Characteristics of origin-destination pair traffic in Funet

In this paper we analyze measurements gathered from a 2.5~Gbps link in the Finnish university network (Funet) in 2004. The traffic is broken down into origin-destination (OD) pair components based on source and destination IP address. We study the traffic characteristics of these components, and identify four typical representative OD pairs. For these pairs we investigate the validity of a moving IID Gaussian model. We find that the statistical properties of these OD pairs differ significantly from each other, with only some of them close to Gaussian. The OD pairs are also found to have some cross-correlation between each other, contradicting an often made assumption about OD pair independence. Furthermore, the existence of a mean-variance relation between the OD pairs is studied. We find that there is a relation between mean and variance, but for some periods of time it is rather weak.     

Stream Classification System Based on Susceptibility to Algal Growth in Response to Nutrients

We developed a stream classification system that is based on stream’s susceptibility to algal growth using a two-step approach. The model portrays algal biomass as a result of stream’s response to nutrient concentrations and the response is governed by various stream factors. In the first step, a nutrient-chlorophyll a relationship was developed to characterize nutrient’s effects on algal biomass. Residuals of the relationship were attributed to stream’s susceptibility to algal growth in response to nutrients and referred to as “observed” susceptibility. In the second step, conditions of other contributing factors were used to explain the variation in the residuals and the developed relationship was used to generate “predicted” susceptibility. Existing data compiled from various monitoring projects of Illinois streams and rivers were used to illustrate the approach. Streams were classified into three (high, medium, and low) categories based on their observed and predicted susceptibility values, respectively. With the available data, the model showed a 40-50% success rate for classifying the streams based on three observed and predicted susceptibility categories. Model entropy also was calculated for selecting the best model. The results show the important role of both nutrients and other contributing factors in explaining the variation of algal biomass. The study also suggests ways to fine tune the model and improve its accuracy, which would make the presented model a more viable tool for stream classification for establishing nutrient criteria to prevent surface streams from eutrophication.     

Phase Equilibria in the Quaternary System Ti-Al-C-N

The quaternary system Ti-Al-C-N and its binary and ternary boundary systems are investigated using powder methods and XRD analysis. Phase equilibria at 1375°C are presented in an isothermal network for alloys up to 50 at.% Ti. In the vertical section Ti₂AIC_1-x-Ti₂AlN_1-x a complete series of solid solutions exists at 1495°C, but a wide miscibility gap occurs at 1375°C. The vertical section Ti₃AlC_1-x-Ti₃AlN_1-x is more complex because of the occurrence of the quaternary, tetragonally distorted phase Ti₃Al(C,N)_1-x ( a = 0.41135(4) nm, c = 0.41366(5) nm) and the transformation of perovskite-type Ti₃AlN_1-x into filled Re₃B-type Ti₃AlN_1-x below 1200°C.     

Application of the FE‐Method to the Simulation of Fatigue Crack Growth in real Structures

In the following paper at first general concepts which have to be considered for the accomplishment of a 3D fatigue crack propagation simulation by the FE‐method in real structures are introduced. In doing so numerical aspects concerning the necessary mesh generation as well as fracture mechanical issues will be discussed. Furthermore the 3D crack simulation program ADAPCRACK3D, which has been developed at the Institute of Applied Mechanics at University of Paderborn, is presented in its general functionality. The simulation example of the crack propagation in a shutter ring of a hydraulic press shows the practical relevance of both the implemented algorithms and fracture mechanical concepts.     

The influence of various reaction parameters on the performance of (α‐diimine)nickel(II) catalysts in ethylene oligomerization reactions

Modified (α‐diimine)nickel(II) catalysts are suitable for ethylene oligomerization reactions. Due to the mechanism (“chain running”), the formation of double‐bond isomers and branched olefins can be observed. The obtained oligomer mixtures show a Schulz–Flory distribution. Increasing ethylene pressure favors the selectivity of α‐olefin formation. The same effect can be observed when Lewis bases like thiophene or furane are added to the oligomerization reaction mixture. These results can be related to an interaction of the additives with the catalytic active species during the oligomerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1356–1361, 2003     

Work-oriented development of knowledge-based systems: a case for multiple perspectives

System development is strongly influenced by the perspectives used by system developers. Current development methods for knowledge-based systems are based on an information processing perspectives of experts and users which has been criticized by a number of researchers. The paper argues that work-oriented development of knowledge-based systems requires the parallel use of multiple perspectives (including the information processing perspective), and that the use of any single perspective is potentially dangerous. As an example of the importance of using multiple perspectives, thepaper presents the situated action perspective, and shows how it complements the information processing perspective.     

