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Sample records for combined pulsed-q dissociation

  1. Identification of Proteins and Phosphoproteins Using Pulsed Q Collision Induced Dissociation (PQD)

    NASA Astrophysics Data System (ADS)

    Wu, Wells W.; Wang, Guanghui; Insel, Paul A.; Hsiao, Cheng-Te; Zou, Sige; Maudsley, Stuart; Martin, Bronwen; Shen, Rong-Fong

    2011-10-01

    Pulsed Q collision induced dissociation (PQD) was developed to facilitate detection of low-mass reporter ions from labeling reagents (e.g., iTRΑQ) in peptide quantification using an LTQ mass spectrometer (MS). Despite the large number of linear ion traps worldwide, the use and optimization of PQD for protein identification have been limited, in part due to less effective ion fragmentation relative to the collision induced dissociation (CID). PQD expands the m/z coverage of fragment ions to the lower m/z range by circumventing the typical low mass cut-off of an ion trap MS. Since database searching relies on the matching between theoretical and observed spectra, it is not clear how ion intensity and peak number might affect the outcomes of a database search. In this report, we systematically evaluated the attributes of PQD mass spectra, performed intensity optimization, and assessed the benefits of using PQD on the identification of peptides and phosphopeptides from an LTQ. Based on head-to-head comparisons between CID (higher intensity) and PQD (better m/z coverage), peptides identified using PQD generally have Xcorr scores lower than those using CID. Such score differences were considerably diminished by the use of 0.1% m-nitrobenzyl alcohol (m-NBA) in mobile phases. The ion intensities of both CID and PQD were adversely affected by increasing m/z of the precursor, with PQD more sensitive than CID. In addition to negating the 1/3 rule, PQD enhances direct bond cleavage and generates patterns of fragment ions different from those of CID, particularly for peptides with a labile functional group (e.g., phosphopeptides). The higher energy fragmentation pathway of PQD on peptide fragmentation was further compared to those of CID and the quadrupole-type activation in parallel experiments.

  2. Combined Infrared Multiphoton Dissociation with Ultraviolet Photodissociation for Ubiquitin Characterization

    NASA Astrophysics Data System (ADS)

    Halim, Mohammad A.; Girod, Marion; MacAleese, Luke; Lemoine, Jérôme; Antoine, Rodolphe; Dugourd, Philippe

    2016-06-01

    Herein we report the successful implementation of the consecutive and simultaneous photodissociation with high (213 nm) and low (10.6 μm) energy photons (HiLoPD, high-low photodissociation) on ubiquitin in a quadrupole-Orbitrap mass spectrometer. Absorption of high-energy UV photon is dispersed over the whole protein and stimulates extensive C-Cα backbone fragmentation, whereas low-energy IR photon gradually increases the internal energy and thus preferentially dissociates the most labile amide (C-N) bonds. We noticed that simultaneous irradiation of UV and IR lasers on intact ubiquitin in a single MS/MS experiment provides a rich and well-balanced fragmentation array of a/x, b/y, and z ions. Moreover, secondary fragmentation from a/x and z ions leads to the formation of satellite side-chain ions (d, v, and w) and can help to distinguish isomeric residues in a protein. Implementation of high-low photodissociation in a high-resolution mass spectrometer may offer considerable benefits to promote a comprehensive portrait of protein characterization.

  3. Combined Infrared Multiphoton Dissociation with Ultraviolet Photodissociation for Ubiquitin Characterization.

    PubMed

    Halim, Mohammad A; Girod, Marion; MacAleese, Luke; Lemoine, Jérôme; Antoine, Rodolphe; Dugourd, Philippe

    2016-09-01

    Herein we report the successful implementation of the consecutive and simultaneous photodissociation with high (213 nm) and low (10.6 μm) energy photons (HiLoPD, high-low photodissociation) on ubiquitin in a quadrupole-Orbitrap mass spectrometer. Absorption of high-energy UV photon is dispersed over the whole protein and stimulates extensive C-Cα backbone fragmentation, whereas low-energy IR photon gradually increases the internal energy and thus preferentially dissociates the most labile amide (C-N) bonds. We noticed that simultaneous irradiation of UV and IR lasers on intact ubiquitin in a single MS/MS experiment provides a rich and well-balanced fragmentation array of a/x, b/y, and z ions. Moreover, secondary fragmentation from a/x and z ions leads to the formation of satellite side-chain ions (d, v, and w) and can help to distinguish isomeric residues in a protein. Implementation of high-low photodissociation in a high-resolution mass spectrometer may offer considerable benefits to promote a comprehensive portrait of protein characterization. Graphical Abstract ᅟ. PMID:27287047

  4. Combined Infrared Multiphoton Dissociation with Ultraviolet Photodissociation for Ubiquitin Characterization

    NASA Astrophysics Data System (ADS)

    Halim, Mohammad A.; Girod, Marion; MacAleese, Luke; Lemoine, Jérôme; Antoine, Rodolphe; Dugourd, Philippe

    2016-09-01

    Herein we report the successful implementation of the consecutive and simultaneous photodissociation with high (213 nm) and low (10.6 μm) energy photons (HiLoPD, high-low photodissociation) on ubiquitin in a quadrupole-Orbitrap mass spectrometer. Absorption of high-energy UV photon is dispersed over the whole protein and stimulates extensive C-Cα backbone fragmentation, whereas low-energy IR photon gradually increases the internal energy and thus preferentially dissociates the most labile amide (C-N) bonds. We noticed that simultaneous irradiation of UV and IR lasers on intact ubiquitin in a single MS/MS experiment provides a rich and well-balanced fragmentation array of a/x, b/y, and z ions. Moreover, secondary fragmentation from a/x and z ions leads to the formation of satellite side-chain ions (d, v, and w) and can help to distinguish isomeric residues in a protein. Implementation of high-low photodissociation in a high-resolution mass spectrometer may offer considerable benefits to promote a comprehensive portrait of protein characterization.

  5. A combination thermal dissociation/electron impact ionization source for RIB generation

    SciTech Connect

    Alton, G.D.; Cui, B.; Welton, R.F.

    1996-12-31

    The flourishing interest in radioactive ion beams (RIBs) with intensities adequate for astrophysics and nuclear physics research place a premium on targets that will swiftly release trace amounts of short lived radio-nuclei in the presence of bulk quantities of target material and ion sources that have the capability of efficiently ionizing the release products. Because of the low probability of simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecules containing the element of interest with conventional, hot-cathode, electron-impact ion sources, the species of interest is often distributed in several mass channels in the form of molecular sideband beams and, consequently, the intensity is diluted. The authors have conceived an ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high efficiency characteristics of an electron impact ionization source to address these problems. If the concept proves to be a viable option, the source will be used as a complement to the electron beam plasma ion sources already in use at the HRIBF. The design features and principles of operation of the source are described in this article.

  6. Combined infrared multiphoton dissociation and electron-capture dissociation using co-linear and overlapping beams in Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Mihalca, Romulus; van der Burgt, Yuri E M; McDonnell, Liam A; Duursma, Marc; Cerjak, Iliya; Heck, Albert J R; Heeren, Ron M A

    2006-01-01

    A novel set-up for Fourier transform ion cyclotron resonance mass spectrometry (FTICR) is reported for simultaneous infrared multiphoton dissociation (IRMPD) and electron-capture dissociation (ECD). An unmodified electron gun ensures complete, on-axis overlap between the electron and the photon beams. The instrumentation, design and implementation of this novel approach are described. In this configuration the IR beam is directed into the ICR cell using a pneumatically actuated mirror inserted into the ion-optical path. Concept validation was made using different combinations of IRMPD and ECD irradiation events on two standard peptides. The ability to perform efficient IRMPD, ECD and especially simultaneous IRMPD and ECD using lower irradiation times is demonstrated. The increase in primary sequence coverage, with the combined IRMPD and ECD set-up, also increases the confidence in peptide and protein assignments. PMID:16705647

  7. Combined impact of entropy and carrier delocalization on charge transfer exciton dissociation at the donor-acceptor interface

    NASA Astrophysics Data System (ADS)

    Ono, Shota; Ohno, Kaoru

    2016-08-01

    Several models of the charge transfer exciton (CTE) have been proposed to explain its dissociation at the donor-acceptor (DA) interface. However, the underlying physics is still under debate. Here, we derive a temperature (T ) dependent tight-binding model for an electron-hole pair at the DA interface. The main finding is the existence of the localization-delocalization transition at a critical T , which can explain the CTE dissociation. The present study highlights the combined effect of entropy (finite T ) and carrier delocalization in the CTE dissociation.

  8. Combined compared to dissociated oral and intestinal sucrose stimuli induce different brain hedonic processes

    PubMed Central

    Clouard, Caroline; Meunier-Salaün, Marie-Christine; Meurice, Paul; Malbert, Charles-Henri; Val-Laillet, David

    2014-01-01

    The characterization of brain networks contributing to the processing of oral and/or intestinal sugar signals in a relevant animal model might help to understand the neural mechanisms related to the control of food intake in humans and suggest potential causes for impaired eating behaviors. This study aimed at comparing the brain responses triggered by oral and/or intestinal sucrose sensing in pigs. Seven animals underwent brain single photon emission computed tomography (99mTc-HMPAO) further to oral stimulation with neutral or sucrose artificial saliva paired with saline or sucrose infusion in the duodenum, the proximal part of the intestine. Oral and/or duodenal sucrose sensing induced differential cerebral blood flow changes in brain regions known to be involved in memory, reward processes and hedonic (i.e., pleasure) evaluation of sensory stimuli, including the dorsal striatum, prefrontal cortex, cingulate cortex, insular cortex, hippocampus, and parahippocampal cortex. Sucrose duodenal infusion only and combined sucrose stimulation induced similar activity patterns in the putamen, ventral anterior cingulate cortex and hippocampus. Some brain deactivations in the prefrontal and insular cortices were only detected in the presence of oral sucrose stimulation. Finally, activation of the right insular cortex was only induced by combined oral and duodenal sucrose stimulation, while specific activity patterns were detected in the hippocampus and parahippocampal cortex with oral sucrose dissociated from caloric load. This study sheds new light on the brain hedonic responses to sugar and has potential implications to unravel the neuropsychological mechanisms underlying food pleasure and motivation. PMID:25147536

  9. Combined infrared multiphoton dissociation and electron capture dissociation with a hollow electron beam in Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Tsybin, Youri O; Witt, Matthias; Baykut, Gökhan; Kjeldsen, Frank; Håkansson, Per

    2003-01-01

    An electron injection system based on an indirectly heated ring-shaped dispenser cathode has been developed and installed in a 7 Tesla Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. This new hardware design allows high-rate electron capture dissociation (ECD) to be carried out by a hollow electron beam coaxial with the ion cyclotron resonance (ICR) trap. Infrared multiphoton dissociation (IRMPD) can also be performed with an on-axis IR-laser beam passing through a hole at the centre of the dispenser cathode. Electron and photon irradiation times of the order of 100 ms are required for efficient ECD and IRMPD, respectively. As ECD and IRMPD generate fragments of different types (mostly c, z and b, y, respectively), complementary structural information that improves the characterization of peptides and proteins by FTICR mass spectrometry can be obtained. The developed technique enables the consecutive or simultaneous use of the ECD and IRMPD methods within a single FTICR experimental sequence and on the same ensemble of trapped ions in multistage tandem (MS/MS/MS or MS(n)) mass spectrometry. Flexible changing between ECD and IRMPD should present advantages for the analysis of protein digests separated by liquid chromatography prior to FTICRMS. Furthermore, ion activation by either electron or laser irradiation prior to, as well as after, dissociation by IRMPD or ECD increases the efficiency of ion fragmentation, including the w-type fragment ion formation, and improves sequencing of peptides with multiple disulfide bridges. The developed instrumental configuration is essential for combined ECD and IRMPD on FTICR mass spectrometers with limited access into the ICR trap. PMID:12872281

  10. Toward understanding the dissociation of I2 in chemical oxygen-iodine lasers: Combined experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Waichman, K.; Rybalkin, V.; Katz, A.; Dahan, Z.; Barmashenko, B. D.; Rosenwaks, S.

    2007-07-01

    The dissociation of I2 molecules at the optical axis of a supersonic chemical oxygen-iodine laser (COIL) was studied via detailed measurements and three-dimensional computational fluid dynamics calculations. The measurements, briefly reported in a recent paper [Rybalkin et al., Appl. Phys. Lett. 89, 021115 (2006)] and reanalyzed in detail here, revealed that the number N of consumed O2(aΔg1) molecules per dissociated I2 molecule depends on the experimental conditions: it is 4.5±0.4 for typical conditions and I2 densities applied for optimal operation of the COIL but increases at lower I2 densities. Comparing the measurements and the calculations enabled critical examination of previously proposed dissociation mechanisms and suggestion of a mechanism consistent with the experimental and theoretical results obtained in a supersonic COIL for the gain, temperature, I2 dissociation fraction, and N at the optical axis. The suggested mechanism combines the recent scheme of Azyazov and Heaven [AIAA J. 44, 1593 (2006)], where I2(A'Π2u3), I2(AΠ1u3), and O2(aΔg1,v) are significant dissociation intermediates, with the "standard" chain branching mechanism of Heidner III et al. [J. Phys. Chem. 87, 2348 (1983)], involving I(P1/22) and I2(XΣg +1,v).

  11. Dissociative electron attachments to ethanol and acetaldehyde: A combined experimental and simulation study

    NASA Astrophysics Data System (ADS)

    Wang, Xu-Dong; Xuan, Chuan-Jin; Feng, Wen-Ling; Tian, Shan Xi

    2015-02-01

    Dissociation dynamics of the temporary negative ions of ethanol and acetaldehyde formed by the low-energy electron attachments is investigated by using the anion velocity map imaging technique and ab initio molecular dynamics simulations. The momentum images of the dominant fragments O-/OH- and CH3- are recorded, indicating the low kinetic energies of O-/OH- for ethanol while the low and high kinetic energy distributions of O- ions for acetaldehyde. The CH3- image for acetaldehyde also shows the low kinetic energy. With help of the dynamics simulations, the fragmentation processes are qualitatively clarified. A new cascade dissociation pathway to produce the slow O- ion via the dehydrogenated intermediate, CH3CHO- (acetaldehyde anion), is proposed for the dissociative electron attachment to ethanol. After the electron attachment to acetaldehyde molecule, the slow CH3- is produced quickly in the two-body dissociation with the internal energy redistributions in different aspects before bond cleavages.

  12. Characterization of water dissociation on α-Al2O3(11[combining macron]02): theory and experiment.

    PubMed

    Wirth, Jonas; Kirsch, Harald; Wlosczyk, Sebastian; Tong, Yujin; Saalfrank, Peter; Campen, R Kramer

    2016-06-01

    The interaction of water with α-alumina (i.e. α-Al2O3) surfaces is important in a variety of applications and a useful model for the interaction of water with environmentally abundant aluminosilicate phases. Despite its significance, studies of water interaction with α-Al2O3 surfaces other than the (0001) are extremely limited. Here we characterize the interaction of water (D2O) with a well defined α-Al2O3(11[combining macron]02) surface in UHV both experimentally, using temperature programmed desorption and surface-specific vibrational spectroscopy, and theoretically, using periodic-slab density functional theory calculations. This combined approach makes it possible to demonstrate that water adsorption occurs only at a single well defined surface site (the so-called 1-4 configuration) and that at this site the barrier between the molecularly and dissociatively adsorbed forms is very low: 0.06 eV. A subset of OD stretch vibrations are parallel to this dissociation coordinate, and thus would be expected to be shifted to low frequencies relative to an uncoupled harmonic oscillator. To quantify this effect we solve the vibrational Schrödinger equation along the dissociation coordinate and find fundamental frequencies red-shifted by more than 1500 cm(-1). Within the context of this model, at moderate temperatures, we further find that some fraction of surface deuterons are likely delocalized: dissociatively and molecularly absorbed states are no longer distinguishable. PMID:27109875

  13. Modeling pure methane hydrate dissociation using a numerical simulator from a novel combination of X-ray computed tomography and macroscopic data

    SciTech Connect

    Gupta, A.; Moridis, G.J.; Kneafsey, T.J.; Sloan, Jr., E.D.

    2009-08-15

    The numerical simulator TOUGH+HYDRATE (T+H) was used to predict the transient pure methane hydrate (no sediment) dissociation data. X-ray computed tomography (CT) was used to visualize the methane hydrate formation and dissociation processes. A methane hydrate sample was formed from granular ice in a cylindrical vessel, and slow depressurization combined with thermal stimulation was applied to dissociate the hydrate sample. CT images showed that the water produced from the hydrate dissociation accumulated at the bottom of the vessel and increased the hydrate dissociation rate there. CT images were obtained during hydrate dissociation to confirm the radial dissociation of the hydrate sample. This radial dissociation process has implications for dissociation of hydrates in pipelines, suggesting lower dissociation times than for longitudinal dissociation. These observations were also confirmed by the numerical simulator predictions, which were in good agreement with the measured thermal data during hydrate dissociation. System pressure and sample temperature measured at the sample center followed the CH{sub 4} hydrate L{sub w}+H+V equilibrium line during hydrate dissociation. The predicted cumulative methane gas production was within 5% of the measured data. Thus, this study validated our simulation approach and assumptions, which include stationary pure methane hydrate-skeleton, equilibrium hydrate-dissociation and heat- and mass-transfer in predicting hydrate dissociation in the absence of sediments. It should be noted that the application of T+H for the pure methane hydrate system (no sediment) is outside the general applicability limits of T+H.

  14. Dissociative electron attachments to ethanol and acetaldehyde: A combined experimental and simulation study

    SciTech Connect

    Wang, Xu-Dong; Xuan, Chuan-Jin; Feng, Wen-Ling; Tian, Shan Xi

    2015-02-14

    Dissociation dynamics of the temporary negative ions of ethanol and acetaldehyde formed by the low-energy electron attachments is investigated by using the anion velocity map imaging technique and ab initio molecular dynamics simulations. The momentum images of the dominant fragments O{sup −}/OH{sup −} and CH{sub 3}{sup −} are recorded, indicating the low kinetic energies of O{sup −}/OH{sup −} for ethanol while the low and high kinetic energy distributions of O{sup −} ions for acetaldehyde. The CH{sub 3}{sup −} image for acetaldehyde also shows the low kinetic energy. With help of the dynamics simulations, the fragmentation processes are qualitatively clarified. A new cascade dissociation pathway to produce the slow O{sup −} ion via the dehydrogenated intermediate, CH{sub 3}CHO{sup −} (acetaldehyde anion), is proposed for the dissociative electron attachment to ethanol. After the electron attachment to acetaldehyde molecule, the slow CH{sub 3}{sup −} is produced quickly in the two-body dissociation with the internal energy redistributions in different aspects before bond cleavages.

  15. A combined electron-ion spectrometer for studying complete kinematics of molecular dissociation upon shell selective ionization

    SciTech Connect

    Saha, K.; Banerjee, S. B.; Bapat, B.

    2013-07-15

    A combined electron-ion spectrometer has been built to study dissociation kinematics of molecular ions upon various electronic decay processes ensuing from ionization of neutral molecules. The apparatus can be used with various ionization agents. Ion time-of-flight (ToF) spectra arising from various electronic decay processes are acquired by triggering the ToF measurement in coincidence with energy analyzed electrons. The design and the performance of the spectrometer in a photoionization experiment is presented in detail. Electron spectra and ion time of flight spectra resulting from valence and 2p{sub 1/2} ionization of Argon and those from valence ionization of CO are presented to demonstrate the capability of the instrument. The fragment ion spectra show remarkable differences (both kinematic and cross sectional) dependent on the energy of the ejected electron, corresponding to various electron loss and decay mechanisms in dissociative photoionization of molecules.

  16. Combined TMS and FMRI reveal dissociable cortical pathways for dynamic and static face perception.

    PubMed

    Pitcher, David; Duchaine, Bradley; Walsh, Vincent

    2014-09-01

    Faces contain structural information, for identifying individuals, as well as changeable information, which can convey emotion and direct attention. Neuroimaging studies reveal brain regions that exhibit preferential responses to invariant [1, 2] or changeable [3-5] facial aspects but the functional connections between these regions are unknown. We addressed this issue by causally disrupting two face-selective regions with thetaburst transcranial magnetic stimulation (TBS) and measuring the effects of this disruption in local and remote face-selective regions with functional magnetic resonance imaging (fMRI). Participants were scanned, over two sessions, while viewing dynamic or static faces and objects. During these sessions, TBS was delivered over the right occipital face area (rOFA) or right posterior superior temporal sulcus (rpSTS). Disruption of the rOFA reduced the neural response to both static and dynamic faces in the downstream face-selective region in the fusiform gyrus. In contrast, the response to dynamic and static faces was doubly dissociated in the rpSTS. Namely, disruption of the rOFA reduced the response to static but not dynamic faces, while disruption of the rpSTS itself reduced the response to dynamic but not static faces. These results suggest that dynamic and static facial aspects are processed via dissociable cortical pathways that begin in early visual cortex, a conclusion inconsistent with current models of face perception [6-9]. PMID:25131678

  17. Effect of Basic Residue on the Kinetics of Peptide Fragmentation Examined Using Surface-Induced Dissociation Combined with Resonant Ejection

    SciTech Connect

    Laskin, Julia

    2015-11-30

    In this work, resonant ejection coupled with surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer is used to examine fragmentation kinetics of two singly protonated hexapeptides, RYGGFL and KYGGFL, containing the basic arginine residue and less basic lysine residue at the N-terminus. The kinetics of individual reaction channels at different collision energies are probed by applying a short ejection pulse (1 ms) in resonance with the cyclotron frequency of a selected fragment ion and varying the delay time between ion-surface collision and resonant ejection while keeping total reaction delay time constant. Rice-Ramsperger-Kassel-Marcus (RRKM) modeling of the experimental data provides accurate threshold energies and activation entropies of individual reaction channels. Substitution of arginine with less basic lysine has a pronounced effect on the observed fragmentation kinetics of several pathways, including the b2 ion formation, but has little or no effect on formation of the b5+H2O fragment ion. The combination of resonant ejection SID, time- and collision energy-resolved SID, and RRKM modeling of both types of experimental data provides a detailed mechanistic understanding of the primary dissociation pathways of complex gaseous ions.

  18. Combined CASSCF and MR-CI study on photoinduced dissociation and isomerization of acryloyl chloride.

    PubMed

    Cui, Gang-Long; Li, Qian-Song; Zhang, Feng; Fang, Wei-Hai; Yu, Jian-Guo

    2006-10-26

    The potential energy surfaces of isomerization and dissociation reactions for CH2CHCOCl in the S0, T1, T2, and S1 states have been mapped with DFT, CASSCF, MP2, and MR-CI calculations. Rate constants for adiabatic and nonadiabatic processes have been calculated with the RRKM rate theory, in conjugation with the vibronic interaction method. Mechanistic photochemistry of CH2CHCOCl at 230-310 nm has been characterized through the computed potential energy surfaces and rate constants. Upon photoexcitation of CH2CHCOCl at 310 nm, the S1-->T1 intersystem crossing is the dominant primary process, which is followed by the 1,3-Cl migration along the T1 pathway. Meanwhile, the S1-->S0 internal conversion occurs with considerable probability and the subsequent trans-cis isomerization proceeds in the ground state. The C-Cl bond cleavage is an exclusive primary channel upon photoexcitation of gaseous CH2CHCOCl at 230 nm. The direct C-Cl bond cleavage is partially blocked by effects of the matrix, and the internal conversion from S1 to S0 becomes an important process for the excited molecule to deactivate in the condensed phase. The present calculations not only provide a reasonable explanation of the experimental findings, but also give new insight into the mechanistic photochemistry of CH2CHCOCl. PMID:17048815

  19. Combined use of ion mobility and collision-induced dissociation to investigate the opening of disulfide bridges by electron-transfer dissociation in peptides bearing two disulfide bonds.

    PubMed

    Massonnet, Philippe; Upert, Gregory; Smargiasso, Nicolas; Gilles, Nicolas; Quinton, Loïc; De Pauw, Edwin

    2015-01-01

    Disulfide bonds are post-translational modifications (PTMs) often found in peptides and proteins. They increase their stability toward enzymatic degradations and provide the structure and (consequently) the activity of such folded proteins. The characterization of disulfide patterns, i.e., the cysteine connectivity, is crucial to achieve a global picture of the active conformation of the protein of interest. Electron-transfer dissociation (ETD) constitutes a valuable tool to cleave the disulfide bonds in the gas phase, avoiding chemical reduction/alkylation in solution. To characterize the cysteine pairing, the present work proposes (i) to reduce by ETD one of the two disulfide bridges of model peptides, resulting in the opening of the cyclic structures, (ii) to separate the generated species by ion mobility, and (iii) to characterize the species using collision-induced dissociation (CID). Results of this strategy applied to several peptides show different behaviors depending on the connectivity. The loss of SH· radical species, observed for all the peptides, confirms the cleavage of the disulfides during the ETD process. PMID:25915795

  20. New Approach for Studying Slow Fragmentation Kinetics in FT-ICR: Surface-Induced Dissociation Combined with Resonant Ejection

    SciTech Connect

    Laskin, Julia; Futrell, Jean H.

    2015-02-01

    We introduce a new approach for studying the kinetics of large ion fragmentation in the gas phase by coupling surface-induced dissociation (SID) in a Fourier transform ion cyclotron resonance mass spectrometer with resonant ejection of selected fragment ions using a relatively short (5 ms) ejection pulse. The approach is demonstrated for singly protonated angiotensin III ions excited by collisions with a self-assembled monolayer of alkylthiol on gold (HSAM). The overall decomposition rate and rate constants of individual reaction channels are controlled by varying the kinetic energy of the precursor ion in a range of 65–95 eV. The kinetics of peptide fragmentation are probed by varying the delay time between resonant ejection and fragment ion detection at a constant total reaction time. RRKM modeling indicates that the shape of the kinetics plots is strongly affected by the shape and position of the energy deposition function (EDF) describing the internal energy distribution of the ion following ion-surface collision. Modeling of the kinetics data provides detailed information on the shape of the EDF and energy and entropy effects of individual reaction channels.

  1. Spondylopelvic dissociation.

    PubMed

    Sullivan, Matthew P; Smith, Harvey E; Schuster, James M; Donegan, Derek; Mehta, Samir; Ahn, Jaimo

    2014-01-01

    Spondylopelvic dissociation is a complex injury pattern resulting in multiplanar instability of the lumbopelvis. These injuries have traditionally been known as "suicide jumper's fractures" and have recently increased in prevalence as a result of under-vehicle explosions seen in the past decade of military conflicts in the Middle East. The hallmarks of spondylopelvic dissociation are bilateral vertical sacral fractures with a horizontal component, resulting in lumbosacral instability in the sagittal and axial planes. Surgical treatment has evolved greatly and both percutaneous and open options are available, with triangular osteosynthesis being the most relied on method of fixation. PMID:24267208

  2. Compound ES of cytochrome c peroxidase contains a Trp {pi}-cation radical. Characterization by CW and pulsed Q-band ENDOR spectroscopy

    SciTech Connect

    Huyett, J.E.; Doan, P.E.; Gurbiel, R.; Houseman, A.L.P.; Sivaraja, M.; Hoffman, B.M.; Goodin, D.B.

    1995-09-06

    The fully oxidized state of cytochrome c peroxidase (CcP), called ES, contains two oxidizing equivalents, one as an oxyferryl heme and the other as an organic radical on an amino acid residue. The unusual electron paramagnetic resonance spectrum of ES has been shown to be due to a weak distributed exchange coupling between the two paramagnetic redox centers. Various residues have been proposed as the radical site over the years. In this paper continuous wave and pulsed Q-band electron nuclear double resonance (ENDOR) spectroscopy confirms that the radical is located on Trp-191, as previously proposed. The paper completes the characterization of the active site of compound ES as being comprized of an oxyferryl heme coupled to the Trp-191 {pi}-cation radical by a weak spin exchange. 47 refs., 11 figs., 2 tabs.

  3. Dissociative disorders in DSM-5.

    PubMed

    Spiegel, David; Lewis-Fernández, Roberto; Lanius, Ruth; Vermetten, Eric; Simeon, Daphne; Friedman, Matthew

    2013-01-01

    The rationale, research literature, and proposed changes to the dissociative disorders and conversion disorder in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) are presented. Dissociative identity disorder will include reference to possession as well as identity fragmentation, to make the disorder more applicable to culturally diverse situations. Dissociative amnesia will include dissociative fugue as a subtype, since fugue is a rare disorder that always involves amnesia but does not always include confused wandering or loss of personality identity. Depersonalization disorder will include derealization as well, since the two often co-occur. A dissociative subtype of posttraumatic stress disorder (PTSD), defined by the presence of depersonalization or derealization in addition to other PTSD symptoms, is being recommended, based upon new epidemiological and neuroimaging evidence linking it to an early life history of adversity and a combination of frontal activation and limbic inhibition. Conversion disorder (functional neurological symptom disorder) will likely remain with the somatic symptom disorders, despite considerable dissociative comorbidity. PMID:23394228

  4. Dissociated Vertical Deviation

    MedlinePlus

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  5. Combined electron capture and infrared multiphoton dissociation for multistage MS/MS in a Fourier transform ion cyclotron resonance mass spectrometer.

    PubMed

    Håkansson, Kristina; Chalmers, Michael J; Quinn, John P; McFarland, Melinda A; Hendrickson, Christopher L; Marshall, Alan G

    2003-07-01

    We have mounted a permanent on-axis dispenser cathode electron source inside the magnet bore of a 9.4-T Fourier transform ion cyclotron resonance mass spectrometer. This configuration allows electron capture dissociation (ECD) to be performed reliably on a millisecond time scale. We have also implemented an off-axis laser geometry that enables simultaneous access to ECD and infrared multiphoton dissociation (IRMPD). Optimum performance of both fragmentation techniques is maintained. The analytical utility of performing either ECD or IRMPD on a given precursor ion population is demonstrated by structural characterization of several posttranslationally modified peptides: IRMPD of phosphorylated peptides results in few backbone (b- and y-type) cleavages, and product ion spectra are dominated by neutral loss of H3PO4. In contrast, ECD provides significantly more backbone (c- and z*-type) cleavages without loss of H3PO4. For N-glycosylated tryptic peptides, IRMPD causes extensive cleavage of the glycosidic bonds, providing structural information about the glycans. ECD cleaves all backbone bonds (except the N-terminal side of proline) in a 3-kDa glycopeptide with no saccharide loss. However, only a charge-reduced radical species and some side chain losses are observed following ECD of a 5-kDa glycopeptide from the same protein. An MS3 experiment involving IR laser irradiation of the charge-reduced species formed by electron capture results in extensive dissociation into c- and z-type fragment ions. Mass-selective external ion accumulation is essential for the structural characterization of these low-abundance (modified) peptides. PMID:12964777

  6. Tailored Noise Waveform/ Collision-Induced Dissociation of Ions Stored in a Linear Ion Trap Combined with Liquid Chromatography/Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

    SciTech Connect

    Vilkov, Andrey N.; Bogdanov, Bogdan; Pasa-Tolic, Liljiana; Prior, David C.; Anderson, Gordon A.; Masselon, Christophe D.; Moore, Ronald J.; Smith, Richard D.

    2004-11-01

    A new collision-induced dissociation (CID) technique based on broadband tailored noise waveform (TNW) excitation of ions stored in a linear ion trap has been developed. In comparison with the conventional sustained off-resonance irradiation (SORI) CID method commonly used in Fourier transform ion cyclotron resonance mass spectrometry, this MS/MS technique increases throughput by eliminating the long pump-down delay associated with gas introduction into the high vacuum ICR cell region. In addition, the TNW-CID method speeds spectrum acquisition since it does not require Fourier transformation, calculation of resonant frequencies and generation of the excitation waveforms. We demonstrate TNW-CID coupled with on-line capillary reverse phase liquid chromatography separations for identification of peptides. The experimental results are compared with data obtained using conventional quadrupole ion trap MS/MS and SORI-CID MS/MS in an ICR cell.

  7. Products of Dissociative Recombination in the Ionosphere

    NASA Technical Reports Server (NTRS)

    Cosby, Philip

    1996-01-01

    SRI International undertook a novel experimental measurement of the product states formed by dissociative ro-combination (DR) of C2(+), NO(+), and N2(+) as a function of both electron energy and reactant ion vibrational level. For these measurements we used a recently developed experimental technique for measuring dissociation product distributions that allows both the branching ratios to be accurately determined and the electronic and ro-vibrational state composition of the reactant ions to be specified. DR is the dominant electron loss mechanism in all regions of the ionosphere. In this process, electron attachment to the molecular ion produces an unstable neutral molecule that rapidly dissociates.

  8. Investigation of the Abstraction and Dissociation Mechanism in the Nitrogen Trifluoride Channels: Combined Post-Hartree-Fock and Transition State Theory Approaches.

    PubMed

    Claudino, D; Gargano, R; Carvalho-Silva, Valter H; E Silva, Geraldo M; da Cunha, W F

    2016-07-21

    The present paper concludes our series of kinetics studies on the reactions involved in the complex mechanism of nitrogen trifluoride decomposition. Two other related reactions that, along with this mechanism, take part in an efficient boron nitride growth process are also investigated. We report results concerning two abstraction reactions, namely NF2 + N ⇄ 2NF and NF3 + NF ⇄ 2NF2, and two dissociations, N2F4 ⇄ 2NF2 and N2F3 ⇄ NF2 + NF. State-of-the-art electronic structure calculations at the CCSD(T)/cc-pVTZ level of theory were considered to determine geometries and frequencies of reactants, products, and transition states. Extrapolation of the energies to the complete basis set limit was used to obtain energies of all the species. We applied transition state theory to compute thermal rate constants including Wigner, Eckart, Bell, and deformed theory corrections in order to take tunneling effects into account. The obtained results are in good agreement with the experimental data available in the literature and are expected to provide a better phenomenological understanding of the NF3 decomposition role in the boron nitride growth for a wide range of temperature values. PMID:27355487

  9. Imaging the molecular dynamics of dissociative electron attachment to water

    SciTech Connect

    Adaniya, Hidihito; Rudek, B.; Osipov, Timur; Haxton, Dan; Weber, Thorsten; Rescigno, Thomas N.; McCurdy, C.W.; Belkacem, Ali

    2009-10-19

    Momentum imaging experiments on dissociative electron attachment to the water molecule are combined with ab initio theoretical calculations of the angular dependence of the quantum mechanical amplitude for electron attachment to provide a detailed picture of the molecular dynamics of dissociation attachment via the two lowest energy Feshbach resonances. The combination of momentum imaging experiments and theory can reveal dissociation dynamics for which the axial recoil approximation breaks down and thus provides a powerful reaction microscope for DEA to polyatomics.

  10. A combined kick-out and dissociative diffusion mechanism of grown-in Be in InGaAs and InGaAsP. A new finite difference-Bairstow method for solution of the diffusion equations

    SciTech Connect

    Koumetz, Serge D. Martin, Patrick; Murray, Hugues

    2014-09-14

    Experimental results on the diffusion of grown-in beryllium (Be) in indium gallium arsenide (In{sub 0.53}Ga{sub 0.47}As) and indium gallium arsenide phosphide (In{sub 0.73}Ga{sub 0.27}As{sub 0.58}P{sub 0.42}) gas source molecular beam epitaxy alloys lattice-matched to indium phosphide (InP) can be successfully explained in terms of a combined kick-out and dissociative diffusion mechanism, involving neutral Be interstitials (Be{sub i}{sup 0}), singly positively charged gallium (Ga), indium (In) self-interstitials (I{sub III}{sup +}) and singly positively charged Ga, In vacancies (V{sub III}{sup +}). A new numerical method of solution to the system of diffusion equations, based on the finite difference approximations and Bairstow's method, is proposed.

  11. The dissociative bond.

    PubMed

    Gordon, Nirit

    2013-01-01

    Dissociation leaves a psychic void and a lingering sense of psychic absence. How do 2 people bond while they are both suffering from dissociation? The author explores the notion of a dissociative bond that occurs in the aftermath of trauma--a bond that holds at its core an understanding and shared detachment from the self. Such a bond is confined to unspoken terms that are established in the relational unconscious. The author proposes understanding the dissociative bond as a transitional space that may not lead to full integration of dissociated knowledge yet offers some healing. This is exemplified by R. Prince's (2009) clinical case study. A relational perspective is adopted, focusing on the intersubjective aspects of a dyadic relationship. In the dissociative bond, recognition of the need to experience mutual dissociation can accommodate a psychic state that yearns for relationship when the psyche cannot fully confront past wounds. Such a bond speaks to the need to reestablish a sense of human relatedness and connection when both parties in the relationship suffer from disconnection. This bond is bound to a silence that becomes both a means of protection against the horror of traumatic memory and a way to convey unspoken gestures toward the other. PMID:23282044

  12. Combined photoelectron, collision-induced dissociation, and computational studies of parent and fragment anions of N-paranitrophenylsulfonylalanine and N-paranitrophenylalanine

    SciTech Connect

    Lambert, Jason; Chen, Jing; Buonaugurio, Angela; Bowen, Kit H. E-mail: kbowen@jhu.edu; Do-Thanh, Chi-Linh; Wang, Yilin; Best, Michael D.; Compton, R. N. E-mail: kbowen@jhu.edu; Sommerfeld, Thomas

    2013-12-14

    After synthesizing the compounds N-paranitrophenylsulfonylalanine (NPNPSA) and N-paranitrophenylalanine (NPNPA), the photoelectron spectrum of the valence anion of N-paranitrophenylsulfonylalanine (NPNPSA){sup −}, was measured and the collision-induced dissociation (CID) pathways of deprotonated N-paranitrophenylsulfonylalanine (NPNPSA-H){sup −} and deprotonated N-paranitrophenylalanine (NPNPA-H){sup −} were determined. Pertinent calculations were conducted to analyze both sets of experimental data. From the valence anion photoelectron spectrum of (NPNPSA){sup −}, the adiabatic electron affinity (AEA) of NPNPSA was determined to be 1.7 ± 0.1 eV, while the vertical detachment energy (VDE) of (NPNPSA){sup −} was found to be 2.3 ± 0.1 eV. Calculations for four low lying conformers of (NPNPSA){sup −} gave AEA values in the range of 1.6–2.1 eV and VDE values in the range of 2.0–2.4 eV. These calculations are in very good agreement with the experimental values. While the NPNPA anion (NPNPSA){sup −} was not observed experimentally it was studied computationally. The six low lying (NPNPSA){sup −} conformers were identified and calculated to have AEA values in the range of 0.7–1.2 eV and VDE values in the range of 0.9–1.6 eV. CID was used to study the fragmentation patterns of deprotonated NPNPA and deprotonated NPNPSA. Based on the CID data and calculations, the excess charge was located on the delocalized π-orbitals of the nitrobenzene moiety. This is made evident by the fact that the dominant fragments all contained the nitrobenzene moiety even though the parent anions used for the CID study were formed via deprotonation of the carboxylic acid. The dipole-bound anions of both molecules are studied theoretically using the results of previous studies on nitrobenzene as a reference.

  13. Dissociation of diatomic gases

    NASA Technical Reports Server (NTRS)

    Hansen, C. F.

    1991-01-01

    The Landau-Zener theory of reactive cross sections has been applied to diatomic molecules dissociating from a ladder of rotational and vibrational states. Although the preexponential factor of the Arrhenius rate expression is shown to be a complex function of the dimensionless activation energy, the average over all states in the ladder is well represented by a single factor that varies about as T exp (-n), where the coefficient n is the order of unity. This relation agrees very well with experimental data for dissociation of O2 and N2, for example. The results validate previous empirical assignment of a single preexponential factor in the Arrhenius expression and justify the extrapolation of the expression well beyond the range of data. The theory is then used to calculate the effect of vibrational nonequilibrium on dissociation rate. For Morse oscillators the results are about the same as for harmonic oscillators, and the dissociation from a ladder of equilibrium rotational and nonequilibrium vibrational states is close to an analytic approximation provided by Hammerling, Kivel, and Teare for harmonic oscillators all dissociating from the ground rotational state.

  14. An unusual family of glycosylated peptides isolated from Dendroaspis angusticeps venom and characterized by combination of collision induced and electron transfer dissociation.

    PubMed

    Quinton, Loïc; Gilles, Nicolas; Smargiasso, Nicolas; Kiehne, Andrea; De Pauw, Edwin

    2011-11-01

    This study describes the structural characterization of a totally new family of peptides from the venom of the snake green mamba (Dendroaspis angusticeps). Interestingly, these peptides differ in several points from other already known mamba toxins. First of all, they exhibit very small molecular masses, ranging from 1.3 to 2.4 kDa. The molecular mass of classical mamba toxins is in the range of 7 to 25 kDa. Second, the new peptides do not contain disulfide bonds, a post-translational modification commonly encountered in animal toxins. The third difference is the very high proportion of proline residues in the sequence accounting for about one-third of the sequence. Finally, these new peptides reveal a carbohydrate moiety, indicating a glycosylation in the sequence. The last two features have made the structural characterization of the new peptides by mass spectrometry a real analytical challenge. Peptides were characterized by a combined use of MALDI- TOF/TOF and nanoESI-IT-ETD experiments to determine not only the peptide sequence but also the composition and the position of the carbohydrate moiety. Anyway, such small glycosylated and proline-rich toxins are totally different from any other known snake peptide and form, as a consequence, a new family of peptides. PMID:21952754

  15. Predicting pressure-dependent unimolecular rate constants using variational transition state theory with multidimensional tunneling combined with system-specific quantum RRK theory: a definitive test for fluoroform dissociation.

    PubMed

    Bao, Junwei Lucas; Zhang, Xin; Truhlar, Donald G

    2016-06-22

    Understanding the falloff in rate constants of gas-phase unimolecular reaction rate constants as the pressure is lowered is a fundamental problem in chemical kinetics, with practical importance for combustion, atmospheric chemistry, and essentially all gas-phase reaction mechanisms. In the present work, we use our recently developed system-specific quantum RRK theory, calibrated by canonical variational transition state theory with small-curvature tunneling, combined with the Lindemann-Hinshelwood mechanism, to model the dissociation reaction of fluoroform (CHF3), which provides a definitive test for falloff modeling. Our predicted pressure-dependent thermal rate constants are in excellent agreement with experimental values over a wide range of pressures and temperatures. The present validation of our methodology, which is able to include variational transition state effects, multidimensional tunneling based on the directly calculated potential energy surface along the tunneling path, and torsional and other vibrational anharmonicity, together with state-of-the-art reaction-path-based direct dynamics calculations, is important because the method is less empirical than models routinely used for generating full mechanisms, while also being simpler in key respects than full master equation treatments and the full reduced falloff curve and modified strong collision methods of Troe. PMID:27273734

  16. Dissociative Reactions to Incest.

    ERIC Educational Resources Information Center

    Hall, J. Mark

    In contrast to Freud's later and revised view of the etiology of hysterical, or dissociative, symptoms, it is now known that real, and not fantasized, sexual experiences in childhood are experienced in disociative symptomatology. It is useful to understand that incest involves both traumatic events, that is, incidents of sexual violation per se,…

  17. Dissociative Identity Disorder

    ERIC Educational Resources Information Center

    Schmidt, Tom

    2007-01-01

    Few psychological disorders in the Diagnostic Statistical Manual have generated as much controversy as Dissociative Identity Disorder (DID). For the past 35 years diagnoses of DID, previously referred to as Multiple Personality Disorder (MPD), have increased exponentially, causing various psychological researchers and clinicians to question the…

  18. Dissociation and psychosis in dissociative identity disorder and schizophrenia.

    PubMed

    Laddis, Andreas; Dell, Paul F

    2012-01-01

    Dissociative symptoms, first-rank symptoms of schizophrenia, and delusions were assessed in 40 schizophrenia patients and 40 dissociative identity disorder (DID) patients with the Multidimensional Inventory of Dissociation (MID). Schizophrenia patients were diagnosed with the Structured Clinical Interview for the DSM-IV Axis I Disorders; DID patients were diagnosed with the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised. DID patients obtained significantly (a) higher dissociation scores; (b) higher passive-influence scores (first-rank symptoms); and (c) higher scores on scales that measure child voices, angry voices, persecutory voices, voices arguing, and voices commenting. Schizophrenia patients obtained significantly higher delusion scores than did DID patients. What is odd is that the dissociation scores of schizophrenia patients were unrelated to their reports of childhood maltreatment. Multiple regression analyses indicated that 81% of the variance in DID patients' dissociation scores was predicted by the MID's Ego-Alien Experiences Scale, whereas 92% of the variance in schizophrenia patients' dissociation scores was predicted by the MID's Voices Scale. We propose that schizophrenia patients' responses to the MID do not index the same pathology as do the responses of DID patients. We argue that neither phenomenological definitions of dissociation nor the current generation of dissociation instruments (which are uniformly phenomenological in nature) can distinguish between the dissociative phenomena of DID and what we suspect are just the dissociation-like phenomena of schizophrenia. PMID:22651674

  19. Pathological Dissociation as Measured by the Child Dissociative Checklist

    ERIC Educational Resources Information Center

    Wherry, Jeffrey N.; Neil, Debra A.; Taylor, Tamara N.

    2009-01-01

    The component structure of the Child Dissociative Checklist was examined among abused children. A factor described as pathological dissociation emerged that was predicted by participants being male. There also were differences in pathological dissociation between groups of sexually abused and physically abused children. Replication of this factor…

  20. Traumatic dissociation as a predictor of posttraumatic stress disorder in South African female rape survivors.

    PubMed

    Nöthling, Jani; Lammers, Kees; Martin, Lindi; Seedat, Soraya

    2015-04-01

    Women survivors of rape are at an increased risk for posttraumatic stress disorder (PTSD). Traumatic dissociation has been identified as a precursor of PTSD. This study assessed the predictive potential of traumatic dissociation in PTSD and depression development.The study followed a longitudinal, prospective design. Ninety-seven female rape survivors were recruited from 2 clinics in Cape Town, South Africa. Clinical interviews and symptom status assessments of the participants were completed to measure dissociation, childhood traumas, resilience, depression, and PTSD.Traumatic dissociation was a significant predictor of PTSD and depression. The linear combination of prior dissociation, current dissociation, and resilience significantly explained 20.7% of the variance in PTSD. Dissociation mediated the relationship between resilience and PTSD.As traumatic dissociation significantly predicts PTSD, its early identification and management may reduce the risk of developing PTSD. Interventions focused on promoting resilience may also be successful in reducing the risk of dissociation following rape. PMID:25906104

  1. Traumatic Dissociation as a Predictor of Posttraumatic Stress Disorder in South African Female Rape Survivors

    PubMed Central

    Nöthling, Jani; Lammers, Kees; Martin, Lindi; Seedat, Soraya

    2015-01-01

    Abstract Women survivors of rape are at an increased risk for posttraumatic stress disorder (PTSD). Traumatic dissociation has been identified as a precursor of PTSD. This study assessed the predictive potential of traumatic dissociation in PTSD and depression development. The study followed a longitudinal, prospective design. Ninety-seven female rape survivors were recruited from 2 clinics in Cape Town, South Africa. Clinical interviews and symptom status assessments of the participants were completed to measure dissociation, childhood traumas, resilience, depression, and PTSD. Traumatic dissociation was a significant predictor of PTSD and depression. The linear combination of prior dissociation, current dissociation, and resilience significantly explained 20.7% of the variance in PTSD. Dissociation mediated the relationship between resilience and PTSD. As traumatic dissociation significantly predicts PTSD, its early identification and management may reduce the risk of developing PTSD. Interventions focused on promoting resilience may also be successful in reducing the risk of dissociation following rape. PMID:25906104

  2. Three dimensions of dissociative amnesia.

    PubMed

    Dell, Paul F

    2013-01-01

    Principal axis factor analysis with promax rotation extracted 3 factors from the 42 memory and amnesia items of the Multidimensional Inventory of Dissociation (MID) database (N = 2,569): Discovering Dissociated Actions, Lapses of Recent Memory and Skills, and Gaps in Remote Memory. The 3 factors' shared variance ranged from 36% to 64%. Construed as scales, the 3 factor scales had Cronbach's alpha coefficients of .96, .94, and .93, respectively. The scales correlated strongly with mean Dissociative Experiences Scale scores, mean MID scores, and total scores on the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised (SCID-D-R). What is interesting is that the 3 amnesia factors exhibited a range of correlations with SCID-D-R Amnesia scores (.52, .63, and .70, respectively), suggesting that the SCID-D-R Amnesia score emphasizes gaps in remote memory over amnesias related to dissociative identity disorder. The 3 amnesia factor scales exhibited a clinically meaningful pattern of significant differences among dissociative identity disorder, dissociative disorder not otherwise specified-1, dissociative amnesia, depersonalization disorder, and nonclinical participants. The 3 amnesia factors may have greater clinical utility for frontline clinicians than (a) amnesia as discussed in the context of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, nosology of the dissociative disorders or (b) P. Janet's (1893/1977 ) 4-fold classification of dissociative amnesia. The author recommends systematic study of the phenomenological differences within specific dissociative symptoms and their differential relationship to specific dissociative disorders. PMID:23282045

  3. Dissociation and psychotic symptoms.

    PubMed

    Steingard, S; Frankel, F H

    1985-08-01

    The literature on hysterical or brief reactive psychosis reflects great diversity both in clinical description and theoretical formulation. The authors describe the case of a 17-year-old girl who presented with a diagnosis of bipolar affective disorder, rapid cycling type, but who, in fact, was experiencing dissociative episodes manifested as psychotic states. The patient's successful treatment with hypnosis is described, along with the clinical and theoretical implications of the case. PMID:4025593

  4. Modeling the electron-impact dissociation of methane

    NASA Astrophysics Data System (ADS)

    Ziółkowski, Marcin; Vikár, Anna; Mayes, Maricris Lodriguito; Bencsura, Ákos; Lendvay, György; Schatz, George C.

    2012-12-01

    The product yield of the electron-impact dissociation of methane has been studied with a combination of three theoretical methods: R-matrix theory to determine the electronically inelastic collisional excitation cross sections, high-level electronic structure methods to determine excited states energies and derivative couplings, and trajectory surface hopping (TSH) calculations to determine branching in the dissociation of the methane excited states to give CH3, CH2, and CH. The calculations involve the lowest 24 excited-state potential surfaces of methane, up to the ionization energy. According to the R-matrix calculations, electron impact preferentially produces triplet excited states, especially for electron kinetic energies close to the dissociation threshold. The potential surfaces of excited states are characterized by numerous avoided and real crossings such that the TSH calculations show rapid cascading down to the lowest excited singlet or triplet states, and then slower the dissociation of these lowest states. Product branching for electron-impact dissociation was therefore estimated by combining the electron-impact excitation cross sections with TSH product branching ratios that were obtained from the lowest singlet and triplet states, with the singlet dissociation giving a comparable formation of CH2 and CH3 while triplet dissociation gives CH3 exclusively. The overall branching in electron-impact dissociation is dominated by CH3 over CH2. A small branching yield for CH is also predicted.

  5. Controllable dissociations of PH3 molecules on Si(001)

    NASA Astrophysics Data System (ADS)

    Liu, Qin; Lei, Yanhua; Shao, Xiji; Ming, Fangfei; Xu, Hu; Wang, Kedong; Xiao, Xudong

    2016-04-01

    We demonstrate for the first time to our knowledge that controllable dissociation of PH3 adsorption products PH x (x = 2, 1) can be realized by STM (scanning tunneling microscope) manipulation techniques at room temperature. Five dissociative products and their geometric structures are identified via combining STM experiments and first-principle calculations and simulations. In total we realize nine kinds of controllable dissociations by applying a voltage pulse among the PH3-related structures on Si(001). The dissociation rates of the five most common reactions are measured by the I-t spectrum method as a function of voltage. The suddenly increased dissociation rate at 3.3 V indicates a transition from multivibrational excitation to single-step excitation induced by inelastic tunneling electrons. Our studies prove that selectively breaking the chemical bonds of a single molecule on semiconductor surface by STM manipulation technique is feasible.

  6. Controllable dissociations of PH3 molecules on Si(001).

    PubMed

    Liu, Qin; Lei, Yanhua; Shao, Xiji; Ming, Fangfei; Xu, Hu; Wang, Kedong; Xiao, Xudong

    2016-04-01

    We demonstrate for the first time to our knowledge that controllable dissociation of PH3 adsorption products PHx (x = 2, 1) can be realized by STM (scanning tunneling microscope) manipulation techniques at room temperature. Five dissociative products and their geometric structures are identified via combining STM experiments and first-principle calculations and simulations. In total we realize nine kinds of controllable dissociations by applying a voltage pulse among the PH3-related structures on Si(001). The dissociation rates of the five most common reactions are measured by the I-t spectrum method as a function of voltage. The suddenly increased dissociation rate at 3.3 V indicates a transition from multivibrational excitation to single-step excitation induced by inelastic tunneling electrons. Our studies prove that selectively breaking the chemical bonds of a single molecule on semiconductor surface by STM manipulation technique is feasible. PMID:26894452

  7. Recurrent dissociative fugue.

    PubMed

    Mamarde, Abhishek; Navkhare, Praveen; Singam, Amrita; Kanoje, Akash

    2013-10-01

    Dissociative fugue is a rarely reported diagnostic entity. It is one of the least understood and yet clinically one of the most fascinating disorders in mental health. Here, we describe a case of fugue in a 32-year-old man who was brought to mental hospital with complete loss of memory for events pertaining to identity of self. This case illustrates the nature of presentation in hospital setting like mental hospital and effort taken to reintegrate his identity and reunite with his family. PMID:24379504

  8. THE DISSOCIATIVE TURN IN PSYCHOANALYSIS.

    PubMed

    Itzkowitz, Sheldon

    2015-06-01

    In his response to the Roundtable Discussions on what is effective in psychoanalytic psychotherapy, the author focuses on the renewed interest in the concept of dissociation that began to emerge toward the end of the 20th century. A contemporary psychoanalytic position informed by the impact of developmental trauma has led to an understanding of and interest in the dissociative mind. The actuality of trauma during infancy and early childhood is recognized as a key factor leading to the emergence of dissociative processes, the potential dissociative structuring of the mind, and mind being characterized by multiple, discontinuous, centers of consciousness. The therapeutic goal in the psychoanalytic work with fragmented patients is to establish communication and understanding between the dissociated self-states. The author offers two brief clinical examples of working with dissociated self-states. PMID:26177756

  9. Dissociative Electron Attachment

    NASA Astrophysics Data System (ADS)

    Arreola, Esmeralda; Esmeralda Arreola Collaboration; Leigh Hargreaves Collaboration

    Since the pioneering work of Boudiaffa et al., it has been understood that electrons, even with energies near or below the ionization threshold, are capable of initiating strand-breaks in human DNA. This discovery raised important questions for cancer treatments, since sub-ionizing electrons are known to be the most copiously produced secondary product of radiation therapy. But even to date these factors are largely excluded from dosimetry calculations. This lack of inclusion is, at least in part, certainly due to the dearth of fundamental data describing low-energy electron interactions with nucleotide molecules that form the basis of DNA. Understanding of how such slow electrons are able to damage DNA remains incomplete, but the strongly peaked nature of Boudiaffa et al.'s data gives strong hints at resonantly driven collision processes. DNA damage is therefore most likely driven by ``dissociative electron attachment'' (DEA). DEA is a rather complicated process to model due to the coupling of electronic and nuclear degrees of freedom in the molecule. At the California State University Fullerton, we are currently commissioning a new spectrometer to study dissociation channels, reaction rates and orientation effects in DEA collisions between slow electrons and nucleotide molecules. At the meeting we will present design parameters and commissioning data for this new apparatus.

  10. Dynamics of dissociative electron attachment to ammonia

    NASA Astrophysics Data System (ADS)

    Rescigno, T. N.; Trevisan, C. S.; Orel, A. E.; Slaughter, D. S.; Adaniya, H.; Belkacem, A.; Weyland, Marvin; Dorn, Alexander; McCurdy, C. W.

    2016-05-01

    Ab initio theoretical studies and momentum-imaging experiments are combined to provide a consistent picture of the dynamics of dissociative electron attachment to ammonia through its 5.5- and 10.5-eV resonance channels. The present study clarifies the character and symmetry of the anion states involved and the dynamics that leads to the observed fragment-ion channels, their branching ratios, and angular distributions.

  11. Hyperglycemia associated dissociative fugue (organic dissociative disorder) in an elderly

    PubMed Central

    Ram, Dushad; Ashoka, H. G; Gowdappa, Basavnna

    2015-01-01

    Inadequate glycemic control in patients with diabetes is known to be associated with psychiatric disorders such as depression, anxiety disorder, and cognitive impairment. However, dissociative syndrome has not been reported so far. Here we are reporting a case of repeated dissociative fugue associated with hyperglycemia, in an elderly with type II diabetes. Possible neurobiological mechanism has been discussed. PMID:26286620

  12. Dissociative States and Neural Complexity

    ERIC Educational Resources Information Center

    Bob, Petr; Svetlak, Miroslav

    2011-01-01

    Recent findings indicate that neural mechanisms of consciousness are related to integration of distributed neural assemblies. This neural integration is particularly vulnerable to past stressful experiences that can lead to disintegration and dissociation of consciousness. These findings suggest that dissociation could be described as a level of…

  13. Orientation-dependent dissociative charge transfer

    SciTech Connect

    Wu, W.; Prior, M.H.; Braeuning, H.

    1998-01-01

    Recoil-ion momentum spectroscopy and molecular fragment imaging techniques are combined to study dissociative electron capture from He by HeH{sup +} at 0.20-a.u. collision velocity. Groups of final HeH states which dissociate to ground or excited H and He atoms are separated. For each group, the experiment provides two-dimensional H fragment distributions with respect to the collision plane and for fixed transverse momentum transfer. These patterns show that the capture probability is highest for HeH{sup +} ions with their axis oriented normal to the scattering plane for two of the three groups populated. {copyright} {ital 1998} {ital The American Physical Society}

  14. Dissociation of I II in chemical oxygen-iodine lasers: experiment, modeling, and pre-dissociation by electrical discharge

    NASA Astrophysics Data System (ADS)

    Katz, A.; Waichman, K.; Dahan, Z.; Rybalkin, V.; Barmashenko, B. D.; Rosenwaks, S.

    2007-06-01

    The dissociation of I II molecules at the optical axis of a supersonic chemical oxygen-iodine laser (COIL) was studied via detailed measurements and three dimensional computational fluid dynamics calculations. Comparing the measurements and the calculations enabled critical examination of previously proposed dissociation mechanisms and suggestion of a mechanism consistent with the experimental and theoretical results obtained in a supersonic COIL for the gain, temperature and I II dissociation fraction at the optical axis. The suggested mechanism combines the recent scheme of Azyazov and Heaven (AIAA J. 44, 1593 (2006)), where I II(A' 3Π 2u), I II(A 3Π 1u) and O II(a1Δ g, v) are significant dissociation intermediates, with the "standard" chain branching mechanism of Heidner et al. (J. Phys. Chem. 87, 2348 (1983)), involving I(2P 1/2) and I II(X1Σ + g, v). In addition, we examined a new method for enhancement of the gain and power in a COIL by applying DC corona/glow discharge in the transonic section of the secondary flow in the supersonic nozzle, dissociating I II prior to its mixing with O II(1Δ). The loss of O II(1Δ) consumed for dissociation was thus reduced and the consequent dissociation rate downstream of the discharge increased, resulting in up to 80% power enhancement. The implication of this method for COILs operating beyond the specific conditions reported here is assessed.

  15. Dissociative absorption: An empirically unique, clinically relevant, dissociative factor.

    PubMed

    Soffer-Dudek, Nirit; Lassri, Dana; Soffer-Dudek, Nir; Shahar, Golan

    2015-11-01

    Research of dissociative absorption has raised two questions: (a) Is absorption a unique dissociative factor within a three-factor structure, or a part of one general dissociative factor? Even when three factors are found, the specificity of the absorption factor is questionable. (b) Is absorption implicated in psychopathology? Although commonly viewed as "non-clinical" dissociation, absorption was recently hypothesized to be specifically associated with obsessive-compulsive symptoms. To address these questions, we conducted exploratory and confirmatory factor analyses on 679 undergraduates. Analyses supported the three-factor model, and a "purified" absorption scale was extracted from the original inclusive absorption factor. The purified scale predicted several psychopathology scales. As hypothesized, absorption was a stronger predictor of obsessive-compulsive symptoms than of general psychopathology. In addition, absorption was the only dissociative scale that longitudinally predicted obsessive-compulsive symptoms. We conclude that absorption is a unique and clinically relevant dissociative tendency that is particularly meaningful to obsessive-compulsive symptoms. PMID:26241024

  16. Recurrent Episodes of Dissociative Fugue

    PubMed Central

    Angothu, Hareesh; Pabbathi, Lokeswar Reddy

    2016-01-01

    Dissociative fugue is rare entity to encounter with possible differentials of epilepsy and malingering. It is one of the dissociative disorders rarely seen in clinical practice more often because of the short lasting nature of this condition. This might also be because of organized travel of the individuals during the episodes and return to their families after the recovery from episodes. This is a case description of a patient who has experienced total three episodes of dissociative fugue. The patient has presented during the third episode and two prior episodes were diagnosed as fugue episodes retrospectively based on the history. Planned travel in this case by the patient to a distant location was prevented because of early diagnosis and constant vigilance till the recovery. As in this case, it may be more likely that persons with Dissociative fugue may develop similar episodes if they encounter exceptional perceived stress. However, such conclusions may require follow-up studies. PMID:27114633

  17. Global functioning and disability in dissociative disorders.

    PubMed

    Mueller-Pfeiffer, Christoph; Rufibach, Kaspar; Perron, Noelle; Wyss, Daniela; Kuenzler, Cornelia; Prezewowsky, Cornelia; Pitman, Roger K; Rufer, Michael

    2012-12-30

    Dissociative disorders are frequent comorbid conditions of other mental disorders. Yet, there is controversy about their clinical relevance, and little systematic research has been done on how they influence global functioning. Outpatients and day care patients (N=160) of several psychiatric units in Switzerland were assessed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV Axis I Disorders, Structured Clinical Interview for DSM-IV Dissociative Disorders, Global Assessment of Functioning Scale, and World Health Organization Disability Assessment Schedule-II. The association between subjects with a dissociative disorder (N=30) and functional impairment after accounting for non-dissociative axis I disorders was evaluated by linear regression models. We found a proportion of 18.8% dissociative disorders (dissociative amnesia=0%, dissociative fugue=0.6%, depersonalization disorder=4.4%, dissociative identity disorder=7.5%, dissociative disorder-not-otherwise-specified=6.3%) across treatment settings. Adjusted for other axis I disorders, subjects with a comorbid dissociative identity disorder or dissociative disorder-not-otherwise-specified had a median global assessment of functioning score that was 0.86 and 0.88 times, respectively, the score of subjects without a comorbid dissociative disorder. These findings support the hypothesis that complex dissociative disorders, i.e., dissociative identity disorder and dissociative disorder-not-otherwise-specified, contribute to functional impairment above and beyond the impact of co-existing non-dissociative axis I disorders, and that they qualify as "serious mental illness". PMID:22578820

  18. LBBB with History of Complete Atrioventricular Dissociation Underwent Bipolar Hemiarthroplasty

    PubMed Central

    Kumar, Indirani H

    2016-01-01

    A 70-year-old female patient, known case of hypertension and incomplete Left bundle branch block (LBBB), posted for bipolar hemiarthroplasty. A geriatric patient with LBBB and systemic hypertension is a fatal combination; it may precipitate into complete AV dissociation during anaesthesia and surgical stress. We are reporting this interesting case as our patient had developed complete Atrioventricular (AV) dissociation when scheduled earlier for surgery and got postponed. We had given combined spinal epidural anaesthesia and managed successfully without any complication. PMID:27504385

  19. Dissociative experiences and dissociative minds: Exploring a nomological network of dissociative functioning.

    PubMed

    Schimmenti, Adriano

    2016-01-01

    In this study, the psychometric properties of the Dissociative Experiences Scale-II (DES-II) were tested in a sample of Italian adults, and a nomological network of dissociative functioning based on current psychodynamic research was examined. A total of 794 participants (55% females) ranging in age from 18 to 64 completed the DES-II and other measures of theory of mind, alexithymia, attachment style, and empathy. The Italian translation of the DES-II showed high internal consistency, adequate item-to-scale homogeneity, and good split-half reliability. A single-factor solution including the 8 items of pathological dissociation (DES-T) adequately fit the data. Participants who reported higher levels of dissociative experiences showed significantly lower scores on theory of mind and empathy than other participants. They also showed significantly higher scores on alexithymia, preoccupied attachment, and fearful attachment. Results of the study support the view that people who suffer from severe dissociative experiences may also have difficulties mentalizing and regulating affects and that they may feel uncomfortable in close relationships because they have a negative view of the self. This can inform clinical work with dissociative individuals, who could benefit from therapies that consider their potential problems with mentalization, empathy, affect regulation, and attachment. PMID:26507547

  20. Dissociative symptomatology in cancer patients

    PubMed Central

    Civilotti, Cristina; Castelli, Lorys; Binaschi, Luca; Cussino, Martina; Tesio, Valentina; Di Fini, Giulia; Veglia, Fabio; Torta, Riccardo

    2015-01-01

    Introduction: The utilization of the post-traumatic stress disorder (PTSD) diagnostic spectrum is currently being debated to categorize psychological adjustment in cancer patients. The aims of this study were to: (1) evaluate the presence of cancer-related traumatic dissociative symptomatology in a sample of cancer patients; (2) examine the correlation of cancer-related dissociation and sociodemographic and medical variables, anxiety, depression, and post-traumatic stress symptomatology; (3) investigate the predictors of cancer-related dissociation. Methods: Ninety-two mixed cancer patients (mean age: 58.94, ds = 10.13) recruited from two hospitals in northern Italy were administered a questionnaire on sociodemographic and medical characteristics, the Karnofsky Scale to measure the level of patient activity and medical care requirements, the Hospital Anxiety and Depression Scale (HADS) to evaluate the presence of anxiety and depression, the Impact of Event Scale Revised (IES-R) to assess the severity of intrusion, avoidance, and hypervigilance, and the Peritraumatic Dissociative Experiences Questionnaire (PDEQ) to quantify the traumatic dissociative symptomatology. Results: 31.5% of participants report a PDEQ score above the cutoff. The results indicated that dissociative symptomatology was positively correlated with HADS scores (HADS-Anxiety: r = 0.476, p < 0.001; HADS-Depression: r = 0.364, p < 0.001) and with IES-R scores (IES-R-Intrusion: r = 0.698, p < 0.001; IES-R-Avoidance: r = 0.619, p < 0.001; IES-R- Hypervigilance: r = 0.681, p < 0.001). A stepwise regression analysis was performed in order to find the predictors of cancer-related traumatic dissociative symptomatology. The results converged on a three predictor model revealing that IES-R-Intrusion, IES-R-Avoidance, and IES-R-Hyperarousal accounted for 53.9% of the explained variance. Conclusion: These findings allow us to hypothesize a specific psychological reaction which may be ascribed to the traumatic

  1. Diffraction dissociation at the LHC

    NASA Astrophysics Data System (ADS)

    Jenkovszky, László; Orava, Risto; Salii, Andrii

    2013-04-01

    We report on recent calculations of low missing mass single (SD) and double (DD) diffractive dissociation at LHC energies. The calculations are based on a dual-Regge model, dominated by a single Pomeron exchange. The diffractively excited states lie on the nucleon trajectory N*, appended by the isolated Roper resonance. Detailed predictions for the squared momentum transfer and missing mass dependence of the differential and integrated single-and double diffraction dissociation in the kinematical range of present and future LHC measurements are given.

