4,043 research outputs found
Lifetime measurement of excited low-spin states via the ) reaction
In this article a method for lifetime measurements in the sub-picosecond
regime via the Doppler-shift attenuation method (DSAM) following the inelastic
proton scattering reaction is presented. In a pioneering experiment we
extracted the lifetimes of 30 excited low-spin states of Ru, taking
advantage of the coincident detection of scattered protons and de-exciting
-rays as well as the large number of particle and -ray
detectors provided by the SONIC@HORUS setup at the University of Cologne. The
large amount of new experimental data shows that this technique is suited for
the measurement of lifetimes of excited low-spin states, especially for
isotopes with a low isotopic abundance, where ) or - in
case of investigating dipole excitations - ()
experiments are not feasible due to the lack of sufficient isotopically
enriched target material
Collisions of rigidly rotating disks of dust in General Relativity
We discuss inelastic collisions of two rotating disks by using the
conservation laws for baryonic mass and angular momentum. In particular, we
formulate conditions for the formation of a new disk after the collision and
calculate the total energy loss to obtain upper limits for the emitted
gravitational energy.Comment: 30 pages, 9 figure
Bounds on the force between black holes
We treat the problem of N interacting, axisymmetric black holes and obtain
two relations among physical parameters of the system including the force
between the black holes. The first relation involves the total mass, the
angular momenta, the distances and the forces between the black holes. The
second one relates the angular momentum and area of each black hole with the
forces acting on it.Comment: 13 pages, no figure
BPPV: Comparison of the SémontPLUS With the Sémont Maneuver: A Prospective Randomized Trial
Objective: To compare the efficacy of the Sémont maneuver (SM) with the new “SémontPLUS maneuver” (SM+) in patients with posterior canal BPPV canalolithiasis (pcBPPVcan). Methods and Patients: In a prospective trinational (Germany, Italy, and Belgium) randomized trial, patients with pcBPPVcan were randomly assigned to SM or SM+; SM+ means overextension of the head by 60+° below earth horizontal line during the movement of the patient toward the affected side. The first maneuver was done by the physician, and the subsequent maneuvers by the patients 9 times/day on their own. Each morning the patient documented whether vertigo could be induced. The primary endpoints were: “How long (in days) does it take until no attacks can be induced?” and “What is the efficacy of a single SM/SM+?” Results: In the 194 patients analyzed (96 SM, 98 SM+), it took 2 days (median, range 1–21 days, mean 3.6 days) for recovery with SM and 1 day (median, range 1-8 days, mean 1.8 days) with SM+ (p = 0.001, Mann-Whitney U-test). There was no difference in the second primary endpoint (chi2-test, p = 0.39). Interpretation: This prospective trial shows that SM+ is more effective than SM when repeated therapeutic maneuvers are performed but not when a single maneuver is performed. It also supports the hypothesis of the biophysical model: overextension of the head during step 2 brings the clot of otoconia beyond the vertex of the canal, which increases the effectivity. Classification of Evidence: This study provides Class I evidence that SM+ is superior to SM for multiple treatment maneuvers of pcBPPVcan. © The Author
Design of a speed meter interferometer proof-of-principle experiment
The second generation of large scale interferometric gravitational wave
detectors will be limited by quantum noise over a wide frequency range in their
detection band. Further sensitivity improvements for future upgrades or new
detectors beyond the second generation motivate the development of measurement
schemes to mitigate the impact of quantum noise in these instruments. Two
strands of development are being pursued to reach this goal, focusing both on
modifications of the well-established Michelson detector configuration and
development of different detector topologies. In this paper, we present the
design of the world's first Sagnac speed meter interferometer which is
currently being constructed at the University of Glasgow. With this
proof-of-principle experiment we aim to demonstrate the theoretically predicted
lower quantum noise in a Sagnac interferometer compared to an equivalent
Michelson interferometer, to qualify Sagnac speed meters for further research
towards an implementation in a future generation large scale gravitational wave
detector, such as the planned Einstein Telescope observatory.Comment: Revised version: 16 pages, 6 figure
Baryon Content of Massive Galaxy Clusters (0.57 < z < 1.33)
We study the stellar, Brightest Cluster Galaxy (BCG) and intracluster medium
(ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with
median redshift and median mass . We
estimate stellar masses for each cluster and BCG using six photometric bands
spanning the range from the ultraviolet to the near-infrared observed with the
VLT, HST and Spitzer. The ICM masses are derived from Chandra and XMM-Newton
X-ray observations, and the virial masses are derived from the SPT
Sunyaev-Zel'dovich Effect signature.
