683 research outputs found
Earthquake detection capacity of Dense Oceanfloor Network system for Earthquakes and Tsunamis (DONET)
We adopted the Probability-based Magnitude of Completeness (PMC) method and
performed a case analysis of the Nankai Trough, a target region monitored for
future megathrust earthquakes. JAMSTEC (Japan Agency for Marine-Earth Science
and Technology) has created a seismicity catalog that includes events in this
region observed by DONET. Using seismicity data for 2015-2019, we found
spatiotemporal variability of completeness magnitude Mp. Mp was lower than 1 in
one of the areas where stations are densely deployed, whereas Mp was larger
than 2 at the periphery and outside of the DONET area. We then evaluated the
temporal evolution of Mp, highlighting how the failure of sets of observing
stations influenced Mp if not repaired. Stations are aggregated around the 12
science nodes (hubs that connect the stations) and connected through the two
oceanfloor backbone cables to JAMSTEC. We explored the possible use of PMC as a
tool with simulation computation of node malfunction. A simulation showed that
completeness estimates in the area near failure nodes were about 1 magnitude
larger. If such failure occurred for nodes near the region which straddles the
rupture zones of the previous Tonankai and Nankai earthquakes in 1940's, it
would most pronouncedly affect earthquake monitoring among nodes' failures. It
is desirable to repair these nodes or replace with new ones when their
malfunction occurs. We then demonstrated an example of how to use Mp
information as prior knowledge to seismicity-related studies. We used the b
value of the Gutenberg-Richter distribution, and computed it taking Mp into
consideration. We found that the spatial and temporal changes in b were
strongly correlated to the magnitude-6 class slow slip that grew over two years
on the Nankai Trough plate boundary, indicating the b value as a proxy that can
help to image stress heterogeneity when there is a slow slip event.Comment: 6 figure
Herbicide retention by mulching in soybean, under no-tillage system
O objetivo deste trabalho foi avaliar a retenção pela palhada, das misturas imazaquin+pendimethalin e sulfentrazone+metribuzin, aplicadas em pré-emergência, no sistema de plantio direto de soja. Os experimentos foram conduzidos na sede do lAPAR em Londrina-PR, na safra 1998/99, utilizando-se palha de aveia-preta (Avena strigosa) como cobertura morta. O delineamento dos experimentos (em número de dois), foi o de blocos ao acaso com cinco repetições. Os tratamentos foram constituídos pelas doses de herbicidas: zero; 0,5 N; N; 1,5 N e 2 N, sendo N a dose normal recomendada para a cultura (no caso, 150 g/ha de imazaquin + 1200 g/ha de pendimethalin e 350 g/ha de sulfentrazone + 360 g/ha de metribuzin). Utilizou-se a cultivar de soja FT-2000. Os herbicidas foram aplicados com pulverizador de precisão propelido a CO2, munido com barra de seis bicos Teejet Flat Spray em leque, 80.02, distanciados 50 em entre sí, vazão de 200 l/ha. Vinte e quatro horas após a aplicação dos herbicidas, os experimentos receberam 48,3 mm de lâmina de água. No dia seguinte, foram amostrados palha e solo em todas as parcelas para análise cromatográfica de resíduos. ôs resultados mostraram que a lâmina de água promoveu a lixiviação de praticamente todo o imazaquin da palha para o solo, o que não ocorreu com o pendimethalin, que ficou todo retido na palha. O sulfentrazone também foi lixiviado para o solo, sendo que 50% do metribuzin aplicado foi detectado no solo após a chuva. The objective of this trial was to study the mulch retention of the herbicide mixtures imazaquin + pendimethalin and sulfentrazone + metribuzin applied in pre-emergence for soybean under no-tillage system. The experiment was settled in Londrina-PR, Brazil, with black oat (Avena strigosa) mulch. A randomized complete block design was used. The treatrnents comprised the following rates of herbicides: zero, 0.5 N, 1.0 N, 1.5 N and 2.0 N (N=normal rate of the herbicide). ln the present study, N=150 g/ha imazaquin + 1200 g/ha pendimethalin and 350 g/ha sulfentrazone + 360 g/ha metribuzin. After twenty four hours ofherbicide applications, 48.3 mm ofwater was applied in the experiments. ln the next day, samples ofsoil and straw were taken for chromatographic analysis purposes. The results showed that 100% of imazaquin and sulfentrazone leached from the straw to the soil. Approximately 50% of metribuzin and 100% of pendimethalin were retained by the oat straw.
