A novel nano-bubble inflation method for determining the viscoelastic properties of ultrathin polymer films.

We describe a novel experimental technique for measuring the absolute creep compliance of ultrathin polymer films. The method is based on the classical bubble inflation technique for measuring the biaxial creep compliance of films, reduced in size to measure films with thicknesses down to at least 11.3 nm. The method uses the imaging capabilities of the atomic force microscope (AFM) to determine the time evolution of the geometry of nano-bubbles and thus avoids the problems with data interpretation that can arise due to "contact mechanics" issues when the AFM is used as a direct mechanical testing device.

Novel nanobubble inflation method for determining the viscoelastic properties of ultrathin polymer films.

We describe a novel experimental technique for measuring the viscoelastic properties of ultrathin polymer films. The method is based on the classic bubble inflation technique for measuring the biaxial creep compliance of films, reduced in size to measure films with thicknesses down to at least 13 nm. The method uses the imaging capabilities of the atomic force microscope to determine the time evolution of the geometry of nanobubbles. Using these data, along with the applied pressure, the absolute creep compliance of the films can be determined.

Dramatic stiffening of ultrathin polymer films in the rubbery regime.

Recently, we (P.A. O'Connell, G.B. McKenna, Science 307, 1760 (2005)) introduced a novel nano-bubble inflation method to measure the absolute creep compliance of nanometer thick polymer films. In that work it was shown that even at film thicknesses as small as 27.5nm the glass temperature was unchanged for poly(vinyl acetate) (PVAc). Perhaps more importantly, and the subject of the present work, was the observation that these ultrathin films show a dramatic stiffening in the rubbery plateau regime, i.e., the compliance was reduced by over two orders of magnitude compared to the bulk material. In the present work we substantiate the previous results in a study of the thickness dependence of the rubbery compliance of PVAc and polystyrene (PS) films for thicknesses from 13nm to 276nm. We show the substantial stiffening of the plateau region for both materials. Furthermore, the rubbery compliance (inverse of stiffness) scales with approximately the second power ( 1.8+/-0.2) in the film thickness for both materials.

Rheological measurements of the thermoviscoelastic response of ultrathin polymer films.

Measurement of the thermoviscoelastic behavior of glass-forming liquids in the nanometer size range offers the possibility of increased understanding of the fundamental nature of the glass-transition phenomenon itself. We present results from use of a previously unknown method for characterizing the rheological response of nanometer-thick polymer films. The method relies on the imaging capabilities of the atomic force microscope and the reduction in size of the classical bubble inflation method of measuring the biaxial creep response of ultrathin polymer films. Creep compliance as a function of time and temperature was measured in the linear viscoelastic regime for films of poly(vinyl acetate) at a thickness of 27.5 nanometers. Although little evidence for a change in the glass temperature is found, the material exhibits previously unobserved stiffening in the rubbery response regime.

Foot deformities in children with cerebral palsy.

Clinical observation suggests that deformities of the foot and ankle are common in children with cerebral palsy. Two hundred children with cerebral palsy attending the Central Remedial Clinic were examined and photographed. The children had no previous surgical intervention and were between 1.5 and 19 years of age. Deformities were assessed and related to the type of cerebral palsy and mobility status.

Fate and risk evaluation of persistent organic contaminants and related compounds in Victoria Harbour, Hong Kong.

The Environment Protection Department of Hong Kong has a monitoring program for persistent organic contaminants in sediments of Victoria Harbour, the main harbour of Hong Kong. A fugacity model has been used, based on this sedimentary data, to estimate inputs to the system (probably from sewage, stormwater and industrial discharges) as well as the fate of the contaminants, particularly in terms of the aqueous and biotic concentrations. The risk of deleterious effects on the natural marine system, as well as on the consumers of seafood from the system, was carried out using the estimated aqueous and biotic concentrations together with accepted environmental quality guidelines. The result of our analysis indicated that the chlorohydrocarbons, PCBs (as Aroclor 1254) total DDT and total HCH pose a significant risk, and probably have caused damage to the marine ecosystem as well as posing a hazard to seafood consumers. Much higher concentrations of the less toxic total alkanes, nonaromatic hydrocarbons, linear alkyl benzenes and the compounds giving a unresolved complex mixture (UCM) cannot be evaluated due to a lack of environmental guidelines and the complexity of these substances. However, it is probable that these substances add adverse effects to those due to the other contaminants.

Prodromal chest pains: clues to the pathogenesis of non-Q wave acute myocardial infarction?

Prodromal chest pains were recorded from consecutive admissions to a single coronary care unit and the symptoms of those with Q wave and non-Q wave acute myocardial infarction were compared. Of 809 admissions there were 201 with Q wave ad 88 with non-Q wave infarction. The non-Q wave infarction group was older, included more women and a greater proportion had suffered a previous myocardial infarct. Effort angina was equally common in both groups, but in the Q wave infarction group, angina was more often of recent onset, within the previous 4 weeks. Symptoms to indicate worsening angina, more prolonged, intense or frequent pain, were equally common in both groups. These findings suggest that although the extent of coronary artery disease may differ, Q wave and non-Q wave myocardial infarction share a common pathogenic mechanism.

Predictors of risk in patients with unstable angina admitted to a district general hospital.

