13,968 research outputs found
Prediction of vertical bearing capacity of waveform micropile
This study proposes a predictive equation for bearing capacity considering the behaviour characteristics of a waveform micropile that can enhance the bearing capacity of a conventional micropile. The bearing capacity of the waveform micropile was analysed by a three-dimensional numerical model with soil and pile conditions obtained from the field and centrifuge tests. The load-transfer mechanism of the waveform micropile was revealed by the numerical analyses, and a new predictive equation for the bearing capacity was proposed. The bearing capacities of the waveform micropile calculated by the new equation were comparable with those measured from the field and centrifuge tests. This validated a prediction potential of the new equation for bearing capacity of waveform micropiles
Putative spin liquid in the triangle-based iridate BaIrTiO
We report on thermodynamic, magnetization, and muon spin relaxation
measurements of the strong spin-orbit coupled iridate BaIrTiO,
which constitutes a new frustration motif made up a mixture of edge- and
corner-sharing triangles. In spite of strong antiferromagnetic exchange
interaction of the order of 100~K, we find no hint for long-range magnetic
order down to 23 mK. The magnetic specific heat data unveil the -linear and
-squared dependences at low temperatures below 1~K. At the respective
temperatures, the zero-field muon spin relaxation features a persistent spin
dynamics, indicative of unconventional low-energy excitations. A comparison to
the isostructural compound BaRuTiO suggests that a concerted
interplay of compass-like magnetic interactions and frustrated geometry
promotes a dynamically fluctuating state in a triangle-based iridate.Comment: Physical Review B accepte
Double polarization hysteresis loop induced by the domain pinning by defect dipoles in HoMnO3 epitaxial thin films
We report on antiferroelectriclike double polarization hysteresis loops in
multiferroic HoMnO3 thin films below the ferroelectric Curie temperature. This
intriguing phenomenon is attributed to the domain pinning by defect dipoles
which were introduced unintentionally during film growth process. Electron
paramagnetic resonance suggests the existence of Fe1+ defects in thin films and
first principles calculations reveal that the defect dipoles would be composed
of oxygen vacancy and Fe1+ defect. We discuss migration of charged point
defects during film growth process and formation of defect dipoles along
ferroelectric polarization direction, based on the site preference of point
defects. Due to a high-temperature low-symmetry structure of HoMnO3, aging is
not required to form the defect dipoles in contrast to other ferroelectrics
(e.g., BaTiO3).Comment: 4 figure
Effects of pressure on the ferromagnetic state of the CDW compound SmNiC2
We report the pressure response of charge-density-wave (CDW) and
ferromagnetic (FM) phases of the rare-earth intermetallic SmNiC2 up to 5.5 GPa.
The CDW transition temperature (T_{CDW}), which is reflected as a sharp
inflection in the electrical resistivity, is almost independent of pressure up
to 2.18 GPa but is strongly enhanced at higher pressures, increasing from 155.7
K at 2.2 GPa to 279.3 K at 5.5 GPa. Commensurate with the sharp increase in
T_{CDW}, the first-order FM phase transition, which decreases with applied
pressure, bifurcates into the upper (T_{M1}) and lower (T_c) phase transitions
and the lower transition changes its nature to second order above 2.18 GPa.
Enhancement both in the residual resistivity and the Fermi-liquid T^2
coefficient A near 3.8 GPa suggests abundant magnetic quantum fluctuations that
arise from the possible presence of a FM quantum critical point.Comment: 5 pages, 5 figure
Electronically highly cubic conditions for Ru in alpha-RuCl3
We studied the local Ru 4d electronic structure of alpha-RuCl3 by means of
polarization dependent x-ray absorption spectroscopy at the Ru-L2,3 edges. We
observed a vanishingly small linear dichroism indicating that electronically
the Ru 4d local symmetry is highly cubic. Using full multiplet cluster
calculations we were able to reproduce the spectra excellently and to extract
that the trigonal splitting of the t2g orbitals is -12 meV, i.e.
negligible as compared to the Ru 4d spin-orbit coupling constant. Consistent
with our magnetic circular dichroism measurements, we found that the ratio of
the orbital and spin moments is 2.0, the value expected for a Jeff = 1/2 ground
state. We have thus shown that as far as the Ru 4d local properties are
concerned, alpha-RuCl3 is an ideal candidate for the realization of Kitaev
physics
Phylogeny and taxonomy of Polyozosia, Sedelnikovaea and Verseghya of the Lecanoraceae (Lecanorales, lichen-forming Ascomycota)
From the combined phylogenetic analysis of multi-locus sequence data of the Lecanoraceae including two nuclear protein-coding markers (RPB2 and RPB1), the internal transcribed spacer and a fragment of the mitochondrial small subunit, found that the originally monotypic eastern Asian genus Verseghya is positioned within the Verseghya-Lecidella-Pyrrhospora clade of the Lecanoraceae and includes one more taxon Verseghya thysanophora widely distributed in Northern Hemisphere.
