6,533 research outputs found
Transpressional Rupture Cascade of the 2016 Mw 7.8 Kaikoura Earthquake, New Zealand
Large earthquakes often do not occur on a simple planar fault but involve rupture of multiple geometrically complex faults. The 2016 M 7.8 Kaikoura earthquake, New Zealand, involved the rupture of at least 21 faults, propagating from southwest to northeast for about 180 km. Here we combine space geodesy and seismology techniques to study subsurface fault geometry, slip distribution, and the kinematics of the rupture. Our finite-fault slip model indicates that the fault motion changes from predominantly right-lateral slip near the epicenter to transpressional slip in the northeast with a maximum coseismic surface displacement of about 10 m near the intersection between the Kekerengu and Papatea faults. Teleseismic back projection imaging shows that rupture speed was overall slow (1.4 km/s) but faster on individual fault segments (approximately 2 km/s) and that the conjugate, oblique-reverse, north striking faults released the largest high-frequency energy. We show that the linking Conway-Charwell faults aided in propagation of rupture across the step over from the Humps fault zone to the Hope fault. Fault slip cascaded along the Jordan Thrust, Kekerengu, and Needles faults, causing stress perturbations that activated two major conjugate faults, the Hundalee and Papatea faults. Our results shed important light on the study of earthquakes and seismic hazard evaluation in geometrically complex fault systems.
Tracing magnetism and pairing in FeTe-based systems
In order to examine the interplay between magnetism and superconductivity, we
monitor the non- superconducting chalcogenide FeTe and follow its transitions
under insertion of oxygen, doping with Se and vacancies of Fe using
spin-polarized band structure methods (LSDA with GGA) starting from the
collinear and bicollinear magnetic arrangements. We use a supercell of Fe8Te8
as our starting point so that it can capture local changes in magnetic moments.
The calculated values of magnetic moments agree well with available
experimental data while oxygen insertions lead to significant changes in the
bicollinear or collinear magnetic moments. The total energies of these systems
indicate that the collinear-derived structure is the more favorable one prior
to a possible superconducting transition. Using a 8-site Betts-cluster-based
lattice and the Hubbard model, we show why this structure favors electron or
hole pairing and provides clues to a common understanding of charge and spin
pairing in the cuprates, pnictides and chalcogenides
A filament of dark matter between two clusters of galaxies
It is a firm prediction of the concordance Cold Dark Matter (CDM)
cosmological model that galaxy clusters live at the intersection of large-scale
structure filaments. The thread-like structure of this "cosmic web" has been
traced by galaxy redshift surveys for decades. More recently the Warm-Hot
Intergalactic Medium (WHIM) residing in low redshift filaments has been
observed in emission and absorption. However, a reliable direct detection of
the underlying Dark Matter skeleton, which should contain more than half of all
matter, remained elusive, as earlier candidates for such detections were either
falsified or suffered from low signal-to-noise ratios and unphysical
misalignements of dark and luminous matter. Here we report the detection of a
dark matter filament connecting the two main components of the Abell 222/223
supercluster system from its weak gravitational lensing signal, both in a
non-parametric mass reconstruction and in parametric model fits. This filament
is coincident with an overdensity of galaxies and diffuse, soft X-ray emission
and contributes mass comparable to that of an additional galaxy cluster to the
total mass of the supercluster. Combined with X-ray observations, we place an
upper limit of 0.09 on the hot gas fraction, the mass of X-ray emitting gas
divided by the total mass, in the filament.Comment: Nature, in pres
Optical signature of symmetry variations and spin-valley coupling in atomically thin tungsten dichalcogenides
Motivated by the triumph and limitation of graphene for electronic
applications, atomically thin layers of group VI transition metal
dichalcogenides are attracting extensive interest as a class of graphene-like
semiconductors with a desired band-gap in the visible frequency range. The
monolayers feature a valence band spin splitting with opposite sign in the two
valleys located at corners of 1st Brillouin zone. This spin-valley coupling,
particularly pronounced in tungsten dichalcogenides, can benefit potential
spintronics and valleytronics with the important consequences of spin-valley
interplay and the suppression of spin and valley relaxations. Here we report
the first optical studies of WS2 and WSe2 monolayers and multilayers. The
