Designing four naphthalene di-imide based small organic solar cells with 5,6-difluoro-3-oxo-2,3-dihydro-indene non-fullerene acceptors

Optical and Quantum Electronics - In this paper, the simultaneous impact of interference and aggregated hardware impairments on the performance of mixed radio frequency/free space optical (RF/FSO)...     

Blue LED Irradiation of Iodonium Ylides Gives Diradical Intermediates for Efficient Metal‐free Cyclopropanation with Alkenes

A facile and highly chemoselective synthesis of doubly activated cyclopropanes is reported where mixtures of alkenes and β‐dicarbonyl‐derived iodonium ylides are irradiated with light from blue LEDs. This metal‐free synthesis gives cyclopropanes in yields up to 96 %, is operative with cyclic and acyclic ylides, and proceeds with a variety of electronically‐diverse alkenes. Computational analysis explains the high selectivity observed, which derives from exclusive HOMO to LUMO excitation, instead of free carbene generation. The procedure is operationally simple, uses no photocatalyst, and provides access in one step to important building blocks for complex molecule synthesis.     

Gas sensing properties of single crystalline ZnO nanowires grown by thermal evaporation technique

The ZnO NWs were applied as effective material for the fabrication of ethanol (C₂H₅OH) and carbon monoxide (CO) gas sensor. The ZnO NWs were grown by thermal evaporation techniques on non-catalytic Si (100) substrates. The average width and length of ZnO NWs was 60 nm and 20 μm, respectively and they were single crystalline in nature. The maximum response was 51.64 at 300 °C for 1000 ppm of CO gas, while 104.23 at 400 °C for 250 ppm of ethanol gas. The response of ZnO NWs was very high for ethanol compared to the CO, whereas the recovery time for ethanol was very poor compare to CO gas. The response of ZnO NWs was about 25 times higher for ethanol compare to CO, at 400 °C for 100 ppm of each gas. The high response for ethanol is related to electron donating effect of ethanol (10e^?) which was higher than the CO gas (2e^?). The high response of ZnO NWs was attributed to large contacting surface area for electrons, oxygen, target gas molecule, and abundant channels for gas diffusion.     

Manipulation of the Conformation and Enzymatic Properties of T1 Lipase by Site-Directed Mutagenesis of the Protein Core

In silico and experimental investigations were conducted to explore the effects of substituting hydrophobic residues, Val, Met, Leu, Ile, Trp, and Phe into Gln 114 of T1 lipase. The in silico investigations accurately predicted the enzymatic characteristics of the mutants in the experimental studies and provided rationalization for some of the experimental observations. Substitution with Leu successfully improved the conformational stability and enzymatic characteristics of T1 lipase. However, replacement of Gln114 with Trp negatively affected T1 lipase and resulted in the largest disruption of protein stability, diminished lipase activity and inferior enzymatic characteristics. These results suggested that the substitution of a larger residue in a densely packed area of the protein core can have considerable effects on the structure and function of an enzyme. This is especially true when the residue is next to the catalytic serine as demonstrated with the Phe and Trp mutation.     

Characterization of deep level defects in sublimation grown p-type 6H-SiC epilayers by deep level transient spectroscopy

In this study deep level transient spectroscopy has been performed on boron–nitrogen co-doped 6H-SiC epilayers exhibiting p-type conductivity with free carrier concentration (N_A–N_D)∼3×10¹⁷ cm⁻³. We observed a hole H₁ majority carrier and an electron E₁ minority carrier traps in the device having activation energies E_v+0.24 eV, E_c −0.41 eV, respectively. The capture cross-section and trap concentration of H₁ and E₁ levels were found to be (5×10⁻¹⁹ cm², 2×10¹⁵ cm⁻³) and (1.6×10⁻¹⁶ cm², 3×10¹⁵ cm⁻³), respectively. Owing to the background involvement of aluminum in growth reactor and comparison of the obtained data with the literature, the H₁ defect was identified as aluminum acceptor. A reasonable justification has been given to correlate the E₁ defect to a nitrogen donor.     

