Ensenada Center for Scientific Research and Higher Education

About: Ensenada Center for Scientific Research and Higher Education is a facility organization based out in Ensenada, Mexico. It is known for research contribution in the topics: Population & Nonlinear system. The organization has 1934 authors who have published 3733 publications receiving 63115 citations.

Learning PID structures in an introductory course of automatic control

Abstract: Proportional-integral-derivative (PID) controllers are described in most automatic control textbooks. The application of PID controllers is widely spread in automation of mechanical processes where control of motors is of concern. This paper focuses on implementation of the PID control when used for regulation of do motors. Two basic PID structures for position regulation of armature-controlled do motors are studied: the classical structure based on PID position loop plus velocity feedback, and a hierarchical two-loop feedback structure invoking a velocity proportional-integral (PI) inner loop. It is shown that the latter requires simpler stability conditions than the former. Basic concepts from automatic control are evoked in this study, namely, transfer function, characteristic polynomial, stability, and Routh-Hurwitz criterion. Experiments on a direct-drive motor are provided to illustrate the PID control performance.

Functional characterization and cellular dynamics of the CDC-42 - RAC - CDC-24 module in Neurospora crassa.

Abstract: Rho-type GTPases are key regulators that control eukaryotic cell polarity, but their role in fungal morphogenesis is only beginning to emerge. In this study, we investigate the role of the CDC-42 – RAC – CDC-24 module in Neurospora crassa. rac and cdc-42 deletion mutants are viable, but generate highly compact colonies with severe morphological defects. Double mutants carrying conditional and loss of function alleles of rac and cdc-42 are lethal, indicating that both GTPases share at least one common essential function. The defects of the GTPase mutants are phenocopied by deletion and conditional alleles of the guanine exchange factor (GEF) cdc-24, and in vitro GDP-GTP exchange assays identify CDC-24 as specific GEF for both CDC-42 and RAC. In vivo confocal microscopy shows that this module is organized as membrane-associated cap that covers the hyphal apex. However, the specific localization patterns of the three proteins are distinct, indicating different functions of RAC and CDC-42 within the hyphal tip. CDC-42 localized as confined apical membrane-associated crescent, while RAC labeled a membrane-associated ring excluding the region labeled by CDC42. The GEF CDC-24 occupied a strategic position, localizing as broad apical membrane-associated crescent and in the apical cytosol excluding the Spitzenkorper. RAC and CDC-42 also display distinct localization patterns during branch initiation and germ tube formation, with CDC-42 accumulating at the plasma membrane before RAC. Together with the distinct cellular defects of rac and cdc-42 mutants, these localizations suggest that CDC-42 is more important for polarity establishment, while the primary function of RAC may be maintaining polarity. In summary, this study identifies CDC-24 as essential regulator for RAC and CDC-42 that have common and distinct functions during polarity establishment and maintenance of cell polarity in N. crassa.

Seasonal Evolution of the Geostrophic Circulation in the Northern Gulf of California

Abstract: An improved description of the seasonal variability of the geostrophic circulation in the northern Gulf of California is obtained from a historical hydrographic database larger than in previous studies. The evolution of the geostrophic circulation consists of: a cyclonic (summer) period, an anticyclonic (winter) period and two transition periods. The cyclonic (summer) period lasts from June to September (four months) and is characterized by a strongly baroclinic cyclonic gyre which dominates the circulation. The anticyclonic (winter) period starts in November and persists until April (six months); the anticyclonic geostrophic circulation is less robust than that in summer. The transition periods take of the order of one month, occurring around October and April–May, and are characterized by the simultaneous presence of both types of gyres. Empirical Orthogonal Function analysis shows a strong seasonal signal in the dynamic height for the first mode (97·2% of the total variance), whose spatial structure is a closed gyre, which oscillates between cyclonic during the summer months and anticyclonic the rest of the year. The results strengthen and extend those from previous work based on analysis of hydrographic data, on limited direct observations, on satellite image analysis, and on numerical modelling.

Characterization of the nonclassical nature of conditionally prepared single photons

Abstract: A reliable single photon source is a prerequisite for linear optical quantum computation and for secure quantum key distribution. A criterion yielding a conclusive test of the single photon character of a given source, attainable with realistic detectors, is therefore highly desirable. In the context of heralded single photon sources, such a criterion should be sensitive to the effects of higher photon number contributions, and to vacuum introduced through optical losses, which tend to degrade source performance. In this Rapid Communication we present, theoretically and experimentally, a criterion meeting the above requirements.