For example, FBATs will fail to detect even very tight linkage in the case where no allelic association exists, while a violation of the assumption of linkage equilibrium will result in biased estimation and reduced efficiency in linkage mapping. In this article, by using a data augmentation technique and the EM algorithm, we propose a likelihood-based approach that embeds both linkage and association analyses into a unified framework for general pedigree data. Relative to either linkage or association analysis, the proposed approach is expected to have greater estimation accuracy and power. Monte Carlo simulations support our theoretical expectations and demonstrate that our new methodology: (1) is more powerful than either FBATs or classic linkage analysis; (2) can unbiasedly estimate genetic parameters regardless of whether association exists, thus remedying the bias and less precision of traditional linkage analysis in the presence of association; and (3) is capable of identifying tight linkage alone. The new approach also holds the theoretical advantage that it can extract statistical information to the maximum extent and thereby improve mapping accuracy and power because it integrates multilocus population-based association study and pedigree-based linkage analysis into a coherent framework. Furthermore, our method is numerically stable and computationally efficient, as compared to existing parametric methods that use the simplex algorithm or Newton-type methods to maximize high-order multidimensional likelihood functions, and also offers the computation of Fisher's information matrix. Finally, we apply our methodology to a genetic study on bone mineral density (BMD) for the vitamin D receptor (VDR) gene and find that VDR is significantly linked to BMD at the one-third region of the wrist.

Algorithms↗
PubMed1999

Galen: a third generation terminology tool to support a multipurpose national coding system for surgical procedures.

GALEN has developed a new generation of terminology tools based on a language independent concept reference model using a compositional formalism allowing computer processing and multiple reuses. During the 4th framework program project Galen-In-Use we applied the modelling and the tools to the development of a new multipurpose coding system for surgical procedures (CCAM) in France. On one hand we contributed to a language independent knowledge repository for multicultural Europe. On the other hand we support the traditional process for creating a new coding system in medicine which is very much labour consuming by artificial intelligence tools using a medically oriented recursive ontology and natural language processing. We used an integrated software named CLAW to process French professional medical language rubrics produced by the national colleges of surgeons into intermediate dissections and to the Grail reference ontology model representation. From this language independent concept model representation on one hand we generate controlled French natural language to support the finalization of the linguistic labels in relation with the meanings of the conceptual system structure. On the other hand the classification manager of third generation proves to be very powerful to retrieve the initial professional rubrics with different categories of concepts within a semantic network.

Abstracting and Indexing↗
PubMed2004

Control of corrosion and aggression in drinking water systems.

Corrosion and/or aggression are common problems arising in pipelines transporting terrestrial waters. The kinetics and severity of such events depend on both the quality of the water being transported and the material properties of the pipeline. Irrespective of the nature of the problem, its solution (or at least its minimisation) is strongly linked to control of pH, calcium concentration and carbonate chemistry of the water (stabilisation). However, application of such chemistry to water treatment problems is complex and time consuming. Various numerical, graphical and computer techniques have been developed to address this, but these are either of insufficient accuracy, too time consuming or lacking in generality. In this paper algorithms are presented for solving a broad spectrum of problems related to control of mineral precipitation/aggression, pH and chemical dosing in water treatment. These have been incorporated into a computer software package, STASOFT, which offers the requisite framework for use in water treatment. Various stabilisation problems pertinent to water supply are addressed.

Chemical Precipitation↗
PubMed2002

CSCW--a paradigm for an efficient management of the healthcare organizations.

This paper reports the first results of the implementation of the research project CSCW--a paradigm for an efficient management of the healthcare organizations. The main objective of the project is to define a standard framework for the design of integrated systems for computer supported cooperative work applications in health management. The project is funded by the Romanian government and is carried on by an interdisciplinary team (researchers, educators, health professionals).

Computers↗
PubMedDate not supplied

[Visual associative memory and the orientation-contingent color after-effect].

The traditional explanation of the McCollough effect (ME) by selective adaptation of single detectors selective to color and orientation suffers from a number of inconsistencies: 1) the ME lasts much longer (from several days up to 3 months) than the ordinary adaptation, the decay of the effect being completely arrested by night sleep or occluding the eye for a long time; 2) the strength of the ME practically does not depend on the intensity of adapting light; and 3) a set of related pattern-contingent after-effects discovered later required for such an explanation new detectors, specific for other patterns. These properties can be explained, however, in the framework of associative memory and novelty filters. A computational model has been developed, which consists of 1) an input layer of two (left and right eyes) square matrices with two analog receptors (red and green) in each pixel, 2) an isomorphic associative neural layer, each analog neuron being synaptically connected with all receptors of both eyes, and 3) an output layer (novelty filter). The modification of synaptic efficacies conforms to the Hebb learning rule. The function of the model was examined by simulation. After a few presentations of colored gratings, the model displays the ME that is slowly destroyed by subsequent presentations of random pictures. With a sufficiently large receptor matrix, the effect lasts a thousand times longer than the period of adaptation. Continuous darkness does not change the strength of the effect. Like in real ME, the model does not display interocular transfer. The model can account for different pattern-contingent color after-effects without assuming any predetermined specific detectors. Such detectors are constructed in the course of adaptation to specific stimuli (gratings).

