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91.
The current study is aimed to determine the antioxidant properties of crude ethanolic extract (CEE) of defatted kenaf seed meal (DKSM) and its derived n-butanol (BF) and aqueous (AqF) fractions. Spectrophotometric assays showed that BF contained the highest amount of phenolic compounds and saponins, followed by CEE and AqF (p < 0.05). Similarly, HPLC-DAD analysis revealed that level of all the detected predominant phenolic compounds was significantly higher in BF (p < 0.05). Through multiple antioxidant assays, BF exhibited higher antioxidant activity than CEE and AqF, except for iron chelating activity (p < 0.05). Antioxidant activity of CEE and fractions were strongly correlated to their phenolic and saponin contents. This study showed that phenolic compounds and saponins could be extracted and partially purified simultaneously from DKSM by employing a simple alcoholic extraction–fractionation procedure. High antioxidative phenolics–saponins rich fraction from DKSM is a potential active ingredient that could be applied in nutraceuticals, functional foods as well as natural food preservatives. 相似文献
92.
Over the past 30 years, the Discrete Element Method (DEM) has rapidly gained popularity as a tool for modelling the behaviour
of granular assemblies and is being used extensively in both scientific and industrial applications. However, it is far from
clear from reviewing the literature whether the large number of DEM codes have been verified and checked against fundamental
benchmark problems. DEM simulates the dynamics of each particle in an assembly by calculating the acceleration resulting from
all the contact forces and body forces. It is clearly necessary that such a model be validated or verified by comparing with
experimental results, analytical solutions or other numerical results (e.g. Finite Element Analysis (FEA) results) at particle
impact level. There appears to be no standard benchmark tests against which DEM codes can be verified. It is thus essential
and useful to establish a set of standard benchmark tests to confirm that these DEM codes are modelling the particle dynamics
as intended. This paper proposes a set of benchmark tests to verify DEM codes at particle impact level for spherical particles.
The analytical solutions derived from elasticity theory for elastic normal collision of two spheres or a sphere with a rigid
plane are first reviewed. These analytical solutions apply only to the elastic regime for normal impact. Secondly, the analytical
solutions of frictional oblique impact between two spheres or a sphere with a rigid plane are scrutinized and derived. These
analytical solutions originate from the dynamics principles and should be satisfied for any DEM contact force model with prescribed
friction and restitution coefficients. A set of eight benchmark tests are designed and performed using commercial DEM codes.
Test 1 and Test 2 consider the elastic normal impact of two spheres or a sphere with a rigid plane, whereas the other tests
(Test 3–Test 8) investigate the energy dissipation due to the collision. These benchmark tests also involve different types
of material. The DEM results were compared with the analytical solutions, experimental or FEA results found in the literature.
All benchmark tests showed good to excellent match, providing a quantitative verification for the codes used in this study.
These benchmark tests not only verify DEM codes but also enhance the understanding of fundamental impact phenomena for modelling
a large number of particles. 相似文献
93.
Raymond E.H. Ooi Dominic C.Y. Foo Denny K.S. Ng Raymond R. Tan 《Chemical Engineering Research and Design》2013
Carbon capture and storage (CCS) is a means for reducing carbon dioxide (CO2) emissions from fossil fuel combustion in power generation and industrial processes. It involves the capture of CO2 for subsequent storage in various geological formations. The selection and matching of the power plants and storage sites are often an issue of optimisation due to various constraints, i.e., time of availability, injection rate, and storage capacity limits. In this work, a novel graphical targeting tool based on pinch analysis is proposed to address the planning problem of the storage of captured CO2 from power generating plants into corresponding reservoirs. The main consideration for the problem is the time of availability of the latter, since reservoirs need to be developed prior to CO2 storage. The time limitation is addressed by the graphical technique where time is taken as the governing element in solving the problem. Hypothetical examples are used to elucidate the proposed approach. 相似文献
94.
