Measuring velocity ratios with correlation functions

We show how to determine the ratio of the transverse velocity of a source to the velocity of emitted particles, using split-bin correlation functions. The technique is to measure $S_2$ and $S_2^{\phi}$, subtract the contributions from the single-particle distribution, and take the ratio as the bin size goes to zero. We demonstrate the technique for two cases: each source decays into two particles, and each source emits a large number of particles.Comment: 9 pages, LaTeX, 2 PostScript figure

Correlation measurements in high-multiplicity events

Requirements for correlation measurements in high--multiplicity events are discussed. Attention is focussed on detection of so--called hot spots, two--particle rapidity correlations, two--particle momentum correlations (for quantum interferometry) and higher--order correlations. The signal--to--noise ratio may become large in the high--multiplicity limit, allowing meaningful single--event measurements, only if the correlations are due to collective behavior.Comment: MN 55455, 20 pages, KSUCNR-011-92 and TPI-MINN-92/47-T (revised). Revised to correct typo in equation (30), and to fill in a few steps in calculations. Now published as Phys. Rev. C 47 (1993) 232

Label Placement in Road Maps

A road map can be interpreted as a graph embedded in the plane, in which each vertex corresponds to a road junction and each edge to a particular road section. We consider the cartographic problem to place non-overlapping road labels along the edges so that as many road sections as possible are identified by their name, i.e., covered by a label. We show that this is NP-hard in general, but the problem can be solved in polynomial time if the road map is an embedded tree.Comment: extended version of a CIAC 2015 pape

Mapping the Arnold web with a GPU-supercomputer

The Arnold diffusion constitutes a dynamical phenomenon which may occur in the phase space of a non-integrable Hamiltonian system whenever the number of the system degrees of freedom is $M \geq 3$. The diffusion is mediated by a web-like structure of resonance channels, which penetrates the phase space and allows the system to explore the whole energy shell. The Arnold diffusion is a slow process; consequently the mapping of the web presents a very time-consuming task. We demonstrate that the exploration of the Arnold web by use of a graphic processing unit (GPU)-supercomputer can result in distinct speedups of two orders of magnitude as compared to standard CPU-based simulations.Comment: 7 pages, 4 figures, a video supplementary provided at http://www.physik.uni-augsburg.de/~seiberar/arnold/Energy15_HD_frontNback.av

An Algorithmic Framework for Labeling Road Maps

Given an unlabeled road map, we consider, from an algorithmic perspective, the cartographic problem to place non-overlapping road labels embedded in their roads. We first decompose the road network into logically coherent road sections, e.g., parts of roads between two junctions. Based on this decomposition, we present and implement a new and versatile framework for placing labels in road maps such that the number of labeled road sections is maximized. In an experimental evaluation with road maps of 11 major cities we show that our proposed labeling algorithm is both fast in practice and that it reaches near-optimal solution quality, where optimal solutions are obtained by mixed-integer linear programming. In comparison to the standard OpenStreetMap renderer Mapnik, our algorithm labels 31% more road sections in average.Comment: extended version of a paper to appear at GIScience 201

The characterization of silica-based sorbents in reversed phase liquid chromatography with application to method development in solid-phase extraction

Despite the wide application of solid-phase extraction (SPE) in the environmental, clinical and pharmaceutical fields, method development for this technique has remained largely an empirical process of trial and error. In an effort to provide a systematic approach to method development, the kinetic and retention properties of four popular siloxane-bonded SPE sorbents have been determined. Kinetic measurements allow the evaluation of the performance of extraction devices and reveal areas in which small changes in design or manufacture could improve sampling characteristics. Application of the solvation parameter model to retention data yields a set of system constants that describe the ability of the solvated stationary phase to compete with the bulk mobile phase for specific, clearly defined, intermolecular interactions with the solute. Once established, system constants can be used for the prediction of retention for any compound for which solute descriptors are available, the identification of new sorbents with sampling properties that set them apart from materials already available, and the prediction of breakthrough volume in SPE. Knowledge of breakthrough volume is a key parameter for predicting extraction conditions which are likely to be successful, thus eliminating a large portion of the guesswork involved in method development

Measuring hadron properties at finite temperature

We estimate the numbers and mass spectra of observed lepton and kaon pairs produced from $\phi$ meson decays in the central rapidity region of an Au+Au collision at lab energy 11.6 GeV/nucleon. The following effects are considered: possible mass shifts, thermal broadening due to collisions with hadronic resonances, and superheating of the resonance gas. Changes in the dilepton mass spectrum may be seen, but changes in the dikaon spectrum are too small to be detectable.Comment: 9 pages (revtex), 3 figures (uuencoded postscript

The Role of Developmental Timing Regulators in Progenitor Proliferation and Cell Fate Specification During Mammalian Neurogenesis

Developmental timing is a key aspect of tissue and organ formation in which distinct cell types are generated through a series of steps from common progenitors. These progenitors undergo specific changes in gene expression that signifies both a distinct progenitor type and developmental time point that thereby specifies a particular cell fate at that stage of development. The nervous system is an important setting for understanding developmental timing because different cell types are produced in a certain order and the switch from stem cells to progenitors requires precise timing and regulation. Notable examples of such regulatory molecules include the RNA-binding protein LIN28, and its downstream target, miRNA let-7. Although LIN28 is known to regulate both cell fate and tissue growth, and at times to promote an undifferentiated state, thus far a unified understanding of LIN28’s biological role at the cellular level has not been attained. Here I address LIN28’s activity in mammalian postnatal neurogenesis. Constitutive expression of LIN28 in cells derived from the subventricular zone of the mouse caused several distinct effects: (1) the number of differentiated neurons was dramatically reduced while the relative abundance of two neuronal sub-types was significantly altered; (2) the population of proliferating neural progenitors in the SVZ was reduced while the proportion of neuroblasts was increased, (3) neuro-blast exit from the SVZ increased, and (4) the number of astrocytes was reduced while occasionally causing them to appear early. Thus, LIN28 acts at a post-stem cell/pre-differentiation step, and its continuous expression caused a precocious, not a reiterative phenotype, as is seen in other experimental systems. I made use of a circular RNA sponge that effectively inhibits let-7 activity to address the degree to which LIN28’s effects are due to its inhibition of let-7. Moreover, since LIN41 contributes to a subset of LIN28’s function in C. elegans, I explored whether LIN41 played a role in mammalian neurogenesis. I found that although LIN28 has a multifaceted role in the number and types of cells produced during postnatal neurogenesis, it appears that its action through let-7 accounts for only a fraction of these effects