Intrinsic Dimensionality as a Metric for the Impact of Mission Design Parameters.

High-resolution space-based spectral imaging of the Earth's surface delivers critical information for monitoring changes in the Earth system as well as resource management and utilization. Orbiting spectrometers are built according to multiple design parameters, including ground sampling distance (GSD), spectral resolution, temporal resolution, and signal-to-noise ratio. Different applications drive divergent instrument designs, so optimization for wide-reaching missions is complex. The Surface Biology and Geology component of NASA's Earth System Observatory addresses science questions and meets applications needs across diverse fields, including terrestrial and aquatic ecosystems, natural disasters, and the cryosphere. The algorithms required to generate the geophysical variables from the observed spectral imagery each have their own inherent dependencies and sensitivities, and weighting these objectively is challenging. Here, we introduce intrinsic dimensionality (ID), a measure of information content, as an applications-agnostic, data-driven metric to quantify performance sensitivity to various design parameters. ID is computed through the analysis of the eigenvalues of the image covariance matrix, and can be thought of as the number of significant principal components. This metric is extremely powerful for quantifying the information content in high-dimensional data, such as spectrally resolved radiances and their changes over space and time. We find that the ID decreases for coarser GSD, decreased spectral resolution and range, less frequent acquisitions, and lower signal-to-noise levels. This decrease in information content has implications for all derived products. ID is simple to compute, providing a single quantitative standard to evaluate combinations of design parameters, irrespective of higher-level algorithms, products, applications, or disciplines.

Remote sensing of plant-water relations: An overview and future perspectives.

Vegetation is a highly dynamic component of the Earth surface and substantially alters the water cycle. Particularly the process of oxygenic plant photosynthesis determines vegetation connecting the water and carbon cycle and causing various interactions and feedbacks across Earth spheres. While vegetation impacts the water cycle, it reacts to changing water availability via functional, biochemical and structural responses. Unravelling the resulting complex feedbacks and interactions between the plant-water system and environmental change is essential for any modelling approaches and predictions, but still insufficiently understood due to currently missing observations. We hypothesize that an appropriate cross-scale monitoring of plant-water relations can be achieved by combined observational and modelling approaches. This paper reviews suitable remote sensing approaches to assess plant-water relations ranging from pure observational to combined observational-modelling approaches. We use a combined energy balance and radiative transfer model to assess the explanatory power of pure observational approaches focussing on plant parameters to estimate plant-water relations, followed by an outline for a more effective use of remote sensing by their integration into soil-plant-atmosphere continuum (SPAC) models. We apply a mechanistic model simulating water movement in the SPAC to reveal insight into the complexity of relations between soil, plant and atmospheric parameters, and thus plant-water relations. We conclude that future research should focus on strategies combining observations and mechanistic modelling to advance our knowledge on the interplay between the plant-water system and environmental change, e.g. through plant transpiration.

Close-range laser scanning in forests: towards physically based semantics across scales.

Laser scanning with its unique measurement concept holds the potential to revolutionize the way we assess and quantify three-dimensional vegetation structure. Modern laser systems used at close range, be it on terrestrial, mobile or unmanned aerial platforms, provide dense and accurate three-dimensional data whose information just waits to be harvested. However, the transformation of such data to information is not as straightforward as for airborne and space-borne approaches, where typically empirical models are built using ground truth of target variables. Simpler variables, such as diameter at breast height, can be readily derived and validated. More complex variables, e.g. leaf area index, need a thorough understanding and consideration of the physical particularities of the measurement process and semantic labelling of the point cloud. Quantified structural models provide a framework for such labelling by deriving stem and branch architecture, a basis for many of the more complex structural variables. The physical information of the laser scanning process is still underused and we show how it could play a vital role in conjunction with three-dimensional radiative transfer models to shape the information retrieval methods of the future. Using such a combined forward and physically based approach will make methods robust and transferable. In addition, it avoids replacing observer bias from field inventories with instrument bias from different laser instruments. Still, an intensive dialogue with the users of the derived information is mandatory to potentially re-design structural concepts and variables so that they profit most of the rich data that close-range laser scanning provides.

Disability and disability benefit seeking in chronic low back pain.

BACKGROUND: Numerous studies suggest psychosocial factors contribute to functional disability in patients with chronic low back pain (CLBP). However, less is known about the association of psychosocial factors, such as depression, with seeking medical disability benefits and their prevalence in benefit seekers compared with patients already receiving such payments. AIMS: To determine if characteristics of disability benefit seekers differ from patients receiving disability benefits and if both differ from patients not dependent on such payments. METHODS: Questionnaire data on pain, health-related quality of life, depression, social support, substance abuse, adverse childhood experiences and disability seeking were obtained from CLBP respondents recruited at 10 primary care clinics throughout Texas. A multinomial logistic regression model was computed using variables significantly associated with disability status and pain severity in univariate models. RESULTS: There were 213 participants. In full models, compared with those not on disability benefits, only depression symptoms were significantly associated with seeking disability benefits (odds ratio [OR] = 1.13; 95% confidence interval [CI] 1.01-1.26) and only duration of pain was significantly associated with being on such benefits (OR = 1.05; 95% CI 1.01-1.09). CONCLUSIONS: Patient characteristics differ between disability benefit seekers and those established on disability benefit payments. Depression may be a modifiable correlate of disability benefit seeking that if treated may reduce the number of patients who eventually come to depend on disability benefits. Additional data collection involving other pain syndromes is warranted to determine if these results are unique to CLBP or apply to other painful conditions.

Vaginal bleeding associated with pregnancy.

