Dual-drug delivery of sodium ceftriaxone and metronidazole by applying salt-assisted chitosan nanoparticles: Stability,drug release,and time-kill assay study against Bacteroides fragilis

The purpose of this study was to develop a polymeric biomaterial with regulated dual drug release and increased bactericidal strength of the antibiotics sodium ceftriaxone (CTX) and metronidazole (MTZ) for the treatment of intra-abdominal infections. Chitosan nanoparticles (CS NPs) were produced by ionic crosslinking process in the presence of NaCl monovalence salt. The antibacterial activity and drug release behavior of CS NPs were investigated against anaerobic Bacteroides fragilis. The optimum initial drug ratio for designing dual drug carriers containing CTX and MTZ in a 4:3 ratio was 1:1. After 6 months, the salt-assisted CTX-MTZ-loaded CS NPs were 300 nm in size and had a polydispersity index of 0.09 with high stability. It has been demonstrated that drug release from NPs is more tightly controlled than drug release from free drugs. Furthermore, the data show that the minimum inhibitory concentration and minimum bactericidal concentration for nanostructure carriers are one-quarter of those of free medicines. Free drugs could completely kill the bacterium after 24 h, but the dual drug carrier could kill the bacteria in 10 h. Finally, salt-assisted CTX-MTZ-loaded CS NPs were proposed as a feasible alternative to standard intra-abdominal infection treatment.     

Study of critical buckling loads and modes of cross-ply laminated annular plates

Buckling of composite annular plates under uniform internal and external radial edge loads have been investigated using energy method. Trefftez rule is used in the stability equations. The symmetric buckling of symmetric cross-ply laminates is considered. In this paper, buckling behavior for the three laminates (90/0)_2s, (90/0₂/90)_s and (90₂/0₂)_s are studied. Influence of some parameters such as thickness, stacking sequence, type of supports and the ratio of hole to sheet radius on buckling loads and modes are investigated. The results of the energy method are compared with the results of numerical method. Based on the results, in the plates with clamped boundary conditions the symmetric buckling assumption is not accurate, contrary to other boundary conditions.     

Economic investigation on the use of internal coating for natural gas trunk-lines

Natural gas transmission through pipeline is the most common method for high capacity gas transmission especially when LNG technology is impossible or uneconomical. These systems are too cost intensive mainly due to fuel consumption of compressor stations. To cope with this problem, internally coated pipeline is considered as an effective approach. A mathematical model was developed in previous study and a visual program was compiled to reach optimum design of natural gas trunk-lines. Effect of different parameters such as pressure, diameter, and material grade can be investigated by developed model. This paper aims to study the effect of surface roughness from economic viewpoint. Results show that internal coating has an insignificant effect on pipeline Life Cycle Cost while it has a considerable decreasing effect on pressure drop and consequently fuel consumption cost. This study shows a coated pipeline is not ever profitable. Internal coating is disadvantageous before breakeven flow rate and breakeven point is a function of other operating conditions. The profitability will increase by increasing flow rate especially at high flow rates. This behavior is a direct result of decrease in laminar sublayer's thickness. Therefore, a detailed economic research seems indispensable over the whole project's lifetime before making any decision about using of internal coating.     

Nanostructured silver fibers: Facile synthesis based on natural cellulose and application to graphite composite electrode for oxygen reduction

The development of cheaper electrocatalysts for fuel cells is an important research area. This work proposes a new, simpler and low-cost approach to develop nanostructured silver electrocatalysts by using natural cellulose as a template. Silver was deposited by reduction of Ag complexes on the surface of cellulose fibers, followed by heat removal of the template to create self-standing nanostructured silver fibers (NSSFs). X-Ray diffraction (XRD) showed fcc silver phase and X-Ray photoelectron spectroscopy (XPS) demonstrated that the surface was partially oxidized. The morphology of the fibers consisted of 50 nm nanoparticles as the building blocks, and they possessed a specific surface area of about 25 m²/g, which is sufficiently high for electrocatalytic applications. The NSSFs were incorporated in a graphite composite electrode. The resulting modified electrode displayed a good electrocatalytic activity for the reduction of dissolved oxygen in basic media. In an O₂-saturated 0.1 M KOH solution, the overpotential to initiate the oxygen reduction reaction reduced and the limiting current increased by increasing the relative amount of silver fibers from 0 to 5 wt%.     

