3,511 research outputs found
Connection between type B (or C) and F factorizations and construction of algebras
In a recent paper (Del Sol Mesa A and Quesne C 2000 J. Phys. A: Math. Gen. 33
4059), we started a systematic study of the connections among different
factorization types, suggested by Infeld and Hull, and of their consequences
for the construction of algebras. We devised a general procedure for
constructing satellite algebras for all the Hamiltonians admitting a type E
factorization by using the relationship between type A and E factorizations.
Here we complete our analysis by showing that for Hamiltonians admitting a type
F factorization, a similar method, starting from either type B or type C ones,
leads to other types of algebras. We therefore conclude that the existence of
satellite algebras is a characteristic property of type E factorizable
Hamiltonians. Our results are illustrated with the detailed discussion of the
Coulomb problem.Comment: minor changes, 1 additional reference, final form to be published in
JP
Alveolar macrophages and Toll-like receptor 4 mediate ventilated lung ischemia reperfusion injury in mice.
BackgroundIschemia-reperfusion (I-R) injury is a sterile inflammatory process that is commonly associated with diverse clinical situations such as hemorrhage followed by resuscitation, transient embolic events, and organ transplantation. I-R injury can induce lung dysfunction whether the I-R occurs in the lung or in a remote organ. Recently, evidence has emerged that receptors and pathways of the innate immune system are involved in recognizing sterile inflammation and overlap considerably with those involved in the recognition of and response to pathogens.MethodsThe authors used a mouse surgical model of transient unilateral left pulmonary artery occlusion without bronchial involvement to create ventilated lung I-R injury. In addition, they mimicked nutritional I-R injury in vitro by transiently depriving cells of all nutrients.ResultsCompared with sham-operated mice, mice subjected to ventilated lung I-R injury had up-regulated lung expression of inflammatory mediator messenger RNA for interleukin-1β, interleukin-6, and chemokine (C-X-C motif) ligand-1 and -2, paralleled by histologic evidence of lung neutrophil recruitment and increased plasma concentrations of interleukin-1β, interleukin-6, and high-mobility group protein B1 proteins. This inflammatory response to I-R required toll-like receptor-4 (TLR4). In addition, the authors demonstrated in vitro cooperativity and cross-talk between human macrophages and endothelial cells, resulting in augmented inflammatory responses to I-R. Remarkably, the authors found that selective depletion of alveolar macrophages rendered mice resistant to ventilated lung I-R injury.ConclusionsThe data reveal that alveolar macrophages and the pattern recognition receptor toll-like receptor-4 are involved in the generation of the early inflammatory response to lung I-R injury
Controlled functional expression of the bacteriocins pediocin PA-1 and bactofencin A in Escherichia coli
peer-reviewedThe bacteriocins bactofencin A (class IId) and pediocin PA-1 (class IIa) are encoded by operons with a similarly clustered gene organization including a structural peptide, an immunity protein, an ABC transporter and accessory bacteriocin transporter protein. Cloning of these operons in E. coli TunerTM (DE3) on a pETcoco-2 derived vector resulted in successful secretion of both bacteriocins. A corresponding approach, involving the construction of vectors containing different combinations of these genes, revealed that the structural and the transporter genes alone are sufficient to permit heterologous production and secretion in this host. Even though the accessory protein, usually associated with optimal disulfide bond formation, was not required for bacteriocin synthesis, its presence did result in greater pediocin PA-1 production. The simplicity of the system and the fact that the associated bacteriocins could be recovered from the extracellular medium provides an opportunity to facilitate protein engineering and the overproduction of biologically-active bacteriocins at industrial scale. Additionally, this system could enable the characterization of new bacteriocin operons where genetic tools are not available for the native producers
Some Advances in the Circuit Modeling of Extraordinary Optical Transmission
