Analytical solutions for the electric field and dielectrophoretic force in a dielectrophoretic focusing electrode structure

The analysis of the movement of particles in a nonuniform field requires accurate knowledge of theelectric field distribution. In this letter, the Schwarz–Christoffel mapping method is used to analytically solve the electric field distribution in a dielectrophoretic focusing electrode structure.The analytical result for the electric field distribution is validated by comparison with numericalsimulations using the finite element method. The electric field solution is used to calculate the dielectrophoretic force on a particle in the syste

Analytical and numerical modeling methods for impedance analysis of single cells on-chip

Electrical impedance spectroscopy (EIS) is a noninvasive method for characterizing the dielectric properties of biological particles. The technique can differentiate between cell types and provide information on cell properties through measurement of the permittivity and conductivity of the cell membrane and cytoplasm. In terms of lab-on-a-chip (LOC) technology, cells pass sequentially through the microfluidic channel at high speed and are analyzed individually, rather than as traditionally done on a mixture of particles in suspension. This paper describes the analytical and numerical modeling methods for EIS of single cell analysis in a microfluidic cytometer. The presented modeling methods include Maxwell’s mixture theory, equivalent circuit model and finite element method. The difference and advantages of these methods have been discussed. The modeling work has covered the static case — an immobilized cell in suspension and the dynamic case — a moving cell in the channel

ASCA observations of two SNRs and NEI analysis

Based on the data from the \asca observation of SNRs Kes79 and W49B, we present here the analysis of their X-ray spectra and morphologies. The Kes79 spectrum can be well fitted by a single NEI component, and the narrow-band images of that source show an inhomogeneous distribution of heavy elements. The heavy elements are richest in the positions S, SE and SW of Kes79, where there may exist interaction between shocks and molecular clouds implied by radio observations. For W49B we present here the non-equilibrium ionization (NEI) analysis based on its emission line diagnostics, and the spectral fit using two NEI components. The reverse shock in W49B may be still hot and we don't find evidence for a hotter blast wave in \asca spectra.Comment: Contributed talk in 32nd COSPAR E1.1, 1998, Nagoya. To appear in Adv. Space Res., 1999, 6 pages, LaTe

A Sino-German λ\lambda6\ cm polarization survey of the Galactic plane VI. Discovery of supernova remnants G178.2-4.2 and G25.1-2.3

Supernova remnants (SNRs) were often discovered in radio surveys of the Galactic plane. Because of the surface-brightness limit of previous surveys, more faint or confused SNRs await discovery. The Sino-German $\lambda$6\ cm Galactic plane survey is a sensitive survey with the potential to detect new low surface-brightness SNRs. We want to identify new SNRs from the $\lambda$6\ cm survey map of the Galactic plane. We searched for new shell-like objects in the $\lambda$6\ cm survey maps, and studied their radio emission, polarization, and spectra using the $\lambda$6\ cm maps together with the $\lambda$11\ cm and $\lambda$21\ cm Effelsberg observations. Extended polarized objects with non-thermal spectra were identified as SNRs. We have discovered two new, large, faint SNRs, G178.2-4.2 and G25.1-2.3, both of which show shell structure. G178.2-4.2 has a size of 72 arcmin x 62 arcmin with strongly polarized emission being detected along its northern shell. The spectrum of G178.2-4.2 is non-thermal, with an integrated spectral index of $\alpha = -0.48\pm0.13$. Its surface brightness is $\Sigma_{1 GHz} = 7.2 x 10^{-23}{Wm^{-2} Hz^{-1} sr^{-1}}$, which makes G178.2-4.2 the second faintest known Galactic SNR. G25.1-2.3 is revealed by its strong southern shell which has a size of 80 arcmin x 30\arcmin. It has a non-thermal radio spectrum with a spectral index of $\alpha = -0.49\pm0.13$. Two new large shell-type SNRs have been detected at $\lambda$6\ cm in an area of 2200 deg^2 along the the Galactic plane. This demonstrates that more large and faint SNRs exist, but are very difficult to detect.Comment: 8 pages, 8 figures, accepted by Astronomy and Astrophysics. For the version with high resolution figures, please go to http://zmtt.bao.ac.cn/6cm/papers/2newSNR.pd

Simulation of the Aerodynamic Interaction between Rotor and Ground Obstacle Using Vortex Method

The mutual aerodynamic interaction between rotor wake and surrounding obstacles is complex, and generates high compensatory workload for pilots, degradation of the handling qualities, and performance, and unsteady force on the structure of the obstacles. The interaction also affects the minimum distance between rotorcrafts and obstacles to operate safely. A vortex-based approach is then employed to investigate the complex aerodynamic interaction between rotors and ground obstacle, and identify the distance where the interaction ends, and this is also the objective of the GARTEUR AG22 working group activities. In this approach, the aerodynamic loads of the rotor blades are described through a panel method, and the unsteady behaviour of the rotor wake is modelled using a vortex particle method. The effects of the ground plane and obstacle are accounted for via a viscous boundary model. The method is then applied to a “Large” and a “Wee” rotor near the ground and obstacle, and compared with the earlier experiments carried out at the University of Glasgow. The results show that predicted rotor induced inflow and flow field compare reasonably well with the experiments. Furthermore, at certain conditions, the tip vortices are pushed up and re-injected into the rotor wake due to the effect of the obstacle resulting in a recirculation. Moreover, contrary to without the obstacle case, peak and thickness of the radial outwash near the obstacle are smaller due to the barrier effect of the obstacle, and an upwash is observed. In addition, as the rotor closes to the obstacle, the rotor slipstreams impinge directly on the obstacle, and the upwash near the obstacle is faster, indicating a stronger interaction between the rotor wake and the obstacle. In addition, contrary to the case without the obstacle, the fluctuations of the rotor thrust, and rolling and pitching moments are obviously strengthened. When the distance between the rotor and the obstacle is larger than 3R, the effect of the obstacle is small

