The subject of the thesis is a study of the projections from low threshold oral and face afferents to the cerebral cortex and of descending motor control mechanisms originating in the cerebral cortex or the hypothalamus and influencing the jaw reflexes.Cats anaesthetized with chi oral ose were used for the experiments. Ipsi- and contralateral nerves from the oral cavity and the face were stimulated electrically. Cortical potentials were averaged and recorded. The location of the projections was related to the cytoarchi-tectonic areas of the cerebral cortex. It was found that the afferents projected to separate maximum points in areas 3a, 3b, 5a and 6aß. The projections to areas 3a and 3b were somatotopically organized, but the layout of the projections on the cortex was not facelike.The effect of monopolar anodal stimulation of the cerebral cortex on the monosynaptic jaw closing and the di synaptic jaw opening reflexes was investigated. A sequence of facilitation and inhibition of both reflexes was elicited by cortical stimulation. The effects were of short latency (2.5 ms) and could start with either facilitation or inhibition. The timecourse of the sequence was sinuslike with a period of 10 ms. The largest effect originated in the "sensory" areas 3a and 3b and not in the "motor" areas 4y and 6ag. It is suggested, that a tri gemino-cortico-tri geminai loop via area 3a may function in reflex modulation of jaw movements.The hypothalamic effects on the jaw reflexes were evoked by electrical stimulation in those parts of the hypothalamus, which are w known to generate defence, attack or feeding responses. A tenfold facilitation of the jaw closing reflex and a facilitation followed by almost complete inhibition of the jaw opening reflex were observed in the anaesthetized animal with intact cerebral cortex. The effects remained but were diminished in amplitude after cortical ablation. The descending path was located in the ventral midbrain tegmentum.It is suggested that the observed hypothalamo-tri geminai mechanism may exercise a tonic influence on the trigeminal motoneurones, thereby controlling the set points of the biting force and the rest position. The implications of this hypothesis on the etiology of bruxism and the myofascial pain-dysfunction are discussed. / <p>Härtill 3 rapporter.</p> / digitalisering@umu

En los últimos años, el análisis numérico de problemas acoplados, como los procesos de degradación de materiales y estructuras relacionados con los efectos medioambientales, ha cobrado especial importancia en la comunidad científica de la mecánica del hormigón. Problemas de este tipo son por ejemplo el ataque químico, el efecto de altas temperaturas o la retracción por secado.Tradicionalmente, los análisis acoplados existentes en la literatura se han realizado a nivel macroscópico, considerando el material como un medio continuo y homogéneo. Sin embargo, es bien conocido que el origen de la degradación observada a nivel macroscópico, a menudo es debida a la interacción entre los áridos y el mortero, sobre todo cuando se dan cambios de volumen diferenciales entre los dos componentes. Esta es la razón por la que el análisis mesomecánico está emergiendo como una herramienta potente para estudios de materiales heterogéneos, aunque actualmente existen escasos modelos numéricos capaces de simular un problema acoplado a esta escala de observación.En esta tesis, la aplicabilidad del modelo meso-mecánico de elementos finitos, desarrollado en el seno del grupo de investigación durante los últimos quince años, se extiende al análisis de problemas acoplados higro-mecánicos y químico-mecánicos, con el fin de estudiar la retracción por secado y el ataque sulfático externo en muestras de hormigón. La generación numérica de mesogeometrías y mallas de elementos finitos con los áridos de mayor tamaño rodeados de la fase mortero se consigue mediante la teoría de Voronoï/Delaunay Adicionalmente, con el fin de simular las principales trayectorias de fisuración, se insertan a priori elementos junta de espesor nulo, equipados con una ley constitutiva basada en la mecánica de fractura no lineal, a lo largo de todos los contactos entre árido y matriz, y también en algunas líneas matriz-matriz.La aportación principal de esta tesis es, conjuntamente con la realización de análisis acoplados sobre una representación mesoestructural del material, la simulación no solo de la formación y propagación de fisuras, sino también la consideración explícita de la influencia de éstas en el proceso de difusión.Los cálculos numéricos se realizan mediante el uso de los códigos de elementos finitos DRAC y DRACFLOW, previamente desarrollados en el seno del grupo de investigación, y acoplados mediante una estrategia staggered. Las simula-ciones realizadas abarcan, entre otros aspectos, la evaluación del compor-tamiento acoplado, el ajuste de parámetros del modelo con resultados experimentales disponibles en la bibliografía, diferentes estudios del efecto de los áridos en la microfisuración inducida por el secado y las expansiones debidas al ataque sulfático, así como el efecto simultáneo de los procesos gobernados por difusión y cargas de origen mecánico. Los resultados obtenidos concuerdan con observaciones experimentales de la fisuración, el fenómeno de spalling y la evolución de las deformaciones, y muestran la capacidad del modelo para ser utilizado en el estudio de problemas acoplados en los que la naturaleza heterogénea y cuasi-frágil del material tiene un papel predominante.

