Conserved domains in DNA repair proteins and evolution of repair systems

A detailed analysis of protein domains involved in DNA repair was performed by comparing the sequences of the repair proteins from two well-studied model organisms, the bacterium Escherichia coli and yeast Saccharomyces cerevisiae, to the entire sets of protein sequences encoded in completely sequenced genomes of bacteria, archaea and eukaryotes. Previously uncharacterized conserved domains involved in repair were identified, namely four families of nucleases and a family of eukaryotic repair proteins related to the proliferating cell nuclear antigen. In addition, a number of previously undetected occurrences of known conserved domains were detected; for example, a modified helix-hairpin-helix nucleic acid-binding domain in archaeal and eukaryotic RecA homologs. There is a limited repertoire of conserved domains, primarily ATPases and nucleases, nucleic acid-binding domains and adaptor (protein-protein interaction) domains that comprise the repair machinery in all cells, but very few of the repair proteins are represented by orthologs with conserved domain architecture across the three superkingdoms of life. Both the external environment of an organism and the internal environment of the cell, such as the chromatin superstructure in eukaryotes, seem to have a profound effect on the layout of the repair systems. Another factor that apparently has made a major contribution to the composition of the repair machinery is horizontal gene transfer, particularly the invasion of eukaryotic genomes by organellar genes, but also a number of likely transfer events between bacteria and archaea. Several additional general trends in the evolution of repair proteins were noticed; in particular, multiple, independent fusions of helicase and nuclease domains, and independent inactivation of enzymatic domains that apparently retain adaptor or regulatory functions.     

Synthesis and spectral,thermal, and photocrosslinking studies of poly(benzylidene phosphoramide ester)s

A new class of poly(benzylidene phosphoramide ester)s containing a photoreactive benzylidene chromophore in the main chain were synthesized from bis(4-hydroxy-3-methoxy benzylidene) acetone with various substituted N-aryl phosphoramidic dichlorides by an interfacial polycondensation technique. The synthesized polymers were characterized by inherent viscosity, IR, and ¹H-, ¹³C-, and ³¹P-NMR spectroscopy. The molecular weights of these polymers were determined by gel permeation chromatography. These polymers were studied for their thermal stability and photochemical properties. Thermal properties were evaluated by thermogravimetric analysis and differential scanning calorimetry. It was found that halogen-containing polymers show a higher thermal stability than that of nonhalogenated polymers. The photocrosslinking property of these polymers was studied by ultraviolet spectroscopy. The photoreactive benzylidene chromophore in the main chain dimerizes via 2π + 2π cycloaddition reaction to form a cyclobutane derivative and leads to crosslinking. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2151–2157, 1997     

Simplified design and analysis method for a waveguide iris filter

A simplified method for design and analysis of a direct coupled waveguide iris filter suitable for computer aided design implementation is presented. A curve fit formula for calculating the aperture dimensions of an iris as a function of normalized shunt inductor values is given. The analysis of the entire filter response is calculated using ABCD parameters. Using proposed equations a five section iris filter at X band has been designed and tested. Comparison between measured and theoretical results is shown. ©1999 John Wiley & Sons, Inc. Int J RF and Microwave CAE 9: 150–154, 1999     

Influence of Load and Sliding Speed on Friction and Interface Temperature of Hypereutectic Alloyed Gray Cast Iron

The influence of incremental sliding speeds and normal loads on friction, wear and interface temperature have been investigated on a series of hypereutectic alloyed gray cast irons. Mass loss and friction coefficient values show inverse trend with sliding speeds. The interfacial temperature increases with incremental speeds and loads while the friction coefficient decrease with the same. The alloys with higher volume of graphite show slightly lower interfacial temperature due to higher thermal transport capacity. The conjoint interaction of asperities and debris possibly predominates at lower speeds and higher mass loss predominates at higher sliding speeds.     

Microstructural, tribological and electrochemical corrosion studies on reactive DC magnetron sputtered zirconium nitride films with Zr interlayer on steel

Thin films of Zirconium Nitride (ZrN) were deposited by DC magnetron sputtering. The structure of the films was examined by X-ray diffraction and the crystallographic parameters were refined by Rietveld analysis. The columnar micro-structure was observed via cross-sectional SEM analysis. Defect induced, first order spectra were observed from Laser Raman studies. XPS showed the presence of Zr (N,O) ZrO₂ phases on the surface of the film. The pitting corrosion was substantially reduced by the employment of Zr film as an interlayer. Corrosion tests revealed that ZrN films with a Zr interlayer exhibited clear passivation characteristics with considerably better corrosion resistance than the film without an interlayer.     

