Brief Introduction (brief + introduction)

Distribution by Scientific Domains


Selected Abstracts


A BRIEF INTRODUCTION TO SCALE-FREE NETWORKS

NATURAL RESOURCE MODELING, Issue 1 2006
WILLIAM J. REED
ABSTRACT. This article provides a brief introduction to scale-free networks. The notion of a scale-free network is defined and some examples given. Properties frequently exhibited by scale-free networks are discussed. The importance of the phenomenon of preferential attachment in generating scale-free networks is illustrated with two examples for the spread of a persistent disease. The models are similar in that they both yield a total infected population (1) which is geometrically distributed, and growing exponentially in expectation; and (2) in which the average distance from the original source of infection grows in a similar way over time. However one model, which has preferential attachment (infection), yields a scale-free network, while the other which has homogeneous infectivity does not. The possible application of the theory of scale-free networks to resource management is briefly discussed. [source]


The Cambridge Platonists: A Brief Introduction , Edited by Tod E. Jones

JOURNAL OF RELIGIOUS HISTORY, Issue 2 2010
Rowan Strong
No abstract is available for this article. [source]


Moral Education in an Age of Globalization

EDUCATIONAL PHILOSOPHY AND THEORY, Issue 4 2010
Nel Noddings
Abstract Care theory is used to describe an approach to global ethics and moral education. After a brief introduction to care ethics, the theory is applied to global ethics. The paper concludes with a discussion of moral education for personal, political, and global domains. [source]


Complexity Theory and the Philosophy of Education

EDUCATIONAL PHILOSOPHY AND THEORY, Issue 1 2008
Mark Mason
Abstract Following a brief introduction to complexity theory, this paper considers how various themes in the field relate to the philosophical study of education. Issues and questions introduced include the challenge of complexity theory for the philosophy of education,and, conversely, some critical challenges for complexity theory from educational philosophy; complexity theory and educational continuity and change; the importance that complexity theory places on interpretive perspectives that are transphenomenal, transdisciplinary and transdiscursive; the risks of simplifying complexity to a point that excludes its ambiguities and includes only its dominant usages; the degree of coherence between Dewey's philosophical orientation and that of complexity theory; how Foucault might be read as a complexity theorist; how educational research informed by complexity theory might ask different questions with different analytical perspectives,connectionist, holistic, non-linear, rather than input,output ,black-box' causal modelling, for example; and how curriculum, teaching, the epistemology of schooling, and the ,education of consciousness',understood s an emergent phenomenon,might be different when viewed from the perspective of complexity theory. [source]


,Schools without walls?' Developments and challenges in dental outreach teaching , report of a recent symposium

EUROPEAN JOURNAL OF DENTAL EDUCATION, Issue 4 2006
K. A. Eaton
Abstract, During the 2004 annual meeting of the International Association for Dental Research, the Education Research Group held a symposium on dental outreach teaching. After a brief introduction, which reviews relevant aspects of the relatively sparse literature, this paper summarises the proceedings, the themes and conclusions that emerged and the research issues that were identified. It aims to describe aspects of current practice around the world and to promote future discussion. Presenters gave details of outreach programmes for dental undergraduates in Australia, Finland, Malaysia (and Southeast Asia), the United Kingdom and the United States. From these presentations four themes emerged. They were: reasons for the introduction of outreach teaching, its perceived beneficial effects, organisational issues, educational issues. The reasons included a recognition of the need to educate dental undergraduates as members of ,care teams' in the environments and communities where they were ultimately like to work and the current shortage of both suitable patients and teachers (faculty) in many dental schools. A wide range of potential benefits and some disadvantages were identified. The organisational issues were, in the main, seen to relate to finance and administration. The educational issues included the need to train and monitor the performance of teachers at outreach clinics and to assess the performance of the undergraduates whilst at the outreach locations. It was concluded that new technology made it easier to teach at a distance and it was possible to create a dental ,school without walls'. It was recognised that few evaluations of dental outreach teaching have been carried out and that there were many research questions to be answered, including: whether it should be a voluntary or compulsory part of the undergraduate curriculum, how long it should last and what type of outcomes should be assessed. [source]


