@misc{9757, abstract = {To fight infectious diseases, host immune defences are employed at multiple levels. Sanitary behaviour, such as pathogen avoidance and removal, acts as a first line of defence to prevent infection [1] before activation of the physiological immune system. Insect societies have evolved a wide range of collective hygiene measures and intensive health care towards pathogen-exposed group members [2]. One of the most common behaviours is allogrooming, in which nestmates remove infectious particles from the body surfaces of exposed individuals [3]. Here we show that, in invasive garden ants, grooming of fungus-exposed brood is effective beyond the sheer mechanical removal of fungal conidiospores as it also includes chemical disinfection through the application of poison produced by the ants themselves. Formic acid is the main active component of the poison. It inhibits fungal growth of conidiospores remaining on the brood surface after grooming and also those collected in the mouth of the grooming ant. This dual function is achieved by uptake of the poison droplet into the mouth through acidopore self-grooming and subsequent application onto the infectious brood via brood grooming. This extraordinary behaviour extends current understanding of grooming and the establishment of social immunity in insect societies.}, author = {Tragust, Simon and Mitteregger, Barbara and Barone, Vanessa and Konrad, Matthias and Ugelvig, Line V and Cremer, Sylvia}, publisher = {Dryad}, title = {{Data from: Ants disinfect fungus-exposed brood by oral uptake and spread of their poison}}, doi = {10.5061/dryad.61649}, year = {2012}, } @misc{9758, abstract = {We propose a two-step procedure for estimating multiple migration rates in an approximate Bayesian computation (ABC) framework, accounting for global nuisance parameters. The approach is not limited to migration, but generally of interest for inference problems with multiple parameters and a modular structure (e.g. independent sets of demes or loci). We condition on a known, but complex demographic model of a spatially subdivided population, motivated by the reintroduction of Alpine ibex (Capra ibex) into Switzerland. In the first step, the global parameters ancestral mutation rate and male mating skew have been estimated for the whole population in Aeschbacher et al. (Genetics 2012; 192: 1027). In the second step, we estimate in this study the migration rates independently for clusters of demes putatively connected by migration. For large clusters (many migration rates), ABC faces the problem of too many summary statistics. We therefore assess by simulation if estimation per pair of demes is a valid alternative. We find that the trade-off between reduced dimensionality for the pairwise estimation on the one hand and lower accuracy due to the assumption of pairwise independence on the other depends on the number of migration rates to be inferred: the accuracy of the pairwise approach increases with the number of parameters, relative to the joint estimation approach. To distinguish between low and zero migration, we perform ABC-type model comparison between a model with migration and one without. Applying the approach to microsatellite data from Alpine ibex, we find no evidence for substantial gene flow via migration, except for one pair of demes in one direction.}, author = {Aeschbacher, Simon and Futschik, Andreas and Beaumont, Mark}, publisher = {Dryad}, title = {{Data from: Approximate Bayesian computation for modular inference problems with many parameters: the example of migration rates}}, doi = {10.5061/dryad.274b1}, year = {2012}, } @article{338, abstract = {The ample chemical and structural freedom of quaternary compounds permits engineering materials that fulfill the requirements of a wide variety of applications. In this work, the mechanisms to achieve unprecedented size, shape, and composition control in quaternary nanocrystals are detailed. The described procedure allows obtaining tetrahedral and penta-tetrahedral quaternary nanocrystals with tuned size distributions and controlled compositions from a plethora of I 2-II-IV-VI 4 semiconductors.