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Biomedical subjects

Christopher Gordon

Publications and source records attributed to Christopher Gordon.

11 recordsLinked to original sources
PubMed2006

Cortical pQCT measures are associated with fractures in dialysis patients.

UNLABELLED: To determine if pQCT could identify HD patients with fractures, we conducted a cross-sectional study in 52 men and women on HD. We found that cortical, but not trabecular, pQCT measures were associated with fractures. INTRODUCTION: Fractures are common in hemodialysis (HD) patients, yet DXA is inconsistently associated with fractures. One explanation for this lack of association may be that HD patients have a selective decrease in cortical density not identified by standard DXA. MATERIALS AND METHODS: We used pQCT to examine cross-sectional associations between cortical and trabecular measures and fractures in 36 men and 16 women, > or = 50 years of age, on HD for at least 1 year. We confirmed low-trauma nonspine fractures since starting HD. Prevalent vertebral fractures were identified by morphometry of lateral spine X-rays. pQCT measurements of the nondominant radius included trabecular density, cortical density, total area, cortical area, and cortical thickness. We also obtained DXA measurements of the hip and lumbar spine. We used logistic regression models, adjusted for age, weight, and sex, to examine the association between fracture (vertebral and/or self-reported nonspine) and each pQCT measure. Results are reported as ORs per SD decrease in the independent variable. RESULTS: The mean age was 65.8 +/- 9.0 (SD) years, the mean weight was 72.3 +/- 15.6 kg, most (32 of 52) subjects were white, and there were 32 fractures in 27 subjects (prevalent vertebral fracture or low-trauma fracture) since starting dialysis. A decrease in cortical density was associated with fractures (OR = 16.67; 95% CI: 2.94-83.33), as was a decrease in cortical area (OR = 3.04; 95% CI: 1.28-7.25) and a decrease in cortical thickness (OR = 3.26; 95% CI: 1.36-7.87). Fractures were not associated with pQCT trabecular density (OR = 1.18; 95% CI: 0.6-2.33), total area (OR = 1.1; 95% CI: 0.59-1.7), or DXA measurements of the hip and spine. CONCLUSIONS: Cortical parameters of the radius were associated with fractures in HD patients. If confirmed in prospective studies, these findings may explain the lack of association between fracture and standard DXA measurements and raise the possibility that pQCT could be used to identify HD patients at high risk of fracture.

Aged↗
PubMed2005

Visualization of electron correlation in autoionizing states above the 3p threshold in magnesium.

The conditional probability density has been calculated for a number of autoionizing states (AIS) in Mg above the 3p threshold. The correlation in such high energy AIS has not been extensively studied and provides insight into the rovibrator behavior of two-electron atoms. The calculations have been done by configuration interaction (CI) with a B-spline basis. This allows for the simultaneous study of the effects of electron correlation and the widths and angular distribution of photoelectrons in multiphoton ionization. The states have been assigned approximate vibrational quantum numbers, and a correlation between the approximate quantum numbers and the photoelectron distribution is observed. Probability distribution for one electron when the other, represented by the small spike, is at its most probable distance from the nucleus. This is a distribution for the doubly-excited 1S(e) state commonly labeled as the 4s2 state.

Algorithms↗
PubMed2004

Cardiovascular and thermal consequences of protective clothing: a comparison of clothed and unclothed states.

We have undertaken a laboratory-based examination of the cardiovascular and thermal impact of wearing thermal (heat) protective clothing during fatiguing exercise in the heat. Seven males completed semi-recumbent, intermittent cycling (39.6 degrees C, 45% relative humidity) wearing either protective clothing or shorts (control). Mean core and skin temperatures, cardiac frequency (f(c)), stroke volume (Q), cardiac output (Q), arterial pressure, forearm blood flow (Q(f)), plasma volume change, and sweat rates were measured. In the clothed trials, subjects experienced significantly shorter times to fatigue (52.5 vs. 58.9 min), at lower peak work rates (204.3 vs. 277.4 W), and with higher core (37.9 degrees vs. 37.5 degrees C) and mean skin temperatures (37.3 degrees vs. 36.9 degrees C). There was a significant interaction between time and clothing on f(c), such that, over time, the clothing effect became more powerful. Clothing had a significant main affect on Q, but not Q, indicating the higher Q was chronotropically driven. Despite a greater sweat loss when clothed (923.0 vs. 547.1 g.m(-2) x h(-1); P<0.05), Q(f) and plasma volume change remained equivalent. Protective clothing reduced exercise tolerance, but did not affect overall cardiovascular function, at the point of volitional fatigue. It was concluded that, during moderately heavy, semi-recumbent exercise under hot, dry conditions, the strain on the unclothed body was already high, such that the additional stress imparted by the clothing ensemble represented a negligible, further impact upon cardiovascular stability.

Adult↗
PubMed2003

The transcervical incision for use in oral and maxillofacial surgical procedures.

PURPOSE: The aim of this study was to evaluate the long-term outcome of the transcervical approach to treat various mandibular problems. MATERIALS AND METHODS: Sixty-two patients (37 males and 25 females; age range, 15 to 80 years; mean age, 45.1 years) were treated via the transcervical approach. Twenty-eight patients (45.1%) had multiple mandibular fractures, 23 (31.7%) had tumor resections and selective neck dissections with microsurgical reconstruction, 7 (11.3%) had severe micrognathia and temporomandibular joint ankylosis, and 4 (6.4%) had mandibular atrophy requiring grafting. The patients were followed up to 15 years. The rates of complications due to surgery were evaluated. RESULTS: The most common complication was dysesthesia at the C2-4 distribution in 54 patients (87.1%), which was usually transient. Nine patients (12.9%) had permanent damage to the inferior alveolar nerve (V3) unilaterally due to segmental mandibulectomy. Other less common complications were transient dysesthesia at the V3 distribution and transient weakness of the lip commissure unilaterally. Hypertrophic scars, seroma formation, soft tissue infection, and orocervical fistula formation were rare. Most of the patients (96.8%) were satisfied with the amount of scarring. CONCLUSION: The transcervical approach provides broad exposure of the mandible and neck structures with excellent access to the operative field and a minimal rate of complications.

