@article{259, abstract = {The Hasse principle and weak approximation is established for non-singular cubic hypersurfaces X over the function field Fq(t), provided that char(Fq) > 3 and X has dimension at least 6.}, author = {Browning, Timothy D and Vishe, Pankaj}, issn = {1420-8970}, journal = {Geometric and Functional Analysis}, number = {3}, pages = {671 -- 732}, publisher = {Springer Nature}, title = {{Rational points on cubic hypersurfaces over F_q(t) }}, doi = {10.1007/s00039-015-0328-5}, volume = {25}, year = {2015}, } @article{2085, abstract = {We study the spectrum of a large system of N identical bosons interacting via a two-body potential with strength 1/N. In this mean-field regime, Bogoliubov's theory predicts that the spectrum of the N-particle Hamiltonian can be approximated by that of an effective quadratic Hamiltonian acting on Fock space, which describes the fluctuations around a condensed state. Recently, Bogoliubov's theory has been justified rigorously in the case that the low-energy eigenvectors of the N-particle Hamiltonian display complete condensation in the unique minimizer of the corresponding Hartree functional. In this paper, we shall justify Bogoliubov's theory for the high-energy part of the spectrum of the N-particle Hamiltonian corresponding to (non-linear) excited states of the Hartree functional. Moreover, we shall extend the existing results on the excitation spectrum to the case of non-uniqueness and/or degeneracy of the Hartree minimizer. In particular, the latter covers the case of rotating Bose gases, when the rotation speed is large enough to break the symmetry and to produce multiple quantized vortices in the Hartree minimizer. }, author = {Nam, Phan and Seiringer, Robert}, journal = {Archive for Rational Mechanics and Analysis}, number = {2}, pages = {381 -- 417}, publisher = {Springer}, title = {{Collective excitations of Bose gases in the mean-field regime}}, doi = {10.1007/s00205-014-0781-6}, volume = {215}, year = {2015}, } @inproceedings{1502, abstract = {We extend the theory of input-output conformance with operators for merge and quotient. The former is useful when testing against multiple requirements or views. The latter can be used to generate tests for patches of an already tested system. Both operators can combine systems with different action alphabets, which is usually the case when constructing complex systems and specifications from parts, for instance different views as well as newly defined functionality of a~previous version of the system.}, author = {Beneš, Nikola and Daca, Przemyslaw and Henzinger, Thomas A and Kretinsky, Jan and Nickovic, Dejan}, isbn = {978-1-4503-3471-6}, location = {Montreal, QC, Canada}, pages = {101 -- 110}, publisher = {ACM}, title = {{Complete composition operators for IOCO-testing theory}}, doi = {10.1145/2737166.2737175}, year = {2015}, } @article{1530, abstract = {In growing cells, protein synthesis and cell growth are typically not synchronous, and, thus, protein concentrations vary over the cell division cycle. We have developed a theoretical description of genetic regulatory systems in bacteria that explicitly considers the cell division cycle to investigate its impact on gene expression. We calculate the cell-to-cell variations arising from cells being at different stages in the division cycle for unregulated genes and for basic regulatory mechanisms. These variations contribute to the extrinsic noise observed in single-cell experiments, and are most significant for proteins with short lifetimes. Negative autoregulation buffers against variation of protein concentration over the division cycle, but the effect is found to be relatively weak. Stronger buffering is achieved by an increased protein lifetime. Positive autoregulation can strongly amplify such variation if the parameters are set to values that lead to resonance-like behaviour. For cooperative positive autoregulation, the concentration variation over the division cycle diminishes the parameter region of bistability and modulates the switching times between the two stable states. The same effects are seen for a two-gene mutual-repression toggle switch. By contrast, an oscillatory circuit, the repressilator, is only weakly affected by the division cycle.