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Biomedical subjects

J R Hardy

Publications and source records attributed to J R Hardy.

At least 19 recordsLinked to original sources
PubMed2005

Strain induced half-metal to semiconductor transition in GdN.

We investigate the electronic structure and magnetic properties of GdN as a function of unit cell volume. Based on the first-principles calculations of GdN, we observe that there is a transformation in the conduction properties associated with the volume increase: first from half-metallic to semimetallic, then ultimately to semiconducting. We show that applying stress can alter the carrier concentration as well as mobility of the holes and electrons in the majority spin channel. In addition, we found that the exchange parameters depend strongly on lattice constant, thus the Curie temperature of this system can be enhanced by applying stress or doping impurities.

Journal Article↗
PubMed2005

Phase transition in single crystal Cs2Nb4O11.

We studied temperature dependence of complex capacitance, impedance, and polarized Raman spectra of single crystal Cs2Nb4O11. First, we observed a sharp lambda-shaped peak at 165 degrees C in the complex capacitance, then found drastic changes in the Raman spectra in the same temperature range. Utilizing the pseudosymmetry search of structure space group, we attributed the observed anomalies to a structural change from the room temperature orthorhombic Pnn2 to another orthorhombic Imm2. We also measured room temperature polarized Raman spectra in different symmetries of normal vibrations and assigned high wavenumber Raman bands to the internal vibrations of NbO6 octahedra and NbO4 tetrahedra.

Journal Article↗
PubMed2001

Quantified kinematics of the injury to the posterior cruciate ligament: a computer-aided design simulation study.

OBJECTIVE: To quantify the kinematics of the injury to the posterior cruciate and the other major knee ligaments as a function of the knee flexion angle at the moment of impact. DESIGN: Computer-aided design modelling was used to investigate the strain response of all major knee ligaments during antero-posterior abnormal tibio-femoral translation at 0-90 degrees knee flexion. BACKGROUND: It is generally believed that the likelihood of injury to the posterior cruciate ligament following anterior impact is higher in the flexed knee. However, there are no kinematical studies to quantify this clinical observation or investigate the role of the other knee ligaments in the above situation. METHODS: Computer calculations of the individual ligament strain were plotted against the magnitude of posterior tibial translation. Additionally, the strain rate for each ligament (defined as the ligament strain produced per mm of posterior tibial linear translation) was calculated as the slope of the strain-displacement curve for all tested degrees of knee flexion. RESULTS: The posterior cruciate ligament has been shown to be the primary restraint to posterior tibial translation in all degrees of knee flexion. However, at 90 degrees of knee flexion the strain rate of the posterior cruciate ligament is approximately half that in the fully extended knee and the posterior cruciate ligament is the only ligament to resist posterior tibial translation. CONCLUSIONS: The strain behaviour of the posterior cruciate ligament during injury is highly dependent on the knee flexion during the moment of impact. Forced posterior tibial translation in the 90 degrees flexed knee may result in isolated posterior cruciate ligament deficit rather than a complex ligament disruption. The strain rate of a ligament as introduced in the present study is a quantified parameter related to the resistance that the ligament imposes to an abnormal joint movement. Relevance. This study provides insight into the differential strain of the knee ligaments during impacts that result in posterior cruciate ligament injury. Studies that quantify the strain behaviour of individual knee ligaments are important to the understanding, diagnosis and prevention of injuries sustained during contact sports and high-energy road traffic accidents.

Biomechanical Phenomena↗
PubMed2001

A phase II study to establish the efficacy and toxicity of sodium valproate in patients with cancer-related neuropathic pain.

