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Comment on "The whole-soil carbon flux in response to warming"

2018-02-22T10:39:40-08:00

In a compelling study, Hicks Pries et al. (Reports, 31 March 2017, p. 1420) showed that 4°C warming enhanced soil CO2 production in the 1-meter soil profile, with all soil depths displaying similar temperature sensitivity (Q10). We argue that some caveats can be identified in their experimental approach and analysis, and that these critically undermine their conclusions and hence their claim that the strength of feedback between the whole-soil carbon and climate has been underestimated in terrestrial models.




Response to Comment on "The whole-soil carbon flux in response to warming"

2018-02-22T10:39:40-08:00

Temperature records and model predictions demonstrate that deep soils warm at the same rate as surface soils, contrary to Xiao et al.’s assertions. In response to Xiao et al.’s critique of our Q10 analysis, we present the results with all data points included, which show Q10 values of >2 throughout the soil profile, indicating that all soil depths responded to warming.




Science matters for the census

2018-02-22T10:39:40-08:00




News at a glance

2018-02-22T10:39:40-08:00




Europe's first artists were Neandertals

2018-02-22T10:39:40-08:00



















Just add science

2018-02-22T10:39:40-08:00




First up: Texas

2018-02-22T10:39:40-08:00




Keeping watch on the ocean

2018-02-22T10:39:40-08:00




Cancer detection: Seeking signals in blood

2018-02-22T10:39:40-08:00







Toward nitrogen-fixing plants

2018-02-22T10:39:40-08:00




Boron compounds tackle dinitrogen

2018-02-22T10:39:40-08:00




The Global Virome Project

2018-02-22T10:39:40-08:00




Earthquake or atomic bomb?

2018-02-22T10:39:40-08:00




Reason (and science) for hope

2018-02-22T10:39:40-08:00







Biocontrol of invasive carp: Risks abound

2018-02-22T10:39:40-08:00




Waterbirds targeted in Iran's wetlands

2018-02-22T10:39:40-08:00







The perfect postdoc

2018-02-22T10:39:40-08:00







Sending a canopy-wide message

2018-02-22T10:39:40-08:00




Improved spy tactics for single cells

2018-02-22T10:39:40-08:00




Memories of exposure

2018-02-22T10:39:40-08:00




Cancer organoids to model therapy response

2018-02-22T10:39:40-08:00




Acid reef-flux

2018-02-22T10:39:40-08:00




Neandertal cave art

2018-02-22T10:39:40-08:00




Irons in the fire

2018-02-22T10:39:40-08:00




Miniaturized optical ranging and tracking

2018-02-22T10:39:40-08:00




The great escape

2018-02-22T10:39:40-08:00




CO2 escaped from the deep

2018-02-22T10:39:40-08:00




Boron learns to give back to nitrogen

2018-02-22T10:39:40-08:00




Patterning a hyperbolic metasurface

2018-02-22T10:39:40-08:00




More than half the fish in the sea

2018-02-22T10:39:40-08:00




SEEK and you may find cancer earlier

2018-02-22T10:39:40-08:00




Putting distance between protein relatives

2018-02-22T10:39:40-08:00




Complete architecture of PRC2

2018-02-22T10:39:40-08:00




A path to multidrug resistance

2018-02-22T10:39:40-08:00







Quantum-secure satellite communication

2018-02-22T10:39:40-08:00




Cholesterol and stem cell proliferation

2018-02-22T10:39:40-08:00







How endothelial cells change identity

2018-02-22T10:39:40-08:00




Tackling the mechanisms behind depression

2018-02-22T10:39:40-08:00




A stringy magnet

2018-02-22T10:39:40-08:00




The shape of things to come

2018-02-22T10:39:40-08:00




Soliton microcomb range measurement

2018-02-22T10:39:40-08:00

Laser-based range measurement systems are important in many application areas, including autonomous vehicles, robotics, manufacturing, formation flying of satellites, and basic science. Coherent laser ranging systems using dual-frequency combs provide an unprecedented combination of long range, high precision, and fast update rate. We report dual-comb distance measurement using chip-based soliton microcombs. A single pump laser was used to generate dual-frequency combs within a single microresonator as counterpropagating solitons. We demonstrated time-of-flight measurement with 200-nanometer precision at an averaging time of 500 milliseconds within a range ambiguity of 16 millimeters. Measurements at distances up to 25 meters with much lower precision were also performed. Our chip-based source is an important step toward miniature dual-comb laser ranging systems that are suitable for photonic integration.




