302 research outputs found
How Inheritances Affect Retirement Plannings
This study uses the German SAVE panel study in order to estimate the effect of
intergenerational transfers on the expected retirement entry age of
individuals. The literature in this field typically estimates the transfer
effect on the actual retirement probability. We suggest to base the analysis
on the expected retirement age instead. This entails two methodological
advantages: First, it is possible to exploit the within individual variation
for the entire sample (even of those who do not retire) and thereby permits to
analyze the life-cycle considerations of younger age groups. Second, the
effect size can easily be expressed in terms of time and thereby monetary
opportunity costs. We find that heirs expect to retire earlier, even when
receipts are expected to some degree. Specifically, heirs plan to retire four
to five months earlier and thereby accept costs in the form of foregone income
and pension entitlements corresponding to 20-30% of the inheritance
Synchrotron and SSC Emission and the Blast-Wave Model of Gamma-Ray Bursts
We investigate the dynamics and radiation from a relativistic blast-wave
which decelerates as it sweeps up ambient matter. The bulk kinetic energy of
the blast-wave shell is converted into internal energy by the process of
accreting external matter. If it takes the form of non-thermal electrons and
magnetic fields, then this internal energy will be emitted as synchrotron and
synchrotron self-Compton radiation. We perform analytic and numerical
calculations for the deceleration and radiative processes and present
time-resolved spectra throughout the evolution of the blast-wave. We also
examine the dependence of the burst spectra and light curves on various
parameters describing the magnetic field and non-thermal electron
distributions. We find that for bursts such as GRB~910503, GRB~910601 and
GRB~910814, the spectral shapes of the prompt gamma-ray emission at the peaks
in strongly constrain the magnetic fields in these bursts to be
well below (\la 10^{-2}) the equipartition values. These calculations are
also considered in the context of the afterglow emission from the recently
detected gamma-ray burst counterparts.Comment: 27 pages, 5 figures, submitted to Ap
Stuck in the Past? Rumination-Related Memory Integration
Memories connected to ruminative concerns repetitively capture attention, even in situations designed to alter them. However, recent research on memory updating suggests that memory for benign substitutes (e.g., reinterpretations) might be facilitated by integration with the ruminative memories. As a first approach, two experiments (Ns = 72) mimicked rumination-related memories with rumination-themed stimuli and an imagery task. College undergraduates screened for ruminative status first studied and imaged ruminative cue-target word pairs, and then in a second phase they studied the same cues re-paired with benign targets (along with new and repeated pairs). On the test of cued recall of benign targets, they judged whether each recalled word had been repeated or changed across the two phases (or was new in the second phase). When target changes were not remembered, recall of benign targets revealed proactive interference that was insensitive to ruminative status. However, when participants remembered change and the ruminative targets, their recall of benign targets was facilitated, particularly if they identified as ruminators (Experiment 1). When the test simply asked for recall of either or both targets (Experiment 2), ruminators recalled both targets more frequently than did others. These outcomes suggest that ruminative memories might provide bridges to remembering associated benign memories, such as reinterpretations, under conditions consistent with everyday ruminative retrieval
Is pore water oxygen content decoupled from productivity on the California Margin? Trace element results from Ocean Drilling Program Hole 1017E, San Lucia slope, California
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95250/1/palo1223.pd
Radio galaxies and magnetic fields in A514
A514 contains six extended and polarized radio sources located at various
projected distances from the cluster center. Here we present a detailed study
of these six radio sources in total intensity and polarization using the Very
Large Array at 3.6 and 6 cm. Since the radio sources sample different lines of
