1,421 research outputs found
Peculiar mean velocity profiles within a porous bed of an open channel
Peer reviewedPublisher PD
Polar Dynamics at the Jahn-Teller Transition in Ferroelectric GaV4S8
We present a dielectric spectroscopy study of the polar dynamics linked to
the orbitally driven ferroelectric transition in the skyrmion host GaV4S8. By
combining THz and MHz-GHz spectroscopy techniques, we succeed in detecting the
relaxational dynamics arising from coupled orbital and polar fluctuations in
this material and traced its temperature dependence in the paraelectric as well
as in the ferroelectric phase. The relaxation time significantly increases when
approaching the critical temperature from both sides of the transition. It is
natural to assume that these polar fluctuations map the orbital dynamics at the
Jahn-Teller transition. Due to the first-order character of the
orbital-ordering transition, the relaxation time shows an enormous jump of
about five orders of magnitude at the polar and structural phase transition.Comment: 5 pages, 4 figure
Polar and magnetic order in GaV4Se8
In the present work, we provide results from specific heat, magnetic
susceptibility, dielectric constant, ac conductivity, and electrical
polarization measurements performed on the lacunar spinel GaV4Se8. With
decreasing temperature, we observe a transition from the paraelectric and
paramagnetic cubic state into a polar, probably ferroelectric state at 42 K
followed by magnetic ordering at 18 K. The polar transition is likely driven by
the Jahn-Teller effect due to the degeneracy of the V4 cluster orbitals. The
excess polarization arising in the magnetic phase indicates considerable
magnetoelectric coupling. Overall, the behavior of GaV4Se8 in many respects is
similar to that of the skyrmion host GaV4S8, exhibiting a complex interplay of
orbital, spin, lattice, and polar degrees of freedom. However, its dielectric
behavior at the polar transition markedly differs from that of the Jahn-Teller
driven ferroelectric GeV4S8, which can be ascribed to the dissimilar electronic
structure of the Ge compound.Comment: 7 pages, 6 figures. Revised version according to suggestions of
referee
Turbulence structure of open channel flows over permeable and impermeable beds : A comparative study
Peer reviewedPublisher PD
Quantum rainbow scattering at tunable velocities
Elastic scattering cross sections are measured for lithium atoms colliding
with rare gas atoms and SF6 molecules at tunable relative velocities down to
~50 m/s. Our scattering apparatus combines a velocity-tunable molecular beam
with a magneto-optic trap that provides an ultracold cloud of lithium atoms as
a scattering target. Comparison with theory reveals the quantum nature of the
collision dynamics in the studied regime, including both rainbows as well as
orbiting resonances
Corrigendum to “Femur associated with the Deep Skull from the West Mouth of the Niah Caves (Sarawak, Malaysia)” [Journal of Human Evolution 127 (2019) 133–148](S0047248418301520)(10.1016/j.jhevol.2018.12.008)
In the original analyses of the Deep Skull femoral midshaft section, anteroposterior (AP) and mediolateral (ML) orientations were transposed, that is, AP and ML second moments of area, as well as linear external breadths, were reversed. Cross-sectional properties were also calculated using an approximate method employing radiographic breadths, while a more accurate method using actual periosteal and endosteal contours is possible given that a complete section is available (MomentMacro; https://fae.johnshopkins.edu/chris-ruff/). When this method is applied and orientations are corrected, the following properties are obtained. C.B. Ruff has been added to the author list of this article as he carried out the analyses that resulted in the new cross-sectional properties. [Table presented] The authors apologize for the original error
Completely splittable representations of affine Hecke-Clifford algebras
We classify and construct irreducible completely splittable representations
of affine and finite Hecke-Clifford algebras over an algebraically closed field
of characteristic not equal to 2.Comment: 39 pages, v2, added a new reference with comments in section 4.4,
added two examples (Example 5.4 and Example 5.11) in section 5, mild
corrections of some typos, to appear in J. Algebraic Combinatoric
Descriptive Analysis of Emancipated Foster Youth Seeking Mental Health Treatment
Current and former foster youth experience increased risk for behavioral, cognitive, and emotional problems due to maltreatment and experiences in foster care. Nonetheless, research indicates a gap between the need for mental health services and service use. The current study describes a sample of self-referring, emancipated foster youth seeking long-term psychotherapy to understand reasons youth seek psychotherapy. This study further compares a subset of youths’ data with reports collected from respective therapists to examine differences in perceptions of symptoms
Structural Fluctuations in the Spin Liquid State of Tb2Ti2O7
High resolution X-ray scattering measurements on single crystal Tb2Ti2O7
reveal finite structural correlations at low temperatures. This geometrically
frustrated pyrochlore is known to exhibit a spin liquid, or cooperative
paramagnetic state, at temperatures below ~ 20 K. Parametric studies of
structural Bragg peaks appropriate to the Fdm space group of Tb2Ti2O7
reveal substantial broadening and peak intensity reduction in the temperature
regime 20 K to 300 mK. We also observe a small, anomalous lattice expansion on
cooling below a density maximum at ~ 18 K. These measurements are consistent
with the development of fluctuations above a cooperative Jahn-Teller,
cubic-tetragonal phase transition at very low temperatures.Comment: 5 pages, 4 figures, submitted for publicatio
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