826 research outputs found
Complement activated granulocytes can cause autologous tissue destruction in man
Activation of polymorphonuclear granulocytes (PMNs) by C5a is thought to be important in the pathogenesis of multiple organ failure during sepsis and after trauma. In our experiment exposure of human PMNs to autologous zymosan activated plasma (ZAP) leads to a rapid increase in chemiluminescence. Heating the ZAP at 56°C for 30 min did not alter the changes, while untreated plasma induced only baseline activity. The respiratory burst could be completely abolished by decomplementation and preincubation with rabbit antihuman C5a antibodies. Observation of human omentum using electron microscopy showed intravascular aggregation of PMNs, with capillary thrombosis and diapedesis of the cells through endothelial junctions 90 s after exposure to ZAP. PMNs caused disruption of connections between the mesothelial cells. After 4 min the mesothelium was completely destroyed, and connective tissue and fat cells exposed. Native plasma and minimum essential medium did not induce any morphological changes. These data support the concept that C5a activated PMNs can cause endothelial and mesothelial damage in man. Even though a causal relationship between anaphylatoxins and organ failure cannot be proved by these experiments C5a seems to be an important mediator in the pathogenesis of changes induced by severe sepsis and trauma in man
Disordered Josephson Junctions of d-Wave Superconductors
We study the Josephson effect between weakly coupled d-wave superconductors
within the quasiclassical theory, in particular, the influence of interface
roughness on the current-phase relation and the critical current of mirror
junctions and asymmetric junctions. For mirror junctions the
temperature dependence of the critical current is non-monotonic in the limit of
low roughness, but monotonic for very rough interfaces. For
asymmetric junctions with a linear dimension much larger than the
superconducting coherence length we find a -like current-phase
relation, whereas for contacts on the scale of the coherence length or smaller
the usual -like behavior is observed. Our results compare well with
recent experimental observations.Comment: 10 pages, 12 figures; accepted for publication in Phys. Rev.
The Periodic Standing-Wave Approximation: Overview and Three Dimensional Scalar Models
The periodic standing-wave method for binary inspiral computes the exact
numerical solution for periodic binary motion with standing gravitational
waves, and uses it as an approximation to slow binary inspiral with outgoing
waves. Important features of this method presented here are: (i) the
mathematical nature of the ``mixed'' partial differential equations to be
solved, (ii) the meaning of standing waves in the method, (iii) computational
difficulties, and (iv) the ``effective linearity'' that ultimately justifies
the approximation. The method is applied to three dimensional nonlinear scalar
model problems, and the numerical results are used to demonstrate extraction of
the outgoing solution from the standing-wave solution, and the role of
effective linearity.Comment: 13 pages RevTeX, 5 figures. New version. A revised form of the
nonlinearity produces better result
Ramond-Ramond Fields, Fractional Branes and Orbifold Differential K-Theory
We study D-branes and Ramond-Ramond fields on global orbifolds of Type II
string theory with vanishing H-flux using methods of equivariant K-theory and
K-homology. We illustrate how Bredon equivariant cohomology naturally realizes
stringy orbifold cohomology. We emphasize its role as the correct cohomological
tool which captures known features of the low-energy effective field theory,
and which provides new consistency conditions for fractional D-branes and
Ramond-Ramond fields on orbifolds. We use an equivariant Chern character from
equivariant K-theory to Bredon cohomology to define new Ramond-Ramond couplings
of D-branes which generalize previous examples. We propose a definition for
groups of differential characters associated to equivariant K-theory. We derive
a Dirac quantization rule for Ramond-Ramond fluxes, and study flat
Ramond-Ramond potentials on orbifolds.Comment: 46 pages; v2: typos correcte
Accurate calibration of test mass displacement in the LIGO interferometers
We describe three fundamentally different methods we have applied to
calibrate the test mass displacement actuators to search for systematic errors
in the calibration of the LIGO gravitational-wave detectors. The actuation
frequencies tested range from 90 Hz to 1 kHz and the actuation amplitudes range
from 1e-6 m to 1e-18 m. For each of the four test mass actuators measured, the
weighted mean coefficient over all frequencies for each technique deviates from
the average actuation coefficient for all three techniques by less than 4%.
