The derivation of the functional response in a prey-predator system with active group defense

Group defense against predator attacks are common for prey species. Some group defense mechanisms are more passive, like swarm confusion. In this thesis the focus is an active type of group defense where the prey fight back against the attacking predator as a group. The aim of this thesis is to formulate a model with active groups defense and to mechanistically derive and analyse the functional response arising from it. The motivation is to understand the impact of this special type of group defense on the functional response of the predator, and hence on the whole dynamics of the model. Some theory about prey-predator models, the functional response and tools for analysing dynamical systems are presented as background first. Following this, the model is formulated from the individual level processes and the functional response derived using the method of time-scale separation. Finally, two special cases of the model are analysed. In the model, the defense of the prey is modelled as a coagulation and fragmentation process, where the prey can join the fight to protect the individual that is being attacked. These fights become clusters where the attacking predator is the coagulation kernel. The clusters can grow or shrink by one prey joining or leaving at a time, or the cluster breaking up completely due to success of either the attack or the defense. This type of coagulation and fragmentation process can be seen as a generalization of the Becker-Döring equations, where the clusters are homogenous groups and the groups can also only grow and shrink by one individual at a time. The cluster dynamics truncated with a maximum size for the clusters was found to have a unique and stable equilibrium for arbitrarily large maximum cluster sizes in both special cases of the model. The stability analysis for cluster dynamics with no maximum cluster size was not successful, even though there is reason to believe the results for the truncated system is generalizable to that case. The functional response was found to take a dome-shaped form, decreasing to zero under certain circumstances, or the form of Holling type II functional response. The determining factor for which type of functional response the model gives rise to is whether the predator’s attack rate is dependent on the cluster size or not. The same dependence of the form of the functional response on the attack rate was found to hold in both special cases of the model

From notochord to vertebral column: studies on Atlantic salmon (Salmo salar L.)

The notochord initially form a single-cell file stage of chordoblasts covered by a three layered sheath comprising a basal lamina, a main collagenous layer and an external elastic membrane. During early ontogeny, the collagenous layer of the sheath goes through changes in configuration from a circular orientation, with fibres oriented perpendicular to the long axis, and to a lamellar organization where alternating layers of parallel collagen fibres form helices, with a tangent angle of 75-80° to the long axis. The shift in collagen arrangement is taking place shortly after hatching and may reflect an adaptation of the notochord to functional demands related to stage of development. The serrated surfaces of the elastica externa encasing the notochord seem to provide an interconnection between the notochord and the myosepta, with a function related to transmission of force from the musculature. The subsequent segmentation process leading to formation of vertebral and intervertebral regions seems to be initiated within the notochord through formation of cellular chordoblast segments. Formation of the cellular segments is closely followed by a segmental pattern of ALP activity within the chordoblast layer and formation of mineralized chordacentra within the collagenous layer of the notochord sheath. Development of the vertebral column thus seem to involve a dual segmentation where notochord derived chordacentra define the vertebral segments and the sclerotome external to the notochord provide further growth to the vertebrae. The salmon vertebral column comprises notochord and sclerotome derived structures that tightly interconnect the vertebrae and the intervertebral regions. There are four distinct layers of bone and mineralized tissues that form the vertebral body. The two inner layers comprise the chordacentrum (mineralization of the notochord sheath) and the inner layer of the amphicoel (mineralization of the intervertebral ligament). The third layer is deposited by osteoblasts, forming the main portion of the amphicoelous centrum, and on its external surface, trabecular bone is deposited. The three inner layers have a lamellar organization, with collagen matrixes oriented perpendicular from layer to layer, while the fourth layer has a woven structure. The 6 layers also differ in osteocyte content. The notochord remains within the full length of the vertebral column and form the inner part of the intervertebral ligament. The sclerotomal external portion of the ligament is incorporated in the vertebrae as it is covered by bone during vertebral growth, while remaining unmineralized intervertebrally. The present studies on salmon shows that the notochord constitutes the main axial support during embryonic and larval stages and that the enforcing rearrangement of the collagen layer of the notochord sheath seems to be important for the properties of the notochord as a fibre-wound hydrostatic skeleton. The notochord further reinforces through formation of chordacentra, generating the segmental pattern of the vertebral column, while sclerotomal tissue external to the notochord provides further growth to the vertebrae and intervertebral structures

Oil and Civil Conflict: On and Off (Shore)

