Analyzing imbalance among homogeneous index servers in a web search system

The performance of parallel query processing in a cluster of index servers is crucial for modern web search systems. In such a scenario, the response time basically depends on the execution time of the slowest server to generate a partial ranked answer. Previous approaches investigate performance issues in this context using simulation, analytical modeling, experimentation, or a combination of them. Nevertheless, these approaches simply assume balanced execution times among homogeneous servers (by uniformly distributing the document collection among them, for instance)—a scenario that we did not observe in our experimentation. On the contrary, we found that even with a balanced distribution of the document collection among index servers, correlations between the frequency of a term in the query log and the size of its corresponding inverted list lead to imbalances in query execution times at these same servers, because these correlations affect disk caching behavior. Further, the relative sizes of the main memory at each server (with regard to disk space usage) and the number of servers participating in the parallel query processing also affect imbalance of local query execution times. These are relevant findings that have not been reported before and that, we understand, are of interest to the research community.     

Play-based Occupational Therapy

In this paper, we will provide an overview of how occupational therapists view play, illustrate how occupational therapists' view of play has evolved, generating a shift in focus for intervention, introduce a model of play as occupation to illustrate how children's ability to play may be influenced by developmental disabilities, outline occupational therapy assessment and treatment using play as the basis for intervention, and finally, identify aspects of best practice. The term developmental disabilities refers to a heterogeneous group of disorders. It is not within the scope of this paper to provide detailed discussion of play-based occupational therapy intervention for all the children who comprise this group. Therefore, we have chosen to illustrate various points made with examples of different types of children with various types of disability.     

Adding Compression to Block Addressing Inverted Indexes

Inverted index compression, block addressing and sequential search on compressed text are three techniques that have been separately developed for efficient, low-overhead text retrieval. Modern text compression techniques can reduce the text to less than 30% of its size and allow searching it directly and faster than the uncompressed text. Inverted index compression obtains significant reduction of its original size at the same processing speed. Block addressing makes the inverted lists point to text blocks instead of exact positions and pay the reduction in space with some sequential text scanning.In this work we combine the three ideas in a single scheme. We present a compressed inverted file that indexes compressed text and uses block addressing. We consider different techniques to compress the index and study their performance with respect to the block size. We compare the index against three separate techniques for varying block sizes, showing that our index is superior to each isolated approach. For instance, with just 4% of extra space overhead the index has to scan less than 12% of the text for exact searches and about 20% allowing one error in the matches.     

‘I could do with a pair of wings’: perspectives on physical activity,bodies and health from young Australian children

There is little research that reports children's perspectives on physical activity, bodies and health. This paper, drawn from a larger multi-method study on physical activity in the lives of seven- and eight-year-old Australian children, attempts to ‘give a voice’ to 13 children's views. Interviews focused on children's activity preferences and related decision making and motivations pertaining to these activities, as well as how they thought about the relationships between physical activity, health and their bodies. Data suggest some tensions surrounding the importance of fun for children alongside their awareness of ‘healthist’ discourses that require self-monitoring and improvement.     

Sweat lactate response during cycling at 30°C and 18°C WBGT

Sweat lactate reflects eccrine gland metabolism. However, the metabolic tendencies of eccrine glands in a hot versus thermoneutral environment are not well understood. Sixteen male volunteers completed a maximal cycling trial and two 60-min cycling trials [30°C?=?30±1°C and 18°C?=?18±1°C wet bulb globe temperature (WBGT)]. The participants were requested to maintain a cadence of 60 rev?·?min^?1 with the intensity individualized at ～ 90% of the ventilatory threshold. Sweat samples at 10, 20, 30, 40, 50 and 60?min were analysed for lactate concentration. Sweat rate at 30°C (1380±325?ml?·?h^?1) was significantly greater (P<0.05) than at 18°C (632±311?ml?·?h^?1). Sweat lactate concentration was significantly greater (P<0.05) at each time point during the 18°C trial, with values between trials tending to converge across time. During the 30°C trial, both heart rate (20, 30, 40, 50 and 60?min) and rectal temperature (30, 40, 50 and 60?min) were significantly higher than in the 18°C trial. Higher sweat lactate concentrations coupled with lower sweat rates may indicate a greater relative contribution of oxygen-independent metabolism within eccrine glands during exercise at 18°C. Decreases in sweat lactate concentration across time suggest either greater dilution due to greater sweat volume or increased reliance on aerobic metabolism within eccrine glands. The convergence of lactate concentrations between trials may indicate that time-dependent modifications in sweat gland metabolism occur at different rates contingent partially on environmental conditions.     

