The Code Red worm is expected to infect more than 250,000 computer systems by the end of the day. What government agency monitors the Internet for attacks like Code Red, and why?

The federal National Infrastructure Protection Center coordinates computer crime investigations in the United States by collecting information from law enforcement agencies, the military, the private sector, and state and local governments. The NIPC's mission to deter, detect, and investigate malicious acts that threaten the Internet also extends to rest of the nation's "critical infrastructure," which includes the telecommunications grid, the electrical power system, the banking and finance system, oil and gas distribution, government operations, transportation systems, and water systems. The NIPC's mission was laid out in a presidential directive issued by President Clinton in 1998.

The NIPC is housed in the Federal Bureau of Investigation headquarters, and it operates under the authority of the attorney general. It divides Internet attacks into three categories: unstructured threats (from individuals and hackers), structured threats (from organized crime or terrorists), and national security threats (from foreign governments). Once the NIPC has determined the source and scope of an attack, it coordinates the response with national security agencies, law enforcement, or the private sector.

Explainer thanks FBI spokeswoman Debbie Weierman and the NIPC Web site.

All publicly traded companies are required by the Securities and Exchange Commission to file a quarterly financial statement, known as a 10-Q, for the first three fiscal quarters of the year. Now that the first quarter statements are coming out, what do some of the terms reported on the reports mean?

If you're reading the reports in the newspaper, you probably see a reference to the actual results compared with the analysts' expectations or forecasts. People who track particular companies for financial firms, for example, are constantly monitoring the performance of that company. As the date for the 10-Q approaches, analysts, often after discussions with the company, predict how much a company will make or lose. And woe to the stock price of a company that does worse than analysts expected.

Quarterly reports will tell you what the company's net income (also called net profit) or net loss was during the previous three months. This is how much the company earned after deducting all its expenses--everything from salaries to debt payments to purchase of equipment. This is usually expressed as a big lump sum. Earnings are, very generally speaking, the net income divided per share of stock, and that is usually expressed in cents, or if things are really good, dollars. For example, if a company's quarterly net income was $600,000 and it has 200,000 in common shares, the company's quarterly earnings would be $3 per share. Gross profit or gross margin is the money the company made in sales minus the direct cost incurred. For example, if a company sells $1 million of widgets in a quarter and it cost $250,000 to actually make the widget, the gross profit is $750,000 for the quarter.

Operating income, or loss, is the money the company makes (or loses) doing its business minus the cost incurred doing that business. This is not necessarily the same as net income. A widget company may be lousy at selling widgets (and who isn't?) but great at investing in stocks. So the money made--or lost--by widget manufacturing--the operating income--is separated out from the money made from stock investing in order for investors to see how the company does at its core business. That non-operating income is called--surprise!--non-operating income. Both are calculated in the net income. Sometimes you will see that a company has to account for an extraordinary item or a one-time gain or loss. This is something that is not expected to occur in the normal course of business--for example, the Mississippi overflowing and shutting down a factory, or the costs of eliminating an entire division, or a huge profit made by selling investment stocks.

And what about dividends? Dividends are a portion of income paid per share of stock. For example, if a company's stock is selling at $100 a share and has an annual dividend of $1 per share, the dividend yield is 1 percent. If you're into technology stocks, you aren't getting any dividends. Old economy companies like utilities and financial concerns tend to pay dividends; how much is usually decided by the board of directors. New economy companies--which eat up huge amounts of capital--usually invest profits, if there are any--back into themselves.

Explainer thanks Diane Garnick of Merrill Lynch.

The San Francisco Chronicle reports today that the grocery delivery company Webvan and the online magazine (and Slate competitor) Salon are both about to be delisted from the Nasdaq stock exchange. How does a stock get delisted, and what do the shareholders do when a stock has been kicked off an exchange?

