Fundamentals and applications of immobilized microfluidic enzymatic reactors

OVERVIEW: Over the last decade, the utility of immobilized microfluidic enzyme reactors (IMERs) has been demonstrated in a wide variety of fields, including medical diagnostics and therapy, biosensors, organic synthesis, drug discovery and many other applications. Of particular interest to the pharmaceutical industry is the potential for high throughput experimentation afforded by these systems, with a view to combinatorial synthesis for drug discovery applications. This article will focus on the current state of IMER systems, including immobilization techniques and microchannel flow generation, with a particular emphasis on applications and future prospects in view of likely directions and market potential of this field. IMPACT: The numerous advantages of attaching enzymes to a solid support, such as reuse of a single batch of enzyme, improved stability and durability, the ability to stop the reaction rapidly by removing the product from the reaction solution and the absence of enzyme contamination of the product are some of the attractive features of such systems. There are, however, a number of issues requiring careful consideration when developing such microsystems, including, but not limited to, surface modifications and exact control of fluid behaviour in microchannels, detection limitations, increased integration, and the reusability of the chips. APPLICATIONS: IMERs have received wide, including commercial, application as diagnostic tools for point‐of‐care applications, and, increasingly, as analytical tools in early drug development. Furthermore, peptide mapping and proteomics have employed IMER systems extensively over the past decade and growth in these areas continues. Copyright © 2011 Society of Chemical Industry     

Determination of the activation energies of diffusion of organic molecules in poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) is a highly inert packaging material that exhibits low interaction with foodstuff and consequently a limited diffusion of migrants. Migration modeling can therefore be used as an alternative to experimental migration tests in order to confirm compliance of PET packaging materials with food laws. The most important factor for predicting migration using mathematical models is the diffusion coefficient of the migrant in PET. However, current models that predict this parameter are typically based on worst‐case scenarios and thereby significantly over‐estimate the degree of migration. The key parameter for developing more realistic migration models is the activation energy of diffusion of potential migrants in PET, but experimental data on this are scarcely available in the scientific literature. The aim of the present study was therefore to develop a fast and precise method for determining diffusion coefficients and activation energies of diffusion of organic compounds in PET. Activation energies of diffusion for 13 organic compounds in PET were determined via their diffusion coefficient temperature dependencies. The molecular weight and activation energy of diffusion for the compounds investigated in this study were correlated, offering a basis for a new approach in predicting diffusion coefficients for use in migration modeling. The proposed method is a suitable tool to establish the datasets needed to refine the current migration model. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Hybrid visualization for white matter tracts using triangle strips and point sprites

Diffusion tensor imaging is of high value in neurosurgery, providing information about the location of white matter tracts in the human brain. For their reconstruction, streamline techniques commonly referred to as fiber tracking model the underlying fiber structures and have therefore gained interest. To meet the requirements of surgical planning and to overcome the visual limitations of line representations, a new real-time visualization approach of high visual quality is introduced. For this purpose, textured triangle strips and point sprites are combined in a hybrid strategy employing GPU programming. The triangle strips follow the fiber streamlines and are textured to obtain a tube-like appearance. A vertex program is used to orient the triangle strips towards the camera. In order to avoid triangle flipping in case of fiber segments where the viewing and segment direction are parallel, a correct visual representation is achieved in these areas by chains of point sprites. As a result, a high quality visualization similar to tubes is provided allowing for interactive multimodal inspection. Overall, the presented approach is faster than existing techniques of similar visualization quality and at the same time allows for real-time rendering of dense bundles encompassing a high number of fibers, which is of high importance for diagnosis and surgical planning.     

Polymers containing formamidine groups

Summary Aliphatic polyformamidines have been synthesized by reaction of aliphatic diamines with triethyl orthoformate in presence of catalytic amounts of acetic acid. The reaction has been carried out in DMSO at 180°C. The polymer structure has been confirmed by IR and NMR spectroscopy. For determination of molecular weights ¹H NMR end group signals have been used.     

Verification of cardiac tissue electrophysiology simulators using an N-version benchmark

Ongoing developments in cardiac modelling have resulted, in particular, in the development of advanced and increasingly complex computational frameworks for simulating cardiac tissue electrophysiology. The goal of these simulations is often to represent the detailed physiology and pathologies of the heart using codes that exploit the computational potential of high-performance computing architectures. These developments have rapidly progressed the simulation capacity of cardiac virtual physiological human style models; however, they have also made it increasingly challenging to verify that a given code provides a faithful representation of the purported governing equations and corresponding solution techniques. This study provides the first cardiac tissue electrophysiology simulation benchmark to allow these codes to be verified. The benchmark was successfully evaluated on 11 simulation platforms to generate a consensus gold-standard converged solution. The benchmark definition in combination with the gold-standard solution can now be used to verify new simulation codes and numerical methods in the future.     

Bücherschau

Ohne Zusammenfassung VDI     

Performance of 1-10-GHz traveling wave amplifiers in 0.18-/spl mu/m CMOS

The authors present two four-stage traveling-wave amplifiers (TWA) fabricated in a 0.18-/spl mu/m CMOS process. A TWA with an internal drain bias network achieved a gain of 5 dB out to 10 GHz, and another TWA without an on-chip bias network achieved a gain of 8 dB out to 10 GHz. These are the highest frequency CMOS TWAs known to the authors.     

Prediction of fracture healing under axial loading,shear loading and bending is possible using distortional and dilatational strains as determining mechanical stimuli

Numerical models of secondary fracture healing are based on mechanoregulatory algorithms that use distortional strain alone or in combination with either dilatational strain or fluid velocity as determining stimuli for tissue differentiation and development. Comparison of these algorithms has previously suggested that healing processes under torsional rotational loading can only be properly simulated by considering fluid velocity and deviatoric strain as the regulatory stimuli. We hypothesize that sufficient calibration on uncertain input parameters will enhance our existing model, which uses distortional and dilatational strains as determining stimuli, to properly simulate fracture healing under various loading conditions including also torsional rotation. Therefore, we minimized the difference between numerically simulated and experimentally measured courses of interfragmentary movements of two axial compressive cases and two shear load cases (torsional and translational) by varying several input parameter values within their predefined bounds. The calibrated model was then qualitatively evaluated on the ability to predict physiological changes of spatial and temporal tissue distributions, based on respective in vivo data. Finally, we corroborated the model on five additional axial compressive and one asymmetrical bending load case. We conclude that our model, using distortional and dilatational strains as determining stimuli, is able to simulate fracture-healing processes not only under axial compression and torsional rotation but also under translational shear and asymmetrical bending loading conditions.