Susceptibility formulation of density matrix perturbation theory.

Density matrix perturbation theory based on recursive Fermi-operator expansions provides a computationally efficient framework for time-independent response calculations in quantum chemistry and materials science. From a perturbation in the Hamiltonian, we can calculate the first-order perturbation in the density matrix, which then gives us the linear response in the expectation values for some chosen set of observables. We present an alternative, dual formulation, where we instead calculate the static susceptibility of an observable, which then gives us the linear response in the expectation values for any number of different Hamiltonian perturbations.

The relationship between preoperative sleep disturbance and acute postoperative pain control: A systematic review and meta-analysis.

Poor preoperative sleep quality and impaired sleep continuity may heighten acute postoperative pain intensity and increase analgesic consumption, with negative implications for recovery, mental and physical health. The main objective of the current review was to investigate the relationship between preoperative sleep disturbance and acute postoperative pain control. Four electronic databases were systematically searched from inception to December 2023.

Timing of menarche and pubertal growth patterns using the QEPS growth model.

Objectives: To explore the timing of menarche, postmenarcheal growth, and to investigate the impact of various variables on menarcheal age and postmenarcheal and pubertal growth.

Study Design: This longitudinal community population-based study analyzed pubertal growth and menarcheal age in 793 healthy term-born Swedish girls, a subset of the GrowUpGothenburg cohort. The timing of menarche and postmenarcheal growth was related to variables from the Quadratic-Exponential-Pubertal-Stop (QEPS) growth model, birth characteristics, and parental height.