Gain enhancement in two-stream free electron laser with a planar wiggler and an axial guide magnetic field

The theory for a two-stream free electron laser (FEL) consisting of a relativistic electron beam transported along the axis of a planar wiggler in the presence of an axial guiding magnetic field is proposed and investigated. The electron trajectories and the small signal gain are derived. The characteristic of the linear gain and the normalized maximum gain are studied numerically. The result shows that the normalized maximum gain is considerably enhanced in comparison with that of the single stream. The effect of the difference between the energies of the two beams in this configuration of FEL is also considered, and we find that the gain is affected by the energy differences between groups 1 and 2.     

Effect of deposition method on the optical and microstructural properties of vacuum-deposited MgF2 thin films

The optical and structural properties of magnesium fluoride films deposited by conventional e-beam evaporation and sputtering have been investigated herein. Deposition processes were carried out on the glass substrates in the absence of any reactive gases. The results show that the deposition method has a considerable effect on the optical and microstructural properties MgF₂ film. Also, the results show that the deposition parameters of the sputtered MgF₂ films can be easily controlled to yield the desired layer. The optical, chemical, and structural properties of the deposited MgF₂ films were characterized by using spectrophotometer, X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and atomic force microscopy.     

N,N,N^{\prime },N^{\prime }-Tetrabromobenzene-1,3-disulfonamide and poly(N-bromo-N-ethylbenzene-1,3-disulfonamide) as new and efficient catalysts for the synthesis of highly substituted 1,6-dihydropyrazine-2,3-dicarbonitrile derivatives

Various mono and bis-1,6-dihydropyrazine-2,3-dicarbonitrile derivatives were efficiently synthesized by reacting 2,3-diaminomaleonitrile (DAMN), isocyanides and ketones in the presence of a catalytic amount of $N,N{,}N^{\prime }{,}N^{\prime }$ -tetrabromobenzene-1,3-disulfonamide [TBBDA] and poly( $N$ -bromo- $N$ -ethylbenzene-1,3-disulfonamide) [PBBS] in EtOH/H $_{2}$ O at ambient temperature. Graphic abstract $N,N,N^{\prime },N^{\prime }$ -Tetrabromobenzene-1,3-disulfonamide and poly( $N$ -bromo- $N$ -ethylbenzene-1,3-disulfonamide) as new and efficient catalysts for the synthesis of highly substituted 1,6-dihydropyrazine-2,3-dicarbonitrile derivatives.      

Synthesis of chromeno[3,4-{\varvec{b}}]quinoline derivatives by heterogeneous [Cu(II)BHPPDAH] catalyst without being immobilized on any support under mild conditions using PEG 300 as green solvent

The efficient synthesis of chromeno[3,4- $b$ ]quinoline derivatives by condensation of O-propargylated salicylaldehyde, or corresponding compounds and primary aromatic amine derivatives using a catalytic amount of heterogeneous Cu(II)BHPPDAH complex without being immobilized on any supports (5.0 mol%) in PEG 300 as a “green” solvent is described. The remarkable features of this protocol are good to high yields in all cases, short reaction times, a cleaner reaction profile in an environmentally benign solvent (PEG 300), and the method is applicable to large-scale operation without any problem. Furthermore, the catalyst was quantitatively recovered from the reaction mixture by simple filtration and reused at least seven times with almost consistent activity.     

Binary Accelerated Particle Swarm Algorithm (BAPSA) for discrete optimization problems

The majority of Combinatorial Optimization Problems (COPs) are defined in the discrete space. Hence, proposing an efficient algorithm to solve the problems has become an attractive subject in recent years. In this paper, a meta-heuristic algorithm based on Binary Particle Swarm Algorithm (BPSO) and the governing Newtonian motion laws, so-called Binary Accelerated Particle Swarm Algorithm (BAPSA) is offered for discrete search spaces. The method is presented in two global and local topologies and evaluated on the 0–1 Multidimensional Knapsack Problem (MKP) as a famous problem in the class of COPs and NP-hard problems. Besides, the results are compared with BPSO for both global and local topologies as well as Genetic Algorithm (GA). We applied three methods of Penalty Function (PF) technique, Check-and-Drop (CD) and Improved Check-and-Repair Operator (ICRO) algorithms to solve the problem of infeasible solutions in the 0–1 MKP. Experimental results show that the proposed methods have better performance than BPSO and GA especially when ICRO algorithm is applied to convert infeasible solutions to feasible ones.     

