Spatially explicit simulation of long-term boreal forest landscape dynamics: incorporating quantitative stand attributes

Spatial simulation models of long-term dynamics of forest landscapes are needed for investigating how different actual or potential disturbance regimes determine the structure and dynamics of forest landscapes. We propose a new approach to bridge the forest stand and landscape processes. Hence, while interested in the boreal forest dynamics at the landscape level, we develop a submodel of stand-level forest dynamics that responds to the landscape-level processes in a spatially explicit landscape model. Compared to the LANDIS model that we used as a starting point, our approach incorporates, in a spatially explicit and quantitative manner: (1) stand-level prediction of basal area and tree volume, and (2) seed dispersal, and sexual and asexual regeneration. Stand development is partly based on growth tables given as model input which means that stand submodel behavior is constrained within a reasonable range. We tested the approach in simulating the development of mixed boreal forests of Quebec, Canada. The simulations demonstrate that stand dynamics can be calibrated to match specific targets and that responses to changes in the initial conditions are realistic. This new modeling approach should allow addressing various theoretical questions and developing, as well as testing, alternative silvicultural and forest management scenarios

The Science Performance of JWST as Characterized in Commissioning

This paper characterizes the actual science performance of the James Webb Space Telescope (JWST), as determined from the six month commissioning period. We summarize the performance of the spacecraft, telescope, science instruments, and ground system, with an emphasis on differences from pre-launch expectations. Commissioning has made clear that JWST is fully capable of achieving the discoveries for which it was built. Moreover, almost across the board, the science performance of JWST is better than expected; in most cases, JWST will go deeper faster than expected. The telescope and instrument suite have demonstrated the sensitivity, stability, image quality, and spectral range that are necessary to transform our understanding of the cosmos through observations spanning from near-earth asteroids to the most distant galaxies.Comment: 5th version as accepted to PASP; 31 pages, 18 figures; https://iopscience.iop.org/article/10.1088/1538-3873/acb29

Numerical prediction of the best heel and trim of a Laser dinghy

As the Laser Olympic dinghy is one of the highest-level sail racing classes in the world, there is an interest in obtaining physical facts around the experience that already exist. For this reason, a numerical investigation has been carried out to find the best heel and trim angles in upwind sailing. Flat water is assumed. The core of the work is a newly developed Inverse Velocity Prediction Program (IVPP) that computes the required wind speed for a given boat speed. Input to the program is both available towing tank data and CFD results. By keeping speed constant interpolation is avoided in the very non-linear resistance-speed relation, reducing considerably the required number of CFD computations. Another reduction is obtained by a special technique for avoiding interpolation in leeway. Systematic CFD computations are carried out to find the optimum trim versus heel at the speeds 2, 3, 4, 5 knots. Using this relation the required wind speed at the four boat speeds can be expressed as a function of heel only. The heel angle corresponding to the smallest wind speed is the best. Knowing this, and the corresponding optimum trim, the position of the sailor is computed. It turns out that the predicted best positions correspond well with practical experience. However, the results highlight the benefit of a small heel in higher winds, which often is regarded as undesired by sailors

Numerical prediction of the best heel and trim of a Laser dinghy

As the Laser Olympic dinghy is one of the highest-level sail racing classes in the world, there is an interest in obtaining physical facts around the experience that already exist. For this reason, a numerical investigation has been carried out to find the best heel and trim angles in upwind sailing. Flat water is assumed. The core of the work is a newly developed Inverse Velocity Prediction Program (IVPP) that computes the required wind speed for a given boat speed. Input to the program is both available towing tank data and CFD results. By keeping speed constant interpolation is avoided in the very non-linear resistance-speed relation, reducing considerably the required number of CFD computations. Another reduction is obtained by a special technique for avoiding interpolation in leeway. Systematic CFD computations are carried out to find the optimum trim versus heel at the speeds 2, 3, 4, 5 knots. Using this relation the required wind speed at the four boat speeds can be expressed as a function of heel only. The heel angle corresponding to the smallest wind speed is the best. Knowing this, and the corresponding optimum trim, the position of the sailor is computed. It turns out that the predicted best positions correspond well with practical experience. However, the results highlight the benefit of a small heel in higher winds, which often is regarded as undesired by sailors

Drp1 loss-of-function reduces cardiomyocyte oxygen dependence protecting the heart from ischemia-reperfusion injury

Mitochondria are key organelles for ATP production in cardiomyocytes, which is regulated by processes of fission and fusion. We hypothesized that the mitochondria fusion protein dynamin-related protein 1 (Drp1) inhibition, attenuates ischemia-reperfusion (I/R) injury through modifications in mitochondrial metabolism. Rats were subjected to I/R through coronary artery ligation, and isolated cardiomyocytes were treated with an ischemia-mimicking solution. In vivo, cardiac function, myocardial infarction area, and mitochondrial morphology were determined, whereas in vitro, viability, mitochondrial membrane potential, intracellular ATP levels, and oxygen consumption rate (OCR) were assessed. In both models, an adenovirus expressing Drp1 dominant-negative K38A (Drp1K38A) was used to induce Drp1 loss-of-function. Our results showed that I/R stimulated mitochondrial fission. Myocardial infarction size and cell death induced by I/R were significantly reduced, whereas cardiac function after I/

Mitochondrial fission is required for cardiomyocyte hypertrophy mediated by a Ca2+-calcineurin signaling pathway

Cardiomyocyte hypertrophy has been associated with diminished mitochondrial metabolism. Mitochondria are crucial organelles for the production of ATP, and their morphology and function are regulated by the dynamic processes of fusion and fission. The relationship between mitochondrial dynamics and cardiomyocyte hypertrophy is still poorly understood. Here, we show that treatment of cultured neonatal rat cardiomyocytes with the hypertrophic agonist norepinephrine promotes mitochondrial fission (characterized by a decrease in mitochondrial mean volume and an increase in the relative number of mitochondria per cell) and a decrease in mitochondrial function. We demonstrate that norepinephrine acts through a1-adrenergic receptors to increase cytoplasmic Ca2+, activating calcineurin and promoting migration of the fission protein Drp1 (encoded by Dnml1) to mitochondria. Dominant-negative Drp1 (K38A) not only prevented mitochondrial fission, it also blocked hypertrophic growth of cardiomyocyt