We use a global (volume averaged) model to study the presence of negative ions and metastable species in low-pressure high-density oxygen discharges. We find the negative oxygen ion O − to be the dominant negative ion in the discharge, the density of the negative ion O − 2 to be small and the density of the negative ion O − 3 to be negligible in the pressure range of interest, 1-100 mTorr. Dissociative attachment of the oxygen molecule in the ground-state O 2 (3 − g) and the metastable oxygen molecule O 2 (a 1 g) are the dominating channels for the creation of the negative oxygen ion O −. At low pressure (<5 mTorr) recombination involving O − and O + ions is the main loss channel for O − ions. At higher pressure, the detachment on O(3 P) becomes the main loss channel for the O − ion. The creation of O − 2 is mainly through dissociative attachment of ozone O 3. Ozone is almost entirely created through detachment by the collision of O − with the metastable oxygen molecule O 2 (a 1 g). The creation of O − 2 is thus greatly influenced by this detachment process and neglecting the detachment has a significant influence on the density of O − 2 ions. At low pressure (<10 mTorr) the O − 2 ion is mainly lost through recombination while at higher pressure the charge transfer to form O 2 is the dominating loss process.

Langmuir probes and a quadrupole mass spectrometer were used to determine the plasma parameters of an oxygen plasma in a planar inductive discharge. The electron density, effective electron temperature, the dc plasma potential and the electron energy probability function (EEPF) in the discharge centre plane were investigated as functions of power, gas pressure and radial position. The ion energy distribution and relative density of positive ions at the radial sheath edge were investigated as functions of power and pressure. A volume-averaged global model of the electronegative oxygen discharge is developed. The model uses a power balance equation to account for energy deposited into the plasma and lost via collisions and particle flux. The particle densities are modelled via rate equations estimated from collision cross sections assuming Maxwellian electron energy distribution functions. The volume-averaged model is shown to predict the experimental trends over a range of process conditions.

Cytoplasmic Linker Associated Proteins (CLASPs) comprise a class of microtubule (MT) plus end-binding proteins (+TIPs) that contribute to the dynamics and organization of MTs during many cellular processes, among them mitosis. Human CLASP proteins contain multiple MT-binding domains, including Tumor Over-expressed Gene (TOG) domains, and a Ser-x-Ile-Pro (SxIP) motif known to target some +TIPs though interaction with End-Binding Protein 1 (EB1). However, how individual domains contribute to CLASP function is poorly understood. We generated full-length recombinant human CLASP1 and a series of truncation mutants and found that two N-terminal TOG domains make the strongest contribution to MT polymerization and bundling, but also identified a third TOG domain that also contributes to CLASP activity. Plus end tracking by CLASP requires the SxIP motif and interaction with EB1. The C-terminal coiled-coil domain mediates dimerization and association with many other factors, including the kinetochore motor CENP-E, and the chromokinesin Xkid. Only the full-length protein was able to rescue spindle assembly in Xenopus egg extracts depleted of endogenous CLASP. Deletion of the C-terminal domain caused aberrant MT polymerization and dramatic spindle phenotypes, even with small amounts of added protein, indicating that proper localization of CLASP activity is essential to control MT polymerization during mitosis.

Langmuir probes and a quadrupole mass spectrometer were used to determine the plasma parameters of an oxygen plasma in a planar inductive discharge. The electron density, effective electron temperature, the dc plasma potential and the electron energy probability function (EEPF) in the discharge centre plane were investigated as functions of power, gas pressure and radial position. The ion energy distribution and relative density of positive ions at the radial sheath edge were investigated as functions of power and pressure. A volume-averaged global model of the electronegative oxygen discharge is developed. The model uses a power balance equation to account for energy deposited into the plasma and lost via collisions and particle flux. The particle densities are modelled via rate equations estimated from collision cross sections assuming Maxwellian electron energy distribution functions. The volume-averaged model is shown to predict the experimental trends over a range of process conditions.