The progressive oxygenation of the Earth’s atmosphere was pivotal to the evolution of life, but the puzzle of when and how atmospheric oxygen (O₂) first approached modern levels (∼21%) remains ...unresolved. Redox proxy data indicate the deep oceans were oxygenated during 435–392 Ma, and the appearance of fossil charcoal indicates O₂ >15–17% by 420–400 Ma. However, existing models have failed to predict oxygenation at this time. Here we show that the earliest plants, which colonized the land surface from ∼470 Ma onward, were responsible for this mid-Paleozoic oxygenation event, through greatly increasing global organic carbon burial—the net long-term source of O₂. We use a trait-based ecophysiological model to predict that cryptogamic vegetation cover could have achieved ∼30% of today’s global terrestrial net primary productivity by ∼445 Ma. Data from modern bryophytes suggests this plentiful early plant material had a much higher molar C:P ratio (∼2,000) than marine biomass (∼100), such that a given weathering flux of phosphorus could support more organic carbon burial. Furthermore, recent experiments suggest that early plants selectively increased the flux of phosphorus (relative to alkalinity) weathered from rocks. Combining these effects in a model of long-term biogeochemical cycling, we reproduce a sustained +2‰ increase in the carbonate carbon isotope (δ13C) record by ∼445 Ma, and predict a corresponding rise in O₂ to present levels by 420–400 Ma, consistent with geochemical data. This oxygen rise represents a permanent shift in regulatory regime to one where fire-mediated negative feedbacks stabilize high O₂ levels.
The use of mesenchymal stem cells (MSC) for the treatment of cutaneous wounds is currently of enormous interest. However, the broad translation of cell therapies into clinical use is hampered by ...their efficacy, safety, manufacturing and cost. MSCs release a broad repertoire of trophic factors and immunomodulatory cytokines, referred to as the MSC secretome, that has considerable potential for the treatment of cutaneous wounds as a cell-free therapy. In this review, we outline the current status of MSCs as a treatment for cutaneous wounds and introduce the potential of the MSC secretome as a cell-free alternative for wound repair. We discuss the challenges and provide insights and perspectives for the future development of the MSC secretome as well as identify its potential clinical translation into a therapeutic treatment.
This handbook explores the applications of polymer foams, and the properties that make them suitable for so many applications, in the detail required by postgraduate students, researchers and the ...many industrial engineers and designers who work with polymer foam in industry. It covers the mechanical properties of foams and foam microstructure, processing of foams, mechanical testing and analysis (using Finite element analysis). In addition, it uniquely offers a broader perspective on the actual engineering of foams and foam based (or foam including) products by including nine detailed case studies which firmly plant the theory of the book in a real world context, making it ideal for both polymer engineers and chemists and mechanical engineers and product designers.* Complete coverage of the mechanical and design aspects of polymer foams from an acknowledged international expert: no other book is available with this breadth making this a plastics engineer's first choice for a single volume Handbook* Polymer foams are ubiquitous in modern life, used everywhere from running shoes to furniture, and this book includes nine extensive case studies covering each key class of application, including biomechanics* Offers a rigorous mechanical and microstructure perspective, plus a computer based chapter: Essential for engineers and designers alike.
Much of the information we hope to extract from the gravitational-wave signatures of compact binaries is only obtainable when we can accurately constrain the inclination of the orbital plane relative ...to the line of sight. In this paper, we discuss in detail a degeneracy between the measurement of the binary distance and inclination that limits our ability to accurately measure the inclination using gravitational waves alone. This degeneracy is exacerbated by the expected distribution of events in the universe, which leads us to prefer face-on systems at a greater distance. We use a simplified model that only considers the binary distance and orientation and show that this gives comparable results to the full parameter estimates obtained from the binary neutron star merger GW170817. For the advanced LIGO-Virgo network, it is only binaries that are close to edge-on, i.e., with inclinations 75°, that will be distinguishable from face-on systems. Extended networks that have good sensitivity to both gravitational-wave polarizations will only be able to constrain the inclination of a face-on binary at a signal-to-noise ratio of 20 to 45°. Even for loud signals with signal-to-noise ratios of 100, face-on signals will only be constrained to have inclinations . In the absence of observable higher modes or orbital precession, this degeneracy will dominate the mass measurements of binary black hole mergers at cosmological distances.
CrCoNi alloy exhibits a remarkable combination of strength and plastic deformation, even superior to the CrMnFeCoNi high-entropy alloy. We connect the magnetic and mechanical properties of CrCoNi, ...via a magnetically tunable phase transformation. While both alloys crystallize as single-phase face-centered-cubic (fcc) solid solutions, we find a distinctly lower-energy phase in CrCoNi alloy with a hexagonal close-packed (hcp) structure. Comparing the magnetic configurations of CrCoNi with those of other equiatomic ternary derivatives of CrMnFeCoNi confirms that magnetically frustrated Mn eliminates the fcc-hcp energy difference. This highlights the unique combination of chemistry and magnetic properties in CrCoNi, leading to a fcc-hcp phase transformation that occurs only in this alloy, and is triggered by dislocation slip and interaction with internal boundaries. This phase transformation sets CrCoNi apart from the parent quinary, and its other equiatomic ternary derivatives, and provides a new way for increasing strength without compromising plastic deformation.
