The health of the ozone layer.



If we were to assume the role of a physician in order to diagnose the health of the ozone layer, no doubt we would state that our patient is in very poor health, and that the patient's condition is getting worse.

• In 1995, 1996 and now in 1997 we have experienced record ozone depletions over both the Southern and Northern hemispheres.

• The 1996 Antarctic ozone hole reached a record 10 million square miles - an area greater than the total surface area of North America, and twice the size of Europe.

• During November and December of 1996, ozone levels over Northern Europe and the north Atlantic were 20% lower than the average measurements between 1957 and 1970. More than 25% ozone depletion was measured over some populated areas.

• Following the trend, in March 1997, the ozone layer was 15 to 25 percent thinner over the Arctic than it was a year earlier, and Environment Canada reported a record of nearly 40% ozone depletion over the North West Territories.

• The European Commission's Environment and Climate Programme reported in May, 1997, that "For the third winter in succession, record low temperatures in the Arctic's lower stratosphere, coupled with the presence of man-made pollutants, have resulted in...up to 40% ozone depletion in the Northern Hemisphere... (with) total ozone as low as 270 Dobson Units near the pole during March this year."

Of further concern is the recurrence of extremely cold spring time temperatures over the Arctic, which is a precondition for increased ozone depletion. The European Commission noted that "Analyses of stratospheric temperature data shows that the stratosphere during March 1997 was by far the coldest on record. The average monthly mean over the Pole was some six degrees lower than the previous minimum average. These very low temperatures in the Arctic springtime for the third successive year give rise to the concern that they may be part of a longer-term trend. It is important to understand whether, for example, this represents part of changes induced by chemistry-climate feedback.


Вариант 20

Задание 1. Измените число существительных с единственного на множественное и внесите соответствующие изменения в остальные члены предложений.

1. There is an apple on this plate.

2. The eagle is a very big bird.                                         

3. The bird is singing in the tree.

4. The cat has caught a mouse.        

5. The hen has 12 chickens.

6. The dog is running in the field.

Задание 2. Измените форму прилагательных, данных в скобках, и переведите предложения на русский язык.

1. I met my (good) friend.

2. You are the (bad) student in the class.

3. It is the (interesting) book of all I have ever read.

4. Next time I'll do it (good).

5. Dorothy is the (young) in the family.

6. Where is the (near) post- office, please?

Задание 3. Вставьте модальные глаголы may, can, must, need.

1. We ... go away just yet; our train doesn't leave for half an hour yet.

2. You ... be at home by 11 o'clock.

3. The bus didn't come and we ... go on foot.

4. I don't have this book, so I... go to the library.

5. The ice is quite thick. We ... walk on it.

6. If you don't know the meaning of a word you... use a dictionary.

Задание 4. Поставьте глаголы , данные в скобках , в нужную форму .

1. When I came he (leave), so we only had time for a few words.

2. Peter and Ann (go) away five minutes ago.

3. He (go) to Moscow next week?

4. When he (arrive)? - He (arrive) at 2.00.

5. When I (to come) home, mom (to make dinner) already and (to bake) something in the oven..

6. He suddenly (understand) that he (travel) in the wrong direction.

Задание 5. Переведите предложения на английский язык.

1. Он обещал звонить ей каждый день.

2. Мы женаты только два месяца.                                                               

3. Если вы готовы, мы можем идти.

4. Я уже видел этот фильм раньше.                           

5. Немногие спортсмены достигают больших успехов.

6. Она собиралась зайти в магазин после работы.

Задание 6. Образуйте отрицательную и вопросительную формы предложений.

1. During the day I work as a film editor in Hollywood.

2. She had long, dark hair.

3. She was wearing a pretty pink dress.

4. They have a baseball team.

5. The children help replant these trees.

Задание 7. Задайте вопросы к каждому члену предложения.

1. I've met a really nice girl called Mary

2. Scientists will find new sources of energy.

3. Several days ago Natalie had her birthday.

4.. She had played a board game.

5. They organized a surprise birthday party.

Задание 8. Задайте общий, специальный, альтернативный и разделительный вопросы к каждому предложению.

1. The plane leaves Moscow at 3 p.m.

2. There are many rivers in the country.                                      

3. My granny always gives me good advice.                           

4. New furniture will cost you a lot of money.

5. We had lunch together.

Задание 9. Переведите текст на русский язык.

WHEN TO USE ISAM (THE INDEXED SEQUENTIAL ACCESS METHOD).

For data files are too large to completely load into memory, ISAM vastly simplifies file manipulation because ISAM support replaces the kind of sorting that can only otherwise be accomplished efficiently by loading all data records in memory simultaneously. This makes ISAM an excellent method for dealing with large amounts of data which require sorted access. An ISAM file can be as large as 128 megabytes. ISAM handles all the work of moving portions of such a huge file in and out of memory during record manipulation.

Whenever data records contain many fields that need to be examined variety of ways, using ISAM simplifies the programming. Although you can write code to sort or index random-access files, ISAM integrates these you with high-level statements that manipulate sophisticated file structures. This lets you easily manipulate records by the values in specific fields, and is far more flexible than a random file's one-dimensional ordering by record number. However, if disk space is at a premium, don't automatically choose ISAM for short, easily-sorted files of relatively constant size. These may be better handled using other methods (for example, by creating and using hash tables). However, if you need to sort on different fields at different times, or if you need very fast access to records according to complex 6ubsorting orders, the benefits of the ISAM file quickly make up for its overhead. Also, consider that for very large files, the amount of descriptive information relative to actual records remains relatively constant, so the percentage of the file devoted to overhead decreases progressively.


Дата добавления: 2018-11-24; просмотров: 260; Мы поможем в написании вашей работы!

Поделиться с друзьями:






Мы поможем в написании ваших работ!