Beating the Productivity Checker Using Embedded Languages

Some total languages, like Agda and Coq, allow the use of guarded corecursion to construct infinite values and proofs. Guarded corecursion is a form of recursion in which arbitrary recursive calls are allowed, as long as they are guarded by a coinductive constructor. Guardedness ensures that programs are productive, i.e. that every finite prefix of an infinite value can be computed in finite time. However, many productive programs are not guarded, and it can be nontrivial to put them in guarded form. This paper gives a method for turning a productive program into a guarded program. The method amounts to defining a problem-specific language as a data type, writing the program in the problem-specific language, and writing a guarded interpreter for this language.Comment: In Proceedings PAR 2010, arXiv:1012.455

Development of Protocols for Metabolomics in Biomedical Research using Chemometrics

Metabolomics is a rapidly growing research field. It aims for quantification of all the metabolites in a biological sample such as plasma, saliva, cerebrospinal fluid or cells. Because the metabolite levels in a biological sample are the end result of the regulatory processes in cells, metabolomics is a very powerful approach for characterisation of phenotypes. Metabolomics has been used to find disease biomarkers, investigate influences of heavy metals on the metabolism and to elucidate gene function. However, analysis of the complete metabolome puts high demands on the methods used. For instance, the methods should be unbiased to accurately depict the in vivo status in the cell. Furthermore, the methods must have very high resolution and sensitivity to allow detection of all metabolites. To approach these high goals, the protocols used in metabolomics need to be thoroughly optimised. The amount of information contained in the metabolome is immense. Consequently, the data set collected from a metabolomics study is very large. To extract the relevant information from such large sets of data, efficient methods are needed both to plan experiments and to convert the data to useful information. For this task, chemometrics is an ideal approach as it allows efficient experimental planning and multivariate data analysis. The experimental planning is sometimes referred to as statistical experimental design or design of experiments. It aims to systematically and simultaneously vary experimental factors in a structured manner. Hence, fewer experiments are generally needed to efficiently map how the system is affected by prevailing factors. The multivariate data analysis employs powerful projection and regression methods to find patterns in data, create system models and classify data. Hence, chemometrics provides a framework for efficient experimental design and an efficient approach for information retrieval. In this thesis two thorough developments of metabolomics protocols and three metabolomics investigations, relevant to metabolic regulation in diabetes patients and insulin-producing cells, are presented. The design of experiments approach and multivariate data analysis were applied. The developed protocols were optimised and validated for the analysis of human blood plasma and adherent cell cultures, respectively, and included optimisation from the sample preparation to the analysis with gas chromatography/mass spectrometry. The first of the metabolomics studies aimed to find biomarkers reflecting metabolic regulation during an oral glucose tolerance test in humans to aid in the diagnosis of diabetes. The second study was performed on clonal β-cells and aimed to find metabolic regulation coupled to the amplifying pathway of insulin secretion. The last study aimed to identify metabolic dysregulation in clonal β-cells growing under lipotoxic and glucotoxic conditions, respectively. In all studies, metabolomics extended and deepened the understanding of metabolic regulation in cells and patients. As such, metabolomics will help to find explanations for metabolic diseases such as diabete

Interest and Recruitment in Science: A Reform, Gender and Experience Perspective

AbstractThis paper reports on Swedish results from a worldwide research project concerned with the Interest and Recruitment in Science Education (the IRIS-International study) together with results from a longitudinal national study on girl's views on out of school experience in science and technology in upper secondary education. The studies are framed in the structural situation of the Swedish educational system. The results show that there are reform and policy effects to consider in the discussion of recruiting more students in STEM. Interest in the subject, earlier school experience, achievement and teacher feedback is found to be important for educational choice in STEM. Specifically girls point out societal relevance as important. In addition there are elements outside the school setting with importance for educational choice. Moreover, girls point out visits to a museum and watching films and boys popularized forms of science and computer games. All students consider TV and activities outside school as important for their educational choice in STEM. When trying to implement outside school experience with girls in a longitudinal study in upper secondary education the interplay with school subject teaching is identified as missing. The friction between subject teaching in schools and connections with the surrounding world is proposed as important for future studies

Practical dependent type checking using twin types

People writing proofs or programs in dependently typed languages can omit some function arguments in order to decrease the code size and improve readability. Type checking such a program involves filling in each of these implicit arguments in a type-correct way. This is typically done using some form of unification.One approach to unification, taken by Agda, involves sometimes starting to unify terms before their types are known to be equal: in some cases one can make progress on unifying the terms, and then use information gleaned in this way to unify the types. This flexibility allows Agda to solve implicit arguments that are not found by several other systems. However, Agda\u27s implementation is buggy: sometimes the solutions chosen are ill-typed, which can cause the type checker to crash.With Gundry and McBride\u27s twin variable technique one can also start to unify terms before their types are known to be equal, and furthermore this technique is accompanied by correctness proofs. However, so far this technique has not been tested in practice as part of a full type checker.We have reformulated Gundry and McBride\u27s technique without twin variables, using only twin types, with the aim of making the technique easier to implement in existing type checkers (in particular Agda). We have also introduced a type-agnostic syntactic equality rule that seems to be useful in practice. The reformulated technique has been tested in a type checker for a tiny variant of Agda. This type checker handles at least one example that Coq, Idris, Lean and Matita cannot handle, and does so in time and space comparable to that used by Agda. This suggests that the reformulated technique is usable in practice

Bostadsområdet Västra Eriksberg - byggnader och långsiktigt hållbar värmeproduktion

