Abstract
Supported atomic metal sites have discrete molecular orbitals. Precise control over the energies of these sites is key to achieving novel reaction pathways with superior selectivity. Here, ...we achieve selective oxygen (O
2
) activation by utilising a framework of cerium (Ce) cations to reduce the energy of 3
d
orbitals of isolated copper (Cu) sites. Operando X-ray absorption spectroscopy, electron paramagnetic resonance and density-functional theory simulations are used to demonstrate that a Cu(I)O
2
3−
site selectively adsorbs molecular O
2
, forming a rarely reported electrophilic η
2
-O
2
species at 298 K. Assisted by neighbouring Ce(III) cations, η
2
-O
2
is finally reduced to two O
2−
, that create two Cu–O–Ce oxo-bridges at 453 K. The isolated Cu(I)/(II) sites are ten times more active in CO oxidation than CuO clusters, showing a turnover frequency of 0.028 ± 0.003 s
−1
at 373 K and 0.01 bar
P
CO
. The unique electronic structure of Cu(I)O
2
3−
site suggests its potential in selective oxidation.
Adolescence is a time of identity exploration, and preliminary evidence indicates the ways adolescents are describing their sexual and gender identities (SOGI) are changing. A nuanced understanding ...of SOGI is necessary for valid assessment in developmental research. Current measures do not capture the diversity of emerging identities among young people. Our study analyzed a national sample of 17,112 sexual and gender minority adolescents (13–17 years) to better understand how identity labels are reported across sexual, gender, and ethnoracial minorities. Adolescents reported 26 distinct SOGI categories; 24% of adolescents utilized nontraditional SOGI labels, such as pansexual and nonbinary. These identifications varied significantly as a function of ethnoracial identity. Results have implications for how scholars conceptualize and measure SOGI among adolescents.
Electroadhesion provides a simple route to rapidly and reversibly control adhesion using applied electric potentials, offering promise for a variety of applications including haptics and robotics. ...Current electroadhesives, however, suffer from key limitations associated with the use of high operating voltages (>kV) and corresponding failure due to dielectric breakdown. Here, a new type of electroadhesion based on heterojunctions between iono‐elastomer of opposite polarity is demonstrated, which can be operated at potentials as low as ≈1 V. The large electric field developed across the molecular‐scale ionic double layer (IDL) when the junction is placed under reverse bias allows for strong adhesion at low voltages. In contrast, under forward bias, the electric field across the IDL is destroyed, substantially lowering the adhesion in a reversible fashion. These ionoelastomer electroadhesives are highly efficient with respect to the force capacity per electrostatic capacitive energy and are robust to defects or damage that typically lead to catastrophic failure of conventional dielectric electroadhesives. The findings provide new fundamental insight into low‐voltage electroadhesion and broaden its possible applications.
A new class of electroadhesives based on ionoelastomer junctions is developed, which can be reversibly operated with potentials of ±1 V. The voltage stored in the ionic double layer formed at the interface of polyanionic and polycationic ionoelastomer layers is used to reversibly modulate the adhesion between the two materials.
The COVID-19 pandemic has brought renewed urgency to air disinfection. Upper room germicidal ultraviolet light (GUV) disinfects room air very efficiently. Its effect on practical outcomes in public ...settings remains unclear, but history may provide some insights. An interrupted time series model was fitted to a newly discovered dataset of attendance records from a preschool between 1941 to 1949, where GUV was installed in December 1945. GUV was associated with a sizable reduction in child absenteeism due to respiratory illnesses of any cause. Odds ratios for the effect ranged from 0.5 to 0.77, depending on the season. In all but high summer, model-predicted absenteeism rates were reduced by between a third and a half by GUV. Wider use of upper room germicidal UV systems in schools and preschools may be worthwhile, to reduce absenteeism due to respiratory illness and the educational, social, and economic consequences that ensue.
Imatinib mesylate is standard treatment for patients who have advanced gastrointestinal stromal tumor (GIST), but not all patients benefit equally. In previous studies, GIST genotype correlated with ...treatment outcome and optimal imatinib dosing.
We examined the relationship between kinase genotype and treatment outcome for 428 patients enrolled on the North American phase III study SWOG S0033/CALGB 150105 and treated with either 400 mg or 800 mg daily doses of imatinib.
The presence of KIT exon 11-mutant genotype (n = 283) correlated with improved treatment outcome when compared with KIT exon 9-mutant (n = 32) and wild-type (WT; n = 67) genotypes for objective response (complete response CR/partial response PR, 71.7% v 44.4% P = .007; and 44.6% P = .0002, respectively); time to tumor progression (TTP; median 24.7 months v 16.7 and 12.8 months, respectively); and overall survival (OS; median 60.0 months v 38.4 and 49.0 months, respectively). The survival outcomes for patients with exon 9-mutant, exon 11-mutant or WT GIST were not affected by imatinib dose. However, there was evidence of improved response rates for patients with exon 9-mutant tumors treated with imatinib 800 mg versus 400 mg (CR/PR, 67% v 17%; P = .02). Patients who had CD117-negative GIST had similar TTP but inferior OS compared with patients who had CD117-positive disease, which suggests that patients who have CD117-negative GIST may benefit from imatinib treatment. In addition, we identified novel but rare mutations of the KIT extracellular domain (exons 8 and 9).
We confirmed the favorable impact of KIT exon 11 genotype when compared with KIT exon 9 and wild-type genotype for patients with advanced GIST who are treated with imatinib.
