Dissociative States Research Articles

Synthesis of Uranium Single Atom from Radioactive Wastewater for Enhanced Water Dissociation and Hydrogen Evolution.

As a common nuclide in radioactive wastewater, uranium (U) is generally treated by landfill, which induces the massive abandonment of uranium resources. In this work, a pulse voltammetry method for the synthesis of U single atoms on MoS2 (U/MoS2 ) nanosheets from radioactive wastewater for the electrocatalytic alkaline hydrogen evolution reaction (HER) is reported. The mass loading of U single atoms is facilely controlled with high selectivity for coexisting ions in radioactive wastewater. In the electrolyte of 1 m of KOH, U/MoS2 nanosheets with 5.2% of U single atoms exhibit relatively low overpotentials of 72 mV at 10 mA cm-2 . The mechanistic study reveals that the HER on U/MoS2 includes the water dissociation on U single atoms to form OH* and H transfer from OH* to adjacent S-edge atoms. This procedure exhibits decreased activation energy for transition state in water dissociation and optimized Gibbs free energy for H* adsorption.

Photodissociation dynamics of CO2 + hv → CO(X1Σ+) + O(1D2) via the 3P1Πu state.

The vacuum ultraviolet (VUV) photodissociation of CO2 is important to understand the primary photochemical processes of CO2 induced by solar VUV excitation in the Earth's atmosphere. Here, we report a detailed study of vibrational-state-specific photodissociation dynamics of the CO(X1Σ+) + O(1D2) channel via the 3P1Πu state by using the time-sliced velocity-mapped ion imaging apparatus combined with the single VUV photoionization detection scheme. By recording the sliced images of the O(1D2) photoproducts formed by VUV photoexcitation of CO2 to the individual vibrational structure of the 3P1Πu state, both the vibrational state distributions of the counterpart CO(X1Σ+) photoproducts and the vibrational-state-specific product anisotropy parameters (β) are determined. The experimental results show that photodissociation of CO2 at 108.22, 107.50, 106.10, and 104.76nm yields less anisotropic (β > 0) and inverted distributed CO(X1Σ+, v) photoproducts. The possible dissociation mechanism for the CO(X1Σ+) + O(1D2) channel may involve the non-adiabatic transition of excited CO2* from the initially prepared state to the 31A' state with potential energy barriers. While at 108.82 and 107.35nm, the vibrational distributions are found to have the population peaked at a low vibrational state, and the anisotropy parameters turn out to be negative. Such variation indicates the possibility of another non-adiabatic dissociation pathway that may involve Coriolis-type coupling to the low-lying dissociative state. These observations show sclear evidence of the influence of the initially vibrational excitations on the photodissociation dynamics of CO2 via the 3P1Πu state.

Activity-State Dependent Reversal of Ketamine-Induced Resting State EEG Effects by Clozapine and Naltrexone in the Freely Moving Rat.

Ketamine is a non-competitive N-Methyl-D-aspartate receptor (NMDAR) antagonist used in the clinic to initiate and maintain anaesthesia; it induces dissociative states and has emerged as a breakthrough therapy for major depressive disorder. Using local field potential recordings in freely moving rats, we studied resting state EEG profiles induced by co-administering ketamine with either: clozapine, a highly efficacious antipsychotic; or naltrexone, an opioid receptor antagonist reported to block the acute antidepressant effects of ketamine. As human electroencephalography (EEG) is predominantly recorded in a passive state, head-mounted accelerometers were used with rats to determine active and passive states at a high temporal resolution to offer the highest translatability. In general, pharmacological effects for the three drugs were more pronounced in (or restricted to) the passive state. Specifically, during inactive periods clozapine induced increases in delta (0.1–4 Hz), gamma (30–60 Hz) and higher frequencies (>100 Hz). Importantly, it reversed the ketamine-induced reduction in low beta power (10–20 Hz) and potentiated ketamine-induced increases in gamma and high frequency oscillations (130–160 Hz). Naltrexone inhibited frequencies above 50 Hz and significantly reduced the ketamine-induced increase in high frequency oscillations. However, some frequency band changes, such as clozapine-induced decreases in delta power, were only seen in locomoting rats. These results emphasise the potential in differentiating between activity states to capture drug effects and translate to human resting state EEG. Furthermore, the differential reversal of ketamine-induced EEG effects by clozapine and naltrexone may have implications for the understanding of psychotomimetic as well as rapid antidepressant effects of ketamine.

