Stress relief as the driving force for self-assembled Bi nanolines

Stress resulting from mismatch between a substrate and an adsorbed material has often been thought to be the driving force for the self-assembly of nanoscale structures. Bi nanolines self-assemble on Si(001), and are remarkable for their straightness and length -- they are often more than 400 nm long, and a kink in a nanoline has never been observed. Through electronic structure calculations, we have found an energetically favourable structure for these nanolines that agrees with our scanning tunneling microscopy and photoemission experiments; the structure has an extremely unusual subsurface structure, comprising a double core of 7-membered rings of silicon. Our proposed structure explains all the observed features of the nanolines, and shows that surface stress resulting from the mismatch between the Bi and the Si substrate are responsible for their self-assembly. This has wider implications for the controlled growth of nanostructures on semiconductor surfaces.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Let

Journey of water in pine cones

Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system.119Ysciescopu

Journey of water in pine cones

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Antipruritic Effect of Acupuncture in Patients with Atopic Dermatitis: Feasibility Study Protocol for a Randomised, Sham-Controlled Trial

© 2017 Yu-Kang Kim et al. This study aims to test the feasibility of a randomised clinical trial to evaluate how acupuncture affects atopic dermatitis (AD) symptoms and quality of life and to explore potential biomarkers that may be associated with AD. It is a sham-controlled trial in which 30 eligible patients will be randomly allocated in a 1: 1: 1 ratio to one of three groups: Verum acupuncture (VA) group 1 (3 times weekly for 4 weeks); VA group 2 (twice weekly for 4 weeks); or sham acupuncture group (SA; twice weekly for 4 weeks). SA will consist of nonpenetrating acupuncture. Outcome measures will include the Visual Analogue Scale for itch, SCORing Atopic Dermatitis, and Eczema Area and Severity Index to evaluate AD symptoms improvement along with the Patient Oriented Eczema Measure and Dermatology Life Quality Index to assess quality of life. Measures will be collected at baseline, once weekly during the treatment period, and after a 4-week follow-up period. Blood collection will be at baseline and 4 and 8 weeks after treatment and compared with healthy controls. Illumina sequencing will be used to profile microRNA expression in each group to explore candidate microRNA biomarkers for specific effects of acupuncture in patients with AD. This trial is registered via US National Institutes of Health Clinical Trials registry (ClinicalTrials.gov) on 15 July 2016, identifier: NCT02844452

Direct observation of the spin polarization in Au atomic wires on Si(553)

The spin-resolved electronic band structure of Au-induced metallic atomic wires on a vicinal silicon surface, Si(553), was investigated using spin-and angle-resolved photoelectron spectroscopy. We directly measured the spin polarization of three partially filled one-dimensional metallic bands, a one-third-filled band, and the doublet of nearly half-filled bands. For the half-filled doublet, the strong apparent spin polarization was observed near the Fermi energy with a minor out-of-plane spin component. This observation is consistent with the Rashba-type spin-orbit splitting and with a recent experiment on a similar doublet of Si(557)-Au. In contrast, the one-third-filled band does not show a substantial spin polarization within the experimental accuracy, indicating a much smaller spin splitting, if any. These results are discussed for the origin of the partially filled bands and for the intriguing broken-symmetry ground state observed at low temperature.X11116sciescopu

Experimental and computational investigations of the effect of the electrode gap on capacitively coupled radio frequency oxygen discharges

Geometrically symmetric capacitively coupled oxygen plasmas are studied experimentally by optical emission spectroscopy and probe measurements as well as via numerical simulations using the kinetic Particle-in-Cell/Monte Carlo collision (PIC/MCC) approach. The experiments reveal that at a fixed pressure of 20 mTorr and a driving frequency of 13.56 MHz, the central electron density increases with an increased electrode gap, while the time averaged optical emission of atomic oxygen lines decreases. These results are reproduced and understood by the PIC/MCC simulations performed under identical conditions. The simulations show that the electron density increases due to a mode transition from the Drift-Ambipolar-mode to the a-mode induced by increasing the electrode gap. This mode transition is due to a drastic change of the electronegativity and the mean electron energy, which leads to the observed reduction of the emission intensity of an atomic oxygen line. The observed mode transition is also found to cause a complex non-monotonic dependence of the O2+ ion flux to the electrodes as a function of the electrode gap. These fundamental results are correlated with measurements of the etch rate of amorphous carbon layers at different gap distances

Dynamical formation and evolution of (2+1)-dimensional charged black holes

In this paper, we investigate the dynamical formation and evolution of 2 + 1-dimensional charged black holes. We numerically study dynamical collapses of charged matter fields in an anti de Sitter background and note the formation of black holes using the double-null formalism. Moreover, we include re-normalized energy-momentum tensors assuming the S-wave approximation to determine thermodynamical back-reactions to the internal structures. If there is no semi-classical effects, the amount of charge determines the causal structures. If the charge is sufficiently small, the causal structure has a space-like singularity. However, as the charge increases, an inner Cauchy horizon appears. If we have sufficient charge, we see a space-like outer horizon and a time-like inner horizon, and if we give excessive charge, black hole horizons disappear. We have some circumstantial evidences that weak cosmic censorship is still satisfied, even for such excessive charge cases. Also, we confirm that there is mass inflation along the inner horizon, although the properties are quite different from those of four-dimensional cases. Semi-classical back-reactions will not affect the outer horizon, but they will affect the inner horizon. Near the center, there is a place where negative energy is concentrated. Thus, charged black holes in three dimensions have two types of curvature singularities in general: via mass inflation and via a concentration of negative energy. Finally, we classify possible causal structures.Comment: 40 pages, 15 figure

Bubble collision with gravitation

In this paper, we study vacuum bubble collisions with various potentials including gravitation, assuming spherical, planar, and hyperbolic symmetry. We use numerical calculations from double-null formalism. Spherical symmetry can mimic the formation of a black hole via multiple bubble collisions. Planar and especially hyperbolic symmetry describes two bubble collisions. We study both cases, when two true vacuum regions have the same field value or different field values, by varying tensions. For the latter case, we also test symmetric and asymmetric bubble collisions, and see details of causal structures. If the colliding energy is sufficient, then the vacuum can be destabilized, and it is also demonstrated. This double-null formalism can be a complementary approach in the context of bubble collisions.Comment: 31 pages, 19 figure