  2. Diffraction dissociation at the LHC

    SciTech Connect

    Jenkovszky, Laszlo; Orava, Risto; Salii, Andrii

    2013-04-15

    We report on recent calculations of low missing mass single (SD) and double (DD) diffractive dissociation at LHC energies. The calculations are based on a dual-Regge model, dominated by a single Pomeron exchange. The diffractively excited states lie on the nucleon trajectory N*, appended by the isolated Roper resonance. Detailed predictions for the squared momentum transfer and missing mass dependence of the differential and integrated single-and double diffraction dissociation in the kinematical range of present and future LHC measurements are given.

  3. Dissociation of pleasure in psychopathology.

    PubMed

    Brown, S L

    1981-01-01

    This paper analyzes the development of the concept of dissociation from 19th century psychological theory through 20th century neurophysiological thought. Recent research is discussed, indicating that normal individuals show an "association" between emitted pleasurable behavior and self-perception of pleasurable activity, whereas depressives and schizophrenics show a lack of association, or "dissociation," between these measures. concomitantly, depressives show an abnormal degree of association between the experience and expression of negative affect. Such a discrepancy in systems of affect is considered as both an important pathological element in mental disorder and also as a valuable new research tool for studying etiology, differential diagnosis, and therapeutic efficacy in psychobiological illness. PMID:7005394

  4. Dissociative Electron Attachment to Carbon Dioxide via the 8.2 eV Feshbach resonance

    SciTech Connect

    Slaughter, Dan; Adaniya, Hidihito; Rescigno, Tom; Haxton, Dan; Orel, Ann; McCurdy, Bill; Belkacem, Ali

    2011-08-17

    Momentum imaging experiments on dissociative electron attachment (DEA) to CO{sub 2} are combined with the results of ab initio calculations to provide a detailed and consistent picture of the dissociation dynamics through the 8.2 eV resonance, which is the major channel for DEA in CO{sub 2}. The present study resolves several puzzling misconceptions about this system.

  5. [Gender differences in dissociative disorders].

    PubMed

    Spitzer, C; Freyberger, H J

    2008-01-01

    The relationship between mental illness, on the one hand, and sex and gender, on the other hand, has received interest since the beginning of medicine in antique times. A prototypical example of a seemingly woman-specific disease is hysteria. The term itself, which is derived from the Greek word for womb, denotes a psychosexual dimension comprising the current attitude towards sexuality and the dominating gender relationship. In addition, the colourful history of hysteria indicates that illness is not exclusively determined by biological factors, but also significantly by socio-cultural influences, for example in the treatment of hysterical women. Even nowadays, there is a wide-spread belief that dissociative symptoms and disorders, which have succeeded hysteria in current classification systems, are predominantly seen in women. However, empirical studies in the general population and in different clinical samples using sound instruments have indicated that dissociative symptoms do not differ between the genders. The seemingly dominance of dissociative disorders in women may also depend on the socio-cultural context, because men with dissociative disorders usually do not enter the general health system, but rather the legal system, i.e. they can be found in jail or forensic institutions. PMID:18185968

  6. Electron Transfer Dissociation Mass Spectrometry of Hemoglobin on Clinical Samples

    NASA Astrophysics Data System (ADS)

    Coelho Graça, Didia; Lescuyer, Pierre; Clerici, Lorella; Tsybin, Yury O.; Hartmer, Ralf; Meyer, Markus; Samii, Kaveh; Hochstrasser, Denis F.; Scherl, Alexander

    2012-10-01

    A mass spectrometry-based assay combining the specificity of selected reaction monitoring and the protein ion activation capabilities of electron transfer dissociation was developed and employed for the rapid identification of hemoglobin variants from whole blood without previous proteolytic cleavage. The analysis was performed in a robust ion trap mass spectrometer operating at nominal mass accuracy and resolution. Subtle differences in globin sequences, resulting with mass shifts of about one Da, can be unambiguously identified. These results suggest that mass spectrometry analysis of entire proteins using electron transfer dissociation can be employed on clinical samples in a workflow compatible with diagnostic applications.

  7. The return of dissociation as absence within absence.

    PubMed

    Gurevich, Hayuta

    2014-12-01

    My aim is to translate Ferenczi's central concepts of the intrapsychic impact and imprint of early developmental trauma into both revived and contemporary conceptualizations. The concept of dissociation was renounced by Freud, yet it is returning as a cornerstone of recent trauma theories. Ferenczi used the concept of "repression," but used it in the sense of an intrapsychic imprint of early external trauma that fragments consciousness, that is, as dissociation. Furthermore, early trauma is double: an absence of protection that threatens existence of the self, combined with an absence of attachment and of recognition of this threat and terror; thus it is an absence-within-absence. This contemporary conceptualization entails a widening of the intrapsychic realm to include an intersubjective one, and regards dissociation as a unique and complex intrapsychic absence, which is a negative of the external absence-within-absence in the early environment. PMID:25434884

  8. Does the tautomeric status of the adenine bases change upon the dissociation of the A*·A(syn) Topal-Fresco DNA mismatch? A combined QM and QTAIM atomistic insight.

    PubMed

    Brovarets', Ol'ha O; Zhurakivsky, Roman O; Hovorun, Dmytro M

    2014-02-28

    We have scrupulously explored the tautomerisation mechanism via the double proton transfer of the A*·A(syn) Topal-Fresco base mispair (C(s) symmetry), formed by the imino and amino tautomers of the adenine DNA base in the anti- and syn-conformations, respectively, bridging quantum-mechanical calculations with Bader's quantum theory of atoms in molecules. It was found that the A*·A(syn) ↔ A·A*(syn) tautomerisation is the asynchronous concerted process. It was established that the A*·A(syn) DNA mismatch is stabilized by the N6H···N6 (6.35) and N1H···N7 (6.17) hydrogen (H) bonds, whereas the A·A*(syn) base mispair (Cs) by the N6H···N6 (8.82) and N7H···N1 (9.78) H-bonds and the C8H···HC2 HH-bond (0.30 kcal mol(-1)). Using the sweeps of the energies of the intermolecular H-bonds, it was observed that the N6H···N6 and N1H···N7/N7H···N1 H-bonds are anti-cooperative and mutually weaken each other in the A*·A(syn) and A·A*(syn) mispairs. It was revealed that the A·A*(syn) DNA mismatch is a dynamically unstable structure with a short lifetime of 1.12 × 10(-13) s and any of its 6 low-frequency intermolecular vibrations can develop during this period of time. This observation makes it impossible to change the tautomeric status of the A bases upon the dissociation of the A*·A(syn) base mispair into the monomers during DNA replication. PMID:24418908

  9. Two-temperature models for nitrogen dissociation

    NASA Astrophysics Data System (ADS)

    da Silva, M. Lino; Guerra, V.; Loureiro, J.

    2007-12-01

    Accurate sets of nitrogen state-resolved dissociation rates have been reduced to two-temperature (translational T and vibrational Tv) dissociation rates. The analysis of such two-temperature dissociation rates shows evidence of two different dissociation behaviors. For Tv < 0.3 T dissociation proceeds predominantly from the lower-lying vibrational levels, whereas for Tv > 0.3 T dissociation proceeds predominantly form the near-dissociative vibrational levels, with an abrupt change of behavior at Tv = 0.3 T. These two-temperature sets have then been utilized as a benchmark for the comparison against popular multitemperature dissociation models (Park, Hansen, Marrone-Treanor, Hammerling, Losev-Shatalov, Gordiets, Kuznetsov, and Macheret-Fridman). This has allowed verifying the accuracy of each theoretical model, and additionally proposing adequate values for any semi-empirical parameters present in the different theories. The Macheret-Fridman model, who acknowledges the existence of the two aforementioned dissociation regimes, has been found to provide significantly more accurate results than the other models. Although these different theoretical approaches have been tested and validated solely for nitrogen dissociation processes, it is reasonable to expect that the general conclusions of this work, regarding the adequacy of the different dissociation models, could be extended to the description of arbitrary diatomic dissociation processes.

  10. Study of the dissociation of molecular hydrogen

    NASA Technical Reports Server (NTRS)

    Vessot, R. F. C.

    1981-01-01

    Dissociators used to obtain an RF plasma discharge for hydrogen masers and the test system used for operation and evaluation of the dissociators are described. A compact sorption cartridge using a graphite matrix is tested as part of a hydrogen scavenging system. Testing of a vacuum enclosed hydrogen dissociator suitable for long term operation in space is described.

  11. Mechanical Dissociation of Retinal Neurons with Vibration

    NASA Astrophysics Data System (ADS)

    Motomura, Tamami; Hayashida, Yuki; Murayama, Nobuki

    The neuromorphic device, which implements the functions of biological neural circuits by means of VLSI technology, has been collecting much attention in the engineering fields in the last decade. Concurrently, progress in neuroscience research has revealed the nonlinear computation in single neuron levels, suggesting that individual neurons are not merely the circuit elements but computational units. Thus, elucidating the properties of neuronal signal processing is thought to be an essential step for developing the next generation of neuromorphic devices. In the present study, we developed a method for dissociating single neurons from specific sublayers of mammalian retinas with using no proteolytic enzymes but rather combining tissue incubation in a low-Ca2+ medium and the vibro-dissociation technique developed for the slices of brains and spinal cords previously. Our method took shorter time of the procedure, and required less elaborated skill, than the conventional enzymatic method did; nevertheless it yielded enough number of the cells available for acute electrophysiological experiments. The isolated retinal neurons were useful for measuring the nonlinear membrane conductances as well as the spike firing properties under the perforated-patch whole-cell configuration. These neurons also enabled us to examine the effects of proteolytic enzymes on the membrane excitability in those cells.

  12. Photoleucine Survives Backbone Cleavage by Electron Transfer Dissociation. A Near-UV Photodissociation and Infrared Multiphoton Dissociation Action Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Shaffer, Christopher J.; Martens, Jonathan; Marek, Aleš; Oomens, Jos; Tureček, František

    2016-04-01

    We report a combined experimental and computational study aimed at elucidating the structure of N-terminal fragment ions of the c type produced by electron transfer dissociation of photo-leucine (L*) peptide ions GL*GGKX. The c 4 ion from GL*GGK is found to retain an intact diazirine ring that undergoes selective photodissociation at 355 nm, followed by backbone cleavage. Infrared multiphoton dissociation action spectra point to the absence in the c 4 ion of a diazoalkane group that could be produced by thermal isomerization of vibrationally hot ions. The c 4 ion from ETD of GL*GGK is assigned an amide structure by a close match of the IRMPD action spectrum and calculated IR absorption. The energetics and kinetics of c 4 ion dissociations are discussed.

  13. Photoleucine Survives Backbone Cleavage by Electron Transfer Dissociation. A Near-UV Photodissociation and Infrared Multiphoton Dissociation Action Spectroscopy Study.

    PubMed

    Shaffer, Christopher J; Martens, Jonathan; Marek, Aleš; Oomens, Jos; Tureček, František

    2016-07-01

    We report a combined experimental and computational study aimed at elucidating the structure of N-terminal fragment ions of the c type produced by electron transfer dissociation of photo-leucine (L*) peptide ions GL*GGKX. The c 4 ion from GL*GGK is found to retain an intact diazirine ring that undergoes selective photodissociation at 355 nm, followed by backbone cleavage. Infrared multiphoton dissociation action spectra point to the absence in the c 4 ion of a diazoalkane group that could be produced by thermal isomerization of vibrationally hot ions. The c 4 ion from ETD of GL*GGK is assigned an amide structure by a close match of the IRMPD action spectrum and calculated IR absorption. The energetics and kinetics of c 4 ion dissociations are discussed. Graphical Abstract ᅟ. PMID:27059977

  14. Photoleucine Survives Backbone Cleavage by Electron Transfer Dissociation. A Near-UV Photodissociation and Infrared Multiphoton Dissociation Action Spectroscopy Study

    NASA Astrophysics Data System (ADS)

    Shaffer, Christopher J.; Martens, Jonathan; Marek, Aleš; Oomens, Jos; Tureček, František

    2016-07-01

    We report a combined experimental and computational study aimed at elucidating the structure of N-terminal fragment ions of the c type produced by electron transfer dissociation of photo-leucine (L*) peptide ions GL*GGKX. The c 4 ion from GL*GGK is found to retain an intact diazirine ring that undergoes selective photodissociation at 355 nm, followed by backbone cleavage. Infrared multiphoton dissociation action spectra point to the absence in the c 4 ion of a diazoalkane group that could be produced by thermal isomerization of vibrationally hot ions. The c 4 ion from ETD of GL*GGK is assigned an amide structure by a close match of the IRMPD action spectrum and calculated IR absorption. The energetics and kinetics of c 4 ion dissociations are discussed.

  15. Coupling capillary zone electrophoresis with electron transfer dissociation and activated ion electron transfer dissociation for top-down proteomics.

    PubMed

    Zhao, Yimeng; Riley, Nicholas M; Sun, Liangliang; Hebert, Alexander S; Yan, Xiaojing; Westphall, Michael S; Rush, Matthew J P; Zhu, Guijie; Champion, Matthew M; Mba Medie, Felix; Champion, Patricia A DiGiuseppe; Coon, Joshua J; Dovichi, Norman J

    2015-01-01

    Top-down proteomics offers the potential for full protein characterization, but many challenges remain for this approach, including efficient protein separations and effective fragmentation of intact proteins. Capillary zone electrophoresis (CZE) has shown great potential for separation of intact proteins, especially for differentially modified proteoforms of the same gene product. To date, however, CZE has been used only with collision-based fragmentation methods. Here we report the first implementation of electron transfer dissociation (ETD) with online CZE separations for top-down proteomics, analyzing a mixture of four standard proteins and a complex protein mixture from the Mycobacterium marinum bacterial secretome. Using a multipurpose dissociation cell on an Orbitrap Elite system, we demonstrate that CZE is fully compatible with ETD as well as higher energy collisional dissociation (HCD), and that the two complementary fragmentation methods can be used in tandem on the electrophoretic time scale for improved protein characterization. Furthermore, we show that activated ion electron transfer dissociation (AI-ETD), a recently introduced method for enhanced ETD fragmentation, provides useful performance with CZE separations to greatly increase protein characterization. When combined with HCD, AI-ETD improved the protein sequence coverage by more than 200% for proteins from both standard and complex mixtures, highlighting the benefits electron-driven dissociation methods can add to CZE separations. PMID:25893372

  16. Coulomb dissociation of N,2120

    NASA Astrophysics Data System (ADS)

    Röder, Marko; Adachi, Tatsuya; Aksyutina, Yulia; Alcantara, Juan; Altstadt, Sebastian; Alvarez-Pol, Hector; Ashwood, Nicholas; Atar, Leyla; Aumann, Thomas; Avdeichikov, Vladimir; Barr, M.; Beceiro, Saul; Bemmerer, Daniel; Benlliure, Jose; Bertulani, Carlos; Boretzky, Konstanze; Borge, Maria J. G.; Burgunder, G.; Caamaño, Manuel; Caesar, Christoph; Casarejos, Enrique; Catford, Wilton; Cederkäll, Joakim; Chakraborty, S.; Chartier, Marielle; Chulkov, Leonid; Cortina-Gil, Dolores; Crespo, Raquel; Datta Pramanik, Ushasi; Diaz-Fernandez, Paloma; Dillmann, Iris; Elekes, Zoltan; Enders, Joachim; Ershova, Olga; Estrade, A.; Farinon, F.; Fraile, Luis M.; Freer, Martin; Freudenberger, M.; Fynbo, Hans; Galaviz, Daniel; Geissel, Hans; Gernhäuser, Roman; Göbel, Kathrin; Golubev, Pavel; Gonzalez Diaz, D.; Hagdahl, Julius; Heftrich, Tanja; Heil, Michael; Heine, Marcel; Heinz, Andreas; Henriques, Ana; Holl, Matthias; Ickert, G.; Ignatov, Alexander; Jakobsson, Bo; Johansson, Hâkan; Jonson, Björn; Kalantar-Nayestanaki, Nasser; Kanungo, Rituparna; Kelic-Heil, Aleksandra; Knöbel, Ronja; Kröll, Thorsten; Krücken, Reiner; Kurcewicz, J.; Kurz, Nikolaus; Labiche, Marc; Langer, Christoph; Le Bleis, Tudi; Lemmon, Roy; Lepyoshkina, Olga; Lindberg, Simon; Machado, Jorge; Marganiec, Justyna; Mostazo Caro, Magdalena; Movsesyan, Alina; Najafi, Mohammad Ali; Nilsson, Thomas; Nociforo, Chiara; Panin, Valerii; Paschalis, Stefanos; Perea, Angel; Petri, Marina; Pietri, S.; Plag, Ralf; Prochazka, A.; Rahaman, Md. Anisur; Rastrepina, Ganna; Reifarth, Rene; Ribeiro, Guillermo; Ricciardi, M. Valentina; Rigollet, Catherine; Riisager, Karsten; Rossi, Dominic; Sanchez del Rio Saez, Jose; Savran, Deniz; Scheit, Heiko; Simon, Haik; Sorlin, Olivier; Stoica, V.; Streicher, Branislav; Taylor, Jon; Tengblad, Olof; Terashima, Satoru; Thies, Ronja; Togano, Yasuhiro; Uberseder, Ethan; Van de Walle, J.; Velho, Paulo; Volkov, Vasily; Wagner, Andreas; Wamers, Felix; Weick, Helmut; Weigand, Mario; Wheldon, Carl; Wilson, G.; Wimmer, Christine; Winfield, J. S.; Woods, Philip; Yakorev, Dmitry; Zhukov, Mikhail; Zilges, Andreas; Zuber, Kai; R3B Collaboration

    2016-06-01

    Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N,2120 are reported. Relativistic N,2120 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19N (n ,γ )20N and 20N (n ,γ ) 21N excitation functions and thermonuclear reaction rates have been determined. The 19 (n ,γ )20N rate is up to a factor of 5 higher at T <1 GK with respect to previous theoretical calculations, leading to a 10% decrease in the predicted fluorine abundance.

  17. [Prison psychosis and dissociative disorders].

    PubMed

    al Chaabani, S; Bataille, M

    2002-12-01

    Through a few clinical case histories stemming from their daily activities at the psychiatric section of the Lantin Prison, the authors propose to revisit the classic concept of Prison psychosis. They broaden its limits to include other psychotic and dissociative phenomena common to the jail population. This requires a strict differential diagnosis, allowing to eliminate some similar pathologies; nevertheless, some difficulties and imperfections persist. The development of the psychosis, the input from the jail architecture and milieu, the predisposing as well as facilitating factors linked to the personality of the inmate, and triggering phenomena are discussed. Finally, the comorbidity between these psychotic/dissociative phenomena and the borderline & histrionic personality disorders is envisaged. PMID:12632838

  18. [Dis-social personality disorder].

    PubMed

    Habermeyer, E; Herpertz, S C

    2006-05-01

    Deviant behavior is gaining in clinical importance if it is founded on stable, characteristic, and enduring patterns of psychopathologically relevant personality traits which have their onset in childhood or adolescence. The classification of these traits shows variations, so that a distinction between the ICD-10 diagnosis of dis-social personality disorder, DSM-IV diagnosis of antisocial personality disorder, and the concept "psychopathy" is necessary. Our knowledge about the biological basis of antisocial behavior includes neurophysiologic, psychophysiologic, and genetic findings. Also relevant are results of neurotransmitter studies and structural resp. functional neuroimaging findings. Psychosocial risk factors include parental deficits, rejection, disregard, unstable relations, and abuse. Efficient psychotherapeutic treatment is cognitive-behavioral. Pharmacologic treatment is largely "off-label". The diagnosis of antisocial and dis-social personality disorders allows no conclusions on criminal responsibility. In addition to psychiatric diagnostics, considerations on the severity of the disorder and its effects on the ability to inhibit actions are necessary. PMID:16609871

  19. [Clinical Handling of Patients with Dissociative Disorders].

    PubMed

    Okano, Kenichiro

    2015-01-01

    This paper discusses the way informed psychiatrists are expected to handle dissociative patients in clinical situations, with a specific focus on dissociative identity disorders and dissociative fugue. On the initial interview with dissociative patients, information on their history of trauma and any nascent dissociative symptoms in their childhood should be carefully obtained. Their level of stress in their current life should also be assessed in order to understand their symptomatology, as well as to predict their future clinical course. A psychoeducational approach is crucial; it might be helpful to give information on dissociative disorder to these patients as well as their family members in order to promote their adherence to treatment. Regarding the symptomatology of dissociative disorders, detailed symptoms and the general clinical course are presented. It was stressed that dissociative identity disorder and dissociative fugue, the most high-profile dissociative disorders, are essentially different in their etiology and clinical presentation. Dissociative disorders are often confused with and misdiagnosed as psychotic disorders, such as schizophrenia. Other conditions considered in terms of the differential diagnosis include borderline personality disorder as well as temporal lobe epilepsy. Lastly, the therapeutic approach to dissociative identity disorder is discussed. Each dissociative identity should be understood as potentially representing some traumatically stressful event in the past. The therapist should be careful not to excessively promote the creation or elaboration of any dissociative identities. Three stages are proposed in the individual psychotherapeutic process. In the initial stage, a secure environment and stabilization of symptoms should be sought. The second stage consists of aiding the "host" personality to make use of other more adaptive coping skills in their life. The third stage involves coaching as well as continuous awareness of

  20. The Child Behavior Checklist as an indicator of posttraumatic stress disorder and dissociation in normative, psychiatric, and sexually abused children.

    PubMed

    Sim, Leslie; Friedrich, William N; Davies, W Hobart; Trentham, Bart; Lengua, Liliana; Pithers, William

    2005-12-01

    Expert ratings and confirmatory factor analyses were used to derive a posttraumatic stress disorder (PTSD), dissociation, and a combined PTSD/dissociation scale from the Child Behavior Checklist (CBCL). Validity was established by examining the relationship of these scales to features of sexual abuse thought to relate to severity and chronicity, as well as to self-report scales of PTSD and dissociation. In addition, this study examined differences between normative, psychiatric, and sexually abused children on the new scales. Both the sexual abuse and psychiatric sample differed significantly from the normative sample on all scales, but not from each other. Despite correlations of the dissociation and PTSD/dissociation combined scale with features of trauma and child self-report of PTSD and dissociation, the absence of differences between the clinical groups on the derived scales suggests that the scales measure generic, as opposed to trauma-related, distress. PMID:16382422

  1. Surface Induced Dissociation Yields Quaternary Substructure of Refractory Noncovalent Phosphorylase B and Glutamate Dehydrogenase Complexes

    NASA Astrophysics Data System (ADS)

    Ma, Xin; Zhou, Mowei; Wysocki, Vicki H.

    2014-03-01

    Ion mobility (IM) and tandem mass spectrometry (MS/MS) coupled with native MS are useful for studying noncovalent protein complexes. Collision induced dissociation (CID) is the most common MS/MS dissociation method. However, some protein complexes, including glycogen phosphorylase B kinase (PHB) and L-glutamate dehydrogenase (GDH) examined in this study, are resistant to dissociation by CID at the maximum collision energy available in the instrument. Surface induced dissociation (SID) was applied to dissociate the two refractory protein complexes. Different charge state precursor ions of the two complexes were examined by CID and SID. The PHB dimer was successfully dissociated to monomers and the GDH hexamer formed trimeric subcomplexes that are informative of its quaternary structure. The unfolding of the precursor and the percentages of the distinct products suggest that the dissociation pathways vary for different charge states. The precursors at lower charge states (+21 for PHB dimer and +27 for GDH hexamer) produce a higher percentage of folded fragments and dissociate more symmetrically than the precusors at higher charge states (+29 for PHB dimer and +39 for GDH hexamer). The precursors at lower charge state may be more native-like than the higher charge state because a higher percentage of folded fragments and a lower percentage of highly charged unfolded fragments are detected. The combination of SID and charge reduction is shown to be a powerful tool for quaternary structure analysis of refractory noncovalent protein complexes, as illustrated by the data for PHB dimer and GDH hexamer.

  2. Religious Dissociation and Economic Appraisal in Brazil.

    PubMed

    François Dengah, H J

    2016-04-01

    Research on the association between religion and health often neglects to provide an explicit theoretical mechanism of influence between faith and well-being. This research posits that dissociative behaviors, such as glossolalia, may provide a biological pathway that influences both physiological and psychological health. This paper argues that religious dissociation acts as a moderator between economic stressors and psychobiological appraisal. Brazil, with its economic inequality and preponderance of religious dissociative rituals, provides an ideal context to examine religious dissociation as a moderator of stress. Utilizing data from a cross section of Brazilian faiths, this paper examines: (1) Whether individuals with low socioeconomic status preferentially participate and experience religious dissociative states and (2) whether dissociative states are correlated with greater psychological appraisal of status. PMID:25687180

  3. Dissociative Tendencies and Facilitated Emotional Processing

    PubMed Central

    Oathes, Desmond J.; Ray, William J.

    2009-01-01

    Dissociation is a process linked to lapses of attention, history of abuse or trauma, compromised emotional memory, and a disintegrated sense of self. It is theorized that dissociation stems from avoiding emotional information, especially negative emotion, to protect a fragile psyche. The present study tested whether or not dissociaters do actually avoid processing emotion by asking groups scoring high or low on the Dissociative Experiences Scale to judge the affective valence of several types of emotional stimuli. Manipulations of valence, modality (pictures or words), task complexity, and personal relevance lead to results suggesting that dissociation is linked to facilitated rather than deficient emotional processing. Our results are consistent with a theory that sensitivity to emotional material may be a contributing factor in subsequent dissociation to avoid further elaboration of upsetting emotion in these individuals. The findings for dissociation further exemplify the influence of individual differences in the link between cognition and emotion. PMID:18837615

  4. Coulomb Dissociation of 27P

    NASA Astrophysics Data System (ADS)

    Beceiro Novo, S.; Sümmerer, K.; Cortina-Gil, D.; Wimmer, C.; Plag, R.; Alvarez-Pol, H.; Aumann, T.; Behr, K.; Boretzky, K.; Casarejos, E.; Chatillon, A.; Datta-Pramanik, U.; Elekes, Z.; Fulop, Z.; Galaviz, D.; Geissel, H.; Giron, S.; Greife, U.; Hammache, F.; Heil, M.; Hoffman, J.; Johansson, H.; Karagiannis, C.; Kiselev, O.; Kurz, N.; Larsson, K.; Le Bleis, T.; Litvinov, Y.; Mahata, K.; Muentz, C.; Nociforo, C.; Ott, W.; Paschalis, S.; Prokopowicz, W.; Rodriguez-Tajes, C.; Rossi, D.; Simon, H.; Stanoiu, M.; Stroth, J.; Typel, S.; Wagner, A.; Wamers, F.; Weick, H.

    2012-09-01

    In this work the astrophysical 26Si(p,γ)27P reaction is studied using the Coulomb dissociation technique. We performed a 27P Coulomb Dissociation experiment at GSI, Darmstadt (28 May-5 June 2007) using the ALADIN-LAND setup which allows complete-kinematic studies. A secondary 27P beam at 498 AMeV impinging a 515mg/cm2 Pb target was used. The relative energy of the outgoing system (26Si+p) is measured obtaining the resonant states of the 27P. Preliminary results show four resonant states measured at 0.36±0.07, 0.88±0.09, 1.5±0.2, 2.3±0.3 MeV and evidence of a higher state at around 3.1 MeV. The preliminary total cross section obtained for relative energies between 0 and 3 MeV has been measured and yields 55±7 mb.

  5. Dissociative recombination in planetary ionospheres

    NASA Technical Reports Server (NTRS)

    Fox, J. L.

    1993-01-01

    Ionization in planetary atmospheres can be produced by solar photoionization, photoelectron impact ionization, and, in auroral regions, by impact of precipitating particles. This ionization is lost mainly in dissociative recombination (DR) of molecular ions. Although atomic ions cannot undergo DR, they can be transformed locally through ion-molecule reactions into molecular ions, or they may be transported vertically or horizontally to regions of the atmosphere where such transformations are possible. Because DR reactions tend to be very exothermic, they can be an important source of kinetically or internally excited fragments. In interplanetary thermospheres, the neutral densities decrease exponentially with altitude. Below the homopause (or turbopause), the atmosphere is assumed to be throughly mixed by convection and/or turbulence. Above the homopause, diffusion is the major transport mechanism, and each species is distributed according to its mass, with the logarithmic derivative of the density with repect to altitude given approximately by -1/H, where H = kT/mg is the scale height. In this expression, T is the neutral temperature, g is the local acceleratiion of gravity, and m is the mass of the species. Thus lighter species become relatively more abundant, and heavier species less abundant, as the altitude increases. This variation of the neutral composition can lead to changes in the ion composition; furthermore, as the neutral densities decrease, dissociative recombination becomes more important relative to ion-neutral reactions as a loss mechanism for molecular ions.

  6. Dissociative Recombination without a Curve Crossing

    NASA Technical Reports Server (NTRS)

    Guberman, Steven L.

    1994-01-01

    Ab initio calculations show that a curve crossing is not always needed for a high dissociative- recombination cross section. For HeH(+), in which no neutral states cross the ion potential curve, dissociative recombination is driven by the nuclear kinetic-energy operator on adiabatic potential curves. The kinetic-energy derivative operator allows for capture into repulsive curves that are outside of the classical turning points for the nuclear motion. The dominant dissociative route is the C (2)Sigma(+) state leading to H(n = 2) atoms. An analogous mechanism is proposed for the dissociative recombination of H3(+).

  7. Degree of somatoform and psychological dissociation in dissociative disorder is correlated with reported trauma.

    PubMed

    Nijenhuis, E R; Spinhoven, P; van Dyck, R; van der Hart, O; Vanderlinden, J

    1998-10-01

    In this study, the prevalence and severity of traumatic experiences as reported by patients with dissociative disorders and with other DSM-IV psychiatric diagnoses were compared. Furthermore, the predictive value of emotional, physical, and sexual trauma with respect to somatoform and psychological dissociation was analyzed. In contrast with comparison patients, dissociative disorder patients reported severe and multifaceted traumatization. Physical and sexual trauma predicted somatoform dissociation, sexual trauma predicted psychological dissociation as well. According to the memories of the dissociative disorder patients, this abuse occurred in an emotionally neglectful and abusive social context. Pathological dissociation was best predicted by early onset of reported intense, chronic and multiple traumatization. Methodological limitations restricting causal inferences between reported trauma and dissociation are discussed. PMID:9870223

  8. Dissociative symptoms and dissociative disorder comorbidity in patients with obsessive-compulsive disorder.

    PubMed

    Belli, Hasan; Ural, Cenk; Vardar, Melek Kanarya; Yesılyurt, Sema; Oncu, Fatıh

    2012-10-01

    The present study attempted to assess the dissociative symptoms and overall dissociative disorder comorbidity in patients with obsessive-compulsive disorder (OCD). In addition, we examined the relationship between the severity of obsessive-compulsive symptoms and dissociative symptoms. All patients admitted for the first time to the psychiatric outpatient unit were included in the study. Seventy-eight patients had been diagnosed as having OCD during the 2-year study period. Patients had to meet the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for OCD. Most (76.9%; n = 60) of the patients were female, and 23.1% (n = 18) of the patients were male. Dissociation Questionnaire was used to measure dissociative symptoms. The Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Dissociative Disorders interviews and Yale-Brown Obsessive Compulsive Checklist and Severity Scale were used. Eleven (14%) of the patients with OCD had comorbid dissociative disorder. The most prevalent disorder in our study was dissociative depersonalization disorder. Dissociative amnesia and dissociative identity disorder were common as well. The mean Yale-Brown score was 23.37 ± 7.27 points. Dissociation Questionnaire scores were between 0.40 and 3.87 points, and the mean was 2.23 ± 0.76 points. There was a statistically significant positive correlation between Yale-Brown points and Dissociation Questionnaire points. We conclude that dissociative symptoms among patients with OCD should alert clinicians for the presence of a chronic and complex dissociative disorder. Clinicians may overlook an underlying dissociative process in patients who have severe symptoms of OCD. However, a lack of adequate response to cognitive-behavioral and drug therapy may be a consequence of dissociative process. PMID:22425531

  9. Molecular dissociation in dilute gas

    SciTech Connect

    Renfrow, S.N.; Duggan, J.L.; McDaniel, F.D. |

    1999-06-01

    The charge state distributions (CSD) produced during molecular dissociation are important to both Trace Element Accelerator Mass Spectrometry (TEAMS) and the ion implantation industry. The CSD of 1.3{endash}1.7 MeV SiN{sup +}, SiMg{sup +}, SiMn{sup +}, and SiZn{sup +} molecules have been measured for elements that do not form atomic negative ions (N, Mg, Mn, and Zn) using a NEC Tandem Pelletron accelerator. The molecules were produced in a Cs sputter negative ion source, accelerated, magnetically analyzed, and then passed through an N{sub 2} gas cell. The neutral and charged breakups where analyzed using an electrostatic deflector and measured with particle detectors. Equilibrium CSD were determined and comparisons made between molecular and atomic ion data. {copyright} {ital 1999 American Institute of Physics.}

  10. The Dissociative Recombination of OH(+)

    NASA Technical Reports Server (NTRS)

    Guberman, Steven L.

    1995-01-01

    Theoretical quantum chemical calculations of the cross sections and rates for the dissociative recombination of the upsilon = 0 level of the ground state of OH(+) show that recombination occurs primarily along the 2 (2)Pi diabatic route. The products are 0((1)D) and a hot H atom with 6.1 eV kinetic energy. The coupling to the resonances is very small and the indirect recombination mechanism plays only a minor role. The recommended value for the rate coefficient is (6.3 +/- 0.7) x 10(exp -9)x (T(e)/1300)(exp -0.48) cu.cm/s for 10 less than T(e) less than 1000 K.

  11. Dissociative ionization of sodium molecules via repulsive Rydberg states

    NASA Astrophysics Data System (ADS)

    Chen, Hong

    In this thesis, an investigation of two color resonance multiphoton ionization (REMPI) and fragmentation processes in Na2 has been performed in combination with Linear Time-of-Flight Mass Spectrometry technique. The ionization and dissociative ionizations channels in the energy range up to 2500cm -1 above the dissociative ionization threshold into Na(3s)+Na ++e have been studied. After a mild supersonic expansion from the beam source, neutral sodium dimers in the ground state have been produced. Two tunable, pulsed lasers excite Na2 molecules via the intermediate A1S+u state to a single ro-vibrational level of the second intermediate 21pig state. Following absorption of a third photon, the total energy is above the dissociation limit into Na(3s) + Na+ + e. Typically, a small portion of atomic ions is produced under our experimental conditions. By varying the total available energy below and through the doubly excited states correlating with the Na(3p)+Na(4s) atom pair, there is no evidence that the doubly excited states positioned in the ionic continuum get involved. By calculation of the expected transition probabilities for all possible channels which can decay directly and indirectly into atomic ions, I find that direct dissociative ionization via 12S+u is impossible. The transition probabilities for dissociative ionization via the repulsive Rydberg states with principal quantum numbers n from 5˜12 converging toward the 12S+u state are three to four orders of magnitude larger than those for direct ionization into the continuum of the X2S+g ground state. These repulsive Rydberg states are much more likely to play a role in the photo-ionization through the intermediate 21Pg state. A semi-classical model which was originally developed for negative ion dissociative attachment (O'MAL'67) describes how dissociative ionization occurs along the repulsive Rydberg states. Its prediction concerning the ratio of atomic to molecular ion production as a function of initial

  12. Dissociative recombination of highly symmetric polyatomic ions.

    PubMed

    Douguet, Nicolas; Orel, Ann E; Greene, Chris H; Kokoouline, Viatcheslav

    2012-01-13

    A general first-principles theory of dissociative recombination is developed for highly symmetric molecular ions and applied to H(3)O(+) and CH(3)(+), which play an important role in astrophysical, combustion, and laboratory plasma environments. The theoretical cross sections obtained for the dissociative recombination of the two ions are in good agreement with existing experimental data from storage ring experiments. PMID:22324682

  13. A Hierarchical Process-Dissociation Model

    ERIC Educational Resources Information Center

    Rouder, Jeffrey N.; Lu, Jun; Morey, Richard D.; Sun, Dongchu; Speckman, Paul L.

    2008-01-01

    In fitting the process-dissociation model (L. L. Jacoby, 1991) to observed data, researchers aggregate outcomes across participant, items, or both. T. Curran and D. L. Hintzman (1995) demonstrated how biases from aggregation may lead to artifactual support for the model. The authors develop a hierarchical process-dissociation model that does not…

  14. Dissociation and the Development of Psychopathology.

    ERIC Educational Resources Information Center

    Putnam, Frank W.; Trickett, Penelope K.

    This paper reviews the research on dissociation and the development of psychopathology in children and adolescents. Definitions and dimensions of dissociation are addressed, noting its range from normative daydreaming to the extremes found in individuals with multiple personality disorder. Memory dysfunctions, disturbances of identity, passive…

  15. Dissociative depression among women in the community.

    PubMed

    Sar, Vedat; Akyüz, Gamze; Oztürk, Erdinç; Alioğlu, Firdevs

    2013-01-01

    This study screened the prevalence and correlates of dissociative disorders among depressive women in the general population. The Dissociative Disorders Interview Schedule and the posttraumatic stress disorder (PTSD) and borderline personality disorder sections of the Structured Clinical Interview for DSM-IV were administered to 628 women in 500 homes. The prevalence of current major depressive episode was 10.0%. Of the women, 26 (40.6%) had the lifetime diagnosis of a DSM-IV, dissociative disorder, yielding a prevalence of 4.1% for dissociative depression. This group was younger (mean age = 30.7 years) than the nondissociative depression women (mean age = 39.6 years). There was no difference between the 2 groups on comorbid somatization disorder, PTSD, or borderline personality disorder. Besides suicide attempts, the dissociative group was characterized by secondary features of dissociative identity disorder; Schneiderian symptoms; borderline personality disorder criteria; and extrasensory perceptions, including possession experiences. They reported suicidality, thoughts of guilt and worthlessness, diminished concentration and indecisiveness, and appetite and weight changes more frequently than the nondissociative group. Early cessation of school education and childhood sexual abuse were frequently reported by the dissociative depression group. With its distinct features, the concept of dissociative depression may facilitate understanding of treatment resistance in, development of better psychotherapy strategies for, and new thinking on the neurobiology and pharmacotherapy of depressive disorders. PMID:23796173

  16. Recent developments in the theory of dissociation

    PubMed Central

    SPITZER, CARSTEN; BARNOW, SVEN; FREYBERGER, HARALD J; GRABE, HANS JOERGEN

    2006-01-01

    Although the construct of dissociation was introduced into psychiatry at the end of the 19th century by Pierre Janet, the term still lacks a coherent conceptualization, which is partially reflected by differences in the classification of dissociative and conversion disorders in ICD-10 and DSM-IV. Given the clinical significance of dissociative psychopathology in numerous clinical conditions, it is very valuable that various efforts have been made to refine and to specify current conceptualizations in recent years. The most promising and convincing approaches converge in subdividing dissociation into qualitatively different types, i.e. pathological versus non-pathological dissociation, and "detachment" versus "compartmentalization". We review these concepts and discuss their scientific and clinical potential as well as their limitations. PMID:16946940

  17. The Shutdown Dissociation Scale (Shut-D)

    PubMed Central

    Schalinski, Inga; Schauer, Maggie; Elbert, Thomas

    2015-01-01

    The evolutionary model of the defense cascade by Schauer and Elbert (2010) provides a theoretical frame for a short interview to assess problems underlying and leading to the dissociative subtype of posttraumatic stress disorder. Based on known characteristics of the defense stages “fright,” “flag,” and “faint,” we designed a structured interview to assess the vulnerability for the respective types of dissociation. Most of the scales that assess dissociative phenomena are designed as self-report questionnaires. Their items are usually selected based on more heuristic considerations rather than a theoretical model and thus include anything from minor dissociative experiences to major pathological dissociation. The shutdown dissociation scale (Shut-D) was applied in several studies in patients with a history of multiple traumatic events and different disorders that have been shown previously to be prone to symptoms of dissociation. The goal of the present investigation was to obtain psychometric characteristics of the Shut-D (including factor structure, internal consistency, retest reliability, predictive, convergent and criterion-related concurrent validity). A total population of 225 patients and 68 healthy controls were accessed. Shut-D appears to have sufficient internal reliability, excellent retest reliability, high convergent validity, and satisfactory predictive validity, while the summed score of the scale reliably separates patients with exposure to trauma (in different diagnostic groups) from healthy controls. The Shut-D is a brief structured interview for assessing the vulnerability to dissociate as a consequence of exposure to traumatic stressors. The scale demonstrates high-quality psychometric properties and may be useful for researchers and clinicians in assessing shutdown dissociation as well as in predicting the risk of dissociative responding. PMID:25976478

  18. Dissociation and Memory Fragmentation in Posttraumatic Stress Disorder: An Evaluation of the Dissociative Encoding Hypothesis

    PubMed Central

    Bedard-Gilligan, Michele; Zoellner, Lori A.

    2012-01-01

    Several prominent theories of posttraumatic stress disorder (PTSD) posit that peritraumatic dissociation results in insufficient encoding of the trauma memory and that persistent dissociation prevents memory elaboration, resulting in memory fragmentation and PTSD. In this review, we summarize the empirical literature on peritraumatic and trait dissociation and trauma narrative fragmentation as measured by meta-memory and rater/objective coding. Across 16 studies to date, the association between dissociation and fragmentation was most prominent when examining peritraumatic dissociation and patient's own ratings of memory fragmentation. This relationship did not hold when examining trait dissociation or rater-coded or computer-generated measures of fragmentation. Thus, initial evidence points more toward a strong self-reported association between constructs that is not supported on more objective fragmentation coding. Measurement overlap, construct ambiguity, and exclusion of potential confounds may underlie lack of a strong association between dissociation and objective-rated fragmentation. PMID:22348400

  19. Shielding of CO from dissociating radiation in interstellar clouds

    NASA Technical Reports Server (NTRS)

    Glassgold, A. E.; Huggins, P. J.; Langer, W. D.

    1985-01-01

    The paper investigates the photodissociation of CO in interstellar clouds in the light of recent laboratory studies which suggest that line rather than continuum processes dominate its dissociation by ultraviolet radiation. Using a simple radiative transfer model, the shielding of representative dissociating bands is estimated, including self-shielding, mutual shielding between different isotopes, and near coincidences with strong lines of H2. Each of these processes materially affects the photodestruction rates of the various isotopic species in the transition regions of molecular clouds. These results are combined with an appropriate gas phase chemical model to determine how the abundances of the CO isotopes vary with depth into the cloud. It is found that self-shielding and mutual shielding cause significant variations in isotopic ratios. In addition, fractionation enhances species containing C-13. The relationship between the column densities of CO and H2 is found to vary for the different isotopes and to be sensitive to local conditions.

  20. From state dissociation to status dissociatus.

    PubMed

    Antelmi, Elena; Ferri, Raffaele; Iranzo, Alex; Arnulf, Isabelle; Dauvilliers, Yves; Bhatia, Kailash P; Liguori, Rocco; Schenck, Carlos H; Plazzi, Giuseppe

    2016-08-01

    The states of being are conventionally defined by the simultaneous occurrence of behavioral, neurophysiological and autonomic descriptors. State dissociation disorders are due to the intrusion of features typical of a different state into an ongoing state. Disorders related to these conditions are classified according to the ongoing main state and comprise: 1) Dissociation from prevailing wakefulness as seen in hypnagogic or hypnopompic hallucinations, automatic behaviors, sleep drunkenness, cataplexy and sleep paralysis 2) Dissociation from rapid eye movement (REM) sleep as seen in REM sleep behavior disorder and lucid dreaming and 3) Dissociation from NREM sleep as seen in the disorders of arousal. The extreme expression of states dissociation is characterized by the asynchronous occurrence of the various components of the different states that prevents the recognition of any state of being. This condition has been named status dissociatus. According to the underlying disorders/diseases and to their severity, among status dissociatus we may recognize disorders in which such an extreme dissociation occurs only at night time or intermittently (i.e., autoimmune encephalopathies, narcolepsy type 1 and IgLON5 parasomnia), and others in which it occurs nearly continuously with complete loss of any conventionally defined state of being, and of the circadian pattern (agrypnia excitata). Here, we render a comprehensive review of all diseases/disorders associated with state dissociation and status dissociatus and propose a critical classification of this complex scenario. PMID:26431902

  1. State dissociation, human behavior, and consciousness.

    PubMed

    Mahowald, Mark W; Cramer Bornemann, Michel A; Schenck, Carlos H

    2011-01-01

    Sleep is clearly not only a whole-brain or global phenomenon, but can also be a local phenomenon. This accounts for the fact that the primary states of being (wakefulness, NREM sleep, and REM sleep) are not necessarily mutually exclusive, and components of these states may appear in various combinations, with fascinating clinical consequences. Examples include: sleep inertia, narcolepsy, sleep paralysis, lucid dreaming, REM sleep behavior disorder, sleepwalking, sleep terrors, out-of-body experiences, and reports of alien abduction. The incomplete declaration of state likewise has implications for consciousness - which also has fluid boundaries. Fluctuations in the degree of consciousness are likely explained by abnormalities of a "spatial and temporal binding rhythm" which normally results in a unified conscious experience. Dysfunctional binding may play a role in anesthetic states, autism, schizophrenia, and neurodegenerative disorders. Further study of the broad spectrum of dissociated states of sleep and wakefulness that are closely linked with states of consciousness and unconsciousness by basic neuroscientists, clinicians, and members of the legal profession will provide scientific, clinical and therapeutic insights, with forensic implications. PMID:21906025

  2. Dissociative Recombination of Molecular Ions for Astrochemistry

    NASA Astrophysics Data System (ADS)

    Savin, Daniel W.; Novotný, O.; Becker, A.; Buhr, H.; Geppert, W.; Hamberg, M.; Krantz, C.; Kreckel, H.; Schwalm, D.; Spruck, K.; Stützel, J.; Wolf, A.; Yang, B.

    2013-06-01

    Dissociative recombination (DR) of molecular ions is a key chemical process in the cold interstellar medium (ISM). DR affects the composition, charge state, and energy balance of such environments. Astrochemical models of the ISM require reliable total DR cross sections as well as knowledge of the chemical composition and excitation states of the neutral DR products. Theory cannot reliably provide these data. We have systematically measured DR for many astrophysically relevant molecular ions utilizing the TSR storage ring at the Max-Planck-Institute for Nuclear Physics in Heidelberg, Germany. We used the merged ion-electron beam technique combined with an energy- and position-sensitive imaging detector and are able to study DR down to plasma temperatures of 10 K. The DR count rate is used to obtain absolute DR rate coefficient. Additionally we determine the masses of the DR products by measuring their kinetic energy. This allows us to assign particular DR fragmentation channels and to obtain their branching ratios. Moreover, the distribution of detected fragment distances provides information on the kinetic energy released in DR and thus also on the internal excitation of the DR products. All this information is particularly important for understanding DR of heteronuclear polyatomic ions. We will present DR results for several ions recently investigated at TSR. This work is supported in part by NASA and the NSF.

  3. The association-dissociation behavior of the ApoE proteins: kinetic and equilibrium studies

    PubMed Central

    Garai, Kanchan; Frieden, Carl

    2010-01-01

    The apolipoprotein E family consists of three major protein isoforms: apolipoprotein E4 (ApoE4), ApoE3 and ApoE2. The isoforms, which contain 299 residues, differ only by single amino acid changes but of the three only ApoE4 is a risk factor for Alzheimer’s Disease. At μM concentrations lipid-free ApoE exists predominantly as tetramers. In more dilute solutions, lower molecular weight species predominate. Using Fluorescence Correlation Spectroscopy (FCS), intermolecular Fluorescence Resonance Energy Transfer (FRET) and sedimentation methods we find that the association-dissociation reaction of ApoE can be modeled with a monomer-dimer-tetramer process. Equilibrium constants have been determined from the sedimentation data while the individual rate constants for association and dissociation are determined by measuring the kinetics of dissociation of ApoE and are in agreement with the equilibrium constants. Dissociation kinetics as measured by intermolecular FRET show two phases reflecting the dissociation of tetramer to dimer and of dimer to monomer with dissociation from tetramer to dimer being more rapid than the dimer to monomer dissociation. The rate constants differ for the different ApoE isoforms showing that the association-dissociation process is isoforms specific. Strikingly, the association rate constants are almost two orders of magnitude slower than expected for a diffusion controlled process. Dissociation kinetics were also monitored by tryptophan fluorescence in presence of acrylamide and the data found to be consistent with the monomer-dimer-tetramer model. The approach combining multiple methods establishes the reaction scheme of ApoE self-association. PMID:20923231

  4. Theory of dissociative tunneling ionization

    NASA Astrophysics Data System (ADS)

    Svensmark, Jens; Tolstikhin, Oleg I.; Madsen, Lars Bojer

    2016-05-01

    We present a theoretical study of the dissociative tunneling ionization process. Analytic expressions for the nuclear kinetic energy distribution of the ionization rates are derived. A particularly simple expression for the spectrum is found by using the Born-Oppenheimer (BO) approximation in conjunction with the reflection principle. These spectra are compared to exact non-BO ab initio spectra obtained through model calculations with a quantum mechanical treatment of both the electronic and nuclear degrees of freedom. In the regime where the BO approximation is applicable, imaging of the BO nuclear wave function is demonstrated to be possible through reverse use of the reflection principle, when accounting appropriately for the electronic ionization rate. A qualitative difference between the exact and BO wave functions in the asymptotic region of large electronic distances is shown. Additionally, the behavior of the wave function across the turning line is seen to be reminiscent of light refraction. For weak fields, where the BO approximation does not apply, the weak-field asymptotic theory describes the spectrum accurately.

  5. Dissociative Ionization of Pyridine by Electron Impact

    NASA Technical Reports Server (NTRS)

    Dateo, Christopher; Huo, Winifred; Kwak, Dochan (Technical Monitor)

    2002-01-01

    In order to understand the damage of biomolecules by electrons, a process important in radiation damage, we undertake a study of the dissociative ionization (DI) of pyridine (C5H5N) from the low-lying ionization channels. The methodology used is the same as in the benzene study. While no experimental DI data are available, we compare the dissociation products from our calculations with the dissociative photoionization measurements of Tixier et al. using dipole (e, e(+) ion) coincidence spectroscopy. Comparisons with the DI of benzene is also made so as to understand the difference in DI between a heterocyclic and an aromatic molecule.

  6. Dissociation of Natural and Artificial Methane Hydrate

    NASA Astrophysics Data System (ADS)

    Misyura, S. Y.

    2016-02-01

    Present work deals with natural and artificial methane hydrate dissociation. The heating of the powder produced due to the temperature difference between the external air and the powder. The dissociation rate was determined by gravimetric method. The range of the partial self-preservation for the natural hydrate is significantly longer than for the artificial one and moved to higher temperatures. The destruction of the natural sample is slower than the artificial one. The time-averaged dissociation rate for the artificial sample is equal to 1,25 %/s and for the natural hydrate corresponds to 0,59 %/s.

  7. Wavepacket theory of collisional dissociation in molecules

    SciTech Connect

    Kulander, K.

    1980-01-01

    An explicit integration scheme is used to solve the time dependent Schroedinger equation for wavepackets which model collisions in the collinear H + H/sub 2/ system. A realistic LEPS-type potential energy surface is used. Collision energies considered are above the dissociation threshold and probabilities for collision induced dissociation are reported. Also quantum mechanical state-to-state transition probabilities are generated. These results are compared to extensive classical trajectory calculations performed on this same system. The time evolution of the wavepacket densities is studied to understand the dynamics of the collinear collisional dissociation process.

  8. Absolute total and partial dissociative cross sections of pyrimidine at electron and proton intermediate impact velocities

    SciTech Connect

    Wolff, Wania Luna, Hugo; Sigaud, Lucas; Montenegro, Eduardo C.; Tavares, Andre C.

    2014-02-14

    Absolute total non-dissociative and partial dissociative cross sections of pyrimidine were measured for electron impact energies ranging from 70 to 400 eV and for proton impact energies from 125 up to 2500 keV. MOs ionization induced by coulomb interaction were studied by measuring both ionization and partial dissociative cross sections through time of flight mass spectrometry and by obtaining the branching ratios for fragment formation via a model calculation based on the Born approximation. The partial yields and the absolute cross sections measured as a function of the energy combined with the model calculation proved to be a useful tool to determine the vacancy population of the valence MOs from which several sets of fragment ions are produced. It was also a key point to distinguish the dissociation regimes induced by both particles. A comparison with previous experimental results is also presented.

  9. A new concept Tandem thermal dissociator/electron impact ion source for RIB generation

    SciTech Connect

    Alton, G.D.; Williams, C.

    1995-12-31

    An innovative thermal dissociation/electron impact ionization positive ion source is presently under design at the Oak Ridge National Laboratory for potential use for generating RIBs at the Holifield Radioactive Ion Beam Facility (HRIBF). Because of the low probability of simultaneously dissociating and efficiently ionizing the individual atomic constituents with conventional, hot-cathode, electron-impact ion sources, the ion beams extracted from these sources often appear as a mixture of several molecular sideband beams. In this way, the intensity of the species of interest is diluted. We have conceived an Ion source that combines the excellent molecular dissociation properties of a thermal dissociator and the high efficiency characteristics of an electron impact ionization source. If the concept proves to be a viable option, the source will be used as a complement to the electron beam plasma ion sources already in use at the HRIBF. The design features and principles of operation of the source are described in this article.

  10. Dissociative identity disorder presenting as dermatitis artefacta.

    PubMed

    Ozmen, Mine; Erdogan, Ayten; Aydemir, Ertugrul H; Oguz, Oya

    2006-06-01

    Dermatitis artefacta is a rare psychiatric condition characterized by rubbing of skin blisters and denial of self-infliction. Dissociation may be comorbid with self-injurious behavior. A background of emotional disturbances during formative years and in later life often results in feelings of isolation and insecurity, which can lead to dissociation as a primary defense mechanism used to overcome traumatic events. In this case report, we describe a female patient with dermatitis artefacta associated with dissociative identity disorder. The patient was a 14-year-old girl. Multiple large, deep ulcerations with unnatural shapes were seen on her left forearm. The ulcerations were thought to be self-inflicted. Psychiatric examination revealed that she had a different identity, and inflicted the lesions when this was assumed. This case leads us to suggest that patients with dermatitis artefacta might have comorbid dissociative experiences, which cannot be identified easily. PMID:16796649

  11. Collision-induced gas phase dissociation rates

    NASA Technical Reports Server (NTRS)

    Hansen, C. Frederick

    1990-01-01

    The Landau-Zener theory of reactive cross sections was applied to diatomic molecules dissociating from a ladder of vibrational states. The result predicts a dissociation rate that is quite well duplicated by an Arrhenius function having a preexponential temperature dependence of about T(sub -1/2), at least for inert collision partners. This relation fits experimental data reasonably well. The theory is then used to calculate the effect of vibrational nonequilibrium on dissociation rate. For Morse oscillators, the results are about the same as given by Hammerling, Kivel, and Teare in their analytic approximation for harmonic oscillators, though at very high temperature a correction for the partition function limit is included. The empirical correction for vibration nonequilibrium proposed by Park, which is a convenient algorithm for CFD calculations, is modified to prevent a drastic underestimation of dissociation rates that occurs with this method when vibrational temperature is much smaller than the kinetic temperature of the gas.

  12. Research Reports: Hallucinogens and Dissociative Drugs

    MedlinePlus

    ... in bizarre or dangerous behavior. Hallucinogens such as LSD, psilocybin, peyote, DMT, and ayahuasca cause emotions to ... Take Hallucinogenic or Dissociative Drugs? How Do Hallucinogens (LSD, Psilocybin, Peyote, DMT, and Ayahuasca) Affect the Brain ...

  13. Quantitative structure-(chromatographic) retention relationship models for dissociating compounds.

    PubMed

    Kubik, Łukasz; Wiczling, Paweł

    2016-08-01

    The aim of this work was to develop mathematical models relating the hydrophobicity and dissociation constant of an analyte with its structure, which would be useful in predicting analyte retention times in reversed-phase liquid chromatography. For that purpose a large and diverse group of 115 drugs was used to build three QSRR models combining retention-related parameters (logkw-chromatographic measure of hydrophobicity, S-slope factor from Snyder-Soczewinski equation, and pKa) with structural descriptors calculated by means of molecular modeling for both dissociated and nondissociated forms of analytes. Lasso, Stepwise and PLS regressions were used to build statistical models. Moreover a simple QSRR equations based on lipophilicity and dissociation constant parameters calculated in the ACD/Labs software were proposed and compared with quantum chemistry-based QSRR equations. The obtained relationships were further used to predict chromatographic retention times. The predictive performances of the obtained models were assessed using 10-fold cross-validation and external validation. The QSRR equations developed were simple and were characterized by satisfactory predictive performance. Application of quantum chemistry-based and ACD-based descriptors leads to similar accuracy of retention times' prediction. PMID:26960942

  14. Isomerization and dissociation in competition: The two-component dissociation rates of methyl propionate ions

    SciTech Connect

    Mazyar, O.A.; Baer, T.

    1999-03-04

    Threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy has been used to investigate the unimolecular chemistry of gas-phase methyl propionate ions. This ion undergoes isomerization to a lower energy enol structure, CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+}, via two different pathways involving two distonic isomers, {sup {sm_bullet}}CH{sub 2}CH{sub 2}C{sup +}(OH)OCH{sub 3} and CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}}. This isomerization reaction is in competition with the direct CH{sub 3}O{sup {sm_bullet}} loss reaction, which leads to two-component dissociation rates of the methyl propionate ions. Detailed modeling of this complex reaction permitted the extraction of the dissociative photoionization threshold for methyl propionate, which at 0 K is 10.83 {+-} 0.01 eV, as well as the isomerization barrier between the distonic CH{sub 3}CH{sub 2}C{sup +}(OH)OCH{sub 2}{sup {sm_bullet}} and enol CH{sub 3}CHC(OH)OCH{sub 3}{sup {sm_bullet}+} ions of 8.5 kcal/mol (relative to the methyl propionate ion). By combining this with the 0 K heats of formation of methyl propionate and the methoxy radical, the authors derive a 0 K heat of formation of the product propanoyl ion of 147 kcal/mol. Also measured was the adiabatic ionization energy of methyl propionate, 10.03 {+-} 0.05 eV.

  15. Dissociation energy of molecules in dense gases

    NASA Technical Reports Server (NTRS)

    Kunc, J. A.

    1992-01-01

    A general approach is presented for calculating the reduction of the dissociation energy of diatomic molecules immersed in a dense (n = less than 10 exp 22/cu cm) gas of molecules and atoms. The dissociation energy of a molecule in a dense gas differs from that of the molecule in vacuum because the intermolecular forces change the intramolecular dynamics of the molecule, and, consequently, the energy of the molecular bond.

  16. STABILITY OF A SPHERICAL ACCRETION SHOCK WITH NUCLEAR DISSOCIATION

    SciTech Connect

    Fernandez, Rodrigo; Thompson, Christopher

    2009-06-01

    We examine the stability of a standing shock wave within a spherical accretion flow onto a gravitating star, in the context of core-collapse supernova explosions. Our focus is on the effect of nuclear dissociation below the shock on the linear growth, and nonlinear saturation, of nonradial oscillations of the shocked fluid. We combine two-dimensional, time-dependent hydrodynamic simulations using FLASH2.5 with a solution to the linear eigenvalue problem, and demonstrate the consistency of the two approaches. Previous studies of this 'standing accretion shock instability' (SASI) have focused either on zero-energy accretion flows without nuclear dissociation, or made use of a detailed finite-temperature nuclear equation of state and included strong neutrino heating. Our main goal in this and subsequent papers is to introduce equations of state of increasing complexity, in order to isolate the various competing effects. In this work, we employ an ideal gas equation of state with a constant rate of nuclear dissociation below the shock, and do not include neutrino heating. We find that a negative Bernoulli parameter below the shock significantly lowers the real frequency, growth rate, and saturation amplitude of the SASI. A decrease in the adiabatic index has similar effects. The nonlinear development of the instability is characterized by an expansion of the shock driven by turbulent kinetic energy at nearly constant internal energy. Our results also provide further insight into the instability mechanism: the rate of growth of a particular mode is fastest when the radial advection time from the shock to the accretor overlaps with the period of a standing lateral sound wave. The fastest-growing mode can therefore be modified by nuclear dissociation.

  17. Dissociative Ionization of Benzene by Electron Impact

    NASA Technical Reports Server (NTRS)

    Huo, Winifred; Dateo, Christopher; Kwak, Dochan (Technical Monitor)

    2002-01-01

    We report a theoretical study of the dissociative ionization (DI) of benzene from the low-lying ionization channels. Our approach makes use of the fact that electron motion is much faster than nuclear motion and DI is treated as a two-step process. The first step is electron-impact ionization resulting in an ion with the same nuclear geometry as the neutral molecule. In the second step the nuclei relax from the initial geometry and undergo unimolecular dissociation. For the ionization process we use the improved binary-encounter dipole (iBED) model. For the unimolecular dissociation step, we study the steepest descent reaction path to the minimum of the ion potential energy surface. The path is used to analyze the probability of unimolecular dissociation and to determine the product distributions. Our analysis of the dissociation products and the thresholds of the productions are compared with the result dissociative photoionization measurements of Feng et al. The partial oscillator strengths from Feng et al. are then used in the iBED cross section calculations.

  18. Collision induced dissociation of alpha hydroxy acids

    NASA Astrophysics Data System (ADS)

    Bandu, Mary L.; Grubbs, Thomas; Kater, Marcus; Desaire, Heather

    2006-03-01

    Alpha hydroxy acids typically dissociate in tandem mass spectrometric experiments to produce product ions representing a neutral loss of 46 Da (CH2O2) in negative ion mode. Although it is widely accepted that the carboxylate group is lost in the dissociation process, the origin of the remaining two hydrogens is unclear. The current study utilizes an alpha hydroxy acid chemical library and deuterium labeling experiments to identify the origin of the two hydrogens lost during dissociation. Secondly, this study investigates the lower m/z region of the CID spectrum, a region previously unexplored, to aid in characterizing the dissociation mechanism. Further experiments testing the energy requirements and time parameters of the dissociation also are consistent with criteria previously defined for ion-neutral complex formation. In addition to describing the mechanism for the loss of CH2O2, we have conducted experiments that demonstrate the important chemical features of molecules that can prevent alpha hydroxy acids from undergoing the loss of 46 Da. By understanding the chemical composition of the 46 Da loss, the dissociation mechanism responsible for the loss, and the factors that hinder this mechanistic pathway, chemical information about alpha hydroxy acids can be obtained from their CID data.

  19. Unimolecular dissociation of cyclopentadiene and indene

    SciTech Connect

    Yi, W.; Chattopadhyay, A.; Bersohn, R. )

    1991-05-01

    The dissociation of hydrogen atoms from the methylene group of cyclopentadiene (CP) and indene (ID) excited with a 193 nm photon has been studied by hydrogen atom laser induced fluorescence. The rate of dissociation of IND was 7.4{times}10{sup 6} s{sup {minus}1} but that of CP was too fast to measure. The ratio of H atoms to D atoms generated from 5-deuteriocyclopentadiene (5-dCP) was 3.91{plus minus}0.46. Rice--Ramsberger--Kassel--Marcus theory was used to calculate the rates of dissociation of CP and 5-dCP. The quantum yield for dissociating H atoms from CP was 0.85{plus minus}0.07. The ejected H atoms have a Maxwell velocity distribution with temperatures which are equal to the vibrational temperatures, 3690 and 2479 K for CP and IND, respectively. The most important result of the work is this confirmation of an earlier finding on a different set of molecules that the translational temperature of the fragments {ital after} the dissociation is equal to the vibrational temperature {ital before} the dissociation. This is explained by the assumption that the motion of the fast, light hydrogen atom is partly decoupled from that of the heavier, slower atoms.

  20. Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates.

    PubMed

    Kwon, Tae-Hyuk; Kneafsey, Timothy J; Rees, Emily V L

    2011-06-30

    Replacement of methane with carbon dioxide in hydrate has been proposed as a strategy for geologic sequestration of carbon dioxide (CO(2)) and/or production of methane (CH(4)) from natural hydrate deposits. This replacement strategy requires a better understanding of the thermodynamic characteristics of binary mixtures of CH(4) and CO(2) hydrate (CH(4)-CO(2) mixed hydrates), as well as thermophysical property changes during gas exchange. This study explores the thermal dissociation behavior and dissociation enthalpies of CH(4)-CO(2) mixed hydrates. We prepared CH(4)-CO(2) mixed hydrate samples from two different, well-defined gas mixtures. During thermal dissociation of a CH(4)-CO(2) mixed hydrate sample, gas samples from the head space were periodically collected and analyzed using gas chromatography. The changes in CH(4)-CO(2) compositions in both the vapor phase and hydrate phase during dissociation were estimated based on the gas chromatography measurements. It was found that the CO(2) concentration in the vapor phase became richer during dissociation because the initial hydrate composition contained relatively more CO(2) than the vapor phase. The composition change in the vapor phase during hydrate dissociation affected the dissociation pressure and temperature; the richer CO(2) in the vapor phase led to a lower dissociation pressure. Furthermore, the increase in CO(2) concentration in the vapor phase enriched the hydrate in CO(2). The dissociation enthalpy of the CH(4)-CO(2) mixed hydrate was computed by fitting the Clausius-Clapeyron equation to the pressure-temperature (PT) trace of a dissociation test. It was observed that the dissociation enthalpy of the CH(4)-CO(2) mixed hydrate lays between the limiting values of pure CH(4) hydrate and CO(2) hydrate, increasing with the CO(2) fraction in the hydrate phase. PMID:21604671

  1. Generating Breathable Air Through Dissociation of N2O

    NASA Technical Reports Server (NTRS)

    Zubrin, Robert; Frankie, Brian

    2006-01-01

    includes one or more "destroyer" subsystems for removing any nitrogen oxides that remain downstream of the main N2O-dissociation reactor. A destroyer includes a carbon bed in series with a catalytic reactor, and is in thermal contact with the main N2O-dissociation reactor. The gas mixture that leaves the main reactor first goes through a carbon bed, which adsorbs all of the trace NO and most of the trace NO2. The gas mixture then goes through the destroyer catalytic reactor, wherein most or all of the remaining NO2 is dissociated. A NOBOSS can be designed to regulate its reactor temperature across a range of flow rates. One such system includes three destroyer loops; these loops act, in combination with a heat sink, to remove heat from the main N2O-dissociation reactor. In this system, the N2O and product gases play an additional role as coolants; thus, as needed, the coolant flow increases in proportion to the rate of generation of heat, helping to keep the main-reactor temperature below 540 C.

  2. "Trip-Sitting" in the Black Hole: A Netnographic Study of Dissociation and Indigenous Harm Reduction.

