Photon generation by laser-Compton scattering at the KEK-ATF

We performed a photon generation experiment by laser-Compton scattering at the KEK-ATF, aiming to develop a Compton based polarized positron source for linear colliders. In the experiment, laser pulses with a 357 MHz repetition rate were accumulated and their power was enhanced by up to 250 times in the Fabry-Perot optical resonant cavity. We succeeded in synchronizing the laser pulses and colliding them with the 1.3 GeV electron beam in the ATF ring while maintaining the laser pulse accumulation in the cavity. As a result, we observed 26.0 +/- 0.1 photons per electron-laser pulse crossing, which corresponds to a yield of 10^8 photons in a second.Comment: 3 pages, 5 figures, Preprint submitted to TIPP09 Proceedings in NIM

Antimicrobial Electrodeposited Silver-Containing Calcium Phosphate Coatings

Biocompatible antimicrobial coatings may enhance the function of many orthopedic implants by combating infection. Hydroxyapatite is a choice mineral for such a coating as it is native to bone and silver would be a possible antimicrobial agent as it is also commonly used in biomedical applications. The aim of the research is to develop a silver-containing calcium phosphate (Ag/Ca-P) coating via electrochemical deposition on titanium substrates as this allows for controlled coating buildup on complex shapes and porous surfaces. Two different deposition approaches are explored: one-step Ag/Ca-P(1) deposition coatings, containing silver ions as microsized silver phosphate particles embedded in the Ca-P matrix; and via a two-step method (Ag/Ca-P(2)) where silver is deposited as metallic silver nanoparticle on the Ca-P coating. The Ag/Ca-P(1) coating displays a bacterial reduction of 76.1 +/- 8.3% via Ag-ion leaching. The Ag/Ca-P(2) coating displays a bacterial reduction of 83.7 +/- 4.5% via contact killing. Interestingly, by preincubation in phosphate-buffered saline solution, bacterial reduction improves to 97.6 +/- 2.7 and 99.7 +/- 0.4% for Ag/Ca-P(1) and Ag/Ca-P(2) coatings, respectively, due to leaching of formed AgClx(x-1)- species. The biocompatibility evaluation indicates that the Ag/Ca-P(1) coating is cytotoxic towards osteoblasts while the Ag/Ca-P(2) coating shows excellent compatibility. The electrochemical deposition of highly bactericidal coatings with excellent biocompatibility will enable us to coat future bone implants even with complex or porous structures

A compact skeletal mechanism for n-dodecane with optimized semi-global low-temperature chemistry for diesel engine simulations

A skeletal mechanism with 54 species and 269 reactions was developed to predict pyrolysis and oxidation of n-dodecane as a diesel fuel surrogate involving both high-temperature (high-T) and low-temperature (low-T) conditions. The skeletal mechanism was developed from a semi-detailed mechanism developed at the University of Southern California (USC). Species and reactions for high-T pyrolysis and oxidation of C5-C12 were reduced by using reaction flow analysis (RFA), isomer lumping, and then merged into a skeletal C0-C4 core to form a high-T sub-mechanism. Species and lumped semi-global reactions for low-T chemistry were then added to the high-T sub-mechanism and a 54-species skeletal mechanism is obtained. The rate parameters of the low-T reactions were tuned against a detailed mechanism by the Lawrence Livermore National Laboratory (LLNL), as well as the Spray A flame experimental data, to improve the prediction of ignition delay at low-T conditions, while the high-T chemistry remained unchanged. The skeletal mechanism was validated for auto-ignition, perfectly stirred reactors (PSR), flow reactors and laminar premixed flames over a wide range of flame conditions. The skeletal mechanism was then employed to simulate three-dimensional turbulent spray flames at compression ignition engine conditions and validated against experimental data from the Engine Combustion Network (ECN)

Wear and friction performance of PTFE filled epoxy composites with a high concentration of SiO2 particles

