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C Roberts

Publications and source records attributed to C Roberts.

At least 91 records · Page 5Linked to original sources
PubMed2000

Comparison of computational analysis with clinical measurement of stresses on below-knee residual limb in a prosthetic socket.

Interface pressures and shear stresses between a below-knee residual limb and prosthetic socket predicted using finite element analyses were compared with experimental measurements. A three-dimensional nonlinear finite element model, based on actual residual geometry and incorporating PTB socket rectification and interfacial friction/slip conditions, was developed to predict the stress distribution. A system for measuring pressures and bi-axial shear stresses was used to measure the stresses in the PTB socket of a trans-tibial amputee. The FE-predicted results indicated that the peak pressure of 226 kPa occurred at the patellar tendon area and the peak shear stress of 50 kPa at the anterolateral tibia area. Quantitatively, FE-predicted pressures were 11%, on average, lower than those measured by triaxial transducers placed at all the measurement sites. Because friction/slip conditions between the residual limb and socket liner were taken into consideration by using interface elements in the FE model, the directions and magnitudes of shear stresses match well between the FE prediction and clinical measurements. The results suggest that the nonlinear mechanical properties of soft tissues and dynamic effects during gait should be addressed in future work.

Amputation Stumps↗
PubMed2000

Latent adenoviral infection modifies the steroid response in allergic lung inflammation.

BACKGROUND: Steroid-resistant asthma develops after adenoviral bronchiolitis. OBJECTIVE: We sought to determine the effect of steroids on allergic lung inflammation in the presence of latent adenoviral infection. METHODS: Guinea pigs with latent adenoviral (n = 12) or sham (n = 12) infections were sensitized and challenged with ovalbumin (OA) or sham sensitized and challenged with saline solution. The effect of steroids (20 mg/kg administered intraperitoneally) on OA-induced lung inflammation was examined by using quantitative histology as the outcome measure. RESULTS: Latent adenoviral infection increased CD8(+) cells in the airway wall and CD8(+) cells, macrophages, B cells, and CD4(+) cells in the lung parenchyma. Ovalbumin challenge, on the other hand, increased eosinophils, macrophages, B cells, and CD4(+) cells in both the airway wall and lung parenchyma independent of the effect of latent adenoviral infection. In the sham-infected groups steroid treatment caused the expected reduction in the eosinophilic infiltrate induced by OA challenge in the airways without affecting the other cells. In the presence of both latent adenoviral infection and OA challenge, steroid treatment had no effect on allergen-induced eosinophilia but reduced CD8(+) cells in the airways and CD8(+) cells, CD4(+) cells, and B cells in the parenchyma. CONCLUSION: Latent adenoviral infection and OA challenge result in different types of lung inflammation, and the presence of latent adenoviral infection causes OA-induced eosinophilic airway inflammation to become steroid resistant.

Adenoviridae Infections↗
PubMed2000

Antenatal transfer of rural women: how does the NSW Inpatient Statistics Collection compare with an audit of hospital records?

The aim of this study was to determine whether the NSW Inpatient Statistics Collection (ISC), a census of hospital admissions, could be used to estimate the magnitude of, and reasons for, antenatal transfer of rural women. Data from the ISC were compared with results of a clinical audit of all antenatal admissions of rural women to perinatal centres in NSW during 1997-1998. While the overall number of perinatal centre admissions identified by the ISC and the audit were similar, the ISC identified only about 70% of antenatal transfers. Rural hospitals identified 12% of women as indigenous compared with 9% at perinatal centres. The ISC showed 28% of rural women admissions and 42% of transfers were for threatened preterm labour compared with 21% and 30% respectively from the audit.

Adolescent↗
PubMed2000

Assessing the appropriateness of paediatric hospital admissions in the United Kingdom.

BACKGROUND: In order to assess whether the documented rise in paediatric admissions was due to inappropriate admissions, an objective measure of the appropriateness of paediatric admissions, modified for use in the United Kingdom, was used to measure the level of inappropriate admissions. The relationship of appropriateness of admissions to age, gender, time of admission and source of referral was investigated. METHODS: A retrospective review was carried out of a sample of paediatric records in 13 NHS district general hospitals in South Eastern England between April 1990 and March 1991 using the Paediatric Appropriateness Evaluation Protocol (PAEP) modified for use in the United Kingdom. RESULTS: A total of 3,324 paediatric admissions in 13 hospitals were assessed. Eight per cent of the sampled admissions were inappropriate. Age [odds ratio (OR)=0.87], gender (OR = 1.39) and weekend admissions (OR = 1.42) were associated with inappropriate admissions. After controlling for these factors, there was no significant variation between hospitals. CONCLUSION: The low level of inappropriate admissions may be a reflection of well-developed primary care services in the United Kingdom. Alternatives to hospital admission for the assessment of minor self-limiting illness in young children may have a role in reducing inappropriate admissions.

