Theses & Dissertations

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https://hdl.handle.net/20.500.11801/5
This collection is exclusively made up of theses, dissertations, and project reports submitted as a requirement for completing a graduate degree at UPR-Mayagüez. If you are a UPRM graduate student and you are looking for information related to the deposit process, please refer to https://libguides.uprm.edu/repositorioUPRM/tesis

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Browsing Theses & Dissertations 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 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 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
    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.
  • Publication
    Abundancia y composición de las comunidades zoopláncticas sobre los arrecifes coralinos en Isla Desecheo, Puerto Rico
    ( 2005-05) Rodríguez-Jerez, Yira A. ; García-Saís, Jorge R. ; College of Arts and Sciences - Sciences ; López, José Manuel ; Armstrong, Roy A. ; Aponte, Nilda E. ; Department of Marine Sciences ; Santos Flores, Carlos J.
    A study of zooplancton taxonomic composition and abundance was performed in the vicinity of Puerto Canoas and Puerto Botes reefs in Isla Desecheo. The main objective of the study was to examine the influence of the coral reefs in the taxonomic structure and abundance of zooplankton. The approach was to sample the zooplankton in a series of six parallel transects at variable distances away from the reefs system in Isla Desecheo. A total of four sampling cruises were performed during June, September and November 2002, and February 2003. Holoplankton was compossed mainly of calanoids copepods and the abundance varied between 539 – 1,888 Ind/m3. The abundance of the meroplanktonic groups, excluding the fish eggs, fluctuated between 9 – 36 Ind/m3. Fish eggs were the numerically dominant zooplankton group throughout all sampling stations and dates. Results suggest that the reefs of Isla Desecheo are important sources of fish eggs that support a large community of zooplanktivorous fishes above the reefs.
  • Publication
    Abundancia y distribución de Pontodrilus litoralis en las costas cercanas al Faro de Cabo Rojo, Puerto Rico
    ( 2010) Boothby-Carlo, Eduardo ; Borges-Delgado, Sonia ; College of Arts and Sciences - Sciences ; Alfaro, Mónica ; Acosta, Jaime ; Department of Biology ; Cruz Pol, Astrid
    The purpose of this investigation was to determine the structure and dynamics of the populations of the oligochate Pontodrilus litoralis on the coasts near the Cabo Rojo Lighthouse in Puerto Rico. During the months of May of 2008 and February 2009, sampling was made at low tide on the sandy littoral shores of two beaches on each side of the lighthouse. Distances from the tide mark in sand was taken into account. Environmental factors such as temperature, pH, soil moisture, organic matter, and surface accumulation of plant debris were registered. Spatial distribution of Pontodrilus litoralis was determined to be aggregate in clusters. These clusters were predominant right at the high tide marking where sand was always humid but never completely submerged under seawater. Organic matter and temperature were determined to be the primary factors in the distribution of the oligochate. Sites with the lowest temperatures recorded seemed to have the most number of individuals. Sites with the most accumulation of surface plant debris recorded the lowest temperatures as well as the highest organic matter contents. Sites with clusters of individuals recorded the most acidic pH due to heightened cell respiration rates where individuals are numerous. Only a small percentage of the individuals sampled had reached adulthood, this indicates a high reproductive output once the juveniles enter the reproductive stage of adulthood but a relatively slow growth to reach it.
