Dissociative Attachment Research Articles

Structural Analysis of Phospholipid Using Hydrogen Abstraction Dissociation and Oxygen Attachment Dissociation in Tandem Mass Spectrometry.

Gas-phase hydrogen radicals were introduced into a quadrupole ion trap containing singly charged phospholipids to obtain structural fragmentation patterns in tandem mass spectrometry (MS/MS). Saturated and unsaturated phosphatidylcholines were used as a model phospholipid, whose chain-length ranges between 16 and 24. The MS/MS spectrum yielded a continuous series of fragment ions with a mass difference of 14 Da, representing the saturated fatty acyl chains. The fragment ions corresponding to the double-bond position within a single fatty acyl chain showed a characteristic mass difference of 12 Da. The detection of these diagnostic product ions enabled the structural analysis of double-bond isomers of phospholipids. To further investigate the potential of radical-induced dissociation for the isomeric analysis of phospholipids, gas-phase hydroxyl radicals, and triplet oxygen atoms were employed in tandem mass spectrometry. The methylene bridges adjacent to the double-bond positions were selectively dissociated, accompanied by oxidation of the double bonds. Tandem mass spectrometry incorporating multiple radical species facilitates the structural analysis of isomeric phospholipids.

Contrast between the mechanisms for dissociative electron attachment to CH3SCN and CH3NCS.

The kinetics of thermal electron attachment to methyl thiocyanate (CH3SCN), methyl isothiocyanate (CH3NCS), and ethyl thiocyanate (C2H5SCN) were measured using flowing afterglow-Langmuir probe apparatuses at temperatures between 300 and 1000 K. CH3SCN and C2H5SCN undergo inefficient dissociative attachment to yield primarily SCN- at 300 K (k = 2 × 10-10 cm3 s-1), with increasing efficiency as temperature increases. The increase is well described by activation energies of 0.17 eV (CH3SCN) and 0.14 eV (C2H5SCN). CN- product is formed at <1% branching at 300 K, increasing to ∼30% branching at 1000 K. Attachment to CH3NCS yields exclusively SCN- ionic product but at a rate at 300 K that is below our detection threshold (k < 10-12 cm3 s-1). The rate coefficient increases rapidly with increasing temperature (k = 6 × 10-11 cm3 s-1 at 600 K), in a manner well described by an activation energy of 0.51 eV. Calculations at the B3LYP/def2-TZVPPD level suggest that attachment to CH3SCN proceeds through a dissociative state of CH3SCN-, while attachment to CH3NCS initially forms a weakly bound transient anion CH3NCS-* that isomerizes over an energetic barrier to yield SCN-. Kinetic modeling of the two systems is performed in an attempt to identify a kinetic signature differentiating the two mechanisms. The kinetic modeling reproduces the CH3NCS data only if dissociation through the transient anion is considered.

Effects of the plasma-facing materials on the negative ion H− density in an ECR (2.45 GHz) plasma

Within the framework of fundamental research, the present work focuses on the role of surface material in the production of H− negative ion, with a potential application of designing cesium-free H− negative ion sources oriented to fusion application. It is widely accepted that the main reaction leading to H− production, in the plasma volume, is the dissociative attachment of low-energy electrons (Te ≤ 1 eV) on highly ro-vibrationally excited hydrogen molecules. In parallel with other mechanisms, the density of these excited molecules may be enhanced by means of the recombinative desorption, i.e. the interaction between surface absorbed atoms with other atoms (surface adsorbed or not) through the path . Accordingly, a systematic study on the role played by the surface in this reaction, with respect to the production of H− ion in the plasma volume, is here performed. Thus, tantalum and tungsten (already known as H− enhancers) and quartz (inert surface) materials are employed as inner surfaces of a test bench chamber. The plasma inside the chamber is produced by electron cyclotron resonance (ECR) driving and it is characterized with conventional electrostatic probes, laser photodetachment, and emission and absorption spectroscopy. Two different positions (close to and away from the ECR driving zone) are investigated under various conditions of pressure and power. The experimental results are supported by numerical data generated by a 1D model. The latter couples continuity and electron energy balance equations in the presence of magnetic field, and incorporates vibrational kinetics, H2 molecular reactions, H electronically excited states and ground-state species kinetics. In the light of this study, recombinative desorption has been evidenced as the most probable mechanism, among others, responsible for an enhancement by a factor of about 3.4, at 1.6 Pa and 175 W of microwave power, in the case of tantalum.

