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41.
Inertial microfluidics has demonstrated the potential to provide a rich range of capabilities to manipulate biological fluids and particles to address various challenges in biomedical science and clinical medicine. Various microchannel geometries have been used to study the inertial focusing behavior of particles suspended in simple buffer solutions or in highly diluted blood. One aspect of inertial focusing that has not been studied is how particles suspended in whole or minimally diluted blood respond to inertial forces in microchannels. The utility of imaging techniques (i.e., high-speed bright-field imaging and long exposure fluorescence (streak) imaging) primarily used to observe particle focusing in microchannels is limited in complex fluids such as whole blood due to interference from the large numbers of red blood cells (RBCs). In this study, we used particle trajectory analysis (PTA) to observe the inertial focusing behavior of polystyrene beads, white blood cells, and PC-3 prostate cancer cells in physiological saline and blood. Identification of in-focus (fluorescently labeled) particles was achieved at mean particle velocities of up to 1.85 m s(-1). Quantitative measurements of in-focus particles were used to construct intensity maps of particle frequency in the channel cross-section and scatter plots of particle centroid coordinates vs. particle diameter. PC-3 cells spiked into whole blood (HCT = 45%) demonstrated a novel focusing mode not observed in physiological saline or diluted blood. PTA can be used as an experimental frame of reference for understanding the physical basis of inertial lift forces in whole blood and discover inertial focusing modes that can be used to enable particle separation in whole blood. 相似文献
42.
Commercial applications of magnetorheological (MR) fluids often require operation at elevated temperatures as a result of surrounding environmental conditions or intense localized viscous heating. Previous experimental investigations of thermal effects on MR fluids have reported significant reductions in the magnetorheological stress with increasing temperature, exceeding the predictions made by considering the thermal variations in the individual physical properties of the fluid and solid constituents of a typical MR fluid. In the low-flux regime, designers of MR fluid actuators can alleviate this thermal reduction in stress by increasing the applied magnetic field strength. However, this is not possible in the high-flux regime because of magnetic saturation, and it becomes necessary to explore and understand the intrinsic limitations of the fluid at elevated temperature. We describe a new magnetorheological fixture, which was designed as an accessory to a commercial torsional shear rheometer, capable of applying magnetic flux densities up to 1 T and controlling the sample temperature up to 150°C. During the design of the instrument, close attention was given to the uniformity of the magnetic field applied to the sample by using numerical simulations. Incorporation of a custom-built magnetic flux sensor which matches the environmental capabilities of the fixture enables in situ measurement of the local magnetic field at each temperature. The numerical results are also validated by spatially resolved measurements of the local magnetic field. Finally, we explore the ability of a shift factor between fluid magnetization and yield strength to describe the measured variation in the MR fluid response at elevated temperatures. 相似文献
43.
When the shear stress measured in large amplitude oscillatory shear (LAOS) deformation is represented as a 2-D Lissajous–Bowditch
curve, the corresponding trajectory can appear to self-intersect and form secondary loops. This self-intersection is a general
consequence of a strongly nonlinear material response to the imposed oscillatory forcing and can be observed for various material
systems and constitutive models. We derive the mathematical criteria for the formation of secondary loops, quantify the location
of the apparent intersection, and furthermore suggest a qualitative physical understanding for the associated nonlinear material
behavior. We show that when secondary loops appear in the viscous projection of the stress response (the 2-D plot of stress
vs. strain rate), they are best interpreted by understanding the corresponding elastic response (the 2-D projection of stress
vs. strain). The analysis shows clearly that sufficiently strong elastic nonlinearity is required to observe secondary loops on the conjugate viscous projection. Such a strong elastic nonlinearity physically corresponds to a nonlinear viscoelastic shear stress overshoot
in which existing stress is unloaded more quickly than new deformation is accumulated. This general understanding of secondary
loops in LAOS flows can be applied to various molecular configurations and microstructures such as polymer solutions, polymer
melts, soft glassy materials, and other structured fluids. 相似文献
44.
