Controlled release formulations of carbaryl based on copper alginate,barium alginate,and alginic acid beads

A controlled release system for reducing environmental impact was produced by encapsulating the pesticide carbaryl (Carb) in the alginate beads. The various bead formulations were prepared by using sodium alginate (NaAlg) as a polymer, CuCl₂, BaCl₂ as a crosslinking agent, and HCl as a linking agent. The surface morphology of prepared beads was characterized with scanning electron microscopy (SEM). SEM confirmed the spherical nature and surface morphology of the particles. Bead characteristics, such as Carb entrapment efficiency, particle size, swelling degree, and Carb release kinetics, were determined. The effects of crosslinker or linker concentration, type, and carbaryl/sodium alginate (Carb/NaAlg) ratio on Carb release from the beads were investigated for 20 days at 25°C. It was observed that Carb release from the beads increased with the increase of Carb/NaAlg ratio whereas decreased with the increase of crosslinker concentration. At the end of 20 days, the Carb release from alginic acid beads was found to be higher than that of copper alginate (Cu‐Alg) and barium alginate (Ba‐Alg) beads. The swelling measurements of the beads supported the release results. Release kinetics were described by Fickian and non‐Fickian approaches. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4245–4253, 2006     

In vitro release study of diltiazem hydrochloride from poly(vinyl pyrrolidone)/sodium alginate blend microspheres

Polymeric blend microspheres of poly(vinyl pyrrolidone) (PVP) with sodium alginate (NaAlg) were prepared by cross‐linking with calcium ions and used to deliver a calcium channel blocker drug, diltiazem hydrochloride (DT). The prepared microspheres were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Scanning electron microscopy confirmed the spherical nature of the particles. Preparation conditions for the microspheres were optimized by considering the percentage entrapment efficiency, particle size, and swelling capacity. Effects of variables such as PVP/NaAlg ratio, molecular weight of PVP, cross‐linker concentration, and drug/polymer ratio on the release of DT were discussed at two different pH values (1.2, 6.8) at 37°C. It was observed that DT release from the microspheres decreased with increasing molecular weight of PVP and extent of cross‐linking. However, DT release increased with increasing PVP content and drug/polymer ratio (d/p) of the blend microspheres. The highest DT release percentage was obtained as 99% for PVP/NaAlg ratio of 1/2 with d/p ratio of 1/2 at the end of 4 h. It was also observed from release results that DT delivery from the microspheres through the external medium are much higher at low pH (1.2) value than that of high pH (6.8) value. The drug release from the microspheres mostly followed Fickian transport. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Polypropylene nanocomposites prepared with natural and ODTABr‐modified montmorillonite

In this study, the main goal is to obtain montmorillonite nanocomposites of polypropylene (PP). To achieve this goal, a two‐phase study was performed. In the first part of the work, organomodified clay (OMMT) was synthesized and characterized. Octadecyltrimethylammonium bromide (ODTABr) cationic surfactant was added to the clay (Na‐activated montmorillonite, MMT) dispersions in different concentrations in the range of 5 × 10^?5–1 × 10^?2 mol/L. Rheologic, electrokinetic, and spectral analyses indicated that ODTABr has interacted with MMT at optimum conditions when the concentration was 1 × 10^?2 mol/L. In the second part, modified (OMMT) and unmodified (MMT) montmorillonite were used to obtain PP nanocomposites (OMMT/PP and MMT/PP, respectively). The nanocomposites were prepared by melt intercalation where the montmorillonite contents were 1 or 5% (w/w) for each case. The thermal analyses showed that the thermal properties of OMMT/PP nanocomposites were better than MMT/PP, and both of them were also better than pure polymer. Increase in the concentration of MMT (or OMMT) decreased the thermal resistance. Based on the IR absorption intensity changes of regularity and conformational bands, it is found that the content of the helical structure of macromolecular chains has increased with increasing concentrations of both MMT and OMMT in the nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Scheduling in robotic cells: process flexibility and cell layout

The focus of this study is the identical parts robotic cell scheduling problem with m machines under the assumption of process and operational flexibility. A direct consequence of this assumption is a new robot move cycle that has been overlooked in the existing literature. We prove that this new cycle dominates all classical robot move cycles considered in the literature for m?=?2. We also prove that changing the layout from an in-line robotic cell to a robot-centered cell reduces the cycle time of the proposed cycle even further, whereas the cycle times of all other cycles remain the same. For the m-machine case, we find the regions where the proposed cycle dominates the classical robot move cycles, and for the remaining regions present its worst case performance with respect to classical robot move cycles. Considering the number of machines as a decision variable, we also find the optimal number of machines that minimizes the cycle time of the proposed cycle.     

The Effect of Olive Leaf Addition on Antioxidant Content and Antioxidant Activity of “Memecik” Olive Oils at Two Maturity Stages

In this study, the effects of leaf addition, maturity stage and storage on the antioxidant content and activity of olive oils (cv. Memecik) were investigated in the 2008/09 and 2009/10 crop seasons. Olive fruits were harvested at two different maturity stages (early and late), and the leaves of the same cultivar were added at different rates (0, 1, and 3 %) prior to oil extraction. After extraction, the oil samples were stored for 18 months and total chlorophyll, α-tocopherol, total phenolic content and the antioxidant activity [DPPH^· (2,2-diphenyl-1-picrylhydrazyl) and ABTS^·+ (2,2-azino-bis(3-ethylbenzothiazoline)-6-sulfonic acid) radical scavenging] were determined at 6 month-intervals. Olive leaf addition induced a significant increase in total chlorophyll, α-tocopherol, total phenolic content, and antioxidant activities in both years (P < 0.001). During the storage period antioxidant content and antioxidant activities in the oils significantly decreased in both years (P < 0.001). However, the oils to which leaf material was added had higher antioxidant contents and activities than those without leaf material addition at the end of the 18-month storage period. After storage, the antioxidant content and DPPH^· radical scavenging activity of control (0 %) samples were lower than those in the leaf added samples (3 %). The data obtained from this study suggested that the addition of olive leaf to oils allowed more functional olive oils with higher antioxidant contents.     

