Search

Search Results

• 321. [Article] Benchtop Minimal-Intervention Anaerobic Digestion of Vegetarian Food Waste for pH and Methane Production: Conceivability and Control Study

  Cities around the world transport large quantities of waste to landfills at a great expense to their residents, infrastructures, and environments. The objective of this study was to run an anaerobic food ...

  Citation × Citation Citation Abstract Copy Title: Benchtop Minimal-Intervention Anaerobic Digestion of Vegetarian Food Waste for pH and Methane Production: Conceivability and Control Study Author: Heleva-Ponaski, Emily J Year: 2014 Cities around the world transport large quantities of waste to landfills at a great expense to their residents, infrastructures, and environments. The objective of this study was to run an anaerobic food waste digester with minimal interference or maintenance. One specific goal of this research was to evaluate the relationship between anaerobic food waste and pH. Two benchop digesters were started with vegetarian food waste collected from the Portland State University campus. Measurements were collected over the course of the digestion process. Due to low pH and lack of biogas production, the digesters were buffered with sodium carbonate and seeded with wastewater digestate. Post recovery, the solids content decreased and methane production began though the process was never fully optimized. The lack of digester performance is thought to be due in part to low operation temperature. Title: Benchtop Minimal-Intervention Anaerobic Digestion of Vegetarian Food Waste for pH and Methane Production: Conceivability and Control Study Author: Heleva-Ponaski, Emily J Year: 2014 Cities around the world transport large quantities of waste to landfills at a great expense to their residents, infrastructures, and environments. The objective of this study was to run an anaerobic food waste digester with minimal interference or maintenance. One specific goal of this research was to evaluate the relationship between anaerobic food waste and pH. Two benchop digesters were started with vegetarian food waste collected from the Portland State University campus. Measurements were collected over the course of the digestion process. Due to low pH and lack of biogas production, the digesters were buffered with sodium carbonate and seeded with wastewater digestate. Post recovery, the solids content decreased and methane production began though the process was never fully optimized. The lack of digester performance is thought to be due in part to low operation temperature. Close

• 322. [Article] Copper electrodeposition in a magnetic field

  The effect of a magnetic field on copper electrodeposition was investigated. Copper was electrodeposited onto square copper cathodes 1 sq cm in area from an aqueous solution (0.5 M CuSO4, 0.5 M H2SO. A ...

  Citation × Citation Citation Abstract Copy Title: Copper electrodeposition in a magnetic field Author: Takeo, Hiroshi Year: 1985 The effect of a magnetic field on copper electrodeposition was investigated. Copper was electrodeposited onto square copper cathodes 1 sq cm in area from an aqueous solution (0.5 M CuSO4, 0.5 M H2SO. A glass cell was placed between the pole pieces of an electromagnet, and the magnetic fields applied were in the range from 0 to 12.5 kG. The current density was in the range from 80 mA/sq cm to 880 mA/sq cm. In each of the experiments, cell current, cell voltage, and cell temperature were monitored with a microcomputer. The weight change, deposit surface and cross section morphology, and the hardness were also found. Anodes used in the experiments were studied to see the effect of various conditions on the surface finish. Copper was also electrodeposited onto copper grids in order to study how the uniformity of the deposit is affected by an applied magnetic field. Title: Copper electrodeposition in a magnetic field Author: Takeo, Hiroshi Year: 1985 The effect of a magnetic field on copper electrodeposition was investigated. Copper was electrodeposited onto square copper cathodes 1 sq cm in area from an aqueous solution (0.5 M CuSO4, 0.5 M H2SO. A glass cell was placed between the pole pieces of an electromagnet, and the magnetic fields applied were in the range from 0 to 12.5 kG. The current density was in the range from 80 mA/sq cm to 880 mA/sq cm. In each of the experiments, cell current, cell voltage, and cell temperature were monitored with a microcomputer. The weight change, deposit surface and cross section morphology, and the hardness were also found. Anodes used in the experiments were studied to see the effect of various conditions on the surface finish. Copper was also electrodeposited onto copper grids in order to study how the uniformity of the deposit is affected by an applied magnetic field. Close

• 323. [Article] The biogeography of Oregon white oak (Quercus garryana) in central Oregon

  The study proceeded as follows: The distribution of Q. garryana was mapped through field reconnaissance. Annual rings from fifteen trees were counted in order to establish age versus trunk diameter ratios. ...

