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[en] Trials were set to assess salinity and water deficit effects on seed germination and recovery of populations of Lotus creticus L. and Lotus ornithopodioides L. species collected from different bioclimatic regions in northern Tunisia. Salinity treatments used were 0, 50, 100, 150, 200 and 250 mM of NaCl whereas water deficits of 0, -0.2, -0.6, -0.8 and 1.0 MPa were induced using polyethylene glycol 8000 (PEG-8000). Seeds of L. creticus L. collected from Tabarka region weighted 3.39 g/1000 seeds which were less than half of this weight for all other Lotus populations but having no effect on seeds germination capacity. Lotus creticus L. seeds collected from Seddine region showed 80% germination at 250 mM of NaCl compared to 55.7% for Tabarka populations. Seed germination of L. ornithopodioides L. was not affected by salinity regardless of population provenance indicating species tolerance to salinity. At -0.4 MPa water potential deficit, seed germination of L. creticusL. collected from Seddine region was reduced by 14% compared to 48.5% reduction for seeds from Tabarka provenance which would indicate its tolerance to water stress. Lotus ornithopodioides L. seed germination was reduced by 47% at -0.2 MPa and almost inhibited at -0.6 MPa water potential indicating species low tolerance to water deficit. Ungerminated seeds of Lotus species due to salinity and PEG-8000 treatments recovered their germination capacity when they were transferred to distilled water regardless of species and provenances indicating osmotic inhibition of seed germination for these two Lotus species. (author)
[en] Kinetic analysis of the non-isothermal degradation of poly(ethylene oxide) has been performed using isoconversional model-free methods, model-fitting methods, invariant kinetic parameters method and Netzsch Thermokinetics software in order to establish whether different kinetic approaches yield consistent kinetic parameters. It has been shown that these approaches yield consistent kinetic parameters and can be combined in such a way as to enhance the reliability and quality of each other and consequently the overall kinetic analysis. The most probable kinetic parameters for the non-isothermal degradation of poly(ethylene oxide) have been determined. These kinetic parameters have been used for prediction of isothermal kinetics of poly(ethylene oxide), and their potential for reliable prediction has been noticed.
[en] Described in this report is stimulated echo pulsed field gradient (STE-PFG) 1H nuclear magnetic resonance (NMR) diffusion on neutral and negatively charged magnetically aligned bicelles incorporating the Pluronic tri-block copolymer F68. Bicelles are model lipid membrane systems composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC). Pluronic F68 incorporated into neutral bicellar mixtures (q= [DMPC]/[DHPC]= 4.5) exhibited resonance intensity decays that are non-exponential and diffusion-time dependent., i.e. non-Gaussian diffusion. In contrast, Pluronic F68 incorporated in negatively charged bicellar mixtures, containing 1 mol% 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG), showed the F68 intensity decays that are exponential and diffusion-time independent, viz., Gaussian diffusion. The implication may be that neutral bicellar mixtures incorporating Pluronic F68 consist of extended lamellae composed of meshed ribbon structures, while negatively charged bicellar mixtures incorporating Pluronic F68 consist of perforated lamellae. Pluronic F68 incorporated into the bicelles reports these morphological differences through its diffusion. (author)
[en] This study shows that microbial growth and decay in a biodegradation process of exogenously depolymerizable polymer are controlled by consumption of monomer units. Experimental outcomes for residual polymer were incorporated in inverse analysis for a degradation rate. The Gauss-Newton method was applied to an inverse problem for two parameter values associated with the microbial population. A biodegradation process of polyethylene glycol was analyzed numerically, and numerical outcomes were obtained. (paper)
