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PubMed2001

[From limitations to possibilities; the advice from the Donner Committee about disability benefits legislation].

In the Netherlands, the number of people declared unfit to work continues to rise: every working day sees more than 100 new benefit claimants. The average age of these claimants is decreasing and the number of women declared unfit for work is showing a disproportionate increase. Against this background, the Dutch government appointed a committee in June 2000 whose task was to examine the functioning of the legislation. The Donner Committee concluded that the claims made under the disability benefits legislation could not be clarified by a worsening of either the public health or the working conditions. The legislation is based on obsolete ideas in which illness effectively excludes employment. This idea fosters a range of social problems in the employment process, which present themselves as medical problems and therefore remain elusive and unsolved. The result is that people are unnecessarily eliminated from society at a time when paid employment is an increasingly important means of social interaction. The Committee proposes a drastic simplification of the legislation so that a disability benefit can only be claimed in the case of complete unfitness for work. Such a claim can only be made in the case of a serious illness which results in permanent and considerable limitations in everyday functioning. For all other cases involving health problems, the employer and employee need to work together to organise appropriate work. The emphasis is on what the employee can do as opposed to what he/she cannot do. If the employer fails to take the necessary measures then he/she will be obliged to continue paying the salary and if the employee fails to cooperate then he/she can be dismissed. If needs be the employee must be prepared to except a salary reduction of 30%. After two years of absence, dismissal is in every case possible. It is anticipated that as a result of the Committee's proposals, more people will remain in employment but that the number of unemployed as well as the number of legal disputes concerning dismissal will increase.

Disability Evaluation↗
PubMed1996

Three-dimensional electrical impedance tomography.

The electrical resistivity of mammalian tissues varies widely and is correlated with physiological function. Electrical impedance tomography (EIT) can be used to probe such variations in vivo, and offers a non-invasive means of imaging the internal conductivity distribution of the human body. But the computational complexity of EIT has severe practical limitations, and previous work has been restricted to considering image reconstruction as an essentially two-dimensional problem. This simplification can limit significantly the imaging capabilities of EIT, as the electric currents used to determine the conductivity variations will not in general be confined to a two-dimensional plane. A few studies have attempted three-dimensional EIT image reconstruction, but have not yet succeeded in generating images of a quality suitable for clinical applications. Here we report the development of a three-dimensional EIT system with greatly improved imaging capabilities, which combines our 64-electrode data-collection apparatus with customized matrix inversion techniques. Our results demonstrate the practical potential of EIT for clinical applications, such as lung or brain imaging and diagnostic screening.

Algorithms↗
PubMed2005

The class effect: is it relevant to geriatrics?

The formulary of medications available today provides a remarkable range of choices to all prescribers and their patients. In some ways, choices have become easier to make, whereas in other ways, choosing has become a nightmare of dueling considerations. One approach to simplification has relied on class effect. The hypothesis is that drugs within a pharmacological class all work similarly, have similar advantages and disadvantages, and are-to a large extent-interchangeable. If one develops familiarity with one or two agents in a class, that is all one needs to know, because there is little difference between agents within a drug class. The question is whether this approach based on class effect is relevant to geriatrics.

Aged↗
PubMed2006

Simplification of the 1H NMR spectra of enantiomers dissolved in chiral liquid crystals, combining variable angle sample spinning and selective refocusing experiments.

This work presents a technique to simplify overcrowded proton spectra in chiral liquid crystal solvents using rotation of the sample near the magic angle, VASS, combined with homonuclear selective refocusing 2D NMR experiments, SERF. This methodology provides a powerful tool to visualise enantiomers out of unresolved proton spectra. A modified SERF sequence is presented where the resulting 2D spectrum can be phased to increase the resolution. Accurate enantiomeric excesses are determined that are not possible to measure on static samples. Two examples are presented.

Journal Article↗
PubMed2004

Constrained quadratic correlation filters for target detection.

