Correction: Ionic liquids of superior thermal stability. Validation of PPh4+ as an organic cation of impressive thermodynamic durability.

[This corrects the article DOI: 10.1039/D0RA03220D.].

Carbon Dioxide Capture Chemistry of Amino Acid Functionalized Metal-Organic Frameworks in Humid Flue Gas.

Metal-organic framework-808 has been functionalized with 11 amino acids (AA) to produce a series of MOF-808-AA structures. The adsorption of CO2 under flue gas conditions revealed that glycine- and dl-lysine-functionalized MOF-808 (MOF-808-Gly and -dl-Lys) have the highest uptake capacities. Enhanced CO2 capture performance in the presence of water was observed and studied by using single-component sorption isotherms, CO2/H2O binary isotherm, and dynamic breakthrough measurements. The key to the favorable performance was uncovered by deciphering the mechanism of CO2 capture in the pores and attributed to the formation of bicarbonate as evidenced by 13C and 15N solid-state nuclear magnetic resonance spectroscopy studies. On the basis of these results, we examined the performance of MOF-808-Gly in simulated coal flue gas conditions and found that it is possible to capture and release CO2 by vacuum swing adsorption. MOF-808-Gly was cycled at least 80 times with full retention of performance. This study significantly advances our understanding of CO2 chemistry in MOFs by revealing how strongly bound amine moieties to the MOF backbone create the chemistry and environment within the pores, leading to the binding and release of CO2 under mild conditions without application of heat.

Water Bridges Substitute for Defects in Amine-Functionalized UiO-66, Boosting CO2 Adsorption.

The binary adsorption of CO2 and water on an amine-functionalized UiO-66 metal-organic framework (MOF) was studied experimentally and computationally. Grand canonical Monte Carlo simulations were used to investigate three additional UiO-66 MOFs with different functionalized linkers. Each MOF was studied in a defect-free form as well as two additional forms with precise linker defects. Binary adsorption isotherms are presented for CO2 at specific water loadings. While water loading in defect-free MOFs reduces the CO2 uptake, the defects slightly boost the CO2 uptake at low water loadings. It was found that water bridges form between the metal oxide cores, replacing the missing linkers. Effectively, this creates smaller pores that are more welcoming of CO2 adsorption. Experimental measurement of the binary isotherms for UiO-66-NH2 shows a behavior that is consistent with this enhancement.

Ionic liquids of superior thermal stability. Validation of PPh4 + as an organic cation of impressive thermodynamic durability.

Recent work by Wasserscheid, et al. suggests that PPh4 + is an organic molecular ion of truly exceptional thermal stability. Herein we provide data that cements that conclusion: specifically, we show that aliphatic moieties of modified PPh4 +-based cations incorporating methyl, methylene, or methine C-H bonds burn away at high temperatures in the presence of oxygen, forming CO, CO2, and water, leaving behind the parent ion PPh4 +. The latter then undergoes no further reaction, at least below 425 °C.

Rapid Cycling and Exceptional Yield in a Metal-Organic Framework Water Harvester.

Sorbent-assisted water harvesting from air represents an attractive way to address water scarcity in arid climates. Hitherto, sorbents developed for this technology have exclusively been designed to perform one water harvesting cycle (WHC) per day, but the productivities attained with this approach cannot reasonably meet the rising demand for drinking water. This work shows that a microporous aluminum-based metal-organic framework, MOF-303, can perform an adsorption-desorption cycle within minutes under a mild temperature swing, which opens the way for high-productivity water harvesting through rapid, continuous WHCs. Additionally, the favorable dynamic water sorption properties of MOF-303 allow it to outperform other commercial sorbents displaying excellent steady-state characteristics under similar experimental conditions. Finally, these findings are implemented in a new water harvester capable of generating 1.3 L kgMOF -1 day-1 in an indoor arid environment (32% relative humidity, 27 °C) and 0.7 L kgMOF -1 day-1 in the Mojave Desert (in conditions as extreme as 10% RH, 27 °C), representing an improvement by 1 order of magnitude over previously reported devices. This study demonstrates that creating sorbents capable of rapid water sorption dynamics, rather than merely focusing on high water capacities, is crucial to reach water production on a scale matching human consumption.

Cancer Immune Checkpoint Inhibitor Therapy and the Gut Microbiota.

The past decade has seen tremendous advances in both our understanding of cancer immunosuppressive microenvironments and colonic bacteria facilitated by immune checkpoint inhibitor antibodies and next generation sequencing, respectively. Because an important role of the host immune system is to communicate with and regulate the gut microbial community, it should not come as a surprise that the behavior of one is coupled to the other. In this review, we will attempt to dissect some of the studies demonstrating cancer immunotherapy modulation by specific gut microbes and discuss possible molecular mechanisms for this effect.

