Regeneration limit of classical Shannon capacity

Since Shannon derived the seminal formula for the capacity of the additive linear white Gaussian noise channel, it has commonly been interpreted as the ultimate limit of error-free information transmission rate. However, the capacity above the corresponding linear channel limit can be achieved when noise is suppressed using nonlinear elements; that is, the regenerative function not available in linear systems. Regeneration is a fundamental concept that extends from biology to optical communications. All-optical regeneration of coherent signal has attracted particular attention. Surprisingly, the quantitative impact of regeneration on the Shannon capacity has remained unstudied. Here we propose a new method of designing regenerative transmission systems with capacity that is higher than the corresponding linear channel, and illustrate it by proposing application of the Fourier transform for efficient regeneration of multilevel multidimensional signals. The regenerative Shannon limit -the upper bound of regeneration efficiency -is derived

Zipf's Law : Balancing signal usage cost and communication efficiency

Copyright: © 2015 Salge et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedWe propose a model that explains the reliable emergence of power laws (e.g., Zipf's law) during the development of different human languages. The model incorporates the principle of least effort in communications, minimizing a combination of the information-Theoretic communication inefficiency and direct signal cost. We prove a general relationship, for all optimal languages, between the signal cost distribution and the resulting distribution of signals. Zipf's law then emerges for logarithmic signal cost distributions, which is the cost distribution expected for words constructed from letters or phonemes. Copyright:Peer reviewedFinal Published versio

Getting patients in the door: medical appointment reminder preferences

Trisha M Crutchfield,1–3 Christine E Kistler2–4 1University of North Carolina Center for Health Promotion and Disease Prevention, 2University of North Carolina Lineberger Comprehensive Cancer Center, 3Cecil G. Sheps Center for Health Services Research, 4Department of Family Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA Purpose: Between 23% and 34% of outpatient appointments are missed annually. Patients who frequently miss medical appointments have poorer health outcomes and are less likely to use preventive health care services. Missed appointments result in unnecessary costs and organizational inefficiencies. Appointment reminders may help reduce missed appointments; particular types may be more effective than other types. We used a survey with a discrete choice experiment (DCE) to learn why individuals miss appointments and to assess appointment reminder preferences.Methods: We enrolled a national sample of adults from an online survey panel to complete demographic and appointment habit questions as well as a 16-task DCE designed in Sawtooth Software’s Discover tool. We assessed preferences for four reminder attributes – initial reminder type, arrival of initial reminder, reminder content, and number of reminders. We derived utilities and importance scores.Results: We surveyed 251 adults nationally, with a mean age of 43 (range 18–83) years: 51% female, 84% White, and 8% African American. Twenty-three percent of individuals missed one or more appointments in the past 12 months. Two primary reasons given for missing an appointment include transportation problems (28%) and forgetfulness (26%). Participants indicated the initial reminder type (21%) was the most important attribute, followed by the number of reminders (10%). Overall, individuals indicated a preference for a single reminder, arriving via email, phone call, or text message, delivered less than 2 weeks prior to an appointment. Preferences for reminder content were less clear.Conclusion: The number of missed appointments and reasons for missing appointments are consistent with prior research. Patient-centered appointment reminders may improve appointment attendance by addressing some of the reasons individuals report missing appointments and by meeting patients’ needs. Future research is necessary to determine if preferred reminders used in practice will result in improved appointment attendance in clinical settings. Keywords: reminders, discrete choice experiment, no-show rates, text messaging, survey, preferences, appointment attendance, DNAs, conjoint analysi

Quantum mechanics can reduce the complexity of classical models

10.1038/ncomms1761Nature Communications3

Older adults’ preferences for colorectal cancer-screening test attributes and test choice

Christine E Kistler,1–3 Thomas M Hess,4 Kirsten Howard,5,6 Michael P Pignone,2,3,7 Trisha M Crutchfield,2,3,8 Sarah T Hawley,9 Alison T Brenner,2 Kimberly T Ward,2 Carmen L Lewis10 1Department of Family Medicine, School of Medicine, 2Cecil G Sheps Center for Health Services Research, 3Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, 4Department of Psychology, North Carolina State University, Raleigh, NC, USA; 5Institute for Choice, University of South Australia, Sydney, NSW, Australia; 6School of Public Health, University of Sydney, Sydney, NSW, Australia; 7Division of General Internal Medicine, School of Medicine, 8Center for Health Promotion and Disease Prevention, University of North Carolina at Chapel Hill, Chapel Hill, NC, 9Department of Medicine, University of Michigan, Ann Arbor, MI, 10Division of General Internal Medicine, Department of Medicine, University of Colorado School of Medicine, Aurora, CO, USA Background: Understanding which attributes of colorectal cancer (CRC) screening tests drive older adults’ test preferences and choices may help improve decision making surrounding CRC screening in older adults.Materials and methods: To explore older adults’ preferences for CRC-screening test attributes and screening tests, we conducted a survey with a discrete choice experiment (DCE), a directly selected preferred attribute question, and an unlabeled screening test-choice question in 116 cognitively intact adults aged 70–90 years, without a history of CRC or inflammatory bowel disease. Each participant answered ten discrete choice questions presenting two hypothetical tests comprised of four attributes: testing procedure, mortality reduction, test frequency, and complications. DCE responses were used to estimate each participant’s most important attribute and to simulate their preferred test among three existing CRC-screening tests. For each individual, we compared the DCE-derived attributes to directly selected attributes, and the DCE-derived preferred test to a directly selected unlabeled test.Results: Older adults do not overwhelmingly value any one CRC-screening test attribute or prefer one type of CRC-screening test over other tests. However, small absolute DCE-derived preferences for the testing procedure attribute and for sigmoidoscopy-equivalent screening tests were revealed. Neither general health, functional, nor cognitive health status were associated with either an individual’s most important attribute or most preferred test choice. The DCE-derived most important attribute was associated with each participant’s directly selected unlabeled test choice.Conclusion: Older adults’ preferences for CRC-screening tests are not easily predicted. Medical providers should actively explore older adults’ preferences for CRC screening, so that they can order a screening test that is concordant with their patients’ values. Effective interventions are needed to support complex decision making surrounding CRC screening in older adults. Keywords: colorectal cancer screening, patient preferences, values clarification, discrete choice experiment, conjoint analysis, test attribute