Towards artificial photosynthesis: Promoting microscale photochemistry in science education

In order to simulate basic features of the natural cycle of photosynthesis and respiration, a model experiment called Photo-Blue-Bottle PBB has been developed. According to the title of this paper, the experiment will be presented and interpreted in accordance to basic contents from science education. An extended version of the PBB experiment also enables the evolution of hydrogen. This is a key step towards a prospective technological scenario with solar light driven production of “green fuels”. The concept of electronically excited state, the “heart of all photoprocesses” (N. J. Turro), will be completed by further teaching experiments and concepts concerning the up-to-date topic of photoactive molecular switches

Atmospheric Chemistry of Venus-like Exoplanets

We use thermodynamic calculations to model atmospheric chemistry on terrestrial exoplanets that are hot enough for chemical equilibira between the atmosphere and lithosphere, as on Venus. The results of our calculations place constraints on abundances of spectroscopically observable gases, the surface temperature and pressure, and the mineralogy of the surface. These results will be useful in planning future observations of the atmospheres of terrestrial-sized exoplanets by current and proposed space observatories such as the Hubble Space Telescope (HST), Spitzer, James Webb Space Telescope (JWST), Terrestrial Planet Finder, and Darwin.Comment: 35 pages, 4 figures, 3 tables; 1 appendix; submitted to ApJ; version

The generation of oxygen radicals during host plant responses to infection

Recent evidence points to significant oxygen radical production by some plant tissues in response to pathogenic challenge. These findings have proved quite controversial, in part because of an inadequate appreciation of the behaviour of oxygen radicals in biological systems. This review critically discusses the evidence to date and outlines several potential roles for oxygen species in host-pathogen interactions. The production of oxygen radicals during plant defence responses is compared to the respiratory burst of mammalian phagocytic cells

Preliminary studies on some chlorophyll fluorescence parameters in Crassulaceae species of different leaf characters under water stress

Chlorophyll fluorescence quenching parameters of ABSTRACT Kalanchoe daigremontiana, K. fedtschenkoi cv. marginata, K. tomentosa, Crassula multicava and Cotyledon ladysmithiensis were compared in well watered and water deficient plants. The maximum quantum yield (Fv/Fm) of photosystem II (PSII) proved to be a very stable parameter in all species and water treatments. The EQY, NPQ, qP and ETR differed in Crassula multicava from those of the other plants. The allocation of absorbed light by PSII that is utilized to photosynthetic electron transport and thermal dissipation was also calculated. Analysis of the chlorophyll fluorescence parameters demonstrated, that Crassula multicava was the only plant, which exhibited a higher proportion of excitation energy allocated to PSII photochemistry under water deficit at 1200 µmol m-2s-1 actinic light (AL) intensity

Transient absorption spectroscopy detection of sensitized delayed fluorescence in chiral benzophenone/naphthalene systems

Transient absorption spectroscopy has proven to be a powerful tool to investigate the formation and decay of excited singlet states upon triplet–triplet annihilation, following T–T energy transfer from a selectively excited sensitizer. Thus, upon selective excitation of benzophenone (BZP) by laser flash photolysis (LFP) at λ = 355 nm in the presence of naphthalene (NPT), a negative band centered at 340 nm has been detected, with growth and decay in the microsecond timescale. It has been assigned to the P-type NPT delayed-fluorescence. In the case of chiral BZP/NPT systems, stereodifferentiation has been observed in the kinetics of the involved photophysical processesFinancial support from the MICINN (Grant CTQ2010-14882 and predoctoral fellowship to P. B.) is gratefully acknowledged.Bonancía Roca, P.; Jiménez Molero, MC.; Miranda Alonso, MÁ. (2011). Transient absorption spectroscopy detection of sensitized delayed fluorescence in chiral benzophenone/naphthalene systems. Chemical Physics Letters. 515(1-3):194-196. https://doi.org/10.1016/j.cplett.2011.08.096S1941965151-

ENHANCING THE BIOLOGICAL CONTROL POTENTIAL OF ENTOMOPATHOGENIC NEMATODES PROTECTION FROM DESICCATION AND UV RADIATION

M.S.M.S. Thesis. University of Hawaiʻi at Mānoa 201

Air-snow exchange investigations at Summit, Greenland: An overview

The Greenland Ice Sheet Project 2 (GISP2) and Greenland Ice Core Project (GRIP) deep drilling programs at Summit, Greenland included support (both logistical and scientific) of extensive investigation of atmospheric transport and air-snow exchange processes of gases and particles relevant to the interpretation of the ice-core records. Much of the sampling for the air-snow exchange investigations was conducted at a unique solar-powered camp 30 km southwest of the GISP2 drill camp (even further from the GRIP camp) and was characterized by a high degree of international collaboration and cooperation. The wide range of expertise and analytical capabilities of the 20-plus investigators participating in these studies has provided important insight into the meteorological, physical, and chemical processes which interact to determine the composition of snow and firn at Summit. Evolving understanding of this system will allow improved reconstruction of the composition of the atmosphere over Greenland in the past from the detailed Summit ice-core records. This paper provides an overview of air-snow exchange investigations at Summit, including their development through the course of the drilling programs (1989–1993), significant findings related to both air-snow exchange issues and the present state of the Arctic free troposphere, as well as the major outstanding questions which are being addressed in ongoing experiments at Summit

Host/Guest Simulation of Fluorescent Probes Adsorbed into Low-Density Polyethylene, 1. Excimer Formation of 1,3-Di(1-pyrenyl)propane

Molecular dynamics and Rotational Isomer State/Monte Carlo techniques with a Dreiding 1.01 Force Field are employed to study the excimer formation of isolated 1,3-di(1-pyrenyl)propane and the probe adsorbed into a low-density polyethylene (LDPE) matrix model. The probability of formation of each molecular conformer at several temperatures was calculated using these theoretical techniques. Conformational statistical analysis of the four torsion angles (ϕ₁, ϕ₂, θ₁, θ₂) of Py3MPy showed that the angles —C—Cᵃʳ— (ϕ₁, ϕ₂) present two states c ± = ±90°; and the angles —C—C— (θ₁, θ₂), the three trans states = 180°, g ± = ±60°. The correlation of θ₁–θ₂ torsion angles showed that the most probable pairs were g⁺g⁻ and g⁻g⁺ for the excimer-like specimens, although these angles are distorted because of interactions with the polymer matrix. The temperature dependence of the excimer-formation probability revealed that this process was thermodynamically controlled in the isolated case. When the probe was adsorbed into the LDPE matrix, the excimer formation process was reversed at T = 375 K. At T > 375 K, the behavior was similar to the isolated case but, at T < 375 K, excimer formation probability increased with temperature as found experimentally by steady-state fluorescence spectroscopy. This temperature was coincident with the onset of the LDPE melting process, determined experimentally by thermal analysis.The authors wish to thank Brite EuRam programme (BE97-4472) and CAM (07N/0002/1998) for support