A dynamic-temperature operation strategy is proposed for SOFC systems, in which the cell temperature varies rapidly to match the SOFC stack power output to a dynamic load requirement. It is ...anticipated that this operation strategy may have benefits for system efficiency, size, and cost for applications with dynamic power load. Metal-supported SOFCs (MS-SOFCs) are operated continuously at 0.7 V while the temperature is varied rapidly between 675 and 800 °C or 670 and 720 °C. During the initial thermal excursion, the current density increases from 0.82 to 1.95 A cm−2 in 6.6 min for 675–800 °C, and from 1.0 to 1.63 A cm−2 in 5.4 min for 670–720 °C. Cells are subjected to continuous dynamic temperature operation for more than 100 cycles.
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•Dynamic-temperature operation proposed as new SOFC operation mode.•Metal-supported SOFCs are operated continuously while temperature is cycled.•Current doubles in a few minutes by rapidly increasing temperature.
Symmetric-structure metal-supported solid oxide fuel cells (MS-SOFC) with YSZ electrolyte are fabricated with porous YSZ backbone electrodes, stainless steel supports, and infiltrated catalysts on ...both anode and cathode side. Durability towards aggressive thermal and redox cycling, and long-term operation is assessed. Many sealing material candidates are screened for compatibility with the cell materials and operating conditions, and a commercial sealing glass, GM31107, is selected. LSM/SDCN cells are then subjected to 200 very fast thermal cycles and 20 complete redox cycles, with minimal impact to cell performance. LSM/SDCN and SDCN/SDCN cells are operated for more than 1200 h at 700 °C. The seal and cell hermeticity is maintained, and cell ohmic impedance does not change significantly during operation. Electrode polarization increases during operation, leading to significant degradation of the cell performance. In-operando EIS and post-mortem SEM/EDS analysis suggest that catalyst coarsening and cathode Cr deposition are the dominant degradation modes.
•Durability of metal-supported SOFCs with stainless steel on both sides is assessed.•Tolerance to deep redox cycling and 15-min heat-up is demonstrated.•Cells are operated at 700 °C for 1200 h•Postmortem suggests catalyst coarsening and Cr deposition dominate degradation.
Desertification of the Sahel region has been debated for decades, while the concept of a "re-greening" Sahel appeared with satellite remote sensing data that allowed vegetation monitoring across wide ...regions and over increasingly long series of years (nowadays 30 years with the GIMMS-3g dataset). However, the scarcity of long-term field observations of vegetation in the Sahel prevents ground validation and deeper analysis of such trends. After assessing the consistency of the new GIMMS-3g NDVI product by comparison to three other AVHRR-NDVI datasets and MODIS NDVI, regional GIMMS-3g NDVI trends over 1981-2011 are analyzed. Trends are found positive and statistically significant almost everywhere in Sahel over the 1981-2011 period. Long-term field observations of the aboveground herbaceous layer mass have been collected within the Gourma region in Mali (1984-2011) and within the Fakara region in western Niger (1994-2011). These observations sample ecosystem and soil diversity, thus enabling estimation of averaged values representative of the Gourma and Fakara. NDVI measurements are found in good agreement with field observations, both over the Gourma and Fakara regions where re-greening and negative trends are observed respectively. A linear regression analysis performed between spatially averaged seasonal NDVI and a weighted average of field measurements explains 59% of the variability for the Gourma region over 1984-2011, and 38% for the Fakara region over 1994-2011. In the Gourma, which is a pastoral region, the re-greening trend is mainly observed over sandy soils, and attests for the ecosystem's resilience to the 1980s' drought, able to react to the more favorable rainfall of the 1990s and 2000s. However, contrasted changes in the landscape's functioning have occurred locally. An increase in erosion and run-off processes in association with decreasing or stable vegetation cover was observed over shallow soils, which occupy 30% of the area. In the agro-pastoral Fakara, the decreasing trends observed both from satellite NDVI and field assessments of herbaceous mass are hardly explained by rainfall. These results give confidence in the dominant positive trends in Sahelian greenness, but indicate that degradation trends can also be observed, both in situ and from satellite time series.
