1,247 research outputs found
General method for extracting the quantum efficiency of dispersive qubit readout in circuit QED
We present and demonstrate a general three-step method for extracting the
quantum efficiency of dispersive qubit readout in circuit QED. We use active
depletion of post-measurement photons and optimal integration weight functions
on two quadratures to maximize the signal-to-noise ratio of the
non-steady-state homodyne measurement. We derive analytically and demonstrate
experimentally that the method robustly extracts the quantum efficiency for
arbitrary readout conditions in the linear regime. We use the proven method to
optimally bias a Josephson traveling-wave parametric amplifier and to quantify
different noise contributions in the readout amplification chain.Comment: 10 pages, 6 figure
Carbon Deficiency in Externally-Polluted White Dwarfs: Evidence for Accretion of Asteroids
Existing determinations show that n(C)/n(Fe) is more than a factor of 10
below solar in the atmospheres of three white dwarfs that appear to be
externally-polluted. These results are not easily explained if the stars have
accreted interstellar matter, and we re-interpret these measurements as
evidence that these stars have accreted asteroids of a chrondritic composition.Comment: 23 pages, 6 figures, accepted for Ap
Laserska desorpcijsko–ionizacijska masena spektroskopija potpomognuta sa C60
An application of C60-assisted laser desorption/ionization mass spectrometry of two organic samples including insulin (5734 Da), bovine albumin (66 000 Da) and a heteropoly inorganic system: phosphotungstic acid H3PO4(WO3)12×H2O, is presented. A nitrogen laser (337 nm) on a linear tandem time-of-flight mass spectrometer is used for the observation of the laser-power dependence of mass spectra.Opisuje se primjena laserske desorpcijsko–ionizacijske masene spektroskopije sa dva organska pripravka, insulin (5734 Da) sa crijevnim albuminom (66 000 Da), te heteropolni anorganski sistem od fosforovolframske kiseline, H3PO4(WO3)12×H2O. Primijenjen je dušikov laser pri linearnom tandem masenom spektrometru s mjerenjem vremena proleta i proučavana je ovisnost masenih spektara o snazi laserskog snopa. Pokazano je da se tehnika slojeva sa C60 kao substratom za desorpciju organskih ili neorganskih molekula, može primijeniti kao alternativna dobro poznatoj MALDI metodi
Investigation of Anti-Relaxation Coatings for Alkali-Metal Vapor Cells Using Surface Science Techniques
Many technologies based on cells containing alkali-metal atomic vapor benefit
from the use of anti-relaxation surface coatings in order to preserve atomic
spin polarization. In particular, paraffin has been used for this purpose for
several decades and has been demonstrated to allow an atom to experience up to
10,000 collisions with the walls of its container without depolarizing, but the
details of its operation remain poorly understood. We apply modern surface and
bulk techniques to the study of paraffin coatings, in order to characterize the
properties that enable the effective preservation of alkali spin polarization.
These methods include Fourier transform infrared spectroscopy, differential
scanning calorimetry, atomic force microscopy, near-edge X-ray absorption fine
structure spectroscopy, and X-ray photoelectron spectroscopy. We also compare
the light-induced atomic desorption yields of several different paraffin
materials. Experimental results include the determination that crystallinity of
the coating material is unnecessary, and the detection of C=C double bonds
present within a particular class of effective paraffin coatings. Further study
should lead to the development of more robust paraffin anti-relaxation
coatings, as well as the design and synthesis of new classes of coating
materials.Comment: 12 pages, 12 figures. Copyright 2010 American Institute of Physics.