  • Publication
    Acceleration of finite field arithmetic with an application to reverse engineering genetic networks
    ( 2008) Ferrer-Moreno, Edgar ; Bollman, Dorothy ; College of Engineering ; Colon, Omar ; Moreno, Oscar ; Santiago, Nayda ; Department of Electrical and Computer Engineering ; Orozco, Edusmildo
    Finite field arithmetic plays an important role in a wide range of applications. This research is originally motivated by an application of computational biology where genetic networks are modeled by means of finite fields. Nonetheless, this work has application in various research fields including digital signal processing, error correcting codes, Reed-Solomon encoders/decoders, elliptic curve cryptosystems, or computational and algorithmic aspects of commutative algebra. We present a set of efficient algorithms for finite field arithmetic over GF(2m), which are implemented on a High Performance Reconfigurable Computing platform. In this way, we deliver new and efficient designs on Field Programmable Gate Arrays (FPGA) for accelerating finite field arithmetic. Among the arithmetic operations, the most frequently used and time consuming operation is multiplication. We have designed a fast and space-saving multiplier, which has been used for creating other efficient architectures for inversion and exponentiation which have in turn been used for developing a new and efficient architecture for finite field interpolation. Here, the bit-level representation of the elements in GF(2m) and some special structures in the formulation of multiplication and inversion algorithms, have been exploited in order to use efficiently the FPGAs resources. Furthermore, we have also proposed a novel approach for multiplication over finite fields GF(pm), with p 6= 2, where the com putational complexity is reduced from O(n2) to O(n log n).
  • Publication
    Accumulation and elimination of copper by the flat-tree oyster Isognomon alatus
    ( 2007-05) Lebrón García, Sandra J. ; Otero Morales, Ernesto ; College of Arts and Sciences - Sciences ; López, José M. ; Massol Deyá, Arturo ; Aponte, Nilda E. ; Department of Marine Sciences ; Ojeda Serrano, Edgardo
    A baseline study of copper concentrations in I. alatus from Bioluminescent Bay during May 2004 to June 2005 was conducted. In general, average copper levels were (7.64-17.1 μg/g dry wt), which are lower than those previously reported for I. alatus. The accumulation dynamics of copper by Isognomon alatus was examined in the laboratory. Accumulation of Cu was observed at concentration ≥0.1 mg Cu/L. Survival was 100% in oysters exposed to concentrations of 0.1-1.0 mg Cu/L. High mortality was observed at concentrations from 1.5 to 3.0 Cu mg/L after 3-5 days of exposure while the average oyster´s Cu tissue content ranged 115-362 μg/g dry wt. At exposure of 3.87 mg Cu/L the oysters reached Cu concentrations of 1022 and 1259 μg/g dry wt, and 100% of mortality was observed. Furthermore, oysters exposed to 0.5 mg Cu/L for 5 days were transplanted to the field during a 14 days depuration/elimination study to determine depuration rates and biological half-lives (B½) of Cu. In average, these oysters reached a maximum of 72 μg/g dry wt within the first day of incubation and 95% of the copper accumulated was eliminated after 11 days of depuration/elimination, reaching final concentration similar to the control (13 μg/g dry wt). An average biological half-live of 6.0 days was observed thus indicating an efficient depuration capacity by I. alatus.
  • Publication
    Acerca de las formas torcidas sobre los grupos lineales algebraicos
    ( 2008) Uribe Guerra, Gabriel D. ; Walker Ramos, Uroyoán R. ; College of Arts and Sciences - Sciences ; Lorenzo, Edgardo ; Cáceres Duque, Luis Fernando ; Department of Mathematics ; Marrero, Pablo
    Working from the Galois theory, we define linear groups via group schemes. We study different properties of these groups such as connectedness, Lie algebras associated to them, which determine their smoothness. Lastly we use tools from Galois cohomology via Γ-groups to determine the twisted forms associated to a linear algebraic group.
