Phase-controlled, speckle-free holographic projection with applications in precision optogenetics.

Holographic speckle is a major impediment to computer-generated holographic (CGH) projections in applications ranging from display, optical tweezers, and machining to optogenetic neural control. We present an iterative phase retrieval algorithm that allows the projection of amplitude-controlled speckle-free one-dimensional patterns with a high degree of pattern uniformity. The algorithm, termed the weighted Gerchberg-Saxton with phase-control (GSW-PC), is shown to have the ability to simultaneously control both the phase and amplitude of projected patterns with high diffraction efficiencies. Furthermore, we show that the framework can address the challenge of projecting volumetric phase and amplitude-controlled patterns, by incorporating GSW-PC with the angular spectrum method. The algorithms' performance is numerically and experimentally tested, and further compared with conventional and modern CGH techniques.

Overcoming barriers to colorectal cancer screening tests.

BACKGROUND: The frequency of colorectal cancer screening tests in Israel is poor, and is much lower than in the United States. This low rate has been attributed to health system failures as well as to barriers on the part of both physicians and patients. OBJECTIVES: To further identify particular health system failures, physician and patient-based barriers, and the effectiveness of public lectures in improving the frequency of performance of CRC screening tests. METHODS: Public lectures on colorectal cancer prevention were held. A gastroenterologist presented the lectures, which were followed immediately by a questionnaire and 4 months later by a telephone call. RESULTS: Of the 80% of attendees who had never undergone any CRC screening test, only 18% reported family physician recommendations for such tests. Eighty-four percent reported willingness to undergo fecal occult blood testing and 52% to undergo colonoscopy; 62% replied that they should undergo some CRC screening test and 90% believed that these tests save lives. Of the women, 47% expressed preference for a female gastroenterologist. Follow-up showed that 34% proceeded to undergo some CRC screening test: 60% chose colonoscopy and 40% FOBT. CONCLUSIONS: Public lectures are effective in improving compliance with the CRC screening test. Physicians should recommend these tests to appropriate individuals. Same-gender gastroenterologists should be considered for individuals uneasy about someone from the opposite gender performing the test. Assessing the various health-promotion efforts can direct us in implementing finite resources to greatest effect. Local cancer institutes and societies may be supportive in disseminating screening information in this way.