Determination of cesium transfer factors by instrumental neutron activation analysis.

Food-chain models are used to predict radionuclide ingestion after fallout deposition. These models include those transfer processes (soil-to-plant transfer factor(s) [TF], plant-to-animal transfer coefficient(s) [TC] and concentration ratio [CR]) that are likely to be important for radiological assessment. The range of variability for transfer factors for the same plant groups is great, about 4-5 orders of magnitude, which limits their applicability. A better way to determine the best estimate the factors for radiocaesium and other important radionuclides is if the site-specific data are available. Soil, plant and animal samples were collected from a pasture area in Hungary during the vegetation period in 2016. Stable 133Cs concentration was analysed by comparative method with neutron activation analysis (NAA). The comparator and the samples were irradiated in thermal neutron flux 2.55 × 1012 ncm-2s-1 for 2 h (soil) and 6 h (vegetation, animal samples) in the TRIGA Mark II research reactor at the Nuclear Engineering Teaching Laboratory. After an appropriate decay time (12 days) the samples were measured by gamma-spectrometry and analysed. The observed stable caesium TCpm (0.48-0.53) and CRpm (0.41-0.45) were very close to 137Cs factors in the IAEA 2009 Report of 0.49 and 0.54, respectively. This methodology is particularly suitable for the simultaneous study of natural caesium in ecosystem compartments. Consequently, the transfer of stable caesium in a pasture field may be regarded as a useful analogy in predicting the long-term changes of 137Cs affected by site-specific environmental factors.

Ultrafast evolution and transient phases of a prototype out-of-equilibrium Mott-Hubbard material.

The study of photoexcited strongly correlated materials is attracting growing interest since their rich phase diagram often translates into an equally rich out-of-equilibrium behaviour. With femtosecond optical pulses, electronic and lattice degrees of freedom can be transiently decoupled, giving the opportunity of stabilizing new states inaccessible by quasi-adiabatic pathways. Here we show that the prototype Mott-Hubbard material V2O3 presents a transient non-thermal phase developing immediately after ultrafast photoexcitation and lasting few picoseconds. For both the insulating and the metallic phase, the formation of the transient configuration is triggered by the excitation of electrons into the bonding a1g orbital, and is then stabilized by a lattice distortion characterized by a hardening of the A1g coherent phonon, in stark contrast with the softening observed upon heating. Our results show the importance of selective electron-lattice interplay for the ultrafast control of material parameters, and are relevant for the optical manipulation of strongly correlated systems.

X-rays only when you want them: optimized pump-probe experiments using pseudo-single-bunch operation.

Laser pump-X-ray probe experiments require control over the X-ray pulse pattern and timing. Here, the first use of pseudo-single-bunch mode at the Advanced Light Source in picosecond time-resolved X-ray absorption experiments on solutions and solids is reported. In this mode the X-ray repetition rate is fully adjustable from single shot to 500 kHz, allowing it to be matched to typical laser excitation pulse rates. Suppressing undesired X-ray pulses considerably reduces detector noise and improves signal to noise in time-resolved experiments. In addition, dose-induced sample damage is considerably reduced, easing experimental setup and allowing the investigation of less robust samples. Single-shot X-ray exposures of a streak camera detector using a conventional non-gated charge-coupled device (CCD) camera are also demonstrated.

Modification of Fibers with Nanostructures Using Reactive Dye Chemistry.

Reactive dyes conventionally used to chemically bind chromophores to fabrics have been used to develop a platform technology that can modify commercially available fibers with nanoscale structures. To illustrate this concept, commercial nylon and cellulose fibers have been modified with gold nanoparticles of three sizes, metal organic framework (MOF) crystals, and quantum dots in five sizes. The gold modified cellulose and nylon samples have colors that vary based on the size of the gold particles, and the particles remained attached to the fibers, even after being washed with solvents, water, and soap. The MOF was grown on the fibers after applying reactive dyes to anchor the metal building unit to the fibers, and the process produced cellulose fibers with surface areas of ~980 m2/g. Both the nylon and cellulose MOF modified fabrics show preferential adsorption of ethylene over ethane and the ability to adsorb ammonia from air. Quantum dot modified nylon and cellulose fibers have fluorescent properties consistent with the unbound particles and remained attached to the fibers after washing with organic solvents, water, and soap. Applications are broad, and this work provides a first step at coupling conventional dyes and nanotechnology.

