Influence of cocoa butter refining on the quality of milk chocolate

A refining step is often crucial for the removal of undesired components in fats and oils. More flexible refining technologies are required due to a global decline in cocoa butter quality and to meet industry’s demand for cocoa butters with improved properties. The aim was to investigate the impact of the cocoa butter refining process on milk chocolate quality. Therefore a crude cocoa butter was subjected to a steam refining at different temperatures and this with or without a silica pretreatment. The major effect of the silica pretreatment was the complete removal of phosphorus (thus phospholipids), iron and alkaline components. During the steam refining step mainly Free Fatty Acids (FFA) were removed at increased temperatures (T ? 200 °C). The refining of the cocoa butter influenced the rheological properties of the chocolate. An increased packed column temperature, coinciding with the removal of FFA, resulted in a lower yield stress and a higher viscosity. Reduction of FFA positively influenced the crystallization kinetics and the formation of the crystal network, resulting in differences on a macroscopic scale.     

In situ measurement of PCB pore water concentration profiles in activated carbon-amended sediment using passive samplers

Vertical pore water profiles of in situ PCBs were determined in a contaminated mudflat in San Francisco Bay, CA, 30 months after treatment using an activated carbon amendment in the upper layer of the sediment. Pore water concentrations were derived from concentrations of PCBs measured in two passive samplers; polyethylene (PE, 51 μm thick) and polyoxymethylene (POM, 17 μm thick) at different sediment depths. To calculate pore water concentrations from PCB contents in the passive samplers, an equilibrium approach and a first-order uptake model were applied, using five performance reference compounds to estimate pore water sampling rates. Vertical pore water profiles showed good agreement among the measurement and calculation methods with variations within a factor of 2, which seems reasonable for in situ measurements. The close agreements of pore water estimates for the two sampler materials (PE and POM) and the two methods used to translate uptake in samplers to pore water concentrations demonstrate the robustness and suitability of the passive sampling approach. The application of passive samplers in the sediment presents a promising method for site monitoring and remedial treatment evaluation of sorbent amendment or capping techniques that result in changes of pore water concentrations in the sediment subsurface.     

Plastic micropump with ferrofluidic actuation

We present the realization and characterization of a new type of plastic micropump based on the magnetic actuation of a magnetic liquid. The pump consists of two serial check-valves that convert the periodic motion of a ferrofluidic plug into a pulsed quasi-continuous flow. The ferrofluid is actuated by the mechanical motion of an external NdFeB permanent magnet. The water-based ferrofluid is synthesized in-house using a coprecipitation method and has a saturation magnetization of 32 mT. The micropump consists of various layers of polymethylmethacrylate (PMMA), which are microstructured by powder blasting or by standard mechanical micromachining techniques, and are assembled in a single plastic structure using a monomer gluing solution. Two soft silicone membranes are integrated in the microfluidic structure to form two check-valves. Water has been successfully pumped at flow rates of up to 30 /spl mu/L/min and pumping is achieved at backpressures of up to 25 mbar.     

