14 research outputs found
A Multiple Case Study Examining the Challenges and Successes in the Development and Implementation of Transition and Post-secondary Education Programs for Students with Intellectual Disabilities
The purpose of this multiple case study was to examine the successes, challenges, and factors identified to mitigate or overcome the identified challenges, as experienced by program directors, faculty, and staff, in the development and implementation of transition and post-secondary education programs, for students identified with intellectual disability at 4-year post-secondary educational institutions. Theories guiding this study were program implementation theory (Weiss, 1997) and disability theory (Mertens, 2009). Sites included three transition and post-secondary education programs for students with intellectual disability, utilizing similarly designed program models at a four-year post-secondary institution. Multiple forms of data collected from each site included participant surveys, interviews, observations, focus group, program related documents, and public information retrieved from social media and institutional web sites were analyzed through in-case and across-case analyses. The study revealed the need for strategic planning to identify the most appropriate program model to ensure sustainability of the program, including planning for funding, staffing, development of policies and procedures, and student admission, prior to student admission in the program. In addition, this study revealed the need for commitment, flexibility, and collaboration among program directors, faculty, and staff to meet the ever changing and fluid environment in serving students within a transition and post-secondary education program for students with ID. Further study is needed to identify best practices in student selection processes, programmatic policies, curriculum, and sustainable funding sources
Ion exchange behavior among metal trisilicates: probing selectivity, structures, and mechanism
One model system for the investigation of selectivity in inorganic ion exchangers
is a group of synthetic analogues of the mineral umbite. Hydrothermally synthesized
trisilicates with the general form A2BSi3O9.H2O, where A is a monovalent cation, and B
= Ti4+, Zr4+, and Sn4+ have been shown to have ion exchange properties.
The extended three dimensional framework structure offers the ability to tune the
selectivity based on the size of the cavities and channels. The unit cell volume, and
therefore the pore size, can be altered by changing the size of the octahedral metal. The
substitution of Ge for Si can also increase the pore size.
A variety of cations have been exchanged into the trisilicates including alkali and
alkaline earths, lanthanides, and actinides. The reason for the selectivity rests in the
pocket of framework oxygens which make up the exchange sites. Close examination of
the cation environments shows that the ions with the greatest affinity are those that have
the closest contacts to the framework oxygens. For example, among alkali cations,
zirconium trisilicate demonstrates the greatest affinity for Rb+ and has the most A-O
contact distances approaching the sum of their ionic radii.
The origins of selectivity also rely upon the valence of the incoming cation.
When cations are of similar ionic radius, a cation of higher charge is always preferred
over the lower valence. Ion exchange studies in binary solutions of cations of different
valence, but similar size (1.0Å ) have proven the selectivity series to be Th4+ > Gd3+ >
Ca2+ > Na+. Through structural characterization, kinetic studies, and use of in situ x-ray
diffraction techniques the origins of selectivity in these inorganic ion exchangers has
been further elucidated. The principles gleaned from these studies can be applied to
other inorganic framework materials. The umbite system has the potential to be altered
and tailored for specific separation needs. The trisilicate materials presented in this
work are representative of the types of advances in inorganic materials research and
prove their potential as applicable compounds useful for solving real world problems
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ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE
Hydrogen storage is one of the greatest challenges for implementing the ever sought hydrogen economy. Here we report a novel cycle to reversibly form high density hydrogen storage materials such as aluminium hydride. Aluminium hydride (AlH{sub 3}, alane) has a hydrogen storage capacity of 10.1 wt% H{sub 2}, 149 kg H{sub 2}/m{sup 3} volumetric density and can be discharged at low temperatures (< 100 C). However, alane has been precluded from use in hydrogen storage systems because of the lack of practical regeneration methods; the direct hydrogenation of aluminium to form AlH{sub 3} requires over 10{sup 5} bars of hydrogen pressure at room temperature and there are no cost effective synthetic means. Here we show an unprecedented reversible cycle to form alane electrochemically, using alkali alanates (e.g. NaAlH{sub 4}, LiAlH{sub 4}) in aprotic solvents. To complete the cycle, the starting alanates can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride being the other compound formed in the electrochemical cell. The process of forming NaAlH{sub 4} from NaH and Al is well established in both solid state and solution reactions. The use of adducting Lewis bases is an essential part of this cycle, in the isolation of alane from the mixtures of the electrochemical cell. Alane is isolated as the triethylamine (TEA) adduct and converted to pure, unsolvated alane by heating under vacuum
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ALUMINUM HYDRIDE: A REVERSIBLE MATERIAL FOR HYDROGEN STORAGE
Hydrogen storage is one of the challenges to be overcome for implementing the ever sought hydrogen economy. Here we report a novel cycle to reversibly form high density hydrogen storage materials such as aluminium hydride. Aluminium hydride (AlH{sub 3}, alane) has a hydrogen storage capacity of 10.1 wt% H{sub 2}, 149 kg H{sub 2}/m{sup 3} volumetric density and can be discharged at low temperatures (< 100 C). However, alane has been precluded from use in hydrogen storage systems because of the lack of practical regeneration methods. The direct hydrogenation of aluminium to form AlH{sub 3} requires over 10{sup 5} bars of hydrogen pressure at room temperature and there are no cost effective synthetic means. Here we show an unprecedented reversible cycle to form alane electrochemically, using alkali metal alanates (e.g. NaAlH{sub 4}, LiAlH{sub 4}) in aprotic solvents. To complete the cycle, the starting alanates can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride being the other compound formed in the electrochemical cell. The process of forming NaAlH{sub 4} from NaH and Al is well established in both solid state and solution reactions. The use of adducting Lewis bases is an essential part of this cycle, in the isolation of alane from the mixtures of the electrochemical cell. Alane is isolated as the triethylamine (TEA) adduct and converted to pure, unsolvated alane by heating under vacuum
Recommended from our members
ALUMINUM HYDRIDE: A REVERSIBLE STORAGE MATERIAL FOR HYDROGEN STORAGE
One of the challenges of implementing the hydrogen economy is finding a suitable solid H{sub 2} storage material. Aluminium (alane, AlH{sub 3}) hydride has been examined as a potential hydrogen storage material because of its high weight capacity, low discharge temperature, and volumetric density. Recycling the dehydride material has however precluded AlH{sub 3} from being implemented due to the large pressures required (>10{sup 5} bar H{sub 2} at 25 C) and the thermodynamic expense of chemical synthesis. A reversible cycle to form alane electrochemically using NaAlH{sub 4} in THF been successfully demonstrated. Alane is isolated as the triethylamine (TEA) adduct and converted to unsolvated alane by heating under vacuum. To complete the cycle, the starting alanate can be regenerated by direct hydrogenation of the dehydrided alane and the alkali hydride (NaH) This novel reversible cycle opens the door for alane to fuel the hydrogen economy
A microporous titanosilicate for selective killing of HeLa cancer cells
Structural distribution of zinc(II) ions in the pore system of three silicate molecular sieves has revealed an unprecedented application of the microporous titanosilicate Zn-ETS-4 as a non toxic, highly efficient and selective inhibitor of HeLa cancer cells