Design and comparison of LQG/LTR and H-infinity controllers for a VSTOL flight control system

In this paper two robust controllers for a multivariable vertical short take-off and landing (VSTOL) aircraft system are designed and compared. The aim of these controllers is to achieve robust stability margins and good performance in step response of the system. LQG/LTR method is a systematic design approach based on shaping and recovering open-loop singular values while mixed-sensitivity H-infinity method is established by defining appropriate weighting functions to achieve good performance and robustness. Comparison of the two controllers show that LQG method requires rate feedback to increase damping of closed-loop system, while H-infinity controller by only proper choose the weighting functions, meets the same performance for step response. Output robustness of both controllers is good but H-infinity controller has poor input stability margin. The net controller order of H-infinity is higher than the LQG/LTR method and the control effort of them is in the acceptable range. (c) 2006 The Franklin Institute. Published by Elsevier Ltd. All rights reserved

Removal of subfoveal perfluorocarbon liquid: Report of 3 cases

Purpose: To report removal of retained subfoveal perfluorocarbon liquid (PFCL) after vitrectomy for retinal detachment. Methods: Three patients underwent 3-port 23-gauge vitrectomy in an attempt to remove retained subfoveal PFCL bubble secondary to retinal detachment surgery. In two patients, removal was achieved via a 23-G needle whereas the third patient with multiple small subfoveal droplets, multiple punctures were required and in that case a small 40-G needle was used.We assessed best corrected visual acuity (BCVA), fundus imaging, and spectral domain optical coherence tomography (SD-OCT) of all patients before and after surgery. Results: The subfoveal PFCL was successfully removed in all 3 eyes and although a functional improvement was documented, outer retinal atrophy and photoreceptor loss was observed in all our cases. Conclusions: SD-OCT allows early recognition of retained subfoveal PFCL. Surgical removal may lead to retinal morphologic restoration and functional improvement. While we achieved complete removal of PFCL with both 23-G and 40-G instrumentation, we believe the versatility and ease justifies the universal usage of 40-G retinotomy needles. Keywords: Subfoveal perfluorocarbon, PFCL, PFCL remova

Effect of Follicular Fluid and Platelet-Activating Factor on Lactate Dehydrogenase C Expression in Human Asthenozoospermic Samples

Background: Application of follicular fluid (FF) and platelet-activating factor (PAF) in artificial insemination improves sperm motility. Lactate dehydrogenase C (LDH-C) is a key enzyme for sperm motility. In this study, the effects of FF and PAF on the sperm motility index and LDH-C expression were investigated. Moreover, LDH-C expression was compared between asthenozoospermic and normozoospermic samples. Methods: The expression of LDH-C was examined by quantitative real-time polymerase chain reaction (q-RT PCR) and western blotting after it was treated with optimized concentrations of FF and PAF in twenty asthenozoospermic samples. Also, LDH-C expression was evaluated in five normozoospermic samples. Results: Samples with 75% FF and 100 nM of PAF had an increase in their percentages of progressive and slowly motile sperms and a decrease in their percentages of non-progressive and non-motile sperms. Moreover, LDH-C mRNA transcripts were not changed following PAF and FF treatment, and LDH-C protein was detected in highly progressive motile specimens treated with FF in the asthenozoospermic samples. Furthermore, LDH-C expression was more detectable in the normal sperms. Conclusion: Our results indicated that PAF had more beneficial effects than FF on sperm motility in the asthenozoospermic samples (P=0.0001), although the LDH-C expressions of the sperms were not changed significantly in both groups. We found no association between LDH-C expression and sperm motility after FF and PAF actions. This finding, however, requires further investigation. The fact that LDH-C protein was detected in the normozoospermic, but not asthenozoospermic, samples could be cited as a reason for the infertility in these patients