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• 131. [Article] Photochemical degradation of sediment organic matter : effect on Zn-65 release

  Columbia River sediment was irradiated with ultraviolet light to determine if organic material could be removed without altering the sorptive properties of the hydrous oxides of iron and manganese. A laboratory ...

  Citation × Citation Citation Abstract Copy Title: Photochemical degradation of sediment organic matter : effect on Zn-65 release Author: Lenaers, William Michael Columbia River sediment was irradiated with ultraviolet light to determine if organic material could be removed without altering the sorptive properties of the hydrous oxides of iron and manganese. A laboratory preparation of Zn-65 spiked hydrous ferric oxide was subjected to ultraviolet irradiation in order to assess the photochemical effect upon Zn-65 release. The photochemically induced release of Mn-54 present on the Columbia River sediment was used to assess the effect on the hydrous oxides of manganese. The ultraviolet irradiation proved effective in removing up to 68% of the sedimentary organic material in 17 hours without causing release of Zn-65 or Sc-46. While the ultraviolet irradiation had no effect upon Zn-65 release from laboratory preparations of hydrous ferric oxides and Zn-65 spiked montmorillonite, a significant release of Mn-54 resulted from the photolysis treatment. The removal of Mn-54 was not accompanied by the release of sorbed Zn-65 or Sc-46 (nuclides expected to be sorbed by hydrous oxides), nor did there appear to be any permanent change in the nature of the Mn-54 on the sediment. Although it is possible that the hydrous oxides of manganese are affected by the ultraviolet treatment, it is likely that another species, such as the carbonate, is the species involved. Photo-oxidation appears to provide a method of obtaining sediments with substantially reduced organic content without affecting the sorptive properties of hydrous oxides or clay minerals. This result should allow the use of uptake studies to determine the importance of organic material in trace metal sorption by sediments. Title: Photochemical degradation of sediment organic matter : effect on Zn-65 release Author: Lenaers, William Michael Columbia River sediment was irradiated with ultraviolet light to determine if organic material could be removed without altering the sorptive properties of the hydrous oxides of iron and manganese. A laboratory preparation of Zn-65 spiked hydrous ferric oxide was subjected to ultraviolet irradiation in order to assess the photochemical effect upon Zn-65 release. The photochemically induced release of Mn-54 present on the Columbia River sediment was used to assess the effect on the hydrous oxides of manganese. The ultraviolet irradiation proved effective in removing up to 68% of the sedimentary organic material in 17 hours without causing release of Zn-65 or Sc-46. While the ultraviolet irradiation had no effect upon Zn-65 release from laboratory preparations of hydrous ferric oxides and Zn-65 spiked montmorillonite, a significant release of Mn-54 resulted from the photolysis treatment. The removal of Mn-54 was not accompanied by the release of sorbed Zn-65 or Sc-46 (nuclides expected to be sorbed by hydrous oxides), nor did there appear to be any permanent change in the nature of the Mn-54 on the sediment. Although it is possible that the hydrous oxides of manganese are affected by the ultraviolet treatment, it is likely that another species, such as the carbonate, is the species involved. Photo-oxidation appears to provide a method of obtaining sediments with substantially reduced organic content without affecting the sorptive properties of hydrous oxides or clay minerals. This result should allow the use of uptake studies to determine the importance of organic material in trace metal sorption by sediments. Close

• 132. [Article] New luminescent materials and high-performance solution-processed oxide thin films

  Crystals of an incongruent-melting compound, Ba₃MgSi₂O₈, were grown by the flux method and its structure was determined by single crystal X-ray diffraction methods. Ba₃MgSi₂O₈ crystallizes in trigonal ...

