Femtosecond dynamics of hydrogen elimination: benzene formation from cyclohexadiene

Using femtosecond-resolved mass spectrometry in a molecular beam, we report real-time study of the hydrogen elimination reaction of 1,4-cyclohexadiene. The experimental observation of the ultrafast stepwise H-elimination elucidates the reaction dynamics and mechanism. With density-functional theory (ground-state) calculations, the nature of the reaction (multiple) pathways is examined. With the help of recent conical-intersection calculations, the excited-state and ground-state pathways are correlated. From these experimental and theoretical results we provide a unifying picture of the thermochemistry, photochemistry and the stereochemistry observed in the condensed phase

Femtosecond β-cleavage dynamics: Observation of the diradical intermediate in the nonconcerted reactions of cyclic ethers

Femtosecond (fs) dynamics of reactions of cyclic ethers, symmetric and asymmetric structures, are reported. The diradical intermediates and their beta-cleavages, which involve simultaneous C-C, C-H sigma-bond breakage and C-O, C-C pi-bond formation, are observed and studied by fs-resolved mass spectrometry. To compare with experiments, we present density functional theory calculations of the potential energy surface and microcanonical rates and product distributions

Nonequilibrium fluctuation induced escape from a metastable state

Based on a simple microscopic model where the bath is in a non-equilibrium state we study the escape from a metastable state in the over-damped limit. Making use of Fokker-Planck-Smoluchowski description we derive the time dependent escape rate in the non-stationary regime in closed analytical form which brings on to fore a strong non-exponential kinetic of the system mode.Comment: 4 pages, no figures, EPJ class file include

Solutions to infection prevention and control challenges in developing countries, do they exist? An integrative review

Implementing sustainable infection prevention and control (IP&C) programs in developing countries is challenging. Many developing countries experience high burdens of disease and political instability. In addition, they are affected by geographical and climatic challenges, and have unique social, cultural and spiritual beliefs, all of which contribute to a higher prevalence of infections. The aim of this integrative review is to identify existing solutions to the challenges faced by developing countries when implementing IP&C programs. An extensive literature review was conducted to explore improvements in infection control in rural hospitals in developing countries. Three electronic databases were searched for relevant articles written between 1980 and 2018, published in peer reviewed English language journals, and relating to hospitals, not community settings. The findings indicate that developing countries continue to face many challenges in implementing IP&C programs. Limited success has been described with some IP&C program components but it is clear that little original research on the topic exists. Notably scarce are studies on the influences that culture, religious and spiritual beliefs have on IP&C program implementation. This review highlights opportunities for further research into healthcare workers perceptions of disease causation and infection transmission, and the role this plays in the effective implementation of an IP&C program. By exploring these opportunities appropriate and culturally sensitive solutions may be identified, which can assist with the design and implementation of culturally relevant IP&C programs in these settings

Direct observation of the femtosecond nonradiative dynamics of azulene in a molecular beam: The anomalous behavior in the isolated molecule

Using femtosecond-resolved mass spectrometry in a molecular beam, we report real-time observation of the nonradiative, anomalous dynamics of azulene. We studied both S_2 and S_1 state dynamics. The motion of the wave packet in S_1 involves two time scales, a dephasing time of less than 100 fs and a 900±100 fs internal conversion. We discuss the dynamical picture in relation to the molecular structures and the conical intersection, and we compare with theory

Fluorescence enhancement induced by quadratic electric-field effects on dynamics of singlet exciton in poly(3-hexylthiophene) dispersed in poly(methyl methacrylate)

The dynamics of the exciton generated by photoexcitation of regioregular poly(3-hexylthiophene) (P3HT) polymer dispersed into a poly(methyl methacrylate) (PMMA) matrix has been examined by using electro-photoluminescence (E-PL) spectroscopy, where electric field effects on photoluminescence (PL) spectra have been measured. The quadratic electric-field effect have been investigated by using the modulation technique, with which the field-induced change in PL intensity synchronized at the second harmonic of a modulation frequency of the applied electric fields was monitored. Absorption and PL spectra are indicative of the formation both of the ordered crystalline aggregates and of the amorphous regions of P3HT polymer chains. Although previous studies of the electric field effects on π-conjugated polymers showed, in general, that the PL intensity was decreased by electric fields, we report that the PL intensity of P3HT increases and the PL lifetime becomes longer, as the quadratic electric-field effect. The magnitude of the change in PL intensity was quantitatively explained in terms of the field-induced decrease in the nonradiative decay rate constants of exciton. We conjecture that a delayed PL which originates from the recombination of the charge carriers is enhanced in the presence of electric fields. It is also implied that the rate constant of the downhill relaxation process of the exciton, which originates from the relaxation in distributed energy levels due to inherent energetic disorder in P3HT aggregates, becomes smaller in the presence of electric fields. The radiative decay rate constant and PL quantum yield of P3HT dissolved in solution, which are evaluated from the molar extinction coefficient and the PL lifetime, are compared with the ones of P3HT dispersed in a PMMA matrix

Impact of ivermectin administered for scabies treatment on the prevalence of head lice in Atoifi, Solomon Islands.

