1,354,690 research outputs found
Pharmacogenomics of ABC transporters and its role in cancer chemotherapy
No full textATP-binding cassette (ABC) genes play a role in the resistance of malignant cells to anticancer agents. The ABC gene products, including ABCB1 (P-glycoprotein), ABCC1 (MRP1), ABCC2 (MRP2, cMOAT), and ABCG2 (BCRP, MXR, ABCP) are also known to influence oral absorption and disposition of a wide variety of drugs. As a result, the expression levels of these proteins in humans have important consequences for an individual's susceptibility to certain drug-induced side effects, interactions, and treatment efficacy. Naturally occurring variants in ABC transporter genes have been identified that might affect the function and expression of the protein. This review focuses on recent advances in the pharmacogenomics of ABC transporters, and discusses potential implications of genetic variants for the chemotherapeutic treatment of cancer
Performance evaluation of a mobile communication system implementing the dual-signal receiver
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Handover on a Highway LAN
No full textHighway Local Area Networks (LANs) require small cell sizes in order to meet the demands for increased capacity which is induced by the large number of users in small areas. As smaller cells are deployed, the number of cell boundary crossings increases. Furthermore, the high velocities of the vehicles moving in a highway result in an increase in the frequency of cell boundary crossings. As a result, handover, defined as the mechanism that transfers an ongoing call from one cell to another as a user moves through the coverage area of the cellular system, will play a very important role in the design and the performance of the highway LAN. This report presents a general overview of handover mechanisms and proposes ways of applying handover on a highway LAN according to the network’s specific characteristics. In order to implement handover in a highway LAN, the modelling of the vehicle distribution and the radiowave propagation effects have been analyzed: The shifted negative exponential distribution can model both the spacing between the vehicles and the distance between the antenna of the base station and the nearest vehicle. The propagation environment is characterized by the path-loss attenuation, the Rice fading and the oxygen absorption (which has been ignored for the needs of this report). The phenomenon of shadowing has been neglected. A general overview of the handover mechanism, i.e. the goals of the handover procedure, performance metrics commonly used to evaluate handover algorithms, and the stages which constitute the procedure of handover, is presented. Handover mechanisms as applied in GSM and DECT have been investigated as examples of applied handover techniques. The issue of handover has not been addressed in the IEEE 802.11 and the HIPERLAN standards. Specific aspects of handover implied by the characteristics of the highway LAN have been examined. The propagation environment of a highway’s cell of 200 m. has been simulated using an exponential smoothing process. The averaging process has provided considerably accurate results and the crossover point can be adequately approximated. An absolute signal strength with velocity adjustable threshold algorithm is recommended for the handover decision procedure. The threshold levels are dynamically adjusted according to the velocity of each vehicle, that is, the higher the velocity of the vehicle is, the higher is the threshold value set. The Signal Prediction Priority Queuing (SPPQ) method is analyzed and proposed, in order to provide the optimum order in the execution of the handovers. A multicast-based handover scheme, known as sub-group buffering scheme, can be adopted in order to accomplish seamless communication service. Any numerical results obtained can not be used for the precise calculation of the parameters involved in the handover procedure, due to various arbitrary assumptions and simplifications. The propagation model still needs to be verified through actual measurements. However, the basic aspects of the handover mechanism have been extensively presented and the various approaches and proposed schemes could form the basis of the handover procedure to be implemented on a highway LAN.Electrical Engineering, Mathematics and Computer ScienceTelecommunicatie- en Verkeersbegeleidingssysteme
Performance Aspects of Introducing ARP in a GSM/GPRS Radio Network
No full textThe telecommunications market is nowadays driven by two trends: growing data traffic and increasing mobility. The expected growth of mobile data traffic requires a wireless ubiquitous data network. Unfortunately, the GSM network is less suitable for data. Connection set-up times are too long, the transmission speed of 9,6 kb/s is too low and the circuit switched GSM network is inefficient for bursty data traffic). The General Packet Radio Service (GPRS) system solves these problems to a certain extent. GPRS provides the GSM network with a parallel packet-switched data network that can deal with bursty traffic. Packet switching makes it possible to bill the actual data traffic. Moreover, the use of packet switching enables a short access time. GPRS increases the transmission speed up to a maximum gross bit rate of 171,2 kb/s. Another issue in GSM networks is the introduction of Dynamic Channel Assignment (DCA), to replace the currently used Fixed Channel Assignment (FCA). FCA results in an inefficient and inflexible fixed frequency-cell relation. DCA algorithms though, do not have such a pre-planned channel-cell relation, or at least they have the capability to adapt it as the offered traffic changes. This report focuses on the introduction of DCA in a