Intrachain Delocalization Effect of Charge Carriers on the Charge-Transfer State Dynamics in Organic Solar Cells

We studied the charge-generation mechanism in low-bandgap polymer (P4TNTz-2F)-fullerene bulk heterojunction (BHJ) organic solar cells (OSCs) using transient absorption (TA) spectroscopy. The highly crystalline nanowire structure of P4TNTz-2F in a blend film prepared with chlorobenzene (CB) and 1,8-diiodooctane (DIO) induced more long-lived charge carriers than those in a blend film prepared with CB only. Pump-wavelength-dependent TA data revealed that the increased charge-delocalization by the intrachain ordering of P4TNTz-2F in the blend film prepared with CB/DIO is the key factor to increasing the OSC efficiency. The intrachain charge-delocalization increased the charge-transfer (CT) state lifetime and suppressed geminate recombination losses, resulting in the efficient dissociation of CT states into free carriers. Our findings provide new insights into the excited-state dynamics study of BHJ blends, which can serve as a good guide for the development of novel OSC materials.

Spontaneous radiative dissociation of the second bound state of positronium hydride

The spontaneous radiative dissociation spectrum of the second bound state of positronium hydride (PsH) located just below the $\mathrm{H}(2p)+\mathrm{Ps}(2p)$ threshold energy is investigated by the variational and complex coordinate rotation methods. Convergence of the transition rates is examined in both length and velocity gauges. The spectrum indicates that the primary channel of radiative dissociation is the transition into the continuum of $\mathrm{H}(1s)+\mathrm{Ps}(2p)$, and the secondary one is that into the $\mathrm{H}(2p)+\mathrm{Ps}(1s)$ continuum. Radiative transition to the resonance state located close to the second bound state is found to exist. The total rate of the radiative dissociation is found to be $9.1(2)\ifmmode\times\else\texttimes\fi{}{10}^{8}\phantom{\rule{4pt}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$.

An assessment of the tropospherically accessible photo-initiated ground state chemistry of organic carbonyls

Abstract. Carbonyls are among the most abundant volatile organic compounds in the atmosphere. They are central to atmospheric photochemistry as absorption of near-UV radiation by the C=O chromophore can lead to photolysis. If photolysis does not occur on electronic excited states, non-radiative relaxation to the ground state will form carbonyls with extremely high internal energy. These “hot” molecules can access a range of ground state reactions. Up to nine potential ground state reactions are investigated at the B2GP-PLYP-D3/def2-TZVP level of theory for a test set of 20 representative carbonyls. Almost all are energetically accessible under tropospheric conditions. Comparison with experiment suggests the most significant ground state dissociation pathways will be concerted triple fragmentation in saturated aldehydes, Norrish type III dissociation to form another carbonyl, and H2 loss involving the formyl H atom in aldehydes. Tautomerisation, leading to more reactive unsaturated species, is also predicted to be energetically accessible and is likely to be important when there is no low-energy ground state dissociation pathway, for example in α,β-unsaturated carbonyls and some ketones. The concerted triple fragmentation and H2-loss pathways have immediate atmospheric implications for global H2 production, and tautomerisation has implications for the atmospheric production of organic acids.