Both major stock exchanges--Nasdaq and the New York Stock Exchange (NYSE)--require listed stocks to maintain a trading price of $1 or more. If a company trades for less than $1 per share for 30 consecutive trading days, as Webvan and Salon have, the process of delisting begins. Each exchange has its own rules about various company problems that could lead to delisting and its own procedures for notification and appeal of a possible delisting. In the case of Nasdaq stocks that fall below the trading minimum, Nasdaq sends a warning that the company has 90 days to get the stock trading at an acceptable level. If the company is unable to do so, Nasdaq then notifies the company of its imminent delisting. A company then has one week to issue a press release telling the world, and its stockholders, the bad news. Failure to issue the release results in a trading halt. Within that seven-day period, the company can also request a hearing to appeal the delisting decision. If it fails in its appeals to Nasdaq, the company can take its case to the SEC and then on to the federal courts. On Nasdaq the delisting procedure for various violations of the exchange's standards can take anywhere from 30 days to seven months. In the first quarter of this year, Nasdaq delisted 95 stocks. That compares to 240 for last year and 440 for 1999. So far this year the NYSE has delisted 17 stocks compared to 61 last year and 58 for 1999.

Once a company is delisted, shareholders have a chance to wonder, "Why, why, why did I ever listen to that stock tip from Uncle Lou?" Being delisted from one exchange does not prevent a stock from getting listed on another, but it must meet that exchange's listing requirements. The stock can also be traded on two different quotation services: the Over the Counter Bulletin Board, which has minimal financial reporting requirements, or on the Pink Sheets, which do not have reporting requirements. Of course, the company could reorganize, turn itself around, get relisted, and prove that Uncle Lou was right after all.

On Sunday, June 18, 58 Chinese asylum seekers were found suffocated in a tomato truck in England, rekindling debate in European Union countries about asylum policy. The Elián González controversy has kept asylum in the news in the United States. What is asylum, and who gets it?

Asylum laws are based on the 1951 U.N. Refugee Convention, which was passed to cope with the masses of World War II refugees in Europe. Most Western countries grant asylum to aliens who can demonstrate a well-founded fear of persecution in their country of origin for one or more of five reasons: race, religion, nationality, social group, or political opinion. Those granted asylum are allowed to work and cannot be returned to their country of origin. In the United States, the attorney general can revoke asylum if the subject breaks laws or if circumstances in the country of origin fundamentally change.

Canada, Germany, Great Britain, the Netherlands, Switzerland, and the United States attract the most asylum applications. In 1997, the United States received (or reopened) 123,000 asylum cases, more than any other country except Germany. Most asylum seekers come from Afghanistan, China, El Salvador, Haiti, Iraq, Mexico, Sri Lanka, and Turkey. In 1997, 35 percent of all asylum applications were approved worldwide, according to the United Nations. The United States approved only 19 percent that year (the U.S. approval rate has increased since then).

Aliens can apply for U.S. asylum by 1) making an affirmative claim before an Immigration and Naturalization Service asylum officer while their visa is still valid; or 2) making a defensive claim before an immigration judge once deportation proceedings have begun. To win a defensive claim hearing before an immigration judge, the applicant must first demonstrate to an immigration officer a credible fear of persecution in his country of origin. Asylum seekers interdicted en route to the United States--usually on the high seas--are often sent to a third country if their claim is successful.

In recent years, many countries have tightened their asylum rules. The United States streamlined its asylum process in 1997, giving INS officers more discretion to deport. Germany and Great Britain have reduced benefits paid to asylum seekers whose cases are pending. Many European Union countries send asylum seekers to third countries through which they traveled and that are deemed safe. France now only accepts applicants who are fleeing from state persecution. Those fleeing from unofficial rebel persecution in, say, Sierra Leone are not eligible. The United States tends not to accept applicants from Haiti because they are considered economic refugees, not political refugees.

The INS refused to consider Elián González's asylum application because under the law, only a parent can seek asylum for his child. By any measure, Elián would have had a hard time meeting any one of the five conditions for asylum, even though his mother fled Cuba.

