We combine ultrafast electron diffraction and time-resolved terahertz spectroscopy measurements to link structure and electronic transport properties during the photoinduced insulator–metal ...transitions in vanadium dioxide. We determine the structure of the metastable monoclinic metal phase, which exhibits antiferroelectric charge order arising from a thermally activated, orbital-selective phase transition in the electron system. The relative contribution of the photoinduced monoclinic and rutile metals to the time-dependent and pump-fluence–dependent multiphase character of the film is established, as is the respective impact of these two distinct phase transitions on the observed changes in terahertz conductivity. Our results represent an important example of how light can control the properties of strongly correlated materials and demonstrate that multimodal experiments are essential when seeking a detailed connection between ultrafast changes in optical-electronic properties and lattice structure.
SnSe is a layered material that currently holds the record for bulk thermoelectric efficiency. The primary determinant of this high efficiency is thought to be the anomalously low thermal ...conductivity resulting from strong anharmonic coupling within the phonon system. Here we show that the nature of the carrier system in SnSe is also determined by strong coupling to phonons by directly visualizing polaron formation in the material. We employ ultrafast electron diffraction and diffuse scattering to track the response of phonons in both momentum and time to the photodoping of free carriers across the bandgap, observing the bimodal and anisotropic lattice distortions that drive carrier localization. Relatively large (18.7 Å), quasi-one-dimensional (1D) polarons are formed on the 300-fs timescale with smaller (4.2 Å) 3D polarons taking an order of magnitude longer (4 ps) to form. This difference appears to be a consequence of the profoundly anisotropic electron-phonon coupling in SnSe, with strong Fröhlich coupling only to zone-center polar optical phonons. These results demonstrate a high density of polarons in SnSe at optimal doping levels. Strong electron-phonon coupling is critical to the thermoelectric performance of this benchmark material and, potentially, high performance thermoelectrics more generally.
Metabolites from intestinal microbiota are key determinants of host-microbe mutualism and, consequently, the health or disease of the intestinal tract. However, whether such host-microbe crosstalk ...influences inflammation in peripheral tissues, such as the lung, is poorly understood. We found that dietary fermentable fiber content changed the composition of the gut and lung microbiota, in particular by altering the ratio of Firmicutes to Bacteroidetes. The gut microbiota metabolized the fiber, consequently increasing the concentration of circulating short-chain fatty acids (SCFAs). Mice fed a high-fiber diet had increased circulating levels of SCFAs and were protected against allergic inflammation in the lung, whereas a low-fiber diet decreased levels of SCFAs and increased allergic airway disease. Treatment of mice with the SCFA propionate led to alterations in bone marrow hematopoiesis that were characterized by enhanced generation of macrophage and dendritic cell (DC) precursors and subsequent seeding of the lungs by DCs with high phagocytic capacity but an impaired ability to promote T helper type 2 (TH2) cell effector function. The effects of propionate on allergic inflammation were dependent on G protein-coupled receptor 41 (GPR41, also called free fatty acid receptor 3 or FFAR3), but not GPR43 (also called free fatty acid receptor 2 or FFAR2). Our results show that dietary fermentable fiber and SCFAs can shape the immunological environment in the lung and influence the severity of allergic inflammation.
The CAZy auxiliary activity family 3 (AA3) comprises enzymes from the glucose-methanol-choline (GMC) family of oxidoreductases, which assist the activity of other AA family enzymes via their reaction ...products or support the action of glycoside hydrolases in lignocellulose degradation. The AA3 family is further divided into four subfamilies, which include cellobiose dehydrogenase, glucose oxidoreductases, aryl-alcohol oxidase, alcohol (methanol) oxidase, and pyranose oxidoreductases. These different enzymes catalyze a wide variety of redox reactions with respect to substrates and co-substrates. The common feature of AA3 family members is the formation of key metabolites such as H
2
O
2
or hydroquinones, which are required by other AA enzymes. The multiplicity of enzymatic functions in the AA3 family is reflected by the multigenicity of AA3 genes in fungi, which also depends on their lifestyle. We provide an overview of the phylogenetic, molecular, and catalytic properties of AA3 enzymes and discuss their interactions with other carbohydrate-active enzymes.
