Bending Relaxation of H2 O by Collision with Para- and Ortho-H2.

We extend our recent theoretical work on the bending relaxation of H2 O in collisions with H2 by including the three water modes of vibration coupled with rotation, as well as the rotation of H2 . Our full quantum close-coupling method (excluding the H2 vibration) is combined with a high-accuracy nine-dimensional potential energy surface. The collisions of para-H2 O and ortho-H2 O with the two spin modifications of H2 are considered and compared for several initial states of H2 O. The convergence of the results as a function of the size of the rotational basis set of the two colliders is discussed. In particular, near-resonant energy transfer between H2 O and H2 is found to control the vibrational relaxation process, with a dominant contribution of transitions with Δ j 2 = j 2 f - j 2 i ${{\rm{\Delta }}j_2 = j_2^f - j_2^i }$ = + 2 , + 4 ${ + 2, + 4}$ , j 2 i ${j_2^i }$ and j 2 f ${j_2^f }$ being respectively the H2 initial and final rotational quantum numbers. Finally, the calculated value of the H2 O bending relaxation rate coefficient at 295 K is found to be in excellent agreement with its experimental estimate.

Scattering resonances in the rotational excitation of HDO by Ne and normal-H2: theory and experiment.

The rotational excitation of a singly deuterated water molecule (HDO) by a heavy atom (Ne) and a light diatomic molecule (H2) is investigated theoretically and experimentally in the near-threshold regime. Crossed-molecular-beam measurements with a variable crossing angle are compared to close-coupling calculations based on high-accuracy potential energy surfaces. The two lowest rotational transitions, 000 → 101 and 000 → 111, are probed in detail and a good agreement between theory and experiment is observed for both transitions in the case of HDO + Ne, where scattering resonances are however blurred out experimentally. In the case of HDO + H2, the predicted theoretical overlapping resonances are faithfully reproduced by experiment for the 000 → 111 transition, while the calculated strong signal for the 000 → 101 transition is not detected. Future work is needed to reconcile this discrepancy.

Imaging and prognostic characterization of fat-containing hepatocellular carcinoma subtypes.

PURPOSE: Steatohepatitic hepatocellular carcinoma (SH-HCC) is characterized by intratumoral fat with > 50% inflammatory changes. However, intratumoral fat (with or without inflammation) can also be found in not-otherwise specified HCC (NOS-HCC). We compared the imaging features and outcome of resected HCC containing fat on pathology including SH-HCC (> 50% steatohepatitic component), NOS-HCC with < 50% steatohepatitic component (SH-NOS-HCC), and fatty NOS-HCC (no steatohepatitic component). MATERIAL AND METHODS: From September 2012 to June 2021, 94 patients underwent hepatic resection for fat-containing HCC on pathology. Imaging features and categories were assessed using LIRADS v2018. Fat quantification was performed on chemical-shift MRI. Recurrence-free and overall survival were estimated. RESULTS: Twenty-one patients (26%) had nonalcoholic steatohepatitis (NASH). The median intra-tumoral fat fraction was 8%, with differences between SH-HCC and SH-NOS-HCC (9.5% vs. 5% p = 0.03). There was no difference in major LI-RADS features between all groups; most tumors were classified as LR-4/5. A mosaic architecture on MRI was rare (7%) in SH-HCC, a fat in mass on CT was more frequently depicted (48%) in SH-HCC. A combination of NASH with no mosaic architecture on MRI or NASH with fat in mass on CT yielded excellent specificity for diagnosing SH-HCC (97.6% and 97.7%, respectively). The median recurrence-free and overall survival were 58 and 87 months, with no difference between groups (p = 0.18 and p = 0.69). CONCLUSION: In patients with NASH, an SH-HCC may be suspected in L4/LR-5 observations with no mosaic architecture at MRI or with fat in mass on CT. Oncological outcomes appear similar between fat-containing HCC subtypes.

A statistical investigation of the rate constants for the H+ + HD reaction at temperatures of astrophysical interest.

The H+ + HD(v, j) reaction has been investigated in detail by means of a statistical quantum method. State-to-state cross sections and rate constants for transitions between reactants and rovibrational states HD(v', j') of the product arrangement with energies below 0.9 eV collision energy [that is, HD(v = 0, j = 0-11) and HD(v = 1, j = 0-6)] have been calculated. For the other product channel, D+ + H2(v', j'), rovibrational states up to (v' = 0, j' = 9) have been considered for the calculation of the corresponding thermal rate. Present predictions are compared with previously reported theoretical and experimental rates. Finally, cooling functions for HD due to proton and atomic hydrogen collisions are computed in the low-density regime. We find that the much larger HD-H+ cooling function, as compared with that of HD-H, does not compensate for the low H+/H abundance ratio in astrophysical media so that HD cooling is dominated by HD-H (or HD-H2) collisions.

