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Trapping
Kinds of Trapping Terms modified by Trapping Selected AbstractsSEDIMENT TRAPPING WITHIN FORESTRY STREAMSIDE MANAGEMENT ZONES: GEORGIA PIEDMONT, USA,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2004Jason M. Ward ABSTRACT: The effectiveness of streamside management zones (SMZs) was assessed for reducing sediment transport from concentrated overland flow draining two Georgia Piedmont clearcuts that had undergone mechanical and chemical site preparation and planting. Silt fences were used to trap sediment transport from zero-order ephemeral swales at the edge of and within SMZs. Four control swales and nine treatment swales were studied. A double mass curve approach was used to graphically compare sediment accumulation rates at the edge of SMZs to accumulation rates within the SMZs at a distance consistent with current recommendations for SMZ width in Georgia. SMZ efficiencies for trapping sediment transported by concentrated flow ranged from 71 to 99 percent. No statistical model was found to explain how SMZ efficiencies varied with SMZ and contributing area characteristics. Measured sediment accumulations at the SMZ boundary were compared to Revised Universal Soil Loss Equation (RUSLE) predictions of up- slope erosion, and a delivery ratio of 0.25 was calculated. SMZs had a quantifiable and substantial ameliorating effect on sediment transport from concentrated overland flow on the clearcut study sites. [source] A general model for predicting brown tree snake capture ratesENVIRONMETRICS, Issue 3 2003Richard M. Engeman Abstract The inadvertent introduction of the brown tree snake (Boiga irregularis) to Guam has resulted in the extirpation of most of the island's native terrestrial vertebrates, has presented a health hazard to small children, and also has produced economic problems. Trapping around ports and other cargo staging areas is central to a program designed to deter dispersal of the species. Sequential trapping of smaller plots is also being used to clear larger areas of snakes in preparation for endangered species reintroductions. Traps and trapping personnel are limited resources, which places a premium on the ability to plan the deployment of trapping efforts. In a series of previous trapping studies, data on brown tree snake removal from forested plots was found to be well modeled by exponential decay functions. For the present article, we considered a variety of model forms and estimation procedures, and used capture data from individual plots as random subjects to produce a general random coefficients model for making predictions of brown tree snake capture rates. The best model was an exponential decay with positive asymptote produced using nonlinear mixed model estimation where variability among plots was introduced through the scale and asymptote parameters. Practical predictive abilities were used in model evaluation so that a manager could project capture rates in a plot after a period of time, or project the amount of time required for trapping to reduce capture rates to a desired level. The model should provide managers with a tool for optimizing the allocation of limited trapping resources. Copyright © 2003 John Wiley & Sons, Ltd. [source] 3,4-Dihydro-3H -pyrrol-2-imines as Conformationally Restrained 1,3-Diazabutadienes: Synthesis, Structural Properties and Protonation,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2009Simon Janich Abstract 5-Aryl-3,3,4,4-tetramethyl-3,4-dihydro-3H -pyrrol-2-imines,conformationally restrained 1,3-diazabuta-1,3-diene derivatives, were easily prepared by treating aryllithium species with 2,2,3,3-tetramethylsuccinonitrile (1). Trapping the reaction intermediate with chlorotrimethylsilane gave N -silylated compounds 2a,e, whereas aqueous workup gave N-H derivatives 3a,b. Pyrenyl-substituted compound 3b was characterised by X-ray diffraction studies, revealing the presence of both intermolecular aromatic face-to-face contacts and the formation of homodimers by twofold H-bonding. N -Silylated derivatives 2a,d were used successfully as nucleophilic components in palladium-catalysed C,N bond-forming reactions to obtain N -arylated compounds 5b,h,j,k,m and 7a,d. The UV spectra of compounds 5 and 7 exhibit long wavelength absorptions up to 462 nm for 7d, thus indicating extended ,,,* conjugation. Dihydropyrrolimine-based compounds with larger conjugated aryl substituents in the 5-position react with Brønsted and Lewis acids displaying a significant colour change that could be used to estimate the pKb of 3a to a value of ,4.5. Derivatives 2c,e and 3a,b, which are not N -arylated, are fluorescent with a Stokes shift of 107 nm (6034 cm,1) for 3a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Vicarious Nucleophilic Substitution of (Chloroalkyl)oxazolines with Nitroarenes: Synthesis of (Nitrobenzyl)oxazolinesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2003Saverio Florio Abstract 2-Chloroalkyloxazolines 1a and 1b react with nitroarenes in the presence of tBuOK in DMSO to give, upon acidic quenching, substituted nitroaryloxazolines 2a, 2b, 3a, 9, 10, 11a,d, 12,19, and 21,22, probably by vicarious nucleophilic substitution (VNS). The reaction of 1a is poorly regioselective, while that of 1b is completely para regioselective, thus showing that the coupling is sterically controlled. Trapping of the carbanionic intermediate B of the VNS reaction with electrophiles furnished ,,,-disubstituted (nitrobenzyl)oxazolines 4,7. Attempts to trap B with PhCHO failed: the [(p -nitrophenyl)oxazolinyl]ethanol 8 was obtained. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Non-salmonids in a salmonid fishway: what do 50 years of data tell us about past and future fish passage?FISHERIES MANAGEMENT & ECOLOGY, Issue 5 2007M. MALLEN-COOPER Abstract, Salmonid fishways have been used in many countries for non-salmonid fishes, including Australia, but generally with poor results. Trapping the entrance and exit of a 1:9 gradient salmonid fishway on the Murray River confirmed very poor passage of native fish, with <1% of the most abundant species ascending. Fifty years of fish passage monitoring showed the numbers of three native species declining by 95,100% and non-native fish becoming dominant. Fishways are now being designed for native fish and being quantitatively assessed, but daily flow management also needs to be addressed. The ecological model for passage of potamodromous fishes has changed from passing adults of a few species to one that incorporates the whole fish community, specifically: immature fish of large-bodied species that dominate numbers migrating upstream; a diverse range of movement strategies; and small-bodied species, crustaceans and low numbers of less-mobile species. [source] Hydrologic versus geomorphic limitation on CPOM storage in stream ecosystemsFRESHWATER BIOLOGY, Issue 8 2008MELANIE J. SMALL Summary 1. Stream ecosystems are the products of interactions between hydrology, geomorphology and ecology, but examining all three components simultaneously is difficult and rarely attempted. Frequently, either geomorphology or hydrology is treated as invariable or static. 2. To examine the validity of treating either hydrology or geomorphology as static, we studied the individual and combined effects of hydrology and channel geomorphology on coarse particulate organic matter (CPOM) storage. Using data from an experimental leaf release in a hydrologically regulated stream we created a simple numerical model. This allowed us to quantify the relative influence of CPOM trapping and CPOM retention on total long-term CPOM storage under variable regimes of flood frequency and geomorphic structure. 3. CPOM storage is a function of supply, flood frequency and the type and frequency of in-stream structures. In-stream structures perform two distinct functions, trapping and retention, whose relative importance in leaf storage changes with stream hydrology. Trapping is more important for CPOM storage in streams with few floods, while retention is more important in streams with frequent floods. Different structures (e.g. boulders, large wood, small wood) perform these functions at different efficiencies. We found that large wood trapped two to three times more leaves than the bank, but that the bank retained leaves two to three times more efficiently. 4. A modelled channel with five times the amount of large wood as the study channel (a ,wood restoration') initially stored 14% more leaves than the modelled ,natural' channel. After six floods, however, the modelled wood restoration channel stored 50% less CPOM than the natural channel as the large wood had high trapping but poor retention. The modelled natural channel contained structures that could both trap and retain. Thus, as different structures performed different functions, the structural complexity buffered the stream allochthonous energy base against changes in hydrology through its balance of trapping and retention. 5. As the frequency of floods increased, the spatial distribution of CPOM became increasingly patchy as storage was driven entirely by structures with high retention. Thus, the coupling of flood frequency and geomorphic structure influenced CPOM availability, which in turn has ramifications for the entire stream food web. [source] Electron Trapping in Higher Adduct Fullerene-Based Solar CellsADVANCED FUNCTIONAL MATERIALS, Issue 18 2009Martijn Lenes Abstract Here, the performance of bulk-heterojunction solar cells based on a series of bisadduct analogues of commonly used derivatives of C60 and C70, such PCBMs and their thienyl versions, is investigated. Due to their higher lowest unoccupied molecular orbital an increase in open-circuit voltage and thus performance is expected. It is shown that the occurrence of a multitude of different isomers results in a decrease in the electron transport for some of the materials. Surprisingly, the solar-cell characteristics are very similar for all materials. This apparent discrepancy is explained by a significant amount of shallow trapping occurring in the fullerene phase that does not hamper the solar cell performance due the filling of these shallow traps during illumination. Furthermore, the trisadduct analogue of [60]PCBM has been investigated, which, despite an even further increase in open-circuit voltage, results in a significantly reduced device performance due to a strong deterioration of the electron mobility in the fullerene phase. [source] Energy Collection, Transport, and Trapping by a Supramolecular Organization of Dyes in Hexagonal Zeolite Nanocrystals,ADVANCED FUNCTIONAL MATERIALS, Issue 2 2006C. Minkowski Abstract The incorporation of guest molecules into the cavities of molecular sieves leads to a large variety of highly interesting materials. Zeolite,L,an aluminosilicate