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ABSTRACT: Some of the progress made in using Raman microscopy to examine the structure and micromechanics of polymer and inorganic fibres is reviewed. Examples of how the technique has been used to verify some of the theories of composite reinforcement are then given. Finally, a specific example of how Raman microscopy has been used, in conjuction with other approaches, to understand the micromechanics of the microbond test, which is often used to measure interfacial shear strength in composite systems, is presented.
Journal of Microscopy 08/2011; 169(2):155 - 161. · 1.63 Impact Factor
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Diabetic Medicine 06/2011; 29(2):284-5. · 2.90 Impact Factor
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ABSTRACT: It has been demonstrated that when aromatic polyamide fibres such as Kevlar 49 are subjected to mechanical deformation, significant frequency shifts are obtained for the peak position of the 1610 cm−1 Raman band using both 632·8 nm and 488 nm laser radiation. Two earlier reports of the deformation of fibres in a 488 nm argon ion laser beam reported no such frequency shifts. It has been shown that this wavelength of laser light can degrade Kevlar fibres. This causes premature failure of the fibres through chain scission and the fibres break at low strains before significant levels of stress or strain can be achieved. Hence, the previous conflicts can be resolved and it has been demonstrated that simultaneous Raman spectroscopy and mechanical deformation is a powerful method of following the micromechanics of fibre deformation.
Polymer International 02/2007; 24(2):71 - 76. · 1.90 Impact Factor
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ABSTRACT: The deformation micromechanics of single-fibre embedded model composites of poly(p-phenylene benzobisoxazole) (PBO) and poly(p-phenylene terephthalamide) (PPTA) fibres, embedded in an epoxy resin have been examined using synchrotron microfocus X-ray
diffraction. Single fibres (in air) were deformed and the c-spacing monitored to establish a calibration of crystal strain against applied stress. Subsequently, the variation in crystal
strain along fibres, embedded in the resin matrix was mapped using synchrotron microfocus X-ray diffraction. Raman spectroscopy
was then used to map molecular deformation on the same samples (recorded as shifts in the Raman band wavenumber) in order
to provide a complementary stress data. A shear-lag analysis was conducted on the axial fibre stress data in order to calculate
interfacial shear stress and identify different stress-transfer modes at fibre/resin interfaces. The results establish that
the axial fibre stress distributions measured by synchrotron microfocus X-ray diffraction correlate well with those obtained
using Raman spectroscopy. The interfacial shear stress data derived from the stress-transfer profiles also show a good degree
of correlation.
Journal of Materials Science 09/2006; 41(20):6813-6821. · 2.02 Impact Factor
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ABSTRACT: Diabetes and its complications are more prevalent among South Asians than people of European origin and there is some evidence that patients of South Asian origin with diabetes receive poorer quality care.
Longitudinal study of patients with diabetes in Blackburn, UK. Processes of care indicators [measurement of blood pressure (BP), cholesterol and glycosolated haemoglobin (HbA1c)] and values of these intermediate outcomes were extracted for all patients registered on a diabetes information system for the period 1995-2001. Differences in processes of care indicators and intermediate outcomes between ethnic groups were estimated after adjusting for the potential confounding factors of sex, age and socioeconomic status (SES). Generalized estimating equations were used to model trends and to test for differences in trends over time.
Process of care was similar in South Asian and European patients. Mean BP and cholesterol concentration fell during the study period. South Asians had a higher level of HbA1c throughout the study period. South Asians had lower levels of BP and cholesterol in 1995 but the differences diminished or were abolished over time. SES did not explain differences between ethnic groups. Analyses stratified by baseline levels of intermediate outcomes (above or within target) demonstrated improvements among above target patients were greater among European patients.
Processes of care indicators are similar in diabetic patients of South Asian and European origin, irrespective of SES. However, there are worrying differences in improvements over time in the intermediate outcomes, and glycaemic control remained poorer among patients of South Asian origin patients throughout.
