72 research outputs found
Limit on sterile neutrino contribution from the Mainz Neutrino Mass Experiment
The recent analysis of the normalization of reactor antineutrino data, the
calibration data of solar neutrino experiments using gallium targets, and the
results from the neutrino oscillation experiment MiniBooNE suggest the
existence of a fourth light neutrino mass state with a mass of O(eV), which
contributes to the electron neutrino with a sizable mixing angle. Since we know
from measurements of the width of the Z0 resonance that there are only three
active neutrinos, a fourth neutrino should be sterile (i.e., interact only via
gravity). The corresponding fourth neutrino mass state should be visible as an
additional kink in beta-decay spectra. In this work the phase II data of the
Mainz Neutrino Mass Experiment have been analyzed searching for a possible
contribution of a fourth light neutrino mass state. No signature of such a
fourth mass state has been found and limits on the mass and the mixing of this
fourth mass states are derived
APLIKASI TEORI PERILAKU TERENCANA: NIAT MELAKUKAN PHYSICAL EXERCISE (LATIHAN FISIK) PADA REMAJA DI SURABAYA
Alasan utama untuk rnengangkat topik ini dalarn penelitian ia1ah penulis berrnaksud untuk rneneliti variabel-variabel yang rnelatarbelakangi perilaku physical exercise yang dilakukan remaja di Surabaya. Tujuannya, peneliti ingin rnenguji apakah ada hubungan antara attitude towards behavior (A TB), subjective norm (SN), dan perceived behavioral control (PBC), baik secara bersama-sama maupun secara parsial, dengan niat berperilaku physical exercise (latihan fisik) pada remaja di Surabaya. Metode angket digunakan dalarn penelitian ini, rnenggunakan teknik penskalaan sernantik diferensial. Rernaja baik pria dan wanita (N=336) di kota Surabaya berpartisipasi dalarn penelitian ini. Hasil uji hipotesis rnenujukkan bahwa : {a). Terdapat hubungan yang signifikan antara ATB, SN, dan PBC, secara bersarna-sarna terhadap niat rnelakukan Physical exersice pada remaja (F = 14.233; p = 0,000). Hasil korelasi parsial menunjukkan ATB, dan SN menjadi prediktor paling kuat terhadap niat melaku.kan Physical Exercise, sedangkan PBC tidak
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Nonequilibrium structural dynamics of nanoparticles in LiNi(1/2)Mn(3/2)O4 cathode under operando conditions.
We study nonequilibrium structural dynamics in LiNi1/2Mn3/2O4 spinel cathode material during fast charge/discharge under operando conditions using coherent X-rays. Our in situ measurements reveal a hysteretic behavior of the structure upon cycling and we directly observe the interplay between different transformation mechanisms: solid solution and two-phase reactions at the single nanoparticle level. For high lithium concentrations solid solution is observed upon both charge and discharge. For low lithium concentration, we find concurrent solid solution and two-phase reactions upon charge, while a pure two-phase reaction is found upon discharge. A delithiation model based on an ionic blockade layer on the particle surface is proposed to explain the distinct structural transformation mechanisms in nonequilibrium conditions. This study addresses the controversy of why two-phase materials show exemplary kinetics and opens new avenues to understand fundamental processes underlying charge transfer, which will be invaluable for developing the next generation battery materials
Strain-induced orbital energy shift in antiferromagnetic RuO2 revealed by resonant elastic x-ray scattering
In its ground state, RuO2 was long thought to be an ordinary metallic
paramagnet. Recent neutron and x-ray diffraction revealed that bulk RuO2 is an
antiferromagnet (AFM) with TN above 300 K. Furthermore, epitaxial strain
induces novel superconductivity in thin films of RuO2 below 2 K. Here, we
present a resonant elastic x-ray scattering (REXS) study at the Ru L2 edge of
the strained RuO2 films exhibiting the strain-induced superconductivity. We
observe an azimuthal modulation of the 100 Bragg peak consistent with canted
AFM found in bulk. Most notably, in the strained films displaying novel
superconductivity, we observe a ~1 eV shift of the Ru eg orbitals to a higher
energy. The energy shift is smaller in thicker, relaxed films and films with a
different strain direction. Our results provide further evidence of the utility
