Fabrication and characterization of exfoliated chitosan–gelatin–montmorillonite nanocomposite nanofibers

Polymeric nanofibers as one of the most known nanotechnology products have huge potential applications in many fields due to their high aspect ratio and porosity, being capable of formation of three-dimensional structures and having great mechanical and biological properties. Chitosan is a natural abundant polymer which has attracted huge interests in biomedical and biological industries due to its biocompatible, biodegradable, and non-toxicity properties. However, electrospinning of chitosan is found to be a great challenge, blending it with other polymers such as gelatin was explored as means to improve the morphological deficiencies of chitosan nanofibers and facilitate its electrospinnability. On the other hand, montmorillonite (MMT) has been attracted great attention due to its remarkable improvement in properties of polymeric composites nanofibers. The main objective of this work was on effect of concretion of gelatin–chitosan blends and MMT on morphology of resulted nanocomposite nanofibers. The x-ray diffraction data demonstrated the exfoliation of MMT layers. The morphology of electrospun chiosan–gelatin–MMT composite nanofibers was characterized using scanning electron microscope (SEM). The miscibility of blend was determined using SEM and Fourier transform infrared spectrometer/attenuated total reflectance.     

Ultrasound assisted nucleation of some liquid and solid model foods during freezing

Power ultrasound has been proven to be useful in promoting the nucleation of ice in water-based solutions, and different mechanisms have been proposed to describe this phenomenon. In the present work, the use of ultrasound waves to induce dynamic nucleation in deionised water, sucrose solution, and agar gel samples was studied, and the mechanism of ultrasound assisted nucleation was discussed. The samples were frozen in an ethylene glycol–water mixture (− 20 °C) in an ultrasonic bath system after putting them into tubing vials. Ultrasound irradiation (25 kHz, 0.25 W cm⁻¹) was applied continuously for 1, 3, 5, 10 or 15 s at different sample's temperatures in the range of 0 °C to − 5 °C. The nucleation temperatures of the water, sucrose solution and agar gel samples without ultrasound irradiation, occurred stochastically at − 7.4 ± 2.4 °C, −10.6 ± 1.7 °C and − 7.5 ± 0.92 °C, respectively and followed normal distributions. Unlike agar gel samples, the nucleation temperatures of water and sucrose were induced by applying ultrasound for 5 s at different temperatures after a short delay, and linear relationships between the ultrasound irradiation temperatures and the nucleation temperatures were observed. Evaluation of the effect of different durations of ultrasound application on agar gels indicated that 1 s was not long enough to induce nucleation, 3 s was optimal, 5 s and 10 s produced heat and inhibited nucleation, and 15 s did not exhibit significant differences from 3 s and 10 s. It was concluded that longer irradiation durations (especially 5 s and 10 s) caused the sample to heat up, which interrupted or delayed the nucleation. Ultrasound irradiation for 3 s induced nucleation in agar gel samples at different temperatures resulting in a linear relationship between irradiation and nucleation temperatures. The observations indicated that the Hickling's theory, according to which vigorous collapses of bubbles are the only driving mechanism of nucleation, is not adequate to describe the ultrasound assisted nucleation. The results, however, were in agreement with results of some other researchers suggesting that secondary phenomena such as flow streams are also important for the initiation of nucleation. In conclusion, the use of ultrasound as a means to control the crystallisation process offers promising application in food freezing, though further investigations are needed for understanding the mechanisms, especially in solid foods.     

Load dispersion-aware VM placement in favor of energy-performance tradeoff

Huge energy consumption in cloud infrastructure has turned into a challenging problem. Virtualization technology, which can be regarded as the first step in energy conservation by offering benefits like on-demand resource provisioning and live migration, creates a platform on which different resource allocation and scheduling policies can be defined on how to accumulate VMs on fewer number of hosts while respecting performance metrics. In this paper, after presenting a classification on VM placement strategies, we propose different combinatorial placement policies that take load dispersion of hosts into account to dynamically adapt their placement decisions. Simulated experiments through Cloudsim showed noteworthy results concerning energy-performance tradeoff.     

Connectivity analysis for dynamic movement of vehicular ad hoc networks

Speed variation is one of the main challenges in deriving the connectivity related predictions in mobile ad-hoc networks, especially in vehicular ad hoc networks (VANETs). In such a dynamic network, a piece of information can be rapidly propagated through dedicated short-range communication, or can be carried by vehicles when multihop connectivity is unavailable. This paper proposes a novel analytical model that carefully computes the connectivity distance for a single direction of a free-flow highway. The proposed model adopts a time-varying vehicular speed assumption and mathematically models the mobility of vehicles inside connectivity. According to the dynamic movability scenario, a novel and accurate closed form formula is proposed for probability density function of connectivity. Moreover, using vehicular spatial distribution, joint Poisson distribution of vehicles in a multilane highway and tail probability of the expected number of vehicles inside single lane in a multilane highway are mathematically investigated. The accuracy of analytical results is verified by simulation. The concluded results provide helpful insights towards designing new applications and improving performance of existing applications on VANETs.     

