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We perform one-dimensional (1D) particle-in-cell (PIC) simulations to study the α and γ modes in an intermediate pressure 1.6 Torr, 2.5 cm gap capacitive nitrogen discharge driven at 13.56 MHz with current density amplitudes J0 = 7 to 150 A m−2. In the α-mode, ion-induced secondary electron emission has minimal effects on the discharge equilibrium, while in the γ-mode, it is essential for sustaining the discharge. As in a previous study of a comparable argon discharge, [Kawamura et al 2020, J. Vac. Sci. Technol. A 38 , 023003], the nitrogen discharge in the α-mode can be described by a 'passive bulk' model in which the ionization is negligible in the central bulk region and is due solely to electron sheath heating. The nitrogen discharge undergoes an α to γ transition in the applied J0 range, characterized by an increase in density and a decrease in electron temperature, sheath widths and sheath voltages. For the γ-mode, we calculate the scalings of the maximum sheath width sm and the rf sheath voltage amplitude V1 with J0. We compare the PIC results in the α-mode to the passive bulk model (modified for nitrogen), and, in the γ-mode with the expected J0-V1 and sm-V1 curves. We find good agreement with the simulations in both the α and γ regimes, and the α to γ transition is well predicted by the models. [ABSTRACT FROM AUTHOR]

A hybrid global-analytical model of an atmospheric pressure radio-frequency driven capacitive discharge is applied to determine the plasma conditions for TiO2 film deposition. The feed gas is mainly argon with a small fraction of O2 and a smaller fraction of TiCl4. Variations of the discharge parameters and species densities with O2 concentration, discharge power, and flow rate are determined. A simplified chemistry model is developed and compared with the simulation results, showing good agreement. For a base case with Ar/O2/TiCl4 flow rates of 203/30/0.17 sccm, the results indicate that a minimum O2 fraction of 7.3×10-4 is required for pure (un-chlorinated) TiO2 film deposition that the active precursor species is TiO2Cl3, with subsequent abstraction of Cl atoms by dissociative electron attachment and that the deposition rates are around 1 nm/s. [ABSTRACT FROM AUTHOR]

A hybrid global-analytical model of an atmospheric pressure radio-frequency driven capacitive discharge is applied to determine the plasma conditions for TiO2 film deposition. The feed gas is mainly argon with a small fraction of O2 and a smaller fraction of TiCl4. Variations of the discharge parameters and species densities with O2 concentration, discharge power, and flow rate are determined. A simplified chemistry model is developed and compared with the simulation results, showing good agreement. For a base case with Ar/O2/TiCl4 flow rates of 203/30/0.17 sccm, the results indicate that a minimum O2 fraction of 7.3 x 10-4 is required for pure (un-chlorinated) TiO2 film deposition that the active precursor species is TiO2CI3, with subsequent abstraction of Cl atoms by dissociative electron attachment and that the deposition rates are around 1 nm/s. [ABSTRACT FROM AUTHOR]

Plasma transport in magnetized discharges is a long-standing problem because it strongly depends on instabilities whose properties and influence on the plasma transport are difficult to predict. A magnetized plasma column is investigated with 2D particle-in-cell (PIC) simulations in the plane transverse to the magnetic field, at gas pressures between 3 and 12 mTorr and magnetic field intensities between 0 and 40 mT. At high magnetic field, instabilities develop and rotate in the diamagnetic drift direction. It is shown theoretically and by simulation that the magnetic field confinement is destroyed by the instability. Predictive formulas of the main parameters of the instability-enhanced plasma transport such as the edge-to-center plasma density ratio (or h factor), and the effective collision frequency are provided and successfully compared with the PIC simulations. [ABSTRACT FROM AUTHOR]

