Velocity-selected molecular pulses produced by an electric guide

Electrostatic velocity filtering is a technique for the production of continuous guided beams of slow polar molecules from a thermal gas. We extended this technique to produce pulses of slow molecules with a narrow velocity distribution around a tunable velocity. The pulses are generated by sequentially switching the voltages on adjacent segments of an electric quadrupole guide synchronously with the molecules propagating at the desired velocity. This technique is demonstrated for deuterated ammonia (ND$_{3}$), delivering pulses with a velocity in the range of $20-100\,\rm{m/s}$ and a relative velocity spread of $(16\pm 2)\,$ at FWHM. At velocities around $60\,\rm{m/s}$, the pulses contain up to $10^6$ molecules each. The data are well reproduced by Monte-Carlo simulations, which provide useful insight into the mechanisms of velocity selection.Comment: 8 pages, 6 figure

Referral patterns of children with poor growth in primary health care

Background. To promote early diagnosis and treatment of short stature, consensus meetings were held in the mid nineteen nineties in the Netherlands and the UK. This resulted in guidelines for referral. In this study we evaluate the referral pattern of short stature in primary health care using these guidelines, comparing it with cut-off values mentioned by the WHO. Methods. Three sets of referral rules were tested on the

Multiple Imputation Ensembles (MIE) for dealing with missing data

Missing data is a significant issue in many real-world datasets, yet there are no robust methods for dealing with it appropriately. In this paper, we propose a robust approach to dealing with missing data in classification problems: Multiple Imputation Ensembles (MIE). Our method integrates two approaches: multiple imputation and ensemble methods and compares two types of ensembles: bagging and stacking. We also propose a robust experimental set-up using 20 benchmark datasets from the UCI machine learning repository. For each dataset, we introduce increasing amounts of data Missing Completely at Random. Firstly, we use a number of single/multiple imputation methods to recover the missing values and then ensemble a number of different classifiers built on the imputed data. We assess the quality of the imputation by using dissimilarity measures. We also evaluate the MIE performance by comparing classification accuracy on the complete and imputed data. Furthermore, we use the accuracy of simple imputation as a benchmark for comparison. We find that our proposed approach combining multiple imputation with ensemble techniques outperform others, particularly as missing data increases

The Social Production of Invited Spaces: Toward an Understanding of the Invitational Character of Spaces for Citizens’ Initiatives

The rise of citizens’ initiatives is changing the relation between governments and citizens. This paper contributes to the discussion of how governments can productively relate to these self-organizing citizens. The study analyzes the relation between the social production of invited spaces and the invitational character of such spaces, as perceived by governments and citizens. Invited spaces are the (institutional, legal, organizational, political and policy) spaces that are created by governments for citizens to take on initiatives to create public value. We characterize four types of invited spaces and compare four cases in Dutch planning to analyze how these types of invited spaces are perceived as invitational. From the analysis, we draw specific lessons for governments that want to stimulate citizens’ initiatives. We conclude with a general insight for public administration scholars; in addition to formal rules and structures, scholars should pay more attention to interactions, attitudes and meaning making of both government officials and citizens

Cold heteromolecular dipolar collisions

We present the first experimental observation of cold collisions between two different species of neutral polar molecules, each prepared in a single internal quantum state. Combining for the first time the techniques of Stark deceleration, magnetic trapping, and cryogenic buffer gas cooling allows the enhancement of molecular interaction time by 10$^5$. This has enabled an absolute measurement of the total trap loss cross sections between OH and ND$_3$ at a mean collision energy of 3.6 cm$^{-1}$ (5 K). Due to the dipolar interaction, the total cross section increases upon application of an external polarizing electric field. Cross sections computed from \emph{ab initio} potential energy surfaces are in excellent agreement with the measured value at zero external electric field. The theory presented here represents the first such analysis of collisions between a $^2\Pi$ radical and a closed-shell polyatomic molecule.Comment: 7 pages, 5 figure

