• The mechanical waves conceptual survey: An analysis of university students' performance, and recommendations for instruction

      Barniol P. (Modestum, 2017-01-01)
      The Mechanical Waves Conceptual Survey (MWCS), presented in 2009, is the most important test to date that has been designed to evaluate university students' understanding of four main topics: propagation, superposition, reflection, and standing waves. In a literature review, we detected a significant need for a study that uses this test as an assessment tool and presents a complete analysis of students' difficulties on the test. This article addresses this need. We administered the MWCS at a private university in Mexico to 541 students. In this article, we present a complete description of these students' performance on the test, a description of their main difficulties, an elaboration of these main difficulties in terms of students' inappropriate conceptions, and recommendations for instruction based on the results obtained by the test. Our analyses may be used by instructors and researchers who intend to use the MWCS or create new instructional material.
    • Medios de comunicación y cultura de la legalidad, hacia la conformación de un diagnóstico en México

      Martínez Garza, Francisco Javier; Lozano Rendón, José Carlos; Tecnológico de Monterrey (2014-12)
      Hace tres años fue creado el Observatorio de Medios y Cultura de la Legalidad, con el objetivo de generar indicadores que permitan identificar y evaluar el manejo que hacen los medios impresos y electrónicos al promover en sus mensajes una cultura de la legalidad. Con los datos obtenidos en el OMCL, en el presente trabajo se realiza un diagnóstico de la forma en que la prensa y los noticieros mexicanos abordan los principios de la cultura de la legalidad en su información, a través del análisis de contenido se monitorearon tres noticieros regiomontanos matutinos (Las Noticias, Info7y Telediario), dos periódicos regiomontanos (El Norte y Milenio), y dos noticieros nacionales nocturnos (El noticiero y Hechos de la noche). El estudio contempla únicamente las noticias relacionadas con violencia, corrupción, comisión de delitos e inseguridad. El instrumento de análisis consta de 8 variables principales que operacionalizan los 8 principios de la cultura de la legalidad. El trabajo realizado por el OMCL resulta relevante por el impacto que pueda tener directamente en los medios noticiosos y contribuir al fomento de la cultura de la legalidad y de una sociedad informada sobre sí misma. Los resultados indican que los medios de comunicación deberían realizar algunas modificaciones en su política editorial a fin de
    • Metabolism of 4-chloro-2-nitrophenol in a Gram-positive bacterium, Exiguobacterium sp. PMA

      Arora, Pankaj K.; Sharma, Ashutosh; Mehta, Richa; Shenoy, Belle D.; Srivastava, Alok; Singh, Vijay P.; Tecnologico de Monterrey (Open Access Publisher, 21/11/2012)
      Abstract Background Chloronitrophenols (CNPs) are widely used in the synthesis of dyes, drugs and pesticides, and constitute a major group of environmental pollutants. 4-Chloro-2-nitrophenol (4C2NP) is an isomer of CNPs that has been detected in various industrial effluents. A number of physicochemical methods have been used for treatment of wastewater containing 4C2NP. These methods are not as effective as microbial degradation, however. Results A 4C2NP-degrading bacterium, Exiguobacterium sp. PMA, which uses 4C2NP as the sole carbon and energy source was isolated from a chemically-contaminated site in India. Exiguobacterium sp. PMA degraded 4C2NP with the release of stoichiometeric amounts of chloride and ammonium ions. The effects of different substrate concentrations and various inoculum sizes on degradation of 4C2NP were investigated. Exiguobacterium sp. PMA degraded 4C2NP up to a concentration of 0.6 mM. High performance liquid chromatography and gas chromatography–mass spectrometry identified 4-chloro-2-aminophenol (4C2AP) and 2-aminophenol (2AP) as possible metabolites of the 4C2NP degradation pathway. The crude extract of 4C2NP-induced PMA cells contained enzymatic activity for 4C2NP reductase and 4C2AP dehalogenase, suggesting the involvement of these enzymes in the degradation of 4C2NP. Microcosm studies using sterile and non-sterile soils spiked with 4C2NP were carried out to monitor the bioremediation potential of Exiguobacterium sp. PMA. The bioremediation of 4C2NP by Exiguobacterium sp. PMA was faster in non-sterilized soil than sterilized soil. Conclusions Our studies indicate that Exiguobacterium sp. PMA may be useful for the bioremediation of 4C2NP-contaminated sites. This is the first report of (i) the formation of 2AP in the 4C2NP degradation pathway by any bacterium and (iii) the bioremediation of 4C2NP by any bacterium.
    • Method for modeling electrorheological dampers using its dynamic characteristics

      Diana Hernández Alcántara; Ricardo Ambrocio Ramírez Mendoza; Rubén Morales Menéndez; Horacio Ahuett Garza
    • Metrics to estimate differential co-expression networks

