The selective capture of carbon dioxide in porous materials has potential for the storage and purification of fuel and flue gases. However, adsorption capacities under dynamic conditions are often ...insufficient for practical applications, and strategies to enhance CO(2)-host selectivity are required. The unique partially interpenetrated metal-organic framework NOTT-202 represents a new class of dynamic material that undergoes pronounced framework phase transition on desolvation. We report temperature-dependent adsorption/desorption hysteresis in desolvated NOTT-202a that responds selectively to CO(2). The CO(2) isotherm shows three steps in the adsorption profile at 195 K, and stepwise filling of pores generated within the observed partially interpenetrated structure has been modelled by grand canonical Monte Carlo simulations. Adsorption of N(2), CH(4), O(2), Ar and H(2) exhibits reversible isotherms without hysteresis under the same conditions, and this allows capture of gases at high pressure, but selectively leaves CO(2) trapped in the nanopores at low pressure.
This primer for eighth edition staging of esophageal and esophagogastric epithelial cancers presents separate classifications for the clinical (cTNM), pathologic (pTNM), and postneoadjuvant ...pathologic (ypTNM) stage groups, which are no longer shared.
For pTNM, pT1 has been subcategorized as pT1a and pT1b for the subgrouping pStage I adenocarcinoma and squamous cell carcinoma. A new, simplified esophagus-specific regional lymph node map has been introduced. Undifferentiated histologic grade (G4) has been eliminated; additional analysis is required to expose histopathologic cell type. Location has been removed as a category for pT2N0M0 squamous cell cancer. The definition of the esophagogastric junction has been revised. ypTNM stage groups are identical for both histopathologic cell types, unlike those for cTNM and pTNM.
Hydrogen adsorption on porous materials is one of the possible methods proposed for hydrogen storage for transport applications. High pressure experimental studies of a wide range of porous materials ...have obtained maximum hydrogen excess capacities of 6-8 wt% at 77 K for metal-organic frameworks (MOFs) and porous carbon materials. Grand canonical Monte Carlo (GCMC) simulation studies indicate that higher hydrogen capacities are possible for covalent organic frameworks (COFs). Currently, the maximum isosteric enthalpies of adsorption of approximately 13 kJ mol(-1) at 77 K have been observed experimentally for metal-organic framework materials and this is higher than for COFs, where the maximum predicted from GCMC simulations is approximately 8 kJ mol(-1). Metal-organic framework materials have structural diversity and scope for modification of surface chemistry to enhance hydrogen surface interactions. The synthesis of MOFs with stronger H(2)-surface interactions to give similar hydrogen capacities at much higher temperatures than 77 K is required and eventually, materials that have these high capacities at ambient temperatures with rapid adsorption/desorption characteristics are necessary for applications as hydrogen storage materials for transport applications. The current methods envisaged for increasing adsorption at higher temperatures involve modification of the surface chemistry, in particular, the inclusion of open metal centres to increase hydrogen surface site interactions, and utilisation of the framework flexibility are discussed.
The demand for xylenes is projected to increase over the coming decades. The separation of xylene isomers, particularly p- and m-xylenes, is vital for the production of numerous polymers and ...materials. However, current state-of-the-art separation is based upon fractional crystallisation at 220 K which is highly energy intensive. Here, we report the discrimination of xylene isomers via refinement of the pore size in a series of porous metal-organic frameworks, MFM-300, at sub-angstrom precision leading to the optimal kinetic separation of all three xylene isomers at room temperature. The exceptional performance of MFM-300 for xylene separation is confirmed by dynamic ternary breakthrough experiments. In-depth structural and vibrational investigations using synchrotron X-ray diffraction and terahertz spectroscopy define the underlying host-guest interactions that give rise to the observed selectivity (p-xylene < o-xylene < m-xylene) and separation factors of 4.6-18 for p- and m-xylenes.
The separation of molecules with similar size and shape is an important technological challenge. For example, rare gases can pose either an economic opportunity or an environmental hazard and there ...is a need to separate these spherical molecules selectively at low concentrations in air. Likewise, chiral molecules are important building blocks for pharmaceuticals, but chiral enantiomers, by definition, have identical size and shape, and their separation can be challenging. Here we show that a porous organic cage molecule has unprecedented performance in the solid state for the separation of rare gases, such as krypton and xenon. The selectivity arises from a precise size match between the rare gas and the organic cage cavity, as predicted by molecular simulations. Breakthrough experiments demonstrate real practical potential for the separation of krypton, xenon and radon from air at concentrations of only a few parts per million. We also demonstrate selective binding of chiral organic molecules such as 1-phenylethanol, suggesting applications in enantioselective separation.
MicroRNA (miRNA)-deficient helper T cells exhibit abnormal IFN-γ production and decreased proliferation. However, the contributions of individual miRNAs to this phenotype remain poorly understood. We ...conducted a screen for miRNA function in primary T cells and identified individual miRNAs that rescue the defects associated with miRNA deficiency. Multiple members of the miR-17 and miR-92 families enhanced miRNA-deficient T cell proliferation whereas miR-29 largely corrected their aberrant interferon-γ (IFN-γ) expression. Repression of IFN-γ production by miR-29 involved direct targeting of both T-bet and Eomes, two transcription factors known to induce IFN-γ production. Although not usually expressed at functionally relevant amounts in helper T cells, Eomes was abundant in miRNA-deficient cells and was upregulated after miR-29 inhibition in wild-type cells. These results demonstrate that miR-29 regulates helper T cell differentiation by repressing multiple target genes, including at least two that are independently capable of inducing the T helper 1 (Th1) cell gene expression program.
