“Can I hug you?” community nurse Joyce Jebambula asks with a smile as she welcomes me back to her village. “Of course,” I say as I put my arms around her. It's an unbelievable moment. Just at the height of the outbreak more than a year ago, there was an “avoid body contact” rule here. It's now been removed.

    One of the most challenging parts of reporting this outbreak over the past 18 months is that I haven't been able to touch anyone in the worst-affected countries. When Ebola(埃博拉病毒) survivors described in tears describing losing their families, I had to almost sit on my hands to avoid reaching out to comfort them.

    The outbreak was declared over in Sierra Leone on 7 November. I returned for the celebrations. But despite reaching this long-awaited milestone, all is not well.

    Ibrahim Koroma, 21, clings to (紧紧抓住) his survivor's certificate (证明) outside the home. All 17 of his family are now dead. The certificate is one of his most prized possessions. "He does not pose any risk to the community" it reads.

    Ibrahim tells me how his landlord has allowed him to stay in one of the rooms of his former family home until the end of the year. He says he doesn't know what he'll do after that. He does some part-time work, relying heavily on help from neighbors. His two little sisters and little brother died in the very room where he now sleeps. He says he often lies awake thinking about them, feeling very bad.

    The Ebola outbreak in West Africa was the worst on record. In past outbreaks there had only been a few hundred deaths and a few hundred survivors. It was thought Ebola could live for only three months. But research has now shown it can linger for at least nine months. Scientists are still trying to find how long it could be infectious.

    Why can some people sleep through noises like a honking car or flushing toilet, while others are awakened by the lightest sound?

    To find the answer, sleep researchers at Massachusetts General Hospital conducted an unusual study of 12 self-described deep sleepers. After tests confirmed that the healthy volunteers were solid sleepers, they took part in a three-night study in the university's sleep laboratory. The participants spent the night in a big and comfortable room. But the room also included four speakers positioned near the top of the bed.

    During the night, the deep sleepers were subjected to 14 different recorded sounds, like street traffic, toilets flushing, and an airplane flying overhead. Next door, the researchers monitored their sleep patterns and brain waves.

    As expected, all of the participants slept relatively well, but there were differences in how they responded to the noisy interruptions. Some of the sleepers didn't wake up even when a sound was blasted at 70 decibels（分贝）; others were awakened by sounds at 40 or 50 decibels.

    The researchers discovered that the difference in a sleeper's reaction to noise could be predicted by the level of brain activity called "sleep spindles（纺锤体）". A sleep spindle is a burst of high-frequency brain activity coming from deep inside the brain during sleep. The source of the spindles is the thalamus（丘脑）, a part of the brain that sends sensory information to the rest of the cortex（皮层）.

    Before the study, the Massachusetts researchers theorized that the spindles are the brain's way of preventing sensory information from passing through the thalamus and waking the rest of the brain during sleep. They found that sleepers who experienced the most sleep spindles during the night were also the soundest sleepers and were least likely to be awakened by noise.

    Scientists already know that most people become lighter sleepers with age, most likely because older people experience less "slow wave sleep", which is the deepest stage of sleep. People also produce fewer sleep spindles as they age. But even when controlling for the stage of sleep a person was in, the number of sleep spindles still predicted their risk for awakening because of noise.

    More research is needed, but the findings suggest that a better understanding of sleep spindles could lead to new behavioral or drug therapies for people with sleep disorders. For example, future studies may try to determine whether diet, exercise or other behaviors may influence the number of sleep spindles a person produces during the night.

Hot Air Balloons

    The basis of how the balloon works is that warmer air rises in cooler air. This is because hot air is lighter than cool air as it has less mass per unit of volume. Mass can be defined by the measure of how much matter something contains. The actual balloon has to be large as it takes a large amount of heated air to lift it off the ground.

    The burner uses propane gas to heat up the air in the envelope to move the balloon off the ground and into the air. The pilot must keep firing the burner at regular intervals throughout the flight to ensure that the balloon continues to the stable. Naturally, the hot air will not escape from the hot at the very bottom of the envelop as firstly, hot air rises and secondly, the floating power keeps it moving up.

    To move the balloon upwards, the pilot opens up the propane value which lets the propane flow to the burner which in turn frees the flame up into the envelope. It works in much the same way as a gas grill: the more you open the valve, the bigger the flame to beat the air and the faster the balloon rises.

