State and output feedback design for robust tracking of linear systems with rate limited actuators

A design technique (Control of Uncertain Systems with Bounded Inputs, Tarbouriech S, Garcia G, (Eds), Lecture Notes in Control and Information Sciences, vol. 227 , Springer: Berlin, 1997; 173–186) recently proposed for stabilization of a linear system with rate‐limited actuators is utilized to design feedback laws that cause the system output to track a desired command signal. This design technique combines two design techniques recently developed for linear systems with position limited actuators, piecewise‐linear LQ control (Automatica, 1994; 30 : 403–416) and low‐and‐high gain feedback (IEEE Trans. Automat. Control, 1996; 41 : 368–378), and hence takes advantage of both design techniques, while avoiding their disadvantages. In the case that only the output is available for feedback, the performance of the state feedback law is preserved by the use of a fast observer. An open‐loop exponentially unstable fighter aircraft is used to demonstrate the effectiveness of the proposed control design method. Copyright © 2002 John Wiley & Sons, Ltd.     

Liver Transplantation Across Rh Blood Group Barriers Increases the Risk of Biliary Complications

Background Cold ischemia time and the presence of postoperative hepatic arterial thrombosis have been associated with biliary complications (BC) after liver transplantation. An ABO-incompatible blood group has also been suggested as a factor for predisposal towards BC. However, the influence of Rh nonidentity has not been studied previously. Materials Three hundred fifty six liver transplants were performed from 1995 to 2000 at our hospital. BC incidence and risk factors were studied in 345 patients. Results Seventy patients (20%) presented BC after liver transplantation. Bile leakage (24/45%) and stenotic anastomosis (21/30%) were the most frequent complications. Presence of BC in Rh-nonidentical graft–host cases (23/76, 30%) was higher than in Rh-identical grafts (47/269, 17%) (P = 0.01). BC was also more frequent in grafts with arterial thrombosis (9/25, 36% vs 60/319, 19%; P = 0.03) and grafts with cold ischemia time longer than 430 min (26/174, 15% vs 44/171, 26%; P = 0.01). Multivariate logistic regression confirmed that Rh graft–host nonidentical blood groups [RR = 2(1.1–3.6); P = 0.02], arterial thrombosis [RR = 2.6(1.1–6.4); P = 0.02] and cold ischemia time longer than 430 min [RR = 1.8(1–3.2); P = 0.02] were risk factors for presenting BC. Conclusion Liver transplantation using Rh graft–host nonidentical blood groups leads to a greater incidence of BC.     

Mixed h2 and h∞ optimal robust control design

This paper introduces a design methodology for a dynamic compensator that simultaneously minimizes the upper bound of a quadratic performance index and the H_∞-norm of a disturbance transfer function matrix of a multiple-input/multiple-output system whose model contains parameter uncertainty in the state and input matrices. The real parameter uncertainty is modelled as additional measurement outputs and as additional weights on the existing noise inputs and measurement outputs of the system. The compensator equations are derived by taking the dual of a system with parameter variation in the state and output matrices, for which the compensator equations have previously been derived, and then taking the dual of the compensator equations. An algorithm for applying this theory is given and an example is shown.     

GC-MS Determination of Targeted Pesticides in Environmental Samples from the Kafue Flats of Zambia

Results of a GC-MS analysis for targeted pesticides i.e. dieldrin, endosulfan, pp-DDT, endrin, HCB, heptachlor, mirex and aldrin in the Kafue Flats of Zambia are presented. Analysis was done in soils, sediments, water and vegetation samples from the Lochinvar and Blue Lagoon National Parks along the Kafue River. A validated analytical method that was used gave recoveries in a spiked soil sample ranging between 60 % and 100 % with limits of detection (LODs) ranging from 0.94 to 8.0 ng/g. The targeted pesticides were not detected in all the samples i.e. were below LODs. Screening using the Automated Mass Spectral Deconvolution and Identification System (AMDIS) simplified the analysis due to its power of deconvolution and identification of analytes of interest.     

