Compartmentation of phosphoglycerate kinase in Trypanosoma brucei plays a critical role in parasite energy metabolism

African trypanosomes compartmentalize glycolysis in a microbody, the glycosome. When growing in the mammalian bloodstream, trypanosomes contain only a rudimentary mitochondrion, and the first seven glycolytic enzymes, including phosphoglycerate kinase, are located in the glycosome. Procyclic trypanosomes, growing in the gut of tsetse flies, possess a fully developed mitochondrion that is active in oxidative phosphorylation. The first six glycolytic enzymes are still glycosomal, but phosphoglycerate kinase is now found in the cytosol. We demonstrate here that bloodstream trypanosomes are killed by expression of cytosolic phosphoglycerate kinase. The toxicity depends on both enzyme activity and cytosolic location. One possible explanation is that cytosolic phosphoglycerate kinase creates an ATP-generating shunt in the cytosol, thus preventing full ATP regeneration in the glycosome and ultimately inhibiting the first, ATP-consuming, steps of glycolysis.     

A 2 MV Van de Graaff accelerator as a tool for planetary and impact physics research

Investigating the dynamical and physical properties of cosmic dust can reveal a great deal of information about both the dust and its many sources. Over recent years, several spacecraft (e.g., Cassini, Stardust, Galileo, and Ulysses) have successfully characterised interstellar, interplanetary, and circumplanetary dust using a variety of techniques, including in situ analyses and sample return. Charge, mass, and velocity measurements of the dust are performed either directly (induced charge signals) or indirectly (mass and velocity from impact ionisation signals or crater morphology) and constrain the dynamical parameters of the dust grains. Dust compositional information may be obtained via either time-of-flight mass spectrometry of the impact plasma or direct sample return. The accurate and reliable interpretation of collected spacecraft data requires a comprehensive programme of terrestrial instrument calibration. This process involves accelerating suitable solar system analogue dust particles to hypervelocity speeds in the laboratory, an activity performed at the Max Planck Institut fu?r Kernphysik in Heidelberg, Germany. Here, a 2 MV Van de Graaff accelerator electrostatically accelerates charged micron and submicron-sized dust particles to speeds up to 80 km s(-1). Recent advances in dust production and processing have allowed solar system analogue dust particles (silicates and other minerals) to be coated with a thin conductive shell, enabling them to be charged and accelerated. Refinements and upgrades to the beam line instrumentation and electronics now allow for the reliable selection of particles at velocities of 1-80 km s(-1) and with diameters of between 0.05 μm and 5 μm. This ability to select particles for subsequent impact studies based on their charges, masses, or velocities is provided by a particle selection unit (PSU). The PSU contains a field programmable gate array, capable of monitoring in real time the particles' speeds and charges, and is controlled remotely by a custom, platform independent, software package. The new control instrumentation and electronics, together with the wide range of accelerable particle types, allow the controlled investigation of hypervelocity impact phenomena across a hitherto unobtainable range of impact parameters.     

Efficient analysis of periodic structures

An algorithm which allows the analysis of optical periodic structures with a very large number of periods with minimum numerical problems is presented, For this purpose the stable impedance transfer is combined with Floquet's theorem. Numerical results for a Bragg grating with up to 20000 periods are presented featuring the very moderate numerical effort     

A COST 240 benchmark test for beam propagation methods applied toan electrooptical modulator based on surface plasmons

Modeling of a waveguide polymer electrooptic (EO) modulator based on a resonant excitation of surface plasmons was used as a benchmark test for several beam propagation methods (BPMs). Wave-optical analysis of the structure is presented, and the results of four implementations of three numerical modeling methods are mutually compared and discussed     

Age-related changes in [3H]strychnine binding in the vestibular nuclei of rats

Glycine plays an important role as a neurotransmitter in the four vestibular nuclei (VN). The objective of this study was to determine if the levels of glycine-receptor binding in the VN change as a function of age. Quantitative receptor autoradiography was performed on brainstem sections from three age groups (3, 18 and 26 months) of Fischer 344 rats to assess binding in the VN. Glycine receptors were localized using [3H]strychnine binding. Strychnine binding declined monotonically with increasing age, such that the level of strychnine binding in each of the VN in the 28-month-old animals was approximately one-half that in the 3-month-olds. The age-related decrease in levels of strychnine binding suggest altered glycinergic function in the VN, which may in turn contribute to disturbances in equilibrium observed in the elderly.     

Numerical techniques for modeling guided-wave photonic devices

Accurate modeling of photonic devices is essential for the development of new, higher performance optical components required by current and future high-bandwidth communications systems. This paper reviews several key techniques for such modeling, many of which are used in commercial design tools. These include several mode-solving techniques, the beam propagation method, the method of lines, and the finite-difference time-domain technique     

Ontology engineering step in design science research methodology: a technique to gather and reuse knowledge

Design science (DS) is an emerging research paradigm in the information systems field. One of its challenges is to systematically structure knowledge for business solution artefacts. In this paper, we address this challenge by presenting an ontology engineering process. It structures gathered knowledge based on domain-specific concepts and relations. Application of the process results in an improvement in DS artefacts in terms of representational information quality. The goal of the paper is to place the ontology engineering process in the DS research methodology and provide pragmatic steps to follow the process.     

Comprehensive modeling of vertical-cavity laser-diodes by themethod of lines

A comprehensive numerical model for the analysis of vertical-surface emitting-lasers is presented. An optical, electrical, and thermal submodel are introduced. The complete analysis is based on the method of lines. The temperature distribution and the current density are calculated in the whole structure. The optical behavior is investigated with a full vectorial wave equation in cylindrical coordinates. Multimode effects are considered when calculating the optical output power. A rate equation for electrons and holes is used, which includes diffusion and recombination effects inside the quantum well. By combining all submodels a self consistent solution is found     

Three-dimensional vectorial eigenmode algorithm for nonparaxialpropagation in reflecting optical waveguide structures

A novel full vectorial eigenmode propagation algorithm based on the method of lines is presented, which is applied to the three-dimensional analysis of reflecting longitudinal varying optical waveguides with high refractive index contrast between the transverse and propagation direction. Results for the computation of the vectorial field in a polarisation converter are shown and discussed in comparison with previously published data