  Citation × Citation Citation Abstract Copy Title: New luminescent materials and high-performance solution-processed oxide thin films Author: Jiang, Kai Crystals of an incongruent-melting compound, Ba₃MgSi₂O₈, were grown by the flux method and its structure was determined by single crystal X-ray diffraction methods. Ba₃MgSi₂O₈ crystallizes in trigonal space group P-3[bar]m1 with a = 5.6123(3) Å, c = 7.2667(9) Å and Z = 1. Eu²⁺ ions prefer one crystallographic Ba site in the structure and exhibit strong blue emissions at 440 nm. A new series of compounds RE₄Zn₄(SiO₄)₅ (RE=Y, La, Eu, Gd, Tb, Dy, Ho, Er), adopting an unprecedented new structure type, was discovered. Crystals of Y₄Zn₄(SiO₄)₅ were grown from a silica-rich eutectic melt and its structure was determined by single-crystal diffraction methods. It crystallizes in tetragonal space group P4₂/n with cell dimensions a = 9.3289(10) Å, c = 9.0509(18) Å and Z = 2. Selected photo-luminescence properties of lanthanide ions doped Y₄Zn₄(SiO₄)₅ are presented. High-purity MgS:Eu phosphors, exhibiting distinct cubic morphology, high luminescence efficacy, and stability against moisture, were synthesized. Thin films of early transition metal oxides (TiO₂, HfO₂, Nb₂O₅, and V₂O₅) have been deposited from peroxo-assisted aqueous solutions. The facile decomposition of peroxo ligands upon annealing allows smooth and efficient transformation of the precursors into high-quality films. Therefore, the films exhibit extraordinary performance in advanced optical and electrical devices, such as dielectric mirrors, microcavities, capacitors, and thin-film transistors (TFTs). The control over film thickness to a single-digit nm thickness is also demonstrated through the fabrication of TiO₂−AlPO nanolaminates using simple beaker chemistry. Title: New luminescent materials and high-performance solution-processed oxide thin films Author: Jiang, Kai Crystals of an incongruent-melting compound, Ba₃MgSi₂O₈, were grown by the flux method and its structure was determined by single crystal X-ray diffraction methods. Ba₃MgSi₂O₈ crystallizes in trigonal space group P-3[bar]m1 with a = 5.6123(3) Å, c = 7.2667(9) Å and Z = 1. Eu²⁺ ions prefer one crystallographic Ba site in the structure and exhibit strong blue emissions at 440 nm. A new series of compounds RE₄Zn₄(SiO₄)₅ (RE=Y, La, Eu, Gd, Tb, Dy, Ho, Er), adopting an unprecedented new structure type, was discovered. Crystals of Y₄Zn₄(SiO₄)₅ were grown from a silica-rich eutectic melt and its structure was determined by single-crystal diffraction methods. It crystallizes in tetragonal space group P4₂/n with cell dimensions a = 9.3289(10) Å, c = 9.0509(18) Å and Z = 2. Selected photo-luminescence properties of lanthanide ions doped Y₄Zn₄(SiO₄)₅ are presented. High-purity MgS:Eu phosphors, exhibiting distinct cubic morphology, high luminescence efficacy, and stability against moisture, were synthesized. Thin films of early transition metal oxides (TiO₂, HfO₂, Nb₂O₅, and V₂O₅) have been deposited from peroxo-assisted aqueous solutions. The facile decomposition of peroxo ligands upon annealing allows smooth and efficient transformation of the precursors into high-quality films. Therefore, the films exhibit extraordinary performance in advanced optical and electrical devices, such as dielectric mirrors, microcavities, capacitors, and thin-film transistors (TFTs). The control over film thickness to a single-digit nm thickness is also demonstrated through the fabrication of TiO₂−AlPO nanolaminates using simple beaker chemistry. Close

• 133. [Article] Ecosystem Analysis of Wetland and Riparian Zone restoration at the Hart Mountain Antelope Refuge over Twenty Years

  Presentation entitled : Ecosystem Analysis of Wetland and Riparian Zone restoration at the Hart Mountain Antelope Refuge over Twenty Years / by Schyler Reis, Lisa Ellsworth and J. Boone Kauffman

  Citation × Citation Citation Abstract Copy Title: Ecosystem Analysis of Wetland and Riparian Zone restoration at the Hart Mountain Antelope Refuge over Twenty Years Author: Reis, Schyler Ainsworth Presentation entitled : Ecosystem Analysis of Wetland and Riparian Zone restoration at the Hart Mountain Antelope Refuge over Twenty Years / by Schyler Reis, Lisa Ellsworth and J. Boone Kauffman Title: Ecosystem Analysis of Wetland and Riparian Zone restoration at the Hart Mountain Antelope Refuge over Twenty Years Author: Reis, Schyler Ainsworth Presentation entitled : Ecosystem Analysis of Wetland and Riparian Zone restoration at the Hart Mountain Antelope Refuge over Twenty Years / by Schyler Reis, Lisa Ellsworth and J. Boone Kauffman Close

• 134. [Article] Riparian canopy and channel response to hillslope disturbance in Elk River Basin, southwest Oregon

  Elk River is a sixth order stream, draining a 200 square kilometer basin in the Klainath Mountain province of southwestern Oregon. Timber harvesting began in the basin during the 1950's, with peak removal ...

