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Biomedical subjects

D R Williams

Publications and source records attributed to D R Williams.

At least 37 records · Page 2Linked to original sources
PubMed2001

Chemical speciation used to assess [S,S']-ethylenediaminedisuccinic acid (EDDS) as a readily-biodegradable replacement for EDTA in radiochemical decontamination formulations.

Preliminary investigations into the replacement of widely used chelating agents for industrial cleansing of radionuclide contaminated items using readily biodegradable alternatives which have equivalent effectiveness, have been made using chemical speciation simulation programs and databases such as the JESS system. The chelation of radionuclide cations by [S,S']-EDDS has been compared with traditional decontamination agents, EDTA and citrate. Models indicate that in many respects, [S,S']-EDDS compares favourably with EDTA.

Americium↗
PubMed2001

The use of inverse phase gas chromatography to measure the surface energy of crystalline, amorphous, and recently milled lactose.

PURPOSE: To assess differences in surface energy due to processing induced disorder and to understand whether the disorder dominated the surfaces of particles. METHODS: Inverse gas chromatography was used to compare the surface energies of crystalline, amorphous, and ball milled lactose. RESULTS: The milling process made ca 1% of the lactose amorphous, however the dispersive contribution to surface energy was 31.2, 37.1, and 41.6 mJ m(-2) for crystalline, spray dried and milled lactose, respectively. A physical mixture of crystalline (99%) and amorphous (1%) material had a dispersive surface energy of 31.5 mJ m(-2). CONCLUSION: Milling had made the surface energy similar to that of the amorphous material in a manner that was very different to a physical mixture of the same amorphous content. The milled material will have similar interfacial interactions to the 100% amorphous material.

Algorithms↗
PubMed2001

Prospective evaluation of thoracic ultrasound in the detection of pneumothorax.

BACKGROUND: Thoracic ultrasound may rapidly diagnose pneumothorax when radiographs are unobtainable; the accuracy is not known. METHODS: We prospectively evaluated thoracic ultrasound detection of pneumothorax in patients at high suspicion of pneumothorax. The presence of "lung sliding" or "comet tail" artifacts were determined in patients by ultrasound before radiologic verification of pneumothorax by residents instructed in thoracic ultrasound. Results were compared with standard radiography. RESULTS: There were 382 patients enrolled; the cause of injury was blunt (281 of 382), gunshot wound (22 of 382), stab wound (61 of 382), and spontaneous (18 of 382). Pneumothorax was demonstrated on chest radiograph in 39 patients and confirmed by ultrasound in 37 of 39 patients (95% sensitivity); two pneumothoraces could not be diagnosed because of subcutaneous air; the true-negative rate was 100%. CONCLUSION: Thoracic ultrasound reliably diagnoses pneumothorax. Expansion of the focused abdominal sonography for trauma (FAST) examination to include the thorax should be investigated for terrestrial and space medical applications.

Humans↗
PubMed2001

Child literacy promotion in the emergency department.

INTRODUCTION: Studies using primary health care settings to promote literacy have demonstrated success. Since socioeconomically disadvantaged children have less access to primary care, obtaining much of their medical care episodically in emergency departments (ED), the purpose of this study is to investigate the effectiveness of a simple literacy promotion program conducted in the ED and to determine its efficacy and if there is a difference in promoting literacy with a brochure alone versus a brochure plus a children's book. METHODS: Medical student study investigators enrolled patients aged 20 months to 7 years undergoing acute care treatment and evaluation in an ED. Subjects were randomized to a literacy promotion brochure versus a brochure plus a children's book. Phone follow-up interviews were conducted to survey the degree of parental reading taking place at home. RESULTS: Fifty-one families were enrolled, 8 could not be contacted for follow-up, which left 43 families. Twenty-eight were randomized to book + handout and 15 were randomized to handout alone. On follow-up phone interviews, no significant change in reading was demonstrated regardless of whether a brochure alone was given or a book was given with the brochure. CONCLUSION: Literacy promotion in the ED was not associated with any measurable improvement in parent-child reading. This could mean that the ED is not an effective place to promote literacy or confounding factors in this study are responsible for failing to demonstrate a measurable benefit.