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► miRNA -deficient T cells exhibit cell-intrinsic defects in IFN-γ signaling ► Individual miRNAs independently rescue specific defects of miRNA-deficient T cells ► miR-29 negatively regulates IFN-γ production in helper T cells ► IFN-γ repression by miR-29 involves regulation of both T-bet and Eomes
Adsorption and desorption of hydrogen from nanoporous materials, such as activated carbon, is usually fully reversible. We have prepared nanoporous metal-organic framework materials with flexible ...linkers in which the pore openings, as characterized in the static structures, appear to be too small to allow H2to pass. We observe hysteresis in their adsorption and desorption kinetics above the supercritical temperature of H2that reflects the dynamical opening of the "windows" between pores. This behavior would allow H2to be adsorbed at high pressures but stored at lower pressures.
Record‐breaking fire seasons in many regions across the globe raise important questions about plant community responses to shifting fire regimes (i.e., changing fire frequency, severity and ...seasonality). Here, we examine the impacts of climate‐driven shifts in fire regimes on vegetation communities, and likely responses to fire coinciding with severe drought, heatwaves and/or insect outbreaks. We present scenario‐based conceptual models on how overlapping disturbance events and shifting fire regimes interact differently to limit post‐fire resprouting and recruitment capacity. We demonstrate that, although many communities will remain resilient to changing fire regimes in the short‐term, longer‐term changes to vegetation structure, demography and species composition are likely, with a range of subsequent effects on ecosystem function. Resprouting species are likely to be most resilient to changing fire regimes. However, even these species are susceptible if exposed to repeated short‐interval fire in combination with other stressors. Post‐fire recruitment is highly vulnerable to increased fire frequency, particularly as climatic limitations on propagule availability intensify. Prediction of community responses to fire under climate change will be greatly improved by addressing knowledge gaps on how overlapping disturbances and climate change‐induced shifts in fire regime affect post‐fire resprouting, recruitment, growth rates, and species‐level adaptation capacity.
Although many vegetation communities will remain resilient to changing fire regimes under climate change in the short‐term, longer‐term changes to vegetation structure, demography and species composition are likely, with subsequent impacts to ecosystem function. Resilience will depend on species‐specific adaptations to fire, with resprouting species likely to be most resilient.
Genomic anatomy of Escherichia coli O157:H7 outbreaks Eppinger, Mark; Mammel, Mark K; Leclerc, Joseph E ...
Proceedings of the National Academy of Sciences - PNAS,
12/2011, Letnik:
108, Številka:
50
Journal Article
Recenzirano
Odprti dostop
The rapid emergence of Escherichia coli O157:H7 from an unknown strain in 1982 to the dominant hemorrhagic E. coli serotype in the United States and the cause of widespread outbreaks of human ...food-borne illness highlights a need to evaluate critically the extent to which genomic plasticity of this important enteric pathogen contributes to its pathogenic potential and its evolution as well as its adaptation in different ecological niches. Aimed at a better understanding of the evolution of the E. coli O157:H7 pathogenome, the present study presents the high-quality sequencing and comparative phylogenomic analysis of a comprehensive panel of 25 E. coli O157:H7 strains associated with three nearly simultaneous food-borne outbreaks of human disease in the United States. Here we present a population genetic analysis of more than 200 related strains recovered from patients, contaminated produce, and zoonotic sources. High-resolution phylogenomic approaches allow the dynamics of pathogenome evolution to be followed at a high level of phylogenetic accuracy and resolution. SNP discovery and study of genome architecture and prophage content identified numerous biomarkers to assess the extent of genetic diversity within a set of clinical and environmental strains. A total of 1,225 SNPs were identified in the present study and are now available for typing of the E. coli O157:H7 lineage. These data should prove useful for the development of a refined phylogenomic framework for forensic, diagnostic, and epidemiological studies to define better risk in response to novel and emerging E. coli O157:H7 resistance and virulence phenotypes.
Human behavior emerges from planning over elaborate decompositions of tasks into goals, subgoals, and low-level actions. How are these decompositions created and used? Here, we propose and evaluate a ...normative framework for task decomposition based on the simple idea that people decompose tasks to reduce the overall cost of planning while maintaining task performance. Analyzing 11,117 distinct graph-structured planning tasks, we find that our framework justifies several existing heuristics for task decomposition and makes predictions that can be distinguished from two alternative normative accounts. We report a behavioral study of task decomposition (N = 806) that uses 30 randomly sampled graphs, a larger and more diverse set than that of any previous behavioral study on this topic. We find that human responses are more consistent with our framework for task decomposition than alternative normative accounts and are most consistent with a heuristic-betweenness centrality-that is justified by our approach. Taken together, our results suggest the computational cost of planning is a key principle guiding the intelligent structuring of goal-directed behavior.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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