An Entropy Stable Nodal Discontinuous Galerkin Method for the Two Dimensional Shallow Water Equations on Unstructured Curvilinear Meshes with Discontinuous Bathymetry

We design an arbitrary high-order accurate nodal discontinuous Galerkin spectral element approximation for the nonlinear two dimensional shallow water equations with non-constant, possibly discontinuous, bathymetry on unstructured, possibly curved, quadrilateral meshes. The scheme is derived from an equivalent flux differencing formulation of the split form of the equations. We prove that this discretisation exactly preserves the local mass and momentum. Furthermore, combined with a special numerical interface flux function, the method exactly preserves the mathematical entropy, which is the total energy for the shallow water equations. By adding a specific form of interface dissipation to the baseline entropy conserving scheme we create a provably entropy stable scheme. That is, the numerical scheme discretely satisfies the second law of thermodynamics. Finally, with a particular discretisation of the bathymetry source term we prove that the numerical approximation is well-balanced. We provide numerical examples that verify the theoretical findings and furthermore provide an application of the scheme for a partial break of a curved dam test problem

LC-MS method development and comparison of sampling materials for the analysis of organic gunshot residues

This study aimed at comparing the efficiency of various sampling materials for the collection and subsequent analysis of organic gunshot residues (OGSR). To the best of our knowledge, it is the first time that sampling devices were investigated in detail for further quantitation of OGSR by LC-MS. Seven sampling materials, namely two "swab"-type and five "stub"-type collection materials, were tested. The investigation started with the development of a simple and robust LC-MS method able to separate and quantify molecules typically found in gunpowders, such as diphenylamine or ethylcentralite. The evaluation of sampling materials was then systematically carried out by first analysing blank extracts of the materials to check for potential interferences and determining matrix effects. Based on these results, the best four materials, namely cotton buds, polyester swabs, a tape from 3M and PTFE were compared in terms of collection efficiency during shooting experiments using a set of 9 mm Luger ammunition. It was found that the tape was capable of recovering the highest amounts of OGSR. As tape-lifting is the technique currently used in routine for inorganic GSR, OGSR analysis might be implemented without modifying IGSR sampling and analysis procedure

A Provably Stable Discontinuous Galerkin Spectral Element Approximation for Moving Hexahedral Meshes

We design a novel provably stable discontinuous Galerkin spectral element (DGSEM) approximation to solve systems of conservation laws on moving domains. To incorporate the motion of the domain, we use an arbitrary Lagrangian-Eulerian formulation to map the governing equations to a fixed reference domain. The approximation is made stable by a discretization of a skew-symmetric formulation of the problem. We prove that the discrete approximation is stable, conservative and, for constant coefficient problems, maintains the free-stream preservation property. We also provide details on how to add the new skew-symmetric ALE approximation to an existing discontinuous Galerkin spectral element code. Lastly, we provide numerical support of the theoretical results

A study of transfer and prevalence of organic gunshot residues

The main goal of the present study was to determine the amounts and distribution of organic gunshot residues (OGSR) on the shooter’s upper body and clothing after discharging a pistol. A preliminary study was also performed to evaluate the prevalence of OGSR in the general population as well as in a police laboratory environment. In the transfer study, results indicated that OGSR are not only transferred to the hand of the shooter, but also to other parts of the upper body. Thus, wrists and forearms also represent interesting targets as they are washed less frequently than hands. Samples from the face and hair of the shooters resulted in no OGSR detection just after firing. It was also observed that the concentrations recovered from clothing are generally higher compared to the same skin area. Prevalence in both general (n = 27) and police populations (n = 25) was very low. No OGSR was detected in the samples from the general population and only two samples from the police population were found positive

Run Generation Revisited: What Goes Up May or May Not Come Down

In this paper, we revisit the classic problem of run generation. Run generation is the first phase of external-memory sorting, where the objective is to scan through the data, reorder elements using a small buffer of size M , and output runs (contiguously sorted chunks of elements) that are as long as possible. We develop algorithms for minimizing the total number of runs (or equivalently, maximizing the average run length) when the runs are allowed to be sorted or reverse sorted. We study the problem in the online setting, both with and without resource augmentation, and in the offline setting. (1) We analyze alternating-up-down replacement selection (runs alternate between sorted and reverse sorted), which was studied by Knuth as far back as 1963. We show that this simple policy is asymptotically optimal. Specifically, we show that alternating-up-down replacement selection is 2-competitive and no deterministic online algorithm can perform better. (2) We give online algorithms having smaller competitive ratios with resource augmentation. Specifically, we exhibit a deterministic algorithm that, when given a buffer of size 4M , is able to match or beat any optimal algorithm having a buffer of size M . Furthermore, we present a randomized online algorithm which is 7/4-competitive when given a buffer twice that of the optimal. (3) We demonstrate that performance can also be improved with a small amount of foresight. We give an algorithm, which is 3/2-competitive, with foreknowledge of the next 3M elements of the input stream. For the extreme case where all future elements are known, we design a PTAS for computing the optimal strategy a run generation algorithm must follow. (4) Finally, we present algorithms tailored for nearly sorted inputs which are guaranteed to have optimal solutions with sufficiently long runs

