Seonah Kim | National Renewable Energy Laboratory (original) (raw)
Papers by Seonah Kim
The journal of physical chemistry. A, Jan 4, 2015
Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration... more Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration to produce olefins, and given their commercial importance, reaction mechanisms in zeolites have long been proposed and studied. Some proposed reaction mechanisms for alcohol dehydration exhibit noncyclic carbocation intermediates or transition states that resemble carbocations, and several previous studies suggest that the tert-butyl cation is the only noncyclic cation more stable than the corresponding chemisorbed species with the hydrocarbon bound to the framework oxygen (i.e., an alkoxide). To determine if carbocations can exist at high temperatures in zeolites, where these catalysts are finding new applications for biomass vapor-phase upgrading (∼500 °C), the stability of carbocations and the corresponding alkoxides were calculated with two ONIOM embedding methods (M06-2X/6-311G(d,p):M06-2X/3-21G) and (PBE-D3/6-311G(d,p):PBE-D3/3-21G) and plane-wave density functional theory (DFT) u...
The journal of physical chemistry. A, Jan 24, 2015
Dehydration over acidic zeolites is an important reaction class for the upgrading of biomass pyro... more Dehydration over acidic zeolites is an important reaction class for the upgrading of biomass pyrolysis vapors to hydrocarbon fuels or to precursors for myriad chemical products. Here, we examine the dehydration of ethanol at a Brønsted acid site, T12, found in HZSM-5 using density functional theory (DFT). The geometries of both cluster and mixed quantum mechanics/molecular mechanics (QM:MM) models are prepared from the ZSM-5 crystal structure . Comparison between these models and different DFT methods is conducted to show similar results among the models and methods used. Inclusion of the full catalyst cavity through a QM:MM approach is found to be important, since activation barriers are computed on average as 7 kcal mol-1 lower than those obtained with a smaller cluster model. Two different pathways, concerted and stepwise, have been considered when examining dehydration and deprotonation steps. The current study shows that a concerted dehydration process is possible with a lower ...
Transplantation proceedings, 2005
We analyzed the preexisting donor factors and isolation variables that affected isolation of huma... more We analyzed the preexisting donor factors and isolation variables that affected isolation of human islets of Langerhans. Sixty-nine pancreata from cadaveric donors were analyzed for donor factors of age, gender, body mass index, cause of death as well as graft factors of cold ischemia time, pancreas status, distensibility during intraductal collagenase distension and time of collagenase expansion and digestion. Islet isolations that recovered >100,000 IEQ (n = 53) were compared to those generating less than 100,000 IEQ (n = 16) to analyze the factors affecting islet yield during donor harvest and isolation procedures. The mean islet recovery was 216.0 x 10(3) (IEQ) or 2840 (IEQ) per gram of pancreas. Mean purity was 54%. The success rate of islet isolation was 76%. Mean age was 31 years, and mean cold ischemia time was 6.9 hours. In univariate analysis, the status of the pancreas was the only significant factor for successful isolation, and gender, time of collagenase expansion a...
Digestive diseases and sciences, 1998
This study investigated the mRNA expression of transforming growth factor-beta1 (TGF-beta1) and m... more This study investigated the mRNA expression of transforming growth factor-beta1 (TGF-beta1) and monocyte chemoattractant protein-1 (MCP-1) in rat gastric tissues in which ulcers had relapsed due to interleukin-1beta (IL-1beta) administration. Rats with healed ulcers were administered IL-1beta (1 microg/kg) and killed after 0, 12, 24, or 48 hr. Both TGF-beta1 and MCP-1 mRNA levels were increased in the scarred gastric tissues at 24 hr (fourfold), when ulcers had not relapsed. Furthermore, the expression of these genes also increased in the ulcerated gastric tissues at 48 hr (fivefold), when 90% of healed ulcers had relapsed. On the other hand, the number of macrophages that had infiltrated the scarred gastric tissues at 24 hr was two times higher than that at 0 hr. At 48 hr, the number of macrophages that had infiltrated gastric tissues in which ulcers had relapsed was similar to that at 24 hr. Thus, TGF-beta1 and MCP-1 may be implicated in the macrophage infiltration, thereby leadin...
