A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2 : evidence from carbon isotope discrimination in paleo and CO2 enrichment studies.

Rising atmospheric [CO2 ], ca , is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO2 ], ci , a constant drawdown in CO2 (ca  - ci ), and a constant ci /ca . These strategies can result in drastically different consequences for leaf gas-exchange. The accuracy of Earth systems models depends in part on assumptions about generalizable patterns in leaf gas-exchange responses to varying ca . The concept of optimal stomatal behavior, exemplified by woody plants shifting along a continuum of these strategies, provides a unifying framework for understanding leaf gas-exchange responses to ca . To assess leaf gas-exchange regulation strategies, we analyzed patterns in ci inferred from studies reporting C stable isotope ratios (δ(13) C) or photosynthetic discrimination (∆) in woody angiosperms and gymnosperms that grew across a range of ca spanning at least 100 ppm. Our results suggest that much of the ca -induced changes in ci /ca occurred across ca spanning 200 to 400 ppm. These patterns imply that ca  - ci will eventually approach a constant level at high ca because assimilation rates will reach a maximum and stomatal conductance of each species should be constrained to some minimum level. These analyses are not consistent with canalization toward any single strategy, particularly maintaining a constant ci . Rather, the results are consistent with the existence of a broadly conserved pattern of stomatal optimization in woody angiosperms and gymnosperms. This results in trees being profligate water users at low ca , when additional water loss is small for each unit of C gain, and increasingly water-conservative at high ca , when photosystems are saturated and water loss is large for each unit C gain.

From Context Comes Expertise: How Do Expert Emergency Physicians Use Their Know-Who to Make Decisions?

STUDY OBJECTIVE: Decisionmaking is influenced by the environment in which it takes place. The objective of our study was to explore the influence of the specific features of the emergency department (ED) environment on decisionmaking. In this paper, we specifically report on the way emergency physicians use their knowledge of their collaborators to make their decisions. METHODS: We conducted a qualitative study on emergency physicians recruited in 3 French hospitals. Physicians were equipped with a microcamera to record their clinical activity from their "own-point-of-view perspective." Semistructured interviews, based on viewing the video, were held with each physician after an actual clinical encounter with a patient. They were then analyzed thematically, using constant comparison and matrices, to identify the central themes. RESULTS: Fifteen expert emergency physicians were interviewed. Almost all of them reported using their knowledge of other health care professionals to assess the seriousness of the patient's overall condition (sometimes even before his or her arrival in the ED) to optimize the patient's treatment and to anticipate future care. CONCLUSION: Emergency physicians interact with many other health care workers during the different stages of the patient's management. The many ways in which experts use their knowledge of other health care professionals to make decisions puts traditional conceptions of expert knowledge into perspective and opens avenues for future research.

How and when do expert emergency physicians generate and evaluate diagnostic hypotheses? A qualitative study using head-mounted video cued-recall interviews.

STUDY OBJECTIVE: The ability to make a diagnosis is a crucial skill in emergency medicine. Little is known about the way emergency physicians reach a diagnosis. This study aims to identify how and when, during the initial patient examination, emergency physicians generate and evaluate diagnostic hypotheses. METHODS: We carried out a qualitative research project based on semistructured interviews with emergency physicians. The interviews concerned management of an emergency situation during routine medical practice. They were associated with viewing the video recording of emergency situations filmed in an "own-point-of-view" perspective. RESULTS: The emergency physicians generated an average of 5 diagnostic hypotheses. Most of these hypotheses were generated before meeting the patient or within the first 5 minutes of the meeting. The hypotheses were then rank ordered within the context of a verification procedure based on identifying key information. These tasks were usually accomplished without conscious effort. No hypothesis was completely confirmed or refuted until the results of investigations were available. CONCLUSION: The generation and rank ordering of diagnostic hypotheses is based on the activation of cognitive processes, enabling expert emergency physicians to process environmental information and link it to past experiences. The physicians seemed to strive to avoid the risk of error by remaining aware of the possibility of alternative hypotheses as long as they did not have the results of investigations. Understanding the diagnostic process used by emergency physicians provides interesting ideas for training residents in a specialty in which the prevalence of reasoning errors leading to incorrect diagnoses is high.

Optometrists' clinical reasoning made explicit: a qualitative study.

