7,827 research outputs found
Short-Chained Oligo(Ethylene Oxide)-Functionalized Gold Nanoparticles: Realization Of Significant Protein Resistance
Protein corona formed on nanomaterial surfaces play an important role in the bioavailability and cellular uptake of nanomaterials. Modification of surfaces with oligoethylene glycols (OEG) are a common way to improve the resistivity of nanomaterials to protein adsorption. Short-chain ethylene oxide (EO) oligomers have been shown to improve the protein resistance of planar Au surfaces. We describe the application of these EO oligomers for improved protein resistance of 30 nm spherical gold nanoparticles (AuNPs). Functionalized AuNPs were characterized using UV-Vis spectroscopy, dynamic light scattering (DLS), and zeta potential measurements. Capillary electrophoresis (CE) was used for separation and quantitation of AuNPs and AuNP-protein mixtures. Specifically, nonequilibrium capillary electrophoresis of equilibrium mixtures (NECEEM) was employed for the determination of equilibrium and rate constants for binding between citrate-stabilized AuNPs and two model proteins, lysozyme and fibrinogen. Semi-quantitative CE analysis was carried out for mixtures of EO-functionalized AuNPs and proteins, and results demonstrated a 2.5-fold to 10-fold increase in protein binding resistance to lysozyme depending on the AuNP surface functionalization and a 15-fold increase in protein binding resistance to fibrinogen for both EO oligomers examined in this study
The multiple junction edge illuminated solar cell
The multiple junction edge illuminated solar cell was devised for high voltage low current applications. Devices to be flight tested in early 1974 with 96 series connected PNN+ junctions in a 2 cm X 2.3 cm size deliver 36 volts at 1 milliampere. Test data of M-J cells fabricated with resistivities of 10, 50, 100, 200, 450, and 1000 ohm cm silicon are presented and problem areas are discussed. An additional potential application of the M-J cell lies in ultilization of its high intensity performance that has been demonstrated at levels in excess of 100 AMO suns
Study of the April 20, 2007 CME-Comet Interaction Event with an MHD Model
This study examines the tail disconnection event on April 20, 2007 on comet
2P/Encke, caused by a coronal mass ejection (CME) at a heliocentric distance of
0.34 AU. During their interaction, both the CME and the comet are visible with
high temporal and spatial resolution by the STEREO-A spacecraft. Previously,
only current sheets or shocks have been accepted as possible reasons for comet
tail disconnections, so it is puzzling that the CME caused this event. The MHD
simulation presented in this work reproduces the interaction process and
demonstrates how the CME triggered a tail disconnection in the April 20 event.
It is found that the CME disturbs the comet with a combination of a
sudden rotation of the interplanetary magnetic field (IMF), followed by a
gradual rotation. Such an interpretation applies our understanding
of solar wind-comet interactions to determine the \textit{in situ} IMF
orientation of the CME encountering Encke.Comment: 13 pages, 3 figures, accepted by the ApJ Letter
15 years of VLBI observations of two compact radio sources in Messier 82
We present the results of a second epoch of 18cm global Very Long-Baseline
Interferometry (VLBI) observations, taken on 23 February 2001, of the central
kiloparsec of the nearby starburst galaxy Messier 82. These observations
further investigate the structural and flux evolution of the most compact radio
sources in the central region of M82. The two most compact radio objects in M82
have been investigated (41.95+575 and 43.31+592). Using this recent epoch of
data in comparison with our previous global VLBI observations and two earlier
epochs of European VLBI Network observations we measure expansion velocities in
the range of 1500-2000km/s for 41.95+575, and 9000-11000km/s for 43.31+592
using various independent methods. In each case the measured remnant expansion
velocities are significantly larger than the canonical expansion velocity
(500km/s) of supernova remnants within M82 predicted from theoretical models.
