Enhanced catalytic performance of copper iodide in 1,2,3-triazole-imidazole hybrid synthesis,and evaluation of their anti-cancer activities along with optical properties besides 1H-tetrazole-imidazole hybrids

New triazole-imidazole and tetrazole-imidazole hybrids were obtained using 2,4,5-triaryl-1-(4-aminophenyl) imidazoles by copper-catalyzedazide-alkyne cycloaddition (CuAAC) and Ugi-azidefour-component(UA-4CRs) process. The synthesis of triazole hybrids was performed in the presence of new copper-incorporated white sandstone nanocatalyst, which was fully characterized by different methods. The construction of newly prepared hybrids was confirmed by spectroscopic techniques. Some of these compounds were evaluated for their anti-cancer properties against MCF-7 cancer cell lines. The absorption and emission parameters of the triazole- and tetrazole-substituted imidazoles were also investigated and compared with each other.     

Equation of state for polymers based on glass transition data

This paper addresses a method for predicting the participating constants in equation of state (EOS) for compressed polymeric fluids using two scaling constants, the surface tension γ _g and the molar density ρ _g, both at the glass transition point. The theoretical EOS undertaken is the one attributed to Tao and Mason. The second virial coefficients are calculated from a two-parameter corresponding states correlation, which is constructed with two constants as scaling parameters, i.e., the surface tension γ _g and the molar density ρ _g. This new correlation has been applied to the Tao–Mason (TM) EOS to predict the volumetric behavior of several polymer melts. The operating temperature range is from 291.25 to 603.4 K and pressures of up to 202.5 MPa. A collection of 516 data points has been examined for the aforementioned polymers. The average absolute deviation between the calculated densities and the experimental ones is of the order of 0.44%.     

Vibration based algorithm for crack detection in cantilever beam containing two different types of cracks

In this paper, a simple method for detection of multiple edge cracks in Euler–Bernoulli beams having two different types of cracks is presented based on energy equations. Each crack is modeled as a massless rotational spring using Linear Elastic Fracture Mechanics (LEFM) theory, and a relationship among natural frequencies, crack locations and stiffness of equivalent springs is demonstrated. In the procedure, for detection of m cracks in a beam, 3m equations and natural frequencies of healthy and cracked beam in two different directions are needed as input to the algorithm.     

One‐Pot Synthesis of 4‐(2,3‐Dihydro‐2‐hydroxy‐1,3‐dioxo‐1H‐inden‐2‐yl)‐Substituted 1‐Aryl‐1H‐pyrazole‐3‐carboxylates via a Tandem Three‐Component Reaction

The hitherto unreported, highly functionalized 1H‐pyrazole‐3‐carboxylates 3 have been synthesized in good yields via a one‐pot three‐component domino reaction of phenylhydrazines, dialkyl acetylenedicarboxylates, and ninhydrin under mild conditions for the first time. No co‐catalyst or activator is required for this multicomponent reaction, and the reaction is, from an experimental point of view, simple to perform (Scheme 1). The structures of compounds 3 were corroborated spectroscopically (IR, ¹H‐ and ¹³C‐NMR, and EI‐MS) and by elemental analyses. A plausible mechanism for this type of cyclization/addition reaction is proposed (Scheme 2).     

A pseudo‐spectral method that uses an overlapping multidomain technique for the numerical solution of sine‐Gordon equation in one and two spatial dimensions

In this article, we study an explicit scheme for the solution of sine‐Gordon equation when the space discretization is carried out by an overlapping multidomain pseudo‐spectral technique. By using differentiation matrices, the equation is reduced to a nonlinear system of ordinary differential equations in time that can be discretized with the explicit fourth‐order Runge–Kutta method. To achieve approximation with high accuracy in large domains, the number of space grid points must be large enough. This yields very large and full matrices in the pseudo‐spectral method that causes large memory requirements. The domain decomposition approach provides sparsity in the matrices obtained after the discretization, and this property reduces storage for large matrices and provides economical ways of performing matrix–vector multiplications. Therefore, we propose a multidomain pseudo‐spectral method for the numerical simulation of the sine‐Gordon equation in large domains. Test examples are given to demonstrate the accuracy and capability of the proposed method. Numerical experiments show that the multidomain scheme has an excellent long‐time numerical behavior for the sine‐Gordon equation in one and two dimensions. Copyright © 2013 John Wiley & Sons, Ltd.     

Simultaneous voltammetric determination of ascorbic acid and dopamine at the surface of electrodes modified with self-assembled gold nanoparticle films

Gold nanoparticles (GNs) could be efficiently immobilized on binary mixed self-assembled monolayers (SAMs) on a gold surface composed of 1,6-hexanedithiol and 1-octanethiol (nano-Au/SAMs gold electrode). This GN chemically modified electrode was used for electrochemical determination of ascorbic acid (AA) and dopamine (DA) in aqueous media. The result showed that the GN-modified electrode could clearly resolve the oxidation peaks of AA and DA, with a peak-to-peak separation (∆E _p) of 110 mV enabling determination of AA and DA in the presence of each other. The linear analytical curves were obtained in the ranges of 0.3–1.4 mM for AA and 0.2–1.2 mM for DA concentrations using differential pulse voltammetry. The detection limits (3σ) were 9.0 × 10⁻⁵ M for AA and 9.0 × 10⁻⁵ M for DA.     

