The Lund Model at Nonzero Impact Parameter

We extend the formulation of the longitudinal 1+1 dimensional Lund model to nonzero impact parameter using the minimal area assumption. Complete formulae for the string breaking probability and the momenta of the produced mesons are derived using the string worldsheet Minkowskian helicoid geometry. For strings stretched into the transverse dimension, we find probability distribution with slope linear in m_T similar to the statistical models but without any thermalization assumptions.Comment: 12 pages, 2 .eps figures, footnotes added, results unchanged, version to be published in Phys.Lett.

Historical land-use information from culturally modified trees

In a global perspective, the human impact on forest ecosystems varies greatly in type, frequency and magnitude. Knowledge of the history of forest use is crucial for understanding the development of forests, which in turn helps to understand how societies react to forest development. Culturally modified trees (CMTs), recorded in the western U.S., northern Scandinavia and south-eastern Australia, are features that can be dated precisely, and they bear witness to unique events of human activity. CMTs are traces from historical uses of forest resources that reflect the activities of local communities and extend far back in time, and therefore offer information not usually available from other sources. In this thesis I argue that CMTs have high potential for assessing human activity and possibly human impacts on forest ecosystems, particularly those concerning local indigenous uses. Periods of increased activity in a certain area are reflected in peaks in the distribution of CMT dates. These also show the time period and speed of abandonment of a traditional forest use in a landscape. The possibility to learn about the people, their behaviour and activities in the forest are good, but their impact on ecosystems will always be difficult to assess when only CMT data are available. Therefore, it is important to learn as much as possible about traditional customs expressed in CMTs, in combination with oral and ethnological sources, and the role of CMTs in the traditional use of the forest. In this way it is possible to estimate what the density and distribution of CMTs in the landscape actually tells us about historical impact on the ecosystem. CMTs contradict the idea of “pristine” forests but symbolize the traditional view that people are part of nature rather than separate from it

Journal Staff

Utifrån en rad perspektiv är det angeläget att antagningssystemet och de instrument som används för urval till högre utbildning har legitimitet hos systemets avnämare. Den undersökning som redovisas har genomförts inom ramen för VALUTAprojektet (Validering av den högre utbildningens antagningssystem). Syftet är att belysa antagningssystemets konsekvenser ur ett avnämarperspektiv genom att undersöka hur olika grupper av högskolestudenter ser på högskoleprovets relevans som urvalsprov samt om de studerande använt sig av strategier, i form av upprepat provdeltagande och komplettering av gymnasiebetyg. Huvudresultaten visar, oberoende av utbildning, kön och social bakgrund, att det delprov som anses vara det mest relevanta är LÄS medan det minst relevanta delprovet är ORD. Vidare att de studerande genomfört och upprepat högskoleprovet samt kompletterat sina gymnasiebetyg, men att dessa strategier använts på olika sätt av olika studerandegrupper vilket är relaterat till utbildning, kön och social bakgrund

Capacity Study of Statistical Multiplexing for IP Telephony

Transmitting telephone calls over the Internet causes problems not present in current telephone technology such as packet loss and delay due to queueing in routers. In this undergraduate thesis we study how a Markov modulated Poisson process is applied as an arrival process to a multiplexer and we study the performance in terms of loss probability. The input consists of the superposition of independent voice sources. The predictions of the model is compared with results obtained with simulations of the multiplexer made with a network simulator. The buffer occupancy distribution is also studied and we see how this distribution changes as the load increases