Antigen-responsive, microfluidic valves for single use diagnostics

The growing need for medical diagnostics in resource limited settings is driving the development of simple, standalone immunoassay devices. A capillary flow device using polymerization based amplification is capable of blocking a microfluidic channel in response to target biomaterials, enabling multiple modes of detection that require little or no supplemental instrumentation.     

Kinetics of pH response for copolymer films with dilute carboxylate functionality

We have investigated the effects of film composition and thickness on the rate of pH-induced response of a copolymer film containing predominately polymethylene with randomly distributed carboxylic acid side groups (denoted as PM-CO2H). These responsive films are prepared directly onto a gold electrode surface by surface-catalyzed polymerization and subsequent hydrolysis. We measured electrochemical impedance at fixed frequency (100 Hz) to monitor the barrier properties of the polymer film during a step change in pH. At a 1-3% molar acid content, the copolymer films exhibit a 2 order of magnitude change in impedance at 100 Hz when the contacting solution pH changes from 11 to 4 (or 4 to 11). For all films, the rate of protonation is slower than that of ionization, consistent with a more gradual transfer of protons through an increasingly hydrophobic film at the outermost nanometers during the protonation step. Increased acid content within the film accelerates both the rate of protonation and ionization. Thinner films (50 nm) with the same acid content show faster response rate in both directions, since water and ions have a shorter transfer path. A large and reversible pH response was obtained for all films studied, but selection of appropriate film composition and thickness can greatly influence the rate of response.     

II: PROPERTIES OF DIATOMIC AND TRIATOMIC MOLECULES

Results are presented from a theoretical study of the × ⁶Σ⁺, A ⁶Σ⁺ and ⁶Δ electronic states of CrH using multiconfiguration second-order perturbation theory in the multi-state formalism (MS-CASPT2). It is shown that the results for the spectroscopic constants and radiative lifetimes for the A state are in agreement with experiment and an earlier multireference configuration interaction study only if the two close lying × and A states are allowed to interact at a level of approximation that includes dynamic correlation.     

A theoretical analysis of the excited states in 2-benzoylthiophene

The lower excited states of 2-benzoylthiophene have been studied using ab initio quantum chemical methods based on multiconfigurational wave functions. Six singlet and six triplet excited states have been characterized. The geometry has been optimized for the two lowest triplet states, which are responsible for the photoreactivity of the chromophore in the photosensitizing drug tiaprofenic acid. The T¹(π → π?) and T₂(n → π?) states have been found to be close in energy with the π → π? state slightly lower. The excited states have been characterized using density difference and spin density plots. The different photochemical behaviour of the two triplet states can be rationalized from the theoretical data.     

Meson production in p + d reactions

Total and differential cross sections for the reactions p + d → ³He + m ⁰ with m=π, η and p + d → ³H+π⁺ were measured with the GEM detector at COSY for beam momenta between threshold and the maximum of the corresponding baryon resonance. For both reactions a strong forward-backward asymmetry was found. The data were compared with model calculations. The aspect of isospin symmetry breaking is studied. Representing the GEM Collaboration