Structural Transformation in a Sulfurized Polymer Cathode to Enable Long-Life Rechargeable Lithium-Sulfur Batteries.

Sulfurized polyacrylonitrile (SPAN) represents a class of sulfur-bonded polymers, which have shown thousands of stable cycles as a cathode in lithium-sulfur batteries. However, the exact molecular structure and its electrochemical reaction mechanism remain unclear. Most significantly, SPAN shows an over 25% 1st cycle irreversible capacity loss before exhibiting perfect reversibility for subsequent cycles. Here, with a SPAN thin-film platform and an array of analytical tools, we show that the SPAN capacity loss is associated with intramolecular dehydrogenation along with the loss of sulfur. This results in an increase in the aromaticity of the structure, which is corroborated by a >100× increase in electronic conductivity. We also discovered that the conductive carbon additive in the cathode is instrumental in driving the reaction to completion. Based on the proposed mechanism, we have developed a synthesis procedure to eliminate more than 50% of the irreversible capacity loss. Our insights into the reaction mechanism provide a blueprint for the design of high-performance sulfurized polymer cathode materials.

Outcome Monitoring After Cardiac Surgery (OMACS): a single-centre prospective cohort study of cardiac surgery patients.

INTRODUCTION: More than 30 000 cardiac surgery procedures are performed in the UK each year, however, postoperative complications and long-term failure of interventions are common, leading to repeated surgeries. This represents a significant burden on the patient and health service.Routinely, patients are discharged to their general practitioner 6 weeks postoperatively and research studies typically only report short-term outcomes up to 1 year after surgery, together this makes long-term outcomes of cardiac surgery difficult to monitor. Further, traditional research methods have yet to advance understanding of what causes early complications and why surgical interventions fail. METHODS AND ANALYSIS: This prospective cohort study will characterise participants undergoing cardiac surgery at baseline, describe short-term, medium-term and long-term health outcomes postoperatively and collect tissue samples.All eligible adult patients undergoing cardiac surgery at the Bristol Heart Institute, UK will be approached for consent. Recruitment is expected to continue for up to 10 years resulting in the largest cohort of cardiac patients reported to date. Blood, urine and waste tissue samples will be collected during admission. Samples, along with anonymised data, will be used to investigate outcomes and inform predictive models of complications associated with cardiac surgery.Data about the surgical admission will be obtained from hospital databases and medical notes. Participants may be monitored up to 5 years postoperatively using data obtained from NHS digital. Participants will complete health questionnaires 3 months and 12 months postoperatively.The analysis of data and tissue samples to address specific research questions will require separate research protocols and ethical approval. ETHICS AND DISSEMINATION: This study was approved by the East Midlands Nottingham 2 Research Ethics Committee.Findings will be disseminated through peer-reviewed publications and presentation at national and international meetings. Participants will be informed of results in annual newsletters. TRIAL REGISTRATION NUMBER: ISRCTN90204321.

A Fiber-Based 3D Lithium Host for Lean Electrolyte Lithium Metal Batteries.

3D hosts are promising to extend the cycle life of lithium metal anodes but have rarely been implemented with lean electrolytes thus impacting the practical cell energy density. To overcome this challenge, a 3D host that is lightweight and easy to fabricate with optimum pore size that enables full utilization of its pore volume, essential for lean electrolyte operations, is reported. The host is fabricated by casting a VGCF (vapor-grown carbon fiber)-based slurry loaded with a sparingly soluble rubidium nitrate salt as an additive. The network of fibers generates uniform pores of ≈3 µm in diameter with a porosity of 80%, while the nitrate additive enhances lithiophilicity. This 3D host delivers an average coulombic efficiency of 99.36% at 1 mA cm-2 and 1 mAh cm-2 for over 860 cycles in half-cell tests. Full cells containing an anode with 1.35-fold excess lithium paired with LiNi0.8 Mn0.1 Co0.1 O2 (NMC811) cathodes exhibit capacity retention of 80% over 176 cycles at C/2 under a lean electrolyte condition of 3 g Ah-1 . This work provides a facile and scalable method to advance 3D lithium hosts closer to practical lithium-metal batteries.

Alloying-realloying enabled high durability for Pt-Pd-3d-transition metal nanoparticle fuel cell catalysts.

Alloying noble metals with non-noble metals enables high activity while reducing the cost of electrocatalysts in fuel cells. However, under fuel cell operating conditions, state-of-the-art oxygen reduction reaction alloy catalysts either feature high atomic percentages of noble metals (>70%) with limited durability or show poor durability when lower percentages of noble metals (<50%) are used. Here, we demonstrate a highly-durable alloy catalyst derived by alloying PtPd (<50%) with 3d-transition metals (Cu, Ni or Co) in ternary compositions. The origin of the high durability is probed by in-situ/operando high-energy synchrotron X-ray diffraction coupled with pair distribution function analysis of atomic phase structures and strains, revealing an important role of realloying in the compressively-strained single-phase alloy state despite the occurrence of dealloying. The implication of the finding, a striking departure from previous perceptions of phase-segregated noble metal skin or complete dealloying of non-noble metals, is the fulfilling of the promise of alloy catalysts for mass commercialization of fuel cells.