OBJECTIVE: To observe the long-term prognosis of patients with unstable angina and select simple criteria to identify high and low risk subgroups. DESIGN: A six month prospective survey with three year follow up. SETTING: One eleven bed coronary care unit. PATIENTS: All patients admitted with chest pain in whom no infarct was confirmed by subsequent electrocardiographic or enzyme changes and for whom no alternative cause of chest pain was found were studied. Unstable angina was also diagnosed if there was evidence of myocardial ischaemia in the form of previous effort angina, previous myocardial infarction, or if transient electrocardiographic changes accompanied the pain. When none of the above were present, chest pain without a known cause, was diagnosed. INTERVENTIONS: No routine intervention. Angiography and revascularisation for persistent symptoms despite medical treatment. OUTCOME MEASURES: Death or non-fatal infarction. RESULTS: In the 141 patients with unstable angina there were eight deaths and five non-fatal infarctions during the first eight weeks. Symptoms of increasing angina before admission were similar in all three groups and did not help predict early complications. Recurrence of pain in hospital, a rise in cardiac enzymes to less than twice the upper limit of normal, and transient electrocardiographic changes were all associated with an increased risk of early events. The presence of either abnormal enzyme activity or more than five episodes of pain in hospital identified a group of 49 in whom 11 of the 13 early events occurred. After three years, 29 of the 141 patients had died and eight had had infarctions (overall event rate 26%). Seventeen had undergone revascularisation (12%) and 51 (36%) were on antianginal treatment. Thirty six (26%) were still alive, without new myocardial infarction, and were free of angina. In the 29 patients with chest pain without a known cause there were no early events and only one non-fatal infarction during the three year follow up. CONCLUSION: When patients are admitted to the coronary care unit with chest pain not due to myocardial infarction, the history, electrocardiography and measurement of cardiac enzymes are sufficient to identify high and low risk subgroups.

The effects of age and renal impairment on the pharmacokinetics of co-administered lisinopril and hydrochlorothiazide.

The pharmacokinetics of combined lisinopril and hydrochlorothiazide have been studied following single and multiple oral doses to 'young' (reference), elderly and renally impaired hypertensive patients. Tablets containing the fixed combination of lisinopril 20 mg and hydrochlorothiazide 12.5 mg were administered as a single dose followed by daily administration for 6-8 days. Serum concentration and haemodynamic measurements were made at intervals up to 48 hours after the first and last doses. The serum profiles of both drugs were comparable with observations from previous studies, showing higher concentrations in the elderly and in the renally impaired patients. Similar differences have been reported for such patient groups when the drugs were administered separately, indicating an absence of pharmacokinetic interaction. Both drugs accumulated by about 30% on multiple daily dosing. There were no differences between the patient groups in the extent of accumulation. The combination of lisinopril and hydrochlorothiazide produced the expected hypotensive response, minimum BP values being recorded 4 and 6 hours after treatment. The higher concentrations in the elderly and renally impaired patients were not associated with a greater reduction in BP. The pharmacokinetic behaviour of lisinopril and hydrochlorothiazide given together to elderly and renally impaired hypertensive patients suggests that a fixed dose combination is appropriate and that no changes to the dosage regimen additional to those used for the individual agents are necessary.

Refractive index determination using an orthogonalized dispersion equation.

An orthogonal form of a general three-term dispersion equation is presented which is useful for determination of the refractive index of transparent optical materials from measured spectral data. The orthogonal basis functions are dependent on the spectral range of the data and whether the spacing of the data is uniform with respect to wavelength or wavenumber. The application of the technique to the reduction of ellipsometric measurements of a single layer thin film of zirconia on a fused silica substrate is presented. The measured data were fit to a Conrady dispersion equation and to the corresponding orthogonal basis set. The convergence to the solution was an order of magnitude faster for the orthogonal form of the dispersion equation.

Prevalence of angina as assessed by a survey of prescriptions for nitrates.

Prescriptions for nitrates issued during a 6-month period in the Nottingham Health District were used to estimate the prevalence of patients thought to have angina who might potentially require specialist investigation and treatment. The 15,451 prescriptions issued were for 6856 patients. Of these, only 435 were known to hospitals. The general practitioner records of 499 patients identified from a 10% sample of general practitioners showed that in 96% the general practitioner had prescribed a nitrate for the treatment of angina. The records of five large practices with some form of diagnostic register suggested, however, that the survey detected only 73% of patients thought to have angina. With these estimates of specificity and sensitivity the prevalence of angina in Nottingham was calculated to be 1.5%. Few of the patients identified had been investigated in detail, and only 26% had attended hospital in the 3 years before the survey. There is clearly a very large potential demand for hospital resources for the investigation and treatment of angina.

Chemiluminescence of guinea pig peritoneal macrophages stimulated by immune precipitates and soluble immune complexes.

The chemiluminescence (CL) response of guinea pig peritoneal macrophages to immune precipitates and soluble immune complexes has been investigated. The rapid burst of intense light emission observed in response to both stimuli, was inhibited by superoxide dismutase (SOD). With soluble immune complexes, this was followed by prolonged CL of lower intensity susceptible to both SOD and catalase inhibition. The magnitude of the CL response was directly related to seize the size of the soluble complexes reacting with the macrophages. These findings suggest that circulating, as distinct from deposited immune complexes, may play a role in the pathogenesis of complex-mediated diseases.