On The Complexity and Completeness of Static Constraints for Breaking Row and Column Symmetry

We consider a common type of symmetry where we have a matrix of decision variables with interchangeable rows and columns. A simple and efficient method to deal with such row and column symmetry is to post symmetry breaking constraints like DOUBLELEX and SNAKELEX. We provide a number of positive and negative results on posting such symmetry breaking constraints. On the positive side, we prove that we can compute in polynomial time a unique representative of an equivalence class in a matrix model with row and column symmetry if the number of rows (or of columns) is bounded and in a number of other special cases. On the negative side, we show that whilst DOUBLELEX and SNAKELEX are often effective in practice, they can leave a large number of symmetric solutions in the worst case. In addition, we prove that propagating DOUBLELEX completely is NP-hard. Finally we consider how to break row, column and value symmetry, correcting a result in the literature about the safeness of combining different symmetry breaking constraints. We end with the first experimental study on how much symmetry is left by DOUBLELEX and SNAKELEX on some benchmark problems.Comment: To appear in the Proceedings of the 16th International Conference on Principles and Practice of Constraint Programming (CP 2010

Domain k-Wise Consistency Made as Simple as Generalized Arc Consistency

Abstract. In Constraint Programming (CP), Generalized Arc Consistency (GAC) is the central property used for making inferences when solving Constraint Satisfaction Problems (CSPs). Developing simple and practical filtering algorithms based on consistencies stronger than GAC is a challenge for the CP community. In this paper, we propose to combine k-Wise Consistency (kWC) with GAC, where kWC states that every tuple in a constraint can be extended to every set of k − 1 additional constraints. Our contribution is as follows. First, we derive a domain-filtering consistency, called Domain k-Wise Consistency (DkWC), from the combination of kWC and GAC. Roughly speaking, this property corresponds to the pruning of values of GAC, when enforced on a CSP previously made kWC. Second, we propose a procedure to enforce DkWC, relying on an encoding of kWC to generate a modified CSP called k-interleaved CSP. Formally, we prove that enforcing GAC on the k-interleaved CSP corresponds to enforcing DkWC on the initial CSP. Consequently, we show that the strong DkWC can be enforced very easily in constraint solvers since the k-interleaved CSP is rather immediate to generate and only existing GAC propagators are required: in a nutshell, DkWC is made as simple and practical as GAC. Our experimental results show the benefits of our approach on a variety of benchmarks.

Constituents of Kawal, fermented Cassia obtusifolia leaves, a traditional food from Chad

Femented leaves of Cassia obtusifolia are used as a substitute of meat or an appetizing agent by people of eastern of Chad and south of Sudan. Chemical composition of the methylene chloride extract from the fermented leaves of this legume was analyzed for the first time by GC and GC/MC. Thirty threeconstituents were identified. The major components are found to be aliphatic acids and identified as hexanoic acid (27%), butyric acid (10.4%) and valeric acid (6.3%) with lesser amounts of p-ethylphenol (17.2%) and p-methylphenol (13%). Examination of the protein fraction from leaves indicated 20.2% inthe crude leaves and 12.9% in the fermented leaves. The participation of 10 g of fermented C. obtusifolia leaves to the daily requirements in essential amino acids of an adult is from 13 to 25% of needed amount. Moreover this traditional food had a high content of potassium and calcium

A distributed optimization method for the geographically distributed data centres problem

The geographically distributed data centres problem (GDDC) is a naturally distributed resource allocation problem. The problem involves allocating a set of virtual machines (VM) amongst the data centres (DC) in each time period of an operating horizon. The goal is to optimize the allocation of workload across a set of DCs such that the energy cost is minimized, while respecting limitations on data centre capacities, migrations of VMs, etc. In this paper, we propose a distributed optimization method for GDDC using the distributed constraint optimization (DCOP) framework. First, we develop a new model of the GDDC as a DCOP where each DC operator is represented by an agent. Secondly, since traditional DCOP approaches are unsuited to these types of large-scale problem with multiple variables per agent and global constraints, we introduce a novel semi-asynchronous distributed algorithm for solving such DCOPs. Preliminary results illustrate the benefits of the new method

Jet-driven outflows of ionized gas in the nearby radio galaxy 3C 293

Fast outflows of gas, driven by the interaction between the radio jets and interstellar medium (ISM) of the host galaxy, are being observed in an increasing number of galaxies. One such example is the nearby radio galaxy 3C 293. In this paper we present integral field unit observations taken with OASIS on the William Herschel Telescope, enabling us to map the spatial extent of the ionized gas outflows across the central regions of the galaxy. The jet-driven outflow in 3C 293 is detected along the inner radio lobes with a mass outflow rate ranging from ∼0.05 to 0.17 M yr−1 (in ionized gas) and corresponding kinetic power of ∼0.5– 3.5 × 1040 erg s−1. Investigating the kinematics of the gas surrounding the radio jets (i.e. not directly associated with the outflow), we find linewidths broader than 300 km s−1 up to 5 kpc in the radial direction from the nucleus (corresponding to 3.5 kpc in the direction perpendicular to the radio axis at maximum extent). Along the axis of the radio jet linewidths >400 km s−1 are detected out to 7 kpc from the nucleus and linewidths of >500 km s−1 at a distance of 12 kpc from the nucleus, indicating that the disturbed kinematics clearly extend well beyond the high surface brightness radio structures of the jets. This is suggestive of the cocoon structure seen in simulations of jet–ISM interaction and implies that the radio jets are capable of disturbing the gas throughout the central regions of the host galaxy in all directions