PURPOSE: Because the clinical reasoning processes engaged in by practicing optometrists have not previous been investigated, until now, there has been no way of knowing whether models of clinical reasoning from other health professions can be transposed to optometry. The purpose of this study has therefore been twofold: making explicit the clinical reasoning processes of optometrists at both the "competent" and "expert" levels and comparing these processes to highlight the characteristics of clinical reasoning expertise. METHODS: Four competent-level optometrists and four expert-level optometrists participated in this qualitative study. Each optometrist performed a complete optometric examination on a preselected patient. Each of these examinations was recorded on a DVD video and followed by a feedback session, also captured on a DVD video. The feedback session was conducted using techniques inspired by a form of interview called the "explicitation interview," aiming to describe optometrists' mental actions and the time sequence of these actions throughout the examination. RESULTS: The results indicate that optometrists' clinical reasoning is patient centered and includes both analytical and nonanalytical modes of reasoning. When compared with a competent-level optometrist, an expert-level optometrist is more patient centered, formulates an earlier mental representation of the patient's clinical situation (including diagnosis formulation), plans examinations more thoroughly, is able to analyze and reflect during cognitively demanding tasks, and draws up his or her care management plan throughout the entire examination. CONCLUSIONS: The verbalization of optometrists' clinical reasoning processes represents a first step toward a better understanding of this competency. The impact of this research on optometric education is discussed. The results open doors to further research in the field, for example, toward defining the stages of clinical reasoning development among optometry students and professionals.

Pine processionary moth outbreaks cause longer growth legacies than drought and are linked to the North Atlantic Oscillation.

Climatic warming is assumed to expand the geographic range of insect pests whose distribution is mainly constrained by low temperatures. This is the case of the pine processionary moth (Thaumetopoea pityocampa), which is one of the main conifer defoliators in the Mediterranean Basin. Warmer winters may lead to a northward/upward expansion of this insect, as short-term studies have shown. However, no long-term data, i.e. spanning at least one century, has been used to examine these projections. We test the hypotheses that climatic warming (i) has caused an upward shift of the pine processionary moth, and (ii) has increased the frequency of severe defoliations. We used dendrochronological methods to reconstruct defoliations over the period 1900-2006 in 14 sites spanning a wide altitudinal range (1070-1675 m) in Teruel, eastern Spain. We built local ring-width chronologies for four co-occurring pine species with different degree of susceptibility against the moth defoliations, from highly suitable or palatable species (Pinus nigra) to moderately (Pinus sylvestris, Pinus halepensis) or rarely defoliated species (Pinus pinaster). We validated the tree-ring reconstructions of outbreaks using a field record of stand defoliations spanning the period 1971-2006. Outbreaks in the most affected P. nigra stands corresponded to abrupt one- to two-year growth reductions (70-90% growth loss). Reconstructed outbreaks occurred on average every 9-14 years. The growth memory of outbreaks was weaker but lasted longer (1-6 years) than that due to droughts (1-3 years). Neither an upward expansion nor an increase in outbreak frequency was observed. Severe PPM defoliations did not increase as climate warmed, rather they were positively related to the winter North Atlantic Oscillation.

Earlywood Vessels in Black Ash (Fraxinus nigra Marsh.) Trees Show Contrasting Sensitivity to Hydroclimate Variables According to Flood Exposure.

In recent years, the utility of earlywood vessels anatomical characteristics in identifying and reconstructing hydrological conditions has been fully recognized. In riparian ring-porous species, flood rings have been used to identify discrete flood events, and chronologies developed from cross-sectional lumen areas of earlywood vessels have been used to successfully reconstruct seasonal discharge. In contrast, the utility of the earlywood vessel chronologies in non-riparian habitats has been less compelling. No studies have contrasted within species their earlywood vessel anatomical characteristics, specifically from trees that are inversely exposed to flooding. In this study, earlywood vessel and ring-width chronologies were compared between flooded and non-flooded control Fraxinus nigra trees. The association between chronologies and hydroclimate variables was also assessed. Fraxinus nigra trees from both settings shared similar mean tree-ring width but floodplain trees did produce, on average, thicker earlywood. Vessel chronologies from the floodplain trees generally recorded higher mean sensitivity (standard deviation) and lower autocorrelation than corresponding control chronologies indicating higher year-to-year variations. Principal components analysis (PCA) revealed that control and floodplain chronologies shared little variance indicating habitat-specific signals. At the habitat level, the PCA indicated that vessel characteristics were strongly associated with tree-ring width descriptors in control trees whereas, in floodplain trees, they were decoupled from the width. The most striking difference found between flood exposures related to the chronologies' associations with hydroclimatic variables. Floodplain vessel chronologies were strongly associated with climate variables modulating spring-flood conditions as well as with spring discharge whereas control ones showed weaker and few consistent correlations. Our results illustrated how spring flood conditions modulate earlywood vessel plasticity. In floodplain F. nigra trees, the use of earlywood vessel characteristics could potentially be extended to assess and/or mitigate anthropogenic modifications of hydrological regimes. In absence of major recurring environmental stressors like spring flooding, our results support the idea that the production of continuous earlywood vessel chronologies may be of limited utility in dendroclimatology.

