397 research outputs found
A very low temperature STM for the local spectroscopy of mesoscopic structures
We present the design and operation of a very-low temperature Scanning
Tunneling Microscope (STM) working at in a dilution refrigerator. The
STM features both atomic resolution and micron-sized scanning range at low
temperature. This work is the first experimental realization of a local
spectroscopy of mesoscopic structures at very low temperature. We present
high-resolution current-voltage characteristics of tunnel contacts and the
deduced local density of states of hybrid Superconductor-Normal metal systems.Comment: 5 pages, 5 figures, slightly corrected versio
Slow Quenches Produce Fuzzy, Transient Vortices
We examine the Zurek scenario for the production of vortices in quenches of
liquid in the light of recent experiments. Extending our previous
results to later times, we argue that short wavelength thermal fluctuations
make vortices poorly defined until after the transition has occurred. Further,
if and when vortices appear, it is plausible that that they will decay faster
than anticipated from turbulence experiments, irrespective of quench rates.Comment: 4 pages, Revtex file, no figures Apart from a more appropriate title,
this paper differs from its predecessor by including temperature, as well as
pressure, quenche
Optical interconnect with densely integrated plasmonic modulator and germanium photodetector arrays
We demonstrate the first chip-to-chip interconnect utilizing a densely integrated plasmonic Mach-Zehnder modulator array operating at 3 x 10 Gbit/s. A multicore fiber provides a compact optical interface, while the receiver consists of germanium photodetectors
Zurek-Kibble domain structures: The Dynamics of Spontaneous Vortex formation in Annular Josephson Tunnel Junctions
Phase transitions executed in a finite time show a domain structure with
defects, that has been argued by Zurek and Kibble to depend in a characteristic
way on the quench rate. In this letter we present an experiment to measure the
Zurek-Kibble scaling exponent sigma. Using symmetric and long Josephson Tunnel
Junctions, for which the predicted index is sigma = 0.25, we find sigma = 0.27
+/- 0.05. Further, there is agreement with the ZK prediction for the overall
normalisation.Comment: To be published in Phys. Rev. Lett
Anesthesiology for Trauma Medicine: Roles, Medications, Airway Management, and Multidisciplinary Team Coordination
Given the complex nature of trauma, a highly organized, multidisciplinary approach is necessary to ensure the best possible outcomes. Anesthesia providers play a critical role in the management and effective treatment of trauma patients. This chapter will address both the multidisciplinary and multitiered management of trauma patients with a focus on the intersection of trauma staff and anesthesia in three phases: the initial evaluation (i.e., in the bay), intraoperative care, and postoperative care. Included is a brief discussion on more recent methodologies and newly incorporated technologies in the resuscitation of trauma patients
Testing the Kibble-Zurek Scenario with Annular Josephson Tunnel Junctions
In parallel with Kibble's description of the onset of phase transitions in
the early universe, Zurek has provided a simple picture for the onset of phase
transitions in condensed matter systems, strongly supported by agreement with
experiments in He3. In this letter we show how experiments with annular
Josephson tunnel Junctions can and do provide further support for this
scenario.Comment: Revised version with correct formula for the Swihart velocity. The
results are qualitatively the same as with the previous version but differ
quantitatively. 4 pages, RevTe
Dynamics of Quantum Phase Transition in an Array of Josephson Junctions
We study the dynamics of the Mott insulator-superfluid quantum phase
transition in a periodic 1D array of Josephson junctions. We show that crossing
the critical point diabatically i.e. at a finite rate with a quench time
induces finite quantum fluctuations of the current around the loop
proportional to . This scaling could be experimentally verified
with in array of weakly coupled Bose-Einstein condensates or superconducting
grains.Comment: 4 pages in RevTex, 3 .eps figures; 2 references added; accepted for
publication in Phys.Rev.Let
Defect Formation and Critical Dynamics in the Early Universe
We study the nonequilibrium dynamics leading to the formation of topological
defects in a symmetry-breaking phase transition of a quantum scalar field with
\lambda\Phi^4 self-interaction in a spatially flat, radiation-dominated
Friedmann-Robertson-Walker Universe. The quantum field is initially in a
finite-temperature symmetry-restored state and the phase transition develops as
the Universe expands and cools. We present a first-principles, microscopic
approach in which the nonperturbative, nonequilibrium dynamics of the quantum
field is derived from the two-loop, two-particle-irreducible closed-time-path
effective action. We numerically solve the dynamical equations for the
two-point function and we identify signatures of topological defects in the
