A thermomechanical analysis of interfaces between the mating parts in ultrasonic wire bonding

Ultrasonic welding (USW) is an alternative solution for the bonding process especially in automotive industry. Ultrasonic welding of metals is a joining technique as a combination of applying pressure and frictional vibrations within the range of ultrasonic frequencies. In automotive industry, ultrasonic welding is often used for wired connections. As an alternative for crimping technology of multi-strand aluminum cables in wire bonding, ultrasonic welding is used. This work presents a thermomechanical analysis of the interface between two mating parts in USW. For this reason, the temperature distribution at bonding locations inside a wire bundle due to frictional vibrations and pressure is investigated using the finite element method (FEM). The obvious difference in microsections from different welding samples, which originates from different local temperature rises, was the motivation for this study to further investigate the thermomechanical aspects of the USW by use of finite element simulations. (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Mechanism of trivalent gold reduction and reactivity of transient divalent and monovalent gold ions studied by gamma and pulse radiolysis

The detailed kinetics of the multistep mechanism of the Au(III) ion reduction into gold clusters have been investigated by radiation chemistry methods in 2-propanol. In particular, a discussion on the steady state radiolysis dose-dependence of the yields concludes to a comproportionation reaction of nascent gold atoms Au(0) with excess Au(III) ions into Au(II) and Au(I). This reaction should be achieved through Au(III) consumption before the coalescence of atoms Au(0) into gold clusters may occur. Then gold clusters catalyze the reduction of Au(I) by 2-propanol. It was also found that a long-lived Au(II) dimer, (Au(II))(2), was transiently formed according to the quantitative analysis of time-resolved absorbance signals obtained by pulse radiolysis. Then the disproportionation of Au(II) is intramolecular in the dimer instead of intermolecular, as usually reported. The yields, reaction rate constants, time-resolved spectra, and molar extinction coefficients are reported for the successive one-electron reduction steps, involving especially the transient species, such as Au(II), (Au(II))(2), and Au(I). The processes are discussed in comparison with other solvents and other metal ions.     

Size-dependent thermodynamic properties of silver aggregates. Simulation of the photographic development process

Pulse radiolysis and time-resolved optical spectroscopy were used to observe the earliest steps of silver aggregation in the presence of an electron donor whose electrochemical potential is close to those of usual photographic developers. A critical size has to be reached by the silver aggregate before it is thermodynamically able to accept electrons from the donor, then to grow by an autocatalytic process with alternate adsorption of Ag⁺ ions and electron scavenging. From a computer simulation the critical aggregation numbern _c is found to be 4 and hence the electrochemical potential of the critical aggregate is ≈?0.4 V/NHE. The size-dependence of the electrochemical potential in an aqueous solution is discussed and compared with that of the ionization potential in the gas phase. A tentative extrapolation of the present interpretation to the mechanism of the photographic development is proposed.     

A Lightweight Image Encryption Algorithm for Secure Communications in Multimedia Internet of Things

Wireless Personal Communications - Devices in the Internet of Things (IoT) have resource constraints in terms of energy, computing power, and memory that make them vulnerable to some security...     

Synthesis and characterization of PEGylated iron and graphene oxide magnetic composite for curcumin delivery

Nowadays, nanostructures have been given significant attention in medical and biological fields. Among these nanostructures, graphene oxide (GO) has been widely used in drug delivery systems, because of its unique properties, and the ability to connect to other nanostructures such as magnetic nanoparticles (NPs) as well as polymers by its functional groups. In this research, first, GO was prepared by exfoliating graphite according to the modified Hummer’s method, and then the Fe₃O₄ NPs were synthesized by a simple co-precipitation method on GO nanosheets. In the next step, with the help of the ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide coupling reagents, the polyethylene glycol (PEG) polymer was bonded to the GO-Fe₃O₄ nanocomposite. Finally, anti-cancer drug, curcumin (Cur) was loaded onto the nanocomposite and the Cur loading ratio was measured at about 8%. The samples were evaluated using Fourier transform-infrared, differential scanning calorimtery, vibrating-sample magnetometry, atomic force microscopy and dynamic light scattering techniques. The results show that the prepared nanocomposite is an appropriate candidate for biomedical applications.     