Determination of load spectra for durability approval of car drive lines

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2002
B. OELMANN
ABSTRACT Knowledge of the significan and representative load spectra is one important requirement for a high-quality, quick durability life approval of vehicle components on a test rig or by calculation. The way that such load spectra can be derived from measurements is demonstrated in this paper by the example of a passenger car drive line. The paper includes a brief introduction followed by an outline of the objectives. The proposed approach will then be illustrated and the results will be presented. Examples of applications will be shown and an outlook for further activities presented. [source]


Lie Theory for Quantum Control

GAMM - MITTEILUNGEN, Issue 1 2008
G. Dirr
Abstract One of the main theoretical challenges in quantum computing is the design of explicit schemes that enable one to effectively factorize a given final unitary operator into a product of basic unitary operators. As this is equivalent to a constructive controllability task on a Lie group of special unitary operators, one faces interesting classes of bilinear optimal control problems for which efficient numerical solution algorithms are sought for. In this paper we give a review on recent Lie-theoretical developments in finite-dimensional quantum control that play a key role for solving such factorization problems on a compact Lie group. After a brief introduction to basic terms and concepts from quantum mechanics, we address the fundamental control theoretic issues for bilinear control systems and survey standard techniques fromLie theory relevant for quantum control. Questions of controllability, accessibility and time optimal control of spin systems are in the center of our interest. Some remarks on computational aspects are included as well. The idea is to enable the potential reader to understand the problems in clear mathematical terms, to assess the current state of the art and get an overview on recent developments in quantum control-an emerging interdisciplinary field between physics, control and computation. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


The polyphonic spree: the case of the Liverpool Dockers

INDUSTRIAL RELATIONS JOURNAL, Issue 4 2003
Chris Carter
This paper is concerned with the possibilities opened up for Trade Unions by the internet age. The paper analyses forms of resistance, their preconditions and organisational backgrounds. It is argued that polyphonic organisation and, closely linked, new organisational forms, provide a strong basis for power relations and strategies of resistance. The paper starts with a brief introduction to the dispute between the Dockers of Liverpool and the Mersey Docks and Harbour Company. Contextualising the evolving issue in the broader picture of trade union crisis and renewal, the case study is theorised using linguistically informed approaches to management and organisation theory. Introducing these theoretical developments, the potential of new organisational forms for power relations and resistance are elaborated. [source]


Lower bound limit analysis of cohesive-frictional materials using second-order cone programming

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2006
A. Makrodimopoulos
Abstract The formulation of limit analysis by means of the finite element method leads to an optimization problem with a large number of variables and constraints. Here we present a method for obtaining strict lower bound solutions using second-order cone programming (SOCP), for which efficient primal-dual interior-point algorithms have recently been developed. Following a review of previous work, we provide a brief introduction to SOCP and describe how lower bound limit analysis can be formulated in this way. Some methods for exploiting the data structure of the problem are also described, including an efficient strategy for detecting and removing linearly dependent constraints at the assembly stage. The benefits of employing SOCP are then illustrated with numerical examples. Through the use of an effective algorithm/software, very large optimization problems with up to 700 000 variables are solved in minutes on a desktop machine. The numerical examples concern plane strain conditions and the Mohr,Coulomb criterion, however we show that SOCP can also be applied to any other problem of lower bound limit analysis involving a yield function with a conic quadratic form (notable examples being the Drucker,Prager criterion in 2D or 3D, and Nielsen's criterion for plates). Copyright © 2005 John Wiley & Sons, Ltd. [source]


Practical performance of digital cellular system in mass rapid transit environments

INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 2 2005
Y. P. ZhangArticle first published online: 13 DEC 200
Abstract Leaky coaxial cables have found applications in the creation of network infrastructures for mobile and personal communication services in underground and enclosed spaces. A digital cellular system based on the GSM 900 standard and using radiated mode leaky coaxial cables has been implemented in an underground mass rapid transit environment. This paper presents the practical performance evaluation of the system. First, we start with a brief introduction of a radiated mode leaky coaxial cable and the digital cellular system GSM 900, and then we move into a full description of the measurement campaign; next we focus on an analysis of the measured performance data about received signal level, received signal quality, speech quality index and grade of service. The results show that the system performance is generally good; however, the poor system performance often occurs at the terminals of the leaky coaxial cable. In addition, it is found that the system performance is highly correlated with the density of train passenger. The higher train passenger density degrades the system performance. Copyright © 2004 John Wiley & Sons, Ltd. [source]


