Efficient Ground-State Recovery of UV-Photoexcited -Nitrophenol in Aqueous Solution by Direct and Multistep Pathways.

Nitroaromatic compounds are found in brown carbon aerosols emitted to the Earth's atmosphere by biomass burning, and are important organic chromophores for the absorption of solar radiation. Here, transient absorption spectroscopy spanning 100 fs-8 μs is used to explore the pH-dependent photochemical pathways for aqueous solutions of -nitrophenol, chosen as a representative nitroaromatic compound. Broadband ultrafast UV-visible and infrared probes are used to characterize the excited states and intermediate species involved in the multistep photochemistry, and to determine their lifetimes under different pH conditions.

Valence Electronic Structure of Interfacial Phenol in Water Droplets.

Biochemistry and a large part of atmospheric chemistry occur in aqueous environments or at aqueous interfaces, where (photo)chemical reaction rates can be increased by up to several orders of magnitude. The key to understanding the chemistry and photoresponse of molecules in and "on" water lies in their valence electronic structure, with a sensitive probe being photoelectron spectroscopy. This work reports velocity-map photoelectron imaging of submicrometer-sized aqueous phenol droplets in the valence region after nonresonant (288 nm) and resonance-enhanced (274 nm) two-photon ionization with femtosecond ultraviolet light, complementing previous liquid microjet studies.

Unraveling the Ultrafast Photochemical Dynamics of Nitrobenzene in Aqueous Solution.

Nitroaromatic compounds are major constituents of the brown carbon aerosol particles in the troposphere that absorb near-ultraviolet (UV) and visible solar radiation and have a profound effect on the Earth's climate. The primary sources of brown carbon include biomass burning, forest fires, and residential burning of biofuels, and an important secondary source is photochemistry in aqueous cloud and fog droplets. Nitrobenzene is the smallest nitroaromatic molecule and a model for the photochemical behavior of larger nitroaromatic compounds.

On the multiphoton ionisation photoelectron spectra of phenol.

The phenol molecule is a prototype for non-adiabatic dynamics and the excited-state photochemistry of biomolecules. In this article, we report a joint theoretical and experimental investigation on the resonance enhanced multiphoton ionisation photoelectron (REMPI) spectra of the two lowest ionisation bands of phenol. The focus is on the theoretical interpretation of the measured spectra using quantum dynamics simulations.

Zero Threshold for Water Adsorption on MAPbBr.

Hybrid organic-inorganic perovskites (HOIPs) have shown great promise in a wide range of optoelectronic applications. However, this performance is inhibited by the sensitivity of HOIPs to various environmental factors, particularly high levels of relative humidity. This study uses X-ray photoelectron spectroscopy (XPS) to determine that there is essentially no threshold to water adsorption on the in situ cleaved MAPbBr (001) single crystal surface.

Wavelength dependent mechanism of phenolate photooxidation in aqueous solution.

Phenolate photooxidation is integral to a range of biological processes, yet the mechanism of electron ejection has been disputed. Here, we combine femtosecond transient absorption spectroscopy, liquid-microjet photoelectron spectroscopy and high-level quantum chemistry calculations to investigate the photooxidation dynamics of aqueous phenolate following excitation at a range of wavelengths, from the onset of the S-S absorption band to the peak of the S-S band. We find that for ≥ 266 nm, electron ejection occurs from the S state into the continuum associated with the contact pair in which the PhO˙ radical is in its ground electronic state.

Can Ingoing Contact Chains and other cattle movement network metrics help predict herd-level bovine tuberculosis in Irish cattle herds?

We used logistic regression to investigate whether the risk of an Irish cattle herd undergoing a bovine tuberculosis (bTB) breakdown increased with the size of the Ingoing Contact Chain (ICC) of previous herd to herd cattle movements, in a sequence up to eight moves back from the most recent, direct, movement into the herd. We further examined whether taking into account the bTB test history of each herd in the chain would improve model fit. We found that measures of cattle movements directly into the herd were risk factors for subsequent bTB restrictions, and the number of herds that animals were coming from was the most important of these.