  Citation × Citation Citation Abstract Copy Title: The biogeography of Oregon white oak (Quercus garryana) in central Oregon Author: Voeks, Robert Allen Year: 1981 The study proceeded as follows: The distribution of Q. garryana was mapped through field reconnaissance. Annual rings from fifteen trees were counted in order to establish age versus trunk diameter ratios. This greatly simplified the dating of trees. Transects were then run through individual groves to determine population age structures. These age structures, along with Q. garryana's distribution patterns, were graphically compared with historic temperature, precipitation, and growing season data. The effect of livestock grazing on oak reproduction was examined. Potential vagility of the species was evaluated by estimating the potential for acorn dispersion by airfall, streams, vertebrates, and the human (aboriginal) population. Finally, pollen evidence was scrutinized in conjunction with acorn dispersal rates in order to determine the longer term history of Q. garryana in this portion cf its range. Title: The biogeography of Oregon white oak (Quercus garryana) in central Oregon Author: Voeks, Robert Allen Year: 1981 The study proceeded as follows: The distribution of Q. garryana was mapped through field reconnaissance. Annual rings from fifteen trees were counted in order to establish age versus trunk diameter ratios. This greatly simplified the dating of trees. Transects were then run through individual groves to determine population age structures. These age structures, along with Q. garryana's distribution patterns, were graphically compared with historic temperature, precipitation, and growing season data. The effect of livestock grazing on oak reproduction was examined. Potential vagility of the species was evaluated by estimating the potential for acorn dispersion by airfall, streams, vertebrates, and the human (aboriginal) population. Finally, pollen evidence was scrutinized in conjunction with acorn dispersal rates in order to determine the longer term history of Q. garryana in this portion cf its range. Close

• 324. [Article] Characterization of a new freshwater methanogen, Methanogenium wolfei sp. nov.

  A recently isolated freshwater methanogenium species, Methanogenium wolfei, is characterized. Cells were irregular cocci, measuring 1.5 to 2.0 micrometers in diameter. No motility was observed, but 1 to ...

  Citation × Citation Citation Abstract Copy Title: Characterization of a new freshwater methanogen, Methanogenium wolfei sp. nov. Author: Moore, Theodore B. Year: 1985 A recently isolated freshwater methanogenium species, Methanogenium wolfei, is characterized. Cells were irregular cocci, measuring 1.5 to 2.0 micrometers in diameter. No motility was observed, but 1 to 2 flagella per cell were observed after staining with Gray's Flagella Stain. Colonies formed by this species were small, shiny, and green-brown in color. Formate or hydrogen plus carbon dioxide served as substrates for growth. The optimal temperature for growth was found to be 45 degrees centigrade with minimal growth below 30 degrees centigrade and above 55 degrees centigrade. The optimal pH for growth was determined to be 6.8. Optimal growth was obtained within a 0.0 to 0.2M range of added sodium chloride. Acetate and arginine were required for growth. DNA base composition was 61.1 mol%. G+C. The presence of coenzyme F-420 at a concentration of 134 mg/kg cells (wet weight) was determined in cell extracts. The enzyme NADP reductase was found to be present and was partially characterized. Title: Characterization of a new freshwater methanogen, Methanogenium wolfei sp. nov. Author: Moore, Theodore B. Year: 1985 A recently isolated freshwater methanogenium species, Methanogenium wolfei, is characterized. Cells were irregular cocci, measuring 1.5 to 2.0 micrometers in diameter. No motility was observed, but 1 to 2 flagella per cell were observed after staining with Gray's Flagella Stain. Colonies formed by this species were small, shiny, and green-brown in color. Formate or hydrogen plus carbon dioxide served as substrates for growth. The optimal temperature for growth was found to be 45 degrees centigrade with minimal growth below 30 degrees centigrade and above 55 degrees centigrade. The optimal pH for growth was determined to be 6.8. Optimal growth was obtained within a 0.0 to 0.2M range of added sodium chloride. Acetate and arginine were required for growth. DNA base composition was 61.1 mol%. G+C. The presence of coenzyme F-420 at a concentration of 134 mg/kg cells (wet weight) was determined in cell extracts. The enzyme NADP reductase was found to be present and was partially characterized. Close

