Physics

Measuring soot formation in a diesel engine is far from easy because the turbulent environment in the combustion cylinder means no two combustion cycles are the same. Furthermore, the measurements are difficult to reproduce as the pressure at which fuel is injected into the cylinder causes an extra source of turbulence.

Bas Bougie, a doctoral candidate at Radboud University Nijmegen created a glass cylinder with an engine so he could investigate soot formation and find ways to optimize diesel performance using laser light.

Laser Induced Incandescence (LII) can be used to investigate optimal engine conditions that reduce soot emission from the engine. LII can be deployed in different types of engines and with different fuels.

It’s a rare case of all light and no heat: A new study reports that a laser can be used to switch a film of vanadium dioxide back and forth between reflective and transparent states without heating or cooling it.

It is one of the first cases that scientists have found where light can directly produce such a physical transition without changing the material’s temperature.

It is also among the most recent examples of “coherent control,” the use of coherent radiation like laser light to affect the behavior of atomic, molecular or electronic systems. The technique has been used to control photosynthesis and is being used in efforts to create quantum computers and other novel electronic and optical devices.

Faint, fleeting blue flashes of radiation emitted by particles that travel faster than the speed of light through the atmosphere may help scientists solve one of the oldest mysteries in astrophysics.

For nearly a century, scientists have wondered about the origin of cosmic rays — subatomic particles of matter that stream in from outer space. “Where exactly, we don’t know,” said Scott Wakely, Assistant Professor in Physics at the University of Chicago. “They’re raining down on the atmosphere of the Earth, tens of thousands of particles per second per square meter.”

Recent results from the Pierre Auger Cosmic Ray Observatory suggest that the highest-energy cosmic rays may come from the centers of active galaxies.

Researchers using supercomputer simulations have exposed a very violent and critical relationship between interstellar gas and dark matter when galaxies are born – one that has been largely ignored by the current model of how the universe evolved.

The van der Waals force, a weak attractive force, is solely responsible for binding certain organic molecules to metallic surfaces. In a model for organic devices, it is this force alone that binds an organic film to a metallic substrate. This data, recently published in Physical Review Letters, represents the latest findings from a National Research Network (NRN) supported by the Austrian Science Fund FWF. These findings mean that numerous calculation models for the physical interactions between thin films and their carrier materials will need to be revised.

Although they fulfil complex functions when used, for example, as computer chips, inorganic semiconductors have a simple construction that greatly limits their application.

University of Wisconsin-Madison researchers are taking a leadership role in the quest for one of Einstein’s greatest predictions – gravitational waves.

“Galileo was the first person to use the telescope to view the cosmos,” says Patrick Brady, a UWM professor of physics. “His observations with the new technology led to the discovery of moons orbiting Jupiter and lent support to the heliocentric model of the solar system.”

A new antenna made of plasma (a gas heated to the point that the electrons are ripped free of atoms and molecules) works just like conventional metal antennas, except that it vanishes when you turn it off.

That's important on the battlefield and in other applications where antennas need to be kept out of sight. In addition, unlike metal antennas, the electrical characteristics of a plasma antenna can be rapidly adjusted to counteract signal jamming attempts.

Plasma antennas behave much like solid metal antennas because electrons flow freely in the hot gas, just as they do in metal conductors. But plasmas only exist when the gasses they're made of are very hot.

The big world of classical physics mostly seems sensible: waves are waves and particles are particles, and the moon rises whether anyone watches or not. The tiny quantum world is different: particles are waves (and vice versa), and quantum systems remain in a state of multiple possibilities until they are measured -- which amounts to an intrusion by an observer from the big world -- and forced to choose: the exact position or momentum of an electron, say.

On what scale do the quantum world and the classical world begin to cross into each other? How big does an "observer" have to be? It's a long-argued question of fundamental scientific interest and practical importance as well, with significant implications for attempts to build solid-state quantum computers.

An Israeli-Jordanian-U.S. cooperative project aimed at measuring air quality in the area between the neighboring southern cities of Aqaba in Jordan and Eilat in Israel has been launched by scientists from the Hebrew University of Jerusalem together with scientists from the Aqaba Special Economic Zone Administration (ASEZA) and the Desert Research Institute of Reno, Nevada, in the US.

The one-month, intensive, transboundary regional air quality research study began earlier this month, with the Israeli team operating a mobile laboratory located north of Eilat, and the Jordanian researchers performing continuous measurements of air quality in Aqaba.

Rutgers University physicists have performed computer simulations that show how electrons become one thousand times more massive in certain metal compounds when cooled to temperatures near absolute zero – the point where all motion ceases.