3,589 research outputs found
Dilatancy relation for overconsolidated clay
A distinct feature of overconsolidated (OC) clays is that their dilatancy behavior is dependent on the degree of overconsolidation. Typically, a heavily OC clay shows volume expansion, whereas a lightly OC clay exhibits volume contraction when subjected to shear. Proper characterization of the stress-dilatancy behavior proves to be important for constitutive modeling of OC clays. This paper presents a dilatancy relation in conjunction with a bounding surface or subloading surface model to simulate the behavior of OC clays. At the same stress ratio, the proposed relation can reasonably capture the relatively more dilative response for clay with a higher overconsolidation ratio (OCR). It may recover to the dilatancy relation of a modified Cam-clay (MCC) model when the soil becomes normally consolidated (NC). A demonstrative example is shown by integrating the dilatancy relation into a bounding surface model. With only three extra parameters in addition to those in the MCC model, the new model and the proposed dilatancy relation provide good predictions on the behavior of OC clay compared with experimental data
Low Frequency Quasi-periodic Oscillation in MAXI J1820+070: Revealing distinct Compton and Reflection Contributions
X-ray low frequency quasi-periodic oscillations (LFQPOs) of black hole X-ray
binaries, especially those type-C LFQPOs, are representative timing signals of
black hole low/hard state and intermediate state, which has been suspected as
to originate due to Lense-Thirring precession of the accretion flow. Here we
report an analysis of one of the \emph{Insight}-HXMT observations of the black
hole transient MAXI J1820070 taken near the flux peak of its hard spectral
state during which strong type-C LFQPOs were detected in all three instruments
up to photon energies above 150 keV. We obtained and analyzed the
short-timescale X-ray spectra corresponding to high- and low-intensity phases
of the observed LFQPO waveform with a spectral model composed of Comptonization
and disk reflection components. We found that the normalization of the spectral
model is the primary parameter that varied between the low and high-intensity
phases. The variation in the LFQPO flux at the hard X-ray band (> 100 keV) is
from the Compton component alone, while the energy-dependent variation in the
LFQPO flux at lower energies (< 30 keV) is mainly caused by the reflection
component with a large reflection fraction in response to the incident Compton
component. The observed X-ray LFQPOs thus should be understood as manifesting
the original timing signals or beats in the hard Compton component, which gives
rise to additional variability in softer energies due to disk reflection.Comment: 8 pages, 4 figures, accepted for publication in MNRA
meson photoproduction in ultrarelativistic heavy ion collisions
The transverse momentum distributions for inclusive meson
described by gluon-gluon interactions from photoproduction processes in
relativistic heavy ion collisions are calculated. We considered the color
singlet (CS) and color octet (CO) components with the framework of
non-relativistic Quantum Chromodynamics (NRQCD) into the production of heavy
quarkonium. The phenomenological values of the matrix elements for the
color-singlet and color-octet components give the main contribution to the
production of heavy quarkonium from the gluon-gluon interaction caused by the
emission of additional gluon in the initial state. The numerical results
indicate that the contribution of photoproduction processes cannot be
negligible for mid-rapidity in p-p and Pb-Pb collisions at the Large Hadron
Collider (LHC) energies.Comment: 11 pages, 2 figure
Energy Spectrum Theory of Incommensurate Systems
Due to the lack of the translational symmetry, calculating the energy
spectrum of an incommensurate system has always been a theoretical challenge.
Here, we propose a natural approach to generalize the energy band theory to the
incommensurate systems without reliance on the commensurate approximation, thus
providing a comprehensive energy spectrum theory of the incommensurate systems.
