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41.
George Souliotis Costas Psychalinos 《International Journal of Circuit Theory and Applications》2007,35(2):165-173
New configurations of harmonic oscillators, realized using current amplifier blocks and only grounded capacitors, are introduced in this article. The proposed configurations are based on a grounded inductor simulator scheme and on a loop constructed from first‐order sections, respectively. Comparison with the already published topologies shows that the new configurations have attractive characteristics concerning their implementation in integrated form. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
42.
Controlled Drug Release and Chemotherapy Response in a Novel Acoustofluidic 3D Tumor Platform 下载免费PDF全文
Ioannis K. Zervantonakis Costas D. Arvanitis 《Small (Weinheim an der Bergstrasse, Germany)》2016,12(19):2616-2626
Overcoming transport barriers to delivery of therapeutic agents in tumors remains a major challenge. Focused ultrasound (FUS), in combination with modern nanomedicine drug formulations, offers the ability to maximize drug transport to tumor tissue while minimizing toxicity to normal tissue. This potential remains unfulfilled due to the limitations of current approaches in accurately assessing and quantifying how FUS modulates drug transport in solid tumors. A novel acoustofluidic platform is developed by integrating a physiologically relevant 3D microfluidic device and a FUS system with a closed‐loop controller to study drug transport and assess the response of cancer cells to chemotherapy in real time using live cell microscopy. FUS‐induced heating triggers local release of the chemotherapeutic agent doxorubicin from a liposomal carrier and results in higher cellular drug uptake in the FUS focal region. This differential drug uptake induces locally confined DNA damage and glioblastoma cell death in the 3D environment. The capabilities of acoustofluidics for accurate control of drug release and monitoring of localized cell response are demonstrated in a 3D in vitro tumor mode. This has important implications for developing novel strategies to deliver therapeutic agents directly to the tumor tissue while sparing healthy tissue. 相似文献
43.
44.
The mechanism of electrostatic spraying of insulating fluids, such as air or organic solvents, into relatively conductive fluids, such as water, is investigated in this work. Experiments with air sprayed into water through an electrified capillary showed that the pressure inside the capillary increases, reaches a maximum, and then decreases as the applied voltage is increased. The initial pressure increase is due to the electric stress on the fluid interface, while the decrease is due to the Coulombic electrohydrodynamic flow generated near the end of the capillary. It is shown that electric fields can cause simultaneous pumping, spraying, and mixing of fluids. This phenomenon is demonstrated for air and kerosene in water. 相似文献
45.
We describe the general dependence of the diffusion coefficient associated with the Van der Waals binary mixture on the temperature, number densities, and relative strengths of molecular interaction parameters. The task is facilitated by the fact that for Kac-type intermolecular potentials, in the long-range limit, the diffusion coefficient becomes simply related to the product of a partial compressibility and the curvature of the equilibrium free energy in the space of number densities. Therefore the different kinds of behavior found can be classified according to the scheme of Scott and Van Konynenburg for the global phase diagram of the same model mixture.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A. 相似文献
46.
Costas S. Iliopoulos 《Acta Informatica》1986,23(6):697-705
Summary We show that the problem of computing a basis for an abelian transitive permutation group is in N C
k and also we show that the problem of computing a basis for an abelian permutation group and the problem of computing the intersection of two abelian groups acting on n points, can be solved in depth (log n)k on a Monte Carlo Boolean circuit of polynomial size. Moreover the latter two problems are shown to be in N C
k in the restricted case of bounded number of generators. 相似文献
47.
Mixing during melt-melt blending of segregated polypropylene melt streams in a co-rotating twin screw extruder was experimentally investigated. The mixing limited reaction between two polymer reactive tracers, which are terminally functionalized polyolefin oligomers, was used to determine the mixing performance of a kneading block section. The selected functional groups were succinic anhydride and a primary amine, and Fourier-Transform Infrared Spectrometry (FT-IR) was used to determine the anhydride conversion. In the absence of interfacial tension, the reaction conversion was directly related to the amount of interfacial area generated. Experiments were completed to study the effects of operating conditions, kneading block design, and polymer material properties. The screw speed effect was observed to be non-linear because of competing contributions from shear rate, residence time, channel fill, and viscous heating. The mixing performance of kneading blocks backed by a reverse conveying element was observed to follow the trend of: forward > reverse > neutral. For each kneading block design, the mixing performance decreased with an increase in polymer viscosity. 相似文献
48.
