13,770 research outputs found
COFS 1 Guest Investigator Program
The process for selecting guest investigators for participation in the Control of Flexible Structures (COFS)-1 program is described. Contracts and grants will be awarded in late CY87. A straw-man list of types of experiments and a distribution of the experiments has been defined to initiate definition of an experiments package which supports development and validation of control structures interaction technology. A schedule of guest investigator participation has been developed
Functionalized platinum nanoparticles with surface charge trigged by pH: synthesis, characterization and stability studies
In this work, the synthesis and characterization of functionalized platinum nanoparticles (PtNPs) have been investigated. PtNPs were obtained by a wet redox procedure using 2-diethylaminoethanethiol hydrochloride (DEA) as capping agent. By varying the Pt/thiol molar ratio, monodispersed and stable particles with diameters in the range of 3-40 nm were isolated. The amino functionality allows neutral particles to be obtained in basic water solution and positive charged nanoparticles in neutral or acidic water solution (pH 7-2), as confirmed by DLS and ζ-potential measurements. FTIR spectroscopy, FE-SEM, DLS and ζ-potential measurements confirmed the size and showed long term water stability (up to three months) of the colloidal system
Compensated Current Injection circuit, theory and applications
This paper presents a detailed description, analysis and example of practical
application of a wide frequency band voltage-to-current converter. The
converter is characterized by a combination of positive and negative feedback
loops. This feature allows compensation for parasitic impedance connected in
parallel with the useful load, which in turn keeps an excitation current
flowing through the useful load independent of its impedance. The simplicity of
the circuit and its good electrical properties are additional advantages of the
scheme.Comment: 9 pages and 7 figures in one PDF fil
Observing the very low-surface brightness dwarfs in a deep field in the VIRGO cluster: constraints on Dark Matter scenarios
We report the discovery of 11 very faint (r< 23), low surface brightness
({\mu}_r< 27 mag/arcsec^2) dwarf galaxies in one deep field in the Virgo
cluster, obtained by the prime focus cameras (LBC) at the Large Binocular
Telescope (LBT). These extend our previous sample to reach a total number of 27
galaxies in a field of just of 0.17 deg^2 located at a median distance of 390
kpc from the cluster center. Their association with the Virgo cluster is
supported by their separate position in the central surface brightness - total
magnitude plane with respect to the background galaxies of similar total
magnitude. For a significant fraction (26\%) of the sample the association to
the cluster is confirmed by spectroscopic follow-up. We show that the mere
abundance of satellite galaxies corresponding to our observed number in the
target field provides extremely tight constraints on Dark Matter models with
suppressed power spectrum compared to the Cold Dark Matter case, independently
of the galaxy luminosity distribution. In particular, requiring the observed
number of satellite galaxies not to exceed the predicted abundance of Dark
Matter sub-halos yields a limit m_X >3 keV at 1-{\sigma} and m_X > 2.3 keV at
2-{\sigma} confidence level for the mass of thermal Warm Dark Matter particles.
Such a limit is competitive with other limits set by the abundance of
ultra-faint satellite galaxies in the Milky Way, is completely independent of
baryon physics involved in galaxy formation, and has the potentiality for
appreciable improvements with next observations. We extend our analysis to Dark
Matter models based on sterile neutrinos, showing that our observations set
tight constraints on the combination of sterile neutrino mass m_{\nu} and
mixing parameter sin^2(2{\theta}). We discuss the robustness of our results
with respect to systematics.Comment: Accepted for publication in Astronomy & Astrophysic
Keck/MOSFIRE Spectroscopy of z=7-8 Galaxies: Ly Emission from a Galaxy at z=7.66
We report the results from some of the deepest Keck/Multi-Object Spectrometer
For Infra-Red Exploration data yet obtained for candidate
galaxies. Our data show one significant line detection with 6.5
significance in our combined 10 hr of integration which is independently
detected on more than one night, thus ruling out the possibility that the
detection is spurious. The asymmetric line profile and non-detection in the
optical bands strongly imply that the detected line is Ly emission from
a galaxy at (Ly, making it the fourth
spectroscopically confirmed galaxy via Ly at . This galaxy is
bright in the rest-frame ultraviolet (UV; ) with a
moderately blue UV slope (), and exhibits a
rest-frame Ly equivalent width of EW(Ly) \AA. The non-detection of the 11 other 7-8
galaxies in our long 10 hr integration, reaching a median 5 sensitivity
of 28 \AA\ in the rest-frame EW(Ly), implies a 1.3 deviation
from the null hypothesis of a non-evolving distribution in the rest-frame
EW(Ly) between and 7-8. Our results are consistent with
previous studies finding a decline in Ly emission at , which may
signal the evolving neutral fraction in the intergalactic medium at the end of
the reionization epoch, although our weak evidence suggests the need for a
larger statistical sample to allow for a more robust conclusion.Comment: 10 pages, 4 figures, ApJ, in pres
High-Resolution Spectroscopy from 3050 to 10000 A of the HDF-S QSO J2233-606 with UVES at the ESO VLT
We report on high-resolution observations () of the Hubble
Deep Field South QSO J2233-606 obtained with the VLT UV-Visual Echelle
Spectrograph (UVES). We present spectral data for the wavelength region \AA. The ratio of the final spectrum is about 50 per
resolution element at 4000 \AA, 90 at 5000 \AA, 80 at 6000 \AA, 40 at 8000 \AA.
Redshifts, column densities and Doppler widths of the absorption features have
been determined with Voigt-profile fitting. A total of 621 lines have been
measured. In particular 270 Ly-alpha lines, 41 Ly-beta and 24 systems
containing metal lines have been identified. Together with other data in the
literature, the present spectrum confirms that the evolution of the number
density of Ly-alpha lines with \huno has an upturn at .Comment: 34 pages Latex, with 3 PostScript figures. Astronomical Journal, in
press. A few revised upper limit
MicrocatheterâAssisted Circumferential Trabeculotomy in Primary Congenital Glaucoma: Long-Term Clinical Outcomes
Purpose: The purpose of this study was to report the long-term efficacy and clinical outcomes of microcatheter-assisted circumferential trabeculotomy (MCT) in children with
primary congenital glaucoma (PCG). Methods: This is a single-center retrospective study including consecutive children with PCG who underwent MCT with > two years follow up. The primary
outcome was surgical success, defined as intraocular pressure (IOP) †21 mmHg with (qualified) or without (complete) medications, measured at six months, one year, and then annually. Secondary
outcomes were visual acuity (VA), refraction, axial length (AXL), complications, reinterventions, and number of medications. Results: Twelve eyes of ten patients were included. In eight children only
one eye was affected. The mean ± standard deviation (SD) age at surgery was 6.3 ± 4.1 months. The mean postoperative follow-up was 66 ± 35 months. The mean IOP was 34.3 ± 9.6 mmHg preoperatively and 14.6 ± 2.3 mmHg postoperatively at the last visit (p < 0.001). Complete success was achieved at all time points in 10 out of 12 eyes, while 2 eyes had a qualified success. At three years of age, the mean VA of the operated eyes was 0.25 ± 0.12 logMAR, the mean spherical equivalent was â0.78 ± 1.43 diopters, and the mean AXL was 23.78 mm. Transient hyphema was the only complication observed. None of the children required additional glaucoma surgery. Conclusions:
Circumferential trabeculotomy for PCG effectively lowers the IOP at more than two years after surgery. Following this procedure, the prognosis for the visual function is good, and the refractive error is low. Postoperative complications were not significant
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