Validation of chlorophyll-α concentration maps from Aqua MODIS over the Gulf of Gabes (Tunisia): comparison between MedOC3 and OC3M bio-optical algorithms

Few studies have focused on the use of ocean colour remote sensors in the Gulf of Gabes (southeastern Tunisia). This work is the first study to evaluate the ocean colour chlorophyll-a product in this area. Chlorophyll-a concentrations were measured during oceanographic cruises performed off the Gulf of Gabes. These measurements were used to validate satellite data acquired from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. First, two atmospheric correction procedures (standard and shortwave infrared) were tested to derive the remote-sensing reflectance, and then a comparison between two bio-optical (OC3M and MedOC3) algorithms were realized using the in situ measurements. Both atmospheric correction procedures gave similar results when applied to our study area indicating that most pixels were non-turbid. The comparison between bio-optical algorithms shows that using the regional bio-optical algorithm MedOC3 improves chlorophyll-a estimation in the Gulf of Gabes for the low values of this parameter.     

Physicochemical properties of fermented Arabian mares' milk

Due to its numerous benefits, including health-promoting characteristics, there is increasing interest in finding product applications for mares' milk. In the present study, the physicochemical properties, turbidity and conductivity of Arabian mares' milk were studied during acidification by fermentation at 30 °C and compared with those of bovine milk. The data for the acidification rate were modelled using a logistic equation. Mares' milk showed a longer latency phase (284 min) and lower acidification rate (μ_max = 0.0052 dpH min^?1) compared with bovine milk (194 min and 0.0098 dpH min^?1 respectively). The general shape of the curves of the turbidity versus time and pH were similar in nature for the acidification of both milks. However, the characteristic points were different, due to the differences in casein micelle composition. Measurement of electrical conductivity during acidification showed that maximum demineralization of casein micelles started around pH 6.09 and 5.31, for mares' and bovine milk, respectively. In conclusion, the technological characteristics of mares' milk were very different from those of bovine milk, due to intrinsic physicochemical properties of both milks.     

Iron(III) and Cobalt(III) Complexes with Oxalate and Phenanthroline: Synthesis,Crystal Structure,Spectroscopy Properties and Magnetic Properties

We report herein the synthesis and physicochemical characterization of two mixed-ligand complexes of the following stoichiometric formulae: [Fe(phen)₂(ox)](NO₃)?2H₂O (1) and [Co(phen)₂(ox)](NO₃)?4H₂O (2) (as phen: 1,10-orthophenanthroline; ox: oxalate dianion). Both compounds have been prepared by slow evaporation at room temperature and characterized by single-crystal X-ray diffraction. They have been characterized by IR and UV–Vis spectra and thermoanalysis (TG and DTA) The structures of these compounds are highly symmetric. Indeed, the two compounds are isomorphous and crystallize in the orthorhombic space group Ibca. In each material, the M^III ion has a slightly distorted square bipyramidal environment, coordinated by one oxalate ion and two 1,10-orthophenanthroline ligands. Structural cohesion is established essentially by π–π interactions between the rings of phen groups and intermolecular O–H…O hydrogen bonds connecting the ionic entities and uncoordinated water molecules. Magnetic susceptibility measurements of (1) in the range 5–300 K exhibit paramagnetic behavior at high temperature. However, at low temperature, the magnetic data show the occurrence of weak antiferromagnetic intermolecular interactions between the local spins.     

A hybrid chaotic map for communication security applications

Recently, the synchronization between two matching chaotic systems to provide confident communication has gained a lot of interest. Continuously, there is a necessity to produce a novel dynamical system to be used in synchronization to implement a strong security system. In this paper, a hybrid chaotic system is suggested and verified for the potential use of secure communication through chaos synchronization. The Lyapunov exponent (LE) and zero‐one (0‐1) tests have been used to verify the performance of the suggested hybrid chaotic system, while National Institute of Standard and Technology (NIST) tests have been applied to verify the randomness properties. And the synchronization has been achieved between master and slave systems by using nonlinear control laws. The simulation outcomes demonstration that the hybrid system has chaotic performance and outstanding randomness characteristic. The statistical results gained for LE test was 0.8822, and for frequency test (FT) was 0.2028, while for the run test (RT) was 0.1924. Accordingly, the suggested hybrid system can be used to evolve functional synchronization algorithms and encryption for image, video, and voice secure communication applications.     

Studies on Cobalt(II) Complexes with Benzenesulfonate: Synthesis,Crystal Structure,and Spectroscopic and Magnetic Properties

Two novel transition metal benzenesulfonate complexes with a formula [Co(H₂O)₆][C₇H₅O₃SO₃]₂?2H₂O (1) and Na₄[Co(H₂O)₂ Cl₄][C₇H₅O₃SO₃]₂?4H₂O (2), have been synthesized and characterized by single-crystal X-ray diffraction technique; thermal analysis was done and spectroscopic and magnetic properties were studied. The [Co(H₂O)₆][C₇H₅O₃SO₃]₂?2H₂O (1) complex crystallizes in the triclinic system; however, the (2) complex crystallizes in the monoclinic crystal system with the C2/c space group. Each Co(II) atom in (1) and (2) is octahedrally coordinated. A hydrogen bond links the complex cation and anion, forming one-dimensional hydrogen-bonded supramolecular chains. The complexes exhibit different decomposition characteristics. Magnetic susceptibility measurement shows that complexes have weak anti-ferromagnetic intermolecular interactions between many local spins. The magnitude and nature of these magnetic interactions are discussed in the light of their respective structures, and they are compared with those reported for related systems. Magnetic moments of both compounds at room temperature are characteristic of high-spin complexes Co(II).     

Creep buckling of cylindrical shells under external lateral pressure

In this paper, the authors present the results of an analysis of creep buckling of cylindrical shells under external lateral pressure. The nature of the material, the dimensions of the specimens and the type of boundary permit an elastic analysis of this phenomenon. The results of tests and calculations show on the one hand that this phenomenon is very sensitive to the presence of initial geometric imperfections; and on the other hand that it is possible to establish a monograph giving the critical time of an electroplated nickel shell as a function of its initial imperfections and of the nominal applied load. In this manner, the same reasoning can be applied to other shells made up of other materials that are sensitive to creep (resins, concretes, wood, metals at high temperatures, etc.).