Localization and functionality of microsporidian iron-sulphur cluster assembly proteins

Microsporidia are highly specialized obligate intracellular parasites of other eukaryotes (including humans) that show extreme reduction at the molecular, cellular and biochemical level. Although microsporidia have long been considered as early branching eukaryotes that lack mitochondria, they have recently been shown to contain a tiny mitochondrial remnant called a mitosome. The function of the mitosome is unknown, because microsporidians lack the genes for canonical mitochondrial functions, such as aerobic respiration and haem biosynthesis. However, microsporidial genomes encode several components of the mitochondrial iron-sulphur (Fe-S) cluster assembly machinery. Here we provide experimental insights into the metabolic function and localization of these proteins. We cloned, functionally characterized and localized homologues of several central mitochondrial Fe-S cluster assembly components for the microsporidians Encephalitozoon cuniculi and Trachipleistophora hominis. Several microsporidial proteins can functionally replace their yeast counterparts in Fe-S protein biogenesis. In E. cuniculi, the iron (frataxin) and sulphur (cysteine desulphurase, Nfs1) donors and the scaffold protein (Isu1) co-localize with mitochondrial Hsp70 to the mitosome, consistent with it being the functional site for Fe-S cluster biosynthesis. In T. hominis, mitochondrial Hsp70 and the essential sulphur donor (Nfs1) are still in the mitosome, but surprisingly the main pools of Isu1 and frataxin are cytosolic, creating a conundrum of how these key components of Fe-S cluster biosynthesis coordinate their function. Together, our studies identify the essential biosynthetic process of Fe-S protein assembly as a key function of microsporidian mitosomes.     

Rendering Grass Blowing in the Wind with Global Illumination

We have simulated a time varying wind field using the lattice Boltzmann model, and its effect on blades of grass with a simple mass-spring model. We present a global illumination model for multiple scattering of incident sun and sky illumination within the field of grass. We model the grass as a continuous distribution of infinitesimal colored scattering flakes and solve a system of differential equations for the radiance transport. We repeat this for a collection of grass bending directions and amounts, an...     

Some new substrates for determinations of phosphatase

Résumé Pour doser l'activité de la phosphomonoestérase, on a fait récemment usage des esters de l'acide phosphorique qui, après hydrolyse par la phosphatase, donnent des produits colorés. L'auteur propose d'employer des esters de l'acide phosphorique dont les producits d'hydrolyse ont un pouvoir fluorescent et peuvent être de ce fait décelés et mesurés dans des solutions très diluées. Il attire tout particulièrement l'attention sur des esters de la fluorescéine, éosine et 4-méthyl-7-oxycumarine et montre leur importance dans les recherches histologiques sur la phosphatase.     

Emission-Based Scatter Correction in SPECT Imaging

Scatter correction in single photon emission computed tomography(SPECT) has been focused on either using multiple-window acquisition technique or the scatter modeling technique in iterative image reconstruction.We propose a technique that uses only the emission data for scatter correction in SPECT.We assume that the scatter data can be approximated by convolving the primary data with a scatter kernel followed by the normalization using the scatter-to-primary ratio(SPR).Since the emission data is the superpo...     

Recent Advance in Non-Krylov Subspace Model Order Reduction of Interconnect Circuits

Model order reduction of interconnect circuits is an important technique to reduce the circuit complexity and improve the efficiency of post-layout verification process in the nanometer VLSI design. Existing works using the Krylov subspace method are very efficient, but the resulting models are less compact and lack global accuracy. Also, existing methods cannot handle interconnect circuits with large input and output ports. Recent advances in reduction techniques using non-Krylov subspace techniques such a...     

CAD到ArcGIS数据转换问题

为将以AutoCAD格式存在的测量基础数据转换成GIS数据,从理论和实践两方面进行了研究。通过AO+VB进行开发设计数据转换程序。最终实现了AutoCAD环境下的大比例尺地形图数据向ArcGIS数据格式的无信息损失转换,降低了地理信息系统开发过程中数据采集的费用。     

金属有机化学气相沉积薄膜制备中传热传质的数值模拟

建立水平式GaAs的金属有机化学气相沉积(metal-organic chemical vapor deposition,MOCVD)数学模型, 采用求解压力耦合方程的半隐式(SIMPLE)算法对反应气体流动进行二维数值模拟, 并基于边界层动量、热量与扩散传质的相关理论分析了薄膜制备过程中化学组分的输运, 以及反应前驱物与气相之间的传热过程. 计算所得的GaAs生长速率与实验结果吻合较好. 同时, 数值讨论了反应器进气流量、操作压力以及基底温度对GaAs生长速率的影响. 薄膜生长的速率峰值随入口气体速度的升高而有所增大, 但薄膜生长逐渐趋于不均匀性. 因此, 选取气流速度为0.104 m/s. 薄膜生长速率随着操作压力的增大而增大, 当压力为6 kPa时, GaAs生长速率较压力为2 kPa时提高了223%, 薄膜具有较好的生长速率和均匀性.基底温度对薄膜生长速率影响显著, 在1 050 K时薄膜有良好的生长速率和均匀性, GaAs生长速率比温度为950 K时提高了123%. 研究结果为优化MOCVD反应条件及其反应器的结构设计提供了理论依据.