Arduino-based chaotic secure communication system using multi-directional multi-scroll chaotic oscillators

The experimental realization of a chaotic secure communication system is introduced herein taking advantage of Arduino’s open source integrated development environment along with its preset functions that reduce development time and complexity. The system uses multi-directional multi-scroll chaotic oscillators that are based on piecewise-linear functions. Experimental results are given for chaos generators in 1-direction (1-D), 2-D and 3-D of up to 20, \(20\times 20\) and \(20\times 20\times 20\) scrolls, respectively. Using two chaos generators, a chaotic secure communication system is implemented in a master–slave topology by applying generalized Hamiltonian forms and observer approach. Finally, we detail experimental results for the synchronization of \(6\times 6\) and \(20\times 20\) scroll attractors, which are used for transmitting a monochromatic image through the Arduino-based chaotic secure communication system.     

On some Closed Magnetic Curves on a 3-torus

We consider two magnetic fields on the 3-torus obtained from two different contact forms on the Euclidean 3-space and we study when their corresponding normal magnetic curves are closed. We obtain periodicity conditions analogues to those for the closed geodesics on the torus.     

Nanofibrilar Polyaniline: Direct Route to Carbon Nanotube Water Dispersions of High Concentration

Water dispersible nanofibrilar polyaniline (NF‐PANI) provides a novel and direct route towards carbon nanotube water dispersions of high concentration. Carrying out the chemical synthesis of NF‐PANI in the presence of carbon nanotubes (CNTs) results in an entirely nanostructured nanofibrilar polyaniline/carbon nanotube (NF‐PANI/CNT) composite material that contains well segregated CNTs partially coated by NF‐PANI. This new approach is simple, fast, and inexpensive, and enables the direct preparation of stable and homogeneous dispersions of the composites in water at concentrations up to 10 mg · mL⁻¹, even for the highest CNT loadings of 50 wt.‐% without the participation of surfactants or stabilizers.

     

Effect of hydrogen bonding in the vibrational spectra of trans‐cinnamic acid

A computationally‐assisted methodology to assign the vibrational spectra of molecular materials (PiMM) has been successfully applied to the Raman and infrared (IR) spectra of trans‐cinnamic acid (t‐CIA) in the solid state. The effects of molecular association through O H···O hydrogen‐bonding in both the wavenumber and the intensity of the bands are accurately described by a single dimer structure. This supports the discrimination between the possible conformers in the solid, the complete evaluation of hydrogen‐bonding effects, and the full assignment of the vibrational spectra of t‐CIA. Copyright © 2008 John Wiley & Sons, Ltd.     

Hydrogen bonding in nitrofurantoin polymorphs: a computation‐assisted spectroscopic study

The importance of hydrogen‐bond formation in the molecular packing arrangements of two anhydrous forms of nitrofurantoin is investigated, combining computational methods and spectroscopic data. The overall results indicate, as expected, that the vibrational modes related to the CO, N H and C H groups are strongly affected by intermolecular hydrogen‐bond formation. Moreover, the importance of weak C‐H···O interactions in conferring additional stability to molecular associations in biological systems is evidenced in this study. The complete assignment of the Raman and infrared spectra of both polymorphs is accomplished by means of a computationally based methodology, which accounts for the effects of intermolecular interactions in the crystal. The vibrational shifts due to crystal packing interactions are evaluated from DFT calculations for a set of suitable molecular pairs, using the B3LYP/6‐31G* approach. This methodology provides an answer to the current demand for a reliable and complete assignment of the vibrational spectra of pharmaceutically active compounds such as nitrofurantoin. Copyright © 2009 John Wiley & Sons, Ltd.     

Absorption and thermal study of dental enamel when irradiated with Nd:YAG laser with the aim of caries prevention

It is widely recognized that Nd:YAG can increase enamel resistance to demineralization; however, the safe parameters and conditions that enable the application of Nd:YAG laser irradiation in vivo are still unknown. The aim of this study was to determine a dye as a photoabsorber for Nd:YAG laser and to verify in vitro a safe condition of Nd:YAG irradiation for caries prevention. Fifty-eight human teeth were selected. In a first morphological study, four dyes (waterproof India ink., iron oxide, caries indicator and coal paste) were tested before Nd:YAG laser irradiation, under two different irradiation conditions: 60 mJ/pulse and 10 Hz (84.9 J/cm²); 80 mJ/pulse and 10 Hz (113.1 J/cm²). In a second study, the enamel surface and pulp chamber temperatures were evaluated during laser irradiations. All dyes produced enamel surface melting, with the exception of the caries indicator, and coal paste was the only dye that could be completely removed. All irradiation conditions produced temperature increases of up to 615.08°C on the enamel surface. Nd:YAG laser irradiation at 60 mJ/pulse, 10 Hz and 84.9 J/cm² promoted no harmful temperature increase in the pulp chamber (ANOVA, p < 0.05). Among all dyes tested, the coal paste was an efficient photoabsorber for Nd:YAG irradiation, considered feasible for clinical practice. Nd:YAG laser at 84.9 J/cm² can be indicated as a safe parameter for use in caries prevention.     

Aquaculture by-product: a source of proteolytic enzymes for detergent additives

Intestine proteases of Nile tilapia (Oreochromis niloticus) were partially purified by heat treatment (purification factor of 3.5, enzyme activity remained almost constant) to reach the maximum activity and stability within an alkaline pH range of 7.2–11.0. The optimum temperature and stability over a 120 min period were found to be at 55°C and at 35–45°C, respectively. The proteases’ activity was not affected by a 1 vol. % saponin surfactant, inactivated by 0.01 g mL^?1 sodium dodecylsulphate after 120 min, and it remained stable for 30 min in a 5 vol. % and 10 vol. % hydrogen peroxide solutions. The proteases were slightly activated by Ca²⁺, Mg²⁺, and K⁺ and the substrate most effectively hydrolysed was casein (40.0 U mg^?1). A 2⁴ full factorial design used to evaluated the influence of independent variables showed that the enzyme extract, detergent concentration and the incubation time had a significant influence on the enzymatic activity. The best conditions to be used concerning detergent additive were found with 0.3 mg mL^?1 of protein and 3.0 mg mL^?1 of detergent for 30 min in the presence of Astrus® detergent.     

Characterization of O-trimethylsilyl oximes of trisaccharides by gas chromatography–mass spectrometry

Gas chromatography (GC) data (linear retention indices and relative areas) and mass spectra (most representative m/z fragments) of 12 reducing trisaccharides as trimethylsilyl oximes (TMSO) and four non-reducing as trimethylsilyl (TMS) ethers have been described for the first time and related to their structural features. Some trends have been observed: earlier elution of non-reducing compounds and fructotrioses; aldotrioses bearing the reducing end with link in position 6 showing the highest retention. Abundance of several fragment ions and their ratios were useful for trisaccharide characterization; some of these features seem to be useful for the characterization of new trisaccharides.