TRR's Warrior Camp: An Intensive Treatment Program for Combat Trauma in Active Military and Veterans of All Eras.

Effective treatments for combat trauma in military service members exist, but barriers to care abound, including poor access, stigma, and dropout. Although the effects of post-traumatic stress disorder (PTSD) can be severe, recovery is possible when proper treatment is implemented. Trauma and Resiliency Resources, Inc.'s Warrior Camp (WC) program is designed to address the effects of combat trauma in military service members and veterans. This intensive, 7-d treatment incorporates eye movement desensitization and reprocessing therapy, equine-assisted psychotherapy, yoga, and narrative writing in context of community. This single-group pretest-posttest design included paired t-tests and effect size analyses for 85 participants of WC. Outcome measures included the Mississippi Scale for Combat-related PTSD, the Patient Health Questionnaire, the Revised Adult Attachment Scales, and the Moral Injury Events Scale. Clinician-administered measures included the Davidson Trauma Scale and the Dissociative Experiences Scale. All measures showed statistically significant reductions in distress. The effect sizes ranged from small to large. Results suggest that WC participants experienced significant improvement in PTSD, depression, moral injury, dissociation and adult attachment. Clinicians should consider the potential benefits of this short-term, intensive treatment when addressing combat-related PTSD among military service members and veterans.

Energy Characteristics of Small Metal Clusters Containing Vacancies

Self-consistent calculations of spatial distributions of electrons, potentials, and energies of dissociation, cohesion, vacancy formation, and electron attachment, as well as the ionization potential of solid Al N , Na N clusters (N ≥ 254), and clusters containing a vacancy (N ≥ 12) have been performed using a model of stable jellium. The contribution of a monovacancy to the energy of the cluster, the size dependences of the characteristics, and their asymptotic forms have been considered. The calculations have been performed on the SKIT-3 cluster at the Glushkov Institute of Cybernetics, National Academy of Sciences of Ukraine (Rpeak = 7.4 Tflops).

Affect dysregulation, adult attachment problems, and dissociation mediate the relationship between childhood trauma and borderline personality disorder symptoms in adulthood

IntroductionBoth borderline personality disorder (BPD) and childhood trauma have been shown to be associated with affect dysregulation, dissociation, and fear-based attachment schemas. However, the inter-relationships of these clinical phenomena have not been studied in unison. ObjectiveTo study the interrelations between childhood psychological trauma and adult BPD mediated by dissociation, attachment schemas, and affect dysregulation in unison while differentiating for inhibitory- and excitatory regulation symptoms. MethodAdult chronic psychiatric patients with BPD, BPD with comorbid somatoform disorder, and two psychiatric control groups with SoD-only, or chronic anxiety or affective disorders com-pleted structured interviews and self reports. Affect dysregulation, fear-based attachment schemas and dissociation were tested simultaneously -in their separate inhibitory- and excitatory form- as potential mediators in the relationship between childhood psychological trauma and BPD symptoms in adulthood. Next, two alternative models partitioning childhood trauma into more specific features as source (primary-caretaker or not), or type i.e. emotional-, physical-, or sexual abuse, while differentiating for developmental epochs, were compared to the original model. Analyses were re-run for participants who report more severe symptoms that meet criteria for a BPD diagnosis. ResultsStructured equation modeling with bootstrap 95% confidence intervals revealed that hallmark features of BPD – affect dysregulation involving extreme emotional intensity and lability (under-regulation), fragmentation of consciousness (positive psychoform dissociation; e.g., flashbacks), and core attachment fears of closeness and abandonment – partially account for the relationship between overall childhood trauma and BPD-symptom severity. The unifying theme for these mediators is excitatory dysregulation. Alternative models distinguishing types and nature of trauma did not fit the data. However, adults who report more severe symptoms that meet criteria for a BPD diagnosis were likely to have experienced sexual trauma in early childhood or adolescence, and to have an intense fear of abandonment, with the path from early childhood sexual trauma to BPD symptoms as strongest direct relationship. ConclusionRelationships between overall childhood trauma and BPD symptoms in adulthood through three mediators i.e., affect dysregulation, fear-based attachment schemas and dissociation were found, over alternative models distinguishing types of perpetrator, nature of trauma, and developmental epoch. These findings contribute to and replicate a substantial research base that highlights sexual trauma in early childhood and severe attachment insecurity (and disorganization) as contributors to adult BPD. Prospective studies are needed to elucidate the complex relationships between childhood trauma and BPD.