}, author = {Ibáñez, Maria and Zamani, Reza and Li, Wenhua and Shavel, Alexey and Arbiol, Jordi and Morante, Joan and Cabot, Andreu}, journal = {Crystal Growth and Design }, number = {3}, pages = {1085 -- 1090}, publisher = {American Chemical Society (ACS)}, title = {{Extending the nanocrystal synthesis control to quaternary compositions}}, doi = {10.1021/cg201709c}, volume = {12}, year = {2012}, } @article{339, abstract = {A high-yield and upscalable colloidal synthesis route for the production of quaternary I 2-II-IV-VI 4 nanocrystals, particularly stannite Cu 2+xCd 1-xSnSe 4, with narrow size distribution and precisely controlled composition is presented. It is also shown here how the diversity of valences in the constituent elements allows an effective control of their electrical conductivity through the adjustment of the cation ratios. At the same time, while the crystallographic complexity of quaternary chalcogenides is associated with intrinsically low thermal conductivities, the reduction of the lattice dimensions to the nanoscale further reduces the materials thermal conductivity. In the specific case of the stannite crystal structure, a convenient slab distribution of the valence band maximum states permits a partial decoupling of the p-type electrical conductivity from both the Seebeck coefficient and the thermal conductivity. Combining these features, we demonstrate how an initial optimization of the nanocrystals Cd/Cu ratio allowed us to obtain low-temperature solution-processed materials with ZT values up to 0.71 at 685 K.}, author = {Ibáñez, Maria and Cadavid, Doris and Zamani, Reza and García Castelló, Nuria and Izquierdo Roca, Victora and Li, Wenhua and Fairbrother, Andrew and Prades, Joan and Shavel, Alexey and Arbiol, Jordi and Pérez Rodríguez, Alejandro and Morante, Joan and Cabot, Andreu}, journal = {Chemistry of Materials}, number = {3}, pages = {562 -- 570}, publisher = {American Chemical Society}, title = {{Composition control and thermoelectric properties of quaternary chalcogenide nanocrystals: The case of stannite Cu2CdSnSe4}}, doi = {10.1021/cm2031812}, volume = {24}, year = {2012}, } @article{340, abstract = {A procedure for the continuous production of Cu 2ZnSnS 4 (CZTS) nanoparticles with controlled composition is presented. CZTS nanoparticles were prepared through the reaction of the metals' amino complexes with elemental sulfur in a continuous-flow reactor at moderate temperatures (300-330 °C). High-resolution transmission electron microscopy and X-ray diffraction analysis showed the nanocrystals to have a crystallographic structure compatible with that of the kesterite. Chemical characterization of the materials showed the presence of the four elements in each individual nanocrystal. Composition control was achieved by adjusting the solution flow rate through the reactor and the proper choice of the nominal precursor concentration within the flowing solution. Single-particle analysis revealed a composition distribution within each sample, which was optimized at the highest synthesis temperatures used. }, author = {Shavel, Alexey and Cadavid, Doris and Ibáñez, Maria and Carrete, Alex and Cabot, Andreu}, journal = {Journal of the American Chemical Society}, number = {3}, pages = {1438 -- 1441}, publisher = {ACS}, title = {{Continuous production of Cu inf 2 inf ZnSnS inf 4 inf nanocrystals in a flow reactor}}, doi = {10.1021/ja209688a}, volume = {134}, year = {2012}, } @article{345, abstract = {Nanocomposites are highly promising materials to enhance the efficiency of current thermoelectric devices. A straightforward and at the same time highly versatile and controllable approach to produce nanocomposites is the assembly of solution-processed nanocrystal building blocks. The convenience of this bottom-up approach to produce nanocomposites with homogeneous phase distributions and adjustable composition is demonstrated here by blending Ag2Te and PbTe colloidal nanocrystals to form Ag2Te–PbTe bulk nanocomposites. The thermoelectric properties of these nanocomposites are analyzed in the temperature range from 300 to 700 K. The evolution of their electrical conductivity and Seebeck coefficient is discussed in terms of the blend composition and the characteristics of the constituent materials. }, author = {Cadavid, Doris and Ibáñez, Maria and Gorsse, Stéphane and López, Antonio and Cirera, Albert and Morante, Joan