Bioorthogonal chemistry: applications in activity-based protein profiling

The close interaction between organic chemistry and biology goes back to the late 18th century, when the modern natural sciences began to take shape. After synthetic organic chemistry arose as a discipline, organic chemists almost immediately began to pursue the synthesis of naturally occurring compounds, thereby contributing to the understanding of their functions in biological processes. Research in those days was often remarkably interdisciplinary; in fact, it constituted chemical biology research before the phrase even existed. For example, histological dyes, both of an organic and inorganic nature, were developed and applied by independent researchers (Gram and Golgi) with the aim of visualizing cellular substructures (the bacterial cell wall and the Golgi apparatus). Over the years, as knowledge within the various fields of the natural sciences deepened, research disciplines drifted apart, becoming rather monodisciplinary. In these years, broadly ranging from the end of World War II to about the 1980s, organic chemistry continued to impact life sciences research, but contributions were of a more indirect nature. As an example, the development of the polymerase chain reaction, from which molecular biology and genetics research have greatly profited, was partly predicated on the availability of synthetic oligonucleotides. These molecules first became available in the late 1960s, the result of organic chemists pursuing the synthesis of DNA oligomers primarily because of the synthetic challenges involved. Today, academic natural sciences research is again becoming more interdisciplinary, and sometimes even multidisciplinary. What was termed "chemical biology" by Stuart Schreiber at the end of the last century can be roughly described as the use of intellectually chemical approaches to shed light on processes that are fundamentally rooted in biology. Chemical tools and techniques that are developed for biological studies in the exciting and rapidly evolving field of chemical biology research include contributions from many areas of the multifaceted discipline of chemistry, and particularly from organic chemistry. Researchers apply knowledge inherent to organic chemistry, such as reactivity and selectivity, to the manipulation of specific biomolecules in biological samples (cell extracts, living cells, and sometimes even animal models) to gain insight into the biological phenomena in which these molecules participate. In this Account, we highlight some of the recent developments in chemical biology research driven by organic chemistry, with a focus on bioorthogonal chemistry in relation to activity-based protein profiling. The rigorous demands of bioorthogonality have not yet been realized in a truly bioorthogonal reagent pair, but remarkable progress has afforded a range of tangible contributions to chemical biology research. Activity-based protein profiling, which aims to obtain information on the workings of a protein (or protein family) within the larger context of the full biological system, has in particular benefited from these advances. Both activity-based protein profiling and bioorthogonal chemistry have been around for approximately 15 years, and about 8 years ago the two fields very profitably intersected. We expect that each discipline, both separately and in concert, will continue to make important contributions to chemical biology research.     

Monolithic micro-direct methanol fuel cell in polydimethylsiloxane with microfluidic channel-integrated Nafion strip

We demonstrate a monolithic polymer electrolyte membrane fuel cell by integrating a narrow (200 μm) Nafion strip in a molded polydimethylsiloxane (PDMS) structure. We propose two designs, based on two 200 μm-wide and two 80 μm-wide parallel microfluidic channels, sandwiching the Nafion strip, respectively. Clamping the PDMS/Nafion assembly with a glass chip that has catalyst-covered Au electrodes, results in a leak-tight fuel cell with stable electrical output. Using 1 M CH₃OH in 0.5 M H₂SO₄ solution as fuel in the anodic channel, we compare the performance of (I) O₂-saturated 0.5 M H₂SO₄ and (II) 0.01 M H₂O₂ in 0.5 M H₂SO₄ oxidant solutions in the cathodic channel. For the 200 μm channel width, the fuel cell has a maximum power density of 0.5 mW cm⁻² and 1.5 mW cm⁻² at room temperature, for oxidants I and II, respectively, with fuel and oxidant flow rates in the 50-160 μL min⁻¹ range. A maximum power density of 3.0 mW cm⁻² is obtained, using oxidant II for the chip with 80 μm-wide channel, due to an improved design that reduces oxidant and fuel depletion effects near the electrodes.     

Differences in Cd and Zn bioaccumulation for the flood-tolerant Salix cinerea rooting in seasonally flooded contaminated sediments

Several authors suggest that a hydrological regime aiming at wetland creation is a potential management option that favours reducing bioavailability for metal-contaminated sites. The hydrological conditions on a site constitute one of the many factors that may affect the availability of potentially toxic trace metals for uptake by plants. Bioavailability of Cd, Mn and Zn on a contaminated dredged sediment landfill (DSL) with variable duration of submersion was evaluated by measuring metal concentrations in the wetland plant species Salix cinerea in field conditions. Longer submersion periods in the field caused lower Cd and Zn concentrations in the leaves in the first weeks of the growing season. Foliar Cd and Zn concentrations at the end of the growing season were highest on the initially flooded plot that emerged early in the growing season. Foliar Zn concentrations were also high at a sandy-textured oxic plot with low soil metal concentrations. Zn uptake in the leaves was markedly slower than Cd uptake for trees growing on soils with prolonged waterlogging during the growing season, pointing at a different availability. Zn availability was lowest when soil was submerged, but metal transfer from stems and twigs to leaves may mask the lower availability of Cd in submerged soils. Especially for Cd, a transfer effect from one growing season to the next season was observed: oxic conditions at the end of the previous growing season seem to determine at least partly the foliar concentrations for S. cinerea through this metal transfer mechanism. Duration of the submersion period is a key factor for bioavailability inasmuch as initially submerged soils emerging only in the second half of the growing season resulted in elevated Cd and Zn foliar concentrations at that time.     

