The mystery of the glowing bubbles
In the 1930s, scientists discovered an intriguing phenomenon: When the bubbles in boiling water are bombarded by ultrasound, they emit brief bursts of both visible and ultraviolet light; in fact, the photons of light created are trillions of times more energetic than the sound waves that created them.
Over the decades, scientists have offered several theories to explain this phenomenon, called sonoluminescence. Some think the glowing bubbles are caused by imploding shock waves that produce miniature sonic booms; others suggest that they may be caused by the same processes that generate static electricity in thunderclouds or to some poorly understood quantum effect. Still others liken the glow to the sparks created by biting down on a mint Lifesaver candy in the dark.
"There are just about as many theories for sonoluminescence as there are theorists, but far too few experiments," says Robert E. Apfel, the Robert Higgin Professor of Mechanical Engineering and a specialist in physical acoustics. In an article in the Nov. 1 issue of the journal Science, Professor Apfel challenged colleagues around the world to come up with new experiments to test the growing list of theories and to bring their ideas to a joint meeting of the Acoustical Societies of America and Japan held Dec. 2-6 in Honolulu.
The first photographs of the light-emitting bubbles created by sonoluminesence were recently captured by Professor Apfel and a research team that included Yale graduate students Joseph Jankovsky and Jeffrey Ketterling and former postdoctoral fellow Yuren Tian. These images appeared in both the Nov. 1 Science journal and the December issue of the Journal of the Acoustical Society of America. The professor's research was partially funded by a grant from NASA's Jet Propulsion Laboratory.
Based on these photographs, the sonoluminescence theory that Professor Apfel favors suggests that the walls of the bubbles rebound at supersonic speeds when bombarded by ultrasound. The imploding shock waves generate temperatures as high as 100,000 degrees Celsius, causing the gas to become a hot, glowing plasma that emits pulses of light with clocklike regularity. Each pulse lasts only trillionths of a second. This theory is supported by recent reports of a popping sound, or a mini-sonic boom. In fact, one team of scientists presented computer simulations of these imploding sonic booms at the Honolulu meeting.
Today, researchers are trying to harness the process of sonoluminescence for possible commercial applications ranging from broad-band underwater sonar to pollution-free energy.
Relief for parents of tongue-tied toddlers
Parents, don't despair if your toddler is less talkative than his or her playmates. A recent study by Yale psychologist J. Steven Reznick suggests that, in terms of toddlers' general intelligence, the number of words the youngsters understand is far more important than the number they speak during the second year of life.
Professor Reznick and his colleagues at the Institute for Behavioral Genetics of the University of Colorado at Boulder reached this conclusion after studying 408 pairs of same-sex twins -- half identical and half fraternal. The study was designed to show how a child's genetic makeup and environment influence the development of language and other cognitive skills.
The researchers found that language comprehension, rather than spoken language, at ages 14 and 20 months was a better predictor of how well the twins would do on intelligence tests at 24 months. The study also showed that environment had a greater impact on how many words a child understood, while genetic and environmental factors each played a role in how much a child talked.
The twin toddlers in the study were given a number of verbal and non-verbal tasks to perform as part of a series of tests called the Bayley Scale of Mental Development. To assess their language comprehension, toddlers were shown slides of two different objects -- a cat and a shoe, for instance -- and then asked to find one of those articles. Researchers then tracked eye motion to determine which slide the child looked toward. By comparing the performance of identical twins, who share the same genes, with that of fraternal twins, who on average share about half their genes, researchers were able to determine which skills were linked primarily to genetics and which could be attributed primarily to environment.
The study, in press in "Monographs of the Society for Research in Child Development," underscored the importance of reading to and talking with infants and toddlers. "A child's environment influences word comprehension, but there is no evidence that talking more than normal will increase word comprehension," Professor Reznick cautions. "A constant barrage of words would likely only confuse a toddler."
A child who cannot respond to simple commands or recognize words for some familiar objects -- like eyes, ears and nose -- by about 14 months of age should be checked by a pediatrician for a possible hearing impairment, says Professor Reznick. On average, children that age can say about 10 words but understand about 100 words. Most children start comprehending words between the ages of 8 and 10 months.
Illuminating the nature of dark matter
Yale has entered into an innovative collaboration in order to compete in the international race to find dark matter, the 90 percent or more of the universe's mass that is unseen and unknown but that exerts a profound influence on the distribution and shape of visible galaxies. Theories about the composition of this missing matter range from exotic new kinds of subatomic particles to black holes, burned out stars or intergalactic dust and gas.
Astronomers and physicists at Yale have pooled their resources with colleagues at Indiana University, the University of the Andes and the CIDA Observatory in Venezuela to equip a powerful telescope located high in the Andes Mountains with a state-of-the- art detector system similar to that used in particle physics. Working on a limited budget, the Quest Project -- an acronym for the Quasar Equatorial Survey Team -- will compete with a number of multi- million-dollar dark matter projects now under construction.
"I find it extremely satisfying that the same kind of detectors designed to explore extremely small subatomic particles will be used to survey vast stretches of the universe -- a difference in size of approximately 40 orders of magnitude," says Charles Baltay, the Higgins Professor and chair of physics. "It is impossible to go from anything smaller to anything bigger." The telescope will systematically survey most of the sky visible from the equator -- a process that could take as few as 100 nights of clear observing, according to Sabatino Sofia, chair of Yale's astronomy department.