Particle transport in a uniformly magnetized electronegative plasma is studied in two-dimensional (2D) geometry with insulating (dielectric) boundaries. A 2D particle-in-cell (PIC) code is employed, with the results compared to analytic one-dimensional models that approximate the end losses as volume losses. A modified oxygen reaction set is used to scale to the low densities used in PIC codes and also to approximately model other gases. The principal study is the limiting of the transverse electron flow due to strong electron magnetization. The plasma in the PIC calculation is maintained by axial currents that vary across the transverse dimension. For a cosine current profile nearly uniform electron temperature is obtained, which at the B-fields studied (600-1200 G) give a small but significant fraction (0.25 or less) of electron to negative ion transverse loss. For a more transverse-confined current, and approximating the higher mass and attachment reaction rate of iodine, the fraction of electron to negative ion transverse loss can be made very small. The models which have been constructed reasonably approximate the PIC results and indicate that the cross-field transport is nearly classical. [ABSTRACT FROM AUTHOR]

Expanding electronegative (EN) plasmas have been previously observed, experimentally, to generate wave activity. Using a particle-in-cell (PIC) code we have investigated these waves in expanding EN plasmas containing a double layer (DL) between an upstream source region and an expanded downstream region. Oxygen reaction rates were used but modified to correspond more closely to experimental conditions. Under a subset of pressures, for which a DL existed, waves were observed traveling upstream in the expanded region, and growing in amplitude in the direction of travel. Both slow and fast waves were observed. The fast wave existed only over part of the slow wave pressure range. The PIC results were compared to both fluid and kinetic theory, both of which assumed axial uniformity. The results of a somewhat simplified fluid theory, ignoring fast wave coupling and collisions with the background gas, gave a remarkable result: if the theory predicted a slow wave instability for any axial parameters in the downstream region, the instability was observed in the simulation. Conversely, if no instability was predicted at any axial position, no instability was observed. More accurate kinetic calculations, including electron and ion Landau damping, and also collisional damping against the background gas, gave wavelengths and growth rates that were consistent with the PIC simulations, and with the fluid results. The kinetic theory also indicated that the fast waves were always stable but became weakly damped for conditions of unstable slow waves. We postulate that nonlinear and nonuniformity effects excite the fast waves. [ABSTRACT FROM AUTHOR]

We have observed relaxation oscillations in an argon capacitive discharge connected to a peripheral grounded chamber through a slot with dielectric spacers. The oscillations, observed from time-varying optical emission of the main discharge chamber, show, for example, a high frequency (∼40 kHz) relaxation oscillation at 100 mTorr, with absorbed power near that for peripheral breakdown, and a low frequency (∼3 Hz) oscillation, at higher absorbed power. The high frequency oscillation is found to ignite a plasma in the slot, but usually not in the periphery. We interpret the high frequency oscillations using an electromagnetic model of the slot impedance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations and indicate a variety of behaviors dependent on the matching conditions. [ABSTRACT FROM AUTHOR]

Relaxation oscillations in charged particle densities are seen in low-pressure inductive discharges, if attaching gases such as SF[SUB6] and Ar/SF[SUB6] mixtures are used, such that the plasma contains negative ions. These oscillations occur in the neighborhood of the transition between lower power capacitive operation and higher power inductive operation. An instability, which occurs around this transition, can be described by a global model, that consists of time-dependent equations for the electrons, ions, and electron temperature. The model qualitatively agrees with experimental observations, but leaves significant quantitative differences to be explained. To understand the reasons for the model's inability to make quantitative predictions, the local conditions for instability are determined for a model somewhat simplified from the one that approximates the experiment, but retains most of the important physics. The simplified model allows explicit determination for the local transition to instability and identifies two parameters that govern the transition. The local criteria are related to the global criterion that all fixed points are unstable. The importance for the instability of the physical parameters of the ion wall loss and of the ratio of capacitive to inductive power transfer has led to a reexamination of the size of these factors, and gives better quantitative agreement of the model to experiments. [ABSTRACT FROM AUTHOR]

