Search

Power-to-chemical technologies with CO2 as feedstock recycle CO2 and store energy into value-added compounds. Plasma discharges fed by renewable electricity are a promising approach to CO2 conversion. However, controlling the mechanisms of plasma dissociation is crucial to improving the efficiency of the technology. We have investigated pulsed nanosecond discharges, showing that while most of the energy is deposited in the breakdown phase, CO2 dissociation only occurs after an order of microsecond delay, leaving the system in a quasi-metastable condition in the intervening time. These findings indicate the presence of delayed dissociation mechanisms mediated by CO2 excited states rather than direct electron impact. This “metastable” condition, favorable for an efficient CO2 dissociation, can be prolonged by depositing more energy in the form of additional pulses and critically depends on a sufficiently short interpulse time.

We study the mechanisms of CO 2 conversion in a nanosecond repetitively pulsed (NRP) discharge, by means of a chemical kinetics model. The calculated conversions and energy efficiencies are in reasonable agreement with experimental results over a wide range of specific energy input values, and the same applies to the evolution of gas temperature and CO 2 conversion as a function of time in the afterglow, indicating that our model provides a realistic picture of the underlying mechanisms in the NRP discharge and can be used to identify its limitations and thus to suggest further improvements. Our model predicts that vibrational excitation is very important in the NRP discharge, explaining why this type of plasma yields energy-efficient CO 2 conversion. A significant part of the CO 2 dissociation occurs by electronic excitation from the lower vibrational levels toward repulsive electronic states, thus resulting in dissociation. However, vibration-translation (VT) relaxation (depopulating the higher vibrational levels) and CO + O recombination (CO + O + M → CO 2 + M), as well as mixing of the converted gas with fresh gas entering the plasma in between the pulses, are limiting factors for the conversion and energy efficiency. Our model predicts that extra cooling, slowing down the rate of VT relaxation and of the above recombination reaction, thus enhancing the contribution of the highest vibrational levels to the overall CO 2 dissociation, can further improve the performance of the NRP discharge for energy-efficient CO 2 conversion.

Over the years, until the present days, a persistent mistake has been found in the literature: the use of the ‘vibrational temperature’ of an emitting electronic state as somewhat representative of the vibrational temperature of the gas in the discharge. Such a temperature is determined by fitting the spectra measured by optical emission spectroscopy. Besides the misuse of the word temperature, the results of such fittings are ambiguously named ‘vibrational temperature’ and sometimes used to argue about the vibrational non-equilibrium and its variation with discharge conditions. What has this temperature to do with the vibrational excitation of the molecules’ ground state, i.e. of the large majority of gas components? It is well established that the connection between the vibrational population of the excited and the ground state exists through the excitation process, the collisional quenching, and the vibrational relaxation in the manifold of the excited state. Nevertheless, this is very often ignored in the literature. In this note, we discuss this subject with the example of the ‘vibrational temperature’ of the N2(C, v) manifold, showing how much all the mentioned parameters can drive to incorrect deductions from an anyway conceptually wrong measurement.

Nanosecond pulsed discharge plasma shows a high degree of non-equilibrium, and exhibits relatively high conversions in the dry reforming of methane. To further improve the application, a good insight of the underlying mechanisms is desired. We developed a chemical kinetics model to explore the underlying plasma chemistry in nanosecond pulsed discharge. We compared the calculated conversions and product selectivities with experimental results, and found reasonable agreement in a wide range of specific energy input. Hence, the chemical kinetics model is able to provide insight in the underlying plasma chemistry. The modeling results predict that the most important dissociation reaction of CO2 and CH4 is electron impact dissociation. C2H2 is the most abundant hydrocarbon product, and it is mainly formed upon reaction of two CH2 radicals. Furthermore, the vibrational excitation levels of CO2 contribute for 85% to the total dissociation of CO2.

The plasma dry reforming reaction of methane with carbon dioxide is investigated in a nanosecond repetitively pulsed discharge, a type of plasma that offers one of the highest non-equilibrium and performance characteristics. The experiment's purpose was to examine the effect of varying the sequence of high-voltage pulses for the same plasma energy. We find that when successive pulses are closer than 500 $\rm \mu$s, a memory-dominated regime gradually develops, which influences subsequent breakdown events. As a result, both a higher reactant conversion and more efficient use of the energy injected into the discharge plasma are achieved., Comment: 12 pages, 12 figures

Endothermic reactions can be used to store renewable electricity in chemical form. Here we report on the reduction of CO 2 to CO and O 2 using a nanosecond repetitively pulsed discharge at atmospheric pressure. We find that by changing the inter-pulse duration, different values for the CO 2 dissociation and energy efficiency can be obtained for the same energy input. This finding opens the way to a better understanding of plasma-based technologies for the valorization of CO 2 .

