Browsing by Title

  • Publication
    16 inch composite material telescope with adaptive optics.key components: wavefront reconstructor & vibration testing
    ( 2006) Sanatiago, Freddy ; Chang, Mark J.L. ; College of Arts and Science - Science ; Roura-Davila, Erick ; Jiménez, Héctor ; Department of Physics ; Castillo, Paul
    Advances in technology has provided means for astronomical optical telescopes to increase the aperture diameter (more light collecting capability) therefore increasing the resolution. Better resolution allows telescopes to observe more details and fainter objects. But an increase in diameter means an increase in optics size, which needs big and heavy structures to support them. New developments in composite materials have allowed Composite Mirror Application(CMA) in Tucson, Arizona to build a carbon fiber reinforced polymer(CFRP) telescope and optics for the Naval Research Laboratory(NRL), reducing significantly its weight. Other than weight, atmospheric turbulence is the other major problem for an increase in telescope resolution, but technologies such as adaptive optics(AO) can mitigate its effects. AO refers to systems which can adapt to compensate for effects introduced by the atmosphere or another medium. This thesis presents the results of two studies done on this next-generation telescope. First it presents work done on the development of two wavefront reconstructors for AO systems that the new telescope will use. The two reconstructors are based on Finite Difference(FD) and Finite Element(FE) methods, respectively. Second, work done on the characterization of the vibration behavior for this new type of composite material telescope is presented. Preliminary analysis of the data was performed using a new technique for analysing nonlinear systems, the Empirical Mode Decomposition(EMD). Data for both experiments was obtained from a 16 inch composite material telescope prototype and from a non-conventional AO system Shack-Hartmann wavefront sensor.
  • Publication
    3D collagen scaffold for peripherial nerve regeneration
    ( 2018-05) Rivera-Martínez, Carol A. ; Latorre-Esteves, Magda ; College of Engineering ; Almodóvar Montañez, Jorge ; Resto Irizarry, Pedro ; Juan, Eduardo J. ; Department of Chemical Engineering ; Acevedo Rullán, Aldo
    The nerve regeneration process is a complex pathway that most of the time is not completed and represents a life of limitations for people that suffers from injury or diseases that compromises neuron functionality involving the peripherial nervous system. The use of allografts and autografts are the primary solutions, although many limitations arise such as donor site morbidity and limited grafting material. Basic requirements for the nerve regeneration process, involve presence of natural components, neurotrophic factors and 3D morphology to promote physical and biological support to surroundings cells. These elements are the fundaments to incorporated within the design of a biomaterial that will promote peripherial nerve regeneration. Nerve conduits have brought interest as powerful solutions based in the fact of been natural polymer 3D structures with highly tunable properties and, that mimic the extracellular matrix (ECM). In this research a 3D collagen type I scaffold will be presented with tunable properties such as nanofiber diameter and orientation. Diameter and orientation of the nanofibers are crucial factors to influence the cell interactions and further cell functionalization towards proliferation and expression of neurotrophic factors and guide the regeneration process. Electrospinning technique was used to develop the scaffold and its versatility made possible the modification to the scaffold properties. The morphology of the scaffold nanofibers was analyzed with Scanning Electron Microscope (SEM), along with a quantitative measured with ImageJ software. The chemical composition of collagen type I was corroborated with Fourier Transform Infrared Spectroscopy (FT-IR). Fluorescent microscopy was used to identify the cell adherence to the scaffold and monitored cell growth direction influenced by the orientation of the scaffold nanofibers. The results showcase the potential of electrospun collagen type I scaffold to promote cell adhesion, along with control of direction and organization of cell growth. The development of the scaffold with variable morphologies (random and align) and diameters promotes a 3D platform, baseline data study for nerve regeneration process and wide design possibilities for a nerve conduit that best fits the cell environment and mimics the ECM.
