The effect of temperature on absorption in end-pumped Yb:YAG thin disk lasers

In this paper, the dependence of the absorbed power on the temperature in an end-pumped CW quasi-three-level Yb:YAG thin disk laser is calculated. Here, we have used the temperature-dependent form of the Boltzmann occupation factors, absorption cross-section and thermal conductivity of the Yb:YAG crystal. A Monte Carlo ray tracing code and a 2D finite element analysis (FEA) with the ANSYS package have been used to calculate the absorbed power and the temperature distribution inside the Yb:YAG thin disk laser, respectively. According to the model, the temperature-dependent absorbed power turns out to be 18% less than the temperature-independent absorbed power in the top center of the Yb:YAG thin disk laser for used parameters.     

Naked Eye Chemosensor and In Vivo Chelating Activity of Iron (III) By Bromopyridine Quinoxaline (BPQ)

Journal of Fluorescence - A wide variety of medical, biomedical, and industrial applications has been reported for quinoxalines derivatives. In this work, a novel quinoxaline derivative was...     

Effect of Satureja khuzestanica essential oil on oxidative stability of sunflower oil during accelerated storage

In this study, the application of various concentrations (0.02%, 0.04%, 0.06% and 0.08%) of Satureja khuzestanica essential oil (EO) was examined on the oxidative stability of sunflower oil and compared to butylated hydroxyanisole (BHA) during storage at 60°C. Gas chromatography (GC) and GC-mass spectrometry analyses of the oils revealed that carvacrol (87.7%) was the major component of EO. Peroxide value and anisidine value measurements in sunflower oil showed that all concentrations of EO had antioxidant effects in comparison to BHA. Oil samples supplemented with EO concentration of 0.08% were the most stable during storage (p?相似文献   

On solving continuous-time dynamic network flows

Temporal dynamics is a crucial feature of network flow problems occurring in many practical applications. Important characteristics of real-world networks such as arc capacities, transit times, transit and storage costs, demands and supplies etc. are subject to fluctuations over time. Consequently, also flow on arcs can change over time which leads to so-called dynamic network flows. While time is a continuous entity by nature, discrete-time models are often used for modeling dynamic network flows as the resulting problems are in general much easier to handle computationally. In this paper, we study a general class of dynamic network flow problems in the continuous-time model, where the input functions are assumed to be piecewise linear or piecewise constant. We give two discrete approximations of the problem by dividing the considered time range into intervals where all parameters are constant or linear. We then present two algorithms that compute, or at least converge to optimum solutions. Finally, we give an empirical analysis of the performance of both algorithms.     

Wideband tunable laser phase noise reduction using single sideband modulation in an electro-optical feed-forward scheme

A wideband laser phase noise reduction scheme is introduced where the optical field of a laser is single sideband modulated with an electrical signal containing the discriminated phase noise of the laser. The proof-of-concept experiments on a commercially available 1549 nm distributed feedback laser show linewidth reduction from 7.5 MHz to 1.8 kHz without using large optical cavity resonators. This feed-forward scheme performs wideband phase noise cancellation independent of the light source and, as such, it is compatible with the original laser source tunability without requiring tunable optical components. By placing the proposed phase noise reduction system after a commercial tunable laser, a tunable coherent light source with kilohertz linewidth over a tuning range of 1530-1570 nm is demonstrated.     