Introduction: Charged species have been detected at various stages of stellar evolution, from pre- and protostellar objects to planet-forming disks, where they can be used as signatures of the build-up in chemical complexity [1, 2, 3, 4, 5]. On the other hand, on planets and planetary bodies with atmospheres exposed to photons and energetic particles, ionic reactions have been suggested as playing a significant role in the build-up of chemical complexity. A good example is the atmosphere of Titan, where the CASSINI mission [6] detected, by mass spectrometry, a wide range of N-containing organic ions, and photochemical models [7, 8] predict that these ions trigger a rich gas-phase chemistry, eventually forming tholins, a key ingredient of Titan’s haze [9]. Similar effects may be expected in the atmospheres of exoplanets, for which simulation experiments indicate that complex photochemistry can take place leading to formation of large molecules [10, 11]. It has been suggested that complex organic molecules (COMs) could be synthesised through reactions on dust grains, a process which might be facilitated by the acceleration of cations in the gas phase towards negatively charged dust grains [12]. It is therefore important to understand the gas-phase ion chemistry of these environments in order to develop reliable chemical models. Results: In our laboratories, we measure kinetic parameters (cross sections, branching ratios and their dependences on collision energy) for the reaction of charged molecules with neutrals, using tandem mass spectrometric techniques and RF octupolar trapping of parent and product ions. In this contribution, we examine the reactions of two isomers of [CNH3]+ that are believed to contribute to the m/z 29 peak observed in the aforementioned mass spectra of Titan’s atmosphere, namely HCNH2+ and H2CNH+, with a range of neutrals including both saturated; CH4; and unsaturated; C2H2, C2H4, C3H4 (allene), C3H4 (propyne) and C3H6; hydrocarbons as well as some simple nitriles; CH3CN and C2H3CN; and CH3OH with the objective of identifying the reaction pathways present as well as their respective rate constants and branching ratios. Experimental Methods: The data presented here for the HCNH2+ and H2CNH+ ions were collected using the CERISES instrument attached to the DESIRS beamline of the French SOLEIL synchrotron [13], using VUV photons to generate ions through either direct photoionization or dissociative photoionization of suitable neutral precursors. The HCNH2+ ion was generated exclusively through dissociative photoionization of cyclopropylamine (C3H7N)[14] while H2CNH+ was generated both through dissociative photoionization of azetidine (C3H7N also) and via direct photoionization of neutral methanimine, produced via a gas-solid reaction between aminoacetonitrile in gas phase and powdered potassium hydroxide [15]. Working in this way allows us to present data as a function of the energy of the photons used in the ionisation; which in the case of direct ionisation is a proxy for the internal energy of the ions; as well as as a function of the collision energy. Ab initio calculations have also been performed for some of these reactions, with work underway on the others, in order to aid the interpretation of the mechanisms involved in the formation of the various products and their respective energy profiles. Conclusions: Our experiments demonstrate that not only can the two isomers of [CNH3]+ be generated selectively, but that they show wide-ranging and varied chemistries with a wide range of different neutral molecules. In addition to undergoing charge transfer, proton-transfer and H-abstraction reactions, these isomers also appear to undergo a range of more complex pathways proceeding via the adduct, demonstrating that these species could indeed play a role in the complex gas-phase chemistry of planetary atmospheres with C and N-containing species. Acknowledgements: D.A. and V.R. acknowledge funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 811312 for the project "Astro-Chemical Origins” (ACO). We acknowledge SOLEIL for provision of synchrotron radiation facilities and the DESIRS beamline team for their assistance, and J-CG would like to thank the Centre National d’Etudes Spatiales (CNES) for their financial support. [1] L. Podio et al., A&A, 565, A64 (2014) [2] C. Vastel et al. , A&A, 591, L2 (2016) [3] A. Bacmann et al. , A&A, 588, L8 (2016) [4] N. Marcelino et al. , A&A, 612, L10 (2018) [5] V.M. Rivilla et al. , MNRAS Lett. , 483, L114 (2019) [6] V. Vuitton , R.V. Yelle and M.J. McEwan, Icarus, 191, 722-742 (2007) [7] V. Vuitton et al., Icarus, 324, 120-197 (2019) [8] S.M. Horst, J. Geophys. Res. Planets, 122, 432-482 (2017) [9] D. Dubois et al. , ApJ Lett, 872, L31 [10] C. He, S.M. Hörst et al. , ACS Earth Space Chem. , 3, 39-50 (2019) [11] J. Bourgalais et al. , ApJ, 897 (77), 13pp (2020) [12] C.R. Stark, C. Helling, D.A. Diver and P.B. Rimmer, Int. J. Astrobiology, 13 (2), 165-172 (2014) [13] D. Ascenzi et al. , Frontiers in Chemistry, 7, 537 (2019) [14] J. Chamot-Rooke, P. Mourgues et al. , Int. J. Mass Spectrom., 226, 249-269 (2003) [15] J.C. Guillemin et al. , Tetrahedron, 44, 4431-4446 (1988)

