On the orientation and magnitude of the black hole spin in galactic nuclei

Massive black holes in galactic nuclei vary their mass M and spin vector J due to accretion. In this study we relax, for the first time, the assumption that accretion can be either chaotic, i.e. when the accretion episodes are randomly and isotropically oriented, or coherent, i.e. when they occur all in a preferred plane. Instead, we consider different degrees of anisotropy in the fueling, never confining to accretion events on a fixed direction. We follow the black hole growth evolving contemporarily mass, spin modulus a and spin direction. We discover the occurrence of two regimes. An early phase (M <~ 10 million solar masses) in which rapid alignment of the black hole spin direction to the disk angular momentum in each single episode leads to erratic changes in the black hole spin orientation and at the same time to large spins (a ~ 0.8). A second phase starts when the black hole mass increases above >~ 10 million solar masses and the accretion disks carry less mass and angular momentum relatively to the hole. In the absence of a preferential direction the black holes tend to spin-down in this phase. However, when a modest degree of anisotropy in the fueling process (still far from being coherent) is present, the black hole spin can increase up to a ~ 1 for very massive black holes (M >~ 100 million solar masses), and its direction is stable over the many accretion cycles. We discuss the implications that our results have in the realm of the observations of black hole spin and jet orientations.Comment: 14 pages, 7 figures, accepted for publication in Ap

A path to radio-loudness through gas-poor galaxy mergers and the role of retrograde accretion

In this proceeding we explore a pathway to radio-loudness under the hypothesis that retrograde accretion onto giant spinning black holes leads to the launch of powerful jets, as seen in radio loud QSOs and recently in LAT/Fermi and BAT/Swift Blazars. Counter-rotation of the accretion disc relative to the BH spin is here associated to gas-poor galaxy mergers progenitors of giant (missing-light) ellipticals. The occurrence of retrograde accretion enters as unifying element that may account for the radio-loudness/galaxy morphology dichotomy observed in AGN.Comment: To appear in the proceedings of the conference "Accretion and Ejection in AGN: A global view, June 22-26 2009 - Como, Italy

Investigating Social Exclusion in Late Prehistoric Italy: Preliminary Results of the ‘‘IN or OUT’’ Project (PHASE 1)

This report presents the preliminary results of the ‘‘IN or OUT’’ Project, a collaborative, interdisciplinary effort which aims to investigate social exclusion, marginality and the adoption of anomalous funerary rites in late prehistoric Italy. In particular, this contribution explores the incidence and meaning of practices of ritual marginalisation and funerary deviancy in the region of Veneto between the Bronze Age and the early Iron Age period

Search for Dark Matter direct production in the monophoton plus missing transverse momentum final state in pp collisions at √s = 8TeV with the ATLAS detector

This paper presents a search for dark matter pair production in association with an energetic photon in 20.3 fb−1 of pp collisions collected at √s = 8TeV by the ATLAS detector at the LHC. The final state investigated in this analysis is defined by large missing transverse momentum (EmissT > 150GeV) and by the presence of an energetic photon (pT > 125 GeV). Observations in data are compared to the Standard Model expectations and no significant excess is found. A modelindependent limit is set on the presence of new physics in data. Data are also interpreted in the framework of effective field theories which describe the interaction between dark matter and incoming partons as a contact interaction parameterized by a set of dimensional operators

All-optical pulse bursts generation from a nonlinear amplifying loop mirror

A novel method for the generation of bursts of optical pulses is proposed. It is shown analytically that a nonlinear amplifying loop mirror in single pass configuration can transform a low power input pulse into a burst consisting of pulses with individual energy up to tens of nJ. The burst features; number of pulses; and their peak power, energy, and duration can be tuned and controlled. Numerical simulations show robustness of the technique to presence of Raman scattering and that sub-picosecond pulse duration can be achieved. The latter highlights the relevance of the proposed pulse bursts generator for material processing and in medical applications involving optical ablation