  • Publication
    3D high-speed photography for characterization of drag and lift fluctuations of a single rising bubble
    ( 2020-12-11) Valle Reyes, Harold ; Cancelos, Silvina ; College of Engineering ; Torres Nieves, Sheilla ; Gutiérrez, Gustavo ; Department of Mechanical Engineering ; Marín Martín, Carlos
    Understanding the bubble motion in fluids is a topic of great interest in multiple applications in nature because of the significant impact and influence that this type of phenomenon has in numerous fields of engineering and science. In nuclear reactors, where the heat transfer process is relevant, accurate measurements to characterize the principal parameters involved in bubble hydrodynamics are required. Unfortunately, there is still a lack of pertinent information, specifically, data for large and deformable bubbles regarding drag, lift, and terminal velocity. This information is essential for improving numerical models of processes where bubbles are encountered. In this work, a 3D experimental study using high-speed photography and the PIV technique was performed to characterize the principal parameters of the bubble such as shape, terminal velocity, drag, and lift in distilled water (DW), tap water at 50 ppm (TW1) and 100 ppm (TW2). Bubble diameters ranging from 0.6 to 3.6 mm were released with the help of an experimental setup that was designed and built to have driven-buoyancy bubbles, typically. Dimensionless parameters in the range of 90
  • Publication
    A Bayesian adaptive smoothing and thresholding approach for activation detection in single-subject fMRI
    ( 2024-07-10) Flórez Coronel, Juan Esteban ; Almodóvar Rivera, Israel ; College of Arts and Sciences - Sciences ; Bustillo Zarate, Alcibiades ; Rivera Santiago, Roberto ; Department of Mathematics ; Romañach, Rodolfo J.
    Functional Magnetic Resonance Imaging (fMRI) is a widely used non-invasive medical procedure for studying brain function. Identifying activated regions of the brain is a common challenge in fMRI analysis. Low-signal and small data cases pose significant difficulties for activation detection. These scenarios arise when studying high-level cognitive tasks or single-subject experiments, respectively. In this study, we propose an innovative algorithm, entitled Bayesian Fast Adaptive Smoothing and Thresholding (BFAST), which utilizes smoothing and extreme value theory on probabilistic maps to find threshold values. The algorithm’s performance was evaluated on artificial data that simulated a range of signal magnitudes. The results were promising, with an average similarity of 85% with respect to the expected output. Furthermore, the proposed procedure was applied to a study that aimed to identify the cerebral regions responsible for processing beliefs and questions as stimuli. Our findings suggest that the BFAST algorithm holds promise for detecting activated areas in the brain with high accuracy, particularly in cases involving low-signal and small data. Such advancements in fMRI analysis algorithms could lead to more accurate and precise studies of brain function, with significant implications for both clinical and research settings.
  • Publication
    A Bayesian machine learning approach for EEG functional connectivity estimation and working memory load classification in human subjects
    ( 2024-05) Gangapuram, Harshini ; Manian, Vidya ; College of Engineering ; Vega, José Fernando ; Juan, Eduardo J. ; Meléndez, José ; Department of Electrical and Computer Engineering ; Cruzado Vélez, Ivette
    Analyzing working memory is essential for understanding cognitive processes and improving educational strategies, mental health diagnostics, and psychological interventions. Electroencephalogram (EEG) signals, known for their high temporal correlation, effectively capture these subtle responses, highlighting the importance of assessing EEG-based functional connectivity across various frequency bands to understand brain dynamics under varying cognitive loads. Traditional methods, typically involving regression models, often face challenges like biased connectivity estimates due to enforced sparsity and inaccuracies from small sample sizes or sampling noise. Addressing these issues, the current study develops a Bayesian structure learning algorithm to learn the functional connectivity of EEG. This approach ensures accurate connectivity analyses across different frequency bands. Next, functional connectivity features are given as an input to graph convolutional network to classify working memory loads. This study analyzes five working memory datasets to evaluate the proposed methodology. The subject-specific classification yields an average sensitivity and specificity of 92% and 94%, respectively. The proposed methodology produced consistent results in functional connectivity estimation compared to state-of-the-art functional connectivity metrics. The study finds that encoding information is critical in altering functional connectivity for different working memory loads rather than its manipulation/retention of tasks.
