264 research outputs found
Calcareous nannoplankton biocoenosis : sediment trap studies in the equatorial Atlantic, central Pacific, and Panama Basin
Sediment traps deployed on three moored vertical arrays collected particles at various
depths in the equatorial Atlantic (Station E), central Pacific (Station P1), and in the
Panama Basin (Station PB1). The calcareous nannoplankton from the <63 ÎĽm size fraction
were studied in order to characterize the flux of coccospheres and coccoliths, the taxa
present, and their condition of preservation throughout the water column.
The average calculated flux of coccospheres ranged from a low value of 24 coccospheres/m2/day in the central Pacific, to an intermediate value of 4725 in the equatorial Atlantic, to
a high of 8030 in the Panama Basin. In general, the coccosphere flux decreased with depth at all three sites.
Coccolith fluxes and flux profiles were significantly different at each of the three sites.
At Station E, the flux decreased regularly with depth but increased sharply at the lowermost
trap (724 m above the bottom). The average flux for the entire column was 316 x
106 coccoliths/m2/day. At Station P1, the flux was low in the shallowest two traps and
increased markedly in the three deepest traps. This increase is due mainly to a suspected
Umbilcosphaera sibogae bloom which occurred shortly before the traps were deployed in
September 1978. The highest coccolith flux was recorded in the Station PB1 traps averaging
910 x 10 6 coccoliths/m2/day. The flux profile at this station was essentially constant in
the shallowest four traps and decreased almost 59% in the lowermost two traps. The average
coccolith carbonate fluxes for the entire columns for the Stations E, P1, and PB1 are, respectively,
2.53, 2.68, and 7.28 mg/m2/day. These fluxes represent minimum values, since
coccospheres and coccoliths were also contained in fecal pellets and other particles larger
than the size fraction studied (<63 ÎĽm).
Scanning electron microscopic examination of the trap samples revealed 56 species belonging
to 33 genera of calcareous nannoplankton. Three new species are described and illustrated:
Alsphaera spatula n. sp., Umbilcosphaera calvata n. sp., ari;d Umbilcosphaera
scituloma n. sp.
A census of taxa present, including their relative frequency and state of preservation, is
presented together with a photographic atlas of the taxa. Station E is the most diverse with
50 species, and is the best preserved of the three sites. Station PBi the least diverse with 26
more poorly preserved species. In general, the best preserved specimens were observed in the
shallowest sample at each of the three sites; diversity and state of preservation diminished
with increasing depth
: Bringing a novel research into the classroom: Carbon sequestration as a new opportunity for science education
This poster was presented at the 41st Annual Conference of the Hoosier Association of Science Teachers, Inc. (HASTI), Indianapolis, Ind., February 9-11, 2011.Carbon sequestration technology is an emerging area of research that is rarely presented in the current middle and high school curriculum. This poster complements a concurrent lecture at HASTI (Kevin Ellet and Cristian Medina) and presents three objectives: (1) to introduce the topic of carbon sequestration as a promising area of research for the mitigation of global warming; (2) to show how this technology draws from different science disciplines (e.g. earth science, physics, chemistry, and mathematics) and thus offers new opportunities for science education; (3) to present skills study can learn by studying this technology, such as the use and display of quantitative data and the use of online resources to perform literature searches. This poster presents issues raised in the HASTI position paper “Science Institutions in Indiana: Global Perspectives” (http://www.hasti.org/paper1.html) and encourages discussion on how to maximize science learning in Indiana classrooms
Halo Star Streams in the Solar Neighborhood
We have assembled a sample of halo stars in the solar neighborhood to look
for halo substructure in velocity and angular momentum space. Our sample
includes red giants, RR Lyrae, and red horizontal branch stars within 2.5 kpc
of the Sun with [Fe/H] less than -1.0. It was chosen to include stars with
accurate distances, space velocities, and metallicities as well as
well-quantified errors. We confirm the existence of the streams found by Helmi
and coworkers, which we refer to as the H99 streams. These streams have a
double-peaked velocity distribution in the z direction. We use the results of
modeling of the H99 streams by Helmi and collaborators to test how one might
use v_z velocity information and radial velocity information to detect
kinematic substructure in the halo. We find that detecting the H99 streams with
radial velocities alone would require a large sample. We use the velocity
distribution of the H99 streams to estimate their age. From our model of the
progenitor of the H99 streams, we determine that it was accreted between 6 and
9 Gyr ago. The H99 streams have [alpha/Fe] abundances similar to other halo
stars in the solar neighborhood, suggesting that the gas that formed these
stars were enriched mostly by Type II SNe. We have also discovered in angular
momentum space two other possible substructures, which we refer to as the
retrograde and prograde outliers. The retrograde outliers are likely to be halo
substructure, but the prograde outliers are most likely part of the smooth
halo. The retrograde outliers have significant structure in the v_phi direction
and show a range of [alpha/Fe]. The methods presented in this paper can be used
to exploit the kinematic information present in future large databases like
RAVE, SDSSII/SEGUE, and Gaia.Comment: 46 pages, 13 figures, and 9 tables. Minor changes to text to match
proofed version of the paper. Low resolution figures. High resolution version
at http://www.astro.wisc.edu/~kepley/solar_streams.p
Infrared Multiple-Photon Dissociation Action Spectroscopy of the b(2)(+) Ion from PPG: Evidence of Third Residue Affecting b(2)(+) Fragment Structure