Introductory review on object oriented paradigm for full-wave microwave CAD

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2002
G. Liotta
Abstract Object oriented (OO) techniques are proving useful in software engineering for dealing with complex systems and for increasing the ease of code development and maintainability. However, their application to electromagnetic modeling is still in its infancy. A brief introduction for microwave engineers to OO paradigms is made. A review of the state of the art in OO full-wave electromagnetic modeling is made, an illustrative example is shown, and likely future trends are discussed. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 341,353, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce10031 [source]


Providing multimedia communications services from high altitude platforms

INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2001
D. Grace
Abstract System level design considerations for high altitude platforms operating in the mm-wave bands are examined. Propagation effects in these bands are outlined, followed by a brief introduction to different platform scenarios. Ground-based and platform-based fixed wireless access scenarios are considered, and it is shown that using a platform, a single base station can supply a much larger coverage area than a terrestrial base station. The effects on performance of platform displacement from its desired location with both fixed and steerable antennas are also examined. It is shown that steerable antennas are of most use when fixed stations are immediately below the platform, with no benefit for fixed stations on the edge of coverage. The bandwidths required to serve several traffic distributions (suburbs and city centre based) are evaluated using the Shannon equation. It is shown that capacity can be constrained when users are located in the city centres, despite longer line of sight paths to users out in the suburbs. The effects of temporal changes in the spatial traffic distribution are investigated. It is shown that bandwith requirements can be reduced if the platform moves to track these changes. Copyright © 2001 John Wiley & Sons, Ltd. [source]


Using Quality Circles to Enhance Student Involvement and Course Quality in a Large Undergraduate Food Science and Human Nutrition Course

JOURNAL OF FOOD SCIENCE EDUCATION, Issue 1 2005
S.J. Schmidt
ABSTRACT: Large undergraduate classes are a challenge to manage, to engage, and to assess, yet such formidable classes can flourish when student participation is facilitated. One method of generating authentic student involvement is implementation of quality circles by means of a Student Feedback Committee (SFC), which is a volunteer problem-solving and decision-making group that communicates student-generated input to the teaching team for the purpose of improving the course content, structure, and environment in the present and redesigning it for the future. Our objective was to implement a SFC in a large introductory Food Science and Human Nutrition (FSHN 101) course to enhance student involvement and course quality. Overall, the SFC provided a continuous and dynamic feedback mechanism for the teaching team, a beneficial experience for the SFC members, and an opportunity for class members to confidentially share their input to enhance the quality of the course throughout the semester. This article includes a brief introduction of the use of quality circles in higher education classrooms, as well as our methods of implementation and assessment after using the SFC for 3 semesters (Spring 2003, Fall 2003, and Spring 2004). [source]


Americans' Nanotechnology Risk Perception:

JOURNAL OF INDUSTRIAL ECOLOGY, Issue 3 2008
Assessing Opinion Change
Summary Although proposed nanotechnology applications hold great promise, little is known about the potential associated risks. This lack of clarity on the level of risk associated with nanotechnology has forced people to make decisions about consumption with incomplete information. A national random digit dialing telephone survey (N= 1014) was conducted in the United States to assess knowledge of nanotechnology and perception of risk in August 2006. This investigation looks critically at individuals' responses to questions about the balance of risks and benefits of nanotechnology, both at the outset of the survey and after respondents were given a brief introduction to the potential benefits and risks of the technology. Models were created to characterzise respondents who said they did not know how nanotechnology's risks and benefits balanced in the "preinformation" condition but who, in the postinformation condition, had a different opinion. Respondents who were highly educated, members of the Republican Party, or male were more likely to switch from "don't know" in the preinformation condition to "benefits outweigh risks" in the postinformation condition, whereas respondents who were less educated, members of the Democratic Party, or female were more likely to switch from "don't know" in the preinformation condition to "risks outweigh benefits" in the postinformation condition. This is the first study to our knowledge to develop a significant model of nanotechnology risk perception change, specifically with regard to gender differences. The power of information provision to sway opinions is also supported, highlighting the importance of developing educational efforts targeting vulnerable populations. [source]


