Lightpath fragmentation for efficient spectrum utilization in dynamic elastic optical networks

The spectrum-sliced elastic optical path network (SLICE) architecture has been presented as an efficient solution for flexible bandwidth allocation in optical networks. An homologous problem to the classical Routing and Wavelength Assignment (RWA) arises in such an architecture, called Routing and Spectrum Assignment (RSA). Imposed by current transmission technologies enabling the elastic optical network concept, the spectrum contiguity constraint must be ensured in the RSA problem, meaning that the bandwidth requested by any connection must be allocated over a contiguous portion of the spectrum along the path between source and destination nodes. In a dynamic network scenario, where incoming connections are established and disconnected in a quite random fashion, spectral resources tend to be highly fragmented, preventing the allocation of large contiguous spectrum portions for high data-rate connection requests. As a result, high data-rate connections experience unfairly increased bocking probability in contrast to low data-rate ones. In view of this, the present article proposes a lightpath fragmentation mechanism that makes use of the idle transponders in the source node of a high data-rate connection request to fragment it into multiple low data-rate ones, more easily allocable in the network. Besides, aiming to support such an operation, a light-weight RSA algorithm is also proposed so as to properly allocate the generated lightpath fragments over the spectrum. Benefits of the proposed approach are quantified through extensive simulations, showing drastically reduced high data-rate connection blocking probability compared to a usual contiguous bandwidth allocation, while keeping the performance of low data-rate requests to similar levels.Postprint (author’s final draft

On the benefits of resource disaggregation for virtual data centre provisioning in optical data centres

Virtual Data Centre (VDC) allocation requires the provisioning of both computing and network resources. Their joint provisioning allows for an optimal utilization of the physical Data Centre (DC) infrastructure resources. However, traditional DCs can suffer from computing resource underutilization due to the rigid capacity configurations of the server units, resulting in high computing resource fragmentation across the DC servers. To overcome these limitations, the disaggregated DC paradigm has been recently introduced. Thanks to resource disaggregation, it is possible to allocate the exact amount of resources needed to provision a VDC instance. In this paper, we focus on the static planning of a shared optically interconnected disaggregated DC infrastructure to support a known set of VDC instances to be deployed on top. To this end, we provide optimal and sub-optimal techniques to determine the necessary capacity (both in terms of computing and network resources) required to support the expected set of VDC demands. Next, we quantitatively evaluate the benefits yielded by the disaggregated DC paradigm in front of traditional DC architectures, considering various VDC profiles and Data Centre Network (DCN) topologies.Peer ReviewedPostprint (author's final draft

Extracellular vesicles secretion by Lenvatinib and Sorafenib in HepG2 cells and their effect on cell death and proliferation

Motivation: Sorafenib, which acts on the RAF / MEK / ERK pathways through the inhibition of Raf kinase and different tyrosine kinases (VEGFR2, PDGFR, c-Kit receptors), is the drug currently used as a first-line treatment in hepatocellular carcinomas of advanced stage. It has recently been shown that Lenvatinib, another multi-kinase inhibitor, also improves mean progression-free survival and mean time to cancer progression. This finding motivated us to study the possible antiproliferative effects of Lenvatinib compared to Sorafenib, in addition to the secretion profile of extracellular vesicles in HepG2 cultures due to its recognized role in tumor progression and metastasis.Methods: To determine the percentage of proliferating cells in culture, the incorporation of bromodeoxyuridine (BrdU) was used as a marker, while the analysis of the apoptotic activity was done through a colorimetric test that allows detecting the amount of caspase 3/7 existing in culture. It is well known that there is a connection between apoptosis and autophagy, so we decided to study the changes that occurred in the latter process after treatment. For this, the level of expression of LC3-II was determined through an SDS-PAGE coupled to a Western-Blot analysis. The changes produced in the expression of VEGFR-2 and EGFR were also monitored and, finally, the secretion profile of extracellular vesicles was studied through the analysis of the expression of different markers (Lamp1, E-Selectin, CD63, TSG101, Grp78, GM130, Annexin V and Prohibitin) in fractions enriched in exosomes, extracellular vesicles and apoptotic bodies.Results and Conclusions: The results for the group treated with Sorafenib reproduced what has been described so far in the literature referring to hepatocellular carcinoma: decrease in cell proliferation caused by the downregulation of the expression of different growth factors (EGFR and VEGFR-2) and increase of cell death by apoptosis. However, Lenvatinib did not reproduce the pattern we expected for an antineoplastic drug, since it increased cell proliferation. With respect to the secretion profile of extracellular vesicles, no convincing results were obtained. We think that this could be due to the capacity of separation of the different fractions of the protocol used or to the difficulty of obtaining, from them, high amounts of proteins to proceed to its analysis by WB

Orchestrated SDN-based VDC provisioning over multi-technology optical data centre networks

©2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.In this paper, we describe some scenarios and technologies that have been proposed to cope with the requirements of current and next generation data centre infrastructure. In particular, we discuss the extensions that have been implemented at both orchestration and control levels to efficiently manage the data centres resources. We put the focus on the integration between the Orchestrator and the SDN Controller by describing the communication interfaces and their interaction to provision optimized Virtual Data Centres (VDC) instances over novel data centre infrastructure, with special mention to the different solutions adopted to manage multiple optical technologies at the data plane.Peer ReviewedPostprint (author's final draft

Detection of open phase condition in power transformers

This article deals with open phase events in power transformers, mainly related to nuclear power plants where several cases have led to a global initiative for a prompt solution for this vulnerability. Different solutions are possible, and one of them, which has already been tested at a Spanish nuclear power plant, is presented here. Field test results are presented together with simulations