    The “Parachute Valve” at the very top of the balloon is what is used to bring the balloon down towards the ground. It is a circle of fabric cut out of the top of the envelop which is controlled by a rope which runs down through the middle of the envelope to the basket. If the pilot wants to bring the balloon down, he or she simply pulls on the rope which will open the valve, letting hot air escape, decreasing the inner air temperature. This cooling of air causes the balloon to slow its rise.

    The pilot can operate horizontally by changing the vertical position of the balloon because the wind blows in different directions at different altitudes. If the pilot wants to move in a particular direction, he or she simply arises and falls to the appropriate level and rides with the wind.

    People living in the country enjoy several advantages that people living in the city cannot enjoy.

    They are in close contact (接触)with nature. They make friends with trees and stones. They breathe fresh air. They fight with strong winds. They listen to the song of birds. This contact with nature is good for health. There are many diseases that are common in the city, but are not to be found in the country. For example, near­sightedness is almost unknown to country people. Because of the absence of cars, one can walk more freely in the country than in the city. There are no rules of the road nor traffic signs to obey. People living in the country can easily get fresh vegetables, fresh fruit and fresh milk, and they get them at lower prices than in the city. Country life is economical (节俭的)in other ways, too. There are practically no temptations to waste money.

    Country people are mostly honest. They say what they mean, and make and keep promises with sincerity (诚意). They do not put on air (摆架子). They do not pretend to have those ridiculous (荒谬的)manners which are necessary in what we call polite society.

    Google previously announced successful tests of machine learning systems designed to assist doctors. In one case, Google reported AI had examined eye diseases with equal accuracy to doctors. Other tests showed that machine learning can be used to study large amounts of patient data to predict future medical events.

    Now the company has published two new studies showing a high level of success in identifying metastatic breast cancer. Metastatic means that cancer has spread from its main area to other parts of the body. Metastatic breast cancer is one of the deadliest, causing about 90 percent of all breast cancer deaths worldwide.

    In metastatic breast cancer patients, the cancer often travels to nearby lymph nodes（淋巴结）. Usually doctors examine lymph node tissue under a microscope to see whether cncer is present Google notes that previous studies have shown that up to one-fourth of metastatic lymph node classifications end up being changed after a second examination. In addition, studies show that small metastatic material can be missed up to 67 percent of the time when examinations happen under extreme time restrictions.

    Google says it created a mathematical algorithm(算法).The algorithm, called Lymph Node Assistant, is trained to find characteristics of tissue affected by metastatic cancer. When the system examined tissue images (图像), it was able to differentiate between metastatic cancer and non-cancer 99 percent of the time. In addition, the Lymph Node

    Assistant is highly effective at finding the positions of the cancers. Some of these positions would be too small for doctors themselves to identify. The research also showed that the algorithm method can reduce the usual time needed to examine the disease by about 50 percent.

    But Google makes clear the Al-based system is not meant to replace the work of medical professionals. Instead, it is designed to reduce the number of false identifications and help doctors work faster and more effectively.

A video of dolphins playing in the wake of the waves near a man-made island, east of the Hong Kong-Zhuhai-Macao Bridge, has caught the attention from netizens across China.

The 55-km Hong Kong-Zhuhai-Macao Bridge is the world's longest cross-sea bridge, connecting the mainland province of Guangdong with the country's two special administrative regions, Hong Kong and Macao.

During the nine-year bridge construction period, researchers have identified and registered a total of 2,367 dolphins, with no injuries of any dolphins reported.

According to local authorities, the Pearl River Estuary Chinese White Dolphin Reserve has supported more than 100 researchers in studying and protecting the mammal and trained thousands of dolphin watchers. Luo Guocai, a certificated dolphin watcher, said his duty was to conduct a 10-minute observation of the sea each time before construction started. The dolphins have to breathe every few minutes above the water, and in order to prevent potential harm, the watchers would knock on their boat a few times to scare them away.

The preservation efforts never stopped even after the construction was completed. "Managerial personnel will continue to monitor the nearby environment and the dolphins via intelligent equipment including the bridge video surveillance(监控) system, the underwater tunnel's environmental monitoring as well as specially established research and observation stations on the man-made islands," said Yu Lie, deputy director of the bridge management bureau.

"Currently, Hong Kong, Macao, the country's two special administrative regions, and Guangdong plan to establish a conservation alliance for the dolphins, involving non-governmental organisations in the routine rescue, information sharing, and scientific research," said Chen Hailiang, head of the administration of the reserve. "We are constructing a bigger rescue and conservation base as well as increasing tissue samples and gene banks in a bid to better preserve the dolphins for generations to come," Chen said.