温岭割包皮大概需要多少钱
时间:2018年11月18日 01:20:12

If I told you there was a large mass of fungus infecting the roots of that lovely pine tree which shades your front lawn, would you be worried? Would you buy a strong fungicide if I said that this fungus survived by sucking valuable sugars, vitamins, and other nutrients out of your trees roots?可爱的松树在前院的草丛上投下了阴凉。如果这时我告诉你这颗松树的根部感染了大量的真菌,你会感到担心吗?如果我告诉你这种真菌是靠吸收根部的糖、维他命以及其它营养物质来生存,你会买来强力除菌剂除掉它们吗?Actually, most species of tree and plant are routinely infected by whats known as “mycorrhizal fungi,” but this is no cause for alarm. Well learn how trees can actually benefit from their fungal friends on todays moment of science.事实上,大多种类的树木和植物的根部都会感染菌根真菌,但你没有理由惊慌。在今天的科学时刻我们会一同学习树木如何与它们的真菌朋友相互依存,互惠互利。Many trees and plants not only host mycorrhizal fungi–they have actually come to depend on them. As the fungi grow, they send fine tentacles streaming into the soil. These tentacles help channel large amounts of water and nutrients back to the host tree, far more water than the tree would be able to trap with its roots alone.许多树木和植物不仅仅是菌根真菌的宿主——它们实际上是在依靠这些真菌。随着真菌不断的繁衍,大量细长的触须涌向土壤。这些触须会将大量的水分和营养物质引回宿主树木的身边,这远比树木的根部自身所捕获的水分要多。One study found that conifers with the fungus are twice as likely to survive a drought as those without. Some mycorrhizal fungi help their host tree in other ways too, secreting a tree hormone that causes the roots to grow new root tips, and a hormone that increases the longevity of these new roots.一个研究发现有真菌的针叶树比没有真菌的针叶树在干旱中幸存的几率高两倍。有些菌根真菌还能在其他方面帮助宿主树木。它们刺激树木的根部分泌激素,以长出新的根须,这种激素也能延长新树根的寿命。Other fungi release natural antibiotics into the soil, further protecting the tree. In fact, the seedlings of many tree species will die if fungus does not develop around their roots during their first year of growth.还有一些真菌会在土壤中释放天然的抗生素,进一步保护树木。实际上,如果幼树在第一年的生长期中没有真菌寄生在其根部,那么大量的幼树都会死亡。This is a striking example of the biological concept of symbiosis, in which two or more unrelated species have co-evolved and now depend on each other for survival. It shows us just how interconnected the delicate web of life is. Which covers our planting earth.生物概念下的共生现象是指两种或者多种不相关联的物种共同进化,互相依存,而树木与真菌就是一个显著的例子。它向我们展示了生命之网的内在联系。生命之网虽然脆弱,但却蕴育了繁茂的地球。原文译文属!201210/205559

If you keep a garden and have never been bothered by aphids, you are lucky. But one day you may find your rose bushes or bean plants covered--almost overnight--with these green, greedy sap-suckers. What allows aphids--and thousands of other species--to appear so fast is a trick these insects have developed for circumventing the old rule about the birds and the bees.如果你有个花园,却从来没被蚜虫侵扰过,那你就很幸运了。但是你有可能发现园子里的玫瑰丛和豌豆叶上,几乎一夜之间爬满了绿幽幽,贪婪狂吃的蚜虫。是什么让这些蚜虫以及其它成千上万种虫子如此迅速地出现,这是虫子为规避鸟类和蜜蜂旧的食物链规则发展而来的诀窍。During the summer months when aphid-food is plentiful, aphids reproduce through a process called ;parthenogenesis,; from the Latin words ;virgin birth.; What that means is that female aphids give birth to more female aphids without ever seeing a male. As soon as those daughters mature, they produce their own offspring, and so on.在夏季的几个月期间,蚜虫的食物充足,它们会通过单性生殖方式繁殖后代,;parthenogenesis;这一词来源于拉丁语“virgin birth(圣灵感)”,意思就是雌性蚜虫不与雄性交配而生出许多雌性蚜虫。雌性蚜虫的女儿们一成熟,就立即繁衍自己的后代,如此以往。Without the search for mates or the ensuing courtship rituals, parthenogenesis means big savings in time and energy: in just one season, a single aphid can give rise to billions of descendants.单性生殖不需要蚜虫去寻找雄性配偶,更省略了随之而来的求爱仪式,因此十分节省时间和精力:在一个季节里,一只蚜虫会繁衍出十多亿后代。But in the fall, fresh food gets harder to find and thered no longer be any reason for producing so many offspring. So now a generation of aphids is born that includes males as well as females. And what happens next between the males and females is just what you might expect.但是到了秋天新鲜食物很难找,这时就没必要去生产那么多子孙了。在新生一代蚜虫里既有雌性也有雄性。你可能会想到在雌雄性蚜虫之间接下来会发生什么。Why aphids would turn from parthenogenesis to something as messy and inefficient as sex is another story, but in short, sexual reproduction is natures way of shuffling the genes to create variety. Each of the offspring inherits a random mix of the parents genes. And variety is what enables species to adapt and evolve as the environment changes.为什么蚜虫会从单性生殖转为即紊乱又效率低下的有性生殖,这又是另一个故事了。简而言之,有性生殖是自然的基因重组方式,以创造多样的个体。每一个后代都遗传了父母随机组合的基因。多样性则是为了物种进化以适应环境的变化。But when summer returns and the living is easy, the aphids give up on variety and reproduce once again in the fastest way they know how. 但是在下一个夏季,生存又变得容易起来,蚜虫就会放弃多样性,以它们掌握的最快的方式重新生殖。201206/185145