A Facile and Green Synthesis of 2,4,6-Triarylpyridine Derivatives Using the Modified Mesoporous Organic Polymer Based on Calix [4]Resorcinarene: As an Efficient and Reusable Heterogeneous Acidic Catalyst

Kinetics and Catalysis - The work describes an efficient one-pot synthesis of 2,4,6-trisubstituted pyridine derivatives through a three-component catalytic reaction. The procedure involves...     

Synthesis of 1<Emphasis Type="Italic">H</Emphasis>-1,3-benzimidazoles,benzothiazoles and 3<Emphasis Type="Italic">H</Emphasis>-imidazo[4,5-c]pyridine using DMF in the presence of HMDS as a reagent under the transition-metal-free condition

An operationally simple method for synthesis of benzimidazole and 3H-imidazo[4,5-c]pyridine from o-phenylenediamine or pyridine-3, 4-diamine and N,N-dimethylformamide (DMF) in the presence of hexamethyldisilazane (HMDS) as a reagent is described. To evaluate the scope of application of this reagent, it was also used to prepare benzothiazole, 1H-perimidine, and benzoxazole, which was successful for benzothiazole and 1H-perimidine but benzoxazole was not formed. This reaction complies with the principles of green chemistry as it does not use toxic solvents, transition metals, or strong acids. The products are obtained in moderate to excellent yields.     

Development and validation of a HPLC method for the determination of buprenorphine hydrochloride, naloxone hydrochloride and noroxymorphone in a tablet formulation

A simple isocratic reversed-phase high-performance liquid chromatographic method (RP-HPLC) was developed for the simultaneous determination of buprenorphine hydrochloride, naloxone hydrochloride dihydrate and its major impurity, noroxymorphone, in pharmaceutical tablets. The chromatographic separation was achieved with 10 mmol L⁻¹ potassium phosphate buffer adjusted to pH 6.0 with orthophosphoric acid and acetonitrile (17:83, v/v) as mobile phase, a C-18 column, Perfectsil Target ODS3 (150 mm × 4.6 mm i.d., 5 μm) kept at 35 °C and UV detection at 210 nm. The compounds were eluted isocratically at a flow rate of 1.0 mL min⁻¹. The average retention times for naloxone, noroxymorphone and buprenorphine were 2.4, 3.8 and 8.1 min, respectively. The method was validated according to the ICH guidelines. The validation characteristics included accuracy, precision, linearity, range, specificity, limit of quantitation and robustness. The calibration curves were linear (r > 0.996) over the concentration range 0.22-220 μg mL⁻¹ for buprenorphine hydrochloride and 0.1-100 μg mL⁻¹ for naloxone hydrochloride dihydrate and noroxymorphone. The recoveries for all three compounds were above 96%. No spectral or chromatographic interferences from the tablet excipients were found. This method is rapid and simple, does not require any sample preparation and is suitable for routine quality control analyses.     

Voltammetric sensor for simultaneous determination of ascorbic acid,acetaminophen, and tryptophan in pharmaceutical products

A novel carbon paste electrode modified with carbon nanotubes and 5-amino-2′-ethyl -biphenyl-2-ol was fabricated. The electrochemical study of the modified electrode, as well as its efficiency for electrocatalytic oxidation of ascorbic acid (AA), is described. The electrode was employed to study the electrocatalytic oxidation of AA, using cyclic voltammetry, chronoamperometry, and square-wave voltammetry (SWV) as diagnostic techniques. It has been found that the oxidation of AA at the surface of modified electrode occurs at a potential of about 250 mV less positive than that of an unmodified carbon paste electrode. SWV exhibits a linear dynamic range from 2.0?×?10^?7 to 5.0?×?10^?4 M and a detection limit of 1.0?×?10^?7 M for AA. In addition, this modified electrode was used for simultaneous determination of AA, acetaminophen (AC), and tryptophan (TRP). Finally, the modified electrode was used for determination of AA, AC, and TRP in pharmaceutical products.     

Design and synthesis of a magnetic hierarchical porous organic polymer: A new platform in heterogeneous phase‐transfer catalysis

Recyclable phase transfer catalysts containing magnetic nanoparticles (MNPs) have been known as a major trend towards sustainable catalysts. In this study, a novel class of magnetic porous polymer on the basis of calix[4]resorcinarene was synthesized starting from silica‐coated Fe₃O₄ core‐shell nanoparticles. This compound was found as an efficient phase transfer catalyst to the conversion of benzyl halides into benzyl azides and cyanides in good yields. The catalyst could be used at least for five consecutive cycles without appreciable loss in the catalytic activity.