Association Learning↗
PubMed1986

Mosaic architecture of the somatic sensory-recipient sector of the cat's striatum.

The striatum is known to have a compartmental organization in which histochemically defined zones called striosomes form branched 3-dimensional labyrinths embedded within the surrounding matrix. We explored how fiber projections from cortical somatic sensory areas representing cutaneous and deep-receptor inputs are organized in relation to this striatal architecture. Areas SI and 3a were mapped electrophysiologically, and distinguishable anterograde tracers (wheat germ agglutinin-HRP and 35S-methionine) were injected into physiologically identified loci. Primary somatic sensory corticostriatal projections were confined to a small, well-defined sector in the dorsolateral corner of the ipsilateral striatum. The somatic sensory afferents were arranged according to a coherent global body map in which rostral body parts were represented more laterally than caudal body parts. Single cortical loci innervated branched and clustered striatal zones that were reminiscent of the striosomes in their range of sizes and shapes yet lay strictly within the extrastriosomal matrix. In contrast to the global orderliness of the striatal body map, there were clear examples of locally complex patterns in which functionally distinct inputs interdigitated with each other. These patterns were often, but not always, produced when corticostriatal afferents carrying different submodality types were labeled. These findings demonstrate the existence of striosome-like striatal compartments within the seemingly uniform extrastriosomal matrix. The principle of mosaic organization thus holds throughout the tissue of the somatic sensory striatum. The striatal architecture delineated here could provide the anatomical substrate for computations requiring cross-modality comparisons within the framework of an overall somatotopy. If a similar multicompartmental architecture also characterizes other striatal regions, as seems likely, it may set general constraints on the nature of associative processing within the striatum as a whole.

Afferent Pathways↗
PubMed1982

Topological aspects of ion transport in complex epithelia (frog skin).

A weak point of the current concept of the kinetics of ion flow in complex epithelial tissue membranes, such as frog skin, is the supposition that these tissue membranes and their exterior environments can be looked upon as a "three compartment system." In the present study a new and more realistic conceptual framework, a "multicompartment system," is applied to a computer assisted kinetic analysis of experimental data. These deal with Na+ flows in "tight" and "leaky" frog skins, prior to and after the treatment with the Na+-blocking drug amiloride. It is shown by numerical examples that unpredictable Na+ flux patterns in frog skin arise from two diverse contributing factors: 1) The constitutive physical relationships which govern the local events at the level of the plasma membranes, and 2) the much neglected topology, i.e., the "connectedness" of the heterogeneous compartments.

Animals↗
PubMed1995

An optimized parsing algorithm well suited to RNA folding.

The application of stochastic context-free grammars to the determination of RNA foldings allows a simple description of the sub-class of sought secondary structures, but it needs efficient parsing algorithms. The more classic thermodynamic model of folding, popularized by Zuker under the framework of dynamic programming algorithms, allows an easy computation of foldings but its use is delicate when constraints have to be introduced on sought secondary structures. We show here that S-attribute grammars unify these two models and we introduce a parsing algorithm whose efficiency enables us to handle problems until then too difficult or too large to deal with. As a matter of fact, our algorithm is as efficient as a standard dynamic programming one when applied to the thermodynamic model (yet it offers a greater flexibility for the expression of constraints) and it is faster and saves more space than other parsing algorithms used so far for stochastic grammars.

Algorithms↗
PubMed1995

Health system re-engineering: a CPRS economic decision model.

The fundamental problem with the health care delivery system remains too little health delivered for too great a cost. Information essential to sound clinical and administrative decision making is too frequently missing at the time and place of decision. Automated systems offer opportunities both to improve health and to reduce cost through effective and efficient information management. Information systems are the enabling technology for those business practice changes which improve the benefit-cost profile of a re-engineered delivery system. The Computer-based Patient Record (CPR) is the organizing framework of an enterprise-wide health information system. Since information management is a core function of the health care enterprise, evaluation of the CPR should include its impact on the value of health outcomes and contribution to the organizational mission, rather than solely by benefits which accrue within the delivery system. This paper proposes a model to measure the impact of information technology and specifically a CPR on a re-engineered health care delivery system.

Decision Support Techniques↗
PubMed1996

[Group work in neuropsychological therapy].

The section "Psychology in the Neurological Department" at the Hardtwaldklinik I, of Bad Zwesten, can look back at 18 years of experience with neuropsychological group therapy within the neurological rehabilitation setting. The functions of the psychological section can be subdivided into diagnostic tasks on the one hand, and therapeutical interventions concerning cognitive and emotional aspects on the other, with psychotherapy having a mediating function, depending on the individual indication at hand. Depending on the kind and degree of the neurological impairment present, and based on detailed diagnostics, the patients are treated in the field of cognitive performance either individually or in groups. There are groups with different degrees of difficulty in line with type and extent of the selective disorders present. Experiences have shown that neuropsychological group therapy in particular is aimed at a holistic approach to the pattern of interference and the patient's personality. The possibilities for intervention and therapy are diverse, and range from play material to computer-based individual or group therapy. In the framework of internal quality assurance, experiences have shown that the effects of neuropsychological group therapy are not easily validated. In this respect, the subjective estimates of therapist and patient are the predominant, if not the only, criteria in terms of improved mental functioning.

Brain Damage, Chronic↗