Estimator stability analysis in SLAM

IFAC Symposium on Intelligent Autonomous Vehicles (IAV), 2004, Lisboa (Portugal)This work presents an analysis of the state estimation error dynamics for a linear system within the Kalman filter based approach to Simultaneous Localization and Map Building. Our objective is to demonstrate that such dynamics is marginally stable. The paper also presents the necessary modifications required in the observation model, in order to guarantee zero mean stable error dynamics. Simulations for a one-dimensional robot and a planar vehicle are presented.This work was supported by the project 'Supervised learning of industrial scenes by means of an active vision equipped mobile robot.' (J-00063).Peer Reviewe

Stochastic State Estimation for Simultaneous Localization and Map Building in Mobile Robotics

En Cutting Edge Robotics, 223-242. Advanced Robotic Systems Press, 2005.The study of stochastic models for Simultaneous Localization and Map Building (SLAM) in mobile robotics has been an active research topic for over fifteen years. Within the Kalman filter (KF) approach to SLAM, seminal work (Smith and Cheeseman, 1986) suggested that as successive landmark observations take place, the correlation between the estimates of the location of such landmarks in a map grows continuously. This observation was later ratified (Dissanayake et al., 2001) with a proof showing that the estimated map converges monotonically to a relative map with zero uncertainty. They also showed how the absolute accuracy of the map reaches a lower bound defined only by the initial vehicle uncertainty, and proved it for a one-landmark vehicle with no process noise. From an estimation theoretic point of view, we address these results as a consequence of partial observability. We show that error free reconstruction of the map state vector is not possible with typical measurement models, regardless of the vehicle model chosen, and show experimentally that the expected error in state estimation is proportional to the number of landmarks used. Error free reconstruction is only possible once full observability is guaranteed.This work was supported by projects: 'Supervised learning of industrial scenes by means of an active vision equipped mobile robot.' (J-00063), 'Integration of robust perception, learning, and navigation systems in mobile robotics' (J-0929).Peer Reviewe

Coherent optical transduction of suspended microcapillary resonators for multi-parameter sensing applications

Characterization of micro and nanoparticle mass has become increasingly relevant in a wide range of fields, from materials science to drug development. The real-time analysis of complex mixtures in liquids demands very high mass sensitivity and high throughput. One of the most promising approaches for real-time measurements in liquid, with an excellent mass sensitivity, is the use of suspended microchannel resonators, where a carrier liquid containing the analytes flows through a nanomechanical resonator while tracking its resonance frequency shift. To this end, an extremely sensitive mechanical displacement technique is necessary. Here, we have developed an optomechanical transduction technique to enhance the mechanical displacement sensitivity of optically transparent hollow nanomechanical resonators. The capillaries have been fabricated by using a thermal stretching technique, which allows to accurately control the final dimensions of the device. We have experimentally demonstrated the light coupling into the fused silica capillary walls and how the evanescent light coming out from the silica interferes with the surrounding electromagnetic field distribution, a standing wave sustained by the incident laser and the reflected power from the substrate, modulating the reflectivity. The enhancement of the displacement sensitivity due to this interferometric modulation (two orders of magnitude better than compared with previous accomplishments) has been theoretically predicted and experimentally demonstrated

Incorporating social opinion in the evolution of an epidemic spread

The evolution of the COVID19 pandemic worldwide has shown that the most common and effective strategy to control it used worldwide involve imposing mobility constrains to the population. A determinant factor in the success of such policies is the cooperation of the population involved but this is something, at least, difficult to measure. In this manuscript, we propose a method to incorporate in epidemic models empirical data accounting for the society predisposition to cooperate with the mobility restriction policiesThis research is supported by the Spanish Ministerio de Economía y Competitividad and European Regional Development Fund, research grant No. COV20/00617 and RTI2018-097063-B-I00 AEI/FEDER, UE; by Xunta de Galicia, Research Grant No. 2018-PG082, and the CRETUS Strategic Partnership, AGRUP2015/02, supported by Xunta de Galicia. All these programs are co-funded by FEDER (UE). We also acknowledge support from the Portuguese Foundation for Science and Technology (FCT) within the Project n. 147S

Efecto de la regulación por pH y la expresión del factor de transcripción PacC sobre la producción de antibióticos betalactámicos en Acremonium chrysogenum

