Search results for "Phosphor"
showing 10 items of 1952 documents
Effect of Iodination on the Photophysics of the Laser Borane anti-B18H22: Generation of Efficient Photosensitizers of Oxygen
2019
Treatment of the laser borane anti-B18H22 (compound 1) with iodine in ethanol gives the monoiodinated derivative 7-I-anti-B18H21 (compound 2) in 67% yield, or, by reaction with iodine or ICl in the presence of AlCl3 in dichloromethane, the diiodinated derivative 4,4'-I2-anti-B18H20 (compound 3) in 85% yield. On excitation with 360 nm light, both compounds 2 and 3 give strong green phosphorescent emissions (λmax = 525 nm, ΦL = 0.41 and λmax = 545 nm, ΦL = 0.71 respectively) that are quenched by dioxygen to produce O2(1Δg) singlet oxygen with quantum yields of ΦΔ = 0.52 and 0.36 respectively. Similarly strong emissions can be stimulated via the nonlinear process of two-photon absorption when …
Room-Temperature Phosphorescence and Efficient Singlet Oxygen Production by Cyclometalated Pt(II) Complexes with Aromatic Alkynyl Ligands
2020
The synthesis of five novel cyclometalated platinum(II) compounds containing five different alkynyl-chromophores was achieved by the reaction of the previously synthesized Pt–Cl cyclometalated compound (1) with the corresponding RC≡CH by a Sonogashira reaction. It was observed that the spectral and photophysical characteristics of the cyclometalated platinum(II) complexes (Pt–Ar) are essentially associated with the platinum-cyclometalated unit. Room-temperature emission of the Pt–Ar complexes was attributed to phosphorescence in agreement with DFT calculations. Broad nanosecond (ns)-transient absorption spectra were observed with decays approximately identical to those obtained from the emi…
Modeling the Effects of Climate Change on the Supply of Phosphate-Phosphorus
2009
The transfer of phosphorus from terrestrial to aquatic ecosystems is a key route through which climate can influence aquatic ecosystems. A number of climatic factors interact in complex ways to regulate the transfer of phosphorus and modulate its ecological effects on downstream lakes and reservoirs. Processes influencing both the amount and timing of phosphorus export from terrestrial watersheds must be quantified before we can assess the direct and indirect effects of the weather on the supply and recycling of phosphorus. Simulation of the export of phosphorus from the terrestrial environment is complicated by the fact that it is difficult to describe seasonal and inter-annual variations …
Responses of aquatic plants to eutrophication in rivers:a revised conceptual model
2018
Compared to research on eutrophication in lakes, there has been significantly less work carried out on rivers despite the importance of the topic. However, over the last decade, there has been a surge of interest in the response of aquatic plants to eutrophication in rivers. This is an area of applied research and the work has been driven by the widespread nature of the impacts and the significant opportunities for system remediation. A conceptual model has been put forward to describe how aquatic plants respond to eutrophication. Since the model was created, there have been substantial increases in our understanding of a number of the underlying processes. For example, we now know the thre…
Community replacement of neritic carbonate organisms during the late Valanginian platform demise: a new record from the Provence Platform.
2012
24 pages; International audience; The Valanginian is marked by amajor platform demise inducing a hiatus in the northern Tethyan neritic carbonate record from the top of the lower Valanginian to the lower Hauterivian. New biostratigraphic and chemostratigraphic data from the Ollioules section (Provence Platform, southern France) are presented here, demonstrating that a large part of the upper Valanginian is preserved in an inner platform environment. The thick, upper Valanginian, aggrading carbonate succession is observed in an aborted rift domain, implying relatively low subsidence. In this context, a relatively long-term sea-level rise was required to sustain a keep-up style of carbonate p…
The stoichiometry of particulate nutrients in Lake Tanganyika — implications for nutrient limitation of phytoplankton
1999
We studied the potential nutrient limitation of phytoplankton by means of seston nutrient stoichiometry and nutrient enrichment bioassays in the epilimnion of Lake Tanganyika. In most cases, the particulate carbon to phosphorus (C:P) ratio was high and indicated moderate P deficiency, while the respective C:N ratio mainly suggested moderate N deficiency. The N:P ratios of seston indicated rather balanced N and P supply. In three two-day enrichment bioassays in April—May 1995, a combined addition of P, N and organic carbon (glucose) always increased primary production in comparison to untreated controls. Primary production also slightly increased after the addition of phosphate-P, while the …
Tropical Andean forests are highly susceptible to nutrient inputs--rapid effects of experimental N and P addition to an Ecuadorian montane forest.
2012
Tropical regions are facing increasing atmospheric inputs of nutrients, which will have unknown consequences for the structure and functioning of these systems. Here, we show that Neotropical montane rainforests respond rapidly to moderate additions of N (50 kg ha -1 yr -1) and P (10 kg ha -1 yr -1). Monitoring of nutrient fluxes demonstrated that the majority of added nutrients remained in the system, in either soil or vegetation. N and P additions led to not only an increase in foliar N and P concentrations, but also altered soil microbial biomass, standing fine root biomass, stem growth, and litterfall. The different effects suggest that trees are primarily limited by P, whereas some pro…
Two maize Kip-related proteins differentially interact with, inhibit and are phosphorylated by cyclin D–cyclin-dependent kinase complexes
2017
Highlight Maize Kip-related proteins can be differentially phosphorylated by different cyclin D–cyclin-dependent kinase complexes and this influences their performance as cyclin-dependent kinase inhibitors.
The Role of Phospholipase D and MAPK Signaling Cascades in the Adaption of Lichen Microalgae to Desiccation: Changes in Membrane Lipids and Phosphopr…
2016
Classically, lichen phycobionts are described as poikilohydric organisms able to undergo desiccation due to the constitutive presence of molecular protection mechanisms. However, little is known about the induction of cellular responses in lichen phycobionts during drying. The analysis of the lipid composition of the desiccated lichen microalga Asterochloris erici revealed the unusual accumulation of highly polar lipids (oligogalactolipids and phosphatidylinositol), which prevents the fusion of membranes during stress, but also the active degradation of cone-shaped lipids (monogalactosyldiacylglycerol and phosphatidylethanolamine) to stabilize membranes in desiccated cells. The level of pho…
Phosphinotripeptidic Inhibitors of Leucylaminopeptidases
2021
Phosphinate pseudopeptide are analogs of peptides containing phosphinate moiety in a place of the amide bond. Due to this, the organophosphorus fragment resembles the tetrahedral transition state of the amide bond hydrolysis. Additionally, it is also capable of coordinating metal ions, for example, zinc or magnesium ions. These two properties of phosphinate pseudopeptides make them an ideal candidate for metal-related protease inhibitors. This research investigates the influence of additional residue in the P2 position on the inhibitory properties of phosphinopeptides. The synthetic strategy is proposed, based on retrosynthetic analysis. The N-C-P bond formation in the desired compounds is …