Relaxations of the satisfiability problem using semidefinite programming

We derive a semidefinite relaxation of the satisfiability (SAT) problem and discuss its strength. We give both the primal and dual formulation of the relaxation. The primal formulation is an eigenvalue optimization problem, while the dual formulation is a semidefinite feasibility problem. It is shown that using the relaxation, the notorious pigeon hole and mutilated chessboard problems are solved in polynomial time. As a byproduct we find a new `sandwich' theorem that is similar to Lov'asz' famous $vartheta$-function. Furthermore, using the semidefinite relaxation 2SAT problems are solved. By adding an objective function to the dual formulation, a specific class of polynomially solvable 3SAT instances can be identified. We conclude with discussing how the relaxation can be used to solve more general SAT problems and some empirical observations

Effect of preoperative endoscopic biliary drainage on infectious morbidity after pancreatoduodenectomy: a case-control study

BackgroundThe utility of preoperative endoscopic biliary drainage (PEBD) in jaundiced patients before pancreatoduodenectomy (PD) is still debated. This is in part due to the heterogeneity of the studied population, including different tumor location, drainage techniques, and surgical procedures. The aim of the current study was to report the influence of PEBD on postoperative infectious morbidity of PD. Materials and Methods Between January 1996 and December 2004, 124 patients underwent a PD and 28. Twenty-eight (22.6%) of these patients underwent a PEBD. This group of patients was matched to 28 control patients who underwent PD without PEBD during the same period. The 2 groups were matched for age, sex, indication of surgery, and serum bilirubin levels. Results The specific morbidity of PEBD before surgery was 10.7% (n = 3). The postoperative overall morbidity, medical morbidity, and surgical morbidity rates were not different between the 2 groups. At the time of surgery, 89.3% (n = 25) of the patients in the PEBD group had positive bile culture in comparison to 19.4% (n = 4) in the control group (P < .001). The number of patients with 1 or more infectious complications was higher in the PEBD group (50%; n = 14) than in the control group (21.4%; n = 6) (P = .05). Conclusions Before PD, PEBD should be routinely avoided whenever possible in patients with potentially resectable pancreatic and peripancreatic lesions. In patients with cholangitis, requiring extensive preoperative assessment (such as liver biopsy) or neoadjuvant treatment, PEBD might still be indicated

L'archéologie française à l'étranger: Nouveaux enjeux de politique scientifique et de coopération internationale pour le Ministère des affaires étrangères et européennes

L'organisation et le financement de la recherche archéologique française hors du territoire national reposent pour une très large part sur le dispositif géré depuis plus d'un demi-siècle par le Ministère des Affaires Etrangères et Européennes : la Commission consultative de la recherche archéologique à l'étranger évalue et propose le financement des projets de recherche grâce à un appel d'offre annuel, les Instituts français de recherche à l'étranger, codirigés avec le CNRS, organisent dans bon nombre de pays hôtes la coordination des actions de recherche et l'accueil de chercheurs grâce à des structures pérennes. Cette double organisation, seule en France à être explicitement et uniquement dévolue à l'archéologie, prend en charge chaque année de 150 à 200 projets dans une organisation fortement internationalisée puisqu'elle permet à près de 1800 personnes, dont près de 800 non français, de travailler à l'étranger (chiffres année 2010). Elle répond avec une grande efficacité aux besoins des projets et des équipes qui s'en félicitent : une organisation administrative et gestionnaire légère permet une adaptation très rapide et souple aux conditions de travail à l'étranger ; un appel d'offre annuel totalement ouvert géographiquement et thématiquement laisse la capacité d'initiative aux acteurs de la discipline ; le soutien sur place des instituts et des services diplomatiques est un outil précieux pour la réalisation des projets en concertation avec les institutions et les collègues des pays hôtes. après avoir décrit le dispositif, le rapport traite quatre aspects : les relations entre les institutions françaises et étrangères intervenant dans la recherche archéologique à l'étranger les thématiques de recherche et l'évaluation des projets l'organisation et la réalisation des projets l'exploitation des projets à travers la production scientifique, la diffusion et la valorisation des résultats. Ces aspects nous permettent de concentrer l'attention sur les enjeux déterminants et les évolutions souhaitables du dispositif général

Variations in water use by a mature mangrove of Avicennia germinans, French Guiana

