We have recently shown that melatonin decreases the late (24 hr) increase in blood–brain barrier (BBB) permeability and the risk of tissue plasminogen activator‐induced hemorrhagic transformation following ischemic stroke in mice. In the study, we further explored whether melatonin would reduce postischemic neurovascular oxidative/nitrosative damage and, therefore, improve preservation of the early increase in the BBB permeability at 4 hr after transient focal cerebral ischemia for 60 min in mice. Melatonin (5 mg/kg) or vehicle was given intraperitoneally at the beginning of reperfusion. Hydroethidine (HEt) in situ detection and immunohistochemistry for nitrotyrosine were used to evaluate postischemic accumulation in reactive oxygen and nitrogen species, respectively, in the ischemic neurovascular unit. BBB permeability was evaluated by spectrophotometric and microscopic quantitation of Evans Blue leakage. Relative to controls, melatonin‐treated animals not only had a significantly reduced superoxide accumulation in neurovascular units in boundary zones of infarction, by reducing 35% and 54% cytosolic oxidized HEt in intensity and cell‐expressing percentage, respectively (P < 0.001), but also exhibited a reduction in nitrotyrosine by 52% (P < 0.01). Additionally, melatonin‐treated animals had significantly reduced early postischemic disruption in the BBB permeability by 53% (P < 0.001). Thus, melatonin reduced postischemic oxidative/nitrosative damage to the ischemic neurovascular units and improved the preservation of BBB permeability at an early phase following transient focal cerebral ischemia in mice. The findings further highlight the ability of melatonin in anatomical and functional preservation for the ischemic neurovascular units and its relevant potential in the treatment of ischemic stroke.

Melatonin protects against transient middle cerebral artery (MCA) occlusion and may be suited as an add-on therapy of tissue plasminogen activator (t-PA) thrombolysis. Herein, we examined whether melatonin would reduce postischemic increase in the blood-brain barrier (BBB) permeability and, therefore, attenuate the risk of hemorrhagic transformation after t-PA therapy in experimental stroke. Twelve mice were subjected to transient occlusion of the MCA for 1 hr, followed by 24 hr of reperfusion. Melatonin (5 mg/kg, i.p.) or vehicle was given at the beginning of reperfusion. BBB permeability was evaluated by quantitation of Evans Blue leakage. An additional 32 mice underwent photothrombotic occlusion of the distal MCA, and were administered vehicle or t-PA (10 mg/kg, i.v.), alone or in combination with melatonin (5 mg/kg, i.p.), at 6 hr postinsult. The animals were then killed after 24 hr for the determination of infarct and hemorrhage volumes. Relative to controls, melatonin-treated animals had significantly reduced BBB permeability (by 52%; P < 0.001). Additionally, we found that at 6 hr after photo-irradiation, either t-PA or melatonin, or a combined administration of t-PA plus melatonin, did not significantly affect brain infarction (P > 0.05), compared with controls. Mice treated with t-PA alone, however, had significantly increased hemorrhagic formation (P < 0.05), and the event was effectively reversed by co-treatment with melatonin (P < 0.05). Thus, melatonin improved postischemic preservation of the BBB permeability and a decreased risk of adverse hemorrhagic transformation after t-PA therapy for ischemic stroke. The findings further highlight melatonin's potential role in the field of thrombolytic treatment for ischemic stroke patients.

The individually designed Pilates-based exercise program was feasible for healthy older adults, and the high attendance rate supports the suitability of the exercise program over a long period. Considering the variability of the baseline measure, small improvement was only observed in the thoracic kyphosis during standing. The long-term effect of Pilates exercise requires further investigation.

