Towards Optimal Moment Estimation in Streaming and Distributed Models

One of the oldest problems in the data stream model is to approximate the p-th moment ||X||_p^p = sum_{i=1}^n X_i^p of an underlying non-negative vector X in R^n, which is presented as a sequence of poly(n) updates to its coordinates. Of particular interest is when p in (0,2]. Although a tight space bound of Theta(epsilon^-2 log n) bits is known for this problem when both positive and negative updates are allowed, surprisingly there is still a gap in the space complexity of this problem when all updates are positive. Specifically, the upper bound is O(epsilon^-2 log n) bits, while the lower bound is only Omega(epsilon^-2 + log n) bits. Recently, an upper bound of O~(epsilon^-2 + log n) bits was obtained under the assumption that the updates arrive in a random order. We show that for p in (0, 1], the random order assumption is not needed. Namely, we give an upper bound for worst-case streams of O~(epsilon^-2 + log n) bits for estimating |X |_p^p. Our techniques also give new upper bounds for estimating the empirical entropy in a stream. On the other hand, we show that for p in (1,2], in the natural coordinator and blackboard distributed communication topologies, there is an O~(epsilon^-2) bit max-communication upper bound based on a randomized rounding scheme. Our protocols also give rise to protocols for heavy hitters and approximate matrix product. We generalize our results to arbitrary communication topologies G, obtaining an O~(epsilon^2 log d) max-communication upper bound, where d is the diameter of G. Interestingly, our upper bound rules out natural communication complexity-based approaches for proving an Omega(epsilon^-2 log n) bit lower bound for p in (1,2] for streaming algorithms. In particular, any such lower bound must come from a topology with large diameter

Randomised trials relevant to mental health conducted in low and middle-income countries: protocol for a survey of studies published in 1991, 1995 and 2000 and assessment of their relevance

BACKGROUND A substantial proportion of the psychiatric burden of disease falls on the world's poorest nations. Despite this, relatively little is known about the quality and content of clinical research undertaken in these countries, or the relevance of the interventions evaluated and specifically that of randomised trials. This project aims to survey the content, quality and accessibility of a sample of trials relevant to mental health conducted within low and middle-income countries; to compare these with studies conducted in high-income countries; and to assess their relevance for the needs of low and middle-income countries. METHODS An extensive search for all trials, or possible trials, published in 1991, 1995 and 2000 with participants in low and middle-income countries has already been conducted. Studies evaluating prevention or treatment of a mental health problem within these three years will be identified and further searches conducted to assess completeness of the initial search. Data on study quality and characteristics will be extracted from each report. Accessibility will be estimated based on whether each citation is available on MEDLINE. Trials relevant to schizophrenia will be compared with a random sample of schizophrenia trials from high-income countries in the same years. Topics covered by the trials will be compared with the estimated burden of disease. CONCLUSION Trials and systematic reviews of trials are the gold standard of evaluation of care and increasingly provide the basis for recommendations to clinicians, to providers of care and to policy makers. Results from this study will present the first assessment of the scope, quality and accessibility of mental health trials in low and middle-income countries

The Making of Cloud Applications An Empirical Study on Software Development for the Cloud

Cloud computing is gaining more and more traction as a deployment and provisioning model for software. While a large body of research already covers how to optimally operate a cloud system, we still lack insights into how professional software engineers actually use clouds, and how the cloud impacts development practices. This paper reports on the first systematic study on how software developers build applications in the cloud. We conducted a mixed-method study, consisting of qualitative interviews of 25 professional developers and a quantitative survey with 294 responses. Our results show that adopting the cloud has a profound impact throughout the software development process, as well as on how developers utilize tools and data in their daily work. Among other things, we found that (1) developers need better means to anticipate runtime problems and rigorously define metrics for improved fault localization and (2) the cloud offers an abundance of operational data, however, developers still often rely on their experience and intuition rather than utilizing metrics. From our findings, we extracted a set of guidelines for cloud development and identified challenges for researchers and tool vendors

Efficacy of Communication Strategies in Augmenting Quality of Life and Participation in Individuals with Aphasia

Use of communication strategies are recommended frequently to individuals with aphasia in order to enhance their communication and societal participation. This study aims to explore the efficacy of communication strategy usage in persons with chronic aphasia and their communicative partners. For this purpose, interviews were conducted with five women and six men with chronic aphasia (N =11) and a qualitative analysis of the same was done. Different factors related to individuals with aphasia, their caregivers and topics of conversation were found to affect the efficacious use of communication strategies. The most important among this was the care givers awareness regarding the need and usage of communication strategies. It was evident from the current research that caregiver training on communication strategies should be an integral goal of aphasia rehabilitation. This will inturn enhance rehabilitation and integration of individuals with aphasia for societal participation

Unimpeded permeation of water through helium-leak-tight graphene-based membranes

Permeation through nanometer pores is important in the design of materials for filtration and separation techniques and because of unusual fundamental behavior arising at the molecular scale. We found that submicron-thick membranes made from graphene oxide can be completely impermeable to liquids, vapors and gases, including helium, but allow unimpeded permeation of water (H2O permeates through the membranes at least 10^10 times faster than He). We attribute these seemingly incompatible observations to a low-friction flow of a monolayer of water through two dimensional capillaries formed by closely spaced graphene sheets. Diffusion of other molecules is blocked by reversible narrowing of the capillaries in low humidity and/or by their clogging with water

Single intra-articular steroid injection of the glenohumeral joint in management of adhesive capsulitis: a comparison between approaches

Background: Adhesive capsulitis is a common, painful musculoskeletal condition of the shoulder associated with loss of range of motion in the glenohumeral joint resulting from contraction of the glenohumeral joint capsule and adherence to the humeral head. Earlier stages of adhesive capsulitis can be treated by intra-articular steroid injections into the glenohumeral joint. This study was designed to study the role of long acting intra-articular corticosteroid injections in combination with simple therapeutic exercises while comparing the outcome of blinded anterior and posterior injection approaches in the management of adhesive capsulitis.Methods: The study comprised of 60 subjects aged 18 years and above who were diagnosed with primary adhesive capsulitis. They were randomly divided into 2 groups i.e., Group A who received blind intra-articular steroid injections via standard anterior approach and group B who received blind intra-articular steroid injection via standard posterior approach. Both groups followed up with a simple home based exercise program. Outcome measures assessed were visual analog scale (VAS) score, shoulder pain assessment disability index (SPADI) and passive shoulder range of motion (ROM).Results: At last follow up, both groups showed statistically significant improvements in all outcome measures i.e., VAS score, SPADI, shoulder ROM. However, comparison between groups did not reveal any statistically significant differences between the two groups.Conclusions: Intra-articular steroid injections into the glenohumeral joint in conjunction with simple physiotherapy are effective in improving pain, function and shoulder ROM in adhesive capsulitis. Both the anterior and posterior injection approaches provide good results