1,237 research outputs found
Nineteenth-Century Popular Science Magazines, Narrative, and the Problem of Historical Materiality
In his Some Reminiscences of a Lecturer, Andrew Wilson emphasizes the importance of narrative to popular science lecturing. Although Wilson promotes the teaching of science as useful knowledge in its own right, he also recognizes that the way science is taught can encourage audiences to take the subject up and read further on their own. Form, according to Wilson, should not be divorced from scientific content and lecturers should ensure that not only is their science accurate, but that it is presented in a way that will provoke curiosity and stimulate interest. This paper discusses the influence of narrative in structuring scientific objects and phenomena, and considers the consequences of such presentations for historical research. As scientific journalism necessarily weaves both its intended audience and the objects under discussion into its accounts, these texts demand that we recognize their nature as social relationships inscribed in historical objects
BLAST: Correlations in the Cosmic Far-Infrared Background at 250, 350, and 500 microns Reveal Clustering of Star-Forming Galaxies
We detect correlations in the cosmic far-infrared background due to the
clustering of star-forming galaxies in observations made with the Balloon-borne
Large Aperture Submillimeter Telescope, BLAST, at 250, 350, and 500 microns. We
perform jackknife and other tests to confirm the reality of the signal. The
measured correlations are well fit by a power law over scales of 5-25
arcminutes, with Delta I/I = 15.1 +/- 1.7%. We adopt a specific model for
submillimeter sources in which the contribution to clustering comes from
sources in the redshift ranges 1.3 <= z <= 2.2, 1.5 <= z <= 2.7, and 1.7 <= z
<= 3.2, at 250, 350, and 500 microns, respectively. With these distributions,
our measurement of the power spectrum, P(k_theta), corresponds to linear bias
parameters, b = 3.8 +/- 0.6, 3.9 +/- 0.6 and 4.4 +/- 0.7, respectively. We
further interpret the results in terms of the halo model, and find that at the
smaller scales, the simplest halo model fails to fit our results. One way to
improve the fit is to increase the radius at which dark matter halos are
artificially truncated in the model, which is equivalent to having some
star-forming galaxies at z >= 1 located in the outskirts of groups and
clusters. In the context of this model we find a minimum halo mass required to
host a galaxy is log (M_min / M_sun) = 11.5 (+0.4/-0.1), and we derive
effective biases $b_eff = 2.2 +/- 0.2, 2.4 +/- 0.2, and 2.6 +/- 0.2, and
effective masses log (M_eff / M_sun) = 12.9 +/- 0.3, 12.8 +/- 0.2, and 12.7 +/-
0.2, at 250, 350, and 500 microns, corresponding to spatial correlation lengths
of r_0 = 4.9, 5.0, and 5.2 +/- 0.7 h^-1 Mpc, respectively. Finally, we discuss
implications for clustering measurement strategies with Herschel and Planck.Comment: Accepted for publication in the Astrophysical Journal. Maps and other
results available at http://blastexperiment.info
Bostonia: The Boston University Alumni Magazine. Volume 31
Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs
Reconstructing the Inflaton Potential---in Principle and in Practice
Generalizing the original work by Hodges and Blumenthal, we outline a
formalism which allows one, in principle, to reconstruct the potential of the
inflaton field from knowledge of the tensor gravitational wave spectrum or the
scalar density fluctuation spectrum, with special emphasis on the importance of
the tensor spectrum. We provide some illustrative examples of such
reconstruction. We then discuss in some detail the question of whether one can
use real observations to carry out this procedure. We conclude that in
practice, a full reconstruction of the functional form of the potential will
not be possible within the foreseeable future. However, with a knowledge of the
dark matter components, it should soon be possible to combine
intermediate-scale data with measurements of large-scale cosmic microwave
background anisotropies to yield useful information regarding the potential.Comment: 39 pages plus 2 figures (upon request:[email protected]), LaTeX,
FNAL--PUB--93/029-A; SUSSEX-AST 93/3-
Breaking the "Redshift Deadlock" -- II: The redshift distribution for the submillimetre population of galaxies
In this paper we apply our Monte-Carlo photometric-redshift technique,
introduced in paper I (Hughes et al. 2002), to the multi-wavelength data
available for 77 galaxies selected at 850um and 1.25mm. We calculate a
probability distribution for the redshift of each galaxy, which includes a
detailed treatment of the observational errors and uncertainties in the
evolutionary model. The cumulative redshift distribution of the submillimetre
galaxy population that we present in this paper, based on 50 galaxies found in
wide-area SCUBA surveys, is asymmetric, and broader than those published
elsewhere, with a significant high-z tail for some of the evolutionary models
considered. Approximately 40 to 90 per cent of the sub-mm population is
expected to have redshifts in the interval 2 < z < 4. Whilst this result is
completely consistent with earlier estimates for the sub-mm galaxy population,
we also show that the colours of many (< 50 per cent) individual sub-mm
sources, detected only at 850um with non-detections at other wavelengths, are
consistent with those of starburst galaxies that lie at extreme redshifts, z >
4. Spectroscopic confirmation of the redshifts, through the detection of
rest-frame FIR--mm wavelength molecular transition-lines, will ultimately
calibrate the accuracy of this technique. We use the redshift probability
distribution of HDF850.1 to illustrate the ability of the method to guide the
choice of possible frequency tunings on the broad-band spectroscopic receivers
