PLA/metal oxide biocomposites for antimicrobial packaging application

ABSTRACT

The effects of metal oxide addition in polylactic acid (PLA) film were investigated in this study. PLA/Metal Oxide biocomposites were prepared by solvent casting method. The incorporation of metal oxide resulted in no chemical structure change of neat PLA. PLA/ZnO and PLA/MgO exhibited the widest inhibition while PLA/TiO₂ resulted in the smallest inhibition zone. The addition of metal oxides caused fracture and void on the surface of PLA. The addition of metal oxide into PLA films decreased the tensile strength at the concentration higher than 0.1 per hundred resin (phr). Incorporation of metal oxides accelerated the thermal degradation of PLA and tends to increase the biodegradability of PLA.     

Measuring effect of the blooming of chemical curatives on the rate of cyclic fatigue crack growth in natural rubber filled with a silanized silica nanofiller

Two rubber compounds with different amounts of chemical curatives were prepared by mixing natural rubber with a high loading of a sulfur‐bearing silanized precipitated amorphous white silica nanofiller. The chemical bonding between the filler and rubber was optimized via the tetrasulfane groups of the silane by adding a sulfenamide accelerator and zinc oxide. The rubber compounds were cured and stored at ambient temperature for 65 days before they were tested. One compound showed extensive blooming as a function of storage time. Thin tensile strips of the rubber vulcanizates containing an edge crack were repeatedly stressed at constant strain amplitude and test frequency at ambient temperature and crack length c was measured as a function of the number of cycles n. The cut growth per cycle, dc/dn, was calculated and plotted against the tearing energy, T. The blooming of the chemical curatives increased dc/dn by up to an order of magnitude at a constant T. This was due to the reagglomeration of the chemical curatives in the rubber and also within a thin layer approximately 15 to 20 μm in size beneath the rubber surface. Under repeated stressing, cracks grew through the relatively weak agglomerated areas in the rubber and this caused the rate of crack growth to increase at a constant T. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Predicting the crease recovery performance and tear strength of cotton fabric treated with modified N‐methylol dihydroxyethylene urea and polyethylene softener

This study aimed at developing a model for predicting the crease recovery performance and tear strength of cotton fabric using modified N‐methylol dihydroxyethylene urea, polyethylene softener, catalyst, curing time and curing temperature as the predictor variables. A quarter factorial design was constructed and, based on the experimental results, regression models were built to predict crease recovery angle and tear strength of the treated fabric. All experimental design and statistical analysis steps were implemented, using Minitab statistical software.     

Direct synthesis of highly crystalline single-phase hexagonal tungsten oxide nanorods by spray pyrolysis

The metastable state hexagonal-tungsten oxide (h-WO₃) has been attracting attention over the past decade because of its high reactivity that arises from the hexagonal channels in its crystal structure. Simplification of the process used to synthesize h-WO₃ is an important step to facilitate the industrial applications of this material. In this study, we addressed this challenge by developing a spray pyrolysis process to synthesize highly crystalline h-WO₃. The ratio of the monoclinic to the hexagonal phase was controlled by adjusting the segregation time. Single-phase h-WO₃ nanorods were synthesized using a carrier gas flow rate of 1?L/min, which was equivalent to a segregation time of 18.4?s. The ability of the h-WO₃ nanorods to adsorb nitrogen and carbon dioxide was evaluated to confirm the presence of hexagonal channels in the crystal structure.     

Homoacetogenesis during hydrogen production by mixed cultures dark fermentation: Unresolved challenge

This paper is a comprehensive review of H₂ consumption during anaerobic mixed culture H₂ dark fermentation with a focus on homoacetogenesis. Homoacetogenesis consumed from 11% to 43% of the H₂ yield in single and repeated batch fermentations, respectively. However, its quantification and extent during continuous fermentation are still not well understood. Models incorporating thermodynamic and kinetic controls are required to provide insight into the dynamic of homoacetogenesis during H₂ dark fermentation. Currently, no adequate method exists to eliminate homoacetogenesis because it does not depend on the culture's source, pre-treatment, substrate, type of reactor, or operation conditions. Controlling CO₂ concentrations during dark fermentation needs further investigation as a potential strategy towards controlling homoacetogenesis. Incorporating radioactive labeling technique in H₂ fermentation research could provide information on simultaneous production and consumption of H₂ during dark fermentation. Genetic studies investigating blocking H₂ consuming pathways and enhancing H₂ evolving hydrogenases are suggested towards controlling homoacetogenesis during dark fermentation.     

