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
  • 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
  • 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
  • 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
  • Publication
    A wide dynamic range RF-DC rectifier circuit for a 900MHz energy harvesting system using 180nm CMOS technology
    ( 2023-12-07) Duran Garces, Camilo ; Serrano Rivera, Guillermo ; College of Engineering ; Ducoudray Acevedo, Gladys O. ; Medina Sanchez, Rafael ; Department of Electrical and Computer Engineering ; Ramos Perez, Angela
    En los captadores de energía de RF, la eficiencia del rectificador RF-DC viene determinada por la potencia de RF de entrada, que suele fluctuar debido a las pérdidas en el espacio libre y a las interferencias de la señal, entre otras causas. Para maximizar la transferencia de potencia de RF, el rectificador RF-DC debe mantener una eficiencia de conversión de potencia (PCE) cercana al máximo en un amplio rango de entrada, conocido como rango dinámico (DR). Sin embargo, esto presenta retos a bajos niveles de potencia debido a la tensión umbral del transistor y a altos niveles de potencia debido a las corrientes de fuga inversas del transistor. Este trabajo presenta un rectificador diferencial RF-DC de 900 MHz para sistemas de captación de energía optimizado para un amplio rango dinámico. La arquitectura propuesta incorpora un circuito de realimentación adaptativo para maximizar la transferencia de potencia a niveles bajos de potencia de entrada y reducir las corrientes de fuga a niveles medios y altos de potencia de entrada. Se ha diseñado, simulado y fabricado un prototipo del rectificador RF-DC en la tecnología CMOS de 180 nm Mixed-Mode/RF de UMC. Los resultados de la simulación muestran dos eficiencias de conversión de potencia de pico del 84,49% a -11,34 dBm y del 82,71% a -24,16 dBm, una RD teórica de 30 dB, una RD práctica de 16.56 dB y una sensibilidad de -18,99 dBm.
  • Publication
    Ab initio and DFT calculations of TNT and its interaction with clay minerals: Changes on TNT spectroscopy signature
    ( 2005) Alzate Rodríguez, Liliana F. ; Mina, Nairmen ; College of Arts and Sciencies - Sciences ; Hernández, Samuel P. ; Muñoz, Miguel A. ; Department of Chemistry ; Briano, Julio
    Computational chemistry has been very useful to study the properties of explosives and molecular interactions between explosives and different types of soils. In this work, we used a computational treatment to calculate the properties of 2,4,6- trinitrotoluene (TNT) and its interactions with clay minerals such as kaolinite. In the first part, we performed a geometry optimization, vibrational analysis and solvation effect on the TNT molecule. In the second part, the intermolecular interaction energy, and the vibration frequencies were calculated for the complex of TNT and the siloxane surface of kaolinite. These calculations were made in order to determine the spectroscopic signature of TNT and the possible changes when the TNT interacts with water and soil. The results obtained for the first part show two lower energy conformers for TNT (Cₛ and C₁). Comparison of the calculated energy of the two structures using several basis sets reveals that, the lowest-energy geometry for the TNT structure corresponds to Cₛ symmetry with B3LYP/6-311+G** level of theory and basis set, respectively. Experimental IR spectra of TNT are presented and assigned assisted by theoretical spectra obtained using the B3LYP/6-311+G** level of theory and basis set, respectively. In the second part, the results provide information about the interaction energy of TNT on soil environments. The binding energy between the TNT and the siloxane surface was -38 kJ/mol, obtained with MP2/6-31+G(d) level of theory and basis set, respectively. The calculated interaction has their minimal at a separation between the two systems of 3.5 Å. The theoretical IR spectra of the interaction was obtained with DFT/B3LYP method and the 6-31+G(d) basis set. The spectra calculated predicted a shifting effect in NO₂ bands, due to the interaction. The frequency shifts were compared and confirmed with experimental spectra obtains with IR spectroscopy.