Rapid degradation of the sulfonylurea herbicide–chlorimuron-ethyl by three novel strains of fungi

Chlorimuron-ethyl is a sulfonylurea herbicide with broad-spectrum weed control characteristics, low utilization rate, relatively high persistence in the soil. Chlorimuron-ethyl has been widely used world-over, and strategies for its removal have attracted increasing attention. Microbial degradation is considered the most acceptable dissipation method. We obtained the best biodegradation conditions using response surface methodology. Through the cleavage of the sulfonylurea bridge, we proposed a metabolic route for chlorimuron-ethyl degradation. Under these conditions (pH 6, 30 °C), Irpex lacteus could degrade 72.40% of the initially supplemented 40 mg L−1 chlorimuron-ethyl within 7 days. The half-life of chlorimuron-ethyl after inoculation was fairly short (4.696 days). The biodegradation rate of chlorimuron-ethyl by Irpex lacteus was 56.1%, which was higher than that of Phlebia sp. (50.8%) and Funalia trogii (25.4%). The pH value has an impact on the free state of the substrate molecule and the dissociation state of the enzyme molecule. The biodegradation rate was the highest (58.5%) at a pH value of 6. When the temperature was 30 °C, 56.3% of chlorimuron-ethyl was eliminated. As the temperature increased, the biodegradation rate of chlorimuron-ethyl by white-rot fungi decreased. Based on the results of LC–MS analysis, a metabolic route for chlorimuron-ethyl biodegradation was proposed. The fragment at m/z 161 (2-amino-4-chloro-6-methoxypyrimidine) originates from the cleavage of the C-N bond of the sulfonylurea bridge, while generating ethyl 2-sulfamoyl benzoate. The fragment at m/z 202 (2-sulfamoyl benzoic acid) corresponds to the ethyl group lost from ethyl 2-sulfamoyl benzoate. Due to the different secreted enzymes, there was a gap between the three strains in the degradation efficiency of chlorimuron-ethyl. The degradation rate of the herbicide by Phlebia sp. was the highest (61.7%), while by Irpex lacteus was the lowest (42.7%). Three white-rot fungi could degrade chlorimuron-ethyl in malt extract. LC–MS analysis indicated that the cleavage of sulfonylurea bridge through Irpex lacteus mediated the degradation of chlorimuron-ethyl. And, inoculation with white-rot fungi enhanced chlorimuron-ethyl degradation in aseptic soil samples. This is the principal report revealing that white-rot fungi can evacuate sulfonylurea herbicides, demonstrating that white-rot fungi will give novel ideas into the biodegradation of herbicides.

Relationship Between Dissociation and Antidepressant Effects of Esketamine Nasal Spray in Patients With Treatment-Resistant Depression.

BackgroundIn this post-hoc analysis, data from 2 positive, pivotal, phase 3 trials of esketamine nasal spray (ESK) in treatment-resistant depression (TRD)—short-term study (TRANSFORM-2) and maintenance study (SUSTAIN-1)—were analyzed to evaluate the relationship between dissociation and antidepressant effects of ESK.MethodsAnalysis by responder status, correlation analysis, and mediation analysis were performed to assess the relationships between peak Clinician Administered Dissociative States Scale (CADSS) scores after first (day 1) and last (day 25) ESK dose and change in Montgomery-Åsberg Depression Rating Scale (MADRS) total scores at the first (day 2) and last assessments (day 28) in TRANSFORM-2 and peak CADSS after first maintenance ESK dose and time to relapse in SUSTAIN-1 (only for mediation analysis).ResultsIn TRANSFORM-2, the percentage of responders (>50% reduction in MADRS) at day 2 and day 28 did not significantly differ between patients who did vs did not manifest significant dissociation (peak CADSS scores >4 or ≤4, respectively) following the first ESK dose. Spearman correlation coefficients between dissociation and depression improvement were nonsignificant and close to zero. CADSS scores did not significantly mediate the reduction in MADRS at day 2 or 28 in TRANSFORM-2 or the time to depression relapse in SUSTAIN-1. The mean difference in MADRS between ESK and active-control arms persisted beyond day 2 without significant change across time, although the mean peak CADSS scores significantly decreased across consecutive doses and fewer patients experienced significant dissociation after the last ESK dose compared with the first.ConclusionWithin the dose range tested, the dissociative and antidepressant effects of ESK were not significantly correlated.Trial registrationNCT02417064 (TRANSFORM-1); NCT02418585(TRANSFORM-2); NCT02493868 (SUSTAIN-1)

Energetics of the charge generation in organic donor-acceptor interfaces.