The genus Lecidella forming the Lecidella-Glaucomaria subclade within the same Verseghya-Lecidella-Pyrrhospora clade of the Lecanoraceae found to have tendency to be polyphyletic after including the recently described eastern Asian taxon Lecidella mandshurica into phylogenetic analysis of the Lecanoraceae. It is shown that Lecidella mandshurica was previously recorded from China sub Lecidella aff. elaeochroma.
The originally monotypic eastern Asian genus Sedelnikovaea forming a monophyletic branch within the Sedelnikovaea-Lecanoropsis subclade and being in out-position to the Rhizoplaca-Protoparmeliopsis s. str. clade of the Lecanoraceae found to include three more taxa, i.e. Sedelnikovaea marginalis, S. pseudogyrophorica, and S. subdiscrepans.
The Eurasian Protoparmeliopsis bolcana, and the eastern Asian P. kopachevskae, are illustrated for the first time as being positioned within the Protopameliopsis branch of the Lecanoraceae, while the South Korean ‘Protoparmeliopsis’ chejuensis found to be positioned in separate monophyletic branch from all other branches of the Rhizoplaca-Protoparmeliopsis s. l. clade of the Lecanoraceae.
The genus Polyozosia A. Massal. as earlier name for the former Myriolecis branch of the Lecanoraceae is accepted as far the type species of the latter genus, i.e. P. poliophaea, found to be positioned within this branch. The Polyozosia robust monophyletic branch is positioned in the outermost position in the Rhizoplaca-Protoparmeliopsis s. str. clade of the Lecanoraceae.
Position and species content of the accepted genera Glaucomaria, Lecanoropsis, Omphalodina, Polyozosia, and Straminella are discussed in separate nrITS and mtSSU, and combined phylogeny based on concatenated sequences of nrITS, mtSSU, RPB2 and RPB1 genes.
Fourty new combinations are proposed: Glaucomaria bicincta, G. carpinea, G. leptyrodes, G. lojkaeana, G. subcarpinea, G. sulphurea, G. swartzii, G. swartzii subsp. caulescens, G. swartzii subsp. nylanderi, Lecanoropsis anopta, L. macleanii, Omphalodina chrysoleuca, O. huashanensis, O. opiniconensis, O. phaedrophthalma, O. pseudistera, Palicella anakeestiicola, Polyozosia albescens, P. andrewii, P. contractula, P. crenulata, P. dispersa, P. hagenii, P. perpruinosa, P. populicola, P. pruinosa, P. reuteri, P. sambuci, P. semipallida, P. straminea, P. thuleana, Sedelnikovaea marginalis, S. pseudogyrophorica, S. subdiscrepans, Straminella bullata, S. burgaziae, S. conizaeoides, S. densa, S. maheui, S. varia, and Verseghya thysanophora. Validation of one name as Polyozosia perpruinosa Fröberg ex S. Y. Kondr. L. Lőkös et Farkas is also proposed
Tailoring a two-dimensional electron gas at the LaAlO3/SrTiO3 (001) interface by epitaxial strain
Recently a metallic state was discovered at the interface between insulating
oxides, most notably LaAlO3 and SrTiO3. Properties of this two-dimensional
electron gas (2DEG) have attracted significant interest due to its potential
applications in nanoelectronics. Control over this carrier density and mobility
of the 2DEG is essential for applications of these novel systems, and may be
achieved by epitaxial strain. However, despite the rich nature of strain
effects on oxide materials properties, such as ferroelectricity, magnetism, and
superconductivity, the relationship between the strain and electrical
properties of the 2DEG at the LaAlO3/SrTiO3 heterointerface remains largely
unexplored. Here, we use different lattice constant single crystal substrates
to produce LaAlO3/SrTiO3 interfaces with controlled levels of biaxial epitaxial
strain. We have found that tensile strained SrTiO3 destroys the conducting
2DEG, while compressively strained SrTiO3 retains the 2DEG, but with a carrier
concentration reduced in comparison to the unstrained LaAlO3/SrTiO3 interface.
We have also found that the critical LaAlO3 overlayer thickness for 2DEG
formation increases with SrTiO3 compressive strain. Our first-principles
calculations suggest that a strain-induced electric polarization in the SrTiO3
layer is responsible for this behavior. It is directed away from the interface
and hence creates a negative polarization charge opposing that of the polar
LaAlO3 layer. This both increases the critical thickness of the LaAlO3 layer,
and reduces carrier concentration above the critical thickness, in agreement
with our experimental results. Our findings suggest that epitaxial strain can
be used to tailor 2DEGs properties of the LaAlO3/SrTiO3 heterointerface
Magnetic charge, angular momentum and negative cosmological constant
We argue that there are no axially symmetric rotating monopole solutions for
a Yang-Mills-Higgs theory in flat spacetime background. We construct axially
symmetric Yang-Mills-Higgs solutions in the presence of a negative cosmological
constant, carrying magnetic charge and a nonvanishing electric charge.
However, these solution are also nonrotating.Comment: 17 pages, LaTeX, 7 figure
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