Flood-Rings Production Modulated by River Regulation in Eastern Boreal Canada.

In northeastern boreal Canada, the long-term perspective on spring flooding is hampered by the absence of long gage records. Changes in the tree-ring anatomy of periodically flooded trees have allowed the reconstruction of historical floods in unregulated hydrological systems. In regulated rivers, the study of flood rings could recover past flood history, assuming that the effects of hydrological regulation on their production can be understood. This study analyzes the effect of regulation on the flood-ring occurrence (visual intensity and relative frequency) and on ring widths in Fraxinus nigra trees growing at five sites distributed along the Driftwood River floodplain. Driftwood River was regulated by a dam in 1917 that was replaced at the same location in 1953. Ring width revealed little, to no evidence, of the impact of river regulation, in contrast to the flood rings. Prior to 1917, high relative frequencies of well-defined flood rings were recorded during known flood years, as indicated by significant correlations with reconstructed spring discharge of the nearby Harricana River. After the construction and the replacement of the dam, relative frequencies of flood rings and their intensities gradually decreased. Flood-ring relative frequencies after 1917, and particularly after 1953, were mostly composed of weakly defined (less distinct) flood rings with some corresponding to known flood years and others likely reflecting dam management. The strength of the correlations with the instrumental Harricana River discharge also gradually decrease starting after 1917. Compared with upper floodplain trees, shoreline trees at each site recorded flood rings less frequently following the construction of the first but especially of the second dam, indicating that water level regulation limited flooding in the floodplains. Compared with the downstream site to the dam, the upstream ones recorded significantly more flood rings in the postdam period, reemphasizing the importance of considering the position of the site along with the river continuum and site conditions in relation to flood exposure. The results demonstrated that sampling trees in multiple riparian stands and along with various hydrological contexts at a far distance of the dams could help disentangle the flooding signal from the dam management signal.

A Novel Approach to Study Medical Decision Making in the Clinical Setting: The "Own-point-of-view" Perspective.

BACKGROUND: Making diagnostic and therapeutic decisions is a critical activity among physicians. It relies on the ability of physicians to use cognitive processes and specific knowledge in the context of a clinical reasoning. This ability is a core competency in physicians, especially in the field of emergency medicine where the rate of diagnostic errors is high. Studies that explore medical decision making in an authentic setting are increasing significantly. They are based on the use of qualitative methods that are applied at two separate times: 1) a video recording of the subject's actual activity in an authentic setting and 2) an interview with the subject, supported by the video recording. Traditionally, activity is recorded from an "external perspective"; i.e., a camera is positioned in the room in which the consultation takes place. This approach has many limits, both technical and with respect to the validity of the data collected. OBJECTIVES: The article aims at 1) describing how decision making is currently being studied, especially from a qualitative standpoint, and the reasons why new methods are needed, and 2) reporting how we used an original, innovative approach to study decision making in the field of emergency medicine and findings from these studies to guide further the use of this method. The method consists in recording the subject's activity from his own point of view, by fixing a microcamera on his temple or the branch of his glasses. An interview is then held on the basis of this recording, so that the subject being interviewed can relive the situation, to facilitate the explanation of his reasoning with respect to his decisions and actions. RESULTS: We describe how this method has been used successfully in investigating medical decision making in emergency medicine. We provide details on how to use it optimally, taking into account the constraints associated with the practice of emergency medicine and the benefits in the study of clinical reasoning. CONCLUSION: The "own-point-of-view" video technique is a promising method to study clinical decision making in emergency medicine. It is a powerful tool to stimulate recall and help physicians make their reasoning explicit, thanks to a greater psychological immersion.

Do emergency physicians trust their patients?