Non-fullerene acceptor materials have posed new paradigms for the design of organic solar cells , whereby efficient carrier generation is obtained with small driving forces, in order to maximize the open-circuit voltage (VOC). In this paper, we use a coarse-grained mixed quantum-classical method, which combines Ehrenfest and Redfield theories, to shed light on the charge generation process in small energy offset interfaces. We have investigated the influence of the energetic driving force as well as the vibronic effects on the charge generation and photovoltaic energy conversion. By analyzing the effects of the Holstein and Peierls vibrational couplings, we find that vibrational couplings produce an overall effect of improving the charge generation. However, the two vibronic mechanisms play different roles: the Holstein relaxation mechanism decreases the charge generation, whereas the Peierls mechanism always assists the charge generation. Moreover, by examining the electron-hole binding energy as a function of time, we evince two distinct regimes for the charge separation: the temperature independent excitonic spread on a sub-100fs timescale and the complete dissociation of the charge-transfer state that occurs on the timescale of tens to hundreds of picoseconds, depending on the temperature. The quantum dynamics of the system exhibits the three regimes of the Marcus electron transfer kinetics as the energy offset of the interface is varied.

Direct UV photodegradation of herbicide triclopyr in aqueous solutions: A mechanistic study

Mechanism of direct UV photolysis of pyridine herbicide triclopyr (TRI) was revealed by the combination of nanosecond laser flash photolysis, steady-state photolysis coupled with high resolution LC-MS and DFT quantum-chemical calculations. Both the detection of short-lived intermediates and the detailed identification of final products were done for the first time. The quantum yield of TRI photodegradation is about 4% at both UVC (254 nm) and UVB (308 nm) excitation. The primary stage is the heterolytic cleavage of C–Cl bond in dissociative triplet state of TRI with the formation of phenyl cation followed by a fast nucleophilic attack by a solvent molecule. The minor channel is the photohydrolysis leading to the formation of 3,5,6-trichloropyridin-2-ol. Primary photoproducts undergo secondary photolysis by the mechanism similar to initial TRI with the formation of products of acetic group elimination, sequential substitution of chlorine atoms to hydroxyl groups and, finally, oxidation and opening of the pyridine ring. Obtained results can be important for understanding the fate of pyridine herbicides in the processes of UVC disinfection and in natural waters under action of the sunlight.

Influence of Long-Range Forces on the Transition States and Dynamics of NaCl Ion-Pair Dissociation in Water.

We study NaCl ion-pair dissociation in a dilute aqueous solution using computer simulations both for the full system with long-range Coulomb interactions and for a well-chosen reference system with short-range intermolecular interactions. Analyzing results using concepts from Local Molecular Field (LMF) theory and the recently proposed AI-based analysis tool "State predictive information bottleneck" (SPIB), we show that the system with short-range interactions can accurately reproduce the transition rate for the dissociation process, the dynamics for moving between the underlying metastable states, and the transition state ensemble. Contributions from long-range interactions can be largely neglected for these processes because long-range forces from the direct interionic Coulomb interactions are almost completely canceled (>90%) by those from solvent interactions over the length scale where the transition takes place. Thus, for this important monovalent ion-pair system, short-range forces alone are able to capture detailed consequences of the collective solvent motion, allowing the use of physically suggestive and computationally efficient short-range models for the dissociation event. We believe that the framework here should be applicable to disentangling mechanisms for more complex processes such as multivalent ion disassociation, where previous work has suggested that long-range contributions may be more important.

