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Fuentes-Figueroa, Angel G.; Department of Physics, UPR-Mayagüez; Soles, Christopher*, Polymers Division, National Institute of Standards and Technology Measuring the diffusion coefficient of different polymer films
To further reduce the size of integrated circuits and improve the performance of computer chips, we have to explore the physical property changes that can occur in thin polymer films, like those used in photolithography, and understand how these property deviations affect our ability to produce better, smaller and faster semiconductor devices. Previous measurements at the National Institute of Standards and Technology (NIST) show that thin films absorb more small molecules penetrants (i.e., water vapor) as compared to thicker films. However, it is also important to understand the behavior of the diffusion coefficient of small molecules when the film thickness is reduced. The diffusion coefficient of small molecules will also affect the photoacid (H+) mobility in the polymer film. Changes in the H+ mobility are alarming for the photolithography community, as the H+ diffusion must be stringently controlled to optimize the resolution of a photoresist formulation. In this presentation we try to find a relationship between the thickness of different polymer films and the diffusion coefficients of small molecule in these films using a Quartz Crystal Microbalance (QCM) device to determine the mass absorption of a solvent (in our case water). The QCM uses the piezoelectric effect to generate a harmonic oscillation in a quartz crystal on which the polymer film has been coated. When air saturated with water is passed over the crystal, the polymer starts absorbing water. This effectively increases the mass of the film and shifts the resonance of the crystal to a lower frequency (co2=k/m). By knowing the mass uptake as a function of time, we can calculate the diffusion coefficient into the thin film. By understanding the kinetics of small molecule and/or photoacid transport in thin polymer films, these experiments will help implement thinner films in deep UV lithography, and therefore the production of smaller integrated chip devices.
Collado-Vega, Yaireska M.*UPR-Mayagüez, Facultad de Artes y Ciencias; Departamento de Física; Reed, Cindy H. National Institute of Standards and Technology- Indoor Air Quality and Ventilation Group (BFRL)
Characterization of Airflow in a Manufactured House
The Indoor Air Quality and Ventilation Group at NIST recently received a manufactured house test facility to conduct research on ventilation and indoor air pollution in residential buildings. To prepare this house for these research projects it is important to create an airflow model of the house. We can then characterize the airflow through the envelope and the ventilation systems both experimentally and through modeling, in this case using a software program developed at NIST CONTAMW2.0. This is a multi zone indoor air quality and ventilation analysis program designed to help determine: airflows, contaminant concentrations and/or personal exposure to contaminants. The house model contains different ventilation system components such as ducts, exhaust fans, and ventilation inlets. Simulations were performed to predict the outdoor air ventilation rates into the house by infiltration and mechanical ventilation. These ventilation rates were also measured experimentally to validate the model. The model predictions and measurements will also help us evaluate requirements to provide adequate levels of outdoor air ventilation in manufactured houses. Results of these simulations will be discussed and presented.
Rivera, Efraín*UPR-Humacao, Física Aplicada a la Electrónica; Ruiz, A. Buenrostros, A. Camacho, A.J. Placeres, J.C.
The Great Moon Buggy Race 2003
Se presentarán las especificaciones y características básicas del carro de la UPR en Humacao que participará en la competencia “The Great Moon Buggy Race 2003” en “Marshall Space Fligth Center” en Huntsville Alabama los dias 11 y 12 de Abril de 2003. Esta competencia es entre carros de propulsión humana disenados para todo tipo de terreno y que puedan llevar dos pasajeros (hombre y mujer). Se exige que el carro desarmado se pueda acomodarse en un espacio de 4*4*4pies. Ademas, suficientemente liviano como para poder ser cargado por sus ocupantes. La ruta consite de un circuito de poco menos de una milla con 19 obtáculos que simulan la superficie lunar. Nuestro Carro es un triciclo con tracción en las tres ruedas y peso aproximado de 31kg. El tiempo aproximado para armarlo es de 15 segundos.
Camacho, Alex*UPR-Humacao, Department of Physics; Ruíz, A. Bruckman, W.A. Buenrostro, A. Rivera, E.
Búsqueda de cráteres de Impacto en el Area de Puerto Rico
Se presentan los resultados de una búsqueda sistemática de cráteres de impacto a lo largo de toda el área de Puerto Rico y aguas circundantes. El trabajo se realizó mediante el uso de imágenes de satélites, fotos aéreas y bancos de datos disponibles. Preliminarmente se han identificado cuatro estructuras, dos en tierra y dos en el mar. Todas presentan morfología circular o semicircular, que podrían ser compatibles con el remanente de un impacto de meteorito
Aponte, Milca*UPR-Humacao, Department of Physics & Electronics;
A Simple Non-Destructive Technique to Measure the Elastic Constants of Concrete during the Curing Process
We designed a novel experiment to measure the transverse and longitudinal Young modulus, the Shear modulus, and the Poisson’s ratio of a homemade concrete sample by analyzing its standing modes of vibration in a way similar to that of the C-215 ASTM Standard. This experiment is the result of an undergraduate research program that was born as a part of an effort to upgrade the contents of the Intermediate Laboratory course in our Applied Physics undergraduate program. Our technique is much simpler than that of the standard, since it only uses ordinary student laboratory equipment and some piezoelectric transducers. The technique works even during the curing of the concrete sample process, something that is not possible with the C-215 ASTM Standard. Our results have a precision comparable to that of the standard. We make the samples following the C-192 ASTM standardized process. The experiment allows us to understand the properties of one of the most useful and complex materials in our society, and to review several concepts about waves such as wave equations, resonant modes of vibrations, dispersion relations, and standing waves.
Acknowledgments: This work is supported by National Science Foundation (DMR 9872689).
