2,009 research outputs found
Structural basis for the extended CAP-Gly domains of p150(glued) binding to microtubules and the implication for tubulin dynamics
p150(glued) belongs to a group of proteins accumulating at microtubule plus ends (+TIPs). It plays a key role in initiating retrograde transport by recruiting and tethering endosomes and dynein to microtubules. p150(glued) contains an N-terminal microtubule-binding cytoskeleton-associated protein glycine-rich (CAP-Gly) domain that accelerates tubulin polymerization. Although this copolymerization is well-studied using light microscopic techniques, structural consequences of this interaction are elusive. Here, using electron-microscopic and spectroscopic approaches, we provide a detailed structural view of p150(glued) CAP-Gly binding to microtubules and tubulin. Cryo-EM 3D reconstructions of p150(glued)-CAP-Gly complexed with microtubules revealed the recognition of the microtubule surface, including tubulin C-terminal tails by CAP-Gly. These binding surfaces differ from other retrograde initiation proteins like EB1 or dynein, which could facilitate the simultaneous attachment of all accessory components. Furthermore, the CAP-Gly domain, with its basic extensions, facilitates lateral and longitudinal interactions of tubulin molecules by covering the tubulin acidic tails. This shielding effect of CAP-Gly and its basic extensions may provide a molecular basis of the roles of p150(glued) in microtubule dynamics
Soziale Innovationen für eine zukunftsfähige Lebensweise:Gemeinschaften und Ökodörfer als experimentierende Lernfelder für sozial-ökologische Nachhaltigkeit
Auf der Suche nach Lösungen für die soziale, ökologische und ökonomische Krise, explorierte die Autorin sozialökologische Ansätze und die Bedeutung der sozialen Dimension der Nachhaltigkeit. Wie entstehen sozial und ökologisch nachhaltige Organisationsstrukturen? Aus Nachhaltigkeitsansätzen wurde ein „Prinzipienkatalog“ zusammengestellt anhand dessen sieben sozialökologische Gemeinschaften und Ökodörfer ausgewählt und mittels je mehrwöchigen teilnehmenden Beobachtungsbesuchen beforscht wurden. Die Umsetzung ihrer Visionen wurde exploriert und ihre Praktiken auf innovative Methoden sozial-ökologisch nachhaltiger Lebensweise ausgewertet. Ergebnis ist eine Zusammenhangsanalyse der Methoden zum Aufbau und Erhalt zukunftsfähiger Sozialwesen: eine werteorientierte Basis, Methoden effektiver Entscheidungsfindungsprozesse, Pflege gemeinschaftlicher Nachbarschaft und Basis nachhaltiger Wirtschaftsmethoden – ein Methodenset zur Anregungen für die Praxis auch in anderen gesellschaftlichen Kontexten.Has modernity killed “community”? What is the social dimension of sustainability and why is community relevant for it? After discussing sociological theories and Communitarian efforts the author generates criteria of sustainable living from contemporary research. For empirical study worthwhile communities were selected according to the criteria. Do intentional communities offer realistic solutions to the ecological, social and economic crises? Do they realize their ambitious visions? In participant observation during several week-long visits in seven intentional communities (mainly in Germany) the cases were specified as “living laboratories” of communal and ecological living. The most innovative methods in sustainable living combining individual freedom and communal cooperation were identified and described in the areas of membership governance, decision making, and communication to show transferrable methods to other communities and groups
Bildet Gemeinschaften - oder geht unter!:Eine Untersuchung selbstverwalteter, subsistenter Gemeinschaftsprojekte und Ökodörfer in Deutschland – Modelle für eine zukunftsfähige Lebensweise?
Nach theoretischen Vorüberlegungen, was nachhaltige Lebensweise ausmacht, lag der Fokus auf Selbstversorgung und Selbstverwaltung unter Verwendung des Subsistenzansatzes und systemtheoretischer Betrachtungsweise. Daraus abgeleitete Kriterien führten im empirischen Teil zu Intentionalen Gemeinschaften, die nachhaltige Lebensweisen erproben. Erstens wurden mittels eines Auswahlverfahrens mit quantitativen Daten aus dem „Eurotopia“ zwei Projekte ausgewählt: das Ökodorf Sieben Linden und die Kommune Niederkaufungen. Zweitens wurden deren Selbstversorgung und Entscheidungsstrukturen mit teilnehmender Beobachtung, Feldforschung und Interviews erforscht. Im Fazit werden die gemeinschaftlichen Praktiken und die gesellschaftliche Wirkung der Projekte reflektiert. Die Spannung zwischen Ideal und Umsetzung zeigte die Projekte weniger als Prototypen, sondern als Experimente, die ein innovatives Feld für nachhaltige Lebensweise kreieren
Effect of Feeding Field Peas on Fresh Beef Quality
Th is study was conducted over two years to evaluate the use of field peas during two phases of production (grazing and finishing) on overall fresh beef quality. The backgrounding treatments included: no supplement, field peas, or dry- rolled corn and finishing treatments included the presence or absence of field peas. Loin samples (n = 232) were aged for 14 d and placed under retail display conditions for 7 d. Dietary treatments had no effect on tenderness (WBSF or SSF) or visual discoloration and minimal effects on objective color, lipid oxidation and fatty acid composition. These data indicate field peas may be used as an alternative feed for growing and finishing cattle with minimal to no negative impact on fresh meat quality
Effect of Feeding Field Peas on Fresh Beef Quality
Th is study was conducted over two years to evaluate the use of field peas during two phases of production (grazing and finishing) on overall fresh beef quality. The backgrounding treatments included: no supplement, field peas, or dry- rolled corn and finishing treatments included the presence or absence of field peas. Loin samples (n = 232) were aged for 14 d and placed under retail display conditions for 7 d. Dietary treatments had no effect on tenderness (WBSF or SSF) or visual discoloration and minimal effects on objective color, lipid oxidation and fatty acid composition. These data indicate field peas may be used as an alternative feed for growing and finishing cattle with minimal to no negative impact on fresh meat quality
Global existence for the spherically symmetric Einstein-Vlasov system with outgoing matter
We prove a new global existence result for the asymptotically flat,
spherically symmetric Einstein-Vlasov system which describes in the framework
of general relativity an ensemble of particles which interact by gravity. The
data are such that initially all the particles are moving radially outward and
that this property can be bootstrapped. The resulting non-vacuum spacetime is
future geodesically complete.Comment: 16 page
Infrared Spectroscopy of a Massive Obscured Star Cluster in the Antennae Galaxies (NGC 4038/4039) with NIRSPEC
We present infrared spectroscopy of the Antennae Galaxies (NGC 4038/4039)
with NIRSPEC at the W. M. Keck Observatory. We imaged the star clusters in the
vicinity of the southern nucleus (NGC 4039) in 0.39" seeing in K-band using
NIRSPEC's slit-viewing camera. The brightest star cluster revealed in the
near-IR (M_K(0) = -17.9) is insignificant optically, but coincident with the
highest surface brightness peak in the mid-IR (12-18 micron) ISO image
presented by Mirabel et al. (1998). We obtained high signal-to-noise 2.03 -
2.45 micron spectra of the nucleus and the obscured star cluster at R ~ 1900.