  Citation × Citation Citation Abstract Copy Title: Riparian canopy and channel response to hillslope disturbance in Elk River Basin, southwest Oregon Author: Ryan-Burkett, Sandra E. Elk River is a sixth order stream, draining a 200 square kilometer basin in the Klainath Mountain province of southwestern Oregon. Timber harvesting began in the basin during the 1950's, with peak removal of wood occurring in the mid to late 1960's. This activity lead to an increase in the frequency of landsliding and surface erosion. The downstream effects of this increase in sediment were evaluated by interpreting aerial photography spanning the period 1956 to 1979. Opening or enlargement of the riparian canopy cover was used as an indicator of sediment impacts. Results indicate that in most basins, changes in downstream channel conditions could not be directly linked to the increase in sediment delivered from harvested areas. Opening on higher order channels occurred throughout the study period, but did not exhibit patterns indicative of a large pulse of sediment moving through the system. Rather, opening in fourth to fifth order channels was attributed to the interaction between local sediment sources and channel morphology, with unconstrained, flat channel segments exhibiting chronic opening. The distribution of constrained and unconstrained channel reaches was defined by a Channel Morphology Index (CMI), which compared relative width and gradient changes to channel averages. A 100-year event in 1964 did not produce effects in Elk River Basin on the same order of magnitude as other basins in the Pacific Northwest. Downstream effects were important in a few areas where landslides and high rates of surface erosion were directly linked to opening and channel widening downstream. Limited channel response to hillslope. disturbance in Elk River Basin over the period 1956-79 was attributed to four factors: lack of debris flows in most areas of the basin, channels constrained by competent hillslopes and bedrock limiting the extent of opening, channel conditions inherited from storms prior to 1956, and essentially pristine conditions over much of the basin at the time of the 1964 storm. Finally, sequential air photo interpretation proved useful in deciphering disturbance history and analyzing processes which create downstream effects. Title: Riparian canopy and channel response to hillslope disturbance in Elk River Basin, southwest Oregon Author: Ryan-Burkett, Sandra E. Elk River is a sixth order stream, draining a 200 square kilometer basin in the Klainath Mountain province of southwestern Oregon. Timber harvesting began in the basin during the 1950's, with peak removal of wood occurring in the mid to late 1960's. This activity lead to an increase in the frequency of landsliding and surface erosion. The downstream effects of this increase in sediment were evaluated by interpreting aerial photography spanning the period 1956 to 1979. Opening or enlargement of the riparian canopy cover was used as an indicator of sediment impacts. Results indicate that in most basins, changes in downstream channel conditions could not be directly linked to the increase in sediment delivered from harvested areas. Opening on higher order channels occurred throughout the study period, but did not exhibit patterns indicative of a large pulse of sediment moving through the system. Rather, opening in fourth to fifth order channels was attributed to the interaction between local sediment sources and channel morphology, with unconstrained, flat channel segments exhibiting chronic opening. The distribution of constrained and unconstrained channel reaches was defined by a Channel Morphology Index (CMI), which compared relative width and gradient changes to channel averages. A 100-year event in 1964 did not produce effects in Elk River Basin on the same order of magnitude as other basins in the Pacific Northwest. Downstream effects were important in a few areas where landslides and high rates of surface erosion were directly linked to opening and channel widening downstream. Limited channel response to hillslope. disturbance in Elk River Basin over the period 1956-79 was attributed to four factors: lack of debris flows in most areas of the basin, channels constrained by competent hillslopes and bedrock limiting the extent of opening, channel conditions inherited from storms prior to 1956, and essentially pristine conditions over much of the basin at the time of the 1964 storm. Finally, sequential air photo interpretation proved useful in deciphering disturbance history and analyzing processes which create downstream effects. Close

• 135. [Article] Contribution of deep-seated bedrock landslides to denudation of a glaciated basin in southern Alaska

  The role of bedrock landslides in the denudation of fluvial catchments has received considerable attention, whereas the relative contribution of deep-seated bedrock landslides to the erosion of glaciated ...