Acremonium chrysogenum es un hongo filamentoso productor de cefalosporina C (CPC), un antibiótico beta-lactámico de amplio espectro y baja toxicidad que sirve de base para la síntesis química de todas las cefalosporinas de uso clínico. Estas características hacen de la CPC un producto de alto valor agregado. Actualmente, A. chrysogenum es el único productor de CPC a nivel industrial. La biosíntesis de CPC se encuentra regulada por diversos factores y uno de los más importantes es el pH ambiental, que ejerce su función reguladora a través del regulador global de transcripción PacC. Cuando las condiciones ambientales de pH son entre ácidas y neutras la proteína PacC se encuentra inactiva, en una conformación cerrada. Cuando las condiciones cambian de neutras a alcalinas, se desencadena una cascada de señalización por pH que resulta en el rompimiento proteolítico del factor de transcripción PacC, llevándolo a su forma activa. Una vez activo, PacC regula positivamente la transcripción de la mayoría de los genes involucrados en la biosíntesis de CPC. Varios estudios han demostrado que la producción de CPC por A. chrysogenum es más alta cuando se utilizan sistemas de cultivo en estado sólido (SSF) en comparación con sistemas sumergidos (SmF). Además, se ha observado que existe un intervalo de valores de pH que favorece la producción de CPC, tanto en SSF como en SmF. En el presente trabajo se estudiaron, desde un punto de vista molecular, las diferencias entre la producción de CPC en SSF y SmF por A. chrysogenum. Se realizó un análisis de expresión de los genes cefD2 y cefEF, que codifican para dos enzimas limitantes de la biosíntesis de CPC, y del gen cefT, que codifica para una enzima involucrada en la secreción del antibiótico; en ambos sistemas de cultivo a pH controlado. Se encontraron diferencias importantes en los niveles de transcripción de estos genes, siendo estadísticamente mayor su expresión relativa (ER) en SSF. La ER máxima del gen cefD2 en SmF fue apenas el 7.46% de la alcanzada en SSF, mientras que la del gen cefEF fue del 65.8%, y la del gen cefT del 42.4%. Estos resultados son las primeras evidencias que reportan diferencias a nivel transcripcional en los genes biosintéticos de CPC de A. chrysogenum, influenciadas por las condiciones del sistema de cultivo. Por otra parte, se activó constitutivamente el factor de transcripción PacC de A. chrysogenum, truncando el gen pacC hasta el sitio correspondiente para que su expresión diera lugar a la forma activa de la proteína, creando un fenotipo de mimetismo alcalino. La mutación se introdujo en la cepa silvestre de A. chrysogenum y en la cepa de alta producción C10 y se observaron sus efectos sobre la producción de antibióticos beta-lactámicos en dos medios diferentes de cultivo, ambos amortiguados a pH ácido. Se observaron incrementos significativos en la producción específica de antibióticos beta-lactámicos, de hasta 21.3 veces en medio definido y hasta 12.4 veces en medio complejo, por una de las mutantes de la cepa silvestre. Sin embargo, no se observaron mejoras significativas de la producción en las mutantes de la cepa C10, sugiriendo que en esta cepa ya se encuentra desregulada la señalización por pH ambiental. Finalmente, se llevó a cabo la inactivación del factor de transcripción PacC en A. chrysogenum mediante la interrupción del gen pacC en la región correspondiente al dominio de unión al ADN y la señal de localización nuclear y el silenciamiento del mismo gen utilizando la tecnología del ARN interferente. La interrupción del gen resultó aparentemente letal para la cepa silvestre de A. chrysogenum. El silenciamiento del gen afectó negativamente al crecimiento en medio sólido pero no en cultivo líquido. La producción específica de antibióticos beta-lactámicos no resultó ser estadísticamente diferente en las cepas con el gen pacC silenciado en comparación con la cepa parental y la cepa control. El presente trabajo continúa con la aplicación de las herramientas moleculares para comprender más en detalle los mecanismos de regulación