and Cabot, Andreu}, journal = {Journal of Nanoparticle Research}, number = {12}, publisher = {Kluwer}, title = {{Bottom-up processing of thermoelectric nanocomposites from colloidal nanocrystal building blocks: The case of Ag2Te–PbTe}}, doi = {10.1007/s11051-012-1328-0}, volume = {14}, year = {2012}, } @article{346, abstract = {Arrays of vertically aligned ZnO : Cl/TiO2 and ZnO : Cl/ZnxTiOy/TiO2 core–shell nanowires (NWs) were prepared by means of the combination of two solution-growth processes. First, single-crystal ZnO NWs with controlled n-type doping were grown on conducting substrates by a low-cost, high-yield and seed-free electrochemical route. These NWs were covered by a titanium oxide shell of tunable thickness mediating successive adsorption-hydrolysis-condensation steps. Using this atomic-layer growth procedure, titania shells with controlled thickness and the anatase TiO2 phase were obtained after sintering at 450 °C. Higher sintering temperatures resulted in the formation of ZnO : Cl/ZnxTiOy/TiO2 core–shell NWs by the interdiffusion of Zn and Ti ions at the ZnO–TiO2 interface. The performance of ZnO : Cl/TiO2 and ZnO : Cl/ZnxTiOy/TiO2 core–shell NWs towards photoelectrochemical (PEC) water splitting was investigated as a function of the titania shell thickness. Furthermore, the performance of such core–shell NWs as photoelectrodes in dye-sensitized solar cells was also characterized. The TiO2 presence at the ZnO : Cl surface promoted a two-fold increase on the produced photocurrent densities, probing their potential for PEC and optoelectronic applications. Electrochemical impedance spectroscopy was used to corroborate the lower resistance for charge transfer between the NWs and the electrolyte in the presence of the TiO2 shell.}, author = {Fan, Jiandong and Zamani, Reza and Fábrega, Cristina and Shavel, Alexey and Flox, Cristina and Ibáñez, Maria and Andreu, Teresa and López, Amtonio and Arbiol, Jordi and Morante, Joan and Cabot, Andreu}, journal = {Journal of Physics D: Applied Physics}, number = {41}, publisher = {IOP Publishing Ltd.}, title = {{Solution-growth and optoelectronic performance of ZnO : Cl/TiO2 and ZnO : Cl/ZnxTiOy/TiO2 core–shell nanowires with tunable shell thickness}}, doi = {10.1088/0022-3727/45/41/415301}, volume = {45}, year = {2012}, } @article{347, abstract = {A synthetic route for producing Cu 2ZnGeSe 4 nanocrystals with narrow size distributions and controlled composition is presented. These nanocrystals were used to produce densely packed nanomaterials by hot-pressing. From the characterization of the thermoelectric properties of these nanomaterials, Cu 2ZnGeSe 4 is demonstrated to show excellent thermoelectric properties. A very preliminary adjustment of the nanocrystal composition has already resulted in a figure of merit of up to 0.55 at 450°C. }, author = {Ibáñez, Maria and Zamani, Reza and Lalonde, Aaron and Cadavid, Doris and Li, Wenhua and Shavel, Alexey and Arbiol, Jordi and Morante, Joan and Gorsse, Stéphane and Snyder, G Jeffrey and Cabot, Andreu}, journal = {Journal of the American Chemical Society}, number = {9}, pages = {4060 -- 4063}, publisher = {ACS}, title = {{Cu 2ZnGeSe 4 nanocrystals: Synthesis and thermoelectric properties}}, doi = {10.1021/ja211952z}, volume = {134}, year = {2012}, } @article{377, abstract = {The potential to control the composition and crystal phase at the nanometer scale enable the production of nanocrystalline materials with enhanced functionalities and new applications. In the present work, we detail a novel colloidal synthesis route to prepare nanoparticles of the ternary semiconductor Cu2GeSe3 (CGSe) with nanometer-scale control over their crystal phases. We also demonstrate the structural effect on the thermoelectric properties of bottom-up-prepared CGSe nanomaterials. By careful adjustment of the nucleation and growth temperatures, pure orthorhombic CGSe nanoparticles with cationic order or polytypic CGSe nanoparticles with disordered cation positions can be produced. In this second type of nanoparticle, a high density of twins can be created to periodically change the atomic plane stacking, forming a hexagonal wurtzite CGSe phase. The high yield of the synthetic routes reported here allows the production of single-phase and multiphase CGSe nanoparticles in the gram scale, which permits characterization of the thermoelectric properties of these materials. Reduced thermal conductivities and a related 2.5-fold increase of the thermoelectric figure of merit for multiphase nanomaterials compared to pure-phase CGSe are systematically obtained. These results are discussed in terms of the density and efficiency of phonon scattering centers in both types of materials.