Experiments have been performed which lead to the conclusion that dichromated gelatin holograms arise as a result of the formation of an air-gelatin interface, with the observed high diffraction efficiencies resulting from the air-gelatin refractive index differential of 0.52 found at the interface. It is postulated that rapid removal of water by isopropanol in the development process creates strains in the gelatin film which are relieved by splitting. The resultant cracks in the hologram manifest themselves in an obvious location, between the highly exposed planes of cross-linked gelatin. Photomicrographic evidence on Bragg-Lippmann and on plane gratings, liquid gate data, lack of thickness reciprocity for the gratings, and observations of grating thickness employing bandpass measurements comprise the bulk of the experimental work. From these data, a model is proposed that is consistent with all the experimental results for both Bragg-Lippmann and plane gratings.
Purpose: Homelessness is a major public health problem facing millions of youths across the United States (U.S.), with lesbian gay, bisexual, transgender, questioning (LGBTQ+) youths and youths of color being disproportionately at higher risk. This study obtains an understanding of the health and health-related social needs of youths experiencing homelessness during the coronavirus disease (COVID-19) pandemic. Methods: A total of 14 youths between the ages of 14 and 24 who (a) lived, worked, or attended school in New Britain, Connecticut (CT) and (b) had at least one experience of homelessness or housing insecurity worked with the research team to conduct a needs assessment regarding youth homelessness. Using photovoice, a community-based participatory research method, participants created photo narratives to share their stories and recommendations for community change. The main goals of photovoice are to enable participants to (1) record and represent their everyday realities; (2) promote critical dialogue and knowledge about person and community strengths and concerns; and (3) reach policy makers. Results: Most of the participants identified as youths of color, and half of the participants identified as members of the LGBTQ+ community. Three major themes that appeared in the youths’ narratives include the following: mental health and substance use challenges, trouble accessing basic human needs, and lack of a social support system. Conclusion: This study uplifts and empowers a vulnerable population to increase visibility around a major public health challenge from their own lived experiences. Despite the challenges that were voiced, many participants shared a sense of hope and resiliency. The major themes endorsed by the youths has the potential of informing practitioners and policy makers of how to better address the needs of youths experiencing homelessness, particularly those most at risk.
For the utilization of photoresist materials it is desirable to describe quantitatively the photoresist image and thereby introduce control over photoresist processing. The photoresist AZ111 has been shown to be a linear image recording medium and a modulation transfer function (MTF) defined and measured. Measured and calculated image profiles in this resist are quite comparable.
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