6,530 research outputs found
The Importance of Superheroes To The American Comic Book Industry, 1958-1962
This paper explores events surrounding fundamental changes that took place in the American comic industry in the time period 1958-1962. Retrospectively it is argued that these changes set the direction of the industry for at least the next fifty years, where the industry has been dominated by two publishers, Marvel Comics and DC Comics, with a heavy reliance on the superhero genre. Of particular importance is the decline of Dell Comics, the dominant publisher of the 1950s. This transformation is briefly examined through the lens of strategic management, specifically SWOT analysis, as an illustration of potential future research
SGR 1806-20 Is a Set of Independent Relaxation Systems
The Soft Gamma Repeater 1806-20 produced patterns of bursts during its 1983
outburst that indicate multiple independent energy accumulation sites, each
driven by a continuous power source, with sudden, incomplete releases of the
accumulated energy. The strengths of the power sources and their durations of
activity vary over several orders of magnitude.Comment: Accepted ApJLett, 15 pages, 3 figure
Men in Nursing: Implications for the Profession and Broader Workforce Trends
Typically,nursing has been considered a gendered profession dominated by women. As traditionally blue-collar, male-dominated occupations such as assembly-line work have declined,the percentage of men in the nursing profession has increased to 12%. This is not a recent phenomenon;a significant percentage of men served as nurses up through the 1800’s.
In this analysis of men serving in the nursing workforce, we begin with a historical review and then discuss implications for the nursing profession, e.g., recruitment,education,practice, retention,and culture, as well as implications for the broader labor market, e.g., compensation trends by industry and gende
Probing the Gamma-Ray Burst Rate with Trigger Simulations of the Swift Burst Alert Telescope
The long gamma-ray burst (GRB) rate is essential for revealing the connection
between GRBs, supernovae and stellar evolution. Additionally, the GRB rate at
high redshift provides a strong probe of star formation history in the early
universe. While hundreds of GRBs are observed by Swift, it remains difficult to
determine the intrinsic GRB rate due to the complex trigger algorithm of Swift.
Current studies usually approximate the Swift trigger algorithm by a single
detection threshold. However, unlike the previously flown GRB instruments,
Swift has over 500 trigger criteria based on photon count rate and additional
image threshold for localization. To investigate possible systematic biases and
explore the intrinsic GRB properties, we developed a program that is capable of
simulating all the rate trigger criteria and mimicking the image trigger
threshold. We use this program to search for the intrinsic GRB rate. Our
simulations show that adopting the complex trigger algorithm of Swift increases
the detection rate of dim bursts. As a result, we find that either the GRB rate
is much higher than previously expected at large redshift, or the luminosity
evolution is non-negligible. We will discuss the best results of the GRB rate
in our search, and their impact on the star-formation history.Comment: 6 pages, 3 figures, 7th Huntsville Gamma-Ray Burst Symposium, GRB
2013: paper 35 in eConf Proceedings C130414
Probing the Cosmic Gamma-Ray Burst Rate with Trigger Simulations of the Swift Burst Alert Telescope
The gamma-ray burst (GRB) rate is essential for revealing the connection
between GRBs, supernovae and stellar evolution. Additionally, the GRB rate at
high redshift provides a strong probe of star formation history in the early
universe. While hundreds of GRBs are observed by Swift, it remains difficult to
determine the intrinsic GRB rate due to the complex trigger algorithm of Swift.
Current studies of the GRB rate usually approximate the Swift trigger algorithm
by a single detection threshold. However, unlike the previously flown GRB
instruments, Swift has over 500 trigger criteria based on photon count rate and
additional image threshold for localization. To investigate possible systematic
biases and explore the intrinsic GRB properties, we develop a program that is
capable of simulating all the rate trigger criteria and mimicking the image
threshold. Our simulations show that adopting the complex trigger algorithm of
Swift increases the detection rate of dim bursts. As a result, our simulations
suggest bursts need to be dimmer than previously expected to avoid
over-producing the number of detections and to match with Swift observations.
Moreover, our results indicate that these dim bursts are more likely to be high
redshift events than low-luminosity GRBs. This would imply an even higher
cosmic GRB rate at large redshifts than previous expectations based on
star-formation rate measurements, unless other factors, such as the luminosity
evolution, are taken into account. The GRB rate from our best result gives a
total number of 4571^{+829}_{-1584} GRBs per year that are beamed toward us in
the whole universe.
SPECIAL NOTE (2015.05.16): This new version incorporates an erratum. All the
GRB rate normalizations () should be a factor of 2 smaller
than previously reported. Please refer to the Appendix for more details. We
sincerely apologize for the mistake.Comment: 52 pages, 17 figures, published in ApJ 783, 24L (2014). An erratum is
included. A typo in Eq. 8 is fixed in this versio
Screening High-z GRBs with BAT Prompt Emission Properties
Detecting high-z GRBs is important for constraining the GRB formation rate,
and tracing the history of re-ionization and metallicity of the universe. Based
on the current sample of GRBs detected by Swift with known redshifts, we
investigated the relationship between red-shift, and spectral and temporal
characteristics, using the BAT event-by-event data. We found red-shift trends
for the peak-flux-normalized temporal width T90, the light curve variance, the
peak flux, and the photon index in simple power-law fit to the BAT event data.