Near-Threshold and Resonance Effects in Rotationally Inelastic Scattering of D2O with Normal-H2.

We present a combined experimental and theoretical study on the rotationally inelastic scattering of heavy water, D2O, with normal-H2. Crossed-molecular beam measurements are performed in the collision energy range between 10 and 100 cm-1, corresponding to the near-threshold regime in which scattering resonances are most pronounced. State-to-state excitation cross-sections are obtained by probing three low-lying rotational levels of D2O using the REMPI technique. These measurements are complemented by quantum close-coupling scattering calculations based on a high-accuracy D2O-H2 interaction potential. The agreement between experiment and theory is within the experimental error bars at 95% confidence intervals, leading to a relative difference of less than 7%: the near-threshold rise and the overall shape of the cross-sections, including small undulations due to resonances, are nicely reproduced by the calculations. Isotopic effects (D2O versus H2O) are also discussed by comparing the shape and magnitude of the respective cross-sections.

Rate constants for the H+ + H2 reaction from 5 K to 3000 K with a statistical quantum method.

An exhaustive investigation of state-to-state H+ + H2(v, j) → H+ + H2(v', j') transitions for rovibrational levels of molecular hydrogen below 1.3 eV from the bottom of the H2 well is carried out by means of a statistical quantum method, which assumes the complex-forming nature of the process. Integral cross sections for transitions involving states H2(v = 0, j = 0-12), H2(v = 1, j = 0-8), and H2(v = 2, j = 0-3) are obtained for collision energies within a range of Emin = 10-5 eV and Emax = 2 eV. Rate constants are then calculated between T = 5 K and 3000 K, and they are compared, when possible, with previous values reported in the literature. As a first application, the cooling rate coefficient of H2 excited by protons is determined and compared with a recent estimate.

Low-Energy Water-Hydrogen Inelastic Collisions.

New molecular beam scattering experiments are reported for the water-hydrogen system. Integral cross sections of the first rotational excitations of para- and ortho-H2O by inelastic collisions with normal-H2 were determined by crossing a beam of H2O seeded in He with a beam of H2. H2O and H2 were cooled in the supersonic expansion down to their lowest rotational levels. Crossed-beam scattering experiments were performed at collision energies from 15 cm-1 (below the threshold for the excitation to the lowest excited rotational state of H2O: 18.6 cm-1) up to 105 cm-1 by varying the beam crossing angle. The measured state-to-state cross-sections were compared to the theoretical cross-sections (close-coupling quantum scattering calculations): the good agreement found further validates both the employed potential energy surface describing the H2O-H2 van der Waals interaction and the state-to-state rate coefficients calculated with this potential in the very low temperature range needed for the modeling of interstellar media.

Potential energy surface and bound states of the H2O-HF complex.

We present the first global five-dimensional potential energy surface for the H2O-HF dimer, a prototypical hydrogen bonded complex. Large scale ab initio calculations were carried out using the explicitly correlated coupled cluster approach with single- and double-excitations together with non-iterative perturbative treatment of triple excitations with the augmented correlation-consistent triple zeta basis sets, in which the water and hydrogen fluoride monomers were frozen at their vibrationally averaged geometries. The ab initio data points were fitted to obtain a global potential energy surface for the complex. The equilibrium geometry of the complex corresponds to the formation of a hydrogen bond with water acting as a proton acceptor and a binding energy of De = 3059 cm-1 (8.75 kcal/mol). The energies and wavefunctions of the lowest bound states of the complex were computed using a variational approach, and the dissociation energies of both ortho-H2O-HF (D0 = 2089.4 cm-1 or 5.97 kcal/mol) and para-H2O-HF (D0 = 2079.6 cm-1 or 5.95 kcal/mol) were obtained. The rotational constant of the complex was found to be in good agreement with the available experimental data.

Rigid-Bender Close-Coupling Treatment of the Inelastic Collisions of H2O with para-H2.

