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Magnetotransport in Sr3PbO antiperovskite with three-dimensional massive Dirac electrons
Novel topological phenomena are anticipated for three-dimensional (3D) Dirac
electrons. The magnetotransport properties of cubic
antiperovskite, theoretically proposed to be a 3D massive Dirac electron
system, are studied. The measurements of Shubnikov-de Haas oscillations and
Hall resistivity indicate the presence of a low density ( ) of holes with an extremely small cyclotron mass of
0.01-0.06. The magnetoresistance is linear in
magnetic field with the magnitude independent of temperature. These results
are fully consistent with the presence of 3D massive Dirac electrons in . The chemical flexibility of the antiperovskites and our findings
in the family member, , point to their potential as a model
system in which to explore exotic topological phases
Model-independent test of gravity with a network of ground-based gravitational-wave detectors
The observation of gravitational waves with a global network of
interferometric detectors such as advanced LIGO, advanced Virgo, and KAGRA will
make it possible to probe into the nature of space-time structure. Besides
Einstein's general theory of relativity, there are several theories of
gravitation that passed experimental tests so far. The gravitational-wave
observation provides a new experimental test of alternative theories of gravity
because a gravitational wave may have at most six independent modes of
polarization, of which properties and number of modes are dependent on theories
of gravity. This paper proposes a method to reconstruct the independent modes
of polarization in time-series data of an advanced detector network. Since the
method does not rely on any specific model, it gives model-independent test of
alternative theories of gravity
Preparaciones de base líquida vs. citología convencional: adecuación de las muestras y coincidencia de diagnóstico en lesiones orales
Objetivo: Comparar la efectividad de la muestra y la coincidencia
de diagnostico entre preparaciones de base liquida y
frotis convencionales en lesiones orales, y probar la viabilidad
de la prueba inmuno-citoquimica en preparaciones de base
liquida de lesiones de carcinoma oral. Material y Metodos: Se
obtuvieron muestras de 44 pacientes. Primeramente se prepararon
frotis convencionales, usando un dispositivo cytobrush.
A continuacion se sumergio el cepillo que contenia el material
residual en un liquido conservante. La muestra en el mismo
fue procesada de acuerdo con las indicaciones del fabricante
(AutoCyte, Inc. Elon College, North Carolina, USA). Se
tineron preparaciones de ambas tecnicas de acuerdo con el
metodo de Papanicolaou. Para la prueba inmuno-citoquimica
se usaron conjuntamente AE1/AE3 (Dako, CA, USA) para
las lesiones de carcinoma oral, de acuerdo con el metodo de
la Estreptovidina-biotina-peroxidasa. Se uso la prueba exacta
de Fisher; fijandose la probabilidad significativa en p . 0.05.
Resultados: Ambas tecnicas coincidieron en el diagnostico
citologico en todos los casos donde se uso una muestra adecuada;
en 3 casos el frotis convencional mostro hipocelularidad y, por
lo tanto, resulto inadecuado para el analisis. En el analisis
de muestras, la citologia de base liquida mostro una mejora
general estadisticamente significativa), de un 41% en espesura
de frotis y de un 66% en la distribucion de celulas (p . 0.05),
ademas de una reduccion en la superposicion de celulas y la
presencia de sangre (p . 0.05). La morfologia celular se observó mejor en las preparaciones de base líquida. Las reacciones de la
prueba inmuno-citoquímica fueron positivas en todos los casos
de malignidad, siendo especialmente clara la observación de
células inmuno-marcadas. Conclusión: Tanto las preparaciones
de base líquida como los frotis convencionales son dignos de
confianza desde el punto de vista del diagnóstico; el método de
base líquida mostró una mejora general en la preservación de
muestras, adecuación de ejemplares, observación de morfología
celular y reproducibilidad.Objective: To compare specimen adequacy and diagnostic
agreement between liquid-based preparations and conventional
smears in oral lesions, and to test the viability of immunocytochemical
assay in liquid-based preparations from oral carcinoma
lesions. Material and Methods: Samples were collected from
44 patients. Conventional smears were prepared first, using a
cytobrush device. Then the brush, containing the residual material,
was immersed in a preservative fluid. The sample in the
preservative fluid was processed according to the manufacturer
directions (AutoCyte, Inc. Elon College, North Carolina, USA).
Slides of both techniques were stained by Papanicolaou method.
For immunocytochemical assay, a cytokeratin pool AE1/AE3
(Dako, CA, USA) was applied in liquid-based preparations
from oral carcinoma lesions following the Streptavidin-biotinperoxidase
method. Fisher's exact test was used; significance
was set for p = 0.05.
Results: Both techniques agreed on cytologic diagnosis in every
case they yielded an adequate specimen; in 3 cases conventional
smear resulted in hypocellularity and therefore inadequate for
analysis. On specimen analysis, the liquid-based cytology demonstrated
a statistically significant, 41% overall improvement
in smear thickness and 66% in cell distribution (p = 0.05), and a
reduction in cell overlapping and presence of blood (p = 0.05).