Last week the White House announced it wanted John M. Klink, who holds dual U.S. and Irish citizenship, to head the U.S. State Department's Population, Refugees, and Migration Bureau. What does it mean to be a citizen of the United States and another country?

It means that as far as the United States is concerned, you are a citizen of the United States and have the same rights, privileges, and responsibilities as any other citizen, but that another country also recognizes you as a citizen of that nation. The U.S. State Department does not track the number of people who hold U.S. and other citizenships. As this State Department Web site points out, while the United States does not prevent dual citizenship, it does not encourage it either because of the potential for conflict in being subject to the laws of more than one nation. For dual citizens the country of residence is generally considered to have the greater claim on allegiance.

The most common routes to dual (or triple or more) citizenship are birth, marriage, or naturalization. For example, if you are born in the United States, you automatically become a citizen here. But if your parents are nationals--citizens--of Mexico, for example, you will also be a Mexican citizen. If your parents are each citizens of different countries, neither of which is the United States, and you are born here, you could have triple citizenship at birth, depending on the laws of your parents' countries. Conversely, if both your parents are Americans who are living abroad when you are born, you will again be considered an American citizen and possibly a citizen of the nation of birth, depending on what their rules are. The laws regarding dual citizenship by birth can get quite filigreed, depending on whether both parents are Americans, if they are married, and which parent is the foreign national.

Some nations confer citizenship if you marry a national of that country. For example, if an American marries a Greek, the American also gets a Greek citizenship. Marriage to an American by a foreign national does not convey citizenship here, just an expedited shot at it. People who become naturalized Americans--that is, they were born citizens of another country but through a legal process become Americans--do not have to give up citizenship of their previous country. In some cases they can't because some nations do not allow people to give up their citizenship, even if they become naturalized citizens of the United States. But the United States expects such naturalized citizens to have primary allegiance to the United States. Dual citizens can, if they want to acknowledge the duality, be issued passports for each country of which they are citizens. But someone with a dual U.S. and other citizenship who gets in trouble abroad, particularly in the country the person holds the additional citizenship in, may not be able to get the same assistance from the U.S. embassy there as an American who has no additional citizenship.

Another potential source of trouble for a dual citizen is getting one's American citizenship revoked. For example, serving as an officer in a foreign military, or having a high-ranking position in a foreign government has the potential to endanger U.S. citizenship. But the ruling principle is that by undertaking these actions one intends to give up American citizenship. It is also possible to voluntarily renounce U.S. citizenship, but simply wanting to stop being an American is not necessarily enough to make it happen. Ask Marc Rich, the fugitive financier who has multiple other citizenships but has not been able to get rid of his U.S one. To start the renunciation procedure, you have to be outside of the United States and swear your oath of renunciation to a U.S. consular officer. If the State Department in Washington grants the request, you are given a certificate of loss of nationality. That decision is irrevocable. That is, you can try to become a U.S. citizen again, but you have no special advantages toward that goal over other foreign nationals.

Explainer thanks Christopher Lamora of the State Department.

Yesterday's elevation of new cardinals by Pope John Paul II increases the number of men who will vote on his eventual successor. Since John Paul is 80 and ailing, can he resign and allow them to choose the next pope now?

Popes can retire--the official word is abdicate--but the last wholly voluntary abdication took place in 1294. That was by Celestine V, a hermit who hated being pope and resigned after less than four months in office. There have been a handful of other, more controversial abdications (Was the removal forced? Was the pope legitimate?), and the last one of these was in 1415.

Just because no pope has abdicated for hundreds of years doesn't mean that a resignation by John Paul isn't much discussed. One of the men he elevated to cardinal, Karl Lehmann of Germany, suggested in a radio interview that because of his health, John Paul might consider stepping down. But John Paul has given no indication that he wants to be around for the party to celebrate the selection of the 263rd pope. As for what happens if a pope becomes permanently incapacitated, there is currently no mechanism for removing him from office. After a pope does die and before a successor is chosen, a cardinal is designated to oversee the day-to-day administration of the Vatican, but he is not considered to have papal authority.