A brief introduction to cell-penetrating peptides

JOURNAL OF MOLECULAR RECOGNITION, Issue 5 2003
Pontus Lundberg
Abstract Cell membranes act as protective walls to exclude most molecules that are not actively imported by living cells. This is an efficient way for a cell to prevent uncontrolled influx or efflux of solutes, which otherwise would be harmful to it. Only compounds within a narrow range of molecular size, polarity and net charge are able to diffuse effectively through cell membranes. In order to overcome this barrier for effective delivery of membrane-impermeable molecules, several chemical and physical methods have been developed. These methods, e.g. electroporation, and more recent methods as cationic lipids/liposomes, have been shown to be effective for delivering hydrophobic macromolecules. The drawbacks of these harsh methods are, primarily, the unwanted cellular effects exerted by them, and, secondly, their limitation to in vitro applications. The last decade's discovery of cell-penetrating peptides translocating themselves across cell membranes of various cell lines, along with a cargo 100-fold their own size, via a seemingly energy-independent process, opens up the possibility for efficient delivery of DNA, antisense peptide nucleic acids, oligonucleotides, proteins and small molecules into cells both in vitro and in vivo. Copyright © 2003 John Wiley & Sons, Ltd. [source]


Measuring Brain Atrophy in Multiple Sclerosis

JOURNAL OF NEUROIMAGING, Issue 2007
Nicola De Stefano MD
ABSTRACT The last decade has seen the development of methods that use conventional magnetic resonance imaging (MRI) to provide sensitive and reproducible assessments of brain volumes. This has increased the interest in brain atrophy measurement as a reliable indicator of disease progression in many neurological disorders, including multiple sclerosis (MS). After a brief introduction in which we discuss the most commonly used methods for assessing brain atrophy, we will review the most relevant MS studies that have used MRI-based quantitative measures of brain atrophy, the clinical importance of these results, and the potential for future application of these measures to understand MS pathology and progression. Despite the number of issues that still need to be solved, the measurement of brain atrophy by MRI is sufficiently precise and accurate. It represents one of most promising in vivo measures of neuroaxonal degeneration in MS, and it should be used extensively in the future to assess and monitor pathological evolution and treatment efficacy in this disease. [source]


Darwinism,a new paradigm for organizational behavior?

JOURNAL OF ORGANIZATIONAL BEHAVIOR, Issue 2 2006
Nigel Nicholson
The Special Issue reflects a growing interest in Darwinian ideas and their increasing application to work and organizational issues, analyzes factors that have impeded its adoption as a paradigm and considers the prospects for future growth. After a brief introduction to key concepts in the new Darwinism, some histories, and controversies are traced. Causes for the particularly slow uptake of the paradigm in Organizational Behavior (OB) are discussed, as well as some of the common misconceptions and incorrect attributions that have been leveled at evolutionary theory. The paper then overviews the scope and contents of the Special Issue (SI) papers, and concludes by considering future prospects for the field. The authors argue that the paradigm has compelling significance and wide applicability to the full range of OB topics and interests. Copyright © 2006 John Wiley & Sons, Ltd. [source]


Proteases implicated in apoptosis: old and new

JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2010
Kelly L. Moffitt
Abstract Objectives The role of proteases in the regulation of apoptosis is becoming increasingly apparent. Whilst many of these proteases are already characterised, some have yet to be identified. Traditionally caspases held the traditional role as the prime mediators of apoptosis; however, attention is now turning towards the contribution made by serine proteases. Key findings As unregulated apoptosis is implicated in various disease states, the emergence of this proteolytic family as apoptotic regulators offers novel and alterative opportunities for therapeutic targets. Summary This review presents a brief introduction and overview of proteases in general with particular attention given to those involved in apoptotic processing. [source]


Impact of Sex: Determination of Alcohol Neuroadaptation and Reinforcement

ALCOHOLISM, Issue 2 2006
Kristine M. Wiren
This article represents the proceedings of a symposium at the Research Society on Alcoholism meeting in Santa Barbara, California. The organizers/chairs were Kristine M. Wiren and Deborah A. Finn. Following a brief introduction by Deborah Finn, the presentations were (1) The Importance of Gender in Determining Expression Differences in Mouse Lines Selected for Chronic Ethanol Withdrawal Severity, by Kristine M. Wiren and Joel G. Hashimoto; (2) Sex Differences in Ethanol Withdrawal Involve GABAergic and Stress Systems, by Paul E. Alele and Leslie L. Devaud; (3) The Influence of Sex on Ethanol Consumption and Reward in C57BL/6 Mice, by Kimber L. Price and Lawrence D. Middaugh; and (4) Sex Differences in Alcohol Self-administration in Cynomolgus Monkeys, by Kathleen A. Grant. [source]


