43 research outputs found
Corporate provision of public goods
Milton Friedman famously suggested that firms ought not divert profits toward public goods because shareholders can better make these contributions themselves. Despite this, activist shareholders are increasingly successful in persuading firms to be “socially responsible.” We study firm behavior when shareholders care about public goods as well as profits and when managerial contracts reflect these concerns. Under these ideal conditions, managers redirect more profits toward public goods than shareholders would when acting separately—shareholders are poorer but happier. Further, so long as the public good is sufficiently desirable, the manager selects the socially optimal level of output, despite the mismatch between shareholder preferences and those of society at large
Corporate provision of public goods
This is the final version. Available from INFORMS via the DOI in this record. Milton Friedman famously suggested that firms ought not divert profits toward public goods because shareholders can better make these contributions themselves. Despite this, activist shareholders are increasingly successful in persuading firms to be “socially responsible.” We study firm behavior when shareholders care about public goods as well as profits and when managerial contracts reflect these concerns. Under these ideal conditions, managers redirect more profits toward public goods than shareholders would when acting separately—shareholders are poorer but happier. Further, so long as the public good is sufficiently desirable, the manager selects the socially optimal level of output, despite the mismatch between shareholder preferences and those of society at large
Optophysiological characterisation of inner retina responses with high-resolution optical coherence tomography
Low coherence laser interferometry has revolutionised quantitative biomedical
imaging of optically transparent structures at cellular resolutions. We report the first
optical recording of neuronal excitation at cellular resolution in the inner retina by
quantifying optically recorded stimulus-evoked responses from the retinal ganglion
cell layer and comparing them with an electrophysiological standard. We imaged
anaesthetised paralysed tree shrews, gated image acquisition, and used numerical
filters to eliminate noise arising from retinal movements during respiratory and
cardiac cycles. We observed increases in contrast variability in the retinal ganglion
cell layer and nerve fibre layer with flash stimuli and gratings. Regions of interest
were subdivided into three-dimensional patches (up to 5-15ÎĽm in diameter) based on
response similarity. We hypothesise that these patches correspond to individual
cells, or segments of blood vessels within the inner retina. We observed a close
correlation between the patch optical responses and mean electrical activity of
afferent visual neurons. While our data suggest that optical imaging of retinal activity
is possible with high resolution OCT, the technical challenges are not trivial
Genesis and evolution of dust in galaxies in the early Universe I. Modeling dust evolution in starburst galaxies
We have developed a numerical galactic chemical evolution model. The model is
constructed such that the effect of a wide range of parameters can be
investigated. It takes into account results from stellar evolution models, a
differentiation between diverse types of core collapse SNe and the contribution
of AGB stars in the mass range 3-8 Msun. We consider the lifetime-dependent
yield injection into the ISM by all sources as well as dust destruction due to
SN shocks in the ISM. We ascertain the temporal progression of the dust mass,
the dust-to-gas and dust-to-metal mass ratios as well as other physical
properties of a galaxy and study their dependence on the mass of the galaxy,
the IMF, dust production efficiencies and dust destruction in the ISM. The
amount of dust and the physical properties of a galaxy strongly depend on the
initial gas mass available. Overall, while the total amount of dust produced
increases with galaxy mass, the detailed outcome depends on the SN dust
production efficiency, the IMF and the strength of dust destruction in the ISM.
Dust masses are higher for IMFs biased towards higher stellar masses, despite
the fact that these IMFs are more strongly affected by dust destruction in the
ISM. The sensitivity to the IMF increases as the mass of the galaxy decreases.