    PubMed

    Hearne, Evelyn; Van Hout, Marie Claire

    2016-01-01

    An array of dissociative novel psychoactive substances, including "methoxetamine," "3-MeO-PCP," and "methoxphenidine," have emerged as substitutes for the illicit substance "ketamine." A netographic research methodology aimed to describe online, dissociative novel psychoactive substance users' perceptions of risk, informed knowledge around use, and indigenous harm-reduction practices as advocated within online drug fora, so as to provide credible information which can be used to inform public online health education and drug prevention. Systematic Internet searches were performed using the terms "synthetic dissociative," "methoxetamine," "methoxphenidine," "diphenidine," "3-MeO-PCP," "4-MeO-PCP," "2-MDP," and "dissociative research chemical" in combination with "forum." Following screening of 3,476 forum threads with removal of duplicates and exclusion criteria, 90 user trip reports and 115 fora threads from seven drug fora websites were analyzed by conducting content analysis. Five themes emerged with 43 categories. The findings illustrated how forum activity within the cyber drug user community disseminated and exchanged "communal folk pharmacology" relating to the use of dissociative novel psychoactive substances. Further research and consistent monitoring of Internet drug fora are advised to explore variations in harm-reduction tactics throughout dissociative NPS populations, and to consider how existing harm-reduction initiatives are influencing these hard-to-reach groups. PMID:27430659

  3. Dissociations between developmental dyslexias and attention deficits

    PubMed Central

    Lukov, Limor; Friedmann, Naama; Shalev, Lilach; Khentov-Kraus, Lilach; Shalev, Nir; Lorber, Rakefet; Guggenheim, Revital

    2014-01-01

    We examine whether attention deficits underlie developmental dyslexia, or certain types of dyslexia, by presenting double dissociations between the two. We took into account the existence of distinct types of dyslexia and of attention deficits, and focused on dyslexias that may be thought to have an attentional basis: letter position dyslexia (LPD), in which letters migrate within words, attentional dyslexia (AD), in which letters migrate between words, neglect dyslexia, in which letters on one side of the word are omitted or substituted, and surface dyslexia, in which words are read via the sublexical route. We tested 110 children and adults with developmental dyslexia and/or attention deficits, using extensive batteries of reading and attention. For each participant, the existence of dyslexia and the dyslexia type were tested using reading tests that included stimuli sensitive to the various dyslexia types. Attention deficit and its type was established through attention tasks assessing sustained, selective, orienting, and executive attention functioning. Using this procedure, we identified 55 participants who showed a double dissociation between reading and attention: 28 had dyslexia with normal attention and 27 had attention deficits with normal reading. Importantly, each dyslexia with suspected attentional basis dissociated from attention: we found 21 individuals with LPD, 13 AD, 2 neglect dyslexia, and 12 surface dyslexia without attention deficits. Other dyslexia types (vowel dyslexia, phonological dyslexia, visual dyslexia) also dissociated from attention deficits. Examination of 55 additional individuals with both a specific dyslexia and a certain attention deficit found no attention function that was consistently linked with any dyslexia type. Specifically, LPD and AD dissociated from selective attention, neglect dyslexia dissociated from orienting, and surface dyslexia dissociated from sustained and executive attention. These results indicate that

  4. Electromagnetic Dissociation and Spacecraft Electronics Damage

    NASA Technical Reports Server (NTRS)

    Norbury, John W.

    2016-01-01

    When protons or heavy ions from galactic cosmic rays (GCR) or solar particle events (SPE) interact with target nuclei in spacecraft, there can be two different types of interactions. The more familiar strong nuclear interaction often dominates and is responsible for nuclear fragmentation in either the GCR or SPE projectile nucleus or the spacecraft target nucleus. (Of course, the proton does not break up, except possibly to produce pions or other hadrons.) The less familiar, second type of interaction is due to the very strong electromagnetic fields that exist when two charged nuclei pass very close to each other. This process is called electromagnetic dissociation (EMD) and primarily results in the emission of neutrons, protons and light ions (isotopes of hydrogen and helium). The cross section for particle production is approximately defined as the number of particles produced in nucleus-nucleus collisions or other types of reactions. (There are various kinematic and other factors which multiply the particle number to arrive at the cross section.) Strong, nuclear interactions usually dominate the nuclear reactions of most interest that occur between GCR and target nuclei. However, for heavy nuclei (near Fe and beyond) at high energy the EMD cross section can be much larger than the strong nuclear interaction cross section. This paper poses a question: Are there projectile or target nuclei combinations in the interaction of GCR or SPE where the EMD reaction cross section plays a dominant role? If the answer is affirmative, then EMD mechanisms should be an integral part of codes that are used to predict damage to spacecraft electronics. The question can become more fine-tuned and one can ask about total reaction cross sections as compared to double differential cross sections. These issues will be addressed in the present paper.

  5. Dissociable Learning Processes Underlie Human Pain Conditioning.

    PubMed

    Zhang, Suyi; Mano, Hiroaki; Ganesh, Gowrishankar; Robbins, Trevor; Seymour, Ben

    2016-01-11

    Pavlovian conditioning underlies many aspects of pain behavior, including fear and threat detection [1], escape and avoidance learning [2], and endogenous analgesia [3]. Although a central role for the amygdala is well established [4], both human and animal studies implicate other brain regions in learning, notably ventral striatum and cerebellum [5]. It remains unclear whether these regions make different contributions to a single aversive learning process or represent independent learning mechanisms that interact to generate the expression of pain-related behavior. We designed a human parallel aversive conditioning paradigm in which different Pavlovian visual cues probabilistically predicted thermal pain primarily to either the left or right arm and studied the acquisition of conditioned Pavlovian responses using combined physiological recordings and fMRI. Using computational modeling based on reinforcement learning theory, we found that conditioning involves two distinct types of learning process. First, a non-specific "preparatory" system learns aversive facial expressions and autonomic responses such as skin conductance. The associated learning signals-the learned associability and prediction error-were correlated with fMRI brain responses in amygdala-striatal regions, corresponding to the classic aversive (fear) learning circuit. Second, a specific lateralized system learns "consummatory" limb-withdrawal responses, detectable with electromyography of the arm to which pain is predicted. Its related learned associability was correlated with responses in ipsilateral cerebellar cortex, suggesting a novel computational role for the cerebellum in pain. In conclusion, our results show that the overall phenotype of conditioned pain behavior depends on two dissociable reinforcement learning circuits. PMID:26711494

  6. Dissociable Learning Processes Underlie Human Pain Conditioning

    PubMed Central

    Zhang, Suyi; Mano, Hiroaki; Ganesh, Gowrishankar; Robbins, Trevor; Seymour, Ben

    2016-01-01

    Summary Pavlovian conditioning underlies many aspects of pain behavior, including fear and threat detection [1], escape and avoidance learning [2], and endogenous analgesia [3]. Although a central role for the amygdala is well established [4], both human and animal studies implicate other brain regions in learning, notably ventral striatum and cerebellum [5]. It remains unclear whether these regions make different contributions to a single aversive learning process or represent independent learning mechanisms that interact to generate the expression of pain-related behavior. We designed a human parallel aversive conditioning paradigm in which different Pavlovian visual cues probabilistically predicted thermal pain primarily to either the left or right arm and studied the acquisition of conditioned Pavlovian responses using combined physiological recordings and fMRI. Using computational modeling based on reinforcement learning theory, we found that conditioning involves two distinct types of learning process. First, a non-specific “preparatory” system learns aversive facial expressions and autonomic responses such as skin conductance. The associated learning signals—the learned associability and prediction error—were correlated with fMRI brain responses in amygdala-striatal regions, corresponding to the classic aversive (fear) learning circuit. Second, a specific lateralized system learns “consummatory” limb-withdrawal responses, detectable with electromyography of the arm to which pain is predicted. Its related learned associability was correlated with responses in ipsilateral cerebellar cortex, suggesting a novel computational role for the cerebellum in pain. In conclusion, our results show that the overall phenotype of conditioned pain behavior depends on two dissociable reinforcement learning circuits. PMID:26711494

  7. Dissociative Recombination of Molecular Ions for Astrochemistry

    NASA Astrophysics Data System (ADS)

    Novotny, Oldrich; Becker, A.; Buhr, H.; Fleischmann, Andreas; Gamer, Lisa; Geppert, W.; Krantz, C.; Kreckel, H.; Schwalm, D.; Spruck, K.; Wolf, A.; Savin, Daniel Wolf

    2014-06-01

    Dissociative recombination (DR) of molecular ions is a key chemical process in the cold interstellar medium (ISM). DR affects the composition, charge state, and energy balance of such environments. Astrochemical models of the ISM require reliable total DR cross sections as well as knowledge of the chemical composition of the neutral DR products. We have systematically measured DR for many astrophysically relevant molecular ions utilizing the TSR storage ring at the Max-Planck-Institute for Nuclear Physics (MPIK) in Heidelberg, Germany. We used the merged ion-electron beam technique combined with an energy- and position-sensitive imaging detector and are able to study DR down to plasma temperatures as low as 10 K. The DR count rate is used to obtain an absolute merged beams DR rate coefficient from which we can derive a thermal rate coefficient needed for plasma models. Additionally we determine the masses of the DR products by measuring their kinetic energy in the laboratory reference frame. This allows us to assign particular DR fragmentation channels and to obtain their branching ratios. All this information is particularly important for understanding DR of heteronuclear polyatomic ions. We will present DR results for several ions recently investigated at TSR. A new Cryogenic Storage Ring (CSR) is currently being commissioned at MPIK. With the chamber cooled down to ~10 K and a base pressure better than 10-13 mbar, this setup will allow internal cooling of the stored ions down to their rotational ground states, thus opening a new era in DR experiments. New technological challenges arise due to the ultracold, ultra-high vacuum environment of the CSR and thus the detection techniques used at TSR cannot be easily transferred to CSR. We will present new approaches for DR fragment detection in cryogenic environment. This work is supported in part by NASA and the NSF.

  8. Incrementally Dissociating Syntax and Semantics

    ERIC Educational Resources Information Center

    Brennan, Jonathan R.

    2010-01-01

    A basic challenge for research into the neurobiology of language is understanding how the brain combines words to make complex representations. Linguistic theory divides this task into several computations including syntactic structure building and semantic composition. The close relationship between these computations, however, poses a strong…

  9. Refractive index change in dissociating shocked benzene

    SciTech Connect

    Erskine, D.J.

    1994-06-01

    A calculation is made of the refractive index of a shocked solution of hydrocarbon species and spheroidal carbon particles that would be the dissociation products of benzene. The results is evaluated for benzene shocked to 15 GPa, both for an arbitrary endpoint distribution of products and reactant, and for a specific endpoint distribution suggested by a statistical-mechanical calculation. In the case of diamond particles, the refractive index is predicted to decrease by a small amount (from 1.96 to 1.75) as the dissociation proceeds. In the case of graphite particles of large oblateness, the refractive index could increase significantly through the dissociation (from 1.96 to 2.75 for infinitely oblate platelets). Thus the measurement of the time dependent refractive index through the dissociation of shocked benzene can indicate the morphology of the carbon particulates as well as the time scale for this reaction. We propose using the refractive index as a measure of completion of the dissociation reaction. This would allow a determination of the instantaneous amount of carbon in particulate form, information which is valuable in conjunction with Mie scattering experiments for example.

  10. Intrinsic disorder accelerates dissociation rather than association.

    PubMed

    Umezawa, Koji; Ohnuki, Jun; Higo, Junichi; Takano, Mitsunori

    2016-08-01

    The intrinsically disordered protein (IDP) has distinct properties both physically and biologically: it often becomes folded when binding to the target and is frequently involved in signal transduction. The physical property seems to be compatible with the biological property where fast association and dissociation between IDP and the target are required. While fast association has been well studied, fueled by the fly-casting mechanism, the dissociation kinetics has received less attention. We here study how the intrinsic disorder affects the dissociation kinetics, as well as the association kinetics, paying attention to the interaction strength at the binding site (i.e., the quality of the "fly lure"). Coarse-grained molecular dynamics simulation of the pKID-KIX system, a well-studied IDP system, shows that the association rate becomes larger as the disorder-inducing flexibility that was imparted to the model is increased, but the acceleration is marginal and turns into deceleration as the quality of the fly lure is worsened. In contrast, the dissociation rate is greatly enhanced as the disorder is increased, indicating that intrinsic disorder serves for rapid signal switching more effectively through dissociation than association. Proteins 2016; 84:1124-1133. © 2016 Wiley Periodicals, Inc. PMID:27122223

  11. Ion-induced dissociation dynamics of acetylene

    SciTech Connect

    De, Sankar; Rajput, Jyoti; Roy, A.; Safvan, C. P.; Ghosh, P. N.

    2008-02-15

    We report on the results of dissociation dynamics of multiple charged acetylene molecules formed in collision with 1.2 MeV Ar{sup 8+} projectiles. Using the coincidence map, we can separate out the different dissociation pathways between carbon and hydrogen ionic fragments as well as complete two-body breakup events. From the measured slopes of the coincidence islands for carbon atomic fragments and theoretical values determined from the charge and momentum distribution of the correlated particles, we observe a diatom like behavior of the C-C charged complex during dissociation of multiply charged C{sub 2}H{sub 2}. We conclude that this behavior in breakup dynamics is a signature of sequentiality in dissociation of this multiply charged molecular species. The shape and orientation of the islands give further information about the momentum balance in the fragmentation process of two- or many-body dissociation pathways. Kinetic energy release of different breakup channels are reported here and compared with values calculated from the pure Coulomb explosion model.

  12. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, Charles G. [Pleasanton, CA

    1978-08-29

    A method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, .sup.235 UF.sub.6 is separated from a UF.sub.6 mixture by selective excitation followed by dissociative electron capture into .sup.235 UF.sub.5 - and F.

  13. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, C.G.

    1978-08-29

    Disclosed is a method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, [sup 235]UF[sub 6] is separated from a UF[sub 6] mixture by selective excitation followed by dissociative electron capture into [sup 235]UF[sub 5]- and F. 2 figs.

  14. Dissociation in virtual reality: depersonalization and derealization

    NASA Astrophysics Data System (ADS)

    Garvey, Gregory P.

    2010-01-01

    This paper looks at virtual worlds such as Second Life7 (SL) as possible incubators of dissociation disorders as classified by the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition3 (also known as the DSM-IV). Depersonalization is where "a person feels that he or she has changed in some way or is somehow unreal." Derealization when "the same beliefs are held about one's surroundings." Dissociative Identity Disorder (DID), previously known as multiple personality disorder fits users of Second Life who adopt "in-world" avatars and in effect, enact multiple distinct identities or personalities (known as alter egos or alters). Select questions from the Structured Clinical Interview for Depersonalization (SCI-DER)8 will be discussed as they might apply to the user's experience in Second Life. Finally I would like to consider the hypothesis that rather than a pathological disorder, dissociation is a normal response to the "artificial reality" of Second Life.

  15. Electron Transfer Dissociation of Oligonucleotide Cations.

    PubMed

    Smith, Suncerae I; Brodbelt, Jennifer S

    2009-06-01

    Electron transfer dissociation (ETD) of multi-protonated 6 - 20-mer oligonucleotides and 12- and 14-mer duplexes is compared to collision activated dissociation (CAD). ETD causes efficient charge reduction of the multi-protonated oligonucleotides in addition to limited backbone cleavages to yield sequence ions of low abundance. Subsequent CAD of the charge-reduced oligonucleotides formed upon electron transfer, in a net process termed electron transfer collision activated dissociation (ETcaD), results in rich fragmentation in terms of w, a, z, and d products, with a marked decrease in the abundance of base loss ions and internal fragments. Complete sequencing was possible for nearly all oligonucleotides studied. ETcaD of an oligonucleotide duplex resulted in specific backbone cleavages, with conservation of weaker non-covalent bonds. PMID:20161288

  16. Psychotherapy and pharmacotherapy for patients with dissociative identity disorder.

    PubMed

    Gentile, Julie P; Dillon, Kristy S; Gillig, Paulette Marie

    2013-02-01

    There is a wide variety of what have been called "dissociative disorders," including dissociative amnesia, dissociative fugue, depersonalization disorder, dissociative identity disorder, and forms of dissociative disorder not otherwise specified. Some of these diagnoses, particularly dissociative identity disorder, are controversial and have been questioned by many clinicians over the years. The disorders may be under-diagnosed or misdiagnosed, but many persons who have experienced trauma report "dissociative" symptoms. Prevalence of dissociative disorders is unknown, but current estimates are higher than previously thought. This paper reviews clinical, phenomenological, and epidemiological data regarding diagnosis in general, and illustrates possible treatment interventions for dissociative identity disorder, with a focus on psychotherapy interventions and a review of current psychopharmacology recommendations as part of a comprehensive multidisciplinary treatment plan. PMID:23556139

  17. Swirling flow of a dissociated gas

    NASA Technical Reports Server (NTRS)

    Wolfram, W. R., Jr.; Walker, W. F.

    1975-01-01

    Most physical applications of the swirling flow, defined as a vortex superimposed on an axial flow in the nozzle, involve high temperatures and the possibility of real gas effects. The generalized one-dimensional swirling flow in a converging-diverging nozzle is analyzed for equilibrium and frozen dissociation using the ideal dissociating gas model. Numerical results are provided to illustrate the major effects and to compare with results obtained for a perfect gas with constant ratio of specific heats. It is found that, even in the case of real gases, perfect gas calculations can give a good estimate of the reduction in mass flow due to swirl.

  18. Dissociation of ultracold molecules with Feshbach resonances

    SciTech Connect

    Duerr, Stephan; Volz, Thomas; Rempe, Gerhard

    2004-09-01

    Ultracold molecules are associated from an atomic Bose-Einstein condensate by ramping a magnetic field across a Feshbach resonance. The reverse ramp dissociates the molecules. The kinetic energy released in the dissociation process is used to measure the widths of four Feshbach resonances in {sup 87}Rb. This method to determine the width works remarkably well for narrow resonances even in the presence of significant magnetic-field noise. In addition, a quasimonoenergetic atomic wave is created by jumping the magnetic field across the Feshbach resonance.

  19. Dissociation and recombination in an inhomogeneous gas

    NASA Astrophysics Data System (ADS)

    Kuščer, Ivan

    1991-09-01

    The system of Boltzmann equations of Ludwig and Heil for a dissociating gas mixture is reviewed and reformulated in terms of differential cross sections. For the purpose of Monte Carlo simulations, collision models of the type of Borgnakke and Larsen are proposed. In case of short-lived transient flows of molecular gases and at not too high temperatures, simulation of scattering collisions is expected to suffice; the distribution function of the dissociated particles can be evaluated afterwards by integration, and recombination can be ignored.

  20. Quantum Zeno control of coherent dissociation

    SciTech Connect

    Khripkov, C.; Vardi, A.

    2011-08-15

    We study the effect of dephasing on the coherent dissociation dynamics of an atom-molecule Bose-Einstein condensate. We show that when phase-noise intensity is strong with respect to the inverse correlation time of the stimulated process, dissociation is suppressed via a Bose enhanced quantum Zeno effect. This is complementary to the quantum Zeno control of phase-diffusion in a bimodal condensate by symmetric noise [Phys. Rev. Lett. 100, 220403 (2008)] in that the controlled process here is phase formation and the required decoherence mechanism for its suppression is purely phase noise.

  1. Carbon monoxide dissociative attachment and resonant dissociation by electron-impact

    NASA Astrophysics Data System (ADS)

    Laporta, V.; Tennyson, J.; Celiberto, R.

    2016-02-01

    Low-energy dissociative electron attachment and resonant electron impact dissociation of CO molecule are considered. Ro-vibrationally resolved cross sections and rate coefficients for both the processes are calculated using an ab-initio model based on the low-lying \\text{X}{{}2}\\Pi resonance of CO-. Final results show that the cross sections increases very rapidly as a function of the ro-vibrational level; these cross sections should be useful for understanding kinetic dissociation of CO in strongly non-equilibrium plasmas.

  2. Kinetic ion thermometers for electron transfer dissociation.

    PubMed

    Pepin, Robert; Tureček, František

    2015-02-19

    Peptide fragment ions of the z-type were used as kinetic ion thermometers to gauge the internal energy of peptide cation-radicals produced by electron transfer in the gas-phase. Electron transfer dissociation (ETD)-produced z2 ions containing the leucine residue, z2(Leu-Lys) and z2(Leu-Arg), were found to undergo spontaneous dissociation by loss of C3H7 that was monitored by time-resolved kinetic measurements on the time scale of the linear ion trap mass spectrometer. Kinetic modeling of the dissociations, including collisional cooling and product loss by neutralization, provided unimolecular rate constants for dissociation that were converted to the z ion internal energies using RRKM theory. The internal energy of z2(Leu-Lys) and z2(Leu-Arg) fragment ions was found to decrease with the increasing size of the precursor peptide ion, indicating vibrational energy partitioning between the ion and neutral fragments and ergodic behavior. The experimentally determined excitation in the peptide cation-radicals upon electron transfer (285-327 kJ mol(-1)) was found to be lower than that theoretically calculated from the reaction exothermicity. The reasons for this missing energy are discussed. PMID:25594857

  3. Double Dissociation between Reading and Spelling Deficits

    ERIC Educational Resources Information Center

    Moll, Kristina; Landerl, Karin

    2009-01-01

    In two studies dissociations between reading and spelling skills were examined. Study 1 reports equally high prevalence rates for isolated deficits in reading (7%) or spelling (6%) in a representative sample (N = 2,029) of German-speaking elementary school children. In Study 2, children with isolated deficits were presented with the same words to…

  4. EVIDENCE FOR CO DISSOCIATION ON RHODIUM SURFACES

    SciTech Connect

    Castner, D.G.; Dubois, L.H.; Sexton, B.A.; Somorjai, G.A.

    1980-06-01

    Carbon monoxide adsorbs molecularly on rhodium surfaces at 300K, but if the rhodium samples are heated in the presence of carbon monoxide, there is evidence for carbon-oxygen bond breaking at step and/or defect sites. The effects of step and defect site density, subsurface oxygen concentration, and oxygen dissolution into the rhodium lattice on CO dissociation are discussed.

  5. Multiphoton dissociation of electrosprayed megadalton-sized DNA ions in a charge-detection mass spectrometer.

    PubMed

    Doussineau, Tristan; Paletto, Pierre; Dugourd, Philippe; Antoine, Rodolphe

    2015-01-01

    Charge detection mass spectrometry in combination with a linear electrostatic ion trap coupled to a continuous wavelength infrared CO2 laser has been used to study the multiphoton dissociation of DNA macromolecular ions. Samples, with masses ranging from 2.23 to 31.5 MDa, include single strand circular M13mp18, double strand circular M13mp18, and double strand linear LambdaPhage DNA fragments. Their activation energies for unimolecular dissociation were determined. Activation energy values slightly increase as a function of the molecular weight. The most important result is the difference between the fragmentations observed for hybridized double-strands and dimers of single strands. PMID:25348472

  6. Dissociative and double photoionization of CO2 from threshold to 90 A

    NASA Technical Reports Server (NTRS)

    Masuoka, T.; Samson, J. A. R.

    1979-01-01

    The molecular photoionization, dissociative photoionization and double photoionization cross sections for CO2 were measured from their onsets down to 90 A by using various combinations of mass spectrometers (a coincidence time-of-flight mass spectrometer and a magnetic mass spectrometer) and light sources (synchrotron radiation, and glow and spark discharge). It is concluded that the one broad peak and the three shoulders in the total adsorption cross section curve between 640 and 90 A are caused completely by dissociative ionization processes. Several peaks observed in the cross section curve for the total fragmentation CO(+)3, O(+) and C(+) are compared with those in the photoelectron spectrum reported for CO2.

  7. Electromagnetic dissociation of relativistic {sup 28}Si by nucleon emission

    SciTech Connect

    Sonnadara, U.J.

    1992-12-01

    A detailed study of the electromagnetic dissociation of {sup 28}Si by nucleon emission at E{sub lab}/A = 14.6 (GeV/nucleon was carried out with {sup 28}Si beams interacting on {sup 208}Pb). {sup 120}Sn. {sup 64}C targets. The measurements apparatus consists of detectors in the target area which measure the energy and charged multiplicity, and a forward spectrometer which measures the position, momentum and energy of the reaction fragments. The exclusive electromagnetic dissociation cross sections for decay channels having multiple nucleons in the final state have been measured which enables the selection of events produced in pure electromagnetic interactions. The measured cross sections agree well with previous measurements obtained for the removal of a few nucleons as well as with measurements on total charge removal cross sections from other experiments. The dependence of the integrated cross sections on the target charge Z{sub T} and the target mass AT confirms that for higher Z targets the excitation is largely electromagnetic. Direct measurements of the excitation energy for the electromagnetic dissociation of {sup 28}Si {yields} p+{sup 27}Al and {sup 28}Si {yields} n+{sup 27}Si have been obtained through a calculation of the invariant mass in kinematically, reconstructed events. The excitation energy spectrum for all targets peak near the isovector giant dipole resonance in {sup 28}Si. These distributions are well reproduced by combining the photon spectrum calculated using the Weizsaecker-Williams approximation with the experimental data on the photonuclear {sup 28}Si({sub {gamma},p}){sup 27}Al and {sup 28}Si({sub {gamma},n}){sup 27}Si. The possibilities of observing double giant dipole resonance excitations in {sup 28}Si have been investigated with cross section measurements as well as with excitation energy reconstruction.

  8. Electromagnetic dissociation of relativistic [sup 28]Si by nucleon emission

    SciTech Connect

    Sonnadara, U.J.

    1992-12-01

    A detailed study of the electromagnetic dissociation of [sup 28]Si by nucleon emission at E[sub lab]/A = 14.6 (GeV/nucleon was carried out with [sup 28]Si beams interacting on [sup 208]Pb). [sup 120]Sn. [sup 64]C targets. The measurements apparatus consists of detectors in the target area which measure the energy and charged multiplicity, and a forward spectrometer which measures the position, momentum and energy of the reaction fragments. The exclusive electromagnetic dissociation cross sections for decay channels having multiple nucleons in the final state have been measured which enables the selection of events produced in pure electromagnetic interactions. The measured cross sections agree well with previous measurements obtained for the removal of a few nucleons as well as with measurements on total charge removal cross sections from other experiments. The dependence of the integrated cross sections on the target charge Z[sub T] and the target mass AT confirms that for higher Z targets the excitation is largely electromagnetic. Direct measurements of the excitation energy for the electromagnetic dissociation of [sup 28]Si [yields] p+[sup 27]Al and [sup 28]Si [yields] n+[sup 27]Si have been obtained through a calculation of the invariant mass in kinematically, reconstructed events. The excitation energy spectrum for all targets peak near the isovector giant dipole resonance in [sup 28]Si. These distributions are well reproduced by combining the photon spectrum calculated using the Weizsaecker-Williams approximation with the experimental data on the photonuclear [sup 28]Si([sub [gamma],p])[sup 27]Al and [sup 28]Si([sub [gamma],n])[sup 27]Si. The possibilities of observing double giant dipole resonance excitations in [sup 28]Si have been investigated with cross section measurements as well as with excitation energy reconstruction.

  9. Experimental Dissociation of Methane Hydrates Through Depressurization

    NASA Astrophysics Data System (ADS)

    Borgfeldt, T.; Flemings, P. B.; Meyer, D.; You, K.

    2015-12-01

    We dissociated methane hydrates by stepwise depressurization. The initial hydrates were formed by injecting gas into a cylindrical sample of brine-saturated, coarse-grained sand at hydrate-stable conditions with the intention of reaching three-phase equilibrium. The sample was initially at 1°C with a pore pressure of 1775 psi and a salinity of 7 wt. % NaBr. The depressurization setup consisted of one pump filled with tap water attached to the confining fluid port and a second pump attached to the inlet port where the methane was injected. Depressurization was conducted over sixteen hours at a constant temperature of 1°C. The pore pressure was stepwise reduced from 1775 psi to atmospheric pressure by pulling known volumes of gas from the sample. After each extraction, we recorded the instantaneous and equilibrium pore pressure. 0.503 moles of methane were removed from the sample. The pore pressure decreased smoothly and nonlinearly with the cumulative gas withdrawn from the sample. We interpret that hydrate began to dissociate immediately with depressurization, and it continued to dissociate when the pressure decreased below the three-phase pressure for 1°C and 0 wt. % salinity. Two breaks in slope in the pressure vs. mass extracted data are bounded by smooth, nonlinear curves with differing slopes on either side. We attribute the breaks to dissociation of three zones of hydrate concentration. We created a box model to simulate the experimental behavior. For a 10% initial gas saturation (estimated from the hydrate formation experiment and based on mass conservation), an initial hydrate saturation of 55% is required to match the total methane extracted from the sample. Future experiments will be conducted over a longer timespan while monitoring hydrate dissociation with CT imaging throughout the process.

  10. Thermal dissociation behavior and dissociation enthalpies of methane-carbon dioxide mixed hydrates

    SciTech Connect

    Kwon, T.H.; Kneafsey, T.J.; Rees, E.V.L.

    2011-02-15

    Replacement of methane with carbon dioxide in hydrate has been proposed as a strategy for geologic sequestration of carbon dioxide (CO{sub 2}) and/or production of methane (CH{sub 4}) from natural hydrate deposits. This replacement strategy requires a better understanding of the thermodynamic characteristics of binary mixtures of CH{sub 4} and CO{sub 2} hydrate (CH{sub 4}-CO{sub 2} mixed hydrates), as well as thermophysical property changes during gas exchange. This study explores the thermal dissociation behavior and dissociation enthalpies of CH{sub 4}-CO{sub 2} mixed hydrates. We prepared CH{sub 4}-CO{sub 2} mixed hydrate samples from two different, well-defined gas mixtures. During thermal dissociation of a CH{sub 4}-CO{sub 2} mixed hydrate sample, gas samples from the head space were periodically collected and analyzed using gas chromatography. The changes in CH{sub 4}-CO{sub 2} compositions in both the vapor phase and hydrate phase during dissociation were estimated based on the gas chromatography measurements. It was found that the CO{sub 2} concentration in the vapor phase became richer during dissociation because the initial hydrate composition contained relatively more CO{sub 2} than the vapor phase. The composition change in the vapor phase during hydrate dissociation affected the dissociation pressure and temperature; the richer CO{sub 2} in the vapor phase led to a lower dissociation pressure. Furthermore, the increase in CO{sub 2} concentration in the vapor phase enriched the hydrate in CO{sub 2}. The dissociation enthalpy of the CH{sub 4}-CO{sub 2} mixed hydrate was computed by fitting the Clausius-Clapeyron equation to the pressure-temperature (PT) trace of a dissociation test. It was observed that the dissociation enthalpy of the CH{sub 4}-CO{sub 2} mixed hydrate lays between the limiting values of pure CH{sub 4} hydrate and CO{sub 2} hydrate, increasing with the CO{sub 2} fraction in the hydrate phase.

  11. Psychotherapy and Pharmacotherapy for Patients with Dissociative Identity Disorder

    PubMed Central

    Gentile, Julie P.; Dillon, Kristy S.

    2013-01-01

    There is a wide variety of what have been called “dissociative disorders,” including dissociative amnesia, dissociative fugue, depersonalization disorder, dissociative identity disorder, and forms of dissociative disorder not otherwise specified. Some of these diagnoses, particularly dissociative identity disorder, are controversial and have been questioned by many clinicians over the years. The disorders may be under-diagnosed or misdiagnosed, but many persons who have experienced trauma report “dissociative” symptoms. Prevalence of dissociative disorders is unknown, but current estimates are higher than previously thought. This paper reviews clinical, phenomenological, and epidemiological data regarding diagnosis in general, and illustrates possible treatment interventions for dissociative identity disorder, with a focus on psychotherapy interventions and a review of current psychopharmacology recommendations as part of a comprehensive multidisciplinary treatment plan. PMID:23556139

  12. What contributes to predicting change in the treatment of dissociation: initial levels of dissociation, PTSD, or overall distress?

    PubMed

    Brand, Bethany L; Stadnik, Ryan

    2013-01-01

    Individuals with dissociative disorders (DDs) suffer from high levels of dissociation as well as posttraumatic stress disorder (PTSD) and general distress. No research has investigated how changes in dissociation relate to changes in other symptoms over the course of treatment in patients with DD. Using a prospective, naturalistic design, we collected reports of symptoms from a sample of therapists and their patients diagnosed with dissociative identity disorder or dissociative disorder not otherwise specified who participated in the Treatment Outcome of Patients with Dissociative Disorders study. The patients completed surveys at intake (Time 1) into the study and at 30-month follow-up (Time 4). We found that dissociative symptoms, including amnesia, depersonalization/derealization, and absorption, at the initial assessment of the study ("initial") were related to initial levels of PTSD and general distress and that changes in dissociative symptoms were related to changes in PTSD and general distress. Initial dissociation was a significant predictor of change in dissociation at 30 months when we controlled for length of time for follow-up, length of time practicing therapy, and length of time treating dissociative patients. Our results suggest that a reduction in dissociative symptoms in DD patients is associated with reductions in the overall severity of dissociative, posttraumatic stress, and distress symptoms. PMID:23627481

  13. The H2 dissociation on the BN, AlN, BP and AlP nanotubes: a comparative study.

    PubMed

    Beheshtian, Javad; Soleymanabadi, Hamed; Kamfiroozi, Mohammad; Ahmadi, Ali

    2012-06-01

    The thermodynamic and kinetic feasibility of H(2) dissociation on the BN, AlN, BP and AlP zigzag nanotubes has been investigated theoretically by calculating the dissociation and activation energies. We determined the BN and AlP tubes to be inert toward H(2) dissociation, both thermodynamically and kinetically. The reactions are endothermic by 5.8 and 3 kcal mol(-1), exhibiting high activation energies of 38.8 and 30.6 kcal mol(-1), respectively. Our results indicated that H(2) dissociation is thermodynamically favorable on both PB and AlN nanotubes. However, in spite of the thermodynamic feasibility of H(2) dissociation on PB types, this process is kinetically unfavorable due to partly high activation energy. Generally, we concluded that among the four studied tubes, the AlN nanotube may be an appropriate model for H(2) dissociation process, from a thermodynamic and kinetic stand point. We also indicated that H(2) dissociation is not homolytic, rather it takes place via a heterolytic bond cleavage. In addition, a comparative study has been performed on the electrical and geometrical properties of the tubes. Our analysis showed that the electrical conductivity of tubes is as follows: BP>AlP>BN>AlN depending on how to combine the electron rich and electron poor atoms. PMID:21979405

  14. Numerical simulation of the dissociation of I2 by O2 (1 Delta) in a two dimensional parallel jet

    NASA Astrophysics Data System (ADS)

    Miller, Jeffrey A.

    1989-03-01

    The thin-shear-layer equations are solved for a two dimensional parallel jet of molecular iodine in singlet delta oxygen freestream, to investigate the effect of mixing and water vapor on molecular iodine dissociation in Chemical Oxygen-Iodine Lasers (COIL). Predicting the dissociation of molecular iodine has been identified as the largest source of error in COIL performance modeling. Recent experimental and modeling experience have indicated that much of the problem may be due to the coupled iodine mixing and dissociation process. The numerical code was used to study the combined mixing and dissociation problem. Comparison of a set of 1-D premixed cases and 2-D jet cases with varying jet velocity ratios (and mixing rates) indicates that, imperfect mixing which results in initial regions of high iodine concentration leads to faster dissociation rates. High laser gain, however, does require efficient mixing. The results of both premixed and jet mixed cases with and without water vapor in the oxygen stream demonstrate the strong dependence of the dissociation efficiency (i.e., the penalty paid to dissociate iodine) on both the device geometry and operating conditions which challenges the wisdom of suing empirically determined efficiency factors to predict COIL performance.

  15. A molecular dynamics study of melting and dissociation of tungsten nanoparticles

    NASA Astrophysics Data System (ADS)

    Li, Min; Wang, Jun; Fu, Baoqin; Hou, Qing

    2015-12-01

    Molecular dynamics simulations were conducted to study the melting and dissociation of free tungsten nanoparticles. For the various interatomic potentials applied, the melting points of the tungsten nanoparticles increased with increasing nanoparticle diameter. Combining these results with the melting point of bulk tungsten in the experiment, the melting point of nanoparticles with diameters ranging from 4 to 12 nm could be determined. As the temperature increases, free nanoparticles are subject to dissociation phenomena. The dissociation rate was observed to follow Arrhenius behavior, and the Meyer-Neldel rule was obeyed. These results are useful in understanding the behavior of tungsten dust generated in nuclear fusion devices as well as for the preparation, formation, and application of tungsten powders.

  16. Comparison of vibration dissociation coupling and radiative heat transfer models for AOTV/AFE flowfields

    NASA Technical Reports Server (NTRS)

    Carlson, Leland A.; Bobskill, Glenn J.; Greendyke, Robert B.

    1988-01-01

    A series of detailed studies comparing various vibration dissociation coupling models, reaction systems and rates, and radiative heating models has been conducted for the nonequilibrium stagnation region of an AFE/AOTV vehicle. Atomic and molecular nonequilibrium radiation correction factors have been developed and applied to various absorption coefficient step models, and a modified vibration dissociation coupling model has been shown to yield good vibration/electronic temperature and concentration profiles. While results indicate sensitivity to the choice of vibration dissociation coupling model and to the nitrogen electron impact ionization rate, by proper combinations accurate flowfield and radiative heating results can be obtained. These results indicate that nonequilibrium effects significantly affect the flowfield and the radiative heat transfer. However, additional work is needed in ionization chemistry and absorption coefficient modeling.

  17. Signatures of bond formation and bond scission dynamics in dissociative electron attachment to methane.

    PubMed

    Douguet, N; Slaughter, D S; Adaniya, H; Belkacem, A; Orel, A E; Rescigno, T N

    2015-10-14

    We present a combined experimental and theoretical investigation of the dynamics and angular dependence of dissociative electron attachment to methane. We show that a triply degenerate (T2) Feshbach resonance is responsible for the broad 10 eV dissociation peak in methane. This resonance alone is shown to correlate asymptotically to the various dissociation channels observed experimentally. The molecular-frame entrance amplitude for electron attachment is calculated for each component of the threefold degenerate resonance. By investigating the topology of the anion potential energy surfaces, we deduce the main pathways to two- and three-body breakup channels involving both bond scission and bond formation. The computed fragment angular distributions reproduce the main trends of the experimental measurements. PMID:26371546

  18. Coherent dissociation of relativistic {sup 9}C nuclei in nuclear track emulsion

    SciTech Connect

    Krivenkov, D. O.; Artemenkov, D. A.; Bradnova, V.; Kattabekov, R. R.; Kondratieva, N. V.; Mamatkulov, K. Z.; Malakhov, A. I.; Rukoyatkin, P. A.; Rusakova, V. V.; Stanoeva, R.; Zarubin, P. I.; Zarubina, I. G.; Haiduc, M.; Kharlamov, S. P.; Orlova, G. I.; Peresadko, N. G.; Polukhina, N. G.; Moiseenko, A. A.; Sarkisyan, V. R.; Vokal, S.

    2010-04-30

    For the first time nuclear track emulsion is exposed to relativistic {sup 9}C nuclei. A systematic pattern of the distributions of charge combinations of fragments in the peripheral interactions of {sup 9}C nuclei in a nuclear track emulsion has been obtained. The main conclusion is that the contribution of the channel {sup 9}C->{sup 8}B+p and {sup 9}C->{sup 7}Be+2p is most important in events that do not involve the production of target-nucleus fragments or mesons (coherent dissociation). It can be concluded that in the peripheral {sup 9}C dissociation the picture hitherto obtained for {sup 8}B and {sup 7}Be with the addition of one or two protons, respectively, is reproduced. Three coherent dissociation events {sup 9}C->3{sup 3}He accompanied by neither target fragments of the nucleus target nor charged mesons are identified.

  19. Hydrogen Dissociation, Spillover, and Desorption from Cu-Supported Co Nanoparticles.

    PubMed

    Lewis, Emily A; Marcinkowski, Matthew D; Murphy, Colin J; Liriano, Melissa L; Sykes, E Charles H

    2014-10-01

    Co-Cu nanoparticles have recently been explored for Fischer-Tropsch synthesis (FTS) as a way to combine the long chain selectivity of Co with Cu's activity for alcohol formation in order to synthesize oxygenated transportation fuels. Depending on particle size, hydrogen dissociation can be a rate-determining step in cobalt-catalyzed FTS. To understand the fundamentals of uptake and release of hydrogen from the Co/Cu bimetallic system, we prepared well-defined Co nanoparticles on Cu(111). We demonstrate that hydrogen spills over from dissociation sites on the Co nanoparticles to the Cu(111) surface via the Co-Cu interface and that desorption of H occurs at a temperature that is lower than from Co or Cu alone, which we attribute to the Co-Cu interface sites. From this data, we have constructed an energy landscape for the facile dissociation, spillover, and desorption of hydrogen on the Co-Cu bimetallic system. PMID:26278448

  20. A molecular dynamics study of melting and dissociation of tungsten nanoparticles

    SciTech Connect

    Li, Min; Wang, Jun; Fu, Baoqin; Hou, Qing

    2015-12-15

    Molecular dynamics simulations were conducted to study the melting and dissociation of free tungsten nanoparticles. For the various interatomic potentials applied, the melting points of the tungsten nanoparticles increased with increasing nanoparticle diameter. Combining these results with the melting point of bulk tungsten in the experiment, the melting point of nanoparticles with diameters ranging from 4 to 12 nm could be determined. As the temperature increases, free nanoparticles are subject to dissociation phenomena. The dissociation rate was observed to follow Arrhenius behavior, and the Meyer–Neldel rule was obeyed. These results are useful in understanding the behavior of tungsten dust generated in nuclear fusion devices as well as for the preparation, formation, and application of tungsten powders.

  1. The dissociation between subjective workload and performance A multiple resource approach

    NASA Technical Reports Server (NTRS)

    Wickens, C. D.; Yeh, Y.-Y.

    1983-01-01

    A theory of the dissociation between subjective measures of mental workload and performance is described. The theory proposes that subjective measures are heavily driven by the number of tasks or task elements that a subject must perform concurrently. However they are relatively less sensitive to whether these tasks compete for common or separate resources, and to the difficulty of a single task, particularly if this difficulty is related to response factors. Performance, on the other hand, is particularly influenced by single task difficulty of both a perceptual and response nature and by resource competition between tasks. A set of three experiments are described to examine the dissociation between subjective difficulty measures and performance. These experiments employ different combinations of three tasks: tracking, memory search, and a simulated air traffic control problem. The results supported all forms of dissociation predicted by the theory and the implications of results to workload measurement are discussed.

  2. Surface induced dissociation yields substructure of Methanosarcina thermophila 20S proteasome complexes

    PubMed Central

    Ma, Xin; Loo, Joseph A.; Wysocki, Vicki H.

    2015-01-01

    Native mass spectrometry (MS) and surface induced dissociation (SID) have been applied to study the stoichiometry and quaternary structure of non-covalent protein complexes. In this study, Methanosarcina thermophila 20S proteasome, which consists of four stacked heptameric rings (α7β7β7α7 symmetry), has been selected to explore the SID dissociation pattern of a complicated stacked ring protein complex. SID produces both α and β subunits while collision induced dissociation (CID) produces only highly charged α subunit. In addition, the charge reduced 20S proteasome produces the α7β7 fragment, reflecting the stacked ring topology of the complex. The combination of SID and charge reduction is shown to be a powerful tool for the study of protein complex structure. PMID:26005366

  3. Revealing Dissociative Electron Attachment Dynamics in Polyatomic Molecules Using Momentum Imaging Experiments and Electron Scattering Calculations

    NASA Astrophysics Data System (ADS)

    Belkacem, Ali; Slaughter, Daniel

    2015-05-01

    Understanding electron-driven chemical reactions is important for improving a variety of technological applications such as materials processing and the important role they play in the radiation damage in bulk matter. Furthermore, dissociative electron attachment often exhibits site-selective bond cleavage, which holds promise for prediction and precise control of electron-driven chemical reactions. Recent dynamical studies of these reactions have demonstrated that an understanding of anion dissociation dynamics beyond simple one-dimensional models is crucial in interpreting the measured fragment angular distributions. We combine ion fragment momentum imaging experiments with electron attachment entrance amplitude calculations to interrogate the non-Born-Oppenheimer dynamics of dissociative electron attachment in polyatomic molecules. We will report recent experimental developments in molecules of technological interest including methanol, methane and uracil. Work supported by Chemical Sciences, Geosciences and Biosciences division of BES/DOE.

  4. Kinetics of Propargyl Radical Dissociation.

    PubMed

    Klippenstein, Stephen J; Miller, James A; Jasper, Ahren W

    2015-07-16

    Due to the prominent role of the propargyl radical for hydrocarbon growth within combustion environments, it is important to understand the kinetics of its formation and loss. The ab initio transition state theory-based master equation method is used to obtain theoretical kinetic predictions for the temperature and pressure dependence of the thermal decomposition of propargyl, which may be its primary loss channel under some conditions. The potential energy surface for the decomposition of propargyl is first mapped at a high level of theory with a combination of coupled cluster and multireference perturbation calculations. Variational transition state theory is then used to predict the microcanonical rate coefficients, which are subsequently implemented within the multiple-well multiple-channel master equation. A variety of energy transfer parameters are considered, and the sensitivity of the thermal rate predictions to these parameters is explored. The predictions for the thermal decomposition rate coefficient are found to be in good agreement with the limited experimental data. Modified Arrhenius representations of the rate constants are reported for utility in combustion modeling. PMID:25871530

  5. Conditional dissociation as a punishment mechanism in the evolution of cooperation

    NASA Astrophysics Data System (ADS)

    Qu, Xinglong; Zhou, Changli; Cao, Zhigang; Yang, Xiaoguang

    2016-05-01

    Recent studies show that conditional dissociation, a.k.a. post-interaction partner-refusal, can promote the emergence and stability of cooperation. However, in most of these studies, players' strategies are restricted to pure ones, which is obviously inconsistent with many biological and economic situations. Another concern with line of these studies is that conditional dissociation is often combined with other mechanisms. These mechanisms may favor cooperation per se, leaving it unclear whether conditional dissociation is indeed a key factor. In this paper, we study a clean model, pruning all the factors other than conditional dissociation that may favor cooperation. We find that conditional dissociation, which could be viewed as a variant of peer punishment, does promote cooperation, no matter whether mixed strategies are allowed or not. This confirms the previous findings in the literature. In addition, compared with the pure strategy scenario, cooperators are less competitive when mixed strategies are allowed. Our main finding is supported by both the numerical simulations and the theoretical analysis of Neutrally Stable Strategy. We also find that cooperative behavior is favored when waiting time and/or the population's lifespan are longer.

  6. Dissociation of acetaldehyde in intense laser field: Coulomb explosion or field-assisted dissociation?

    NASA Astrophysics Data System (ADS)

    Elshakre, Mohamed E.; Gao, Lirong; Tang, Xiaoping; Wang, Sufan; Shu, Yafei; Kong, Fanao

    2003-09-01

    Dissociation of acetaldehyde in moderate strong laser field of 1013-1014W/cm2 was investigated. Singly charged parent ion CH3CHO+ and fragmental ions CH3+, CHO+, C2H4+, O+, CH2CHO+, and H+ were produced by 800 nm laser of 100 fs pulse duration and recorded by time-of-flight mass spectrometer. The CH3+ fragment further dissociated to CH2+, CH+, and C+ ions at higher intensity. Ab initio calculated results show that the singly-, doubly-, and triply charged parent ions are stable. So, the dissociation mechanism was not due to Coulomb explosion of multicharged ion. A field-assisted dissociation (FAD) theory, which assumes that only one bond undergoes dissociation while the rest of the molecular geometry stays unchanged, was employed to treat the dissociation dynamics. Accordingly, the dressed potential energy surfaces of the ground state for the parent and the fragment ions were calculated. Corresponding quasiclassical trajectory calculations show that the bond ruptures take place in the order of C-C, C-O, and C-H, agreeing with the observation. The observed angular dependence and charge distribution of the product ions can also be interpreted by the FAD theory.

  7. Does phasic trauma treatment make patients with dissociative identity disorder treatment more dissociative?

    PubMed

    Brand, Bethany; Loewenstein, Richard J

    2014-01-01

    Proponents of the iatrogenic model of the etiology of dissociative identity disorder (DID) have expressed concern that treatment focused on direct engagement and interaction with dissociated self-states harms DID patients. However, empirical data have shown that this type of DID treatment is beneficial. Analyzing data from the prospective Treatment of Patients With Dissociative Disorders (TOP DD) Study, we test empirically whether DID treatment is associated with clinically adverse manifestations of dissociated self-states: acting so differently that one feels like different people, hearing voices, and dissociative amnesia. We show that, over the course of the study, there were significant decreases in feeling like different people and hearing voices. These results indicate that this form of DID treatment does not lead to symptomatic worsening in these dimensions, as predicted by the iatrogenic model. Indeed, treatment provided by TOP DD therapists reduced, rather than increased, the extent to which patients experienced manifestations of pathological dissociation. Because severe symptomatology and impairment are associated with DID, iatrogenic harm may come from depriving DID patients of treatment that targets DID symptomatology. PMID:24377972

  8. In-Vacuum Dissociator for Atomic-Hydrogen Masers

    NASA Technical Reports Server (NTRS)

    Vessot, R. F.

    1987-01-01

    Thermal control and vacuum sealing achieved while contamination avoided. Simple, relatively inexpensive molecular-hydrogen dissociator for atomic-hydrogen masers used on Earth or in vacuum of space. No air cooling required, and absence of elastomeric O-ring seals prevents contamination. In-vacuum dissociator for atomic hydrogen masers, hydrogen gas in glass dissociator dissociated by radio-frequency signal transmitted from surrounding 3-turn coil. Heat in glass conducted away by contacting metal surfaces.

  9. Cognitive Processes in Dissociation: Comment on Giesbrecht et al. (2008)

    ERIC Educational Resources Information Center

    Bremner, J. Douglas

    2010-01-01

    In their recent review "Cognitive Processes in Dissociation: An Analysis of Core Theoretical Assumptions," published in "Psychological Bulletin", Giesbrecht, Lynn, Lilienfeld, and Merckelbach (2008) have challenged the widely accepted trauma theory of dissociation, which holds that dissociative symptoms are caused by traumatic stress. In doing so,…

  10. 21 CFR 886.1910 - Spectacle dissociation test system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Spectacle dissociation test system. 886.1910... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1910 Spectacle dissociation test system. (a) Identification. A spectacle dissociation test system is an AC-powered or...

  11. 21 CFR 886.1910 - Spectacle dissociation test system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Spectacle dissociation test system. 886.1910... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1910 Spectacle dissociation test system. (a) Identification. A spectacle dissociation test system is an AC-powered or...

  12. 21 CFR 886.1910 - Spectacle dissociation test system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Spectacle dissociation test system. 886.1910... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1910 Spectacle dissociation test system. (a) Identification. A spectacle dissociation test system is an AC-powered or...

  13. 21 CFR 886.1910 - Spectacle dissociation test system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Spectacle dissociation test system. 886.1910... (CONTINUED) MEDICAL DEVICES OPHTHALMIC DEVICES Diagnostic Devices § 886.1910 Spectacle dissociation test system. (a) Identification. A spectacle dissociation test system is an AC-powered or...

  14. Development, Reliability, and Validity of a Child Dissociation Scale.

    ERIC Educational Resources Information Center

    Putnam, Frank W.; And Others

    1993-01-01

    Evaluation of the Child Dissociative Checklist found it to be a reliable and valid observer report measure of dissociation in children, including sexually abused girls and children with dissociative disorder and with multiple personality disorder. The checklist, which is appended, is intended as a clinical screening instrument and research measure…

  15. Speech-Language Dissociations, Distractibility, and Childhood Stuttering

    PubMed Central

    Conture, Edward G.; Walden, Tedra A.; Lambert, Warren E.

    2015-01-01

    Purpose This study investigated the relation among speech-language dissociations, attentional distractibility, and childhood stuttering. Method Participants were 82 preschool-age children who stutter (CWS) and 120 who do not stutter (CWNS). Correlation-based statistics (Bates, Appelbaum, Salcedo, Saygin, & Pizzamiglio, 2003) identified dissociations across 5 norm-based speech-language subtests. The Behavioral Style Questionnaire Distractibility subscale measured attentional distractibility. Analyses addressed (a) between-groups differences in the number of children exhibiting speech-language dissociations; (b) between-groups distractibility differences; (c) the relation between distractibility and speech-language dissociations; and (d) whether interactions between distractibility and dissociations predicted the frequency of total, stuttered, and nonstuttered disfluencies. Results More preschool-age CWS exhibited speech-language dissociations compared with CWNS, and more boys exhibited dissociations compared with girls. In addition, male CWS were less distractible than female CWS and female CWNS. For CWS, but not CWNS, less distractibility (i.e., greater attention) was associated with more speech-language dissociations. Last, interactions between distractibility and dissociations did not predict speech disfluencies in CWS or CWNS. Conclusions The present findings suggest that for preschool-age CWS, attentional processes are associated with speech-language dissociations. Future investigations are warranted to better understand the directionality of effect of this association (e.g., inefficient attentional processes → speech-language dissociations vs. inefficient attentional processes ← speech-language dissociations). PMID:26126203

  16. Cognitive Processes in Dissociation: An Analysis of Core Theoretical Assumptions

    ERIC Educational Resources Information Center

    Giesbrecht, Timo; Lilienfield, Scott O.; Lynn, Steven Jay; Merckelbach, Harald

    2008-01-01

    Dissociation is typically defined as the lack of normal integration of thoughts, feelings, and experiences into consciousness and memory. The present article critically evaluates the research literature on cognitive processes in dissociation. The authors' review indicates that dissociation is characterized by subtle deficits in neuropsychological…

  17. MDMA, cannabis, and cocaine produce acute dissociative symptoms.

    PubMed

    van Heugten-Van der Kloet, Dalena; Giesbrecht, Timo; van Wel, Janelle; Bosker, Wendy M; Kuypers, Kim P C; Theunissen, Eef L; Spronk, Desirée B; Jan Verkes, Robbert; Merckelbach, Harald; Ramaekers, Johannes G

    2015-08-30

    Some drugs of abuse may produce dissociative symptoms, but this aspect has been understudied. We explored the dissociative potential of three recreational drugs (3,4-methylenedioxymethamphetamine (MDMA), cannabis, and cocaine) during intoxication and compared their effects to literature reports of dissociative states in various samples. Two placebo-controlled studies were conducted. In Study 1 (N=16), participants received single doses of 25, 50, and 100 mg of MDMA, and placebo. In Study 2 (N=21), cannabis (THC 300 µg/kg), cocaine (HCl 300 mg), and placebo were administered. Dissociative symptoms as measured with the Clinician-Administered Dissociative States Scale (CADSS) significantly increased under the influence of MDMA and cannabis. To a lesser extent, this was also true for cocaine. Dissociative symptoms following MDMA and cannabis largely exceeded those observed in schizophrenia patients, were comparable with those observed in Special Forces soldiers undergoing survival training, but were lower compared with ketamine-induced dissociation. Cocaine produced dissociative symptoms that were comparable with those observed in schizophrenia patients, but markedly less than those in Special Forces soldiers and ketamine users. Thus, MDMA and cannabis can produce dissociative symptoms that resemble dissociative pathology. The study of drug induced dissociation is important, because it may shed light on the mechanisms involved in dissociative psychopathology. PMID:26003508

  18. Rate coefficients for dissociative attachment and resonant electron-impact dissociation involving vibrationally excited O{sub 2} molecules

    SciTech Connect

    Laporta, V.; Celiberto, R.; Tennyson, J.

    2014-12-09

    Rate coefficients for dissociative electron attachment and electron-impact dissociation processes, involving vibrationally excited molecular oxygen, are presented. Analytical fits of the calculated numerical data, useful in the applications, are also provided.

  19. Vibrational relaxation and dissociation in nitrogen

    NASA Technical Reports Server (NTRS)

    Varghese, Philip L.; Gonzales, David A.

    1991-01-01

    Calculations of the vibrational and dissociation transition probabilities are made for N2-N2 and N2-N collisions by means of a semiclassical N-state approximation. The flaws in previous techniques are reviewed, with special attention given to the prediction of overtones. The method presented ignores the effects of molecular rotation and employs a revised extended Rydberg intermolecular potential to describe diatom-diatom and diatom-atom collisions. The collision velocities investigated exhibit probabilities of less than unity by means of the N-state method. The continuum is quantized to treat dissociation, and the collision results demonstrate probability enhancements for V-V-T transitions in both bound-bound and bound-free transitions. The technique is of particular interest for the theoretical modeling of reentry flows such as those encountered in aerobraking maneuvers.

  20. The dissociation energy of N2

    NASA Technical Reports Server (NTRS)

    Almloef, Jan; Deleeuw, Bradley J.; Taylor, Peter R.; Bauschlicher, Charles W., Jr.; Siegbahn, Per

    1989-01-01

    The requirements for very accurate ab initio quantum chemical prediction of dissociation energies are examined using a detailed investigation of the nitrogen molecule. Although agreement with experiment to within 1 kcal/mol is not achieved even with the most elaborate multireference CI (configuration interaction) wave functions and largest basis sets currently feasible, it is possible to obtain agreement to within about 2 kcal/mol, or 1 percent of the dissociation energy. At this level it is necessary to account for core-valence correlation effects and to include up to h-type functions in the basis. The effect of i-type functions, the use of different reference configuration spaces, and basis set superposition error were also investigated. After discussing these results, the remaining sources of error in our best calculations are examined.

  1. Vibration dissociation coupling in nonequilibrium flows

    NASA Technical Reports Server (NTRS)

    Candler, Graham V.

    1992-01-01

    The final report on research between North Carolina State University and the NASA Ames Research Center is presented. The research was aimed at using the Schwartz, Slawsky, Herzfeld (SSH) theory to simulate the vibrational relaxation of nitrogen molecules undergoing dissociation or recombination over a wide range of conditions. The results of these simulations were then treated as exact, and they were used to develop a model for the coupled vibration-dissociation process. This new model is simple enough to be used in computational fluid dynamics codes, but still captures the physics of the complex process. The model is used to simulate the flow over typical geometries to test it and to determine how much impact it has on the flow field. The key elements of this research are summarized.

  2. Fluid hydrogen at high density - Pressure dissociation

    NASA Technical Reports Server (NTRS)

    Saumon, Didier; Chabrier, Gilles

    1991-01-01

    A model for the Helmholtz free energy of fluid hydrogen at high density and high temperature is developed. This model aims at describing both pressure and temperature dissociation and ionization and bears directly on equations of state of partially ionized plasmas, as encountered in astrophysical situations and high-pressure experiments. This paper focuses on a mixture of hydrogen atoms and molecules and is devoted to the study of the phenomenon of pressure dissociation at finite temperatures. In the present model, the strong interactions are described with realistic potentials and are computed with a modified Weeks-Chandler-Andersen fluid perturbation theory that reproduces Monte Carlo simulations to better than 3 percent. Theoretical Hugoniot curves derived from the model are in excellent agreement with experimental data.

  3. The charmonium dissociation in an ''anomalous wind''

    DOE PAGESBeta

    Sadofyev, Andrey V.; Yin, Yi

    2016-01-11

    We study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries "anomalous flow" induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the "anomalous flow" would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the "anomalous flow" experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and it qualitative difference between anomalous effects on the charmoniummore » color screening length which are model-dependent and those on the heavy quark drag force which are fixed by the second law of thermodynamics. As a result, we speculate on the possible charmonium dissociation induced by the chiral anomaly in heavy ion collisions.« less

  4. On the dissociation pathways of nitrobenzene

    NASA Astrophysics Data System (ADS)

    Kosmidis, C.; Ledingham, K. W. D.; Clark, A.; Marshall, A.; Jennings, R.; Sander, J.; Singhal, R. P.

    1994-08-01

    The fragmentation of nitrobenzene has been studied in the wavelength range 225-275 nm using a single dye laser, frequency doubled, in conjunction with a time-of-flight (TOF) mass spectrometer. The parent (C6H5NO2+), nitrosobenzene (C6H5NO+), phenoxy (C6H5O+) and phenyl (C6H5+) ions were all observed in addition to many other lighter daughter fragments. The formation of the nitrobenzene, phenoxy and phenyl ions are all explained invoking pathways where dissociation of the parent molecule from an excited state takes place first, followed by ionization after the absorption of further photons (DI) by the fragmented neutrals. Ionization of the parent molecule to states which are dissociative (ID) can explain the increase in the production of phenyl ions at wavelengths shorter than 230 nm.

  5. The charmonium dissociation in an "anomalous wind"

    NASA Astrophysics Data System (ADS)

    Sadofyev, Andrey V.; Yin, Yi

    2016-01-01

    We study the charmonium dissociation in a strongly coupled chiral plasma in the presence of magnetic field and axial charge imbalance. This type of plasma carries "anomalous flow" induced by the chiral anomaly and exhibits novel transport phenomena such as chiral magnetic effect. We found that the "anomalous flow" would modify the charmonium color screening length by using the gauge/gravity correspondence. We derive an analytical expression quantifying the "anomalous flow" experienced by a charmonium for a large class of chiral plasma with a gravity dual. We elaborate on the similarity and qualitative difference between anomalous effects on the charmonium color screening length which are model-dependent and those on the heavy quark drag force which are fixed by the second law of thermodynamics. We speculate on the possible charmonium dissociation induced by the chiral anomaly in heavy ion collisions.

  6. Theoretical dissociation energies for ionic molecules

    NASA Technical Reports Server (NTRS)

    Langhoff, S. R.; Bauschlicher, C. W., Jr.; Partridge, H.

    1986-01-01

    Ab initio calculations at the self-consistent-field and singles plus doubles configuration-interaction level are used to determine accurate spectroscopic parameters for most of the alkali and alkaline-earth fluorides, chlorides, oxides, sulfides, hydroxides, and isocyanides. Numerical Hartree-Fock (NHF) calculations are performed on selected systems to ensure that the extended Slater basis sets employed for the diatomic systems are near the Hartree-Fock limit. Extended Gaussian basis sets of at least triple-zeta plus double polarization equality are employed for the triatomic system. With this model, correlation effects are relatively small, but invariably increase the theoretical dissociation energies. The importance of correlating the electrons on both the anion and the metal is discussed. The theoretical dissociation energies are critically compared with the literature to rule out disparate experimental values. Theoretical (sup 2)Pi - (sup 2)Sigma (sup +) energy separations are presented for the alkali oxides and sulfides.

  7. Dynamics of Dissociative Electron Attachment to Methane

    NASA Astrophysics Data System (ADS)

    Rescigno, T. N.; Douguet, N.; Fonseca, S.; Orel, A. E.; Slaughter, D. S.; Belkacem, A.

    2015-05-01

    We present the results of a theoretical ad experimental study of dissociative electron attachment (DEA) to CH4. The total DEA cross section is dominated by a single broad peak centered near 10 eV, leading predominantly to H-/CH4 and CH2-/CH4dissociation channels. We will present evidence that both of these ion channels result from excitation of a triply degenerate Feshbach resonance (doubly excited negative ion state) of 2T2 symmetry whose parent is the lowest excited triplet state of the neutral molecule. We will present calculated angular distributions based on analysis of the entrance amplitudes obtained from the results of complex Kohn scattering calculations along with experimentally measured angular distributions obtained using the COLTRIMS method. Work performed under the auspices of the US DOE by the LBNL and supported by the U.S. DOE Office of Basic Energy Sciences, Division of Chemical Sciences.

  8. Dissociative Disorders: Between Neurosis and Psychosis

    PubMed Central

    Devillé, C.; Moeglin, C.; Sentissi, O.

    2014-01-01

    Dissociative disorders are a set of disorders defined by a disturbance affecting functions that are normally integrated with a prevalence of 2.4 percent in industrialised countries. These disorders are often poorly diagnosed or misdiagnosed because of sharing common clinical features with psychotic disorders, but requiring a very different trajectory of care. Repeated clinical situations in a crisis centre in Geneva provided us with a critical overview of current evidence of knowledge in clinical and etiopathological field about dissociative disorders. Because of their multiple expressions and the overlap with psychotic disorders, we focused on the clinical aspects using three different situations to better understand their specificity and to extend our thinking to the relevance of terms “neurosis” and “psychosis.” Finally, we hope that this work might help physicians and psychiatrists to become more aware of this complex set of disorders while making a diagnosis. PMID:25405051

  9. Dissociative Recombination Dynamics of the Ozone Cation

    SciTech Connect

    Zhaunerchyk, Vitali; Geppert, W.; sterdahl, F.; Larsson, Mats; Thomas, R. D.; Bahati Musafiri, Eric; Bannister, Mark E; Fogle, Mark R.; Vane, C Randy

    2008-02-01

    The dissociative recombination of the ozone cation has been studied at the heavy-ion storage ring CRYRING. The total cross section and branching fractions have been measured. The cross section from {approx}0eV to 0.2 eV follows a nearly E{sup -1} dependence, which was theoretically predicted to be a characteristic of the direct dissociative recombination mechanism. The thermal rate coefficient has been deduced from the cross section to be 7.37x10{sup -7}(T/300){sup -0.55}cm{sup 3}s{sup -1}. The branching fraction analysis carried out at {approx}0eV interaction energy has shown a strong propensity (94%) to dissociate through the three-body channel. Due to the overwhelming dominance of this channel it has been investigated in more detail. Of the six energetically available three-body pathways only three are significantly populated, such that the production of O(S1) is highly unfavored and all atomic oxygen fragments are predominantly formed in P3 and D1 states. Analysis of the breakup geometries has been performed by means of the Dalitz plot. It is observed that the molecules dissociating through the O(P3)+O(P3)+O(P3) and O(P3)+O(P3)+O(D1) channels have an open linear geometry where the cleavage of two valence bonds occurs preferentially in unison, while the O(P3)+O(D1)+O(D1) breakup might proceed partly through a sequential mechanism.

  10. The Bond Dissociation Energies of 1-Butene

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Langhoff, Stephen R. (Technical Monitor)

    1994-01-01

    The bond dissociation energies of 1-butene and several calibration systems are computed using the G2(MP2) approach. The agreement between the calibration systems and experiment is very good. The computed values for 1-butene are compared with calibration systems and the agreement between the computed results for 1-butene and the "rule of thumb" values from the smaller systems is remarkably good.

  11. Dissociative recombination of N2H+

    NASA Astrophysics Data System (ADS)

    dos Santos, S. Fonseca; Ngassam, V.; Orel, A. E.; Larson, Å.

    2016-08-01

    The direct and indirect mechanisms of dissociative recombination of N2H+ are theoretically studied. At low energies, the electron capture is found to be driven by recombination into bound Rydberg states, while at collision energies above 0.1 eV, the direct capture and dissociation along electronic resonant states becomes important. Electron-scattering calculations using the complex Kohn variational method are performed to obtain the scattering matrix as well as energy positions and autoionization widths of resonant states. Potential-energy surfaces of electronic bound states of N2H and N2H+ are computed using structure calculations with the multireference configuration interaction method. The cross section for the indirect mechanism is calculated using a vibrational frame transformation of the elements of the scattering matrix at energies just above the ionization threshold. Here vibrational excitations of the ionic core from v =0 to v =1 and v =2 for all three normal modes are considered and autoionization is neglected. The cross section for the direct dissociation along electronic resonant states is computed with wave-packet calculations using the multiconfiguration time-dependent Hartree method, where all three internal degrees of freedom are considered. The calculated cross sections are compared to measurements.

  12. Kinetics of single DNA hairpin dissociation

    NASA Astrophysics Data System (ADS)

    Rogers, William; Crocker, John

    2010-03-01

    Over the past decade, groups have used a variety of single molecule techniques to study the unfolding and unbinding of nucleic acids, proteins and other biomolecules. While some experiments on the dissociation of nucleic acids find exponential lifetime distributions, as expected for a process governed by a single rate-limiting pathway, other experiments find nonexponential lifetime distributions. In our work, we address this discrepancy by probing the force dependence of a single DNA hairpin under thermal dissociation. We use a scanning line optical tweezers instrument to measure the bound lifetimes of two DNA-coated microspheres under negligible applied tension. The two microspheres share a user-specified potential along the scan direction and are strongly confined in the perpendicular dimensions. The trapping laser intensity is modulated synchronously with a resonant scanning mirror to null all optical contributions to the pair interaction potential near contact. In addition, the laser polarization can be rotated to produce a continuously adjustable optical repulsion, allowing the instrument to double as a passive force clamp over a modest range of applied tensions. This unique experimental approach allows us to investigate many of the proposed explanations for nonexponential kinetics in nucleic acid dissociation that have, until now, been difficult to isolate.

  13. The infrared multiphoton dissociation of three nitrolkanes

    NASA Astrophysics Data System (ADS)

    Wodtke, A. M.; Hintsa, E. J.; Lee, Y. T.

