Time filter

Source Type

Mexico City, Mexico

The Center for Research and Advanced Studies of the National Polytechnic Institute is a Mexican non-governmental scientific research affiliated to the National Polytechnic Institute and founded by president Adolfo López Mateos on 17 April 1961, initially planned as a posgraduate department of the National Polytechnic Institute, which was later modified by President José López Portillo, on the 17 September 1982.The modification by President Portillo stipulates that it is a decentralized organ of public interest, with legal personality and own patrimony. Cinvestav receives an annual subsidy by the Federal Government to fund its operations. Wikipedia.

Clempner J.B.,Center for Economics | Poznyak A.S.,Mexican Center for Research and Advanced Studies
Journal of Systems Science and Systems Engineering | Year: 2014

In this paper, we present a new method for finding a fixed local-optimal policy for computing the customer lifetime value. The method is developed for a class of ergodic controllable finite Markov chains. We propose an approach based on a non-converging state-value function that fluctuates (increases and decreases) between states of the dynamic process. We prove that it is possible to represent that function in a recursive format using a one-step-ahead fixed-optimal policy. Then, we provide an analytical formula for the numerical realization of the fixed local-optimal strategy. We also present a second approach based on linear programming, to solve the same problem, that implement the c-variable method for making the problem computationally tractable. At the end, we show that these two approaches are related: after a finite number of iterations our proposed approach converges to same result as the linear programming method. We also present a non-traditional approach for ergodicity verification. The validity of the proposed methods is successfully demonstrated theoretically and, by simulated credit-card marketing experiments computing the customer lifetime value for both an optimization and a game theory approach. © 2014, Systems Engineering Society of China and Springer-Verlag Berlin Heidelberg. Source

Schnoor M.,Mexican Center for Research and Advanced Studies
Journal of Immunology | Year: 2015

The endothelium is the first barrier that leukocytes have to overcome during recruitment to sites of inflamed tissues. The leukocyte extravasation cascade is a complex multistep process that requires the activation of various adhesionmolecules and signaling pathways, as well as actin remodeling, in both leukocytes and endothelial cells. Endothelial adhesion molecules, such as E-selectin or ICAM-1, are connected to the actin cytoskeleton via actin-binding proteins (ABPs). Although the contribution of receptor-ligand interactions to leukocyte extravasation has been studied extensively, the contribution of endothelial ABPs to the regulation of leukocyte adhesion and transendothelial migration remains poorly understood. This review focuses on recently published evidence that endothelial ABPs, such as cortactin, myosin, or α-actinin, regulate leukocyte extravasation by controlling actin dynamics, biomechanical properties of endothelia, and signaling pathways, such as GTPase activation, during inflammation. Thus, ABPs may serve as targets for novel treatment strategies for disorders characterized by excessive leukocyte recruitment. Copyright © 2015 by The American Association of Immunologists, Inc. 0022-1767/15/$25.00. Source

Rocha L.,Mexican Center for Research and Advanced Studies
Pharmacology and Therapeutics | Year: 2013

In spite of the high success rate of many surgical procedures for pharmacoresistant epilepsy, a substantial number of patients do not become seizure-free. Different strategies for electrical modulation of the brain such as Deep Brain Stimulation, Vagal Nerve Stimulation and Transcraneal Magnetic Stimulation have gained considerable interest in the last decade as alternative therapies for patients with medically refractory epilepsy. Research into the mechanism of action of the strategies for electrical modulation of the brain suggests a crucial role of different molecules and channels such as glutamate, γ-aminobutyric acid, adenosine, brain-derived neurotrophic factor, calcium channels, sodium channels as well as extracellular potassium. Electrical modulation of the brain may reduce the overexpression of P-glycoprotein, a drug efflux transporter that reduces the absorption of antiepileptic drugs. Electrical modulation of the brain induces long-term effects associated with beneficial consequences on clinical symptoms observed during the postictal state. In addition, electrical modulation of the brain might also promote the neurogenesis in subjects with pharmacoresistant epilepsy in whom this process is decreased. Targeting the regulatory pathways in charge of the effects of electrical modulation of the brain is discussed as a means to improve its efficacy. Electrical modulation of the brain combined with pharmacotherapy may represent an innovative approach to avoid epileptogenesis, reduce seizure activity, induce beneficial effects during the postictal state, diminish the amount of antiepileptic drugs, and improve alertness, memory and mood in pharmacoresistant epilepsy. © 2013 Elsevier Inc. Source

