Search results for: exchange interactions

Authors: Karan R. Chavan, Paula Saavalainen, Kumudini V. Marathe, Riitta L. Keiski, Ganapati D. Yadav

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Co-contamination of groundwaters by arsenic in different forms is often observed around the globe. Arsenic is introduced into the waters by several mechanisms and different technologies are proposed and practiced for effective removal. The assessment of three prominent technologies, namely, adsorption, ion exchange and nanofiltration was carried out in this study based on lifecycle methodology. The life of the technologies was divided into two stages: cradle to gate (C-G) and gate to gate (G-G), in order to find out the impacts in different categories of environmental burdens, human health and resource consumption. Life cycle inventory was estimated by use of models and design equations concerning with the different technologies. Regeneration was considered for each technology and over the course of its full lifetime. The impact values of adsorption technology for the C-G stage are greater by thousand times (103) and million times (106) compared to ion exchange and nanofiltration technologies, respectively. The impact of G-G stage of the lifecycle is the major contributor of the impact for all the 3 technologies due to electricity consumption during the operation. Overall, the ion Exchange technology fares well in this study of removal of As (V) only.

Keywords: arsenic, nanofiltration, lifecycle assessment, membrane technology

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Authors: Erfan Memarian, Seyyed Fazayel Alizadeh

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This study aims to evaluate the impacts of the oil and financial markets of the United States on Iran stock exchange and to develop an ARDL model to predict the short and long-term relationship between these markets. In this regard, all 713 weekly data between 28 July 1999 and 20 March 2013 were analyzed by using Microfit4.0 and Eviews7 econometric softwares. The independent variable of the study is the “Price and Yield Index (TEDPIX)” of Tehran Stock Exchange and the independent variables include S & P 500 Index, the US three-month treasury bill rate and West Texas Intermediate oil spot price index. The results show that the West Texas Intermediate oil spot price and the S&P 500 indices have significant positive relationships with Iran's TEDPIX. Also, there exists a significant negative relationship between Iran's TEDPIX and the US three-month Treasury bill rate.

Keywords: TEDPIX; Tehran Stock Exchange; S&P 500 index; USA three-month Treasury bill rate; West Texas Intermediate oil

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Authors: N. Amraoui, D. Hammoutene

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We have performed a theoretical study using dispersion-corrected Density Functional Methods to evaluate a variety of artificial nucleobases as candidates for metal-mediated Hoogsteen-type base pairs. We focus on A-M-T Hoogsteen-type base pair with M=Co(II), Ru(I), Ni(I). All calculations are performed using (ADF 09) program. Metal-mediated Hoogsteen-type base pairs are studied as drug candidates, their geometry optimizations are performed at ZORA/TZ2P/BLYP-D level. The molecular geometries and different energies as total energies, coordination energies, Pauli interactions, orbital interactions and electrostatic energies are determined.

Keywords: chemistry, biology, density functional method, orbital interactions

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Authors: Mohammad Abu Nassar, Mahmoud Al Khalilah, Hussein Abu Nassar

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The purpose of this study is to examine whether corporate tax avoidance practices can impact firm value in the Jordanian context. The study employs a quantitative approach using s sample of (124) industrial and services companies listed on the Amman Stock Exchange for the period from 2010 to 2019. Multiple linear regression analysis has been applied to test the study's hypothesis. The study employs effective tax rate and book-tax difference to measure tax avoidance and Tobin's Q factor to measure firm value. The results of the study revealed that tax avoidance practices, when measured using effective tax rates, do not significantly impact firm value. When the book-tax difference is used to measure tax avoidance, the study results showed a negative impact on firm value. The result of the study has not supported the traditional view of tax avoidance as a transfer of wealth from the government to shareholders for industrial and services companies listed on the Amman Stock Exchange, indicating that Jordanian firms should not use tax avoidance strategies to enhance their value.

Keywords: tax avoidance, effective tax rate, book-tax difference, firm value, Amman stock exchange

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Authors: G. S. Sudha, Smita Mohanty, S. K. Nayak

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Epoxidized oils can replace petroleum derived materials in numerous industrial applications, because of their respectable oxirane oxygen content and high reactivity of oxirane ring. Epoxidized castor oil (ECO) has synthesized in the presence of a sulphonated polystyrene type cation exchange resin. The formation of the oxirane ring was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) analysis. The epoxidation reaction was evaluated by Nuclear Magnetic Resonance (NMR) studies. ECO is used as a toughening phase to increase the toughness of petroleum-based epoxy resin.