Lying behavior in dairy cattle can provide insight into how cows interact with their environment. Although lying behavior is a useful indicator of cow comfort, it can be time consuming to measure. In ...response to these time constraints, using data loggers to automate behavioral recording has become increasingly common. We tested the accuracy of the Onset Pendant G data logger (Onset Computer Corporation, Bourne, MA) for measuring lying behavior in dairy cattle (n=24 cows; 12 in each of 2 experiments). Cows wore the logger on the lateral (experiment 1) or medial (experiment 2) side of the hind leg above the metatarsophalangeal joint. Loggers recorded behavior at 4 sampling intervals (6, 30, 60, and 300s) for at least 1.5 d. Data were smoothed using 3 editing methods to examine the effects of short, potentially erroneous readings. For this purpose, Microsoft Excel macros (Microsoft Corp., Redmond, WA) converted readings (i.e., lying events bordered by standing or vice versa) occurring singly or in consecutive runs of ≤2 or ≤6. Behavior was simultaneously recorded with digital video equipment. The logger accurately measured lying and standing. For example, predictability, sensitivity, and specificity were >99% using 30-s sampling and the single-event filter compared with continuously scored video recordings. The 6- and 30-s sampling intervals were comparable for all aspects of lying behavior when short events were filtered from the data set. Estimates of lying time generated from the 300-s interval unfiltered regimen were positively related (R2 ≥ 0.99) to estimates of lying time from video, but this sampling regimen overestimated the number of lying bouts. This is likely because short standing and lying bouts were missed (12 and 34% of lying and standing bouts were <300s in experiment 1 and 2, respectively). In summary, the data logger accurately measured all aspects of lying behavior when the sampling interval was ≤30s and when short readings of lying and standing were filtered from the data set.
The mass adoption of electric vehicles is hindered by the inadequate extreme fast charging (XFC) performance (i.e., less than 15 min charging time to reach 80% state of charge) of commercial ...high-specific-energy (i.e., >200 Wh/kg) lithium-ion batteries (LIBs). Here, to enable the XFC of commercial LIBs, we propose the regulation of the battery's self-generated heat via active thermal switching. We demonstrate that retaining the heat during XFC with the switch OFF boosts the cell's kinetics while dissipating the heat after XFC with the switch ON reduces detrimental reactions in the battery. Without modifying cell materials or structures, the proposed XFC approach enables reliable battery operation by applying <15 min of charge and 1 h of discharge. These results are almost identical regarding operativity for the same battery type tested applying a 1 h of charge and 1 h of discharge, thus, meeting the XFC targets set by the United States Department of Energy. Finally, we also demonstrate the feasibility of integrating the XFC approach in a commercial battery thermal management system.
We statistically evaluated the relative orientation between gas column density structures, inferred from Herschel submillimetre observations, and the magnetic field projected on the plane of sky, ...inferred from polarized thermal emission of Galactic dust observed by the Balloon-borne Large-Aperture Submillimetre Telescope for Polarimetry (BLASTPol) at 250, 350, and 500 μm, towards the Vela C molecular complex. First, we find very good agreement between the polarization orientations in the three wavelength-bands, suggesting that, at the considered common angular resolution of 3.́0 that corresponds to a physical scale of approximately 0.61 pc, the inferred magnetic field orientation is not significantly affected by temperature or dust grain alignment effects. Second, we find that the relative orientation between gas column density structures and the magnetic field changes progressively with increasing gas column density, from mostly parallel or having no preferred orientation at low column densities to mostly perpendicular at the highest column densities. This observation is in agreement with previous studies by the Planck collaboration towards more nearby molecular clouds. Finally, we find a correspondencebetween (a) the trends in relative orientation between the column density structures and the projected magnetic field; and (b) the shape of the column density probability distribution functions (PDFs). In the sub-regions of Vela C dominated by one clear filamentary structure, or “ridges”, where the high-column density tails of the PDFs are flatter, we find a sharp transition from preferentially parallel or having no preferred relative orientation at low column densities to preferentially perpendicular at highest column densities. In the sub-regions of Vela C dominated by several filamentary structures with multiple orientations, or “nests”, where the maximum values of the column density are smaller than in the ridge-like sub-regions and the high-column density tails of the PDFs are steeper, such a transition is also present, but it is clearly less sharp than in the ridge-like sub-regions. Both of these results suggest that the magnetic field is dynamically important for the formation of density structures in this region.
