451 research outputs found
Superhyperfine interactions in Ce3+ doped LiYF4 crystal: ENDOR measurements
The first observation of the resolved Mims electron-nuclear double resonance
(ENDOR) spectra from the nearby and remote nuclei of 19F and 7Li nuclei on
impurity Ce3+ ions in LiYF4 crystal is reported. It shows that LiYF4:Ce3+
system can be exploited as a convenient matrix for performing spin
manipulations and adjusting quantum computation protocols while ENDOR technique
could be used for the investigation of electron-nuclear interaction with all
the nuclei of the system and exploited for the electron-nuclear spin
manipulations.Comment: 4 pages, 2 figures, 1 Table. Reported on Theor-2017 (Kazan, Russia)
Conferenc
Hypervelocity dust particle impacts observed by the Giotto Magnetometer and Plasma Experiments
We report thirteen very short events in the magnetic field of the inner magnetic pile‐up region of comet Halley observed by the Giotto magnetometer experiment together with simultaneous plasma data obtained by the Johnstone plasma analyzer and the ion mass spectrometer experiments. The events are due to dust impacts in the milligram range on the spacecraft at the relative velocity between the cemetery dust and the spacecraft of 68 km/sec. They are generally consistent with dust impact events derived from spacecraft attitude perturbations by the Giotto camera [Curdt and Keller, private communication]. Their characteristic shape generally involves a sudden decrease in magnetic field magnitude, a subsequent overshoot beyond initial field values and an asymptotic approach to the initial field somewhat reminiscent of the magnetic field signature after the AMPTE releases in the solar wind. These observations give a new way of analyzing ultra‐fast dust particles incident on a spacecraft
The Large Scale Distribution of Neutral Hydrogen in the Fornax Region
Using HIPASS data, we have searched for HI in a ~25x25 sq.deg. region centred
on the Fornax cluster. Within a velocity search range of 300 - 3700 km/s and a
lower flux limit of ~40 mJy, 110 galaxies with HI emission were detected, one
of which is previously uncatalogued. None of the detections has early-type
morphology. Previously unknown velocities for 14 galaxies have been determined,
with a further 4 velocity measurements being significantly dissimilar to
published values. Identification of an optical counterpart is relatively
unambiguous for more than ~90% of our HI galaxies. The galaxies appear to be
embedded in a sheet at the cluster velocity which extends for more than 30 deg
across the search area. At the nominal cluster distance of ~20 Mpc, this
corresponds to an elongated structure more than 10 Mpc in extent. A velocity
gradient across the structure is detected, with radial velocities increasing by
\~500 km/s from SE to NW. The clustering of galaxies evident in optical surveys
is only weakly suggested in the spatial distribution of our HI detections. Our
results suggest a considerable deficit of HI-rich galaxies in the centre of the
cluster. However, relative to the field, there is a 3(+/-1)-fold excess of
HI-rich galaxies in the outer parts of the cluster where galaxies may be
infalling towards the cluster for the first time.Comment: 16 pages, 14 figures, 110 HI spectra. To be published in MNRA
Environmental effects on galaxy evolution. II: quantifying the tidal features in NIR-images of the cluster Abell 85
This work is part of a series of papers devoted to investigate the evolution
of cluster galaxies during their infall. In the present article we imaged in
NIR a selected sample of galaxies through- out the massive cluster Abell 85 (z
= 0.055). We obtained (JHK) photometry for 68 objects, reaching 1 mag/arcsec^2
deeper than 2MASS. We use these images to unveil asymmetries in the outskirts
of a sample of bright galaxies and develop a new asymmetry index, alpha_An,
which allows to quantify the degree of disruption by the relative area occupied
by the tidal features on the plane of the sky. We measure the asymmetries for a
subsample of 41 large area objects finding clear asymmetries in ten galaxies,
most of them being in groups and pairs projected at different clustercentric
distances, some of them located beyond R500 . Combining information on the
Hi-gas content of blue galaxies and the distribution of sub-structures across
Abell 85, with the present NIR asymmetry analysis, we obtain a very powerful
tool to confirm that tidal mechanisms are indeed present and are currently
affecting a fraction of galaxies in Abell 85. However, when comparing our deep
NIR images with UV-blue images of two very disrupted (jellyfish) galaxies in
this cluster, we discard the presence of tidal 1 interactions down to our
detection limit. Our results suggest that ram-pressure stripping is at the
origin of such spectacular disruptions. We conclude that across a complex
cluster like Abell 85, environment mechanisms, both gravitational and
hydrodynamical, are playing an active role in driving galaxy evolution.Comment: 30 pages, 13 figures, Accepted for Publication in A
Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields
When a micron-sized magnetizable particle is introduced into a suspension of
nanosized magnetic particles, the nanoparticles accumulate around the
microparticle and form thick anisotropic clouds extended in the direction of
the applied magnetic field. This phenomenon promotes colloidal stabilization of
bimodal magnetic suspensions and allows efficient magnetic separation of
nanoparticles used in bioanalysis and water purification. In the present work,
size and shape of nanoparticle clouds under the simultaneous action of an
external uniform magnetic field and the flow have been studied in details. In
experiments, dilute suspension of iron oxide nanoclusters (of a mean diameter
of 60 nm) was pushed through a thin slit channel with the nickel microspheres
(of a mean diameter of 50m) attached to the channel wall. The behavior of
nanocluster clouds was observed in the steady state using an optical
microscope. In the presence of strong enough flow, the size of the clouds
monotonically decreases with increasing flow speed in both longitudinal and
transverse magnetic fields. This is qualitatively explained by enhancement of
hydrodynamic forces washing the nanoclusters away from the clouds. In the
longitudinal field, the flow induces asymmetry of the front and the back
clouds. To explain the flow and the field effects on the clouds, we have
developed a simple model based on the balance of the stresses and particle
fluxes on the cloud surface. This model, applied to the case of the magnetic
field parallel to the flow, captures reasonably well the flow effect on the
size and shape of the cloud and reveals that the only dimensionless parameter
governing the cloud size is the ratio of hydrodynamic-to-magnetic forces - the
Mason number. At strong magnetic interactions considered in the present work
(dipolar coupling parameter ), the Brownian motion seems not to
affect the cloud behavior
Observation of an orbital interaction-induced Feshbach resonance in 173-Yb
We report on the experimental observation of a novel inter-orbital Feshbach
resonance in ultracold 173-Yb atoms, which opens the possibility of tuning the
interactions between the 1S0 and 3P0 metastable state, both possessing
vanishing total electronic angular momentum. The resonance is observed at
experimentally accessible magnetic field strengths and occurs universally for
all hyperfine state combinations. We characterize the resonance in the bulk via
inter-orbital cross-thermalization as well as in a three-dimensional lattice
using high-resolution clock-line spectroscopy.Comment: 5 pages, 4 figure
Influence of the Orifice on Measured Pressures
The influence of different orifices on the result of measuring the same pressure distributions is the subject of this note. A circular cylinder is exposed to an air stream perpendicular to its axis and its pressure distribution is repeatedly determined. The pressures measured on the downstream half of the cylinder do not change for the orifice sizes used in the tests
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