• 325. [Article] Mineral Evidence for Generating Compositionally Zoned Rhyolites of the Devine Canyon Tuff, High Lava Plains, Oregon

  Large-volume silicic eruptions are often evacuated from magma reservoirs which display gradients in composition, temperature, crystallinity, and volatile content. The 9.7 Ma Devine Canyon Tuff (DCT) of ...

  Citation × Citation Citation Abstract Copy Title: Mineral Evidence for Generating Compositionally Zoned Rhyolites of the Devine Canyon Tuff, High Lava Plains, Oregon Author: Shafer, Erik Paul Year: 2017 Large-volume silicic eruptions are often evacuated from magma reservoirs which display gradients in composition, temperature, crystallinity, and volatile content. The 9.7 Ma Devine Canyon Tuff (DCT) of eastern Oregon represents such an eruption, with >300 km3 of compositionally zoned pyroclastic material deposited as a variably-welded ignimbrite. The ignimbrite displays homogenous bulk tuff major element compositions with a wide range of trace element compositions, allowing for the investigation of how these magmas were generated, stored, and modified in the magma reservoir by studying pumices which represent the primary magmas composing the DCT. Five pumices ranging from dacite to rhyolite bulk compositions were selected across the range of trace element compositions and were crushed and sieved to measure how crystallinity and mineral abundances change within each pumice at different particle size fractions. Single alkali feldspar and clinopyroxene crystals were analyzed using EMP and LA ICP-MS from each pumice. Physical results yielded a systematic decrease in crystallinity from 22% to 3% going from the dacite to the most evolved rhyolite composition, with the highest crystallinity occurring between Title: Mineral Evidence for Generating Compositionally Zoned Rhyolites of the Devine Canyon Tuff, High Lava Plains, Oregon Author: Shafer, Erik Paul Year: 2017 Large-volume silicic eruptions are often evacuated from magma reservoirs which display gradients in composition, temperature, crystallinity, and volatile content. The 9.7 Ma Devine Canyon Tuff (DCT) of eastern Oregon represents such an eruption, with >300 km3 of compositionally zoned pyroclastic material deposited as a variably-welded ignimbrite. The ignimbrite displays homogenous bulk tuff major element compositions with a wide range of trace element compositions, allowing for the investigation of how these magmas were generated, stored, and modified in the magma reservoir by studying pumices which represent the primary magmas composing the DCT. Five pumices ranging from dacite to rhyolite bulk compositions were selected across the range of trace element compositions and were crushed and sieved to measure how crystallinity and mineral abundances change within each pumice at different particle size fractions. Single alkali feldspar and clinopyroxene crystals were analyzed using EMP and LA ICP-MS from each pumice. Physical results yielded a systematic decrease in crystallinity from 22% to 3% going from the dacite to the most evolved rhyolite composition, with the highest crystallinity occurring between Close

• 326. [Article] The Changing Extent of the Glaciers Along the Western Ross Sea, Antarctica

  We examine the change in terminus positions of glaciers flowing into the western Ross Sea, Antarctica, between 71°S and 78°S as a proxy for changes in snowfall and/or summer air temperature. This coastline's ...

