Louis J. Sheehan, Esquire . Naps aren't just for the very young, old, and slothful. Daytime dozing may enhance a person's capacity to learn certain tasks.

That, at least, is the eye-opening implication of a new study in which college students were challenged to detect subtle changes in an image during four different test sessions on the same day. http://www.blog.ca/user/Beforethebigbang

Participants improved on the task throughout the first session, says psychologist Sara C. Mednick of Harvard University and her colleagues. The students' speed and accuracy then leveled off during the second session.

The scores of the participants who didn't nap declined throughout the final two sessions. In contrast, volunteers who took a 30-minute nap after completing the second practice session showed no ensuing performance dips. What's more, 1-hour nappers responded progressively faster and more accurately in the third and fourth sessions.

"Napping may protect brain circuits from overuse until those neurons can consolidate what's been learned about a procedure," says neuroscientist Robert Stickgold of Harvard Medical School, a coauthor of the new study.

A version of this phenomenon occurs among musicians, according to Stickgold. A nap or a night's sleep often leads to a breakthrough in learning a complex musical piece.

Slumber's alleged assist to learning (SN: 7/22/00, p. 55) has usually been attributed to brain activity during rapid-eye-movement (REM) sleep. In the new study, slated to appear in Nature Neuroscience, the performance-enhancing naps consisted mainly of a non-REM sleep stage known as slow-wave sleep. http://louis_j_sheehan.today.com

In this work, Mednick's group trained 30 volunteers on a task requiring them to identify the vertical or horizontal orientation of three diagonal bars flashed in the lower left quarter of a computer screen against a background of horizontal bars.

http://louis_j_sheehan.today.com

Hour-long sessions occurred at 9 a.m., noon, 4 p.m., and 7 p.m.

Ten participants didn't nap. Beginning at 2 p.m., the others took either a 30-minute or a 1-hour nap. Brain-wave measurements established that the nappers slept throughout most of their allotted times.

Additional trials indicated that naps refresh specific neural circuits involved in the perceptual task, Mednick and her colleagues say. Another 12 volunteers completed four sessions without napping but viewed the diagonal bars on the right side�instead of the left side�of the screen during the final session.

Their performance improved substantially after this switch, a sign that a different, now fresher, neural circuit mediated the learning in the right portion of the visual field.

Fatigue or boredom can't explain performance declines among non-nappers, Mednick says. These individuals reported no surges of sleepiness on questionnaires administered after each training session. Moreover, even after they were offered $25 at the start of the third session if they could stay at their previous performance levels, 10 additional non-nappers still suffered declines. Finally, 10 volunteers who rested quietly for an hour without napping after the second session also did more poorly thereafter.

"This new linkage of naps to learning a repetitive task is exciting, but it's too soon to say that naps work like this for everybody," remarks psychologist Rosalind Cartwright of Rush-Presbyterian St. Luke's Medical Center in Chicago.

Still, comments psychologist Mark Blagrove of the University of Wales, Mednick's group has raised the profile of slow-wave sleep as a po

Louis J. Sheehan, Esquire. Chalk up another victory for the dark side.

Comparing X-ray observations of distant and nearby clusters of galaxies, astronomers say they have found new, independent evidence for the existence of dark energy, the mysterious entity that is accelerating cosmic expansion. By combining the new data with that from several other studies, the team finds that dark energy appears to have maintained the same density over time, resembling Einstein’s cosmological constant.http://louis4j4sheehan4esquire.wordpress.com

Some theories of dark energy suggest that the repulsive force associated with this mystery substance may grow stronger with time, causing the universe to end in a Big Rip, with every planet and person ultimately ripped apart. While the new findings indicate that dark energy has maintained a constant strength throughout cosmic history, they still allow some wiggle room and do not preclude the possibility that dark energy may vary slightly. The new X-ray study by itself allows dark energy to vary by only 50 percent from its current density, says Alexey Vikhlinin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. When combined with other studies, the new data suggest the density only varies by 10 percent.