The efficacy and toxicity of sodium valproate for cancer-related neuropathic pain was evaluated in a phase II study at this cancer center. Twenty-five patients entered the study over a 13 month period. Pain was assessed using a pain scale based on the Brief Pain Inventory at days 0, 8 and 15. Nineteen patients completed the two week study period, one patient discontinued treatment because of toxicity, and five discontinued because of progressive disease. The most frequently observed side effects were drowsiness, unsteadiness, nausea, and decreased appetite. Response was defined as a decrease in pain score in the absence of increased need for analgesic medication. The response rate for average pain at day 15 in assessable patients was 55.6% (30.8-78.5%, 95% CI), but response rates varied considerably depending on the mode of analysis. Baseline efficacy data have been gained on which to base future comparative studies against antidepressants.

Adult↗
PubMed2001

A prospective survey of the use of dexamethasone on a palliative care unit.

One hundred and six consecutive patients started on glucocorticosteroids (steroids) according to a defined prescription policy were surveyed each week to document the indications for use, any beneficial effect, any toxicity incurred and the reason for stopping. All patients had advanced malignant disease and survived for a median of 40.5 days (range 1-398+ days) from the start of steroid treatment. Fifty-seven per cent of patients completed three or more assessments. The most common specific indications for starting steroids were spinal cord compression, cerebral metastases, lymphangitis carcinomatosa and intestinal obstruction. The most common non-specific indications were anorexia, nausea, low mood, pain and vomiting. The median duration of steroid use was 21.5 days (range 1-89 days). The most common reason for the discontinuation of steroids was death or deteriorating condition. Symptom scores improved at some stage for the majority of patients started on steroids for anorexia, nausea, pain, low mood, vomiting and weakness but not in patients complaining of dyspnoea or poor mobility. The most common side-effects that were most probably attributable to steroid therapy were oral candidosis and proximal myopathy. The benefits of steroids when used according to defined guidelines were thought to outweigh toxicity.

Anti-Inflammatory Agents↗
PubMed2000

Fracture stiffness measurement using the orthometer: reproducibility and sources of error.

OBJECTIVES: To elicit the reproducibility and the common sources of error in the use of the Orthometer, a commercially available goniometer based system, designed to measure the stiffness of healing fractures. DESIGN: A laboratory based study. BACKGROUND: The Orthometer is widely used to measure the progress of fracture healing in a quantitative manner. It has been shown previously that the bending stiffness of a fracture increases with healing and that a stiffness of 15 Nm/degree equates with the functional union of a tibial fracture. METHODS: The Orthometer was attached in a standard manner to nylon bars of known stiffness to determine the accuracy of the device. The Orthometer was then set up with changes in a single positional variable to assess the effect of this variable on the measurement accuracy. A number of different clinicians were asked to use the Orthometer before and after a simple training session and any improvements in the measurement accuracy were observed. RESULTS: Stiffness could be measured to within 10% or less of the true stiffness. Markedly different degrees of error were introduced with the various set-up variables. A simple training session improved clinician accuracy. CONCLUSIONS: Although the Orthometer does allow some degree of safety margin, it is essential that set-up is performed carefully, and that the clinician has been trained in the use of the device. RELEVANCE: Quantitative measurements of fracture healing have enormous potential benefits over manual and radiological methods of assessments. Provided these are carefully performed, the accuracy of these measurements is good.

Elasticity↗
PubMed2000

Outcome of malignant spinal cord compression at a cancer center: implications for palliative care services.

One hundred sixty-six patients presented to a cancer center with malignant spinal cord compression (SCC) proven by magnetic resonance imaging (MRI). The majority of patients (92%) were treated with radiotherapy. Changes in functional capability over time were assessed using performance (PS) and neurological status (NS). Over the course of treatment, there was no significant change in PS or NS. The median survival from confirmation of SCC was 82 days (range 1-1349 days). Survival was significantly better for those presenting with good functional status. One hundred thirteen patients (68%) were discharged from hospital; 88 (78%) were discharged home, 11% were sent to another hospital, 4% were transferred to a rehabilitation unit, and 5% went to a hospice. Fifty-three patients (32%) died before discharge. The confirmation that PS and NS have prognostic significance in the functional outcome of patients with SCC may prove helpful in decisions regarding care planning for individual patients with SCC who are discharged from hospital.

