“Academic success depends on research and publications.”
Philip Zimbardo
Lugo, Ariel E.; Cuevas, Elvira; Medina, Ernesto; Ramos, Olga Ecological and physiological aspects of Caribbean shrublands Journal Article Forthcoming In: Caribbean Naturalist, Forthcoming. @article{Lugo2018, | |
Hernandez, Jose A.; Fonseca, Luis F.; Ruiz, Angel Thermoelectric properties of SnSe nanowires with different diameters Journal Article In: Scientific Reports, vol. 8, no. 11966, pp. 8, 2018. @article{joseHernandez2018,Tin selenide (SnSe) has been the subject of great attention in the last years due to its highly efficient thermoelectricity and its possibilities as a green material, free of Pb and Te. Here, we report for the first time a thermoelectricity and transport study of individual SnSe micro- and nano-wires with diameters in the range between 130 nm and 1.15 μm. X-ray diffraction and transmission electron microscopy analyses confirm an orthorhombic SnSe structure with Pnma (62) symmetry group and 1:1 Sn:Se atomic ratio. Electrical and thermal conductivity and the Seebeck coefficient were measured in each individual nanowire using a specialized suspended microdevice in the 150–370 K temperature range, yielding a thermal conductivity of 0.55 Wm−1 K−1 at room temperature and ZT ~ 0.156 at 370 K for the 130 nm diameter nanowire. The measured properties were correlated with electronic information obtained by model simulations and with phonon scattering analysis. The results confirm these structures as promising building blocks to develop efficient temperature sensors, refrigerators and thermoelectric energy converters. The thermoelectric response of the nanowires is compared with recent reports on crystalline, polycrystalline and layered bulk structures. | |
Arias, María F. Barberena; Cuevas, Elvira Physico-chemical foliar traits predict assemblages of litter/humus detritivore arthropods Journal Article In: In tech open- Tropical Forests, vol. 1, no. 1, pp. 19, 2018. @article{Arias2018,Plant functional traits influence the decomposition of their own residues occurring underneath individual plant species. Arthropods associated to litter are critical components influencing decomposition. Nevertheless, few studies have established a direct relation between plant traits and belowground arthropods. To address this relation at the individual plant species scale, this study was conducted in the Guánica dry forest, Puerto Rico, by selecting five tree species and ten isolated trees/species where variations due to neighbor trees are reduced. Mature green leaves, litter, and associated arthropods were sampled from November 2004 through September 2005. Collected arthropods were counted and classified, and abundances were standardized to ind/m2. Arthropod abundance did not differ among plant species, but richness, and species and trophic composition were different among the plant species. Predators, omnivores, and sucking herbivores showed a similar species composition among plant species, while detritivore was the only trophic groups with a different species composition among plants. These results are further supported by canonical correspondence analysis results showing that detritivore arthropod species composition covaries with the physicochemical characteristics of mature green leaves of plants. These findings support that the plant idiosyncratic characteristics affect the structure of litter/humus arthropods up to the first consumer level. | |
Hernandez, Jose A.; Fonseca, Luis F. Thermoelectric properties and thermal tolerance o indium tin oxide nanowires Journal Article In: Nanotechnology, vol. 29, no. 364001, pp. 7, 2018. @article{Hernandez2018,Highly crystalline indium tin oxide (ITO) nanowires were grown via a vapor–liquid–solid method, with thermal tolerance up to ~1300 °C. We report the electric and thermoelectric properties of the ITO nanowires before and after heat treatments and draw conclusions about their applicability as thermoelectric building blocks in nanodevices that can operate in high temperature conditions. The Seebeck coefficient and the thermal and electrical conductivities were measured in each individual nanowire by means of specialized micro-bridge thermometry devices. Measured data was analyzed and explained in terms of changes in charge carrier density, impurities and vacancies due to the thermal treatments. | |
