Shear thickening effects of drag-reducing nanofluids for low permeability reservoir

Drag-reducing nanofluids are complex non-Newtonian fluids. Their constitutive characteristics are the basis of flow mechanism analysis in porous media. However, the rheological effects of drag-reducing nanofluids have not been thoroughly studied. In the present work, rheological properties of several nanofluids were measured, and the shear thickening mechanism was investigated experimentally. The results show that all the nanofluids examined have complex characteristics and critical shear rates. The viscosity exhibits a slow linear increase with the shear rate below the critical shear rate, while the shear thickening power-law fluid behaviour appears above the critical shear rate. The critical shear rate increases with the increase of particle concentration, which indicates the injection rate needs to be controlled to avoid significant increase of nanofluids viscosity. The rheological curve of increasing shear rate nearly coincides with that of decreasing shear rate, which indicates that the shear thickening of nanofluids studied in this work is transient and reversible. A constant index constitutive equation with an exponent of 0.5 is obtained from test results by the fixed index method, and its coefficient k(c) is a linear function of the concentration, which can replace a set of conventional constitutive equations with different concentrations. The constant index constitutive equation also clarifies the coefficient dimension. Similar results have been obtained by analysing several other nanofluids using the fixed index method, which validates the new effective method for constructing the constitutive equations of non-Newtonian nanofluids.Cited as: Gu, C., Qiu, R., Liu, S., You, Z., Qin, R. Shear thickening effects of drag-reducing nanofluids for low permeability reservoir. Advances in Geo-Energy Research, 2020, 4(3): 317-325, doi: 10.46690/ager.2020.03.0

VPRSM Based Decision Tree Classifier

A new approach for inducing decision trees is proposed based on the Variable Precision Rough Set Model. From the rough set theory point of view, in the process of inducing decision trees with evaluations of candidate attributes, some methods based on purity measurements, such as information entropy based methods, emphasize the effect of class distribution. The more unbalanced the class distribution is, the more favorable it is. The rough set based approaches emphasize the effect of certainty. The more certain it is, the better. The criterion for node selection in the new method is based on the measurement of the variable precision explicit regions corresponding to candidate attributes. We compared the presented approach with C4.5 on some data sets from the UCI machine learning repository, which instantiates the feasibility of the proposed method

3-(2-Bromo­benz­yl)-1-methyl-1H-imidazol-3-ium bromide

In the title compound, C11H12BrN2 +·Br−, the imidazole and phenyl rings are nearly perpendicular, making a dihedral angle of 87.71 (7)°. The crystal structure is stabilized by non-classical inter­molecular C—H⋯Br hydrogen bonds and inversion-related mol­ecules are linked through π–π inter­actions between the imidazole ring systems [centroid–centroid distance = 3.472 (6) Å]

Heavy flavor quenching and flow: the roles of initial condition, pre-equilibrium evolution and in-medium interaction

Within an advanced Langevin-hydrodynamics framework coupled to a hybrid fragmentation-coalescence hadronization model, we study heavy flavor quenching and flow in relativistic heavy-ion collisions. We investigate how the initial heavy quark spectrum, the energy loss and hadronization mechanisms of heavy quarks in medium, the evolution profile of pre-equilibrium stage, the flow of medium and the temperature dependence of heavy quark diffusion coefficient influence the suppression and elliptic flow of heavy mesons at RHIC and the LHC. Our result shows that different modeling of initial conditions, pre-equilibrium evolution and in-medium interaction can individually yield about 10-40% uncertainties in D meson suppression and flow at low transverse momentum. We also find that a proper combination of collisional versus radiative energy loss, coalescence versus fragmentation in hadronization, and the inclusion of medium flow are the most important factors for describing the suppression and elliptic flow of heavy mesons.Comment: 9 pages, 7 figures; to be published in Chinese Physics

Constraining the equation of state with heavy quarks in the quasi-particle model of QCD matter

In a quasi-particle model of QCD matter at finite temperature with thermal masses for quarks and gluons from hard thermal loops, the equation of state (EOS) can be described by an effective temperature dependence of the strong coupling $g(T)$. Assuming the same effective coupling between the exchanged gluon and thermal partons, the EOS can also be related to parton energy loss.} Based on the quasi-particle linear Boltzmann transport (QLBT) model coupled to a (3+1)-dimensional viscous hydrodynamic model of the quark-gluon plasma (QGP) evolution and a hybrid fragmentation-coalescence model for heavy quark hadronization, we perform a Bayesian analysis of the experimental data on $D$ meson suppression $R_{\rm AA}$ and anisotropy $v_2$ at RHIC and the LHC. We achieve a simultaneous constraint on the QGP EOS and the heavy quark transport coefficient, both consistent with the lattice QCD results.Comment: 8 pages, 5 figure

Acupuncture modulates temporal neural responses in wide brain networks: evidence from fMRI study

