Direct synthesis of nitrogen-rich carbon sheets via polybenzoxazine as highly active electrocatalyst for water splitting

In this work, we propose a novel nitrogen-rich carbon sheets (N-CSs), with conceivable use as efficient catalysts for hydrogen evolution reaction (HER). N-CSs are directly synthesized from polybenzoxazine (PBz) by carbonization followed by KOH activation. PBz was prepared from eugenol, melamine, and paraformaldehyde through ring-opening polymerization. FT-IR and NMR spectroscopy confirmed the corresponding chemical structures of the new benzoxazine monomer. The morphology, structure and surface properties of the N-CSs are investigated by Raman spectroscopy, wide-angle X-ray diffraction, and X-ray photoelectron spectroscopy. The catalytic activity of N-CSs towards HER is thoroughly investigated by electrochemical techniques. In N-CSs, it is established that nitrogen gratified electrocatalytic activity, and hence nitrogen atoms should enhance the electrocatalytic properties by increasing the active sites. As the kinetic current is stabilized by the outer nitrogen atom as such, HER is proposed to proceed on these active sites by the Volmer-Heyrovsky mechanism. The N-CSs show outstanding catalytic activity towards HER with lowest onset-potential (?10 mV_RHE) and Tafel slope (45 mV dec^?1) in 0.5 M H₂SO₄ aqueous electrolyte.     

Effect of size of fly ash particle on enhancement of mullite content and glass formation

Quartz is widely replaced by fly ash in traditional porcelain composite. Increased strength and stability of the fly ash-mixed composite depends on the quantity and crystallinity of the mullite phase in the fly ash. Our aim in this investigation is to increase the formation of mullite in nanocrystalline form and study the effect of temperature. Quantitative estimation of mullite and residual quartz content were done by X-ray diffraction (XRD) and nanostructure and crystallization were studied using differential thermal analysis (DTA), field effect scanning electron microscopy (FESEM), XRD and Fourier transform infrared (FTIR) spectroscopy. The results show that fly ash sieved through 250 holes/cm² mesh contain more mullite initially and growth of mullite as well as glass formation was faster in this sample compared to coarse fly ash. The maximum mullite in these samples was formed at 1600°C. Transformation of quartz and cristobalite phases into glassy phase was also faster for smaller particle sizes of fly ash.     

Kozeny–Carman permeability relationship with disintegration process predicted from early dissolution profiles of immediate release tablets

This study was oriented toward the disintegration profiling of the diclofenac sodium (DS) immediate-release (IR) tablets and development of its relationship with medium permeability k_perm based on Kozeny–Carman equation. Batches (L1–L9) of DS IR tablets with different porosities and specific surface area were prepared at different compression forces and evaluated for porosity, in vitro dissolution and particle-size analysis of the disintegrated mass. The k_perm was calculated from porosities and specific surface area, and disintegration profiles were predicted from the dissolution profiles of IR tablets by stripping/residual method. The disintegration profiles were subjected to exponential regression to find out the respective disintegration equations and rate constants k_d. Batches L1 and L2 showed the fastest disintegration rates as evident from their bi-exponential equations while the rest of the batches L3–L9 exhibited the first order or mono-exponential disintegration kinetics. The 95% confidence interval (CI_95%) revealed significant differences between k_d values of different batches except L4 and L6. Similar results were also spotted for dissolution profiles of IR tablets by similarity (f₂) test. The final relationship between k_d and k_perm was found to be hyperbolic, signifying the initial effect of k_perm on the disintegration rate. The results showed that disintegration profiling is possible because a relationship exists between k_d and k_perm. The later being relatable with porosity and specific surface area can be determined by nondestructive tests.     

