Photocatalytic ozonation degradation of ciprofloxacin using ZnO nanoparticles immobilized on the surface of stones

Ciprofloxacin is used in the treatment of bacterial infections. Because ciprofloxacin is not effectively degraded by biological processes, advanced oxidation processes such as photocatalytic ozonation are applied to remove this antibiotic from wastewater. The aim of this study was to investigate photocatalytic ozonation for the removal of ciprofloxacin from aquatic environments and optimization of the effective parameters of the process. For this purpose, ZnO nanoparticles were synthesized using the thermal method and immobilized on the surface of stones. The structural properties of the nanoparticles were determined by XRD, TEM, Photoluminescence (PL) and SEM. Experiments were carried out in a Plexiglas reactor supported with the continuous injection of ozone. The effective parameters for removal efficiency were reaction time, initial concentration of ciprofloxacin, pH, photocatalyst concentration and reaction kinetics. The highest ciprofloxacin removal efficiency occurred at the following optimal conditions: pH of 7, reaction time of 30?min, photocatalyst concentration of 3?g/L and initial ciprofloxacin concentration of 10?mg/L. Removal efficiency of 96% was obtained under these conditions. Linear kinetic models showed that the process followed pseudo-first order and Langmuir-Hinshelwood kinetics. This process had a high removal efficiency and suitable for removal of ciprofloxacin from aquatic environments.GRAPHICAL ABSTRACT     

Design and construction of a 110 W green laser for medical application

In this paper, the design and the construction of a high-power side-diode-pumped Nd:YAG solid-state laser at repetition rates of 6 and 10 kHz has been presented. Second harmonic of the Nd:YAG laser with green light at 532 nm, with an average power of 111.5 W at 10 kHz repetition rate, and with 90 ns pulse duration, has been obtained by the nonlinear crystal of KTP with 59% conversion efficiency and 12% diode-to-green optical–optical efficiency in the linear resonator. Beam spot size and divergence is 4 mm and 8 mrad, respectively. The laser stability is about 97%. As a medical application of this laser, investigation of degree of effectiveness and penetration depth of laser on adenomas of resected prostate after open prostatectomy has been done.     

On the approximation of local efflux/influx bed discharge in the shallow water equations based on a wave propagation algorithm

In cities, flood waves may propagate over street surfaces below which lie complicated pipe networks used for storm drainage and sewage. The flood and pipe flows can interact at connections between the underground pipes and the street surface. The present paper examines this interaction, using the shallow water equations to model the flood wave hydrodynamics. Sources and sinks in the mass conservation equation are used to model the pipe inflow and outflow conditions at bed connections. We consider the problem reduced to one dimension. The shallow water equations are solved using a Godunov‐type wave propagation scheme. Wave speeds are modified in the wave propagation algorithm to enable flows to be simulated over nearly dry beds and dry states. First, the model is used to simulate vertical flows through finite gaps in the bed. Next, the interaction of the vertical flows with a dam break flow is considered for both dry and wet beds. An efflux number, En, is defined based on the vertical efflux velocity and the gap length. Comparisons are made with numerical predictions from STAR‐CD, a commercial Navier–Stokes solver that models the free‐surface motions, and a parameter study is undertaken to investigate the effect of the one‐dimensional approximation of the present model, for a range of non‐dimensional efflux numbers. It is found that the shallow flow model gives sensible predictions at all time provided En<0.5, and for long durations for En>0.5. Dam break flow over an underground connecting pipe is also considered. Copyright © 2010 John Wiley & Sons, Ltd.     

Theoretical study of the electronic conduction through organic nanowires

A substantial amount of researches have been carried out on the electron transport properties of gold surfaces. In order to study the role of linkage in the conductive properties of a molecular wire, different linkers such as sulfur, nitrogen, oxygen, CS, SH, NS, and CN are considered in our study. It is found that nitrogen or sulfur linkages can bond Au covalently to cis- and trans-butadiene, whereas on the other hand, oxygen linkage with the same shows a weak interaction and a non-covalent character. Further, this research is also an attempt to study the dependence of the molecular electronic structure of gold-molecule complexes on the external electric field. In addition, electronic conduction has been investigated from the perspective of alteration in shape of molecular orbitals and the development of the HOMO-LUMO gap of moleculegold complexes under the effect of an electric field.     

Resampling based inference for a distribution function using censored ranked set samples

This article deals with constructing confidence intervals/bands for a distribution function based on censored ranked set samples. Toward this end, a resampling plan is suggested and its validity is investigated. Monte Carlo simulations are used to compare performances of the bootstrap confidence intervals with their asymptotic analogs, and their modifications by jackknife. An environmental data set is finally analyzed.     