Europes biggest defense contractor and its biggest aerospace firm are in advance talks to merge. BAE Systems and EADS reveal they have aly agreed to most of the details of the combining group but theyve yet to pull the trigger.欧洲最大的防务承包商及最大的航空公司的合并谈判已进入高级阶段。英国宇航系统公司(BAE Systems)和空客母公司欧洲宇航防务集团(EADS)透露双方已就两大公司的合并细节基本达成一致,不过现在还未扣动扳机。If the mega merge went ahead, the two remain separately listed companies but with a new parent company above them with the ability to massively cut costs at a time when defense budgets are under strain. The two firms aly work closely on projects like the Airbus A380 super-jumbo project and the Eurofighter Typhoon attack jet.如果此次大型合并得以成功施行,这两家公司仍将保留其独立上市公司身份,但是两家公司将同属一新母公司旗下,该母公司将有能力在欧美国防预算缩减局面下,大幅度降低成本。两家公司目前已在一些项目上展开亲密合作,如空客巨无霸A380大型机项目及欧洲战机台风战斗机。A merger will need approval of both boards but also regulators around Europe, and importantly, regulators in the ed States where BAE Systems has steadily become one of the biggest defence contractors for the Pentagon. Some US aerospace firms may also have something to say about a massive new kit on the block. 这样一个商业合并不仅要经双方董事会的同意,还要有欧洲境内的相关监管机构的许可,重要的是,需要美国相关监管机构的同意, 因为BAE Systems已经成为五角大楼最大的固定国防业务承包商之一。一些美国航空公司可能也会对此次合并发表其意见。EADS has been trying to build up a bigger military presence in the US and rely less on its commercial aircraft site for growth.EADS一直努力想在美国打造一个更大的军用飞机制造分公司,以此减少对民用商务飞机业务增长的依赖。BAE Systems shares soared in the last 45 minutes of trading Wednesday before the announcement was made official.两大巨头合并的官方申明宣布之前的周三,当日交易时间结束的最后45分钟内,BAE Systems的股票暴涨。Jim Bowe, CNN, London. Jim Bowe,CNN,伦敦。201210/202654

Yael: I just about an exciting technique. Researchers found a way to convert types A and B blood into type O blood—the type that can be transfused into any patient. This advance could help avoid blood shortages in the future.雅艾尔:我刚刚读了一条振奋人心的技术。研究人员找到了一种可以把A型、B型血转变为O型血的方法。而O型血可以输给任何病人。这项先进的技术能够避免出现缺血的情况。Don: Wow, that is exciting. But what makes type O blood so special?唐:哇,太振奋人心了。但为什么O型血这么特殊呢?Yael: Blood types result from different carbohydrates, called antigens, on the surface of human blood cells. Your blood ;type; denotes the kinds of antigens you have on the surface of your cells. People with type A blood have A antigens; those with type B have B antigens. If you have both kinds of antigens, youre type AB; if you have neither one, youre type O.雅艾尔:血型因不同的碳水化合物而产生,这种关键的碳水化合物就是抗原,它长在人体血细胞的表面。你的血型表示你的血细胞表面有哪种抗体。A血型的人有A抗体;B血型的人有B抗体。如果你有A和B两种抗体,那你就是AB血型的人;如果二者都没有,那你就是O型血了。Your immune system recognizes the antigens on your blood as ;self;, but attack cells with ;foreign; antigens. So if you ever need a blood transfusion, its important that you only receive blood compatible with your own type.免疫系统把血液中的这些抗体认作;自己人;,却会攻击那些带有;外来;抗体的细胞。因此,如果你需要输血时,你只能接受与自己血型相同的血,这很重要。Don: I see. So if a type A person receives type B or AB blood, her immune system will see the B-antigens as foreign, and attack the donor blood cells?唐:我明白了。所以如果A型血的人接受了B型血或者AB型血,她的免疫系统会视B抗体为外来者,于是就会攻击供体的血细胞。Yael: Exactly. But type O is called the ;universal donor; since it doesnt have any antigens that would set off the bodys defense system.雅艾尔:正是如此。O型血之所以被称为;万能血;,是因为它没有任何抗体,不会和身体的防卫系统相抵触。A team of Danish scientists has identified enzymes that remove the A and B antigens from blood cells. The enzymes, which were extracted from a bacteria and a fungus, essentially change any donated blood into type O.一个丹麦科学家小组已经找到了一种可以消除细胞中A、B抗体的酶。这种酶是从一种细菌和真菌中提取出来的, 可以把献血者的血型完全变成O型。Clinical trials are underway to test whether the treated blood is safe and effective. If so, the technology could help save lives, since type O blood is such a precious commodity.临床试验正在测试这种转化后的血是否安全有效。如果没什么问题,这项技术将挽救不少性命,因为O型血确实很紧缺。原文译文属!201303/230055


文章编辑: 飞度养生在线
>>图片新闻