Natural ageing of tri-layer polyethylene film: Evolution of properties and lifetime in North Africa region

The effects of natural ageing in the north Algeria of tri-layer films lay down hot greenhouse made of low-density polyethylene are presented in this work. Ageing was monitored by observing the changes of physical, mechanical and structural effects on the various greenhouse faces. It has been shown that the structural change occur on the outside face of the films, while the inside faces are protected by the dye. The study shows that the measured parameters are directly related to the criteria of evaluation of the greenhouse effectiveness. The lifetime of these films under natural conditions in north Algerian was estimated to be 10 months.     

Effects of reaction time and citric acid contents on the morphologies of BaCO3 via PVP-assisted method

BaCO₃ with different morphologies, such as dumbbell-like, pillar-like, peanut-like and ellipsoid-like have been successfully synthesized using citric acid (CA) as chelating ligand via a simple polyvinylpyrrolidone (PVP)-assisted method. The effects of the pH of the starting solutions, reaction time and the molar ratio of CA/Ba²⁺ on the morphologies of BaCO₃ were investigated. X-ray diffraction (XRD), transmission electron microscope (TEM) and the infrared (IR) spectrum of the sample are used to characterize the obtained products.     

Reduction of Campylobacter jejuni by natural antimicrobials in chicken meat-related conditions

Nowadays it is essential to test new preservation and decontamination procedures using naturally occurring chemicals against important pathogenic bacteria in meat. We tested the antimicrobial effect of rosemary extracts and the bacteriocin nisin against Campylobacter jejuni at a low storage temperature (8 °C) with or without short-term pre-freezing. The antimicrobial effect of rosemary extract was four times greater in laboratory media than in chicken meat juice. Furthermore, low temperature storage conditions prolonged the survival of C. jejuni in chicken meat juice. Nisin, with an approximately 1.0 log reduction was neither effective alone nor in combination with the extract. Pre-freezing with plant extract addition proved to be effective treatment by more than 3.0 log reduction in 48 h. The results in chicken meat food model again showed the synergistic effect of freezing and plant extract antimicrobial activity. As the combination of pre-freezing and plant extract treatment reduced the cell number by more than 2.0 log reduction, studies should be conducted to further evaluate this promising treatment for Campylobacter reduction in the poultry meat supply.     

Alginate-Coated Alginate-Polyethyleneimine Beads for Prolonged Release of Furosemide in Simulated Intestinal Fluid

Furosemide-loaded calcium alginate (ALG), calcium alginate-polyethyleneimine (ALG-PEI) and alginate-coated ALG-PEI (ALG-PEI-ALG) beads were prepared by ionotropic/polyelectrolyte complexation method to achieve controlled release of the drug. Effects of several formulation factors on the characteristics of the beads were investigated. Although variation in formulation factors did not influence the drug-loading efficiency (DLE) of ALG beads, rapid release of the drug in simulated intestinal fluid (SIF) could not be prevented. PEI treatment of ALG beads, however, prolonged the drug release considerably. Ionic interaction, as appeared from FTIR studies, between alginate and PEI led to the formation of polyelectrolyte complex membrane, the thickness of which was dependent on the conditions of PEI treatment as demonstrated by scanning electron microscopy (SEM). The membrane acted as a physical barrier to drug release from ALG-PEI beads. Alginate coating of ALG-PEI beads further prolonged the release of the drug by increasing membrane thickness and reducing swelling of the beads possibly by blocking the surface pores. Differential scanning calorimetry (DSC) study indicated that drug was not degraded by PEI treatment. The release data from ALG-PEI beads showed a good fit in power law expression, whereas the release data from ALG-PEI-ALG beads were found to fit in modified power law expression, and the mechanism of drug release changed from super case II transport to nearly Fickian transport, depending on the degree of gelation and formation of polyelectrolyte complex membrane.     

Silica ceramic nanofiber membrane with ultra-softness and high temperature insulation

Silica ceramic nanofiber (SCNF) membranes with ultra-softness were fabricated by electrospinning and precursor derived ceramic technology. Firstly, the precursor fiber membrane was obtained by electrospinning from spinnable precursor sol, which was prepared by using silica sol as raw material and polyvinyl alcohol (PVA) as spinning aid, and after heat treatment, it was converted into the SCNF membrane composed of pure inorganic components, which had the ultra-softness to restore the original shape after arbitrary folding. Then the effects of different PVA dosages and heat treatment temperatures on the fiber morphology, thermal stability, mechanical properties, and thermal conductivity of SCNF membranes were investigated. Among all the membranes, the SCNF membrane that was made with a precursor sol of 5% PVA and sintered at 900 °C (Ss?+?PVA 5%-900 °C) showed the smoothest as well as the most uniform fiber morphology, with an average fiber diameter of 285.19 nm, a density of 0.106 g cm^?3, the best mechanical properties (tensile strength of 4.145 MPa), and it also had the lowest thermal conductivity of 0.05285 Wm^?1 K^?1. The Ss?+?PVA 5%-900 °C SCNF membrane still maintained intact fiber morphology after being treated at 1200 °C. These excellent properties make the SCNF membrane have a potential application prospect as an insulation material in ultra-high temperature environments.

