High dose implantation of Eu into α-Fe

Abstract

At the UNILAC injector at GSI ¹⁵¹Eu was implanted into an α-Fe foil [8]. According to our simulation code of the energy loss of the implanted ions an energy of 1.5 MeV was chosen to minimize the sputter yield during implantation and to produce the highest possible Eu concentration near the surface of the sample. After the irradiation with a dose of 3.6 · 10¹⁷ Eu/cm² the implantation profile should reach its maximum of 8 at. % Eu at the surface of the sample and its width should be 1700 Å.     

Dispositif optique pour implantation et micro-usinage par projection d'images ioniques Ion imaging for ion implantation and for micromachining

It is well known that more and more precise doping is needed for producing high performance's electronic components and circuits of increasingly enhanced complexity. An ion optic can be used to directly produce a localised implantation allowing to free one self from all masking techniques. The experimental set up mainly consist in a projecting lens which focuses the reduced image of a “model”, structure partially transparent to the ion beam, on the crystal to be implanted. One of the difficult points is connected with the tine control of the focusing of the ion image on the surface of the target. In order to check this focusing an “Ion Image Converter” is used as the projection lens. On the one hand the 10 keV energy positive ion beam is post accelerated to a hundred keV as it is focused on the target; on the other hand, the secondary electrons ejected from the target are accelerated and focused backwards permitting the formation of an electron image which is an enlargement of the ion figure projected on the target; this auxiliary image after further magnification is observed on a fluorescent screen allowing to adjust and to control the focusing and the illumination of the ion image.     

Black holes and black hole thermodynamics without event horizons

We investigate whether black holes can be defined without using event horizons. In particular we focus on the thermodynamic properties of event horizons and the alternative, locally defined horizons. We discuss the assumptions and limitations of the proofs of the zeroth, first and second laws of black hole mechanics for both event horizons and trapping horizons. This leads to the possibility that black holes may be more usefully defined in terms of trapping horizons. We also review how Hawking radiation may be seen to arise from trapping horizons and discuss which horizon area should be associated with the gravitational entropy.     

Cell separation by the combination of microfluidics and optical trapping force on a microchip

We investigated properties of cells affecting their optical trapping force and successfully established a novel cell separation method based on the combined use of optical trapping force and microfluidics on a microchip. Our investigations reveal that the morphology, size, light absorption, and refractive index of cells are important factors affecting their optical trapping force. A sheath flow of sample solutions created in a microchip made sample cells flow in a narrow linear stream and an optical trap created by a highly focused laser beam captured only target cells and altered their trajectory, resulting in high-efficiency cell separation. An optimum balance between optical trapping force and sample flow rate was essential to achieve high cell separation efficiency. Our investigations clearly indicate that the on-chip optical trapping method allows high-efficiency cell separation without cumbersome and time-consuming cell pretreatments. In addition, our on-chip optical trapping method requires small amounts of sample and may permit high-throughput cell separation and integration of other functions on microchips. Figure Optical trapping in a microchannel allows high-efficiency separation of cells, e.g., dead and live HeLa cells

Single-molecule measurements of trapped and migrating circular DNA during electrophoresis in agarose gels

The effect of agarose gel concentration and field strength on the electrophoretic trapping of open (relaxed) circular DNA was investigated using microscopic measurements of individual molecules stained with a fluorescent dye. Three open circles with sizes of 52.5, 115, and 220 kbp were trapped by the electric field (6 V/cm) and found to be predominately fixed and stretched at a single point in the gel. The length of the stretched circles did not significantly change with agarose concentration of the gels (mass fractions of 0.0025, 0.01, and 0.02). The relaxation kinetics of the trapped circles was also measured in the gels. The relaxation of the large open circles was found to be a slow process, taking several seconds. The velocity and average length of the 52.5 kbp open circles and 48.5 kbp linear DNA were measured during electrophoresis in the agarose gels. The velocity increased when the agarose concentrations were lowered, but the average length of the open-circle DNA (during electrophoresis) did not significantly change with agarose gel concentrations. The circles move through the gels by cycles of stretching and relaxation during electrophoresis. Linear dichroism was also used to investigate the trapping and alignment of the 52.5 kbp open circles. The results in this study provide information that can be used to improve electrophoretic separations of circular DNA, an important form of genetic material and commonly used to clone DNA.     

