Fluorescence scanning near-field optical microscopy of polyfluorene composites

Fluorescence scanning near-field optical microscopy (SNOM) is used to investigate binary polyfluorene-based composites of varying composition. The samples investigated contain blends of the polymer poly(9,9'-dioctylfluorene-cobenzothiadiazole), F8BT, with similar polyfluorenes of wider band gap. Images acquired from a film containing 50% by weight F8BT exhibit a high degree of correlation between the topography and fluorescence, with an F8BT-rich phase which protrudes from the surface of the film forming isolated regions with sizes from hundreds of nanometres to several micrometres. A film containing 10% by weight F8BT also has micrometre-size F8BT-rich regions, but also present are small and locally varying proportions of F8BT in the other polyfluorene component phase, indicating a hierarchy of phases within this sample. The fluorescence and topographic images of a third sample studied, containing 90% by weight F8BT, display no correlation, demonstrating that it is not always appropriate to use topographic information to determine the phase structure within polymer blends. The fluorescence SNOM images acquired from these samples are able to assist our understanding of the photovoltaic efficiency of devices fabricated from these films, which are governed by the extent of the interfacial area between these two constituent polymers.     

Micron and sub-micron level hardness testing for failure analysis

The important aspects of microhardness and nanohardness testing for failure analysis applications are reviewed. Fundamentals of hardness testing and measurement are discussed. Popular indenter geometries are addressed, with their benefits and limitations highlighted. Common applications of hardness testing to determine mechanical property data are outlined. The most common problems associated with small length scale hardness testing, such as the indentation size effect (ISE) and indentation induced cracking (IIC), are discussed. Practical solutions to these problems are presented and their overall implications discussed.     

Comparison of 14C-sucrose delivery to the brain by intravenous, intraventricular, and convection-enhanced intracerebral infusion

OBJECT: The authors evaluated convection-enhanced delivery (CED) of 14C-sucrose to the rat brain as a method of enhancing cerebral drug delivery and compared it with intravenous (i.v.) and intraventricular (i.v.t.) routes of administration. METHODS: Groups of rats received 14C-sucrose by bolus i.v. infusion, i.v.t. infusion for 1, 2, or 7 days at 0.17 microl/minute, or CED at rates from 0.01 to 0.5 microl/minute for periods from 1 hour to 7 days. Radioisotope distribution and concentration in tissue were analyzed using quantitative autoradiography. Intravenously administered sucrose reached the entire brain, but levels in tissue were low. After i.v.t. administration, sucrose levels in tissue were high at, and declined exponentially away from, the ventricular surface. Chronic CED administration maintained high levels of sucrose in tissue that focally were up to 10,000 times higher than in the i.v. group. The isotope distribution pattern after chronic CED infusions indicated a central component that resulted from convention and a peripheral component in gray matter that was the result of diffusion. The brain influx (0.42 microl/g/min) and diffusion constants of sucrose (2.8 x 10(-6) cm2/second) were similar to reported values. The total brain efflux constant was 0.0044 minute, whereas the blood-brain barrier (BBB) efflux constant was 0.0016 minute. There were no pathological changes in the brains after CED except those associated with cannula insertion. Sucrose, which was thought to be inert, was found to interact with brain tissue; up to 25% was bound to an unidentified tissue component. CONCLUSIONS: Chronic CED appears to be a potentially useful method for significantly circumventing the BBB and increasing delivery of water-soluble drugs to the brain.     

