Risk factors prediction of 6-month mortality after noncardiac surgery of older patients in China: a multicentre retrospective cohort study.

BACKGROUND: Identifying the risk factors associated with perioperative mortality is crucial, particularly in older patients. Predicting 6-month mortality risk in older patients based on large datasets can assist patients and surgeons in perioperative clinical decision-making. This study aimed to develop a risk prediction model of mortality within 6 months after noncardiac surgery using the clinical data from 11 894 older patients in China. MATERIALS AND METHODS: A multicentre, retrospective cohort study was conducted in 20 tertiary hospitals. The authors retrospectively included 11 894 patients (aged ≥65 years) who underwent noncardiac surgery between April 2020 and April 2022. The least absolute shrinkage and selection operator model based on linear regression was used to analyse and select risk factors, and various machine learning methods were used to build predictive models of 6-month mortality. RESULTS: The authors predicted 12 preoperative risk factors associated with 6-month mortality in older patients after noncardiac surgery. Including laboratory-associated risk factors such as mononuclear cell ratio and total blood cholesterol level, etc. Also including medical history associated risk factors such as stroke, history of chronic diseases, etc. By using a random forest model, the authors constructed a predictive model with a satisfactory accuracy (area under the receiver operating characteristic curve=0.97). CONCLUSION: The authors identified 12 preoperative risk factors associated with 6-month mortality in noncardiac surgery older patients. These preoperative risk factors may provide evidence for a comprehensive preoperative anaesthesia assessment as well as necessary information for clinical decision-making by anaesthesiologists.

Investigation on spin-flip reaction of Re + CH3CN by relativistic density functional theory.

To explore the integrated reaction mechanisms for Re atom with acetonitrile theoretically, density functional theory with zero-order regular approximation (ZORA) relativistic corrections has been employed at the BP86/TZ2P level. There have been three adiabatic potential energy surfaces in the study along sextet, quartet and doublet spin states. However, the detailed minimum energy reaction pathway altogether contains six stationary states () to (), five transition states (), and two intersystem crossings with spin inversion (marked by ⇒): (6)Re + CH3CN → η(1)-ReNCCH3 () → ⇒ η(2)-Re(NC)CH3 () → → η(3)-HRe(NCCH2) () → → CH3-ReNC () → → CH2[double bond, length as m-dash]Re(H)NC () ⇒ → CH[triple bond, length as m-dash]Re(H)2NC (). Thereinto, the lowest energy crossing points (LECP) have been determined by the DFT fractional-occupation-number (FON) approach. The first spin inversion has transferred the potential energy surfaces from high-spin sextet to the quartet intermediate () with the subsequent C-C bond breakage. The second one from the quartet to the low-spin doublet state accompanies the C-H activation, decreasing the transition barrier by 157 kJ mol(-1). The overall reaction could be exothermic by about 210 kJ mol(-1). Harmonic vibration frequencies and NBO, WBO analysis are also applied to verified the experimental observed information.

Spin-flip reactions of Zr + C2H6 researched by relativistic density functional theory.

Density functional theory (DFT) with relativistic corrections of zero-order regular approximation (ZORA) has been applied to explore the reaction mechanisms of ethane dehydrogenation by Zr atom with triplet and singlet spin-states. Among the complicated minimum energy reaction path, the available states involves three transition states (TS), and four stationary states (1) to (4) and one intersystem crossing with spin-flip (marked by -->): (3) Zr + C 2 H 6 → (3) Zr-CH 3 -CH 3 ((3)1) → (3)TS 1/2 → (3) ZrH-CH 2 -CH 3 ((3)2) → (3) TS 2/3 --> (1) ZrH2-CH2 = CH2 ((1) 3) → (1) TS 3/4 → (1) ZrH 3 -CH = CH 2 ((1)4). The minimum energy crossing point is determined with the help of the DFT fractional-occupation-number (FON) approach. The spin inversion leads the reaction pathway transferring from the triplet potential energy surface (PES) to the singlet's accompanying with the activation of the second C-H bond. The overall reaction is calculated to be exothermic by about 231 kJ mol(-1). Frequency and NBO analysis are also applied to confirm with the experimental observed data.

Investigation of spin-flip reactions of Zr + CH3CN by relativistic density functional theory.