Glass-like recovery of antiferromagnetic spin ordering in a photo-excited manganite Pr0.7Ca0.3MnO3.

Electronic orderings of charges, orbitals and spins are observed in many strongly correlated electron materials, and revealing their dynamics is a critical step toward undertsanding the underlying physics of important emergent phenomena. Here we use time-resolved resonant soft x-ray scattering spectroscopy to probe the dynamics of antiferromagnetic spin ordering in the manganite Pr0.7Ca0.3MnO3 following ultrafast photo-exitation. Our studies reveal a glass-like recovery of the spin ordering and a crossover in the dimensionality of the restoring interaction from quasi-1D at low pump fluence to 3D at high pump fluence. This behavior arises from the metastable state created by photo-excitation, a state characterized by spin disordered metallic droplets within the larger charge- and spin-ordered insulating domains. Comparison with time-resolved resistivity measurements suggests that the collapse of spin ordering is correlated with the insulator-to-metal transition, but the recovery of the insulating phase does not depend on the re-establishment of the spin ordering.

Experimental pain sensitivity differs as a function of clinical pain severity in symptomatic knee osteoarthritis.

OBJECTIVE: Pain in knee osteoarthritis (OA) has historically been attributed to peripheral pathophysiology; however, the poor correspondence between objective measures of disease severity and clinical symptoms suggests that non-local factors, such as altered central processing of painful stimuli, also contribute to clinical pain in knee OA. Consistent with this notion, recent evidence demonstrates that patients with knee OA exhibit increased sensitivity to painful stimuli at body sites unaffected by clinical pain. DESIGN: In order to further investigate the contribution of altered pain processing to knee OA pain, the current study tested the hypothesis that symptomatic knee OA is associated with enhanced sensitivity to experimental pain stimuli at the knee and at remote body sites unaffected by clinical pain. We further anticipated that pain sensitivity would differ as a function of the OA symptom severity. Older adults with and without symptomatic knee OA completed a series of experimental pain assessments. A median split of the Western Ontario and McMaster Universities Index of Osteoarthritis (WOMAC) was used to stratify participants into low vs high OA symptom severity. RESULTS: Compared to controls and the low symptom group, individuals in the high symptom group were more sensitive to suprathreshold heat stimuli, blunt pressure, punctuate mechanical, and cold stimuli. Individuals in the low symptomatic OA group subgroup exhibited experimental pain responses similar to the pain-free group on most measures. No group differences in endogenous pain inhibition emerged. CONCLUSIONS: These findings suggest that altered central processing of pain is particularly characteristic of individuals with moderate to severe symptomatic knee OA.

Chemisorption of cyanogen chloride by spinel ferrite magnetic nanoparticles.

Spinel ferrite magnetic nanoparticles, MnFe2O4, NiFe2O4, and CoFe2O4, were synthesized and used as gas-phase adsorbents for the removal of cyanogen chloride from dry air. Fixed-bed adsorption breakthrough experiments show adsorption wave behavior at the leading edge of the breakthrough curve that is not typical of physically adsorbed species. Fourier transform infrared spectroscopy (FTIR) results indicate that CK is reacting with the spinel ferrite surface and forming a carbamate species. The reaction is shown to be a function of the hydroxyl groups and adsorbed water on the surface of the particles as well as the metallic composition of the particles. The surface reaction decreases the remnant and saturation magnetism of the MnFe2O4 and CoFe2O4 particles by approximately 25%.

Mass transfer and adsorption equilibrium for low volatility alkanes in BPL activated carbon.

The structure of a molecule and its concentration can strongly influence diffusional properties for transport in nanoporous materials. We study mass transfer of alkanes in BPL activated carbon using the concentration-swing frequency response method, which can easily discriminate among mass transfer mechanisms. We measure concentration-dependent diffusion rates for n-hexane, n-octane, n-decane, 2,7-dimethyloctane, and cyclodecane, which have different carbon numbers and geometries: straight chain, branched chain, and cyclic. Micropore diffusion is determined to be the controlling mass transfer resistance except at low relative saturation for n-decane, where an external mass transfer resistance also becomes important, showing that the controlling mass transfer mechanism can change with system concentration. Micropore diffusion coefficients are found to be strongly concentration dependent. Adsorption isotherm slopes obtained from measured isotherms, the concentration-swing frequency response method, and a predictive method show reasonably good agreement.

Vitamin D, race, and experimental pain sensitivity in older adults with knee osteoarthritis.