The scientists will probe the universe for missing matter using the light from quasars, the oldest and brightest objects in the universe. According to Einstein's General Theory of Relativity, the fabric of spacetime is warped in the vicinity of massive objects like black holes, causing light passing nearby to bend, a phenomenon called "gravitational lensing."
"When gravitational lensing occurs, light from a single source, such as a quasar, appears as two or more images widely separated from each other," explains Professor Baltay. "These distinctive patterns of multiple images from a single light source, called macrolensing, could tell us indirectly about the presence of black holes or other invisible structures scattered throughout the universe." Gravitational lensing also can cause an increase in the brightness of light as it passes near a massive object, a phenomenon called microlensing. The Yale project is expected to be unique in its ability to detect both micro- and macro-lensing with its highly sensitive detectors.
When the survey is completed, Quest astronomers will analyze the masses of data to learn whether missing matter is distributed relatively evenly throughout the universe or whether it is clumped together, which could tell them whether the missing mass is primarily in the form of subatomic particles or large objects such as black holes or dark galaxies.
The researchers will also use the information from the study of quasars to estimate the rate at which the universe is expanding and, thus, calculate its age.
Beyond the IQ test
The old adage "It's not what you've got, but how you use it" is especially applicable in the matter of IQ, says Robert Sternberg, the IBM Professor of Psychology and Education Psychology.
Professor Sternberg, a long-time critic of standardized tests measuring intelligence, notes that there is little difference in the IQs of people who are more successful by society's standards and those who are less successful. In his book "Successful Intelligence: How Practical and Creative Intelligence Determine Success in Life," the psychologist writes: "Successful individuals may or may not succeed on conventional tests, but they have something in common that is much more important than high test scores -- they capitalize on their strengths and compensate for or correct their weaknesses."
As proof of the inadequacy of standardized tests in predicting success, Professor Sternberg points to a study of 166 first- and second-year graduate students in Yale's psychology department that he and former graduate student Wendy Williams conducted over the course of 12 years. They found that students' success in the program after the first year was not predicted by their scores on the Graduate Record Exam -- GRE -- a test required for admission to graduate school.
"Today's over-emphasis on university admission tests -- SATs, GREs, LSATs, GMATs and LCATs -- can cause us to confuse scores with the value of the person," says Professor Sternberg. "We need to view intellectual ability as dynamic and flexible rather than static and fixed -- something that standardized tests often prevent us from doing."
In fact, Professor Sternberg has devised his own intelligence test -- the Sternberg Triarchic Abilities Test or STAT, which measures a broad range of skills, including a person's analytical, practical and creative abilities. The psychologist and his colleagues used the STAT test in a study of 199 high school students, who were enrolled in a college-level introductory psychology course at Yale. All the students heard the same lecture in the morning and were divided into five groups for afternoon sessions taught by specially trained teachers using either an analytical, practical or creative approach. The researchers found that students who were placed in afternoon sessions that matched their natural pattern of abilities made better grades than those who were mismatched.
"This study demonstrates that the triarchic test is good at pinpointing intellectual talents, and that it is possible to teach in ways that enhance learning in each of the three areas of successful intelligence," says Professor Sternberg.
"I am not suggesting that we abandon intelligence tests altogether," he cautions. "But we need to enhance these assessments by looking at a broader range of abilities."
Eeek! A 3-D mouse!
The challenge of developing better robots has sparked an exchange of ideas between researchers in robotic vision and the world of computer animation, according to Gregory D. Hager, associate professor in computer science.
At the Yale Center for Computational Vision and Control, scientists are working to develop software that can make it possible for robots to sense and respond to changes in the surrounding environment, or for humans to guide their movements more accurately. These range from a three-dimensional computer mouse that can control the motion of a robotic arm to visual tracking systems that can allow robots to navigate in an unfamiliar environment.
"The reason the field of robotics reached a plateau after a growth spurt in the early 1980s is because expectations were very high that researchers could develop a complex, generalized vision system applicable to a wide array of tasks, much like the human vision system," says Professor Hager. "That turned out to be a much harder nut to crack than anybody thought it would be."
Instead, Professor Hager is developing task-specific software solutions -- a paradigm shift made possible by the increasing speed of desktop computers. "I can create a demonstration software program in 45 minutes that solves a particular problem, such as inserting a disk in a disk drive, and then move on to a completely new software solution for the next problem," he says. "That may not be the way humans perform vision tasks, but it seems to be a practical strategy for computers and machines."
In 1993, with the help of a graduate student, Professor Hager developed a software program called XVision, which "is very much like computer animation," he explains. "Both represent complex objects in terms of a small set of simple components. In animation, the software program draws those components to create an image, while XVision analyzes the camera's image to detect and track underlying simple components. Both approaches rely on linking primitive commands together."
XVision forms the basis for all the tasks performed in the robotics laboratory that require visual tracking. One program, for example, can superimpose a clown face over a human face on a television monitor, latching onto and following the human's eye and mouth motions. This program could have applications in automated video surveillance, teleconferencing or computer animation.
Graduate student Kentaro Toyama has also developed a 3-D computer mouse that he calls a "Surfball." The device consists of a racquet ball that is suspended by elastic bands in a stationary frame; a color video camera tracks the movement of dots painted on the ball. By manipulating the Surfball, an operator can guide a robotic arm as it performs a precise 3-D task, such as inserting a disk into a computer drive. The promising invention, for which Yale and Mr. Toyama have filed a provisional patent application, could provide greater motion control than a joystick for playing 3-D video games, and may be used to control robots in outer space or in contaminated environments that are unsafe for humans.