1,102 research outputs found
Reentrant behavior in the superconducting phase-dependent resistance of a disordered 2-dimensional electron gas
We have investigated the bias-voltage dependence of the phase-dependent
differential resistance of a disordered T-shaped 2-dimensional electron gas
coupled to two superconducting terminals. The resistance oscillations first
increase upon lowering the energy. For bias voltages below the Thouless energy,
the resistance oscillations are suppressed and disappear almost completely at
zero bias voltage. We find a qualitative agreement with the calculated
reentrant behavior of the resistance and discuss quantitative deviations.Comment: 4 pages, 5 figures, to be published in Phys. Rev.
Fe I Oscillator Strengths for the Gaia-ESO Survey
The Gaia-ESO Public Spectroscopic Survey (GES) is conducting a large-scale
study of multi-element chemical abundances of some 100 000 stars in the Milky
Way with the ultimate aim of quantifying the formation history and evolution of
young, mature and ancient Galactic populations. However, in preparing for the
analysis of GES spectra, it has been noted that atomic oscillator strengths of
important Fe I lines required to correctly model stellar line intensities are
missing from the atomic database. Here, we present new experimental oscillator
strengths derived from branching fractions and level lifetimes, for 142
transitions of Fe I between 3526 {\AA} and 10864 {\AA}, of which at least 38
are urgently needed by GES. We also assess the impact of these new data on
solar spectral synthesis and demonstrate that for 36 lines that appear
unblended in the Sun, Fe abundance measurements yield a small line-by-line
scatter (0.08 dex) with a mean abundance of 7.44 dex in good agreement with
recent publications.Comment: Accepted for publication in Mon. Not. R. Astron. So
Optimising the multiplex factor of the frequency domain multiplexed readout of the TES-based microcalorimeter imaging array for the X-IFU instrument on the Athena Xray observatory
Athena is a space-based X-ray observatory intended for exploration of the hot
and energetic universe. One of the science instruments on Athena will be the
X-ray Integrated Field Unit (X-IFU), which is a cryogenic X-ray spectrometer,
based on a large cryogenic imaging array of Transition Edge Sensors (TES) based
microcalorimeters operating at a temperature of 100mK. The imaging array
consists of 3800 pixels providing 2.5 eV spectral resolution, and covers a
field of view with a diameter of of 5 arc minutes. Multiplexed readout of the
cryogenic microcalorimeter array is essential to comply with the cooling power
and complexity constraints on a space craft. Frequency domain multiplexing has
been under development for the readout of TES-based detectors for this purpose,
not only for the X-IFU detector arrays but also for TES-based bolometer arrays
for the Safari instrument of the Japanese SPICA observatory. This paper
discusses the design considerations which are applicable to optimise the
multiplex factor within the boundary conditions as set by the space craft. More
specifically, the interplay between the science requirements such as pixel
dynamic range, pixel speed, and cross talk, and the space craft requirements
such as the power dissipation budget, available bandwidth, and electromagnetic
compatibility will be discussed
High resolution charge-exchange spectroscopic measurements of aluminum impurity ions in a high temperature plasma
Charge-exchange recombination spectroscopy, which is generally used to measure low-Z impurities in fusion devices, has been used for measuring Al+11 and Al+13 impurities in the Madison Symmetric Torus reversed field pinch. To obtain the impurity ion temperature, the experimental emission spectrum is fitted with a model which includes fine structure in the atomic transition. Densities of these two ionization states, calculated from charge-exchange emission brightness, are used in combination with a collisional radiative model to estimate the abundance of all other charge states of aluminum in the plasma and the contribution of aluminum to the effective ionic charge of the plasma
Effect of connective tissue grafting on peri-implant tissue in single immediate implant sites:A RCT