Carbon cycling in the coastal zone affects global carbon budgets and is critical for understanding the urgent issues of hypoxia, acidification, and tidal wetland loss. However, there are no regional ...carbon budgets spanning the three main ecosystems in coastal waters: tidal wetlands, estuaries, and shelf waters. Here we construct such a budget for eastern North America using historical data, empirical models, remote sensing algorithms, and process‐based models. Considering the net fluxes of total carbon at the domain boundaries, 59 ± 12% (± 2 standard errors) of the carbon entering is from rivers and 41 ± 12% is from the atmosphere, while 80 ± 9% of the carbon leaving is exported to the open ocean and 20 ± 9% is buried. Net lateral carbon transfers between the three main ecosystem types are comparable to fluxes at the domain boundaries. Each ecosystem type contributes substantially to exchange with the atmosphere, with CO2 uptake split evenly between tidal wetlands and shelf waters, and estuarine CO2 outgassing offsetting half of the uptake. Similarly, burial is about equal in tidal wetlands and shelf waters, while estuaries play a smaller but still substantial role. The importance of tidal wetlands and estuaries in the overall budget is remarkable given that they, respectively, make up only 2.4 and 8.9% of the study domain area. This study shows that coastal carbon budgets should explicitly include tidal wetlands, estuaries, shelf waters, and the linkages between them; ignoring any of them may produce a biased picture of coastal carbon cycling.
Plain Language Summary
A carbon budget for a particular site or region describes the inputs and outputs of carbon to that site or region as well as the processes that change carbon from one form to another. A carbon budget is needed to fully understand many important issues facing coastal waters. We constructed the carbon budget for coastal waters of eastern North America. We found that about 60% of the carbon entering the domain is from rivers and about 40% is from the atmosphere, while about 80% of the carbon leaving the domain goes to the open ocean and about 20% is buried. Transfers of carbon from wetlands to estuaries and from estuaries to the ocean were as important as transfers of carbon at the domain boundaries. Tidal wetlands and estuaries were found to be important to the carbon budget despite making up only 2.4 and 8.9% of the study domain area, respectively. This study shows that coastal carbon budgets should explicitly consider tidal wetlands, estuaries, shelf waters, and the linkages between them; ignoring any of them may produce a biased picture of coastal carbon cycling.
Key Points
Tidal wetlands, estuaries, and shelf waters each contribute substantially to the carbon budget of eastern North American coastal waters
Study region net ecosystem production, atmospheric uptake, and burial are 20.2 ± 4.4, 5.1 ± 2.4, and 2.5 ± 0.7 Tg C yr−1, respectively
Net lateral carbon fluxes between tidal wetlands, estuaries, and shelf waters are large terms in the carbon budget of eastern North American coastal waters
To assess the ability of a recently developed tricalcium silicate-based cement (Biodentine™) to induce reparative dentine synthesis and to investigate its capacity to modulate pulp cells TGF-β1 ...secretion.
Biodentine™ was directly applied onto the dental pulp in an entire human tooth culture model. After various culture periods, the interaction of the material with dental pulp tissue was analysed on tissue sections. The effect of increasing surface area of this material on TGF-β1 secretion was investigated on pulp cell cultures and compared with that of MTA, calcium hydroxide and Xeno(®) III adhesive resin. After performing artificial injuries on pulp cell cultures, the materials eluates were added for 24 h and then TGF-β1 secretion was quantified by ELISA. Controls were performed by incubating intact cells with the culture medium, while injured cells TGF-β1 level was used as the baseline value.
Biodentine™ induced mineralized foci formation early after its application. The mineralization appeared under the form of osteodentine and expressed markers of odontoblasts. Biodentine™ significantly increased TGF-β1 secretion from pulp cells (P < 0.03) independently of the contact surface increase. This increase was also observed with calcium hydroxide and MTA, but not with the resinous Xeno(®) III. The statistical analysis showed statistically significant differences between capping materials and the resinous Xeno(®) III (P < 0.001).
When Biodentine™ was applied directly onto the pulp, it induced an early form of reparative dentine synthesis, probably due to a modulation of pulp cell TGF-β1 secretion.