  Citation × Citation Citation Abstract Copy Title: The Changing Extent of the Glaciers Along the Western Ross Sea, Antarctica Author: Fountain, Andrew G., Glenn, Bryce, Scambos, Ted A. Year: 2017 We examine the change in terminus positions of glaciers flowing into the western Ross Sea, Antarctica, between 71°S and 78°S as a proxy for changes in snowfall and/or summer air temperature. This coastline's major glaciers terminate in ice tongues, which are particularly sensitive to changes in flow rate and calving. Using historic maps and satellite imagery spanning 60 yr (A.D. 1955-2015), the terminus positions, ice speed, calving rates, and ice front advance and retreat rates for 34 glaciers are documented. Additionally, changes in regional ice flow speed from 2008 to 2014 are examined. No significant spatial or temporal patterns of terminus position, flow speed, or calving emerged, implying that the conditions associated with ice tongue stability are unchanged. A weak trend of advance may be present in the northernmost part of the coast, consistent with estimates of increased snow accumulation and glacier mass balance in that region. The stability of these glaciers over the past half century contrasts sharply with the rapidly shrinking glaciers of the Antarctic Peninsula and suggests that no significant climate change, as manifest in glacier change, has reached this region of Antarctica. The changing extent of the glaciers along the western Ross Sea, Antarctica. Title: The Changing Extent of the Glaciers Along the Western Ross Sea, Antarctica Author: Fountain, Andrew G., Glenn, Bryce, Scambos, Ted A. Year: 2017 We examine the change in terminus positions of glaciers flowing into the western Ross Sea, Antarctica, between 71°S and 78°S as a proxy for changes in snowfall and/or summer air temperature. This coastline's major glaciers terminate in ice tongues, which are particularly sensitive to changes in flow rate and calving. Using historic maps and satellite imagery spanning 60 yr (A.D. 1955-2015), the terminus positions, ice speed, calving rates, and ice front advance and retreat rates for 34 glaciers are documented. Additionally, changes in regional ice flow speed from 2008 to 2014 are examined. No significant spatial or temporal patterns of terminus position, flow speed, or calving emerged, implying that the conditions associated with ice tongue stability are unchanged. A weak trend of advance may be present in the northernmost part of the coast, consistent with estimates of increased snow accumulation and glacier mass balance in that region. The stability of these glaciers over the past half century contrasts sharply with the rapidly shrinking glaciers of the Antarctic Peninsula and suggests that no significant climate change, as manifest in glacier change, has reached this region of Antarctica. The changing extent of the glaciers along the western Ross Sea, Antarctica. Close

• 327. [Article] An ice-shelf model test based on the Ross ice shelf

  A standard numerical experiment featuring the Ross Ice Shelf, Antarctica, is presented as a test package for the development and intercomparison of ice-shelf models. The emphasis of this package is solution ...

  Citation × Citation Citation Abstract Copy Title: An ice-shelf model test based on the Ross ice shelf Author: MacAyeal, D. R., Rommelaere, V., Huybrechts, P., Hulbe, Christina L., Determann, J., Ritz, C. Year: 1996 A standard numerical experiment featuring the Ross Ice Shelf, Antarctica, is presented as a test package for the development and intercomparison of ice-shelf models. The emphasis of this package is solution of stress-equilibrium equations for an ice-shelf velocity consistent with present observations. As a demonstration, we compare five independently developed ice-shelf models based on finite-difference and finite-element methods. Our results suggest that there is little difference between finite-element and finite-difference methods in capturing the basic, large-scale flow features of the ice shelf. We additionally show that the fit between model and observed velocity depends strongly on the ice-shelf temperature field for which there is presently little observational control. The main differences between model results are due to the equations being solved, the boundary conditions at the ice front and the discretization method (finite element vs. finite difference) Title: An ice-shelf model test based on the Ross ice shelf Author: MacAyeal, D. R., Rommelaere, V., Huybrechts, P., Hulbe, Christina L., Determann, J., Ritz, C. Year: 1996 A standard numerical experiment featuring the Ross Ice Shelf, Antarctica, is presented as a test package for the development and intercomparison of ice-shelf models. The emphasis of this package is solution of stress-equilibrium equations for an ice-shelf velocity consistent with present observations. As a demonstration, we compare five independently developed ice-shelf models based on finite-difference and finite-element methods. Our results suggest that there is little difference between finite-element and finite-difference methods in capturing the basic, large-scale flow features of the ice shelf. We additionally show that the fit between model and observed velocity depends strongly on the ice-shelf temperature field for which there is presently little observational control. The main differences between model results are due to the equations being solved, the boundary conditions at the ice front and the discretization method (finite element vs. finite difference) Close