Transplantation Proceedings, 2008
Adult porcine islet xenotransplantation into humans is greatly diminished by the difficulty to is... more Adult porcine islet xenotransplantation into humans is greatly diminished by the difficulty to isolate islets because of their fragility. The goal of this study was to improve the efficacy of islet yields using endogenous trypsin inhibitor and histidine-tryptophan-ketoglutarate (HTK) perfusate. We compared two porcine islet isolation protocols: Eurocollins solution for in situ pancreas perfusion without use of an endogenous trypsin inhibitor versus HTK solution including endogenous trypsin inhibitor for pancreas perfusion. Endogenous trypsin inhibitor and HTK strategies significantly improved total islet yield, recovery, and islet index after purification (P < .05), whereas unpurified islet yield did not increase. An average of 228,000 +/- 95,000 islet equivalents (IEQ) (n = 20) purified islets were obtained in the first group compared with 115,000 +/- 56,000 IEQ (n = 18) in the second group. The average islet index was significantly increased in the first group compared with the second group before and after purification: before: 0.28 versus 0.49 versus after: 0.25 versus 0.4 (P < .05). At this time, islet purity, viability, and stimulation index did not show a significant difference between groups. Our study showed that endogenous trypsin inhibitor and HTK strategies significantly improved purified islet isolation efficacy because of reduction of islet fragility.
Transplantation Proceedings, 2008
Transplantation of microencapsulated islets is proposed as an ideal therapy for the treatment of ... more Transplantation of microencapsulated islets is proposed as an ideal therapy for the treatment of type 1 diabetes mellitus without immunosuppression. This strategy is based on the principle that foreign cells are protected from the host immune system by an artificial membrane. The aim of this study was to establish an ideal condition of microencapsulation using an air-driven droplet generator and alginate in vitro. The optimal conditions for islet encapsulation were an alginate inflow rate of 10 mL/h, CO2 flow rate of 2.0 L/min in a concentration of 2% alginate. For 2.5% alginate, the alginate inflow rate of 20 mL/h, CO2 flow rate 3.0 L/min was ideal; alginate inflow rate of 40 mL/h, CO2 flow rate of 4.0 L/min showed good microcapsules at 3% alginate. Viability of encapsulated islets was greater than 90%. In terms of insulin secretion, encapsulated islets secreted insulin in response to glucose in static culture medium. However, there was no normal response to low or high glucose challenge with a stimulation index less than 2.0. Microencapsulation of pig islets was successfully performed with air-driven droplet generator and alginate in vitro. Further studies about biocompatibility and glucose control in vivo may provide a useful tool for treatment of patients with diabetes mellitus.
Several mono‐ or bi‐nuclear nickel, copper, and zinc complexes of some multidentate ligands conta... more Several mono‐ or bi‐nuclear nickel, copper, and zinc complexes of some multidentate ligands containing a pyridine ring have been synthesized and characterized by elemental analyses, molar conductivity, IR, UV, H NMR and TG‐DTA. The deprotonation behavior upon coordination is discussed.
Page 1. J. King Saud Univ., Vol. 9 {Science), 2t pp. 189-199 (AH 1417/1997) Synthesis and Charact... more Page 1. J. King Saud Univ., Vol. 9 {Science), 2t pp. 189-199 (AH 1417/1997) Synthesis and Characterization of Metal Complexes with a Schiff Base Formed by Condensation of S-Benzyldithiocarbazate with Furoin Mahmoud ...
Lignin is a major component of plant cell walls that is typically underutilized in selective conv... more Lignin is a major component of plant cell walls that is typically underutilized in selective conversion strategies for renewable fuels and chemicals. The mechanisms by which thermal and catalytic treatments deconstruct lignin remain elusive. In this work, we have investigated the kinetics of the catalytic deconstruction of lignin model compounds using a ruthenium catalyst reported by Bergman et al. in
We report electronic transport measurements of molecular thin film devices. Single devices consis... more We report electronic transport measurements of molecular thin film devices. Single devices consisting of 1e8 molecules in parallel display both hysteresis and asymmetry in their nonlinear current-voltage (I-V) characteristic suggesting applications in molecular scale memory and molecular scale logic devices. The tested devices are two terminal metal/oxide/molecular film/metal structures of micron scale surface area incorporating single species Langmuir films. Several molecular species have been characterized. We present time dependent transport measurements in an attempt to understand the asymmetric and hysteretic I-V behaviors.
