要了解一點核知識
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3/30/2011
3/28/2011
大華府地區僑學界慶祝中華民國建國一百年 4月2日聯歡晚會
大華府地區僑學界為慶祝中華民國建國一百年將於4月2日在 Richard Montgomery High School Auditorium 擧辦百人大合唱及民族舞蹈聯歡晚會。您要是有家人、同學和朋友住在大華府地區，
http://wdc100.blogspot.com
http://wdc100.blogspot.com
RADIATION EMERGENCIES - Measuring Radiation
When scientists measure radiation, they use different terms depending on whether they are discussing radiation coming from a radioactive source, the radiation dose absorbed by a person, or the risk that a person will suffer health effects (biological risk) from exposure to radiation. This fact sheet explains some of the terminology used to discuss radiation measurement.
Units of Measure
Most scientists in the international community measure radiation using the System Internationale (SI), a uniform system of weights and measures that evolved from the metric system. In the United States, however, the conventional system of measurement is still widely used.
Different units of measure are used depending on what aspect of radiation is being measured. For example, the amount of radiation being given off, or emitted, by a radioactive material is measured using the conventional unit curie (Ci), named for the famed scientist Marie Curie, or the SI unit becquerel (Bq). The radiation dose absorbed by a person (that is, the amount of energy deposited in human tissue by radiation) is measured using the conventional unit rad or the SI unitgray (Gy). The biological risk of exposure to radiation is measured using the conventional unit remor the SI unit sievert (Sv).
Measuring Emitted Radiation
When the amount of radiation being emitted or given off is discussed, the unit of measure used is the conventional unit Ci or the SI unit Bq.
A radioactive atom gives off or emits radioactivity because the nucleus has too many particles, too much energy, or too much mass to be stable. The nucleus breaks down, or disintegrates, in an attempt to reach a nonradioactive (stable) state. As the nucleus disintegrates, energy is released in the form of radiation.
The Ci or Bq is used to express the number of disintegrations of radioactive atoms in a radioactive material over a period of time. For example, one Ci is equal to 37 billion (37 X 109) disintegrations per second. The Ci is being replaced by the Bq. Since one Bq is equal to one disintegration per second, one Ci is equal to 37 billion (37 X 109) Bq.
Ci or Bq may be used to refer to the amount of radioactive materials released into the environment. For example, during the Chernobyl power plant accident that took place in the former Soviet Union, an estimated total of 81 million Ci of radioactive cesium (a type of radioactive material) was released.
Measuring Radiation Dose
When a person is exposed to radiation, energy is deposited in the tissues of the body. The amount of energy deposited per unit of weight of human tissue is called the absorbed dose. Absorbed dose is measured using the conventional rad or the SI Gy.
The rad, which stands for radiation absorbed dose, was the conventional unit of measurement, but it has been replaced by the Gy. One Gy is equal to 100 rad.
Measuring Biological Risk
A person's biological risk (that is, the risk that a person will suffer health effects from an exposure to radiation) is measured using the conventional unit rem or the SI unit Sv.
To determine a person's biological risk, scientists have assigned a number to each type of ionizing radiation (alpha and beta particles, gamma rays, and x-rays) depending on that type's ability to transfer energy to the cells of the body. This number is known as the Quality Factor (Q).
When a person is exposed to radiation, scientists can multiply the dose in rad by the quality factor for the type of radiation present and estimate a person's biological risk in rems. Thus, risk in rem = rad X Q.
The rem has been replaced by the Sv. One Sv is equal to 100 rem.
Abbreviations for Radiation Measurements
When the amounts of radiation being measured are less than 1, prefixes are attached to the unit of measure as a type of shorthand. This is called scientific notation and is used in many scientific fields, not just for measuring radiation. The table below shows the prefixes for radiation measurement and their associated numeric notations.
Prefix Equal to Which is this much Abbreviation Example
atto- 1 X 10-18.000000000000000001 a aCi
femto- 1 X 10-15.000000000000001 f fCi
pico- 1 X 10-12.000000000001 p pCi
nano- 1 X 10-9 .000000001 n nCi
micro- 1 X 10-6.000001 m m Ci
milli- 1 X 10-3.001 m mCi
centi- 1 x 10-2.01 c cGy
When the amount to be measured is 1000 (that is, 1 X 103) or higher, prefixes are attached to the unit of measure to shorten very large numbers (also scientific notation). The table below shows the prefixes used in radiation measurement and their associated numeric notations.