Fretting fatigue behavior of surface modified biomedical titanium alloys

Fretting is a form of adhesive wear normally occurring at the contact points gradually leading to premature failure of load bearing medical implants made of titanium alloys. The aim of this work is to characterize the fretting fatigue damage features of PVD TiN coated, plasma nitrided, ion implanted, laser nitrided and thermally oxidized Ti-6Al-4V and Ti-6Al-7Nb contact pairs. The surface layers were characterized. The damage progression during fretting process is apparently explained with tangential force coefficient curves. Plasma nitrided pairs showed highest fretting fatigue life compared to others. PVD TiN coated pairs have experienced early failures due to third body mode of contact interaction with irregular tangential force coefficient pattern. Ion implanted layers showed similar damage as unmodified alloys. Laser nitrided and thermally oxidized pairs experienced early failures due to brittle and irregular modified layers.     

Peak Stir Zone Temperatures during Friction Stir Processing

The stir zone (SZ) temperature cycle was measured during the friction stir processing (FSP) of NiAl bronze plates. The FSP was conducted using a tool design with a smooth concave shoulder and a 12.7-mm step-spiral pin. Temperature sensing was accomplished using sheathed thermocouples embedded in the tool path within the plates, while simultaneous optical pyrometry measurements of surface temperatures were also obtained. Peak SZ temperatures were 990 °C to 1015 °C (0.90 to 0.97 T _Melt) and were not affected by preheating to 400 °C, although the dwell time above 900 °C was increased by the preheating. Thermocouple data suggested little variation in peak temperature across the SZ, although thermocouples initially located on the advancing sides and at the centerlines of the tool traverses were displaced to the retreating sides, precluding direct assessment of the temperature variation across the SZ. Microstructure-based estimates of local peak SZ temperatures have been made on these and on other similarly processed materials. Altogether, the peak-temperature determinations from these different measurement techniques are in close agreement.     

Assessment of SGS closure for isochoric combustion of hydrogen-air mixture

Direct numerical simulation (DNS) data of freely propagating turbulent premixed flame of stoichiometric hydrogen air mixture inside a closed vessel is analysed to study a sub-grid combustion closure based on unstrained flamelet approach. This modeling framework needs closures for the sub-grid scale (SGS) reaction rate and scalar dissipation rate. The results show that the closure models for these two SGS quantities work quite well. The dissipation rate closure involves a scale dependent parameter, ${\beta }_c$, which is related to the flame curvature induced effects. The reactivity of reactant mixture increases with time in isochoric combustion because the mixture temperature and pressure increase with time. This also influences the parameter ${\beta }_c$ and thus the dynamic evaluation of this parameter is investigated using the DNS data.     

A mathematical model to evaluate the role of agility enablers and criteria in a manufacturing environment

Modern manufacturing arena necessitates the need for responsiveness by practicing agile manufacturing (AM) principles. AM imposes the transformation of the manufacturing organisation so as to respond to dynamic market changes. This article focuses towards the application of graph theory (GT) for conceptual modelling the agile system and to compute the dependencies among the individual agile enabler, criteria and attributes as a top-down approach. Using GT approach, digraphs were systematically constructed for agile enablers and variable permanent matrix values were computed for different scenarios and the relative importance of agility enablers were determined. The permanent values of ‘Management responsibility’ enabler and technology enabler are found to be 920 (minimum) and 3529?×?10¹⁴, respectively for the existing situation, whereas for the practically base case situation, it was found to be 1185 (minimum) and 5081.17?×?10¹⁴ (maximum), respectively. The Comprehensive Agility Index was found to be 1.3996?×?10⁴⁵, which can be even used to benchmark with other best-in-class agile organisations.     

Charge Transfer at Junctions of a Single Layer of Graphene and a Metallic Single Walled Carbon Nanotube

Junctions between a single walled carbon nanotube (SWNT) and a monolayer of graphene are fabricated and studied for the first time. A single layer graphene (SLG) sheet grown by chemical vapor deposition (CVD) is transferred onto a SiO₂/Si wafer with aligned CVD‐grown SWNTs. Raman spectroscopy is used to identify metallic‐SWNT/SLG junctions, and a method for spectroscopic deconvolution of the overlapping G peaks of the SWNT and the SLG is reported, making use of the polarization dependence of the SWNT. A comparison of the Raman peak positions and intensities of the individual SWNT and graphene to those of the SWNT‐graphene junction indicates an electron transfer of 1.12 × 10¹³ cm^?2 from the SWNT to the graphene. This direction of charge transfer is in agreement with the work functions of the SWNT and graphene. The compression of the SWNT by the graphene increases the broadening of the radial breathing mode (RBM) peak from 3.6 ± 0.3 to 4.6 ± 0.5 cm^?1 and of the G peak from 13 ± 1 to 18 ± 1 cm^?1, in reasonable agreement with molecular dynamics simulations. However, the RBM and G peak position shifts are primarily due to charge transfer with minimal contributions from strain. With this method, the ability to dope graphene with nanometer resolution is demonstrated.