2,022 research outputs found
MONEY ILLUSION, GORMAN AND LAU
Any demand equation satisfying Lauâs (1982) Fundamental Theorem of Exact Aggregation and 0° homogeneity in prices and income will have a Gorman (1981) functional form for each income term. This property does not depend on symmetry or adding up. The implications of this result are illustrated by an extensive example.Demand, exact aggregation, functional form, homogeneity
Womenâs empowerment and violent death among women and men in Europe: An ecological study
Background This study examined the association between mortality due to injury and poisoning among men and women in Europe and nine indicators of women's empowerment (i.e. women's challenging of existing power structures that subordinate women). Methods A cross-sectional ecological design was used, with 24 countries from the European Union plus two countries within the European Economic Area and Switzerland. Results Most of the nine indicators of women's empowerment were unrelated to men's, as well as women's, death rates from injury and poisoning. However, multiple linear regression models showed that a few indicators of women's empowerment were significantly associated with mortality due to injury and poisoning for both women and men. When three Baltic States with considerably higher mortality rates (Latvia, Lithuania and Estonia) were excluded from the analysis, however, only one indicator (female economic activity as a percentage of male economic activity) remained a significant predictor of men's death rates. Conclusion These data suggest that some indicators of women's empowerment may be associated with mortality due to injury and poisoning for men, although the association was dependent on which countries were included in the analysis. This highlights the importance of examining in greater detail the influence of changing gender roles on the health behaviours of women and men
Training for tactical operations in tropical environments: Challenges, risks, & strategies for risk management
Automated Design of Network Security Metrics
Many abstract security measurements are based on characteristics of a graph that represents the network. These are typically simple and quick to compute but are often of little practical use in making real-world predictions. Practical network security is often measured using simulation or real-world exercises. These approaches better represent realistic outcomes but can be costly and time-consuming. This work aims to combine the strengths of these two approaches, developing efficient heuristics that accurately predict attack success. Hyper-heuristic machine learning techniques, trained on network attack simulation training data, are used to produce novel graph-based security metrics. These low-cost metrics serve as an approximation for simulation when measuring network security in real time. The approach is tested and verified using a simulation based on activity from an actual large enterprise network. The results demonstrate the potential of using hyper-heuristic techniques to rapidly evolve and react to emerging cybersecurity threats
Gene regulatory interactions limit the gene expression diversity
The diversity of expressed genes plays a critical role in cellular
specialization, adaptation to environmental changes, and overall cell
functionality. This diversity varies dramatically across cell types and is
orchestrated by intricate, dynamic, and cell type-specific gene regulatory
networks (GRNs). Despite extensive research on GRNs, their governing
principles, as well as the underlying forces that have shaped them, remain
largely unknown. Here, we investigated whether there is a tradeoff between the
diversity of expressed genes and the intensity of GRN interactions. We have
developed a computational framework that evaluates GRN interaction intensity
from scRNA-seq data and used it to analyze simulated and real scRNA-seq data
collected from different tissues in humans, mice, fruit flies, and C. elegans.
We find a significant tradeoff between diversity and interaction intensity,
driven by stability constraints, where the GRN could be stable up to a critical
level of complexity - a product of gene expression diversity and interaction
intensity. Furthermore, we analyzed hematopoietic stem cell differentiation
data and find that the overall complexity of unstable transition states cells
is higher than that of stem cells and fully differentiated cells. Our results
suggest that GRNs are shaped by stability constraints which limit the diversity
of gene expression
The Infrared Properties of Submillimeter Galaxies: Clues From Ultra-Deep 70 Micron Imaging
We present 70 micron properties of submillimeter galaxies (SMGs) in the Great
Observatories Origins Deep Survey (GOODS) North field. Out of thirty
submillimeter galaxies (S_850 > 2 mJy) in the central GOODS-N region, we find
two with secure 70 micron detections. These are the first 70 micron detections
of SMGs. One of the matched SMGs is at z ~ 0.5 and has S_70/S_850 and S_70/S_24
ratios consistent with a cool galaxy. The second SMG (z = 1.2) has
infrared-submm colors which indicate it is more actively forming stars. We
examine the average 70 micron properties of the SMGs by performing a stacking
analysis, which also allows us to estimate that S_850 > 2 mJy SMGs contribute 9
+- 3% of the 70 micron background light. The S_850/S_70 colors of the SMG
population as a whole is best fit by cool galaxies, and because of the
redshifting effects these constraints are mainly on the lower z sub-sample. We
fit Spectral Energy Distributions (SEDs) to the far-infrared data points of the
