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Abstract The symmetry breaking in octahedral silsesquioxane and its germanium analogues (Si₈O₁₂H₈and Ge₈O₁₂H₈) has been investigated using the M06-2X/6-31++G(3df, 3pd) method and group theory. Both structures undergo$${O}_{h}\downarrow {T}_{h}$$symmetry breaking, characterized by pseudo-Jahn−Teller stabilization energies of 0.22 kcal/mol for Si-POSS and 9.82 kcal/mol for Ge-POSS. Under the influence of the pseudo-Jahn–Teller effect, the distortion vector involves the vibrational a_2gmode with imaginary frequency. The distortion forces in O_h-POSS are predominantly localized on the oxygen atoms and driven by the coupling between the lowest unoccupied molecular orbital (a_1g) and the highest occupied molecular orbital (a_2g). The symmetry breaking is attributed to a pseudo-Jahn–Teller mechanism of type (a_2gx a_1g) = a_2g. The symmetrical substitution of oxygen atoms by X (where X = C, N, P) results in viable T_h-Si₈X₁₂H₈and T_h-Ge₈X₁₂H₈structures. The observed pseudo-Jahn–Teller distortion and substitutional symmetry breaking caused by X indicates a consistent electronic relaxation mechanism, characterized by the formation of C=C, N=N and P=P bonds on the POSS cubic faces, which serves as hallmarks of stability. Additionally, we find that the volume of substituted T_h-symmetrical POSS is sufficiently large to accommodate small ions. 

Abstract This work presents Neural Optimization for Melting-temperature Enabled by Leveraging Translation (NOMELT), a novel approach for designing and ranking high-temperature stable proteins using neural machine translation. The model, trained on over 4 million protein homologous pairs from organisms adapted to different temperatures, demonstrates promising capability in targeting thermal stability. A designed variant of theDrosophila melanogasterEngrailed Homeodomain shows a melting temperature increase of 15.5 K. Furthermore, NOMELT achieves zero-shot predictive capabilities in ranking experimental melting and half-activation temperatures across a number of protein families. It achieves this without requiring extensive homology data or massive training datasets as do existing zero-shot predictors by specifically learning thermophilicity, as opposed to all natural variation. These findings underscore the potential of leveraging organismal growth temperatures in context-dependent design of proteins for enhanced thermal stability. 

ABSTRACT The energies and geometries of the lowest lying singlet and triplet states of the four diradicals formed by removing two H atoms from thiophene have been characterized. We utilized the highly correlated, multireference methods configuration interaction with single and double excitations with and without the Pople correction for size‐extensivity (MR‐CISD+Q and MR‐CISD) and averaged quadratic coupled cluster theory (MR‐AQCC). CAS (8,7) and CAS (10,8) active spaces involving σ, σ*, π, and π* orbitals were employed along with the cc‐pVDZ and cc‐pVTZ basis sets. The larger active space included the two electrons in the nonbonding sp²hybrid orbital on sulfur. We find that all didehydro isomers exist as planar, stable ground state singlets. The singlet‐triplet (S‐T) adiabatic gaps range from 15 to 25 kcal/mol while the vertical splittings are 21–35 kcal/mol. The 2,3 isomer has the lowest absolute ground state singlet energy and the largest adiabatic and vertical S‐T splitting. The ground states of the 2,3‐, and 2,5‐didehydrothiophene isomers are predicted to exhibit the smallest and largest diradical character, respectively, based on their electronic structures, spin densities and bonding analysis. To our knowledge, no experimental excitation energies of any of the didehydrothiophene isomers are available, and our computed MR‐AQCC/cc‐pVTZ data are believed to be among the most accurate computed results. This extensive study shows a competitive performance between MR‐AQCC and MR‐CISD+Q. 

Abstract Superconductivity and exciton condensation are fundamental phenomena in condensed matter physics, associated with the condensation of electron–electron and electron–hole pairs, respectively, into coherent quantum states. In this study, we present evidence of a superconductor to exciton condensate transition within the context of the three-band Hubbard model of copper-oxide-like materials. As the electron–electron repulsion increases, the superconducting phase is superseded by exciton condensation. In support of theoretical predictions—not yet realized experimentally—we observe the coexistence of the two condensates in the vicinity of the transition where the quantum states become a superposition of electron–electron and electron–hole condensates. Coexistence is rigorously computed from large eigenvalues and their eigenvectors in both the two-electron reduced density matrix (2-RDM) and the particle-hole RDM, which we obtain from a direct variational ground-state energy minimization with respect to the 2-RDM by semidefinite programming. We further discern that adjacentdorbitals and interveningporbitals facilitate electron–electron pairing between copper orbitals, thereby supporting the superexchange mechanism for superconductivity. These observations suggest the feasibility of witnessing a superconductor to exciton condensate transition in copper-oxide analogs, bearing significant implications for identifying materials conducive to efficient transport processes. 

