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The rapid spread of COVID-19 and disruption of normal supply chains has resulted in severe shortages of personal protective equipment (PPE), particularly devices with few suppliers such as powered air-purifying respirators (PAPRs). A scarcity of information describing design and performance criteria for PAPRs represents a substantial barrier to mitigating shortages. We sought to apply open-source product development (OSPD) to PAPRs to enable alternative sources of supply and further innovation. We describe the design, prototyping, validation, and user testing of locally manufactured, modular, PAPR components, including filter cartridges and blower units, developed by the Greater Boston Pandemic Fabrication Team (PanFab). Two designs, one with a fully custom-made filter and blower unit housing, and the other with commercially available variants (the “Custom” and “Commercial” designs, respectively) were developed; the components in the Custom design are interchangeable with those in Commercial design, although the form factor differs. The engineering performance of the prototypes was measured and safety validated using National Institutes for Occupational Safety and Health (NIOSH)-equivalent tests on apparatus available under pandemic conditions at university laboratories. Feedback was obtained from four individuals; two clinicians working in ambulatory clinical care and two research technical staff for whom PAPR use is standard occupational PPE; these individuals were asked to compare PanFab prototypes to commercial PAPRs from the perspective of usability and suggest areas for improvement. Respondents rated the PanFab Custom PAPR a 4 to 5 on a 5 Likert-scale 1) as compared to current PPE options, 2) for the sense of security with use in a clinical setting, and 3) for comfort compared to standard, commercially available PAPRs. The three other versions of the designs (with a Commercial blower unit, filter, or both) performed favorably, with survey responses con

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005., Includes bibliographical references (p. 91-94)., A. method used to obtain frequencies in precise ratios of 2/3 and 1/3 of the pump is described as a possible way to extend the usable range of octave-spanning optical frequency combs for frequency metrology applications. The divider is based on a self- phase locked optical parametric oscillation in a doubly resonant semi-monolithic optical cavity containing a dual-grating periodically poled lithium niobate. The design, implementation and evaluation of such a frequency divider are described. Preliminary experimental data from the self-phase locked optical frequency divider is presented. We have obtained sub-100 mW threshold for the optical parametric oscillator with stable operation over 1 s without servo locking the cavity length. Preliminary results suggest that self-phase locking has been observed., by Pavel Vladimir Gorelik., M.Eng.