Center for Mathematical Research


Center for Mathematical Research

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Shamah-Levy T.,National Institute of Public Health | Mundo-Rosas V.,National Institute of Public Health | Mendez-Gomez-Humaran I.,Center for Mathematical Research
Journal of Nutrition | Year: 2014

Background: Anemia is a major cause of maternal mortality. Household food insecurity (HFI) may increase the risk of anemia among women of reproductive age although this hypothesis remains largely untested in representative samples from low- and middle-income countries. Objective: Our objective was to investigate the association of HFI with anemia in a nationally representative, cross-sectional sample of Mexican women of reproductive age (12-49 y old). Methods: We tested the association between HFI and anemia among 16,944 women of reproductive age using the multiple logistic regression among adolescent (12-20 y) and adult women (21-49 y). HFI was measured with the use of the Latin American and Caribbean Food Security Scale. Hemoglobin was measured with capillary hemoglobin with the use of HemoCue photometer (HemoCue, Inc.) and anemia was defined with the use of WHO standards. Results: The association of HFI and anemia was not significant (P > 0.05) for adolescent women (12-20 y), whereas in adult women (21-49 y), the adjusted odds of having anemia were 31-43% higher among those living in mild to severely food insecure households than adult women residing in food secure households (P < 0.05). Conclusions: HFI is associated with anemia among adult Mexican women. Programs that reduce HFI may also be effective at reducing the risk of anemia among Mexican women. © 2014 American Society for Nutrition.

Goring S.,University of Wisconsin - Madison | Williams J.W.,University of Wisconsin - Madison | Blois J.L.,University of Wisconsin - Madison | Jackson S.T.,University of Wyoming | And 5 more authors.
Quaternary Science Reviews | Year: 2012

Age-depth relationships in sedimentary archives such as lakes, wetlands and bogs are non-linear with irregular probability distributions associated with calibrated radiocarbon dates. Bayesian approaches are thus well-suited to understanding relationships between age and depth for use in paleoecological studies. Bayesian models for the accumulation of sediment and organic matter within basins combine dated material from one or more records with prior information about the behavior of deposition times (yr/cm) based on expert knowledge. Well-informed priors are essential to good modeling of the age-depth relationship, but are particularly important in cases where data may be sparse (e.g., few radiocarbon dates), or unclear (e.g., age-reversals, coincident dates, age offsets, outliers and dates within a radiocarbon plateau).Here we assessed Holocene deposition times using 204 age-depth models obtained from the Neotoma Paleoecology Database ( for both lacustrine and palustrine environments across the northeastern United States. These age-depth models were augmented using biostratigraphic events identifiable within pollen records from the northeastern United States during the Holocene and late-Pleistocene.Deposition times are significantly related to depositional environment (palustrine and lacustrine), sediment age, and sediment depth. Spatial variables had non-significant relationships with deposition time when site effects were considered. The best-fit model was a generalized additive mixed model that relates deposition time to age, stratified by depositional environment with site as a random factor. The best-fit model accounts for 63.3% of the total deviance in deposition times. The strongly increasing accumulation rates of the last 500-1000 years indicate that gamma distributions describing lacustrine deposition times (α = 1.08, β = 18.28) and palustrine deposition times (α = 1.23, β = 22.32) for the entire Holocene may be insufficient for Bayesian approaches since there is strong variation in the gamma parameters both in the most recent sediments and throughout the Holocene. Time-averaged gamma distributions for lacustrine (α = 1.35, β = 19.64) and palustrine samples (α = 1.40, β = 20.72) show lower overall deposition times, but variability remains. The variation in gamma parameters through time may require the use of multiple gamma distributions during the Holocene to generate accurate age-depth models. We present estimates of gamma parameters for deposition times at 1000 yr intervals. The parameters generated in this study can be used directly within Bacon to act as Bayesian priors for sedimentary age models. © 2012 Elsevier Ltd.

Velasco Elizondo P.,Center for Mathematical Research | Lau K.-K.,University of Manchester
Journal of Systems and Software | Year: 2010

Component-based development is based on the idea of building software systems by composing pre-existing components. Connectors are the 'glue' for composing components. Therefore, it is important to consider connectors as first-class entities and provide adequate descriptions of them to facilitate their understanding and promote their reuse. We have defined a catalogue of component connectors to support the process of 'development with reuse'. The categories and connector types in the catalogue were obtained through an analysis of the activities involved in this process as well as considering the syntax and semantics of a new component model. © 2010 Elsevier Inc. All rights reserved.

Vasquez-Gomez J.I.,National Institute of Astrophysics, Optics and Electronics | Sucar L.E.,National Institute of Astrophysics, Optics and Electronics | Murrieta-Cid R.,Center for Mathematical Research
IEEE International Conference on Intelligent Robots and Systems | Year: 2014

The task addressed in this paper is to plan iteratively a set views in order to reconstruct an object using a mobile manipulator robot with an 'eye-in-hand' sensor. The proposed method plans views directly in the configuration space avoiding the need of inverse kinematics. It is based on a fast evaluation and rejection of a set of candidate configurations. The main contributions are: a utility function to rank the views and an evaluation strategy implemented as a series of filters. Given that the candidate views are configurations, motion planning is solved using a rapidly-exploring random tree. The system is experimentally evaluated in simulation, contrasting it with previous work. We also present experiments with a real mobile manipulator robot, demonstrating the effectiveness of our method. © 2014 IEEE.

