Due to the early administration of antibiotics, meningococcal disease is increasingly difficult to diagnose by culturing. Laboratory studies have shown PCR to be sensitive and specific, but there have been few clinical studies. The objectives of this study were to determine the diagnostic accuracy and clinical usefulness of meningococcal PCR through a prospective comparison of real-time PCR, nested PCR, and standard culturing of blood and cerebrospinal fluid (CSF). The setting was a tertiary-care pediatric hospital in Australia, and the participans were 118 children admitted with possible septicemia or meningitis. The main outcome measuressensitivity, specificity, and positive and negative predictive values-were compared to a "gold standard " fulfilling clinical and laboratory criteria. For 24 cases of meningococcal disease diagnosed by the gold standard, culturing of blood or CSF was positive for 15 (63%), nested PCR was positive for 21 (88%), and real-time PCR was positive for 23 (96%). The sensitivity, specificity, and positive and negative predictive values of real-time PCR (the most sensitive test) for all specimens were, respectively, 96% (95% confidence interval, 79 to 99%), 100% (95% confidence interval, 96 to100%), 100% (95% confidence interval, 85 to 100%), and 99% (95% confidence interval, 94 to 100%). Of 54 patients with suspected meningococcal disease at admission, 23 had positive PCR results. Only one PCR specimen was positive in a patient thought unlikely to have meningococcal disease at admission. Blood PCR remained positive for 33% of patients tested at up to 72 h. Real-time PCR has high positive and negative predictive values in this clinical setting, with better confirmation of cases than nested PCR. Targeting patients for PCR based on admission criteria appears to be practical, and the test may remain useful for several days after the start of antibiotic administration.Meningococcal septicemia and meningitis are life-threatening diseases. Rapid, accurate diagnosis is essential for optimal management of patients and the provision of prompt prophylaxis to contacts. Confirmation of the diagnosis allows physicians to use narrow-spectrum antibiotics, limit the duration of treatment, and provide prognostic information. It also provides vital disease burden information, including data to inform vaccine policy.It is becoming increasingly difficult to confirm the diagnosis of meningococcal infection by conventional microscopy and culturing techniques (6). Blood cultures are positive in about 50% of untreated patients with clinically suspected meningococcal septicemia. This rate is reduced to 5% when antibiotics have been administered prior to admission; primary care practitioners are encouraged in this practice early for suspected cases (8,9,19). Cerebrospinal fluid (CSF) microscopy or culturing is positive in 80 to 90% of untreated cases of meningococcal meningitis, but this rate is also reduced by prior antibiotic administration. In addition, many patients do not undergo a lumbar puncture early in t...
SUMMARYIn this paper, a fault reconstruction scheme for a class of discrete-time descriptor linear parameter-varying systems is investigated. A discrete-time polytopic descriptor linear parameter-varying system subject to external disturbances and actuator faults is first established; then, using H 1 techniques and regional pole constraints, a novel polytopic unknown-input proportional-integral observer is constructed to simultaneously reconstruct system states and actuator faults. Existence conditions for the new polytopic unknown-input proportional-integral observer are explicitly derived. The stability and convergence of the presented observer are proved through Lyapunov theory and linear matrix inequalities. Using a slack-matrix-variable technique, less conservative results for observer design are obtained. At last, an illustrative example is simulated to verify the effectiveness of the proposed fault reconstruction approach.
In this study, the ultrafine copper-based powders were fabricated by a facile two-step chemical reduction method. Glucose (C6H12O6) and ascorbic acid (AA) were taken as a pre-reductant and a second reductant, respectively. Polyvinylpyrrolidone (PVP) was applied as the capping agent. Effects of parameters, such as glucose content, PVP content and PH value on the ultimate reduction products were analyzed. Microstructure and composition of the products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). It was found that when the amount of glucose was increased from half to full and then excessive, the powder gradually changed from flaky to spherical, from pure copper powder to a mixture of copper and cuprous oxide (Cu2O). With the amount of PVP increasing from 0g to 0.64 g, the shape of the pure copper powder changed from cubic to spherical or HYPERLINK "javascript:void (0);" icosahedron. When the PH value changed from 10-14, the powder changed from spherical to regular octahedron and Irregular polyhedron, from pure copper powder to pure cuprous oxide powder. Therefore, copper-based powders with different morphologies and different compositions can be prepared by changing PH value and the amount of reductant.
In this work, the optimal sintering temperature and time of commercial copper paste were tested experimentally. The electrical properties of conductive paste including square resistance and resistivity were characterized and analyzed. The influence of diatomite with different purification processes on the electrical properties of commercial copper paste was analyzed. The performance of copper slurry modified by copper-based modified diatomite prepared by two-step reduction method was analyzed. The optimum square resistance and resistivity was obtained with copper paste doped by 0.25wt.% and 1 h-ball milled diatomite and was 0.02Ω/ϒ and 0.011Ω·mm, respectively.
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