    1986-01-01

    Infrared multiphoton dissociation in a molecular beam has been studied in order to elucidate the collision free, 'thermal' chemistry and dynamics of nitromethane, nitroethane and 2-nitropropane. The isomerization of CH3NO2 to CH3ONO was observed by detecting the CH3O and NO products from the dissociation of the very internally hot, isomerized nitromethane. A novel application of RRKM theory was used to estimate the barrier height to isomerization at 55.5 kcal/mol. The barrier height determination method was tested and found to give excellent results by applying it to the determintaion of the barrier height to HONO elimination from nitroethane, a value which is well known from activation energy measurements. The method was then applied to the case of HONO elimination from 2-nitropropane and it appears that there is good to believe that the barrier height is 3-5 kcal/mol lower in 2-nitropropane than in nitroethane. The success of this method for determining barrier heights shows how a microscopic molecular beam experiment, using infrared multiphoton dissociation where the concept of temperature has no place, can be quantitatively related to pyrolysis experiments which are conducted under collisional, thermal conditions and measure phenomenological quantities such as activation energies.

  14. Regional dissociated heterochrony in multivariate analysis.

    PubMed

    Mitteroecker, P; Gunz, P; Weber, G W; Bookstein, F L

    2004-12-01

    Heterochrony, the classic framework to study ontogeny and phylogeny, in essence relies on a univariate concept of shape. Though principal component plots of multivariate shape data seem to resemble classical bivariate allometric plots, the language of heterochrony cannot be translated directly into general multivariate methodology. We simulate idealized multivariate ontogenetic trajectories and demonstrate their behavior in principal component plots in shape space and in size-shape space. The concept of "dissociation", which is conventionally regarded as a change in the relationship between shape change and size change, appears to be algebraically the same as regional dissociation - the variation of apparent heterochrony by region. Only if the trajectories of two related species lie along exactly the same path in shape space can the classic terminology of heterochrony apply so that pure dissociation of size change against shape change can be detected. We demonstrate a geometric morphometric approach to these issues using adult and subadult crania of 48 Pan paniscus and 47 P. troglodytes. On each specimen we digitized 47 landmarks and 144 semilandmarks on ridge curves and the external neurocranial surface. The relation between these two species' growth trajectories is too complex for a simple summary in terms of global heterochrony. PMID:15646279

  15. Gas Hydrate Dissociation in the Ocean

    NASA Astrophysics Data System (ADS)

    Conroy, Devin; Smith, Stefan Llewellyn

    2006-11-01

    Methane gas is known to exist in extremely large quantities below the sea floor in the sediment of the deep and cold oceanic and in permafrost regions. Due to the large hydrostatic pressure and cool temperatures the gas reacts with the surrounding water to form a crystalline substance known as a gas hydrate. The fate of these reserves is very important to climate on earth because methane is a much more efficient greenhouse gas then carbon dioxide. The dissociation process in general can occur by either a decrease in pressure or an increase in temperature. In this study we concentrate on the latter. Once the hydrate dissociates, water and free gas remain above the phase boundary, occupying a larger volume than the original solid, and are be transported through the sediment. We have modeled this physical mechanism using volume averaged equations in a porous medium with a coupled two-phase flow. The movement of the phase boundary, which is proportional to the rate of heat transfer to this interface, is modeled as a Stefan type melting problem. The resultant governing equations are solved numerically, using a front fixing method to fix the phase boundary, to determine the rate of gas flux through the sediment and the dissociation rate.

  16. How thioredoxin dissociates its mixed disulfide.

    PubMed

    Roos, Goedele; Foloppe, Nicolas; Van Laer, Koen; Wyns, Lode; Nilsson, Lennart; Geerlings, Paul; Messens, Joris

    2009-08-01

    The dissociation mechanism of the thioredoxin (Trx) mixed disulfide complexes is unknown and has been debated for more than twenty years. Specifically, opposing arguments for the activation of the nucleophilic cysteine as a thiolate during the dissociation of the complex have been put forward. As a key model, the complex between Trx and its endogenous substrate, arsenate reductase (ArsC), was used. In this structure, a Cys29(Trx)-Cys89(ArsC) intermediate disulfide is formed by the nucleophilic attack of Cys29(Trx) on the exposed Cys82(ArsC)-Cys89(ArsC) in oxidized ArsC. With theoretical reactivity analysis, molecular dynamics simulations, and biochemical complex formation experiments with Cys-mutants, Trx mixed disulfide dissociation was studied. We observed that the conformational changes around the intermediate disulfide bring Cys32(Trx) in contact with Cys29(Trx). Cys32(Trx) is activated for its nucleophilic attack by hydrogen bonds, and Cys32(Trx) is found to be more reactive than Cys82(ArsC). Additionally, Cys32(Trx) directs its nucleophilic attack on the more susceptible Cys29(Trx) and not on Cys89(ArsC). This multidisciplinary approach provides fresh insights into a universal thiol/disulfide exchange reaction mechanism that results in reduced substrate and oxidized Trx. PMID:19675666

  17. Dissociative Disorders Among Chinese Inpatients Diagnosed With Schizophrenia

    PubMed Central

    Yu, Junhan; Ross, Colin A.; Keyes, Benjamin B.; Li, Ying; Dai, Yunfei; Zhang, Tianhong; Wang, Lanlan; Fan, Qing; Xiao, Zeping

    2010-01-01

    The purpose of the study was to assess the prevalence of dissociative disorders in a sample of Chinese psychiatric inpatients. Participants in the study consisted of 569 consecutively admitted inpatients at Shanghai Mental Health Center, China, of whom 84.9% had a clinical diagnosis of schizophrenia based on the Chinese Classification and Diagnostic Criteria for Mental Disorders, Version 3 (CCMD-3). All participants completed a self-report measure of dissociation, the Dissociative Experiences Scale (DES) and none had a prior diagnosis of a dissociative disorder. Ninety-six randomly selected participants were interviewed with a structured interview, the Dissociative Disorders Interview Schedule (DDIS) and a clinical interview. These 96 patients did not differ significantly from the 473 patients who were not interviewed on any demographic measures or on the self-report measure dissociation. A total of 28 (15.3%, after weighting of the data) patients received a clinical diagnosis of a dissociative disorder based on DSM-IV-TR criteria. Dissociative identity disorder was diagnosed in 2 (0.53%, after weighting) patients. Compared to the patients without a dissociative disorder, patients with dissociative disorders were significantly more likely to report childhood abuse (57.1% versus 22.1%), but the two groups did not differ significantly on any demographic measures. Dissociative disorders were readily identified in an inpatient psychiatric population in China. PMID:20603768

  18. Dissociation, PTSD, and substance abuse: an empirical study.

    PubMed

    Najavits, Lisa M; Walsh, Marybeth

    2012-01-01

    Few studies have examined the relationship between posttraumatic stress disorder (PTSD), substance use disorder, and dissociation. We studied 77 women with current PTSD and substance dependence, classified into high- versus low-dissociation groups per the Dissociative Experiences Scale. They were compared on trauma- and substance-related symptoms, cognitions, coping skills, social adjustment, trauma history, psychiatric symptoms, and self-harm/suicidal behaviors. We found the high-dissociation group consistently more impaired than the low-dissociation group. Also, the sample overall evidenced relatively high levels of dissociation, indicating that even in the presence of recent substance use, dissociation remains a major psychological phenomenon. Indeed, the high-dissociation group reported stronger expectation that substances could manage their psychiatric symptoms. The high-dissociation group also had more trauma-related symptoms and childhood histories of emotional abuse and physical neglect. The discussion addresses methodology, the "chemical dissociation" hypothesis, and the need for a more nuanced understanding of how substances are experienced in relation to dissociative phenomena. PMID:22211445

  19. Size-dependent dissociation of carbon monoxide on cobalt nanoparticles.

    PubMed

    Tuxen, Anders; Carenco, Sophie; Chintapalli, Mahati; Chuang, Cheng-Hao; Escudero, Carlos; Pach, Elzbieta; Jiang, Peng; Borondics, Ferenc; Beberwyck, Brandon; Alivisatos, A Paul; Thornton, Geoff; Pong, Way-Faung; Guo, Jinghua; Perez, Ruben; Besenbacher, Flemming; Salmeron, Miquel

    2013-02-13

    In situ soft X-ray absorption spectroscopy (XAS) was employed to study the adsorption and dissociation of carbon monoxide molecules on cobalt nanoparticles with sizes ranging from 4 to 15 nm. The majority of CO molecules adsorb molecularly on the surface of the nanoparticles, but some undergo dissociative adsorption, leading to oxide species on the surface of the nanoparticles. We found that the tendency of CO to undergo dissociation depends critically on the size of the Co nanoparticles. Indeed, CO molecules dissociate much more efficiently on the larger nanoparticles (15 nm) than on the smaller particles (4 nm). We further observed a strong increase in the dissociation rate of adsorbed CO upon exposure to hydrogen, clearly demonstrating that the CO dissociation on cobalt nanoparticles is assisted by hydrogen. Our results suggest that the ability of cobalt nanoparticles to dissociate hydrogen is the main parameter determining the reactivity of cobalt nanoparticles in Fischer-Tropsch synthesis. PMID:23339635

  20. Development, reliability, and validity of a child dissociation scale.

    PubMed

    Putnam, F W; Helmers, K; Trickett, P K

    1993-01-01

    Dissociation is a complex psychophysiological process that ranges along a continuum from minor, normal dissociation to Axis I psychopathology. High levels of dissociation are associated with increased self-destructive behaviors and other symptoms. Although several validated measures of dissociation exist for adults, no measures are available for children. The Child Dissociative Checklist (CDC) was developed to meet this need and is a reliable and valid observer report measure of dissociation in children. The CDC had a 1-year test-retest reliability coefficient of rho = .69 (N = 73, p = .0001) in a sample of normal and sexually abused girls. The CDC had high discriminant validity among four test samples including: normal control girls, sexually abused girls, boys and girls with dissociative disorder NOS and boys and girls with multiple personality disorder. The CDC is intended as a clinical screening instrument and as a research measure. The CDC is not designed to be used as a diagnostic instrument. PMID:8287286

  1. Exploring the relationships between dissociation, victimization, and juvenile sexual offending.

    PubMed

    Leibowitz, George S; Laser, Julie A; Burton, David L

    2011-01-01

    An etiological model of sexually abusive behavior including dissociation could have utility for researchers and treatment providers working with sexually abusive youth with trauma histories. This article explores relationships between dissociation, victimization, and juvenile sexual offending. Self-reported data on dissociation and 5 types of abuse were collected from 2 racially/ethnically diverse groups of sexually abusive and general delinquent male adolescents (n = 502). Bivariate analysis showed significant correlations between all types of child abuse and dissociation with the exception of emotional neglect. Hierarchical logistic regression analysis indicated that dissociation was significant in predicting sexual offender status. Moreover, dissociation, sexual victimization, and physical abuse showed significant effects in predicting membership in the sexual offender group. The results confirm the need for additional research in the areas of assessment and treatment of dissociation among sexually abusive youth. PMID:21240737

  2. Ab initio calculations of dissociative attachment and dissociative recombination of electrons and polyatomic species

    NASA Astrophysics Data System (ADS)

    Haxton, Daniel

    2009-05-01

    Interactions of free electrons with neutral and positively charged molecular species play a role in various physical systems. In interstellar space, reactions such as dissociative recombination determine the balance of various charged and neutral species. In a laboratory equipped with an apparatus like a COLTRIMS device, the dissociative attachment process can be used as a microscope to study polyatomic molecular dynamics. We discuss the theoretical and numerical methods used to calculate dissociative attachment and dissociative recombination of electrons with larger molecules from first principles. Studies using these methods are complimentary to other methods that yield more approximate reaction rates at greatly lesser numerical cost; they may yield precise information about the dissociation dynamics, product distribution, and differential cross section that approximate methods cannot. We discuss calculations performed to date on the target species H2O, NO2, and LiH2^+. We discuss the scaling of our numerical methods with the number of atoms, and the prospects of applying them to tetra-atomics.

  3. Zero-Point Energy Constraint for Unimolecular Dissociation Reactions. Giving Trajectories Multiple Chances To Dissociate Correctly.

    PubMed

    Paul, Amit K; Hase, William L

    2016-01-28

    A zero-point energy (ZPE) constraint model is proposed for classical trajectory simulations of unimolecular decomposition and applied to CH4* → H + CH3 decomposition. With this model trajectories are not allowed to dissociate unless they have ZPE in the CH3 product. If not, they are returned to the CH4* region of phase space and, if necessary, given additional opportunities to dissociate with ZPE. The lifetime for dissociation of an individual trajectory is the time it takes to dissociate with ZPE in CH3, including multiple possible returns to CH4*. With this ZPE constraint the dissociation of CH4* is exponential in time as expected for intrinsic RRKM dynamics and the resulting rate constant is in good agreement with the harmonic quantum value of RRKM theory. In contrast, a model that discards trajectories without ZPE in the reaction products gives a CH4* → H + CH3 rate constant that agrees with the classical and not quantum RRKM value. The rate constant for the purely classical simulation indicates that anharmonicity may be important and the rate constant from the ZPE constrained classical trajectory simulation may not represent the complete anharmonicity of the RRKM quantum dynamics. The ZPE constraint model proposed here is compared with previous models for restricting ZPE flow in intramolecular dynamics, and connecting product and reactant/product quantum energy levels in chemical dynamics simulations. PMID:26738691

  4. Dissociative depression among women with fibromyalgia or rheumatoid arthritis.

    PubMed

    Kilic, Ozge; Sar, Vedat; Taycan, Okan; Aksoy-Poyraz, Cana; Erol, Turgut C; Tecer, Ozlem; Emul, Murat H; Ozmen, Mine

    2014-01-01

    The aim of this study was to inquire about the possible relations of childhood trauma, anger, and dissociation to depression among women with fibromyalgia or rheumatoid arthritis. Fifty female patients diagnosed as having fibromyalgia (n = 30) or rheumatoid arthritis (n = 20) participated in the study. The Childhood Trauma Questionnaire, Somatoform Dissociation Questionnaire (SDQ), Dissociation Questionnaire (DIS-Q), Beck Depression Inventory (BDI), Spielberger State-Trait Anger Expression Inventory, and Dissociative Disorders Interview Schedule were administered to all participants. Women with a lifetime diagnosis of depressive disorder had higher scores for somatoform and psychoform dissociation than the nondepressive patients. However, childhood trauma scores did not differ between the 2 groups. In regression analysis, current severity of depression (BDI) was predicted by psychoform dissociation (DIS-Q) and lower education, and lifetime diagnosis of major depression was predicted by somatoform dissociation (SDQ). Whereas childhood emotional neglect predicted somatoform dissociation, psychoform dissociation was predicted by childhood sexual abuse. Mental processing of anger seems to be 1 of the dimensions of psychodynamics in trauma-related depressive conditions. In the context of the perceived threat of loss of control due to expressed anger and mental disintegration, somatoform dissociation seems to contribute to overmodulation of emotions in dissociative depression. Among patients suffering from physical illness with possible psychosomatic dimensions, assessment of somatoform dissociation in addition to psychoform dissociation may be helpful to understand diverse psychopathological trajectories emerging in the aftermath of childhood adversities. The recently proposed category of "dissociative depression" (Sar, 2011) seems to be a promising concept for future research on psychosomatic aspects of traumatic stress. PMID:24228798

  5. Mechanisms and energetics of hydride dissociation reactions on surfaces of plasma-deposited silicon thin films

    NASA Astrophysics Data System (ADS)

    Singh, Tejinder; Valipa, Mayur S.; Mountziaris, T. J.; Maroudas, Dimitrios

    2007-11-01

    We report results from a detailed analysis of the fundamental silicon hydride dissociation processes on silicon surfaces and discuss their implications for the surface chemical composition of plasma-deposited hydrogenated amorphous silicon (a-Si:H) thin films. The analysis is based on a synergistic combination of first-principles density functional theory (DFT) calculations of hydride dissociation on the hydrogen-terminated Si(001)-(2×1) surface and molecular-dynamics (MD) simulations of adsorbed SiH3 radical precursor dissociation on surfaces of MD-grown a-Si :H films. Our DFT calculations reveal that, in the presence of fivefold coordinated surface Si atoms, surface trihydride species dissociate sequentially to form surface dihydrides and surface monohydrides via thermally activated pathways with reaction barriers of 0.40-0.55eV. The presence of dangling bonds (DBs) results in lowering the activation barrier for hydride dissociation to 0.15-0.20eV, but such DB-mediated reactions are infrequent. Our MD simulations on a-Si :H film growth surfaces indicate that surface hydride dissociation reactions are predominantly mediated by fivefold coordinated surface Si atoms, with resulting activation barriers of 0.35-0.50eV. The results are consistent with experimental measurements of a-Si :H film surface composition using in situ attenuated total reflection Fourier transform infrared spectroscopy, which indicate that the a-Si :H surface is predominantly covered with the higher hydrides at low temperatures, while the surface monohydride, SiH(s ), becomes increasingly more dominant as the temperature is increased.

  6. Dissociative symptoms and dissociative disorders comorbidity in obsessive compulsive disorder: Symptom screening, diagnostic tools and reflections on treatment.

    PubMed

    Belli, Hasan

    2014-08-16

    Borderline personality disorder, conversion disorder and obsessive compulsive disorder frequently have dissociative symptoms. The literature has demonstrated that the level of dissociation might be correlated with the severity of obsessive compulsive disorder (OCD) and that those not responding to treatment had high dissociative symptoms. The structured clinical interview for DSM-IV dissociative disorders, dissociation questionnaire, somatoform dissociation questionnaire and dissociative experiences scale can be used for screening dissociative symptoms and detecting dissociative disorders in patients with OCD. However, a history of neglect and abuse during childhood is linked to a risk factor in the pathogenesis of dissociative psychopathology in adults. The childhood trauma questionnaire-53 and childhood trauma questionnaire-40 can be used for this purpose. Clinicians should not fail to notice the hidden dissociative symptoms and childhood traumatic experiences in OCD cases with severe symptoms that are resistant to treatment. Symptom screening and diagnostic tools used for this purpose should be known. Knowing how to treat these pathologies in patients who are diagnosed with OCD can be crucial. PMID:25133142

  7. Dissociation, PTSD, and Substance Abuse: An Empirical Study

    PubMed Central

    Najavits, Lisa; Walsh, Marybeth

    2012-01-01

    Few studies have examined the relationship between posttraumatic stress disorder (PTSD), substance use disorder (SUD) and dissociation. We studied 77 women with current PTSD and substance dependence, classified into high- versus low-dissociation on the Dissociative Experiences Scale. They were compared on trauma- and substance-related symptoms, cognitions, coping skills, social adjustment, trauma history, psychiatric symptoms, and self-harm/suicidal behaviors. We found the high-dissociation group consistently more impaired than the low-dissociation group. Also, the sample overall evidenced relatively high levels of dissociation, indicating that even in the presence of recent substance use, dissociation remains a major psychological phenomenon. Indeed, the high-dissociation group reported stronger expectation that substances could manage their psychiatric symptoms. The high-dissociation group also had more trauma-related symptoms and childhood histories of emotional abuse and physical neglect. Discussion addresses methodology, the “chemical dissociation” hypothesis, and the need for more nuanced understanding of how substances are experienced in relation to dissociative phenomena. PMID:22211445

  8. The role of water in gas hydrate dissociation

    USGS Publications Warehouse

    Circone, S.; Stern, L.A.; Kirby, S.H.

    2004-01-01

    When raised to temperatures above the ice melting point, gas hydrates release their gas in well-defined, reproducible events that occur within self-maintained temperature ranges slightly below the ice point. This behavior is observed for structure I (carbon dioxide, methane) and structure II gas hydrates (methane-ethane, and propane), including those formed with either H2O- or D2O-host frameworks, and dissociated at either ambient or elevated pressure conditions. We hypothesize that at temperatures above the H2O (or D2O) melting point: (1) hydrate dissociation produces water + gas instead of ice + gas, (2) the endothermic dissociation reaction lowers the temperature of the sample, causing the water product to freeze, (3) this phase transition buffers the sample temperatures within a narrow temperature range just below the ice point until dissociation goes to completion, and (4) the temperature depression below the pure ice melting point correlates with the average rate of dissociation and arises from solution of the hydrate-forming gas, released by dissociation, in the water phase at elevated concentrations. In addition, for hydrate that is partially dissociated to ice + gas at lower temperatures and then heated to temperatures above the ice point, all remaining hydrate dissociates to gas + liquid water as existing barriers to dissociation disappear. The enhanced dissociation rates at warmer temperatures are probably associated with faster gas transport pathways arising from the formation of water product.

  9. Different urea stoichiometries between the dissociation and denaturation of tobacco mosaic virus as probed by hydrostatic pressure.

    PubMed

    Santos, Jose L R; Aparicio, Ricardo; Joekes, Inés; Silva, Jerson L; Bispo, Jose A C; Bonafe, Carlos F S

    2008-05-01

    Viruses are very efficient self-assembly structures, but little is understood about the thermodynamics governing their directed assembly. At higher levels of pressure or when pressure is combined with urea, denaturation occurs. For a better understanding of such processes, we investigated the apparent thermodynamic parameters of dissociation and denaturation by assuming a steady-state condition. These processes can be measured considering the decrease of light scattering of a viral solution due to the dissociation process, and the red shift of the fluorescence emission spectra, that occurs with the denaturation process. We determined the apparent urea stoichiometry considering the equilibrium reaction of TMV dissociation and subunit denaturation, which furnished, respectively, 1.53 and 11.1 mol of urea/mol of TMV subunit. The denaturation and dissociation conditions were arrived in a near reversible pathway, allowing the determination of thermodynamic parameters. Gel filtration HPLC, electron microscopy and circular dichroism confirmed the dissociation and denaturation processes. Based on spectroscopic results from earlier papers, the calculation of the apparent urea stoichiometry of dissociation and denaturation of several other viruses resulted in similar values, suggesting a similar virus-urea interaction among these systems. PMID:18367310

  10. A preliminary study of cortisol and norepinephrine reactivity to psychosocial stress in borderline personality disorder with high and low dissociation.

    PubMed

    Simeon, Daphne; Knutelska, Margaret; Smith, Lisa; Baker, Bryann R; Hollander, Eric

    2007-01-15

    The goal of the current study was to investigate subjective and neurohormonal reactivity to acute psychosocial stress in borderline personality disorder (BPD) as a function of dissociative symptoms. Five BPD subjects with high dissociation, 8 BPD subjects with low dissociation, and 11 healthy control subjects were compared in basal urinary cortisol and norepinephrine, as well as in plasma cortisol and norepinephrine reactivity to the Trier Social Stress Test (TSST). Subjective stress rating and emotional response to the TSST were also measured. The three groups differed significantly in cortisol stress reactivity, with the high-dissociation BPD group demonstrating the most robust response. The three groups did not significantly differ in norepinephrine stress reactivity. In the combined BPD sample, dissociation severity tended to be inversely correlated with basal urinary norepinephrine, was positively correlated with norepinephrine stress reactivity. Childhood trauma was inversely correlated with basal urinary cortisol. In conclusion, despite its small sample size this pilot study suggests that dissociative symptomatology may be a marker of heightened biological vulnerability to stress in BPD, and merits further study. PMID:17169436

  11. Imagination and dissociation in hypnotic responding.

    PubMed

    Bowers, K S

    1992-10-01

    A neodissociative model of mind is better equipped than a social-psychological model to deal with the complexities of hypnosis, and of human behavior generally. It recognizes, as Coe's (1992) model does not, that behavior can be more automatically activated than strategically enacted. In particular, Coe's emphasis on human behavior as purposeful and goal directed does not distinguish between goal-directed behavior that serves a purpose, and goal-directed behavior that is performed on purpose. It is this distinction that permits goal-directed behavior to be dissociated from a person's conscious plans and intentions. In addition to offering a critique of Coe's "limited process" view of hypnosis, 4 main points are made in the interest of developing a slightly modified, neodissociation view of hypnosis. First, it is argued that goal-directed fantasies are more limited in their ability to mediate hypnotic responding than is commonly appreciated; as well, they do not seem to account for the nonvolitional quality of hypnotic responding. Second, it is argued that hypnotic ability is not unidimensional, with compliance and social influence more apt to account for the low than for the high hypnotizable's responsiveness to suggestion. Third, compared to low hypnotizables, the hypnotic responsiveness of high hypnotizables seems more likely to result from dissociated control. In other words, for high hypnotizables, hypnotic suggestions may often directly activate subsystems of cognitive control. Consequently, the need for executive initiative and effort to produce hypnotically suggested behavior is minimized, and such responses are therefore experienced as nonvolitional. Fourth and finally, while goal-directed fantasies typically accompany hypnotically suggested responses, they are in many cases more a marker of dissociated control than a mediator of suggested effects. PMID:1468834

  12. Kinetics of calcium dissociation from its high-affinity transport sites on sarcoplasmic reticulum ATPase.

    PubMed

    Orlowski, S; Champeil, P

    1991-01-15

    We investigated the kinetics of calcium dissociation from its high-affinity transport sites on sarcoplasmic reticulum Ca2(+)-ATPase by combining fast filtration with stopped-flow fluorescence measurements. At pH 6 and 20 degrees C, in the absence of potassium and in the presence of 20 mM MgCl2, isotopic exchange of bound calcium exhibited biphasic kinetics, with two phases of equal amplitude, regardless of the initial extent of binding site saturation. The rapidly exchangeable site, whose occupancy by calcium controlled the rate constant of the slow phase, had an apparent affinity for calcium of about 3-6 microM. A similar high affinity was also deduced from measurements of the calcium dependence of the rate constant for ATPase fluorescence changes. This affinity was higher than the overall affinity for calcium deduced from the equilibrium binding measurements (dissociation constant of 15-20 microM); this was consistent with the occurrence of cooperativity (Hill coefficient of 1.6-1.8). The drop in intrinsic fluorescence observed upon chelation of calcium was always slightly faster than the dissociation of calcium itself, although the rates for both this drop in fluorescence and calcium dissociation varied slightly from one preparation to the other. This fluorescence drop was therefore mainly due to dissociation of the bound ions, not to slow transconformation of the ATPase. Dissociation of the two bound calcium ions in a medium containing EGTA exhibited monophasic kinetics in the presence of a calcium ionophore, with a rate constant about half that of the fast phase of isotopic exchange. This particular pattern was observed over a wide range of experimental conditions, including the presence of KCl, dimethyl sulfoxide, 4-nonylphenol, or a nucleotide analogue, at pH 6 or 7, and at various temperatures. The kinetics of calcium dissociation under the above various conditions were not correlated with the ATPase affinity for calcium deduced from equilibrium

  13. Occipitocervical dissociation-incidence, evaluation, and treatment.

    PubMed

    Kasliwal, Manish K; Fontes, Ricardo B; Traynelis, Vincent C

    2016-09-01

    Traumatic occipitocervical dissociation (OCD) results from ligamentous injury to the craniocervical junction and is associated with a high rate of mortality and significant neurologic morbidity. The diagnosis is frequently missed on initial lateral cervical spinal radiographs mainly due to inadequate visualization of radiological landmarks and low degree of suspicion. Widespread availability of multidetector computed tomography (MDCT) of the spine and development of better diagnostic radiological criteria has allowed timely diagnosis and good clinical outcome following posterior occipitocervical fusion and instrumentation for a pathology that was once considered uniformly fatal. The present paper reviews the clinical features, diagnosis, and management of OCD in light of most recent literature. PMID:27255101

  14. On the dissociation energy of Mg2

    NASA Technical Reports Server (NTRS)

    Partridge, Harry; Bauschlicher, Charles W., Jr.; Pettersson, Lars G. M.; Mclean, A. D.; Liu, Bowen

    1990-01-01

    The bonding in the X 1Sigma(+)g state of Mg2 is investigated using near-complete valence one-particle Slater and Gaussian basis sets containing up to h functions. It is shown that the four-electron complete CI limit can be approached using a sequence of either second-order CI (SOCI) or interacting correlated fragment (ICF) calculations. At the valence level, the best estimate of the dissociation energy D(e) was 464/cm. This is a lower limit and is probably within 5/cm of the complete basis value.

  15. Spin–orbit interaction mediated molecular dissociation

    SciTech Connect

    Kokkonen, E. Jänkälä, K.; Kettunen, J. A.; Heinäsmäki, S.; Karpenko, A.; Huttula, M.; Löytynoja, T.

    2014-05-14

    The effect of the spin–orbit interaction to photofragmentation is investigated in the mercury(II) bromide (HgBr{sub 2}) molecule. Changes in the fragmentation between the two spin–orbit components of Hg 5d photoionization, as well as within the molecular-field-splitted levels of these components are observed. Dissociation subsequent to photoionization is studied with synchrotron radiation and photoelectron-photoion coincidence spectroscopy. The experimental results are accompanied by relativistic ab initio analysis of the photoelectron spectrum.

  16. Dissociative Ionization of Aromatic and Heterocyclic Molecules

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.

    2003-01-01

    Space radiation poses a major health hazard to humans in space flight. The high-energy charged particles in space radiation ranging from protons to high atomic number, high-energy (HZE) particles, and the secondary species they produce, attack DNA, cells, and tissues. Of the potential hazards, long-term health effects such as carcinogenesis are likely linked to the DNA lesions caused by secondary electrons in the 1 - 30 eV range. Dissociative ionization (DI) is one of the electron collision processes that can damage the DNA, either directly by causing a DNA lesion, or indirectly by producing radicals and cations that attack the DNA. To understand this process, we have developed a theoretical model for DI. Our model makes use of the fact that electron motion is much faster than nuclear motion and assumes DI proceeds through a two-step process. The first step is electron-impact ionization resulting in a particular state of the molecular ion in the geometry of the neutral molecule. In the second step the ion undergoes unimolecular dissociation. Thus the DI cross section sigma(sup DI)(sub a) for channel a is given by sigma(sup DI)(sub a) = sigma(sup I)(sub a) P(sub D) with sigma(sup I)(sub a) the ionization cross section of channel a and P(sub D) the dissociation probability. This model has been applied to study the DI of H2O, NH3, and CH4, with results in good agreement with experiment. The ionization cross section sigma(sup I)(sub a) was calculated using the improved binary encounter-dipole model and the unimolecular dissociation probability P(sub D) obtained by following the minimum energy path determined by the gradients and Hessians of the electronic energy with respect to the nuclear coordinates of the ion. This model is used to study the DI from the low-lying channels of benzene and pyridine to understand the different product formation in aromatic and heterocyclic molecules. DI study of the DNA base thymine is underway. Solvent effects will also be discussed.

  17. Towards an accurate dissociative potential for water

    NASA Astrophysics Data System (ADS)

    Akin-Ojo, Omololu

    2014-03-01

    Most models of water describe the molecule as rigid, i.e., with fixed bond angles and bond lengths, or as flexible in which the bond angles and bond lengths vary but the chemical bonds cannot be broken. In this work we present our progress in the development of a water model which allows for the breaking and formation of chemical bonds. The force field was obtained by fitting ab initio (not DFT) energies, forces, and molecular properties. The ability of the model to predict properties of water at ambient and extreme conditions will be presented. We will also report on the modeling of small clusters of water using the dissociative force field.

  18. Dissociative experience and cultural neuroscience: narrative, metaphor and mechanism.

    PubMed

    Seligman, Rebecca; Kirmayer, Laurence J

    2008-03-01

    Approaches to trance and possession in anthropology have tended to use outmoded models drawn from psychodynamic theory or treated such dissociative phenomena as purely discursive processes of attributing action and experience to agencies other than the self. Within psychology and psychiatry, understanding of dissociative disorders has been hindered by polemical "either/or" arguments: either dissociative disorders are real, spontaneous alterations in brain states that reflect basic neurobiological phenomena, or they are imaginary, socially constructed role performances dictated by interpersonal expectations, power dynamics and cultural scripts. In this paper, we outline an approach to dissociative phenomena, including trance, possession and spiritual and healing practices, that integrates the neuropsychological notions of underlying mechanism with sociocultural processes of the narrative construction and social presentation of the self. This integrative model, grounded in a cultural neuroscience, can advance ethnographic studies of dissociation and inform clinical approaches to dissociation through careful consideration of the impact of social context. PMID:18213511

  19. Strain-induced water dissociation on supported ultrathin oxide films

    PubMed Central

    Song, Zhenjun; Fan, Jing; Xu, Hu

    2016-01-01

    Controlling the dissociation of single water molecule on an insulating surface plays a crucial role in many catalytic reactions. In this work, we have identified the enhanced chemical reactivity of ultrathin MgO(100) films deposited on Mo(100) substrate that causes water dissociation. We reveal that the ability to split water on insulating surface closely depends on the lattice mismatch between ultrathin films and the underlying substrate, and substrate-induced in-plane tensile strain dramatically results in water dissociation on MgO(100). Three dissociative adsorption configurations of water with lower energy are predicted, and the structural transition going from molecular form to dissociative form is almost barrierless. Our results provide an effective avenue to achieve water dissociation at the single-molecule level and shed light on how to tune the chemical reactions of insulating surfaces by choosing the suitable substrates. PMID:26953105

  20. Being in rhythm: dissociative attunement in therapeutic process.

    PubMed

    Hopenwasser, Karen

    2008-01-01

    Dissociative attunement is a profound rhythmic encounter in therapeutic treatment. Attunement is a synchronized awareness of implicit knowing that is nonlinear and bidirectional. Empathically attuned clinicians are like microtonal tuning forks. They resonate with a variety of emotional pitches and will resonate with nuanced shifting of emotional tone. This resonance is the basis of dissociative attunement. Concepts such as empathic attunement, affect attunement, "the unthought known," "implicit relational knowing," and "a two-person unconscious" help us to understand unique aspects of projective identification, transference, and countertransference within the dissociative frame. However, "dissociative" attunements are systemically self-emergent moments in which multiple self-states are shared by means other than projection. Using clinical vignettes, I demonstrate how dissociative attunement can paradoxically appear to be misattunement. By synthesizing scientific and theoretical concepts applied to these clinical moments, we can understand dissociative attunement as a therapeutic tool as well as a pathway to vicarious traumatization. PMID:19042783

  1. Strain-induced water dissociation on supported ultrathin oxide films

    NASA Astrophysics Data System (ADS)

    Song, Zhenjun; Fan, Jing; Xu, Hu

    2016-03-01

    Controlling the dissociation of single water molecule on an insulating surface plays a crucial role in many catalytic reactions. In this work, we have identified the enhanced chemical reactivity of ultrathin MgO(100) films deposited on Mo(100) substrate that causes water dissociation. We reveal that the ability to split water on insulating surface closely depends on the lattice mismatch between ultrathin films and the underlying substrate, and substrate-induced in-plane tensile strain dramatically results in water dissociation on MgO(100). Three dissociative adsorption configurations of water with lower energy are predicted, and the structural transition going from molecular form to dissociative form is almost barrierless. Our results provide an effective avenue to achieve water dissociation at the single-molecule level and shed light on how to tune the chemical reactions of insulating surfaces by choosing the suitable substrates.

  2. Dissociative detachment relates to psychotic symptoms and personality decompensation.

    PubMed

    Allen, J G; Coyne, L; Console, D A

    1997-01-01

    Previous studies have addressed the prominence of psychotic symptoms in conjunction with multiple personality disorder (now dissociative identity disorder). The present study examines the relation between psychotic symptoms and a more pervasive form of dissociative disturbance, namely dissociative detachment. Two hundred sixty-six women in inpatient treatment for severe trauma-related disorders completed the Dissociative Experiences Scale (DES), and 102 of these patients also completed the Millon Clinical Multiaxial Inventory (MCMI-III). A factor analysis of the DES yielded two dimensions of dissociative detachment: detachment from one's own actions and detachment from the self and the environment. Each of these DES dimensions relates strongly to the thought disorder and schizotypal personality disorder scales of the MCMI-III. We propose that severe dissociative detachment, by virtue of loosening the moorings in inner and outer reality, is conducive to psychotic symptoms and personality decompensation. PMID:9406738

  3. Dissociation in individuals denying trauma exposure: findings from two samples.

    PubMed

    Briere, John; Runtz, Marsha

    2015-06-01

    A number of studies suggest that dissociation is reliably related to trauma exposure, and that inadequate regulation of posttraumatic distress may be a significant factor. We examined whether affect dysregulation predicts dissociation in those denying any lifetime exposure to trauma. These relationships were evaluated in a general population sample and a second sample of nontraumatized university students. In the first study, multivariate analyses indicated that, along with gender, affect dysregulation was a relatively strong predictor, accounting for 27% of the variance in dissociation. In the replication study, dissociation was associated with affect dysregulation, but not gender. Affect dysregulation seems to predict dissociative symptomatology in nontraumatized individuals. It is hypothesized that emotional distress, whether from trauma or other etiologies, motivates dissociation to the extent that it challenges the individual's compromised capacity for affect regulation. Treatment implications may include the potential helpfulness of interventions that increase emotion regulation skills. PMID:25974057

  4. The relationship between catatonia and dissociation: A preliminary investigation.

    PubMed

    Ross, Colin A; Browning, Elena

    2016-01-01

    Unlike the relationship between dissociation and Schneiderian first-rank symptoms, the relationship between dissociation and catatonia has not been investigated empirically. In order to gather some initial data about catatonia, dissociation, and childhood adverse experiences, we administered the Bush-Francis Catatonia Scale (BFCS), the Dissociative Experiences Scale (DES), the Adverse Childhood Experiences Questionnaire, and the Dissociative Disorders Interview Schedule to 100 inpatients in a hospital trauma program. The average DES score was 44.1 (SD = 22.4), and 86 participants were in the DES-Taxon. The average score on the BFCS was 7.7 (SD = 10.3); 81 participants scored 2 or higher, and 67 scored 5 or higher. The results showed that, in this sample, catatonic symptoms are frequent and related to adverse childhood experiences but seem to be a separate symptom category from both dissociation and psychosis. PMID:26751346

  5. Visible/Infrared Dissociation of NO3: Roaming in the Dark or Roaming on the Ground?

    PubMed

    Fernando, Ravin; Dey, Arghya; Broderick, Bernadette M; Fu, Bina; Homayoon, Zahra; Bowman, Joel M; Suits, Arthur G

    2015-07-16

    We present a DC slice imaging study of roaming dynamics in the photodissociation of the nitrate radical, NO3, contrasting pure visible excitation with a combination of visible and CO2 laser excitation at 10.6 μm. Images of specific rotational levels of NO are seen to reflect dissociation on the ground and first excited electronic states, as reported in previous work. The branching is obtained for specific rotational levels by comparison to quasiclassical trajectory calculations of the dynamics on these two surfaces. The results for the visible dissociation are found to be very similar to the combination of visible and infrared, raising questions about the nature of the coupling of these surfaces, the extent to which roaming takes place on both, and how the final product branching is determined. PMID:25407947

  6. Ictal symptoms of anxiety, avoidance behaviour, and dissociation in patients with dissociative seizures

    PubMed Central

    Goldstein, L H; Mellers, J D C

    2006-01-01

    Objective To examine anxiety related seizure symptoms and avoidance behaviour in adults with dissociative (psychogenic non‐epileptic) seizures (DS) in comparison with a group suffering from partial epilepsy. Methods 25 DS and 19 epilepsy patients completed an attack symptom measure, the hospital anxiety and depression scale, the dissociative experiences scale, and the fear questionnaire. Results DS patients reported the presence of significantly greater numbers of somatic symptoms of anxiety during their attacks than the epilepsy group, despite not reporting subjectively higher levels of anxiety. The DS patients also reported higher levels of agoraphobic‐type avoidance behaviour than the epilepsy group. Measures of dissociation were higher in the DS group, who also reported greater symptoms of depression. Conclusions The findings support a model whereby DS occur as a paroxysmal, dissociative response to heightened arousal in the absence of raised general anxiety levels. The model has practical implications for clinical assessment and treatment: in clinical practice, inquiry about these symptoms may help in the diagnosis of DS; with respect to treatment, the anxiety related symptoms and avoidance behaviour prevalent in DS are a potential focus for a cognitive behavioural approach analogous to that used in the treatment of other anxiety disorders. PMID:16614021

  7. Simulation studies of the dissociation of H 2 on stepped surfaces

    NASA Astrophysics Data System (ADS)

    Kaukonen, H.-P.; Nieminen, R. M.

    1991-05-01

    We have simulated the dissociation reaction of H 2 on stepped ideal honeycomb, square and hexagonal surfaces with a simple kinetic model based on the idea proposed by Poelsema and Comsa [Scattering of Thermal Energy Atoms from Disordered Surfaces, Springer Tracts in Modern Physics 115 (Springer, Berlin, 1989)] that dissociation on a stepped Pt(111) surface occurs exclusively on step sites. The observed sticking coefficient sH 2 of H 2 consists of two competing channels: (1) physisorbed molecules incident on terrace sites diffusing to the step, and (2) direct dissociation of molecules incident on or near a step site. The results support this picture qualitatively and indicate that the behaviour of the system can be separated depending on surface temperature into three domains in each of which a different mechanism dominates. (1) T < T1: a geometric effect, i.e. the cluster size distribution of vacant adsorption sites on the surface, (2) T1 < T < T2: a geometric effect combined with nearest neighbour interactions due to ad atoms, and (3) T > T2: direct adsorption near a step site. Of the three surfaces structures studied the honeycomb structure corresponds most closely to the observed H 2 dissociation.

  8. The molecular dynamics of adsorption and dissociation of O{sub 2} on Pt(553)

    SciTech Connect

    Jacobse, Leon Dunnen, Angela den; Juurlink, Ludo B. F.

    2015-07-07

    Molecular adsorption and dissociation of O{sub 2} on the stepped Pt(553) surface have been investigated using supersonic molecular beam techniques and temperature programmed desorption. The initial and coverage-dependent sticking probability was determined with the King and Wells technique for various combinations of incident kinetic energy, surface temperature, incident angle, and surface coverage. A comparison with similar data for Pt(533) and Pt(110)(1 × 2) shows quantitatively the same high step-induced sticking at low incident energies compared to Pt(111). The enhancement is therefore insensitive to the exact arrangement of atoms forming surface corrugation. We consider energy transfer and electronic effects to explain the enhanced sticking. On the other hand, dissociation dynamics at higher incident kinetic energies are strongly dependent on step type. The Pt(553) and Pt(533) surfaces are more reactive than Pt(111), but the (100) step shows higher sticking than the (110) step. We relate this difference to a variation in the effective lowering of the barrier to dissociation from molecularly adsorbed states into atomic states. Our findings are in line with results from experimental desorption studies and theoretical studies of atomic binding energies. We discuss the influence of the different step types on sticking and dissociation dynamics with a one-dimensional potential energy surface.

  9. Autobiographical memory specificity in dissociative identity disorder.

    PubMed

    Huntjens, Rafaële J C; Wessel, Ineke; Hermans, Dirk; van Minnen, Agnes

    2014-05-01

    A lack of adequate access to autobiographical knowledge has been related to psychopathology. More specifically, patients suffering from depression or a history of trauma have been found to be characterized by overgeneral memory, in other words, they show a relative difficulty in retrieving a specific event from memory located in time and place. Previous studies of overgeneral memory have not included patients with dissociative disorders. These patients are interesting to consider, as they are hypothesized to have the ability to selectively compartmentalize information linked to negative emotions. This study examined avoidance and overgeneral memory in patients with dissociative identity disorder (DID; n = 12). The patients completed the autobiographical memory test (AMT). Their performance was compared with control groups of posttraumatic stress disorder (PTSD) patients (n = 26), healthy controls (n = 29), and DID simulators (n = 26). Specifically, we compared the performance of separate identity states in DID hypothesized to diverge in the use of avoidance as a coping strategy to deal with negative affect. No significant differences in memory specificity were found between the separate identities in DID. Irrespective of identity state, DID patients were characterized by a lack of memory specificity, which was similar to the lack of memory specificity found in PTSD patients. The converging results for DID and PTSD patients add empirical evidence for the role of overgeneral memory involved in the maintenance of posttraumatic psychopathology. PMID:24886016

  10. Dissociation of silica at high pressure

    NASA Astrophysics Data System (ADS)

    Hicks, Damien; Boehly, Tom

    2005-07-01

    Measurements of the temperature and optical reflectivity of quartz and fused silica under shock loading from 100 to 1000 GPa have revealed evidence for dissociation of silica between ˜150 and 400 GPa. Using attenuating laser-driven shock waves a continuous record of the temperature and reflectivity dependence on pressure has been obtained in both materials allowing the specific heat capacity and electronic conductivity to be deduced. Results show that between 150 and 400 GPa the specific heat rises significantly above that expected from the Dulong-Petit law, indicating the presence of a latent energy. Coincident with this anomalous specific heat is a rapid rise in electronic conductivity. Both these observables suggest that dissociation is occurring in the dense fluid. In addition temperature measurements near 5000 K detect a discontinuity at the melt transition, as measured earlier on gas gun experiments. This work was performed under the auspices of the US DOE by LLNL under Contract No. W-7405-ENG-48 and by the University of Rochester under Cooperative Agreement No. DE-FC03-92SF19460.

  11. Grammatical category dissociation in multilingual aphasia.

    PubMed

    Faroqi-Shah, Yasmeen; Waked, Arifi N

    2010-03-01

    Word retrieval deficits for specific grammatical categories, such as verbs versus nouns, occur as a consequence of brain damage. Such deficits are informative about the nature of lexical organization in the human brain. This study examined retrieval of grammatical categories across three languages in a trilingual person with aphasia who spoke Arabic, French, and English. In order to delineate the nature of word production difficulty, comprehension was tested, and a variety of concomitant lexical-semantic variables were analysed. The patient demonstrated a consistent noun-verb dissociation in picture naming and narrative speech, with severely impaired production of verbs across all three languages. The cross-linguistically similar noun-verb dissociation, coupled with little evidence of semantic impairment, suggests that (a) the patient has a true "nonsemantic" grammatical category specific deficit, and (b) lexical organization in multilingual speakers shares grammatical class information between languages. The findings of this study contribute to our understanding of the architecture of lexical organization in bilinguals. PMID:20830631

  12. Multigenerational Dissociation: A Framework for Building Narrative.

    PubMed

    McCollum, Sally E

    2015-01-01

    This paper presents the concept of Multigenerational Dissociation (MGD), a behavior pattern that occurs in families in which violence and abuse are re-enacted from one generation to the next, accompanied by denial that the trauma occurred, or if it did, that it was destructive. While revictimization, reenactment, and the intergenerational transmission of trauma are discussed extensively in the literature, MGD helps to view them within a broad historical framework. This is useful for conceptualizing cases therapeutically, and it can also contribute to research on dissociation and recovered memories of trauma and abuse by demonstrating the value of narrative clinical data. Case material is used to illustrate how MGD occurs in people's lives and affects their memories, demonstrating how it becomes a frame within which to convey the dynamics of how traumatic experiences are remembered. This also demonstrates that when clinicians contribute their own narrative data to research on traumatic memory, the science is more accurate, relevant, and comprehensible to clinical and nonclinical researchers. PMID:26158318

  13. Dissociative excitation study of iron pentacarbonyl molecule

    NASA Astrophysics Data System (ADS)

    Ribar, Anita; Danko, Marián; Országh, Juraj; Ferreira da Silva, Filipe; Utke, Ivo; Matejčík, Štefan

    2015-04-01

    The processes of dissociative excitation (DE) and dissociative ionisation with excitation (DIE) of iron pentacarbonyl, Fe(CO)5, have been studied using a crossed electron-molecule beam experimental apparatus (Electron Induced Fluorescence Apparatus, EIFA). Using EIFA we were able to record the emission spectrum of the molecule in the UV-VIS range, as well as the photon efficiency curves initiated by electron impact. The emission spectrum of Fe(CO)5 initiated by impact of 50 eV electrons was recorded in the spectral range between 200 nm and 470 nm. It shows a high density of emission lines and bands (mainly iron lines and carbonyl bands). Additionally, we have measured photon efficiency curves (PECs) as a function of the electron impact energy for several lines and bands. On the basis of the PECs we have discussed the reaction mechanism and the energetics of the reactions associated with the DE and DIE processes. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Štefan Matejčík, John Tanis and Kurt H. Becker.

  14. Dissociable behavioural outcomes of visual statistical learning

    PubMed Central

    Turk-Browne, Nicholas B.; Seitz, Aaron R.

    2016-01-01

    Statistical learning refers to the extraction of probabilistic relationships between stimuli and is increasingly used as a method to understand learning processes. However, numerous cognitive processes are sensitive to the statistical relationships between stimuli and any one measure of learning may conflate these processes; to date little research has focused on differentiating these processes. To understand how multiple processes underlie statistical learning, here we compared, within the same study, operational measures of learning from different tasks that may be differentially sensitive to these processes. In Experiment 1, participants were visually exposed to temporal regularities embedded in a stream of shapes. Their task was to periodically detect whether a shape, whose contrast was staircased to a threshold level, was present or absent. Afterwards, they completed a search task, where statistically predictable shapes were found more quickly. We used the search task to label shape pairs as “learned” or “non-learned”, and then used these labels to analyse the detection task. We found a dissociation between learning on the search task and the detection task where only non-learned pairs showed learning effects in the detection task. This finding was replicated in further experiments with recognition memory (Experiment 2) and associative learning tasks (Experiment 3). Taken together, these findings are consistent with the view that statistical learning may comprise a family of processes that can produce dissociable effects on different aspects of behaviour.

  15. Dissociative recombination of molecular ions with electrons

    NASA Technical Reports Server (NTRS)

    Johnsen, Rainer

    1990-01-01

    An overview is presented for the present state of the art of laboratory measurements of the dissociative recombination of molecular ions with electrons. Most work has focussed on obtaining rates and their temperature dependence, as these are of primary interest for model calculations of ionospheres. A comparison of data obtained using the microwave afterglow method, the flowing afterglow technique, and the merged beam technique shows that generally the agreement is quite good, but there are some serious discrepancies, especially in the case of H(3+) recombination, that need to be resolved. Results of some earlier experimental work need to be reexamined in the light of more recent developments. Such cases are pointed out and a compilation of rate coefficients that have withstood scrutiny is presented. Recent advances in experimental methods, such as the use of laser-in-duced fluorescence, make it possible to identify some neutral products of dissociative recombination. What has been done so far and what results one might expect from future work are briefly reviewed.

  16. Dissociation of methane under high pressure.

    PubMed

    Gao, Guoying; Oganov, Artem R; Ma, Yanming; Wang, Hui; Li, Peifang; Li, Yinwei; Iitaka, Toshiaki; Zou, Guangtian

    2010-10-14

    Methane is an extremely important energy source with a great abundance in nature and plays a significant role in planetary physics, being one of the major constituents of giant planets Uranus and Neptune. The stable crystal forms of methane under extreme conditions are of great fundamental interest. Using the ab initio evolutionary algorithm for crystal structure prediction, we found three novel insulating molecular structures with P2(1)2(1)2(1), Pnma, and Cmcm space groups. Remarkably, under high pressure, methane becomes unstable and dissociates into ethane (C(2)H(6)) at 95 GPa, butane (C(4)H(10)) at 158 GPa, and further, carbon (diamond) and hydrogen above 287 GPa at zero temperature. We have computed the pressure-temperature phase diagram, which sheds light into the seemingly conflicting observations of the unusually low formation pressure of diamond at high temperature and the failure of experimental observation of dissociation at room temperature. Our results support the idea of diamond formation in the interiors of giant planets such as Neptune. PMID:20950018

  17. Electron Impact Ionization and Dissociative Ionization of C2H2

    NASA Technical Reports Server (NTRS)

    Srivastava, S. K.

    1995-01-01

    By utilizing a crossed electron beam collision geometry, a combination of time-of-flight (TOF) and quadrupole mass spectrometers, and the relative flow technique1 normalized values of cross sections and appearance energies (AP) were obtained for the formation of singly and multiply ionized species resulting from the ionization and dissociation of C2H2. Details ont he apparatus and technique have been published previously.2,3.

  18. The vibrational dynamics of 3D HOCl above dissociation

    SciTech Connect

    Lin, Yi-Der; Reichl, L. E.; Jung, Christof

    2015-03-28

    We explore the classical vibrational dynamics of the HOCl molecule for energies above the dissociation energy of the molecule. Above dissociation, we find that the classical dynamics is dominated by an invariant manifold which appears to stabilize two periodic orbits at energies significantly above the dissociation energy. These stable periodic orbits can hold a large number of quantum states and likely can support a significant quasibound state of the molecule, well above the dissociation energy. The classical dynamics and the lifetime of quantum states on the invariant manifold are determined.

  19. Childhood maltreatment and intimate partner violence in dissociative disorder patients

    PubMed Central

    Webermann, Aliya R.; Brand, Bethany L.; Chasson, Gregory S.

    2014-01-01

    Background Childhood maltreatment (CM) is a risk factor for subsequent intimate partner violence (IPV) in adulthood, with high rates of retrospectively reported CM among IPV victims and perpetrators. A theorized mechanism of the link between CM and IPV is dissociation. Dissociation may allow perpetrators of violence to remain emotionally distant from their behavior and minimize empathy toward those they victimize, enabling them to commit acts of violence similar to their own experiences. Indeed, elevated rates of dissociation and dissociative disorders (DD) have been found among IPV survivors and perpetrators. In addition, in pilot studies, DD clinicians have reported high levels of violent behavior among DD patients. Objective The present study investigates IPV among DD patients with Dissociative Identity Disorder and Dissociative Disorder Not Otherwise Specified, a group with CM rates of 80–95% and severe dissociative symptoms. Methods DD clinicians reported on rates of CM and IPV among 275 DD patients in outpatient treatment. DD patients also completed a self-report measure of dissociation. Analyses assessed the associations between CM typologies and IPV, as well as trait dissociation and IPV. Results Physical and emotional child abuse were associated with physical IPV, and childhood witnessing of domestic violence (DV) and childhood neglect were associated with emotional IPV. Conclusions The present study is the first to provide empirical support for a possible CM to adult IPV developmental trajectory among DD patients. Future research is needed to better understand the link between CM and IPV among those with trauma and DD. PMID:25279109

  20. Autocatalytic water dissociation on Cu(110) at near ambient conditions

    SciTech Connect

    Mulleregan, Alice; Andersson, Klas; Ketteler, Guido; Bluhm, Hendrik; Yamamoto, Susumu; Ogasawara, Hirohito; Pettersson, Lars G.M.; Salmeron, Miquel; Nilsson, Anders

    2007-05-16

    Autocatalytic dissociation of water on the Cu(110) metal surface is demonstrated based on X-ray photoelectron spectroscopy studies carried out in-situ under near ambient conditions of water vapor pressure (1 Torr) and temperature (275-520 K). The autocatalytic reaction is explained as the result of the strong hydrogen-bond in the H{sub 2}O-OH complex of the dissociated final state, which lowers the water dissociation barrier according to the Broensted-Evans-Polanyi relations. A simple chemical bonding picture is presented which predicts autocatalytic water dissociation to be a general phenomenon on metal surfaces.

  1. Psychometric validation of the State Scale of Dissociation (SSD).

    PubMed

    Krüger, Christa; Mace, Chris J

    2002-03-01

    Although dissociative phenomena are often transient features of mental states, existing measures of dissociation are designed to measure enduring traits. A new present-state self-report measure, sensitive to changes in dissociative states, was therefore developed and psychometrically validated. Fifty-six items were formulated to measure state features, and sorted according to seven subscales: derealization, depersonalization, identity confusion, identity alteration, conversion, amnesia and hypermnesia. The State Scale of Dissociation (SSD) was administered with other psychiatric scales (DES, BDI, BAI, SCI-PANSS) to 130 participants with DSM-IV major depressive disorder schizophrenia, alcohol withdrawal, dissociative disorders and controls. In these sample populations, the SSD was demonstrated as a valid and reliable measure of changes in and the severity of dissociative states. Discriminant validity, content, concurrent, predictive, internal criterion-related, internal construct and convergent validities, and internal consistency and split-half reliability were confirmed statistically. Clinical observations of dissociative states, and their comorbidity with symptoms of depression and psychotic illness, were confirmed empirically. The SSD, an acceptable, valid and reliable scale measuring state features of dissociation at the time of completion, was obtained. This is a prerequisite for further investigation of correlations between changes in dissociative states and concurrent physiological parameters. PMID:12006198

  2. The vibrational dynamics of 3D HOCl above dissociation

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Der; Reichl, L. E.; Jung, Christof

    2015-03-01

    We explore the classical vibrational dynamics of the HOCl molecule for energies above the dissociation energy of the molecule. Above dissociation, we find that the classical dynamics is dominated by an invariant manifold which appears to stabilize two periodic orbits at energies significantly above the dissociation energy. These stable periodic orbits can hold a large number of quantum states and likely can support a significant quasibound state of the molecule, well above the dissociation energy. The classical dynamics and the lifetime of quantum states on the invariant manifold are determined.

  3. The Vibrational Dynamics of 3D HOCl Above Dissociation

    NASA Astrophysics Data System (ADS)

    Lin, Yi-Der; Reichl, Linda; Jung, Christof

    2015-03-01

    We have analyzed the vibrational dynamics of HOCl above dissociation using a 3D energy surface which governs the vibrational dynamics of HOCl above dissociation. The dynamics is dominated by an invariant manifold which is transversally unstable for small spacing between Cl and HO complex, and stable for large spacing. Above dissociation, the InM separates two mirror image periodic orbits, embedded in a large chaotic sea, that can hold a large number of quantum states. These periodic orbits have the capability of forming significant quasibound states of the molecule above dissociation. Welch Foundation.

  4. Dissociability of free and peptidyl-tRNA bound ribosomes.

    PubMed

    Surguchov, A P; Fominykch, E S; Lyzlova, L V

    1978-06-16

    The influence of peptidyl-tRNA on the dissociation of yeast 80 S ribosomes into subunits was studied. For this purpose temperature-sensitive (ts) suppressor strain of yeast Saccharomyces cervisiae carrying a defect in peptide chain termination was used. It was found that peptidyl-tRNA did not influence the dissociation of ribosomes either at high salt concentration or in the presence of dissociation factor (DF) from yeast. After dissociation of yeast ribosomes in 0.5 M KCl, peptidyl-tRNA remains bound to the 60 S subunit. Some characteristics of the termination process and release of nascent polypeptides from yeast ribosomes are discussed. PMID:355860

  5. Dissociation curves of diatomic molecules: A DC-DFT study

    SciTech Connect

    Sim, Eunji; Kim, Min-Cheol; Burke, Kieron

    2015-12-31

    We investigate dissociation of diatomic molecules using standard density functional theory (DFT) and density-corrected density functional theory (DC-DFT) compared with CCSD(T) results as reference. The results show the difference between the HOMO values of dissociated atomic species often can be used as an indicator whether DFT would predict the correct dissociation limit. DFT predicts incorrect dissociation limits and charge distribution in molecules or molecular ions when the fragments have large HOMO differences, while DC-DFT and CCSD(T) do not. The criteria for large HOMO difference is about 2 ∼ 4 eV.

  6. Controls on Gas Hydrate Formation and Dissociation

    SciTech Connect

    Miriam Kastner; Ian MacDonald

    2006-03-03

    The main objectives of the project were to monitor, characterize, and quantify in situ the rates of formation and dissociation of methane hydrates at and near the seafloor in the northern Gulf of Mexico, with a focus on the Bush Hill seafloor hydrate mound; to record the linkages between physical and chemical parameters of the deposits over the course of one year, by emphasizing the response of the hydrate mound to temperature and chemical perturbations; and to document the seafloor and water column environmental impacts of hydrate formation and dissociation. For these, monitoring the dynamics of gas hydrate formation and dissociation was required. The objectives were achieved by an integrated field and laboratory scientific study, particularly by monitoring in situ formation and dissociation of the outcropping gas hydrate mound and of the associated gas-rich sediments. In addition to monitoring with the MOSQUITOs, fluid flow rates and temperature, continuously sampling in situ pore fluids for the chemistry, and imaging the hydrate mound, pore fluids from cores, peepers and gas hydrate samples from the mound were as well sampled and analyzed for chemical and isotopic compositions. In order to determine the impact of gas hydrate dissociation and/or methane venting across the seafloor on the ocean and atmosphere, the overlying seawater was sampled and thoroughly analyzed chemically and for methane C isotope ratios. At Bush hill the pore fluid chemistry varies significantly over short distances as well as within some of the specific sites monitored for 440 days, and gas venting is primarily focused. The pore fluid chemistry in the tub-warm and mussel shell fields clearly documented active gas hydrate and authigenic carbonate formation during the monitoring period. The advecting fluid is depleted in sulfate, Ca Mg, and Sr and is rich in methane; at the main vent sites the fluid is methane supersaturated, thus bubble plumes form. The subsurface hydrology exhibits both

  7. Products of Dissociative Recombination in the Ionosphere

    NASA Technical Reports Server (NTRS)

    Cosby, Philip

    1996-01-01

    SRI International undertook a novel experimental measurement of the product states formed by dissociative recombination (DR) of O2(+), NO(+), and N2(+) as a function of both electron energy and reactant ion vibrational level. For these measurements we used a recently developed experimental technique for measuring dissociation product distributions that allows both the branching ratios to be accurately determined and the electronic and rovibrational state composition of the reactant ions to be specified. DR is the dominant electron loss mechanism in all regions of the ionosphere. In this process, electron attachment to the molecular ion produces an unstable neutral molecule that rapidly dissociates. For a molecular ion such as O2(+), the dissociation recombination reaction is (1) O2(+) + e yields O + O + W. The atomic products of this reaction, in this case two oxygen atoms, can be produced in a variety of excited states and with a variety of kinetic energies, as represented by W in Eq. (1). These atoms are not only active in the neutral chemistry of the ionosphere, but are also especially important because their optical emissions are often used to infer in situ concentrations of the parent molecular ion and ambient electron densities. Many laboratory measurements have been made of DR reaction rates under a wide range of electron temperatures, but very little is known about the actual distributions among the final states of the atomic products. This lack of knowledge seriously limits the validity and effectiveness of efforts to model both natural and man-made ionospheric disturbances. Bates recently identified major deficiencies in the currently accepted branching ratios for O2(+) as they relate to blue and green line emission measurements in the nocturnal F-region. During our two-year effort, we partially satisfied our ambitious goals. We constructed and operated a variable pressure, electron-impact ion source and a high pressure, hollow-cathode discharge ion

  8. Acetylated histone H3 increases nucleosome dissociation

    NASA Astrophysics Data System (ADS)

    Simon, Marek; Manohar, Mridula; Ottesen, Jennifer; Poirier, Michael

    2009-03-01

    Chromatin's basic unit structure is the nucleosome, i.e. genomic DNA wrapped around a particular class of proteins -- histones -- which due to their physical hindrance, block vital biological processes, such as DNA repair, DNA replication, and RNA transcription. Histone post-translational modifications, which are known to exist in vivo, are hypothesized to regulate these biological processes by directly altering DNA-histone interactions and thus nucleosome structure and stability. Using magnetic tweezers technique we studied the acetylation of histone H3 in the dyad region, i.e. at K115 and K122, on reconstituted arrays of nucleosomes under constant external force. Based on the measured increase in the probability of dissociation of modified nucleosomes, we infer that this double modification could facilitate histone chaperone mediated nucleosome disassembly in vivo.

  9. Dissociative electron attachment studies on acetone

    SciTech Connect

    Prabhudesai, Vaibhav S. Tadsare, Vishvesh; Ghosh, Sanat; Gope, Krishnendu; Davis, Daly; Krishnakumar, E.

    2014-10-28

    Dissociative electron attachment (DEA) to acetone is studied in terms of the absolute cross section for various fragment channels in the electron energy range of 0–20 eV. H{sup −} is found to be the most dominant fragment followed by O{sup −} and OH{sup −} with only one resonance peak between 8 and 9 eV. The DEA dynamics is studied by measuring the angular distribution and kinetic energy distribution of fragment anions using Velocity Slice Imaging technique. The kinetic energy and angular distribution of H{sup −} and O{sup −} fragments suggest a many body break-up for the lone resonance observed. The ab initio calculations show that electron is captured in the multi-centered anti-bonding molecular orbital which would lead to a many body break-up of the resonance.

  10. Molecular Dissociation Induced by Electron Collisions

    NASA Astrophysics Data System (ADS)

    Wolf, Andreas

    2009-05-01

    Free electrons can efficiently break molecules or molecular ions in low-energy collisions by the processes of dissociative recombination or attachment. These processes make slow electrons efficient chemical agents in many environments. For dissociative recombination, in particular, studies of the underlying reaction paths and mechanisms have become possible on a uniquely elementary level in recent years both for theory and experiment. On the experimental side, collisions can be prepared at resolved collision energies down to the meV (10 Kelvin) level, increasingly gaining control also over the initial molecular quantum level, and individual events are detected and kinematically analyzed by fast-beam coincidence fragment imaging. Experiments are reported from the ion cooler ring TSR in Heidelberg. Stored beams of molecular ions cooled in their external and internal degrees of freedom are collinearly merged with intense and cold electron beams from cryogenic GaAs photocathodes, recently shown to yield fast cooling of the center-of-mass motion also for heavy and correspondingly slow molecular ion beams. To reconstruct the molecular fragmentation events multiparticle imaging can now be used systematically with collision energies set a wide range, especially aiming at specific electron capture resonances. Thus, for CF^+ it is found that the electronic state of the C fragment (^3P or ^1D) switches resonantly when the collision energy is changed by only a small fraction. As a new powerful tool, an energy-sensitive multi-strip surface-barrier detector (EMU) has been set up to measure with near-unity efficiency the masses of all fragments together with their hit positions in high-multiplicity events. Among many uses, this device allows internal molecular excitations to be derived for individual chemical channels in polyatomic fragmentation. New results will be presented in particular on the breakup of the hydronium ion (D3O^+).

  11. Memory Abilities in Williams Syndrome: Dissociation or Developmental Delay Hypothesis?

    ERIC Educational Resources Information Center

    Sampaio, Adriana; Sousa, Nuno; Fernandez, Montse; Henriques, Margarida; Goncalves, Oscar F.

    2008-01-01

    Williams syndrome (WS) is a neurodevelopmental genetic disorder often described as being characterized by a dissociative cognitive architecture, in which profound impairments of visuo-spatial cognition contrast with relative preservation of linguistic, face recognition and auditory short-memory abilities. This asymmetric and dissociative cognition…

  12. Dissociative Spectrum Disorders in the Primary Care Setting.

    PubMed

    Elmore, James L.

    2000-04-01

    Dissociative disorders have a lifetime prevalence of about 10%. Dissociative symptoms may occur in acute stress disorder, posttraumatic stress disorder, somatization disorder, substance abuse, trance and possession trance, Ganser's syndrome, and dissociative identity disorder, as well as in mood disorders, psychoses, and personality disorders. Dissociative symptoms and disorders are observed frequently among patients attending our rural South Carolina community mental health center. Given the prevalence of mental illness in primary care settings and the diagnostic difficulties encountered with dissociative disorders, such illness may be undiagnosed or misdiagnosed in primary care settings. We developed an intervention model that may be applicable to primary care settings or helpful to primary care physicians. Key points of the intervention are identification of dissociative symptoms, patient and family education, review of the origin of the symptoms as a method of coping with trauma, and supportive reinforcement of cognitive and relaxation skills during follow-up visits. Symptom recognition, Education of the family, Learning new skills, and Follow-up may be remembered by the mnemonic device SELF. We present several cases to illustrate dissociative symptoms and our intervention. Physicians and other professionals using the 4 steps and behavioral approaches will be able to better recognize and triage patients with dissociative symptoms. Behaviors previously thought to be secondary to psychosis or personality disorders may be seen in a new frame of reference, strengthening the therapeutic alliance while reducing distress and acting-out behaviors. PMID:15014580

  13. Coherent dissociation of relativistic {sup 9}C nuclei

    SciTech Connect

    Krivenkov, D. O.; Artemenkov, D. A.; Bradnova, V.; Vokal, S.; Zarubin, P. I. Zarubina, I. G.; Kondratieva, N. V.; Malakhov, A. I.; Moiseenko, A. A.; Orlova, G. I.; Peresadko, N. G.; Polukhina, N. G.; Rukoyatkin, P. A.; Rusakova, V. V.; Sarkisyan, V. R.; Stanoeva, R.; Haiduc, M.; Kharlamov, S. P.

