711 research outputs found
Structural characterizations of the navigational expressiveness of relation algebras on a tree
Given a document D in the form of an unordered node-labeled tree, we study
the expressiveness on D of various basic fragments of XPath, the core
navigational language on XML documents. Working from the perspective of these
languages as fragments of Tarski's relation algebra, we give characterizations,
in terms of the structure of D, for when a binary relation on its nodes is
definable by an expression in these algebras. Since each pair of nodes in such
a relation represents a unique path in D, our results therefore capture the
sets of paths in D definable in each of the fragments. We refer to this
perspective on language semantics as the "global view." In contrast with this
global view, there is also a "local view" where one is interested in the nodes
to which one can navigate starting from a particular node in the document. In
this view, we characterize when a set of nodes in D can be defined as the
result of applying an expression to a given node of D. All these definability
results, both in the global and the local view, are obtained by using a robust
two-step methodology, which consists of first characterizing when two nodes
cannot be distinguished by an expression in the respective fragments of XPath,
and then bootstrapping these characterizations to the desired results.Comment: 58 Page
Similarity and bisimilarity notions appropriate for characterizing indistinguishability in fragments of the calculus of relations
Motivated by applications in databases, this paper considers various
fragments of the calculus of binary relations. The fragments are obtained by
leaving out, or keeping in, some of the standard operators, along with some
derived operators such as set difference, projection, coprojection, and
residuation. For each considered fragment, a characterization is obtained for
when two given binary relational structures are indistinguishable by
expressions in that fragment. The characterizations are based on appropriately
adapted notions of simulation and bisimulation.Comment: 36 pages, Journal of Logic and Computation 201
Uniting to end the TB epidemic: advances in disease control from prevention to better diagnosis and treatment.
Tuberculosis is a major global cause of morbidity and mortality. Despite recent advances in containing the epidemic, several challenges continue to slow progress towards elimination including the continuing impact of drug resistant disease, and the lack of appropriate tools. Curtailing the transmission of tuberculosis remains a challenge especially in high burden countries. New developments in measuring correlates of protection are urgently needed to support the evaluation of vaccines. Similarly, despite progress in molecular diagnostics, better tools are required to identify resistance to antibiotics in multi and extensively drug resistant tuberculosis. Whole Genome Sequencing may lead to the next generation of assays to rapidly detect resistance and evaluate transmission. Advances on shortening treatment are hampered by the lack of a biomarker of cure which obviates the current long wait for relapses in trials. New research is urgently needed to support development of new vaccines and better diagnostics tools and shorter treatment for drug sensitive and resistant tuberculosis
Relative Expressive Power of Navigational Querying on Graphs
Motivated by both established and new applications, we study navigational
query languages for graphs (binary relations). The simplest language has only
the two operators union and composition, together with the identity relation.
We make more powerful languages by adding any of the following operators:
intersection; set difference; projection; coprojection; converse; and the
diversity relation. All these operators map binary relations to binary
relations. We compare the expressive power of all resulting languages. We do
this not only for general path queries (queries where the result may be any
binary relation) but also for boolean or yes/no queries (expressed by the
nonemptiness of an expression). For both cases, we present the complete Hasse
diagram of relative expressiveness. In particular the Hasse diagram for boolean
queries contains some nontrivial separations and a few surprising collapses.Comment: An extended abstract announcing the results of this paper was
presented at the 14th International Conference on Database Theory, Uppsala,
Sweden, March 201
‘These whites never come to our game. What do they know about our soccer?’ Soccer fandom, race, and the Rainbow Nation in South Africa
South African political elites framed the country’s successful bid to host the 2010
FIFA World Cup in terms of nation-building, evoking imagery of South African
unity. Yet, a pre-season tournament in 2008 featuring the two glamour soccer clubs
of South Africa, Kaizer Chiefs and Orlando Pirates, and the global brand of
Manchester United, revealed a racially fractured soccer fandom that contradicted
these notions of national unity through soccer.
This thesis examines the racial divisions in Johannesburg soccer fandom, exploring
the continuing wider importance of racial identities in post-apartheid South Africa.