Diabetic Medicine 10/2005; 22(9):1226-33. · 2.90 Impact Factor
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ABSTRACT: It is demonstrated that Raman spectroscopy can be used to study both the deformation micromechanics of high-performance aramid polymer fibres and of these fibres in model, single-fibre epoxy resin matrix composites. It is shown that the peak position of the 1610 cm−1 aramid Raman band shifts to lower frequency under the action of tensile stress or strain due to the macroscopic deformation leading to direct stretching of the polymer molecules. These strain-induced band shifts can be used to map the distribution of stress or strain along a discontinuous, aramid fibre inside an epoxy resin matrix from which the interfacial shear stress can be calculated. It is shown that the behaviour is consistent with that predicted by the classical shear-lag analysis. The technique was also used to study the fragmentation process for an aramid fibre in an epoxy resin matrix in which the matrix strain exceeds the failure strain of the fibre. It is further demonstrated that the technique can be used to compare the interfacial properties of aramid fibres where the interfacial shear stress is found to be higher for sized fibres than for those which have been de-sized.
Journal of Raman Spectroscopy 04/2005; 24(8):539 - 544. · 3.09 Impact Factor
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ABSTRACT: Our aim was to investigate trends in provision and outcomes of care by socio-economic status among patients with diabetes in Salford, United Kingdom.
Salford is a deprived urban area in North West England. Data for people with diabetes who were younger than 20 years of age (4034 patients in the year 1993 and 5671 by the year 2000) were extracted from the Diabetes Information System. Age-standardised means, proportions and attainment of targets were calculated for: processes of care indicators, intermediate outcomes and prescribing of preventive drug treatments in 1993 to 1994 and in 2000 to 2001 by quintiles of Townsend deprivation score. We did comparisons of means and proportions using age-adjusted linear regression and of trends using generalised estimating equations. Rate ratios for first microvascular and first macrovascular complication were estimated from proportional hazards models.
Marked improvements occurred in all indicators. For patients managed in primary care, blood pressure and cholesterol measurement increased from 53% to 64% (p<0.001) and 27% to 61% (p<0.001) respectively; whilst mean systolic blood pressure decreased from 147 to 140 mmHg (p<0.001) and cholesterol concentrations from 6.0 to 5.1 mmol/l (p<0.001). Mean HbA(1c) increased from 7.8 to 8.1% (p<0.001). Prescribing of aspirin, anti-hypertensive and lipid-lowering drugs increased greatly. Trends varied little by socio-economic status. Patients from more affluent areas generally received more frequent clinical monitoring and preventive treatments, and had a lower BMI (29.5 vs 30.2 kg/m(2); p=0.009) and HbA(1c) (7.8 vs 8.2% p=0.006), though risks of first microvascular or macrovascular complications were similar.
Improvements in process and outcomes of care are possible for patients from all socio-economic groups. Socio-economic deprivation does not preclude high quality diabetes care.
Diabetologia 06/2003; 46(6):750-9. · 6.81 Impact Factor
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ABSTRACT: Changes in crystal strain and crystallite orientation of three varieties of PBO fibre (namely PBO AS, HM and HM+) have been investigated during deformation from the analysis of diffraction patterns obtained across single filaments, using a synchrotron X-ray source. Crystal strain was measured from the positions of the meridional reflections and orientation calculated from azimuthal broadening of the equatorial reflections. It has been demonstrated that no difference in crystal strain across the fibre exists, with the calculated strain being equal between fibre skin and core at a given level of stress. Further skin-core crystallite orientation analysis (calculation of the orientation parameter
sin2 q
\left\langle {\sin ^2 \theta } \right\rangle
) proved that the AS fibre was the only PBO variety with a significant difference in orientation across the fibre, with the core region being less oriented due to the processing conditions. The skin and core orientation of all three fibres was found to improve with deformation, with the core of the AS fibre showing a significantly higher rate of improvement. This resulted in a similar level of orientation for both skin and core regions of the PBO AS fibre at high levels of stress. The fibre modulus was found to increase with the increasing initial degree of crystallite orientation. Furthermore, improvement in orientation with external stress was related to
sin2 q
\left\langle {\sin ^2 \theta } \right\rangle
= 0, with higher values resulting in greater shear forces on the crystallites and therefore a greater rate of orientation improvement.
Journal of Materials Science 04/2003; 38(10):2105-2115. · 2.02 Impact Factor
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ABSTRACT: Diabetic pregnancies have an increased risk of respiratory distress syndrome (RDS) and preterm delivery. Antenatal corticosteroids can prevent RDS but induce acute severe hyperglycaemia. We have developed a protocol which prevents hyperglycaemia and can be used easily by ward staff.