Indoor exposure to air contaminants penetrating from the outdoor environment depends on a number of key processes and parameters such as the ventilation rate, the geometric characteristics of the indoor environment, the outdoor concentration and the indoor removal mechanisms. In this study two alternative methods are used, an analytical and a numerical one, in order to study the time lag and the reduction of the variances of the indoor concentrations, and to estimate the deposition rate of the air contaminants in the indoor environment employing both indoor and outdoor measurements of air contaminants. The analytical method is based on a solution of the mass balance equation involving an outdoor concentration pulse which varies sinusoidally with the time, while the numerical method involves the application of the MIAQ indoor air quality model assuming a triangular pulse. The ratio of the fluctuation of the indoor concentrations to the outdoor ones and the time lag were estimated for different values of the deposition velocity, the ventilation rate and the duration of the outdoor pulse. Results have showed that the time lag between the indoor and outdoor concentrations is inversely proportional to the deposition and ventilation rates, while is proportional to the duration of the outdoor pulse. The decrease of the ventilation and the deposition rate results in a rapid decrement of the variance ratio of indoor to outdoor concentrations and to an increment of the variance ratio, respectively. The methods presented here can be applied for gaseous species as well as for particulate matter. The nomograms and theoretical relationships that resulted from the simulation results and the analytical methods respectively were used in order to study indoor air phenomena. In particular they were used for the estimation of SO2 deposition rate. Implications of the studied parameters to exposure studies were estimated by calculating the ratio of the indoor exposure to the exposure outdoors. Limitations of the methods were explored by testing various scenarios which are usually met in the indoor environment. Strong indoor emissions, intense chemistry and varying ventilation rates (opening and closing of the windows) were found to radically influence the time lag and fluctuation ratios. 相似文献
49.
Catherine C. Sampson Peter J. Metaxas Mark T. J. Barwood Rebecca Sinclair-Adamson Peter E. Falloon Paul L. Stanwix Michael L. Johns Eric F. May 《American Institute of Chemical Engineers》2023,69(4):e18001
In cryogenic liquefaction processes, CO2 poses a solid-formation risk even in trace concentrations. We present solid–fluid equilibrium (SFE) data for CO2 in liquid methane at CO2 concentrations from (52 to 500) ppm, extending the available data and indicating that models tuned to existing data over predict the solubility of CO2 at LNG storage temperatures (~112 K) by nearly a factor of 3. The new data are used to improve the SFE model in the ThermoFAST software package. The formation kinetics of CO2 solids in liquid methane are elucidated at conditions relevant to cryogenic gas processing. Repeated, ramped-temperature formation measurements provide a statistical basis for quantifying solidification risk. Nucleation rates extracted from the ramped-temperature data, consistent with those measured at fixed temperature, were used to extract parameters describing CO2 solid formation in methane. These results significantly improve the ability to predict CO2 solid formation risk in cryogenic natural gas processing. 相似文献
50.
Sandra Pérez-Quirce Felicidad Ronda Carmen Melendre Athina Lazaridou Costas G. Biliaderis 《Food and Bioprocess Technology》2016,9(9):1562-1573
The apparent reduction of β-glucan (BG) molecular weight in rice-based gluten-free (GF) breads fortified with cereal BG concentrates reveals the presence of β-glucanase activity in rice flour. Inactivation of endogenous β-glucanase in rice flour thus seems to be a necessary step when developing GF breads enriched with BG of high molecular weight. The aim of this work was to study the thermal inactivation of endogenous β-glucanase in rice flour by means of microwave (MW) processing; rice flours preconditioned at four different moisture levels (13, 16, 19, 25 %) were treated by MW radiation at 900 W and five MW treatment times (ranging from 40 s to 8 min, applied stepwise at 20-s intervals). The effects of microwaves on starch crystallinity, pasting, and thermal properties of MW-treated rice flours were also explored. The β-glucanase activity in rice flours was assessed by the rate of decrease in specific viscosity of a dilute solution of a purified β-glucan preparation, upon addition of flour extracts. MW proved to be a useful alternative for thermal inactivation of endogenous β-glucanase in rice flours when applied to moistened samples. The inactivation process followed a first-order kinetic response and the apparent rate constant of thermal inactivation increased exponentially with the moisture content of the flour, M, according to the equation 0.0146·exp (0.212·M) (R 2?=?0.97). The MW time required for complete β-glucanase inactivation was only 4 min when the initial flour moisture increased to 25 %. Following MW treatment, the starch crystallinity was unaffected (p?>?0.05) and the side effects of the treatment on flour pasting and thermal properties were rather negligible. 相似文献