    2010-12-15

    Results on the coherent dissociation of relativistic {sup 9}C nuclei in a nuclear track emulsion are described. These results include the charge topology and kinematical features of final states. Events of {sup 9}C {yields} 3{sup 3}He coherent dissociation are identified.

  14. Errors of Logic and Scholarship Concerning Dissociative Identity Disorder

    ERIC Educational Resources Information Center

    Ross, Colin A.

    2009-01-01

    The author reviewed a two-part critique of dissociative identity disorder published in the "Canadian Journal of Psychiatry". The two papers contain errors of logic and scholarship. Contrary to the conclusions in the critique, dissociative identity disorder has established diagnostic reliability and concurrent validity, the trauma histories of…

  15. The rise and fall of dissociative identity disorder.

    PubMed

    Paris, Joel

    2012-12-01

    Dissociative identity disorder (DID), once considered rare, was frequently diagnosed during the 1980s and 1990s, after which interest declined. This is the trajectory of a medical fad. DID was based on poorly conceived theories and used potentially damaging treatment methods. The problem continues, given that the DSM-5 includes DID and accords dissociative disorders a separate chapter in its manual. PMID:23197123

  16. Dissociative Spectrum Disorders in the Primary Care Setting

    PubMed Central

    Elmore, James L.

    2000-01-01

    Dissociative disorders have a lifetime prevalence of about 10%. Dissociative symptoms may occur in acute stress disorder, posttraumatic stress disorder, somatization disorder, substance abuse, trance and possession trance, Ganser's syndrome, and dissociative identity disorder, as well as in mood disorders, psychoses, and personality disorders. Dissociative symptoms and disorders are observed frequently among patients attending our rural South Carolina community mental health center. Given the prevalence of mental illness in primary care settings and the diagnostic difficulties encountered with dissociative disorders, such illness may be undiagnosed or misdiagnosed in primary care settings. We developed an intervention model that may be applicable to primary care settings or helpful to primary care physicians. Key points of the intervention are identification of dissociative symptoms, patient and family education, review of the origin of the symptoms as a method of coping with trauma, and supportive reinforcement of cognitive and relaxation skills during follow-up visits. Symptom recognition, Education of the family, Learning new skills, and Follow-up may be remembered by the mnemonic device SELF. We present several cases to illustrate dissociative symptoms and our intervention. Physicians and other professionals using the 4 steps and behavioral approaches will be able to better recognize and triage patients with dissociative symptoms. Behaviors previously thought to be secondary to psychosis or personality disorders may be seen in a new frame of reference, strengthening the therapeutic alliance while reducing distress and acting-out behaviors. PMID:15014580

  17. Dissociative Disorders in Children: Behavioral Profiles and Problems.

    ERIC Educational Resources Information Center

    Putnam, Frank W.

    1993-01-01

    Clinical research has established a connection between childhood trauma and the development of dissociative disorders in adults. Pathological dissociation produces a range of symptoms and behaviors such as amnesias, rapid shifts in mood and behavior, and auditory and visual hallucinations. Many of these symptoms are misdiagnosed as attention,…

  18. Early Indicators of Pathological Dissociation in Sexually Abused Children.

    ERIC Educational Resources Information Center

    McElroy, Linda Provus

    1992-01-01

    This paper reviews factors in the professional neglect of multiple personality disorder (MPD) and sexual abuse in childhood, as well as recent diagnostic developments in childhood dissociative disorders. The identification of subtle dissociative symptomatology in children is illustrated, and two case examples are presented. (Author)

  19. Switch Function and Pathological Dissociation in Acute Psychiatric Inpatients

    PubMed Central

    Chiu, Chui-De; Tseng, Mei-Chih Meg; Chien, Yi-Ling; Liao, Shih-Cheng; Liu, Chih-Min; Yeh, Yei-Yu; Hwu, Hai-Gwo

    2016-01-01

    Swift switching, along with atypical ability on updating and inhibition, has been found in non-clinical dissociators. However, whether swift switching is a cognitive endophenotype that intertwines with traumatisation and pathological dissociation remains unknown. Unspecified acute psychiatric patients were recruited to verify a hypothesis that pathological dissociation is associated with swift switching and traumatisation may explain this relationship. Behavioural measures of intellectual function and three executive functions including updating, switching and inhibition were administered, together with standardised scales to evaluate pathological dissociation and traumatisation. Our results showed superior control ability on switching and updating in inpatients who displayed more symptoms of pathological dissociation. When all three executive functions were entered as predictors, in addition to intellectual quotient and demographic variables to regress upon pathological dissociation, switching rather than updating remained the significant predictor. Importantly, the relationship between pathological dissociation and switching became non-significant when the effect of childhood trauma were controlled. The results support a trauma-related switching hypothesis which postulates swift switching as a cognitive endophenotype of pathological dissociation; traumatisation in childhood may explain the importance of swift switching. PMID:27123578

  20. RAIRS observation of photoinduced dissociation of NO on Ni(111)

    NASA Astrophysics Data System (ADS)

    Magkoev, Tamerlan T.; Song, Moon-Bong; Fukutani, Katsuyuki; Murata, Yoshitada

    1995-06-01

    The properties of the {NO}/{Ni(111) } system under nanosecond ultraviolet laser light irradiation are studied by reflection absorption infrared spectroscopy. It is found that adsorbed NO molecules are dissociated by laser light. Dissociation proceeds effectively in a dilute NO layer, whereas it is suppressed in a saturated overlayer.

  1. Self-Destructive Behavior in People with Dissociative Disorders.

    ERIC Educational Resources Information Center

    Saxe, Glenn N.; Chawla, Neharika; Van der Kolk, Bessel

    2002-01-01

    Study assesses self-destructive behavior in a group of inpatients who have dissociative disorders compared to those who report few dissociative symptoms. Results reveal that these patients more frequently engage in self-destructive behaviors, use more methods of self-injury, and begin to injure themselves at an earlier age then patients who do not…

  2. Peritraumatic dissociation after loss: latent structure and associations with psychopathology.

    PubMed

    Boelen, Paul A; Keijsers, Loes; van den Hout, Marcel A

    2012-04-01

    This study investigated the factor-structure of retrospectively assessed peritraumatic dissociation in the moments surrounding the death of a loved one and concurrent and prospective associations of such peritraumatic dissociation with loss-related emotional distress. Data were available from 168 people, bereaved in the preceding year. They completed the Peritraumatic Dissociative Experiences Questionnaire with their loss as the index event, together with measures of prolonged grief disorder, depression, and posttraumatic stress disorder; 117 completed symptom measures again 1 year later. Confirmatory factor analysis comparing the fit of four competing models showed that the eight-item one-factor model found in the first study using the Peritraumatic Dissociative Experiences Questionnaire provided the best fit to the data. Peritraumatic dissociation predicted concurrent and prospective symptom levels even when controlling for neuroticism and demographic and loss-related variables. PMID:22456592

  3. Dissociation of methane hydrate in aqueous NaCl solutions.

    PubMed

    Yagasaki, Takuma; Matsumoto, Masakazu; Andoh, Yoshimichi; Okazaki, Susumu; Tanaka, Hideki

    2014-10-01

    Molecular dynamics simulations of the dissociation of methane hydrate in aqueous NaCl solutions are performed. It is shown that the dissociation of the hydrate is accelerated by the formation of methane bubbles both in NaCl solutions and in pure water. We find two significant effects on the kinetics of the hydrate dissociation by NaCl. One is slowing down in an early stage before bubble formation, and another is swift bubble formation that enhances the dissociation. These effects arise from the low solubility of methane in NaCl solution, which gives rise to a nonuniform spatial distribution of solvated methane in the aqueous phase. We also demonstrate that bubbles form near the hydrate interface in dense NaCl solutions and that the hydrate dissociation proceeds inhomogeneously due to the bubbles. PMID:25237735

  4. Dissociative Symptoms and Mother's Marital Status in Young Adult Population

    PubMed Central

    Bob, Petr; Selesova, Petra; Raboch, Jiri; Kukla, Lubomir

    2015-01-01

    Abstract Current findings suggest that mother's marital status indicating father's absence or conflicting relationship to father may be specifically related to dissociation and other stress-related symptoms. We have assessed relationships of mother's marital status, dissociative symptoms, and other psychopathological manifestations in a sample of 19 years’ old young adults (N = 364) participating in European longitudinal study (European Longitudinal Study of Parenthood and Childhood). The results show clinically significant manifestations of dissociative symptoms in young adult men whose mothers were fatherless and in women whose mothers were re-married. Other psychopathological symptoms did not reach clinically significant manifestations. The results suggest that significant factor related to high level of dissociative symptoms in men growing in fatherless families might be linked with disturbed and conflicting attachment to a father's figure and pathological dependent attachment to mother. In women dissociative symptoms likely are linked to conflicting relationship between mother and daughter associated with stepfather’ presence in the family. PMID:25590849

  5. Dissociation rate constant of the biotin-streptavidin complex.

    PubMed

    Piran, U; Riordan, W J

    1990-10-01

    We measured the dissociation rate constants of the biotin/streptavidin and biotin/egg avidin complexes by following the release of radiolabeled biotin from the preformed complexes in the presence of excess unlabeled biotin. For separation of bound and free labeled biotin we employed ultrafiltration with disposable microconcentrators. The dissociation rate constant for underivatized streptavidin was 2.4 x 10(-6) s-1, or approximately 30-fold higher than that observed for egg avidin 7.5 x 10(-8) s-1). The value for streptavidin was further increased after derivatization with an acridinium ester label. Both biotin binding proteins exhibited a faster initial phase, suggesting binding site heterogeneity due to partial subunit dissociation or denaturation. The convenience of the method and the relatively fast dissociation of biotin from streptavidin render the dissociation rate constant a practical experimental criterion for monitoring the integrity of the binding site during purification and derivatization procedures. PMID:2212686

  6. Promotion of Methane Hydrate Dissociation by Underwater Ultrasonic Wave

    NASA Astrophysics Data System (ADS)

    Miura, Hikaru; Takata, Makoto; Tajima, Daisuke; Tsuyuki, Kenichirou

    2006-05-01

    The methane hydrate that exists in the abyssal floor is receiving attention as a nonconventional type of natural gas resource. An efficient dissociation technology is necessary and indispensable to achieve a steady supply of methane from methane hydrate because it does not easily dissociate in a stable environment of high pressure and low temperature. We consider that underwater ultrasonic wave irradiation may be a method of promoting the dissociation of methane hydrate on the basis of the facilitator effect. We carried out a preliminary examination using dry ice at various pressures, water temperatures, and input electric power. Methane hydrate was similarly examined. As a result, it was clarified that the dissociation time was shorted by the ultrasonic wave, and the wave was effective when the water temperature was low at the time of dissociation.

  7. Dissociation of gadolinium chelates in mice: relationship to chemical characteristics.

    PubMed

    Wedeking, P; Kumar, K; Tweedle, M F

    1992-01-01

    Tissue distributions of seven 153Gd-labeled Gd chelates were determined at five residence intervals (5 min to 14 days) following intravenous administration of 0.4 mmol/kg to mice. Relationships were sought among physicochemical parameters: thermodynamic and conditional (pH 7.4) equilibrium stability constants (log K and log K'), acid dissociation rate constants (k(obs)), lipophilicity (log P), overall charge, and size (molecular weight). Size and lipophilicity did not correlate with tissue distributions. There were possible correlations between anionic charge and rapid, early renal excretion and between stability constants and long-term residual Gd deposition. Strong correlations (r greater than 0.99) were found between acid dissociation rates and long-term deposition of Gd in the whole body, liver, and femur. This is attributed to dissociation of Gd from the chelates in vivo. Acid dissociation rates may be useful in predicting dissociation of Gd from chelates in vivo. PMID:1501535

  8. Unresolved mourning, supernatural beliefs and dissociation: a mediation analysis.

    PubMed

    Thomson, Paula; Jaque, S Victoria

    2014-01-01

    Unresolved mourning is marked by disorganized behavior and states of mind. In this study, we speculated that pathological dissociation would mediate the effects of unresolved mourning on supernatural beliefs. This hypothesis was determined based on findings that indicate an association between higher levels of dissociation, stronger beliefs in the supernatural and unresolved mourning. We examined two groups of participants, one classified as non-unresolved (non-U) (n = 56) and the other as unresolved (n = 26) (U) with respect to past loss/trauma as measured by the Adult Attachment Interview (AAI). Two self-report instruments were administered to measure supernatural beliefs and dissociation. As hypothesized, the multivariate analysis of variance indicated mean differences between the two groups. The unresolved group had greater belief in the supernatural and more pathological dissociative processes. The mediation analysis demonstrated that pathological dissociation fully mediated the effects of unresolved mourning on supernatural beliefs. PMID:24913392

  9. Multiphoton Dissociation of Electrosprayed MegaDalton-Sized DNA Ions in a Charge-Detection Mass Spectrometer

    NASA Astrophysics Data System (ADS)

    Doussineau, Tristan; Paletto, Pierre; Dugourd, Philippe; Antoine, Rodolphe

    2015-01-01

    Charge detection mass spectrometry in combination with a linear electrostatic ion trap coupled to a continuous wavelength infrared CO2 laser has been used to study the multiphoton dissociation of DNA macromolecular ions. Samples, with masses ranging from 2.23 to 31.5 MDa, include single strand circular M13mp18, double strand circular M13mp18, and double strand linear LambdaPhage DNA fragments. Their activation energies for unimolecular dissociation were determined. Activation energy values slightly increase as a function of the molecular weight. The most important result is the difference between the fragmentations observed for hybridized double-strands and dimers of single strands.

  10. Dissociative, depressive, and PTSD symptom severity as correlates of nonsuicidal self-injury and suicidality in dissociative disorder patients.

    PubMed

    Webermann, Aliya R; Myrick, Amie C; Taylor, Christina L; Chasson, Gregory S; Brand, Bethany L

    2016-01-01

    The present study investigates whether symptom severity can distinguish patients diagnosed with dissociative identity disorder and dissociative disorder not otherwise specified with a recent history of nonsuicidal self-injury (NSSI) and suicide attempts from those patients without recent self-harm. A total of 241 clinicians reported on recent history of patient NSSI and suicide attempts. Of these clinicians' patients, 221 completed dissociative, depressive, and posttraumatic stress disorder symptomatology measures. Baseline cross-sectional data from a naturalistic and prospective study of dissociative disorder patients receiving community treatment were utilized. Analyses evaluated dissociative, depressive, and posttraumatic stress disorder symptom severity as methods of classifying patients into NSSI and suicide attempt groupings. Results indicated that dissociation severity accurately classified patients into NSSI and suicidality groups, whereas depression severity accurately classified patients into NSSI groups. These findings point to dissociation and depression severity as important correlates of NSSI and suicidality in patients with dissociative disorders and have implications for self-harm prevention and treatment. PMID:26211678

  11. Sequential Collision- and Ozone-Induced Dissociation Enables Assignment of Relative Acyl Chain Position in Triacylglycerols.

    PubMed

    Marshall, David L; Pham, Huong T; Bhujel, Mahendra; Chin, Jacqueline S R; Yew, Joanne Y; Mori, Kenji; Mitchell, Todd W; Blanksby, Stephen J

    2016-03-01

    Unambiguous identification of isomeric lipids by mass spectrometry represents a significant analytical challenge in contemporary lipidomics. Herein, the combination of collision-induced dissociation (CID) with ozone-induced dissociation (OzID) on an ion-trap mass spectrometer is applied to the identification of triacylglycerol (TG) isomers that vary only by the substitution pattern of fatty acyl (FA) chains esterified to the glycerol backbone. Isolated product ions attributed to loss of a single FA arising from CID of [TG + Na](+) ions react rapidly with ozone within the ion trap. The resulting CID/OzID spectra exhibit abundant ions that unequivocally reveal the relative position of FAs along the backbone. Isomeric TGs containing two or three different FA substituents are readily differentiated by diagnostic ions present in their CID/OzID spectra. Compatibility of this method with chromatographic separations enables the characterization of unusual TGs containing multiple short-chain FAs present in Drosophila. PMID:26799085

  12. Dissociation dynamics of noble-gas dimers in intense two-color IR laser fields

    NASA Astrophysics Data System (ADS)

    Magrakvelidze, M.; Thumm, U.

    2013-07-01

    We numerically model the dissociation dynamics of the noble-gas dimer ions He2+, Ne2+, Ar2+, Kr2+, and Xe2+ in ultrashort pump and probe laser pulses of different wavelengths. Our calculations reveal a distinguished “gap” in the kinetic energy spectra, observed experimentally for the Ar2 dimer [J. Wu , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.110.033005 110, 033005 (2013)], for all noble-gas dimers for appropriate wavelength combinations. This striking phenomenon can be explained by the dissociation of dimer ions on dipole-coupled Born-Oppenheimer adiabatic potential curves. Comparing pump-probe-pulse-delay-dependent kinetic-energy-release spectra for different noble-gas dimer cations of increasing mass, we discuss increasingly prominent (i) fine-structure effects in and (ii) classical aspects of the nuclear vibrational motion.

  13. Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

    SciTech Connect

    Haxton, D.; Adaniya, H.; Slaughter, D. S.; Rudek, B.; Osipov, T.; Weber, T.; Rescigno, T. N.; McCurdy, C. W.; Belkacem, A.

    2011-08-11

    Following prior work on the lower-energy resonances, we apply techniques of momentum imaging and ab initio scattering calculations to the process of dissociative electron attachment to water via the highest-energy {sup 2}B{sub 2} resonance. We focus on the H{sup -} anion fragment, which is produced via dynamics passing through and avoiding the conical intersection with the lower A{sub 1} state, leading to OH ({sup 2}{Pi} ) and OH ({sup 2}{Sigma} ), respectively. The momentum imaging technique, when combined with theoretical calculations on the attachment amplitude and dissociation dynamics, demonstrates that the angular distributions provide a signature of the location of the conical intersection in the space of nuclear configurations.

  14. Observation of the dynamics leading to a conical intersection in dissociative electron attachment to water

    SciTech Connect

    Haxton, Dan; Adaniya, Hidihito; Slaughter, Dan; Rudek, B.; Osipov, Timur; Weber, Thorsten; Rescigno, Tom; McCurdy, Bill; Belkacem, Ali

    2011-06-08

    Following prior work on the lower-energy resonances, we apply techniques of momentum imaging and ab initio scattering calculations to the process of dissociative electron attachment to water via the highest-energy {sup 2}B{sub 2} resonance. We focus on the H{sup -} anion fragment, which is produced via dynamics passing through and avoiding the conical intersection with the lower A{sub 1} state, leading to OH ((sup 2}{Pi}#5;) and OH ({sup 2}{Sigma}#6;), respectively. The momentum imaging technique, when combined with theoretical calculations on the attachment amplitude and dissociation dynamics, demonstrates that the angular distributions provide a signature of the location of the conical intersection in the space of nuclear con#12;gurations.

  15. Association-dissociation and denaturation behaviour of an oligomeric seed protein alpha-globulin of Sesamum indicum L. in acid and alkaline solutions.

    PubMed

    Prakash, V; Nandi, P K

    1977-01-01

    The association-dissociation and denaturation behaviour of the major protein fraction, alpha-globulin of sesame seed (Sesamum indicum L.), in acid and alkaline solutions in the ranges of pH 4.2-1.5 and pH 7-12 have been studied. The results of gel filtration, fluorescence and viscosity measurements indicate dissociation and denaturation of the protein up to pH approximately 3. The difference spectrum in this region arises from a combination of dissociation, denaturation and charge effect on the chromophore. In still stronger acid solution, reassociation of the dissociated fraction takes place by hydrophobic interaction. In alkaline solution dissociation takes place around pH 8, and above pH 10 dissociation and denaturation proceed simultaneously as has been evidenced by sedimentation, fluorescence, spectral change, optical rotation and viscosity measurements. The phenolic group (pKInt=10.6) in the protein is abnormal and denaturation in alkaline solution is irreversible. Above pH 11.5 further dissociation of the protein takes place. Characteristic pH values of transition from 10.6-10.8 indicate that the transition of the protein involves a single step in alkaline solution. PMID:19367

  16. Dissociations of the night: individual differences in sleep-related experiences and their relation to dissociation and schizotypy.

    PubMed

    Watson, D

    2001-11-01

    The author examined the associations among sleep-related experiences (e.g., hypnagogic hallucinations, nightmares, waking dreams, and lucid dreams), dissociation, schizotypy, and the Big Five personality traits in 2 large student samples. Confirmatory factor analyses indicated that (a) dissociation and schizotypy are strongly correlated-yet distinguishable-constructs, and (b) the differentiation between them can be enhanced by eliminating detachment/depersonalization items from the dissociation scales. A general measure of sleep experiences was substantially correlated with both schizotypy and dissociation (especially the latter) and more weakly related to the Big Five. In contrast, an index of lucid dreaming was weakly related to all of these other scales. These results suggest that measures of dissociation, schizotypy, and sleep-related experiences all define a common domain characterized by unusual cognitions and perceptions. PMID:11727942

  17. Shot through with voices: Dissociation mediates the relationship between varieties of inner speech and auditory hallucination proneness

    PubMed Central

    Alderson-Day, Ben; McCarthy-Jones, Simon; Bedford, Sarah; Collins, Hannah; Dunne, Holly; Rooke, Chloe; Fernyhough, Charles

    2014-01-01

    Inner speech is a commonly experienced but poorly understood phenomenon. The Varieties of Inner Speech Questionnaire (VISQ; McCarthy-Jones & Fernyhough, 2011) assesses four characteristics of inner speech: dialogicality, evaluative/motivational content, condensation, and the presence of other people. Prior findings have linked anxiety and proneness to auditory hallucinations (AH) to these types of inner speech. This study extends that work by examining how inner speech relates to self-esteem and dissociation, and their combined impact upon AH-proneness. 156 students completed the VISQ and measures of self-esteem, dissociation and AH-proneness. Correlational analyses indicated that evaluative inner speech and other people in inner speech were associated with lower self-esteem and greater frequency of dissociative experiences. Dissociation and VISQ scores, but not self-esteem, predicted AH-proneness. Structural equation modelling supported a mediating role for dissociation between specific components of inner speech (evaluative and other people) and AH-proneness. Implications for the development of “hearing voices” are discussed. PMID:24980910

  18. Freshly dissociated mature hippocampal astrocytes exhibit passive membrane conductance and low membrane resistance similarly to syncytial coupled astrocytes

    PubMed Central

    Du, Yixing; Ma, Baofeng; Kiyoshi, Conrad M.; Alford, Catherine C.; Wang, Wei

    2015-01-01

    Mature astrocytes exhibit a linear current-to-voltage K+ membrane conductance (passive conductance) and an extremely low membrane resistance (Rm) in situ. The combination of these electrophysiological characteristics establishes a highly negative and stable membrane potential that is essential for basic functions, such as K+ spatial buffering and neurotransmitter uptake. However, astrocytes are coupled extensively in situ. It remains to be determined whether the observed passive behavior and low Rm are attributable to the intrinsic properties of membrane ion channels or to gap junction coupling in functionally mature astrocytes. In the present study, freshly dissociated hippocampal tissues were used as a new model to examine this basic question in young adult animals. The morphologically intact single astrocytes could be reliably dissociated from animals postnatal day 21 and older. At this animal age, dissociated single astrocytes exhibit passive conductance and resting membrane potential similar to those exhibited by astrocytes in situ. To precisely measure the Rm from single astrocytes, dual-patch single-astrocyte recording was performed. We show that dissociated single astrocytes exhibit a low Rm similarly to syncytial coupled astrocytes. Functionally, the symmetric expression of high-K+ conductance enabled rapid change in the intracellular K+ concentrations in response to changing K+ drive force. Altogether, we demonstrate that freshly dissociated tissue preparation is a highly useful model for study of the functional expression and regulation of ion channels, receptors, and transporters in astrocytes and that passive behavior and low Rm are the intrinsic properties of mature astrocytes. PMID:25810481

  19. Characterization and Modeling of the Collision Induced Dissociation Patterns of Deprotonated Glycosphingolipids: Cleavage of the Glycosidic Bond

    NASA Astrophysics Data System (ADS)

    Rožman, Marko

    2016-01-01

    Glycosphingolipid fragmentation behavior was investigated by combining results from analysis of a series of negative ion tandem mass spectra and molecular modeling. Fragmentation patterns extracted from 75 tandem mass spectra of mainly acidic glycosphingolipid species (gangliosides) suggest prominent cleavage of the glycosidic bonds with retention of the glycosidic oxygen atom by the species formed from the reducing end (B and Y ion formation). Dominant product ions arise from dissociation of sialic acids glycosidic bonds whereas product ions resulting from cleavage of other glycosidic bonds are less abundant. Potential energy surfaces and unimolecular reaction rates of several low-energy fragmentation pathways leading to cleavage of glycosidic bonds were estimated in order to explain observed dissociation patterns. Glycosidic bond cleavage in both neutral (unsubstituted glycosyl group) and acidic glycosphingolipids was the outcome of the charge-directed intramolecular nucleophilic substitution (SN2) mechanism. According to the suggested mechanism, the nucleophile in a form of carboxylate or oxyanion attacks the carbon at position one of the sugar ring, simultaneously breaking the glycosidic bond and yielding an epoxide. For gangliosides, unimolecular reaction rates suggest that dominant product ions related to the cleavage of sialic acid glycosidic bonds are formed via direct dissociation channels. On the other hand, low abundant product ions related to the dissociation of other glycosidic bonds are more likely to be the result of sequential dissociation. Although results from this study mainly contribute to the understanding of glycosphingolipid fragmentation chemistry, some mechanistic findings regarding cleavage of the glycosidic bond may be applicable to other glycoconjugates.

  20. Dissociative identity disorder: adaptive deception of self and others.

    PubMed

    Beahrs, J O

    1994-01-01

    Dissociative identity disorder (multiple personality) is increasingly diagnosed, often follows childhood trauma, and is characterized by rigidification of phenomena that resemble hypnosis. To interpret dissociated aspects of selfhood as autonomous entities is a useful heuristic; but when taken too literally, it leads to three kinds of anomaly: (1) legal: dissociators remain culpable for misdeeds carried out beyond apparent awareness or control; (2) clinical: legitimization sometimes leads not to relief, but to escalating cycles of regressive dependency; and (3) scientific: the form of dissociated entities varies with how they are defined, in ways that are intrinsically motivated and clinically manipulable. These anomalies yield to an evolutionary perspective that views dissociative identity disorder as an evolved strategy of adaptive deception of self and others; e.g., a beaten subordinate avoids further retribution by "pleading illness." Such a deceit best avoids detection when fully experienced; through its intensity and persistence, it becomes real at a new level. One's basic competencies remain intact, however, and are the source of the anomalies described. They can be clinically accessed and empowered, providing the key to therapeutic change when dissociative processes are problematic. Overall, despite clear impairment in subjective awareness and volition, dissociative-disordered individuals are best held fully accountable for the consequences of their actions. PMID:7949411

  1. Forgetting the unforgotten affective autobiographical memories in nonclinical dissociators.

    PubMed

    Chiu, Chui-De; Lin, Chi-Chin; Yeh, Yei-Yu; Hwu, Hai-Gwo

    2012-10-01

    Inefficient memory inhibition has been observed in nonclinical and clinical dissociators. Paradoxically, dissociators also report unusual forgetfulness. Investigating how forgetting emerges in dissociators may uncover the antecedents for their self-report memory problems. We postulated that set switch can link inefficient memory inhibition to forgetting. Recollection detour, which involves an affect switch, may elicit forgetting of previously uninhibited memories in nonclinical dissociators. This hypothesis was verified in participants with high- and low-dissociation proneness via a retrieval practice paradigm using positive and negative autobiographical memories. After the study and retrieval-practice phases, memories of the practiced affect category were tested without and with intervening recall of the unpracticed affect category in the control and detour condition, respectively. Nondissociators showed reduced recall in the control condition, replicating the retrieval-induced forgetting (RIF) effect and recollection detour did not alter the RIF effect. By contrast, nonclinical dissociators showed the RIF effect in the detour condition but not in the control condition. Detour to recollecting memories of another affect category rendered an aftereffect of forgetting of previously uninhibited memories in nonclinical dissociators. PMID:22023361

  2. [Results of ligament reconstruction in advanced scapholunate dissociation].

    PubMed

    Wieloch, P T; Martini, A-K; Daecke, W

    2005-04-01

    Scapholunate dissociation is one of the most common disorders of the wrist. Untreated it might lead to osteoarthrosis (scapholunate advanced collapse, SLAC wrist). Choosing the best surgical treatment option is still challenging, especially in cases of carpal collapse in combination with beginning osteoarthrosis of the radial styloid and the proximal pole of the scaphoid. We report the results of a homogenous group of eight patients with reducible carpal collapse and beginning arthrosis treated by reconstruction of the scapholunate ligament. The operation was performed 66 (range: 20 to 252) months after trauma. The average length of follow-up was two years. Five patients stated general improvement, while three reported a change for the worse. At follow-up, the average total range of motion of the operated wrist was decreased by 16 % compared to the unaffected side. The average grip-strength (measured with a Jamar dynamometer) was 77 % of the uninvolved wrist. The DASH score was 43 +/- 25. In three cases the Martini score showed a good or an excellent result. The average scapholunate angle was 72.3 degrees preoperatively and decreased to 61.0 degrees at follow-up. At follow-up as well as pre- and postoperatively the carpal height ratio showed pathologic mean values. Therefore, reconstruction of the carpal alignment was not achieved in most of the cases. Progression of the osteoarthrosis has to be expected. Reconstruction of the scapholunate ligament for treatment of carpal collapse with beginning osteoarthrosis therefore remains an unsolved problem. PMID:15877269

  3. Infrared Multiple Photon Dissociation Spectroscopy Of Metal Cluster-Adducts

    NASA Astrophysics Data System (ADS)

    Cox, D. M.; Kaldor, A.; Zakin, M. R.

    1987-01-01

    Recent development of the laser vaporization technique combined with mass-selective detection has made possible new studies of the fundamental chemical and physical properties of unsupported transition metal clusters as a function of the number of constituent atoms. A variety of experimental techniques have been developed in our laboratory to measure ionization threshold energies, magnetic moments, and gas phase reactivity of clusters. However, studies have so far been unable to determine the cluster structure or the chemical state of chemisorbed species on gas phase clusters. The application of infrared multiple photon dissociation IRMPD to obtain the IR absorption properties of metal cluster-adsorbate species in a molecular beam is described here. Specifically using a high power, pulsed CO2 laser as the infrared source, the IRMPD spectrum for methanol chemisorbed on small iron clusters is measured as a function of the number of both iron atoms and methanols in the complex for different methanol isotopes. Both the feasibility and potential utility of IRMPD for characterizing metal cluster-adsorbate interactions are demonstrated. The method is generally applicable to any cluster or cluster-adsorbate system dependent only upon the availability of appropriate high power infrared sources.

  4. Surface-Induced Dissociation of Peptide Ions: Kinetics and Dynamics

    SciTech Connect

    Laskin, Julia; Futrell, Jean H.; Shukla, Anil K.

    2003-12-01

    Kinetics and dynamics studies have been carried out for the surface-induced dissociation (SID) of a set of model peptides utilizing a specially designed electrospray ionization Fourier Transform ion cyclotron resonance mass spectrometer in which mass-selected and vibrationally relaxed ions are collided on a orthogonally-mounted fluorinated self-assembled monolayer on Au{l_brace}111{r_brace} crystal. The sampling time in this apparatus can be varied from hundreds of microseconds to tens of seconds, enabling the investigation of kinetics of ion decomposition over an extended range of decomposition rates. RRKM-based modeling of these reactions for a set of polyalanines demonstrates that SID kinetics of these simple peptides is very similar to slow, multiple-collision activation and that the distribution of internal energies following collisional activation is indistinguishable from a thermal distribution. For more complex peptides comprised of several amino acids and with internal degrees of freedom ( DOF) of the order of 350 there is a dramatic change in kinetics in which RRKM kinetics is no longer capable of describing the decomposition of these complex ions. A combination of RRKM kinetics and the sudden death approximation, according to which decomposition occurs instantaneously, is a satisfactory description. This implies that a population of ions-which is dependant on the nature of the peptide, kinetic energy and sampling time-decomposes on or very near the surface. The shattering transition is described quantitatively for the limited set of molecules examined to date

  5. Surface-Induced Dissociation of Peptide Ions: Kinetics and Dynamics

    SciTech Connect

    Laskin, Julia; Futrell, Jean H.

    2003-12-01

    Kinetics and dynamics studies have been carried out for the surface-induced dissociation (SID) of a set of model peptides utilizing a specially designed electro spray ionization Fourier Transform Ion cyclotron resonance mass spectrometer in which mass-selected and vibrationally relaxed ions are collided on an orthogonally-mounted fluorinated self-assembled monolayer on Au {111} crystal. The sampling time in this apparatus can be varied from hundreds of microseconds to tens of seconds, enabling the investigation of kinetics of ion decomposition over an extended range of decomposition rates. RRKM-based modeling of these reactions for a set of polyalanines demonstrates that kinetics of these simple peptides is very similar to slow, multiple-collision activation and that the distribution of internal energies following collisional activation is indistinguishable from a thermal distribution. For more complex peptides comprised of several amino acids and with internal degrees of freedom (DOF) of the order of 350 there is a dramatic change in kinetics in which RRKM kinetics is no longer capable of describing the decomposition of these complex ions. A combination of RRKM kinetics and the “sudden death” approximation, according to which decomposition occurs instantaneously, is a satisfactory description. This implies that a population of ions – which is dependant on the nature of the peptide, kinetic energy and sampling time – decomposes on or very near the surface. The shattering transition is described quantitatively for the limited set of molecules examined to date.

  6. A complete look at the multi-channel dissociation of propenal photoexcited at 193 nm: branching ratios and distributions of kinetic energy.

    PubMed

    Chaudhuri, Chanchal; Lee, Shih-Huang

    2011-04-28

    We observed fifteen photofragments upon photolysis of propenal (acrolein, CH(2)CHCHO) at 193 nm using photofragment translational spectroscopy and selective vacuum-ultraviolet (VUV) photoionization. All the photoproducts arise from nine primary and two secondary dissociation pathways. We measured distributions of kinetic energy of products and determined branching ratios of dissociation channels. Dissociation to CH(2)CHCO + H and CH(2)CH + HCO are two major primary channels with equivalent branching ratios of 33%. The CH(2)CHCO fragment spontaneously decomposes to CH(2)CH + CO. A proportion of primary products CH(2)CH from the fission of bond C-C of propenal further decompose to CHCH + H but secondary dissociation HCO → H + CO is negligibly small. Binary dissociation to CH(2)CH(2) (or CH(3)CH) + CO and concerted three-body dissociation to C(2)H(2) + CO + H(2) have equivalent branching ratios of 14%-15%. The other channels have individual branching ratios of ∼1%. The production of HCCO + CH(3) indicates the formation of intermediate methyl ketene (CH(3)CHCO) and the production of CH(2)CCH + OH and CH(2)CC + H(2)O indicate the formation of intermediate hydroxyl propadiene (CH(2)CCHOH) from isomerization of propenal. Distributions of kinetic energy release and dissociation mechanisms are discussed. This work provides a complete look and profound insight into the multi-channel dissociation mechanisms of propenal. The combination of a molecular beam apparatus and synchrotron VUV ionization allowed us to untangle the complex mechanisms of nine primary and two secondary dissociation channels. PMID:21423979

  7. Visuomotor Dissociation in Cerebral Scaling of Size.

    PubMed

    Potgieser, Adriaan R E; de Jong, Bauke M

    2016-01-01

    Estimating size and distance is crucial in effective visuomotor control. The concept of an internal coordinate system implies that visual and motor size parameters are scaled onto a common template. To dissociate perceptual and motor components in such scaling, we performed an fMRI experiment in which 16 right-handed subjects copied geometric figures while the result of drawing remained out of sight. Either the size of the example figure varied while maintaining a constant size of drawing (visual incongruity) or the size of the examples remained constant while subjects were instructed to make changes in size (motor incongruity). These incongruent were compared to congruent conditions. Statistical Parametric Mapping (SPM8) revealed brain activations related to size incongruity in the dorsolateral prefrontal and inferior parietal cortex, pre-SMA / anterior cingulate and anterior insula, dominant in the right hemisphere. This pattern represented simultaneous use of a 'resized' virtual template and actual picture information requiring spatial working memory, early-stage attention shifting and inhibitory control. Activations were strongest in motor incongruity while right pre-dorsal premotor activation specifically occurred in this condition. Visual incongruity additionally relied on a ventral visual pathway. Left ventral premotor activation occurred in all variably sized drawing while constant visuomotor size, compared to congruent size variation, uniquely activated the lateral occipital cortex additional to superior parietal regions. These results highlight size as a fundamental parameter in both general hand movement and movement guided by objects perceived in the context of surrounding 3D space. PMID:26963705

  8. Tissue dissociation enzyme neutral protease assessment.

    PubMed

    Breite, A G; Dwulet, F E; McCarthy, R C

    2010-01-01

    Neutral proteases, essential components of purified tissue dissociation enzymes required for successful human islet isolation, show variable activities and effects of substrate on their activities. Initially we used a spectrophotometric endpoint assay with azocasein substrate to measure neutral protease activity. After critical review of the results, we observed these data to be inconsistent and not correlating expected differences in specific activities between thermolysin and Bacillus polymyxa proteases. This observation led to the development of a fluorescent microplate assay using fluorescein isothyocyanate-conjugated bovine serum albumin (FITC-BSA) as the substrate. This simpler, more flexible method offered a homogeneous, kinetic enzyme assay allowing determination of steady state reaction rates of sample replicates at various dilutions. The assay had a linear range of 4- to 8-fold and interassay coefficients of variation for B polymyxa protease and thermolysin of <9% and <15%, respectively, which were lower than those using the spectrophotometric endpoint assay, namely, 54% and 36%, respectively. This format allowed for incorporation of enzyme inhibitors, as illustrated by addition of sulfhydryl protease inhibitors, which, consistent with earlier reports, strongly indicated that the main contaminant in purified collagenase preparations was clostripain. Determination of the specific activities for several purified neutral proteases showed that the B polymyxa and Clostridium histolyticum proteases had approximately 40% and 15% specific activities, respectively, of those obtained with purified thermolysin, indicating the different characteristics of neutral protease enzymes for cell isolation procedures. PMID:20692405

  9. Activated Dissociation of HCl on Au(111).

    PubMed

    Shirhatti, Pranav R; Geweke, Jan; Steinsiek, Christoph; Bartels, Christof; Rahinov, Igor; Auerbach, Daniel J; Wodtke, Alec M

    2016-04-01

    We report zero-coverage reaction probabilities (S0) for HCl dissociative adsorption on Au(111) obtained by the seeded molecular beam hot-nozzle method. For measurements at normal incidence with mean translational energies ranging from 0.94 to 2.56 eV (nozzle temperatures 296 to 1060 K), S0 increased from 6 × 10(-6) to 2 × 10(-2). S0 also increased with increasing nozzle temperature for fixed incidence energy associated with the motion normal to the surface. Accounting for the influence of the vibrational state population and translational energy distributions in the incident beam, we are able to compare the experimental results to recent theoretical predictions. These calculations, performed employing 6-D quantum dynamics on an electronically adiabatic potential energy surface obtained using density functional theory at the level of the generalized gradient approximation and the static surface approximation, severely overestimate the reaction probabilities when compared with our experimental results. We discuss some possible reasons for this large disagreement. PMID:26990513

  10. The mechanics of motility in dissociated cytoplasm.

    PubMed Central

    Dembo, M

    1986-01-01

    We stimulate the dynamical behavior of dissociated cytoplasm using the Reactive Flow Model (Dembo, M., and F. Harlow, 1986, Biophys. J., 50:109-121). We find that for the most part the predicted dynamical behavior of the cytoplasm is governed by three nondimensional numbers. Several other nondimensional parameters, the initial conditions, and boundary conditions are found to have lesser effects. Of the three major nondimensional parameters, one (D#) controls the percentage of ectoplasm, the second (C#) controls the sharpness of the endoplasm-ectoplasm boundary, and the third (R#) controls the topological complexity of the endoplasm-ectoplasm distribution. If R# is very small, then the cytoplasm contracts into a single uniform mass, and there is no bulk streaming. If R# is very large, then the cytoplasmic mass breaks up into a number of clumps scattered throughout the available volume. Between these clumps the solution undergoes turbulent or chaotic patterns of streaming. Intermediate values of R# can be found such that the mass of cytoplasm remains connected and yet undergoes coherent modes of motility similar to flares (Taylor, D.L., J.S. Condeelis, P.L. Moore, and R.D. Allen, 1973, J. Cell Biol., 59:378-394) and rosettes (Kuroda, K., 1979, Cell Motility: Molecules and Organization, 347-362). Images FIGURE 1 FIGURE 1B FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 PMID:3801576

  11. Visuomotor Dissociation in Cerebral Scaling of Size

    PubMed Central

    Potgieser, Adriaan R. E.; de Jong, Bauke M.

    2016-01-01

    Estimating size and distance is crucial in effective visuomotor control. The concept of an internal coordinate system implies that visual and motor size parameters are scaled onto a common template. To dissociate perceptual and motor components in such scaling, we performed an fMRI experiment in which 16 right-handed subjects copied geometric figures while the result of drawing remained out of sight. Either the size of the example figure varied while maintaining a constant size of drawing (visual incongruity) or the size of the examples remained constant while subjects were instructed to make changes in size (motor incongruity). These incongruent were compared to congruent conditions. Statistical Parametric Mapping (SPM8) revealed brain activations related to size incongruity in the dorsolateral prefrontal and inferior parietal cortex, pre-SMA / anterior cingulate and anterior insula, dominant in the right hemisphere. This pattern represented simultaneous use of a ‘resized’ virtual template and actual picture information requiring spatial working memory, early-stage attention shifting and inhibitory control. Activations were strongest in motor incongruity while right pre-dorsal premotor activation specifically occurred in this condition. Visual incongruity additionally relied on a ventral visual pathway. Left ventral premotor activation occurred in all variably sized drawing while constant visuomotor size, compared to congruent size variation, uniquely activated the lateral occipital cortex additional to superior parietal regions. These results highlight size as a fundamental parameter in both general hand movement and movement guided by objects perceived in the context of surrounding 3D space. PMID:26963705

  12. Transcultural aspects of dissociative and somatoform disorders.

    PubMed

    Escobar, J I

    1995-09-01

    A brief review of the cross-cultural literature on dissociative and somatoform disorders with emphasis on US Hispanic populations has been provided. A brief description of the psychopathology of somatizing syndromes has been given as have some critiques of current nosologic systems. Cultural influences that may color the expression of somatic manifestations have been outlined. Although it is often difficult to disentangle the contribution of ethnicity from other demographic factors, and although there are plenty of methodologic shortcomings, most studies reinforce the view that culture exerts a powerful influence in shaping symptom presentation and determining health-related attitudes. Future work using instruments such as the Composite International Diagnostic Interview (CIDI) (Rubio-Stipec M: The somatization schedule of the Composite International Diagnostic Interview: The use of the probe in 17 different countries; unpublished manuscript) that include a more culturally congruent list of somatizing symptoms may shed new light on the international distribution and mechanisms at play in these symptom presentations. PMID:8545267

  13. Dissociative recombination of rotationally cold H+3

    NASA Astrophysics Data System (ADS)

    McCall, B. J.; Huneycutt, A. J.; Saykally, R. J.; Djuric, N.; Dunn, G. H.; Semaniak, J.; Novotny, O.; Al-Khalili, A.; Ehlerding, A.; Hellberg, F.; Kalhori, S.; Neau, A.; Thomas, R. D.; Paal, A.; Österdahl, F.; Larsson, M.

    2004-11-01

    This paper presents the first dissociative recombination (DR) measurement of electrons with rotationally and vibrationally cold H+3 ions. A dc discharge pinhole supersonic jet source was developed and characterized using infrared cavity ringdown spectroscopy before installation on the CRYRING ion storage ring for the DR measurements. Rotational state distributions ( Trot ˜30 K ) produced using the source were comparable to those in the diffuse interstellar medium. Our measurement of the electron energy dependence of the DR cross section showed resonances not clearly seen in experiments using rotationally hot ions, and allowed calculation of the thermal DR rate coefficient for ions at interstellar temperatures, αDR (23 K)=2.6× 10-7 cm3 s-1 . This value is in general agreement with recent theoretical predictions by

    Kokoouline and Greene [Phys. Rev. A 68, 012703 (2003)
    ]. The branching fractions of the two breakup channels, H+H+H and H+ H2 , have also been measured for rotationally and vibrationally cold H+3 .

  14. Dissociable brain biomarkers of fluid intelligence.

    PubMed

    Paul, Erick J; Larsen, Ryan J; Nikolaidis, Aki; Ward, Nathan; Hillman, Charles H; Cohen, Neal J; Kramer, Arthur F; Barbey, Aron K

    2016-08-15

    Cognitive neuroscience has long sought to understand the biological foundations of human intelligence. Decades of research have revealed that general intelligence is correlated with two brain-based biomarkers: the concentration of the brain biochemical N-acetyl aspartate (NAA) measured by proton magnetic resonance spectroscopy (MRS) and total brain volume measured using structural MR imaging (MRI). However, the relative contribution of these biomarkers in predicting performance on core facets of human intelligence remains to be well characterized. In the present study, we sought to elucidate the role of NAA and brain volume in predicting fluid intelligence (Gf). Three canonical tests of Gf (BOMAT, Number Series, and Letter Sets) and three working memory tasks (Reading, Rotation, and Symmetry span tasks) were administered to a large sample of healthy adults (n=211). We conducted exploratory factor analysis to investigate the factor structure underlying Gf independent from working memory and observed two Gf components (verbal/spatial and quantitative reasoning) and one working memory component. Our findings revealed a dissociation between two brain biomarkers of Gf (controlling for age and sex): NAA concentration correlated with verbal/spatial reasoning, whereas brain volume correlated with quantitative reasoning and working memory. A follow-up analysis revealed that this pattern of findings is observed for males and females when analyzed separately. Our results provide novel evidence that distinct brain biomarkers are associated with specific facets of human intelligence, demonstrating that NAA and brain volume are independent predictors of verbal/spatial and quantitative facets of Gf. PMID:27184204

  15. Dermatitis artefacta in a vulnerable adult with a dissociative state.

    PubMed

    Ahmed, A; Bewley, A; Taylor, R

    2013-12-01

    Dermatitis artefacta (DA), a factitious skin disorder, often occurs as a response to traumatic life events or as a factitious behaviour, which may result in secondary gain. It can be difficult to get patients to engage with health services, and they seldom admit to causing the lesions themselves. The possibility of DA lesions occurring in dissociative states is less well known. We present a case of DA diagnosed in a vulnerable adult, who we believe caused the lesions during periods of dissociation. We discuss the way in which the concept of dissociation can provide an acceptable way of discussing the behaviour with patients and initiating psychological therapy. PMID:23758341

  16. General features of the dissociative recombination of polyatomic molecules

    DOE PAGESBeta

    Pratt, S. T.; Jungen, Ch.; Schneider, I. F.; Dulieu, O.; Robert, J.

    2015-01-29

    We discuss some aspects of a simple expression for the low-energy dissociative recombination cross section that applies when the recombination process is dominated by the indirect mechanism. In most previous applications, this expression has been applied to capture into vibrationally excited Rydberg states with the assumption that capture is always followed by prompt dissociation. Here we consider the dissociative recombination of larger polyatomic ions and electrons. More specifically, we consider capture into electronically core-excited Rydberg states, and begin to assess its potential importance for larger systems.

  17. Narratives of dissociation: insights into the treatment of dissociation in individuals who were sexually abused as children.

    PubMed

    Hirakata, Pam

    2009-01-01

    This article provides an in-depth understanding of the treatment of dissociation from the perspective of 7 individuals who have a history of childhood sexual abuse and engage in moderate to high levels of dissociative behavior. Levels of dissociation were screened using the Dissociative Experiences Scale (E. Bernstein-Carlson & F. Putnam, 1993), and individual interviews were conducted to gain insight into how dissociation can best be treated in a therapeutic context. From a narrative research design with a holistic-content analysis (A. Lieblich, R. Tuval-Mashiach, & T. Zilber, 1998), 3 major themes and 16 subthemes were revealed. The major themes included (a) identifying specific tools and techniques that were recognized as critical in managing dissociative symptoms, (b) challenging the dominant medical paradigm by underscoring the importance of helping clients contextualize and normalize dissociative behavior, and (c) highlighting specific characteristics of the therapeutic relationship that create the necessary trust and safety to facilitate reparation. A detailed description of the 3 major themes and 16 subthemes is provided. Implications for both clinical theory and practice are identified. PMID:19585338

  18. Final report. Surface-induced dissociation versus collision-induced dissociation

    SciTech Connect

    Futrell, Jean H.

    2001-04-19

    A 7-Tesla Fourier transform ion-cyclotron resonance (FTICR) mass spectrometer was modified to insert a surface inside the cell for ion-surface collisions leading to the dissociation of impacting ions. Modifications were made to the software/hardware to collide the ions brought into the cell and trap the resulting fragment and undissociated primary ions inside the cell. The trapping plates were also ramped to determine kinetic energy distributions of these ions. The surface-induced dissociation (SID) of benzene and chromium hexacarbonyl ions was first studied as test cases for the instrument. Then a systematic study of the SID of small protonated peptides formed by electrospray ionization was begun. A series of small alanine(A)-containing peptides, viz., AA, AAA, AAAA, AAAAA, and PAAAA were used in the study. In the absence of any direct comparisons of the SID processes with the commonly used technique of tandem mass spectrometry of collision-induced dissociations (CID) via collisions with a neutral gas, a comparative study of CID and SID using the same protonated peptides was made. Since multiple collisions are often used to enhance dissociation efficiency in CID, the CID was performed under single as well as multiple collisional activation conditions. Both on-resonance and sustained off-resonance irradiation excitation were used for CID experiments. Kinetic energy of the ions was varied by changing peak-to-peak voltage applied to the excitation plates. Results are shown in a series of graphs, and a simple theoretical model is presented. This direct comparison of the two activation techniques on the same instrument provided insights into the similarities and differences between these two. The results suggest that internal energy distributions of ions activated by ion-surface collision and multiple collision ion-gaseous neutral collisions are quite comparable. The results also suggest that, in ion-surface collisions, the ion collides with only a small fraction of th

  19. Dissociative amnesia in dissociative disorders and borderline personality disorder: self-rating assessment in a college population.

    PubMed

    Sar, Vedat; Alioğlu, Firdevs; Akyuz, Gamze; Karabulut, Sercan

    2014-01-01

    Dissociative amnesia (DA) among subjects with a dissociative disorder and/or borderline personality disorder (BPD) recruited from a nonclinical population was examined. The Steinberg Dissociative Amnesia Questionnaire (SDAQ), the Childhood Trauma Questionnaire, and the self-report screening tool of the BPD section of the Structured Clinical Interview for DSM-IV(SCID-BPD) were administered to 1,301 college students. A total of 80 participants who were diagnosed with BPD according to the clinician-administered SCID-BPD and 111 nonborderline controls were evaluated using the Structured Clinical Interview for DSM-IV Dissociative Disorders (SCID-D) by a psychiatrist blind to diagnosis and scale scores. Internal consistency analyses and test-retest evaluations suggested that the SDAQ is a reliable instrument for the population studied. Of the participants, 20.6% reported an SDAQ score of 20 or above and impairment by DA. Those who had both dissociative disorder and BPD (n = 78) had the highest SDAQ scores. Both disorders had significant effects on the SCID-D total and amnesia scores in the variance analysis. On SDAQ scores, however, only BPD had this effect. There was a significant interaction between the 2 disorders for the SCID-D total but not for the SDAQ or SCID-D amnesia scores. BPD represented the severity of dissociation and childhood trauma in this study group. However, in contrast to the dissociative disorders, BPD was characterized by better awareness of DA in self-report. The discrepancies between self-report and clinical interview associated with BPD and dissociative disorders are discussed in the context of betrayal theory (J. J. Freyd, 1994) of BPD and perceptual theory (D. B. Beere, 2009) of dissociative disorders. PMID:24678926

  20. Cognitive therapy of dissociative symptoms associated with trauma.

    PubMed

    Kennerley, H

    1996-09-01

    The presentation of dissociative symptoms is not uncommon in clinical settings, particularly when the client has suffered trauma. The phenomenon of dissociation ranges from benign incidents, such as daydreaming, to potentially life-threatening experiences when it precipitates self-harm. Its presentation may be subtle, belying the distress which it can provoke. Cognitive therapists are well equipped to help clients formulate a working conceptualization of the dissociative episode and to develop a range of coping skills to manage and overcome the experience. This paper discusses practical ways in which the cognitive therapist can use standard and schema-focused cognitive therapy to help clients to better deal with the distressing aspects of dissociation. PMID:8889075

  1. Dissociative electron attachment to the radiosensitizing chemotherapeutic agent hydroxyurea.

    PubMed

    Huber, S E; Śmiałek, M A; Tanzer, K; Denifl, S

    2016-06-14

    Dissociative electron attachment to hydroxyurea was studied in the gas phase for electron energies ranging from zero to 9 eV in order to probe its radiosensitizing capabilities. The experiments were carried out using a hemispherical electron monochromator coupled with a quadrupole mass spectrometer. Diversified fragmentation of hydroxyurea was observed upon low energy electron attachment and here we highlight the major dissociation channels. Moreover, thermodynamic thresholds for various fragmentation reactions are reported to support the discussion of the experimental findings. The dominant dissociation channel, which was observed over a broad range of energies, is associated with formation of NCO(-), water, and the amidogen (NH2) radical. The second and third most dominant dissociation channels are associated with formation of NCNH(-) and NHCONH2 (-), respectively, which are both directly related to formation of the highly reactive hydroxyl radical. Other ions observed with significant abundance in the mass spectra were NH2 (-)/O(-), OH(-), CN(-), HNOH(-), NCONH2 (-), and ONHCONH2 (-). PMID:27306009

  2. Dissociative electron attachment to the radiosensitizing chemotherapeutic agent hydroxyurea

    NASA Astrophysics Data System (ADS)

    Huber, S. E.; Śmiałek, M. A.; Tanzer, K.; Denifl, S.

    2016-06-01

    Dissociative electron attachment to hydroxyurea was studied in the gas phase for electron energies ranging from zero to 9 eV in order to probe its radiosensitizing capabilities. The experiments were carried out using a hemispherical electron monochromator coupled with a quadrupole mass spectrometer. Diversified fragmentation of hydroxyurea was observed upon low energy electron attachment and here we highlight the major dissociation channels. Moreover, thermodynamic thresholds for various fragmentation reactions are reported to support the discussion of the experimental findings. The dominant dissociation channel, which was observed over a broad range of energies, is associated with formation of NCO-, water, and the amidogen (NH2) radical. The second and third most dominant dissociation channels are associated with formation of NCNH- and NHCONH2-, respectively, which are both directly related to formation of the highly reactive hydroxyl radical. Other ions observed with significant abundance in the mass spectra were NH2-/O-, OH-, CN-, HNOH-, NCONH2-, and ONHCONH2-.

  3. Rates for dissociative recombination of LiH+ ions

    NASA Astrophysics Data System (ADS)

    Čurík, R.; Greene, C. H.

    2008-05-01

    We review recent progress in developing a theoretical treatment of the dissociative recombination (DR) process for the LiH+ molecule, in which a low energy electron is captured and causes the molecule to dissociate into neutral fragments. This e+LiH+ system is prototypical of the indirect class of DR processes, in which the incident electron destroys the molecule through Rydberg capture pathways. The conventional mechanism characteristic of most species with a high DR rate, which normally involves direct capture into a dissociative resonance potential curve, is entirely absent here. We have adopted ab initio multichannel quantum defect theory (MQDT) and a rovibrational frame transformation based on Siegert pseudostates to calculate indirect dissociative recombination for this simple diatomic ion. It is based on a set of ab-initio quantum defects as functions of the internuclear distance, which have been calculated using the R-matrix approach. The calculated DR rate coefficient is found to agree with recent experimental data [1].

  4. Catalytic efficiency of Nb and Nb oxides for hydrogen dissociation

    SciTech Connect

    Isobe, Shigehito; Kudoh, Katsuhiro; Hino, Satoshi; Hashimoto, Naoyuki; Ohnuki, Somei; Hara, Kenji

    2015-08-24

    In this letter, catalytic efficiency of Nb, NbO, Nb{sub 2}O{sub 3}, NbO{sub 2}, and Nb{sub 2}O{sub 5} for dissociation and recombination of hydrogen were experimentally investigated. On the surface of Nb and Nb oxides in a gas mixture of H{sub 2} and D{sub 2}, H{sub 2} and D{sub 2} molecules can be dissociated to H and D atoms; then, H{sub 2}, D{sub 2}, and HD molecules can be produced according to the law of probability. With increase of frequency of the dissociation and recombination, HD ratio increases. The ratio of H{sub 2} and HD gas was analyzed by quadrupole mass spectrometry. As a result, NbO showed the highest catalytic activity towards hydrogen dissociation and recombination.

  5. How Many Water Molecules Does it Take to Dissociate HCl?

    PubMed

    Vargas-Caamal, Alba; Cabellos, Jose Luis; Ortiz-Chi, Filiberto; Rzepa, Henry S; Restrepo, Albeiro; Merino, Gabriel

    2016-02-18

    The potential energy surfaces of the HCl(H2O)n (n is the number of water molecules) clusters are systematically explored using density functional theory and high-level ab initio computations. On the basis of electronic energies, the number of water molecules needed for HCl dissociation is four as reported by some experimental groups. However, this number is five owing to the inclusion of entropic factors. Wiberg bond indices are calculated and analyzed, and the results provide a quadratic correlation and classification of clusters according to the nondissociated, partially dissociated, and fully dissociated character of the H-Cl bond. Our computations show that if temperature is not controlled during the experiment, the values obtained for the dipole moment (or for any measurable property) are susceptible to change, providing a different picture of the number of water molecules needed for HCl dissociation in a nanoscopic droplet. PMID:26774026

  6. Negligible Isotopic Effect on Dissociation of Hydrogen Bonds.

    PubMed

    Ge, Chuanqi; Shen, Yuneng; Deng, Gang-Hua; Tian, Yuhuan; Yu, Dongqi; Yang, Xueming; Yuan, Kaijun; Zheng, Junrong

    2016-03-31

    Isotopic effects on the formation and dissociation kinetics of hydrogen bonds are studied in real time with ultrafast chemical exchange spectroscopy. The dissociation time of hydrogen bond between phenol-OH and p-xylene (or mesitylene) is found to be identical to that between phenol-OD and p-xylene (or mesitylene) in the same solvents. The experimental results demonstrate that the isotope substitution (D for H) has negligible effects on the hydrogen bond kinetics. DFT calculations show that the isotope substitution does not significantly change the frequencies of vibrational modes that may be along the hydrogen bond formation and dissociation coordinate. The zero point energy differences of these modes between hydrogen bonds with OH and OD are too small to affect the activation energy of the hydrogen bond dissociation in a detectible way at room temperature. PMID:26967376

  7. Communication: Enhanced dissociative chemisorption of CO2 via vibrational excitation

    NASA Astrophysics Data System (ADS)

    Jiang, Bin; Guo, Hua

    2016-03-01

    A fully coupled global nine-dimensional potential energy surface for the dissociative chemisorption of CO2 on Ni(100) is constructed from ˜18 000 density functional points. It reveals a complex reaction pathway dominated by two near iso-energetic transition states. The dissociation probabilities obtained by quasi-classical trajectories on the potential energy surface reproduced experimental trends, and indicate that vibrational excitations of CO2 significantly promote the dissociation. Using the sudden vector projection model, the behavior of the reactivity is rationalized by couplings with the reaction coordinate at each transition state. These results offer plausible rationalization for the observed enhancement of CO2 dissociation in non-thermal plasmas by metal surfaces.

  8. Communication: Enhanced dissociative chemisorption of CO2 via vibrational excitation.

    PubMed

    Jiang, Bin; Guo, Hua

    2016-03-01

    A fully coupled global nine-dimensional potential energy surface for the dissociative chemisorption of CO2 on Ni(100) is constructed from ∼18,000 density functional points. It reveals a complex reaction pathway dominated by two near iso-energetic transition states. The dissociation probabilities obtained by quasi-classical trajectories on the potential energy surface reproduced experimental trends, and indicate that vibrational excitations of CO2 significantly promote the dissociation. Using the sudden vector projection model, the behavior of the reactivity is rationalized by couplings with the reaction coordinate at each transition state. These results offer plausible rationalization for the observed enhancement of CO2 dissociation in non-thermal plasmas by metal surfaces. PMID:26957149

  9. Process for producing high purity isoolefins and dimers thereof by dissociation of ethers

    DOEpatents

    Smith, Jr., Lawrence A.; Jones, Jr., Edward M.; Hearn, Dennis

    1984-01-01

    Alkyl tertiary butyl ether or alkyl tertiary amyl ether is dissociated by vapor phase contact with a cation acidic exchange resin at temperatures in the range of 150.degree. to 250.degree. F. at LHSV of 0.1 to 20 to produce a stream consisting of unreacted ether, isobutene or isoamylene and an alcohol corresponding to the alkyl radical. After the alcohol is removed, the ether/isoolefin stream may be fractionated to obtain a high purity isoolefin (99+%) or the ether/isoolefin stream can be contacted in liquid phase with a cation acidic exchange resin to selectively dimerize the isoolefin in a highly exothermic reaction, followed by fractionation of the dimerization product to produce high purity diisoolefin (97+%). In the case where the alkyl is C.sub.3 to C.sub.6 and the corresponding alcohol is produced on dissociation of the ether, combined dissociation-distillation may be carried out such that isoolefin is the overhead product and alcohol the bottom.

  10. Process for producing high purity isoolefins and dimers thereof by dissociation of ethers

    DOEpatents

    Smith, L.A. Jr.; Jones, E.M. Jr.; Hearn, D.

    1984-05-08

    Alkyl tertiary butyl ether or alkyl tertiary amyl ether is dissociated by vapor phase contact with a cation acidic exchange resin at temperatures in the range of 150 to 250 F at LHSV of 0.1 to 20 to produce a stream consisting of unreacted ether, isobutene or isoamylene and an alcohol corresponding to the alkyl radical. After the alcohol is removed, the ether/isoolefin stream may be fractionated to obtain a high purity isoolefin (99+%) or the ether/isoolefin stream can be contacted in liquid phase with a cation acidic exchange resin to selectively dimerize the isoolefin in a highly exothermic reaction, followed by fractionation of the dimerization product to produce high purity diisoolefin (97+%). In the case where the alkyl is C[sub 3] to C[sub 6] and the corresponding alcohol is produced on dissociation of the ether, combined dissociation-distillation may be carried out such that isoolefin is the overhead product and alcohol the bottom. 2 figs.

  11. Novel 2-alkyl-1-ethylpyridinium ionic liquids: synthesis, dissociation energies and volatility.

    PubMed

    Vilas, Miguel; Rocha, Marisa A A; Fernandes, Ana M; Tojo, Emilia; Santos, Luís M N B F

    2015-01-28

    This work presents the synthesis, volatility study and electrospray ionization mass spectrometry with energy-variable collision induced dissociation of the isolated [(cation)2(anion)](+) of a novel series of 2-alkyl-1-ethyl pyridinium based ionic liquids, [(2)CN-2(1)C2Py][NTf2]. Compared to the imidazolium based ionic liquids, the new ionic liquid series presents a higher thermal stability and lower volatility. The [(cation)2(anion)](+) collision induced dissociation energies of both [(2)CN-2(1)C2Py][NTf2] and [CNPy][NTf2] pyridinium series show an identical trend with a pronounced decrease of the relative cation-anion interaction energy towards an almost constant value for N = 6. It was found that the lower volatility of [(2)CN-2(1)C2Py][NTf2] with a shorter alkyl chain length is due to its higher enthalpy of vaporization. Starting from [(2)C3(1)C2Py][NTf2], the lower volatility is governed by the combination of slightly lower entropies and higher enthalpies of vaporization, an indication of a higher structural disorder of the pyridinium based ionic liquids than the imidazolium based ionic liquids. Dissociation energies and volatility trends support the cohesive energy interpretation model based on the overlapping of the electrostatic and van der Waals functional interaction potentials. PMID:25493639

  12. Photoinduced molecular dissociation and photoinduced recombination mediated by superfluid helium nanodroplets.

    PubMed

    Kautsch, Andreas; Koch, Markus; Ernst, Wolfgang E

    2015-05-14

    We have investigated photoinduced chemical reaction dynamics of cold, isolated Cr2 molecules in helium nanodroplets (HeN), exploiting the quantum state specific spatial separation of solvated and surface locations on the droplet. The molecules are excited to achieve dissociation to a ground state (a(7)S3) and a metastable state (a(5)S2) atom. State specific spatial separation, in combination with efficient translational cooling to avoid ejection, causes the ground state atom to be solvated inside the droplet while the metastable atom migrates to the surface. A barrier between the two reactants formed by the HeN prevents recombination. We apply a resonance-enhanced multiphoton ionization scheme including the y(5)P°(1,2,3) <-- a(5)S(2) transition of the surface atom as well as a two-laser scheme including the y(7)P°(2,3,4) <-- a(7)S(3) transition of the solvated atom in order to verify the locations and separation of the dissociation products. Furthermore, ionization of the a(5)S2 surface atom triggers solvation followed by geminate recombination with the a(7)S3 atom, which is verified by the detection of Cr2(+) molecular ions. For small Cr clusters, our results indicate that they may be composed of chromium dimers that exhibit the same dissociation behavior. PMID:25894482

  13. Electron shuttling in electron transfer dissociation

    NASA Astrophysics Data System (ADS)

    Neff, Diane; Smuczynska, Sylwia; Simons, Jack

    2009-06-01

    Ab initio electronic structure calculations have been performed on two model systems containing a disulfide linkage and one or two positively charged sites, aimed at gaining further insight into how and where electrons attach to positively charged peptides under electron capture (ECD) and electron transfer dissociation (ETD) mass spectroscopy conditions. Couplings among electronic states involving (i) an entrance-channel with the excess electron residing on a donor anion interacting with the positively charged peptide, (ii) a state in which the electron has been transferred to the SS [sigma]* orbital to cause bond cleavage, and (iii) a manifold of states in which the electron has been transferred to a ground- or excited-Rydberg orbital on a positive site. The results of this study suggest that specific excited Rydberg states play a key role in effecting electron shuttling to the SS [sigma]* orbital. The excited-Rydberg orbitals close in energy to the SS [sigma]* orbital and with sufficient radial extent to span the distance between the positive site and the SS [sigma]* orbital play the key role. Then, when the anion donor, excited-Rydberg, and SS [sigma]* orbitals achieve spatial proximity and similarity in energies, one can have what is termed here a shuttle of an electron from the donor to the SS [sigma]* orbital, which results in SS bond cleavage. For the singly and doubly charged systems studied here, it was the 3p and 3d Rydberg orbitals, respectively, that met these criteria of spatial and energetic proximity. For other peptides having different charge states, it will be other Rydberg orbitals that meet these criteria because the relative energies of the SS [sigma]* and Rydberg orbitals are governed by the (different) Coulomb stabilizations these orbitals experience. However, the evidence suggests that it is not very high-energy Rydberg states but states with 3 < n < 10 that are involved in the rate limiting steps in ECD, ETD, and ECID experiments.

  14. [Persistent Perpetrator Contact in a Patient with Dissociative Identity Disorder].

