Understanding the properties of electronically excited states is a challenging task that becomes increasingly important for numerous applications in chemistry, molecular physics, molecular biology, and materials science. A substantial impact is exerted by the fascinating progress in time-resolved spectroscopy, which leads to a strongly growing demand for theoretical methods to describe the characteristic features of excited states accurately. Whereas for electronic ground state problems of stable molecules the quantum chemical methodology is now so well developed that informed nonexperts can use it efficiently, the situation is entirely different concerning the investigation of excited states. This review is devoted to a specific class of approaches, usually denoted as multireference (MR) methods, the generality of which is needed for solving many spectroscopic or photodynamical problems. However, the understanding and proper application of these MR methods is often found to be difficult due to their complexity and their computational cost. The purpose of this review is to provide an overview of the most important facts about the different theoretical approaches available and to present by means of a collection of characteristic examples useful information, which can guide the reader in performing their own applications.

Prostaglandins (PGs) are important lipid mediators involved in the development of inflammatory associated pain and fever. PGE2 is a well-established endogenous pyrogen activated by proinflammatory cytokine interleukin (IL)-1β. P2X7 receptors (P2X7Rs) expressed by inflammatory cells are stimulated by the danger signal extracellular ATP to activate the inflammasome and release IL-1β. Here we show that P2X7R activation is required for the release of PGE2 and other autacoids independent of inflammasome activation, with an ATP EC(50) for PGE2 and IL-1β release of 1.58 and 1.23 mM, respectively. Furthermore, lack of P2X7R or specific antagonism of P2X7R decreased the febrile response in mice triggered after intraperitoneal LPS or IL-1β inoculation. Accordingly, LPS inoculation caused intraperitoneal ATP accumulation. Therefore, P2X7R antagonists emerge as novel therapeutics for the treatment for acute inflammation, pain and fever, with wider anti-inflammatory activity than currently used cyclooxygenase inhibitors.-Barberà-Cremades, M., Baroja-Mazo, A., Gomez, A. I., Machado, F., Di Virgilio, F., Pelegrín, P. P2X7 receptor-stimulation causes fever via PGE2 and IL-1β release.

The cumulative comoving number-density of galaxies as a function of stellar mass or central velocity dispersion is commonly used to link galaxy populations across different epochs. By assuming that galaxies preserve their number-density in time, one can infer the evolution of their properties, such as masses, sizes, and morphologies. However, this assumption does not hold in the presence of galaxy mergers or when rank ordering is broken owing to variable stellar growth rates. We present an analysis of the evolving comoving number density of galaxy populations found in the Illustris cosmological hydrodynamical simulation focused on the redshift range 0 ≤ z ≤ 3. Our primary results are as follows: 1) The inferred average stellar mass evolution obtained via a constant comoving number density assumption is systematically biased compared to the merger tree results at the factor of ∼2(4) level when tracking galaxies from redshift z = 0 out to redshift z = 2(3); 2) The median number density evolution for galaxy populations tracked forward in time is shallower than for galaxy populations tracked backward in time; 3) A similar evolution in the median number density of tracked galaxy populations is found regardless of whether number density is assigned via stellar mass, stellar velocity dispersion, or dark matter halo mass; 4) Explicit tracking reveals a large diversity in galaxies' assembly histories that cannot be captured by constant number-density analyses; 5) The significant scatter in galaxy linking methods is only marginally reduced by considering a number of additional physical and observable galaxy properties as realized in our simulation. We provide fits for the forward and backward median evolution in stellar mass and number density for use with observational data and discuss the implications of our analysis for interpreting multi-epoch galaxy property observations as related to galaxy evolution.

Semiempirical theories of bonding in molecules containing transition metals are often merely interpretive. That is, given the experimental fact that a molecule exists and has a particular shape, theory is used to provide a plausible ad hoc justification. Much interpretation of this type uses molecular orbital theory1 and ascribes bonding effects to orbital mixing. Earlier approaches such as ligand-field theory have been more or less abandoned along with the alternative insights they provided. Modern ab initio methods, on the other hand, have the possibility of being quantitatively predictive. They can be used to study the relative energies of the observed structure and nonobserved plausible alternatives. They can also be used to examine * Author to whom correspondence should be addressed. i Deceased, March 28, 1991.

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The binding energy of Cr(C0)6 was investigated using correlated methods. The multireference CI and QDVARPT approaches yield estimates of the binding energy which are about 72% and 90% of the experimental value.The radial correlation between electrons in the 5aeg, 3d*eg, 3dt2,, and 27r*tzg orbitals is the predominant source of the correlation correction to the bonding.

Accurate potential energy curves, transition moments, spectroscopic constants, radiative transition probabilities, and lifetimes for the states X 2 Σ + and A 2 Π of BeF, MgF and CaF are reported using high level calculations. Diagonal transitions dominate for the A 2 Π → X 2 Σ + system. Radiative lifetimes for ν = 0 are predicted to be 6.81 ns, 7.16 ns and 19.48 ns, respectively for BeF, MgF and CaF. The result calculated for the CaF molecule are in excellent agreement with the experimental result equal to 21.9 ± 4.0 ns.

High level ab initio calculations ranging from coupled cluster methods including explicitly correlated approaches to standard second order Møller-Plesset theory using spin scaling (SOS-MP2) have been performed on sandwich and slipped parallel dimer structures of a series of quasi one-dimensional acenes and on two-dimensional sheets containing the series pyrene to coronene encircled with two layers of benzene rings. Sandwich (graphitic AA type) and slipped parallel (AB type) structures were considered and, within given symmetry restrictions, full geometry optimizations were performed. Basis set superposition effects have