Dominant Perversions; Perverse Dominance: Eroticized Schemata and Dissociative Phenomena in the Case of Daniel

In this paper, I describe my ongoing journey with Daniel, a patient with a severe dissociative disorder. With detailed explorations of major enactments, I illustrate how issues around desire, excitement, and intimacy shape our eroticized transference-countertransference imbrication and compel episodic relational states of deadness and terror. Reflecting on the shifting roles of dominance, submission and states of dissociation, I explicate the powerful effects of spontaneity and self-disclosure in the navigation of seemingly intractable stalemates.

Low-Energy Protons in Strong-Field Dissociation of H 2 + via Dipole-Transitions at Large Bond Lengths

More than ten years ago, the observation of the low-energy structure in the photoelectron energy spectrum, regarded as an “ionization surprise,” has overthrown our understanding of strong-field physics. However, the similar low-energy nuclear fragment generation from dissociating molecules upon the photon energy absorption, one of the well-observed phenomena in light-molecule interaction, still lacks an unambiguous mechanism and remains mysterious. Here, we introduce a time-energy-resolved manner using a multicycle near-infrared femtosecond laser pulse to identify the physical origin of the light-induced ultrafast dynamics of molecules. By simultaneously measuring the bond-stretching times and photon numbers involved in the dissociation of H 2 + driven by a polarization-skewed laser pulse, we reveal that the low-energy protons (below 0.7 eV) are produced via dipole-transitions at large bond lengths. The observed low-energy protons originate from strong-field dissociation of high vibrational states rather than the low ones of H 2 + cation, which is distinct from the well-accepted bond-softening picture. Further numerical simulation of the time-dependent Schrödinger equation unveils that the electronic states are periodically distorted by the strong laser field, and the energy gap between the field-dressed transient electronic states may favor the one- or three-photon transitions at the internuclear distance larger than 5 a.u. The time-dependent scenario and our time-energy-resolved approach presented here can be extended to other molecules to understand the complex ultrafast dynamics.

Experience of Late Miscarriage and Practical Implications for Post-Natal Health Care: Qualitative Study.

Miscarriage is the most common reason for pregnancy loss, affecting around one in four pregnancies. It is classified as a traumatic event, associated with an increased risk for depression, anxiety, post-traumatic stress, alcohol dependence, somatic symptoms, sexual dysfunction, suicide, and complicated grief. This study aimed to analyse experiences of late miscarriage and to describe practical implications for post-natal health care based on characteristics of pregnancy loss revealed in a qualitative study. Seven women who had late miscarriages participated in in-depth biographical interviews. A phenomenological thematic analysis was applied. Experiential characteristics of late miscarriage were described by four themes and 13 subthemes: the initial splitting state (Dissociation, An Opened Void, An impaired Symbiosis, and The Body is Still Pregnant while the Psyche is Mourning); Betrayal of the body (Symbolic Experience of Internalised Death, Shocking Materiality of the Ongoing Miscarriage, Lost control of the Body, and Confusing Body Signals); Disconnecting (Depersonalising Medical Environment, Guilt Falsifies perception, and Retreat as a means of Self-Preservation); and Reconnecting (Collecting Shatters and Reinterpretation of Maternal Identity). Based on the results of the experiential analysis, another four themes represent practical recommendations for post-natal health care: Informing, Opportunity for Goodbye, Attention to Emotional Wellbeing, and Respectful Hospital Environment.