  • Publication
    Aclimatación precoz y suplementación dietética con vitamina e y zinc como alternativas para el manejo del estrés calórico en pollos de engorde
    ( 2008) Martínez-Benavides, Javier A. ; Santiago-Anadón, Héctor L. ; College of Agricultural Sciences ; Latorre Acevedo, José R. ; Riquelme Villagrán, Ernesto O. ; Department of Animal Science ; Román Paoli, Elvin
    The production of broiler chickens in open houses with minimal control of the environment typically takes place in areas of high temperatures causing bird stress and negative effects on the industry. There are diverse procedures to mitigate these effects, such as diet alteration and changes in husbandry practices. Among these alternatives are the early thermal conditioning, the dietary addition of vitamin E and zinc, with the main objective of strengthening the birds immune system in a direct or indirect manner. Experiment 1: The purpose of this investigation was to evaluate the effect of the application of early thermal conditioning (ETC) and the dietary addition of vitamin E and zinc on broiler chicken performance. A total of 600 day-old broilers were raised in a poultry house equipped with 40 floor pens until 42 d of age. A completely randomized design with a factorial arrangement of 2 x 2 x 2 was used where the main effects were: the application of ETC (ETC and without ETC), and the dietary addition of vitamin E (0 and 250 mg/kg) and zinc (0 and 40 mg/kg) for a total of 8 treatments with 5 replicas. The ETC consisted in submitting the birds to a temperature of 41 o C for 6 h at the third d of age. Birds and feed were weighed weekly to determine body weight (BW), feed intake (FI), feed conversion (FC), and mortality. In addition, body temperature (BT) was monitored weekly on 15 birds per treatment measuring the rectal temperature with a digital thermometer. At the end of the rearing period, 25 birds per treatment were randomly selected, slaughtered, and processed to evaluate carcass composition. The yield of hot carcass (HCY), chilled carcass (CCY), breast muscle (BMY), tender muscle (TMY), and fat pad (FPY) expressed as a percentage of live weight. No significant differences among the main effects were found for BW, FI, FC, BT, HCY, CCY, FPY, BMY and TMY. The addition of vitamin E at 250 mg/kg of feed increased bird mortality and reduced carcass FPY. The addition of 250 mg/kg of vitamin E and 40 mg/kg of zinc improved FC of birds when compared to the other treatments, but the differences did not reach statistical significance. In conclusion, the application of ETC, the addition of vitamin E and zinc in the feed at the levels evaluated did not provide any advantages in most of the variables studied. However, the addition of 250 mg/kg of vitamin E and 40 mg/kg of zinc had a positive effect on FC that could justify its commercial utilization. Experiment 2: The purpose of this investigation was to evaluate the most appropriate time for the application of early thermal conditioning (ETC) and its effect on productive performance of broiler chickens raised in a tropical environment. A total of 540 day-old birds were randomly assigned to three treatments and raised until market age (42 d) in an open house with 18 floor pens equipped with tube feeders and nipple drinkers. A completely randomized design with three (3) treatments and six (6) replicas was used in the study. Birds and feed were weighed weekly to determine body weight (BW), feed intake (FI), feed conversion (FC), and mortality. Body temperature (BT) was obtained by measuring the rectal temperature of 18 birds per treatment at the end of each week. At 42 d, a random sample of 36 birds per treatment was chosen for processing and determination of yields and carcass composition. The yield of hot carcass (HCY), chilled carcass (CCY), breast muscle (BMY), tender muscle (TMY), and fat pad (FPY) expressed as a percentage of the birds live weight. No significant differences among treatments were found for BW, FI, FC, BT, HCY , CCY , FPY , BMY , and TMY . The application of ETC at the first d of live resulted in a higher percentage of mortality at the end of the rearing period, while the application of ETC at the third d of life resulted in a lower mortality. In conclusion, the effects on all broiler productive performance parameters except mortality rates were not significantly affected by the application of ETC at any of the days evaluated in this study.
