275 research outputs found
Radioactive Iron Rain: Transporting Fe in Supernova Dust to the Ocean Floor
Several searches have found evidence of Fe deposition, presumably from
a near-Earth supernova (SN), with concentrations that vary in different
locations on Earth. This paper examines various influences on the path of
interstellar dust carrying Fe from a SN through the heliosphere, with
the aim of estimating the final global distribution on the ocean floor. We
study the influences of magnetic fields, angle of arrival, wind and ocean
cycling of SN material on the concentrations at different locations. We find
that the passage of SN material through the mesosphere/lower thermosphere (MLT)
is the greatest influence on the final global distribution, with ocean cycling
causing lesser alteration as the SN material sinks to the ocean floor. SN
distance estimates in previous works that assumed a uniform distribution are a
good approximation. Including the effects on surface distributions, we estimate
a distance of pc for a SN progenitor. This
is consistent with a SN occurring within the Tuc-Hor stellar group 2.8
Myr ago with SN material arriving on Earth 2.2 Myr ago. We note that the
SN dust retains directional information to within through its
arrival in the inner Solar System, so that SN debris deposition on inert bodies
such as the Moon will be anisotropic, and thus could in principle be used to
infer directional information. In particular, we predict that existing lunar
samples should show measurable Fe differences.Comment: 18 pages, 8 figures. Comments welcom
Astrophysical Shrapnel: Discriminating Among Near-Earth Stellar Explosion Sources of Live Radioactive Isotopes
We consider the production and deposition on Earth of isotopes with
half-lives in the range 10 to 10 years that might provide
signatures of nearby stellar explosions, extending previous analyses of
Core-Collapse Supernovae (CCSNe) to include Electron-Capture Supernovae
(ECSNe), Super-Asymptotic Giant Branch (SAGBs) stars, Thermonuclear/Type Ia
Supernovae (TNSNe), and Kilonovae/Neutron Star Mergers (KNe). We revisit
previous estimates of the Fe and Al signatures, and extend these
estimates to include Pu and Mn. We discuss interpretations of
the Fe signals in terrestrial and lunar reservoirs in terms of a nearby
stellar ejection ~2.2 Myr ago, showing that (i) the Fe yield rules out
the TNSN and KN interpretations, (ii) the Fe signals highly constrain a
SAGB interpretation but do not completely them rule out, (iii) are consistent
with a CCSN origin, and (iv) are highly compatible with an ECSN interpretation.
Future measurements could resolve the radioisotope deposition over time, and we
use the Sedov blast wave solution to illustrate possible time-resolved
profiles. Measuring such profiles would independently probe the blast
properties including distance, and would provide additional constraints the
nature of the explosion.Comment: 38 pages, 6 figures. Comments welcom
Rotational spectrum of cis–cis HOONO
The pure rotational spectrum of cis-cis peroxynitrous acid, HOONO, has been observed. Over 220 transitions, sampling states up to J(')=67 and K-a(')=31, have been fitted with an rms uncertainty of 48.4 kHz. The experimentally determined rotational constants agree well with ab initio values for the cis-cis conformer, a five-membered ring formed by intramolecular hydrogen bonding. The small, positive inertial defect Delta=0.075667(60) amu A(2) and lack of any observable torsional splittings in the spectrum indicate that cis-cis HOONO exists in a well-defined planar structure at room temperature
Rotational spectroscopy and dipole moment of cis-cis HOONO and DOONO
The rotational spectrum of cis-cis HOONO has been studied over a broad range of frequencies, 13–840 GHz, using pulsed beam Fourier-transform microwave spectroscopy and room-temperature flow cell submillimeter spectroscopy. The rotational spectrum of the deuterated isotopomer, cis-cis DOONO, has been studied over a subset of this range, 84–640 GHz. Improved spectroscopic constants have been determined for HOONO, and the DOONO spectrum is analyzed for the first time. Weak-field Stark effect measurements in the region of 84–110 GHz have been employed to determine the molecular dipole moments of cis-cis HOONO [µa=0.542(8) D,µb=0.918(15) D,µ=1.07(2) D] and DOONO [µa=0.517(9) D,µb=0.930(15) D,µ=1.06(2) D]. The quadrupole coupling tensor in the principal inertial axis system for the 14N nucleus has been determined to be chiaa=1.4907(25) MHz,chibb=–4.5990(59) MHz,chiab=3.17(147) MHz, and chicc=3.1082(59) MHz. Coordinates of the H atom in the center-of-mass frame have been determined with use of the Kraitchman equations, |aH|=0.516 Å and |bH|=1.171 Å. The inertial defects of HOONO and DOONO are consistent with a planar equilibrium structure with significant out-of-plane H atom torsional motion. Comparisons of the present results are made to ab initio calculations
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Superior lentiviral vectors designed for BSL-0 environment abolish vector mobilization.
