Secondary metabolism in Penicillium expansum: Emphasis on recent advances in patulin research

The plant pathogenic fungus Penicillium expansum is a major concern of the global food industry due to its wide occurrence and ability to produce various mycotoxins, of which the most significant is patulin. Relatively less highlighted in the literature, in comparison with the other food-borne mycotoxins, patulin is one of the main factors in economic losses of vegetables and fruits. Otherwise, patulin is a health hazard which results in both short-term and long-term risks. This review includes knowledge on the biosynthetic mechanisms used for secondary metabolite production in P. expansum, with special emphasis on patulin biosynthesis. The abiotic factors triggering the production of patulin and the strategies developed to reduce or prevent the contamination by this mycotoxin are comprehensively discussed. The database presented in this review would be useful for the prioritization and development of future research.     

Co-αAl2O3-Cu as shaped catalyst in NaBH4 hydrolysis

A study about catalytic films of Co-supported-over-αAl₂O₃ fabricated by electrophoretic deposition (EPD) is reported, the as-prepared shaped catalysts being intended to catalyze NaBH₄ hydrolysis. Co-αAl₂O₃ supported over Cu substrate can be prepared by a 2-step route: (i) preparation of the supported catalyst Co-αAl₂O₃ (in powder form) by wet impregnation of CoCl₂ over αAl₂O₃, followed by a reduction, and (ii) fabrication of Co-αAl₂O₃-Cu (thin film over Cu) by EPD. Both types of catalysts, whatever their form, are highly efficient in hydrolyzing NaBH₄, conversions of 100% and HGRs of tens of mL(H₂) min⁻¹ being achieved at 60–80 °C. The Co-αAl₂O₃-Cu catalysts are even more reactive than the Co-αAl₂O₃ catalysts because the surface of the former materials becomes much more acid than that of the latter ones in the course of the EPD process. The respective rate laws and reaction kinetics have been determined. Independently on the catalyst form, apparent activation energies of about 52 kJ mol⁻¹ and positive reaction orders versus the initial NaBH₄ concentration (i.e. 0.3–0.7) were calculated, suggesting that the EPD does not affect the reaction mechanisms. Besides, it is showed that the hydrolysis is really catalytic as well as typical of a heterogeneous process. For example, an apparent reaction order versus the Co content of 0.9 was calculated. All of these results among others are reported and discussed in the present article.     

Photoconductive optically driven deformable membrane under high-frequency bias: fabrication, characterization, and modeling

The fabrication and characterization of an optically addressable deformable mirror for a spatial light modulator are described. Device operation utilizes an electrostatically driven pixelated aluminized polymeric membrane mirror supported above an optically controlled photoconductive GaAs substrate. A 5 mum thick grid of patterned photoresist supports the 2 mum thick aluminized Mylar membrane. A conductive ZnO layer is placed on the backside of the GaAs wafer. Similar devices were also fabricated with InP. A standard Michelson interferometer is used to measure mirror deformation data as a function of illumination, applied voltage, and frequency. The device operates as an impedance distribution between two cascaded impedances of deformable membrane substrate, substrate, and electrode. An analysis of device's operation under several bias conditions, which relates membrane deformation to operating parameters, is presented.     

Properties of t-zirconia prepared by a composite-assisted nonhydrolytic sol-gel

High surface area and highly crystalline tetragonal Ni-Si-doped ZrO₂ samples were prepared using a nonhydrolytic sol-gel method. The synthesis involved the condensation of zirconium chloride and isopropyl ether in the presence of a chitosan-based composites containing Ni and Si (Ni@Si-CS), followed by calcination to remove the CS. The interactions between the zirconium precursor and the Ni@Si-CS composites were studied and correlated with the effect on morphologies, crystalline structure, phase compositions, and surface area. These parameters were evaluated for different Ni@Si-CS to ZrO₂ mass ratios. It was found that increasing the concentration of Ni@Si-CS composite led to smaller grains of ZrO₂ nanocrystals and an overall material with a higher surface area. The stability of the tetragonal/cubic phases following calcination at 800°C was correlated with the presence of low amounts of Ni²⁺ in the sublattice of ZrO₂ and the presence of the Si-chitosan, which acted as steric stabilizer.     

The dartos flap as an adjunct in preventing urethrocutaneous fistulas in repeat hypospadias surgery

PURPOSE: Vascularized flaps for repeat hypospadias repair are often limited. We report our experience with the dartos flap in children undergoing secondary hypospadias and complex urethral repair. MATERIALS AND METHODS: The dartos flap is fibroadipose tissue between the scrotal skin and tunica vaginalis layers with its vascular pedicle based at the penoscrotal angle. The flap reaches the distal penile shaft without tension. Eight patients 1 to 17 years old (mean age 6) underwent urethral surgery and an interposed dartos flap procedure in 1994 to 1995. RESULTS: Of 6 patients cosmesis was excellent in 84%, erections were straight in 100%, and urinary streams were of good quality and without fistula in 100% after repeat hypospadias surgery. Following staged repair for anterior urethral valves a urethrocutaneous fistula developed in 1 patient and following urethral duplication repair results were excellent in 1. Mean followup was 1 year. CONCLUSIONS: The dartos flap is easy to mobilize and it provides excellent coverage for repeat proximal hypospadias surgery, since the dartos remains undisturbed. We endorse its use for complex urethral surgery and believe that the extra layer of closure helps to prevent urethrocutaneous fistulas.     