Piezoelectric composites with periodic multi-coated inhomogeneities

A new, robust homogenization scheme for determination of the effective properties of a periodic piezoelectric composite with general multi-coated inhomogeneities is developed. In this scheme the coating does not have to be thin, the shape and orientation of the inclusion and coatings do not have to be identical, their centers do not have to coincide, their properties do not have to remain uniform, and the microstructure can be with the 2D elliptic or the 3D ellipsoidal inclusions. The development starts from the local electromechanical equivalent inclusion principle through the introduction of the position-dependent equivalent eigenstrain and electric field. Then with a Fourier series expansion and a superposition procedure, the volume-averaged equivalent eigenstrain and electric field for each phase are obtained. The results in turn are used in an energy equivalent criterion to determine the effective properties of the composite. In this model the interphase interactions in each multi-coated particle and the long-range interactions between the periodically distributed particles are fully accounted for. To demonstrate its wide range of applicability, we applied it to examine the properties of several periodic composites: (i) piezoelectric PZT spherical particles in a polymer matrix, (ii) continuous glassy fibers with thin PZT coating in an epoxy matrix, (iii) spherical PZT particles coated by thick or functionally graded piezoelectric layer, (iv) spheroidal voids coated with a thick non-piezoelectric layer in a PZT matrix, and (v) spherical piezoelectric inhomogeneities with eccentric, non-uniform thickness coating. The calculated results reflect the complex nature of interplay between the properties of core, matrix, and coating, as well as whether the coating is uniform, functionally graded, or eccentric. The accuracy of this new scheme is checked against the double-inclusion and other micromechanics models, and good agreement is observed.     

Observability of light charged Higgs decay to muon in top quark pair events at LHC

The European Physical Journal C - In this paper the charged Higgs signal through the decay to a pair of muon and neutrino (H ±→μν) is analyzed. The analysis attempts to...     

Kinetic–Spectrophotometric Determination of Trace Silver(I) Using Its Catalytic Effect on the Oxidation Reaction of Fuchsin by Peroxodisulfate in the Presence of 1,10-Phenanthroline As an Activator

A kinetic spectrophotometric method for the determination of trace amounts of Ag(I) in the range of 2–20 ng mL^–1 is reported. The method is based on the catalytic effect of Ag(I) on the oxidation reaction of fuschin by potassium peroxodisulfate in the presence of 1,10-phenanthroline as an activator at pH = 5. The reaction is followed spectrophotometrically by measuring the change in absorbance (A) at 544 nm using a fixed time method (6 min). The reaction variables were optimized in order to achieve the highest sensitivity. The 3s criterion detection limit was 0.7 ng mL^–1, and the relative standard deviation for ten replicate measurements of 16 ng mL^–1 of Ag(I) was 0.95% (n = 10). The method was successfully applied to the determination of silver in expired black and white photographic films and results showed good agreements with those obtained by atomic absorption spectrometry.     

Aromatization of <Emphasis Type="Italic">Hantzsch</Emphasis> 1,4-Dihydropyridines by Hydrogen Peroxide in the Presence of Cobalt(II) Acetate

Summary.  Hydrogen peroxide readily oxidizes Hantzsch type 1,4-dihydropyridines in the presence of cobalt(II) acetate as catalyst at room temperature. No evidence of a dealkylation process for 4-alkyl 1,4-dihydropyridines has been observed. Corresponding author. E-mail: mhashemi@sharif.ac.ir Received January 16, 2002; accepted (revised) April 20, 2002     

Selective homogeneous liquid-liquid extraction and preconcentration of copper(II) into a micro droplet using a benzo-substituted macrocyclic diamide, and its determination by electrothermal atomic absorption spectrometry

A fast and reliable method was developed for the selective separation and preconcentration of Cu²⁺ ions using homogeneous liquid-liquid extraction using a novel benzo-substituted macrocyclic diamide, 5,6,7,8,9,10-hexahydro-2H-1,13,4,7,10-benzodioatriazacyclo-pentadecine-3,11(4 H,12 H)-dione, as a selective complexing agent. An aqueous solution of Zonyl FSA (FSA) was used as a phase-separation agent at pH 4.5. Electrothermal atomic absorption spectrometry was used for Cu²⁺ determination after preconcentration. The influences of pH, type and volume of the water-miscible organic solvent, concentration of FSA, concentration of the ligand and the effect of diverse ions were investigated. Factorial design and response surface methods were used for the optimization purposes. Under the optimum experimental conditions, 50 ng of Cu²⁺ in 5 mL aqueous sample could be extracted quantitatively into 76 µL of the sediment phase. The maximum preconcentration factor was 65. The calibration curve was linear in the concentration range 0.2 to 4.0 µg L^?1. The detection limit and relative standard deviation were 4 ng L^?1 and 4.6%, respectively. The method was successfully applied to the extraction and determination of Cu²⁺ in natural water samples.