Optical Darboux Transformer

The Optical Darboux Transformer is introduced as a photonic device which performs the Darboux transformation directly in the optical domain. This enables two major advances for signal processing based on the nonlinear Fourier transform: (i) the multiplexing of different solitonic waveforms corresponding to arbitrary number of discrete eigenvalues of the Zakharov-Shabat system in the optical domain, and (ii) the selective filtering of an arbitrary number of individual solitons too. The Optical Darboux Transformer can be built using existing commercially available photonic technology components and constitutes a universal tool for signal processing, optical communications, optical rogue waves generation, and waveform shaping and control in the nonlinear Fourier domain

Developmental Effects of Chronic Low-Level Arsenic Exposure in Mouse Embryonic Stem Cells and in Human Induced Pluripotent Stem Cells

Arsenic is an environmental contaminant commonly found in food and drinking water. Exposure to arsenic during embryonic development has been linked to reduced muscle growth, disrupted muscle development and locomotor activity, impaired neurodevelopment, reduced IQ, impaired memory and learning deficits. While the mechanisms responsible for developmental changes following in utero exposure to arsenic are not well known, one possibility is that arsenic might disrupt proper cellular differentiation. Therefore, we aimed to investigate the mechanisms by which arsenic exposure could alter stem cell differentiation into neurons. First, we continuously exposed P19 mouse embryonic stem (ES) cells to 0.1 μM (7.5 ppb) arsenic for 28 weeks to assess if chronic, low level arsenic exposure would delay cellular differentiation into neuronal cells. Importantly, this concentration is below the current drinking water standard of 10 ppb. The results show temporal changes of genes associated with pluripotency and cellular differentiation. Specifically, starting at week 12, transcript levels of the pluripotency markers Sox2 and Oct4 were increased by 1.9- to 2.5- fold in arsenic-exposed cells. By week 16, SOX2 protein expression was increased, and starting at week 20, the expression of a SOX2 target protein, N-cadherin, was also increased. Concurrently, by week 16, levels of the differentiation marker Gdf3 were decreased by 3.4- fold, along with the reduced phosphorylation of the GDF3 target protein SMAD2/3. To investigate the mechanisms responsible for maintaining pluripotency and hindering cellular differentiation into neurons, RNA sequencing was performed in control and arsenic-exposed cells at week 8, 16 and 24. This analysis revealed significant exposure-dependent changes in gene expression starting at week 16. Pathway analysis showed that arsenic exposure disrupts the Hippo signaling pathway, which is involved in pluripotency maintenance and embryonic development. Immunohistochemistry revealed that the ratios between nuclear (active) and cytoplasmic (inactive) expression of the main effector YAP and the main transcription factor TEAD were significantly increased in arsenic-exposed cells at week 16 and 28. Consistently, expression of the Hippo pathway target genes Ctgf and c-Myc were also significantly upregulated following arsenic exposure. These results indicate that chronic arsenic exposure impairs the Hippo signaling pathway resulting in increased YAP activation, thereby reducing neuronal differentiation. Previous studies have shown that P19 cells differentiate into sensory neurons, so we also wanted to investigate whether arsenic impaired differentiation into motor neurons. Thus, we switched to using human induced pluripotent stem (iPS) cells, which can differentiate into day 6 neuroepithelial progenitors (NEPs), day 12 motor neuron progenitors (MNPs), day 18 early motor neurons (MNs) and day 28 mature MNs. During this process, cells were exposed to arsenic concentrations up to 0.75 μM (56.25 ppb), and morphological alterations along with pluripotency and stage-specific neuronal markers were assessed. Day 6 NEPs exposed to arsenic had reduced levels of the neural progenitor/stem cell marker NES and neuroepithelial progenitor marker SOX1, while levels of these transcripts were increased in MNPs at day 12. Additionally, levels of the motor neuron progenitor marker OLIG2 were increased in day 12 MNPs while levels of the cholinergic neuron marker CHAT were reduced by 2.5- fold in MNPs exposed arsenic. RNA sequencing and pathway analysis showed that the cholinergic synapse pathway was impaired following exposure to 0.5 μM arsenic, and that transcript levels of genes involved in acetylcholine synthesis (CHAT), transport (SLC18A3 and SLC5A7) and degradation (ACHE) were all downregulated in early motor neurons at day 18. In mature motor neurons at day 28, expression of MAP2 and ChAT protein was significantly downregulated by 2.8- and 2.1- fold, respectively, concomitantly with a reduction in neurite length by 1.8- fold following exposure to 0.5 μM arsenic. Similarly, adult mice exposed to 100 ppb arsenic for five weeks had significantly reduced hippocampal ChAT levels. Taken all together, the results of the dissertation show that environmentally relevant levels of arsenic have detrimental effects on neuronal differentiation

