Cucurbiturils as Reaction Containers for Photocycloaddition of Olefins

The [2+2] photocycloaddition (PCA [2+2]) of alkenes is one of the most synthetically useful photoreactions. It is a convenient one-step reaction that is useful for generating substituted cyclobutanes, polymers, and biologically relevant molecules. However, the reaction efficiency is limited by its bimolecular nature requiring encounter between two reactants within the narrow window of excited state lifetime of the photoactive alkene, and competition from the unimolecular photoisomerization. Our groups have utilized macrocyclic cavitands, especially cucurbiturils(CB), to confine two alkene molecules within their cavities and steer them towards a single dimer regio- and stereoselectively. Although, primarily the review focuses on photocycloaddition within CBs, such reactions in closely related cavitands such as cyclodextrins (CD) and calixarenes (CA) are also briefly mentioned to provide a comparison with CBs. Studies on photocycloaddition of olefins within CB by other research groups are also briefly highlighted. A mechanistic model, with ability to predict the nature of the dimer product formed within the above reaction containers is included.     

Synthesis of elastin‐based polymer and evaluation of its intermolecular interactions with hydroxypropyl methylcellulose

The parent repeating sequence of elastin, poly(GVGVP), was synthesized using solution phase method and characterized by ¹³C‐ and ¹H‐NMR spectroscopy. In order to study the polymer–polymer interactions between poly(GVGVP) and hydroxyl propyl methyl cellulose (HPMC), the blends were prepared both in aqueous and solid phase and examined using various analytical techniques. The viscometric measurements have been carried out at 24 °C and the interaction parameters such as α, β, µ, and Δ[η]_m revealed the miscible nature of the poly(GVGVP)/HPMC blend systems. In addition, Fourier‐transform infrared spectroscopy showed the formation of strong intermolecular hydrogen bond between poly(GVGVP) and HPMC networks. This result was further supported by glass transition temperature (T_g), scanning electron microscopic, and X‐ray diffraction studies. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45283.     

Separation of phenylacetic acid using tri-n-butyl phosphate in hexanol: Equilibrium and kinetics

Equilibrium and kinetics studies are required to design the continuous extraction process for the acid-extraction system. In the present study, an attempt has been made to investigate the equilibrium and kinetics parameters for the reactive extraction of phenylacetic acid (PAA) with tri-n-butyl phosphate (TBP) in hexanol. The equilibrium results show that the formation of the (1:1) PAA–TBP complex in the organic phase with an overall equilibrium complexation constant (K_e) was 78.74 and 29.15 m³.kmol^?1 for TBP concentrations of 0.734 and 1.464 kmol.m^?3, respectively. The mass transfer coefficients (k_L) for PAA were found to be in the range of 3.7 × 10^–5–6.2 × 10^–5 m.s^?1. Based on the Hatta number (H_a = 8.48), the reaction was found to be fast chemical reaction (regime 3) with the order of reaction as 0.77 and 0.36 with respect to PAA and TBP, respectively. The rate constant of the reaction was obtained as 0.017 kmol.m^?3.s^?1.     

Low leakage and high CMRR CMOS differential amplifier for biomedical application

In order to increase user experience in using near field communication smartcard, analog front-end (AFE) module is required to provide a sufficient and a well-regulated voltage regardless the distance between the card and the reader. A highly stable AFE design for energy harvesting purpose is introduced in this paper. The design consists of antenna, rectifier, voltage limiter, bandgap reference, and low-dropout (LDO) voltage regulator circuit. The antenna is designed to resonate at 13.56 MHz as regulated by ISO/IEC 14443-2. In order to simplify the implementation using 0.18 μm CMOS process, a full-wave rectifier circuit is built of all low-threshold-voltage diode-connected PMOS transistors. To protect the system from undesired excessive input voltages, a voltage limiter circuit is included in the module. Moreover, control and maintain a stable supply voltage for the whole system, a robust LDO voltage regulator and bandgap circuits are specially designed for this purpose. The LDO is able to provide a stable 1.8 V of supply voltage with a sub-1% ripple factor even under a low input current as low as 20 mA.     

Design and manufacturing of travelling wave thermo-acoustic engine with varying regenerator length

ABSTRACT

Thermo-acoustic engines are devices suitable to convert heat energy into acoustic energy and vice versa. In this paper, travelling wave thermo-acoustic engine was designed and fabricated for the operating conditions of 30?bar mean pressure of working fluid (Air, Helium, Hydrogen, Nitrogen) and 500°C hot side temperature. The regenerator was made up of the can(s) of stainless steel SA-347and can be adjusted to achieve the required length. The access to change wire mesh size and its length enables to reduce the test set-up time and to enhance flexibility during experimentation. The modified secondary cold heat exchanger was developed for effective heat extraction from the working fluid and the effect of modified regenerator on the intensity of the thermo-acoustic power was also addressed. The present study shares the suitable alternatives for material selection, design considerations and preliminary estimation of heat exchangers at the operating temperature and pressure. It provides initial dimensions and enables to make a prototype.     

