Characterization And Flammability Of Ethylene Vinyl Acetate (Eva)/Zeolite Composites

This thesis describes the fabrication, characterization and properties of natural zeolite as filler in ethylene vinyl acetate (EVA) composites. One of the main objectives of this research is to determine the effect of zeolite loading on properties of EVA matrix composites. EVA composites at different loading of zeolite (5-25 vol. %) were prepared using Thermo Haake Polydrive internal mixer and were then compression molded according to standard test specimen. Tensile test and dynamic mechanical analysis (DMA) were performed to characterize the mechanical properties of EVA/zeolite composites. The tensile test can also be explained from the analysis of Scanning Electron Microscopy (SEM) micrograph of the tensile fractured surfaces. Besides, the influences of surface modifications on the properties of EVA/zeolite composites were also investigated. The interfacial interactions between EVA and zeolite were modified by crosslinking of EVA with dicumyl peroxide (DCP); cation exchange method using organic surfactant (octadecylamine) and also silane treatment using 3-aminopropyltriethoxysilane (AMPTES). In addition, Fourier Transform Infra red (FTIR) spectra analyses were performed in order to study the interaction between the composites and functional group of the surface modifiers. The application of surface modifications was proved to enhance the mechanical and morphological properties of EVA/zeolite composites. Thermal properties of the composites were also characterized by means of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Intumescent flame retardant system consisting of ammonium polyphosphate (APP)/ pentaerythritol (PER) was used to enhance the thermal properties and fire retardancy of EVA/zeolite composites. The mechanical properties examined by tensile test indicated that the introduction of both flame retardants lead to deterioration of tensile strength and elongation at break of EVA/zeolite composites. However, the tensile modulus of the composites was significantly enhanced attributed to the rigidity of APP particles. The results of DSC and TGA showed that both types of flame retardants have the ability to enhance the thermal stability of EVA/zeolite composites. Meanwhile the results of vertical burning testing (UL-94-V) and limiting oxygen index (LOI) measurement revealed that the flame retardants could also reduce the flammability of the composites by achieving V-0 UL94-v rating and increased LOI value, respectively

Real-Space Approach for the Electronic Calculation of Twisted Bilayer Graphene Using the Orthogonal Polynomial Technique

We discuss technical issues involving the implementation of a computational method for the electronic structure of material systems of arbitrary atomic arrangement. The method is based on the analysis of time evolution of electron states in the real lattice space. The Chebyshev polynomials of the first kind are used to approximate the time evolution operator.  We demonstrate that the developed method is powerful and efficient since the computational scaling law is linear. We invoked the method to study the electronic properties of special twisted bilayer graphene whose atomic structure is quasi-crystalline. We show the density of states of an electron in this graphene system as well as the variation of the associated time auto-correlation function. We find the fluctuation of electron density on the lattice nodes forming a typical pattern closely related to the typical atomic pattern of the quasi-crystalline bilayer graphene configuration

Technical efficiency of smallholder banana production: a case study in Viet Nam

Bananas are considered one of the leading trading crops due to their high demand all over the globe. Since the increasing demand leads to the expansion of global import, the existing literature is in dire need of updating, especially from the producing economies that fall in the category of developing nations. The study, thus, intends to estimate the critical efficiency of said area. Along with it, the study aims to determine the elements of banana production in the context of Vietnam using a stochastic frontier approach and technical efficiency technique. The sample of the study is the province of Vietnam named Hung Yen, and it made sure to collect the data from 160 farmers in 2022. Results of the study reveal that the farmers' technical efficiency fluctuates between the range of 89.68- 97.81%. However, the average technical efficiency of banana farmers was reported to be 95.92%. From the result, it is gauged that factors such as potassium, manure, distance, capital, and training showed positive signs at a 0.01 significance level. Also, the education and area coefficient show a positive sign at a 0.05 significance level. Finally, distance and district variables, which were the dummy variable, show a negative sign at 0.01 and 0.05 significance levels, respectively.Hoang Van Hung (Hung Yen University of Technology and Education (UTEHY)), Nguyen Van Huong (Hung Yen University of Technology and Education (UTEHY)), Le Thi Thuong (Hung Yen University of Technology and Education (UTEHY)), Thai Thi Kim Oanh (Vinh University (VU)), Nguyen Van Chuong (University of Financial – Business Administration (UFBA)), Nguyen Cong Tiep (Viet Nam National University of Agriculture (VNUA)), Thai Van Ha (Ha Noi University of Business and Technology (HUBT)), Nguyen Thi Luong (Can Tho University (CTU))Includes bibliographical references

Occurrence, Toxicity and Adsorptive Removal of the Chloramphenicol Antibiotic in Water: A Review

Chloramphenicol is a broad-spectrum bacterial antibiotic used against conjunctivitis, meningitis, plague, cholera, and typhoid fever. As a consequence, chloramphenicol ends up polluting the aquatic environment, wastewater treatment plants, and hospital wastewaters, thus disrupting ecosystems and inducing microbial resistance. Here, we review the occurrence, toxicity, and removal of chloramphenicol with emphasis on adsorption techniques. We present the adsorption performance of adsorbents such as biochar, activated carbon, porous carbon, metal-organic framework, composites, zeolites, minerals, molecularly imprinted polymers, and multi-walled carbon nanotubes. The effect of dose, pH, temperature, initial concentration, and contact time is discussed. Adsorption is controlled by π-π interactions, donor-acceptor interactions, hydrogen bonding, and electrostatic interactions. We also discuss isotherms, kinetics, thermodynamic data, selection of eluents, desorption efficiency, and regeneration of adsorbents. Porous carbon-based adsorbents exhibit excellent adsorption capacities of 500-1240 mg

