oalib

OALib Journal期刊

ISSN: 2333-9721

费用:99美元

投稿

匹配条件: “Essa Ebtessam” ,找到相关结果约91条。
列表显示的所有文章,均可免费获取
第1页/共91条
每页显示
Effect of formulation and processing variables on the particle size of sorbitan monopalmitate niosomes
Essa Ebtessam
Asian Journal of Pharmaceutics , 2010,
Abstract: In the last two decades, there was an extensive research focused on the study of synthetic amphiphilic vesicles, prepared by nonionic surfactants (niosomes). The particle size of these vesicles is critical for their intended therapeutic benefits. Formulation and processing factors affect greatly the physical characteristics of the resulted nanosystems. Therefore, the present work was adopted to investigate how proper manipulation of various formulations and processing factors on vesicular Z-average particle size. The selected variables were membrane additives, [including cholesterol (CHO), dicetylphosphate (DCP) and stearylamine (SA)], sonication time as well as drug loading factor (using mannitol and estradiol). Sorbitan monopalmitate (span 40) niosomes were prepared by the conventional thin film hydration method. Particle size, measured by Photon Correlation Spectroscopy, and polydispersity indices were measured and compared. The results indicated that CHO increased the vesicular size, with 2:1 and 1:1 (span 40:CHO) ratios showing the same size. Sonication reduced the vesicle size by 23, 35 and 42% after 10, 20 and 30 min, respectively. After 30 min, the effect of sonication was minor. The addition of charge inducing agents changed the zeta potential depending on the type of the additives. Surface charge increased the size by 24 and 11% when using DCP and SA, respectively. Drug incorporation increased the vesicle size to an extent based on its aqueous solubility. There were about 35 and 6.2% increase in vesicular size for estradiol and mannitol, respectively, supporting the partitioning of lipophilic drug within the fatty acyl side chains of the bilayer membrane.
Plasticization Effect on the Photodegradation of Poly (4-Chlorostyrene) and Poly (4-Bromostyrene) Films  [PDF]
Khalid E. Al Ani, Afrah Essa Ramadhan
Materials Sciences and Applications (MSA) , 2010, DOI: 10.4236/msa.2010.16052
Abstract: The photodegradation of thin films of poly (4-chlorostyrene) and poly (4-bromostyrene) with 265 nm radiation in the presence of oxygen and as a function of irradiation time has been studied mainly using fluorescence, FT-IR, and UV-VIS spectroscopic techniques. The influence of phthalate and terephthalate plasticizers on photo-oxidative degradation was also investigated. Phthalate and terephthalate-plasticizers were found to increase the photodegradation processes in polymeric chains. On the other hand, the intensity of absorption was also found to increase with irradiation time and in the intensity of a new absorption band at longer wavelength. The appearance of new fluorescence bands in the irradiated polymer films can well indicate a possibility of photodegradation of polymer films. In addition, the observed increase in the intensities of the carbonyl and hydroxyl regions of the FT-IR spectra, providing evidence for the photodegradation as well as the photo-oxidation of polymeric chains. The increase in the analyzed ranges was attributed to the formation of alcohols, aliphatic ketones and to the increase in the number of (C=C) that resulted from hydrogen abstraction during chains - scission.
Kinetic Study of the Effect of Plasticization on Photodegradation of Polystyrene Solid Films  [PDF]
Khalid E. Al Ani, Afrah Essa Ramadhan
Materials Sciences and Applications (MSA) , 2015, DOI: 10.4236/msa.2015.67064
Abstract: The effects of UV-irradiation on stability of pure and blended polystyrene films with phthalate and terephthalate plasticizers were studied in presence of air. UV-visible, fluorescence and FT-IR techniques were used to study the photodegradation of irradiated polystyrene films. Increase of irradiation times of polystyrene films caused an increase in the intensity of the main absorption band and the increase in the intensity of a new absorption band at longer wavelength, thus indicating a possibility of photo degradation of polystyrene chains. The influence of added plasticizers, dimethyl terephthalate, diethyl terephthalate, dioctyl terephthalate, dioctylphthalate, and dibutyl phthalate on photo-quenching of the polymer fluorescence band was also investigated, and found to increase the photodegradation processes in polymeric chains. On the other hand, the intensity of excimer and monomer fluorescence bands maxima was also found to decrease with a small red shift with the increase in irradiation times. These changes may be attributed to the formation of new photo-products resulted from the photodegradation of irradiated polymeric chains. The photo- quenching rate constant was found to increase with the increase of the molar mass and bulkiness of the used plasticizers and to increase with the increase in irradiation time. The rate constant of the photo quenching process was found to decrease with the increase in the percent of added plasticizers, indicating that the added plasticizers might act as UV-absorbers which inhibited the photodegradation process. The analysis of the FT-IR spectra of the irradiated and nonirradiated samples showed a noticeable formation of new broad band centered at 1727 cm-1, and its intensity was found to increase with the increase in irradiation time and also with the increase in the amount of added plasticizer. In addition, the observed increase in the intensities of the carbonyl and hydroxyl absorption regions of the FT-IR spectra provided evidence for the photodegradation as well as photo-oxidation of polymeric chains.