Generation of quantum-entangled twin photons by waveguide nonlinear-optic devices

LASER & PHOTONICS REVIEWS, Issue 4 2009
T. Suhara
Abstract This paper reviews the quasi-phase-matched (QPM) waveguide nonlinear-optic device technologies for generation of quantum-entangled twin photons indispensable for quantum-information techniques. After a brief introduction to the concept of entanglement, quantum theory analysis of twin-photon generation (TPG) is outlined to clarify the properties of twin photons. Then, methods for entangled-photon generation are discussed. Practical design and theoretical performances of LiNbO3 waveguide QPM TPG devices, as well as the fabrication techniques, are described. Finally, experimental demonstrations of polarization-entangled twin-photon generation by waveguide Type-I and Type-II QPM TPG devices are presented. [source]


Upconversion: road to El Dorado of the fluorescence world

LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 4 2010
Li Ching Ong
Abstract Upconversion nanoparticles (UCNs), in the recent times have attracted attention due to their unique properties, which makes them ideal fluorophores for use in biological applications. There have been various reports on their use for targeted cell imaging, drug and gene delivery and also for diffuse optical tomography. Here we give a brief introduction on what are UCNs and the mechanism of upconversion, followed by a discussion on the biological applications of UCNs and further on what the future holds for UCNs. Copyright © 2010 John Wiley & Sons, Ltd. [source]


Development, principles, and applications of automated ice fabric analyzers

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 1 2003
L.A. Wilen
Abstract We review the recent development of automated techniques to determine the fabric and texture of polycrystalline ice. The motivation for the study of ice fabric is first outlined. After a brief introduction to the relevant optical concepts, the classic manual technique for fabric measurement is described, along with early attempts at partial automation. Then, the general principles behind fully automated techniques are discussed. We describe in some detail the similarities and differences of the three modern instruments recently developed for ice fabric studies. Next, we discuss briefly X-ray, radar, and acoustic techniques for ice fabric characterization. We also discuss the principles behind automated optical techniques to measure fabric in quartz rock samples. Finally, examples of new applications that have been facilitated by the development of the ice fabric instruments are presented. Microsc. Res. Tech. 62:2,18, 2003. © 2003 Wiley-Liss, Inc. [source]


A BRIEF INTRODUCTION TO SCALE-FREE NETWORKS

NATURAL RESOURCE MODELING, Issue 1 2006
WILLIAM J. REED
ABSTRACT. This article provides a brief introduction to scale-free networks. The notion of a scale-free network is defined and some examples given. Properties frequently exhibited by scale-free networks are discussed. The importance of the phenomenon of preferential attachment in generating scale-free networks is illustrated with two examples for the spread of a persistent disease. The models are similar in that they both yield a total infected population (1) which is geometrically distributed, and growing exponentially in expectation; and (2) in which the average distance from the original source of infection grows in a similar way over time. However one model, which has preferential attachment (infection), yields a scale-free network, while the other which has homogeneous infectivity does not. The possible application of the theory of scale-free networks to resource management is briefly discussed. [source]


Developmental cross talking in the ectomycorrhizal symbiosis: signals and communication genes

NEW PHYTOLOGIST, Issue 1 2001
Francis Martin
Summary Development of ectomycorrhizas involves multiple genes that are implicated in a complex series of interdependent, sequential steps. Current research into ectomycorrhiza development and functioning is aimed at understanding this plant,microbe interaction in a framework of the developmental and physiological processes that underlie colonization and morphogenesis. After a brief introduction to the ectomycorrhizal symbiosis, the present article highlights recent work on the early signal exchange taking place between symbionts, and sketches the way functional genomics is altering our thinking about changes in gene expression during the early steps of the ectomycorrhiza development. [source]


