Background: Hispanic adults in the United States are at particular risk for diabetes and inadequa... more Background: Hispanic adults in the United States are at particular risk for diabetes and inadequate blood pressure control. Physical activity improves these health problems; however Hispanic adults also have a low rate of recommended aerobic physical activity. To address improving physical inactivity, one area of rapidly growing technology that can be utilized is text messaging (short message service, SMS). A physical activity research team, Text4Walking, had previously developed an initial database of motivational physical activity text messages in English that could be used for physical activity text messaging interventions. However, the team needed to translate these existing English physical activity text messages into Spanish in order to have culturally meaningful and useful text messages for those adults within the Hispanic population who would prefer to receive text messages in Spanish. Objective: The aim of this study was to translate a database of English motivational physical activity messages into Spanish and review these text messages with a group of Spanish speaking adults to inform the use of these text messages in an intervention study.
In situ small-angle X-ray scattering (SAXS) studies have been conducted to monitor the structural... more In situ small-angle X-ray scattering (SAXS) studies have been conducted to monitor the structural changes of sepiolite clay upon heating. The samples were heated first under nitrogen to establish the temperature at which pure sepiolite folds. Then, propylene was incorporated into the sepiolite channels and carbonized in situ. SAXS results indicate that the incorporation of carbon raises the structural stability of sepiolite in that the folding temperature increases from 465°C to near 550°C.
Recent experiments have shown that a curved carbon lattice can adsorb 4 % by weight hydrogen at r... more Recent experiments have shown that a curved carbon lattice can adsorb 4 % by weight hydrogen at room temperature and at a pressure of 100 bars. In this system, hydrogen is fully released at 80°C. Carbon hydrogen bonds exist in the carbon lattice as confirmed by neutron ...
Grossie et al. [Li 2 (C 3 H 6 O) 4 (H 2 O) 2 ][Li 2 (C 3 H 6 O) 2 (H 2 O) 4 ] m827 Acta Crystallo... more Grossie et al. [Li 2 (C 3 H 6 O) 4 (H 2 O) 2 ][Li 2 (C 3 H 6 O) 2 (H 2 O) 4 ] m827 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 Di-l-acetone-j 2 O:O-bis[(acetone-jO)-aqualithium(I)] di-l-acetone-j 2 O:O-bis-[diaqualithium(I)] tetrakis{[phthalocyan-inato(2À)-j 4 N,N 0 0 0 ,N 0 0 00 0 0 ,N 0 0 00 0 00 0 0 ]lithiate(I)} Key indicators Single-crystal X-ray study T = 100 K Mean (C–C) = 0.002 Å R factor = 0.049 wR factor = 0.136 Data-to-parameter ratio = 17.0 For details of how these key indicators were automatically derived from the article, see The crystals of the title compound, [Li 2 (C 3 H 6 O) 4 (H 2 O) 2 ]-[Li 2 (C 3 H 6 O) 2 (H 2 O) 4 ] [Li(C 32 H 16 N 8)] 4 , were obtained by a recrystallization of dilithium phthalocyanine from an acetone/ water/toluene solution. The title structure consists of two independent Li–phthalocyanine complexes along with acetone-bridged lithium dimers. The lithium dimers are located on inversion centers. The crystal structur...
C401 In-situ diffraction experiments were performed on SOFC under standard operating conditions, ... more C401 In-situ diffraction experiments were performed on SOFC under standard operating conditions, more specifically during successive cycles of reduction and reoxidation at ~ 850 °C. The experiment was performed with the spiral slit set-up at beamline ID15 at the ESRF and an X-ray wavelength of = 0.173 Å. The strain distribution within the three constituent layers of the SOFC was determined from the distortion of the monitored Debye-Scherrer-rings. Dilithium phthalocyanine is a compound that shows promise as the dielectric for lithium-lithium ion batteries. The compound forms small, flakey crystals from the few solvents in which it can be dissolved. Experimental evidence indicates that the lithium atoms within the solid structure migrate in the presence of an electric field. The determination of the crystal and molecular structure was initiated so as to determine the pathways through which the lithium ions move.
Unique carbonaceous materials suitable as anodes for lithium secondary batteries have been synthe... more Unique carbonaceous materials suitable as anodes for lithium secondary batteries have been synthesized and characterized. The synthesis is based on the use of pillared clays and various organic precursors, including pyrene. Pyrolysis was performed at 500, 700 and 1000 °C followed by inorganic matrix removal. Xray powder diffraction data show that the carbon samples have a highly disordered structure.