  • Publication
    Ab initio treatment of the RDX-siloxane site surface of clay minerals
    ( 2006) Hernández Cordero, Neiza M. ; Mina, Nairmen ; College of Arts and Sciencies - Sciences ; Castro, Miguel E. ; Hernández-Rivera, Samuel P. ; Department of Chemistry ; Briano, Julio
    The identification of landmines in soil is actually a particular problem around the world. One of the high explosives studied in the past few years is hexahydro-1,3,5-trinitro-s-triazine as well know as RDX. In this work, interactions of RDX with the basal siloxane surface of the clay mineral kaolinite has been perform using computational modeling (Gaussian 03), in order to determine the spectroscopic signature of RDX adsorbed onto clay minerals. In the first part of this work, we performed the optimization geometry and vibrational analysis of three lower-energy conformers. The three lower-energy conformers are distinguished by the arrangement of the nitro groups relative to the triazine ring of the RDX molecule. Two of these conformers have C₃ᵥ symmetry which corresponds to β form, while the third conformer has Cₛ symmetry and corresponds to the α form. The best results, in the optimization of the three conformers were perform using density functional methods (DFT) at the B3LYP/6-311+G (d,p) level of theory. These theoretical calculations were compared to experimental results obtained for the RDX explosive using the FT-IR technique. We also studied the solvation effects on the lowest-energy conformation of RDX molecule. In the second part of this work we used the lowest energy conformation of RDX to carry out the interaction with the siloxane surface. The results point out that the nitro group in pseudo-equatorial position interacts with the siloxane surface. HF, DFT//HF and MP2//HF levels of theory with basis set superposition error (BSSE) correction were perform to obtain the binding energies (E𝘣) and the contribution of dispersion interaction to the binding energies (DE𝘣). The E𝘣 decrease by a factor of ~1.5 once we applied the BSSE correction at different basis sets. Furthermore, the results indicate a decrease in the E𝘣 (~ 13 kJ/mol) when polarization functions (6-31G (d), 6-31G (d,p), 6-311G (d) and 6-311G (d,p)) are added. The calculated binding energy of the RDX-siloxane surface complex is ~ 57 kJ/mol using MP2//HF/6-31+G (d) level of theory and basis set, respectively.
  • Publication
    Above ground forest biomass and carbon status in the Rio Grande de Arecibo watershed
    ( 2005) Suárez-Rozo, María del R. ; Pérez-Alegría, Luis R. ; College of Agricultural Sciences ; Sotomayor Ramirez, David ; Macchiavelli, Raul ; Department of Crops and Agro-Environmental Sciences ; Padilla Cestero, Ingrid
    Tropical forest ecosystems, especially young secondary-rapid growing forests, naturally or artificially developed, have great potential for long term carbon sequestration and storage. This ecosystem function helps to reduce the continuous CO2 emissions to the atmosphere. The objective of this investigation is to generate a base line that will serve as basis to estimate above-ground biomass and carbon fluxes of forest lands in the Rio Grande de Arecibo watershed. Biomass and carbon contents in above-ground vegetation were estimated from forest inventory data taken in the summer, 2003 in the Rio Grande de Arecibo watershed (RGA). The data collected also allowed for structural and species composition analyses of the vegetation. A Geographic Information System using land use, geology and ecological life zone maps of the study area, was developed and used as the basis for stratified random sampling of forests lands in the study area. Above-ground biomass was calculated from prediction equations developed for tropical forests as a function of life zones and rock formation types. Mean above-ground biomass for the RGA was estimated to be 72.8 Ton/ha, and it varies from 69.0 to 88.3 Ton/ha, depending on life zone. These estimates correspond mostly to early secondary forests, with crown closure between 50 and 80%. Statistical analyses showed no significant differences in above-ground biomass content when taking into account rock formation types within a life zone, or among volcanic, plutonic or limestone rock formations. However, a slight, but important difference was detected at the 5% level of significance in above-ground biomass content between life zones (wet, moist and wet lower montane forests). A total of 81 trees species were found in the RGA watershed with Importance Value Indices (I.V.I.) ranging from 0.5 to 16.23. Dominant species are Guarea guidonia, Cecropia schereberiana, Inga vera, Prestoea montana, Dendropanax arboreus, Didymopanax morototoni, and Syzygium jambos, accounting for 50.1% of the I.V.I value and almost 54.6% of the basal area. Dead standing trees accounted for almost 8% of the total I.V.I. value and third ranking position, indicating a large proportion of snags in the forest. The I.V.I. curves of each life zone are fairly steep with long tails, reflecting high dominance of few species, especially in wet lower montane forests where Prestoea montana has an I.V.I. value of 31.54.