Non-Abelian electric field correlator at NLO for dark matter relic abundance and quarkonium transport

We perform a complete next-to-leading order calculation of the non-Abelian electric field correlator in a SU(Nc) plasma, which encodes properties of the plasma relevant for heavy particle bound state formation and dissociation, and is different from the correlator for the heavy quark diffusion coefficient. The calculation is carried out in the real-time formalism of thermal field theory and includes both vacuum and finite temperature contributions. By working in the Rξ gauge, we explicitly show the results are gauge independent, infrared and collinear safe. The renormalization group equation of this electric field correlator is determined by that of the strong coupling constant. Our next-to-leading order calculation can be directly applied to any dipole singlet-adjoint transition of heavy particle pairs. For example, it can be used to describe dissociation and (re)generation of heavy quarkonia inside the quark-gluon plasma well below the melting temperature, as well as heavy dark matter pairs (or charged co-annihilating partners) in the early universe.

The Comparison of the Efficacy of Early versus Late Administration of Dexmedetomidine on Postoperative Emergence Agitation in Children Undergoing Oral Surgeries: A Randomized Clinical Trial.

Background: Emergence Agitation (EA) is a dissociated state of consciousness characterized by irritability, uncompromising stance, and inconsolability. The etiology of EA is not completely understood. Dexmedetomidine is a highly selective α2-adrenoreceptor agonist with sedative and analgesic properties, which has been used to reduce the incidence of EA. We aimed to assess the efficacy of early versus late administration of dexmedetomidine on EA in children undergoing oral surgery.Methods: A randomized, parallel, double-blind clinical trial was conducted at Mofid Children’s Hospital affiliated to Shahid Beheshti University of Medical Sciences (Tehran, Iran) from November 2016 to March 2017. A total of 81 children, who underwent adenotonsillectomy or cleft palate repair surgery were enrolled in the study. Based on simple randomization, the children were assigned to two groups, namely early (group A, n=41) and late (group B, n=40) administration of dexmedetomidine. Intra-operative and postoperative hemodynamic variables, extubation time, post-anesthesia care unit (PACU) length of stay, and the scores on Ramsay sedation scale and FLACC pain scale were measured and compared. The data were analyzed using SPSS software (version 20.0), and P<0.05 were considered statistically significant.Results: The mean FLACC score was lower in the late group than in the early group (2.0±1.5 vs. 4.2±1.6, P<0.001). The mean Ramsay sedation score was higher in the late group than in the early group (3.5±1.4 vs. 1.8±0.8, P<0.001).Conclusion: Late administration of dexmedetomidine 1 µg/kg reduced the incidence of EA and PACU length of stay and improved postoperative pain management.Trial registration number: IRCT 2016122031497N1.

Complex Trauma Symptoms after Childhood Maltreatment: Strengths and Challenges of the Therapy Program STAIR-NT

The number and type of traumatic experiences (especially childhood maltreatment) appear to increase the risk of developing complex trauma symptoms. There is initial evidence that patients with complex trauma benefit from phase-based therapeutic approaches. STAIR-NT (Skills Training in Affective and Interpersonal Regulation with Narrative Therapy) is a two-phase trauma therapy approach: emotion regulation and interpersonal skills are learned in the STAIR phase, and in the narrative therapy phase (NT) the exposure to trauma aims at recognizing and changing dysfunctional, trauma-associated assumptions. Experiences with STAIR-NT in the context of a current treatment study show that the two phases provide a clear structure and more security for the treatment. First clinical experiences with STAIR-NT as well as short case vignettes are presented and recommendations for the treatment of patients with complex trauma are given. Concrete practical recommendations are offered for the implementation and individualization on interventions, which among others relate to offender contact, motivational work, handling dissociative states, therapeutic methods (especially exposure), and therapy completion. The close connection between theory and practice facilitates the transfer of learning experiences into everyday life and promotes the strengthening of patients’ self-efficacy and autonomy.

