Inhibitory effect of Acacia hamulosa methanolic extract on the corrosion of mild steel in 1 M hydrochloric acid

The flora of Saudi Arabia comprises about 18 species of Acacia species including Acacia hamulosa Benth. The methanolic extract of the flowering tops of A. hamulosa was tested for its radical scavenging activity toward 2,2-diphenyl-1-pricylhydrazyl (DPPH) radical and the activity was compared with L-ascorbic acid, quercetin and Trolox as standards. The total phenolic content was determined using Folin-Ciocalteu method. In addition the methanolic extract has been evaluated as a corrosion inhibitor for steel in 1 M HCl solution by means of weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS). Tafel polarization study revealed that extract of Acacia hamulosa acts as a cathodic type inhibitor. Inhibition was found to increase with increasing concentration of the extract of Acacia hamulosa. Values of inhibition efficiency calculated from weight loss, Tafel polarization curves, and EIS are in good agreement. The effect of temperature on the corrosion behaviour of mild steel in 1 M HCl with addition of extract was also studied and thermodynamic parameters were determined and discussed.               KEY WORDS: Acacia hamulosa, Extract, Polyphenols, Antioxidant corrosion, Electrochemical study Bull. Chem. Soc. Ethiop. 2018, 32(2), 323-335.DOI: https://dx.doi.org/10.4314/bcse.v32i2.1

Using Catalysis To Control The Morphology And Stiffness Of Shape Memory Poly(isocyanurate-urethane) (PIR-PUR) Aerogels

A large array of anhydrous metal ions were tested as catalysts in the preparation of shape memory poly(isocyanurate-urethane) (PIR-PUR) aerogels from the reaction of 1,3,5-tris(6-isocyanatohexyl)-1,3,5-triazinane-2,4,6-trione (Desmodur N3300A: a well-known isocyanurate-based aliphatic triisocyanate) and triethylene glycol (TEG) in anhydrous acetonitrile. The reaction yielded wet gels that were dried into aerogels in an autoclave with supercritical fluid CO2. The catalytic activity was mostly identified among CH3CN-soluble salts (mainly chlorides) of third-row d-block elements from iron to zinc, group 13 elements from aluminum to thallium, as well as cadmium, bismuth, and tin. Tin (119Sn) NMR indicated that the metal ion complexes with TEG, followed by reaction with the isocyanate. By using a fixed monomer concentration (20% w/w) and varying only the chemical identity and concentration of the catalysts, it was possible to demonstrate that the micromorphology of the resulting aerogels depended only on the gelation time. That is, for equal gelation times, the morphology was approximately the same, irrespective of the catalyst. For short gelation times (around 5 min or less), the aerogel frameworks were bicontinuous, changing to small spheroids at around 20 min and to large microspheres for gelation times around 75 min or more. Having obtained control over micromorphology, leaving other material properties such as density and porosity practically unaffected, it was possible to demonstrate that the bicontinuous structures of PIR-PUR aerogels can be up to 4 times stiffer and up to 2 times better thermal conductors than structures consisting of microspheres. This finding was attributed to the different widths of the neck zones between particles, noting that in bicontinuous morphologies, the neck diameters were almost equal to the particle diameters

Hydrogen effect modeling on Ziegler-Natta catalyst and final product properties in propylene polymerization

Hydrogen, as chain transfer agent, effects on kinetic of propylene polymerization; consequently variation of hydrogen concentration leads to change final product properties and also activates site of used catalyst. This phenomenon is one of the most important process variables is to adjust the final product properties and optimize the operating conditions. This work has attempted to present a mathematical model that cable to calculate the most important indices of end used product, such as melt flow index, number and weight average molecular weight and poly dispersity index. The model can predict profile polymerization rates determining important kinetic parameters such as the activation energy, lumped deactivation reaction initial reaction rate and deactivation constant. The mathematical model was implemented in Matlab/Simulink environment for slurry polymerization in laboratory scale. The modeling approach is based on polymer moment balance method in the slurry semi-batch reactor. In addition, in this work have provided a model that calculating fraction activated sites catalyst via hydrogen concentration. The model was validated by experimental data from lab scale, reactor. The experimental and model outputs were compared; consequently, the errors were within acceptable range.               KEY WORDS: Mathematical modeling, Propylene polymerization, Kinetics study, Hydrogen response, population balance Bull. Chem. Soc. Ethiop. 2018, 32(2), 371-386.DOI: https://dx.doi.org/10.4314/bcse.v32i2.1