Smart cards are small, portable, tamper-resistant computers used in security-sensitive applications ranging from identification and access control to payment systems. Side-channel attacks, which use clues from timing, power consumption, or even electromagnetic (EM) signals, can compromise the security of these devices and have been an active research area since 1996. Newer ``contactless'' cards communicate using radio frequency (RF), without physical contact. These contactless smart cards are sometimes grouped with radio frequency identification (RFID) devices in popular usage of the term. This thesis investigates devices that use the ISO 14443 (proximity card) protocol, a large class of contactless/RFID devices. Although contactless smart cards are increasingly common, very few reproducible practical attacks have been published. Presently, there are no known documented side-channel attacks against contactless Java Cards (open standard multi-application cards) using generic unmodified hardware. This thesis develops a research-friendly platform for investigating side-channel attacks on ISO 14443 contactless smart cards. New techniques for measurement and analysis, as well as the first fully documented EM side-channel monitoring procedure, are presented for a contactless Java Card. These techniques use unmodified, commercial off-the-shelf hardware and are both practical and broadly applicable to a wide range of ISO 14443 devices, including many payment cards and electronic passports.

Demands on the quality and reliability of Volunteered Geographic Information have increased because of its rising popularity. Due to the less controlled data entry, there is a risk that people provide false or inaccurate information to the database. One factor that affects the effect of such updates is the network structure of the database schema, which might reveal the database’s robustness against different kinds of false updates. Therefore, network analyses are needed. The aim is to analyse GIS data models, stored in UML class diagrams, for scale-free and small-world properties. Moreover, a robustness analysis is to be carried out on selected data models in order to find out their error and attack tolerance against, for example, false updates. Three graphs were specified from the UML class diagrams: (1) class graphs: classes as nodes and their interactive relationships as connections; (2) attribute graphs: classes and attributes as nodes, with connections between the classes and their attributes; and (3) schema graphs: attributes as nodes and their interactive relationships inside and outside the tables as links. The analysed class diagrams were stored in XMI, and therefore transformed with XSLT to the Pajek network format. Thereafter, small-world and scale-free analyses as well as a robustness analysis were performed on the graphs.  The results from the scale-free analyses showed no strict power-laws. Nevertheless, the classes’ relationships and attributes, and the betweenness in the schema graphs were long-tailed distributed. Furthermore, the schema graphs had small-world properties, and the analysed class and schema graphs were robust against errors but fragile against attacks. In a network structure perspective, these results indicate that false updates on random tables of a database should usually do little harm, but falsely updating the most central cells or tables may cause big damage. Consequently, it may be necessary to monitor and constrain sensitive cells and tables in order to protect them from attacks

Smart cards are small, portable, tamper-resistant computers used in security-sensitive applications ranging from identification and access control to payment systems. Side-channel attacks, which use clues from timing, power consumption, or even electromagnetic (EM) signals, can compromise the security of these devices and have been an active research area since 1996. Newer ``contactless'' cards communicate using radio frequency (RF), without physical contact. These contactless smart cards are sometimes grouped with radio frequency identification (RFID) devices in popular usage of the term. This thesis investigates devices that use the ISO 14443 (proximity card) protocol, a large class of contactless/RFID devices. Although contactless smart cards are increasingly common, very few reproducible practical attacks have been published. Presently, there are no known documented side-channel attacks against contactless Java Cards (open standard multi-application cards) using generic unmodified hardware. This thesis develops a research-friendly platform for investigating side-channel attacks on ISO 14443 contactless smart cards. New techniques for measurement and analysis, as well as the first fully documented EM side-channel monitoring procedure, are presented for a contactless Java Card. These techniques use unmodified, commercial off-the-shelf hardware and are both practical and broadly applicable to a wide range of ISO 14443 devices, including many payment cards and electronic passports.