Explainer thanks Bruce Miller of the Catholic University of America and Dr. Lawrence Cunningham of the University of Notre Dame.

To clarify Pope John Paul II's position on stem-cell research, the Vatican quoted from his 1995 encyclical, Evangelium Vitae. What's an encyclical, and how does it differ from a papal bull?

The Catholic Church articulates and develops its teachings primarily through encyclicals. Traditionally, an encyclical is a letter from the pope to the church's bishops, but during the past 40 years the pope has also addressed them to the faithful and to "all people of good will." Pope John Paul II has issued 13 encyclicals, the latest being 1998's Fides Et Ratio ("Faith and Reason"). Notable encyclicals include Paul VI's 1968 Humanae Vitae ("On Human Life"), which affirmed the church's stance against contraception, and John Paul II's 1995 Evangelium Vitae ("The Gospel of Life"), which condemned the "culture of death" the pope saw manifested in abortion, euthanasia, and capital punishment. The first encyclical was circulated by Benedict XIV in 1740.

Prior to the 18th century, the church expressed its teachings through apostolic bulls, more legalistic and solemn documents than encyclicals. ("Bull" refers to the Latin bulla, or seal, which is affixed to the document.) The condemnation of Martin Luther, for example, came in a papal bull. Today, the Vatican issues bulls mostly to confer the titles of bishops and cardinals or to proclaim the canonization of a saint.

Encyclicals are authoritative, not to be criticized or rejected lightly by members of the church, but they are not infallible. Only three doctrines developed in the past 200 years are considered infallible, and all were issued as bulls: the Immaculate Conception (that Mary was born without original sin), the Assumption (that Mary was taken up body and soul into heaven), and the definition of papal infallibility issued by the First Vatican Council.

Explainer thanks the Rev. John Langan, S.J., of Georgetown University and the Catholic Word Book.

Recent news reports out of Britain are giving credence to the theory that cellular phone use increases the risk of brain cancer. What are the facts?

Think of cellular phones as little radio stations, beaming voice and data to the telephone network via electromagnetic waves called radio frequency (RF) radiation. Cell phones emit RF radiation with a 800-900 MHz frequency, which is close to the 2,450 MHz frequency used by microwave ovens. The 1,000-watt power of the average microwave oven, however, is significantly greater than a cell phone's 0.6-watt output. Exposure to high levels of RF--many times the amount emitted by cell phones--causes biological damage, but the effects of lower exposure levels are not well established. Since this radiation penetrates the human body, critics theorize that cellular phones could cause physical damage to cells--either through heating or another form of energy release.

Some scientists dispute this hypothesis, arguing that RF energy from cellular phones is significantly weaker than the energy occurring naturally in the body's cells, and would therefore be unable to physically alter them. They also contend that even after long exposure periods, the phones could only cause a fraction of a degree increase in cell temperature--well within the body's normal range. In the absence of another plausible mechanism by which RF radiation could cause damage, they say that cell phones should be presumed safe.

Most RF exposure studies are inconclusive. They either fail to find effects, or have produced statistically insignificant findings. Selecting subjects for ongoing cellular phone studies is a challenge, since the highly exposed population remains relatively small, and many forms of cancer may take years to develop. But one recent British study found that RF may cause brain cells to react as if they were being heated (though no temperature increase was observed), which investigators hypothesized may damage cell function over long periods of time. Another found that cellular phone use was associated with an increased frequency of a certain type of brain tumor (although the overall risk of cancer was not found to increase). Most scientists call for further research and testing. Some cellular phone users are reducing possible risk by using earpiece and microphone headsets that plug into the telephone and make it possible to talk without the phone being held to the head.

Regulatory agencies like the Food and Drug Administration and Federal Communications Commission hedge on the issue, neither guaranteeing cellular phones' safety nor recommending that users stop using them. And the greatest danger posed by cellular phones yet discovered is an increased likelihood of car accidents involving inattentive users.

