Ground and Airborne Methane Measurements Using Optical Parametric Amplifiers

We report on ground and airborne methane measurements with an active sensing instrument using widely tunable, seeded optical parametric generation (OPG). The technique has been used to measure methane, CO2, water vapor, and other trace gases in the near and mid-infrared spectral regions. Methane is a strong greenhouse gas on Earth and it is also a potential biogenic marker on Mars and other planetary bodies. Methane in the Earth's atmosphere survives for a shorter time than CO2 but its impact on climate change can be larger than CO2. Carbon and methane emissions from land are expected to increase as permafrost melts exposing millennial-age carbon stocks to respiration (aerobic-CO2 and anaerobic-CH4) and fires. Methane emissions from c1athrates in the Arctic Ocean and on land are also likely to respond to climate warming. However, there is considerable uncertainty in present Arctic flux levels, as well as how fluxes will change with the changing environment. For Mars, methane measurements are of great interest because of its potential as a strong biogenic marker. A remote sensing instrument that can measure day and night over all seasons and latitudes can localize sources of biogenic gas plumes produced by subsurface chemistry or biology, and aid in the search for extra-terrestrial life. In this paper we report on remote sensing measurements of methane using a high peak power, widely tunable optical parametric generator (OPG) operating at 3.3 micrometers and 1.65 micrometers. We have demonstrated detection of methane at 3.3 micrometers and 1650 nanometers in an open path and compared them to accepted standards. We also report on preliminary airborne demonstration of methane measurements at 1.65 micrometers

Participant retention practices in longitudinal clinical research studies with high retention rates

Abstract Background There is a need for improving cohort retention in longitudinal studies. Our objective was to identify cohort retention strategies and implementation approaches used in studies with high retention rates. Methods Longitudinal studies with ≥200 participants, ≥80% retention rates over ≥1 year of follow-up were queried from an Institutional Review Board database at a large research-intensive U.S. university; additional studies were identified through networking. Nineteen (86%) of 22 eligible studies agreed to participate. Through in-depth semi-structured interviews, participants provided retention strategies based on themes identified from previous literature reviews. Synthesis of data was completed by a multidisciplinary team. Results The most commonly used retention strategies were: study reminders, study visit characteristics, emphasizing study benefits, and contact/scheduling strategies. The research teams were well-functioning, organized, and persistent. Additionally, teams tailored their strategies to their participants, often adapting and innovating their approaches. Conclusions These studies included specialized and persistent teams and utilized tailored strategies specific to their cohort and individual participants. Studies’ written protocols and published manuscripts often did not reflect the varied strategies employed and adapted through the duration of study. Appropriate retention strategy use requires cultural sensitivity and more research is needed to identify how strategy use varies globally

Airborne Measurements of Atmospheric Methane Column Abundance Made Using a Pulsed IPDA Lidar

We report airborne measurements of the column abundance of atmospheric methane made over an altitude range of 3-11 km using a direct detection IPDA lidar with a pulsed laser emitting at 1651 nm. The laser transmitter was a tunable, seeded optical parametric amplifier (OPA) pumped by a Nd:YAG laser and the receiver used a photomultiplier detector and photon counting electronics. The results follow the expected changes with aircraft altitude and the measured line shapes and optical depths show good agreement with theoretical calculations

Ground and Airborne Methane Measurements with an Optical Parametric Amplifier

Here we report on measurements made with an improved CO2 Sounder lidar during the ASCENDS 2014 and 2016 airborne campaigns. The changes made to the 2011 version of the lidar included incorporating a rapidly wavelength-tunable, step-locked seed laser in the transmittter, using a much more sensitive HgCdTe APD detector andusing an analog digitizer with faster readout time in the receiver. We also improved the lidar's calibration approach and the XCO2 retrieval algorithm. The 2014 and 2016 flights were made over several types of topographic surfaces from3 to 12 km aircraft altitudes in the continental US. The results are compared to the XCO2 values computed from an airborne in situ sensor during spiral-down maneuvers. The 2014 results show significantly better performance and include measurement of horizontal gradients in XCO2 made over the Midwestern US that agree with chemistry transport models. The results from the 2016 airborne lidar retrievals show precisions of 0:7 parts per million (ppm) with 1 s averaging over desert surfaces, which is an improvement of about 8 times compared to similar measurements made in 2011. Measurements in 2016 were also made over fresh snow surfaces that have lower surface reflectance at the laser wavelengths. The results from both campaigns showed that the mean values of XCO2 retrieved from the lidar consistently agreed with those based on the in situ sensor to within 1 ppm. The improved precision and accuracy demonstrated in the 2014 and 2016 flights should benefit future airborne science ampaigns and advance the technique's readiness for a spacebased instrument

Physiological and Psychological Stress among Left Ventricular Assist Device Patients