In this essay i argue that there are three different variables that may be able to control the outcome of certain foreign policy choices. These three variables are External Threats, government division and public opinion. The Essay also tries to identify former president Bush motives behind the 2003 Iraqi War. It is partly argued that the three variables had a certain amount of influence on Bush decision making process. But the main focus lies on the motives behind the attack. There are several official motives identifies through different types of statements from different members of the elite group, the main motives being the threat that the Bush administration felt the former Iraqi president Saddam Hussein was responsible for and of course weapons of mass destruction, as you will notice while you read this essay there are more but in some way smaller motives that doesn't take as much place as the threat and WMD aspects.

The threat of malicious Internet activities such as Distributed Denial of Service (DDoS) attacks, spam emails or Internet worms/viruses has been increasing in the last several years. The impact and frequency of these malicious activities are expected to grow unless they are properly addressed. In this thesis, we propose to design and evaluate a set of practical and effective protection measures against potential malicious activities in current and future networks. Our research objective is twofold. First, we design the methods to defend against DDoS attacks. Our research focuses on two important issues related to DDoS attack defense mechanisms. One issue is the method to trace the sources of attacking packets, which is known as IP traceback. We propose a novel packet logging based (i.e., hash-based) traceback scheme using only a one-bit marking field in IP header. It reduces processing and storage cost by an order of magnitude than the existing hash-based schemes, and is therefore scalable to much higher link speed (e.g., OC-768). Next, we propose an improved traceback scheme with lower storage overhead by using more marking space in IP header. Another issue in DDoS defense is to investigate protocol-independent techniques for improving the throughput of legitimate traffic during DDoS attacks. We propose a novel technique that can effectively filter out the majority of DDoS traffic, thus improving the overall throughput of the legitimate traffic. Second, we investigate the problem of distributed network monitoring. We propose a set of novel distributed data streaming algorithms that allow scalable and efficient monitoring of aggregated traffic. Our algorithms target the specific network monitoring problem of finding common content in traffic traversing several nodes/links across the Internet. These algorithms find applications in network-wide intrusion detection, early warning for fast propagating worms, and detection of hot objects and spam traffic.

Wireless sensor networks (WSNs) have been widely used in many areas, such as early earthquake monitoring, building structure monitoring, and military surveillance. In this thesis, we focus on the wireless sensor network deployed in the battlefield, using random key predistribution scheme. Firstly we presented an analysis of the security impacts by node capture attack. Also, based on the node cloning attack, we proposed a new attack scheme, called compromised key redistribution attack, and discussed related attack scenarios. Besides, we have found out and conjectured that, when the overlapping factor of compromised key set is larger than 0.05, it is very possible (almost 90%) that the number of distinct compromised keys is 10.5% of the original key pool. This conjecture helps the adversary estimate the approximated size of original key pool by calculating the overlapping factor, thus calculate the probability that malicious nodes successfully establish connections with legitimate nodes.

