The oxidation of rocky planet surfaces and atmospheres, which arises from the twin forces of stellar nucleosynthesis and gravitational differentiation, is a universal process of key importance to ...habitability and exoplanet biosignature detection. Here we take a generalized approach to this phenomenon. Using a single parameter to describe the redox state, we model the evolution of terrestrial planets around nearby M stars and the Sun. Our model includes atmospheric photochemistry, diffusion and escape, line-by-line climate calculations, and interior thermodynamics and chemistry. In most cases, we find abiotic atmospheric buildup around M stars during the pre-main-sequence phase to be much less than calculated previously, because the planet's magma ocean absorbs most oxygen liberated from photolysis. However, loss of noncondensing atmospheric gases after the mantle solidifies remains a significant potential route to abiotic atmospheric subsequently. In all cases, we predict that exoplanets that receive lower stellar fluxes, such as LHS1140b and TRAPPIST-1f and g, have the lowest probability of abiotic buildup and hence may be the most interesting targets for future searches for biogenic . Key remaining uncertainties can be minimized in future by comparing our predictions for the atmospheres of hot, sterile exoplanets such as GJ1132b and TRAPPIST-1b and c with observations.
Solid polymer electrolyte (SPE) membranes are a critical component of high specific energy rechargeable Li-metal polymer (LMP) batteries. SPEs exhibit low volatility and thus increase the safety of ...Li-based batteries compared to current state-of-the-art Li-ion batteries that use flammable small-molecule electrolytes. However, most SPEs exhibit low ionic conductivity at room temperature, and often allow the growth of lithium dendrites that short-circuit the batteries. Both of these deficiencies are significant barriers to the commercialization of LMP batteries. Herein we report a cross-linked polyethylene/poly(ethylene oxide) SPE with both high ionic conductivity (>1.0 × 10–4 S/cm at 25 °C) and excellent resistance to dendrite growth. It has been proposed that SPEs with shear moduli of the same order of magnitude as lithium could be used to suppress dendrite growth, leading to increased lifetime and safety for LMP batteries. In contrast to the theoretical predictions, the low-modulus (G′ ≈ 1.0 × 105 Pa at 90 °C) cross-linked SPEs reported herein exhibit remarkable dendrite growth resistance. These results suggest that a high-modulus SPE is not a requirement for the control of dendrite proliferation.
Polymer–particle composites are used in virtually every field of technology. When the particles approach nanometer dimensions, large interfacial regions are created. In favorable situations, the ...spatial distribution of these interfaces can be controlled to create new hybrid materials with physical and transport properties inaccessible in their constituents or poorly prepared mixtures. This review surveys progress in the last decade in understanding phase behavior, structure, and properties of nanoparticle‐polymer composites. The review takes a decidedly polymers perspective and explores how physical and chemical approaches may be employed to create hybrids with controlled distribution of particles. Applications are studied in two contexts of contemporary interest: battery electrolytes and electrodes. In the former, the role of dispersed and aggregated particles on ion‐transport is considered. In the latter, the polymer is employed in such small quantities that it has been historically given titles such as binder and carbon precursor that underscore its perceived secondary role. Considering the myriad functions the binder plays in an electrode, it is surprising that highly filled composites have not received more attention. Opportunities in this and related areas are highlighted where recent advances in synthesis and polymer science are inspiring new approaches, and where newcomers to the field could make important contributions.
Polymer–particle composites are used in virtually every field of technology. When the particles approach nanometer dimensions, large interfacial regions are created that can be exploited for applications. The fundamental approaches and bottom‐up synthesis strategies for understanding and controlling nanoparticle dispersion in polymers are reviewed. Applications of these approaches for creating polymer–particle composite electrolytes and electrodes for energy storage are also considered.
