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Biomedical subjects

S Hayden

Publications and source records attributed to S Hayden.

15 recordsLinked to original sources
PubMed2004

Anisotropy of the incommensurate fluctuations in Sr2RuO4: a study with polarized neutrons.

The anisotropy of the magnetic incommensurate fluctuations in Sr2RuO4 has been studied by inelastic neutron scattering with polarized neutrons. We find a sizable enhancement of the out-of-plane component by a factor of 2 for intermediate energy transfer, which appears to decrease for higher energies. Our results qualitatively confirm calculations of the spin-orbit coupling, but the experimental anisotropy and its energy dependence are weaker than predicted.

Journal Article↗
PubMed2001

Using action research in paediatric oncology to develop an oral care algorithm.

The concurrent use of an oral assessment guide and oral care algorithm proved valuable in providing a more consistent approach to the oral care of children on a particular paediatric oncology ward (Gibson et al. 1997). However, as action research was chosen to develop practice, the diagnosis of new problems was anticipated. The identification of problem areas arose from two sources-informal feedback from the practice setting and via a formal audit using a tripartite approach consisting of a structured interview, vignettes and an analysis of existing documentation. The findings firstly demonstrated that practitioners experienced problems associated with the interpretation of the information contained within the existing algorithm. Secondly, there was also strong evidence to show that the production of a second 'therapeutic' algorithm would be beneficial to patient care. Finally, to ensure clarity, minor changes were required to the oral assessment guide. By using a collaborative approach between researchers and practitioners a positive resolution to a commonly identified clinical problem was expedited.

Journal Article↗
PubMed2000

Transition of the blastomere cell cycle from cell size-independent to size-dependent control at the midblastula stage in Xenopus laevis.

Dissociated animal cap blastomeres of Xenopus laevis blastulae were cultured at a low Ca level (1 microM) from 9th to 18th cell cycle at 22 +/- 1 degrees C and observed by a time-lapse video recorder. Blastomeres cleaved unequally to increase variability in cell size as cell cycles progressed, but synchronously at a constant cell cycle time of about 30 min up to the 12th cleavage in diploid cells, and up to the 13th cleavage in haploid cells, regardless of their cell sizes. Thereafter, blastomeres cleaved asynchronously at varying cell cycle times in proportion to the inverse square of their radii. The transition from the cell size-independent to -dependent cell cycles occurred at the critical cell radius, 37.5 microm for the diploid and 27.9 microm for the haploid. While the protein synthesis inhibitor, cycloheximide (CHX) lengthened cell cycle times two- to six-fold, epidermal growth factor (EGF) had no significant effect on the cell cycle. CHX-treated blastomeres synchronously cleaved at a constant cell cycle time of 60 min up to the 12th cleavage. Thereafter, cell cycle times became variable in proportion to the inverse square of radii in the presence of CHX at 0.10-0.14 microg/ml, but to the inverse cube of radii at 0.18 microg/ml. The critical cell size of CHX-treated blastomeres for the transition from cell size-independent to -dependent cell cycles remained the same as that of untreated blastomeres. Frequency distributions of cell cycle times of synchronous cell cycles were monomodal with the peak at 30 min, except for CHX-treated blastomeres with the peak at 60 min. In contrast, frequency distributions of asynchronous cell cycles were polymodal with peaks at multiples of a unit time of 30-35 min. To explain these results, we propose that blastomere cytoplasm has 30-min cycles that repeatedly produce mitosis promoting factor (MPF) in a quantity proportional to the cell surface area. MPF is neutralized when it titrates a nuclear inhibitor present in a quantity proportional to the genome size, and sequestered in the nucleus. When the total amount of MPF produced exceeds the threshold required to titrate all of the inhibitor, mitosis is initiated.

Animals↗
PubMed2000

NaI detector neutron activation spectra for PGNAA applications

When NaI detectors are used in prompt gamma-ray neutron activation analysis devices, they are activated by neutrons that penetrate the detector. While thermal neutron filters like boron or lithium can be used to reduce this activation, it can never be completely eliminated by this approach since high energy neutrons can penetrate the detector and thermalize inside it. This activation results in the emission of prompt gamma rays from both the I and Na and the production of the radioisotopes 128I and 24Na that subsequently decay and emit their characteristic beta particles and gamma rays. The resulting three spectra represent a background for this measurement. An experimental method for obtaining these three spectra is described and results are reported for 2" x 2", 5" x 5", 6" x 6", and 1" x 6" NaI detectors using the thermal neutron beam of the NCSU PULSTAR nuclear reactor. In addition, Monte Carlo simulation programs have been developed and used for simulating these spectra. Good results have been obtained by the Monte Carlo method for the two radioisotope spectra, and it is anticipated that good results will also be obtained for the prompt gamma-ray spectrum when the I and Na coincidence schemes are known.

Journal Article↗
PubMed1997

Early identification of dementia: predictive validity of the clock test.

