9,111 research outputs found
A multiwavelength survey of interacting galaxies
Galaxy-galaxy collisions are known to produce drastic changes in morphology and, in many cases, enhance the level of star formation activity in galaxies. In order to better quantify the effects that interactions have on the star formation characteristics of galaxies the authors undertook a multiwavelength survey of a large sample of interacting disk-type galaxies. The sample is optically-selected, the inclusion of systems having been based upon the presence of unusual morphological features--such as tidal tails, plumes, rings, warped disks--suggestive of tidal interaction. The sample is composed of about 115 systems, most of which are spiral-spiral pairs, with a few spiral-elliptical pairs and a few merging systems (see Bushouse 1986 for more details of the sample selection). This sample has now been studied in the optical, infrared, and radio regimes, including optical spectra and H alpha images, near-infrared photometry and imaging, far-infrared photometry, H I 21 cm emission-line measurements, Very Large Array (VLA) 20 cm maps, and CO emission-line measurements. This paper presents an overview and comparison of the results of the optical, infrared and CO surveys. With these data the authors can compare the far-infrared and CO properties of the galaxies with the classic optical and radio indicators of star formation activity and thereby determine what, if any, relationships exist between star formation activity and the far-infrared and CO properties of the galaxies
Specific Rab GTPase-activating proteins define the Shiga toxin and epidermal growth factor uptake pathways
Rab family guanosine triphosphatases (GTPases) together with their regulators define specific pathways of membrane traffic within eukaryotic cells. In this study, we have investigated which Rab GTPase-activating proteins (GAPs) can interfere with the trafficking of Shiga toxin from the cell surface to the Golgi apparatus and studied transport of the epidermal growth factor (EGF) from the cell surface to endosomes. This screen identifies 6 (EVI5, RN-tre/USP6NL, TBC1D10A–C, and TBC1D17) of 39 predicted human Rab GAPs as specific regulators of Shiga toxin but not EGF uptake. We show that Rab43 is the target of RN-tre and is required for Shiga toxin uptake. In contrast, RabGAP-5, a Rab5 GAP, was unique among the GAPs tested and reduced the uptake of EGF but not Shiga toxin. These results suggest that Shiga toxin trafficking to the Golgi is a multistep process controlled by several Rab GAPs and their target Rabs and that this process is discrete from ligand-induced EGF receptor trafficking
Large-Scale Magnetic-Field Generation by Randomly Forced Shearing Waves
A rigorous theory for the generation of a large-scale magnetic field by
random non-helically forced motions of a conducting fluid combined with a
linear shear is presented in the analytically tractable limit of low Rm and
weak shear. The dynamo is kinematic and due to fluctuations in the net
(volume-averaged) electromotive force. This is a minimal proof-of-concept
quasilinear calculation aiming to put the shear dynamo, a new effect recently
found in numerical experiments, on a firm theoretical footing. Numerically
observed scalings of the wavenumber and growth rate of the fastest growing
mode, previously not understood, are derived analytically. The simplicity of
the model suggests that shear dynamo action may be a generic property of
sheared magnetohydrodynamic turbulence.Comment: Paper substantially rewritten, results changed (relative to v1).
Revised versio
A new chiral electro-optic effect: Sum-frequency generation from optically active liquids in the presence of a dc electric field
We report the observation of sum-frequency signals that depend linearly on an
applied electrostatic field and that change sign with the handedness of an
optically active solution. This recently predicted chiral electro-optic effect
exists in the electric-dipole approximation. The static electric field gives
rise to an electric-field-induced sum-frequency signal (an achiral third-order
process) that interferes with the chirality-specific sum-frequency at
second-order. The cross-terms linear in the electrostatic field constitute the
effect and may be used to determine the absolute sign of second- and
third-order nonlinear optical susceptibilities in isotropic media.Comment: Submitted to Physical Revie
An algorithm for generating quasiperiodic patterns and their approximants
An algorithm for projecting the interior of a hypercube in N-dimensions on to an m-dimensional subspace has been developed and incorporated into a computer program for generating quasiperiodic and periodic patterns in an n-dimensional subspace. Some aspects of the resulting orthorhombic approximants to Penrose tiling patterns are discussed and illustrated
Religion and Diplomacy
Archbishop Runcie\u27s presentation represents well his interest in and experience of the complex intersection between religion and world events. Both his consideration of the difficult history of the Christian Church, and his call to greater understanding of other religions reflect his long work with and commitment to these issues. His refusal to simplify the problems tied to religion is characteristic both of his efforts to find real solutions to world problems and his intellectual rigor
The History of Farm Foxes Undermines the Animal Domestication Syndrome
The Russian Farm-Fox Experiment is the best known experimental study in animal domestication. By subjecting a population of foxes to selection for tameness alone, Dimitry Belyaev generated foxes that possessed a suite of characteristics that mimicked those found across domesticated species. This \u27domestication syndrome\u27 has been a central focus of research into the biological pathways modified during domestication. Here, we chart the origins of Belyaev\u27s foxes in eastern Canada and critically assess the appearance of domestication syndrome traits across animal domesticates. Our results suggest that both the conclusions of the Farm-Fox Experiment and the ubiquity of domestication syndrome have been overstated. To understand the process of domestication requires a more comprehensive approach focused on essential adaptations to human-modified environments
International Labor Standards, Soft Regulation, and National Government Roles
[Excerpt] In this article, we briefly describe the different approaches to the regulation of international labor standards, and then argue for a new role for national governments based on soft rather than hard regulation approaches. We argue that this new role shows potential for significantly enhancing progress in international labor standards, since it enables governments to articulate a position without having to deal with the enforcement issues that hard regulation mandates. We justify this new role for governments based on the increasing use of soft regulation in the international arena. Of course, this approach is not without its own problems, but given that existing approaches have all provided imperfect solutions to the problem of improving labor standards globally, re-visiting the role of national governments is in our view, highly important
- …