Physicochemical properties and antimicrobial activity of biocompatible carboxymethylcellulose‐silver nanoparticle hybrids for wound dressing and epidermal repair

Skin loss can be caused by accident, burn, trauma, chronic wounds, and diseases, which is severely aggravated by multidrug‐resistant bacterial infections. Soft hybrids based on biopolymers combined with silver nanoparticles (AgNPs) have potential applications as wound dressing supports and skin tissue repair. Thus, our study focused on the design, green synthesis, and comprehensive characterization of carboxymethyl cellulose (CMC–AgNP) nanocomposites for producing hydrogel membranes, with tunable physicochemical properties, cytocompatibility, and biocidal activity for potential application as wound dressing and skin repair. These nanocomposites were prepared using CMC with two degrees of carboxymethylation, distinct concentrations of citric acid (CA) crosslinker, and AgNPs by in situ chemical reduction, forming hybrid membranes by the solvent casting method. The results demonstrated that superabsorbent hydrogels were produced with swelling and degradation behaviors dependent on the concentration of CA crosslinker, degree of carboxymethylation of CMC, and content of AgNP in the matrices. Moreover, the Fourier transform infrared spectroscopy analysis evidenced that the CMC functional groups (e.g., ? COOH and ? OH) were directly involved in the chemical reactions for the formation of AgNPs and hydrogel crosslinking pathway. These nanocomposites were cytocompatible using in vitro 3‐(4,5‐dimethyl‐2‐thiazolyl)‐2,5‐diphenyltetrazolium bromide cell viability assay with of human embryonic kidney cells. Conclusively, the CMC–AgNP nanohybrids demonstrated to be simultaneously non‐toxic combined with highly effective antibacterial activity against gram‐positive multi‐resistant wound/skin pathogens (Staphylococcus aureus) and moderate effect towards gram‐negative strains (Escherichia coli and Pseudomonas aeruginosa). © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45812.     

α-Amylase Mediates Host Acceptance in the Braconid Parasitoid <Emphasis Type="Italic">Cotesia flavipes</Emphasis>

Foraging parasitoids use chemical signals in host recognition and selection processes. Although, the volatiles play a relevant role in the localization by parasitoids of their hosts feeding on plants, the host identification process for acceptance occurs mainly during contact between the parasitoid and its host where host products related to feeding activities, fecal pellets and oral secretions, play a crucial role. The purpose of this study was to identify the nature of the contact kairomone(s) that mediate the acceptance for oviposition of the parasitoid Cotesia flavipes Cameron (Hymenoptera, Braconidae), which was released in Kenya in 1993 to control the invasive crambid Chilo partellus (Swinhoe). Using host and non-hosts of C. flavipes, we showed that it is mainly the oral secretions of the larvae that harbour the active compound(s) that mediate host acceptance for oviposition by C. flavipes. Using an integration of behavioral observations and biochemical approaches, the active compound of the oral secretions was identified as an α-amylase. Using synthetized α-amylases from Drosophila melanogaster (an insect model for which syntheses of active and inactive α-amylases are available), we observed that the conformation of the enzyme rather than its catalytic site as well as its substrate and its degradation product is responsible for host acceptance and oviposition mediation of C. flavipes females. The results suggest that the α-amylase from oral secretions of the caterpillar host is a good candidate for an evolutionary solution to host acceptance for oviposition in C. flavipes.     

Scaling laws in network models: porous medium property prediction during morphological evolution

A 3-D network model was used to represent a porous medium and the macroscopic properties of the network (like permeability) were simulated by Monte Carlo method. It was shown that these macroscopic properties can be related to network parameters (throat-size distribution parameters, network size and connectivity) through power law correlations, as can be inferred from percolation theory. In this way, macroscopic properties evaluation during the morphological evolution of a 3-D network requires less computational effort, which facilitates the incorporation of this model into oil flow simulators.     

Gas‐Liquid Direct‐Contact Evaporation: A Review

Gas‐liquid direct‐contact evaporators are characterized by the bubbling of a superheated gas through the solution to be concentrated. In other words, they are nonisothermal bubble columns. Despite their simplicity of construction, these units exhibit rather complex hydrodynamics and, similar to what occurs to isothermal bubble columns, the design of such units still poses a problem. The present paper reviews the literature regarding this kind of equipment, addressing both experimental studies and modeling efforts. The covered issues include classic and potential applications, bubbling regimes, gas holdup and bubble size distributions, as well as mathematical models proposed for simulating the unit. Additionally, pertinent literature on isothermal bubble columns is also discussed. Recommendations are made for future research.     

Two-fluid simulation on the mixed convection flow pattern in a nonisothermal water model of continuous casting tundish

A transient two-fluid model is applied to simulate fluid flow and heat transfer in a nonisothermal water model of continuous casting (CC) tundish. The original liquid in the bath is defined as the first fluid, and the inlet stream, with the temperature variation, is defined as the second fluid. The flow patterns and heat transfer are predicted by solving the three-dimensional (3-D) transient transport equations for each fluid. The results predicted by the two-fluid model make the effect of natural convection more clear compared with the generally used single fluid model k-ɛ turbulence model.     

Droplet breakage and coalescence models for the flow of water-in-oil emulsions through a valve-like element

An experimental and theoretical study was carried out regarding the evolution of droplet size distributions for the flow of water in oil emulsions through a valve-like element that simulates a mixing valve. The water droplets had diameters in the 0.1–100 μm range, which includes droplets that are either smaller or larger than the Kolmogorov length scale for the experimental conditions. Droplet breakage and coalescence models that can be used for this size range were proposed. A simplified population balance model was developed to interpret the experimental data and solved by the method of classes. The model parameters were estimated by the orthogonal distance regression method. The simplifying assumption of the model was verified by global optimization using a parallel implementation of the particle swarm optimization method. The agreement between simulated and experimental droplet volume size distributions was good. The predictions of the DeBroukere mean diameter, d₄₃, were unbiased with mean errors of 8%.     

An Experimental Study of Number Concentration Gradients of Inclusions during Deoxidation using Inductive and Gas Stirring

Concentration gradients of inclusions during inductive and gas stirring of AISI H13 tool steel in a ladle have been studied using a unique experimental technique at Uddeholm Tooling AB in Sweden. A specially designed sampling equipment, which allows five samples to be taken at the same time and at different depths was used. The aim was to experimentally quantify the existence of inclusion size population gradients in different positions of the steel melt. One experiment was carried out using induction stirring and one using gas stirring. The main findings from the induction stirring experiment was that i) concentration gradients of inclusions exist, ii) the number of inclusions decreases with stirring time in all positions, and iii) that the superficial positions show a more rapid decrease than the deeper ones. The main findings from the gas stirring experiment are that i) concentration gradients of inclusions exist, ii) the superficial positions are mostly affected by the gas plumes, and show a very pronounced decrease of the number of inclusions with stirring time, and iii) the deeper positions and also one of the superficial position (no “3”) shows no decreasing trend.     

Gestational trophoblastic disease. New approaches to diagnosis

Although considerable progress has been made in the understanding of the biology of gestational trophoblastic tumors, future generations will undoubtedly classify our current knowledge base as basic. It is our hope that by more precisely defining the genetic basis for these diverse lesions, we may be able to develop better diagnostic, surveillance, and treatment modalities for affected patients.