Implementation of a Distributed Architecture for Managing Collection and Dissemination of Data for Fetal Alcohol Spectrum Disorder

We implemented a distributed system for management of data for an international collaboration studying Fetal Alcohol Spectrum Disorders (FASD). Subject privacy was protected, researchers without dependable Internet access were accommodated, and researchers’ data were shared globally. Data dictionaries codified the nature of the data being integrated, data compliance was assured through multiple consistency checks, and recovery systems provided a secure, robust, persistent repository. The system enabled new types of science to be done, using distributed technologies that are expedient for current needs while taking useful steps towards integrating the system in a future grid-based cyberinfrastructure. The distributed architecture, verification steps, and data dictionaries suggest general strategies for researchers involved in collaborative studies, particularly where data must be de-identified before being shared. The system met both the collaboration’s needs and the NIH Roadmap’s goal of wide access to databases that are robust and adaptable to researchers’ needs

Implementation of a Shared Data Repository and Common Data Dictionary for Fetal Alcohol Spectrum Disorders Research

Many previous attempts by fetal alcohol spectrum disorders researchers to compare data across multiple prospective and retrospective human studies have failed due to both structural differences in the collected data as well as difficulty in coming to agreement on the precise meaning of the terminology used to describe the collected data. Although some groups of researchers have an established track record of successfully integrating data, attempts to integrate data more broadly amongst different groups of researchers have generally faltered. Lack of tools to help researchers share and integrate data has also hampered data analysis. This situation has delayed improving diagnosis, intervention, and treatment before and after birth. We worked with various researchers and research programs in the Collaborative Initiative on Fetal Alcohol Spectrum Disorders (CI-FASD) to develop a set of common data dictionaries to describe the data to be collected, including definitions of terms and specification of allowable values. The resulting data dictionaries were the basis for creating a central data repository (CI-FASD Central Repository) and software tools to input and query data. Data entry restrictions ensure that only data which conform to the data dictionaries reach the CI-FASD Central Repository. The result is an effective system for centralized and unified management of the data collected and analyzed by the initiative, including a secure, long-term data repository. CI-FASD researchers are able to integrate and analyze data of different types, collected using multiple methods, and collected from multiple populations, and data are retained for future reuse in a secure, robust repository

Global kinetic modeling of hydrothermal aging of NH3-SCR over Cu-zeolites

In this study, a kinetic model describing the effect of hydrothermal aging (at 500, 600, 700, 800 and 900 degrees C) on Cu-zeolites is developed. The model accounts for the impact of hydrothermal aging on key reactions such as ammonia adsorption/desorption, NH3 oxidation, NO oxidation, standard SCR, rapid SCR, and NO2 SCR. In addition, a mechanism for the complex N2O formation were developed. The effect of aging on ammonia adsorption and desorption were established using micro-calorimeter data. Thereafter, an aging factor model was developed containing two aging factors, one related to over-exchanged copper sites and the other to under-exchanged copper sites. This approach worked well for ammonia and NO oxidation up to an aging temperature of 800 degrees C, whereas for the SCR reactions only to 700 degrees C. According to UV-vis, fresh and mildly aged catalysts are dominated by copper hydroxyls, while after aging at high temperature copper oxides are observed. We therefore introduce one SCR reaction associated with copper oxides, simultaneously with one SCR reaction associated with ion-exchanged Cu sites and the updated model could describe the experimental findings well. The results from the model also suggest that the standard SCR reaction is more deactivated during aging compared to SCR with NO2 present in the feed. After the 900 degrees C aging the BEA structure had collapsed, resulting in that several parameters in the model needed to be retuned. The results from this modeling study clearly show how complex the hydro thermal aging is over copper zeolites

Heat of adsorption for NH3, NO2 and NO on Cu-Beta zeolite using microcalorimeter for NH3 SCR applications