Araya, Esteban*UPR-Rio Piedras, Natural Sciences, Physics Depart.; Physics Department Hofner, Peter Physics Department, UPR-RP & Arecibo Observatory, Baan, Willem, ASTRON & Westerbork Observatory, Netherlands
Arecibo Survey of Extragalactic Formaldehyde
We present the results of our extragalactic formaldehyde survey conducted at the Arecibo Observatory. The 6cm K-doublet transition of ortho-formaldehyde was observed toward a sample of 63 extragalactic objects which comprise: nearby spiral galaxies, ultra-luminous FIR galaxies with known OH megamaser activity and OH absorbers. The hydrogen recombination line H110alpha was observed toward a subsample of 54 sources. We report the discovery of formaldehyde absorption toward NGC 520 and the first detection of H110alpha toward NGC 604. This research is partially supported by the Puerto Rico NASA Space Grant Consortium.
Benson, Elixia*UPR-Humacao, Department of Physics and Electronics, Cotto, Desireé; Orama, Maite; Rosado, Ileana; Carrión, Pedro; Muller, Rafael
Measuring position angles and separation of binary stars
We have analyzed the information obtained at the NURO 31-inch telescope located in Flagstaff, Arizona. We have measured the separation and position angle of standard binaries, like Xi Bootis, and neglected binaries, like KZA 80. The separation is measured in arcsec (seconds in an arc) after pixelizing the image, while the position angle is measured in degrees after locating the north of the system. Then we compared the results obtained with the ones in the Washington Double Star Catalog. Using this information we are able to find the masses, luminosity and distance of these systems, which is extremely valuable information for the study of the stars.
Calderín Ojeda, Cynthia* UPR-Humacao, Physics and Electronics Department/University of Puerto Rico at Humacao; Furlan, Rogelio, Physics and Electronics Department/University of Puerto Rico at Humacao
Study and Characterization of Microfluidic Devices
Microdevices with no movable parts built using Micro-Electro-Mechanical System (MEMS) Technology, microfluidic amplifiers, are being analyzed in terms of input and output flows and pressures. These devices, formed with microchannels etched in silicon and sealed with glass, are being placed on a setup that contains a special support to access the input and output microchannels, and also mass flow and pressure sensors. We are investigating operation conditions to obtain gas flow control. In a microfluidic amplifier a jet emerging from the supply port interacts with flows from the control ports in a interaction region, and as a result, the jet from the supply port is directed to one or another output. Vent outputs can also be used, as in our case, to decrease the internal pressure. In this research we are characterizing a microfluidic amplifier with a hydraulic diameter higher than 40 µm. The analysis of this device as a flow divider demonstrates that a symmetric output flow can be obtained, depending on the supply pressure, and that the asymmetric behavior can be related to internal turbulence, as observed for microfluidic amplifiers with a hydraulic diameter of ~ 40 µm. For a higher hydraulic diameter the range of control resulted very limited and we are investigating how to improve it. This work has been supported by PR-AMP, IDEAS-ER (NASA) and NSF-DMR-9872689.
Castillo, Roberto*UPR-Humacao, Physics and Electronics Department/University of Puerto Rico at Humacao; Furlan, Rogerio Physics and Electronics Department Ramos, Idalia Physics and Electronics Department
Analysis of Low Temperature Co-Fired Ceramics (LTCC) as a Mechanical Substrate for Microfluidic Applications
Low Temperature Co-Fired Ceramics (LTCC), also known as green tapes, represent a promising alternative to be used as a mechanical substrate to replace silicon in meso and micro fabrication. Microfluidic systems can be built on these substrates by defining microchannels on the ceramics and using sealing with ceramics or glass. In order to use LTCC tapes as a mechanical substrate, their characteristics of rigidity, flatness and surface roughness have to be investigated. Thus, in this work, we cut the tape (Dupont 951 AT) in small pieces, 10mm x 15mm, a size that can be considered typical for microfluidic devices. These samples were placed on a substrate of alumina and heated in air at temperatures ranging from 500 C to 900 C. After thermal treatment the samples were visually inspected for analysis of flatness and rigidity, and the roughness was measured using a profilometer (Alpha Step 500, Tencor). Our results demonstrate that a better condition is obtained for a thermal treatment at 700 C. After been heated at this temperature the sample presents sufficient rigidity to be manipulated and presents a maximum roughness lower than 1 µm, which is tolerable in terms of anodic bonding, i.e. a process that we will explore to seal the ceramic substrate with glass. This work has been supported by NASA Space Grant Scholarship/Fellowship, IDEAS-ER (NASA) and NSF-DMR-9872689.
Carrión, Pedro*UPR-Humacao, Physics and Electronics
Using Electroless Deposition of Metals on Paper and Transparency for the Construction of Simple Electronic Circuitry
In some industrial applications, there are manufacturing processes that fabricate electronic devices using materials that are very expensive. Thus, it is important to discover new manufacturing processes that minimize the cost in device fabrication. We report on the deposition of metals on paper and on transparencies for the purpose of building simple electronic circuitry. We will report on our conductivity measurements of the metal deposited on paper and on transparencies. In addition, we shall apply this technology to build simple electronic circuits that will be used to operate for example a light bulb. In this process we use a computer with an appropriate program like Microsoft Paint 2000 and design a circuit and print it on regular “Xerox” paper or on overhead transparencies using a standard laser printer. We combine the method of “Line Patterning” with the electroless deposition technique to achieve our objective. The later technique was used mainly for conducting polymers, but now modified to be used with metals. The metals that we plan to deposit will be nickel and gold. The ultimate goal to this endeavor is to be able to fabricate cheap, throw away electronic circuits. This work was supported by NSF.