The journal of physical chemistry. A, Jan 4, 2015
Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration... more Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration to produce olefins, and given their commercial importance, reaction mechanisms in zeolites have long been proposed and studied. Some proposed reaction mechanisms for alcohol dehydration exhibit noncyclic carbocation intermediates or transition states that resemble carbocations, and several previous studies suggest that the tert-butyl cation is the only noncyclic cation more stable than the corresponding chemisorbed species with the hydrocarbon bound to the framework oxygen (i.e., an alkoxide). To determine if carbocations can exist at high temperatures in zeolites, where these catalysts are finding new applications for biomass vapor-phase upgrading (∼500 °C), the stability of carbocations and the corresponding alkoxides were calculated with two ONIOM embedding methods (M06-2X/6-311G(d,p):M06-2X/3-21G) and (PBE-D3/6-311G(d,p):PBE-D3/3-21G) and plane-wave density functional theory (DFT) u...
The journal of physical chemistry. A, Jan 24, 2015
Dehydration over acidic zeolites is an important reaction class for the upgrading of biomass pyro... more Dehydration over acidic zeolites is an important reaction class for the upgrading of biomass pyrolysis vapors to hydrocarbon fuels or to precursors for myriad chemical products. Here, we examine the dehydration of ethanol at a Brønsted acid site, T12, found in HZSM-5 using density functional theory (DFT). The geometries of both cluster and mixed quantum mechanics/molecular mechanics (QM:MM) models are prepared from the ZSM-5 crystal structure . Comparison between these models and different DFT methods is conducted to show similar results among the models and methods used. Inclusion of the full catalyst cavity through a QM:MM approach is found to be important, since activation barriers are computed on average as 7 kcal mol-1 lower than those obtained with a smaller cluster model. Two different pathways, concerted and stepwise, have been considered when examining dehydration and deprotonation steps. The current study shows that a concerted dehydration process is possible with a lower ...
Transplantation proceedings, 2005
We analyzed the preexisting donor factors and isolation variables that affected isolation of huma... more We analyzed the preexisting donor factors and isolation variables that affected isolation of human islets of Langerhans. Sixty-nine pancreata from cadaveric donors were analyzed for donor factors of age, gender, body mass index, cause of death as well as graft factors of cold ischemia time, pancreas status, distensibility during intraductal collagenase distension and time of collagenase expansion and digestion. Islet isolations that recovered >100,000 IEQ (n = 53) were compared to those generating less than 100,000 IEQ (n = 16) to analyze the factors affecting islet yield during donor harvest and isolation procedures. The mean islet recovery was 216.0 x 10(3) (IEQ) or 2840 (IEQ) per gram of pancreas. Mean purity was 54%. The success rate of islet isolation was 76%. Mean age was 31 years, and mean cold ischemia time was 6.9 hours. In univariate analysis, the status of the pancreas was the only significant factor for successful isolation, and gender, time of collagenase expansion a...
Digestive diseases and sciences, 1998
This study investigated the mRNA expression of transforming growth factor-beta1 (TGF-beta1) and m... more This study investigated the mRNA expression of transforming growth factor-beta1 (TGF-beta1) and monocyte chemoattractant protein-1 (MCP-1) in rat gastric tissues in which ulcers had relapsed due to interleukin-1beta (IL-1beta) administration. Rats with healed ulcers were administered IL-1beta (1 microg/kg) and killed after 0, 12, 24, or 48 hr. Both TGF-beta1 and MCP-1 mRNA levels were increased in the scarred gastric tissues at 24 hr (fourfold), when ulcers had not relapsed. Furthermore, the expression of these genes also increased in the ulcerated gastric tissues at 48 hr (fivefold), when 90% of healed ulcers had relapsed. On the other hand, the number of macrophages that had infiltrated the scarred gastric tissues at 24 hr was two times higher than that at 0 hr. At 48 hr, the number of macrophages that had infiltrated gastric tissues in which ulcers had relapsed was similar to that at 24 hr. Thus, TGF-beta1 and MCP-1 may be implicated in the macrophage infiltration, thereby leadin...