Keywords: epoxy resin, epoxidized castor oil, sulphonated polystyrene type cation exchange resin, petroleum derived materials

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Authors: Brian Basvi

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A technique for analyzing a security's intrinsic value is called fundamental analysis. It involves looking at relevant financial, economic, and other qualitative and quantitative aspects. Earnings Per Share (EPS), a crucial metric in fundamental analysis, is calculated by dividing a company's net income by the total number of outstanding shares. With more than 70 listed businesses, the Zimbabwe Stock Exchange (ZSE) is the primary stock exchange in Zimbabwe. This study applies the EPS financial ratio and stock valuation techniques to historical stock data from 68 companies listed on the Zimbabwe Stock Exchange. According to a ZSE study, EPS significantly affects share prices that are listed on the market. The study's objective was to assess how fundamental analysis affected the idea of EPS in ZSE stock valuation. It concluded that EPS is an important consideration for investors when they make judgments about their investments. According to the study's findings, fundamental analysis is a useful tool for ZSE investors since it offers insightful information about a company's financial performance and aids in decision-making. Investors can have a better understanding of a company's underlying worth and prospects for future growth by looking into EPS and other basic aspects.

Keywords: fundamental analysis, stock valuation, EPS, share pricing

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Authors: T. Ul Rehman, S. Agnello, F. M. Gelardi, M. M. Calvino, G. Lazzara, G. Buscarino, M. Cannas

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Metal-Organic Frameworks (MOFs) have emerged as promising candidates for detecting metal ions owing to their large surface area, customizable porosity, and diverse functionalities. In recent years, there has been a surge in research focused on MOFs with luminescent properties. These frameworks are constructed through coordinated bonding between metal ions and multi-dentate ligands, resulting in inherent fluorescent structures. Their luminescent behavior is influenced by factors like structural composition, surface morphology, pore volume, and interactions with target analytes, particularly metal ions. MOFs exhibit various sensing mechanisms, including photo-induced electron transfer (PET) and charge transfer processes such as ligand-to-metal (LMCT) and metal-to-ligand (MLCT) transitions. Among these, MIL-53(Al) stands out due to its flexibility, stability, and specific affinity towards certain metal ions, making it a promising platform for selective metal ion sensing. This study investigates the structural, thermal, and luminescent properties of MIL-53(Al) metal-organic framework (MOF) upon Fe3+ cation exchange. Two separate sets of samples were prepared to activate the MOF powder at different temperatures. The first set of samples, referred to as MIL-53(Al), activated (120°C), was prepared by activating the raw powder in a glass tube at 120°C for 12 hours and then sealing it. The second set of samples, referred to as MIL-53(Al), activated (300°C), was prepared by activating the MIL-53(Al) powder in a glass tube at 300°C for 70 hours. Additionally, 25 mg of MIL-53(Al) powder was dispersed in 5 mL of Fe3+ solution at various concentrations (0.1-100 mM) for the cation exchange experiment. The suspension was centrifuged for five minutes at 10,000 rpm to extract MIL-53(Al) powder. After three rounds of washing with ultrapure water, MIL-53(Al) powder was heated at 120°C for 12 hours. For PXRD and TGA analyses, a sample of the obtained MIL-53(Al) was used. We also activated the cation-exchanged samples for time-resolved photoluminescence (TRPL) measurements at two distinct temperatures (120 and 300°C) for comparative analysis. Powder X-ray diffraction patterns reveal amorphization in samples with higher Fe3+ concentrations, attributed to alterations in coordination environments and ion exchange dynamics. Thermal decomposition analysis shows reduced weight loss in Fe3+-exchanged MOFs, indicating enhanced stability due to stronger metal-ligand bonds and altered decomposition pathways. Raman spectroscopy demonstrates intensity decrease, shape disruption, and frequency shifts, indicative of structural perturbations induced by cation exchange. Photoluminescence spectra exhibit ligand-based emission (π-π* or n-π*) and ligand-to-metal charge transfer (LMCT), influenced by activation temperature and Fe3+ incorporation. Quenching of luminescence intensity and shorter lifetimes upon Fe3+ exchange result from structural distortions and Fe3+ binding to organic linkers. In a nutshell, this research underscores the complex interplay between composition, structure, and properties in MOFs, offering insights into their potential for diverse applications in catalysis, gas storage, and luminescent devices.

Keywords: Fe³⁺ cation exchange, luminescent metal-organic frameworks (LMOFs), MIL-53(Al), solid-state analysis

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Authors: Noureddine Benharkat, Abdelkader Chouaih, Nourdine Boukabcha

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A thiourea derivative compound was synthesized and subjected to structural analysis using single-crystal X-ray diffraction (XRD). The crystallographic data unveiled its crystallization in the P21/c space group within the monoclinic system. Examination of the dihedral angles indicated a notable non-planar structure. To support and interpret these resulats, density functional theory (DFT) calculations were conducted utilizing the B3LYP functional along with a 6–311 G (d, p) basis set. Additionally, to assess the contribution of intermolecular interactions, Hirshfeld surface analysis and 2D fingerprint plots were employed. Various types of interactions, whether weak intramolecular or intermolecular, within a molecule can significantly impact its stability. The distinctive signature of non-covalent interactions can be detected solely through electron density analysis. The NCI-RDG analysis was employed to investigate both repulsive and attractive van der Waals interactions while also calculating the energies associated with intermolecular interactions and their characteristics. Additionally, a molecular docking study was studied to explain the structure-activity relationship, revealing that the title compound exhibited an affinity energy of -6.8 kcal/mol when docked with B-DNA (1BNA).