Intramuscular dexamethasone is given in two doses 12 h apart. Subcutaneous insulin and diet are continued but from the first dexamethasone dose until 12 h after the second, supplementary intravenous insulin is infused according to hourly blood glucose measurements. The protocol incorporates four graded sliding scales. The initial scale is selected according to the patient's current subcutaneous insulin dose and advanced if the blood glucose is > or = 10.1 mmol/l for 2 consecutive hours.
In a 10-month period eight (three gestational, five pre-gestational) women received antenatal corticosteroids from a total of 37 diabetic pregnancies. The median amount of supplementary intravenous insulin required was 74 U (range 32-88 U); the median glucose values achieved were 5.8-8.9 mmol/l. Seventy-five percent of glucose measurements were within an acceptable range of 4-10 mmol/l. Only one baby developed RDS.
Large amounts of supplementary intravenous insulin are needed to achieve even moderate glycaemic control. This protocol enables routine ward staff to manage this successfully.
Diabetic Medicine 01/2003; 20(1):73-5. · 2.90 Impact Factor
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ABSTRACT: To devise a system for assessing in-patient glycaemic control and care satisfaction in diabetic patients admitted to hospital for reasons other than their diabetes.
Consecutive January to March 2001 case-notes were reviewed. Admissions with acute metabolic complications, acute myocardial infarction and pregestational or gestational diabetes were excluded. Glycaemic control, frequency of blood monitoring and management of hyperglycaemia were recorded. The diabetes treatment satisfaction questionnaire was used to assess preadmission satisfaction with care. Post-admission a 12-stem questionnaire was used to assess satisfaction with in-patient diabetes management.
Hypoglycaemia was common. Although none developed a hyperglycaemic emergency, high blood glucose was prevalent and, frequently, persistent hyperglycaemia or recurrent hypoglycaemia was not acted on appropriately. The overall score for in-patient satisfaction with treatment was fair (4.1 +/- 1.8 on a six-point scale; 6 = very satisfied and 1 = very dissatisfied). Scores were higher among patients on surgical wards than on medical wards (P = 0.008), but satisfaction did not vary when patients were stratified according to sex, age and mode of treatment.
Current systems are not achieving satisfactory in-patient glycaemic control and there is poor satisfaction with medical in-patient diabetes care. Following changes intended to produce improvements, this assessment system can be used recurrently to monitor in-patient care and satisfaction.
Diabetic Medicine 06/2002; 19(5):412-6. · 2.90 Impact Factor
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Mineral Processing and Extractive Metallurgy IMM Transactions section C 11/2001; 110(3):169-175.
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ABSTRACT: Fungal infection of diabetic foot ulcers has not been described. We analysed the features of 17 patients with diabetic foot ulcers probably infected with fungi.
Seventeen patients were identified with clinically infected foot ulcers, (i) which had failed to heal despite prolonged antibiotic therapy and intensive podiatric care, (ii) from which Candida spp. was isolated or hyphae +/- yeasts were visualized in material from ulcers or surrounding skin.
Multiple ulcers arising simultaneously were present in 10 patients (59%), preceded by blistering in seven cases. Single ulcers with markedly ulcerated margins were present in seven (41%) patients and were preceded by blisters in two. All 17 cases had neuropathy and 15 (88%) had severe peripheral vascular disease. All ulcers responded to antifungal therapy.
Candida spp. is associated with two distinctive patterns of protracted ulceration in diabetic feet which improve following systemic antifungal therapy. Diabet. Med. 18, 567-572 (2001)
Diabetic Medicine 08/2001; 18(7):567-72. · 2.90 Impact Factor
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ABSTRACT: To investigate the relationship among plantar foot pressure, plantar subcutaneous tissue thickness, severity of neuropathy (vibration perception threshold [VPT]), callus, and BMI in a large group of neuropathic diabetic patients at risk of foot ulceration.
A total of 157 diabetic neuropathic patients (VPT >25 V) without either peripheral vascular or ulcer history were studied. Plantar foot pressure and plantar tissue thickness were measured at each metatarsal head (MTH) using an optical pedobarograph and an ultrasound scanning platform, respectively.