New synthesis processes of polyetheramines: Comparison of three different developed amination routes

In this work, three different novel processes are reported for the preparation of polyetheramines (PEAs) from polyethylene glycols (PEGs) and polypropylene glycols (PPGs). The processes are the nucleophilic substitution, oxidation/reduction, and catalytic aminations. The novelties of the processes lay in environmentally friendly routes, the variety of possible precursors (i.e., PEG and PPG with different molecular weights), and extraction methods. The formation of the PEAs with no chain cleavage was confirmed by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC) results. Based on the comparison study, the nucleophilic substitution and catalytic aminations were the most efficient (conversion >90%) and shortest (yield >90%) methods, respectively. For nucleophilic substitution, the amination of PEG and PPG intermediates was performed in different solvent media due to the difference in solubility parameters of PEGs and PPGs. The catalytic route (using [Zn(tu)₃]SO₄/aqueous ammonia system) can be considered a green method; however, catalytic amination of the PPGs is impossible due to insolubility of PPGs in aqueous ammonia. Therefore, the oxidation/reduction method using Leuckart reaction appears to be the most environmentally friendly route for the amination of PPGs. Moreover, PEGs and PPGs with different molecular weights showed various behaviors during reaction and separation protocols.     

A novel green synthesis of zero valent iron nanoparticles (NZVI) using three plant extracts and their efficient application for removal of Cr(VI) from aqueous solutions

In the present study, NZVI particles were synthesized from the plant extracts including Rosa damascene (RD), Thymus vulgaris (TV), and Urtica dioica (UD). The FTIR arspectshowed that polyphenols, proteins and organic acids which serve as reducing and stabilizing agents play a significant role in the synthesis of NPs and reduce the possibility of aggregation of NPs compared to chemical techniques of NPs synthesis. The amount and type of compounds in plant extracts affect the structure and also agglomeration of NPs after adsorption process. Based on the results, the highest removal efficiency occurred at pH 2. With increase in contact time and amount of dose, the percentage removal increases. Inversely, increase of initial concentration of Cr(VI) decreases the removal efficiency of the contaminant. These nanoparticles have a high adsorption capacity. Accordingly, by applying a dose of 0.2 g/l and contact time of 10 min, the three NPs yielded >90% removal efficiency. Also, for 1 min contact time, the percentage removal was 94.87%, 83.48% and 86.8% for RD-Fe, UD-Fe and TV-Fe, respectively. By an increase to 25 min, the removal percentage reached to 100% for TV-Fe and UD-Fe. Moreover, 30 min was required to remove Cr(VI) completely by RD-F.     

Oxidative and non-oxidative degradation pathways of L-ascorbic acid

L-Ascorbic acid (AA) is an essential component for organisms and is responsible for various functions in the human body. Its structure is in a way that suffering significant structural changes during storage. Herein, the stability of L-ascorbic acid aqueous solution at various thermal (25 and 90 °C ± 2) and atmospheric oxygen or argon was monitored by optical rotation changes as a function of time intervals. Under oxygen, specific optical rotation [α] of the solution was decreased from + 22.0 to + 2.0 after 32 days and under argon + 11.5 after 9 months at 25 °C. The loss of [α] increased at 90 °C under both oxygen and argon atmospheres. Subsequently, the obtained reaction mixtures were evaporated to dryness and analysed by FT-IR, ¹H-NMR and GC-MS techniques. Results of these analyses indicate that AA was decomposed to a complex mixture of reaction products.     

Geochemical characteristics of upper Jurassic carbonate reservoir bitumen in the Eastern Kopeh-Dagh,NE Iran

Geochemical characteristics of solid bitumen in Upper Jurassic carbonate reservoir are investigated. Aromatic maturity parameters indicate peak to late oil window level of maturity for the bitumen samples. Regular sterane distributions, conical variable (CV), plots of δ¹³C_Sat versus δ¹³C_Aro and Pr/nC₁₇ against Ph/n_C18, predominance of C₂₃ tricyclic terpane, ratios of steranes/hopanes and C₂₃/C₂₁ tricyclic terpane indicate charging from clastic-rich anoxic marine source rocks. Ratios of C₂₉/C₃₀ hopane, Ts/Ts+ Tm, C₂₄ tetracyclic terpane/C_20-26 tricyclic terpanes and plot of C₂₂/C₂₁ versus C₂₄/C₂₃ tricyclic terpanes show influences of carbonate/marl facies. All these would throw crucial guiding light on the interpretation of the future exploration.     

A scene image classification technique for a ubiquitous visual surveillance system

Multimedia Tools and Applications - The concept of smart cities has quickly evolved to improve the quality of life and provide public safety. Smart cities mitigate harmful environmental impacts and...