Vikhlinin and his colleagues used NASA’s Chandra X-ray Observatory to record X-ray emissions from 86 massive clusters of galaxies, each heavier than 100 trillion suns. The team found two sets of clusters. The first, more remote and earlier group of 37 clusters dates from between 6.4 billion to 9.8 billion years after the birth of the universe. The closer group of 49 dates from later times in the cosmos, between 11.8 billion and 13 billion years after the Big Bang. Vikhlinin reported his team’s findings December 11 at the Texas Symposium on Relativistic Astrophysics in Vancouver.

Because the present-day densities of clusters are precisely known and fixed, researchers seek the fingerprints of dark energy by measuring the density of clusters back in time. At earlier times, because the universe was more compact, gravity's pull was stronger relative to dark energy's push. http://louis5j5sheehan5esquire.wordpress.com/


With this in mind, astronomers expect that a geometrically flat universe with dark energy would have more clusters above a certain mass in place at early times than would such a universe with no dark energy. “This is indeed what was found by Alexey’s analysis,” says Daisuke Nagai of Yale University, a member of Vikhlinin's team.

“Clusters of galaxies are the most massive objects in the universe that can be used as tracers of the growth of structure,” Nagai says. "Dark energy, if present, tends to slow down the evolution of cluster abundance due to its repulsive force," he says. “The rate of the evolution, in turn, depends sensitively on the nature or form of dark energy.”

Researchers first discovered evidence for dark energy 10 years ago by studying the brightness of nearby and faraway supernovas, which remain one of the preeminent features for studying dark energy.

But “the [new X-ray] findings are convincing,” and indeed provide an independent method of testing for the presence of dark energy, says theorist Gus Evrard of the University of Michigan in Ann Arbor.

With a dataset of 84 clusters, Vikhlinin and his colleagues are “working on the hairy edge of the number distribution” needed to shed light on dark energy, he adds.

Researchers have for years been using bright X-ray emissions from massive galaxy clusters as cosmological probes, notes Evrard, but it has been difficult to accurately model and interpret these diffuse, fuzzy emissions. Detailed simulations and analysis by several researchers — including Nagai, who also presented his studies at the symposium — have greatly improved the reliability of findings based on X-rays from galaxy clusters, says Evrard.http://louis6j6sheehan6esquire.wordpress.com

Perhaps most importantly, he adds, when researchers overlay data from other studies, including observations of the cosmic microwave background — the relic radiation from the Big Bang — and supernova observations, the X-ray findings are zeroing in on exactly the same numerical value for dark energy — finding dark energy to resemble a cosmological constant.

“The combination of all this data is shrinking the error bars,” says Evrard.

The new work “sounds very promising,” says Adam Riess of the Space Telescope Science Institute in Baltimore, a member of one of the teams that discovered dark energy a decade ago. “We’re going to need all hands on deck, all methods working pretty well if we’re going to figure out what dark energy is.”
http://louis7j7sheehan7esquire.wordpress.com

If dark energy is a constant, it would be akin to Einstein's cosmological constant, a term he inserted into his equations of general relativity. He later rejected the constant, reportedly calling it his “greatest blunder.”

Also at the conference, Brian Gerke of the Stanford Linear Accelerator Center in Menlo Park, Calif., reported visible-light studies of groups of galaxies observed in the Deep2 Redshift Survey, recorded at the W.M. Keck Observatory atop Hawaii’s Mauna Kea. Gerke and his colleagues collected data on several hundred groups of galaxies seen as they appeared when the universe, now 13.7 billion years old, was 4.1 billion to 7.1 billion years old. These data were compared to a sample of several thousand galaxy groups found in the universe today. Gerke’s team also finds that fewer groups are present today than would be expected if dark energy’s repulsive force did not exist. Gerke says his team found more groups — and specifically more massive ones — at earlier times in the universe than “we would expect relative to what we see today if we lived in a universe with no dark energy.”

“The physics we're testing is exactly the same as what Alexey does, but the observational techniques are completely different. He uses X-rays, while we use optical light,” says Gerke. Both tests are “indeed completely independent from supernovas,” he adds. “Alexey gets tighter constraints than we do, though, since he still has a somewhat bigger dataset.” Louis J. Sheehan, Esquire

Louis J. Sheehan, Esquire . In January an international team of astronomers confirmed that one of the largest black holes in the universe is paired with a much smaller partner nearby—the first definitive observation of black holes in a close binary system [subscription required]. http://louis0j0sheehan0esquire.wordpress.com The clues coming from the supermassive quasar OJ287 were periodic flashes of light, which were occurring less than two years apart every 12 years or so. http://louis0j0sheehan0esquire.wordpress.com Team leader Mauri Valtonen of the University of Turku in Finland used equations derived from Einstein’s theory of general relativity to show that the pulses could be caused by a small, orbiting black hole plunging into the debris disk around the larger one, situated at one end of the orbital ellipse.