A Fast Interpretation Method for Inverse Modeling of Residual Gravity Anomalies Caused by Simple Geometry
Khalid S. Essa
Journal of Geological Research , 2012, DOI: 10.1155/2012/327037
Abstract: An inversion technique using a fast method is developed to estimate, successively, the depth, the shape factor, and the amplitude coefficient of a buried structure using residual gravity anomalies. By defining the anomaly value at the origin and the anomaly value at different points on the profile, the problem of depth estimation is transformed into a problem of solving a nonlinear equation of the form ()=0. Knowing the depth, the shape factor can be estimated and finally the amplitude coefficient can be estimated. This technique is applicable for a class of geometrically simple anomalous bodies, including the semiinfinite vertical cylinder, the infinitely long horizontal cylinder, and the sphere. The efficiency of this technique is demonstrated with gravity anomaly due to a theoretical model, in each case with and without random errors. Finally, the applicability is illustrated using the residual gravity anomaly of Mobrun ore body, situated near Noranda, QC, Canada. The interpreted depth and the other model parameters are in good agreement with the known actual values.
Differentiation between females of ostrich breeding trios based on egg weights
F Essa, SWP Cloete
South African Journal of Animal Science , 2004,
Abstract: Data, collected during the 1997-1998 breeding season from 14 ostrich trios, were used to determine whether two females in a trio could be differentiated based on egg size. For eight of the trios a difference between egg weights could be discerned and eggs could be assigned to one or to the other female. An average egg weight of approximately 1.5 kg and an average chick weight of approximately 0.9 kg was recorded. Coefficients of variation ranged from 9.8% for chick weight to 10.7% for egg weight. Overall hatchability was 53%. The repeatability of service sire observations for egg weight and chick weight were 0.32 and 0.28 respectively, whereas a higher repeatability of 0.82 and 0.67, respectively, was recorded for these traits when based on individual females. Four of the eight trios showed differences in the assumed hatchability between the females. These results suggest a preference of certain males for specific females. This study shows that the process of differentiating between females and their eggs based on the egg weight is feasible and could contribute to better data structures for ostrich breeders during genetic evaluation. South African Journal of Animal Science Supp 2 2004: 20-22
Improving student success using predictive models and data visualisations
Alfred Essa,Hanan Ayad
Research in Learning Technology , 2012, DOI: 10.3402/rlt.v20i0.19191
Abstract: The need to educate a competitive workforce is a global problem. In the US, for example, despite billions of dollars spent to improve the educational system, approximately 35% of students never finish high school. The drop rate among some demographic groups is as high as 50–60%. At the college level in the US only 30% of students graduate from 2-year colleges in 3 years or less and approximately 50% graduate from 4-year colleges in 5 years or less. A basic challenge in delivering global education, therefore, is improving student success. By student success we mean improving retention, completion and graduation rates. In this paper we describe a Student Success System (S3) that provides a holistic, analytical view of student academic progress.1 The core of S3 is a flexible predictive modelling engine that uses machine intelligence and statistical techniques to identify at-risk students pre-emptively. S3 also provides a set of advanced data visualisations for reaching diagnostic insights and a case management tool for managing interventions. S3's open modular architecture will also allow integration and plug-ins with both open and proprietary software. Powered by learning analytics, S3 is intended as an end-to-end solution for identifying at-risk students, understanding why they are at risk, designing interventions to mitigate that risk and finally closing the feedback look by tracking the efficacy of the applied intervention.