Microfluidic protein preconcentrator using a microchannel-integrated nafion strip: experiment and modeling

We propose a simple microfluidic device for protein preconcentration based on the electrokinetic trapping principle. It comprises a narrow Nafion strip that is simply cut from a commercial membrane and is integrated into a molded poly(dimethylsiloxane) (PDMS) microfluidic structure using a guiding channel. Mechanically clamping the PDMS/Nafion assembly with a glass substrate results in a rapid prototypable, leak-tight, and easily disposable device. Our device preconcentrates negatively charged fluorescent proteins located at the anodic microfluidic compartment side of the Nafion strip within a few minutes and up to a concentration factor of 10(4). Moreover, we present a numerical study of the preconcentration effect by solving the coupled Poisson, Nernst-Planck, and Navier-Stokes equations for our type of device, which provides microscopic insight into the mechanism of preconcentration. The electrical field across the ion-permselective Nafion generates concentration polarization, i.e., ion depletion at the anodic side and ion enrichment at the cathodic side for both types of ions, with a local excess of mobile positive ions in the depleted concentration polarization zone, inducing a nonequilibrium electrical double layer in close proximity to the Nafion membrane. A voltage difference applied over the anodic compartment is used to generate the electrophoretic flow velocity of the negatively charged tracer biomolecules. This, in combination with the electroosmotic flow in the opposite direction, which originates from the fixed charges on the channel walls and the induced space charge near the membrane, provides the basis for the local preconcentration of the negative tracer biomolecules.     

WeNMR: Structural Biology on the Grid

The WeNMR (http://www.wenmr.eu) project is a European Union funded international effort to streamline and automate analysis of Nuclear Magnetic Resonance (NMR) and Small Angle X-Ray scattering (SAXS) imaging data for atomic and near-atomic resolution molecular structures. Conventional calculation of structure requires the use of various software packages, considerable user expertise and ample computational resources. To facilitate the use of NMR spectroscopy and SAXS in life sciences the WeNMR consortium has established standard computational workflows and services through easy-to-use web interfaces, while still retaining sufficient flexibility to handle more specific requests. Thus far, a number of programs often used in structural biology have been made available through application portals. The implementation of these services, in particular the distribution of calculations to a Grid computing infrastructure, involves a novel mechanism for submission and handling of jobs that is independent of the type of job being run. With over 450 registered users (September 2012), WeNMR is currently the largest Virtual Organization (VO) in life sciences. With its large and worldwide user community, WeNMR has become the first Virtual Research Community officially recognized by the European Grid Infrastructure (EGI).     

Micromachining of glass inertial sensors

We demonstrate the feasibility of a powder blasting micro-erosion process for the micromachining of accelerometer devices in glass. Using high-speed abrasive microparticles and a metal contact mask, we structure millimeter-size cantilever beams from simple glass slides. By metalizing one side of the glass substrate, we demonstrate both capacitive and piezoresistive/strain gauge detection of the vibrating cantilever mass and measure the frequency response of mechanically excited cantilever beams. We think that our approach opens new perspectives for manufacture of inertial sensing devices in a technology alternative to Si     

Characterization of generation–recombination noise using a physics-based device noise simulator

The implementation of generation–recombination (g–r) noise in a partial differential equation based device simulator is presented. Derived from the Shockley–Read–Hall model, the strength of each local g–r noise source is calculated based on the carrier transition rates between the conduction band, valence band, and trap states. The perturbations of these local g–r noise sources are then transmitted to the electrodes of the simulated device through scalar Green’s functions. g–r noise simulations are compared with existing measurements made on a four trap level, p-type silicon resistor. Good agreement between measured and simulated data is observed.