Lively children trapped in an island of disadvantage: Verbal play of Cantonese working-class schoolboys in Hong Kong

In this paper I describe the mocking and playful verbal practices of some Cantonese working-class secondary schoolboys in an English language lesson in Hong Kong. I show how these Cantonese-speaking adolescents seek to assert their indigenous identity and their ingenious Cantonese competence in an educational system that places Cantonese at the bottom of the hierarchy of languages. These self-asserting verbal practices of working- class schoolboys, while in themselves artful and playful, do not contribute to the breaking through of the reproduction and perpetuation of these schoolboys' subordinated and insulated Cantonese sociocultural world, where there is little access to the socioeconomically dominant symbolic resource of English. Without access to English, they can hardly access the middle-class bilingual identity and the socioeconomic success and social status that come with it. Paradoxically, by acting out resistance to an alienating English curriculum, they contribute to the perpetuation of their own insularity and subordination and are trapped in a cycle of disadvantage. The paper concludes with a discussion of the possible impact of the transition of Hong Kong from a British colony to a Special Administrative Region (SAR) of China on language, identity, and social class in post-1997 Hong Kong. © Walter de Gruyter.postprin

The Rise and Fall of S&P500 Variance Futures

Volatility is an indispensible component of sensible portfolio risk management. The volatility of an asset of composite index can be traded by using volatility derivatives, such as volatility and variance swaps, options and futures. The most popular volatility index is VIX, which is a key measure of market expectations of volatility, and hence is a key barometer of investor sentiment and market volatility. Investors interpret the VIX cash index as a “fear” index, and of VIX options and VIX futures as derivatives of the “fear” index. VIX is based on S&P500 call and put options over a wide range of strike prices, and hence is not model based. Speculators can trade on volatility risk with VIX derivatives, with views on whether volatility will increase or decrease in the future, while hedgers can use volatility derivatives to avoid exposure to volatility risk. VIX and its options and futures derivatives has been widely analysed in recent years. An alternative volatility derivative to VIX is the S&P500 variance futures, which is an expectation of the variance of the S&P500 cash index. Variance futures are futures contracts written on realized variance, or standardized variance swaps. The S&P500 variance futures are not model based, so the assumptions underlying the index do not seem to have been clearly understood. As these two variance futures are thinly traded, their returns are not easy to model accurately using a variety of risk models. This paper analyses the S&P500 3-month variance futures before, during and after the GFC, as well as for the full data period, for each of three alternative conditional volatility models and three densities, in order to determine whether exposure to risk can be incorporated into a financial portfolio without taking positions on the S&P500 index itself.Risk management, financial derivatives, futures, options, swaps, 3-month variance futures, 12-month variance futures, risk exposure, volatility.

Suppression of parasitic resonance in piezoresistively transduced longitudinal mode MEMS resonators

This paper demonstrates the suppression of parasitic resonance in a piezoresistively transduced longitudinal mode MEMS resonator, wherein beams are electrostatically excited in a combined extensional mode with an associated frequency-Q product of 3.28 Ã? 1012. The response of the beam is sensed using both capacitive and piezoresistive transduction principles. The resonator consists of six parallel beams linked to a central anchor and a pair of symmetrical parallel beams that force the beams to vibrate in-phase. The mode suppression in the resonator is compared with other structures by finite element analysis (FEA). The relative distribution of strain energies in both the resonant structure and anchors and in both primary and secondary directions of vibration are proposed as figures of merit to compare this device to previously reported longitudinal mode beam resonators. The design optimization of longitudinal mode beam resonators is also discussed

Electrostatically transduced face-shear mode silicon MEMS microresonator

Silicon microresonators are increasingly viewed as attractive candidates for a variety of frequency selective signal processing applications due to miniaturization and potential for integration with CMOS. In this work, we present a new electrostatically transduced face-shear (FS) mode square plate single crystal silicon resonator that rivals previously reported bulk mode resonator topologies and demonstrates good frequency scaling. A microfabricated face-shear mode resonator with 800 ?m side length demonstrates a resonant frequency of 3.638 MHz, Q of 11193 in air and 836283 in vacuum as well as a TCF of -19ppm/K

Mechanically coupled bulk-mode dual resonator mass sensor

The adaptation of micro- and nanomechanical resonators as mass balances for biochemical sensing has received much attention in recent years due to the potential for very high resolution and electrical readout of target analyte in a label-free format. However, several implementation challenges arise from the necessity of operation in compatible biological buffer solutions. These challenges include minimizing undesired effects of fluid-structure interaction and buffer interference with signal transduction. Electrical readout of the sensor response is complicated by coupling to the electrical properties of the buffer solution and voltage limitations due to the possibility of undesired electrochemical reactions on the sensor surface. To address this problem we propose a novel dual resonator platform, wherein electrical transduction and sensing are spatially separated onto two different mechanically coupled resonators. In this work, we demonstrate the functionality of the dual resonator system as a mass sensing platform, with a mass responsivity of 37 Hz/ng

