The solvability of consensus in iterated models extended with safe-consensus

The safe-consensus task was introduced by Afek, Gafni and Lieber (DISC'09) as a weakening of the classic consensus. When there is concurrency, the consensus output can be arbitrary, not even the input of any process. They showed that safe-consensus is equivalent to consensus, in a wait-free system. We study the solvability of consensus in three shared memory iterated models extended with the power of safe-consensus black boxes. In the first model, for the $i$-th iteration, processes write to the memory, invoke safe-consensus boxes and finally they snapshot the memory. We show that in this model, any wait-free implementation of consensus requires $\binom{n}{2}$ safe-consensus black-boxes and this bound is tight. In a second iterated model, the processes write to memory, then they snapshot it and finally they invoke safe-consensus boxes. We prove that in this model, consensus cannot be implemented. In the last iterated model, processes first invoke safe-consensus, then they write to memory and finally they snapshot it. We show that this model is equivalent to the previous model and thus consensus cannot be implemented.Comment: 49 pages, A preliminar version of the main results appeared in the SIROCCO 2014 proceeding

An Introduction to the Topological Theory of Distributed Computing with Safe-consensus

AbstractThe theory of distributed computing shares a deep and fascinating connection with combinatorial and algebraic topology. One of the key ideas that facilitates the development of the topological theory of distributed computing is the use of iterated shared memory models. In such a model processes communicate through a sequence of shared objects. Processes access the sequence of objects, one-by-one, in the same order and asynchronously. Each process accesses each shared object only once. In the most basic form of an iterated model, any number of processes can crash, and the shared objects are snapshot objects. A process can write a value to such an object, and gets back a snapshot of its contents.The purpose of this paper is to give an introduction to this research area, using an iterated model based on the safe-consensus task (Afek, Gafni and Lieber, DISCʼ09). In a safe-consensus task, the validity condition of consensus is weakened as follows. If the first process to invoke an object solving a safe-consensus task returns before any other process invokes it, then the process gets back its own input; otherwise the value returned by the task can be arbitrary. As with consensus, the agreement requirement is that always the same value is returned to all processes.A safe-consensus-based iterated model is described in detail. It is explained how its runs can be described with simplicial complexes. The usefulness of the iterated memory model for the topological theory of distributed computing is exhibited by presenting some new results (with very clean and well structured proofs) about the solvability of the (n,k)-set agreement task. Throughout the paper, the main ideas are explained with figures and intuitive examples

Panorama de las relaciones Cubano-Argentinas en los noventa.

En españolSe analizan los aspectos más importantes en las relaciones entre Cuba y Argentina desde 1989 hasta la actualidad, y se presentan sus perspectivas a corto plazo. El autor califica a las relaciones Buenos Aires - La Habana como una triangulación condicionada: lo primero por los vínculos entre Argentina y Estados Unidos y lo segundo por la influencia que éstos ejercen en Buenos Aires respecto de Cuba. Nos muestra el cambio de estrategia que está teniendo lugar en la política exterior cubana para romper ese esquema y propiciar así un acercamiento con la Argentina.En inglésThe author analyses the outstanding aspects in Cuban-Argentine relations since 1989, outlining the short term perspectives of these relations. The Havana- Buenos Aires relations are characterised as a "conditioned triangulation": the latter, because of the links between Argentina and the USA; the former, due to the influence these links exert over Buenos Aires as regards Cuba. The author also points at the change of strategy which is currently taking place in Cuban Foreign Policy, in order to erode that state of affairs and thus propitiate a close relationship with Argentina

Adipokines and Osteoarthritis: Novel Molecules Involved in the Pathogenesis and Progression of Disease

Obesity has been considered a risk factor for osteoarthritis and it is usually accepted that obesity contributes to the development and progression of osteoarthritis by increasing mechanical load of the joints. Nevertheless, recent advances in the physiology of white adipose tissue evidenced that fat cells produce a plethora of factors, called adipokines, which have a critical role in the development of ostearthritis, besides to mechanical effects. In this paper, we review the role of adipokines and highlight the cellular and molecular mechanisms at play in osteoarthritis elicited by adipokines. We also emphasize how defining the role of adipokines has broadned our understanding of the diversity of factors involved in the genesis and progression of osteoarthritis in the hope of modifying it to prevent and treat diseases

Beyond Fat Mass: Exploring the Role of Adipokines in Rheumatic Diseases

The cloning of leptin in 1994 by Zhang et al. introduced a novel concept about white adipose tissue (WAT) as a very dynamic organ that releases a plethora of immune and inflammatory mediators, such as adipokines and cytokines, which are involved in multiple diseases. Actually, adipokines exert potent modulatory actions on target tissues involved in rheumatic diseases including cartilage, synovial, bone and immune cells. The goal of this paper is to elucidate the recent findings concerning the involvement of adipokines in rheumatic diseases, such as rheumatoid arthritis (RA), osteoarthritis (OA), and systemic lupus erythematosus (SLE)

