Augmenting graphs to minimize the diameter

We study the problem of augmenting a weighted graph by inserting edges of bounded total cost while minimizing the diameter of the augmented graph. Our main result is an FPT 4-approximation algorithm for the problem.Comment: 15 pages, 3 figure

Cache-Oblivious Persistence

Partial persistence is a general transformation that takes a data structure and allows queries to be executed on any past state of the structure. The cache-oblivious model is the leading model of a modern multi-level memory hierarchy.We present the first general transformation for making cache-oblivious model data structures partially persistent

Is there a social gradient of sarcopenia? A meta-analysis and systematic review protocol

Introduction: Sarcopenia (or loss of muscle mass and function) is a relatively new area within the field of musculoskeletal research and medicine. Investigating whether there is a social gradient, including occupation type and income level, of sarcopenia, as observed for other diseases, will contribute significantly to the limited evidence base for this disease. This new information may inform the prevention and management of sarcopenia and widen the evidence base to support existing and future health campaigns. Methods and analysis: We will conduct a systematic search of the databases PubMed, Ovid, CINAHL, Scopus and EMBASE to identify articles that investigate associations between social determinants of health and sarcopenia in adults aged 50 years and older. Eligibility of the selected studies will be determined by two independent reviewers. The methodological quality of eligible studies will be assessed according to predetermined criteria. Established statistical methods to identify and control for heterogeneity will be used, and where appropriate, we will conduct a meta-analysis. In the event that heterogeneity prevents numerical synthesis, a best evidence analysis will be employed. This systematic review protocol adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols reporting guidelines and will be registered with the International Prospective Register of Systematic Reviews (PROSPERO). Ethics and dissemination: This systematic review will use published data, thus ethical permissions will not be required. In addition to peer-reviewed publication, our results will be presented at (inter)national conferences relevant to the field of sarcopenia, ageing and/or musculoskeletal health and disseminated both electronically and in print. PROSPERO registration number: CRD4201707225

Fast Locality-Sensitive Hashing Frameworks for Approximate Near Neighbor Search

The Indyk-Motwani Locality-Sensitive Hashing (LSH) framework (STOC 1998) is a general technique for constructing a data structure to answer approximate near neighbor queries by using a distribution $\mathcal{H}$ over locality-sensitive hash functions that partition space. For a collection of $n$ points, after preprocessing, the query time is dominated by $O(n^{\rho} \log n)$ evaluations of hash functions from $\mathcal{H}$ and $O(n^{\rho})$ hash table lookups and distance computations where $\rho \in (0,1)$ is determined by the locality-sensitivity properties of $\mathcal{H}$. It follows from a recent result by Dahlgaard et al. (FOCS 2017) that the number of locality-sensitive hash functions can be reduced to $O(\log^2 n)$, leaving the query time to be dominated by $O(n^{\rho})$ distance computations and $O(n^{\rho} \log n)$ additional word-RAM operations. We state this result as a general framework and provide a simpler analysis showing that the number of lookups and distance computations closely match the Indyk-Motwani framework, making it a viable replacement in practice. Using ideas from another locality-sensitive hashing framework by Andoni and Indyk (SODA 2006) we are able to reduce the number of additional word-RAM operations to $O(n^\rho)$.Comment: 15 pages, 3 figure

