Analysis of changes in optical fibers during arc-fusion splicing by use of quantitative phase imaging

A non-interferometric imaging technique in conjunction with Abel inversion is used to directly and quantitatively examine the changes in optical fibers due to the heating produced during arc-fusion splicing as a function of fusion arc parameters. Phase images in the vicinity of a fusion splice are obtained using Quantitative Phase Microscopy, allowing the refractive-index change to be reconstructed with high spatial resolution. This simple, nondestructive method confirms that, for a fixed arc current, while the fusion time increases, the refractive-index of both fiber cores within the fusion region decreases in magnitude, the core region broadens, and the axial gradient decreases.     

Self-assembled virus-like particles with magnetic cores

Efficient encapsulation of functionalized spherical nanoparticles by viral protein cages was found to occur even if the nanoparticle is larger than the inner cavity of the native capsid. This result raises the intriguing possibility of reprogramming the self-assembly of viral structural proteins. The iron oxide nanotemplates used in this work are superparamagnetic, with a blocking temperature of about 250 K, making these virus-like particles interesting for applications such as magnetic resonance imaging and biomagnetic materials. Another novel feature of the virus-like particle assembly described in this work is the use of an anionic lipid micelle coat instead of a molecular layer covalently bound to the inorganic nanotemplate. Differences between the two functionalization strategies are discussed.     

Correlation of tensile strength with fracture modes of KAOWOOL- and SAFFIL-reinforced 339 aluminum

The tensile strengths of composites of 339 aluminum reinforced with either SAFFIL or KAOWOOL fibers are compared over the temperature range of 20°C to 300°C. For this type of composite, in which the discontinuous fibers are randomly oriented, the fibers perpendicular to the applied stress play a critical role, which in turn creates a dependence upon the interfacial bond strength. The KAOWOOL fibers form a strong interfacial bond so that tensile failure occurs either in the matrix at 300 °C or by fiber cleavage at 20°C. In the T5 condition, the SAFFIL interface is weaker than the matrix alloy so that failure occurs by delamination of the transverse fibers. Thus, although the SAFFIL fibers are 40 pct stronger than the KAOWOOL fibers, the T5 composites have the same ultimate tensile strengths. A T6 heat treatment promotes an interfacial reaction with magnesium. This strengthens the SAFFIL interface so that failure occurs primarily in the matrix, producing higher composite strengths. The reaction with the KAOWOOL fibers is so extensive that the matrix, and therefore the composite strength, is drastically decreased. When account is taken of the different fracture modes, together with the matrix strengths as determined by nanoindentation, the calculated values of composite strength are in good agreement with experiment.     

Chromatographic purification for the determination of dissolved silicon isotopic compositions in natural waters by high-resolution multicollector inductively coupled plasma mass spectrometry

A procedure is described for accurate Si isotope ratio measurements by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). Dissolved silicon was preconcentrated and separated from other elements present in natural surface waters using anion-exchange chromatography. The optimized procedure provides virtually complete elimination of major inorganic constituents while maintaining Si recovery in excess of 97%. High-resolution capabilities of MC-ICPMS used in this study allow interference-free measurements of 28Si and 29Si isotopes using conventional solution nebulization sample introduction without aerosol desolvation. Owing to the magnitude of polyatomic ion contributions in the region of mass 30, mostly from 14N16O+, measurements of the 30Si isotope can be affected by tailing of the interference signals, making exact matching of analyte and nitric acid concentrations in all measurement solutions mandatory. Isotope abundance ratio measurements were performed using the bracketing standards approach and on-line correction for mass-bias variations using an internal standard (Mg). Uncertainties, expressed as 95% confidence intervals, for replication of the entire procedure are better than +/-0.18/1000 for delta29Si and +/-0.5/1000 for delta30Si. For the first time with MC-ICPMS, the quality of Si isotope abundance ratio measurements could be verified using a three-isotope plot. All samples studied were isotopically heavier than the IRMM-018 Si isotopic reference material.     

Investigating the effects of reduced size on the properties of ferroelectrics

A series of experiments has been undertaken to understand more about the fundamental origin of the thickness-induced permittivity collapse often observed in conventional thin film ferroelectric heterostructures. The various experiments are discussed, highlighting the eventual need to examine permittivity collapse in thin film single crystal material. It has been seen that dielectric collapse is not a direct consequence of reduced size, and neither is it a consequence of unavoidable physics associated with the ferroelectric-electrode boundary. Research on three-dimensional shape-constrained ferroelectrics, emphasizing self-assembled structures based on nanoporous alumina templates and on FIB-milled single crystals, is also presented, and appears to represent an exciting area for ongoing research.     

“I've seen it all before”: Explaining age-related impairments in object recognition. Theoretical comment on Burke et al. (2010).

