黄土高原西北部砂田西瓜集雨补灌效应研究

在黄土高原西北部地区对砂田西瓜的集雨补灌效应进行了研究。试验采用滴灌方式,设0mm(D0)、22．5mm(D1)、45．0mm(D2)和67．5mm(D3)4个灌水量处理。区组内各处理随机排列,四次重复。试验结果表明：在西瓜全生育期,每个处理0～120cm土层的土壤水分含量均呈下降趋势,下降的幅度随着补灌量的增加而减小。全生育期补灌67．5mm的处理土壤含水量最高,比没有补灌的对照处理高2．2％。土壤水分的变化在0～40cm土层比较活跃。其次是40～80cm土层,而80～120cm土层的含水量变化相对比较稳定。对砂田西瓜进行补灌可以提高产量和水分利用效率。补灌45mm和67．5mm的处理比对照分别增产36．3％和45．7％。补灌67．5mm处理的水分利用率最高,为26．7kg／m^3。比对照增加17．0％;该处理的净利润和每单位(m^3)水的净利润也最高,分别达43．677元／hm^2和18．48元／m^3,比不补灌的对照处理高29．9％和15．3％。补灌量对西瓜的含糖量也有影响,补灌量低于45mm,各处理之间含糖量的差异不大,补灌量为67．5mm,西瓜含糖量降低0．44％。补灌对西瓜的产量、含糖量和水分利用率均有影响,砂田西瓜只有补灌量控制在45mm左右,才能既提高产量和水分利用率,又不降低西瓜品质。     

Development of an innovative one-step nested PCR strategy for virus detection using the LNA technique

<正>Dear Editor,Polymerase chain reaction (PCR) is a molecular diagnostic technique that has been widely used for diagnosing viral diseases. Nested PCR (N-PCR) is a variation on the standard PCR technique that involves two amplification steps, yielding greater sensitivity and specificity. But there are two main disadvantages:the protocol is more complex than conven-     

Application of 3-Dimensional Printing Technology to Construct an Eye Model for Fundus Viewing Study

Objective

To construct a life-sized eye model using the three-dimensional (3D) printing technology for fundus viewing study of the viewing system.

Methods

We devised our schematic model eye based on Navarro''s eye and redesigned some parameters because of the change of the corneal material and the implantation of intraocular lenses (IOLs). Optical performance of our schematic model eye was compared with Navarro''s schematic eye and other two reported physical model eyes using the ZEMAX optical design software. With computer aided design (CAD) software, we designed the 3D digital model of the main structure of the physical model eye, which was used for three-dimensional (3D) printing. Together with the main printed structure, polymethyl methacrylate(PMMA) aspherical cornea, variable iris, and IOLs were assembled to a physical eye model. Angle scale bars were glued from posterior to periphery of the retina. Then we fabricated other three physical models with different states of ammetropia. Optical parameters of these physical eye models were measured to verify the 3D printing accuracy.

Results

In on-axis calculations, our schematic model eye possessed similar size of spot diagram compared with Navarro''s and Bakaraju''s model eye, much smaller than Arianpour''s model eye. Moreover, the spherical aberration of our schematic eye was much less than other three model eyes. While in off- axis simulation, it possessed a bit higher coma and similar astigmatism, field curvature and distortion. The MTF curves showed that all the model eyes diminished in resolution with increasing field of view, and the diminished tendency of resolution of our physical eye model was similar to the Navarro''s eye. The measured parameters of our eye models with different status of ametropia were in line with the theoretical value.

Conclusions

The schematic eye model we designed can well simulate the optical performance of the human eye, and the fabricated physical one can be used as a tool in fundus range viewing research.     

A NEW SPECIES OF GENUS EUDINOSTIGMA (HYMENOPTERA: BRACONIDAE) FROM CHINA

Abstract  This paper describes a new species Eudinostigma longus Wu et Chen, collected from Hubei Province. The new species is characterized distinctly by the following features: rather long antenna, with 24 segments, notaulix distinct anteriorly, oval midpit deep, propodeum with a longitudinal medial carina and forked carina, areola absent, length of robust hind femur 3. 6 times its width, and length of petiole 1. 7 times its width. Type species is deposited in Beneficial Insects Laboratory, Fujian Agricultural University, Fuzhou, Fujian Province.