4,369 research outputs found
Radial gradients and anisotropies of cosmic rays in the interplanetary medium
Radial gradients and anisotropies of cosmic rays in interplanetary mediu
Magnetic measurements at pressures above 10 GPa in a miniature ceramic anvil cell for a superconducting quantum interference device magnetometer
A miniature ceramic anvil high pressure cell (mCAC) was earlier designed by
us for magnetic measurements at pressures up to 7.6 GPa in a commercial
superconducting quantum interference (SQUID) magnetometer [N. Tateiwa et al.,
Rev. Sci. Instrum. 82, 053906 (2011)]. Here, we describe methods to generate
pressures above 10 GPa in the mCAC. The efficiency of the pressure generation
is sharply improved when the Cu-Be gasket is sufficiently preindented. The
maximum pressure for the 0.6 mm culet anvils is 12.6 GPa when the Cu-Be gasket
is preindented from the initial thickness of 0.30 to 0.06 mm. The 0.5 mm culet
anvils were also tested with a rhenium gasket. The maximum pressure attainable
in the mCAC is about 13 GPa. The present cell was used to study YbCu2Si2 which
shows a pressure induced transition from the non-magnetic to magnetic phases at
8 GPa. We confirm a ferromagnetic transition from the dc magnetization
measurement at high pressure. The mCAC can detect the ferromagnetic ordered
state whose spontaneous magnetic moment is smaller than 1 mB per unit cell. The
high sensitivity for magnetic measurements in the mCAC may result from the the
simplicity of cell structure. The present study shows the availability of the
mCAC for precise magnetic measurements at pressures above 10 GPa
Magnetotransport in the low carrier density ferromagnet EuB_6
We present a magnetotransport study of the low--carrier density ferromagnet
EuB_6. This semimetallic compound, which undergoes two ferromagnetic
transitions at T_l = 15.3 K and T_c = 12.5 K, exhibits close to T_l a colossal
magnetoresistivity (CMR). We quantitatively compare our data to recent
theoretical work, which however fails to explain our observations. We attribute
this disagreement with theory to the unique type of magnetic polaron formation
in EuB_6.Comment: Conference contribution MMM'99, San Jos
Purging of a multilayer insulation with dacron tuft spacer by gas diffusion
The time and purge gas usage required to purge a multilayer insulation (MLI) panel with gaseous helium by means of gas diffusion to obtain a condensable gas (nitrogen) concentration of less than 1 percent within the panel are stipulated. Two different, flat, rectangular MLI panels, one incorporating a butt joint, were constructed of of 11 double-aluminized Mylar (DAM) radiation shields separated by Dacron tuft spacers. The DAM/Dacron tuft concept is known commercially as Superfloc. The nitrogen gas concentration as a function of time within the MLI panel could be adequately predicted by using a simple, one dimensional gas diffusion model in which the boundary conditions at the edge of the MLI panel were time dependent. The time and purge gas usage required to achieve 1 percent nitrogen gas concentration within the MLI panel varied from 208 to 86 minutes and 34.1 to 56.5 MLI panel purge volumes, respectively, for gaseous helium purge rates from 10 to 40 MLI panel volumes per hour
Proceedings of the Symposium on the Study of the Sun and Interplanetary Medium in Three Dimensions
A series of papers are presented from a symposium attended by over 200 European and American scientists to examine the importance of exploring the interplanetary medium and the sun by out-of-the-ecliptic space missions. The likely scientific returns of these missions in the areas of solar, interplanetary, and cosmic ray physics is examined. Theoretical models of the solar wind and its interaction with interplanetary magnetic fields are given
A New Heavy-Fermion Superconductor CeIrIn5: Relative of the Cuprates?
CeIrIn5 is a member of a new family of heavy-fermion compounds and has a
Sommerfeld specific heat coefficient of 720 mJ/mol-K2. It exhibits a bulk,
thermodynamic transition to a superconducting state at Tc=0.40 K, below which
the specific heat decreases as T2 to a small residual T-linear value.
