Search results for " Dissociation"

Electric field enhanced water dissociation at the bipolar membrane junction from ac impedance spectra measurements

1998

Abstract Preliminary experimental results of the ac impedance spectra of a bipolar ion-exchange membrane are reported and interpreted on the basis of a previous theoretical model based on the Nernst–Planck/Poisson equations. It is shown that the experiments can provide valuable electrochemical information about the bipolar junction structure and the electric-field enhanced water dissociation phenomenon that occurs at this junction, although the high number of unknown parameters involved makes it difficult to obtain accurate values for the parameters characteristic of this phenomenon.

Cell Dissociation and Reaggregation

1973

Can Tumor Oxygenation be Improved by Reducing Cellular Oxygen Consumption?

1999

Tumor hypoxia, which can be found in many experimental and human tumors is an important factor influencing the therapeutic efficacy of standard radiotherapy, O2-dependent chemotherapy and photodynamic therapy (Hall, 1994) and might be responsible for the development of aggressive tumor cell subpopulations (Graeber et al., 1996). Since this oxygen deficiency results from a disparity between O2 supply to the tumor tissue and the oxygen demand of the cells, several attempts have been undertaken to improve tumor oxygenation primarily by increasing the arterial oxygen supply. The O2 supply to the tumor cells can be improved by (a) increasing the arterial O2 content (by breathing hyperoxic gases …

The fragmentation of 5- and 3-substituted thiophene-2-carboxamides under electron impact

1980

The 70 eV electron impact mass spectra of twelve 5- and 3-substituted thiophene-2-carboxamides are discussed with the aid of exact mass measurements and labelling experiments. All mass spectra exhibit pronounced molecular ions. Some isomeric 5- and 3-substituted title compounds can be differentiated by mass spectrometry. The fragmentation is influenced by a strong ‘ortho-effect’ which activates the NH3 elimination. In the other cases the most important fragmentation is NH2˙ loss, followed by CO elimination.

Multicollision-induced dissociation of multiply charged gold clusters, Aun2+, n = 7–35, and Aun3+, n = 19–35

2000

Abstract Multicollision-induced dissociation (MCID) has been applied to gold clusters, Au n 2+ (n = 7–35) and Au n 3+ (n = 19–35) stored in a Penning trap. By application of ion cyclotron resonance excitation and pulses of argon collision gas, fragmentation yields have been measured as a function of the clusters’ kinetic energy. The corresponding dissociation energies have been determined by use of the impulsive collision theory and the quantum Rice–Ramsperger–Kassel (RRK) model for the energy transfer to internal cluster modes and for delayed dissociation, respectively. As compared to earlier measurements of singly charged gold clusters the variation of the stability as a function of clust…

Studies in organic mass spectrometry. Part 17—Formation of phenol radical ions by rearrangement of the molecular ions of someN-arylthiophenecarboxami…

1995

It has been shown by exact mass measurements and collision-induced dissociation mass-analysed ion kinetic energy spectra that the structure of the m/z 124 ion observed in the mass spectra of N-(4-methoxyphenyl)thiophene-2-carboxamide, N-(4-methoxyphenyl)thiophene-3-carboxamide, N-(4-methoxyphenyl)-5-nitrothiophene-3-carboxamide and N-(4-methoxyphenyl)benzamide is identical with that of the molecular ion of 4-methoxyphenol. This ion becomes abundant in metastable energy window reactions. A probable mechanism for its formation is discussed.

Unveiling anion-induced folding in tripodal imidazolium receptors by ion-mobility mass spectrometry.

2021

The anion-induced folding of tripodal imidazolium receptors has been investigated by NMR spectroscopy, electrospray ionization ion mobility mass spectrometry and DFT calculations. Such folding can be switched by anion release upon collision induced dissociation.

Solution and solid state studies with the bis-oxalato building block [Cr(pyim)(C2O4)2]− [pyim = 2-(2′-pyridyl)imidazole]

2013

The preparation, X-ray structure, and variable temperature magnetic study of the new compound {Ba(H2O)3/2[Cr(pyim)(C2O4)2]2}n·9/2nH2O (1) [pyim = 2-(2′-pyridyl)imidazole and C2O42− = dianion of oxalic acid], together with the potentiometric and spectrophotometric studies of the protonation/deprotonation equilibria of the pyim ligand and the ternary complex [Cr(pyim)(C2O4)2]−, are reported herein. The crystal structure of 1 consists of neutral chains, with diamond-shaped units sharing barium(II), with the two other corners occupied by chromium(III). The two metal centers are connected through bis(bidentate) oxalate. Very weak antiferromagnetic interactions between the chromium(III) ions occu…

Selected dissociation‐ and correlation‐consistent configuration interaction by a perturbative criterion

1990

We propose a perturbative criterion to select the most important dissociation‐ or correlation‐consistent type of contributions to perform generalized valence bond‐configuration interaction (GVB‐CI) calculations, dissociation‐consistent configuration interaction (DCCI) or correlation‐consistent configuration interaction (CCCI) approach, respectively. The procedure presented is computationally less demanding than the CCCI proposed by Goddard and co‐workers. To ensure the distance consistency of the MOs used, the nonvalence virtual orbitals are obtained by a projection technique. The results obtained for a few test calculations show the ability of the suggested approach to get close results to…

Measurement of the inelastic proton-proton cross-section at √s = 7 TeV with the ATLAS detector

2011

The dependence of the rate of proton–proton interactions on the centre-of-mass collision energy, √s, is of fundamental importance for both hadron collider physics and particle astrophysics. The dependence cannot yet be calculated from first principles; therefore, experimental measurements are needed. Here we present the first measurement of the inelastic proton–proton interaction cross-section at a centre-of-mass energy, √s, of 7 TeV using the ATLAS detector at the Large Hadron Collider. Events are selected by requiring hits on scintillation counters mounted in the forward region of the detector. An inelastic cross-section of 60.3±2.1 mb is measured for ξ>5×10[superscript −6], where ξ is ca…