}, author = {Bierbaum, Veronika and Klumpp, Stefan}, journal = {Physical Biology}, number = {6}, publisher = {IOP Publishing}, title = {{Impact of the cell division cycle on gene circuits}}, doi = {10.1088/1478-3975/12/6/066003}, volume = {12}, year = {2015}, } @article{1536, abstract = {Strigolactones, first discovered as germination stimulants for parasitic weeds [1], are carotenoid-derived phytohormones that play major roles in inhibiting lateral bud outgrowth and promoting plant-mycorrhizal symbiosis [2-4]. Furthermore, strigolactones are involved in the regulation of lateral and adventitious root development, root cell division [5, 6], secondary growth [7], and leaf senescence [8]. Recently, we discovered the strigolactone transporter Petunia axillaris PLEIOTROPIC DRUG RESISTANCE 1 (PaPDR1), which is required for efficient mycorrhizal colonization and inhibition of lateral bud outgrowth [9]. However, how strigolactones are transported through the plant remained unknown. Here we show that PaPDR1 exhibits a cell-type-specific asymmetric localization in different root tissues. In root tips, PaPDR1 is co-expressed with the strigolactone biosynthetic gene DAD1 (CCD8), and it is localized at the apical membrane of root hypodermal cells, presumably mediating the shootward transport of strigolactone. Above the root tip, in the hypodermal passage cells that form gates for the entry of mycorrhizal fungi, PaPDR1 is present in the outer-lateral membrane, compatible with its postulated function as strigolactone exporter from root to soil. Transport studies are in line with our localization studies since (1) a papdr1 mutant displays impaired transport of strigolactones out of the root tip to the shoot as well as into the rhizosphere and (2) DAD1 expression and PIN1/PIN2 levels change in plants deregulated for PDR1 expression, suggestive of variations in endogenous strigolactone contents. In conclusion, our results indicate that the polar localizations of PaPDR1 mediate directional shootward strigolactone transport as well as localized exudation into the soil.}, author = {Sasse, Joëlle and Simon, Sibu and Gübeli, Christian and Liu, Guowei and Cheng, Xi and Friml, Jirí and Bouwmeester, Harro and Martinoia, Enrico and Borghi, Lorenzo}, journal = {Current Biology}, number = {5}, pages = {647 -- 655}, publisher = {Cell Press}, title = {{Asymmetric localizations of the ABC transporter PaPDR1 trace paths of directional strigolactone transport}}, doi = {10.1016/j.cub.2015.01.015}, volume = {25}, year = {2015}, } @inproceedings{1541, abstract = {We present XSpeed a parallel state-space exploration algorithm for continuous systems with linear dynamics and nondeterministic inputs. The motivation of having parallel algorithms is to exploit the computational power of multi-core processors to speed-up performance. The parallelization is achieved on two fronts. First, we propose a parallel implementation of the support function algorithm by sampling functions in parallel. Second, we propose a parallel state-space exploration by slicing the time horizon and computing the reachable states in the time slices in parallel. The second method can be however applied only to a class of linear systems with invertible dynamics and fixed input. A GP-GPU implementation is also presented following a lazy evaluation strategy on support functions. The parallel algorithms are implemented in the tool XSpeed. We evaluated the performance on two benchmarks including an 28 dimension Helicopter model. Comparison with the sequential counterpart shows a maximum speed-up of almost 7× on a 6 core, 12 thread Intel Xeon CPU E5-2420 processor. Our GP-GPU implementation shows a maximum speed-up of 12× over the sequential implementation and 53× over SpaceEx (LGG scenario), the state of the art tool for reachability analysis of linear hybrid systems. Experiments illustrate that our parallel algorithm with time slicing not only speeds-up performance but also improves precision.}, author = {Ray, Rajarshi and Gurung, Amit and Das, Binayak and Bartocci, Ezio and Bogomolov, Sergiy and Grosu, Radu}, location = {Haifa, Israel}, pages = {3 -- 18}, publisher = {Springer}, title = {{XSpeed: Accelerating reachability analysis on multi-core processors}}, doi = {10.1007/978-3-319-26287-1_1}, volume = {9434}, year = {2015}, } @inbook{1549, abstract = {Nature has incorporated small photochromic molecules, colloquially termed 'photoswitches', in photoreceptor proteins to sense optical cues in photo-taxis and vision. While Nature's ability to employ light-responsive functionalities has long been recognized, it was not until recently that scientists designed, synthesized and applied synthetic photochromes to manipulate many of which open rapidly and locally in their native cell types, biological processes