Search results for "fragmentation"
showing 10 items of 798 documents
Studies in organic mass spectrometry.VIII. The electron impact mass spectra of 2,4-substituted-3-diazo-5-phenylpyrroles
1990
The electron impact mass spectra (75 eV) of the β-diazopyrroles always show the molecular ions and undergo as the main fragmentation process the elimination of nitrogen followed by ring opening reactions leading to benzonitrile either as neutral or charged species. The peaks at 26 amu below the molecular ions, which are a general feature of these spectra, are due to the presence of the corresponding pyrroles which are formed by reductive reactions during the vaporization process of the samples.
Influences of landscape structure on diversity of beetles associated with bracket fungi in Brazilian Atlantic Forest
2015
Abstract Brazilian Atlantic forest ecosystem is a global biodiversity hotspot. We studied the effects of area, connectivity and habitat quality of conservation areas on the diversity of beetles associated with basidiomes of wood-decaying fungi. Moreover, we analyzed the beetles' composition to verify what the process that produces the differentiation between the patches (β diversity). Species richness of fungivorous beetles increased the larger the area and the better the connectivity of conservation areas; however, neither area nor connectivity had an independent effect on beetle richness. Furthermore, the fungivorous beetle community was affected by the reduction in resource availability …
Modifying the body distribution of HPMA-based copolymers by molecular weight and aggregate formation.
2011
There is a recognized need to create well-defined polymer probes for in vivo and clinical positron emission tomography (PET) imaging to guide the development of new generation polymer therapeutics. Using the RAFT polymerization technique in combination with the reactive ester approach, here we have synthesized well-defined and narrowly distributed N-(2-hydroxypropyl)methacrylamide homopolymers (pHPMA) (P1* and P2*) and random HPMA copolymers consisting of hydrophilic HPMA and hydrophobic lauryl methacrylate comonomers (P3* and P4*). The polymers had molecular weights below (P1* and P3*) and above the renal threshold (P2* and P4*). Whereas the homopolymers dissolve in isotonic solution as in…
Synthesis, structural investigations on organotin(IV) chlorin-e6 complexes, their effect on sea urchin embryonic development and induced apoptosis
2004
Four new organotin(IV) chlorin derivatives, [chlorin=chlorin-e(6)=21H,23H-porphine-2-propanoic acid, 18-carboxy-20-(carboxymethyl)-8-ethenyl-13-ethyl-2,3-di-hydro-3,7,12,17-tetramethyl-(2S-trans)-], with formula (R(2)Sn)(3)(chlorin)(2).2H(2)O (R=Me, n-Bu) and (R(3)Sn)(3)chlorin.2H(2)O (R=Me, Ph) have been synthesized. The solid state and solution phase structures have been investigated by FT-IR, (119)Sn Mössbauer, (1)H and (13)C NMR spectroscopy. In the solid state, (R(2)Sn)(3)(chlorin)(2).2H(2)O complexes contain six coordinated Sn(IV), in a skew trapezoidal environment by forming trans-R(2)SnO(4) polymeric units. As far as (R(3)Sn)(3)chlorin.2H(2)O complexes are concerned, Sn(IV) is five …
Mass spectra of halogenated esters: 8. Methyl esters of 2,3-dichloro-, bromochloro- and dibromopropenoic acids
1988
The mass spectral fragmentation of methyl esters of E and Z isomers of 2,3-dichloro-, 2-bromo-3-chloro-, 3-bromo-2-chIoro- and 2,3-dibromopropenoic acids have been investigated. The M+˙ peak is shown with all isomers, the [M − OCH3]+, [M − X]+, [M − OCH3 − CO]+, [M − OCH3 − CO − X]+˙ and [M − OCH3 − CO − X − X]+ ions constituting abundant peaks in all spectra. The results, particularly from the bromochloro isomers, show that a halogen atom is eliminated from the 3- rather than the 2- position and from the Z rather than the E isomer. Bromine as a bulky atom is preferentially lost.
Fossilized Bronze, Invisible Bronze
2023
The systematic field surveys carried out since the beginning of the 2000s around the fortified site of the Camp du Château at Salins-les-Bains (Jura, France) have led to the discovery of 74 Bronze Age hoards, a density rarely observed in France. Dating from the beginning of the Middle Bronze Age to the Late Bronze Age, this dataset is unique as it provides detailed information on the composition of the hoards and their distribution within a defined territorial and chronological framework.These hoards are mainly made up of fragments, as around 90% of the objects are broken. This is deliberate and seems to correspond to a codified ritual of destruction which could be related to the notion of …
Controlled radical polymerization of styrene in miniemulsion polymerization using reversible addition fragmentation chain transfer
2003
Abstract Miniemulsion polymerizations of styrene in the presence of two reversible addition–fragmentation chain-transfer (RAFT) agents were studied. The rates were significantly retarded by the presence of a RAFT agents S -(thiobenzoyl)thioglycolic acid, 1 , or dithiobenzoic acid 1-phenylethyl ester, 2 . Control in miniemulsion polymerization is not as good as for bulk polymerizations. The miniemulsions could also be stabilized against Ostwald ripening by a polymer terminated by a dithiobenzoic moiety. In this case, the polymerization was not controlled because of the generation of renucleated particles. To cite this article: I. Uzulina et al., C. R. Chimie 6 (2003).
Butor, Mondrian et la fragmentation de l’espace: parcours génétique d’un roman-laboratoire
2018
Passage de Milan est sans aucune doute le chantier où Butor commence à travailler sur la forme du roman qui trouve son contrepoint théorique dans les essais publiés juste après sa parution. Parmi les épisodes qui se trouvent en relation métonymique avec le roman, c’est par la description du tableau de Martin De Vere, claire allusion au néoplasticisme de Mondrian, que Butor nous donne une représentation à échelle réduite de l’édifice et de ses habitants. Ce tableau inachevé où tous les éléments sont provisoires n’est que l’image du roman en gestation qui s’écrit au fur et à mesure que la narration avance. Les phases d’élaboration de cet épisode permettent d’éclaircir la technique de fragment…
Measurement of the lifetime of tau-lepton
1996
The tau lepton lifetime is measured with the L3 detector at LEP using the complete data taken at centre-of-mass energies around the Z pole resulting in tau_tau = 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs. The comparison of this result with the muon lifetime supports lepton universality of the weak charged current at the level of six per mille. Assuming lepton universality, the value of the strong coupling constant, alpha_s is found to be alpha_s(m_tau^2) = 0.319 +/- 0.015(exp.) +/- 0.014 (theory). The tau lepton lifetime is measured with the L3 detector at LEP using the complete data taken at centre-of-mass energies around the Z pole resulting in τ τ =293.2 ± 2.0 (stat) ± 1.5 (syst) fs . The c…
Charged particle multiplicity distributions in restricted rapidity intervals in Z0 hadronic decays.
1991
The multiplicity distributions of charged particles in restricted rapidity intervals in Z0 hadronic decays measured by the DELPHI detector are presented. The data reveal a shoulder structure, best visible for intervals of intermediate size, i.e. for rapidity limits around ±1.5. The whole set of distributions including the shoulder structure is reproduced by the Lund Parton Shower model. The structure is found to be due to important contributions from 3-and 4-jet events with a hard gluon jet. A different model, based on the concept of independently produced groups of particles, "clans", fluctuating both in number per event and particle content per clan, has also been used to analyse the pres…