de la biosíntesis de CPC y persigue mejorar genéticamente la producción de este antibiótico haciendo uso de los conocimientos sobre la señalización por pH ambiental.Acremonium chrysogenum is a filamentous fungus capable to produce cephalosporin C (CPC), a broad spectrum beta-lactam antibiotic with relatively low toxicity. CPC is mainly used to produce the whole array of cephalosporins for clinic use. A. chrysogenum is the only known CPC producing microorganism. For these reasons, CPC is a high value-added product of great clinic and industrial interest. The CPC biosynthesis pathway is regulated in several ways. Ambient pH signaling is one of the most important regulating factors. pH regulation is exerted through the general transcription factor PacC. When the pH of the culture medium is acidic to neutral, PacC is inactive. When the pH becomes alkaline a signaling cascade begins, resulting in two successive proteolytic cleavages of PacC, leading to its active form. Once it has been activated, PacC upregulates the transcription of most genes involved in CPC biosynthesis. Some studies had demonstrated that CPC production by A. chrysogenum is higher when solid-state fermentation (SSF) systems are utilized, in comparison with submerged fermentations (SmF). Furthermore, it has been observed that there is a pH range in which the CPC production is better in both systems. In this work, we studied, from a molecular point of view, the differences between SSF and SmF during CPC production. We performed an expression analysis of the cefD2, cefEF and cefT genes from A. chrysogenum. The first two encode two limiting enzymes for CPC biosynthesis, and the last encodes for a transporter protein involved in the antibiotic exportation. Both types of fermentation were made within a controlled pH interval. We found important differences at transcriptional level for the expression of these genes. In the three cases, the relative expression (RE) of the genes was statistically higher in SSF than in SmF. The highest RE for the cefD2 gene in SmF was only 7.46% of that observed in SSF, whereas the corresponding to the cefEF gene was 65.8%, and for the cefT gene was 42.4%. These results are the first evidence of the differences, at the transcriptional level, of the CPC biosynthetic genes, whose expression is influenced by the conditions of the fermentation system. On the other hand, we activated constitutively the transcription factor PacC from A. chrysogenum, by truncating the pacC gene to the site corresponding for the direct expression of the active form of the protein, creating an alkaline-mimicking phenotype. The mutation was introduced in the wild type (WT) and C10 (high producer) strains of A. chrysogenum, and its effects were observed on the beta-lactam antibiotics production, carried on two different fermentation medium buffered at acidic pH. Significant increases were observed in the specific production (SP) of beta-lactam antibiotics. For example, the P17 mutant of the WT strain, reached up to 21.3-fold the SP observed in the parental strain in a defined medium, and up to 12.4-fold in a complex medium. Nevertheless, no significant increase was observed in the SP of the C10 mutants, which suggests that this strain has already deregulated the ambient-pHsignaling pathway. Finally, we inactivated the transcriptional factor PacC in A. chrysogenum, by disrupting the pacC gene in the DNA-binding domain and the nuclear localization signal, and silenced the pacC gene by interference RNA. Disruption was apparently lethal for A. chrysogenum wild type. Silencing negatively affected the growth in solid medium but not in liquid culture. The specific production of beta-lactam antibiotics was not statistically different in pacC-silenced strains compared to the wild type and control strains. This work continues with the application of molecular tools to further understanding of the regulation mechanisms of CPC biosynthesis, and attempts to improve genetically CPC production, using the knowledge on the ambient-pH signaling

