Surface Properties of Al2O3 for Understanding Metal-Support Interaction and Catalytic Properties of Al2O3-based Catalysts

Department of Chemical Engineering??-Al2O3 is one of the most important heterogeneous catalytic materials that has been used as a support for a wide range of applications in petroleum chemistry and automobile emission control. Thanks to its intrinsic acidity, it can also participate in acid-catalyzed reactions such as alcohol dehydration. For decades, numerous studies have been devoted to understanding the fundamental nature of Al2O3 owing to its practical importance in catalysis. The catalytic properties of oxides, such as activity, selectivity, and distribution of active phases on the support, are significantly affected by their surface characteristics because chemical processes mainly occur on the surface. However, understanding the surface properties of aluminas have been challenging due to unresolved structures, mixed effects of various factors (morphology, phases, impurities, and additives), and difficulties of characterization. Therefore, comprehensive approaches should include the preparation of well-defined model aluminas and sensitive characterization tools. This thesis focuses on understanding the surface properties of aluminas and their role in the interaction with the active phases (Pt) and the corresponding catalytic behavior of Al2O3-based catalysts. By preparing the model aluminas for morphology, phase, additive and using ethanol TPD as a surface characterization tool, we studied the surface properties of Al2O3 with various modification and further investigated the interaction with Pt and its reduction behavior on alumina surfaces. First, we synthesized a series of well-defined platelet ??-Al2O3 with the systematic change of (100) facets and investigated the catalytic role of (100) facets by ethanol dehydration. By controlling pH during the preparation of boehmite (??-AlOOH), precursor for ??-Al2O3, (001) facet of boehmite increased under acidic condition. Topotactic transformation of boehmite into ??-Al2O3 maintained their morphologies, leading to platelet ??-Al2O3 with increased (100) facets of ??-Al2O3. Ethylene formation increased with increasing (100) facets, clearly demonstrating the critical role of (100) facets as active sites for ethanol dehydration on ??-Al2O3. In chapter 3, We investigated the effect of morphology, phases, and additives on the surface properties of Al2O3 and which factors are the most important for surface properties of Al2O3 by preparing model aluminas with various modifications and using ethanol TPD. Ethanol TPD showed the desorption temperature (at a maximum rate of ethylene desorption, Td) of dissociative ethanol was significantly dependent on morphology, crystalline phase, and additives. Here, the additives affected the desorption temperature of ethylene most significantly. Ethanol dehydration tests showed that ethylene formation rates, normalized with respect to the amount of dissociative ethanol (quantified by ethanol TPD), exhibited an inverse correlation with Td on Al2O3 with various morphologies, crystalline phases, and additives, which suggests that Td can be used as a descriptor for surface properties of Al2O3, irrespective of modification origins. The activities and activation barriers of various commercial Al2O3 on ethanol dehydration were also consistent with our empirical model. Based on understanding for surface properties of Al2O3, we study how these surface properties of aluminas affect the active phases (Pt) and the catalytic behavior of Pt/Al2O3. We chose two sets of model alumina having different number of sites with the identical properties and different properties of sites with the same number based on ethanol TPD. With two model aluminas, how the number and properties of specific sites on alumina surfaces affect the specific interaction between Pt and alumina was investigated. Pt showed higher dispersion with increasing number of sites and interaction strength because the Pt atoms can interact with specific sites on alumina in greater numbers and more strongly. However, these Pt dispersion changes do not represent the gradual size change, but the relative population change of small (10 nm). The number of highly dispersed Pt clusters increased with increasing number of sites and interaction strength. When Pt showed higher dispersion from more number of sites and stronger interaction on alumina, Pt/Al2O3 showed higher activity for benzene hydrogenation due to more available highly dispersed Pt. Finally, specific interaction between Pt and alumina strongly affected the reduction behavior of oxidized Pt on alumina. We studied the reduction of three-dimensional (3D) PtO2, two-dimensional (2D) PtO2, and atomically dispersed Pt on Pt/Al2O3. Under oxidizing atmosphere, morphologies and sizes of PtO2 on Pt/Al2O3 are determined by the specific interaction between Pt and Al2O3 through Pt-O-Al bond, leading to highly dispersed Pt as ~1 nm 2D-raft PtO2 and atomically dispersed Pt on Al2O3. When all the Pt atoms can???t interact with anchoring sites on support under high Pt loading or SiO2 which has very weak metal-support interaction, 3D PtO2 was formed. Due to weak interaction with support, 3D PtO2 was reduced earlier (-20~-60 oC) than 2D PtO2 (~110 oC) and atomically dispersed Pt (>300 oC). Furthermore, when Pt/Al2O3 was calcined at 500-700 oC, PtO2 was reduced without a reducing agent (auto-reduction) with Pt sintering. Interaction strength also influences auto-reduction when calcination temperature increases. 3D PtO2 was auto-reduced after 550-600 oC calcination, but 2D PtO2 was more difficult to be reduced (50 oC higher). So, the interaction strength with the support determines how long Pt oxide can maintain as Pt oxide rather Pt metal. These morphologies of Pt oxide also affect their sintering behavior. Because 3D PtO2 is more easily auto-reduced than 2D PtO2 and atomically dispersed Pt, 3D metallic Pt clusters become less mobile than 2D PtO2 and atomically dispersed Pt (still, oxidized Pt). So, 3D PtO2 showed more sinter-resistant behavior than 2D PtO2 and atomically dispersed Pt. The metal-support interaction between Pt and alumina is important for the reduction of oxidized Pt on Pt/Al2O3, suggesting the guideline about a careful activation for the efficient utilization of metallic Pt for catalytic reactions.clos