  Citation × Citation Citation Abstract Copy Title: Contribution of deep-seated bedrock landslides to denudation of a glaciated basin in southern Alaska Author: Arsenault, Ann Michelle The role of bedrock landslides in the denudation of fluvial catchments has received considerable attention, whereas the relative contribution of deep-seated bedrock landslides to the erosion of glaciated basins is less well known. A glaciated basin in the Chugach-St. Elias Range of southern Alaska was chosen to investigate the contribution of bedrock landslides because the debris from four major landslides on the surface of a glacier is easily distinguished from moraines and other supraglacial material. The sediment in the landslides was derived entirely from the hillslopes, as evidenced by large scars visible on the basin walls. A series of aerial and satellite photos from 1978 to 2000 and field observations in 2001 and 2002 indicate that three of the four landslides have fallen onto the surface of the glacier since -1978. The landslides originated from the steeply dipping (60-70°) bedrock walls and were deposited onto the glacier in the ablation zone. Landslide material is currently being transported downstream supraglacially. Valley walls are composed of high-grade metamorphic rock, have a steep north-dipping foliation, are fractured by numerous large joints, and have an average relief of -400 meters. A total landslide volume of - 2.3 x 105 m3 was determined by combining surface profiles, area, and thickness from high-resolution survey data. This volume indicates that deep-seated landslides resulted in a basin-scale erosion rate of 0.4 mm yr 1.Other investigations that have attempted to quantify the sediment contribution from supraglacial sources, report that sediment derived from the basin walls could represent 24-60% of the overall erosion. If correct, the total landslide volume can be used to infer an overall, basin-scale erosion rate of 0.7 to 1.7 mm yrt. Title: Contribution of deep-seated bedrock landslides to denudation of a glaciated basin in southern Alaska Author: Arsenault, Ann Michelle The role of bedrock landslides in the denudation of fluvial catchments has received considerable attention, whereas the relative contribution of deep-seated bedrock landslides to the erosion of glaciated basins is less well known. A glaciated basin in the Chugach-St. Elias Range of southern Alaska was chosen to investigate the contribution of bedrock landslides because the debris from four major landslides on the surface of a glacier is easily distinguished from moraines and other supraglacial material. The sediment in the landslides was derived entirely from the hillslopes, as evidenced by large scars visible on the basin walls. A series of aerial and satellite photos from 1978 to 2000 and field observations in 2001 and 2002 indicate that three of the four landslides have fallen onto the surface of the glacier since -1978. The landslides originated from the steeply dipping (60-70°) bedrock walls and were deposited onto the glacier in the ablation zone. Landslide material is currently being transported downstream supraglacially. Valley walls are composed of high-grade metamorphic rock, have a steep north-dipping foliation, are fractured by numerous large joints, and have an average relief of -400 meters. A total landslide volume of - 2.3 x 105 m3 was determined by combining surface profiles, area, and thickness from high-resolution survey data. This volume indicates that deep-seated landslides resulted in a basin-scale erosion rate of 0.4 mm yr 1.Other investigations that have attempted to quantify the sediment contribution from supraglacial sources, report that sediment derived from the basin walls could represent 24-60% of the overall erosion. If correct, the total landslide volume can be used to infer an overall, basin-scale erosion rate of 0.7 to 1.7 mm yrt. Close

• 136. [Article] Tandem intramolecular photocycloaddition-retro-Mannich fragmentation as a route to indole and oxindole

  Irradiation of a tryptamine linked through its side-chain nitrogen to an alkylidene malonate residue results in an intramolecular [2 + 2] cycloaddition to the indole 2,3-double bond. The resultant cyclobutane ...