Multigrid Method for the Numerical Solution of the Modified Equal Width Wave Equation  [PDF]
Yasser M. Abo Essa
Applied Mathematics (AM) , 2016, DOI: 10.4236/am.2016.710102
Abstract: Numerical solutions of the modified equal width wave equation are obtained by using the multigrid method and finite difference method. The motion of a single solitary wave, interaction of two solitary waves and development of the Maxwellian initial condition into solitary waves are studied using the proposed method. The numerical solutions are compared with the known analytical solutions. Using error norms and conservative properties of mass, momentum and energy, accuracy and efficiency of the mentioned method will be established through comparison with other methods.
The Numerical Solution of the MRLW Equation Using the Multigrid Method  [PDF]
Yasser Mohamed Abo Essa, Ibrahim Abouefarag, El-Desouky Rahmo
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.521310
Abstract: In this paper, we obtained the numerical solutions of the modified regularized long-wave (MRLW) equation\"\", by using the multigrid method and finite difference method. The solitary wave motion, interaction of two and three solitary waves, and development of the Maxwellian initial condition into solitary waves are studied using the proposed method. The numerical solutions are compared with the known analytical solutions. Using\"\"error norms and conservative properties of mass, momentum and energy, accuracy and efficiency of the mentioned method will be established through comparison with other techniques.
Evaluation of Myocardial Performance in Hypertensive Patients with Type 2 Diabetes and Normal Ejection Fraction  [PDF]
Muataz F. Hussein, Samar I. Essa, Anmar Z. Saleh
Health (Health) , 2015, DOI: 10.4236/health.2015.712187
Abstract: Diabetes (DM) and hypertension (HT) cause changes in cardiac performance. Long-term diabetes and hypertension can lead to changes in cardiac contractility, reduced left ventricular efficiency and heart failure. The aim of this study is to evaluate the effect of the coexistence of diabetes mellitus and hypertension on left ventricular myocardial performance and structural changes. The study involved 45 patients with essential hypertension and type 2 diabetes (14 males and 31 females, their mean age was 53.28 ± 13.28 years), and 45 healthy subjects (10 males and 35 females, their mean age was 48.11 ± 13.07 years) as a control group. Transthoracic echocardiography was done for all patients. The echocardiographic measurements included: left ventricle internal diameter at end diastole (LVIDd), left ventricle internal diameter at end systole (LVIDs), peak velocity of early transmitral flow (E), peak velocity of late transmitral flow (A), ejection fraction (EF%), isovolumic relaxation time (IVRT), isovolumic contraction time (IVCT) and ejection time (ET) from which the index of myocardial performance (IMP) was calculated. Results revealed a significant change in the ratio (E/A) between patients and controls (-32.45%) with p value < 0.05, and the change in (LVIDd) and (LVIDs) between patients and control groups were (4.61%) and (0.754%) respectively with insignificant p value. The change in IMP was (44.65%), with p value < 0.05, and the change in ejection fraction (EF%) was (-1.49) with p value > 0.05. In conclusion, diabetic patients with hypertension had an increase in IMP and reduced E/A indicating deterioration in cardiac performance despite normal ejection fraction and insignificant change in LV dimensions.
Study the Influence of UV-Irradiation on the Photo Stability of Pure and Plasticized Poly (4-Vinyl Biphenyl) in Solid Films  [PDF]
Khalid Essa Al Ani, Afrah Essa Ramadhan, Suha Khanfar
Materials Sciences and Applications (MSA) , 2017, DOI: 10.4236/msa.2017.813075
Abstract: The effect of UV irradiation and blending with phthalate and terephthalate plasticizers on the photo-stability of Poly (4-vinyl biphenyl) was studied at different intervals of irradiation time and in presence of air. The increase in irradiation time on the photodegradation of polymer thin films caused a change in the intensity and shape of the fluorescence band. It has been found that the stability of the polymer decreases with the increase of irradiation time, and to increases with the increase of the amount of added phthalate and terephthalate plasticizers, which is evidence of polymer photodegradation. The FT-IR spectra of irradiated pure and blended polymer with phthalate and terephthalate plasticizers showed a decrease in some absorption bands and increase in the other bands, this is also another factor for the occurrence of photo degradation of the irradiated polymer. The increase in the intensity of absorption of carbonyl and hydroxyl region, indicates a possible photogegradation of polymeric chains and the formation of alcohols, aliphatic ketones and to the increase in the number of (C=C) that resulted from hydrogen abstraction during chains-scission.
第1页/共91条
每页显示


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.