Explicit dynamics simulation of blade cutting of thin elastoplastic shells using "directional" cohesive elements in solid-shell finite element models

The intentional or accidental cutting of thin shell structures by means of a sharp object is of interest in many engineering applications. The process of cutting involves several types of nonlinearities, such as large deformations, contact, crack propagation and, in the case of laminated shells, delamination. In addition to these, a special difficulty is represented by the blade sharpness, whose accurate geometric resolution would require meshes with characteristic size of the order of the blade curvature radius. A computational finite element approach for the simulation of blade cutting of thin shells is proposed and discussed. The approach is developed in an explicit dynamics framework. Solid-shell elements are used for the discretization, in view of possible future inclusion in the model of delamination processes. Since a sharp blade can interfere with the transmission of cohesive forces between the crack flanks in the cohesive process zone, standard cohesive interface elements are not suited for the simulation of this type of problems unless extremely fine meshes, with characteristic size comparable to the blade curvature radius, are used. To circumvent the problem, the use of a new type of directional cohesive interface element, previously proposed for the simulation of crack propagation in elastic shells, is further developed and reformulated for application to the cutting of elastoplastic thin structures, discretized by solid-shell elements. The proposed approach is validated by means of application to several cutting problems of engineering interest

Pushing 1D CCSNe to explosions: model and SN 1987A

We report on a method, PUSH, for triggering core-collapse supernova explosions of massive stars in spherical symmetry. We explore basic explosion properties and calibrate PUSH such that the observables of SN1987A are reproduced. Our simulations are based on the general relativistic hydrodynamics code AGILE combined with the detailed neutrino transport scheme IDSA for electron neutrinos and ALS for the muon and tau neutrinos. To trigger explosions in the otherwise non-exploding simulations, we rely on the neutrino-driven mechanism. The PUSH method locally increases the energy deposition in the gain region through energy deposition by the heavy neutrino flavors. Our setup allows us to model the explosion for several seconds after core bounce. We explore the progenitor range 18-21M$_{\odot}$. Our studies reveal a distinction between high compactness (HC) and low compactness (LC) progenitor models, where LC models tend to explore earlier, with a lower explosion energy, and with a lower remnant mass. HC models are needed to obtain explosion energies around 1 Bethe, as observed for SN1987A. However, all the models with sufficiently high explosion energy overproduce $^{56}$Ni. We conclude that fallback is needed to reproduce the observed nucleosynthesis yields. The nucleosynthesis yields of $^{57-58}$Ni depend sensitively on the electron fraction and on the location of the mass cut with respect to the initial shell structure of the progenitor star. We identify a progenitor and a suitable set of PUSH parameters that fit the explosion properties of SN1987A when assuming 0.1M$_{\odot}$ of fallback. We predict a neutron star with a gravitational mass of 1.50M$_{\odot}$. We find correlations between explosion properties and the compactness of the progenitor model in the explored progenitors. However, a more complete analysis will require the exploration of a larger set of progenitors with PUSH.Comment: revised version as accepted by ApJ (results unchanged, text modified for clarification, a few references added); 26 pages, 20 figure