Cross Sections for Electron Collisions with NF3

Cross section data are compiled from the literature for electron collisions with nitrogen trifluoride (NF3) molecules. Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment. For each of these processes, the recommended values of the cross sections are presented. The literature has been surveyed until end of 2016.

Reactivity of prehydrated electrons toward nucleobases and nucleotides in aqueous solution.

DNA damage induced via dissociative attachment by low-energy electrons (0 to 20 eV) is well studied in both gas and condensed phases. However, the reactivity of ultrashort-lived prehydrated electrons ([Formula: see text]) with DNA components in a biologically relevant environment has not been fully explored to date. The electron transfer processes of [Formula: see text] to the DNA nucleobases G, A, C, and T and to nucleosides/nucleotides were investigated by using 7-ps electron pulse radiolysis coupled with pump-probe transient absorption spectroscopy in aqueous solutions. In contrast to previous results, obtained by using femtosecond laser pump-probe spectroscopy, we show that G and A cannot scavenge [Formula: see text] at concentrations of ≤50 mM. Observation of a substantial decrease of the initial yield of hydrated electrons ([Formula: see text]) and formation of nucleobase/nucleotide anion radicals at increasing nucleobase/nucleotide concentrations present direct evidence for the earliest step in reductive DNA damage by ionizing radiation. Our results show that [Formula: see text] is more reactive with pyrimidine than purine nucleobases/nucleotides with a reactivity order of T > C > A > G. In addition, analyses of transient signals show that the signal due to formation of the resulting anion radical directly correlates with the loss of the initial [Formula: see text] signal. Therefore, our results do not agree with the previously proposed dissociation of transient negative ions in nucleobase/nucleotide solutions within the timescale of these experiments. Moreover, in a molecularly crowded medium (for example, in the presence of 6 M phosphate), the scavenging efficiency of [Formula: see text] by G is significantly enhanced. This finding implies that reductive DNA damage by ionizing radiation depends on the microenvironment around [Formula: see text].

Quantum dynamics calculations for e+ + LiH → Li+ + [H−; e+] dissociative positron attachment using a pseudopotential model

We theoretically discuss the dynamics of the chemical reaction process induced by positron attachment, e+ + LiH → Li+ + [H−; e+]. Simple model pseudopotentials were developed on the basis of the electrostatic interaction between e+ and LiH with a large dipole moment, where some numerical parameters were chosen to qualitatively reproduce the previous-reported ab initio positron-bound adiabatic potential energy curve of [LiH; e+]. Using the developed pseudopotential models, we have performed time-independent quantum scattering calculations using the hyperspherical coordinate. Although the main scattering processes of the e+ + LiH collision are rotational and vibrational excitation processes, it is found that the calculated probabilities for the dissociative positron attachment (DPA) process are not very small within the present pseudopotential framework. This suggest that the DPA process to LiH can be observed in the future experiments.

Associations between Trauma, Dissociation, Adult Attachment and Proneness to Hallucinations.

Childhood adversity, dissociation and adult attachment have all been implicated in the development of hallucinations or 'voice-hearing'. Testing psychological models in relation to subclinical phenomena, such as proneness to hallucinations in non-clinical samples, provides a convenient methodology to develop understanding of the processes and mechanisms underlying clinical symptoms. This paper investigates the relative contribution of childhood adversity, dissociation and adult attachment in explaining hallucination proneness in a non-clinical sample. Students and staff with no previous contact with secondary care at the University of Manchester were recruited. Participants completed a series of self-report measures: the Launay‒Slade Hallucination Scale (LSHS), the Relationship Scale Questionnaire (RSQ), the Childhood Trauma Questionnaire (CTQ), the Dissociative Experiences Schedule (DES II) and the Positive and Negative Affect Schedule (PANAS). As hypothesized, insecure attachment, childhood adversity and dissociative symptoms were correlated with hallucination proneness. Multiple regression analysis, controlling for confounds of age and negative affect, indicated that the RSQ, CTQ and DES II predicted hallucination proneness. Only DES II and RSQ avoidant attachment were significant independent predictors in the final model. This study provides further evidence to support the idea that attachment and dissociation are important psychological mechanisms involved in voice-hearing proneness. Further testing is required with a clinical population.

