Nonlinear effects of agricultural drought on vegetation productivity in the Yellow River Basin, China.

Agricultural drought (AD) is the main environmental factor affecting vegetation productivity (VP) in the Yellow River Basin (YRB). In recent years, the nonlinear effects of AD on VP in the YRB have attracted much attention. However, it is still unclear whether fluctuating AD will have complex nonlinear effects on VP in the YRB, and there are scant previous studies at large scale on whether there is a threshold for nonlinear effects of AD on VP in the YRB. Therefore, this study used a newly developed agricultural drought index to explore nonlinear effects on VP revealing the nonlinear effects of AD on VP in the YRB. First, we developed a kernel temperature vegetation drought index (kTVDI) based on kernel normalized difference vegetation index (kNDVI) and land surface temperature data to study the spatiotemporal variation of AD in the YRB. Second, we used GPP data from solar-induced chlorophyll fluorescence inversion as an indicator to explore the spatiotemporal variation of VP in the YRB. Finally, we used several statistical indicators and a distributed lag nonlinear model (DLNM) to analyze the nonlinear effect of AD on VP in the YRB. The results showed that AD decreased significantly during 2000-2020, mainly in the southeast of the Loess Plateau, while GPP increased significantly in 80.93 % of the YRB. Meanwhile, moderate and severe AD stress limited VP growth, with the negative effects gradually decreasing, while mild AD had an increasingly positive promoting effect on VP. AD stress resulted in a VP decrease of 69.78 %, and severe AD stress resulted in a VP decrease of 65.52 %, mainly distributed in the northern Loess and Ordos Plateau. AD had significant nonlinear effects on VP. The effects of moderate and severe AD on the sustained nonlinear lag of vegetation were more obvious, and those of moderate and severe AD on the nonlinear lag of VP were the largest when the lag was approximately 1 month and 7 months. The effect of AD on the nonlinear hysteresis of VP in YRB was significantly different under different vegetation types, and forests were more able to withstand longer and more severe droughts than grasslands and croplands. The results of the study provide a theoretical basis for evaluating AD and analyzing the nonlinear impact of AD on VP. This will provide scientific basis for studying the mechanism of drought effect on vegetation in other regions.

Greenhouse gas emissions and reduction strategies for the world's largest greenhouse gas emitters.

In the context of climate change, it is crucial to examine the contributions of leading countries in greenhouse gas (GHG) emissions. This research provides an overview of global GHG emissions from 1970 to 2022 for the world's most polluting countries: the United States, China, India, Russia, Brazil, Indonesia, Japan, Iran, Mexico, and Saudi Arabia. These countries collectively account for approximately 64% of GHG emissions. The aim is to understand the impact of various economic sectors, such as industry, energy, agriculture, and transportation, on overall emissions. The analysis highlights the disparity in per capita emissions, with smaller but major oil-producing countries in the Persian Gulf, such as Qatar and the United Arab Emirates, exhibiting high per capita emission levels, while more populated countries like the United States and South Korea show lower per capita values but significant total emission volumes. The study suggests that transitioning to renewable energy, improving energy efficiency in industry, promoting sustainable agriculture, reforestation, and electrifying transportation are key methods to achieve United Nations Sustainable Development Goals (UN SDG). Recommendations include encouraging technological innovations, implementing stringent government regulations and standards, and garnering active support for GHG reduction programs from governments, financial institutions, and the business community. The urgency is emphasized for global efforts to combat climate change for ensuring a sustainable future.

A Comparison between Predictions of the Miller-Macosko Theory, Estimates from Molecular Dynamics Simulations, and Long-Standing Experimental Data of the Shear Modulus of End-Linked Polymer Networks.

Long-standing experimental data on the elastic modulus of end-linked poly(dimethylsiloxane) (PDMS) networks are employed to corroborate the validity of the Miller-Macosko theory (MMT). The validity of MMT is also confirmed by molecular dynamics (MD) simulations that mimic the experimentally realized networks. It becomes apparent that for a network formed from bulk, where the fractions of the loops are small, it is sufficient to account for the topological details of a reference tree-like network, i.e., for its degree of completion, junction functionalities, and trapped entanglements, in order to practically predict the modulus. However, a mismatch is identified between the MMT and MD simulations in relating the fraction of the soluble material to the extent of reaction. A large contribution of entanglements to the modulus of PDMS networks prepared with short precursor chains is presented, suggesting that the elastic modulus of commonly used end-linked PDMS networks is in fact entanglement-dominated.

