Matching Subsequences in Trees

Given two rooted, labeled trees $P$ and $T$ the tree path subsequence problem is to determine which paths in $P$ are subsequences of which paths in $T$. Here a path begins at the root and ends at a leaf. In this paper we propose this problem as a useful query primitive for XML data, and provide new algorithms improving the previously best known time and space bounds.Comment: Minor correction of typos, et

TimeMachine: Timeline Generation for Knowledge-Base Entities

We present a method called TIMEMACHINE to generate a timeline of events and relations for entities in a knowledge base. For example for an actor, such a timeline should show the most important professional and personal milestones and relationships such as works, awards, collaborations, and family relationships. We develop three orthogonal timeline quality criteria that an ideal timeline should satisfy: (1) it shows events that are relevant to the entity; (2) it shows events that are temporally diverse, so they distribute along the time axis, avoiding visual crowding and allowing for easy user interaction, such as zooming in and out; and (3) it shows events that are content diverse, so they contain many different types of events (e.g., for an actor, it should show movies and marriages and awards, not just movies). We present an algorithm to generate such timelines for a given time period and screen size, based on submodular optimization and web-co-occurrence statistics with provable performance guarantees. A series of user studies using Mechanical Turk shows that all three quality criteria are crucial to produce quality timelines and that our algorithm significantly outperforms various baseline and state-of-the-art methods.Comment: To appear at ACM SIGKDD KDD'15. 12pp, 7 fig. With appendix. Demo and other info available at http://cs.stanford.edu/~althoff/timemachine

Uso de acidólisis por fosfolipasa A1 inmovilizada para la producción de fosfatidilcolina estructurada con elevado contenido de ácido linoleico conjugado

Structured phosphatidylcholine (SPC) was successfully produced via immobilized phospholipase A1 (PLA1) – catalyzed acidolysis of phosphatidylcholine (PC) with conjugated linoleic acid (CLA). The effects of enzyme loading (2, 5, 10, 15 and 20%, with respect to the weight of substrates), temperature (20, 30, 40, 50 and 60 °C) and the molar ratio of substrates (1:2, 1:4, 1:6, 1:8 and 1:10, PC/CLA) were evaluated to maximize the incorporation of CLA into PC. The maximum incorporation of CLA achieved was ca. 90% for 24 h of reaction at 50 °C and 200 rpm, using a 1:4 substrate molar ratio and an enzyme loading of 15%.Fosfatidilcolina estructurada (SPC) fue producida por acidólisis de fosfatidilcolina (PC) y ácido linoleico conjugado (CLA) usando fosfolipasa A1 (PLA1) inmovilizada. Los efectos de carga de enzima (2, 5, 10, 15 y 20%, respecto al peso de los sustratos), temperatura (20, 30, 40, 50 y 60 °C) y la relación molar de sustratos (1:2, 1:4, 1:6, 1:8 y 1:10, PC/CLA) fueron evaluados para alcanzar la más elevada incorporación de CLA en PC. La máxima incorporación de CLA obtenida fue de 90% a 50 °C y 200 rpm, para una relación molar 1:4 con una carga de enzima de 15% después de 24 h

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

Psychometric properties of the Disordered Eating Attitude Scale for adult men

OBJECTIVE: To evaluate psychometric properties of the Disordered Eating Attitude Scale (DEAS) for men. METHODS: Two hundred and twenty-eight undergraduate male students (18-39 years old) answered the DEAS, originally developed and validated for women. Internal consistency was evaluated by Cronbach's Alpha; convergent validity by comparing DEAS and the Eating Attitude (EAT) and Restraint Scale (RS) scores using Pearson's coefficient. Test-retest reliability was evaluated with a subsample (n = 38) in a month interval by means of intraclass correlation coefficient (ICC). Known-groups validity was obtained comparing scores in DEAS among undergraduate students and men with eating disorders (ED) (n = 28). RESULTS: Internal consistency of scale was 0.63. DEAS score correlated with EAT (r = 0.65) and RS (r = 0.51); ICC between test and retest was 0.948. Known-groups analysis differentiated ED patients and undergraduate students (p < 0.001). CONCLUSIONS: The scale presented adequate psychometric properties and could be used in studies with adult men, since the construct is not explored among males. Nevertheless, it is recommended to revise the scale and to develop specific instruments for male public.OBJETIVO: Avaliar as propriedades psicométricas da Escala de Atitudes Alimentares Transtornadas (EAAT) para o sexo masculino. MÉTODOS: Duzentos e vinte e oito universitários (18-39 anos) responderam à EAAT, originalmente desenvolvida e validada para o sexo feminino. A consistência interna foi avaliada pelo Alpha de Cronbach e a validade convergente, por meio do coeficiente de correlação de Pearson comparando os escores da EAAT, do Teste de Atitudes Alimentares (EAT) e da Escala de Restrição (RS). A reprodutibilidade foi avaliada aplicando a escala numa subamostra (n = 38) com um mês de intervalo utilizando o coeficiente de correlação intraclasse (CCI). A validade known-groups foi obtida comparando o escore dos universitários na EAAT com o escore de homens com diagnóstico de transtornos alimentares (TA) (n = 28). RESULTADOS: A consistência interna da escala foi de 0,63. O escore da EAAT foi correlacionado com a EAT (r = 0,65) e RS (r = 0,51), e o CCI entre o teste e o reteste foi de 0,948. A análise known-groups diferenciou pacientes com TA de estudantes universitários (p < 0,001). CONCLUSÕES: A escala apresentou propriedades psicométricas adequadas e pode ser utilizada em estudos com homens adultos - uma vez que o constructo é pouco explorado em homens. Recomenda-se, de qualquer forma, uma revisão da escala e desenvolvimento de instrumentos específicos para o público masculino.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Universidade de São Paulo Faculdade de Saúde Pública Departamento de NutriçãoUniversidade Federal de Juiz de Fora Programa de Pós-Graduação em PsicologiaUniversidade Federal de São Paulo (UNIFESP) Departamento de Saúde, Clínica e InstituiçõesUNIFESP, Depto. de Saúde, Clínica e InstituiçõesSciEL

