Reasoning About Foreign Function Interfaces Without Modelling the Foreign Language (Artifact)

There are two components to this artifact. First, a we provide a mechanization of the formalization in the paper, as well as mechanized proofs of the main results from the paper. Second, we provide a full implementation of Poseidon Lua, the language implemented in the paper. Instructions for all components of the artifact are included this document

Blame for Null

Multiple modern programming languages, including Kotlin, Scala, Swift, and C#, have type systems where nullability is explicitly specified in the types. All of the above also need to interoperate with languages where types remain implicitly nullable, like Java. This leads to runtime errors that can manifest in subtle ways. In this paper, we show how to reason about the presence and provenance of such nullability errors using the concept of blame from gradual typing. Specifically, we introduce a calculus, ?_null, where some terms are typed as implicitly nullable and others as explicitly nullable. Just like in the original blame calculus of Wadler and Findler, interactions between both kinds of terms are mediated by casts with attached blame labels, which indicate the origin of errors. On top of ?_null, we then create a second calculus, ?_null^s, which closely models the interoperability between languages with implicit nullability and languages with explicit nullability, such as Java and Scala. Our main result is a theorem that states that nullability errors in ?_null^s can always be blamed on terms with less-precise typing; that is, terms typed as implicitly nullable. By analogy, this would mean that NullPointerExceptions in combined Java/Scala programs are always the result of unsoundness in the Java type system. We summarize our result with the slogan explicitly nullable programs can\u27t be blamed. All our results are formalized in the Coq proof assistant

Reasoning About Foreign Function Interfaces Without Modelling the Foreign Language

Foreign function interfaces (FFIs) allow programs written in one language (called the host language) to call functions written in another language (called the guest language), and are widespread throughout modern programming languages, with C FFIs being the most prevalent. Unfortunately, reasoning about C FFIs can be very challenging, particularly when using traditional methods which necessitate a full model of the guest language in order to guarantee anything about the whole language. To address this, we propose a framework for defining whole language semantics of FFIs without needing to model the guest language, which makes reasoning about C FFIs feasible. We show that with such a semantics, one can guarantee some form of soundness of the overall language, as well as attribute errors in well-typed host language programs to the guest language. We also present an implementation of this scheme, Poseidon Lua, which shows a speedup over a traditional Lua C FFI

Blame for Null (Artifact)

This artifact is a companion to the paper "Blame for Null", where we formalize multiple calculi to reason about the interoperability between languages where nullability is explicit and those where nullability is implicit. Our main result is a theorem that states that nullability errors can always be blamed on terms with less-precise typing; that is, terms typed as implicitly nullable. We summarize our result with the slogan explicitly nullable programs can\u27t be blamed. The artifact consists of a mechanized Coq proof of the results presented in the paper

Older people as equal partners in creative design

Active older people want to be actively engaged by contributing their experiences to design better services and products. This paper demonstrates the importance of older peoples engagement in the creative design process in a small study where older people were engaged together with designers in the design of digital devices. Three creative workshops were conducted: the first with designers, the second with designers and older people, and the third with older people only. During the illumination stage of the creative process flexibility and flow were measured with topics and turns. Results show that when older people were working with designers more topics and a higher total number of turns were developed than by older people or designers working on their own, which indicates that they had the highest flexibility of ideas and possibly also the greatest flow

Advanced Fluorescence Microscopy Techniques-FRAP, FLIP, FLAP, FRET and FLIM

Fluorescence microscopy provides an efficient and unique approach to study fixed and living cells because of its versatility, specificity, and high sensitivity. Fluorescence microscopes can both detect the fluorescence emitted from labeled molecules in biological samples as images or photometric data from which intensities and emission spectra can be deduced. By exploiting the characteristics of fluorescence, various techniques have been developed that enable the visualization and analysis of complex dynamic events in cells, organelles, and sub-organelle components within the biological specimen. The techniques described here are fluorescence recovery after photobleaching (FRAP), the related fluorescence loss in photobleaching (FLIP), fluorescence localization after photobleaching (FLAP), Forster or fluorescence resonance energy transfer (FRET) and the different ways how to measure FRET, such as acceptor bleaching, sensitized emission, polarization anisotropy, and fluorescence lifetime imaging microscopy (FLIM). First, a brief introduction into the mechanisms underlying fluorescence as a physical phenomenon and fluorescence, confocal, and multiphoton microscopy is given. Subsequently, these advanced microscopy techniques are introduced in more detail, with a description of how these techniques are performed, what needs to be considered, and what practical advantages they can bring to cell biological research