Overconfidence is a well-established bias in which someone's subjective confidence in their own judgments is systematically greater than their objective accuracy. There is abundant anecdotal evidence that overconfident people increase their exposure to risk. In this paper, we test whether overconfident people underestimate the probability of incurring an avalanche accident. An avalanche accident is a typical "black swan" event because it has a low probability of occurring but has potential dramatic consequences. To test whether the overconfidence bias affects the decision of backcountry skiers to go on a ski trip under different levels of avalanche risk, we measured individual cognitive traits and then used a random effect logit model to measure their effects on the probability to take the tour, by controlling for other observable characteristics of the respondent. We show that 1) overconfidence is widespread even in our sample and 2) practitioners who are more prone to overestimate their knowledge are also more likely to take the risk associated with a ski trip exposed to avalanche danger. This suggests that overconfident people are more exposed to black swan events.

Electrical discharges are increasingly used to dissociate CO2 in CO and O2. This reaction is the first step in the way for the synthesis of value-added compounds from CO2 by using renewable electricity. If efficient, this technology might allow at the same time recycling CO2 and storing renewable energy in chemical form. At present, while the dissociation degree is measured in the reactor exhaust, little is experimentally known about the dissociation kinetics in the discharge and post-discharge. This knowledge is however critical to increasing the overall efficiency of the plasma process. To estimate the time dependence of the CO2 dissociation following a discharge event, we have coupled a LIF diagnostics to a nanosecond repetitively pulsed discharge in a mixture of CO2 and H2O. This paper discusses a procedure to obtain data on the time evolution of the CO2 dissociation, its limits and future perspectives. In addition, the local gas temperature is measured as well. We find that a few microseconds after the discharge pulse, CO2 is highly dissociated with a temperature around 2500 K. In about 100 µs, the temperature decreases at about 1500 K while the dissociation is reduced by about a factor of three.

Nanosecond repetitively pulsed discharges at atmospheric pressure have shown comparatively high performances for CO2 reduction to CO and O2. However, mechanisms of CO2 dissociation in these transient discharges are still a matter of discussion. In the present work, we have used time-resolved optical emission spectroscopy to investigate the CO2 discharge progression from the initial breakdown event to the final post-discharge. We discover a complex temporal structure of the spectrally resolved light, which gives some insights into the underlying electron and chemical kinetics. We could estimate the electron density using the Stark broadening of O and C lines and the electron temperature with C+ and C++ lines. By adding a small amount of nitrogen, we could also monitor the time evolution of the gas temperature using the second positive system bands of N2. We conclude that the discharge evolves from a breakdown to a spark phase, the latter being characterised by a peak electron density around 1018 cm−3 and a mean electron temperature around 2 eV. The spark phase offers beneficial conditions for vibrationally enhanced dissociation, which might explain the high CO2 conversion observed in these plasma discharges.

Long-range intermolecular forces play a crucial role in controlling the outcome of ion-molecule chemical reactions, such as those determining the disappearance of organic or inorganic "complex" molecules recently detected in various regions of the interstellar medium due to collisions with abundant interstellar atomic ions (e.g. H+ and He+ ). Theoretical treatments, for example, based on simple capture models, are nowadays often adopted to evaluate the collision-energy dependence of reactive cross sections and the temperature dependent rate coefficients of many ion-molecule reactions. The obtained results are widely used for the modelling of phenomena occurring in different natural environments or technological applications such as astrophysical and laboratory plasmas. Herein it is demonstrated, through a combined experimental and theoretical investigation on a prototype ion-molecule reaction (He+ +methyl formate), that the dynamics, investigated in detail, shows some intriguing features that can lead to rate coefficients at odds with the expectations (e.g. Arrhenius versus anti-Arrhenius behaviour). Therefore, this study casts light on some new and general guidelines to be properly taken into account for a suitable evaluation of rate coefficients of ion-molecule reactions.

