Electrical properties of GaN deposited on nitridated sapphire by molecular beam epitaxy using NH3 cracked on the growing surface

We have found that GaN epilayers grown by NH3-source molecular beam epitaxy (MBE) contain hydrogen. Dependent on the hydrogen concentration, GaN on (0001) sapphire can be either under biaxially compressive strain or under biaxially tensile strain. Furthermore, we notice that background electrons in GaN increase with hydrogen incorporation. X-ray photoelectron spectroscopy (XPS) measurements of the N1s region indicate that hydrogen is bound to nitrogen. So, the microdefect Ga...H-N is an effective nitrogen vacancy in GaN, and it may be a donor partly answering for the background electrons. (C) 1999 Elsevier Science B.V. All rights reserved.

Electrical properties of GaN deposited on nitridated sapphire by molecular beam epitaxy using NH3 cracked on the growing surface

We have found that GaN epilayers grown by NH3-source molecular beam epitaxy (MBE) contain hydrogen. Dependent on the hydrogen concentration, GaN on (0001) sapphire can be either under biaxially compressive strain or under biaxially tensile strain. Furthermore, we notice that background electrons in GaN increase with hydrogen incorporation. X-ray photoelectron spectroscopy (XPS) measurements of the N1s region indicate that hydrogen is bound to nitrogen. So, the microdefect Ga...H-N is an effective nitrogen vacancy in GaN, and it may be a donor partly answering for the background electrons. (C) 1999 Elsevier Science B.V. All rights reserved.

甜高粱在青海高原种植的初步研究；Preliminary study on sweet sorghum growing on Qinghai Plateau

为探讨甜高粱(Sorghum bicolor)在青海作为饲料作物种植的可能性,在青海高原上做了初步试验,结果显示:密度对茎秆高度、茎粗、产量有显著影响,对生育期、单株质量影响不显著,株行距为0.40 m×0.20m时,产量最高;浇水次数对甜高粱的生育期、茎秆高度、茎粗、单株质量、产量没有显著影响,表明甜高粱对水分依赖不高,具有很强的耐旱和抗旱性;地膜对甜高粱有极显著影响,使其生育期提前,茎秆高度增高,单株质量增加、产量提高;糖分含量在开花-收获期为15.93%~16.67%,比不盖地膜增加了29.19%~47.98%;大田示范密度0.50 m×0.20 m,开花-收获期666.7 m2产量达4 890.8 kg,投入产出比为1∶1.78,效益显著。研究表明,在青海高原东部农业区盖地膜种植饲用甜高粱,用作饲料是完全可行的。

Fruit anatomy,seed germination and seedling development in the Japanese seagrass phyllospadix

Phyllospadix iwatensis Makino and phyllospadix japonicus Makino have similar frunt morphology and anatomy.The rhomboid fruit of Japanese phyllospadix is dark brown in colour and is characterized by two arms bearing stiff inflected bristles which can act as an anchoring system. The fruit covering consists of a thin cuticular seed coat and pericarp remains mainly fibrous endocarp. In the groove region of the fruit.the cuticular seed coat and endocarp are replaced by nucellus cells with wall in growths and crushed pigment strands with lignified walls.these tissues appera to control the transfer of nutrients to developing seed.the seed is oval with a small embryo and a large hypocotyl. the embryo is straight and simple,with the plumule containing three leaf primordia and a pair of root primordia surrounded by a cotyledon.the hypocotyl has large vontral lobe containing central provascular tissue and two small dorsal lobes.the hypocotyl contains starch.lipid and protein.and acts as a nutrient store.the seed of P.iwatensis has a dormancy period of 2-6 weeks and germination eventually reaches-65%.but is not synchronized.during germination the leaves emerge first.and then after at least three young leaves have formed and abseised.the roots emerge,usually?6 months after the commencement of germination.Utilizaton of the nutrient reserves is initially from the perihpery of the hypocotyl and then progressively towards its centre.

A biofuel cell harvesting energy from glucose-air and fruit juice-air

The membraneless biofuel cell (BFC) is facile prepared based on glucose oxidase and laccase as anodic and cathodic catalyst, respectively, by using 1,1'-dicarboxyferrocene as the mediators of both anode and cathode. The BFC can work by taking glucose as fuel in air-saturated solution, in which air serves as the oxidizer of the cathode. More interestingly, the fruit juice containing glucose, e.g. grape, banana or orange juice as the fuels substituting for glucose can make the BFC work. The BFC shows several advantages which have not been reported to our knowledge: (1) it is membraneless BFC which can work with same mediator on both anode and cathode; (2) fruit juice can act as fuels of BFCs substituting for usually used glucose; (3) especially, the orange juice can greatly enhance the power output rather than that of glucose, grape or banana juice. Besides, the facile and simple preparation procedure and easy accessibility of fruit juice as well as air being whenever and everywhere imply that our system has promising potential for the development and practical application of BFCs.