Journal of New Materials for Electrochemical Systems
The performance of a commercial Pt-black electrocatalyst was investigated in a Direct Methanol Fu... more The performance of a commercial Pt-black electrocatalyst was investigated in a Direct Methanol Fuel Cell (DMFC). A method for establishing the validity of anode polarization (without the use of a reference electrode) was shown by purging hydrogen and argon gas at the cathode under an asymmetric electrode configuration. It was found that hydrogen crossover to the cathode has a negligible effect on the polarization curve. In order to study methanol oxidation kinetics, the effects of mass transfer and ohmic resistances are eliminated and the correction techniques are discussed. At ≈ 0.55 V, E a changes from 60 kJ/mol to 40 kJ/mol (the removal of surface carbon monoxide) which points to the change in the rate determining step of the methanol oxidation reaction. Based on the value of the Tafel slope (138 mV/dec),the rate-determining step on the platinum surface can be the first electron transfer step (first C-H bond breakage of methanol or the activation of water) before 0.55 V.
Journal of New Materials for Electrochemical Systems
We think of membranes as simple devices to facilitate filtration. In fact, membranes play a role ... more We think of membranes as simple devices to facilitate filtration. In fact, membranes play a role in chemical, biological, and engineering processes such as catalysis, separation, and sensing by control of molecular transport and recognition. Critical factors that influence membrane discrimination properties include composition, pore size (as well as homogeneity), chemical functionalization, and electrical transport properties. There is increasing interest in using nanomaterials for the production of novel membranes due to the unique selectivity that can be achieved. Clay-polymer nanocomposites show particular promise due to their ease of manufacture (large sheets), their rigidity (self supporting), and their excellent mechanical properties. However, the process of lithium ion transport through the clay-polymer nanocomposite and mechanisms of pore size selection are poorly understood at the ionic and molecular level. In addition, manufacturing of clay-polymer nanocomposite membranes ...
Journal of New Materials for Electrochemical Systems
A pure carbon-based material was synthesized using different fractions of sepiolite clay. The pro... more A pure carbon-based material was synthesized using different fractions of sepiolite clay. The produced carbon was initially characterized to determine its purity and surface properties. The hydrogen storage capability exhibited in carbon nanofibers at room temperature and 10 Mpa is close to 2.2% w/w. The results indicated that there is a correlation of the hydrogen storage ability and the surface properties of the template sepiolite.
New hectorite and organo-hectorite clays have been prepared using different silica sol sources, i... more New hectorite and organo-hectorite clays have been prepared using different silica sol sources, in order to examine the importance of sol particle size, pH, and surface chemistry on the final matrix. Polymer-clay nanocomposites (PCN) are prepared by intercalating polyethylene oxide in the clay layers of lithium hectorites. The resulting films are physically and electrochemically evaluated. Conductivity values, activation energies, and lithium transference numbers indicate that the PCNs are single ion conductors with transference numbers close to unity. The activation energies are in the range of 0.02 V, two orders of magnitude lower than the conventional polymer electrolytes.
stepped off the bus for her first day of undergraduate schooling at the University of Costa Rica,... more stepped off the bus for her first day of undergraduate schooling at the University of Costa Rica, she was met with an unfamiliar world. The community of 40,000 students was much different than that of the small, farming community where she was raised. As the first person in her family to go to college, Giselle faced additional challenges beyond attending class and studying hard. She had to learn how to navigate the academic seas, define her career path, and maintain eligibility for the scholarship that allowed her family to support her dream of pursuing higher education. Luckily, she found trusted mentors to help her through these challenges and is now a Ph.D.
A toroid cavity nuclear magnetic resonance (NMR) detector capable of quantitatively recording rad... more A toroid cavity nuclear magnetic resonance (NMR) detector capable of quantitatively recording radial concentration profiles, diffusion constants, displacements of charge carriers, and radial profiles of spin-lattice relaxation time constants was employed to investigate the charge/discharge cycle of a solid-state electrochemical cell. One-dimensional radial concentration profiles (1D-images) of ions solvated in a polyethylene oxide matrix were recorded by ¹â¹F and â·Li NMR for several cells. A sequence of ¹â¹F NMR images, recorded at different stages of cell polarization, revealed the evolution of a region of the polymer depleted of charge carriers. From these images it is possible to extract the transference number for the Li{sup +} ion. Spatially localized diffusion coefficients and spin-lattice relaxation time constants can be measured simultaneously for the ions in the polymer electrolyte by a spin-labeling method that employs the radial Bâ-field gradient of the toroid cavi...
