One of the most striking features of human cognition is the ability to plan. Two aspects of human planning stand out-its efficiency and flexibility. Efficiency is especially impressive because plans ...must often be made in complex environments, and yet people successfully plan solutions to many everyday problems despite having limited cognitive resources
. Standard accounts in psychology, economics and artificial intelligence have suggested that human planning succeeds because people have a complete representation of a task and then use heuristics to plan future actions in that representation
. However, this approach generally assumes that task representations are fixed. Here we propose that task representations can be controlled and that such control provides opportunities to quickly simplify problems and more easily reason about them. We propose a computational account of this simplification process and, in a series of preregistered behavioural experiments, show that it is subject to online cognitive control
and that people optimally balance the complexity of a task representation and its utility for planning and acting. These results demonstrate how strategically perceiving and conceiving problems facilitates the effective use of limited cognitive resources.
There are numerous applications of nanoporous materials, including gas storage, separation, and purification. In recent years, the number of available nanoporous materials has increased ...substantially, with new material classes, such as metal-organic frameworks and microporous organic polymers, joining the traditional adsorbents, which include activated carbons, porous silicas, and zeolites. The determination of the gas adsorption properties of these materials is critical to both the development of new materials for targeted applications and the assessment of the suitability of a material for a particular technology. In this article, we provide an overview of nanoporous materials and their gas adsorption properties, existing and future applications for new materials, adsorption measurement methods, and the experimental challenges involved in the determination of gas adsorption both at elevated pressures and from multicomponent mixtures.
Four porous isostructural mixed-metal–organic frameworks (M′MOFs) have been synthesized and structurally characterized. The pores within these M′MOFs are systematically tuned by the interplay of both ...the metalloligands and organic ligands which have enabled us not only to direct their highly selective separation of chiral alcohols 1-phenylethanol (PEA), 2-butanol (BUT), and 2-pentanol (2-PEN) with the highest ee up to 82.4% but also to lead highly selective separation of achiral C2H2/C2H4 separation. The potential application of these M′MOFs for the fixed bed pressure swing adsorption (PSA) separation of C2H2/C2H4 has been further examined and compared by the transient breakthrough simulations in which the purity requirement of 40 ppm in the outlet gas can be readily fulfilled by the fixed bed M′MOF-4a adsorber at ambient conditions.
Planning underpins the impressive flexibility of goal-directed behavior. However, even when planning, people can display surprising rigidity in how they think about problems (e.g., “functional ...fixedness”) that lead them astray. How can our capacity for behavioral flexibility be reconciled with our susceptibility to conceptual inflexibility? We propose that these tendencies reflect avoidance of two cognitive costs: the cost of representing task details and the cost of switching between representations. To test this hypothesis, we developed a novel paradigm that affords participants opportunities to choose different families of simplified representations to plan. In two preregistered, online studies (Ns = 377 and 294 adults), we found that participants’ optimal behavior, suboptimal behavior, and reaction time were explained by a computational model that formalized people’s avoidance of representational complexity and switching. These results demonstrate how the selection of simplified, rigid representations leads to the otherwise puzzling combination of flexibility and inflexibility observed in problem solving.
Abstract Stem cell transplantation may repair the injured heart, but tissue regeneration is limited by death of transplanted cells. Most cell death occurs in the first few days post-transplantation, ...likely from a combination of ischemia, anoikis and inflammation. Interventions known to enhance transplanted cell survival include heat shock, over-expressing anti-apoptotic proteins, free radical scavengers, anti-inflammatory therapy and co-delivery of extracellular matrix molecules. Combinatorial use of such interventions markedly enhances graft cell survival, but death still remains a significant problem. We review these challenges to cardiac cell transplantation and present an approach to systematically address them. Most anti-death studies use histology to assess engraftment, which is time- and labor-intensive. To increase throughput, we developed two biochemical approaches to follow graft viability in the mouse heart. The first relies on LacZ enzymatic activity to track genetically modified cells, and the second quantifies human genomic DNA content using repetitive Alu sequences. Both show linear relationships between input cell number and biochemical signal, but require correction for the time lag between cell death and loss of signal. Once optimized, they permit detection of as few as 1 graft cell in 40,000 host cells. Pro-survival effects measured biochemically at three days predict long-term histological engraftment benefits. These methods permitted identification of carbamylated erythropoietin (CEPO) as a pro-survival factor for human embryonic stem cell-derived cardiomyocyte grafts. CEPO's effects were additive to heat shock, implying independent survival pathways. This system should permit combinatorial approaches to enhance graft viability in a fraction of the time required for conventional histology.
Most HIV-1-specific neutralizing antibodies isolated to date exhibit unusual characteristics that complicate their elicitation. Neutralizing antibodies that target the V1V2 apex of the HIV-1 envelope ...(Env) trimer feature unusually long protruding loops, which enable them to penetrate the HIV-1 glycan shield. As antibodies with loops of requisite length are created through uncommon recombination events, an alternative mode of apex binding has been sought. Here, we isolated a lineage of Env apex-directed neutralizing antibodies, N90-VRC38.01-11, by using virus-like particles and conformationally stabilized Env trimers as B cell probes. A crystal structure of N90-VRC38.01 with a scaffolded V1V2 revealed a binding mode involving side-chain-to-side-chain interactions that reduced the distance the antibody loop must traverse the glycan shield, thereby facilitating V1V2 binding via a non-protruding loop. The N90-VRC38 lineage thus identifies a solution for V1V2-apex binding that provides a more conventional B cell pathway for vaccine design.