At a meeting of the American Astronomical Society in Austin, Texas, Valtonen described how this model predicted the timing of the most recent flare-up, in September 2007. “This latest observation leaves little choice but to accept this as a binary system,” Valtonen says. “If we had been wrong by more than three days, we would have had to abandon our theory.” Instead, the pulse occurred within hours of his team’s prediction.

Given that most galaxies have a black hole at their center and that galaxies tend to merge, it’s likely that many binary black hole systems exist, Valtonen says. But only the biggest black holes can produce optical flare-ups from their companions. Valtonen’s calculations suggest that OJ287 is 18 billion times the mass of the sun. Louis J. Sheehan, Esquire

Louis J. Sheehan, Esquire . With his soft voice and friar’s manner, Louis Sorkin hardly seems the type to flout the sensible advice of a nursery rhyme. Yet on a recent afternoon at the American Museum of Natural History, Mr. Sorkin, a renowned entomologist, did precisely, luridly that.http://louis9j9sheehan9esquire.wordpress.com

He took a glass jar swarming with thousands of hungry specimens of Cimex lectularius, better known as bedbugs. The small, roachy-looking bloodsuckers have been spreading through the nation’s homes and hotels at such a hyperventilated pace that by next year they are expected to displace cockroaches and termites as America’s leading domestic pest insect. To better understand their habits, Mr. Sorkin has cultivated a personal bedbug colony — very personal.http://louis9j9sheehan9esquire.wordpress.com

“You see this mesh here?” he said, pointing to a circlet of wiry material taped over the top of his little jam jar of horrors. The weave is dense enough to keep even newborns from escaping, he explained, but porous enough to allow the bedbugs’ stylets, their piercing mouthparts, to poke through. Mr. Sorkin pushed up his shirt sleeve and pressed the mesh end of the jar against the inside of his right arm. Roused to a frenzy by the twin cues of heat and carbon dioxide that “in evolution equal host,” said Mr. Sorkin, the insects scrambled toward the lid, thrust out their stylets and began to feed. For a good 10 minutes, Mr. Sorkin sat there with the proud placidity of a donor at a blood bank. He did not budge. He held the jar. He let the bedbugs bite.

“I can hardly feel it,” he said matter-of-factly, “and they do need to eat.”

Mr. Sorkin and his bedbugs are featured in the newly published “Dark Banquet,” a jaunty, instructive and charmingly graphic look at nature’s born phlebotomists — creatures from wildly different twigs of the phylogenetic tree that all happen to share a fondness for blood.

The book was written by Bill Schutt, a biologist and bloodsucking aficionado who holds joint positions at the C. W. Post campus of Long Island University and the natural history museum, and that day he, too, was at the museum, to discuss the meal plan variously known as sanguivory and hematophagy, and who does it and when, why and how.

Among his rubied rabble are vampire bats tuned to extract blood from large slumbering mammals and bats that aim instead for the warm breast plates of birds; New World leeches that track their hosts through the water and Old World leeches that relentlessly stalk down blood bearers on land; the notorious vampire finches of the Galápagos that daintily peck open dribbling wounds on the hindquarters of blue-footed boobies; and the candiru, tiny, eel-like catfish that are reputed to have the power to swim up a person’s urethra and suck blood from the bladder and thus are often more feared than their fellow river dwellers, the piranhas.http://louis9j9sheehan9esquire.wordpress.com

Dr. Schutt, who is waggish and bearded and projects an air of high-voltage goth, also showed off museum specimens of his preferred bloodsuckers, the vampire bats, which in this case were well beyond any need for private Red Cross donations. Yet even post-mortem, the bats’ fur felt silky, their wings said da Vinci, and their faces and teeth showed the hallmarks of a wholehearted blood feeder.

