87 research outputs found
Sensitivity analysis of laterally loaded piles embedded in stiff clay above water table.
This study presents the theoretical formulation and numerical investigation of sensitivity analysis of laterally loaded piles embedded in stiff clay located above the water table. Single piles with various lengths and boundary conditions subjected to static and cyclic loadings applied to the pile-head as lateral forces and bending moments are analyzed. The cyclicity is introduced explicitly to p-y curve. The p-y soil response is of quasi static type. The pile groups of 3 x 3 piles with various spacing (2D, 3D, 4D and 5D) are also analyzed in the study. For single piles, the pile structure is considered as one-dimensional beam and the supporting stiff clay is defined by means of p-y relationship. For groups of piles, the pile members are considered as one-dimensional beams and the pile cap is considered as plate. The behaviour of a pile-soil system in the pile group is simulated also by means of p-y relationship, which is modified by the fm factor that is dependent on the spacing of the piles and the locations of the piles in the groups. The pile material parameter and soil physical parameters are taken as the design variables. The adjoint method for nonlinear system is used to analyze the sensitivity of the piles and pile groups. The changes of maximum generalized deflection located at the pile head of the pile due to the changes of the design variables are explored by means of sensitivity integrands associated with each of the design variables. The numerical results in terms of spatial distributions of sensitivity integrands are presented and discussed in detail. The sensitivity integrands are integrated and the assessment of the result is carried out. The Matlab programmings are used to conduct the numerical investigations of single pile and pile groups.* *This dissertation is a compound document (contains both a paper copy and a CD as part of the dissertation).Dept. of Civil and Environmental Engineering. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2004 .L58. Source: Masters Abstracts International, Volume: 43-01, page: 0265. Adviser: B. B. Budkowska. Thesis (M.A.Sc.)--University of Windsor (Canada), 2004
Proto-Tethys magmatic evolution along northern Gondwana: Insights from Late Silurian–Middle Devonian A-type magmatism, East Kunlun Orogen, Northern Tibetan Plateau, China
The East Kunlun Orogen records the geological evolutions of the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean and Late Paleozoic–Mesozoic Paleo-Tethys Ocean along northern Gondwana. However, the late-stage evolution of the Proto-Tethyan Ocean and the configuration of peri-Gondwana microcontinents during the Silurian – Devonian is under debate. Here we report new geochronological and geochemical data of A-type granites from the western Wulonggou and the eastern Gouli areas in the East Kunlun Orogen to deepen our understanding of these problems. Zircon LA-ICP-MS UPb data reveal that the Danshuigou monzogranite and Shenshuitan syenogranite from the western Wulonggou area were emplaced simultaneously at 418 ± 3 Ma, while the Niantang syenogranite from the eastern Gouli area was emplaced at 403 ± 2 Ma. All these rocks display high-K calcic-alkalic to shoshonitic and metaluminous to slight peraluminous signatures, with relatively low CaO, Al2O3, MgO and Sr, and high FeOt/MgO, Ga/Al, Zr, and Nb, indicating their A-type affinity. Their moderate whole-rock εNd(t) (−5.3 to −0.6) and zircon εHf(t) (−6.3–6.4) are different from those of depleted mantle and old basement rocks, but similar to those of the Ordovician–Silurian granitoids in the East Kunlun Orogen. These chemical signatures, together with the anhydrous, low-pressure and high-temperature characteristics of the magmas, indicate that partial melting of the Ordovician–Silurian granitoids generated these A-type granites. Regionally, these A-type granites and previously reported A-type granites in the East Kunlun Orogen compose a Late Silurian – Middle Devonian A-type granite belt. This belt, together with the regionally coeval molasse formation and mafic-ultramafic rocks, indicate a post-collisional extensional regime for the East Kunlun Orogen during the Late Silurian – Middle Devonian. Given that extensive contemporaneous post-collision-related magmatic rocks have also been revealed in the neighboring West Kunlun, Altyn, Qilian and Qinling blocks/terranes, we contend that the Neoproterozoic – Early Paleozoic Proto-Tethyan Ocean that separated these blocks/terranes from Gondwana had closed by the Late Silurian – Middle Devonian, which]resulted in the re-welding of the above blocks/terranes to northern Gondwana or Gondwana-derived microcontinents
Spin excitations in metallic kagome lattice FeSn and CoSn
In two-dimensional (2D) metallic kagome lattice materials, destructive
interference of electronic hopping pathways around the kagome bracket can
produce nearly localized electrons, and thus electronic bands that are flat in
momentum space. When ferromagnetic order breaks the degeneracy of the
electronic bands and splits them into the spin-up majority and spin-down
minority electronic bands, quasiparticle excitations between the spin-up and
spin-down flat bands should form a narrow localized spin-excitation Stoner
continuum coexisting with well-defined spin waves in the long wavelengths. Here
we report inelastic neutron scattering studies of spin excitations in 2D
metallic Kagome lattice antiferromagnetic FeSn and paramagnetic CoSn, where
angle resolved photoemission spectroscopy experiments found spin-polarized and
nonpolarized flat bands, respectively, below the Fermi level. Although our
initial measurements on FeSn indeed reveal well-defined spin waves extending
well above 140 meV coexisting with a flat excitation at 170 meV, subsequent
experiments on CoSn indicate that the flat mode actually arises mostly from
hydrocarbon scattering of the CYTOP-M commonly used to glue the samples to
aluminum holder. Therefore, our results established the evolution of spin
excitations in FeSn and CoSn, and identified an anomalous flat mode that has
been overlooked by the neutron scattering community for the past 20 years
Disorder-induced excitation continuum in a spin-1/2 cobaltate on a triangular lattice
A spin-1/2 triangular-lattice antiferromagnet is a prototypical frustrated
quantum magnet, which exhibits remarkable quantum many-body effects that arise
from the synergy between geometric spin frustration and quantum fluctuations.