Bringing Order to Special Cases of Klee's Measure Problem

Klee's Measure Problem (KMP) asks for the volume of the union of n axis-aligned boxes in d-space. Omitting logarithmic factors, the best algorithm has runtime O*(n^{d/2}) [Overmars,Yap'91]. There are faster algorithms known for several special cases: Cube-KMP (where all boxes are cubes), Unitcube-KMP (where all boxes are cubes of equal side length), Hypervolume (where all boxes share a vertex), and k-Grounded (where the projection onto the first k dimensions is a Hypervolume instance). In this paper we bring some order to these special cases by providing reductions among them. In addition to the trivial inclusions, we establish Hypervolume as the easiest of these special cases, and show that the runtimes of Unitcube-KMP and Cube-KMP are polynomially related. More importantly, we show that any algorithm for one of the special cases with runtime T(n,d) implies an algorithm for the general case with runtime T(n,2d), yielding the first non-trivial relation between KMP and its special cases. This allows to transfer W[1]-hardness of KMP to all special cases, proving that no n^{o(d)} algorithm exists for any of the special cases under reasonable complexity theoretic assumptions. Furthermore, assuming that there is no improved algorithm for the general case of KMP (no algorithm with runtime O(n^{d/2 - eps})) this reduction shows that there is no algorithm with runtime O(n^{floor(d/2)/2 - eps}) for any of the special cases. Under the same assumption we show a tight lower bound for a recent algorithm for 2-Grounded [Yildiz,Suri'12].Comment: 17 page

Dynamic Set Intersection

Consider the problem of maintaining a family $F$ of dynamic sets subject to insertions, deletions, and set-intersection reporting queries: given $S,S'\in F$, report every member of $S\cap S'$ in any order. We show that in the word RAM model, where $w$ is the word size, given a cap $d$ on the maximum size of any set, we can support set intersection queries in $O(\frac{d}{w/\log^2 w})$ expected time, and updates in $O(\log w)$ expected time. Using this algorithm we can list all $t$ triangles of a graph $G=(V,E)$ in $O(m+\frac{m\alpha}{w/\log^2 w} +t)$ expected time, where $m=|E|$ and $\alpha$ is the arboricity of $G$. This improves a 30-year old triangle enumeration algorithm of Chiba and Nishizeki running in $O(m \alpha)$ time. We provide an incremental data structure on $F$ that supports intersection {\em witness} queries, where we only need to find {\em one} $e\in S\cap S'$. Both queries and insertions take O\paren{\sqrt \frac{N}{w/\log^2 w}} expected time, where $N=\sum_{S\in F} |S|$. Finally, we provide time/space tradeoffs for the fully dynamic set intersection reporting problem. Using $M$ words of space, each update costs $O(\sqrt {M \log N})$ expected time, each reporting query costs $O(\frac{N\sqrt{\log N}}{\sqrt M}\sqrt{op+1})$ expected time where $op$ is the size of the output, and each witness query costs $O(\frac{N\sqrt{\log N}}{\sqrt M} + \log N)$ expected time.Comment: Accepted to WADS 201

O letramento e o ensino de literatura mediados por jogos digitais educacionais

A partir da dificuldade nacompreensão de textos literáriosque alunos do ensino médio apresentam, geralmente associada a pouca valoração da leitura, desenvolveu-se uma pesquisa que explora o jogo digital como motivador do interesse pela leitura de obras pertencentes ao sistema literário brasileiro, bem como no desenvolvimento do letramento deste aluno. A pesquisa apresenta resultados ainda preliminares e dá-se por meio de revisão bibliográfica, análises quanti/qualitativas, a formação de grupos de estudo com alunos de nível médio em instituições de ensino técnico e tecnológico e a criação de um fórum de discussão disponibilizado em uma importante rede social. O emprego do jogo a ser desenvolvido apoia-se nos conceitos de aprendizagem significativa, em estudos sobre a formação social da mente, bem como no conceito de zona de desenvolvimento proximal. Os sistemas de regras, a jogabilidade e a dimensão estética do jogo serão os diferenciais abordados como elementos motivacionais do aluno/leitor.XI Workshop tecnología informática aplicada en educaciónRed de Universidades con Carreras en Informática (RedUNCI

Ist ein bisschen Deradikalisierung besser als keine? Zur Ausstiegsarbeit mit Rückkehrerinnen und Rückkehrern aus dschihadistischen Gruppen in Deutschland