A significant association was observed between peak plantar pressure and plantar tissue thickness at all MTHs (-0.26 < r < -0.61, P < 0.0001), with the least pronounced association at the first MTH. In addition, the pressure time integral was significantly associated with plantar tissue thickness (-0.24 < r < -0.57, P < 0.0001). BMI was significantly related to plantar tissue thickness (0.18 < r < 0.45, P < 0.05), but not to peak forefoot pressures. Subjects with callus had significantly reduced plantar tissue thickness at all MTHs except the first MTH and increased peak pressures at all MTHs (P < 0.001).
This study confirms a strong inverse relationship between plantar tissue thickness and dynamic foot pressure measurements. Long-term follow-up of this patient population will confirm whether reduced plantar tissue thickness predicts the development of diabetic foot ulcers.
Diabetes Care 08/2001; 24(7):1270-4. · 8.09 Impact Factor
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Diabetes, nutrition & metabolism 05/2001; 14(2):104-7.
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ABSTRACT: This research is concerned with an investigation into the determination of the micromechanical properties of particulate form of cellulose; namel microcr stalline cellulose. Using the technique of Raman spectroscop the shift in the 1095cm–1 Raman band, characteristic of cellulose, with strain is monitored and compared to the deformation of natural cellulose fibres (flax and hemp). From the values of the shift rate of the 1095cm–1 band for flax and hemp and the experimentally-determined value for microcrystalline cellulose the value for the Young's modulus of microcrystalline cellulose was estimated to be 254GPa. It has been shown that this value is consistent with the measured degree of crystallinity of microcrystalline cellulose. Theoretical modelling has also enabled the Young's modulus for compacted microcrystalline cellulose to be determined for fibres in either 2-D in-plane and 3-D arrangements. These values have been show to be consistent with recent direct measurements of the modulus of compacted material.
Cellulose 01/2001; 8(3):197-207. · 3.60 Impact Factor
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ABSTRACT: This paper constitutes the first part of a study to assess the influence of processing conditions on the final properties of poly(p-phenylene benzobisoxazole) PBO fibres. Three different samples were selected: as-spun (AS), high-modulus (HM), and ultra-high modulus (HM+) fibres. Synchrotron radiation was used to obtain single-fibre diffraction patterns. It is the first time this approach is taken to estimate the effects of deformation on the crystal properties of PBO fibres. The crystal modulus of the different types of fibre was calculated from the variation with stress of the c-spacing determined from the shift of the (005) and (006) reflections. The HM fibre was found to have the highest crystal modulus of the three fibres, with AS and HM+ PBO being lower. In comparison with tensile data, none of the fibres were found to have a Young''s modulus near to the crystal modulus value, although the HM+ fibre was closest due to its production route. These results could be compared to previous diffraction experiments, where the crystal modulus of PBO fibres were determined using fibre-bundles, assuming homogeneous stress in the bundle. Also, Raman spectroscopy experiments were carried out to examine the differences in Raman bandshift rates in response to both stress and strain. The Raman results showed both the HM and HM+ fibres to have stress-induced bandshifts of approximately –4 cm–1/GPa. The AS fibre value was significantly lower, this being attributed to the non-uniformity of the fibre cross-section. The strain-induced Raman bandshifts were found to be dependent on the tensile modulus of the fibre.
Journal of Materials Science 01/2001; 36(13):3079-3087. · 2.02 Impact Factor
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ABSTRACT: To examine changes in diabetes care provision after the introduction of a district diabetes information system.
All patients with diabetes registered on the system between 1993 and 1998 (n = 6544) were included in the analysis. Drop-out cohort analysis was used to handle population changes, logistic regression models with general estimating equations were used to examine changes in clinical performance over time.
After the introduction of the system, care processes improved appreciably, in both primary and secondary care. The proportion of patients receiving a preventative care review within the calendar year rose from 56% in 1993 to 67% in 1998. The proportion of these in whom each process was completed improved in all categories from 1993 to 1998: blood pressure 96% to 98%; glycaemic check 67% to 93%; lipid check 31% to 68%; renal check 46% to 87%; fundoscopy 79% to 92%; foot screen 87% to 87%. Similarly there was an increase in the proportion of patients achieving intermediate outcome treatment targets (HbA1c < or = 9.0% from 29% to 43%; cholesterol < or = 5.5 mmol/1 5% to 19%; blood pressure < or = 160/90 37% to 46%).