A STUDY ON THE FACTORS INFLUENCING THE INTENTION OF BLOG USAGE

Blogs are a new type of media that have recently become popular users on the World Wide Web and have influence throughout society. The purpose of this study is to examine social motivations influencing intention of blog usage. Based on Technology Acceptance Model and Motivation Theory, This study considered perceived usefulness, perceived ease of use, reputation, reciprocity, enjoyment of helping, social identity as the determinants of influencing the intention of blog usage. The purposed model was empirically evaluated using online survey data collected from 342 user of popular blog site in Korea (NAVER Blog , cyworld mihompy, daum blog, yahoo blog etc) The results revealed that perceived usefulness, perceived ease of use, reciprocity, social identity affected directly the intention of blog usage. Also social identity has moderate effect via reciprocity and enjoyment of helping on blog usage. This study contributes to a theoretical understanding of the factors as social motivation that affect the usage of blogs. Practically this study results provide blog service providers useful strategic insights and service guideline to enhance user\u27s intention of blogs

Glutaminase 1 inhibition reduces thymidine synthesis in NSCLC

AbstractWe found that non-small cell lung cancer (NSCLC) is remarkably sensitive to the regulation of glutamine supply by testing the metabolic dependency of 11 cancer cell lines against regulation of glycolysis, autophagy, fatty acid synthesis, and glutamine supply. Glutamine is known as a key supplement of cancer cell growth that is converted to α-ketoglutarate for anabolic biogenesis via glutamate by glutaminase 1 (GLS1). GLS1 inhibition using 10 μM of bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (BPTES) showed about 50% cell growth arrest by SRB assay. By testing the synergistic effects of conventional therapeutics, BPTES combined with 5-fluorouracil (5-FU), an irreversible inhibitor of thymidylate synthase, significant effects were observed on cell growth arrest in NSCLC. We found that GLS1 inhibition using BPTES reduced metabolic intermediates including thymidine and carbamoyl phosphate. Reduction of thymidine and carbamoyl-phosphate synthesis by BPTES treatment exacerbated pyrimidine supply by combination with 5-FU, which induced cell death synergistically in NSCLC

SAVER: SNARK-friendly, Additively-homomorphic, and Verifiable Encryption and decryption with Rerandomization