Organic gunshot residues: observations about sampling and transfer mechanisms

This work aimed at studying the sampling, storage, transfer and persistence of organic gunshot residue (OGSR), mainly stabilizers, using liquid chromatography hyphenated to mass spectrometry. Collection using swabs and stubs was compared through sequential sampling in terms of amount of residues left on the hand of a shooter. While stubs collected nearly all residues, swabs left about 50% of the residues on the hands. Moreover, the study of storage conditions after sampling showed that stubs were more stable than swabs and could be held at room temperature without significant compound loss up to two weeks. Then, shooting experiments were performed to evaluate transfer of OGSR. It was not possible to differentiate different brands of ammunition based on a single compound concentration. Moreover, a memory effect was identified when different ammunition was shot using the same firearm. Finally, various exposed skin surfaces and hair as well as clothing were sampled to estimate what surfaces might be the best targets for OGSR sampling by comparing results just after discharge and two hours after discharging a pistol. The results indicated that OGSR were more rapidly lost from hands than from clothing. Moreover, it was shown that the face and hair of a suspect might be contaminated through secondary transfer. Thus, OGSR might remain longer on other skin surfaces, hair and clothing than on the hands of a suspect. As a consequence, sampling should also include clothing, hair and face

COLOPHON 2013

International audienceIn 2010 the Mimar Sinan University of Istanbul started a research project on the Ionian town of Colophon which is conducted in close collaboration with the University of Vienna [1]. It aims at the exploration of the ancient urban area as well as on the distribution of the necropoleis. For the campaign of the year 2013 the Austrian research team concentrated on the following topics [2]. 1. Survey in the area of the ancient city This year, the main focus of the investigations in the area within the fortification walls was laid on the exploration of the urbanistic organisation of the city by magnetic survey and by ground penetrating radar. For this purpose two areas were chosen. The first area consisted of fields in the plain between the brooks Kabaklidere and Kurudere in the north eastern quarters of the ancient city. Here the existence of houses has been proven by excavations by the museum of Izmir about 10–15 years ago. The remains of walls were also visible in several trenches opened by illegal diggers both on the plains and in the forested area near the slopes of the surrounding hills. The geophysical prospection confirmed the assumed existence of several buildings and streets in the area. In addition we conducted an extensive survey in adjacent fields and collected pottery from the holes dug by illegal diggers. The finds included roof tiles and a small amount of pottery with a chronological range from the 6 th to the 4 th c. BC. A detailed documentation of the present land-use and land-division of this area, already begun in 2012, was continued with the aim of a diachronical understanding of the landscape's historical development. This included the description of modern features in the fields as well as interviews with owners and tenants. The second area chosen for a geophysical prospection is situated to the south of the Halil Ağa Tepesi, where W. Höpfner proposed to locate the ancient agora [3]. Both magnetic survey and ground penetrating radar prospections were carried out here. Further examination of the data is currently being carried out. The exemplary geophysical prospection will give important insights into the organisation and layou

COLOPHON 2013

International audienceIn 2010 the Mimar Sinan University of Istanbul started a research project on the Ionian town of Colophon which is conducted in close collaboration with the University of Vienna [1]. It aims at the exploration of the ancient urban area as well as on the distribution of the necropoleis. For the campaign of the year 2013 the Austrian research team concentrated on the following topics [2]. 1. Survey in the area of the ancient city This year, the main focus of the investigations in the area within the fortification walls was laid on the exploration of the urbanistic organisation of the city by magnetic survey and by ground penetrating radar. For this purpose two areas were chosen. The first area consisted of fields in the plain between the brooks Kabaklidere and Kurudere in the north eastern quarters of the ancient city. Here the existence of houses has been proven by excavations by the museum of Izmir about 10–15 years ago. The remains of walls were also visible in several trenches opened by illegal diggers both on the plains and in the forested area near the slopes of the surrounding hills. The geophysical prospection confirmed the assumed existence of several buildings and streets in the area. In addition we conducted an extensive survey in adjacent fields and collected pottery from the holes dug by illegal diggers. The finds included roof tiles and a small amount of pottery with a chronological range from the 6 th to the 4 th c. BC. A detailed documentation of the present land-use and land-division of this area, already begun in 2012, was continued with the aim of a diachronical understanding of the landscape's historical development. This included the description of modern features in the fields as well as interviews with owners and tenants. The second area chosen for a geophysical prospection is situated to the south of the Halil Ağa Tepesi, where W. Höpfner proposed to locate the ancient agora [3]. Both magnetic survey and ground penetrating radar prospections were carried out here. Further examination of the data is currently being carried out. The exemplary geophysical prospection will give important insights into the organisation and layou

High energy Coulomb-scattered electrons for relativistic particle beam diagnostics

A new system used for monitoring energetic Coulomb-scattered electrons as the main diagnostic for accurately aligning the electron and ion beams in the new Relativistic Heavy Ion Collider (RHIC) electron lenses is described in detail. The theory of electron scattering from relativistic ions is developed and applied to the design and implementation of the system used to achieve and maintain the alignment. Commissioning with gold and 3He beams is then described as well as the successful utilization of the new system during the 2015 RHIC polarized proton run. Systematic errors of the new method are then estimated. Finally, some possible future applications of Coulomb-scattered electrons for beam diagnostics are briefly discussed.Comment: 16 pages, 23 figure

On a Tree and a Path with no Geometric Simultaneous Embedding

Two graphs $G_1=(V,E_1)$ and $G_2=(V,E_2)$ admit a geometric simultaneous embedding if there exists a set of points P and a bijection M: P -> V that induce planar straight-line embeddings both for $G_1$ and for $G_2$. While it is known that two caterpillars always admit a geometric simultaneous embedding and that two trees not always admit one, the question about a tree and a path is still open and is often regarded as the most prominent open problem in this area. We answer this question in the negative by providing a counterexample. Additionally, since the counterexample uses disjoint edge sets for the two graphs, we also negatively answer another open question, that is, whether it is possible to simultaneously embed two edge-disjoint trees. As a final result, we study the same problem when some constraints on the tree are imposed. Namely, we show that a tree of depth 2 and a path always admit a geometric simultaneous embedding. In fact, such a strong constraint is not so far from closing the gap with the instances not admitting any solution, as the tree used in our counterexample has depth 4.Comment: 42 pages, 33 figure