Variable selection under multiple imputation using the bootstrap in a prognostic study

Background: Missing data is a challenging problem in many prognostic studies. Multiple imputation (MI) accounts for imputation uncertainty that allows for adequate statistical testing. We developed and tested a methodology combining MI with bootstrapping techniques for studying prognostic variable selection. Method: In our prospective cohort study we merged data from three different randomized controlled trials (RCTs) to assess prognostic variables for chronicity of low back pain. Among the outcome and prognostic variables data were missing in the range of 0 and 48.1%. We used four methods to investigate the influence of respectively sampling and imputation variation: MI only, bootstrap only, and two methods that combine MI and bootstrapping. Variables were selected based on the inclusion frequency of each prognostic variable, i.e. the proportion of times that the variable appeared in the model. The discriminative and calibrative abilities of prognostic models developed by the four methods were assessed at different inclusion levels. Results: We found that the effect of imputation variation on the inclusion frequency was larger than the effect of sampling variation. When MI and bootstrapping were combined at the range of 0% (full model) to 90% of variable selection, bootstrap corrected c-index values of 0.70 to 0.71 and slope values of 0.64 to 0.86 were found. Conclusion: We recommend to account for both imputation and sampling variation in sets of missing data. The new procedure of combining MI with bootstrapping for variable selection, results in multivariable prognostic models with good performance and is therefore attractive to apply on data sets with missing values

The relationship between socioeconomic status and white matter microstructure in pre-reading children: A longitudinal investigation

Reading is a learned skill crucial for educational attainment. Children from families of lower socioeconomic status (SES) tend to have poorer reading performance and this gap widens across years of schooling. Reading relies on the orchestration of multiple neural systems integrated via specific white-matter pathways, but there is limited understanding about whether these pathways relate differentially to reading performance depending on SES background. Kindergarten white-matter FA and second-grade reading outcomes were investigated in an SES-diverse sample of 125 children. The three left-hemisphere white-matter tracts most associated with reading, and their right-hemisphere homologs, were examined: arcuate fasciculus (AF), superior longitudinal fasciculus (SLF), and inferior longitudinal fasciculus (ILF). There was a significant and positive association between SES and fractional anisotropy (FA) in the bilateral ILF in kindergarten. SES moderated the association between kindergarten ILF and second grade reading performance, such that it was positive in lower-SES children, but not significant in higher-SES children. These results have implications for understanding the role of the environment in the development of the neural pathways that support reading

Structure of low-density nanoporous dielectrics revealed by low-vacuum electron microscopy and small-angle x-ray scattering

We use low-vacuum scanning electron microscopy to image directly the ligament and pore size and shape distributions of representative aerogels over a wide range of length scales ({approx} 10{sup 0}-10{sup 5} nm). The images are used for unambiguous, real-space interpretation of small-angle scattering data for these complex nanoporous systems

‘Test Driving’ a Financing Instrument for Climate Adaptation: Analyzing Institutional Dilemmas using Simulation Gaming

Urban physical public infrastructure is a frontline defense mechanism to manage and mitigate climate-related impacts. Market instruments are often cited as possible means to spread risk and reduce financial burdens on the public sector. The authors argue that existing research tends to focus on the technical issues of instruments and neglects considering institutional dynamics that may enable or constrain local market-based financing mechanisms. In this article, three core dilemmas (values uncertainty, planning horizon, and indirect benefits) are used to analyze the responses of practitioners to a possible financing instrument. The findings indicate that the practitioner’s responses to tax increment financing were largely shaped by the adaptation dilemmas and not the characteristics of the instrument per se. By mapping the dilemmas onto whether they would recommend it, participants imposed a financial barrier on climate adaptation investments. The authors conclude that a key imperative in the design of policy instruments is to pay attention to the congruency of informal institutions at the ‘street level’ in order to be in-step with the current sociopolitical conditions. The findings also point to four key attributes that a local market-based instrument would need to be aligned and responsive to the Dutch planning and development context