2,817 research outputs found
Current-Induced Motion of Narrow Domain Walls and Dissipation in Ferromagnetic Metals
Spin transport equations in a non-homogeneous ferromagnet are derived in the
limit where the sd exchange coupling between the electrons in the conduction
band and those in the d band is dominant. It is shown that spin diffusion in
ferromagnets assumes a tensor form. The diagonal terms are renormalized with
respect to that in normal metals and enhances the dissipation in the magnetic
system while the off-diagonal terms renormalize the precessional frequency of
the conduction electrons and enhances the non-adiabatic spin torque. To
demonstrate the new physics in our theory, we show that self-consistent
solutions of the spin diffusion equations and the Landau-Lifshitz equations in
the presence of a current lead to a an increase in the terminal velocity of a
domain wall which becomes strongly dependent on its width. We also provide a
simplified equation that predicts damping due to the conduction electrons
Prenatal diagnosis of facial clefts: evaluation of a specialised counselling.
Prenatal diagnosis of cleft lip and palate has raised many questions concerning the best way to inform the parents and offer appropriate support during the remaining pregnancy to help prepare a positive birth experience. Prenatal counselling differs according to who is responsible, and to that person's knowledge of the practical aspects of care and the impact of the malformation on the child's quality of life. The aim of the study was to evaluate our current techniques and modify them when appropriate.
29 couples having experienced prenatal diagnosis were asked to respond retrospectively to a questionnaire. Personal obstetric and family history, timing and quality of information provided and their impressions at birth were considered.
The parents used several sources of information: the obstetrician, the counsel by the cleft team surgeon, the parents support groups and the Internet. 93% of the parents felt well prepared psychologically for the birth of their child and concerning the practical aspects of care. 54% felt relieved that their child was less affected than imagined. 96% considered prenatal diagnosis a benefit.
Basic information should be provided soon after ultrasound confirmation, followed by progressively more detailed technical discussions over the remaining pregnancy
Magnetization dynamics in dysprosium orthoferrites via inverse Faraday effect
The ultrafast non-thermal control of magnetization has recently become
feasible in canted antiferromagnets through photomagnetic instantaneous pulses
[A.V. Kimel {\it et al.}, Nature {\bf 435}, 655 (2005)]. In this experiment
circularly polarized femtosecond laser pulses set up a strong magnetic field
along the wave vector of the radiation through the inverse Faraday effect,
thereby exciting non-thermally the spin dynamics of dysprosium orthoferrites. A
theoretical study is performed by using a model for orthoferrites based on a
general form of free energy whose parameters are extracted from experimental
measurements. The magnetization dynamics is described by solving coupled
sublattice Landau-Lifshitz-Gilbert equations whose damping term is associated
with the scattering rate due to magnon-magnon interaction. Due to the inverse
Faraday effect and the non-thermal excitation, the effect of the laser is
simulated by magnetic field Gaussian pulses with temporal width of the order of
hundred femtoseconds. When the field is along the z-axis, a single resonance
mode of the magnetization is excited. The amplitude of the magnetization and
out-of-phase behavior of the oscillations for fields in z and -z directions are
in good agreement with the cited experiment. The analysis of the effect of the
temperature shows that magnon-magnon scattering mechanism affects the decay of
the oscillations on the picosecond scale. Finally, when the field pulse is
along the x-axis, another mode is excited, as observed in experiments. In this
case the comparison between theoretical and experimental results shows some
discrepancies whose origin is related to the role played by anisotropies in
orthoferrites.Comment: 10 pages, 6 figure
Performance of an automated multiplex immunofluorescence assay for detection of Chlamydia trachomatis immunoglobulin G.
Chlamydia serology is indicated to investigate etiology of miscarriage, infertility, pelvic inflammatory disease, and ectopic pregnancy. Here, we assessed the reliability of a new automated-multiplex immunofluorescence assay (InoDiag test) to detect specific anti-C. trachomatis immunoglobulin G. Considering immunofluorescence assay (IF) as gold standard, InoDiag tests exhibited similar sensitivities (65.5%) but better specificities (95.1%-98%) than enzyme-linked immunosorbent assays (ELISAs). InoDiag tests demonstrated similar or lower cross-reactivity rates when compared to ELISA or IF
Development, characterization, and use of a fetal skin cell bank for tissue engineering in wound healing.
Wound healing in fetal skin is characterized by the absence of scar tissue formation, which is not dependent on the intrauterine environment and amniotic fluid. Fetal cells have the capacity of extraordinary expansion and we describe herein the development of a fetal skin cell bank where from one organ donation (2-4 cm2) it is possible to produce several hundred million fetal skin constructs of 9 x 12 cm2. Fetal cells grow three to four times more rapidly than older skin cells cultured in the same manner and these banked fetal cells are very resistant against physical and oxidative stress when compared to adult skin cells under the same culture conditions. They are up to three times more resistant to UVA radiation and two times more resistant towards hydrogen peroxide treatment. This mechanism may be of major importance for fetal cells when they are delivered to hostile wound environments. For fetal cell delivery to patients, cells were associated with a collagen matrix to form a three-dimensional construct in order to analyze the capacity of these cells for treating various wounds. We have seen that fetal cells can modify the repair response of skin wounds by accelerating the repair process and reducing scarring in severe bums and wounds of various nature in children. Hundreds of thousands of patients could potentially be treated for acute and chronic wounds from one standardized and controlled cell bank
Does femtosecond time-resolved second-harmonic generation probe electron temperatures at surfaces?
Femtosecond pump-probe second-harmonic generation (SHG) and transient linear
reflectivity measurements were carried out on polycrystalline Cu, Ag and Au in
air to analyze whether the electron temperature affects Fresnel factors or
nonlinear susceptibilities, or both. Sensitivity to electron temperatures was
attained by using photon energies near the interband transition threshold. We
find that the nonlinear susceptibility carries the electron temperature
dependence in case of Ag and Au, while for Cu the dependence is in the Fresnel
factors. This contrasting behavior emphasizes that SHG is not a priori
sensitive to electron dynamics at surfaces or interfaces, notwithstanding its
cause.Comment: 11 pages, 4 figure
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