In-situ-Messung der Stickoxidkonzentration in turbulenten Diffusionsflammen

Zusammenfassung Die laserspektroskopischen Me?methoden laserinduzierte Fluoreszenz und spontane Ramanspektroskopie werden eingesetzt zur Messung der Konzentrationen von Stickoxid, Hydroxyl sowie der chemischen Hauptkomponenten und der Temperatur. Betrachtet wird die thermische Umsetzung von Wasserstoff mit Luftsauerstoff. Es wird die experimentelle Vorgehensweise und Problematik dargestellt. Ebenso wird der Weg der Modellierung und Berechnung turbulenter Verbrennungsvorg?nge am konkreten Beispiel skizziert. Die Annahme chemischen Gleichgewichts stellt sich als ungenügend in der Berechnung der Stickoxid- und Hydroxylkonzentrationen heraus. Eine deutlich bessere Vorhersage wird durch Einführen einer Reaktionsfortschrittsvariablen für das chemische Modell erreicht.     

Pulmonary and allergy subspecialty care in adults with asthma. Treatment, use of services, and health outcomes

This study examined the relationship of several maternal variables to the duration of exclusive breast-feeding and the total duration of breast-feeding, along with attitudes, perceptions, and beliefs about breast-feeding among women living in poor neighborhoods of Managua, Nicaragua. The field work was carried out in December 1992 and January 1993 using qualitative and quantitative methods. A structured questionnaire was administered in interviews with 556 mothers of children under 12 months of age, and meetings of four directed discussion groups were held, in which a total of 20 women participated. At one week of age, almost all the children of the mothers who were surveyed had been breast-fed, but only 45% had been exclusively breast-fed. At 12 weeks old, 30% were already completely weaned. The discussion groups revealed the coexistence of positive opinions about both breast-feeding and bottle-feeding. However, exclusive breast-feeding was considered harmful for the mother, and breast milk was not thought to be sufficient nourishment for the child. Previous experience was strongly related to the duration of exclusive breast-feeding and to total breast-feeding duration. Attitudes, social support, and work situation were important factors influencing the total length of time women breast-fed a child. In general, the results obtained through the interviews and in the discussion groups were in agreement and showed that the elements needed to promote exclusive breast-feeding were social support, a favorable community environment, and policies that dealt with problems faced by working mothers. The complementary research methods were useful for obtaining information about the relative importance of different factors that determine the duration of breast-feeding and for understanding that practice in greater depth from the mother's point of view.     

Interleukin-8 expression in normal nasal epithelium and its modulation by infection with respiratory syncytial virus and cytokines tumor necrosis factor, interleukin-1, and interleukin-6

Inflammation in nasal and airway tissue caused by allergens, microbial infection, and air pollution are likely to be regulated by inflammatory mediators produced by airway epithelial cells. We have therefore investigated the baseline expression of a number of cytokine genes known to be important inducers and modulators of inflammation, in freshly isolated human nasal epithelium. Cells were obtained by superficial scraping of turbinate tissue, and cDNA for polymerase chain reaction (PCR) amplification was reverse-transcribed directly from lysates of 3 x 10(3) to 5 x 10(3) epithelial cells using random hexamers. Constitutive expression of relatively high levels of interleukin-8 (IL-8) mRNA but undetectable levels (< 1 mRNA copy/cell) of granulocyte/macrophage colony-stimulating factor (GM-CSF), IL-6, IL-1, or tumor necrosis factor (TNF) mRNA were found after PCR amplification of the cDNA. IL-8 protein, but not IL-6, was identified in the nasal epithelial cells by immunocytochemistry. Infection with respiratory syncytial virus (RSV) or stimulation of nasal epithelium for 4 h with TNF or IL-1 in vitro resulted in a 4- to 10-fold increase in IL-8 mRNA expression but not in the expression of detectable levels of mRNA for the other cytokines. IL-8 was secreted by RSV-, IL-1-, and TNF-stimulated as well as unstimulated nasal epithelial cells after 6 to 20 h of culture. Neither IL-6, GM-CSF, nor TNF activity/immunoreactivity was detectable in the culture supernatants. Thus, it appears that IL-8 is a major cytokine of human nasal epithelium, constitutively expressed and readily secreted upon virus infection or stimulation with IL-1 and TNF.