323 research outputs found
Non-Hermitian oscillator Hamiltonian and su(1,1): a way towards generalizations
The family of metric operators, constructed by Musumbu {\sl et al} (2007 {\sl
J. Phys. A: Math. Theor.} {\bf 40} F75), for a harmonic oscillator Hamiltonian
augmented by a non-Hermitian -symmetric part, is re-examined in the
light of an su(1,1) approach. An alternative derivation, only relying on
properties of su(1,1) generators, is proposed. Being independent of the
realization considered for the latter, it opens the way towards the
construction of generalized non-Hermitian (not necessarily -symmetric)
oscillator Hamiltonians related by similarity to Hermitian ones. Some examples
of them are reviewed.Comment: 11 pages, no figure; changes in title and in paragraphs 3 and 5;
final published versio
The Age of the Galactic Disk
I review different methods devised to derive the age of the Galactic Disk,
namely the Radio-active Decay (RD), the Cool White Dwarf Luminosity Function
(CWDLF), old opne clusters (OOC) and the Color Magnitude Diagram (CMD) of the
stars in the solar vicinity. I argue that the disk is likely to be 8-10 Gyr
old. Since the bulk of globulars has an age around 13 Gyr, the possibility
emerges that the Galaxy experienced a minimum of Star Formation at the end of
the halo/bulge formation. This minimum might reflect the time at which the
Galaxy started to acquire material to form the disk inside-out.Comment: 10 pages, 4 figure, invited review, in "The chemical evolution of the
Milky Way : Stars vs Clusters, Vulcano (Italy), 20-24 September 199
Branding the nation: Towards a better understanding
This paper aims to clarify some misunderstanding about nation branding. It examines the origins and interpretations of the concept, and draws a comparison between nation branding and commercial branding. A new definition is offered that emphasises the need to shift from “branding” the nation to nation image management
Radioactive 26Al and massive stars in the Galaxy
Gamma-rays from radioactive 26Al (half life ~7.2 10^5 yr) provide a
'snapshot' view of ongoing nucleosynthesis in the Galaxy. The Galaxy is
relatively transparent to such gamma-rays, and emission has been found
concentrated along the plane of the Galaxy. This led to the conclusion1 that
massive stars throughout the Galaxy dominate the production of 26Al. On the
other hand, meteoritic data show locally-produced 26Al, perhaps from spallation
reactions in the protosolar disk. Furthermore, prominent gamma-ray emission
from the Cygnus region suggests that a substantial fraction of Galactic 26Al
could originate in localized star-forming regions. Here we report high spectral
resolution measurements of 26Al emission at 1808.65 keV, which demonstrate that
the 26Al source regions corotate with the Galaxy, supporting its Galaxy-wide
origin. We determine a present-day equilibrium mass of 2.8 (+/-0.8) M_sol of
26Al. We use this to estimate that the frequency of core collapse (i.e. type
Ib/c and type II) supernovae to be 1.9(+/- 1.1) events per century.Comment: accepted for publication in Nature, 24 pages including Online
Supplements, 11 figures, 1 tabl
The Hubble Deep Field South Flanking Fields
As part of the Hubble Deep Field South program, a set of shorter 2-orbit
observations were obtained of the area adjacent to the deep fields. The WFPC2
flanking fields cover a contiguous solid angle of 48 square arcminutes.
Parallel observations with the STIS and NICMOS instruments produce a patchwork
of additional fields with optical and near-infrared (1.6 micron) response.
Deeper parallel exposures with WFPC2 and NICMOS were obtained when STIS
observed the NICMOS deep field. These deeper fields are offset from the rest,
and an extended low surface brightness object is visible in the deeper WFPC2
flanking field. In this data paper, which serves as an archival record of the
project, we discuss the observations and data reduction, and present SExtractor
source catalogs and number counts derived from the data. Number counts are
broadly consistent with previous surveys from both ground and space. Among
other things, these flanking field observations are useful for defining slit
masks for spectroscopic follow-up over a wider area around the deep fields, for
studying large-scale structure that extends beyond the deep fields, for future
supernova searches, and for number counts and morphological studies, but their
ultimate utility will be defined by the astronomical community.Comment: 46 pages, 15 figures. Images and full catalogs available via the
HDF-S at http://www.stsci.edu/ftp/science/hdfsouth/hdfs.html at present. The
paper is accepted for the February 2003 Astronomical Journal. Full versions
of the catalogs will also be available on-line from AJ after publicatio
The Policy Dystopia Model:an interpretive analysis of tobacco industry political activity
BACKGROUND: Tobacco industry interference has been identified as the greatest obstacle to the implementation of evidence-based measures to reduce tobacco use. Understanding and addressing industry interference in public health policy-making is therefore crucial. Existing conceptualisations of corporate political activity (CPA) are embedded in a business perspective and do not attend to CPA's social and public health costs; most have not drawn on the unique resource represented by internal tobacco industry documents. Building on this literature, including systematic reviews, we develop a critically informed conceptual model of tobacco industry political activity. METHODS AND FINDINGS: We thematically analysed published papers included in two systematic reviews examining tobacco industry influence on taxation and marketing of tobacco; we included 45 of 46 papers in the former category and 20 of 48 papers in the latter (n = 65). We used a grounded theory approach to build taxonomies of "discursive" (argument-based) and "instrumental" (action-based) industry strategies and from these devised the Policy Dystopia Model, which shows that the industry, working through different constituencies, constructs a metanarrative to argue that proposed policies will lead to a dysfunctional future of policy failure and widely dispersed adverse social and economic consequences. Simultaneously, it uses diverse, interlocking insider and outsider instrumental strategies to disseminate this narrative and enhance its persuasiveness in order to secure its preferred policy outcomes. Limitations are that many papers were historical (some dating back to the 1970s) and focused on high-income regions. CONCLUSIONS: The model provides an evidence-based, accessible way of understanding diverse corporate political strategies. It should enable public health actors and officials to preempt these strategies and develop realistic assessments of the industry's claims