with the temporal and spatial resolution of light. Ion channels in particular have come to the forefront of proteins that can be put under the designer control of synthetic photochromes. Photochromic ion channel controllers are comprised of three classes, photochromic soluble ligands (PCLs), photochromic tethered ligands (PTLs) and photochromic crosslinkers (PXs), and in each class ion channel functionality is controlled through reversible changes in photochrome structure. By acting as light-dependent ion channel agonists, antagonist or modulators, photochromic controllers effectively converted a wide range of ion channels, including voltage-gated ion channels, 'leak channels', tri-, tetra- and pentameric ligand-gated ion channels, and temperaturesensitive ion channels, into man-made photoreceptors. Control by photochromes can be reversible, unlike in the case of 'caged' compounds, and non-invasive with high spatial precision, unlike pharmacology and electrical manipulation. Here, we introduce design principles of emerging photochromic molecules that act on ion channels and discuss the impact that these molecules are beginning to have on ion channel biophysics and neuronal physiology.}, author = {Mckenzie, Catherine and Sanchez Romero, Inmaculada and Janovjak, Harald L}, booktitle = {Novel chemical tools to study ion channel biology}, isbn = {978-1-4939-2844-6}, pages = {101 -- 117}, publisher = {Springer}, title = {{Flipping the photoswitch: Ion channels under light control}}, doi = {10.1007/978-1-4939-2845-3_6}, volume = {869}, year = {2015}, } @article{1878, abstract = {Petrocoptis is a small genus of chasmophytic plants endemic to the Iberian Peninsula, with some localized populations in the French Pyrenees. Within the genus, a dozen species have been recognized based on morphological diversity, most of them with limited distribution area, in small populations and frequently with potential threats to their survival. To date, however, a molecular evaluation of the current systematic treatments has not been carried out. The aim of the present study is to infer phylogenetic relationships among its subordinate taxa by using plastidial rps16 intron and nuclear internal transcribed spacer (ITS) DNA sequences; and evaluate the phylogenetic placement of the genus Petrocoptis within the family Caryophyllaceae. The monophyly of Petrocoptis is supported by both ITS and rps16 intron sequence analyses. Furthermore, time estimates using BEAST analyses indicate a Middle to Late Miocene diversification (10.59 Myr, 6.44–15.26 Myr highest posterior densities [HPD], for ITS; 14.30 Myr, 8.61–21.00 Myr HPD, for rps16 intron).}, author = {Cires Rodriguez, Eduardo and Prieto, José}, journal = {Journal of Plant Research}, number = {2}, pages = {223 -- 238}, publisher = {Springer}, title = {{Phylogenetic relationships of Petrocoptis A. Braun ex Endl. (Caryophyllaceae), a discussed genus from the Iberian Peninsula}}, doi = {10.1007/s10265-014-0691-6}, volume = {128}, year = {2015}, } @article{1834, abstract = {Huge body of evidences demonstrated that volatile anesthetics affect the hippocampal neurogenesis and neurocognitive functions, and most of them showed impairment at anesthetic dose. Here, we investigated the effect of low dose (1.8%) sevoflurane on hippocampal neurogenesis and dentate gyrus-dependent learning. Neonatal rats at postnatal day 4 to 6 (P4-6) were treated with 1.8% sevoflurane for 6 hours. Neurogenesis was quantified by bromodeoxyuridine labeling and electrophysiology recording. Four and seven weeks after treatment, the Morris water maze and contextual-fear discrimination learning tests were performed to determine the influence on spatial learning and pattern separation. A 6-hour treatment with 1.8% sevoflurane promoted hippocampal neurogenesis and increased the survival of newborn cells and the proportion of immature granular cells in the dentate gyrus of neonatal rats. Sevoflurane-treated rats performed better during the training days of the Morris water maze test and in contextual-fear discrimination learning test. These results suggest that a subanesthetic dose of sevoflurane promotes hippocampal neurogenesis in neonatal rats and facilitates their performance in dentate gyrus-dependent learning tasks.