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A study of the percentage and total intake of certain elements by calciphilic and calciphobic plants grown on soils varying in pH.
Thesis (M.S.
Ineffectiveness of Pad\'e resummation techniques in post-Newtonian approximations
We test the resummation techniques used in developing Pad\'e and Effective
One Body (EOB) waveforms for gravitational wave detection. Convergence tests
show that Pad\'e approximants of the gravitational wave energy flux do not
accelerate the convergence of the standard Taylor approximants even in the test
mass limit, and there is no reason why Pad\'e transformations should help in
estimating parameters better in data analysis. Moreover, adding a pole to the
flux seems unnecessary in the construction of these Pad\'e-approximated flux
formulas. Pad\'e approximants may be useful in suggesting the form of fitting
formulas. We compare a 15-orbit numerical waveform of the Caltech-Cornell group
to the suggested Pad\'e waveforms of Damour et al. in the equal mass,
nonspinning quasi-circular case. The comparison suggests that the Pad\'e
waveforms do not agree better with the numerical waveform than the standard
Taylor based waveforms. Based on this result, we design a simple EOB model by
modifiying the ET EOB model of Buonanno et al., using the Taylor series of the
flux with an unknown parameter at the fourth post-Newtonian order that we fit
for. This simple EOB model generates a waveform having a phase difference of
only 0.002 radians with the numerical waveform, much smaller than 0.04 radians
the phase uncertainty in the numerical data itself. An EOB Hamiltonian can make
use of a Pad\'e transformation in its construction, but this is the only place
Pad\'e transformations seem useful.Comment: 13 pages, 7 figures. added some reference
Bounding biomass in the Fisher equation
The FKPP equation with a variable growth rate and advection by an
incompressible velocity field is considered as a model for plankton dispersed
by ocean currents. If the average growth rate is negative then the model has a
survival-extinction transition; the location of this transition in the
parameter space is constrained using variational arguments and delimited by
simulations. The statistical steady state reached when the system is in the
survival region of parameter space is characterized by integral constraints and
upper and lower bounds on the biomass and productivity that follow from
variational arguments and direct inequalities. In the limit of
zero-decorrelation time the velocity field is shown to act as Fickian diffusion
with an eddy diffusivity much larger than the molecular diffusivity and this
allows a one-dimensional model to predict the biomass, productivity and
extinction transitions. All results are illustrated with a simple growth and
stirring model.Comment: 32 Pages, 13 Figure
The Epoch of Giant Planet Migration Planet Search Program. I. Near-Infrared Radial Velocity Jitter of Young Sun-like Stars
We present early results from the Epoch of Giant Planet Migration program, a
precise RV survey of over one hundred intermediate-age (20200 Myr) G
and K dwarfs with the Habitable-Zone Planet Finder spectrograph (HPF) at
McDonald Observatory's Hobby-Eberly Telescope (HET). The goals of this program
are to determine the timescale and dominant physical mechanism of giant planet
migration interior to the water ice line of Sun-like stars. Here, we summarize
results from the first 14 months of this program, with a focus on our custom RV
pipeline for HPF, a measurement of the intrinsic near-infrared RV activity of
young Solar analogs, and modeling the underlying population-level distribution
of stellar jitter. We demonstrate on-sky stability at the sub-2 m s
level for the K2 standard HD 3765 using a least-squares matching method to
extract precise RVs. Based on a subsample of 29 stars with at least three RV
measurements from our program, we find a median RMS level of 34 m s.
This is nearly a factor of 2 lower than the median RMS level in the optical of
60 m s for a comparison sample with similar ages and spectral types as
our targets. The observed near-infrared jitter measurements for this subsample
are well reproduced with a log-normal parent distribution with and
. Finally, by compiling RMS values from previous planet search
programs, we show that near-infrared jitter for G and K dwarfs generally decays
with age in a similar fashion to optical wavelengths, albeit with a shallower
slope and lower overall values for ages 1 Gyr
De Novo Design of a Single Chain Diphenylporphyrin Metalloprotein
We describe the computational design of a single-chain four-helix bundle that noncovalently self-assembles with fully synthetic non-natural porphyrin cofactors. With this strategy, both the electronic structure of the cofactor as well as its protein environment may be varied to explore and modulate the functional and photophysical properties of the assembly. Solution characterization (NMR, UV-vis) of the protein showed that it bound with high specificity to the desired cofactors, suggesting that a uniquely structured protein and well-defined site had indeed been created. This provides a genetically expressed single-chain protein scaffold that will allow highly facile, flexible, and asymmetric variations to enable selective incorporation of different cofactors, surface-immobilization, and introduction of spectroscopic probes
Diagnostic and clinical experience of patients with pantothenate kinase-associated neurodegeneration
BACKGROUND: Pantothenate kinase-associated neurodegeneration (PKAN) is an autosomal recessive neurodegenerative disorder with brain iron accumulation (NBIA).
OBJECTIVES: To assess PKAN diagnostic pathway, history, and burden across the spectrum of PKAN severity from patient and/or caregiver perspectives.
METHODS: Caregivers of patients (n = 37) and patients themselves (n = 2) were interviewed in a validation study of the PKAN-Activities of Daily Living (ADL) scale. The current study used quartiles of the PKAN-ADL total score to divide patients by severity of impairment (Lowest, Second Lowest, Third Lowest, Highest). Diagnostic and treatment history, healthcare utilization, disease burden, and caregiver experience were compared between groups.
