A comparison of different inverse carbon flux estimation approaches for application on a regional domain

We have implemented six different inverse carbon flux estimation methods in a regional carbon dioxide (CO<sub>2</sub>) flux modeling system for the Netherlands. The system consists of the Regional Atmospheric Mesoscale Modeling System (RAMS) coupled to a simple carbon flux scheme which is run in a coupled fashion on relatively high resolution (10 km). Using an Ensemble Kalman filter approach we try to estimate spatiotemporal carbon exchange patterns from atmospheric CO<sub>2</sub> mole fractions over the Netherlands for a two week period in spring 2008. The focus of this work is the different strategies that can be employed to turn first-guess fluxes into optimal ones, which is known as a fundamental design choice that can affect the outcome of an inversion significantly. <br><br> Different state-of-the-art approaches with respect to the estimation of net ecosystem exchange (NEE) are compared quantitatively: (1) where NEE is scaled by one linear multiplication factor per land-use type, (2) where the same is done for photosynthesis (GPP) and respiration (<i>R</i>) separately with varying assumptions for the correlation structure, (3) where we solve for those same multiplication factors but now for each grid box, and (4) where we optimize physical parameters of the underlying biosphere model for each land-use type. The pattern to be retrieved in this pseudo-data experiment is different in nearly all aspects from the first-guess fluxes, including the structure of the underlying flux model, reflecting the difference between the modeled fluxes and the fluxes in the real world. This makes our study a stringent test of the performance of these methods, which are currently widely used in carbon cycle inverse studies. <br><br> Our results show that all methods struggle to retrieve the spatiotemporal NEE distribution, and none of them succeeds in finding accurate domain averaged NEE with correct spatial and temporal behavior. The main cause is the difference between the structures of the first-guess and true CO<sub>2</sub> flux models used. Most methods display overconfidence in their estimate as a result. A commonly used daytime-only sampling scheme in the transport model leads to compensating biases in separate GPP and <i>R</i> scaling factors that are readily visible in the nighttime mixing ratio predictions of these systems. <br><br> Overall, we recommend that the estimate of NEE scaling factors should not be used in this regional setup, while estimating bias factors for GPP and <i>R</i> for every grid box works relatively well. The biosphere parameter inversion performs good compared to the other inversions at simultaneously producing space and time patterns of fluxes and CO<sub>2</sub> mixing ratios, but non-linearity may significantly reduce the information content in the inversion if true parameter values are far from the prior estimate. Our results suggest that a carefully designed biosphere model parameter inversion or a pixel inversion of the respiration and GPP multiplication factors are from the tested inversions the most promising tools to optimize spatiotemporal patterns of NEE

MUSCULOSKELETAL MODELLING OF HANDCYCLING MOTION ON AN EROGOMETER: INFLUENCE OF CRANK POSITION ON TRAINING PURPOSES.

The objective of this study was to examine the influence of crank position during hand cycling on muscle forces and Glenohumeral joint reaction forces. Twelve male subjects performed 16 trials with variation in crank parameters. 3D motion capturing (Vicon) and custom made handlebars (Kistler force sensors) were used to determine kinematic and kinetic data. Musculoskeletal modelling (AnyBody) was used for calculations of joint contact and muscle forces. Significant difference was found between settings and muscle forces (p=0.006) and Glenohumeral joint reaction forces (p=0.000). For the m. Brachialis, the m. Latissimus Dorsi and the m. Deltoideus Scapularis, an optimal setting was found. The antero- posterior and distraction force are minimized with horizontal handlebars, a small crank width and long crank arms

HANDLE REACTION FORCES IN HANDCYCLING ON AN ERGOMETER

The purpose of this study was to develop a three dimensional sensitive dynamometric handcycling grip and to examine the influence of grip positioning on hand contact forces during low resistance arm cranking. Contact forces of ten male subjects were measured at a neutral grip position, increased crank arm length and increased grip width. The findings suggest a pushdown-pull cranking pattern. Therefore shoulder extensors and elbow flexors may have an important role in force generation. Changes at the grip position have a clear effect on grip contact forces, thus the interaction is complex due to subject specific variations. The data sets the basis for an inverse dynamic model and provides information about involved muscles which is helpful for the training process and injury prevention

Local diagnostic reference levels for skeletal surveys in suspected physical child abuse

