Compatible finite element methods for numerical weather prediction

This article takes the form of a tutorial on the use of a particular class of mixed finite element methods, which can be thought of as the finite element extension of the C-grid staggered finite difference method. The class is often referred to as compatible finite elements, mimetic finite elements, discrete differential forms or finite element exterior calculus. We provide an elementary introduction in the case of the one-dimensional wave equation, before summarising recent results in applications to the rotating shallow water equations on the sphere, before taking an outlook towards applications in three-dimensional compressible dynamical cores.Comment: To appear in ECMWF Seminar proceedings 201

How Do Firms Exercise Unilateral Market Power? Evidence from a Bid-Based Wholesale Electricity Market

This paper uses the framework in Wolak (2003a,b and 2007) and data on half-hourly offer curves and market-clearing prices and quantities from the New Zealand wholesale electricity market over the period January 1, 2001 to June 30, 2007 to characterize how the four large suppliers in this imperfectly competitive industry exercise market power. To accomplish this we introduce half-hourly measures of the firm-level ability and incentive of an individual supplier to exercise unilateral market power that are derived from a simplified model of expected profit-maximizing offer behaviour in a multi-unit auction market. We then show that half-hourly market-clearing prices are highly correlated with the half-hourly values of the firm-level and firm-average measures of both the ability and incentive of the four large suppliers in New Zealand to exercise market power. We then present evidence consistent with the view that this increasing relationship between the ability or incentive of individual suppliers to exercise market power and higher market-clearing prices is caused by the four large suppliers submitting higher offer prices when they have a greater ability or incentive to exercise unilateral market power. We show that after controlling for changes in input fossil fuel prices and other factors that impact the opportunity cost of producing electricity during that half hour, each of the four suppliers submits a higher offer price into the wholesale market when it has a greater ability or incentive to exercise unilateral market power. To strengthen the case that this increasing relationship between market prices and the ability and incentive of each of the suppliers to exercise unilateral market power is actually caused by the four large suppliers exercising unilateral market power by changing their offer prices in response to their ability and incentive to exercise market power, we also perform a test of the implications of the null hypothesis that the four large suppliers behave as if they had no ability to exercise market power. We find strong evidence against this null hypothesis and instead find that these hypothesis testing results are consistent with the perspective that these suppliers are exercising all available unilateral market power.Classification-JEL:Unilateral Market power analysis,New Zealand,Electricity Market,multi-unit auction

Giant Electron-hole Charging Energy Asymmetry in Ultra-short Carbon Nanotubes

Making full usage of bipolar transport in single-wall carbon nanotube (SWCNT) transistors could permit the development of two-in-one quantum devices with ultra-short channels. We report on clean $\sim$10 to 100 nm long suspended SWCNT transistors which display a large electron-hole transport asymmetry. The devices consist of naked SWCNT channels contacted with sections of SWCNT-under-annealed-gold. The annealed gold acts as an n-doping top gate which creates nm-sharp barriers at the junctions between the contacts and naked channel. These tunnel barriers define a single quantum dot (QD) whose charging energies to add an electron or a hole are vastly different ($e-h$ charging energy asymmetry). We parameterize the $e-h$ transport asymmetry by the ratio of the hole and electron charging energies $\eta_{e-h}$. We show that this asymmetry is maximized for short channels and small band gap SWCNTs. In a small band gap SWCNT device, we demonstrate the fabrication of a two-in-one quantum device acting as a QD for holes, and a much longer quantum bus for electrons. In a 14 nm long channel, $\eta_{e-h}$ reaches up to 2.6 for a device with a band gap of 270 meV. This strong $e-h$ transport asymmetry survives even at room temperature

Carbohydrate-electrolyte drink ingestion and skill performance in tennis

ABSTRACT Aim: To examine the effect of ingesting a carbohydrate-electrolyte drink (CHO-E) compared to a flavoured matched placebo electrolyte drink (PL) on maintenance of skill and performance over 2 hours of indoor tennis match play. Method: Twenty-two nationally ranked tennis players (15 male, 7 female; mean (SD) height 177 (8) cm, weight 69.2 (9.5) kg) reported to the test centre on four separate occasions, with the first two visits for screening and familiarisation. The final two visits were main trials and participants attended the lab 3 hours post-prandial for baseline nude body mass and blood sample collection. They then performed a standardised warm-up and pre-match skill test, a 2 hour tennis match with ingestion of either CHO-E (Lucozade Sport, GlaxoSmithKline Nutritional Healthcare) or PL beverage administered as a bolus volume (5ml/kg) prior to warm-up, and subsequent volumes (3 ml/kg) every 20 minutes. A final post-match skill test was performed and nude body mass recorded. During the trials, participant’s heart rate and movement intensity were monitored, and the match was recorded using a video camera for later match analysis. Results: There was no difference in environmental conditions or hydration status measures between trials and no difference in skill test scores pre and post-match or between trials at each of these times. Participants on the CHO-E trial had elevated blood glucose concentration throughout the match and also reported feeling more energetic (general activation) and more tense (high activation) one hour into the match compared to baseline, which was not observed in the placebo trial (time x trial interaction p<0.05). In addition, accelerometer data showed participants on the CHO-E trial spent more time in moderate intensity activity and less time in low intensity activity than on PL. Match analysis data revealed that ingestion of the CHO-E beverage significantly increased overall percentage of successful serves (mean ± SD = 68 ± 7% for CHO-E compared to 66 ± 7% for PL; p<0.05), in particular first serves (65 ± 9% for CHO-E, 61 ± 7% for PL; p<0.01) and serves to the advantage side (70 ± 9% for CHO-E, 66 ± 7% for PL; p<0.05) over the duration of the whole match. Furthermore, a significant increase in return success rates was observed during the second set of the match (p<0.05) on the CHO-E trial. However, performance improvements on the serve and return were found not to be associated with the increase in blood glucose nor player ability. Conclusions: CHO-E drink ingestion during a tennis match can contribute towards maintaining performance by increasing overall percentage of successful serves and increasing return success rates. These changes may be linked to increased perceived activation, and increased intensity of movement sustained on court. However, the improvements in serve and return success rates are not associated with player ability or glucose elevation, but may reflect a more generic central brain mediated effect of carbohydrate ingestion on skill. This work was supported by GlaxoSmithKline Nutritional Healthcare

Child Abuse: Signs, Symptoms, and the Role of the School Counselor

Victims of abuse experience trauma which affects their academic and social/emotional well being. The purpose of this paper is to examine the prevalence of abuse, to be able to identify signs and symptoms of abuse, and to explore the school counselor’s role ethically in reporting suspected child abuse in addition to their role in providing direct and indirect services to students. Common perpetrators of abuse and physical, emotional/behavioral, and academic warning signs will be discussed. Lastly, school counselors’ ethical responsibilities to respond to child abuse, the importance of confidentiality and informed consent/mandated reporting, how to report to Child Protective Services (CPS), and how to provide various direct and indirect services to meet the needs of all students will be addressed