Adolescent↗
PubMed2000

The passage of bacteria through surgical drapes.

The passage of bacteria through surgical drapes is a potential cause of wound infection. Previous studies have shown that liquids and human albumin penetrate certain types of drapes. We studied the passage of bacteria through seven different types of surgical drape and an operating tray. Bacteria easily penetrated all the woven re-usable fabrics within 30 min. The disposable non-woven drapes proved to be impermeable, as did the operating tray. We recommend the use of non-woven disposable drapes or woven drapes with an impermeable operating tray in all surgical cases.

Bacteria↗
PubMed1999

Sequence analysis of rabbit haemorrhagic disease virus (RHDV) in Australia: alterations after its release.

Liver samples from rabbits killed by RHDV, collected from five States in Australia in 1996 and 1997 were analysed by RT-PCR. A 398 bp fragment of the capsid protein (VP60) gene was amplified by PCR and directly sequenced. The alignment of the nucleotide and amino acid sequences and their comparison with the original strain of the virus released in Australia indicated genetic changes after two years have been small with 98.2% to 100% identity. The constructed phylogenetic tree suggests slight differences in nucleotide substitutions in various States but there is no clear evidence of clustering of sequences according to their geographic origin. In practical terms, sequencing of viral RNA provides a means of testing the efficacy of further releases and subsequent spread of the virus if such a strategy is employed as a means of enhancing RHD as a biological control of the wild rabbit in Australia.

Amino Acid Sequence↗
PubMed1999

Digital image analysis: improving accuracy and reproducibility of radiographic measurement.

OBJECTIVE: To assess the accuracy and reproducibility of a digital image analyser and the human eye, in measuring radiographic dimensions. DESIGN: We experimentally compared radiographic measurement using either an image analyser system or the human eye with digital caliper. BACKGROUND: The assessment of total hip arthroplasty wear from radiographs relies on both the accuracy of radiographic images and the accuracy of radiographic measurement. METHODS: Radiographs were taken of a slip gauge (30+/-0.00036 mm) and slip gauge with a femoral stem. The projected dimensions of the radiographic images were calculated by trigonometry. The radiographic dimensions were then measured by blinded observers using both techniques. RESULTS: For a single radiograph, the human eye was accurate to 0.26 mm and reproducible to +/-0.1 mm. In comparison the digital image analyser system was accurate to 0.01 mm with a reproducibility of +/-0.08 mm. In an arthroplasty model, where the dimensions of an object were corrected for magnification by the known dimensions of a femoral head, the human eye was accurate to 0.19 mm, whereas the image analyser system was accurate to 0.04 mm. CONCLUSIONS: The digital image analysis system is up to 20 times more accurate than the human eye, and in an arthroplasty model the accuracy of measurement increases four-fold. We believe such image analysis may allow more accurate and reproducible measurement of wear from standard follow-up radiographs.

Hip Prosthesis↗
PubMed1999

The use of the Rotterdam Symptom Checklist in palliative care.

The Rotterdam Symptom Checklist (RSCL), which measures both physical and psychological aspects of quality of life (QOL), was given to all new patients admitted to a palliative care unit who were thought capable of filling out a questionnaire as an outcome measure of symptom control. Assessments were obtained from 52 patients at baseline (week 1). This represented only 53% of the new patients admitted to the unit. Thirty-one patients completed a second questionnaire at week 2, and only 28 patients completed a third (week 3). In these selected patients, the median overall RSCL scores were 57, 52, and 49 at weeks 1, 2, and 3. There was a significant improvement in QOL scores across the three measurements with a significant difference between weeks 1 and 3 (P = 0.05) but not between weeks 1 and 2. Primarily because of the inability of many patients to complete the questionnaire and the high attrition rate, the appropriateness of this tool as a symptom control measure in palliative care patients is questioned.

Adult↗