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Sensitizer ion

Energy Transfer. In addition to either emitting a photon or decaying nonradiatively to the ground state, an excited sensitizer ion may also transfer energy to another center either radiatively or nonradiatively, as illustrated in Figure 4. [Pg.286]

Nonradiative energy transfer is induced by an interaction between the state of the system, in which the sensitizer is in the excited state and the activator in the ground state, and the state in which the activator is in the excited and the sensitizer in the ground state. In the presence of radiative decay, nonradiative decay, and energy transfer the emission of radiation from a single sensitizer ion decays exponentially with time, /. [Pg.286]

The role of cerium in these lighting phosphors is not as the emitting atom but rather as the sensitizer. The initial step in the lighting process is the efficient absorption of the 254 nm emission Ce ", with broad absorption bands in the uv, is very suitable. This absorbed energy is then transferred to the sublattice within the crystalline phosphor eventually the activator ion is fed and emission results. Cerium, as a sensitizer ion, is compatible in crystal lattices with other lanthanide ions, such as Eu and Tb, the usual activator atoms. [Pg.371]

The X-ray determination of REE in geological samples is normally complicated by the relatively low concentrations of the REE, their complex X-ray spectra, the high concentration of matrix elements and the lack of reference standards with certified values for REE. A rapid and sensitive ion exchange and X-ray fluorescence procedure for the determination of trace quantities of rare earths is described. The REE in two U.S.G.S. standards, two inhouse synthetic mixtures and three new Japanese standards have been determined and corrections for inter-rare earth element interferences are made. [Pg.205]

Resolution Quadrupole instruments are not capable of achieving the high resolution that is common with double-focusing magnetic-sector instruments. In GC/MS analyses, a compromise is struck between sensitivity (ion transmission) and mass resolution. In the quadrupole instrument, the resolution is set to the lowest possible value commensurate with resolving peaks differing by 1 Dalton (unit resolution). [Pg.204]

Once again these measurements are not limited to concrete materials, most MR sensitive ions can be measured in porous media using these techniques. [Pg.300]

Analysis by the Detection of Scattered Ions. Ions generally penetrate the specimen much less deeply than electrons of equivalent energy, so they are more surface-sensitive. Ion-based surface analytical techniques are popular because of their sensitivity and their ability, in some cases, to reveal the depth composition profile. [Pg.205]

Why should we study the structural properties of the channel macromolecules themselves Although biophysical techniques define the functional properties of voltage-sensitive ion channels clearly, it is important to relate those functional properties to the structure of the channel proteins. We focus first on the discovery of the ion channel proteins, in which three different experimental approaches were used... [Pg.101]

The SR may contribute to excitation-contraction (EC) coupling in two ways firstly, by the release of Ca2+ for contraction as described above, but secondly by modulating membrane excitability. As will be described elsewhere in this book, the SR is an important mediator of surface membrane ion channel activity, and hence, excitability. Spontaneous Ca2+ release from the SR can activate Ca2+-sensitive ion channels. Both K+ (Kca) and Cl- (Clsmooth muscle cell membrane can be activated by SR Ca2+. If Kca channels are activated there will be a hyperpolarization, as K+ ions leave the cell and spontaneous transient outward currents (STOCs) can be recorded (Carl et al 1996, Nelson Quayle... [Pg.212]

The cysteine motifs in this polydnavirus gene family are structurally analogous to the cysteine motifs of the >-conotoxins. The a>-conotoxins are high-affinity ligands with different receptor specificity for voltage-sensitive ion channels (64, 65). The mature w-conotoxins have three... [Pg.83]

Figure 9.7 Sensitivity (ion counts per second/concentration in ppb) as a function of mass number in ICP-MS analysis. A semiquantitative analysis for elements not available as standards can be carried out by interpolating from such a graph. Figure 9.7 Sensitivity (ion counts per second/concentration in ppb) as a function of mass number in ICP-MS analysis. A semiquantitative analysis for elements not available as standards can be carried out by interpolating from such a graph.
Once an action potential is initiated at the hillock, it continues in a self-propagating fashion to the end of the axon. Voltage-sensitive ion channels are opened by the depolarization, allowing further influx of Na+ and a spread of the action potential. Thus, the action potential is a self-regenerating spread of membrane depolarization. [Pg.46]