Fuzzy PID Control of a Five DOF Robot Arm

This paper studies the application of fuzzy logic control on a five degrees of freedom (DOF) robot arm, the Maker 100 of U.S. Robots. The elaboration of the fuzzy control laws is based on two structures of coupled rules fuzzy PID controllers. The fuzzy PID controllers are numerically simulated and the simulation results confirm the success of the fuzzy PID control in trajectory tracking problems. Seeking a performance optimization, a systematic study of the choice of tuning parameters of the controllers is done. The success of the proposed fuzzy control law is again affirmed by a comparative evaluation with respect to the computed torque control method and the direct adaptive control method, the last two controls being also numerically implemented using the same dynamic model of the robot arm.     

Enhancing Paraoxon Binding to Organophosphorus Hydrolase Active Site

Organophosphorus hydrolase (OPH) is a metalloenzyme that can hydrolyze organophosphorus agents resulting in products that are generally of reduced toxicity. The best OPH substrate found to date is diethyl p-nitrophenyl phosphate (paraoxon). Most structural and kinetic studies assume that the binding orientation of paraoxon is identical to that of diethyl 4-methylbenzylphosphonate, which is the only substrate analog co-crystallized with OPH. In the current work, we used a combined docking and molecular dynamics (MD) approach to predict the likely binding mode of paraoxon. Then, we used the predicted binding mode to run MD simulations on the wild type (WT) OPH complexed with paraoxon, and OPH mutants complexed with paraoxon. Additionally, we identified three hot-spot residues (D253, H254, and I255) involved in the stability of the OPH active site. We then experimentally assayed single and double mutants involving these residues for paraoxon binding affinity. The binding free energy calculations and the experimental kinetics of the reactions between each OPH mutant and paraoxon show that mutated forms D253E, D253E-H254R, and D253E-I255G exhibit enhanced substrate binding affinity over WT OPH. Interestingly, our experimental results show that the substrate binding affinity of the double mutant D253E-H254R increased by 19-fold compared to WT OPH.     

Determination of the interfacial dynamic velocity in silicon solar cells

A detailed theoretical method is presented for the determination of the interfacial dynamic velocity (IDV) S_d introduced at the edge of the space-charge region in the base of a solar cell. The method is based on a dynamic measurement at an arbitrary point on the I–V curve and exploits measurements carried out on a solar cell under illumination. A transient regime between two steady states around the operating point is investigated. The theory takes into account the carrier generation and recombination rates. The measured values of S_d are shown to depend on the cell operating conditions, and the error in the determination of S_d increases with the light intensity that is kept constant during measurements. The interfacial dynamic velocity characterizes the junction as an active interface related to the current flow through the device and appears to allow solar cell quality control since it also depends on the cell structure parameters.     

Characterization of high-density current stressed IGBTs and simulation with an adapted SPICE sub-circuit

Insulated Gate Bipolar Transistors are devices integrating a MOSFET and a bipolar transistor in a Darlington configuration. These devices have been studied before and after conduction stress. During high temperature operations (200°C) hot carriers can induce degradation in gate oxide, at silicon–oxide interface and into the base–emitter junction. The used IGBT SPICE sub-circuit can describe electrical aging in dynamic and static operation. The knowledge of which parameters are influenced during specific functional stress permits us to compensate for these changes or improve the implementation of the component in a circuit, as well as its use in field conditions.     

On the fractal dimension of isosurfaces

A (3D) scalar grid is a regular n1 x n2 x n3 grid of vertices where each vertex v is associated with some scalar value sv. Applying trilinear interpolation, the scalar grid determines a scalar function g where g(v) = sv for each grid vertex v. An isosurface with isovalue σ is a triangular mesh which approximates the level set g(-1)(σ). The fractal dimension of an isosurface represents the growth ;in the isosurface as the number of grid cubes increases. We define and discuss the fractal isosurface dimension. Plotting the fractal ;dimension as a function of the isovalues in a data set provides information about the isosurfaces determined by the data set. We present statistics on the average fractal dimension of 60 publicly available benchmark data sets. We also show the fractal dimension is highly correlated with topological noise in the benchmark data sets, measuring the topological noise by the number of connected components in the isosurface. Lastly, we present a formula predicting the fractal dimension as a function of noise and validate the formula with experimental results.