Infrared multiple-photon dissociation (IRMPD) action spectroscopy was performed on the b2 + fragment ion from the protonated PPG tripeptide. Comparison of the experimental infrared spectrum with computed spectra for both oxazolone and diketopiperazine structures indicates that the majority of the fragment ion population has an oxazolone structure with the remainder having a diketopiperazine structure. This result is in contrast with a recent study of the IRMPD action spectrum of the PP b2 + fragment ion from PPP, which was found to be nearly 100% diketopiperazine (Martens et al. Int. J. Mass Spectrom. 2015, 377, 179). The diketopiperazine b2 + ion is thermodynamically more stable than the oxazolone but normally requires a trans/cis peptide bond isomerization in the dissociating peptide. Martens et al. showed through IRMPD action spectroscopy that the PPP precursor ion was in a conformation in which the first peptide bond is already in the cis conformation and thus it was energetically favorable to form the thermodynamically-favored diketopiperazine b2 + ion. In the present case, solution-phase NMR spectroscopy and gas-phase IRMPD action spectroscopy show that the PPGprecursor ion has its first amide bond in a trans configuration suggesting that the third residue is playing an important role in both the structure of the peptide and the associated ring-closure barriers for oxazolone and diketopiperazine formation
Aircraft engine with inter-turbine engine frame supported counter rotating low pressure turbine rotors
An aircraft gas turbine engine assembly includes an inter-turbine frame axially located between high and low pressure turbines. Low pressure turbine has counter rotating low pressure inner and outer rotors with low pressure inner and outer shafts which are at least in part rotatably disposed co-axially within a high pressure rotor. Inter-turbine frame includes radially spaced apart radially outer first and inner second structural rings disposed co-axially about a centerline and connected by a plurality of circumferentially spaced apart struts. Forward and aft sump members having forward and aft central bores are fixedly joined to axially spaced apart forward and aft portions of the inter-turbine frame. Low pressure inner and outer rotors are rotatably supported by a second turbine frame bearing mounted in aft central bore of aft sump member. A mount for connecting the engine to an aircraft is located on first structural ring
Resolving the Formation of Protogalaxies. II. Central Gravitational Collapse
Numerous cosmological hydrodynamic studies have addressed the formation of
galaxies. Here we choose to study the first stages of galaxy formation,
including non-equilibrium atomic primordial gas cooling, gravity and
hydrodynamics. Using initial conditions appropriate for the concordance
cosmological model of structure formation, we perform two adaptive mesh
refinement simulations of ~10^8 M_sun galaxies at high redshift. The
calculations resolve the Jeans length at all times with more than 16 cells and
capture over 14 orders of magnitude in length scales. In both cases, the dense,
10^5 solar mass, one parsec central regions are found to contract rapidly and
have turbulent Mach numbers up to 4. Despite the ever decreasing Jeans length
of the isothermal gas, we only find one site of fragmentation during the
collapse. However, rotational secular bar instabilities transport angular
momentum outwards in the central parsec as the gas continues to collapse and
lead to multiple nested unstable fragments with decreasing masses down to
sub-Jupiter mass scales. Although these numerical experiments neglect star
formation and feedback, they clearly highlight the physics of turbulence in
gravitationally collapsing gas. The angular momentum segregation seen in our
calculations plays an important role in theories that form supermassive black
holes from gaseous collapse.Comment: Replaced with accepted version. To appear in ApJ v681 (July 1
Fashionably Late? Building up the Milky Way's Inner Halo
Using a sample of 248 metal-poor stars (RR Lyraes, red giants and RHB stars)
which is remarkable for the accuracy of its 6-D kinematical data, we find a new
component for the local halo which has an axial ratio c/a ~ 0.2, a similar
flattening to the thick disk. It has a small prograde rotation but is supported
by velocity anisotropy, and contains more intermediate-metallicity stars (with
-1.5 < [Fe/H] < -1.0) than the rest of our sample. We suggest that this
component was formed quite late, during or after the formation of the disk. It
formed either from the gas that was accreted by the last major mergers
experienced by the Galaxy, or by dynamical friction of massive infalling
satellite(s) with the halo and possibly the stellar disk or thick disk. The
remainder of the stars in our sample exhibit a clumpy distribution in energy
and angular momentum, suggesting that the early, chaotic conditions under which
the inner halo formed were not violent enough to erase the record of their
origins. The clumpy structure suggests that a relatively small number of
progenitors were responsible for building up the inner halo, in line with
theoretical expectations. We find a difference in mean binding energy between
the RR Lyrae variables and the red giants in our sample, suggesting that more
of the RR Lyraes in the sample belong to the outer halo, and that the outer
halo may be somewhat younger, as first suggested by Searle and Zinn (1978). We
also find that the RR Lyrae mean rotation is more negative than the red giants,
which is consistent with the recent result of Carollo et al.(2007) that the
outer halo has a retrograde rotation and with the difference in kinematics seen
between RR Lyraes and BHB stars by Kinman et al.(2007).Comment: 16 pages, 10 figures, this version accepted by Ap
The Case for the Dual Halo of the Milky Way
Carollo et al. have recently resolved the stellar population of the Milky Way
halo into at least two distinct components, an inner halo and an outer halo.