Gomez W.,Mexican Center for Research and Advanced Studies | Pereira W.C.A.,Federal University of Rio de Janeiro | Infantosi A.F.C.,Federal University of Rio de Janeiro
IEEE Transactions on Medical Imaging | Year: 2012

In this paper, we investigated the behavior of 22 co-occurrence statistics combined to six gray-scale quantization levels to classify breast lesions on ultrasound (BUS) images. The database of 436 BUS images used in this investigation was formed by 217 carcinoma and 219 benign lesions images. The region delimited by a minimum bounding rectangle around the lesion was employed to calculate the gray-level co-occurrence matrix (GLCM). Next, 22 co-occurrence statistics were computed regarding six quantization levels (8, 16, 32, 64, 128, and 256), four orientations (0° , 45° , 90° , and 135° ), and ten distances (1, 2,..,10 pixels). Also, to reduce feature space dimensionality, texture descriptors of the same distance were averaged over all orientations, which is a common practice in the literature. Thereafter, the feature space was ranked using mutual information technique with minimal-redundancy-maximal- relevance (mRMR) criterion. Fisher linear discriminant analysis (FLDA) was applied to assess the discrimination power of texture features, by adding the first m-ranked features to the classification procedure iteratively until all of them were considered. The area under ROC curve (AUC) was used as figure of merit to measure the performance of the classifier. It was observed that averaging texture descriptors of a same distance impacts negatively the classification performance, since the best AUC of 0.81 was achieved with 32 gray levels and 109 features. On the other hand, regarding the single texture features (i.e., without averaging procedure), the quantization level does not impact the discrimination power, since AUC=0.87 was obtained for the six quantization levels. Moreover, the number of features was reduced (between 17 and 24 features). The texture descriptors that contributed notably to distinguish breast lesions were contrast and correlation computed from GLCMs with orientation of 90° and distance more than five pixels. © 1982-2012 IEEE. Source

Clempner J.,National Polytechnic Institute of Mexico | Poznyak A.,Mexican Center for Research and Advanced Studies
International Journal of Applied Mathematics and Computer Science | Year: 2011

We introduce the concept of a Lyapunov game as a subclass of strictly dominated games and potential games. The advantage of this approach is that every ergodic system (repeated game) can be represented by a Lyapunov-like function. A direct acyclic graph is associated with a game. The graph structure represents the dependencies existing between the strategy profiles. By definition, a Lyapunov-like function monotonically decreases and converges to a single Lyapunov equilibrium point identified by the sink of the game graph. It is important to note that in previous works this convergence has not been guaranteed even if the Nash equilibrium point exists. The best reply dynamics result in a natural implementation of the behavior of a Lyapunov-like function. Therefore, a Lyapunov game has also the benefit that it is common knowledge of the players that only best replies are chosen. By the natural evolution of a Lyapunov-like function, no matter what, a strategy played once is not played again. As a construction example, we show that, for repeated games with bounded nonnegative cost functions within the class of differentiable vector functions whose derivatives satisfy the Lipschitz condition, a complex vector-function can be built, where each component is a function of the corresponding cost value and satisfies the condition of the Lyapunov-like function. The resulting vector Lyapunov-like function is a monotonic function which can only decrease over time. Then, a repeated game can be represented by a one-shot game. The functionality of the suggested method is successfully demonstrated by a simulated experiment. Source

Discover hidden collaborations