Denial of Service (DoS) in Internet Protocol (IP) Network and Information Centric Network (ICN): An Impediment to Network Quality of Service (QoS).

This paper compares and analyses the Denial-of-Service attacks in the two different Network architectures. The two architectures are based on different routing approaches: Hop-by-Hop IP routing and source-routing using Bloom filters. In Hop-by-Hop IP routing, the packet header contains the address, and the route is decided node by node. Forwarding in this method requires a node to have a routing table which contains the port through which the packet should traverse depending on the address of the destination. Instead in source-routing, the forwarding identifier is encoded with the path a packet should take and it is placed in the packet header. The forwarding identifier in this approach does not require a forwarding table for look ups like the IP routing; it relies on Line Speed Publish/Subscribe (LIPSIN) forwarding solution that focuses on using named links not nodes or interfaces. The forwarding identifier encompasses a set of Link ID’s which specifies the path to the recipient and they are encoded in a Bloom filter. The In-packet Bloom filters serve as both path selectors and as capabilities, and they are generated dynamically. However, this thesis is going to focus on the latter network technology by looking at both its benefits and drawbacks as well as analysing the possibilities of having a Denial of service attack. Keywords: DoS, DDoS, TCP/IP Protocol Suite, ICMP flood, E-mail Bomb, Ping of Death, TCP and UD

Comparative Analysis of QoS Guarantee on IEEE 802.11e and IEEE 802.11g Wireless Local Area Networks

For this project, we propose to compare the 802.11g and the 802.11e Wireless Local Area Networks (WLANs). The 802.11g WLAN standards are good for data applications. However, the 802.11g standard is not well-equipped to deal with the intended delay and bandwidth requirements of multimedia applications, such as video and voice over wireless IP. For this reason, an approved amendment (802.11e) was added to the IEEE 802.11 standard. The 802.11e implements Quality of Service (QoS), which enables features through changes in the Medium Access Control (MAC) layer. The performance of 802.11e will be evaluated using OPNET simulation and compared with the 802.11g WLAN standard.   Keyword: QoS, IEEE 802.11, WLAN, MAC, OPNET, WiFi, CSMA/CA

Qualitative Investigation of the Performance of Real-Time Application of IEEE 802.16e standard WiMAX Relay Networks

The ability of an application to adapt its behavior to changing network conditions depends on the available bandwidth, throughput, delay and packet loss in a network path. These are of major importance in congestion control, streaming applications, quality of service verification, relay selection and many other areas in WiMAX relay stations. Mobile WiMAX, which is based on the IEEE 802.16e standard, provides support for and enables full mobility to users. In an effort to optimize and enhance the overall network throughput, this paper will propose a mobile relay framework. WiMAX is based on the IEEE 802.16e standard, and can support various types of handovers, while allowing for full mobility from the user endpoint. Different methodologies were used to compare different aspects of WiMAX relay stations including throughput, delay, SNR and network load. OPNET modular was used to develop and measure these set of network performance metrics. To accurately measure and evaluate the aforementioned network parameters we employed techniques that were able to process large amounts of data, this aided in provision of much more informed recommendations as to the type of relay station modes that should be installed engender enhanced, improved and optimal Quality of Service (QoS) within the network perimeter. This paper measured the overall network throughput, delay, SNR and network load of relay networks comprising mainly of multimedia applications. Keywords: WiMAX, QoS, Relay Station, Simulation, Topology, Throughput, Delay, Packet Los

Enrolment and Retention of Students in German Language Classes: Influencing School Based Factors in Meru and Tharaka-Nithi Counties, Kenya

German is a language spoken by more than 100 million people as a mother tongue in Europe. It is one of the foreign languages taught and examined in secondary schools in Kenya. German as an optional subject is characterized by low number of students at form four level. The purpose of this study was to investigate school based factors that influence enrolment and retention of students in German language classes in Meru and Tharaka-Nithi Counties in Kenya. The study adapted the descriptive survey research design. Both purposive and random sampling techniques were used to select the respondents. Questionnaires and interview schedule were used. Data was analyzed using frequencies and percentages. The study found out that students’ career orientation, teachers’ teaching methods, teachers’ handling of students’ learning difficulties, students’ performance in German in form one and two, learning resources and prospects of German language influence enrolment and retention of students in German language classes. The findings of this study will provide knowledge in regard to enrolment and retention of students in German language classes and provide a foundation for future studies. Keywords: Enrolment, Retention, School based, factors

Lung Malignancy in Prostate Cancer: a Report of Both Metastatic and Primary Lung Lesions

Prostate cancer is the most common non-cutaneous malignancy diagnosed in men. When it metastasizes, it usually spreads to bone and/or lymph nodes. A handful of cases have described prostatic metastases to the lung; however, this is usually in the setting of existing bone lesions. Here we describe a unique case in which a patient was found to have both metastatic prostate cancer to the lung and a primary lung cancer in the absence of any other evidence of extra-prostatic disease