Transplantation Proceedings, 2008
Adult porcine islet xenotransplantation into humans is greatly diminished by the difficulty to is... more Adult porcine islet xenotransplantation into humans is greatly diminished by the difficulty to isolate islets because of their fragility. The goal of this study was to improve the efficacy of islet yields using endogenous trypsin inhibitor and histidine-tryptophan-ketoglutarate (HTK) perfusate. We compared two porcine islet isolation protocols: Eurocollins solution for in situ pancreas perfusion without use of an endogenous trypsin inhibitor versus HTK solution including endogenous trypsin inhibitor for pancreas perfusion. Endogenous trypsin inhibitor and HTK strategies significantly improved total islet yield, recovery, and islet index after purification (P < .05), whereas unpurified islet yield did not increase. An average of 228,000 +/- 95,000 islet equivalents (IEQ) (n = 20) purified islets were obtained in the first group compared with 115,000 +/- 56,000 IEQ (n = 18) in the second group. The average islet index was significantly increased in the first group compared with the second group before and after purification: before: 0.28 versus 0.49 versus after: 0.25 versus 0.4 (P < .05). At this time, islet purity, viability, and stimulation index did not show a significant difference between groups. Our study showed that endogenous trypsin inhibitor and HTK strategies significantly improved purified islet isolation efficacy because of reduction of islet fragility.
Transplantation Proceedings, 2008
Transplantation of microencapsulated islets is proposed as an ideal therapy for the treatment of ... more Transplantation of microencapsulated islets is proposed as an ideal therapy for the treatment of type 1 diabetes mellitus without immunosuppression. This strategy is based on the principle that foreign cells are protected from the host immune system by an artificial membrane. The aim of this study was to establish an ideal condition of microencapsulation using an air-driven droplet generator and alginate in vitro. The optimal conditions for islet encapsulation were an alginate inflow rate of 10 mL/h, CO2 flow rate of 2.0 L/min in a concentration of 2% alginate. For 2.5% alginate, the alginate inflow rate of 20 mL/h, CO2 flow rate 3.0 L/min was ideal; alginate inflow rate of 40 mL/h, CO2 flow rate of 4.0 L/min showed good microcapsules at 3% alginate. Viability of encapsulated islets was greater than 90%. In terms of insulin secretion, encapsulated islets secreted insulin in response to glucose in static culture medium. However, there was no normal response to low or high glucose challenge with a stimulation index less than 2.0. Microencapsulation of pig islets was successfully performed with air-driven droplet generator and alginate in vitro. Further studies about biocompatibility and glucose control in vivo may provide a useful tool for treatment of patients with diabetes mellitus.
Several mono‐ or bi‐nuclear nickel, copper, and zinc complexes of some multidentate ligands conta... more Several mono‐ or bi‐nuclear nickel, copper, and zinc complexes of some multidentate ligands containing a pyridine ring have been synthesized and characterized by elemental analyses, molar conductivity, IR, UV, H NMR and TG‐DTA. The deprotonation behavior upon coordination is discussed.
Page 1. J. King Saud Univ., Vol. 9 {Science), 2t pp. 189-199 (AH 1417/1997) Synthesis and Charact... more Page 1. J. King Saud Univ., Vol. 9 {Science), 2t pp. 189-199 (AH 1417/1997) Synthesis and Characterization of Metal Complexes with a Schiff Base Formed by Condensation of S-Benzyldithiocarbazate with Furoin Mahmoud ...
Lignin is a major component of plant cell walls that is typically underutilized in selective conv... more Lignin is a major component of plant cell walls that is typically underutilized in selective conversion strategies for renewable fuels and chemicals. The mechanisms by which thermal and catalytic treatments deconstruct lignin remain elusive. In this work, we have investigated the kinetics of the catalytic deconstruction of lignin model compounds using a ruthenium catalyst reported by Bergman et al. in
We report electronic transport measurements of molecular thin film devices. Single devices consis... more We report electronic transport measurements of molecular thin film devices. Single devices consisting of 1e8 molecules in parallel display both hysteresis and asymmetry in their nonlinear current-voltage (I-V) characteristic suggesting applications in molecular scale memory and molecular scale logic devices. The tested devices are two terminal metal/oxide/molecular film/metal structures of micron scale surface area incorporating single species Langmuir films. Several molecular species have been characterized. We present time dependent transport measurements in an attempt to understand the asymmetric and hysteretic I-V behaviors.