Molecular Interactions Leading to the Coadsorption of Surfactant Dodecyltrimethylammonium Bromide and Poly(styrenesulfonate) at the Oil/Water Interface.

The strong synergistic adsorption of mixed polymer/surfactant (P/S) systems at the oil/water interface shows promise for applications such as oil remediation and emulsion stabilization, especially with respect to the formation of tunable mesoscopic multilayers. There is some evidence that a combination of dodecyltrimethylammonium bromide (DTAB) and sodium poly(styrenesulfonate) (PSS) exhibits the adsorption of a secondary P/S layer, though the structure of this layer has long eluded researchers. The focus of this study is to determine whether the DTAB-assisted adsorption of PSS at the oil/water interface occurs as a single layer or with subsequent multilayers. The study presented uses vibrational sum-frequency spectroscopy and interfacial tensiometry to determine the degree of PSS adsorption and orientation of its charged groups relative to the interface at three representative concentrations of DTAB. At low and intermediate DTAB concentrations, a single mixed DTAB/PSS monolayer adsorbs at the oil/water interface. No PSS adsorbs above the system critical micelle concentration. The interfacial charge is found to be similar to that of P/S complexes solvated in the aqueous solution. The surface adsorbate and P/S complexes in the bulk both exhibit a charge inversion at around the same DTAB concentration. This study demonstrates the importance of techniques which can differentiate between coadsorbing species and calls into question current models of P/S adsorption at an oil/water interface.

The heterodimeric assembly of the CD94-NKG2 receptor family and implications for human leukocyte antigen-E recognition.

The CD94-NKG2 receptor family that regulates NK and T cells is unique among the lectin-like receptors encoded within the natural killer cell complex. The function of the CD94-NKG2 receptors is dictated by the pairing of the invariant CD94 polypeptide with specific NKG2 isoforms to form a family of functionally distinct heterodimeric receptors. However, the structural basis for this selective pairing and how they interact with their ligand, HLA-E, is unknown. We describe the 2.5 A resolution crystal structure of CD94-NKG2A in which the mode of dimerization contrasts with that of other homodimeric NK receptors. Despite structural homology between the CD94 and NKG2A subunits, the dimer interface is asymmetric, thereby providing a structural basis for the preferred heterodimeric assembly. Structure-based sequence comparisons of other CD94-NKG2 family members, combined with extensive mutagenesis studies on HLA-E and CD94-NKG2A, allows a model of the interaction between CD94-NKG2A and HLA-E to be established, in which the invariant CD94 chain plays a more dominant role in interacting with HLA-E in comparison to the variable NKG2 chain.

The NMR solution structure of the relaxin (RXFP1) receptor lipoprotein receptor class A module and identification of key residues in the N-terminal region of the module that mediate receptor activation.

The receptors for the peptide hormones relaxin and insulin-like peptide 3 (INSL3) are the leucine-rich repeat-containing G-protein-coupled receptors LGR7 and LGR8 recently renamed as the relaxin family peptide (RXFP) receptors, RXFP1 and RXFP2, respectively. These receptors differ from other LGRs by the addition of an N-terminal low density lipoprotein receptor class A (LDLa) module and are the only human G-protein-coupled receptors to contain such a domain. Recently it was shown that the LDLa module of the RXFP1 and RXFP2 receptors is essential for ligand-stimulated cAMP signaling. The mechanism by which the LDLa module modulates receptor signaling is unknown; however, it represents a unique paradigm in understanding G-protein-coupled receptor signaling. Here we present the structure of the RXFP1 receptor LDLa module determined by solution NMR spectroscopy. The structure is similar to other LDLa modules but shows small differences in side chain orientations and inter-residue packing. Interchange of the module with the second ligand binding domain of the LDL receptor, LB2, results in a receptor that binds relaxin with full affinity but is unable to signal. Furthermore, we demonstrate via structural studies on mutated LDLa modules and functional studies on mutated full-length receptors that a hydrophobic surface within the N-terminal region of the module is essential for activation of RXFP1 receptor signal in response to relaxin stimulation. This study has highlighted the necessity to understand the structural effects of single amino acid mutations on the LDLa module to fully interpret the effects of these mutations on receptor activity.

The human LGR7 low-density lipoprotein class A module requires calcium for structure.

The relaxin and INSL3 receptors, LGR7 and LGR8, are the only human G-protein-coupled receptors to contain a low-density lipoprotein class-A (LDL-A) module. LDL-A modules are well characterized in a variety of diverse biological functions that involve ligand binding to elicit a response. Common features of the LDL-A modules characterized to date are the conservation of three disulfide bonds and the structural arrangement around a bound calcium ion. In this study we recombinantly produce the human LGR7 LDL-A module for NMR studies and demonstrate that calicum is required for the module to form a stable and correctly folded structure.