Microcalorimetry is a powerful technique with which to measure the heat of adsorption (Delta H), producing values that are very important when developing kinetic models. The method provides a way of determining these parameters independently. For kinetic models describing NH3 SCR it is critical to be able to accurately describe the storage of ammonia and NO in order to simulate rapid transients occurring in the experiments. The objective of our study is to measure the heat of adsorption of NH3, NO2 and NO on Cu-Beta. An ammonia TPD experiment was conducted at 150 degrees C using the microcalorimeter, resulting in the observation of an exotherm when introducing ammonia due to adsorption. This resulted in an average heat of adsorption of -100 kJ/mol. A good reproducibility was found when using a second sample, resulting in -97 kJ/mol. In order to investigate the coverage dependence of the heat of adsorption, an ammonia stepwise experiment was conducted. First, the catalyst was exposed to NH3 at 500 degrees C, resulting in the adsorption of strongly bound ammonia and obtaining a heat of adsorption of -110 kJ/mol. Thereafter, the catalyst was cooled in Ar and at 400 degrees C, NH3 was again introduced. Due to that the temperature is lower the ammonia that adsorbed was weaker. The procedure was repeated at 300, 200 and 100 degrees C, resulting in a coverage dependent activation energy for ammonia desorption (if assuming zero activation for adsorption) according to the following formula: E-desorption,NH3 = 120.0 (1 - 0.38 theta(NH3)) where theta(NH3) is the coverage of ammonia on the surface. The NO and NO2 adsorption and desorption were investigated using NO and NO2 TPD experiments, respectively. For the NO2 TPD experiment, approximately three NO2 were stored for each NO produced, corresponding to the disproportionation mechanism. This resulted in Delta H of -65 kJ/mol per NO2 consumed. The NO TPD experiment resulted in that only small amounts of NO was adsorbed. (C) 2010 Elsevier B.V. All rights reserved

A kinetic model for sulfur poisoning and regeneration of Cu/SSZ-13 used for NH3-SCR

In this study, we have developed a multi-site kinetic model that describes the sulfur poisoning and gradual sulfur removal over Cu/SSZ-13 used for NH3-SCR. Sulfur poisoning was conducted under SCR conditions and thereafter, repeated SCR experiments were conducted to examine the effect of such poisoning and the subsequent gradual removal of sulfur. In addition, the effect of sulfur poisoning was examined on NH3 TPD and ammonia oxidation experiments. The following sites were used in the kinetic model: copper in the six-membered rings as described by S1Cu, copper in the larger cages with S2 and S3 as a site where physisorbed ammonia can attach. Further, ammonia was also adsorbed on the Br\uf6nsted sites, represented by S1Br\uf6n in the model, but in order not to further complicate the model, small amounts of ammonia storage on Br\uf6nsted sites were also lumped into S2. In the model, SO2 was adsorbed on the sites containing copper, which are S1Cu and S2. It should be noted that S1Cu and S2 represents hydrated copper sites. Interestingly, we observed experimentally that ammonia storage was larger after sulfur poisoning compared to before, which is why we added ammonia storage and desorption to the S1Cu-SO2 and S2-SO2 sites. However, ammonia was already adsorbing on the copper site; thus, these steps did not result in increased storage. Consequently, reaction steps were added where additional ammonia was adsorbed to form S1Cu-SO2-(NH3)2 and S2-SO2-(NH3)2 species, which could be interpreted as precursors to ammonium sulfates. Another aspect that must be addressed in the model is the observation in the literature that SO2 is more easily desorbed in SO2+NH3+O2 TPD than SO2+O2 TPD. Reversible reaction steps were therefore added whereby the S1Cu-SO2-NH3 and S2-SO2-NH3 species were decomposed to form SO2. A final reaction step was incorporated into the model to describe the SCR reaction with ammonia attached to the sulfur sites. The developed model could well describe the sulfur poisoning and gradual regeneration during repeated SCR experiments. In addition, the model well described the NH3 TPD and NH3 oxidation before and after sulfur poisoning

The effect of accelerated hydrothermal aging on NH 3-SCR over Cu-Hbea catalyst

Diesel engines have good fuel efficiency. However, the excess of oxygen that is fed into the engine is also present in the exhaust stream. This disables the selectivity of the standard three-way catalyst towards NO x. The influence of hydrothermal aging on the SCR mechanism was studied. A trend towards less strong bound ammonia for higher aging temperatures is observed, which agreed with TPD experiments. Ammonia SCR is an important technique for reducing NO x from diesel and lean burn gasoline engines. Zeolite based catalysts are a good choice for this reaction. However, they can be hydrothermally aged. This is an abstract of a paper presented at the 2011 AIChE Annual Meeting (Minneapolis, MN 10/16-21/2011)