1,320 research outputs found
Cost-of-Living Adjustment Clauses in Union Contracts
Our paper seeks to provide an explanation for why the prevalence of COLA provisions and their characteristics vary widely across U.S. industries. We develop models of optimal risk sharing between a firm and union that allows us to investigate the determinants of a number of characteristics of union contracts. These include the presence of wage indexation, the degree of wage indexation if it exists, the magnitude of deferred noncontingent (on the price level) wage increases, the duration of labor contracts and the trade-off between temporary layoffs and wage indexation. Preliminary empirical tests of some of the implications of the model are conducted using industry data on both the prevalence of COLA provisions and layoff rates, and using contract level data on the characteristics of COLA provisions and contract duration. One key finding is that the level of unemployment insurance benefits appears to simultaneously influence the level of layoffs and the extent of COLA coverage.
Interview Magazine: Art & Fame
The world today is radically different from the world of the 1960s. Andy Warhol was the pinnacle of Pop, and print publications were supreme in the industry of news and fashion alike. What was Pop culture in 1969 seems foreign and antiquated today, and yet there are similarities to be drawn between the era of mod and the modern era.
In the research paper Interview Magazine: Art & Fame, I aim to explore the connection between the artistic excellence that launched the publication’s success and the obsession with celebrity that charged its passion — a bond that formed to act as the crux of the magazine that impacted the industry with innovative clout
Unravelling the chemical inhomogeneity of PNe with VLT FLAMES integral-field unit spectroscopy
Recent weak emission-line long-slit surveys and modelling studies of PNe have
convincingly argued in favour of the existence of an unknown component in the
planetary nebula plasma consisting of cold, hydrogen-deficient gas, as an
explanation for the long-standing recombination-line versus forbidden-line
temperature and abundance discrepancy problems. Here we describe the rationale
and initial results from a detailed spectroscopic study of three Galactic PNe
undertaken with the VLT FLAMES integral-field unit spectrograph, which advances
our knowledge about the small-scale physical properties, chemical abundances
and velocity structure of these objects across a two-dimensional field of view,
and opens up for exploration an uncharted territory in the study and modelling
of PNe and photoionized nebulae in general.Comment: 4 pages; 3 figures; invited paper to appear in proceedings of IAU
Symp. No. 234, 2006, Planetary Nebulae in our Galaxy and Beyond (held in
Hawaii, April 2006
Spectral statistics of random geometric graphs
We use random matrix theory to study the spectrum of random geometric graphs,
a fundamental model of spatial networks. Considering ensembles of random
geometric graphs we look at short range correlations in the level spacings of
the spectrum via the nearest neighbour and next nearest neighbour spacing
distribution and long range correlations via the spectral rigidity Delta_3
statistic. These correlations in the level spacings give information about
localisation of eigenvectors, level of community structure and the level of
randomness within the networks. We find a parameter dependent transition
between Poisson and Gaussian orthogonal ensemble statistics. That is the
spectral statistics of spatial random geometric graphs fits the universality of
random matrix theory found in other models such as Erdos-Renyi, Barabasi-Albert
and Watts-Strogatz random graph.Comment: 19 pages, 6 figures. Substantially updated from previous versio
A deep survey of heavy element lines in planetary nebulae -- II. Recombination line abundances and evidence for ultra-cold plasma
[Abridged] Deep optical observations of the spectra of 12 Galactic planetary
nebulae (PNe) and 3 Magellanic Cloud PNe were presented in Paper I by Tsamis et
al. (2003b), who carried out an abundance analysis using the collisionally
excited forbidden lines. Here, the relative intensities of faint optical
recombination lines (ORLs) from ions of carbon, nitrogen and oxygen are
analysed in order to derive the abundances of these ions relative to hydrogen.
We define an abundance discrepancy factor (ADF) as the ratio of the abundance
derived for a heavy element ion from its recombination lines to that derived
for the same ion from its ultraviolet, optical or infrared collisionally
excited lines (CELs). All of the PNe in our sample are found to have ADF's that
exceed unity. There is no dependence of the magnitude of the ADF upon the
excitation energy of the UV, optical or IR CEL transition used, indicating that
classical nebular temperature fluctuations--i.e. in a chemically homogeneous
medium--are not the cause of the observed abundance discrepancies. Instead, we
conclude that the main cause of the discrepancy is enhanced ORL emission from
cold ionized gas located in hydrogen-deficient clumps inside the main body of
the nebulae. We have developed a new electron temperature diagnostic, based
upon the relative intensities of the OII 4f-3d 4089A and 3p-3s 4649A
recombination transitions. For six out of eight PNe for which both transitions
are detected, we derive O2+ ORL electron temperatures of <300 K, very much less
than the O2+ forbidden-line and Balmer jump temperatures derived for the same
nebulae. These results provide direct observational evidence for the presence
of H-deficient, cold plasma regions within the nebulae, consistent with gas
cooled largely by infrared fine structure and recombination transitions.Comment: 27 pages, 7 figures, submitted to the MNRA
Obesity, Acute Kidney Injury, and Mortality in Critical Illness
Objectives: Although obesity is associated with risk for chronic kidney disease and improved survival, less is known about the associations of obesity with risk of acute kidney injury and post acute kidney injury mortality. Design: In a single-center inception cohort of almost 15,000 critically ill patients, we evaluated the association of obesity with acute kidney injury and acute kidney injury severity, as well as in-hospital and 1-year survival. Acute kidney injury was defined using the Kidney Disease Outcome Quality Initiative criteria. Measurements and Main Results: The acute kidney injury prevalence rates for normal, overweight, class I, II, and III obesity were 18.6%, 20.6%, 22.5%, 24.3%, and 24.0%, respectively, and the adjusted odds ratios of acute kidney injury were 1.18 (95% CI, 1.06-1.31), 1.35 (1.19-1.53), 1.47 (1.25-1.73), and 1.59 (1.31-1.87) when compared with normal weight, respectively. Each 5-kg/m 2 increase in body mass index was associated with a 10% risk (95% CI, 1.06-1.24; p < 0.001) of more severe acute kidney injury. Within-hospital and 1-year survival rates associated with the acute kidney injury episodes were similar across body mass index categories. Conclusion: Obesity is a risk factor for acute kidney injury, which is associated with increased short-and long-term mortality.National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant 2R01 EB001659)National Institutes of Health (U.S.) (Grant R01-EB001659
A deep survey of heavy element lines in planetary nebulae - I. Observations and forbidden-line densities, temperatures and abundances
We present spectrophotometry of 12 Galactic and 3 Magellanic Cloud planetary
nebulae (PNe). Nine of the Galactic PNe were observed by scanning the slit
across the PN. We use the fluxes of collisionally excited lines (CELs) to
derive electron densities (D's) and temperatures (T's), and ionic abundances.