We report the INTernational Gamma-ray Astrophysics Laboratory (INTEGRAL) detection of the short gamma-ray burst GRB 170817A (discovered by Fermi-GBM) with a signal-to-noise ratio of 4.6, and, for the ...first time, its association with the gravitational waves (GWs) from binary neutron star (BNS) merging event GW170817 detected by the LIGO and Virgo observatories. The significance of association between the gamma-ray burst observed by INTEGRAL and GW170817 is 3.2 , while the association between the Fermi-GBM and INTEGRAL detections is 4.2 . GRB 170817A was detected by the SPI-ACS instrument about 2 s after the end of the GW event. We measure a fluence of (1.4 0.4 0.6) × 10−7 erg cm−2 (75-2000 keV), where, respectively, the statistical error is given at the 1 confidence level, and the systematic error corresponds to the uncertainty in the spectral model and instrument response. We also report on the pointed follow-up observations carried out by INTEGRAL, starting 19.5 hr after the event, and lasting for 5.4 days. We provide a stringent upper limit on any electromagnetic signal in a very broad energy range, from 3 keV to 8 MeV, constraining the soft gamma-ray afterglow flux to <7.1 × 10−11 erg cm−2 s−1 (80-300 keV). Exploiting the unique capabilities of INTEGRAL, we constrained the gamma-ray line emission from radioactive decays that are expected to be the principal source of the energy behind a kilonova event following a BNS coalescence. Finally, we put a stringent upper limit on any delayed bursting activity, for example, from a newly formed magnetar.
Dietary fiber protects against chronic inflammatory diseases by dampening immune responses through short-chain fatty acids (SCFAs). Here we examined the effect of dietary fiber in viral infection, ...where the anti-inflammatory properties of SCFAs in principle could prevent protective immunity. Instead, we found that fermentable dietary fiber increased survival of influenza-infected mice through two complementary mechanisms. High-fiber diet (HFD)-fed mice exhibited altered bone marrow hematopoiesis, characterized by enhanced generation of Ly6c− patrolling monocytes, which led to increased numbers of alternatively activated macrophages with a limited capacity to produce the chemokine CXCL1 in the airways. Blunted CXCL1 production reduced neutrophil recruitment to the airways, thus limiting tissue immunopathology during infection. In parallel, diet-derived SCFAs boosted CD8+ T cell effector function by enhancing cellular metabolism. Hence, dietary fermentable fiber and SCFAs set an immune equilibrium, balancing innate and adaptive immunity so as to promote the resolution of influenza infection while preventing immune-associated pathology.
Display omitted
•The fermentable fiber inulin and SCFAs protect against influenza-induced pathology•SCFAs alter hematopoiesis by increasing macrophage precursors in the bone marrow•SCFAs shape macrophage functionality to alleviate neutrophil-mediated tissue damage•SCFAs enhance CD8+ T cell functionality by altering their metabolism
Trompette et al. report that a diet rich in the fermentable fiber inulin and the associated metabolites—short-chain fatty acids—improve the response of mice to influenza infection by dampening deleterious immunopathology caused by neutrophils while enhancing anti-viral CD8+ T cell responses through a boost in T cell metabolism.
Changes in the pulmonary microbiota are associated with progressive respiratory diseases including chronic obstructive pulmonary disease (COPD). Whether there is a causal relationship between these ...changes and disease progression remains unknown.
To investigate the link between an altered microbiota and disease, we used a murine model of chronic lung inflammation that is characterized by key pathological features found in COPD and compared responses in specific pathogen-free (SPF) mice and mice depleted of microbiota by antibiotic treatment or devoid of a microbiota (axenic).
Mice were challenged with LPS/elastase intranasally over 4 weeks, resulting in a chronically inflamed and damaged lung. The ensuing cellular infiltration, histological damage, and decline in lung function were quantified.
Similar to human disease, the composition of the pulmonary microbiota was altered in diseased animals. We found that the microbiota richness and diversity were decreased in LPS/elastase-treated mice, with an increased representation of the genera Pseudomonas and Lactobacillus and a reduction in Prevotella. Moreover, the microbiota was implicated in disease development as mice depleted, or devoid, of microbiota exhibited an improvement in lung function, reduced inflammation, and lymphoid neogenesis. The absence of microbial cues markedly decreased the production of IL-17A, whereas intranasal transfer of fluid enriched with the pulmonary microbiota isolated from diseased mice enhanced IL-17A production in the lungs of antibiotic-treated or axenic recipients. Finally, in mice harboring a microbiota, neutralizing IL-17A dampened inflammation and restored lung function.
Collectively, our data indicate that host-microbial cross-talk promotes inflammation and could underlie the chronicity of inflammatory lung diseases.
PDF
