7,870 research outputs found

    Radio frequency baseband recording technique

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    Technique uses a helical-scan video recorder with auxiliary signal-conditioning equipment to provide an inexpensive, high-capacity magnetic tape recording of a 112 channel, phase-locked, multiplexed, baseband signal

    Local Starbursts in a Cosmological Context

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    In this contribution I introduce some of the major issues that motivate the conference, with an emphasis on how starbursts fit into the ``big picture''. I begin by defining starbursts in several different ways, and discuss the merits and limitations of these definitions. I will argue that the most physically useful definition of a starburst is its ``intensity'' (star formation rate per unit area). This is the most natural parameter to compare local starbursts with physically similar galaxies at high redshift, and indeed I will argue that local starbursts are unique laboratories to study the processes at work in the early universe. I will describe how NASA's GALEX mission has uncovered a rare population of close analogs to Lyman Break Galaxies in the local universe. I will then compare local starbursts to the Lyman-Break and sub-mm galaxies high redshift populations, and speculate that the multidimensional ``manifold'' of starbursts near and far can be understood largely in terms of the Schmidt/Kennicutt law and galaxy mass-metallicity relation. I will briefly summarize he properties of starburst-driven galactic superwinds and their possible implications for the evolution of galaxies and the IGM. These complex multiphase flows are best studied in nearby starbursts, where we can study the the hot X-ray gas that contains the bulk of the energy and newly produced metals.Comment: Proceedings of the Conference "Starbursts: Fropm 30 Doradus to Lyman Break Galaxies

    T-Branes and Monodromy

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    We introduce T-branes, or "triangular branes," which are novel non-abelian bound states of branes characterized by the condition that on some loci, their matrix of normal deformations, or Higgs field, is upper triangular. These configurations refine the notion of monodromic branes which have recently played a key role in F-theory phenomenology. We show how localized matter living on complex codimension one subspaces emerge, and explain how to compute their Yukawa couplings, which are localized in complex codimension two. Not only do T-branes clarify what is meant by brane monodromy, they also open up a vast array of new possibilities both for phenomenological constructions and for purely theoretical applications. We show that for a general T-brane, the eigenvalues of the Higgs field can fail to capture the spectrum of localized modes. In particular, this provides a method for evading some constraints on F-theory GUTs which have assumed that the spectral equation for the Higgs field completely determines a local model.Comment: 110 pages, 5 figure

    The Footprint of F-theory at the LHC

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    Recent work has shown that compactifications of F-theory provide a potentially attractive phenomenological scenario. The low energy characteristics of F-theory GUTs consist of a deformation away from a minimal gauge mediation scenario with a high messenger scale. The soft scalar masses of the theory are all shifted by a stringy effect which survives to low energies. This effect can range from 0 GeV up to ~ 500 GeV. In this paper we study potential collider signatures of F-theory GUTs, focussing in particular on ways to distinguish this class of models from other theories with an MSSM spectrum. To accomplish this, we have adapted the general footprint method developed recently for distinguishing broad classes of string vacua to the specific case of F-theory GUTs. We show that with only 5 fb^(-1) of simulated LHC data, it is possible to distinguish many mSUGRA models and low messenger scale gauge mediation models from F-theory GUTs. Moreover, we find that at 5 fb^(-1), the stringy deformation away from minimal gauge mediation produces observable consequences which can also be detected to a level of order ~ +/- 80 GeV. In this way, it is possible to distinguish between models with a large and small stringy deformation. At 50 fb^(-1), this improves to ~ +/- 10 GeV.Comment: 85 pages, 37 figure

    On the Escape of Ionizing Radiation from Starbursts

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    Far-ultraviolet spectra obtained with FUSEFUSE show that the strong CIIλCII\lambda1036 interstellar absorption-line is essentially black in five of the UV-brightest local starburst galaxies. Since the opacity of the neutral ISM below the Lyman-edge will be significantly larger than in the CIICII line, these data provide strong constraints on the escape of ionizing radiation from these starbursts. Interpreted as a a uniform absorbing slab, the implied optical depth at the Lyman edge is huge (τ0≥102\tau_0 \geq 10^2). Alternatively, the areal covering factor of opaque material is typically ≥\geq 94%. Thus, the fraction of ionizing stellar photons that escape the ISM of each galaxy is small: our conservative estimates typically yield fesc≤6f_{esc} \leq 6%. Inclusion of extinction due to dust will further decrease fescf_{esc}. An analogous analysis of the rest-UV spectrum of the star-forming galaxy MS1512−CB58MS 1512-CB58 at zz =2.7 leads to similar constraints on fescf_{esc}. These new results agree with the constraints provided by direct observations below the Lyman edge in a few other local starbursts. However, they differ from the recently reported properties of star-forming galaxies at z≥z \geq 3. We assess the idea that the strong galactic winds seen in many powerful starbursts clear channels through their neutral ISM. We show empirically that such outflows may be a necessary - but not sufficient - part of the process for creating a relatively porous ISM. We note that observations will soon document the cosmic evolution in the contribution of star-forming galaxies to the metagalactic ionizing background, with important implications for the evolution of the IGM.Comment: 17 pages; ApJ, in pres

    Push-Pull Control of Motor Output

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    Inhibition usually decreases input–output excitability of neurons. If, however, inhibition is coupled to excitation in a push–pull fashion, where inhibition decreases as excitation increases, neuron excitability can be increased. Although the presence of push–pull organization has been demonstrated in single cells, its functional impact on neural processing depends on its effect on the system level. We studied push–pull in the motor output stage of the feline spinal cord, a system that allows independent control of inhibitory and excitatory components. Push–pull organization was clearly present in ankle extensor motoneurons, producing increased peak-to-peak modulation of synaptic currents. The effect at the system level was equally strong. Independent control of the inhibitory component showed that the stronger the background of inhibition, the greater the peak force production. This illustrates the paradox at the heart of push–pull organization: increased force output can be achieved by increasing background inhibition to provide greater disinhibition

    How Can We Improve Government Performance?

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    We expect our governments to tackle a diverse array of problems and take on a myriad of responsibilities. Often, we are frustrated at their apparent lack of success at doing so. What are the key factors that impact how effectively government agencies perform? Drawing upon my own empirical research and the public administration literature, I present a framework for thinking about the answer to this question, along with ideas for how to improve government performance. Specifically, I focus on the impact of management quality on government performance; including its interrelationship with other important factors such as resources, politics, and the nature of the problem situation. The poster also offers ideas for advancing scholarship that seeks to make practical recommendations for improving public management and government performance. Citizens and scholars interested in developing a better understanding of how to assess and improve government should find this poster offers valuable food for thought.https://fuse.franklin.edu/ss2014/1022/thumbnail.jp

    Ethical Leadership: Creating Ethical Organizations

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    Many scholars examine this issue primarily from an individual perspective and in abstract or stylistic manner in which the leader serves as sort of an ethical judge making a ruling. This poster examines the issue of ethical leadership from an organizational and practical perspective where a leader must think systemically about how to create an ethical organization. In doing so, the leader has to think like an engineer who takes action to design organizational structures that shape and direct action systematically in order to help create an ethical environment. The author applies systems thinking and uses the McKinsey 7-S to present ideas about how to create an ethical organization. The presentation is designed to stimulate a dialogue about what it means to be an ethical leader and how leaders can make their organizations ethical. In short, the author introduces the idea of ethical leadership as a systemic organizational responsibility that goes well beyond simply making ethical decisions from an individual perspective.https://fuse.franklin.edu/ss2014/1033/thumbnail.jp
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