Effective structure factor of osmotically deformed nanoemulsions

Extreme osmotic compression of nanoemulsion droplets, achieved by ultracentrifugation, can create solidlike biliquid foams without causing significant droplet coalescence. Using small-angle neutron scattering (SANS), we probe the structure of a uniform silicone oil-in-water nanoemulsion stabilized by sodium dodecyl sulfate over a wide range of volume fractions, phi, up to and beyond the limit associated with maximal random jamming of spheres, phiMRJ = 0.64. Although some features in the structure can be understood at lower phi using simple predictions for hard spheres, the anionic repulsion and deformability of the droplet interfaces creates departures from these predictions at higher phi. For phi near and beyond phiMRJ, the effective structure factor, Seff, as a function of wavenumber, q, exhibits a primary peak that is subunity. We speculate that this striking feature is due to the deformation of the droplets into nonspherical shapes as the system begins to approach the limit of a random array of nanoscopic thin films, Plateau borders, and vertexes characteristic of a polyhedral foam.     

Simultaneous Raman spectroscopic and differential double-layer capacitance measurements of pyridine adsorbed on roughened silver electrodes

It is shown that differential double-layer capacitance data can be obtained simultaneously with the recording of the Raman spectra of adsorbates at a roughened silver microelectrode. The use of such data to provide information about the structure of the silver electrode/aqueous KCl (0.1 M)/pyridine (0.1 M) interface is demonstrated.     

The use of electrodialysis to prepare aqueous bread extracts for bromate determination by chemiluminescence

A cleanup procedure based on electrodialysis is described for the preparation of aqueous bread extracts for bromate determination by chemiluminescence. The technique utilizes electrophoresis with 3 chambers separated by semipermeable membranes. The relative merits of reverse osmosis (RO), ultrafiltration, and nanofiltration membranes with various molecular weight cutoffs were evaluated. The best results were obtained with an RO membrane manufactured from thin-film (composite) polysulfone as support for polyamide. A 0.14 M sodium sulfate solution in the center or collection chamber provides optimum conductivity. Aqueous hydroxylamine sulfate (30 mM) was selected for the anode compartment as a reductant for the anode oxidation products. The constant current mode at 150 mA with a potential of ca 100 volts was used. After electrophoretic separation, the bromate concentration in the collection chamber was typically 2 to 3 times greater than the concentration in the bread extract. The chemiluminescent reaction of bromate with sulfite with hydrocortisone as the enhancer was selected for detection of bromate. The emission, with a wavelength maximum at 575 nm, was found to "glow" rather than "flash" after the reagents were mixed; therefore, it was possible to optimize the light collection period. The method was validated with a variety of commercial bread products. White bread, hot dog buns, hamburger rolls, and a multigrain bread from 7 different manufacturers were studied.     

Three-dimensional spatiokinetic distributions of sputtered andscattered products of Ar+ and Cu+ impacts onto theCu surface: molecular dynamics simulations

Energy and angular distributions of reflections and sputtered atoms are essential inputs for feature profile evolution simulations. Molecular dynamics simulations are used to compute the three-dimensional energy and angular distributions for reflected and sputtered products when both Ar⁺ and Cu⁺ ions bombard a copper surface. We term these “spatiokinetic” distribution functions (SKDF's). We show by example that SKDF's for reflected Ar⁺ ions focus as the incident angle &thetas;_i (normal=0°) is increased from 60-75° and broaden as the incident energy E_i is increased from 55-175 eV. We show that the SKDF's for glancing-angle reflected Cu⁺ ions focus when E_i is increased from 55-175 eV. We show that the SKDF's for copper atoms sputtered by 175 eV Ar⁺ are insensitive to &thetas;_i;. We report total sputter yields for Ar⁺ and Cu⁺ ions at 55 and 175 eV for incident angles between 0° and 85°, and sticking probabilities for Cu⁺ ions for these energies and angles. Comparison to representative experimental results (Doughty et al., 1997) is given     

