By using a laser beam to focus and push particles against a substrate, scientist Lars Helseth of Nanyang Technological University in Singapore has designed and built a unique type of colloidal printer. Taking advantage of the electrical and paramagnetic properties of tiny beads, Helseth's printer provides a new printing method that may have applications in printing chemical and biological patterns.
"To the best of my knowledge, this is the first printer based on the laser-pushing of colloids," Helseth told PhysOrg.com. "I got the idea after reading about some fascinating experiments done by Arthur Ashkin and coworkers in the 1970s and 1980s. He demonstrated how one can push colloids around using optical forces. I have recently been working a lot with methods for trapping colloidal particles using nanomagnets, and during the last year been able to combine optical and magnetic tweezers in order to probe small (femtonewton) forces in particle systems."
Science & Technology
The day after Valentine's Day, flower bouquets from sweethearts around the world begin to fade. A rose's vibrant red dulls to dried-out brown, and flowers begin to droop. Some say adding a citrus-flavored soda, such as 7-Up or Sprite, or an alcohol like vodka to the vase of water will lengthen the time these flowers remain beautiful.
According to floriculturists, they are right; if the mixture of soda and water is in the correct proportion, a bouquet will remain bright, because the combination provides the flowers with the water and food they need. "The 7-Up formula works really well," says Susan Han, a professor in the plant, soil and insect science department at the University of Massachusetts Amherst. Vodka also works as a flower preservative by interfering with the plant's ripening process but it is less practical to use.
According to floriculturists, they are right; if the mixture of soda and water is in the correct proportion, a bouquet will remain bright, because the combination provides the flowers with the water and food they need. "The 7-Up formula works really well," says Susan Han, a professor in the plant, soil and insect science department at the University of Massachusetts Amherst. Vodka also works as a flower preservative by interfering with the plant's ripening process but it is less practical to use.
A physicist in Australia has come up with an experiment that could potentially reveal a flaw in Newton's law of gravitation. If the flaw exists, it would be the first evidence in support of theories that explain the movement of galaxies without having to introduce "dark matter".
For the past 70 years or so, physicists have been bothered by a nagging question: why do the centres of galaxies rotate too fast for the amount of mass we can see through telescopes? The most popular answer is that most of the mass is hidden in large bands of "dark matter", a substance that is invisible because it doesn't interact strongly with light. If it exists, dark matter could account for 95% of the mass in galaxies, and would explain many other aspects of the universe.
For the past 70 years or so, physicists have been bothered by a nagging question: why do the centres of galaxies rotate too fast for the amount of mass we can see through telescopes? The most popular answer is that most of the mass is hidden in large bands of "dark matter", a substance that is invisible because it doesn't interact strongly with light. If it exists, dark matter could account for 95% of the mass in galaxies, and would explain many other aspects of the universe.
Cockroaches are infamous for their tenacity, and are often cited as the most likely survivors of a nuclear war. Some even claim that they can live without their heads. It turns out that these armchair exterminators (and their professional brethren) are right. Headless roaches are capable of living for weeks.
To understand why cockroaches - and many other insects - can survive decapitation, it helps to understand why humans cannot, explains physiologist and biochemist Joseph Kunkel at the University of Massachusetts Amherst, who studies cockroach development. First off, decapitation in humans results in blood loss and a drop in blood pressure hampering transport of oxygen and nutrition to vital tissues. "You'd bleed to death," Kunkel notes.
To understand why cockroaches - and many other insects - can survive decapitation, it helps to understand why humans cannot, explains physiologist and biochemist Joseph Kunkel at the University of Massachusetts Amherst, who studies cockroach development. First off, decapitation in humans results in blood loss and a drop in blood pressure hampering transport of oxygen and nutrition to vital tissues. "You'd bleed to death," Kunkel notes.
Mars's southern polar ice cap contains enough water to cover the entire planet approximately 36 feet (11 meters) deep if melted, according to a new radar study.
It's the most precise calculation yet for the thickness of the red planet's ice, according to the international team of researchers responsible for the discovery.