We have observed instabilities in low-pressure planar inductive discharges in CF[sub 4] gas, in many ways similar to those seen in other attaching gases. The plasma emitted light exhibits oscillations, with the intensity modulated from 15% to 100%. The instability regions were investigated as a function of pressure, CF[sub 4] flow rate and radio-frequency power. Two matching configurations were used. When the terminus of the planar spiral antenna was directly connected to ground, we observed low-frequency oscillations between 0.5 Hz and 15 Hz. When a 400 pF capacitance was added between the terminus and ground (i.e., the capacitive coupling was reduced), the oscillation frequencies ranged from 100 Hz to 1.5 kHz. Oscillations in the concentrations of unsaturated radicals (CF and CF[sub 2]) were measured during the instability, using time-resolved laser induced fluorescence. The radical dynamics were significant at frequencies of about 1 kHz. Mechanisms are proposed for these variations, including gas temperature changes and chemical reactions. A global model originally developed for SF[sub 6] chemistry was adapted to this system. The appropriate rate coefficients for CF[sub 4] were incorporated and an expression for the positive ion flux in the low electronegativity case was developed. Gas heating effects were also included. [ABSTRACT FROM AUTHOR]

We report on the effect of Ar addition to an O[sub 2] plasma on photoresist etching in an inductively coupled, traveling wave driven, large area plasma source (LAPS). We also develop a simplified spatially varying O[sub 2]/Ar mixture discharge model corresponding to the LAPS in a two-dimensional geometry in order to account for the effect of Ar addition. A photoresist etch kinetics model and spatially varying O[sub 2]/Ar mixture discharge model are used to explain the experimental data. We find that the addition of 50% Ar increases the plasma density and etch rate approximately by a factor of 2. From the simulation we find that argon metastables (Ar*) play an important role in the mixture plasma. The simulation predicts an enhancement in O-atom density due to Ar addition, even in the presence of dilution of the feed gas. The experimental data and predicted etch rates from the simulation are generally in good agreement, indicating that the increase in the etch rate with Ar addition is due to both the increase in the plasma density and the enhancement in O-atom density attributable to the dissociation of O[sub 2] by Ar*. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on the effect of ion energy on photoresist etching in an inductively coupled large area plasma source driven by a 13.56 MHz traveling wave with oxygen gas. To control the ion energy at the substrate surface, the electrode on which the substrate is placed is independently driven by a capacitively coupled 1 MHz power source. The etch rate increases with increasing ion energy for gas pressure ranging from 1 to 100 mTorr. Ion-induced desorption rate constants (etch yields) are shown to be proportional to the square root of the ion energy. An increase in the ion energy leads to etch-uniformity improvement over the processing area of 40 cmx50 cm, particularly at a low gas pressure of 5 mTorr. A modified photoresist etch kinetics model combined with a spatially-varying oxygen discharge model is used to explain these experimental results. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We report on experimental and modeling results for photoresist etching with oxygen gas in an inductively coupled large area plasma source (LAPS). The source is driven by a 13.56 MHz traveling wave launched along a serpentine antenna embedded in the plasma and has a processing area as large as 40 cmx50 cm. We describe a new series-parallel antenna coil configuration, and we present experimental observations for oxygen plasma density profiles, photoresist etch rates, and etch profiles. We introduce a simplified spatially varying oxygen discharge model corresponding to a two-dimensional LAPS geometry in order to account for the generation and loss of both etchant atoms (O atoms) and bombarding ions. The model and experimental results on plasma density are compared. A simplified photoresist etch kinetics model combined with the spatially varying oxygen discharge model is then described. The ion flux and O-atom density predicted by the model are compared with the etch rate data. In order to gain insight into the underlying physical mechanism, we also compare the data with the scaling behavior of the etch rates predicted by a volume-averaged (global) oxygen discharge model. The models and experimental results are generally in good agreement. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Presents information on a study which re-examined the operation of a metal-vapor buffer-gas hollow cathode discharge using modeling techniques that have been developed for electromagnetic discharges. Basic equations; Numerical calculation of neon-copper discharge; Density profiles of the neutral and ion components; Conclusions.

