Selective and Stable CO2 Electroreduction to CH4 via Electronic Metal-Support Interaction upon Decomposition/Redeposition of MOF.

The CO2 electroreduction to fuels is a feasible approach to provide renewable energy sources. Therefore, it is necessary to conduct experimental and theoretical investigations on various catalyst design strategies, such as electronic metal-support interaction, to improve the catalytic selectivity. Here a solvent-free synthesis method is reported to prepare a copper (Cu)-based metal-organic framework (MOF) as the precursor. Upon electrochemical CO2 reduction in aqueous electrolyte, it undergoes in situ decomposition/redeposition processes to form abundant interfaces between Cu nanoparticles and amorphous carbon supports. This Cu/C catalyst favors the selective and stable production of CH4 with a Faradaic efficiency of ≈55% at -1.4 V versus reversible hydrogen electrode (RHE) for 12.5 h. The density functional theory calculation reveals the crucial role of interfacial sites between Cu and amorphous carbon support in stabilizing the key intermediates for CO2 reduction to CH4 . The adsorption of COOH* and CHO* at the Cu/C interface is up to 0.86 eV stronger than that on Cu(111), thus promoting the formation of CH4 . Therefore, it is envisioned that the strategy of regulating electronic metal-support interaction can improve the selectivity and stability of catalyst toward a specific product upon electrochemical CO2 reduction.

Surface charge as activity descriptors for electrochemical CO2 reduction to multi-carbon products on organic-functionalised Cu.

Intensive research in electrochemical CO2 reduction reaction has resulted in the discovery of numerous high-performance catalysts selective to multi-carbon products, with most of these catalysts still being purely transition metal based. Herein, we present high and stable multi-carbon products selectivity of up to 76.6% across a wide potential range of 1 V on histidine-functionalised Cu. In-situ Raman and density functional theory calculations revealed alternative reaction pathways that involve direct interactions between adsorbed histidine and CO2 reduction intermediates at more cathodic potentials. Strikingly, we found that the yield of multi-carbon products is closely correlated to the surface charge on the catalyst surface, quantified by a pulsed voltammetry-based technique which proved reliable even at very cathodic potentials. We ascribe the surface charge to the population density of adsorbed species on the catalyst surface, which may be exploited as a powerful tool to explain CO2 reduction activity and as a proxy for future catalyst discovery, including organic-inorganic hybrids.

Insight into the Origin of Trapping in Polymer/Fullerene Blends with a Systematic Alteration of the Fullerene to Higher Adducts.

The bimolecular recombination characteristics of conjugated polymer poly[(4,4'-bis(2-ethylhexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,5-bis 3-tetradecylthiophen-2-yl thiazolo 5,4-d thiazole)-2,5diyl] (PDTSiTTz) blended with the fullerene series PC60BM, ICMA, ICBA, and ICTA have been investigated using microsecond and femtosecond transient absorption spectroscopy, in conjunction with electroluminescence measurements and ambient photoemission spectroscopy. The non-Langevin polymer PDTSiTTz allows an inspection of intrinsic bimolecular recombination rates uninhibited by diffusion, while the low oscillator strengths of fullerenes allow polymer features to dominate, and we compare our results to those of the well-known polymer Si-PCPDTBT. Using µs-TAS, we have shown that the trap-limited decay dynamics of the PDTSiTTz polaron becomes progressively slower across the fullerene series, while those of Si-PCPDTBT are invariant. Electroluminescence measurements showed an unusual double peak in pristine PDTSiTTz, attributed to a low energy intragap charge transfer state, likely interchain in nature. Furthermore, while the pristine PDTSiTTz showed a broad, low-intensity density of states, the ICBA and ICTA blends presented a virtually identical DOS to Si-PCPDTBT and its blends. This has been attributed to a shift from a delocalized, interchain highest occupied molecular orbital (HOMO) in the pristine material to a dithienosilole-centered HOMO in the blends, likely a result of the bulky fullerenes increasing interchain separation. This HOMO localization had a side effect of progressively shifting the polymer HOMO to shallower energies, which was correlated with the observed decrease in bimolecular recombination rate and increased "trap" depth. However, since the density of tail states remained the same, this suggests that the traditional viewpoint of "trapping" being dominated by tail states may not encompass the full picture and that the breadth of the DOS may also have a strong influence on bimolecular recombination.

