Observation of enhanced rate coefficients in the H2+_2^+ + H2_2 →\rightarrow H3+_3^+ + H reaction at low collision energies

The energy dependence of the rate coefficient of the H$_2^+\ + {\rm H}_2 \rightarrow {\rm H}_3^+ + {\rm H}$ reaction has been measured in the range of collision energies between $k_\mathrm{B}\cdot 10$ K and $k_\mathrm{B}\cdot 300$ mK. A clear deviation of the rate coefficient from the value expected on the basis of the classical Langevin-capture behavior has been observed at collision energies below $k_\mathrm{B}\cdot 1$ K, which is attributed to the joint effects of the ion-quadrupole and Coriolis interactions in collisions involving ortho-H$_2$ molecules in the $j = 1$ rotational level, which make up 75% of the population of the neutral H$_2$ molecules in the experiments. The experimental results are compared to very recent predictions by Dashevskaya, Litvin, Nikitin and Troe (J. Chem. Phys., in press), with which they are in agreement.Comment: 14 pages, 3 figure

Using a direct simulation Monte Carlo approach to model collisions in a buffer gas cell

A direct simulation Monte Carlo (DSMC) method is applied to model collisions between He buffer gas atoms and ammonia molecules within a buffer gas cell. State-tostate cross sections, calculated as a function of collision energy, enable the inelastic collisions between He and NH3 to be considered explicitly. The inclusion of rotationalstate-changing collisions affects the translational temperature of the beam, indicating that elastic and inelastic processes should not be considered in isolation. The properties of the cold molecular beam exiting the cell are examined as a function of the cell parameters and operating conditions; the rotational and translational energy distributions and are in accord with experimental measurements. The DSMC calculations show that thermalisation occurs well within the typical 10-20 mm length of many buffer gas cells, suggesting that shorter cells could be employed in many instances – yielding a higher flux of cold molecules

Using a direct simulation Monte Carlo approach to model collisions in a buffer gas cell - supporting material

The dataset includes results from our direct simulation Monte Carlo (DSMC) modelling of the collisions between buffer gas atoms and ammonia molecules within a buffer gas cell. Both elastic and inelastic collisions are considered, through the inclusion of energy-dependent state-to-state collision cross sections. The properties of the resulting molecular beam are examined as a function of cell parameters and operating conditions – yielding good agreement with available experimental measurements. This study represents an important extension of previous investigations into buffer-gas cooling. We demonstrate that thermalisation occurs well within the typical 10-20mm length of typical experimental buffer gas cells, suggesting that a shorter cell could be employed in many applications. Our DSMC calculations indicate that shorter cells would achieve comparable molecular beam properties (translational and rotational temperature) with the benefit of significantly increased molecular density. The data were created from 2015-2016 and are discussed in detail in the accompanying publication. The labelling of each data file corresponds to the labelling adopted for the associated figure in the publicatio

Using a direct simulation Monte Carlo approach to model collisions in a buffer gas cell - supporting material

The dataset includes results from our direct simulation Monte Carlo (DSMC) modelling of the collisions between buffer gas atoms and ammonia molecules within a buffer gas cell. Both elastic and inelastic collisions are considered, through the inclusion of energy-dependent state-to-state collision cross sections. The properties of the resulting molecular beam are examined as a function of cell parameters and operating conditions – yielding good agreement with available experimental measurements. This study represents an important extension of previous investigations into buffer-gas cooling. We demonstrate that thermalisation occurs well within the typical 10-20mm length of typical experimental buffer gas cells, suggesting that a shorter cell could be employed in many applications. Our DSMC calculations indicate that shorter cells would achieve comparable molecular beam properties (translational and rotational temperature) with the benefit of significantly increased molecular density. The data were created from 2015-2016 and are discussed in detail in the accompanying publication. The labelling of each data file corresponds to the labelling adopted for the associated figure in the publicatio

Stereotactic Radiofrequency Ablation of Breast Cancer Liver Metastases: Short- and Long-Term Results with Predicting Factors for Survival.