In the pairing-based zero-knowledge succinct non-interactive arguments of knowledge (zk-SNARK), there often exists a requirement for the proof system to be combined with encryption. As a typical example, a blockchain-based voting system requires the vote to be confidential (using encryption), while verifying voting validity (using zk-SNARKs). In these combined applications, a typical solution is to extend the zk-SNARK circuit to include the encryption code. However, complex cryptographic operations in the encryption algorithm increase the circuit size, which leads to impractically large proving time and CRS size. In this paper, we propose SNARK-friendly, Additively-homomorphic, and Verifiable Encryption and decryption with Rerandomization or SAVER, which is a novel approach to detach the encryption from the SNARK circuit. The encryption in SAVER holds many useful properties. It is SNARK-friendly: the encryption is conjoined with an existing pairing-based SNARK, in a way that the encryptor can prove pre-defined properties while encrypting the message apart from the SNARK. It is additively-homomorphic: the ciphertext holds a homomorphic property from the ElGamal-based encryption. It is a verifiable encryption: one can verify arbitrary properties of encrypted messages by connecting with the SNARK system. It provides a verifiable decryption: anyone without the secret can still verify that the decrypted message is indeed from the given ciphertext. It provides rerandomization: the proof and the ciphertext can be rerandomized as independent objects so that even the encryptor (or prover) herself cannot identify the origin. For the representative application, we also propose a Vote-SAVER based on SAVER, which is a novel voting system where voter\u27s secret key lies only with the voter himself. The Vote-SAVER satisfies receipt-freeness (which implies ballot privacy), individual verifiability (which implies non-repudiation), vote verifiability, tally uniqueness, and voter anonymity. The experimental results show that our SAVER with respect to the Vote-SAVER relation yields 0.7s for zk-SNARK proving time and 10ms for encryption, with the CRS size of 16MB

Human Plasmablast Migration Toward CXCL12 Requires Glucose Oxidation by Enhanced Pyruvate Dehydrogenase Activity via AKT

Migration of human plasmablast to the bone marrow is essential for the final differentiation of plasma cells and maintenance of effective humoral immunity. This migration is controlled by CXCL12/CXCR4-mediated activation of the protein kinase AKT. Herein, we show that the CXCL12-induced migration of human plasmablasts is dependent on glucose oxidation. Glucose depletion markedly inhibited plasmablast migration by 67%, and the glucose analog 2-deoxyglucose (2-DG) reduced the migration by 53%; conversely, glutamine depletion did not reduce the migration. CXCL12 boosted the oxygen consumption rate (OCR), and 2-DG treatment significantly reduced the levels of all measured tricarboxylic acid (TCA) cycle intermediates. AKT inhibitors blocked the CXCL12-mediated increase of OCR. CXCL12 enhanced the pyruvate dehydrogenase (PDH) activity by 13.5-fold in an AKT-dependent manner to promote mitochondrial oxidative phosphorylation. The knockdown and inhibition of PDH confirmed its indispensable role in CXCL12-induced migration. Cellular ATP levels fell by 91% upon exposure to 2-DG, and the mitochondrial ATP synthase inhibitor oligomycin inhibited CXCL12-induced migration by 85%. Low ATP levels inhibited the CXCL12-induced activation of AKT and phosphorylation of myosin light chains by 42%, which are required for cell migration. Thus, we have identified a mechanism that controls glucose oxidation via AKT signaling and PDH activation, which supports the migration of plasmablasts. This mechanism can provide insights into the proper development of long-lived plasma cells and is, therefore, essential for optimal humoral immunity. To our knowledge, this study is the first to investigate metabolic mechanisms underlying human plasmablast migration toward CXCL12

Changes in Clinical Activity, Serum Autoantibody Levels, and Chorioretinal Vessels After Systemic Glucocorticoid Therapy in Thyroid Eye Disease

Abstract Introduction The aim of this study was to investigate changes in the Clinical Activity Score, serum thyroid-stimulating hormone receptor antibody and thyroid-stimulating immunoglobulin levels, chorioretinal blood vessels, and extraocular muscle thickness in patients with thyroid eye disease following systemic steroid treatment. Methods This prospective observational study enrolled 57 patients with active thyroid eye disease who received systemic intravenous glucocorticoids for 12 weeks. Demographics, clinical activity scores, optical coherence tomography images, and serum thyroid-stimulating immunoglobulin and thyroid-stimulating hormone receptor antibody levels were assessed at baseline, at 6 and 12 weeks after intravenous (IV) GC therapy initiation, and 2 months after IV GC therapy termination. The extraocular muscle thickness, choroidal thickness, and choroidal vascularity index were measured. Results The clinical activity scores showed a significant decrease. Serum thyroid-stimulating immunoglobulin levels dropped continuously for 2 months. The thyroid-stimulating hormone receptor antibody level decreased until 12 weeks after treatment but returned to within the normal range in 75% of patients after 77 and 126 days, respectively. The choroidal thickness decreased at all time points. The thickness of the medial and inferior rectus muscles decreased at 2 months after treatment. The clinical activity score decreased to < 3 points in 50% of patients after 78 days. Conclusion Intravenous glucocorticoid therapy improved the clinical activity score, chorioretinal blood flow, and extraocular muscle thickness. The serum autoantibody levels were normalized in patients with active thyroid eye disease 2 months after IV GC termination. The serum thyroid-stimulating immunoglobulin and thyroid-stimulating hormone receptor antibody levels correlated with restoration of chorioretinal capillary perfusion and improved clinical symptoms and muscle thickness. Non-invasive optical coherence tomography findings and serologic factors predict the response to intravenous glucocorticoid therapy