<p>Abstract</p> <p>Background</p> <p>Accumulating neuroimaging studies in humans have shown that acupuncture can modulate a widely distributed brain network, large portions of which are overlapped with the pain-related areas. Recently, a striking feature of acupuncture-induced analgesia is found to be associated with its long-last effect, which has a delayed onset and gradually reaches a peak even after acupuncture needling being terminated. Identifying temporal neural responses in these areas that occur at particular time -- both acute and sustained effects during acupuncture processes -- may therefore shed lights on how such peripheral inputs are conducted and mediated through the CNS. In the present study, we adopted a non-repeated event-related (NRER) fMRI paradigm and control theory based approach namely change-point analysis in order to capture the detailed temporal profile of neural responses induced by acupuncture.</p> <p>Results</p> <p>Our findings demonstrated that neural activities at the different stages of acupuncture presented distinct temporal patterns, in which consistently positive neural responses were found during the period of acupuncture needling while much more complex and dynamic activities found during a post-acupuncture period. These brain responses had a significant time-dependent effect which showed different onset time and duration of neural activities. The amygdala and perigenual anterior cingulate cortex (pACC), exhibited increased activities during the needling phase while decreased gradually to reach a peak below the baseline. The periaqueductal gray (PAG) and hypothalamus presented saliently intermittent activations across the whole fMRI session. Apart from the time-dependent responses, relatively persistent activities were also identified in the anterior insula and prefrontal cortices. The overall findings indicate that acupuncture may engage differential temporal neural responses as a function of time in a wide range of brain networks.</p> <p>Conclusions</p> <p>Our study has provided evidence supporting a view that acupuncture intervention involves complex modulations of temporal neural response, and its effect can gradually resolve as a function of time. The functional specificity of acupuncture at ST36 may involve multiple levels of differential activities of a wide range of brain networks, which are gradually enhanced even after acupuncture needle being terminated.</p

Charmed hadron chemistry in relativistic heavy-ion collisions

We develop for charmed hadron production in relativistic heavy-ion collisions a comprehensive coalescence model that includes an extensive set of $s$ and $p$-wave hadronic states as well as the strict energy-momentum conservation, which ensures the boost invariance of the coalescence probability and the thermal limit of the produced hadron spectrum. By combining our hadronization scheme with an advanced Langevin-hydrodynamics model that incorporates both elastic and inelastic energy loss of heavy quarks inside the dynamical quark-gluon plasma, we obtain a successful description of the $p_\mathrm{T}$-integrated and differential $\Lambda_c/D^0$ and $D_s/D^0$ ratios measured at RHIC and the LHC. We find that including the effect of radial flow of the medium is essential for describing the enhanced $\Lambda_c/D^0$ ratio observed in relativistic heavy-ion collisions. We also find that the puzzling larger $\Lambda_c/D^0$ ratio observed in Au+Au collisions at RHIC than in Pb+Pb collisions at the LHC is due to the interplay between the effects of the QGP radial flow and the charm quark transverse momentum spectrum at hadronization. Our study further suggests that charmed hadrons have larger sizes in medium than in vacuum.Comment: 6 pages, 5 figure

Effect of Corilagin on the Proliferation and NF- κ

Background. This study is to explore the effect of corilagin on the proliferation and NF-κB signaling pathway in U251 glioblastoma cells and U251 glioblastoma stem-like cells. Methods. CD133 positive U251 glioblastoma cells were separated by immunomagnetic beads to isolate glioblastoma stem-like cells. U251 cells and stem-like cells were intervened by different corilagin concentrations (0, 25, 50, and 100 μg/mL) for 48 h, respectively. Cell morphology, cell counting kit-8 assay, flow cytometry, dual luciferase reporter assay, and a western blot were used to detect and analyze the cell proliferation and cell cycle and investigate the expression of IKBα protein in cytoplasm and NF-κB/p65 in nucleus. Results. Corilagin inhibited the cell proliferation of U251 cells and their stem-like cells and the inhibition role was stronger in U251 stem-like cells (P<0.05). The cell cycle was arrested at G2/M phase in the U251 cells following corilagin intervention; the proportion of cells in G2/M phase increased as the concentration of corilagin increased (P<0.05). The U251 stem-like cells were arrested at the S phase following treatment with corilagin; the proportion of cells in the S phase increased as the concentration of corilagin increased (P<0.05). The ratio of dual luciferase activities of U251 stem-like cells was lower than that of U251 cells in the same corilagin concentration. With increasing concentrations of corilagin, the IKBα expression in cytoplasm of U251 cells and U251 stem-like cells was increased, but the p65 expression in nucleus of U251 cells and U251 stem-like cells was decreased (P<0.05). Conclusion. Corilagin can inhibit the proliferation of glioblastoma cells and glioblastoma stem-like cells; the inhibition on glioblastoma stem-like cell proliferation is stronger than glioblastoma cells. This different result indicates that the effect of corilagin on U251 cells and U251 stem-like cells may have close relationships with mechanism of cell cycle and NF-κB signaling pathway; however, the real antitumor mechanism of corilagin is not yet clear and requires further study

Microfluidic Enhancement of Intramedullary Pressure Increases Interstitial Fluid Flow and Inhibits Bone Loss in Hindlimb Suspended Mice

Interstitial fluid flow (IFF) has been widely hypothesized to mediate skeletal adaptation to mechanical loading. Although a large body of in vitro evidence has demonstrated that fluid flow stimulates osteogenic and antiresorptive responses in bone cells, there is much less in vivo evidence that IFF mediates loading-induced skeletal adaptation. This is due in large part to the challenges associated with decoupling IFF from matrix strain. In this study we describe a novel microfluidic system for generating dynamic intramedullary pressure (ImP) and IFF within the femurs of alert mice. By quantifying fluorescence recovery after photobleaching (FRAP) within individual lacunae, we show that microfluidic generation of dynamic ImP significantly increases IFF within the lacunocanalicular system. In addition, we demonstrate that dynamic pressure loading of the intramedullary compartment for 3 minutes per day significantly eliminates losses in trabecular and cortical bone mineral density in hindlimb suspended mice, enhances trabecular and cortical structural integrity, and increases endosteal bone formation rate. Unlike previously developed modalities for enhancing IFF in vivo, this is the first model that allows direct and dynamic modulation of ImP and skeletal IFF within mice. Given the large number of genetic tools for manipulating the mouse genome, this model is expected to serve as a powerful investigative tool in elucidating the role of IFF in skeletal adaptation to mechanical loading and molecular mechanisms mediating this process. © 2010 American Society for Bone and Mineral Research