Synthesis of [Zn(ΙΙ)BHPPDAH] as New Heterogeneous Catalyst without Being Immobilized on Any Support and Applied for Mannich Reaction

In this paper, a novel heterogeneous complex of zinc with N,N‐bis(2‐hydroxyphenyl)pyridine‐2,6‐dicarboxamide(BHPPDAH) was synthesized. The catalyst was found to be a highly effective catalyst for the three‐component coupling reactions of aldehydes, alkynes, and amines (A3 coupling) via C–H activation. The reactions could be applied to both aromatic and aliphatic aldehydes and alkynes. Nearly quantitative yields of the desired products were obtained in most cases. The reaction proceeds without any cocatalyst or activator, and water is the only byproduct. The catalyst was quantitatively recovered from the reaction by a simple filtration and reused for five cycles with almost consistent activity.     

Spectroscopic observation of nitrous oxide pentamers

Two new infrared bands in the ν(1) fundamental region of N(2)O are observed in a supersonic jet expansion and assigned to nitrous oxide pentamers. Each band is measured using both (14)N(2)(16)O and (15)N(2)(16)O. Although they are similar in appearance, the bands have slightly different lower state rotational parameters, and are thus assigned to distinct structural isomers of the pentamer. Cluster calculations using two N(2)O intermolecular potentials give results in good agreement with the observed spectra, and indicate that the two isomers probably have the same basic structure (which is unsymmetrical), but differ in the alignment (N-N-O or O-N-N) of one or two of the constituent monomers. Calculations using a resonant dipole interaction model also support the proposed assignment and structure. These are the first reported high-resolution spectra for N(2)O pentamers.     

Molecular beacon probes of oligonucleotides photodamaged by psoralen

Ultraviolet A (UVA)-irradiated 4'-hydroxymethyl-4,5',8-trimethyl psoralen (HMT) in the presence of a poly-dT(17) and dA(7) TTA(8) oligonucleotides produces HMT-dT(17) and HMT-dA(7) TTA(8) adducts in aqueous solution. In this article, we determine whether these HMT-dT(17) and HMT-dA(7) TTA(8) adducts can be detected with a molecular beacon (MB) probe. We measure the degree of damage in dT(17) and dA(7) TTA(8) solutions containing UVA-activated HMT via monitoring the decrease in MB fluorescence. Photoproduct formation is confirmed by MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-fight mass spectrometry measurements) and absorption spectroscopy. The MB fluorescence decreases upon UVA irradiation in the presence of HMT with a single-exponential time constants of 114.2 ± 6.5 min for HMT-dT(17) adducts and 677.8 ± 181.8 min for HMT-dA(7) TTA(8) adducts. Our results show that fluorescent MB probes are a selective, robust and accurate tool for detecting UVA-activated HMT-induced DNA damage.     

Improved Homogeneous Liquid–Liquid Extraction Combined with GC–ECD for the Determination of Organochlorinated Pesticides in Water

In this study, improved homogeneous liquid–liquid extraction (HLLE), equipped with GC–ECD has been developed for the extraction and determination of organochlorinated pesticides (OCPs) in water. The phase separation phenomenon occurred by temperature in a ternary solvent (water/methanol/chloroform) system. Several factors influencing the extraction efficiency were investigated and optimized with orthogonal array design. Furthermore, in this study, for the first time, before immiscible organic phase formation, different volumes of deionized water were subjected to homogeneous solution to investigate the effect of this factor on the extraction performance of HLLE. Optimal results were as follows: volume of the extracting solvent (chloroform), 50?μL; volume of the consolute solvent (methanol), 1.2?mL; volume of the sample, 2.5?mL; volume of the deionized water, 0.5?mL; time of centrifuge, 7?min. Under the optimum conditions, repeatability was obtained by spiking OCPs at concentration level of 20?μg?L^?1, the RSDs varied between 4.8 and 10.7% (n?=?4). The limits of detection of 0.02–0.12?μg?L^?1 were obtained for the OCPs. Enrichment factors and the extraction percent of the studied compounds were in the range of 240–300 and 69.2–84.0%, respectively. Finally, the results of the proposed HLLE method were compared with the same HLLE method without addition of deionized water. The results indicated that the proposed method has higher enrichment factors and lower detection limits.