On nonstandard chemotactic dynamics with logistic growth induced by a modified complex Ginzburg–Landau equation

The author is partially supported by MINECO-Feder (Spain), research grant number RTI2018- 098850-B-I00, as well as by Junta de Andalucía (Spain), Project PY18-RT-2422, and A-FQM-311- UGR18.In this paper, we derive a variant of the classical Keller-Segel model of chemotaxis incorporating a growth term of logistic type for the cell population n(t,x), say nu n(1-n) with nu>0, and a nonstandard chemical production-degradation mechanism involving first- and second-order derivatives of the logarithm of the cell density, say f lambda ab(n,nx,nxx)=lambda n+anxxn+bnx2n2 with lambda,a,b is an element of R, via the (n,S)-hydrodynamical system associated with a modified Ginzburg-Landau equation governing the evolution of the complex wavefunction psi=neiS. In a chemotactic context, S(t,x) will play the role of the concentration of chemical substance. Then, after carrying out a detailed analysis of the modulational stability of uniform-in-space plane waves, dark soliton-shaped traveling wave densities of the former system are constructed from solitary wave solutions of the latter.Junta de Andalucia European Commission PY18-RT-2422 and AFQM-311-UGR18MINECO-Feder (Spain

Quid Pro Quo: A Mechanism for Fair Collaboration in Networked Systems

Collaboration may be understood as the execution of coordinated tasks (in the most general sense) by groups of users, who cooperate for achieving a common goal. Collaboration is a fundamental assumption and requirement for the correct operation of many communication systems. The main challenge when creating collaborative systems in a decentralized manner is dealing with the fact that users may behave in selfish ways, trying to obtain the benefits of the tasks but without participating in their execution. In this context, Game Theory has been instrumental to model collaborative systems and the task allocation problem, and to design mechanisms for optimal allocation of tasks. In this paper, we revise the classical assumptions and propose a new approach to this problem. First, we establish a system model based on heterogenous nodes (users, players), and propose a basic distributed mechanism so that, when a new task appears, it is assigned to the most suitable node. The classical technique for compensating a node that executes a task is the use of payments (which in most networks are hard or impossible to implement). Instead, we propose a distributed mechanism for the optimal allocation of tasks without payments. We prove this mechanism to be robust event in the presence of independent selfish or rationally limited players. Additionally, our model is based on very weak assumptions, which makes the proposed mechanisms susceptible to be implemented in networked systems (e.g., the Internet).Comment: 23 pages, 5 figures, 3 algorithm

Resource location based on precomputed partial random walks in dynamic networks

The problem of finding a resource residing in a network node (the \emph{resource location problem}) is a challenge in complex networks due to aspects as network size, unknown network topology, and network dynamics. The problem is especially difficult if no requirements on the resource placement strategy or the network structure are to be imposed, assuming of course that keeping centralized resource information is not feasible or appropriate. Under these conditions, random algorithms are useful to search the network. A possible strategy for static networks, proposed in previous work, uses short random walks precomputed at each network node as partial walks to construct longer random walks with associated resource information. In this work, we adapt the previous mechanisms to dynamic networks, where resource instances may appear in, and disappear from, network nodes, and the nodes themselves may leave and join the network, resembling realistic scenarios. We analyze the resulting resource location mechanisms, providing expressions that accurately predict average search lengths, which are validated using simulation experiments. Reduction of average search lengths compared to simple random walk searches are found to be very large, even in the face of high network volatility. We also study the cost of the mechanisms, focusing on the overhead implied by the periodic recomputation of partial walks to refresh the information on resources, concluding that the proposed mechanisms behave efficiently and robustly in dynamic networks.Comment: 39 pages, 25 figure

A repertoire of repulsive Keller–Segel models with logarithmic sensitivity: Derivation, traveling waves, and quasi-stationary dynamics

In this paper, we show how the chemotactic model {partial derivative(t)rho = d(1) Delta(x)rho - del(x) . (rho del(x)c) partial derivative(t)c = d(2) Delta(x)c + F(rho, c, del(x)rho, del(x)c, Delta x rho) introduced in Alejo and Lopez (2021), which accounts for a chemical production-degradation operator of Hamilton-Jacobi type involving first- and second-order derivatives of the logarithm of the cell concentration, namely, F = mu + tau c - sigma rho + A Delta(x)rho/rho + B vertical bar del(x)rho vertical bar(2)/rho(2) + C vertical bar del(x)c vertical bar(2), with mu, tau, sigma, A, B, C is an element of R, can be formally reduced to a repulsive Keller-Segel model with logarithmic sensitivity { partial derivative(t)rho = D-1 Delta(x)rho + chi del(x) . (rho del(x) log(c)), chi, lambda, beta > 0, partial derivative(t)c = D-2 Delta(x)c + lambda rho c - beta c whenever the chemotactic parameters are appropriately chosen and the cell concentration keeps strictly positive. In this way, some explicit solutions (namely, traveling waves and stationary cell density profiles) of the former system can be transferred to a number of variants of the the latter by means of an adequate change of variables.Spanish Government RTI2018-098850-B-I00 Junta de AndaluciaEuropean Commission PY18-RT-2422 B-FQM-580-UGRUniversidad de Granada/CBU

