Web assisted teaching: an undergraduate experience

The emergence of the Internet has created a number of claims as to the future of education and the possibility of dramatically changing the way in which education is delivered. Much of the attention has focussed on the adoption of teaching methods that are solely web-based. We set out to incorporate web-based teaching as support for more traditional teaching methods to improve the learning outcomes for students. This first step into web-based teaching was developed to harness the benefits of web-based teaching tools without supplanting traditional teaching methods. The aim of this paper is to report our experience with web-assisted teaching in two undergraduate courses, Accounting Information Systems and Management Accounting Services, during 2000. The paper evaluates the approach taken and proposes a tentative framework for developing future web-assisted teaching applications. We believe that web-assisted and web-based teaching are inevitable outcomes of the telecommunications and computer revolution and that academics cannot afford to become isolated from the on-line world. A considered approach is needed to ensure the integration of web-based features into the overall structure of a course. The components of the course material and the learning experiences students are exposed to need to be structured and delivered in a way that ensures they support student learning rather than replacing one form of learning with another. Therefore a careful consideration of the structure, content, level of detail and time of delivery needs to be integrated to create a course structure that provides a range of student learning experiences that are complimentary rather than competing. The feedback was positive from both extramural (distance) and internal students, demonstrating to us that web sites can be used as an effective teaching tool in support of more traditional teaching methods as well as a tool for distance education. The ability to harness the positives of the web in conjunction with more traditional teaching modes is one that should not be overlooked in the move to adopt web based instruction methods. Web-based teaching need not be seen as an all or nothing divide but can be used as a useful way of improving the range and type of learning experiences open to students. The Web challenges traditional methods and thinking but it also provides tools to develop innovative solutions to both distance and on campus learning. Further research is needed to determine how we can best meet the needs of our students while maintaining high quality learning outcomes

Pair plasma cushions in the hole-boring scenario

Pulses from a 10 PW laser are predicted to produce large numbers of gamma-rays and electron-positron pairs on hitting a solid target. However, a pair plasma, if it accumulates in front of the target, may partially shield it from the pulse. Using stationary, one-dimensional solutions of the two-fluid (electron-positron) and Maxwell equations, including a classical radiation reaction term, we examine this effect in the hole-boring scenario. We find the collective effects of a pair plasma "cushion" substantially reduce the reflectivity, converting the absorbed flux into high-energy gamma-rays. There is also a modest increase in the laser intensity needed to achieve threshold for a non-linear pair cascade.Comment: 17 pages, 5 figures. Accepted for publication in Plasma Physics and Controlled Fusion. Typos corrected, reference update

Analysis and identification of subsynchronous vibration for a high pressure parallel flow centrifugal compressor

The summary of a complete analytical design evaluation of an existing parallel flow compressor is presented and a field vibration problem that manifested itself as a subsynchronous vibration that tracked at approximately 2/3 of compressor speed is reviewed. The comparison of predicted and observed peak response speeds, frequency spectrum content, and the performance of the bearing-seal systems are presented as the events of the field problem are reviewed. Conclusions and recommendations are made as to the degree of accuracy of the analytical techniques used to evaluate the compressor design

Neuromuscular factors contributing to reductions in muscle force after repeated, high-intensity muscular efforts

Fatigue can accumulate sufficiently to limit muscular force production during repeated, forceful muscle contractions, including those that occur in the occupational, clinical and athletic settings. Fatigue during such efforts is likely to result from disturbances to multiple processes in the nervous system and muscle. However, previous research examining the mechanisms underpinning fatigue have typically required subjects to perform low-level constant-force contractions or to repeat maximal efforts in a single set format. Such tasks do not translate well to occupational, daily living or athletic situations where high-intensity, yet submaximal, repeated efforts may be performed in work bouts (or sets) with brief rest periods for recovery. Therefore, the overall aim of the present research was to investigate the neuromuscular mechanisms contributing to force loss after repeated, high-intensity muscular efforts with longer (90 s) periods of rest separating repetitions into sets of contractions. In Experiment 1, 16 resistance trained men performed 6 sets of unilateral isometric plantar flexor contractions of the right leg (3 s contraction/2 s rest) reaching a target level of 85% maximal voluntary contraction (MVC). Sets were separated by a 90-s inter-set rest and completed to failure (i.e. In Experiment 1, a significant reduction in maximum voluntary isometric plantar flexion torque (12.2%; p \u3c 0.001) was observed post-exercise, which did not recover by POST-20. Significant reductions in triceps surae EMG/M (-6%; p = 0.024) and MEP/M amplitude (9%; p = 0.01) were found post-exercise but recovered by POST-10. Cortical silent period (an indicator of GABAB-mediated intracortical inhibition) was reduced (-4%; p = 0.016) post-exercise and did not recover by POST-20. In Experiment 2, temporal changes in torque were similar to Experiment 1. Significant reductions in the evoked torque response from 20 Hz (p \u3c 0.001), 80 Hz (p \u3c 0.001) and VFT (p \u3c 0.001) stimulations were observed at POST and did not recover by POST-20, however no changes in 20:80 and 20:VFT ratios were observed. Finally, significant reductions in both Tvib (-13%; p = 0.035) and Tsust (-25%; p = 0.035) were found post-exercise but recovered by POST-10. The ingestion of caffeine allowed for a greater overall torque production and neural drive (EMG/M) but the lack of condition time interaction effect indicated that it did not clearly affect the time course of fatigue or recovery. Further, no detectable effects were observed compared to the non-caffeine condition in corticospinal excitability, MN excitability or E-C coupling, as shown by the negligible changes in MEP/M amplitude, PIC facilitation, and torque during 20-Hz, 80-Hz and VFT stimulations. These data suggest that corticospinal tract efficiency and PIC-mediated facilitation of the MN pool can be compromised and are likely to account in part for the force loss immediately following an acute bout of repeated, high-intensity muscular efforts performed in sets (with 90 s rest). However, changes in E-C coupling efficiency (i.e. ‘peripheral fatigue) are likely to explain the ongoing, prolonged loss of force, at least to 20 min post-exercise. Therefore, it is likely that both changes in the nervous system as well as the muscle contribute to the loss of force following repeated, high-intensity muscular efforts