NoIntroduction: The purpose was to determine if an age based, local diagnostic reference level for paediatric skeletal surveys could be established using retrospective data. Methods: All children below two years of age referred for a primary skeletal survey as a result of suspected physical abuse during 2017 or 2018 (n ¼ 45) were retrospectively included from a large Danish university hospital. The skeletal survey protocol included a total of 33 images. Dose Area Product (DAP) and acquisition parameters for all images were recorded from the Picture Archival and Communication System (PACS) and effective dose was estimated. The 75th percentile for DAP was considered as the diagnostic reference level (DRL). Results: The 75th percentile for DAP was 314 mGy*cm2 , 520 mGy*cm2 and 779 mGy*cm2 for children <1 month, 1e11 months and 12 < 24 months of age respectively. However, only the age group 1e11 months had a sufficient number of children (n ¼ 27) to establish a local DRL. Thus, for the other groups the DAP result must be interpreted with caution. Effective dose was 0.19, 0.26 and 0.18 mSv for children <1, 1e11 months and 12 < 24 months of age respectively. Conclusion: For children between 1 and 11 months of age, a local diagnostic reference level of 520 mGy*cm2 was determined. This may be used as an initial benchmark for primary skeletal surveys as a result of suspected physical abuse for comparison and future discussion. Implications for practice: While the data presented reflects the results of a single department, the suggested diagnostic reference level may be used as a benchmark for other departments when auditing skeletal survey radiation dose

Non-Equilibrium Fractionation Factors for D/H and 18O/16O During Oceanic Evaporation in the North-West Atlantic Region

Ocean isotopic evaporation models, such as the Craig-Gordon model, rely on the description of nonequilibrium fractionation factors that are, in general, poorly constrained. To date, only a few gradient-diffusion type measurements have been performed in ocean settings to test the validity of the commonly used parametrization of nonequilibrium isotopic fractionation during ocean evaporation. In this work, we present 6 months of water vapor isotopic observations collected from a meteorological tower located in the northwest Atlantic Ocean (Bermuda) with the objective of estimating nonequilibrium fractionation factors (k, ‰) for ocean evaporation and their wind speed dependency. The Keeling Plot method and Craig-Gordon model combination were sensitive enough to resolve nonequilibrium fractionation factors during evaporation resulting into mean values of k18 = 5.2 ± 0.6‰ and k2 = 4.3 ± 3.4‰. Furthermore, we evaluate the relationship between k and 10-m wind speed over the ocean. Such a relationship is expected from current evaporation theory and from laboratory experiments made in the 1970s, but observational evidence is lacking. We show that (a) in the observed wind speed range [0–10 m s−1], the sensitivity of k to wind speed is small, in the order of −0.2‰ m−1 s for k18, and (b) there is no empirical evidence for the presence of a discontinuity between smooth and rough wind speed regime during isotopic fractionation, as proposed in earlier studies. The water vapor d-excess variability predicted under the closure assumption using the k values estimated in this study is in agreement with observations over the Atlantic Ocean.publishedVersio

Waiting in the queue on Hotelling’s Main Street

We consider a variant of Hotelling’s location model that was proposed by Kohlberg (1983): when choosing a firm, consumers take travel time and also (expected) waiting time, which again depends on the number of consumers choosing that firm, into consideration. If we assume that firms are symmetric, then we show that a subgame perfect equilibrium exists if there is an even, but small, number of firms and no subgame perfect equilibrium exists if there is an odd, but small, number of firms. Further, we illustrate by means of examples what other subgame perfect equilibria exist if we allow for asymmetric firms

Claim games for estate division problems

This paper considers the estate division problem from a non-cooperative perspective. The integer claim game initiated by O'Neill (1982) and extended by Atlamaz et al. (2011) is generalized by considering different sharing rules to divide every interval among the claimants. For problems with an estate larger than half of the total entitlements, we show that every sharing rule satisfying four fairly general axioms yields the same set of Nash equilibrium profiles and corresponding payoffs. Every rule that always results in such equilibrium payoff vector is characterized by the properties minimal rights first and lower bound of degree half. Well-known examples are the Talmud rule, the adjusted proportional rule and the random arrival rule. Then our focus turns to more specific claim games, i.e. games that use the constrained equal awards rule, the Talmud rule, or the constrained equal losses rule as a sharing rule. Also a variation on the claim game is considered by allowing for arbitrary instead of integer claims

Constrained Willmore Surfaces

Constrained Willmore surfaces are conformal immersions of Riemann surfaces that are critical points of the Willmore energy $W=\int H^2$ under compactly supported infinitesimal conformal variations. Examples include all constant mean curvature surfaces in space forms. In this paper we investigate more generally the critical points of arbitrary geometric functionals on the space of immersions under the constraint that the admissible variations infinitesimally preserve the conformal structure. Besides constrained Willmore surfaces we discuss in some detail examples of constrained minimal and volume critical surfaces, the critical points of the area and enclosed volume functional under the conformal constraint.Comment: 17 pages, 8 figures; v2: Hopf tori added as an example, minor changes in presentation, numbering changed; v3: new abstract and appendix, several changes in presentatio