Magnetic resonance imaging screening in women at genetic risk of breast cancer: imaging and analysis protocol for the UK multicentre study. UK MRI Breast Screening Study Advisory Group

The imaging and analysis protocol of the UK multicentre study of magnetic resonance imaging (MRI) as a method of screening for breast cancer in women at genetic risk is described. The study will compare the sensitivity and specificity of contrast-enhanced MRI with two-view x-ray mammography. Approximately 500 women below the age of 50 at high genetic risk of breast cancer will be recruited per year for three years, with annual MRI and x-ray mammography continuing for up to 5 years. A symptomatic cohort will be measured in the first year to ensure consistent reporting between centres. The MRI examination comprises a high-sensitivity three-dimensional contrast-enhanced assessment, followed by a high-specificity contrast-enhanced study in equivocal cases. Multiparametric analysis will encompass morphological assessment, the kinetics of contrast agent uptake and determination of quantitative pharmacokinetic parameters. Retrospective analysis will identify the most specific indicators of malignancy. Sensitivity and specificity, together with diagnostic performance, diagnostic impact and therapeutic impact will be assessed with reference to pathology, follow-up and changes in diagnostic certainty and therapeutic decisions. Mammography, lesion localisation, pathology and cytology will be performed in accordance with the UK NHS Breast Screening Programme quality assurance standards. Similar standards of quality assurance will be applied for MR measurements and evaluation.     

The extension and completion of the universal measure and the dual of the space of measures

Every vector measure μ factors uniquely by μ = $\text{}\text{?}$gm ° χ where χ is a universal measure and $\text{}\text{?}$gm is a linear map continuous on simple functions in the strict topology. The completion of χ describes the dual of the space of measures by uniform closure based on χ-measurable sets and also as the completion of the simple functions in the strict topology.     

Characterization and purification of supramolecular metal complexes using gel-permeation chromatography

Gel-permeation chromatography (GPC) has been used to analyze transition-metal-based squares, triangles, and related supramolecular complexes. Using rhenium-containing molecular squares of different sizes, a linear calibration curve has been established, which was used for confirming the relative sizes of other assemblies. GPC can also discriminate cyclic trimers and tetramers of a dirhodium building block. Preparative GPC has been used to resolve macroscopic samples of a rhenium-based supramolecular mixture into pure syn and anti isomers. A mixture of "triangle" and "square" has also been successfully separated.     

Lewis acid-catalyzed Csp3–H functionalization of methyl azaarenes with α-trifluoromethyl carbonyl compounds

A Lewis acid promoted Csp³–H bond functionalization of methyl azaarenes with α-trifluoromethylated carbonyl compounds is described. Catalytic amounts of Yb(OTf)₃ provided a straightforward access to the corresponding trifluoromethylated alcohols in excellent yields up to 94% under mild reaction conditions.     

Matching an RF sheath model to a bulk plasma model

In this paper, we present a combined plasma-sheath model designed for the study of high density discharges, or other systems with thin sheaths. Sheaths in high density plasmas are typically less than 1 mm in thickness. When modeling multidimensional discharges, fully resolving the sheaths can be prohibitively expensive computationally, especially when RF power is coupled capacitively into the discharge. However, the sheath impedance often strongly affects instantaneous and period-averaged plasma potential, which in turn can strongly influence crucial processing characteristics such as the ion energy and angular distributions impacting surfaces. In the combined plasma-sheath model we present, the sheaths are treated independently from the plasma region, and different length scales are employed for each. The Godyak-Sternberg sheath model [Phys. Rev. A, 42, 2299 (1990)] is used to represent the sheaths. The bulk plasma portion of the discharge is represented using a fluid model. Boundary conditions at the plasma-sheath interfaces transfer information dynamically between the sheath and bulk plasma portions of the model. Results from the combined plasma-sheath model are compared to results from a discharge model that fully resolves the sheaths, with generally good to excellent agreement