Influence of ultrasound on cadmium ion removal by sorption process

This study presents the removal of Cd(II) from aqueous solution by the sorption process in the presence (sono-sorption) and absence (conventional method) of ultrasound. Batch experiments were conducted to study the main parameters such as sorbate concentration, amount of sorbent, contact time, and ultrasound intensity. In addition, the sorbate/sorbent concentration ratios were studied in two different ways: (a) in a constant sorbate concentration and variable amount of sorbent, (b) in a constant amount of sorbent and variable sorbate concentration. The results indicated that under proper conditions, there was a possibility to remove cadmium ion very fast and efficiently from aqueous solution. In addition, the intensity of ultrasound and the sorbate/sorbent concentration ratio were two important factors for the removal of this pollutant and therefore, this study was focused mostly on these two variables.     

Effect of operational parameters on degradation of Malachite Green by ultrasonic irradiation

The aim of the present study was to apply ultrasonic technique to remove Malachite Oxalate Green (MG) from aqueous solution. An ultrasonic bath with frequency of 35 kHz was used to investigate the effect of different operational parameters such as MG concentration, power density, temperature, mechanical agitation and addition of EtOH, 2-PrOH and iso-BuOH. Decolorization of MG follows a first order kinetics and hydroxyl radicals have an important role in degradation of MG. The apparent reaction rate constant (k(ap)) was influenced by variation of operational parameters. The activation energy was 30.95 kJ/mol in temperature range of 21-34 degrees C, suggesting a diffusion-controlled reaction. Alcohols act as hydroxyl radicals scavengers having undesirable contribution. UV-vis spectral change of MG showed hypsochromic shift occurred with increasing sonication time, proposing N-demethylation process of MG.     

Fragmentation of chitosan by ultrasonic irradiation

Kinetics of chitosan fragmentation by ultrasonic irradiation at frequency of 20 kHz, and the effects of experimental variables (power of ultrasound, chitosan concentration and solution temperature) on fragmentation were investigated. The kinetics studies were followed by measuring solution viscosity of the original and its fragments, and determining average number of chain scission of the fragments. The effects of ultrasonic power, chitosan concentration and solution temperature on fragmentation process were followed by viscometry and size exclusion chromatography. The chemical structure of the original chitosan and its fragments were examined by (1)H NMR spectroscopy and elemental analysis. The experimental results showed that the rate of fragmentation increased with an increase in power of ultrasound. Chain scission increased with an increase in power of ultrasound; and solution temperature, but a decrease in chitosan concentration. The chemical structure and polydispersity of the original and the fragments were nearly identical. A model based on experimental data to describe the relationship between chain scission and experimental variables (power of ultrasound; irradiation time; reduced concentration, c[eta]; and solution temperature) was proposed. It was concluded that ultrasonic irradiation is a suitable method to perform partial depolymerization and to obtain moderate macromolecules from large ones.     

Suppressing shape instabilities to discover the Bjerknes force instability (L)

For sufficiently strong acoustic forcing in a standing wave field, subresonant size bubbles are predicted to be repelled from the pressure antinode. Single bubble sonoluminescence (SBSL) conditions in water do not allow the observation of this instability. This study investigates the possibility that increasing the viscosity of the host liquid can preferentially suppress shape instabilities of a bubble and allow SBSL experiments to be limited by the Bjerknes force instability.     

Time-stretch oscilloscope with dual-channel differential detection front end for monitoring of 100 Gb/s return-to-zero differential quadrature phase-shift keying data

Optical performance monitoring of high-capacity networks is one of the enabling technologies of future reconfigurable optical switch networks. In such networks, rapid performance evaluation of data streams becomes challenging due to the use of advanced modulation formats and high data rates. The time-stretch enhanced recording oscilloscope offers a potential solution to monitoring high-rate data in a practical time scale. Here we demonstrate an architecture with a differential detection front end for simultaneous I/Q data monitoring of a 100 gigabits/s return-to-zero differential quadrature phase-shift keying signal. This demonstration shows the potential of this technology for rapid performance monitoring of high-rate optical data streams that employ advanced modulation formats.     