Keywords: computational chemistry, density functional theory, crystallography, molecular docking, molecular structure, powder x-ray diffraction, single crystal x-ray diffraction

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Authors: Delphine Duval, Morgan Mangeas, Charlie Huveneers, Adam Barnett, Laurent Vigliola

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The global number of shark bites has increased over the past four decades with, however, high regional variability both in space and time. A systematic review, aligned with the 2020 PRISMA guidelines, explored the peer-reviewed literature published between 1960 and 2023 to identify factors potentially explaining trends in human-shark interactions. Results revealed that variations in the frequency of human-shark interactions could be explained by a plethora of factors, including changes in prey availability, environmental conditions, human and shark population density and behavior, as well as habitat destruction. However, to our best knowledge, only five studies have conducted statistical assessments of the relative contribution of these factors. The increased number in human-shark interactions and the frequent clusters of shark bites within short timeframes offer opportunities to test the causative factors that may explain trends in unprovoked shark bites. it study aims to evaluate the impact of marine protected areas (MPAs) on the number of human-shark interactions, using data from the Global Shark Attack File and the World Database on Protected Areas. Results indicate contrasting effects of MPAs at different spatial scales. Enhancing our understanding of the factors contributing to shark bites is essential for improving risk reduction policies for humans and conservation plans for shark populations.

Keywords: unprovoked shark interactions, marine protected areas, attack risk, human-wildlife interaction

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Authors: Nomakhosi Tshuma, Carley Chetty

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This study employed panel regression analysis to investigate the financial performance determinants of MTN and Vodacom’s rest of Africa businesses between 2012 to 2020. It used net profit margin, return on assets (ROA), and return on equity (ROE) as financial performance proxies. Financial performance determinants investigated were asset size, debt ratio, liquidity, number of subscribers, and exchange rate. Data relating to exchange rates were obtained from the World Bank website, while financial data and subscriber information were obtained from the companies’ audited financial statements. The study found statistically significant negative relationships between debt and both ROA and net profit, exchange rate and both ROA and net profit, and subscribers and ROE. It also found significant positive relationships between ROE and both asset size and exchange rate. The study recommends strategic options that optimise on the above findings, and these include infrastructure sharing to reduce infrastructure costs and the minimisation of foreign-denominated debt.

Keywords: financial performance, determinants of financial performance, business in Africa, telecommunications industry

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Authors: H. Hajmohammadi , A. H. Jafari, M. Eskandari Nasab

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The ion exchange method was used to assess the absorption of sulfate media from laboratory-grade materials. The Taguchi method was employed for determining the optimum conditions for scandium adsorption. Results show that optimum conditions for scandium adsorption from sulfate were obtained by Purolite C100 cationic resin in 0.1 g/l sulfuric acid and scandium concentration of 2 g/l at 25 °C. Studies also showed that lowering H₂SO₄ concentration and aqueous phase temperature leads to an increase in Sc adsorption. Visual Minteq software was used to ascertain the various possible cation types and the effect of concentration of scandium ion species on scandium adsorption by cationic resins. The simulation results of the above software show that scandium ion species are often cationic species that are consistent with experimental data.

Keywords: scandium, ion exchange resin, simulation, leach copper

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Authors: Angélique Laurent, Marie-Josée Letarte, Jean-Pascal Lemelin, Marie-France Morin

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This study aims at exploring teacher-child interactions within learning contexts in public prekindergartens of the province of Québec (Canada). It is based on previous research showing that teacher-child interactions in preschools have direct and determining effects on the quality of early childhood education and could directly or indirectly influence child development. However, throughout a typical preschool day, children experience different learning contexts to promote their learning opportunities. Depending on these specific contexts, teacher-child interactions could vary, for example, between free play and shared book reading. Indeed, some studies have found that teacher-directed or child-directed contexts might lead to significant variations in teacher-child interactions. This study drew upon both the bioecological and the Teaching Through Interactions frameworks. It was conducted through a descriptive and correlational design. Fifteen teachers were recruited to participate in the study. At Time 1 in October, they completed a diary to report the learning contexts they proposed in their classroom during a typical week. At Time 2, seven months later (May), they were videotaped three times in the morning (two weeks’ time between each recording) during a typical morning class. The quality of teacher-child interactions was then coded with the Classroom Assessment Scoring System (CLASS) through the contexts identified. This tool measures three main domains of interactions: emotional support, classroom organization, and instruction support, and10 dimensions scored on a scale from 1 (low quality) to 7 (high quality). Based on the teachers’ reports, five learning contexts were identified: 1) shared book reading, 2) free play, 3) morning meeting, 4) teacher-directed activity (such as craft), and 5) snack. Based on preliminary statistical analyses, little variation was observed within the learning contexts for each domain of the CLASS. However, the instructional support domain showed lower scores during specific learning contexts, specifically free play and teacher-directed activity. Practical implications for how preschool teachers could foster specific domains of interactions depending on learning contexts to enhance children’s social and academic development will be discussed.