}, author = {Chen, Chong and Wang, Chao and Zhao, Xuan and Zhou, Tao and Xu, Dao and Wang, Zhi and Wang, Ying}, journal = {ASN Neuro}, number = {2}, publisher = {SAGE Publications}, title = {{Low-dose sevoflurane promoteshippocampal neurogenesis and facilitates the development of dentate gyrus-dependent learning in neonatal rats}}, doi = {10.1177/1759091415575845}, volume = {7}, year = {2015}, } @article{11967, abstract = {An experimentally easy to perform method for the generation of alumina-supported Fe3O4 nanoparticles [(6±1) nm size, 0.67 wt %]and the use of this material in hydrazine-mediated heterogeneously catalyzed reductions of nitroarenes to anilines under batch and continuous-flow conditions is presented. The bench-stable, reusable nano-Fe3O4@Al2O3 catalyst can selectively reduce functionalized nitroarenes at 1 mol % catalyst loading by using a 20 mol % excess of hydrazine hydrate in an elevated temperature regime (150 °C, reaction time 2–6 min in batch). For continuous-flow processing, the catalyst material is packed into dedicated cartridges and used in a commercially available high-temperature/-pressure flow device. In continuous mode, reaction times can be reduced to less than 1 min at 150 °C (30 bar back pressure) in a highly intensified process. The nano-Fe3O4@Al2O3 catalyst demonstrated stable reduction of nitrobenzene (0.5 M in MeOH) for more than 10 h on stream at a productivity of 30 mmol h−1 (0.72 mol per day). Importantly, virtually no leaching of the catalytically active material could be observed by inductively coupled plasma MS monitoring.}, author = {Moghaddam, Mojtaba Mirhosseini and Pieber, Bartholomäus and Glasnov, Toma and Kappe, C. Oliver}, issn = {1864-564X}, journal = {ChemSusChem}, number = {11}, pages = {3122--3131}, publisher = {Wiley}, title = {{Immobilized iron oxide nanoparticles as stable and reusable catalysts for hydrazine-mediated nitro reductions in continuous flow}}, doi = {10.1002/cssc.201402455}, volume = {7}, year = {2014}, } @article{2227, abstract = {The Balkan Peninsula, characterized by high rates of endemism, is recognised as one of the most diverse and species-rich areas of Europe. However, little is known about the origin of Balkan endemics. The present study addresses the phylogenetic position of the Balkan endemic Ranunculus wettsteinii, as well as its taxonomic status and relationship with the widespread R. parnassiifolius, based on nuclear DNA (internal transcribed spacer, ITS) and plastid regions (rpl32-trnL, rps16-trnQ, trnK-matK and ycf6-psbM). Maximum parsimony and Bayesian inference analyses revealed a well-supported clade formed by accessions of R. wettsteinii. Furthermore, our phylogenetic and network analyses supported previous hypotheses of a likely allopolyploid origin for R. wettsteinii between R. montenegrinus and R. parnassiifolius, with the latter as the maternal parent.}, author = {Cires Rodriguez, Eduardo and Baltisberger, Matthias and Cuesta, Candela and Vargas, Pablo and Prieto, José}, issn = {1439-6092}, journal = {Organisms Diversity and Evolution}, number = {1}, pages = {1 -- 10}, publisher = {Springer}, title = {{Allopolyploid origin of the Balkan endemic Ranunculus wettsteinii (Ranunculaceae) inferred from nuclear and plastid DNA sequences}}, doi = {10.1007/s13127-013-0150-6}, volume = {14}, year = {2014}, } @article{252, abstract = {For any number field k, upper bounds are established for the number of k-rational points of bounded height on non-singular del Pezzo surfaces defined over k, which are equipped with suitable conic bundle structures over k.}, author = {Timothy Browning and Jones, Michael S}, journal = {Acta Arithmetica}, number = {3}, pages = {271 -- 298}, publisher = {Instytut Matematyczny}, title = {{Counting rational points on del Pezzo surfaces with a conic bundle structure}}, doi = {10.4064/aa163-3-6}, volume = {163}, year = {2014}, } @article{2716, abstract = {Multi-dimensional mean-payoff and energy games provide the mathematical foundation for the quantitative study of reactive systems, and play a central role in the emerging quantitative theory of verification and synthesis. In this work, we study the strategy synthesis problem for games with such multi-dimensional objectives along with a parity condition, a canonical way to express ω ω -regular conditions. While in general, the winning strategies in such games may require infinite memory, for synthesis the most relevant problem is the construction of a finite-memory winning strategy (if one exists). Our main contributions are as follows. First, we show a tight exponential bound (matching upper and lower bounds) on the memory required for finite-memory winning strategies in both multi-dimensional mean-payoff and energy games along with parity objectives. This significantly improves the triple exponential upper bound for multi energy games (without parity) that could be derived from results in literature for games on vector addition systems with states. Second, we present an optimal symbolic and incremental algorithm to compute a finite-memory winning strategy (if one exists) in such games. Finally, we give a complete characterization of when finite memory of strategies can be traded off for randomness. In particular, we show that for one-dimension mean-payoff parity games, randomized memoryless strategies are as powerful as their pure finite-memory counterparts.