315 research outputs found
Gender collaborative training in elite university sport:Challenging gender essentialism through integrated training in gender-segregated sports
Sea Bed Sand Waves Studied To Help Pipeline Planners
The article cites a study that offers information on the variability of sand wave characteristics in the North Sea. The sand waves variability includes a statement that pipelines may start vibrating due to turbulence generated under the free span and navigational channels often need to be dredged for ships to pass safely. The study used multi-beam measurement of three fields in the North Sea in which sand waves occur. Moreover, the study concludes that understanding the variability of sand waves can help determine the optimal depth of a pipeline trench
Mitochondrial dysfunction in Autism Spectrum Disorders
Autism spectrum disorders (ASD) are classified as neurodevelopmental disorders characterised by diminished social communication and interaction. Recently, evidence has accrued that a significant proportion of individuals with autism have concomitant diseases such as mitochondrial disease and abnormalities of energy generation. This has therefore led to the hypothesis that autism may be linked to mitochondrial dysfunction. We review such studies reporting decreased activity of mitochondrial electron transport chain (ETC) complexes and reduced gene expression of mitochondrial genes, in particular genes of respiratory chain complexes, in individuals with autism. Overall, the findings support the hypothesis that there is an association of ASD with impaired mitochondrial function; however, many of the studies have small sample sizes and there is variability in the techniques utilised. There is therefore a vital need to utilise novel imaging techniques, such as near-infrared spectroscopy, that will allow noninvasive measurement of metabolic markers for neuronal activity such as cytochrome c oxidase, in order to better establish the link between autism and mitochondrial dysfunction
Costs and effects of genetic screening with application to cystic fibrosis and fragile X syndrome
Two to six percent of all newborn children have a disorder with a genetic cause (1-3).
For an increasing number of these diseases, the precise genetic cause is known and
this can lead to new treatment opportunities (see Appendix A for a basic description
of the mechanisms of genetic inheritance). However, for most disorders total cure is
not yet possible. For example, complications in patients with cystic fibrosis can be
reduced by intensive treatment, but many patients will still die of lung problems
caused by the disease. For diseases for which cure is not yet possible genetic
screening might be a (temporary) solution. For example, a genetic screening
programme in most Western countries is the offer of amniocentesis to pregnant
women of a specified age (36 years and older in The Netherlands) to detect Down
syndrome. Women in whom a foetus with Down syndrome is detected can then
decide to prepare for the birth of an affected child or to avoid its birth by induced
abortion. A list with examples of tests to detect disorders with a genetic cause or
component currently offered in The Netherlands is given in Table 1.1. Because of the
increasing number of genetic diseases that can be detected early, this list will
probably continue to be extended
The Local-Time Variation of the Quiet Plasmasphere: Geosynchronous Observations and Kinetic Theory
The quiet-time structure of the plasmaspheric density was investigated using observations of the Los Alamos geosynchronous satellites, and these observations were compared with theoretical predictions of the quasi-static localtime variation by a kinetic model. It was found that the coupling to the ionosphere (via the local-time variation of the exobase) played a key role in determining the density structure at 6.6 RE. The kinetic model predicts that most of the local-time variation at geosynchronous orbit is due to the variation of the exobase parameters. During quiet times, when the convection electric field is dominated by the corotation field, the effects due to flux-tube convection are less prominent than those due to the exobase variation. In addition, the kinetic model predicts that the geosynchronous plasmaspheric density level is at most only 25% of saturation density, even when geomagnetic activity is low. The low night-time densities of the ionospheric footpoints, and the subsequent long trapping time scales, prevent the equatorial densities from reaching saturatio
The Role of Poly(Acrylic Acid) in Conventional Glass Polyalkenoate Cements
Glass polyalkenoate cements (GPCs) have been used in dentistry for over 40 years. These novel bioactive materials are the result of a reaction between a finely ground glass (base) and a polymer (acid), usually poly (acrylic acid) (PAA), in the presence of water. This article reviews the types of PAA used as reagents (including how they vary by molar mass, molecular weight, concentration, polydispersity and content) and the way that they control the properties of the conventional GPCs (CGPCs) formulated from them. The article also considers the effect of PAA on the clinical performance of CGPCs, including biocompatibility, rheological and mechanical properties, adhesion, ion release, acid erosion and clinical durability. The review has critically evaluated the literature and clarified the role that the polyacid component of CGPCs plays in setting and maturation. This review will lead to an improved understanding of the chemistry and properties of the PAA phase which will lead to further innovation in the glass-based cements field
