273 research outputs found
Spectrophotometry of Michigan-Tololo quasars
Emission-line quasar characteristics are confirmed for 80% of the objects observed, including at least four new quasars with spectral features indicative of supernova-like outflow. Approximately 73% of the redshifts predicted from the discovery plates are found accurate with a mean error in z of 0.03, and a large range of z (from about 0.1 to 3.16) is represented in the sample. The observed redshift distribution for quasars is marginally consistent with a constant co-moving quasar density above z approximately 2.0. The shape of the redshift distribution may be used as an isotropy probe with a cosmic time resolution of a few times one-hundred million years in the early universe; therefore, continued surveys of this sort are important even if accurate magnitudes are not determined
Multiple sclerosis or neuromyelitis optica? Re-evaluating an 18th-century illness using 21st-century software
In this paper we report the application of an extensive database of symptoms, signs, laboratory findings and illnesses, to the diagnosis of an historical figure. The medical diagnosis of Augustus d'Este (1794–1848) – widely held to be the first documented case of multiple sclerosis – is reviewed, using the detailed symptom diary, which he kept over many years, as clinical data. Some of the reported features prompted the competing claim that d'Este suffered from acute porphyria, which in turn was used in support of the hypothesis that his grandfather, King George III, also suffered from the disease. We find that multiple sclerosis is statistically the most likely diagnosis, with neuromyelitis optica a strong alternative possibility. The database did not support a diagnosis of any of the acute porphyrias
Trapped Ion Imaging with a High Numerical Aperture Spherical Mirror
Efficient collection and analysis of trapped ion qubit fluorescence is
essential for robust qubit state detection in trapped ion quantum computing
schemes. We discuss simple techniques of improving photon collection efficiency
using high numerical aperture (N.A.) reflective optics. To test these
techniques we placed a spherical mirror with an effective N.A. of about 0.9
inside a vacuum chamber in the vicinity of a linear Paul trap. We demonstrate
stable and reliable trapping of single barium ions, in excellent agreement with
our simulations of the electric field in this setup. While a large N.A.
spherical mirror introduces significant spherical aberration, the ion image
quality can be greatly improved by a specially designed aspheric corrector lens
located outside the vacuum system. Our simulations show that the spherical
mirror/corrector design is an easy and cost-effective way to achieve high
photon collection rates when compared to a more sophisticated parabolic mirror
setup.Comment: 5 figure
Investigation of the features of three dimensional paths of spark breakdowns in air
2000-2001 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe
On the application of radio frequency voltages to ion traps via helical resonators
Ions confined using a Paul trap require a stable, high voltage and low noise
radio frequency (RF) potential. We present a guide for the design and
construction of a helical coil resonator for a desired frequency that maximises
the quality factor for a set of experimental constraints. We provide an
in-depth analysis of the system formed from a shielded helical coil and an ion
trap by treating the system as a lumped element model. This allows us to
predict the resonant frequency and quality factor in terms of the physical
parameters of the resonator and the properties of the ion trap. We also compare
theoretical predictions with experimental data for different resonators, and
predict the voltage applied to the ion trap as a function of the Q-factor,
input power and the properties of the resonant circuit
The stellar content of the Hamburg/ESO survey. II. A large, homogeneously-selected sample of high latitude carbon stars
We present a sample of 403 faint high latitude carbon (FHLC) stars selected
from the digitized objective prism plates of the Hamburg/ESO Survey (HES).
Because of the ~15 Angstroem spectral resolution and high signal-to-noise ratio
of the HES prism spectra, our automated procedure based on the detection of C_2
and CN molecular bands permits high-confidence identification of carbon stars
without the need for follow-up spectroscopy. From a set of 329 plates (87% of
the survey), covering 6400 square degrees to a magnitude limit of V~16.5, we
analyze the selection efficiency and effective surface area of the HES FHLC
survey to date. The surface density of FHLC stars that we detect (0.072 +/-
0.005 square degrees) is 2-4 times higher than that of previous objective prism
and CCD surveys at high galactic latitude, even though those surveys claimed a
limiting magnitude up to 1.5 magnitudes fainter. This attests to the highest
selection sensitivity yet achieved for these types of stars.Comment: 8 pages, 6 figures; A&A in pres
Modular Hybrid Energy Concept Employing a Novel Control Structure Based on a Simple Analog System
This paper proposes a novel control topology which enables the setup of a low cost analog system leading to the implementation of a modular energy conversion system. The modular concept is based on hybrid renewable energy (solar and wind) and uses high voltage inverters already available on the market. An important feature of the proposed topology is a permanently active current loop, which assures short circuit protection and simplifies the control loops compensation. The innovative analogue solution of the control structure is based on a dedicated integrated circuit (IC) for power factor correction (PFC) circuits, used in a new configuration, to assure an efficient inverter start-up. The energy conversion system (control structure and maximum power point tracking algorithm) is simulated using a new macromodel-based concept, which reduces the usual computational burden of the simulator and achieves high processing speed. The proposed novel system is presented in this article from concept, through the design and implementation stages, is verified through simulation and is validated by experimental results
Preferential Re-Replication of Drosophila Heterochromatin in the Absence of Geminin
To ensure genomic integrity, the genome must be duplicated exactly once per cell cycle. Disruption of replication licensing mechanisms may lead to re-replication and genomic instability. Cdt1, also known as Double-parked (Dup) in Drosophila, is a key regulator of the assembly of the pre-replicative complex (pre-RC) and its activity is strictly limited to G1 by multiple mechanisms including Cul4-Ddb1 mediated proteolysis and inhibition by geminin. We assayed the genomic consequences of disregulating the replication licensing mechanisms by RNAi depletion of geminin. We found that not all origins of replication were sensitive to geminin depletion and that heterochromatic sequences were preferentially re-replicated in the absence of licensing mechanisms. The preferential re-activation of heterochromatic origins of replication was unexpected because these are typically the last sequences to be duplicated in a normal cell cycle. We found that the re-replication of heterochromatin was regulated not at the level of pre-RC activation, but rather by the formation of the pre-RC. Unlike the global assembly of the pre-RC that occurs throughout the genome in G1, in the absence of geminin, limited pre-RC assembly was restricted to the heterochromatin by elevated cyclin A-CDK activity. These results suggest that there are chromatin and cell cycle specific controls that regulate the re-assembly of the pre-RC outside of G1
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