Fabrication of DNA-magnetite hybrid nanofibers for water detoxification

DNA-magnetite hybrid nanofibers were fabricated by electrospinning a spin dope consisting of oleic acid coated magnetite nanoparticles and DNA-CTMA in ethanol/chloroform mixed solvent. The fabricated nanofibers exhibit superparamagnetic behaviour owing to embedded magnetite nanoparticles. It is demonstrated that these nanofibers can be used as effective detoxification materials in aqueous media as a combined result of DNA's affinity to both organic and inorganic toxicants, high surface area of the nanofibers and the fast and easy separation due to magnetite nanoparticles under external magnetic field. In addition to detoxification, these novel hybrid nanofibers have potential applications in many technological areas such as catalysis and drug delivery.     

Solids flow pattern in gas-flowing solids-fixed bed contactors. Part I: Experimental

An experimental investigation of the solids flow pattern in gas-flowing solids-fixed bed contactors is presented. The apparatus and procedures for determining the dynamic and static solids holdups, solids residence time distribution and the extent and rate of the exchange between particles in the static and dynamic solids holdup are described in detail.Experiments were performed in a bench scale system, containing a column (diameter ) packed with glass beads of 16 mm in diameter packed up to the height of 0.8 m. Tracer experiments with a step input in flowing solids phase were used for determining the residence time distribution and exchange between particles. Fine solids (spheres with mean diameter of ) of two different colors (all other properties being the same) were used in the tracer experiments to determine the residence time distribution and the exchange between static and dynamic solids holdup. In both types of experiments, the response curves have been obtained via color analysis of digital photos. All experiments have been repeated at different operating conditions, with a broad variation of solids mass flux and gas velocity, and reproducibility at set conditions was checked.The obtained experimental results are discussed and the observed important characteristics of the solids flow pattern are outlined. The effects of the solids flux and gas velocity on the solids flow pattern are presented and analyzed.     

Two dimensional analytical modeling for asymmetric 3T and 4T double gate tunnel FET in sub-threshold region: Potential and electric field

In this paper a two dimensional analytical model of channel potential and electric field for an asymmetric and symmetric double gate three-terminal (3T) and four-terminal (4T) silicon n-tunnel field effect transistor (Si-nTFET) device in sub-threshold region, without surface accumulation or inversion, is presented. Since the modeling has been done in subthreshlod regime operation, no Quantum Mechanical (QM) study has been taken. A very good agreement of analytically modeled results with the TCAD simulated results for the three-terminal (3T) and four-terminal (4T) Si-nTFET device was found. The model presented is based on the physics of the device. The modeling is for a 3T/4T asymmetric Tunnel FET and with appropriate changes in the device parameters we can also model for symmetric devices as well. The modeling scheme is thus quite robust.     

Laminin Receptor-Avid Nanotherapeutic EGCg-AuNPs as a Potential Alternative Therapeutic Approach to Prevent Restenosis

In our efforts to develop new approaches to treat and prevent human vascular diseases, we report herein our results on the proliferation and migration of human smooth muscles cells (SMCs) and endothelial cells (ECs) using epigallocatechin-3-gallate conjugated gold nanoparticles (EGCg-AuNPs) as possible alternatives to drug coated stents. Detailed in vitro stability studies of EGCg-AuNPs in various biological fluids, affinity and selectivity towards SMCs and ECs have been investigated. The EGCg-AuNPs showed selective inhibitory efficacy toward the migration of SMCs. However, the endothelial cells remained unaffected under similar experimental conditions. The cellular internalization studies have indicated that EGCg-AuNPs internalize into the SMCs and ECs within short periods of time through laminin receptor mediated endocytosis mode. Favorable toxicity profiles and selective affinity toward SMCs and ECs suggest that EGCg-AuNPs may provide attractive alternatives to drug coated stents and therefore offer new therapeutic approaches in treating cardiovascular diseases.     

Nonlinear Frequency Response Method for Evaluating Forced Periodic Operations of Chemical Reactors

Nonlinear Frequency Response (NFR) method is a relatively new method which can be used for fast evaluation of possible process improvements through periodic operations. The method is analytical and approximate. Its main task is to give an answer whether periodic modulation of one or more process inputs can result in improved process performance. The method is explained in brief and an overview of the existing applications is given. The review covers simple reactions performed in isothermal and non-isothermal stirred tank reactors exposed to different modulated inputs (inlet concentration, flow-rate, inlet temperature, temperature of the heating/cooling medium). Processes with two simultaneously modulated inputs and different shapes of the periodic input are also considered. The results of the NFR method are compared with the results of numerical simulation and a critical evaluation of the method is given.     

CO2 Conversion Enhancement in a Periodically Operated Sabatier Reactor: Nonlinear Frequency Response Analysis and Simulation-based Study

Conversion of CO₂ into synthetic CH₄ via thermocatalytic hydrogenation (the Sabatier reaction), has recently gained increasing interest as a possible route for CO₂ utilization and energy storage pathway. Herein, we analyze the possibility of increasing the CO₂ conversion through periodic operation of the reactor. The analysis is performed by using the Nonlinear Frequency Response (NFR) method, a recently developed analytical technique, suitable for fast evaluation of periodic reactor operations. The NFR analysis predicts a significant conversion gain (up to 50 %) for certain frequencies of the feed flow rate modulation. This prediction is validated by numerical simulations with a reaction rate expression obtained by CO₂ conversion experiments using a Ni/Al₂O₃ catalysts. Both the NFR analysis and numerical simulations predict that it is possible to obtain 70 % CO₂ conversion at 500 K, 5 bar, and average space velocity of 7600 h⁻¹ by a periodic modulation of the feed flow rate, as compared to the corresponding steady state CO₂ conversion of 43 %.     

Evaluation of the potential of periodically operated reactors based on the second order frequency response function

A new, fast and easy method for analysing the potential for improving reactor performance by replacing steady state by forced periodic operation is presented. The method is based on Volterra series, generalized Fourier transform and the concept of higher-order frequency response functions (FRFs). The second order frequency response function, which corresponds to the dominant term of the non-periodic (DC) component, G₂(ω, −ω), is mainly responsible for the average performance of the periodically operated processes. Based on that, in order to evaluate the potential of periodic reactor operation, it is enough to derive and analyze G₂(ω, −ω). The sign of this function defines the sign of the DC component and reveals whether a performance improvement by cycling is possible compared to optimal steady state process. The method is used to analyze the periodic performance of a continuous stirred tank reactor (CSTR), a plug flow tubular reactor (PFTR) and a dispersive flow tubular reactor (DFTR), after introducing periodic changes of the input concentrations. A homogeneous, n-th order reaction is studied under isothermal conditions.