To explore the details of the reaction mechanisms of Zr atoms with acetonitrile molecules, the triplet and singlet spin-state potential energy surfaces have been investigated. Density functional theory (DFT) with the relativistic zero-order regular approximation at the PW91/TZ2P level has been applied. The complicated minimum energy reaction path involves four transition states (TS), stationary states 1-5 and one spin inversion (indicated by ⇒): (3)Zr + NCCH(3) → (3)Zr-η(1)-NCCH(3) ((3)1) → (3)TS(1/2) → (3)Zr-η(2)-(NC)CH(3) ((3)2) → (3)TS(2/3) → (3)ZrH-η(3)-(NCCH(2)) ((3)3) → (3)TS(3/4) → CNZrCH(3) ((3)4) ⇒ (1)TS(4/5) → CN(ZrH)CH(2) ((1)5). The minimum energy crossing point was determined with the help of the DFT fractional-occupation-number approach. The spin inversion leading from the triplet to the singlet state facilitates the activation of a C-H bond, lowering the rearrangement-barrier by 78 kJ/mol. The overall reaction is calculated to be exothermic by about 296 kJ/mol. All intermediate and product species were frequency and NBO analyzed. The species can be rationalized with the help of Lewis type formulas.

Investigation of spin-flip reactions of Nb + CH3CN by relativistic density functional theory.

In order to explore the details of the reaction mechanisms of Nb atoms with acetonitrile molecules, the sextet, quartet, and doublet spin state potential energy surfaces have been investigated. Density functional theory (DFT) with the relativistic zero-order regular approximation at the PW91/TZ2P level has been applied. The complicated minimum energy reaction path involves four transition states (TS), stationary states (1) to (5) and two intersystem crossings from spin sextets to quartets to doublets (indicated by ⇒): (6)Nb + NCCH3→(6)Nb η(1)-NCCH3 ((6)1) →(6)TS1/2⇒(4)Nb η(2)-(NC)CH3 ((4)2) →(4)TS2/3→(4)NbH η(3)-(NCCH2) ((4)3) →(4)TS3/4→ CNNbCH3 ((4)4) ⇒(2)TS4/5→ CN(NbH)CH2 ((2)5). The minimum energy crossing points were determined with the help of the DFT fractional-occupation-number approach. The first spin inversion leads from the sextet to an energetically low intermediate quartet ((4)2) with final insertion of Nb into the C-C bond. The second one from the quartet to the doublet state facilitates the activation of a C-H bond, lowering the rearrangement-barrier by 44 kJ mol(-1). The overall reaction is calculated to be exothermic by about 170-180 kJ mol(-1). All intermediate and product species were frequency and NBO analyzed. The species can be rationalized with the help of Lewis type formulas.

Spin-flip reaction of Re + CH4--a relativistic density functional theory investigation.

To explore the reaction mechanisms of methane dehydrogenation by gas-phase Re atom, the sextet, quartet, and doublet potential energy surfaces have been performed using density functional theory (DFT) and zero-order regular approximation relativistic corrections at the PW91/TZ2P level. The minimum energy reaction path is found to proceed through the following steps: (6)Re + CH(4) --> ReCH(4) ((6)1) --> H(3)CReH ((4)2) --> (4)TS2/3 --> H(2)CReH(2) ((4)3) --> (2)TS3/4 --> HCReH(3) ((2)4). Also, the reaction path involves the spin inversion twice in the different reaction steps. To better understand the spin inversion processes, the low energy crossing point is determined with the help of the density functional fractional occupation number approach. The first spin inversion, from the sextet state to the quartet state, makes the activation of the C-H bond energetically spontaneous. The second transition from the quartet state to the doublet state facilitates the cleavage of the second C-H bond, lowering the barrier from 186.1 to 24.2 kJ/mol. The overall reaction is calculated to be exothermic by 149.8 kJ/mol, and the final products in three spin states are investigated by NBO analysis, to compare the Re-C bonds and the C-H bonds.

All-Electron Scalar Relativistic Basis Sets for Third-Row Transition Metal Atoms.

A family of segmented all-electron relativistically contracted (SARC) basis sets for the elements Hf-Hg is constructed for use in conjunction with the Douglas-Kroll-Hess (DKH) and zeroth-order regular approximation (ZORA) scalar relativistic Hamiltonians. The SARC basis sets are loosely contracted and thus offer computational advantages compared to generally contracted relativistic basis sets, while their sufficiently small size allows them to be used in place of effective core potentials (ECPs) for routine studies of molecules. Practical assessments of the SARC basis sets in DFT calculations of atomic (ionization energies) as well as molecular properties (geometries and bond dissociation energies for MHn complexes) confirm that the basis sets yield accurate and reliable results, providing a balanced description of core and valence electron densities. CCSD(T) calculations on a series of gold diatomic compounds also demonstrate the applicability of the basis sets to correlated methods. The SARC basis sets will be of most utility in calculating molecular properties for which the core electrons cannot be neglected, such as studies of electron paramagnetic resonance, Mössbauer and X-ray absorption spectra, and topological analysis of electron densities.