combined voice and data radio network. Only Autonomous Reuse Partitioning (ARP) will be considered, as a specific class of DCA algorithms, in comparison with FCA. Both aggressive and conditional ARP will be investigated. Most important performance measures are the blocking and dropping probabilities. A theoretical FCAmodel for systems with two independent classes of negative exponential traffic is presented in this report, where one class has priority over the other. The model has also been extended to the case where resources have been reserved for the low priority class. Simulation results will be presented for a linear cellular network model closed in a loop, in which voice traffic has priority over data. Both voice and data traffic have been modelled as Poisson processes where service times are negative exponentially distributed. Simulations have been run for adaptations of FCA, aggressive ARP and conditional ARP. The applied traffic pattern will vary in time and per cell. FCA is shown to perform reasonably for the voice traffic in terms of blocking and dropping probability for constant loads. However, it cannot deal with the extra GPRS traffic. It performs worse for voice traffic too, when the voice traffic load becomes heavier. The implemented aggressive ARP algorithm will be shown to perform well in terms of both voice and GPRS call blocking probability. Unfortunately, the aggressive ARP algorithm causes over 20% of the voice calls to drop, which makes aggressive ARP an unattractive option to support GPRS in a GSM network. This report shows that conditional ARP performs outstanding in terms of voice and data call blocking and dropping probabilities. Therefore, it seems an ideal candidate to implement DCA for a combined GSM/GPRS radio network. It releases capacity for GPRS traffic and deals better with changing traffic loads.Applied SciencesElectrical EngineeringTelecommunications and Traffic Control Systems laborator
Variations on the Author
No full text“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Mathematical model for the performance measures of Dynamic Channel Selection in a bounded DECT system
No full textDECT is an ETSI standard for digital wireless communications, and uses a Dynamic Channel Selection algorithm for the allocation of channels at run-time. Contrary to Fixed Channel Allocation, where the channels are allocated according to location, the channels are allocated according to channel quality at the time of use. A previous study was made on a mathematical model for an infinite area using Dynamic Channel Selection as defined in the DECT standard. This model was used to make a model for areas of limited size, in order to calculate with boundary effects. Channel availability, desired signal power and interfering signal power has been calculated, as well as call blocking probabilities. The results were compared to results from previous models and simulations.Applied SciencesElectrical EngineeringTelecommunications and Traffic Control Systems Grou
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Association of a CYP17 polymorphism with overall survival in Caucasian patients with androgen-independent prostate cancer
No full textOBJECTIVES:
To investigate the association between a cytochrome P450 17alpha-hydroxylase gene (CYP17) polymorphism and survival in Caucasian patients with androgen-independent prostate cancer (AIPC).
METHODS:
The study used 222 samples acquired from Caucasian patients with AIPC. The CYP17 polymorphism (-34T>C) was analyzed using polymerase chain reaction amplification followed by restriction fragment length polymorphism detection.
RESULTS:
No significant differences were observed in the frequencies of the CYP17 genotype in relation to categorized Gleason scores, age at diagnosis, or hormone therapy. The median survival was significantly longer in 126 patients with the CYP17 A2 allele (8.9 years) genotype than in 96 patients with the A1 allele (6.7 years) genotype (P = 0.040 by log-rank test). Similarly, the estimated survival probability at 10 years (24% in A1 allele versus 43% in A2 allele) showed a statistically significant difference between the two groups (P = 0.002 by the permutation test).
CONCLUSIONS:
These results suggest that the CYP17 polymorphism is associated with overall survival in patients with AIPC
A rare case of adult rhabdomyosarcoma
No full textBACKGROUND: Rhabdomyosarcoma is a rare, soft tissue malignancy, diagnosed particularly in adults. It commonly metastasizes to the bone marrow. We present a rare case of an adult rhabdomyosarcoma which illustrates the importance of magnetic resonance imaging in identifying early changes in the internal bone structure. CASE REPORT: A 50-year-old male presented with acute urinary retention. The patient initially had a CT scan of the lumbar spine which only revealed a protrusion of the L5-S1 intervertebral disc and no apparent cause for the patient's symptoms. One week later, an MRI was performed which showed extensive bone marrow metastases throughout the lumbar spine and a soft tissue mass in the lower sacral region. The bony metastases were not evident on the CT scan and the soft tissue mass was out of the coverage area of the CT. Subsequent biopsy of the soft tissue mass was performed and histopathology concluded the tissue to be a rhabdomyosarcoma. Unfortunately, the patient died one week after diagnosis. CONCLUSIONS: Although adult rhabdomyosarcomas are very rare, this case highlights the advantage of MRI over CT in identifying early changes in the internal bone structure. Therefore, CT should not be relied upon to exclude bony metastases, particularly in the setting of primary cancer with a known tendency to metastasize to the bone marrow
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