Fluxoid dynamics in superconducting thin film rings

We have measured the dynamics of individual magnetic fluxoids entering and leaving photolithographically patterned thin film rings of the underdoped high-temperature superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$, using a variable sample temperature scanning SQUID microscope. These results can be qualitatively described using a model in which the fluxoid number changes by thermally activated nucleation of a Pearl vortex in, and transport of the Pearl vortex across, the ring wall.Comment: 9 pages, 10 figures, fixed typo

Examining the construct and known-group validity of a composite endpoint for the Older Persons and Informal Caregivers Survey Minimum Data Set (TOPICS-MDS); A largescale data sharing initiative

Background Preference-weighted multi-faceted endpoints have the potential to facilitate comparative effectiveness research that incorporates patient preferences. The Older Persons and Informal Caregivers Survey Composite endpoint (TOPICS-CEP) is potentially a valuable outcome measure for evaluating interventions in geriatric care as it combines multiple outcomes relevant to older persons in a single metric. The objective of this study was to validate TOPICS-CEP across different study settings (general population, primary care and hospital). Methods Data were extracted from TOPICS Minimum Dataset (MDS), a pooled public-access national database with information on older persons throughout the Netherlands. Data of

Measurement properties of the EQ-5D across four major geriatric conditions: Findings from TOPICS-MDS

Background: As populations age, chronic geriatric conditions linked to progressive organ failure jeopardize health-related quality of life (HRQoL). Thus, this research assessed the validity and applicability of the EQ-5D (a common HRQoL instrument) across four major chronic geriatric conditions: hearing issues, joint damage, urinary incontinence, or dizziness with falls. Methods: The study sample comprised 25,637 community-dwelling persons aged 65 years and older residing in the Netherlands (Data source: TOPICS-MDS, www.topics-mds.eu ). Floor and ceiling effects were examined. To assess convergent validity, random effects meta-correlations (Spearman's rho) were derived between individual EQ-5D domains and related survey items. To further examine construct validity, the association between sociodemographic characteristics and EQ-5D summary scores were assessed using linear mixed models. Outcomes were compared to the overall study population as well as a 'healthy' subgroup reporting no major chronic conditions. Results: Whereas ceiling effects were observed in the overall study population and the 'healthy' subgroup, such was not the case in the geriatric condition subgroups. The majority of hypotheses regarding correlations between survey items and sociodemographic associations were supported. EQ-5D summary scores were lower in respondents who were older, female, widowed/single, lower educated, and living alone. Increasing co-morbidity had a clear negative effect on EQ-5D scores. Conclusion: This study supported the construct validity of the EQ-5D across four major geriatric conditions. For older persons who are generally healthy, i.e. reporting few to no chronic conditions, the EQ-5D confers poor discriminative ability due to ceiling effects. Although the overall dataset initially suggested poor discriminative ability for the EQ-5D, such was not the case within subgroups presenting with major geriatric conditions

Three‐way methods for the calibration of chromatographic systems:Comparing PARAFAC and three‐way PLS

For the calibration of chromatographic systems, different methods can be used. One class of methods utilizes three-way approaches. The calibration problem is stated in such a way that the decomposition of a three-way array can serve for the prediction of retention on new stationary phases. Two three-way approaches are presented: the Unfold-PCA and PARAFAC models. The theory of both methods is presented and the differences are highlighted, the main difference being that PARAFAC is a trilinear decomposition whereas Unfold-PCA is not. Both three-way methods are evaluated on a small data set consisting of retention measurements of eight solutes at six mobile phase compositions on six stationary phases. The differences in performance of the two models are minor. For calibration purposes, two variants of the methods are discussed: three-way PLS and an extension of PARAFAC. Again the theory and differences between the two methods are explained. The predictive performance of the two methods is compared using the same data set as earlier. The differences in predictive performance, however, are minor. Both methods are capable of predicting 98% of the variation in the test sets. Yet, there are other considerations when comparing methods than predictive performance, e.g. the quality of the predictions

Simple validatory tools for judging the predictive performance of parafac and three‐way PLS

The methods PARAFAC and three-way PLS are compared with respect to their ability to predict reversed-phase retention values. Special attention is paid to simple validatory tools, the meaning and use of which are explained. The simple validatory tools consist of percentages of explained variation in the training set and those that can be calculated with the use of markers. These markers are special (reference) solutes, the retention values of which are used to gain information about a new object for which predictions are wanted. Different validatory tools can be calculated with the use of these marker retention values: percentages of used variation and mean sum of squared residuals after applying the model to these marker retention values. The validatory tools are evaluated on their power to estimate their test set counterparts: the percentages of explained variation in the test set and mean sum of squared prediction errors in the test set. Two different data sets from reversed-phase chromatography are used to evaluate the validatory tools. The first data set has a high signal-to-noise ratio and is measured under the same measurement conditions. The second data set has a low signal-to-noise ratio and is measured under different measurement conditions. Some of the simple validatory tools seem to have relevance to their test set counterparts, even in the case of the second data set

Multivariate calibration strategy for reversed-phase chromatographic systems based on the characterization of stationary-mobile phase combinations with markers

Calibration of chromatographic systems serves several purposes. One of the goals is the correction of retention values in order to make them less dependent on the stationary and mobile phases. Another goal is the transfer of retention values measured on one system to another system. A strategy serving this purpose is reviewed. An example is given which makes use of the latter strategy to correct for batch-to-batch variations of stationary phases. This leaves the way open to update the optimum mobile phase composition. The strategy makes use of special selected compounds: the marker

Multivariate characterization of solvent strength and solvent selectivity in reversed-phase high-performance liquid chromatography

Principal component analysis was used to determine the dimensionality and structure of three data sets consisting of the capacity factors of eleven to twenty different solutes measured in nine different mobile phase compositions consisting of water and methanol and/or acetonitrile on three reversed-phase columns. Principal component analysis showed that two principal components could account for the total variance in the data and that the percentage variance explained by the first principal component (about 80-95%) was much greater than the percentage explained by the second principal component, but that the percentage depended strongly on the choice of solutes for the sample. The first principal component could be associated with solvent strength and solvent strength selectivity and the second principal component with modifier selectivity. Solutes that showed strong modifier selectivity could be distinguished from solutes that have almost zero modifier selectivity, which could be useful for the definition of an empirical solvent strength scale