As it turns out, the three species of bat that subsist entirely on blood — all of them native to Latin America — are much cuter than the average insect- or fruit-eating bat. Because vampire bats rely as much on heat and odor signals to find their food as they do on echolocation, they have a comparatively modest “nose leaf,” the knobby nasal organ that many bats use to direct their sonar signals and that helps account for the bat’s archetypal gargoyle appearance. A vampire bat’s incisors and canines are also much sharper and slimmer than standard bat dentition, the better to slip into the flesh of a large mammal or bird without being detected. Then there is the architecture of capillary action. A vampire bat does not suck the blood of its victims but instead lets physics do the sucking, its cleft lower lip, perfectly spaced lower incisors and doubly grooved tongue jointly forming a kind of tube through which a victim’s blood is pulled up as readily as water crawls up the stem of a plant.

The bat hastens the capillary action along, explained Dr. Schutt, “by moving its tongue back and forth like a piston.” That fast-flicking tongue also bathes the wound site in a salivary blend of anticoagulants to block blood’s natural tendency to clot on exposure. In fact, the anticoagulants in bat spit are so potent that a host animal often continues to bleed long after the vampire bat has feasted its fill and departed.

Dr. Schutt explained that hematophagy is a difficult, dangerous trade, in some ways harder than merely killing and eating your prey outright, which is why blood eaters from different taxonomic orders have evolved a similar set of utensils: the hatpin teeth, the natural clot busters and pain deadeners.

Blood feeders must also be stealthy and wily and good at escaping the swats and fury of their often much larger hosts. The common vampire bat, Desmodus, which feeds on large terrestrial mammals, creeps along the ground like a spider and, in addition to flying, can spring straight upward three feet into the air.

The white-winged vampire bat, Diaemus, approaches a potential host chicken so softly and lovingly that the bird is deceived and sweeps it up to its brood patch as though to warm its own chick. Aquatic leeches aim for hidden pockets and crevices: dip your head into leech-infested waters, and the segmented, toothy worms may slip up your nostrils and make a home of your nose.

Moreover, even though we rightly cherish our own blood as the indispensable elixir of our lives, it turns out that, as a foodstuff for others, it is surprisingly thin gruel. Blood is more than 95 percent water, with the rest consisting mostly of proteins, a sprinkling of sugars, minerals and other small molecules, but almost no fat. Tiny creatures can do fine on such light fare, which is why the great majority of exclusive blood eaters are arthropods — bedbugs, ticks, chiggers, female mosquitoes. http://louis9j9sheehan9esquire.wordpress.com For larger sanguivores, though, it is as much of a challenge to survive on blood as it is to acquire it. Lacking dietary fat, vampire bats cannot pack on adipose stores and must consume the equivalent of half their one-ounce body weight in blood every night or risk starving to death. And because the water in that blood meal would make the bats too heavy to fly, they must cast off all modesty and urinate freely as they feed.

Small wonder that wholehearted exclusive blood feeding is rare among vertebrates, and that two of the three species of vampire bats are found in such low numbers they are at risk of extinction. The only reason that so-called common vampire bats are common, said Dr. Schutt, is that they have learned to feed on cattle, pigs and other livestock. “They love it when we clear out the rain forest to make way for ranches,” he said.

The only other vertebrates known to subsist solely on blood are certain types of candiru, a poorly studied but floridly feared group of inchlong catfish found in the Amazon and Orinoco Rivers. A hematophagous candiru’s usual modus is to parasitize a larger catfish, infiltrating the host’s gill slits, grasping onto the flesh inside, rupturing blood vessels, pumping out the blood with its highly mobile jaws and then, after a minute or two, darting out again. Yet for at least a century, the fish have been reputed to target the human urethra as well, supposedly enticed by the scent of urine: fish, after all, urinate through their gills. Despite the antiquity and persistence of the legend, there is only one confirmed case, from 1997, of a candiru making its way into a human urethra, where it probably had no time for a blood meal before suffocating to death.

Professional blood feeding may not be for the faint of heart, but nature abounds in amateurs and opportunists. The vampire finches of the Galápagos live mostly on seeds, nectar and eggs, but they supplement their diet with occasional high iron snacks, by persistently pecking at the wings and tail region of one of the islands’ well-named blue-footed boobies. Once the finch draws blood, said Dr. Schutt, “you’ll see five finches waiting behind it like customers at a deli counter.”