    PubMed

    Tschöke, Stefan; Eisele, Frank; Steinert, Tilman

    2016-05-01

    The case of a young woman with still ongoing incest and forced prostitution is presented. The criteria for a dissociative identity disorder (DID) were met. Due to persistent contact to the perpetrator she was repeatedly revictimized. Based on the model of trauma-related dissociation we discuss to what extent she was capable of self-determined decision making as well as therapeutic consequences resulting therefrom. PMID:26556682

  15. The effect of elevated methane pressure on methane hydrate dissociation

    USGS Publications Warehouse

    Circone, S.; Stern, L.A.; Kirby, S.H.

    2004-01-01

    Methane hydrate, equilibrated at P, T conditions within the hydrate stability field, was rapidly depressurized to 1.0 or 2.0 MPa and maintained at isobaric conditions outside its stability field, while the extent and rate of hydrate dissociation was measured at fixed, externally maintained temperatures between 250 and 288 K. The dissociation rate decreases with increasing pressure at a given temperature. Dissociation rates at 1.0 MPa parallel the complex, reproducible T-dependence previously observed between 250 and 272 K at 0.1 MPa. The lowest rates were observed near 268 K, such that >50% of the sample can persist for more than two weeks at 0.1 MPa to more than a month at 1 and 2 MPa. Varying the pressure stepwise in a single experiment increased or decreased the dissociation rate in proportion to the rates observed in the isobaric experiments, similar to the rate reversibility previously observed with stepwise changes in temperature at 0.1 MPa. At fixed P, T conditions, the rate of methane hydrate dissociation decreases monotonically with time, never achieving a steady rate. The relationship between time (t) and the extent of hydrate dissociation is empirically described by: Evolved gas (%) = A??tB where the pre-exponential term A ranges from 0 to 16% s-B and the exponent B is generally <1. Based on fits of the dissociation results to Equation 1 for the full range of temperatures (204 to 289 K) and pressures (0.1 to 2.0 MPa) investigated, the derived parameters can be used to predict the methane evolution curves for pure, porous methane hydrate to within ??5%. The effects of sample porosity and the presence of quartz sand and seawater on methane hydrate dissociation are also described using Equation 1.

  16. Energetics from Slow Infrared Multiphoton Dissociation of Biomolecules

    PubMed Central

    Jockusch, Rebecca A.; Paech, Kolja

    2005-01-01

    Photodissociation kinetics of the protonated pentapeptide leucine enkephalin measured using a cw CO2 laser and a Fourier-transform mass spectrometer are reported. A short induction period, corresponding to the time required to raise the internal energy of the ion population to a (dissociating) steady state, is observed. After this induction period, the dissociation data are accurately fit by first-order kinetics. A plot of the log of the unimolecular dissociation rate constant, kuni, as a function of the log of laser power is linear at low laser powers (<9 W, kuni <0.05 s−1), but tapers off at high laser power (9–33 W, kuni = 0.05–7 s−1). The entire measured dissociation curve can be accurately fit by an exponential function plus a constant. The experiment is simulated using a master equation formalism. In the model, the laser radiation is described as an energetically flat-topped distribution which is spatially uniform. This description is consistent with experimental results which indicate that ion motion within the cell averages out spatial inhomogeneities in the laser light. The model has several adjustable parameters. The effect of varying these parameters on the calculated kinetics and power dependence curves is discussed. A procedure for determining a limited range of threshold dissociation energy, Eo, which fits both the measured induction period and power dependence curves, is presented. Using this procedure, Eo of leucine enkephalin is determined to be 1.12–1.46 eV. This result is consistent with, although less precise than, values measured previously using blackbody infrared radiative dissociation. Although the blackbody dissociation results were used as a starting point to search for fits of the master equation model to experiment, these results demonstrate that it is, in principle, possible to determine a limited range of Eo from slow infrared multiphoton dissociation data alone. PMID:16467893

  17. 4-HNE Adduct Stability Characterized by Collision-Induced Dissociation and Electron Transfer Dissociation Mass Spectrometry

    PubMed Central

    Fritz, Kristofer S.; Kellersberger, Katherine A.; Gomez, Jose D.; Petersen, Dennis R.

    2012-01-01

    4-hydroxynonenal (4-HNE) alters numerous proteomic and genomic processes. Understanding chemical mechanisms of 4-HNE interactions with biomolecules and their respective stabilities may lead to new discoveries in biomarkers for numerous diseases of oxidative stress. Collision-induced dissociation (CID) and electron transfer dissociation (ETD) MS/MS were utilized to examine the stability of a 4-HNE-Cys Michael adduct. CID conditions resulted in the neutral loss of 4-HNE, also known as a retro-Michael addition reaction (RMA). Consequently, performing ETD fragmentation on this same adduct did not result in RMA. Interestingly, 4-HNE adduct reduction via sodium borohydride (NaBH4) treatment stabilized against the CID induced RMA. In a direct comparison of three forms of 4-HNE adducts, computational modeling revealed sizeable shifts in the shape and orientation of the lowest unoccupied molecular orbital (LUMO) density around the 4-HNE-Cys moiety. These findings demonstrate that ETD MS/MS analysis can be used to improve the detection of 4-HNE-protein modifications by preventing RMA reactions from occurring. PMID:22404378

  18. Hole localization, water dissociation mechanisms, and band alignment at aqueous-titania interfaces

    NASA Astrophysics Data System (ADS)

    Lyons, John L.

    Photocatalytic water splitting is a promising method for generating clean energy, but materials that can efficiently act as photocatalysts are scarce. This is in part due to the fact that exposure to water can strongly alter semiconductor surfaces and therefore photocatalyst performance. Many materials are not stable in aqueous environments; in other cases, local changes in structure may occur, affecting energy-level alignment. Even in the simplest case, dynamic fluctuations modify the organization of interface water. Accounting for such effects requires knowledge of the dominant local structural motifs and also accurate semiconductor band-edge positions, making quantitative prediction of energy-level alignments computationally challenging. Here we employ a combined theoretical approach to study the structure, energy alignment, and hole localization at aqueous-titania interfaces. We calculate the explicit aqueous-semiconductor interface using ab initio molecular dynamics, which provides the fluctuating atomic structure, the extent of water dissociation, and the resulting electrostatic potential. For both anatase and rutile TiO2 we observe spontaneous water dissociation and re-association events that occur via distinct mechanisms. We also find a higher-density water layer occurring on anatase. In both cases, we find that the second monolayer of water plays a crucial role in controlling the extent of water dissociation. Using hybrid functional calculations, we then investigate the propensity for dissociated waters to stabilize photo-excited carriers, and compare the results of rutile and anatase aqueous interfaces. Finally, we use the GW approach from many-body perturbation theory to obtain the position of semiconductor band edges relative to the occupied 1b1 level and thus the redox levels of water, and examine how local structural modifications affect these offsets. This work was performed in collaboration with N. Kharche, M. Z. Ertem, J. T. Muckerman, and M. S

  19. CO chemisorption and dissociation at high coverages during CO hydrogenation on Ru catalysts.

    PubMed

    Loveless, Brett T; Buda, Corneliu; Neurock, Matthew; Iglesia, Enrique

    2013-04-24

    Density functional theory (DFT) and infrared spectroscopy results are combined with mechanism-based rate equations to assess the structure and thermodynamics of chemisorbed CO (CO*) and its activation during Fischer-Tropsch synthesis (FTS). CO* binding becomes weaker with increasing coverage on Ru(0001) and Ru201 clusters, but such decreases in binding energy occur at higher coverages on Ru201 clusters than on Ru(0001) surfaces (CO*/Ru = 1.55 to 0.75); such differences appear to reflect weaker repulsive interactions on the curved surfaces prevalent on small Ru201 clusters. Ru201 clusters achieve stable supramonolayer coverages (CO*/Ru > 1) by forming geminal dicarbonyls at low-coordination corner/edge atoms. CO* infrared spectra on Ru/SiO2 (~7 nm diameter) detect mobile adlayers that anneal into denser structures at saturation. Mechanism-based FTS rate equations give activation energies that reflect the CO*-saturated surfaces prevalent during catalysis. DFT-derived barriers show that CO* predominantly reacts at (111) terraces via H-assisted reactions, consistent with measured effects of H2 and CO pressures and cluster size effects on rates and O-rejection selectivities. Barriers are much higher for unassisted CO* dissociation on (111) terraces and low-coordination atoms, including step-edge sites previously proposed as active sites for CO* dissociation during FTS. DFT-derived barriers indicate that unassisted CO* dissociation is irreversible, making such steps inconsistent with measured rates. The modest activation barriers of H-assisted CO* dissociation paths remove a requirement for special low-coordination sites for unassisted CO* activation, which is inconsistent with higher rates on larger clusters. These conclusions seem generally applicable to Co, Fe, and Ru catalysts, which show similar FTS rate equations and cluster size effects. This study also demonstrates the feasibility and relevance of DFT treatments on the curved and crowded cluster surfaces where

  20. Thermochemistry and Kinetic Analysis of the Unimolecular Oxiranyl Radical Dissociation Reaction: A Theoretical Study.

    PubMed

    Wang, Heng; Bozzelli, Joseph W

    2016-07-01

    Oxirane structures are important in organic synthesis, and they are important initial products in the oxidation reactions of alkyl radicals. The thermochemical properties (enthalpy of formation, entropy, and heat capacity) for the reaction steps of the unimolecular oxiranyl radical dissociation reaction are determined and compared with the available literature. The overall ring opening and subsequent steps involve four types of reactions: β-scission ring opening, intramolecular hydrogen transfer, β-scission hydrogen elimination, and β-scission methyl radical elimination. The enthalpies of formation of the transition states are determined and evaluated using six popular Density Functional Theory (DFT) calculation methods (B3LYP, B2PLYP, M06, M06-2X, ωB97X, ωB97XD), each combined with three different basis sets. The DFT enthalpy values are compared with five composite calculation methods (G3, G4, CBS-QB3, CBS-APNO, W1U), and by CCSD(T)/aug-cc-pVTZ. Kinetic parameters are determined versus pressure and temperature for the unimolecular dissociation pathways of an oxiranyl radical, which include the chemical activation reactions of the ring-opened oxiranyl radical relative to the ring-opening barrier. Multifrequency quantum Rice Ramsperger Kassel (QRRK) analysis is used to determine k(E) with master equation analysis for falloff. The major overall reaction pathway at lower combustion temperatures is oxiranyl radical dissociation to a methyl radical and carbon monoxide. Oxiranyl radical dissociation to a ketene and hydrogen atom is the key reaction path above 700 K. PMID:26990491

  1. Photodissociation resonances of jet-cooled NO2 at the dissociation threshold by CW-CRDS.

    PubMed

    Dupré, Patrick

    2015-05-01

    Around 398 nm, the jet-cooled-spectrum of NO2 exhibits a well identified dissociation threshold (D0). Combining the continuous-wave absorption-based cavity ringdown spectroscopy technique and laser induced fluorescence detection, an energy range of ∼25 cm(-1) is analyzed at high resolution around D0. In addition to the usual molecular transitions to long-lived energy levels, ∼115 wider resonances are observed. The position, amplitude, and width of these resonances are determined. The resonance width spreads from ∼0.006 cm(-1) (i.e., ∼450 ps) to ∼0.7 cm(-1) (∼4 ps) with large fluctuations. The identification of at least two ranges of resonance width versus the excess energy can be associated with the opening of the dissociation channels NO2→NO(X(2)Π1/2, v=0, J=1/2+O((3)P2) and NO2→NO(X(2)Π1/2, v=0, J=3/2)+O((3)P2). This analysis corroborates the existence of loose transition states close to the dissociation threshold as reported previously and in agreement with the phase space theory predictions as shown by Tsuchiya's group [Miyawaki et al., J. Chem. Phys. 99, 254-264 (1993)]. The data are analyzed in the light of previously reported frequency- and time-resolved data to provide a robust determination of averaged unimolecular dissociation rate coefficients. The density of reactant levels deduced (ρreac ∼ 11levels/cm(-1)) is discussed versus the density of transitions, the density of resonances, and the density of vibronic levels. PMID:25956098

  2. Risk Recognition, Attachment Anxiety, Self-Efficacy, and State Dissociation Predict Revictimization

    PubMed Central

    Bockers, Estelle; Roepke, Stefan; Michael, Lars; Renneberg, Babette; Knaevelsrud, Christine

    2014-01-01

    Background Previous research has identified a number of variables that constitute potential risk factors for victimization and revictimization. However, it remains unclear which factors are associated not only with childhood or adolescent victimization, but specifically with revictimization. The aim of this study was to determine whether risk recognition ability and other variables previously associated with revictimization are specifically able to differentiate individuals with childhood victimization only from revictimized individuals, and thus to predict revictimization. Methods Participants were N = 85 women aged 21 to 64 years who were interpersonally victimized in childhood or adolescence only, interpersonally revictimized in another period of life, or not victimized. A logistic regression analysis was conducted to examine whether risk recognition ability, sensation seeking, self-efficacy, state dissociation, shame, guilt, assertiveness, and attachment anxiety predicted group membership. Results The logistic regression analysis revealed risk recognition ability, attachment anxiety, state dissociation, and self-efficacy as significant predictors of revictimization. The final model accurately classified 82.4% of revictimized, 59.1% of victimized and 93.1% of non-victimized women. The overall classification rate was 80%. Conclusions This study suggests that risk recognition ability, attachment anxiety, self-efficacy, and state dissociation play a key role in revictimization. Increased risk recognition ability after an interpersonal trauma may act as a protective factor against repeated victimization that revictimized individuals may lack. A lack of increased risk recognition ability in combination with higher attachment anxiety, lower self-efficacy, and higher state dissociation may increase the risk of revictimization. PMID:25238153

  3. Insights on finite size effects in ab initio study of CO adsorption and dissociation on Fe 110 surface

    NASA Astrophysics Data System (ADS)

    Chakrabarty, Aurab; Bouhali, Othmane; Mousseau, Normand; Becquart, Charlotte S.; El-Mellouhi, Fedwa

    2016-08-01

    Adsorption and dissociation of hydrocarbons on metallic surfaces represent crucial steps on the path to carburization, eventually leading to dusting corrosion. While adsorption of CO molecules on Fe surface is a barrier-less exothermic process, this is not the case for the dissociation of CO into C and O adatoms and the diffusion of C beneath the surface that are found to be associated with large energy barriers. In practice, these barriers can be affected by numerous factors that combine to favour the CO-Fe reaction such as the abundance of CO and other hydrocarbons as well as the presence of structural defects. From a numerical point of view, studying these factors is challenging and a step-by-step approach is necessary to assess, in particular, the influence of the finite box size on the reaction parameters for adsorption and dissociation of CO on metal surfaces. Here, we use density functional theory (DFT) total energy calculations with the climbing-image nudged elastic band method to estimate the adsorption energies and dissociation barriers for different CO coverages with surface supercells of different sizes. We further compute the effect of periodic boundary condition for DFT calculations and find that the contribution from van der Waals interaction in the computation of adsorption parameters is important as they contribute to correcting the finite-size error in small systems. The dissociation process involves carbon insertion into the Fe surface causing a lattice deformation that requires a larger surface system for unrestricted relaxation. We show that, in the larger surface systems associated with dilute CO-coverages, C-insertion is energetically more favourable, leading to a significant decrease in the dissociation barrier. This observation suggests that a large surface system with dilute coverage is necessary for all similar metal-hydrocarbon reactions in order to study their fundamental electronic mechanisms, as an isolated phenomenon, free from

  4. Light-induced dissociation of antenna complexes in the symbionts of scleractinian corals correlates with sensitivity to coral bleaching

    NASA Astrophysics Data System (ADS)

    Hill, R.; Larkum, A. W. D.; Prášil, O.; Kramer, D. M.; Szabó, M.; Kumar, V.; Ralph, P. J.

    2012-12-01

    Elevated temperatures in combination with moderate to high irradiance are known to cause bleaching events in scleractinian corals, characterised by damage to photosystem II (PSII). Photoprotective mechanisms of the symbiont can reduce the excitation pressure impinging upon PSII. In the bleaching sensitive species, Acropora millepora and Pocillopora damicornis, high light alone induced photoprotection through the xanthophyll cycle, increased content of the antioxidant carotenoid, β-carotene, as well as the dissociation of the light-harvesting chlorophyll complexes. The evidence is compatible with either the membrane-bound chlorophyll a-chlorophyll c 2-peridinin-protein (acpPC) complex or the peripheral peridinin-chlorophyll-protein complex, or both, disconnecting from PSII under high light. The acpPC complex potentially showed a state transition response with redistribution towards photosystem I to reduce PSII over-excitation. This apparent acpPC dissociation/reassociation was promoted by the addition of the xanthophyll cycle inhibitor, dithiothreitol, under high irradiance. Exposure to thermal stress as well as high light promoted xanthophyll de-epoxidation and increased β-carotene content, although it did not influence light-harvesting chlorophyll complex (LHC) dissociation, indicating light, rather than temperature, controls LHC dissociation. Photoinhibition was avoided in the bleaching tolerant species, Pavona decussata, suggesting xanthophyll cycling along with LHC dissociation may have been sufficient to prevent photodamage to PSII. Symbionts of P. decussata also displayed the greatest detachment of antenna complexes, while the more thermally sensitive species, Pocillopora damicornis and A. millepora, showed less LHC dissociation, suggesting antenna movement influences bleaching susceptibility.

  5. [Dissociative disorders: from Janet to DSM-IV].

    PubMed

    Nakatani, Y

    2000-01-01

    I reviewed the literature on dissociation and dissociative disorders from Pierre Janet to DSM-IV, and examined the current trends in research. Janet's theory on hysteria is multifaceted, and is based on three psychological models. Based on a hierarchical model, Janet related hysteric symptoms to the activities within the lower strata of mental hierarchy (automatisms psychologiques), which were demonstrably shown in somnambulism. A second model was based on the concept of a psychological system, which was hypothetically composed of ideas, images, feelings, sensations, and movements. According to this model, dissociation of psychological functions was fundamental to the mechanism of hysteria: loss of integration was thought to engender fixed ideas (ideas fixes) and to lead to the development of a system totally isolated from the whole personality system. Janet also attempted to explain various mental disorders using an economic model. He referred to a loss of equilibration between psychological force and psychological tension. Thus, an unexpected emotional experience was conceived to cause a consumption of reserved psychological force, which was in turn followed by exhaustion associated with hysteric symptoms. Whereas most current researchers regard Janet as the first to study psychological trauma as a principal cause of dissociation, I feel it is important to note that he also emphasized the role of stigmata, i.e., permanent traits of hysteric patients, which were represented as a suggestibility and a tendency toward a narrowing of the consciousness field. Discussion about dissociation and its relation to trauma all but disappeared after Janet. However, during the Second World War and post-war period, some psychiatrists began to pay attention to two emerging phenomena: a high incidence of dissociative symptoms such as fugue and amnesia among combatants, and traumatic neurosis frequently observed among ex-inmates of concentration camps. In the 1970s, interest in

  6. The many faces of dissociation: opportunities for innovative research in psychiatry.

    PubMed

    Şar, Vedat

    2014-12-01

    It has been claimed that the progress of psychiatry has lagged behind that of other medical disciplines over the last few decades. This may suggest the need for innovative thinking and research in psychiatry, which should consider neglected areas as topics of interest in light of the potential progress which might be made in this regard. This review is concerned with one such field of psychiatry: dissociation and dissociative disorders. Dissociation is the ultimate form of human response to chronic developmental stress, because patients with dissociative disorders report the highest frequency of childhood abuse and/or neglect among all psychiatric disorders. The cardinal feature of dissociation is a disruption in one or more mental functions. Dissociative amnesia, depersonalization, derealization, identity confusion, and identity alterations are core phenomena of dissociative psychopathology which constitute a single dimension characterized by a spectrum of severity. While dissociative identity disorder (DID) is the most pervasive condition of all dissociative disorders, partial representations of this spectrum may be diagnosed as dissociative amnesia (with or without fugue), depersonalization disorder, and other specified dissociative disorders such as subthreshold DID, dissociative trance disorder, acute dissociative disorders, and identity disturbances due to exposure to oppression. In addition to constituting disorders in their own right, dissociation may accompany almost every psychiatric disorder and operate as a confounding factor in general psychiatry, including neurobiological and psycho-pharmacological research. While an anti- dissociative drug does not yet exist, appropriate psychotherapy leads to considerable improvement for many patients with dissociative disorders. PMID:25598819

  7. The Many Faces of Dissociation: Opportunities for Innovative Research in Psychiatry

    PubMed Central

    2014-01-01

    It has been claimed that the progress of psychiatry has lagged behind that of other medical disciplines over the last few decades. This may suggest the need for innovative thinking and research in psychiatry, which should consider neglected areas as topics of interest in light of the potential progress which might be made in this regard. This review is concerned with one such field of psychiatry: dissociation and dissociative disorders. Dissociation is the ultimate form of human response to chronic developmental stress, because patients with dissociative disorders report the highest frequency of childhood abuse and/or neglect among all psychiatric disorders. The cardinal feature of dissociation is a disruption in one or more mental functions. Dissociative amnesia, depersonalization, derealization, identity confusion, and identity alterations are core phenomena of dissociative psychopathology which constitute a single dimension characterized by a spectrum of severity. While dissociative identity disorder (DID) is the most pervasive condition of all dissociative disorders, partial representations of this spectrum may be diagnosed as dissociative amnesia (with or without fugue), depersonalization disorder, and other specified dissociative disorders such as subthreshold DID, dissociative trance disorder, acute dissociative disorders, and identity disturbances due to exposure to oppression. In addition to constituting disorders in their own right, dissociation may accompany almost every psychiatric disorder and operate as a confounding factor in general psychiatry, including neurobiological and psycho-pharmacological research. While an anti- dissociative drug does not yet exist, appropriate psychotherapy leads to considerable improvement for many patients with dissociative disorders. PMID:25598819

  8. A structural view of the dissociation of Escherichia coli tryptophanase.

    PubMed

    Green, Keren; Qasim, Nasrin; Gdaelvsky, Garik; Kogan, Anna; Goldgur, Yehuda; Parola, Abraham H; Lotan, Ofra; Almog, Orna

    2015-12-01

    Tryptophanase (Trpase) is a pyridoxal 5'-phosphate (PLP)-dependent homotetrameric enzyme which catalyzes the degradation of L-tryptophan. Trpase is also known for its cold lability, which is a reversible loss of activity at low temperature (2°C) that is associated with the dissociation of the tetramer. Escherichia coli Trpase dissociates into dimers, while Proteus vulgaris Trpase dissociates into monomers. As such, this enzyme is an appropriate model to study the protein-protein interactions and quaternary structure of proteins. The aim of the present study was to understand the differences in the mode of dissociation between the E. coli and P. vulgaris Trpases. In particular, the effect of mutations along the molecular axes of homotetrameric Trpase on its dissociation was studied. To answer this question, two groups of mutants of the E. coli enzyme were created to resemble the amino-acid sequence of P. vulgaris Trpase. In one group, residues 15 and 59 that are located along the molecular axis R (also termed the noncatalytic axis) were mutated. The second group included a mutation at position 298, located along the molecular axis Q (also termed the catalytic axis). Replacing amino-acid residues along the R axis resulted in dissociation of the tetramers into monomers, similar to the P. vulgaris Trpase, while replacing amino-acid residues along the Q axis resulted in dissociation into dimers only. The crystal structure of the V59M mutant of E. coli Trpase was also determined in its apo form and was found to be similar to that of the wild type. This study suggests that in E. coli Trpase hydrophobic interactions along the R axis hold the two monomers together more strongly, preventing the dissociation of the dimers into monomers. Mutation of position 298 along the Q axis to a charged residue resulted in tetramers that are less susceptible to dissociation. Thus, the results indicate that dissociation of E. coli Trpase into dimers occurs along the molecular Q axis. PMID

  9. Charge Transfer and Dissociation in Collisions of Metal Clusters with Atoms

    NASA Astrophysics Data System (ADS)

    Bréchignac, C.; Cahuzac, Ph.; Concina, B.; Leygnier, J.; Ruiz, L. F.; Zarour, B.; Hervieux, P. A.; Hanssen, J.; Politis, M. F.; Martín, F.

    2002-10-01

    We present a combined theoretical and experimental study of charge transfer and dissociation in collisions of slow Li2+31 clusters with Cs atoms. We provide a direct quantitative comparison between theory and experiment and show that good agreement is found only when the exact experimental time of flight and initial cluster temperature are taken into account in the theoretical modeling. We demonstrate the validity of the simple physical image that consists in explaining evaporation as resulting from a collisional energy deposit due to cluster electronic excitation during charge transfer.

  10. Selective dissociation of the stronger bond in HCN using an optical centrifuge

    NASA Astrophysics Data System (ADS)

    Hasbani, R.; Ostojic, B.; Bunker, P. R.; Ivanov, M. Yu.

    2002-06-01

    Using the example of the HCN molecule, we study theoretically the possibility of selectively breaking the stronger bond in a triatomic molecule by rotationally accelerating it in an optical centrifuge using a combination of two oppositely chirped and counter-rotating strong laser fields. In our simulation the resultant field forces rotational acceleration of the HCN molecule to a point where the centrifugal force between the two heavy atoms (C and N) exceeds the strength of their (triple) bond. The effects of bending, rovibrational coupling, and the Coriolis force, which conspire to prevent the molecule from rotational dissociation into HC+N, can be efficiently counteracted by simple optimization of the frequency chirp.

  11. Multiple nucleon knockout by Coulomb dissociation in relativistic heavy-ion collisions

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Norbury, John W.; Townsend, Lawrence W.

    1988-01-01

    The Coulomb dissociation contributions to fragmentation cross sections in relativistic heavy ion collisions, where more than one nucleon is removed, are estimated using the Weizsacker-Williams method of virtual quanta. Photonuclear cross sections taken from experimental results were used to fold into target photon number spectra calculated with the Weizsacker-Williams method. Calculations for several projectile target combinations over a wide range of charge numbers, and a wide range of incident projectile energies, are reported. These results suggest that multiple nucleon knockout by the Coulomb field may be of negligible importance in galactic heavy ion studies for projectiles lighter than Fe-56.

  12. Photodissociation dynamics of nitromethane and methyl nitrite by infrared multiphoton dissociation imaging with quasiclassical trajectory calculations: Signatures of the roaming pathway

    NASA Astrophysics Data System (ADS)

    Dey, Arghya; Fernando, Ravin; Abeysekera, Chamara; Homayoon, Zahra; Bowman, Joel M.; Suits, Arthur G.

    2014-02-01

    We combine the techniques of infrared multiphoton dissociation (IRMPD) with state selective ion imaging to probe roaming dynamics in the unimolecular dissociation of nitromethane and methyl nitrite. Recent theoretical calculations suggest a "roaming-mediated isomerization" pathway of nitromethane to methyl nitrite prior to decomposition. State-resolved imaging of the NO product coupled with infrared multiphoton dissociation was carried out to examine this unimolecular decomposition near threshold. The IRMPD images for the NO product from nitromethane are consistent with the earlier IRMPD studies that first suggested the importance of an isomerization pathway. A significant Λ-doublet propensity is seen in nitromethane IRMPD but not methyl nitrite. The experimental observations are augmented by quasiclassical trajectory calculations for nitromethane and methyl nitrite near threshold for each dissociation pathway. The observation of distinct methoxy vibrational excitation for trajectories from nitromethane and methyl nitrite dissociation at the same total energy show that the nitromethane dissociation bears a nonstatistical signature of the roaming isomerization pathway, and this is possibly responsible for the nitromethane Λ-doublet propensity as well.

  13. An outpatient clinical study of dissociative disorder not otherwise specified.

    PubMed

    Yanartaş, Ömer; Özmen, Hülya Akar; Citak, Serhat; Zincir, Selma Bozkurt; Sünbül, Esra Aydin

    2014-05-01

    The relatively high prevalence of the diagnosis of dissociative disorder not otherwise specified is frequently considered to be disproportionate. The disproportionate rate of this diagnosis is thought to be related to nosologic and/or diagnostic issues in dissociative identity disorder. We sought to investigate and compare the symptom patterns of these two clinical entities. We conducted a cross-sectional study involving 1314 participants who were screened with the Dissociative Experience Scale (DES) and the Somatoform Dissociation Questionnaire (SDQ). Of the participants, 272 who scored above the cut-off points for the screening questionnaires (DES score>30 and/or SDQ score>40 points) were invited to complete a structured interview using the Dissociative Disorders Interview Schedule (DDIS); of this subsample, only 190 participants agreed to participate in the second phase of the study. The mean score for the DES was 18.55±17.23, and the mean score for the SDQ was 30.19±13.32. Of the 190 participants, 167 patients were diagnosed as having a dissociative disorder (87.8%). We found that DD-NOS was the most prevalent category of dissociative disorder. There was a significantly larger percentage of patients in the DID group than in the DD-NOS group according to secondary features of DID and Schneiderian symptoms. The secondary features of DID and Schneiderian symptoms appeared to be more specific for DID, while no differences were detected between DID and DD-NOS based on most of the items on the SCL 90R. Further longitudinal studies are needed to determine the features that are similar and dissimilar between DD-NOS and DID. PMID:24461163

  14. Ion Mobility Spectrometry Reveals Duplex DNA Dissociation Intermediates

    NASA Astrophysics Data System (ADS)

    Burmistrova, Anastasia; Gabelica, Valérie; Duwez, Anne-Sophie; De Pauw, Edwin

    2013-11-01

    Electrospray ionization (ESI) soft desolvation is widely used to investigate fragile species such as nucleic acids. Tandem mass spectrometry (MS/MS) gives access to the gas phase energetics of the intermolecular interactions in the absence of solvent, by following the dissociation of mass-selected ions. Ion mobility mass spectrometry (IMS) provides indications on the tridimensional oligonucleotide structure by attributing a collision cross section (CCS) to the studied ion. Electrosprayed duplexes longer than eight bases pairs retain their helical structure in a solvent-free environment. However, the question of conformational changes under activation in MS/MS studies remains open. The objective of this study is to probe binding energetics and characterize the unfolding steps occurring prior to oligonucleotide duplex dissociation. Comparing the evolution of CCS with collision energy and breakdown curves, we characterize dissociation pathways involved in CID-activated DNA duplex separation into single strands, and we demonstrate here the existence of stable dissociation intermediates. At fixed duplex length, dissociation pathways were found to depend on the percentage of GC base pairs and on their position in the duplex. Our results show that pure GC sequences undergo a gradual compaction until reaching the dissociation intermediate: A-helix. Mixed AT-GC sequences were found to present at least two conformers: a classic B-helix and an extended structure where the GC tract is a B-helix and the AT tract(s) fray. The dissociation in single strands takes place from both conformers when the AT base pairs are enclosed between two GC tracts or only from the extended conformer when the AT tract is situated at the end(s) of the sequence.

  15. Electron-impact dissociation and ionization of NO+ ions

    NASA Astrophysics Data System (ADS)

    Belic, D. S.; Urbain, X.; Cherkani-Hassani, H.; Defrance, P.

    2016-07-01

    Absolute cross sections for electron-impact ionization and dissociation of NO+ ions are reported. Simple ionization to NO2+ ion and production of singly charged N+ and O+ and doubly charged N2+ and O2+ fragments have been investigated. The animated electron-ion crossed-beam method is applied in the energy range from the respective thresholds up to 2.5 keV. The maximum of the simple ionization cross section is found to be (3.49 ± 0.07) × 10‑17 cm2 at 135 eV. The total cross sections for N+ and O+ fragments at the maximum are found to be (13.9 ± 1.0) × 10‑17 cm2 and (14.0 ± 1.4) × 10‑17 cm2, respectively, both at an energy of 85 eV. By performing careful magnetic field scans of the detected signal, contributions of dissociative excitation and dissociative ionization to N+ and O+ production are determined separately. The cross sections for asymmetric dissociative ionization to N2+ and O2+ are found to be over one order of magnitude smaller. Distributions of the kinetic energy release to the fragments are determined for all dissociation processes.

  16. Dissociative experiences as mediators between childhood trauma and auditory hallucinations.

    PubMed

    Perona-Garcelán, Salvador; Carrascoso-López, Francisco; García-Montes, José M; Ductor-Recuerda, María Jesús; López Jiménez, Ana Ma; Vallina-Fernández, Oscar; Pérez-Álvarez, Marino; Gómez-Gómez, María Teresa

    2012-06-01

    The purpose of this work was to study the relationship between reported traumatic experiences in childhood and positive psychotic symptoms. We hypothesized that dissociative experiences were potential mediators between childhood trauma and hallucinations, but not delusions. The sample comprised 71 patients diagnosed with psychoses. They were assessed with the Dissociative Experiences Scale (DES-II; Carlson & Putnam, 1993), a questionnaire on trauma (TQ; Davidson, Hughes, & Blazer, 1990), and the Positive and Negative Syndrome Scale (PANSS; Kay, Opler, & Lindenmayer, 1988) delusions and hallucinations items. The results showed that childhood trauma was positively associated with the dissociation scale scores (r = .40) and also the hallucination (r = .36) and delusions scale scores (r = .32). Furthermore, it was demonstrated that the dissociation variable was a potential mediator between childhood trauma and hallucinations, but not between childhood trauma and delusions. Of the 3 DES-II factors, only depersonalization showed a mediating relationship between childhood trauma and hallucinations. The main conclusion is that the impact of childhood trauma on hallucinations may not simply be direct, but mediated by dissociative experiences, especially depersonalization. Clinical implications are also briefly discussed. PMID:22589015

  17. Enhancement of burning velocity by dissociated oxygen atoms

    NASA Astrophysics Data System (ADS)

    Akashi, Haruaki; Yoshinaga, Tomokazu; Sasaki, Koichi

    2015-09-01

    Green technology, such as preventing global warming, has been developed for years. Researches on plasma assisted combustion is one of the technologies and have been done for investigating more efficient combustion, more efficient use of fossil fuel with plasmas or applying electric fields. In the ignition time delay analyses with the dissociated oxygen atoms which is generated by non-equilibrium plasma had significant effect on the ignition time. In this paper, dissociated oxygen could effect on burning velocity or not has been examined using CHEMKIN. As a result, no effect can be seen with dissociation degree of lower than 10-3. But there is an effect on the enhancement of burning velocity with higher degree of 10-3. At the dissociation degree of 5×10-2, the burning velocity is enhanced at a factor of 1.24. And it is found that the distributions of each species in front of preheat zone are completely different. The combustion process is proceeded several steps in advance, and generation of H2O, CO and CO2 can be seen before combustion in higher dissociation case. This work was supported by KAKENHI (22340170).

  18. Dynamics of exciton dissociation in donor-acceptor polymer heterojunctions.

    PubMed

    Sun, Zhen; Stafström, Sven

    2013-04-28

    Exciton dissociation in a donor-accepter polymer heterojunction has been simulated using a nonadiabatic molecular dynamics approach, which allows for the coupled evolution of the nuclear degrees of freedom and the electronic degrees of freedom described by multiconfigurational electronic wavefunctions. The simulations reveal important details of the charge separation process: the exciton in the donor polymer first dissociates into a "hot" charge transfer state, which is best described as a polaron pair. The polaron pair can be separated into free polaron charge carriers if a sufficiently strong external electric field is applied. We have also studied the effects of inter-chain interaction, temperature, and the external electric field strength. Increasing inter-chain interactions makes it easier for the exciton to dissociate into a polaron pair state, but more difficult for the polaron pair to dissociate into free charge carriers. Higher temperature and higher electric field strength both favor exciton dissociation as well as the formation of free charge carriers. PMID:23635169

  19. Energy and Entropy Effects in Dissociation of Peptide Radical Anions

    SciTech Connect

    Laskin, Julia; Yang, Zhibo; Lam, Corey; Chu, Ivan K.

    2012-04-15

    Time- and collision energy-resolved surface-induced dissociation (SID) of peptide radical anions was studied for the first time using a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) configured for SID experiments. Peptide radical cations and anions were produced by gas-phase fragmentation of CoIII(salen)-peptide complexes. The effect of the charge, radical, and the presence of a basic residue on the energetics and dynamics of dissociation of peptide ions was examined using RVYIHPF (1) and HVYIHPF (2) as model systems. Comparison of the survival curves for of [M+H]{sup +}, [M-H]{sup -}, M{sup +{sm_bullet}}, and [M-2H]{sup -{sm_bullet}} ions of these precursors demonstrated that even-electron ions are more stable towards fragmentation than their odd-electron counterparts. RRKM modeling of the experimental data demonstrated that the lower stability of the positive radicals is mainly attributed to lower dissociation thresholds while entropy effects are responsible the relative instability of the negative radicals. Substitution of arginine with less basic histidine residue has a strong destabilizing effect on the [M+H]{sup +} ions and a measurable stabilizing effect on the odd-electron ions. Lower threshold energies for dissociation of both positive and negative radicals of 1 are attributed to the presence of lower-energy dissociation pathways that are most likely promoted by the presence of the basic residue.

  20. Deprotonated purine dissociation: experiments, computations, and astrobiological implications.

    PubMed

    Cole, Callie A; Wang, Zhe-Chen; Snow, Theodore P; Bierbaum, Veronica M

    2015-01-15

    A central focus of astrobiology is the determination of abiotic formation routes to important biomolecules. The dissociation mechanisms of these molecules lend valuable insights into their synthesis pathways. Because of the detection of organic anions in the interstellar medium (ISM), it is imperative to study their role in these syntheses. This work aims to experimentally and computationally examine deprotonated adenine and guanine dissociation in an effort to illuminate potential anionic precursors to purine formation. Collision-induced dissociation (CID) products and their branching fractions are experimentally measured using an ion trap mass spectrometer. Deprotonated guanine dissociates primarily by deammoniation (97%) with minor losses of carbodiimide (HNCNH) and/or cyanamide (NH2CN), and isocyanic acid (HNCO). Deprotonated adenine fragments by loss of hydrogen cyanide and/or isocyanide (HCN/HNC; 90%) and carbodiimide (HNCNH) and/or cyanamide (NH2CN; 10%). Tandem mass spectrometry (MS(n)) experiments reveal that deprotonated guanine fragments lose additional HCN and CO, while deprotonated adenine fragments successively lose HNC and HCN. Every neutral fragment observed in this study has been detected in the ISM, highlighting the potential for nucleobases such as these to form in such environments. Lastly, the acidity of abundant fragment ions is experimentally bracketed. Theoretical calculations at the B3LYP/6-311++G(d,p) level of theory are performed to delineate the mechanisms of dissociation and analyze the energies of reactants, intermediates, transition states, and products of these CID processes. PMID:25559322

  1. Foil dissociation of fast molecular ions into atomic excited states

    SciTech Connect

    Berry, H.G.; Gay, T.J.; Brooks, R.L.

    1980-01-01

    The intensity and polarizations of light emitted from atomic excited states of dissociated molecular ions were measured. The dissociations are induced when fast molecular ions (50 to 500 keV/amu) are transmitted through thin carbon foils. A calculation of multiple scattering and the Coulomb explosion gives the average internuclear separation of the projectile at the foil surface. Experimentally, the foil thickness is varied to give varying internuclear separations at the foil surface and observe the consequent variation in light yield and optical polarization. Using HeH/sup +/ projectiles, factors of 1 to 5 enhancements of the light yields from n = 3, /sup 1/ /sup 3/P,D states of He I and some He II and H I emissions were observed. The results can be explained in terms of molecular level crossings which provide mixings of the various final states during dissociation of the molecular ions at the exit surface. They suggest a short range surface interaction of the electron pick-up followed by a slow molecular dissociation. Alignment measurements confirm the essential features of the model. Observations of Lyman ..cap alpha.. emission after dissociation of H/sub 2//sup +/ amd H/sub 3//sup +/ show rapid variations in light yield for small internuclear separations at the foil surface.

  2. Does Electron Capture Dissociation Cleave Protein Disulfide Bonds?

    PubMed Central

    Ganisl, Barbara; Breuker, Kathrin

    2012-01-01

    Peptide and protein characterization by mass spectrometry (MS) relies on their dissociation in the gas phase into specific fragments whose mass values can be aligned as ‘mass ladders’ to provide sequence information and to localize possible posttranslational modifications. The most common dissociation method involves slow heating of even-electron (M+n H)n+ ions from electrospray ionization by energetic collisions with inert gas, and cleavage of amide backbone bonds. More recently, dissociation methods based on electron capture or transfer were found to provide far more extensive sequence coverage through unselective cleavage of backbone N–Cα bonds. As another important feature of electron capture dissociation (ECD) and electron transfer dissociation (ETD), their unique unimolecular radical ion chemistry generally preserves labile posttranslational modifications such as glycosylation and phosphorylation. Moreover, it was postulated that disulfide bond cleavage is preferred over backbone cleavage, and that capture of a single electron can break both a backbone and a disulfide bond, or even two disulfide bonds between two peptide chains. However, the proposal of preferential disulfide bond cleavage in ECD or ETD has recently been debated. The experimental data presented here reveal that the mechanism of protein disulfide bond cleavage is much more intricate than previously anticipated. PMID:24363980

  3. Double imaging photoelectron photoion coincidence sheds new light on the dissociation of energy-selected CH3Cl(+) ions.

    PubMed

    Tang, Xiaofeng; Lin, Xiaoxiao; Zhang, Weijun; Garcia, Gustavo A; Nahon, Laurent

    2016-09-14

    The vacuum ultraviolet (VUV) photoionization and dissociative photoionization of CH3Cl in the energy range of 11-17 eV have been investigated in detail by combining synchrotron radiation and double imaging photoelectron photoion coincidences (i(2)PEPICO). Three low-lying electronic states of the CH3Cl(+) molecular ion, X(2)E, A(2)A1 and B(2)E, were prepared and analyzed. The appearance energies of the energetically accessible fragment ions, CH2Cl(+), CHCl(+), CH3(+) and CH2(+), have been obtained from their respective mass-selected threshold photoelectron spectra (TPES) or photoionization efficiency (PIE) curves. The dissociation mechanisms of energy-selected CH3Cl(+) ions, prepared in the A(2)A1 and the B(2)E electronic states, as well as outside the Franck-Condon region, have been revealed to be state-specific via ion/electron kinetic energy correlation diagrams. In particular, the umbrella mode vibrational progression of the CH3(+) fragment ion in the direct dissociation of the A(2)A1 electronic state was identified and assigned indicating that this state correlates to the CH3(+)(1(1)A1') + Cl((2)P1/2) dissociation limit, in agreement with the theoretical calculations performed in this work. PMID:27524637

  4. Somatostatin binding to dissociated cells from rat cerebral cortex

    SciTech Connect

    Colas, B.; Prieto, J.C.; Arilla, E. )

    1990-11-01

    A method has been developed for the study of somatostatin (SS) binding to dissociated cells from rat cerebral cortex. Binding of {sup 125}I (Tyr11)SS to cells obtained by mechanical dissociation of rat cerebral cortex was dependent on time and temperature, saturable, reversible and highly specific. Under conditions of equilibrium, i.e., 60 min at 25 degrees C, native SS inhibited tracer binding in a dose-dependent manner. The Scatchard analysis of binding data was linear and yielded a dissociation constant of 0.60 +/- 0.08 nM with a maximal binding capacity of 160 +/- 16 fmol/mg protein. The binding of {sup 125}I (Tyr11)SS was specific as shown in experiments on tracer displacement by the native peptides, SS analogues, and unrelated peptides.

  5. Dissociative Identity Disorders in Korea: Two Recent Cases.

    PubMed

    Kim, Ilbin; Kim, Daeho; Jung, Hyun-Jin

    2016-03-01

    Although dissociative identity disorder (DID), the most severe of the dissociative disorders, has retained its own diagnostic entity since its introduction in the DSM-III, cases of DID are rarely seen in South and East Asia, likely due to the higher prevalence of possession disorder. We report two patients with DID who were recently admitted to our inpatient psychiatric unit and demonstrated distinct transitions to several identities. Their diagnoses were confirmed through a structured interview for dissociative disorders and possible differential diagnoses were ruled out by psychological, neuroimaging, and laboratory tests. The rapid transition to a Westernized, individualized society along with an increase in child abuse, might contribute to an increase in DID, previously under-diagnosed in this region. PMID:27081389

  6. Oxygen atom roaming and multiple dissociation pathways of NO3

    NASA Astrophysics Data System (ADS)

    Grubb, Michael; Warter, Michelle; Johnson, Kurt; North, Simon

    2011-03-01

    The role of nitrate radical (NO3) photolysis in atmospheric has long been known, but mysteries remain regarding the mechanism of the dissociation. In particular, the NO + O2 channel has proven to be a challenge both theoretically and experimentally. High resolution velocity map ion imaging studies reveal that there are two distinct mechanisms to form the NO + O2 products. Additionally, the dominant of these mechanisms appears to be the non-traditional state ``roaming'' mechanism recently identified in formaldehyde dissociation. The roaming mechanism involves large amplitude motion associated with a frustrated radical dissociation before roaming oxygen atom abstraction to form O2 . The identification of roaming in the NO3 reaction may imply the widespread importance of this type of mechanism in atmospheric chemistry.

  7. Reaction paths of phosphine dissociation on silicon (001)

    NASA Astrophysics Data System (ADS)

    Warschkow, O.; Curson, N. J.; Schofield, S. R.; Marks, N. A.; Wilson, H. F.; Radny, M. W.; Smith, P. V.; Reusch, T. C. G.; McKenzie, D. R.; Simmons, M. Y.

    2016-01-01

    Using density functional theory and guided by extensive scanning tunneling microscopy (STM) image data, we formulate a detailed mechanism for the dissociation of phosphine (PH3) molecules on the Si(001) surface at room temperature. We distinguish between a main sequence of dissociation that involves PH2+H, PH+2H, and P+3H as observable intermediates, and a secondary sequence that gives rise to PH+H, P+2H, and isolated phosphorus adatoms. The latter sequence arises because PH2 fragments are surprisingly mobile on Si(001) and can diffuse away from the third hydrogen atom that makes up the PH3 stoichiometry. Our calculated activation energies describe the competition between diffusion and dissociation pathways and hence provide a comprehensive model for the numerous adsorbate species observed in STM experiments.

  8. Hopping approach towards exciton dissociation in conjugated polymers

    SciTech Connect

    Emelianova, E. V.; Auweraer, M. van der; Baessler, H.

    2008-06-14

    By employing random walk an analytic theory for the dissociation of singlet excitons in a random organic solid, for instance, a conjugated polymer, has been developed. At variance of conventional three-dimensional Onsager theory, it is assumed that an exciton with finite lifetime can first transfer endothermically an electron to an adjacent site, thereby generating a charge transfer state whose energy is above the energy of that of the initial exciton. In a second step the latter can fully dissociate in accordance with Onsager's concept Brownian motion. The results indicate that, depending of the energy required for the first jump, the first jump contributes significantly to the field dependence of the dissociation yield. Disorder weakens the temperature dependence of the yield dramatically and precludes extracting information on the exciton binding energy from it.

  9. A patient with distinct dissociative and hallucinatory fugues

    PubMed Central

    Mortati, Katherine; Grant, Arthur C

    2012-01-01

    A 62-year-old man presented with a history suggesting both dissociative fugue and a distinct fugue-like hallucination. The dissociative fugues included unplanned travel, loss of personal identity, inability to recall his past and amnesia for the fugue interval. The subjective fugues consisted of a stereotyped hallucination wherein he would travel to a social gathering place, meet his ‘imaginary friends’ and engage with them in conversation. He experienced the subjective fugues as if they were real, recognised them as hallucinations when he was normally conscious, and remembered them in great detail. A hallucinatory fugue episode occurred during video-EEG monitoring. The patient engaged in semipurposeful behaviour for which he had no memory, and the EEG demonstrated waking rhythms. Epilepsy, sleep disorder, factitious disorder and malingering were excluded from the differential diagnosis, leaving a patient with both dissociative and hallucinatory fugues, likely made possible by remote traumatic injury to limbic, arousal and motor circuits. PMID:22665872

  10. Dissociative Identity Disorders in Korea: Two Recent Cases

    PubMed Central

    Kim, Ilbin; Jung, Hyun-Jin

    2016-01-01

    Although dissociative identity disorder (DID), the most severe of the dissociative disorders, has retained its own diagnostic entity since its introduction in the DSM-III, cases of DID are rarely seen in South and East Asia, likely due to the higher prevalence of possession disorder. We report two patients with DID who were recently admitted to our inpatient psychiatric unit and demonstrated distinct transitions to several identities. Their diagnoses were confirmed through a structured interview for dissociative disorders and possible differential diagnoses were ruled out by psychological, neuroimaging, and laboratory tests. The rapid transition to a Westernized, individualized society along with an increase in child abuse, might contribute to an increase in DID, previously under-diagnosed in this region. PMID:27081389

  11. Translation-vibration-dissociation coupling in nonequilibrium hypersonic flows

    NASA Technical Reports Server (NTRS)

    Candler, Graham

    1989-01-01

    A new simple and computationally efficient model was developed, describing the evolution of vibrational states during relaxation and dissociation. The model is based on dividing the nitrogen molecules into two types, those in the vibrational states at a lower level, whose vibrational energy is below a cutoff energy, and those in an upper level, with vibrational energy above the cutoff. Dissociation occurs at the upper level, and recombination returns molecules to the lower level. The model was applied to two flows of engineering interest, the flow through a normal Mach 15 shock wave at 60 km, and a supersonic quasi-one-dimensional flow in a nozzle. Results are compared to those obtained by existing translation-vibration-dissociation coupling models, with results indicating significant differences between the models.

  12. A patient with distinct dissociative and hallucinatory fugues.

    PubMed

    Mortati, Katherine; Grant, Arthur C

    2012-01-01

    A 62-year-old man presented with a history suggesting both dissociative fugue and a distinct fugue-like hallucination. The dissociative fugues included unplanned travel, loss of personal identity, inability to recall his past and amnesia for the fugue interval. The subjective fugues consisted of a stereotyped hallucination wherein he would travel to a social gathering place, meet his 'imaginary friends' and engage with them in conversation. He experienced the subjective fugues as if they were real, recognised them as hallucinations when he was normally conscious, and remembered them in great detail. A hallucinatory fugue episode occurred during video-EEG monitoring. The patient engaged in semipurposeful behaviour for which he had no memory, and the EEG demonstrated waking rhythms. Epilepsy, sleep disorder, factitious disorder and malingering were excluded from the differential diagnosis, leaving a patient with both dissociative and hallucinatory fugues, likely made possible by remote traumatic injury to limbic, arousal and motor circuits. PMID:22665872

  13. Control of ionization and dissociation by optical pulse trains.

    PubMed

    Kirrander, A; Jungen, Ch; Fielding, H H

    2010-08-21

    Ever since the first lasers were built over 40 years ago, chemists and physicists have been attempting to exploit them as tools for controlling the outcome of chemical reactions. Over the last decade this dream has become a reality. The most successful approaches have employed learning algorithms to shape femtosecond laser pulses; however, in these experiments, the laser light effectively learns for itself what pulse shape is required to generate a specific product and it is not always easy to unravel the underlying physics of the control process. In this theoretical investigation we unravel the mechanism of ionisation/dissociation control in the prototypical H(2) molecule. We track the excited state molecular dynamics from the moment of interaction with the laser field to ionization and dissociation, and determine how sequences of carefully tuned laser pulses are able to change the ionization/dissociation branching ratio. PMID:20532353

  14. Trapping and dissociation of propafenone derivatives in HERG channels

    PubMed Central

    Windisch, A; Timin, EN; Schwarz, T; Stork-Riedler, D; Erker, T; Ecker, GF; Hering, S

    2011-01-01

    BACKGROUND AND PURPOSE Human ether-a-go-go related gene (HERG) channel inhibitors may be subdivided into compounds that are trapped in the closed channel conformation and others that dissociate at rest. The structural peculiarities promoting resting state dissociation from HERG channels are currently unknown. A small molecule-like propafenone is efficiently trapped in the closed HERG channel conformation. The aim of this study was to identify structural moieties that would promote dissociation of propafenone derivatives. EXPERIMENTAL APPROACH Human ether-a-go-go related gene channels were heterologously expressed in Xenopus oocytes and potassium currents were recorded using the two-microelectrode voltage clamp technique. Recovery from block by 10 propafenone derivatives with variable side chains, but a conserved putative pharmacophore, was analysed. KEY RESULTS We have identified structural determinants of propafenone derivatives that enable drug dissociation from the closed channel state. Propafenone and four derivatives with ‘short’ side chains were trapped in the closed channel. Five out of six bulky derivatives efficiently dissociated from the channel at rest. One propafenone derivative with a similar bulk but lacking an H-bond acceptor in this region was trapped. Correlations were observed between molecular weight and onset of channel block as well as between pKa and recovery at rest. CONCLUSION AND IMPLICATIONS The data show that extending the size of a trapped HERG blocker-like propafenone by adding a bulky side chain may impede channel closure and thereby facilitate drug dissociation at rest. The presence of an H-bond acceptor in the bulky side chain is, however, essential. PMID:21175572

  15. X-ray Computed Tomography Observation of Methane Hydrate Dissociation

    USGS Publications Warehouse

    Tomutsa, L.; Freifeld, B.; Kneafsey, T.J.; Stern, L.A.

    2002-01-01

    Deposits of naturally occurring methane hydrate have been identified in permafrost and deep oceanic environments with global reserves estimated to be twice the total amount of energy stored in fossil fuels. The fundamental behavior of methane hydrate in natural formations, while poorly understood, is of critical importance if the economic recovery of methane from hydrates is to be accomplished. In this study, computed X-ray tomography (CT) scanning is used to image an advancing dissociation front in a heterogeneous gas hydrate/sand sample at 0.1 MPa. The cylindrical methane hydrate and sand aggregate, 2.54 cm in diameter and 6.3 cm long, was contained in a PVC sample holder that was insulated on all but one end. At the uninsulated end, the dissociated gas was captured and the volume of gas monitored. The sample was initially imaged axially using X-ray CT scanning within the methane hydrate stability zone by keeping the sample temperature at 77??K. Subsequently, as the sample warmed through the methane hydrate dissociation point at 194??K and room pressure, gas was produced and the temperature at the bottom of the sample plug was monitored while CT images were acquired. The experiment showed that CT imaging can resolve the reduction in density (as seen by a reduction in beam attenuation) of the hydrate/sand aggregate due to the dissociation of methane hydrate. In addition, a comparison of CT images with gas flow and temperature measurements reveals that the CT scanner is able to resolve accurately and spatially the advancing dissociation front. Future experiments designed to better understand the thermodynamics of hydrate dissociation are planned to take advantage of the temporal and spatial resolution that the CT scanner provides.

  16. The Dissociation Energy of Hydrogen and of Deuterium

    NASA Astrophysics Data System (ADS)

    Balakrishnan, Ashok

    The ab initio computation and experimental determination of the dissociation energy (D_0) of the hydrogen and deuterium molecules has long been an important problem in molecular spectroscopy. Kolos, Monkhorst, and Szalewicz (1986) have calculated D_0 with an accuracy of +/-0.1 cm^{-1} while including fine interactions such as relativistic effects, non-adiabatic mixing, and radiative shifts. These terms introduce corrections as small as 0.2 cm^{-1}, and experimental precision must exceed this to test the calculation in all of its aspects. In our experiment, a jet of H_2 (or D_2 ) was probed with coherent and tunable radiation at ~84 nm, near the second dissociation limit which leads to the products H(n = 2) + H(1s). Molecules in their ground state were excited into the highest vibronic levels of the electronic states B, B^' , and C, and into the dissociation continuum by tuning the radiation across the dissociation threshold. Metastable H(2s) photofragments were detected by applying a delayed electric field to mix the 2s with 2p states, thereby quenching H(2s) atoms to yield fluorescence at the Lyman- alpha wavelength. The onset of quenched fluorescence marked the second dissociation limit; from this energy, the atomic 2s-1s interval was subtracted, thus yielding D_0. We obtained the values D _0(H_2) = 36 118.11 +/- 0.08 cm^{ -1} and D_0(D _2) = 36 748.38 +/- 0.07 cm^{-1}, which are in excellent agreement with the most recent theoretical calculations. Thus, a long-standing discrepancy between experiment and theory has been resolved, and the ab initio calculation of D_0 appears to be successful. Finally, from our D_0 values, the dissociation energies of the molecular ions were deduced, and they also confirm the latest (1991) ab initio values of D_0(H_sp {2}{+}) and D_0 (D_sp{2}{+}).

  17. Dissociation of F-actin induced by hydrostatic pressure.

    PubMed

    Garcia, C R; Amaral Júnior, J A; Abrahamsohn, P; Verjovski-Almeida, S

    1992-11-01

    F-actin purified from rabbit skeletal muscle undergoes reversible dissociation when subjected to hydrostatic pressures up to 240 MPa. Dissociation and reversibility were detected by the following procedures: fluorescence spectral changes observed under pressure, when either intrinsic tryptophan or pyrenyl emission of N-(1-pyrenyl)iodoacetamide-labeled actin were monitored; electron microscopy of samples fixed under pressure; size-exclusion HPLC of pressurized actin. The effect of pressure upon F-actin that had been polymerized in the presence of either Mg2+, Ca2+ or K+ was studied. The standard volume changes for the association of actin subunits, calculated from pressure/dissociation curves were 74 +/- 14 ml/mol for Mg-F-actin, 79 +/- 12 ml/mol for Ca-F-actin and 328 +/- 63 ml/mol for K-F-actin, indicating that actin subunits are packed differently in the polymer depending on which cation is present. All pressure/dissociation data could be fitted by a model for dissociation of a dimer, which suggests that in the F-actin filament there is a predominant intersubunit interaction interface, most likely the head-to-tail intrastrand interaction between two subunits which repeats itself along the polymer. A tenfold change in total protein concentration from 20 micrograms to 200 micrograms/ml Mg-F-actin did not cause a change in the pressure required for half-maximal dissociation. This indicates a heterogeneity of free energy of association among actin monomers in the Mg-F-actin polymer, suggesting that, in addition to the predominant intersubunit interaction, the disordered interactions in the filament significantly contribute to the heterogeneity of microenvironments in the interface between the subunits. PMID:1425683

  18. Absolute cross sections for dissociative electron attachment to HCN and DCN

    SciTech Connect

    May, O.; Kubala, D.; Allan, M.

    2010-07-15

    Absolute partial cross sections for the formation of CN{sup -} in dissociative electron attachment to HCN and DCN have been measured using a time-of-flight ion spectrometer combined with a trochoidal electron monochromator to be 940pm{sup 2} for CN{sup -}/HCN and 340pm{sup 2} for CN{sup -}/DCN at peaks of the bands due to the {sup 2{Pi}}-shape resonance. The dissociative electron attachment bands were then recorded under higher resolution, 60 meV, with a trochoidal monochromator plus quadrupole mass filter combination and found to have a nearly vertical onset at the threshold energy and to peak at 1.85 eV. Broad structure was observed on the bands, assigned to formation of vibrationally excited CN{sup -}, from which the branching ratios could be determined to be 1,0.49, and 0.22 for the formation of CN{sup -} in the v=0,1, and 2 states, respectively. The results are compared to the recent multidimensional ab initio calculations of Chourou and Orel [Phys. Rev. A 80, 032709 (2009)].

  19. Hydrogen Generation from the Dissociation of Water Using Microwave Plasmas

    NASA Astrophysics Data System (ADS)

    Yong, Ho Jung; Soo Ouk, Jang; Hyun Jong, You

    2013-06-01

    Hydrogen is produced by direct dissociation of water vapor, i.e., splitting water molecules by the electrons in water plasma at low pressure (<10-50 Torr) using microwave plasma discharge. This condition generates a high electron temperature, which facilitates the direct dissociation of water molecules. A microwave plasma source is developed, utilizing the magnetron of a microwave oven and a TE10 rectangular waveguide. The quantity of the generated hydrogen is measured using a residual gas analyzer. The electron density and temperature are measured by a Langmuir probe, and the neutral temperature is calculated from the OH line intensity.

  20. Adult attachment as a predictor of posttraumatic stress and dissociation.

    PubMed

    Sandberg, David A

    2010-01-01

    This study examined whether K. Bartholomew's (1990) self-report dimensions of adult attachment (secure, dismissing, preoccupied, and fearful) mediate or moderate links from victimization/abuse to posttraumatic stress and dissociation. Participants were 199 college women with and without a history of childhood physical abuse, childhood sexual victimization, and adolescent/adult sexual victimization. Path analysis revealed no significant mediation effects for attachment; however, hierarchical multiple linear regression indicated that dismissing attachment moderated the link between victimization/abuse and posttraumatic stress (i.e., the relationship was strongest for women with high dismissing scores). All 4 attachment dimensions uniquely predicted posttraumatic stress, whereas only fearful attachment uniquely predicted dissociation. PMID:20603764

  1. A theoretical study on ascorbic acid dissociation in water clusters.

    PubMed

    Demianenko, Eugeniy; Ilchenko, Mykola; Grebenyuk, Anatoliy; Lobanov, Victor; Tsendra, Oksana

    2014-03-01

    Dissociation of ascorbic acid in water has been studied by using a cluster model. It was examined by density functional theory (DFT) with the В3LYP, M06, and wB97XD functionals and a 6-311++G(d,p) basis set. The thermodynamic and kinetic characteristics of proton transfer from ascorbic acid molecule to water clusters were calculated as well as the equilibrium constants (pK a ) for the related processes. The used functionals in the DFT method together with continuum solvent models provided results close to the experimental data for the dissociation constant of ascorbic acid in aqueous solution. PMID:24567154

  2. Higher-order dynamical effects in Coulomb dissociation

    SciTech Connect

    Esbensen, H.; Bertsch, G.F.; Bertulani, C.A.

    1995-08-01

    Coulomb dissociation is a technique commonly used to extract the dipole response of nuclei far from stability. This technique is applicable if the dissociation is dominated by dipole transitions and if first-order perturbation theory is valid. In order to assess the significance of higher-order processes we solve numerically the time evolution of the wave function for a two-body breakup in the Coulomb field from a high Z target. We applied this method to the breakup reactions: {sup 11}Be {yields} {sup 10}Be + n and {sup 11}Li {yields} +2n. The latter is treated as a two-body breakup, using a di-neutron model.

  3. The dissociation of histone from deoxyribonucleohistone by gamma-irradiation.

    PubMed

    Lloyd, P H; Peacocke, A R

    1968-09-01

    1. Experiments were carried out to determine the extent of dissociation of histone from deoxyribonucleohistone as a result of irradiation with gamma-rays from (60)Co. 2. The bulk of the nucleohistone was removed from the irradiated solutions either by sedimentation or by precipitation with dilute sodium chloride solution. The supernatants were then analysed for DNA and histone. 3. The ratios of histone to DNA in these supernatants were less than for the original nucleohistone. This indicated that histone was dissociated by the irradiation, and then aggregated either with itself or with other nucleohistone molecules, and so was removed with the bulk of the nucleohistone during sedimentation or precipitation. PMID:5685855

  4. Electron-driven excitations and dissociation of molecules

    SciTech Connect

    Miller, Greg; Orel, Ann E.

    2015-02-13

    This program studied how energy is interchanged in electron and photon collisions with molecules leading to ex-citation and dissociation. Modern ab initio techniques, both for the photoionization and electron scattering, and the subsequent nuclear dynamics studies, are used to accurately treat these problems. This work addresses vibrational ex-citation and dissociative attachment following electron impact, and the dynamics following inner shell photoionzation. These problems are ones for which a full multi-dimensional treatment of the nuclear dynamics is essential and where non-adiabatic effects are expected to be important.

  5. Optical observations of molecular dissociation in thin foils

    SciTech Connect

    Berry, H.G.; Gay, T.J.; Brooks, R.L.

    1981-01-01

    We have measured the intensity and polarizations of light emitted from atomic excited states of dissociated molecular ions. Using HeH/sup +/ projectiles, we have observed factors of 1 to 5 enhancements of the light from n=3, /sup 1/ /sup 3/P,D states of He I and some He II and H I emissions. Observations of Lyman-..cap alpha.. emission after dissociation of H/sub 2//sup +/ and H/sub 3//sup +/ show rapid variations in light yield for small internuclear separations at the foil surface.

  6. VUV study of electron impact dissociative excitation of thymine

    NASA Astrophysics Data System (ADS)

    Tiessen, C. J.; Trocchi, J. A.; Hein, J. D.; Dech, J.; Kedzierski, W.; McConkey, J. W.

    2016-06-01

    Dissociative excitation of thymine following electron impact was studied in the energy range up to 430 eV. Emissions in the vacuum ultra-violet spectral region below 150 nm were studied and found to be dominated by the hydrogen Lyman series. Emission cross section data reveal that Lyman-α excitation displays a broad maximum at an electron impact energy of 160 eV. The probability of extracting other excited atoms from the parent molecule is found to be insignificant. Possible excitation and dissociation mechanisms in the parent molecule are discussed.

  7. Dissociation of oxygen on Ag(100) induced by inelastic electron tunneling.

    PubMed

    Sprodowski, Carsten; Mehlhorn, Michael; Morgenstern, Karina

    2010-07-01

    Scanning tunneling microscopy (STM) is used to study the dissociation of molecular oxygen on Ag(100) induced by inelastic electron tunneling (IET) at 5 K. This dissociation is possible above 3.3 V with a yield of (3.63 ± 0.47) × 10(-9) per electron. Dissociation leads to three different types of hot atom motion: lateral motion, a cannon ball mechanism, and abstractive dissociation. Analysis of the I-t characteristics during dissociation suggests that the dissociation is proceeded by an adsorption site change. PMID:21386462

  8. Characterization and Modeling of the Collision Induced Dissociation Patterns of Deprotonated Glycosphingolipids: Cleavage of the Glycosidic Bond.

    PubMed

    Rožman, Marko

    2016-01-01

    Glycosphingolipid fragmentation behavior was investigated by combining results from analysis of a series of negative ion tandem mass spectra and molecular modeling. Fragmentation patterns extracted from 75 tandem mass spectra of mainly acidic glycosphingolipid species (gangliosides) suggest prominent cleavage of the glycosidic bonds with retention of the glycosidic oxygen atom by the species formed from the reducing end (B and Y ion formation). Dominant product ions arise from dissociation of sialic acids glycosidic bonds whereas product ions resulting from cleavage of other glycosidic bonds are less abundant. Potential energy surfaces and unimolecular reaction rates of several low-energy fragmentation pathways leading to cleavage of glycosidic bonds were estimated in order to explain observed dissociation patterns. Glycosidic bond cleavage in both neutral (unsubstituted glycosyl group) and acidic glycosphingolipids was the outcome of the charge-directed intramolecular nucleophilic substitution (SN2) mechanism. According to the suggested mechanism, the nucleophile in a form of carboxylate or oxyanion attacks the carbon at position one of the sugar ring, simultaneously breaking the glycosidic bond and yielding an epoxide. For gangliosides, unimolecular reaction rates suggest that dominant product ions related to the cleavage of sialic acid glycosidic bonds are formed via direct dissociation channels. On the other hand, low abundant product ions related to the dissociation of other glycosidic bonds are more likely to be the result of sequential dissociation. Although results from this study mainly contribute to the understanding of glycosphingolipid fragmentation chemistry, some mechanistic findings regarding cleavage of the glycosidic bond may be applicable to other glycoconjugates. PMID:26297186

  9. Enhanced Dissociation of Intact Proteins with High Capacity Electron Transfer Dissociation

    NASA Astrophysics Data System (ADS)

    Riley, Nicholas M.; Mullen, Christopher; Weisbrod, Chad R.; Sharma, Seema; Senko, Michael W.; Zabrouskov, Vlad; Westphall, Michael S.; Syka, John E. P.; Coon, Joshua J.