Electronic transport descriptors for the rapid screening of thermoelectric materials.

The discovery of novel materials for thermoelectric energy conversion has potential to be accelerated by data-driven screening combined with high-throughput calculations. One way to increase the efficacy of successfully choosing a candidate material is through its evaluation using transport descriptors. Using a data-driven screening, we selected 12 potential candidates in the trigonal ABX2 family, followed by charge transport property simulations from first principles. The results suggest that carrier scattering processes in these materials are dominated by ionised impurities and polar optical phonons, contrary to the oft-assumed acoustic-phonon-dominated scattering. Using these data, we further derive ground-state transport descriptors for the carrier mobility and the thermoelectric powerfactor. In addition to low carrier mass, high dielectric constant was found to be an important factor towards high carrier mobility. A quadratic correlation between dielectric constant and transport performance was established and further validated with literature. Looking ahead, dielectric constant can potentially be exploited as an independent criterion towards improved thermoelectric performance. Combined with calculations of thermal conductivity including Peierls and inter-branch coherent contributions, we conclude that the trigonal ABX2 family has potential as high performance thermoelectrics in the intermediate temperature range for low grade waste heat harvesting.

Temporal Trends of Revision Etiologies in Total Knee Arthroplasty at a Single High-Volume Institution: An Epidemiological Analysis.

BACKGROUND: Temporal changes in revision total knee arthroplasty (rTKA) may have implications in determining the etiology for implant failure. The purpose of this study was to 1) perform an epidemiologic analysis of etiologies that required rTKA and 2) determine whether temporal changes existed for revision over the study period. METHODS: All rTKA procedures performed at a single institution from 2009 to 2019 were analyzed. Revision procedures were stratified into 2 time periods, 2009-2013 and 2014-2019, to assess for changes over time. Patients' electronic medical record, operative report, and radiographs were reviewed to ensure diagnosis information was accurately documented in relation to the predominate etiology necessitating the revision procedure. RESULTS: Three thousand and nine patients undergoing rTKA between 2009 and 2019 were identified with a mean age of 64.6 years. A total of 1,666 (55.4%) patients were female, and the majority of patients were Caucasian (2,306, 76.6%). The 3 most frequent rTKA etiologies were aseptic loosening (35.1%), periprosthetic infection (33.2%), and instability (16.0%). A higher proportion of patients underwent rTKA for arthrofibrosis (5.1% vs 3.4%, P = .023) and periprosthetic joint infection (38.9% vs 28.6%, P < .001) between 2009 and 2013, while a significantly higher proportion of patients underwent rTKA for instability (12.6% vs 18.8%, P < .001) between 2014 and 2019. CONCLUSION: Aseptic loosening was the most common cause for rTKA over the last decade. rTKA for arthrofibrosis and periprosthetic joint infection was more frequent between 2009 and 2013, while a significantly higher proportion of patients underwent rTKA for instability in 2014-2019. Future studies will need to focus on identifying and reducing risk factors for the trending causes of rTKA.

An epidemiological analysis of revision aetiologies in total hip arthroplasty at a single high-volume centre.

AIMS: Advances in surgical technique and implant design may influence the incidence and mechanism of failure resulting in revision total hip arthroplasty (rTHA). The purpose of the current study was to characterize aetiologies requiring rTHA, and to determine whether temporal changes existed in these aetiologies over a ten-year period. METHODS: All rTHAs performed at a single institution from 2009 to 2019 were identified. Demographic information and mode of implant failure was obtained for all patients. Data for rTHA were stratified into two time periods to assess for temporal changes: 2009 to 2013, and 2014 to 2019. Operative reports, radiological imaging, and current procedural terminology (CPT) codes were cross-checked to ensure the accurate classification of revision aetiology for each patient. RESULTS: In all, 2,924 patients with a mean age of 64.6 years (17 to 96) were identified. There were 1,563 (53.5%) female patients, and the majority of patients were Caucasian (n = 2,362, 80.8%). The three most frequent rTHA aetiologies were infection (27.2%), aseptic loosening (25.2%), and wear (15.2%). The frequency of rTHA for adverse local tissue reaction (ALTR) was significantly greater from 2014 to 2019 (4.7% vs 10.0%; p < 0.001), while the frequency of aseptic loosening was significantly greater from 2009 to 2013 (28.6% vs 21.9%; p < 0.001). CONCLUSION: Periprosthetic joint infection was the most common cause for rTHA in the current cohort of patients. Complications associated with ALTR necessitating rTHA was more frequent between 2014 to 2019, while aseptic loosening necessitating rTHA was significantly more frequent between 2009 to 2013. Optimizing protocols for prevention and management of infection and ALTR after THA may help to avoid additional financial burden to institutions and healthcare systems.Cite this article: Bone Joint Open 2020;2(1):16-21.