Keywords: teacher practices, teacher-child interactions, preschool education, learning contexts, child development

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Authors: Hebe Wong, Luz Fernandez Calventos

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Tandem language learning, a language exchange process based on the principles of autonomy and reciprocity, provides opportunities for interlocutors to learn each other’s language by communicating online or face-to-face. While much attention has been paid to the process and outcomes of tandem learning via email, little has been discussed about the effectiveness of face-to-face tandem learning on language and culture exchange for university students. The LACTS (Language and Culture Tandem Scheme), an 8-week project, was set up to study students’ perceptions of conducting tandem learning to assist their language and culture exchange. Students of both post-graduate and undergraduate programmes (N=103) from a Hong Kong SAR university were put in groups of 4 to 6 according to their availability and language preferences and met for an hour a week. While sample task sheets on a range of topics were provided to assist the language exchange, all groups were encouraged to take charge of their meeting format and choose their own topics. At the end of the project, a 19-item questionnaire, which included both open-and closed-ended questions investigating students’ perceptions of reciprocal teaching and cultural exchange, was administered. Thirty-minute individual interviews were conducted to elicit students’ views and experiences in the LACTS activities. Quantitative and qualitative data analysis showed that most students agreed that the project had enhanced their cultural awareness and helped create an inclusive and participatory learning environment. Significant differences were found in students’ confidence in speaking their targeted language after joining the scheme. The interviews also provided rich data on the variety of formats and leadership patterns in student-led meetings, which could shed light on student autonomy and future tandem language learning projects.

Keywords: autonomy, reciprocity, tandem language learning, university students

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Authors: E. K. Hardwick, L. B. Siwela, J. G. Falconer, M. E. Mathibela, W. Rolfe

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Lithium-ion battery (LiB) demand has increased with the advancement in technologies. The applications include electric vehicles, cell phones, laptops, and many more devices. Typical components of the cathodes include lithium, cobalt, nickel, and manganese. Recycling the spent LiBs is necessary to reduce the ecological footprint of their production and use and to have a secondary source of valuable metals. A hydrometallurgical method was investigated for the recovery of cobalt and nickel from LiB cathodes. The cathodes were leached using a chloride solution. Ion exchange was then used to recover the chloro-complexes of the metals. The aim of the research was to determine the efficiency of a chloride leach, as well as ion exchange operating capacities that can be achieved for LiB recycling, and to establish the optimal operating conditions (ideal pH, temperature, leachate and eluant, flowrate, and reagent concentrations) for the recovery of the cathode metals. It was found that the leaching of the cathodes could be hindered by the formation of refractory metal oxides of cathode components. A reducing agent was necessary to improve the leaching rate and efficiency. Leaching was achieved using various chloride-containing solutions. The chloro-complexes were absorbed by the ion exchange resin and eluted to produce concentrated cobalt, nickel, lithium, and manganese streams. Chromatographic separation of these elements was achieved. Further work is currently underway to determine the optimal operating conditions for the recovery by ion exchange.

Keywords: cobalt, ion exchange, leachate formation, lithium-ion batteries, manganese, nickel

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Authors: P. F. Msomi, P. T. Nonjola, P. G. Ndungu, J. Ramontja

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In view of the projected global energy demand and increasing levels of greenhouse gases and pollutants issues have inspired an intense search for alternative new energy technologies, which will provide clean, low cost and environmentally friendly solutions to meet the end user requirements. Alkaline anion exchange membrane fuel cells (AAEMFC) have been recognized as ideal candidates for the generation of such clean energy for future stationary and mobile applications due to their many advantages. The key component of the AAEMFC is the anion exchange membrane (AEM). In this report, a series of quaternized poly (2.6 dimethyl – 1.4 phenylene oxide)/ polysulfone (QPPO/PSF) blend anionic exchange membranes (AEM) were successfully fabricated and characterized for alkaline fuel cell application. Zinc Oxide (ZnO) nanoparticles were introduced in the polymer matrix to enhance the intrinsic properties of the AEM. The characteristic properties of the QPPO/PSF and QPPO/PSF-ZnO blend membrane were investigated with X-ray diffraction (XRD), thermogravimetric analysis (TGA) scanning electron microscope (SEM) and contact angle (CA). To confirm successful quaternisation, FT-IR spectroscopy and proton nuclear magnetic resonance (1H NMR) were used. Other properties such as ion exchange capacity (IEC), water uptake, contact angle and ion conductivity (IC) were also undertaken to check if the prepared nanocomposite materials are suitable for fuel cell application. The membrane intrinsic properties were found to be enhanced by the addition of ZnO nanoparticles. The addition of ZnO nanoparticles resulted to a highest IEC of 3.72 mmol/g and a 30-fold IC increase of the nanocomposite due to its lower methanol permeability. The above results indicate that QPPO/PSF-ZnO is a good candidate for AAEMFC application.