Cotto, Desireé*UPR-Humacao, Física Aplicada a la Electrónica; Benson, Elixia, Física Aplicada a la Electrónica, UPR-Humacao, Orama, Maite, Física, Aplicada a la Electrónica, UPR-Humacao Rosado, Ileana Física, Aplicada a la Electrónica, UPR-Humacao Carrión, Pedro, Física Aplicada a la Electrónica, UPR-Humacao, Muller, Rafael, Prof. Departamento Física y Electrónica, UPR-Humacao
Position Angle and Separation of Binary Stars
Our research is focused in the study of binary stars. We are analyzing data obtained at the 31-inch NURO Telescope in Flagstaff, Arizona. The data is analyzed using computational methods. Our specific interest is to determinate the angle and separation of binary stars. This information is very important because it yields the mass of visual binary stars. We have obtained the position/angle of the following neglected binaries: ES 204, STT 434, HJ 560, HJ 1264, HJ 2777, STF 3064, HJ 1899, HJ 1839, AG 423, MLB 424, HJ 1479, AG 375 and HJ 1349. Our methodology includes pixelizing images to obtain separation with a known plate scale. This method seems to be accurate and promising.
Delgado-Martí, Hugo J.*UPR-Río Piedras, Departamento de Física Ciencias Naturales; Hofner, Peter, Physics Department, University of Puerto Rico at Río Piedras & Arecibo Observatory, Whitney, Barbara, Space Science Institute, Churchwell, Ed, University of Wisconsin-Madison, Watson, Alan M., Instituto de Astronomía Universidad Nacional Autónoma de Mexico
Chandra Study of X-ray Sources near the W3 Star Forming Region
W3 is a well known, but complex, star forming region located at around 2.3 kpc. The high resolution and the great positional accuracy of the Chandra X-ray telescope allowed us to identify the X-ray emission in W3 as 236 distinct X-ray point sources with significant emission within the field of view. Around 101 of these point sources are located near the W3 core. Here we present an analysis of the X-ray properties of the W3 region, including variability and spectroscopy. The X-ray light curves show significant variability on different time-scales and we have detected a few sources which exhibit flaring behavior. We have studied the spectra of the brightest sources and found that these are consistent with an absorbed thermal plasma. We also have used new NIR data covering the entire W3 core to identify infrared sources with their X-ray counterparts. This research was funded in part by Research Corporation grant CC 4996 and NSF grant AST-0098524.
Diaz, Melissa*UPR-Humacao, Dept. Physics and Electronics; Figueroa, Glendalys, Dept. Physics and Electronics, UPR Humacao, Rodrigues, Ana Neilde, Univ of Sao Paulo Ramos, Idalia, Dept. Physics and Electronics, UPR Humacao, Furlan, Rogerio, Dept. Physics and Electronics,UPR Humacao, Santiago-Aviles, Jorge J., Univ. of Pennsylvania
Dielectric Characterization of Low Temperature Co-Fired Ceramics
Low Temperature Co-Fired Ceramic (LTCC) is a glass-ceramic composite material. This ceramic have this name because they can be fired at low temperatures. The ceramic component its alumina, glass mostly silica and lead oxides. LTCC also knows as green tape because of its color and flexibility before being fired or sintered. The study of the microstructural and the dielectric properties of sintered LTCC are important for micro and meso electromechanical systems application. The samples are fired for periods of 1 to 3 hours and for temperatures ranging from 350 to 950ºC. The grain characteristic (average grain size and grain size distribution) is analyzed using scanning electron and atomic force microcopies. The dielectric properties (real permittivity and dielectric loss) for frequencies in the range 100kHz to 1.2GHz are measured using a high frequency materials analyzer and correlations between the results are established. This work was supported by NSF Collaborative to Integrate Research and Education (Grant #9872689)
Font, Carlos O.*UPR-Mayagüez, Physics Department
Development of a Laser Spark Plug
Laser spark ignition is an innovative technique that can be used to increase the efficiency of the combustion in an engine. At the same time that potentially decreases the environment contamination produced by the regular combustion process and the maintenance cost of the engine. Q-switched Nd:YAG lasers are a good option for the development of this technique because they can be focused to produce a plasma spark with sufficient energy to ignite a flammable gas mixture. Current technology allows building a compact diode laser pumped Nd:YAG laser with all the requirements to apply this technique. In the near future, because of developments in diode pump lasers, this could be a cost effective spark plug for a natural gas powered engine used in distributed power generation.
This presentation defines needed operating parameters for efficient operation of a laser spark plug. It also includes a discussion of the construction of a Nd:YAG laser prototype to substitute a regular spark plug. Operation of a reciprocating engine with flash lamp pumped Nd:YAG laser spark ignition is also discussed
Garcia, Laiza*UPR-Humacao, Physics and Electronics; María Lucía Pereira DaSilva University of Sao Paulo, Ramos, Idalia, Dept. Physics and Electronics, UPR Humacao Furlan, Rogerio, Dept. Physics and Electronics, UPR Humacao, Jorge J. Santiago University of Pennsylvania
Study of Chemical Mechanisms on LTCC Etching]
The objective of this work is to study the dissolution rate of Low Temperature Co- fired Ceramics (LTCC). LTCC is composed of 40% Alumina (Al2O3), 45% glasses and 15 % of organics. The LTCC sample is immersed in a solvent (acetone) and the etch produced on it is measured using a profilometer. Etch rate is analyzed as a function of the time of exposure and carrier gas. The results will be used to have a better understanding of Jet Vapor Etching, a technique used to produce features on LTCC samples by using an atomized jet of acetone. This work is supported by NSF grant # 9872689 and the Puerto Rico Alliance for Minority Participation (PR-AMP).
