Semiclassical stability analysis of a two-photon laser including spatial variation of the cavity field

We investigate the dynamics of a two-photon laser under conditions where the spatial variation of the cavity field along the cavity axis is important. Main attention is paid to linear stability analysis and numerical investigation of a two-photon laser for the Maxwell-Bloch equations. The model assumes pumping to the upper state of the two-photon transition. We consider the Maxwell-Bloch equations on the basis of which we study the stability analysis of the steady state of the system. The system is taken to be contained in a ring-laser cavity. Asymptotic expansion of the eigenvalue and analytic information are obtained in some realistic limits, such as very large reflectivity, very small cavity losses, or very small population relaxation rate. The results are illustrated with an application to a specific atomic system (Potassium) as an amplifying medium.Comment: 17 pages, 3 figure

A study of the vibrational spectra of some monosubstituted pyridines

Infrared spectra in the range (4000-250 cm-1) and Raman spectra in the range (4000-150 cm-1) of pyridine, 2-, 3- and 4-chloro-, bromo-, and methylpyridines, 2-fluoro-, 2-amino and 4-ethylpyridines have been measured. The spectra, vibration and assignments of the observed frequencies of 2-amino-, and 4-ethylpyridines are presented for the first time. The infrared data for 2-fluoropyridine is combined with the previously reported Raman data of Stephenson and Voelz to allow complete vibrational assignments for this compound for the first time. Frequency assignments for the other molecules are re-examined and where necessary changes and/or additions in frequency assignments are made. Correlations between related series of pyridine and pyridine derivatives are investigated. The possible correlations between the vibrations of monosubstituted pyridines and the corresponding vibrations of monosubstituted benzene compounds were studied and it was found that they show a few similarities. Also, the location of the substituted on the ring is seen to influence the frequency of some of the vibrations. Further, other than C-H stretching vibrations, 5 vibrational modes are similar for the 1-, 2-, and 3-substituted pyridines (i.e., frequencies are independent of the location of the substituent and analogous to the corresponding vibrations of the monosubstituted benzene compounds. The correlations between a substituted pyridine and a monosubstituted benzene are seen to be useful in making vibrational assignments on other related compounds

The role of small manufacturing enterprises in sustainable regional development: Ismailia governorate as a case study in Egypt

During the last ten years the small manufacturing enterprises (SMEs) sector has become firmly established at the top of the development agenda for many countries, hence, marking this sector's increasingly acknowledged economic importance. Evidence from various parts of the world has shown clear signs of the growth of SMEs. Despite this, little attention has been given to understanding the environmental impacts these enterprises produce or to defining the role these entities play in terms of sustainable regional development. This thesis sets out to contribute to a better understanding of the influence of SMEs on sustainable regional development, as well as the contribution of SMEs to the economy in terms of job creation in the context of developing countries using Egypt and its Ismailia region as the basis for case study. Three main hypotheses were formulated relevant to the role of SMEs in sustainable regional development. In general, these hypotheses relate to the following: 1) The contribution of SMEs to the regional economy; 2) Problems and barriers SMEs face in achieving sustainable development; and 3) The potential for SMEs to utilize available existing resources to enhance their role in achieving sustainable regional development. In order to test these three hypotheses and to answer related questions, an analysis was undertaken within the framework of two spatial tiers: national and regional, that is Egypt and Ismailia, respectively. Two types of data were used - primary and secondary. A sample of 101 entrepreneurs and 100 workers were interviewed from the Ismailia region. The results of these interviews were analyzed in the empirical portions of this thesis. Chapter one pertains to the justification of the thesis; its objectives; the development of related research questions and hypotheses; the methodology used for data analysis; data sources used; questionnaire design; survey methods; and problems of data collection. Chapter two discusses the concept of SMEs worldwide and in Egypt as a basis from which to provide a concrete definition of SMEs that is used in the empirical portion of this study. In addition, the potential of SMEs and the problems facing SMEs in terms of sustainable regional development, the differences between SMEs and larger enterprises, as well as the importance of SMEs for the Egyptian economy are discussed in this chapter. The relationship between SMEs and sustainable urban and regional development is highlighted in more detail in chapter three. This relationship is discussed within the context of the notions of the overall concept of sustainable development, the sustainable regional development agenda in Egypt and related regulations, and the positive characteristics SMEs need in order to bring sustainable urban and regional development to fruition. Chapter four examines the first hypothesis of this study; this hypothesis states that, in general, SMEs have a positive effect on the economic and social development of a region. This chapter evaluates the ability of SMEs to drive the regional and national chains of economic added value; the capability of SMEs to create job opportunities at the regional level; and the effects of SMEs in terms of improved life-style and standard of living of workers and their families. Chapter five tests the second hypothesis in this thesis which states that the affects of a variety of types and sizes of SMEs on regional sustainable development is limited, at least for the time being. This chapter provides an analysis of economic, social and environmental obstacles and constraints that SMEs must face on a daily basis to achieve sustainable development in the region. In chapter six the potential by which SMEs can utilize their assets to enhance their contribution to sustainable regional development is evaluated; the potential opportunities available to SMEs to make better use of local raw materials and to drive the chain of economic activity within the Ismailia region were examined. The ability of SMEs to work more efficiently through the use of clusters and networks as a potential strategy is clarified. Chapter Seven presents a compilation of the detailed findings of this thesis along with the lessons that have emerged as a result of the research conducted. A series of policies and recommendations are provided as a means from which to create favourable conditions to encourage SMEs to play a more significant role in the national economy and in subsequent sustainable regional development. From a national perspective, the activities of SMEs are not usually the most serious source of environmental degradation, but, collectively, their sheer numbers may translate into substantial impacts on the eco-system. While the individual SME has financial problems related to the treatment and disposal of its waste, the adoption of an industrial cluster strategy for SMEs can provide an efficient solution to this problem. A cluster should consist of several single enterprises located in close proximity to one another, thereby, improving the ease of and costs associated with the treatment and disposal of environmental wastes. This study advocates the necessity of raising the degree of environmental awareness for organizations, syndicates, unions and societies related to SMEs, as well as entrepreneurs and labourers in their respective domains. Opportunities for raising environmental awareness can be implemented through a series of organized seminars, meetings and workshops designed to motivate individuals and small businesses within the society of SMEs to incorporate an ecological sense and approach into their daily behaviour and practices. A national policy must be adopted in Egypt in order for the SMEs sector to be successful in its contribution to sustainable development. Such policy must be all-inclusive and provide for the technical support of SMEs, financial support to SMEs, environmental support to SMEs, as well as provide overarching legislative support relevant to this particular sector of the business environment