[en] This paper presents an experimental study using image processing to investigate width and width uniformity of sub-micrometer polyethylene oxide (PEO) lines fabricated by near-filed electrospinning (NFES) technique. An adaptive thresholding method was developed to determine the optimal gray values to accurately extract profiles of printed lines from original optical images. And it was proved with good feasibility. The mechanism of the proposed thresholding method was believed to take advantage of statistic property and get rid of halo induced errors. Triangular method and relative standard deviation (RSD) were introduced to calculate line width and width uniformity, respectively. Based on these image processing methods, the effects of process parameters including substrate speed (v), applied voltage (U), nozzle-to-collector distance (H), and syringe pump flow rate (Q) on width and width uniformity of printed lines were discussed. The research results are helpful to promote the NFES technique for fabricating high resolution micro and sub-micro lines and also helpful to optical image processing at sub-micro level. (paper)
[en] Polymer micelles, formed mostly by core-shell structures, are one kind of nano-carriers, which are used in the therapy of cancer through diverse methods. The shell is usually formed by polyethylene glycol (PEG) thus having the advantage of preparing amphiphilic and biocompatible drug-carriers. With different drugs as the core, multi-functions such as magnetic thermal, photothermal, targeting, contrast etc. were discovered to be used in the therapeutic system. Simultaneously, the loading and delivery of drugs can be adjusted under the control of polymer micelles, so that drug-releasing in vivo is enabled to be quantified, accompanied by the change of external conditions in the sake for reduction of cytotoxicity. Therefore, polymer micelles have crucial significance for the treatment of cancer. This essay introduces the latest research progress of polymer micelles to make simple guides for researchers who are getting touched with this field so as to broaden the scope and propose innovations. (paper)
[en] The correlation between crystallite structural changes and polarization properties of a linear crystallized [–CH2CH2O–]n polyethylene oxide polymer is studied. The average spherulite radius and polarization of polyethylene oxide are inspected as functions of molecular weight of polymer and crystallization temperature from melt in a nonuniform temperature field.
[en] Obtaining high purity of xylitol is a stone corner in medicine industries. Many conventional techniques (crystallization and adsorption) were used for xylitol purification from fermentation media. Recently, membrane technology received a great attention due to its high performance in xylitol purification. Among renowned copolymers used for polymer blending to produce membranes, pluronic is receiving much attention due to its strong hydrophilic characteristic and could work as pore former and surface modifier. Polyethersulfone (PES) polymer has been reportedly used for polymer blending as it possesses mechanical and chemical stabilities. Therefore, this work demonstrates the preparation of nanofiltration (NF) membrane using: (1) PES and (2) PES blended with 1.71 % and 5 % of Pluronic (F127), via phase inversion method. All fabricated membranes were subjected to investigations such as contact angle for hydrophilicity and water and solution flux for membrane performance. The findings showed increasing in water flux from 24.6 L/m2.h to 70.2 L/m2.h as 5 % of Pluronic added. Further, the hydrophilicity improved from 80.1±1.93 degree to 72±0.3 degree and 67.6±0.72 degree when 1.71 and 5 % of Pluronic F127 added respectively. Therefore, the addition of Pluronic f127 has a great impact on PES membrane for xylitol permeation. (author)
[en] The effect of drought stress on 11 durum wheat (Triticum durum Desf.) cultivars was determined at the germination stage. Cultivars were screened for drought tolerance. Six levels of osmotic stress (0, -0.47, -1.48, -3.02, -5.11 and -7.73 bars) were assessed by applying different concentrations of polyethylene glycol (PEG-8000). There were significant differences between treatments for all seedling characteristics (p<0.05, p<0.001), except mean daily germination (MDG). All seedling traits also differed significantly (p<0.001) among all cultivars. In general, osmotic stress decreased seed germination percentage, germination rate (GR), coleoptile length (CL), shoot length (SL), root length (RL), root/shoot (R/S) length ratio, and root number (RN). Averaged over all osmotic stress levels, Mahmoudi had high MDG (0.55), GR (1.88), CL (4.20 cm), SL (10.45 cm), and RL (9.93 cm), suggesting that this variety was highly tolerant to drought stress. There were high correlation coefficients between different characteristics: SL had a positive and significant (p<0.01) correlation with CL (r =0.83), RL (r = 0.74), and R/S length ratio (r = 0.67). This study showed that, based on morphological traits, preliminary screening at an early stage for drought stress using PEG-8000 may facilitate the choice of an adequate cultivar for growth under water stressed conditions. (author)