@inbook{7303, abstract = {The electrolyte in the non-aqueous (aprotic) lithium air battery has a profound influence on the reactions that occur at the anode and cathode, and hence its overall operation on discharge/charge. It must possess a wide range of attributes, exceeding the requirements of electrolytes for Lithium ion batteries by far. The most important additional issues are stability at both anode and cathode in the presence of O2. The known problems with cycling the Li metal/non-aqueous electrolyte interface are further complicated by O2. New and much less understood are the reactions at the O2 cathode/electrolyte interface where the highly reversible formation/decomposition of Li2O2 on discharge/charge is critical for the operation of the non-aqueous lithium air battery. Many aprotic electrolytes exhibit decomposition at the cathode during discharge and charge due to the presence of reactive reduced O2 species affecting potential, capacity and kinetics on discharge and charge, cyclability and calendar life. Identifying suitable electrolytes is one of the key challenges for the non-aqueous lithium air battery at the present time. Following the realisation that cyclability of such cells in the initially used organic carbonate electrolytes is due to back-to-back irreversible reactions the stability of the non-aqueous electrolytes became a major focus of research on rechargeable lithium air batteries. This realisation led to the establishment of a suite of experimental and computational methods capable of screening the stability of electrolytes. These allow for greater mechanistic understanding of the reactivity and guide the way towards designing more stable systems. A range of electrolytes based on ethers, amides, sulfones, ionic liquids and dimethyl sulfoxide have been investigated. All are more stable than the organic carbonates, but not all are equally stable. Even though it was soon realised, by a number of groups, that ethers exhibit side reactions on discharge and charge, they still remain the choice in many studies. To date dimethyl sulfoxide and dimethylacetamide were identified as the most stable electrolytes. In conjunction with the investigation of electrolyte stability the importance of electrode stability became more prominent. The stability of the electrolyte cannot be considered in isolation. Its stability depends on the synergy between electrolyte and electrode. Carbon based electrodes promote electrolyte decomposition and decompose on their own. Although great progress has been made in only a few years, future work on aprotic electrolytes for Li-O2 batteries will need to explore other electrolytes in the quest for yet lower cost, higher safety, stability and low volatility.}, author = {Freunberger, Stefan Alexander and Chen, Yuhui and Bardé, Fanny and Takechi, Kensuke and Mizuno, Fuminori and Bruce, Peter G.}, booktitle = {The Lithium Air Battery: Fundamentals}, editor = {Imanishi, Nobuyuki and Luntz, Alan C. and Bruce, Peter}, isbn = {9781489980618}, pages = {23--58}, publisher = {Springer Nature}, title = {{Nonaqueous Electrolytes}}, doi = {10.1007/978-1-4899-8062-5_2}, year = {2014}, } @article{7304, abstract = {Lithium-air batteries have received extraordinary attention recently owing to their theoretical gravimetric energies being considerably higher than those of Li-ion batteries. There are, however, significant challenges to practical implementation, including low energy efficiency, cycle life, and power capability. These are due primarily to the lack of fundamental understanding of oxygen reduction and evolution reaction kinetics and parasitic reactions between oxygen redox intermediate species and nominally inactive battery components such as carbon in the oxygen electrode and electrolytes. In this article, we discuss recent advances in the mechanistic understanding of oxygen redox reactions in nonaqueous electrolytes and the search for electrolytes and electrode materials that are chemically stable in the oxygen electrode. In addition, methods to protect lithium metal against corrosion by water and dendrite formation in aqueous lithium-air batteries are discussed. Further materials innovations lie at the heart of research and development efforts that are needed to enable the development of lithium-oxygen batteries with enhanced round-trip efficiency and cycle life.}, author = {Kwabi, D.G. and Ortiz-Vitoriano, N. and Freunberger, Stefan Alexander and Chen, Y. and Imanishi, N. and Bruce, P.G. and Shao-Horn, Y.