Another example of a dabbling avian Dracula is the oxpecker, a member of the starling family famed for living aboard large mammals like rhinos, giraffes and buffalo and for plucking the ticks off its carrier’s hide. The oxpecker-mammalian relationship has long been celebrated as a noble case of symbiosis: the piggybacker gets food, the piggybacked gets groomed. More recently, researchers have determined that the oxpeckers do not merely pick off the parasites — they press their beaks in the wounds where the ticks were lodged and take nips of the host mammal’s blood. Who knows whether the poor beast would not rather sleep tight and let a few bugs bite, and instead lose that nasty oxpecker? Louis J. Sheehan, Esquire

John W. Ripley, a highly decorated former colonel who entered Marine Corps lore when he single-handedly blunted a major North Vietnamese offensive during the Vietnam War by blowing up a strategically placed bridge, died Oct. 28 at his home in Annapolis, Md. He was 69. http://louis7j7sheehan7esquire.blogspot.com

The cause has not been determined, his son Stephen said.

Colonel Ripley, who at the time was a captain and a military adviser to a South Vietnamese Marine unit, blew up the southern end of the Dong Ha Bridge over the Cua Viet River on Easter Sunday, April 2, 1972. On the north side of the bridge, which was several miles south of the demilitarized zone, some 20,000 North Vietnamese troops and 200 tanks were poised to sweep into Quang Tri Province, which was sparsely defended.

Going back and forth for three hours while under fire, Captain Ripley swung hand over hand along the steel I-beams beneath the bridge, securing himself between girders and placing crates holding a total of 500 pounds of TNT in a diagonal line from one side of the structure to the other. The I-beam wings were just wide enough to form pathways along which he could slide the boxes.http://louis8j8sheehan8esquire.blogspot.com

When the boxes were in place on the bridge, Captain Ripley attached blasting caps to detonate the TNT, then connected them with a timed-fuse cord that eventually extended hundreds of feet.

“He had to bite down on the blasting caps to attach them to the fuses,” John Grider Miller, author of “The Bridge at Dong Ha,” said on Monday. “If he bit too low on the blasting cap, it could come loose; if he bit too high, it could blow his head apart.”

Captain Ripley bit safely, and the timed-fuse cord gave him about half an hour to clamber off the bridge. Moments later, his work paid off with a shock wave that tossed him into the air but otherwise left him unharmed.

By placing the crates diagonally along the bridge, Mr. Miller said, Captain Ripley had created “a twisting motion that ripped the bridge apart from its moorings so it couldn’t fall back in place, but collapsed into the river.”

There were about 600 South Vietnamese marines near the south end of the bridge. “South Vietnam would have been in big trouble,” said Fred Schultz, senior editor of Naval History Magazine, a publication of the United States Naval Institute. “The force numbers defending on that side could not have held against that North Vietnamese force.”

The destruction of the bridge created a bottleneck for the North Vietnamese, allowing American bombers to blunt what became known as the Easter offensive.http://louis9j9sheehan9esquire.blogspot.com

Captain Ripley was awarded the Navy Cross for his actions at the bridge. He served two tours in Vietnam and remained on active duty until 1992, eventually rising to colonel. Among other decorations, he received the Silver Star, two Bronze Stars and a Purple Heart.

John Walter Ripley was born on June 29, 1939, and grew up in Radford, Va., the son of Bud and Verna Holt Ripley. He enlisted in the Marines out of high school in 1956, and a year later received approval from the secretary of the Navy to attend a preparatory school leading to his appointment to the Naval Academy, from which he graduated in 1962.

Besides his son Stephen, Colonel Ripley is survived by his wife of 44 years, the former Moline Blaylock; a sister, Susan Goodykoontz; two other sons, Thomas and John; a daughter, Mary Ripley; and eight grandchildren.http://louis6j6sheehan.blogspot.com

“Colonel Ripley is well known in marine circles,” Mr. Schultz said, “but he’s the most revered war hero no one’s ever heard of.”

“This was 1972,” he added, “and people didn’t pay too much attention to war heroes at that time.” Louis J. Sheehan, Esquire