101 research outputs found
Self-reported Physical Activity and Objective Aerobic Fitness: Differential Associations with Gray Matter Density in Healthy Aging
Aerobic fitness (AF) and self-reported physical activity (srPA) do not represent the same construct. However, many exercise and brain aging studies interchangeably use AF and srPA measures, which may be problematic with regards to how these metrics are associated with brain outcomes, such as morphology. If AF and PA measures captured the same phenomena, regional brain volumes associated with these measures should directly overlap. This study employed the general linear model to examine the differential association between objectively-measured AF (treadmill assessment) and srPA (questionnaire) with gray matter density (GMd) in 29 cognitively unimpaired community- dwelling older adults using voxel based morphometry. The results show significant regional variance in terms of GMd when comparing AF and srPA as predictors. Higher AF was associated with greater GMd in the cerebellum only, while srPA displayed positive associations with GMd in occipito-temporal, left perisylvian, and frontal regions after correcting for age. Importantly, only AF level, and not srPA, modified the relationship between age and GMd, such that higher levels of AF were associated with increased GMd in older age, while decreased GMd was seen in those with lower AF as a function of age. These results support existing literature suggesting that both AF and PA exert beneficial effects on GMd, but only AF served as a buffer against age-related GMd loss. Furthermore, these results highlight the need for use of objective PA measurement and comparability of tools across studies, since results vary dependent upon the measures used and whether these are objective or subjective in nature
Synthesis of endoperoxides by domino reactions of ketones and molecular oxygen
Domino reactions of ketones with molecular oxygen in the presence of potassium hydroxide and potassium t-butoxide afford cyclic hydroperoxy acetals (3,5-dihydroxy-1,2-dioxanes). Mixed endoperoxides can also be obtained in a three-component reaction of two ketones and oxygen.Supplementary material: [http://cherry.chem.bg.ac.rs/handle/123456789/3442
Supplementary data for article: Novkovic, L.; Trmcic, M.; Rodic, M.; Bihelovic, F.; Zlatar, M.; Matovic, R.; Saicic, R. N. Synthesis of Endoperoxides by Domino Reactions of Ketones and Molecular Oxygen. RSC Advances 2015, 5 (120), 99577–99584. https://doi.org/10.1039/c5ra13476e
Supplementary material for: [https://doi.org/10.1039/c5ra13476e]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2000
Supplementary information for: "Dissociative electron attachment and electronic excitation in Fe(CO)(5)"
Geometry of Fe(CO)5 (xyz coordinates); Excited states: Spin and dipole allowed transitions; Spin allowed, dipole forbidden transitions; Singlet-triplet transitions.The supplementary information for: Allan, M., Lacko, M., Papp, P., Matejcik, S., Zlatar, M., Fabrikant, I. I., Kocisek, J.,& Fedor, J. (2018). Dissociative electron attachment and electronic excitation in Fe(CO)(5). Physical Chemistry Chemical Physics, Royal Soc Chemistry, Cambridge., 20(17), 11692-11701. [https://doi.org/10.1039/c8cp01387j]The published version of the article: [https://cer.ihtm.bg.ac.rs/handle/123456789/2312]The peer-reviewed version of the article: [http://cer.ihtm.bg.ac.rs/handle/123456789/2659
Density functional theory study of the multimode Jahn-Teller effect – ground state distortion of benzene cation
The multideterminental-DFT approach performed to analyze Jahn-Teller (JT) active molecules is described. Extension of this method for the analysis of the adiabatic potential energy surfaces and the multimode JT effect is presented. Conceptually a simple model, based on the analogy between the JT distortion and reaction coordinates gives further information about microscopic origin of the JT effect. Within the harmonic approximation the JT distortion can be expressed as a linear combination of all totally symmetric normal modes in the low symmetry minimum energy conformation, which allows calculating the Intrinsic Distortion Path, IDP, exactly from the high symmetry nuclear configuration to the low symmetry energy minimum. It is possible to quantify the contribution of different normal modes to the distortion, their energy contribution to the total stabilization energy and how their contribution changes along the IDP. It is noteworthy that the results obtained by both multideterminental-DFT and IDP methods for different classes of JT active molecules are consistent and in agreement with available theoretical and experimental values. As an example, detailed description of the ground state distortion of benzene cation is given
Nuclear Tunnelling and Dynamical Jahn-Teller Effect in Graphene with Vacancy
We show that the substitutional vacancy in graphene forms a dynamical
Jahn-Teller center. The adiabatic potential surface resulting from the
electron-lattice coupling was computed using density-functional methods and
subsequently the Schr\"odinger equation was solved for the nuclear motion. Our
calculations show a large tunnelling splitting of about 86
cm. %, which is large as compared to the typical strain splitting. The
effect results in a large delocalization of the carbon nuclear wave functions
around the vacancy leading to a significant broadening of the Jahn-Teller
active electron states. The tunnelling splitting should be