  Citation × Citation Citation Abstract Copy Title: Tandem intramolecular photocycloaddition-retro-Mannich fragmentation as a route to indole and oxindole Author: Li, Yang Irradiation of a tryptamine linked through its side-chain nitrogen to an alkylidene malonate residue results in an intramolecular [2 + 2] cycloaddition to the indole 2,3-double bond. The resultant cyclobutane undergoes spontaneous retro-Mannich fission to produce a spiro[indoline-3,3-pyrrolenine] with relative configuration defined by the orientation of substituents in the transient cyclobutane. The novel tandem intramolecular photocycloaddition- retro-Mannich (TIPCARM) sequence leads to a spiropyrrolidine which is poised to undergo a second retro-Mannich fragmentation [TIPCA(RM)₂] that expels the malonate unit present in the photo substrate and generates transiently an indolenine. The indolenine undergoes rearrangement to a β-carboline which can undergo further rearrangement under oxidizing conditions to an oxindole. Three oxindole natural products, coerulescine, horsfiline and elacomine, were synthesized using this strategy. The TIPCARM strategy was extended to an approach that would encompass the Vinca alkaloids vindorosine and minovine. In this case, the TIPCARM sequence was followed by an intramolecular cyclization that provided tetracyclic ketone 5.86 containing rings A, B, C and D of vindorosine. A tetracyclic intermediate was synthesized which could also provided access to the Vinca alkaloid minovine. Title: Tandem intramolecular photocycloaddition-retro-Mannich fragmentation as a route to indole and oxindole Author: Li, Yang Irradiation of a tryptamine linked through its side-chain nitrogen to an alkylidene malonate residue results in an intramolecular [2 + 2] cycloaddition to the indole 2,3-double bond. The resultant cyclobutane undergoes spontaneous retro-Mannich fission to produce a spiro[indoline-3,3-pyrrolenine] with relative configuration defined by the orientation of substituents in the transient cyclobutane. The novel tandem intramolecular photocycloaddition- retro-Mannich (TIPCARM) sequence leads to a spiropyrrolidine which is poised to undergo a second retro-Mannich fragmentation [TIPCA(RM)₂] that expels the malonate unit present in the photo substrate and generates transiently an indolenine. The indolenine undergoes rearrangement to a β-carboline which can undergo further rearrangement under oxidizing conditions to an oxindole. Three oxindole natural products, coerulescine, horsfiline and elacomine, were synthesized using this strategy. The TIPCARM strategy was extended to an approach that would encompass the Vinca alkaloids vindorosine and minovine. In this case, the TIPCARM sequence was followed by an intramolecular cyclization that provided tetracyclic ketone 5.86 containing rings A, B, C and D of vindorosine. A tetracyclic intermediate was synthesized which could also provided access to the Vinca alkaloid minovine. Close

• 137. [Article] Development, validation and the application of a congener specific photodegradation model for PBDEs

  The thermodynamic properties of 39 PBDEs have been calculated using Gaussian 03 on the B3LYP/6-31G(d)//B3LYP/6-31G(d) level. The PBDE congeners' enthalpies of formation increase with increasing number ...

  Citation × Citation Citation Abstract Copy Title: Development, validation and the application of a congener specific photodegradation model for PBDEs Author: Zeng, Xia The thermodynamic properties of 39 PBDEs have been calculated using Gaussian 03 on the B3LYP/6-31G(d)//B3LYP/6-31G(d) level. The PBDE congeners' enthalpies of formation increase with increasing number of bromines and show a strong dependence on the bromine substitution pattern. The effects of bromine substitution pattern have been quantitatively studied by GAM model based on the output of the theoretical calculations. Based on the GAM model, the enthalpies of formation of the 209 PBDE congeners were calculated. A photodegradation model was developed and validated to predict the products, and their relative concentrations, from the photodegradation of PBDEs. Photodegradation experiments were conducted for octa-BDE technical mixture and its individual components together with BDE-209, 184, 100, 99 and 47. Based on the results of the photodegradation experiments, as well as the model predictions, the photodegradation of PBDEs is a first order reaction and, further, the rate determining step is the stepwise loss of bromine. The predicted reaction time profiles of the photodegradation products correlate well with the experimental results. In addition, the photodegradation results were compared with anaerobic biodegradation. The PBDE products measured in the anaerobic biodegradation were found to be the major products in the photodegradation experiments. The photodegradation experiments and the model predictions were also compared with zero-valent iron reduction of BDE-209, 100 and 47 from a previous study and the same products were found in both photo and Fe⁰ degradation. Good correlation between 15 previously reported photodegradation rate constants of PBDE congeners and their calculated LUMO energies was found. This indicates that, similar to the Fe⁰ reduction, debromination by UV light is caused by electron transfer. Furthermore, the rate constants for the three different degradation processes are controlled by C-Br bond dissociation energy. The model was proved to be predictive for the photodegradation of PBDEs and it should be predictive for anaerobic biodegradation and Fe⁰ reduction of PBDEs. Title: Development, validation and the application of a congener specific photodegradation model for PBDEs Author: Zeng, Xia The thermodynamic properties of 39 PBDEs have been calculated using Gaussian 03 on the B3LYP/6-31G(d)//B3LYP/6-31G(d) level. The PBDE congeners' enthalpies of formation increase with increasing number of bromines and show a strong dependence on the bromine substitution pattern. The effects of bromine substitution pattern have been quantitatively studied by GAM model based on the output of the theoretical calculations. Based on the GAM model, the enthalpies of formation of the 209 PBDE congeners were calculated. A photodegradation model was developed and validated to predict the products, and their relative concentrations, from the photodegradation of PBDEs. Photodegradation experiments were conducted for octa-BDE technical mixture and its individual components together with BDE-209, 184, 100, 99 and 47. Based on the results of the photodegradation experiments, as well as the model predictions, the photodegradation of PBDEs is a first order reaction and, further, the rate determining step is the stepwise loss of bromine. The predicted reaction time profiles of the photodegradation products correlate well with the experimental results. In addition, the photodegradation results were compared with anaerobic biodegradation. The PBDE products measured in the anaerobic biodegradation were found to be the major products in the photodegradation experiments. The photodegradation experiments and the model predictions were also compared with zero-valent iron reduction of BDE-209, 100 and 47 from a previous study and the same products were found in both photo and Fe⁰ degradation. Good correlation between 15 previously reported photodegradation rate constants of PBDE congeners and their calculated LUMO energies was found. This indicates that, similar to the Fe⁰ reduction, debromination by UV light is caused by electron transfer. Furthermore, the rate constants for the three different degradation processes are controlled by C-Br bond dissociation energy. The model was proved to be predictive for the photodegradation of PBDEs and it should be predictive for anaerobic biodegradation and Fe⁰ reduction of PBDEs. Close