Self-consistency of electron-THF cross sections using electron swarm techniques.

The drift velocity and first Townsend ionization coefficient of electrons in gaseous tetrahydrofuran are measured over the range of reduced electric fields 4-1000 Td using a pulsed-Townsend technique. The measured drift velocities and Townsend ionization coefficients are subsequently used, in conjunction with a multi-term Boltzmann equation analysis, as a further discriminative assessment on the accuracy and completeness of a recently proposed set of electron-THF vapor cross sections. In addition, the sensitivity of the transport coefficients to uncertainties in the existing cross sections is presented. As a result of that analysis, a refinement of the momentum transfer cross section for electron-THF scattering is presented, along with modifications to the neutral dissociation and dissociative electron attachment cross sections. With these changes to the cross section database, we find relatively good self-consistency between the measured and simulated drift velocities and Townsend coefficients.

The interaction of low-energy electrons with fructose molecules

Using a hypocycloidal electronic spectrometer, the interactions of low energy electrons (0–8.50 eV) with fructose molecules, namely, electron scattering and dissociative attachment, are studied. The results of these studies showed that the fragmentation of fructose molecules occurs effectively even at an electron energy close to zero. In the total electron-scattering cross section by molecules, resonance features (at energies ~3.10 and ~5.00 eV) were first observed near the formation thresholds of light ion fragments OH– and H–. The correlation of the features observed in the cross sections of electron scattering and dissociative attachment is analyzed.

Production of radical species by electron beam deposition in an ArF* lasing medium

The electron-beam-pumped ArF laser is a laser technology capable of providing very high lasing energies at the shortest wavelength (λ = 193 nm) among the rare gas halide lasers and therefore has the potential to be a superior driver for inertial fusion. The electron kinetics are rigorously treated by numerically solving the steady-state, spatially averaged electron Boltzmann equation in Ar-F2 gas. The e-beam energy deposition and collisional reaction rates with electrons are calculated from the electron energy distribution function for a wide range of e-beam deposition powers (Pbeam = 10 kW/cm3–3 MW/cm3) and fluorine concentrations (xF2 = 0.01 – 10%). The rates are reduced to a set of coefficients that are fitted with analytical formulas as a function of two universal parameters: Pbeam/p and xF2, where p is the gas pressure. It is found that in the regime of high e-beam power deposition, the fluorine molecules are rapidly destroyed through dissociative attachment and neutral dissociation. The loss of F2 over the duration of the beam is proportional to the e-beam energy deposition per unit volume, εbeam, and follows ΔnF2(cm−3)≅4×1017εbeam(J/cm3), in agreement with experimental data. The fluorine molecule conversion to other fluorine species, including atomic fluorine, is shown to have a very small effect on the index of refraction even at percent level concentrations.

Microwave Interferometry of Chemically Active Plasma of RF Discharge in Mixtures Based on Fluorides of Silicon and Germanium

The free electron concentration in hydrogen and chemically active plasmas in H2 + SiF4 and H2 + GeF4 mixtures was measured by microwave interferometry. The investigations were carried out under conditions of a RF capacitive-coupled discharge at a pressure of 1 Torr. In hydrogen plasma the concentration of free plasma electrons is 1.5 ± 0.03 × 1012 cm−3. When the fluoride is added to the hydrogen plasma, the electron concentration is reduced to 1.1 ± 0.05 × 1012 cm−3 for SiF4 and 9.8 ± 0.05 × 1011 cm−3 for GeF4. It is suggested that the main mechanism responsible for reducing the concentration of free electrons is the mechanism of dissociative attachment of electrons to SiF4 and GeF4 molecules. The difference in the electron concentration for these mixtures is due to the difference in the electron-acceptor ability of the SiF4 and GeF4 molecules determined by the affinity for the electron.

