Jump-Preserving Regression and Smoothing using Local Linear Fitting: A Compromise

This paper deals with nonparametric estimation of a regression curve, where the estimation method should preserve possible jumps in the curve. At each point x at which one wants to estimate the regression function, the method chooses in an adaptive way among three estimates: a local linear estimate using only datapoints to the left of x, a local linear estimate based on only datapoints to the right of x, and finally a local linear estimate using data in a two-sided neighbourhood around x. The choice among these three estimates is made by looking at differences of the weighted residual mean squares of the three fits. The resulting estimate preserves the jumps well and in addition gives smooth estimates of the continuity parts of the curve. This property of compromise between local smoothing and jump-preserving is what distinguishes our method from most previously proposed methods, that mainly focused on local smoothing and consequently blurred possible jumps, or mainly focused on jump-preserving and hence led to rather noisy estimates in continuity regions of the underlying regression curve. Strong consistency of the estimator is established and its performance is tested via a simulation study. This study also compares the current method with some existing methods. The current method is illustrated in analyzing a real dataset.     

Optimal design of railway vehicles

Summary A well-designed railway vehicle has to meet two conflicting requirements. Firstly, it must be able to move freely through a curve. Secondly, the fundamental movement must be stable even at high running speeds.A. H. Wickens has indicated how these requirements can be formulated in a quantitative way. In the present paper we shall describe, explain and slightly extend his method and, moreover, we shall show that the calculations can be simplified by using linear algebra. The method is illustrated by applying the results on the case that the vehicle has a running gear with two wheelsets.

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Optimaler Entwurf von Eisenbahnfahrzeugen

Übersicht Bin richtig entworfenes Eisenbahnfahrzeug soll zwei einander widersprechende Forderungen erfüllen. Erstens soll es imstande sein, frei durch einen Gleisbogen zu laufen. Zweitens soll die Grundbewegung auch bei großen Fahrgeschwindigkeiten stabil sein.A. H. Wickens hat angegeben, wie diese Forderungen quantitativ formuliert werden können. Im vorliegenden Aufsatz werden wir seine Methode beschreiben, erklären und ein wenig erweitern. Zudem werden wir zeigen, daß die Berechnungen sich vereinfachen lassen, indem man lineare Algebra benützt. Die Methode wird dadurch erläutert, daß die Ergebnisse auf den Fall eines Fahrzeug-Laufwerks mit zwei Radsätzen angewandt werden.

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Dedicated to Academician Yu. A. Mitropolski, member of the Ukrainian Academy of Sciences, on the occasion of bis 70^th anniversary. January 3, 1987     

Pre- and postfunctionalized self-assembled π-conjugated fluorescent organic nanoparticles for dual targeting

There is currently a high demand for novel approaches to engineer fluorescent nanoparticles with precise surface properties suitable for various applications, including imaging and sensing. To this end, we report a facile and highly reproducible one-step method for generating functionalized fluorescent organic nanoparticles via self-assembly of prefunctionalized π-conjugated oligomers. The engineered design of the nonionic amphiphilic oligomers enables the introduction of different ligands at the extremities of inert ethylene glycol side chains without interfering with the self-assembly process. The intrinsic fluorescence of the nanoparticles permits the measurement of their surface properties and binding to dye-labeled target molecules via F?rster resonance energy transfer (FRET). Co-assembly of differently functionalized oligomers is also demonstrated, which enables the tuning of ligand composition and density. Furthermore, nanoparticle prefunctionalization has been combined with subsequent postmodification of azide-bearing oligomers via click chemistry. This allows for expanding ligand diversity at two independent stages in the nanoparticle fabrication process. The practicability of the different methods entails greater control over surface functionality. Through labeling with different ligands, selective binding of proteins, bacteria, and functionalized beads to the nanoparticles has been achieved. This, in combination with the absence of unspecific adsorption, clearly demonstrates the broad potential of these nanoparticles for selective targeting and sequestration. Therefore, controlled bifunctionalization of fluorescent π-conjugated oligomer nanoparticles represents a novel approach with high applicability to multitargeted imaging and sensing in biology and medicine.     

Simultaneous cavity-enhanced and cavity ringdown absorption spectroscopy using optical feedback

We present a scheme of optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) including a fast optical switch to produce cavity ringdown spectra (OF-CRDS) simultaneously. This also works as a dynamically adjustable variable attenuator allowing to compensate for reduced signal levels in correspondence with absorption lines. For this, an acousto-optic deflector is used in a double-pass configuration to eliminate the single-pass frequency shift, which is incompatible with optical feedback. This is probably the most effective device providing the required fast response and the high extinction ratio necessary to perform clean ringdown measurements. The resulting direct comparison of OF-CEAS and OF-CRDS shows that these produce almost equivalent spectral data, with 0.3 % maximal difference at the top of an absorption line having a signal-to-noise ratio (S/N) of 3,300. OF-CEAS is largely winning on the short-term noise level while OF-CRDS appears to be more immune from interference fringes, delivering cleaner spectra after longer averaging.