Propylthiouracil-induced autoimmune disease

Hyperthyroidism is a condition characterized by excessive production of thyroid hormones. Propylthiouracil (PTU) is commonly used as first line drug in the management of hyperthyroidism. This is a case report of 24-year-old female, a known case of hyperthyroidism since 4 years, who came with a history of fever and myalgia since 3 days and dyspnea with coughing out of blood since 1 day. Patient was taking PTU (100 mg per day) since 4 years for hyperthyroidism. Patient was immediately intubated for type-II respiratory failure. Diagnosed to be having PTU-induced autoimmune disease. PTU was stopped and treated with methylprednisolone and cyclophosphamide. Clinical features improved over a period of 8 days and discharged home successfully. Having a high suspicion for the onset of autoimmune disease in hyperthyroidism patients who are on PTU therapy and timely treatment with immunosuppressants and supportive care along with the withdrawal of the drug can make a difference in morbidity and mortality.     

Salmonella infections of the abdominal aorta cured with prolonged antibiotic treatment

Three cases of endovascular infection of atherosclerotic aneurysm of the abdominal aorta due to Salmonella spp. are described. 'Breakthrough' or relapsing bacteraemia were major clues for diagnosis in each case. They were treated with a prolonged course of bactericidal antibiotics before surgery. Resection with an interposed graft was performed in all cases and antibiotic treatment continued. Two of our patients have survived for more than two years and the other for 18 months without evidence of relapse. Thus, it would appear possible at times to treat successfully mycotic aneurysm of the abdominal aorta with antimicrobial agents plus resection of the aneurysm followed by in situ bypass grafting. Extra-anatomical grafts should be kept for infections due to antimicrobial-resistant organisms or when periaortic infection is widespread.     

Human complement receptor 2 (CR2/CD21) as a receptor for DNA: Implications for its roles in the immune response and the pathogenesis of systemic lupus erythematosus (SLE)

Human CR2 is a B cell membrane glycoprotein that plays a central role in autoimmunity. Systemic lupus erythematosus (SLE) patients show reduced CR2 levels, and complete deficiency of CR2 and CR1 promotes the development of anti-DNA antibodies in mouse models of SLE. Here we show that multiple forms of DNA, including bacterial, viral and mammalian DNA, bind to human CR2 with moderately high affinity. Surface plasmon resonance studies showed that methylated DNA bound with high affinity with CR2 at a maximal K(D) of 6nM. DNA was bound to the first two domains of CR2 and this binding was blocked by using a specific inhibitory anti-CR2 mAb. DNA immunization in Cr2(-/-) mice revealed a specific defect in immune responses to bacterial DNA. CR2 can act as a receptor for DNA in the absence of complement C3 fixation to this ligand. These results suggest that CR2 plays a role in the recognition of foreign DNA during host-immune responses. This recognition function of CR2 may be a mechanism that influences the development of autoimmunity to DNA in SLE.     

Isolation of a nonmitogenic angiogenesis factor from wound fluid.

Angiogenesis, or new capillary growth, is essential to normal growth and wound healing. It is also active in several pathologic states, including the growth of malignant tumors. An extracellular, nonneoplastic angiogenesis factor has been isolated from cell-free rabbit wound fluid by pore-limit dialysis and chromatography on a size-exclusion HPLC column. The isolated angiogenesis factor was purified 9,600-fold with a yield of 81% and has a molecular weight between 2,000 and 14,000. Wound fluid angiogenesis factor was completely separated from the mitogenic activity of wound fluid; it did not increase the number of capillary endothelial cells in vitro or stimulate [3H]thymidine uptake by these cells. The isolated angiogenesis factor stimulated endothelial cell migration in vitro, and less than 200 ng of the factor stimulated angiogenesis in vivo in the corneal implant assay.