The Asymptotic Behaviour of a Curved Line Source Plume within an Enclosure

A line source of heat is situated in an enclosure with inletsand an outlet for the contained fluid. The convection plumeformed must take a curved shape because of the asymmetry ofthe enclosure. We show how boundary-layer theory can be usedto find this shape in the case where the plume's deflectionis small. Two effects govern the shape of the curve; a buoyancyeffect and an inertial effect due to the bounding walls. Bysolving the outer potential flow problem, both effects can beincluded in the model. Finally, a stability analysis is carriedout for steady plumes which shows that any steady solution withan inflection point, as well as several other solutions, isunstable. A comparison is made with previous work which doesnot include all these effects, and with some experimental results.     

RING-OPENING PHOTOREACTIONS OF CYTOSINE AND 5-METHYLCYTOSINE WITH ALIPHATIC ALCOHOLS

Abstract Several reports in the late 1950s and early 1960s indicated that ultraviolet irradiation of dilute solutions of cytosine or 5-methylcytosine in aliphatic alcohols, such as methanol or ethanol, leads to reaction mixtures containing products with an absorption maximum around 300 nm. The present work reports the isolation and characterization of the products responsible for this absorption in the photochemical reactions of cytosine and 5-methylcytosine with methanol, ethanol and 2-propanol at concentrations in the neighborhood of 200 μM. Under these conditions the reactions have been shown, in each nucleobase/alcohol system, to give almost exclusively a single type of primary photopro-duct; each product shows an absorption maximum in the region of 300 nm. Structural analysis showed the products to be alcohol adducts with an ester linkage at C2 of the ring-opened base and an enamine structure at C6. For example, in the case of the reaction of cytosine with methanol, the product is N-carbomethoxy-3-aminoacrylamidine (IIIa). The occurrence of this type of photoreaction suggests a mode by which alcoholic functional groups on amino acid side chains could contribute to photoinduced DNA-protein cross-linking.     

Ⅷ.O-乙基N,N-二乙氨基一(或二)硫代磷酸钠的制备及其化学反应

1.本文报告以O-乙基N,N-二乙氨基硫代磷酰氯(Ⅲ)为原料,合成O-乙基N,N-二乙氨基一(或二)硫代磷酸钠(Ⅰ)、(Ⅱ)的方法。2.Ⅰ和Ⅱ分别与卤代烷反应,得到相应的酯(Ⅴ),(Ⅵ)。Ⅰ和Ⅱ在低温下用稀盐酸酸化则转化成相应的酸(Ⅶ)和(Ⅷ),后者分别与碘乙烷、重氮甲烷、环己胺等作用得到相应的酯(Ⅸ)和铵盐(Ⅺ)。3.Ⅱ与卤素(溴或碘)反应形成二硫化物(Ⅻ),后者与等量氯反应得到磷酰氯(Ⅲ)。     

锗、硅、锑化铟和砷化镓的热膨涨——用X射线衍射法测量

本工作是用X射线衍射法测量锗、硅和合金InSb及GaAs在不同温度的点阵常数,观察它们的热膨涨,并求得它们的膨涨系数。     

Perturbational Results for Diffraction of Water-waves by Nearly-vertical Barriers

An exact solution (Ursell, 1947) is known for the diffractionof surface waves by a thin, flat, two-dimensional barrier, extendingdownwards from the surface to a fixed submerged point. We considerperturbations to this result caused by changing the shape ofthe barrier slightly. By using an integral equation formulation,first-order corrections to the reflection and transmission coefficientsare given in terms of two integrals of the shape. The methodcan be used both for thin, shaped barriers and for symmetric,slender shapes. A similar technique is used for barriers whichoscillate with the frequency of the incoming wave. A comparisonis made between this theory and some rival methods, and it isfound to be superior in many respects.     

STRUCTURE OF PHOTOSYSTEM I AND PHOTOSYSTEM II OF PLANT CHLOROPLASTS*,†,§

Abstract— The action of Triton X-100 upon photosynthetic membranes which are devoid of carotenoids produces a small Photosystem I particle (HP700 particle) which is active in N ADP photoreduction and has a [Chl]/[P700] ratio of 30. The properties of the HP700 particle indicate that it is a reaction center complex which is served by an accessory complex containing the additional light-harvesting chlorophyll of Photosystem I as well as the cytochromes and plastoquinone. When Photosystem II particles obtained by the action of Triton X-100 are further washed with a solution 0.5 M in sucrose and 0.05 M in Tris buffer (pH 8.0), chlorophyll-containing material is released. After centrifugation, the supernatant contains about 1 per cent of the chlorophyll and contains three types of particles which can be separated by sucrose density gradient centrifugation. One of these particles, designated TSF-2b, has the same pigment composition as the original Photosystem II fragment, contains cytochrome 559, and shows Photosystem II activity (DCMU-sensitive diphenylcarbazide-supported photoreduction of 2,6-dichlorophenolindophenol). The other two particles (TSF-2a and TSF-2a′) have a [Chl a]/[Chl b] ratio of 8, have a low concentration of xanthophylls, and show a [Chl]/[Cyt 5591 ratio of about 20. Only the TSF-2a particle is active in the Photosystem II reaction described above. On the basis of these data, it is proposed that the Photosystem II unit consists of a reaction center complex which contains Chl a, Cyt 559, and an acceptor for the photochemical reaction. The reaction center complex would be served by an accessory complex which contains the light-harvesting pigments, Chl a. Chi b, and xanthophyils.