Switched wave packets: A route to nonperturbative quantum control

The dynamic Stark effect due to a strong nonresonant but nonionizing laser field provides a route to quantum control via the creation of novel superposition states. We consider the creation of a field-free "switched" wave packet through adiabatic turn-on and sudden turn-off of a strong dynamic Stark interaction. There are two limiting cases for such wave packets. The first is a Raman-type coupling, illustrated by the creation of field-free molecular axis alignment. An experimental demonstration is given. The second case is that of dipole-type coupling, illustrated by the creation of charge localization in an array of quantum wells

Sequential and direct ionic excitation in the strong-field ionization of 1-butene molecules

We study the Strong-Field Ionization (SFI) of the hydrocarbon 1-butene as a function of wavelength using photoion-photoelectron covariance and coincidence spectroscopy. We observe a striking transition in the fragment-associated photoelectron spectra: from a single Above Threshold Ionization (ATI) progression for photon energies less than the cation D0–D1 gap to two ATI progressions for a photon energy greater than this gap. For the first case, electronically excited cations are created by SFI populating the ground cationic state D0, followed by sequential post-ionization excitation. For the second case, direct sub-cycle SFI to the D1 excited cation state contributes significantly. Our experiments access ionization dynamics in a regime where strong-field and resonance-enhanced processes can interplay

Following the excited state relaxation dynamics of indole and 5-hydroxyindole using time-resolved photoelectron spectroscopy

Time-resolved photoelectron spectroscopy was used to obtain new information about the dynamics of electronic relaxation in gas-phase indole and 5-hydroxyindole following UV excitation with femtosecond laser pulses centred at 249 nm and 273 nm. Our analysis of the data was supported by ab initio calculations at the coupled cluster and complete-active-space self-consistent-field levels. The optically bright 1La and 1Lb electronic states of 1\u3c0\u3c0* character and spectroscopically dark and dissociative 1\u3c0\u3c3* states were all found to play a role in the overall relaxation process. In both molecules we conclude that the initially excited 1La state decays non-adiabatically on a sub 100 fs timescale via two competing pathways, populating either the subsequently long-lived 1Lb state or the 1\u3c0\u3c3* state localised along the N-H coordinate, which exhibits a lifetime on the order of 1 ps. In the case of 5-hydroxyindole, we conclude that the 1\u3c0\u3c3* state localised along the O-H coordinate plays little or no role in the relaxation dynamics at the two excitation wavelengths studied.Peer reviewed: YesNRC publication: Ye

Extension of corporate services brands: the effect of perceived similarity extension and perceived quality brand

O principal objetivo deste estudo é avaliar o efeito da qualidade percebida da marca-mãe e da similaridade percebida sobre as avaliações de extensões de marcas corporativas de serviços. Adicionalmente, também se deseja verificar se a elaboração das características da extensão contribuem para a sua avaliação. As hipóteses foram testadas por meio de três experimentos que envolveram no total 1.131 respondentes. No Estudo 1 foram utilizadas marcas fictícias como estímulo e verificou-se que a qualidade da marca-mãe teve efeito mais importante que a similaridade percebida sobre as avaliações de uma extensão de marca de serviços. No Estudo 2, utilizando como estímulos marcas reais, os mesmos resultados do Estudo 1 foram obtidos. No Estudo 3 verificou-se que a elaboração das características da extensão contribuiu positivamente apenas para uma das extensões propostas para a marca-mãe de alta qualidade, mas não teve nenhum efeito para as extensões propostas para a marca-mãe de baixa qualidade. Tomados em conjunto, os resultados sugerem que a qualidade percebida da marca-mãe tem papel fundamental na avaliação de extensões de marcas corporativas de serviços. O estudo contribui ainda com diversas hipóteses para estudos futuros e implicações gerenciais para gerentes de marcas corporativas de serviços.The main objective of this study is to assess the effect of parent brand perceived quality and perceived similarity on the evaluation of corporate service brand extensions. It is also the intention of this study to verify whether providing information cues about the characteristics of the extension contributes to the brand extension evaluation. The hypotheses were tested by means of three experiments involving 1,131 subjects. The results of Study 1, conducted with fictitious brands as stimuli, demonstrated that the perceived quality of the parent brand played a more significant role than perceived similarity on the evaluations of brand extensions. In Study 2, where real brands were used as stimuli, the results were the same as in Study 1. Study 3 found that providing information cues about the characteristics of the extensions had a positive effect for one of the extensions of the high quality parent brand but not for the two proposed extensions of the low quality parent brand. Taken as a whole, the results suggest that the perceived quality of the parent-brand plays a fundamental role in the evaluation of corporate service brand extensions. The study also contributes several hypotheses for future studies and managerial implications for managers of corporate service brands