Ultrafast optical ranging using microresonator soliton frequency combs

2018-02-22T10:39:40-08:00

Light detection and ranging is widely used in science and industry. Over the past decade, optical frequency combs were shown to offer advantages in optical ranging, enabling fast distance acquisition with high accuracy. Driven by emerging high-volume applications such as industrial sensing, drone navigation, or autonomous driving, there is now a growing demand for compact ranging systems. Here, we show that soliton Kerr comb generation in integrated silicon nitride microresonators provides a route to high-performance chip-scale ranging systems. We demonstrate dual-comb distance measurements with Allan deviations down to 12 nanometers at averaging times of 13 microseconds along with ultrafast ranging at acquisition rates of 100 megahertz, allowing for in-flight sampling of gun projectiles moving at 150 meters per second. Combining integrated soliton-comb ranging systems with chip-scale nanophotonic phased arrays could enable compact ultrafast ranging systems for emerging mass applications.




Infrared hyperbolic metasurface based on nanostructured van der Waals materials

2018-02-22T10:39:40-08:00

Metasurfaces with strongly anisotropic optical properties can support deep subwavelength-scale confined electromagnetic waves (polaritons), which promise opportunities for controlling light in photonic and optoelectronic applications. We developed a mid-infrared hyperbolic metasurface by nanostructuring a thin layer of hexagonal boron nitride that supports deep subwavelength-scale phonon polaritons that propagate with in-plane hyperbolic dispersion. By applying an infrared nanoimaging technique, we visualize the concave (anomalous) wavefronts of a diverging polariton beam, which represent a landmark feature of hyperbolic polaritons. The results illustrate how near-field microscopy can be applied to reveal the exotic wavefronts of polaritons in anisotropic materials and demonstrate that nanostructured van der Waals materials can form a highly variable and compact platform for hyperbolic infrared metasurface devices and circuits.




Nitrogen fixation and reduction at boron

2018-02-22T10:39:40-08:00

Currently, the only compounds known to support fixation and functionalization of dinitrogen (N2) under nonmatrix conditions are based on metals. Here we present the observation of N2 binding and reduction by a nonmetal, specifically a dicoordinate borylene. Depending on the reaction conditions under which potassium graphite is introduced as a reductant, N2 binding to two borylene units results in either neutral (B2N2) or dianionic ([B2N2]2–) products that can be interconverted by respective exposure to further reductant or to air. The 15N isotopologues of the neutral and dianionic molecules were prepared with 15N-labeled dinitrogen, allowing observation of the nitrogen nuclei by 15N nuclear magnetic resonance spectroscopy. Protonation of the dianionic compound with distilled water furnishes a diradical product with a central hydrazido B2N2H2 unit. All three products were characterized spectroscopically and crystallographically.




Breakup of last glacial deep stratification in the South Pacific

2018-02-22T10:39:40-08:00

Stratification of the deep Southern Ocean during the Last Glacial Maximum is thought to have facilitated carbon storage and subsequent release during the deglaciation as stratification broke down, contributing to atmospheric CO2 rise. Here, we present neodymium isotope evidence from deep to abyssal waters in the South Pacific that confirms stratification of the deepwater column during the Last Glacial Maximum. The results indicate a glacial northward expansion of Ross Sea Bottom Water and a Southern Hemisphere climate trigger for the deglacial breakup of deep stratification. It highlights the important role of abyssal waters in sustaining a deep glacial carbon reservoir and Southern Hemisphere climate change as a prerequisite for the destabilization of the water column and hence the deglacial release of sequestered CO2 through upwelling.




Tracking the global footprint of fisheries

2018-02-22T10:39:40-08:00

Although fishing is one of the most widespread activities by which humans harvest natural resources, its global footprint is poorly understood and has never been directly quantified. We processed 22 billion automatic identification system messages and tracked >70,000 industrial fishing vessels from 2012 to 2016, creating a global dynamic footprint of fishing effort with spatial and temporal resolution two to three orders of magnitude higher than for previous data sets. Our data show that industrial fishing occurs in >55% of ocean area and has a spatial extent more than four times that of agriculture. We find that global patterns of fishing have surprisingly low sensitivity to short-term economic and environmental variation and a strong response to cultural and political events such as holidays and closures.




