Generation of 40-as few-cycle pulse through chirp manipulation

We discuss theoretically how supercontinuum spectra produced from high-order harmonic generation processes in a synthesized same-color laser field is optimized by adjusting the chirp parameter of the controlling pulse. Furthermore, a 40-attosecond isolated pulse with an effective bandwidth of 121 orders is obtained from He+ ion when the chirp rate ratio of pulses has a small value. The numerical results show that the efficiency of single as pulse generation is enhanced, and the quantum paths are controlled successfully. Our simulation shows that the produced pulses with high signal-to-noise ratio are obtained straightforwardly without any phase compensation. These results are explained using the classical approach.     

Optical sensing of nanoparticles in the infrared by use of silica nanowires

We numerically investigate an optical sensor in the infrared based on a Mach?CZehnder interferometer (MZI) assembled with two single-mode silica nanowires immersed in acetonitrile. We propose to use acetonitrile as the detecting solution because, in contrast to water which has very high losses in the infrared, it has negligible losses at important wavelengths of 1,300 and 1550?nm. By solving for the fundamental mode of a three-layer nanowire, we calculate the propagation constant difference between the sensing and reference arms at the output of the MZI optical sensor. For nanoparticles with a size of 12?nm and an index of refraction of 1.4, the sensitivity of the optical sensor becomes a maximum for a wire diameter of 1.23???m. An optical sensor operating at a wavelength of 325?nm and using water as the detecting solution requires nanowires with a diameter of 240?nm, which is much more difficult to implement.     

Solitary wave solutions of the nonlinear generalized Pochhammer–Chree and regularized long wave equations

In this paper, we implement some fast and high accuracy numerical algorithms to obtain the solitary wave solutions of generalized Pochhammer?CChree (PC) and regularized long wave (RLW) equations. We employ the discrete Fourier transform to discretize the original partial differential equations (PDEs) in space and obtain a system of ordinary differential equations (ODEs) in Fourier space which will be solved with fourth order time-stepping methods. The proposed methods are fast and accurate due to the use of the fast Fourier transform in combination with explicit fourth-order time stepping methods. For RLW equation we investigate the propagation of a single solitary and interaction of two and three solitary waves. Moreover, three invariants of motion (mass, energy, and momentum) are evaluated to determine the conservation properties of the problem, and the numerical schemes lead to accurate results. The numerical results are compared with analytical solutions and with those of other recently published methods to confirm the accuracy and efficiency of the presented schemes.     

Experimental study on convective heat transfer of TiO2 nanofluids

In this study, nanofluids with different TiO₂ nanoparticle concentrations were synthesized and measured in different constant heat fluxes for their heat transfer behavior upon flowing through a vertical pipe. Addition of nanoparticles into the base fluid enhances the forced convective heat transfer coefficient. The results show that the enhancement of the convective heat transfer coefficient in the mixture consisting of ethylene glycol and distilled water is more than distilled water as a base fluid.     

Proximal Point Algorithm for Quasi-Convex Minimization Problems in Metric Spaces

In this paper, the proximal point algorithm for quasi-convex minimization problem in nonpositive curvature metric spaces is studied. We prove Δ-convergence of the generated sequence to a critical point (which is defined in the text) of an objective quasi-convex, proper and lower semicontinuous function with at least a minimum point as well as some strong convergence results to a minimum point with some additional conditions. The results extend the recent results of the proximal point algorithm in Hadamard manifolds and CAT(0) spaces.     