Investigation of the Radio-Frequency Discharge in a High Current Negative Hydrogen Ion Source With a Global Enhanced Vibrational Kinetic Model

A numerical investigation of the radio-frequency hydrogen discharge in the high current negative hydrogen ion source (HCNHIS) is presented using a global enhanced vibrational kinetic model (GEVKM). The HCNHIS consists of a high-pressure (2–65 torr) radio-frequency discharge chamber where the main production of high-lying vibrational states of the hydrogen molecules occurs. The hydrogen plasma flow in the discharge chamber is reduced by a series of bypass tubes and enters through a nozzle into a low-pressure (1–15 mtorr) negative hydrogen ion production chamber where H− are generated mainly by the dissociative attachment of low-energy electrons to rovibrationally excited hydrogen molecules. The GEVKM is applied to the HCNHIS discharge and involves volume-averaged equations for 21 hydrogen species (atoms, ions, and molecules in excited states) and electrons. The GEVKM is supplemented with outlet boundary conditions for the nozzle and bypass tubes of the HCNHIS and accounts for compressibility, viscous, and rarefaction effects. GEVKM simulations of the RF discharge are performed with inlet flow rates of 5–1000 sccm and absorbed powers of 200–1000 W using the HCNHIS-2 design which is configured with an extractor grid attached to a short negative ion production region. These simulations investigate the effects of the absorbed power and the inlet flow rate on the chemical composition, electron and heavy particles temperature, wall temperature, the maximum extractable H− current in the discharge chamber, as well as optimum operational parameters of HCNHIS-2. GEVKM simulations of the HCNHIS-2 discharge are used to obtain estimates of the H− current and compared with Faraday cup measurements taken at the extraction grid.

Measurement of F−, O− and densities in 60 and 100 MHz asymmetric capacitively coupled plasma discharge produced in an Ar/O2/C4F8 gas mixture

The behaviour of absolute electron density and density of F−, O− and is studied in asymmetric capacitively coupled plasma discharge produced in an Ar/O2/C4F8 (80:10:10) gas mixture excited at 60 and 100 MHz. The measurements are performed using a hairpin probe and laser photo-detachment at 532 nm and 355 nm laser wavelengths. For both 60 and 100 MHz driving frequencies, the results show that the electrons and F− density increases almost linearly with the increase in rf power. On the other hand, the O− density increases in 60 MHz and decreases in 100 MHz with a rise in rf power. For a fixed rf power in the 60 MHz discharge, the O− density increases and electron density decreases with gas pressure. The corresponding F− density first increases, reaching a maximum value, and then decreases with a further increase in gas pressure. A similar trend in electron, F− and O− density versus gas pressure is observed in 100 MHz suggesting that the initial increase in densities is dominated by the ionization and dissociative attachment, whereas, at a higher gas pressure, electron–ion recombination, ion-neutral recombination and ion–ion neutralization play a significant role in the losses of charged particles. The ratio of F− density to O− density is ~80:20 and ~95:5 in 60 MHz and 100 MHz respectively. The density of both electrons and F− is higher in 100 MHz when compared to 60 MHz discharge. The observed trend is explained on the basis of productions and loss mechanisms for electrons and negative ions. It is concluded that the higher F− density in 100 MHz in comparison to 60 MHz is mainly due to higher electron density and dissociation degree.

Air breakdown induced by the microwave with two mutually orthogonal and heterophase electric field components**Project supported by the National Natural Science Foundation of China (Grant Nos. 61501358, 61431010, and 61627901) and the Fundamental Research Funds for the Central Universities, China.

The air breakdown is easily caused by the high-power microwave, which can have two mutually orthogonal and heterophase electric field components. For this case, the electron momentum conservation equation is employed to deduce the electric field power and effective electric field for heating electrons. Then the formula of the electric field power is introduced into the global model to simulate the air breakdown. The breakdown prediction from the global model agrees well with the experimental data. Simulation results show that the electron temperature is sensitive to the phase difference between the two electron field components, while the latter can affect obviously the growth of the electron density at low electron temperature amplitudes. The ionization of nitrogen and oxygen induces the growth of electron density, and the density loss due to the dissociative attachment and dissociative recombination is obvious only at low electron temperatures.

