5,495 research outputs found
Novel sputtering-technology for grain-size control
In this paper, we present a description of a novel high-rate plasma sputtering system that allows the control of grain size in sputtered films. Additionally, the system has the advantage of a better utilization of the target material (around 80% to 90%) by eliminating the race track at the target as in conventional plasma magnetron sputtering systems. The potential and capabilities of this novel plasma sputtering device are demonstrated in this paper by the deposition of a number of different Cr thin films suitable for underlayers in thin-film media and for which we have performed a systematic X-ray and TEM analysis to determine the grain-size histograms, mean grain diameters, and their relationship to the sputtering processes
Growth rate effects in soft CoFe films
We report on growth rate effects in sputter-deposited CoFe films prepared using high target utilization sputtering technology (HiTUS). We find that the grain structure of these polycrystalline films is closely related to the growth rate. By changing the growth rate, samples were prepared with different grain structure, which in turn had the effect of changing the magnetic properties of the films. We demonstrate control of the coercivity, which varied by a factor of more than ten. This was achieved via grain size control in CoFe films of thickness 20 nm. Furthermore, by employing a two-step sputtering process, in which two extreme growth rates are used sequentially, we were able to tune the saturation magnetization
The Spectrum of Pluto, 0.40 - 0.93 m I. Secular and longitudinal distribution of ices and complex organics
Context. During the last 30 years the surface of Pluto has been
characterized, and its variability has been monitored, through continuous
near-infrared spectroscopic observations. But in the visible range only few
data are available. Aims. The aim of this work is to define the Pluto's
relative reflectance in the visible range to characterize the different
components of its surface, and to provide ground based observations in support
of the New Horizons mission. Methods. We observed Pluto on six nights between
May and July 2014, with the imager/spectrograph ACAM at the William Herschel
Telescope (La Palma, Spain). The six spectra obtained cover a whole rotation of
Pluto (Prot = 6.4 days). For all the spectra we computed the spectral slope and
the depth of the absorption bands of methane ice between 0.62 and 0.90 m.
To search for shifts of the center of the methane bands, associated with
dilution of CH4 in N2, we compared the bands with reflectances of pure methane
ice. Results. All the new spectra show the methane ice absorption bands between
0.62 and 0.90 m. The computation of the depth of the band at 0.62 m
in the new spectra of Pluto, and in the spectra of Makemake and Eris from the
literature, allowed us to estimate the Lambert coefficient at this wavelength,
at a temperature of 30 K and 40 K, never measured before. All the detected
bands are blue shifted, with minimum shifts in correspondence with the regions
where the abundance of methane is higher. This could be indicative of a
dilution of CH4:N2 more saturated in CH4. The longitudinal and secular
variations of the parameters measured in the spectra are in accordance with
results previously reported in the literature and with the distribution of the
dark and bright material that show the Pluto's albedo maps from New Horizons.Comment: This manuscript may change and improve during the reviewing process.
The data reduction and calibration is reliable and has been checked
independently using different reduction approaches. The data will be made
publicily available when the paper is accepted. If you need them before,
please, contact the autho
Transition state theory and the dynamics of hard disks
The dynamics of two and five disk systems confined in a square has been
studied using molecular dynamics simulations and compared with the predictions
of transition state theory. We determine the partition functions Z and
Z^\ddagger of transition state theory using a procedure first used by Salsburg
and Wood for the pressure. Our simulations show this procedure and transition
state theory are in excellent agreement with the simulations. A generalization
of the transition state theory to the case of a large number of disks N is made
and shown to be in full agreement with simulations of disks moving in a narrow
channel. The same procedure for hard spheres in three dimensions leads to the
Vogel-Fulcher-Tammann formula for their alpha relaxation time.Comment: 1 new author, new simulations and figures, less speculation. Now 6
pages, 6 figures, 1 animation. Animation may be viewed at
http://www.theory.physics.manchester.ac.uk/~godfrey/supplement/activated_dynamics2.htm
The ISO LWS high resolution spectral survey towards Sagittarius B2
A full spectral survey was carried out towards the Giant Molecular Cloud
complex, Sagittarius B2 (Sgr B2), using the ISO Long Wavelength Spectrometer
Fabry-Perot mode. This provided complete wavelength coverage in the range
47-196 um (6.38-1.53 THz) with a spectral resolution of 30-40 km/s. This is an
unique dataset covering wavelengths inaccessible from the ground. It is an
extremely important region of the spectrum as it contains both the peak of the
thermal emission from dust, and crucial spectral lines of key atomic (OI, CII,
OIII, NII and NIII) and molecular species (NH3, NH2, NH, H2O, OH, H3O+, CH,
CH2, C3, HF and H2D+). In total, 95 spectral lines have been identified and 11
features with absorption depth greater than 3 sigma remain unassigned. Most of
the molecular lines are seen in absorption against the strong continuum,
whereas the atomic and ionic lines appear in emission (except for absorption in
the OI 63 um and CII 158 um lines). Sgr B2 is located close to the Galactic
Centre and so many of the features also show a broad absorption profile due to
material located along the line of sight. A full description of the survey
dataset is given with an overview of each detected species and final line lists
for both assigned and unassigned features.Comment: Accepted for publication in MNRA
Combinatorial Games with a Pass: A dynamical systems approach
By treating combinatorial games as dynamical systems, we are able to address
a longstanding open question in combinatorial game theory, namely, how the
introduction of a "pass" move into a game affects its behavior. We consider two
well known combinatorial games, 3-pile Nim and 3-row Chomp. In the case of Nim,
we observe that the introduction of the pass dramatically alters the game's
underlying structure, rendering it considerably more complex, while for Chomp,
the pass move is found to have relatively minimal impact. We show how these
results can be understood by recasting these games as dynamical systems
describable by dynamical recursion relations. From these recursion relations we
are able to identify underlying structural connections between these "games
with passes" and a recently introduced class of "generic (perturbed) games."
This connection, together with a (non-rigorous) numerical stability analysis,
allows one to understand and predict the effect of a pass on a game.Comment: 39 pages, 13 figures, published versio
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