This result indicates that systematic errors in the calibration of the
responses of the LIGO detectors to differential length variations are within
the stated uncertainties.Comment: 10 pages, 6 figures, submitted on 31 October 2009 to Classical and
Quantum Gravity for the proceedings of 8th Edoardo Amaldi Conference on
Gravitational Wave
GEO 600 and the GEO-HF upgrade program: successes and challenges
The German-British laser-interferometric gravitational wave detector GEO 600
is in its 14th year of operation since its first lock in 2001. After GEO 600
participated in science runs with other first-generation detectors, a program
known as GEO-HF began in 2009. The goal was to improve the detector sensitivity
at high frequencies, around 1 kHz and above, with technologically advanced yet
minimally invasive upgrades. Simultaneously, the detector would record science
quality data in between commissioning activities. As of early 2014, all of the
planned upgrades have been carried out and sensitivity improvements of up to a
factor of four at the high-frequency end of the observation band have been
achieved. Besides science data collection, an experimental program is ongoing
with the goal to further improve the sensitivity and evaluate future detector
technologies. We summarize the results of the GEO-HF program to date and
discuss its successes and challenges
Evaluating the impact of Relative Total Dose Intensity (RTDI) on patients' short and long-term outcome in taxane- and anthracycline-based chemotherapy of metastatic breast cancer- a pooled analysis
Background: Chemotherapy dose delay and/or reduction lower relative total dose intensity (RTDI) and may affect short- and long-term outcome of metastatic breast cancer (MBC) patients.
Methods: Based on 933 individual patients' data of from 3 randomized MBC trials using an anthracycline and taxane we examined the impact of RTDI on efficacy and determined the lowest optimal RTDI for MBC patients.
Results: Median time to disease progression (TTDP) and overall survival (OS) of all patients were 39 and 98 weeks. Overall higher RTDI was correlated with a shorter TTDP (log-rank p = 0.0525 for 85% RTDI cut-off). Proportional hazards assumption was violated, there was an early drop in the TTDP-curve for the high RTDI group. It was explained by the fact that patients with primary disease progression (PDP) do have a high RTDI per definition. Excluding those 114 patients with PDP the negative correlation between RTDI and TTDP vanished. However, non-PDP patients with RTDI-cut-off levels <85% showed a shorter OS than patients with higher RTDI levels (p = 0.0086).
Conclusions: Optimizing RTDI above 85% appears to improve long-term outcome of MBC patients receiving first-line chemotherapy. Lowering RTDI had no negative influence on short term outcome like OR and TTDP
Huddle test measurement of a near Johnson noise limited geophone
In this paper, the sensor noise of two geophone configurations (L-22D and L-4C geophones from Sercel with custom built amplifiers) was measured by performing two huddle tests. It is shown that the accuracy of the results can be significantly improved by performing the huddle test in a seismically quiet environment and by using a large number of reference sensors to remove the seismic foreground signal from the data. Using these two techniques, the measured sensor noise of the two geophone configurations matched the calculated predictions remarkably well in the bandwidth of interest (0.01 Hzâ100 Hz). Low noise operational amplifiers OPA188 were utilized to amplify the L-4C geophone to give a sensor that was characterized to be near Johnson noise limited in the bandwidth of interest with a noise value of 10â11âm/HzâŻâŻâŻâŻâŻâ10â11âm/Hz at 1 Hz
Adaptive filtering techniques for gravitational wave interferometric data: Removing long-term sinusoidal disturbances and oscillatory transients
It is known by the experience gained from the gravitational wave detector
proto-types that the interferometric output signal will be corrupted by a
significant amount of non-Gaussian noise, large part of it being essentially
composed of long-term sinusoids with slowly varying envelope (such as violin
resonances in the suspensions, or main power harmonics) and short-term ringdown
noise (which may emanate from servo control systems, electronics in a
non-linear state, etc.). Since non-Gaussian noise components make the detection
and estimation of the gravitational wave signature more difficult, a denoising
algorithm based on adaptive filtering techniques (LMS methods) is proposed to
separate and extract them from the stationary and Gaussian background noise.
The strength of the method is that it does not require any precise model on the
observed data: the signals are distinguished on the basis of their
autocorrelation time. We believe that the robustness and simplicity of this
method make it useful for data preparation and for the understanding of the
first interferometric data. We present the detailed structure of the algorithm
and its application to both simulated data and real data from the LIGO 40meter
proto-type.Comment: 16 pages, 9 figures, submitted to Phys. Rev.
Benefits of Artificially Generated Gravity Gradients for Interferometric Gravitational-Wave Detectors
We present an approach to experimentally evaluate gravity gradient noise, a
potentially limiting noise source in advanced interferometric gravitational
wave (GW) detectors. In addition, the method can be used to provide sub-percent
calibration in phase and amplitude of modern interferometric GW detectors.
Knowledge of calibration to such certainties shall enhance the scientific
output of the instruments in case of an eventual detection of GWs. The method
relies on a rotating symmetrical two-body mass, a Dynamic gravity Field
Generator (DFG). The placement of the DFG in the proximity of one of the
interferometer's suspended test masses generates a change in the local
gravitational field detectable with current interferometric GW detectors.Comment: 16 pages, 4 figure
- âŠ