sight across the cluster, an analysis of the Faraday Rotation Measures (RMs)
provides information on the strength and the structure of the cluster magnetic
field. These sources show a decreasing Faraday Rotation Measure with increasing
distance from the cluster center. We estimate the strength of the magnetic
field to be ~3-7 uG in the cluster center. From the RM structure across the
stronger and more extended sources we estimate the coherence length of the
magnetic field to be about 9 kpc at the cluster center.Comment: 16 pages, 18 ps figures accepted by A&
Submarine groundwater discharge to a small estuary estimated from radon and salinity measurements and a box model
Author Posting. © 2005 Author(s). This work is licensed under a Creative Commons License. The definitive version was published Biogeosciences 2 (2005): 141-157, doi:10.5194/bg-2-141-2005.Submarine groundwater discharge was quantified by a variety of methods for a 4-day period during the early summer of 2004, in Salt Pond, adjacent to Nauset Marsh, on Cape Cod, USA. Discharge estimates based on radon and salinity took advantage of the presence of the narrow channel connecting Salt Pond to Nauset Marsh, which allowed constructing whole-pond mass balances as water flowed in and out due to tidal fluctuations. The data suggest that less than one quarter of the discharge in the vicinity of Salt Pond happened within the pond itself, while three quarters or more of the discharge occurred immediately seaward of the pond, either in the channel or in adjacent regions of Nauset Marsh. Much of this discharge, which maintains high radon activities and low salinity, is carried into the pond during each incoming tide. A box model was used as an aid to understand both the rates and the locations of discharge in the vicinity of Salt Pond. The model achieves a reasonable fit to both the salinity and radon data assuming submarine groundwater discharge is fresh and that most of it occurs either in the channel or in adjacent regions of Nauset Marsh. Salinity and radon data, together with seepage meter results, do not rule out discharge of saline groundwater, but suggest either that the saline discharge is at most comparable in volume to the fresh discharge or that it is depleted in radon. The estimated rate of fresh groundwater discharge in the vicinity of Salt Pond is 3000-7000 m3 d-1. This groundwater flux estimated from the radon and salinity data is comparable to a value of 3200-4500 m3 d-1 predicted by a recent hydrologic model (Masterson, 2004; Colman and Masterson, 2004), although the model predicts this rate of discharge to the pond whereas our data suggest most of the groundwater bypasses the pond prior to discharge. Additional work is needed to determine if the measured rate of discharge is representative of the long-term average, and to better constrain the rate of groundwater discharge seaward of Salt Pond.Financial support was provided by the US Geological Survey
and by National Science Foundation grant #OCE-0346933 to MAC
Absorption of 10 Gev--1 Tev Gamma Rays by Radiation from Broad-Line Region in 3C 279
In this paper, we study the photon-photon pair production optical depth for
10 GeV--1 TeV gamma rays from 3C 279 due to the diffuse radiation of broad-line
region (BLR). Assuming a power-law spectrum of for the
photon intensity of very high energy (VHE) gamma rays, and
are inferred by the integrated photon fluxes measured by MAGIC
and HESS. Based on this power-law spectrum, the pre-absorbed spectra are
inferred by correcting the photon-photon absorption on the diffuse photons of
the BLR (internal absorption) and the extragalactic background light (external
absorption). Position of gamma-ray emitting region determines
the relative contributions of this two diffuse radiation to the total
absorption for 10 GeV--1 TeV gamma rays. The internal absorption could make
spectral shape of gamma rays more complex than only corrected for the external
absorption, and could lead to the formation of arbitrary softening and
hardening gamma-ray spectra. It should be necessary for the internal absorption
to be considered in studying 10 GeV--1 TeV gamma rays from powerful blazars.
The energies of annihilated gamma-ray photons due to the internal absorption
are likely to be mainly reradiated around GeV. Our results indicate that
may be between the inner and outer radii of the BLR for 3C
279. This implies for powerful blazars that might be neither
inside the BLR cavity nor outside the BLR, but be within the BLR shell.