• 138. [Article] Neutron shadow holography: a feasibility study

  Neutron shadow holography is a method of obtaining a three-dimensional neutron radiograph of an object using a Fresnel zone plate as an encoding aperture. The object is reconstructed by passing laser light ...

  Citation × Citation Citation Abstract Copy Title: Neutron shadow holography: a feasibility study Author: Coe, Douglas H. Neutron shadow holography is a method of obtaining a three-dimensional neutron radiograph of an object using a Fresnel zone plate as an encoding aperture. The object is reconstructed by passing laser light through a miniature copy of the radiograph. The technique has been applied extensively with X-rays and gamma rays but only recently with neutrons. This project is only the second known of its kind in the United States. The requirements for this type of work include the availability of an intense thermal neutron beam such as that produced by a nuclear research reactor, high resolution photo-reduction capability of up to 40 to 1, and high quality optics and laser equipment. In addition, the capability must exist to properly construct a zone plate encoding aperture. This project utilized all of the above facilities, equipment, and capabilities available at Oregon State University to successfully demonstrate the feasibility of performing neutron shadow holography experiments. An historical review is given of developments leading to the present state-of-art neutron holography technique. The physical properties and limitations of the classical Fresnel zone plate are extensively reviewed as they apply to shadow holography. The effect of the neutronic self-shielding properties of target objects on object resolution is discussed and shown to be generally the most limiting. Finally, contributions to the current literature on this subject are made in two areas. First, an improved zone plate construction method was successfully demonstrated which should substantially improve object reproducibility. Second, an analysis of the neutron energy spectrum effect on hologram quality is reported for the first time and shown to be substantial. Further refinement of the shadow holography technique at Oregon State University is necessary to achieve the level of success enjoyed by other researchers. This project has shown that such refinement is well within the capability of existing facilities and equipment. Title: Neutron shadow holography: a feasibility study Author: Coe, Douglas H. Neutron shadow holography is a method of obtaining a three-dimensional neutron radiograph of an object using a Fresnel zone plate as an encoding aperture. The object is reconstructed by passing laser light through a miniature copy of the radiograph. The technique has been applied extensively with X-rays and gamma rays but only recently with neutrons. This project is only the second known of its kind in the United States. The requirements for this type of work include the availability of an intense thermal neutron beam such as that produced by a nuclear research reactor, high resolution photo-reduction capability of up to 40 to 1, and high quality optics and laser equipment. In addition, the capability must exist to properly construct a zone plate encoding aperture. This project utilized all of the above facilities, equipment, and capabilities available at Oregon State University to successfully demonstrate the feasibility of performing neutron shadow holography experiments. An historical review is given of developments leading to the present state-of-art neutron holography technique. The physical properties and limitations of the classical Fresnel zone plate are extensively reviewed as they apply to shadow holography. The effect of the neutronic self-shielding properties of target objects on object resolution is discussed and shown to be generally the most limiting. Finally, contributions to the current literature on this subject are made in two areas. First, an improved zone plate construction method was successfully demonstrated which should substantially improve object reproducibility. Second, an analysis of the neutron energy spectrum effect on hologram quality is reported for the first time and shown to be substantial. Further refinement of the shadow holography technique at Oregon State University is necessary to achieve the level of success enjoyed by other researchers. This project has shown that such refinement is well within the capability of existing facilities and equipment. Close

