Potential energy surfaces of charge transfer states

In this paper the potential energy curves of charge transfer (CT) electronic states and their interaction with local ones have been investigated. Besides the global view of these curves, special attention has been paid to the region of the crossing and the infinite separation limit. It was found that triple excitations are needed to accurately describe potential energy surfaces of CT states. Among the cheaper variants, both STEOM-CCSD and CCSD(T)(a)* methods are promising in this respect. The somewhat larger error of CCSD for CT states can be explained by its size extensivity error and the overestimation of the asymptotic excitation energy. Second order approximations are not advantageous for the error cancellation, in fact CC2 is much worse for CT states than any other method investigated here. The results also show that the location of the (avoided) crossings of local and CT states depend very much on the accurate description of the CT states. Failure to describe this topology might affect dynamics, and a warning, in particular in case of CC2, should be issued if CT states play a role in the physics of the problem

Polyaromatic Hydrocarbons with an Imperfect Aromatic System as Catalysts of Interstellar H2_{2} Formation

Although H$_{2}$ is the simplest and the most abundant molecule in the Universe, its formation in the interstellar medium, especially in the photodissociation regions is far from being fully understood. According to suggestions, the formation of H$_{2}$ is catalyzed by polyaromatic hydrocarbons (PAHs) on the surface of interstellar grains. In the present study, we have investigated the catalytic effect of small PAHs with an imperfect aromatic system. Quantum chemical computations were performed for the H-atom-abstraction and H-atom-addition reactions of benzene, cyclopentadiene, cycloheptatriene, indene, and 1H-phenalene. Heights of reaction barriers and tunneling reaction rate constants were computed with density functional theory using the MPWB1K functional. For each molecule, the reaction path and the \warn{rate constants} were determined at 50 K using ring-polymer instanton theory, and the temperature dependence of the \warn{rate constants} was investigated for cyclopentadiene and cycloheptatriene. The computational results reveal that defects in the aromatic system compared to benzene can increase the rate of the catalytic H$_{2}$ formation at 50 K

Comparison of approximate intermolecular potentials for ab initio fragment calculations on medium sized N‐heterocycles

The ground state intermolecular potential of bimolecular complexes of N‐heterocycles is analyzed for the impact of individual terms in the interaction energy as provided by various, conceptually different theories. Novel combinations with several formulations of the electrostatic, Pauli repulsion, and dispersion contributions are tested at both short‐ and long‐distance sides of the potential energy surface, for various alignments of the pyrrole dimer as well as the cytosine–uracil complex. The integration of a DFT/CCSD density embedding scheme, with dispersion terms from the effective fragment potential (EFP) method is found to provide good agreement with a reference CCSD(T) potential overall; simultaneously, a quantum mechanics/molecular mechanics approach using CHELPG atomic point charges for the electrostatic interaction, augmented by EFP dispersion and Pauli repulsion, comes also close to the reference result. Both schemes have the advantage of not relying on predefined force fields; rather, the interaction parameters can be determined for the system under study, thus being excellent candidates for ab initio modeling

Introduction of a pharmacological neurovascular uncoupling model in rats based on results of mice

Our aim was to establish a pharmacologically induced neurovascular uncoupling (NVU) method in rats as a model of human cognitive decline. Pharmacologically induced NVU with subsequent neurological and cognitive defects was described in mice, but not in rats so far. We used 32 male Hannover Wistar rats. NVU was induced by intraperitoneal administration of a pharmacological “cocktail” consisting of N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide (MSPPOH, a specific inhibitor of epoxyeicosatrienoic acid-producing epoxidases, 5 mg kg−1), L-NG-nitroarginine methyl ester (L-NAME, a nitric oxide synthase inhibitor, 10 mg kg−1) and indomethacin (a nonselective inhibitor of cyclooxygenases, 1 mg kg−1) and injected twice daily for 8 consecutive days. Cognitive performance was tested in the Morris water-maze and fear-conditioning assays. We also monitored blood pressure. In a terminal operation a laser Doppler probe was used to detect changes in blood-flow (CBF) in the barrel cortex while the contralateral whisker pad was stimulated. Brain and small intestine tissue samples were collected post mortem and examined for prostaglandin E2 (PGE2) level. Animals treated with the “cocktail” showed no impairment in their performance in any of the cognitive tasks. They had higher blood pressure and showed cca. 50 decrease in CBF. Intestinal bleeding and ulcers were found in some animals with significantly decreased levels of PGE2 in the brain and small intestine. Although we could evoke NVU by the applied mixture of pharmacons, it also induced adverse side effects such as hypertension and intestinal malformations while the treatment did not cause cognitive impairment. Thus, further refinements are still required for the development of an applicable model

A laparoszkópia szerepe a colitis ulcerosa kezelésében = Use of laparoscopic technique in the treatment of ulcerative colitis

Bevezetés: A colitis ulcerosában szenvedő betegpopuláció 20–30%-a szorul élete során sebészi kezelésre. Napjainkban a proctocolectomia ileoanalis pouch képzésével az általánosan elfogadott műtéti módszer, melynél egyre szélesebb körben alkalmazzák a laparoszkópos technikát. Célkitűzés: Az elmúlt 13 évben szerzett tapasztalatainkat mutatjuk be colitis ulcerosa kezelésében a hagyományos és a minimálisan invazív technika vonatkozásában. Módszer: 2005. január 1. és 2018. május 31. között 89 beteg (48 nő és 41 férfi) került műtétre intézetünkben colitis ulcerosa miatt. A betegek átlagéletkora a laparoszkópos és a nyitott csoportban 45,06 ± 14,4, illetve 39,8 ± 13,4 év volt. Vizsgáltuk a műtétre kerülő betegek általános állapotát, a műtéti beavatkozások korai és késői eredményeit, különös tekintettel a szövődményekre és az életminőség változásaira. Eredmények: Perioperatív időszakban a két csoport ápolási napjainak számában (10,3 ± 3,3 vs. 11,2 ± 3,7) és transz- fúziós igényében (2,6 ± 2,2 vs. 2,8 ± 1,7) különbséget nem találtunk, azonban a laparoszkópos műtéteket követően az intenzív osztályon töltött napok száma (2,1 ± 0,9 vs. 2,5 ± 1,6) és a passzázs megindulásának napja (1,2 ± 0,5 vs. 1,6 ± 0,7) szignifikánsan rövidebb volt. Hosszú távú szövődmények, mint a passzázszavar, a septicus állapot, a poszt- operatív sérvek és az „egyéb” komplikációk száma a laparoszkópos csoportban szignifikánsan kevesebb volt. Az akut műtéteket vizsgálva a laparoszkópia szignifikáns előnye igazolódott a műtét utáni passzázsrendeződés napjainak kap- csán (1,2 ± 0,4 vs. 1,8 ± 0,7). Következtetés: A colitis ulcerosa sebészi kezelésében a minimálisan invazív technika a nyitott műtétekhez képest ked- vezőbb perioperatív eredményeket és hosszú távon jobb életminőséget biztosít, a kevesebb késői szövődmény meg- jelenésének és a betegek stabilabb pszichés állapotának következtében