Photonic temporal integration of broadband intensity waveforms over long operation time windows

We propose and experimentally demonstrate a novel design for temporal integration of microwave and optical intensity waveforms with combined high processing speed and a long operation time window. It is based on concatenating in series a discrete-time (low-speed) photonic integrator and a high-speed analog time-limited intensity integrator. This scheme is demonstrated here using a cascaded fiber-based interferometers' system (as a passive eight-point discrete-time integrator) and an analog time-limited intensity integrator. The latter is based on temporal intensity modulation of the input waveform with a rectangular-like incoherent energy spectrum followed by linear dispersion. Using this setup, we experimentally achieve accurate time integration of intensity signals with ~36 GHz bandwidths over an operation time window of ~4 ns, corresponding to a processing time-bandwidth product of >144.     

Numerical study of magnetic nanoparticles concentration in biofluid (blood) under influence of high gradient magnetic field

Ferrofluids are widely used in pharmaceutical industries as magnetic separation tools, anti-cancer drug carriers and micro-valve applications. The purpose of the current study is to investigate the effect of a magnetic field on the volume concentration of magnetic nanoparticles of a non-Newtonian biofluid (blood) as a drug carrier. The effect of particles on the flow field is considered. The governing non-linear differential equations, concentration and Naviar-stokes are coupled with the magnetic field. To solve these equations, a finite volume based code is developed and utilized. The results show accumulation of magnetic nanoparticles near the magnetic source until it looks like a solid object. The accumulation of nanoparticles is due to the magnetic force that overcomes the fluid drag force. As the magnetic strength and size of the magnetic particles increase, the accumulation of nanoparticles increases, as well. The magnetic susceptibility of particles also affects the flow field and the contour of the concentration considerably.     

Terahertz imaging through self-mixing in a quantum cascade laser

We demonstrate terahertz (THz) frequency imaging using a single quantum cascade laser (QCL) device for both generation and sensing of THz radiation. Detection is achieved by utilizing the effect of self-mixing in the THz QCL, and, specifically, by monitoring perturbations to the voltage across the QCL, induced by light reflected from an external object back into the laser cavity. Self-mixing imaging offers high sensitivity, a potentially fast response, and a simple, compact optical design, and we show that it can be used to obtain high-resolution reflection images of exemplar structures.     

Pyrophosphate Selective Recognition in Aqueous Solution Based on Fluorescence Enhancement of a New Aluminium Complex

A novel and simple fluorescence enhancement method for selective pyrophosphate(PPi) sensing was proposed based on a 1:1 metal complex formation between bis(8-hydroxy quinoline-5-solphonat) chloride aluminum(III) (Al(QS)₂Cl), (L) and PPi in aqueous solution. The linear response range covers a concentration range of 1.6 × 10⁻⁷ to 1.0 × 10⁻⁵ mol/L of PPi and the detection limit of 2.3 × 10⁻⁸ mol/L. The association constant of L-PPi complex was calculated 2.6 × 10⁵ L/mol. L was found to show selectively and sensitively fluorescence enhancement toward PPi over than I₃^-, NO₃^-, CN⁻, CO₃²⁻, Br⁻, Cl⁻, F⁻, H₂PO4⁻ and SO₄²⁻, which was attributed to higher stability of inorganic complex between pyrophosphate and L.     

Effects of Cs treatment on field emission properties of capped carbon nanotubes

Within the methodology [M. Khazaei, A.A. Farajian, Y. Kawazoe, Phys. Rev. Lett. 95 (2005) 177602] based on first-principles electronic structure calculations, the effects of Cs treatment on current emissions and emission patterns of capped carbon nanotubes are considered at low deposition densities when the nanotubes are under an electric field 0.2 V/Å. The results show that the current emission from the cap with one adsorbed Cs is 3.4 times larger than the cap without any Cs. It is 9.6 times larger in the cap with two adsorbed Cs atoms. After Cs deposition the emission patterns become asymmetric (current emission from the carbon atoms located at the topmost pentagon ring close to Cs atoms is larger than the other atomic sites). There are very few localized states on Cs atoms. Hence, although the tunneling probability of electron emission from Cs atoms is significant, there is no current from Cs atoms. In addition, the effect of Cs on work function reduction of nanotubes is explained in terms of Cs deposition densities and the surface dipole moments.