Fast Two-Robot Disk Evacuation with Wireless Communication

In the fast evacuation problem, we study the path planning problem for two robots who want to minimize the worst-case evacuation time on the unit disk. The robots are initially placed at the center of the disk. In order to evacuate, they need to reach an unknown point, the exit, on the boundary of the disk. Once one of the robots finds the exit, it will instantaneously notify the other agent, who will make a beeline to it. The problem has been studied for robots with the same speed~\cite{s1}. We study a more general case where one robot has speed $1$ and the other has speed $s \geq 1$. We provide optimal evacuation strategies in the case that $s \geq c_{2.75} \approx 2.75$ by showing matching upper and lower bounds on the worst-case evacuation time. For $1\leq s < c_{2.75}$, we show (non-matching) upper and lower bounds on the evacuation time with a ratio less than $1.22$. Moreover, we demonstrate that a generalization of the two-robot search strategy from~\cite{s1} is outperformed by our proposed strategies for any $s \geq c_{1.71} \approx 1.71$.Comment: 18 pages, 10 figure

Time-Energy Tradeoffs for Evacuation by Two Robots in the Wireless Model

Two robots stand at the origin of the infinite line and are tasked with searching collaboratively for an exit at an unknown location on the line. They can travel at maximum speed $b$ and can change speed or direction at any time. The two robots can communicate with each other at any distance and at any time. The task is completed when the last robot arrives at the exit and evacuates. We study time-energy tradeoffs for the above evacuation problem. The evacuation time is the time it takes the last robot to reach the exit. The energy it takes for a robot to travel a distance $x$ at speed $s$ is measured as $xs^2$. The total and makespan evacuation energies are respectively the sum and maximum of the energy consumption of the two robots while executing the evacuation algorithm. Assuming that the maximum speed is $b$, and the evacuation time is at most $cd$, where $d$ is the distance of the exit from the origin, we study the problem of minimizing the total energy consumption of the robots. We prove that the problem is solvable only for $bc \geq 3$. For the case $bc=3$, we give an optimal algorithm, and give upper bounds on the energy for the case $bc>3$. We also consider the problem of minimizing the evacuation time when the available energy is bounded by $\Delta$. Surprisingly, when $\Delta$ is a constant, independent of the distance $d$ of the exit from the origin, we prove that evacuation is possible in time $O(d^{3/2}\log d)$, and this is optimal up to a logarithmic factor. When $\Delta$ is linear in $d$, we give upper bounds on the evacuation time.Comment: This is the full version of the paper with the same title which will appear in the proceedings of the 26th International Colloquium on Structural Information and Communication Complexity (SIROCCO'19) L'Aquila, Italy during July 1-4, 201

Faster Approximate String Matching for Short Patterns

We study the classical approximate string matching problem, that is, given strings $P$ and $Q$ and an error threshold $k$, find all ending positions of substrings of $Q$ whose edit distance to $P$ is at most $k$. Let $P$ and $Q$ have lengths $m$ and $n$, respectively. On a standard unit-cost word RAM with word size $w \geq \log n$ we present an algorithm using time $$O(nk \cdot \min(\frac{\log^2 m}{\log n},\frac{\log^2 m\log w}{w}) + n)$$ When $P$ is short, namely, $m = 2^{o(\sqrt{\log n})}$ or $m = 2^{o(\sqrt{w/\log w})}$ this improves the previously best known time bounds for the problem. The result is achieved using a novel implementation of the Landau-Vishkin algorithm based on tabulation and word-level parallelism.Comment: To appear in Theory of Computing System