4,760 research outputs found
Dynamic Meta-Theorems for Distance and Matching
No full textReachability, distance, and matching are some of the most fundamental graph problems that have been of particular interest in dynamic complexity theory in recent years [Samir Datta et al., 2018; Samir Datta et al., 2018; Samir Datta et al., 2020]. Reachability can be maintained with first-order update formulas, or equivalently in DynFO in general graphs with n nodes [Samir Datta et al., 2018], even under O(log(n)/log log(n)) changes per step [Samir Datta et al., 2018]. In the context of how large the number of changes can be handled, it has recently been shown [Samir Datta et al., 2020] that under a polylogarithmic number of changes, reachability is in DynFOpar in planar, bounded treewidth, and related graph classes - in fact in any graph where small non-zero circulation weights can be computed in NC.
We continue this line of investigation and extend the meta-theorem for reachability to distance and bipartite maximum matching with the same bounds. These are amongst the most general classes of graphs known where we can maintain these problems deterministically without using a majority quantifier and even maintain witnesses. For the bipartite matching result, modifying the approach from [Stephen A. Fenner et al., 2016], we convert the static non-zero circulation weights to dynamic matching-isolating weights.
While reachability is in DynFOar under O(log(n)/log log(n)) changes, no such bound is known for either distance or matching in any non-trivial class of graphs under non-constant changes. We show that, in the same classes of graphs as before, bipartite maximum matching is in DynFOar under O(log(n)/log log(n)) changes per step. En route to showing this we prove that the rank of a matrix can be maintained in DynFOar, also under O(log(n)/log log(n)) entry changes, improving upon the previous O(1) bound [Samir Datta et al., 2018]. This implies a similar extension for the non-uniform DynFO bound for maximum matching in general graphs and an alternate algorithm for maintaining reachability under O(log(n)/log log(n)) changes [Samir Datta et al., 2018]
Norfloxacin For Hepatopulmonary Syndrome: A Pilot Study of a Rare Disease
No full textNorfloxacin For Hepatopulmonary Syndrome: A Pilot Study of a Rare Disease
Samir Gupta, Masters of Science, 2008
Graduate Department of Health Policy, Management and Evaluation
University of Toronto
Introduction: Hepatopulmonary Syndrome is a rare disease characterized by abnormal gas-exchange and a poor prognosis, with no known effective medical therapy. A rat model and preliminary human data suggest that this disease may be caused by intestinal bacterial overgrowth, systemic endotoxemia and increased nitric oxide. Methods: We conducted a pilot crossover randomized controlled trial of norfloxacin versus placebo over four weeks, in seven subjects with HPS or a milder condition called pre-HPS, with a primary outcome of alveolar-arterial oxygen gradient (AaDO2). Results: There was no trend toward improved AaDO2, this outcome and other intermediate outcomes were highly variable, and results suggested that a longer treatment course might be necessary. We identified multiple obstacles to recruitment. Conclusion: We believe that a full-scale study of norfloxacin therapy for HPS will require 1) a six-month therapeutic period, 2) more specific HPS diagnostic criteria for clinical and study populations, and 3) creative recruitment maneuvers.MAS
Norfloxacin For Hepatopulmonary Syndrome: A Pilot Study of a Rare Disease
No full textNorfloxacin For Hepatopulmonary Syndrome: A Pilot Study of a Rare Disease
Samir Gupta, Masters of Science, 2008
Graduate Department of Health Policy, Management and Evaluation
University of Toronto
Introduction: Hepatopulmonary Syndrome is a rare disease characterized by abnormal gas-exchange and a poor prognosis, with no known effective medical therapy. A rat model and preliminary human data suggest that this disease may be caused by intestinal bacterial overgrowth, systemic endotoxemia and increased nitric oxide. Methods: We conducted a pilot crossover randomized controlled trial of norfloxacin versus placebo over four weeks, in seven subjects with HPS or a milder condition called pre-HPS, with a primary outcome of alveolar-arterial oxygen gradient (AaDO2). Results: There was no trend toward improved AaDO2, this outcome and other intermediate outcomes were highly variable, and results suggested that a longer treatment course might be necessary. We identified multiple obstacles to recruitment. Conclusion: We believe that a full-scale study of norfloxacin therapy for HPS will require 1) a six-month therapeutic period, 2) more specific HPS diagnostic criteria for clinical and study populations, and 3) creative recruitment maneuvers.MAS
Correction to: Isolation and Characterization of Extracellular Vesicles from Keratinocyte Cultures
No full textThe original version of this chapter was inadvertently published with incorrect spelling of surname of the authors. The names should read Sebastian Sjöqvist, Aya Imafuku, Danu Gupta, and Samir EL Andaloussi, and not Sebastian Sjöqvist, Aya Imafuku, Dhanu Ghupta, and Samir E. L. Andaloussi
