Theoretical Model of the Bistable Semiconductor Laser Diode Based on the Rate Equations

The paper describes theoretical and experimental results that enabled the authors to proof optical bistability behavior of a specially modified bistable semiconductor laser diode (BLD) created on a structure with a saturable absorption section. A mathematical model of the light-current characteristic, condition for bistability and the basic parameters of the hysteresis loop were derived by solving a system of three rate equations. That system was used for simulation of the light-current characteristic and conditions of bistability of the realized BLDs. For selected operating points of the simulated light-current characteristic the parameters of hysteresis loop and element values of the BLD electrical equivalent circuit for small signal variations were calculated. The bistability was experimentally measured by the new time method devised for impulse bistability verification (IBV). The basic measured and calculated parameters of the hysteresis loop of the BLD light-current characteristic were compared

Design of Polymer Wavelength Splitter 1310 nm/1550 nm Based on Multimode Interferences

We report about design of 1x2 1310/1550 nm optical wavelength division multiplexer based on polymer waveguides. The polymer splitter was designed by using RSoft software based on beam propagation method. Epoxy novolak resin polymer was used as core waveguides layer, silicon substrate with silica layer was used as buffer layer and polymethylmethacrylate was used as protection cover layer. The simulation shows that the output energy for the fundamental mode is 67.1 % for 1310 nm and 67.8 % for 1550 nm wavelength

Differential effects of antibiotics in combination with G-CSF on survival and polymorphonuclear granulocyte cell functions in septic rats

<p>Abstract</p> <p>Background</p> <p>In addition to their antimicrobial activity, antibiotics modulate cellular host defence. Granulocyte-colony stimulating factor (G-CSF) is also a well known immunomodulator; however little is known about the interactions of G-CSF with antibiotics. We investigated in septic rats the effects of two antibiotic combinations with G-CSF.</p> <p>Methods</p> <p>In two clinic modelling randomised trials (CMRTs), male Wistar rats were anesthetized, given antibiotic prophylaxis, had a laparotomy with peritoneal contamination and infection (PCI), and were randomly assigned (n = 18 rats/group) to: 1) PCI only; 2) PCI+antibiotic; and, 3) PCI+antibiotic+G-CSF prophylaxis (20 μg/kg, three times). This sequence was conducted first with 10 mg/kg coamoxiclav, and then with ceftriaxone/metronidazole (Cef/met, 10/3 mg/kg). In additional animals, the blood cell count, migration and superoxide production of PMNs, systemic TNF-α and liver cytokine mRNA expression levels were determined.</p> <p>Results</p> <p>Only the combination coamoxiclav plus G-CSF improved the survival rate (82 vs. 44%, p < 0.001). Improved survival with this combination was accompanied by normalised antimicrobial PMN migratory activity and superoxide production, along with normalised systemic TNF-α levels and a reduced expression of TNF-α and IL-1 in the liver.</p> <p>Conclusion</p> <p>There are substantial differences in the interaction of antibiotics with G-CSF. Therefore, the selection of the antibiotic for combination with G-CSF in sepsis treatment should be guided not only by the bacteria to be eliminated, but also by the effects on antimicrobial functions of PMNs and the cytokine response.</p

Design, Fabrication and Properties of Rib Poly(methylmethacrylimide) Optical Waveguides

We report about design, fabrication and properties of the polymer optical waveguides deposited on silica-on-silicon substrate. The design of the waveguides is based on a concept that geometric dimensions of the single mode polymer waveguide are determined by geometrical parameters of the silica layer. The design of the waveguides was schemed for 650 nm, 850 nm, 1310 nm and 1550 nm wavelength. The design of the presented planar waveguides was realized on the bases of modified dispersion equation while the ridge waveguides design was proposed following the Fischbeck concept. Both designs were refined applying RSoft software using beam propagation method. Proposed shapes of the waveguides were etched by standard photolithography process into the silica layers and polymer waveguide layers were subsequently deposited into the treated substrate by spin coating. Poly(methylmethacrylimide) was used as the waveguide core material and polymethylmethacrylate was used as a cover protection layer. Propagation optical loss measurements were done by using the cut-back method and the best samples had optical losses lower than 0.6 dB/cm at 650 nm, 1310 nm and 1550 nm