    2016-03-01

    Electron transfer dissociation (ETD) is a valuable tool for protein sequence analysis, especially for the fragmentation of intact proteins. However, low product ion signal-to-noise often requires some degree of signal averaging to achieve high quality MS/MS spectra of intact proteins. Here we describe a new implementation of ETD on the newest generation of quadrupole-Orbitrap-linear ion trap Tribrid, the Orbitrap Fusion Lumos, for improved product ion signal-to-noise via ETD reactions on larger precursor populations. In this new high precursor capacity ETD implementation, precursor cations are accumulated in the center section of the high pressure cell in the dual pressure linear ion trap prior to charge-sign independent trapping, rather than precursor ion sequestration in only the back section as is done for standard ETD. This new scheme increases the charge capacity of the precursor accumulation event, enabling storage of approximately 3-fold more precursor charges. High capacity ETD boosts the number of matching fragments identified in a single MS/MS event, reducing the need for spectral averaging. These improvements in intra-scan dynamic range via reaction of larger precursor populations, which have been previously demonstrated through custom modified hardware, are now available on a commercial platform, offering considerable benefits for intact protein analysis and top down proteomics. In this work, we characterize the advantages of high precursor capacity ETD through studies with myoglobin and carbonic anhydrase.

  10. A theoretical analysis of photoactivated unimolecular dissociation: The overtone dissociation of t-butyl hydroperoxide

    NASA Astrophysics Data System (ADS)

    Chandler, David W.; Miller, James A.

    1984-07-01

    We have used the master equation formalism to analyze the photoactivated unimolecular dissociation of a large polyatomic molecule, t-butyl hydroperoxide (t-BuOOH). Our results are compared to the experimental results of Chandler, Farneth, and Zare and of Chuang et al. We find that the curvature in their Stern-Volmer plots cannot be explained by a collisional energy transfer mechanism. At high pressure, the theoretical Stern-Volmer plots are linear, independent of the collisional energy transfer properties. This linearity is related to the existence of a limiting high pressure ``reactive distribution.'' We identify three different pressure regimes that exist in photoactivated unimolecular reaction experiments, and we relate these regimes to the properties of the reactive distribution. In particular, we find that, when a Stern-Volmer analysis is used, curvature at very low pressure can result in systematic errors in determining the unimolecular rate constants. In addition, we have successfully analyzed the real time experiments of Rizzo and Crim using the same molecular model and parameters necessary to predict the experiments of Chandler et al.

  11. Theoretical analysis of photoactivated unimolecular dissociation: The overtone dissociation of t-butyl hydroperoxide

    SciTech Connect

    Chandler, D.W.; Miller, J.A.

    1984-07-01

    We have used the master equation formalism to analyze the photoactivated unimolecular dissociation of a large polyatomic molecule, t-butyl hydroperoxide (t-BuOOH). Our results are compared to the experimental results of Chandler, Farneth, and Zare and of Chuang et al. We find that the curvature in their Stern-Volmer plots cannot be explained by a collisional energy transfer mechanism. At high pressure, the theoretical Stern--Volmer plots are linear, independent of the collisional energy transfer properties. This linearity is related to the existence of a limiting high pressure ''reactive distribution.'' We identify three different pressure regimes that exist in photoactivated unimolecular reaction experiments, and we relate these regimes to the properties of the reactive distribution. In particular, we find that, when a Stern-Volmer analysis is used, curvature at very low pressure can result in systematic errors in determining the unimolecular rate constants. In addition, we have successfully analyzed the real time experiments of Rizzo and Crim using the same molecular model and parameters necessary to predict the experiments of Chandler et al.

  12. Electronic shell model contemplation of the dissociation dynamics of Al 8+: a collision-induced dissociation study

    NASA Astrophysics Data System (ADS)

    Ingólfsson, Oddur; Takeo, Harutoshi; Nonose, Shinji

    1999-10-01

    For the collision-induced dissociation of small cationic aluminum clusters, the release of Al + is known to dominate. An exception is Al 8+, where we find the neutral atom evaporation to be energetically favorable, and to couple strongly with the Al + release. These experimental results are discussed in the frame of the Clemenger-Nilsson electronic shell model. We find the electronic shell model to offer a consistent interpretation of the energy dependence of the dissociation dynamics of Al 8+, if the crucial role of collisional deformation is taken into account.

  13. Dissociation Dynamics of Molecular Ions in High dc Electric Field.

    PubMed

    Blum, Ivan; Rigutti, Lorenzo; Vurpillot, François; Vella, Angela; Gaillard, Aurore; Deconihout, Bernard

    2016-05-26

    In an atom probe, molecular ions can be field evaporated from the analyzed material and, then, can dissociate under the very intense electric field close to the field emitter. In this work, field evaporation of ZnO reveals the emission of Zn2O2(2+) ions and their dissociation into ZnO(+) ions. It is shown that the repulsion between the produced ZnO(+) ions is large enough to have a measurable effect on both the ion trajectories and times of flight. Comparison with numerical simulations of the ion trajectories gives information on the lifetime of the parent ions, the energy released by the dissociation and repulsion, and also the dissociation direction. This study not only opens the way to a new method to obtain information on the behavior of molecular ions in high electric fields by using an atom probe, but also opens up the interesting perspective to apply this technique to a wide class of materials and molecules. PMID:27136453

  14. Towards simple orbital-dependent density functionals for molecular dissociation

    NASA Astrophysics Data System (ADS)

    Zhang, Igor Ying; Richter, Patrick; Scheffler, Matthias

    2015-03-01

    Density functional theory (DFT) is one of the leading first-principles electronic-structure theories. However, molecular dissociation remains a challenge, because it requires a well-balanced description of the drastically different electronic structure at different bond lengths. One typical and well-documented case is the dissociation of both H2+ and H2, for which all popular DFT functionals fail. We start from the Bethe-Goldstone equation to propose a simple orbital-dependent correlation functional which generalizes the linear adiabatic connection approach. The resulting scheme is based on second-order perturbation theory (PT2), but includes the self-consistent coupling of electron-hole pairs, which ensures the correct H2 dissociation limit and gives a finite correlation energy for systems with a (near)-degenerate energy gap. This coupling PT2-like (CPT2) approximation delivers a significant improvement over all existing functionals for both H2 and H2+ dissociation. We will demonstrate the reason for this improvement analytically for H2 in a minimal basis.

  15. Dissociation of the Ethyl Radical: An Exercise in Computational Chemistry

    ERIC Educational Resources Information Center

    Nassabeh, Nahal; Tran, Mark; Fleming, Patrick E.

    2014-01-01

    A set of exercises for use in a typical physical chemistry laboratory course are described, modeling the unimolecular dissociation of the ethyl radical to form ethylene and atomic hydrogen. Students analyze the computational results both qualitatively and quantitatively. Qualitative structural changes are compared to approximate predicted values…

  16. Double Dissociations in Visual and Spatial Short-Term Memory

    ERIC Educational Resources Information Center

    Klauer, Karl Christoph; Zhao, Zengmei

    2004-01-01

    A visual short-term memory task was more strongly disrupted by visual than spatial interference, and a spatial memory task was simultaneously more strongly disrupted by spatial than visual interference. This double dissociation supports a fractionation of visuospatial short-term memory into separate visual and spatial components. In 6 experiments,…

  17. A Validation Study of the Adolescent Dissociative Experiences Scale

    ERIC Educational Resources Information Center

    Keck Seeley, Susan. M.; Perosa, Sandra, L.; Perosa, Linda, M.

    2004-01-01

    Objective: The purpose of this study was to further the validation process of the Adolescent Dissociative Experiences Scale (A-DES). In this study, a 6-item Likert response format with descriptors was used when responding to the A-DES rather than the 11-item response format used in the original A-DES. Method: The internal reliability and construct…

  18. Electron ionization and dissociation of aliphatic amino acids

    NASA Astrophysics Data System (ADS)

    Papp, P.; Shchukin, P.; Kočíšek, J.; Matejčík, Š.

    2012-09-01

    We present experimental and theoretical study of electron ionization and dissociative ionization to the gas phase amino acids valine, leucine, and isoleucine. A crossed electron/molecular beams technique equipped with quadrupole mass analyzer has been applied to measure mass spectra and ion efficiency curves for formation of particular ions. From experimental data the ionization energies of the molecules and the appearance energies of the fragment ions were determined. Ab initio calculations (Density Functional Theory and G3MP2 methods) were performed in order to calculate the fragmentation paths and interpret the experimental data. The experimental ionization energies of parent molecules [P]+ 8.91 ± 0.05, 8.85 ± 0.05, and 8.79 ± 0.05 eV and G3MP2 ionization energies (adiabatic) of 8.89, 8.88, and 8.81 eV were determined for valine, leucine, and isoleucine, respectively, as well as the experimental and theoretical threshold energies for dissociative ionization channels. The comparison of experimental data with calculations resulted in identification of the ions as well as the neutral fragments formed in the dissociative reactions. Around 15 mass/charge ratio fragments were identified from the mass spectra by comparison of experimental appearance energies with calculated reaction enthalpies for particular dissociative reactions.

  19. Channel competition in strong-field dissociation of CS+

    NASA Astrophysics Data System (ADS)

    Jochim, Bethany; Zohrabi, M.; Betsch, K. J.; Ablikim, U.; Berry, Ben; Severt, T.; Summers, A. M.; Carnes, K. D.; Esry, B. D.; Ben-Itzhak, I.

    2015-05-01

    We study intense ultrafast laser-induced dissociation of a CS+ ion beam, utilizing a coincidence 3-D momentum imaging technique. Over a laser intensity range of 1010-1016 W/cm2, we find clear intensity-dependent behavior of the C++S and C+S+ branching ratios. Specifically, we observe that the branching ratios are nearly equal at low intensities (~1010-1012 W/cm2) and deviate from each other at higher intensities (>1013 W/cm2), where C+S+ dominates. We propose that the low-intensity branching ratio behavior is due to strong mixing of states corresponding to the relevant dissociation limits mediated by the non-adiabatic couplings, and we identify possible dissociation pathways involving these couplings. Another aspect of channel competition, closing and opening of the two dissociation channels as a function of total energy, is distinctly observed, and this behavior is characterized using the well-known Wigner law for near-threshold behavior. Supported by the Chemical Sciences, Geosciences, and Biosciences Division, Office of Basic Energy Sciences, Office of Science, U.S. Department of Energy. BJ is also supported by DOE-SCGF (DE-AC05-06OR23100).

  20. Photon diffractive dissociation in deep-inelastic scattering

    SciTech Connect

    Levin, E. ); Wuesthoff, M. )

    1994-10-01

    This paper is mainly devoted to the presentation and discussion of formulas for the cross section of photon diffractive dissociation. The calculations which we present in a very detailed way are based on perturbative QCD. We improve formulas which describe this process in the triple Regge limit where the square of the missing mass [ital M][sub [ital X

  1. Proton dependence of tobacco mosaic virus dissociation by pressure.

    PubMed

    Santos, Jose L R; Bispo, Jose A C; Landini, Gustavo F; Bonafe, Carlos F S

    2004-09-01

    Tobacco mosaic virus (TMV) is an intensely studied model of viruses. This paper reports an investigation into the dissociation of TMV by pH and pressure up to 220 MPa. The viral solution (0.25 mg/ml) incubated at 277 K showed a significant decrease in light scattering with increasing pH, suggesting dissociation. This observation was confirmed by HPLC gel filtration and electron microscopy. The calculated volume change of dissociation (DeltaV) decreased (absolute value) from -49.7 ml/mol of subunit at pH 3.8 to -21.7 ml/mol of subunit at pH 9.0. The decrease from pH 9.0 to 3.8 caused a stabilization of 14.1 kJ/mol of TMV subunit. The estimated proton release calculated from pressure-induced dissociation curves was 0.584 mol H(+)/mol of TMV subunit. These results suggest that the degree of virus inactivation by pressure and the immunogenicity of the inactivated structures can be optimized by modulating the surrounding pH. PMID:15450375

  2. Assessing the Dissociability of Recollection and Familiarity in Recognition Memory

    ERIC Educational Resources Information Center

    Pratte, Michael S.; Rouder, Jeffrey N.

    2012-01-01

    Recognition memory is often modeled as constituting 2 separate processes, recollection and familiarity, rather than as constituting a single process mediated by a generic latent strength. One way of stating evidence for the more complex 2-process model is to show dissociations with select manipulations, in which one manipulation affects…

  3. Coherent dissociation of relativistic {sup 12}N nuclei

    SciTech Connect

    Kattabekov, R. R.; Mamatkulov, K. Z.; Alikulov, S. S.; Artemenkov, D. A.; Bekmirzaev, R. N.; Bradnova, V.; Zarubin, P. I. Zarubina, I. G.; Kondratieva, N. V.; Kornegrutsa, N. K.; Krivenkov, D. O.; Malakhov, A. I.; Olimov, K.; Peresadko, N. G.; Polukhina, N. G.; Rukoyatkin, P. A.; Rusakova, V. V.; Stanoeva, R.; Kharlamov, S. P.

    2013-10-15

    The dissociation of relativistic {sup 12}N nuclei having a momentum of 2 GeV/c per nucleon and undergoing the most peripheral interactions in a track emulsion is studied. The picture of charged topology of product ensembles of relativistic fragments and special features of their angular distributions are presented.

  4. Dissociation and Mass Transfer Coefficients for Ammonia Volatilization Models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Process-based models are being used to predict ammonia emissions from manure sources, but their accuracy has not been fully evaluated for cattle manure. Laboratory trials were conducted to measure the dissociation and mass transfer coefficients for ammonia volatilization from media of buffered ammon...

  5. Dissociations in Processing Derivational Morphology: The Right Basal Ganglia Involvement

    ERIC Educational Resources Information Center

    Marangolo, Paola; Piras, Fabrizio

    2008-01-01

    In the neuropsychological literature, there is converging evidence for a dominant role of the left hemisphere in morphological processing. However, two right hemisphere patients were described with a clear dissociation between impaired derivational morphology and preserved inflectional processing. A recent fMRI experiment confirmed the involvement…

  6. Dissociative Identity Disorder in Felonious Offenders: Two Case Studies.

    ERIC Educational Resources Information Center

    Culiner, Ty

    1997-01-01

    Describes the case studies of two inmates detained in a maximum security prison having been diagnosed with Dissociative Identity Disorder and receiving individual therapy. Although treatment is ongoing, mid-treatment progress indicates the treatment is successful and the prognosis is excellent. Accentuates the practicality and rewards of working…

  7. Clinical Assessment of Dissociative Identity Disorder among College Counseling Clients

    ERIC Educational Resources Information Center

    Levy, Benjamin; Swanson, Janine E.

    2008-01-01

    College counseling professionals address a wide range of complex student mental health concerns. Among these, accurately identifying client presentations of dissociative identity disorder (DID) can be especially challenging because students with DID sometimes present as if they are experiencing another problem, such as a mood, anxiety, or…

  8. The degradation of space shuttle TPS metals in dissociated oxygen.

    NASA Technical Reports Server (NTRS)

    Gilbreath, W. P.

    1972-01-01

    The interaction of space shuttle orbiter Thermal Protection System (TPS) metals with the chemical environment to which it is exposed during reentry is considered with emphasis on the effects of dissociated oxygen. Experimental results comparing the interactions of atomic (dissociated) and molecular oxygen with five candidate shuttle TPS metals, Ni-20Cr-2ThO2, Ni-20Cr-3.5Al-2ThO2, Ni-16Cr-15Fe-2Mn-.5Si-.3La-2ThO2, Haynes Alloy Number 188, and Ti-6Al-4V at their maximum planned use temperature are presented. As measured by metal recession, weight change, rate of oxide scale formation, and scale spalling, the first four metals show enhanced degradation in a dissociated oxygen environment. The enhanced degradation appears to result from differing rates of alloy constituent reactions in the two environments. The dissociated oxygen environmental tests are found to better assess the usefulness of shuttle skin materials for the planned mission than do conventional molecular (either flowing or static) oxidation experiments.-

  9. Experimental studies of the dissociative recombination of H3 +

    NASA Astrophysics Data System (ADS)

    Larsson, M.

    2000-09-01

    Despite many experimental efforts over several decades, no consensus has bee n reached concerning the rate of dissociative recombination of H3+. We review the current status concerning different experimental appro aches to the measurement of the cross-section, rate coefficient and branching r atios in electron recombination of H3+.

  10. School Shock: Learning Disability as a Dissociative Reaction.

    ERIC Educational Resources Information Center

    Zitani, E. Alfredo

    Learning disability is suggested to be a dissociative reaction (school shock) similar to shell shock in wartime requiring appropriate theoretical and remedial approaches. Psychoanalytic and learning theory viewpoints are applied to the nature of learning disabilities. Also considered are the relation of anxiety to achievement and hypnosis to…

  11. Dissociation of a polyethylene liner from an acetabular cup.

    PubMed

    Cameron, H U

    1993-10-01

    A polyethylene linear dissociated from a metal acetabular shell that could not be removed at the time of hip revision because the hexagonal hole in its screw head had become rounded off. A high-speed metal cutting burr was used to remove the screw and allow cup revision. PMID:8265224

  12. Electromagnetic dissociation effects in galactic heavy-ion fragmentation

    NASA Technical Reports Server (NTRS)

    Norbury, J. W.; Townsend, L. W.

    1986-01-01

    Methods for calculating cross sections for the breakup of galactic heavy ions by the Coulomb fields of the interacting nuclei are presented. By using the Weizsacker-Williams method of virtual quanta, estimates of electromagnetic dissociation cross sections for a variety of reactions applicable to galactic cosmic ray shielding studies are presented and compared with other predictions and with available experimental data.

  13. Dissociation in Children and Adolescents: A Developmental Perspective.

    ERIC Educational Resources Information Center

    Putnam, Frank W.

    From amnesia to auditory hallucinations, the symptoms of pathological dissociation are among the most devastating effects of childhood maltreatment. Ways in which therapists can provide a comprehensive developmental approach to understanding, diagnosing, and treating this challenging clinical population are presented in this text. After reviewing…

  14. Semiempirical and DFT Investigations of the Dissociation of Alkyl Halides

    ERIC Educational Resources Information Center

    Waas, Jack R.

    2006-01-01

    Enthalpy changes corresponding to the gas phase heats of dissociation of 12 organic halides were calculated using two semiempirical methods, the Hartree-Fock method, and two DFT methods. These calculated values were compared to experimental values where possible. All five methods agreed generally with the expected empirically known trends in the…

  15. Particulate bioluininescence in dinoflagellates: dissociation and partial reconstitution.

    PubMed

    Fuller, C W; Kreiss, P; Seliger, H H

    1972-09-01

    With the same extraction conditions used for Gonyaulax polyedra, soluble and particulate bioluminescence can be isolated from two additional species, Pyrodinium bahamense and Pyrocystis lunula. We have been able, for all three species, to dissociate soluble luciferin and luciferase from the particulate system. Luciferin can be incorporated into both reacted and unreacted particulate systems. PMID:17780988

  16. Affective Association: An Effective Intervention in Countering Fragmentation and Dissociation

    ERIC Educational Resources Information Center

    Hart, Carolyn

    2008-01-01

    This paper is concerned with the processes, both psychoanalytic and neuroscientific, involved in the undoing of dissociation in a 3-year-old, who was seen weekly over a nine month period. A neuroscientific and psychoanalytic developmental framework is used to follow a sequence of phenomena that emerged over the duration of relatively brief once…

  17. Dissociation in hysteria and hypnosis: evidence from cognitive neuroscience.

    PubMed

    Bell, Vaughan; Oakley, David A; Halligan, Peter W; Deeley, Quinton

    2011-03-01

    Jean-Martin Charcot proposed the radical hypothesis that similar brain processes were responsible for the unexplained neurological symptoms of 'hysteria', now typically diagnosed as 'conversion disorder' or 'dissociative (conversion) disorder', and the temporary effects of hypnosis. While this idea has been largely ignored, recent cognitive neuroscience studies indicate that (i) hypnotisability traits are associated with a tendency to develop dissociative symptoms in the sensorimotor domain; (ii) dissociative symptoms can be modelled with suggestions in highly hypnotisable subjects; and (iii) hypnotic phenomena engage brain processes similar to those seen in patients with symptoms of hysteria. One clear theme to emerge from the findings is that 'symptom' presentation, whether clinically diagnosed or simulated using hypnosis, is associated with increases in prefrontal cortex activity suggesting that intervention by the executive system in both automatic and voluntary cognitive processing is common to both hysteria and hypnosis. Nevertheless, while the recent literature provides some compelling leads into the understanding of these phenomena, the field still lacks well controlled systematically designed studies to give a clear insight into the neurocognitive processes underlying dissociation in both hysteria and hypnosis. The aim of this review is to provide an agenda for future research. PMID:20884677

  18. Spectroscopic study of HNO3 dissociation on ice.

    PubMed

    Marchand, Patrick; Marcotte, Guillaume; Ayotte, Patrick

    2012-12-13

    A detailed spectroscopic study of HNO(3):H(2)O binary amorphous mixtures, and of the adsorption of HNO(3) onto ice, is reported. Using a classical optics model, the extent of intermixing and of ionic dissociation of adsorbed HNO(3), which forms a strong acid with liquid water, is determined as a function of HNO(3) coverage and temperature. Even at temperatures as low as 45 K, where intermixing is limited to at most a few molecular layers at the interface, ionic dissociation of adsorbed HNO(3) is observed to be extensive. While some amount of molecularly adsorbed HNO(3) is observed at the surface of ice at 45 K, its ionic dissociation occurs irreversibly upon heating the ice substrate to 120 K. The molecularly adsorbed state of HNO(3) is not restored upon cooling, suggesting HNO(3) is a metastable entity at the surface of ice. Therefore, despite ionic dissociation of HNO(3) being thermodynamically favored, it appears to be kinetically inhibited at the surface of amorphous solid water at temperatures below 120 K. PMID:23130955

  19. Self-Entanglement and the Dissociation of Homonuclear Diatomic Molecules

    SciTech Connect

    Gonis, Antonios; Zhang, Xiaoguang; Nicholson, Don M; Stocks, George Malcolm

    2014-01-01

    The concept of self-entanglement is introduced to describe a mixed state or ensemble density as a pure state in an augmented Hilbert space formed by the products of the individual states forming a mixed state (or ensemble). We use this representation of mixed states to show that upon dissociation a neutral homonuclear diatomic molecule will separate into two neutral atoms.

  20. 21 CFR 886.1910 - Spectacle dissociation test system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Spectacle dissociation test system. 886.1910 Section 886.1910 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... device, such as a Lancaster test system, that consists of a light source and various filters, usually...

  1. The dissociation of subjective measures of mental workload and performance

    NASA Technical Reports Server (NTRS)

    Yeh, Y. H.; Wickens, C. D.

    1984-01-01

    Dissociation between performance and subjective workload measures was investigated in the theoretical framework of the multiple resources model. Subjective measures do not preserve the vector characteristics in the multidimensional space described by the model. A theory of dissociation was proposed to locate the sources that may produce dissociation between the two workload measures. According to the theory, performance is affected by every aspect of processing whereas subjective workload is sensitive to the amount of aggregate resource investment and is dominated by the demands on the perceptual/central resources. The proposed theory was tested in three experiments. Results showed that performance improved but subjective workload was elevated with an increasing amount of resource investment. Furthermore, subjective workload was not as sensitive as was performance to differences in the amount of resource competition between two tasks. The demand on perceptual/central resources was found to be the most salient component of subjective workload. Dissociation occurred when the demand on this component was increased by the number of concurrent tasks or by the number of display elements. However, demands on response resources were weighted in subjective introspection as much as demands on perceptual/central resources. The implications of these results for workload practitioners are described.

  2. Simulations of dissociation constants in low pressure supercritical water

    NASA Astrophysics Data System (ADS)

    Halstead, S. J.; An, P.; Zhang, S.

    2014-09-01

    This article reports molecular dynamics simulations of the dissociation of hydrochloric acid and sodium hydroxide in water from ambient to supercritical temperatures at a fixed pressure of 250 atm. Corrosion of reaction vessels is known to be a serious problem of supercritical water, and acid/base dissociation can be a significant contributing factor to this. The SPC/e model was used in conjunction with solute models determined from density functional calculations and OPLSAA Lennard-Jones parameters. Radial distribution functions were calculated, and these show a significant increase in solute-solvent ordering upon forming the product ions at all temperatures. For both dissociations, rapidly decreasing entropy of reaction was found to be the controlling thermodynamic factor, and this is thought to arise due to the ions produced from dissociation maintaining a relatively high density and ordered solvation shell compared to the reactants. The change in entropy of reaction reaches a minimum at the critical temperature. The values of pKa and pKb were calculated and both increased with temperature, in qualitative agreement with other work, until a maximum value at 748 K, after which there was a slight decrease.

  3. Stochastic Approaches to Understanding Dissociations in Inflectional Morphology

    ERIC Educational Resources Information Center

    Plunkett, Kim; Bandelow, Stephan

    2006-01-01

    Computer modelling research has undermined the view that double dissociations in behaviour are sufficient to infer separability in the cognitive mechanisms underlying those behaviours. However, all these models employ "multi-modal" representational schemes, where functional specialisation of processing emerges from the training process. Targeted…

  4. Possible isomers in ligand protected Ag11 cluster ions identified by ion mobility mass spectrometry and fragmented by surface induced dissociation.

    PubMed

    Baksi, Ananya; Harvey, Sophie R; Natarajan, Ganapati; Wysocki, Vicki H; Pradeep, Thalappil

    2016-03-01

    This communication reports the identification of gas phase isomers in monolayer-protected silver clusters. Two different isomers of Ag11(SG)7(-) (SG-gulathione thiolate) with different drift times have been detected using combined electrospray ionization (ESI) and ion mobility (IM) mass spectrometry (MS). Surface induced dissociation (SID) of the 3(-) charge state of such clusters shows charge stripping to give the 1(-) charged ion with some sodium attachment, in addition to fragmentation. SID and collision induced dissociation (CID) for Ag11(SG)7(-) suggest different pathways being accessed with each method. SID was introduced for the first time for the study of monolayer-protected clusters. PMID:26864967

  5. Precision Measurement of the Ionization and Dissociation Energies of H_2, HD and D_2

    NASA Astrophysics Data System (ADS)

    Sprecher, Daniel; Liu, Jinjun; Merkt, Frédéric; Jungen, Christian; Ubachs, Wim

    2010-06-01

    The ionization and dissociation energies of H_2, HD and D_2 are benchmark quantities in molecular quantum mechanics. Comparison between experimental and theoretical values for these quantities has a long history starting with the early measurement of Beutler and the calculations of James and Coolidge. Transition wave numbers from the EF ^1Σ g^+ (v=0,N=0,1) state to selected np Rydberg states (n ≈ 60) below the X+ ^2Σ^+u (v^+=0,N^+=0,1)} ionization threshold have been measured in H_2, HD and D_2 at a precision better than 10 MHz (0.0003 cm-1). Combining the results with previous experimental and theoretical data for other energy level intervals, the ionization and dissociation energies of H_2, HD and D_2 could be determined at an absolute accuracy of better than 20 MHz. These new results represent an improvement over previous experimental results by more than one order of magnitude and the most precise values of dissociation and ionization energies measured to date in a molecular system. The results therefore offer the opportunity of a comparison with theoretical values. In particular they will be compared to the latest ab initio calculations which include nonadiabatic, relativistic and radiative effects. The comparison indicates that relativistic and radiative quantum electrodynamics corrections of order up to α^4 are needed to account for the experimental results. H. Beutler, Z. Phys. Chem. 29, 315 (1935) H. M. James and A. S. Coolidge, J. Chem. Phys. 1, 825 (1933) J. Liu, E. J. Salumbides, U. Hollenstein, J. C. J. Koelemeij, K. S. E. Eikema, W. Ubachs, and F. Merkt, J. Chem. Phys. 130, 174306 (2009) J. Liu, D. Sprecher, Ch. Jungen, W. Ubachs, and F. Merkt, submitted to J. Chem. Phys. K. Piszczatowski, G. Łach, M. Przybytek, J. Komasa, K. Pachucki, and B. Jeziorski, J. Chem. Theory Comput. 5, 3039 (2009)

  6. Developments in Power efficient dissociation of CO2 using non-equilibrium plasma activation

    NASA Astrophysics Data System (ADS)

    van de Sanden, Richard

    2013-09-01

    Sustainable energy generation by means of, either photovoltaic conversion, concentrated solar power or wind, will certainly form a significant part of the energy mix in 2025. The intermittency as well as the temporal variation and the regional spread of this energy source, however, requires a means to store and transport energy on a large scale. In this presentation the means of storage will be addressed of sustainable energy transformed into fuels and the prominent role plasma science and technology can play in this great challenge. The storage of sustainable energy in these so called solar fuels, e.g. hydrocarbons and alcohols, by means of artificial photosynthesis from the feedstock CO2 and H2O, will enable a CO2 neutral power generation infrastructure, which is close to the present infrastructure based on fossil fuels. The challenge will be to achieve power efficient dissociation of CO2 or H2O or both, after which traditional chemical conversion (Fisher-Tropsch, Sabatier, etc.) towards fuels can take place. A promising route is the dissociation or activation of CO2 by means of plasma, possible combined with catalysis. Taking advantage of non-equilibrium plasma conditions to reach optimal energy efficiency we have started a solar fuels program at the beginning of 2012 focusing on CO2 plasma dissociation into CO and O2. The plasma is generated in a low loss microwave cavity with microwave powers up to 10 kW using a supersonic expansion to quench the plasma and prevent vibrational-translational relaxation losses. New ideas on the design of the facility and results on power efficient conversion (more then 50%) of large CO2 flows (up to 75 standard liter per minute with 11% conversion) at low gas temperatures will be presented.

  7. Do dissociated or associated phoria predict the comfortable prism?

    PubMed Central

    Otto, Joanna M. N.; Kromeier, Miriam; Bach, Michael

    2008-01-01

    Background Dissociated and associated phoria are measures of latent strabismus under artificial viewing conditions. We examined to what extent dissociated and associated phoria predict the “comfortable prism”, i.e. the prism that appears most comfortable under natural viewing conditions. Methods For associated phoria, a configuration resembling the Mallett test was employed: both eyes were presented with a fixation cross, surrounded by fusionable objects. Nonius lines served as monocular markers. For dissociated phoria, the left eye was presented with all the Mallett elements, while only a white spot was presented to the right eye. To determine the comfortable prism, all the Mallett elements, including the Nonius lines, were shown to both eyes. In each of the three tests, the observer had to adjust a pair of counterrotating prisms. To avoid any (possibly prejudiced) influence of the experimenter, the prismatic power was recorded with a potentiometer. Twenty non-strabismic subjects with a visual acuity of ≥1.0 in each eye were examined. Results The range of the intertrial mean was for dissociated phoria from +9.3 eso to −5.9 cm/m exo, for associated phoria from +11.2 eso to −3.3 cm/m exo, and for the comfortable prism from +4.8 eso to −4.1 cm/m exo (cm/m = prism dioptre). In most observers, the phoria parameters differed greatly from the comfortable prism. On average, the phoria values were shifted about 2 cm/m towards the eso direction in relation to the comfortable prism (associated phoria not less than dissociated phoria). Conclusions The deviation of both, dissociated and associated phoria, from the comfortable prism suggests that the abnormal viewing conditions under which the phoria parameters are determined induce artefacts. Accordingly, the findings cast doubt on current textbook recommendations to use dissociated or associated phoria as a basis for therapeutic prisms. Rather, patients should be allowed to determine their comfortable prism

  8. Photofragment translational spectroscopy of three body dissociations and free radicals

    SciTech Connect

    North, S.W.

    1995-04-01

    This dissertation describes several three-body dissociations and the photodissociation of methyl radicals studied using photofragment translational spectroscopy. The first chapter provides an introduction to three body dissociation, examines current experimental methodology, and includes a discussion on the treatment of photofragment translational spectroscopy data arising from three-body fragmentation. The ultraviolet photodissociation of azomethane into two methyl radicals and nitrogen is discussed in chapter 2. Chapter 3 describes the photodissociation of acetone at 248 nm and 193 nm. At 248 nm the translational energy release from the initial C-C bond cleavage matches the exit barrier height and a comparison with results at 266 nm suggests that is invariant to the available energy. A fraction of the nascent CH{sub 3}CO radicals spontaneously dissociate following rotational averaging. The for the second C-C bond cleavage also matches the exit barrier height. At 193 nm the experimental data can be successfully fit assuming that the dynamics are analogous to those at 248 nm. A simplified model of energy partitioning which adequately describes the experimental results is discussed. Experiments on acetyl halides provide additional evidence to support the proposed acetone dissociation mechanism. A value of 17.0{+-}1.0 kcal/mole for the barrier height, CH{sub 3}CO decomposition has been determined. The photodissociation of methyl radical at 193 nm and 212.8 nm is discussed in the chapter 5. The formation of CH{sub 2} ({sup 1}A{sub l}) and H ({sup 2}S) was the only single photon dissociation pathway observed at both wavelengths.

  9. Dissociation predicts later attention problems in sexually abused children

    PubMed Central

    Kaplow, Julie B.; Hall, Erin; Koenen, Karestan C.; Dodge, Kenneth A.; Amaya-Jackson, Lisa

    2008-01-01

    Objective The goals of this research are to develop and test a prospective model of attention problems in sexually abused children that includes fixed variables (e.g., gender), trauma, and disclosure-related pathways. Methods At Time 1, fixed variables, trauma variables, and stress reactions upon disclosure were assessed in 156 children aged 8 to 13 years. At the Time 2 follow-up (8 to 36 months following the initial interview), 56 of the children were assessed for attention problems. Results A path analysis involving a series of hierarchically-nested, ordinary least squares multiple regression analyses indicated two direct paths to attention problems including the child’s relationship to the perpetrator (β = .23) and dissociation measured immediately after disclosure (β = .53), while controlling for concurrent externalizing behavior (β = .43). Posttraumatic stress symptoms were only indirectly associated with attention problems via dissociation. Taken together, these pathways accounted for approximately 52% of the variance in attention problems and provided an excellent fit to the data. Conclusions Children who report dissociative symptoms upon disclosure of CSA and/or were sexually abused by someone within their family are at an increased risk of developing attention problems. Practice Implications: Findings from this study indicate that children who experienced sexual abuse at an earlier age, by someone within their family, and/or report symptoms of dissociation during disclosure are especially likely to benefit from intervention. Effective interventions should involve (1) providing emotion regulation and coping skills; and (2) helping children to process traumatic aspects of the abuse to reduce the cyclic nature of traumatic reminders leading to unmanageable stress and dissociation. PMID:18308391

  10. Parameterized cross sections for Coulomb dissociation in heavy-ion collisions

    NASA Technical Reports Server (NTRS)

    Norbury, John W.; Cucinotta, F. A.; Townsend, L. W.; Badavi, F. F.

    1988-01-01

    Simple parameterizations of Coulomb dissociation cross sections for use in heavy-ion transport calculations are presented and compared to available experimental dissociation data. The agreement between calculation and experiment is satisfactory considering the simplicity of the calculations.

  11. Peas, please: a case report and neuroscientific review of dissociative amnesia and fugue.

    PubMed

    MacDonald, Kai; MacDonald, Tina

    2009-01-01

    Dissociative amnesia that encompasses one's entire life and identity is a rare disorder, as is dissociative fugue. In evaluating such cases, a dichotomy is often invoked between functional and organic etiologies. However, this dichotomy suffers from both conceptual and ethical flaws. Conceptually, putative brain-based, organic etiologies for many dissociative disorders-including dissociative amnesia-exist. Ethically, such dichotomies may result in dismissive care for patients with distress-based disorders like dissociative amnesia. In support of humane, neurobiologically informed treatment of patients with dissociative amnesia, we present excerpts from 2 post-event interviews with a patient who suffered and recovered from an episode of dissociative amnesia and fugue. Following this, we review current neurobiological models of dissociative amnesia that undermine the dichotomy of functional versus organic, and suggest that the crucial distinction in such cases is between a patient's willful, conscious deceit and processes that occur without conscious intent. PMID:19821177

  12. Theoretical shaping of femtosecond laser pulses for ultrafast molecular photo-dissociation with control techniques based on time-dependent density functional theory.

    PubMed

    Castro, Alberto

    2013-05-10

    The combination of time-dependent density functional theory and quantum optimal control formalism is used to optimize the shape of ultra-short laser pulses in order to achieve the photodissociation of the hydrogen molecule. The very short pulse durations used in this work (a few femtoseconds) do not allow for significant nuclear movement during irradiation, and thus the dissociation mechanism is sequential. During pulse irradiation, a large sudden momentum is communicated which can be understood in terms of population of excited, bound or unbound, dissociative electronic states. The target is defined in terms of the average opposing force during the action of the pulse, or equivalently, in terms of the final dissociative velocity. PMID:23532962

  13. Collisionally activated dissociation and electron capture dissociation of several mass spectrometry-identifiable chemical cross-linkers.

    PubMed

    Chowdhury, Saiful M; Munske, Gerhard R; Tang, Xiaoting; Bruce, James E

    2006-12-15

    One of the challenges in protein interaction studies with chemical cross-linking stems from the complexity of intra-, inter-, and dead-end cross-linked peptide mixtures. We have developed new cross-linkers to study protein-protein interactions with mass spectrometry to improve the ability to deal with this complexity. Even the accurate mass capabilities of FTICR-MS alone cannot unambiguously identify cross-linked peptides from cell-labeling experiments due to the complexity of these mixtures resultant from the enormous number of possible cross-linked species. We have developed novel cross-linkers that have unique fragmentation features in the gas phase. The characteristics of these cross-linkers combined with the accurate mass capability of FTICR-MS can help distinguish cross-linking reaction products and assign protein identities. These cross-linkers that we call protein interaction reporters (PIRs) have been constructed with two reactive groups attached through two bonds that can be preferentially cleaved by low-energy CID of the respective protonated precursor ions. After cleavage of the labile bonds, the middle part of the linker serves as a reporter ion to aid identification of cross-linked peptides. This report highlights three new PIRs with new features that have been developed to improve the efficiency of release of reporter ions. The new cross-linkers reported here were tuned with the addition of an affinity tag, a hydrophilic group, a photocleavable group, and new low-energy MS/MS cleavable bonds. This report presents our investigation of the MSMS fragmentation behavior of selected protonated ions of the new compounds. The comprehensive fragmentation of these PIRs and PIR-labeled cross-linked peptides with low-energy collisions and an example of electron capture dissociation in FTICR-MS is presented. These new cross-linkers will contribute to current systems biology research by allowing acquisition of global or large-scale data on protein

  14. Psychopharmacologic treatment of dissociative fugue and PTSD in an Ethiopian refugee.

    PubMed

    Liu-Barbaro, Dorothy; Stein, Murray

    2015-07-01

    Despite widespread awareness of their frequent co-occurrence, little is known about treatment of individuals with comorbid posttraumatic stress disorder (PTSD) and dissociative disorders. Patients with dissociative disorders do not respond well to standard exposure therapy, and few psychopharmacologic trials exist. Fluoxetine proved ineffective for depersonalization disorder, but paroxetine showed efficacy in decreasing dissociative symptoms in PTSD patients. PMID:26115334

  15. Evaluation of the Evidence for the Trauma and Fantasy Models of Dissociation

    ERIC Educational Resources Information Center

    Dalenberg, Constance J.; Brand, Bethany L.; Gleaves, David H.; Dorahy, Martin J.; Loewenstein, Richard J.; Cardena, Etzel; Frewen, Paul A.; Carlson, Eve B.; Spiegel, David

    2012-01-01

    The relationship between a reported history of trauma and dissociative symptoms has been explained in 2 conflicting ways. Pathological dissociation has been conceptualized as a response to antecedent traumatic stress and/or severe psychological adversity. Others have proposed that dissociation makes individuals prone to fantasy, thereby…

  16. A comparative study of Dissociative Ionization of N2 and CO

    NASA Astrophysics Data System (ADS)

    Pandey, Amrendra; Bapat, B.; Shamsundar, K. R.

    2014-04-01

    A comparative study on the properties of charge symmetric dissociation (CSD) and charge asymmetric dissociation (CAD) of doubly ionized N2 and CO is performed. Kinetic energy release (KER) distributions resulting from the dissociation of doubly charged molecular ions are explained on the basis of calculated potential energy curves.

  17. Neural Dissociation of Number from Letter Recognition and Its Relationship to Parietal Numerical Processing

    ERIC Educational Resources Information Center

    Park, Joonkoo; Hebrank, Andrew; Polk, Thad A.; Park, Denise C.

    2012-01-01

    The visual recognition of letters dissociates from the recognition of numbers at both the behavioral and neural level. In this article, using fMRI, we investigate whether the visual recognition of numbers dissociates from letters, thereby establishing a double dissociation. In Experiment 1, participants viewed strings of consonants and Arabic…

  18. Triplet Mediated C-N Dissociation versus Internal Conversion in Electronically Excited N-Methylpyrrole.

    PubMed

    Blancafort, Lluís; Ovejas, Virginia; Montero, Raúl; Fernández-Fernández, Marta; Longarte, Asier

    2016-04-01

    The photochemical and photophysical pathways operative in N-methylpyrrole, after excitation in the near part of its ultraviolet absorption spectrum, have been investigated by the combination of time-resolved total ion yield and photoelectron spectroscopies with high-level ab initio calculations. The results collected are remarkably different from the observations made for pyrrole and other aromatic systems, whose dynamics is dictated by the presence of πσ* excitations on X-H (X: N, O, S, ...) bonds. The presence of a barrier along the C-N dissociation coordinate that can not be tunneled triggers two alternative decay mechanisms for the S1 A″ πσ* state. While at low vibrational content the C-N dissociation occurs on the surface of a lower (3)ππ* state reached after efficient intersystem crossing, at higher excitation energies, the A″ πσ* directly internally converts to the ground state through a ring-twisted S1/S0 conical intersection. The findings explain previous observations on the molecule and may be relevant for more complex systems containing similar C-N bonds, such as the DNA nucleotides. PMID:26978190

  19. Mapping the Dissociative Ionization Dynamics of Molecular Nitrogen with Attosecond Time Resolution

    NASA Astrophysics Data System (ADS)

    Trabattoni, A.; Klinker, M.; González-Vázquez, J.; Liu, C.; Sansone, G.; Linguerri, R.; Hochlaf, M.; Klei, J.; Vrakking, M. J. J.; Martín, F.; Nisoli, M.; Calegari, F.

    2015-10-01

    Studying the interaction of molecular nitrogen with extreme ultraviolet (XUV) radiation is of prime importance to understand radiation-induced processes occurring in Earth's upper atmosphere. In particular, photoinduced dissociation dynamics involving excited states of N2 + leads to N and N+ atomic species that are relevant in atmospheric photochemical processes. However, tracking the relaxation dynamics of highly excited states of N2 + is difficult to achieve, and its theoretical modeling is notoriously complex. Here, we report on an experimental and theoretical investigation of the dissociation dynamics of N2+ induced by isolated attosecond XUV pulses in combination with few-optical-cycle near-infrared/visible (NIR/VIS) pulses. The momentum distribution of the produced N+ fragments is measured as a function of pump-probe delay with subfemtosecond resolution using a velocity map imaging spectrometer. The time-dependent measurements reveal the presence of NIR/VIS-induced transitions between N2 + states together with an interference pattern that carries the signature of the potential energy curves activated by the XUV pulse. We show that the subfemtosecond characterization of the interference pattern is essential for a semiquantitative determination of the repulsive part of these curves.

  20. Infrared Multiple-Photon Dissociation spectroscopy of group II metal complexes with salicylate

    SciTech Connect

    Ryan P. Dain; Gary Gresham; Gary S. Groenewold; Jeffrey D. Steill; Jos Oomens; Michael J. van Stipdonk

    2011-07-01

    Ion-trap tandem mass spectrometry with collision-induced dissociation, and the combination of infrared multiple-photon dissociation (IRMPD) spectroscopy and density functional theory (DFT) calculations were used to characterize singly-charged, 1:1 complexes of Ca2+, Sr2+ and Ba2+ with salicylate. For each metal-salicylate complex, the CID pathways are: (a) elimination of CO2 and (b) formation of [MOH]+ where M=Ca2+, Sr2+ or Ba2+. DFT calculations predict three minima for the cation-salicylate complexes which differ in the mode of metal binding. In the first, the metal ion is coordinated by O atoms of the (neutral) phenol and carboxylate groups of salicylate. In the second, the cation is coordinated by phenoxide and (neutral) carboxylic acid groups. The third mode involves coordination by the carboxylate group alone. The infrared spectrum for the metal-salicylate complexes contains a number of absorptions between 1000 – 1650 cm-1, and the best correlation between theoretical and experimental spectra for the structure that features coordination of the metal ion by phenoxide and the carbonyl group of the carboxylic acid group, consistent with calculated energies for the respective species.

  1. Defect creation via dissociative recombination of ionic centers in solid Ne matrices

    NASA Astrophysics Data System (ADS)

    Savchenko, E. V.; Khyzhniy, I. V.; Uyutnov, S. A.; Bludov, M. A.; Gumenchuk, G. B.; Bondybey, V. E.

    2016-05-01

    Recombination of the intrinsic ionic centers Ne2+ (self-trapped holes) with the detrapped electrons in solid Ne matrices and relaxation channels have been studied. The experiments were performed employing combination of the cathodoluminescence (CL) with current and optical activation spectroscopy techniques. CL spectra were recorded simultaneously in the VUV and visible range. Yields of spectrally resolved thermally and photon-stimulated luminescence (TSL, PSL) and thermally and photon-stimulated exoelectron emission (TSEE, PSEE) were measured in the time-correlated manner. It was found that the recombination reaction proceeds with irreversible dissociation of the transient Ne2∗∗ centers and the dissociative recombination (DR) products exit the matrix cage. Products of the DR reaction are found to be in 3s and 3p states. The detection of "defect" components in the TSL and PSL points to the defect formation via DR in Ne matrices. The temperature range of the electron traps stability is elucidated. A long-lasting "afteremission" of electrons and afterglow of VUV photons observed on switching off the irradiation suggest the accumulation of the uncompensated negative charge.

  2. Somatic and vicarious pain are represented by dissociable multivariate brain patterns

    PubMed Central

    Krishnan, Anjali; Woo, Choong-Wan; Chang, Luke J; Ruzic, Luka; Gu, Xiaosi; López-Solà, Marina; Jackson, Philip L; Pujol, Jesús; Fan, Jin; Wager, Tor D

    2016-01-01

    Understanding how humans represent others’ pain is critical for understanding pro-social behavior. ‘Shared experience’ theories propose common brain representations for somatic and vicarious pain, but other evidence suggests that specialized circuits are required to experience others’ suffering. Combining functional neuroimaging with multivariate pattern analyses, we identified dissociable patterns that predicted somatic (high versus low: 100%) and vicarious (high versus low: 100%) pain intensity in out-of-sample individuals. Critically, each pattern was at chance in predicting the other experience, demonstrating separate modifiability of both patterns. Somatotopy (upper versus lower limb: 93% accuracy for both conditions) was also distinct, located in somatosensory versus mentalizing-related circuits for somatic and vicarious pain, respectively. Two additional studies demonstrated the generalizability of the somatic pain pattern (which was originally developed on thermal pain) to mechanical and electrical pain, and also demonstrated the replicability of the somatic/vicarious dissociation. These findings suggest possible mechanisms underlying limitations in feeling others’ pain, and present new, more specific, brain targets for studying pain empathy. DOI: http://dx.doi.org/10.7554/eLife.15166.001 PMID:27296895

  3. Dissociation of cephamycin C and clavulanic acid biosynthesis by 1,3-diaminopropane in Streptomyces clavuligerus.

    PubMed

    Leite, Carla A; Cavallieri, André P; Baptista, Amanda S; Araujo, Maria L G C

    2016-01-01

    Streptomyces clavuligerus produces simultaneously cephamycin C (CephC) and clavulanic acid (CA). Adding 1,3-diaminopropane to culture medium stimulates production of beta-lactam antibiotics. However, there are no studies on the influence of this diamine on coordinated production of CephC and CA. This study indicates that 1,3-diaminopropane can dissociate CephC and CA productions. Results indicated that low diamine concentrations (below 1.25 g l(-1)) in culture medium increased CA production by 200%, but not that of CephC. Conversely, CephC production increased by 300% when 10 g l(-1) 1,3-diaminopropane was added to culture medium. Addition of just L-lysine (18.3 g l(-1)) to culture medium increased both biocompounds. On the other hand, while L-lysine plus 7.5 g l(-1) 1,3-diaminopropane increased volumetric production of CephC by 1100%, its impact on CA production was insignificant. The combined results suggest that extracellular concentration of 1,3-diaminopropane may trigger the dissociation of CephC and CA biosynthesis in S. clavuligerus. PMID:26564965

  4. State-specific Dissociation Rates for H2(v, j) + H2(v‧, j‧)

    NASA Astrophysics Data System (ADS)

    Mandy, M. E.

    2016-08-01

    State-specific rate coefficients for the dissociation of H2 as the result of collisions with H2 were calculated for all combinations of (v, j) with an internal energy below 1 eV. Full-dimensional quasiclassical trajectories were calculated using the BMKP2 interaction potential with a minimum of 80,000 trajectories at each translational energy. Additional large batches of trajectories were carried out to calculate the cross sections near the threshold to dissociation to attain the desired precision of the rate coefficients. A piecewise linear excitation function was used to calculate the rate coefficient between 100 and 100,000 K. The resulting state-specific rate coefficients, γ, were parametrized as a function of temperature over the range 600–10,000 K using: {{log}}10 γ (t)=a+{bz}+{{cz}}2-d≤ft(\\displaystyle \\frac{1}{t}-1\\right) where t=T/4500 K and z={{log}}10 t. The values of the resulting rate coefficients were sensitive to the internal energy of both molecules, with initial vibrational energy having a slightly greater effect than rotational energy. This effect diminished as temperature increased.

  5. Complexity and Chaos Theories as Potential Paradigms for Understanding and Treating Dissociative Disorders.

    NASA Astrophysics Data System (ADS)

    Drinkard, Lynne Bradford

    1995-01-01

    Early systems theory was a precursor of complexity theory, a global theory that suggests that the universe is an open system interacting on many dimensions. Chaos theory, a subset of complexity theory, states that in seeming chaos there is an underlying order. Between chaos and order lies emergence, from which healthy growth and change occur. Twenty years ago, chaos theory did not have a name and dissociative disorders were largely written off as rare or more imaginative than real. After physicists and mathematicians explained chaos and complexity in language understood by those outside their fields, scientists and practitioners from disparate disciplines were struck by the potential for applying the theories to their respective fields. Complexity and chaos theory combine reductionistic and holistic approaches to explain phenomena. Many mental health practitioners have suggested that a systems framework based in complexity theory may lead to greater understanding of human nature and ultimately toward more effective treatment of different disorders. This paper proposes that complexity and chaos theories may offer insight into the efficacy of various treatments for dissociative disorders.

  6. Roles of acetone and diacetone alcohol in coordination and dissociation reactions of uranyl complexes.

    PubMed

    Rios, Daniel; Schoendorff, George; Van Stipdonk, Michael J; Gordon, Mark S; Windus, Theresa L; Gibson, John K; de Jong, Wibe A

    2012-12-01

    Combined collision-induced dissociation mass spectrometry experiments with DFT and MP2 calculations were employed to elucidate the molecular structures and energetics of dissociation reactions of uranyl species containing acetone and diacetone alcohol ligands. It is shown that solutions containing diacetone alcohol ligands can produce species with more than five oxygen atoms available for coordination. Calculations confirm that complexes with up to four diacetone alcohol ligands can be energetically stable but that the effective number of atoms coordinating with uranium in the equatorial plane does not exceed five. Water elimination reactions of diacetone alcohol ligands are shown to have two coordination-dependent reaction channels, through formation of mesityl oxide ligands or formation of alkoxide and protonated mesityl oxide species. The present results provide an explanation for the implausible observation of "[UO(2)(ACO)(6,7,8)](2+)" in and observed water-elimination reactions from purportedly uranyl-acetone complexes (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem. 2011, 50, 4781). PMID:23146003

  7. Electromagnetic dissociation of relativistic sup 28 Si into p + sup 27 Al

    SciTech Connect

    Barrette, J.; Bellwied, R.; Braun-Munzinger, P.; Cleland, W.E.; David, G.; Dee, J.; Dietzsch, O.; Duek, E.; Fatyga, M.; Fox, D.; Greene, S.V.; Hall, J.R.; Hemmick, T.K.; Herrmann, N.; Hogue, R.W.; Hong, B.; Jayananda, K.; Kraus, D.; Shiva Kumar, B.; Lacasse, R.; Lissauer, D.; Llope, W.J.; Ludlam, T.; Majka, R.; Makowiecki, D.; Mark, S.K.; McCorkle, S.; Mitchell, J.T.; Muthuswamy, M.; O'Brien, E.; Polychronakos, V.; Pruneau, C.; Rotondo, F.S.; Sandweiss, J.; Simon-Gillo, J.; Sonnadara, U.; Stachel, J.; Takai, H.; Takagui, E.M.; Throwe, T.G.; Waters, L.; Willis, W.J.; Winter, C.; Wolf, K.; Wolfe, D.; Woody, C.L.; Xu, N.; Zhang, Y.; Zhang, Z.; Zou, Z. European Organization for Nuclear Research , Geneva Los Alamos National Laboratory, Los Alamos, New Mexico 87545 McGill University, Montreal, Quebec, H3A 2K6 University of New Mexico, Albuquerque, New Mexico 87131

    1992-05-01

    We report a direct measurement of the final-state energy spectrum in the electromagnetic dissociation of {sup 28}Si into {ital p}+ {sup 27}Al at an energy of 14.6 GeV/nucleon. The final-state energy is obtained through a calculation of the {ital p}-{sup 27}Al invariant mass in kinematically reconstructed events. The final-state energy spectrum for all targets is peaked near the isovector giant-dipole resonance in {sup 28}Si and the dependence of the magnitude of the cross section on target charge confirms that the excitation is largely electromagnetic. By exploiting the expected scaling behavior on target {ital Z} and {ital A}, the background from nuclear interactions is evaluated and subtracted, leaving a pure electromagnetic dissociation final-state energy distribution. This distribution is well reproduced by simulated events, in which the photon spectrum calculated in the Weiszaecker-Williams approximation is combined with experimental data on the photonuclear reaction {sup 28}Si({gamma},{ital p}) {sup 27}Al, and slight differences are observed only at low final-state energy.

  8. The simultaneous determination of hydrophobicity and dissociation constant by liquid chromatography-mass spectrometry.

    PubMed

    Wiczling, P; Struck-Lewicka, W; Kubik, L; Siluk, D; Markuszewski, M J; Kaliszan, R

    2014-06-01

    Convenient methods for testing drug candidates' lipophilicity and acidity are highly requested in modern pharmaceutical research and drug development strategies. Reversed-phase high-performance liquid chromatography (RP HPLC) might be particularly useful for the determination of both dissociation constant and the (pH-dependent) partition coefficient related parameters, applicable in high-throughput analysis of multi-component mixtures. The general theory of combined pH/organic modifier gradient has recently provided equations relating gradient retention time and pH of the mobile phase. The purpose of this work was to facilitate the identification of analytes in this technique by its transfer to RP HPLC coupled with time-of-flight mass spectrometry with electrospray ionization source (ESI-TOF-MS). The accuracy of the proposed methodology was assessed by analyzing a set of known drugs. The ammonium formate, ammonium acetate or ammonium bicarbonate buffers were used to control pH during chromatographic analysis. In result, the pKa and hydrophobicity parameters were determined and the accuracy of the estimated values was assessed by comparing them with literature data. The gradient RP HPLC coupled with ESI-TOF-MS methods allowed for the rapid determination of dissociation constant and hydrophobicity and was shown to be especially applicable for complex mixtures. The use of ESI-TOF-MS detection allowed to achieve the medium-throughput screening rate (100 compounds/day) and provided a simple approach to assess pharmacokinetically important physicochemical properties of drugs. PMID:24598171

  9. Dissociation of multicharged CO molecular ions produced in collisions with 97-MeV Ar14+: Dissociation fractions and branching ratios

    NASA Astrophysics Data System (ADS)

    Wohrer, K.; Sampoll, G.; Watson, R. L.; Chabot, M.; Heber, O.; Horvat, V.

    1992-10-01

    Data on the production and dissociation of COQ+ molecular ions (where Q=1 through 7) obtained by ion-ion coincidence time-of-flight measurements were analyzed to determine production yields, dissociation fractions, and branching ratios. A detailed comparison of the dissociation fractions for CO+ and CO2+ for several collision systems in the same perturbative regime revealed them to be quite similar, whereas the dissociation fraction for CO+ produced by valence-electron photoionization is a factor of 1.8 to 3.6 larger. The results for Q>=2 indicated a preference for dissociation channels leading to symmetric or nearly symmetric charge division. An enhancement of the total ionization yields for Q>4 was observed, and it suggests that electron transfer followed by LMM Auger decay plays an important role in determining the final charges of the dissociation products.

  10. Analytical studies of hypersonic viscous dissociated flows

    NASA Technical Reports Server (NTRS)

    Inger, George R.

    1995-01-01

    This project primarily dealt with integral boundary-layer solution techniques that are directly applicable to the problem of determining aerodynamic heating rates of hypersonic vehicles like X-33 in the vicinity of stagnation points, windward centerlines, and swept-wing leading edges. The analyses include effects of finite-rate gas chemistry across the boundary layer and finite-rate catalysis of atom recombination at the surface. A new approach for combining the insight afforded by integral boundary-layer analysis with comprehensive (and expensive) computational fluid dynamic (CFD) flowfield solutions of the thin-layer Navier-Stokes equations was developed. The approach extracts CFD derived quantities at the wall and at the boundary layer edge for inclusion in a post-processing boundary-layer analysis. The post-processed data base allows a designer at a workstation to ask and answer the following questions: (1) How much does the heating change if one uses a thermal protection system (TPS) with different catalytic properties than was used in the original CFD solution? (2) How does the heating change when one moves the interface of two different TPS materials with different catalytic efficiencies for the purpose of reducing vehicle weight and expense? The answer to the second question is particularly critical, because abrupt changes from low catalytic efficiency to high catalytic efficiency can lead to localized increase in heating which exceeds the usually conservative estimate provided by a fully catalytic wall assumption. A secondary issue that was addressed involves the prediction of heating levels in the vicinity of sharp corners that are transverse to or aligned with the flow. An example of the first case is heating at the edge of the COMET reentry module. An example of the second case is heating along the side edge of a deflected body flap on an SSV. The difficulty of putting grids in the vicinity of such corners with continuously varying metric coefficients

  11. Ionization and dissociation dynamics of molecules in strong laser fields

    NASA Astrophysics Data System (ADS)

    Lai, Wei

    The fast advancement of ultrashort-pulsed high-intensity laser technology allows for generating an electric field equivalent to the Coulomb field inside an atom or a molecule (e.g., EC=5.14x109 V/cm at the 1s orbit radius a0=0.0529 nm of the hydrogen atom, which corresponds to an intensity of 3.54x1016 W/cm2). Atoms and molecules exposed in such a field will easily be ionized, as the external field is strong enough to remove the electrons from the core. This is usually referred to "strong field". Strong fields provide a new tool for studying the interaction of atoms and molecules with light in the nonlinear nonperturbative regime. During the past three decades, significant progress has been made in the strong field science. Today, most phenomena involving atoms in strong fields have been relatively well understood by the single-active-electron (SAE) approximation. However, the interpretation of these responses in molecules has encountered great difficulties. Not like atoms that only undergo excitation and ionization, various dissociation channels accompanying excitation and ionization can occur in molecules during the laser pulse interaction, which imparts further complexity to the study of molecules in strong fields. Previous studies have shown that molecules can behave significantly different from rare gas atoms in phenomena as simple as single and double ionization. Molecular dissociation following ionization also presents challenges in strong fields compared to what we have learned in the weak-field regime. This dissertation focuses on experimental studies on ionization and dissociation of some commonly-seen small molecules in strong laser fields. Previous work of molecules in strong fields will be briefly reviewed, particularly on some open questions about multiple dissociation channels, nonsequential double ionization, enhanced ionization and molecular alignment. The identification of various molecular dissociation channels by recent experimental technical

  12. Potential function and dissociation energy of alkali halide

    NASA Astrophysics Data System (ADS)

    Srivastava, Abhay P.; Pandey, Anjani K.; Pandey, Brijesh K.

    2016-05-01

    Dissociation energy of some alkali halides have been calculated by using different interaction potential function such as Born-Mayer, Varshani-Shukla and L5 potential model. The theoretical calculation is compared with experimental values. The Result shows that the values of dissociation energy as calculated by using different potential models have an equal amount of deviation with experimental values. The above said deviation with experimental values can be explained by consideration of rotational-vibrational coupling between the constituents of molecules in the limelight of molecular spectroscopy. Findings of present work suggest that the existing potential model need to be reviewed in view of the correction factors solely depending on the rotational, vibrational and electronic coupling between the constituents of molecules.

  13. Rate coefficients for N2(+)(v) dissociative recombination

    NASA Astrophysics Data System (ADS)

    Bates, D. R.; Mitchell, J. B. A.

    1991-09-01

    The data of Zipf (1980) on N2(+)(v) dissociative recombination are analyzed taking into account the fact that there is coupling due to reversible symmetrical resonance charge transfer, N2(+)(v) + N2(0) yields N2(+)(0) + N2(v). The vibrational deactivation in N2(+)(v)-Ne collisions is also considered. A reported experimental value of the vibrational deactivation coefficient is found to be much higher than can be reconciled with the results of Zipf and it is therefore rejected. The analysis shows that the recombination coefficient for N2(+)(0) is about 2.6 x 10 exp-7 cu cm/s at 300 K and that recombination coefficients for N2(+)(1) and N2(+)(2) are substantially smaller. It is concluded that these coefficients conflict with the dissociative recombination cross section vs energy curve obtained by the merged beam method.

  14. Accurate bond dissociation energies (D 0) for FHF- isotopologues

    NASA Astrophysics Data System (ADS)

    Stein, Christopher; Oswald, Rainer; Sebald, Peter; Botschwina, Peter; Stoll, Hermann; Peterson, Kirk A.

    2013-09-01

    Accurate bond dissociation energies (D 0) are determined for three isotopologues of the bifluoride ion (FHF-). While the zero-point vibrational contributions are taken from our previous work (P. Sebald, A. Bargholz, R. Oswald, C. Stein, P. Botschwina, J. Phys. Chem. A, DOI: 10.1021/jp3123677), the equilibrium dissociation energy (D e ) of the reaction ? was obtained by a composite method including frozen-core (fc) CCSD(T) calculations with basis sets up to cardinal number n = 7 followed by extrapolation to the complete basis set limit. Smaller terms beyond fc-CCSD(T) cancel each other almost completely. The D 0 values of FHF-, FDF-, and FTF- are predicted to be 15,176, 15,191, and 15,198 cm-1, respectively, with an uncertainty of ca. 15 cm-1.

  15. Tunneling, diffusion, and dissociation of Feshbach molecules in optical lattices

    NASA Astrophysics Data System (ADS)

    Bailey, Taylor; Bertulani, Carlos A.; Timmermans, Eddy

    2012-03-01

    The quantum dynamics of an ultracold diatomic molecule tunneling and diffusing in a one-dimensional optical lattice exhibits unusual features. While it is known that the process of quantum tunneling through potential barriers can break up a bound-state molecule into a pair of dissociated atoms, interference and reassociation produce intricate patterns in the time-evolving site-dependent probability distribution for finding atoms and bound-state molecules. We find that the bound-state molecule is unusually resilient against break up at ultralow binding energy Eb (Eb much smaller than the barrier height of the lattice potential). After an initial transient, the bound-state molecule spreads with a width that grows as the square root of time. Surprisingly, the width of the probability of finding dissociated atoms does not increase with time as a power law.

  16. Dissociation of gaseous zwitterion glycine-betaine by slow electrons.

    PubMed

    Kopyra, J; Abdoul-Carime, H

    2010-05-28

    In this work, we investigate dissociation processes induced by low-energy electrons to gas phase N,N,N-trimethylglycine [glycine-betaine, (CH(3))(3)N(+)CH(2)COO(-)] molecules. Glycine-betaine represents a model system for zwitterions. All negative fragments are observed to be produced only at subelectronic excitation energies (<4 eV). With the exception of the loss of a neutral H atom that could arise from any C[Single Bond]H bond breaking, we tentatively suggest that the zwitterion dissociates exclusively from the fragmentation of the cation site of the molecule, subsequent to the attachment of the excess electron. Within the context of radiation induced damage to biological systems, the present findings contribute to a more complete description of the fragmentation mechanism occurring to amino acids, peptides, and proteins since they adopt usually a zwitterion structure. PMID:20515090

  17. Water dissociation on silica in the presence of atomic platinum

    NASA Astrophysics Data System (ADS)

    Klett, Joachim; Elger, Benjamin; Krähling, Stephan; Kaiser, Bernhard; Jaegermann, Wolfram; Schäfer, Rolf

    2016-07-01

    We have investigated the adsorption of water on well-defined silica and silica/Pt interfaces by synchrotron X-Ray Photoelectron Spectroscopy (SXPS). For that purpose silica surfaces grown on Si have been covered with atomic platinum in order to facilitate water dissociation. Water was adsorbed from the gas phase at cryogenic temperatures and its dissociation was observed on clean and platinum coated surfaces. After desorption the adsorbed hydroxides decompose on the blank surface, whereas the hydroxides remain stable if the surface was modified with platinum. The principal reversibility of the hydroxylation process implies the necessity of point defects in order to stabilize hydroxides on well-ordered silica surfaces. Deposited platinum atoms are able to stabilize hydroxides in their proximity and act as an acceptor state on the silica surface.

  18. Developmental dissociation in morphological evolution of the stickleback opercle

    PubMed Central

    Kimmel, Charles B.; Ullmann, Bonnie; Currey, Mark; Hohenlohe, Paul A.; Cresko, William A.

    2012-01-01

    SUMMARY Oceanic threespine sticklebacks have repeatedly and independently evolved new morphologies upon invasions of freshwater habitats. A consistent derived feature of the freshwater form across populations and geography is a shape change of the opercle, a large early developing facial bone. We show that the principal multivariate axis describing opercle shape development from the young larva to the full adult stage of oceanic fish matches the principal axis of evolutionary change associated with relocation from the oceanic to freshwater habitat. The opercle phenotype of freshwater adults closely resembles the phenotype of the bone in juveniles. Thus evolution to the freshwater condition is in large part by truncation of development; the freshwater fish do not achieve the full ancestral adult bone shape. Additionally, the derived state includes dissociated ontogenetic changes. Dissociability may reflect an underlying modular pattern of opercle development, and facilitate flexibility of morphological evolution. PMID:22765204

  19. Charmonium dissociation in matter: perspectives from CERN to Jlab

    SciTech Connect

    A. Sibirtsev

    2010-07-01

    The J/Psi-meson dissociation in nuclear matter remains one of the most surprising problems in physics. In 2000 the NA50 Collaboration at CERN reported anomalous results on J/Psi absorption that was considered as evidence of Quark-Gluon Plasma formation. On the other hand, there may be other mechanisms which produce an increase in J/Psi absorption in a hot dense medium due to the modification of the charm mesons. Our detailed calculations were one of the first indications that the CERN data can indeed be well explained by a mechanism different from QGP formation. For further clarification we proposed to study the modification of charm in nuclei through antiproton annihilation, which is now part of the PANDA project at FAIR GSI. The experiment on charmonium dissociation in nuclei is under discussion at JLab as part of its 12 GeV upgrade.