Unravelling V6O13 Diffusion Pathways via CO2 Modification for High-Performance Zinc Ion Battery Cathode.

Vanadium-based oxide is widely investigated as a zinc ion battery (ZIB) cathode due to its ability to react reversibly with Zn2+. Despite its successful demonstration, modification with simple molecules has shown some promise in enhancing the performance of ZIBs. Thus, this presents an immense opportunity to explore simple molecules that can dramatically improve the electrochemical performance of electrodes. Thus, the effect of CO2 modification is studied in this work by decomposing oxalic acid within a hydrated V6O13 framework. Based on the collective results, the presence of CO2 drastically lowers the relative energy of Zn2+ diffusion through the pathways by forming weak electrostatic interactions between OCO2 and Zn2+. This leads to an enlarged diffusion contribution, which consequently results in enhanced stability and better rate performance. The as-synthesized CO2-V6O13 electrode delivers one of the highest specific capacities reported for vanadium-based oxides of ca. 471 mAh g-1. Furthermore, an excellent cyclic stability of 80% capacity retention after 4000 cycles at 2 A g-1 is recorded for CO2-V6O13, which suggests the importance of simple molecules in the material framework toward the enhancement of ZIB cathode performance.

Multi Band Gap Electronic Structure in CH3NH3PbI3.

Organo-lead halide perovskite solar cells represent a revolutionary shift in solar photovoltaics, introducing relatively soft defect containing semiconductors as materials with excellent charge collection for both electrons and holes. Although they are based on the nominally simple cubic perovskite structure, these compounds are in fact very complex. For example, in (CH3NH3)PbI3 the dynamics and ensuing structural fluctuations associated with the (CH3NH3)+ ions and the interplay with the electronic properties are still not fully understood, despite extensive study. Here, using ab-initio calculations, we show that at room and higher temperature, the rotation of CH3NH3 molecules can be viewed as effectively giving local structures that are cubic and tetragonal like from the point of view of the PbI3 framework, though in fact having lower symmetry. Both of these structures are locally polar, with sizable polarization, ~10 µC/cm2 due to the dipoles on the organic. They become energetically degenerate in the volume range, V ~ 250 Å3/f.u-265 Å3/f.u. We also find very significant dependence of the band gap on the local structure. This type of transition is analogous to a transition between two ferroelectric structures, where in-spite of strong electron phonon coupling, there is strong screening of charged defects which can lead to enhanced mobility and charge collection. The results provide insights into the enhanced light absorption near the band edge and good charge collection in this material.

The Effect of Depression on Patient-Reported Outcomes After Total Joint Arthroplasty Is Modulated by Baseline Mental Health: A Registry Study.

