Deceleration and electrostatic trapping of OH radicals

A pulsed beam of ground state OH radicals is slowed down using a Stark decelerator and is subsequently loaded into an electrostatic trap. Characterization of the molecular beam production, deceleration and trap loading process is performed via laser induced fluorescence detection inside the quadrupole trap. Depending on details of the trap loading sequence, typically $10^5$ OH ($X^2\Pi_{3/2}, J=3/2$) radicals are trapped at a density of around $10^7$ cm$^{-3}$ and at temperatures in the 50-500 mK range. The 1/e trap lifetime is around 1.0 second.Comment: 4 pages, 3 figure

Photoassociation inside an optical dipole trap: absolute rate coefficients and Franck-Condon factors

We present quantitative measurements of the photoassociation of cesium molecules inside a far-detuned optical dipole trap. A model of the trap depletion dynamics is derived which allows to extract absolute photoassociation rate coefficients for the initial single-photon photoassociation step from measured trap-loss spectra. The sensitivity of this approach is demonstrated by measuring the Franck-Condon modulation of the weak photoassociation transitions into the low vibrational levels of the outer well of the 0g- state that correlates to the 6s+6p3/2 asymptote. The measurements are compared to theoretical predictions. In a magneto-optical trap these transitions have previously only been observed indirectly through ionization of ground state molecules

To shift, or not to shift: Adequate selection of an internal standard in mass-shift approaches using tandem ICP-mass spectrometry (ICP-MS/MS)

The use of an internal standard to correct for potential matrix effects and instrument instability is common practice in ICP-MS. However, with the introduction of a new generation of ICP-MS instrumentation with a tandem mass spectrometry configuration (ICP-MS/MS), the use of chemical resolution in a mass-shift approach has become much more popular, suggesting that the appropriate selection of an internal standard needs revision. In this particular case, it needs to be decided whether the internal standard should also be subjected to a mass-shift or can simply be monitored on-mass ("to shift, or not to shift"). In this work, 17 elements covering a wide range of masses (24-205 amu) and ionization energies (3.89-9.39 eV) were measured via on-mass and/or mass-shift strategies, and the corresponding atomic ions and reaction product ions were monitored during various systematic experiments. For mass-shifting, an NH3/He gas mixture was used to obtain NH3-based reaction product ions (cluster formation). Product ion scanning (PIS) was used for assessing the differences in reactivity between the different analytes and for the identification of the best suited reaction product ions. It was found that the use of chemical resolution can significantly affect the short-term signal stability and that ion signals measured on-mass are not affected in the same way as those measured mass-shifted. Variations affecting the signal intensities of both atomic and reaction product ions can be attributed to the ion-molecule chemistry occurring within the collision/reaction cell and were found to be related with some degree of initial instability in the cell and differences in reactivity. The use of a sufficiently long stabilization time, however, avoids or at least mitigates such differences in the behavior between signals monitored on-mass and after mass-shifting, respectively. Furthermore, the introduction of cell disturbances, such as those generated after quickly switching between different sets of operating conditions in a multi-tune method, revealed significant differences in signal behavior between atomic and reaction product ions, potentially hampering the use of an internal standard monitored on-mass when the analysis is based on an analyte monitored after mass-shifting. However, the use of a reasonable waiting time again greatly mitigates such differences, with the duration of this stabilization time depending on the magnitude of the cell disturbances (e.g., switch between vented and pressurized mode or only between pressurized modes using different gas flow rates). In addition, also the effect of varying different instrument settings (plasma power, torch position, and gas and liquid flow rates) was evaluated, but no remarkable differences were found between signals monitored on-mass and those mass-shifted. Interestingly, a statistical evaluation of the influence of the different settings on the signal intensities of all ions monitored did not reveal the a priori important role of some properties traditionally suggested for adequate selection of analyte/internal standard pairs, such as mass number or ionization energy, as also suggested in other recent studies. © The Royal Society of Chemistry

THU0334 LASER SPECKLE CONTRAST ANALYSIS FOR MEASUREMENT OF PERIPHERAL BLOOD PERFUSION IN SYSTEMIC SCLEROSIS PATIENTS: CAN IT PREDICT FUTURE ISCHEMIC DIGITAL TROPHIC LESIONS?

