The present study sought to extend knowledge of the role of boldness, a transdiagnostic bipolar trait dimension involving low sensitivity to threat, in emotional reactivity and regulation using ...physiological and report-based measures. One prior study found that boldness was associated with reduced late positive potential (LPP) while passively viewing aversive images, but not during emotion regulation; a disconnect between LPP and self-reported reactivity was also observed. Here, participants (N = 63) completed an emotion regulation task in which they either passively viewed or effortfully up- or downregulated their emotional reactivity to pleasant, unpleasant, and neutral pictures while EEG activity was recorded; they later retrospectively rated the success of their regulation efforts. ANOVAs examining the interactive effects of regulation instruction and boldness on LPP amplitude revealed that lower boldness (higher trait fearfulness) was associated with paradoxical increases in LPP to threat photos during instructed downregulation, relative to passive viewing, along with lower reported regulation success on these trials. Unexpectedly, similar LPP effects were observed for affective images overall, and especially nurturance photos. Although subject to certain limitations, these results suggest that individual differences in boldness play a role not only in general reactivity to aversive stimuli, as evidenced by prior work, but in the ability to effortfully downregulate emotional response.
•The boldness-trait fear dimension plays a role in effortful emotion regulation.•Less-bold people showed an enhanced brain response when trying to downregulate.•Boldness results were consistent across physiology and self-report for threat images.•Physiological effects for boldness extended to other kinds of affective images.
DFT calculations support an arenium cation-based mechanism for the Scholl reaction converting hexaphenylbenzene to hexa-peri-benzocoronene. The curve connecting fully benzenoid intermediates on the ...potential energy diagram is convex. This “slippery slope” provides an explanation for the ease of this cascade Scholl reaction. The calculated reaction coordinate predicts that intermediates will not accumulate; this prediction is verified by experiment.
A strategy for the synthesis of polycyclic aromatic hydrocarbons (PAHs) by the ring-closing olefin metathesis (RCM) of pendant olefins on a phenylene backbone has been developed. RCM of 2,4‘,6‘,2‘ ...‘-tetravinyl-1,1‘;3‘,1‘ ‘terphenyl and 2,2‘,5‘,2‘ ‘-tetravinyl-1,1‘;4‘,1‘terphenyl affords in high yield the isomeric a,j and a,h dibenzanthracenes, respectively. In contrast with other intramolecular annulation methods, such as Friedel−Crafts acylations, this reaction is completely regioselective. Since RCM is reversible and PAHs are often thermodynamic sinks, this strategy is an effective and general method for the preparation of PAHs. Density functional theory calculations support these results. Carbon disulfide is a suitable solvent for these reactions.
The application of the Clar aromatic sextet valence bond (VB) model to extended, defect-free single-walled carbon nanotubes (CNTs) with roll-up vectors (m, n) provides a real space model of their ...electronic structure. If m − n = 3k, where k is an integer, then all π-electrons can be represented by aromatic sextets, and the CNT is fully benzenoid; the converse is also true. Since m − n = 3k is known to be a necessary criterion for conductivity in CNTs, only fully benzenoid CNTs are metallic, and only potentially metallic CNTs are fully benzenoid. This behavior contrasts with that of planar polycyclic aromatic hydrocarbons, in which the fully benzenoid structures are known to have large HOMO−LUMO gaps. For CNTs that are not fully benzenoid, e.g., m − n = 3k + l, where l = 1 or 2 and k is an integer, a seam of double bonds wraps about an otherwise benzenoid CNT at the chiral angle − 60° or the chiral angle, respectively. Nucleus-independent chemical shift calculations on hydrogen-terminated CNT segments support this, and show that the magnetic manifestation of aromatic sextets is not due to electron correlation. The resonance hybrid of the Clar VB structures corresponds to patterns occasionally observed in scanning tunneling microscopy images of CNTs.
Quantum bits (qubits) are the fundamental building blocks of quantum information processors, such as quantum computers. A qubit comprises a pair of well characterized quantum states that can in ...principle be manipulated quickly compared to the time it takes them to decohere by coupling to their environment. Much remains to be understood about the manipulation and decoherence of semiconductor qubits. Here we show that hydrogen-atom-like motional states of electrons bound to donor impurities in currently available semiconductors can serve as model qubits. We use intense pulses of terahertz radiation to induce coherent, damped Rabi oscillations in the population of two low-lying states of donor impurities in GaAs. Our observations demonstrate that a quantum-confined extrinsic electron in a semiconductor can be coherently manipulated like an atomic electron, even while sharing space with ∼105 atoms in its semiconductor host. We anticipate that this model system will be useful for measuring intrinsic decoherence processes, and for testing both simple and complex manipulations of semiconductor qubits.
Crystal Structure of n-Bu3Sn+ CB11Me12 Zharov, Ilya; King, Benjamin T; Havlas, Zdeněk ...
Journal of the American Chemical Society,
10/2000, Letnik:
122, Številka:
41
Journal Article
Salts of 12-alkyl and 12-phenyl derivatives of the CB11H12 - anion are prepared in 50−60% yields from the 12-iodo-CB11H11 - anion by Pd-catalyzed cross-coupling with Grignard reagents. The tropylium ...ylide 12-C7H6 +-CB11H11 - is made in 54% yield by reaction of C7H7 + with CB11H12 -. Its ground-state dipole moment is 11.25 ± 0.1 D and its first hyperpolarizability is β = 236 × 10-30 esu at 1064 nm, as determined by hyper-Rayleigh scattering measurement. This value is ten times that of p-nitroaniline and is surprisingly large considering that the compound is colorless.
Benzene and 1,2-dichloroethane solutions of the Li+ salt of the weakly coordinating anion CB11Me12 - catalyze the rearrangement of cubane to cuneane, quadricyclane to norbornadiene, basketene to ...Nenitzescu's hydrocarbon, and diademane to triquinacene. The Claisen rearrangement of phenyl allyl ether is also strongly accelerated.
A search for single top production (e(+)e(-) --> t (c) over bar) via flavour changing neutral currents (FCNC) was performed using the data taken by the DELPHI detector at LEP2. The data analyzed have ...been accumulated at center-of-mass energies ranging from 189 to 208 GeV. Limits at 95% confidence level were obtained on the anomalous coupling parameters kappa(gamma) and kappa(Z). (C) 2004 Published by Elsevier B.V.
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