}, author = {Chatterjee, Krishnendu and Randour, Mickael and Raskin, Jean}, journal = {Acta Informatica}, number = {3-4}, pages = {129 -- 163}, publisher = {Springer}, title = {{Strategy synthesis for multi-dimensional quantitative objectives}}, doi = {10.1007/s00236-013-0182-6}, volume = {51}, year = {2014}, } @article{2178, abstract = {We consider the three-state toric homogeneous Markov chain model (THMC) without loops and initial parameters. At time T, the size of the design matrix is 6 × 3 · 2T-1 and the convex hull of its columns is the model polytope. We study the behavior of this polytope for T ≥ 3 and we show that it is defined by 24 facets for all T ≥ 5. Moreover, we give a complete description of these facets. From this, we deduce that the toric ideal associated with the design matrix is generated by binomials of degree at most 6. Our proof is based on a result due to Sturmfels, who gave a bound on the degree of the generators of a toric ideal, provided the normality of the corresponding toric variety. In our setting, we established the normality of the toric variety associated to the THMC model by studying the geometric properties of the model polytope.}, author = {Haws, David and Martin Del Campo Sanchez, Abraham and Takemura, Akimichi and Yoshida, Ruriko}, journal = {Beitrage zur Algebra und Geometrie}, number = {1}, pages = {161 -- 188}, publisher = {Springer}, title = {{Markov degree of the three-state toric homogeneous Markov chain model}}, doi = {10.1007/s13366-013-0178-y}, volume = {55}, year = {2014}, } @phdthesis{1404, abstract = {The co-evolution of hosts and pathogens is characterized by continuous adaptations of both parties. Pathogens of social insects need to adapt towards disease defences at two levels: 1) individual immunity of each colony member consisting of behavioural defence strategies as well as humoral and cellular immune responses and 2) social immunity that is collectively performed by all group members comprising behavioural, physiological and organisational defence strategies. To disentangle the selection pressure on pathogens by the collective versus individual level of disease defence in social insects, we performed an evolution experiment using the Argentine Ant, Linepithema humile, as a host and a mixture of the general insect pathogenic fungus Metarhizium spp. (6 strains) as a pathogen. We allowed pathogen evolution over 10 serial host passages to two different evolution host treatments: (1) only individual host immunity in a single host treatment, and (2) simultaneously acting individual and social immunity in a social host treatment, in which an exposed ant was accompanied by two untreated nestmates. Before starting the pathogen evolution experiment, the 6 Metarhizium spp. strains were characterised concerning conidiospore size killing rates in singly and socially reared ants, their competitiveness under coinfecting conditions and their influence on ant behaviour. We analysed how the ancestral atrain mixture changed in conidiospere size, killing rate and strain composition dependent on host treatment (single or social hosts) during 10 passages and found that killing rate and conidiospere size of the pathogen increased under both evolution regimes, but different depending on host treatment. Testing the evolved strain mixtures that evolved under either the single or social host treatment under both single and social current rearing conditions in a full factorial design experiment revealed that the additional collective defences in insect societies add new selection pressure for their coevolving pathogens that compromise their ability to adapt to its host at the group level. To our knowledge, this is the first study directly measuring the influence of social immunity on pathogen evolution.