Vaginal bleeding during pregnancy provokes physical and emotional stress to patients and physicians. Physicians must be prepared to assess the medical implications of acute blood loss to these patients and their unborn children quickly. When mother and fetus are stable, the recognition and treatment of the underlying cause is essential to decreasing additional maternal and fetal morbidity and mortality associated with the bleeding episode.

Evaluation and management of dyspepsia.

Dyspepsia, often defined as chronic or recurrent discomfort centered in the upper abdomen, can be caused by a variety of conditions. Common etiologies include peptic ulcers and gastroesophageal reflux. Serious causes, such as gastric and pancreatic cancers, are rare but must also be considered. Symptoms of possible causes often overlap, which can make initial diagnosis difficult. In many patients, a definite cause is never established. The initial evaluation of patients with dyspepsia includes a thorough history and physical examination, with special attention given to elements that suggest the presence of serious disease. Endoscopy should be performed promptly in patients who have "alarm symptoms" such as melena or anorexia. Optimal management remains controversial in young patients who do not have alarm symptoms. Although management should be individualized, a cost-effective initial approach is to test for Helicobacter pylori and treat the infection if the test is positive. If the H. pylori test is negative, empiric therapy with a gastric acid suppressant or prokinetic agent is recommended. If symptoms persist or recur after six to eight weeks of empiric therapy, endoscopy should be performed.

Alcohol-related problems: recognition and intervention.

Early identification of alcohol-related problems is important because these problems are prevalent, pose serious health risks to patients and their families, and are amenable to intervention. Physicians may be able to help patients change their drinking behaviors. The most effective tool for screening is a thorough history of the patient's drinking behavior, designed to identify patterns of alcohol-related difficulties with physical and mental health, family life, legal authorities and employment. Alcohol drinkers can be categorized as at-risk, problem or alcohol dependent, according to a protocol developed by the National Institute on Alcohol Abuse and Alcoholism. The severity of the alcohol problem and the patient's readiness to change should determine the intervention selected by the family physician.

Medical school application essays and specialty choice.

OBJECTIVE: To identify factors that could be used to predict physician specialty selection at the level of admissions to medical school. METHODS: Content analysis was performed on 161 personal statements from the American Medical College Admission Service application form. Randomly selected graduates analyzed were from the classes of 1985-1987 from a Midwestern public medical school. RESULTS: Fifty percent of those who stated that they had contact with a medical specialty entered either that specialty or a closely related specialty. Of the 11 applicants who stated a goal of entering family practice, one entered family practice. CONCLUSIONS: Contact with a specialty prior to entering medical school may be a significant predictor of the prospective student's eventual specialty selection. However, goals mentioned in the statements are not predictors of specialty choice.

Community attitudes and knowledge about advance care directives.

BACKGROUND: Patients and their physicians are increasingly being encouraged to discuss end-of-life decisions. The purpose of this study was to enhance understanding of the public's attitudes and knowledge about medical decision making and advance care directives. METHODS: Eight focus groups of community members discussed their understanding of and attitudes about advance care directives. Transcripts of these discussions were analyzed using coding categories created from the transcripts. RESULTS: Eighty-three people attended the focus groups. Most discussions of advance care directives involved family members in the setting of family or personal illness. Elderly persons commonly confused wills with living wills. Most who had given advance directives did so either to make others follow their wishes or to ease family burdens. Among the great variety of reasons for not using advance directives was a perceived lack of personal relevance, as well as conceptual, moral, and practical difficulties. Participants were divided about whether it was appropriate for physicians to initiate discussions about life-sustaining care with their patients. We discerned three themes affecting individuals' opinions about personal decision making about advance directives: (1) trust in family and the medical system, (2) need for control, and (3) knowledge about advance directives. CONCLUSIONS: Although living wills are advocated by many authorities, and many of our participants endorsed their use, our participants also cited numerous cautions and impediments to their use. As the role of advance care directives changes, physicians will need to be aware of their patients' perceptions, as well as the legalities of these documents.

The physician's decision to use tube feedings: the role of the family, the living will, and the Cruzan decision.

OBJECTIVE: To determine the relative importance of factors influencing physicians to use tube feedings in patients lacking decision-making capacity. DESIGN: Survey. SETTING AND PARTICIPANTS: Four hundred thirty-nine members of the Missouri Academy of Family Physicians. MEASUREMENTS: Using a mailed questionnaire, physicians were asked for a decision about feeding tube placement in an 89-year-old man who was unable to swallow or communicate after a stroke. Changing the conditions of the scenario, we then evaluated the influence of patient age, duration of disability, a living will, the Cruzan decision, and family preferences on the physician's decision. RESULTS: After reading the initial case history, 47% of physicians opposed tube feedings. Physicians who were told that the patient signed a living will specifically excluding tube feedings were more likely to oppose tube feedings than those who were told that he signed only a standard living will (53% vs 42%; P = 0.02). Forty-two percent of physicians who initially suggested a feeding tube changed their recommendation if the family opposed it. Sixty-six percent of physicians who initially opposed a feeding tube changed their recommendation if the family "pushed" for it. Thirty-three percent of physicians who initially opposed tube feedings under the living will scenario would favor tube feedings if the patient had not signed a living will. Twenty-two percent of physicians who initially opposed tube feedings would change to favor them if the issue had arisen before the Cruzan decision. CONCLUSIONS: Among this group of physicians, there was no consensus on whether tube feedings should be initiated. However, it was found that the family's opinion was the most influential factor affecting the physician's recommendation about tube feedings. Most physicians endorsed family preferences for tube feedings even when this intervention was specifically opposed in the patient's living will.