809 research outputs found
Two-dimensional Navier--Stokes simulation of deformation and break up of liquid patches
The large deformations and break up of circular 2D liquid patches in a high
Reynolds number (Re=1000) gas flow are investigated numerically. The 2D, plane
flow Navier--Stokes equations are directly solved with explicit tracking of the
interface between the two phases and a new algorithm for surface tension. The
numerical method is able to pursue the simulation beyond the breaking or
coalescence of droplets. The simulations are able to unveil the intriguing
details of the non-linear interplay between the deforming droplets and the
vortical structures in the droplet's wake.Comment: 13 pages including 4 postscript figures; Revised version as
resubmitted to PRL. Title has change
Similarities between Insect Swarms and Isothermal Globular Clusters
Previous work has suggested that disordered swarms of flying insects can be well modeled as selfgravitating systems, as long as the “gravitational” interaction is adaptive. Motivated by this work we compare the predictions of the classic, mean-field King model for isothermal globular clusters to observations of insect swarms. Detailed numerical simulations of regular and adaptive gravity allow us to expose the features of the swarms’ density and velocity profiles that are due to longrange interactions, and are captured by the King model phenomenology, and those that are due to adaptivity and short-range repulsion. Our results provide further support for adaptive gravity as a model for swarms
Microwave Assisted Synthesis of Py-Im Polyamides
Microwave synthesis was utilized to rapidly build Py-Im polyamides in high yields and purity using Boc-protection chemistry on Kaiser oxime resin. A representative polyamide targeting the 5′-WGWWCW-3′ (W = A or T) subset of the consensus Androgen and Glucocorticoid Response Elements was synthesized in 56% yield after 20 linear steps and HPLC purification. It was confirmed by Mosher amide derivatization of the polyamide that a chiral α-amino acid does not racemize after several additional coupling steps
JLab Measurement of the He Charge Form Factor at Large Momentum Transfers
The charge form factor of ^4He has been extracted in the range 29 fm
fm from elastic electron scattering, detecting He
nuclei and electrons in coincidence with the High Resolution Spectrometers of
the Hall A Facility of Jefferson Lab. The results are in qualitative agreement
with realistic meson-nucleon theoretical calculations. The data have uncovered
a second diffraction minimum, which was predicted in the range of this
experiment, and rule out conclusively long-standing predictions of dimensional
scaling of high-energy amplitudes using quark counting.Comment: 4 pages, 2 figure
Polarization transfer in wide-angle Compton scattering and single-pion photoproduction from the proton
Wide-angle exclusive Compton scattering and single-pion photoproduction from the proton have been investigated via measurement of the polarization transfer from a circularly polarized photon beam to the recoil proton. The wide-angle Compton scattering polarization transfer was analyzed at an incident photon energy of 3.7 GeV at a proton scattering angle of θpcm=70°. The longitudinal transfer KLL, measured to be 0.645±0.059±0.048, where the first error is statistical and the second is systematic, has the same sign as predicted for the reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton. However, the observed value is ∼3 times larger than predicted by the generalized-parton-distribution-based calculations, which indicates a significant unknown contribution to the scattering amplitude
Freight distribution performance indicators for service quality planning in large transportation networks
This paper studies the use of performance indicators in routing problems to estimate how transportation cost is affected by the quality of service offered. The quality of service is assumed to be directly dependent on the size of the time windows. Smaller time windows mean better service. Three performance indicators are introduced. These indicators are calculated directly from the data without the need of a solution method. The introduced indicators are based mainly on a "request compatibility", which describes whether two visits can be scheduled consecutively in a route. Other two indicators are introduced, which get their values from a greedy constructive heuristic. After introducing the indicators, the correlation between indicators and transportation cost is examined. It is concluded that the indicators give a good first estimation on the transportation cost incurred when providing a certain quality of service. These indicators can be calculated easily in one of the first planning steps without the need of a sophisticated solution tool. The contribution of the paper is the introduction of a simple set of performance indicators that can be used to estimate the transportation cost of a routing problem with time window
Somatostatin subtype-2 receptor-targeted metal-based anticancer complexes
Conjugates of a dicarba analogue of octreotide, a potent somatostatin agonist whose receptors are overexpressed on tumor cells, with [PtCl 2(dap)] (dap = 1-(carboxylic acid)-1,2-diaminoethane) (3), [(η 6-bip)Os(4-CO 2-pico)Cl] (bip = biphenyl, pico = picolinate) (4), [(η 6-p-cym)RuCl(dap)] + (p-cym = p-cymene) (5), and [(η 6-p-cym)RuCl(imidazole-CO 2H)(PPh 3)] + (6), were synthesized by using a solid-phase approach. Conjugates 3-5 readily underwent hydrolysis and DNA binding, whereas conjugate 6 was inert to ligand substitution. NMR spectroscopy and molecular dynamics calculations showed that conjugate formation does not perturb the overall peptide structure. Only 6 exhibited antiproliferative activity in human tumor cells (IC 50 = 63 ± 2 μ in MCF-7 cells and IC 50 = 26 ± 3 μ in DU-145 cells) with active participation of somatostatin receptors in cellular uptake. Similar cytotoxic activity was found in a normal cell line (IC 50 = 45 ± 2.6 μ in CHO cells), which can be attributed to a similar level of expression of somatostatin subtype-2 receptor. These studies provide new insights into the effect of receptor-binding peptide conjugation on the activity of metal-based anticancer drugs, and demonstrate the potential of such hybrid compounds to target tumor cells specifically. © 2012 American Chemical Society
Measurements of the Electric Form Factor of the Neutron up to Q2=3.4 GeV2 using the Reaction He3(e,e'n)pp
The electric form factor of the neutron was determined from studies of the
reaction He3(e,e'n)pp in quasi-elastic kinematics in Hall A at Jefferson Lab.
Longitudinally polarized electrons were scattered off a polarized target in
which the nuclear polarization was oriented perpendicular to the momentum
transfer. The scattered electrons were detected in a magnetic spectrometer in
coincidence with neutrons that were registered in a large-solid-angle detector.
More than doubling the Q2-range over which it is known, we find GEn = 0.0225
+/- 0.0017 (stat) +/- 0.0024 (syst), 0.0200 +/- 0.0023 +/- 0.0018, and 0.0142
+/- 0.0019 +/- 0.0013 for Q2 = 1.72, 2.48, and 3.41 GeV2, respectively.Comment: submitted to PR
Low Q^2 measurements of the proton form factor ratio
We present an updated extraction of the proton electromagnetic form factor
ratio, mu_p G_E/G_M, at low Q^2. The form factors are sensitive to the spatial
distribution of the proton, and precise measurements can be used to constrain
models of the proton. An improved selection of the elastic events and reduced
background contributions yielded a small systematic reduction in the ratio mu_p
G_E/G_M compared to the original analysis.Comment: 12 pages, 5 figures, archival paper for proton form factor extraction
from Jefferson Lab "LEDEX" experimen
A precise extraction of the induced polarization in the 4He(e,e'p)3H reaction
We measured with unprecedented precision the induced polarization Py in
4He(e,e'p)3H at Q^2 = 0.8 (GeV/c)^2 and 1.3 (GeV/c)^2. The induced polarization
is indicative of reaction-mechanism effects beyond the impulse approximation.
Our results are in agreement with a relativistic distorted-wave impulse
approximation calculation but are over-estimated by a calculation with strong
charge-exchange effects. Our data are used to constrain the strength of the
spin independent charge-exchange term in the latter calculation.Comment: submitted to Physical Review Letter
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