With the dramatic expansion of computers and communication networks, computer crimes, such as threatening letters, fraud, and theft of intellectual property have been growing at a dreadful rate. The increasing frequency of malicious computer attacks on government agencies and Internet businesses has caused severe economic waste and unique social threats. The problems of protecting data and information on computers and communication networks has become even more critical and challenging, since the widespread adoption of the Internet and the Web. Consequently, it is very urgent to design an integrated network-security architecture so as to make information safer, proactively or reactively defeat any network attack, make attackers accountable, and help the law enforcement system to collect the forensic evidences. Among a variety of attacks on computer servers or communication networks, a prevalent, famous, and serious network-security subject is known as "Denial of Service" (DoS) or "Distributed Denial of Service" (DDoS) attacks. According to an investigation on computer crime conducted by CSI/FBI in 2003, Internet DoS/DDoS have increased in frequency, severity, and sophistication, and have caught international attentions to the vulnerability of the Internet. DoS/DDoS attacks consume the resources of a remote host or network, thereby denying or degrading service to legitimate users. Such attacks are among the hardest security problems to address because they are simple to implement, difficult to prevent, and very difficult to trace. Therefore, this dissertation will firstly concentrate on how to resolve these troublesome DoS/DDoS problems. This is considered as the first step to overcome generic network security problems, and to achieve the final goal for accomplishing a total solution of network security. Instead of tolerating DoS/DDoS attacks by mitigating their effect, to trace back the attacking source for eliminating the attacker is an aggressive and better approach. However, it is difficult to find out the true attacking origin by utilizing the incorrect source IP address faked by the attacker. Accordingly, this dissertation will aim at conquering this representative network security problem, i.e. DoS/DDoS attacks, with IP traceback, and designing an optimal IP traceback. IP traceback ¡X the ability to trace IP packets to their origins¡Xis a significant step toward identifying, and thus stopping, attackers. A promising solution to the IP traceback is probabilistic packet marking (PPM). This traceback approach can be applied during or after an attack, and it does not require any additional network traffic, router storage, or packet size increase. Therefore, the IP traceback research on countering DoS/DDoS attacks will be based on PPM scheme. In this dissertation, three outstanding improvements among four PPM criteria¡Xthe convergency, the computational overhead, and the incomplete PPM deployment problem¡Xhas been achieved. PPM-NPC is proposed to improve the PPM convergency and computational overhead. With non-preemptively compensation, the probability of each marked packet arrived at the victim equals its original marking probability. Therefore, PPM-NPC will efficiently achieve the optimal convergent situation by simply utilizing a 2-byte integer counter. Another better scheme, CPPM, is also proposed, such that the marked packets can be fully compensated as well while they are remarked. With CPPM, the probability of each marked packet arrived at the victim will also equal its original marking probability. Consequently, CPPM will achieve the optimal convergent situation efficiently as well. Furthermore, RPPM-NPC is presented to advance the accuracy of a reconstructed path in an incomplete PPM deployment environment by correcting and recovering any discontinuous individual transparent router and any segment of consecutive double transparent routers. This scheme may also reduce the deployment overhead without requiring the participation of all routers on the attack path. Except for these improved criteria, PPM robustness, some weak assumptions in PPM, and a few unsolved problems for PPM, e.g. reflective DDoS attacks, will also be improved in the future. It is also interesting in combining other network security researches, such as IDS, system access control mechanism, etc., for constructing a more complete network security architecture. Therefore, this research hereby is done in order to completely resolve the troublesome flood-style DoS/DDoS problems, and as the basis for accomplishing a total solution of network security.

Denial of Service (DoS) attacks aim at rendering a computer or network incapable of providing normal services by exploiting bugs or holes of system programs or network communication protocols. Existing DoS attack defense mechanisms (e.g., firewalls, intrusion detection systems, intrusion prevention systems) typically rely on data gathered from gateways of network systems. Because these data are IP-layer or above packet information, existing defense mechanisms are incapable of detecting internal attacks or attackers who disguise themselves by spoofing the source IP addresses of their packets. To address the aforementioned limitations of existing DoS attack defense mechanisms, we propose a classification-based DoS attack detection technique on the basis of the SNMP MIB II data from the network interface to induce a DoS detection model from a set of training examples that consist of both normal and attack traffic data). The constructed DoS detection model is then used for predicting whether a network traffic from the network interface is a DoS attack. To empirically evaluate our proposed classification-based DoS attack detection technique, we collect, with various traffic aggregation intervals (including 1, 3, and 5 minutes), normal network traffic data from two different environments (including an enterprise network, and a university campus network) and attack network traffics (including TCP SYN Flood, Land, Fake Ping, and Angry Ping) from an independent experimental network. Our empirical evaluation results show that the detection accuracy of the proposed technique reaches 98.59% or above in the two network environments. The evaluation results also suggest that the proposed technique is insensitive to the traffic aggregation intervals examined and has a high distinguishing power for the four types of DoS attacks under investigation.