Previously [E. Kawamura et al., Plasma Sources Sci. Technol. 25, 054009 (2016) and E. Kawamura et al., J. Phys. D: Appl. Phys. 50, 145204 (2017)], one dimensional (1D) particle-in-cell (PIC) simulations of 1 to 4 mm gap, He/2%H2O atmospheric pressure plasma discharges showed an ionization instability resulting in bulk striations. Assuming that the ionization rate coefficient Kiz is related to the root mean square electric field E by Kiz ∝ Eq, a striation theory showed that q < 0 is a necessary condition for the instability. A local calculation yielded q > 0, implying that nonlocal electron kinetics are required for the instability. Wider gaps can fit in a wider range of wavelengths, resulting in multi-mode striations. Previously, we assumed a single mean q value for each discharge, and did not calculate q for each mode separately. Here, we develop a wavelength resolved global striation model and apply it to 1D PIC simulations of 4 mm gap discharges with input currents Jrf = 0.04 to 0.30 A/cm2. We first examine a base case at 0.23 A/cm2 and observe a mixture of unstable modes within a window of wavelengths λ. At shorter λ, the modes are suppressed by diffusion. At longer λ, we observe a transition to locality in which q becomes less negative with increasing λ, approaching its local positive value and stabilizing the modes. The window of unstable modes shifts to shorter λ with increasing Jrf, causing the modes to be suppressed by diffusion at higher Jrf. At lower Jrf, the decrease in bulk plasma density with decreasing Jrf suppresses the striations. [ABSTRACT FROM AUTHOR]

It is shown that the transport in low temperature, collisional, bound plasma is enhanced by instabilities at a high magnetic field. While the magnetic field confines the electrons in a stable plasma, the instability completely destroys the confinement such that the transport becomes independent of the magnetic field in the highly magnetized limit. An analytical expression of the instability-enhanced collision frequency is proposed, based on a magnetic field independent edge-to-center density ratio. [ABSTRACT FROM AUTHOR]

Discusses a study which used spherical and cylindrical many-particle models to stimulate radio frequency discharges. Computational formula for Poisson's equation; Theoretical models for radio frequency discharges; Difference between plasma potential and driven electrode potential.

Focuses on a general one-dimensional model to study the plasma-immersion ion implantation process in different coordinate systems. Analytic expressions for normal ion velocity distribution and other parameters; Effect of a charge-exchange collision on an ion; Equation concerning the average ion velocity at the target.

Presents a study that applied an electron-beam probe to make time- and space-resolved measurements of the electric field in a parallel plate radio frequency discharge. Positions of the electron gun, deflection plates, discharge chamber and scintillating plastic; Electric field as a function of time at various positions in a plasma; Capacitive probe measurement of oscillations in the plasma potential.

Presents a study that examined the multilayer structures etched in an electron cyclotron resonance oxygen plasma with a mirror magnetic field. Information on optical emission spectroscopy; Analysis of the angle of wafer relative to plasma; Assessment of temperature effects.

Presents a study that developed an analytical model to determine the time-varying implantation current, the total dose and the energy distribution of the implanted ions. Drawbacks of conventional implantation; Demonstration of metallurgical and semiconductor implantation processes; Current and energy distribution of implanted ions.

Investigates the plasma density in a complex geometry relative flow discharge chamber using a noninvasive microwave diagnostic. Overview of the spatial density profile; Electric field profiles of the modes; Measurement of the radial variations of the electric field.

Presents a study which developed a simple spherical shell model to determine the sheath scaling law and the density profile in the thermal plasma in an asymmetric discharge. Description of the spherical shell model; Details on the thermal electron ionization; Role of sheath properties in determining the self-bias voltage at the powered electrode; Method used in the scaling of the electrode bias voltages with discharge asymmetry.