Effect of polyaniline concentration on the photoconversion efficiency of nano-TiO<Subscript>2</Subscript> based dye sensitized solar cells

Extensive research have been made in improving the dye sensitized solar cells (DSSC) performance by designing, tailoring and enhancing the photoconversion properties of the matrix. The approaches used are material synthesis, dye permutation combinations, use of natural extracts or using several sensitizers. The polymers are also being explored in this regards in their pristine or composite forms. Therefore, in this study an attempt is made to synthesize a mesoporous polyaniline–titanium dioxide (PANI–TiO₂) nanocomposites with one pot synthesis approach at different concentrations of PANI (0.3–0.7 ml). Titanium isopropoxide was used as precursor for TiO₂ with aniline and the material was synthesized at ice bath temperature. Morphological observations showed that the composite is a mesoporous material with tubular structure where TiO₂ particles are seen entrapped in the polymer matrix and found that intercalation can be tailored with PANI concentration. Structural, functional and optical characterization indicate anatase phase of TiO₂, with several functional bands that can help in dye interaction and broad absorption bands within visible region. The photocurrent-voltage response was measured with simulated light and source-meter. It is interesting to note that increasing PANI concentration enhances the mesoporous structure and hence increases the dye loading capacity and photoconductivity of the material. The efficiency increased by about 22 % with addition of 0.5 ml of PANI from 0.3 ml. The proposed study has indicated that such material have the potential to be used for DSSC fabrication with which the device performance can further be increased to a better levels.     

Thermophysical Properties of Binary Mixtures of Methanol with Chlorobenzene and Bromobenzene from 293 K to 313 K

Densities and viscosities have been measured for the binary mixtures of methanol with chlorobenzene and with bromobenzene from 293 K to 313 K over the complete composition range. Densities were used to compute the excess molar volume ( , for these binary systems. The results have been discussed in terms of molecular interactions. Furthermore, viscosity results were compared with a corresponding-states model. The average absolute deviation was found to be 1.9 %.     

Design of high performance copyright protection watermarking based on lifting wavelet transform and bi empirical mode decomposition

This paper developed new and efficient image watermarking scheme for copyright protection based on Lifting wavelet transform (LWT) and Bi- dimensional Empirical Mode Decomposition (BEMD). A LWT has been selected because it is fast, less computational cost and maintains the integrity of the recovered watermark. The BEMD transform can separate the image from the most robust to the least sensitive or fragile frequency bands. This advantage is utilised in this study for the purpose of embedding the watermark in the robust part of BEMD, i.e. the residue (r). In addition, the embedding process has been performed in the low sub-band of LWT decomposed image as the low sub-band is more robust to image processing such as JPEG compression. The robust watermark which is grey scale image is decomposed using DWT to enhance the security and select only high sub-band as it has less impact on the quality of the watermarked image. As a result, the original image’s visual quality can be preserved and the concealed watermark could be successfully retrieved even if the watermarked images have undergone severe attacks like JPEG, rotation, Gamma correction, filtering, additive noise, translation, shearing, and scaling. Furthermore, the improved scheme offers greater robustness against many image processing operations, in comparison to the current schemes about copyright protection.     

Prevalence, characterization and sources of Listeria monocytogenes in blue crab (Callinectus sapidus) meat and blue crab processing plants

Seven blue crab processing plants were sampled to determine the prevalence and sources of Listeria spp. and Listeria monocytogenes for two years (2006–2007). A total of 488 raw crabs, 624 cooked crab meat (crab meat) and 624 environmental samples were tested by standard methods. Presumptive Listeria spp. were isolated from 19.5% of raw crabs, 10.8% of crab meat, and 69.5% of environmental samples. L. monocytogenes was isolated from 4.5% of raw crabs, 0.2% of crab meat, and 2.1% of environmental samples. Ninety-seven percent of the isolates were resistant to at least one of the ten antibiotics tested. Eight different serotypes were found among 76 L. monocytogenes isolates tested with the most common being 4b, 1/2b and 1/2a. Automated EcoRI ribotyping differentiated 11 ribotypes among the 106 L. monocytogenes isolates. Based on ribotyping analysis, the distribution of the ribotypes in each processing plant had a unique contamination pattern. A total of 92 ApaI and 88 AscI pulsotypes among the 106 L. monocytogenes isolates were found and distinct pulsotypes were observed in raw crab, crab meat and environmental samples. Ribotypes and serotypes recovered from crab processing plants included subtypes that have been associated with listeriosis cases in other food outbreaks. Our findings suggest that molecular methods may provide critical information about sources of L. monocytogenes in crab processing plants and will augment efforts to improve food safety control strategies such as targeting specific sources of contamination and use of aggressive detergents prior to sanitizing.