of epitaxial strain as a tuning parameter in complex oxides.Comment: 20 pages, 3 main figures, 3 supplementary figure
Disorder Dynamics in Battery Nanoparticles During Phase Transitions Revealed by Operando Single-Particle Diffraction
Structural and ion-ordering phase transitions limit the viability of
sodium-ion intercalation materials in grid scale battery storage by reducing
their lifetime. However, the combination of phenomena in nanoparticulate
electrodes creates complex behavior that is difficult to investigate,
especially on the single nanoparticle scale under operating conditions. In this
work, operando single-particle x-ray diffraction (oSP-XRD) is used to observe
single-particle rotation, interlayer spacing, and layer misorientation in a
functional sodium-ion battery. oSP-XRD is applied to
Na[NiMn]O, an archetypal P2-type sodium-ion
positive electrode material with the notorious P2-O2 phase transition induced
by sodium (de)intercalation. It is found that during sodium extraction, the
misorientation of crystalline layers inside individual particles increases
before the layers suddenly align just prior to the P2-O2 transition. The
increase in the long-range order coincides with an additional voltage plateau
signifying a phase transition prior to the P2-O2 transition. To explain the
layer alignment, a model for the phase evolution is proposed that includes a
transition from localized to correlated Jahn-Teller distortions. The model is
anticipated to guide further characterization and engineering of sodium-ion
intercalation materials with P2-O2 type transitions. oSP-XRD therefore opens a
powerful avenue for revealing complex phase behavior in heterogeneous
nanoparticulate systems.Comment: 23 pages, 4 main figures, 9 supplemental figure
Scientific Opportunities with an X-ray Free-Electron Laser Oscillator
An X-ray free-electron laser oscillator (XFELO) is a new type of hard X-ray
source that would produce fully coherent pulses with meV bandwidth and stable
intensity. The XFELO complements existing sources based on self-amplified
spontaneous emission (SASE) from high-gain X-ray free-electron lasers (XFEL)
that produce ultra-short pulses with broad-band chaotic spectra. This report is
based on discussions of scientific opportunities enabled by an XFELO during a
workshop held at SLAC on June 29 - July 1, 2016Comment: 21 pages, 12 figure
Real-space imaging of polar and elastic nano-textures in thin films via inversion of diffraction data
Exploiting the emerging nanoscale periodicities in epitaxial, single-crystal
thin films is an exciting direction in quantum materials science: confinement
and periodic distortions induce novel properties. The structural motifs of
interest are ferroelastic, ferroelectric, multiferroic, and, more recently,
topologically protected magnetization and polarization textures. A critical
step towards heterostructure engineering is understanding their nanoscale
structure, best achieved through real-space imaging. X-ray Bragg coherent
diffractive imaging visualizes sub-picometer crystalline displacements with
tens of nanometers spatial resolution. Yet, it is limited to objects spatially
confined in all three dimensions and requires highly coherent, laser-like
x-rays. Here we lift the confinement restriction by developing real-space
imaging of periodic lattice distortions: we combine an iterative phase
retrieval algorithm with unsupervised machine learning to invert the diffuse
scattering in conventional x-ray reciprocal-space mapping into real-space
images of polar and elastic textures in thin epitaxial films. We first
demonstrate our imaging in PbTiO3/SrTiO3 superlattices to be consistent with
published phase-field model calculations. We then visualize strain-induced
ferroelastic domains emerging during the metal-insulator transition in Ca2RuO4
thin films. Instead of homogeneously transforming into a low-temperature
structure (like in bulk), the strained Mott insulator splits into nanodomains
with alternating lattice constants, as confirmed by cryogenic scanning
transmission electron microscopy. Our study reveals the type, size,
orientation, and crystal displacement field of the nano-textures. The
non-destructive imaging of textures promises to improve models for their
dynamics and enable advances in quantum materials and microelectronics
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