High Accuracy Measurement of Aperture Area Relative to a Standard Known Aperture

Precise knowledge of the area of apertures used in high precision radiometry is extremely important. A method is presented here for the determination of the area of round and irregularly shaped apertures by comparison to a standard aperture which has been measured by other means to high accuracy. The method presented here is quick and has no physical contact with the fragile edge of the aperture opening. Total flux transfer methods are used in the area determination with total relative standard uncertainty of 0.033 % for 2 mm to 25 mm mean diameter apertures not including the area uncertainty of the standard aperture used. Currently the relative standard uncertainty in the area measurement for the stadard aperture is 0.022 %. The worst case relative standard uncertainty of the transfer measurement is 0.04 % including the uncertainty of the standard aperture area.     

Hybridization-modulated ion fluxes through peptide-nucleic-acid- functionalized gold nanotubes. A new approach to quantitative label-free DNA analysis

The inner walls of gold nanotubes, prepared by template synthesis in the nanopores of polycarbonate track etch membranes, have been chemically modified with peptide nucleic acid (PNA) and used for label-free quantification of complementary DNA sequences. Selective binding of DNA to the PNA-modified nanotubes is shown to decrease the flux of optically detected anionic markers through the nanotubes in a concentration-dependent manner. The strong dependence of the biorecognition-modulated ion transport through the nanopores on the ionic strength suggests a dominantly electrostatic exclusion mechanism of the ion flux decrease as a result of DNA binding to the PNA-modified nanopores.     

Thermophysical properties of multi-wall carbon nanotube bundles at elevated temperatures up to 830 K

Thermal transport measurements in multi-wall carbon nanotube (MWCNT) bundles at elevated temperatures up to 830 K are reported using a novel generalized electrothermal technique. Compared with individual CNTs, the thermal conductivity (k) of MWCNT bundles is two to three orders of magnitude lower, suggesting the thermal transport in MWCNT bundles is dominated by the tube-to-tube thermal contact resistance. The effective density for the two MWCNT bundles, which is difficult to measure using other techniques, is determined at 116 kg/m³ and 234 kg/m³. The thermal diffusivity slightly decreases with temperature while k exhibits a small increase with temperature up to 500 K and then decreases. For the first time, the behavior of specific heat for MWCNTs above room temperature is determined. The specific heat is close to graphite at 300–400 K but is lower than that for graphite above 400 K, indicating that the behavior of phonons in MWCNT bundles is dominated by boundary scattering rather than by the three-phonon Umklapp process. The analysis of the radiation heat loss suggests that it needs to be considered when measuring the thermophysical properties of micro/nano wires of high aspect ratios at elevated temperatures, especially for individual MWCNTs due to their extremely small diameters.     

Scanning Near-Field Ellipsometry Microscopy: imaging nanomaterials with resolution below the diffraction limit

We introduce a simple Scanning Near-Field Ellipsometer Microscopy (SNEM) setup to address the rapidly increasing need for simple, routine optical imaging techniques with resolution well below the diffraction limit. Our setup is based on the combination of commercially available atomic force microscope (AFM) and ellipsometry equipment with gold-coated AFM tips to obtain near-field optical images with a demonstrated resolution below λ/10. AFM topographical data, obtained in contact mode, and near-field optical data were acquired simultaneously using a combined AFM-ellipsometer. The highly enhanced field due to lightning-rod effects and localized surface plasmons excited at the end of the gold-coated tip allowed us to resolve and identify metallic nanoparticles embedded in poly(methyl methacrylate) as well as microphases in microphase-separated block copolymer films.     