  • Publication
    A bimetallic Be/Cu pillared-layered porous coordination polymer for selective CO2 removal via adsorption
    ( 2023-05-06) Tous Granados, Alberto M. ; Hernández Maldonado, Arturo J. ; College of Engineering ; Pagán Torres, Yomaira ; Méndez Román, Rafael ; Department of Chemical Engineering ; Ramos Pérez, Ángela
    The removal of carbon dioxide from gas mixtures via adsorption is of utmost importance to mitigate global warming and for air purification in confined spaces. New combinations of chemical species and topologies can be incorporated into porous coordination polymers (PCPs) to develop novel functional adsorbents. In this work, an adaptation of the metalloligand two-step approach was demonstrated as an effective method to construct a new bimetallic beryllium/copper pillared-layered PCP reported for the first time. The resulting compound [Cu2(pzdc)2(Be(pyac)2)]n [pzdc: pyrazine-2,3-dicarboxylate; Be(pyac)2: Bis[3-(4-pyridyl)pentane-2,4-dionato]beryllium(II)] was characterized by elemental analysis, Rietveld refinement of powder X-ray diffraction data, textural properties, and thermal stability. The new compound has an estimated BET surface area of about 284 m2 g-1 and is stable to about 250 °C. The heterometallic Cu/Be pillared PCP was probed to have the ability to strongly interact with CO2 molecules, evidenced by larger heat of adsorption (41 kJ mol-1) and IAST selectivity >60 for separating CO2/N2 (15:85) mixtures at 25 °C and 1 atm, compared to similar but monometallic PCPs. It is finally proposed that bimetallic synergy may prove useful in future syntheses of specific gas adsorbents.
  • Publication
    A classic of situatedness: The Second Sex and its feminist effects
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 2002) Anderlini D'Onofrio, Serena ; University of Puerto Rico at Mayagüez ; Department of Humanities
  • Publication
    A comparison framework for optimizing seizure prediction from reduced scalp EEG channels based on spectral features and DNN meta-learning
    ( 2023-05-12) Romney Díaz, Aníbal ; Manian, Vidya ; College of Engineering ; Vega, José F. ; Juan, Eduardo J. ; Torres García, Wandaliz ; Other ; Pérez Muñoz, Ferando
    Epileptogenesis and unprovoked recurrent seizure are the main obstacles posed in the study of epilepsy. Recent studies are focusing on non-invasive methods for the prediction of seizure onset. Limitations of most seizure prediction methods include a need for a reduced and personalized scalp electrode selection, a model algorithm capable of training with small data samples, and more flexible computational resources. To tackle these limitations, this study presents a patient-specific reduced scalp channel selection for seizure prediction based on model-agnostic meta-learning (MAML). MAML is used to optimize a deep neural network (DNN) trained on a reduced and personalized set of electrodes. The implemented MAML prediction model learns patterns in the preictal and ictal states from each selected group of subject-dependent electrodes. Sequential feature selection (SFS) and empirical ensemble mode decomposition (EEMD) are used to select and extract feature vectors from the most significant electrodes. The EEMD extracted all intrinsic mode oscillatory functions (IMFs) in the segmented frame in the preictal and interictal states. Sixteen IMFs per channel were obtained, and Relief filtered the IMFs with the most significant features to fit the prediction model at different horizon times. The power spectral density in the preictal region exhibits higher values than in the interictal transition, confirming the presence of signature patterns of the preictal stage. These distinctive values in the IMF oscillations were consistent across all horizon times, resulting in a small number of gradient updates for an optimized model. The experiment results yield an average sensitivity and specificity of 91% and 90%, respectively. The False Positive Rate per hour (FPR/h) over three-horizon times was measured as 0.26. This work demonstrates that the proposed non-invasive method represents a compelling alternative to reducing the number of channels in the scalp EEG with a horizon time from 5 minutes to 1 hour.
  • Publication
    A contraluz
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 2000) Montobbio, Santiago ; National University of Distance Education (UNED), Spain
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    A contribution to the knowledge of the avifauna of the Sierra de Luquillo, Puerto Rico
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 1966) Recher, Harry F. ; Recher, Judy T.
    Observations on population density, distribution and behavior of the bird suecies found in the El Yunque region of the Sierra de Luquillo are presented. Some comments are made on the status of rare or reportedly extinct species.
