117,181 research outputs found
NEW SPECTROSCOPIC TECHNIQUES FOR STUDYING THE ORIGIN OF PHOSPHORESCENCE.
No full textM.A. El-Sayed has been an Alfred P. Sloan Fellow. M.A. El-Sayed, D.S. Tinti and D.V. Owens, Chem, Phys. Letters, in press. D.S. Tinti, M.A. El-Sayed, A.H. Maki and C.B. Harris, Chem. Phys. Letters, in press. The yz plane is parallel to the molecular plane with the z-axis being the long molecular axis.Author Institution: Department of Chemistry, University of California at Los AngelesAt temperatures for which the electron spin-lattice relaxation times between the zero-field levels of the lowest triplet state are comparable to or longer than the phosphorescence lifetimes, the relative intensity of the different vibronic bands in the phosphorescence spectrum and the observed decays are sensitive to changes in application of magnetic and saturation of the zero-field transitions with microwave From the changes in the spectrum and in the decays upon applying these perturbations, the zero-field level(s) responsible for the intensity of each vibronic band can be determined, as well as the complete description of the spin-orbit coupling scheme. The above techniques are demonstrated for 2,3-dichloroquinoxaline in a durene host crystal. The intersystem crossing route in the guest molecule is established to be . By means of optical-detection of the zero-field transitions, the usual spin Hamiltonian parameters for the lowest triplet state of 2,3-dichloroquinoxaline are found to be
Experiencing the armed struggle : the Soweto generation and after
No full textIncludes bibliographical references (p. 354-369).This study explores the experiences of the rank-and-file soldiers of Umkhonto we Sizwe and the Azanian People's Liberation Anny. Extensive interviews by the author and other researchers reveal the voices of the soldiers themselves. The African National Congress and Pan African Congress archives at the University of the Western Cape and the University of Fort Hare supplement and verify these oral testimonies, as do some published sources. Most previously published materials about the armed struggle against apartheid have already focused on diplomacy, strategy and tactics, operations, leadership, and human rights abuses to the neglect of the soldiers' actual experiences. This study complements these with significant new oral history materials from the Soweto generation of soldiers and their successors. When dealing with MK, many authors have documented issues of the camp structure in Angola, and operations inside South Africa, so much of this detail is only addressed briefly, leaving space to explore the soldiers' experiences. In the case of APLA, very little has been written on its history, and more detail is provided on these subjects. This study therefore deals with the soldiers' politicisation and motivation for joining the armed struggle, their experiences in leaving South Africa and training in exile, the crises in exile which limited their effectiveness for a time, their return to fight in South Africa, and their difficulties in the "new" South Africa. These materials reveal that vast problems remain facing these veterans of the struggle against apartheid, and that they have the potential, if properly supported and employed, to contribute substantially to the development of present day South Africa. Conversely, if their neglect continues, they also have the potential to bring vast harm to the country. Further use of the investigative tools of oral history, especially if extended to the former soldiers' vernacular languages, is necessary to augment the history of South Africa, and these soldiers' contributions
Conservation in an Islamic context a case study of Makkah
No full textThe Holy Qu’ rān contains many injunctions for Muslims to respect and conserve the natural environment but few address the built environment. Habitat at the time of the Prophet (PBOH) was in the vernacular and relatively impermanent. The first habitat was the cave, the second the tent and then simple flat roofed buildings of post and lintel construction made of mud and rubble. Later buildings were not indigenous but reflected the architectural styles and techniques of Muslim pilgrims from beyond the Arabian Peninsula. Permanent exotic buildings were later erected as reminders of holy places and events. This work advances a case to restore and preserve historic and religious sites in Makkah, Saudi Arabia. Makkah is the destination for millions of Muslim pilgrims who annually pay homage to Allah during the occasions of Hajj, Ramadan and Umra. The tranquillity and peaceful ambience that one associates with the holiest of Islamic experiences have, over the years, given way to jostling crowds of people who must be expediently housed, fed, transported, and protected. Due to the lack of planning and the insensitive but profitable development of the city, Makkah is in grave danger of becoming a bustling metropolis instead of a sanctuary where pilgrims gather to perform their religious rites and reaffirm their dedication to Allah. The author calls for professional planning and international cooperation to guide future development for this expanding and sensitive area. The author's ideas are grounded in practical and aesthetic study, therefore, the political, environmental and economic issues are examined in relationship to religious, historic and artistic values. The author makes proposals for a future Makkah that would provide pilgrims with the physical comforts, security, and serene environment they deserve—without destroying the city they came to visit. The author discusses preservation and conservation in the western world and the need for their acceptance in Muslim countries, the former being an aesthetic and intellectual concept sustained by law and the latter being the prescribed free expression of the individual unhindered by material considerations. Both worlds are rapidly being overwhelmed by materialism, but body, mind and spirit combine in making us aware of our surroundings and the way in what we see around us has come into being