that equip the large aperture single-dish mm and cm-wavelength telescopes.Comment: Accepted in MNRAS, 16 pages, 12 figures, an appendix with 25
additional pages of figures is available at
http://www.inaoep.mx/~itziar/papers/dlIIapp.pd
Integrated Carbon Budget Models for the Everglades Terrestrial-Coastal-Oceanic Gradient: Current Status and Needs for Inter-Site Comparisons
Recent studies suggest that coastal ecosystems can bury significantly more C than tropical forests, indicating that continued coastal development and exposure to sea level rise and storms will have global biogeochemical consequences. The Florida Coastal Everglades Long Term Ecological Research (FCE LTER) site provides an excellent subtropical system for examining carbon (C) balance because of its exposure to historical changes in freshwater distribution and sea level rise and its history of significant long-term carbon-cycling studies. FCE LTER scientists used net ecosystem C balance and net ecosystem exchange data to estimate C budgets for riverine mangrove, freshwater marsh, and seagrass meadows, providing insights into the magnitude of C accumulation and lateral aquatic C transport. Rates of net C production in the riverine mangrove forest exceeded those reported for many tropical systems, including terrestrial forests, but there are considerable uncertainties around those estimates due to the high potential for gain and loss of C through aquatic fluxes. C production was approximately balanced between gain and loss in Everglades marshes; however, the contribution of periphyton increases uncertainty in these estimates. Moreover, while the approaches used for these initial estimates were informative, a resolved approach for addressing areas of uncertainty is critically needed for coastal wetland ecosystems. Once resolved, these C balance estimates, in conjunction with an understanding of drivers and key ecosystem feedbacks, can inform cross-system studies of ecosystem response to long-term changes in climate, hydrologic management, and other land use along coastlines
The Role of Industry, Geography and Firm Heterogeneity in Credit Risk Diversification
In theory the potential for credit risk diversification for banks could be substantial. Portfolio diversification is driven broadly by two characteristics: the degree to which systematic risk factors are correlated with each other and the degree of dependence individual firms have to the different types of risk factors. We propose a model for exploring these dimensions of credit risk diversification: across industry sectors and across different countries or regions. We find that full firm-level parameter heterogeneity matters a great deal for capturing differences in simulated credit loss distributions. Imposing homogeneity results in overly skewed and fat-tailed loss distributions. These differences become more pronounced in the presence of systematic risk factor shocks: increased parameter heterogeneity greatly reduces shock sensitivity. Allowing for regional parameter heterogeneity seems to better approximate the loss distributions generated by the fully heterogeneous model than allowing just for industry heterogeneity. The regional model also exhibits less shock sensitivity
BLAST: A Far-Infrared Measurement of the History of Star Formation
We directly measure redshift evolution in the mean physical properties
(far-infrared luminosity, temperature, and mass) of the galaxies that produce
the cosmic infrared background (CIB), using measurements from the Balloon-borne
Large Aperture Sub-millimeter Telescope (BLAST), and Spitzer which constrain
the CIB emission peak. This sample is known to produce a surface brightness in
the BLAST bands consistent with the full CIB, and photometric redshifts are
identified for all of the objects. We find that most of the 70 micron
background is generated at z <~ 1 and the 500 micron background generated at z
>~ 1. A significant growth is observed in the mean luminosity from ~ 10^9 -
10^12 L_sun, and in the mean temperature by 10 K, from redshifts 0< z < 3.
However, there is only weak positive evolution in the comoving dust mass in
these galaxies across the same redshift range. We also measure the evolution of
the far-infrared luminosity density, and the star-formation rate history for
these objects, finding good agreement with other infrared studies up to z ~1,
exceeding the contribution attributed to optically-selected galaxies.Comment: Accepted for publication in the Astrophysical Journal. Maps available
at http://blastexperiment.info
Age-associated B cells predict impaired humoral immunity after COVID-19 vaccination in patients receiving immune checkpoint blockade
Age-associated B cells (ABC) accumulate with age and in individuals with different immunological disorders, including cancer patients treated with immune checkpoint blockade and those with inborn errors of immunity. Here, we investigate whether ABCs from different conditions are similar and how they impact the longitudinal level of the COVID-19 vaccine response. Single-cell RNA sequencing indicates that ABCs with distinct aetiologies have common transcriptional profiles and can be categorised according to their expression of immune genes, such as the autoimmune regulator (AIRE). Furthermore, higher baseline ABC frequency correlates with decreased levels of antigen-specific memory B cells and reduced neutralising capacity against SARS-CoV-2. ABCs express high levels of the inhibitory FcγRIIB receptor and are distinctive in their ability to bind immune complexes, which could contribute to diminish vaccine responses either directly, or indirectly via enhanced clearance of immune complexed-antigen. Expansion of ABCs may, therefore, serve as a biomarker identifying individuals at risk of suboptimal responses to vaccination
Investment Opportunity Set, Product Mix, and the Relationship between Bank CEO Compensation and Risk-Taking
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