Estimating Self-Sustainability in Peer-to-Peer Swarming Systems

Peer-to-peer swarming is one of the \emph{de facto} solutions for distributed content dissemination in today's Internet. By leveraging resources provided by clients, swarming systems reduce the load on and costs to publishers. However, there is a limit to how much cost savings can be gained from swarming; for example, for unpopular content peers will always depend on the publisher in order to complete their downloads. In this paper, we investigate this dependence. For this purpose, we propose a new metric, namely \emph{swarm self-sustainability}. A swarm is referred to as self-sustaining if all its blocks are collectively held by peers; the self-sustainability of a swarm is the fraction of time in which the swarm is self-sustaining. We pose the following question: how does the self-sustainability of a swarm vary as a function of content popularity, the service capacity of the users, and the size of the file? We present a model to answer the posed question. We then propose efficient solution methods to compute self-sustainability. The accuracy of our estimates is validated against simulation. Finally, we also provide closed-form expressions for the fraction of time that a given number of blocks is collectively held by peers.Comment: 27 pages, 5 figure

Metadata analysis of systematic literature reviews on academic spin-offs: an overview of reviews

Besides assuming the role of teaching, research, and extension, the university, has expanded the boundaries of scientific knowledge to promote a business ecosystem. The business-related activities can be driven by the leadership of students with an entrepreneurial capacity, based on the technology transfer produced by the academic research and generated by companies that somehow have been idealized or had the active participation of the faculty members and the technology under their control. This model of companies, named in the literature as academic spin-off, has increased the attention of researchers at two main points: i. understanding the phenomenon itself and ii. contribute to identifying the lack of the process, whether related to the support structure or capacitation of faculty members to develop the entrepreneurial activities, as well as in understanding the commercialization of knowledge as technology transfer. In this context, the present work provided a metadata analysis of systematic literature reviews on the academic spin-off, mapping the knowledge on the subject and searching for reviews that cover the technology transfer models to study the viability of protecting the academic intellectual property as a product. Methodology: the data used in this study were retrieved from the database Web of Science and revised according to the protocol Extension for Scoping Reviews (PRISMA-ScR). The bibliometric analysis of metadata was conducted in RStudio software with the package Bibliometrix and its web interface Biblioshiny. Results: 40 review articles published in peer-reviewed journals from 2006 to 2021 were selected from the initial collection. Then, as result of the bibliometric analysis, it was obtained the data of production indices (main authors, sources, and most cited articles), the evolution of chronological discussion on the subject, and other complementary. Conclusion: it was found indications of studies that discuss technology transfer models and others that examined empiric models in the academic scenario. However, in the selected collection, was not identified any review papers on academic entrepreneurship that were related to the viability of intellectual property as products to be commercialized. Also, it was identified that the word academic entrepreneurship stands out as the main keyword word to represent the research

Shot noise and spin-orbit coherent control of entangled and spin polarized electrons

We extend our previous work on shot noise for entangled and spin polarized electrons in a beam-splitter geometry with spin-orbit (\textit{s-o}) interaction in one of the incoming leads (lead 1). Besides accounting for both the Dresselhaus and the Rashba spin-orbit terms, we present general formulas for the shot noise of singlet and triplets states derived within the scattering approach. We determine the full scattering matrix of the system for the case of leads with \textit{two} orbital channels coupled via weak \textit{s-o} interactions inducing channel anticrossings. We show that this interband coupling coherently transfers electrons between the channels and gives rise to an additional modulation angle -- dependent on both the Rashba and Dresselhaus interaction strengths -- which allows for further independent coherent control of the electrons traversing the incoming leads. We derive explicit shot noise formulas for a variety of correlated pairs (e.g., Bell states) and lead spin polarizations. Interestingly, the singlet and \textit{each} of the triplets defined along the quantization axis perpendicular to lead 1 (with the local \textit{s-o} interaction) and in the plane of the beam splitter display distinctive shot noise for injection energies near the channel anticrossings; hence, one can tell apart all the triplets, in addition to the singlet, through noise measurements. We also find that spin-orbit induced backscattering within lead 1 reduces the visibility of the noise oscillations, due to the additional partition noise in this lead. Finally, we consider injection of two-particle wavepackets into leads with multiple discrete states and find that two-particle entanglement can still be observed via noise bunching and antibunching.Comment: 30 two-column pages and 7 figure