In the tropical intertidal zones, little is known on water uptake by mangroves. Transpiration rates are generally measured at leaf level, but few studies exist on water use at tree or stand levels. The objective of this study was to measure sap flow in trees of different sizes to appreciate the range of variation in water use that may exist in a site dominated by 80% mature Avicennia germinans. The results showed that from the dry to the wet season the mean water use increased from 3.2 to 5.3 dm3 d−1 in small trees (DBH ∼ 13 cm), from 11.5 to 30.8 dm3 d−1 in medium trees (∼24 cm) and from 40.8 to 64.1 dm3 d−1 in large ones (∼45 cm). Sapwood remained active up to a depth of 8 cm with radial variations within the stem. Weak correlations were obtained with VPD and net radiation. This study confirmed that transpiration was larger under low levels of salinity. Water use at stand level (∼1900 living stems ha−1) was estimated to be in the range of 5.8 to 11.8 m3 ha−1 d−1 according to the season

Magnetic field strength and orientation effects on co-fe discontinuous multilayers close to percolation

International audienceMagnetization and magnetoresistance in function of the magnitude and orientation of applied magnetic field were studied in Co-Fe discontinuous multilayers close to their structural percolation. The high pulsed magnetic fields up to 33 T were used in the 120–310 K temperature range. Comparison between longitudinal and transverse with respect to the film plane field configurations was made in the low-field and high-field regimes in order to clarify the nature of the measured negative magnetoresistance. Coexistence of two distinct magnetic fractions, superparamagnetic SPM, consisting of small spherical Co-Fe granules and superferromagnetic SFM, by bigger Co-Fe clusters, was established in this system. These fractions were shown to have different relevance for the system magnetization and magnetotransport. While the magnetization is almost completely up to 97% defined by the SFM contribution and practically independent of temperature in this range, the magnetoresistance experiences a crossover from a regime dominated by Langevin correlations suppressed with temperature between neighbor SPM and SFM moments at low fields, to that dominated by spin scattering enhanced with temperature of charge carriers within SFM clusters at high fields. Also, the demagnetizing effects, sensitive to the field orientation, were found to essentially define the low-field behavior and characteristic crossover field

Sequential versus combination chemotherapy for the treatment of advanced colorectal cancer (FFCD 2000-05): an open-label, randomised, phase 3 trial

BACKGROUND: The optimum use of cytotoxic drugs for advanced colorectal cancer has not been defined. Our aim was to investigate whether combination treatment is better than the sequential administration of the same drugs in patients with advanced colorectal cancer. METHODS: In this open-label, randomised, phase 3 trial, we randomly assigned patients (1:1 ratio) with advanced, measurable, non-resectable colorectal cancer and WHO performance status 0-2 to receive either first-line treatment with bolus (400 mg/m(2)) and infusional (2400 mg/m(2)) fluorouracil plus leucovorin (400 mg/m(2)) (simplified LV5FU2 regimen), second-line LV5FU2 plus oxaliplatin (100 mg/m(2)) (FOLFOX6), and third-line LV5FU2 plus irinotecan (180 mg/m(2)) (FOLFIRI) or first-line FOLFOX6 and second-line FOLFIRI. Chemotherapy was administered every 2 weeks. Randomisation was done centrally using minimisation (minimisation factors were WHO performance status, previous adjuvant chemotherapy, number of disease sites, and centre). The primary endpoint was progression-free survival after two lines of treatment. Analyses were by intention-to-treat. This trial is registered at ClinicalTrials.gov, NCT00126256. FINDINGS: 205 patients were randomly assigned to the sequential group and 205 to the combination group. 161 (79%) patients in the sequential group and 161 (79%) in the combination group died during the study. Median progression-free survival after two lines was 10·5 months (95% CI 9·6-11·5) in the sequential group and 10·3 months (9·0-11·9) in the combination group (hazard ratio 0·95, 95% CI 0·77-1·16; p=0·61). All six deaths caused by toxic effects of treatment occurred in the combination group. During first-line chemotherapy, significantly fewer severe (grade 3-4) haematological adverse events (12 events in 203 patients in sequential group vs 83 events in 203 patients in combination group; p<0·0001) and non-haematological adverse events (26 events vs 186 events; p<0·0001) occurred in the sequential group than in the combination group. INTERPRETATION: Upfront combination chemotherapy is more toxic and is not more effective than the sequential use of the same cytotoxic drugs in patients with advanced, non-resectable colorectal cancer. FUNDING: Sanofi-Aventis France

Multimessenger astronomy with the Einstein Telescope

Gravitational waves (GWs) are expected to play a crucial role in the development of multimessenger astrophysics. The combination of GW observations with other astrophysical triggers, such as from gamma-ray and X-ray satellites, optical/radio telescopes, and neutrino detectors allows us to decipher science that would otherwise be inaccessible. In this paper, we provide a broad review from the multimessenger perspective of the science reach offered by the third generation interferometric GW detectors and by the Einstein Telescope (ET) in particular. We focus on cosmic transients, and base our estimates on the results obtained by ET's predecessors GEO, LIGO, and Virgo.Comment: 26 pages. 3 figures. Special issue of GRG on the Einstein Telescope. Minor corrections include