Statin Therapy and Risk of Developing Type 2 Diabetes: A Meta-Analysis
OBJECTIVE: Although statin therapy reduces cardiovascular risk, its relationship with the development of diabetes is controversial. The first study (West of Scotland Coronary Prevention Study [WOSCOPS]) that evaluated this association reported a small protective effect but used nonstandardized criteria for diabetes diagnosis. However, results from subsequent hypothesis-testing trials have been inconsistent. The aim of this meta-analysis is to evaluate the possible effect of statin therapy on incident diabetes. RESEARCH DESIGN AND METHODS: A systematic literature search for randomized statin trials that reported data on diabetes through February 2009 was conducted using specific search terms. In addition to the hypothesis-generating data from WOSCOPS, hypothesis-testing data were available from the Heart Protection Study (HPS), the Long-Term Intervention with Pravastatin in Ischemic Disease (LIPID) Study, the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT), the Justification for the Use of Statins in Prevention: an Intervention Trial Evaluating Rosuvastatin (JUPITER), and the Controlled Rosuvastatin Multinational Study in Heart Failure (CORONA), together including 57,593 patients with mean follow-up of 3.9 years during which 2,082 incident diabetes cases accrued. Weighted averages were reported as risk ratios (RRs) with 95% CIs using a random-effects model. Statistical heterogeneity scores were assessed with the Q and I2 statistic.RESULTS In the meta-analysis of the hypothesis-testing trials, we observed a small increase in diabetes risk (RR 1.13 [95% CI 1.03–1.23]) with no evidence of heterogeneity across trials. However, this estimate was attenuated and no longer significant when the hypothesis-generating trial WOSCOPS was included (1.06 [0.93–1.25]) and also resulted in significant heterogeneity (Q 11.8 [5 d.f.], P = 0.03, I2 = 57.7%). CONCLUSIONS: Although statin therapy greatly lowers vascular risk, including among those with and at risk for diabetes, the relationship of statin therapy to incident diabetes remains uncertain. Future statin trials should be designed to formally address this issue
Origin of the Weak Pseudo-gap Behaviors in Na_{0.35}CoO_2: Absence of Small Hole Pockets
We analyze the ``normal electronic states'' of Na_{0.35}CoO_2 based on the
effective d-p model with full d-orbital freedom using the fluctuation-exchange
(FLEX) approximation. They sensitively depend on the topology of the Fermi
surfaces, which changes as the crystalline electric splitting (CES) due to the
trigonal deformation. We succeed in reproducing the weak pseudo-gap behaviors
in the density of states (DOS) and in the uniform magnetic susceptibility below
300K, assuming that six small hole-pockets predicted by LDA band calculations
are absent. When they exist, on the contrary, then ``anti-pseudo-gap
behaviors'' should inevitably appear. Thus, the present study strongly supports
the absence of the small hole-pockets in Na_{0.35}CoO_2, as reported by recent
ARPES measurements. A large Fermi surface around the \Gamma-point would account
for the superconductivity in water-intercalated samples.Comment: 5pages, to appear in J. Phys. Soc. Jpn. Vol.74 (2005) No.
Probing ultrafast spin-relaxation and precession dynamics in a cuprate Mott insulator with 7-fs optical pulses
A charge excitation in a two-dimensional Mott insulator is strongly coupled
with the surrounding spins, which is observed as magnetic-polaron formations of
doped carriers and a magnon sideband in the Mott-gap transition spectrum.
However, the dynamics related to the spin sector are difficult to measure.
Here, we show that pump-probe reflection spectroscopy with 7-fs laser pulses
can detect the optically induced spin dynamics in NdCuO, a cuprate Mott
insulator. The bleaching signal at the Mott-gap transition is enhanced at
18 fs, which corresponds to the spin-relaxation time in magnetic-polaron
formations and is characterized by the exchange interaction. More importantly,
ultrafast coherent oscillations appear in the time evolutions of the
reflectivity changes, and their frequencies (1400-2700 cm) are equal to
the probe energy measured from the Mott-gap transition peak. These oscillations
originate from interferences between charge excitations with two magnons and
provide direct evidence for charge-spin coupling.Comment: 20 pages including 4 figures (Supplementary materials: 11 pages
including 4 figures
Flat bands in topological media
Topological media are systems whose properties are protected by topology and
thus are robust to deformations of the system. In topological insulators and
superconductors the bulk-surface and bulk-vortex correspondence gives rise to
the gapless Weyl, Dirac or Majorana fermions on the surface of the system and
inside vortex cores. Here we show that in gapless topological media, the
bulk-surface and bulk-vortex correspondence is more effective: it produces
topologically protected gapless fermions without dispersion -- the flat band.
Fermion zero modes forming the flat band are localized on the surface of
topological media with protected nodal lines and in the vortex core in systems
with topologically protected Fermi points (Weyl points). Flat band has an
extremely singular density of states, and we show that this property may give
rise in particular to surface superconductivity which could exist even at room
temperature.Comment: 9 pages, 5 figures, version to appear in JETP Letter
Deformation of Electronic Structures Due to CoO6 Distortion and Phase Diagrams of NaxCoO2.yH2O
Motivated by recently reported experimental phase diagrams, we study the
effects of CoO6 distortion on the electronic structure in NaxCoO2.yH2O. We
construct the multiband tight-binding model by employing the LDA result.
Analyzing this model, we show the deformation of band dispersions and
Fermi-surface topology as functions of CoO2-layer thickness. Considering these
results together with previous theoretical ones, we propose a possible
schematic phase diagram with three successive phases: the extended s-wave
superconductivity (SC), the magnetic order, and the spin-triplet SC phases when
the Co valence number s is +3.4. A phase diagram with only one phase of
spin-triplet SC is also proposed for the s=+3.5 case.Comment: 4 pages, 5 figure
Topology of Andreev Bound States with Flat Dispersion
A theory of dispersionless Andreev bound states on surfaces of time-reversal
invariant unconventional superconductors is presented. The generalized
criterion for the dispersionless Andreev bound state is derived from the
bulk-edge correspondence, and the chiral spin structure of the dispersionless
Andreev bound states is argued from which the Andreev bound state is
stabilized. Then we summarize the criterion in a form of index theorems. The
index theorems are proved in a general framework to certify the bulk-edge
correspondence. As concrete examples, we discuss (i) dxy-wave superconductor
(ii) px-wave superconductor, and (iii) noncentrosymmetric superconductors. In
the last example, we find a peculiar time-reversal invariant Majorana fermion.
The time-reversal invariant Majorana fermion shows an unusual response to the
Zeeman magnetic field, which can be used to identify it experimentally.Comment: 56 pages, 11 figures, references are adde
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