Non-invasive measurement of a metabolic marker of infant brain function
While near-infrared spectroscopy (NIRS) haemodynamic measures have proven to be vastly useful in investigating human brain development, the haemodynamic response function (HRF) in infants is not yet fully understood. NIRS measurements of the oxidation state of mitochondrial enzyme cytochrome-c-oxidase (oxCCO) have the potential to yield key information about cellular oxygen utilisation and therefore energy metabolism. We used a broadband NIRS system to measure changes in oxCCO, in addition to haemodynamic changes, during functional activation in a group of 33 typically developing infants aged between 4 and 6 months. The responses were recorded over the right temporal lobe while the infants were presented with engaging videos containing social content. A significant increase in oxCCO was found in response to the social stimuli, with maximum increase of 0.238 ± 0.13 μM. These results are the first reported significant change in oxCCO in response to stimulus-evoked activation in human infants and open new vistas for investigating human infant brain function and its energy metabolism
Severity-Stratified Discrete Choice Experiment Designs for Health State Evaluations
__Background:__ Discrete choice experiments (DCEs) are increasingly used for health state valuations. However, the values derived from initial DCE studies vary widely. We hypothesize that these findings indicate the presence of unknown sources of bias that must be recognized and minimized. Against this background, we studied whether values derived from a DCE are sensitive to how well the DCE design spans the severity range.
__Methods:__ We constructed an experiment involving three variants of DCE tasks for health state valuation: standard DCE, DCE-death, and DCE-duration. For each type of DCE, an experimental design was generated under two different conditions, enabling a comparison of health state values derived from current best practice Bayesian efficient DCE designs with values derived from ‘severity-stratified’ designs that control for coverage of the severity range in health state selection. About 3000 respondents participated in the study and were randomly assigned to one of the six study arms.
__Results:__ Imposing the severity-stratified restriction had a large effect on health states sampled for the DCE-duration approach. The unstratified efficient design returned a skewed distribution of selected health states, and this introduced bias. The choice probability of bad health states was underestimated, and time trade-offs to avoid bad states were overestimated, resulting in too low values. Imposing the same restriction had limited effect in the DCE-death approach and standard DCE.
__Conclusion:__ Variation in DCE-derived values can be partially explained by differences in how well selected health states spanned the severity range. Imposing a ‘severity stratification’ on DCE-duration designs is a validity requirement
Comparison of two assays for human kallikrein 2
BACKGROUND: We compared two recently developed research assays for the
measurement of human kallikrein 2 (hK2) in serum: one fully automated
assay (Beckman Coulter Access immunoanalyzer) and one manual assay based
on the DELFIA technology. METHODS: We used two subsets of clinical
specimens consisting of 48 samples from prostate cancer patients and 210
samples from participants in an ongoing screening study (ERSPC). Both
subsets were measured in the Rotterdam laboratory, and the prostate cancer
samples were used for analytical comparison with the originating sites for
the assays: Beckman Coulter Research Department (San Diego, CA) and Turku
University (Turku, Finland). RESULTS: Both the Beckman Coulter and the
Turku assays performed very similarly between the Rotterdam laboratory and
the originating sites: the R(2) value for both comparisons was 0.99, and
the slope difference between sites was <20%. Deming regression analysis of
the DELFIA (y) and Access (x) assays yielded the following: for the
prostate cancer group, y = 1.17x - 0.01 (R(2) = 0.88; n = 48); and for the
ERSPC group, y = 0.62x - 0.01 (R(2) = 0.77). Breakdown of the latter group
into subgroups (nondiseased, benign prostatic hyperplasia, and prostate
cancer samples) gave only minor differences. The Access calibrators were
underrecovered by 13% in the DELFIA assay, whereas the DELFIA calibrators
were overrecovered by 45% in the Access assay. CONCLUSION: The DELFIA and
Access assays for hK2, which have similar analytical features, show
differences that cannot be explained by calibration
State Sum Models and Simplicial Cohomology
We study a class of subdivision invariant lattice models based on the gauge
group , with particular emphasis on the four dimensional example. This
model is based upon the assignment of field variables to both the - and
-dimensional simplices of the simplicial complex. The property of
subdivision invariance is achieved when the coupling parameter is quantized and
the field configurations are restricted to satisfy a type of mod- flatness
condition. By explicit computation of the partition function for the manifold
, we establish that the theory has a quantum Hilbert space
which differs from the classical one.Comment: 28 pages, Latex, ITFA-94-13, (Expanded version with two new sections
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