Battistig, G., et al., High-Sensitivity Ion Beam Anal) tical Method for Studying Ion-Implanted SiC, Mater. Sci. Forum, Vol. 433-436, 2003, pp. 625-628. [Pg.150]

Nurnberger J Jr, Jimerson DC, Allen JR, et al Red cell ouabain-sensitive Na -K -adenosine triphosphatase a state marker in affective disorder inversely related to plasma cortisol. Biol Psychiatry 17 981-992, 1982 Nutt D, Montgomery SA Moclobemide in the treatment of social phobia. Int Clin Psychopharmacol 11 (suppl 3 77-82, 1996 Nutt DJ, Glue P, Lawson GW, et al Elumazenil provocation of panic attacks evidence for altered benzodiazepine receptor sensitivity ion panic disorder. Arch Gen Psychiatry 47 917-925, 1990... [Pg.711]

Since many toxins act on ion channels, they provide a wealth of chemical tools for studying the function of these channels. In fact, much of our current understanding of the properties of ion channels comes from studies utilizing only a small percentage of the highly potent and selective toxins that are now available. The toxins typically target voltage-sensitive ion channels, but a number of very useful toxins block ionotropic neurotransmitter receptors. Table 21-1 lists some of the toxins most commonly used in research, their mode of action, and their source. [Pg.449]

GC-MS SIM analysis for prenatal diagnosis requires a different calibration standard from that used for urine from children and adults. Table 5.3.12 shows the steroids present in our external standard and the monitored ions. For serum analysis we employ the highly sensitive ion-trap MS/MS technique described at the beginning of this chapter. Many steroid ratios have been calculated that can be used to distinguish causes of low-estriol, a few that we consider useful are given below, values considered positive for particular disorders are in parenthesis. [Pg.597]

A simple, rapid, and sensitive ion-pair liquid chromatographic method was described by Fletouris et al. (338) for the determination in milk of the sulfoxide, sulfone, and 2-aminosulfone metabolites that comprise the marker residue of albendazole. According to this method, a 1 ml aliquot of milk sample is alkalinized with sodium hydroxide solution, extracted with 7 ml ethyl acetate, and the extract is cleaned up by partition with 1 ml water. Following centrifugation, the top... [Pg.1026]

An ion-selective electrode responds to the activity of free analyte, not complexed analyte. For example, when the Pb2+ in tap water at pH 8 was measured with a sensitive ion-selective electrode, the result was [Pb2+] = 2 X 10 10 M.25 When lead in the same tap water was measured by inductively coupled plasma-mass spectrometry (Section 21-6), the result was more than 10 times greater 3 X 10-9M. The discrepancy arose because the inductively coupled plasma measures all lead and the ion-selective electrode measures free Pb2+. In tap water at pH 8, much of the lead is complexed by CO -, OH, and other anions. When the pH of tap water was adjusted to 4, Pb2+ dissociated from its complexes and the concentration indicated by the ion-selective electrode was 3 X 10-9M—equal to that measured by inductively coupled plasma. [Pg.313]

In suppressed-ion chromatography, a separator column separates ions of interest, and a suppressor membrane converts eluent into a nonionic form so that analytes can be detected by their conductivity. Alternatively, nonsuppressed ion chromatography uses an ion-exchange column and low-concentration eluent. If the eluent absorbs light, indirect spectrophotometric detection is convenient and sensitive. Ion-pair chromatography utilizes an ionic surfactant in the eluent to make a reversed-phase column function as an ion-exchange column. [Pg.623]


See other pages where Sensitizer ion is mentioned: [Pg.203]    [Pg.286]    [Pg.287]    [Pg.280]    [Pg.401]    [Pg.309]    [Pg.321]    [Pg.83]    [Pg.560]    [Pg.240]    [Pg.27]    [Pg.327]    [Pg.353]    [Pg.123]    [Pg.221]    [Pg.9]    [Pg.163]    [Pg.20]    [Pg.69]    [Pg.158]    [Pg.162]    [Pg.131]    [Pg.25]    [Pg.92]    [Pg.108]    [Pg.113]    [Pg.226]    [Pg.292]    [Pg.1769]    [Pg.490]    [Pg.496]   
See also in sourсe #XX -- [ Pg.286 ]




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ION SENSITIVITY

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