Syftet med denna rapport är att, utifrån miljö och kostnader, hitta det mest lämpliga värmeproduktionssystemet för bostadsområdet Västra Eriksberg i Göteborg samt att studera skillnader mellan två hustyper. Uppdragsgivare är Norra Älvstranden Utveckling AB.Hustyperna skiljer sig åt när det gäller material- och energibehov. Den ena hustypen är mer välisolerad samt har ett mer avancerat ventilationssystem, vilket medför att denna hustyp inte är i behov av ett radiatorsystem. Totalkostnaden för byggnationen är lika stor för de två hustyperna. Miljöpåverkan från husens driftfas är större än från dess byggfas, vilket medför att den mer energisnåla hustypen är bättre för miljön.Tre värmeproduktionssystem studeras: fjärrvärme, pelletsförbränning och värmepumpar. De två sistnämnda kompletteras med naturgasförbränning vid större värmebehov. Beroende på vilka bedömningsgrunder och villkor man har som utgångspunkt varierar det vilket system som är lämpligast för Västra Eriksberg. Billigast är ett pelletssystem och dyrast är ett värmepumpsystem. För den lokala miljön är ett värmepumpsystem den bästa lösningen medan ett pelletssystem är den sämsta. Beroende på hur driftelen till värmepumparna produceras har detta system antingen minst eller störst total miljöpåverkan. Fjärrvärme kan ses som ett medelalternativ, både när det gäller kostnader och miljöpåverkan

Anisotropic intrinsic lattice thermal conductivity of phosphorene from first principles

Phosphorene, the single layer counterpart of black phosphorus, is a novel two-dimensional semiconductor with high carrier mobility and a large fundamental direct band gap, which has attracted tremendous interest recently. Its potential applications in nano-electronics and thermoelectrics call for a fundamental study of the phonon transport. Here, we calculate the intrinsic lattice thermal conductivity of phosphorene by solving the phonon Boltzmann transport equation (BTE) based on first-principles calculations. The thermal conductivity of phosphorene at $300\,\mathrm{K}$ is $30.15\,\mathrm{Wm^{-1}K^{-1}}$ (zigzag) and $13.65\,\mathrm{Wm^{-1}K^{-1}}$ (armchair), showing an obvious anisotropy along different directions. The calculated thermal conductivity fits perfectly to the inverse relation with temperature when the temperature is higher than Debye temperature ($\Theta_D = 278.66\,\mathrm{K}$). In comparison to graphene, the minor contribution around $5\%$ of the ZA mode is responsible for the low thermal conductivity of phosphorene. In addition, the representative mean free path (MFP), a critical size for phonon transport, is also obtained.Comment: 5 pages and 6 figures, Supplemental Material available as http://www.rsc.org/suppdata/cp/c4/c4cp04858j/c4cp04858j1.pd

Young Peoples’ Online Science Practices as a Gateway to Higher Education STEM

The purpose of this manuscript is to explore how students perceive that online practices have enabled their participation in university physics programmes. In order to conceptualise how students bridge their science participation across physical and online spaces, we make use of the learning ecology perspective. This perspective is complemented with the notion of science capital, analysing how students have been able to strengthen different aspects of science capital through online participation. Data has been generated through semi-structured interviews guided by a timeline, constructed in collaboration between the interviewer and the interviewee. Twenty-one students enrolled in higher education physics have been interviewed, with a focus on their trajectories into higher education physics. The findings focus on four students who in various ways all have struggled to access science learning resources and found ways to utilise online spaces as a complement to their physical learning ecologies. In the manuscript, we show how online practices have contributed to the students’ learning ecologies, e.g. in terms of building networks and functioning as learning support, and how resources acquired through online science practices have both use and exchange value in the wider science community. Online science participation is thus both curiosity driven and founded in instrumental reasons (using online tutoring to pass school science). Furthermore, we argue that online spaces have the potential to offer opportunities for participation and network building for students who do not have access to science activities and science people in their everyday surroundings.The purpose of this manuscript is to explore how students perceive that online practices have enabled their participation in university physics programmes. In order to conceptualise how students bridge their science participation across physical and online spaces, we make use of the learning ecology perspective. This perspective is complemented with the notion of science capital, analysing how students have been able to strengthen different aspects of science capital through online participation. Data has been generated through semi-structured interviews guided by a timeline, constructed in collaboration between the interviewer and the interviewee. Twenty-one students enrolled in higher education physics have been interviewed, with a focus on their trajectories into higher education physics. The findings focus on four students who in various ways all have struggled to access science learning resources and found ways to utilise online spaces as a complement to their physical learning ecologies. In the manuscript, we show how online practices have contributed to the students’ learning ecologies, e.g. in terms of building networks and functioning as learning support, and how resources acquired through online science practices have both use and exchange value in the wider science community. Online science participation is thus both curiosity driven and founded in instrumental reasons (using online tutoring to pass school science). Furthermore, we argue that online spaces have the potential to offer opportunities for participation and network building for students who do not have access to science activities and science people in their everyday surroundings

Comparing Employment Trajectories before and after First Imprisonment in Four Nordic Countries

Employment plays a crucial role in the re-entry process and in reducing recidivism among offenders released from prison. But at the same time, imprisonment is generally regarded as harmful to post-release employment prospects. Little is known, however, about whether or not offenders’ employment trajectories before and after imprisonment are similar across countries. As a first step towards filling this gap in research, this paper provides evidence on employment trajectories before and after imprisonment in four Nordic welfare states: Denmark, Finland, Norway and Sweden. Using data gathered from administrative records on incarcerated offenders, the analysis focuses on individuals imprisoned for the first time and who served a prison sentence less than one year in length. Results show that although employment trajectories develop in mostly similar ways before and after imprisonment across these countries, important differences exist.Peer reviewe