ABSTRACT
A realistic double many-body expansion potential energy surface (PES) is developed for the 2Aâ³ state of the carbon-nitrogen-oxygen (CNO) system based on MRCI-F12/cc-pVQZ-F12 ab initio energies. The new PES reproduces the fitted points with chemical accuracy (root mean square deviation up to 0.043 eV) and explicitly incorporates long range energy terms that can accurately describe the electrostatic and dispersion interactions. Thermal rate coefficients were computed for the C(3P) + NO(2Π) reaction for temperatures ranging from 15 K to 10 000 K, and the values are compared to previously reported results. The differences are rationalized, and the major importance of long range forces in predicting the rate coefficients for barrierless reactions is emphasized.
ABSTRACT
The predicted rate constants for C + NO and O + CN collisions in three potential energy surfaces (PESs) for the 2A' state of the CNO molecule are compared using quasiclassical trajectories. Different temperature dependencies are obtained for the C + NO reaction, which are explained in terms of the long-range properties of the PESs. Recommended values and mechanistic details are also reported. For O + CN collisions, a better agreement between the theoretical results is found, except for temperatures below 100 K.
ABSTRACT
We report a new global double many-body expansion potential energy surface for the ground state of the CNO(2A') manifold, calculated by the explicit correlation multireference configuration interaction method. The functional form was accurately fitted to 3701 ab initio points with a root mean squared deviation of 0.99 kcal mol-1. All stationary points reported in previous forms are systematically described and improved, in addition to three new ones and a characterization of an isomerization transition state between the CNO and NCO minima. The novel proposed form gives a realistic description of both short-range and long-range interactions and hence is commended for dynamics studies.
ABSTRACT
Sickle cell anemia (SCA) causes dysfunction of multiple organs, with pulmonary involvement as a major cause of mortality. Recently, there has been growing interest in the nitrogen single-breath washout (N2SBW) test, which is able to detect ventilation heterogeneity and small airway disease when the results of other pulmonary function tests (PFTs) are still normal. Thus, the objectives of the present study were to assess the heterogeneity in the ventilation distribution in adults with SCA and to determine the association between the ventilation distribution and the clinical, cardiovascular, and radiological findings. This cross-sectional study included 38 adults with SCA who underwent PFTs, echocardiography, computed tomography (CT), and 6-min walk test. To evaluate the ventilation heterogeneity, the patients were categorized according to the phase III slope of the N2SBW (SIIIN2). Compared with adults with lower SIIIN2 values, adults with higher SIIIN2 values showed lower hemoglobin levels (P=0.048), a history of acute chest syndrome (P=0.001), an elevated tricuspid regurgitation velocity (P=0.039), predominance of a reticular pattern in the CT (P=0.002), a shorter 6-min walking distance (6MWD) (P=0.002), and lower peripheral oxygen saturation (SpO2) after exercise (P=0.03). SIIIN2 values correlated significantly with hemoglobin (rs=-0.344; P=0.034), forced vital capacity (rs=-0.671; P<0.0001), diffusing capacity for carbon monoxide (rs=-0.376; P=0.019), 6MWD (rs=-0.554; P=0.0003), and SpO2 after exercise (P=0.040). Heterogeneity in the ventilation distribution is one of the most common pulmonary dysfunctions in adults with SCA. Moreover, relationships exist between ventilation heterogeneity, worsening of pulmonary structural damage, and reduced tolerance for exercise.