ABSTRACT
Second-order Møller-Plesset perturbation theory (MP2) constitutes the simplest form of many-body wavefunction theory and often provides a good compromise between efficiency and accuracy. There are, however, well-known limitations to this approach. In particular, MP2 is known to fail or diverge for some prototypical condensed matter systems like the homogeneous electron gas (HEG) and to overestimate dispersion-driven interactions in strongly polarizable systems. In this paper, we explore how the issues of MP2 for metallic, polarizable, and strongly correlated periodic systems can be ameliorated through regularization. To this end, two regularized second-order methods (including a new, size-extensive Brillouin-Wigner approach) are applied to the HEG, the one-dimensional Hubbard model, and the graphene-water interaction. We find that regularization consistently leads to improvements over the MP2 baseline and that different regularizers are appropriate for the various systems.
ABSTRACT
The structural and optoelectronic properties of mixed halide perovskite colloidal precursor dispersions are investigated. With increasing concentration, we observe four stages of growing structures, which affect the thin film morphology: (I) nanoparticles, (II) increasing size of nanoparticles, (III) formation of large aggregates/complex clusters and (IV) fragmentation of large aggregates.
ABSTRACT
BACKGROUND: Androgen excess may provoke or aggravate acne by inducing seborrhea. In women, androgen disorders are frequently suspected when acne is accompanied by hirsutism or irregularities of the menstrual cycle. In men, however, acne may be the only sign of androgen excess. OBJECTIVE: Our aim was to investigate whether male patients with acne display pathologic androgen blood values. METHODS: This case-control study at a university dermatology department with referred and unreferred patients investigated male acne patients (n = 82, consecutive sample) in whom the diagnosis of mild to severe acne was made, as well as a control group of men without acne (n = 38). The main outcome measures were androgen parameters including morning values of testosterone, luteinizing hormone, follicle-stimulating hormone, dehydroepiandrosterone sulfate, androstenedione, and 17-hydroxyprogesterone; as well as a corticotropin stimulation test. RESULTS: 17-Hydroxyprogesterone levels were significantly higher (P = .01) in acne patients than in the control group, whereas the other parameters did not differ significantly. In addition, the corticotropin stimulation test revealed abnormal 17-hydroxyprogesterone induction values in 10 of 82 patients. LIMITATIONS: The analysis is limited to a selection of androgen parameters. CONCLUSION: The results suggest that in men irregularities of adrenal steroid metabolism may be a factor contributing to acne.