A method for designing and implementing quadratic correlation filters (QCFs) for shift-invariant target detection in imagery is presented. The QCFs are quadratic classifiers that operate directly on the image data without feature extraction or segmentation. In this sense the QCFs retain the main advantages of conventional linear correlation filters while offering significant improvements in other respects. Not only is more processing required for detection of peaks in the outputs of multiple linear filters but choosing the most suitable among them is an error-prone task. All channels in a QCF work together to optimize the same performance metric and to produce a combined output that leads to considerable simplification of the postprocessing scheme. The QCFs that are developed involve hard constraints on the output of the filter. Inasmuch as this design methodology is indicative of the synthetic discriminant function (SDF) approach for linear filters, the filters that we develop here are referred to as quadratic SDFs (QSDFs). Two methods for designing QSDFs are presented, an efficient architecture for achieving them is discussed, and results from the Moving and Stationary Target Acquisition and Recognition synthetic aperture radar data set are presented.

Journal Article↗
PubMed2003

Abfraction and anisotropy--effects of prism orientation on stress distribution.

This work discusses the effect of enamel anisotropy in the stress concentration at the cement-enamel junction (CEJ), a probable cause of fracture in enamel leading to abfraction. Usual simplifications when developing computer models in dentistry are to consider enamel isotropic, or that the direction of the prisms is orthogonal to either the dentine-enamel interface or the tooth outer surface. In this paper, a more refined model for the material behavior is described, based on laboratory observation and on the work of Fernandes and Chevitarese. The material description is used in a two-dimensional (2D) finite element model of the first upper premolar, and the analysis is performed for two different situations: vertical loads, typical of normal mastication and horizontal loads, dominant in bruxism. The analyses were performed using a unit load, which under the hypothesis of linear response of the tooth, allows the combinations described in the text to simulate different functional and parafunctional loads. The results indicate that a realistic enamel description in terms of mechanical properties and spatial distribution of its prisms alters significantly the resulting stress distribution. For all cases included in this study, the detailed description of prism orientation and resulting anisotropy led to improved response in terms of stress distribution, even when loading was horizontal.

Anisotropy↗
PubMed2003

Metabolic isotopomer labeling systems. Part II: structural flux identifiability analysis.

Metabolic flux analysis using carbon labeling experiments (CLEs) is an important tool in metabolic engineering where the intracellular fluxes have to be computed from the measured extracellular fluxes and the partially measured distribution of 13C labeling within the intracellular metabolite pools. The relation between unknown fluxes and measurements is described by an isotopomer labeling system (ILS) (see Part I [Math. Biosci. 169 (2001) 173]). Part II deals with the structural flux identifiability of measured ILSs in the steady state. The central question is whether the measured data contains sufficient information to determine the unknown intracellular fluxes. This question has to be decided a priori, i.e. before the CLE is carried out. In structural identifiability analysis the measurements are assumed to be noise-free. A general theory of structural flux identifiability for measured ILSs is presented and several algorithms are developed to solve the identifiability problem. In the particular case of maximal measurement information, a symbolical algorithm is presented that decides the identifiability question by means of linear methods. Several upper bounds of the number of identifiable fluxes are derived, and the influence of the chosen inputs is evaluated. By introducing integer arithmetic this algorithm can even be applied to large networks. For the general case of arbitrary measurement information, identifiability is decided by a local criterion. A new algorithm based on integer arithmetic enables an a priori local identifiability analysis to be performed for networks of arbitrary size. All algorithms have been implemented and flux identifiability is investigated for the network of the central metabolic pathways of a microorganism. Moreover, several small examples are worked out to illustrate the influence of input metabolite labeling and the paradox of information loss due to network simplification.

Algorithms↗
PubMed2006

Image, imagination, and reality: on effectiveness of introductory work with vocalists.

Fifty-four sung tokens, each consisting of eight images were generated with the help of magnetic resonance imaging (MRI) technique to demonstrate the work of intrapharyngeal muscles when singing and speaking, and to help the educational process. The MRI images can be used as a part of a visualization feed-back method in vocal education and contribute to creation of proper mental images. The use of visualization (pictures, drafts, graphs, spectra, MRI images, etc.), along with mental images, facilitates simplification and acceleration of the process of understanding and learning how to master the basics of vocal technique, especially in the initial period of study. It is shown that work on muscle development and use of imagination should progress with close interaction between the two. For higher effectiveness and tangible results, mental images used by a vocal pedagogue should correspond to the technical and emotional level of a student. Therefore, mental images have to undertake the same evolution as articulation technique-from simplified and comprehensible to complex and abstract. Our integrated approach suggests continuing the work on muscle development and use of imagination in singing classes, employing the experience of voice-speech teachers. Their exercises are modified using the empirical method and other techniques developed creatively by singing teachers. In this method, sensitivity towards the state of the tissues becomes increasingly refined; students acquire a conscious control over the muscle work, students gain full awareness of both sensation and muscle activity. As a result, a complex of professional conditioned reflexes is being developed. A case study of the New Zealand experience was conducted with groups of Maori and European students. Unique properties and trends in the voices of Maori people are discussed.

