The role of aerodynamic resistance in thermal remote sensing-based evapotranspiration models

Aerodynamic resistance (hereafter ra) is a preeminent variable in evapotranspiration (ET) modelling. The accurate quantification of ra plays a pivotal role in determining the performance and consistency of thermal remote sensing-based surface energy balance (SEB) models for estimating ET at local to regional scales. Atmospheric stability links ra with land surface temperature (LST) and the representation of their interactions in the SEB models determines the accuracy of ET estimates. The present study investigates the influence of ra and its relation to LST uncertainties on the performance of three structurally different SEB models. It used data from nine Australian OzFlux eddy covariance sites of contrasting aridity in conjunction with MODIS Terra and Aqua LST and leaf area index (LAI) products. Simulations of the sensible heat flux (H) and the latent heat flux (LE, the energy equivalent of ET in W/m2) from the SPARSE (Soil Plant Atmosphere and Remote Sensing Evapotranspiration), SEBS (Surface Energy Balance System) and STIC (Surface Temperature Initiated Closure) models forced with MODIS LST, LAI, and in-situ meteorological datasets were evaluated against flux observations in water-limited (arid and semi-arid) and energy-limited (mesic) ecosystems from 2011 to 2019. Our results revealed an overestimation tendency of instantaneous LE by all three models in the water-limited shrubland, woodland and grassland ecosystems by up to 50% on average, which was caused by an underestimation of H. Overestimation of LE was associated with discrepancies in ra retrievals under conditions of high atmospheric instability, during which uncertainties in LST (expressed as the difference between MODIS LST and in-situ LST) apparently played a minor role. On the other hand, a positive difference in LST coincided with low ra (high wind speeds) and caused a slight underestimation of LE at the water-limited sites. The impact of ra on the LE residual error was found to be of the same magnitude as the influence of LST uncertainties in the semi-arid ecosystems as indicated by variable importance in projection (VIP) coefficients from partial least squares regression above unity. In contrast, our results for the mesic forest ecosystems indicated minor dependency on ra for modelling LE (VIP \u3c 0.4), which was due to a higher roughness length and lower LST resulting in the dominance of mechanically generated turbulence, thereby diminishing the importance of buoyancy production for the determination of ra

Insights Into the Aerodynamic Versus Radiometric Surface Temperature Debate in Thermal-Based Evaporation Modeling

Global evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State-of-the-art one-source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non-parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio-temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research

Insights into the aerodynamic versus radiometric surface temperature debate in thermal-based evaporation modeling

Global evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State-of-the-art one-source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non-parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio-temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research

Vibration isolation active control techniques and testing in a micro-gravity environment

Since orbitting space stations do not provide a perfect micro-gravity environment, vibration isolation techniques must be employed for sensitive experiments, such as crystal growing. A non-contact approach using magnetic levitation for active vibration isolation has been developed previously that can be used in all micro-gravity situations. Using advanced controller techniques, it should be possible to lower the stiffness of the magnetic coupling below levels achievable by PID control. This thesis examines controlling magnetic levitation (MAGLEV) for improved vibration isolation on Earth and in a micro-gravity environment. Lorentz forces are used to levitate a large platform holding the application in an experimental system using this MAGLEV technology. This technology is described and two designs of it's application are presented. Vibration control techniques are investigated, with and Q-parameterization algorithms explained and employed in active control in a normal gravity environment. A smaller magnetically levitated wrist device is then described and employed in a coarse-fine approach to isolating acceleration disturbances in the microgravity environment provided by NASA's DC-9 performing parabolic flights. Results of the testing done on the flight is given and analyzed.Applied Science, Faculty ofElectrical and Computer Engineering, Department ofGraduat

The Effects of Delayed Visual Feedback on Postural Dynamics

We report on experiments and modeling of the interactions between delayed visual feedback and postural control in human quiet stance. A heuristic model is derived based on physiological and psychophysical parameters. The level of agreement found between the data and the model was found to be very good for power spectral densities, probability density functions and mean-squared displacements (or Hurst exponents). The stochastic delayed differential model identifies critical time scales of postural corrections. We also investigate properties of the model such as stability, small delay approximations and the power spectral density. Lastly, we use nonlinear time series techniques to investigate the temporal structure of the experimental postural dynamics. We propose the first dynamical model of visually assisted posture control

The contribution of Chinese-educated physicians to health care in the United States.

