Influence of Viscosity Modifying Admixture (VMA) on the Properties of SCC Produced Using Locally Supplied Materials in Bahrain

The reluctance in utilizing the advantages of Self Compacting Concrete (SCC) in Bahrain stems from two contributing factors: Lack of research or published data pertaining to locally produced SCC, and a feeling of doubt and uncertainty in the minds of practicing engineers about reliability and suitability of SCC in hardened stage. The primary aim of this study is to explore the influence of viscosity modifying admixtures available in Bahrain on the fresh and hardened properties of SCC. For this purpose, three self-compacting concrete mixes and one control mix were prepared with same water/powder ratio and other ingredients, but with different fluidity. Control mix is considered to compare the strength of SCC with that of the normal concrete. The fluidity was varied by altering the dosage of VMA in different SCC mixes. The filling ability, passing ability and resistance to segregation were evaluated to make sure that prepared mixes satisfy the SCC basic criteria. From each SCC mix and control mix, 9 cubes were cast to obtain compressive strength of SCC in hardened stage after 3, 7 and 28 days of curing. Also, for each SCC mix and control mix, three prisms were cast and their flexural strength was tested after 28 days of curing. The test results of the specimens were used to carry out a comparison of compressive and flexural strength of different mixes of SCC and the control mix. The study shows that SCC prepared using locally supplied materials is also equally reliable as conventional concrete, provided that it satisfies all the basic requirements of SCC in fresh stage and maintains a minimum slump flow of 600 mm

Evaluation of FRP concrete compression member under repeated load and harsh environment

Strengthening and rehabilitation have been increasingly applied in many structures to improve their capacity and serviceability. Fiber Reinforced Polymer (FRP) materials are universally known for their ability to improve the load capacity of damaged structural elements because of their high linear-elastic behavior. However, enhancing the capacity of structural elements that are exposed to repeated load coupled with harsh environment is an area that requires further investigation. This research focused on experimental analysis of the behavior and response of confined and unconfined concrete compression members (300mm x 150mm) under repeated load while exposed to 1440 cycles of seawater splash zone in United Arab Emirates (UAE). Confining concrete compression members with Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) sheets have increased the load capacity compared to the control sample at room temperature by 110% and 84%, respectively. Results showed that the average value of compressive strength for the confined concrete exposed to sea water splash zone conditions for CFRP and GFRP specimens has decreased by 33% and 23%, respectively, compared to the confined concrete in the room temperature. However, GFRP specimens showed higher performance in compressive strength under sea water splash zone than those of the CFRP specimens. Different mode of failures such as delamination, de-bonding and combination of such modes were observed and related to various exposure factors and mechanical properties

The Potential of Shading Devices for Temperature Reduction in High-Rise Residential Buildings in the Tropics

AbstractThe present study focuses on the effect of shading devices on the indoor temperature of high-rise residential buildings in the hot–humid climate of Malaysia. Several methods can be employed to improve indoor thermal environment, including using a reflective glazing system, using light colors for external surfaces, and using the appropriate thermal properties of external walls and roofs. However, before using any of these methods, it is important to have an optimum shading device to reduce the solar radiation absorption that leads to an overheated indoor environment and an increase in cooling energy loads. Therefore, the main objective of the current paper is to find the extent of a building's solar heat gain and, consequently, the indoor air temperature that is influenced by the external shading devices. A computerized simulation tool (IES<VE>) is used to carry out the investigation, taking Penang as the empirical background of the hot–humid climate. The results indicate that egg-crate shading has a significant impact on decreasing discomfort hours compared with other shading types

Synthesis of N-benzothiazole derivative imide on polymeric chain, have possible biological activity

In this reserch Some new substituted and unsubstituted poly imides compounds. were synthesized by reaction of acrylol chloride with different amides (aliphatic and aromatic) in a suitable solvent in the presence amount triethyl amine (Et3N) with heating. The Structure confirmation of all polymers were confirmed using FT-IR,1H-NMR,13C-NMR and UV spectroscopy. Thermal analysis (TG) for some polymers showed their thermal stabilities. Other physical properties including softening points, melting point and solubility of the polymers were also measure

Optimal Design of Failure-Censored Constant-Stress Life Test Plans for the Inverse Weibull Distribution

This paper presents the optimal design of constant-stress partially accelerated life tests (CSPALT) using type-II censored data from the inverse Weibull distribution. The maximum likelihood approach is applied to estimate the distribution parameters and the corresponding factor. In addition, the corresponding confidence interval estimates are obtained. Moreover, optimal CSPALT plans are developed using the D-optimality criterion. That is, the proportion of test units that should be allocated to run under accelerated condition is optimally determined. This proportion is obtained such that the generalized asymptotic variance of the maximum likelihood estimators of the model parameters is minimized. To illustrate the theoretical results presented in this paper, simulation studies are conducted.Предложена модель ускоренных ресурсных испытаний при постоянном напряжении с использованием данных, подвергнутых цензурированию типа II с обратным распределением Вейбулла. С помощью метода максимального правдоподобия определены параметры распределения и коэффициента ускорения. Выполнены оценка соответствующего доверительного интервала и оптимизация ускоренных ресурсных испытаний при постоянном напряжении по D-критерию оптимальности. При этом выборка части программы нагружения для ускоренных ресурсных испытаний оптимизируется таким образом, чтобы минимизировать обобщенную асимптотическую дисперсию показателей максимальной вероятности. Работоспособность предложенного подхода показана на тестовом примере.Запропоновано модель прискорених ресурсних випробувань при постійній напрузі з використанням даних, підданих цензурування типу II із зворотним розподілом Вейбулла. За допомогою методу максимальної правдоподібності визначені параметри разподілу і коефіцієнта прискорення. Виконано оцінка відповідного довірчого інтервалу і оптимізація прискорених ресурсних випробувань при постійній напрузі по D-критерієм оптимальності. При цьому вибірка частини програми навантаження для прискорених ресурсних випробувань оптимізується таким чином, щоб мінімізувати узагальнену асимптотичну дисперсію показників максимальної ймовірності. Працездатність запропонованого підходу показана на тестовому прикладі