efficiency of second harmonic generation shows a dramatic even-odd oscillation
with the number of layers, consistent with the presence (absence) of inversion
symmetry in even-layer (odd-layer). Photoluminescence (PL) measurements show
the crossover from an indirect band gap semiconductor at mutilayers to a
direct-gap one at monolayers. The PL spectra and first-principle calculations
consistently reveal a spin-valley coupling of 0.4 eV which suppresses
interlayer hopping and manifests as a thickness independent splitting pattern
at valence band edge near K points. This giant spin-valley coupling, together
with the valley dependent physical properties, may lead to rich possibilities
for manipulating spin and valley degrees of freedom in these atomically thin 2D
materials
Economic factors influencing zoonotic disease dynamics: demand for poultry meat and seasonal transmission of avian influenza in Vietnam
While climate is often presented as a key factor influencing the seasonality of diseases, the importance of anthropogenic factors is less commonly evaluated. Using a combination of methods-wavelet analysis, economic analysis, statistical and disease transmission modelling-we aimed to explore the influence of climatic and economic factors on the seasonality of H5N1 Highly Pathogenic Avian Influenza in the domestic poultry population of Vietnam. We found that while climatic variables are associated with seasonal variation in the incidence of avian influenza outbreaks in the North of the country, this is not the case in the Centre and the South. In contrast, temporal patterns of H5N1 incidence are similar across these 3 regions: periods of high H5N1 incidence coincide with Lunar New Year festival, occurring in January-February, in the 3 climatic regions for 5 out of the 8 study years. Yet, daily poultry meat consumption drastically increases during Lunar New Year festival throughout the country. To meet this rise in demand, poultry production and trade are expected to peak around the festival period, promoting viral spread, which we demonstrated using a stochastic disease transmission model. This study illustrates the way in which economic factors may influence the dynamics of livestock pathogens
Half-Metallic Graphene Nanoribbons
Electrical current can be completely spin polarized in a class of materials
known as half-metals, as a result of the coexistence of metallic nature for
electrons with one spin orientation and insulating for electrons with the
other. Such asymmetric electronic states for the different spins have been
predicted for some ferromagnetic metals - for example, the Heusler compounds-
and were first observed in a manganese perovskite. In view of the potential for
use of this property in realizing spin-based electronics, substantial efforts
have been made to search for half-metallic materials. However, organic
materials have hardly been investigated in this context even though
carbon-based nanostructures hold significant promise for future electronic
device. Here we predict half-metallicity in nanometre-scale graphene ribbons by
using first-principles calculations. We show that this phenomenon is realizable
if in-plane homogeneous electric fields are applied across the zigzag-shaped
edges of the graphene nanoribbons, and that their magnetic property can be
controlled by the external electric fields. The results are not only of
scientific interests in the interplay between electric fields and electronic
spin degree of freedom in solids but may also open a new path to explore
spintronics at nanometre scale, based on graphene
Proactive and politically skilled professionals: What is the relationship with affective occupational commitment?
The aim of this study is to extend research on employee affective commitment in three ways: (1) instead of organizational commitment the focus is on occupational commitment; (2) the role of proactive personality on affective occupational commitment is examined; and (3) occupational satisfaction is examined as a mediator and political skills as moderator in the relationship between proactive personality and affective occupational commitment. Two connected studies, one in a hospital located in the private sector and one in a university located in the public sector, are carried out in Pakistan, drawing on a total sample of over 400 employees. The results show that proactive personality is positively related to affective occupational commitment, and that occupational satisfaction partly mediates the relationship between proactive personality and affective occupational commitment. No effect is found for a moderator effect of political skills in the relationship between proactive personality and affective occupational commitment. Political skills however moderate the relationship between proactive personality and affective organizational commitment
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