Background It remains unclear whether radial access (RA), compared with femoral access (FA), mitigates the risk of acute kidney injury (AKI). Objectives The authors assessed the incidence of AKI in patients with acute coronary syndrome (ACS) enrolled in the MATRIX-Access (Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of Angiox) trial. Methods Among 8,404 patients, 194 (2.3%) were excluded due to missing creatinine values, no or an incomplete coronary angiogram, or previous dialysis. The primary AKI-MATRIX endpoint was AKI, defined as an absolute (>0.5 mg/dl) or a relative (>25%) increase in serum creatinine (sCr). Results AKI occurred in 634 patients (15.4%) with RA and 712 patients (17.4%) with FA (odds ratio [OR]: 0.87; 95% confidence interval [CI]: 0.77 to 0.98; p = 0.0181). A >25% sCr increase was noted in 633 patients (15.4%) with RA and 710 patients (17.3%) with FA (OR: 0.87; 95% CI: 0.77 to 0.98; p = 0.0195), whereas a >0.5 mg/dl absolute sCr increase occurred in 175 patients (4.3%) with RA versus 223 patients (5.4%) with FA (OR: 0.77; 95% CI: 0.63 to 0.95; p = 0.0131). By implementing the Kidney Disease Improving Global Outcomes criteria, AKI was 3-fold less prevalent and trended lower with RA (OR: 0.85; 95% CI: 0.70 to 1.03; p = 0.090), with stage 3 AKI occurring in 28 patients (0.68%) with RA versus 46 patients (1.12%) with FA (p = 0.0367). Post-intervention dialysis was needed in 6 patients (0.15%) with RA and 14 patients (0.34%) with FA (p = 0.0814). Stratified analyses suggested greater benefit with RA than FA in patients at greater risk for AKI. Conclusions In ACS patients who underwent invasive management, RA was associated with a reduced risk of AKI compared with FA. (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX [MATRIX]; NCT01433627 )

Aims To assess whether radial compared with femoral access is associated with consistent outcomes in patients with ST-segment elevation myocardial infarction (STEMI) and non-ST-segment elevation acute coronary syndrome (NSTE-ACS). Methods and results In the Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX (MATRIX) programme patients were randomized to radial or femoral access, stratified by STEMI (2001 radial, 2009 femoral) and NSTE-ACS (2196 radial, 2198 femoral). The 30-day co-primary outcomes were major adverse cardiovascular events (MACE), defined as death, myocardial infarction, or stroke, and net adverse clinical events (NACE), defined as MACE or major bleeding In the overall study population, radial access reduced the NACE but not MACE endpoint at the prespecified 0.025 alpha. MACE occurred in 121 (6.1%) STEMI patients with radial access vs. 126 (6.3%) patients with femoral access [rate ratio (RR) = 0.96, 95% CI = 0.75–1.24; P = 0.76] and in 248 (11.3%) NSTE-ACS patients with radial access vs. 303 (13.9%) with femoral access (RR = 0.80, 95% CI = 0.67–0.96; P = 0.016) (Pint = 0.25). NACE occurred in 142 (7.2%) STEMI patients with radial access and in 165 (8.3%) patients with femoral access (RR = 0.86, 95% CI = 0.68–1.08; P = 0.18) and in 268 (12.2%) NSTE-ACS patients with radial access compared with 321 (14.7%) with femoral access (RR = 0.82, 95% CI = 0.69–0.97; P = 0.023) (Pint = 0.76). All-cause mortality and access site-actionable bleeding favoured radial access irrespective of ACS type (Pint = 0.11 and Pint = 0.36, respectively). Conclusion Radial as compared with femoral access provided consistent benefit across the whole spectrum of patients with ACS, without evidence that type of presenting syndrome affected the results of the random access allocation.

Waste treatment plants emit volatile organic compounds (VOCs) in the atmosphere, which can be both toxic and unpleasant for their smell. Biofiltration is a valuable option to decrease the amount of emitted VOCs under stationary conditions, while it suffers from problems under transient conditions. To overcome this drawback, an additional treatment before the biofiltration stage might be an effective strategy. In the present work, we evaluated the plasma treatment on some typical VOCs (α-pinene, ethyl isovalerate, and dimethyl disulphide) by considering, in particular, the energy cost of different removal rates and the consequent economic costs of scaling the laboratory setup to real-size plants. Depending on the desired target, the operating costs of different process schemes have been considered, and the most convenient operational mode has been identified. Our results suggest that the use of non-thermal plasmas as a pretreatment of a biofiltration stage in the waste treatment might be a valuable option.

