Carbon nanotubes,science and technology part (I) structure,synthesis and characterisation

Since their discovery in 1991 by the Japanese scientist “Sumio Iijima”, carbon nanotubes have been of great interest, both from a fundamental point of view and for future applications. Different types of carbon nanotubes can be produced in various ways. Economically feasible large-scale production and purification techniques are still under development. Carbon nanotubes are discussed in this review in terms of history, types, structure, synthesis and characterisation methods. Carbon nanotubes have attracted the fancy of many scientists worldwide. The unique and unusual properties of these structures make them a unique material with a whole range of promising applications.     

Antimicrobial and antioxidant activities of the methanolic extracts of three Salvia species from Tunisia

This study examines the in vitro antimicrobial and antioxidant activities of the methanolic extracts of three Salvia species from Tunisia: Salvia aegyptiaca L., S. argentea L. and S. verbenaca Ssp. clandestina L. Pugsley. The extracts inhibited the growth of dermatophytes and of bacteria responsible for unpleasant odours to varying degrees; the pathogenic yeasts Candida albicans and Cryptococcus neoformans, the filamentous fungi Aspergillus fumigatus and selected dog otitis bacteria were all resistant to each of the extracts. The extracts were screened for their antioxidant activities using 2,2-diphenyl-1-picrylhydrazyl free radical scavenging and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) test systems, and gave positive results in both tests. The extracts of S. aegyptiaca were the most active in both tests, followed by those of S. verbenaca, then S. argentea. These results confirm the antimicrobial and antioxidant activities of the genus Salvia and underline the potential of these plants either as natural preservatives or in pharmaceutical applications.     

Scalar conservation laws with general boundary condition and continuous flux function

We introduce a notion of entropy solution for a scalar conservation law on a bounded domain with nonhomogeneous boundary condition: ut+divΦ(u)=f on Q=(0,T)×Ω, u(0,⋅)=u₀ on Ω and “u=a on some part of the boundary (0,T)×∂Ω.” Existence and uniqueness of the entropy solution is established for any Φ∈C(R;RN), u₀∈L^∞(Ω), f∈L^∞(Q), a∈L^∞((0,T)×∂Ω). In the L¹-setting, a corresponding result is proved for the more general notion of renormalised entropy solution.     

Numerical analysis of SOA performance over a wide optical bandwidth in a CO-OFDM transmission system

We present a numerical analysis of the impact of the optical amplification by semiconductor optical amplifiers (SOAs) in a Coherent Optical-Orthogonal Frequency Division Multiplexing transmission link at 100 Gb/s. The numerical modeling of SOA is developed to be able to simulate all of nonlinear effects of the SOA, particularly four-wave mixing effect. This model is integrated into a co-simulation platform to perform a simulation at a system level. Error Vector Magnitude (EVM) measurement is given with respect to the number of subcarriers and phase-amplitude coupling. We show also the dependence of the EVM at the signal wavelength by performing our simulations on a wide optical bandwidth, taking into account the main parameters of the SOA—such as the phase-amplitude coupling factor, the saturation power and the noise figure—that influence the non-linear effects.

     

Reversible and irreversible denaturation processes in globular proteins: from collective to molecular spectroscopic analysis

Different spectroscopic techniques were applied for studying the structural properties of lysozyme in salt‐free aqueous solutions. The results of vibrational and Brillouin scattering measurements were compared to obtain both single‐molecule and collective properties of the solutions. The characterization of the protein system, from the conformation of the polypeptide chain to the exposure of side chains to the solvent and the arrangement of the solution network, was then achieved in the range 25–85 °C. Through the analysis of the indole breathing mode, a different environment for the six tryptophan residues of an unfolded lysozyme could be evidenced. Short and long exposures to high temperatures were used to modulate the competition between the thermally induced reversible and irreversible denaturation processes. These different thermal treatments were applied to distinguish between the effects of global unfolding of the single molecule from those of self‐aggregation and gel formation. It has been observed that clusterization occurs at melting temperatures with slow kinetics; also, aggregates evolve from the completely unfolded state of the protein and lead to a sensitive increase in viscosity. This effect probably hinders any further conformational rearrangement of the molecules in the aggregate; thus as a consequence, the disordered structure of clusters does not change to give the β‐sheet organization, characteristic of filaments or fibrils. Copyright © 2011 John Wiley & Sons, Ltd.     