Dr. Ramiz A. Boulos Nikki Y. T. Man Dr. Nigel A. Lengkeek Prof. Katherine A. Hammer Dr. Niki F. Foster Natalie A. Stemberger Prof. Brian W. Skelton Pan Yu Wong Prof. Boris Martinac Prof. Thomas V. Riley Prof. Allan J. McKinley Prof. Scott G. Stewart 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(52):17980-17988
Herein we describe the preparation and structure‐activity relationship studies on range of stilbene based compounds and their antibacterial activity. Two related compounds, each bearing carboxylic acid moieties, exhibit good activity against several bacterial strains, including methicillin‐resistant Staphylococcus aureus MRSA (ATCC 33592 and NCTC 10442). Compound 10 was most active against Moraxella catarrhalis with minimum inhibitory concentrations (MICs) of 0.12–0.25 μg mL?1 and against Staphylococcus spp. with MICs ranging from 2–4 μg mL?1. The derivative 17 showed increased activity with MICs of 0.06–0.25 μg mL?1 against M. catarrhalis and 0.12–1 against Staphylococcus spp. This level of activity is similar to that reported for S. aureus for antibiotics, such as vancomycin, with MICs of ≤2.0 μg mL?1 and clindamycin with MICs of ≤0.5 μg mL?1. As an indicator of toxicity, 17 was tested for its ability to lyse sheep erythrocytes, and showed low haemolytic activity. Such results highlight the value of tris(stilbene) compounds as antibacterial agents providing suitable properties for further development. 相似文献
45.
Eric Verploegen Dr. Johannes Soulages Dr. Mariel Kozberg Tejia Zhang Gareth McKinley Prof. Dr. Paula Hammond Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(19):3494-3498
Manipulation makes light work : The morphology and rheological properties of a liquid‐crystalline system can be dynamically manipulated with UV light by attaching photoresponsive liquid‐crystalline moieties to a siloxane‐based polymer. Stimulation with UV light induces a conformational change in the molecule, which disrupts the liquid‐crystalline mesophase (see picture), and results in a dramatic change in its rheological properties.
46.
A nuclear model consisting of a core plus several particles is considered with interactions between each particle and the core and among the particles. It is shown that the energy levels of a several-particle nucleus can be expressed in terms of the levels of the one- and two-particle nuclei. An application is then made to 193Au and 195Au in which it is seen that the core-particle interaction alone is sufficient to account for the features of the observed levels. 相似文献
47.
In this paper the relation betweenEP--matrices andE
k
P--matrices over an arbitrary filedF is studied. Further, conditions for the product ofE
k
P--matrices to be anE
k
P--matrix and for the reverse order law to hold for the polynomial Moore-Penrose inverse of the product ofE
k
P--matrices are determined 相似文献
48.
49.
V. ARÁMBULA-VILLAZANA M. SOLACHE-RÍOS M. T. OLGUÍN 《Journal of inclusion phenomena and macrocyclic chemistry》2006,55(3-4):237-245
Many factors may affect the heavy metals sorption on natural zeolites among them the temperature, for this reason in this paper the cadmium retention behavior on Mexican zeolitic rich tuff as a function of temperature is considered. The kinetic and the isotherms were determined at 303, 318, and 333 K, the remaining cadmium in the solution samples was analyzed by atomic absorption spectrometry. The pseudo-second order rate constant, k, as well as the apparent diffusion coefficients were calculated from the cadmium uptake by the zeolitic rock as a function of the contact time and temperature, the highest amounts were found for the experiments done at 333 K. The maximum cadmium adsorption capacity by the zeolitic material was 12.2 mg Cd2+/g at 318 K corresponding to 20% of the effective ion exchange capacity of the Chihuahua zeolitic rock. In order to explain the cadmium sorption behavior different kinetics and isotherm models were considered. 相似文献
50.
O'Donnell CJ Singer RA Brubaker JD McKinley JD 《The Journal of organic chemistry》2004,69(17):5756-5759
A general approach to preparing 1,5-methano- (1) and 1,5-ethano-2,3,4,5-tetrahydro-1H-3-benzazepine (2) is discussed. This strategy involves converting an indanone or tetralone (4) to a cyanohydrin (3) which is subjected to hydrogenolysis followed by lactamization and reduction to provide bicyclic aryl piperidine (1) and bicyclic aryl homopiperidine (2). 相似文献