We find that the D's derived from optical CEL ratios are systematically higher
than those derived from the ratios of the IR fine-structure (FS) lines of
[OIII], indicating the presence of significant density variations within the
PNe. We also compare T's obtained from the ratio of optical nebular to auroral
[OIII] lines with those obtained from the ratio of [OIII] optical to IR FS
lines. We find that when the latter are derived using D's based on the [OIII]
52um/88um ratio, they yield values that are significantly higher than the
optical [OIII] T's. Contrasting this, [OIII] optical/IR T's derived using the
higher D's obtained from [ClIII] 5517A/5537A ratios show much closer agreement
with optical [OIII] T's, implying that the observed [OIII] optical/IR ratios
are significantly weighted by D's in excess of the critical densities of both
[OIII] FS lines. Consistent with this, ionic abundances derived from [OIII] and
[NIII] FS lines using D's from optical CELs show much better agreement with
abundances derived for the same ions from optical and UV CELs than do
abundances derived from the FS lines using the lower D's obtained from the
52um/88um ratios. The behaviour of T's obtained making use of the T-insensitive
IR FS lines provides no support for significant T-fluctuations within the PNe
that could be responsible for derived Balmer jump T's being lower than those
obtained from the much more T-sensitive [OIII] optical lines.Comment: 36 pages; 3 figures; to be published in MNRA
Five Years of Mid-Infrared Evolution of the Remnant of SN 1987A: The Encounter Between the Blast Wave and the Dusty Equatorial Ring
We have used the Spitzer satellite to monitor the mid-IR evolution of SN
1987A over a 5 year period spanning the epochs between days 6000 and 8000 since
the explosion. The supernova (SN) has evolved into a supernova remnant (SNR)
and its radiative output is dominated by the interaction of the SN blast wave
with the pre-existing equatorial ring (ER). The mid-IR spectrum is dominated by
emission from ~180 K silicate dust, collisionally-heated by the hot X-ray
emitting gas with a temperature and density of ~5x10^6 K and 3x10^4 cm-3,
respectively. The mass of the radiating dust is ~1.2x10^(-6) Msun on day 7554,
and scales linearly with IR flux. The infrared to soft-X-ray flux ratio is
roughly constant with a value of 2.5. Gas-grain collisions therefore dominate
the cooling of the shocked gas. The constancy of of this ratio suggests that
very little grain processing or gas cooling have occurred throughout this
epoch. The shape of the dust spectrum remained unchanged during the
observations while the total flux increased with a time dependence of t^(0.87),
t being the time since the first encounter between the blast wave and the ER.
These observations are consistent with the transitioning of the blast wave from
free expansion to a Sedov phase as it propagates into the main body of the ER.Comment: Accepted for publication in the ApJ, 11 pages, 11 figure
Association of hypermagnesemia and blood pressure in the critically ill
BACKGROUND: Although magnesium is important in the biology of blood pressure regulation, little clinical data exist on the association of hypermagnesemia and blood pressure. METHOD:: We examined the association of hypermagnesemia and SBP in a cross-sectional study of 10 521 ICU patients from a single tertiary care medical center, 6% of whom had a serum magnesium above 2.6 mg/dl at time of admission. RESULTS:: In a multivariable analysis, hypermagnesemia was associated with SBP 6.2 mmHg lower [95% confidence interval (CI) -8.2, -4.2, P < 0.001] than in patients with admission values of serum magnesium 2.6 mg/dl or less. Each mg/dl increase in serum magnesium was associated with a decrease in SBP of 4.3 mmHg (95% CI -5.5, -3.1, P < 0.001). In addition, hypermagnesemic patients had a 2.48-fold greater likelihood (95% CI 2.06, 3.00, P < 0.001) of receiving intravenous vasopressors during the first 24h of ICU care, independent of admission SBP. CONCLUSION:: Our findings add support to the biologic importance of magnesium regulation in blood pressure control.National Institute of Biomedical Imaging and Bioengineering (U.S.) (Grant 2R01 EB001659
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