Isotope Effects in the Predissociation of Excited States of N2+ Produced by Photoionization of 14N2 and 15N2 at Energies Between 24.2 and 25.6 eV

Photoelectron/photoion imaging spectrometry employing dispersed VUV radiation from the SOLEIL synchrotron has been used to study the predissociation of N2+ states located up to 1.3 eV above the ion's first dissociation limit. Branching ratios for unimolecular decay into either N2+ or N+ were obtained by measuring coincidences between threshold electrons and mass-selected product ions, using a supersonic beam of either 14N2 or 15N2 as photoionization target. The results confirm that predissociation of the C2Σu+ state of 14N2+ is faster than emission to the electronic ground-state by a factor 10 or more for all vibrational levels v′ ≥ 3, while for 15N2+ the two decay modes have comparable probabilities for the levels v′ = 3, 4, and 5. In contrast, no significant isotope effect could be observed for the other states of N2+ identified in the photoelectron spectrum. For both 14N2+ and 15N2+ isotopologues all vibrational levels of these other states decay to an extent of at least 95% by predissociation

The emergence and evolution of Neolithic cattle farming in southeastern Europe:New zooarchaeological and stable isotope data from Džuljunica-Smărdeš, in northeastern Bulgaria (ca. 6200–5500 cal. BCE)

Cattle were of great importance for the Neolithic farmers of southeastern Europe, in particular as farming expanded towards the well-watered regions of Džuljunica (ca. 6200–5500 cal. BCE), one of the earliest known Neolithic settlements in northeastern Bulgaria. The clear stratigraphy and the substantial Bos assemblage from Džuljunica Provided us with a great opportunity to investigate the beginning and evolution of cattle husbandry in the northern Balkans through stable isotope and zooarchaeological analyses. The relative abundance of Bos at Džuljunica leaves no doubt about the importance of beef and cattle herding. Mortality profiles suggest a transition in the early phases of the Neolithic from beef-oriented to mixed beef and milk production husbandry, enabled through intensified post-lactation culling. Stable carbon and oxygen isotope analysis of tooth enamel on a limited number of samples provides no evidence for an extended calving season for increasing milk availability or for vertical mobility. Stable carbon and nitrogen isotope values of bone collagen suggest that cattle were kept near the site, where C3 and C4 plants were available in summer, and that they were occasionally foddered with forest resources in the winter. Cattle experience a diachronic reduction in size on a regional scale, possibly due to farmers' choices aimed at more manageable herds consisting of smaller individuals. Restricting intermixing with local aurochs and the arrival of a new type of cattle may also have contributed to this change. Local factors or inter-regional influences may have influenced the ways cattle husbandry evolved at Džuljunica in particular and in northeastern Bulgaria more generally. More data from the region are necessary to flesh out the role of the interplay among environmental factors, local developments, and inter-regional contacts that facilitate the transfer of skills and traditions relating to the changing modes of cattle husbandry

An initial application of computerized adaptive testing (CAT) for measuring disability in patients with low back pain

<p>Abstract</p> <p>Background</p> <p>Recent approaches to outcome measurement involving Computerized Adaptive Testing (CAT) offer an approach for measuring disability in low back pain (LBP) in a way that can reduce the burden upon patient and professional. The aim of this study was to explore the potential of CAT in LBP for measuring disability as defined in the International Classification of Functioning, Disability and Health (ICF) which includes impairments, activity limitation, and participation restriction.</p> <p>Methods</p> <p>266 patients with low back pain answered questions from a range of widely used questionnaires. An exploratory factor analysis (EFA) was used to identify disability dimensions which were then subjected to Rasch analysis. Reliability was tested by internal consistency and person separation index (PSI). Discriminant validity of disability levels were evaluated by Spearman correlation coefficient (r), intraclass correlation coefficient [ICC(2,1)] and the Bland-Altman approach. A CAT was developed for each dimension, and the results checked against simulated and real applications from a further 133 patients.</p> <p>Results</p> <p>Factor analytic techniques identified two dimensions named "body functions" and "activity-participation". After deletion of some items for failure to fit the Rasch model, the remaining items were mostly free of Differential Item Functioning (DIF) for age and gender. Reliability exceeded 0.90 for both dimensions. The disability levels generated using all items and those obtained from the real CAT application were highly correlated (i.e. > 0.97 for both dimensions). On average, 19 and 14 items were needed to estimate the precise disability levels using the initial CAT for the first and second dimension. However, a marginal increase in the standard error of the estimate across successive iterations substantially reduced the number of items required to make an estimate.</p> <p>Conclusion</p> <p>Using a combination approach of EFA and Rasch analysis this study has shown that it is possible to calibrate items onto a single metric in a way that can be used to provide the basis of a CAT application. Thus there is an opportunity to obtain a wide variety of information to evaluate the biopsychosocial model in its more complex forms, without necessarily increasing the burden of information collection for patients.</p

Measured mass to stoichoimetric formula through exhaustive search

International audienceElectrospray ionisation has revolutionised mass spectrometry. Coupled to high mass resolution, it provides the stoichiometric formula of a lot of molecules in a mixture. The link between the mass spectrometry data and the chemical description relies on an interpretation of the measured masses. We present here the tools and tricks developed to exploit Orbitrap mass spectra. This piece of work focuses on the numerical method to assign a molecular formula to a measured mass. The problem is restrained to the solving of the Diophantine equation where the constant coefficients are stoichiometric groups. Peculiar case of a set of convenient groups is given with the chemical constraints it brings to the problem