Dwivedi V.,Carnegie Mellon University | Velasco-Elizondo P.,Center for Mathematical Research | Maria Fernandes J.,University of Aveiro | Garlan D.,Carnegie Mellon University | Schmerl B.,Carnegie Mellon University
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

Computations are pervasive across many domains, where end users have to compose various heterogeneous computational entities to perform professional activities. Service-Oriented Architecture (SOA) is a widely used mechanism that can support such forms of compositions as it allows heterogeneous systems to be wrapped as services that can then be combined with each other. However, current SOA orchestration languages require writing scripts that are typically too low-level for end users to write, being targeted at professional programmers and business analysts. To address this problem, this paper proposes a composition approach based on an end user specification style called SCORE. SCORE is an architectural style that uses high-level constructs that can be tailored for different domains and automatically translated into executable constructs by tool support. We demonstrate the use of SCORE in two domains - dynamic network analysis and neuroscience, where users are intelligence analysts and neuroscientists respectively, who use the architectural style based vocabulary in SCORE as a basis of their domain-specific compositions that can be formally analyzed. © 2011 Springer-Verlag.

Dalmau O.,Center for Mathematical Research | Rivera M.,Center for Mathematical Research | Gonzalez A.,Ibero-American University of Mexico
Optics Communications | Year: 2016

We first present two closed formulas for computing the phase shift in interferograms with unknown phase step. These formulas obtain theoretically the exact phase step in fringe pattern without noise and only require the information in two pixels of the image. The previous formulas allows us to define a functional that yields an estimate of the phase step in interferograms corrupted by noise. In the experiment we use the standard Least Square formulation which also yields a closed formula, although the general formulation admits a robust potential. We provide two possible implementations of our approach, one in which the sites can be randomly selected and the other in which we can scan the whole image. The experiments show that the proposed algorithm presents the best results compared with state of the art algorithms. © 2016, Elsevier B.V. All rights reserved.

Estrada E.,University of Strathclyde | Estrada E.,Center for Mathematical Research | Sheerin M.,University of Strathclyde
Physica D: Nonlinear Phenomena | Year: 2016

A random rectangular graph (RRG) is a generalization of the random geometric graph (RGG) in which the nodes are embedded into a rectangle with side lengths a and b=1/a, instead of on a unit square [0,1]2. Two nodes are then connected if and only if they are separated at a Euclidean distance smaller than or equal to a certain threshold radius r. When a=1 the RRG is identical to the RGG. Here we apply the consensus dynamics model to the RRG. Our main result is a lower bound for the time of consensus, i.e., the time at which the network reaches a global consensus state. To prove this result we need first to find an upper bound for the algebraic connectivity of the RRG, i.e., the second smallest eigenvalue of the combinatorial Laplacian of the graph. This bound is based on a tight lower bound found for the graph diameter. Our results prove that as the rectangle in which the nodes are embedded becomes more elongated, the RRG becomes a 'large-world', i.e., the diameter grows to infinity, and a poorly-connected graph, i.e., the algebraic connectivity decays to zero. The main consequence of these findings is the proof that the time of consensus in RRGs grows to infinity as the rectangle becomes more elongated. In closing, consensus dynamics in RRGs strongly depend on the geometric characteristics of the embedding space, and reaching the consensus state becomes more difficult as the rectangle is more elongated. © 2015 Elsevier B.V.

Velasco-Elizondo P.,Center for Mathematical Research
CCE 2011 - 2011 8th International Conference on Electrical Engineering, Computing Science and Automatic Control, Program and Abstract Book | Year: 2011

Several works on using Component-based Development to construct Software Product Lines have been reported. However, shortcomings in both approaches have limited the benefits of combining them in practice for the development of software asset variants. This paper explores the feasibility of using composition operators to construct such variants from pre-existing software components. The variants are implemented as composite components, which provide variant behaviours that can be reused in a Software Product Line. Via a case study, we will show that the use of these operators enables a consistent and systematic approach to variant construction. Other benefits of our approach are design preservation, modularity and automation. © 2011 IEEE.

Velasco Elizondo P.,Center for Mathematical Research
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

Software Product Line (SPL) approaches enable the development of software product variants by reusing a set of software core assets. These assets could have variant features themselves that can be configured in different ways to provide different behaviours. Unfortunately, in many SPL approaches software core assets are constructed from scratch and in an ad hoc manner. © 2010 Springer-Verlag Berlin Heidelberg.

Vigueras J.F.,Center for Mathematical Research | Rivera M.,Center for Mathematical Research
Pattern Recognition | Year: 2010

We introduce a two-step iterative segmentation and registration method to find coplanar surfaces among stereo images of a polyhedral environment. The novelties of this paper are: (i) to propose a user-defined initialization easing the image matching and segmentation, (ii) to incorporate color appearance and planar projection information into a Bayesian segmentation scheme, and (iii) to add consistency to the projective transformations related to the polyhedral structure of the scenes. The method utilizes an assisted Bayesian color segmentation scheme. The initial user-assisted segmentation is used to define search regions for planar homography image registration. The two reliable methods cooperate to obtain probabilities for coplanar regions with similar color information that are used to get a new segmentation by means of quadratic Markov measure fields (QMMF). We search for the best regions by iterating both steps: registration and segmentation. © 2009 Elsevier Ltd. All rights reserved.

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