Measuring air pollution from the 2021 Canary Islands volcanic eruption.

The eruption of the Cumbre Vieja volcano on the island of La Palma (Canary Islands, Spain) began on September 19, 2021 and ended on December 13, 2021. It lasted continuously for 85 days with short periods of calm when lava did not exit the cone of the volcano. Vast amounts of volcanic material, including ash and gases, were emitted into the environment. This research focuses on these emissions. The main objective is to use available open-source data to examine the impact on regional and local air quality. Data from the following sources were used: 1) Copernicus Atmosphere Monitoring Service (CAMS) data was used to track the transfer of volcanic SO2 in the troposphere in early October over long distances from the source of the eruption, including Western and Eastern Europe, across the Atlantic Ocean and the Caribbean; 2) Data from ground monitoring stations measured the concentrations of SO2 and PM10 near the source; 3) AErosol RObotic NETwork (AERONET) data from the La Palma station that showed high Aerosol Optical Depth (AOD) values (over 0.4) during the active phase of emissions on September 24 and 28, as well as on October 3; 4) Ångström Exponent (AE) values indicated the presence of particles of different sizes. On September 24, high AE values (>1.5), showed the presence of fine-mode fraction scattering aerosols such as sulfates; 5) Cloud Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) data additionally confirmed the presence of sulfate and dust aerosols in the atmosphere over the region. However, the influence of Saharan dust on the atmosphere of the entire region could not be excluded. This research helps forecast air pollution resulting from large-scale volcanic eruptions and associated health risks to humans.

The evolution of dog diet and foraging: Insights from archaeological canids in Siberia.

Research on the evolution of dog foraging and diet has largely focused on scavenging during their initial domestication and genetic adaptations to starch-rich food environments following the advent of agriculture. The Siberian archaeological record evidences other critical shifts in dog foraging and diet that likely characterize Holocene dogs globally. By the Middle Holocene, body size reconstruction for Siberia dogs indicates that most were far smaller than Pleistocene wolves. This contributed to dogs' tendencies to scavenge, feed on small prey, and reduce social foraging. Stable carbon and nitrogen isotope analysis of Siberian dogs reveals that their diets were more diverse than those of Pleistocene wolves. This included habitual consumption of marine and freshwater foods by the Middle Holocene and reliance on C4 foods by the Late Holocene. Feeding on such foods and anthropogenic waste increased dogs' exposure to microbes, affected their gut microbiomes, and shaped long-term dog population history.

Modern Siberian dog ancestry was shaped by several thousand years of Eurasian-wide trade and human dispersal.

Dogs have been essential to life in the Siberian Arctic for over 9,500 y, and this tight link between people and dogs continues in Siberian communities. Although Arctic Siberian groups such as the Nenets received limited gene flow from neighboring groups, archaeological evidence suggests that metallurgy and new subsistence strategies emerged in Northwest Siberia around 2,000 y ago. It is unclear if the Siberian Arctic dog population was as continuous as the people of the region or if instead admixture occurred, possibly in relation to the influx of material culture from other parts of Eurasia. To address this question, we sequenced and analyzed the genomes of 20 ancient and historical Siberian and Eurasian Steppe dogs. Our analyses indicate that while Siberian dogs were genetically homogenous between 9,500 to 7,000 y ago, later introduction of dogs from the Eurasian Steppe and Europe led to substantial admixture. This is clearly the case in the Iamal-Nenets region (Northwestern Siberia) where dogs from the Iron Age period (∼2,000 y ago) possess substantially less ancestry related to European and Steppe dogs than dogs from the medieval period (∼1,000 y ago). Combined with findings of nonlocal materials recovered from these archaeological sites, including glass beads and metal items, these results indicate that Northwest Siberian communities were connected to a larger trade network through which they acquired genetically distinctive dogs from other regions. These exchanges were part of a series of major societal changes, including the rise of large-scale reindeer pastoralism ∼800 y ago.

Storing fish?: a dog's isotopic biography provides insight into Iron Age food preservation strategies in the Russian Arctic.