Prototype ATLAS IBL Modules using the FE-I4A Front-End Readout Chip

The ATLAS Collaboration will upgrade its semiconductor pixel tracking detector with a new Insertable B-layer (IBL) between the existing pixel detector and the vacuum pipe of the Large Hadron Collider. The extreme operating conditions at this location have necessitated the development of new radiation hard pixel sensor technologies and a new front-end readout chip, called the FE-I4. Planar pixel sensors and 3D pixel sensors have been investigated to equip this new pixel layer, and prototype modules using the FE-I4A have been fabricated and characterized using 120 GeV pions at the CERN SPS and 4 GeV positrons at DESY, before and after module irradiation. Beam test results are presented, including charge collection efficiency, tracking efficiency and charge sharing.Comment: 45 pages, 30 figures, submitted to JINS

Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector

The inclusive and dijet production cross-sections have been measured for jets containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The measurements use data corresponding to an integrated luminosity of 34 pb^-1. The b-jets are identified using either a lifetime-based method, where secondary decay vertices of b-hadrons in jets are reconstructed using information from the tracking detectors, or a muon-based method where the presence of a muon is used to identify semileptonic decays of b-hadrons inside jets. The inclusive b-jet cross-section is measured as a function of transverse momentum in the range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet cross-section is measured as a function of the dijet invariant mass in the range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets and the angular variable chi in two dijet mass regions. The results are compared with next-to-leading-order QCD predictions. Good agreement is observed between the measured cross-sections and the predictions obtained using POWHEG + Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet cross-section. However, it does not reproduce the measured inclusive cross-section well, particularly for central b-jets with large transverse momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final version published in European Physical Journal

Measurement of the top quark-pair production cross section with ATLAS in pp collisions at \sqrt{s}=7\TeV

A measurement of the production cross-section for top quark pairs(\ttbar) in $pp$ collisions at \sqrt{s}=7 \TeV is presented using data recorded with the ATLAS detector at the Large Hadron Collider. Events are selected in two different topologies: single lepton (electron $e$ or muon $\mu$) with large missing transverse energy and at least four jets, and dilepton ($ee$, $\mu\mu$ or $e\mu$) with large missing transverse energy and at least two jets. In a data sample of 2.9 pb-1, 37 candidate events are observed in the single-lepton topology and 9 events in the dilepton topology. The corresponding expected backgrounds from non-\ttbar Standard Model processes are estimated using data-driven methods and determined to be $12.2 \pm 3.9$ events and $2.5 \pm 0.6$ events, respectively. The kinematic properties of the selected events are consistent with SM \ttbar production. The inclusive top quark pair production cross-section is measured to be \sigmattbar=145 \pm 31 ^{+42}_{-27} pb where the first uncertainty is statistical and the second systematic. The measurement agrees with perturbative QCD calculations.Comment: 30 pages plus author list (50 pages total), 9 figures, 11 tables, CERN-PH number and final journal adde

Inclusive search for same-sign dilepton signatures in pp collisions at root s=7 TeV with the ATLAS detector

An inclusive search is presented for new physics in events with two isolated leptons (e or mu) having the same electric charge. The data are selected from events collected from p p collisions at root s = 7 TeV by the ATLAS detector and correspond to an integrated luminosity of 34 pb(-1). The spectra in dilepton invariant mass, missing transverse momentum and jet multiplicity are presented and compared to Standard Model predictions. In this event sample, no evidence is found for contributions beyond those of the Standard Model. Limits are set on the cross-section in a fiducial region for new sources of same-sign high-mass dilepton events in the ee, e mu and mu mu channels. Four models predicting same-sign dilepton signals are constrained: two descriptions of Majorana neutrinos, a cascade topology similar to supersymmetry or universal extra dimensions, and fourth generation d-type quarks. Assuming a new physics scale of 1 TeV, Majorana neutrinos produced by an effective operator V with masses below 460 GeV are excluded at 95% confidence level. A lower limit of 290 GeV is set at 95% confidence level on the mass of fourth generation d-type quarks