BACKGROUND: Depression and poor mental health are known to be negative predictors of patient-reported outcomes after total joint arthroplasty. Although previous studies have examined these risk factors in isolation to each other, they are, in reality, closely related, and yet each represents a different aspect of one's psychological well-being. The objective of this study was to investigate the association between depression and patient-reported outcomes, taking into account patients' baseline mental health. METHODS: Our prospective, institutional joint registry was queried for patients who had undergone primary elective total joint arthroplasty and had a minimum follow-up of 1 year. Baseline mental health was measured by the Short Form-12 Mental Component Summary (SF-12 MCS). Four cohorts were analyzed on the basis of the presence or absence of depression and patients' SF-12 MCS scores at the time of the surgical procedure, which were categorized as either poor or good on the basis of previously defined cutoffs. The primary outcomes were the net changes in SF-12 MCS, SF-12 Physical Component Summary (PCS), and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores at 4 and 12 months postoperatively. Univariate and mixed-effects model analyses were performed to control for potential confounding factors. RESULTS: Patients with depression but good baseline mental health achieved gains in patient-reported outcomes that were comparable with those of normal controls (p > 0.05). Patients with poor baseline mental health achieved significant gains in all patient-reported outcomes, but the changes were largest for those without depression (p < 0.05). Only patients with depression and poor baseline mental health did not cross the threshold for good mental health at the time of the latest follow-up despite achieving similar gains in physical function compared with their counterparts who did not have depression. CONCLUSIONS: The effect of depression on patient-reported outcomes is more complex but less pessimistic than previously thought. Patients with depression undergoing total joint arthroplasty may have significant improvements in their patient-reported outcomes, but the net gains are modulated by their mental health at the time of the surgical procedure. Preoperative screening of patients with depression using the SF-12 MCS may help to identify those who are at risk for attaining suboptimal patient-reported outcomes and may benefit from counseling or psychiatric referral for optimization before undergoing a surgical procedure. LEVEL OF EVIDENCE: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Orbital-Engineering-Based Screening of π-Conjugated d8 Transition-Metal Coordination Polymers for High-Performance n-Type Thermoelectric Applications.

Extraordinary progress has been achieved in polymer-based thermoelectric materials in recent years. New emerging π-conjugated transition-metal coordination polymers are one of the best n-type polymer-based thermoelectric materials. However, the microscopic descriptions on geometric structures, orbital characteristics, and most importantly, thermoelectric properties remain elusive, which has seriously hampered the experimentalists to draw a straightforward design strategy for new n-type polymer-based thermoelectric materials. Herein, we assess the n-type thermoelectric properties of 20 π-conjugated d8 metal center coordination polymers and rationalize their thermoelectric properties in terms of molecular geometry, orbital nature, and electron-phonon coupling based on first-principles calculations. An explicit screening rule for high-performance n-type π-conjugated transition-metal coordination polymeric thermoelectric materials was found, i.e., smaller metal center d orbital component ratio in the conduction band minimum, weaker electron-phonon coupling, higher intrinsic mobility, and thereby higher thermoelectric power factor can be achieved. Guided by this rule, poly(Pd-C2S4) and poly(Ni-C2Se4) show very high power factors. We built a map of high-performance π-conjugated transition-metal coordination polymers for n-type thermoelectric applications, which will help to accelerate the screening and design of innovative n-type thermoelectric polymers.

Site specificity of halogen bonding involving aromatic acceptors.

Halogen bonding (XB) has become one of the most studied non-covalent interactions in the past two decades, owing to its wide range of applications in materials and biological applications. Most of the current theoretical and experimental studies focus on XB involving lone-pair acceptors due to its predictability in terms of crystal geometries. However, recent reports have advocated the importance of XB materials involving aromatic-type acceptors because of their relevance in functional materials, catalysis and biological systems. Herein, we report the XB site-specificity in several polycyclic aromatic hydrocarbons (PAHs) and N-heteroaromatic compounds that are ubiquitous in chemical systems. Based on a series of quantum chemical studies of Cl2 and Br2 XB complexes with 14 representative systems, these XB sites can be easily predicted using occupied molecular orbitals and atomic charges. We envisage that the predicted site maps will be useful for materials and drug design involving this class of non-covalent interactions.

Thioamide-Directed Cobalt(III)-Catalyzed Selective Amidation of C(sp3 )-H Bonds.

A mild, oxidant-free, and selective Cp*CoIII -catalyzed amidation of thioamides with robust dioxazolone amidating agents via C(sp3 )-H bond activation to generate the desired amidated products is reported. The method is efficient and allows for the C-H amidation of a wide range of functionalized thioamides with aryl-, heteroaryl-, and alkyl-substituted dioxazolones under the Cp*CoIII -catalyzed conditions. The observed regioselectivity towards primary C(sp3 )-H activation is supported by computational studies and the cyclometalation is proposed to proceed by means of an external carboxylate-assisted concerted metalation/deprotonation mechanism. The reported method is a rare example of the use of a directing group other than the commonly used pyridine and quinolone classes for Cp*CoIII -catalyzed C(sp3 )-H functionalization and the first to exploit thioamides.