Gutierrez, Keily; Piñero, Dalice M.; Corchado, Juan; Lin, Shiru In: Inorganica Chimica Acta, vol. 474, no. 118, pp. 9, 2018. @article{Gutierrez2018,Three mononuclear metal complexes of Co2+, Ni2+ and Cu2+ with the Salen type ligand ((2,2′-[(1-methyl-1,2-ethanediyl) bis(nitriloethylidyne)] bis(1-naphthalenol)), H2Naphpren or L) were synthesized and structurally characterized. All metal complexes have square planar geometries and crystallize in the P21/c space group. Structural characterization of the ligand shows contribution of the bis(ketone) tautomer in the crystalline phase, in agreement with density functional theory (DFT) computations. However, according to the UV-vis spectrum, there is a stronger influence of the bis(phenol) tautomer in solution. Cyclic voltammetry experiments showed that the ligand undergoes a single irreversible oxidation process at 0.434 V (vs Fc/Fc+) while the complexes with Co2+, Ni2+ and Cu2+ suffer electroxidative process on the surface of the working electrode in addition to solution-assigned redox processes. The CoL oxidation is localized on the metal center, however, the CuL and NiL oxidations are considered as metal-ligand based processes. DFT calculations confirmed our experimental findings. The UV-vis spectra of the complexes illustrate ligand characteristic bands: in the case of the Cu2+ complex, the metal-to-ligand charge transfer (MLCT) band is present at 385 nm, while in the case of Co2+ complex this same type of MLCT band appears at 377 nm. | |
Rivera, Manuel; Feng, Peter; Velazquez, Rafael UV photodetector based on energy bandgap shifted hexagonal boron nitride nanosheets for high-temperature environments Journal Article In: vol. 51, no. 045102, pp. 9, 2018. @article{Rivera2018,We extend our investigations in the use of boron nitride nanosheets (BNNSs) as sensing material for UV photodetectors by exploring the energy bandgap shift in a new BNNSs arrangement on silicon substrate produced by a pulsed laser plasma deposition (PLPD) technique. Characterizations by XRD and Raman spectrum analysis indicate that the material is composed of high purity hexagonal boron nitride (hBN). SEM and AFM images confirm this particular arrangement of BNNSs is made of randomly orientated hBN nanosheets. The BNNS on silicon substrate material exhibits higher conductivity and photosensitivity in deep UV region than previously investigated BNNS thin films. The material is also sensitive to the UVB region, indicative of having a lower band gap width than that of bulk or thin films, while remaining visible-blind. The observed decrease in cut-off frequency was a direct result of the structural arrangement of the BNNSs in the film. This has the advantage of avoiding doping in order to tune bandgap width, which can compromise intrinsic desirable properties of hBN. Additionally, the material performed extremely well as a UV photodetector even at temperatures as high as 400 °C, making this particular arrangement of BNNSs an ideal candidate for applications where UV sensing in high-temperature environments is required. | |
Feng, Peter X. A compact design of a characterization station for far UV photodetectors Journal Article In: Review of Scientific Instruments, vol. 89, no. 15001, pp. 8, 2018. @article{Feng2018,A newly fabricated characterization station is presented. It is a compact, cost-effective, and easily adjustable apparatus. Each part including 4-pin probe, manipulators, operating temperature, and applied bias can be independently controlled. The station can provide highly reliable, reproducible, and economical methods to quickly conduct and complete the characterizations of a large amount of sensing materials within a short period of time. It is particularly suitable for studies of various nanostructured materials and their related thermal effect, polarization effect, sensitivity, and electrical and electronic properties. | |
Ortiz, Mónica Salazar; Cuevas, Elvira Land use and land management during the past century determine mangrove dynamics in northwestern Puerto Rico: the case of the Maracayo Mangrove Journal Article In: Journal of Environmental Science and Engineering, vol. b6, no. 593, pp. 30, 2017. @article{Ortiz2017,Political and economic decisions have determined throughout the history of Puerto Rico land use for agriculture, livestock and urban sprawl. Knowing this, this study is imperative to understand how these changes caused by the various uses and management affected adjoining wetlands. It is hypothesized that these changes affected the hydrology of the area, resulting in increased salinity, providing the right niche for the development of current mangrove. The resources used were aerial photographs, oral history, a report done in 1979 by the Department of Natural and Environmental Resources of the Government of Puerto Rico and analyses of salinity, pH and conductivity of soils in three different sites. The conclusion of this study was that the wetland underwent changes in ecosystem composition by ambitious elimination of sand dunes due to hydrological changes and marine effects. The oral history confirms the presence of springs in the past and present. Salinity intrusion was documented in those springs in the 1979 report due to land use change and elimination of sand dunes, changing the habitat, therefore allowing a mangrove community to be established. The continuity of ecophysiological and hydrogeological studies of the area will allow for a predictive understanding of how the mangrove wetland will continue developing. |