Coral reefs will transition to net dissolving before end of century

2018-02-22T10:39:40-08:00

Ocean acidification refers to the lowering of the ocean’s pH due to the uptake of anthropogenic CO2 from the atmosphere. Coral reef calcification is expected to decrease as the oceans become more acidic. Dissolving calcium carbonate (CaCO3) sands could greatly exacerbate reef loss associated with reduced calcification but is presently poorly constrained. Here we show that CaCO3 dissolution in reef sediments across five globally distributed sites is negatively correlated with the aragonite saturation state (ar) of overlying seawater and that CaCO3 sediment dissolution is 10-fold more sensitive to ocean acidification than coral calcification. Consequently, reef sediments globally will transition from net precipitation to net dissolution when seawater ar reaches 2.92 ± 0.16 (expected circa 2050 CE). Notably, some reefs are already experiencing net sediment dissolution.




U-Th dating of carbonate crusts reveals Neandertal origin of Iberian cave art

2018-02-22T10:39:40-08:00

The extent and nature of symbolic behavior among Neandertals are obscure. Although evidence for Neandertal body ornamentation has been proposed, all cave painting has been attributed to modern humans. Here we present dating results for three sites in Spain that show that cave art emerged in Iberia substantially earlier than previously thought. Uranium-thorium (U-Th) dates on carbonate crusts overlying paintings provide minimum ages for a red linear motif in La Pasiega (Cantabria), a hand stencil in Maltravieso (Extremadura), and red-painted speleothems in Ardales (Andalucía). Collectively, these results show that cave art in Iberia is older than 64.8 thousand years (ka). This cave art is the earliest dated so far and predates, by at least 20 ka, the arrival of modern humans in Europe, which implies Neandertal authorship.




Molecular structure of human P-glycoprotein in the ATP-bound, outward-facing conformation

2018-02-22T10:39:40-08:00

The multidrug transporter permeability (P)–glycoprotein is an adenosine triphosphate (ATP)–binding cassette exporter responsible for clinical resistance to chemotherapy. P-glycoprotein extrudes toxic molecules and drugs from cells through ATP-powered conformational changes. Despite decades of effort, only the structures of the inward-facing conformation of P-glycoprotein are available. Here we present the structure of human P-glycoprotein in the outward-facing conformation, determined by cryo–electron microscopy at 3.4-angstrom resolution. The two nucleotide-binding domains form a closed dimer occluding two ATP molecules. The drug-binding cavity observed in the inward-facing structures is reorientated toward the extracellular space and compressed to preclude substrate binding. This observation indicates that ATP binding, not hydrolysis, promotes substrate release. The structure evokes a model in which the dynamic nature of P-glycoprotein enables translocation of a large variety of substrates.




Patient-derived organoids model treatment response of metastatic gastrointestinal cancers

2018-02-22T10:39:40-08:00

Patient-derived organoids (PDOs) have recently emerged as robust preclinical models; however, their potential to predict clinical outcomes in patients has remained unclear. We report on a living biobank of PDOs from metastatic, heavily pretreated colorectal and gastroesophageal cancer patients recruited in phase 1/2 clinical trials. Phenotypic and genotypic profiling of PDOs showed a high degree of similarity to the original patient tumors. Molecular profiling of tumor organoids was matched to drug-screening results, suggesting that PDOs could complement existing approaches in defining cancer vulnerabilities and improving treatment responses. We compared responses to anticancer agents ex vivo in organoids and PDO-based orthotopic mouse tumor xenograft models with the responses of the patients in clinical trials. Our data suggest that PDOs can recapitulate patient responses in the clinic and could be implemented in personalized medicine programs.




Detection and localization of surgically resectable cancers with a multi-analyte blood test

2018-02-22T10:39:40-08:00

Earlier detection is key to reducing cancer deaths. Here, we describe a blood test that can detect eight common cancer types through assessment of the levels of circulating proteins and mutations in cell-free DNA. We applied this test, called CancerSEEK, to 1005 patients with nonmetastatic, clinically detected cancers of the ovary, liver, stomach, pancreas, esophagus, colorectum, lung, or breast. CancerSEEK tests were positive in a median of 70% of the eight cancer types. The sensitivities ranged from 69 to 98% for the detection of five cancer types (ovary, liver, stomach, pancreas, and esophagus) for which there are no screening tests available for average-risk individuals. The specificity of CancerSEEK was greater than 99%: only 7 of 812 healthy controls scored positive. In addition, CancerSEEK localized the cancer to a small number of anatomic sites in a median of 83% of the patients.




