The lifetime of the lowest excited singlet (S 1 ) state of peridinin and many other carbonyl-containing carotenoids and polyenes has been reported depend on the polarity of the solvent. This effect has been attributed to the presence of an intramolecular charge transfer (ICT) state in the manifold of excited states for these molecules. The nature of this ICT state has yet to be elucidated. In the present work, steady-state and ultrafast time-resolved optical spectroscopy have been performed on peridinin and three synthetic analogues, C 33 -peridinin, C 35 -peridinin, and C 39 -peridinin which have different numbers of conjugated carbon-carbon double bonds. Otherwise, the molecules are structurally similar in that they posses the same functional groups. The trends in the positions of the steady-state and transient spectral profiles for this systematic series of molecules allow an assignment of the spectral features to transitions involving the S 0 , S 1 , S 2 and ICT states. A kinetics analysis reveals the lifetimes of the excited states and the dynamics of their excited state deactivation pathways. The most striking observation in the data is that the lifetime of the ICT state converges to the same value of 10.0 ± 2.0 ps in the polar solvent, methanol, for all the peridinin analogues regardless of the extent of π-electron conjugation. This suggests that the ICT state is highly localized on the lactone ring which is a common structural feature in all the molecules. The data further suggest that the S 1 and ICT states behave independently and that the ICT state is populated both from both S 1 and S 2 , the rate and efficiency from S 1 being dependent on the length of the π-electron chain of the carotenoid and the solvent polarity. Keywords peridinin; peridinin analogue; carotenoid; ICT state; excited state; kinetics analysis *Author to whom correspondence should be addressed: Harry A. Frank, Department of Chemistry, 55 North Eagleville Road, University of Connecticut, Storrs,. harry.frank@uconn.edu. Supporting Information available: Overlay of the fluorescence spectra of C 33 -peridinin, C 35 -peridinin and peridinin taken at room temperature in carbon disulfide and n-hexane, NIR transient spectra of all four analogues taken at room temperature in methanol, and steady-state absorption spectra of C 33 -peridinin, C 35 -peridinin, peridinin and C 39 -peridinin taken at room temperature in methanol, extended to high energy to show the "cis-peak" region between 27,000 and 40,000 cm −1 . This material is available free of charge via the Internet at

In the vadose zone, air–water interfaces play an important role in particle fate and transport, as particles can attach to the air–water interfaces by action of capillary forces. This attachment can either retard or enhance the movement of particles, depending on whether the air–water interfaces are stationary or mobile. Here we use three standard PTFE particles (sphere, circular cylinder, and tent) and seven natural mineral particles (basalt, granite, hematite, magnetite, mica, milky quartz, and clear quartz) to quantify the capillary forces between an air–water interface and the different particles. Capillary forces were determined experimentally using tensiometry, and theoretically assuming volume-equivalent spherical, ellipsoidal, and circular cylinder shapes. We experimentally distinguished between the maximum capillary force and the snap-off force when the air–water interface detaches from the particle. Theoretical and experimental values of capillary forces were of similar order of magnitude. The sphere gave the smallest theoretical capillary force, and the circular cylinder had the largest force due to pinning of the air–water interface. Pinning was less pronounced for natural particles when compared to the circular cylinder. Ellipsoids gave the best agreement with measured forces, suggesting that this shape can provide a reasonable estimation of capillary forces for many natural particles.

The capillary forces exerted by moving air-water interfaces can dislodge particles from stationary surfaces. The magnitude of the capillary forces depends on particle shape, orientation, and surface properties, such as contact angle and roughness. The objective was to quantify, both experimentally and theoretically, capillary force variations as an air-water interface moves over the particles. We measured capillary forces as a function of position, i.e., force-position curves, on particles of different shape by using force tensiometry. The particles (5 mm nominal size) were made of polyacrylate and were fabricated using a 3D printer. Experimental measurements were compared with theoretical calculations. We found that force-position curves could be classified into in three categories according to particle shapes: (1) curves for particles with round cross sections, such as spheroidal particles, (2) curves for particles with fixed cross sections, such cylindrical or cubical particles, and (3) curves for particles with tapering cross sections, such as prismatic or tetrahedral particles. Spheroidal particles showed a continuously varying capillary force. Cylindrical or cubical particles showed pronounced pinning of the air-water interface line at edges. The pinning led to an increased capillary force, which was relaxed when the interface snapped off from the edges. Particles with tapering cross section did not show pinning and showed reduced capillary forces as the air-water interface line perimeter and displacement cross section continuously decrease when the air-water interface moved over the particles.

Peridinin exhibits an anomalous solvent dependence of its S 1 excited state lifetime attributed to the presence of an intramolecular charge transfer (ICT) state. The nature of this state has yet to be elucidated. Ultrafast time-resolved optical spectroscopy has been performed on a synthetic analog, C 35 -peridinin, having one less conjugated double bond than peridinin. The data reveal the lifetime decreases from 1.5 ns in n-hexane to 9.2 ps in methanol, an order of magnitude larger than peridinin. This is the strongest solvent dependence on the lifetime of an S 1 state of a carotenoid yet reported. The data support the view that the S 1 and ICT states are strongly coupled.

The spectroscopic properties and dynamics of the lowest excited singlet states of peridinin and two derivatives have been studied by steady-state absorption and fast-transient optical spectroscopic techniques. One derivative denoted PerOlEs, possesses a double bond and a methyl ester group instead of the r-ylid-enebutenolide of peridinin. Another derivative denoted PerAcEs, is the biosynthetic precursor of peridinin and possesses a triple bond and a methyl ester group corresponding to the r-ylidenbutenolide function. Ultrafast time-resolved spectroscopic experiments in the visible and near-infrared regions were performed on the molecules and reveal the energies and regarding the structural features and interactions responsible for the unusual solvent-induced changes in the steady-state and transient absorption spectra and dynamics of dynamics of the excited electronic states. The data also provide information peridinin.

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The study aims to understand land degradation in the ≈ 2000 ha , humid and mountainous Papung khola catchment in the Sikkim Sivalik Range using the revised universal soil loss equation on a GIS platform. The catchment drains into the Tista River and is part of the data-sparse Eastern Himalayan ecoregion. Catchment land-use is changing from broadleaf forests to mixed land-use driven by rising population, and livelihood changes from primary production (forestry, agriculture) to service sectors (tourism, trade, construction). The study uses data on soil characteristics, ground and satellite precipitation and aerial land cover to predict potential soil erosion. Results indicate transitions in land cover/land use from forests to agriculture, disturbances due to construction and the potential increase in frequency of extreme climate events posing a unique risk to soils of the steep catchment causing decrease in soil cover and resultant loss of land productivity. The catchment can be currently categorized under a "very low" or "slightly erosive" regime (mean erosion rates 3.53 t ha −1 year −1 , with > 99% under cover of < 5 t ha −1 year −1 ) with around three-quarters of the catchment under forest cover. High precipitation, intensification of diurnal and seasonal wetting-drying cycles, human disturbances to the top soil and rapid land use/land cover changes combining with the extreme topography and slow soil development is driving land degradation, which may stymie sustainable development and livelihood diversification in the future. Moderate erosion levels of ≈ 10 t ha −1 year −1 can be expected in the future in areas with intact vegetation cover leading to complete top soil loss given the shallow profile depths.