378 research outputs found
The starburst phenomenon from the optical/near-IR perspective
The optical/near-IR stellar continuum carries unique information about the
stellar population in a galaxy, its mass function and star-formation history.
Star-forming regions display rich emission-line spectra from which we can
derive the dust and gas distribution, map velocity fields, metallicities and
young massive stars and locate shocks and stellar winds. All this information
is very useful in the dissection of the starburst phenomenon. We discuss a few
of the advantages and limitations of observations in the optical/near-IR region
and focus on some results. Special attention is given to the role of
interactions and mergers and observations of the relatively dust-free starburst
dwarfs. In the future we expect new and refined diagnostic tools to provide us
with more detailed information about the IMF, strength and duration of the
burst and its triggering mechanisms.Comment: 6 pages, 3 figures, to appear in "Starbursts: from 30 Doradus to
Lyman Break Galaxies" 2005, eds. R. de Grijs and R. M. Gonzalez Delgado
(Kluwer
Risks, alternative knowledge strategies and democratic legitimacy: the conflict over co-incineration of hazardous industrial waste in Portugal.
The decision to incinerate hazardous industrial waste in cement plants (the socalled
‘co-incineration’ process) gave rise to one of the most heated environmental
conflicts ever to take place in Portugal. The bitterest period was between 1997 and
2002, after the government had made a decision. Strong protests by residents,
environmental organizations, opposition parties, and some members of the
scientific community forced the government to backtrack and to seek scientific
legitimacy for the process through scientific expertise. The experts ratified the
government’s decision, stating that the risks involved were socially acceptable.
The conflict persisted over a decade and ended up clearing the way for a more
sustainable method over which there was broad social consensus – a multifunctional
method which makes it possible to treat, recover and regenerate most
wastes. Focusing the analysis on this conflict, this paper has three aims: (1) to
discuss the implications of the fact that expertise was ‘confiscated’ after the
government had committed itself to the decision to implement co-incineration and
by way of a reaction to the atmosphere of tension and protest; (2) to analyse the
uses of the notions of ‘risk’ and ‘uncertainty’ in scientific reports from both
experts and counter-experts’ committees, and their different assumptions about
controllability and criteria for considering certain practices to be sufficiently safe
for the public; and (3) to show how the existence of different technical scientific
and political attitudes (one more closely tied to government and the corporate
interests of the cement plants, the other closer to the environmental values of reuse
and recycling and respect for the risk perception of residents who challenged
the facilities) is closely bound up with problems of democratic legitimacy. This
conflict showed how adopting more sustainable and lower-risk policies implies a
broader view of democratic legitimacy, one which involves both civic movements
and citizens themselves
Renal pericytes: regulators of medullary blood flow
Regulation of medullary blood flow (MBF) is essential in maintaining normal kidney function. Blood flow to the medulla is supplied by the descending vasa recta (DVR), which arise from the efferent arterioles of juxtamedullary glomeruli. DVR are composed of a continuous endothelium, intercalated with smooth muscle-like cells called pericytes. Pericytes have been shown to alter the diameter of isolated and in situ DVR in response to vasoactive stimuli that are transmitted via a network of autocrine and paracrine signalling pathways. Vasoactive stimuli can be released by neighbouring tubular epithelial, endothelial, red blood cells and neuronal cells in response to changes in NaCl transport and oxygen tension. The experimentally described sensitivity of pericytes to these stimuli strongly suggests their leading role in the phenomenon of MBF autoregulation. Because the debate on autoregulation of MBF fervently continues, we discuss the evidence favouring a physiological role for pericytes in the regulation of MBF and describe their potential role in tubulo-vascular cross-talk in this region of the kidney. Our review also considers current methods used to explore pericyte activity and function in the renal medulla
Average flow constraints and stabilizability in uncertain production-distribution systems
We consider a multi-inventory system with controlled flows and uncertain demands (disturbances) bounded within assigned compact sets. The system is modelled as a first-order one integrating the discrepancy between controlled flows and demands at different sites/nodes. Thus, the buffer levels at the nodes represent the system state. Given a long-term average demand, we are interested in a control strategy that satisfies just one of two requirements: (i) meeting any possible demand at each time (worst case stability) or (ii) achieving a predefined flow in the average (average flow constraints). Necessary and sufficient conditions for the achievement of both goals have been proposed by the authors. In this paper, we face the case in which these conditions are not satisfied. We show that, if we ignore the requirement on worst case stability, we can find a control strategy driving the expected value of the state to zero. On the contrary, if we ignore the average flow constraints, we can find a control strategy that satisfies worst case stability while optimizing any linear cost on the average control. In the latter case, we provide a tight bound for the cost
The First Magnetic Fields
We review current ideas on the origin of galactic and extragalactic magnetic
fields. We begin by summarizing observations of magnetic fields at cosmological
redshifts and on cosmological scales. These observations translate into
constraints on the strength and scale magnetic fields must have during the
early stages of galaxy formation in order to seed the galactic dynamo. We
examine mechanisms for the generation of magnetic fields that operate prior
during inflation and during subsequent phase transitions such as electroweak
symmetry breaking and the quark-hadron phase transition. The implications of
strong primordial magnetic fields for the reionization epoch as well as the
first generation of stars is discussed in detail. The exotic, early-Universe
mechanisms are contrasted with astrophysical processes that generate fields