Interplay of information quantifiers and the modified Jaynes-Cummings model

The dynamics of the Buck and Sukumar model (B. Buck and C. V. Sukumar, Phys. Lett. A 81, 132 (1981)) is investigated using different semi-classical information-theory tools. Their interplay reveals somewhat unexpected features. A new signature for the classical-quantum barrier is encountered thereby.Instituto de Física La Plat

Interplay of information quantifiers and the modified Jaynes-Cummings model

The dynamics of the Buck and Sukumar model (B. Buck and C. V. Sukumar, Phys. Lett. A 81, 132 (1981)) is investigated using different semi-classical information-theory tools. Their interplay reveals somewhat unexpected features. A new signature for the classical-quantum barrier is encountered thereby.Instituto de Física La Plat

Entropy squeezing for qubit - field system under decoherence effect

We study in detail the dynamics of field entropy squeezing FES) for a qubit - field system whose dynamics is described by the phase-damped model. The results of calculations show that the initial state and decoherence play a crucial role in the evolution of FES. During the temporal evolution of the system under decoherence effect, an interesting monotonic relation between FES, Wehrl entropy (WE)and negativity is observed

Rainwater in Egypt: quantity, distribution and harvesting

Egypt has limited water resources, and it will be under water stress within the year 2030. Therefore, Egypt should consider the natural and non-conventional water resources to overcome such problem. Rain harvesting is one solution; but not all; particularly on the north coast by the Mediterranean Sea and the Red sea. In this paper, the rainwater issue is reviewed and discussed in terms of the quantities and distribution at different selected areas in Egypt. The amount of rain falls at different location in Egypt was collected for a period of 16 months. The data indicated that rainfall in Egypt is very scarce, with an annual average of 12 mm and ranges from 0 mm/year in the desert to 200 mm/year in the north coastal region. The maximum total amount of rain does not exceed 1.8 billion m3per year. However, the average annual amount of rainfall water that is effectively utilized for agriculture purposes is estimated to be 1 billion m3. Harvesting pilot plant was constructed and implemented in Alexandria directly on the Mediterranean Sea. The harvested rain was used for irrigation and treated for drinking. It was, therefore, recommended to develop sustainable catchments at appropriate locations in the rain-fed areas at the north coast as well as cost effective grafting of the indigenous technologies with the innovative techniques

An overview of role of retinoids in management of warts: Review article

Background: Human papillomavirus (HPV)-inducing HPV-types can cause a wide range of cutaneous wart morphology and histological patterns that are distinct from one another. Certain forms of warts are more commonly related with various HPVs that cause cutaneous warts. It is essential that treatments for different forms of warts are both safe and painless. As warts can resolve up to two-thirds of the time without treatment, and treatments should not increase morbidity, this is particularly significant. In contrast, a large number of warts do not self-resolve fast and are associated with diminished quality of life, embarrassment, and pain in the skin. In terms of structure and function, retinoids resemble vitamin A in many ways. Both the differentiation and proliferation of keratinocytes and the immune system are hampered by their immunomodulatory effects. Objective: Assessment of role of retinoids in management of warts.Conclusion: Oral retinoids such as isotretinoin and acitretin are safe and reported to be effective therapy for different types of wart

Exploiting the molecular subtypes and genetic landscape in pancreatic cancer: the quest to find effective drugs

Pancreatic Ductal Adenocarcinoma (PDAC) is a very lethal disease that typically presents at an advanced stage and is non-compliant with most treatments. Recent technologies have helped delineate associated molecular subtypes and genetic variations yielding important insights into the pathophysiology of this disease and having implications for the identification of new therapeutic targets. Drug repurposing has been evaluated as a new paradigm in oncology to accelerate the application of approved or failed target-specific molecules for the treatment of cancer patients. This review focuses on the impact of molecular subtypes on key genomic alterations in PDAC, and the progress made thus far. Importantly, these alterations are discussed in light of the potential role of drug repurposing in PDAC

Interplay of information quantifiers and the modified Jaynes-Cummings model

The dynamics of the Buck and Sukumar model (B. Buck and C. V. Sukumar, Phys. Lett. A 81, 132 (1981)) is investigated using different semi-classical information-theory tools. Their interplay reveals somewhat unexpected features. A new signature for the classical-quantum barrier is encountered thereby.Instituto de Física La Plat