Observes the mechanism for electron heating in radio frequency discharges. Information on the Hamiltonian dynamics; Details on the Fokker-Planck calculation; Description of the self-consistent model; Conclusions.

Presents a study that developed a simple analytic model valid for all collisionality regimes to describe the power deposition in a cylindrical inductively coupled plasma source with a planar coil. Characteristics of the heating process; Cause of the low-pressure collisionless heating; Determination of the plasma density profile.

Develops a macroscopic analytic model for a three-component electronegative plasma. Energy and particle balance in electronegative plasmas; Equation of Bohm flux condition in the electropositive region; Comparison of analytic theory with simulation of a parallel-plate capacitive radio frequency discharge in oxygen.

Presents a study which numerically calculated reflection and absorption of right-hand polarized waves and reflection of left-hand polarized waves propagating into a cyclotron resonance zone. Effective collisionality near resonance; Equilibrium power balance; Conclusions.

Presents a study wherein in plasma immersion ion implantation, a target is immersed in a plasma and a series of negative, high-voltage pulses are applied to implant ions into the target. Comparison of results with numerical simulations; Details of the scaling rules for the implanted current and energy distribution; Description of the applied voltage wave form.

Reports on the effects of direct current bias on the kinetics and electrical properties of silicon dioxide grown in an electron cyclotron resonance plasma. Explanation for the oxidation kinetics under anodic conditions; Relationship between oxide thickness, overall potential drop and ion current in the space-charge limited transport region; Role of silicon oxidation in metal-oxide-semiconductor device fabrication.

The ion energy distribution (IED) at a surface is an important parameter for processing in multiple radio frequency driven capacitive discharges. An analytical model is developed for the IED in a low pressure discharge based on a linear transfer function that relates the time-varying sheath voltage to the time-varying ion energy response at the surface. This model is in good agreement with particle-in-cell simulations over a wide range of single, dual, and triple frequency driven capacitive discharge excitations. [ABSTRACT FROM AUTHOR]

Two radially propagating surface wave modes, "symmetric," in which the upper and lower axial sheath fields (Ez) are aligned, and "anti-symmetric," in which they are opposed, can exist in capacitively coupled plasma (CCP) discharges. For a symmetric (equal electrode areas) CCP driven symmetrically, we expected to observe only the symmetric mode. Instead, we find that when the applied rf frequency f is above or near an anti-symmetric spatial resonance, both modes can exist in combination and lead to unexpected non-symmetric equilibria. We use a fast 2D axisymmetric fluid-analytical code to study a symmetric CCP reactor at low pressure (7.5 mTorr argon) and low density (∼3 × 1015 m−3) in the frequency range of f = 55 to 100 MHz which encompasses the first anti-symmetric spatial resonance frequency fa but is far below the first symmetric spatial resonance fs. For lower frequencies such that f is well below fa, the symmetric CCP is in a stable symmetric equilibrium, as expected, but at higher frequencies such that f is near or greater than fa, a non-symmetric equilibrium appears which may be stable or unstable. We develop a nonlinear lumped circuit model of the symmetric CCP to better understand these unexpected results, indicating that the proximity to the anti-symmetric spatial resonance allows self-exciting of the anti-symmetric mode even in a symmetric system. The circuit model results agree well with the fluid simulations. A linear stability analysis of the symmetric equilibrium describes a transition with increasing frequency from stable to unstable. [ABSTRACT FROM AUTHOR]

We show that metric abstract elementary classes (mAECs) are, in the sense of [15], coherent accessible categories with directed colimits, with concrete ℵ1-directed colimits and concrete monomorphisms. More broadly, we define a notion of κ-concrete AEC—an AEC-like category in which only the κ-directed colimits need be concrete—and develop the theory of such categories, beginning with a category-theoretic analogue of Shelah’s Presentation Theorem and a proof of the existence of an Ehrenfeucht–Mostowski functor in case the category is large. For mAECs in particular, arguments refining those in [15] yield a proof that any categorical mAEC is μ-d-stable in many cardinals below the categoricity cardinal. [ABSTRACT FROM PUBLISHER]