BACKGROUND:Migration of physicians has been a cause for global concern. In China, reforms of the higher education and healthcare systems have led to a shortage of postgraduate training positions relative to the number of medical graduates. Medical graduates opt for non-clinical roles or move abroad to pursue further training and practice opportunities. The impact of this physician migration is not known. This study quantifies where Chinese migrant physicians to the U.S. were educated, where they went to practice, and how these trends have changed over time. METHODS:We combined data on physician characteristics from the 2008 and 2017 American Medical Association Physician Masterfiles with demographic information from the Educational Commission for Foreign Medical Graduates. Using a repeated cross-sectional approach, we reviewed the available data, including citizenship at entry to medical school, medical school attended, practice specialty, and practice location. RESULTS:The number of Chinese-educated physicians (CEPs) to the United States (US) has increased over the past 10 years, from 3,878 in 2008 to 5,355 in 2017 (+38.1%). The majority held Chinese citizenship at entry to medical school (98.4% vs 97.1%) with the remainder being citizens of other East Asian nations. Of the Chinese citizens identified in 2008, 913 (19.3%) attended medical school outside of China; in 2017, 376 (6.7%) attended medical school outside of China, representing a decrease of 58.8%. Overall, in 2017, four Chinese medical schools provided 32.1% of all Chinese-educated physicians in the US. Over 50% of the CEPs were practicing in Internal Medicine, Anatomic/ Clinical Pathology, Anesthesiology, Family Medicine or Neurology. Compared with all IMGs, CEPs are more likely to be Anatomic/ Clinical Pathologists and Anesthesiologists. CEPs were concentrated in several states, including New York, California and Massachusetts. In 2017, a lower proportion of CEPs in the US healthcare workforce were in residency training, compared to 2008 (13.2% vs 22.8%). CONCLUSIONS:Unlike trends from some other South Asian countries, the number of CEPs in the US has increased over the past 10 years. Migration trends may vary depending on citizenship and country of medical school training. The majority of Chinese-educated graduates come to the US from relatively few medical schools. Fewer CEPs currently in residency training might indicate lower success rates in securing GME training in the US

Phenomenological model of auditory nerve population responses to cochlear implant stimulation

ISSN:0165-0270ISSN:1872-678

Burden of Pertussis in Individuals with a Diagnosis of Asthma: A Retrospective Database Study in England

Purpose: The impact of pertussis in individuals with asthma is not fully understood. We estimated the incidence, health care resource utilization (HCRU), and direct medical costs (DMC) of pertussis in patients with asthma. Patients and methods: In this retrospective cohort study, the incidence rate of pertussis (identified using diagnostic codes) among individuals aged ≥50 years with an asthma diagnosis was assessed during 2009-2018 using Clinical Practice Research Datalink and Hospital Episode Statistics databases. HCRU and DMC were compared - between patients with diagnoses of asthma and pertussis (asthma+/pertussis+) and propensity score-matched patients with a diagnosis of asthma without pertussis (asthma+/pertussis-) - in the months around the pertussis diagnosis (-6 to +11). Results: Among 687,105 individuals, 346 had a reported pertussis event (incidence rate: 9.6/100,000 person-years of follow-up; 95% confidence interval: 8.6-10.7). HCRU and DMC were assessed among 314 asthma+/pertussis+ patients and 1256 matched asthma+/pertussis- controls. Baseline HCRU was similar in both cohorts, but increases were observed in the asthma+/pertussis+ cohort from -6 to -1 month before to 2-5 months after diagnosis. Rates of accident and emergency visits, general practitioner (GP)/nurse visits, and GP prescriptions were 4.3-, 3.1-, and 1.3-fold, respectively, in the asthma+/pertussis+ vs asthma+/pertussis- cohorts during the month before diagnosis; GP/nurse visit rates were 2.0- and 1.2-fold during 0-2 and 2-5 months after diagnosis, respectively (all p<0.001). DMC was 1.9- and 1.6-fold during the month before and 2 months from diagnosis, respectively, in the asthma+/pertussis+ vs asthma+/pertussis- cohorts (both p<0.001). During months -1 to +11, DMC in the asthma+/pertussis+ cohort was £370 higher than in the asthma+/pertussis- controls. Conclusion: A pertussis diagnosis among adults aged ≥50 years with asthma resulted in significant increases in HCRU and DMC across several months around diagnosis, suggesting lengthy diagnosis times and highlighting the need for prevention strategies

Insights Into the Aerodynamic Versus Radiometric Surface Temperature Debate in Thermal-Based Evaporation Modeling

International audienceGlobal evaporation monitoring from Earth observation thermal infrared satellite missions is historically challenged due to the unavailability of any direct measurements of aerodynamic temperature. State-of-the-art one-source evaporation models use remotely sensed radiometric surface temperature as a substitute for the aerodynamic temperature and apply empirical corrections to accommodate for their inequality. This introduces substantial uncertainty in operational drought mapping over complex landscapes. By employing a non-parametric model, we show that evaporation can be directly retrieved from thermal satellite data without the need of any empirical correction. Independent evaluation of evaporation in a broad spectrum of biome and aridity yielded statistically significant results when compared with eddy covariance observations. While our simplified model provides a new perspective to advance spatio-temporal evaporation mapping from any thermal remote sensing mission, the direct retrieval of aerodynamic temperature also generates the highly required insight on the critical role of biophysical interactions in global evaporation research