Measurements of the Neutron Spectrum n the Tevatron Tunnel with Application to the SSC

This is an agreement between Fermilab and the experimenters to carry out an experiment to determine the radiation background in the Tevatron tunnel. The goal will be to determine the spectrum of neutrons in the tunnel while the Tevatron is operating (while gating all effects of the Main Ring ltout U) and for the Main Ring plus Tevatron (no gating). The detectors will also give information on the flux of charged particles near the Tevatron. The purpose is to obtain information on radiation fields in the tunnel in order to estimate possible radiation effects on equipment in such an environment. These data will be useful in desiqning the SSC tunnel and in assessing detector backgrounds. A preliminary description of the experiment is given in a memorandum from J.B. McCaslin to M. Tiqner, dated July 11, 1985, which is attached as Appendix I

Hawking Radiation as Tunneling through the Quantum Horizon

Planck-scale corrections to the black-hole radiation spectrum in the Parikh-Wilczek tunneling framework are calculated. The corrective terms arise from modifications in the expression of the surface gravity in terms of the mass-energy of the black hole-emitted particle system. The form of the new spectrum is discussed together with the possible consequences for the fate of black holes in the late stages of evaporation.Comment: 13 pages; the contents of this paper overlap somewhat with the earlier submissions hep-th/0504188 and gr-qc/0505015; (v2) references added and various cosmetic (but no physics) changes, to appear in JHE

Cardiovascular disease in a cohort exposed to the 1940-45 Channel Islands occupation

BACKGROUND To clarify the nature of the relationship between food deprivation/undernutrition during pre- and postnatal development and cardiovascular disease (CVD) in later life, this study examined the relationship between birth weight (as a marker of prenatal nutrition) and the incidence of hospital admissions for CVD from 1997–2005 amongst 873 Guernsey islanders (born in 1923–1937), 225 of whom had been exposed to food deprivation as children, adolescents or young adults (i.e. postnatal undernutrition) during the 1940–45 German occupation of the Channel Islands, and 648 of whom had left or been evacuated from the islands before the occupation began. METHODS Three sets of Cox regression models were used to investigate (A) the relationship between birth weight and CVD, (B) the relationship between postnatal exposure to the occupation and CVD and (C) any interaction between birth weight, postnatal exposure to the occupation and CVD. These models also tested for any interactions between birth weight and sex, and postnatal exposure to the occupation and parish of residence at birth (as a marker of parish residence during the occupation and related variation in the severity of food deprivation). RESULTS The first set of models (A) found no relationship between birth weight and CVD even after adjustment for potential confounders (hazard ratio (HR) per kg increase in birth weight: 1.12; 95% confidence intervals (CI): 0.70 – 1.78), and there was no significant interaction between birth weight and sex (p = 0.60). The second set of models (B) found a significant relationship between postnatal exposure to the occupation and CVD after adjustment for potential confounders (HR for exposed vs. unexposed group: 2.52; 95% CI: 1.54 – 4.13), as well as a significant interaction between postnatal exposure to the occupation and parish of residence at birth (p = 0.01), such that those born in urban parishes (where food deprivation was worst) had a greater HR for CVD than those born in rural parishes. The third model (C) found no interaction between birth weight and exposure to the occupation (p = 0.43). CONCLUSION These findings suggest that the levels of postnatal undernutrition experienced by children, adolescents and young adults exposed to food deprivation during the 1940–45 occupation of the Channel Islands were a more important determinant of CVD in later life than the levels of prenatal undernutrition experienced in utero prior to the occupatio

Large Nc and Chiral Dynamics

We study the dependence on the number of colors of the leading pi pi scattering amplitude in chiral dynamics. We demonstrate the existence of a critical number of colors for and above which the low energy pi pi scattering amplitude computed from the simple sum of the current algebra and vector meson terms is crossing symmetric and unitary at leading order in a truncated and regularized 1/Nc expansion. The critical number of colors turns out to be Nc=6 and is insensitive to the explicit breaking of chiral symmetry. Below this critical value, an additional state is needed to enforce the unitarity bound; it is a broad one, most likely of "four quark" nature.Comment: RevTeX4, 6 fig., 5 page

Mechanism for a next-to-lowest lying scalar meson nonet

Recent work suggests the existence of a non-conventional lowest-lying scalar nonet containing the a0(980). Then the a0(1450) and also the K0*(1430) are likely candidates to belong to a conventional p-wave $q \bar q$ nonet. However a comparison of their properties with those expected on this basis reveals a number of puzzling features. It is pointed out that these puzzles can be resolved in a natural and robust way by assuming a ``bare'' conventional p-wave scalar $q \bar q$ nonet to mix with a lighter four quark $qq \bar q \bar q$ scalar nonet to form new ``physical'' states. The essential mechanism is driven by the fact that the isospinor is lighter than the isovector in the unmixed $qq \bar q \bar q$ multiplet.Comment: 22 pages, 6 figure