It can host quantum frustrated magnetic topological phenomena like quantum spin
liquid (QSL) states, highlighted by the presence of fractionalized
quasiparticles within a continuum of magnetic excitations. In this work, we use
neutron scattering to study CoZnMoO, which has a triangular lattice of
Jeff = 1/2 Co2+ ions with octahedral coordination. We found a
wave-vector-dependent excitation continuum at low energy that disappears with
increasing temperature. Although these excitations are reminiscent of a spin
excitation continuum in a QSL state, their presence in CoZnMoO
originates from magnetic intersite disorder-induced dynamic spin states with
peculiar excitations. Our results, therefore, give direct experimental evidence
for the presence of a disorder-induced spin excitation continuum
Intertwined magnetism and charge density wave order in kagome FeGe
Electron correlations often lead to emergent orders in quantum materials.
Kagome lattice materials are emerging as an exciting platform for realizing
quantum topology in the presence of electron correlations. This proposal stems
from the key signatures of electronic structures associated with its lattice
geometry: flat band induced by destructive interference of the electronic
wavefunctions, topological Dirac crossing, and a pair of van Hove singularities
(vHSs). A plethora of correlated electronic phases have been discovered amongst
kagome lattice materials, including magnetism, charge density wave (CDW),
nematicity, and superconductivity. These materials can be largely organized
into two types: those that host magnetism and those that host CDW order.
Recently, a CDW order has been discovered in the magnetic kagome FeGe,
providing a new platform for understanding the interplay between CDW and
magnetism. Here, utilizing angle-resolved photoemission spectroscopy, we
observe all three types of electronic signatures of the kagome lattice: flat
bands, Dirac crossings, and vHSs. From both the observation of a
temperature-dependent shift of the vHSs towards the Fermi level as well as
guidance via first-principle calculations, we identify the presence of the vHSs
near the Fermi level (EF) to be driven by the development of underlying
magnetic exchange splitting. Furthermore, we show spectral evidence for the CDW
order as gaps that open on the near-EF vHS bands, as well as evidence of
electron-phonon coupling from a kink on the vHS band together with phonon
hardening observed by inelastic neutron scattering. Our observation points to
the magnetic interaction-driven band modification resulting in the formation of
the CDW order, indicating an intertwined connection between the emergent
magnetism and vHS charge order in this moderately-correlated kagome metal.Comment: submitted on April 22, 202
Discovery of charge density wave in a correlated kagome lattice antiferromagnet
A hallmark of strongly correlated quantum materials is the rich phase diagram
resulting from competing and intertwined phases with nearly degenerate ground
state energies. A well-known example is the copper oxides, where a charge
density wave (CDW) is ordered well above and strongly coupled to the magnetic
order to form spin-charge separated stripes that compete with
superconductivity. Recently, such rich phase diagrams have also been revealed
in correlated topological materials. In two-dimensional kagome lattice metals
consisting of corner-sharing triangles, the geometry of the lattice can produce
flat bands with localized electrons, non-trivial topology, chiral magnetic
order, superconductivity and CDW order. While CDW has been found in weakly
electron correlated nonmagnetic AV3Sb5 (A = K, Rb, Cs), it has not yet been
observed in correlated magnetic ordered kagome lattice metals. Here we report
the discovery of CDW within the antiferromagnetic (AFM) ordered phase of kagome
lattice FeGe. The CDW in FeGe occurs at wavevectors identical to that of
AV3Sb5, enhances the AFM ordered moment, and induces an emergent anomalous Hall
effect. Our findings suggest that CDW in FeGe arises from the combination of
electron correlations-driven AFM order and van Hove singularities-driven
instability possibly associated with a chiral flux phase, in stark contrast to
strongly correlated copper oxides and nickelates, where the CDW precedes or
accompanies the magnetic order.Comment: 36 pages, 4 figures in main tex
Minipool Caprylic Acid Fractionation of Plasma Using Disposable Equipment: A Practical Method to Enhance Immunoglobulin Supply in Developing Countries
Plasma-derived immunoglobulin G (IgG) is on WHO’s Essential Medicines List, yet developing countries face severe shortages of this critical treatment. Infusion of IgG prepared from locally-collected plasma provides an advantageous mix of antibodies to viral and bacterial pathogens found in the living environment, and this can reduce recurrent infections in immune-deficient patients. We developed a simple manufacturing process using disposable equipment (blood bags, hemodialyzer, and filters) to isolate immunoglobulins from minipools of 20 plasma donations. This process yields a ca. 90% pure virally-inactivated immunoglobulin fraction at 50–60% recovery. Anti-hepatitis B and anti-rubella immunoglobulins were enriched fourfold to sixfold. The product was free of in-vitro thrombogenic and proteolytic activity, confirming its expected clinical safety profile. Virus validations showed caprylic acid treatment robustly inactivated or removed infectivity of lipid-enveloped viruses, including human immunodeficiency virus (HIV) and hepatitis C virus model. This simple and cost-effective process is implemented in Egypt to prepare experimental batches for clinical evaluation. It can enhance immunoglobulin supplies to treat immunodeficient patients through passive transmission of antibodies directed against local pathogens. The method requires minimal training and reasonable infrastructure, and is a practical means to prepare convalescent hyperimmune IgG during infectious outbreaks such as the current Ebola episode.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias de la Salud::Instituto Clodomiro Picado (ICP)UCR::Vicerrectoría de Docencia::Salud::Facultad de Microbiologí
- …