However, in the case of the Class II network, the pairs of optimum Z mi and Z si values can be chosen according to the required bandwidth and desired stub impedance.To verify the electrical performances of the proposed structures, three independent phase shifters of 45°, 90°, and 180°, as shown in Figure 3, were fabricated using a teflon substrate ( r ϭ 2.17, H ϭ 0.508 mm, T ϭ 0.5 oz.). The impedance values of each phase shifter operating at 3 GHz were obtained from the design graph (see Fig. 2).The electrical performances for the input return and insertion loss, and the relative phase shift of each phase bit, were measured using a vector network analyser and are plotted in Figure 4 together with the simulation result for comparison.The measured performances in Figure 4 were in very close agreement with the theoretical predictions. All input return losses, including the SMA connector's characteristic, were more than 19 dB in the range 2.2-3.6 GHz. In general, as the phase shift increases, the operating bandwidth decreases. The results shown in Figure 4(b)-(d) show that the Class I network provides octave bandwidths at 90°phase shift, which is the same as that in [3], and also shows approximately 50% fractional bandwidth at 180°phase shift, which cannot be realized in [3]. CONCLUSIONA broadband phase shifter using a new switched network of two parallel double stubs has been presented. A theoretical analysis of the proposed structures has been performed, and a design graph has also been provided to find the optimum Z m and Z s values as a function of the desired phase shift. The Class I structure is appropriate for phase shifts of more than 90°and 180°, and the Class II structure is recommended for less than 90°-for example, 45°.

of the printed PIFA show no special distinction when compared with those of the hybrid PIFA shown here. Thus, the radiation patterns of the printed PIFA are not shown for brevity. Figure 10 presents the measured antenna gain and simulated radiation efficiency over the lower and upper bands of the hybrid PIFA studied in Figure 3. For the lower band from 1.88 to 2.75 GHz, the antenna gain is varied in the range of 1.3-2.5 dBi, while the radiation efficiency is about 85% over the band. As for the upper band from 4.89 to 5.90 GHz, the antenna gain is varied from about 4.1 to 5.5 dBi, and the radiation efficiency is also about 85% over the band. The corresponding results of the printed PIFA studied in Figure 4 are shown in Figure 11. It can be seen that the obtained antenna gain and radiation efficiency are about the same as those shown in Figure 10. That is, similar radiation characteristics of the hybrid and printed PIFAs studied here are obtained. CONCLUSIONTwo kinds of promising PIFAs (hybrid PIFA and printed PIFA) for application in a USB dongle have been proposed, fabricated, and tested. Both the hybrid and printed PIFAs occupy a compact volume and can easily be embedded inside the casing of the general USB dongle as internal antennas. In addition, both the two PIFAs can provide two wide operating bands for covering UMTS/ WLAN/WiMAX multi-network operation. Easy adjustment of the two wide operating bands of the proposed hybrid and printed PIFAs has also been obtained. The two PIFAs also show good radiation characteristics over their two wide operating bands. ACKNOWLEDGMENT

A printed diversity dual-band planar inverted-F antenna (PIFA) mounted vertically at the edge of a PCMCIA network card (such that the protruded portion of the network card from the housing of the laptop has a minimum length) for WLAN operation in the 2.4-GHz band (2400 -2484 MHz) and 5.2-GHz band (5150 -5350 MHz) is presented. The diversity antenna studied comprises two back-to-back stacked PIFAs and has a low profile of 10 mm to the network card. Across the two operating bands, the measured reflection coefficient S 11 and isolation S 21 are all less than Ϫ14 dB (1.5:1 VSWR) and Ϫ24 dB, respectively. In addition, the measured radiation patterns of the two stacked PIFAs in general cover complementary space regions, thereby making it possible for providing spatial diversity for WLAN operation. ABSTRACT:The microstrip-via-microstrip is a popular interconnect structure in multilayer circuits at microwave frequency. The microstrip connecting angle is an arbitrary angle due to layout and technical error. The relationship between the propagation characteristics of via and the microstrip connecting angle was analyzed by using the Ansoft simulator. The obtained results have important application value for the design of a similar multilayer circuit.

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A folded inverted‐F strip antenna printed on a dielectric substrate and fed by a coplanar waveguide is presented. A prototype with a small area of 25×8 mm2 having a 10 dB impedance bandwidth of about 20% centered at about 2.0 GHz has been constructed and studied. The constructed prototype also showed good radiation characteristics, and is suitable for UMTS (Universal Mobile Telecommunication System, 1920–2170 MHz) applications. The experimental results of the constructed prototype are presented, and are also compared with those of a corresponding simple inverted‐F strip antenna. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 364–366, 2002.