Characterisation of oat bran products with and without supercritical carbon dioxide extraction

Morphology, starch structures and thermal and pasting properties of oat bran concentrate (OBC) and Nutrim‐OB (NOB), a jet‐cooked oat bran product, with or without supercritical carbon dioxide extraction (SCD) were studied. Oil composition was analysed. OBC had three thermal transitions, starch gelatinisation and two amylose–lipid complex transitions. NOB only had amorphous amylose–lipid transition. SCD significantly decreased gelatinisation temperatures of OBC. Pasting properties, showed NOB had significantly higher peak viscosity and breakdown, with significantly lower final viscosity, setback and pasting temperature compared with OBC. SCD increased peak viscosity for NOB and final viscosity for OBC. Thermogravimetric analysis showed NOB had higher water‐holding capacity (WHC) than OBC, while SCD decreased WHC. Amylopectin molecular weight was 3.4 × 10⁸ for OBC and was significantly lower for NOB (1.4 × 10⁸). Predominant fatty acids were oleic (41%), linoleic (38%) and palmitic (16%). Study showed NOB had different properties from OBC thereby expanding industrial applications.     

Real-time measurement of radiation exposure to patients during diagnostic coronary angiography and percutaneous interventional procedures

An important research question in the study of the genetics of coronary artery disease (CAD) is whether information about genetic variation will improve our ability to predict CAD beyond established risk factors. This question is especially relevant to the goal of identifying young, asymptomatic adults with coronary atherosclerosis who would benefit most from interventions to reduce risk. Coronary artery calcification (CAC) detected by electron-beam computed tomography is a relatively new method for detecting coronary atherosclerosis in asymptomatic individuals that has been shown to be a more accurate indicator of coronary atherosclerosis in asymptomatic individuals than other noninvasive techniques. In a study of asymptomatic women (n=169) and men (n=160) between the ages of 20 and 59 representative of the Rochester, Minnesota population, we used logistic regression to ask whether the most common Apolipoprotein (Apo) E genotypes (epsilon3/2, epsilon3/3, and epsilon4/3) predict the presence of CAC. The addition of information about ApoE genotypes to logistic models containing each separate risk factor did not improve prediction of CAC (P>0.10 in both women and men). However, there was significant evidence (P<0.10) that associations between variation in the probability of having CAC and variation in body mass index, plasma total cholesterol, and plasma ApoB in men and body mass index, plasma triglycerides, plasma ApoA1, and plasma ApoE in women were dependent on ApoE genotype. Thus, variation in the gene coding for ApoE may play a role in determining the contribution of established risk factors to risk of CAC.     

Novel critical point drying (CPD) based preparation and transmission electron microscopy (TEM) imaging of protein specific molecularly imprinted polymers (HydroMIPs)

We report the transmission electron microscopy (TEM) imaging of a hydrogel based molecularly imprinted polymer (HydroMIP) specific to the template molecule bovine haemoglobin (BHb). A novel critical point drying based sample preparation technique was employed to prepare the molecularly imprinted polymer (MIP) samples in a manner that would facilitate the use of TEM to image the imprinted cavities, and provide an appropriate degree of both magnification and resolution to image polymer architecture in the <10 nm range. For the first time, polymer structure has been detailed that tentatively suggests molecularly imprinted cavities, ranging from 5 to 50 nm in size, that correlate (in terms of size) with the protein molecule employed as the imprinting template. The modified critical point drying sample preparation technique used may potentially play a key role in the imaging of all molecularly imprinted polymers, particularly those prepared in the aqueous phase.     

Long-term ageing and materials degradation of hybrid mica compressive seals for solid oxide fuel cells

Hybrid phlogopite mica seals with silver interlayers were evaluated in long-term isothermal ageing tests in a dual environment consisting of dilute hydrogen versus air at 800 °C. High-temperature leak tests with helium showed very stable leakage of 0.01-0.02 sccm cm⁻¹ for 28,366 h under a low applied compressive stress of 82 kPa (12 psi). Post-mortem SEM and EDS analyses of the mica showed minimum degradation in terms of changes in microstructure and chemical composition, although there appeared to be some Ag migration and segregation at interstices between mica flakes. Fluorine was also found to be released from mica. Overall, the low, constant leakage through the hybrid mica/Ag seals clearly demonstrated a very promising candidate for SOFC sealing.