The objective of this study was to compare the spatial occurrences of droughts, detected by remotely sensed drought-indices over the desert-steppe and desert geo-botanical zones of Mongolia. All ...indices were derived from reflectance and thermal data sets, obtained from the NOAA–AVHRR data between 1982 and 1999. One group of the drought-indices is based on vegetation state derived from the reflective channels. This group includes the Normalized Difference Vegetation Index (NDVI), Anomaly of Normalized Difference Vegetation Index (NDVIA), Standardized Vegetation Index (SVI), and Vegetation Condition Index (VCI). Another group, based on surface brightness temperature derived from the thermal channel of NOAA–AVHRR, includes the Temperature Condition Index (TCI). The third group is based on combination between the reflective and thermal channels includes the ratio between Land Surface Temperature (LST) and NDVI (LST/NDVI), the Vegetation Health Index (VH), and the Drought Severity Index (DSI). Change detection procedure was performed by using the Change Vector Analysis in the temporal domain. Comparison analysis among the drought-indices reveals that there is no spatial coincidence between them, even when the vegetation growing period was divided into 2-month sub-periods — beginning, middle, and end. Based on the statistical analysis, higher correlations were found among the reflective indices while lesser or no relationships were found between the thermal and combination of the thermal and reflective indices. Furthermore, no agreement was found between the spatial extent of the satellite-derived drought-indices and the meteorological-based Palmer Drought Severity Index (PDSI) and also between the traditional ground-observed drought-affected-areas (DAA) maps. It was found that the combination of satellite-derived drought-indices can identify wider drought-occurred areas rather than the PDSI and the DAA maps. In summary, this study concludes that it is difficult to point out the most reliable drought index, and that the ground observations cannot provide sufficient information for validation of satellite derived drought indices.
Engineering commensal organisms for challenging applications, such as modulating the gut ecosystem, is hampered by the lack of genetic parts. Here, we describe promoters, ribosome-binding sites, and ...inducible systems for use in the commensal bacterium Bacteroides thetaiotaomicron, a prevalent and stable resident of the human gut. We achieve up to 10,000-fold range in constitutive gene expression and 100-fold regulation of gene expression with inducible promoters and use these parts to record DNA-encoded memory in the genome. We use CRISPR interference (CRISPRi) for regulated knockdown of recombinant and endogenous gene expression to alter the metabolic capacity of B. thetaiotaomicron and its resistance to antimicrobial peptides. Finally, we show that inducible CRISPRi and recombinase systems can function in B. thetaiotaomicron colonizing the mouse gut. These results provide a blueprint for engineering new chassis and a resource to engineer Bacteroides for surveillance of or therapeutic delivery to the gut microbiome.
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We develop sets of genetic parts for a human commensal bacteriumPromoter and RBS libraries control gene expression over a 10,000-fold dynamic rangeOrthogonal, inducible sensors enable synthetic genetic memory and CRISPRiGenetic circuits respond to stimuli in a complex mouse gut microbiota
The development of genetic parts to precisely program the human commensal gut bacterium Bacteroides thetaiotaomicron lays the foundation for microbiome engineering.
Multidrug-resistant bacteria are spreading at alarming rates, and despite extensive efforts no new class of antibiotic with activity against Gram-negative bacteria has been approved in over fifty ...years. Natural products and their derivatives have a key role in combating Gram-negative pathogens. Here we report chemical optimization of the arylomycins-a class of natural products with weak activity and limited spectrum-to obtain G0775, a molecule with potent, broad-spectrum activity against Gram-negative bacteria. G0775 inhibits the essential bacterial type I signal peptidase, a new antibiotic target, through an unprecedented molecular mechanism. It circumvents existing antibiotic resistance mechanisms and retains activity against contemporary multidrug-resistant Gram-negative clinical isolates in vitro and in several in vivo infection models. These findings demonstrate that optimized arylomycin analogues such as G0775 could translate into new therapies to address the growing threat of multidrug-resistant Gram-negative infections.
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