Expansion properties of a random regular graph after random vertex deletions

We investigate the following vertex percolation process. Starting with a random regular graph of constant degree, delete each vertex independently with probability p, where p=n^{-alpha} and alpha=alpha(n) is bounded away from 0. We show that a.a.s. the resulting graph has a connected component of size n-o(n) which is an expander, and all other components are trees of bounded size. Sharper results are obtained with extra conditions on alpha. These results have an application to the cost of repairing a certain peer-to-peer network after random failures of nodes.Comment: 14 page

Microheater Array Powder Sintering (MAPS) for Printing Flexible Electronics

Microheater array powder sintering (MAPS) is a novel additive manufacturing process that uses an array of microheaters to selectively sinter powder particles. MAPS shows great promise as a new method of printing flexible electronics by enabling digital curing of conductive inks on a variety of substrates. MAPS operation relies on establishing a precision air gap of a few microns between an array of microheaters, which can reach temperatures of 600°C, and a layer of conductive ink which can be deposited onto a flexible substrate. This system presents challenges, being: the fabrication of a microheater that can reach suitable temperatures in an acceptable time frame and is reliable, electronic control of a single microheater, electronic control of an array of microheaters, and precise control of the position of the array of microheaters relative to the substrate. This work describes the design and fabrication of a printer which uses this novel technology to print flexible circuit boards. Various simulations are discussed which are used to explore the parameters affecting the MAPS printing process. Then, a small microheater array is fabricated and controlled using an electronic circuit using a PID feedback loop. This microheater array is used in an experimental proof of concept machine to print conductive lines onto a flexible substrate. Finally, a prototype MAPS printer is developed which is capable of using an improved microheater array to print simple circuits onto flexible substrates

Mechanisms responsible for the development of causal perception in infancy.

The aim of the current dissertation was to investigate the mechanisms that contribute to the emergence of causal perception in infancy. Previous research suggests that the experience of self-produced causal action may be necessary to promote the development of causal perception (Rakison & Krogh, 2012). The goal of the current study was two-fold: (1) to further explore the roles of self-produced action, haptic, proprioceptive and visual information, and parental interaction on young infants’ understanding of causality. To assess the impact of these factors on infants’ causal learning, 4½-month-olds were randomly assigned to one four conditions. Three of the conditions (Active with Parent Interaction, Active Without Parent Interaction, and Passive with Parent Interaction) provided infants with object-manipulation training in which infants wore “sticky mittens” that allowed them to manipulate Velcro-covered toys. The fourth condition was a no-training control condition. Following training, infants’ ability to perceive the difference between causal and non-causal versions of simple collision events (one ball colliding with another) was tested. It was hypothesized that both of the active training conditions would facilitate infants’ causal perception, while passive training would produce no effects relative to the control condition. Results demonstrated that 4½-month-old infants who received no training, and same-aged infants who received passive training that controlled for perceptual aspects of self-produced causal action experience (haptic, proprioceptive, and visual information), did not show evidence of causal perception. As hypothesized, active training experience facilitated causal perception in 4½-month-olds. However, surprisingly, active training only facilitated learning in the condition in which parents were instructed not to interact with their infants. Comparisons of the two active training groups (with and without parent interaction) revealed that the groups did not differ on a number of infant characteristics and behaviors. The results of this study suggest: (1) self-produced causal actions constitute a mechanism by which causal perception arises in infancy, and (2) parental interactions during infants’ object explorations may interfere with learning

Viral Ecology and the Maintenance of Novel Host Use

Viruses can occasionally emerge by infecting new host species. However, the early phases of emergence can hinge upon ecological sustainability of the virus population, which is a product of both within‐host population growth and between‐host transmission. Insufficient growth or transmission can force virus extinction before the latter phases of emergence, where genetic adaptations that improve host use may occur. We examined the early phase of emergence by studying the population dynamics of RNA phages in replicated laboratory environments containing native and novel host bacteria. To predict the breadth of transmission rates allowing viral persistence on each species, we developed a simple model based on in vitro data for phage growth rate over a range of initial population densities on both hosts. Validation of these predictions using serial passage experiments revealed a range of transmission rates for which the native host was a source and the novel host was a sink. In this critical range of transmission rates, periodic exposure to the native host was sufficient for the maintenance of the viral population on the novel host. We argue that this effect should facilitate adaptation by the virus to utilize the novel host—often crucial in subsequent phases of emergence