Using non-empirically tuned range-separated functionals with simulated emission bands to model fluorescence lifetimes.

Fluorescence lifetimes were evaluated using TD-DFT under different approximations for the emitting molecule and various exchange-correlation functionals, such as B3LYP, BMK, CAM-B3LYP, LC-BLYP, M06, M06-2X, M11, PBE0, ωB97, ωB97X, LC-BLYP*, and ωB97X* where the range-separation parameters in the last two functionals were tuned in a non-empirical fashion. Changes in the optimised molecular geometries between the ground and electronically excited states were found to affect the quality of the calculated lifetimes significantly, while the inclusion of vibronic features led to further improvements over the assumption of a vertical electronic transition. The LC-BLYP* functional was found to return the most accurate fluorescence lifetimes with unsigned errors that are mostly within 1.5 ns of experimental values.

High-Throughput Survey of Ordering Configurations in MXene Alloys Across Compositions and Temperatures.

2D transition metal carbides and nitrides known as MXenes are gaining increasing attention. About 20 of them have been synthesized (more predicted) and their applications in fields ranging from energy storage and electromagnetic shielding to medicine are being explored. To facilitate the search for double-transition-metal MXenes, we explore the structure-stability relationship for 8 MXene alloy systems, namely, (V1-xMox)3C2, (Nb1-xMox)3C2, (Ta1-xMox)3C2, (Ti1-xMox)3C2, (Ti1-xNbx)3C2, (Ti1-xTax)3C2, (Ti1-xVx)3C2, and (Nb1-xVx)3C2, with 0 ≤ x ≤ 1, using high-throughput computations. Starting from density-functional theory calculated formation energies, we used the cluster expansion method to build quick-to-compute interactions, enabling us to scan through the formation energies of millions of alloying configurations. For the Mo-rich MXenes, (M11-xMox)3C2 (where M1: Ti, V, Nb, Ta) Mo atoms prefer to occupy the surface layers, and ordering persists to high temperatures, based on our Monte Carlo simulations. When Ti is alloyed with Nb or Ta, in the Ti-rich MXenes, Ti atoms prefer the surface layers (e.g., Ti-C-Nb-C-Ti sequence), and in the Nb- or Ta-rich MXenes, Ti occupies only one surface layer and the other two layers are Nb or Ta (e.g., Ti-C-Nb-C-Nb), exhibiting asymmetric ordering. However, alloying Ti with V results in solid solutions across all compositions. (Nb1-xVx)3C2 phase separates at lower temperatures but forms solid solutions at synthesis temperatures. Postsynthesis annealing at moderate temperatures (800 to 1000 K) increases the ordering for all the compositions. Lastly, by investigating the stability of their precursor MAX phases and surface-terminated MXenes, we discuss the synthesis possibilities of highly ordered MXenes.

Regeneration of Articular Cartilage by Human ESC-Derived Mesenchymal Progenitors Treated Sequentially with BMP-2 and Wnt5a.

The success of cell-based therapies to restore joint cartilage requires an optimal source of reparative progenitor cells and tight control of their differentiation into a permanent cartilage phenotype. Bone morphogenetic protein 2 (BMP-2) has been extensively shown to promote mesenchymal cell differentiation into chondrocytes in vitro and in vivo. Conversely, developmental studies have demonstrated decreased chondrocyte maturation by Wingless-Type MMTV Integration Site Family, Member 5A (Wnt5a). Thus, we hypothesized that treatment of human embryonic stem cell (hESC)-derived chondroprogenitors with BMP-2 followed by Wnt5a may control the maturational progression of these cells into a hyaline-like chondrocyte phenotype. We examined the effects of sustained exposure of hESC-derived mesenchymal-like progenitors to recombinant Wnt5a or BMP-2 in vitro. Our data indicate that BMP-2 promoted a strong chondrogenic response leading to terminal maturation, whereas recombinant Wnt5a induced a mild chondrogenic response without promoting hypertrophy. Moreover, Wnt5a suppressed BMP-2-mediated chondrocyte maturation, preventing the formation of fibrocartilaginous tissue in high-density cultures treated sequentially with BMP-2 and Wnt5a. Implantation of scaffoldless pellets of hESC-derived chondroprogenitors pretreated with BMP-2 followed by Wnt5a into rat chondral defects induced an articular-like phenotype in vivo. Together, the data establish a novel role for Wnt5a in controlling the progression from multipotency into an articular-like cartilage phenotype in vitro and in vivo. Stem Cells Translational Medicine 2017;6:40-50.

