Moving silicon atoms in graphene with atomic precision

ScienceDaily – Richard Feynman [2, 3, 4, 5] famously posed the question in 1959: is it possible to see and manipulate individual atoms in materials?

For a time his vision seemed more science fiction than science, but starting with groundbreaking experiments in the late 1980s and more recent developments in electron microscopy instrumentation it has become scientific reality. However, damage caused by the electron beam is often an issue in such experiments.

Besides being beautiful physics, the findings open promising possibilities for atomic-scale engineering: “What makes our results truly intriguing is that the bond flip is directional — the silicon moves to take the place of the carbon atom that was hit by a probe electron,” explains Toma Susi, physicist and FWF Lise Meitner Fellow at the University of Vienna. more> http://tinyurl.com/phra9ao

Fluid mechanics suggests alternative to quantum orthodoxy

ScienceDaily – The system by Yves Couder and Emmanuel Fort consists of a bath of fluid vibrating at a rate just below the threshold at which waves would start to form on its surface. A droplet of the same fluid is released above the bath; where it strikes the surface, it causes waves to radiate outward. The droplet then begins moving across the bath, propelled by the very waves it creates.

“This system is undoubtedly quantitatively different from quantum mechanics,” John Bush says.

“It’s also qualitatively different: There are some features of quantum mechanics that we can’t capture, some features of this system that we know aren’t present in quantum mechanics. But are they philosophically distinct?” more> http://tinyurl.com/o4kcmpf

Monitoring of singlet oxygen in individual cells with InGaAs camera

R&D – Singlet oxygen, the first excited state of molecular oxygen, is a highly reactive species that plays an important role in a wide range of biological processes, including cell signaling, immune response, macromolecule degradation, and elimination of neoplastic tissue during photodynamic therapy. Often, a photosensitizing process is employed to produce singlet oxygen from ground state oxygen.

The researchers at Charles Univ. utilized two detection channels (VIS and NIR) to perform real-time imaging of the very weak near-infrared phosphorescence of singlet oxygen and photosensitizer simultaneously with visible fluorescence of the photosensitizer. Their new experimental setup enables acquisition of spectral images based on singlet oxygen and photosensitizer luminescence from individual cells. more> http://tinyurl.com/kuhbuzc

Synthesis of structurally pure carbon nanotubes using molecular seeds

R&D – For 20 years, carbon nanotubes (CNTs) have been the subject of intensive fundamental as well as applied research.

With a diameter of roughly one nanometre, single-wall CNTs (or SWCNTs) need to be considered as quantum structures; the slightest structural changes, such as differences in diameter or in the alignment of the atomic lattice, may result in dramatic changes to the electronic properties: one SWCNT may be metallic, whilst another one with a slightly different structure is a semiconductor.

Hence, there is a great deal of interest in reliable methods of making SWCNTs as structurally uniform as possible. In fact, corresponding synthesis concepts were formulated about 15 years ago.

However, it is only now that surface physicists at Empa and chemists at the Max Planck Institute have successfully implemented one of these ideas in the laboratory. more> http://tinyurl.com/mdntjs4

Postcards from the photosynthetic edge

By Lynn Yarris – Photo-oxidation of water by photosystem II is responsible for most of the oxygen in Earth’s atmosphere.

At the core of photosystem II is a manganese-calcium (Mn4Ca) metalloenzyme complex that when energized by solar photons catalyzes a four photon-step cycle of oxidation states (S0-to-S3) that ultimately yields molecular oxygen. Scientists need to observe intact x-ray crystallography of the Mn4Ca ion in action but the molecule is highly sensitive to radiation.

The LCLS (Linac Coherent Light Source) is the world’s only source of x-rays capable of providing femtosecond pulses at the high intensities that allow intact photosystem II crystals to be imaged before they are destroyed by exposure to the x-ray beams. more> http://tinyurl.com/nlxrcf8