Physical activity as a dimension of family life for lower primary school children

While questions of children's engagement in physical activity are being widely debated, little is known about how physical activity is valued and managed within families. This paper reports on qualitative data from a multi-method study on lower primary aged children. The focus of the broader study was to determine the relationships between young children's physical activity patterns, skills, and recreational interests, and their families' location, income, commitment to physical activity, and other responsibilities. Drawing on interviews with 12 purposively selected families, it was found that physical activity was highly valued across different family contexts, that children's engagement was shaped by their interests, friendships, and safety, and that issues such as income, family configuration, parental work commitments, and transport were potential barriers to further engagement.     

Physical activity and depressive symptoms in American adolescents

This study employed ordinal logistic regression analyses to investigate the relationship between American adolescents' participation in physical activity and depressive symptomatology. Data were drawn from the second Child Development Supplement to the Panel Study of Income Dynamics (CDS II), which was conducted over 2002-2003. Fewer than 60% of adolescents were found to accumulate 60 min of moderate-to-vigorous physical activity (MVPA) outside of school hours on week or weekend days. Accumulated duration of MVPA was not, however, significantly associated with severity of depressive symptoms for either gender. Males who were not involved in sporting clubs or lessons were more likely than males who were highly involved to experience greater severity of depressive symptoms (OR = 3.24, CI = 1.33, 7.87). Results highlight gender variability in the psychosocial correlates of sporting participation and prompt further investigation of the relevance of current physical activity guidelines for mental health in adolescence.     

Website replica detection with distant supervision

Duplicate content on the Web occurs within the same website or across multiple websites. The latter is mainly associated with the existence of website replicas—sites that are perceptibly similar. Replication may be accidental, intentional or malicious, but no matter the reason, search engines suffer greatly either from unnecessarily storing and moving duplicate data, or from providing search results that do not offer real value to the users. In this paper, we model the detection of website replicas as a pairwise classification problem with distant supervision. That is, (heuristically) finding obvious replica and non-replica cases is trivial, but learning effective classifiers requires a representative set of non-obvious labeled examples, which are hard to obtain. We employ efficient Expectation-Maximization (EM) algorithms in order to find non-obvious examples from obvious ones, enlarging the training-set and improving the classifiers iteratively. Our classifiers employ association rules, being thus incrementally updated as the EM process iterates, making our algorithms time-efficient. Experiments show that: (1) replicas are fully eliminated at a false-positive rate lower than 0.005, incurring in + 19% reduction in the number of duplicate URLs, (2) reduction increases to + 21% by using our site-level algorithms in conjunction with existing URL-level algorithms, and (3) our classifiers are more than two orders of magnitude faster than semi-supervised alternative solutions.     

Classifying documents with link-based bibliometric measures

Automatic document classification can be used to organize documents in a digital library, construct on-line directories, improve the precision of web searching, or help the interactions between user and search engines. In this paper we explore how linkage information inherent to different document collections can be used to enhance the effectiveness of classification algorithms. We have experimented with three link-based bibliometric measures, co-citation, bibliographic coupling and Amsler, on three different document collections: a digital library of computer science papers, a web directory and an on-line encyclopedia. Results show that both hyperlink and citation information can be used to learn reliable and effective classifiers based on a kNN classifier. In one of the test collections used, we obtained improvements of up to 69.8% of macro-averaged F ₁ over the traditional text-based kNN classifier, considered as the baseline measure in our experiments. We also present alternative ways of combining bibliometric based classifiers with text based classifiers. Finally, we conducted studies to analyze the situation in which the bibliometric-based classifiers failed and show that in such cases it is hard to reach consensus regarding the correct classes, even for human judges.