}, issn = {0883-7694}, journal = {MRS Bulletin}, number = {5}, pages = {443--452}, publisher = {CUP}, title = {{Materials challenges in rechargeable lithium-air batteries}}, doi = {10.1557/mrs.2014.87}, volume = {39}, year = {2014}, } @article{7305, abstract = {When lithium–oxygen batteries discharge, O2 is reduced at the cathode to form solid Li2O2. Understanding the fundamental mechanism of O2 reduction in aprotic solvents is therefore essential to realizing their technological potential. Two different models have been proposed for Li2O2 formation, involving either solution or electrode surface routes. Here, we describe a single unified mechanism, which, unlike previous models, can explain O2 reduction across the whole range of solvents and for which the two previous models are limiting cases. We observe that the solvent influences O2 reduction through its effect on the solubility of LiO2, or, more precisely, the free energy of the reaction LiO2* ⇌ Li(sol)+ + O2−(sol) + ion pairs + higher aggregates (clusters). The unified mechanism shows that low-donor-number solvents are likely to lead to premature cell death, and that the future direction of research for lithium–oxygen batteries should focus on the search for new, stable, high-donor-number electrolytes, because they can support higher capacities and can better sustain discharge.}, author = {Johnson, Lee and Li, Chunmei and Liu, Zheng and Chen, Yuhui and Freunberger, Stefan Alexander and Ashok, Praveen C. and Praveen, Bavishna B. and Dholakia, Kishan and Tarascon, Jean-Marie and Bruce, Peter G.}, issn = {1755-4330}, journal = {Nature Chemistry}, number = {12}, pages = {1091--1099}, publisher = {Springer Nature}, title = {{The role of LiO2 solubility in O2 reduction in aprotic solvents and its consequences for Li–O2 batteries}}, doi = {10.1038/nchem.2101}, volume = {6}, year = {2014}, } @article{7361, abstract = {Bistable switches are fundamental regulatory elements of complex systems, ranging from electronics to living cells. Designed genetic toggle switches have been constructed from pairs of natural transcriptional repressors wired to inhibit one another. The complexity of the engineered regulatory circuits can be increased using orthogonal transcriptional regulators based on designed DNA-binding domains. However, a mutual repressor-based toggle switch comprising DNA-binding domains of transcription-activator-like effectors (TALEs) did not support bistability in mammalian cells. Here, the challenge of engineering a bistable switch based on monomeric DNA-binding domains is solved via the introduction of a positive feedback loop composed of activators based on the same TALE domains as their opposing repressors and competition for the same DNA operator site. This design introduces nonlinearity and results in epigenetic bistability. This principle could be used to employ other monomeric DNA-binding domains such as CRISPR for applications ranging from reprogramming cells to building digital biological memory.}, author = {Lebar, Tina and Bezeljak, Urban and Golob, Anja and Jerala, Miha and Kadunc, Lucija and Pirš, Boštjan and Stražar, Martin and Vučko, Dušan and Zupančič, Uroš and Benčina, Mojca and Forstnerič, Vida and Gaber, Rok and Lonzarić, Jan and Majerle, Andreja and Oblak, Alja and Smole, Anže and Jerala, Roman}, issn = {2041-1723}, journal = {Nature Communications}, number = {1}, publisher = {Springer Nature}, title = {{A bistable genetic switch based on designable DNA-binding domains}}, doi = {10.1038/ncomms6007}, volume = {5}, year = {2014}, } @article{7455, abstract = {The reaction between NiO and (0001)- and ([1\bar102])-oriented Al2O3 single crystals has been investigated on model experimental systems by using the ReflEXAFS technique. Depth-sensitive information is obtained by collecting data above and below the critical angle for total reflection. A systematic protocol for data analysis, based on the recently developed CARD code, was implemented, and a detailed description of the reactive systems was obtained. In particular, for ([1\bar102])-oriented Al2O3, the reaction with NiO is almost complete after heating for 6 h at 1273 K, and an almost uniform layer of spinel is found below a mixed (NiO + spinel) layer at the very upmost part of the sample. In the case of the (0001)-oriented Al2O3, for the same temperature and heating time, the reaction shows a lower advancement degree and a residual fraction of at least 30% NiO is detected in the ReflEXAFS spectra. }, author = {Costanzo, Tommaso and Benzi, Federico and Ghigna, Paolo and Pin, Sonia and Spinolo, Giorgio and d'Acapito, Francesco}, issn = {1600-5775}, journal = {Journal of Synchrotron Radiation}, number = {2}, pages = {395--400}, publisher = {International Union of Crystallography}, title = {{Studying the surface reaction between NiO and Al2O3viatotal reflection EXAFS (ReflEXAFS)}}, doi = {10.1107/s1600577513031299}, volume = {21}, year = {2014}, } @misc{9888, abstract = {Detailed description of the experimental prodedures, data analyses and additional statistical analyses of the results.