Activation of polymer blend carbon nanofibres by alkaline hydroxides and their hydrogen storage performances

In the present work we study the hydroxide activation (NaOH and KOH) of phenol-formaldehyde resin derived CNFs prepared by a polymer blend technique to prepare highly porous activated carbon nanofibres (ACNFs). Morphology and textural characteristics of these ACNFs were studied and their hydrogen storage capacities at 77 K (at 0.1 MPa and at high pressures up to 4 MPa) were assessed, and compared, with reported capacities of other porous carbon materials.Phenol-formaldehyde resin derived carbon fibres were successfully activated with these two alkaline hydroxides rendering highly microporous ACNFs with reasonable good activation process yields up to 47 wt.% compared to 7 wt.% yields from steam activation for similar surface areas of 1500 m²/g or higher. These nano-sized activated carbons present interesting H₂ storage capacities at 77 K which are comparable, or even higher, to other high quality microporous carbon materials. This observation is due, in part, to their nano-sized diameters allowing to enhance their packing densities to 0.71 g/cm³ and hence their resulting hydrogen storage capacities.     

The Effects of Mg Substitution in Bi-2223 Superconductors

The effects of Mg substitution in Bi-2223 superconductor system has been studied for the Bi_1.7Pb_0.3Sr₂Ca₂Cu_3−x Mg _x O _y nominal composition (x=0.00, 0.05, 0.10, 0.15 and 0.20) which was prepared by the conventional solid-state reaction. The properties of these compounds have been investigated by measuring the electrical resistivity, X-ray diffraction (XRD) and density. Also, scanning electron microscopy (SEM) was employed to investigate the surface microstructure of the samples. It has been found that the effects of Mg substitution support the development of both the Bi-2212 and Bi-2223 phases. These measurements and analyses enable us to discuss the effects of Mg dopant on superconducting properties. We found that onset critical temperatures (T _c, onset) decrease with addition x>0.10 in resistivity measurements. The presence of Mg influenced the microstructure of the samples and decreased the mean grain size of Bi-2223 grains up to x=0.10.     

Sodium alginate/poly(vinyl alcohol) alloy membranes for the pervaporation, vapour permeation and vapour permeation with temperature difference separation of dimethylformamide/water mixtures: A comparative study

In this study, sodium alginate (NaAlg)/poly(vinyl alcohol) (PVA) membranes were prepared for the separation of dimethylformamide (DMF)/water mixtures. The two polymer components were independently crosslinked chemically with glutaraldehyde. The crosslinked membranes were characterized by fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). The permeation and separation characteristics of water/DMF mixtures were investigated using the vacuum processes pervaporation (PV), vapour permeation (VP) and vapour permeation with temperature difference (TDVP) methods. The effects of NaAlg/PVA ratio, membrane thickness, operating temperature and temperature of the membrane surroundings, feed concentration on the transmembrane permeation rate and separation factor were investigated. Optimum NaAlg/PVA ratio was determined as 80/20 (w/w) for the separation. The permeation rate in VP was lower than those in PV, whereas the separation factors were higher. The activation energies of permeation in PV and VP were calculated to be 5.070 and 2.229 kcal/mol, respectively, for a 20 wt% of DMF solution.     

Crystal structure change of Li2+xTiO3+y tritium breeder under moist air

To investigate the aging behavior of Li_2+xTiO_3+y, the materials Li_2.0TiO_3+y, Li_2.2TiO_3+y and Li_2.4TiO_3+y were stored under moist air at ambient temperature. Under these conditions the weight of Li_2.0TiO_3+y increased by only 1% in 100 days, which provides evidence for the high chemical stability of Li₂TiO₃. In comparison, under the same storage conditions the weights of Li_2.2TiO_3+y and Li_2.4TiO_3+y increased by 14% and 18%, respectively. The observed weight gain is attributed to the uptake of water, and to the reaction of a by-product of Li_2+xTiO_3+y with water and carbon dioxide. The weight gain curves were evaluated by the Jander equation. From the analysis, it was possible to obtain the diffusion coefficient of water through Li₂TiO₃ particles at ambient temperature. The determined value was 2 × 10⁻¹⁷ m²/s.     

Stability Charts for the Collapse of Residual Soil in Karst

Collapse of the residual soil over bedrock cavities often occurs during construction in karst terrain, particularly when the thickness of the residuum is reduced during excavation. Even if an estimate of the strength of the residual soil is known, uncertainty with respect to the size/geometry of the subterranean voids makes a detailed analysis difficult, and straightforward methods to check the stability are needed. In this study, numerical analyses were performed to develop a stability chart expressed in terms of a dimensionless stability number and the geometry of a potential void in the residual soil. The stability charts include the effect of friction angle, and are also developed to allow the investigation of the effect of the inverted strength profile typically observed in karst terrain. Such stability numbers may be useful to estimate the stability of a given site based on the expected thickness of the soil overburden and the likely range of anticipated soil void diameters.