González Lisojo, José J.*UPR-Arecibo, Rodriguez Lamourt, Keidy; Rodriguez Lamout, Emilitza; Cruz Vélez, Jessica; Martínez Rios, Luis, Departamento de Física - Química
Produción de Metano por Bioreacción de Materia Orgánica
El petróleo y
sus derivados como combustible para la producción de energía es el más usado
en el mundo. No obstante, también es una de las mayores causas de
contaminación de nuestro ambiente. La producción de metano por el proceso de
bioreacción o fermentación de desechos orgánicos es una técnica conocida,
pero innovadora en la producción de nuevas fuentes de energía a nivel
mundial, especialmente en Japón, India, y U.S.A. En este proyecto, la
producción de metano se llevó a cabo en un fermentador anaeróbico. Se
trabajó con tres tipos de materia orgánica, estiercol de ganado vacuno,
estiercol de ganado porcino y jacintos de agua con el propósito de evaluar
su rendimiento en metano y establecer parámetros físicos más adecuados. Se
determinó que a temperaturas de 32- 36 C y un pH 6.47- 7.17 la producción
es más alta. Por cromatografía de gases se determinó el pico característico
del metano y la precensia de benceno y bióxido de carbono. El mejor
rendimiento de metano se logró a partir de la fermentación de estiercol de
ganado vacuno y jacinto de agua (10- 14 L). La producción de la mezcla de
estiercol y jacinto comenzó a partir de los primeros cuatro días
incrementando su producción a los 20 días hasta un periodo de 44 días. La
producción de metano a partir de estiercol vacuno es mucho más baja (2.5-3
L) en un periodo de 4-30 días. En futuros proyectos se tratará de comprimir
el gas para consumo doméstico y energía eléctrica en las fincas ganaderas
del área de Arecibo y Hatillo.
González, Rosana*UPR-Humacao, Department of Physics & Electronics
Ka-Band Geo Propagation Experiment in the Tropics
The scope of the work is to analyze rain attenuation and rainfall data in a tropical zone at the Ka-band frequency of 20.7 GHz. At this frequency band the rain attenuation factor is of great concern for the development of space communication systems.
The Ka-Band GEO Propagation Experiment is a campaign lead by NASA Glenn Research Center to measure signal attenuation due to rainfall. The data will be recorded at the University of Puerto Rico, Humacao Campus to study propagation effects.
Humacao is a tropical rain zone area. This area is characterized to have many rain events and heavy rainfall during the year. The ground station consists of a 1.2 meters offset reflector antenna, a radiometer that also works at 20.7 GHz and a digital receiver to process the satellite beacon signal. Also a meteorological station provides us with a wind speed indicator, a tipping bucket to measure cumulative rain, and two other instruments to obtain the temperature, relative humidity and barometric pressure data.
The data collection on Humacao started on July 2001. Summary of research:
1. Develop MathCAD and Matlab Programs to statistically analysed collected data.
2. Develop Matlab codes for correlating rain rates to signal attenuation.
3. Validate prediction models with data collected.
Lind, Miguel A.*UPR-Humacao, Biology Department; R. Gonzales; Dr. J.C.Cersocimo; P.E. L. A.Gonzáles, Department of Physics and Electronics UPR Humacao
Unique Hardware for Propagation Measurements at 20.7 GHz (Ka-Band)
Since the early years of satellite telecommunications, the evolution of systems has led to a strong increase in satellite capacity, a decrease of boarded equipment size and a significant cost reduction. In order to achieve the above mentioned goals, it is necessary to operate at higher frequency bands. The main concern with these frequency bands is the influence of the atmosphere on radio wave propagation, this effect directly influence what service availability will be supplied to the user.
This presentation
describes a propagation data collection experiment that locates a unique
data collection terminal in Humacao, Puerto Rico. This site is located in a
tropical rain region. The Ka-band propagation experiment in the tropics
will utilize the EHF propagation payload on the United States’ GBS
satellite. The results from this experiment will be used to improve the
statistical models in these higher frequency bands in wet climates. A detail
description of the data acquisition and data collection hardware will be
presented.
Martínez Muñoz, Carlos*UPR-Humacao, Física aplicada a la Electrónica; Propiedades físicas de los polímeros PVDF en Dimethyl-Acetamide y EB en DMPU
Durante el período de investigación se estudiaron los polímeros semiconductores y sus propiedades físicas como su conductividad. Luego de preparar soluciones de estos polímeros estos se preparaban en forma de fibras y láminas delgadas. Uno de los experimentos realizados fue preparando una solución de 20 wt% Poly(vinylidene)fluoride (PVDF) en Dimethyl-Acetamide. Esto se logró utilizando 2.3425g. de PVDF en 10ml. de Dimethyl-Acetamide. Luego se le realizó “electrospinning” a 20KV con la posición de la pipeta 90o bajo la horizontal. Las fibras se recogieron en agua y en placas de silicio. También se prepararon películas finas de esta solución en laminillas. Se pudo concluir que las fibras se pueden sacar del agua y que estiran mucho. De la misma manera se prepararon soluciones de 5 wt% y 10 wt% de PVDF en Dimethyl-Acetamide. Estos requirieron 0.4932g. y 1.0411g. respectivamente en 10ml. de Dimethyl-Acetamide. También se preparó una solución 15 wt% Emeraldine Base Polyaniline (EBP) en NN’-dimethylpropylene urea (DMPU), para lo que se requirieron 0.9353g. de EB. De esta última solución se prepararon fibras con jeringuilla depositándolas en una solución 70 vol% H2O y 30 vol% NMP. A esta fibra se le añadió HCl para doparla. Luego de dejarlo una noche se le hicieron conexiones y se midió la conductividad, la cual fue de 0.051 S/cm. En esta presentación se mostrarán los datos de conductividad de las fibras de EB y las medidas del diámetro estas fibras utilizando un Microscopio Atómico de Fuerza (AFM).