Particle acceleration at ultrarelativistic shocks: an eigenfunction method

We extend the eigenfunction method of computing the power-law spectrum of particles accelerated at a relativistic shock fronts to apply to shocks of arbitrarily high Lorentz factor. In agreement with the findings of Monte-Carlo simulations, we find the index of the power-law distribution of accelerated particles which undergo isotropic diffusion in angle at an ultrarelativistic, unmagnetized shock is s=4.23 (where s=-d(ln f)/dp with f the Lorentz invariant phase-space density and p the momentum). This corresponds to a synchrotron index for uncooled electrons of a=0.62 (taking cooling into account a=1.12), where a=-d(ln F)/dn, F is the radiation flux and n the frequency. We also present an approximate analytic expression for the angular distribution of accelerated particles, which displays the effect of particle trapping by the shock: compared with the non-relativistic case the angular distribution is weighted more towards the plane of the shock and away from its normal. We investigate the sensitivity of our results to the transport properties of the particles and the presence of a magnetic field. Shocks in which the ratio of Poynting to kinetic energy flux upstream is not small are less compressive and lead to larger values of $s$.Comment: Minor additions on publicatio

Individual differences in the discrimination of novel speech sounds: effects of sex, temporal processing, musical and cognitive abilities

This study examined whether rapid temporal auditory processing, verbal working memory capacity, non-verbal intelligence, executive functioning, musical ability and prior foreign language experience predicted how well native English speakers (N = 120) discriminated Norwegian tonal and vowel contrasts as well as a non-speech analogue of the tonal contrast and a native vowel contrast presented over noise. Results confirmed a male advantage for temporal and tonal processing, and also revealed that temporal processing was associated with both non-verbal intelligence and speech processing. In contrast, effects of musical ability on non-native speech-sound processing and of inhibitory control on vowel discrimination were not mediated by temporal processing. These results suggest that individual differences in non-native speech-sound processing are to some extent determined by temporal auditory processing ability, in which males perform better, but are also determined by a host of other abilities that are deployed flexibly depending on the characteristics of the target sounds

X-Ray Spectral Variability of Extreme BL Lac AGN H1426+428

Between 7 March 2002 and 15 June 2002, intensive X-ray observations were carried out on the extreme BL Lac object H1426+428 with instruments on board the Rossi X-ray Timing Explorer (RXTE). These instruments provide measurements of H1426+428 in the crucial energy range that characterizes the first peak of its spectral energy distribution. This peak, which is almost certainly due to synchrotron emission, has previously been inferred to be in excess of 100 keV. By taking frequent observations over a four-month campaign, which included $\sim$450 ksec of RXTE time, studies of flux and spectral variability on multiple timescales were performed, along with studies of spectral hysteresis. The 3-24 keV X-ray flux and spectra exhibited significant variability, implying variability in the location of the first peak of the spectral energy distribution. Hysteresis patterns were observed, and their characteristics have been discussed within the context of emission models.Comment: accepted for publication in Astrophysical Journa

Growth rates of the Weibel and tearing mode instabilities in a relativistic pair plasma

We present an algorithm for solving the linear dispersion relation in an inhomogeneous, magnetised, relativistic plasma. The method is a generalisation of a previously reported algorithm that was limited to the homogeneous case. The extension involves projecting the spatial dependence of the perturbations onto a set of basis functions that satisfy the boundary conditions (spectral Galerkin method). To test this algorithm in the homogeneous case, we derive an analytical expression for the growth rate of the Weibel instability for a relativistic Maxwellian distribution and compare it with the numerical results. In the inhomogeneous case, we present solutions of the dispersion relation for the relativistic tearing mode, making no assumption about the thickness of the current sheet, and check the numerical method against the analytical expression.Comment: Accepted by PPC