Keywords: anion exchange membrane, fuel cell, zinc oxide nanoparticle, nanocomposite

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Authors: Ernest Nweke, Enkhtuya Bavuudorj

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The Mongolia Stock Exchange (MSE) serves as a vehicle for executing the privatization policy of Mongolian Government as it transitioned from socialist to free market economy. It was also the intention of the Government to develop the investment and securities market through its establishment and to further boost the ailing Mongolian economy. This paper focuses on the contributions of the Mongolian Stock Exchange (MSE) to the industrial and economic development of Mongolia via Corporate fund mobilization for listed companies in Mongolia. A study of this nature is imperative as economic development in Mongolia has been accelerated by corporate investments. The key purpose of the research was to critically analyze the operations of the MSE to ascertain the extent to which the objectives for which it was established have been accomplished and to assess its contributions to industrial and economic development of Mongolia. In achieving this, secondary data on the activities of the MSE; its market capitalization over the years were collected and analyzed vis-à-vis the figures for Mongolia’s macro-economic data for the same time period to determine whether the progressive increase in market capitalization of the MSE has positively impacted on Mongolia’s economic growth. Regression analysis package was utilized in dissecting the data. It was proven that the Mongolian Stock Exchange has contributed positively and significantly to Mongolia’s economic development though not yet to the desired level. Against the findings of this research, recommendations were made to address, the problems facing the MSE and to enhance its performance and ultimately its contributions to industrial and economic development of the Mongolian nation.

Keywords: Corporate Fund Mobilization, Gross Domestic Product (GDP), market capitalization, purchasing power, stock exchange

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Authors: Mohammad Q. M. Momani

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The objective of this study is to examine whether the value relevance of ownership structure changed as the Amman Stock Exchange market conditions changed. Using data from 2005 to 2014, the study finds that the performance of portfolios that contain firms with concentrated ownership structure declines significantly during the post-crisis period. These portfolios exhibit poor performance relative to portfolios that contain firms with dispersed ownership structure during the post-crisis period. The results argue that uninspired performance of the Amman Stock Exchange during the post-crisis period, increased the incentives for controlling shareholders to expropriate. Investors recognized these incentives and discounted firms that were more likely to expropriate.

Keywords: value relevance, ownership structure, portfolio performance, Jordan, ASE

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Authors: Ishan Arora, Anurag Rathore

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The primary objective of this work was to study the effect of resin chemistry, pH and molarity of binding and elution buffer on aggregate removal using Cation Exchange Chromatography and find the optimum conditions which can give efficient aggregate removal with minimum loss of yield. Four different resins were used for carrying out the experiments: Fractogel EMD SO3-(S), Fractogel EMD COO-(M), Capto SP ImpRes and S Ceramic HyperD. Runs were carried out on the AKTA Avant system. Design of Experiments (DOE) was used for analysis using the JMP software. The dependence of the yield obtained using different resins on the operating conditions was studied. Success has been achieved in obtaining yield greater than 90% using Capto SP ImpRes and Fractogel EMD COO-(M) resins. It has also been found that a change in the operating conditions generally has different effects on the yields obtained using different resins.

Keywords: aggregates, cation exchange chromatography, design of experiments, monoclonal antibodies

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Authors: Ishan Arora, Anurag Rathore

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The primary objective of this work was to study the effect of resin chemistry, pH and molarity of binding and elution buffer on aggregate removal using Cation Exchange Chromatography and find the optimum conditions which can give efficient aggregate removal with minimum loss of yield. Four different resins were used for carrying out the experiments: Fractogel EMD SO3-(S), Fractogel EMD COO-(M), Capto SP ImpRes and S Ceramic HyperD. Runs were carried out on the AKTA Avant system. Design of Experiments (DOE) was used for analysis using the JMP software. The dependence of the yield obtained using different resins on the operating conditions was studied. Success has been achieved by obtaining yield greater than 90% using Capto SP ImpRes and Fractogel EMD COO-(M) resins. It has also been found that a change in the operating conditions generally has different effects on the yields obtained using different resins.