We reconsider the relationship between oil and conflict, focusing on the location of oil resources. In a panel of 132 countries over the period 1962-2009, we show that oil windfalls increase the probability of conflict in onshore-rich countries, while they decrease this probability in offshore-rich countries. We use a simple model of conflict to illustrate how these opposite effects can be explained by a fighting capacity mechanism, whereby the government can use offshore oil income to increase its fighting capacity, while onshore oil may be looted by oppositional groups to finance a rebellion. We provide empirical evidence supporting this interpretation: we find that oil windfalls increase both the number and strength of active rebel groups in onshore-rich countries, while they strengthen the government in offshore-rich ones

Information dynamics shape the networks of Internet-mediated prostitution

Like many other social phenomena, prostitution is increasingly coordinated over the Internet. The online behavior affects the offline activity; the reverse is also true. We investigated the reported sexual contacts between 6,624 anonymous escorts and 10,106 sex-buyers extracted from an online community from its beginning and six years on. These sexual encounters were also graded and categorized (in terms of the type of sexual activities performed) by the buyers. From the temporal, bipartite network of posts, we found a full feedback loop in which high grades on previous posts affect the future commercial success of the sex-worker, and vice versa. We also found a peculiar growth pattern in which the turnover of community members and sex workers causes a sublinear preferential attachment. There is, moreover, a strong geographic influence on network structure-the network is geographically clustered but still close to connected, the contacts consistent with the inverse-square law observed in trading patterns. We also found that the number of sellers scales sublinearly with city size, so this type of prostitution does not, comparatively speaking, benefit much from an increasing concentration of people

Fingerprint identification technology for its implementation in the Schengen Information System II (SIS-II)

This report presents the results of a JRC study on the readiness and availability of Automatic Fingerprint Identification System (AFIS) technologies for their introduction in the second generation Schengen Information System (SIS-II), The study summarises a review of the scientific literature, visits to authorities managing AFIS in nine Member States and in the United States of America and consultations with eu-LISA and with AFIS vendors. An external scientific board of international experts reviewed the results and conclusions of the study. The report concludes that AFIS technology has reached a satisfactory level of readiness and availability and proposes a series of recommendations in order to accomplish a successful implementation of a SIS-II AFIS.JRC.G.6 - Digital Citizen Securit

VATDIS Web Mapping - A Report on the Application of Open Standards and Open Architecture in Geospatial Interoperability for Emergency Management

This report provides an overview of the web mapping activities carried out in the VATDIS action in 2007. These web mapping activities aimed at integrating the work done for the Orchestra, Floodsite and Preview IP into one single demonstrator. In the main section of this report an outline is given of the reasons for integrating the projects and the contents of this integration. The report should be seen as a summary of the technical choices made in order to accomplish this integration. The annexes on this report help the more technical reader to understand the design of the demonstrator and to duplicate it for its own purposes.JRC.G.7-Traceability and vulnerability assessmen

Cryptographic security mechanism of the next generation digital tachograph system

JRC is in the process of evaluating the impact of update of the cryptographic security mechanisms for the next generation Digital Tachograph. The purpose of this document is to give background information about the cryptographic security mechanisms and vulnerabilities regarding the security mechanisms of the current Digital Tachograph System along with suggestions for the next generation Digital Tachograph security mechanisms. This document can be referred as an important reference to update the technical appendixes of the Tachograph regulation.JRC.G.7-Digital Citizen Securit

Geovisualization, Geometric Modelling and Displacement Analysis- Applications to Rockslide Investigations

This thesis addresses different aspects of spatial data handling in connection with investigations of large rockslides. As such, most of the research was carried out in a cross disciplinary and highly applied context. The focus of the thesis is on spatial data handling methodology which directly or indirectly can be used to support in rockslide investigations. Rockslide investigation is a comprehensive term covering all aspects of the evaluation process; from the initial planning of field investigations to data analysis and communication of final results. Central topics addressed in this thesis are; a) How data reduction affect the geometrical accuracy of digital terrain models b) How interactive geometric modelling and geovisualization can be used in complex rockslide investigations and c) How statistical analyses can be used to evaluate displacement measurements of unstable rock slopes. Digital terrain modelling forms an important component of the methodology used for rockslide investigations. The first subtopic addressed in this thesis is related to the construction of Triangulated Irregular Networks (TINs) from Light Detection and Ranging (LIDAR) data. As the LIDAR technology tends to generate large data volumes, the resulting terrain models are generally too large to be efficiently handled by ordinary workstations. Therefore, comparisons of various data reduction (decimation) methods were conducted. Their performances were evaluated by means of deviations from terrain models constructed from full datasets. Evaluation criteria included deviations in volume, surface area and elevation. The results showed that the method using a vertical point selection threshold combined with a data dependent triangulation had the overall best performance when tested on 30 different test datasets. The main objective of the geovisualization part of this thesis was to determine the geometric shapes and locations of potential basal sliding surfaces, for the Åknes rockslide in western Norway, along with the volumes of unstable rock associated with different sliding scenarios. The Åknes rockslide is one of the world's most investigated rockslides due to its potentially catastrophic consequences. A custom written geovisualization application for the Åknes investigation provided the visual context needed for data interpretation and interactive geometric modelling of sliding surfaces. This geovisualization approach enabled geoscientists to develop different sliding scenarios. A scenario putting the basal sliding surface at a depth of 105m to 115m below the topographic surface, delineating an unstable rock volume of 43 million m3, was considered as the most realistic. Statistical approaches for analyzing displacement measurements were also addressed in this thesis. Several methods including regression analysis, spectral analysis and hypothesis testing were demonstrated to measurements obtained from Global Positioning System (GPS), total stations and extensometers at the Åknes rockslide. Displacement measurements obtained from lasers and crackmeters at the Nordnes rockslide in Northern Norway were also analysed. As with the Åknes rockslide, the Nordnes rockslide has the potential for devastating consequences in terms tsunami generation. Consequently, thorough statistical analyses of the available displacement data are crucial in order to obtain accurate estimates for the displacement rates as well as for gaining insight into the sliding processes. Displacement data from both sites clearly showed seasonal variations but the overall long term displacements were regarded constant. Prediction intervals were derived from the current monitoring data from the Nordnes site. These prediction intervals are considered useful for evaluation of future displacement measurements.  PhD i bygg, anlegg og transportPhD in Civil and Transport Engineerin