}, author = {Stock, Miriam}, pages = {101}, publisher = {IST Austria}, title = {{Evolution of a fungal pathogen towards individual versus social immunity in ants}}, year = {2014}, } @article{1913, abstract = {Deposits of phosphorylated tau protein and convergence of pathology in the hippocampus are the hallmarks of neurodegenerative tauopathies. Thus we aimed to evaluate whether regional and cellular vulnerability patterns in the hippocampus distinguish tauopathies or are influenced by their concomitant presence. Methods: We created a heat map of phospho-tau (AT8) immunoreactivity patterns in 24 hippocampal subregions/layers in individuals with Alzheimer's disease (AD)-related neurofibrillary degeneration (n = 40), Pick's disease (n = 8), progressive supranuclear palsy (n = 7), corticobasal degeneration (n = 6), argyrophilic grain disease (AGD, n = 18), globular glial tauopathy (n = 5), and tau-astrogliopathy of the elderly (n = 10). AT8 immunoreactivity patterns were compared by mathematical analysis. Results: Our study reveals disease-specific hot spots and regional selective vulnerability for these disorders. The pattern of hippocampal AD-related tau pathology is strongly influenced by concomitant AGD. Mathematical analysis reveals that hippocampal involvement in primary tauopathies is distinguishable from early-stage AD-related neurofibrillary degeneration. Conclusion: Our data demonstrate disease-specific AT8 immunoreactivity patterns and hot spots in the hippocampus even in tauopathies, which primarily do not affect the hippocampus. These hot spots can be shifted to other regions by the co-occurrence of tauopathies like AGD. Our observations support the notion that globular glial tauopathies and tau-astrogliopathy of the elderly are distinct entities.}, author = {Milenković, Ivan and Petrov, Tatjana and Kovács, Gábor}, issn = {1420-8008}, journal = {Dementia and Geriatric Cognitive Disorders}, number = {5-6}, pages = {375 -- 388}, publisher = {Karger Publishers}, title = {{Patterns of hippocampal tau pathology differentiate neurodegenerative dementias}}, doi = {10.1159/000365548}, volume = {38}, year = {2014}, } @article{1923, abstract = {We derive the equations for a thin, axisymmetric elastic shell subjected to an internal active stress giving rise to active tension and moments within the shell. We discuss the stability of a cylindrical elastic shell and its response to a localized change in internal active stress. This description is relevant to describe the cellular actomyosin cortex, a thin shell at the cell surface behaving elastically at a short timescale and subjected to active internal forces arising from myosin molecular motor activity. We show that the recent observations of cell deformation following detachment of adherent cells (Maître J-L et al 2012 Science 338 253-6) are well accounted for by this mechanical description. The actin cortex elastic and bending moduli can be obtained from a quantitative analysis of cell shapes observed in these experiments. Our approach thus provides a non-invasive, imaging-based method for the extraction of cellular physical parameters.}, author = {Berthoumieux, Hélène and Maître, Jean-Léon and Heisenberg, Carl-Philipp J and Paluch, Ewa and Julicher, Frank and Salbreux, Guillaume}, journal = {New Journal of Physics}, publisher = {IOP Publishing}, title = {{Active elastic thin shell theory for cellular deformations}}, doi = {10.1088/1367-2630/16/6/065005}, volume = {16}, year = {2014}, } @article{2022, abstract = {Radial glial progenitors (RGPs) are responsible for producing nearly all neocortical neurons. To gain insight into the patterns of RGP division and neuron production, we quantitatively analyzed excitatory neuron genesis in the mouse neocortex using Mosaic Analysis with Double Markers, which provides single-cell resolution of progenitor division patterns and potential in vivo. We found that RGPs progress through a coherent program in which their proliferative potential diminishes in a predictable manner. Upon entry into the neurogenic phase, individual RGPs produce ∼8–9 neurons distributed in both deep and superficial layers, indicating a unitary output in neuronal production. Removal of OTX1, a transcription factor transiently expressed in RGPs, results in both deep- and superficial-layer neuron loss and a reduction in neuronal unit size. Moreover, ∼1/6 of neurogenic RGPs proceed to produce glia. These results suggest that progenitor behavior and histogenesis in the mammalian neocortex conform to a remarkably orderly and deterministic program.