• 328. [Article] Characterization and correction of dark current in compact consumer cameras

  A study of dark current in digital imagers within consumer grade digital cameras is presented. Dark current is shown to vary with temperature, exposure time, and ISO setting. Further, dark current is shown ...

  Citation × Citation Citation Abstract Copy Title: Characterization and correction of dark current in compact consumer cameras Author: Dunlap, Justin Charles, Bodegom, Erik, Widenhorn, Ralf Year: 2010 A study of dark current in digital imagers within consumer grade digital cameras is presented. Dark current is shown to vary with temperature, exposure time, and ISO setting. Further, dark current is shown to increase in successive images during a series of images. Consumer cameras are often designed to be as compact as possible and therefore the digital imagers within the camera frame are prone to heat generated by nearby elements within the camera body. It is the scope of this work to characterize the dark current in such cameras and to show that the dark current, in part due to heat generated by the camera itself, can be corrected for by using hot pixels on the imager. This method generates computed dark frames based on the dark current indicator value of the hottest pixels on the chip. We compare this method to standard methods of dark current correction. Title: Characterization and correction of dark current in compact consumer cameras Author: Dunlap, Justin Charles, Bodegom, Erik, Widenhorn, Ralf Year: 2010 A study of dark current in digital imagers within consumer grade digital cameras is presented. Dark current is shown to vary with temperature, exposure time, and ISO setting. Further, dark current is shown to increase in successive images during a series of images. Consumer cameras are often designed to be as compact as possible and therefore the digital imagers within the camera frame are prone to heat generated by nearby elements within the camera body. It is the scope of this work to characterize the dark current in such cameras and to show that the dark current, in part due to heat generated by the camera itself, can be corrected for by using hot pixels on the imager. This method generates computed dark frames based on the dark current indicator value of the hottest pixels on the chip. We compare this method to standard methods of dark current correction. Close

• 329. [Article] Dark current in an active pixel complementary metal-oxide-semiconductor sensor

  We present an analysis of dark current from a complementary metal?oxide?semiconductor (CMOS) active pixels sensor with global shutter. The presence of two sources of dark current, one within the collection ...