•VLPs and stabilized Env trimers identify HIV-1-neutralizing N90-VRC38 Ab lineage•Co-crystal structure of Ab N90-VRC38.01 with scaffolded V1V2-Env apex•N90-VRC38 lineage targets the apex of HIV-1 Env trimer with non-protruding loops•New mechanism of Ab:trimer-apex binding informs V1V2 vaccine strategies
To date, long recognition loops have been a hallmark of apex-targeting antibodies. Cale et al. identify a lineage of HIV-1-neutralizing antibodies that target the envelope trimer apex. The N90-VRC38 lineage uses a loop of average length—a feature that may make it a useful prototype for vaccine design.
Nitrogen dioxide (NO
) is a major air pollutant causing significant environmental
and health problems
. We report reversible adsorption of NO
in a robust metal-organic framework. Under ambient ...conditions, MFM-300(Al) exhibits a reversible NO
isotherm uptake of 14.1 mmol g
, and, more importantly, exceptional selective removal of low-concentration NO
(5,000 to <1 ppm) from gas mixtures. Complementary experiments reveal five types of supramolecular interaction that cooperatively bind both NO
and N
O
molecules within MFM-300(Al). We find that the in situ equilibrium 2NO
↔ N
O
within the pores is pressure-independent, whereas ex situ this equilibrium is an exemplary pressure-dependent first-order process. The coexistence of helical monomer-dimer chains of NO
in MFM-300(Al) could provide a foundation for the fundamental understanding of the chemical properties of guest molecules within porous hosts. This work may pave the way for the development of future capture and conversion technologies.
Highlights • This trial included emergency department patients with risky opioid medication use. • The intervention used a motivational interviewing framework and a computer aid. • The intervention ...reduced overdose risk behaviors more than enhanced usual care. • The approach is feasible and potentially effective for promoting safer opioid use
Background Robotic technology has enabled totally endoscopic coronary artery bypass (TECAB) grafting. Little information is available on factors associated with successful and safe performance of ...TECAB. We report a 10-year multicenter experience with 500 cases, elucidating on predictors of success and safety in TECAB procedures. Methods Between 2001 and 2011, 500 patients (364 73% men; 136 27% women; median age minimum-maximum 60 years 31−90 years, median EuroSCORE 2 0−13), underwent TECAB. Single, double, triple, and quadruple TECAB was performed in 334, 150, 15, and 1 patient, respectively. Univariate analysis and binary regression models were used to identify predictors of success and safety. Success was defined as freedom from any adverse event and conversion procedure, safety was defined as freedom from major adverse cardiac and cerebral events, major vascular injury, and long-term ventilation. Results Success and safety rates were 80% (400 cases) and 95% (474 cases), respectively. Intraoperative conversions to larger thoracic incisions were required in 49 (10%) patients. The median operative time was 305 minutes (112−1,050 minutes), and the mean lengths of stay in the intensive unit (ICU) and in hospital were 23 hours (11−1,048 hours) and 6 days (2−4 days), respectively. Independent predictors of success were single-vessel TECAB ( p = 0.004), arrested-heart (AH)-TECAB ( p = 0.027), non−learning curve case ( p = 0.049), and transthoracic assistance ( p = 0.035). The only independent predictor of safety was EuroSCORE ( p = 0.002). Conclusions Single-vessel and multivessel TECAB procedures can be safely performed with good reproducible results. Predictors of success include procedure simplicity and non−learning curve cases, whereas predictors of safety are mainly associated with patient selection.
Shale gas from unconventional resources will contribute to meeting the energy demand during the transition to a net-zero carbon economy. In this minireview, the current status of understanding ...methane adsorption on kerogens and shales is discussed in relation to methane storage capacity. Standard subcritical adsorption studies provide characterization data (micropore volumes, total pore volumes, surface areas, and pore size distributions) for the porous structures of shales and kerogens. However, supercritical methane adsorption measurements under simulated geological conditions are necessary to assess realistic methane adsorption storage capacities. Supercritical methane adsorption on shale and shale components (kerogens and clays) under high pressure and temperature conditions that simulated geological conditions is compared. Kerogen structural characteristics are discussed in relation to supercritical methane isotherms and isobars. The contribution of adsorbed methane gas relative to “free” or compressed gas to the total gas stored in shale is considered. The importance of kerogens in both storage of the adsorbed phase and as the source of methane is highlighted, and the areas where knowledge and understanding are deficient are identified, in particular, the relationship of kerogen type and maturity with supercritical methane adsorption under simulated geological conditions. The competitive adsorption of water on methane capacity is also an area where more detailed studies are necessary. These are challenges to address gaps in the current knowledge and understanding, which require future research.
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