Convergent Concordant Mode Approach for Molecular Vibrations: CMA-2.

The concordant mode approach (CMA) is a promising new scheme for dramatically increasing the system size and level of theory achievable in quantum chemical computations of molecular vibrational frequencies. Here, we achieve advances in the CMA hierarchy by computations targeting CCSD(T)/cc-pVTZ (coupled cluster singles and doubles with perturbative triples using a correlation-consistent polarized-valence triple-ζ basis set) benchmarks within the G2 molecular test set, executing a statistical analysis for 1501 frequencies from 111 compounds and then separately solving the refractory case of pyridine. First, MP2/cc-pVTZ (second-order Møller-Plesset perturbation theory with the same basis set) proves to be an excellent and preferred choice for generating the underlying (Level B) normal modes of the CMA scheme.

Resolution of Acute Respiratory Distress Syndrome-Induced Takotsubo Cardiomyopathy with Venovenous Extracorporeal Membrane Oxygenation.

Introduction: Takotsubo cardiomyopathy (TTCM) can occur in acute respiratory distress syndrome (ARDS) and a few cases in literature were reported to be associated with hemodynamic instability. All these patients were managed with venoarterial extracorporeal membrane oxygenation (VA-ECMO).Case presentation: We present two patients with ARDS-induced TTCM who were managed successfully with venovenous ECMO (VV-ECMO).

Fulminic acid: a quasibent spectacle.

Fulminic acid (HCNO) played a critical role in the early development of organic chemistry, and chemists have sought to discern the structure and characteristics of this molecule and its isomers for over 200 years. The mercurial nature of the extremely flat H-C-N bending potential of fulminic acid, with a nearly vanishing harmonic vibrational frequency at linearity, remains enigmatic and refractory to electronic structure theory, as dramatic variation with both orbital basis set and electron correlation method is witnessed. To solve this problem using rigorous electronic wavefunction methods, we have employed focal point analyses (FPA) to ascertain the limit of optimized linear and bent geometries, corresponding vibrational frequencies, and the HCN + O() → HCNO reaction energy.

Value of Imaging Measurements in Micrognathia-Related Fetal Airway Obstruction Within a Fetal Center.

Objective: Fetal imaging often identifies signs of upper airway obstruction due to micrognathia that may require airway intervention at delivery. This study investigated the role of quantitative fetal imaging measurements in predicting the need for otolaryngology consultation and intervention within a multidisciplinary Fetal Center.

Methods: Data were retrospectively collected from expectant mothers attending a multidisciplinary Fetal Center from January 2017 to October 2023.

Correction: Pericyclic reaction benchmarks: hierarchical computations targeting CCSDT(Q)/CBS and analysis of DFT performance.

Correction for 'Pericyclic reaction benchmarks: hierarchical computations targeting CCSDT(Q)/CBS and analysis of DFT performance' by Pascal Vermeeren , , 2022, , 18028-18042, https://doi.org/10.1039/D2CP02234F.

Remimazolam Sedation and Neuraxial Anesthesia in a Patient with Amyotrophic Lateral Sclerosis Undergoing an Open Colectomy: A Case Report.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease involving the upper and lower motor neurons. Perioperative management of patients with ALS can be challenging due to the risk of hemodynamic instability, aspiration, and ventilatory failure. We discuss a 58-year-old male patient with ALS who underwent open abdominal surgery under regional anesthesia utilizing a remimazolam infusion for sedation.

Preemptive Venoarterial Extracorporeal Membrane Oxygenation for Liver Transplantation-Judicious Candidate Selection.

Portopulmonary hypertension is a relatively common pathologic condition in patients with end-stage liver disease. Traditionally, severe pulmonary hypertension is regarded as a contraindication to liver transplantation (LT) due to a high perioperative mortality rate. Recently, extracorporeal membrane oxygenation (ECMO) has been utilized for intraoperative management of LT.

The multichannel i-propyl + O2 reaction system: A model of secondary alkyl radical oxidation.

The i-propyl + O2 reaction mechanism has been investigated by definitive quantum chemical methods to establish this system as a benchmark for the combustion of secondary alkyl radicals. Focal point analyses extrapolating to the ab initio limit were performed based on explicit computations with electron correlation treatments through coupled cluster single, double, triple, and quadruple excitations and basis sets up to cc-pV5Z. The rigorous coupled cluster single, double, and triple excitations/cc-pVTZ level of theory was used to fully optimize all reaction species and transition states, thus, removing some substantial flaws in reference geometries existing in the literature.