Keywords: aggregates, cation exchange chromatography, design of experiments, monoclonal antibodies

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Authors: Gultekin Gurcay

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The objective of this study was to examine the relationship between transformational leadership and innovative work behavior and to evaluate the mediating role of leader-member exchange relationships (LMX) on the assumed relationship. This study has focused on the suggestion that LMX might emerge through transformational leadership behaviors and thus could mediate the relationship between transformational leadership and innovative behavior. A cross-sectional survey research has been conducted on the relationship these leadership approaches and their impact on organizational HRM-outcomes has been conducted on two organizations operating in the technical sector in Istanbul-Turkey. The results of the research have supported the hypotheses. Transformational leadership was positively related to the innovative behaviors and LMX emerged to mediate that relationship.

Keywords: innovative leadership, leader-member exchange, transformational leadership, Turkey

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Authors: Fatma Ismailia, Malek Saihi

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This research provides an explanation of exchange incentives on the Tunis stock market from a behavioural point of view. The elucidation of the anomalies of excessive volume of transactions and that of excessive volatility cannot be done without the recourse to the psychological aspects of investors. The excessive confidence has been given the predominant role for the explanation of these phenomena. Indeed, when investors store increments, they become more confident about the precision of their private information and their exchange activities then become more aggressive on the subsequent periods. These overconfident investors carry out the intensive exchanges leading to an increase of securities volatility. The objective of this research is to identify whether the trading volume and the excessive volatility of securities observed on the Tunisian stock market come from the excessive exchange of overconfident investors. We use a sample of daily observations over the period January 1999 - October 2007 and we relied on various econometric tests including the VAR model. Our results provide evidence on the importance to consider the bias of overconfidence in the analysis of Tunis stock exchange specificities. The results reveal that the excess of confidence has a major impact on the trading volume while using daily temporal intervals.

Keywords: overconfidence, trading volume, efficiency, rationality, anomalies, behavioural finance, cognitive biases

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Authors: Rancy Chepchirchir Kosgey, John Olukuru

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This study examines the impact of introduction of futures trading on the spot price volatility in the commodity market. The paper considers the United States of America, South Africa and Ethiopian economies. Three commodities i.e. coffee, maize and wheat from New York Merchantile Exchange, South African Futures Exchange and Ethiopian Commodity Exchange are analyzed. ARCH LM test is used to check for heteroskedasticity and GARCH and EGARCH are used to check for the behavior of volatility between the pre- and post-futures periods. For all the three economies, the results indicate presence of the ARCH effect in the log returns. For conditional and unconditional variances; spot price volatility for coffee has decreased after futures trading in all the economies and the EGARCH has also shown reduction in persistence of volatility in the post-futures period in the three economies; while that of maize has reduced for the Ethiopian economy while there has been an increase in both the US and South African economies. For wheat, the conditional variance has been found to rise in the post-futures period in all the three economies.

Keywords: derivatives, futures exchange, agricultural commodities, spot price volatility

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Authors: Daseul Lee, Jeong Jun Lee, Ok-Sang Jung

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Self-assembly of a series of ZnX2 (X- = Cl-, Br-, and I-) with 2,3-bis(4’-nicotinamidephenoxy)naphthalene (L) as a new bidentate pyridyl-donor ligand yields systematic metallacyclodimeric unit, [ZnX2L]2. The supramolecule constitutes a characteristically stacked forming both 1D suprachannels and cages. Weak C-H⋯π and inter-digitated π⋯π interactions are main driving forces in the formation of both suprachannels and cages. The slightly different features between the suprachannel and cage have been investigated by 1H NMR and TG analysis, which solvent quantitatively exchange within only suprachannels. Photo-unstable CH2I2 molecules are stabilized via capturing within suprachannels, which is monitored by UV-Vis spectroscopy. Furthermore, the photoluminescence intensity, from the chromophore naphthyl moiety of [ZnCl2L]2, gradually decreases with the addition of CH2I2. And washing off the CH2I2 by dichloromethane returned the PL intensity back to its approximately original signal.

Keywords: metallacyclodimer, suprachannel, π⋯π interaction, molecular recognition

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Authors: Mohamad H. Atyeh, Wael Alrashed, Steven Telford

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The main objective of this research is to measure if there have been any notable changes in the trading actives of the Kuwait stock Exchange (KSE) after the privatization process that took place on the 25th of April 2016. The data that are used to test if there is any change in the KSE market performance are the daily indices for the period from the 25th of April 2016 till the 24th of October 2016 (after privatization) and a similar six months period before the date of the privatization from the 24th of October 2015 till the 24th of April 2016. In addition, as a control, the study included a period that is a period parallel to the six months period after the privatization. The results indicate that privatization is associated with lower variability for the majority of variables, but that the observed switch in slope direction is not actually a product of privatization, but rather one of serial correlation.

