Nonribosomal peptide synthesis in Schizosaccharomyces pombe and the architectures of ferrichrome-type siderophore synthetases in fungi

A nonribosomal peptide synthetase (NRPS) in Schizosaccharomyces pombe, which possesses an unusual structure incorporating three adenylation domains, six thiolation domains and six condensation domains, has been shown to produce the cyclohexapeptide siderophore ferrichrome. One of the adenylation domains is truncated and contains a distorted key motif. Substrate-binding specificities of the remaining two domains were assigned by molecular modelling to glycine and to N-acetyl-N-hydroxy-L-ornithine. Hexapeptide siderophore synthetase genes of Magnaporthe grisea and Fusarium graminearum were both identified and analyzed with respect to substrate-binding sites, and the predicted product ferricrocin was identified in each. A comparative analysis of these synthetase systems, including those of the basidiomycete Ustilago maydis, the homobasidiomycete Omphalotus olearius and the ascomycetes Aspergillus nidulans, Aspergillus fumigatus, Fusarium graminearum, Cochliobolus heterostrophus, Neurospora crassa and Aureobasidium pullulans, revealed divergent domain compositions with respect to their number and positioning, although all produce similar products by iterative processes. A phylogenetic analysis of both NRPSs and associated L-N5-ornithine monooxygenases revealed that ferrichrome-type siderophore biosynthesis has coevolved in fungi with varying in trans interactions of NRPS domains.     

An investigation of the consequences of primary dust explosions in interconnected vessels

In this article Eulerian-Lagrangian 2D computer simulations of consequences of primary dust explosions in two vessels connected by a duct are described. After an explosion in the primary vessel a propagation of hot pressurised gases to the secondary vessel, initially uniformly filled with dust particles, is simulated. The gas phase is described by the standard equations and it is coupled with the particulate phase through the drag force and the convective heat transfer. No chemical reaction is considered in the model since the objective was to model the system up to the time of ignition. The computation was performed for different lengths and diameters (heights) of the linking duct. Having analysed the results, it was concluded that the simulations agree with experimental observations in that the probability of transmission of an explosion from the primary to the secondary vessel decreases with decreasing diameter (height) and increasing length of the connecting pipeline. Snapshots of particle positions for different times are presented. The work illustrates the behaviour of the mixture in the secondary vessel: the particles tend to concentrate in clouds, and domains with no particles are observed. This may influence the explosion characteristics of the system.     

Functionally based augmented sculpting

In this paper we describe an approach to computer‐aided sculpting concerned with the creation and modification of digital models based on physical abstract sculptures. We begin by presenting a survey of current methods for the creation of computer‐aided sculptured artefacts. Then we proceed to present some original methods and tools based on the function representation of geometric models. We introduce a specialized computer language, named HyperFun, which facilitates the modelling of complex objects. As well as presenting computer‐generated animated models of pre‐existing sculptures by Russian artist Igor Seleznev, we also show how some interesting novel shapes can be generated using the HyperFun system. Finally we outline two advanced projects concerned with creating a sculpture‐based augmented reality which allows for the interactive participation of the observer. In this paper, we present experimental results, which hopefully have some artistic appeal. These results were produced by an international team of researchers and students collaborating through the Internet. Copyright © 2005 John Wiley & Sons, Ltd.     

COMPARISON OF CHARACTERIZATION TECHNIQUES IN P-ON-N HgCdTe LWIR PHOTODIODES TECHNOLOGY 

IntroductionAt present Hg Cd Te is the most widely used variable-gap semiconductor for infrared( IR) photodetectors.Over the years it has successfully fought off majorchallenges from extrinsic silicon and lead- tin telluridedevices despite that it has more competitors todaythan ever before.These include Schottky barriers onsilicon,Si Ge heterojunctions,Al Ga As multiplequantum wells,Ga In Sb strained layer superlattices,high temperature superconductors and especially twotypes of thermal …     

