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Glass has the ability to refract, reflect, and transmit light following geometrical optics, without scattering it. It is used in the manufacture of lenses and windows. Common glass has a refraction index around 1.5. This may be modified by adding low-density materials such as boron, which lowers the index of refraction (see crown glass), or increased (to as much as 1.8) with high-density materials such as (classically) lead oxide (see flint glass and lead glass), or in modern uses, less toxic oxides of zirconium, titanium, or barium. These high-index glasses (inaccurately known as "crystal" when used in glass vessels) cause more chromatic dispersion of light, and are prized for their diamond-like optical properties.
What can be used to make glass less dense?
A: unanswerable

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The implications are multiple as various research traditions are now[when?] heavily utilizing the lens of identity to examine phenomena.[citation needed] One implication of identity and of identity construction can be seen in occupational settings. This becomes increasing challenging in stigmatized jobs or "dirty work" (Hughes, 1951). Tracy and Trethewey (2005) state that "individuals gravitate toward and turn away from particular jobs depending in part, on the extent to which they validate a "preferred organizational self" (Tracy & Tretheway 2005, p. 169). Some jobs carry different stigmas or acclaims. In her analysis Tracy uses the example of correctional officers trying to shake the stigma of "glorified maids" (Tracy & Tretheway 2005). "The process by which people arrive at justifications of and values for various occupational choices." Among these are workplace satisfaction and overall quality of life (Tracy & Scott 2006, p. 33). People in these types of jobs are forced to find ways in order to create an identity they can live with. "Crafting a positive sense of self at work is more challenging when one's work is considered "dirty" by societal standards" (Tracy & Scott 2006, p. 7). "In other words, doing taint management is not just about allowing the employee to feel good in that job. "If employees must navigate discourses that question the viability of their work, and/ or experience obstacles in managing taint through transforming dirty work into a badge of honor, it is likely they will find blaming the client to be an efficacious route in affirming their identity" (Tracy & Scott 2006, p. 33).
Various research traditions are using what lens to examine phenomena?
A: the lens of identity

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When modern architecture was first practiced, it was an avant-garde movement with moral, philosophical, and aesthetic underpinnings. Immediately after World War I, pioneering modernist architects sought to develop a completely new style appropriate for a new post-war social and economic order, focused on meeting the needs of the middle and working classes. They rejected the architectural practice of the academic refinement of historical styles which served the rapidly declining aristocratic order. The approach of the Modernist architects was to reduce buildings to pure forms, removing historical references and ornament in favor of functionalist details. Buildings displayed their functional and structural elements, exposing steel beams and concrete surfaces instead of hiding them behind decorative forms.
Whose needs were no longer relevant to the new style?
A: the rapidly declining aristocratic order

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Oklahoma City, lying in the Great Plains region, features one of the largest livestock markets in the world. Oil, natural gas, petroleum products and related industries are the largest sector of the local economy. The city is situated in the middle of an active oil field and oil derricks dot the capitol grounds. The federal government employs large numbers of workers at Tinker Air Force Base and the United States Department of Transportation's Mike Monroney Aeronautical Center (these two sites house several offices of the Federal Aviation Administration and the Transportation Department's Enterprise Service Center, respectively).
What offices employ US transportation and Air force bases?
A:
Tinker Air Force Base and the United States Department of Transportation's Mike Monroney Aeronautical Center