Adolescent↗
PubMed2003

Evaluation of long-term stability in second metatarsal reconstruction of the temporomandibular joint.

PURPOSE: Our goal was to evaluate long-term stability and function of 5 condyles reconstructed with vascularized second metatarsal joint grafts. MATERIALS AND METHODS: Four patients were reconstructed with 5 vascularized metatarsal grafts. These reconstructed joints were then followed for an average of 12.5 years. These patients represent the entire series and were all successfully contacted and reevaluated for this article. Measures of opening, deviation, excursion, symmetry, and clinical symptoms relating to the reconstructed joints are evaluated. RESULTS: Mean preoperative interincisal aperture was 12 mm, and postoperative aperture 48.5 mm. Three unilaterally treated patients had lateral excursion with opening. The mean deflection was 4.3 mm toward the operated side. Lateral and protrusive movements were limited in reconstructed joints, but up to 3 mm of protrusion was shown at 12.5 years. Subjectively, all patients rated their function as acceptable and were able to occlude and masticate without difficulty. Symmetry at rest was improved by surgery. CONCLUSIONS: Vascularized metatarsal joints represent a potentially suitable long-term substitute for condylar reconstruction. This limited series shows the technical viability of the procedure. A larger series may be warranted to compare this promising technique with conventional methods of temporomandibular joint reconstruction.

Adolescent↗
PubMed2002

Comorbidity of depression with other medical diseases in the elderly.

A major factor in the context of evaluating depression in the elderly is the role of medical problems. With aging there is a rapid increase in the prevalence of a number of medical disorders, including cancer, heart disease, Parkinson's disease, Alzheimer's disease, stroke, and arthritis. In this article, we hope to bring clarity to the definition of comorbidity and then discuss a number of medical disorders as they relate to depression. We evaluate medical comorbidity as a risk factor for depression as well as the converse, that is, depression as a risk factor for medical illness. Most of the disorders that we focus on occur in the elderly, with the exception of HIV infection. This review focuses exclusively on unipolar disorder. The review summarizes the current state of the art and also makes recommendations for future directions.

Acquired Immunodeficiency Syndrome↗
PubMed2002

Correlated perturbations from inflation and the cosmic microwave background.

We compare the latest cosmic microwave background data with theoretical predictions including correlated adiabatic and cold dark matter (CDM) isocurvature perturbations with a simple power-law dependence. We find that there is a degeneracy between the amplitude of correlated isocurvature perturbations and the spectral tilt. A negative (red) tilt is found to be compatible with a larger isocurvature contribution. Estimates of the baryon and CDM densities are found to be almost independent of the isocurvature amplitude. The main result is that current microwave background data do not exclude a dominant contribution from CDM isocurvature fluctuations on large scales.

Journal Article↗
PubMed2002

Tuberculous granuloma and adenoid cystic carcinoma presenting as a single buccal space mass.

We report an unusual case of a 58-year-old man with a "collision lesion" of the buccal space. Initially diagnosed as tuberculoma, the patient showed only partial response to an extensive course of antibiotics, prompting more vigorous investigation. This revealed the presence of a concomitant malignancy, specifically adenoid cystic carcinoma. Definitive treatment was then achieved by surgical resection and flap reconstruction with postoperative radiation therapy.

Carcinoma, Adenoid Cystic↗
PubMed2002

Developing deep learning approaches and personal teaching efficacy within a preservice teacher education context.

BACKGROUND: University students' approaches to learning have been demonstrated to affect learning outcomes across a wide range of courses, favouring the use of a deep approach. Interventions to promote the use of deep approaches have had mixed success, with the most successful interventions involving large-scale course redesign. AIMS: This paper describes a study in which contextual modifications were implemented in an existing preservice teacher education programme to increase students' use of deep approaches to learning and reduce their reliance on the use of surface approaches, without the need for major redesign. Students' perceptions of their competence in performing the tasks of teaching (personal teaching efficacy) were also expected to improve in response to improvements in quality learning. SAMPLE: Three cohorts of students (N = 134), enrolled in a preservice teacher education degree programme at a rural university in New South Wales, Australia participated in the study. METHOD: A longitudinal quasi-experimental design was used, with Cohort 1 acting as a control while Cohorts 2 and 3 represented treatment groups. Repeated measures were taken on Biggs' (1987b) Study Process Questionnaire, a modified version of Gibson and Dembo's (1984) Teacher Efficacy Scale and the Academic subscale within Lefcourt's (1981) Multidimensional-Multiattributional Causality Scale. An action research paradigm was embedded to enable the development and refinement of the altered teaching approaches. RESULTS: Results indicated that the modifications to teaching methods, task requirements and assessment processes applied to the treatment group encouraged changes in students' approaches to learning by firstly reducing their use of surface approaches and later increasing the use of deep approaches. While both treatment and contrast groups exhibited equivalent growth in teaching efficacy, differences between cohorts were noted in the sources that informed personal teaching efficacy at the conclusion of the course. CONCLUSIONS: These findings suggest that the study succeeded in its major goal of improving the quality of teaching and learning in this teacher education programme. The results conform to the findings of previous research and are consistent with learning approach theory. While the specific contextual modifications used in the current study may not necessarily be transferable to other settings, the processes employed in the generation of those modifications could find wider applicability.

Achievement↗