Response of the thermohaline circulation to cold climates

A coupled atmosphere-ocean-sea ice-land surface-ice sheet model of intermediate complexity, the so-called McGill Paleoclimate Model, is employed to study the response of the thermohaline circulation (THC) to various global climate coolings, which are realized by increasing the present-day planetary emissivity to various values. Generally, it is found that the response of the THC to global cooling is nonlinear: For a slightly cold climate the THC in the North Atlantic and the Pacific upwelling become intensified. For a very cold climate the THC in the North Atlantic may be weakened or even collapsed. The associated Pacific upwelling for a very cold climate also becomes weak when the THC is weakened, and intermediate deep water may form in the Pacific when the THC is collapsed. Some support for this nonlinear response is found in recent paleoceanographic data. The reduced atmospheric poleward moisture transport due to the global cooling is mainly responsible for the intensification of the THC in the North Atlantic for a slightly cold climate. For a very cold climate the global cooling may lead to a decrease of the meridional surface density gradient and an increase of the vertical density difference (lower layer density minus upper layer density) in the deep water formation region, which can weaken or shut down the THC. It is the temperature-dependent part of the density differences that is mainly responsible for the weakening or shutting down of the THC. The potential influence of surface temperature changes must be taken into account for a full understanding of the role of the THC in the climate system

AI is a viable alternative to high throughput screening: a 318-target study

: High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery

Measurement of the B0^0 and B+^+ meson lifetimes with fully reconstructed hadronic final states

The B0 and B+ meson lifetimes have been measured in e+e- annihilation data collected in 1999 and 2000 with the BABAR detector at center-of-mass energies near the Upsilon(4S) resonance. Events are selected in which one B meson is fully reconstructed in a hadronic final state while the second B meson is reconstructed inclusively. A combined fit to the B0 and the B+ decay time difference distributions yields tau_{B0} = 1.546 +/- 0.032 (stat) +/- 0.022(syst) ps, tau_{B+} = 1.673 +/- 0.032 (stat) +/- 0.023 (syst) ps and tau_{B+} / tau_{B0} = 1.082 +/- 0.026 (stat) +/- 0.012 (syst

Ion homeostasis in the Chloroplast

peer reviewedThe chloroplast is an organelle of high demand for macro- and micro-nutrient ions, which are required for the maintenance of the photosynthetic process. To avoid deficiency while preventing excess, homeostasis mechanisms must be tightly regulated. Here, we describe the needs for nutrient ions in the chloroplast and briefly highlight their functions in the chloroplastidial metabolism. We further discuss the impact of nutrient deficiency on chloroplasts and the acclimation mechanisms that evolved to preserve the photosynthetic apparatus. We finally present what is known about import and export mechanisms for these ions. Whenever possible, a comparison between cyanobacteria, algae and plants is provided to add an evolutionary perspective to the description of ion homeostasis mechanisms in photosynthesis