Dynamic response of water droplet coated silicon MEMS resonators

This paper studies the dynamic response of silicon bulk acoustic mode resonators spotted with water droplets of varying volume on the top surface. Three different cases were compared: (i) bare silicon resonators, (ii) parylene C coated resonators and (iii) hydrophobic self assembled monolayer coated resonators. Experimentally derived variations in quality factor are compared with those obtained analytically for the electrostatically driven square extensional mode resonator. The measured quality factors showed a good agreement with the models

Enhanced transduction methods for electrostatically driven MEMS resonators

Electrically addressed silicon bulk acoustic wave microresonators offer high Q solutions for applications in sensing and signal processing. However, the electrically transduced motional signal is often swamped by parasitic feedthrough in hybrid technologies. With the aim of enhancing the ratio of the motional to feedthrough current at nominal operating voltages, this paper benchmarks a variety of drive and detection principles for electrostatically driven square-extensional mode resonators operating in air and in a foundry MEMS process utilizing 2 µm gaps. A new detection technique, combining second harmonic capacitive actuation and piezoresistive detection, outperforms previously reported methods utilizing voltages as low as plusmn 3 V in air providing a promising solution for low voltage CMOS-MEMS integration

Recruitment Strategies and the Retention of Obese Urban Racial/Ethnic Minority Adolescents in Clinical Trials: The FIT Families Project, Michigan, 2010–2014

Introduction The successful recruitment and retention of participants is integral to the translation of research findings. We examined the recruitment and retention rates of racial/ethnic minority adolescents at a center involved in the National Institutes of Health Obesity Research for Behavioral Intervention Trials (ORBIT) initiative by the 3 recruitment strategies used: clinic, informatics, and community. Methods During the 9-month study, 186 family dyads, each composed of an obese African American adolescent and a caregiver, enrolled in a 6-month weight-loss intervention, a sequential multiple assignment randomized trial. We compared recruitment and retention rates by recruitment strategy and examined whether recruitment strategy was related to dyad baseline characteristics. Results Of the 186 enrolled families, 110 (59.1%) were recruited through clinics, 53 (28.5%) through informatics, and 23 (12.4%) through community. Of those recruited through community, 40.4% enrolled in the study, compared with 32.7% through clinics and 8.2% through informatics. Active refusal rate was 3%. Of the 1,036 families identified for the study, 402 passively refused to participate: 290 (45.1%) identified through informatics, 17 (29.8%) through community, and 95 (28.3%) through clinics. Recruitment strategy was not related to the age of the adolescent, adolescent comorbidities, body mass index of the adolescent or caregiver, income or education of the caregiver, or retention rates at 3 months, 7 months, or 9 months. Study retention rate was 87.8%. Conclusion Using multiple recruitment strategies is beneficial when working with racial/ethnic minority adolescents, and each strategy can yield good retention. Research affiliated with health care systems would benefit from the continued specification, refinement, and dissemination of these strategies

Assessment of density functional approximations for the hemibonded structure of water dimer radical cation

Due to the severe self-interaction errors associated with some density functional approximations, conventional density functionals often fail to dissociate the hemibonded structure of water dimer radical cation (H2O)2+ into the correct fragments: H2O and H2O+. Consequently, the binding energy of the hemibonded structure (H2O)2+ is not well-defined. For a comprehensive comparison of different functionals for this system, we propose three criteria: (i) The binding energies, (ii) the relative energies between the conformers of the water dimer radical cation, and (iii) the dissociation curves predicted by different functionals. The long-range corrected (LC) double-hybrid functional, omegaB97X-2(LP) [J.-D. Chai and M. Head-Gordon, J. Chem. Phys., 2009, 131, 174105.], is shown to perform reasonably well based on these three criteria. Reasons that LC hybrid functionals generally work better than conventional density functionals for hemibonded systems are also explained in this work.Comment: 10 pages, 5 figures, 4 table

Computational modeling to elucidate molecular mechanisms of epigenetic memory

How do mammalian cells that share the same genome exist in notably distinct phenotypes, exhibiting differences in morphology, gene expression patterns, and epigenetic chromatin statuses? Furthermore how do cells of different phenotypes differentiate reproducibly from a single fertilized egg? These are fundamental problems in developmental biology. Epigenetic histone modifications play an important role in the maintenance of different cell phenotypes. The exact molecular mechanism for inheritance of the modification patterns over cell generations remains elusive. The complexity comes partly from the number of molecular species and the broad time scales involved. In recent years mathematical modeling has made significant contributions on elucidating the molecular mechanisms of DNA methylation and histone covalent modification inheritance. We will pedagogically introduce the typical procedure and some technical details of performing a mathematical modeling study, and discuss future developments.Comment: 36 pages, 4 figures, 2 tables, book chapte