11,711 research outputs found
Magnetic Properties of the Novel Low-Dimensional Cuprate Na5RbCu4(AsO4)4Cl2
The magnetic properties of a new compound, Na5RbCu4(AsO4)4Cl2 are reported.
The material has a layered structure comprised of square Cu4O4 tetramers. The
Cu ions are divalent and the system behaves as a low-dimensional S=1/2
antiferromagnet. Spin exchange in Na5RbCu4(AsO4)4Cl2 appears to be
quasi-two-dimensional and non-frustrated. Measurements of the bulk magnetic
susceptibility and heat capacity are consistent with low-dimensional magnetism.
The compound has an interesting, low-entropy, magnetic transition at T = 17 K.Comment: 4 pages, 5 figure
Two Conditions for Galaxy Quenching: Compact Centres and Massive Haloes
We investigate the roles of two classes of quenching mechanisms for central
and satellite galaxies in the SDSS (): those involving the halo and
those involving the formation of a compact centre. For central galaxies with
inner compactness ,
the quenched fraction is strongly correlated with
with only weak halo mass dependence. However, at higher and lower
, sSFR is a strong function of and mostly
independent of . In other words, divides galaxies into those with high sSFR
below and low sSFR above this range. In both the upper and lower regimes,
increasing shifts the entire sSFR distribtuion to lower sSFR
without a qualitative change in shape. This is true even at fixed , but
varying at fixed adds no quenching information. Most of the
quenched centrals with are dense (), suggesting compaction-related
quenching maintained by halo-related quenching. However, 21% are diffuse,
indicating only halo quenching. For satellite galaxies in the outskirts of
halos, quenching is a strong function of compactness and a weak function of
host . In the inner halo, dominates quenching, with
of the satellites being quenched once . This regional effect is greatest for the least massive
satellites. As demonstrated via semi-analytic modelling with simple
prescriptions for quenching, the observed correlations can be explained if
quenching due to central compactness is rapid while quenching due to halo mass
is slow.Comment: 16 pages, 11 figures, MNRAS accepte
Exact Zeros of the Partition Function for a Continuum System with Double Gaussian Peaks
We calculate the exact zeros of the partition function for a continuum system
where the probability distribution for the order parameter is given by two
asymmetric Gaussian peaks. When the positions of the two peaks coincide, the
two separate loci of zeros which used to give first-order transition touch each
other, with density of zeros vanishing at the contact point on the positive
real axis. Instead of the second-order transition of Ehrenfast classification
as one might naively expect, one finds a critical behavior in this limit.Comment: 13 pages, 6 figures, revtex, minor changes in fig.2, to be published
in Physical Review
Quantitative study of molecular N_2 trapped in disordered GaN:O films
The structure of disordered GaN:O films grown by ion-assisted deposition is
investigated using x-ray absorption near-edge spectroscopy and Raman
spectroscopy. It is found that between 4 and 21 % of the nitrogen in the films
is in the form of molecular N_2 that interacts only weakly with the surrounding
matrix. The anion to cation ratio in the GaN:O host remains close to unity, and
there is a close correlation between the N_2 fraction, the level of oxygen
impurities, and the absence of short-range order in the GaN:O matrix.Comment: 5 pages, 3 figure
An Econometric Analysis of the NW/KLM Corporate Alliance
This thesis investigates whether a corporate alliance between international air carriers is beneficial, considering the changes in the global air transport system. Dividing the research method into three phases, the author first lists and identifies the recent changes in world air transport trends. Then, the author defines the different types of alliances and studies the advantages and disadvantages of these corporate alliances. Finally, a multiple regression analysis is performed using the KLM/Northwest Airlines alliance as a case analysis
A new approximation scheme in quantum mechanics
An approximation method which combines the perturbation theory with the
variational calculation is constructed for quantum mechanical problems. Using
the anharmonic oscillator and the He atom as examples, we show that the present
method provides an efficient scheme in estimating both the ground and the
excited states. We also discuss the limitations of the present method.Comment: 14pages, to be published in Eur. J. Phy
Au-SN Flip-Chip Solder Bump for Microelectronic and Optoelectronic Applications
As an alternative to the time-consuming solder pre-forms and pastes currently
used, a co-electroplating method of eutectic Au-Sn alloy was used in this
study. Using a co-electroplating process, it was possible to plate the Au-Sn
solder directly onto a wafer at or near the eutectic composition from a single
solution. Two distinct phases, Au5Sn and AuSn, were deposited at a composition
of 30at.%Sn. The Au-Sn flip-chip joints were formed at 300 and 400 degrees
without using any flux. In the case where the samples were reflowed at 300
degrees, only an (Au,Ni)3Sn2 IMC layer formed at the interface between the
Au-Sn solder and Ni UBM. On the other hand, two IMC layers, (Au,Ni)3Sn2 and
(Au,Ni)3Sn, were found at the interfaces of the samples reflowed at 400
degrees. As the reflow time increased, the thickness of the (Au,Ni)3Sn2 and
(Au,Ni)3Sn IMC layers formed at the interface increased and the eutectic
lamellae in the bulk solder coarsened.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
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