Zig-zag arrangement of four electrodes for ac electro-osmotic micropumps.

This paper deals with the mathematical modeling of traveling-wave ac electro-osmotic micropumps with a zig-zag arrangement of microelectrodes. A mathematical model based on the Poisson-Nernst-Planck-Navier-Stokes description is used in this study within the physically relevant ranges of the model parameters. We present an extensive set of parametrical studies concerning the dependence of the net velocity on a variety of parameters. We also demonstrate limits of the validity of the commonly used Capacitor-Resistor-Capacitor model. In order to achieve high net velocities, we found that there are the optimal values of the electrode length, the shift between the top and bottom electrode arrays, and the signal frequency. Performance of the zig-zag micropumps is evaluated by the means of back-pressure loads. The suggested zig-zag design brings two main benefits: (i) it allows an easier construction of four-phase traveling-wave micropumps without the need of spatially complicated electrode connections, and (ii) the zig-zag pumps can provide higher flow rates than those with single-sided coplanar arrangements. Another robust feature of the proposed zig-zag system is that a single flow reversal is observed at the ac frequency approximately six times higher than the reciprocal resistor-capacitor time even in low-amplitude regimes.

[The experiences of a hospital radiology department with outside referrals for the preoperative marking of suspicious breast lesions]. / Erfahrungen einer radiologischen Spitalsabteilung mit auswärtigen Zuweisungen zur präoperativen Markierung suspekter Mammaläsionen.

PURPOSE: To outline the experience of a referral radiology department with preoperative localisation procedures on the basic of mammograms obtained by other facilities. MATERIAL AND METHODS: 342 consecutive female patients aged 56.5 +/- 11.9 years underwent preoperative breast localisation procedures prior to surgery. Of these patients 241 had their mammograms obtained in various private practices and 101 in the radiology department. Retrospectively all mammograms were classified by lesions morphology, lesion size and presence or absence of calcifications. RESULTS: The overall benign-to-malignant ratio (B/M-ratio) was 1.7:1. In the referred patient group the B/M-ratio was 1.9:1, compared to a B/M-ratio of 1.3:1 obtained by the radiology department. Referred patients presented significantly (p < 0.001) more often with calcifications that patients from the radiology department. CONCLUSION: Possible factors for the higher B/M-ratio in referred patients are prompt referral to surgical biopsy, misinterpretation of mammograms, failure in the written report, lack of a second opinion and lack of feedback and communication between surgeon, pathologist and radiologist.

Development of a methylprednisolone protocol for use in acute spinal cord injuries.

Acute spinal cord injury is a serious medical condition that results in 10,000 new cases of paralysis each year. Initial physical damage to the spinal cord is followed by chemical damage, resulting in cell death and scar tissue formation. Methylprednisolone therapy has proven effective in suppressing the chemical damage, particularly when started within 8 hours of injury. A protocol developed by the Pharmacy Department at Methodist Medical Center in Dallas, Texas, is described. This protocol facilitates accurate, efficient preparation and administration of this emergency therapy. The protocol takes advantage of the pharmacist's unique expertise to lessen the risk of calculation errors and mistakes in preparation, by providing a tailored drug admixture for administration at a fixed flow rate. The protocol and a sample of the pharmacy work sheet are presented.

[Cell culture preservation by automatic freezing in the adapted Höppler ultrathermostat of the NBE type]. / Konzervace bunecných kultur automatickým mrazením na upraveném ultratermostatu Höppler typu NBE.

A description is presented of an adapted ultrathermostat, respecting the requirement for a continuous decrease in temperature by 1 degree C per minute, as necessary for keeping the frozen cultures alive. Viability was evaluated in the primary cells of calf kidneys in the first subpassage and permanent cell lines PK and TL 72 after their freezing and preservation at -192 degrees C for 30 days. In comparison with regularly passaged cultures, the frozen cells had a high viability.

An interferometric rejection filter for Raman spectroscopy.

A three-mirror, multiple beam interferometer is described and analyzed in use as a rejection filter for elastically scattered light in a Raman scattering experiment. A prototype filter capable of attenuating laser source frequency light by a factor of 450 and passing 88% of Raman scattered signal is reported.