Hypergonadotropic secondary amenorrhea: clinical analysis of 126 cases

OBJECTIVE: To study the etiology and early diagnosis of hypergonadotropic amenorrhea and to explore the appropriate treatment for preserving their reproductive function. METHODS: 126 cases of secondary amenorrhea with serum follicular stimulating hormone (FSH) levels > or = 40 IU/I, were analysed. Their clinical manifestations, karyotypes, ovarian morphology and histology, reproductive hormone assays, and responses to estrogen therapy and ovulation induction were studied. RESULTS: 6 cases presented with histories of ovarian surgery, radiotherapy or chemotherapy. Among the other 120 cases, 18 manifested amenorrhea before or at 25 years of age, 102 developed amenorrhea after age 25. In the former group, 16 (88.9%) showed unilateral or bilateral gonadal dysgenesis, and the other 2(11.1%) were defined as resistant ovaries. Abnormalities of sex chromosome karyotype occurred in 44.4% (8/ 18). In the latter group, 68 underwent laparotomy or laparoscopy examination. Morphological and histological examinations of both ovaries showed atrophic ovaries in all cases accompanied by 30.9% (21/ 68) unilateral gonadal dysgenesis; sex chromosomal abnormality was found in only one with no sexual immaturation. The efficacy of estrogen treatment was significantly better among cases with amenorrhea less than 1 year as compared with those longer than 1 year. Clomiphene challenge test given to 8 cases during their irregular menstrual stages produced an elevation of FSH levels to > 20 IU/I. without any response of estradiol secretion. CONCLUSIONS: The earlier estrogen therapy is initiated, the greater possibility of pregnancy will be achieved in cases suffering from hypergonadotropic amenorrhea. The clomiphene challenge test may provide evidence of waning ovarian function for early diagnosis.     

P-N double quantum well resonant interband tunneling diode withpeak-to-valley current ratio of 144 at room temperature

The current-voltage characteristics of the P-N double quantum well resonant interband tunneling (RIT) diodes in InAlAs-InGaAs system have been improved in this letter. The peak-to-valley current ratio (PVCR) is as high as 144 at room temperature. As we know, this is the highest room temperature PVCR ever reported in any tunneling devices. Moreover, the influence of the central barrier thickness varying from 10 Å to 30 Å on the device characteristics is also studied     

Low RF noise and power loss for ion-implanted Si having an improved implantation process

Very-low-transmission line noise of <0.25 dB at 18 GHz and low power loss /spl les/0.6 dB at 110 GHz have been measured on transmission lines fabricated on proton-implanted Si. In contrast, a standard Si substrate gave much higher noise of 2.5 dB and worse power loss of 5 dB. The good RF integrity of proton-implanted Si results from the high isolation impedance to ground, as analyzed by an equivalent circuit model. The proton implantation is also done after forming the transmission lines at a reduced implantation energy of /spl sim/4 MeV. This enables easier process integration into current VLSI technology.     

Flammability and thermal stability studies of ABS/Montmorillonite nanocomposite

Acrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry     

一种基于DBF的双基地雷达系统的性能分析与实验研究

讨论了一种基于数字波束形成的脉冲追赶式双基地雷达系统的构成和基本工作原理．对该双基地雷达的性能进行了理论分析，并通过实验结果进行了验证。     

Location management of correlated mobile users in the UMTS

In this paper, we propose concurrently searching for correlated mobile users in mobile communications networks. Previous work either focuses on locating a single mobile user or assumes that the locations of mobile users are statistically independent. We first propose a mobility model in which the movements of mobile users are statistically correlated. Next, we use the theory of Markov chain to derive the joint probability density function of the locations of mobile users. In addition, we propose a novel approach to discover the correlations among the locations of mobile users without explicitly calculating the joint probability density function. Our simulation results indicate that exploring the correlations among the locations of mobile users could significantly reduce the average paging delay and increase the maximum stable throughput.     

Computerised trace method for establishing equations for dimensions and tolerances in design and manufacture

A computerised trace method has been developed for determining the relationships of assembly requirements with design dimensions and tolerances of the components in an assembly, and the relationships of design specifications and machining allowance requirements with manufactured dimensions and tolerances of the component in a process plan. This method traces from the proposed components or planned operations only the dimensions and tolerances that affect the given requirement, and therefore the equations for design or for manufacture can be established simultaneously and accurately. Hence it is possible to establish constraints for the optimisation of dimensions and tolerances for design or for manufacture.     

与商业比肩而行

“许多美术行为都是与商业客户相结合的。以商业的视角看待作品更重视在整个概念部分是不是能够从设计的观点很忠实地传达出商业诉求，并引起更大共鸣”。[编者按]     

广州市西村水厂生物预处理试验研究

介绍广州市西村水厂生物预处理试验研究,探讨用生物预处理工艺处理西村水厂现有原水的效果。试验结果表明生物预处理对改善西村水厂现有水源水质效果显著,"生物预处理 常规处理"后的最终出水的考察项目全部符合《生活饮用水卫生标准》。指出实施生物预处理工艺与西江引水工程相衔接,完全可以保障西村水厂的供水水质。     

Measurement of three-phase transformer derating and reactive power demand under nonlinear loading conditions

The measurement of real and apparent power derating of three-phase transformers is important for transformers feeding nonlinear loads. This paper presents a new digital data-acquisition method for measuring derating and reactive power demand of three-phase transformers under full or partial load conditions. The accuracy requirements of the instruments employed (potential, current transformers, shunts, voltage dividers, optocouplers volt- and current meters) are addressed. Application examples demonstrate the usefulness of this new digital data-acquisition method.