A Strategy to Quantify Water Supply of an Agricultural Reservoir for Integrated Water Management Policy

A data-driven approach is required to scientifically manage agricultural water resources in accordance with the integrated water management policy of South Korea. In this study, a quantification strategy is presented to calculate reservoir supply by comparing the results with the actual reservoir water storage. Strategies considering current calculation methods were divided into canal flow measurement (S1), theoretical flow rate (S2), water storage decrease in field practice (S3), and water demand in design practice (S4), utilizing water levels of the reservoir and its canal and the level–flow rate curve obtained from surveying the canal flow. Each strategy was assessed through hydrological verification of reservoir water balance modeling. Based on the determination coefficient (R2), Nash–Sutcliffe efficiency (NSE), and relative error (RE) values, the S1 method was found to be the most suitable. S2 had lower reliability than S1, while S3 and S4 satisfied neither R2 nor NSE and had a larger RE than S1 and S2. To accurately quantify agricultural water supplies, the importance of directly measuring reservoir canal flows must be emphasized using automatic water level and flow gauges in canals. This study provides insights into more scientific management of agricultural reservoir water supplies and more effective monitoring of agricultural water usage

Varying importance of the work-life balance dimension of career success for Korean accountants: The effects of gender and generation

In this study, we examine the effects of gender, generation, and the interaction between gender and generation on Korean accountants’ perception of career success. With the large survey data collected from 1,000 accountants working in South Korea, we found that Korean female accountants have higher perceived importance of work-life balance dimension of career success than male accountants; and younger generations (Millennials or younger) have higher perceived importance for this dimension than older generations (Generation X or older). No interaction effects between gender and generation were found in relation to the perceived importance of work-life balance dimension of career success. Specifically, female accountants had higher perceived importance of work-life balance than their male counterparts regardless of generation; and while the mean was higher for younger generations the gap between the female accountants’ means and the male accountants’ means of work-life balance dimension has not been reduced. The insignificant interaction effects between gender and generation regarding the perceived level of the work-life balance dimension of career success suggest that, despite the national and organizational efforts in changing the gender discriminating practices, Korean accounting field may still be making a very slow progress in breaking its glass ceiling

Effect of number and properties of specific sites on alumina surfaces for Pt-Al2O3 catalysts

In this work, how the number and properties of specific sites on alumina surfaces affect the specific interaction between Pt and alumina was investigated by using X-ray diffraction, ethanol temperature programmed desorption, diffuse reflectance infrared Fourier transform spectroscopy, H2 chemisorption, scanning transmission electron microscopy and benzene hydrogenation reaction. Here, we chose two sets of model aluminas having different number of sites with the identical properties and different properties of sites with the same number based on ethanol TPD. The H2 chemisorption results for the model aluminas show that H/Pt are all similar for low Pt loadings, but significantly different for high Pt loadings. For 1 wt% Pt/Al2O3, the number of specific sites on all the aluminas was sufficient to disperse all the Pt, leading to only highly dispersed Pt clusters (???1 nm). However, at 10 wt% Pt/Al2O3, the number of Pt atoms is greater than that of the specific sites on the alumina surface, resulting in a bimodal distribution of large agglomerated Pt (&gt;10 nm) and highly dispersed Pt clusters (&lt;3 nm) revealed by XRD and TEM. Overall, the results clearly demonstrated that Pt shows higher dispersion with increasing number of sites and interaction strength, because the Pt atoms can interact with specific sites on alumina in greater numbers and more strongly. However, these Pt dispersion changes do not represent the gradual change in Pt cluster sizes, but the relative population change of small (&lt;3 nm) and large agglomerated Pt clusters (&gt;10 nm) under bimodal distribution. The number of large agglomerated Pt clusters decreased with increasing number of sites and interaction strength. This fundamental understanding provides an important perspective for designing Al2O3-based supported catalysts