DO YOUTH LEARN LIFE SKILLS THROUGH THEIR INVOLVEMENT IN HIGH SCHOOL SPORT? A CASE STUDY

In this study we examined whether and how youth learned life skills through their involvement on a high school soccer team. We collected data from fieldwork and interviews with 12 male student‐athletes and the head coach from one team. Results showed that the coach’s philosophy involved building relationships and involving student‐athletes in decision making. Issues relating to three life skills (initiative, re‐ spect, and teamwork/leadership) were identified. Although we observed little direct teaching of these life skills, we saw that players generally were producers of their own experiences that supported the development of these skills. Key words: ecological systems, positive development Les auteurs ont cherché à savoir si et comment les jeunes acquièrent certaines compétences de la vie courante en étant membres d’une équipe de soccer au secondaire. Les chercheurs ont colligé des données sur le terrain et interviewé 12 élèves‐athlètes de sexe masculin ainsi que l’entraîneur principal d’une équipe. Les résultats indiquent que l’entraîneur avait pour philosophie de favoriser l’établissement de relations et d’impliquer les élèves‐athlètes dans les prises de décision. Des problèmes reliés à trois compétences de la vie courante (l’initiative, le respect et l’esprit d’équipe/le leadership) ont été identifiés. Bien que les auteurs aient observé que ces compétences sont peu enseignées comme telles, ils ont constaté que observé que ces compétences sont peu enseignées comme telles, ils ont constaté que les joueurs étaient les producteurs de leurs propres expériences, qui favorisaient effectivement le développement de ces compétences.Mots clés : systèmes écologiques, développement positif

MalDICT: Benchmark Datasets on Malware Behaviors, Platforms, Exploitation, and Packers

Existing research on malware classification focuses almost exclusively on two tasks: distinguishing between malicious and benign files and classifying malware by family. However, malware can be categorized according to many other types of attributes, and the ability to identify these attributes in newly-emerging malware using machine learning could provide significant value to analysts. In particular, we have identified four tasks which are under-represented in prior work: classification by behaviors that malware exhibit, platforms that malware run on, vulnerabilities that malware exploit, and packers that malware are packed with. To obtain labels for training and evaluating ML classifiers on these tasks, we created an antivirus (AV) tagging tool called ClarAVy. ClarAVy's sophisticated AV label parser distinguishes itself from prior AV-based taggers, with the ability to accurately parse 882 different AV label formats used by 90 different AV products. We are releasing benchmark datasets for each of these four classification tasks, tagged using ClarAVy and comprising nearly 5.5 million malicious files in total. Our malware behavior dataset includes 75 distinct tags - nearly 7x more than the only prior benchmark dataset with behavioral tags. To our knowledge, we are the first to release datasets with malware platform and packer tags

Short-term effects of hardened wood ash and nitrogen fertilisation on understory vegetation in a Norway spruce forest in south-east Norway

In a fertiliser experiment in a Norway spruce forest in SE Norway, four treatments were applied in a block design with three replicates per treatment. Treatments included 3 t wood ash ha−1 (Ash), 150 kg nitrogen ha−1 (N), wood ash and nitrogen combined (Ash + N), and unfertilised control (Ctrl). Treatment effects on understory plant species numbers, single abundances of species and (summarised) cover of main species groups were studied. Two years after treatment there were no significant changes for species numbers or abundances of woody species, dwarf shrubs or pteridophytes, nor for Sphagnum spp. in the bottom layer. The cover of graminoids decreased in Ctrl plots. Herb cover increased significantly in Ash + N and N plots due to the increase of Melampyrum sylvaticum. In Ash + N plots, mosses decreased significantly in species number, while their cover increased. Moss cover also decreased significantly in N plots. The species number and cover of hepatics decreased significantly in Ash and Ash + N plots. Hepatics cover also decreased in Ctrl plots. Both the lichen number and cover decreased in Ash + N plots. Single species abundances decreased for many bryophytes in fertilised plots. To conclude, fertilisation had modest effects on vascular plants, while bryophytes were more strongly affected, especially by Ash + N.acceptedVersio

Selective resistive sintering--a new additive manufacturing method

A system and method for selective heating and/or sintering of a material including first and second substrates, an array of one or more resistive heating elements arranged on a planar surface of a substrate and material to be heated located on the other substrate