Child↗
PubMed2001

Compensation of corneal aberrations by the internal optics in the human eye.

The objective was to study the relative contribution of the optical aberrations of the cornea and the internal ocular optics (with the crystalline lens as the main component) to overall aberrations in the human eye. Three sets of wave-front aberration data were independently measured in the eyes of young subjects: for the anterior surface of the cornea, the complete eye, and internal ocular optics. The amount of aberration of both the cornea and internal optics was found to be larger than for the complete eye, indicating that the first surface of the cornea and internal optics partially compensate for each other's aberrations and produce an improved retinal image. This result has a number of practical implications. For example, it shows the limitation of corneal topography as a guide for new refractive procedures and provides a strong endorsement of the value of ocular wave-front sensing for those applications.

Accommodation, Ocular↗
PubMed2001

Using wound fluid analyses to identify trace element requirements for efficient healing.

A series of wound fluid and blood plasma samples from 20 patients with breast cancer were analysed by Potentiometric Stripping Analysis and computer-aided chemical speciation to quantify the concentrations of the trace elements of copper and zinc in the samples and to investigate the individual species of copper and zinc present. Comparisons were made between total concentrations of copper and zinc in wound fluid, pre-operative blood plasma levels and reference values. A wound fluid model constructed using JESS identified the main copper and zinc species present. It was also used to investigate the effects of a change in pH and changes in the total concentrations of certain components on their predominance. The clinical significance of the research is discussed, together with suggestions for a continuation in the research.

Breast Neoplasms↗
PubMed2001

Food insufficiency and the physical and mental health of low-income women.

Poor women with children are disproportionately represented among the food insufficient. Recent research has linked food insufficiency with dietary deficiencies, but further research linking this problem to health and mental health problems is needed to inform health and social policy. We analyzed the relationship between food insufficiency and physical and mental health in a random sample of 724 single women who were welfare recipients in February, 1997. Food insufficiency was significantly associated with poor or fair self-rated health and physical limitations, and with respondents' meeting DSM-III-R criteria for recent major depression. Although the cross-sectional design of this study precludes causal inference, these findings add to a growing body of evidence that food insufficiency is associated with serious adverse physical and mental health consequences.

Adult↗
PubMed2001

Reline materials--handle with care? An investigation into the effect of varying the powder/liquid ratio on some properties of auto-polymerising acrylic resin materials.

INTRODUCTION: The fit of the denture base to the alveolar ridge progressively declines with alveolar ridge resorption. Once a denture becomes ill-fitting there are two main treatment options: to construct a new denture or to restore the fit of the existing denture. A denture may be relined as a laboratory procedure or at the chairside in the dental clinic. The chairside reline technique involves the direct application of auto-polymerising acrylic resin materials to the prepared denture base and the material is allowed to polymerise in the patient's mouth. The reline materials are generally supplied as a powder and a liquid. Clinicians and laboratory dental staff do not always follow manufacturers' recommended guidelines and the tendency can be simply to add varying quantities of powder and liquid until the desired consistency is achieved. This method however may have deleterious effects on the properties of the resultant material. MATERIALS AND METHOD: The aim of the study was to investigate the effect of varying the powder/liquid ratio on some properties of three auto-polymerising acrylic resin reline materials. The properties investigated were the flow characteristics in terms of the manipulation and setting time and the hardness. Four powder and liquid ratios were chosen. RESULTS AND CONCLUSIONS: For all the materials studied, a clinically useful lengthening of the manipulation time can be achieved by increasing the amount of liquid added to the powder. However, this is perhaps offset by the fact that it is associated with a corresponding increase in the setting time and resultant increase in clinical chairside time. There were significant differences in surface hardness when the powder/liquid ratio was altered.

Acrylic Resins↗
PubMed2001

Dynamics of the eye's wave aberration.