Direct CO2 capture from atmospheric air is gaining increased attention as one of the most scalable negative carbon approaches available to tackle climate change if coupled with the sequestration of ...CO2 geologically. Furthermore, it can also provide CO2 for further utilization from a globally uniform source, which is especially advantageous for economies without natural sources of carbon-based feedstocks. Solid-supported amine-based materials are effective for direct air capture (DAC) due to their high CO2 uptakes and acceptable sorption kinetics at ambient temperature. In this work, we describe the application of polymer/silica fiber sorbents functionalized with a primary amine-rich polymer, poly(ethylenimine) (PEI), for DAC. Monolithic fiber sorbents composed of cellulose acetate and SiO2 are synthesized via the dry-jet, wet quench spinning technique. These fibers are then functionalized with PEI (M w 800 Da) in a simple and scalable postspinning infusion step and tested for CO2 capture under pseudoequilibrium conditions as well as under breakthrough conditions. An investigation to study the effect of feed flow rate, adsorption temperature, and presence of moisture in the feed on the CO2 breakthrough performance of a densely packed fiber sorbent module is conducted to highlight the potential application of this class of structured contactors in direct air capture. The pressure drop of these contactors at high gas velocities is also evaluated. Finally, a vacuum-assisted desorption step is demonstrated for production of high-purity CO2 from both dry and humid ambient air mixtures.
A method using calcium triflimide Ca(NTf2)2 as a Lewis acid to activate sulfonyl fluorides toward nucleophilic addition with amines is described. The reaction converts a wide array of sterically and ...electronically diverse sulfonyl fluorides and amines into the corresponding sulfonamides in good yield.
Nanoporous zeolitic imidazolate frameworks (ZIFs) form structural topologies equivalent to zeolites. ZIFs containing only one type of imidazole linker show separation capability for limited molecular ...pairs. We show that the effective pore size, hydrophilicity, and organophilicity of ZIFs can be continuously and drastically tuned using mixed-linker ZIFs containing two types of linkers, allowing their use as a more general molecular separation platform. We illustrate this remarkable behavior by adsorption and diffusion measurements of hydrocarbons, alcohols, and water in mixed-linker ZIF-8 x -90100–x materials with a large range of crystal sizes (338 nm to 120 μm), using volumetric, gravimetric, and PFG-NMR methods. NMR, powder FT-Raman, and micro-Raman spectroscopy unambiguously confirm the mixed-linker nature of individual ZIF crystals. Variation of the mixed-linker composition parameter (x) allows continuous control of n-butane, i-butane, butanol, and isobutanol diffusivities over 2–3 orders of magnitude and control of water and alcohol adsorption especially at low activities.
Porous organic cages (POCs) are individual soluble, porous molecules. When fabricated into mixed‐matrix membranes (MMMs), the soluble POC molecules have the potential to exhibit intimate ...molecular‐level mixing with the polymer matrix. POCs have only recently been incorporated into mixed matrix membrane materials, but this process has not yet resulted in significant improvements of membrane performance. Now, vertex‐functionalized amorphous scrambled porous organic cages (ASPOCs) have been utilized as membrane performance enhancers and the amorphous ASPOC mixtures are observed to distribute throughout the matrix without any indication of particle formation or agglomeration, creating unique, molecularly mixed composite membranes. Overall, the molecularly mixed composite membrane provide significant increases in both membrane permeability and selectivity, offering new avenues for creation of membranes with unique properties in industrially relevant separations.
Molecular mixing of filler and polymer results in a homogeneous pathway for molecules and dramatic improvements in membrane performance. Left: traditional mixed matrix membrane; right: molecularly mixed.
Due to the dramatically increased atmospheric CO2 concentration and consequential climate change, significant effort has been made to develop sorbents to directly capture CO2 from ambient air (direct ...air capture, DAC) to achieve negative CO2 emissions in the immediate future. However, most developed sorbents have been studied under a limited array of temperature (>20 °C) and humidity conditions. In particular, the dearth of experimental data on DAC at sub-ambient conditions (e.g., −30 to 20 °C) and under humid conditions will severely hinder the large-scale implementation of DAC because the world has annual average temperatures ranging from −30 to 30 °C depending on the location and essentially no place has a zero absolute humidity. To this end, we suggest that understanding CO2 adsorption from ambient air at sub-ambient temperatures, below 20 °C, is crucial because colder temperatures represent important practical operating conditions and because such temperatures may provide conditions where new sorbent materials or enhanced process performance might be achieved. Here we demonstrate that MIL-101(Cr) materials impregnated with amines (TEPA, tetraethylenepentamine, or PEI, poly(ethylenimine)) offer promising adsorption and desorption behavior under DAC conditions in both the presence and absence of humidity under a wide range of temperatures (−20 to 25 °C). Depending on the amine loading and adsorption temperature, the sorbents show different CO2 capture behavior. With 30 and 50 wt % amine loadings, the sorbents show weak and strong chemisorption-dominant CO2 capture behavior, respectively. Interestingly, at −20 °C, the CO2 adsorption capacity of 30 wt % TEPA-impregnated MIL-101(Cr) significantly increased up to 1.12 mmol/g from 0.39 mmol/g at ambient conditions (25 °C) due to the enhanced weak chemisorption. More importantly, the sorbents also show promising working capacities (0.72 mmol/g) over 15 small temperature swing cycles with an ultralow regeneration temperature (−20 °C sorption to 25 °C desorption). The sub-ambient DAC performance of the sorbents is further enhanced under humid conditions, showing promising and stable CO2 working capacities over multiple humid small temperature swing cycles. These results demonstrate that appropriately designed DAC sorbents can operate in a weak chemisorption modality at low temperatures even in the presence of humidity. Significant energy savings may be realized via the utilization of small temperature swings enabled by this weak chemisorption behavior. This work suggests that significant work on DAC materials that operate at low, sub-ambient temperatures is warranted for possible deployment in temperate and polar climates.
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