Simultaneous dielectric monitoring of microfluidic channels at microwaves utilizing a metamaterial transmission line structure.

The paper presents a technique that allows the simultaneous monitoring of the dielectric properties of liquids in microfluidic channels at microwave frequencies. It is capable of being integrated within the lab-on-a-chip concept and uses a composite right/left-handed transmission line resonator which is detuned by the dielectric loading of the liquids in the channels. By monitoring the change in the resonance spectrum of the resonator the loading profile can be derived with the multi-resonant perturbation method. From the value of the dielectric constant inference on the substances like cells or chemicals in the channels can be drawn. The paper presents concept, design, fabrication and characterization of prototype sensors. The sensors have been designed to operate between 20 and 30 GHz and were tested with water and water ethanol mixtures.

Surgery for recurrent goitre: its complications and their risk factors.

OBJECTIVE: To find out the morbidity of reoperation for benign recurrent thyroid disease, and the risk factors associated with it. DESIGN: Retrospective study. SETTING: Specialist endocrine unit, Germany. SUBJECTS: 1031 patients operated on for recurrent goitre between 1 January 1983 and 31 December 1996. MAIN OUTCOME MEASURES: Incidence of recurrent laryngeal nerve palsy and hypocalcaemia. RESULTS: 82/1031 patients were excluded from assessment for recurrent laryngeal nerve function leaving 949 for analysis. There were no cases of bilateral permanent palsy, but 1 patient developed temporary bilateral palsy. 33 patients (3%) developed permanent unilateral palsy and 46 (5%) temporary palsy. 1307 nerves were at risk, and the rate of permanent palsy was therefore 2% of nerves at risk. This was 5 times the rate after the initial operation. Hyperthyroidism and not exposing the nerve during operation were predisposing factors. 118 patients were excluded from assessment of hypocalcaemia leaving 913 for analysis. 23 patients developed temporary hypocalcaemia (2%), but only 5 (0.5%) developed permanent hypocalcaemia. Because so few patients developed hypocalcaemia we were unable to designate risk factors. CONCLUSION: Because of the high risk of complications operations for recurrent goitre should be done only if the patient cannot be treated in any other way. The risk of recurrence should be minimised by excision of all nodules during the initial operation.

Effect of differential spinal cord transection on human cerebral blood flow.

Regional cerebral blood flow (rCBF) was measured by 133Xe inhalation in 17 patients with chronic spinal cord transection. This was done to investigate any effects such spinal cord deafferentation might have on resting rCBF and to test whether resulting chronic preganglionic sympathectomy influenced cerebral vasomotor CO2 responsiveness and autoregulation. Thirteen patients had complete cervical cord transection (CCT) at levels C4--C6 (age 37 +/- 15 years, time interval, 2 months--20 years). Four patients had complete thoracic cord transection at levels T3--4, T8 and T12 (TCT; age 49 +/- 22 years; time interval 2--5 months). CO2 responsiveness was tested by induced hypercapnia in 11 patients with CCT and 2 patients with TCT. Autoregulation was tested in 10 patients with CCT and 4 patients with TCT by decreasing cerebral perfusion pressure during postural tilting. Mean resting hemispheric Fg values (MHFg) were significantly reduced only in patients with CCT (MHFg = 69 +/- 12 ml/100 g brain/min), while brain stem-cerebellar Fg values (BSC Fg) were reduced significantly both in patients with CCT (BSC Fg = 85 +/- 10) and with TCT (BSC Fg = 88 +/- 12) compared to values measured in healthy normals (N = 21, MHFg = 81 +/- 10, BSC Fg = 98 +/- 10). Hemispheric CO2 responsiveness showed a trend toward reduction in patients with CCT but this was not statistically significant. Hemispheric autoregulation was significantly impaired in CCT compared to healthy normals but improved with time and rehabilitation.