153 research outputs found
Philanthropy in Complex, Multi-Generational Families: Balancing Individual Preference with Collective Purpose
Researchers from Lansberg Gersick Advisors hypothesized that families' abilities to work together effectively in their philanthropy is dependent not only on the way they design their collective family foundation, but also in how they structure the philanthropic activities outside of it. From 2018-2022, they conducted surveys and interviews and found that as families evolve, they face common dilemmas regarding their philanthropy—most critically, the choices they make about balancing the individual philanthropic priorities of their members with a collective family philanthropic endeavor.Learn about the range of philanthropic vehicles, strategies, and practices that multi-generational families are leveraging to meet both individual and collective aspirations of their expanding family and lessons learned on successful approaches for those with hopes of generational continuity
Shine a Light: The Role of Consultants in Fostering a Learning Culture at Foundations
Noticeably absent on the list of reasons foundations cite for engaging consultants is learning – a particularly important attribute for foundations that grapple with complex issues in dynamic environments.
Consultants are particularly well positioned to help foundations in the learning process. They help organizations understand and create models and frameworks, implement strategies and mechanisms within them, overcome roadblocks to learning, and put them on a path toward a dynamic and sustainable learning culture.
This article proposes that being explicit about the value of fostering a learning culture in a foundation within the context of any consulting engagement will enable both parties to more proactively strive for and achieve learning results. Our analysis uses this premise as a jumping-off point to a deeper exploration of the myriad ways – some simple, some complex – that consultants help foundations cultivate a learning mindset
The Pre-Explosion Mass Distribution of Hydrogen-Poor Superluminous Supernova Progenitors and New Evidence for a Mass-Spin Correlation
Despite indications that superluminous supernovae (SLSNe) originate from
massive progenitors, the lack of a uniformly analyzed statistical sample has so
far prevented a detailed view of the progenitor mass distribution. Here we
present and analyze the pre-explosion mass distribution of hydrogen-poor SLSN
progenitors as determined from uniformly modelled light curves of 62 events. We
construct the distribution by summing the ejecta mass posteriors of each event,
using magnetar light curve models presented in our previous works (and using a
nominal neutron star remnant mass). The resulting distribution spans
M, with a sharp decline at lower masses, and is best fit by a broken
power law described by at
M and at M.
We find that observational selection effects cannot account for the shape of
the distribution. Relative to Type Ib/c SNe, the SLSN mass distribution extends
to much larger masses and has a different power-law shape, likely indicating
that the formation of a magnetar allows more massive stars to explode as some
of the rotational energy accelerates the ejecta. Comparing the SLSN
distribution with predictions from single and binary star evolution models, we
find that binary models for a metallicity of Z are
best able to reproduce its broad shape, in agreement with the preference of
SLSNe for low metallicity environments. Finally, we uncover a correlation
between the pre-explosion mass and the magnetar initial spin period, where
SLSNe with low masses have slower spins, a trend broadly consistent with the
effects of angular momentum transport evident in models of rapidly-rotating
carbon-oxygen stars.Comment: 18 pages, 11 figures, Submitted to Ap
SN 2016iet: The Pulsational or Pair Instability Explosion of a Low Metallicity Massive CO Core Embedded in a Dense Hydrogen-Poor Circumstellar Medium
We present optical photometry and spectroscopy of SN 2016iet, an
unprecedented Type I supernova (SN) at with no obvious analog in the
existing literature. The peculiar light curve has two roughly equal brightness
peaks ( mag) separated by 100 days, and a subsequent slow decline
by 5 mag in 650 rest-frame days. The spectra are dominated by emission lines of
calcium and oxygen, with a width of only km s, superposed on a
strong blue continuum in the first year, and with a large ratio of at late times. There is no clear evidence
for hydrogen or helium associated with the SN at any phase. We model the light
curves with several potential energy sources: radioactive decay, central
engine, and circumstellar medium (CSM) interaction. Regardless of the model,
the inferred progenitor mass near the end of its life (i.e., CO core mass) is
M and up to M, placing the event in the
regime of pulsational pair instability supernovae (PPISNe) or pair instability
supernovae (PISNe). The models of CSM interaction provide the most consistent
explanation for the light curves and spectra, and require a CSM mass of
M ejected in the final decade before explosion. We further
find that SN 2016iet is located at an unusually large offset ( kpc) from
its low metallicity dwarf host galaxy ( Z, M), supporting the PPISN/PISN interpretation. In the final
