Gravity on a multifractal

Despite their diversity, many of the most prominent candidate theories of quantum gravity share the property to be effectively lower-dimensional at small scales. In particular, dimension two plays a fundamental role in the finiteness of these models of Nature. Thus motivated, we entertain the idea that spacetime is a multifractal with integer dimension 4 at large scales, while it is two-dimensional in the ultraviolet. Consequences for particle physics, gravity and cosmology are discussed.     

Dynamics of the infinitely-thin kink

We consider the dynamics of the domain-wall kink soliton, in particular we study the zero mode of translation. In the infinitely-thin kink limit, we show that the zero mode is almost completely frozen out, the only remnant being a dynamically constrained four-dimensional mode of a single but arbitrary frequency. In relation to this result, we show that the usual mode expansion for dealing with zero modes - implicit collective coordinates - is not in fact a completely general expansion, and that one must use instead a traditional generalised Fourier analysis.     

Low temperature Si homo-epitaxy by reduced pressure chemical vapor deposition using dichlorosilane,silane and trisilane

Dichlorosilane (DCS), silane and trisilane have been investigated as Si precursors for low temperature (<700 °C) Si reduced pressure chemical vapor deposition. DCS and silane are limited to growth temperatures higher than 600–650 and 500 °C, respectively. At lower temperatures, absence of either Cl or H desorption from the surface impedes Si growth with acceptable growth rate (>5 Å/min). Trisilane permits the growth of Si at lower temperatures below 350 °C due to a specific growth mechanism enhancing H desorption. Layers grown at temperatures lower than 500 °C are defective, irrespective of the carrier gas, pressure and precursor flow used.     

Field emission characteristics of screen-printed carbon nanotubes cold cathode by hydrogen plasma treatment

Selective plasma etching and hydrogen plasma treatment were introduced in turn to improve field emission characteristics of screen-printed carbon nanotubes (CNTs) cold cathode, which was prepared by using slurry of mixture of multi-wall CNTs, organic vehicles and inorganic binder, i.e. silicon dioxide sol. The results show that selective plasma etching process could effectively remove parts of surface inorganic vehicle (SiO₂) layer and expose more smooth and clean CNTs on cathode surface, which could significantly decrease the operating field of CNTs cathode. There are some nanoparticles emerging on the out of CNTs wall after hydrogen plasma treatment, which are equivalent to increase field emission point of cathode. At the same time, these nanoparticles can increase the local electric field of CNTs, which can decrease operating voltage of CNTs cathode and improve uniformity field emission.     

A refined integro-surface energy-based model for vibration of magnetically actuated double-nanowire-systems carrying electric current

A novel surface energy-based model is developed to examine more precisely vibrations of current-carrying double-nanowire-systems immersed in a longitudinal magnetic field. Using Biot-Savart and Lorentz laws, a more refined version of interwire interactional magnetic forces is presented. By employing Rayleigh beam theory, the equations of motion are derived. In fact, these are coupled integro-differential equations which are more accurate with respect to those of the previously developed models. For simply supported and clamped nanosystems, governing equations are analyzed via assumed mode method. The effects of interwire distance, slenderness ratio, electric current, magnetic field strength, and surface effect on the fundamental frequency are addressed carefully. The obtained results display the importance of exploiting the refined model for vibration analysis of nanosystems with low interwire distance, high electric current, and high magnetic field strength.     

Lattice simulation of a center symmetric three-dimensional effective theory for SU(2) Yang-Mills

We perform simulations of an effective theory of SU(2) Wilson lines in three dimensions. Our action includes a kinetic term, the one-loop perturbative potential for the Wilson line, a non-perturbative “fuzzy-bag” contribution and spatial gauge fields. We determine the phase diagram of the theory and confirm that, at moderately weak coupling, the non-perturbative term leads to eigenvalue repulsion in a finite region above the deconfining phase transition.     

Differential pulse cathodic stripping voltammetric determination of nanomolar levels of dissolved sulfide applicable to field analysis of groundwater

Conventional batch mode analysis of dissolved sulfide by cathodic stripping voltammetry (CSV) is known to suffer from loss of sulfide in the cell to the waste mercury pool, compromising quantification of sulfide. Here we report a simple alternative approach to batch-mode differential pulse CSV (DPCSV). A fresh aliquot of sample is used for each voltammetric scan to minimize loss of sulfide through reaction with the mercury by limiting the time for sulfide-mercury contact, which is found to be more important in suppressing the sulfide signal than the amount of free mercury in the cell. Our improved batch-mode method exhibited a limit of detection of 1.3 nM, a relative standard deviation of 2.5% in NaOH supporting electrolyte and a linear response to as high a concentration as 1600 nM in a supporting electrolyte composed of Na₂CO₃/NaHCO₃ (pH 8.3) mixed with an equal volume of oxic groundwater. A relative standard deviation of 4.5% was obtained for a groundwater sample in Na₂CO₃/NaHCO₃ (pH 8.3) supporting electrolyte. These values are comparable to previously published results. Compared to other sensitive sulfide analytical techniques such as gas chromatography or high performance liquid chromatography (HPLC), DPCSV is preferred for sulfide analysis in the field due to its simple and portable instrumentation, lack of complex sample preparation, and short analysis time. The method was applied on site to analyze Fe-rich, reducing groundwater samples collected at a landfill site in Winthrop, Maine. Sulfide concentrations ranged from undetectable (<4 nM) to 7340 nM, generally increasing as the oxidation/reduction potential (ORP) of the water became more negative. We also demonstrate, for the first time, that the onset of sulfate reduction as indicated by the presence of small amounts of sulfide (tens to hundreds of nM) occurs in groundwater systems when the ORP value reaches −130 mV.     

Field Patterns of the TE Modes in Ridge-Trough Waveguide

A single-ridge waveguide with a symmetrical longitudinal trough, designated as a ridge-trough waveguide has been used as a transition in a V-band (50-75 GHz) wafer probe recently. In this paper, the field patterns for the dominant TE mode and the first higher TE mode in ridge-trough waveguide with different configurations are presented by finite element method. The field patterns in this paper have important values for us to understand the transmission characteristics of ridge-trough waveguide, and will be of practical significance in designing ridge-trough waveguide components in microwave and millimeter wave engineering.     

阿尔芬波加热研究的进展

本文概述了阿尔芬波加热的理论和实验情况。讨论了阿尔芬波加热的基本物理问题,并介绍了某些重要的实验结果。对在大托卡马克上采用阿尔芬波加热的可能性进行了全面论述。