A New Framework for Distributed Submodular Maximization

A wide variety of problems in machine learning, including exemplar clustering, document summarization, and sensor placement, can be cast as constrained submodular maximization problems. A lot of recent effort has been devoted to developing distributed algorithms for these problems. However, these results suffer from high number of rounds, suboptimal approximation ratios, or both. We develop a framework for bringing existing algorithms in the sequential setting to the distributed setting, achieving near optimal approximation ratios for many settings in only a constant number of MapReduce rounds. Our techniques also give a fast sequential algorithm for non-monotone maximization subject to a matroid constraint

The Power of Randomization: Distributed Submodular Maximization on Massive Datasets

A wide variety of problems in machine learning, including exemplar clustering, document summarization, and sensor placement, can be cast as constrained submodular maximization problems. Unfortunately, the resulting submodular optimization problems are often too large to be solved on a single machine. We develop a simple distributed algorithm that is embarrassingly parallel and it achieves provable, constant factor, worst-case approximation guarantees. In our experiments, we demonstrate its efficiency in large problems with different kinds of constraints with objective values always close to what is achievable in the centralized setting

W-exchange and W-annihilation processes of B mesons

Using the PQCD method we calculate the W-exchange and the W-annihilation processes of B mesons, which in general involve a charm quark or anti-quark in the final state. The nonvanishing amplitudes of these processes are found to be suppressed by a factor of $m_c/m_b$ compared to the tree or the time-like penguin processes, but some of them are within the reach of observation at the future B-factories, and $\bar B_d^0 \to D^+_s K^-$ whose branching ratio is found to be $6.6 \times 10^{-6}$ can be found even before the B-factory era. Comparisons with the results based on the BSW model are also given.Comment: 11 Pages including figures, accepted in Phys. Lett.

Authoritarian neoliberalism between Johnson and Jupiter: declining legitimacy and the elevation of home affairs in post-Brexit Britain and Macron's France

In the face of protracted stagnation following the global financial crisis, democratic governments who remain committed to neoliberalism are still required to secure popular support for their programmes. This article evaluates how this dilemma has presaged a shift in the relationship between governmental attempts to maintain neoliberal legitimacy and the imposition of authoritarian reforms. We argue that, in the aftermath of the 2015 refugee crisis, this shift has consisted of the elevation of home affairs policy and the advance of a ‘mutated’ politics of legitimation characterised by explicit forms of ‘othering’ and hostility towards the wider political system. Drawing on the examples of the UK and France, we show how this deepening authoritarianism has manifested along two interconnected axes: (1) increased police powers and suppression of protests and civil liberties; (2) enhanced border security and restrictions on citizenship. Contributing to scholarship on authoritarian neoliberalism, we argue that this elevation of home affairs not only augurs the intensification of authoritarianism, but also reveals how governments have utilised popular resistance to authoritarian reforms to generate new forms of reactionary ‘consent’

Biogas production by co-ensiling catch crops and straw, effect of substrate blend and microbial communities

The combination of catch crop (CC) and barley straw(S) for biogas production was investigated in order to evaluate the ensiling process in batch assay and in continuous process. Based on two new agriculture strategies designed to produce energy and improve nutrient cycling in organic farming are being evaluated, one of them consisting on the harvest of straw and catch crop in different periods whereas the other strategy consists on harvesting them at the same time. Catch crops is promoted to reduce nutrient leaching during rainy season and straw that is not used for animal feeding or bedding is generally left in the field. Mixtures of CC and S provides several advantages: 1) Provides adequate TS for silage, 2) Absorbs the silage effluent, 3) Produces high LAB activity, and 4) Provides an optimal C/N for anaerobic digestion (AD). The effect of feeding compositions (straw or manurea ddition) on the microbial community structures were also investigated

Pleistocene uplift and palaeoenvironments of Macquarie Island: evidence from palaeobeaches and sedimentary deposits