Interpretation of File System Metadata in a Criminal Investigation Context

The reliable reconstruction of digital events is imperative for solving criminal cases. Computers, servers, mobile and IoT devices, vehicles, and EV charging infrastructure all use either local or remote storage (cloud). The storage needs to use a file system in order to store and retrieve files. Currently, digital forensic tools implement support for the most popular file systems, either fully or partially. In order to determine what has taken place, investigators today are dependent on tools that automate much of the investigation. Unfortunately, these tools use techniques that are not necessarily published, tested or peer-reviewed, which increases the uncertainty of their results. Furthermore, investigators normally use well known artifacts from the Operating System (OS) when trying to determine what occurred, however, file system interpretation is often automated by the tools and trusted as reliable and complete by the investigators. In many cases the OS is not available, for instance, when an external storage device is seized. This means the investigator only has the file system and the file content available for investigation. We found metadata structures that may connect an external device to the computers used to create files on the device, which order these files have been created, and when the computers were booted. These findings will help investigators to identify which computers are relevant for the investigation, create timelines, and detect timestamp manipulation, but also identify which files users have created, opened, or saved. It is not unusual that external devices are damaged or reformatted with new file systems. In this context it is important to be able to recover files from the damaged file system. We were able to invent a novel and generic method to carve and identify metadata for files using equality or approximate equality to identify timestamps that are co-located, a pattern typical for file metadata structures in most file systems. Our prototype tool outperforms the other tools we tested in recovery from damaged file systems. Investigators often use timestamps to create timelines or to limit their investigation to a particular time frame. We found that both tools and different file system drivers are implemented differently, not necessarily following the file system specifications. Even normal usage of an external USB disk on multiple operating systems may change timestamps to invalid settings, and it is imperative that investigators are able to identify such usage. This thesis will focus on interpreting the file system metadata to identify and understand the accurate meaning of structures that the digital forensic tools currently do not support or only partly support, identifying new knowledge that will increase the quality of digital investigations

An experimental study of salt precipitation in porous media and its potential implications on CO2 injection strategies

This thesis aims to support climate change mitigation efforts through improved carbon sequestration and thus contribute to an overall goal of reducing global warming. The goal of this thesis is to improve the understanding of how salt precipitation in porous media affects reservoir porosity and permeability. This insight is important for developing more effective CO2 injection strategies in saline aquifers. Laboratory experiments were conducted on core samples of Indiana limestone and Bentheimer sandstone, using brine solutions of varying salinity. The brine-saturated cores were dried to simulate near-wellbore dry-out conditions, then subjected to multiple imbibition and drying cycles to investigate the phenomenon of cumulative salt precipitation. Permeability and porosity were measured throughout these cycles. In addition, a simulation was performed using TOUGH, a reservoir simulator, to complement the experimental work. Key findings indicate that higher brine salinities cause a significant reduction in permeability in both rock types. A permeability reduction of up to 96% was observed in limestone cores, compared to approximately 66% reduction in sandstone cores. In contrast, porosity reductions were comparatively minor. Repeated imbibition cycles demonstrated that salt damage is cumulative, with each cycle further reducing permeability and slowing brine uptake in the cores.Masteroppgave i energiENERGI399I5MAMN-ENE