      Gonzalez-Valbuena, Elpidio-Emmanuel; Trevino, Victor; Tecnologico de Monterrey (BioMed Central, 2017-11-10)
      Abstract Background Detecting the differences in gene expression data is important for understanding the underlying molecular mechanisms. Although the differentially expressed genes are a large component, differences in correlation are becoming an interesting approach to achieving deeper insights. However, diverse metrics have been used to detect differential correlation, making selection and use of a single metric difficult. In addition, available implementations are metric-specific, complicating their use in different contexts. Moreover, because the analyses in the literature have been performed on real data, there are uncertainties regarding the performance of metrics and procedures. Results In this work, we compare four novel and two previously proposed metrics to detect differential correlations. We generated well-controlled datasets into which differences in correlations were carefully introduced by controlled multivariate normal correlation networks and addition of noise. The comparisons were performed on three datasets derived from real tumor data. Our results show that metrics differ in their detection performance and computational time. No single metric was the best in all datasets, but trends show that three metrics are highly correlated and are very good candidates for real data analysis. In contrast, other metrics proposed in the literature seem to show low performance and different detections. Overall, our results suggest that metrics that do not filter correlations perform better. We also show an additional analysis of TCGA breast cancer subtypes. Conclusions We show a methodology to generate controlled datasets for the objective evaluation of differential correlation pipelines, and compare the performance of several metrics. We implemented in R a package called DifCoNet that can provide easy-to-use functions for differential correlation analyses.
    • Microbial degradation of indole and its derivatives

    • MIMO channel capacity using antenna selection and water pouring

      Cuan Cortes, Jose V.; Vargas-Rosales, Cesar; Munoz Rodriguez, David (Springer Open, 30/12/2014)
      Abstract The use of multiple-input multiple-output (MIMO) communication systems has attracted considerable attention due to capacity and performance improvements without increasing the required bandwidth or transmission power. Although MIMO improves the transmission rate and provides reliable communication, these advantages come at a high cost, since multiple radio frequency (RF) chains have to be employed. Therefore, cost-effective implementation of MIMO systems remains as an important challenge. In this sense, antenna selection techniques (AST) can help reduce the high cost of MIMO systems, while retaining most of their benefits; and in order to improve channel capacity, transmission power can be allocated efficiently according to the channel experienced by each antenna element. In this paper, we show the channel capacity improvement of MIMO systems, by combining the use of AST and transmission power allocation through the water-pouring algorithm (WPA) for different antenna configurations. We apply WPA and allocate more power to the channel with better conditions, when the MIMO channel is Rayleigh distributed and noise is Gaussian. By employing these two techniques (AST and WPA), we show that channel capacity is significantly improved, with higher capacity values than those obtained using traditional systems which just spread equal power among all the transmit antennas. We also show that bounds on the capacity can be considered when these improvements are used in a MIMO system.
    • MIMO channel capacity using antenna selection and water pouring

      César Vargas Rosales; David Muñoz Rodríguez
    • Mitigation of salt stress in white clover (Trifolium repens) by Azospirillum brasilense and its inoculation effect

      Khalid, Muhammad; Bilal, Muhammad; Hassani, Danial; Iqbal, Hafiz M N; Wang, Hang; Huang, Danfeng; Khalid, Muhammad; Bilal, Muhammad; Hassani, Danial; Iqbal, Hafiz M N; Wang, Hang; Huang, Danfeng (03/01/2017)
      Abstract Background Salinity is one of the increasingly serious environmental problems worldwide for cultivating agricultural crops. The present study was aimed to ascertain the potential of beneficial soil bacterium Azospirillum brasilense to alleviate saline stress in Trifolium repens. Experimental plants (white clover) were grown from seeds and inoculated with or without A. brasilense bacterial strain supplemented with 0, 40, 80, or 120 mM NaCl into soil. Results The growth attributes including, shoot heights, root lengths, fresh and dry weights, leaf area and chlorophyll content were significantly enhanced in T. repens plants grown in A. brasilense inoculated soil than un-inoculated controls, particularly under elevated salinity conditions (40, 80 and 120 mM NaCl). Malondialdehyde content of leaf was recorded to be declined under saline conditions. Moreover, the K+/Na+ ratio was also improved in bacterium-inoculated plants, since A. brasilense significantly reduced the root and shoot Na+ level under high salty environment. Conclusions Results revealed that soil inoculation with A. brasilense could significantly promote T. repens growth under both non-saline and saline environments, and this study might be extended to other vegetables and crops for the germination and growth enhancement.
    • Modelling gene expression profiles related to prostate tumor progression using binary states

      Martinez, Emmanuel; Trevino, Victor (Open Access Publisher, 31/05/2013)
      Abstract Background Cancer is a complex disease commonly characterized by the disrupted activity of several cancer-related genes such as oncogenes and tumor-suppressor genes. Previous studies suggest that the process of tumor progression to malignancy is dynamic and can be traced by changes in gene expression. Despite the enormous efforts made for differential expression detection and biomarker discovery, few methods have been designed to model the gene expression level to tumor stage during malignancy progression. Such models could help us understand the dynamics and simplify or reveal the complexity of tumor progression. Methods We have modeled an on-off state of gene activation per sample then per stage to select gene expression profiles associated to tumor progression. The selection is guided by statistical significance of profiles based on random permutated datasets. Results We show that our method identifies expected profiles corresponding to oncogenes and tumor suppressor genes in a prostate tumor progression dataset. Comparisons with other methods support our findings and indicate that a considerable proportion of significant profiles is not found by other statistical tests commonly used to detect differential expression between tumor stages nor found by other tailored methods. Ontology and pathway analysis concurred with these findings. Conclusions Results suggest that our methodology may be a valuable tool to study tumor malignancy progression, which might reveal novel cancer therapies.