Keywords: privatization, Kuwait stock exchange (KSE), market capitalization (MCAP), capital markets authority (CMA), Boursa Kuwait securities company (BKSC)

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Authors: Mahani Razali, Abd Halim Masnan, Nordin Mamat, Seah Siok Peh

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This research is based on three main objectives which are to identify children`s social interaction behaviour during computer play activities, teacher’s role and to explore teacher’s beliefs, views and knowledge about computers use in four Malaysian pre-schools.This qualitative study was carried out among 25 pre-school children and three teachers as the research sample. The data collection procedures involved structured observation which was to identify social interaction behavior among pre-school children through computer play activities; as for semi-structured interviews, it was done to study the perception of the teachers on the acquired of social interaction behavior development among the children. A variety of patterns can be seen within the peer interactions indicating that children exhibit a vast range of social interactions at the computer, and they varied each day. The findings of this study guide us to certain conclusions, which have implications in understanding the phenomena of how computers were used and how its relationship to the children’s social interactions emerge in the four Malaysian preschools. This study provides evidence that the children’s social interactions with peers and adults were mediated by the engagement of the children in the computer environments.

Keywords: computer, play, preschool, social interaction

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Authors: Kritsada Pipitthapan

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WO3/SiO2 catalysts were modified by an ion exchange method with sodium hydroxide or potassium hydroxide solution. The performance of the modified catalysts was tested in the metathesis of ethylene and trans-2-butene to propylene. During ion exchange, sodium and potassium ions played different roles. Sodium modified catalysts revealed constant trans-2-butene conversion and propylene selectivity when the concentrations of sodium in the solution were varied. In contrast, potassium modified catalysts showed reduction of the conversion and increase of the selectivity. From these results, potassium hydroxide may affect the transformation of tungsten oxide active species, resulting in the decrease in conversion whereas sodium hydroxide did not. Moreover, the modification of catalysts by this method improved the catalyst stability by lowering the amount of coke deposited on the catalyst surface.

Keywords: acid sites, alkali metal, isomerization, metathesis

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Authors: Natalia M. Acevedo, Luis M. Jimenez, Erick Lambis

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Imperfections in the capital market are used to argue the relevance of the corporate risk management function. With corporate hedge, the value of the company is increased by reducing the volatility of the expected cash flow and making it possible to face a lower bankruptcy costs and financial difficulties, without sacrificing tax advantages for debt financing. With the propose to avoid exchange rate troubles over cash flows of Colombian exporting firms, this dissertation uses financial options, over exchange rate between Peso and Dollar, for realizing a financial hedge. In this study, a strategy of hedge is designed for an exporting company in Colombia with the objective of preventing fluctuations because, if the exchange rate down, the number of Colombian pesos that obtains the company by exports, is less than agreed. The exchange rate of Colombia is measured by the TRM (Representative Market Rate), representing the number of Colombian pesos for an American dollar. First, the TMR is modelled through the Geometric Brownian Motion, with this, the project price is simulated using Montecarlo simulations and finding the mean of TRM for three, six and twelve months. For financial hedging, currency options were used. The 6-month projection was covered with financial options on European-type currency with a strike price of $ 2,780.47 for each month; this value corresponds to the last value of the historical TRM. In the compensation of the options in each month, the price paid for the premium, calculated with the Black-Scholes method for currency options, was considered. Finally, with the modeling of prices and the Monte Carlo simulation, the effect of the exchange hedging with options on the exporting company was determined, this by means of the unit price estimate to which the dollars in the scenario without coverage were changed and scenario with coverage. After using the scenarios: is determinate that the TRM will have a bull trend and the exporting firm will be affected positively because they will get more pesos for each dollar. The results show that the financial options manage to reduce the exchange risk. The expected value with coverage is approximate to the expected value without coverage, but the 5% percentile with coverage is greater than without coverage. The foregoing indicates that in the worst scenarios the exporting companies will obtain better prices for the sale of the currencies if they cover.

Keywords: currency hedging, futures, geometric Brownian motion, options

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Authors: Zhiwei Zhong, Xiaofei Li, Deli Wang

Abstract:

Ecosystem engineering is a powerful force shaping community structure and ecosystem function. Yet, very little is known about the mechanisms by which engineers affect vital ecosystem processes like trophic interactions. Here, we examine the potential for a herbivore ecosystem engineer, domestic sheep, to affect trophic interactions between the web-building spider Argiope bruennichi, its grasshopper prey Euchorthippus spp., and the grasshoppers’ host plant Leymus chinensis. By integrating small- and large-scale field experiments, we demonstrate that: 1) moderate sheep grazing changed the structure of plant communities by suppressing strongly interacting forbs within a grassland matrix; 2) this change in plant community structure drove interaction modifications between the grasshoppers and their grass host plants and between grasshoppers and their spider predators, and 3) these interaction modifications were entirely mediated by plasticity in grasshopper behavior. Overall, ecosystem engineering by sheep grazing strengthened bottom-up effects and weakened top-down effects via trait-mediated interactions, resulting in a nearly two-fold increase in grasshopper densities. Interestingly, the grasshopper behavioral shifts which reduced spider per capita predation rates in the microcosms did not translate to reduced spider predation rates at the larger system scale because increased grasshopper densities offset behavioral effects at larger scales. Our findings demonstrate that 1) ecosystem engineering can strongly alter trophic interactions, 2) such effects can be driven by cryptic trait-mediated interactions, and 3) the relative importance of trait- versus density effects as measured by microcosm experiments may not reflect the importance of these processes at realistic ecological scales due to scale-dependent interactions.