Growth, optical, mechanical and thermal studies of diglycine cadmium chloride single crystal

Transparent single crystals of diglycine cadmium chloride were grown by slow evaporation solution technique. To confirm the crystal structure, the grown crystals were subjected to single crystal as well as powder X-ray diffraction measurements and the structure was found to be monoclinic. The elemental analysis was carried out by energy dispersive X-ray spectroscopy. The crystalline perfection of the grown crystal was assessed by high-resolution X-ray diffractometry and found that the crystal quality is fairly good. The optical study reveals that the grown crystal is highly transparent in the region 250?C900?nm. Thermal studies reveal that the grown crystal is stable up to 245?°C. The michrohardness analysis revealed that the grown crystal belongs to soft material category. The high dielectric constant (>30) and low loss (<0.01) value also confirms that the grown crystal is a good candidate for device fabrications.     

Vibrational mechanics in an optical lattice: controlling transport via potential renormalization

We demonstrate theoretically and experimentally the phenomenon of vibrational resonance in a periodic potential, using cold atoms in an optical lattice as a model system. A high-frequency (HF) drive, with a frequency much larger than any characteristic frequency of the system, is applied by phase modulating one of the lattice beams. We show that the HF drive leads to the renormalization of the potential. We used transport measurements as a probe of the potential renormalization. The very same experiments also demonstrate that transport can be controlled by the HF drive via potential renormalization.     

On the Green function in visco‐elastic media obeying a frequency power‐law

In this work, we present an explicit expression for the Green function in a visco‐elastic medium. We choose Szabo and Wu's frequency power law model to describe the visco‐elastic properties and derive a generalized visco‐elastic wave equation. We express the ideal Green function (without any viscous effect) in terms of the viscous Green function using an attenuation operator. By means of an approximation of the ideal Green function, we address the problem of reconstructing a small anomaly in a visco‐elastic medium from wavefield measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Swelling and drug release properties of acrylamide/carboxymethyl cellulose networks formed by gamma irradiation

Hydrogels based on acrylamide monomer (AM) and different ratios (5–20 wt%) of carboxymethyl cellulose (CMC) were synthesized by gamma irradiation. The hydrogels were characterized in terms of gel content, swelling and drug release characters. The effect of temperature and pH on the degree of swelling was also studied. The results showed that the gel fraction of AM/CMC hydrogels decreases greatly with increasing the contents of CMC in the initial feeding solution. The kinetic study showed that the swelling of all the hydrogels tends to reach the equilibrium state after 5 h. However, the swelling of AM/CMC hydrogels was greater than the hydrogel based on pure AM. On the other hand, it was found that the swelling of all the hydrogels changes within the temperature range 30–40 °C and within the pH range 4–8. The AM/CMC hydrogels was evaluated for the possible use in drug delivery systems. In this respect, the release properties of methylene blue indicator, as a drug model, was investigated. It was found that the percentage release from the hydrogels increase with time to reach ～80% after 3 h at pH of 2 compared to ～100% at pH of 8.     

Novel ultrasonic‐assisted deep eutectic solvent‐based dispersive liquid–liquid microextraction for determination of vanadium in food samples by electrothermal atomic absorption spectrometry: A multivariate study

A green, efficient, simple and sensitive pre‐concentration method has been developed for the determination of vanadium(V) in foodstuffs using deep eutectic solvent–ultrasonic‐assisted dispersive liquid–liquid microextraction. In the developed procedure, the extraction of vanadium(V) was achieved using 2‐hydroxy‐3‐methoxybenzaldehyde thiosemicarbazone as a chelating agent, choline chloride–phenol as extracting solvent and tetrahydrofuran as dispersive solvent. Vanadium(V) concentration was measured using electrothermal atomic absorption spectrometry. Various analytical parameters including pH, type and molar ratio of deep eutectic solvent, ultrasonication time and amount of ligand were studied. A multivariate study was carried out for optimization of the variables. The pre‐concentration factor was calculated as 50. Under optimal conditions, limit of detection, limit of quantification and relative standard deviation were calculated as 0.025 μg l^?1, 0.175 μg l^?1 and 3.4%, respectively. The accuracy of the procedure was confirmed using certified reference materials and standard addition method. The obtained results confirm adequate recoveries for vanadium(V) (>96%). This technique was fruitfully applied for determination of vanadium in foodstuffs.