Except for a truncation dependent weighting factor, the formulae of this theory
are formally almost identical to that of the Bloch electrons, making it
particularly suitable for complex incommensurate structures. To illustrate the
application of this theory, we give three typical examples: one-dimensional
bichromatic and trichromatic incommensurate potential model, as well as a
moir\'{e} quasicrystal. Our theory establishes a fundamental framework for
understanding the incommensurate systems.Comment: 7 pages, 3 figure
Molecular Authentication of the Medicinal Species of Ligusticum (Ligustici Rhizoma et Radix, “Gao-ben”) by Integrating Non-coding Internal Transcribed Spacer 2 (ITS2) and Its Secondary Structure
Ligustici Rhizoma et Radix (LReR), an important Chinese medicine known as “Gao-ben,” refers to Ligusticum sinense Oliv. or Ligusticum jeholense Nakai et Kitag. However, a number of other species are commonly sold as “Gao-ben” in the herbal medicine market, which may result in a series of quality control problems and inconsistent therapeutic effects. The “Gao-ben” is commonly sold sliced and dried, making traditional identification methods difficult. Here, the mini barcode ITS2 region was examined on 68 samples representing LReR and 7 potential adulterant or substitute species. The results showed 100% success rates of PCR and sequencing and the existence of a barcoding gap. The neighbor-joining (NJ) tree indicated that all the tested samples could be exactly identified. The ITS2 secondary structure revealed a clear difference between true “Gao-ben” and three adulterant species. We therefore recommend the use of ITS2 as a mini barcode for distinguishing between closely or distantly related plant species that may be used in Chinese medicine
Efficient nano iron particle-labeling and noninvasive MR imaging of mouse bone marrow-derived endothelial progenitor cells
In this study, we sought to label mouse bone marrow-derived endothelial progenitor cells (EPCs) with Resovist® in vitro and to image them using 7.0 Tesla (T) magnetic resonance imaging (MRI). Mouse bone marrow-derived EPCs were cultured in endothelial basal medium with endothelial growth supplement. They were then characterized by immunocytochemistry, flow cytometry, and fluorescence quantitative polymerase chain reaction. Their functions were evaluated by measuring their uptake of 1,1-dioctadecyl-3,3,3,3-tetramethylindocarbocyanine-labeled acetylated low-density lipoprotein (Dil-Ac-LDL), binding of fluorine isothiocyanate (FITC)-labeled Ulex europaeus agglutinin (UEA), and formation of capillary-like networks. EPCs were labeled with superparamagnetic iron oxide (SPIO) and their proliferation was then assessed in a water-soluble tetrazolium (WST-8)-based cell proliferation assay. Spin echo sequence (multislice, multiecho [MSME]) and gradient echo sequence (2D-FLASH) were used to detect differences in the numbers of labeled cells by 7.0 T MRI. The results showed that the cultured cells were of “cobblestone”-like shape and positive for CD133, CD34, CD31, von Willebrand factor, kinase domain receptor, and CD45, but negative for F4/80. They could take up Dil-Ac-LDL, bind FITC-UEA, and form capillary-like networks on Matrigel in vitro. Prussian-blue staining demonstrated that the cells were efficiently labeled with SPIO. The single-cell T2* effect was more obvious in the 2D-FLASH sequence than in the MSME sequence. Further, there were almost no adverse effects on cell vitality and proliferation. In conclusion, mouse bone marrow-derived EPCs can be efficiently labeled with SPIO and imaged with 7.0-T MRI. They may thus be traced by MRI following transplantation for blood vessel disorders and cancer treatment
A new result on observer-based sliding mode control design for a class of uncertain Ito^ stochastic delay systems
© 2017 The Franklin Institute This paper develops a new observer-based sliding mode control (SMC) scheme for a general class of Ito^ stochastic delay systems (SDS). The key merit of the presented scheme lies in its simplicity and integrity in design process of the traditional sliding mode observer (SMO) strategy, i.e., the state observer and sliding surface design as well as the associated sliding mode controller synthesis. For guaranteeing to use the scheme, a new LMIs-based criterion is established to ensure the exponential stability of the underlying sliding mode dynamics (SMDs) in mean-square sense with H∞ performance. A bench test example is provided to numerically demonstrate the efficacy of the scheme and illustrate the application procedure for potential readers/users with interest in their ad hoc applications and methodology expansion
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