The primary focus of research on the physician-patient relationship has been on patients' trust in their physicians. In this study, we explored physicians' trust in their patients. We held semi-structured interviews with expert emergency physicians concerning a patient they had just been managing. The physicians had been equipped with a head-mounted micro camera to film the encounter from an "own point of view perspective". The footage was used to stimulate recall during the interviews. Several participants made judgments on the reliability of their patients' accounts from the very beginning of the encounter. If accounts were not deemed reliable, participants implemented a variety of specific strategies in pursuing their history taking, i.e. checking for consistency by asking the same question at several points in the interview, cross-referencing information, questioning third-parties, examining the patient record, and systematically collecting data held to be objective. Our study raises the question of the influence of labeling patients as "reliable" or "unreliable" on their subsequent treatment in the emergency department. Further work is necessary to examine the accuracy of these judgments, the underlying cognitive processes (i.e. analytic versus intuitive) and their influence on decision-making.

Flood-Ring Formation and Root Development in Response to Experimental Flooding of Young Quercus robur Trees.

Spring flooding in riparian forests can cause significant reductions in earlywood-vessel size in submerged stem parts of ring-porous tree species, leading to the presence of 'flood rings' that can be used as a proxy to reconstruct past flooding events, potentially over millennia. The mechanism of flood-ring formation and the relation with timing and duration of flooding are still to be elucidated. In this study, we experimentally flooded 4-year-old Quercus robur trees at three spring phenophases (late bud dormancy, budswell, and internode expansion) and over different flooding durations (2, 4, and 6 weeks) to a stem height of 50 cm. The effect of flooding on root and vessel development was assessed immediately after the flooding treatment and at the end of the growing season. Ring width and earlywood-vessel size and density were measured at 25- and 75-cm stem height and collapsed vessels were recorded. Stem flooding inhibited earlywood-vessel development in flooded stem parts. In addition, flooding upon budswell and internode expansion led to collapsed earlywood vessels below the water level. At the end of the growing season, mean earlywood-vessel size in the flooded stem parts (upon budswell and internode expansion) was always reduced by approximately 50% compared to non-flooded stem parts and 55% compared to control trees. This reduction was already present 2 weeks after flooding and occurred independent of flooding duration. Stem and root flooding were associated with significant root dieback after 4 and 6 weeks and mean radial growth was always reduced with increasing flooding duration. By comparing stem and root flooding, we conclude that flood rings only occur after stem flooding. As earlywood-vessel development was hampered during flooding, a considerable number of narrow earlywood vessels present later in the season, must have been formed after the actual flooding events. Our study indicates that root dieback, together with strongly reduced hydraulic conductivity due to anomalously narrow earlywood vessels in flooded stem parts, contribute to reduced radial growth after flooding events. Our findings support the value of flood rings to reconstruct spring flooding events that occurred prior to instrumental flood records.

From a Medical Problem to a Health Experience: How Nursing Students Think in Clinical Situations.

BACKGROUND: Nursing clinical judgment (NCJ) is a core competency that must be developed in nursing education. The objective of this study is to explore the development of NCJ among undergraduate nursing students, according to teachers and preceptors. METHOD: The collaborative group, composed of three educators, three nurse preceptors, and one researcher, analyzed six situations in which students in the program were assessed for NCJ. RESULTS: Key learnings and development indicators were identified for each of the three levels of NCJ development. Reasoning process, type of relationships with patients and their families, perception of the nursing role, and reflection are parameters of NCJ that exert a mutual influence and evolve from one level to the next. CONCLUSION: Knowing this evolution can help educators to plan the curriculum, select effective teaching methods, and provide feedback that will support NCJ development. For students, these developmental markers support self-evaluation with a view to self-regulation.

Insights into emergency physicians' minds in the seconds before and into a patient encounter.

Clinical reasoning is a core competency in medical practice. No study has explored clinical reasoning occurring before a clinical encounter, when physicians obtain preliminary information about the patient, and during the first seconds of the observation phase. This paper aims to understand what happens in emergency physicians' minds when they acquire initial information about a patient, and when they first meet a patient. The authors carried out in-depth interviews based on the video recordings of emergency situations filmed in an "own-point-of-view-perspective". 15 expert emergency physicians were interviewed between 2011 and 2012. Researchers analysed data using an interpretive approach based on thematic analysis and constant comparison. Almost all participants used a few critical pieces of information to generate hypotheses even before they actually met the patient. Pre-encounter hypotheses played a key role in the ensuing encounter by directing initial data gathering. Initial data, collected within the first few seconds of the encounter, included the patient's position on the stretcher, the way they had been prepared, their facial expression, their breathing, and their skin colour. Physicians also rapidly appraised the seriousness of the patient's overall condition, which determined their initial goals, i.e. initiating emergency treatment or pursuing the diagnostic investigation. The study brings new insights on what happens at the very beginning of the encounter between emergency physicians and patients. The results obtained from an innovative methodological approach open avenues for the development of clinical reasoning in learners.

