160,019 research outputs found
Severe cytomegalovirus gastritis during natalizumab-mediated immunosuppression
We report a 35-year-old female receiving natalizumab as monotherapy for multiple sclerosis who subsequently developed severe cytomegalovirus gastritis. As cytomegalovirus gastritis has not been previously described during natalizumab treatment, we discuss the biological plausibility of this potential association and avenues for further study
Supersymmetry and the Systematics of T-duality Rotations in Type-II Superstring Theories
We describe a systematic method of studying the action of the T-duality group
O(d,d) on space-time fermions and R-R field strengths and potentials in type-II
string theories, based on space-time supersymmetry. The formalism is then used
to show that the couplings of non-Abelian D-brane charges to R-R potentials can
be described by an appropriate Clifford multiplication.Comment: 6 pages, LaTeX, uses espcrc2.sty; Contribution to the proceedings of
the D. V. Volkov memorial conference on ``Supersymmetry and Quantum Field
Theory'', Kharkov, July 25-29, 2000 (to appear in the Nucl. Phys. B
Conference Supplements
Acceptance and usage of webcasting among users of selected cyber cafes in Klang Valley
The Malaysian public now has access to the Internet not only at home and the workplace, but also at cyber cafés. This study aims to examine the level of acceptance of webcasting among users of selected cyber cafés in the Klang Valley. The specific objectives of the study are: to determine the profile of webcasting users and its usage; to determine the types of webcasting technology most frequently used, level of knowledge of webcasting and the main source of knowledge in becoming aware of webcasting; to determine the acceptance of webcasting among non-users of webcasting; and to determine the relationship between behavioral intention to use and the actual usage of webcasting among users of webcasting. This study used the survey design, using purposive sampling to select the cyber cafés and visitors of these cafés. The findings indicate that usage of webcasting is still relatively low among users of selected cyber cafés in the Klang Valley. Users of webcasting were found to be mostly male, young and relatively well educated with at least a diploma as the highest level of education obtained
On Partially Massless Bimetric Gravity
We extend the notion of the Higuchi bound and partial masslessness to
ghost-free nonlinear bimetric theories. This can be achieved in a simple way by
first considering linear massive spin-2 perturbations around maximally
symmetric background solutions, for which the linear gauge symmetry at the
Higuchi bound is easily identified. Then, requiring consistency between an
appropriate subset of these transformations and the dynamical nature of the
backgrounds, fixes all but one parameter in the bimetric interaction potential.
This specifies the theory up to the value of the Fierz-Pauli mass and leads to
the unique candidate for nonlinear partially massless bimetric theory.Comment: Latex, 11 pages; references added, discussion extended; matches
published versio
Performance Modelling and Optimisation of Multi-hop Networks
A major challenge in the design of large-scale networks is to predict and optimise the
total time and energy consumption required to deliver a packet from a source node to a
destination node. Examples of such complex networks include wireless ad hoc and sensor
networks which need to deal with the effects of node mobility, routing inaccuracies, higher
packet loss rates, limited or time-varying effective bandwidth, energy constraints, and the
computational limitations of the nodes. They also include more reliable communication
environments, such as wired networks, that are susceptible to random failures, security
threats and malicious behaviours which compromise their quality of service (QoS) guarantees.
In such networks, packets traverse a number of hops that cannot be determined
in advance and encounter non-homogeneous network conditions that have been largely
ignored in the literature. This thesis examines analytical properties of packet travel in
large networks and investigates the implications of some packet coding techniques on both
QoS and resource utilisation.
Specifically, we use a mixed jump and diffusion model to represent packet traversal
through large networks. The model accounts for network non-homogeneity regarding
routing and the loss rate that a packet experiences as it passes successive segments of a
source to destination route. A mixed analytical-numerical method is developed to compute
the average packet travel time and the energy it consumes. The model is able to capture
the effects of increased loss rate in areas remote from the source and destination, variable
rate of advancement towards destination over the route, as well as of defending against
malicious packets within a certain distance from the destination. We then consider sending
multiple coded packets that follow independent paths to the destination node so as to
mitigate the effects of losses and routing inaccuracies. We study a homogeneous medium
and obtain the time-dependent properties of the packet’s travel process, allowing us to
compare the merits and limitations of coding, both in terms of delivery times and energy
efficiency. Finally, we propose models that can assist in the analysis and optimisation
of the performance of inter-flow network coding (NC). We analyse two queueing models
for a router that carries out NC, in addition to its standard packet routing function. The
approach is extended to the study of multiple hops, which leads to an optimisation problem
that characterises the optimal time that packets should be held back in a router, waiting
for coding opportunities to arise, so that the total packet end-to-end delay is minimised
Regenerative and Adaptive schemes Based on Network Coding for Wireless Relay Network
Recent technological advances in wireless communications offer new
opportunities and challenges for relay network.To enhance system performance,
Demodulate-Network Coding (Dm-NC) scheme has been examined at relay node; it
works directly to De-map the received signals and after that forward the
mixture to the destination. Simulation analysis has been proven that the
performance of Dm-NC has superiority over analog-NC. In addition, the
Quantize-Decode-NC scheme (QDF-NC) has been introduced. The presented
simulation results clearly provide that the QDF-NC perform better than
analog-NC. The toggle between analogNC and QDF-NC is simulated in order to
investigate delay and power consumption reduction at relay node.Comment: 11 pages, 8 figures, International Journal of Computer Networks &
Communications (IJCNC), Vol.4, No.3, May 201
Implementation and self-checking of different adder circuits
The function of addition in arithmetic unit that can be used in complement operations, encoding and decoding [1]. It can be implemented in different arrangement or using different basic logic gates with different bits and become different type of adders. Basically, all types of the complex adder circuits are made up from the simple adder circuits (or called basic building blocks of adder) like half adder and full adder
Effective CAL: Theory and practice
This paper looks at the creation of CAL material in theory and practice through the perspective of a CAL development unit, the Hypertext Support Unit at the University of Kent. With similar units now in place in other institutions, the production of CAL is taking place at a rapid pace, often with the evaluation of the applications disproportionately lagging behind. This inevitably raises questions of whether what we are producing is effective CAL, and what approaches should be taken to use the potential of multimedia in a learning environment
- …