Spectral background and transmission characteristics of fiber optic imaging bundles

The emission and transmission properties of three commercially produced coherent fiber optic imaging bundles were evaluated. Full fluorescence excitation versus emission data were collected from 250 to 650 nm excitation for high-resolution Sumitomo, Fujikura, and Schott fiber bundles. The results generated show regions of autofluorescence and inelastic Raman scattering in the imaging bundles that represent a wavelength-dependent background signal when these fibers are used for imaging applications. The high-resolution fiber bundles also exhibit significant variation in transmission with the angle of illumination, which affects the overall coupling and transmission efficiency. Knowledge of these properties allows users of high-resolution imaging bundles to optimally design systems that utilize such bundles.     

Unfermented and fermented rooibos teas (Aspalathus linearis) increase plasma total antioxidant capacity in healthy humans

The aim of the study was to assess the effect of drinking rooibos tea (Aspalathus linearis) on total antioxidant capacity (TAC), lipid triacylglycerols, cholesterol and glycaemia plasma levels in humans. In vitro, unfermented rooibos tea displayed a 28% higher value of TRAP than did the fermented beverage. An acute intervention study, cross-over design, was performed, with 15 healthy volunteers who consumed 500 ml of either water, unfermented or fermented rooibos teas. Plasma antioxidant capacity increased significantly with both teas, reaching a peak at 1 h post-consumption (+6.6%, p < 0.05 fermented tea; +2.9%, p < 0.01 unfermented tea). No changes in triacylglycerols, cholesterol or uric acid were observed with any of the treatments. A transitory increase in glycaemia at 30 min was linked to glucose upload. The data show that rooibos teas represent a source of dietary antioxidants in humans.     

Targeted Analysis of Sphingolipids in Turkeys Fed Fusariotoxins: First Evidence of Key Changes That Could Help Explain Their Relative Resistance to Fumonisin Toxicity

The effects of fumonisins on sphingolipids in turkeys are unknown, except for the increased sphinganine to sphingosine ratio (Sa:So) used as a biomarker. Fumonisins fed at 20.2 mg/kg for 14 days were responsible for a 4.4 fold increase in the Sa:So ratio and a decrease of 33% and 36% in C14-C16 ceramides and C14-C16 sphingomyelins, respectively, whereas C18-C26 ceramides and C18-C26 sphingomyelins remained unaffected or were increased. Glucosyl- and lactosyl-ceramides paralleled the concentrations of ceramides. Fumonisins also increased dihydroceramides but had no effect on deoxysphinganine. A partial least squfares discriminant analysis revealed that all changes in sphingolipids were important in explaining the effect of fumonisins. Because deoxynivalenol and zearalenone are often found in feed, their effects on sphingolipids alone and in combination with fumonisins were investigated. Feeding 5.12 mg deoxynivalenol/kg reduced dihydroceramides in the liver. Zearalenone fed at 0.47 mg/kg had no effect on sphingolipids. When fusariotoxins were fed simultaneously, the effects on sphingolipids were similar to those observed in turkeys fed fumonisins alone. The concentration of fumonisin B1 in the liver of turkeys fed fumonisins was 0.06 µmol/kg. Changes in sphingolipid concentrations differed but were consistent with the IC50 of fumonisin B1 measured in mammals; these changes could explain the relative resistance of turkeys to fumonisins.     

Optimisation of a humidity chamber method for the quantitative evaluation of vapour phase corrosion inhibitors for mild steel

During manufacturing, storage and transport, corrosive substances in the environment easily attack metal items. Corrosion inhibitors are substances, which, when added to corrosive environments in relatively small dosages, will drastically reduce corrosion rates. Vapour phase corrosion inhibitors or volatile corrosion inhibitors (VCIs), also called vapour phase inhibitors (VPIs), are similar to the organic adsorption-type inhibitors but they possess a high vapour pressure.     