We present a new method taking explicitly into account the coupling between rotation and bending of a nonlinear triatomic molecule colliding with an atom. This approach based on a rigid-bender treatment of the triatomic molecule was originally developed for the case of triatomic molecule linear at equilibrium. It is here extended to the case of a colliding bent triatomic molecule at equilibrium and applied to the case of the para-H2 + H2O inelastic collision using a new H2O-para-H2 adiabatically reduced 4D potential. The results of the method for purely rotational transitions are compared to those of rigid-rotor calculations while vibrational quenching rates of the first exited bending level are calculated for the first time at the close-coupling level.

Relaxation before Debriefing during High-fidelity Simulation Improves Memory Retention of Residents at Three Months: A Prospective Randomized Controlled Study.

BACKGROUND: High-fidelity simulation is known to improve participant learning and behavioral performance. Simulation scenarios generate stress that affects memory retention and may impact future performance. The authors hypothesized that more participants would recall three or more critical key messages at three months when a relaxation break was performed before debriefing of critical event scenarios. METHODS: Each resident actively participated in one scenario and observed another. Residents were randomized in two parallel-arms. The intervention was a 5-min standardized relaxation break immediately before debriefing; controls had no break before debriefing. Five scenario-specific messages were read aloud by instructors during debriefings. Residents were asked by telephone three months later to recall the five messages from their two scenarios, and were scored for each scenario by blinded investigators. The primary endpoint was the number of residents participating actively who recalled three or more messages. Secondary endpoints included: number of residents observing who recalled three or more messages, anxiety level, and debriefing quality. RESULTS: In total, 149 residents were randomized and included. There were 52 of 73 (71%) residents participating actively who recalled three or more messages at three months in the intervention group versus 35 of 76 (46%) among controls (difference: 25% [95% CI, 10 to 40%], P = 0.004). No significant difference was found between groups for observers, anxiety or debriefing quality. CONCLUSIONS: There was an additional 25% of active participants who recalled the critical messages at three months when a relaxation break was performed before debriefing of scenarios. Benefits of relaxation to enhance learning should be considered for medical education.

Uncontrolled donation after circulatory death: comparison of two kidney preservation protocols on graft outcomes.

BACKGROUND: Kidney transplantation following uncontrolled donation after circulatory death (uDCD) presents a high risk of delayed graft function due to prolonged warm ischemia time. In order to minimise the effects of ischemia/reperfusion injury during warm ischemia, normothermic recirculation recently replaced in situ perfusion prior to implantation in several institutions. The aim of this study was to compare these preservation methods on kidney graft outcomes. METHODS: The primary endpoint was the one-year measured graft filtration rate (mGFR). We collected retrospective data from 64 consecutive uDCD recipients transplanted over a seven-year period in a single centre. RESULTS: Thirty-two grafts were preserved by in situ perfusion and 32 by normothermic recirculation. The mean ± SD mGFR at 1 year post-transplantation was 43.0 ± 12.8 mL/min/1.73 m2 in the in situ perfusion group and 53.2 ± 12.8 mL/min/1.73 m2 in the normothermic recirculation group (p = 0.01). Estimated GFR levels were significantly higher in the normothermic recirculation group at 12 months (p = 0.01) and 24 months (p = 0.03) of follow-up. We did not find any difference between groups regarding patient and graft survival, delayed graft function, graft rejection, or interstitial fibrosis. CONCLUSIONS: Function of grafts preserved by normothermic recirculation was better at 1 year and the results suggest that this persists at 2 years, although no difference was found in short-term outcomes. Despite the retrospective design, this study provides an additional argument in favour of normothermic recirculation.

Hypothermic pulsatile preservation of kidneys from uncontrolled deceased donors after cardiac arrest - a retrospective study.

Kidneys from uncontrolled donors after cardiac arrest (uDCD) suffer from a period of warm ischemia between cardiac arrest and cold flushing. Aim of the study was to evaluate renal outcomes of uDCD kidneys selected on the basis of renal Resistance Index (RI) and its influence on graft function and survival. The study included 44 kidneys procured from 26 uDCD starting 1.1.2006 until 12.31.2013. The donors (Maastricht category II) underwent cardiopulmonary resuscitation by assisted ventilation and chest compression; the organs were preserved with in situ cold perfusion or a normothermic regional perfusion. All kidneys were perfused on hypothermic (1-4 °C) pulsatile perfusion machine (RM3; Waters Medical System) and discarded when RI ≥0.5 mmHg/ml/min after 6 h of perfusion. There was one (2.2%) primary non function, while 37 recipients (84.1%) experienced delayed graft function. Graft survival was 97.6% at 1 and 3 post-transplantation years. Linear regression models showed that lower values of RI at the end of perfusion were associated with higher values of Modification of Diet in Renal Disease at 3 (P = 0.049) and 6 months after transplantation (P = 0.010) and with higher values of inulin clearance at 1 year (P = 0.030). RI showed to be a useful tool to select uDCD kidneys allowing to achieve good clinical results.