This result has been criticized by Schoenrich et al., who claim that the
retrograde signature associated with the outer halo is due to the adoption of
faulty distances. We refute this claim, and demonstrate that the Schoenrich et
al. photometric distances are themselves flawed because they adopted an
incorrect main-sequence absolute magnitude relationship from the work of
Ivezi\'c et al. When compared to the recommended relation from Ivezi\'c et al.,
which is tied to a Milky Way globular cluster distance scale and accounts for
age and metallicity effects, the relation adopted by Schoenrich et al. yields
up to 18% shorter distances for stars near the main-sequence turnoff (TO). Use
of the correct relationship yields agreement between the distances assigned by
Carollo et al. and Ivezi\'{c} et al. for low-metallicity dwarfs to within
6-10%. Schoenrich et al. also point out that intermediate-gravity stars (3.5 <=
log g <= 4.0) with colors redder than the TO region are likely misclassified,
with which we concur. We implement a new procedure to reassign luminosity
classifications for the TO stars that require it. New derivations of the
rotational behavior demonstrate that the retrograde signature and high velocity
dispersion of the outer-halo population remains. We summarize additional lines
of evidence for a dual halo, including a test of the retrograde signature based
on proper motions alone, and conclude that the preponderance of evidence
strongly rejects the single-halo interpretation.Comment: 46 pages, 2 tables, 15 figures, Accepted for publication in the
Astrophysical Journa
Conducting a Supportive Oncology Clinical Trial During the COVID-19 Pandemic: Challenges and Strategies
The coronavirus disease 2019 (COVID-19) pandemic resulted in severe interruptions to clinical research worldwide. This global public health crisis required investigators and researchers to rapidly develop and implement new strategies and solutions to mitigate its negative impact on the progress of clinical trials. In this paper, we describe the challenges, strategies, and lessons learned regarding the continuation of a supportive oncology clinical trial during the pandemic. We hope to provide insight into the implementation of clinical trials during a public health emergency to be better prepared for future instances.
Trial registration: ClinicalTrials.gov, a service of the US National Institute of Health (NCT03030859). Registered on 22 January 2017
The Seventh Data Release of the Sloan Digital Sky Survey
This paper describes the Seventh Data Release of the Sloan Digital Sky Survey
(SDSS), marking the completion of the original goals of the SDSS and the end of
the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most
of the roughly 2000 deg^2 increment over the previous data release lying in
regions of low Galactic latitude. The catalog contains five-band photometry for
357 million distinct objects. The survey also includes repeat photometry over
250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A
coaddition of these data goes roughly two magnitudes fainter than the main
survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2
in the Northern Galactic Cap, closing the gap that was present in previous data
releases. There are over 1.6 million spectra in total, including 930,000
galaxies, 120,000 quasars, and 460,000 stars. The data release includes
improved stellar photometry at low Galactic latitude. The astrometry has all
been recalibrated with the second version of the USNO CCD Astrograph Catalog
(UCAC-2), reducing the rms statistical errors at the bright end to 45
milli-arcseconds per coordinate. A systematic error in bright galaxy photometr
is less severe than previously reported for the majority of galaxies. Finally,
we describe a series of improvements to the spectroscopic reductions, including
better flat-fielding and improved wavelength calibration at the blue end,
better processing of objects with extremely strong narrow emission lines, and
an improved determination of stellar metallicities. (Abridged)Comment: 20 pages, 10 embedded figures. Accepted to ApJS after minor
correction
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