Search results for "fragmentation"
showing 10 items of 798 documents
Fragmentations and reactions of some isotopically labelled dimethyl methyl phosphono and trimethyl phosphoro thiolates and thionates studied by elect…
2005
In this paper, studies on electrospray ionisation ion trap mass spectrometry of organophosphates are extended to a series of dimethyl methylphosphono and trimethyl phosphoro thionates and thiolates and some deuterated isotopomers. Of particular, interest is the comparison of the collision-induced fragmentation of ions from these compounds with those of the non-sulphur containing analogues reported previously. The thiono and thiolo isomeric structures of the sulphur containing ions analogous to I and II (see below) have very similar energies and undergo a ready interconversion. In the case of the phosphono compounds, the electronic structure calculations show that the methyl migration implic…
Cadmium induces an apoptotic response in sea urchin embryos.
2007
Cadmium is a heavy metal toxic for living organisms even at low concentrations. It does not have any biological role, and since it is a permanent metal ion, it is accumulated by many organisms. In the present paper we have studied the apoptotic effects of continuous exposure to subacute/sublethal cadmium concentrations on a model system: Paracentrotus lividus embryos. We demonstrated, by atomic absorption spectrometry, that the intracellular amount of metal increased during exposure time. We found, using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, that long treatments with cadmium triggered a severe DNA fragmentation. We demonstrated, by immunocytochemistry …
Determination of dissociation energies by use of energy-dependent decay pathway branching ratios
2001
Abstract We present a method for the determination of dissociation energies of polyatomic systems that undergo sequential fragmentation with energy-dependent decay pathway branching. It allows to experimentally determine the dissociation energy of any polyatomic system that shows such fragmentation behaviour without the need for a specific modelling of the system or of its fragmentation process, thus eliminating several systematic errors of traditional methods. The new method has been applied to the sequential fragmentation of Au+14 and Au+16. The resulting dissociation energies are highly accurate and in good agreement with model-free values based on rates of sequential decays.
Describing urban soils through a faceted system ensures more informed decision-making
2016
Urban areas are increasing worldwide at a dramatic rate and their soils definitely deserve more attention than they have received in the past. In urban environments, soils potentially provide the same ecosystem services as in rural and wild environments, although in some cases they are depleted of their basic functions, such as when they lose their productive and filtering capacities because of sealing, and become mere supports for infrastructures. In other cases, soils of urban areas acquire new functions that are unique to these environments. Current soil classifications fail to effectively account for the complexity of urban soils and the information that is required for their management…
Hydrogen Arrangements on Defective Quasi-Molecular BN Fragments
2019
Considering the ever-increasing interest in metal-free materials, some potential chemical applications of quasi-molecular boron nitride (BN) derivatives were tested. Specifically, the behavior of BN fragments was analyzed when given defects, producing local electron density changes, were introduced by using topological engineering approaches. The inserted structural faults were Schottky-like divacancy (BN-d) defects, assembled in the fragment frame by the subtraction of one pair of B and N atoms or Stone-Wales (SW) defects. This study is aimed at highlighting the role of these important classes of defects in BN materials hypothesizing their future use in H-2-based processes, related to eith…
Outgassing: Influence on speed of magma fragmentation
2013
[1] Predicting explosive eruptions remains an outstanding challenge. Knowledge of the controlling parameters and their relative importance is crucial to deepen our understanding of conduit flow dynamics and accurately model the processes involved. This experimental study sheds light on one important parameter—outgassing—and evaluates its influence on magma fragmentation behavior. We perform fragmentation experiments based on the shock tube theory at room temperature on natural pyroclastic material with a connected porosity ranging from 15% to 78%. For each sample series, we determine the initial pressure (P) required to initiate magma fragmentation (fragmentation threshold, Pth). Furthermor…
Effect of diluent composition on the dynamics of sperm DNA fragmentation and other sperm quality parameters in ram during incubation at 37°C
2015
Abstract This study was conducted to assess the effect of different semen extenders on the dynamics of sperm DNA fragmentation (SDF) and other quality sperm parameters in ram. To this end, second ejaculates from 6 adult males were collected using an artificial vagina and diluted in either INRA-96 ® , milk, MOPS, TRIS, TES, HEPES, citrate or phosphate-based extenders. Semen samples were incubated at 37 °C and the SDF, motility and membrane integrity were assessed after 0, 3, 6 and 24 h intervals. Significantly higher SDF indexes were obtained at 6 and 24 h of incubation in the milk-based than in all the buffer-based extenders. At 24 h, sperm diluted in INRA also reached a higher SDF than MOP…
Synthesis of fluorinated allylic amines: Reaction of 2-(trimethylsilyl)ethyl sulfones and sulfoxides with fluorinated imines
2007
A new synthesis of fluorinated allylamines through the reaction of 2-(trimethylsilyl)ethyl sulfones and sulfoxides (as vinyl anion equivalents) with imines and imino esters has been described. The process includes a TBAF-mediated fragmentation of 2-(trimethylsilyl)ethyl sulfones to afford the desired allylic amines. When the reaction is performed with the corresponding sulfoxides, the fragmentation takes place under the addition conditions, affording the final products in a single step. (C) 2007 Elsevier B.V. All rights reserved.
Liquid chromatography‐Orbitrap Tribrid high‐resolution mass spectrometry using data dependent‐tandem mass spectrometry with triple stage fragmentatio…
2021
A new, fast, and automatic approach has been applied for the tentative identification of unknown substances released by food contact epoxy resin after performing a migration test with food simulant. This approach combines intelligent data acquisition with AcquireX linked to liquid chromatography-Orbitrap Tribrid high-resolution mass spectrometry using data dependent-tandem mass spectrometry with triple stage fragmentation coupled to Compound Discoverer™ software for automated data processing and compound identification. The identification of the observed features was performed using a set of identification criteria, including exact mass, isotope pattern, tandem mass spectrometry spectra mat…
Linking woodland key habitat inventory and forest inventory data to prioritize districts needing conservation efforts
2012
Woodland key habitat (WKH) inventories have been conducted in northern European countries, with the aim to create networks of minimally disturbed forest stands for protection. The goal of national forest inventory is to provide information relevant to forest management, such as on forest types, trees species composition, age structure and wood volume. The aim of this study was to link these two inventory databases to identify districts of Latvia most deficient in connectivity and habitat quality, in order to prioritize districts needing conservation effort. As an example, the area of deciduous forest with nemoral tree species (oak, ash, lime, maple and elm) and aspen was chosen. These fores…