2018 |
|
Lugo, Ariel E.; Cuevas, Elvira; Medina, Ernesto; Ramos, Olga Ecological and physiological aspects of Caribbean shrublands Journal Article Forthcoming In: Caribbean Naturalist, Forthcoming. @article{Lugo2018, | |
Hernandez, Jose A.; Fonseca, Luis F.; Ruiz, Angel Thermoelectric properties of SnSe nanowires with different diameters Journal Article In: Scientific Reports, vol. 8, no. 11966, pp. 8, 2018. @article{joseHernandez2018,Tin selenide (SnSe) has been the subject of great attention in the last years due to its highly efficient thermoelectricity and its possibilities as a green material, free of Pb and Te. Here, we report for the first time a thermoelectricity and transport study of individual SnSe micro- and nano-wires with diameters in the range between 130 nm and 1.15 μm. X-ray diffraction and transmission electron microscopy analyses confirm an orthorhombic SnSe structure with Pnma (62) symmetry group and 1:1 Sn:Se atomic ratio. Electrical and thermal conductivity and the Seebeck coefficient were measured in each individual nanowire using a specialized suspended microdevice in the 150–370 K temperature range, yielding a thermal conductivity of 0.55 Wm−1 K−1 at room temperature and ZT ~ 0.156 at 370 K for the 130 nm diameter nanowire. The measured properties were correlated with electronic information obtained by model simulations and with phonon scattering analysis. The results confirm these structures as promising building blocks to develop efficient temperature sensors, refrigerators and thermoelectric energy converters. The thermoelectric response of the nanowires is compared with recent reports on crystalline, polycrystalline and layered bulk structures. | |
Arias, María F. Barberena; Cuevas, Elvira Physico-chemical foliar traits predict assemblages of litter/humus detritivore arthropods Journal Article In: In tech open- Tropical Forests, vol. 1, no. 1, pp. 19, 2018. @article{Arias2018,Plant functional traits influence the decomposition of their own residues occurring underneath individual plant species. Arthropods associated to litter are critical components influencing decomposition. Nevertheless, few studies have established a direct relation between plant traits and belowground arthropods. To address this relation at the individual plant species scale, this study was conducted in the Guánica dry forest, Puerto Rico, by selecting five tree species and ten isolated trees/species where variations due to neighbor trees are reduced. Mature green leaves, litter, and associated arthropods were sampled from November 2004 through September 2005. Collected arthropods were counted and classified, and abundances were standardized to ind/m2. Arthropod abundance did not differ among plant species, but richness, and species and trophic composition were different among the plant species. Predators, omnivores, and sucking herbivores showed a similar species composition among plant species, while detritivore was the only trophic groups with a different species composition among plants. These results are further supported by canonical correspondence analysis results showing that detritivore arthropod species composition covaries with the physicochemical characteristics of mature green leaves of plants. These findings support that the plant idiosyncratic characteristics affect the structure of litter/humus arthropods up to the first consumer level. | |
Hernandez, Jose A.; Fonseca, Luis F. Thermoelectric properties and thermal tolerance o indium tin oxide nanowires Journal Article In: Nanotechnology, vol. 29, no. 364001, pp. 7, 2018. @article{Hernandez2018,Highly crystalline indium tin oxide (ITO) nanowires were grown via a vapor–liquid–solid method, with thermal tolerance up to ~1300 °C. We report the electric and thermoelectric properties of the ITO nanowires before and after heat treatments and draw conclusions about their applicability as thermoelectric building blocks in nanodevices that can operate in high temperature conditions. The Seebeck coefficient and the thermal and electrical conductivities were measured in each individual nanowire by means of specialized micro-bridge thermometry devices. Measured data was analyzed and explained in terms of changes in charge carrier density, impurities and vacancies due to the thermal treatments. | |
