Model Scenarios for Direction-Selective Adaptive Antennas in Cellular Mobile Communication Systems – Scanning the Literature

Intelligent antennas offer the possibility of greatly increasing the capacity of cellular mobile radio systems. We give a comprehensive overview of the literature concerning model scenarios for applications of direction-selective intelligent antennas. Measurement campaigns and simplified models are described that have been derived from these measurements or from physical considerations. Furthermore, directional fading simulators are reviewed which are essential for testing of smart antenna systems.     

Modification of the sensitivity of glucose sensor implanted into subcutaneous tissue

The mechanism of reducing the glucose sensitivity of sensors implanted into the subcutaneous tissue of the normal rat was evaluated (n = 10) by comparing sensitivities observed in vitro and in vivo. In vivo sensitivity was significantly lower than that observed in vitro before implantation (p < 0.005). Most interestingly, in vitro sensitivity immediately after explanation did not differ from that in vivo and increased progressively during rinsing (p < 0.02 after 30 min). These results demonstrate that the reduction of in vivo sensitivity was not due to a local factor or factors but to a reversible alteration of the glucose sensor characteristics induced in vivo by some local factor(s). This suggests that modifications of the outer sensor membrane, the nature of which remains to be determined, may prevent this effect and resolve the problem.     

Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures

High-frequency electric fields can be used to induce deformation of red blood cells. In the temperature domain T = 0 degrees to -15 degrees C (supercooled suspension) and for 25 degrees C this paper examines for human erythrocytes (discocytes, young cell population suspended in a low ionic strength solution with conductivity sigma(25 degrees) = 154 microS/cm) in a sinusoidal electric field (nu = 1 MHz, E0 = 0-18 kV/cm) the following properties and effects as a function of field strength and temperature: 1) viscoelastic response, 2) (shear) deformation (steady-state value obtained from the viscoelastic response time), 3) stability (by experimentally observed breakdown of cell polarization and hemolysis), 4) electrical membrane breakdown and field-induced hemolysis (theoretical calculations for ellipsoidal particles), and 5) mechanical hemolysis. The items 2-4 were also examined for the frequency nu = 100 kHz and for a nonionic solution of very low conductivity (sigma(25 degrees) = 10 microS/cm) to support our interpretations of the results for 1 MHz. Below 0 degrees C with decreasing temperature the viscoelastic response time tau(res)(T) for the cells to reach steady-state deformation values d(infinity,E) increases and the deformation d(infinity,E)(T) decreases strongly. Both effects are especially high for low field strengths. The longest response time of approximately 30 s was obtained for -15 degrees C and small deformations. For 1 MHz the cells can be highly elongated up to 2.3 times their initial diameter a0 for 25 degrees and 0 degrees C, 2.1a0 for -10 degrees C and still 1.95a0 for -15 degrees C. For T > or = 0 degrees C the deformation is limited by hemolysis of the cells, which sets in for E0(lysis)(25 degrees) approximately 8 kV/cm and E0(lysis)(0 degrees) approximately 14 kV/cm. These values are approximately three times higher than the corresponding calculated critical field strengths for electrically induced pore formation. Nevertheless, the observed depolarization and hemolysis of the cells is provoked by electrical membrane breakdown rather than by mechanical forces due to the high deformation. For the nonionic solution, where no electrical breakdown is expected in the whole range for E0, the cells can indeed be deformed to even higher values with a low hemolytic rate. Below 0 degrees C we observe no hemolysis at all, not even for the frequency 100 kHz, where the cells hemolyze at 25 degrees C for the much lower field strength E0(lysis) approximately 2.5 kV/cm. Obviously, pore formation and growth are weak for subzero temperatures.     

Numerical methods for ultraparabolic equations

We analyze semidiscrete and fully discrete finite element approximations to the solution of an initial boundary value problem for a model ultraparabolic equation.     

Delayed neuropsychologic sequelae after carbon monoxide poisoning: prevention by treatment with hyperbaric oxygen

STUDY OBJECTIVE: Carbon monoxide (CO) poisoning is a major clinical problem. The risk of morbidity and the most effective treatment have not been clearly established. We measured the incidence of delayed neurologic sequelae (DNS) in a group of patients acutely poisoned with CO and tested the null hypothesis that the incidence would not be affected by treatment with hyperbaric oxygen (HBO). DESIGN: We conducted a prospective, randomized study in patients with mild to moderate CO poisoning who presented within 6 hours. Patients had no history of loss of consciousness or cardiac instability. INTERVENTIONS: The incidence of DNS was compared between groups treated with ambient pressure 100% oxygen or HBO (2.8 ATA for 30 minutes followed by 2.0 ATA oxygen for 90 minutes). DNS were defined as development of new symptoms after oxygen treatment plus deterioration on one or more subtests of a standardized neuropsychologic screening battery. RESULTS: In 7 of 30 patients (23%), DNS developed after treatment with ambient-pressure oxygen, whereas no sequelae developed in 30 patients after HBO treatment (P < .05). DNS occurred 6 +/- 1 (mean +/- SE) days after poisoning and persisted 41 +/- 8 days. At follow-up 4 weeks after poisoning, patients who had been treated with ambient pressure oxygen and had not sustained DNS exhibited a worse mean score on one subtest, Trail Making, compared with the group treated with HBO and with a control group matched according to age and education level. There were no differences in scores between the control group and the hyperbaric oxygen group. CONCLUSION: DNS after CO poisoning cannot be predicted on the basis of a patient's clinical history or CO level. HBO treatment decreased the incidence of DNS after CO poisoning.     

A study of the metal sulfide-sulfur dioxide reaction in aqueous media by reaction pressure characterization and ultraviolet spectrophotometry

The metal sulfide-sulfur dioxide reaction has been characterized for seven different sulfide ores by using the changes in sulfur dioxide pressure during the reaction and by ultraviolet spectrophotometric analysis of the reaction products. The UV analysis, which showed that thiosulfuric acid is a major product of the metal sulfide-sulfur dioxide reaction, was used to monitor the r rate of formation of thiosulfuric acid during the reaction. Results from a series of base-line experiments using ferrous sulfide showed a high correlation between the rate of change of sulfur dioxide pressure, the rate of appearance of ferrous ion, and the rate of formation of thiosulfuric acid. These results were compared with those obtained in similar experiments with six naturally-occurring sulfide ores. Finally, the UV method was employed to monitor the kinetics of the decomposition of thiosulfuric acid into elemental sulfur. Using these results, in conjunction with the mechanisms previously developed for the Wackenroder reaction and the acid decomposition of thiosulfate, a mechanism is proposed for the acid oxidative dissolution of sulfide ores which accounts for the formation of elemental sulfur.     

An error estimate for theH −1 Galerkin method for a parabolic problem with non-smooth initial data

A non-smooth data error estimate with respect to theL ₂ norm is shown for a semidiscrete Galerkin-Petrov method for a parabolic problem in one space dimension. If the trial and test spaces consist of piecewise polynomials of degreer−1 inC ^k anr+1 inC ^k+2 , respectively, with test functions satisfying boundary conditions, then the error norm is bounded byCh ^r t ^−r/2 fort positive, whereh is the maximum mesh size.