two detected SMGs and the average low redshift SMG (z_{median}= 1.4). We find
that the average low-z SMG has a cooler dust temperature than local
ultraluminous infrared galaxies (ULIRGs) of similar luminosity and an SED which
is best fit by scaled up versions of normal spiral galaxies. The average low-z
SMG is found to have a typical dust temperature T = 21 -- 33 K and infrared
luminosity L_{8-1000 micron} = 8.0 \times 10^11 L_sun. We estimate the AGN
contribution to the total infrared luminosity of low-z SMGs is less than 23%.Comment: Accepted by ApJ. 14 pages, 6 figures. Minor revisions 20th Dec 200
Dust attenuation in 2<z<3 star-forming galaxies from deep ALMA observations of the Hubble Ultra Deep Field
17 pages, 7 figures, accepted version to be published in MNRASWe present the results of a new study of the relationship between infrared excess (IRX ⥠L IR/L UV), ultraviolet (UV) spectral slope (β) and stellar mass at redshifts 2 < z < 3, based on a deep Atacama Large Millimeter Array (ALMA) 1.3-mm continuum mosaic of the Hubble Ultra Deep Field. Excluding the most heavily obscured sources, we use a stacking analysis to show that z â 2.5 star-forming galaxies in the mass range 9.25 ⤠log(M*/M â) ⤠10.75 are fully consistent with the IRX-β relation expected for a relatively grey attenuation curve, similar to the commonly adopted Calzetti law. Based on a large, mass-complete sample of 2 ⤠z ⤠3 star-forming galaxies drawn frommultiple surveys, we proceed to derive a new empirical relationship between β and stellar mass, making it possible to predict UV attenuation (A1600) and IRX as a function of stellar mass, for any assumed attenuation law. Once again, we find that z â 2.5 star-forming galaxies follow A1600-M* and IRX-M* relations consistent with a relatively grey attenuation law, and find no compelling evidence that star-forming galaxies at this epoch follow a reddening law as steep as the Small Magellanic Cloud (SMC) extinction curve. In fact, we use a simple simulation to demonstrate that previous determinations of the IRX-β relation may have been biased towards low values of IRX at red values of β, mimicking the signature expected for an SMC-like dust law. We show that this provides a plausible mechanism for reconciling apparently contradictory results in the literature and that, based on typical measurement uncertainties, stellar mass provides a cleaner prediction of UV attenuation than β. Although the situation at lower stellar masses remains uncertain, we conclude that for 2 < z < 3 star-forming galaxies with log(M*/M â) ⼠9.75, both the IRX-β and IRX-M* relations are well described by a Calzetti-like attenuation law.Peer reviewe
An AzTEC 1.1 mm Survey of the GOODS-N Field I: Maps, Catalogue, and Source Statistics
We have conducted a deep and uniform 1.1 mm survey of the GOODS-N field with
AzTEC on the James Clerk Maxwell Telescope (JCMT). Here we present the first
results from this survey including maps, the source catalogue, and 1.1 mm
number-counts. The results presented here were obtained from a 245 sq-arcmin
region with near uniform coverage to a depth of 0.96-1.16 mJy/beam. Our robust
catalogue contains 28 source candidates detected with S/N >= 3.75, only 1-2 of
which are expected to be spurious detections. Of these source candidates, 8 are
also detected by SCUBA at 850 um in regions where there is good overlap between
the two surveys. The major advantage of our survey over that with SCUBA is the
uniformity of coverage. We calculate number counts using two different
techniques: the first using a frequentist parameter estimation, and the second
using a Bayesian method. The two sets of results are in good agreement. We find
that the 1.1 mm differential number counts are well described in the 2-6 mJy
range by the functional form dN/dS = N' (S'/S) exp(-S/S') with fitted
parameters S' = 1.25 +/-0.38 mJy and dN/dS = 300 +/- 90 per mJy per sq-deg at 3
mJy.Comment: 13 pages, 8 figures, 3 tables. Submitted revision to MNRAS 23 June
200
The local FIR Galaxy Colour-Luminosity distribution: A reference for BLAST, and Herschel/SPIRE sub-mm surveys
We measure the local galaxy far-infrared (FIR) 60-to-100 um colour-luminosity
distribution using an all-sky IRAS survey. This distribution is an important
reference for the next generation of FIR--submillimetre surveys that have and
will conduct deep extra-galactic surveys at 250--500 um. With the peak in
dust-obscured star-forming activity leading to present-day giant ellipticals
now believed to occur in sub-mm galaxies near z~2.5, these new
FIR--submillimetre surveys will directly sample the SEDs of these distant
objects at rest-frame FIR wavelengths similar to those at which local galaxies
were observed by IRAS. We have taken care to correct for temperature bias and
evolution effects in our IRAS 60 um-selected sample. We verify that our
colour-luminosity distribution is consistent with measurements of the local FIR
luminosity function, before applying it to the higher-redshift Universe. We
compare our colour-luminosity correlation with recent dust-temperature
measurements of sub-mm galaxies and find evidence for pure luminosity evolution
of the form (1+z)^3. This distribution will be useful for the development of
evolutionary models for BLAST and SPIRE surveys as it provides a statistical
distribution of rest-frame dust temperatures for galaxies as a function of
luminosity.Comment: 12 pages, 7 figures. MNRAS in press. This revision matches final
published version. Fixes typos in footnote 1 and equation 8. Minor
modifications to text and references. Final results unchange
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