  • Publication
    Acople de HSPF - Un modelo de simulación hidrológica con CE-QUAL-W2 de calidad de agua en el Lago Cerrillos, Ponce, Puerto Rico
    ( 2014) Castro-García, Gustavo ; Pérez-Alegría, Luis R. ; College of Engineering ; Zapata López, Raúl E. ; Segarra, Rafael ; Department of Civil Engineering ; Santana, Alberto
    Este documento presenta el acople del modelo de simulación hidrológica HSPF (Hydrologic Simulation Program FORTRAN) y el modelo de calidad de agua en lagos (CE-QUAL-W2), realizado en la cuenca del Río Cerrillos y su correspondiente lago en Ponce, Puerto Rico. Puerto Rico cuenta con 44 lagos que fueron construidos con propósitos múltiples que incluían control de inundaciones, abasto de agua potable, riego agrícola, generación de energía y recreación. Debido a su importancia para el bienestar de los habitantes de la Isla, constituyen uno de los elementos más importantes en el Plan Integral de Conservación, Desarrollo y Uso de los Recursos de Agua (DRNA, 2007). En este estudio se desarrolló el modelo de simulación hidrológica (HSPF) para estimar flujo y parámetros físico-químicos como datos de entrada para el modelo de calidad de agua del lago (CE-QUALW2). Con este modelo de simulación de calidad de agua se puede predecir la temperatura y el oxígeno disuelto en la columna de agua del lago, y este acople permitiera contestar preguntas relacionadas con el manejo de la cuenca y el lago. El modelo hidrológico y de calidad de agua en el lago se utilizó para evaluar varios escenarios de cambio del uso del terreno en la cuenca del Río Cerrillos de tal manera que se puedan evidenciar como se afecta la calidad de agua en el lago. Los parámetros de calibración del modelo HSPF se obtuvieron a partir de rangos estudiados para cuencas de Puerto Rico. Los parámetros más influyentes en la calibración de modelo hidrológico fueron LZSN, INFIL, UZNS, INTFW, AGWR. Los parámetros más influyentes para la calibración de sedimentos fueron (SST) JSER, KSER, JGER, KASND, EXPSND, TAUCS y M. Para nitrato (NO3) los parámetros fueron SQO y SQOLIM, y para fósforo total (FT) fueron POTFW y POTFS. Los parámetros de calibración del modelo CE-QUAL-W2 se obtuvieron a partir de rangos de valores estudiados para lagos tropicales, y un análisis de sensitividad estimando los parámetros más influyentes. Los datos utilizados en la calibración del modelo de calidad de agua del lago fueron obtenidos del proyecto Z-247 de la Estación Experimental Agrícola de la Universidad de Puerto Rico. Finalmente, se estudiaron tres escenarios de manejo que consistieron en la reducción del área de bosque (15%, 30% y 45%). Esta reducción generó un aumento del flujo de escorrentía y de las concentraciones de los nutrientes y sedimentos a la entrada del lago. A su vez se logró observar una disminución en la cantidad de oxígeno disuelto en el hipolimnio del lago.
  • Publication
    An acoustic method for real time air bubble detection in simulated blood vessels
    ( 2012) Valentín Rodríguez, Francisco I. ; Cancelos, Silvina ; College of Engineering ; Leonardi, Stefano ; Gutierrez, Gustavo ; Department of Mechanical Engineering ; Calcagno, Barbara
    Exposure to significant changes in ambient pressure commonly occurs in divers during surfacing. These changes induce the formation of nitrogen bubbles in tissues and the presence of these bubbles can cause symptoms of decompression sickness (DCS) to appear. Existing methods to minimize the formation of bubbles include denitrogenation strategies and the use of decompression tables. Although these tables are calculated using large safety margins, they are not guaranteed and the occurrence of DCS has been reported even in those who followed suggested protocols. Therefore, the development of a system capable of monitoring bubble presence, number and size, in real time, would be a reliable method for DCS prevention. In this work, we demonstrate a novel technique for bubble detection using a piezoelectric ring (PZT) placed around the human upper thigh and set to resonate at a specific frequency. Our approach uses microphones to monitor distortions in the resonant condition that were induced by the presence of bubbles. A prototype of a simplified human upper thigh was built and bubbles of controlled size were injected into the artificial blood vessel. Using a digitalized data acquisition system, electrical signals on the PZT and microphone were acquired. The results suggested that the presence of a single bubble within the chamber disrupted the signal, displaying a peak in current and phase angles as the bubble crossed the actuation area of the PZT ring. For stationary bubbles, electrical admittance (measured as a function of frequency) demonstrated a higher Pearson correlation coefficient as the bubble was insonated near its resonance frequency than in the absence of bubbles. A summation of Fourier coefficients of voltage signals captured from the pill microphones in the presence of bubbles demonstrated a 94% accuracy in detecting single bubbles, when compared to signals taken in the absence of bubbles. It was concluded that the proposed system produced a measurable response to the presence of large bubbles.