Background: Hispanic adults in the United States are at particular risk for diabetes and inadequa... more Background: Hispanic adults in the United States are at particular risk for diabetes and inadequate blood pressure control. Physical activity improves these health problems; however Hispanic adults also have a low rate of recommended aerobic physical activity. To address improving physical inactivity, one area of rapidly growing technology that can be utilized is text messaging (short message service, SMS). A physical activity research team, Text4Walking, had previously developed an initial database of motivational physical activity text messages in English that could be used for physical activity text messaging interventions. However, the team needed to translate these existing English physical activity text messages into Spanish in order to have culturally meaningful and useful text messages for those adults within the Hispanic population who would prefer to receive text messages in Spanish. Objective: The aim of this study was to translate a database of English motivational physical activity messages into Spanish and review these text messages with a group of Spanish speaking adults to inform the use of these text messages in an intervention study.
In situ small-angle X-ray scattering (SAXS) studies have been conducted to monitor the structural... more In situ small-angle X-ray scattering (SAXS) studies have been conducted to monitor the structural changes of sepiolite clay upon heating. The samples were heated first under nitrogen to establish the temperature at which pure sepiolite folds. Then, propylene was incorporated into the sepiolite channels and carbonized in situ. SAXS results indicate that the incorporation of carbon raises the structural stability of sepiolite in that the folding temperature increases from 465°C to near 550°C.
Recent experiments have shown that a curved carbon lattice can adsorb 4 % by weight hydrogen at r... more Recent experiments have shown that a curved carbon lattice can adsorb 4 % by weight hydrogen at room temperature and at a pressure of 100 bars. In this system, hydrogen is fully released at 80°C. Carbon hydrogen bonds exist in the carbon lattice as confirmed by neutron ...
Grossie et al. [Li 2 (C 3 H 6 O) 4 (H 2 O) 2 ][Li 2 (C 3 H 6 O) 2 (H 2 O) 4 ] m827 Acta Crystallo... more Grossie et al. [Li 2 (C 3 H 6 O) 4 (H 2 O) 2 ][Li 2 (C 3 H 6 O) 2 (H 2 O) 4 ] m827 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 Di-l-acetone-j 2 O:O-bis[(acetone-jO)-aqualithium(I)] di-l-acetone-j 2 O:O-bis-[diaqualithium(I)] tetrakis{[phthalocyan-inato(2À)-j 4 N,N 0 0 0 ,N 0 0 00 0 0 ,N 0 0 00 0 00 0 0 ]lithiate(I)} Key indicators Single-crystal X-ray study T = 100 K Mean (C–C) = 0.002 Å R factor = 0.049 wR factor = 0.136 Data-to-parameter ratio = 17.0 For details of how these key indicators were automatically derived from the article, see The crystals of the title compound, [Li 2 (C 3 H 6 O) 4 (H 2 O) 2 ]-[Li 2 (C 3 H 6 O) 2 (H 2 O) 4 ] [Li(C 32 H 16 N 8)] 4 , were obtained by a recrystallization of dilithium phthalocyanine from an acetone/ water/toluene solution. The title structure consists of two independent Li–phthalocyanine complexes along with acetone-bridged lithium dimers. The lithium dimers are located on inversion centers. The crystal structur...
C401 In-situ diffraction experiments were performed on SOFC under standard operating conditions, ... more C401 In-situ diffraction experiments were performed on SOFC under standard operating conditions, more specifically during successive cycles of reduction and reoxidation at ~ 850 °C. The experiment was performed with the spiral slit set-up at beamline ID15 at the ESRF and an X-ray wavelength of = 0.173 Å. The strain distribution within the three constituent layers of the SOFC was determined from the distortion of the monitored Debye-Scherrer-rings. Dilithium phthalocyanine is a compound that shows promise as the dielectric for lithium-lithium ion batteries. The compound forms small, flakey crystals from the few solvents in which it can be dissolved. Experimental evidence indicates that the lithium atoms within the solid structure migrate in the presence of an electric field. The determination of the crystal and molecular structure was initiated so as to determine the pathways through which the lithium ions move.
Unique carbonaceous materials suitable as anodes for lithium secondary batteries have been synthe... more Unique carbonaceous materials suitable as anodes for lithium secondary batteries have been synthesized and characterized. The synthesis is based on the use of pillared clays and various organic precursors, including pyrene. Pyrolysis was performed at 500, 700 and 1000 °C followed by inorganic matrix removal. Xray powder diffraction data show that the carbon samples have a highly disordered structure.
