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

Tick-Borne Pathogens in Ticks and Blood Samples Collected from Camels in Riyadh Province, Saudi Arabia

Background and Objective: Domestic animals, including camels, in Saudi Arabia suffer from various diseases, among which tick-borne infections are important because they reduce the productivity of these animals. However, knowledge of tick-borne pathogens in camels in Saudi Arabia is very limited, so the aims of this study were to quantify the abundance and distribution of tick species infesting camels from different districts of Riyadh province and use molecular tools to detect tick-borne pathogens in both the ticks and blood samples. Materials and Methods: A total of 218 ticks were collected from 116 camels from the 5 districts of Riyadh. The ticks and camel blood samples were analyzed for Borrelia, Babesia and Theileria pathogens using conventional and real-time PCR. Results: The results showed that five different tick species were identified. Majority of the ticks were Hyalomma dromedarii (70.6%), which were collected from camels in all 5 districts. This was followed by Hyalomma impeltatum species (25.2%), which was again found in all the districts. The other species found were Hyalomma anatolicum, Haemaphysalis sp. and Rhipicephalus turanicus. The only one H. dromedarii tick was positive for Theileria sp. DNA. Although the sample size and the area of tick collection were limited, the data suggest that the prevalence of pathogens in the Riyadh province, Saudi Arabia is relatively low. Conclusion: The study provides useful preliminary data to inform future full-scale country-wide surveys

Transverse cracking of micro-alloyed steel slabs during continuous casting, handling and charging into the hot strip mill

Stahl ist einer der weltweit wichtigsten Werkstoffe in Bezug auf Nachfrage und wirtschaftliche Auswirkungen und wird in vielen Anwendungen als unersetzlich angesehen. Materialfehler während der Stahlproduktion führt zu Unterbrechungen des Nonstop-Produktionsprozesses, was zu einer verringerten Produktionseffizienz oder sogar zu Materialverlust und Anlagenschäden führt. In einem Weltproduktionsmaßstab; Energie-, Zeit- und Materialverluste durch Risse an Stahlbrammen kosten die Stahlindustrie jedes Jahr Hunderte Millionen Euro. Einer der gravierenden Defekte bei der Brammenqualität und Kontinuität des geplanten Walzprogramms ist die Oberflächenquerrissbildung beim Stranggießen, Transport/Lagerung oder Warmwalzen. Mikrolegierte Stahlsorten sind eine der anfälligsten Sorten, die aufgrund der Ausscheidung feiner Partikeln in kritischen Größen und Verteilungen für diese Art von Versagen anfällig sind. Die Defektmöglichkeit ist nach Ferritbildung in niedrigen Temperaturbereichen höher. Weitere kritische Effekte beim Abkühlen einer Bramme treten später im Brammenlager oder durch Wiedererwärmung in der Warmbandstraße auf. Das Verständnis der Bedingungen, die zu Rissen führen, und die Durchsicht ihrer Verhinderung/Vorhersage stehen im Fokus des Interesses, da die Vermeidung von Rissen enorme finanzielle Auswirkungen hat, indem sie den Energieverbrauch sowie unter Umweltaspekten reduziert. Das Hauptziel dieser Arbeit war es, die möglichen Ursachen für die Querrissentstehung in Stahlbrammen ausgesuchter rissempfindlicher Sorten durch einen industriellen Ansatz in einem integrierten Hüttenwerk zu analysieren und zu bewerten, um diesen als Grundlage für ein Vorhersagemodell zur Rissentstehung in Brammen zu nutzen. Basis dazu waren neben der Analyse von Betriebsdaten auch Laboruntersuchungen an diesen kritischen Sorten. Rissempfindliche Sorten unterliegen im betrieblichen Ablauf speziellen Vorschriften für das Stranggießen (Gießgeschwindigkeit, Sekundärabkühlung) und das Handling im Brammenlager und der Lagerung bis zum Einstoß in die Wiedererwärmöfen im Warmwalzwerk. Die statistische Analyse der über mehrere Jahre defekten/gerissenen Brammen ermöglichte die Erfassung der Temperatur- und Umformungshistorie der Bramme und mögliche Abweichungen von den für diese Sorten geltenden Vorgaben. Kritische Parameter konnten definiert, klassifiziert und nach ihrem Einfluss auf das Rissrisiko eingestuft werden. Die Auswirkung von (erkannt kritischen) Prozessschwankungen/-störungen auf die Querrissbildung wurde untersucht und bewertet für die zwei Stahlsorten Alloy-1 (0,08% C, 0,12% Ti und 0,05% Nb) und Alloy-0 (0,08% C und 0,001% Ti). Die während des Stranggießens auftretenden Defekte wurden durch Warmzugversuche, die im Umform-dilatometer DIL805 A/T durchgeführt wurden, Mikrostrukturuntersuchungen und Simulation der Ausscheidungskinetik von Ti- und Nb-Karbonitride mit MatCalc Software untersucht. Darüber hinaus wurde ein FEM-Temperaturmodell (Finite Elemente Methode) mit Abaqus CAE entwickelt, um die Temperaturprofile auf verschiedenen Brammenbereichen während der Brammenabkühlung auf verschiedenen Erzeugungsrouten zu berechnen. Die validierte Temperaturvorhersage half dabei, die Auswirkung verschiedener Routen - entsprechend der geplanten Einstoßtemperatur in die Warmbandstraße - auf die Phasenumwandlung und die Materialeigenschaften vor dem Ofeneinsatz zu beschreiben. Schließlich wurden die kritischen Situationen während der Produktion - die möglicherweise zu Rissen führen - definiert, erklärt und durch die industrielle Analyse bestätigt. Die Rissmechanismen dieser Stahlsorten können vorhergesagt und als Grundlage für die Erweiterung auf weitere kritische Sorten genutzt werden.Steel is still one of the most important materials worldwide in terms of demand and economic impact and considered irreplaceable in many applications. Products/parts made of steel can be found mainly in the automotive and transport areas, construction as well as household appliances. Material defects during steel production and downstream cause interruptions to the nonstop production process resulting in reduced production efficiency or even material loss and machinery damage. In a world production scale; energy, time and material loses due to steel slab cracking costs the steel industry hundreds of millions of euros every year. One of the serious defects facing slab quality and continuity of the planned rolling schedule is surface transverse cracking during continuous casting (CC), transportation/storage or hot rolling. Micro-alloyed steel grades are one of the most susceptible grades prone to this kind of failure due to precipitation of fine particles in critical sizes and distribution. The defect possibility is higher after ferrite formation at lower temperature ranges. Other critical effects during slab cooling emerge later on in the slab storage area or by reheating in the hot strip mill (HSM). Understanding the conditions leading to cracking and perusing its prevention/prediction is in the focus of interest as crack avoidance has an enormous monetary impact by reducing the energy consumption as well as from environmental aspects. The main objective of this work is to understand and evaluate the potential cracking reasons of steel slabs of the crack sensitive grades (CSG) through an industrial approach in a steel plant. This is considered the base for a prediction model for slab cracking behaviour based on both industrial and laboratorial results. CSG follow a special casting and handling set of regulations in terms of casting speed, secondary cooling, stockyard handling and temperature for charging into the reheating furnaces. The statistical analysis of the defected/cracked slabs enlightened the slab temperature and deformation histories and possible deviations from ideal/set production instructions. Critical failure parameters were defined, classified and ranked according to their influence on the cracking risk. The effect of process variations and disturbances on surface cracking for the two steel grades; Alloy-1 (0.08% C, 0.12% Ti and 0.05% Nb) and Alloy-0 (0.08% C and 0.001% Ti) was evaluated. The defects during the CC process were studied by hot tensile testing (Baehr DIL805 A/T), microstructure investigation, and simulation of precipitation kinetics of Ti- and Nb-carbonitrides using MatCalc software. Furthermore, a FEM (finite element method) temperature model (by Abaqus CAE) was developed to evaluate temperature profiles on different slab regions during slab cooling at different handling routes. The validated temperature prediction helped to study the effect of different routes - according to the planned charging temperature into the HSM - on phase transformation and material properties before furnace charging. Finally, the critical situations during production that possibly lead to cracking were defined, explained and confirmed by industrial analyses. The cracking mechanisms of these types of steel grades could be predicted and will be used as a base for the extension to further critical grades