Attachment and dissociation as mediators of the link between childhood trauma and psychotic experiences

Exposure to childhood trauma has been implicated in the development of paranoia and hearing voices, but the mechanisms responsible for these associations remain unclear. Understanding these mechanisms is essential for ensuring that targeted interventions can be developed to better support people experiencing distress associated with paranoia and voices. Recent models have proposed that dissociation may be a mechanism specifically involved in the development of voices and insecure attachment in the development of paranoia. Recent theoretical proposals have added to this and argued that fearful attachment could also lead to increased vulnerability for voices. This study was the first to examine whether dissociation and insecure attachment styles mediated the relationship between childhood trauma and these psychotic experiences. One hundred and twelve participants experiencing clinical levels of psychosis completed measures of dissociation, childhood trauma, attachment, voices, and paranoia. Results revealed positive associations between fearful (but not dismissive and anxious) attachment, dissociation, trauma, and psychotic experiences. Mediation analyses indicated that dissociation, but not fearful attachment, significantly mediated the relationship between trauma and voices. Conversely, both dissociation and fearful attachment significantly mediated the relationship between trauma and paranoia. The findings suggest that insecure attachment might be more strongly related to paranoia than hallucinations and suggest that fearful attachment may be a more promising mechanism to explain this relationship. Furthermore, the findings suggest that the impact of dissociation on psychotic experiences may extend to paranoia. Future research is required to replicate these findings using interview-based attachment measures.

Multifold study of volume plasma chemistry in Ar/CF4 and Ar/CHF3 CCP discharges

Low-pressure RF plasma in fluorohydrocarbon gas mixtures is widely used in modern microelectronics, e.g. in the etching of materials with a low dielectric constant (low-k) materials). The multifold experimental and theoretical study of a radio frequency capacitively coupled plasma at 81 MHz in Ar/CF4/CHF3 has been carried out at 50 mTorr and 150 mTorr gas pressures. A wide set of experimental diagnostics together with hybrid PIC MC model calculations were applied to a detailed study of the plasmas. Measurements of the F atoms, HF molecules and CFx radicals, electron density, electronegativity and positive ion composition were performed. Absolutely calibrated VUV spectrometry was carried out to measure the VUV photon fluence towards the electrode. This combined experimental and model approach allowed us to establish the fundamental mechanisms of the charged and neutral species elementary reactions. Dissociative charge transfer reactions and fluoride transfer reactions influence the main ion (CF, CHF) composition in Ar/CF4/CHF3 plasma a lot. The mechanisms of heavy ion formation in Ar/CHF3 are also discussed. The important role of additional attachment mechanisms (besides dissociative attachment to the feedstock gases, CF4, CHF3) was analyzed. The catalytic chain mechanism, including the HF molecules, which defines the CFx kinetics in Ar/CHF3 plasma, was validated. This multifold approach enabled us to determine the complicated plasma chemical composition of the active species as well as the fluxes of VUV photons at the surface of the processed material, and is a result that is important for understanding low-k damage.

Molecular activated recombination in divertor simulation plasma on GAMMA 10/PDX

In the tandem mirror GAMMA 10/PDX, molecular activated recombination (MAR) leading to plasma detachment has been observed by additional hydrogen gas injection to the divertor simulation plasma (i.e. end loss plasma) which is exposed to the V-shaped target in the divertor simulation experimental module (D-module). The temperature near the corner of the V-shaped target decreased from ∼23eV to ∼2eV as the neutral pressure in the D-module increased. A clear density rollover was observed at ∼2Pa. A position of the density maximum moves to upstream of the plasma with increase in the neutral pressure and the density near the corner of the target decreases to detach the plasma from the target. After the occurrence of the density rollover, the Balmer β intensity decreases as with the density but the Balmer α intensity continues to increase, indicating the dissociative attachment process in MAR is more dominant than the ion conversion process although the rate coefficient of the former process is lower than that of the latter one, which is calculated by using a collisional radiative model. This would be caused by the MAR process related to triatomic hydrogen molecules which significantly contributed to the detachment process.