Gutierrez, Keily; Piñero, Dalice M.; Corchado, Juan; Lin, Shiru In: Inorganica Chimica Acta, vol. 474, no. 118, pp. 9, 2018. @article{Gutierrez2018,Three mononuclear metal complexes of Co2+, Ni2+ and Cu2+ with the Salen type ligand ((2,2′-[(1-methyl-1,2-ethanediyl) bis(nitriloethylidyne)] bis(1-naphthalenol)), H2Naphpren or L) were synthesized and structurally characterized. All metal complexes have square planar geometries and crystallize in the P21/c space group. Structural characterization of the ligand shows contribution of the bis(ketone) tautomer in the crystalline phase, in agreement with density functional theory (DFT) computations. However, according to the UV-vis spectrum, there is a stronger influence of the bis(phenol) tautomer in solution. Cyclic voltammetry experiments showed that the ligand undergoes a single irreversible oxidation process at 0.434 V (vs Fc/Fc+) while the complexes with Co2+, Ni2+ and Cu2+ suffer electroxidative process on the surface of the working electrode in addition to solution-assigned redox processes. The CoL oxidation is localized on the metal center, however, the CuL and NiL oxidations are considered as metal-ligand based processes. DFT calculations confirmed our experimental findings. The UV-vis spectra of the complexes illustrate ligand characteristic bands: in the case of the Cu2+ complex, the metal-to-ligand charge transfer (MLCT) band is present at 385 nm, while in the case of Co2+ complex this same type of MLCT band appears at 377 nm. | |
Rivera, Manuel; Feng, Peter; Velazquez, Rafael UV photodetector based on energy bandgap shifted hexagonal boron nitride nanosheets for high-temperature environments Journal Article In: vol. 51, no. 045102, pp. 9, 2018. @article{Rivera2018,We extend our investigations in the use of boron nitride nanosheets (BNNSs) as sensing material for UV photodetectors by exploring the energy bandgap shift in a new BNNSs arrangement on silicon substrate produced by a pulsed laser plasma deposition (PLPD) technique. Characterizations by XRD and Raman spectrum analysis indicate that the material is composed of high purity hexagonal boron nitride (hBN). SEM and AFM images confirm this particular arrangement of BNNSs is made of randomly orientated hBN nanosheets. The BNNS on silicon substrate material exhibits higher conductivity and photosensitivity in deep UV region than previously investigated BNNS thin films. The material is also sensitive to the UVB region, indicative of having a lower band gap width than that of bulk or thin films, while remaining visible-blind. The observed decrease in cut-off frequency was a direct result of the structural arrangement of the BNNSs in the film. This has the advantage of avoiding doping in order to tune bandgap width, which can compromise intrinsic desirable properties of hBN. Additionally, the material performed extremely well as a UV photodetector even at temperatures as high as 400 °C, making this particular arrangement of BNNSs an ideal candidate for applications where UV sensing in high-temperature environments is required. | |
Feng, Peter X. A compact design of a characterization station for far UV photodetectors Journal Article In: Review of Scientific Instruments, vol. 89, no. 15001, pp. 8, 2018. @article{Feng2018,A newly fabricated characterization station is presented. It is a compact, cost-effective, and easily adjustable apparatus. Each part including 4-pin probe, manipulators, operating temperature, and applied bias can be independently controlled. The station can provide highly reliable, reproducible, and economical methods to quickly conduct and complete the characterizations of a large amount of sensing materials within a short period of time. It is particularly suitable for studies of various nanostructured materials and their related thermal effect, polarization effect, sensitivity, and electrical and electronic properties. | |
2017 |
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Ortiz, Mónica Salazar; Cuevas, Elvira Land use and land management during the past century determine mangrove dynamics in northwestern Puerto Rico: the case of the Maracayo Mangrove Journal Article In: Journal of Environmental Science and Engineering, vol. b6, no. 593, pp. 30, 2017. @article{Ortiz2017,Political and economic decisions have determined throughout the history of Puerto Rico land use for agriculture, livestock and urban sprawl. Knowing this, this study is imperative to understand how these changes caused by the various uses and management affected adjoining wetlands. It is hypothesized that these changes affected the hydrology of the area, resulting in increased salinity, providing the right niche for the development of current mangrove. The resources used were aerial photographs, oral history, a report done in 1979 by the Department of Natural and Environmental Resources of the Government of Puerto Rico and analyses of salinity, pH and conductivity of soils in three different sites. The conclusion of this study was that the wetland underwent changes in ecosystem composition by ambitious elimination of sand dunes due to hydrological changes and marine effects. The oral history confirms the presence of springs in the past and present. Salinity intrusion was documented in those springs in the 1979 report due to land use change and elimination of sand dunes, changing the habitat, therefore allowing a mangrove community to be established. The continuity of ecophysiological and hydrogeological studies of the area will allow for a predictive understanding of how the mangrove wetland will continue developing. | |