Guest Editorial: Knowledge transfer and the path of translational medicine

NURSING & HEALTH SCIENCES, Issue 3 2010
Charmaine Childs rgn, bnurs, mphil, phdArticle first published online: 24 JUN 2010
Abstract Translational medicine is at the forefront of academic health care. Although readers might recognize the term, few will be familiar with the principles of this emerging discipline. For many years, clinicians and scientists were concerned that discovery and innovation in cutting-edge science and biomedicine were not being used to cure or treat patients. This "problem" fostered a new academic paradigm, the aims being to develop a pathway to bridge the preclinical to clinical care interface and, ultimately, to bring treatments and therapies to the real world of patients and of health-care providers. There are three integrated "phases" of the "bench-to-bedside" translational medicine journey. A brief introduction to the discipline of translational medicine is presented. [source]


Is Semantic Information Meaningful Data?

PHILOSOPHY AND PHENOMENOLOGICAL RESEARCH, Issue 2 2005
LUCIANO FLORIDI
There is no consensus yet on the definition of semantic information. This paper contributes to the current debate by criticising and revising the Standard Definition of semantic Information (SDI) as meaningful data, in favour of the Dretske-Grice approach: meaningful and well-formed data constitute semantic information only if they also qualify as contingently truthful. After a brief introduction, SDI is criticised for providing necessary but insufficient conditions for the definition of semantic information. SDI is incorrect because truth-values do not supervene on semantic information, and misinformation (that is, false semantic information) is not a type of semantic information, but pseudo-information, that is not semantic information at all. This is shown by arguing that none of the reasons for interpreting misinformation as a type of semantic information is convincing, whilst there are compelling reasons to treat it as pseudo-information. As a consequence, SDI is revised to include a necessary truth-condition. The last section summarises the main results of the paper and indicates some interesting areas of application of the revised definition. [source]


The Present State of Charles Bonnet Syndrome

PSYCHOGERIATRICS, Issue 1 2002
Takeshi Terao
Abstract: This review attempts to integrate the present, somewhat confusing, state of the research on Charles Bonnet syndrome (CBS). After a brief introduction giving the history of CBS and its diagnostic criteria, relevant case reports and studies are reviewed. As a result of this review, it is revealed that CBS may have heterogenous causes: peripheral (visual impairment), central (organic brain lesion), and both. The neuroimaging findings on CBS are inconsistent, but in the pharmacotherapy for CBS, it has been found that anticonvulsants may be effective, although randomized controlled studies are needed. Moreover, the time course of CBS seems to vary: remission, continuation, development into dementia, and so on. With respect to a possible association between CBS and dementia, it is suggested that clinicians follow such patients up longitudinally, because the available diagnostic criteria for CBS are almost exclusively based on cross-sectional observations. [source]


Canine neoplasia , Introductory paper

APMIS, Issue 2008
HANS GAMLEM
The paper gives a brief introduction to canine oncology, including its comparative aspects as basis for recording tumours in the animal kingdom. In an abbreviated presentation of the Norwegian Canine Cancer Project for the years 1990 , 1998, the data (n=14,401) were divided into age groups, each of two years, into different categories of tumours, and into age and gender. As expected, cutaneous histiocytoma was the dominant tumour type in both sexes during the two first years of life. In the age group 2 , 3.99 years histiocytoma was still the largest group in males, but was surpassed by benign epithelial skin tumours in females. After the age of 4 years, benign epithelial skin tumours constituted the greatest circumscribed group in males, and mammary tumours in females, although the summated other tumours, not explained in this survey, dominated overall in males. Maligancies (cancer) were shown in the same way, by corresponding groups of gender and age. While mastocytoma was the most common tumour and non-Hodgkin's lymphoma the second most common during the two first years of life in females, the situation was reversed in males. Later, mammary tumours dominated in females, while different tumour types not further specified in this summarized report dominated in males, until the end of the age registration (above 14 years). Number, sex and location of most common tumours are shown in a tabular outline. Comparative aspects between human and dog tumours are considered: mammary and testicular neoplasia seemed more frequent in dogs than in humans in Norway, while intestinal, pulmonary and prostatic malignancies were less common in dogs. In our study, vascular tumours and tumour-like lesions constituted about 3% of the total data. As benign vascular tumours are incompletely reported to the human Cancer Registry, no dependable comparison may be made, but malignant vascular tumours have been on the rise during the last decades in the Norwegian human population, more so in men then in women. Finally, the article deals briefly with the development of endothelial cells, and the sparse information on causal factors of vascular tumours. [source]


