1,721,129 research outputs found
Amyloidogenesis in its biological environment: challenging a fundamental issue in protein misfolding diseases.
Full text linkThe inability of a protein to adopt its native and soluble conformation (protein misfolding) is the origin of an increasing number of human diseases. The misfolding of a protein is often associated with its assembly into extracellular fibrillar aggregates, commonly termed amyloid fibrils. Despite the many efforts expended to characterise amyloid formation in vitro, it is increasingly evident that the biological environment in which aggregation occurs naturally influences the mechanism and rate of the process, as well as the structure and stability of the resulting fibrils. This problem is not trivial because of the inherent complexity of biology and difficulty to design proper experiments able to address the molecular level of the phenomenon in vivo. We will show successful approaches that have been used recently and will illustrate some of the results that have contributed to elucidate important structural aspects of amyloid formation in vivo
Un metodo di calibrazione di divisori di tensione induttiva per confronto e lettura diretta
No full textFast distributed bi-directional authentication for wireless sensor networks
No full textIn this paper, we present the comparison between a distributed and a centralized authentication protocol for wireless sensor networks (WSN). We outline the difference between authentication and key-agreement schemes and we propose a novel approach based on the use of polynomial functions to produce a distributed bi-directional authentication. The advantages of this approach are: speed of operation that can allow multiple subsequent authentications, thus support to mobility; balanced energy consumption if compared with the imbalanced centralized approach and the prevention of partition attac
QoS provisioning in GEO satellite with onboard processing using predictor algorithms
No full textRecently, IP satellite networks have attracted considerable interest as a technology to deliver high-bandwidth IP-based multimedia services to nationwide areas. In particular, IP satellite networks seem to be one of the most promising technologies for connecting users in rural areas, where a wired high-speed network (e.g., xDSL) is not foreseen to be used. However, one of the main problems arising here is to guarantee specific quality of service constraints in order to have good performance for each traffic class. Among various QoS approaches used in the Internet, recently the DiffServ technique has become the most promising solution, mainly for its scalability with respect to the IntServ approach. Moreover, in satellite communication systems, DiffServ computational capabilities are placed at the edge points, reducing the implementation complexity of the satellite onboard equipment. This article deals with the problem of QPS provisioning for packet traffic by considering some resource allocation schemes, including bandwidth allocation techniques and priority-driven onboard switching algorithms. As to the first aim, the proposed technique takes advantage of proper statistical traffic modeling to predict future bandwidth requests. This approach,takes into consideration DiffServ-based traffic management to guarantee QoS priority among different users. Moreover, the satellite onboard switching problem has been addressed by considering a suitable implementation of the DiffServ policy based on a cellular neural network
Lichen biomonitoring of trace metals in the Pistoia area (central northern Italy)
No full textThe epiphytic lichen Parmelia caperata (L.) Ach. was used as bioaccumulator of the heavy metals Cd, Cr, Cu, Hg, Ni, Pb and Zn in the environs of the town of Pistoia (central northern Italy). The concentrations of Cd, Cr, Ni, Hg and Pb were comparable with those found in areas not subject to atmospheric pollution. Copper and especially Zn were found in rather high concentrations. Fertilizers and pesticides were the main source of atmospheric contamination
Characterizing intermolecular interactions that initiate native-like protein aggregation
No full textFolded proteins can access aggregation-prone states without the need for transitions that cross the energy barriers for unfolding. In this study we characterized the initial steps of aggregation from a native-like state of the acylphosphatase from Sulfolobus solfataricus (Sso AcP). Using computer simulations restrained by experimental hydrogen/deuterium (H/D) exchange data, we provide direct evidence that under aggregation-promoting conditions Sso AcP populates a conformational ensemble in which native-like structure is retained throughout the sequence in the absence of local unfolding (N), although the protein exhibits an increase in hydrodynamic radius and dynamics. This transition leads an edge strand to experience an increased affinity for a specific unfolded segment of the protein. Direct measurements by means of H/D exchange rates, isothermal titration calorimetry, and intermolecular relaxation enhancements show that after formation of N, an intermolecular interaction with an antiparallel arrangement is established between the edge strand and the unfolded segment of the protein. However, under conditions that favor the fully native state of Sso AcP, such an interaction is not established. Thus, these results reveal a novel (to our knowledge) self-assembly mechanism for a folded protein that is based on the increased flexibility of highly aggregation-prone segments in the absence of local unfolding. © 2012 Biophysical Society
Effect of buffers and solvents on the structure and aggregation of the Sulfolobus solfataricus acrylphosfhatase.
No full textVirtual Functions Placement with Time Constraints in Fog Computing: a Matching Theory Perspective
Full text linkThis paper proposes two virtual function (VFs) placement approaches in a Fog domain. The considered solutions formulate a matching game with externalities, aiming at minimizing both the worst application completion time and the number of applications in outage, i.e., the number of applications with an overall completion time greater than a given deadline. The first proposed matching game is established between the VFs set and the Fog Nodes (FNs) set by taking into account the ordered sequence of services (i.e., chain) requested by each application. Conversely, the second proposed method overlooks the applications service chain structure in formulating the VF placement problem, with the aim at lowering the computation complexity without loosing the performance. Furthermore, in order to complete our analysis, the stability of the reached matchings has been theoretically proved for both the proposed solutions. Finally, performance comparisons of the proposed MT approaches with different alternatives are provided to highlight the superior performance of the proposed methods
Performance evaluation of a virtual queuing - channel allocation scheme for microcellular networks
No full textThis paper deals with the performance evaluation of a novel distributed channel allocation scheme that attains a high resource reuse in cellular networks. A suitable interference model has been envisaged. Resources are nominally assigned to cells with Fixed Channel Allocation (FCA), according to a given reuse distance. Whenever a channel demand from a mobile user does not find a free nominal resource in a cell, a channel is temporarily borrowed violating the reuse distance constraint, provided that the co-channel interference level is acceptable. As soon as a nominal channel becomes available in this cell, the borrowed resource is released (virtual queuing). The performance of the proposed channel allocation scheme has been evaluated considering both uniform and non-uniform traffic patterns. A performance analysis approach has been also developed and validated by simulations. Comparisons with the classical FCA scheme and other dynamic and borrowing channel allocation strategies have permitted to highlight the good performance of the proposed technique
An efficient DiffServ switch for satellite communication systems based on cellular neural networks
No full textQuality of Sendee (QoS) has become an important topic in modern telecommunication network in order to guarantee multimedia traffic. In IP networks, DiffServ seems to be the best approach to satisfy QoS constraints, due to its end-to-end philosophy. Actual trend is to consider satellite on-board switching capabilities for managing multibeam input and output. In this paper, for reducing computational complexity, a Cellular Neural Network (CNN) has been proposed for the on-board switching problem; several traffic classes have been considered and switching algorithm has been implemented within a CNN taking into account their priority, queue length and time spent inside queues. Numerical results shows performance similar to optimal switching solution, but with a higher flexibility due to neural techniques. Simulation results have been driven with memoryless distribution and heavy-tailed distribution for several input buffer size and switch dimension
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