Identification of determinants for rescheduling travel mode choice and transportation policies to reduce car use in urban areas

[EN] This paper presents a qualitative analysis about the determinants related to rescheduling travel mode decisions during the activity scheduling process. Notably, we were interested to study changes between intention and behavior. Data used came from an in-depth Computer Assisted Telephone Interview (CATI) follow up survey to habitual drivers carried out during the implementation of a panel survey. An interpretative qualitative method based on Analytic Induction was used to cope with the complex nature of rescheduling decisions and the characteristics of the data. The Theory of Planned Behavior has been used to gain a better understanding of the reasons associated with rescheduling travel mode decisions and to obtain a possible explanation of the phenomena studied. In our sample, 12 codes were identified as the main determinants of travel mode changing. Main reasons for rescheduling a travel mode are different considering gender, age, and the type of travel mode change. Main reasons for changing a nonprivate preplanned travel mode to a private travel mode are different considering the type of travel mode preplanned. New determinants of rescheduling decisions different from those associated with other activity scheduling decisions previously identified emerge when analyzing travel mode changes. A number of important sustainable transportation policies to reduce car use in urban areas are derived from the results of this study.This research is partially funded by MINERVA project founded by the ICDCi National Program of Society Challenges of the Spanish Ministerio de Econom ıa, Industria y Competitividad (TRA2015-71184-C2-1-R).Mars, L.; Ruiz Sánchez, T.; Arroyo-López, MR. (2018). Identification of determinants for rescheduling travel mode choice and transportation policies to reduce car use in urban areas. International Journal of Sustainable Transportation. 1-11. https://doi.org/10.1080/15568318.2017.1416432S11

Is Individualism Suicidogenic? Findings From a Multinational Study of Young Adults From 12 Countries

The associations of individualistic versus collectivistic value orientations with suicidal ideation and attempts, attitudes towards suicide and towards suicidal individuals, and psychological distress were investigated across 12 nations (N = 5572 university students). We expected differential associations of value orientations with suicidal behavior and moderating effects of the prevailing value orientations in the various countries. Findings showed that intermediate levels of individualism appeared protective against suicide attempts across all investigated nations, but that, otherwise, there seemingly are no universal associations of individualism and collectivism with suicidal behaviors. High collectivism was associated with less suicidal ideation only in individualistic countries. Low individualism appeared to be a risk factor for suicidal ideation specifically in Muslim collectivistic cultures, whereas high individualism in Asian collectivistic cultures. Collectivistic values are uniformly associated with less permissive attitudes to suicide, whereas individualistic values with a more stigmatized view of suicidal behavior. Both individualistic and collectivistic values were associated with socially accepting attitudes to a suicidal peer, helping a suicidal friend, and emotional involvement. The associations of individualistic and collectivistic values with disapproving attitudes to suicidal disclosure were complex. Beliefs in punishment after death for suicide, seeing suicide as mental illness, and emotional involvement with a suicidal friend were lower in high-suicide-rate countries. These evidence patterns are discussed in the light of related research evidence, along with directions for future research in this area

Carbon stable isotope analysis of cereal remains as a way to reconstruct water availability: preliminary results

Reconstructing past water availability, both as rainfall and irrigation, is important to answer questions about the way society reacts to climate and its changes and the role of irrigation in the development of social complexity. Carbon stable isotope analysis of archaeobotanical remains is a potentially valuable method for reconstructing water availability. To further define the relationship between water availability and plant carbon isotope composition and to set up baseline values for the Southern Levant, grains of experimentally grown barley and sorghum were studied. The cereal crops were grown at three stations under five different irrigation regimes in Jordan. Results indicate that a positive but weak relationship exists between irrigation regime and total water input of barley grains, but no relationship was found for sorghum. The relationship for barley is site-specific and inter-annual variation was present at Deir ‘Alla, but not at Ramtha and Khirbet as-Samra

Lung Development Genes and Adult Lung Function

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