An elementary introduction to the JWKB approximation

ASTRONOMISCHE NACHRICHTEN, Issue 3-4 2007
D. O. Gough
Abstract Asymptotic expansion of the second-order linear ordinary differential equation ,, + k2f (z), = 0, in which the real constant k is large and f = O(1), can be carried out in the manner of Liouville and Green provided f does not vanish. If f does vanish, however, at x0 say, then Liouville-Green expansions can be carried out either side of the turning point z = z0, but it is then necessary to ascertain how to connect them. This was first accomplished by Jeffreys, by a comparison of the differential equation with Airy's equation. Soon afterwards, the situation was found to arise in quantum mechanics, and was discussed by Brillouin, Wentzel and Kramers, after whom the method was initially named. It arises throughout classical physics too, and is encountered frequently when studying waves propagating in stars. This brief introduction is aimed at clarifying the principles behind the method, and is illustrated by considering the resonant acoustic-gravity oscillations (normal modes) of a spherical star. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Gekoppelter Wärme- und Stofftransport einschließlich der Korrosionsprozesse in porösen Baustoffen mit dem Simulationsprogramm AStra

BAUPHYSIK, Issue 3 2007
Rosa Maria Espinosa Dr.-Ing.
Zur Beschreibung von Wärme- und Feuchtetransportvorgängen gekoppelt mit Stofftransportprozessen in porösen Baustoffen ist ein Differentialgleichungssystem bestehend aus der Energieerhaltungsgleichung und den Massenerhaltungsgleichungen aller beteiligten Stoffe einschließlich des Wassers aufzulösen. Hierzu ist die Modellierung der stattfindenden Phasenumwandlungen der vorliegenden Stoffe und der chemischen Reaktionen der Porenlösung mit der Baustoffmatrix erforderlich. Zu unterscheiden sind dazu inerte, nicht reaktive Baustoffe und reaktionsfähige, zementgebundene Baustoffe. Für die numerische Simulation dieser Vorgänge bzw. die praktische Handhabbarkeit der Problemlösung wurde eine benutzerfreundliche Programmoberfläche AStra geschaffen, die neben dem eigentlichen Berechnungsmodul die benötigten Pre- und Postprocessing Möglichkeiten beinhaltet. Für die Berechnung des zeitlichen Verlaufs eines lösenden oder treibenden Angriffs auf zementgebundene Baustoffe wird durch eine in Abhängigkeit der beteiligten Spezies geeignete Vorauswahl von ablaufenden Reaktionen der Rechenaufwand für die Vorhersage von Nichtgleichgewichtszuständen optimiert und damit die Möglichkeit geschaffen zeitliche Abhängigkeiten mit vertretbarem Berechnungsaufwand zu beschreiben. Zusätzlich können mechanische Beanspruchungen als Folge von Kristallisationsvorgängen zumindest qualitativ vorhergesagt werden. Im Folgenden werden eine Übersicht der implementierten Berechnungsmodelle sowie drei Anwendungsbeispiele von AStra vorgestellt. Coupled heat and mass transfer simulation including corrosion in porous building materials with the program AStra. For the description of corrosion processes of porous building materials, it is necessary to solve a system of coupled (non-linear) differential equations, which consists of a conservation equation for the energy and one for the mass of each substance (including water and air), whose content may change within the simulated time period. Indeed, it must be distinguished between degradation of reactive and of inert materials. The computation program AStra simulates a coupled transport of heat, moisture, air and chemical substances in porous materials. AStra consists of a user interface for pre- and post-processing and a computation module (solver), which contains the necessary algorithms to solve the system of coupled differential equations. Mathematical models for phase changes of salts and for chemical reactions between substances, including the components of the material matrix in case of cementitious materials, were developed. Furthermore, the computational cost for the prediction of the corrosion of cementitious materials was optimized by means of an adequate pre-selection of chemical reactions. Thus, it is possible to simulate corrosion processes within justifiable simulation time. On the other hand, a simulation of the mechanical stress resulting from crystallization processes is possible. This paper presents some applications of the programs and a brief introduction into their theoretical basis. [source]