430 research outputs found
All-optical retrieval of the global phase for two-dimensional Fourier-transform spectroscopy
A combination of spatial interference patterns and spectral interferometry
are used to find the global phase for non-collinear two-dimensional
Fourier-transform (2DFT) spectra. Results are compared with those using the
spectrally resolved transient absorption (STRA) method to find the global phase
when excitation is with co-linear polarization. Additionally cross-linear
polarized 2DFT spectra are correctly phased using the all-optical technique,
where the SRTA is not applicable.Comment: 6 pages, 7 figures, journal publicatio
Phase distortions of attosecond pulses produced by resonance-enhanced high harmonic generation
Resonant enhancement of high harmonic generation can be obtained in plasmas
containing ions with strong radiative transitions resonant with harmonic
orders. The mechanism for this enhancement is still debated. We perform the
first temporal characterization of the attosecond emission from a tin plasma
under near-resonant conditions for two different resonance detunings. We show
that the resonance considerably changes the relative phase of neighbouring
harmonics. For very small detunings, their phase locking may even be lost,
evidencing strong phase distortions in the emission process and a modified
attosecond structure. These features are well reproduced by our simulations,
allowing their interpretation in terms of the phase of the recombination dipole
moment
Isoflurane cracks the polycarbonate connector of extra-corporeal circuit -A case report-
Cardiopulmonary bypass (CPB) is widely used for cardiac surgery by virtue of its proven safety over the course of its use during the past half century. Even though perfusion is safer, incidents still occur. During the repair of a ventricular-septal defect in an 11-month-old infant, we experienced a critical incident related to the potential hazardous effect of volatile anesthetics on the polycarbonate connector of extra-corporeal circuit. The damage to the polycarbonate connector had occurred after spillage of isoflurane during the filling of the vaporizer, causing it to crack and leak. The incident was managed by replacement of the cracked connector during a temporary circulatory arrest. The patient was hypothermic and the time off bypass was less than 1.5 min. There were no neurologic sequelae, the patient made an uneventful recovery. In conclusion, the spillage of volatile anesthetics can cause cracks in the polycarbonate connector of the extra-corporeal circuit, leading to potentially interruption of CPB
Attosecond emission from chromium plasma
International audienceWe present the first measurement of the attosecond emission generated from underdense plasma produced on a solid target. We generate high-order harmonics of a femtosecond Ti:sapphire laser focused in a weakly ionized underdense chromium plasma. Using the " Reconstruction of Attosecond Beating by Interference of Two-photon Transitions " (RABITT) technique, we show that the 11 th to the 19 th harmonic orders form in the time domain an attosecond pulse train with each pulse having 300 as duration, which is only 1.05 times the theoretical Fourier transform limit. Measurements reveal a very low positive group delay dispersion of 4200 as 2. Beside its fundamental interest, high-order harmonic generation in plasma plumes could thus provide an intense source of attosecond pulses for applications
Evidence of magnetic mechanism for cuprate superconductivity
A proper understanding of the mechanism for cuprate superconductivity can
emerge only by comparing materials in which physical parameters vary one at a
time. Here we present a variety of bulk, resonance, and scattering measurements
on the (Ca_xLa_{1-x})(Ba_{1.75-x}La_{0.25+x})Cu_3O_y high temperature
superconductors, in which this can be done. We determine the superconducting,
Neel, glass, and pseudopage critical temperatures. In addition, we clarify
which physical parameter varies, and, equally important, which does not, with
each chemical modification. This allows us to demonstrate that a single energy
scale, set by the superexchange interaction J, controls all the critical
temperatures of the system. J, in-turn, is determined by the in plane Cu-O-Cu
buckling angle.Comment: 17 pages, 13 figure
Ab initio evaluation of the charge-ordering in
We report {\it ab initio} calculations of the charge ordering in
using large configurations interaction methods on
embedded fragments. Our major result is that the electrons of the
bridging oxygen of the rungs present a very strong magnetic character and
should thus be explicitly considered in any relevant effective model. The most
striking consequence of this result is that the spin and charge ordering differ
substantially, as differ the experimental results depending on whether they are
sensitive to the spin or charge density.Comment: 4 page
Proton Zemach radius from measurements of the hyperfine splitting of hydrogen and muonic hydrogen
While measurements of the hyperfine structure of hydrogen-like atoms are
traditionally regarded as test of bound-state QED, we assume that theoretical
QED predictions are accurate and discuss the information about the
electromagnetic structure of protons that could be extracted from the
experimental values of the ground state hyperfine splitting in hydrogen and
muonic hydrogen. Using recent theoretical results on the proton polarizability
effects and the experimental hydrogen hyperfine splitting we obtain for the
Zemach radius of the proton the value 1.040(16) fm. We compare it to the
various theoretical estimates the uncertainty of which is shown to be larger
that 0.016 fm. This point of view gives quite convincing arguments in support
of projects to measure the hyperfine splitting of muonic hydrogen.Comment: Submitted to Phys. Rev.
- …