RFUVA catalyzes cross-linking reactions that require production of singlet oxygen ((1)O(2)), whose half-life is extended by D(2)O. Carbonyl-based cross-linking reactions dominate in the corneal stroma, but other possible reaction schemes are proposed. The use of D(2)O as solution media for RF would enable concentration decreases or significant strength enhancement in treated corneas.
Variations in photosynthesis still cause substantial uncertainties in predicting photosynthetic CO2 uptake rates and monitoring plant stress. Changes in actual photosynthesis that are not related to greenness of vegetation are difficult to measure by reflectance based optical remote sensing techniques. Several activities are underway to evaluate the sun-induced fluorescence signal on the ground and on a coarse spatial scale using space-borne imaging spectrometers. Intermediate-scale observations using airborne-based imaging spectroscopy, which are critical to bridge the existing gap between small-scale field studies and global observations, are still insufficient. Here we present the first validated maps of sun-induced fluorescence in that critical, intermediate spatial resolution, employing the novel airborne imaging spectrometer HyPlant. HyPlant has an unprecedented spectral resolution, which allows for the first time quantifying sun-induced fluorescence fluxes in physical units according to the Fraunhofer Line Depth Principle that exploits solar and atmospheric absorption bands. Maps of sun-induced fluorescence show a large spatial variability between different vegetation types, which complement classical remote sensing approaches. Different crop types largely differ in emitting fluorescence that additionally changes within the seasonal cycle and thus may be related to the seasonal activation and deactivation of the photosynthetic machinery. We argue that sun-induced fluorescence emission is related to two processes: (i) the total absorbed radiation by photosynthetically active chlorophyll and (ii) the functional status of actual photosynthesis and vegetation stress. Abstract Variations in photosynthesis still cause substantial uncertainties in predicting photosynthetic CO 2 uptake rates and monitoring plant stress. Changes in actual photosynthesis that are not related to greenness of vegetation are difficult to measure by reflectance based optical remote sensing techniques. Several activities are underway to evaluate the sun-induced fluorescence signal on the ground and on a coarse spatial scale using space-borne imaging spectrometers. Intermediate-scale observations using airborne-based imaging spectroscopy, which are critical to bridge the existing gap between small-scale field studies and global observations, are still insufficient. Here we present the first validated maps of sun-induced fluorescence in that critical, intermediate spatial resolution, employing the novel airborne imaging spectrometer HyPlant. HyPlant has an unprecedented spectral resolution, which allows for the first time quantifying sun-induced fluorescence fluxes in physical units according to the Fraunhofer Line Depth Principle that exploits solar and atmospheric absorption bands. Maps of sun-induced fluorescence show a large spatial variability between different vegetation types, which complement classical remote sensing approaches. Different crop types largely differ in emitting fluorescence that additionally changes within the seaso...
Thermal stability and optical transparency are important factors for flexible electronics and heat-related applications of pressure-sensitive adhesives (PSAs). However, current acryl- and rubber-based PSAs cannot attain the required thermal stability, and silicon-based PSAs are much more expensive than the alternatives. Oleo-chemicals including functionalized plant oils have great potential to replace petrochemicals. In this study, novel biobased PSAs from soybean oils were developed with excellent thermal stability and transparency as well as peel strength comparable to current PSAs. In addition, the fast curing (drying) property of newly developed biobased PSAs is essential for industrial applications. The results show that soybean oil-based PSA films and tapes have great potential to replace petro-based PSAs for a broad range of applications including flexible electronics and medical devices because of their thermal stability, transparency, chemical resistance, and potential biodegradability from triglycerides.
A systematic study of alkyne metathesis catalyzed by trialkoxymolybdenum(VI) alkylidyne complexes is reported, in which substrate functional groups, alkynyl substituents, and catalyst ligands are varied. Sterically hindered trisamidomolybdenum(VI) propylidyne complex 5 was prepared conveniently through a previously communicated reductive recycle strategy. Alcoholysis of 5 with various phenols/alcohols provides a set of active catalysts for alkyne metathesis at room temperature, among which the catalyst with p-nitrophenol as ligand shows the highest catalytic activity and is compatible with a variety of functional groups and solvents. A key finding that enabled the use of highly active molybdenum(VI) catalysts is replacement of the commonly used propynyl substituents on the starting alkyne substrates with butynyl groups. Under reduced pressure using 1,2,4-trichlorobenzene as an involatile solvent, the alkyne metathesis of butynyl substituted compounds proceeds well at 30 degrees C providing high yields (83%-97%) of dimers. Rationalization of the special role played by butynyl substrates is discussed.
The asymmetric hydrogenation of tetrasubstituted olefins provides direct access to very useful biological molecules and intermediates. The development of the technology has been slow, due in part to the synthetic challenges involved in developing chiral catalysts for a successful asymmetric induction. We briefly recount the breakthroughs in functionalized and unfunctionalized tetrasubstituted olefins, from the reports of Zhou and Buchwald for functionalized and unfunctionalized substrates, respectively, to the advent of chiral phosphoramidite ligands. The main emphasis of this Perspective lies in bringing into focus the complexity and challenges of inducing an asymmetric reduction for these substrates, which includes a brief discussion of the mechanism, the latest developed chiral catalysts, and the enormous scientific opportunities that still exist in developing "go to" catalyst systems for the various substrate types.
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