It is well known that the eye's optics exhibit temporal instability in the form of microfluctuations in focus; however, almost nothing is known of the temporal properties of the eye's other aberrations. We constructed a real-time Hartmann-Shack (HS) wave-front sensor to measure these dynamics at frequencies as high as 60 Hz. To reduce spatial inhomogeneities in the short-exposure HS images, we used a low-coherence source and a scanning system. HS images were collected on three normal subjects with natural and paralyzed accommodation. Average temporal power spectra were computed for the wave-front rms, the Seidel aberrations, and each of 32 Zernike coefficients. The results indicate the presence of fluctuations in all of the eye's aberration, not just defocus. Fluctuations in higher-order aberrations share similar spectra and bandwidths both within and between subjects, dropping at a rate of approximately 4 dB per octave in temporal frequency. The spectrum shape for higher-order aberrations is generally different from that for microfluctuations of accommodation. The origin of these measured fluctuations is not known, and both corneal/lenticular and retinal causes are considered. Under the assumption that they are purely corneal or lenticular, calculations suggest that a perfect adaptive optics system with a closed-loop bandwidth of 1-2 Hz could correct these aberrations well enough to achieve diffraction-limited imaging over a dilated pupil.

Accommodation, Ocular↗
PubMed2001

Effect of rotation and translation on the expected benefit of an ideal method to correct the eye's higher-order aberrations.

An ideal correcting method, such as a customized contact lens, laser refractive surgery, or adaptive optics, that corrects higher-order aberrations as well as defocus and astigmatism could improve vision. The benefit achieved with this ideal method will be limited by decentration. To estimate the significance of this potential limitation we studied the effect on image quality expected when an ideal correcting method translates or rotates with respect to the eye's pupil. Actual wave aberrations were obtained from ten human eyes for a 7.3-mm pupil with a Shack-Hartmann sensor. We computed the residual aberrations that appear as a result of translation or rotation of an otherwise ideal correction. The model is valid for adaptive optics, contact lenses, and phase plates, but it constitutes only a first approximation to the laser refractive surgery case where tissue removal occurs. Calculations suggest that the typical decentrations will reduce only slightly the optical benefits expected from an ideal correcting method. For typical decentrations the ideal correcting method offers a benefit in modulation 2-4 times higher (1.5-2 times in white light) than with a standard correction of defocus and astigmatism. We obtained analytical expressions that show the impact of translation and rotation on individual Zernike terms. These calculations also reveal which aberrations are most beneficial to correct. We provided practical rules to implement a selective correction depending on the amount of decentration. An experimental study was performed with an aberrated artificial eye corrected with an adaptive optics system, validating the theoretical predictions. The results in a keratoconic subject, also corrected with adaptive optics, showed that important benefits are obtained despite decentrations in highly aberrated eyes.

Eye↗
PubMed2001

Monochromatic aberrations of the human eye in a large population.

From both a fundamental and a clinical point of view, it is necessary to know the distribution of the eye's aberrations in the normal population and to be able to describe them as efficiently as possible. We used a modified Hartmann-Shack wave-front sensor to measure the monochromatic wave aberration of both eyes for 109 normal human subjects across a 5.7-mm pupil. We analyzed the distribution of the eye's aberrations in the population and found that most Zernike modes are relatively uncorrelated with each other across the population. A principal components analysis was applied to our wave-aberration measurements with the resulting principal components providing only a slightly more compact description of the population data than Zernike modes. This indicates that Zernike modes are efficient basis functions for describing the eye's wave aberration. Even though there appears to be a random variation in the eye's aberrations from subject to subject, many aberrations in the left eye were found to be significantly correlated with their counterparts in the right eye.

Adult↗
PubMed2001

Changing to the 2000 standard million: are declining racial/ethnic and socioeconomic inequalities in health real progress or statistical illusion?

OBJECTIVES: This study determined the effects of changing from the 1940 to the 2000 standard million on monitoring socioeconomic and racial/ethnic inequalities in health. METHODS: Using the 1940, 1970, and 2000 standard million, we calculated and compared age-adjusted rates for selected health outcomes stratified by socioeconomic level. RESULTS: Changing from the 1940 to the 2000 standard million markedly reduced the age-adjusted relative risks for self-reported fair or poor health status of poor Americans compared with high-income Americans. CONCLUSIONS: Public health researchers and practitioners should give serious consideration to the implications of the change to the 2000 standard million for monitoring social inequalities in health.