Probing the morphology and nanoscale mechanics of single poly(N-isopropylacrylamide) microgels across the lower-critical-solution temperature by atomic force microscopy

Submicrometer-sized particles of poly(N-isopropylacrylamide) (PNIPAM) are synthesized by surfactant-free radical polymerization. The morphology and nanomechanical properties of individual, isolated PNIPAM microgel particles at the silicon/air and silicon/water interfaces, below and above the PNIPAM volume-phase-transition temperature (VPTT), are probed by atomic force microscopy. In air, and in water below the VPTT, the PNIPAM spheres are flattened and adopt a pancakelike shape. Interestingly, above the VPTT the microgels adopt a more spherical form with increased height and decreased width, which is attributed to reduced interactions of the particles with the substrate. The elastic modulus calculated from force-indentation curves obtained for individual microgel spheres reveals that the stiffness of the particle's surface decreases by two orders of magnitude upon swelling in water. Additionally, the modulus of the PNIPAM spheres in water increases by one order of magnitude when crossing the VPTT from the swollen to the collapsed states, indicating a more compact chain packing at the particle surface.     

Effect of Ultrafiltration on Anthocyanin and Flavonol Content of Black Currant Juice (Ribes nigrum L.)

This paper evaluates the efficiency of ultrafiltration and the effects of processing on the total anthocyanin and flavonol contents of black currant juice at chosen operational conditions. Ultrafiltration of black currant juices was carried out using Biomax 100?kDa polyethersulfone membrane. Ultrafiltration was used to process the juice prior concentration by reverse osmosis; with the aim to enhance the efficiency of the concentration process in terms of permeate flux. To avoid the fouling of the membrane, the juices were depectinized with Panzym Super E liquid enzyme preparation. The ultrafiltration was carried out at a transmembrane pressure of 2?bars and the operating temperature of 25?°C. The effect of processing on the valuable anthocyanin and flavonol content of the juices was evaluated based on the results of high-performance liquid chromatography analyses. The article includes detailed analyses of anthocyanin and flavonol compounds of the enzyme treated and ultrafiltered juice as compared with the original juice. The results indicate that, due to the enzymatic treatment, the valuable compound content of the juice increases. However, the ultrafiltration process resulted in a significant loss of a valuable content; 54% of total flavonol and 50% of total anthocyanins maintained in ultrafiltered juice when compared to the feed samples.     

Visualizing resonance energy transfer in supramolecular surface patterns of β-CD-functionalized quantum dot hosts and organic dye guests by fluorescence lifetime imaging

Detection of an analyte via supramolecular host-guest binding and quantum dot (QD)-based fluorescence resonance energy transfer (FRET) signal transduction mechanism is demonstrated. Surface patterns consisting of CdSe/ZnS QDs functionalized at their periphery with β-cyclodextrin (β-CD) were obtained by immobilization of the QDs from solution onto glass substrates patterned with adamantyl-terminated poly(propylene imine) dendrimeric "glue." Subsequent formation of host-guest complexes between vacant β-CD on the QD surface and an adamantyl-functionalized lissamine rhodamine resulting in FRET was confirmed by fluorescence microscopy, spectroscopy, and fluorescence lifetime imaging microscopy (FLIM).     

hERG Optimization of Benzofuro−Pyridine and Pyrazino−Indole Derivatives as MCHR1 Antagonists

Obesity is a global epidemic associated with multiple severe diseases. Several pharmacotherapies have been investigated including the antagonists of melanin concentrating hormone receptor 1 (MCHR1). The design, synthesis, and biological studies of novel MCHR1 antagonists based on benzofuro−pyridine and pyrazino−indole scaffold was performed. We confirmed that fine-tuning lipophilicity and basic pK_a by modifying the benzyl group and introducing different substituents on the aliphatic nitrogen sidechain decreases both hERG inhibition and metabolic clearance. We have succeeded to develop excellent in vitro parameters in the case of compounds 17 (4-[(5-chloropyridin-2-yl)methoxy]-1-[4-(2-hydroxyethyl)-8-oxa-4-azatricyclo[7.4.0.0²,⁷]trideca-1(13),2(7),9,11-tetraen-11-yl]-1,2-dihydropyridin-2-one monohydrochloride) and 23 g (4-[(5-chloropyridin-2-yl)methoxy]-1-(1,2,3,4-tetrahydropyrazino[1,2-a]indol-8-yl)pyridin-2(1H)-one monohydrochloride), which can be considered as valuable tools for further pharmacological investigation.