Capturing spiral radial growth of conifers using the superellipse to model tree-ring geometric shape.

Tree-rings are often assumed to approximate a circular shape when estimating forest productivity and carbon dynamics. However, tree rings are rarely, if ever, circular, thereby possibly resulting in under- or over-estimation in forest productivity and carbon sequestration. Given the crucial role played by tree ring data in assessing forest productivity and carbon storage within a context of global change, it is particularly important that mathematical models adequately render cross-sectional area increment derived from tree rings. We modeled the geometric shape of tree rings using the superellipse equation and checked its validation based on the theoretical simulation and six actual cross sections collected from three conifers. We found that the superellipse better describes the geometric shape of tree rings than the circle commonly used. We showed that a spiral growth trend exists on the radial section over time, which might be closely related to spiral grain along the longitudinal axis. The superellipse generally had higher accuracy than the circle in predicting the basal area increment, resulting in an improved estimate for the basal area. The superellipse may allow better assessing forest productivity and carbon storage in terrestrial forest ecosystems.

Impact of future climate on radial growth of four major boreal tree species in the Eastern Canadian boreal forest.

Immediate phenotypic variation and the lagged effect of evolutionary adaptation to climate change appear to be two key processes in tree responses to climate warming. This study examines these components in two types of growth models for predicting the 2010-2099 diameter growth change of four major boreal species Betula papyrifera, Pinus banksiana, Picea mariana, and Populus tremuloides along a broad latitudinal gradient in eastern Canada under future climate projections. Climate-growth response models for 34 stands over nine latitudes were calibrated and cross-validated. An adaptive response model (A-model), in which the climate-growth relationship varies over time, and a fixed response model (F-model), in which the relationship is constant over time, were constructed to predict future growth. For the former, we examined how future growth of stands in northern latitudes could be forecasted using growth-climate equations derived from stands currently growing in southern latitudes assuming that current climate in southern locations provide an analogue for future conditions in the north. For the latter, we tested if future growth of stands would be maximally predicted using the growth-climate equation obtained from the given local stand assuming a lagged response to climate due to genetic constraints. Both models predicted a large growth increase in northern stands due to more benign temperatures, whereas there was a minimal growth change in southern stands due to potentially warm-temperature induced drought-stress. The A-model demonstrates a changing environment whereas the F-model highlights a constant growth response to future warming. As time elapses we can predict a gradual transition between a response to climate associated with the current conditions (F-model) to a more adapted response to future climate (A-model). Our modeling approach provides a template to predict tree growth response to climate warming at mid-high latitudes of the Northern Hemisphere.

An analysis of clinical reasoning through a recent and comprehensive approach: the dual-process theory.

CONTEXT: Clinical reasoning plays a major role in the ability of doctors to make diagnoses and decisions. It is considered as the physician's most critical competence, and has been widely studied by physicians, educationalists, psychologists and sociologists. Since the 1970s, many theories about clinical reasoning in medicine have been put forward. PURPOSE: This paper aims at exploring a comprehensive approach: the "dual-process theory", a model developed by cognitive psychologists over the last few years. DISCUSSION: After 40 years of sometimes contradictory studies on clinical reasoning, the dual-process theory gives us many answers on how doctors think while making diagnoses and decisions. It highlights the importance of physicians' intuition and the high level of interaction between analytical and non-analytical processes. However, it has not received much attention in the medical education literature. The implications of dual-process models of reasoning in terms of medical education will be discussed.

A cognitive learning model of clinical nursing leadership.

Cognitive modeling of competencies is important to facilitate learning and evaluation. Clinical nursing leadership is considered a competency, as it is a "complex know-act" that students and nurses develop for the quality of care of patients and their families. Previous research on clinical leadership describes the attributes and characteristics of leaders and leadership, but, to our knowledge, a cognitive learning model (CLM) has yet to be developed. The purpose of our research was to develop a CLM of the clinical nursing leadership competency, from the beginning of a nursing program to expertise. An interpretative phenomenological study design was used 1) to document the experience of learning and practicing clinical leadership, and 2) to identify critical-learning turning points. Data was gathered from interviews with 32 baccalaureate students and 21 nurses from two clinical settings. An inductive analysis of data was conducted to determine the learning stages experienced: awareness of clinical leadership in nursing; integration of clinical leadership in actions; active leadership with patient/family; active leadership with the team; and, embedded clinical leadership extended to organizational level and beyond. The resulting CLM could have significant impact on both basic and continuing nursing education.