This article may be downloaded for personal use only. Any other use requires
prior permission of the author and the American Institute of Physics. The
following article appeared in the Journal of Chemical Physics and may be
found at http://link.aip.org/link/?JCP/133/14470
Luminous infrared galaxies as possible sources of the UHE cosmic rays
Ultra High Energy (UHE) particles coming from discrete extragalactic sources
are potential candidates for EAS events above a few tens of EeV. In particular,
galaxies with huge infrared luminosity triggered by collision and merging
processes are possible sites of UHECR acceleration. Using the PSCz catalogue of
IR galaxies we calculate a large scale anisotropy of UHE protons originating in
the population of the luminous infrared galaxies (LIRGs). Small angle particle
scattering in weak irregular extragalactic magnetic fields as well as
deflection by regular Galactic field are taken into account. We give analytical
formulae for deflection angles with included energy losses on cosmic microwave
background (CMB). The hypotheses of the anisotropic and isotropic distributions
of the experimental data above 40 EeV from AGASA are checked, using various
statistical tests. We show that on the basis of the small scale clustering
analysis there is a much better correlation of the UHECRs data below GZK
cut-off with the predictions of the LIRG origin than with those of isotropy. We
derive analytical formulae for a probability of a given number of doublets,
triplets and quadruplets for any density distribution of independent events on
the sky. The famous AGASA UHE triple event is found to be very well correlated
on the sky with the brightest extragalactic infrared source within 70 Mpc -
merger galaxies Arp 299 (NGC 3690 + IC 694).Comment: 17 pages, 10 figures, accepted for publ: Journal of Physics
First results from the GPS atmosphere sounding experiment TOR aboard the TerraSAR-X satellite
GPS radio occultation events observed between 24 July and 17 November 2008 by the IGOR occultation receiver aboard the TerraSAR-X satellite are processed and analyzed. The comparison of 15 327 refractivity profiles with collocated ECMWF data yield a mean bias between zero and −0.30 % at altitudes between 5 and 30 km. Standard deviations decrease from about 1.4 % at 5 km to about 0.6 % at 10 km altitude, however, increase significantly in the upper stratosphere. At low latitudes mean biases and standard deviations are larger, in particular in the lower troposphere. The results are consistent with 15 159 refractivity observations collected during the same time period by the BlackJack receiver aboard GRACE-A and processed by GFZ's operational processing system. The main difference between the two occultation instruments is the implementation of open-loop signal tracking in the IGOR (TerraSAR-X) receiver which improves the tropospheric penetration depth in terms of ray height by about 2 km compared to the conventional closed-loop data acquired by BlackJack (GRACE-A)
Gene Expression Disruptions of Organism versus Organ in Drosophila Species Hybrids
Hybrid dysfunctions, such as sterility, may result in part from disruptions in the regulation of gene expression. Studies of hybrids within the Drosophila simulans clade have reported genes expressed above or below the expression observed in their parent species, and such misexpression is associated with male sterility in multigenerational backcross hybrids. However, these studies often examined whole bodies rather than testes or had limited replication using less-sensitive but global techniques. Here, we use a new RNA isolation technique to re-examine hybrid gene expression disruptions in both testes and whole bodies from single Drosophila males by real-time quantitative RT-PCR. We find two early-spermatogenesis transcripts are underexpressed in hybrid whole-bodies but not in assays of testes alone, while two late-spermatogenesis transcripts seem to be underexpressed in both whole-bodies and testes alone. Although the number of transcripts surveyed is limited, these results provide some support for a previous hypothesis that the spermatogenesis pathway in these sterile hybrids may be disrupted sometime after the expression of the early meiotic arrest genes
Gas Evolution in Operating Lithium-Ion Batteries Studied in Situ by Neutron Imaging
Gas generation as a result of electrolyte decomposition is one of the major issues of highperformance rechargeable batteries. Here, we report the direct observation of gassing in operating lithium-ion batteries using neutron imaging. This technique can be used to obtain qualitative as well as quantitative information by applying a new analysis approach. Special emphasis is placed on high voltage LiNi0.5Mn1.5O4/graphite pouch cells. Continuous gassing due to oxidation and reduction of electrolyte solvents is observed. To separate gas evolution reactions occurring on the anode from those associated with the cathode interface and to gain more insight into the gassing behavior of LiNi0.5Mn1.5O4/graphite cells, neutron experiments were also conducted systematically on other cathode/anode combinations, including LiFePO4/graphite, LiNi0.5Mn1.5O4/Li4Ti5O12 and LiFePO4/Li4Ti5O12. In addition, the data were supported by gas pressure measurements. The results suggest that metal dissolution in the electrolyte and decomposition products resulting from the high potentials adversely affect the gas generation, particularly in the first charge cycle (i.e., during graphite solid-electrolyte interface layer formation)
Near-Infrared Mapping and Physical Properties of the Dwarf-Planet Ceres
We study the physical characteristics (shape, dimensions, spin axis
direction, albedo maps, mineralogy) of the dwarf-planet Ceres based on
high-angular resolution near-infrared observations. We analyze adaptive optics
J/H/K imaging observations of Ceres performed at Keck II Observatory in
September 2002 with an equivalent spatial resolution of ~50 km. The spectral
behavior of the main geological features present on Ceres is compared with
laboratory samples. Ceres' shape can be described by an oblate spheroid (a = b
= 479.7 +/- 2.3 km, c = 444.4 +/- 2.1 km) with EQJ2000.0 spin vector
coordinates RA = 288 +/- 5 deg. and DEC = +66 +/- 5 deg. Ceres sidereal period
is measured to be 9.0741 +/- 0.0001 h. We image surface features with diameters
in the 50-180 km range and an albedo contrast of ~6% with respect to the
average Ceres albedo. The spectral behavior of the brightest regions on Ceres
is consistent with phyllosilicates and carbonate compounds. Darker isolated
regions could be related to the presence of frost.Comment: 11 pages, 8 Postscript figures, Accepted for publication in A&
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