Leptin, a railroad switch enabling crossover signals among inflammation, immunity and metabolism

White adipose tissue is currently considered as an active endocrine organ that secretes a plethora of factors named adipokines, some of them being of pro-inflammatory nature that likely contribute to the low-level systemic inflammation, a status that is often present in metabolic syndrome-associated chronic pathologies such as obesity, type 2 diabetes, and atherosclerosis. Leptin is historically indisputably one of the most important adipokine secreted by fat cells, with a variety of physiological roles ranging from to the control of metabolism, energy homeostasis and inflammatory response to cognition. Leptin is also implicated in the connection between nutritional status and immune competence, modulating both the innate and adaptive immune responses in normal as well as pathological conditions. It has been shown that conditions characterized by low leptin levels are associated with increased infection susceptibility. Conversely, immune-mediated disorders such as autoimmune diseases are associated with increased secretion of leptin and production of proinflammatory cytokines. Thus, leptin can be easily considered as a frank mediator of metabolic and inflammatory/immune responses.Adipobiology 2010; 2: 33-40

Dickkopf-3 (DKK3) Signaling in IL-1a-Challenged Chondrocytes: Involvement of the NF-?B Pathway

Objective: Osteoarthritis (OA) is an age-related biomechanical and low-grade inflammometabolic disease of the joints and one of the costliest and disabling forms of arthritis. Studies on matrix-degrading enzymes such as metalloproteases, which are implicated in the increased catabolism of extracellular matrix, are of paramount relevance. DKK3 is a member of DKK family and is best known for its role in cancer. Although there is some information about the participation of DKK3 in cartilage pathophysiology and on metalloproteases regulation, in particular, little is known about DKK3 signaling mechanisms. Thus, the aim of this study is to explore how DKK3 regulates matrix metalloproteinase-13 (MMP-13) expression. Design: Gene, protein expression and protein phosphorylation in primary human chondrocytes and ATDC5 mouse cells were assessed by RT-qPCR and Western blot analysis. Further studies on DKK3 activity were performed by targeting DKK3 gene with a specific siRNA. Results: DKK3 expression was found to be higher in OA human chondrocytes than healthy cells, being its expression decreased in interleukin-1? (IL-1?)-stimulated cells. DKK3 knockdown increased the induction of MMP-13 elicited by IL-1? in human and mouse chondrocytes and after the analysis of different signalling pathways, we observed that NF-?B pathway was involved in the regulation of MMP-13 expression by DKK3. Conclusions: Herein we have demonstrated, for the first time, that DKK3 gene silencing exacerbated NF-?B activation, resulting in an increased IL-1?-driven induction of MMP-13. Our results further confirm that DKK3 may play a protective role in OA by attenuating NF-?B activation and the subsequent production of metalloproteases.Funding: OG and FL are Staff Personnel of Xunta de Galicia (Servizo Galego de Saude, SERGAS) through a research-staff stabilization contract (ISCIII/SERGAS). JC is “Miguel Servet” Researcher “CP19/00172 (ISCIII/FEDER), MS and VF are currently “Sara Borrell” Researchers funded by ISCIII and FEDER (CD16/00111). RG is a “Miguel Servet” Researcher funded by Instituto de Salud Carlos III (ISCIII) and FEDER. CR is a predoctoral research scholar funded by ISCIII and FEDER (Exp. 18/00188). OG, RG, and MAGG are members of RETICS Programme, RD16/0012/0014 (RIER: Red de Investigación en Inflamación y Enfermedades Reumáticas) via Instituto de Salud Carlos III (ISCIII) and FEDER. FL is a member of CIBERCV (Centro de Investigación Biomédica en Red de Enfermedades Cardiovasculares). The work of OG and JP (PI17/00409), RG (PI16/01870 and CP15/00007) and FL (PI15/00681 PI18/00821 and CB16/11/00226) was funded by Instituto de Salud Carlos III and FEDER. OG is a beneficiary of a project funded by Research Executive Agency of the European Union in the framework of MSCA-RISE Action of the H2020 Programme (Project number 734899). OG is beneficiary of a project funded by Xunta de Galicia, Consellería de emprego e industria (GAIN) (IN607B2019/10). RG is beneficiary of a project funded by Mutua Madrileña 2018. AM wishes to acknowledge financial support from the European Structural and Social Funds through the Research Council of Lithuania (Lietuvos Mokslo Taryba) according to the activity ‘Improvement of researchers’ qualification by implementing world-class R&D projects’ of Measure No. 09.3.3-LMT-K-712 (grant application code: 09.3.3-LMT-K-712-01-0157, agreement No. DOTSUT-215) and the new funding programme: Attracting Foreign Researchers for Research Implementation (2018–2022)