2,950 research outputs found
Development, fabrication, testing, and delivery of advanced filamentary composite nondestructive test standards Final report
Development and fabrication of filament composite nondestructive test standard
The cosmological origin of the Tully-Fisher relation
We use high-resolution cosmological simulations that include the effects of
gasdynamics and star formation to investigate the origin of the Tully-Fisher
relation in the standard Cold Dark Matter cosmogony. Luminosities are computed
for each model galaxy using their full star formation histories and the latest
spectrophotometric models. We find that at z=0 the stellar mass of model
galaxies is proportional to the total baryonic mass within the virial radius of
their surrounding halos. Circular velocity then correlates tightly with the
total luminosity of the galaxy, reflecting the equivalence between mass and
circular velocity of systems identified in a cosmological context. The slope of
the relation steepens slightly from the red to the blue bandpasses, and is in
fairly good agreement with observations. Its scatter is small, decreasing from
\~0.45 mag in the U-band to ~0.34 mag in the K-band. The particular
cosmological model we explore here seems unable to account for the zero-point
of the correlation. Model galaxies are too faint at z=0 (by about two
magnitudes) if the circular velocity at the edge of the luminous galaxy is used
as an estimator of the rotation speed. The Tully-Fisher relation is brighter in
the past, by about ~0.7 magnitudes in the B-band at z=1, at odds with recent
observations of z~1 galaxies. We conclude that the slope and tightness of the
Tully-Fisher relation can be naturally explained in hierarchical models but
that its normalization and evolution depend strongly on the star formation
algorithm chosen and on the cosmological parameters that determine the
universal baryon fraction and the time of assembly of galaxies of different
mass.Comment: 5 pages, 4 figures included, submitted to ApJ (Letters
Patchy Amphiphilic Dendrimers Bind Adenovirus and Control Its Host Interactions and in Vivo Distribution
The surface of proteins is heterogeneous with sophisticated but precise hydrophobic and hydrophilic patches, which is essential for their diverse biological functions. To emulate such distinct surface patterns on macromolecules, we used rigid spherical synthetic dendrimers (polyphenylene dendrimers) to provide controlled amphiphilic surface patches with molecular precision. We identified an,. I optimal spatial arrangement of these patches on certain dendrimers that enabled their interaction with human adenovirus 5 (Ads). Patchy dendrimers bound to the surface of Ads formed a synthetic polymer corona that greatly altered various host interactions of Ads as well as in vivo distribution. The dendrimer corona (1) improved the ability of Ad5-derived gene transfer vectors to transduce cells deficient for the primary Ad5 cell membrane receptor and (2) modulated the binding of Ads to blood coagulation factor X, one of the most critical virus host interactions in the bloodstream. It significantly enhanced the transduction efficiency of Ad5 while also protecting it from neutralization by natural antibodies and the complement system in human whole blood. Ads with a synthetic dendrimer corona revealed profoundly altered in vivo distribution, improved transduction of heart, and dampened vector sequestration by liver and spleen. We propose the design of bioactive polymers that bind protein surfaces solely based on their amphiphilic surface patches and protect against a naturally occurring protein corona, which is highly attractive to improve Ad5-based in vivo gene therapy applications
The Berry-Keating operator on L^2(\rz_>, x) and on compact quantum graphs with general self-adjoint realizations
The Berry-Keating operator H_{\mathrm{BK}}:=
-\ui\hbar(x\frac{
\phantom{x}}{
x}+{1/2}) [M. V. Berry and J. P. Keating,
SIAM Rev. 41 (1999) 236] governing the Schr\"odinger dynamics is discussed in
the Hilbert space L^2(\rz_>,
x) and on compact quantum graphs. It is
proved that the spectrum of defined on L^2(\rz_>,
x) is
purely continuous and thus this quantization of cannot yield
the hypothetical Hilbert-Polya operator possessing as eigenvalues the
nontrivial zeros of the Riemann zeta function. A complete classification of all
self-adjoint extensions of acting on compact quantum graphs
is given together with the corresponding secular equation in form of a
determinant whose zeros determine the discrete spectrum of .
In addition, an exact trace formula and the Weyl asymptotics of the eigenvalue
counting function are derived. Furthermore, we introduce the "squared"
Berry-Keating operator which is a special case of the
Black-Scholes operator used in financial theory of option pricing. Again, all
self-adjoint extensions, the corresponding secular equation, the trace formula
and the Weyl asymptotics are derived for on compact quantum
graphs. While the spectra of both and on
any compact quantum graph are discrete, their Weyl asymptotics demonstrate that
neither nor can yield as eigenvalues the
nontrivial Riemann zeros. Some simple examples are worked out in detail.Comment: 33p
Dosing pole recommendations for lymphatic filariasis elimination: A height-weight quantile regression modeling approach
BACKGROUND: The World Health Organization (WHO) currently recommends height or age-based dosing as alternatives to weight-based dosing for mass drug administration lymphatic filariasis (LF) elimination programs. The goals of our study were to compare these alternative dosing strategies to weight-based dosing and to develop and evaluate new height-based dosing pole scenarios.
METHODOLOGY/PRINCIPAL FINDINGS: Age, height and weight data were collected from \u3e26,000 individuals in five countries during a cluster randomized LF clinical trial. Weight-based dosing for diethylcarbamazine (DEC; 6 mg/kg) and ivermectin (IVM; 200 ug/kg) with tablet numbers derived from a table of weight intervals was treated as the gold standard for this study. Following WHO recommended age-based dosing of DEC and height-based dosing of IVM would have resulted in 32% and 27% of individuals receiving treatment doses below those recommended by weight-based dosing for DEC and IVM, respectively. Underdosing would have been especially common in adult males, who tend to have the highest LF prevalence in many endemic areas. We used a 3-step modeling approach to develop and evaluate new dosing pole cutoffs. First, we analyzed the clinical trial data using quantile regression to predict weight from height. We then used weight predictions to develop new dosing pole cutoff values. Finally, we compared different dosing pole cutoffs and age and height-based WHO dosing recommendations to weight-based dosing. We considered hundreds of scenarios including country- and sex-specific dosing poles. A simple dosing pole with a 6-tablet maximum for both DEC and IVM reduced the underdosing rate by 30% and 21%, respectively, and was nearly as effective as more complex pole combinations for reducing underdosing.
CONCLUSIONS/SIGNIFICANCE: Using a novel modeling approach, we developed a simple dosing pole that would markedly reduce underdosing for DEC and IVM in MDA programs compared to current WHO recommended height or age-based dosing
Insecurity for compact surfaces of positive genus
A pair of points in a riemannian manifold is secure if the geodesics
between the points can be blocked by a finite number of point obstacles;
otherwise the pair of points is insecure. A manifold is secure if all pairs of
points in are secure. A manifold is insecure if there exists an insecure
point pair, and totally insecure if all point pairs are insecure.
Compact, flat manifolds are secure. A standing conjecture says that these are
the only secure, compact riemannian manifolds. We prove this for surfaces of
genus greater than zero. We also prove that a closed surface of genus greater
than one with any riemannian metric and a closed surface of genus one with
generic metric are totally insecure.Comment: 37 pages, 11 figure
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