Background:Vasculopathy is a hallmark of systemic sclerosis (SSc). Laser speckle contrast analysis (LASCA) is a research tool to assess peripheral blood perfusion (PBP) (1). At this moment, its reliability has been attested in SSc patients, but its predictive value for future ischemic digital trophic lesions (DTL) is unknown (1).Objectives:To investigate in an unselected, prospective SSc cohort if baseline LASCA PBP measurements can discriminate between patients who will develop ischemic DTL (iDTL) and those who will not.Methods:Patients (fulfilling 2013 ACR/EULAR criteria and/or 2001 LeRoy and Medsger criteria) were recruited during the period of December 2017 to September 2018. LASCA was performed at baseline, in standardized conditions (1). Regions of interest (ROIs) (diameter 1 cm) were outlined at the 2nd-5thfingertip both volar and dorsal. The 'average PBP' of these ROIs was calculated (expressed in arbitrary perfusion units [PU]). A monthly telephone survey was conducted for 1 year to investigate DTL occurrence. DTL were considered 'ischemic' if not related to calcinosis. Logistic regression and ROC analysis were used to assess if average PBP is predictive of future iDTL.Results:Of the 106 patients with complete follow-up (92 women [86,8%]; 18 limited SSc [17,0%], 82 limited cutaneous SSc [77,4%], 6 diffuse cutaneous SSc [5,7%]), 29 patients (27,4%) had a DTL history. Forty-nine patients (46,2%) were on vasodilator therapy. Only 7 patients developed at least 1 iDTL during follow-up (6,6%) (Figure 1a). Performing univariate logistic regression (ULR), average PBP was not predictive for future iDTL (Table 1). Of note, analyzing only the patients not taking vasodilators, average PBP in the 'iDTL group' (n = 3) was median 46,8 PU (min. 45,6 - max. 68,8) vs. median 141,4 PU (min. 24,4 - max. 269,5) in the 'no iDTL group' (n = 54) (Figure 1b). In this subgroup, all 3 patients who developed iDTL (100%) had an average PBP ≤ 70 PU whereas only 9 of the 54 patients without iDTL development (16,7%) had such PBP values.Table 1.Results of ULRSummary statisticsULRVariableiDTL cases(n = 7)Non-iDTL cases(n = 99)ParameterOR(95% CI)pROC AUC(95% CI)Average PBP (PU) mean (+/- SD)123,0 (74,6)142,9 (61,9)Average PBP (linear)0,995(0,982-1,007)0,4180,597(0,352-0,843)Conclusion:In this pilot study with an unselected day-to-day SSc population, where patients were allowed to continue vasodilators, there was an unexpected low iDTL incidence, undermining the power of our study. Even though, the observations in the subgroup of patients not taking vasodilators deserve future investigation to assess whether low PBP values, as measured by LASCA, are associated with a higher iDTL incidence.References:[1]Cutolo M, Vanhaecke A, et al. Autoimmun Rev. 2018;17(8):775-80.Figure 1.Distribution of 'average PBP' as measured by LASCA for 'no iDTL group' and 'iDTL group'Disclosure of Interests:Claire Debusschere: None declared, Amber Vanhaecke: None declared, Maurizio Cutolo Grant/research support from: Bristol-Myers Squibb, Actelion, Celgene, Consultant of: Bristol-Myers Squibb, Speakers bureau: Sigma-Alpha, Ellen Deschepper: None declared, Vanessa Smith Grant/research support from: The affiliated company received grants from Research Foundation - Flanders (FWO), Belgian Fund for Scientific Research in Rheumatic diseases (FWRO), Boehringer Ingelheim Pharma GmbH & Co and Janssen-Cilag NV, Consultant of: Boehringer-Ingelheim Pharma GmbH & Co, Speakers bureau: Actelion Pharmaceuticals Ltd, Boehringer-Ingelheim Pharma GmbH & Co and UCB Biopharma Spr

Towards magnetic slowing of atoms and molecules

We outline a method to slow paramagnetic atoms or molecules using pulsed magnetic fields. We also discuss the possibility of producing trapped particles by adiabatic deceleration of a magnetic trap. We present numerical simulation results for the slowing and trapping of molecular oxygen