OBJECTIVE: Low circulating serum levels of 25-hydroxyvitamin D (referred to hereafter as vitamin D) have been correlated with many health conditions, including chronic pain. Recent clinical practice guidelines define vitamin D levels <20 ng/ml as deficient and levels of 21-29 ng/ml as insufficient. Vitamin D insufficiency, including the most severe levels of deficiency, is more prevalent in black Americans. Ethnic and race group differences have been reported in both clinical and experimental pain, with black Americans reporting increased pain. The purpose of this study was to examine whether variations in vitamin D levels contribute to race differences in knee osteoarthritis pain. METHODS: The sample consisted of 94 participants (74% women), including 45 blacks and 49 whites with symptomatic knee osteoarthritis. Their average age was 55.8 years (range 45-71 years). Participants completed a questionnaire on knee osteoarthritis symptoms and underwent quantitative sensory testing, including measures of sensitivity to heat-induced and mechanically induced pain. RESULTS: Blacks had significantly lower levels of vitamin D compared to whites, demonstrated greater clinical pain, and showed greater sensitivity to heat-induced and mechanically induced pain. Low levels of vitamin D predicted increased experimental pain sensitivity, but did not predict self-reported clinical pain. Group differences in vitamin D levels significantly predicted group differences in heat pain and pressure pain thresholds at the index knee and ipsilateral forearm. CONCLUSION: These data demonstrate that race differences in experimental pain are mediated by differences in the vitamin D level. Vitamin D deficiency may be a risk factor for increased knee osteoarthritis pain in black Americans.

Thin water film formation on metal oxide crystal surfaces.

Reactions taking place at hydrated metal oxide surfaces are of considerable environmental and technological importance. Surface-sensitive X-ray methods can provide structural and chemical information on stable interfacial species, but it is challenging to perform in situ studies of reaction kinetics in the presence of water. We have implemented a new approach to creating a micrometer-scale water film on a metal oxide surface by combining liquid and gas jets on a spinning crystal. The water films are stable indefinitely and sufficiently thin to allow grazing incidence X-ray reflectivity and spectroscopy measurements. The approach will enable studies of a wide range of surface reactions and is compatible with interfacial optical-pump/X-ray-probe studies.

X-ray and optical wave mixing.

Light-matter interactions are ubiquitous, and underpin a wide range of basic research fields and applied technologies. Although optical interactions have been intensively studied, their microscopic details are often poorly understood and have so far not been directly measurable. X-ray and optical wave mixing was proposed nearly half a century ago as an atomic-scale probe of optical interactions but has not yet been observed owing to a lack of sufficiently intense X-ray sources. Here we use an X-ray laser to demonstrate X-ray and optical sum-frequency generation. The underlying nonlinearity is a reciprocal-space probe of the optically induced charges and associated microscopic fields that arise in an illuminated material. To within the experimental errors, the measured efficiency is consistent with first-principles calculations of microscopic optical polarization in diamond. The ability to probe optical interactions on the atomic scale offers new opportunities in both basic and applied areas of science.

Adsorption of ammonia by sulfuric acid treated zirconium hydroxide.

The adsorption of ammonia on Zr(OH)(4), as well as Zr(OH)(4) treated with sulfuric acid, were examined. The results show that treating Zr(OH)(4) with sulfuric acid leads to the formation of a sulfate on the surface of the material, and that the sulfate contributes to the ammonia adsorption capacity through the formation of an ammonium sulfates species. Calcination of Zr(OH)(4) decreases the ammonia adsorption capacity of the material and limits the formation of sulfate species. NMR and FTIR spectroscopy results are presented that show the presence of two distinct ammonium species on the surface of the material. The adsorption capacity of the materials is shown to be a complex phenomenon that is impacted by the surface area, the sulfur content, and the pH of the material. The results illustrate that Zr(OH)(4), which is known to adsorb acidic gases, can be modified and used to adsorb basic gases.

Adsorption of sulfur dioxide by CoFe2O4 spinel ferrite nanoparticles and corresponding changes in magnetism.

Adsorption of sulfur dioxide on 10 nm CoFe(2)O(4) spinel ferrite nanoparticles was examined. Adsorption loadings of sulfur dioxide at breakthrough conditions were determined to be approximately 0.62 mol/kg, which is significant given the 150 m(2)/g surface area of the nanoparticles. Adsorption proceeds through a chemisorption mechanism with sulfur dioxide forming a sulfate upon adsorption on the particle surface, which leads to a 23% decrease in the remnant magnetization, a 20% decrease in the saturation magnetization, and a 9% decrease in the coercivity of the magnetic nanoparticles. Adsorbent materials that provide a magnetic signal when adsorption occurs could have broad implications on adsorption-based separations.