关于人眼视力发展的非线性成长率理论

目的使用非线性成长率理论分析人眼视力发展规律。方法使用高斯光学及成像方程推导出两个参数：屈光状态改变率（M）及眼轴成长率（N），用以预测MOS（初始近视）、年龄（A^＊）及其后视力的发展情况。结果当有效焦距F=（21-22）、密码M=（2．67—2．9）（D／mm）时，此计算值符合实验平均值（2．7）。当年龄A^＊=（3，6）岁的屈光度变化已知时，我们计算其MOS预测年龄为A^＊=（7．3，21．8）岁（在不同条件下）。此值反比于M值在A=6及A=3的比值或N=N—N^＊，即非正视态及正视态的眼轴成长率之差。本理论也可用来预测在年龄A=25时的近视度，分别为D=-14及-0．49的上述两例情况，同时也能分析Lain等人的测量值（由出生到青年期的视力发展情况）。结论本理论可预测MOS、其后发展情况及其符合实验值（M）。使用成长率差值（dN）比使用L/rl比值能更准确地预测MOS。     

Intraluminal brachytherapy in the treatment of bile duct carcinomas

Patients with carcinoma of the biliary tract have a poor prognosis because the disease is often unresectable at diagnosis. Intraluminal brachytherapy has been reported as an effective treatment for localized cholangiocarcinoma of the biliary tract. The purpose of our study was to analyse the survival of patients treated with brachytherapy and make some recommendations regarding its use. Fifteen patients underwent brachytherapy via a trans-hepatic approach at the Royal Prince Alfred Hospital from 1983 to 1993. Eleven patients had low-dose rate brachytherapy and four patients had high-dose rate treatment. There were nine males and six females. The median age was 64 years. Other treatment included bypass procedures in two patients, endoscopic stents in 14 patients and external beam irradiation in one patient. The median survival was 12.5 months and 47% of the patients survived 1 year. The only complication reported was cholangitis which was seen in one patient. There did not seem to be any difference in survival or complications between low- and high-dose rate brachytherapy. We conclude that the addition of intraluminal brachytherapy after biliary drainage prolongs survival and is a safe and effective treatment, but patients still have a high rate of local failure, and further studies will be needed to address this problem.     

Uterine leiomyomas in the infertile patient: preoperative localization with MR imaging versus US and hysterosalpingography

Eleven women with a history of infertility and uterine leiomyomas underwent magnetic resonance (MR) imaging of the pelvis prior to myomectomy. Nine also underwent preoperative pelvic ultrasonography (US), and ten underwent hysterosalpingography. All studies were interpreted prospectively by independent observers. With each imaging modality, the location (one of 11 anatomic segments), size, and appearance of detected uterine leiomyomas were determined and compared with surgical and histologic findings. Among the nine patients who underwent both MR and US, the sensitivity (85%) and accuracy (94%) of MR imaging for abnormal segments was significantly better than that of US (sensitivity = 69%, P = .015; accuracy = 87%, P = .043). For the ten patients who underwent both MR and hysterosalpingography, the sensitivity (91%) and accuracy (96%) of MR imaging was better than that of hysterosalpingography (sensitivity = 18%, P = .0005; accuracy = 72%, P = .0005). The specificities of the three modalities did not significantly differ (100%, 97%, and 98% for MR, US, and hysterosalpingography, respectively). These data suggest that MR imaging is superior to US or hysterosalpingography for preoperatively locating uterine leiomyomas.     

Quality assessment and assurance in diagnostic imaging. Theoretical and practical considerations and a quality audit of the excretory urogram

Concepts necessary to an understanding of the basics of quality assurance audits are presented. Included are specific examples that bridged theory and practice by applying the protocol to a real-life diagnostic imaging situation. This method meets the present requirements of the Joint Commission of the Accrediation of Hospitals.     

Bacteriophage Qβ Replicase Contains the Protein Biosynthesis Elongation Factors EF Tu and EF Ts

The enzyme, Qβ replicase, responsible for the replication of the RNA of Escherichia coli pahge Qβ, is composed of four nonidentical subunits, three of which, I, III, and IV, are coded for by the bacterial genome, while subunit II is phage-specific.