Food sometimes gets poisoned with harmful things. A person who eats such food can get an illness called food poisoning. Food poisoning is usually not serious, but some types are deadly. The symptoms of food poisoning usually begin within hours of eating the poisoned food. Fever is one of the most common symptoms.

Certain microorganisms(微生物)cause most types of food poisoning. Bacteria and other microorganisms can poison eggs, meat, vegetables, and many other foods. After entering the body, these tiny living things release(释放)poisons that make people sick.

Some chemicals can also cause food poisoning. They are often added to food while it is being grown, processed, or prepared. For example, many farmers spray chemicals on crops to kill weeds and insects. Some people may have a bad reaction to those chemicals when they eat the crops.

Some plants and animals contain natural poisons that are harmful to people. These include certain kinds of seafood, grains, nuts, seeds, beans, and mushrooms.

When people handle food properly, the risk of food poisoning is very small. Microorganisms multiply rapidly in dirty places and in warm temperatures. This means that people should never touch food with dirty hands or put food on unwashed surfaces. Food should be kept in a refrigerator to stop microorganisms from growing. Meat needs to be cooked thoroughly to kill any dangerous microorganisms. People should also wash food covered with chemicals before eating it. Finally, people should not eat wild mushrooms or other foods that grow in the wild. Some of these foods may contain natural materials that are poisonous to humans. In addition, some types of fish can be poisonous.

Most people recover from food poisoning after a few days of resting and drinking extra water. If people eat natural poisons, they must go to the hospital right away to have their stomachs emptied.

Patients in the early stages of Alzheimer’s disease often struggle to remember recently learned information, meaning they forget things like important appointments or where they left their keys. But it seems that these memories are not lost. They are still filed away in the brain somewhere; they just can’t be easily accessed.

Now, researchers at MIT have developed a means of getting back memories in mice suffering from Alzheimer’s. The method relies on a technique that uses light to control genetically modified neurons (转基因神经元). Currently it is too early to be used in human trials as it involves inserting light emitting (发光) equipment into the subjects’ brains, but the same principles still apply, the researchers said.

“The important point is that this is evidence of concept. That is, even if a memory seems to be gone, it is still there. It’s a matter of how to get it back,” said senior researcher Susumu Tonegawa.

The team took two groups of mice, one genetically engineered to develop Alzheimer’s and one healthy. They then placed them into a room and gave them a mild electric shock. All of the mice showed fear when put back in an hour later. When placed in the room a third time several days later, the Alzheimer’s mice acted normally. They had forgotten the shock.

The researchers were then able to bring back the memory of the shock by activating (激活) the cells in which the memories were stored. Even when the mice were put into an unfamiliar room, they showed fear when the cells associated with the shock were activated.

“Short-term memory seems to be normal, on the order of hours. But for long-term memory, these early-Alzheimer’s mice seem to be damaged,” said lead researcher Dheeraj Roy. “Directly activating the cells that we believe are holding the memory helps them get it back. This suggests that it is indeed an access problem to the information, not that they’re unable to learn or store this memory.”

Reading is thought to be a kind of conservation between the reader and the text. The reader puts questions, as it were, to the text and gets answers. In the light of these he puts further questions, and so on.

       For most of the time this “conservation” goes on below the level of consciousness. At times, however, we become aware of it. This is usually when we are running into difficulties, when mismatching is occurring between expectation and meaning. When successful matching is being experienced , our questioning of the text continues at the unconscious level.

Different people converse with the text differently. Some stay very close to the words on the page; others take off imaginatively from the words, interpreting, criticizing, analyzing and examining. The former represents a kind of comprehension which is written in the text. The latter represents higher levels of comprehension. The balance between these is important, especially for advanced readers. There is another conservation which from our point of view is equally important, and that is not to do with what is read but how it is read. We call this a “process” conservation as opposed to a “content” conservation. It is concerned not with meaning but with the strategies we employ in reading. If we are an advanced reader, our ability to hold a content conservation with a text is usually pretty well developed. Not so our ability to hold a process conservation. It is precisely this kind of conservation that is of importance when we are seeking to develop our reading to meet the new demands being placed upon us by studying at a higher level.