Stem cells are like master cells that can produce any kind of tissue in the body.

"Our long-term goal is to create embryonic stem cells from a patient's tissues, correct the genetic defects, and get the repaired cells back into the patients," said George Daley, who will lead one research project at Boston Children's Hospital.

In the meantime, Daley said his team plans to use embryonic stem cells to increase the chances of a successful transfer while answering basic questions about stem cell biology.

Some people object to cloning human embryos on ethical grounds.

The project has been carefully reviewed and the team will follow strict guidelines, Harvard Provost Stephen Hyman told reporters Tuesday.

The project will cost millions, paid for exclusively by private donors, Daley said.

Earlier this year, a scandal erupted among stem cell researchers. Investigators concluded a South Korean scientist who claimed to create 11 lines of embryonic stem cells matched to human patients had faked the results.

Independent scientists will be able to verify the Harvard findings, Daley said.

The lab will use donor eggs and embryos left over from in-vitro fertilization (IVF) treatment.

Bovens estimates that if the rhythm method is 90 per cent effective, and if conceptions outside the fertile period are about twice as likely to fail as to survive, then "millions of rhythm method cycles per year globally depend for their success on massive embryonic death".

If he's right,couples using the rhythm method for religious reasons may want to think again. "Even a policy of practising condom usage and having an abortion in case of failure would cause less embryonic deaths than the rhythm method," Bovens writes (Journal of Medical Ethics, vol 32, p 355).

Roger Gosden at the Center for Reproductive Medicine and Infertility in New York says the suggestion is reasonable.

"It's quite plausible that more abnormal embryos are conceived at the limits of sperm and especially egg viability," he says, "and that these are more frequent in women practising rhythm contraception than those having unprotected intercourse at random stages of the menstrual cycle."

From issue 2554 of New Scientist magazine, 03 June 2006, page 19

The Gulfport-Biloxi region, which lost 41,000 people from before Katrina to January, was the second among metropolitan areas for population loss, the figures show.

Census officials warned that some of the figures are subject to larger than normal margins of error and, moreover, that the figures are already at least five months old.

David Bowman, a researcher for the Louisiana Recovery Authority, estimated that the population of New Orleans has grown from 156,000 in January to 192,000 in May. About 450,000 people lived there before Katrina.

The sad discovery was not unique. Since 1993, when the Clinton administration began a crackdown on border crossings in San Diego and El Paso, more than 3,500 people have died trying to cross into the United States through desert. And, as officials work to put more patrols and fencing along the U.S.-Mexico border, immigrant advocates fear there will be more deaths among the tens of thousands who attempt the trip.

Most of the deaths so far - 959 since Oct. 1, 2001, according to local government statistics and the Mexican government - have been in Arizona, where the landscape comprises mountains, ranches, Indian reservations, military proving grounds and endless miles of cactus-filled desert. The boy, who was found on May 16 and whose name could not be ascertained from U.S. or Mexican officials, was one of the latest additions to the list.

Border Patrol statistics show that while the death toll mounts annually, the number of those apprehended while crossing the border has not changed significantly since 1993. But because federal agencies have tightened the border in urban areas, smugglers who move the men, women and children seeking to enter the United States illegally have funneled them onto increasingly perilous trails where temperatures are high, water is scarce and danger is abundant.

"All the evidence is that increased enforcement on the border has achieved no benefit at all except in additional employment of Border Patrol agents," said John Fife, a Tucson pastor and founder of No More Deaths, a coalition of charities devoted to stopping deaths during desert border crossings. "What has changed is the devastating elements of this policy. You have a number of deaths that surpasses the number of American deaths in Iraq. And yet still we are determined to persist and redouble our efforts."

The other view is that a tipping point could be reached if the flow of agents and materiel to the border continues to increase. Since 1993, the Border Patrol has tripled in size and President Bush has pledged to add 6,000 more agents. He also has ordered the National Guard, which began deploying to the border Monday, to help build new fencing and other protections. "America has the best technology in the world, and we will ensure that the Border Patrol has the technology they need to do their job and secure our border," Bush said May 15 in a nationally televised speech.

Even as the president was speaking, McClafferty was searching the Arizona desert.

A Toxic Mix

The 3-year-old's mother's name was Edith Rodreguez. She and her son crossed into the United States from Sasabe, Mexico, on May 11, said a spokesman for the Mexican consulate in Tucson. A native of the Mexican state of Veracruz, a major source for illegal immigration, the 25-year-old woman was traveling in a group of eight to 10 people, herded north by a smuggler, called a coyote.