The cell morphology was better visualized in the liquid-based
preparations. The immunocytochemical assay reactions were
positive in all malignant cases, the visualization of the immu-nostained cells being especially clear.
Conclusion: Both, the liquid-based preparation and conventional
smear, are diagnostically reliable; the liquid-based method
showed an overall improvement on sample preservation, specimen
adequacy, visualization of cell morphology and reproducibility
The hydration structure of Cu2+: More tetrahedral than octahedral?
A comprehensive multi-technique approach has been used to address the controversial question of the preferred geometric form of the Cu2+ aqua-ion hydration shell. A combination of H/D isotopic substitution neutron scattering and X-ray scattering has been used to refine atomistic models of 0.5 m and 2.0 m solutions of Cu(ClO4)2, that have also been constrained to simultaneously reproduce detailed local structure information about the cation environment obtained by X-ray Absorption spectroscopy. The adoption of the Empirical Potential Structure Refinement (EPSR) technique as a single unified analytical framework minimises the chances for biasing the result in favour of a specific pre-conceived outcome. The results are consistent with an average coordination for each Cu2+ ion of 4.5 ± 0.6 water molecules that matches the more recent picture of five-fold coordination in a 2.0 m solution, but interestingly this combined study highlights that the preferred local geometry of the ion sites is found to have a mixed character of tetrahedral, trigonal bipyramidal and octahedral components. A further point to note is that this new model adds support to a largely ignored result in the literature relating to the linear electric field effect induced g-shifts observed in the electron paramagnetic resonance spectra of glassy Cu2+ complexes (Peisach and Mims, Chem. Phys. Lett., 1976, 37, 307–310) that first highlighted the importance of tetrahedral distortions in the cation's hydration shell structure
Searches for gravitational waves associated with pulsar glitches using a coherent network algorithm
Pulsar glitches are a potential source of gravitational waves for current and
future interferometric gravitational wave detectors. Some pulsar glitch events
were observed by radio and X-ray telescopes during the fifth LIGO science run.
It is expected that glitches from these same pulsars should also be seen in the
future. We carried out Monte Carlo simulations to estimate the sensitivity of
possible gravitational wave signals associated with a pulsar glitch using a
coherent network analysis method. We show the detection efficiency and evaluate
the reconstruction accuracy of gravitational waveforms using a matched filter
analysis on the estimated gravitational waveforms from the coherent analysis
algorithm.Comment: submitted to CQ
Inverse-perovskites A3BO (A = Sr, Ca, Eu/B = Pb, Sn) : a platform for control of Dirac and Weyl fermions
This work was partly supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (Grant Nos. 24224010, 15K13523, JP15H05852, JP15K21717, and 17H01140), EPSRC (Grant No. EP/P024564/1), and the Alexander von Humboldt FoundationBulk Dirac electron systems have attracted strong interest for their unique magnetoelectric properties as well as their close relation to topological (crystalline) insulators. Recently, the focus has been shifting toward the role of magnetism in stabilizing Weyl fermions as well as chiral surface states in such materials. While a number of nonmagnetic systems are well known, experimental realizations of magnetic analogs are a key focus of current studies. Here, we report on the physical properties of a large family of inverse perovskites A3BO (A = Sr, Ca, Eu/B = Pb, Sn) in which we are able to not only stabilize 3D Dirac electrons at the Fermi energy but also chemically control their properties. In particular, it is possible to introduce a controllable Dirac gap, change the Fermi velocity, tune the anisotropy of the Dirac dispersion, and—crucially—introduce complex magnetism into the system. This family of compounds therefore opens up unique possibilities for the chemical control and systematic investigation of the fascinating properties of such topological semimetals.Publisher PDFPeer reviewe
Extracting structural information of Au colloids at ultra-dilute concentrations: Identification of growth during nanoparticle immobilization
Sol-immobilization is increasingly used to achieve supported metal nanoparticles (NPs) with controllable
size and shape; it affords a high degree of control of the metal particle size and yields a narrow particle
size distribution. Using state-of-the-art beamlines, we demonstrate how X-ray absorption fine structure
(XAFS) techniques are now able to provide accurate structural information on nano-sized colloidal Au
solutions at mM concentrations. This study demonstrates: (i) the size of Au colloids can be accurately
tuned by adjusting the temperature of reduction, (ii) Au concentration, from 50 mM to 1000 mM, has little
influence on the average size of colloidal Au NPs in solution and (iii) the immobilization step is
responsible for significant growth in Au particle size, which is further exacerbated at increased Au
concentrations. The work presented demonstrates that an increased understanding of the primary steps
in sol-immobilization allows improved optimization of materials for catalytic application
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