spectrum, we detect narrow H emission at the SN location, likely due to
a dim underlying galaxy host or an H II region. Despite the overall consistency
of the SN and its unusual environment with PPISNe and PISNe, we find that the
inferred properties of SN\,2016iet challenge existing models of such events.Comment: 26 Pages, 17 Figures, Submitted to Ap
The Intermediate Luminosity Optical Transient SN 2010da: The Progenitor, Eruption and Aftermath of a Peculiar Supergiant High-mass X-ray Binary
We present optical spectroscopy, ultraviolet to infrared imaging and X-ray
observations of the intermediate luminosity optical transient (ILOT) SN 2010da
in NGC 300 (d=1.86 Mpc) spanning from -6 to +6 years relative to the time of
outburst in 2010. Based on the light curve and multi-epoch SEDs of SN 2010da,
we conclude that the progenitor of SN 2010da is a ~10-12 Msol yellow supergiant
possibly transitioning into a blue loop phase. During outburst, SN 2010da had a
peak absolute magnitude of M<-10.4 mag, dimmer than other ILOTs and supernova
impostors. We detect multi-component hydrogen Balmer, Paschen, and Ca II
emission lines in our high-resolution spectra, which indicate a dusty and
complex circumstellar environment. Since the 2010 eruption, the star has
brightened by a factor of ~5 and remains highly variable in the optical.
Furthermore, we detect SN 2010da in archival Swift and Chandra observations as
an ultraluminous X-ray source (L~6x10^{39} erg/s). We additionally attribute He
II 4686 Angstrom and coronal Fe emission lines in addition to a steady X-ray
luminosity of ~10^{37} erg/s to the presence of a compact companion.Comment: published; updated citations and other minor edit
The Luminous and Double-Peaked Type Ic Supernova 2019stc: Evidence for Multiple Energy Sources
We present optical photometry and spectroscopy of SN\,2019stc
(=ZTF19acbonaa), an unusual Type Ic supernova (SN Ic) at a redshift of
. SN\,2019stc exhibits a broad double-peaked light curve, with the
first peak having an absolute magnitude of mag, and the second
peak, about 80 rest-frame days later, mag. The total radiated
energy is large, erg. Despite its large
luminosity, approaching those of Type I superluminous supernovae (SLSNe),
SN\,2019stc exhibits a typical SN Ic spectrum, bridging the gap between SLSNe
and SNe Ic. The spectra indicate the presence of Fe-peak elements, but modeling
of the first light curve peak with radioactive heating alone leads to an
unusually high nickel mass fraction of ( M). Instead, if we model the first peak with a combined
magnetar spin-down and radioactive heating model we find a better match with
M, a magnetar spin period of ms and magnetic field of G, and (consistent with SNe Ic). The prominent second peak cannot be naturally
accommodated with radioactive heating or magnetar spin-down, but instead can be
explained as circumstellar interaction with of
hydrogen-free material located AU from the progenitor. Including
the remnant mass leads to a CO core mass prior to explosion of
M. The host galaxy has a metallicity of Z, low
for SNe Ic but consistent with SLSNe. Overall, we find that SN\,2019stc is a
transition object between normal SNe Ic and SLSNe.Comment: 14 pages, 13 figures, Accepted to Ap
FLEET: A Redshift-Agnostic Machine Learning Pipeline to Rapidly Identify Hydrogen-Poor Superluminous Supernovae
Over the past decade wide-field optical time-domain surveys have increased
the discovery rate of transients to the point that are being
spectroscopically classified. Despite this, these surveys have enabled the
discovery of new and rare types of transients, most notably the class of
hydrogen-poor superluminous supernovae (SLSN-I), with about 150 events
confirmed to date. Here we present a machine-learning classification algorithm
targeted at rapid identification of a pure sample of SLSN-I to enable
spectroscopic and multi-wavelength follow-up. This algorithm is part of the
FLEET (Finding Luminous and Exotic Extragalactic Transients) observational
strategy. It utilizes both light curve and contextual information, but without
the need for a redshift, to assign each newly-discovered transient a
probability of being a SLSN-I. This classifier can achieve a maximum purity of
about 85\% (with 20\% completeness) when observing a selection of SLSN-I
candidates. Additionally, we present two alternative classifiers that use
either redshifts or complete light curves and can achieve an even higher purity
and completeness. At the current discovery rate, the FLEET algorithm can
provide about SLSN-I candidates per year for spectroscopic follow-up with
85\% purity; with the Legacy Survey of Space and Time we anticipate this will
rise to more than events per year.Comment: 17 pages, 12 figures, submitted to Ap
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Playground equipment-related extremity fractures in children presenting to US emergency departments, 2006–2016
Background
Despite updated playground equipment and improved industry standards, playgrounds remain a common source of childhood injury. Fractures account for 35% of all playground injuries presenting to emergency departments (EDs). We aimed to examine the time trends and epidemiologic patterns of playground equipment-related extremity fractures in children in the United States.