Lentiviral vector mobilization following HIV-1 infection of vector-transduced cells poses biosafety risks to vector-treated patients and their communities. The self-inactivating (SIN) vector design has reduced, however, not abolished mobilization of integrated vector genomes. Furthermore, an earlier study demonstrated the ability of the major product of reverse transcription, a circular SIN HIV-1 vector comprising a single-Â long terminal repeat (LTR) to support production of high vector titers. Here, we demonstrate that configuring the internal vector expression cassette in opposite orientation to the LTRs abolishes mobilization of SIN vectors. This additional SIN mechanism is in part premised on induction of host PKR response to double-stranded RNAs comprised of mRNAs transcribed from cryptic transcription initiation sites around 3'SIN-LTR's and the vector internal promoter. As anticipated, PKR response following transfection of opposite orientation vectors, negatively affects their titers. Importantly, shRNA-mediated knockdown of PKR rendered titers of SIN HIV-1 vectors comprising opposite orientation expression cassettes comparable to titers of conventional SIN vectors. High-titer vectors carrying an expression cassette in opposite orientation to the LTRs efficiently delivered and maintained high levels of transgene expression in mouse livers. This study establishes opposite orientation expression cassettes as an additional PKR-dependent SIN mechanism that abolishes vector mobilization from integrated and episomal SIN lentiviral vectors
Resistance training and youth
This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?vid=4&sid=34ab1967-2aea-457b-b261-e90e7b05e38c%40sessionmgr11&hid=2&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=20752095The use of resistance training for children has increased in popularity and
interest. It appears that children are capable of voluntary strength gains. Exercise
prescription in younger populations is critical and requires certain program
variables to be altered tTom adult perspectives. Individualization is vital,
as the rate of physiological maturation has an impact on the adaptations that
occur, The major difference in programs for children is the use of lighter
loads (i.e., > 6 RM loads). It appears that longer duration programs (i.e.,
10-20 wks) are better for observing training adaptations. This may be due
to the fact that it takes more exercise to stimulate adaptational mechanisms
related to strength performance beyond that of normal growth rates. The risk
of injury appears low during participation in a resistance training program,
and this risk is minimized with proper supervision and instruction. Furthermore,
with the incidence of injury in youth sports, participation in a resistance
training program may provide a protective advantage in one's preparation
for sports participation
Stable isotope monitoring of benthic–planktonic coupling using salt marsh fish
Author Posting. © Inter-Research, 2008. This article is posted here by permission of Inter-Research for personal use, not for redistribution. The definitive version was published in Marine Ecology Progress Series 369 (2008): 193-204, doi:10.3354/meps07644.Salt marshes are important coastal ecosystems whose trophic function can be monitored with stable isotopes of abundant fish biosentinel species such as the mummichog Fundulus heteroclitus and the Atlantic silverside Menidia menidia. We compared movement patterns and feeding biology of these species in the summers of 1999 and 2000 in the Rowley River salt marsh estuary north of Boston, Massachusetts, USA. A 15N tracer addition experiment showed that fish of both species were more resident than transient, with mummichogs resident at scales of 1 km or less. Natural abundance stable isotope C, N, and S distributions showed that mummichogs feed more strongly in the benthic food web while silversides feed more in the planktonic food web, with % benthic feeding respectively averaging 58 ± 5 and 32 ± 3% (mean ± 95% confidence limit, CL). For both species, isotope results indicated considerable individual specialization in foraging behavior, likely related to use of channel habitat versus use of the marsh. Power analysis showed that measuring 3 composite samples each comprising 10 to 15 individual fish should provide relatively low errors of 0.5‰ (95% CL) or less around stable isotope averages. Use of such composite samples in monitoring programs will allow detection of significant temporal and spatial changes in benthic-planktonic coupling for salt marsh ecosystems, as recorded in average fish diets. Analyzing some individual fish also is recommended to obtain more detailed information on fish food sources, feeding specializations, and end-member isotope values used in estimating importance of benthic and planktonic food sources.This work
was supported by Louisiana SeaGrant Projects R/CEH-13 and
R-EFH-07, NOAA MULTISTRESS award 16OP2670, and NSF
award DEB 9815598 and BES SGER award 0553138-001
Effect of a liquid multi-vitamin-mineral supplement on anaerobic exercise performance
This is the publisher's version, also found at http://ehis.ebscohost.com/ehost/detail?sid=10f44d64-ddff-470e-a85a-b4c63b016efa%40sessionmgr10&vid=1&hid=2&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=s3h&AN=20338872The purpose of this study was to determine if supplementation with a
liquid multi-vitamin/mineral would improve anaerobic exercise performance.
Fourteen resistance-trained men performed a 30-second cycle
sprint and one set of squat exercise on 2 separate days before and following
8 weeks of supplementation with either a liquid multi-vitamin/
mineral or a placebo. Heart rate, perceived exertion, blood lactate, peak
and mean power, and rate of fatigue were determined for all tests. No
differences were noted for any variable (P > 0.05). When controlling for
presupplementation values, however, a decreased rate of fatigue was
noted for both exercise tests following the multi-vitamin/mineral supplementation.
These data suggest that in resistance trained men consuming
a nutritionally sound diet, supplementation with a liquid
multi-vitamin/mineral does not favorably impact most anaerobic exercise
performances. Such supplementation, however, may result in a
minor decreased rate of fatigue. It appears that, in terms of improved
short duration anaerobic exercise performance, supplemental micronutrients
may not be efficient ergogenic agents for well-trained individuals
consuming an adequate diet
Proposed Lunar Measurements of -Process Radioisotopes to Distinguish Origin of Deep-sea 244Pu
244Pu has recently been discovered in deep-sea deposits spanning the past 10
Myr, a period that includes two 60Fe pulses from nearby supernovae. 244Pu is
among the heaviest -process products, and we consider whether it was created
in the supernovae, which is disfavored by nucleosynthesis simulations, or in an
earlier kilonova event that seeded 244Pu in the nearby interstellar medium that
was subsequently swept up by the supernova debris. We discuss how these
possibilities can be probed by measuring 244Pu and other -process
radioisotopes such as 129I and 182Hf, both in lunar regolith samples returned
to Earth by missions such as Chang'e and Artemis, and in deep-sea deposits.Comment: Extensive rewrite of v1 with added emphasis of lunar sample return
missions, including Artemis and Chang'e. 11 pages, 4 figures, 2 tabl
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