Age Distribution↗
PubMed2000

Hitting up in the top end: characteristics of needle exchange clients in Darwin.

OBJECTIVE: Little is known about injecting drug use (IDU) and blood-borne viral (BBV) infection in rural Australia. METHOD: These repeat cross-sectional studies were conducted during a two-week period in July and October-November 1998 at the Darwin needle exchange, with 129 and 121 respondents respectively. RESULTS: The commonest drug of choice was heroin, but the commonest drug injected was morphine. Self-reported sharing of needles and syringes was uncommon. Self-reported serostatus for HIV was high (8% and 11.4% respectively), but seemingly mostly associated with sexual rather than IDU risk; for hepatitis C (HCV) status, these were 54% and 37%. Among IDUs of Aboriginal or Torres Strait Islander (ATSI) background, who made up 14% of the first round respondents, patterns of IDU and of BBV infection were the same as among non-ATSI respondents. CONCLUSIONS: These surveys reveal patterns of IDU in Darwin that have both similarities and differences with those in the major urban centres in Australia. In the absence of a comprehensive methadone maintenance program, many participate in a more or less informal morphine substitution program. HIV is present among these IDUs, and the risks of further sexual transmission may be high. IMPLICATIONS: These surveys confirm the presence among injecting drug users in Darwin of HIV, HBV and HCV, and of the risk for further spread of these viruses. Control of blood-borne virus transmission among IDUs requires an even greater commitment to abolishing sharing of needles and syringes, and therefore continued support and enhancement of needle and syringe availability.

Adult↗
PubMed2000

Preoperative histological classification of primary lung cancer: accuracy of diagnosis and use of the non-small cell category.

AIMS: To compare the preoperative classification of lung carcinoma made on cytological and histological specimens with the postoperative classification made on the resected specimen. In addition, to find out how often the term "non-small cell lung cancer, not otherwise specified" (NSCLC) was used, and in such cases to note the final diagnosis. METHODS: Between 1991 and 1995, 303 patients had a lung resection in Aberdeen for primary carcinoma. For each patient, the departmental records were examined for preoperative specimens (cytological and histological). A note was made of whether each specimen was positive or negative for malignancy and, if positive, what the cell type was. Where patients had more than one sample submitted, the most specific result was taken. RESULTS: Fifty four per cent of patients had a correct specific preoperative diagnosis of malignancy, whereas 34% were labelled as NSCLC. Patients with squamous carcinoma were more likely to have a diagnosis of malignancy (88%) that was specifically correct (75%). Patients who had adenocarcinoma were less likely to have a preoperative diagnosis of malignancy (64%) that was specifically correct (35%). For those in whom a diagnosis of NSCLC was made, 55% turned out to have adenocarcinoma whereas 24% had squamous carcinoma. CONCLUSIONS: By adhering strictly to criteria, a high accuracy of diagnosis can be achieved for squamous carcinoma, but the diagnosis of adenocarcinoma seems to be more of a challenge. NSCLC is a useful and appropriate classification, the use of which reduces the rate of inaccurate specific diagnosis. There are occasions when pathologists can provide a more accurate diagnosis by being less precise.

Adenocarcinoma↗
PubMed2000

Chorionic villus sampling for sex determination in a western lowland gorilla (Gorilla gorilla gorilla).

Chorionic villus sampling was undertaken on an anesthetized gorilla (Gorilla gorilla gorilla) to determine the fetal sex in the first trimester of pregnancy. The tissue samples were subject to sex determination by polymerase chain reaction, fluorescent in situ hybridization, and cell culture with cytogenetic analysis. Polymerase chain reaction testing was found to be the most accurate and rapid method of sex determination on this tissue sample.

Animals↗
PubMed2000

Assessment of muscle oxygenation in the horse by near infrared spectroscopy.