Aflatoxins: Biosynthesis,Occurrence, Toxicity,and Remedies

Food contagion with aflatoxins is the modern concern and has received a great awareness during the last few decades. The intermittent incidence of these toxins in agricultural commodities has negative role on the economy of the affected regions where harvest and postharvest techniques for the prevention of mold growth, are seldom practiced. Aflatoxins are difuranocoumarin derivatives produced by a polyketide pathway by the fungus Aspergillus flavus and Aspergillus parasiticus via polyketide pathway which are highly hepatotoxic, hepatocarcinogenic, teratogenic, and mutagenic in nature and contaminate a wide variety of important agricultural commodities before, during, and after harvest in various environmental conditions. The production of aflatoxins in innate substrates depends upon the various factors, that is, type of substrate, fungal species, moisture contents of the substrate, minerals, humidity, temperature, and physical damage of the kernels. These toxins cause several ailments such as cancer, hepatitis, mutation abnormalities, and reproduction disorders. Minimization and inactivation of aflatoxins contaminants through proper crop management at farm level and with physical, chemical, and biological techniques are the limelight of the article.     

Sludge characteristics in anaerobic SBR system producing hydrogen gas

In this study, sludge characteristics of anaerobic sequencing batch reactor (ASBR) were investigated to improve and optimize the efficiency of the system converting starch into biohydrogen. The effect of stratification in settling phase on H2-producing ASBR, which results in settleable and non-settleable sludge, was observed using a batch experiment. It was concluded that specific H2 activity of decanting non-settleable sludge was higher than that of settleable sludge, which may be the reason of low yield in H2-producing ASBR. In addition, effect of settling time on settleable sludge, which is another key operational parameter, was also analysed using another set of batch experiment. Settling time of the sludge was found to be an important parameter in H2-producing ASBR. Specific H2 activity varied inversely with the duration for which settleable microorganisms were contained in settling phase. Microbial species, responsible for H2 activity in each condition, were identified using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) analysis.     

Dynamic release of gentamicin sulfate (GS) from alginate dialdehyde (AD)-crosslinked casein (CAS) films for antimicrobial applications

In the present work, antibiotic drug gentamicin sulfate (GS) has been loaded into alginate dialdehyde-crosslinked casein (CAS) films for wound dressing applications. The films have been characterized by Fourier transform infrared spectroscopy, X-ray diffraction analysis and scanning electron microscopy. The dynamic release of model drug GS has been investigated in the physiological fluid at 37 °C. The drug release data has been interpreted in the terms of various kinetic models such as Power function model, first order model and Schott model. The release data was found to be well fitted by Schott model. The various diffusion coefficients are also evaluated. The adsorption of model therapeutic protein BSA on the film has been investigated. The maximum adsorption is found to be 5.7 mg/cm².The films were tested for their antibacterial and anti-fungal action. Finally, the in vivo wound healing study was carried out on Albino wistar rats.     

Big Data Analytics Using Graph Signal Processing

The networks are fundamental to our modern world and they appear throughout science and society. Access to a massive amount of data presents a unique opportunity to the researcher’s community. As networks grow in size the complexity increases and our ability to analyze them using the current state of the art is at severe risk of failing to keep pace. Therefore, this paper initiates a discussion on graph signal processing for large-scale data analysis. We first provide a comprehensive overview of core ideas in Graph signal processing (GSP) and their connection to conventional digital signal processing (DSP). We then summarize recent developments in developing basic GSP tools, including methods for graph filtering or graph learning, graph signal, graph Fourier transform (GFT), spectrum, graph frequency, etc. Graph filtering is a basic task that allows for isolating the contribution of individual frequencies and therefore enables the removal of noise. We then consider a graph filter as a model that helps to extend the application of GSP methods to large datasets. To show the suitability and the effeteness, we first created a noisy graph signal and then applied it to the filter. After several rounds of simulation results. We see that the filtered signal appears to be smoother and is closer to the original noise-free distance-based signal. By using this example application, we thoroughly demonstrated that graph filtration is efficient for big data analytics.