Martínez Rios, Luis*UPR-Arecibo, Crespo, Yolanda; Sánchez, Liannett; Cruz, Ignivette; DeJesus , Wanda, Departamento de Física - Química
Diseño y Construcción de Equipo de Bombas para Experimentos de Mecánica de Fluidos e Hidráulica
En este proyecto
se diseñó y construyó un equipo de bombas en serie y en paralelo para correr
experimentos de Mecánica de Fluidos e Hidráulica. El equipo se construyó con
tuberías de PVC de 1/2", provista de medidores de presión en la entrada y
salida del sistema, tres válvulas para controlar el flujo en serie y en
paralelo. Las bombas utilizadas fueron de 1/12 HP. y de velocidad variable.
Se corrieron experimentos de medición de flujo y caída de presión a
diferentes velocidades comparando con un equipo industrial, para validar los
resultados, utilizando las ecuaciones de Bernoulli y pérdidas de carga por
fricció de acuerdo a la ecuación de Darcy Weisbach. Los resultados
obtenidos son satisfactorias y se acercan casi un 100% al equipo de control.
Medina, Eric*UPR-Humacao, Physics and Electronics Department/University of Puerto Rico at Humacao; Furlan, Rogerio, Physics and Electronics Department/University of Puerto Rico at Humacao
Development and Characterization of an Apparatus for Anodic Bonding
Most of the Micro-Electromechanical Systems (MEMS) are built using more than one substrate. An efficient and reliable way of joining two different substrates has proven to be the “Anodic Bonding” process. In this process the substrates are heated and submitted to an electric field. The internal movement of ions caused by the external electric field creates charge layers with different polarities at both sides of the interface, with an associated electrostatic force. The high temperature and the strong electrostatic attraction normally cause the formation of chemical bonds that permanently join the substrates. In this work we are developing an interface between a computer and a high-voltage power supply (PS310 from Stanford Research System) using Lab View, in order to allow the automatic monitoring of the process. Also, the bonding of different types of substrates will be investigated. This work has been supported by PR-AMP, IDEAS-ER (NASA) and NSF-DMR-9872689.
Mora Medina Pedro J.; Ponce de León, Jaime*UPR-Río Piedras, Department of Physics
Equation of motion of a test-particle around a spherical non-spinning star
We study the motion of a test-particle in spacetime by applying the geodesic equation to the Schwarzschild's metric. This leads to an expression for the total energy E in which appears an extra term due to the dynamical character of time in relativity theory. It is expected that this extra term goes to zero as the space around the particle becomes flat. This expression can be transformed into a differential equation for the trajectory of the particle. After the function describing the motion is found, we will compare our results with those in the literature, specially that of the perihelion of the planet Mercury. It is not possible to predict its orbit using Newtonian Mechanics alone. General Relativity correctly predicts and explains this phenomenon, and that precisely is the purpose of this work.
Ocasio Yomayra*UPR-Humacao, Physics and Electronics; Esteban, ErnestoPhysics and Electronics, UPR-Humacao
Cell Survival Curves for Space Radiation
We have developed a mathematical model for radiation-induced cell carcinogenesis. This multistep model, valid for low and high-LET radiation, assumes “n” mutations before an irradiated cell becomes a cancer cell. Two applications are carried out. First, we have obtained for the simplest cases (n=0,1), the survival curves for radiation-induced myelopoiesis. Namely, a numerical solution for low-LET energy , and an exact close form solutions for high-LET energy.
Second, we discuss how our exact solutions can be implemented in deep space, i.e. in an interplanetary travel from the Earth to Mars.
Orama, Maite*UPR-Humacao, Física Aplicada a la Electrónica; Rosado, Ileana, Física Aplicada a la Electrónica, Carrión, Pedro, Física Aplicada a la Electrónica, Cotto, Desireé Física Aplicada a la Electrónica, Benson, Elixia Física, Aplicada a la Electrónica
Analizing position angle and separation of binary stars
We are using the data from the 31- inch NURO telescope in Flagstaff, Arizona to measure the angle and separation of the binary stars. Those measurements help us determinate the mass and distance. We first calculate the effective focal length of the NURO telescope to know the precise plate scale of the telescope. With this value we can calculate the separation of “standard” and “neglected” binaries”. Then we measured the separation of the neglected binaries. We compare the data with the results in the Washington Double Star Catalog.
Otero, César*UIA-Bayamón, Engineering Department, Inter American University of Puerto Rico, Bayamon Campus; Isham, Brett, Natural Sciences Department, Inter American University of Puerto Rico, Bayamon Campus
Observations of Radio Waves Interactions with the Electrons in the Ionosphere
Interferometric measurements were made of radio waves interacting with electrons in the ionosphere using the European Incoherent Scatter (EISCAT) high power, high frequency (HF) transmitter and a two-antenna receiving station. The signal was received separately on the two antennas, digitally sampled, and then processed. The HF wave reflected from the ionosphere at about 300 km in altitude. We are searching for stimulated electromagnetic emission (SEE) in order to measure variations in the SEE spectrum versus incidence angle.
Pérez-Andújar, Angelica*UPR-Mayagüez, University of Puerto Rico, Mayagüez Campus; Leticia Pibida, National Institude of Standards and Thecnology
Detectors Performance for Radioactivity Measurements for Homeland Security
Due to the latest terrorist attacks the awareness to measure Radioactive Materials has increased. Measurements of a great variety of radionuclides for a wide range of activity levels are necessary. Some of the radioactive sources that are of great concern due to their relatively easy access, as they are used in industrial and medical applications, are 60Co, 137Cs, 170Tm, 192Ir, 125I, 99mTc, 241Am and 266Ra. These materials could be released by planes, “dirty bombs” in cities and in water or in food supplies. Information about the adequate equipment required for the measurement of these sources is of great importance.