}, author = {Ibáñez, Maria and Zamani, Reza and Li, Wenhua and Cadavid, Doris and Gorse, Stéphane and Katchoi, Nebll and Shavel, Alexey and López, Antonioo and Morante, Joan and Arbiol, Jordi and Cabot, Andreu}, journal = {Chemistry of Materials}, number = {23}, pages = {4615 -- 4622}, publisher = {American Chemical Society}, title = {{Crystallographic control at the nanoscale to enhance functionality: Polytypic Cu2GeSe3 nanoparticles as thermoelectric materials}}, doi = {10.1021/cm303252q}, volume = {24}, year = {2012}, } @article{3836, abstract = {Hierarchical Timing Language (HTL) is a coordination language for distributed, hard real-time applications. HTL is a hierarchical extension of Giotto and, like its predecessor, based on the logical execution time (LET) paradigm of real-time programming. Giotto is compiled into code for a virtual machine, called the EmbeddedMachine (or E machine). If HTL is targeted to the E machine, then the hierarchicalprogram structure needs to be flattened; the flattening makes separatecompilation difficult, and may result in E machinecode of exponential size. In this paper, we propose a generalization of the E machine, which supports a hierarchicalprogram structure at runtime through real-time trigger mechanisms that are arranged in a tree. We present the generalized E machine, and a modular compiler for HTL that generates code of linear size. The compiler may generate code for any part of a given HTL program separately in any order.}, author = {Ghosal, Arkadeb and Iercan, Daniel and Kirsch, Christoph and Henzinger, Thomas A and Sangiovanni Vincentelli, Alberto}, journal = {Science of Computer Programming}, number = {2}, pages = {96 -- 112}, publisher = {Elsevier}, title = {{Separate compilation of hierarchical real-time programs into linear-bounded embedded machine code}}, doi = {10.1016/j.scico.2010.06.004}, volume = {77}, year = {2012}, } @article{3846, abstract = {We summarize classical and recent results about two-player games played on graphs with ω-regular objectives. These games have applications in the verification and synthesis of reactive systems. Important distinctions are whether a graph game is turn-based or concurrent; deterministic or stochastic; zero-sum or not. We cluster known results and open problems according to these classifications.}, author = {Chatterjee, Krishnendu and Henzinger, Thomas A}, journal = {Journal of Computer and System Sciences}, number = {2}, pages = {394 -- 413}, publisher = {Elsevier}, title = {{A survey of stochastic ω regular games}}, doi = {10.1016/j.jcss.2011.05.002}, volume = {78}, year = {2012}, } @article{387, abstract = {In this Letter we present detailed study of the density of states near defects in Bi 2Se 3. In particular, we present data on the commonly found triangular defects in this system. While we do not find any measurable quasiparticle scattering interference effects, we do find localized resonances, which can be well fitted by theory once the potential is taken to be extended to properly account for the observed defects. The data together with the fits confirm that while the local density of states around the Dirac point of the electronic spectrum at the surface is significantly disrupted near the impurity by the creation of low-energy resonance state, the Dirac point is not locally destroyed. We discuss our results in terms of the expected protected surface state of topological insulators. © 2012 American Physical Society.}, author = {Alpichshev, Zhanybek and Biswas, Rudro and Balatsky, Alexander and Analytis, James and Chu, Jiunhaw and Fisher, Ian and Kapitulnik, Aharon}, journal = {Physical Review Letters}, number = {20}, publisher = {American Physical Society}, title = {{STM imaging of impurity resonances on Bi 2Se 3}}, doi = {10.1103/PhysRevLett.108.206402}, volume = {108}, year = {2012}, }