The cluster is very young (4 Myr old), massive (16e6 M_sun), and compact
(density ~ 115 M_sun pc^(-3) within a 32 pc half-light radius), assuming a
Salpeter IMF (0.1 - 100 M_sun). Its hot stars have a radiation field
characterized by T_eff ~ 39,000 K, and they ionize a compact H II region with
n_e ~ 1e4 cm^(-3). The stars are deeply embedded in gas and dust (A_V ~ 9-10
mag), and their strong FUV field powers a clumpy photodissociation region with
densities n_H >= 1e5 cm^(-3) on scales of up to 200 pc, radiating L[H_2 1-0
S(1)] = 9600 L_sun.Comment: 4 pages, 5 embedded figures. To appear in proceedings of 33d ESLAB
Symposium: Star Formation from the Small to the Large Scale, held in
Noordwijk, The Netherlands, Nov. 1999. Also available at
http://astro.berkeley.edu/~agilber
Mid-infrared diagnostics of starburst galaxies: clumpy, dense structures in star-forming regions in the Antennae (NGC 4038/4039)
Recently, mid-infrared instruments have become available on several large
ground-based telescopes, resulting in data sets with unprecedented spatial
resolution at these long wavelengths. In this paper we examine
'ground-based-only' diagnostics, which can be used in the study of star-forming
regions in starburst galaxies. By combining output from the stellar population
synthesis code Starburst 99 with the photoionization code Mappings, we model
stellar clusters and their surrounding interstellar medium, focusing on the
evolution of emission lines in the N- and Q-band atmospheric windows (8-13 and
16.5-24.5 micron respectively) and those in the near-infrared. We address the
detailed sensitivity of various emission line diagnostics to stellar population
age, metallicity, nebular density, and ionization parameter. Using our model
results, we analyze observations of two stellar clusters in the overlap region
of the Antennae galaxies obtained with VLT Imager and Spectrometer for mid
Infrared (VISIR). We find evidence for clumpy, high density, ionized gas. The
two clusters are young (younger than 2.5 and 3 Myr respectively), the
surrounding interstellar matter is dense (10^4 cm^-3 or larger) and can be
characterized by a high ionization parameter (logU > -1.53). Detailed analysis
of the mid-infrared spectral features shows that a (near-)homogeneous medium
cannot account for the observations, and that complex structure on scales below
the resolution limit, containing several young stellar clusters embedded in
clumpy gas, is more likely.Comment: 24 pages, 16 figures (3 in color), accepted for publication in Ap
High-Resolution Imaging of Molecular Gas and Dust in the Antennae (NGC 4038/39): Super Giant Molecular Complexes
We present new aperture synthesis CO maps of the Antennae (NGC 4038/39)
obtained with the Caltech Millimeter Array. These sensitive images show
molecular emission associated with the two nuclei and a partial ring of star
formation to the west of NGC 4038, as well as revealing the large extent of the
extra-nuclear region of star formation (the ``overlap region''), which
dominates the CO emission from this system. The largest molecular complexes
have masses of 3-6x10^8 M_sun, typically an order of magnitude larger than the
largest structures seen to date in more quiescent galaxy disks. The extremely
red luminous star clusters identified previously with HST are well-correlated
with the CO emission, which supports the conclusion that they are highly
embedded young objects rather than old globular clusters. There is an excellent
correlation between the CO emission and the 15 micron emission seen with ISO,
particularly for the brightest regions. The most massive complexes in the
overlap region have similar [NeIII]/[NeII] ratios, which implies that all these
regions are forming many massive stars. However, only the brightest
mid-infrared peak shows strong, rising continuum emission longward of 10
microns, indicative of very small dust grains heated to high temperatures by
their proximity to nearby luminous stars. Since these grains are expected to be
removed rapidly from the immediate environment of the massive stars, it is
possible that this region contains very young (< 1 Myr) sites of star
formation. Alternatively, fresh dust grains could be driven into the sphere of
influence of the massive stars, perhaps by the bulk motions of two giant
molecular complexes. The kinematics and morphology of the CO emission in this
region provide some support for this second scenario.Comment: Accepted for publication in The Astrophysical Journal, 13 pages, 5
figures, higher quality color images available at
http://www.astro.cornell.edu/staff/vassilis/papers/ngc4038_co.ps.g
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