Humans↗
PubMed2004

Quadratic correlation filter design methodology for target detection and surveillance applications.

A novel method is presented for optimization of quadratic correlation filters (QCFs) for shift-invariant target detection in imagery. The QCFs are quadratic classifiers that operate directly on the image data without feature extraction or segmentation. In this sense, the QCFs retain the main advantages of conventional linear correlation filters while offering significant improvements in other respects. For example, multiple correlators work in parallel to optimize jointly the QCF performance metric and produce a single combined output, which leads to considerable simplification of the postprocessing scheme. In addition, QCFs also yield better performance than their linear counterparts for comparable throughput requirements. The primary application considered is target detection in infrared imagery for surveillance applications. In the current approach, the class-separation metric is formulated as a Rayleigh quotient that is maximized by the QCF solution. It is shown that the proposed method results in considerable improvement in performance compared with a previously reported QCF design approach and many other detection techniques. The results of independent tests and evaluations at the U.S. Army's Night Vision Laboratory are also presented.

Journal Article↗
PubMed1984

Biomechanics of human movement with applications to the study of human locomotion.

A review of the biomechanics of human movement is presented and covers the neural control of voluntary movement, as it manifests itself in the electromyogram, through to detailed kinetic analyses and simulation studies. The body of knowledge of muscle performance is covered in detail, from the individual motor unit characteristics, through recruitment patterns to the static and dynamic characteristics of the total muscle and its relationship to the electromyogram. A summary of research into the movement of the skeletal (segmental) system itself covers the kinematic data collection systems, the link-segment modeling with anthropometric measures, and the inverse dynamics solution of the joint kinetics. A critique of current simulation models reveals a diversity of simplifications and assumptions that seriously affect the interpretation of results. Similarly, a critical assessment of the literature pertaining to mechanical energy, work, power and efficiency exposes many varied and anomalous techniques and correspondingly confusing interpretations. At all phases of the review the author attempts to reconcile differences, criticize obvious errors, and identify important contributions.

Biomechanical Phenomena↗
PubMed1997

[Image reconstruction of computerized tomography pictures using functional algebra].

A detailed presentation of the process for calculating computed tomograms from the measured data by means of functional algebra is given and an attempt is made to demonstrate the relationships to those inexperienced in mathematics. Suggestions are also made to the manufacturers for improving tomography software although the authors cannot exclude the possibility that some of the recommendations may have already been realized. An interpolation in Fourier space to right-angled coordinates was not employed so that additional computer time and errors resulting from the interpolation are avoided. The savings in calculation time can only be estimated but should amount to about 25%. The error-correction calculation is merely a suggestion since it depends considerably on the apparatus used. Functional algebra is introduced here because it is not so well known but does provide appreciable simplifications in comparison to an explicit presentation. Didactic reasons as well as the possibility for reducing calculation time provided the foundation for this work.

Artifacts↗
PubMed2005

Approximating the coalescent with recombination.

The coalescent with recombination describes the distribution of genealogical histories and resulting patterns of genetic variation in samples of DNA sequences from natural populations. However, using the model as the basis for inference is currently severely restricted by the computational challenge of estimating the likelihood. We discuss why the coalescent with recombination is so challenging to work with and explore whether simpler models, under which inference is more tractable, may prove useful for genealogy-based inference. We introduce a simplification of the coalescent process in which coalescence between lineages with no overlapping ancestral material is banned. The resulting process has a simple Markovian structure when generating genealogies sequentially along a sequence, yet has very similar properties to the full model, both in terms of describing patterns of genetic variation and as the basis for statistical inference.

Chromosomes↗
PubMed1999

Thiopurine methyltransferase pharmacogenetics: alternative molecular diagnosis and preliminary data from Northern Portugal.