Journal of New Materials for Electrochemical Systems
The performance of a commercial Pt-black electrocatalyst was investigated in a Direct Methanol Fu... more The performance of a commercial Pt-black electrocatalyst was investigated in a Direct Methanol Fuel Cell (DMFC). A method for establishing the validity of anode polarization (without the use of a reference electrode) was shown by purging hydrogen and argon gas at the cathode under an asymmetric electrode configuration. It was found that hydrogen crossover to the cathode has a negligible effect on the polarization curve. In order to study methanol oxidation kinetics, the effects of mass transfer and ohmic resistances are eliminated and the correction techniques are discussed. At ≈ 0.55 V, E a changes from 60 kJ/mol to 40 kJ/mol (the removal of surface carbon monoxide) which points to the change in the rate determining step of the methanol oxidation reaction. Based on the value of the Tafel slope (138 mV/dec),the rate-determining step on the platinum surface can be the first electron transfer step (first C-H bond breakage of methanol or the activation of water) before 0.55 V.
Journal of New Materials for Electrochemical Systems
We think of membranes as simple devices to facilitate filtration. In fact, membranes play a role ... more We think of membranes as simple devices to facilitate filtration. In fact, membranes play a role in chemical, biological, and engineering processes such as catalysis, separation, and sensing by control of molecular transport and recognition. Critical factors that influence membrane discrimination properties include composition, pore size (as well as homogeneity), chemical functionalization, and electrical transport properties. There is increasing interest in using nanomaterials for the production of novel membranes due to the unique selectivity that can be achieved. Clay-polymer nanocomposites show particular promise due to their ease of manufacture (large sheets), their rigidity (self supporting), and their excellent mechanical properties. However, the process of lithium ion transport through the clay-polymer nanocomposite and mechanisms of pore size selection are poorly understood at the ionic and molecular level. In addition, manufacturing of clay-polymer nanocomposite membranes ...
Journal of New Materials for Electrochemical Systems
A pure carbon-based material was synthesized using different fractions of sepiolite clay. The pro... more A pure carbon-based material was synthesized using different fractions of sepiolite clay. The produced carbon was initially characterized to determine its purity and surface properties. The hydrogen storage capability exhibited in carbon nanofibers at room temperature and 10 Mpa is close to 2.2% w/w. The results indicated that there is a correlation of the hydrogen storage ability and the surface properties of the template sepiolite.
New hectorite and organo-hectorite clays have been prepared using different silica sol sources, i... more New hectorite and organo-hectorite clays have been prepared using different silica sol sources, in order to examine the importance of sol particle size, pH, and surface chemistry on the final matrix. Polymer-clay nanocomposites (PCN) are prepared by intercalating polyethylene oxide in the clay layers of lithium hectorites. The resulting films are physically and electrochemically evaluated. Conductivity values, activation energies, and lithium transference numbers indicate that the PCNs are single ion conductors with transference numbers close to unity. The activation energies are in the range of 0.02 V, two orders of magnitude lower than the conventional polymer electrolytes.
stepped off the bus for her first day of undergraduate schooling at the University of Costa Rica,... more stepped off the bus for her first day of undergraduate schooling at the University of Costa Rica, she was met with an unfamiliar world. The community of 40,000 students was much different than that of the small, farming community where she was raised. As the first person in her family to go to college, Giselle faced additional challenges beyond attending class and studying hard. She had to learn how to navigate the academic seas, define her career path, and maintain eligibility for the scholarship that allowed her family to support her dream of pursuing higher education. Luckily, she found trusted mentors to help her through these challenges and is now a Ph.D.
A toroid cavity nuclear magnetic resonance (NMR) detector capable of quantitatively recording rad... more A toroid cavity nuclear magnetic resonance (NMR) detector capable of quantitatively recording radial concentration profiles, diffusion constants, displacements of charge carriers, and radial profiles of spin-lattice relaxation time constants was employed to investigate the charge/discharge cycle of a solid-state electrochemical cell. One-dimensional radial concentration profiles (1D-images) of ions solvated in a polyethylene oxide matrix were recorded by ¹â¹F and â·Li NMR for several cells. A sequence of ¹â¹F NMR images, recorded at different stages of cell polarization, revealed the evolution of a region of the polymer depleted of charge carriers. From these images it is possible to extract the transference number for the Li{sup +} ion. Spatially localized diffusion coefficients and spin-lattice relaxation time constants can be measured simultaneously for the ions in the polymer electrolyte by a spin-labeling method that employs the radial Bâ-field gradient of the toroid cavi...
Uploads
Papers by Giselle Sandí