Bacterial synthesis of copper/copper oxide nanoparticles

A bacterial mediated synthesis of copper/copper oxide nanoparticle composite is reported. A Gram-negative bacterium belonging to the genus Serratia was isolated from the midgut of Stibara sp., an insect of the Cerambycidae family of beetles found in the Northwestern Ghats of India. This is a unique bacterium that is quite specific for the synthesis of copper oxide nanoparticles as several other strains isolated from the same insect and common Indian mosquitoes did not result in nanoparticle formation. By following the reaction systematically, we could delineate that the nanoparticle formation occurs intracellularly. However, the process results in the killing of bacterial cells. Subsequently the nanoparticles leak out as the cell wall disintegrates. The nanoparticles formed are thoroughly characterized by UV-Vis, TEM, XRD, XPS and FTIR studies.     

Urea–formaldehyde crosslinked starch and guar gum matrices for encapsulation of natural liquid pesticide [Azadirachta Indica A. Juss. (neem) seed oil]: swelling and release kinetics

Polymeric granules were prepared by matrix encapsulation containing 20, 35 and 50% (w/w) of natural liquid pesticide viz., Azadirachta Indica A. Juss. (neem) seed oil (NSO) per dry weight of urea formaldehyde crosslinked starch (UF-St), guar gum (UF-GG) and UF-(St + GG) matrices. Results of swelling and cumulative release kinetics are presented at 35°C for these matrices. The static dissolution experiments have been carried out at 35°C for seven days. The percentage cumulative release kinetic data have been analyzed using an empirical equation to study the release pattern of NSO through the polymeric membranes employed. Transport follows the Super Case II mechanism as tested by an empirical equation. It is found that the release of the active ingredient depends upon the type of the matrix and its swelling ability. The percentage loading of NSO with different matrices and their density exerted an influence on the release data. The FTIR results indicated the absence of chemical interactions between the matrices and the NSO. In the majority of cases, entrapment efficiency was generally more than 95% indicating the efficient encapsulation. Furthermore, the experimental results are discussed in terms of the nature and the combined effect of the individual matrices as well as the percentage loading of NSO. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2437–2446, 1999     

Effect of Different Shapes of Conformal Cooling Channel on the Parameters of Injection Molding

Cooling system improvement is important in injection molding to get better quality and productivity. The aim of this paper was to compare the different shapes of the conformal cooling channels (CCC) with constant surface area and CCC with constant volume in injection molding using Mold-flow Insight 2016 software. Also the CCC results were compared with conventional cooling channels. Four different shapes of the CCC such as circular, elliptical, rectangular and semi-circular were proposed. The locations of the cooling channels were also kept constant. The results in terms of cooling time, cycle time reduction and improvement in quality of the product shows that no significant effect of CCC’s shapes when surface area of CCC kept constant. On the other hand the rectangular CCC shows better result as compared to other shapes of CCC when volume of CCC were kept constant.     

Structural transition in nanostructured Eu2O3 under high pressures

We report here studies on the effect of high pressure on the structural properties of nano-sized Europium sesquioxide (Eu2O3) up to a pressure of about 16.4 GPa. At ambient conditions, the starting sample was found to be predominantly cubic type Eu2O3 or in Eu3+ state with a trace of Eu2+. The presence of Eu2+ state is assumed to be arising due to the non-stoichiometric Eu(1-x)O phase which is obtained from XPS studies by the deconvolution of the Eu 3d-core levels. The Raman studies at ambient show a strong peak at about 333 cm(-1), which is known to occur due to the Fg mode of cubic Eu2O3 and in a similar way, the XRD data shows major peaks corresponding to the cubic phase of Eu2O3. A Mao-Bell type diamond anvil cell (DAC) was used to generate high pressures for XRD and Raman spectroscopy studies. It was observed that the material undergoes a structural change from cubic to monoclinic structure with an on set transition pressure at around 2 GPa and completes at around 8 GPa. This has been inferred from the fact that above about 2.0 GPa pressure, Raman studies show the emergence of a new peak corresponding to the monoclinic phase which increases in intensity and shifts further with increase in pressure, while the XRD studies show that above about 2.0 GPa, the peaks corresponding to monoclinic phase emerge, which show a slight increase in preferred orientation as the pressure is increased. A detailed discussion has been provided to explain this fact.     

Experimental Investigation of Low-Velocity Repeated Impacts on Glass Fiber Metal Composites

The aim of this study was to experimentally investigate the effect of repeated low-velocity impacts on tensile strength of fiber metal laminates (FMLs) using instrumented drop weight impact tester. FMLs were fabricated layer by layer intercalating three layers of aluminum 6061 and two layers of glass fiber-reinforced epoxy. The FMLs were subjected to repeated low-velocity impacts (<10?m/s) at the same location on the FML. The degradation of mechanical property due to impact(s) was studied using Zwick UTM at distances of 0, 20, 40, and 60?mm from the impact point. Results indicate that ultimate tensile strength, failure strain, and ductility of all specimens initially decrease, and then remain constant with increase in number of impacts. A closer examination of impacted FML by scanning electron microscope indicates that thinning and shear fracture in aluminum layers, as well as delamination, and fiber failure in composites plies were present.