The thiopurine methyltransferase (TPMT) genetic polymorphism has been shown to have a highly significant clinical impact, namely in the therapeutic efficiency of thiopurine drugs used in the treatment of a wide range of diseases. Available diagnostic methods, although reproducible and sensitive, are relatively laborious. Thus population studies are still very scarce. In this work we describe a new polymerase chain reaction-single strand confirmational analysis based protocol for TPMT specific detection which introduces a substantial technical simplification avoiding the use of restriction enzyme treatment after polymerase chain reaction amplification. Additionally, the use of this protocol allows the simultaneous detection of a T474 to C substitution, a frequent silent mutation in the North Portuguese population (TPMT*1S = 0.215). In a sample of 310 unrelated Northern Portuguese individuals, 15 were found to be heterozygous for the TPMT*3A allele (defined by the presence of two transitions, G460 to A and A719 to G) which is associated with TPMT enzymatic deficiency; the corresponding gene frequency estimate was 0.024. We also attempted to evaluate the relationship between the molecular TPMT genotype and the reaction to treatments involving thiopurine drugs by analysing a sample of 24 children submitted to curative therapy of acute lymphoblastic leukaemia. Four of them were shown to be heterozygous for the TPMT*3A allele. An examination of their clinical histories showed that all four patients exhibited signs of severe hepatic toxicity during treatment.

Antineoplastic Agents↗
PubMed2004

Organisational simplification and secondary complexity in health services for adults with learning disabilities.

This paper explores the role of complexity and simplification in the delivery of health care for adults with learning disabilities, drawing upon qualitative data obtained in a study carried out in NE England. It is argued that the requirement to manage complex health needs with limited resources causes service providers to simplify, standardise and routinise care. Simplified service models may work well enough for the majority of clients, but can impede recognition of the needs of those whose characteristics are not congruent with an adopted model. The data were analysed in relation to the core category, identified through thematic analysis, of secondary complexity arising from organisational simplification. Organisational simplification generates secondary complexity when operational routines designed to make health complexity manageable cannot accommodate the needs of non-standard service users. Associated themes, namely the social context of services, power and control, communication skills, expertise and service inclusiveness and evaluation are explored in relation to the core category. The concept of secondary complexity resulting from organisational simplification may partly explain seemingly irrational health service provider behaviour.

Adult↗
PubMed2001

Applying science to changing dietary patterns.

The intake of 400-600 g/d of fruits and vegetables is associated with reduced incidence of many common forms of cancer. These foods contain phytochemicals that can modulate gene expression to inhibit carcinogenesis via multiple pathways. Many phytochemicals are colorful, providing an easy way to communicate increased diversity of fruits and vegetables to the public. Red foods contain lycopene, the pigment in tomatoes, which is localized in the prostate gland and may be involved in maintaining prostate health. Yellow-green vegetables, such as corn and leafy greens, contain lutein and zeaxanthin, which are localized in the retina where age-related macular degeneration occurs. Red-purple foods contain anthocyanins, which are powerful antioxidants found in red apples, grapes, berries and wine. Orange foods, including carrots, mangos, apricots, pumpkin and winter squash, contain beta-carotene. Orange-yellow foods, including oranges, tangerines and lemons contain citrus flavonoids. Green foods, including broccoli, Brussels sprouts and kale, contain glucosinolates. White-green foods in the onion family contain allyl sulfides. Consumers are advised to ingest one serving of each of the above groups daily, putting this recommendation within the National Cancer Institute and American Institute for Cancer Research guidelines of five to nine servings per day. The color code provides simplification, but it is also important as a way to help consumers to find common fruits and vegetables easily while traveling, eating in restaurants or working. At home, simple ways of preparing foods rapidly and easily are needed to influence dietary patterns.

Antioxidants↗
PubMed1979

An improvement of the analytical description of temporal variations of plasma and total platelet activities, studied using 75Se-methionin as an in vivo tracer.

In this work we have re-examined our previous model for the analytical description of temporal variations of plasma and total platelet activities, introducing a mathematical simplification by means of elimination of a cumbersome and deforming parameter. We give here 1) interpolation formula 2) complete list of instructions of our program for computer data processing.

Computers↗