The phenomenon of extraordinary optical transmission (EOT) through electrically small holes perforated on opaque metal screens has been a hot topic in the optics community for more than one decade. This experimentally observed frequency-selective enhanced transmission of electromagnetic power through holes, for which classical Bethe\'s theory predicts very poor transmission, later attracted the attention of engineers working on microwave engineering or applied electromagnetics. Extraordinary transmission was first linked to the plasma-like behavior of metals at optical frequencies. However, the primary role played by the periodicity of the distribution of holes was soon made evident, in such a way that extraordinary transmission was disconnected from the particular behavior of metals at optical frequencies. Indeed, the same phenomenon has been observed in the microwave and millimeter wave regime, for instance. Nowadays, the most commonly accepted theory explains EOT in terms of the interaction of the impinging plane wave with the surface plasmon-polariton-Bloch waves (SPP-Bloch) supported by the periodically perforated plate. The authors of this paper have recently proposed an alternative model whose details will be briefly summarized here. A parametric study of the predictions of the model and some new potential extensions will be reported to provide additional insight
Contribución al conocimiento de los Insectos Miridos de Navarra (Heteroptera, Miridae, Hahn 1831)
Se han identificado un total de 795 ejemplares de Míridos
(Insecta, Heteroptera, Miridae), que corresponden a 35 géneros de
58 especies, de 64 localidades de Navarra. Dos especies son nuevas
citas para la fauna de España: Trigonotylus ruficornis y Lyqus
punctatus. Se aportan datos sobre el regimen alimenticio y la
distribución geográfica de los Míridos
Carbon and oxygen abundances from recombination lines in low-metallicity star-forming galaxies. Implications for chemical evolution
We present deep echelle spectrophotometry of the brightest emission-line
knots of the star-forming galaxies He 2-10, Mkn 1271, NGC 3125, NGC 5408, POX
4, SDSS J1253-0312, Tol 1457-262, Tol 1924-416 and the HII region Hubble V in
the Local Group dwarf irregular galaxy NGC 6822. The data have been taken with
the Very Large Telescope Ultraviolet-Visual Echelle Spectrograph in the
3100-10420 {\AA} range. We determine electron densities and temperatures of the
ionized gas from several emission-line intensity ratios for all the objects. We
derive the ionic abundances of C and/or O from faint pure
recombination lines (RLs) in several of the objects, permitting to derive their
C/H and C/O ratios. We have explored the chemical evolution at low
metallicities analysing the C/O vs. O/H, C/O vs. N/O and C/N vs. O/H relations
for Galactic and extragalactic HII regions and comparing with results for halo
stars and DLAs. We find that HII regions in star-forming dwarf galaxies occupy
a different locus in the C/O vs. O/H diagram than those belonging to the inner
discs of spiral galaxies, indicating their different chemical evolution
histories, and that the bulk of C in the most metal-poor extragalactic HII
regions should have the same origin than in halo stars. The comparison between
the C/O ratios in HII regions and in stars of the Galactic thick and thin discs
seems to give arguments to support the merging scenario for the origin of the
Galactic thick disc. Finally, we find an apparent coupling between C and N
enrichment at the usual metallicities determined for HII regions and that this
coupling breaks in very low-metallicity objects.Comment: 27 pages, 12 figures, Accepted for publication in Monthly Notices of
the Royal Astronomical Societ
The Chilean Pension Reform Turns 25: Lessons From the Social Protection Survey
In 1980, Chile dramatically reformed its retirement system, replacing what was an old insolvent PAYGO program with a new structure that relies heavily on funded defined contribution individual accounts. In addition, eligibility and benefit requirements were standardized, and a safety net for old-age poverty was strengthened. Twenty-five years after this reform, the Chilean model is being re-assessed, in terms of coverage, contribution, investment, and retirement benefit outcomes. This paper introduces a recently-developed longitudinal survey of individual respondents in Chile, the Social Protection Survey (or Encuesta de Previsión Social, EPS), and illustrates some uses of this survey for microeconomic analysis of key aspects of the Chilean system.
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