Application of calcium oxide as an efficient phase separation agent in temperature-induced counter-current homogenous liquid-liquid extraction of aflatoxins from dried fruit chips followed by high-performance liquid chromatography-tandem mass spectrometry determination

A temperature-induced counter-current homogenous liquid-liquid extraction procedure performed in a burette has been proposed for the isolation of aflatoxins B1, B2, G1, and G2 from various fruit chip samples. In this method, a homogenous solution of deionized water and cyclohexylamine is added to the solid sample and the resulted mixture is vortexed. In the following, the liquid phase is taken and passed through the burette filled with a mixture of calcium oxide (as a phase separation agent) and sand (to avoid clumping the calcium oxide). By doing so, the temperature of the solution is increased by hydration of calcium oxide and consequently, the homogenous state is broken and the aflatoxins are migrated into the resulted tiny droplets of cyclohexylamine. This phase is collected on the top of the solution owing to its low density with respect to an aqueous solution. Numerous parameters which can affect the efficiency of the suggested approach were evaluated and under the best situations, great repeatability, low limits of determination and quantification, and high extraction recoveries were acquired. In the end, the suggested approach was employed for the quantification of the selected aflatoxins in various fruit chips samples marketed in Tabriz City, Iran.     

Production of a water disinfectant by membrane electrolysis of brine solution and evaluation of its quality change during the storage time

Anolyte solution produced by membrane electrolysis of NaCl solution contains a high level of available chlorine content (ACC) and other oxidizing compounds, rendering this solution a strong disinfectant property. In this paper, some process parameters affecting the anolyte production efficiency, such as total inlet flow (240–320 L/h), saline solution concentration (1.65–3.50 g/L), and the type of membrane (cation exchange, anion exchange, and bipolar membranes) were investigated in an electrolysis cell. Changes in the quality of anolytes produced at three initial concentrations of very high (ACC₁ = 816.5 mg/L), relatively high (ACC₂ = 461.5 mg/L), and medium (ACC₃ = 355.0 mg/L) during storage (from the production up to 20 weeks) were examined by adjusting the total inlet flow, saline concentrations, and membrane types. Changes in the ACC of the produced anolyte solution were generally affected by the type of membrane used in the electrolysis cell. The use of anion exchange membrane resulted in the lowest durability of anolyte quality (60–80% ACC reduction after 4 weeks of storage) and the cation exchange membrane had the highest durability (less than 40% decrease after 4 weeks of storage). In addition, changes in the pH and the oxidation–reduction potential of the anolyte were investigated during the storage period, which had a different trend depending on the type of applied membrane.     

Voltammetric determination of droxidopa in the presence of carbidopa using a nanostructured base electrochemical sensor

A novel carbon paste electrode modified with ZnO nanorods and 2-(4-oxo-3-phenyl-3,4-dihydroquinazolinyl)-N′-phenyl-hydrazinecarbothioamide (2PHCZNCPE) was fabricated and employed to study the electrocatalytic oxidation of droxidopa, using cyclic voltammetry, chronoamperometry and square wave voltammetry as diagnostic techniques. It has been found that the oxidation of droxidopa at the surface of modified electrode occurs at a potential of about 435 mV less positive than that of an unmodified carbon paste electrode. Square wave voltammetry exhibits a linear dynamic range from 7.0 × 10^–8 to 3.0×10^?4 M and a detection limit of 45.0 nM for droxidopa. Finally this modified electrode was used for simultaneous determination of droxidopa and carbidopa.     

Molecular springs, muscles, rheostats, and precessing gyroscopes: from review to preview

The concepts of molecular springs and gyroscopes have existed for some time, and there have been numerous reports published about these fascinating topics. Here we describe our interest in this topic, reviewing our initial progress. This is not a complete story, rather an offering of synthetic strategies, interesting molecular structures, observations, and possibilities. In many cases, the "properties" component of the structure-property relationship for a given compound is the result of a computational prediction. Given the present state of theoretical chemistry, a computer's predictive power can far exceed that which can be presently accomplished by existing experimental analytical means. The theoretical results reported here allude to intriguing possibilities. Hopefully, this intrigue will help catalyze the development of definitive, albeit rather esoteric, single-molecule analytical experiments. The intentionally speculative nature of this review is intended to stimulate new challenges for and perspectives from those in related fields of interest; hopefully presenting a preview of what is to come.