Aim: We investigated how accurate observations of canonical babbling (CB) were and explored predictive babbling measures in children with and without medical diagnoses of conditions that can lead to speech and language problems.Methods: From 2012 to 2014 this Stockholm-based study recruited 38 children aged nine months to 21 months with medical diagnoses and 30 children aged 10 months without diagnoses and included 21 previously studied 12-month-old children without medical diagnoses. CB and consonant sound production were directly observed by video recording natural play with a caregiver. The percentage of CB was calculated from each recording, and a validated observation form was used. How accurately the children with and without CB were classified was investigated with sensitivity and specificity. The groups were compared using predictive babbling variables.Results: The observation method identified children with and without CB well, with a specificity of 0.89 and sensitivity of 0.93, respectively. Children with predictive babbling measures were identified in the clinical group (specificity 0.93-0.97), and a lack of these measures indicated a risk of being in the clinical group (odds ratios > 10). The sensitivity was low (0.32-0.42).Conclusion: Observation effectively identified a lack of CB and supported the importance of assessing babbling measures. [ABSTRACT FROM AUTHOR]

We show that a number of results on abstract elementary classes (AECs) hold in accessible categories with concrete directed colimits. In particular, we prove a generalization of a recent result of Boney on tameness under a large cardinal assumption. We also show that such categories support a robust version of the Ehrenfeucht–Mostowski construction. This analysis has the added benefit of producing a purely language-free characterization of AECs, and highlights the precise role played by the coherence axiom. [ABSTRACT FROM PUBLISHER]

It is well-known that standing waves having radially center-high radio frequency (rf) voltage profiles exist in high frequency capacitive discharges. In this work, we determine the symmetric and antisymmetric radially propagating waves in a cylindrical capacitive discharge that is asymmetrically driven at the lower electrode by an rf voltage source. The discharge is modeled as a uniform bulk plasma which at lower frequencies has a thicker sheath at the smaller area powered electrode and a thinner sheath at the larger area grounded electrode. These are self-consistently determined at a specified density using the Child law to calculate sheath widths and the electron power balance to calculate the rf voltage. The fields and the system resonant frequencies are determined. The centerto- edge voltage ratio on the powered electrode is calculated versus frequency, and central highs are found near the resonances. The results are compared with simulations in a similar geometry using a two-dimensional hybrid fluid-analytical code, giving mainly a reasonable agreement. The analytic model may be useful for finding good operating frequencies for a given discharge geometry and power. [ABSTRACT FROM AUTHOR]

The electrons in capacitively coupled plasmas (CCPs) absorb energy via ohmic heating due to electron-neutral collisions and stochastic heating due to momentum transfer from high voltage moving sheaths. We use Particle-in-Cell (PIC) simulations to explore these heating mechanisms and to compare the PIC results with available theories on ohmic and stochastic heating. The PIC results for ohmic heating show good agreement with the ohmic heating calculation of Lafleur et al. [Phys. Plasmas 20, 124503 (2013)]. The PIC results for stochastic heating in low pressure CCPs with collisionless sheaths show good agreement with the stochastic heating model of Kaganovich et al. [IEEE Trans. Plasma Sci. 34, 696 (2006)], which revises the hard wall asymptotic model of Lieberman [IEEE Trans. Plasma Sci. 16, 638 (1988)] by taking current continuity and bulk oscillation into account. [ABSTRACT FROM AUTHOR]

