Papers by RAFAEL MENDOZA CRUZ
IEEE Transactions on Signal Processing, 2015
This paper considers the problem of estimating and tracking channels in a distributed transmissio... more This paper considers the problem of estimating and tracking channels in a distributed transmission system with transmit nodes and receive nodes. Since each node in the distributed transmission system has an independent local oscillator, the effective channel between each transmit node and each receive node has time-varying phase and frequency offsets which must be tracked and predicted to facilitate coherent transmission. A linear time-invariant state-space model is developed and is shown to be observable but nonstabilizable. To quantify the steady-state performance of a Kalman filter channel tracker, two methods are developed to efficiently compute the steady-state prediction covariance. The first method requires the solution of a-dimensional discrete-time algebraic Riccati equation, but allows for nonhomogenous oscillator parameters. The second method requires the solution of four two-dimensional discrete-time algebraic Riccati equations but requires homogenous oscillator parameters for all nodes in the system. An asymptotic analysis is also presented for the homogenous oscillator case for systems with a large number of transmit and receive nodes with closed-form results for all of the elements in the asymptotic prediction covariance as a function of the carrier frequency, oscillator parameters, and channel measurement period. Numeric results confirm the analysis and demonstrate the effect of the oscillator parameters on the ability of the distributed transmission system to achieve coherent transmission.
International Journal of Molecular Sciences, 2020
Unlike seed plants, ferns leaves are considered to be structures with delayed determinacy, with a... more Unlike seed plants, ferns leaves are considered to be structures with delayed determinacy, with a leaf apical meristem similar to the shoot apical meristems. To better understand the meristematic organization during leaf development and determinacy control, we analyzed the cell divisions and expression of Class I KNOX genes in Mickelia scandens, a fern that produces larger leaves with more pinnae in its climbing form than in its terrestrial form. We performed anatomical, in situ hybridization, and qRT-PCR experiments with histone H4 (cell division marker) and Class I KNOX genes. We found that Class I KNOX genes are expressed in shoot apical meristems, leaf apical meristems, and pinnae primordia. During early development, cell divisions occur in the most distal regions of the analyzed structures, including pinnae, and are not restricted to apical cells. Fern leaves and pinnae bear apical meristems that may partially act as indeterminate shoots, supporting the hypothesis of homology b...
Comparative medicine, 2016
Biomedical translational research frequently incorporates collection of CSF from NHP, because CSF... more Biomedical translational research frequently incorporates collection of CSF from NHP, because CSF drug levels are used as a surrogate for CNS tissue penetration in pharmacokinetic and dynamic studies. Surgical placement of a CNS ventricular catheter reservoir for CSF collection is an intensive model to create and maintain and thus may not be feasible or practical for short-term studies. Furthermore, previous NHP lumbar port models require laminectomy for catheter placement. The new model uses a minimally invasive technique for percutaneous placement of a lumbar catheter to create a closed, subcutaneous system for effective, repeated CSF sample collection. None of the rhesus macaques (Macaca mulatta; n = 10) implanted with our minimally invasive lumbar port (MILP) system experienced neurologic deficits, postoperative infection of the surgical site, or skin erosion around the port throughout the 21.7-mo study. Functional MILP systems were maintained in 70% of the macaques, with multip...
Plant Systematics and Evolution
The aim of the study is to compare distinct morphological characters of Metrodorea (Rutaceae) wit... more The aim of the study is to compare distinct morphological characters of Metrodorea (Rutaceae) with those of related genera, under a phylogenetic approach. Morphoanatomy of leaves was analyzed, and data concerning reproductive structures were compiled from the literature. We used available molecular sequences to recover a maximum likelihood tree, and we present a reconstruction of ancestral morphological character states made with the maximum likelihood criterion. The topologies obtained retrieve as synapomorphic characters of Metrodorea: aborted leaflets, vascularized intrapetiolar stipules, sinuous cell walls contour in the surface view of the epidermis, glandular trichomes on the adaxial and proximal region of the petiole, good development of areoles, muricate fruits, and valvate estivation of the corolla. The specific relationships within Metrodorea and between Metrodorea and other genera of Rutoideae are supported by characters as the location of crystals, type of adherence at leaf bases, and presence/absence of trichomes on the blade. The close relationship of Metrodorea and Raulinoa is strongly supported by several synapomorphies. Our data are mostly consistent with recent phylogenies, showing that the monophyly of Esenbeckia cannot be confirmed and that the clade Helietta-Balfourodendron (formerly included in another subfamily) is closely related to Raulinoa and Metrodorea (both part of Pilocarpinae) than to Pilocarpus itself. Possible relationships between these genera are discussed based on the morphological states found, and most of them supporting the hypothesis that Metrodorea is the sister group of Raulinoa.
Latin American …, 2000
REPORTS FLAKED STONE AND SOCIAL INTERACTION IN THE CASAS GRANDES REGION, CHIHUAHUA, MEXICO Todd L... more REPORTS FLAKED STONE AND SOCIAL INTERACTION IN THE CASAS GRANDES REGION, CHIHUAHUA, MEXICO Todd L. VanPool, Christine S. VanPool, Rafael Cruz Antillón, Robert D. Leonard, and Marcel J. Harmon This analysis uses flaked stone ...
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Papers by RAFAEL MENDOZA CRUZ