This study examined the ability of near infrared spectroscopy (NIRS) to noninvasively determine changes to muscle oxygenation in the resting horse. Five horses had (NIRS) performed over extremity muscle while under general anaesthesia, first with 8 min limb ischaemia, then systemic hypoxaemia for 5 min. A second group of 6 awake horses had NIRS performed over extremity muscle while being administered hypoxic gas (F(I)O2 0.10) for 5 min, and after return to steady state, limb ischaemia was induced for an additional 5 min. In the anaesthetised horses' ischaemia induced marked and significant muscle deoxygenation of haemoglobin/myoglobin (P<0.01), with corresponding arterial saturation decreasing from 98.9 to 81.9%. Hypoxaemia induced small yet significant muscle deoxygenation (P<0.01) that was 3.2% of the ischaemia deoxygenation signal, with a corresponding decrease in arterial saturation from 98.6 to 90.4%. In the awake horses muscle deoxygenation was not detectable during hypoxia despite reduction of arterial saturation from 97.8 to 86.8%, whereas ischaemia induced rapid and significant deoxygenation of muscle (P<0.05), with corresponding reduction of venous saturation from 78.4 to 75.4%. In neither group of horses was there evidence of cytochrome aa3 reduction, despite complete ischaemia for up to 8 min. NIRS changes in the resting horse muscle clearly differed between ischaemia and hypoxaemia, and can readily show muscle deoxygenation in clinically relevant hypoxaemia in the horse under anaesthesia. Further, as the deoxygenation signal induced by ischaemia was clearly detectable above a background movement artefact, NIRS application to study of muscle oxygenation in the working horse should be explored.

Animals↗
PubMed2000

Intersession repeatability of macular thickness measurements with the Humphrey 2000 OCT.

PURPOSE: This study was designed to determine intersession repeatability of measurements of macular thickness made with a commercially available optical coherence tomography (OCT) system. The images that can be routinely acquired with the commercial instrument differ significantly in quality from the images in the literature, which have mostly been acquired on prototype systems. METHODS: Multiple OCT images of the nasal macula were obtained from the right eye during three independent measuring sessions, using the Humphrey 2000 OCT system (Humphrey, San Leandro, CA). Twenty-six volunteers with no history of ocular disease participated in this investigation. Eyes in all subjects were undilated during scan acquisition. Scans were horizontal, 3 mm long, and through the fovea. Five scans were used from each session, for a total of 15 scans per subject. Retinal boundaries were automatically detected using custom software. Statistical software was used to calculate intersession and intrasession repeatability. Manual correction was performed on the automatically detected boundaries, and a second analysis was performed using these boundaries. RESULTS: When no manual correction of boundaries was performed, there were no significant effects between different sessions (P = 0.529) or between different scans within the same session (P = 0.509). Average retinal thickness was found to be 274 +/- 17 microm for a 1-mm long region 0.75 mm from the fovea. Individual scan averages differed from overall patient averages by 0 +/- 4.3 microm (99% confidence interval, 11.2 microm). CONCLUSIONS: OCT measurements of macular thickness made with the Humphrey 2000 OCT system are repeatable over different sessions with an expected variation of less than 11 microm (99% confidence interval).

Adult↗
PubMed2000

Peripheral corneal contour measured by topography influences soft toric contact lens fitting success.

PURPOSE: Empirical fitting success is important to expanding the soft toric contact lens market. Previous study has lead to the hypothesis that lens flexure may alter expected fitting relationships and back vertex power (BVP) in situ. In this study, baseline topographic features as potential variables in predicting soft toric fitting success were analyzed. METHODS: One-hundred forty-nine eyes were empirically fit with back surface toric soft lenses after placido-based videokeratography was performed. Measurements recorded from baseline instantaneous maps included: flat simulated keratometry (Sim-K) value (in diopters) and axis, steep Sim-K value (in diopters) and axis, eccentricity of the flat meridian, and the form of corneal astigmatism. Astigmatism was classified as types I-V based upon differences between central and peripheral corneal toricity. RESULTS: Ninety-three of 149 (62.4%) eyes were successfully fit empirically with the first trial lens. One-hundred thirty-five of 149 (90.6%) eyes were ultimately successful after unsuccessful trial lenses were adjusted and reordered. There were no differences between the empirically fit success and failure groups in instrument reported eccentricity, Sim-K values, or Sim-K axes (P>0.05). Of 115 eyes classified for form of corneal astigmatism, 76 (66%) were classified with high or irregular peripheral astigmatism (types IV and V). There was a significant association between fitting success and the form of corneal toricity (P=0.0327). Thirty-nine of 115 (34%) eyes were classified as corneal types I-III (spherical or minimally toric corneal periphery) and were associated with empirical fitting success (P=0.0092). CONCLUSION: Empirical soft toric fitting success can be anticipated in spherical corneas, central astigmatism, or corneas with peripheral toricity which matches the central toricity. However, high and irregular peripheral corneal toricity occurs in the majority of astigmatic patients. Corneal topography is a valuable tool to assess peripheral astigmatism which may be one factor influencing unexpected lens performance.

