Photodissociation dynamics of the methyl perthiyl radical at 248 nm via photofragment translational spectroscopy

Photofragment translational spectroscopy was used to study the photodissociation of the methyl perthiyl radical CH 3 SS at 248 nm. The radical was produced by flash pyrolysis of dimethyl disulfide (CH 3 SSCH 3 ). Two channels were observed: CH 3 + S 2 and CH 2 S + SH. Photofragment translational energy distributions indicate that CH 3 + S 2 results from C-S bond fission on the ground state surface. The CH 2 S + SH channel can proceed through isomerization to CH 2 SSH on the ground state surface but also may involve production of electronically excited CH 2 S

Clostridium difficile infection.

Infection of the colon with the Gram-positive bacterium Clostridium difficile is potentially life threatening, especially in elderly people and in patients who have dysbiosis of the gut microbiota following antimicrobial drug exposure. C. difficile is the leading cause of health-care-associated infective diarrhoea. The life cycle of C. difficile is influenced by antimicrobial agents, the host immune system, and the host microbiota and its associated metabolites. The primary mediators of inflammation in C. difficile infection (CDI) are large clostridial toxins, toxin A (TcdA) and toxin B (TcdB), and, in some bacterial strains, the binary toxin CDT. The toxins trigger a complex cascade of host cellular responses to cause diarrhoea, inflammation and tissue necrosis - the major symptoms of CDI. The factors responsible for the epidemic of some C. difficile strains are poorly understood. Recurrent infections are common and can be debilitating. Toxin detection for diagnosis is important for accurate epidemiological study, and for optimal management and prevention strategies. Infections are commonly treated with specific antimicrobial agents, but faecal microbiota transplants have shown promise for recurrent infections. Future biotherapies for C. difficile infections are likely to involve defined combinations of key gut microbiota

Global urban environmental change drives adaptation in white clover.

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

Global urban environmental change drives adaptation in white clover

Urbanization transforms environments in ways that alter biological evolution. We examined whether urban environmental change drives parallel evolution by sampling 110,019 white clover plants from 6169 populations in 160 cities globally. Plants were assayed for a Mendelian antiherbivore defense that also affects tolerance to abiotic stressors. Urban-rural gradients were associated with the evolution of clines in defense in 47% of cities throughout the world. Variation in the strength of clines was explained by environmental changes in drought stress and vegetation cover that varied among cities. Sequencing 2074 genomes from 26 cities revealed that the evolution of urban-rural clines was best explained by adaptive evolution, but the degree of parallel adaptation varied among cities. Our results demonstrate that urbanization leads to adaptation at a global scale

THEORETICAL INVESTIGATION OF LARGE AMPLITUDE TORSIONAL MOTION IN THE METHYL PEROXY RADICAL

Author Institution: Department of Chemistry,; The Ohio State University, 120 W. 18$^{th}$ Avenue, Columbus, Ohio,; 43202Organic peroxy radicals are key intermediates in the oxidation of hydrocarbons. The simplest organic peroxy radical, methyl peroxy CH$_3$O$_2$, is obviously the starting point for understanding the alkyl peroxies from both a theoretically and a spectroscopic point of view. The $\widetilde{A}-\widetilde{X}$ NIR electronic transition was first observed in 1976 by Hunziker. In 2000, our laboratory observed this transition using room temperature cavity ringdown spectroscopy (CRDS). In none of the previous reports has detailed consideration been given to the large amplitude torsional motion between the methyl top and O$_2$ moeity. In order to investigate this torsional mode, we computed the potential energy surface (PES) as a function of the OOCH torsion angle for both the $\widetilde{X}$ and $\widetilde{A}$ electronic states, minimizing the potential energy with respect to the remaining eleven internal coordinates. After fitting the calculated PES with an analytical form for the potential, we obtain the eigenvalues and eigenfunctions for the torsional motion and simulate the corresponding transition in the room temperature CRDS spectrum. The simulated spectra allowed us to understand the effect of the tunneling splitting associated with the torsional sequence bands and also allowed us to assign atypical spectral features associated with transitions from the free rotor regime of methyl peroxy

OBSERVATION OF THE A~2\widetilde{A}^{2}A′^{\prime} - X~2\widetilde{X}^{2}A′′^{\prime\prime} ELECTRONIC TRANSITION OF VINOXY RADICAL USING CAVITY RINGDOWN SPECTROSCOPY

Author Institution: Laser Spectroscopy Facility, Department of Chemistry, The Ohio State University, Columbus, OH 43210\maketitle Free radicals are key components in the oxidation ofhydrocarbons, both in combustion and in our atmosphere. More specifically, the vinoxy radical, CH$_2$CHO, is a prototypical alkenoxy radical, which is known to play an important role in the reaction of O($^3$P) and OH with olefins and olefinic radicals. While the $\widetilde{B}$ - $\widetilde{X}$ transition of vinoxy has been studied in considerable detail over the last twenty years, the $\widetilde{A}$ - $\widetilde{X}$ transition remains relatively unexplored because of its much weaker absorption cross-section. Due to its low oscillator strengh, cavity ringdown spectroscopy (CRDS) has been applied to study the $\widetilde{A}$ - $\widetilde{X}$ near-IR electronic transition of vinoxy radical. In addition, \textit{ab initio} calculations were conducted in order to predict the $\widetilde{A}$ - $\widetilde{X}$ origin frequency, as well as to aid in assigning other vibrational structure in the spectrum