Computational and Experimental Investigation of the Structure of Peptide Monolayers on Gold Nanoparticles.

The self-assembly and self-organization of small molecules on the surface of nanoparticles constitute a potential route toward the preparation of advanced proteinlike nanosystems. However, their structural characterization, critical to the design of bionanomaterials with well-defined biophysical and biochemical properties, remains highly challenging. Here, a computational model for peptide-capped gold nanoparticles (GNPs) is developed using experimentally characterized Cys-Ala-Leu-Asn-Asn (CALNN)- and Cys-Phe-Gly-Ala-Ile-Leu-Ser-Ser (CFGAILSS)-capped GNPs as a benchmark. The structure of CALNN and CFGAILSS monolayers is investigated using both structural biology techniques and molecular dynamics simulations. The calculations reproduce the experimentally observed dependence of the monolayer secondary structure on the peptide capping density and on the nanoparticle size, thus giving us confidence in the model. Furthermore, the computational results reveal a number of new features of peptide-capped monolayers, including the importance of sulfur movement for the formation of secondary structure motifs, the presence of water close to the gold surface even in tightly packed peptide monolayers, and the existence of extended 2D parallel ß-sheet domains in CFGAILSS monolayers. The model developed here provides a predictive tool that may assist in the design of further bionanomaterials.

A Review of Databases Used in Orthopaedic Surgery Research and an Analysis of Database Use in Arthroscopy: The Journal of Arthroscopic and Related Surgery.

PURPOSE: The purpose of this study was to evaluate how database use has changed over time in Arthroscopy: The Journal of Arthroscopic and Related Surgery and to inform readers about available databases used in orthopaedic literature. METHODS: An extensive literature search was conducted to identify databases used in Arthroscopy and other orthopaedic literature. All articles published in Arthroscopy between January 1, 2006, and December 31, 2015, were reviewed. A database was defined as a national, widely available set of individual patient encounters, applicable to multiple patient populations, used in orthopaedic research in a peer-reviewed journal, not restricted by encounter setting or visit duration, and with information available in English. RESULTS: Databases used in Arthroscopy included PearlDiver, the American College of Surgeons National Surgical Quality Improvement Program, the Danish Common Orthopaedic Database, the Swedish National Knee Ligament Register, the Hospital Episodes Statistics database, and the National Inpatient Sample. Database use increased significantly from 4 articles in 2013 to 11 articles in 2015 (P = .012), with no database use between January 1, 2006, and December 31, 2012. CONCLUSIONS: Database use increased significantly between January 1, 2006, and December 31, 2015, in Arthroscopy. LEVEL OF EVIDENCE: Level IV, systematic review of Level II through IV studies.

Empirical and Computational Insights into N-Arylation Reactions Catalyzed by Palladium meta-Terarylphosphine Catalyst.

An in situ generated Pd-Cy*Phine catalyst has been successfully applied to the N-arylation of primary and secondary amines, and it exhibited high performance across multiple substrate classes. The performance induced by the meta-terarylphosphine motif of the Cy*Phine ligand for C-N cross-coupling displayed only subtle differences to that of its biarylphosphine congener XPhos. DFT studies demonstrated comparable reaction energetics in the catalytic cycle steps for both Pd-Cy*Phine and Pd-XPhos, which was consistent with previous findings. The computational investigation also indicated that a putative rate-determining step occurred after amine binding, which was likely to have annulled the expected benefits of having a meta-terarylphosphine ligand architecture.