RESULTS: The analyses included data from 39 patients. Mean age at PKAN symptom onset (P = 0.0007), initial MRI (P = 0.0150), and genetic testing (P = 0.0016) generally decreased across the PKAN severity spectrum. The mean duration of illness did not differ among PKAN severity groups (range, 9.7-15.2 years; P = 0.3029). First MRI led to diagnosis in 56.4% of patients (range, 30.0-90.0%). A mean (SD) of 13.0 (13.1) medical and 55.2 (78.5) therapy visits (eg, physical, speech) occurred in the past year. More patients in the higher PKAN severity groups experienced multiple current functional losses and/or earlier onset of problems (P-values \u3c 0.0500). Over half (56.8%) of caregivers experienced a change in employment because of caregiving. The percentage of patients requiring full-time caregiving increased across the PKAN severity spectrum (range, 11.1-100%; P = 0.0021).
CONCLUSIONS: PKAN diagnosis was often delayed, most probably due to low awareness. Considerable burden of functional impairment and high healthcare utilization were found across the PKAN severity spectrum
Structural parameters for globular clusters in NGC 5128. III. ACS surface-brightness profiles and model fits
We present internal surface-brightness profiles, based on HST/ACS imaging in
the F606W bandpass, for 131 globular cluster (GC) candidates with luminosities
10^4 - 3 x 10^6 solar, in the giant elliptical galaxy NGC 5128. Several
structural models are fit to the profile of each cluster and combined with
mass-to-light ratios from population-synthesis models, to derive a catalogue of
fundamental structural and dynamical parameters parallel in form to the
catalogues recently produced by McLaughlin & van der Marel and Barmby et al.
for GCs and massive young star clusters in Local Group galaxies. As part of
this, we provide corrected and extended parameter estimates for another 18
clusters in NGC 5128, which we observed previously. We show that, like GCs in
the Milky Way and some of its satellites, the majority of globulars in NGC 5128
are well fit by isotropic Wilson models, which have intrinsically more
distended envelope structures than the standard King lowered isothermal
spheres. We use our models to predict internal velocity dispersions for every
cluster in our sample. These predictions agree well in general with the
observed dispersions in a small number of clusters for which spectroscopic data
are available. In a subsequent paper, we use these results to investigate
scaling relations for GCs in NGC 5128.Comment: MNRAS, in press. 28 pages. Full data tables available at
http://www.astro.keele.ac.uk/~dem/clusters.htm
The Globular Cluster/Central Black Hole Connection in Galaxies
We explore the relation between the total globular cluster population in a
galaxy (N_GC) and the the mass of its central black hole (M_BH). Using a sample
of 33 galaxies, twice as large as the original sample discussed by Burkert &
Tremaine (2010), we find that N_GC for elliptical and spiral galaxies increases
in almost precisely direct proportion to M_BH. The S0-type galaxies by contrast
do not follow a clear trend, showing large scatter in M_BH at a given N_GC.
After accounting for observational measurement uncertainty, we find that the
mean relation defined by the E and S galaxies must also have an intrinsic or
"cosmic" scatter of +-0.2 in either logN_GC or logM_BH. The residuals from this
correlation show no trend with globular cluster specific frequency. We suggest
that these two types of galaxy subsystems (central black hole and globular
cluster system) may be closely correlated because they both originated at high
redshift during the main epoch of hierarchical merging, and both require
extremely high-density conditions for formation. Lastly, we note that roughly
10% of the galaxies in our sample (one E, one S, and two S0) deviate strongly
from the main trend, all in the sense that their M_BH is at least 10x smaller
than would be predicted by the mean relation.Comment: 7 pages, 4 figures; accepted for publication in MNRA
Using α-Helical Coiled-Coils to Design Nanostructured Metalloporphyrin Arrays
We have developed a computational design strategy based on the alpha-helical coiled-coil to generate modular peptide motifs capable of assembling into metalloporphyrin arrays of varying lengths. The current study highlights the extension of a two-metalloporphyrin array to a four-metalloporphyrin array through the incorporation of a coiled-coil repeat unit. Molecular dynamics simulations demonstrate that the initial design evolves rapidly to a stable structure with a small rmsd compared to the original model. Biophysical characterization reveals elongated proteins of the desired length, correct cofactor stoichiometry, and cofactor specificity. The successful extension of the two-porphyrin array demonstrates how this methodology serves as a foundation to create linear assemblies of organized electrically and optically responsive cofactors
Control of intestinal stem cell function and proliferation by mitochondrial pyruvate metabolism.
Most differentiated cells convert glucose to pyruvate in the cytosol through glycolysis, followed by pyruvate oxidation in the mitochondria. These processes are linked by the mitochondrial pyruvate carrier (MPC), which is required for efficient mitochondrial pyruvate uptake. In contrast, proliferative cells, including many cancer and stem cells, perform glycolysis robustly but limit fractional mitochondrial pyruvate oxidation. We sought to understand the role this transition from glycolysis to pyruvate oxidation plays in stem cell maintenance and differentiation. Loss of the MPC in Lgr5-EGFP-positive stem cells, or treatment of intestinal organoids with an MPC inhibitor, increases proliferation and expands the stem cell compartment. Similarly, genetic deletion of the MPC in Drosophila intestinal stem cells also increases proliferation, whereas MPC overexpression suppresses stem cell proliferation. These data demonstrate that limiting mitochondrial pyruvate metabolism is necessary and sufficient to maintain the proliferation of intestinal stem cells
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