Study of Complex Formation between Kryptofix 21 with La<Superscript>3+</Superscript>, Y<Superscript>3+</Superscript> and Ce<Superscript>3+</Superscript> Cations in Some Binary Mixed Non-Aqueous Solvents Using the Conductometric Method

The complexation reactions between La³⁺, Y³⁺ and Ce³⁺ cations with the macrocyclic ligand, kryptofix 21, were studied in methanol-acetonitrile (MeOH-AN) and methanol-methylacetate (MeOHMeOAc) binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that in most solvent systems, the kryptofix 21 forms a 1: 1 [M: L] complex with La³⁺, Y³⁺ and Ce³⁺ metal cations, but in the case of Y³⁺ cation in pure methylacetate, in addition of formation of a 1: 1 [ML] complex, 1: 2 [ML₂] and 1: 3 [ML₃] complexes are formed in solution. In the case of Ce³⁺cation, a 1: 1 [ML] and also a 1: 2 [ML₂] complexes are formed in this solvent system at all studied temperatures. The electrical conductance data in acetonitrile, show that a 1: 1 [ML] and also a 1: 2 [ML₂] complexes are formed between the ligand and La³⁺ and Ce³⁺ metal cations at different temperatures. The stability constants of the 1: 1 [ML] complexes were determined using the conductometric data and a computer program, GENPLOT. A non-monotonic relationship was observed between log_{K f} of the 1: 1 complexes with the composition of the binary solvent solutions which was discussed in term of solvent-solvent interactions and also preferential solvation of the metal cations and the ligand in solutions. The selectivity order of the ligand for the metal cations in MeOH–AN and MeOH–MeOAc binary solvent solutions, at 25°C was found to be: Y³⁺ > La³⁺ > Ce³⁺ and La³⁺ > Y³⁺ > Ce³⁺, respectively. The values of the standard thermodynamic quantities (ΔH _c ^° and ΔS _c ^° ) for formation of the 1: 1 complexes were obtained from temperature dependence of the stability constans of the complexes and the results show that the thermodynamics of the complexation reactions between kryptofix 21 and La³⁺, Y³⁺ and Ce³⁺ cations, is affected by the nature and composition of the mixed solvents systems.     

Influence of temperature,pressure, nanotube’s diameter and intertube distance on methane adsorption in homogeneous armchair open-ended SWCNT triangular arrays

The physisorption of methane in homogeneous armchair open-ended SWCNT triangular arrays for the tubes of diameter of 10.85, 13.57, 16.28 and 19.00 Å [(8,8), (10,10), (12,12) and (14,14), respectively] at temperature of 273, 298, 323 and 373 K and at fugacity of 0.5–9.0 Mpa is evaluated by means of Grand Canonical ensemble Monte Carlo simulation. The applied intermolecular forces are modeled using Lennard-Jones potential model. The absolute, excess and delivery adsorption isotherms of methane in various carbon nanotube arrays are calculated. Besides, specific surface areas and the isosteric heats of adsorption, Q _st, are studied, also different isotherm models were fitted on the simulation adsorption data, and the model parameters are correlated. A novel geometrical relationship is introduced to calculate accessible interstitial and intratubular volumes. According to our simulation results, one can reaches to 96% of the US Department of Energy target for CH₄ storage of 180 v/v at 298 K and 35 bar by using the SWCNT array with nanotube’s diameter of 19 Å as adsorbent. For intertube distance equal 3.4 Å, no gas adsorption is observed in interstitial channel except for the arrays bigger than 15.4 Å in nanotube’s diameter, and multi-layer adsorption starts to form in nanotube’s diameter of 16.28 Å at the pressure of 2.0 MPa.     

Some Aspects of Current Interruption Physics in High Voltage Circuit Breakers

Recent results of experimental and theoretical investigations on current interruption processes are presented with a focus on SF₆ high voltage circuit breakers. Various aspects of thermal interruption at the zero crossing of the current are shown, including the scatter and the distribution of arc voltage shortly before CZ and the role of turbulence. The thermal interruption capability of air and CO₂ are compared to that of SF₆. Investigations on the dielectric recovery are shown for SF₆ and CO₂. The breakdown voltage during the dielectric recovery can be described by simple streamer and leader inception models. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Partitioning of Recombinant Pseudomonas putida POS-F84 Proline Dehydrogenase in Aqueous Two-Phase Systems: Optimization Using Response Surface Methodology

Applied Biochemistry and Biotechnology - Empirical modeling the partition behavior and recovery of a recombinant Pseudomonas putida POS-F84 proline dehydrogenase (ProDH) in aqueous two-phase...     

A robust UV–visible light‐driven SBA‐15‐PS/phthalhydrazide nanohybrid material with enhanced photocatalytic activity in the photodegradation of methyl orange

SBA‐15‐PS/phthalhydrazide (PHD) is presented as a new heterogeneous inorganic–organic nanohybrid photocatalyst with high stability, superior recyclability and remarkable performance in the degradation of methyl orange (MO). Distinctive parameters, including photocatalyst and dye concentrations, pH and degradation time, were assessed for MO degradation catalysed by SBA‐15‐PS/PHD. This new heterogeneous nanocatalyst was characterized using Fourier transform infrared and UV–visible spectroscopies, thermogravimetric analysis, scanning and transmission electron microscopies and elemental analysis. Photodegradation of MO of up to 92% under the optimum conditions (photocatalyst = 0.015 g, [MO] = 4 ppm, pH = 2) was accomplished in 25 min using SBA‐15‐PS/PHD. A preliminary kinetic investigation was performed, and pseudo‐first‐order kinetics with a high rate constant (0.068 min^?1) was found for MO degradation. Additional results showed that the photodegradation of MO was increased in the presence of hole scavengers. Therefore a photoreduction mechanism for MO degradation is proposed.