Adolescent↗
PubMed2001

Ultrasound evaluation of the magnitude of pneumothorax: a new concept.

Pneumothorax is commonly seen in trauma patients; the diagnosis is confirmed by radiography. The use of ultrasound where radiographic capabilities are absent, is being investigated by the National Aeronautics and Space Administration. We investigated the ability of ultrasound to assess the magnitude of pneumothorax in a porcine model. Sonography was performed on anesthetized pigs in both ground-based laboratory (n = 5) and microgravity conditions (0 x g) aboard the KC-135 aircraft during parabolic flight (n = 4). Aliquots of air (50-100 cm3) were introduced into the chest to simulate pneumothorax. Results were videorecorded and digitized for later interpretation. Several distinct sonographic patterns of partial lung sliding were noted including the combination of a sliding zone with a still zone and a "segmented" sliding zone. These "partial lung sliding" patterns exclude massive pneumothorax manifested by a complete separation of the lung from the parietal pleura. In 0 x g, the sonographic picture is more diverse; one x g differences between posterior and anterior aspects are diminished. Modest pneumothorax can be inferred by the ultrasound sign of "partial lung sliding." This finding, which increases the negative predictive value of thoracic ultrasound, may be attributed to intermittent pleural contact, small air spaces, or alterations in pleural lubricant. Further studies of these phenomena are warranted.

Animals↗
PubMed2001

Neighborhood disadvantage, stress, and drug use among adults.

This paper explores the relationships among neighborhood disadvantage, stress, and the likelihood of drug use in a sample of adults (N = 1,101). Using the 1995 Detroit Area Study in conjunction with tract-level data from the 1990 census, we find a positive relationship between neighborhood disadvantage and drug use, and this relationship remains statistically significant net of controls for individual-level socioeconomic status. Neighborhood disadvantage is moderately associated with drug related behaviors, indirectly through increased social stressors and higher levels of psychological distress among residents of disadvantaged neighborhoods. A residual effect of neighborhood disadvantage remains, net of a large number of socially relevant controls. Finally, results from interactive models suggest that the relationship between neighborhood disadvantage and drug use is most pronounced among individuals with lower incomes.

Adult↗
PubMed2001

Racism, discrimination and hypertension: evidence and needed research.

This paper reviews the available scientific evidence that relates racism to the elevated rates of hypertension for African Americans. Societal racism can indirectly affect the risk of hypertension by limiting socioeconomic opportunities and mobility for African Americans. Racism can also affect hypertension by 1) restricting access to desirable goods and services in society, including medical care; and 2) creating a stigma of inferiority and experiences of discrimination. This paper evaluates the available evidence for perceptions of discrimination. African Americans frequently experience discrimination and these experiences are perceived as stressful. Several lines of evidence suggest that stressors are positively related to hypertension risk. Exposure to racial stressors under laboratory conditions reliably predicts cardiovascular reactivity and such responses have been associated with longer-term cardiovascular risk. Few population-based studies have examined the association between exposure to racial discrimination and hypertension, and the findings, though suggestive of a positive association between racial bias and blood pressure, are neither consistent nor clear. However, the existing literature identifies important new directions for the comprehensive measurement of discrimination and the design of rigorous empirical studies that can evaluate theoretically derived ideas about the association between discrimination and hypertension.

Denial, Psychological↗
PubMed2000

Construction of 4-hydroxy-2-pyridinones. Total synthesis of (+)-sambutoxin.

Total synthesis of (+)-sambutoxin has been achieved, establishing the relative and absolute stereochemistry of the naturally occurring mycotoxin. Efforts feature methodology for enantiocontrolled construction of 1,3-anti-dimethyl arrays and a novel Saegusa oxidation to provide a pyridinone methide leading to formation of the central dihydropyran ring.

Fusarium↗