observable in electron paramagnetic resonance and two-photon resonance
scattering experiments.Comment: 5 pages, 4 figure
Exploring the Role of Relational Practices in Water Governance Using a Game-Based Approach
The growing complexity and interdependence of water management processes requires the involvement of multiple stakeholders in water governance. Multi-party collaboration is increasingly vital at both the strategy development and implementation levels. Multi-party collaboration involves a process of joint decision-making among key stakeholders in a problem domain directed towards the future of that domain. However, the common goal is not present from the beginning; rather, the common goal emerges during the process of collaboration. Unfortunately, when the conflicting interests of different actors are at stake, the large majority of environmental multi-party efforts often do not reliably deliver sustainable improvements to policy and/or practice. One of the reasons for this, which has been long established by many case studies, is that social learning with a focus on relational practices is missing. The purpose of this paper is to present the design and initial results of a pilot study that utilized a game-based approach to explore the effects of relational practices on the effectiveness of water governance. This paper verifies the methods used by addressing the following question: are game mechanisms, protocols for facilitation and observation, the recording of decisions and results, and participant surveys adequate to reliably test hypotheses about behavioral decisions related to water governance? We used the “Lords of the Valley” (LOV) game, which focuses on the local-level management of a hypothetical river valley involving many stakeholders. We used an observation protocol to collect data on the quality of relational practices and compared this data with the quantitative outcomes achieved by participants in the game. In this pilot study, we ran the game three times with different groups of participants, and here we provide the outcomes within the context of verifying and improving the methods
Supplementary data for article: Novkovic, L.; Trmcic, M.; Rodic, M.; Bihelovic, F.; Zlatar, M.; Matovic, R.; Saicic, R. N. Synthesis of Endoperoxides by Domino Reactions of Ketones and Molecular Oxygen. RSC Advances 2015, 5 (120), 99577–99584. https://doi.org/10.1039/c5ra13476e
Supplementary material for: [https://doi.org/10.1039/c5ra13476e]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/2000
Dissociative electron attachment and electronic excitation in Fe(CO)5
In a combined experimental and theoretical study we characterize dissociative electron attachment (DEA) to, and electronically excited states of, Fe(CO)5. Both are relevant for electron-induced degradation of Fe(CO)5. The strongest DEA channel is cleavage of one metal–ligand bond that leads to production of Fe(CO)4−. High- resolution spectra of Fe(CO)4− reveal fine structures at the onset of vibrational excitation channels. Effective range R-matrix theory successfully reproduces these structures as well as the dramatic rise of the cross section at very low energies and reveals that virtual state scattering dominates low-energy DEA in Fe(CO)5 and that intramolecular vibrational redistribution (IVR) plays an essential role. The virtual state hypothesis receives further experimental support from the rapid rise of the elastic cross section at very low energies and intense threshold peaks in vibrational excitation cross sections. The IVR hypothesis is confirmed by our measurements of kinetic energy distributions of the fragment ions, which are narrow (∼0.06 eV) and peak at low energies (∼0.025 eV), indicating substantial vibrational excitation in the Fe(CO)4− fragment. Rapid IVR is also revealed by the yield of thermal electrons, observed in two-dimensional (2D) electron energy loss spectroscopy. We further measured mass-resolved DEA spectra at higher energies, up to 12 eV, and compared the bands observed there to resonances revealed by the spectra of vibrational excitation cross sections. Dipole-allowed and dipole/spin forbidden electronic transitions in Fe(CO)5—relevant for neutral dissociation by electron impact—are probed using electron energy loss spectroscopy and time-dependent density functional theory calculations. Very good agreement between theory and experiment is obtained, permitting assignment of the observed bands
Lipophilicity Assessment of Ruthenium(II)-Arene Complexes by the Means of Reversed-Phase Thin-Layer Chromatography and DFT Calculations
The lipophilicity of ten ruthenium(II)-arene complexes was assessed by reversed-phase thin-layer chromatography (RP-TLC) on octadecyl silica stationary phase. The binary solvent systems composed of water and acetonitrile were used as mobile phase in order to determine chromatographic descriptors for lipophilicity estimation. Octanol-water partition coefficient, log OW , of tested complexes was experimentally determined using twenty-eight standard solutes which were analyzed under the same chromatographic conditions as target substances. In addition, ab initio density functional theory (DFT) computational approach was employed to calculate log OW values from the differences in Gibbs' free solvation energies of the solute transfer from n-octanol to water. A good overall agreement between DFT calculated and experimentally determined log OW values was established (R 2 = 0.8024-0.9658)
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