Autoethnographic Animation and The Metabolism of Trauma: A Multimethod Investigation

This paper provides an overview of my practice-based doctoral research: Bearing Witness: Autoethnographic Animation and the Metabolism of Trauma, which uses a multimethod approach (cognitive focus, thematic analysis of qualitative data and artistic practice), to investigate autoethnographic animation’s capacity to moderate psychological trauma. Traumatic events such as child abuse, domestic violence and military conflict often present a major health challenge for survi­vors, with many experiencing significantly impaired function due to symptoms such as nightmares, emotional dysregulation, negative cognitions and dissociative states. The symptoms most commonly reported are intrusive memories-sensory-perceptu­al impressions that involuntarily intrude into consciousness, causing distress and a sense of reexperiencing the trauma. A number of cognitive studies have measured how these intrusions may be moderated through models that either interfere with imagery, simulate trauma, or change its narrative. My research uses interviews, thematic analysis and artistic practice to inves­tigate whether animation may similarly moderate intrusions through processes that utilise the medium’s visuospatial capacities and its potential for rescripting, or changing, the trauma narrative. The desire to use personal experience as data motivated my interest in autoethnography as a methodology for qualitative inquiry. Autoethnography is a reflexive approach that explores autobiographical stories and connects these to wider socio-cultural-polit­ical issues through writing, performance and other media. In this research I am using autoethnography to both address my lived experience of trauma and to moderate its symptoms through my animation practice.

Kinetic and Computational Analysis of CO Substitution in a Dinuclear Osmium Carbonyl Complex: Intersection between Dissociative and Dissociative-Interchange Mechanisms.

The mechanism for the CO substitution reaction involving the diosmium carbonyl sawhorse complex Os2(μ-O2CH)2(CO)6, which contains an Os-Os single bond, two axial CO ligands, and four equatorial CO ligands, was investigated experimentally and theoretically. Kinetic measurements show 13CO axial substitution proceeding by a dissociative reaction that is first-order in the complex and zero-order in 13CO but with an unexpectedly negative entropy of activation. The corresponding electronic structure calculations yield an enthalpy of activation for axial CO dissociation that is much larger than that determined by the kinetic experiments, but in agreement with the complex's stability with respect to CO loss. Additional calculations yield a dissociative interchange transition state whose free energy, enthalpy, and entropy of activation are in good agreement with those obtained from the kinetic measurements for the apparently dissociative substitution. These results point to an exchange reaction mechanism that is surprisingly close to the poorly understood transition from a dissociative mechanism with a CO-loss intermediate to a dissociative interchange mechanism with a transition state involving both the entering and the leaving COs. The key to explain these findings is provided by the vibrational analysis, which shows very low energy wagging motions for the axial COs. Thus, the incoming CO only displaces the outgoing CO when the complex has an outgoing CO near the wag's turning point. This dissociative interchange mechanism predicted by the calculation explains the unexpected combination of kinetics and stability characteristics. Kinetics reveals that the reaction is first-order in the Os dimer with a negative Eyring entropy, while a stability study shows that the Os dimer's decomposition rate is several orders of magnitude slower than CO exchange.

Thermodynamics analysis and temperature response mechanism during methane hydrate production by depressurization

Methane hydrate is expected as a future energy to satisfy the long-term energy needs worldwide. Yet, the thermodynamics behaviors and temperature response mechanism during methane hydrate production by depressurization are still unclear. In this study, four methane hydrate-bearing sandy sediments with different initial pressures (6.0, 5.5, 4.8 and 4.2 MPa) are depressurized to 3.0 MPa at a slow rate, and the temperature decreases with the depressurization progresses and will be accelerated from the hydrates start to dissociate. The dissociation rate of hydrates gradually increase to and keep at a highest value under a rated production flux, when the temperature is strictly response to the pressure and the pressure and temperature trajectories are parallel to the hydrate phase equilibrium line. At this stage, the external heat transfer is almost used for the hydrate dissociation, and it is called stationary state of hydrate dissociation in this study. When the pressure turns constant, the hydrate dissociation changes to a lower rate than the depressurization stage, and then the declined dissociation rate consumes less heat and therefore can warm the whole sediment. The results reveal the temperature response differences before, in and after the hydrate dissociation process and provide direct thermodynamic criterion for the field monitoring of methane hydrate production.