报刊阅读,第四版12
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四版报纸主要栏目和内容
四版报纸主要栏目和内容如下:
四版报纸开设了淘旧书、读书乐、旧书新知、藏书、集报界、收藏世界、古籍知识等栏目,还有一个特色栏目供求热线(调剂。
转让。
求购。
交换)。
投稿的作者既有名家作者,也有普通作者;既有一二线城市作者,也有身边市县作者的文章,看了非常解渴。
那时的文章短小精悍、信息容量大,努力展示古旧书业风采,为读书藏书者服务。
曾任石家庄作家协会主席的刘章这样评价:报小鸿儒爱书香,遍九州从来不媚俗,高雅自风流。
英语四级课文阅读文章杂志Net Aroma: E-mail tries out a sense of smellYou could soon be able to spice up your e-mails with your favourite perfume.UK net provider Telewest Broadband is testing a system to let people to send aromatic e-mails over the internet.It has developed a kind of hi-tech air freshener that plugs into a PC and sprays a smell linked to the message.Telewest say it could be used by supermarkets to tempt people with the smell of fresh bread or by holiday companies seeking to stir up images of sun-kissed beaches."This could bring an extra whiff of realism to the internet," said Chad Raube, director of internet services at Telewest Broadband."We are always looking at ways to enhance the broadband internet experience of the future and this time we are sure consumers will come up smelling of roses."Emotional responseThe technology behind the idea was originally developed by US company Trisenx. Scientists at Telewest's labs in Woking, Surrey, have built on that research to come up with the ideaof a "scent dome".The dome comes with a cartridge containing 20 basic aromas, which can be combined to produce up to 60 different smells.A "scented e-mail" would contain electronic signals that would tell the dome to release the smell of flowers, perfume or coffee."Our sense of smell is directly connected to our emotions," said anthropologist Kate Fox, director of the Social Issues Research Centre in Oxford."Smells trigger very powerful and deep-seated emotional responses, and this additional element to the internet will enhance users' online experience by adding that crucial third dimension."But the chance to sniff your e-mails not may come cheap. Telewest says its "scent dome" could cost around 250 and would only work with a high-speed, broadband connection.净香气:电子邮件尝试了一种嗅觉你很快就可以用你最喜欢的香水为你的电子邮件增添情趣了。
12 核苷酸代谢1.你如何解释以下现象:细菌调节嘧啶核苷酸合成的酶是天冬氨酸-氨基甲酰转移酶,而人类调节嘧啶核苷酸合成的酶主要是氨基甲酰磷酸合成酶。
解答:氨基甲酰磷酸合成酶参与两种物质的合成,嘧啶核苷酸的合成和精氨酸的合成。
在细菌体内,这两种物质的合成发生在相同的部位(细菌无细胞器的分化),如果调节嘧啶核苷酸合成的酶是此酶的话,对嘧啶核苷酸合成的控制将会影响到精氨酸的正常合成。
而人体细胞内有两种氨基甲酰磷酸合成酶,即定位于线粒体内的氨基甲酰磷酸合成酶Ⅰ和定位于细胞质内的氨基甲酰磷酸合成酶Ⅱ,它们分别参与尿素循环(精氨酸合成),嘧啶核苷酸的合成。
2.假如细胞中存在合成核苷酸的全部前体物质,①从核糖-5-磷酸合成1mol腺苷酸需要消耗多少摩尔ATP?②如果用补救途径合成1mol腺苷酸,细胞可节省多少摩尔ATP?解答:①从核糖-5-磷酸合成磷酸核糖焦磷酸(PRPP)时,需要将1mol焦磷酸基团从ATP转移到核糖-5-磷酸分子上去,在合成IMP途径的后续步骤中,该焦磷酸被释放并迅速水解生成2mol Pi,相当于消耗2mol ATP。
随后在生成甘氨酰胺核苷酸、甲酰甘氨咪唑核苷酸、5-氨基咪唑核苷酸和甲酰胺核苷酸四步反应中,各有1mol ATP的消耗,生成了IMP。
在IMP转化成腺苷酸时,由腺苷琥珀酸合成酶催化的反应又另外消耗1mol GTP。
所以,从核糖-5-磷酸合成1mol腺苷酸需要消耗7mol ATP。
②补救途径合成腺苷酸反应为:腺嘌呤+ 核糖-5-磷酸→腺苷+Pi ,腺苷 + ATP → AMP + ADP ,可见从腺嘌呤补救途径合成1mol 腺苷酸只消耗1mol ATP,比从头合成核糖-5-磷酸节省6mol ATP 。
3.使用放射性标记的尿苷酸可标记DNA分子中所有的嘧啶碱基,而使用次黄苷酸可标记DNA分子中所有的嘌呤碱基,试解释以上的结果。
解答:使用放射性标记尿苷酸后,尿苷酸(UMP)→UDP→CTP→CDP→dCDP→dCTP;UDP →dUDP→dUMP→dTMP→dTDP→dTTP。