Various clock scoring procedures have been developed in recent years as dementia screening measures. The current longitudinal study was developed to assess the predictive validity of the Clock Test (Tuokko, Hadjistavropoulos, Miller, Horton, & Beattie, 1995). Within a sample of subjects who initially did not meet dementia criteria, Clock Test scores (drawing, setting, and reading) distinguished between those who later met criteria for dementia as compared to subjects who did not. When impaired performance was identified as falling below cut-off on two or more subtests of the Clock Test, sensitivity and specificity were found to be 91% and 95% relative to time two diagnosis. Clock errors among the current sample were compared against normal control subjects from the Canadian Study of Health and Aging (CSHA). These comparative analyses attest to the relative normality of the clinic sample at the time of their initial assessment.

Journal Article↗
PubMed1996

Response biases as a confound to expressed burden among spousal caregivers of suspected dementia patients.

Burden among family caregivers has yet to be adequately assessed relative to social desirability response sets. This study examined the impact of two different response biases relative to expressed burden among spousal caregivers of suspected dementia patients. In addition to individual social desirability, it was hypothesized that a distinct social desirability construct exists as a function of one's perception of self within relationships. As predicted, a significant inverse association was apparent between expressed burden and this systemic response bias (as measured by the Edmonds Marital Conventionality Scale), whereas this association was not apparent with a measure of individual social desirability (the Marlowe-Crowne Social Desirability Scale). This finding suggests that systemic social desirability may exist as a significant response bias.

Aged↗
PubMed1995

Three-dimensional computed tomographic angiography in the preoperative evaluation of cerebrovascular lesions.

Although three-dimensional computed tomographic angiography was developed as a screening tool for use in patients with suspected cerebrovascular disease, this imaging modality has also proven to be of value in surgical planning for patients with large or unusual vascular lesions of the brain. The three-dimensional images generated by this technique yield valuable information regarding the size and configuration of intracranial aneurysms and vascular malformations, the presence and extent of intra-aneurysmal thrombus, the relationship of the vascular lesion to other cerebrovascular or skeletal structures, aneurysm wall thickness, and the presence and orientation of an aneurysm neck. The use of three-dimensional computed tomographic angiography in representative cases of patients with large or unusual cerebrovascular lesions is presented. It has been our experience that this imaging modality displays anatomical information that is not readily available from standard, intra-arterial angiography, provides better detail for surgical planning than magnetic resonance angiography, and is less expensive than either of these other imaging modalities.

Adult↗
PubMed1994

Comparative performance of mildly impaired patients with Alzheimer's disease and multiple cerebral infarctions on tests of memory and functional capacity.

There is increasing evidence that mildly impaired patients with Alzheimer's disease (AD) may be distinguished from mildly impaired patients with multi-infarct cognitive disorder (MICD) by their degree of semantic memory impairment. However, despite these observed group differences, it is unknown whether AD and MICD patients differ in their ability to perform a broad array of functional activities required for daily living and the degree to which severity of cognitive impairment is associated with functional deficits. Using a measure assessing numerous functional domains within the clinical setting, we were able to directly compare the functional capacity of mildly impaired AD and MICD patients, as well as a more cognitively impaired AD group. Although mildly impaired AD patients scored significantly lower on tests of semantic memory relative to their mildly impaired MICD counterparts, deficits in functional capacity were relatively equivalent. The AD group with more severe cognitive impairment scored lower on both memory and functional measures. A relatively high proportion of mildly impaired AD and MICD subjects evidenced impairment across a number of functional domains, suggesting that functional impairment may occur with relatively high frequency in these patient groups.

Activities of Daily Living↗
PubMed1992

A comparative analysis of functional status among Spanish- and English-speaking patients with dementia.

The assessment of functional capacity is regarded as an important part of a comprehensive diagnostic work-up for dementia. However, there is a paucity of data regarding comparative functional performance among different ethnic/cultural groups. In this study, we compared Spanish- and English-speaking dementia patients and normal controls on a comprehensive functional assessment battery administered within the clinical setting. Despite equivalent levels of cognitive impairment, Spanish-speaking dementia patients evidenced more difficulties on certain functional tasks relative to their English-speaking counterparts. On the other hand, Spanish- and English-speaking controls did not differ with regards to their functional performance. Results suggest that the extent of deterioration in specific functional subskills may be related to the degree to which they have been overlearned and practiced. Further, they indicate the potential utility of direct functional assessment in both Spanish- and English-speaking populations.

Activities of Daily Living↗
PubMed1992

Three-dimensional computerized tomography angiography in the diagnosis of cerebrovascular disease.

Computer-generated three-dimensional reconstruction of the intracranial vascular system obtained by contrast-enhanced computerized tomography (CT) has been used in the diagnosis of 20 patients with known or suspected intracranial cerebrovascular disease. This technique allows visualization of the intracranial vasculature without exposing patients to the risks associated with intra-arterial angiography. The color prints and videotape images generated have been used to diagnose the presence of intracranial aneurysms, arteriovenous malformations, and venous angiomas. They have also been used to rule out structural abnormalities in patients with suspected intracranial vascular pathology and to screen patients with a strong family history of intracranial aneurysm. In 11 patients who underwent both three-dimensional CT angiography and intra-arterial angiography, the diagnostic correlation was 100%. No complications from the procedures or from incorrect diagnosis have been encountered. Although this technique requires further development and clinical evaluation, the authors' early experience with three-dimensional CT angiography suggests that this may become a valuable tool in the diagnosis of patients with cerebrovascular disease.

Adolescent↗