Structural principles that enable oligomeric small heat-shock protein paralogs to evolve distinct functions

2018-02-22T10:39:40-08:00

Oligomeric proteins assemble with exceptional selectivity, even in the presence of closely related proteins, to perform their cellular roles. We show that most proteins related by gene duplication of an oligomeric ancestor have evolved to avoid hetero-oligomerization and that this correlates with their acquisition of distinct functions. We report how coassembly is avoided by two oligomeric small heat-shock protein paralogs. A hierarchy of assembly, involving intermediates that are populated only fleetingly at equilibrium, ensures selective oligomerization. Conformational flexibility at noninterfacial regions in the monomers prevents coassembly, allowing interfaces to remain largely conserved. Homomeric oligomers must overcome the entropic benefit of coassembly and, accordingly, homomeric paralogs comprise fewer subunits than homomers that have no paralogs.




Single-cell bioluminescence imaging of deep tissue in freely moving animals

2018-02-22T10:39:40-08:00

Bioluminescence is a natural light source based on luciferase catalysis of its substrate luciferin. We performed directed evolution on firefly luciferase using a red-shifted and highly deliverable luciferin analog to establish AkaBLI, an all-engineered bioluminescence in vivo imaging system. AkaBLI produced emissions in vivo that were brighter by a factor of 100 to 1000 than conventional systems, allowing noninvasive visualization of single cells deep inside freely moving animals. Single tumorigenic cells trapped in the mouse lung vasculature could be visualized. In the mouse brain, genetic labeling with neural activity sensors allowed tracking of small clusters of hippocampal neurons activated by novel environments. In a marmoset, we recorded video-rate bioluminescence from neurons in the striatum, a deep brain area, for more than 1 year. AkaBLI is therefore a bioengineered light source to spur unprecedented scientific, medical, and industrial applications.




Structures of human PRC2 with its cofactors AEBP2 and JARID2

2018-02-22T10:39:40-08:00

Transcriptionally repressive histone H3 lysine 27 methylation by Polycomb repressive complex 2 (PRC2) is essential for cellular differentiation and development. Here we report cryo–electron microscopy structures of human PRC2 in a basal state and two distinct active states while in complex with its cofactors JARID2 and AEBP2. Both cofactors mimic the binding of histone H3 tails. JARID2, methylated by PRC2, mimics a methylated H3 tail to stimulate PRC2 activity, whereas AEBP2 interacts with the RBAP48 subunit, mimicking an unmodified H3 tail. SUZ12 interacts with all other subunits within the assembly and thus contributes to the stability of the complex. Our analysis defines the complete architecture of a functionally relevant PRC2 and provides a structural framework to understand its regulation by cofactors, histone tails, and RNA.




New Products

2018-02-22T10:39:40-08:00




Independent but not alone

2018-02-22T10:39:40-08:00




BAK/BAX macropores facilitate mitochondrial herniation and mtDNA efflux during apoptosis

2018-02-22T10:39:40-08:00

Mitochondrial apoptosis is mediated by BAK and BAX, two proteins that induce mitochondrial outer membrane permeabilization, leading to cytochrome c release and activation of apoptotic caspases. In the absence of active caspases, mitochondrial DNA (mtDNA) triggers the innate immune cGAS/STING pathway, causing dying cells to secrete type I interferon. How cGAS gains access to mtDNA remains unclear. We used live-cell lattice light-sheet microscopy to examine the mitochondrial network in mouse embryonic fibroblasts. We found that after BAK/BAX activation and cytochrome c loss, the mitochondrial network broke down and large BAK/BAX pores appeared in the outer membrane. These BAK/BAX macropores allowed the inner mitochondrial membrane to herniate into the cytosol, carrying with it mitochondrial matrix components, including the mitochondrial genome. Apoptotic caspases did not prevent herniation but dismantled the dying cell to suppress mtDNA-induced innate immune signaling.