Excess low frequency noise/I-V studies in p-on-n MBE LWIR Hg1−xCdxTe detectors

Excess low frequency noise is investigated for the first time in infrared MBE grown LWIR Hg_1−xCd_xTe double layer planar heterostructure (DLPH) detectors grown on lattice matched substrates. LWIR detectors having R₀A_opt values at 40K in the 10¹–10⁷ Θ-cm² range have been characterized as a function of temperature between 120 and 20K. Detectors with R₀A_opt≥10³Θ-cm² at 40K have theoretical diffusion limited performance down to 78K and detectors with R₀A_opt ≥10⁵ Θ-cm² at 40K are within a factor of two of theoretical diffusion limited performance for T>65K. Activation energies extracted from noise (V_d=−100 mV) and dark current (V_d=−100 mV) vs temperature measurements were detector dependent. The activation energy for detectors with R₀A_opt≈10⁶ Θ-cm² at 40K is ∼0.90*E_g to 0.99*E_g. The noise measured between 78 and 105K in the intermediate performance (R₀A_opt∼10³–10⁴ Θ-cm² at 40K) detectors are higher than the noise measured in the higher performance (R₀A_opt∼10⁵–10⁷ Θ-cm²) detectors. In addition, the excess low frequency noise and the dark current at −100 mV in the intermediate and poor (R₀A_opt∼10¹ Θ-cm²) performance detectors are temperature independent. For each detector measured, the activation energy extracted from noise (V_d=−100 mV) vs temperature measurements is equal to the activation energy extracted from the total dark current (V_d=−100 mV) vs temperature measurements. For different dark current mechanisms, the excess low frequency noise varies with temperature and also with area within statistical accuracy in the same manner as the total dark current through the detector. At 78K, the Tobin¹⁴ expression holds in the general sense for equal area detectors dominated by different current mechanisms and also for detectors with a wide range of implant dimensions (A_imp=3.85×10⁻⁷ cm² to A_imp=6.25×10⁻⁴ cm²). Following measurements, the detectors were stripped of the passivation and overlaying metal layers and dressed by a defect etch to reveal defects in each detector. A correlation among noise, leakage current and defect type has been determined for each detector.     

Comparison of Quantitative Detection Methods Based on Molecular Fluorescence Spectroscopy and Chromatographic Techniques Used for the Determination of Bisphenol Compounds

Analytical methods using the fluorescence properties of bisphenols (BPA, BPF and BPS) and their complexes with β-cyclodextrin and methyl-β-cyclodextrin were developed. The methods were applied for the analysis of thermal paper and canned food. Their performance was compared with a standard HPLC approach with a diode array and fluorescence detections. For comparison purposes, basic validation parameters (linear range, limit of detection, sensitivity, precision) were evaluated. It was concluded the developed methods facilitate fast and cost-effective determination of three bisphenol species in liquid samples, similar to the HPLC performance. They are also environmentally friendly. BPA, BPF and BPS can be routinely determined with the presented approach.     

Space–time blending

Shape transformation between objects of different topology and positions in space is an open modelling problem. We propose a new approach to solving this problem for two given 2D or 3D shapes. The key steps of the proposed algorithm are: increase dimension by converting two input kD shapes into half‐cylinders in (k+1)D space–time, applying bounded blending with added material to the half‐cylinders, and making cross‐sections for getting intermediate shapes under the transformation. The additional dimension is considered as a time coordinate for making animation. We use the bounded blending set operations in space–time defined using R‐functions and displacement functions with the localized area of influence applied to the functionally defined half‐cylinders. The proposed approach is general enough to handle input shapes with arbitrary topology defined as polygonal objects with holes and disjoint components, set‐theoretic objects, or analytically defined implicit surfaces. The obtained unusual amoeba‐like behaviour of the shape combines metamorphosis with the non‐linear motion. Copyright © 2004 John Wiley & Sons, Ltd.     

A neural network approach to adaptive protective systems problem in the complex power generating units

Practical successes have been achieved with neural network models in a variety of domains, including energy‐related industry. The large, complex design space of electrical power systems (EPS) is only minimally explored in current practice. The satisfactory results that nevertheless have been obtained testify that neural networks are a robust modeling technology; at the same time, however, the lack of a systematic design approach implies that the best neural network models generally remain undiscovered for most applications. This paper presents an approach to an adaptive protective systems problem in the complex power generating units. First, we demonstrate the complex interdependencies between various parameters of EPS protection systems. We then present an approach, based on protection and adaptation criteria, for designing a neural network based adaptive protection system. © 2000 John Wiley & Sons, Inc.     

A method of measuring ‘zero-wear’ of the cylinder liner

In this paper, new methods of linear wear estimation of the cylinder liner are proposed. They can be used if the deepest honed valleys remain unaltered during the wear process. In the first part of the paper, the possibility of using various amplitude parameters as measures of wear is studied. The second part presents a new procedure for cylinder liner wear analysis based on the ‘fax-film’ method that allows us to estimate the wear of the cylinder liner without disassembly of the cylinder-piston-piston ring group.     

Constructive texturing based on hypervolume modeling

The concept of solid texturing is extended in two directions: constructive modeling of space partitions for texturing and modeling of multidimensional textured objects called hypervolumes. A hypervolume is considered as a point set with attributes of both physical (density, temperature, etc.) and photometric (color, transparency, diffuse and specular reflections, etc.) nature. The point set geometry and attributes are modeled independently using real‐valued scalar functions of several variables. Each real‐valued function defining geometry or an attribute is evaluated at the given point by a procedure traversing a constructive tree structure with primitives in the leaves and operations in the nodes of the tree. This approach provides a framework for modeling, texturing and visualization of 3D solids, time‐dependent and multidimensional objects in a completely uniform manner. We introduced a special modeling language and implemented software tools supporting the proposed approach. The concept of constructive hypervolume textures is independent of the geometry representation. We provide examples of textured Frep and BRep objects as illustrations. Copyright © 2002 John Wiley & Sons, Ltd.