徐庶读音Digest Of The. Economist. 2006(4-5)
讨价还价的意思
Hot to trot
正常体温是多少度A new rvice hopes to do for texting what Skype did for voice calls
TALK is cheap—particularly since the appearance of voice-over-internet rvices such as Skype. Such rvices, which make possible very cheap (or even free) calls by routing part or all of each call over the internet, have forced traditional telecoms firms to cut their prices. And now the same thing could be about to happen to mobilephone text messages, following the launch this week of Hotxt, a British start-up.
Urs download the Hotxt software to their handts, just as they would a game or a ringtone. They choo a ur name, and can then exchange as many messages as they like with other Hotxt urs for £1 ($1.75) per week. The messages are nt as data packets across the internet, rather than being routed through operators' textmessaging infrastructure. As a result, urs pay only a tiny data-transport charge, typically of a penny o
r so per message. Since text messages typically cost 10p, this is a big saving—particularly for the cost-conscious teenagers at whom the rvice is aimed.
Most teenagers in Britain, and elwhere in Europe, pay for their mobile phones on a “pre-paid” basis, rather than having a monthly contract with a regular bill. Pre-paid tariffs are far more expensive: bundles of free texts and other special deals, which can reduce the cost of text messaging, are generally not available. For a teenager who nds ven messages a day, Hotxt can cut the cost of texting by 75%, saving £210 per year, says Doug Richard, the firm's co-founder. For really intensive text-messagers, the savings could be even bigger: Josh Dhaliwal of mobileYouth, a market-rearch firm, says that some teenagers—chiefly boys aged 15-16 and girls aged 14-15— are “supertexters” who nd as many as 50 messages per day.
While this sounds like good news for urs, it could prove painful for mobile operators. Text-messaging accounts for around 20% of a typical operator's revenues. With margins on text messages in excess of 90%, texting also accounts for nearly half of an operator's
profits. Mr Richard is confident that there is no legal way that operators can block his rvice; they could rai data-transport costs, but that would undermine their own efforts to push new rvices. Hotxt plans to launch in other countries soon.
“The challenge is getting that initial momentum,” says Mr Dhaliwal. Hotxt needs to persuade people to sign up, so that they will persuade their friends to sign up, and so on. Unlike Skype, Hotxt is not free, so urs may be less inclined to give it a try. But as Skype has also shown, once a disruptive, low-cost communications rvice starts to spread, it can quickly become very big indeed. And that in turn can lead to lower prices, not just for its urs, but for everyone.
一分钟快速开嗓A discerning view
A new way of processing X-rays gives much clearer images
X-RAYS are the mysterious phenomenon for which Wilhelm Röntgen was awarded the first Nobel prize in physics, in 1901. Since then, they have shed their mystery and found widespread u in medicine and industry, where they are ud to reveal期中考试奖状
the inner properties of solid bodies.
Some properties, however, are more easily discerned than others. Conventional Xray imaging relies on the fact that different materials absorb the radiation to different degrees. In a medical context, for example, bones absorb X-rays readily, and so show up white on an X-radiograph, which is a photographic negative. But Xrays are less good at discriminating between different forms of soft tissue, such as muscles, tendons, fat and blood vesls. That, however, could soon change. For Franz Pfeiffer of the Paul Scherrer Institute in Villigen, Switzerland, and his colleagues report, in the April edition of Nature Physics, that they have manipulated standard X-ray imaging techniques to show many more details of the inner body.
The trick needed to discern this fine detail, according to Dr Pfeiffer, is a simple one. The rearchers took advantage not only of how tissues absorb X-rays but also of how much they slow their passage. This slowing can be en as changes in the pha of the radiation that emerges—in other words of the relative positions of the peaks and troughs of the waves of which X-rays are compod.
忠诚守信电脑怎么强制重启
画的图片Subtle changes in pha are easily picked up, so doctors can detect even small variations in the composition of the tissue under investigation, such as might be caud by the early stages of breast cancer. Indeed, this trick—known as pha-contrast imaging—is already ud routinely in optical microscopy and transmission electron microscopy. Until now, however, no one had thought to u it for medical X-radiography.
To perform their trick, the rearchers ud a ries of three devices called transmission gratings. They placed one between the source of the X-rays and the body under examination, and two between the body and the X-ray detector that forms the image. The first grating gathers information on the phas of the X-rays passing through it. The cond and third work together to produce the detailed pha-contrasted image. The approach generates two parate images—the classic X-ray image and the pha-contrasted image—which can then be combined to produce a high-resolution picture.
