Practice of orthokeratology by a group of contact lens practitioners in Hong Kong

Purpose: The aim of the study was to provide information about the characteristics of three main types of orthokeratology (ortho‐k) lenses used in Hong Kong and to report on their performance based on the clinical impressions of a group of ortho‐k practitioners. Method: Twelve ortho‐k practitioners were interviewed between 1 March and 30 June 2001. Results: Most ortho‐k lenses were ordered from three manufacturers: DreimLens, Fargo and Contex. The median maximum myopia reduction reported for DreimLens, Contex and Fargo lenses were 6.25 D, 6.00 D and 4.50 D respectively. The time to reduce myopia by up to 4.00 D could be up to three weeks for Contex and DreimLens and up to four weeks for Fargo. For reduction of myopia by up to 4.00 D, the treatment usually required only one or two lenses per eye for all three types of lenses. The incidence of lens binding and lens tightening after achieving the optimal reduction was reported to be higher with the DreimLens design. Good centration, less lens binding, relatively lower incidence of complications and lens tightening after achieving the optimal reduction were reported with the Fargo lenses. Conclusions: DreimLens tended to be more effective for myopia reduction. However, some practitioners were concerned with the aggressiveness of myopia reduction using this lens design and the higher potential for ocular complications. Selection of the lens design is dependent on various factors, in particular, practitioners need to be comfortable with the design they choose and to consider the needs of their patients and the final goal of the treatment.     

中国贫困医疗救助模式的制度缺陷及其改进思路

讨论现行国内医疗救助模式的基本经验与存在的缺陷。现行国内医疗救助模式无论在制度设计还是具体实施中部存在许多缺陷，如在制度设计方面，救助标准与水平总体上都比较低，大病痛种的规定大大限制和缩小了贫困医疗救助的范围，而定点医院限制了救助对象选择的空间等。     

Optimal response in siso ripple-free deadbeat systems

The ripple-free deadbeat control problem for SISO plants subjected to arbitrary reference signals is considered. The trade-off between the settling time and the integral square error between the system output and reference signal is investigated. Given a specific order of the controller, it is shown how to design an optimal ripple-free deadbeat controller. An illustrative example is presented to show the feasibility of the proposed algorithm.     

Measurement of axial edge lift of rigid corneal lenses*

A simple but reliable method was used to measure the axial edge lift at the total diameter over a range of back optic zone radii of several proprietary designs of rigid gas-permeable corneal lens. One of these was found to have a constant axial edge lift construction.     

New approaches to QSAR: Neural networks and machine learning

Summary Neural networks and machine learning are two methods that are increasingly being used to model QSARs. They make few statistical assumptions and are nonlinear and nonparametric. We describe back-propagation from the field of neural networks, and GOLEM from machine learning, and illustrate their learning mechanisms using a simple expository problem. Back-propagation and GOLEM are then compared with multiple linear regression (using the parameters and their squares) on two real drug design problems: the inhibition ofEscherichia coli dihydrofolate reductase (DHFR) by pyrimidines and the inhibition of rat/mouse tumour DHFR by triazines.     

汽车后送伤员附加装置隔振设计

采用钢丝绳隔振器设计了运输车后送伤员附加装置的隔振结构，并进行了隔振性能试验。5名受试者的试验结果表明，隔振装置的隔振性能良好，可衰减40％—70％的振动能量。本文为运输车后送伤员附加装置的隔振设计提供了一种新方法。     

正交设计在确定混合血清法检测丙型肝炎抗体实验条件中的应用

目的探讨封闭温度、时间、ＢＳＡ浓度、Ｔｗｅｎ２０浓度及混合标本个数５因素各２水平对混合血清法检测抗－ＨＣＶ的影响。方法应用正交设计的方法进行实验分组，采用ＥＩＡ法检测抗－ＨＣＶ。结果封闭条件为０．５％ＢＳＡ，３７℃，３０ｍｉｎ；洗涤液为０．１５％Ｔｗｅｅｎ２０，混合标本个数为５。采用正交设计的实验方法可减少７５％的实验次数。结论在进行多因素的实验研究时，正交设计是一种高效的设计方法。     

Influence of handedness on calcaneal ultrasound: Implications for assessment of osteoporosis and study design

Calcaneal ultrasound has been increasingly studied for its potential in the assessment of osteoporotic fracture risk. The accuracy of such an assessment is, in part, dependent on the reproducibility of the measurement. This study examines the impact of handedness on ultrasound measurements [broadband ultrasound attenuation (BUA) and velocity of sound (VOS)] in the calcaneus. Two hundred and sixty-four subjects (57 men and 297 women) aged 51.1+13.6 years (mean ± SD) were studied. For each subject, calcaneal ultrasound measurements were performed on both heels with a McCue CUBA ultrasound densitometer. Right-handed dominance (94.7%) was determined by structured interview. In men, BUA measurements were significantly higher on the dominant side: mean difference 4.1±1.5 dB/MHz (mean ± SD;p=0.009), equivalent to 4.2+1.5% and more than 4 times the average rate of annual change in BUA. The difference between sides was greater in young (<50 years) than old men (>50 years). Among the women, the difference was not statistically significant (0.7±0.9 dB/MHz;p=0.4); however, it was significant in younger women (20–30 years) (99±4 vs 90±4 dB/MHz,p=0.01). By contrast VOS did not differ between sides in either men or women irrespective of age. Within-subject standard deviation of BUA was 9.8 dB/MHz for men and 8.6 dB/ MHz for women and the component due to right and left difference was 8.4 dB/MHz for men and 6.9 dB/MHz for women. This variability of BUA between right and left heels could increase the false-positive rate by up to 28% for a cut-off of 2 SD below the mean. These data indicate that variation between left and right heel measurements of BUA is higher than that of random error measurements, particularly in men and younger, presumably more physically active subjects. Although VOS measurements were not side dependent, in the smaller number of studies examining VOS and fracture risk, VOS appears to have a weaker predictive power than BUA. Clinical and epidemiological studies involving calcaneal BUA measurements should standardize the side measured to either the dominant or non-dominant heel, to reduce within-subject variation and increase their power.     

三种泻心汤及其类方不同配伍对正常大鼠胃粘液成分的影响

目的:探讨半夏泻心汤及其类方不同配伍对正常大鼠粘液含量的影响.方法:用均匀设计法对半夏泻心汤及其类方进行组方药量变化,以胃粘液含量为药理学指标,对所得的药理实验数据进行逐步回归分析.结果:与胃粘液含量关联度最大的为黄连,可以显著降低其含量,其次对半夏、大枣和甘草的交互项,可增加胃粘液含量.药物之间存在复杂的交互作用.结论:均匀设计为研究类方配伍提供了一种可供参考的试验设计方法.