  20. Does Infrared Multiphoton Dissociation of Vinyl Chloride Yield Cold Vinylidene?

    PubMed

    Fernando, Ravin; Qu, Chen; Bowman, Joel M; Field, Robert W; Suits, Arthur G

    2015-07-01

    Velocity map imaging of the infrared multiphoton dissociation of vinyl chloride shows the formation of HCl in rotational levels below J = 10 that are associated with the three-center elimination pathway. The total translational energy release is observed to peak at 3-5 kcal/mol, which is consistent with the low reverse barrier predicted for the formation of HCl with vinylidene coproducts. Direct dynamics trajectory studies from the three-center transition state reproduce the observed distributions and show that the associated vinylidene is formed with only modest rotational excitation, precluding Coriolis-induced mixing among the excited vibrational levels of acetylene that would lead to distribution of vinylidene character into many vibrationally mixed acetylene vibrational levels. The results suggest that infrared multiphoton dissociation of vinyl chloride is an efficient route to synthesis of stable, cold vinylidene. PMID:26266719

  1. Possession experiences in dissociative identity disorder: a preliminary study.

    PubMed

    Ross, Colin A

    2011-01-01

    Dissociative trance disorder, which includes possession experiences, was introduced as a provisional diagnosis requiring further study in the Diagnostic and Statistical Manual of Mental Disorders (4th ed.). Consideration is now being given to including possession experiences within dissociative identity disorder (DID) in the Diagnostic and Statistical Manual of Mental Disorders (5th ed.), which is due to be published in 2013. In order to provide empirical data relevant to the relationship between DID and possession states, I analyzed data on the prevalence of trance, possession states, sleepwalking, and paranormal experiences in 3 large samples: patients with DID from North America; psychiatric outpatients from Shanghai, China; and a general population sample from Winnipeg, Canada. Trance, sleepwalking, paranormal, and possession experiences were much more common in the DID patients than in the 2 comparison samples. The study is preliminary and exploratory in nature because the samples were not matched in any way. PMID:21667381

  2. The Concept of Peritraumatic Dissociation: A Qualitative Approach.

    PubMed

    Mattos, Patrícia Ferreira; Pedrini, João Alencar; Fiks, José Paulo; de Mello, Marcelo Feijó

    2016-06-01

    Peritraumatic dissociation has been considered an important feature for the development of post-traumatic stress disorders, but this concept remains widely unclear. To explore the peritraumatic experience, we interviewed eight victims of urban violence shortly after their traumatic events. The data collected were compared and analyzed according to the systematic set of procedures of Grounded Theory (GT). The alterations reported by participants were coded and categorized according to their perceptions of their inner and outer world, and the impressions of others involved, including the examiner's observations. The theoretical perspective for interpreting this study has parallels with Jaspers' psychopathology. Peritraumatic dissociation was conceived as a failure of synthesis among emerging stimuli from the internal and the external world, including the time-space flow structure, even when cognitive-perceptual tools remain intact. This synthesis qualifies the totality of the perceptual experience as coherent and meaningful to conscience, enabling possibilities for being/existing. PMID:26531878

  3. Dissociating neural mechanisms of temporal sequencing and processing phonemes.

    PubMed

    Gelfand, Jenna R; Bookheimer, Susan Y

    2003-06-01

    Using fMRI, we sought to determine whether the posterior, superior portion of Broca's area performs operations on phoneme segments specifically or implements processes general to sequencing discrete units. Twelve healthy volunteers performed two sequence manipulation tasks and one matching task, using strings of syllables and hummed notes. The posterior portion of Broca's area responded specifically to the sequence manipulation tasks, independent of whether the stimuli were composed of phonemes or hummed notes. In contrast, the left supramarginal gyrus was somewhat more specific to sequencing phoneme segments. These results suggest a functional dissociation of the canonical left hemisphere language regions encompassing the "phonological loop," with the left posterior inferior frontal gyrus responding not to the sound structure of language but rather to sequential operations that may underlie the ability to form words out of dissociable elements. PMID:12797966

  4. Threshold collision induced dissociation experiment for azobenzene and its derivatives

    NASA Astrophysics Data System (ADS)

    Rezaee, Mohammadreza; Compton, Robert

    In this study we investigated protonated azobenzene cation and properties of trans 2,2',6,6'-tetrafluoroazobenzene anion using the collision induced dissociation method and the results are compared with the results from ab initio electronic structure calculations. We measured the bond dissociation energies experimentally and found which theoretical quantum chemistry methods yield best results. Several high accuracy multi-level calculations such as CBS-QB3, G3 and G4 had been carried out to obtain reliable thermochemical information for azobenzene and several of its derivatives and their anion or cation. We also performed other experiments such as Raman spectroscopy to study these light sensitive molecules with promising applications such as photo-switching.

  5. Dissociated vertical deviation-a clinical and laboratory study.

    PubMed Central

    Helveston, E M

    1980-01-01

    The previously reported nomenclature and clinical characteristics of dissociated vertical deviation have been recorded. The incidence and characteristics of DVD have been determined by evaluation of 1,000 consecutive strabismus or nystagmus patients, and with selected chart study carried out on the 111 DVD patients found in this series. Electro-oculographic studies of selected patients with DVD provided objective evidence of the speed and amplitude of the ocular movements in DVD. Bell phenomenon, strabismus sursoadductorius and the Bielschowsky phenomenon were recorded and compared to clinical findings of strabismus patients with DVD. The technique for the results of surgery for DVD were described. Dissociated vertical deviation was characterized as a component of the overall strabismus picture. Images FIGURE 1 A FIGURE 1 B FIGURE 1 C FIGURE 1 D FIGURE 1 E FIGURE 2 A FIGURE 2 B FIGURE 2 C FIGURE 3 A FIGURE 3 B FIGURE 3 C FIGURE 4 A FIGURE 4 B PMID:7020216

  6. Dissociation rates of diatomic molecules. Final report, 15 September 1985-15 May 1992

    SciTech Connect

    Cosby, P.C.; Helm, H.

    1992-12-01

    Absolute cross sections were measured for the electron-impact dissociation of simple molecules using a novel fast beam technique with multicoincident detection of the dissociation fragments. Translational energy released in the dissociation and product mass ratios were explicitly measured, allowing a detailed understanding of the dissociation mechanisms. The technique was applied to the molecules of nitrogen, oxygen, carbon monoxide, carbon dioxide, nitrogen dioxide, chlorine, and other molecules. A detailed description of the measurement technique is presented together with the measured data.... Dissociation, electron impact, cross sections, nitrogen, oxygen, carbon monoxide, carbon dioxide, nitrogen dioxide, chlorine.

  7. Collisionless dissociation of SF6 using two resonant frequency CO2 laser fields

    NASA Technical Reports Server (NTRS)

    Gower, M. C.; Gustafson, T. K.

    1977-01-01

    The collisionless dissociation of SF6 has been studied using simultaneous irradiation by two frequencies from a CO2 laser which are both nearly resonant with the SF6nu3 absorption band. It was found that the dissociation was enhanced, and occurred over a wider frequency range, than for single frequency dissociation. No threshold effect was observed for a weak resonant and a much higher energy field pumping slightly off-resonance. For such two frequency irradiation, the peak in the dissociation curve was found to be shifted to lower frequencies with respect to that for single frequency dissociation.

  8. Dissociative experiences in obsessive-compulsive disorder and trichotillomania: clinical and genetic findings.

    PubMed

    Lochner, Christine; Seedat, Soraya; Hemmings, Sian M J; Kinnear, Craig J; Corfield, Valerie A; Niehaus, Dana J H; Moolman-Smook, Johanna C; Stein, Dan J

    2004-01-01

    A link between dissociation proneness in adulthood and self-reports of childhood traumatic events (including familial loss in childhood, sexual/physical abuse and neglect) has been documented. Several studies have also provided evidence for an association between dissociative experiences and trauma in patients with various psychiatric disorders, including post-traumatic stress disorder, borderline personality, dissociative identity and eating disorders. Based on the relative paucity of data on dissociation and trauma in obsessive-compulsive disorder (OCD) and trichotillomania (TTM), the primary objective of this study was to examine the relationship between trauma and dissociative experiences (DE) in these two diagnostic groups. Furthermore, the availability of clinical and genetic data on this sample allowed us to explore clinical and genetic factors relevant to this association. A total of 110 OCD and 32 TTM patients were compared with respect to the degree of dissociation (using the Dissociative Experiences Scale [DES]) and childhood trauma (using the Childhood Trauma Questionnaire [CTQ]). Patients were classified on the DES as either "high" (mean DES score >/= 30) or "low" (mean DES score < 30) dissociators. Additional clinical and genetic factors were also explored with chi-square and t tests as appropriate. A total of 15.8% of OCD patients and 18.8% of TTM patients were high dissociators. OCD and TTM groups were comparable on DES and CTQ total scores, and in both OCD and TTM groups, significant positive correlations were found between mean DES scores and mean CTQ subscores of emotional abuse, physical abuse, sexual abuse, and physical neglect. In the OCD group, high dissociators were significantly younger than low dissociators, and significantly more high dissociators than low dissociators reported a lifetime (current and past) history of tics (P <.001), Tourette's syndrome (P =.019), bulimia nervosa (P =.003), and borderline personality disorder (P =.027

  9. Dislocation dissociation in some f.c.c. metals

    NASA Technical Reports Server (NTRS)

    Esterling, D. M.

    1980-01-01

    The dissociation of a perfect screw dislocation into a stacking fault in an f.c.c. lattice is modeled by the modified lattice statics. The interatomic potentials are obtained from the work of Esterling and Swaroop and differ substantially from those empirical potentials usually employed in defect simulations. The calculated stacking fault widths for aluminum, copper, and silver are in good agreement with weak beam microscopy results.

  10. DNA sequence of the maize transposable element Dissociation.

    PubMed

    Döring, H P; Tillmann, E; Starlinger, P

    The DNA sequence of the terminal 4.2 kilobases (kb) of the 30-kb insertion in the endosperm sucrose synthase gene of maize mutant sh-m5933 shows that it comprises two identical 2,040-base pair (bp) segments, one inserted in the reverse direction into the other. We suggest that the 2,040-bp sequence is an example of the transposable element Dissociation described by Barbara McClintock. PMID:6318121

  11. A perfusion chamber for physiological studies with acutely dissociated neurons.

    PubMed

    Wonderlin, W F; Weinreich, D

    1987-11-01

    We describe a recording chamber that immobilizes acutely dissociated neurons on an ultra-fine mesh grid positioned above a moving stream of perfusate. This chamber is easily fabricated and has two attributes for single-electrode voltage-clamp or patch-clamp recording: (1) shallow immersion (less than 20 micron) of the neurons, and (2) stable recording with rapid perfusion rates. PMID:3695568

  12. Projectile and Lab Frame Differential Cross Sections for Electromagnetic Dissociation

    NASA Technical Reports Server (NTRS)

    Norbury, John W.; Adamczyk, Anne; Dick, Frank

    2008-01-01

    Differential cross sections for electromagnetic dissociation in nuclear collisions are calculated for the first time. In order to be useful for three - dimensional transport codes, these cross sections have been calculated in both the projectile and lab frames. The formulas for these cross sections are such that they can be immediately used in space radiation transport codes. Only a limited amount of data exists, but the comparison between theory and experiment is good.

  13. Rotamers and Migration: Investigating the Dissociative Photoionization of Ethylenediamine.

    PubMed

    Muller, Giel; Voronova, Krisztina; Sztáray, Bálint; Meloni, Giovanni

    2016-06-01

    The unimolecular dissociation of energy-selected ethylenediamine cations was studied by threshold photoelectron photoion coincidence spectroscopy (TPEPICO) in the photon energy range of 8.60-12.50 eV. Modeling the breakdown diagram and time-of-flight distributions with rigid activated complex RRKM theory yielded 0 K appearance energies for eight dissociation channels, leading to NH2CHCH2(+)(•) at 9.120 ± 0.010 eV, CH3C(NH2)2(+) at 9.200 ± 0.012 eV, NH2CHCH3(+) at 9.34 ± 0.08 eV, CH2NH2(+) at 9.449 ± 0.025 eV, CH2NH3(+) at 9.8 ± 0.1 eV, c-C2H4NH2(+) at 10.1 ± 0.1 eV, CH3NHCHCH2(+) at 10.2 ± 0.1 eV, and the reappearance of CH2NH2(+) at 10.2 ± 0.1 eV. The CBS-QB3-calculated pathways highlighted the influence of intramolecular hydrogen attractions on the dissociation processes, presenting novel isomers and low-energy van der Waals intermediates that led to fragments in good agreement with experimental results. While most of the dissociation channels take place through reverse barriers, the 0 K heat of formation of (•)CH2NH2 was determined to be 147.6 ± 3.7 kJ mol(-1), in excellent agreement with literature, and the 0 K heat of formation of CH2NH3(+) at 844 ± 10 kJ mol(-1) is the first experimentally measured value available and is in good agreement with theory. PMID:27177327

  14. [Dissociating between Enhancing and Impairing Effects of Emotion on Cognition].

    PubMed

    Dolcos, Florin; Denkova, Ekaterina

    2016-01-01

    Objectives Emerging evidence suggests that emotion can have both enhancing and impairing effects on various cognitive processes. These opposing effects can be identified at different levels, both within the same cognitive process and across different processes, as well as at more general levels, such as in the case of the response to stress. The aim of the present review is to discuss recent advances in the mechanisms underlying the enhancing and impairing effects of emotion on different aspects within the same process (e.g., episodic memory) and across specific cognitive processes (perception vs. episodic memory, working memory vs. episodic memory), as well as in the context of the response to stress.Emerging Evidence The available evidence points to a number of aspects that dissociate the opposing effects of emotion on cognition. (i) Opposing effects within episodic memory can be attributed to different accounts, involving dissociation at different levels: central vs. peripheral trade-off, high vs. low prioritization of information processing, and items encoding vs. the formation of complex associations. (ii) The opposing effects across cognitive processes, such as perception and episodic memory, can be linked to dissociation between immediate/impairing vs. long-term/enhancing effects, which are mediated by common and dissociable neural mechanisms, involving bottom-up and top-down processes. (iii) Finally, in the larger context of the response to stress, emotional stress can lead to opposing effects depending on the degree, context, and controllability of the stressors.Conclusions Overall, the present review highlights the need to consider the various factors that can influence enhancing or impairing effects of emotion on cognition, in studies investigating emotion-cognition interactions. These issues are important for understanding mechanisms of emotion-cognition interactions not only in healthy functioning but also in emotional disturbances, where these

  15. Dissociation dynamics of core excited N[sub 2]O

    SciTech Connect

    LeBrun, T. DRECAM, SPAM, CEA, CEN Saclay, 9119, Gif sur Yvette Cedex Physics Division, Argonne National Laboratory, Argonne, Illinois 60439 ); Lavollee, M. ); Simon, M.; Morin, P. DRECAM, SPAM, CEA, CEN Saclay, 9119, Gif sur Yvette Cedex )

    1993-02-15

    Fragmentation of N[sub 2]O after selective core excitation of terminal and central nitrogen, has been studied by a multicoincidence technique (PEPIPICO) using synchrotron radiation. We show that dissociation dynamics is dependent upon the excited site, especially in the case of the atomization'' of the molecule. The central nitrogen is always found with very little kinetic energy, except after Nt[r arrow][Pi]* transition. A bent intermediate geometry is proposed to explain this observation.

  16. Numerical simulation of unsteady flows generated by dissociating nitrogen diffusion

    NASA Technical Reports Server (NTRS)

    Marraffa, Lionel; Dulikravich, George S.; Deiwert, George S.

    1989-01-01

    An explicit time accurate predictor-corrector scheme, similar to MacCormack's, has been used to simulate unsteady nonequilibrium laminar chemically-reacting diffusion-reaction generated flows. A zonal approach, along with nonstructured boundaries, allows computation of internal and external flow with the same computer code. Results for equilibrium flows generated by dissociating, vibrationally relaxing nitrogen in a rectangular chamber are presented. The unsteady flows were generated strictly by the chemical reactions and concentration gradients.

  17. Observation of Color-Transparency in Diffractive Dissociation of Pions

    NASA Astrophysics Data System (ADS)

    Aitala, E. M.; Amato, S.; Anjos, J. C.; Appel, J. A.; Ashery, D.; Banerjee, S.; Bediaga, I.; Blaylock, G.; Bracker, S. B.; Burchat, P. R.; Burnstein, R. A.; Carter, T.; Carvalho, H. S.; Copty, N. K.; Cremaldi, L. M.; Darling, C.; Denisenko, K.; Devmal, S.; Fernandez, A.; Fox, G. F.; Gagnon, P.; Gerzon, S.; Gobel, C.; Gounder, K.; Halling, A. M.; Herrera, G.; Hurvits, G.; James, C.; Kasper, P. A.; Kwan, S.; Langs, D. C.; Leslie, J.; Lichtenstadt, J.; Lundberg, B.; Maytal-Beck, S.; Meadows, B.; de Mello Neto, J. R.; Mihalcea, D.; Milburn, R. H.; de Miranda, J. M.; Napier, A.; Nguyen, A.; D'Oliveira, A. B.; O'Shaughnessy, K.; Peng, K. C.; Perera, L. P.; Purohit, M. V.; Quinn, B.; Radeztsky, S.; Rafatian, A.; Reay, N. W.; Reidy, J. J.; Dos Reis, A. C.; Rubin, H. A.; Sanders, D. A.; Santha, A. K.; Santoro, A. F.; Schwartz, A. J.; Sheaff, M.; Sidwell, R. A.; Slaughter, A. J.; Sokoloff, M. D.; Solano, J.; Stanton, N. R.; Stefanski, R. J.; Stenson, K.; Summers, D. J.; Takach, S.; Thorne, K.; Tripathi, A. K.; Watanabe, S.; Weiss-Babai, R.; Wiener, J.; Witchey, N.; Wolin, E.; Yang, S. M.; Yi, D.; Yoshida, S.; Zaliznyak, R.; Zhang, C.

    2001-05-01

    We have studied the diffractive dissociation into dijets of 500 GeV/c pions scattering coherently from carbon and platinum targets. Extrapolating to asymptotically high energies (where tmin-->0), we find that when the per-nucleus cross section for this process is parametrized as σ = σ0Aα, α has values near 1.6, the exact result depending on jet transverse momentum. These values are in agreement with those predicted by theoretical calculations of color-transparency.

  18. Differential tapasin dependence of MHC class I molecules correlates with conformational changes upon peptide dissociation: A molecular dynamics simulation study

    SciTech Connect

    Sieker, Florian; Straatsma, TP; Springer, Sebastian; Zacharias, Martin W

    2008-08-01

    Efficiency of peptide loading to MHC class I molecules in the endoplasmatic reticulum depends on the class I allele and can involve interaction with tapasin and other proteins of the loading complex. Allele HLA-B*4402 (Asp at position 116) depends on tapasin for efficient peptide loading whereas HLA-B*4405 (identical to B*4402 except for Tyr116) can efficiently load peptides in the absence of tapasin. Both alleles adopt very similar structures in the presence of the same peptide. Molecular dynamics (MD) simulations on induced peptide termini dissociation from the α1/α2 peptide binding domains have been performed to characterize free energy changes and associated structural changes in the two alleles. A smooth free energy change along the distance dissociation coordinate was obtained for N terminus dissociation. A different shape and magnitude of the calculated free energy change and was obtained for induced peptide C terminus dissociation in case of the tapasin independent allele B*4405 compared to B*4402. Structural changes during C terminus dissociation occurred mainly in the first segment of the α2-1 helix that flanks the peptide C-terminus binding region (F-pocket) and contacts residue 116. This segment is also close to the proposed tapasin contact region. For B*4402, a stable shift towards an altered open F-pocket structure deviating significantly from the bound form was observed. In contrast, B*4405 showed only a transient opening of the F-pocket followed by relaxation towards a structure close to the bound form upon C terminus dissociation. The greater tendency for peptide-receptive conformation in the absence of peptide combined with a more long-range character of the interactions with the peptide C terminus facilitates peptide binding to B*4405 and could be responsible for the tapasin independence of this allele. A possible role of tapasin in case of HLA-B*4402 and other tapasin-dependent alleles could be the stabilization of a peptide receptive class I

  19. Nitrogen Dissociation in N_2-Ar Microwave Plasmas

    NASA Astrophysics Data System (ADS)

    Henriques, J.; Tatarova, E.; Ferreira, C. M.

    2002-10-01

    Microwave N_2-Ar discharges driven by a traveling surface wave (SW) attract attention due to their advantageous properties for plasma processing technologies, in particular for nitriding surfaces. Nitrogen atoms are the most important precursors in gas discharge nitriding and the study of their production and loss mechanisms is of fundamental importance. The kinetics of dissociation of N2 in N_2-Ar microwave plasmas was investigated as a function of the spatial position, mixture composition and pressure. A theoretical model(J. Henriques, E. Tatarova, V. Guerra and C.M. Ferreira, J. Appl. Phys. 91 5622 (2002).) was developed for the following situation: an azimuthally symmetric SW (TM_00, ω/2π=2.45 GHz) propagates and sustains an N_2-Ar plasma column in a dielectric tube (a=0.75 cm, \\varepsilon_d=3.78) surrounded by a metal screen (R=2.5 cm). The model account in a self-consistent way for the electron and heavy particle kinetics, gas thermal balance and wave electrodynamics. It is demonstrated that charge transfer Ar^+ + N2 arrow N_2^+ + Ar followed by dissociative recombination e + N_2^+ arrow N(^4S) + N(^4S) increases the dissociation degree of nitrogen at high Ar fractional percentage in the mixture. The predictions are validated by optical emission spectroscopy(J. Henriques, E. Tatarova, F.M. Dias and C.M. Ferreira, J. Appl. Phys. 91 5632 (2002).).

  20. Dissociative attachment reactions of electrons with strong acid molecules

    NASA Astrophysics Data System (ADS)

    Adams, Nigel G.; Smith, David; Viggiano, A. A.; Paulson, John F.; Henchman, Michael J.

    1986-06-01

    Using the flowing afterglow/Langmuir probe (FALP) technique, we have determined (at variously 300 and 570 K) the dissociative attachment coefficients β for the reactions of electrons with the common acids HNO3 (producing NO-2) and H2SO4 (HSO-4), the superacids FSO3H (FSO-3), CF3SO3H (CF3SO-3), ClSO3H (ClSO-3,Cl-), the acid anhydride (CF3SO2)2O (CF3SO-3), and the halogen halides HBr (Br-) and HI (I-). The anions formed in the reactions are those given in the parentheses. The reactions with HF and HCl were investigated, but did not occur at a measurable rate since they are very endothermic. Dissociative attachment is rapid for the common acids, the superacids, and the anhydride, the measured β being appreciable fractions of the theoretical maximum β for such reactions, βmax. The HI reaction is very fast ( β˜βmax) but the HBr reaction occurs much more slowly because it is significantly endothermic. The data indicate that the extreme acidity of the (Bronsted-type) superacids has its equivalence in the very efficient gas-phase dissociative attachment which these species undergo when reacting with free electrons. The anions of the superacids generated in these reactions, notably FSO-3 and CF3SO-3, are very stable (unreactive) implying exceptionally large electron affinities for the FSO3 and CF3SO3 radicals.

  1. Dissociation and mindfulness in patients with auditory verbal hallucinations.

    PubMed

    Escudero-Pérez, Silvia; León-Palacios, María Gracia; Úbeda-Gómez, Juan; Barros-Albarrán, María Dolores; López-Jiménez, Ana María; Perona-Garcelán, Salvador

    2016-01-01

    The very few studies relating mindfulness and dissociation have found a negative association between them (depersonalization and absorption). However, all of these studies have been done in nonclinical populations, and there are no data on the relationship between these variables in psychiatric patients with auditory hallucinations. This study was designed to study the relationship between mindfulness and the two dissociative variables, absorption and depersonalization, as well as their predictive power for the severity of auditory hallucinations and the distress they cause in a clinical population. A total of 55 psychiatric patients with hallucinations were given the following tests: the Mindful Attention Awareness Scale (K. Brown & R. Ryan, 2003), the Tellegen Absorption Scale (A. Tellegen & G. Atkinson, 1974), the Cambridge Depersonalization Scale (M. Sierra & G. E. Berrios, 2000), the Psychotic Symptom Rating Scales (G. Haddock, J. McCarron, N. Tarrier, & E. B. Faragher, 1999), and the Positive and Negative Syndrome Scale (S. R. Kay, L. A. Opler, & J.-P. Lindenmayer, 1988). A significant negative correlation was found between mindfulness and the dissociative variables and between mindfulness and the distress caused by the hallucinations. A positive correlation was found between absorption and distress caused by hallucinations and between depersonalization and the severity of hallucinations. Finally, the variable with the most predictive power for severity of the voices was depersonalization, and the variable with the most predictive power for distress caused by the voices was mindfulness. Interventions addressing training in mindfulness techniques could diminish the distress associated with hearing voices. PMID:26536908

  2. A Neuroanatomical Dissociation for Emotion Induced by Music

    PubMed Central

    Johnsen, Erica L.; Tranel, Daniel; Lutgendorf, Susan; Adolphs, Ralph

    2008-01-01

    Does feeling an emotion require changes in autonomic responses, as William James proposed? Can feelings and autonomic responses be dissociated? Findings from cognitive neuroscience have identified brain structures that subserve feelings and autonomic response, including those induced by emotional music. In the study reported here, we explored whether feelings and autonomic responses can be dissociated by using music, a stimulus that has a strong capacity to induce emotional experiences. We tested two brain regions predicted to be differentially involved in autonomic responsivity (the ventromedial prefrontal cortex) and feeling (the right somatosensory cortex). Patients with damage to the ventromedial prefrontal cortex were impaired in their ability to generate skin conductance responses to music, but generated normal judgments of their subjective feelings in response to music. Conversely, patients with damage to the right somatosensory cortex were impaired in their self-rated feelings in response to music, but generated normal skin conductance responses to music. Control tasks suggested that neither impairment was due to basic defects in hearing the music or in cognitively recognizing the intended emotion of the music. The findings provide evidence for a double dissociation between feeling emotions and autonomic responses to emotions, in response to music stimuli. PMID:18824047

  3. Detection method for dissociation of multiple-charged ions

    DOEpatents

    Smith, Richard D.; Udseth, Harold R.; Rockwood, Alan L.

    1991-01-01

    Dissociations of multiple-charged ions are detected and analyzed by charge-separation tandem mass spectrometry. Analyte molecules are ionized to form multiple-charged parent ions. A particular charge parent ion state is selected in a first-stage mass spectrometer and its mass-to-charge ratio (M/Z) is detected to determine its mass and charge. The selected parent ions are then dissociated, each into a plurality of fragments including a set of daughter ions each having a mass of at least one molecular weight and a charge of at least one. Sets of daughter ions resulting from the dissociation of one parent ion (sibling ions) vary in number but typically include two to four ions, one or more multiply-charged. A second stage mass spectrometer detects mass-to-charge ratio (m/z) of the daughter ions and a temporal or temporo-spatial relationship among them. This relationship is used to correlate the daughter ions to determine which (m/z) ratios belong to a set of sibling ions. Values of mass and charge of each of the sibling ions are determined simultaneously from their respective (m/z) ratios such that the sibling ion charges are integers and sum to the parent ion charge.

  4. Photoinduced nonadiabatic decay and dissociation dynamics of dimethylnitramine.

    PubMed

    Zhuang, Xuhui; Wang, Jun; Lan, Zhenggang

    2013-06-13

    Dimethylnitramine (DMNA) is a prototype system used in the investigation of the unimolecular decomposition mechanism of the nitramine-compound family. The photoinduced excited-state nonadiabatic processes and successive unimolecular dissociation of DMNA were investigated by trajectory surface-hopping dynamics at the semiempirical OM2/MRCI level. Two S1/S0 conical intersections (CI01α and CI01β) were found to play essential roles in the nonadiabatic decay dynamics of DMNA. After the S1 → S0 decay, the excess kinetic energy finally results in the cleavage of the N-N bond in the ground electronic state. The two reaction channels through CI01α and CI01β show differences in molecular motions and decay features. The trajectories passing CI01α can hop one or several times, and the intramolecular vibrational energy transfer in the ground state takes place before dissociation, whereas trajectories following the CI01β channel mainly dissociate directly after only one S1 → S0 hop. PMID:23672370

  5. Even harmonic generation in isotropic media of dissociating homonuclear molecules.

    PubMed

    Silva, R E F; Rivière, P; Morales, F; Smirnova, O; Ivanov, M; Martín, F

    2016-01-01

    Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schrödinger equation for and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are produced is controlled by pulse duration. Our results (i) show how the interplay of femtosecond nuclear and attosecond electronic dynamics, which affects the charge flow inside the dissociating molecule, is reflected in the nonlinear response, and (ii) force one to augment standard selection rules found in nonlinear optics textbooks by considering light-induced modifications of the medium during the generation process. PMID:27596609

  6. Electron capture dissociation mass spectrometry of metallo-supramolecular complexes.

    PubMed

    Kaczorowska, Malgorzata A; Hotze, Anna C G; Hannon, Michael J; Cooper, Helen J

    2010-02-01

    The electron capture dissociation (ECD) of metallo-supramolecular dinuclear triple-stranded helicate Fe(2)L(3)(4+) ions was determined by Fourier transform ion cyclotron resonance mass spectrometry. Initial electron capture by the di-iron(II) triple helicate ions produces dinuclear double-stranded complexes analogous to those seen in solution with the monocationic metal centers Cu(I) or Ag(I). The gas-phase fragmentation behavior [ECD, collision-induced dissociation (CID), and infrared multiphoton dissociation (IRMPD)] of the di-iron double-stranded complexes, (i.e., MS(3) of the ECD product) was compared with the ECD, CID, and IRMPD of the Cu(I) and Ag(I) complexes generated from solution. The results suggest that iron-bound dimers may be of the form Fe(I)(2)L(2)(2+) and that ECD by metallo-complexes allows access, in the gas phase, to oxidation states and coordination chemistry that cannot be accessed in solution. PMID:20004114

  7. Quantum enhancement of vibrational predissociation near the dissociation threshold

    SciTech Connect

    Cote, R.; Dashevskaya, E.I.; Nikitin, E.E.; Troe, J.

    2004-01-01

    We discuss quantum enhancement of the quasiclassical vibrational predissociation (VP) rate of an atom (A)-diatom (BC) van der Waals (vdW) complex A-BC from a state lying close to the dissociation threshold. The enhancement is due to the accumulation of a noticeable fraction of the state population near the outer turning point of the A-BC bond. For potentials behaving as power-laws at large separations, the enhancement manifests itself in the variation of the energy dependence of the VP frequency factor from the classical frequency to its quantum counterpart. We show that it is related to the complex scattering length associated with the vibrational relaxation of BC in collisions with A. We also discuss the corrected quasiclassical quantization condition for energy levels of a diatom lying very close to the dissociation threshold. Our results generalize those of J. Trost, C. Eltshka, and H. Friedrich [J. Phys. B 31, 361 (1998)] and C. Boisseau et al. [Eur. Phys. J. D 12, 199 (2000)] for the calculation of complex energy levels of an anharmonic oscillator that dissociates from highly excited states under the action of a weak high-frequency perturbation.

  8. A neuroanatomical dissociation for emotion induced by music.

    PubMed

    Johnsen, Erica L; Tranel, Daniel; Lutgendorf, Susan; Adolphs, Ralph

    2009-04-01

    Does feeling an emotion require changes in autonomic responses, as William James proposed? Can feelings and autonomic responses be dissociated? Findings from cognitive neuroscience have identified brain structures that subserve feelings and autonomic response, including those induced by emotional music. In the study reported here, we explored whether feelings and autonomic responses can be dissociated by using music, a stimulus that has a strong capacity to induce emotional experiences. We tested two brain regions predicted to be differentially involved in autonomic responsivity (the ventromedial prefrontal cortex) and feeling (the right somatosensory cortex). Patients with damage to the ventromedial prefrontal cortex were impaired in their ability to generate skin-conductance responses to music, but generated normal judgments of their subjective feelings in response to music. Conversely, patients with damage to the right somatosensory cortex were impaired in their self-rated feelings in response to music, but generated normal skin-conductance responses to music. Control tasks suggested that neither impairment was due to basic defects in hearing the music or in cognitively recognizing the intended emotion of the music. The findings provide evidence for a double dissociation between feeling emotions and autonomic responses to emotions, in response to music stimuli. PMID:18824047

  9. Association and dissociation of Feshbach molecules in a microgravity environment

    NASA Astrophysics Data System (ADS)

    D'Incao, Jose P.; Willians, Jason R.

    2016-05-01

    NASA's Cold Atom Laboratory (CAL) is a multi-user facility scheduled for launch to the ISS in 2017. Our flight experiments with CAL will characterize and mitigate leading-order systematics in dual-atomic-species atom interferometers in microgravity relevant for future fundamental physics missions in space. Here, we study the RF association and dissociation of weakly bound heteronuclear Feshbach molecules for expected parameters relevant for the microgravity environment of CAL. This includes temperatures on the pico-Kelvin range and atomic densities as low as 108/ cm3. We show that under such conditions, thermal and loss effects can be greatly suppressed, resulting in high efficiency in both association and dissociation of extremely weakly bound Feshbach molecules and allowing for high accuracy determination coherent properties of such processes. Our theoretical model for 41 K-87 Rb mixture includes thermal, loss, and density effects in a simple and conceptually clear manner. We derive several conditions in terms of the temperature, density and scattering lengths, determining the regime in which one can achieve efficient association and dissociation. This research is supported by the National Aeronautics and Space Administration.

  10. Deferred Feedback Sharply Dissociates Implicit and Explicit Category Learning

    PubMed Central

    Smith, J. David; Boomer, Joseph; Zakrzewski, Alexandria; Roeder, Jessica; Church, Barbara A.; Ashby, F. Gregory

    2014-01-01

    The controversy over multiple category-learning systems is reminiscent of the controversy over multiple memory systems. Researchers continue to seek paradigms to sharply dissociate explicit category-learning processes (featuring verbalizeable category rules) from implicit category-learning processes (featuring learned stimulus-response associations that lie outside of declarative cognition). We contribute a new dissociative paradigm, adapting from comparative psychology the technique of deferred-rearranged reinforcement. Participants learned matched category tasks that had either a one-dimensional, rule-based solution or a multidimensional, information-integration solution. They received feedback only after each block of trials, with their positive outcomes grouped and their negative outcomes grouped. Deferred-rearranged reinforcement qualitatively eliminated implicit, information-integration category learning. It left intact explicit, rule-based category learning. Moreover, implicit category learners—facing deferred-rearranged reinforcement—turned by default and information-processing necessity to rule-based strategies that poorly suited their nominal category task. The results represent one of the strongest explicit-implicit dissociations yet seen in the categorization literature. PMID:24335605

  11. Deferred feedback sharply dissociates implicit and explicit category learning.

    PubMed

    Smith, J David; Boomer, Joseph; Zakrzewski, Alexandria C; Roeder, Jessica L; Church, Barbara A; Ashby, F Gregory

    2014-02-01

    The controversy over multiple category-learning systems is reminiscent of the controversy over multiple memory systems. Researchers continue to seek paradigms to sharply dissociate explicit category-learning processes (featuring category rules that can be verbalized) from implicit category-learning processes (featuring learned stimulus-response associations that lie outside declarative cognition). We contribute a new dissociative paradigm, adapting the technique of deferred-rearranged reinforcement from comparative psychology. Participants learned matched category tasks that had either a one-dimensional, rule-based solution or a multidimensional, information-integration solution. They received feedback either immediately or after each block of trials, with the feedback organized such that positive outcomes were grouped and negative outcomes were grouped (deferred-rearranged reinforcement). Deferred reinforcement qualitatively eliminated implicit, information-integration category learning. It left intact explicit, rule-based category learning. Moreover, implicit-category learners facing deferred-rearranged reinforcement turned by default and information-processing necessity to rule-based strategies that poorly suited their nominal category task. The results represent one of the strongest explicit-implicit dissociations yet seen in the categorization literature. PMID:24335605

  12. Dissociating sensory from decision processes in human perceptual decision making

    PubMed Central

    Mostert, Pim; Kok, Peter; de Lange, Floris P.

    2015-01-01

    A key question within systems neuroscience is how the brain translates physical stimulation into a behavioral response: perceptual decision making. To answer this question, it is important to dissociate the neural activity underlying the encoding of sensory information from the activity underlying the subsequent temporal integration into a decision variable. Here, we adopted a decoding approach to empirically assess this dissociation in human magnetoencephalography recordings. We used a functional localizer to identify the neural signature that reflects sensory-specific processes, and subsequently traced this signature while subjects were engaged in a perceptual decision making task. Our results revealed a temporal dissociation in which sensory processing was limited to an early time window and consistent with occipital areas, whereas decision-related processing became increasingly pronounced over time, and involved parietal and frontal areas. We found that the sensory processing accurately reflected the physical stimulus, irrespective of the eventual decision. Moreover, the sensory representation was stable and maintained over time when it was required for a subsequent decision, but unstable and variable over time when it was task-irrelevant. In contrast, decision-related activity displayed long-lasting sustained components. Together, our approach dissects neuro-anatomically and functionally distinct contributions to perceptual decisions. PMID:26666393

  13. Emotion and reward are dissociable from error during motor learning.

    PubMed

    Festini, Sara B; Preston, Stephanie D; Reuter-Lorenz, Patricia A; Seidler, Rachael D

    2016-06-01

    Although emotion is known to reciprocally interact with cognitive and motor performance, contemporary theories of motor learning do not specifically consider how dynamic variations in a learner's affective state may influence motor performance during motor learning. Using a prism adaptation paradigm, we assessed emotion during motor learning on a trial-by-trial basis. We designed two dart-throwing experiments to dissociate motor performance and reward outcomes by giving participants maximum points for accurate throws and reduced points for throws that hit zones away from the target (i.e., "accidental points"). Experiment 1 dissociated motor performance from emotional responses and found that affective ratings tracked points earned more closely than error magnitude. Further, both reward and error uniquely contributed to motor learning, as indexed by the change in error from one trial to the next. Experiment 2 manipulated accidental point locations vertically, whereas prism displacement remained horizontal. Results demonstrated that reward could bias motor performance even when concurrent sensorimotor adaptation was taking place in a perpendicular direction. Thus, these experiments demonstrate that affective states were dissociable from error magnitude during motor learning and that affect more closely tracked points earned. Our findings further implicate reward as another factor, other than error, that contributes to motor learning, suggesting the importance of incorporating affective states into models of motor learning. PMID:26746312

  14. Even harmonic generation in isotropic media of dissociating homonuclear molecules

    PubMed Central

    Silva, R. E. F.; Rivière, P.; Morales, F.; Smirnova, O.; Ivanov, M.; Martín, F.

    2016-01-01

    Isotropic gases irradiated by long pulses of intense IR light can generate very high harmonics of the incident field. It is generally accepted that, due to the symmetry of the generating medium, be it an atomic or an isotropic molecular gas, only odd harmonics of the driving field can be produced. Here we show how the interplay of electronic and nuclear dynamics can lead to a marked breakdown of this standard picture: a substantial part of the harmonic spectrum can consist of even rather than odd harmonics. We demonstrate the effect using ab-initio solutions of the time-dependent Schrödinger equation for and its isotopes in full dimensionality. By means of a simple analytical model, we identify its physical origin, which is the appearance of a permanent dipole moment in dissociating homonuclear molecules, caused by light-induced localization of the electric charge during dissociation. The effect arises for sufficiently long laser pulses and the region of the spectrum where even harmonics are produced is controlled by pulse duration. Our results (i) show how the interplay of femtosecond nuclear and attosecond electronic dynamics, which affects the charge flow inside the dissociating molecule, is reflected in the nonlinear response, and (ii) force one to augment standard selection rules found in nonlinear optics textbooks by considering light-induced modifications of the medium during the generation process. PMID:27596609

  15. Cyanobacterial phycobilisomes: selective dissociation monitored by fluorescence and circular dichroism

    SciTech Connect

    Rigbi, M.; Rosinski, J.; Siegelman, H.W.; Sutherland, J.C.

    1980-04-01

    Phycobilisomes are supramolecular assemblies of phycobiliproteins responsible for photosynthetic light collection in red algae and cyanobacteria. They can be selectively dissociated by reduction of temperature and buffer concentration. Phycobilisomes isolated from Fremyella diplosiphon transfer energy collected by C-phycoerythrin and C-phycocyanin to allophycocyanin. The energy transfer to allophycocyanin is nearly abolished at 2/sup 0/C, as indicated by a blue shift in fluorescence emission, and is accompanied by a decrease in the circular dichroism in the region of allophycocyanin absorbance. Further dissociation of the phycobilisomes can be attained by reduction of buffer concentration and holding at 2/sup 0/C. Energy transfer to C-phycocyanin is nearly abolished, and decreases occur in the circular dichroism in the region of C-phycocyanin and C-phycoerythrin absorbance. Complete dissociation of the phycobilisomes at low buffer concentration and 2/sup 0/C requires extended time. Energy transfer to C-phycocyanin is further reduced and the circular dichroism maximum of C-phycoerythrin at 575 nm is lost. Circular dichroism provides information on the hexamer-monomer transitions of the phycobiliproteins, whereas fluorescence is indicative of hexamer-hexamer interactions. We consider that hydrophobic interactions are fundamental to the maintenance of the structure and function of phycobilisomes.

  16. Controlling dissociation by trapping trajectories in highly energetic states

    NASA Astrophysics Data System (ADS)

    de Almeida, A. K., Jr.; Egydio de Carvalho, R.; de Lima, E. F.

    2016-05-01

    We consider the non-linear dynamics of a polar diatomic molecule under the action of laser-field interactions and in the presence of a dissipation mechanism, described by the classical damped and driven one-dimensional Morse oscillator. In the absence of laser fields and dissipation, the phase space consists of a negative-energy bound region and a positive-energy dissociative region. Laser-molecule interaction changes the phase space allowing transitions from the bound to the dissociative region through chaotic routes. We show that for a spatially dependent dipole force, resonances with positive energies allow the trapping of trajectories in pseudo-bound states. We also show that, upon the introduction of dissipation, there exist non-trivial point attractors as well as chaotic attractors, which capture the trajectories in pseudo-bound states. Consequently, in addition to the parameters associated with the laser-molecule interaction, the amplitude of the dissipation acts as a control parameter of the photo-dissociation dynamics.

  17. Molecular origins of the slow streptavidin-biotin dissociation kinetics

    SciTech Connect

    Chilkoti, A.; Stayton, P.S.

    1995-11-01

    The association of streptavidin and avidin with biotin is among the strongest known noncovalent protein-ligand interactions (K{sub a} nearly equals 2.5 x 10{sup 13} M{sup -1}) and is controlled by an exceptionally slow off-rate. We have used this model system to elucidate the role of aromatic tryptophan side-chain binding contacts in the dissociation reaction coordinate and relatedly to the construction of the activation barrier and to the structure of the transition state. We have also conducted a transition state analysis of the temperature-dependent dissociation kinetics, which along with the independent estimation of the equilibrium biotin-binding free energies and enthalpies has provided thermodynamic profiles defining the enthalpic, entropic, and free energy barriers to dissociation for the mutants relative to wild-type streptavidin. The increased biotin off-rate for W79F, which contacts the valeric acid moiety of biotin, and for W120F, which partially caps the bicyclic ring system, is caused largely by free energy destabilization of the ligand-bound ground state relative to wild-type streptavidin. W79F displays an increased equilibrium binding enthalpy relative to wild-type, and thus streptavidin sacrifices potential binding enthalpy to minimize the entropic costs of biotin immobilization. 26 refs., 5 figs., 4 tabs.

  18. Economics of microwave plasma dissociation of H sub 2 S

    SciTech Connect

    Daniels, E.J.; Harkness, J.B.L.; Doctor, R.D.

    1992-01-01

    The conventional treatment technology for hydrogen-sulfide is based on Claus chemistry; elemental sulfur is recovered but the hydrogen is lost as water although the fuel value of the hydrogen is recovered as heat. A new waste treatment technology, reported in the Soviet literature, has been validated in an experimental program at Argonne National Laboratory. The new technology uses microwave energy to dissociate hydrogen-sulfide and recovers both elemental sulfur and hydrogen. Recovery of the hydrogen provides for its reuse for its chemical value. A comparative economic analysis of the microwave technology and conventional sulfur recovery and tail-gas treatment technology such as Claus/SCOT is presented. The sensitivity of the comparative economics to process variables such as dissociation energy and conversion rate, and cost variables, such as the value of hydrogen and the cost-of-electricity is evaluated. Under the conditions of this analysis, the conclusion is that it is more cost-effective to recover the hydrogen for its chemical value via microwave dissociation rather than to accept its conversion to water and effective use as a fuel.

  19. Modeling Proton Dissociation and Transfer Using Dissipative Particle Dynamics Simulation.

    PubMed

    Lee, Ming-Tsung; Vishnyakov, Aleksey; Neimark, Alexander V

    2015-09-01

    We suggest a coarse-grained model for dissipative particle dynamics (DPD) simulations of solutions with dissociated protons. The model uses standard short-range soft repulsion and smeared charge electrostatic potentials between the beads, representing solution components. The proton is introduced as a separate charged bead that forms dissociable bonds with proton receptor base beads, such as water or deprotonated acid anions. The proton-base bonds are described by Morse potentials. When the proton establishes the Morse bonds with two bases, they form an intermediate complex, and the proton is able to "hop" between the bases artificially mimicking the Grotthuss diffusion mechanism. By adjusting the Morse potential parameters, one can regulate the potential barrier associated with intermediate complex formation and breakup and control the hopping frequency. This makes the proposed model applicable to simulations of proton mobility and reaction equilibria between protonated and deprotonated acid forms in aqueous solutions. The proposed model provides quantitative agreement with experiments for the proton self-diffusion coefficient and hopping frequency, as well as for the degree of dissociation of benzenesulfonic acid. PMID:26575931

  20. Modeling heating curve for gas hydrate dissociation in porous media.

    PubMed

    Dicharry, Christophe; Gayet, Pascal; Marion, Gérard; Graciaa, Alain; Nesterov, Anatoliy N

    2005-09-15

    A method for modeling the heating curve for gas hydrate dissociation in porous media at isochoric conditions (constant cell volume) is presented. This method consists of using an equation of state of the gas, the cumulative volume distribution (CVD) of the porous medium, and a van der Waals-Platteeuw-type thermodynamic model that includes a capillary term. The proposed method was tested to predict the heating curves for methane hydrate dissociation in a mesoporous silica glass for saturated conditions (liquid volume = pore volume) and for a fractional conversion of water to hydrate of 1 (100% of the available water was converted to hydrate). The shape factor (F) of the hydrate-water interface was found equal to 1, supporting a cylindrical shape for the hydrate particles during hydrate dissociation. Using F = 1, it has been possible to predict the heating curve for different ranges of pressure and temperature. The excellent agreement between the calculated and experimental heating curves supports the validity of our approach. PMID:16853195

  1. Photoinduced ionization and dissociation of aniline-(methanol)n clusters

    NASA Astrophysics Data System (ADS)

    Park, Hye Sun; Nam, Sang Hwan; Song, Jae Kyu; Park, Seung Min

    2007-04-01

    A linear tandem-type time-of-flight mass spectrometer was employed to study unimolecular dissociation of metastable aniline+-(methanol)n (An+-(CH3OH)n, n = 2-9) cluster cations formed by two-photon ionization of neutral clusters. The dominant dissociation channel was to liberate a single methanol molecule, namely, An+-(CH3OH)n --> An+-(CH3OH)n-1 + CH3OH. The decay time constant of the ions ranged from 65 to 460 [mu]s and turned out to be highly dependent on the cluster size. Also, hydrogen transfer mechanism in the formation of An+-(CH3OH)nH was examined by analyzing experimental results from isotopomers, such as deuterated An-d7+-(CH3OD) and An-d7+-(CD3OD) cluster ions. Density functional theory calculations were carried out to obtain optimized structures for neutral and ionic clusters and to support mechanisms related to the hydrogen transfer and unimolecular dissociation reaction.

  2. Dissociative photodetachment dynamics of the iodide-aniline cluster

    NASA Astrophysics Data System (ADS)

    Bowen, M. Shane; Becucci, Maurizio; Continetti, Robert E.

    2006-10-01

    The photodetachment dynamics of the iodide-aniline cluster, I-(C6H5NH2), were investigated using photoelectron-photofragment coincidence spectroscopy at several photon energies between 3.60 and 4.82eV in concert with density functional theory calculations. Direct photodetachment from the solvated I- chromophore and a wavelength-independent autodetachment process were observed. Autodetachment is attributed to a charge-transfer-to-solvent reaction in which incipient continuum electrons photodetached from I- are temporarily captured by the nascent neutral iodine-aniline cluster configured in the anion geometry. Subsequent dissociation of the neutral cluster removes the stabilization, leading to autodetachment of the excess electron. The dependence of the dissociative photodetachment (DPD) and autodetachment dynamics on the final spin-orbit electronic state of the iodine fragment is characterized. The dissociation dynamics of the neutral fragments correlated with autodetached electrons were found to be identical to the DPD dynamics of the I atom product spin-orbit state closest to threshold at a given photon energy, lending support to the proposed sequential mechanism.

  3. Precursor anion states in dissociative electron attachment to chlorophenol isomers

    NASA Astrophysics Data System (ADS)

    Kossoski, F.; Varella, M. T. do N.

    2016-07-01

    We report a theoretical study on low-energy (<10 eV) elastic electron scattering from chlorophenol isomers, namely, para-chlorophenol (pCP), meta-chlorophenol (mCP), and ortho-chlorophenol (oCP). The calculations were performed with the Schwinger multichannel method with pseudopotentials, and analysis of the computed integral cross sections and virtual orbitals revealed one σCCl ∗ , one σOH ∗ , and three π∗ shape resonances. We show that electron capture into the two lower lying π∗ orbitals initiates dissociative processes that lead to the elimination of the chloride ion, accounting for the two overlapping peaks where this fragment was observed. Despite the relatively small differences on the energetics of the π∗ resonances, a major isomeric effect was found on their corresponding autodetachment lifetimes, which accounts for the observed increasing cross sections in the progression pCP < mCP < oCP. In particular, dissociation from the π1 ∗ anion of pCP is largely suppressed because of the unfavorable mixing with the σCCl ∗ state. We found the intramolecular hydrogen bond present in oCP to have the opposite effects of stabilizing the σCCl ∗ resonance and destabilizing the σOH ∗ resonance. We also suggest that the hydrogen abstraction observed in chlorophenols and phenol actually takes place by a mechanism in which the incoming electron is directly attached to the dissociative σOH ∗ orbital.

  4. Unusual dissociative adsorption of H2 over stoichiometric MgO thin film supported on molybdenum

    NASA Astrophysics Data System (ADS)

    Song, Zhenjun; Xu, Hu

    2016-03-01

    The dissociation of a hydrogen molecule on perfect MgO(0 0 1) films deposited on Mo(0 0 1) surface is investigated systematically using periodic density-functional theory (DFT) method. The unusual adsorption behavior of heterolytic dissociative hydrogen molecule at neighboring surface oxygen and surface magnesium, is clarified here. To our knowledge, this heterolytic dissociative state has never been found before on bulk MgO(0 0 1) or metal supported perfect MgO(0 0 1) surfaces (without low coordination sites). The results confirm that, in all cases, the heterolytic dissociation is much more favorable that homolytic dissociation both energetically and kinetically. The energy differences between two dissociative states are very large, in the range of 1.1 eV-1.5 eV for Mo supported 1 ML-3 ML oxide films, which inhibits, to a great extent, the homolytic dissociation in the respect of reaction thermodynamics. The energy barriers of heterolytic dissociation are about 0.5 eV, much lower that the barrier of homolytic dissociation. The transformation reaction on thick films will be more endothermic. Passing through heterolytic dissociation state has significantly lowered the reaction heat and the energy barrier for obtaining homolytic dissociative structure, which makes the homolytic splitting of H2 easier on 2 ML oxide films. The results provide a useful strategy for enhancing the reactivity of the nonreducible metal oxide.

  5. DSM-5's posttraumatic stress disorder with dissociative symptoms: challenges and future directions.

    PubMed

    Dorahy, Martin J; van der Hart, Onno

    2015-01-01

    The Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, formally recognizes a dissociative subtype of posttraumatic stress disorder (PTSD; PTSD with dissociative symptoms). This nomenclative move will boost empirical and theoretical efforts to further understand the links between dissociation, trauma, and PTSD. This article examines the empirical literature showing that patients with PTSD can be divided into 2 different groups based on their neurobiology, psychological symptom profile, history of exposure to early relational trauma, and depersonalization/derealization symptoms. It then explores the conceptual and empirical challenges of conceiving 1 of these types as reflecting a "dissociative" type of PTSD. First, this classification is based on the presence of a limited subset of dissociative symptoms (i.e., depersonalization, derealization). This sets aside an array of positive and negative psychoform and somatoform dissociative symptoms that may be related to PTSD. Second, empirical evidence suggests heightened dissociation in PTSD compared to many other disorders, indicating that dissociation is relevant to PTSD more broadly rather than simply to the so-called dissociative subtype. This article sets out important issues to be examined in the future study of dissociation in PTSD, which needs to be informed by solid conceptual understandings of dissociation. PMID:24983300

  6. Dissociation and symptoms of culture-bound syndromes in North America: a preliminary study.

    PubMed

    Ross, Colin A; Schroeder, Elizabeth; Ness, Laura

    2013-01-01

    The aim of this study was to determine whether classical culture-bound syndromes occur among psychiatric inpatients with dissociative disorders in North America. The Dissociative Trance Disorder Interview Schedule, the Dissociative Experiences Scale, and the Dissociative Disorders Interview Schedule were administered to 100 predominantly Caucasian, American, English-speaking trauma program inpatients at a hospital in the United States. The participants reported high rates of childhood physical and/or sexual abuse (87%), dissociative disorders (73%), and membership in the dissociative taxon (78%). They also reported a wide range of possession experiences and exorcism rituals, as well as the classical culture-bound syndromes of latah, bebainan, amok, and pibloktoq. Our data are consistent with the view that possession and classical culture-bound syndromes are predominantly dissociative in nature and not really culture-bound from the perspective of Caucasian, English-speaking America. PMID:23406226

  7. DFT studies of oxygen dissociation on the 116-atom platinum truncated octahedron particle.

    PubMed

    Jennings, Paul C; Aleksandrov, Hristiyan A; Neyman, Konstantin M; Johnston, Roy L

    2014-12-28

    Density functional theory calculations are performed to investigate oxygen dissociation on 116-atom truncated octahedron platinum particles. This work builds on results presented previously [Jennings et al., Nanoscale, 2014, 6, 1153], where it was shown that shell flexibility played an important role in facilitating fast oxygen dissociation. In this study, through investigation of the larger particle size, it is shown that oxygen dissociation on the (111) facet of pure platinum species is still aided by shell flexibility at larger sizes. Only the hollow sites close to the edges of the (111) facet mediate oxygen dissociation; oxygen is bound too weakly at other hollow sites for dissociation to occur. Further studies are performed on the (100) facet, which is larger for the Pt116 particle than for either the Pt38 or Pt79 ones. Much higher dissociation barriers are found on the (100) facet compared to the (111) facet, where the bridge sites are favourable for oxygen dissociation. PMID:25070716

  8. Quality of early care and childhood trauma: a prospective study of developmental pathways to dissociation.

    PubMed

    Dutra, Lissa; Bureau, Jean-Francois; Holmes, Bjarne; Lyubchik, Amy; Lyons-Ruth, Karlen

    2009-06-01

    Kihlstrom (2005) has recently called attention to the need for prospective longitudinal studies of dissociation. The present study assesses quality of early care and childhood trauma as predictors of dissociation in a sample of 56 low-income young adults followed from infancy to age 19. Dissociation was assessed with the Dissociative Experiences Scale; quality of early care was assessed by observer ratings of mother-infant interaction at home and in the laboratory; and childhood trauma was indexed by state-documented maltreatment, self-report, and interviewer ratings of participants' narratives. Regression analysis indicated that dissociation in young adulthood was significantly predicted by observed lack of parental responsiveness in infancy, while childhood verbal abuse was the only type of trauma that added to the prediction of dissociation. Implications are discussed in the context of previous prospective work also pointing to the important contribution of parental emotional unresponsiveness in the development of dissociation. PMID:19525736

  9. Posttraumatic stress symptoms, dissociation, and alexithymia in an Italian sample of flood victims

    PubMed Central

    Craparo, Giuseppe; Gori, Alessio; Mazzola, Elvira; Petruccelli, Irene; Pellerone, Monica; Rotondo, Giuseppe

    2014-01-01

    Background Several studies have demonstrated a significant association between dissociation and posttraumatic symptoms. A dissociative reaction during a traumatic event may seem to predict the later development of posttraumatic stress symptoms. Moreover, several researchers also observed an alexithymic condition in a variety of traumatized samples. Methods A total of 287 flood victims (men =159, 55.4%; women =128, 44.6%) with an age range of 17–21 years (mean =18.33; standard deviation =0.68) completed the following: Impact of Event Scale–Revised, Dissociative Experiences Scale II, Twenty-Item Toronto Alexithymia Scale, and Peritraumatic Dissociative Experiences Questionnaire. Results We found significant correlations among all variables. Linear regression showed that peritraumatic dissociation plays a mediator role between alexithymia, dissociation, and post-traumatic stress symptoms. Conclusion Our results seem to confirm the significant roles of both dissociation and alexithymia for the development of posttraumatic symptoms. PMID:25489247

  10. Co-occurrence of dissociative identity disorder and borderline personality disorder.

    PubMed

    Ross, Colin A; Ferrell, Lynn; Schroeder, Elizabeth

    2014-01-01

    The literature indicates that, among individuals with borderline personality disorder, pathological dissociation correlates with a wide range of impairments and difficulties in psychological function. It also predicts a poorer response to dialectical behavior therapy for borderline personality disorder. We hypothesized that (a) dissociative identity disorder commonly co-occurs with borderline personality disorder and vice versa, and (b) individuals who meet criteria for both disorders have more comorbidity and trauma than individuals who meet criteria for only 1 disorder. We interviewed a sample of inpatients in a hospital trauma program using 3 measures of dissociation. The most symptomatic group was those participants who met criteria for both borderline personality disorder and dissociative identity disorder on the Dissociative Disorders Interview Schedule, followed by those who met criteria for dissociative identity disorder only, then those with borderline personality disorder only, and finally those with neither disorder. Greater attention should be paid to the relationship between borderline personality disorder and dissociative identity disorder. PMID:24377974

  11. Betrayal trauma theory of dissociative experiences: stroop and directed forgetting findings.

    PubMed

    Giesbrecht, Timo; Merckelbach, Harald

    2009-01-01

    According to betrayal trauma theory, many survivors of childhood sexual abuse learn to compartmentalize (i.e., dissociate) their traumatic experiences from conscious awareness by dividing attention. This theory predicts that those who dissociate extensively should be at an advantage during dual tasks. Using a modified Stroop task in Experiment 1 and a direct forgetting task in Experiment 2, we tried to replicate Freyd and colleagues' finding that high-dissociative people perform better under dual task conditions. However, in Experiment 1 we found that, relative to low-dissociative people, high-dissociative people exhibit a slowing of their Stroop reaction times that is independent of valence and attentional context. In Experiment 2, performance on a directed forgetting task was found to be unrelated to dissociation. Our 2 studies provide no evidence for the betrayal trauma theory, nor do they support other theories assuming that dissociation is the manifestation of an automatic defense mechanism. PMID:19827703

  12. Dissociation pathways of a single dimethyl disulfide on Cu(111): Reaction induced by simultaneous excitation of two vibrational modes

    SciTech Connect

    Motobayashi, Kenta; Kim, Yousoo; Arafune, Ryuichi; Ohara, Michiaki; Ueba, Hiromu; Kawai, Maki

    2014-05-21

    We present a novel reaction mechanism for a single adsorbed molecule that proceeds via simultaneous excitation of two different vibrational modes excited by inelastic tunneling electrons from a scanning tunneling microscope. Specifically, we analyze the dissociation of a single dimethyl disulfide (DMDS, (CH{sub 3}S){sub 2}) molecule on Cu(111) by using a versatile theoretical method, which permits us to simulate reaction rates as a function of sample bias voltage. The reaction is induced by the excitation of C-H stretch and S-S stretch modes by a two-electron process at low positive bias voltages. However, at increased voltages, the dissociation becomes a single-electron process that excites a combination mode of these stretches, where excitation of the C-H stretch is the energy source and excitation of the S-S stretch mode enhances the anharmonic coupling rate. A much smaller dissociation yield (few orders of magnitude) at negative bias voltages is understood in terms of the projected density of states of a single DMDS on Cu(111), which reflects resonant excitation through the molecular orbitals.

  13. Laser-induced dissociation dynamics of triatomic molecule in electronic excited states: A full-dimensional quantum mechanics study.

    PubMed

    Sun, Zhaopeng; Yang, Chuanlu; Zheng, Yujun

    2015-12-14

    We present a detailed theoretical approach to investigate the laser-induced dissociation dynamics of a triatomic molecule on its electronic excited state in full dimensional case. In this method, the time evolution of the time-dependent system is propagated via combined the split operator method and the expansion of Chebyshev polynomials (or short-time Chebyshev propagation) and the system wave functions are expanded in terms of molecular rotational bases. As an example of the application of this formalism, the dissociation dynamics of H3(+)→H2(+)+H induced by ultrashort UV laser pulses are investigated on new Born-Oppenheimer potential energy surfaces. Our numerical results show that the signals of dissociation products will be easier to observe as the increasing of field strength. Driving by a 266 nm laser beam, the calculated central value of kinetic-energy-release is 2.04 eV which shows excellent agreement with the experimental estimation of 2.1 eV. When the H3(+) ion is rotationally excited, the spatial distribution of product fragments will become well converged. PMID:26671377

  14. A quantum mechanics-molecular mechanics study of dissociative electron transfer: The methylchloride radical anion in aqueous solution

    NASA Astrophysics Data System (ADS)

    Soriano, Alejandro; Silla, Estanislao; Tuñón, Iñaki

    2002-04-01

    The dissociative electron transfer reaction CH3Cl+e-→CH3•+Cl- in aqueous solution is studied by using a QM/MM method. In this work the quantum subsystem (a methylchloride molecule plus an electron) is described using density functional theory while the solvent (300 water molecules) is described using the TIP3P classical potential. By means of molecular dynamics simulations and the thermodynamic integration technique we obtained the potential of mean force (PMF) for the carbon-chlorine bond dissociation of the neutral and radical anion species. Combining these two free energy curves we found a quadratic dependence of the activation free energy on the reaction free energy in agreement with Marcus' relationship, originally developed for electron transfer processes not involving bond breaking. We also investigated dynamical aspects by means of 60 dissociative trajectories started with the addition of an extra electron to different configurations of a methylchloride molecule in solution. The PMF shows the existence of a very flat region, in which the system is trapped during some finite time if the quantum subsystem quickly losses its excess kinetic energy transferring it to the solvent molecules. One of the most important factors determining the effectiveness of this energy transfer seems to be the existence of close contacts (hydrogen bonds) between the solute and the solvent.

  15. X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium

    PubMed Central

    Davis, P.; Döppner, T.; Rygg, J. R.; Fortmann, C.; Divol, L.; Pak, A.; Fletcher, L.; Becker, A.; Holst, B.; Sperling, P.; Redmer, R.; Desjarlais, M. P.; Celliers, P.; Collins, G. W.; Landen, O. L.; Falcone, R. W.; Glenzer, S. H.

    2016-01-01

    Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase. PMID:27079420

  16. Roles of Acetone and Diacetone Alcohol in Coordination and Dissociation Reactions of Uranyl Complexes

    SciTech Connect

    Rios, Daniel; Schoendorff, George E.; Van Stipdonk, Michael J.; Gordon, Mark S.; Windus, Theresa L.; Gibson, John K.; De Jong, Wibe A.

    2012-12-03

    Combined collision-induced dissociation mass-spectrometry experiments and DFT calculations were employed to elucidate the molecular structure of "hypercoordinated" species and the energetics of water-elimination reactions of uranyl acetone complexes observed in earlier work (Rios, D.; Rutkowski, P. X.; Van Stipdonk, M. J.; Gibson, J. K. Inorg. Chem. 2011, 50, 4781). It is shown that the "hypercoordinated" species contain diacetone alcohol ligands bonded in either bidentate or monodentate fashion, which are indistinguishable from (acetone)2 in mass spectrometry. Calculations confirm that four diacetone ligands can form stable complexes, but that the effective number of atoms coordinating with uranium in the equatorial plane does not exceed five. Diacetone alcohol ligands are shown to form mesityl oxide ligands and alkoxide species through the elimination of water, providing an explanation for the observed water-elimination reactions.

  17. Exciton fission, dissociation and transport in organic conjugated materials: Modeling insights

    NASA Astrophysics Data System (ADS)

    Beljonne, David

    2014-03-01

    Electronic excited states in conjugated organic materials involve an admixture of localized (Frenkel-like) and charge-transfer (CT) excitations. We will first review some recent modeling work showing that this mixed Frenkel-CT character steers the Davydov splitting, mediates singlet fission and prompts triplet energy migration in oligoacenes crystals. Ultrafast and efficient charge separation occurs at interfaces between properly designed molecular donors and acceptors, despite the large electron-hole Coulomb binding energy. In a second part of the talk, we will describe the various mechanisms for such a dissociation process and assess them from atomistic simulations based on a combination of force-field, quantum-chemical and model Hamiltonian calculations.

  18. Calculation of bond dissociation energies of diatomic molecules using bond function basis sets with counterpoise corrections

    SciTech Connect

    Li, Z.; Pan, Y.K.; Tao, F.M.

    1996-01-15

    Bond function basis sets combined with the counterpoise procedure are used to calculate the molecular dissociation energies D{sub e} of 24 diatomic molecules and ions. The calculated values of D{sub e} are compared to those without bond functions and/or counterpoise corrections. The equilibrium bond lengths r{sub e}, and harmonic frequencies w{sub e} are also calculated for a few selected molecules. The calculations at the fourth-order-Moller-Plesset approximation (MP4) have consistently recovered about 95-99% of the experimental values for D{sub e}, compared to as low as 75% without use of bond functions. The calculated values of r{sub 3} are typically 0.01 {Angstrom} larger than the experimental values, and the calculated values of w{sub e} are over 95% of the experimental values. 37 refs., 2 tabs.

  19. Charge transport-induced recoil and dissociation in double quantum dots.

    PubMed

    Pozner, Roni; Lifshitz, Efrat; Peskin, Uri

    2014-11-12

    Colloidal quantum dots (CQDs) are free-standing nanostructures with chemically tunable electronic properties. This combination of properties offers intriguing new possibilities for nanoelectromechanical devices that were not explored yet. In this work, we consider a new scanning tunneling microscopy setup for measuring ligand-mediated effective interdot forces and for inducing motion of individual CQDs within an array. Theoretical analysis of a double quantum dot structure within this setup reveals for the first time voltage-induced interdot recoil and dissociation with pronounced changes in the current. Considering realistic microscopic parameters, our approach enables correlating the onset of mechanical motion under bias voltage with the effective ligand-mediated binding forces. PMID:25259800

  20. X-ray scattering measurements of dissociation-induced metallization of dynamically compressed deuterium.

    PubMed

    Davis, P; Döppner, T; Rygg, J R; Fortmann, C; Divol, L; Pak, A; Fletcher, L; Becker, A; Holst, B; Sperling, P; Redmer, R; Desjarlais, M P; Celliers, P; Collins, G W; Landen, O L; Falcone, R W; Glenzer, S H

    2016-01-01

    Hydrogen, the simplest element in the universe, has a surprisingly complex phase diagram. Because of applications to planetary science, inertial confinement fusion and fundamental physics, its high-pressure properties have been the subject of intense study over the past two decades. While sophisticated static experiments have probed hydrogen's structure at ever higher pressures, studies examining the higher-temperature regime using dynamic compression have mostly been limited to optical measurement techniques. Here we present spectrally resolved x-ray scattering measurements from plasmons in dynamically compressed deuterium. Combined with Compton scattering, and velocity interferometry to determine shock pressure and mass density, this allows us to extract ionization state as a function of compression. The onset of ionization occurs close in pressure to where density functional theory-molecular dynamics (DFT-MD) simulations show molecular dissociation, suggesting hydrogen transitions from a molecular and insulating fluid to a conducting state without passing through an intermediate atomic phase. PMID:27079420