Prefix Equal to Which is this much Abbreviation Example
kilo- 1 X 1031000 k kCi
mega- 1 X 1061,000,000 M MCi
giga- 1 X 109100,000,000 G GBq
tera- 1 X 1012100,000,000,000 T TBq
peta- 1 X 1015 100,000,000,000,000 P PBq
exa- 1 x 1018100,000,000,000,000,000 E EBq
Common Radiation Exposures
People are exposed to radiation daily from different sources, such as naturally occurring radioactive materials in the soil and cosmic rays from outer space (of which we receive more when we fly in an airplane). Some common ways that people are exposed to radiation and the associated doses are shown in the table below.
Source of exposure Dose in rem Dose in sievert (Sv)
Exposure to cosmic rays during a roundtrip airplane flight from New York to Los Angeles 3 mrem 0.03 mSv
One dental x-ray 4?15 mrem 0.04?0.15 mSv
One chest x-ray 10 mrem 0.1 mSv
One mammogram 70 mrem 0.7 mSv
One year of exposure to natural radiation (from soil, cosmic rays, etc.) 300 mrem 3 mSv
For more information
For more information about radiation measurement, you may visit the website for the Health Physics Society, or the Environmental Protection Agency's "Radiation Topics".
For more information about radiation, see CDC's Radiation Emergencies website. You may also call the CDC public response hotline at 800-CDC-INFO or 888-232-6348 (TTY).
The Centers for Disease Control and Prevention (CDC) protects people's health and safety by preventing and controlling diseases and injuries; enhances health decisions by providing credible information on critical health issues; and promotes healthy living through strong partnerships with local, national, and international organizations.
The Centers for Disease Control and Prevention (CDC) protects people's health and safety by preventing and controlling diseases and injuries; enhances health decisions by providing credible information on critical health issues; and promotes healthy living through strong partnerships with local, national, and international organizations.
3/24/2011
一杯冰拿鐵 Iced Latte 的幸福
老婆婆個子不高又很胖，坐在輪椅已好一陣子了
每一個星期，老爺爺都準時的陪著老婆婆回來拿藥，
一天晚上，老婆婆掛急診入院，電腦掃描顯示腦下皮層出血。
我告訴老爺爺，他茫然地看著，只見他眼中閃過一絲的淚光。
神蹟般的，老婆婆的頭腦清醒，情況好極了..
老婆婆住院住了半個月，低聲的問我：
我巡房完後，順口問了那層的義工，原來老爺爺出了車禍，
而他們夫妻倆，竟沒有半個親人在台灣。
過了幾天，老爺爺的病情剛好轉，便嚷著出院照顧老伴。
幾番商量之後，台大的學弟想出折衷辦法，老爺爺轉院到馬偕，
隔天，老爺爺坐進輪椅，由義工推到老婆婆病房門口。
他吃力的坐在老婆婆床沿，端著義工幫忙買的冰拿鐵，
老婆婆笑著接了過來：「好幾天沒看見你，怎麼啦？」
老爺爺也笑著說：「走路時摔了一跤，沒事的。」
這是我聽過最心疼的一個謊話。
老爺爺的身體一天天康復，當他準備出院那天，竟因心肌梗塞，
簽完死亡證明，我交代護士先別告訴老婆婆，免得她剌激太大!
巡房時，老婆婆告訴我，他與老爺爺住在倫敦時，
實習的學妹微笑著哄著：「您健忘了，
隔天早上，我發覺床頭多了一杯冰拿鐵，學妹告訴老婆婆：「
看著安心的老婆婆，我不安的心也稍稍舒緩下來。
當天下午，老婆婆病房的緊急鈴響了起來，
我一邊開立證明，一邊想起今早老婆婆所說的「幸福」。「幸福」
真正的幸福永遠是住在心裡面，儘管經歷著生老病死，
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