AimTo assess the effect of connective tissue grafting on the mid-buccal mucosal level (MBML) of immediately placed and provisionalized single implants in the maxillofacial aesthetic zone.Materials and methodsSixty patients with a failing tooth were provided with an immediately placed and provisionalized implant. During implant placement, patients randomly received either a connective tissue graft from the maxillary tuberosity (n=30, test group) or no graft (n=30, control group). Follow-up visits were at one (T-1) and twelve months (T-12) after final crown placement. The primary outcome measure was any change in MBML compared to the pre-operative situation. In addition, gingival biotype, aesthetics (using the Pink Esthetic Score-White Esthetic Score), marginal bone level, soft tissue peri-implant parameters and patient satisfaction were assessed.ResultsThe mean MBML change at T-12 was -0.51.1mm in the control group and 0.1 +/- 0.8mm in the test group (p=.03). No significant differences regarding other outcome variables were observed, neither was gingival biotype associated with a gain or loss in MBML.ConclusionsThis one-year study shows that connective tissue grafting in single, immediately placed and provisionalized implants leads to less recession of the peri-implant soft tissue at the mid-buccal aspect, irrespective of the gingival biotype (: TC3815).</p
Significance of Buccopalatal Implant Position, Biotype, Platform Switching, and Pre-implant Bone Augmentation on the Level of the Midbuccal Mucosa
This study assessed whether buccopalatal implant position, biotype, platform switching, and pre-implant bone augmentation affects the level of the midbuccal mucosa (MBM). Ninety patients with a single-tooth implant in the esthetic zone were included. The level of the MBM was measured on photographs taken 1 year after crown placement. The factors analyzed only explained 22% of the level of the MBM. The more an implant was placed to the buccal, the more the MBM was positioned apically. A comparable phenomenon was observed in cases with a thick biotype and cases that underwent pre-implant bone augmentation. Platform switching did not affect the level of the MBM
Dynamical response of the "GGG" rotor to test the Equivalence Principle: theory, simulation and experiment. Part I: the normal modes
Recent theoretical work suggests that violation of the Equivalence Principle
might be revealed in a measurement of the fractional differential acceleration
between two test bodies -of different composition, falling in the
gravitational field of a source mass- if the measurement is made to the level
of or better. This being within the reach of ground based
experiments, gives them a new impetus. However, while slowly rotating torsion
balances in ground laboratories are close to reaching this level, only an
experiment performed in low orbit around the Earth is likely to provide a much
better accuracy.
We report on the progress made with the "Galileo Galilei on the Ground" (GGG)
experiment, which aims to compete with torsion balances using an instrument
design also capable of being converted into a much higher sensitivity space
test.
In the present and following paper (Part I and Part II), we demonstrate that
the dynamical response of the GGG differential accelerometer set into
supercritical rotation -in particular its normal modes (Part I) and rejection
of common mode effects (Part II)- can be predicted by means of a simple but
effective model that embodies all the relevant physics. Analytical solutions
are obtained under special limits, which provide the theoretical understanding.
A simulation environment is set up, obtaining quantitative agreement with the
available experimental data on the frequencies of the normal modes, and on the
whirling behavior. This is a needed and reliable tool for controlling and
separating perturbative effects from the expected signal, as well as for
planning the optimization of the apparatus.Comment: Accepted for publication by "Review of Scientific Instruments" on Jan
16, 2006. 16 2-column pages, 9 figure
Radiolysis of NaCl at high and low temperatures: development of size distribution of bubbles and colloids
New experimental results are presented on low temperature irradiation (18 °C) of rock-salt samples which had been exposed to initial doses up to 320 GRad at 100 °C. Differential scanning calorimetry (DSC) shows that the latent heat of melting (LHM) of sodium colloids decreases during subsequent low-temperature irradiation, whereas the stored energy (SE) increases slowly, indicating that the process of radiolysis continues. The decrease of the LHM is due to dissolution of large colloids, because the intensities of the melting peaks decrease during the second stage irradiation at low temperature. The model is formulated to describe the nucleation kinetics and the evolution of the size distribution of chlorine precipitates and sodium colloids in NaCl under high dose irradiation. It is shown that the mechanism of dissolution of large Na colloids during low temperature irradiation can be related to melting of sodium colloids.
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