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Galaxies live in very different types of environment. Those different environments are relics from the evolution of the Universe since the Big Bang. This network of structures observed via large scale surveys is called Cosmic Web. Within this web, galaxies can be isolated, in a filament, in a group, or in a cluster. When part of a cluster of galaxies, their morphologies, gas content (cold and hot), and star formation activities is seen to be affected by other galaxies, or by the gas inside the cluster. However, the long-term effects of the local environment on galaxy evolution remain unclear. Also, it has been observed that a pre-processing is happening long before the galaxies enter the cluster cores, which could explain the build-up of the passive galaxy sequence, where galaxies have quenched star formation. The aim of this thesis is to see if and how the cold molecular gas reservoir of galaxies is modified when star formation activity is decreasing and if there is a link with the position of the galaxy in the CW around the cluster. We gathered unprecedented observations: the first and largest survey of the molecular gas content of galaxies in and around the same cluster environment at intermediate redshifts. These Atacama Large Millimeter Array observations are part of a larger survey called Spatially Extended ESO Distant Cluster Survey. We are focusing on two clusters at a redshift of 0.5, which benefit from previous deep photometric and spectroscopic observations. This will allow us to derive accurate stellar masses and star formation rates, in order to compare those galaxies to other surveys of the cold gas content of galaxies, either in the field or inside different clusters. We unveiled a new population of galaxies with normal star formation rates but less cold molecular gas than other galaxies at the same stellar mass. This could be an indication that the gas reservoir responsible for the star formation changes either in mass or properties, before the star formation is affected. We also noticed that galaxies with the lowest cold-molecular-gas-to-stellar-mass ratios are preferentially either in the cluster core or in overdensities away from the cluster, confirming the existence of a pre-processing in overdensities surrounding the cluster. But active galaxies inside or close to the cluster, do not always have depleted CO reservoir. This thesis opens up new prospects on the study of the cold gas content of galaxies at intermediate redshift. It showed the necessity to observe galaxies that are in a transition regime between star forming and passive, in order to understand how star formation is suppressed around clusters. Those results could be extended to much larger samples, with the help of the upcoming new generation of instruments such as the Square Kilometer Array.

Nonreciprocal wave propagation is important for signal processing and wave-based computing, but has not been realized in spin-wave devices. The authors engineer such nonreciprocity for spin waves in a transversely magnetized ferromagnetic bilayer so that the waves completely stop in one direction while still propagating with significant velocity in the opposite one. Electrical and optical measurements are combined with analytical and numerical modeling to provide a picture of the chiral mode hybridization responsible for this phenomenon. This work is an experimental realization of a magnonic diode and paves the way for designing complex spin-wave devices required for magnon computing.

International audience; Metamaterials, tunable artificial materials, are useful playgrounds to investigate magnetic systems. So far, artificial Ising spin systems have revealed unusual features like emergent magnetic monopoles[1,2] and charge fragmentation[3]. Here, we present a metasystem composed of a lattice of dipolarly-coupled nanomagnets. The magnetic spin of each nanomagnet is constrained to lie along a body diagonal, yielding four possible spin states. We show that the magnetic ordering of this metasystem (antiferromagnetic, ferromagnetic or spin-ice like) is determined by the spin states orientation relative to the underlying lattice. The dipolar four-state Potts model explains our experimental observations and sheds light on the role of symmetry, as well as short-and long-range dipolar magnetic interactions, in such non-Ising spin systems. Dipolar interactions in magnetic systems have been heavily studied because of their exotic physics and strongly affect essential technologies such as permanent magnets or hard disk drives [4-6]. In addition, statistical physics covers a host of applications ranging from fundamental physics to business analysis. In both cases, Ising model holds a central role. This two-spin state model has been widely used to grasp the essence of a variety of effects belonging to the field of condensed matter physics, such as phase transitions, spin glasses, magnetism, spin chains and geometric frustration. In 2006, Zhang and collaborators conducted the first experiments on artificial Ising spin systems at a

Équipe 101 : Nanomagnétisme et électronique de spin; International audience; The value and sign of V/Fe interface anisotropy are investigated. Epitaxial V/Fe/V/Au layers with different iron thicknesses were grown on single crystalline (001) MgO substrate by ultra high vacuum molecular beam epitaxy. Magnetometry was used to measure magnetization and out anisotropy field. From these values, we quantify the number of dead layers due to V/Fe or Fe/V interfaces, and compare it with the literature. We deduce that dead layers occur mostly at the bottom V/Fe interface. An average value for V/Fe and Fe/V interface anisotropy around 0 +/- 0.1 erg/cm(2) (mJ/m(2)) was thus deduced.

International audience; A crystal of emerging magnetic charges is expected in the phase diagram of the dipolar kagome spin ice. An observation of charge crystallites in thermally demagnetized artificial spin ice arrays has been recently reported by S. Zhang and coworkers and explained through the thermodynamics of the system as it approaches a charge-ordered state. Following a similar approach, we have generated a partial order of magnetic charges in an artificial kagome spin ice lattice made out of ferrimagnetic material having a Curie temperature of 475 K. A statistical study of the size of the charge domains reveals an unconventional sawtooth distribution. This distribution is in disagreement with the predictions of the thermodynamic model and is shown to be a signature of the kinetic process governing the remagnetization.

Importance Postoperative mortality after junctional and gastric adenocarcinoma resection remains a significant issue. Objective To identify factors predictive of mortality within 30 days of junctional and gastric adenocarcinoma resection in a large national multicenter cohort. Design A retrospective study collecting data from a multicenter database of patients who underwent resection for junctional and gastric adenocarcinoma from January 1, 1997, through January 31, 2010. A stepwise logistic regression model was built to identify, by multivariate analysis, variables independently predictive of 30-day postoperative mortality (POM). Setting Nineteen university teaching hospitals in France. Participants Two thousand six hundred seventy patients with available data. Main Outcome Measures The primary end point was POM. Secondary end points included (1) late mortality (30-90 days after resection) and (2) postoperative morbidity. Results One thousand eight hundred ninety-six patients (71.01%) had gastric adenocarcinoma and 774 (28.99%) had junctional tumors. Neoadjuvant treatment was given to 655 patients (24.53%), and 114 patients (4.27%) died within 30 days of surgery. Postoperative mortality was higher in patients who experienced grades III and IV toxic effects during neoadjuvant treatment compared with those who did not (8.7% vs 2.9%, respectively; P = .007). Multivariate analysis revealed metastatic disease at diagnosis (odds ratio, 9.13 [95% CI, 3.29-25.35]; P P = .02) as being independently predictive of POM. Centers performing at least 10 resections per year were found to be protective against POM (odds ratio, 0.29 [95% CI, 0.12-0.72]; P = .008). Conclusions and Relevance This large national cohort study confirms that advanced disease heightens the risk of POM; centralization of junctional and gastric adenocarcinoma resection is warranted. The novel finding that grades III to IV toxic effects during neoadjuvant therapy increase POM has significant implications for decision making in this subgroup of patients. Trial Registration clinicaltrials.gov Identifier:NCT01249859