UV Photoelectron Spectroscopy of Aqueous Solutions.

Knowledge of the electronic structure of an aqueous solution is a prerequisite to understanding its chemical and biological reactivity and its response to light. One of the most direct ways of determining electronic structure is to use photoelectron spectroscopy to measure electron binding energies. Initially, photoelectron spectroscopy was restricted to the gas or solid phases due to the requirement for high vacuum to minimize inelastic scattering of the emitted electrons.

Single-crystal organometallic perovskite optical fibers.

Semiconductors in their optical-fiber forms are desirable. Single-crystal organometallic halide perovskites have attractive optoelectronic properties and therefore are suitable fiber-optic platforms. However, single-crystal organometallic perovskite optical fibers have not been reported before due to the challenge of one-directional single-crystal growth in solution.

Accurate Vertical Ionization Energy of Water and Retrieval of True Ultraviolet Photoelectron Spectra of Aqueous Solutions.

Ultraviolet (UV) photoelectron spectroscopy provides a direct way of measuring valence electronic structure; however, its application to aqueous solutions has been hampered by a lack of quantitative understanding of how inelastic scattering of low-energy (<5 eV) electrons in liquid water distorts the measured electron kinetic energy distributions. Here, we present an efficient and widely applicable method for retrieving true UV photoelectron spectra of aqueous solutions. Our method combines Monte Carlo simulations of electron scattering and spectral inversion, with molecular dynamics simulations of depth profiles of organic solutes in aqueous solution.

A study of the interaction of cationic dyes with gold nanostructures.

The interaction of methylene blue and crystal violet dyes with a range of gold nanoparticles (AuNPs), gold nanoclusters and gold/silver nanoclusters is reported. It is found that 20 nm citrate-capped AuNPs have strong interactions with these two dyes that result in red-shifted absorption peaks in their electronic absorption spectra. Transmission electron microscopy and dynamic light scattering measurements show that this can be attributed to these AuNPs combining into large agglomerates.

Intramolecular thiomaleimide [2 + 2] photocycloadditions: stereoselective control for disulfide stapling and observation of excited state intermediates by transient absorption spectroscopy.

Thiomaleimides undergo efficient intermolecular [2 + 2] photocycloaddition reactions and offer applications from photochemical peptide stapling to polymer crosslinking; however, the reactions are limited to the formation of the head-to-head isomers. Herein, we present an intramolecular variation which completely reverses the stereochemical outcome of this photoreaction, quantitatively generating adducts which minimise the structural disturbance of the disulfide staple and afford a 10-fold increase in quantum yield. We demonstrate the application of this reaction on a protein scaffold, using light to confer thiol stability to an antibody fragment conjugate.

Liquid-microjet photoelectron spectroscopy of the green fluorescent protein chromophore.

Green fluorescent protein (GFP), the most widely used fluorescent protein for in vivo monitoring of biological processes, is known to undergo photooxidation reactions. However, the most fundamental property underpinning photooxidation, the electron detachment energy, has only been measured for the deprotonated GFP chromophore in the gas phase. Here, we use multiphoton ultraviolet photoelectron spectroscopy in a liquid-microjet and high-level quantum chemistry calculations to determine the electron detachment energy of the GFP chromophore in aqueous solution.

Free-roaming dog population dynamics in Ranchi, India.

Rabies causes approximately 20,000 human deaths in India each year. Nearly all of these occur following dog bites. Large-scale, high-coverage dog rabies vaccination campaigns are the cornerstone of rabies elimination strategies in both human and dog populations, although this is particularly challenging to achieve in India as a large proportion of the dog population are free-roaming and unowned.

Early palliative interventions for improving outcomes in people with a primary malignant brain tumour and their carers.

Background: Primary malignant brain tumours can have an unpredictable course, but high-grade gliomas typically have a relentlessly progressive disease trajectory. They can cause profound symptom burden, affecting physical, neurocognitive, and social functioning from an early stage in the illness. This can significantly impact on role function and on the experiences and needs of informal caregivers.