To prevent and detect the handling or spread of radioactive materials it is necessary to develop standards that can ensure the selection of the right equipment for radiological measurements. At NIST we are working on the characterization of CdTe, High Purity Germanium (HPGe) and NaI detectors for measurements of gamma-ray emitting sources. To determine under which circumstances each one of these detectors could be used it is necessary to know the detector’s efficiency, detection limits and energy resolution .The efficiency of a detector is given by the ratio of the measured activity to the total activity emitted by the source. On the other hand the energy resolution can be use as a tool for determine the presence of particular radionuclides. Another relevant characteristic is the detection limit that gives a measure of the capability of the detector to detect the presence of a radioactive source above background radiation.
The applicability of a given type of detector depends on the circumstance it is going to be used, for example the NaI detector has a higher efficiency than the HPGe detector but a lower energy resolution that makes the HPGe detector better suited for nuclide identification measurements. Another example is that the HPGE detector can not be use at room temperature but the CdTe and NaI detector do, this ability makes these detectors good instruments for field measurements.
Pérez, Raul*UPR-Humacao, Physics and Electronics; Diaz, Melissa, Physics and Electronics Ramos, Idalia, Physics and Electronics
Dielectric Properties of Electrospun Nanofibers of Conducting Polymers
We report dielectric permittivity results on nanofibers of polyethylene oxide and polyaniline/polyethylene oxide blends. The nanofibers will be prepared using the electrospinning technique. In this technique, a polymer is dissolved in a low boiling point solvent like chloroform and placed in a pipette. Then a high voltage is applied to a copper wire inserted into the polymer solution in order to create an electrical field between the polymer solution and a metallic cathode (aluminum foil) that is kept a few centimeters away from the tip of the pipette. As the voltage to the polymer increases a jet is produced and as the solvent evaporates, ultrafine fibers of the polymer are seen to accumulate on the cathode. Using a Scanning Electron Microscope and an Atomic Force Microscope we will study the morphology of the nanofibers. The non woven fiber mat of the electrospun fibers will be placed between the parallel plates of a capacitor and used in conjunction with a Hewlett Packard Impedance Analyzer to investigate its dielectric properties. The purpose of this experiment is to investigate if the electrospinning process leads to any change in the dielectric properties of the fiber when compared to the bulk film of the same material.
Posada, Yuri*UPR-Río Piedras, Dept de Física; San Miguel, L. Fonseca, L.F. Resto, O. Weisz, Z., Dept of Physics, University of Puerto Rico, Río Piedras Campus
Optical Properties of Silicon Nanoparticles in Silica Gel Monoliths
We have synthesized highly photoluminescent monoliths by incorporating nanocrystalline Silicon (nc-Si) from Porous Silicon (PSi) into a Sol Gel Silica matrix. The optically transparent samples are the result of mixing an acid catalyzed solution of Sol-Gel and nc-Si that forms a solution of Si-nanoclusters (Si-n) that eventually after condensation for three days produces the final luminescent material. Photoluminescence (PL) basic studies show a very high orange emission band with a maximum peak that ranges between 600 nm and 750 nm. The PL emission intensity was increased up to ten times the luminescence of the native nano material PSi, the mechanical and thermal stability properties were also greatly improved. The PL corresponds to different concentrations or preparations of Sol-Gel with Si-n (Sol-Si) with a broad size distribution that produces orange and blue emissions, and for this reason we take as our future work to tailor samples with very high Si-n densities for semiconducting and photonic applications.
Quiñones Jessika*UPR-Humacao, Departamento de Física y Electrónica
Electrical Characterization of AMPSA doped polyaniline films and fibers
In this work we present our results on the conductivity of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) dopes plyaniline films and fibers prepared from dichloroacetic acid (DCA) as a function of temperature. Emeraldine base (0.38g) and AMPSA (0.52g) were mixed in a motar and prestle and added to DCA (44.1g)(1) The resulting solution was centrifuged for 30 minutes at 3200 rmp. In order to prepare the film, a small portion was pored in a glass slide and left in a oven at 343 K for 24 hours. The film was peeed out and cut into a rectangular shape of 2.6mm x 3.9mm x .04mm. Four in-line contacs were made on the film and the conductivity was measured. Preliminary results at room temperature gave a conductivity of ~53 S/cm. We plan to use the electrospinning technique to produce a fiber of th polymer. The purpose of measuring the conductivity of the fibers is to check if the electrospinning process leads to any polymer alignment within the fiber. Such a result would lead to a value of the conductivity slightly higher than that of the bulk film. This work is supported by NSF.
(1) P.N. Adams, S.J. Pomfret and A.P. Monkmen, Synth. Metals 101, 776 (1999)
Rivas, Guillermo*UPR-Humacao, Physics and Electronics, Department/University of Puerto Rico at Humacao; Furlan, Rogerio, Physics and Electronics, Department/University of Puerto Rico at Humacao, Ramos, Idalia, Physics and Electronics, DepartmentUniversity of Puerto Rico at Humacao
Pressure and Flow Characterization in a Jet Vapor Etching Reactor
Jet Vapor Etching (JVE) is a technique used to define features with meso and micro dimensions in Low Temperature Co-Fired Ceramic (LTCC) tapes, known as green tapes (fabricated by DuPont). In this technique a nitrogen jet carrying acetone vapor is used to impact and dissolve the tape. In order to obtain micro features with a good degree of process control, the characteristics inside the reactor chamber have to be known in terms of pressure and flow. The same is valid in terms of the characteristics of the jet at the output nozzle, which has microdimensions, being then considered a microjet. This project aims at the characterization and analysis of the control parameters of a JVE system, by using sensors strategically placed in the reactor. The obtained results will be used as input to a numerical simulator, which will be used to define the best conditions to obtain features with micro dimensions. This work has been supported by PR-AMP, IDEAS-ER (NASA) and NSF-DMR-9872689.