SNe are primarily responsible for a significant enrichment with dust at early
epochs (< 200 Myr). Dust production with a dominant contribution by AGB stars
is found to be insufficient to account for dust masses in excess of 10^8 Msun
within 400 Myr after starburst. We find that galaxies with initial gas masses
between 1-5 x 10^11 Msun are sufficiently massive to enable production of dust
masses >10^8 Msun. Our preferred scenario is dominated by SN dust production in
combination with top-heavy IMFs and moderate dust destruction in the ISM.Comment: 20 pages, 13 figures, 4 table
The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report
The Habitable Exoplanet Observatory, or HabEx, has been designed to be the Great Observatory of the 2030s. For the first time in human history, technologies have matured sufficiently to enable an affordable space-based telescope mission capable of discovering and characterizing Earthlike planets orbiting nearby bright sunlike stars in order to search for signs of habitability and biosignatures. Such a mission can also be equipped with instrumentation that will enable broad and exciting general astrophysics and planetary science not possible from current or planned facilities. HabEx is a space telescope with unique imaging and multi-object spectroscopic capabilities at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities allow for a broad suite of compelling science that cuts across the entire NASA astrophysics portfolio. HabEx has three primary science goals: (1) Seek out nearby worlds and explore their habitability; (2) Map out nearby planetary systems and understand the diversity of the worlds they contain; (3) Enable new explorations of astrophysical systems from our own solar system to external galaxies by extending our reach in the UV through near-IR. This Great Observatory science will be selected through a competed GO program, and will account for about 50% of the HabEx primary mission. The preferred HabEx architecture is a 4m, monolithic, off-axis telescope that is diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two starlight suppression systems: a coronagraph and a starshade, each with their own dedicated instrument
The Habitable Exoplanet Observatory (HabEx) Mission Concept Study Final Report
The Habitable Exoplanet Observatory, or HabEx, has been designed to be the
Great Observatory of the 2030s. For the first time in human history,
technologies have matured sufficiently to enable an affordable space-based
telescope mission capable of discovering and characterizing Earthlike planets
orbiting nearby bright sunlike stars in order to search for signs of
habitability and biosignatures. Such a mission can also be equipped with
instrumentation that will enable broad and exciting general astrophysics and
planetary science not possible from current or planned facilities. HabEx is a
space telescope with unique imaging and multi-object spectroscopic capabilities
at wavelengths ranging from ultraviolet (UV) to near-IR. These capabilities
allow for a broad suite of compelling science that cuts across the entire NASA
astrophysics portfolio. HabEx has three primary science goals: (1) Seek out
nearby worlds and explore their habitability; (2) Map out nearby planetary
systems and understand the diversity of the worlds they contain; (3) Enable new
explorations of astrophysical systems from our own solar system to external
galaxies by extending our reach in the UV through near-IR. This Great
Observatory science will be selected through a competed GO program, and will
account for about 50% of the HabEx primary mission. The preferred HabEx
architecture is a 4m, monolithic, off-axis telescope that is
diffraction-limited at 0.4 microns and is in an L2 orbit. HabEx employs two
starlight suppression systems: a coronagraph and a starshade, each with their
own dedicated instrument.Comment: Full report: 498 pages. Executive Summary: 14 pages. More information
about HabEx can be found here: https://www.jpl.nasa.gov/habex
Production of dust by massive stars at high redshift
The large amounts of dust detected in sub-millimeter galaxies and quasars at
high redshift pose a challenge to galaxy formation models and theories of
cosmic dust formation. At z > 6 only stars of relatively high mass (> 3 Msun)
are sufficiently short-lived to be potential stellar sources of dust. This
review is devoted to identifying and quantifying the most important stellar
channels of rapid dust formation. We ascertain the dust production efficiency
of stars in the mass range 3-40 Msun using both observed and theoretical dust
yields of evolved massive stars and supernovae (SNe) and provide analytical
expressions for the dust production efficiencies in various scenarios. We also
address the strong sensitivity of the total dust productivity to the initial
mass function. From simple considerations, we find that, in the early Universe,
high-mass (> 3 Msun) asymptotic giant branch stars can only be dominant dust
producers if SNe generate <~ 3 x 10^-3 Msun of dust whereas SNe prevail if they
are more efficient. We address the challenges in inferring dust masses and
star-formation rates from observations of high-redshift galaxies. We conclude
that significant SN dust production at high redshift is likely required to
reproduce current dust mass estimates, possibly coupled with rapid dust grain
growth in the interstellar medium.Comment: 72 pages, 9 figures, 5 tables; to be published in The Astronomy and
Astrophysics Revie
The limits of meritocracy
This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordWe show that meritocracy, in the sense of accuracy of performance ranking, can be too much of a good thing: in contests with sufficiently homogeneous agents, it reduces output and is Pareto inefficient. In contests with sufficiently heterogeneous agents, discouragement and complacency effects further reduce the benefits of meritocracy. Perfect meritocracy may be optimal only for intermediate levels of heterogeneity