after recombination. For example, a Biermann-type battery can operate in a
proto-galaxy during the early stages of structure formation. Moreover, magnetic
fields in either an early generation of stars or active galactic nuclei can be
dispersed into the intergalactic medium.Comment: Accepted for publication in Space Science Reviews. Pdf can be also
downloaded from http://canopus.cnu.ac.kr/ryu/cosmic-mag1.pd
A novel 65 kDa RNA-binding protein in squid presynaptic terminals
Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Neuroscience 166 (2010): 73-83, doi:10.1016/j.neuroscience.2009.12.005.A polyclonal antibody (C4), raised against the head domain of chicken myosin Va,
reacted strongly towards a 65 kDa polypeptide (p65) on western blots of extracts from squid optic
lobes but did not recognize the heavy chain of squid myosin V. This peptide was not recognized by
other myosin Va antibodies, nor by an antibody specific for squid myosin V. In an attempt to
identify it, p65 was purified from optic lobes of Loligo plei by cationic exchange and reverse phase
chromatography. Several peptide sequences were obtained by mass spectroscopy from p65 cut from
SDS-PAGE gels. BLAST analysis and partial matching with ESTs from a Loligo pealei data bank
indicated that p65 contains consensus signatures for the hnRNP A/B family of RNA-binding
proteins. Centrifugation of post mitochondrial extracts from optic lobes on sucrose gradients after
treatment with RNase gave biochemical evidence that p65 associates with cytoplasmic RNP
complexes in an RNA-dependent manner. Immunohistochemistry and immunofluorescence studies
using the C4 antibody showed partial co-labeling with an antibody against squid synaptotagmin in
bands within the outer plexiform layer of the optic lobes and at the presynaptic zone of the stellate
ganglion. Also, punctate labeling by the C4 antibody was observed within isolated optic lobe
synaptosomes. The data indicate that p65 is a novel RNA-binding protein located to the presynaptic
terminal within squid neurons and may have a role in synaptic localization of RNA and its
translation or processing.REL, JCR and JEM received
financial support from the Fundação de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP), the
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and the Fundação de
Apoio ao Ensino, Pesquisa e Assistência do Hospital das Clínicas da FMRP-USP (FAEPA). JAD
received financial support from the RI-INBRE Program Grant #P20RR016457 from the Nation
Center for Research Resources, NIH, Bethesda, MD. DTPL, LC, SBFT, EJRV and MMAB were
recipients of research fellowships from FAPESP and CNPq. REL and JEM received Productivityin-
Research fellowships from CNPq
Association of branched-chain amino acids and other circulating metabolites with risk of incident dementia and Alzheimer's disease: A prospective study in eight cohorts
Introduction: Metabolite, lipid, and lipoprotein lipid profiling can provide novel insights into mechanisms underlying incident dementia and Alzheimer's disease. Methods: We studied eight prospective cohorts with 22,623 participants profiled by n
A Theoretical Model of a Molecular-Motor-Powered Pump
The motion of a cylindrical bead in a fluid contained within a two-dimensional channel is investigated using the boundary element method as a model of a biomolecular-motor-powered microfluidics pump. The novelty of the pump lies in the use of motor proteins (kinesin) to power the bead motion and the few moving parts comprising the pump. The performance and feasibility of this pump design is investigated using two model geometries: a straight channel, and a curved channel with two concentric circular walls. In the straight channel geometry, it is shown that increasing the bead radius relative to the channel width, increases the flow rate at the expense of increasing the force the kinesins must generate in order to move the bead. Pump efficiency is generally higher for larger bead radii, and larger beads can support higher imposed loads. In the circular channel geometry, it is shown that bead rotation modifies the force required to move the bead and that shifting the bead inward slightly reduces the required force. Bead rotation has a minimal effect on flow rate. Recirculation regions, which can develop between the bead and the channel walls, influence the stresses and force on the bead. These results suggest this pump design is feasible, and the kinesin molecules provide sufficient force to deliver pico- to atto- l/s flows.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44478/1/10544_2005_Article_6168.pd
Effects of Intermittent IL-2 Alone or with Peri-Cycle Antiretroviral Therapy in Early HIV Infection: The STALWART Study
The Study of Aldesleukin with and without antiretroviral therapy (STALWART) evaluated whether intermittent interleukin-2 (IL-2) alone or with antiretroviral therapy (ART) around IL-2 cycles increased CD4+ counts compared to no therapy
Titan's cold case files - Outstanding questions after Cassini-Huygens
Abstract The entry of the Cassini-Huygens spacecraft into orbit around Saturn in July 2004 marked the start of a golden era in the exploration of Titan, Saturn's giant moon. During the Prime Mission (2004–2008), ground-breaking discoveries were made by the Cassini orbiter including the equatorial dune fields (flyby T3, 2005), northern lakes and seas (T16, 2006), and the large positive and negative ions (T16 & T18, 2006), to name a few. In 2005 the Huygens probe descended through Titan's atmosphere, taking the first close-up pictures of the surface, including large networks of dendritic channels leading to a dried-up seabed, and also obtaining detailed profiles of temperature and gas composition during the atmospheric descent. The discoveries continued through the Equinox Mission (2008–2010) and Solstice Mission (2010–2017) totaling 127 targeted flybys of Titan in all. Now at the end of the mission, we are able to look back on the high-level scientific questions from the start of the mission, and assess the progress that has been made towards answering these. At the same time, new scientific questions regarding Titan have emerged from the discoveries that have been made. In this paper we review a cross-section of important scientific questions that remain partially or completely unanswered, ranging from Titan's deep interior to the exosphere. Our intention is to help formulate the science goals for the next generation of planetary missions to Titan, and to stimulate new experimental, observational and theoretical investigations in the interim
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