Molecular Auger Interferometry

We propose a theory of interferometric measurement of a normal Auger decay width in molecules. Molecular Auger interferometry is based on the coherent phase control of Auger dynamics in a two-colour (ω/2ω) laser field. We show that, in contrast to atoms, in oriented molecules of certain point groups (e.g. CH3F) the relative ω/2ω phase modulates the total ionisation yield. A simple analytical formula is derived for the extraction of the widths of Auger-active states from a molecular Auger interferogram, avoiding the need of either attosecond or high-resolution spectroscopy

An experimental and theoretical study of the resonant Auger spectrum of the ethene molecule

Resonant Auger spectra of the ethene molecule excited at energies across the C1s → π* energy band are reported. Our measurements address the unexpected variation of the intensity of the A state with respect to the other singly ionized valence states. An approach, based on group theory and calculations using Coulomb 4-center integrals, is proposed to explain the behaviour of the intensity of the ground state and excited states of the ion upon resonant excitation. The new method provides a calculationally inexpensive route to predict relative intensities of different resonant Auger bands in polyatomic molecules, without the need for an exhaustive knowledge of the potential energy surfaces of the electronic states involved

Molecular Auger Interferometry

We introduce and present a theory of interferometric measurement of a normal Auger decay lifetime in molecules. Molecular Auger interferometry is based on the coherent phase control of Auger dynamics in a two-color (ω/2ω) laser field. We show that, in contrast to atoms, in oriented molecules of certain point groups the relative ω/2ω phase modulates the total ionization yield. A simple analytical formula is derived for the extraction of the lifetimes of Auger-active states from a molecular Auger interferogram, circumventing the need in either high-resolution or attosecond spectroscopy. We demonstrate the principle of the interferometric Auger lifetime measurement using inner-valence decay in CH3F

The pathway to secondary prevention of Alzheimer\u27s disease

Alzheimer\u27s disease (AD) is a continuum consisting of a preclinical stage that occurs decades before symptoms appear. As researchers make advances in investigating the continuum, the importance of developing drugs for secondary prevention is garnering increased discussion. For efficacious drug development for secondary prevention it is important to define what are the earliest biological stages of AD. The Alzheimer\u27s Association Research Roundtable convened November 27 to 28, 2018 to focus on pre-clinical AD. This review will address the biological approach to defining pre-clinical AD, detection, identification of at-risk individuals, and lessons learned from trials such as A4 and TOMMORROW

Tracking the ultraviolet-induced photochemistry of thiophenone during and after ultrafast ring opening

Photoinduced isomerization reactions lie at the heart of many chemical processes in nature. The mechanisms of such reactions are determined by a delicate interplay of coupled electronic and nuclear dynamics occurring on the femtosecond scale, followed by the slower redistribution of energy into different vibrational degrees of freedom. Here we apply time-resolved photoelectron spectroscopy with a seeded extreme ultraviolet free-electron laser to trace the ultrafast ring opening of gas-phase thiophenone molecules following ultraviolet photoexcitation. When combined with ab initio electronic structure and molecular dynamics calculations of the excited- and ground-state molecules, the results provide insights into both the electronic and nuclear dynamics of this fundamental class of reactions. The initial ring opening and non-adiabatic coupling to the electronic ground state are shown to be driven by ballistic S–C bond extension and to be complete within 350 fs. Theory and experiment also enable visualization of the rich ground-state dynamics that involve the formation of, and interconversion between, ring-opened isomers and the cyclic structure, as well as fragmentation over much longer timescales

Transient Alteration of Cellular Redox Buffering before Irradiation Triggers Apoptosis in Head and Neck Carcinoma Stem and Non-Stem Cells

Background: Head and neck squamous cell carcinoma (HNSCC) is an aggressive and recurrent malignancy owing to intrinsic radioresistance and lack of induction of apoptosis. The major focus of this work was to design a transient glutathione depleting strategy during the course of irradiation of HNSCC in order to overcome their radioresistance associated with redox adaptation. Methodology/Principal Findings: Treatment of SQ20B cells with dimethylfumarate (DMF), a GSH-depleting agent, and L-Buthionine sulfoximine (BSO), an inhibitor of GSH biosynthesis 4 h before a 10 Gy irradiation led to the lowering of the endogenous GSH content to less than 10 % of that in control cells and to the triggering of radiation-induced apoptotic cell death. The sequence of biochemical events after GSH depletion and irradiation included ASK-1 followed by JNK activation which resulted in the triggering of the intrinsic apoptotic pathway through Bax translocation to mitochondria. Conclusions: This transient GSH depletion also triggered radiation-induced cell death in SQ20B stem cells, a key event to overcome locoregional recurrence of HNSCC. Finally, our in vivo data highlight the relevance for further clinical trials o

Maternal exposure to polychlorinated biphenyls and the secondary sex ratio: an occupational cohort study

Though commercial production of polychlorinated biphenyls was banned in the United States in 1977, exposure continues due to their environmental persistence. Several studies have examined the association between environmental polychlorinated biphenyl exposure and modulations of the secondary sex ratio, with conflicting results. Our objective was to evaluate the association between maternal preconceptional occupational polychlorinated biphenyl exposure and the secondary sex ratio. We examined primipara singleton births of 2595 women, who worked in three capacitor plants at least one year during the period polychlorinated biphenyls were used. Cumulative estimated maternal occupational polychlorinated biphenyl exposure at the time of the infant's conception was calculated from plant-specific job-exposure matrices. A logistic regression analysis was used to evaluate the association between maternal polychlorinated biphenyl exposure and male sex at birth (yes/no). Maternal body mass index at age 20, smoking status, and race did not vary between those occupationally exposed and those unexposed before the child's conception. Polychlorinated biphenyl-exposed mothers were, however, more likely to have used oral contraceptives and to have been older at the birth of their first child than non-occupationally exposed women. Among 1506 infants liveborn to polychlorinated biphenyl-exposed primiparous women, 49.8% were male; compared to 49.9% among those not exposed (n = 1089). Multivariate analyses controlling for mother's age and year of birth found no significant association between the odds of a male birth and mother's cumulative estimated polychlorinated biphenyl exposure to time of conception. Based on these data, we find no evidence of altered sex ratio among children born to primiparous polychlorinated biphenyl-exposed female workers