Efecto de una mutación de mimetismo alcalino en el factor de transcripción PacC de Acremonium chrysogenum sobre la producción de antibióticos beta-lactámicos

Cephalosporin C (CPC) belongs to the beta-lactam antibiotics group, which are currently the most prescribed antimicrobials, and economically the most important drugs. This compound is the core of overall semisynthetic cephalosporins for clinical use. Cephalosporins have low toxicity and wide spectrum against Gram-negative and Grampositive bacteria, in small concentrations. CPC is exclusively produced by the filamentous fungus Acremonium chrysogenum. The biosynthesis pathway of CPC is strongly regulated by environmental pH signaling through transcription factor PacC. When environmental pH is acidic to neutral, transcription factor PacC (621 aminoacid residues) has a closed conformation. When environmental pH becomes alkaline, a signal transduction pathway is activated which results in processing of PacC by two successive proteolytic steps, turning it to an active form (~ 250 aminoacid residues). At this point, activated PacC migrates to nucleus and stimulates the transcription of the majority of the CPC biosynthetic genes. In this work, using genetic engineering techniques, we designed a mutation in the A. chrysogenum transcription factor PacC, removing 366 aminoacid residues from the Cterminal end, so that the mutated pacC resulted directly in its active form. Mutated PacC was expressed in A. chrysogenum wild type under the control of a constitutive promoter and its own promoter, with the aim to demonstrate the hypothesis that this mutation would allow an alkaline mimicking phenotype, so that we could obtain an increase of beta-lactams titers, including CPC, irrespective of the pH values in the fermentation broth. We obtained eleven strains with our mutation, and three of them showed a significant increase of beta-lactams production, in comparison with the parental strain, both in alkaline fermentation medium or in acidic buffered medium. In this way, the majority of the mutated strains showed higher levels than parental strain, in a chemically defined medium whith pH buffered to 5.5. These results confirm that our genetic engineering strategy increased significantly beta-lactams production in A. chrysogenum wild type.La cefalosporina C (CPC) pertenece al grupo de antibióticos beta-lactámicos, los compuestos antimicrobianos más prescritos en la actualidad y los más importantes desde el punto de vista económico. La CPC es la base de las cefalosporinas semisintéticas de uso clínico, un grupo de antibióticos de amplio espectro y baja toxicidad, altamente efectivos contra microorganismos Gram-negativos y Gram-positivos, en concentraciones relativamente bajas. Actualmente, la CPC se produce exclusivamente a partir del hongo filamentoso Acremonium chrysogenum y su biosíntesis se encuentra regulada, entre otros mecanismos, por el factor de transcripción PacC, a través de la señalización por pH ambiental. Cuando las condiciones de pH ambiental son ácidas a neutras, el factor de transcripción PacC, con 621 residuos de aminoácidos, se encuentra en una conformación cerrada. Cuando las condiciones cambian a alcalinas ocurre toda una cascada de eventos que concluye en dos rompimientos proteolíticos sucesivos del factor de transcripción PacC, dejándolo en su forma activa, de aproximadamente 250 residuos de aminoácidos. Una vez activado, PacC se dirige al núcleo y promueve la transcripción de la mayoría de los genes involucrados en la biosíntesis de CPC. En el presente trabajo se realizó, mediante técnicas de ingeniería genética, una eliminación de 366 residuos de aminoácidos del extremo carboxilo terminal en el factor de transcripción PacC de A. chrysogenum, de manera que la mutación generara directamente la forma activa de PacC. La mutación se expresó en la cepa silvestre de A. chrysogenum bajo el control de un promotor constitutivo y del propio promotor del gen pacC, con la hipótesis de que la mutación introducida conduciría a un fenotipo de mimetismo alcalino y, por lo tanto, se podría observar un aumento en la producción de antibióticos beta-lactámicos, incluyendo la producción de CPC, aún cuando los valores de pH fuesen ácidos. Como resultado, se obtuvieron once cepas portadoras de la mutación, de las cuales tres mostraron un incremento significativo en la producción de antibióticos betalactámicos en comparación con la cepa parental, tanto en un medio de fermentación con pH alcalino, como en uno amortiguado a pH ácido. Así mismo, la mayoría de las cepas mutantes mostraron niveles de producción superiores a la cepa parental, utilizando un medio definido con pH amortiguado a 5.5. Se confirma así que la estrategia empleada permitió mejorar significativamente la producción de antibióticos beta-lactámicos en una cepa silvestre de A. chrysogenum

Hybrid metaheuristics for the accessibility windows assembly line balancing problem level 2 (AWALBP-L2)

This paper addresses an assembly line balancing problem in which the length of the workpieces is larger than the width of the workstations. The problem differs from traditional variants of assembly line balancing in the sense that only a portion of the workpiece, or portions of two consecutive workpieces, can be reached from any workstation. Consequently, at any stationary stage of the cycle, each workstation can only process a portion of the tasks, namely, those which are inside the area of a workpiece that is reachable from the workstation. The objective is to find a (cyclic) movement scheme of the workpieces along the line and a task assignment to stationary stages of the production process, while minimizing the cycle time. We propose three hybrid approaches of metaheuristics and mathematical programming - one based on simulated annealing and the other two based on tabu search, relying on different neighborhood definitions. The two former approaches make use of a classical neighborhood, obtained by applying local changes to a current solution. The latter approach, in contrast, draws ideas from the corridor method to define a corridor around the current solution, via the imposition of exogenous constraints on the solution space of the problem. An extensive computational experiment is carried out to test the performance of the proposed approaches, improving the best results published to date.Postprint (author's final draft

Estrategias de subsistencia para la obtención del ingreso y consumo de los miembros de las unidades domésticas en situación de pobreza y pobreza extrema : el caso de dos colonias del municipio de General Mariano Escobedo, Nuevo León

Tesis (Maestría en Trabajo Social) UANLUANLhttp://www.uanl.mx