Amino acids in the syntheses of heterocyclic systems: Syntheses and radiostability of novel biologically active triazoles containing the sulfonamide moiety

A number of novel triazoles 2a–f, 4, 9, 10, 12, 15 ; triazolothiadiazoles 6, 8, 11, 16 ; triazolothiadiazine 5 ; and triazolotriazine 14 were synthesized and characterized by elemental analyses and spectral data. Six of the compounds showed antifungal activity compared with the fungicide Mycostatine. Radiosterilization of the biologically active compounds 4, 8, 9b , and 10 in the dry state may prove to be applicable at the sterile dose 25 kGy. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:316–323, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10037     

Boosting COVID-19 Image Classification Using MobileNetV3 and Aquila Optimizer Algorithm

Currently, the world is still facing a COVID-19 (coronavirus disease 2019) classified as a highly infectious disease due to its rapid spreading. The shortage of X-ray machines may lead to critical situations and delay the diagnosis results, increasing the number of deaths. Therefore, the exploitation of deep learning (DL) and optimization algorithms can be advantageous in early diagnosis and COVID-19 detection. In this paper, we propose a framework for COVID-19 images classification using hybridization of DL and swarm-based algorithms. The MobileNetV3 is used as a backbone feature extraction to learn and extract relevant image representations as a DL model. As a swarm-based algorithm, the Aquila Optimizer (Aqu) is used as a feature selector to reduce the dimensionality of the image representations and improve the classification accuracy using only the most essential selected features. To validate the proposed framework, two datasets with X-ray and CT COVID-19 images are used. The obtained results from the experiments show a good performance of the proposed framework in terms of classification accuracy and dimensionality reduction during the feature extraction and selection phases. The Aqu feature selection algorithm achieves accuracy better than other methods in terms of performance metrics.     

Naproxen in heterocyclic chemistry: Novel syntheses of triazoles,triazolothiadiazines, triazolothiadiazoles,and triazolothiadiazepine bearing an asymmetric carbon atom and radiostability of the biologically active compounds

Several s‐triazoles 2, 7a, 10, 12 ; s‐triazolo[3,4‐b][1,3,4]thiadiazines ( 3–5 ); s‐triazolo[3,4‐b][1,3,4]thiadiazoles ( 6, 8, 11, 15 ); and s‐triazolo[3,4‐b][1,3,4]thiadiazepine ( 14 ) were synthesized starting from 2‐(6‐methoxy‐2‐naphthyl)propanoic acid ( 1 ) (Naproxen). The structures of the synthesized compounds were elucidated by elemental analyses and spectral data. Compounds 2, 5, 11, 12, 14 , and 15 exhibited a remarkable antifungal activity compared with the standard fungicide Mycostatine. Radiosterilization of the biologically active compounds 2, 5, 11 , and 14 in the dry state may prove to be applicable (retaining their structures unchanged up to 40 kGy). © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:199–206, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10019     

Compatibilization of PA6/rubber blends by using an oxazoline functionalized rubber

The compatibilization of blends of polyamide 6 with a nitrile butadiene rubber has been investigated. The procedure consists of two steps: modification of the nitrile groups of the rubber into oxazoline in the melt through condensation of ethanolamine with formation of a molecule of ammonia, followed by use of the modified rubber as a compatibilizing precursor which is melt mixed with the polyamide to produce the compatibilized blend. The modification reaction has been detected by NMR analysis and a rheological, mechanical and thermomechanical characterization has been carried out on the all the blends. The results indicate that the modification reaction occurs but the conversion of nitrile into oxazoline is relatively low. Use of the modified rubber in the preparation of binary polyamide/rubber blends, leads to an increase in viscosity, which is typical of compatibilized systems, and to enhanced tensile, impact and thermomechanical properties. These phenomena can be explained by the formation of in situ rubber/polyamide copolymers that act as compatibilizers, due to the reaction between oxazoline and the end groups of the polyamide. The presence of residual low molecular compounds, from the modification or from the purification of the rubber worsens all of the properties and inhibits the compatibilizing effect of the modified rubber.