We have constructed criteria for screening GRBs with high red-shifts. This will
enable us to provide a much faster alert to the GRB community of possible
high-z bursts.Comment: 4 pages, 4 figures, to be published in the proceedings of ''Gamma Ray
Bursts 2007'', Santa Fe, New Mexico, November 5-
Mapping and explaining the productivity of Pinus radiata in New Zealand
Mapping Pinus radiata productivity for New Zealand not only provides useful information for forest owners, industry stakeholders and policy managers, but also enables current and future plantations to be visualised, quantified, and planned. Using an extensive set of permanent sample plots, split into fitting (n = 1,146) and validation (n = 618) datasets, models of P. radiata 300 Index (an index of volume mean annual increment) and Site Index (an index of height growth) were developed using a regression kriging technique. Spatial predictions were accurate and accounted for 61% and 70% of the variance for 300 Index and Site Index, respectively. Productivity predicted from these surfaces for the entire plantation estate averaged 27.4 m³ ha⁻¹ yr⁻¹ for the 300 Index and 30.4 m for Site Index. Surfaces showed wide regional variation in this productivity, which was attributable mainly to variation in air temperature and root-zone water storage from site to site
Relativistic Particle-In-Cell Simulation Studies of Prompt and Early Afterglows from GRBs
Nonthermal radiation observed from astrophysical systems containing
relativistic jets and shocks e.g. gamma-ray bursts (GRBs) active galactic
nuclei (AGNs) and microquasars commonly exhibit power-law emission spectra.
Recent PIC simulations of relativistic electron-ion (or electron-positron) jets
injected into a stationary medium show that particle acceleration occurs within
the downstream jet. In collisionless relativistic shocks particle (electron,
positron and ion) acceleration is due to plasma waves and their associated
instabilities (e.g. the Weibel (filamentation) instability) created in the
shock region. The simulations show that the Weibel instability is responsible
for generating and amplifying highly non-uniform small-scale magnetic fields.
These fields contribute to the electron's transverse deflection behind the jet
head. The resulting ``jitter'' radiation from deflected electrons has different
properties compared to synchrotron radiation which assumes a uniform magnetic
field. Jitter radiation may be important for understanding the complex time
evolution and/or spectra in gamma-ray bursts, relativistic jets in general and
supernova remnants.Comment: 19 pages,7 figures, contributed talk at Seventh European Workshop on
Collisionless Shocks, Paris, 7- 9 November 2007. High resolution version can
be obtained at http://gammaray.nsstc.nasa.gov/~nishikawa/shockws07.pd
Cadmium Malonate Complexation in Aqueous Sodium Trifluoromethanesulfonate Media to 75°C; Including Dissociation Quotients of Malonic Acid
The molal formation quotients for cadmium-malonate complexes were measured potentiometrically from 5 to 75°C, at ionic strengths of 0.1, 0.3, 0.6 and 1.0 molal in aqueous sodium trifluoromethanesulfonate (NaTf) media. In addition, the stepwise dissociation quotients for malomc acid were measured in the same medium from 5 to 100°C, at ionic strengths of 0.1, 0.3, 0.6, and 1.0 molal by the same method. The dissociation quotients for malonic acid were modeled as a function of temperature and ionic strength with empirical equations formulated such that the equilibrium constants at infinite dilution were consistent, within the error estimates, with the malonic acid dissociation constants obtained in NaCl media. The equilibrium constants calculated for the dissociation of malonic acid at 25°C and infinite dilution are log K1a = -2.86 ± 0.01 and log K2a = -5.71 ± 0.01. A single Cd-malonate species, CdCH2C2O4, was identified from the complexation study and the formation quotients for this species were also modeled as a function of temperature and ionic strength. Thermodynamic parameters obtained by differentiating the equation with respect to temperature for the formation of CdCH2C2O4 at 25°C and infinite dilution are: log K = 3.45 ± 0.09, ΔH° = 7 ± 6 kJ-mol-1, ΔS° = 91 ± 22 J-K-1-mol-1, and ΔC°p = 400 ± 300J-K-1-mol-1
TPS Sizing for Access-to-Space Vehicles
A study was carried out to identify, develop, and benchmark simulation techniques needed for optimum thermal protection system (TPS) material selection and sizing for reusable launch vehicles. Fully viscous, chemically reacting, Navier-Stokes flow solutions over the Langley wing-body single stage to orbit (SSTO) configuration were generated and coupled with an in-depth conduction code. Results from the study provide detailed TPS heat shield materials selection and thickness sizing for the wing-body SSTO. These results are the first ever achieved through the use of a complete, trajectory based hypersonic, Navier-Stokes solution database. TPS designs were obtained for both laminar and turbulent entry trajectories using the Access-to-Space baseline materials such as tailorable advanced blanket insulation. The TPS design effects (materials selection and thickness) of coupling material characteristics to the aerothermal environment are illustrated. Finally, a sample validation case using the shuttle flight database is included
- …