1,721,250 research outputs found
Jackson Mac Low
Full text linkPoet and performance artist Jackson Mac Low conducting a small orchestra for instrument and voice, and reading his own poetry. Performance at the First Towbin Poetry Festival, Bard Hall, 10/25/1975. Introduced by Robert Kelly.https://digitalcommons.bard.edu/poetry_at_bard/1221/thumbnail.jp
Jackson Mac Low
Full text linkPoet and performance artist Jackson Mac Low leading students in sound performance, and reading his own work. Bard College, 03/27/1979. It includes various experimental poems, some derived from other texts, and explores themes of language, sound, and meaning. The speaker also discusses their creative process and inspirations.
Due to machine malfunction, parts of this recording skip and fluctuate. The listener is encouraged to explore both the edited MP3 (for clarity) and the unedited WAV (for strange and protracted silences, as well as oscillations in volume; whose inclusion is perhaps more in the spirit of Mr. Mac Low’s work, and its relationship to chance)https://digitalcommons.bard.edu/poetry_at_bard/1222/thumbnail.jp
Cosmological feedback from high-redshift dwarf galaxies
No full textWe model how repeated supernova explosions in high-redshift dwarf starburst galaxies drive superbubbles and winds out of the galaxies. We compute the efficiencies of metal and mass ejection and energy transport from the galactic potentials, including the effect of cosmological infall of external gas. The starburst bubbles quickly blow out of small, high-redshift galactic disks, but must compete with the ram pressure of the infalling gas to escape into intergalactic space. We show that the assumed efficiency of the star formation rate dominates the bubble evolution and the metal, mass, and energy feedback efficiencies. With a star formation efficiency f 0:01, the ram pressure of infall can confine the bubbles around high-redshift dwarf galaxies with circular velocities vck 52 km s1. We can expect high metal and mass ejection efficiencies and moderate energy transport efficiencies in halos with vc 30 50 km s1 and f 0:01 as well as in halos with vc 100 km s1 and f30:01. Such halos collapse successively from 1–2 peaks in CDMGaussian density perturbations as time progresses. These dwarf galaxies can probably enrich low- and high-density regions of intergalactic space with metals to 103 to 102 Z as they collapse at z 8 and zP 5, respectively. They also may be able to provide adequate turbulent energy to prevent the collapse of other nearby halos, as well as to significantly broaden Ly- absorption lines to vrms 20 40 km s1. We compute the timescales for the next starbursts if gas freely falls back after a starburst, and find that for star formation efficiencies as low as fP 0:01 the next starburst should occur in less than half the Hubble time at the collapse redshift. This suggests that episodic star formation may be ubiquitous in dwarf galaxies
Comparing the statistics of interstellar turbulence in simulations and observations. Solenoidal versus compressive turbulence forcing
No full textContext. Density and velocity fluctuations on virtually all scales observed with modern telescopes show that molecular clouds (MCs) are turbulent. The forcing and structural characteristics of this turbulence are, however, still poorly understood. <BR /> Aims: To shed light on this subject, we study two limiting cases of turbulence forcing in numerical experiments: solenoidal (divergence-free) forcing and compressive (curl-free) forcing, and compare our results to observations. <BR /> Methods: We solve the equations of hydrodynamics on grids with up to 10243 cells for purely solenoidal and purely compressive forcing. Eleven lower-resolution models with different forcing mixtures are also analysed. <BR /> Results: Using Fourier spectra and Ãâ-variance, we find velocity dispersion-size relations consistent with observations and independent numerical simulations, irrespective of the type of forcing. However, compressive forcing yields stronger compression at the same rms Mach number than solenoidal forcing, resulting in a three times larger standard deviation of volumetric and column density probability distributions (PDFs). We compare our results to different characterisations of several observed regions, and find evidence of different forcing functions. Column density PDFs in the <ASTROBJ>Perseus MC</ASTROBJ> suggest the presence of a mainly compressive forcing agent within a shell, driven by a massive star. Although the PDFs are close to log-normal, they have non-Gaussian skewness and kurtosis caused by intermittency. Centroid velocity increments measured in the <ASTROBJ>Polaris Flare</ASTROBJ> on intermediate scales agree with solenoidal forcing on that scale. However, Ãâ-variance analysis of the column density in the <ASTROBJ>Polaris Flare</ASTROBJ> suggests that turbulence is driven on large scales, with a significant compressive component on the forcing scale. This indicates that, although likely driven with mostly compressive modes on large scales, turbulence can behave like solenoidal turbulence on smaller scales. Principal component analysis of <ASTROBJ>G216-2.5</ASTROBJ> and most of the <ASTROBJ>Rosette MC</ASTROBJ> agree with solenoidal forcing, but the interior of an ionised shell within the <ASTROBJ>Rosette MC</ASTROBJ> displays clear signatures of compressive forcing. <BR /> Conclusions: The strong dependence of the density PDF on the type of forcing must be taken into account in any theory using the PDF to predict properties of star formation. We supply a quantitative description of this dependence. We find that different observed regions show evidence of different mixtures of compressive and solenoidal forcing, with more compressive forcing occurring primarily in swept-up shells. Finally, we emphasise the role of the sonic scale for protostellar core formation, because core formation close to the sonic scale would naturally explain the observed subsonic velocity dispersions of protostellar cores. A movie is only available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A
22. The Role of the Machine in the Experiment of Egoless Poetry: Jackson Mac Low and the Programmable Film Reader
No full textSimulations of the star-forming molecular gas in an interacting M51-like galaxy
No full textWe present here the first of a series of papers aimed at better understanding the evolution and properties of giant molecular clouds (GMCs) in a galactic context. We perform high-resolution, three-dimensional AREPO simulations of an interacting galaxy inspired by the well-observed M51 galaxy. Our fiducial simulations include a non-equilibrium, time-dependent, chemical network that follows the evolution of atomic and molecular hydrogen as well as carbon and oxygen self-consistently. Our calculations also treat gas self-gravity and subsequent star formation (described by sink particles), and coupled supernova feedback. In the densest parts of the simulated interstellar medium (ISM), we reach sub-parsec resolution, granting us the ability to resolve individual GMCs and their formation and destruction self-consistently throughout the galaxy. In this initial work, we focus on the general properties of the ISM with a particular focus on the cold star-forming gas. We discuss the role of the interaction with the companion galaxy in generating cold molecular gas and controlling stellar birth. We find that while the interaction drives large-scale gas flows and induces spiral arms in the galaxy, it is of secondary importance in determining gas fractions in the different ISM phases and the overall star formation rate. The behaviour of the gas on small GMC scales instead is mostly controlled by the self-regulating property of the ISM driven by coupled feedback
Dynamical Properties of Molecular-forming Gas Clumps in Galaxies at the Epoch of Reionization
Full text linkWe study the properties of molecular-forming gas clumps (MGCs) at the epoch of reionization using cosmological zoom-in simulations. We identify MGCs in a z ∼ 6 prototypical galaxy ("Althæa") using an H2 density-based clump finder. We compare their mass, size, velocity dispersion, gas surface density, and virial parameter (αvir) to observations. In Althæa, the typical MGC mass and size are Mgas ≃ 10 6.5 M· and R ≃ 45-100 pc, which are comparable to those found in nearby spirals and starburst galaxies. MGCs are highly supersonic and supported by turbulence, with rms velocity dispersions of σgas ≃ 20-100 km s-1 and pressure of P/KB sime; 10 K 7.6 cm-3 (i.e., >1000× with respect to the Milky Way), similar to those found in nearby and z sim; 2 gas-rich starburst galaxies. In addition, we perform stability analysis to understand the origin and dynamical properties of MGCs. We find that MGCs are globally stable in the main disk of Althæa. Densest regions where star formation is expected to take place in clouds and cores on even smaller scales instead have lower αvir and Toomre Q values. Detailed studies of the star-forming gas dynamics at the epoch of reionization thus require a spatial resolution of ≲40 pc (≃0.′′01), which is within reach with the Atacama Large (sub-)Millimeter Array and the Next Generation Very Large Array
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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