Four deoxynucleoside kinase activities from Drosophila melanogaster are contained within a single monomeric enzyme, a new multifunctional deoxynucleoside kinase

In mammalian cells, there are three pyrimidine nucleoside salvage enzymes with the capacity to phosphorylate all four deoxynucleosides, the two thymidine kinase isoenzymes, TK1 and TK2, and the deoxycytidine kinase, dCK. TK1 is cell cycle-regulated; TK2 is expressed constitutively and can phosphorylate deoxycytidine to the same extent as thymidine. dCK phosphorylates deoxycytidine, deoxyadenosine, and deoxyguanosine, but not thymidine. In addition, the three kinases can phosphorylate a number of medically important analogs. In cultured Drosophila melanogaster embryonic cells, only one pyrimidine deoxynucleoside kinase was present. This kinase was purified and showed a broad substrate specificity, since it was able to phosphorylate all four deoxynucleosides with high efficiency, as compared with the kinases in mammalian cells. Additionally, a number of nucleoside analogs such as arabinofuranosyl pyrimidines, deoxyuridine, and 5'-fluorodeoxyuridine, were phosphorylated. There was negligible 3'-azidothymidine and no dTMP phosphorylation. The enzyme was active as a monomer of about 30 kDa. We suggest the name D. melanogaster deoxynucleoside kinase for this multifunctional kinase. The substrate specificity, size, and other characteristics show that this enzyme is more related to human TK2 than to the other mammalian deoxyribonucleoside kinases, but is unique with respect to the capacity to phosphorylate all four deoxynucleosides.     

Quick guide to polyketide synthase and nonribosomal synthetase genes in Fusarium

Fusarium species produce a plethora of bioactive polyketides and nonribosomal peptides that give rise to health problems in animals and may have drug development potential. Using the genome sequences for Fusarium graminearum, F. oxysporum, F. solani and F. verticillioides we developed a framework for future polyketide synthases (PKSs) and nonribosomal peptides synthetases (NRPSs) nomenclature assignment and classification. Sequence similarities of the adenylation and ketosynthase domain sequences were used to group the identified NRPS and PKS genes. We present the current state of knowledge of PKS and NRPS genes in sequenced Fusarium species and their known products. With the rapid increase in the number of sequenced fungal genomes a systematic classification will greatly aid the scientific community in obtaining an overview of the number of different NRPS and PKS genes and their potential as producers of known bioactive compounds.     

Two-dimensional Kagome photonic bandgap waveguide

The transverse-magnetic photonic-bandgap-guidance properties are investigated for a planar two-dimensional (2-D) Kagome waveguide configuration using a full-vectorial plane-wave-expansion method. Single-moded well-localized low-index guided modes are found. The localization of the optical modes is investigated with respect to the width of the 2D Kagome waveguide, and the number of modes existing for specific frequencies and waveguide widths is mapped out     

Space-mapping optimization of microwave circuits exploitingsurrogate models

A powerful new space-mapping (SM) optimization algorithm is presented in this paper. It draws upon recent developments in both surrogate model-based optimization and modeling of microwave devices, SM optimization is formulated as a general optimization problem of a surrogate model. This model is a convex combination of a mapped coarse model and a linearized fine model. It exploits, in a novel way, a linear frequency-sensitive mapping. During the optimization iterates, the coarse and fine models are simulated at different sets of frequencies. This approach is shown to be especially powerful if a significant response shift exists. The algorithm is illustrated through the design of a capacitively loaded 10:1 impedance transformer and a double-folded stub filter. A high-temperature superconducting filter is also designed using decoupled frequency and SMs     

Photonic crystal distributed feedback fiber lasers with Bragggratings

Two new types of optical fibers, where air-holes are running down their length, are considered for making fiber lasers with Bragg gratings. The mode areas for pump and signal in these fiber lasers may be either larger or smaller compared to the corresponding mode areas for fiber lasers based on standard step index fibers. This makes possible realization of fiber lasers with a low pump threshold (small mode area), and fiber lasers suitable for high-power applications (large mode area)     

Viscous and Joulean power losses in liquid-metal sliding electricalcontacts with finite electrically conducting electrodes

Designing high performance liquid-metal sliding electrical contacts for homopolar machinery requires a precise knowledge of the magnitudes of the viscous and Joulean losses under various operating conditions. The liquid metal, which is confined to a channel between a rotor and stator, is subjected to a large external magnetic induction while transporting current. Significant power losses can occur in these devices. The geometry and electrical conductivity of the channel walls have a significant effect on these losses. In past theoretical work, copper electrodes were generally treated as perfect electrical conductors as compared to liquid metals. Calculations based on this perfectly conducting electrode approximation predicted unrealistically high power losses. In the present study, the effects of electrodes with finite conductivity on both the viscous dissipation and Joulean heating are explored. Numerical results are presented for both radial and axial magnetic inductions. It is found that the magnetic induction orientation has a significant impact on the losses. The results of this type of analysis can be used to minimize the power losses in the design of liquid-metal sliding electrical contacts     

Computational analysis of contractility in engineered heart tissue

Engineered heart tissue (EHT) is a potential therapy for heart failure and the basis of functional in vitro assays of novel cardiovascular treatments. Self-organizing EHT can be generated in fiber form, which makes the assessment of contractile function convenient with a force transducer. Contractile function is a key parameter of EHT performance. Analysis of EHT force data is often performed manually; however, this approach is time consuming, incomplete and subjective. Therefore, the purpose of this study was to develop a computer algorithm to efficiently and objectively analyze EHT force data. This algorithm incorporates data filtering, individual contraction detection and validation, inter/intracontractile analysis and intersample analysis. We found the algorithm to be accurate in contraction detection, validation and magnitude measurement as compared to human operators. The algorithm was efficient in processing hundreds of data acquisitions and was able to determine force-length curves, force-frequency relationships and compare various contractile parameters such as peak systolic force generation. We conclude that this computer algorithm is a key adjunct to the objective and efficient assessment of EHT contractile function.     

Spontaneous emission in two-dimensional photonic crystalmicrocavities

The properties of the radiation field in a two-dimensional photonic crystal with and without a microcavity introduced are investigated through the concept of the position-dependent photon density of states. The position-dependent rate of spontaneous radiative decay for a two-level atom with random orientation is deduced from the photon density of states using the Fermi Golden Rule     

Low-loss silicon-on-insulator photonic crystal waveguides

Silicon-on-insulator-based 2D photonic crystal waveguides have been optically characterised. The measured total insertion loss is below 19 dB in the waveguides with unpolarised light. With the length mask technique, it is found that the photonic crystal waveguides show propagation losses below 4 dB/mm     

EM-based optimization exploiting partial space mapping and exact sensitivities

We present a family of robust techniques for exploiting sensitivities in electromagnetic (EM)-based circuit optimization through space mapping (SM) technology. We utilize derivative information for parameter extractions and mapping updates. We exploit a partial SM (PSM) concept, where a reduced set of parameters is sufficient for parameter extraction optimization. It reflects the idea of tuning and execution time is reduced. Upfront gradients of both EM (fine) model and coarse surrogates can initialize possible mapping approximations. We introduce several effective approaches for updating the mapping during the optimization iterations. Examples include the classical Rosenbrock function, modified to illustrate the approach, a two-section transmission-line 10:1 impedance transformer and a microstrip bandstop filter with open stubs.