Using an ice-penetrating radar to map the south pole's underlying terrain, the scientists calculated that the ice is up to 2.2 miles (3,500 meters) thick in places, said the study's leader, Jeffrey Plaut of NASA's Jet Propulsion Laboratory in Pasadena, California.
It's the most precise calculation yet for the thickness of the red planet's ice, according to the international team of researchers responsible for the discovery.
Using an ice-penetrating radar to map the south pole's underlying terrain, the scientists calculated that the ice is up to 2.2 miles (3,500 meters) thick in places, said the study's leader, Jeffrey Plaut of NASA's Jet Propulsion Laboratory in Pasadena, California.
FOR a century, they have been on display in the Louvre museum in Paris, labelled as Canopic jars holding the embalmed innards of the great Egyptian pharaoh Rameses II. But the four pots, covered in hieroglyphs, are not what they seem.
The common view that nerves transmit impulses through electricity is wrong and they really transmit sound, according to a team of Danish scientists.
The Copenhagen University researchers argue that biology and medical textbooks that say nerves relay electrical impulses from the brain to the rest of the body are incorrect.
The Copenhagen University researchers argue that biology and medical textbooks that say nerves relay electrical impulses from the brain to the rest of the body are incorrect.
Before reading this column, please make a note of what its subject will be. If you answer correctly it will be of special interest to some people at Princeton University.
The subject is things we cannot explain, such as extrasensory perception (ESP) and paranormal events. Such matters have been studied at a Princeton laboratory since 1979, but the laboratory will close at the end of February.
Robert G. Jahn, 76, who founded Princeton Engineering Anomalies Research (PEAR), has his own explanation of why the laboratory is being closed:
"For 28 years we have done what we wanted to do," Jahn told the New York Times. "If people don't believe us after all the results we've produced, they never will."
The subject is things we cannot explain, such as extrasensory perception (ESP) and paranormal events. Such matters have been studied at a Princeton laboratory since 1979, but the laboratory will close at the end of February.
Robert G. Jahn, 76, who founded Princeton Engineering Anomalies Research (PEAR), has his own explanation of why the laboratory is being closed:
"For 28 years we have done what we wanted to do," Jahn told the New York Times. "If people don't believe us after all the results we've produced, they never will."
© REUTERS/ESA/Handout
This map shows the topography of the south polar region of Mars, including topography buried by thick deposits of icy material.
This map shows the topography of the south polar region of Mars, including topography buried by thick deposits of icy material.
The scientists used a joint NASA-Italian Space Agency radar instrument on the European Space Agency Mars Express spacecraft to gauge the thickness and volume of ice deposits at the Martian south pole covering an area larger than Texas.
The deposits, up to 2.3 miles thick, are under a polar cap of white frozen carbon dioxide and water, and appear to be composed of at least 90 percent frozen water, with dust mixed in, according to findings published in the journal Science.
In January, James Randi secured a mystery item in a specially designated locker in his Florida office, and challenged clairvoyants everywhere to use their remote viewing skills to divine its nature and claim a million dollar prize. The contents were "devined" by a pair of cryptographers.
Comment: From the actual paper:
"On the action potential as a propagating density pulse and the role of anesthetics"
Authors: Thomas Heimburg, Andrew D. Jackson
Subj-class: Biological Physics; Medical Physics
The Hodgkin-Huxley model of nerve pulse propagation relies on ion currents through specific resistors called ion channels. We discuss a number of classical thermodynamic findings on nerves that are not contained in this classical theory. Particularly striking is the finding of reversible heat changes, thickness and phase changes of the membrane during the action potential.
Data on various nerves rather suggest that a reversible density pulse accompanies the action potential of nerves.
Here, we attempted to explain these phenomena by propagating solitons that depend on the presence of cooperative phase transitions in the nerve membrane. These transitions are, however, strongly influenced by the presence of anesthetics. Therefore, the thermodynamic theory of nerve pulses suggests a explanation for the famous Meyer-Overton rule that states that the critical anesthetic dose is linearly related to the solubility of the drug in the membranes. "
That is "density pulse", which for the public has been translated as "sound", "accompanies the action potential" rather than replaces it.
A density pulse is the movement of a fluid.