At the BCG mass constitutes %
of the halo mass for a cluster, and this fraction
falls as . The cluster stellar mass function has a
characteristic mass , and the number of
galaxies per unit mass in clusters is larger than in the field by a factor
. Both results are consistent with measurements on group scales and
at lower redshift. We combine our SPT sample with previously published samples
at low redshift that we correct to a common initial mass function and for
systematic differences in virial masses. We then explore mass and redshift
trends in the stellar fraction (fstar), the ICM fraction (fICM), the cold
baryon fraction (fc) and the baryon fraction (fb). At a pivot mass of
and redshift , the characteristic values are
fstar=%, fICM=%, fc=% and fb=%.
These fractions all vary with cluster mass at high significance, indicating
that higher mass clusters have lower fstar and fc and higher fICM and fb. When
accounting for a 15% systematic virial mass uncertainty, there is no
statistically significant redshift trend at fixed mass in these baryon
fractions.
(abridged)Comment: Accepted for publication in MNRA
Verification of the code DYN3D for calculations of neutron flux fluctuations
Insufficiently explained magnitudes and patterns of flux fluctuation observed mainly in KWU PWRs are recently investigated by various European institutions. Among the numerical tools used to investigate the\ua0neutron flux\ua0fluctuations is the time-domain reactor dynamics code\ua0DYN3D. As\ua0DYN3D\ua0and comparable codes have not been developed with the primary intention to simulate low-amplitude neutron flux fluctuations, their applicability in this field has to be verified.In order to contribute to the verification of\ua0DYN3D\ua0for the simulation of neutron flux fluctuations, two special cases of perturbations of the neutron flux (a localized absorber of variable/oscillatory strength and a travelling oscillatory perturbation) are considered with\ua0DYN3D\ua0on the one hand and with the frequency-domain neutron noise tool\ua0CORE SIM\ua0as well as analytical frequency-domain approaches, respectively, on the other hand. The obtained results are compared with respect to the distributions of the amplitude and the phase of the induced neutron flux fluctuations. The comparisons are repeated with varied amplitudes and frequencies of the perturbation.The results agree well both qualitatively and quantitatively for each of the conducted calculations. The remaining deviations between the\ua0DYN3D\ua0results and the reference results exhibit a dependence on the perturbation magnitude, which is attributed to the neglect of higher-order terms (linear theory) of the perturbed quantities in the calculation of the reference solutions
Import of cytochrome c into mitochondria
The import of cytochrome c into mitochondria can be resolved into a number of discrete steps. Here we report on the covalent attachment of heme to apocytochrome c by the enzyme cytochrome c heme lyase in mitochondria from Neurospora crassa.
A new method was developed to measure directly the linkage of heme to apocytochrome c. This method is independent of conformational changes in the protein accompanying heme attachment. Tryptic peptides of [35S]cysteine-labelled apocytochrome c, and of enzymatically formed holocytochrome c, were resolved by reverse-phase HPLC. The cysteine-containing peptide to which heme was attached eluted later than the corresponding peptide from apocytochrome c and could be quantified by counting 35S radioactivity as a measure of holocytochrome c formation. Using this procedure, the covalent attachment of heme to apocytochrome c, which is dependent on the enzyme cytochrome c heme lyase, could be measured. Activity required heme (as hemin) and could be reversibly inhibited by the analogue deuterohemin. Holocytochrome c formation was stimulated 5–10-fold by NADH > NADPH > glutathione and was independent of a potential across the inner mitochondrial membrane. NADH was not required for the binding of apocytochrome c to mitochondria and was not involved in the reduction of the cysteine thiols prior to heme attachment. Holocytochrome c formation was also dependent on a cytosolic factor that was necessary for the heme attaching step of cytochrome c import. The factor was a heat-stable, protease-insensitive, low-molecular-mass component of unknown function.
Cytochrome c heme lyase appeared to be a soluble protein located in the mitochondrial intermembrane space and was distinct from the previously identified apocytochrome c binding protein having a similar location. A model is presented in which the covalent attachment of heme by cytochrome c heme lyase also plays an essential role in the import pathway of cytochrome c
17 ways to say yes:Toward nuanced tone of voice in AAC and speech technology
People with complex communication needs who use speech-generating devices have very little expressive control over their tone of voice. Despite its importance in human interaction, the issue of tone of voice remains all but absent from AAC research and development however. In this paper, we describe three interdisciplinary projects, past, present and future: The critical design collection Six Speaking Chairs has provoked deeper discussion and inspired a social model of tone of voice; the speculative concept Speech Hedge illustrates challenges and opportunities in designing more expressive user interfaces; the pilot project Tonetable could enable participatory research and seed a research network around tone of voice. We speculate that more radical interactions might expand frontiers of AAC and disrupt speech technology as a whole
Non-existence of stationary two-black-hole configurations: The degenerate case
In a preceding paper we examined the question whether the spin-spin repulsion
and the gravitational attraction of two aligned sub-extremal black holes can
balance each other. Based on the solution of a boundary value problem for two
separate (Killing-) horizons and a novel black hole criterion we were able to
prove the non-existence of the equilibrium configuration in question. In this
paper we extend the non-existence proof to extremal black holes.Comment: 18 pages, 2 figure
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