Galaxy-wide radio-induced feedback in a radio-quiet quasar

We report the discovery of a radio-quiet type 2 quasar (SDSS J165315.06+234943.0 nicknamed the ‘Beetle’ at z = 0.103) with unambiguous evidence for active galactic nucleus (AGN) radio-induced feedback acting across a total extension of ∼46 kpc and up to ∼26 kpc from the AGN. To the best of our knowledge, this is the first radio-quiet system where radio-induced feedback has been securely identified at ≫several kpc from the AGN. The morphological, ionization and kinematic properties of the extended ionized gas are correlated with the radio structures. We find along the radio axis (a) enhancement of the optical line emission at the location of the radio hotspots (b) turbulent gas kinematics (FWHM ∼ 380–470 km s−1) across the entire spatial range circumscribed by them (c) ionization minima for the turbulent gas at the location of the hot spots, (d) high temperature Te ≳ 1.9 × 104 K at the NE hotspot. Turbulent gas is also found far from the radio axis, ∼25 kpc in the perpendicular direction. We propose a scenario in which the radio structures have perforated the interstellar medium of the galaxy and escaped into the circumgalactic medium. While advancing, they have interacted with in situ gas modifying its properties. Our results show that jets of modest power can be the dominant feedback mechanism acting across huge volumes in radio-quiet systems, including highly accreting luminous AGNs, where radiative mode feedback may be expected

Etude comparative de vocalisations de bébés humains et de bébés robots

In order to assess infants' motor skills during speech development, we used a statistical model of the vocal tract that integrates growth of the effector system. This model allowed us to infer, from actual vocalizations, the likeliest explored acoustic regions, articulatory degrees of freedom and vocal tract shapes, and to test MacNeilage and Davis' cooccurrence hypothesis. Our results will feed the building of a virtual robot, modelling speech development

Ionized outflows in luminous type 2 AGNs at z < 0.6: no evidence for significant impact on the host galaxies

We investigate the presence of extended ionized outflows in 18 luminous type 2 AGNs (11 quasars and 7 high-luminosity Seyfert 2s) at 0.3 <z< 0.6 based on VLT-FORS2 spectroscopy. We infer typical lower limits on the radial sizes of the outflows Ro several × 100 pc and upper limits Ro 1–2 kpc. Our results are inconsistent with related studies which suggest that large scale (Ro ∼ several-15 kpc) are ubiquitous in QSO2. We study the possible causes of discrepancy and propose that seeing smearing is the cause of the large inferred sizes. The implications in our understanding of the feedback phenomenon are important since the mass Mo (through the density), mass injection M˙ o and energy injection E˙ o rates of the outflows become highly uncertain. One conclusion seems unavoidable: Mo, M˙ o and E˙ o are modest or low compared with previous estimations. We obtain typically Mo (0.4–22) × 106 M (median 1.1 × 106 M) assuming n = 1000 cm−3. These are ∼102–104 times lower than values reported in the literature. Even under the most favourable assumptions, we obtain M˙ o 10 M yr−1 in general, 100–1000 times lower than claimed in related studies. Although the uncertainties are large, it is probable that these are lower than typical star-forming rates. In conclusion, no evidence is found supporting that typical outflows can affect the interstellar medium of the host galaxies across spatial scales 1–2 kpc

Antiplasmodial volatile extracts from Cleistopholis patens Engler & Diels and Uvariastrum pierreanum Engl. (Engl. & Diels) (Annonaceae) growing in Cameroon

In a search for alternative treatment for malaria, plant-derived essential oils extracted from the stem barks and leaves of Cleistopholis patens and Uvariastrum pierreanum (Annonaceae) were evaluated in vitro for antiplasmodial activity against the W2 strain of Plasmodium falciparum. The oils were obtained from 500 g each of stem barks and leaves, respectively, by hydrodistillation, using a Clevenger-type apparatus with the following yields: 0.23% and 0.19% for C. patens and 0.1% and 0.3% for U. pierreanum (w/w relative to dried material weight). Analysis of 10% (v/v) oil in hexane by gas chromatography and mass spectrometry identified only terpenoids in the oils, with over 81% sesquiterpene hydrocarbons in C. patens extracts and U. pierreanum stem bark oil, while the leaf oil from the latter species was found to contain a majority of monoterpenes. For C. patens, the major components were α-copaene, δ-cadinene, and germacrene D for the stem bark oil and β-caryophyllene, germacrene D, and germacrene B for the leaf oil. The stem bark oil of U. pierreanum was found to contain mainly β-bisabolene and α-bisabolol, while α- and β-pinenes were more abundant in the leaf extract. Concentrations of oils obtained by diluting 1-mg/mL stock solutions were tested against P. falciparum in culture. The oils were active, with IC50 values of 9.19 and 15.19 μg/mL for the stem bark and leaf oils, respectively, of C. patens and 6.08 and 13.96 μg/mL, respectively, for those from U. pierreanum. These results indicate that essential oils may offer a promising alternative for the development of new antimalarials