Search

Cyclical electrical field flow fractionation (Cy/ElFFF) is demonstrated in a standard electrical field flow fractionation (ElFFF) channel for the first time. Motivation for the use of alternating current (AC) fields in a traditionally direct current (DC) technique are discussed. The function of the system over a wide range of operating conditions is explored and challenges associated with various operating conditions reported. Retention of polystyrene nanoparticle standards is accomplished and the effect of varying parameters of the applied field, such as voltage and frequency, are explored. The first separations using this technique are demonstrated. The experimental results are compared to analytical models previously reported in the literature. The general trend of the experimental results is similar to those predicted in theoretical models and possible reasons for discrepancies are elucidated. Suggestions are made for improving the separation and analysis method, and possible applications explored.

We have developed a polyimide based neural interface electrode to record nerve signals from the sciatic nerve of a rat. The neural interface electrode has a split-ring shape, with four protruding gold electrodes for recording, and two reference gold electrodes around the split-ring. The split-ring electrode can be opened up to encircle the sciatic nerve. The four electrodes can be bent to sit on top of the nerve and hold the device in position, while the split-ring frame remains flat. In comparison, while traditional cuff electrodes can only fit certain sizes of the nerve, the developed device can fit a variety of rat sciatic nerve dimensions from 0.6 mm to 1.0 mm, and adapt to the chronic changes in the nerve as the electrode tips are bendable. The electrochemical impedance spectroscopy measurement was conducted. The gold electrode impedance is on the order of 10 kΩ, showing excellent charge injection capacity to record neural signals., {"references":["L. Weiner and K. L. Reed, \"Peripheral neurostimulation for control of intractable occipital neuralgia,\" Neuromodulation, vol. 2, no. 3, pp. 217–221, 1999.","R. M. Paicius, C. A. Bernstein, and C. Lempert-Cohen, \"Peripheral nerve field stimulation for the treatment of chronic low back pain: Preliminary results of long term follow-up: A case series,\" Neuromodulation, vol. 10, no. 3, pp. 279–290, 2007.","H. E. Nelson Jr, M. B. Smith, B. R. Bowman, and R. L. Waters, \"Electrode effectiveness during transcutaneous motor stimulation,\" Arch Phys Med Rehabil, vol. 61, pp. 73-77, 1980.","N. Bhadra, K. L. Kilgore, and P. H. Peckham, \"Implanted stimulatorsfor restoration of function in spinal cord injury,\"Med Eng Phys, vol. 23, pp. 19–28, 2001.","T. Stieglitz, H. Beutel, M. Schuettler, and J. U. Meyer, \"Micromachined, polyimide-based devices for flexible neural interfaces,\" Biomed Microdev, vol. 2, pp.283–294, 2000.","S. M. Lawrence, G. S. Dhillon, and K. W. Horch, \"Fabrication and characteristics of an implantable, polymer-based, intrafascicular electrode,\" J Neurosci Methods, vol. 131, pp. 9–26, 2003.","L. Wallman, Y. Zhang, T. Laurell, and N. Danielsen, \"The geometric design of micromachined silicon sieve electrodes influences functional nerve regeneration,\" Biomaterials, vol. 22, pp. 1187–1193, 2001."]}

Protrusion of a bowel segment into another (intussusception) produces severe abdominal pain and culminates in intestinal obstruction. In adults, intestinal obstruction due to intussusception is relatively rare phenomenon, as it accounts for minority of intestinal obstructions in this population demographic. Organic lesion is usually identifiable as the cause of adult intussusceptions, neoplasms account for the majority. Therefore, surgical resection without reduction is almost always necessary and is advocated as the best treatment of adult intussusception. Here, we describe a rare case of a 44-year-old male with a diffuse large B-cell lymphoma involving the terminal ileum, which had caused ileocolic intussusception and subsequently developed intestinal obstruction requiring surgical intervention. This case emphasizes the importance of recognizing intussusception as the initial presentation for bowel malignancy.

Cyclical electrical field flow fractionation (CyElFFF) is a variation on electrical field flow fractionation (ElFFF) where cyclical electrical fields are used instead of steady DC fields to increase the effective field experienced by particles in the flow channel. Even though the effective field increases more than 20-fold compared to normal ElFFF, the retention and resolution in CyElFFF has not been shown to be better than in ElFFF. In this paper we report how one can optimize operational parameters in CyElFFF to obtain good retention and resolution in CyElFFF. The effects of offset voltage, frequency, flowrate, concentration of particles and sample size on retention, resolution and retained peak/void peak ratio have been observed. The results obtained from these experiments were analyzed and suggestions have been made to improve both retention and resolution. A 4-fold improvement in retention without a significant increase in band broadening is reported.

We present the fabrication of highly P-doped single crystal silicon electrodes on a silicon probe through complementary metal-oxide-semiconductor (CMOS)-compatible processes. The electrode with diameter of 50 μm and a separation of 200 μm is designed for recording/stimulating purposes. Electrochemical impedance spectroscopy indicates that the interfacial impedance of silicon electrodes at 1 KHz is 2.5 ± 0.4 MΩ, which is equivalent to the result reported from the gold (Au) electrode. To further enhance the charge storage capacity, composites of multi-wall carbon nanotubes (MWCNTs) and Au nanoparticles are electroplated onto the highly P-doped silicon electrode after surface roughness treatments. With optimized electroplating processes, MWCNTs and Au nanoparticles are selectively coated onto the electrode site with only a minimum enlargement in physical diameter of electrode (

A microscale cyclical electrical field flow fractionation (CyElFFF) channel is characterized with regard to the effect of various operating parameters and comparison made to recent theoretical developments. Challenges associated with various operating conditions are reported along with some of the optimized operating parameters. The effect of retention wall choice, an offset voltage, relaxation steps, and flow rates, along with the basic operating parameters of voltage, frequency, and electrophoretic mobility are reported. Retention of polystyrene nanoparticle standards is accomplished and the first separations using this technique in a microscale system are also demonstrated. Relaxation steps and offset voltages are found to be effective in eliminating early peaks and in improving plate heights. Plate heights were also found to decrease with increasing flow rates, which is the opposite of the behavior seen in most existing chromatographic systems. The experimental results are compared to the analytical and empirical models of CyElFFF and found to be compatible. Suggestions are made for improving the separation and analysis methods used with CyElFFF.