Ordering Properties of the First Eigenvector of Certain Similarity Matrices

It is shown for coefficient matrices of Russell-Rao coefficients and two asymmetric Dice coefficients that ordinal information on a latent variable model can be obtained from the eigenvector corresponding to the largest eigenvalue

Properties of Bangdiwala's B

Cohen's kappa is the most widely used coefficient for assessing interobserver agreement on a nominal scale. An alternative coefficient for quantifying agreement between two observers is Bangdiwala's B. To provide a proper interpretation of an agreement coefficient one must first understand its meaning. Properties of the kappa coefficient have been extensively studied and are well documented. Properties of coefficient B have been studied, but not extensively. In this paper, various new properties of B are presented. Category B-coefficients are defined that are the basic building blocks of B. It is studied how coefficient B, Cohen's kappa, the observed agreement and associated category coefficients may be related. It turns out that the relationships between the coefficients are quite different for 2x2 tables than for agreement tables with three or more categories

A Comparison of Reliability Coefficients for Ordinal Rating Scales

Kappa coefficients are commonly used for quantifying reliability on a categorical scale, whereas correlation coefficients are commonly applied to assess reliability on an interval scale. Both types of coefficients can be used to assess the reliability of ordinal rating scales. In this study, we compare seven reliability coefficients for ordinal rating scales: the kappa coefficients included are Cohen’s kappa, linearly weighted kappa, and quadratically weighted kappa; the correlation coefficients included are intraclass correlation ICC(3,1), Pearson’s correlation, Spearman’s rho, and Kendall’s tau-b. The primary goal is to provide a thorough understanding of these coefficients such that the applied researcher can make a sensible choice for ordinal rating scales. A second aim is to find out whether the choice of the coefficient matters. We studied to what extent we reach the same conclusions about inter-rater reliability with different coefficients, and to what extent the coefficients measure agreement in a similar way, using analytic methods, and simulated and empirical data. Using analytical methods, it is shown that differences between quadratic kappa and the Pearson and intraclass correlations increase if agreement becomes larger. Differences between the three coefficients are generally small if differences between rater means and variances are small. Furthermore, using simulated and empirical data, it is shown that differences between all reliability coefficients tend to increase if agreement between the raters increases. Moreover, for the data in this study, the same conclusion about inter-rater reliability was reached in virtually all cases with the four correlation coefficients. In addition, using quadratically weighted kappa, we reached a similar conclusion as with any correlation coefficient a great number of times. Hence, for the data in this study, it does not really matter which of these five coefficients is used. Moreover, the four correlation coefficients and quadratically weighted kappa tend to measure agreement in a similar way: their values are very highly correlated for the data in this study

Ordering Properties of the First Eigenvector of Certain Similarity Matrices

It is shown for coefficient matrices of Russell-Rao coefficients and two asymmetric Dice coefficients that ordinal information on a latent variable model can be obtained from the eigenvector corresponding to the largest eigenvalue

Direct magneto-optical compression of an effusive atomic beam for high-resolution focused ion beam application

An atomic rubidium beam formed in a 70 mm long two-dimensional magneto-optical trap (2D MOT), directly loaded from a collimated Knudsen source, is analyzed using laser-induced fluorescence. The longitudinal velocity distribution, the transverse temperature and the flux of the atomic beam are reported. The equivalent transverse reduced brightness of an ion beam with similar properties as the atomic beam is calculated because the beam is developed to be photoionized and applied in a focused ion beam. In a single two-dimensional magneto-optical trapping step an equivalent transverse reduced brightness of $(1.0\substack{+0.8-0.4})$ $\times 10^6$ A/(m$^2$ sr eV) was achieved with a beam flux equivalent to $(0.6\substack{+0.3-0.2})$ nA. The temperature of the beam is further reduced with an optical molasses after the 2D MOT. This increased the equivalent brightness to $(6\substack{+5-2})$$\times 10^6$ A/(m$^2$ sr eV). For currents below 10 pA, for which disorder-induced heating can be suppressed, this number is also a good estimate of the ion beam brightness that can be expected. Such an ion beam brightness would be a six times improvement over the liquid metal ion source and could improve the resolution in focused ion beam nanofabrication.Comment: 10 pages, 8 figures, 1 tabl

Value of urinary N-methylhistamine measurements m childhood mastocytosis

Background: Histamine is an indicator of mast cell activation. N- methylhistamine (NMH) is a metabolite of histamine that can be measured in urine. Objective: Our purpose was to assess the usefulness of determining urinary NMH levels for the diagnosis and follow-up of patients with mastocytosis. Methods: Urinary NMH levels were determined in 44 patients and were correlated with disease activity and extension. The control group consisted of 24 children without mastocytosis or any other skin disease. Results: A significant negative correlation was found between NMH and age in patients with active mastocytosis and in the control group. Adjusted for age, NMH values were significantly higher in patients with active mastocytosis. There was a significant difference in NMH values between patients with diffuse cutaneous mastocytosis, patients with active urticaria pigmentosa, and patients with active mastocytomas. However, there was a substantial overlap of NMH values in the different subgroups. Conclusion: Urinary NMH values tend to decrease with age. Urinary NMH values correlated with the extent and the activity of the disease. High NMH values suggest more extensive involvement

Direct Observation of Sub-Poissonian Temporal Statistics in a Continuous Free Electron Beam with Sub-picosecond Resolution

Recently, interest in anti-bunched electron beams has surged because of their potential in free electron quantum optics and electron microscopy. However, the limited temporal resolution of available detectors poses a challenge in observing the statistics of such beams. We propose a novel method to measure the arrival time statistics of continuous electron beams with sub-ps resolution. We developed a 2D streak camera based on the combination of RF-cavity-based electron beam deflection and fast single electron imaging. We observed Poissonian statistics within time bins from 100~ns to 1~ns and increasingly pronounced sub-Poissonian statistics as the time bin decreases from 2~ps to 340~fs