Lifeboat Foundation

Light-emitting diodes made of indium gallium nitride provide better luminescence efficiency than many of the other materials used to create blue and green LEDs. But a big challenge of working with InGaN is its known dislocation density defects that make it difficult to understand its emission properties.

In the Journal of Applied Physics, researchers in China report an InGaN LED structure with high luminescence efficiency and what is believed to be the first direct observation of transition carriers between different localization states within InGaN. The localization states were confirmed by temperature-dependent photoluminescence and excitation power-dependent photoluminescence.

Localization states theory is commonly used to explain the high luminescence efficiency gained via the large number of dislocations within InGaN materials. Localization states are the energy minima states believed to exist within the InGaN quantum well region (discrete energy values), but a direct observation of localization states was elusive until now.

From the fictional universe of Stargate Atlantis and Marvel Comic’s Realm of Kings to NASA’s Eagleworks Propulsion laboratory, zero-point energy, also known as vacuum energy, is touted as a potentially limitless and ubiquitous source of energy, if one can only find the means to harness it. [1] Zero-point energy can be formulated in a few different ways, but in its most basic form, it is the minimal yet non-zero energy of a quantum mechanical system. In quantum field theory, zero-point energy can be considered by computing the expected energy of the zero photon mode. [2] In a system with no physical boundaries, the expected energy of the zero photon mode diverges! Yet, if this energy uniformly permeates all of space-time, it is not directly observable.

Conceptual Framework

For pedagogical reasons, we will consider the popular formulation of zero-point energy. The most interesting and relevant framework for zero-point energy can be understood from the quantum field theory for photons and electrons: quantum electrodynamics. Glossing over an exceptional amount of mathematical and conceptual background, the energy of a state in quantum field theory is computed as an expectation of a Hamiltonian„ which describes the energy of the state in terms of operators acting on wavefunctions. The final computation usually requires an integral over the allowed momenta of particles in the state.

Dr. Chris Bernhardt, professor of mathematics at Fairfield University, tells Tonya Hall that quantum computing could eventually be useful for everyone through different problem solving processes.

“Over decades, both military and space programs all around the world have known the negative impact of radiation on semiconductor-based electronics,” says Meyya Meyyappan, Chief Scientist for Exploration Technology at the Center for Nanotechnology, at NASA’s Ames Research Center. What has changed with the push towards nanoscale feature sizes is that terrestrial levels of radiation can now also cause problems that had previously primarily concerned applications in space and defence. Packaging contaminants can cause alpha radiation that create rogue electron-hole pairs, and even the ambient terrestrial neutron flux at sea level – around 20 cm⁻² h⁻¹ – can have adverse implications for nanoscale devices.

Fortunately work to produce radiation-hardy electronics has been underway for some time at NASA, where space mission electronics are particularly prone to radiation exposure and cumbersome radiation shielding comes with a particularly costly load penalty. Vacuum electronics systems, the precursors to today’s silicon world, are actually immune to radiation damage. Alongside Jin-Woo Han and colleagues Myeong-Lok Seol, Dong-Il Moon and Gary Hunter at Ames and NASA’s Glenn Research Centre, Meyyappan has been working towards a renaissance of the old technology with a nano makeover.

In a recent Nature Electronics article, they report how with device structure innovations and a new material platform they can demonstrate nanoscale vacuum channel transistors that compete with solid-state system responses while proving impervious to radiation exposure.

Circa 2009

In just over a day, a powerful computer program accomplished a feat that took physicists centuries to complete: extrapolating the laws of motion from a pendulum’s swings.

Developed by Cornell researchers, the program deduced the natural laws without a shred of knowledge about physics or geometry.

Continue reading “Computer Program Self-Discovers Laws of Physics” »

Truthfully, it has been some time since Moore’s law, the propensity for processors to double in transistor count every two years, has been entirely accurate. The fundamental properties of silicon are beginning to limit development and will significantly curtail future performance gains, yet with 50 years and billions invested, it seems preposterous that any ‘beyond-silicon’ technology could power the computers of tomorrow. And yet, Nano might do just that, by harnessing its ability to be designed and built like a regular silicon wafer, while using carbon to net theoretical triple performance at one-third the power.

Nano began life much like all processors, a 150mm wafer with a pattern carved out of it by a regular chip fab. Dipped into a solution of carbon nanotubes bound together like microscopic spaghetti, it re-emerged with its semi-conductive carbon nanotubes stuck in the pattern of transistors and logic gates already etched on it. It then undergoes a process called ‘RINSE,’ removal of incubated nanotubes through selective exfoliation, by being coated with a polymer then dipped in a solvent. This has the effect of reducing the CNT layer to being just one tube, removing the large clumps of CNTs that stick together over 250 times more effectively than previous methods.

One of the challenges facing CNT processors has been difficulty in separating N-type and P-type transistors, which are “on” for 1 bit and “off” for 0 bit and the reverse, respectively. The difference is important for binary computing, and to perfect it, the researchers introduced ‘MIXED,’ metal interface engineering crossed with electrostatic doping. Occurring after RINSE, small platinum or titanium components are added to each transistor, then the wafer is coated in an oxide which acts as a sealant, improving performance. After that, Nano was just about done.

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This week a collaborative effort among computer scientists and academics to safeguard data is winning attention and it has quantum computing written all over it.

The Netherlands’ Centrum Wiskunde & Informatica (CWI), national research institute for mathematics and computer science, had the story: IBM Research developed “quantum-safe algorithms” for securing data. They have done so by working with international partners including CWI and Radboud University in the Netherlands.

IBM and partners share concerns that data protected by current encryption methods may become insecure within the next 10 to 30 years.

A team of researchers at the University of Virginia has recently carried out a large-scale analysis aimed at identifying features in film trailers that best predict a movie’s genre and estimated budget. In their study, outlined in a paper pre-published on arXiv, the researchers specifically compared the effectiveness of visual, audio, text, and metadata-based features.

“Video understanding is the next frontier after image understanding,” Vicente Ordonez, one of the researchers who carried out the study, told TechXplore. “However, much work on video understanding has so far focused on short clips with a human performing a single action. We wanted something longer, but there is also the issue of computational power. Video trailers seemed like an intermediate compromise, as they display a multitude of things, from scary to funny.”

Movie trailers are short and can easily be paired with movie descriptions. Ordonez and his colleagues realized that these characteristics make them ideal to investigate parallels between video and language.