Rodríguez, Emilio*UPR-Río Piedras, Departamento de Física; González, Adolfo, UPR - Río Piedras, De Jesus, Joel, UPR - Río Piedras, Vargas, Iris M., UPR - Río Piedras, Weiner, Brad R. UPR - Río Piedras, Morell, Gerardo, UPR - Río Piedras
Effects of Heavy-Ion Radiation ofn the Electron Field Emission Properties of Sulfur-Doped Nanocomposites
The effects of heavy ion radiation over the electron field emission (EFE) properties of sulfurdoped nanocomposite carbon (n-C:S) films were investigated. Two identical sets of n-C:S films were prepared in a hot filament chemical vapor deposition (HFCVD) system using CH4, H2 and H2S. Films with various sp3 C and sp2 C fractions were present within each set, which were obtained by varying the substrate temperature (300-900 oC), the CH4 concentration (0.3 and 2.0%) and the H2S concentration (0 and 500 ppm). Raman spectroscopy revealed the characteristic diamond (tetragonal sp3 C) band at around 1332 cm-1 and the graphitic (trigonal sp2 C) D and G bands at around 1350 and 1590 cm-1, respectively, evidencing the composite nature of the films. One set of films was submitted to Simulated Space Radiation (a 20 Krad dose of energetic Si and Fe ions) at Brookhaven National Laboratory's Alternating Gradient Synchrotron (AGS). It was found that there is an enhancement of the current density (J) and threshold field (Ec) as result of irradiation for some nC:S materials, while others did not show significant variations in their EFE properties. These changes depend critically on the initial aggregation state of trigonallybonded carbon within the films, which was evaluated through a quantitative analysis of the corresponding Raman spectra. A comprehensive analysis of the results suggests that longterm stable electron field emitters can be fabricated using nanocomposite carbon materials that would remain unchanged in their EFE properties while absorbing ionizing radiation. Such behavior goes beyond the concept of radiation hardness and into radiation insensitiveness.
Rodríguez, Teddy*UPR-Mayagüez, Departamento de Física
Development of compact high-value resistors using e-beam lithography
Using electron beam (e-beam) lithography, we are constructing devices with sub-micron scale features, which are designed to have a resistance of 100M and fit in a reduced working area of 90 x 90 m2. To do the lithography, we employ the Nanometer Pattern Generation System (NPGS) to control the Cambridge Scanning Electron Microscope (SEM) through computer interface during the e-beam writing. A range of thicknesses of CrSi thin films provides a range of sheet resistances between 500-1000/•. With the program DesignCAD™, we are able to do different designs of the resistor, and vary the e-beam pattern width and dose to achieve the desired line width and spacing of 0.1 – 0.2 µm. Precision in the design and focus control during the writing is very important due to the small working area, and the tolerance required for proper e-beam alignment to insure lines of the desired width. At the conclusion of this project, the resistance as a function of the device’s length will be measured to verify that each segment of the resistor is continuous and uniform. Noise measurements with a bias current applied will check whether the absence of resistance fluctuations observed in larger area CrSi devices holds true also for the miniaturized resistors.
Rosado-De Jesus, Iliana*UPR-Humacao; Muller. Rafael; Cersosimo ,J. C.; Benson, Elixia; Orama, Maite; Cotto, Dessiré, Departamento de Física y Electrónica
Calculation of systematic error in measurements of angle of binary stars.
Our research project consist of the analysis of binary stars systems with the final objective of calculating the mass of the stars involved. The initial phase of the project involves the calculation of position/angle of neglected binaries. We analyze images of neglected binaries obtained using the NURO Telescope in Flagstaff, Arizona. A systematic error in measurements of the angle is introduced by the positioning of the CCD Camera at the telescope. This systematic error in the angles of known pairs of binaries obtained from calibrated images has to be corrected. We use error analysis techniques to obtain the offset. The resulting numbers are use to confirm the angular values of the standard stars. Then those results are used in the calculation of the angles of neglected binaries. The offset helped us to correct the differences of the angles of the neglected binary stars and confirm the data. Using this technique we can expect precise and concrete information of the obtained data.
Serrano Luis A.*UPR-Humacao, Physics and Electronics; Ramos, Idalia, Dept. Physics and Electronics, UPR Humacao, Furlan, Rogerio, Dept. Physics and ElectronicsUPR Humacao
Study of Temperature Fluctuations for Jet Vapor Etching
Jet Vapor Etching (JVE) is a technique used to produce features on Low Temperature Co-Fired Ceramics (LTCC) for the construction of meso (intermediate size) systems. LTTC is a glass ceramic composite with an organic binder. In JVE a jet of heated acetone in a Nitrogen carrier impinges on the LTCC dissolving the organic binder and mechanically removing the alumina and glass grains. The features on the tape are a function of the pressure, temperature, nozzle opening, and distance between jet and sample. In the original system, we monitor the temperature of the acetone inside the glass reactor before the jet is shot. To have a better understanding of the JVE process we measure the temperature of the jet in a 1cm3 space between the nozzle and the sample holder. This is done using thermocouples connected to a PC Laptop with a data acquisition card and the software LabVIEW. We monitor the temperature for a period of 30s, before and after the shot of the acetone jet for various temperatures inside the reactor. This work is supported by NSF Grant #9872689.
