Development of Antibacterial Xanthan/Chitosan Biguanidine Hydrochlo ride Polyelectrolyte Complexes Decorated with Eco-friendly Prepared Silver Nanoparticles

Background:: Novel eco-friendly silver nanocomposites of xanthan/chitosan biguanidine hydrochloride polyelectrolyte complexes were successfully prepared. Methods:: Silver nanoparticles (AgNPs) were formed through an insitu eco-friendly reduction by the non-toxic polysaccharides without the usage of toxic reagents. FTIR confirmed the successful preparation of the nanocomposites while XRD confirmed the presence of AgNPs with face-centered cubic structures. TEM confirmed the homogeneous distribution of AgNPs with an average size of 14.1 nm. SEM was used to study the surface morphology of the nanocomposites while the energy-dispersive X-ray spectroscopy (EDX) confirmed the presence of AgNPs. Results:: Thermogravimetric analysis showed that the thermal stability was improved in the presence of AgNPs as detected from the calculated integral procedure decomposition temperature. Antibacterial activity against different bacteria species was significantly improved upon increasing the content of AgNPs. Conclusion:: Due to their interesting properties, the prepared polyelectrolyte complexes and their AgNPs nanocomposites could be employed potentially in many biomedical applications like drug delivery.

Effect of silanized sisal fiber on thermo-mechanical properties of reinforced epoxy composites

An effective method was adopted to improve the thermo-mechanical properties of the epoxy composite by functionalization of the sisal fiber. Initially, a neat sisal fiber was acetylated with molar solution of acidic mixture (0.5:1 of HNO3:H2SO4) that removed the content of lignin and hemicellulose and increased the crystallinity of the sisal fiber. The acetylated sisal ( a-sisal) fiber was further treated with 3-aminpropyltriethoxy silane to graft the silanol moieties on sisal fiber. The functionalization of the sisal fiber with 3-aminpropyltriethoxy silane exhibits the strong interaction with epoxy, resulting in homogenous dispersion of the sisal fiber in epoxy. The composite possesses great enhancement in thermal and mechanical properties. The tensile strength in functionalized sisal epoxy composite ( CP-f-Sisal) was significantly enhanced up to 23% in comparison to non-functionalized sisal epoxy composite ( CP-n-Sisal) by adding 15 wt.% of the sisal fiber. In addition, the functionalized sisal epoxy composite ( CP-f-sisal) shows better thermal stability as compared to non-functionalized sisal epoxy composite ( CP-n-sisal). Similar results are attributed by investigating the kinetics of thermal stability parameters that include activation energy and integral procedure decomposition temperature.

Hybrid Analytical and MLS-Based NMM for the Determination of Generalized Stress Intensity Factors

The numerical manifold method (NMM) is characterized by its two cover systems, the mathematical cover and the physical cover. In the standard NMM, the mathematical cover is required to cover the whole problem domain. In this study, however, around each crack tip we specify a small domain on which the displacement is taken as the truncated Williams’ displacement series. And accordingly all such small domains are not covered by the mathematical cover that only covers the rest of the problem domain. Meanwhile, the mathematical cover is constructed by designating all supports of the scattered nodes arising in the moving least squares interpolation as the mathematical patches. In this way, any physical patch contains no crack tip and can be approximated by polynomials. As a result, no blending element issue exists as in the extended finite element method and NMM. In addition to high precision, the proposed procedure is especially suitable for the situation where a crack tip is very close to other cracks, a case difficult to treat by the interaction integral procedure that is commonly used in the extraction of the stress intensity factors of mixed mode cracks.

Thermal Behavior of Epoxy Resins Containing Manganese Compounds

A novel cheap macromolecular intumescent flame retardants (Mn-MIFR), was synthesized. Epoxy resins (EP) were modified with Mn-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Mn contents of 4.0 % get a LOI of 26.5% and char yield of 18.2%. Dilatation, SDR and MSD of EP/Mn-MIFR decreased. The degradation behavior of the EP/Mn-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Mn and P at the residue were increased.

Public Involvement in Environmental Governance: Review of Benin's Experiences

Nowadays public participation is recognized as an integral procedure to achieving sustainable development as well as a good method of environmental governance. This study aimed to improve the quality of public participation in the field of environmental governance. To this end, it used Benin republic as a case study to provide an analytical review of two public participation approaches developed in Republic of Benin for environmental management. Results highlighted some keys limitation of each of those approaches. The study concludes with recommendations to improve the quality of public participation application in Benin.

Thermal Degradation of Epoxy Resins Containing Aluminum Compounds

A novel cheap macromolecular intumescent flame retardants (Al-MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus-aluminum characterized by IR. Epoxy resins (EP) were modified with Al-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Al contents of 4.0 % get a LOI of 26.8% and char yield of 19.5%. Dilatation, SDR and MSD of EP/Al-MIFR decreased. The degradation behavior of the EP/Al-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Al and P at the residue were increased.

Bifurcation and Strange Behavior for a Nonlinear Viscoelastic Rod System

Longitudinal vibration of a nonlinear viscoelastic rod system with one end fixed and another end subjected to an axial periodical excitation was studied under the consideration of transverse inertia. By using Galerkin method, a combined Parametric and Forcing Excited cubic nonlinear dynamic system is derived for hard stiffness nonlinear material. Furthermore, arc-length technique is used for an accurate integral procedure, and numeric results are given detailedly. The process of the system evolved from stable periodic motion to chaos is illustrated in a period-doubling bifurcation graph in a parameter space, and the Lyapunov exponent spectrum is also given that is perfectly consistent with bifurcation process. The strange attractor obtained from Poincaré Map is present, which has different fractal dimension from Duffing’s one, so it may be a new chaotic attractor.

Thermal Degradation of Epoxy Resins Containing Copper Compounds

A novel cheap macromolecular intumescent flame retardants (Cu-MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus-copper characterized by IR. Epoxy resins (EP) were modified with Cu-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Cu contents of 3.0 % get a LOI of 27.0% and char yield of 19.4%. Dilatation, SDR and MSD of EP/Cu-MIFR decreased. The degradation behavior of the EP/Cu-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Cu and P at the residue were increased.