Animal models are useful in elucidating the neural basis of age-related impairments in cognition. Burke, Wallace, Nematollahi, Uprety, and Barnes (2010) tested young and aged rats in several different protocols to measure object recognition memory and found that object recognition deficits in aged rats were consistent with these rats behaving as if novel objects were familiar, rather than familiar objects being treated as novel (that is, forgotten). A similar pattern of behavior has been observed in young rats with perirhinal cortex lesions. Moreover, age-related impairments in object recognition were uncorrelated with deficits in spatial learning in the water maze, a task that requires the integrity of the hippocampus and is also reliably impaired in aged rats. Taken together, these findings support functional specialization of structures within the medial temporal lobe “memory system,” as well as the independence of age-related deficits in different cognitive domains. They also potentially form a foundation for neurobiological study of age-related impairments in perirhinal cortex function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

OXYGEN LIMITATION IN MICROFLUIDIC BIOFUEL CELLS

Biofuel cells are devices that use biocatalysts (enzymes or microbes) to convert biochemical energy directly into electrical energy. Microfluidic biofuel cells exploit the lack of active mixing at microscale dimensions to eliminate the use of proton exchange membranes that separate anolyte and catholyte streams. Simulation of this system, by solving the governing 3-D conservation equations (flow, species transport), reveals that oxygen availability limits the performance of the cathode. An exponential decay in the availability of oxygen at the cathode is observed along the length of the microchannel, indicating that increasing the number of electrode pairs reduces the overall current density. This conclusion is consistent with experimental observations. Increasing electrolyte flow rates can reduce the mass transport limitations by decreasing the diffusion boundary-layer thickness, but disparity between the flow rates of the anolyte and catholyte can induce wastage of dissolved oxygen.     

Effects of high-pressure processing on the safety, quality, and shelf life of ready-to-eat meats

Ready-to-eat (RTE) meats (low-fat pastrami, Strassburg beef, export sausage, and Cajun beef) were pressure treated at 600 MPa, 20 degrees C, for 180 s to evaluate the feasibility of using high-pressure processing (HPP) for the safe shelf-life extension of these products. After processing, samples were stored at 4 degrees C for 98 days during which time microbiological enumeration and enrichments were performed. Additionally, sensory analyses were undertaken to determine consumer acceptability and purchase intent over the duration of storage. Counts of aerobic and anaerobic mesophiles, lactic acid bacteria, Listeria spp., staphylococci, Brochothrix thermosphacta, coliforms, and yeasts and molds revealed that there were undetectable or low levels for all types of microorganisms throughout storage. Comparison of consumer hedonic ratings for unprocessed and processed meats revealed no difference in consumer acceptability, and no deterioration in the sensory quality was evident for any of the products tested during the study. Additionally, inoculated pack studies were conducted to determine if HPP could be used as a postlethality treatment to reduce or eliminate Listeria monocytogenes and thus assess the potential use of HPP in a hazard analysis critical control point plan for production of RTE meats. Inoculated samples (initial level of 10(4) CFU/g) were pressure treated (600 MPa, 20 degrees C, for 180 s) and stored at 4 degrees C, and survival of L. monocytogenes was monitored for 91 days. L. monocytogenes was not detected by plating methods until day 91, but selective enrichments showed sporadic recovery in three of the four products examined. The results show that HPP at 600 MPa, 20 degrees C, for 180 s can extend the refrigerated shelf life of RTE meats and reduce L. monocytogenes numbers by more than 4 log CFU/g in inoculated product.     

MALTING AND BREWING WITH BARLEYS HAVING BLUE ALEURONES

Blue aleurones in barley are associated with elevated levels of polyphenolic materials such as anthocyanins and anthocyanidins. A rapid method has been developed for assessing the anthocyanin content of barleys, malts and worts. Malts were prepared from a range of barleys, some of which had intensely blue aleurones, while others were only slightly blue or showed no visible pigmentation. The malting quality of barley was not affected by aleurone colour and ales and lagers of sound flavour as well as acceptable analytical parameters were brewed from malts having pronounced blue aleurones. In some cases sweet worts prepared from blue aleurone malts had a slight pinkish tinge, but this disappeared during wort boiling, and beer colours were normal. Levels of anthocyanins in barley correlated with those in malt and in wort. However, the concentration of anthocyanins was unrelated to the amount of anthocyanogens or total polyphenols. High anthocyanin levels in either barley or beer had no deleterious effects on beer flavour or the rate of haze development.     

Farm‐Scale Experiments to Compare Infestation and Quality Changes in Malting Barley Stored at Three Moisture Contents

Comparison of changes in temperature, moisture content, infestation and germination were made in six aerated 20 t bins of malting barley. Two were at about 13.5% moisture content, three at about 15.5% moisture content, and one at about 16.5% moisture content. The grain started at between 20–25°C and, during aeration, fell at a rate dependent on the moisture content, damper grain being cooler, presumably due to evaporative cooling. The ‘high’ moisture content grain was often over 5°C cooler at 1m and 2m than the ‘low’ moisture content bins. Moisture uptake at the surface was related to bulk moisture content and trends in mite population changes were related to moisture content. Mite population achieved highest numbers at the grain surface but usually before the moisture content absorption was at its peak. They were commonest in the ‘high’ moisture content bin and least numerous in the ‘low’ moisture content bins. There were no apparent differences between bins in the numbers of insects trapped, for instance they were not less numerous in the coolest ‘high’ moisture content bin. However, the trends of numbers trapped followed a similar pattern in all bins; normally O. surinamensis and S. granarius only began to decline after nine weeks storage in December when temperatures fell below 10°C. Germination loss at the surface of the dampest bin was sufficient to cause rejection of the entire bulk for malting. Micromalting indicated that yield of extract and friability were particularly affected by the changes at the surface of the dampest barley.