  • Publication
    Acoustic signal representation for environmental surveillance monitoring (esm)
    ( 2007) Yunes, Yuji ; Rodríguez, Domingo ; College of Engineering ; Santiago, Nayda ; Juan, Eduardo ; Department of Electrical and Computer Engineering ; Aponte, Luis
    This work presents an integrated development framework, with scalable and reconfigurable hard- ware/software co-design components, for space-time computational signal processing embed- ded system applications such as acoustic beamforming, aperture synthesis image formation, dis- tributed adaptive signal correlation, correlated interferometry, and distributed virtual instrumen- tation; termed here as the WALSAIP Sensor Grid (WSG), were WALSAIP stands for Wide Area Large Scale Automated Information Processing. The WSG is used as a basis to develop an off- the-shelf approach for the Acoustic Environmental Surveillance Monitoring (ESM) of puerto rican crested toads Bufo lemur. The WSG is based on a centralized architecture, i.e. there exist a central or master node that interacts with the lower nodes and it is responsible for collecting, pro- cessing, and communicating the information from the observatory to an end user or to a server. This design is the result of years of experience working and evaluating other platforms including digital signal processors (DSP), field programmable gate arrays (FPGA), and wireless sensor net- works (WSN) or Motes. The main advantage of the system is that we now have a very flexible tool that can be modified to adress specific needs. We developed the WSG for the treatment of acous- tic signals, since acoustic signals presents the perfect balance between computational complexity and the state of the art on computational platforms. We also formulated the Short-Time Fourier Transform (STFT) under the framework of signal algebra operators. A comparisson between a Cyclic-STFT and Cornell University Raven audio analysis software is presented. Our algorithm produces better resolution graphics at the expense of computational power. Finally, a variant of the STFT was implemented on ARM-powered Gumstix single board computers (SBC) showing a performance comparable with more advanced digital signal processor units such as the Texas Instruments C6713.|Este trabajo de investigación presenta un marco de desarrollo integrado compuesto por elementos de hardware y software reconfigurables y escalables para aplicaciones de procesamiento de señales con atributos espacio-temporales en sistemas embebidos como lo son el beamforming acústico, síintesis para formación de imágenes, correlación de señales distribuídas y adaptivas, interferometría correlacionada e instrumentación virtual distribuída. A este nuevo marco le denominamos con el nombre de WALSAIP Sensor Grid, en donde el término WALSAIP se deriva de la traducción al inglés del procesamiento automatizado de la información a gran escala en áreas amplias. El WSG es usado como base para desarrollar una solución "off-the-shelf" (del anaquel) para tratar el problema de monitoreo y vigilancia ambiental del sapo concho puertorriqueño Bufo lemur. EI WSG esta basado en una arquitectura centralizada, donde un nodo maestro interactúa con nodos inferiores en términos de computación y disponibilidad de recursos con la finalidad de recolectar, procesar y transmitir información sobre el área bajo observación hacia un usuario final de esta información o hacia otros servidores. Esta solución es el resultado de la evaluación de otros sistemas que a nuestro entender eran comparables como los DSP, FPGA y los Motes. La gran ventaja de este sistema radica en la flexibilidad que otorga para tratar aplicaciones heterogéneas utilizando los mismos conceptos fundamentales. La aplicación a tratar fue la de monitoreo ambiental basado en señales acústicas. Elegimos las señales acústicas debido a que presentan un buen balance entre complejidad computacional y el estado del arte en cuanto a plataformas computacionales. Este trabajo formula también la Short-Time Fourier Transform bajo el marco conceptual de teoría de operadores. Una versión cíclica de este algoritmo es puesta en comparación con Raven, un software para el análisis de audio desarrollado por la Universidad de Cornell. Nuestro algoritmo presenta mejores resultados en términos de resolución que Raven a expensas de un incremento en la complejidad computacional. Finalmente, una variante de la STFT es implementada en las computadoras embebidas basadas en una arquitectura de procesadores ARM fabricadas por Gumstix, mostrando un desempeño comparable con arquitecturas mas poderosas como el DSP modelo C6713 del fabricante Texas Instruments.