}, author = {Gao, Peng and Postiglione, Maria P and Krieger, Teresa and Hernandez, Luisirene and Wang, Chao and Han, Zhi and Streicher, Carmen and Papusheva, Ekaterina and Insolera, Ryan and Chugh, Kritika and Kodish, Oren and Huang, Kun and Simons, Benjamin and Luo, Liqun and Hippenmeyer, Simon and Shi, Song}, journal = {Cell}, number = {4}, pages = {775 -- 788}, publisher = {Cell Press}, title = {{Deterministic progenitor behavior and unitary production of neurons in the neocortex}}, doi = {10.1016/j.cell.2014.10.027}, volume = {159}, year = {2014}, } @article{17642, abstract = {The presence of quasars at redshifts z > 6 indicates the existence of supermassive black holes (SMBHs) as massive as a few times 10^9 Msun, challenging models for SMBH formation. One pathway is through the direct collapse of gas in T_{vir} > 10^4 K halos; however, this requires the suppression of H_2 cooling to prevent fragmentation. In this paper, we examine a proposed new mechanism for this suppression which relies on cold-mode accretion flows leading to shocks at high densities (n > 10^4 cm^{-3}) and temperatures (T > 10^4 K). In such gas, H_2 is efficiently collisionally dissociated. We use high-resolution numerical simulations to test this idea, demonstrating that such halos typically have lower temperature progenitors, in which cooling is efficient. Those halos do show filamentary flows; however, the gas shocks at or near the virial radius (at low densities), thus preventing the proposed collisional mechanism from operating. We do find that, if we artificially suppress H_2 formation with a high UV background, so as to allow gas in the halo center to enter the high-temperature, high-density "zone of no return", it will remain there even if the UV flux is turned off, collapsing to high density at high temperature. Due to computational limitations, we simulated only three halos. However, we demonstrate, using Monte Carlo calculations of 10^6 halo merger histories, that a few rare halos could assemble rapidly enough to avoid efficient H_2 cooling in all of their progenitor halos, provided that the UV background exceeds J_{21} ~ few at redshifts as high as z ~ 20}, author = {Fernandez, Ricardo and Bryan, Greg L. and Haiman, Zoltán and Li, Miao}, issn = {1365-2966}, journal = {Monthly Notices of the Royal Astronomical Society}, number = {4}, pages = {3798--3807}, publisher = {Oxford University Press}, title = {{H2 suppression with shocking inflows: Testing a pathway for supermassive black hole formation}}, doi = {10.1093/mnras/stu230}, volume = {439}, year = {2014}, } @article{17643, abstract = {Explaining the existence of supermassive black holes (SMBHs) larger than ∼10^9M⊙ at redshifts z>∼6 remains an open theoretical question. One possibility is that gas collapsing rapidly in pristine atomic cooling halos (Tvir>∼10^4K) produces 10^4−10^6M⊙ black holes. Previous studies have shown that the formation of such a black hole requires a strong UV background to prevent molecular hydrogen cooling and gas fragmentation. Recently it has been proposed that a high UV background may not be required for halos that accrete material extremely rapidly or for halos where gas cooling is delayed due to a high baryon-dark matter streaming velocity. In this work, we point out that building up a halo with Tvir>∼104K before molecular cooling becomes efficient is not sufficient for forming a direct collapse black hole (DCBH). Though molecular hydrogen formation may be delayed, it will eventually form at high densities leading to efficient cooling and fragmentation. The only obvious way that molecular cooling could be avoided in the absence of strong UV radiation, is for gas to reach high enough density to cause collisional dissociation of molecular hydrogen (∼10^4 cm^−3) before cooling occurs. However, we argue that the minimum core entropy, set by the entropy of the intergalactic medium (IGM) when it decouples from the CMB, prevents this from occurring for realistic halo masses. This is confirmed by hydrodynamical cosmological simulations without radiative cooling. We explain the maximum density versus halo mass in these simulations with simple entropy arguments. The low densities found suggest that DCBH formation indeed requires a strong UV background.}, author = {Visbal, Eli and Haiman, Zoltán and Bryan, Greg L.}, issn = {1745-3933}, journal = {Monthly Notices of the Royal Astronomical Society: Letters}, number = {1}, pages = {L100--L104}, publisher = {Oxford University Press}, title = {{A no-go theorem for direct collapse black holes without a strong ultraviolet background}}, doi = {10.1093/mnrasl/slu063}, volume = {442}, year = {2014}, }