Multiple lines of evidence were used to document the natural attenuation of perchlorate in a shallow alluvial aquifer. In the upgradient, aerobic portion of the aquifer, perchlorate did not biodegrade. However, natural flushing by groundwater flow is reducing perchlorate concentrations in the aquifer over time. Perchlorate concentrations in the source area are expected to meet cleanup criteria in 11 to 27 years without active remedial measures. At the distal end of the plume, perchlorate is rapidly degraded as it migrates upward through organic rich littoral zone sediments. Apparent first-order degradation rates in groundwater were about 0.20 d−1and are consistent with laboratory macrocosm rates (0.12 d−1). qPCR results show a distinct region of the littoral zone where perchlorate degraders are elevated. The Eh within this zone varies from +0.1 to +0.3 V indicating perchlorate degraders can thrive in moderately oxidizing conditions. The study has shown that (i) there was no apparent perchlorate biodegradation in aerobic aquifer; (ii) perchlorate declines over time in aerobic aquifer due to flushing; (iii) there was a rapid perchlorate attenuation in organic rich littoral zone; and, (iv) qPCR results show large increases in perchlorate degraders in the littoral zone. [ABSTRACT FROM AUTHOR]

The oopd1 particle-in-cell Monte Carlo collision (PIC-MCC) code is used to simulate a capacitively coupled discharge in oxygen. oopd1 is a one-dimensional object-oriented PIC-MC code in which the model system has one spatial dimension and three velocity components. It contains a model for planar geometry and will contain models for cylindrical and spherical geometries, and replaces the xpdx1 series, which is not object-oriented. The oopd1 also allows for different weights of simulation particles and relativistic treatment of electrons. The revised oxygen model includes, in addition to electrons, the oxygen molecule in the ground state, the oxygen atom in the ground state, the negative ion O- and the positive ions O+ and O2+ . The cross sections for the collisions among the oxygen species have been significantly revised from earlier work using the xpdp1 code and the electron kinematics have been enhanced. Here we make a benchmark study and compare the oopd1 code to the well-established planar xpdp1 code and discuss the differences using a limited cross section set with O2+ ions, O- ions and electrons as the charged particles. We compare the electron energy distribution function, the electron temperature profile, the density profiles of charged particles and electron heating rates for a capacitively coupled oxygen discharge at 50mTorr with electrode separation of 4.5 cm. Then we explore the effect of adding O atoms and O+ ions on the overall discharge. [ABSTRACT FROM AUTHOR]

A one-dimensional hybrid analytical-numerical global model of atmospheric-pressure, radio-frequency (rf) driven capacitive discharges is developed. The feed gas is assumed to be helium with small admixtures of oxygen or nitrogen. The electrical characteristics are modeled analytically as a current-driven homogeneous discharge. The electron power balance is solved analytically to determine a time-varying Maxwellian electron temperature, which oscillates on the rf timescale. Averaging over the rf period yields effective rate coefficients for gas phase activated processes. The particle balance relations for all species are then integrated numerically to determine the equilibrium discharge parameters. The coupling of analytical solutions of the time-varying discharge and electron temperature dynamics, and numerical solutions of the discharge chemistry, allows for a fast solution of the discharge equilibrium. Variations of discharge parameters with discharge composition and rf power are determined. Comparisons are made to more accurate but numerically costly fluid models, with space and time variations, but with the range of parameters limited by computational time. [ABSTRACT FROM AUTHOR]

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) commonly occurs in individuals receiving bisphosphonates (BPs) with clinical manifestations of the exposed necrotic bone. Although defective wound healing of soft tissue is frequently, if not always, observed in BRONJ, the effects of BPs on oral soft tissue or cells remain unknown. To investigate the effects of BPs on cells of oral mucosal tissue, we studied the effect of pamidronate (PAM), one of the BPs most commonly administered to cancer patients, on the phenotypes of normal human oral keratinocytes (NHOK) and fibroblasts (NHOF). When exposed to PAM at 10 µM, NHOK, not NHOF, underwent senescence: NHOK overexpressed senescence-associated β-galactosidase (SA-β-Gal), p16INK4A, IL-6, and IL-8. When exposed to a higher level (50 µM) of PAM, NHOK maintained senescent phenotypes, but NHOF underwent apoptosis. PAM-induced senescence in NHOK is mediated, in part, via geranylgeranylation of the mevalonate pathway. Our in vitro 3D oral mucosal tissue construction studies further demonstrated that PAM induced senescence and impaired re-epithelialization of oral mucosa. Analysis of these data indicates that premature senescence of oral mucosal cells and subsequent defective soft-tissue wound healing might be partly responsible for the development of BRONJ in individuals receiving PAM or other BPs. [ABSTRACT FROM PUBLISHER]