• 139. [Article] Photochemistry of some bromoarenes

  The photodebromination of selected bromoarenes has been studied at 300 nm to determine the the possible mechanistic pathways leading to product. Irradiation of 4-bromobiphenyl (BpBr) at this wavelength ...

  Citation × Citation Citation Abstract Copy Title: Photochemistry of some bromoarenes Author: Jang, Jung-suk The photodebromination of selected bromoarenes has been studied at 300 nm to determine the the possible mechanistic pathways leading to product. Irradiation of 4-bromobiphenyl (BpBr) at this wavelength leads to the product biphenyl. The quantum yield of intersystem crossing (0.98) and quenching studies with cis-1 ,3-pentadiene suggest that the reaction occurs only via the triplet state. The observed increase of quantum yield of reaction with increasing concentration of BpBr suggests formation of a triplet excimer between the triplet state and ground state of BpBr as the key reactive intermediate. The log of the rate constant for excimer formation showed a linear increase with solvent polarity. The correlation of rate constants for excimer formation with linear solvation energy parameters indicates only a weak polarization of the excimer species. In order to understand the extent of radical anion character in the excimer, the regiochemistry of the photo-debromination of 3,4-dibromobiphenyl (3,4-BpBr) was studied. 3,4-BpBr was irradiated with and without an electron donor (triethylamine). 3,4-BpBr was also chemically reduced with lithium biphenylide (LiDBB). The difference in the regiochemistries under these conditions has been interpreted in terms of reaction via a free radical anion in the case of reactions with triethylamine and LiDBB and a weakly polarized excimer in the case of direct irradiation. In order to understand the extent of polarization in the excimers and their conformation, it was decided to study systems where the structure of the molecule would fix the geometry of potential intramolecular charge-transfer complexes. Towards this goal, brominated [2.2]paracyclophanes, 4-bromo[2.2]para-cylophane (CpBr), pseudo-para-dibromo[2.2]cyclophane (ps-p-CpBr) and pseudo-ortho-dibromo[2.2]cyclophane (ps-o-CpBr), were studied. The effect of substitution pattern of the bromines on the efficiency of excimer formation was also investigated. The brominated [2.2]para-cyclophanes showed varying efficiencies of formation of intermolecular excimer and intramolecular charge-transfer. A probable conformation for the excimer from BpBr has been proposed based on these results. Title: Photochemistry of some bromoarenes Author: Jang, Jung-suk The photodebromination of selected bromoarenes has been studied at 300 nm to determine the the possible mechanistic pathways leading to product. Irradiation of 4-bromobiphenyl (BpBr) at this wavelength leads to the product biphenyl. The quantum yield of intersystem crossing (0.98) and quenching studies with cis-1 ,3-pentadiene suggest that the reaction occurs only via the triplet state. The observed increase of quantum yield of reaction with increasing concentration of BpBr suggests formation of a triplet excimer between the triplet state and ground state of BpBr as the key reactive intermediate. The log of the rate constant for excimer formation showed a linear increase with solvent polarity. The correlation of rate constants for excimer formation with linear solvation energy parameters indicates only a weak polarization of the excimer species. In order to understand the extent of radical anion character in the excimer, the regiochemistry of the photo-debromination of 3,4-dibromobiphenyl (3,4-BpBr) was studied. 3,4-BpBr was irradiated with and without an electron donor (triethylamine). 3,4-BpBr was also chemically reduced with lithium biphenylide (LiDBB). The difference in the regiochemistries under these conditions has been interpreted in terms of reaction via a free radical anion in the case of reactions with triethylamine and LiDBB and a weakly polarized excimer in the case of direct irradiation. In order to understand the extent of polarization in the excimers and their conformation, it was decided to study systems where the structure of the molecule would fix the geometry of potential intramolecular charge-transfer complexes. Towards this goal, brominated [2.2]paracyclophanes, 4-bromo[2.2]para-cylophane (CpBr), pseudo-para-dibromo[2.2]cyclophane (ps-p-CpBr) and pseudo-ortho-dibromo[2.2]cyclophane (ps-o-CpBr), were studied. The effect of substitution pattern of the bromines on the efficiency of excimer formation was also investigated. The brominated [2.2]para-cyclophanes showed varying efficiencies of formation of intermolecular excimer and intramolecular charge-transfer. A probable conformation for the excimer from BpBr has been proposed based on these results. Close