The effect of ultrasound irradiation on the convective heat transfer rate during immersion cooling of a stationary sphere

It has been proven that ultrasound irradiation can enhance the rate of heat transfer processes. The objective of this work was to study the heat transfer phenomenon, mainly the heat exchange at the surface, as affected by ultrasound irradiation around a stationary copper sphere (k=386W m(-1)K(-1), C(p)=384J kg(-1)K(-1), ρ=8660kg m(-3)) during cooling. The sphere (0.01m in diameter) was immersed in an ethylene glycol-water mixture (-10°C) in an ultrasonic cooling system that included a refrigerated circulator, a flow meter, an ultrasound generator and an ultrasonic bath. The temperature of the sphere was recorded using a data logger equipped with a T-type thermocouple in the center of the sphere. The temperature of the cooling medium was also monitored by four thermocouples situated at different places in the bath. The sphere was located at different positions (0.02, 0.04 and 0.06m) above the transducer surface of the bath calculated considering the center of the sphere as the center of the reference system and was exposed to different intensities of ultrasound (0, 120, 190, 450, 890, 1800, 2800, 3400 and 4100W m(-2)) during cooling. The frequency of the ultrasound was 25kHz. It was demonstrated that ultrasound irradiation can increase the rate of heat transfer significantly, resulting in considerably shorter cooling times. Higher intensities caused higher cooling rates, and Nu values were increased from about 23-27 to 25-108 depending on the intensity of ultrasound and the position of the sphere. However, high intensities of ultrasound led to the generation of heat at the surface of the sphere, thus limiting the lowest final temperature achieved. An analytical solution was developed considering the heat generation and was fitted to the experimental data with R(2) values in the range of 0.910-0.998. Visual observations revealed that both cavitation and acoustic streaming were important for heat transfer phenomenon. Cavitation clouds at the surface of the sphere were the main cause of heating effect. The results showed that closer distances to the transducer surface showed higher cooling rates. On the other hand, despite having a bigger distance from the transducer, when the sphere was located close to the gas-liquid interface the enhancement factor of heat transfer was higher. Ultrasound irradiation showed promising effect for the enhancement of convective heat transfer rate during immersion cooling. More investigations are required to demonstrate the behavior of ultrasound assisted heat transfer and resolve the proper way of the application of ultrasound to assist the cooling and/or freezing processes.     

Investigation of the effect of power ultrasound on the nucleation of water during freezing of agar gel samples in tubing vials

Nucleation, as an important stage of freezing process, can be induced by the irradiation of power ultrasound. In this study, the effect of irradiation temperature (−2 °C, −3 °C, −4 °C and −5 °C), irradiation duration (0 s, 1 s, 3 s, 5 s, 10 s or 15 s) and ultrasound intensity (0.07 W cm⁻², 0.14 W cm⁻², 0.25 W cm⁻², 0.35 W cm⁻² and 0.42 W cm⁻²) on the dynamic nucleation of ice in agar gel samples was studied. The samples were frozen in an ethylene glycol-water mixture (−20 °C) in an ultrasonic bath system after putting them into tubing vials. Results indicated that ultrasound irradiation is able to initiate nucleation at different supercooled temperatures (from −5 °C to −2 °C) in agar gel if optimum intensity and duration of ultrasound were chosen. Evaluation of the effect of 0.25 W cm⁻² ultrasound intensity and different durations of ultrasound application on agar gels showed that 1 s was not long enough to induce nucleation, 3 s induced the nucleation repeatedly but longer irradiation durations resulted in the generation of heat and therefore nucleation was postponed. Investigation of the effect of ultrasound intensity revealed that higher intensities of ultrasound were effective when a shorter period of irradiation was used, while lower intensities only resulted in nucleation when a longer irradiation time was applied. In addition to this, higher intensities were not effective at longer irradiation times due to the heat generated in the samples by the heating effect of ultrasound. In conclusion, the use of ultrasound as a means to control the crystallization process offers promising application in freezing of solid foods, however, optimum conditions should be selected.     

The relative stabilities of 11-vertex nido- and 12-vertex closo-heteroboranes and -borates: facile estimation by structural or connection increments

The relative thermodynamic stabilities of ortho-, meta- and para-isomers of 12-vertex closo-heteroboranes and -borates with different p-block heteroatoms were determined using density functional theory. More electronegative (smaller) heteroatoms tend to occupy non-adjacent, whereas less electronegative (larger) heteroatoms tend to occupy adjacent vertices in the thermodynamically most stable closo-diheterododecaborane isomers. The computed relative stabilities agree perfectly with experimental observations. The energy differences of para- and meta- relative to ortho-isomers of 12-vertex closo-heteroboranes generally depend on the extent of electron localization by a given heteroatom and show highly periodic trends, i.e. increase along the period and decrease down the group. The energy penalties for the HetHet structural feature (two heteroatoms adjacent to each other) for the 12-vertex closo-cluster are apparently significantly different from those for the 11-vertex nido-cluster. Reformulating two 11-vertex nido-structural features, i.e. Het(5k)(2) and HetHet, in terms of connection increments along with the additional structural feature HetHet(m) give the relative stabilities of various isomeric 11-vertex nido- as well as 12-vertex closo-heteroboranes and -borates, using one unique set of increments.