Rotational excitation of the interstellar NH2 radical by H2.

We present quantum close-coupling calculations for the rotational excitation of the interstellar amidogen radical NH2 due to collisions with H2 molecules. The calculations are based on a recent, high-accuracy full-dimensional NH4 potential energy surface adapted for rigid-rotor scattering calculations. The collisional cross section calculations are performed for all transitions among the first 15 energy levels of both ortho- and para-NH2 and for total energies up to 1500 cm-1. Both para- and ortho-H2 colliding partners are considered. The cross sections for collision with para- and ortho-H2 are found to differ significantly, the magnitude of the ortho-H2 ones being dominant. No strong propensity rules are observed but transitions with Δkc=0 are slightly favored.

Nuclear-spin selection rules in the chemistry of interstellar nitrogen hydrides.

Nitrogen hydrides are at the root of the nitrogen chemistry in interstellar space. The detailed modeling of their gas phase formation, however, requires the knowledge of nuclear-spin branching ratios for chemical reactions involving multiprotonated species. We investigate in this work the nuclear-spin selection rules in both exothermic and near thermoneutral ion­molecule reactions involved in the synthesis of ammonia, assuming full scrambling of protons in the reaction complexes. The formalism of Oka [ J. Mol. Spectrosc. 2004, 228, 635] is employed for highly exothermic ion­molecule and dissociative recombination reactions. For thermoneutral reactions, a simple state-to-state statistical approach is suggested, which is in qualitative agreement with both quantum scattering and microcanonical statistical calculations. This model is applied to the seven atom reaction NH4(+) + H2, of possible importance in the nuclear-spin thermalization of ammonia.

Spin-orbit quenching of the C+(2P) ion by collisions with para- and ortho-H2.

Spin-orbit (de-)excitation of C(+)((2)P) by collisions with H2, a key process for astrochemistry, is investigated. Quantum-mechanical calculations of collisions between C(+) ions and para- and ortho-H2 have been performed in order to determine the cross section for the C(+) (2)P3∕2 → (2)P1∕2 fine-structure transition at low and intermediate energies. The calculation are based on new ab initio potential energy surfaces obtained using the multireference configuration interaction method. Corresponding rate coefficients were obtained for temperatures ranging from 5 to 500 K. These rate coefficients are compared to previous estimations, and their impact is assessed through radiative transfer computation. They are found to increase the flux of the (2)P3∕2 → (2)P1∕2 line at 158 µm by up to 30% for typical diffuse interstellar cloud conditions.

Communication: the rotational excitation of D2 by H: on the importance of the reactive channels.

We report fully-quantum time-independent calculations of cross sections and rate coefficients for the collisional excitation and dissociation of D(2) by H, two astrophysically relevant processes. Our calculations are based on the recent H(3) global potential energy surface of Mielke et al. [J. Chem. Phys. 116, 4142 (2002)]. Results of exact three-dimensional calculations, i.e., including the reactive channels, are compared to pure inelastic two-dimensional calculations based on the rigid rotor approximation. A reasonable agreement is found between the two sets of inelastic cross sections over the whole energy range 10-9000 cm(-1). At the highest collisional energies, where the reactive channels are significant, the rigid rotor approach slightly overestimates the cross sections, as expected. At moderate collisional energies, however, the opposite behaviour is observed. The rigid rotor approach is found to be reliable at temperatures below ~500 K, with a significant but moderate contribution from reactive channels.

Rotational excitation of H2O by para-H2 from an adiabatically reduced dimensional potential.

Cross sections and rate coefficients for low lying rotational transitions in H(2)O colliding with para-hydrogen pH(2) are computed using an adiabatic approximation which reduces the dimensional dynamics from a 5D to a 3D problem. Calculations have been performed at the close-coupling level using the recent potential of Valiron et al. [J. Chem. Phys. 129, 134306 (2008)]. A good agreement is found between the reduced adiabatic calculations and the 5D exact calculations, with an impressive time saving and memory gain. This adiabatic reduction of dimensionality seems very promising for scattering studies involving the excitation of a heavy target molecule by a light molecular projectile.