A simple density functional fractional occupation number procedure to determine the low energy transition region of spin-flip reactions.

A computationally simple three-step procedure to survey the energy landscape and to determine the molecular transition structure and activation energy at the intersection of two weakly coupled electronic potential energy surfaces of different symmetry is suggested. Only commercial software is needed to obtain the transition states of, for instance, spin-flip reactions. The computational expense is only two to three times larger than that of the standard determination of an adiabatic reaction path. First, the structures of the two electronic initial and final states along a chosen reaction coordinate are individually optimized. At the "projected crossing," the two states have the same energy at the same value of the reaction coordinate, but different state-optimized partial structures. Second, the unique optimized structure of a low energy crossing point between the two states is determined with the help of the density functional fractional occupation number approach. Finally, the respective energy of the two states at the crossing is estimated by a single point calculation. The prescription is successfully applied to some simple topical examples from organic and from inorganic chemistry, respectively, concerning the spin-flip reactions (3)H(3)CS(+)-->(1)H(2)CSH(+) and (7)MoCO(2)-->(5)MoCO(2)-->(3)OMoCO.

Relativistic DFT study on the reaction mechanism of second-row transition metal Ru with CO2.

To estimate the importance of relativistic effects on the reaction mechanisms between Ru and CO2, the potential energy surfaces have been performed in the triplet and quintet electronic states using quasi-relativistic (Pauli), zero-order regularly approximated (ZORA), and nonrelativistic (NR) density functional theory (DFT) at the PW91/TZP level. The results demonstrate that there are two rival reaction mechanisms: one is an addition mechanism and the other is an insertion mechanism in the triplet state. The only mechanism in the quintet state is the insertion mechanism. The most favored reaction mechanism in Ru + CO2 is that the Ru atom in its ground state first attacks the CO bond of CO2, forming q-Ru(CO)O (5A'') with the insertion mechanism, and then undergoes an intersystem crossing to t-Ru(CO)O (3A''). Then it crosses t-TS3 to produce t-ORuCO molecule. The relativistic effects are important for reactivity of the second-row transition metal to CO2. In the key step of t-Ru(CO)O via t-TS3 to t-ORuCO, relativistic effects reduce the barrier energy by 10.3 kcal/mol, which is nearly half the nonrelativistic barrier energy.

Modulation in spinal circuits and corticospinal connections following nerve stimulation and operant conditioning.

Neural plasticity occurs throughout adult life. In healthy individuals, different spinal pathways are differently modulated during different daily activities. Drastic changes to nervous system activity and connections caused by injuries or diseases alter spinal reflexes, and this is often related to disturbed motor functions. In both health and disease, spinal reflexes are subject to substantial modifications. Plasticity in supraspinal descending connections is even more remarkable; corticospinal connectivity has been shown to be extremely plastic. In this session, we describe two approaches for possibly improving recovery after central nervous system (CNS) lesions. They are very different, but both involve repetitive nerve stimulation and CNS plasticity. The first approach is functional electrical stimulation (FES) of the common peroneal nerve, which has been used to treat foot drop in patients with CNS lesions. The second approach is operant conditioning of a spinal reflex. Spinal reflex operant conditioning studies in animal models have shown plastic changes in spinal cord neurons associated with this form of learning and improved locomotor function in incomplete spinal cord injured rats. Thus, reflex conditioning might be a robust approach to inducing plasticity at spinal and supraspinal levels. As a first step in establishing this approach and characterizing its effects in the human adult CNS, we are currently investigating the extent and time course of operant conditioning of the soleus H-reflex in healthy subjects. In results to date, all subjects (n=5) have changed reflex size in the correct direction to various degree (16-36%) over 2-3 months of conditioning, indicating possibility that H-reflex conditioning can occur in humans. At the same time, the substantial inter-subject variation in the time course and extent of conditioning suggest that additional data are needed to establish its principal features. We hope that studying modulation and modification o- f the CNS by different approaches will help us further understand the plasticity of the human adult nervous system.