infrared portion of the momentum-space power spectrum. We find that the density
of topological defects formed after the phase transition scales as a power law
with the expansion rate of the Universe. We calculate the equilibrium critical
exponents of the correlation length and relaxation time for this model and show
that the power law exponent of the defect density, for both overdamped and
underdamped evolution, is in good agreement with the "freeze-out" scenario of
Zurek. We introduce an analytic dynamical model, valid near the critical point,
that exhibits the same power law scaling of the defect density with the quench
rate. By incorporating the realistic quench of the expanding Universe, our
approach illuminates the dynamical mechanisms important for topological defect
formation. The observed power law scaling of the defect density with the quench
rate, observered here in a quantum field theory context, provides evidence for
the "freeze-out" scenario in three spatial dimensions.Comment: 31 pages, RevTex, 8 figures in EPS forma
Unraveling critical dynamics: The formation and evolution of topological textures
We study the formation of topological textures in a nonequilibrium phase
transition of an overdamped classical O(3) model in 2+1 dimensions. The phase
transition is triggered through an external, time-dependent effective mass,
parameterized by quench timescale \tau. When measured near the end of the
transition the texture separation and the texture width scale respectively as
\tau^(0.39 \pm 0.02) and \tau^(0.46 \pm 0.04), significantly larger than
\tau^(0.25) predicted from the Kibble-Zurek mechanism. We show that
Kibble-Zurek scaling is recovered at very early times but that by the end of
the transition the power-laws result instead from a competition between the
length scale determined at freeze-out and the ordering dynamics of a textured
system. In the context of phase ordering these results suggest that the
multiple length scales characteristic of the late-time ordering of a textured
system derive from the critical dynamics of a single nonequilibrium correlation
length. In the context of defect formation these results imply that significant
evolution of the defect network can occur before the end of the phase
transition. Therefore a quantitative understanding of the defect network at the
end of the phase transition generally requires an understanding of both
critical dynamics and the interactions among topological defects.Comment: 12 pages, revtex, 9 figures in eps forma
Does native Trypanosoma cruzi calreticulin mediate growth inhibition of a mammary tumor during infection?
Indexación: Web of Science.Background: For several decades now an antagonism between Trypanosoma cruzi infection and tumor development has been detected. The molecular basis of this phenomenon remained basically unknown until our proposal that T. cruzi Calreticulin (TcCRT), an endoplasmic reticulum-resident chaperone, translocated-externalized by the parasite, may mediate at least an important part of this effect. Thus, recombinant TcCRT (rTcCRT) has important in vivo antiangiogenic and antitumor activities. However, the relevant question whether the in vivo antitumor effect of T. cruzi infection is indeed mediated by the native chaperone (nTcCRT), remains open. Herein, by using specific modified anti-rTcCRT antibodies (Abs), we have neutralized the antitumor activity of T. cruzi infection and extracts thereof, thus identifying nTcCRT as a valid mediator of this effect.
Methods: Polyclonal anti-rTcCRT F(ab')(2) Ab fragments were used to reverse the capacity of rTcCRT to inhibit EAhy926 endothelial cell (EC) proliferation, as detected by BrdU uptake. Using these F(ab')(2) fragments, we also challenged the capacity of nTcCRT, during T. cruzi infection, to inhibit the growth of an aggressive mammary adenocarcinoma cell line (TA3-MTXR) in mice. Moreover, we determined the capacity of anti-rTcCRT Abs to reverse the antitumor effect of an epimastigote extract (EE). Finally, the effects of these treatments on tumor histology were evaluated.
Results: The rTcCRT capacity to inhibit ECs proliferation was reversed by anti-rTcCRT F(ab')(2) Ab fragments, thus defining them as valid probes to interfere in vivo with this important TcCRT function. Consequently, during infection, these Ab fragments also reversed the in vivo experimental mammary tumor growth. Moreover, anti-rTcCRT Abs also neutralized the antitumor effect of an EE, again identifying the chaperone protein as an important mediator of this anti mammary tumor effect. Finally, as determined by conventional histological parameters, in infected animals and in those treated with EE, less invasive tumors were observed while, as expected, treatment with F(ab')(2) Ab fragments increased malignancy.
Conclusion: We have identified translocated/externalized nTcCRT as responsible for at least an important part of the anti mammary tumor effect of the chaperone observed during experimental infections with T. cruzi.http://bmccancer.biomedcentral.com/articles/10.1186/s12885-016-2764-
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