Surprisingly, the electrical resistivity drops below instrumental resolution at
a much higher temperature T0=1.2 K. These behaviors are highly reproducible and
field-dependent studies indicate that T0 and Tc arise from the same underlying
electronic structure. The layered crystal structure of CeIrIn5 suggests a
possible analogy to the cuprates in which spin/charge pair correlations develop
well above Tc
Tuning Low Temperature Physical Properties of CeNiGe by Magnetic Field
We have studied the thermal, magnetic, and electrical properties of the
ternary intermetallic system CeNiGe by means of specific heat,
magnetization, and resistivity measurements. The specific heat data, together
with the anisotropic magnetic susceptibility, was analyzed on the basis of the
point charge model of crystalline electric field. The \,=\,5/2 multiplet of
the Ce is split by the crystalline electric field (CEF) into three
Kramers doublets, where the second and third doublet are separated from the
first (ground state) doublet by 100\,K and
170\,K, respectively. In zero field CeNiGe exhibits an
antiferromangeic order below = 5.0\,K. For
\textbf{H}\,\,\textbf{a} two metamagnetic transitions are clearly
evidenced between 2\,\,4\,K from the magnetization isotherm and extended
down to 0.4\,K from the magnetoresistance measurements. For
\textbf{H}\,\,\textbf{a}, shifts to lower temperature as
magnetic field increases, and ultimately disappears at
32.5\,kOe. For , the electrical resistivity shows the quadratic
temperature dependence (). For , an
unconventional -dependence of with emerges, the
exponent becomes larger as magnetic field increases. Although the
antiferromagnetic phase transition temperature in CeNiGe can be
continuously suppressed to zero, it provides an example of field tuning that
does not match current simple models of Quantum criticality.Comment: accepted PR
Aquatic Animal Health Training Scheme. Fish disease diagnosis, biosecurity & disease management training for fish farming industry of Australia.
This workshop delivered new knowledge and technical skills with hands-on training to 24 participants representing of Australian fish-farming and government veterinarian sectors. The workshop focused on delivering training in both theory and practical aspects, with delivering hands-on technical skills, relating directly to fish disease detection, diagnosis, treatment, control, disease emergency response, disease reporting, fish health certification, fish toxicology and fish kills. The workshop was held in Townsville, Queensland on July 17th-18th, 2015, and was organized and delivered by Dr Rachel Bowater, Mr Andrew Fisk, Dr Kitman Dyrting, Dr Ian Anderson and Dr Roger Chong, with whom collectively have >100 years of experience in fish diagnostics, research, pathology, policy and aquaculture extension
Guarding curvilinear art galleries with edge or mobile guards via 2-dominance of triangulation graphs
AbstractIn this paper we consider the problem of monitoring an art gallery modeled as a polygon, the edges of which are arcs of curves, with edge or mobile guards. Our focus is on piecewise-convex polygons, i.e., polygons that are locally convex, except possibly at the vertices, and their edges are convex arcs.We transform the problem of monitoring a piecewise-convex polygon to the problem of 2-dominating a properly defined triangulation graph with edges or diagonals, where 2-dominance requires that every triangle in the triangulation graph has at least two of its vertices in its 2-dominating set. We show that: (1) ⌊n+13⌋ diagonal guards are always sufficient and sometimes necessary, and (2) ⌊2n+15⌋ edge guards are always sufficient and sometimes necessary, in order to 2-dominate a triangulation graph. Furthermore, we show how to compute: (1) a diagonal 2-dominating set of size ⌊n+13⌋ in linear time and space, (2) an edge 2-dominating set of size ⌊2n+15⌋ in O(n2) time and O(n) space, and (3) an edge 2-dominating set of size ⌊3n7⌋ in O(n) time and space.Based on the above-mentioned results, we prove that, for piecewise-convex polygons, we can compute: (1) a mobile guard set of size ⌊n+13⌋ in O(nlogn) time, (2) an edge guard set of size ⌊2n+15⌋ in O(n2) time, and (3) an edge guard set of size ⌊3n7⌋ in O(nlogn) time. All space requirements are linear. Finally, we show that ⌊n3⌋ mobile or ⌈n3⌉ edge guards are sometimes necessary.When restricting our attention to monotone piecewise-convex polygons, the bounds mentioned above drop: ⌈n+14⌉ edge or mobile guards are always sufficient and sometimes necessary; such an edge or mobile guard set, of size at most ⌈n+14⌉, can be computed in O(n) time and space
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