To keep the group moving fast, the coyote handed out a Mexican over-the-counter drug called Sedalmerk, consulate spokesman Alejandro Ramos Cardoso said after Mexican officials interviewed Rodreguez. Sedalmerk is a combination of caffeine, Tylenol and the herbal supplement ephedra - an amphetamine precursor that is banned in the United States.

Sedalmerk may be safe to use as a pick-me-up in a normal environment but it is a toxic mix when combined with a trek through the desert because it accelerates dehydration, McClafferty said. Two days into the journey, the boy's energy was flagging and he was dehydrated. On May 13, Ramos Cardoso said, the coyote and the rest of the crossers abandoned Rodreguez and her son, leaving them to walk in the desert by themselves.

Rodreguez began carrying the child, moving north through a sliver of earth hemmed in by two mountain ranges on land belonging to the Tohono O'odham Indian reservation. Sometime that day, the boy lost consciousness, Ramos Cardoso said. But Rodreguez kept on walking, clutching him.

A Search for a Child

In early January, the Border Patrol began concentrating on Arizona's Altar Valley, which had become a virtual highway into the United States for thousands of illegal immigrants and is dotted with natural water holes and water stations serviced by American charities. The renewed enforcement there resulted in traffic being diverted to the Tohono O'odham land that has less water.

Some religious and charitable groups have placed water barrels in the desert and handed out maps in Mexico showing their locations, drawing the ire of those who seek tougher enforcement along the border. One of the groups, Humane Borders, received permission to keep water barrels on land belonging to the Bureau of Land Management, the Interior Department, the city of Tucson and Pima County. But the Tohono O'odham tribe has declined to give its permission.

It was on that land that Rodreguez found herself walking with her son. She carried him for more than a day, Ramos Cardoso said, before placing him under the paloverde tree and going to look for help.

Like many who cross the border illegally, Rodreguez had been in the United States before. She worked menial jobs in Kentucky, where she met a man who apparently was married. The two had a relationship and Rodreguez got pregnant, Ramos Cardoso said. She decided to have the baby in Veracruz so her mother could help her. Returning to Mexico to have a baby was an unusual decision - many Mexican women make the reverse trip, traveling to the United States to have their babies so their children will be U.S. citizens.

Earlier this year, Rodreguez decided to return to the United States to show the boy to his father, Ramos Cardoso said. She traveled to Sasabe, joined the coyote's group and walked across the border.

After placing her son under the tree, Rodreguez chanced upon Highway 86, which runs through the heart of Tohono O'odham. There, on the afternoon of May 15, Border Patrol agents picked her up.

Ramos Cardoso said she told the agents immediately that she had left her son in the desert, but Gustavo Soto, a Border Patrol spokesman, said they learned of a missing boy four hours later after she was sent to a processing center in the border town of Nogales before she was returned to Mexico.

McClafferty received word about the missing boy that night. He is a member of BorStar, the Border Patrol's elite search and rescue unit, established in 1998 to help save illegal immigrants lost in the desert. When McClafferty went searching for the boy, it was unclear whether he was alive. He said he was told that the mother was so distraught that Border Patrol agents understood only that her son was missing.

McClafferty and three other agents began bushwhacking through the desert scrub, looking for footprints, where Rodreguez had been found. There were thousands, making it impossible to track the boy that way.

Back at Nogales, Border Patrol agents photographed the bottom of Rodreguez's shoes and faxed the image to McClafferty. Just as the sun was setting, he found matches in the dust. For the next seven hours he and the other agents tracked them by flashlight.

"We figured she was in bad shape," McClafferty said. "She was walking around in circles. She went for help then went back to her son but couldn't find him."

In the end, McClafferty smelled the boy's remains before he found them.

"She carried her kid in the desert for four or five hours and not one of them helped her," McClafferty said of the others who walked in with Rodreguez. "I've seen a lot in six years, but this kid thing was one of those that I just couldn't file away."

More Deaths Expected

After being expelled from the United States, Rodreguez was allowed back on May 18 on a short-term humanitarian visa to identify her son's body. An autopsy revealed that the probable cause of death was dehydration and exposure to the sun. The temperature had been above 100 degrees during their journey.

Eric Peters, deputy chief medical examiner for Pima County, placed the time of death between May 13 and May 14, meaning the boy had probably died in his mother's arms.

The last time a young child died on the border, according to Pima County records, was November, when a 1-year-old girl succumbed to pneumonia. Peters said authorities told him they had seen women with babies trudging through the reservation lands, and he and his colleagues are bracing for more child deaths this summer.

The Tohono O'odham police considered charging Rodreguez with child endangerment, but the Pima County attorney's office said it had no interest in prosecuting her. Rodreguez returned to Mexico on May 20 and her son's body followed two days later.

