Publications

Vibronic coupling is key to efficient energy flow in molecular systems and a critical component of most mechanisms invoking quantum effects in biological processes. Despite increasing evidence for coherent coupling of electronic states being mediated by vibrational motion, it is not clear how and to what degree properties associated with vibrational coherence such as phase and coupling of atomic motion can impact the efficiency of light-induced processes under natural, incoherent illumination. Here, we show that deuteration of the H11–C11=C12–H12 double-bond of the 11-cis retinal chromophore in the visual pigment rhodopsin significantly and unexpectedly alters the photoisomerization yield while inducing smaller changes in the ultrafast isomerization dynamics assignable to known isotope effects. Combination of these results with non-adiabatic molecular dynamics simulations reveals a vibrational phase-dependent isotope effect that we suggest is an intrinsic attribute of vibronically coherent photochemical processes.

Quantum dot (QD) solids and arrays hold a great potential for novel applications which are aimed at exploiting quantum properties in room-temperature devices. Careful tailoring of the QD energy levels and coupling between dots could lead to efficient energy-harvesting devices. Here, we used a self-assembly method to create a disordered layered structure of QDs, coupled by covalently bonded organic molecules. Energy transfer rates from small (donor) to large (acceptor) QDs are measured. Best tailoring of the QDs energy levels and the length of the linking molecules results in an energy transfer rate as high as 30 ps–1. Such rates approach energy transfer rates of the highly efficient photosynthesis complexes and are compatible with a coherent mechanism of energy transfer. These results may pave way for new controllable building blocks for future technologies.

In the present study, we examined the effects of feedback that corrects and contrasts a

student's own erroneous solutions with the canonical, correct one (CEC&C feedback)

on learning in a conceptual change task. Sixty undergraduate students received

expository instruction about natural selection, which presented the canonical,

scientifically accepted account in detail. Two-third of these received CEC&C feedback on their self-generated solutions to open-ended test items. Students either received this feedback on their pretest solutions (prior to instruction), or on their immediate post-test solutions (following instruction). Students in the control condition only received the correct canonical answers to the immediate post-test items and compared these with their own solutions autonomously. Conceptual understanding on transfer items was assessed after one week. Results showed that students in the CEC&C feedback conditions outperformed control students. Timing of feedback did not affect learning, however. These findings add to accumulating evidence from different lines of research on the importance of instructional support that explicitly compares and contrasts between erroneous student models and canonical models in conceptual change tasks.

Absorption cross-section spectra for gold nanoparticles were calculated using fully quantum Stochastic Density Functional Theory and a classical Finite-Difference Time Domain Maxwell solver. Spectral shifts were monitored as a function of size (1.3–) and shape (octahedron, cubeoctahedron and truncated cube). Even though the classical approach is forced to fit the quantum time-dependent density functional theory at , at smaller sizes there is a significant deviation as the classical theory is unable to account for peak splitting and spectral blueshifts even after quantum spectral corrections. We attribute the failure of classical methods at predicting these features to quantum effects and low density of states in small nanoparticles. Classically, plasmon resonances are modelled as collective conduction electron excitations, but at small nanoparticle size these excitations transition to few or even individual conductive electron excitations, as indicated by our results.

In the current issue of Molecular Cell, Szoradi et al. (2018) present compelling data demonstrating how the newly identified SHRED pathway in yeast selectively shifts the E3 ligase Ubr1 specificity from N-end rule substrates to misfolded proteins in cells under proteostatic stress.

A game of threats on a finite set of players, N, is a function d that assigns a real number to any coalition, S⊆N, such that d(S)=−d(N∖S). A game of threats is not necessarily a coalitional game as it may fail to satisfy the condition d(∅)=0. We show that analogs of the classic Shapley axioms for coalitional games determine a unique value for games of threats. This value assigns to each player an average of d(S) across all the coalitions that include the player. Games of threats arise naturally in value theory for strategic games, and may have applications in other branches of game theory.