with one-dimensional channels of open diameter 7.1,Å,is a very versatile material for building highly organized host,guest systems. We present materials where organic dye molecules have been incorporated into the channels of zeolite,L by means of diffusion, to build artificial photonic antenna systems. The channel entrance can be plugged by adding closure molecules that then connect the guest molecules inside with materials or molecules outside of the zeolite channels, since they can act as extensions of the interior of the zeolite crystal. The photophysical processes taking place in such dye-loaded zeolite,L antennae can be studied either on single-micrometer- or submicrometer-sized crystals or on crystals dispersed in a solvent or coated as thin layers on a support. The energy-transfer process occurring is of the Förster-type, and its transfer rate can be tuned by separating the donor dyes and the acceptor dyes locally by varying amounts of spacer molecules. The distribution of the dye molecules and empty sites within a zeolite crystal has been modeled by means of a Monte Carlo simulation. The Förster energy migration and transfer steps are described as a random walk. [source] Charge Trapping at the Dielectric of Organic Transistors Visualized in Real Time and Space,ADVANCED MATERIALS, Issue 5 2008Scanning Kelvin probe microscopy demonstrates that water-induced charge trapping at the SiO2 dielectric , visualized in real time and space , is responsible for the commonly observed gate-bias-induced threshold-voltage shift in organic field-effect transistors. When a bias is applied to the electrodes, charges are injected onto the SiO2 (see background of the figure). When the contacts are grounded, the charges are released again (foreground picture). [source] Acute gastric dilatation causing bacterial cerebral aneurysm,Case reportINTERNATIONAL JOURNAL OF EATING DISORDERS, Issue 4 2008Takeshi Matsuyama MD Abstract Objective: Acute gastric dilatation (AGD) is a very rare entity which can sometimes be life-threatening. We report a case of a patient presenting with a rupture of a BCA during the treatment of AGD. Method: A 24-year-old woman, who had a history of bulimia and vomiting episodes, was transferred in shock with marked abdominal distension. A large nasogastric tube was inserted, and 9 liters of viscous gastric contents were drained out. Her circulation became stable. Results: About 3 months after admission, she became drowsy and presented with a right hemiparesis and aphasia. Computed tomography of the head showed a diffuse thick subarachnoid hemorrhage. Left carotid angiograms revealed an obscurely-shaped aneurysm in the left middle cerebral artery. Conclusion: Trapping of the aneurysm was performed. Thirty-four days after admission, the patient had a residual right hemiparesis and motor aphasia, and was discharged. © 2008 by Wiley Periodicals, Inc. Int J Eat Disord 2008 [source] Cover Picture: Microscopic Evidence for Spatially Inhomogeneous Charge Trapping in Pentacene (Adv. Mater.ADVANCED MATERIALS, Issue 11 200511/2005) Abstract Trapped charge has been observed in polycrystalline pentacene films by electric force microscopy in work reported by Muller and Marohn on p.,1410. The cover shows an optical fiber watching the motion of a metal-coated cantilever hovering over a polycrystalline pentacene film. The film occupies the 6.5,,,m gap in a working field-effect transistor. Trapped charge (dark blue and black areas in the pentacene) appears as large patches randomly distributed throughout the device, implying that long-lived traps in polycrystalline pentacene are not correlated with grain boundaries. [source] On the Trapping of Vinylgold IntermediatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2010A. Stephen Abstract An internal aryl-substituted ortho -alkynylphenol and a similar aniline with stoichiometric amounts of N,N, -bis(2,6-diisopropylphenyl)imidazol-2-ylidene-gold tosylate [(IPr)AuOTs] and triethylamine gave the aurated heterocycles as stable intermediates of the corresponding gold(I)-catalysed hydrooxylation and hydroamination reactions. X-ray crystal structure analyses of both products could be obtained. A similar internal alkyl-substituted ortho -alkynylphenol gave only the cycloisomerised product, no aurated intermediate could be detected. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Trapping of Active Methylene Intermediates with Alkenes, Indoles or Thiols: Towards Highly Selective Multicomponent ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Yanlong Gu Abstract In this paper, a basic method to access new multicomponent reactions (MCRs) is reported. The mechanism of these MCRs is based on the trapping of methylene intermediates, formed in situ by reaction of formaldehyde with electron-rich carbons, with alkene, thiol or indole derivatives. According to our strategy, a wide range of valuable skeletons has been obtained in a one-pot reaction, thus allowing a minimization of waste, cost and labor. The presented methodology exhibits a broad substrate scope and electron-rich carbons in the ,-position of a hydroxy or carbonyl group were found to be particularly efficient. More generally, this work offers new tools for creating molecular complexity and diversity from one of the simplest organic building blocks, formaldehyde. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 14-15 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 7-8 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 6 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 3 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Cover Picture: (Adv. Synth.ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Catal. The cover picture, provided by Maurice S. Brookhart, shows an example of a cationic palladium diimine complex which catalyzes polymerization of ethylene to high molecular weight, highly branched polyethylene. The catalyst resting states are the alkyl ethylene complexes as modeled by the ethyl ethylene complex shown. Migratory insertion of these alkyl ethylene species leads to ,-agostic complexes in which palladium can rapidly migrate along the chain ("chain-walking") through ,-elimination/readdition reactions. Trapping of branched alkyl complexes followed by insertion leads to formation of branches in the polymer chain. Polyethylenes formed exhibit branches-on-branches since chain-walking through tertiary centers is facile. [source] Niche overlap between marsupial and eutherian carnivores: does competition threaten the endangered spotted-tailed quoll?JOURNAL OF APPLIED ECOLOGY, Issue 2 2008A. S. Glen Summary 1The significance of top-down regulation by carnivores is receiving increasing global recognition. As a consequence, key objectives in many programmes that seek to maintain ecosystem function now include conserving carnivores and understanding their interactions. This study examined overlap in resource use (space and diet) of introduced eutherian carnivores and an endangered marsupial carnivore, the spotted-tailed quoll Dasyurus maculatus, in eastern Australia. We also investigated mechanisms of niche partitioning and evidence for interspecific aggression. 2Dietary overlap between quolls, red foxes Vulpes vulpes and wild dogs Canis lupus ssp. was assessed by analysis of scats. Trapping, radio-tracking and direct observations were used to quantify spatial overlap between quolls, foxes, wild dogs and feral cats Felis catus. 3Dietary overlap among the carnivores was extensive. Medium-sized mammals were the most important prey for all three predators, indicating potential for exploitative interactions. However, hunting of different size classes of secondary prey and consumption by quolls of more arboreal prey than their counterparts may assist coexistence. Remains of quoll were found in two dog scats, and cat hair in another, possibly indicating intraguild predation. 4We observed extensive spatial overlap between quolls and eutherian carnivores. However, we inferred from dietary data that quolls foraged primarily in forested habitat, while canids foraged mainly in cleared habitat. 5Synthesis and applications. Our results indicate strong potential for competition between spotted-tailed quolls and eutherian carnivores, and thus a situation where control of introduced predators may be desirable, not only for the conservation of prey species but also for the protection of native carnivores. Concern over potential non-target mortality of quolls has hindered efforts to control foxes in eastern Australia using poison baits. We contend that, rather than harming quoll populations, baiting for foxes should aid the conservation of quolls and should be implemented in areas of sympatry where fox numbers are high. [source] Extracellular neutrophil traps in periodontitisJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2009L. Vitkov Background and Objective:, Chronic periodontitis, the chronic inflammatory disease of the periodontium, is caused by bacteria and is characterized by an influx of neutrophils into the gingival crevice. Recently, a ,new' extracellular neutrophil defense mechanism , neutrophil extracellular traps , has been described. However, their role in periodontitis has not yet been investigated. Material and Methods:, Clinical examinations, transmission and scanning electron microscopy, as well as cytology and confocal laser-scanning microscopy, were employed to analyze gingiva biopsies and crevicular exudate from patients with chronic periodontitis. Results:, An abundance of neutrophil extracellular traps and some phagocytic neutrophils was found on the gingival pocket surface and in the purulent crevicular exudate. Finding neutrophil extracellular traps in the spontaneously effused purulent crevicular exudate clearly indicated that they are flushed from the pocket by the crevicular exudate. In cases of dispersal of subgingival plaque bacteria, their trapping by neutrophil extracellular traps in purulent crevicular exudate and on the gingival surface was demonstrated. Conclusion:, Trapping the crevicular bacteria prevents their adhesion to and invasion of the gingiva. The combination of neutrophil extracellular traps and crevicular exudate outflow appears to be a ,novel' defense mechanism for the clearance of crevicular bacteria in chronic periodontitis. [source] Trapping a Difluorocarbene,Platinum Fragment by Base Coordination,ANGEWANDTE CHEMIE, Issue 25 2010Sonia Martínez-Salvador Dipl.-Chem. Ertappt! Der Nachweis von Difluorcarben-Platin-Intermediaten bei der säureinduzierten Spaltung von Pt-CF3 -Bindungen gelang durch das Abfangen einer basestabilisierten PtCF2 -Einheit (siehe Schema). Beim Angriff eines N-Nucleophils (py*) auf das hoch elektrophile und extrem reaktive Kohlenstoffatom des Difluorcarbens wird eine C-N-Bindung gebildet. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||