     

Investigation of Natural Radioactivity in Wadi El Reddah Stream Sediments and Its Radiological Implications

Radiochemistry - Wadi El Reddah has radiation exposure due to the presence of different types of complexed rocks along with a huge sector of Hammamat sedimentary rocks, monzongranites of Gabal El...     

Evaluation of pH-sensitivity and drug release characteristics of (polyacrylamide-grafted-xanthan)-carboxymethyl cellulose-based pH-sensitive interpenetrating network hydrogel beads

Novel pH-sensitive interpenetrating network hydrogel beads of polyacrylamide-grafted-xanthan (PAAm-g-XG) and sodium carboxymethyl cellulose (NaCMC) loaded with ketoprofen were prepared and evaluated for pH sensitivity and drug release characteristics. The pH-sensitive PAAm-g-XG copolymer was synthesized by free radical polymerization under the nitrogen atmosphere followed by alkaline hydrolysis. The grafting and alkaline hydrolysis reactions were confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetry and X-ray diffraction studies were carried out to know the crystalline nature of encapsulated drug. Scanning electron microscopic study revealed that the interpenetrating polymer network (IPN) beads possess porous matrix structure in alkaline pH whereas nonporous matrix structure was observed in acidic pH. The swelling of the beads and drug release was significantly increased when pH of the medium was changed from acidic to alkaline. The results of pulsatile swelling study indicated that the IPN beads changed their swelling behavior when pH of the external medium was altered. As pH of the medium was changed from 1.2 to 7.4, a considerable increase in swelling was observed for all the beads. However, swelling process was slower than the deswelling. At higher pH values, the carboxyl functional groups of hydrogels undergo ionization and the osmotic pressure inside the beads increases resulting in higher swelling. Drug release followed case II transport mechanism in acidic medium whereas anomalous/non-Fickian transport mechanism was observed in alkaline medium.     

Thermal stability and melt rheology of poly(<Emphasis Type="Italic">p</Emphasis>-dioxanone)

Melt viscosities of poly(p-dioxanone) (PPDO) samples having different molecular weights were studied using a controlled-strain rotational rheometer under a nitrogen atmosphere. First, PPDO’s thermal stability was evaluated by recording changes in its viscosity with time. The result, that samples’ viscosities decreased with time when heated, demonstrated that PPDO is thermally unstable: its degradation activation energy, obtained by using a modified MacCallum equation, was a relatively low 71.8 kJ/mol K. Next, viscoelastic information was acquired through dynamic frequency measurements, which showed a shear thinning behavior among high molecular weight PPDOs, but a Newtonian flow behavior in a low molecular weight polymer (M _w = 18 kDa). Dynamic viscosity values were transferred to steady shear viscosities according to the Cox–Merz rule, and zero shear viscosities were derived according to the Cross model with a shear thinning index of 0.80. Then flow activation energy (48 kJ/mol K) was extrapolated for PPDO melts using an Arrhenius type equation. This activation energy is independent of polymer molecular weight. A linear relationship between zero shear viscosity and molecular weight was obtained using a double-logarithmic plot with a slope of 4.0, which is near the usually observed value of 3.4 for entangled linear polymers. Finally, the rheological behaviors of PPDO polymer blends having bimodal molecular weight distributions were investigated, with the results indicating that the relationship between zero shear viscosity and low molecular weight composition fraction can be described with a Christov model.     

Series resistance determination of Au/Polypyrrole/p-Si/Al structure by current–voltage measurements at low temperatures

The current–voltage (I–V) characteristics of Polypyrrole(PPy)/p-Si/Al structure have been investigated as a function of temperature. A modified Norde function combined with conventional forward I–V method has been used to extract the junction parameters including the ideality factor, barrier height and series resistance. Norde function has been compared with the Cheung functions and it has been seen that there is a good agreement with both method for the barrier height values. However, the values of series resistance have very different especially towards to the lower temperatures. This is attributed to non-ideal I–V characteristics of the Au/PPy/p-Si/Al structure and non-pure Thermionic emission theory due to the low temperature effects.