‘We change People’s Lives’: Commodification of English in Thailand

This study explores the commodification of English in Thailand by examining promotional materials produced by a private English language school. There is a lack of research that has investigated the ways in which the English language has been commodified in the private sector in the Thai context. This study provides some insights into the process of commodification of the language by examining marketing materials of Wall Street Institute of English, one of the most prominent private language schools in Thailand. The study adopts Critical Discourse Analysis as a theoretical framework to shed light on these questions. The study found several ideologies present in advertisements of Wall Street Institute and a major ideology is that of English as the key to a better future. Based on these findings, some relevant implications for the English language education in Thailand and recommendations for future research are offered

Temperature-resolution anomalies in the reconstruction of time dynamics from energy-loss experiments

Inelastic scattering techniques provide a powerful approach to studying electron and nuclear dynamics, via reconstruction of a propagator that quantifies the time evolution of a system. There is now growing interest in applying such methods to very low energy excitations, such as lattice vibrations, but in this limit the cross section is no longer proportional to a propagator. Significant deviations occur due to the finite temperature Bose statistics of the excitations. Here we consider this issue in the context of high-resolution electron energy loss experiments on the copper-oxide superconductor Bi$_2$Sr$_2$CaCu$_2$O$_{8+x}$. We find that simple division of a Bose factor yields an accurate propagator on energy scales greater than the resolution width. However, at low energy scales, the effects of resolution and finite temperature conspire to create anomalies in the dynamics at long times. We compare two practical ways for dealing with such anomalies, and discuss the range of validity of the technique in light of this comparison.Comment: 19 pages, 2 figures, submitted to Journal of Physics

Adsorption properties and third sound propagation in superfluid 4^4He films on carbon nanotubes

We consider the adsorption properties of superfluid $^4$He films on carbon nanotubes. One major factor in the adsorption is the surface tension force arising from the very small diameter of the nanotubes. Calculations show that surface tension keeps the film thickness on the tubes very thin even when the helium vapor is increased to the saturated pressure. The weakened Van der Waals force due to the cylindrical geometry also contributes to this. Both of these effects act to lower the predicted velocity of third sound propagation along the tubes. It does not appear that superfluidity will be possible on single-walled nanotubes of diameter about one nm, since the film thickness is less than 3 atomic layers even at saturation. Superfluidity is possible on larger-diameter nanotube bundles and multi-walled nanotubes, however. We have observed third sound signals on nanotube bundles of average diameter 5 nm which are sprayed onto a Plexiglass surface, forming a network of tubes.Comment: 4 pages, accepted for Journal of Physics: Conference Series (Proceedings of LT25

Collective excitations in layered materials with momentum-resolved electron energy loss spectroscopy

Strong Coulomb interactions are either suspected or known to play a prominent role in material classes such as high temperature superconductors, charge density waves, and Mott insulators among many others. These interactions are quantified by the charge density response function, chi(q,w) (or the closely related inverse dielectric function). The measurement of the energy- and momentum-resolved chi(q,w) over a large phase space of q and w, however, presents a significant experimental challenge. Traditional methods to measure chi(q,w) have suffered from either one or more major drawbacks. To address this problem, the development of a spectroscopic technique, momentum-resolved electron energy loss spectroscopy (M-EELS), was undertaken. Because many of the material classes that exhibit these unusual ground states tend to be layered or quasi-two dimensional, M-EELS presents a promising approach to measuring the energy- and momentum-resolved charge density response. Since the technique is not widely used, however, the M-EELS results obtained as part of this thesis were compared to other probes in the relevant ranges of phase space to ensure consistency. Furthermore, a theoretical framework was worked out to demonstrate explicitly the relationship between the scattering cross section and c(q,w). M-EELS experiments were conducted on a high-temperature superconductor, Bi2Sr2CaCu2O8+d, a charge density wave material, TiSe2, and a topological insulator, Bi2Se3. It was determined that the bosonic origin of quasiparticle kinks often seen in angle-resolved photoemission studies can be identified using M-EELS. Lastly, the observation of a novel electronic collective mode in TiSe2 is presented as strong evidence for an excitonic insulator phase in this compound

Amplitude dynamics of charge density wave in LaTe3_3: theoretical description of pump-probe experiments

We formulate a dynamical model to describe a photo-induced charge density wave (CDW) quench transition and apply it to recent multi-probe experiments on LaTe$_3$ [A. Zong et al., Nat. Phys. 15, 27 (2019)]. Our approach relies on coupled time-dependent Ginzburg-Landau equations tracking two order parameters that represent the modulations of the electronic density and the ionic positions. We aim at describing the amplitude of the order parameters under the assumption that they are homogeneous in space. This description is supplemented by a three-temperature model, which treats separately the electronic temperature, temperature of the lattice phonons with stronger couplings to the electronic subsystem, and temperature of all other phonons. The broad scope of available data for LaTe$_3$ and similar materials as well as the synergy between different time-resolved spectroscopies allow us to extract model parameters. The resulting calculations are in good agreement with ultra-fast electron diffraction experiments, reproducing qualitative and quantitative features of the CDW amplitude evolution during the initial few picoseconds after photoexcitation.Comment: 21 pages, 14 figures; this version is almost identical to the published version; comparing to the earlier arXiv submission, current version contains a new figure (Fig.10), and a broader discussion of theoretical results and approximation

A reexamination of the effective fine structure constant of graphene, as measured in graphite

We present a refined and improved study of the influence of screening on the effective fine structure constant of graphene, $\alpha^*$, as measured in graphite using inelastic x-ray scattering. This follow-up to our previous study [J. P. Reed, et al., Science 330, 805 (2010)] was carried out with two times better energy resolution, five times better momentum resolution, and improved experimental setup with lower background. We compare our results to RPA calculations and evaluate the relative importance of interlayer hopping, excitonic corrections, and screening from high energy excitations involving the $\sigma$ bands. We find that the static, limiting value of $\alpha^*$ falls in the range 0.25 to 0.35, which is higher than our previous result of 0.14, but still below the value expected from RPA. We show the reduced value is not a consequence of interlayer hopping effects, which were ignored in our previous analysis, but of a combination of excitonic effects in the $\pi \rightarrow \pi^*$ particle-hole continuum, and background screening from the $\sigma$-bonded electrons. We find that $\sigma$-band screening is extremely strong at distances of the order of a few nm, and should be highly effective at screening out short-distance, Hubbard-like interactions in graphene, as well as other carbon allotropes.Comment: 23 pages, 5 figure