Observations of , MAGIC, HESS, and VERITAS in the near future could
give more constraints on the position of the gamma-ray emitting region relative
to the BLR.Comment: 29 pages, 7 figures, Received: 4 June 2008, Accepted in ApJ: 18 Jul
200
Seawater redox variations during the deposition of the Kimmeridge Clay Formation, United Kingdom (Upper Jurassic): evidence from molybdenum isotopes and trace metal ratios
The Kimmeridge Clay Formation (KCF) and its equivalents worldwide represent one of the most prolonged periods of organic carbon accumulation of the Mesozoic. In this study, we use the molybdenum (Mo) stable isotope system in conjunction with a range of trace metal paleoredox proxies to assess how seawater redox varied both locally and globally during the deposition of the KCF. Facies with lower organic carbon contents (TOC 1â7 wt %) were deposited under mildly reducing (suboxic) conditions, while organic-rich facies (TOC >7 wt %) accumulated under more strongly reducing (anoxic or euxinic) local conditions. Trace metal abundances are closely linked to TOC content, suggesting that the intensity of reducing conditions varied repeatedly during the deposition of the KCF and may have been related to orbitally controlled climate changes. Long-term variations in ?98/95Mo are associated with the formation of organic-rich intervals and are related to third-order fluctuations in relative sea level. Differences in the mean ?98/95Mo composition of the organic-rich intervals suggest that the global distribution of reducing conditions was more extensive during the deposition of the Pectinatites wheatleyensis and lower Pectinatites hudlestoni zones than during the deposition of the upper Pectinatites hudlestoni and Pectinatites pectinatus zones. The global extent of reducing conditions during the Kimmerigidan was greater than today but was less widespread than during the Toarcian (Early Jurassic) oceanic anoxic event. This study also demonstrates that the Mo isotope system in Jurassic seawater responded to changes in redox conditions in a manner consistent with its behavior in present-day sedimentary environment
Fermi Large Area Telescope Observations of the Cygnus Loop Supernova Remnant
We present an analysis of the gamma-ray measurements by the Large Area
Telescope(LAT) onboard the \textit{Fermi Gamma-ray Space Telescope} in the
region of the supernova remnant(SNR) Cygnus Loop(G74.08.5). We detect
significant gamma-ray emission associated with the SNR in the energy band
0.2--100 GeV. The gamma-ray spectrum shows a break in the range 2--3 GeV. The
gamma-ray luminosity is erg s between 1--100
GeV, much lower than those of other GeV-emitting SNRs. The morphology is best
represented by a ring shape, with inner/outer radii 0.7
0.1 and 1.6 0.1. Given the association among
X-ray rims, \halpha filaments and gamma-ray emission, we argue that gamma rays
originate in interactions between particles accelerated in the SNR and
interstellar gas or radiation fields adjacent to the shock regions. The decay
of neutral pions produced in nucleon-nucleon interactions between accelerated
hadrons and interstellar gas provides a reasonable explanation for the
gamma-ray spectrum.Comment: accepted by ApJ, 34 pages, 6 figure
Export Production in the Subarctic North Pacific over the Last 800 kyrs: No Evidence for Iron Fertilization?
The subarctic North Pacific is a high nitrate-low chlorophyll (HNLC) region, where phytoplankton growth rates, especially those of diatoms, are enhanced when micronutrient Fe is added. Accordingly, it has been suggested that glacial Fe-laden dust might have increased primary production in this region. This paper reviews published palaeoceanographic records of export production over the last 800 kyrs from the open North Pacific (north of âŒ35°N). We find different patterns of export production change over time in the various domains of the North Pacific (NW and NE subarctic gyres, the marginal seas and the transition zone). However, there is no compelling evidence for an overall increase in productivity during glacials in the subarctic region, challenging the paradigm that dust-born Fe fertilization of this region has contributed to the glacial draw down of atmospheric CO 2 . Potential reasons for the lack of increased glacial export production include the possibility that Fe-fertilization rapidly drives the ecosystem towards limitation by another nutrient. This effect would have been exacerbated by an even more stable mixed layer compared to today.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41539/1/10872_2004_Article_5383267.pd
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