Scabies and head lice are ubiquitous ectoparasitic infestations that are common across the Pacific Islands. Ivermectin is an effective treatment for both conditions, although the doses used vary. At a community level, mass drug administration (MDA) with ivermectin is an effective strategy to decrease prevalence of scabies. To what extent MDA with ivermectin will also reduce prevalence of head lice is unknown. Head lice prevalence was assessed before and after MDA with oral ivermectin (at a dose of 200 micrograms per kilogram of body weight) administered on day 1 and day 8. The primary outcome was the change in prevalence of head louse infestation at two weeks compared to baseline. Longer term efficacy was assessed three months after MDA. 118 participants were enrolled. Baseline prevalence of active head louse infestation was 25.4% (95% CI 18.4-34.0). At three-month follow-up, prevalence was 7.5% (95% CI 2.7-12.3), a relative reduction of 70.6% (95% CI 72.7%-91.4%, p <0.001). Head louse infestation was associated with younger age (age ≤10 years: prevalence 46.7%; adjusted odds ratio compared to adults of 7.2, 95%CI 2.0-25.9) and with having at least one other member of the household with active head louse infestation (adjusted odds ratio 4.3, 95%CI 1.7-11.1). Head louse infestation is common in the Solomon Islands. This proof of principle study shows that oral ivermectin at a dose of 200 micrograms per kilogram can reduce the burden of active head louse infestation, offering an additional collateral benefit of MDA with ivermectin for scabies control. ClinicalTrials.gov NCT03236168

First-principles GW-BSE excitations in organic molecules

We present a first-principles method for the calculation of optical excitations in nanosystems. The method is based on solving the Bethe-Salpeter equation (BSE) for neutral excitations. The electron self-energy is evaluated within the GW approximation, with dynamical screening effects described within time-dependent density-functional theory in the adiabatic, local approximation. This method is applied to two systems: the benzene molecule, C$_6$H$_6$, and azobenzene, C$_{12}$H$_{10}$N$_2$. We give a description of the photoisomerization process of azobenzene after an $n-\pi^\star$ excitation, which is consistent with multi-configuration calculations

Incidental mosquitocidal effect of an ivermectin mass drug administration on Anopheles farauti conducted for scabies control in the Solomon Islands.

Background: The Solomon Islands is targeting elimination of malaria by 2030. The dominant vector is the predominantly exophagic, exophilic Anopheles farauti sensu strictu. This biting behaviour limits the efficacy of conventional vector control tools and highlights the need for new strategies. When administered to humans ivermectin has been shown to have a mosquitocidal effect. Mass drug administration (MDA) with ivermectin is an emerging strategy in the control of scabies. In this study we explored any incidental effect of ivermectin MDA conducted for scabies control on mosquitoes. Methods: MDA for scabies was conducted in three villages. We performed human landing catches and measured 5-day mortality amongst Anopheles mosquitoes caught before and after MDA. Cox regression was used to calculate hazard ratios (HR) for mortality between mosquitoes caught before and after MDA. Results: There was a significant increase in 5-day mortality in anopheline mosquitoes caught post-MDA which was highest on the day of MDA itself (HR 4.2 95% CI 1.8 to 10.1, p=0.001) and the following day (HR 4.4 95% CI 1.8 to 10.8, p=0.002) compared to mosquitoes caught before MDA. Conclusions: This study shows a possible mosquitocidal effect of ivermectin MDA conducted for scabies control. Studies with a larger sample size with clinical as well as entomological outcomes should be conducted in this population

Avian richness and habitat characteristics in primary and logged hill dipterocarp tropical rainforest of Peninsular Malaysia

Hill dipterocarp tropical rainforest provides a variety of habitats for understorey bird species. These habitats are under severe pressure due to deforestation and logging activities which adversely affect the understorey bird species directly or indirectly through habitat fragmentation, reduced food resources and increase risk of predation. This study examined the effects of habitat disturbance on understorey bird species due to logging in hill dipterocarp tropical rain forest in Peninsular Malaysia. Understorey bird species richness and habitat characteristics between primary and logged forest were determined using mist-netting and plot quadrant method respectively. A total of 431individuals of 60 bird species representing 23 families was captured in both logged and primary forests (212 individuals of 34 species from primary forest and 219 individuals of 42 species from logged forest). Spectacled Bulbul and Cream–vented Bulbul (each 3.48%) were the two most dominant understorey bird species captured in logged forest. In contrast, Rufous–Collared Kingfisher (4.64%) and Grey–Headed Babbler (3.71%) were the most abundant bird species of primary forest. The results indicated that understorey bird species of primary forest was significantly different from the logged forest (F1, 120 = 1.95, P < 0.05). In addition, a total of 66 tree species representing 22 families was recorded from primary and logged forest. Out of the total, 53 tree species belong to 22 families were sampled from primary forest and 14 species belong to 10 families from logged forest. Primary forest was dominated with White Skin and Great Woolly Nutmeg (3.57%) while logged forest with Pigeon Wood/Indian Nettle Tree (17.86%) and Ant Plant (12.50%). Comparison analysis indicated that the mean vegetation relative abundance of primary forest was significantly different from the logged forest (F1, 134 = 10.5, P < 0.005). Selective logging has also altered the microclimate characteristics. The findings of this study revealed that primary forest may harbour a higher understorey bird species diversity and richness than logged forest. This study indicated that forest logging affects the understorey birds and the effects may vary from species to species