United Arab Emirates v. Iran the dispute over the islands of Abu Musa, Greater Tunb, and Lesser Tunb - by Carol Mohsen El-Sayed
No full textThesis (M.A.)--Dept. of Political Studies and Public Administration, AUB, 2003.;"Advisor: Dr. Nizar Hamzeh, Associate Professor, Political Studies and Public Administration--Member of Committee: Dr. Hilal Khashan, Professor, Political Studies and Public ABibliography : leaves 118-127.This study analyzes the UAE v. Iran dispute around the sovereignty over the Persian Gulf islands of Abu Musa, Greater Tunb, and Lesser Tunb according to the rules of international law governing title to territory. The aim is to provide a legal assessmen
Simultaneous determination of linezolid, meropenem and theophylline in plasma
No full textThe data presented in this article are related to the research article entitled “Voltammeric monitoring of linezolid, meropenem and theophylline in plasma” (A.K. Attia, M.A. Al-Ghobashy, G.M. El-Sayed, S.M. Kamal, accepted in Anal. Biochem. 2018). This article describes a sensitive square wave voltammetric (SWV) method for simultaneous monitoring of linezolid (LIN), meropenem (MERO) and theophylline (THEO) in spiked plasma and in plasma of healthy volunteers. Keywords: Voltammetry, Determination, Linezolid, Meropenem, Theophylline, Plasm
The Pherobase
No full textThe Pherobase was developed by Dr. Ashraf El-Sayed, a research scientist at HortResearch in New Zealand, with the primary objective of providing "coverage of the literature published on chemical communication in insects." The Pherobase is intended for use by both scientific and non-scientific communities and currently contains "over 10000 entries, around 3000 molecules, and over 32000 static html pages that make it the world's largest database of behavior modifying chemicals." The site contains multiple Insect indices for such categories as Order, Family A-Z, and Species; References indices such as Discovery by Author, Discovery by Year, and References A-Z; and indices for Compounds, Compounds by Family, and Compounds by Genus. The site also contains a Contribution Form, and number of online forums relating to The Pherobase
A comparison of various optimization algorithms on a multilevel problem
No full textIn many problems in science and engineering, there are often a number of computational models that can be used to simulate the problem at hand. Models of physical systems can differ according to computational cost, accuracy and precision. This paper presents the concept of multilevel optimization, where different models of the problem are used in combination. This initial study compares several strategies for combining fast evaluations of limited accuracy with a few accurate calculations. It also attempts to show how different optimizers work under these different combination strategies. A specially designed test function is used to carry out these comparisons. Of the proposed strategies and optimisers, a sequential mixing strategy applied to a genetic algorithm with clustering gives the best results. This paper highlights the need to develop specialized optimization algorithms for this kind of problem
Onset of the Henry constant for supercritical adsorption into carbonaceous porous materials
No full textThe Henry constant is commonly used as a measure of how strong an adsorbate is attracted towards a solid surface and is regarded as one of the fundamental parameters in adsorption studies. Having a sound basis in thermodynamics, the Henry Law is often used as a criterion to evaluate the validity of adsorption isotherm equations. However, the application of the Henry Law for microporous materials, especially microporous activated carbon, remains questionable. It is the aim of this paper to examine the Henry Law behavior of supercritical adsorbates in carbonaceous pores of different sizes, and to define the conditions for the Henry Law to be applicable for carbonaceous adsorbents
A natural approach to multilevel optimization in engineering design
No full textIn many design optimization problems, the designer is faced with the dilemma of how to simulate the problem at hand using a number of different models. Some models maybe quite elaborate in their representation of the problem and hence tend to be computationally expensive. Other models may be far less elaborate and hence computationally cheaper. The computationally chap models tend to be less accurate than the expensive ones. The designer uses his/her experience, and understanding of the problem domain to switch between different models. S/He goes through a few iterations till a satisfactory design is found. Designs created in such a fashion are not necessarily optimal and they could be improved upon, given more design iterations and an adequate search technique. It is hence important to develop techniques that make maximal use of the many models available within a limited computational budget. Conducting search on such an environment where there are multiple models for evaluation fitness is what is meant by the term Multilevel optimization (MLO).
Suitable methods for conduction MLO maybe sought using algorithms and techniques gleaned from natural process, mainly Evolutionary Algorithms and Artificial Neural Networks.
In this thesis, an exposition is made of the issues to be considered when carrying out multilevel optimization. This is followed by a comparison of how various optimization algorithms perform in a multilevel problem using three simple model selection strategies. Having established that evolutionary inspired search methods work well in such an environment a topological mapping based model selection approach is then presented. Finally, Gaussian processes based metamodeling and model fusion approaches are explored. Results suggest that there are significant gains to be made in the synthesis between evolutionary and neural computation techniques for MLO
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