High lithium transference number, t Li+ , electrolytes are desired for use in both lithium-ion and lithium metal rechargeable battery technologies. Historically, low t Li+ electrolytes have hindered ...device performance by allowing ion concentration gradients within the cell, leading to high internal resistances that ultimately limit cell lifetime, charging rates, and energy density. Herein, we report on the synthesis and electrochemical features of electrolytes based on nanoparticle salts designed to provide high t Li+ . The salts are created by cofunctionalization of metal oxide nanoparticles with neutral organic ligands and tethered lithium salts. When dispersed in a conducting fluid such as tetraglyme, they spontaneously form a charged, nanoporous network of particles at moderate nanoparticle loadings. Modification of the tethered anion chemistry from −SO3 – to −SO3BF3 – is shown to enhance ionic conductivity of the electrolytes by facilitating ion pair dissociation. At a particle volume fraction of 0.15, the electrolyte exists as a self-supported, nanoporous gel with an optimum ionic conductivity of 10–4 S/cm at room temperature. Galvanostatic polarization measurements on symmetric lithium metal cells containing the electrolyte show that the cell short circuit time, t SC, is inversely proportional to the square of the applied current density t SC ∼ J –2, consistent with previously predicted results for traditional polymer-in-salt electrolytes with low t Li+ . Our findings suggest that electrolytes with t Li+ ≈ 1 and good ion-pair dissociation delay lithium dendrite nucleation and may lead to improved lithium plating in rechargeable batteries with metallic lithium anodes.
Significance Cooperation is subject to social cheating. Cheats benefit from the activity of cooperators and gain a fitness advantage. One way higher organisms prevent infiltration by cheats is ...policing: Cooperators penalize cheats at some cost to themselves. Cooperating groups of bacteria are susceptible to social cheating, but little is known about bacterial policing. We have built on an understanding a quorum-sensing regulated cooperative activity in Pseudomonas aeruginosa to show that quorum sensing control of and resistance to cyanide production serves as a cheater policing mechanism. Understanding how bacteria cooperate and how they control social cheats has evolutionary implications, provides important insights about ways to control bacterial populations, and has ramifications with respect to synthetic system design.
The bacterium Pseudomonas aeruginosa is an opportunistic human pathogen that uses a quorum sensing signal cascade to activate expression of dozens of genes when sufficient population densities have been reached. Quorum sensing controls production of several key virulence factors, including secreted proteases such as elastase. Cooperating groups of bacteria growing on protein are susceptible to social cheating by quorum-sensing defective mutants. A possible way to restrict cheater emergence is by policing where cooperators produce costly goods to sanction or punish cheats. The P. aeruginosa LasR-LasI quorum sensing system controls genes including those encoding proteases and also those encoding a second quorum-sensing system, the RhlR-RhlI system, which controls numerous genes including those for cyanide production. By using RhlR quorum sensing mutants and cyanide synthesis mutants, we show that cyanide production is costly and cyanide-producing cooperators use cyanide to punish LasR-null social cheaters. Cooperators are less susceptible to cyanide than are LasR mutants. These experiments demonstrate policing in P. aeruginosa , provide a mechanistic understanding of policing, and show policing involves the cascade organization of the two quorum sensing systems in this bacterium.
Purpose: Epidermal growth factor receptor (EGFR) antibody therapy is established in patients with wild-type KRAS colorectal carcinoma; however, up to 50% of these patients do not respond to this ...therapy. To identify the possible causes
of this therapy failure, we searched for mutations in different EGFR-dependent signaling proteins and analyzed their distribution
patterns in primary tumors and corresponding metastases.
Experimental Design: Tumor tissues, macrodissected from tumor centers, invasion fronts ( n = 100), lymph nodes ( n = 55), and distant metastases ( n = 20), respectively, were subjected to DNA extraction and mutation analysis of KRAS, BRAF , and PIK3CA .
Results: Activating mutations were detected in 41% ( KRAS ), 7% ( BRAF ), and 21% ( PIK3CA ) of the primary tumors. By comparing tumor centers and invasion fronts, the intratumoral heterogeneity of KRAS, BRAF , and PIK3CA mutations was observed in 8%, 1%, and 5% of primary tumors, respectively. Heterogeneity between primary tumors and lymph
node metastases was found in 31% ( KRAS ), 4% ( BRAF ), and 13% ( PIK3CA ) of the cases. Heterogeneity between primary tumors and distant metastases was present in two patients (10%) for KRAS and one patient for PIK3CA (5%), but not for BRAF . Discordant results between primary tumors and metastases could markedly be reduced by testing the additional tumor samples.
Conclusions: Failure of EGFR antibody therapy in patients with wild-type KRAS colorectal cancer may result from activating BRAF or PIK3CA mutations and false-negative sequencing results caused by intratumoral heterogeneity. Due to the particularly high rates
of heterogeneity between primary tumors and lymph node metastases, the latter are least suitable for diagnostic mutation analysis.