Optimum Constant-Stress Partially Accelerated Life Test Plans Using Type-I Censored Data from the Inverse Weibull Distribution

In this paper, a constant stress partially accelerated life test (CSPALT) model is presented and analyzed using type-I censored data from the inverse Weibull distribution. The maximum likelihood estimates (point and interval) of the distribution parameters and the acceleration factor are obtained. CSPALT plans are developed. The proportion of test units that should be allocated to run under accelerated condition is optimally determined. To demonstrate the theoretical results, simulation studies are made.Предложенная модель частично ускоренных ресурсных испытаний применена к данным, цензурированным по типу I для обратного распределения Вейбулла. Оценка максимальной вероятности параметров распределения и коэффициента ускорения выполнена в точечном и интервальном видах. Осуществлено планирование ускоренных ресурсных испытаний с оптимизацией доли испытаний, которые необходимо проводить при нормальных эксплуатационных условиях. Численное моделирование тестовой задачи подтвердило точность аналитических расчетов.Запропоновану модель частково прискорених ресурсних випробувань застосовано до даних, цензурованих по типу I для зворотного розподілу Вейбулла. Оцінку максимально ї ймовірності параметрів розподілу і коефіцієнта прискорення виконано в точковому й інтервальному вигляді. Виконано планування прискорених ресурсних випробувань з оптимізацією частки випробувань, які необхідно проводити при нормальних експлуатаційних умовах. Чисельне моделювання тестової задачі підтвердило точність аналітичних розрахунків

Screening for Anti-Cancer Compounds in Marine Organisms in Oman

Objectives: Marine organisms are a rich source of bioactive molecules with potential applications in medicine, biotechnology and industry; however, few bioactive compounds have been isolated from organisms inhabiting the Arabian Gulf and the Gulf of Oman. This study aimed to isolate and screen the anti-cancer activity of compounds and extracts from 40 natural products of marine organisms collected from the Gulf of Oman. Methods: This study was carried out between January 2012 and December 2014 at the Sultan Qaboos University, Muscat, Oman. Fungi, bacteria, sponges, algae, soft corals, tunicates, bryozoans, mangrove tree samples and sea cucumbers were collected from seawater at Marina Bandar Al-Rowdha and Bandar Al-Khayran in Oman. Bacteria and fungi were isolated using a marine broth and organisms were extracted with methanol and ethyl acetate. Compounds were identified from spectroscopic data. The anti-cancer activity of the compounds and extracts was tested in a Michigan Cancer Foundation (MCF)-7 cell line breast adenocarcinoma model. Results: Eight pure compounds and 32 extracts were investigated. Of these, 22.5% showed strong or medium anti-cancer activity, with malformin A, kuanoniamine D, hymenialdisine and gallic acid showing the greatest activity, as well as the soft coralSarcophyton sp. extract. Treatment of MCF-7 cells at different concentrations of Sarcophyton sp. extracts indicated the induction of concentration-dependent cell death. Ultrastructural analysis highlighted the presence of nuclear fragmentation, membrane protrusion, blebbing and chromatic segregation at the nuclear membrane, which are typical characteristics of cell death by apoptosis induction. Conclusion: Some Omani marine organisms showed high anti-cancer potential. The efficacy, specificity and molecular mechanisms of anti-cancer compounds from Omani marine organisms on various cancer models should be investigated in future in vitro and in vivo studies

Knowledge Regarding Secondary Prevention Lifestyle Practices Among Patients with Ischaemic Heart Disease in Oman : Pilot study

Objectives: Secondary prevention of ischaemic heart disease (IHD) is very important. This study aimed to assess knowledge of necessary lifestyle changes among Omani patients diagnosed with IHD. Methods: This cross-sectional pilot study took place between October 2015 and February 2016 at the Sultan Qaboos University Hospital (SQUH), Muscat, Oman. A total of 30 random patients with IHD from the Cardiology Outpatient Clinic of SQUH were included. A 30-item survey was used to determine patients’ knowledge of necessary lifestyle practices following their IHD diagnosis, with scores of &lt;70% indicating poor knowledge. Results: Overall, 21 patients (70.0%) had low knowledge levels. Scores ranged from 38.9−94.4% (mean: 60.7% ± 14.1%). No demographic factors were found to predict low scores, although there were some differences in individual questions. Conclusion: Low knowledge levels regarding lifestyle changes were observed among IHD patients in Oman. More efforts should be made to educate these patients for the secondary prevention of IHD

Synthesis, Characterization and Antibacterial Activity of Cefalexin Dervatives

New series of Schiff bases 2(a-j) and corresponding beta-lactam derivatives 3(a-j) were synthesized from cefalexin (1) as starting material. The compound (1) was reacted with different aldehydes and ketones to give Schiff bases derivatives 2(a-j). The synthesized Schiff bases were cyclized by chloroacetyl chloride in the presence of triethylamine to form beta-lactam derivatives 3(a-j). The compounds were characterized by deremination melting point, FT-IR and 1H NMR. The beta-lactam derivatives were screened in vitro antibacterial against some bacterial specie