}, author = {Wolf, Stephan and Mcmahon, Dino and Lim, Ka and Pull, Christopher and Clark, Suzanne and Paxton, Robert and Osborne, Juliet}, publisher = {Public Library of Science}, title = {{Supporting information}}, doi = {10.1371/journal.pone.0103989.s003}, year = {2014}, } @article{9931, abstract = {Gene duplication is important in evolution, because it provides new raw material for evolutionary adaptations. Several existing hypotheses about the causes of duplicate retention and diversification differ in their emphasis on gene dosage, subfunctionalization, and neofunctionalization. Little experimental data exist on the relative importance of gene expression changes and changes in coding regions for the evolution of duplicate genes. Furthermore, we do not know how strongly the environment could affect this importance. To address these questions, we performed evolution experiments with the TEM-1 beta lactamase gene in Escherichia coli to study the initial stages of duplicate gene evolution in the laboratory. We mimicked tandem duplication by inserting two copies of the TEM-1 gene on the same plasmid. We then subjected these copies to repeated cycles of mutagenesis and selection in various environments that contained antibiotics in different combinations and concentrations. Our experiments showed that gene dosage is the most important factor in the initial stages of duplicate gene evolution, and overshadows the importance of point mutations in the coding region.}, author = {Dhar, Riddhiman and Bergmiller, Tobias and Wagner, Andreas}, issn = {1558-5646}, journal = {Evolution}, number = {6}, pages = {1775--1791}, publisher = {Wiley}, title = {{Increased gene dosage plays a predominant role in the initial stages of evolution of duplicate TEM-1 beta lactamase genes}}, doi = {10.1111/evo.12373}, volume = {68}, year = {2014}, } @misc{9932, abstract = {Gene duplication is important in evolution, because it provides new raw material for evolutionary adaptations. Several existing hypotheses about the causes of duplicate retention and diversification differ in their emphasis on gene dosage, sub-functionalization, and neo-functionalization. Little experimental data exists on the relative importance of gene expression changes and changes in coding regions for the evolution of duplicate genes. Furthermore, we do not know how strongly the environment could affect this importance. To address these questions, we performed evolution experiments with the TEM-1 beta lactamase gene in E. coli to study the initial stages of duplicate gene evolution in the laboratory. We mimicked tandem duplication by inserting two copies of the TEM-1 gene on the same plasmid. We then subjected these copies to repeated cycles of mutagenesis and selection in various environments that contained antibiotics in different combinations and concentrations. Our experiments showed that gene dosage is the most important factor in the initial stages of duplicate gene evolution, and overshadows the importance of point mutations in the coding region.}, author = {Dhar, Riddhiman and Bergmiller, Tobias and Wagner, Andreas}, publisher = {Dryad}, title = {{Data from: Increased gene dosage plays a predominant role in the initial stages of evolution of duplicate TEM-1 beta lactamase genes}}, doi = {10.5061/dryad.jc402}, year = {2014}, } @article{3263, abstract = {Adaptation in the retina is thought to optimize the encoding of natural light signals into sequences of spikes sent to the brain. While adaptive changes in retinal processing to the variations of the mean luminance level and second-order stimulus statistics have been documented before, no such measurements have been performed when higher-order moments of the light distribution change. We therefore measured the ganglion cell responses in the tiger salamander retina to controlled changes in the second (contrast), third (skew) and fourth (kurtosis) moments of the light intensity distribution of spatially uniform temporally independent stimuli. The skew and kurtosis of the stimuli were chosen to cover the range