Background: Advanced heart failure patients who face end-of-life may require a left ventricular assist device (LVAD) and emotional distress and psychological sequelae have been noted following device insertion. The purpose of this study was to describe physiological and psychological stress and to examine relationships between physiological and psychological stress response and outcomes among LVAD patients. Design: A descriptive observational design was used to describe physiological and psychological stress response among LVAD patients. Methods: Data was collected for patients more than 3 months post-LVAD implantation. Surveys, a Six Minute Walk Test and salivary specimens were collected. Relationships among indicators of stress and outcomes were examined using descriptive statistics and regression models. Results: The overall sample (N = 62) was male (78%), black (47%), and married (66%) with mean age 56.5± 13 years. Normal cortisol awakening response (n = 44) was seen in most participants (62%). There were no differences in cortisol, sleep, psychological stress or outcomes between bridge to transplant and destination therapy patients. However, when comparing the sample by perceived stress level, those with moderate to high perceived stress had worse depression, fatigue and more mal-adaptive coping. Poor sleep quality was correlated with increased psychological stress and QOL (p< 0.01). Regression analysis demonstrated perceived stress and fatigue were significant correlates of overall HRQOL (adj. R2=0.41, p < 0.0001). High social support moderated the relationship between perceived stress and QOL when controlling for fatigue (R2 = 0.49, p< 0.0001). Conclusions: This study reveals important links between physiological and psychological stress response among LVAD patients. The overall sample seemed to have a moderate stress profile: moderate perceived stress, low depressive symptoms and moderate fatigue, with a lot of social support. We did not find differences by implant strategy. In addition, higher perceived stress was related to worse sleep quality, depression, fatigue and mal-adaptive coping. Further, the influence of high levels of social support to improve QOL despite fatigue is confirmation of the need to continually assess the social support available to LVAD patients. Future research should investigate how interventions may be tailored to meet the psychosocial needs of this vulnerable population

Talking Around It: A Qualitative Study Exploring Dyadic Congruence in Managing the Uncertainty of Living With a Ventricular Assist Device.

BACKGROUND: Vital components of communicating goals of care and preferences include eliciting the patient and caregivers definition of quality of life, understanding meaningful activities and relationships, and exploring wishes for care at the end of life. Although current literature suggests framing conversations regarding end of life through the lens of meaning and quality of life, there is limited literature exploring dyadic congruence surrounding these important constructs among patients with ventricular assist devices (VADs) and their caregivers. OBJECTIVES: The purpose of this study was to explore congruence of VAD patient and caregiver perspectives regarding end of life, definitions of quality of life, and meaning in life while managing the uncertainty of living with a VAD. METHODS: We used thematic analysis to analyze semistructured qualitative interviews of 10 patient-caregiver dyads 3 to 12 months after VAD implantation. RESULTS: Three major themes were identified: (1) differing trajectories of uncertainty and worry, (2) a spectrum of end-of-life perspectives, and (3) enjoying everyday moments and independence. Overall, patients and caregivers had differing perspectives regarding uncertainty and end of life. Within-dyad congruence was most evident as dyads discussed definitions of meaning or quality of life. CONCLUSIONS: Dyadic perspectives on end of life, meaning in life, and quality of life can inform how palliative care and VAD teams approach conversations about planning for the end of life. Findings from this study can inform future shared decision-making interventions for patients living with VADs and their caregivers

What matters when doctors die: A qualitative study of family perspectives.

BackgroundThe challenges of supporting the end-of-life preferences of patients and their families have often been attributed to poor understanding of the patient's condition. Understanding how physicians, as patients, communicate their end-of-life care preferences to their families may inform shared decision making at end of life.ObjectivesThe purpose of this study was to understand what matters to families of physicians when decision making with and for a physician who is approaching the end of life.DesignCross-sectional qualitative design.ParticipantsWe conducted interviews with family members of deceased physicians.ApproachWe analyzed the data using the constant comparison method to identify themes.Key resultsFamily members (N = 26) rarely were unclear about the treatment preferences of physicians who died. Three overarching themes emerged about what matters most to physicians' families: (1) honoring preferences for the context of end-of-life care; (2) supporting the patient's control and dignity in care; and, (3) developing a shared understanding of preferences. Families struggled to make decisions and provide the care needed by the physicians at the end of life, often encountering significant challenges from the healthcare system.ConclusionsEven when disease and prognosis are well understood as in this group of physicians, families still experienced difficulties in end-of-life decision making. These findings highlight the need to specifically address preferences for caregiver, care setting and symptom management in shared end-of-life decision making conversations with patients and families

Multi-level correlates of received social support among heart transplant recipients in the international BRIGHT Study: a secondary analysis

Social support is critical in follow-up of patients after heart transplant (HTx) and positively influences well-being and clinical outcomes such as medication adherence. The purpose of this study was to (i) explore received social support variation (emotional and practical) in HTx recipients at country and centre level and (ii) to assess multi-level correlates.; Secondary data analysis of the multi-level cross-sectional BRIGHT study was conducted in 36 HTx centres in 11 countries. Received social support related to medication adherence was measured with emotional and practical sub-scales. The Conceptual Model of Social Networks and Health guided selection of patient, micro (interpersonal and psychosocial), meso (HTx centre) and macro-level (country health system) factors. Descriptive statistics, intraclass correlations, and sequential multiple ordinal mixed logistic regression analysis were used. A total of 1379 adult HTx recipients were included. Patient level correlates (female sex, living alone, and fewer depressive symptoms) and micro-level correlates (higher level of chronic disease management and trust in the healthcare team) were associated with better emotional social support. Similarly, patient level (living alone, younger age, and male sex), micro-level and meso-level (patient and clinician-rated higher level of chronic disease management) were associated with better practical social support. Social support varied at country and centre levels for emotional and practical dimensions.; Social support in HTx recipients varies by country, centre, and was associated with multi-level correlates. Qualitative and longitudinal studies are needed to understand influencing factors of social support for intervention development, improvement of social support, and clinical outcomes