Zwischen 2013 und 2019 verließen mehr als 1.000 zumeist junge Menschen Deutschland, um sich in Syrien und dem Irak dschihadistischen Gruppen anzuschließen. Die bekannteste von ihnen ist der sogenannte "Islamische Staat", auf dessen Konto in den Jahren 2015 und 2016 auch mehrere Anschläge in Europa gingen. An diesen Terrorakten beteiligten sich zurückgekehrte europäische Dschihadisten. Inzwischen gilt der "Islamische Staat" zwar als weitgehend besiegt und ein knappes Drittel der nach Syrien und Irak Ausgereisten ist wieder zurück in Deutschland. Doch nicht alle dieser Rückkehrerinnen und Rückkehrer sind desillusioniert. Einige hängen nach wie vor islamistischen Ideologien an, fast alle sind zudem traumatisiert. Ein nicht unerheblicher Teil befindet sich in Haft. Es stellt sich die Frage, wie der Sicherheitsbedrohung, die von diesen Rückkehrerinnen und Rückkehrern ausgeht, zu begegnen ist. Deutschland beschreitet dabei unter anderem den Weg der Resozialisierung: Ausstiegs- und Reintegrationsmaßnahmen sollen diesen Personen den Weg zurück in die Gesellschaft ermöglichen. Durchgeführt werden solche Maßnahmen sowohl von staatlichen Programmen, als auch von zivilgesellschaftlichen Trägern. Dieses BICC Working Paper untersucht, wie Fachkräfte solcher Träger dieser Aufgabe nachkommen und welchen Hindernissen sie dabei begegnen. Um dies zu erläutern, stellt das Paper den gesamten Komplex von der Rückreise ehemaliger Dschihadistinnen und Dschihadisten aus dem Konfliktgebiet, über ihre psychische und soziale Wiedereingliederung nach der Ankunft in Deutschland bis zum Abschluss des Ausstiegsprozesses dar und untersucht die Herausforderungen, die sich dabei für soziale Arbeit und Prävention ergeben. Hierzu gehören besondere Aspekte der Fallarbeit wie der Umgang mit Traumatisierungen, die Bedarfe minderjähriger Rückkehrerinnen und Rückkehrer, die Arbeit in Haftanstalten sowie die Aufarbeitung extremistischer Ideologien. Die Untersuchung zeigt, dass Fachkräfte sich ihrer Aufgabe zwar professionell gewachsen sehen, jedoch einigen strukturellen Herausforderungen gegenüberstehen. Diese umfassen etwa zeitlich und finanziell begrenzte Projektförderungen, einen Mangel an therapeutischen Kapazitäten sowie Abstimmungsprobleme mit den Justizbehörden bei der Arbeit mit inhaftierten Rückkehrerinnen und Rückkehrern

Children and young people living through a serious family illness: structural, interpersonal and personal perspectives

This study explores the experiences of children and young people in Britain living through a serious family illness. The study considers the interplay between social structures, social relationships and individual agency. We draw on data from the Millennium Cohort Study to estimate the number of children and young people affected nationally and on seven in-depth interviews to understand young people’s experiences and the effects on their daily lives. Living through a serious family illness impacts on young people’s educational achievements, mental health and social relationships over long periods. Policy and service responses are suggested

Measuring and forecasting progress in education: what about early childhood?

A recent Nature article modelled within-country inequalities in primary, secondary, and tertiary education and forecast progress towards Sustainable Development Goal (SDG) targets related to education (SDG 4). However, their paper entirely overlooks inequalities in achieving Target 4.2, which aims to achieve universal access to quality early childhood development, care and preschool education by 2030. This is an important omission because of the substantial brain, cognitive and socioemotional developments that occur in early life and because of increasing evidence of early-life learning's large impacts on subsequent education and lifetime wellbeing. We provide an overview of this evidence and use new analyses to illustrate medium- and long-term implications of early learning, first by presenting associations between pre-primary programme participation and adolescent mathematics and science test scores in 73 countries and secondly, by estimating the costs of inaction (not making pre-primary programmes universal) in terms of forgone lifetime earnings in 134 countries. We find considerable losses, comparable to or greater than current governmental expenditures on all education (as percentages of GDP), particularly in low- and lower-middle-income countries. In addition to improving primary, secondary and tertiary schooling, we conclude that to attain SDG 4 and reduce inequalities in a post-COVID era, it is essential to prioritize quality early childhood care and education, including adopting policies that support families to promote early learning and their children's education