• 140. [Article] Impacts of the Internet on academic culture in Aceh, Indonesia

  The adoption and increasing uses of the Internet in higher education in many parts of the world have resulted in fundamental changes in academic cultures. The transfer of information is essential to academic life, ...

  Citation × Citation Citation Abstract Copy Title: Impacts of the Internet on academic culture in Aceh, Indonesia Author: Daud, Darni M. The adoption and increasing uses of the Internet in higher education in many parts of the world have resulted in fundamental changes in academic cultures. The transfer of information is essential to academic life, and the Internet offers faster and easier access to information and communication between people than ever before. Since the effect of the Internet and the significance of the changes differs from one academic setting to another, it is important to study the impacts of the Internet on one particular academic community. This ethnographic study aims to examine the impacts of the Internet on the academic culture of higher education in Aceh, Indonesia. Data were collected by using ethnography, a method commonly employed in the examination of a culture. While this method consists mainly of interviews and observations, other techniques such as collection of related written materials (E-mail messages and/or communications), documents, and photos were used to supplement the data gathered from interviews and observations in Darussalam, the main campus of higher education in Aceh. Data collected from August 1996 through October 1998 revealed distinct themes in the Internet's impacts on the academic culture in Aceh. Findings of this study show that the Internet allows greater access to information, and facilitates communication, especially between students and faculty. The academics' interest in using the Internet builds a new and different academic culture. This new culture is more open to multiple schools of thought in different fields of study. While traditionally academics were isolated from dynamic knowledge development by their lack of access to information, today the Internet provides a bridge for Darussalam academia to the rest of the academic world. People now see that isolation weakens academic life, and are more open to pluralistic academic paradigms. Thus, the Internet changes the perception, performance, and daily activity in academia. This new culture tends to be democratic and to allow freedom in the development of teaching, learning, research, and other academic activities in Darussalam, Aceh. Title: Impacts of the Internet on academic culture in Aceh, Indonesia Author: Daud, Darni M. The adoption and increasing uses of the Internet in higher education in many parts of the world have resulted in fundamental changes in academic cultures. The transfer of information is essential to academic life, and the Internet offers faster and easier access to information and communication between people than ever before. Since the effect of the Internet and the significance of the changes differs from one academic setting to another, it is important to study the impacts of the Internet on one particular academic community. This ethnographic study aims to examine the impacts of the Internet on the academic culture of higher education in Aceh, Indonesia. Data were collected by using ethnography, a method commonly employed in the examination of a culture. While this method consists mainly of interviews and observations, other techniques such as collection of related written materials (E-mail messages and/or communications), documents, and photos were used to supplement the data gathered from interviews and observations in Darussalam, the main campus of higher education in Aceh. Data collected from August 1996 through October 1998 revealed distinct themes in the Internet's impacts on the academic culture in Aceh. Findings of this study show that the Internet allows greater access to information, and facilitates communication, especially between students and faculty. The academics' interest in using the Internet builds a new and different academic culture. This new culture is more open to multiple schools of thought in different fields of study. While traditionally academics were isolated from dynamic knowledge development by their lack of access to information, today the Internet provides a bridge for Darussalam academia to the rest of the academic world. People now see that isolation weakens academic life, and are more open to pluralistic academic paradigms. Thus, the Internet changes the perception, performance, and daily activity in academia. This new culture tends to be democratic and to allow freedom in the development of teaching, learning, research, and other academic activities in Darussalam, Aceh. Close