Clevidipine for severe hypertension in patients with renal dysfunction: A VELOCITY trial analysis
Introduction. Acute and severe hypertension is common, especially in patients with renal dysfunction (RD). Clevidipine is a rapidly acting (t½∼1 min) intravenous (IV) dihydropyridine calcium-channel blocker metabolized by blood and tissue esterases and may be useful in patients with RD. The purpose of this analysis was to assess the safety and efficacy of clevidipine in patients with RD. Methods. VELOCITY, a multicenter open-label study of severe hypertension, enrolled 126 patients with persistent systolic blood pressure (SBP) >180 mmHg. Investigators pre-specified a SBP initial target range (ITR) for each patient to be achieved within 30 min. Blood pressure monitoring was by cuff. Clevidipine was infused via peripheral IV at 2 mg/h for at least 3 min, then doubled every 3 min as needed to a maximum of 32 mg/h (non-weightbased treat-to-target protocol). Per protocol, clevidipine was continued for at least 18 h (96 h maximum). RD was diagnosed and reported as an end-organ injury by the investigator and was defined as requiring dialysis or an initial creatinine >2.0 mg/dl. Primary endpoints were the percentage of patients within the ITR by 30 min and the percentage below the ITR after 3 min of clevidipine infusion. Results. Of the 24 patients with moderate to severe RD, most (13/24) were dialysis dependent. Forty-six percent were male, with mean age 51 >14 years; 63% were black and 96% had a hypertension history. Median time to achieve the ITR was 8.5 min. Almost 90% of patients reached the ITR in 30 min without evidence of overshoot and were maintained on clevidipine through 18 h. Most patients (88%) transitioned to oral antihypertensive therapy within 6 h of clevidipine termination. Conclusions. This report is the first demonstrating that clevidipine is safe and effective in RD complicated by severe hypertension. Prolonged infusion maintained blood pressure within a target range and allowed successful transition to oral therapy
c-Rel Deficiency Increases Caspase-4 Expression and Leads to ER Stress and Necrosis in EBV-Transformed Cells
LMP1-mediated activation of nuclear factor of kappaB (NF-κB) is critical for the ligand independent proliferation and cell survival of in vitro EBV-transformed lymphoblastoid cell lines (LCLs). Previous experiments revealed that a majority of LMP1-dependent responses are regulated by NF-κB. However, the extent that individual NF-κB family members are required for these responses, in particular, c-Rel, whose expression is restricted to mature hematopoietic cells, remains unclear. Here we report that low c-Rel expression in LCLs derived from a patient with hyper-IgM syndrome (Pt1), resulted in defects in proliferation and cell survival. In contrast to studies that associated loss of NF-κB with increased apoptosis, Pt1 LCLs failed to initiate apoptosis and alternatively underwent autophagy and necrotic cell death. Whereas the proliferation defect appeared linked to a c-Rel-associated decrease in c-myc expression, identified pro-survival and pro-apoptotic targets were expressed at or near control levels consistent with the absence of apoptosis. Ultrastructural examination of Pt1 LCLs revealed a high level of cellular and ER stress that was further supported by gene expression profiling showing the upregulation of several genes involved in stress and inflammation. Apoptosis-independent cell death was accompanied by increased expression of the inflammatory marker, caspase-4. Using gene overexpression and siRNA knockdown we demonstrated that levels of c-Rel directly modulated expression of caspase-4 as well as other ER stress genes. Overall, these findings reveal the importance of c-Rel in maintaining LCL viability and that decreased expression results in ER stress and a default response leading to necrotic cell death
Gaia-ESO Survey: INTRIGOSS - A New Library of High-resolution Synthetic Spectra
We present a high resolution synthetic spectral library, INTRIGOSS, designed
for studying FGK stars. The library is based on atmosphere models computed with
specified individual element abundances via ATLAS12 code. Normalized SPectra
(NSP) and surface Flux SPectra (FSP), in the 4830-5400 A, wavelength range,
were computed with the SPECTRUM code. INTRIGOSS uses the solar composition by
Grevesse et al. 2007 and four [alpha/Fe] abundance ratios and consists of
15,232 spectra. The synthetic spectra are computed with astrophysical gf-values
derived by comparing synthetic predictions with a very high SNR solar spectrum
and the UVES-U580 spectra of five cool giants. The validity of the NSPs is
assessed by using the UVES-U580 spectra of 2212 stars observed in the framework
of the Gaia-ESO Survey and characterized by homogeneous and accurate
atmospheric parameter values and by detailed chemical compositions. The greater
accuracy of NSPs with respect to spectra from the AMBRE, GES_Grid, PHOENIX,
C14, and B17 synthetic spectral libraries is demonstrated by evaluating the
consistency of the predictions of the different libraries for the UVES-U580
sample stars. The validity of the FSPs is checked by comparing their prediction
with both observed spectral energy distribution and spectral indices. The
comparison of FSPs with SEDs derived from ELODIE, INDO--U.S., and MILES
libraries indicates that the former reproduce the observed flux distributions
within a few percent and without any systematic trend. The good agreement
between observational and synthetic Lick/SDSS indices shows that the predicted
blanketing of FSPs well reproduces the observed one, thus confirming the
reliability of INTRIGOSS FSPs
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