Tallberg, I.M., Carlsson, S. & Lieberman, M. (2011). Children's word fluency strategies. Scandinavian Journal of Psychology 52, 35-42. Two word fluency tasks, the FAS letter fluency task and the 'animal' semantic fluency task, were administered to 130 healthy Swedish-speaking children between 6 and 15 years of age. The main aim was to gather normative data on these word fluency tasks for Swedish-speaking children. Another purpose was to examine the switching and clustering strategies used, along with the occurrence of erroneous responses, in relation to demographic data and number of words retrieved. Both phonological and semantic analyses of switching and clustering were conducted. Higher age was found to be related to a more effective use of phonological and semantic switching and clustering strategies. The reference data resulting from this study may be of clinical value in examinations of children with various diagnoses, including language impairment. [ABSTRACT FROM AUTHOR]

The formation of a double layer (DL) in a two-dimensional (2D) electronegative plasma with a source (heating) section connected to a larger downstream section is described. A 2D particle-in-cell (PIC) code is used to exhibit the DL, which appears near the transition between the source and downstream chambers, over a range of pressures and electronegativities. Diagnostics of the PIC code allow the calculation of various plasma parameters, not easily measured in experiments, to be compared with an analytic theory. The theory consists of a collisionless one-dimensional model of a DL connected to 2D source and downstream global models. The conditions of positive and negative ion balance upstream and downstream, and the downstream energy balance determine the DL potential, electron temperatures, and other plasma parameters. A rescaled oxygen reaction set is used both for the simulation and for the analytic comparison. The PIC simulations exhibit a Maxwellian electron distribution in the source region at temperature Th, and a bi-Maxwellian distribution downstream, with a low energy population at temperature Tch and with a hotter tail also having temperature Th. At the upstream DL edge, an accelerated electron component is observed. Using these results in the model, a DL is found in reasonable agreement with that obtained in the simulation. [ABSTRACT FROM AUTHOR]

Background Symptom improvement in irritable bowel syndrome (IBS) treatment trials varies widely, with only 50–70% of patients qualifying as responders. Factors predicting treatment responsiveness are not known, although we have demonstrated that symptom improvement with the 5-HT3R antagonist alosetron is correlated with reduced amygdala activity. Aim To determine whether neural activity during rectal discomfort or psychological distress predicts symptom improvement following treatment with alosetron. Methods Basal psychological distress and neural activity (15O PET) during uncomfortable rectal stimulation were measured in 17 nonconstipated IBS patients who then received 3 weeks of alosetron treatment. Results Greater symptom improvement was predicted by less activity in bilateral orbitofrontal cortex (OFC) and medial temporal gyrus during pre-treatment scans. Lower levels of interpersonal sensitivity predicted greater symptom improvement and were positively related to activity in left OFC. Connectivity analysis revealed a positive relationship between activity in the left OFC and right amygdala. Conclusions Irritable bowel disease symptom improvement with 5-HT3R antagonist alosetron is related to pre-treatment reactivity of the left OFC, which may be partially captured by subjective measures of interpersonal sensitivity. The left OFC may fail to modulate amygdala response to visceral stimulation, thereby diminishing effectiveness of treatment. Psychological factors and their neurobiological correlates are plausible predictors of IBS treatment outcome. [ABSTRACT FROM AUTHOR]