observed in natural scenes. We quantified adaptation in ganglion cells by studying linear-nonlinear models that capture well the retinal encoding properties across all stimuli. We found that the encoding properties of retinal ganglion cells change only marginally when higher-order statistics change, compared to the changes observed in response to the variation in contrast. By analyzing optimal coding in LN-type models, we showed that neurons can maintain a high information rate without large dynamic adaptation to changes in skew or kurtosis. This is because, for uncorrelated stimuli, spatio-temporal summation within the receptive field averages away non-gaussian aspects of the light intensity distribution.}, author = {Tkacik, Gasper and Ghosh, Anandamohan and Schneidman, Elad and Segev, Ronen}, journal = {PLoS One}, number = {1}, publisher = {Public Library of Science}, title = {{Adaptation to changes in higher-order stimulus statistics in the salamander retina}}, doi = {10.1371/journal.pone.0085841}, volume = {9}, year = {2014}, } @article{348, abstract = {Bi2S3-xTex bulk nanocomposites with crystal domain sizes in the range from 50 nm to 100 nm were obtained from the reaction of Bi2S3 nanorods with Te powder. The thermoelectric properties of the obtained nanocomposites were analysed in the temperature range from 0°C to 300°C. We observed how the thermoelectric properties of the material improved with the annealing temperature, being a spark plasma sintering process needed to maintain the material nanostructuration while maximising its electrical properties. Finally thermoelectric dimensionless figures of merit ZT up to 0.42 were obtained before any charge carrier concentration optimisation. Copyright © 2014 Inderscience Enterprises Ltd. }, author = {Cadavid, Doris and Ibáñez, Maria and Anselmi Tamburini, Umberto and Durá, Oscar and De La Torre, Marco and Cabot, Andreu}, journal = {International Journal of Nanotechnology}, number = {9-11}, pages = {773 -- 784}, publisher = {Inderscience Enterprises Limited }, title = {{Thermoelectric properties of bottom up assembled Bi2S 3-xTex nanocomposites}}, doi = {10.1504/IJNT.2014.063787}, volume = {11}, year = {2014}, } @article{349, abstract = {Thermoelectricity is a key technology with the potential to improve the efficiency of energy conversion processes, which may strongly benefit from advances in the field of nanotechnology. Nanostructured materials are very appealing for thermoelectric applications, but the full development of their potential requires precise control of their properties at the nanoscale. Bottom-up assembly of nanoparticles provides access to a three-dimensional composition control at the nanoscale not attainable in any other technology. In particular, colloidal nanoheterostructures are especially interesting building blocks for the bottom-up production of functional nanomaterials. In the present work, we use PbTe@PbS core-shell nanoparticles as building blocks for the bottom-up production of PbTe-PbS nanocomposites. We used a ligand exchange strategy and a hot press process to promote the electrical conductivity of the nanocomposite and to increase its density. These two approaches allowed us to improve the performance of bottom-up assembled PbTe-PbS bulk nanostructured materials. }, author = {Ortega, Silvia and Ibáñez, Maria and Cadavid, Doris and Cabot, Andreu}, journal = {International Journal of Nanotechnology}, number = {9-11}, pages = {955 -- 970}, publisher = {Inderscience Enterprises Limited }, title = {{Bottom up processing of PbTe PbS thermoelectric nanocomposites}}, doi = {10.1504/IJNT.2014.063802}, volume = {11}, year = {2014}, } @article{350, abstract = {Herein, a colloidal synthetic route to produce highly monodisperse Cu2HgGeSe4 (CHGSe) nanoparticles (NPs) is presented in detail. The high yield of the developed procedure allowed the production of CHGSe NPs at the gram scale. A thorough analysis of their structural and optical properties is shown. CHGSe NPs displayed poly-tetrahedral morphology and narrow size distributions with average size in the range of 10–40 nm and size dispersions below 10 %. A 1.6 eV optical band gap was measured by mean of UV–Vis. By adjusting the cation ratio, an effective control of their electrical conductivity is achieved. The prepared NPs are used as building blocks for the production of CHGSe bulk nanostructured materials. The thermoelectric properties of CHGSe nanomaterials are studied in the temperature range from 300 to 730 K. CHGSe nanomaterials reached electrical conductivities up to 5 × 104 S m−1, Seebeck coefficients above 100 μV K−1, and thermal conductivities below 1.0 W m−1 K−1 which translated into thermoelectric figures of merit up to 0.34 at 730 K.}, author = {Li, Wenhua and Ibáñez, Maria and Cadavid, Doris and Zamani, Reza and Rubio Garcia, Javier and Gorsse, Stéphane and Morante, Joan and Arbiol, Jordi and Cabot, Andreu}, journal = {Journal of Nanoparticle Research}, number = {3}, publisher = {Kluwer}, title = {{Colloidal synthesis and functional properties of quaternary Cu based semiconductors: Cu2HgGeSe4}}, doi = {10.1007/s11051-014-2297-2}, volume = {16}, year = {2014}, } @article{358, abstract = {Monodispersed Pt3Sn nanoparticles were prepared through a mild thermal synthesis in the presence of surfactants. The performance of Pt3Sn for the electrooxidation of ethanol and adsorbed carbon monoxide (COad) in acid medium was studied by a combination of electrochemical and insitu spectroscopic methods, namely, infrared reflection absorption spectroscopy and differential electrochemical mass spectrometry (DEMS), and the results were compared to those obtained with the use of Pt black. The formation of the Pt3Sn solid solution promoted the oxidation of COad at less-positive potentials than those required for Pt black. Also, the electrooxidation of ethanol, especially at lower potentials, was more favorable with Pt3Sn, as deduced from the higher faradaic currents recorded during the ethanol oxidation reaction (EOR). However, the distribution of products as deduced by DEMS analysis suggested that the formation of C1 products, CO2 inclusive, is less significant on Pt3Sn than on Pt. In fact, the higher faradaic current recorded with the former catalyst can be attributed to the greater amounts of acetaldehyde and acetic acid formed. After the EOR, the surface of both Pt and Pt3Sn remained covered by ethanol adsorbates. Whereas C2 fragments were the main adsorbates at the surface of Pt3Sn after the EOR, both C1 and C2 species remained adsorbed at Pt black.}, author = {Herranz, Tirma and Ibáñez, Maria and Gómez De La Fuente, José and Pérez Alonso, Francisco and Peña, Miguel and Cabot, Andreu and Rojas, Sergio}, journal = {ChemElectroChem}, number = {5}, pages = {885 -- 895}, publisher = {Wiley-Blackwell}, title = {{In situ study of ethanol electrooxidation on monodispersed Pt inf 3 inf Sn nanoparticles}}, doi = {10.1002/celc.201300254}, volume = {1}, year = {2014}, } @article{359, abstract = {An appropriate way of realizing property nanoengineering in complex quaternary chalcogenide nanocrystals is presented for Cu2Cd xSnSey(CCTSe) polypods. The pivotal role of the polarity in determining morphology, growth, and the polytypic branching mechanism is demonstrated. Polarity is considered to be responsible for the formation of an initial seed that takes the form of a tetrahedron with four cation-polar facets. Size and shape confinement of the intermediate pentatetrahedral seed is also attributed to polarity, as their external facets are anion-polar. The final polypod extensions also branch out as a result of a cation-polarity-driven mechanism. Aberration-corrected scanning transmission electron microscopy is used to identify stannite cation ordering, while ab initio studies are used to show the influence of cation ordering/distortion, stoichiometry, and polytypic structural change on the electronic band structure.}, author = {Zamani, Reza and Ibáñez, Maria and Luysberg, Martina and García Castelló, Nuria and Houben, Lothar and Prades, Joan and Grillo, Vincenzo and Dunin Borkowski, Rafal and Morante, Joan and Cabot, Andreu and Arbiol, Jordi}, journal = {ACS Nano}, number = {3}, pages = {2290 -- 2301}, publisher = {American Chemical Society}, title = {{Polarity-driven polytypic branching in Cu-based quaternary chalcogenide nanostructures}}, doi = {10.1021/nn405747h}, volume = {8}, year = {2014}, } @article{1733, abstract = {The classical (boolean) notion of refinement for behavioral interfaces of system components is the alternating refinement preorder. In this paper, we define a distance for interfaces, called interface simulation distance. It makes the alternating refinement preorder quantitative by, intuitively, tolerating errors (while counting them) in the alternating simulation game. We show that the interface simulation distance satisfies the triangle inequality, that the distance between two interfaces does not increase under parallel composition with a third interface, that the distance between two interfaces can be bounded from above and below by distances between abstractions of the two interfaces, and how to synthesize an interface from incompatible requirements. We illustrate the framework, and the properties of the distances under composition of interfaces, with two case studies.}, author = {Cerny, Pavol and Chmelik, Martin and Henzinger, Thomas A and Radhakrishna, Arjun}, journal = {Theoretical Computer Science}, number = {3}, pages = {348 -- 363}, publisher = {Elsevier}, title = {{Interface simulation distances}}, doi = {10.1016/j.tcs.2014.08.019}, volume = {560}, year = {2014}, } @article{17614, abstract = {The first generation of stars produces a background of Lyman–Werner (LW) radiation which can photodissociate molecular hydrogen, increasing the mass of dark matter haloes required to host star formation. Previous studies have determined the critical mass required for efficient molecular cooling with a constant LW background. However, the true background is expected to increase rapidly at early times. Neglecting this evolution could underestimate star formation in small haloes that may have started to cool in the past when the LW intensity was much lower. Background evolution is a large source of uncertainty in pre-reionization predictions of the cosmological 21cm signal, which can be observed with future radio telescopes. To address this, we perform zero-dimensional one-zone calculations that follow the density, chemical abundances, and temperature of gas in the central regions of dark matter haloes, including hierarchical growth and an evolving LW background. We begin by studying the physics of haloes subjected to a background that increases exponentially with redshift. We find that when the intensity increases more slowly than JLW(z)∝10−z/5, cooling in the past is a relatively small effect. We then self-consistently compute the cosmological LW background over z = 15–50 and find that cooling in the past due to an evolving background has a modest impact. Finally, we compare these results to three-dimensional hydrodynamical cosmological simulations with varying LW histories. While only a small number of haloes were simulated, the results are consistent with our one-zone calculations.}, author = {Visbal, Eli and Haiman, Zoltán and Terrazas, Bryan and Bryan, Greg L. and Barkana, Rennan}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {1}, pages = {107--114}, publisher = {Oxford University Press}, title = {{High-redshift star formation in a time-dependent Lyman–Werner background}}, doi = {10.1093/mnras/stu1710}, volume = {445}, year = {2014}, } @article{17617, abstract = {Most standard descriptions of Type II migration state that massive, gap-opening planets must migrate at the viscous drift rate. This is based on the idea that the disk is separated into an inner and outer region and gas is considered unable to cross the gap. In fact, gas easily crosses the gap on horseshoe orbits, nullifying this necessary premise which would set the migration rate. In this work, it is demonstrated using highly accurate numerical calculations that the actual migration rate is dependent on disk and planet parameters, and can be significantly larger or smaller than the viscous drift rate. In the limiting case of a disk much more massive than the secondary, the migration rate saturates to a constant that is sensitive to disk parameters and is not necessarily of the order of the viscous rate. In the opposite limit of a low-mass disk, the migration rate decreases linearly with disk mass. Steady-state solutions in the low disk mass limit show no pile-up outside the secondary's orbit, and no corresponding drainage of the inner disk.}, author = {Duffell, Paul C. and Haiman, Zoltán and MacFadyen, Andrew I. and D'Orazio, Daniel J. and Farris, Brian D.}, issn = {2041-8213}, journal = {The Astrophysical Journal}, number = {1}, publisher = {American Astronomical Society}, title = {{The migration of gap-opening planets is not locked to viscous disk evolution}}, doi = {10.1088/2041-8205/792/1/l10}, volume = {792}, year = {2014}, } @article{17620, abstract = {We present the results of two-dimensional (2D) hydrodynamical simulations of circumbinary disk accretion using the finite-volume code DISCO. This code solves the 2D viscous Navier–Stokes equations on a high-resolution moving mesh which shears with the fluid flow, greatly reducing advection errors in comparison with a fixed grid. We perform a series of simulations for binary mass ratios in the range 0.026 ⩽ q ⩽ 1.0, each lasting longer than a viscous time so that we reach a quasi-steady accretion state. In each case, we find that gas is efficiently stripped from the inner edge of the circumbinary disk and enters the cavity along accretion streams, which feed persistent "mini disks" surrounding each black hole. We find that for q ≳ 0.1, the binary excites eccentricity in the inner region of the circumbinary disk, creating an overdense lump which gives rise to enhanced periodicity in the accretion rate. The dependence of the periodicity on mass ratio may provide a method for observationally inferring mass ratios from measurements of the accretion rate. We also find that for all mass ratios studied, the magnitude of the accretion onto the secondary is sufficient to drive the binary toward larger mass ratio. This suggests a mechanism for biasing mass-ratio distributions toward equal mass.}, author = {Farris, Brian D. and Duffell, Paul and MacFadyen, Andrew I. and Haiman, Zoltán}, issn = {0004-637X}, journal = {The Astrophysical Journal}, number = {2}, publisher = {American Astronomical Society}, title = {{Binary black hole accretion from a circumbinary disk: Gas dynamics inside the central cavity}}, doi = {10.1088/0004-637x/783/2/134}, volume = {783}, year = {2014}, } @article{17623, abstract = {Residual errors in shear measurements, after corrections for instrument systematics and atmospheric effects, can impact cosmological parameters derived from weak lensing observations. Here we combine convergence maps from our suite of ray-tracing simulations with random realizations of spurious shear. This allows us to quantify the errors and biases of the triplet (Ωm,w,σ8) derived from the power spectrum (PS), as well as from three different sets of non-Gaussian statistics of the lensing convergence field: Minkowski functionals (MF), low--order moments (LM), and peak counts (PK). Our main results are: (i) We find an order of magnitude smaller biases from the PS than in previous work. (ii) The PS and LM yield biases much smaller than the morphological statistics (MF, PK). (iii) For strictly Gaussian spurious shear with integrated amplitude as low as its current estimate of σ2sys≈10−7, biases from the PS and LM would be unimportant even for a survey with the statistical power of LSST. However, we find that for surveys larger than ≈100 deg2, non-Gaussianity in the noise (not included in our analysis) will likely be important and must be quantified to assess the biases. (iv) The morphological statistics (MF,PK) introduce important biases even for Gaussian noise, which must be corrected in large surveys. The biases are in different directions in (Ωm,w,σ8) parameter space, allowing self-calibration by combining multiple statistics. Our results warrant follow-up studies with more extensive lensing simulations and more accurate spurious shear estimates.}, author = {Petri, Andrea and May, Morgan and Haiman, Zoltán and Kratochvil, Jan M.}, issn = {1550-7998}, journal = {Physical Review D}, number = {12}, publisher = {American Physical Society}, title = {{Impact of spurious shear on cosmological parameter estimates from weak lensing observables}}, doi = {10.1103/physrevd.90.123015}, volume = {90}, year = {2014}, } @article{17625, abstract = {We present the results of 2D, moving mesh, viscous hydrodynamical simulations of accretion on to merging supermassive black hole (SMBH) binaries. We include viscous heating, shock heating, and radiative cooling, and simulate the transition from the ‘pre-decoupling’ epoch, where the inspiral time-scale is longer than the viscous time-scale, to the ‘post-decoupling’ epoch, where the inspiral time-scale is shorter than the viscous time-scale. We find that there is no abrupt halt to the accretion at decoupling, but rather the accretion shows a slow decay, with significant accretion well after the expected decoupling. Moreover, we find that the luminosity in X-rays is significantly higher prior to the merger, as orbital energy from the SMBH binary is converted to heat via strong shocks inside the cavity, and radiated away. Following the merger, the cavity refills viscously and the accretion rate relaxes to the Shakura–Sunyaev value, while the X-ray luminosity drops as the shocks quickly dissipate.}, author = {Farris, Brian D. and Duffell, Paul and MacFadyen, Andrew I. and Haiman, Zoltán}, issn = {1745-3933}, journal = {Monthly Notices of the Royal Astronomical Society: Letters}, number = {1}, pages = {L80--L84}, publisher = {Oxford University Press}, title = {{Binary black hole accretion during inspiral and merger}}, doi = {10.1093/mnrasl/slu184}, volume = {447}, year = {2014}, }