3,627 research outputs found
Study of H2/N2Mixture Plasma Treatment on the AISI 1045
In the present work, we analyzed the effect of the plasma treatment of 80% H2/20% N2 mixture plasma over the AISI 1045 steel. To produce the plasma, an AC discharge of 0.1 A at 350 V was produced at a total pressure of 3.0 Torr. The mixture plasma was analyzed using optical emission spectroscopy (OES), in the wavelength range of 200 to 1100 nm. The principal species observed in the plasma were NH, N2, N2+, H2, and Hα. The electron temperature and ion density have been measured using a double Langmuir probe. The samples of steel were treated by plasma at different discharge times, between 3 and 12 h, at the same pressure and AC parameters (0.1 A and 350 V). The treated samples were characterized using X-ray analysis, finding the phases gamma and epsilon of iron nitride. The thickness of the nitrided layers was measured using a scanning electron microscope (SEM). From the images obtained, it is possible to appreciate the interphase between the nitrided layer and the steel matrix. The relationship between the morphology of the surface of nitrided steel and the wetting was analyzed by measuring the contact angle between the surface and a drop of 5 μL of distilled water. The contact angle of the drop increased with the increase of plasma treatment time. The control sample without treatment presented a smaller angle, and after the treatment the surfaces of the steel became hydrophobic. This may be related to the morphology change of the steel surface produced by plasma treatment
Universality of the 1/3 shot-noise suppression factor in nondegenerate diffusive conductors
Shot-noise suppression is investigated in nondegenerate diffusive conductors
by means of an ensemble Monte Carlo simulator. The universal 1/3 suppression
value is obtained when transport occurs under elastic collision regime provided
the following conditions are satisfied: (i) The applied voltage is much larger
than the thermal value; (ii) the length of the device is much longer than both
the elastic mean free path and the Debye length. By fully suppressing
carrier-number fluctuations, long range Coulomb interaction is essential to
obtain the 1/3 value in the low-frequency limit.Comment: RevTex, 4 pages, 4 figure
Plasticity and memory effects in the vortex solid phase of twinned YBa2Cu3O7 single crystals
We report on marked memory effects in the vortex system of twinned YBa2Cu3O7
single crystals observed in ac susceptibility measurements. We show that the
vortex system can be trapped in different metastable states with variable
degree of order arising in response to different system histories. The pressure
exerted by the oscillating ac field assists the vortex system in ordering,
locally reducing the critical current density in the penetrated outer zone of
the sample. The robustness of the ordered and disordered states together with
the spatial profile of the critical current density lead to the observed memory
effects
Temperature and thickness dependence of the thermal conductivity in 2D ferromagnet FeGeTe
The emergence of symmetry-breaking orders such as ferromagnetism and the weak
interlayer bonding in van der Waals materials, offers a unique platform to
engineer novel heterostructures and tune transport properties like thermal
conductivity. Here, we report the experimental and theoretical study of the
cross-plane thermal conductivity, , of the van der Waals 2D
ferromagnet FeGeTe. We observe a non-monotonic increase of
with the thickness and a large suppression in
artificially-stacked layers, indicating a diffusive transport regime with
ballistic contributions. These results are supported by the theoretical
analyses of the accumulated thermal conductivity, which show an important
contribution of phonons with mean free paths between 10 and 200 nm. Moreover,
our experiments show a reduction of the in the low-temperature
ferromagnetic phase occurring at the magnetic transition. The calculations show
that this reduction in is associated with a decrease in the
group velocities of the acoustic phonons and an increase in the phonon-phonon
scattering of the Raman modes that couple to the magnetic phase. These results
demonstrate the potential of van der Waals ferromagnets for thermal transport
engineering
A spectral line survey of Orion KL in the bands 486-492 and 541-577 GHz with the Odin satellite I. The observational data
Spectral line surveys are useful since they allow identification of new
molecules and new lines in uniformly calibrated data sets. Nonetheless, large
portions of the sub-millimetre spectral regime remain unexplored due to severe
absorptions by H2O and O2 in the terrestrial atmosphere. The purpose of the
measurements presented here is to cover wavelength regions at and around 0.55
mm -- regions largely unobservable from the ground. Using the Odin
astronomy/aeronomy satellite, we performed the first spectral survey of the
Orion KL molecular cloud core in the bands 486--492 and 541--576 GHz with
rather uniform sensitivity (22--25 mK baseline noise). Odin's 1.1 m size
telescope, equipped with four cryo-cooled tuneable mixers connected to broad
band spectrometers, was used in a satellite position-switching mode. Two mixers
simultaneously observed different 1.1 GHz bands using frequency steps of 0.5
GHz (25 hours each). An on-source integration time of 20 hours was achieved for
most bands. The entire campaign consumed ~1100 orbits, each containing one hour
of serviceable astro-observation. We identified 280 spectral lines from 38
known interstellar molecules (including isotopologues) having intensities in
the range 80 to 0.05 K. An additional 64 weak lines remain unidentified. Apart
from the ground state rotational 1(1,0)--1(0,1) transitions of ortho-H2O, H218O
and H217O, the high energy 6(2,4)--7(1,7) line of para-H2O and the
HDO(2,0,2--1,1,1) line have been observed, as well as the 1,0--0,1 lines from
NH3 and its rare isotopologue 15NH3. We suggest assignments for some
unidentified features, notably the new interstellar molecules ND and SH-.