Analysis of individual animal bodies can provide numerous useful insights in archeology, including how humans provisioned such animals, which in turn informs on a variety of other past behaviors such as human dietary patterns. In this study, we conducted stable carbon (δ 13C) and nitrogen (δ 15N) isotope analysis of collagen and keratin from four types of tissues from a dog burial at the Ust'-Polui site in the Iamal region of Arctic Russia. Ust'-Polui is an Iron Age site located on the Lower Ob River, a major northern fishery characterized by extreme seasonal shifts in fish presence. During a 6-month period stretching over the coldest months of the year, fish are nearly entirely absent in the Lower Ob River. Despite this, the stable isotope compositions of the dog's bone and dentine collagen and hair and nail keratin all indicate a monotonous diet focusing on local fish. This pattern indicates the dog was provisioned year-round with fish. This was likely accomplished by mass harvesting of fish using nets or traps. Such fish were then processed and frozen for consumption during the non-fishing season. These findings suggest that people in the Ust'-Polui region also relied to some extent on fish throughout the year. Stored fish likely provided a dietary buffer for uneven returns from reindeer and bird hunting, both of which also are well-evidenced at the site.

Templated Assembly of Pore-forming Peptides in Lipid Membranes.

Pore-forming peptides are of interest due to their antimicrobial activity and ability to form gateways through lipid membranes. Chemical modification of these peptides makes it possible to arrange several peptide monomers into well-defined pore-forming structures using various templating strategies. These templated super-structures can exert antimicrobial activity at significantly lower total peptide concentration than their untemplated equivalents. In addition, the chemical moieties used for templating may be functionalized to interact specifically with targeted membranes such as those of pathogens or cancer cells. A range of molecular templates has been explored, including dimerization of pore-forming monomers, their covalent attachment to cyclodextrin, porphyrin or fullerene scaffolds as well as attachment of amino acid linkers or nucleic acid constructs to generate assemblies of 4 to 26 peptides or proteins. Compared to free peptide monomers, templated pore assemblies showed increased membrane affinity, prolonged open-state lifetimes of the pores and more frequent pore formation due to higher local concentration. These constructs are useful model systems for biophysical studies to understand porin and ion channel proteins and their mechanisms of insertion into lipid membranes. Recently designed DNA-templates are expanding the usefulness of templated pore assemblies beyond applications of cell killing and may include targeted drug delivery and accelerate the emerging field of single-molecule detection and characterization of biomolecules by nanopore-based resistive pulse sensing.

Three-Dimensional Geometric Morphometric Analysis of Fossil Canid Mandibles and Skulls.

Much of the fossil record for dogs consists of mandibles. However, can fossil canid mandibles be reliably identified as dogs or wolves? 3D geometric morphometric analysis correctly classifies 99.5% of the modern dog and wolf mandibles. However, only 4 of 26 Ust'-Polui fossil mandibles, a Russian Arctic site occupied from 250BCE to 150CE, were identified as dogs and none of the 20 Ivolgin mandibles, an Iron Age site in southern Russia, were identified as dogs. Three of the Ust'-Polui mandibles and 8 of the Ivolgin mandibles were identified as wolves. In contrast, all 12 Ivolgin skulls and 5 Ust'-Polui skulls were clearly identified as dogs. Only the classification of the UP6571 skull as a dog (Dog Posterior Probability = 1.0) was not supported by the typical probability. Other evidence indicates these canids were domesticated: they were located within human dwellings, remains at both sites have butchery marks indicating that they were consumed, and isotope analysis of canid and human remains from Ust'-Polui demonstrate that both were consuming freshwater protein; indicating that the humans were feeding the canids. Our results demonstrate that the mandible may not evolve as rapidly as the cranium and the mandible is not reliable for identifying early dog fossils.

Multispeed models in off-lattice Boltzmann simulations.

The lattice Boltzmann method is a highly promising approach to the simulation of complex flows. Here, we realize recently proposed multispeed lattice Boltzmann models [S. Chikatamarla, Phys. Rev. Lett. 97 190601 (2006)] by exploiting the flexibility offered by off-lattice Boltzmann methods. The approach is based on the general characteristic-based algorithm for off-lattice Boltzmann simulations that preserves all appealing properties of the standard lattice Boltzmann method while extending the method to unstructured grids. We show that the use of multispeed models indeed gives rise to major improvements in accuracy. The suggested approach thus renders truly large-scale off-lattice Boltzmann computations practical.

Finite element mapping for spring network representations of the mechanics of solids.

We present a general finite element mapping procedure for defining spring network representations of solid mechanics. The procedure is rigorous and equally suitable for setting regular and unstructured spring network models of generally anisotropic solids. We use the procedure to define close-packed triangular and simple cubic lattice spring models of isotropic 2D and 3D elastic media, respectively. We extend the study to heterogeneous solids and show that the mapped spring network approach constitutes an appealing route for incorporating subelement level constitutive equations.