Keywords: bottom-up effects, ecosystem engineering, trait-mediated indirect effects, top-down effects

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Authors: Andrey A. Lipovskii, Alexey V. Redkov, Vyacheslav V. Rusan, Dmitry K. Tagantsev, Valentina V. Zhurikhina

Abstract:

The presented research is related to the development of recently proposed technique of the formation of composite materials, like optical glass-ceramics, with predetermined structure and properties of the crystalline component. The technique is based on the control of the size and concentration of the crystalline grains using the phenomenon of glass-ceramics decrystallization (vitrification) induced by ion-exchange. This phenomenon was discovered and explained in the beginning of the 2000s, while related theoretical description was given in 2016 only. In general, the developed theory enables one to model the process and optimize the conditions of ion-exchange processing of glass-ceramics, which provide given properties of crystalline component, in particular, profile of the average size of the crystalline grains. The optimization is possible if one knows two dimensionless parameters of the theoretical model. One of them (β) is the value which is directly related to the solubility of crystalline component of the glass-ceramics in the glass matrix, and another (γ) is equal to the ratio of characteristic times of ion-exchange diffusion and crystalline grain dissolution. The presented study is dedicated to the development of experimental technique and simulation which allow determining these parameters. It is shown that these parameters can be deduced from the data on the space distributions of diffusant concentrations and average size of crystalline grains in the glass-ceramics samples subjected to ion-exchange treatment. Measurements at least at two temperatures and two processing times at each temperature are necessary. The composite material used was a silica-based glass-ceramics with crystalline grains of Li2OSiO2. Cubical samples of the glass-ceramics (6x6x6 mm3) underwent the ion exchange process in NaNO3 salt melt at 520 oC (for 16 and 48 h), 540 oC (for 8 and 24 h), 560 oC (for 4 and 12 h), and 580 oC (for 2 and 8 h). The ion exchange processing resulted in the glass-ceramics vitrification in the subsurface layers where ion-exchange diffusion took place. Slabs about 1 mm thick were cut from the central part of the samples and their big facets were polished. These slabs were used to find profiles of diffusant concentrations and average size of the crystalline grains. The concentration profiles were determined from refractive index profiles measured with Max-Zender interferometer, and profiles of the average size of the crystalline grains were determined with micro-Raman spectroscopy. Numerical simulation were based on the developed theoretical model of the glass-ceramics decrystallization induced by ion exchange. The simulation of the processes was carried out for different values of β and γ parameters under all above-mentioned ion exchange conditions. As a result, the temperature dependences of the parameters, which provided a reliable coincidence of the simulation and experimental data, were found. This ensured the adequate modeling of the process of the glass-ceramics decrystallization in 520-580 oC temperature interval. Developed approach provides a powerful tool for fine tuning of the glass-ceramics structure, namely, concentration and average size of crystalline grains.

Keywords: diffusion, glass-ceramics, ion exchange, vitrification

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Authors: Yingjeng James Li, Chiao-Chih Hu

Abstract:

Membrane electrode assemblies (MEAs) for proton exchange membrane fuel cell (PEMFC) applications were prepared by using 10 and 15 um PEMs. Except for different membrane thicknesses, these MEAs were prepared by the same conditions. They were prepared by using catalyst coated membrane (CCM) process. The catalyst employed is 40% Pt/C, and the Pt loading is 0.5mg/cm² for the sum of anode and cathode. Active area of the MEAs employed in this study is 5cm*5cm=25cm². In polarization measurements, the flow rates were always set at 1.2 stoic for anode and 3.0 stoic for cathode. The outlets were in open-end mode. The flow filed is tri-serpentine design. The cell temperatures and the humidification conditions were varied for the purpose of MEA performance observations. It was found that the performance of these two types of MEAs is about the same at fully or partially humidified operation conditions; however, 10um MEA exhibits higher current density in dry or low humidified conditions. For example, at 70C cell, 100% RH, and 0.6V condition, both MEAs have similar current density which is 1320 and 1342mA/cm² for 15um and 10um product, respectively. However, when in operation without external humidification, 10um MEA can produce 1085mA/cm²; whereas 15um MEA produces only 720mA/cm².

Keywords: fuel cell, membrane electrode assembly, PEFC, PEMFC, proton exchange membrane

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