Severe blends have been detected in the line wings of the H218O, H217O and 13CO
lines changing the true linewidths of the outflow emission.Comment: 21 pages, 10 figures, 7 tables, accepeted for publication in
Astronomy and Astrophysics 30 August 200
Measurement of the radiative capture cross section of the s-process branching points 204Tl and 171Tm at the n-TOF facility (CERN)
The neutron capture cross section of some unstable nuclei is especially relevant for s-process nucleosynthesis studies. This magnitude is crucial to determine the local abundance pattern, which can yield valuable information of the s-process stellar environment. In this work we describe the neutron capture (n,Îł) measurement on two of these nuclei of interest, 204Tl and 171Tm, from target production to the final measurement, performed successfully at the n_TOF facility at CERN in 2014 and 2015. Preliminary results on the ongoing experimental data analysis will also be shown. These results include the first ever experimental observation of capture resonances for these two nuclei.The authors acknowledge financial support by the Spanish FPA2014-52823-C2-2-P project, by the EC
Marie Curie Action “NeutAndalus” (FP7-PEOPLE-2012-CIG- 334315), by the ARGOS scholarship of
the Spanish Nuclear Safety Council (CSN) and the Universitat Politècnica de Catalunya, and by the
University of Sevilla via the VI PPIT-US program
Influence of nuclear structure on sub-barrier hindrance in Ni+Ni fusion
Fusion-evaporation cross sections for Ni+Ni have been measured
down to the 10 nb level. For fusion between two open-shell nuclei, this is the
first observation of a maximum in the -factor, which signals a strong
sub-barrier hindrance. A comparison with the Ni+Ni,
Ni+Ni, and Ni+Ni systems indicates a strong
dependence of the energy where the hindrance occurs on the stiffness of the
interacting nuclei.Comment: Submitted to Phys. Rev. Lett. 4 pages, 3 figure
Equilibration and Dynamic Phase Transitions of a Driven Vortex Lattice
We report on the observation of two types of current driven transitions in
metastable vortex lattices. The metastable states, which are missed in usual
slow transport measurements, are detected with a fast transport technique in
the vortex lattice of undoped
2H-NbSe. The transitions are seen by following the evolution of these
states when driven by a current. At low currents we observe an equilibration
transition from a metastable to a stable state, followed by a dynamic
crystallization transition at high currents.Comment: 5 pages, 4 figure
Interval between first dose and booster affected antibody production in cattle vaccinated against rabies
In this study, we compared the levels of neutralizing antibodies induced by inactivated rabies vaccine in cattle by using three alternative immunization procedures. Forty-five bovines (breed nelore) were then organized in three groups (A, B and C, with 15 animals/group). Group A received only one vaccine dose at day zero and Group B received the first dose at day zero and then another dose at day 30 (early booster). Group C was also immunized with two doses; however, the booster was postponed until day 180 after the first dose (delayed booster). Blood samples were withdrawn at days zero (before the first dose) and 30, 210, 390, and 540 after the beginning of immunization and the antibody titers were evaluated by mouse neutralization test. The protocol used to immunize Group C (booster at day 180) was clearly more efficient. In this group, antibody levels were higher and also remained higher for longer periods in comparison with the other two groups. These results show that booster timing significantly affected antibody levels. Therefore, programs addressed to control this disease in cattle should consider not only the use of a booster but also its administration time
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