Ramos Cardoso said he tried to persuade Rodreguez to speak to the media because the consulate hoped her story would encourage others not to follow her.

"She had been through a lot of suffering," he said. "She told us she just wanted to go home."

Ian St James-Roberts of the University of London's Institute of Education and his colleagues recruited new parents from London and Copenhagen, Denmark. They also recruited a group of "proximal-care" parents from the UK, Denmark and the US, who planned to hold their infants for much of the time that they were awake and respond rapidly if they cried.

The parents were asked to keep a diary of their infants' crying and night waking as well as their own responses at 8-14 days, 5-6 weeks and 10-14 weeks of age. These were backed up by audio recordings, questionnaires on the babies' feeding and sleeping patterns, and home visits by the researchers.

At 10 days proximal-care parents held their babies for around 16 hours a day, and were more likely than other parents to sleep in the same bed as them at night. London parents held their babies for around 8 hours 30 minutes a day, and Copenhagen parents for just under 10 hours a day. The London parents also left their crying or fussing babies for much longer than both of the other groups.

The hands-off approach adopted by the London parents appeared to backfire: their children fussed and cried 50 per cent more than the other two groups at two and five weeks of age, and they were still crying more after 12 weeks.

The results also suggest there is little to gain from giving your baby a very high level of comfort and care. In general, Copenhagen babies cried as little as those given proximal care, and at 12 weeks they woke and cried slightly less often at night.

Comforting your baby on demand could minimise fussing and crying during the early weeks, concludes St James-Roberts, who presented his findings at a conference on infant sleeping and crying in Leicester, UK, last month. "But it makes no difference to the unsoothable bouts of crying that are the core of colic."

The results will be published in Pediatrics this week.

From issue 2554 of New Scientist magazine, 01 June 2006, page 17

Objects are visible simply because light scatters off their surfaces and into your eyes. So in theory, a cloaking device could work by steering light around an object so that you see only the light from behind it, and not the object itself. Now John Pendry, a theoretical physicist at Imperial College London, and his colleagues have worked out how this could be done with a spherical cloak that channels light around an object hidden at its centre (see Diagram).

The stuff that makes this plausible is a new generation of "metamaterials", which can be tailored to have exotic electrical and magnetic properties not found in nature. The metamaterials developed so far consist of complex arrays of metal washer-like shapes and wires. The metal shapes are smaller than the wavelength of light and so interact with it, explains Pendry. "On these scales, it is not the chemical properties of the metal that determine how it interacts with light, it's the metal's structure."

The new idea is to build a sphere of metamaterial whose components are arranged in such a way that they bend radiation around the central cavity before sending it on its way, like a ring road diverting traffic around a town.

Team member David Smith at Duke University in North Carolina has already created a metamaterial that bends microwaves, and is now putting the cloaking idea into practice to make a microwave invisibility shield. "The theory tells us the material properties we need at each point," says Smith. "The challenge is to match those theoretical requirements in the actual material, point-by-point." The team hopes to complete it within a year.

The principle is exactly the same for visible light, but you may have to wait a little while for your invisibility bubble: nobody has yet succeeded in making metamaterials that work at optical wavelengths. However, "many teams are already involved in shrinking metamaterials down to these scales," says Smith.

Another hurdle is that the materials can only steer light in a narrow band of wavelengths, which is fine for microwave radar, for example, but not the entire spectrum of visible light (Science, DOI: 10.1126/science.1125907).

From issue 2554 of New Scientist magazine, 03 June 2006, page 13

Bloomberg said New Yorkers may have to pick up the slack.

The Department of Homeland Security said one of the reasons it reduced the city's security funding is because of problems with New York's application. But local politicians argued that there is no excuse when it comes to protecting a high terror target.

"I think the Homeland Security application process should be designed and tailored to meet the needs and threats that exist in this country," said Congressman Vito Fossella.

Fossella called on the White House to intervene in the matter. Many New York lawmakers tried to reverse the department's decision.

Former Mayor Rudolph Giuliani said the cuts were based on "odd" and "incompetent" evaluations on what constitutes a monument. As a result, neither the Statue of Liberty, the Empire State Building nor the New York Stock Exchange are considered monuments by the agency.

Giuliani said he would join the fight to get the money reinstated.

New York Senator Charles Schumer accused Homeland Security Secretary Michael Chertoff of playing politics, and tried to introduce legislation to safeguard the city against future cuts by requiring federal funds be distributed based solely on the level of risk.

In his meeting with Chertoff on Monday, Bloomberg said he was disappointed with the 40-percent cut in federal funding. He also criticized the decision to categorize many cities as "high risk," spreading the money around thinly.