Authentication, Authorization, and Accounting in WebRTC PaaS Infrastructures: The Case of Kurento

Server infrastructures for Web Real-Time Communications (WebRTC) are useful for creating rich applications. Developers commonly use them to access capabilities such as group communications, archiving, and transcoding. Kurento is an open source project that provides a WebRTC media server and a platform as a service (PaaS) cloud built on top. The authors present its API and analyze different security models for it, investigating the suitability of using simple access control lists and capability-based security schemes to provide authorization.This work is supported by the European Commission under projects FI-WARE FP7-2011-ICT-FI, GA-285248, and NUBOMEDIA FP7-ICT-2013-1.6, GA-610576

The social importance of the university’s commitment to the promotion of entrepreneurial initiatives as a strategic goal in the transfer of knowledge, the modification of the model of production and an increase in social welfare

[Resumo] O desenvolvemento dunha sociedade baséase na capacidade dos seus membros para detectar oportunidades, emprender e crear novas empresas con ideas innovadoras. O impacto da cultura emprendedora e a creación de empresas no benestar e o progreso social é un feito constatado, polo que a universidade debe asumir o compromiso de fomentar o espírito emprendedor como un obxectivo estratéxico que, ao mesmo tempo sirva como medio para transmitir coñecementos á sociedade. O logro deste obxectivo favorecerá a aparición unha xeración de novos emprendedores provenientes do ámbito universitario que transformarán a estrutura económica e social do país, o que contribuirá ao ansiado cambio de modelo produtivo, á creación de empregos que requiran maior cualificación, á igualdade de oportunidades e á repartición máis equitativa da riqueza.[Abstract] The development of a society is based on the capacity of its members to discover opportunities, to undertake and create new companies with innovative ideas. The impact of entrepreneurial culture and the creation of companies in welfare and social progress is a known fact, and sothe university has to take on a commitment to foster the entrepreneurial spirit as a strategic aim that, at the same time works as a means of transmitting knowledge to society at large. Complying with this aim will favour the appearance of a generation of new entrepreneurs from the university field who will transform the economic and social structure of the country, contributing therefore to a much-neede change in the model of production, in the creation of employment that require higher qualifications, and in the equality of opportunities and a more even distribution of wealth

Actitud de los universitarios ante las nuevas tecnologías de la información

[Resumen] En la actualidad las Universidades Españolas están impulsando nuevas propuestas de innovación educativa que llevan a una mejor calidad de la enseñanza. Esto se debe, en parte, al esfuerzo en pro de conseguir una convergencia europea de la enseñanza superior y, en parte, al impacto que están ejerciendo las Nuevas Tecnologías de la Información y Comunicación (NTIC). Bajo la acción de estos dos impulsos, la enseñanza universitaria se halla inmersa en un proceso de cambio profundo y de renovación de los esquemas didácticos. Esta investigación tiene como objetivo primordial el de analizar las actitudes hacia las NTIC en una muestra compuesta por 582 estudiantes de la Universidad de Vigo (Campus de Ourense). De ellos 403 eran mujeres y 179 hombres. El rango de edad oscilaba entre los 18 y 30 años. La media de edad era de 20.86 años y una desviación típica de 2.55. Los resultados obtenidos nos ponen de manifiesto que la gran mayoría afirma que Internet puede ser una fuente de información que facilita el aprendizaje, que las páginas educativas son útiles para adquirir conocimientos teóricos y prácticos y reconocen que las NTIC les permiten ser más activos en el proceso de enseñanza-aprendizaje y construir su propio conocimiento. No obstante, el 25.5% sigue prefiriendo la lectura de textos escritos a los presentados por ordenador y más de un tercio sostiene que el uso de Internet les supone mucho tiempo y esfuerzo[Abstract] At the present time the Spanish Universities are impelling new proposals of educative innovation that take to one better quality of education. This must, in part, to the effort for obtaining an European convergence of superior education and, partly, to the impact that is exerting the New Technologies of the Information and Comunicación (NTIC). Under the action of these two impulses, university education is immersed in a process of deep change and renovation of the didactic schemes. This investigation has as objective fundamental the one to analyze the attitudes towards the NTIC in a sample composed by 582 students of the University of Vigo (Campus of Ourense). Of them 403 were women and 179 men. The age rank oscillated between the 18 and 30 years. The age average was of 20,86 years and one standard deviation of 2.55. The obtained results show to us that the great majority affirms that Internet can be a source of intelligence that facilitates the learning, that the educative pages are useful to acquire theoretical and practical knowledge and recognize that the NTIC allow them to be more active in the education- learning process and to construct their own knowledge. However, the 25,5% continue preferring the reading of texts written the presented/ displayed ones by computer and more of a third it maintains that the use of Internet supposes long time and effort to the

Lista de los peces de la provincia de Jujuy

Fil: Fernández, Luis A.. Fundación Miguel Lillo. Tucumán; ArgentinaFil: Nadalin, Diego Oscar. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: López, Hugo Luis. División Zoología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin