@article{17653, abstract = {Observations of quasars at redshifts z > 6 reveal that 10^9 Msol supermassive black holes (SMBHs) had already formed when the Universe was < 0.9 Gyr old. One hypothesis for the origins of these SMBHs is that they grew from the remnants of the first generation of massive stars, which formed in low-mass (~ 10^5 to 10^6 Msol) dark matter minihaloes at z > 20. This is the regime where baryonic streaming motions--the relative velocities of baryons with respect to dark matter in the early Universe--most strongly inhibit star formation by suppressing gas infall and cooling. We investigate the impact of this effect on the growth of the first SMBHs using a suite of high-fidelity, ellipsoidal-collapse Monte Carlo merger-tree simulations. We find that the suppression of seed BH formation by the streaming motions significantly reduces the number density of the most massive BHs at z > 15, but the residual effect at lower redshifts is essentially negligible. The streaming motions can reduce by a factor of few the number density of the most luminous quasars at z ~ 10-11, where such objects could be detected by the James Webb Space Telescope. We conclude, with minor theoretical caveats, that baryonic streaming motions are unlikely to pose a significant additional obstacle to the formation of the observed high-redshift quasar SMBHs. Nor do they appreciably affect the heating and reionization histories of the Universe or the merger rates of nuclear BHs in the mass and redshift ranges of interest for proposed gravitational-wave detectors.}, author = {Tanaka, Takamitsu L. and Li, Miao and Haiman, Zoltán}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3559--3567}, publisher = {Oxford University Press}, title = {{The effect of baryonic streaming motions on the formation of the first supermassive black holes}}, doi = {10.1093/mnras/stt1553}, volume = {435}, year = {2013}, } @article{17995, abstract = {We have measured the single-molecule conductance of a family of bithiophene derivatives terminated with methyl sulfide gold-binding linkers using a scanning tunneling microscope based break-junction technique. We find a broad distribution in the single-molecule conductance of bithiophene compared with that of a methyl sulfide terminated biphenyl. Using a combination of experiments and calculations, we show that this increased breadth in the conductance distribution is explained by the difference in 5-fold symmetry of thiophene rings as compared to the 6-fold symmetry of benzene rings. The reduced symmetry of thiophene rings results in a restriction on the torsion angle space available to these molecules when bound between two metal electrodes in a junction, causing each molecular junction to sample a different set of conformers in the conductance measurements. In contrast, the rotations of biphenyl are essentially unimpeded by junction binding, allowing each molecular junction to sample similar conformers. This work demonstrates that the conductance of bithiophene displays a strong dependence on the conformational fluctuations accessible within a given junction configuration, and that the symmetry of such small molecules can significantly influence their conductance behaviors.}, author = {Dell, Emma J. and Capozzi, Brian and DuBay, Kateri H. and Berkelbach, Timothy C. and Moreno, Jose Ricardo and Reichman, David R. and Venkataraman, Latha and Campos, Luis M.}, issn = {1520-5126}, journal = {Journal of the American Chemical Society}, number = {32}, pages = {11724--11727}, publisher = {American Chemical Society}, title = {{Impact of molecular symmetry on single-molecule conductance}}, doi = {10.1021/ja4055367}, volume = {135}, year = {2013}, } @article{7595, abstract = {Inositol 1,3,4-trisphosphate 5/6 kinase (ITPK) phosphorylates inositol 1,3,4-trisphosphate to form inositol 1,3,4,5-tetrakisphosphate and inositol 1,3,4,6-tetrakisphosphate which can be finally transferred to inositol hexaphosphate (IP6) and play important roles during plant growth and development. There are 4 putative ITPK members in Arabidopsis. Expression pattern analysis showed that ITPK2 is constitutively expressed in various tissues. A T-DNA knockout mutant of ITPK2 was identified and scanning electron microscopy (SEM) analysis showed that the epidermis structure of seed coat was irregularly formed in seeds of itpk2-1 mutant, resulting in the increased permeability of seed coat to tetrazolium salts. Further analysis by gas chromatography coupled with mass spectrometry of lipid polyester monomers in cell wall confirmed a dramatic decrease in composition of suberin and cutin, which relate to the permeability of seed coat and the formation of which is accompanied with seed coat development. These results indicate that ITPK2 plays an essential role in seed coat development and lipid polyester barrier formation.}, author = {Tang, Yong and Tan, Shutang and Xue, Hongwei}, issn = {1745-7270}, journal = {Acta Biochimica et Biophysica Sinica}, number = {7}, pages = {549--560}, publisher = {Oxford University Press}, title = {{Arabidopsis inositol 1,3,4-trisphosphate 5/6 kinase 2 is required for seed coat development}}, doi = {10.1093/abbs/gmt039}, volume = {45}, year = {2013}, } @article{8461, abstract = {Solid-state NMR provides insight into protein motion over time scales ranging from picoseconds to seconds. While in solution state the methodology to measure protein dynamics is well established, there is currently no such consensus protocol for measuring dynamics in solids. In this article, we perform a detailed investigation of measurement protocols for fast motions, i.e. motions ranging from picoseconds to a few microseconds, which is the range covered by dipolar coupling and relaxation experiments. We perform a detailed theoretical investigation how dipolar couplings and relaxation data can provide information about amplitudes and time scales of local motion. We show that the measurement of dipolar couplings is crucial for obtaining accurate motional parameters, while systematic errors are found when only relaxation data are used. Based on this realization, we investigate how the REDOR experiment can provide such data in a very accurate manner. We identify that with accurate rf calibration, and explicit consideration of rf field inhomogeneities, one can obtain highly accurate absolute order parameters. We then perform joint model-free analyses of 6 relaxation data sets and dipolar couplings, based on previously existing, as well as new data sets on microcrystalline ubiquitin. We show that nanosecond motion can be detected primarily in loop regions, and compare solid-state data to solution-state relaxation and RDC analyses. The protocols investigated here will serve as a useful basis towards the establishment of a routine protocol for the characterization of ps–μs motions in proteins by solid-state NMR.}, author = {Haller, Jens D. and Schanda, Paul}, issn = {0925-2738}, journal = {Journal of Biomolecular NMR}, keywords = {Spectroscopy, Biochemistry}, number = {3}, pages = {263--280}, publisher = {Springer Nature}, title = {{Amplitudes and time scales of picosecond-to-microsecond motion in proteins studied by solid-state NMR: a critical evaluation of experimental approaches and application to crystalline ubiquitin}}, doi = {10.1007/s10858-013-9787-x}, volume = {57}, year = {2013}, } @article{894, abstract = {Background: Genetic variation at the melanocortin-1 receptor (MC1R) gene is correlated with melanin color variation in many birds. Feral pigeons (Columba livia) show two major melanin-based colorations: a red coloration due to pheomelanic pigment and a black coloration due to eumelanic pigment. Furthermore, within each color type, feral pigeons display continuous variation in the amount of melanin pigment present in the feathers, with individuals varying from pure white to a full dark melanic color. Coloration is highly heritable and it has been suggested that it is under natural or sexual selection, or both. Our objective was to investigate whether MC1R allelic variants are associated with plumage color in feral pigeons. Findings. We sequenced 888 bp of the coding sequence of MC1R among pigeons varying both in the type, eumelanin or pheomelanin, and the amount of melanin in their feathers. We detected 10 non-synonymous substitutions and 2 synonymous substitution but none of them were associated with a plumage type. It remains possible that non-synonymous substitutions that influence coloration are present in the short MC1R fragment that we did not sequence but this seems unlikely because we analyzed the entire functionally important region of the gene. Conclusions: Our results show that color differences among feral pigeons are probably not attributable to amino acid variation at the MC1R locus. Therefore, variation in regulatory regions of MC1R or variation in other genes may be responsible for the color polymorphism of feral pigeons.}, author = {Derelle, Romain and Kondrashov, Fyodor and Arkhipov, Vladimir and Corbel, Hélène and Frantz, Adrien and Gasparini, Julien and Jacquin, Lisa and Jacob, Gwenaël and Thibault, Sophie and Baudry, Emmanuelle}, journal = {BMC Research Notes}, number = {1}, publisher = {BioMed Central}, title = {{Color differences among feral pigeons (Columba livia) are not attributable to sequence variation in the coding region of the melanocortin-1 receptor gene MC1R}}, doi = {10.1186/1756-0500-6-310}, volume = {6}, year = {2013}, } @article{11751, abstract = {The Seebeck coefficients, electrical resistivities, total thermal conductivities, and magnetization are reported for temperatures between 5 and 350 K for n-type Bi0.88Sb0.12 nano-composite alloys made by Ho-doping at the 0, 1, and 3 % atomic levels. The alloys were prepared using a dc hot-pressing method, and are shown to be single phase for both Ho contents with grain sizes on the average of 900 nm. We find the parent compound has a maximum of ZT = 0.28 at 231 K, while doping 1 % Ho increases the maximum ZT to 0.31 at 221 K and the 3 % doped sample suppresses the maximum ZT = 0.24 at a temperature of 260 K.}, author = {Lukas, K. C. and Joshi, G. and Modic, Kimberly A and Ren, Z. F. and Opeil, C. P.}, issn = {1573-4803}, journal = {Journal of Materials Science}, number = {15}, pages = {5729--5734}, publisher = {Springer Nature}, title = {{Thermoelectric properties of Ho-doped Bi0.88Sb0.12}}, doi = {10.1007/s10853-012-6463-6}, volume = {47}, year = {2012}, } @inbook{2399, abstract = {Bose–Einstein condensation (BEC) in cold atomic gases was first achieved experimentally in 1995 [1, 6]. After initial failed attempts with spin-polarized atomic hydrogen, the first successful demonstrations of this phenomenon used gases of rubidium and sodium atoms, respectively. Since then there has been a surge of activity in this field, with ingenious experiments putting forth more and more astonishing results about the behavior of matter at very cold temperatures. }, author = {Robert Seiringer}, booktitle = {Quantum Many Body Systems}, editor = {Rivasseau, Vincent and Robert Seiringer and Solovej, Jan P and Spencer, Thomas}, pages = {55 -- 92}, publisher = {Springer}, title = {{Cold quantum gases and bose einstein condensation}}, doi = {10.1007/978-3-642-29511-9_2}, volume = {2051}, year = {2012}, } @article{2771, abstract = {We consider a magnetic Schrödinger operator in two dimensions. The magnetic field is given as the sum of a large and constant magnetic field and a random magnetic field. Moreover, we allow for an additional deterministic potential as well as a magnetic field which are both periodic. We show that the spectrum of this operator is contained in broadened bands around the Landau levels and that the edges of these bands consist of pure point spectrum with exponentially decaying eigenfunctions. The proof is based on a recent Wegner estimate obtained in Erdos and Hasler (Commun. Math. Phys., preprint, arXiv:1012.5185) and a multiscale analysis.}, author = {László Erdös and Hasler, David G}, journal = {Journal of Statistical Physics}, number = {5}, pages = {900 -- 923}, publisher = {Springer}, title = {{Anderson localization at band edges for random magnetic fields}}, doi = {10.1007/s10955-012-0445-6}, volume = {146}, year = {2012}, } @article{2773, abstract = {Recently we proved [3, 4, 6, 7, 9, 10, 11] that the eigenvalue correlation functions of a general class of random matrices converge, weakly with respect to the energy, to the corresponding ones of Gaussian matrices. Tao and Vu [15] gave a proof that for the special case of Hermitian Wigner matrices the convergence can be strengthened to vague convergence at any fixed energy in the bulk. In this article we show that this theorem is an immediate corollary of our earlier results. Indeed, a more general form of this theorem also follows directly from our work [2].}, author = {László Erdös and Yau, Horng-Tzer}, journal = {Electronic Journal of Probability}, publisher = {Institute of Mathematical Statistics}, title = {{A comment on the Wigner-Dyson-Mehta bulk universality conjecture for Wigner matrices}}, doi = {10.1214/EJP.v17-1779}, volume = {17}, year = {2012}, } @article{21105, abstract = {The hexamer duplex d(CACGCG).d(CGCGTG) produces unusual hexagonal ring shaped crystals when crystallized in the presence of cobalt hexammine chloride. Observation of the growth of these crystals over a period of about 6 days indicated that this morphology resulted from radial dissolution of the crystal from the center of the well-formed hexagonal plates. X-ray diffraction studies were carried out for crystals of four stages in the ring crystal morphology. The structure of the DNA in all four crystals was the Z type DNA double helix. The packing mode of the Z DNA duplex in all four crystal structures was that of the ‘spermine’ form. The crystal morphology changes from hexagonal plates to hexagonal rings without any apparent change in the molecular structure of the oligonucleotide or helical packing of the duplexes.}, author = {Mandal, Pradeep K and Chandrasekaran, Arun Richard and Madhanagopal, Bharath Raj and Venkadesh, Sarkarai and Gautham, Namasivayam}, issn = {0022-0248}, journal = {Journal of Crystal Growth}, number = {1}, pages = {20--26}, publisher = {Elsevier}, title = {{Ring crystals of oligonucleotides: Growth stages and X-ray diffraction studies}}, doi = {10.1016/j.jcrysgro.2012.05.029}, volume = {354}, year = {2012}, } @inbook{18737, abstract = {Supermassive black holes (SMBHs) are common in local galactic nuclei, and SMBHs as massive as several billion solar masses already exist at redshift z = 6. These earliest SMBHs may grow by the combination of radiation-pressure-limited accretion and mergers of stellar-mass seed BHs, left behind by the first generation of metal-free stars, or may be formed by more rapid direct collapse of gas in rare special environments where dense gas can accumulate without first fragmenting into stars. This chapter offers a review of these two competing scenarios, as well as some more exotic alternative ideas. It also briefly discusses how the different models may be distinguished in the future by observations with JWST, LISA and other instruments.}, author = {Haiman, Zoltán}, booktitle = {The First Galaxies}, editor = {Wiklind, Tommy and Mobasher, Bahram and Brumm, Volker}, isbn = {9783642323614}, issn = {2214-7985}, pages = {293--341}, publisher = {Springer Berlin Heidelberg}, title = {{The Formation of the First Massive Black Holes}}, doi = {10.1007/978-3-642-32362-1_6}, year = {2012}, } @article{493, abstract = {The BCI competition IV stands in the tradition of prior BCI competitions that aim to provide high quality neuroscientific data for open access to the scientific community. As experienced already in prior competitions not only scientists from the narrow field of BCI compete, but scholars with a broad variety of backgrounds and nationalities. They include high specialists as well as students.The goals of all BCI competitions have always been to challenge with respect to novel paradigms and complex data. We report on the following challenges: (1) asynchronous data, (2) synthetic, (3) multi-class continuous data, (4) sessionto-session transfer, (5) directionally modulated MEG, (6) finger movements recorded by ECoG. As after past competitions, our hope is that winning entries may enhance the analysis methods of future BCIs.}, author = {Tangermann, Michael and Müller, Klaus and Aertsen, Ad and Birbaumer, Niels and Braun, Christoph and Brunner, Clemens and Leeb, Robert and Mehring, Carsten and Miller, Kai and Müller Putz, Gernot and Nolte, Guido and Pfurtscheller, Gert and Preissl, Hubert and Schalk, Gerwin and Schlögl, Alois and Vidaurre, Carmen and Waldert, Stephan and Blankertz, Benjamin}, journal = {Frontiers in Neuroscience}, publisher = {Frontiers Research Foundation}, title = {{Review of the BCI competition IV}}, doi = {10.3389/fnins.2012.00055}, volume = {6}, year = {2012}, } @inproceedings{497, abstract = {One central issue in the formal design and analysis of reactive systems is the notion of refinement that asks whether all behaviors of the implementation is allowed by the specification. The local interpretation of behavior leads to the notion of simulation. Alternating transition systems (ATSs) provide a general model for composite reactive systems, and the simulation relation for ATSs is known as alternating simulation. The simulation relation for fair transition systems is called fair simulation. In this work our main contributions are as follows: (1) We present an improved algorithm for fair simulation with Büchi fairness constraints; our algorithm requires O(n 3·m) time as compared to the previous known O(n 6)-time algorithm, where n is the number of states and m is the number of transitions. (2) We present a game based algorithm for alternating simulation that requires O(m2)-time as compared to the previous known O((n·m)2)-time algorithm, where n is the number of states and m is the size of transition relation. (3) We present an iterative algorithm for alternating simulation that matches the time complexity of the game based algorithm, but is more space efficient than the game based algorithm. © Krishnendu Chatterjee, Siddhesh Chaubal, and Pritish Kamath.}, author = {Chatterjee, Krishnendu and Chaubal, Siddhesh and Kamath, Pritish}, location = {Fontainebleau, France}, pages = {167 -- 182}, publisher = {Schloss Dagstuhl - Leibniz-Zentrum für Informatik}, title = {{Faster algorithms for alternating refinement relations}}, doi = {10.4230/LIPIcs.CSL.2012.167}, volume = {16}, year = {2012}, } @article{1055, abstract = {In July, 2011, a 32-year-old man presented with thoracic pain radiating to the left arm and upper dorsum, shortness of breath, and palpitations. He had had upper back tension for 6 months. Medical history was unremarkable apart from moderate nicotine use (two pack-years). Echocardiography, electrocardiography, and laboratory tests were unremarkable, excluding a cardiac event. CT of the chest after chest radiography showed a large bulla of 16 cm diameter in the right hemithorax (figure A). We did not detect radiological evidence of underlying pulmonary disease. The bulla wall was unremarkable and no structures were seen within the bulla.}, author = {Erne, Barbara and Graff, Mareike and Klemm, Wolfram and Danzl, Johann G and Leschber, Gunda}, journal = {The Lancet}, number = {9849}, publisher = {Elsevier}, title = {{Bulla in the lung}}, doi = {10.1016/S0140-6736(12)60690-4}, volume = {380}, year = {2012}, } @article{3111, abstract = {PIN-FORMED (PIN) protein-mediated auxin polar transport is critically important for development, pattern formation, and morphogenesis in plants. Auxin has been implicated in the regulation of polar auxin transport by inhibiting PIN endocytosis [1, 2], but how auxin regulates this process is poorly understood. Our genetic screen identified the Arabidopsis SPIKE1 (SPK1) gene whose loss-of-function mutations increased lateral root density and retarded gravitropic responses, as do pin2 knockout mutations [3]. SPK1 belongs to the conserved DHR2-Dock family of Rho guanine nucleotide exchange factors [4-6]. The spk1 mutations induced PIN2 internalization that was not suppressed by auxin, as did the loss-of-function mutations for Rho-like GTPase from Plants 6 (ROP6)-GTPase or its effector RIC1. Furthermore, SPK1 was required for auxin induction of ROP6 activation. Our results have established a Rho GTPase-based auxin signaling pathway that maintains PIN2 polar distribution to the plasma membrane via inhibition of its internalization in Arabidopsis roots. Our findings provide new insights into signaling mechanisms that underlie the regulation of the dynamic trafficking of PINs required for long-distance auxin transport and that link auxin signaling to PIN-mediated pattern formation and morphogenesis.}, author = {Lin, Deshu and Nagawa, Shingo and Chen, Jisheng and Cao, Lingyan and Xu Chen and Xu, Tongda and Hongjiang Li and Dhonukshe, Pankaj and Yamamuro, Chizuko and Jirí Friml and Scheres, Ben and Fu, Ying and Yang, Zhenbiao}, journal = {Current Biology}, number = {14}, pages = {1319 -- 1325}, publisher = {Cell Press}, title = {{A ROP GTPase dependent auxin signaling pathway regulates the subcellular distribution of PIN2 in Arabidopsis roots}}, doi = {10.1016/j.cub.2012.05.019}, volume = {22}, year = {2012}, } @article{3166, abstract = {There is evidence that the genetic code was established prior to the existence of proteins, when metabolism was powered by ribozymes. Also, early proto-organisms had to rely on simple anaerobic bioenergetic processes. In this work I propose that amino acid fermentation powered metabolism in the RNA world, and that this was facilitated by proto-adapters, the precursors of the tRNAs. Amino acids were used as carbon sources rather than as catalytic or structural elements. In modern bacteria, amino acid fermentation is known as the Stickland reaction. This pathway involves two amino acids: the first undergoes oxidative deamination, and the second acts as an electron acceptor through reductive deamination. This redox reaction results in two keto acids that are employed to synthesise ATP via substrate-level phosphorylation. The Stickland reaction is the basic bioenergetic pathway of some bacteria of the genus Clostridium. Two other facts support Stickland fermentation in the RNA world. First, several Stickland amino acid pairs are synthesised in abiotic amino acid synthesis. This suggests that amino acids that could be used as an energy substrate were freely available. Second, anticodons that have complementary sequences often correspond to amino acids that form Stickland pairs. The main hypothesis of this paper is that pairs of complementary proto-adapters were assigned to Stickland amino acids pairs. There are signatures of this hypothesis in the genetic code. Furthermore, it is argued that the proto-adapters formed double strands that brought amino acid pairs into proximity to facilitate their mutual redox reaction, structurally constraining the anticodon pairs that are assigned to these amino acid pairs. Significance tests which randomise the code are performed to study the extent of the variability of the energetic (ATP) yield. Random assignments can lead to a substantial yield of ATP and maintain enough variability, thus selection can act and refine the assignments into a proto-code that optimises the energetic yield. Monte Carlo simulations are performed to evaluate the establishment of these simple proto-codes, based on amino acid substitutions and codon swapping. In all cases, donor amino acids are assigned to anticodons composed of U+G, and have low redundancy (1-2 codons), whereas acceptor amino acids are assigned to the the remaining codons. These bioenergetic and structural constraints allow for a metabolic role for amino acids before their co-option as catalyst cofactors. Reviewers: this article was reviewed by Prof. William Martin, Prof. Eors Szathmary (nominated by Dr. Gaspar Jekely) and Dr. Adam Kun (nominated by Dr. Sandor Pongor)}, author = {Vladar, Harold}, journal = {Biology Direct}, publisher = {BioMed Central}, title = {{Amino acid fermentation at the origin of the genetic code}}, doi = {10.1186/1745-6150-7-6}, volume = {7}, year = {2012}, } @article{17613, abstract = {We study the interaction of a supermassive black hole (SMBH) binary and a standard radiatively efficient thin accretion disk. We examine steady-state configurations of the disk and migrating SMBH system, self-consistently accounting for tidal and viscous torques and heating, radiative diffusion limited cooling, gas and radiation pressure, and the decay of the binary's orbit. We obtain a "phase diagram" of the system as a function of binary parameters, showing regimes in which both the disk structure and migration have a different character. Although massive binaries can create a central gap in the disk at large radii, the tidal barrier of the secondary causes a significant pile-up of gas outside of its orbit, which can lead to the closing of the gap. We find that this spillover occurs at an orbital separation as large as ~200 M_7^{-1/2} gravitational radii, where M = 10^7 M_7 Msun is the total binary mass. If the secondary is less massive than ~10^6 Msun, then the gap is closed before gravitational waves (GWs) start dominating the orbital decay. In this regime, the disk is still strongly perturbed, but the piled-up gas continuously overflows as in a porous dam, and crosses inside the secondary's orbit. The corresponding migration rate, which we label Type 1.5, is slower than the usual limiting cases known as Type I and II migration. Compared to an unperturbed disk, the steady-state disk in the overflowing regime is up to several hundred times brighter in the optical bands. Surveys such as PanSTARRS or LSST may discover the periodic variability of this population of binaries. Our results imply that the circumbinary disks around SMBHs can extend to small radii during the last stages of their merger, when they are detectable by LISA, and may produce coincident electromagnetic (EM) emission similar to active galactic nuclei (AGN).}, author = {Kocsis, Bence and Haiman, Zoltán and Loeb, Abraham}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {3}, pages = {2680--2700}, publisher = {Oxford University Press}, title = {{Gas pile-up, gap overflow and Type 1.5 migration in circumbinary discs: Application to supermassive black hole binaries}}, doi = {10.1111/j.1365-2966.2012.22118.x}, volume = {427}, year = {2012}, } @inproceedings{17651, abstract = {A decade after their first discovery, the origin of giant supermassive black holes (SMBHs), with masses in excess of 109 Msolar, at redshifts as early as z > 6, remains a puzzle. One possibility is that stellar-mass ``seed'' BHs, left behind by the first stars, accrete gas at close to the Eddington limit during a large fraction (>~ 50%) of the time. While maintaining such a high accretion rate may itself be difficult, here we focus on another, less commonly discussed problem in this scenario: unless BH seed formation and growth are preferentially suppressed in less massive protogalaxies, the mass density in M~106Msolar SMBHs at z ~ 6 already exceeds the locally observed SMBH mass density by several orders of magnitude. We show that the X-rays from the earliest accreting BHs themselves can cause a self-regulation, by partially ionizing and heating the intergalactic medium (IGM). This ``global warming'' suppresses the formation and growth of subsequent generations of BHs in low-mass halos, and can produce excellent agreement with recent estimates of the z = 6 SMBH mass function, without impeding the growth of the largest (M>~109Msolar) holes, which reside in the most massive galaxies that formed first. The proposed gravitational-wave observatory eLISA could detect several tens of major mergers between SMBHs at z > 6.