Investigation of salt-tolerant rhizosphere bacteria from seawater-intruding paddy rice field in Vietnam

Salt‐tolerant plant growth‐promoting rhizobacteria (ST‐PGPR) are known as potential tools to improve rice salinity tolerance. In this study, we aimed to investigate the plant growth‐promoting rhizobacteria community richness of the paddy rice fields in Soc Trang and Ben Tre Provinces where were seriously affected by sea level rise. The salinity in the sampling sites ranged from 0.14‰ to 2.17‰ in November 2018, the rainy season. The microbial abundance of samples was evaluated by spreading the samples in tryptic soy agar (TSA) medium supplemented with various concentrations of NaCl. With the increase of salt concentration up to 10% NaCl, a total number of bacteria decreased for all the samples, ranging from 106 to 104 CFU/g, and bacterial colonies were not observed at 30% NaCl. Among a total of 48 salt-resisting bacteria isolated from the rice paddy field mud surrounding the rice root, 22 isolates were able to produce indole-3-acetic acid (IAA: phytohormone for the plant growth). Seventeen out of 48 isolates were able to grow in the medium without nitrogen or phosphor sources. Six isolates having high IAA producing activity, nitrogen fixation and phosphate solubilization were belonged to Bacillus (DT6, LT16, and LHT8), Halobacillus (DT8), Aeromonas (LHT1), and Klebsiella (LHT7) genera. All the sequences of the strains DT6, DT8, LT16, LHT1, LHT7, and LHT8 were registered in the GeneBank with the accession numbers MK335670, MK335671, MK335672, MK335673, MK335674, and MK335675, respectively.

SomBe:Self-Organizing Map for Unstructured and Non-Coordinated iBeacon Constellations

Bluetooth Low Energy (BLE) devices such as iBeacons have been popularly deployed for Location Based Services (LBS), including indoor infrastructure monitoring, positioning, and navigation. In these applications, the positions of iBeacons are assumed to be known. However, the location information is often unavailable or inaccurate as most iBeacons were deployed by different external parties. In addition, manual localizing the already-deployed iBeacons is costly and even impractical, especially in large-scale and complex indoor environments. Therefore, we propose a novel method, namely SomeBe, which can localize deployed iBeacons with a minimal effort and invasiveness to existing infrastructures. Specifically, our approach uses cooperative multilateration based on Received Signal Strength (RSS) of available smartphones and WiFi access points (APs) in the environment. Both Bluetooth signal strengths (between smartphones and iBeacons) and WiFi signal strengths (between smartphones and APs) are jointly employed in a single optimization cost function to surpass the local minima. Requiring that the positions of the APs are known only, the proposed cost function can also localize the iBeacons without knowing the positions of smartphones. To improve the localization accuracy, we employ a clustering method based on the RSS values for the coarse estimation of iBeacons' positions. SomBe also can be used to simplify iBeacon deployment as it can localize the iBeacons with a minimal effort. The performance evaluation results of our testbed experiments as well as realistic simulations show that SomBe outperforms non-cooperative approaches with 85% better in terms of accuracy

Facile Synthesis of Carbon Quantum Dots by Plasma-liquid Interaction Method

Carbon quantum dots (CQDs) are a novel type of fluorescent nano-materials with various unique properties. They are recently attracting enormous interest due to their superiority in water solubility, chemical inertness, low toxicity, ease of functionalization as well as resistance to photo-bleaching and potential applications in biomedical indication, photo-catalysis, energy conversion, optoelectronics, and sensing. In this work, we present a facile and environmentally friendly synthesis of CQDs based on plasma - liquid interaction method. This is a single-step method and does not use toxic chemicals. The size distribution of obtained CQDs is rather uniform at approximately 3 nm. The emission peak of CQDs shifts from 427 nm to 523 nm as the excitation wavelength is varied from 340 nm to 460 nm. The non-equilibrium reactive chemistry of plasma liquid interaction is responsible for acceleration of the CQDs formation process

Synthesis of acyclovir as an antiherpes-virus drug

A one-pot process for high-yield regioselective synthesis of 9-[(2-hydroxyethoxy) methyl]guanine (acyclovir),  an antiherpetic agent, was achieved from guanine via the steps of reacting of N2,N9 -diprotected guanine with 1-acetyl-2-acetylmethoxy-ethyleneglycol in presence of phosphoric acid or polyphosphoric acid. Total yield of product was 59%. The obtained acyclovir meets the standards in the British Pharmacopoeia 2007 (BP2007). Its activity as inhibitor of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) was evaluated according to the plaque reduction assay method and compared with the standard compound. The synthesized acyclovir showed a similar activity as the control. Keywords: Acyclovir, Herpes simplex virus, Nucleoside, One- pot synthesis