We determined the structure of a complete, dimeric F1Fo-ATP synthase from yeast Yarrowia lipolytica mitochondria by a combination of cryo-EM and X-ray crystallography. The final structure resolves 58 ...of the 60 dimer subunits. Horizontal helices of subunit a in Fo wrap around the c-ring rotor, and a total of six vertical helices assigned to subunits a, b, f, i, and 8 span the membrane. Subunit 8 (A6L in human) is an evolutionary derivative of the bacterial b subunit. On the lumenal membrane surface, subunit f establishes direct contact between the two monomers. Comparison with a cryo-EM map of the F1Fo monomer identifies subunits e and g at the lateral dimer interface. They do not form dimer contacts but enable dimer formation by inducing a strong membrane curvature of ∼100°. Our structure explains the structural basis of cristae formation in mitochondria, a landmark signature of eukaryotic cell morphology.
Display omitted
•Cryo-EM structure of a yeast F1Fo-ATP synthase dimer•Inhibitor-free X-ray structure of the F1 head and rotor complex•Mechanism of ATP generation by rotary catalysis•Structural basis of cristae formation in the inner mitochondrial membrane
ATP synthases are complex macromolecular machines that supply most of the ATP in cells. Hahn et al. present the structure of a complete ATP synthase dimer, which provides insights into both the mechanism of these nanomotors and how they cause membrane bending to form cristae in the inner mitochondrial membrane.
The chloroplast adenosine triphosphate (ATP) synthase uses the electrochemical proton gradient generated by photosynthesis to produce ATP, the energy currency of all cells. Protons conducted through ...the membrane-embedded F
motor drive ATP synthesis in the F
head by rotary catalysis. We determined the high-resolution structure of the complete cF
F
complex by cryo-electron microscopy, resolving side chains of all 26 protein subunits, the five nucleotides in the F
head, and the proton pathway to and from the rotor ring. The flexible peripheral stalk redistributes differences in torsional energy across three unequal steps in the rotation cycle. Plant ATP synthase is autoinhibited by a β-hairpin redox switch in subunit γ that blocks rotation in the dark.
Micronutrient deficiencies account for an estimated one million premature deaths annually, and for some nations can reduce gross domestic product
by up to 11%, highlighting the need for food policies ...that focus on improving nutrition rather than simply increasing the volume of food produced
. People gain nutrients from a varied diet, although fish-which are a rich source of bioavailable micronutrients that are essential to human health
-are often overlooked. A lack of understanding of the nutrient composition of most fish
and how nutrient yields vary among fisheries has hindered the policy shifts that are needed to effectively harness the potential of fisheries for food and nutrition security
. Here, using the concentration of 7 nutrients in more than 350 species of marine fish, we estimate how environmental and ecological traits predict nutrient content of marine finfish species. We use this predictive model to quantify the global spatial patterns of the concentrations of nutrients in marine fisheries and compare nutrient yields to the prevalence of micronutrient deficiencies in human populations. We find that species from tropical thermal regimes contain higher concentrations of calcium, iron and zinc; smaller species contain higher concentrations of calcium, iron and omega-3 fatty acids; and species from cold thermal regimes or those with a pelagic feeding pathway contain higher concentrations of omega-3 fatty acids. There is no relationship between nutrient concentrations and total fishery yield, highlighting that the nutrient quality of a fishery is determined by the species composition. For a number of countries in which nutrient intakes are inadequate, nutrients available in marine finfish catches exceed the dietary requirements for populations that live within 100 km of the coast, and a fraction of current landings could be particularly impactful for children under 5 years of age. Our analyses suggest that fish-based food strategies have the potential to substantially contribute to global food and nutrition security.
The Community Earth System Model Version 2 (CESM2) has an equilibrium climate sensitivity (ECS) of 5.3 K. ECS is an emergent property of both climate feedbacks and aerosol forcing. The increase in ...ECS over the previous version (CESM1) is the result of cloud feedbacks. Interim versions of CESM2 had a land model that damped ECS. Part of the ECS change results from evolving the model configuration to reproduce the long‐term trend of global and regional surface temperature over the twentieth century in response to climate forcings. Changes made to reduce sensitivity to aerosols also impacted cloud feedbacks, which significantly influence ECS. CESM2 simulations compare very well to observations of present climate. It is critical to understand whether the high ECS, outside the best estimate range of 1.5–4.5 K, is plausible.
Key Points
The Community Earth System Model Version 2 (CESM2) has an Equilibrium Climate Sensitivity (ECS) of 5.3 K
ECS change is mostly due to atmospheric cloud feedbacks, with land surface impacts in intermediate versions
Processes that impact ECS through cloud feedbacks also impact aerosol forcing of climate
PDF
