The bed should be reserved as a place for sleep，but people tend to read an iPad a lot in bed before they go to sleep．

Charles Czeisler，a professor at Harvard Medical School，and his colleagues got a small group of people for an experiment．For five days in a row，the people read either a paper book or an iPad for four hours before sleep．Their sleep patterns were monitored all night．Before and after each trial period，the people took hourly blood tests to paint a day-long picture of just how much melatonin（褪黑激素）was in their blood at any given time．

When subjects read on the iPad as compared to the paper books，they reported feeling less sleepy at night and less active the following morning．People also took longer to fall asleep on the iPad nights，and the blood tests showed that their melatonin secretion（分泌）was delayed by an hour and a half．

The researchers conclude in today's journal article that gives the rise of e-readers and the increasingly widespread use of e-things among children and adolescents，more research into the"long-term consequences of these devices on health and safety is urgently needed．"Czeisler and colleagues go on，in the research paper，to note"Reading an iPad in bed may increase cancer risk．"

However，software has been developed that can reduce some of the blue light from the screens of phones and computers according to time of day，and there are also glasses that are made to filter（过滤）short wavelengths．While they seem like a logical solution for the nighttime tech users，it needs more research．

NOT all memories are sweet. Some people spend all their lives trying to forget bad experiences. Violence and traffic accidents can leave people with terrible physical and emotional scars. Often they relive these experiences in nightmares.

Now American researchers think they are close to developing a pill, which will help people forget bad memories. The pill is designed to be taken immediately after a frightening experience. They hope it might reduce ,or possibly erase(抹去),the effect of painful memories.

In November, experts tested a drug on people in the US and France. The drug stops the body releasing chemicals that fix memories in the brain. So far the research has suggested that only the emotional effects of memories may be reduced, not that the memories are erased.

The research has caused a great deal of argument. Some think it is a bad idea, while others support it.

Supporters say it could lead to pills that prevent or treat soldiers' troubling memories after war. They say that there are many people who suffer from terrible memories.

"Some memories can ruin people's lives. They come back to you when you don't want to have them in a daydream or nightmare. They usually come with very painful emotions," said Roger Pitman, a professor of psychiatry at Harvard Medical School. "This could relieve a lot of that suffering."

But those who are against the research say that changing memories is very dangerous because memories give us our identity (特质). They also help us all avoid the mistakes of the past.

Back in the 1980s when monkeypox(猴痘)was still an extremely rare disease, scientists kept warning: Over time, the monkeypox outbreaks will increase. At that time, there were only about 50 monkeypox cases a year in West and Central Africa where people caught the disease mainly from direct contact with wild animals. Infection between humans was very limited. But in 2022, the world is facing the first international outbreak, with more than 5,000 cases reported in 44 countries within six months.

So how could the scientists know in the 1980s that monkeypox would grow in size and spread internationally?

Their warnings were based on the successful campaign against smallpox(天花), one of the deadliest diseases in human history, which killed up to 30% of the people infected. Thanks to a worldwide campaign, smallpox disappeared in the late 1970s. However, the end of smallpox opened the door for monkeypox to emerge.

Monkeypox, whose present version kills less than 1% of people infected, is closely related to smallpox. Having a smallpox infection-or a smallpox vaccine(疫苗)-offers really good protection against smallpox as well as monkeypox. Perhaps about 85% protection. But in the late 1970s, the world stopped vaccining people for smallpox. So over the past decades, human resistance to smallpox and monkeypox has dropped sharply.

“We’re actually at a point where our immunity against monkeypox is the lowest in thousands of years,” says Jo Walker of the Yale School of Public Health. Without some resistance against the disease, people are more likely to catch monkeypox from animals and spread it to someone else. So it is time that people who might come into contact with infected people were vaccined for monkeypox. Otherwise, it could become a permanent presence in the world, since every time there’s an outbreak the virus has a chance to figure out how to spread more quickly among people.

Indeed, this new outbreak in Europe may be a sign that the virus has changed-even if just a bit-and may be increasing its ability to spread among people.