Banana peel and grape stalk: potential of valorization through the evaluation of chemical composition and physical-chemical properties

CHISA 2008 - 18th International Congress of Chemical and Process Engineering (CD-ROM of Full Texts)Bioconversion of food processing residues (agr o-based industrial residues) in valuable products has been receiving an increasing attention in the last years. In fact, the main problem experienced by agro-based industries in several c ountries is the management of their residues. As a consequence, many research centers and government departments are preparing scientific strategies in order to develop biotechnological processes capable of transforming these residues in new bio-products or as sources of other chemicals. Most of these agro-industrial residues are lignocellulosic materials constituted basically of cellulose, hemicelluloses, and lignin. In particular, banana production is one of the main economic resources of several regions in many countries, an important crop in the tropical and sub- tropical regions and one of the most consumed fruits in the world. Grapes are other of the world’s largest fruit crops, mainly grown for direct consumption, grape juice and wine- making processes. These agricultural/industrial activities generate large amounts of residues such as banana fruit peel and grape stalk. Taking in consideration these facts, it is fundamental to know their chemical composition and physical-chemical properties, in order to evaluate perspectives of applications and improvement of procedures towards an efficient utilization of these residues. For this reason, following hydrolysis, the residues obtained were analyzed by HPLC, FTIR, TGA and DSC. Preliminary results indicate the attractiveness of these materials for further applications due to their chemical composition and physical-chemical properties: glucan and xylan contents of banana peel are 23.2 ± 0.2% and 18.9 ± 0.5%, respectively, while grape stalk contains 26.5 ± 1.5% and 16.8 ± 0.4%, respectively. These results are in agreement with those obtained with some other agro-industrial residues. These approaches offer several advantages, since the several fractions obtained from the hydrolysis of these annually produced materials can be applied as raw-materials to reduce the existence of environmentally hazardous situations and/or to increase the supply of energy or chemicals produced from renewable resourcesFCT(Portugal), FAPESP(Brazil) and CAPES/GRICES(Brazil/Portugal)info:eu-repo/semantics/publishedVersio

Carbon Nanotube–Liposome Complexes in Hydrogels for Controlled Drug Delivery via Near-Infrared Laser Stimulation

Externally controllable drug delivery systems are crucial for a variety of biological applications where the dosage and timing of drug delivery need to be adjusted based on disease diagnosis and progression. Here, we have developed an externally controllable drug delivery system by combining three extensively used platforms: hydrogels, liposomes, and single-walled carbon nanotubes (SWCNTs). We have developed carbon nanotube–liposome complexes (CLCs) and incorporated these structures into a 3D alginate hydrogel for use as an optically controlled drug delivery system. The CLC structures were characterized by using a variety of imaging and spectroscopic techniques, and an optimal SWCNT/lipid ratio was selected. The optimal CLCs were loaded with a model drug (FITC-Dex), incorporated into a hydrogel, and their release profile was studied. It was shown that release of the drug cargo can be triggered by using an NIR laser stimulation tuned to the optical resonance of a particular SWCNT species. It was further shown that the amount of released cargo can be tuned by varying the NIR stimulation time. This system demonstrates the externally controlled delivery of drug cargo and can be used for different applications including cancer chemotherapy delivery

Key Aspects for Implementing ISO/IEC 17025 Quality Management Systems at Materials Science Laboratories

Implementing a quality management system based on the requirements specified in ISO/IEC 17025 standard at materials science laboratories is challenging, mainly due to two main factors: (i) the high technical complexity degree of some tests used for materials characterization and (ii) the fact that most materials science laboratories provide materials characterization tests and also carry out research and development activities. In this context, this chapter presents key subjects while implementing a quality management system at materials science laboratories and some considerations on strategies for effectively implementing such systems