In this paper we discuss the implications of these measured expansion
velocities with respect to the high density environment that the SNR are
expected to reside in within the centre of the M82 starburst.Comment: Accepted for publication in MNRAS, 9 pages, 8 figure
Nonlinear force-free reconstruction of the global solar magnetic field: methodology
We present a novel numerical method that allows the calculation of nonlinear
force-free magnetostatic solutions above a boundary surface on which only the
distribution of the normal magnetic field component is given. The method relies
on the theory of force-free electrodynamics and applies directly to the
reconstruction of the solar coronal magnetic field for a given distribution of
the photospheric radial field component. The method works as follows: we start
with any initial magnetostatic global field configuration (e.g. zero, dipole),
and along the boundary surface we create an evolving distribution of tangential
(horizontal) electric fields that, via Faraday's equation, give rise to a
respective normal field distribution approaching asymptotically the target
distribution. At the same time, these electric fields are used as boundary
condition to numerically evolve the resulting electromagnetic field above the
boundary surface, modelled as a thin ideal plasma with non-reflecting,
perfectly absorbing outer boundaries. The simulation relaxes to a nonlinear
force-free configuration that satisfies the given normal field distribution on
the boundary. This is different from existing methods relying on a fixed
boundary condition - the boundary evolves toward the a priori given one, at the
same time evolving the three-dimensional field solution above it. Moreover,
this is the first time a nonlinear force-free solution is reached by using only
the normal field component on the boundary. This solution is not unique, but
depends on the initial magnetic field configuration and on the evolutionary
course along the boundary surface. To our knowledge, this is the first time
that the formalism of force-free electrodynamics, used very successfully in
other astrophysical contexts, is applied to the global solar magnetic field.Comment: 18 pages, 5 figures, Solar Physic
- shell gap reduction in neutron-rich systems and cross-shell excitations in O
Excited states in O were populated in the reaction
Be(C,) at Florida State University. Charged particles
were detected with a particle telescope consisting of 4 annularly segmented Si
surface barrier detectors and radiation was detected with the FSU
detector array. Five new states were observed below 6 MeV from the
- and -- coincidence data. Shell model
calculations suggest that most of the newly observed states are core-excited
1p-1h excitations across the shell gap. Comparisons between
experimental data and calculations for the neutron-rich O and F isotopes imply
a steady reduction of the - shell gap as neutrons are added
Cytomolecular identification of individual wheat-wheat chromosome arm associations in wheat-rye hybrids
Chromosome pairing in the meiotic metaphase I of wheatrye
hybrids has been characterized by sequential genomic
and fluorescent in situ hybridization allowing not only the
discrimination of wheat and rye chromosomes, but also the
identification of the individual wheat and rye chromosome
arms involved in the chromosome associations. The majority
of associations (93.8%) were observed between the wheat
chromosomes. The largest number of wheat-wheat chromosome
associations (53%) was detected between the A and D
genomes, while the frequency of B-D and A-B associations
was significantly lower (32 and 8%, respectively). Among the
A-D chromosome associations, pairing between the 3AL and
3DL arms was observed with the highest frequency, while
the most frequent of all the chromosome associations (0.113/
cell) was found to be the 3DS-3BS. Differences in the pairing
frequency of the individual chromosome arms of wheat-rye
hybrids have been discussed in relation to the homoeologous
relationships between the constituent genomes of
hexaploid wheat
Prevalence and molecular epidemiology of Clostridium difficile infection in Indonesia
Clostridium difficile has not been studied in detail in Asia, particularly Southeast Asia. We thus performed a prevalence study across four hospitals in Central Java province, Indonesia. Stool samples were collected from patients with diarrhoea and tested by enzyme immunoassay for glutamate dehydrogenase (GDH) and toxin A/B (C DIFF QUIK CHEK COMPLETE, TechLab). Specimens were cultured and molecular typing was performed. In total, 340 samples were tested, of which 70 (20.6%) were GDH positive, with toxin detected in 19 (5.6%). Toxigenic C. difficile was isolated from 37 specimens (10.9%), while a further 36 (10.6%) nontoxigenic isolates were identified. The most common strain was ribotype 017 (24.3% of 74 isolates), followed by nontoxigenic types QX 224 (9.5%), and QX 238 and QX 108 (both 8.1%). The high prevalence of C. difficile highlights a need for ongoing surveillance of C. difficile infection in Indonesia
Optical monitoring of the z=4.40 quasar Q 2203+292
We report Cousins R-band monitoring of the high-redshift (z=4.40) radio quiet
quasar Q 2203+292 from May 1999 to October 2007. The quasar shows maximum
peak-to-peak light curve amplitude of ~0.3 mag during the time of our
monitoring, and ~0.9 mag when combined with older literature data. The rms of a
fit to the light curve with a constant is 0.08 mag and 0.2 mag, respectively.
The detected changes are at ~3-sigma level. The quasar was in a stable state
during the recent years and it might have undergone a brightening event in the
past. The structure function analysis concluded that the object shows
variability properties similar to those of the lower redshift quasars. We set a
lower limit to the Q 2203+292 broad line region mass of 0.3-0.4 M_odot.
Narrow-band imaging search for redshifted Ly_alpha from other emission line
objects at the same redshift shows no emission line objects in the quasar
vicinity.Comment: 9 pages, 8 figures, accepted for publication in MNRA
Magnetic Structure of Rapidly Rotating FK Comae-Type Coronae
We present a three-dimensional simulation of the corona of an FK Com-type
rapidly rotating G giant using a magnetohydrodynamic model that was originally
developed for the solar corona in order to capture the more realistic,
non-potential coronal structure. We drive the simulation with surface maps for
the radial magnetic field obtained from a stellar dynamo model of the FK Com
system. This enables us to obtain the coronal structure for different field
topologies representing different periods of time. We find that the corona of
such an FK Com-like star, including the large scale coronal loops, is dominated
by a strong toroidal component of the magnetic field. This is a result of part
of the field being dragged by the radial outflow, while the other part remains
attached to the rapidly rotating stellar surface. This tangling of the magnetic
field,in addition to a reduction in the radial flow component, leads to a
flattening of the gas density profile with distance in the inner part of the
corona. The three-dimensional simulation provides a global view of the coronal
structure. Some aspects of the results, such as the toroidal wrapping of the
magnetic field, should also be applicable to coronae on fast rotators in
general, which our study shows can be considerably different from the
well-studied and well-observed solar corona. Studying the global structure of
such coronae should also lead to a better understanding of their related
stellar processes, such as flares and coronal mass ejections, and in
particular, should lead to an improved understanding of mass and angular
momentum loss from such systems.Comment: Accepted to ApJ, 10 pages, 6 figure
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