Astigmatism↗
PubMed1999

Development of a protocol for the automated analysis of amino acids in brain tissue samples and microdialysates.

An automated precolumn derivatisation method has been developed for the measurement of fourteen amino acids in brain tissue and microdialysate samples. The method involves labelling amino acids with naphthalene-2,3-dicarboxaldehyde (NDA) in the presence of cyanide (CN-). The resulting highly stable N-substituted 1-cyanobenz[f]isoindole (CBI) derivatives were separated using a binary gradient elution profile and detected fluorometrically. The order of elution of the derivatised amino acids was confirmed by using liquid chromatography with fluorescence and mass spectrometric detection in tandem. Linear calibration plots were obtained for all amino acids in the range studied (0.2-12.5 microM). The limit of detection for CBI derivatives of amino acids was in the range 5-20 fmol (S/N=2) using a 5 microl injection volume. The method has been used for the measurement of amino acids in microdialysates from rat brain and tissue homogenates from different regions of mouse brain.

Amino Acids↗
PubMed1999

The implications of variation in outcome between health professionals for the design and analysis of randomized controlled trials.

Methodological work on randomized trials has largely concerned pharmacological interventions in which the effects of the attending health professional may be regarded as minor. In other clinical settings, such as surgery, talk or physical therapies, staff specific variation may make generalization problematic, undermining the value of the trial. Such variation has been the basis of some objections to controlled trial methodology and non-acceptance of trial results. The implication of this source of variation will be considered for studies in which different types of health professional deliver the intervention in each arm of the trial. Such a trial may involve individual patient or group randomization. Whichever method is used, it is argued that variation in outcome between health professionals may lead to design effects. These issues will be illustrated using data from a large trial comparing primary care service delivered by two types of medical doctor. Random effect models are most suitable for analyzing this type of trial, as they allow adjustment for patient characteristics whilst controlling for design effects. This type of model illustrates that there can be substantial variation in the performance within each category of doctor.

Bias↗
PubMed1999

Magma intrusion beneath long valley caldera confirmed by temporal changes in gravity

Precise relative gravity measurements conducted in Long Valley (California) in 1982 and 1998 reveal a decrease in gravity of as much as -107 +/- 6 microgals (1 microgal = 10(-8) meters per square second) centered on the uplifting resurgent dome. A positive residual gravity change of up to 64 +/- 15 microgals was found after correcting for the effects of uplift and water table fluctuations. Assuming a point source of intrusion, the density of the intruding material is 2.7 x 10(3) to 4.1 x 10(3) kilograms per cubic meter at 95 percent confidence. The gravity results require intrusion of silicate magma and exclude in situ thermal expansion or pressurization of the hydrothermal system as the cause of uplift and seismicity.

Journal Article↗
PubMed1999

Optical properties of human trabecular meshwork in the visible and near-infrared region.

BACKGROUND AND OBJECTIVES: Despite disparate treatment parameters, similar success in laser trabeculoplasty (LT) is attained using the argon (514.5 nm) and diode (810 nm) laser. However, the mechanism of this success remains unresolved. To further understand LT, this study characterizes the optical properties of trabecular meshwork (TM). STUDY DESIGN/MATERIALS AND METHODS: Reflectance was measured from 10 TM samples over wavelengths of 400-820 nm, using an integrating sphere/spectrophotometer. Corrections were made for reflections at boundaries of refractive index mismatch. Kubelka-Munk coefficients were calculated and converted to linear transport coefficients. RESULTS: Scattering greatly dominated absorption. The scattering and absorption coefficients were, respectively, 141.20 +/- 15.80 cm(-1) and 4.89 +/- 1.95 cm(-1) at 514.5 nm, and 94.44 +/- 15.03 cm(-1) and 0.0874 +/- 0.111 cm(-1) at 810 nm (estimated anisotropy of 0.90). The corresponding penetration depths (1/e) were 69 microm (514.5 nm) and 106 microm (810 nm). CONCLUSION: The absorption coefficient of 514 nm energy is two orders of magnitude greater than 810 nm energy, while scattering coefficients are much closer. The fluence used at 514.5 nm is higher at the surface than that at 810 nm, but falls below it deep within the TM due to the differential absorption. Therefore, similar initial therapeutic effects are obtained with 810 nm using less total absorbed energy. Thermal damage resultant from excess energy deposited at 514.5 nm may be related to the lack of success in repeat argon LT, pointing out the need for studies of repeat diode LT.

Anisotropy↗