C.G. Ching P.K. Ooi S.S. Ng M.A. Ahmad Z. Hassan H. Abu Hassan M.J. Abdullah 《Materials Science in Semiconductor Processing》2013,16(1):70-76
We described the fabrication of porous ZnO using the electrochemical etching method. ZnO thin films deposited by radiofrequency sputtering were etched electrochemically using 10 wt% KOH solution as an etching medium to obtain porous ZnO surface structure. A constant voltage of 15 V was applied to enhance the etching process. The etched samples were then characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL) spectroscopy to examine their structural and optical properties. XRD spectra showed that by performing the electrochemical etching process, porous ZnO could be obtained without severely deteriorating the crystallinity of the samples. Moreover, SEM characterization revealed that hillock-type porous ZnO was fabricated successfully. In addition, the cross-sectional SEM images revealed that there were only minimal changes in the layer thickness after the ZnO had been etched for various lengths of time. This finding shows the dominance of the vertical etching process. Notably, the intensity of PL spectra increased and the PL excitation peak exhibited a red shift trend as the etching time increased. These observations are due to the increase of the surface to volume ratio of the ZnO surface and the strain relaxation along the dislocation and grain boundary. 相似文献
95.
A new memory efficient testing procedure for method of moment (MoM) has been proposed for solving combined field integral equation (CFIE) using adaptive integral method (AIM) for closed perfect electric conductor (PEC) scatterers. CFIE is a linear combination of electric field integral equation (EFIE) and magnetic field integral equation (MFIE) and hence the iterative solution for CFIE requires the simultaneous evaluation of both EFIE and MFIE. Using AIM, the MoM testing procedure is obtained by interpolating the grid potentials, computed using fast Fourier transform (FFT), onto the testing functions. For EFIE, the same set of multipole coefficients of the basis functions can be used as the testing functions, without the need to store additional interpolation coefficients. In this paper, we propose a similar simple but efficient and accurate method for the testing procedure for the MFIE using the same multipole coefficients for the basis functions. This enables CFIE to be solved using the same memory resources as EFIE. The accuracy of the radar cross section (RCS) computed for various geometries using CFIE with the proposed testing procedure is shown to be as accurate as the existing method. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
96.
实验探索了脂肪醇聚氧乙烯醚硫酸盐 (AES)、氯化十六烷基吡啶 (CPC)、β -萘磺酸聚合物 (NS)以及烷基酚聚氧乙烯醚 (TX -10 )等四种不同类型的表面活性剂在普通硅酸盐水泥表面的吸附行为。研究表明 ,AES在水泥颗粒表面的吸附是一种快吸附 ,属于LS型 ;CPC在水泥颗粒表面的吸附过程则是一种慢吸附 ,受动力学因素所控制 ;NS的吸附量与其浓度成线性关系 :TX -10则基本上不被吸附。结果显示 ,被吸附的三种表面活性剂都是疏水基朝向水相 ,增加了水泥颗粒的疏水性。然而AES随着添加量的增大 ,由于吸附胶束的形成 ,使水泥颗粒表面经由亲水 -疏水 -亲水的变化过程。从表面电荷的变化来看 ,AES、NS的添加均使水泥表面Zeta电位有所增加 ,而CPC却使得水泥颗粒表面从带负电变到带正电。文中所提出的改进Stern双电层模型能很好地说明几种表面活性剂在水泥颗粒表面的吸附特性 相似文献
97.
This paper presents an extension of the recently-developed finite element–scaled boundary finite element (FEM–SBFEM) coupled method to model multiple crack propagation in concrete. The concrete bulk and fracture process zones are modelled using SBFEM and nonlinear cohesive interface finite elements (CIEs), respectively. The CIEs are automatically inserted into the SBFEM mesh as the cracks propagate. The algorithm previously devised for single crack propagation is augmented to model problems with multiple cracks and to allow cracks to initiate in an un-cracked SBFEM mesh. It also addresses crack propagation from one subdomain into another, as a result of partitioning a coarse SBFEM mesh, required for some mixed–mode problems. Each crack in the SBFEM mesh propagates when the sign of the Mode-I stress intensity factor at the crack tip turns positive from negative. Its propagation angle is determined using linear elastic fracture mechanics criteria. Three concrete beams involving multiple crack propagation are modelled. The predicted crack propagation patterns and load–displacement curves are in good agreement with data reported in literature. 相似文献
98.
