The Algebra of Type Unification

Type unification takes type inference a step further by allowing non-local flow of information. By exposing the algebraic structure of type unification, we obtain even more flexibility as well as clarity in the implementation. In particular, the main contribution is an explicit description of the arithmetic of universe levels and consistency of constraints of universe levels, with hints at how row types and general unification/subsumption can fit into the same framework of constraints. The compositional nature of the algebras involved ensure correctness and reduce arbitrariness: properties such as associativity mean that implementation details of type inference do not leak in error messages, for example. This project is a discovery and implementation of these ideas by extending the type theory of the Dhall programming language, with implementation in PureScript

Particpants' Proceedings on the Workshop: Types for Program Analysis

As a satellite meeting of the TAPSOFT'95 conference we organized a small workshop on program analysis. The title of the workshop, ``Types for Program Analysis´´, was motivated by the recent trend of letting the presentation and development of program analyses be influenced by annotated type systems, effect systems, and more general logical systems. The contents of the workshop was intended to be somewhat broader; consequently the call for participation listed the following areas of interest:- specification of specific analyses for programming languages,- the role of effects, polymorphism, conjunction/disjunction types, dependent types etc.in specification of analyses,- algorithmic tools and methods for solving general classes of type-based analyses,- the role of unification, semi-unification etc. in implementations of analyses,- proof techniques for establishing the safety of analyses,- relationship to other approaches to program analysis, including abstract interpretation and constraint-based methods,- exploitation of analysis results in program optimization and implementation.The submissions were not formally refereed; however each submission was read by several members of the program committee and received detailed comments and suggestions for improvement. We expect that several of the papers, in slightly revised forms, will show up at future conferences. The workshop took place at Aarhus University on May 26 and May 27 and lasted two half days

Refugial pattern of Bromus erectus in central Europe based on ISSR fingerprinting

We studied the thermophilous grass Bromus erectus in Central Europe to determine its pattern of population genetic structure and genetic diversity, using ISSR-PCR fingerprinting to analyze 200 individuals from 37 populations. We found three genetic groups with a clear geographic structure, based on a Bayesian approach. The first group occurred west and south of the Alps, the second east and north of the Alps, and the third was formed by four genetically depauperated populations in Germany. The populations from Germany formed a subset of the Bohemian-Moravian populations, with one private allele. Two differentiation centers, one in the Atlantic-Mediterranean and the second in the Pannonian-Balkan area, were recognized by species distribution modeling. The geographic distribution of the genetic groups coincides with the syntaxonomic split of the Festuco-Brometea class into the Festucetalia valesiaceae and Brometalia erecti orders. We found a statistically significant decrease in mean ISSR bands per individual from south to north, and to a lesser extent from the east to west. The former was explained by Holocene long-distance migrations from southern refugia, the latter by the difference in the gradient of anthropopression. We hypothesize a cryptic northern shelter of the species in Central Europe in the putative Moravian-Bohemian refugium

Genetic diversity among early provitamin A quality protein maize inbred lines and the performance of derived hybrids under contrasting nitrogen environments

Open Access JournalInformation on population structure and genetic diversity of germplasm in a breeding programme is useful because it enhances judicious utilisation of genetic resources to achieve breeding objectives. Seventy early maturing provitamin A (PVA) quality protein maize (QPM) inbreds developed by the IITA- maize improvement programme were genotyped using 8171 DArTseq markers. Furthermore, 96 hybrids derived from 24 selected inbreds plus four checks were evaluated under low-N and optimal environments in Nigeria during 2016 and 2017. Genotypic and phenotypic data of inbreds and hybrids respectively, were analysed to (i) assess the level of genetic dissimilarities and population structure of the inbreds, and (ii) investigate the grain yield performance of derived hybrids under low-N, optimal and across environments

Modular Probabilistic Models via Algebraic Effects

Probabilistic programming languages (PPLs) allow programmers to construct statistical models and then simulate data or perform inference over them. Many PPLs restrict models to a particular instance of simulation or inference, limiting their reusability. In other PPLs, models are not readily composable. Using Haskell as the host language, we present an embedded domain specific language based on algebraic effects, where probabilistic models are modular, first-class, and reusable for both simulation and inference. We also demonstrate how simulation and inference can be expressed naturally as composable program transformations using algebraic effect handlers

Genetic Relationships Among Populations of Aedes Aegypti in Taiwan by Using Phenotypic and Random Amplified DNA-Polymerase Chain Reaction Markers

Volume: 1

Using Botnet Technologies to Counteract Network Traffic Analysis

Botnets have been problematic for over a decade. They are used to launch malicious activities including DDoS (Distributed-Denial-of-Service), spamming, identity theft, unauthorized bitcoin mining and malware distribution. A recent nation-wide DDoS attacks caused by the Mirai botnet on 10/21/2016 involving 10s of millions of IP addresses took down Twitter, Spotify, Reddit, The New York Times, Pinterest, PayPal and other major websites. In response to take-down campaigns by security personnel, botmasters have developed technologies to evade detection. The most widely used evasion technique is DNS fast-flux, where the botmaster frequently changes the mapping between domain names and IP addresses of the C&C server so that it will be too late or too costly to trace the C&C server locations. Domain names generated with Domain Generation Algorithms (DGAs) are used as the \u27rendezvous\u27 points between botmasters and bots. This work focuses on how to apply botnet technologies (fast-flux and DGA) to counteract network traffic analysis, therefore protecting user privacy. A better understanding of botnet technologies also helps us be pro-active in defending against botnets. First, we proposed two new DGAs using hidden Markov models (HMMs) and Probabilistic Context-Free Grammars (PCFGs) which can evade current detection methods and systems. Also, we developed two HMM-based DGA detection methods that can detect the botnet DGA-generated domain names with/without training sets. This helps security personnel understand the botnet phenomenon and develop pro-active tools to detect botnets. Second, we developed a distributed proxy system using fast-flux to evade national censorship and surveillance. The goal is to help journalists, human right advocates and NGOs in West Africa to have a secure and free Internet. Then we developed a covert data transport protocol to transform arbitrary message into real DNS traffic. We encode the message into benign-looking domain names generated by an HMM, which represents the statistical features of legitimate domain names. This can be used to evade Deep Packet Inspection (DPI) and protect user privacy in a two-way communication. Both applications serve as examples of applying botnet technologies to legitimate use. Finally, we proposed a new protocol obfuscation technique by transforming arbitrary network protocol into another (Network Time Protocol and a video game protocol of Minecraft as examples) in terms of packet syntax and side-channel features (inter-packet delay and packet size). This research uses botnet technologies to help normal users have secure and private communications over the Internet. From our botnet research, we conclude that network traffic is a malleable and artificial construct. Although existing patterns are easy to detect and characterize, they are also subject to modification and mimicry. This means that we can construct transducers to make any communication pattern look like any other communication pattern. This is neither bad nor good for security. It is a fact that we need to accept and use as best we can

Risk of gene introgression from transgenic wheat to jointed goatgrass

Department Head: Gary Peterson.2010 Summer.Includes bibliographical references (pages 95-97).To view the abstract, please see the full text of the document