  • Publication
    A la muerte
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 2012) Ríos Cordero, Hugo ; Rutgers University
  • Publication
    A morphological and molecular contribution on bethic ostracods, with emphasis on the populations of caribbean meshophotic reefs
    ( 2015) Galindo Estronza, Alexandra M. ; Alfaro, Mónica ; College of Arts and Sciencies - Sciences ; V. Schizas, Nikolaos ; Santos, Carlos ; Department of Biology ; Ojeda Serrano, Edgardo
    Ostracods are tiny crustaceans enclosed in a bivalve shell that are found worldwide inhabiting many aquatic environments. The taxonomy, distribution and ecology of marine ostracods remain incomplete in the Caribbean, even though they are among the most successful microcrustaceans of marine ecosystems. In an effort to increase our knowledge of the biodiversity, abundance and distribution of benthic ostracods, several sediment samples from mesophotic coral ecosystems (MCEs) of Puerto Rico and US Virgin Islands were collected at different depths (30-102 m) using technical diving. Ostracods were either hand sorted directly from the sediment samples or after a Ludox AM-30 colloidal silica resuspension and centrifugation step, used for mass-extraction of meiofauna and macrofauna. The highest densities of ostracods with the most abundant and diverse assemblages were found in the deepest samples (≥ 61 m). All ostracods collected belong to the subclasses Myodocopa and Podocopa. The Myodocopa was represented by the families Cylindroleberididae, Sarsiellidae, Cypridinidae, Rutidermatidae and Philomedidae; on the other hand, the families or superfamilies that represented the Podocopa were Bairdiidae, Xestoleberididae, Macrocyprididae, Pontocyprididae, Cytherellidae, Cytheroidea, Loxoconchidae, Cytheromatidae, Bythocytheridae, and Candonidae. The subclass Podocopa showed the highest number of individuals and species. Using a morphological (shell shape, shell patterns and ornamentation) and molecular barcoding approach (28S rDNA), we provide the first report of the biodiversity of ostracods in the MCEs of NE Caribbean.
  • Publication
    A Native American in Paris: Landscapes of dislocation in the heartsong of charging elk and three day road
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 2013) Jaskulski, Józef ; University of Warsaw-Poland
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    A new race of Otophryne robusta boulunger (Amphibia, salientia) from the Chimanta - Tepui of Venezuela
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 1967) Rivero, Juan A. ; University of Puerto Rico at Mayagüez ; Department of Biology
    A race of Otophryne robusta is described from high elevations in the Chimanta-tepui of Venezuela. The race, Otophryne robusta steyermarki, can be distin guished from the typical form by lacking a vertical, triangular knob at the angle of the jaw, by its more extensively webbed toes and perhaps by its different coloration and longer hind linb.
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    A new species of parasitic copepod from the Caribbean
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 1966) Price, Charles E. ; North Texas State University, Denton, Texas
    A new species of parasitic Copepoda was recovered from the gills of the queen angelfish, Holocanthus ciliaris (L.), taken from various regions in the vicinity of Miami. Florida. This new species, Anuretes fedderni, is morphologically described. Notes concerning the status of Pseudanuretes Yamagutl, 1936 are included.
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    A note on the reinvestigation of the foraminiferal localities of the Cipero Coast, Trinidad, West Indies
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 1966) Cater, Maxwell C.
    Erosion has somewhat changed the profile of the Cipero type section. It was therefore necessary to resample the area prior to the Fourth Caribbean Geological Conference. The results of this work together with a new map of the Coast are given.
  • Publication
    A post-colonial Ursula Le Guin
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 2010) Caesar, Judith ; American University of Sharjah, United Arab Emirates
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    A short history of the deer of St. Croix
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 1966) Seaman, G.A.
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    A stranded sperm whale, Physeter catodon, at Cayo Santiago, Puerto Rico
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 1988) Mignucci Giannoni, Antonio A. ; San Juan, Puerto Rico
  • Publication
    A suspended, timeless universe: Macrohistoric appropriations of caravaggism in Chevalier's Virgin narrative
    (Centro de Publicaciones Académicas, Facultad de Artes y Ciencias, Universidad de Puerto Rico en Mayagüez, 2009) Elston, M. Melissa ; University of Texas - Permian Basin