ABSTRACT The aggregation of plasmonic nanoparticles can lead to new and controllable properties useful for numerous applications. We recently showed the reversible aggregation of gold nanoparticles (AuNPs) via a small, cationic di‐arginine peptide; however, the mechanism underlying this aggregation is not yet comprehensively understood. Here, we seek insights into the intermolecular interactions of cationic peptide‐induced assembly of citrate‐capped AuNPs by empirically measuring how peptide identity impacts AuNP aggregation. We examined the nanoscale interactions between the peptides and the AuNPs via UV‐vis spectroscopy to determine the structure‐function relationship of peptide length and charge on AuNP aggregation. Careful tuning of the sequence of the di‐arginine peptide demonstrated that the mechanism of assembly is driven by a reduction in electrostatic repulsion. We show that acetylated N‐terminals and carboxylic acid C‐terminals decrease the effectiveness of the peptide in inducing AuNP aggregation. The increase in peptide size through the addition of glycine or proline units hinders aggregation and leads to less redshift. Arginine‐based peptides were also found to be more effective in assembling the AuNPs than cysteine‐based peptides of equivalent length. We also illustrate that aggregation is independent of peptide stereochemistry. Finally, we demonstrate the modulation of peptide‐AuNP behavior through changes to the pH, salt concentration, and temperature. Notably, histidine‐based and tyrosine‐based peptides could reversibly aggregate the AuNPs in response to the pH. 

Abstract Oligomeric models of linear ladder silanes, siloxanes and siloxazanes with seven repeat units consisting of four-, six-, or eight-membered rings were designed and their conformations in chloroform were explored. The Low Mode–Monte Carlo conformational method was used to explore oligomeric flexibility on the OPLS-2005/GBSA(CHCl₃) potential energy surface to obtain a set of low energy structures for each oligomer. These structures were then optimized using B3LYP/6-31G*/SCRF-PBF(CHCl₃) calculations. The results indicate complex conformational dynamics with mostly non-planar, curved structures. Electron delocalization from the lone pair of electrons on N or O into empty 3d orbitals on Si was not observed. 

Environmental contextIron-containing combustion particles are likely to contribute to environmental iron deposition, while atmospheric acidic processing of such particles can promote their dissolution. Here we report the surface-mediated dissolution of iron from ashes generated by biomass burning power plants and kilns. Examination of the dissolution process at several environmentally relevant pHs, suggests that pH has little impact on the fraction of bioavailable Fe(II) that dissolves into the aqueous phase, although Fe(III) is heavily pH dependent. RationaleAnthropogenic combustion particles, such as ash produced in power plants or kilns, are byproducts with limited use that accumulate in large deposits and become materials of environmental concern. While stored, these particles can be carried by winds into the atmosphere or into soil or near water bodies. Recent studies suggest that a fraction of metals present in the environment come from combustion particles. MethodologyIn this study, we carry out a comparative study of iron dissolution and speciation from two different combustion particles: bottom ash from a biomass-fired power plant (BA) and lime kiln dust (LKD). Samples were fully characterised and their iron leaching was investigated in aqueous suspensions under environmentally relevant acidic conditions. Iron analysis and speciation was carried out calorimetrically. ResultsFor the combustion particles examined, the fraction of bioavailable Fe2+ is lower than Fe3+. The solubility of Fe3+ is highly dependent on pH, dropping significantly at pHs higher than 3. On the other hand, the solubility of Fe2+ from both BA and LKD was found to be relatively constant over the range of pH investigated. DiscussionIron availability from combustion particles with similar mineralogy is driven by the particle’s surface properties. While iron from LKD dissolves faster than that from BA, the initial rate of dissolution of iron remains statistically constant at pHs relevant for the atmospheric aerosol deliquescent layer, decreasing at pHs above 3. This work provides insight into the ability of combustion particles to provide iron micronutrients under different environmentally relevant acidic conditions. 

ABSTRACT In this editorial, written by early-career scientists, we advocate for the invaluable role of society journals in our scientific community. By choosing to support these journals as authors, peer reviewers, and as editors, we can reinforce our academic growth and benefit from their re-investment back into the scientific ecosystem. Considering the numerous clear merits of this system for future generations of microbiologists and more broadly, society, we argue that early-career researchers should publish our high-quality research in society journals to shape the future of science and scientific publishing landscape. 

Abstract Quantum computers are promising tools for simulating many-body quantum systems due to their potential scaling advantage over classical computers. While significant effort has been expended on many-fermion systems, here we simulate a model entangled many-boson system with the contracted quantum eigensolver (CQE). We generalize the CQE to many-boson systems by encoding the bosonic wavefunction on qubits. The CQE provides a compact ansatz for the bosonic wave function whose gradient is proportional to the residual of a contracted Schrödinger equation. We apply the CQE to a bosonic system, whereNquantum harmonic oscillators are coupled through a pairwise quadratic repulsion. The model is relevant to the study of coupled vibrations in molecular systems on quantum devices. Results demonstrate the potential efficiency of the CQE in simulating bosonic processes such as molecular vibrations with good accuracy and convergence even in the presence of noise. 

Abstract We report hydroboration of carbodiimide and isocyanate substrates catalyzed by a cyclic carbodiphosphorane catalyst. The cyclic carbodiphosphorane outperformed the other Lewis basic carbon species tested, including other zerovalent carbon compounds, phosphorus ylides, anN‐heterocyclic carbene, and anN‐heterocyclic olefin. Hydroborations of seven carbodiimides and nine isocyanates were performed at room temperature to formN‐boryl formamidine andN‐boryl formamide products. Intermolecular competition experiments demonstrated the selective hydroboration of alkyl isocyanates over carbodiimide and ketone substrates. DFT calculations support a proposed mechanism involving activation of pinacolborane by the carbodiphosphorane catalyst, followed by hydride transfer and B−N bond formation.