Rami T. ElAfandy Ayman F. AbuElela Pawan Mishra Bilal Janjua Hassan M. Oubei Ulrich Büttner Mohammed A. Majid Tien Khee Ng Jasmeen S. Merzaban Boon S. Ooi 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(7)
Knowledge of materials' thermal‐transport properties, conductivity and diffusivity, is crucial for several applications within areas of biology, material science and engineering. Specifically, a microsized, flexible, biologically integrated thermal transport sensor is beneficial to a plethora of applications, ranging across plants physiological ecology and thermal imaging and treatment of cancerous cells, to thermal dissipation in flexible semiconductors and thermoelectrics. Living cells pose extra challenges, due to their small volumes and irregular curvilinear shapes. Here a novel approach of simultaneously measuring thermal conductivity and diffusivity of different materials and its applicability to single cells is demonstrated. This technique is based on increasing phonon‐boundary‐scattering rate in nanomembranes, having extremely low flexural rigidities, to induce a considerable spectral dependence of the bandgap‐emission over excitation‐laser intensity. It is demonstrated that once in contact with organic or inorganic materials, the nanomembranes' emission spectrally shift based on the material's thermal diffusivity and conductivity. This NM‐based technique is further applied to differentiate between different types and subtypes of cancer cells, based on their thermal‐transport properties. It is anticipated that this novel technique to enable an efficient single‐cell thermal targeting, allow better modeling of cellular thermal distribution and enable novel diagnostic techniques based on variations of single‐cell thermal‐transport properties. 相似文献
99.
Mingliang Zhang Christopher M. Earhart Chinchun Ooi Robert J. Wilson Mary Tang Shan X. Wang 《Nano Research》2013,6(10):745-751
Synthetic antiferromagnetic (SAF) nanoparticles are layer-structured particles with high single-particle magnetic moments. In order to covalently bind these nanopartides to cells, they were coated with a silica shell followed by conjugation with streptavidin. The silica coating generates both SAF@SiO2 core-shell nano- particles and silica core-free nanopartides. Using a simple magnetic separation, silica nanoparticles were removed and SAF@SiO2 nanoparticles were purified. After streptavidin conjugation, these particles were used to stain lung cancer cells, making them highly magnetically responsive. The stained cells can rotate in response to an external magnetic field and can be captured when a blood sample containing these cells flows through the sifter. 相似文献
100.
Reece Andrew Sophocleous Lezanne Ooi Ronald Sluyter 《International journal of molecular sciences》2022,23(10)
The adenosine 5′-triphosphate-gated P2X4 receptor channel is a promising target in neuroinflammatory disorders, but the ability to effectively target these receptors in models of neuroinflammation has presented a constant challenge. As such, the exact role of P2X4 receptors and their cell signalling mechanisms in human physiology and pathophysiology still requires further elucidation. To this end, research into the molecular mechanisms of P2X4 receptor activation, modulation, and inhibition has continued to gain momentum in an attempt to further describe the role of P2X4 receptors in neuroinflammation and other disease settings. Here we provide an overview of the current understanding of the P2X4 receptor, including its expression and function in cells involved in neuroinflammatory signalling. We discuss the pharmacology of P2X4 receptors and provide an overview of P2X4-targeting molecules, including agonists, positive allosteric modulators, and antagonists. Finally, we discuss the use of P2X4 receptor modulators and antagonists in models of neuroinflammatory cell signalling and disease. 相似文献