PURPOSE: To evaluate safety, local oncological control, long-term outcome and potential prognostic factors of stereotactic RFA (SRFA) for the treatment of BCLMs. METHODS: Between July 2003 and December 2019, 42 consecutive female patients with median age 54.0 years were treated with SRFA at our institution for 110 BCLMs in 48 ablation sessions. Median tumor size was 3.0 cm (0.8-9.0). Eighteen (42.9%) patients had extrahepatic metastasis at initial SRFA. RESULTS: Technical success rate was 100%, i.e., all coaxial needles were inserted with appropriate accuracy within 10 mm off plan and 107/110 (92.3%) BCLMs were successfully ablated at initial SRFA. Four Grade 1 (8.3%, 4/48) and one Grade 2 (2.1%, 1/48) complications occurred. No perioperative deaths occurred. Local recurrence developed in 8 of 110 tumors (7.3%). Overall survival (OS) rates of all patients at 1, 3, and 5 years from the date of the first SRFA were 84.1%, 49.3%, and 20.8% with a median OS of 32.3 months. Univariable cox regression analyses revealed age > 60 years and extrahepatic disease (without bone only metastases) as significant predictors of worse OS (p = 0.013 and 0.025, respectively). Size and number of metastases, hormone receptor status and time onset did not significantly affect OS after initial SRFA. CONCLUSIONS: SRFA is a safe, minimally invasive treatment option in the management of BCLMs, especially in younger patients without advanced extrahepatic metastasis, including those with large liver tumors

Simulating rotationally inelastic collisions using a direct simulation Monte Carlo method

A new approach to simulating rotational cooling using a Direct Simulation Monte Carlo (DSMC) method is described and applied to the rotational cooling of ammonia seeded into a helium supersonic jet. The method makes use of {\it ab initio} rotational state changing cross sections calculated as a function of collision energy. Each particle in the DSMC simulations is labelled with a vector of rotational populations that evolves with time. Transfer of energy into translation is calculated from the mean energy transfer for this population at the specified collision energy. The simulations are compared with a continuum model for the on-axis density, temperature and velocity; rotational temperature as a function of distance from the nozzle is in accord with expectations from experimental measurements. The method could be applied to other types of gas mixture dynamics under non-uniform conditions, such as buffer gas cooling of NH$_3$ by He. Cross sections for He NH3 rotationally inelastic collisions in text file format. Results from a direct simulation Monte Carlo simulation of a supersonic expansion in HDF5 format. Python scripts to generate paper figures from simulation results

Frequency and risk factors for major complications after stereotactic radiofrequency ablation of liver tumors in 1235 ablation sessions: a 15-year experience.

OBJECTIVES: To assess the frequency of major complications after multi-probe stereotactic radiofrequency ablation (SRFA) in a large cohort of patients over 15 years and to elucidate risk factors for adverse events. MATERIALS AND METHODS: A retrospective study was carried out between July 2003 and December 2018. Seven hundred ninety-three consecutive patients (median 65.0 years (0.3-88), 241 women and 552 men, were treated in 1235 SRFA sessions for 2475 primary and metastatic liver tumors with a median tumor size of 3.0 cm (0.5-18 cm). The frequency of major complications was evaluated according to SIR guidelines and putative predictors of adverse events analyzed using simple and multivariable logistic regression. RESULTS: Thirty-day mortality after SRFA was 0.5% (6/1235) with an overall major complication rate of 7.4% (91/1235). The major complication rate decreased from 11.5% (36/314) (before January 2011) to 6.0% (55/921) (p = 0.001). 50.5% (46/91) of major complications were successfully treated in the same anesthetic session by angiographic coiling for hemorrhage and chest tube insertion for pneumothorax. History of bile duct surgery/intervention, number of coaxial needles, and location of tumors in segment IVa or VIII were independent prognostic factors for major complications following multivariable logistic regression analysis. Simple logistic regression revealed the number of tumors, tumor size, location close to the diaphragm, tumor conglomerate, and segment VII as other significant predictors. CONCLUSION: SRFA of liver tumors is safe and can extend the treatment spectrum of conventional RFA. Adaptations over time combined with increasing experience resulted in a significant decrease in complications. KEY POINTS: • In 1235 ablation sessions in 793 patients over 15 years, we found a mortality rate of 0.5% (6/1235) and an overall major complication rate of 7.4%, which fell from 11.5 (36/314) to 6.0% (55/921, p = 0.001) after January 2011, likely due to procedural adaptations. • History of bile duct surgery/intervention (p = 0.013, OR = 3.290), number of coaxial needles (p = 0.026, OR = 1.052), and location of tumors in segment IVa (p = 0.016, OR = 1.989) or VIII (p = 0.038, OR = 1.635) were found to be independent prognostic factors. • Simple logistic regression revealed that number of tumors, tumor size, location close to the diaphragm, tumor conglomerates, and segment VII were other significant predictors of major complications