A photoelectron imaging study of the deprotonated GFP chromophore anion and RNA fluorescent tags.

Green fluorescent protein (GFP), together with its family of variants, is the most widely used fluorescent protein for imaging. Numerous spectroscopic studies of the isolated GFP chromophore have been aimed at understanding the electronic properties of GFP. Here, we build on earlier work [A.

Spatial and temporal variation in proximity networks of commercial dairy cattle in Great Britain.

The nature of contacts between hosts can be important in facilitating or impeding the spread of pathogens within a population. Networks constructed from contacts between hosts allow examination of how individual variation might influence the spread of infections. Studying the contact networks of livestock species managed under different conditions can additionally provide insight into their influence on these contact structures.

Chemical Modification of Polaronic States in Anatase TiO(101).

Two polymorphs of TiO, anatase and rutile, are employed in photocatalytic applications. It is broadly accepted that anatase is the more catalytically active and subsequently finds wider commercial use. In this work, we focus on the Ti polaronic states of anatase TiO(101), which lie at ∼1.

Polaron-Adsorbate Coupling at the TiO(110)-Carboxylate Interface.

Understanding how adsorbates influence polaron behavior is of fundamental importance in describing the catalytic properties of TiO. Carboxylic acids adsorb readily at TiO surfaces, yet their influence on polaronic states is unknown. Using UV photoemission spectroscopy (UPS), two-photon photoemission spectroscopy (2PPE), and density functional theory (DFT) we show that dissociative adsorption of formic and acetic acids has profound, yet different, effects on the surface density, crystal field, and photoexcitation of polarons in rutile TiO(110).

Timing of reproduction and association with environmental factors in female free-roaming dogs in southern India.

Annual peaks in reproductive activity have been identified in multiple domestic dog populations. However, there is little evidence to describe how these peaks may be associated with environmental factors such as daylength, which plays a well-established role in breeding patterns of seasonally-reproductive species. Data were collected 2016-2020 during 7,743 and 4,681 neuter surgeries on adult female unowned free-roaming dogs in veterinary clinics in Goa and Tamil Nadu respectively.

Characterization of potential superspreader farms for bovine tuberculosis: A review.

Background: Variation in host attributes that influence their contact rates and infectiousness can lead some individuals to make disproportionate contributions to the spread of infections. Understanding the roles of such 'superspreaders' can be crucial in deciding where to direct disease surveillance and controls to greatest effect. In the epidemiology of bovine tuberculosis (bTB) in Great Britain, it has been suggested that a minority of cattle farms or herds might make disproportionate contributions to the spread of Mycobacterium bovis, and hence might be considered 'superspreader farms'.

Shining light on the electronic structure and relaxation dynamics of the isolated oxyluciferin anion.

Firefly bioluminescence is exploited widely in imaging in the biochemical and biomedical sciences; however, our fundamental understanding of the electronic structure and relaxation processes of the oxyluciferin that emits the light is still rudimentary. Here, we employ photoelectron spectroscopy and quantum chemistry calculations to investigate the electronic structure and relaxation of a series of model oxyluciferin anions. We find that changing the deprotonation site has a dramatic influence on the relaxation pathway following photoexcitation of higher lying electronically excited states.

Ecology of domestic dogs (Canis familiaris) as a host for Guinea worm (Dracunculus medinensis) infection in Ethiopia.

The global programme for the eradication of Guinea worm disease, caused by the parasitic nematode Dracunculus medinensis, has been successful in driving down human cases, but infections in non-human animals, particularly domestic dogs (Canis familiaris), now present a major obstacle to further progress. Dog infections have mainly been found in Chad and, to a lesser extent, in Mali and Ethiopia. While humans classically acquire infection by drinking water containing infected copepods, it has been hypothesized that dogs might additionally or alternatively acquire infection via a novel pathway, such as consumption of fish or frogs as possible transport or paratenic hosts.