Remote Sensing of Environment: Current status of Landsat program, science, and applications

Formal planning and development of what became the first Landsat satellite commenced over 50 years ago in 1967. Now, having collected earth observation data for well over four decades since the 1972 launch of Landsat- 1, the Landsat program is increasingly complex and vibrant. Critical programmatic elements are ensuring the continuity of high quality measurements for scientific and operational investigations, including ground systems, acquisition planning, data archiving and management, and provision of analysis ready data products. Free and open access to archival and new imagery has resulted in a myriad of innovative applications and novel scientific insights. The planning of future compatible satellites in the Landsat series, which maintain continuity while incorporating technological advancements, has resulted in an increased operational use of Landsat data. Governments and international agencies, among others, can now build an expectation of Landsat data into a given operational data stream. International programs and conventions (e.g., deforestation monitoring, climate change mitigation) are empowered by access to systematically collected and calibrated data with expected future continuity further contributing to the existing multi-decadal record. The increased breadth and depth of Landsat science and applications have accelerated following the launch of Landsat-8, with significant improvements in data quality. Herein, we describe the programmatic developments and institutional context for the Landsat program and the unique ability of Landsat to meet the needs of national and international programs. We then present the key trends in Landsat science that underpin many of the recent scientific and application developments and followup with more detailed thematically organized summaries. The historical context offered by archival imagery combined with new imagery allows for the development of time series algorithms that can produce information on trends and dynamics. Landsat-8 has figured prominently in these recent developments, as has the improved understanding and calibration of historical data. Following the communication of the state of Landsat science, an outlook for future launches and envisioned programmatic developments are presented. Increased linkages between satellite programs are also made possible through an expectation of future mission continuity, such as developing a virtual constellation with Sentinel-2. Successful science and applications developments create a positive feedback loop—justifying and encouraging current and future programmatic support for Landsat

Using a field radiometer to estimate instantaneous sky clearness

Reflectance measurements of crop plants and canopies show promise for guiding within-season, variable-rate nitrogen (N) application. Most research results have been obtained around solar noon with clear skies. However, for practical application, the system must work under cloudy skies or away from solar noon. The objective of this work was to assess the effect of cloud conditions on reflectance measurements of a corn canopy. The approach was to estimate an instantaneous sky clearness index (ICI) which could be used to correct field radiometer data for variations in cloud cover, such that the same reflectance reading would be obtained (and the same N recommendation made) for the same plants regardless of cloud conditions. Readings were taken from morning until night over 11 days with a range of sky conditions (sunny, overcast, partly cloudy). Data from clear days were used to estimate the theoretical expected spectral global radiation incident on a horizontal surface. The ICI was calculated as the ratio between the actual spectral global radiation and the corresponding theoretical global radiation. Analysis of the ICI for each band showed that the influence of cloudiness was different for each band. Thus, the cloud effect could not be compensated by the use of a band ratio or vegetation index

Tobacco promotion and the initiation of tobacco use: assessing the evidence for causality

OBJECTIVE: We sought to determine whether there is evidence of a causal link between exposure to tobacco promotion and the initiation of tobacco use by children. METHODS: We conducted a structured search in Medline, PsycINFO, and ABI/INFORM Global to identify relevant empirical research. The literature was examined against the Hill epidemiologic criteria for determining causality. RESULTS: (1) Children are exposed to tobacco promotion before the initiation of tobacco use; (2) exposure increases the risk for initiation; (3) there is a dose-response relationship, with greater exposure resulting in higher risk; (4) the increased risk is robust; it is observed with various study methods, in multiple populations, and with various forms of promotion and persists after controlling for other factors; (5) scientifically plausible mechanisms whereby promotion could influence initiation exist; and (6) no explanation other than causality can account for the evidence. CONCLUSIONS: Promotions foster positive attitudes, beliefs, and expectations regarding tobacco use. This fosters intentions to use and increases the likelihood of initiation. Greater exposure to promotion leads to higher risk. This is seen in diverse cultures and persists when other risk factors, such as socioeconomic status or parental and peer smoking, are controlled. Causality is the only plausible scientific explanation for the observed data. The evidence satisfies the Hill criteria, indicating that exposure to tobacco promotion causes children to initiate tobacco use

Remote Sensing of Environment: Current status of Landsat program, science, and applications

Formal planning and development of what became the first Landsat satellite commenced over 50 years ago in 1967. Now, having collected earth observation data for well over four decades since the 1972 launch of Landsat- 1, the Landsat program is increasingly complex and vibrant. Critical programmatic elements are ensuring the continuity of high quality measurements for scientific and operational investigations, including ground systems, acquisition planning, data archiving and management, and provision of analysis ready data products. Free and open access to archival and new imagery has resulted in a myriad of innovative applications and novel scientific insights. The planning of future compatible satellites in the Landsat series, which maintain continuity while incorporating technological advancements, has resulted in an increased operational use of Landsat data. Governments and international agencies, among others, can now build an expectation of Landsat data into a given operational data stream. International programs and conventions (e.g., deforestation monitoring, climate change mitigation) are empowered by access to systematically collected and calibrated data with expected future continuity further contributing to the existing multi-decadal record. The increased breadth and depth of Landsat science and applications have accelerated following the launch of Landsat-8, with significant improvements in data quality. Herein, we describe the programmatic developments and institutional context for the Landsat program and the unique ability of Landsat to meet the needs of national and international programs. We then present the key trends in Landsat science that underpin many of the recent scientific and application developments and followup with more detailed thematically organized summaries. The historical context offered by archival imagery combined with new imagery allows for the development of time series algorithms that can produce information on trends and dynamics. Landsat-8 has figured prominently in these recent developments, as has the improved understanding and calibration of historical data. Following the communication of the state of Landsat science, an outlook for future launches and envisioned programmatic developments are presented. Increased linkages between satellite programs are also made possible through an expectation of future mission continuity, such as developing a virtual constellation with Sentinel-2. Successful science and applications developments create a positive feedback loop—justifying and encouraging current and future programmatic support for Landsat

The Natural History and Diagnosis of Nicotine Addiction

Addicted smokers experience nicotine withdrawal anytime they go too long without smoking. Withdrawal presents as a continuum of symptoms of escalating severity described by smokers as “wanting,” then “craving,” and eventually “needing” to smoke. These may be followed by irritability, impatience, moodiness, difficulty concentrating, restlessness, and sleep disturbances. This spectrum of intensifying withdrawal symptoms creates a compulsion to smoke that makes quitting difficult. The compulsion to smoke is the core feature of nicotine addiction accounting for its clinical course, physiological characteristics, prognosis, and behavioral manifestations. A compulsion can develop quickly, having been experienced by one third of youth who have smoked only 3 or 4 cigarettes. Its physiologic basis is evident in neurophysiological measures and its recurrence after each cigarette at a characteristic interval. At first, a single cigarette can keep withdrawal at bay for weeks, but as addiction progresses, cigarettes must be smoked at progressively shorter intervals to suppress withdrawal symptoms. The physiologic need to repeatedly self-administer nicotine at shorter intervals explains a full spectrum of addictive symptoms ranging from the prodromal symptom of wanting, to chain smoking. The early process of nicotine addiction is recognized if a person experiences regular wanting for a cigarette. When symptoms include craving or needing, the now addicted patient is experiencing a compulsion to smoke. This simple diagnostic approach covers the full spectrum of addiction in smokers of all ages and levels of tobacco use, and is more valid than a clinical diagnosis based on the current Diagnostic and Statistical Manual criteria