The Relationship between the Spatial Arrangement of Pigments and Exciton Transition Moments in Photosynthetic Light-Harvesting Complexes

Considering bacteriochlorophyll molecules embedded in the protein matrix of the light-harvesting complexes of purple bacteria (known as LH2 and LH1-RC) as examples of systems of interacting pigment molecules, we investigated the relationship between the spatial arrangement of the pigments and their exciton transition moments. Based on the recently reported crystal structures of LH2 and LH1-RC and the outcomes of previous theoretical studies, as well as adopting the Frenkel exciton Hamiltonian for two-level molecules, we performed visualizations of the LH2 and LH1 exciton transition moments. To make the electron transition moments in the exciton representation invariant with respect to the position of the system in space, a system of pigments must be translated to the center of mass before starting the calculations. As a result, the visualization of the transition moments for LH2 provided the following pattern: two strong transitions were outside of LH2 and the other two were perpendicular and at the center of LH2. The antenna of LH1-RC was characterized as having the same location of the strongest moments in the center of the complex, exactly as in the B850 ring, which actually coincides with the RC. Considering LH2 and LH1 as supermolecules, each of which has excitation energies and corresponding transition moments, we propose that the outer transitions of LH2 can be important for inter-complex energy exchange, while the inner transitions keep the energy in the complex; moreover, in the case of LH1, the inner transitions increased the rate of antenna-to-RC energy transfer.

Knee-stretched walking with toe-off and heel-strike for a position-controlled humanoid robot based on model predictive control

Knee-stretched walking is considered to be a human-like and energy-efficient gait. The strategy of extending legs to obtain vertical center of mass trajectory is commonly used to avoid the problem of singularities in knee-stretched gait generation. However, knee-stretched gait generation utilizing this strategy with toe-off and heel-strike has kinematics conflicts at transition moments between single support and double support phases. In this article, a knee-stretched walking generation with toe-off and heel-strike for the position-controlled humanoid robot has been proposed. The position constraints of center of mass have been considered in the gait generation to avoid the kinematics conflicts based on model predictive control. The method has been verified in simulation and validated in experiment.

Associations of situational and performance variables with defensive transitions outcomes in FIFA World Cup 2018

Transition moments play a major role in match outcome and constitute an important part of the soccer coaching process. Nevertheless, the body of literature on match analysis reveals a lack of knowledge regarding transition moments, particularly the defensive ones. This study aimed to analyse how several situational and performance variables were associated with different defensive transition outcomes. A sample of 977 defensive transitions from 15 matches of FIFA World Cup 2018 was coded using a bespoke observational system. Data were analysed through log-linear modelling and Pearson’s chi-square. Regarding performance variables, final position ( p ≤ 0.001; ES = 0.390[≥0.290]; large effect size), duration ( p ≤ 0.001; ES = 0.206[0.07; 0.21]) , defensive approach ( p ≤ 0.001; ES = 0.419[0.30; 0.50]) , defensive pressure ( p ≤ 0.001; ES = 0.147[0.05; 0.15]; medium effect sizes), numerical relations ( p ≤ 0.05; ES = 0.113[0.07; 0.21]) , initial position ( p ≤ 0.05; ES = 0.092[0.06; 0.17]) , initial number of zones ( p ≤ 0.05; ES = 0.083[0.05; 0.15]) , final number of zones ( p ≤ 0.001; ES = 0.112[0.05; 0.15]) and defensive coverage ( p ≤ 0.001; ES = 0.130[0.05; 0.15]; small effect sizes) were significantly associated with the defensive transitions outcomes. A small-sized and non-significant association ( p = 0.126; ES = 0.080[0.07; 0.21]) was found for type of ball loss. Concerning the situational variables, a small-sized and significant association between match outcome and defensive transitions outcome was identified ( p ≤ 0.05; ES = 0.092[0.07; 0.21]). Our findings provide new knowledge on factors that influence team success in defensive transitions. The coaching staff should be aware that the exploitation of areas behind the most retreated player of the midfield sector ought to be avoided. Furthermore, a reduction in the space available to ball carriers and an increased effort to quickly recover possession should be encouraged.

Pear-shaped atomic nuclei

This review presents the current status of experimental evidence for the occurrence of reflection-asymmetric or ‘pear’ shapes in atomic nuclei, which arises from the presence of strong octupole correlations in the nucleon–nucleon interactions. The behaviour of energy levels and electric octupole transition moments is reviewed, with particular emphasis on recent measurements. The relevance of nuclear pear shapes to measurements of fundamental interactions is also discussed.

Orthogonally spin-labeled rulers help to identify crosstalk signals and improve DEER signal fidelity

DEER spectroscopy applied to orthogonally spin-labeled proteins is a versatile technique which allows simplifying the assignment of distances in complex spin systems and thereby increasing the information content that can be obtained per sample. In fact, orthogonal spin labels can be independently addressed in DEER experiments due to spectroscopically non-overlapping central transitions, distinct relaxation times and/or transition moments. Here we focus on molecular rulers orthogonally labeled with nitroxide (NO) and gadolinium (Gd) spins, which give access to three distinct DEER channels, probing NO-NO, NO-Gd and Gd-Gd distances. It has been previously suggested that crosstalk signals between individual DEER channels might occur, for example, between NO and Gd due to their inevitable spectral overlap. However, a systematic study to address these issues has not yet been carried out. Here, we perform a thorough three-channel DEER analysis on mixtures of NO-NO, NO-Gd and Gd-Gd molecular rulers characterized by distinct, non-overlapping distance distributions to study under which conditions crosstalk signals occur and how they can be identified or suppressed to improve signal fidelity. This study will help to improve the assignment of the correct distances in homo- and hetero-complexes of orthogonally spin-labeled proteins.

Kenya's Difficult Political Transitions Ethnicity and the Role of Media

Kenya's political transitions at different points in its history have had tremendous impact on the country's media. This chapter argues that there is a close relationship between the country's political transitions, ethnicity and the role of the media. Making reference to different transition moments such as independence in the early 1960s, the attempted coup in 1982, the advent of multiparty politics in the early 1990s and the more recent disputed elections of 2007, the chapter demonstrates the manifestations of these connections, on the perceptions of the role of the media in Kenya, and how this ultimately has affected the media, including attendant policies by the state.

Selective mercury(ii) detection in aqueous solutions upon the absorption changes corresponding to the transition moments polarized along the short axis of an azobenzene chemosensor

A completely water-soluble azobenzene chemosensor shows selective Hg2+ detection properties in wide pH ranges and under different light conditions.