Electric and magnetic field gradients, arising from sufficiently strong anisotropic intermolecular forces, tend to induce molecular polarization which can often modify substantially the results of molecular collisions, especially at low rotational temperatures and low collision energies. The knowledge of these phenomena, today still not fully understood, is of general relevance for the control of the stereo-dynamics of elementary chemical-physical processes, involving neutral and ionic species under a variety of conditions. This paper reports on results obtained by combining information from scattering, spectroscopic and reactivity experiments, within a collaboration between the research groups in Perugia and Trento. We addressed particular attention to the reactions of small atomic ions with polar neutrals for their relevance in several environments, including interstellar medium, planetary atmospheres, and laboratory plasmas. In the case of ion-molecule reactions, alignment/orientation is a general phenomenon due to the electric field generated by the charged particle. Such phenomenon originates critical stereo-dynamic effects that can either suppress (when the orientation drives the collision complex into non-reactive or less reactive configurations), or enhance the reactivity (when orientation confines reagents in the most appropriate configuration for reaction). The associated rate coefficients show the propensity to follow an Arrhenius and a non-Arrhenius behavior, respectively.

A nanosecond discharge imposes severe challenges to the application of laser induced fluorescence (LIF), due to the nature of its variable and hot collisional environment. In this paper, we review these difficulties, the current knowledge on collision processes and the concept of collision energy transfer LIF (CET-LIF). The application of CET-LIF to nanosecond discharges for CO2 dissociation shows results that make this challenge worth pursuing.

To correctly model the abundances of interstellar complex organic molecules (iCOMS) in different environments, both formation and destruction routes should be appropriately accounted for. While several scenarios have been explored for the formation of iCOMs via grain and gas-phase processes, much less work has been devoted to understanding the relevant destruction pathways, with special reference to (dissociative) charge exchange or proton transfer reactions with abundant atomic and molecular ions such as He$^+$, H$_3^+$ and HCO$^+$. By using a combined experimental and theoretical methodology we provide new values for the rate coefficients and branching ratios (BRs) of the reactions of He$^+$ ions with two important iCOMs, namely dimethyl ether (DME) and methyl formate (MF). We also review the destruction routes of DME and MF by other two abundant ions, namely H$_3^+$ and HCO$^+$. Based on our recent laboratory measurements of cross sections and BRs for the DME/MF + He$^+$ reactions over a wide collision energy range, we extend our theoretical insights on the selectivity of the microscopic dynamics to calculate the rate coefficients $k(T)$ in the temperature range from 10 to 298 K. We implement these new and revised kinetic data in a general model of cold and warm gas, simulating environments where DME and MF have been detected. Due to stereodynamical effects present at low collision energies, the rate coefficients, BRs and temperature dependences here proposed differ substantially from those reported in KIDA and UDfA, two of the most widely used astrochemical databases. These revised rates impact the predicted abundances of DME and MF, with variations up to 40% in cold gases and physical conditions similar to those present in prestellar cores, Comment: accepted for publication in Astronomy and Astrophysics (manuscript no. AA/2018/34585), 10 pages, 3 figures

Knowledge of molecular energy-transfer processes is a key ingredient for using laser-induced fluorescence, LIF, as a quantitative optical diagnostic method at high pressure. At present, rate constants of electronic quenching and vibrational energy transfer of electronic quenching and vibrational energy transfer in the OH(A2Σ+; ν' = 0,1) manifold for many colliders are known only in the condition of thermal equilibrium of the rotational population of the A electronic state. However, this condition is seldom met in molecular gases. Therefore, the rotational distributions in the OH(A2Σ+; ν' = 0,1) manifold are often non-thermal and close to the nascent ones. In the present work, a new set of rate constants has been measured in the condition of non-thermal rotational distribution, for the excitation of three rotational levels, N'= 0,1, 2, of OH(A2Σ+; ν' = 1) with CO2, CO, O2, CH4 and H2 as colliders. For N'= 2 the temperature dependence of the rate constants has also been measured for the first time from 300 to over 2000 K. These new data are crucial for the quantification of OH by LIF in gas discharges at high pressure and to fully exploit the CET-LIF (Collision Energy Transfer LIF) technique for measuring the CO2 dissociation as a function of time in a nanosecond repetitively pulsed discharge.

Vibrational activation of N2 molecules in a flowing microwave plasma is investigated in the context of utilising electrical energy for chemical conversion. Spatial profiles of rotational (Tr) and vibrational (T v) temperatures are measured by Raman scattering. Maximum values of T r = 3500 K and T v = 6000 K were observed in the centre of the plasma at low pressure (50 mbar). A detailed quantification of the local energy content shows how the strong non-equilibrium character of low pressure discharges compares with a closer-to-equilibrium energy distribution at higher pressures. Measurements performed downstream of the plasma display the ability of the microwave flowing reactor to deliver up to 48% of the specific energy input (SEI) into internal degrees of freedom of the gas molecules. Specifically, 23% of the SEI is loaded into the vibrational mode, which is potentially available to enhance chemical reactivity of endothermic reactions.