Our results suggest appreciable improvements in diabetes care between 1993 and 1998. These changes apply to an entire population of patients across primary and shared care. We believe that these improvements could, in part, be attributable to the way in which the district diabetes information system has facilitated the structured cascade of diabetes care.
Diabetologia 07/2000; 43(7):836-43. · 6.81 Impact Factor
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ABSTRACT: A reduction of 50% or more in diabetes-related amputations is a primary target of the St Vincent Declaration. This is thought to be achievable because both primary and secondary preventative healthcare strategies are effective in reducing the incidence of diabetic foot ulceration and progression to amputation. Unfortunately there is a group who cannot benefit from preventative health care, that is, newly diagnosed diabetic patients with already established severe complications. Using our population-based district diabetes information system we investigated, during the period 1 January 1992 to 31 December 96, the incidence and prevalence of lower extremity amputations (LEAs) and the proportion occurring in patients newly or recently diagnosed as having diabetes. Seventy-nine diabetic patients (59 male, 20 female) were recorded as having had 94 LEAs, the incidence of diabetes-related LEA being 475 per 100,000 diabetic patient-years. Of these LEAs 16 (20.2%) were performed within 1 year of diabetes being diagnosed. This study highlights an appreciable and previously unrecognized problem: patients presenting with established complications of diabetes who cannot benefit from secondary preventative healthcare. These patients pose a potential obstacle to achieving targets for reductions in diabetes-related amputations.
Diabetic Medicine 10/1998; 15(9):760-4. · 2.90 Impact Factor
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ABSTRACT: Observations have been made on the structure of the paranodal region at nodes of Ranvier in the sural nerve of patients with diabetic sensory polyneuropathy. The structure of the paranodes was examined with particular attention to the definition and assessment of axoglial dysjunction, which has been claimed to be a characteristic feature of both human and experimental diabetic neuropathy and which has been related to paranodal swelling. In the present series of cases it was not possible to confirm that axoglial dysjunction is a distinctive feature of diabetic polyneuropathy in fibres not undergoing active demyelination or wallerian-type degeneration, neither was excessive paranodal enlargement found.
Acta Neuropathologica 01/1997; 92(6):614-20. · 9.32 Impact Factor
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ABSTRACT: IGF-I and -II levels are altered in patients with atherogenic lipid profiles and may contribute to the development of macrovascular disease in NIDDM. We examined cardiovascular risk factors, IGF-I, IGF-II and IGFBP-1 in 74 NIDDM patients analysed as a whole group and according to treatment type. IGF-I was not significantly associated with cardiovascular risk factors but IGF-II levels correlated positively with total and LDL cholesterol most markedly in the diet treated group (0.72, p < 0.01 and 0.76, p < 0.01 respectively). In the whole group reduced IGFBP-1 levels were significantly associated with factors known to increase cardiovascular risk: i.e. low HDL cholesterol (0.31, p < 0.01) and elevated blood pressure (-0.35, p < 0.01), BMI (-0.37, p < 0.01), insulin (-0.29, p < 0.01) and proinsulin (-0.24, p < 0.01). In the treatment groups IGFBP-1 was lower in patients on diet alone (n = 11, 42.6 +/- 11.6 mu g/l) and sulphonylurea +/- insulin (n = 39, 53.2 +/- 7.6 mu g/l) relative to insulin treatment (n = 24, 103.0 +/- 19, 7 mu g/l, p < 0.05). The lower levels of IGFBP-1 were not due to a significant change in phosphorylation status from the highly phosphorylated circulating form since lesser and non-phosphorylated variants were undetectable in 53/74 patients. Multiple regression analysis revealed the best predictors of IGFBP-1 were BMI and MAP (R2 = 0.2. p < 0.001) and for blood pressure, IGFBP-1 and age (R2 = 0.47, p < 0.001). These findings indicate that in NIDDM patients low IGFBP-1 levels are associated with multiple factors predisposing to atherogenesis.
Journal of Clinical Endocrinology & Metabolism 03/1996; 81(2):860-3. · 6.50 Impact Factor