Physicochemical Properties of Foam‐Templated Oleogel Based on Gelatin and Xanthan Gum

In this paper, gelatin and xanthan are applied to produce a foam‐templated oleogel. For this reason, the oleogel is prepared at different concentrations of biopolymers and the properties of solution, cryogel, and related oleogel are determined. The results show that xanthan addition increases viscosity and foam stability of solution. Also, an increment in biopolymer concentration increases cryogel network density (ND) and firmness but has no significant effect on moisture sorption. The oil binding capacity of all oleogels is >92%. In terms of high foam stability (96.87 ± 4.42), low ND (0.016 ± 0.00), and consequently suitable oil sorption (46.10 ± 4.40), the oleogel containing 3% gelatin and 0.2% xanthan is selected as the best sample. Complementary tests exhibit that the oleogel, with thixotropic behavior and 60% structural recovery, can bind the oil at temperature <100 °C. The oleogel network can protect the edible oil from oxidative reaction during 2 month storage. Nonetheless, more studies are needed to attest the application of this oleogel type in food products. Practical Application: Biopolymers of gelatin and xanthan are GRAS and available so that they are applied in many food products. This research shows that the cryogel of these biopolymers, as a hydrophilic oleogelator, can be utilized to structure oil and produce oleogel in an indirect method. This procedure that forms strong gel and keeps oil even at high temperatures can be of interest to scientists who are searching for solid fat substitutes in food products such as cakes, biscuits, and muffins.     

Unprecedented Selective Oxidation of Styrene Derivatives using a Supported Iron Oxide Nanocatalyst in Aqueous Medium

Iron oxide nanoparticles supported on mesoporous silica‐type materials have been successfully utilized in the aqueous selective oxidation of alkenes under mild conditions using hydrogen peroxide as green oxidant. The supported catalyst could be easily recovered after completion of the reaction and reused several times without any loss in activity (no metal leaching observed during the reaction), constituting a facile and straightforward example of aqueous oxidation chemistry promoted by iron‐based heterogeneous systems.     

Mass transfer from nanofluid drops in a pulsed liquid–liquid extraction column

Mass transfer in gas–liquid systems has been significantly enhanced by recent developments in nanotechnology. However, the influence of nanoparticles in liquid–liquid systems has received much less attention. In the present study, both experimental and theoretical works were performed to investigate the influence of nanoparticles on the mass transfer behaviour of drops inside a pulsed liquid–liquid extraction column (PLLEC). The chemical system of kerosene–acetic acid–water was used, and the drops were organic nanofluids containing hydrophobic SiO₂ nanoparticles at concentrations of 0.01, 0.05, and 0.1 vol%. The experimental results indicate that the addition of 0.1 vol% nanoparticles to the base fluid improves the mass transfer performance by up to 60%. The increase in mass transfer with increased nanoparticle content was more apparent for lower pulsation intensities (0.3–1.3 cm/s). At high pulsation intensities, the Sauter mean diameter (d₃₂) decreased to smaller sizes (1.1–2.2 mm), leading to decreased Brownian motion in the nanoparticles. Using an analogy for heat and mass transfer, an approach for determining the mass diffusion coefficient was suggested. A new predictive correlation was proposed to calculate the effective diffusivity and mass transfer coefficient in terms of the nanoparticle volume fraction, Reynolds number, and Schmidt number. Finally, model predictions were directly compared with the experimental results for different nanofluids. The absolute average relative error (%AARE) of the proposed correlation for the mass transfer coefficient and effective diffusivity were 5.3% and 5.4%, respectively.     