Voltage-controlled trapping of excitons and “storage of light” in lateral superlattices

Voltage-controlled lateral superlattices of various periods are employed to demonstrate the trapping of photogenerated excitons in quasi-one-dimensional regions and to store light in form of ionised excitons in the quantum well of a semiconductor heterostructure. The superlattices are induced by applying spatially alternating external voltages via interdigitated metal gates. Exciton localisation arises from a periodical modulation of the strength of the quantum confined Stark effect in the plane of the quantum well. At large superlattice potential amplitudes the excitons are ionised due to the strong lateral electric fields. The thus spatially separated electrons and holes can be stored efficiently in the structure. Resetting the potential amplitude to zero induces their radiative recombination after very long storage times.     

Development and Application of the 2D Relativistic Fokker-Planck Package

The Fokker Planck package which without the relativity effect has been developed in 2002. The package with relativity effect, which induced from Italy, is now developed. It conrains relativity effect, and is bounce averaged. It can deal with such as the trapping effect, wave heating, neutral beam injecting, and particle losses. It is very useful for our HL-2A experimental results analysis.     

Tractor beam for fully immersed multiple objects: Long distance pulling,trapping, and rotation with a single optical set‐up

In this article, we have theoretically demonstrated the mechanism of an active tractor beam for multiple fully immersed objects with additional abilities to yielding stable long distance levitation, a controlled rotation and a desired 3D trapping. This is demonstrated with a single optical set‐up by using two coaxial, or even non‐coaxial, superimposed higher order monochromatic Bessel beams of reverse helical nature and different frequencies. The superimposed beams can possess periodic intensity variations both along and around the beam‐axis due to a difference in longitudinal wave‐numbers and beam orders, respectively. The difference in frequencies of the two laser beams makes the intensity pattern to move along and around the beam‐axis in a continuous way without manual ramping of phase, which allows for bidirectional movement of completely immersed multiple particles. The condition for increasing or decreasing the dimension of binding regions is also proposed here to manipulate multiple immersed objects of different sizes under dipole approximation.

     

Enantioselective synthesis of the bicyclo[4.3.0]nonane ring system of the pinguisane-type sesquiterpenoids via a Brønsted acid promoted transannular enol alkylation

The bicyclo[4.3.0]nonane ring system of the pinguisane-type sesquiterpenoid natural products, including the vicinal quaternary stereocentres, has been synthesised as a single enantiomer via a novel Brønsted acid promoted transannular alkylation of an enol with an unactivated alkene.     

Nano-manipulation performance with enhanced evanescent field close to near-field optical probes

Recently, interest in nano-manipulation using the evanescent wave generated by nano-objects has been growing, but the analyses of manipulation flexibility and performance haven't been solved. In this paper the near-field optical trap utilizing a tapered metalized probe used in NSOM is described in detail. By employing a generalization of the conservation law for momentum using three-dimensional FDTD method, rigorous calculations of field distributions and trapping forces in near-field region are conducted. Calculations show that the particle with radius larger than the aperture is pushed away from the metal-coated fiber probe, while it tends to be trapped in larger effective region as its radius becoming smaller. The particle that is placed very near the aperture and around two field peaks intends to be dragged to the aperture edge, while the particle placed at other position tends to be attracted to the center surface of the probe tip. Furthermore, a preferable method using the combination of the near-field optical fiber probe and the AFM metallic probe is proposed, for more efficient non-contact manipulation and better observation of one single nano-particle. The analyses of trapping potential along the probe axis and the near-field distribution show the possibility of particle trapping.