MSC904977 Supplemental Material2 - Supplemental material for Interventions to ensure follow-up of positive fecal immunochemical tests: An international survey of screening programs
No full textSupplemental material, MSC904977 Supplemental Material2 for Interventions to ensure follow-up of positive fecal immunochemical tests: An international survey of screening programs by Kevin Selby, Carlo Senore, Martin Wong, Folasade P May, Samir Gupta and Peter S Liang in Journal of Medical Screening</p
MSC904977 Supplemental Material1 - Supplemental material for Interventions to ensure follow-up of positive fecal immunochemical tests: An international survey of screening programs
No full textSupplemental material, MSC904977 Supplemental Material1 for Interventions to ensure follow-up of positive fecal immunochemical tests: An international survey of screening programs by Kevin Selby, Carlo Senore, Martin Wong, Folasade P May, Samir Gupta and Peter S Liang in Journal of Medical Screening</p
Effective Resource Competition Model for Species Coexistence
No full textLocal coexistence of species in large ecosystems is traditionally explained within the broad framework of niche theory. However, its rationale hardly justifies rich biodiversity observed in nearly homogeneous environments. Here we consider a consumer-resource model in which a coarse-graining procedure accounts for a variety of ecological mechanisms and leads to effective spatial effects which favor species coexistence. Herein, we provide conditions for several species to live in an environment with very few resources. In fact, the model displays two different phases depending on whether the number of surviving species is larger or smaller than the number of resources. We obtain conditions whereby a species can successfully colonize a pool of coexisting species. Finally, we analytically compute the distribution of the population sizes of coexisting species. Numerical simulations as well as empirical distributions of population sizes support our analytical findings
Data for Gupta et al., "Estimating the Meridional Extent of Adiabatic Mixing in the Stratosphere using Age-of-Air", JGR:Atmospheres,
No full textModel data and post-processed data supporting the creation of the manuscript "Estimating the Meridional Extent of Adiabatic Mixing in the Stratosphere using Age-of-Air" submitted to JGR:Atmospheres in August 2022.
1) The netCDF files created through post-processing of full model data in FORTRAN are shared in the /data/ directory. These file contains the zonal mean circulation statistics based on Gupta et al. (2020), age-of-air transport diagnostics based on Linz et al. (2021), and the novel \Gamma-\Theta circulation streamfunction introduced in this study. The /data/ directory also contains MATLAB .mat data files for the transport diagnostics obtained from WACCM. 150 days of actual GFDL-FV3 model data in the northern hemisphere, between 0.1 hPa-500 hPa pressure levels is also provided to support external computations and validation.
2) The Jupyter notebook used for final computation and figures production is provided in .ipynb, .html and .pdf formats in /code/. All the files referred to in the notebook are stored in the /data/ directory.
Corresponding author : Aman Gupta, [email protected], [email protected], [email protected]
Constant Factor Approximation Algorithm for Uniform Hard Capacitated Knapsack Median Problem
No full textIn this paper, we give the first constant factor approximation algorithm for capacitated knapsack median problem (CKnM) for hard uniform capacities, violating the budget by a factor of 1+epsilon and capacities by a 2+epsilon factor. To the best of our knowledge, no constant factor approximation is known for the problem even with capacity/budget/both violations. Even for the uncapacitated variant of the problem, the natural LP is known to have an unbounded integrality gap even after adding the covering inequalities to strengthen the LP. Our techniques for CKnM provide two types of results for the capacitated k-facility location problem. We present an O(1/epsilon^2) factor approximation for the problem, violating capacities by (2+epsilon). Another result is an O(1/epsilon) factor approximation, violating the capacities by a factor of at most (1 + epsilon) using at most 2k facilities for a fixed epsilon>0. As a by-product, a constant factor approximation algorithm for capacitated facility location problem with uniform capacities is presented, violating the capacities by (1 + epsilon) factor. Though constant factor results are known for the problem without violating the capacities, the result is interesting as it is obtained by rounding the solution to the natural LP, which is known to have an unbounded integrality gap without violating the capacities. Thus, we achieve the best possible from the natural LP for the problem. The result shows that the natural LP is not too bad
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