Unsteady Aerodynamic Interaction Between Rotor and Ground Obstacle

The mutual aerodynamic interaction between rotor wake and surrounding obstacles is complex, and generates high compensatory workload for pilots, degradation of the handling qualities and performance, and unsteady force on the structure of the obstacles. The interaction also affects the minimum distance between rotorcrafts and obstacles to operate safely. A vortex-based approach is then employed to investigate the complex aerodynamic interaction between rotors and ground obstacle, and identify the distance where the interaction ends, and this is also the objective of the GARTEUR AG22 working group activities. In this approach, the aerodynamic loads of the rotor blades are described through a panel method, and the unsteady behaviour of the rotor wake is modelled using a vortex particle method. The effects of the ground plane and obstacle are accounted for via a viscous boundary model. The method is then applied to a “Large” and a “Wee” rotor near the ground and obstacle, and compared with the earlier experiments carried out at the University of Glasgow. The results show that the predicted rotor induced inflow and flow field compare reasonably well with the experiments. Furthermore, at certain conditions the tip vortices are pushed up and re-injected into the rotor wake due to the effect of the obstacle resulting in a recirculation. Moreover, contrary to without the obstacle case, the peak and thickness of the radial outwash near the obstacle is smaller due to the barrier effect of the obstacle, and an up-wash is observed. Additionally, as the rotor closes to the obstacle, the rotor slipstreams impinge directly on the obstacle, and the up-wash near the obstacle is faster, indicating a stronger interaction between the rotor wake and the obstacle. Also, contrary to the case without the obstacle, the fluctuations of the rotor thrust, rolling and pitching moments are obviously strengthened. When the distance between the rotor and the obstacle is larger than 3R, the effect of the obstacle is small

The evaluation of the rate constants for a reversible unimolecular hydrogen transfer reaction that involves a cyclic transition state

Intermolecular hydrogen transfer free radical reactions are common in the combustion process and in a number of organic chemistry reactions. Therefore, evaluating the pressure and temperature-dependent rate constants of them is of great importance. Basing on microcanonical Rice-Ramsperger-Kassel-Marcus (RRKM) theory, tunnelling correction, and internal rotation correction, we present a simple model that is able to give an estimate of the desired rate constants of a reversible unimolecular reaction. We then extend the simple reversible reaction model to calculate the overall relaxation rate constants of the combustion process of propane

Parking and the visual perception of space

Using measured data we demonstrate that there is an amazing correspondence among the statistical properties of spacings between parked cars and the distances between birds perching on a power line. We show that this observation is easily explained by the fact that birds and human use the same mechanism of distance estimation. We give a simple mathematical model of this phenomenon and prove its validity using measured data

D-Instanton in AdS_5 and Instanton in SYM_4

Following the observation of Banks and Green that the D-instantons in AdS_5 correspond to the instantons in 4-dimensional supersymmetric Yang-Mills theory, we study in more detail this correspondence for individual instantons. The supergravity solution for a D-instanton in AdS_5 is found using the ansatz used previously for D-instantons in flat space. We check that the actions and supersymmetries match between the D-instanton solution and the Yang-Mills instanton. Generalizing this result, we propose that any supergravity solution satisfying the ansatz corresponds to a (anti-)self-dual Yang-Mills configuration. Using this ansatz a family of identities for correlation functions in the supersymmetric Yang-Mills theory are derived.Comment: LaTeX, 19 pages, no figure, some typos correcte

Helical CT angiography of fenestrated stent grafting of abdominal aortic aneurysms

Fenestrated stent grafts have been developed to treat patients with abdominal aortic aneurysms (AAA) associated with complicated aneurysm necks, such as short necks, severe angulated or poor quality necks (presence of calcification or thrombus). The technique is performed by creating an opening in the graft material so that the stent graft can be placed above the renal and other visceral branches without compromising blood perfusion to these vessels. In most situations, a supporting stent is inserted into the fenestrated vessel to provide fixation of the fenestrated vessel against stent grafts, as well as to preserve patency of the vessel. Helical CT angiography (CTA) is the preferred imaging modality in both pre-operative planning and post-procedural follow-up of fenestrated repair of AAA. The main concerns of fenestrated stent grafting lie in the following two aspects: patency of the fenestrated vessels and position of the fenestrated stents in relation to the artery branches. In this article, the author presents the clinical applications of 2D and 3D visualizations in the follow-up of patients with AAA treated with fenestrated stent grafts, with the aim of providing useful information to readers and increasing their knowledge of an increasingly used technique, fenestrated stent grafting in the treatment of AAA