Priabonian Sharks and Rays (Late Eocene: Neoselachii) From Minqar Tabaghbagh In The Western Qattara Depression, Egypt

http://deepblue.lib.umich.edu/bitstream/2027.42/90948/1/Contributions32no06-c04-30-2012.pd

THE DECISION TO INVADE: AN INTERNAL PERSPECTIVE TO THE RUSSIAN INVASION OF UKRAINE

The invasion of Ukraine by Russia marked a new turning point in the history of the 21st century and has had far-reaching effects for much of the globalized world. The intensity of such an unexpected and unprovoked war has made it crucial to seek out the reasons why Russia decided to wage war on Ukraine. As such, there is a need to look for a deeper origin of the conflict, especially the unique circumstances that led to such policy being pursued. A comprehensive and theoretical approach that connects all the dots into one chronological picture is required. To that end, this research attempts to analyze the war in Ukraine and explore the root causes of why Russia decided to invade, primarily through its internal perspective and the intervening variables that made it happen. It may serve as a reminder of how the compounding effects of a nation’s traumatic past, the corruption of power by its elites, the pacification of its civil society, and the hubris of its leaders, could lead to a disastrous and unforeseen outcome

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

Imprisonment as a form of punishment: a case study of Maldives

Today punishment of imprisonment is seen to be given a less prominent significance in terms of punishing offenders as a means of rehabilitation and reducing recidivism rates throughout the world. However, it is found that the Maldivian courts have adopted a pattern of punishing offenders through imprisonment as a general form of punishment for almost all types of crimes despite considering the severity and mitigating factors of a given case. This pattern of punishing offenders through imprisonment alone is practiced by an authority of discretion given to the judges in the Penal Code of Maldives even though the same Penal Code allows for the application of other forms of alternative punishments. Whilst some may argue on the effectiveness of imprisonment as a general form of punishment, our argument lies in resorting away from a punishment that yields less possible avenues for rehabilitation and reintegration of offenders back into the society and that the preference should be given to alternative forms of punishments based on the circumstances surrounding any individual case