Methods
We analyzed data from the National Electronic Injury Surveillance System. Children ≤14 years presenting to US emergency departments from 2006 to 2016 with playground equipment-related injuries were included. We used weighted complex survey analysis to describe the epidemiologic patterns and severity of playground equipment-related extremity fractures and Joinpoint linear weighted regression analysis to determine trends in extremity fractures.
Results
An annual average of 72,889 children were treated in US EDs for playground equipment-related extremity fractures, yielding a national annual incidence rate of 119.2 per 100,000 children. Playground equipment-related extremity fractures accounted for 33.9% of ED presentations and 78.7% of hospitalizations for playground equipment-related injuries. Of patients with playground equipment-related extremity fractures, 11.2% had severe fractures requiring hospitalization. The annual rate of ED visits due to playground equipment-related extremity fractures remained stable (annual rate of change = 0.74, p = 0.14) from 2006 to 2016. Adjusted for age, injuries on monkey bars or climbing gyms were associated with significantly increased odds of extremity fractures in comparison to injuries from other playground equipment (adjusted odds ratio [aOR]: 2.0; 95% CI: 1.9–2.1). Overall, 49.8% of extremity fractures and 54.7% of severe extremity fractures (i.e. those requiring hospitalization) occurred on monkey bars or climbing gyms.
Conclusions
Despite enhanced playground safety standards, national rates of playground equipment-related extremity fractures have remained stable in the US. Extremity fractures remain the most common type of playground injury presenting to EDs and most commonly occur on monkey bars and climbing gyms
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Fundamental chemistry, Characterization, and Separation of Technetium Complexes in Hanford Waste
The ultimate goal of this proposal is to separate technetium from Hanford tank waste. Our recent work has shown that a large portion of the technetium is not pertechnetate (TcO4-) and is not easily oxidized. This has serious repercussions for technetium partitioning schemes because they are designed to separate this chemical form. Rational attempts to oxidize these species to TcO4- for processing or to separate the nonpertechnetate species themselves would be facilitated by knowing the identity of these complexes and understanding their fundamental chemistry. Tank characterization work has not yet identified any of the non-pertechnetate species. However, based on the types of ligands available and the redox conditions in the tank, a reasonable speculation can be made about the types of species that may be present. Thus, this proposal will synthesize and characterize the relevant model complexes of Tc(III), Tc(IV), and Tc(V) that may have formed under tank waste conditions. Once synthesized, these complexes will be used as standards for developing and characterizing the non-pertechnetate species in actual waste using instrumental techniques such as capillary electrophoresis electrospray mass spectrometry (CE-MS), x-ray absorbance spectroscopy (EXAFS and XANES), and multi-nuclear NMR (including 99Tc NMR). We will study the redox chemistry of the technetium complexes so that more efficient and selective oxidative methods can be used to bring these species to TcO4- for processing purposes. We will also study their ligand substitution chemistry, which could be used to develop separation methods for non-pertechnetate species. Understanding the fundamental chemistry of these technetium complexes will enable technetium to be efficiently removed from the Hanford tank waste and help DOE to fulfill its remediation mission
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