}, author = {Haiman, Zoltán and Tanaka, Takamitsu and Perna, Rosalba}, booktitle = {AIP Conference Proceedings}, issn = {0094-243X}, location = {Kyoto, Japan}, pages = {303--308}, publisher = {American Institute of Physics}, title = {{Self-regulating the early growth of black holes through global warming}}, doi = {10.1063/1.4754372}, volume = {1480}, year = {2012}, } @article{17678, abstract = {The spectra of several high-redshift (z>6) quasars have shown evidence for a Gunn-Peterson (GP) damping wing, indicating a substantial mean neutral hydrogen fraction (x_HI > 0.03) in the z ~ 6 intergalactic medium (IGM). However, previous analyses assumed that the IGM was uniformly ionized outside of the quasar's HII region. Here we relax this assumption and model patchy reionization scenarios for a range of IGM and quasar parameters. We quantify the impact of these differences on the inferred x_HI, by fitting the spectra of three quasars: SDSS J1148+5251 (z=6.419), J1030+0524 (z=6.308), and J1623+3112 (z=6.247). We find that the best-fit values of x_HI in the patchy models agree well with the uniform case. More importantly, we confirm that the observed spectra favor the presence of a GP damping wing, with peak likelihoods decreasing by factors of > few - 10 when the spectra are modeled without a damping wing. We also find that the Ly alpha absorption spectra, by themselves, cannot distinguish the damping wing in a relatively neutral IGM from a damping wing in a highly ionized IGM, caused either by an isolated neutral patch, or by a damped Ly alpha absorber (DLA). However, neutral patches in a highly ionized universe (x_HI < 0.01), and DLAs with the large required column densities (N_HI > few x 10^{20} cm^{-2}) are both rare. As a result, when we include reasonable prior probabilities for the line of sight (LOS) to intercept either a neutral patch or a DLA at the required distance of ~ 40-60 comoving Mpc away from the quasar, we find strong lower limits on the neutral fraction in the IGM, x_HI > 0.1 (at 95% confidence). This strengthens earlier claims that a substantial global fraction of hydrogen in the z~6 IGM is in neutral form.}, author = {Schroeder, Joshua and Mesinger, Andrei and Haiman, Zoltán}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3058--3071}, publisher = {Oxford University Press}, title = {{Evidence of Gunn–Peterson damping wings in high-z quasar spectra: Strengthening the case for incomplete reionization at z ∼ 6–7}}, doi = {10.1093/mnras/sts253}, volume = {428}, year = {2012}, } @article{17705, abstract = {Observations of high-redshift quasars at z>6 imply that supermassive black holes (SMBHs) with masses over a billion solar masses were in place less than 1 Gyr after the Big Bang. If these SMBHs assembled from "seed" BHs left behind by the first stars, then they must have accreted gas at close to the Eddington limit during a large fraction (>50%) of the time. A generic problem with this scenario, however, is that the mass density in million-solar-mass SMBHs at z=6 already exceeds the locally observed SMBH mass density by several orders of magnitude; in order to avoid this overproduction, BH seed formation and growth must become significantly less efficient in less massive protogalaxies, while proceeding uninterrupted in the most massive galaxies that formed first. Using Monte-Carlo realizations of the merger and growth history of BHs, we show that X-rays from the earliest accreting BHs can provide such a feedback mechanism. Our calculations paint a self-consistent picture of black-hole-made climate change, in which the first miniquasars---among them the ancestors of the z>6 quasar SMBHs---globally warm the IGM and suppress the formation and growth of subsequent generations of BHs. We present two specific models with global miniquasar feedback that provide excellent agreement with recent estimates of the z=6 SMBH mass function. For each of these models, we estimate the rate of BH mergers at z>6 that could be detected by the proposed gravitational-wave observatory eLISA/NGO.}, author = {Tanaka, Takamitsu and Perna, Rosalba and Haiman, Zoltán}, issn = {0035-8711}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {2974--2987}, publisher = {Oxford University Press}, title = {{X-ray emission from high-redshift miniquasars: Self-regulating the population of massive black holes through global warming}}, doi = {10.1111/j.1365-2966.2012.21539.x}, volume = {425}, year = {2012}, }