Macquarie Island (54°30'S, 159°00'E) is an emergent part of the Macquarie Ridge Complex composed of ocean-floor rocks of Miocene age now 4000 m above the ocean floor. A number of landforms, including palaeobeaches now above sea level (a.s.l.)on Macquarie Island, were formed by marine erosion during uplift of the island. During the last Pleistocene period of low sea level (c. 20 ka) the island was three times larger than now. Thermoluminescence (TL) dating of two palaeobeaches indicates Pleistocene ages: 172 ± 40 ka for one at 100 m a.s.l. and 340 ± 80 ka for another at 263 m a.s.l. Matching the altitude sequence of palaeobeaches on Macquarie Island with the pattern of peaks in world sea level determined from deep sea cores allows an independent estimate of beach ages. Comparison of the altitude and sea level sequences most plausibly places the 100 m palaeobeach in Oxygen Isotope Stage 5e (130-125 ka) and the 263 m palaeobeach in Stage 9 (340-330 ka), matching reasonably with the TL dates. Other palaeobeaches at about 50 m and 170-190 m a.s.l. then correlate with high sea levels. We calculate an average rate of uplift forthe island of 0.8 mma-I . At this rate, 4000 m of Macquarie Ridge uplift would have taken about five million years and the top of the island may first have emerged some 700 to 600 ka. During the six Pleistocene glacial-interglacial cycles since then, there has been periglacial rather than glacial activity on cold uplands, but conditions suitable for vegetation of the present type persisted close to sea level

Advancing Small Satellite Earth Observation: Operational Spacecraft, Planned Missions and Future Concepts

The launch of Surrey’s UoSAT-12 in April 1999 heralded a new era in small-satellite Earth observation. The UoSAT-12 mission, Surrey’s first mini-satellite, supports a variety of payloads, including a 10-m panchromatic imager and a 32-m multispectral imager - both built at Surrey using COTS technology. In building these imagers, Surrey applied the lessons learned over sixteen microsatellite missions, and took advantage of the minisatellite class platform, which can support larger payloads and more complex missions. In the year since launch, UoSAT-12 has succeeded in a series of demonstrations of key remote-sensing technologies and techniques including autonomous station keeping, repeat ground track maintenance, high-speed communications, slewing and ground target tracking. This paper reviews these operational achievements and also describes next-generation remote sensing missions under development at Surrey. Spurred by the outstanding success of UoSAT-12, Surrey is already planning more ambitious remote sensing missions. Already, minisatellite advances are feeding back into microsatellites, such as an enhanced microsatellite with 12-m panchromatic and 24-m multispectral imaging. Future minisatellite missions are pushing the boundaries further, including 4-m panchromatic and 13-m multispectral payloads based on COTS technology. Planned missions and future concepts are presented which include use of pushbroom imagers, development of new imagers, Earth observations constellations and improved data handling as applied to small satellites. UoSAT-12 has proven that small satellites can offer rapid development, cost-constrained Earth observations missions. These affordable missions offer the opportunity for governmental and commercial organisation to target specific applications and provide emerging space nations with independent Earth observation

Structure Preserving Parallel Algorithms for Solving the Bethe-Salpeter Eigenvalue Problem

The Bethe-Salpeter eigenvalue problem is a dense structured eigenvalue problem arising from discretized Bethe-Salpeter equation in the context of computing exciton energies and states. A computational challenge is that at least half of the eigenvalues and the associated eigenvectors are desired in practice. We establish the equivalence between Bethe-Salpeter eigenvalue problems and real Hamiltonian eigenvalue problems. Based on theoretical analysis, structure preserving algorithms for a class of Bethe-Salpeter eigenvalue problems are proposed. We also show that for this class of problems all eigenvalues obtained from the Tamm-Dancoff approximation are overestimated. In order to solve large scale problems of practical interest, we discuss parallel implementations of our algorithms targeting distributed memory systems. Several numerical examples are presented to demonstrate the efficiency and accuracy of our algorithms

Inherited predisposition to spontaneous preterm delivery

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