Physicochemical and antibacterial properties of chitosan‐polyvinylpyrrolidone films containing self‐organized graphene oxide nanolayers

Chitosan films have a great potential to be used for wound dressing and food‐packaging applications if their physicochemical properties including water vapor permeability, optical transparency, and hydrophilicity are tailored to practical demands. To address these points, in this study, chitosan (CS) was combined with polyvinylpyrrolidone (PVP) and graphene oxide (GO) nanosheets (with a thickness of ～1 nm and lateral dimensions of few micrometers). Flexible and transparent films with a high antibacterial capacity were prepared by solvent casting methods. By controlling the evaporation rate of the utilized solvent (1 vol % acidic acid in deionized water), self‐organization of GO in the polymer matrix was observed. The addition of PVP to the CS/GO films significantly increased their water vapor permeability and optical transmittance. A blue shift in the optical absorption edge was also noticed. Thermal analysis coupled with Fourier transform infrared spectroscopy suggested that the superior thermal stability of the nanocomposite films was due to the formation of hydrogen bonds between the functional groups of chitosan with those of the graphene oxide. An improved bactericidal capacity of the nanocomposite films against gram‐positive Staphylococcus aureus and gram‐negative Escherichia coli bacteria was also observed. Highly flexible, transparent (opacity of 6.95), and antimicrobial CS/25 vol % PVP/1 wt % GO films were prepared. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43194.     

Multi-Objective Hydraulic Optimization of Diversion Dam’s Cut-Off

The seepage flow beneath a hydraulic structure is formed by the hydraulic head difference between the upstream and downstream sides. Cut-off walls are often applied, as an expedience, to reduce the seepage flow through the foundation of diversion dams and to enhance the efficiency of these dams. In this research, perhaps for the first time, a novel methodology is propounded to assess the optimum characteristics of cut-off walls in diversion dams in order to ameliorate hydraulic interactions between the diversion dam foundation and the cut-off walls behavior, also their construction cost is minimized. The results are used to train and validate the Multi-Layer Perceptron (MLP) simulation model. Then MLP, as a meta-model for simulation of the hydraulic behavior of cut-off walls, is coupled with a robust multi-objective optimization algorithm, Non-dominated Sorting Genetic Algorithm-ΙΙ (NSGA-ΙΙ), to create a trade-off between the intended goals. Finally, Preference Ranking Organization METHod for Enrichment Evaluation (PROMETHEE) decision making model and Nash-Harsanyi bargaining model are utilized to find the compromise design optimal solution on the trade-off curve. Results demonstrate that the best agreed-upon design optimal solution using PROMETHEE and Nash-Harsanyi bargaining models can be considered as (10, 3.84, 32) meters and (2.47, 10, 29.22) meters for optimum depth of the upstream and downstream cut-off walls and the optimum distance between them, respectively.     

Directional properties of ordered 3‐3 piezocomposites fabricated by sacrificial template

Fabrication of piezoelectric composites with 3‐3 connectivity and their properties have attracted attention due to the application of these composites in acoustic transducers, medical imaging, and nondestructive testing. In this research, directional piezoelectric‐polymer composites with 3‐3 connectivity are prepared by a relatively simple fabrication process of dipping an ordered polymeric template (mesh) into lead zirconate titanate suspension followed by drying, pyrolysis, and sintering. The resulting porous ordered structures of lead zirconate titanate‐5A ranging from 18 to 32 vol% ceramic were subjected to polymer injection to form composites to be cut and polarized in different directions. In the composites, the effects of (i) polarization direction and (ii) active piezoelectric phase content on the dielectric and piezoelectric properties were investigated. The results showed that the dielectric constant and the piezoelectric properties are significantly dependent on the direction in composites of directional structure. In these composites, dielectric constant values were found to be higher in the direction parallel to ceramic ligaments. Moreover, the highest values for piezoelectric charge and voltage coefficient and figure of merit were found in the direction 45° to ceramic ligaments. In all composites, both dielectric constant and piezoelectric property values were proportional to the active piezoelectric phase content.