Cyclopropyl cyanide and other simple nitriles detected in Titan's atmosphere could be precursors leading to the formation of organic macromolecules in the atmosphere of Saturn's largest satellite. Proposing a thermodynamically possible mechanism that explains their formation and supports experimental results represents a difficult challenge. Experiments done in the Atomic and Molecular Physics Laboratory at the University of Trento (AMPL) have studied the ion-molecule reaction between cyclopropyl cyanide and its protonated form, with reaction products being characterized by mass spectrometry. In addition to the expected ion-molecule adduct stabilized by non-covalent long-range interactions, in this work we prove that another distinct species having the same mass to charge ratio (m/z) of 135 is also produced. Moreover, from a previous study of the neutral cyclopropyl cyanide potential energy surface (PES) which shows a partial biradical character it has been possible to characterize the formation through the bimolecular reaction of a new covalent cyclic organic molecule. Calculations have been carried out at the ab initio Møller-Plesset (MP2) level of theory, ensuring the connectivity of the stationary points by using the intrinsic reaction coordinate (IRC) procedure. In order to characterize the reaction transition state, multireference calculations were done using a complete active space involving six electrons and six molecular orbitals [CAS (6 e􏰀, 6 m.o.)]. This study opens the possibility of exploring the formation of new organic molecules by gaseous phase ion-molecule interaction schemes, with such molecules having relevance in interstellar space and in astrobiology (and may be involved in prebiotic molecular evolution).

A CO2 nanosecond repetitively pulsed discharge (NRP) is a harsh environment for laser induced fluorescence (LIF) diagnostics. The difficulties arise from it being a strongly collisional system in which the gas composition, pressure and temperature, have quick and strong variations. The relevant diagnostic problems are described and illustrated through the application of LIF to the measurement of the OH radical in three different discharge configurations, with gas mixtures containing CO2 + H2O. These range from a dielectric barrier NRP with He buffer gas, a less hostile case in which absolute OH density measurement is possible, to an NRP in CO2+H2O, where the full set of drawbacks is at work. In the last case, the OH density measurement is not possible with laser pulses and detector time resolution in the ns time scale. Nevertheless, it is shown that with a proper knowledge of the collisional rate constants involved in the LIF process, a collisional energy transfer-LIF methodology is still applicable to deduce the gas composition from the analysis of LIF spectra.

Summary Background The Minimizing Adverse Haemorrhagic Events by Transradial Access Site and Systemic Implementation of Angiox (MATRIX) programme was designed to assess the comparative safety and effectiveness of radial versus femoral access and of bivalirudin versus unfractionated heparin with optional glycoprotein IIb/IIIa inhibitors in patients with the whole spectrum of acute coronary syndrome undergoing invasive management. Here we describe the prespecified final 1-year outcomes of the entire programme. Methods MATRIX was a programme of three nested, randomised, multicentre, open-label, superiority trials in patients with acute coronary syndrome in 78 hospitals in Italy, the Netherlands, Spain, and Sweden. Patients with ST-elevation myocardial infarction were simultaneously randomly assigned (1:1) before coronary angiography to radial or femoral access and to bivalirudin, with or without post-percutaneous coronary intervention infusion or unfractionated heparin (one-step inclusion). Patients with non-ST-elevation acute coronary syndrome were randomly assigned (1:1) before coronary angiography to radial or femoral access and, only if deemed eligible to percutaneous coronary intervention after angiography (two-step inclusion), entered the antithrombin type and treatment duration programmes. Randomisation sequences were computer generated, blocked, and stratified by intended new or current use of P2Y12 inhibitor (clopidogrel vs ticagrelor or prasugrel), and acute coronary syndrome type (ST-elevation myocardial infarction, troponin-positive, or troponin-negative non-ST-elevation acute coronary syndrome). Bivalirudin was given as a bolus of 0·75 mg/kg, followed immediately by an infusion of 1·75 mg/kg per h until completion of percutaneous coronary intervention. Heparin was given at 70–100 units per kg in patients not receiving glycoprotein IIb/IIIa inhibitors, and at 50–70 units per kg in patients receiving glycoprotein IIb/IIIa inhibitors. Clinical follow-up was done at 30 days and 1 year. Co-primary outcomes for MATRIX access and MATRIX antithrombin type were major adverse cardiovascular events, defined as the composite of all-cause mortality, myocardial infarction, or stroke up to 30 days; and net adverse clinical events, defined as the composite of non-coronary artery bypass graft-related major bleeding, or major adverse cardiovascular events up to 30 days. The primary outcome for MATRIX treatment duration was the composite of urgent target vessel revascularisation, definite stent thrombosis, or net adverse clinical events up to 30 days. Analyses were done according to the intention-to-treat principle. This trial is registered with ClinicalTrials.gov, number NCT01433627. Findings Between Oct 11, 2011, and Nov 7, 2014, we randomly assigned 8404 patients to receive radial (4197 patients) or femoral (4207 patients) access. Of these 8404 patients, 7213 were included in the MATRIX antithrombin type study and were randomly assigned to bivalirudin (3610 patients) or heparin (3603 patients). Patients assigned to bivalirudin were included in the MATRIX treatment duration study, and were randomly assigned to post-procedure infusion (1799 patients) or no post-procedure infusion (1811 patients). At 1 year, major adverse cardiovascular events did not differ between patients assigned to radial access compared with those assigned to femoral access (14·2% vs 15·7%; rate ratio 0·89, 95% CI 0·80–1·00; p=0·0526), but net adverse clinical events were fewer with radial than with femoral access (15·2% vs 17·2%; 0·87, 0·78–0·97; p=0·0128). Compared with heparin, bivalirudin was not associated with fewer major adverse cardiovascular (15·8% vs 16·8%; 0·94, 0·83–1·05; p=0·28) or net adverse clinical events (17·0% vs 18·4%; 0·91, 0·81–1·02; p=0·10). The composite of urgent target vessel revascularisation, stent thrombosis, or net adverse clinical events did not differ with or without post-procedure bivalirudin infusion (17·4% vs 17·4%; 0·99, 0·84–1·16; p=0·90). Interpretation In patients with acute coronary syndrome, radial access was associated with lower rates of net adverse clinical events compared with femoral access, but not major adverse cardiovascular events at 1 year. Bivalirudin with or without post-procedure infusion was not associated with lower rates of major adverse cardiovascular events or net adverse clinical events. Radial access should become the default approach in acute coronary syndrome patients undergoing invasive management. Funding Italian Society of Invasive Cardiology, The Medicines Company, Terumo, amd Canada Research Chairs Programme.