In this work, the tribological performance of PTFE filled SiO2 particles–epoxy composites is investigated. Under a load of 60 N (~140 MPa contact pressure), the optimum content of PTFE lies between 10 and 15 wt%, which yields an ultralow coefficient of friction (CoF) in conjunction with a low wear rate of the composite when dry sliding against bearing steel balls within 1000 m. With 12.5 wt% PTFE in the composite, a CoF around 0.095 and a wear rate as low as 8.4×10−7 mm3/Nm were measured up to a sliding distance of around 2000 m. After 2000 m, eventually the gradual accumulation of the fractured SiO2 particles and back-transferred steel on the worn composite surface leads to a significant increase of CoF. In the steady-state of sliding, smearing of the PTFE particles along the worn surface was observed together with fracturing of the SiO2 particles and cracking of the epoxy matrix. Successive EDS mapping shows the formation and evolution of a PTFE-containing third-body tribolayer on the worn surface of the composite. The thickness of the tribolayer was measured about 20–30 nm on the surface of SiO2 particles after sliding for more than 700 m

Cross-modal extinction in a boy with severely autistic behaviour and high verbal intelligence

Anecdotal reports from individuals with autism suggest a loss of awareness to stimuli from one modality in the presence of stimuli from another. Here we document such a case in a detailed study of T.M., a 13-year-old boy with autism in whom significant autistic behaviors are combined with an uneven IQ profile of superior verbal and low performance abilities. Although T.M.'s speech is often unintelligible and his behavior is dominated by motor stereotypies and impulsivity, he can communicate by typing or pointing independently within a letter board. A series of experiments using simple and highly salient visual, auditory, and tactile stimuli demonstrated a hierarchy of cross-modal extinction, in which auditory information extinguished other modalities at various levels of processing. T.M. also showed deficits in shifting and sustaining attention. These results provide evidence for mono-channel perception in autism and suggest a general pattern of winner-takes-all processing in which a stronger stimulus-d riven representation dominates behavior, extinguishing weaker representations

Neutrino masses, leptogenesis and dark matter in hybrid seesaw

We suggest a hybrid seesaw model where relatively ``light''right-handed neutrinos give no contribution to the neutrino mass matrix due to a special symmetry. This allows their Yukawa couplings to the standard model particles to be relatively strong, so that the standard model Higgs boson can decay dominantly to a left and a right-handed neutrino, leaving another stable right-handed neutrino as cold dark matter. In our model neutrino masses arise via the type-II seesaw mechanism, the Higgs triplet scalars being also responsible for the generation of the matter-antimatter asymmetry via the leptogenesis mechanism.Comment: 4 page

On the adhesion and wear resistance of DLC films deposited on nitrile butadiene rubber:A Ti-C interlayer

To promote the adhesion strength between diamond-like carbon (DLC) films and nitrile butadiene rubber (NBR) substrates, titanium-doped carbon (Ti-C) films prepared by dual-target magnetron sputtering under varied substrate bias voltages were used as an interlayer on the rough NBR. The surface topography and structure of Ti-C films were investigated by atomic force microscopy (AFM) and Raman spectra. Raman analysis indicates that the increase of substrate bias voltage leads to an increase of the number or the size of sp2 clusters in the Ti-C interlayer. The adhesion strength and tribological properties of DLC films coated on NBR substrate were scrutinized by a scratch tester and a ball-on-disk tribometer, respectively. It was found that DLC film with a Ti-C interlayer at a certain bias voltage exhibited superior wear resistance with a low coefficient of friction (CoF) during the sliding of 6000 laps. No clear damages in the coatings were observed from the wear tracks. Besides, the scratch test also revealed a reliable adhesion when the interlayer was prepared at −150 V, as confirmed by a scratch crack width of ~50 μm as compared to that of the pure DLC film increasing to ~ 120 μm. Therefore, a Ti-C interlayer could significantly enhance the adhesion and wear resistance of DLC thin films deposited on NBR

Tunable self-organization of nanocomposite multilayers

In this letter we report the controlled growth and microstructural evolution of self-assembled nanocomposite multilayers that are induced by surface ion-impingement. The nanoscale structures together with chemical composition, especially at the growing front, have been investigated with high-resolution transmission electron microscopy. Concurrent ion impingement of growing films produces an amorphous capping layer 3 nm in thickness where spatially modulated phase separation is initiated. It is shown that the modulation of multilayers as controlled by the self-organization of nanocrystallites below the capping layer, can be tuned through the entire film.