Clin Cancer Res; 16(3); 790–9
Gasdermin-D (GSDMD) is the ultimate effector of pyroptosis, a form of programmed cell death associated with pathogen invasion and inflammation. After proteolytic cleavage by caspases, the GSDMD ...N-terminal domain (GSDMD
NT
) assembles on the inner leaflet of the plasma membrane and induces the formation of membrane pores. We use atomistic molecular dynamics simulations to study GSDMD
NT
monomers, oligomers, and rings in an asymmetric plasma membrane mimetic. We identify distinct interaction motifs of GSDMD
NT
with phosphatidylinositol-4,5-bisphosphate (PI(4,5)P
2
) and phosphatidylserine (PS) headgroups and describe their conformational dependence. Oligomers are stabilized by shared lipid binding sites between neighboring monomers acting akin to double-sided tape. We show that already small GSDMD
NT
oligomers support stable, water-filled, and ion-conducting membrane pores bounded by curled beta-sheets. In large-scale simulations, we resolve the process of pore formation from GSDMD
NT
arcs and lipid efflux from partial rings. We find that high-order GSDMD
NT
oligomers can crack under the line tension of 86 pN created by an open membrane edge to form the slit pores or closed GSDMD
NT
rings seen in atomic force microscopy experiments. Our simulations provide a detailed view of key steps in GSDMD
NT
-induced plasma membrane pore formation, including sublytic pores that explain nonselective ion flux during early pyroptosis.
Batteries based on alternatives to lithium are now of global research interest. Magnesium metal batteries are particularly attractive for their potential high energy density. Polymer electrolytes for ...high density rechargeable batteries have been sought for decades, due to their improved thermal stability compared with liquids and their lower density and cost compared with inorganic solids. Yet, little success has so far been realized in polymer electrolytes for magnesium metal batteries. In this review, the magnesium polymer electrolyte literature is comprehensively explored. Differences between requirements for lithium polymer and magnesium polymer batteries are discussed as well as the consequences on necessary considerations for impactful magnesium polymer electrolyte research.
Global sea surface temperatures (SSTs) are increasing, and in Hawai'i, rates of ocean warming are projected to double by the end of the 21st century. However, current nearshore warming trends and ...their possible impacts on intertidal communities are not well understood. This study represents the first investigation into the possible effects of rising SST on intertidal algal and invertebrate communities across the Main Hawaiian Islands (MHI). By utilizing citizen-science data coupled with high-resolution, daily SST satellite measurements from 12 intertidal sites across the MHI from 2004-2019, the response of intertidal algal and invertebrate abundance and community diversity to changes in SST was investigated across multiple spatial scales. Results show high rates of SST warming (0.40°C Decade-1) over this study's timeframe, similar to predicted rates of warming for Hawai'i by the end of the 21st century. Changes in abundance and diversity in response to SST were variable among intertidal sites, but differences in antecedent SST among intertidal sites were significantly associated with community dissimilarity. In addition, a statistically significant positive relationship was found between SST and Simpson's diversity index, and a significant relationship was also found between SST and the abundance of six dominant taxa. For five of these six dominant taxa, antecedent SSTs over the 6-12 months preceding sampling were the most influential for describing changes to abundance. The increase in community diversity in response to higher SSTs was best explained by temperatures in the 10 months preceding sampling, and the resultant decreased abundance of dominant turf algae. These results highlight rapidly warming nearshore SSTs in Hawai'i and the longer-term effects of antecedent SSTs as significant drivers of change within Hawaiian intertidal communities. Therefore, we suggest that future research and management should consider the possibility of lagging effects of antecedent SST on intertidal communities in Hawai'i and elsewhere.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Surface soil moisture plays an important role in the dynamics of land-atmosphere interactions and many current and upcoming models and satellite sensors. In situ data will be required to provide ...calibration and validation datasets. Therefore, there is a need for sensor networks at a variety of scales that provide near-real-time soil moisture and temperature data combined with other climate information for use in natural resource planning, drought assessment, water resource management, and resource inventory. The U.S. Department of Agriculture (USDA)-Natural Resources Conservation Service (NRCS)-National Water and Climate Center has established a continental-scale network to address this need, called the Soil Climate Analysis Network (SCAN). This ever-growing network has more than 116 stations located in 39 states, most of which have been installed since 1999. The stations are remotely located and collect hourly atmospheric, soil moisture, and soil temperature data that are available to the public online in near-real time. New stations are located on benchmark soils when possible. Future plans for the network include increasing the number of stations, improving on user-friendly data summaries, increasing data quality, and scaling the stations to the surrounding region. PUBLICATION ABSTRACT
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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