  • Publication
    Absorción de CD por Brachiaria Brizantha y Chloris Gayana en tres suelos con diferentes propiedades químicas, físicas y mineralógicas.
    ( 2011) Giuliani-Castillo, Isabelle ; de la Torre, Winston ; College of Agricultural Sciences ; Román, Félix ; Muñoz, Miguel A. ; Department of Crops and Agro-Environmental Sciences ; Harmsen, Dr.Erick
    Phytoremediation is an ecologically friendly, cost effective technique that uses plants to remediate contaminated soil and water. One of the objectives in this study is to evaluate the absorption of cadmium (Cd) by two forage species Brachiaria brizantha and Chloris gayana on three soil series with different chemical, physical and mineralogical properties. The soil series that were evaluated were: San Antón, Coloso and Corozal. On a complete random design with a factorial arrange 2 x 3 x 4 forty-eight plants for each forage species were transplanted in a pots with different concentrations of Cd: control, 10 ppm, 50 ppm and 500 ppm. This experiment was conducted on a seven week period. The parameters studied were plant height, and the number of the leaves. On two different occasions during the experiment, the soils were fertilized and each pot was maintained at the field capacity. Chemical analysis of shoots and roots were performed to determine the total absorption of the metal showing that on roots have significant differences. Showing that Choris gayana at Coloso soil with 500ppm of Cd absorbs 1ppm on the roots. And on the shoots did not have significant differences in the treatments. On plants height and the number of leaves, there were no significant differences. Soil analyses were also done including a sequential extraction to determine the Cd content also showed significant differences in the soil series, indicating that Corozal soil series had more Cd in the soil.
  • Publication
    Abundance, composition and survivorship of juvenile corals in the southwestern Puerto Rico, la Parguera
    ( 2006) Irizarry-Soto, Emmanuel ; Weil, Ernesto F. ; College of Arts and Sciences - Sciences ; Aponte, Nilda E. ; Yoshioka, Paul M. ; Department of Marine Sciences ; Valdés Pizzini, Manuel
    The distribution, abundance, species composition and survivorship of juvenile corals over natural substratum were quantified in 6 reefs along the insular shelf off La Parguera Puerto Rico from August 2003 to August 2005. Juvenile corals were measured in 6 1m2 quadrats randomly placed along four 20 m long transects in four depth intervals (n = 96 quadrats /reef). Survivorship was estimated using six quadrats of 0.25 m2 randomly placed along the same 20 m long transects in each reef. Spatial heterogeneity was estimated with the chain method along each transect line. Spatial variability of juvenile densities was determined with a nested ANOVA model I with quadrats nested within transects, transects within depths, depths within reefs and reefs within zones. A total of 882 juvenile colonies from 26 species were counted in an area of 576m2 (1.5 ± 0.11 col/m2). Juvenile densities increased from shallow habitats (lowest densities) to intermediate and deep habitats within reefs. The spatial scales that explained 85% of the total variability in juvenile distribution was found between the intermediate scales transects (meters) and depths (hundred of meters). Survivorship and recruitment were tested with a Repeated Measures ANOVA and G-test of independence. Survivorship was higher in the intermediate (50%) habitat compare to shallow and deeper habitats. The most abundant genera were Diploria, Montastraea, Porites, Siderastrea and Agaricia and were distributed across and inshore offshore gradient. Juvenile abundances and survivorship were higher at intermediate depths 2.45 (C.I: 2.06-2.92) compare to the shallow 1.31 (C.I: 1.18-1.46) col/m2 and deep intervals 1.81 (C.I: 1.65-1.99) col/m2. New recruits were observed for all the six reefs survey and Media Luna show a total of 30 new individuals among all reefs. Coral recruitment and juvenile survivorship in southwestern Puerto Rico was variable at spatial and temporal scales. This variation was explained by factors such as life history strategies, settlement orientation, the interaction with reef organisms and the possible effects of swells produced by passing hurricanes during the study period.