Diminishing Signaling Traffic for Authentication in Mobile Communication System

To identify a mobile station (MS) and validate legal service requests, authentication functions are utilized in the location registration, call origination and call termination procedures. In GSM, the VLR requests the HLR for assistance in authenticating the visiting user. The authentication center (AuC) in the home network generates 3-tuples and sends them back to the VLR for subsequent authentications during the user’s residence. If these 3-tuples are used up before the MS’s leaving, another request is issued by the VLR. The request is expensive, because it needs to access the HLR/AuC. Traditionally, a fixed-K strategy is used. That is, K 3-tuples are sent to the VLR for each request. Lager K is preferred to reduce the number of the expensive requests for 3-tuples. However, much waste of 3-tuples is observed, especially when an inactive user is considered. Hence, K value should be determined based on the usage pattern of the user. We propose a dynamic-K (DK) strategy to reduce the waste and diminish the signaling traffic for authentication. Simulation results show that the DK strategy can effectively determine the appropriate K value. Not only the waste but also the number of requests are diminished efficiently

Albumin fibrillization induces apoptosis via integrin/FAK/Akt pathway

[[abstract]]Background: Numerous proteins can be converted to amyloid-like fibrils to increase cytotoxicity and induce apoptosis, but the methods generally require a high concentration of protein, vigorous shaking, or fibril seed. As well, the detailed mechanism of the cytotoxic effects is not well characterized. In this study, we have developed a novel process to convert native proteins into the fibrillar form. We used globular bovine serum albumin (BSA) as a model protein to verify the properties of the fibrillar protein, investigated its cellular effects and studied the signaling cascade induced by the fibrillar protein. Results: We induced BSA, a non-cytotoxic globular protein, to become fibril by a novel process involving Superdex-200 column chromatography in the presence of anionic or zwittergenic detergent(s). The column pore size was more important than column matrix composite in fibril formation. The fibrillar BSA induced apoptosis in BHK-21 cell as well as breast cancer cell line T47D. Pre-treating cells with anti-integrin antibodies blocked the apoptotic effect. Fibrillar BSA, but not globular BSA, bound to integrin, dephosphorylated focal adhesion kinase (FAK), Akt and glycogen synthase kinase-3β (GSK-3β). Conclusion: We report on a novel process for converting globular proteins into fibrillar form to cause apoptosis by modulating the integrin/FAK/Akt/GSK-3β/caspase-3 signaling pathway. Our findings may be useful for understanding the pathogenesis of amyloid-like fibrils and applicable for the development of better therapeutic agents that target the underlying mechanism(s) of the etiologic agents. ? 2009 Huang et al; licensee BioMed Central Ltd

Mitigating Routing Misbehavior Using Ant-Tabu-Based Routing Algorithm for Wireless Ad-Hoc

Summary Routing is a key factor in the design of modern communication networks, especially in wireless ad-hoc networks (WANs). In WANs, both selfish and malicious nodes are misbehaving nodes and cause severely routing and security problems. Selfish nodes may drop routing and data packets and malicious nodes may redirect the packets to another routing path or launch denial-of-service (DoS) attacks. In this paper, an efficient routing algorithm is proposed, Ant-Tabu-Based Routing Algorithm (ATBRA), to mitigate selfish problem and reduce routing overheads. In ATBRA, both the concepts of ant-based routing algorithm and Tabu search are applied. We compare the performance of the proposed scheme with that of DSR in terms of two performance metrics: successful delivery rate (SDR) and routing overhead (RO). By comparisons, we notice that the proposed algorithm outperforms DSR in all two categories. The simulation results also indicate that the proposed algorithm is more efficient than DSR

Combustion Synthesis of Mullite/Metal Boride Composites

Formation of composite materials composed of mullite (3Al2O3×2SiO2) and transition metal borides (NbB2 and TaB2) was studied by self-propagating high-temperature synthesis (SHS). Starting materials included not only metal oxides (Nb2O5 and Ta2O5) and boron oxide (B2O3) as the sources of metallic elements and boron, but also Al and Si powders as the reducing agents. The evolution of mullite from in situ formed SiO2 and Al2O3 and synthesis of NbB2 and TaB2 were investigated. The effect of excess Si addition was studied on the combustion temperature, flame-front propagation velocity, and phase composition of the final product. For formation of the NbB2/mullite composites, the combustion velocity about 2.5 mm/s and reaction temperature around 1500 oC decreased slightly as the Si content increased. However, a considerable decrease in combustion front velocity from 2.74 to 1.43 mm/s and in reaction temperature from 1600 to 1250 oC was observed for the production of the TaB2/mullite composites. The XRD patterns of the final products confirmed the role of excess Si in the improvement of silicothermic reduction of B2O3 and subsequent evolution of NbB2, TaB2, and mullite. The EDS analysis indicated an atomic proportion close to that of 3Al2O3×2SiO2 for the mullite grains synthesized in this study

HPV infection and p53 inactivation in pterygium

PurposeOur recent report indicated that tumor suppressor gene (p53) mutations and protein aberrant expression were detected in pterygium. Inactivation of p53 by Human papillomavirus (HPV) 16/18 E6 plays a crucial role in cervical tumorigenesis. In this study, we further speculate that p53 inactivation may be linked with HPV infection in pterygium pathogenesis. To investigate the involvement of HPV 16/18 E6 in p53 inactivation in pterygium, the association between HPV 16 or HPV 18 infection, the HPV E6 oncoprotein, and p53 protein expression was analyzed in this study.MethodsHPV 16/18 infection was detected by nested-polymerase chain reaction (nested-PCR), the p53 mutation was detected by direct sequencing, and the p53 and the HPV 16/18 E6 proteins were studied using immunohistochemistry on 129 pterygial specimens and 20 normal conjunctivas.ResultsThe HPV 16/18 was detected in 24% of the pterygium tissues (31 of 129) but not in the normal conjunctiva, and the HPV16/18 E6 oncoprotein was detected in 48.3% of HPV 16/18 DNA-positive pterygium tissues (15 of 31). In addition, p53 protein negative expression in pterygium was correlated with HPV16/18 E6 oncoprotein expression but not with a p53 mutation.ConclusionsHPV 16/18 E6 contributes to HPV-mediated pterygium pathogenesis as it is partly involved in p53 inactivation and is expressed in HPV DNA-positive pterygium

Lasing on nonlinear localized waves in curved geometry

The use of geometrical constraints opens many new perspectives in photonics and in fundamental studies of nonlinear waves. By implementing surface structures in vertical cavity surface emitting lasers as manifolds for curved space, we experimentally study the impacts of geometrical constraints on nonlinear wave localization. We observe localized waves pinned to the maximal curvature in an elliptical-ring, and confirm the reduction in the localization length of waves by measuring near and far field patterns, as well as the corresponding dispersion relation. Theoretically, analyses based on a dissipative model with a parabola curve give good agreement remarkably to experimental measurement on the transition from delocalized to localized waves. The introduction of curved geometry allows to control and design lasing modes in the nonlinear regime.Comment: 6 pages, 6 figure