The epidemiology and phenotype of inflammatory bowel disease (IBD) in the Chinese population is not well-known. We performed a comprehensive search of the Chinese biomedical literature database from 1989 to 2007 using the following key words: inflammatory bowel disease (IBD), ulcerative colitis (UC), Crohn's disease (CD). The investigation of hospitalized IBD patients from 1990 to 2003 was also carried out in 23 medical centers of 11 cities over China. There are some notable epidemiological and phenotypical differences between Chinese IBD and Caucasian IBD, including a lack of familial clustering, male predominance, a relatively later onset of the illness with no second peak age occurrence after 50 years old, a milder clinical course, less extra-intestinal manifestations and complications, and less fistulous and peri-anal complications in Chinese CD. The data indicate an increased incidence of IBD in China with many complicated clinical problems, which offers potential opportunities to study the disease prospectively and identify the etiological factors, leading also to the better management of this disease in China.
Abstract-The concept of using a long mismatched transmission line to measure noise parameters has been known for some time. However, it has been limited to narrow-bandwidth applications, and a wide-band extension has never been reported. In order to measure the cryogenic noise parameters of a wide-band low-noise amplifier (LNA), a wide-band frequency-variation method is proposed. In this method, the four noise parameters at each frequency are derived numerically from a set of matched and mismatched noise temperatures measured within a surrounding frequency-sampling window. By scanning this frequency-sampling window, noise parameters over a wide frequency range can be obtained. Since this approach can be easily incorporated into existing noise measurement systems, a tuner is not required, and the technique can be applied to a cryogenic amplifier. This paper details the theory, implementation, and verification of this new method. The measured noise parameters of a cryogenic wide-band LNA are presented.Index Terms-Frequency-variation method, noise-parameter measurement.
In this letter, a wide-band low-noise amplifier (LNA) design is presented with 10 dB input reflection coefficient and 100-K noise temperature over the 8-20-GHz frequency range at room temperature. This LNA can be cooled down in a liquid Helium cryostat to have 10-K noise temperature for the purpose of radio-astronomy application. To achieve its wide-band characteristics, a novel input matching mechanism is proposed, which combines the high-frequency inductive feedback and the low-frequency capacitive feedback. The recognition and comprehensive interpretation of this new input matching mechanism is crucial for future development of ultra-wide-band LNAs.Index Terms-Input matching, low-noise amplifier (LNA), wideband.
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