Sierra, Yomayra*UPR-Arecibo, Física-Química; Torres, Keila, Rivera, Yamayra Reyes, Katia Peña, Guido Ph.D Prof. UPRA - Arecibo
Inhibición Bacteriana de los Extractos Lipo Solubles de Algas Rojas y Pardas
Se obtuvieron extractos lipo-solubles de la selección de algas rojas y pardas, para comparar la acción inhibitoria de estos extractos con la de la Penicilina sobre cuatro cultivos de bacterias. La inhibición bacteriana de los extractos de las algas Spyridia filamentosa, Padina, Stypopodium zonale y Acanthophora; fue analizada en pruebas de sensibilidad antibiótica con cuatro cepas de bacterias. Los microorganismos utilizados fueron: Escherichia coli, Pseudomona aureoginosa, Staphylococcus aureus y Bacilus subtilis. Mediante procesos de filtración al vacío, extracción y rotoevaporación, se llevó a cabo la separación de los extractos lipo solubles de cada alga. Se inocularon las bacterias en el medio de cultivo TSA, mediante la técnica de difusión. Posteriormente se insertaron discos estériles previamente sumergidos en los extractos obtenidos de las algas. Se utilizaron discos estériles sumergidos en Penicilina como elemento de control. Tomando lecturas en períodos de 24, 48 y 72 horas se observó que el extracto del alga Padina inhibió el crecimiento de las bacterias, S. aureus y B. Subtilis, siendo ésta la única que logró el efecto inhibitorio. Al obtener este resultado se repitió el experimento con el extracto del alga Padina solamente, obteniendo resultados óptimos ya que este extracto logró inhibir las cuatro cepas de bacterias ya mencionadas. El alga parda Padina alcanzó y superó nuestras expectativas como agente inhibidor.
Soto Candelaria, Mariely*UPR-Arecibo, Physic-Chemistry; Vega, Keila, Physic-Chemistry, UPR-Arecibo, Nuñez, Lydia Physic-Chemestry, UPR-Arecibo Villanueva, Abigail Physic-Chemestry, UPR-Arecibo
Análisis Físico, Químico y Biológico del Río Grande de Arecibo
El propósito de este trabajo es caracterizar el Río Grande de Arecibo mediante la medición de los parámetros físicos, químicos y biológicos a fin de establecer la calidad del agua. Para ello se seleccionaron 10 puntos claves en el estuario, en los cuales se recolectaron muestras de agua. Usando equipos de medición de campo se determinó: temperatura, pH, oxígeno disuelto, turbidez y % de saturación del agua. Se colectaron muestras de agua para llevarlas al laboratorio y detreminar la concentración en ppm de: N-NH3, PO4, NO2, NO3, Bromo en Cloro y SO4. Se identificaron las diferentes especies de Fitoplanton y Zooplanton. Se determinaron colonias de coliformes fecales y totales. Se estableció la concentración de metales pesados en los sedimentos. El pH promedio del agua se mantuvo en 7.1 y la temperatura se mantuvo en un rango de 22 a 31.2, la concentración más baja de oxígeno disuelto se ha encontrado en el canal #1 (próximo a la comunidad de Buenos Aires). Las concentraciones de los iones analizados están bajo los parámetros establecidos por la EPA. La NASA analizó las concentraciones en ppm de: Ca ( 37.8-55.9), K ( 2.6-16.4), Mg ( 12.9-65.2), Na ( 66.0-495.4). También las concentraciones en ppb de los siguientes metales pesados: As (<1), Cu (<1), Fe (<1), Pb (<1), Zn (<1) y Hg (<1). En el canal #2 la concentración de Fe fue de 8 ppb. Es de preocupación la presencia de los compuestos orgánicos en ppb de: 1,3 diclorobenceno (4 -24), “dimethyldisulfide” (<1 – 8.9), y cloroformo ( <1 – 18.7) en ppb, analizados por la NASA. Además se encontraron 6 distintos tipos de colonias de coliformes fecales y totales que se reproducen en la bacteria E. coli.
Velázquez Rafael*UPR-Río Piedras, Departamento de Física; De Jesus, Joel, UPR - Río Piedras, Vargas, Iris M., UPR - Rio Piedras, Weiner, Brad R., UPR - Río Piedras, Weiss, Brock L., University of California at Sonoma, Morell, Gerardo, UPR - Río Piedras
Synthesis of Boron Nitride Nanotubes for Aerospace Applications
Boron nitride nanotubes (BNNTs) have an exceptionally high elastic modulus (1.2 TPa) while at the same time being resistant to oxidation in air at high temperatures. Therefore, they are promising materials for reinforcing metals, polymers and ceramics. Once BNNTs are assembled in ropes or bundles, they can be incorporated into these materials in order to improve their performance. In this way, BNNTs will help fulfill the NASA goals of lighter, stronger, safer, and more reliable space ships and airplanes.
We have performed research on the synthesis of BNNTs by arch discharge (AD), and on the structure and properties of the resulting BN nanomaterials. We succeeded in growing BNNT with large aspect ratios and conical ends, as revealed by Transmission Electron Microscopy (TEM). These BNNTs were grown using boron powder and ammonia sources of B and N, respectively.
In the second stage of this research project, we will explore the CVD growth of BNNTs using ammonia and diborane as the sources of N and B, respectively. These gases will be highly diluted in hydrogen, and fed in a 2:1 proportion in order to obtain a 1:1 proportion for N and B. Tungsten substrates heated to 600 oC will support the growing material. The effects of substrate temperature (300-1200 oC) and pressure (10-100 Torr) over the morphology of the BNNTs grown will be systematically studied. The overall goal is to learn to grow extremely long (100 um) BNNTs in large quantities and generally self-organized over a patterned substrate. We also aim at learning to grow helicity-specific nanotube bundles, from armchair to zigzag, through parameter control that will allow direct use of the CVD-grown BNNTs for reinforcing metals, polymers and ceramics.