Concordant Mode Approach for Molecular Vibrations.

The Concordant Mode Approach (CMA) is advanced as a novel hierarchy for increasing the system size and level of theory feasible for quantum chemical computations of harmonic vibrational frequencies. The key concept behind CMA is that transferrable, internal-coordinate normal modes computed at an appropriate lower level of theory (B) comprise a superb basis for converging to vibrational frequencies given by a higher level of theory (A). Accordingly, high-level harmonic frequencies can be evaluated via CMA from a collection of single-point energies that essentially scales linearly in the number of atoms, providing nearly order-of-magnitude CPU time speedups.

Pericyclic reaction benchmarks: hierarchical computations targeting CCSDT(Q)/CBS and analysis of DFT performance.

Hierarchical, convergent benchmark computations were performed followed by a systematic analysis of DFT performance for five pericyclic reactions comprising Diels-Alder, 1,3-dipolar cycloaddition, electrocyclic rearrangement, sigmatropic rearrangement, and double group transfer prototypes. Focal point analyses (FPA) extrapolating to the limit were executed explicit quantum chemical computations with electron correlation treatments through CCSDT(Q) and correlation-consistent Gaussian basis sets up to aug'-cc-pV5Z. Optimized geometric structures and vibrational frequencies of all stationary points were obtained at the CCSD(T)/cc-pVTZ level of theory.

The Year in Graduate Medical Education: Selected Highlights From 2021.

This special article is the first in a planned annual series for the Journal of Cardiothoracic and Vascular Anesthesia that will highlight significant literature from the world of graduate medical education (GME) that was published over the past year. The major themes selected for this inaugural review are the educational value of simulation and training workshops, the expanding role of social media and other information technologies in GME and recruitment, the state of residency and fellowship training before the COVID-19 pandemic, and the inevitable effects COVID-19 has had on graduate medical education. The authors would like to thank the editorial board for allowing us to shine a light on a small subset of the writing and research produced in this field, so that educators may understand how best to educate and train the next generation of anesthesiologists.

Identification and Reactivity of -,--Dihydroxycarbene, a New [CHO] Intermediate.

We report the first preparation of the -,- conformer of dihydroxycarbene () by means of pyrolysis of oxalic acid, isolation of the lower-energy -,- () and -,- () product conformers at cryogenic temperatures in a N matrix, and subsequent narrow-band near-infrared (NIR) laser excitation to give . Carbene converts quickly to via quantum-mechanical tunneling with an effective half-life of 22 min at 3 K. The potential energy surface features around were pinpointed by convergent focal point analysis targeting the AE-CCSDT(Q)/CBS level of electronic structure theory.

Lung Transplantation Using a Hybrid Extracorporeal Membrane Oxygenation Circuit.

Extracorporeal circulation (ECC) support using intraoperative extracorporeal membrane oxygenation (ECMO) during lung transplantation (LTx) is now a routine practice for many high volume centers. Circuits that are dedicated to ECMO alone can be expensive and do not allow full cardiopulmonary bypass (CPB) to be performed. We describe our technique of instituting venoarterial ECMO during LTx using a less-expensive hybrid circuit that facilitates easy and immediate conversion to full CPB if needed, without interruption of ECC.

Reaction Profiles and Kinetics for Radical-Radical Hydrogen Abstraction via Multireference Coupled Cluster Theory.

Radical-radical abstractions in hydrocarbon oxidation chemistry are disproportionation reactions that are generally exothermic with little or no barrier yet are underappreciated and poorly studied. Such challenging multireference electronic structure problems are tackled here using the recently developed state-specific multireference coupled cluster methods Mk-MRCCSD and Mk-MRCCSD(T), as well as the companion perturbation theory Mk-MRPT2 and the established MRCISD, MRCISD+Q, and CASPT2 approaches. Reaction paths are investigated for five prototypes involving radical-radical hydrogen abstraction: H + BeH → H+ Be, H + NH → H + NH, CH + CH → CH + CH, H + CH → H + CH, and H + HCO → H + CO.

Wigner numbers.