  Citation × Citation Citation Abstract Copy Title: Dark current in an active pixel complementary metal-oxide-semiconductor sensor Author: Dunlap, Justin Charles, Porter, William Christian, Bodegom, Erik, Widenhorn, Ralf Year: 2011 We present an analysis of dark current from a complementary metal?oxide?semiconductor (CMOS) active pixels sensor with global shutter. The presence of two sources of dark current, one within the collection area of the pixel and another within the sense node, present complications to correction of the dark current. The two sources are shown to generate unique and characteristic dark current behavior with respect to varying exposure time, temperature, and/or frame rate. In particular, a pixel with storage time in the sense node will show a dark current dependence on frame rate and the appearance of being a ?stuck pixel? with values independent of exposure time. On the other hand, a pixel with an impurity located within the collection area will show no frame rate dependence, but rather a linear dependence on exposure time. A method of computing dark frames based on past dark current behavior of the sensor is presented and shown to intrinsically compensate for the two different and unique sources. In addition, dark frames requiring subtraction of negative values, arising from the option to modify the bias offset, are shown to be appropriate and possible using the computational method. Title: Dark current in an active pixel complementary metal-oxide-semiconductor sensor Author: Dunlap, Justin Charles, Porter, William Christian, Bodegom, Erik, Widenhorn, Ralf Year: 2011 We present an analysis of dark current from a complementary metal?oxide?semiconductor (CMOS) active pixels sensor with global shutter. The presence of two sources of dark current, one within the collection area of the pixel and another within the sense node, present complications to correction of the dark current. The two sources are shown to generate unique and characteristic dark current behavior with respect to varying exposure time, temperature, and/or frame rate. In particular, a pixel with storage time in the sense node will show a dark current dependence on frame rate and the appearance of being a ?stuck pixel? with values independent of exposure time. On the other hand, a pixel with an impurity located within the collection area will show no frame rate dependence, but rather a linear dependence on exposure time. A method of computing dark frames based on past dark current behavior of the sensor is presented and shown to intrinsically compensate for the two different and unique sources. In addition, dark frames requiring subtraction of negative values, arising from the option to modify the bias offset, are shown to be appropriate and possible using the computational method. Close

• 330. [Article] Annealing Effect on Photovoltaic Performance of CdSe Quantum-Dots-Sensitized TiO2 Nanorod Solar Cells

  Large area rutile TiO₂ nanorod arrays were grown on F:SnO₂ (FTO) conductive glass using a hydrothermal method at low temperature. CdSe quantum dots (QDs) were deposited onto single-crystalline TiO₂ nanorod ...

  Citation × Citation Citation Abstract Copy Title: Annealing Effect on Photovoltaic Performance of CdSe Quantum-Dots-Sensitized TiO2 Nanorod Solar Cells Author: Li, Yitan, Wei, Lin, Zhang, Ruizi, Chen, Yanxue, Jiao, Jun Year: 2012 Large area rutile TiO₂ nanorod arrays were grown on F:SnO₂ (FTO) conductive glass using a hydrothermal method at low temperature. CdSe quantum dots (QDs) were deposited onto single-crystalline TiO₂ nanorod arrays by a chemical bath deposition (CBD) method to make a photoelectrode. The solar cell was assembled using a CdSe-TiO₂ nanostructure as the photoanode and polysulfide solution as the electrolyte. The annealing effect on optical and photovoltaic properties of CdSe quantum-dotssensitized TiO₂ nanorod solar cells was studied systematically. A significant change of the morphology and a regular red shift of band gap of CdSe nanoparticles were observed after annealing treatment. At the same time, an improved photovoltaic performance was obtained for quantum-dots-sensitized solar cell using the annealed CdSe-TiO₂ nanostructure electrode. The power conversion efficiency improved from 0.59% to 1.45% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by annealing treatment. Title: Annealing Effect on Photovoltaic Performance of CdSe Quantum-Dots-Sensitized TiO2 Nanorod Solar Cells Author: Li, Yitan, Wei, Lin, Zhang, Ruizi, Chen, Yanxue, Jiao, Jun Year: 2012 Large area rutile TiO₂ nanorod arrays were grown on F:SnO₂ (FTO) conductive glass using a hydrothermal method at low temperature. CdSe quantum dots (QDs) were deposited onto single-crystalline TiO₂ nanorod arrays by a chemical bath deposition (CBD) method to make a photoelectrode. The solar cell was assembled using a CdSe-TiO₂ nanostructure as the photoanode and polysulfide solution as the electrolyte. The annealing effect on optical and photovoltaic properties of CdSe quantum-dotssensitized TiO₂ nanorod solar cells was studied systematically. A significant change of the morphology and a regular red shift of band gap of CdSe nanoparticles were observed after annealing treatment. At the same time, an improved photovoltaic performance was obtained for quantum-dots-sensitized solar cell using the annealed CdSe-TiO₂ nanostructure electrode. The power conversion efficiency improved from 0.59% to 1.45% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by annealing treatment. Close