This paper investigates the feasibility of exploiting a non-thermal plasma (NTP) to treat the gaseous effluents released by the mechanical-biological treatments (MBTs) of waste and overcome the typical disadvantages of biofilters, whose removal efficiency is limited during acclimatization of bacteria, peaks of pollutant concentration or unstable airflow rates. A dielectric barrier discharge was applied to two mixtures of volatile organic compounds (VOCs) and air. Ethanol and ethyl acetate (Mixture 1) and benzene, toluene and octane (Mixture 2), in addition to being typical constituents of the waste air released by MBTs of waste, also represent real emissions from two specific sectors that use biofiltration for air pollution control (APC): the printing (Mixture 1) and the petrochemical industries (Mixture 2). At the highest specific energy densities applied to the discharge (900–2520 J L −1 ), all the initial VOCs were removed by 95–100%. With respect to ethyl acetate, the maximal CO 2 selectivity and the maximal energy yield resulted in 62–70% and 6–11 g kW −1 h −1 , respectively; with regards to benzene, the same parameters resulted in 52–90% and 0.17–0.72 g kW −1 h −1 , respectively. At medium-low energy, acetaldehyde and acetic acid were detected as the main byproducts of Mixture 1, while several trace compounds were found as the byproducts of Mixture 2. Interestingly, the byproducts generated are more polar than the initial compounds and, thus, their solubility in water is higher. Therefore, NTPs can be considered as a promising technology to help the biodegradation of VOCs in facilities where biofilters are used as APC systems.

The methyl carbocation is ubiquitous in gaseous environments, such as planetary ionospheres, cometary comae, and the interstellar medium, as well as combustion systems and plasma setups for technological applications. Here we report on a joint experimental and theoretical study on the mechanism of the reaction CH

Long-range intermolecular forces play a crucial role in controlling the outcome of ion-molecule chemical reactions, such as those determining the disappearance of organic or inorganic "complex" molecules recently detected in various regions of the interstellar medium due to collisions with abundant interstellar atomic ions (e.g. H

The fate of dimethyl ether (DME, CH3OCH3) in collisions with He+ ions is of high relevance for astrochemical models aimed at reproducing the abundances of complex organic molecules in the interstellar medium. Here we report an investigation on the reaction of He+ ions with DME carried out using a Guided Ion Beam Mass Spectrometer (GIB-MS), which allows the measurement of reactive cross-sections and branching ratios (BRs) as a function of the collision energy. We obtain insights into the dissociative charge (electron) exchange mechanism by investigating the nature of the non-adiabatic transitions between the relevant potential energy surfaces (PESs) in an improved Landau–Zener approach. We find that the large interaction anisotropy could induce a pronounced orientation of the polar DME molecule in the electric field generated by He+ so that at short distances the collision complex is confined within pendular states, a particular case of bending motion, which gives rise to intriguing stereodynamic effects. The positions of the intermolecular potential energy curve crossings indicate that He+ captures an electron from an inner valence orbital of DME, thus causing its dissociation. In addition to the crossing positions, the symmetry of the electron density distribution of the involved DME orbitals turns out to be a further major point affecting the probability of electron transfer. Thus, the anisotropy of the intermolecular interaction and the electron densities of the orbitals involved in the reaction are the key “ingredients” for describing the dynamics of this dissociative charge transfer.