On Sept. 23, the $123 million Mars Climate Orbiter was lost when it veered off course and burned up in the Martian atmosphere. Last week, NASA revealed the cause: One part of the orbiter's navigation system was speaking in English units and another in metric. Why hasn't the U.S. adopted the metric system?

The metric system originated in France in the late 17th century to combat rampant commercial fraud by farmers and shopkeepers who used the varied systems of weights and measures to their advantage. Scientists were also demanding a standardized system to facilitate international cooperation on research. While old systems seemed arbitrary, the new standardized system had an apparent basis in nature: The meter was defined as 1/10,000,000 of the distance between the equator and either pole (it has since been redefined in terms of the speed of light). It was also easier to remember than other systems because it was based on the decimal system.

France officially adopted the metric system in the early 1800s, and the rest of the continent quickly followed in hopes that a standardized measurement system would spur international trade. Over the next hundred years, the metric system spread globally. The British Commonwealth resisted abandoning their traditional measures, but in the early 1970s--under the slogan "Metric: 10 times better"--they, too, metricated. (Some road signs and body weights, however, remain "customary.") Today, the U.S. is one of only three countries--along with Myanmar and Liberia--where the metric system is not commonly used.

Officially, at least, the U.S. has gone metric. The yard, the pound, and the gallon--prototypes of which were once held in London--are now officially defined by reference to metric units. In 1975, the federal government adopted metric as the nation's "preferred measurement system" and established the United States Metric Board to manage the transition. The changeover was ineffective, however, and by the early 1980s, the only tangible progress was that liquor and wine had to be labeled in liters. Metrication was revived in 1988, when Congress required that all government agencies be metric by 1992 to the extent "feasible." Today, agencies with large international or scientific operations--like the Department of Defense and NASA--are almost fully converted; others--like the Department of Education--have done little, citing the rights of states to decide such matters. America's private sector is similarly mixed: Large corporations with overseas exports are at least partly converted, but most small businesses still use the English system.

American metric advocates encountered stiff opposition in the '70s and '80s. Labor unions worried that workers would be unable to learn a new system. Businesses protested that redesigning machines and products to metric standards would be costly. States objected to the expense of replacing road signs and revising laws. And average citizens argued that change was unnecessary and said the metric system--with its multiples of 10, instead of the more intuitive halves and quarters of English measures--was not compatible with human experience. In contrast, there was no natural constituency for the pro-metric cause.

But similar obstacles were encountered--and overcome--in other countries. So, some metric advocates attribute America's non-conversion to national character. American individualism, they say, makes us more resistant to government-mandated change than other cultures. For example, Mother Jones reported that the National Cowboy Hall of Fame sued to block metrication, claiming "the West was won by the inch, foot, yard, and mile." Metric supporters also see xenophobia in Americans' distaste for a foreign system of measurement. In the 1970s, some opponents suggested that metric road signs would facilitate a Russian invasion.

Others ascribe American inaction to logistical obstacles. It is a classic instance of path dependency: Once a course is chosen, it is difficult to induce people to switch. And until the 1990s, the U.S. had little incentive to do so, since the economy was sufficiently dominant in its trade relationships to enforce English units on its partners. (This may soon change, as the European Union plans to ban products labeled in English units at the end of the year.) Also, unlike other nations, the United States' metrication legislation has been entirely voluntary, so few organizations have transitioned. The Department of Commerce's Metric Program--which took up the cause when the Metric Board was abolished in 1982--now focuses on outreach to the business community, instead of legislation. The year's marquee event, "Metric Week," begins this Sunday--the 10th day of the 10th month.

In the new Fox television series Dark Angel, America in 2019 is in a decade-long collapse because terrorists exploded a nuclear weapon high in our atmosphere, unleashing an electromagnetic pulse (EMP) that annihilated our communications systems. Could such an explosion destroy modern life?

