Enhanced fragmentation

Droplet fragmentation enhanced when striking wind girder and liquids... 

An enhancement of the simple substructure approach is the Fragment Reduced to an Environment that is Limited (FREL) method introduced by Dubois et al. [7] With the FREL method several centers of the molecule are described, including their chemical environment. By taking the elements H, C, N, O, and halogens into account and combining all bond types (single, double, triple, aromatic), the authors found descriptors for 43 different FREL centers that can be used to characterize a molecule. 

Metastable ions yield valuable information on fragmentation in mass spectrometry, providing insight into molecular structure. In electron ionization, metastable ions appear naturally along with the much more abundant normal ions. Abundances of metastable ions can be enhanced by collisionally induced decomposition. 

CLAIMS UNITERM adds enhanced indexing to the chemical and chemically related patent records general terms to describe processes, properties, end products, etc specific compound terms (over 15,000) and chemical fragment terms to describe generic compounds. 

CLAIMS COMPREHENSIUE (subscriber access only) further enhances the UNITERM indexing from 1964 with roles for aH iadexed compounds and polymer class terms and with links and negation codes for the fragment terms describiag chemical compounds (94). 

A large number of radiometric techniques have been developed for Pu analysis on tracer, biochemical, and environmental samples (119,120). In general the a-particles of most Pu isotopes are detected by gas-proportional, surface-barrier, or scintillation detectors. When the level of Pu is lower than 10 g/g sample, radiometric techniques must be enhanced by preliminary extraction of the Pu to concentrate the Pu and separate it from other radioisotopes (121,122). Alternatively, fission—fragment track detection can detect Pu at a level of 10 g/g sample or better (123). Chemical concentration of Pu from urine, neutron irradiation in a research reactor, followed by fission track detection, can achieve a sensitivity for Pu of better than 1 mBq/L (4 X 10 g/g sample) (124). 

Another subclass of proteases attacks internal peptide bonds and Hberates large peptide fragments. Bromelain, a plant protease derived from the stem of the pineapple plant, can even produce detectable semm proteolysis after oral adrninistration (180). Oral therapy with bromelain significantly reduces bmising that stems from obstetrical manipulations (181). Bromelain—pancreatin combinations have been more effective in digestive insufficiency compared to either pancreatin or placebo (182,183). Bromelain may also enhance the activity of antibiotics, especially tetracycline, when adrninistered concurrently (184). 

Cesium ions are also sometimes used to enhance the secondary-ion yield of negative elemental ions and that of some polymer fragments [3.6]. They are produced by surface ionization with an extraction technique similar to that of FI sources. 

The size distribution of the clusters produced in the cluster source is quite smooth, containing no information about the clusters except their composition. To obtain information about, for example, the relative stability of clusters, it is often useful to heat the clusters. Hot clusters will evaporate atoms and molecules, preferably until a more stable cluster composition is reached that resists further evaporation. This causes an increase in abundance of the particularly stable species (i.e., enhancing the corresponding peak in the mass spectrum, then commonly termed fragmentation spectrum ). Using sufficiently high laser fluences (=50 /iJ/mm ), the clusters can be heated and ionized simultaneously with one laser pulse. 

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