The complaints arising from the problem of odorants released by composting plants may impede the construction of new composting facilities, preclude the proper activity of existing facilities or even lead to their closure, with negative implications for waste management and local economy. Improving the knowledge on VOC emissions from composting processes is of particular importance since different VOCs imply different odour impacts. To this purpose, three different organic matrices were studied in this work: dewatered sewage sludge (M1), digested organic fraction of municipal solid waste (M2) and untreated food waste (M3). The three matrices were aerobically biodegraded in a bench-scale bioreactor simulating composting conditions. A homemade device sampled the process air from each treatment at defined time intervals. The samples were analysed for VOC detection. The information on the concentrations of the detected VOCs was combined with the VOC-specific odour thresholds to estimate the relative weight of each biodegraded matrix in terms of odour impact. When the odour formation was at its maximum, the waste gas from the composting of M3 showed a total odour concentration about 60 and 15,000 times higher than those resulting from the composting of M1 and M2, respectively. Ethyl isovalerate showed the highest contribution to the total odour concentration (>99%). Terpenes (α-pinene, β-pinene, p-cymene and limonene) were abundantly present in M2 and M3, while sulphides (dimethyl sulphide and dimethyl disulphide) were the dominant components of M1.

Laser induced fluorescence is intensively used for the detection of OH in many atmospheric pressure discharge devices. At this pressure, a quantitative knowledge of the collision phenomena in the upper excited state is critical. Here we report the measurement at T = 300 K of a set of rate constants of electronic quenching and vibrational relaxation of the OH electronic state, by collision with N2, O2, H2O, CO2, CO, H2, D2, CH4, C2H2, C2H4, C2H6. These are the main gases in applications like plasma medicine, hydrocarbons reforming and CO2 conversion. Available literature data are revisited, and new data are added, mostly relevant to quenching and vibrational relaxation.

The catalytic effect of the electrode surface is investigated in a dielectric barrier discharge of CO2 and CH4 at atmospheric pressure. An increased production of carboxylic acids, especially formic acid, is observed for copper and nickel electrodes. This suggests the occurrence of CO2 hydrogenation reactions on the metal surface.

In the plasma dry reforming, CH4 and CO2 are dissociated by electron collisions producing fragments that in turn react to form new molecules. While the production of CO, H2, and small hydrocarbons has been investigated extensively, much less is known about the plasma synthesis of oxygenated molecules, which is the target of the present work. In addition to experimental results, gas phase reactions for the production of acetic, formic and propanoic acid were investigated by DFT calculations.

Aims The radial approach is safer than the femoral for percutaneous coronary procedures. However its feasibility is lower, mainly for technical issues, often related to failure to puncture or cannulate the radial artery. The ulnar approach is a valid alternative to radial. We aimed to test the incidence, feasibility and safety of a direct homolateral ulnar approach in case of failed radial sheath insertion. Methods and results Five operators collected their 1-year activity (diagnostic and interventional) with focus on entry site. Entry site choice was left to operators' discretion. In case of failed radial sheath insertion, an attempt to cannulate the homolateral ulnar artery was mandated, if ulnar pulse was present. All patients in whom this attempt was performed were followed until discharge. Out of 2403 procedures (1271 interventions), the final successful entry site was radial in 66.5%, femoral in 31.0%, ulnar in 2.1% and brachial in 0.4%. Radial failure occurred in 117 patients (6.9%). In 75 patients, the radial failure was not due to sheath insertion (which was successful), but to lack of catheter support or to tortuosity of the subclavian/brachial arteries. In the remaining 42 (35.9% of all radial failures), a homolateral ulnar approach was attempted. A successful cannulation of the ulnar artery occurred in 36 patients (85.7%) with further performance of the complete procedure. Concerning local complications, 1 radial pseudo-aneurysm (treated with additional compression) occurred, while no cases of early hand ischemia were reported. Conclusions In this multicenter registry, in case of failed radial sheath insertion, switching directly to the homolateral ulnar artery for percutaneous coronary procedures is feasible and it appears to be safe, without cases of symptomatic hand ischemia.