Magnetism of small V clusters embedded in a Cu fcc matrix: an ab initio study

We present extensive first principles density functional theory (DFT) calculations dedicated to analyze the magnetic and electronic properties of small V$_{n}$ clusters (n=1,2,3,4,5,6) embedded in a Cu fcc matrix. We consider different cluster structures such as: i) a single V impurity, ii) several V$_{2}$ dimers having different interatomic distance and varying local atomic environment, iii) V$_{3}$ and iv) V$_{4}$ clusters for which we assume compact as well as 2- and 1-dimensional atomic configurations and finally, in the case of the v) V$_{5}$ and vi) V$_{6}$ structures we consider a square pyramid and a square bipyramid together with linear arrays, respectively. In all cases, the V atoms are embedded as substitutional impurities in the Cu network. In general, and as in the free standing case, we have found that the V clusters tend to form compact atomic arrays within the cooper matrix. Our calculated non spin-polarized density of states at the V sites shows a complex peaked structure around the Fermi level that strongly changes as a function of both the interatomic distance and local atomic environment, a result that anticipates a non trivial magnetic behavior. In fact, our DFT calculations reveal, in each one of our clusters systems, the existence of different magnetic solutions (ferromagnetic, ferrimagnetic, and antiferromagnetic) with very small energy differences among them, a result that could lead to the existence of complex finite-temperature magnetic properties. Finally, we compare our results with recent experimental measurements.Comment: 7 pages and 4 figure

Status of Schottky Diagnostics in the ANKA Storage Ring

The status of longitudinal and transverse Schottky observation systems for the synchrotron light source ANKA is presented. ANKA regularly operates in a dedicated low alpha mode with short bunches for the generation of coherent THz radiation. The Schottky measurement results are shown and compared with theoretical predictions for the regular as well as the different stages of the low alpha mode of operation. Special care had to be taken to control and mitigate the impact from strong coherent lines of the short bunches on the signal processing chain. The system setup is shown, expected and unexpected observations as well as applications are discussed

Tuning the size, composition and structure of Au and Co50Au50 Nanoparticles by High-Power Impulse Magnetron Sputtering in gas-phase Synthesis

Gas-phase synthesis of nanoparticles with different structural and chemical distribution is reported using a circular magnetron sputtering in an ion cluster source by applying high-power impulses. The influence of the pulse characteristics on the final deposit was evaluated on Au nanoparticles. The results have been compared with the more common direct current approach. In addition, it is shown for the first time that high-power impulses in magnetron based gas aggregation sources allows the growth of binary nanoparticles, CoAu in this case, with a variety of crystalline and chemical arrangements which are analyzed at the atomic level

Perpendicular magnetic anisotropy in chemically disordered FePd-FeV(100) alloy thin films

We find that the use of V(100) buffer layers on MgO(001) substrates for the epitaxy of FePd binary alloys yields to the formation at intermediate and high deposition temperatures of a FePd¿FeV mixed phase due to strong V diffusion accompanied by a loss of layer continuity and strong increase of its mosaic spread. Contrary to what is usually found in this kind of systems, these mixed phase structures exhibit perpendicular magnetic anisotropy (PMA) which is not correlated with the presence of chemical order, almost totally absent in all the fabricated structures, even at deposition temperatures where it is usually obtained with other buffer layers. Thus the observed PMA can be ascribed to the V interdiffusion and the formation of a FeV alloy, being the global sample saturation magnetization also reduced

Versatile Graphene-Based Platform for Robust Nanobiohybrid Interfaces

Technologically useful and robust graphene-based interfaces for devices require the introduction of highly selective, stable, and covalently bonded functionalities on the graphene surface, whilst essentially retaining the electronic properties of the pristine layer. This work demonstrates that highly controlled, ultrahigh vacuum covalent chemical functionalization of graphene sheets with a thiol-terminated molecule provides a robust and tunable platform for the development of hybrid nanostructures in different environments. We employ this facile strategy to covalently couple two representative systems of broad interest: metal nanoparticles, via S-metal bonds, and thiol-modified DNA aptamers, via disulfide bridges. Both systems, which have been characterized by a multi-technique approach, remain firmly anchored to the graphene surface even after several washing cycles. Atomic force microscopy images demonstrate that the conjugated aptamer retains the functionality required to recognize a target protein. This methodology opens a new route to the integration of high-quality graphene layers into diverse technological platforms, including plasmonics, optoelectronics, or biosensing. With respect to the latter, the viability of a thiol-functionalized chemical vapor deposition graphene-based solution-gated field-effect transistor array was assessed