1,267 research outputs found
Room temperature ferromagnetic behavior in the hollandite-type titanium oxide
A hollandite-type K(x)Ti(8)O(16) polycrystalline sample has been prepared and studied by magnetization, resistivity and x-ray photoelectron spectroscopy (XPS). Room temperature ferromagnetic behavior is observed in the magnetic hysteresis measurement. The sample shows a semiconductive temperature dependence in the resistivity measurement. Analysis of the Ti 2p(3/2) core-level XPS spectrum indicates that the titanium ions have a mixed valence of Ti(4+) and Ti(3+). In addition, the valence band spectrum reveals that the 3d electrons tend to localize on Ti(3+) ions in the hollandite-type TiO(2) lattice. Also, analysis of the valence band spectrum shows that the prepared sample is a wide-gap oxide with a band gap of 3.6 eV. These results indicate that the present hollandite-type K(x)Ti(8)O(16) sample can be classified as a TiO(2)-based wide-gap semiconductor with Curie temperature above room temperature. Room temperature ferromagnetism (RTFM) decreases in the sample prepared under a strong reducing gas atmosphere, accompanied with the decrease in the resistivity. The results imply that the localized 3d electrons are responsible for the RTFM of the K(x)Ti(8)O(16) sample
Applicability of the Fisher Equation to Bacterial Population Dynamics
The applicability of the Fisher equation, which combines diffusion with
logistic nonlinearity, to population dynamics of bacterial colonies is studied
with the help of explicit analytic solutions for the spatial distribution of a
stationary bacterial population under a static mask. The mask protects the
bacteria from ultraviolet light. The solution, which is in terms of Jacobian
elliptic functions, is used to provide a practical prescription to extract
Fisher equation parameters from observations and to decide on the validity of
the Fisher equation.Comment: 5 pages, 3 figs. include
HELIUM ISOTOPES AND TECTONICS IN SOUTHERN ITALY
Geodynamic evolution of southern Italy can
be understood within the framework of the Mediterranean-
Alpine System. Subduction of a plate along the Sicily-
Calabrian forearc under the Tyrrhenian Sea has been suggested
by many geophysicists, although it is not yet confirmed
and remains somewhat controversial. Helium isotope
ratios provide useful information on the geotectonic structure
of the region. We report here the 3He/4He ratios of
terrestrial gas samples from southern Italy. The observed
3He/4He ratios are relatively high in the Eolian volcanic arc
region and low in the other areas. Dichotomous explanations
are presented. Firstly volcanic arc-forearc hypothesis
suggests the subduction along the Sicily-Calabrian forearc.
Secondly horizontal transport hypothesis is described based
on the relationship between the ratios and radial distance
from the recent spreading basin in Southern Tyrrhenian Sea
Asymptotics of a discrete-time particle system near a reflecting boundary
We examine a discrete-time Markovian particle system on the quarter-plane
introduced by M. Defosseux. The vertical boundary acts as a reflecting wall.
The particle system lies in the Anisotropic Kardar-Parisi-Zhang with a wall
universality class. After projecting to a single horizontal level, we take the
longtime asymptotics and obtain the discrete Jacobi and symmetric Pearcey
kernels. This is achieved by showing that the particle system is identical to a
Markov chain arising from representations of the infinite-dimensional
orthogonal group. The fixed-time marginals of this Markov chain are known to be
determinantal point processes, allowing us to take the limit of the correlation
kernel.
We also give a simple example which shows that in the multi-level case, the
particle system and the Markov chain evolve differently.Comment: 16 pages, Version 2 improves the expositio
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Loss of testosterone impairs anti-tumor neutrophil function.
In men, the incidence of melanoma rises rapidly after age 50, and nearly two thirds of melanoma deaths are male. The immune system is known to play a key role in controlling the growth and spread of malignancies, but whether age- and sex-dependent changes in immune cell function account for this effect remains unknown. Here, we show that in castrated male mice, neutrophil maturation and function are impaired, leading to elevated metastatic burden in two models of melanoma. Replacement of testosterone effectively normalized the tumor burden in castrated male mice. Further, the aberrant neutrophil phenotype was also observed in prostate cancer patients receiving androgen deprivation therapy, highlighting the evolutionary conservation and clinical relevance of the phenotype. Taken together, these results provide a better understanding of the role of androgen signaling in neutrophil function and the impact of this biology on immune control of malignancies
Remote detection of fumarolic gas chemistry at Vulcano, Italy, using an FT-IR spectral radiometer
An infrared absorption spectroscopy remote sensing technique was used to determine the S02/HCl ratio in fumarolic
plumes at Vulcano, Italy. The measurements were made from the southern crater rim of Fossa Grande Crater, about 400 m
from the fumarolic area in the crater. Infrared absorption spectra of HCl and SO, were observed for four fumaroles a few
tens of metres apart using the hot fumarolic surface as an infrared light source. The measured S02/HCl ratios in the FA,
F47, FW and lower parti of the F21 fumaroles were 4.5-5.4, 3.5, 9.5-11.2 and 5.8 respectively. The S02/HCl ratio of the
FA fumarole was higher than that of the gas collected directly in the fumarolic vent (S02/HCl ratio = 2.9), and was closer
to the S~,,,,,,/HCl ratio (= 4.6) of the collected gas. Our results show that the SO,/HCl ratios of two fumaroles only a few
tens of metres apart exhibits differences of about twofold. This suggests that this remote monitoring technique is capable of
detecting spatial distribution in the S02/HCl ratios of volcanic plumes. Because temporal variations in S/Cl ratios can
provide precursory signals for volcanic eruptions [l-31, this remote sensing technique can used efficiently for evaluation of
volcanic activity
Determination of the local structure of SrMIrO (M = K, La) as a function of doping and temperature
The local structure of correlated spin-orbit insulator SrMIrO
(M = K, La) has been investigated by Ir L-edge extended x-ray absorption
fine structure measurements. The measurements were performed as a function of
temperature for different dopings induced by substitution of Sr with La or K.
It is found that Ir-O bonds have strong covalency and they hardly show any
change across the N\'eel temperature. In the studied doping range, neither Ir-O
bonds nor their dynamics, measured by their mean square relative displacements,
show any appreciable change upon carrier doping, indicating possibility of a
nanoscale phase separation in the doped system. On the other hand, there is a
large increase of the static disorder in Ir-Sr correlation, larger for K doping
than La doping. Similarities and differences with respect to the local lattice
displacements in cuprates are briefly discussed.Comment: Main text: 6 pages, 4 figures, Supplemental information: 2 pages, 2
figure
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