Sport is not merely a leisure activity but a space in which everyday identities are
negotiated and contested. Specifically, soccer in South Africa has been a site in
which racial divisions have been both entrenched and subverted, spanning the
colonial era to the present day. However, in focusing on race, this thesis seeks to
move beyond simple binaries that have characterised the debates on identity in
South Africa; particularly race versus class. Race, through the perspective of
creolisation, becomes unfixed and fluid. However, despite reinterpreting race, racial
divisions still scar the post-apartheid city.
Extensive ethnographic fieldwork with the supporters’ organisations of Kaizer
Chiefs, Bidvest Wits and Manchester United football clubs in Johannesburg draws
out narratives of fandom often marginalised in Africanist scholarship. Drawing on
wide-ranging sources including participant observation, semi-structured interviews
and local newspapers, themes of racial difference and otherness emerge. The
divided Johannesburg soccer landscape reinforced feelings of disenfranchisement
and marginalisation in everyday life from the predominantly white Manchester
United supporters while the exclusively black Kaizer Chiefs constructed the
domestic game as a black cultural space. While Bidvest Wits offers a symbolic case
of multi-racial interaction, certain supporters began to challenge such fractures;
some United supporters showed interest in attending domestic games while the
Chiefs supporters viewed the researcher as a conduit to attracting these white
supporters. Furthermore, the national euphoria generated during 2010 World Cup
did temporarily alter perspectives of the city and how the supporters travelled
through it, challenging perceived barriers. Yet, themes of exclusion and division
remained, brought back to the fore after the tournament
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Real-Time and Wireless Assessment of Adherence to Antiretroviral Therapy With Co-Encapsulated Ingestion Sensor in HIV-Infected Patients: A Pilot Study.
Adherence with antiretroviral therapy is important for preventing disease progression and HIV transmission. The co-encapsulated pill sensor system sends a signal through a cutaneous patch and allows real-time monitoring of pill ingestion. A 16-week pilot study used a sensor system in 15 HIV-infected individuals with real-time monitoring of pill-taking with a personalized short message system text. System acceptability was assessed by survey at weeks 4, 8, 12, and 16. Follow-up occurred in 80% of subjects through 8Â weeks. The system effectively collected measures of pill ingestion, which triggered text message reminders. Only 2 of 14 participants stated that co-encapsulated pills were "unable to take" or "poorly tolerated." At least 75% of respondents stated at each visit that the patch was very or somewhat comfortable. With regard to text message reminders, only 10-15% of the participants at any visit did not find the messages to be helpful. Larger studies will define the utility of this system to assess antiretroviral adherence relative to standard measures
World TB Day 2016: an interview with leading experts in tuberculosis research.
In this interview, we talk to leading tuberculosis (TB) experts from University College London and the London School of Hygiene and Tropical Medicine about the current challenges in TB research. The video of this interview is available here: https://www.youtube.com/watch?v=75Die7MQBec&feature=youtu.be . The video can also be downloaded via Additional file 1
The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project
The Wide-field Infrared Survey Explorer (WISE) is a powerful tool for finding
nearby brown dwarfs and searching for new planets in the outer solar system,
especially with the incorporation of NEOWISE and NEOWISE-Reactivation data. So
far, searches for brown dwarfs in WISE data have yet to take advantage of the
full depth of the WISE images. To efficiently search this unexplored space via
visual inspection, we have launched a new citizen science project, called
"Backyard Worlds: Planet 9," which asks volunteers to examine short animations
composed of difference images constructed from time-resolved WISE coadds. We
report the discovery of the first new substellar object found by this project,
WISEA J110125.95+540052.8, a T5.5 brown dwarf located approximately 34 pc from
the Sun with a total proper motion of 0.7 as yr. WISEA
J110125.95+540052.8 has a WISE magnitude of , this
discovery demonstrates the ability of citizen scientists to identify moving
objects via visual inspection that are 0.9 magnitudes fainter than the
single-exposure sensitivity, a threshold that has limited prior motion-based
brown dwarf searches with WISE.Comment: 9 pages, 4 figures, 1 table. Accepted for publication in the
Astrophysical Journal Letter
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