The disruptive abilities of an EMP were unintentionally demonstrated in 1962 when the United States conducted a high-altitude nuclear weapons test in the South Pacific. About 1,000 miles away, in Hawaii, radio transmissions were interrupted, telephones didn't work, and streetlights went out. With the end of the Cold War, concern about a direct nuclear attack has faded, making way for worry about more esoteric threats like EMP. The House Armed Services Committee is sufficiently alarmed by the prospect of an EMP attack that they just ordered creation of a commission to investigate the United States' vulnerability.

To produce an EMP, a nuclear device must be detonated in the upper atmosphere (about 30 to 300 miles up). The gamma rays that are produced interact with molecules found lower in the atmosphere, causing a cascade of reactions that result in an extraordinarily intense, microsecond burst of energy delivered to earth. When this pulse hits any device with electrical wiring--from broadcast systems to power grids to your car's ignition--the energy can be conducted through it, either temporarily or permanently disabling it. For a nuclear event, an EMP is people-friendly. Humans aren't directly injured by the blast because it's so distant and because there is no radioactive fallout.

To defend against EMP, the military "hardens" or insulates its weapons, surveillance, and communications systems primarily by shielding their electrical innards in relatively inexpensive metal casings. But the big question would be the effect on civilian systems. Power grids, for example, are supposed to be able to compensate if one or several points fail. And financial institutions have duplicate information-storing systems. But no one, except perhaps James Cameron, creator of Dark Angel and the Terminator, knows how bad it could get. But if he's right, one thing's certain: In a post-EMP world, there will be no hit television series.

Explainer thanks John Pike and Steven Aftergood of the Federation of American Scientists, retired Rear Adm. Eugene Carroll of the Center for Defense Information, Andrew Drozd of Andro Consulting Services, and Slate reader Alan Allport for posing the question.

An American doctor was evacuated last week from an Antarctic research station after treating herself for breast cancer for five months. Who lives in Antarctica? What sort of research is done there? And who is in charge?

At 5.5 million square miles, Antarctica is the fifth largest continent (Australia and Europe are smaller), but its forbidding climate has kept the population from exceeding 4,000. With a mean annual temperature of 70 degrees below zero Fahrenheit and a surface that is 98 percent covered in ice, Antarctica has no indigenous inhabitants and very few native plants and animals. Fossil discoveries suggest that it was part of Gondwanaland, the single temperate continent, 200 million years ago.

Antarctica was unknown to humans until American sealer John Davis made landfall in 1821. For the next 100 years, a dozen countries shared the continent. Some--like Norway and Sweden--were interested in whaling and fur sealing. Others--like Britain and the U.S.--were primarily concerned with exploration and scientific research. First to reach the South Pole was Norway's Roald Amundsen in 1911. The continent was mapped in the late 1920s, setting off an international land rush.

In 1959, 12 nations including the U.S. and the Soviet Union signed the Antarctic Treaty. It guarantees cooperation and free movement among scientific operations, prohibits military activities, and suspends indefinitely all territorial claims. Under the treaty, Antarctica is governed through consultative meetings of the nations--now numbering 27--that maintain extensive Antarctic facilities. Most meetings focus on environmental protections: In 1991, the group banned oil and mineral exploration for the next 50 years. They have also restricted fishing and banned sealing altogether. American laws apply to U.S. nationals in Antarctica, except when they are in foreign-operated research stations.

Since adoption of the treaty, Antarctica has been inhabited exclusively by scientific researchers and support staff. Antarctica is uniquely suited for many types of research, including astronomy, atmospheric science, meteorology, oceanography, and geophysics. There are 80 research stations scattered across Antarctica, only 40 of which are active in the winter. McMurdo station, run by the U.S., is the largest, with 80 buildings and 1,000 summer residents. The settlements are isolated during the eight winter months, March through October, when brutal weather makes air travel all but impossible. As a result, few researchers stay in Antarctica for more than one or two years at a time.