All reduced Wigner rotation matrix elements d (θ) can be evaluated very efficiently as a linear combination of either cos(Nθ) or sin(Nθ) terms as N runs in unit steps from either 0 or 12 to J. Exact, infinite-precision formulas are derived here for the Fourier coefficients in these d (θ) expressions by finding remarkable analytic solutions for the normalized eigenvectors of arbitrarily large matrices that represent the Ĵ angular momentum operator in the basis of Ĵ eigenstates. The solutions involve collections of numbers W for (m, n) = (J-M, J-N) ∈ [0, 2J] that satisfy the recursion relation (m+1)W -2(J-n)W +(2J-m+1)W =0.

Phonomotor Versus Semantic Feature Analysis Treatment for Anomia in 58 Persons With Aphasia: A Randomized Controlled Trial.

Purpose The ultimate goal of anomia treatment should be to achieve gains in exemplars trained in the therapy session, as well as generalization to untrained exemplars and contexts. The purpose of this study was to test the efficacy of phonomotor treatment, a treatment focusing on enhancement of phonological sequence knowledge, against semantic feature analysis (SFA), a lexical-semantic therapy that focuses on enhancement of semantic knowledge and is well known and commonly used to treat anomia in aphasia. Method In a between-groups randomized controlled trial, 58 persons with aphasia characterized by anomia and phonological dysfunction were randomized to receive 56-60 hr of intensively delivered treatment over 6 weeks with testing pretreatment, posttreatment, and 3 months posttreatment termination.

Riddles of the structure and vibrational dynamics of HO resolved near the ab initio limit.

The hydridotrioxygen (HO) radical has been investigated in many previous theoretical and experimental studies over several decades, originally because of its possible relevance to the tropospheric HO cycle but more recently because of its fascinating chemical bonding, geometric structure, and vibrational dynamics. We have executed new, comprehensive research on this vexing molecule via focal point analyses (FPA) to approach the ab initio limit of optimized geometric structures, relative energies, complete quartic force fields, and the entire reaction path for cis-trans isomerization. High-order coupled cluster theory was applied through the CCSDT(Q) and even CCSDTQ(P) levels, and CBS extrapolations were performed using cc-pVXZ (X = 2-6) basis sets.

Probing the Delicate Balance between Pauli Repulsion and London Dispersion with Triphenylmethyl Derivatives.

The long-known, ubiquitously present, and always attractive London dispersion (LD) interaction was probed with hexaphenylethane (HPE) derivatives. A series of all- meta hydrocarbyl [Me, Pr, Bu, Cy, Ph, 1-adamantyl (Ad)]-substituted triphenylmethyl (TPM) derivatives [TPM-H, TPM-OH, (TPM-O), TPM] was synthesized en route, and several derivatives were characterized by single-crystal X-ray diffraction (SC-XRD). Multiple dimeric head-to-head SC-XRD structures feature an excellent geometric fit between the meta-substituents; this is particularly true for the sterically most demanding Bu and Ad substituents.

Most favorable cumulenic structures in iron-capped linear carbon chains are short singlet odd-carbon dications: a theoretical view.

Iron-capped, linear-carbon-chain dications have been investigated at the M06L/DZP level of quantum chemistry in order to determine their structural and electronic properties, focusing on differences between chains containing odd and even numbers of carbon atoms. Such differences result from changes in the electronic states and the acetylenic or cumulenic nature of the carbon chain. Interestingly, the short even-carbon chains exhibit distinct properties, but upon chain lengthening undergo a transition to structures similar to those of odd-carbon chains, with a turning point around [FeC10Fe]2+.

Nucleophilic Influences and Origin of the S 2 Allylic Effect.

The potential energy surfaces for the S 2 reactions of allyl and propyl chlorides with 21 anionic and neutral nucleophiles was studied by using ωB97X-D/6-311++G(3df,2pd) computations. The "allylic effect" on S 2 barriers was observed for all reactions, and compared with propyl substrates, the energy barriers differed by -0.2 to -4.

A Universal Integrated Rate Equation for Chemical Kinetics.

The overarching analytic integrated rate equation for the chemical kinetics of any reversible or irreversible reaction involving an arbitrary number of species and any integral orders is shown to be Π [1 - f ξ( t)] = e, where ξ( t) is the extent of reaction variable, the f are roots of a polynomial of order r, the exponents are determined by γ = Π ( f - f ), and F is a factor involving the stoichiometric coefficients and rate constants ( k). All integrated rate equations of elementary reactions appearing in chemical kinetics are special cases of this universal solution. Not only does the solution provide insight into the analytical form of the exponents γ and F that govern the time evolution of the system, but it also provides an elegant framework for the pedagogy and application of kinetics in physical chemistry.