Steady and Time-Resolved Photoelectron Spectra Based on Nuclear Ensembles

Semiclassical methods to simulate both steady and time-resolved photoelectron spectra are presented. These approaches provide spectra with absolute band shapes and vibrational broadening beyond the Condon approximation, using an ensemble of nuclear configurations built either via distribution samplings or nonadiabatic dynamics simulations. Two models to account for the electron kinetic energy modulation due to vibrational overlaps between initial and final states are discussed. As illustrative examples, the steady photoelectron spectra of imidazole and adenine and the time- and kinetic-energy-resolved photoelectron spectrum of imidazole were simulated within the frame of time-dependent density functional theory. While for steady spectra only electrons ejected with maximum allowed kinetic energy need to be considered, it is shown that to properly describe time-resolved spectra, electrons ejected with low kinetic energies must be considered in the simulations as well. The results also show that simulations based either on full computation of photoelectron cross section or on simple Dyson orbital norms provide results of similar quality

Dissociative photoionization of the NO molecule studied by photoelectron-photon coincidence technique

Low-energy photoelectron–vacuum ultraviolet (VUV) photon coincidences have been measured using synchrotron radiation excitation in the inner-valence region of the nitric oxide molecule. The capabilities of the coincidence set-up were demonstrated by detecting the 2s−1 → 2p−1 radiative transitions in coincidence with the 2s photoelectron emission in Ne. In NO, the observed coincidence events are attributed to dissociative photoionization with excitation, whereby photoelectron emission is followed by fragmentation of excited NO+ ions into O+ + N* or N+ + O* and VUV emission from an excited neutral fragment. The highest coincidence rate occurs with the opening of ionization channels which are due to correlation satellites of the 3σ photoionization. The decay time of VUV photon emission was also measured, implying that specific excited states of N atoms contribute significantly to observed VUV emission

Dendritic Polyglycerol Amine: An Enhanced Substrate to Support Long-Term Neural Cell Culture

Long-term stable cell culture is a critical tool to better understand cell function. Most adherent cell culture models require a polymer substrate coating of poly-lysine or poly-ornithine for the cells to adhere and survive. However, polypeptide-based substrates are degraded by proteolysis and it remains a challenge to maintain healthy cell cultures for extended periods of time. Here, we report the development of an enhanced cell culture substrate based on a coating of dendritic polyglycerol amine (dPGA), a non-protein macromolecular biomimetic of poly-lysine, to promote the adhesion and survival of neurons in cell culture. We show that this new polymer coating provides enhanced survival, differentiation and long-term stability for cultures of primary neurons or neurons derived from human induced pluripotent stem cells (hiPSCs). Atomic force microscopy analysis provides evidence that greater nanoscale roughness contributes to the enhanced capacity of dPGA-coated surfaces to support cells in culture. We conclude that dPGA is a cytocompatible, functionally superior, easy to use, low cost and highly stable alternative to poly-cationic polymer cell culture substrate coatings such as poly-lysine and poly-ornithine. Summary statement Here, we describe a novel dendritic polyglycerol amine-based substrate coating, demonstrating superior performance compared to current polymer coatings for long-term culture of primary neurons and neurons derived from induced pluripotent stem cells

Hexamethylcyclopentadiene: time-resolved photoelectron spectroscopy and ab initio multiple spawning simulations

Progress in our understanding of ultrafast light-induced processes in molecules is best achieved through a close combination of experimental and theoretical approaches. Direct comparison is obtained if theory is able to directly reproduce experimental observables. Here, we present a joint approach comparing time-resolved photoelectron spectroscopy (TRPES) with ab initio multiple spawning (AIMS) simulations on the MS-MR-CASPT2 level of theory. We disentangle the relationship between two phenomena that dominate the immediate molecular response upon light absorption: a spectrally dependent delay of the photoelectron signal and an induction time prior to excited state depopulation in dynamics simulations. As a benchmark molecule, we have chosen hexamethylcyclopentadiene, which shows an unprecedentedly large spectral delay of (310 \ub1 20) fs in TRPES experiments. For the dynamics simulations, methyl groups were replaced by "hydrogen atoms" having mass 15 and TRPES spectra were calculated. These showed an induction time of (108 \ub1 10) fs which could directly be assigned to progress along a torsional mode leading to the intersection seam with the molecular ground state. In a stepladder-type approach, the close connection between the two phenomena could be elucidated, allowing for a comparison with other polyenes and supporting the general validity of this finding for their excited state dynamics. Thus, the combination of TRPES and AIMS proves to be a powerful tool for a thorough understanding of ultrafast excited state dynamics in polyenes.Peer reviewed: YesNRC publication: Ye

Systematic Review of Scales for Measuring Infectious Disease–Related Stigma

This is the final version. Available on open access from the Centers for Disease Control and Prevention via the DOI in this recordInfectious disease outbreaks are associated with substantial stigma, which can have negative effects on affected persons and communities and on outbreak control. Thus, measuring stigma in a standardized and validated manner early in an outbreak is critical to disease control. We reviewed existing scales used to assess stigma during outbreaks. Our findings show that many different scales have been developed, but few have been used more than once, have been adequately validated, or have been tested in different disease and geographic contexts. We found that scales were usually developed too slowly to be informative early during an outbreak and were published a median of 2 years after the first case of an outbreak. A rigorously developed, transferable stigma scale is needed to assess and direct responses to stigma during infectious disease outbreaks

Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order harmonic generation

High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20-26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected