A Monte Carlo analysis of possible cell dose enhancement effects by uranium microparticles in photon fields

Uranium microparticles (radii: 50 nm-1.25 μm) were modelled surrounded by tissue and exposed to natural background radiation, in order to investigate potential dose enhancements from photon interactions. Generally, the results depended on the microparticle size. For a 0.5 μm radius microparticle in an isotropic field, it was found that the combined photon/electron doses deposited in 1 and 10 μm radii shells around it were raised by factors of ～3.8 and ～1.1, respectively; for a typical background photon fluence rate, these would correspond to increased energy depositions of a few 10s and a few 100s of eV y(-1), which are far less than the likely deposition rate resulting from the radioactive decay of a (238)U microparticle. The health hazard from uranium microparticle interactions with background photons was concluded to be negligible.     

Biological scanning electrochemical microscopy and its application to live cell studies

Progress in instrumental design continues to pave the way for high-resolution, real-time electrochemical measurements with living cells.     

Fabrication and characterization of laser pulled platinum microelectrodes with controlled geometry

The development of a reproducible procedure for the fabrication of Pt disk-shaped microelectrodes with characteristic dimensions ranging from 50 nm to 1 μm in diameter was carried out using a laser pulling technique. The governing physical phenomena involved in their fabrication are discussed, and the importance of adding a critical quartz thinning step in the general procedure is demonstrated. The preparation of the microelectrodes involves sealing a platinum wire inside a quartz tubing using a pipet puller, thinning the composite material (platinum/quartz assembly), and laser pulling it to obtain two microelectrodes. The resulting microelectrodes display reproducible well-controlled geometry, which is important to downstream quantitative scanning electrochemical studies and imaging. Mechanical polishing of the microelectrode is required and remains the critical step in the fabrication of nanometer size electrodes. Following production, the microelectrodes are characterized by electron microscopy, scanning electrochemical microscopy, and cyclic voltammetry. Development of these microelectrodes is motivated by their subsequent application to electrocatalysis and their potential in theoretical study because of their well-defined geometry.     

A Direct Approach to Organic/Inorganic Semiconductor Hybrid Particles via Functionalized Polyfluorene Ligands

Controlled Suzuki–Miyaura coupling polymerization of 7′‐bromo‐9′,9′‐dioctyl‐fluoren‐2′‐yl‐4,4,5,5‐tetramethyl‐[1,3,2]dioxaborolane initiated by bromo(4‐tert‐butoxycarbonylamino‐phenyl)(tri‐tert‐butylphosphine)palladium ( 1 ) or bromo(4‐diethoxyphosphoryl‐phenyl)(tri‐tert‐butylphosphine)palladium ( 2 ) yields functionalized polyfluorenes (M_n = 4 × 10³ g mol^?1, M_w/M_n < 1.2) with a single amine or phosphonic acid, respectively, end‐group. High temperature synthesis of cadmium selenide quantum dots with these functionalized polyfluorenes as stabilizing ligands yields hybrid particles consisting of good quality (e.g. emission full width at half maximum of 30 nm; size distribution σ < 10%) inorganic nanocrystals with polyfluorene attached to the surface, as corroborated by transmission electron microscopy analysis and analytical ultracentrifugation. Sedimentation studies on particle dispersions show that a substantial portion (ca. half) of the phosphonic acid terminated polyfluorene ligands is bound to the inorganic nanocrystals, versus ca. 5% for the amino‐functionalized polyfluorene ligands. Single particle micro‐photoluminescence spectroscopy shows an efficient and complete energy transfer from the polyfluorene layer to the inorganic quantum dot.     

Determination of absolute configurations of crystal structures using electron diffraction patterns by means of least-squares refinement

A simple method is reported to determine the absolute configuration of the crystal structure from electron diffraction patterns taken from very small areas. The method is based on the differences in the Friedel reflections, which are in general much larger than for X-rays due to the dynamical behaviour of the electron scattering. We express the absolute configuration with a parameter similar to the one Flack (Acta Cryst. A 39 (1983) 876) introduced in X-ray crystallography. This parameter is added to a refinement procedure that uses a multi-slice calculation to calculate diffraction patterns. The validity and strength of the method are shown with simulated and experimental data sets of GaN in the [0 1 0]-zone and a more complex compound, Ce5Cu19P12 in the [0 0 1] zone.     

The effect of geometric imperfections on the vibrations of anisotropic cylindrical shells

Analytical–numerical models to analyse the flexural vibration behaviour of anisotropic cylindrical shells are presented. The two models (denoted as Level-1 and Level-2 Analysis) have different levels of complexity and can be used to study the influence of important parameters, such as geometric imperfections, static loading, and boundary conditions. A specific anisotropic shell is used in the calculations in this paper. The influence of the imperfection shape and amplitude on the natural frequency is investigated for this shell via both the Level-1 and the Level-2 Analysis. Imperfections with the shape of the “lowest vibration mode” give a decrease of the natural frequency with increasing imperfection amplitude. The results of the Level-2 Analysis for the effect of imperfections on the natural frequency are in reasonable agreement with Finite Element calculations.     

Randomized controlled trial of omeprazole or endoscopy in patients with persistent dyspepsia: a cost-effectiveness analysis

BACKGROUND: Cost-effectiveness analysis, Helicobacter pylori research and the development of proton pump inhibitors are having an increasing impact on the management of dyspepsia. However, clinical trials have not always included both H. pylori diagnosis and proton pump inhibitors in their protocols. METHODS: Patients who were referred for upper gastrointestinal endoscopy by their general practitioner were randomized to either prompt endoscopy followed by directed medical treatment (conventional group, n=38), or to empirical treatment with omeprazole and, in the case of symptom relapse, serological screening for H. pylori infection followed by eradication therapy in seropositive patients (empirical group, n=42). The study lasted for up to 1 year. RESULTS: In the empirical group, only 13 patients (31%) underwent endoscopy. The average number of days for which the patients kept records of their dyspeptic symptoms was 266 (95% CI: 226-307) in the empirical group, of which 166 (95% CI: 128-204) were symptom-free. In the conventional group, 159 (95% CI: 119-198) out of 255 days (95% CI: 209-302) were recorded as symptom-free. The average medical cost in the empirical group was $284 (95% CI: 218-350) and in the conventional group $491 (95% CI: 383-600). In the empirical group, two malignancies were found, whereas in the conventional group one malignancy was found. CONCLUSIONS: The empirical drug treatment strategy in patients with persistent dyspeptic symptoms resulted in 69% fewer diagnostic endoscopies with lower medical costs and equal effectiveness in the first year, compared to prompt endoscopy followed by directed medical treatment.     

Persistent erythema and edema of the face associated with rosacea and lymph vessel dysplasia

A 24-year-old woman with lymph vessel dysplasia had experienced a progressive edema of her legs since her second year of life and progressive facial edema for the past year. She also had telangiectasias and papules on the background of a diffuse erythema as well as marked seborrhea on her face. Histopathological examination of a representative facial lesion revealed a granulomatous dermatitis with periadnexal distribution mainly consisting of lymphocytes and histiocytes. In addition, there was a moderate fibrosis of the dermis with numerous mast cells. By duplex ultrasound, a diagnosis of a massive edema of the legs without evidence for chronic venous insufficiency was made. The clinical and histopathological findings were consistent with solid persistent erythema and edema of the face associated with rosacea and lymph vessel dysplasia. The chronic course, absence of serological abnormalities and nonspecific histopathological features as well as resistance to therapy are the most important diagnostic criteria of this disease also known as Morbihan's disease.