A coupled Ericksen/Allen–Cahn model for liquid crystal droplets

We present a model and discretization that couples the Ericksen model of liquid crystals with variable degree of orientation to the Allen–Cahn equations with a mass constraint. The coupled system models liquid crystal droplets with anisotropic surface tension effects due to the liquid crystal molecular alignment. The total energy consists of the Ericksen energy, phase-field (Allen–Cahn) energy, and a weak anchoring energy that couples the liquid crystal to the diffuse interface. We describe our discretization of the total energy along with a method to compute minimizers via a discrete gradient flow algorithm which has a strictly monotone energy decreasing property. Numerical experiments are given in three dimensions that illustrate a wide variety of droplet shapes that result from their interaction with defects.     

Design and demonstration of a miniature catheter for a confocal microendoscope

The fluorescence confocal microendoscope provides high-resolution, in vivo imaging of cellular pathology during optical biopsy. The confocal microendoscope employs a flexible fiber-optic catheter coupled to a custom-built slit-scan confocal microscope. The catheter consists of a fiber-optic imaging bundle linked to a miniature objective and focus assembly. The 3-mm-diameter catheter may be used on its own or routed though the instrument channel of a commercial endoscope, adding microscopic imaging capability to conventional endoscopy. The design and performance of the miniature objective and focus assembly are discussed. Primary applications of the system include diagnosis of disease in the gastrointestinal tract and female reproductive system.     

Function Follows Form: From Semiconducting to Metallic toward Superconducting PbS Nanowires by Faceting the Crystal

In the realm of colloidal nanostructures, with their immense capacity for shape and dimensionality control, the form is undoubtedly a driving factor for the tunability of optical and electrical properties in semiconducting or metallic materials. However, influencing the fundamental properties is still challenging and requires sophisticated surface or dimensionality manipulation. Such a modification is presented for the example of colloidal lead‐sulfide nanowires. It is shown that the electrical properties of lead sulfide nanostructures can be altered from semiconducting to metallic with indications of superconductivity, by exploiting the flexibility of the colloidal synthesis to sculpt the crystal and to form different surface facets. A particular morphology of lead sulfide nanowires is prepared through the formation of {111} surface facets, which shows metallic and superconducting properties in contrast to other forms of this semiconducting crystal, which contain other surface facets ({100} and {110}). This effect, which is investigated with several experimental and theoretical approaches, is attributed to the presence of lead‐rich {111} facets. The insights promote new strategies for tuning the properties of crystals and new applications for lead sulfide nanostructures.     

Sized controlled synthesis, purification, and cell studies with silicon quantum dots

This article describes the size control synthesis of silicon quantum dots with simple microemulsion techniques. The silicon nanocrystals are small enough to be in the strong confinement regime and photoluminesce in the blue region of the visible spectrum and the emission can be tuned by changing the nanocrystal size. The silicon quantum dots were capped with allylamine either a platinum catalyst or UV-radiation. An extensive purification protocol is reported and assessed using (1)H NMR to produce ultra pure silicon quantum dots suitable for biological studies. The highly pure quantum dots were used in cellular uptake experiments and monitored using confocal microscopy. The results showed that the amine terminated silicon nanocrystals accumulated in lysosome but not in nuclei and could be used as bio-markers to monitor cancer cells over long timescales.     

Slow and very slow desorption of organic compounds from sediment: influence of sorbate planarity

The kinetics of desorption of in situ chlorobenzenes, PAHs, and PCBs from four different sediments was studied employing Tenax beads as an infinite sink for sorbates. Rate constants for slow desorption were 2.9+/-0.4 x 10(-2) x h(-1), irrespective of the extent of sorbate planarity. Rate constants for very slow desorption were 2.1+/-0.5 x 10(-4) and 6.7+/-1.4 x 10(-4) x h(-1) for planar and non-planar compounds, respectively. Comparison with literature data suggests a priori estimates for rate constants for slow desorption to be 3 x 10(-2) x h(-1), and to be 2 x 10(-4) and 7 x 10(-4) x h(-1) for very slow desorption of planar and non-planar compounds, respectively. The ratio between the fractions in the very slowly desorbing domain and the rapidly desorbing domain was 15-38 for planar compounds which is higher than for non-planar compounds for which the ratio was 2.8-5.2. The ratio between the fractions in the slowly desorbing domain and the rapidly desorbing domain was 1.3-1.8 and independent of the sorbate planarity. The difference in influence of sorbate planarity on the very slowly desorbing domain as compared to the slowly desorbing domain points to different environments for the slowly and the very slowly desorbing fractions.