Short-run performance of recent Australian on-market share buy-back announcements

Share buy-backs (or share repurchases) have become increasingly popular among Australian companies during the recent times. One of the aims of share buy-back is to increase the shareholders' wealth by increasing the market price of company shares. While there are several ways of buying backs shares, on-market buy-backs is the most popular method of share repurchase in Australia. Australian listed companies have announced more than two hundred on-market share buy-backs over the past three years. The aim of this paper is to examine the short-run market performance of these recent on-market buy-back announcements.

Short-term effect of on-market buy-back announcements on the share price is an issue, which is theoretically interesting and practically important. Buy-back announcements are believed to convey a signal to the market (i.e., signalling effect). If the market considers this signal positively, the short-run price of the shares would increase. If the signal were considered negatively, the short-run price of shares would decrease. If there is no signalling content or the signal is neutral the price would remain the same. In this study, signalling effect of share buy-back announcements is empirically examined using most recent Australian data. The total population of on-market buy-back announcements that have been lodged with Australian Stock Exchange by Australian listed companies during the period from 1 January 2000 to 10 March 2003 are included in this study. The abnormal market return over the short-run (announcement day and 10 trading days centred on the announcement date) is examined using the All Ordinaries Accumulation Index as the reference portfolio. The daily abnormal returns (AR) and cumulative abnormal returns (CAR) during the event period are computed. The results indicate that the Australian market generally positively reacts to on-market buy-back announcements.

Mobility modelling and trajectory prediction for cellular networks with mobile base stations

This paper provides mobility estimation and prediction for a variant of GSM network which resembles an adhoc wireless mobile network where base stations and users are both mobile. We propose using Robust Extended Kalman Filter (REKF)as a location heading altitude estimator of mobile user for next node (mobile-base station)in order to improve the connection reliability and bandwidth efficiency of the underlying system. Through analysis we demonstrate that our algorithm can successfully track the mobile users with less system complexity as it requires either one or two closest mobile-basestation measurements. Further, the technique is robust against system uncertainties due to inherent deterministic nature in the mobility model. Through simulation, we show the accuracy and simplicity in implementation of our prediction algorithm.

Robust extended kalman filter applied to location tracking and trajectory prediction for PCS networks

Provisioning of real-time multimedia sessions over wireless cellular network poses unique challenges due to frequent handoff and rerouting of a connection. For this reason, the wireless networks with cellular architecture require efficient user mobility estimation and prediction. This paper proposes using robust extended Kalman filter (REKF) as a location heading altitude estimator of mobile user for next cell prediction in order to improve the connection reliability and bandwidth efficiency of the underlying system. Through analysis we demonstrate that our algorithm reduces the system complexity (compared to existing approach using pattern matching and Kalman filter) as it requires only two base station measurements or only the measurement from the closest base station. Further, the technique is robust against system uncertainties due to inherent deterministic nature in the mobility model and more effective in comparison with the standard Kalman filter.

2001 Volvo Award winner in clinical studies : effects of a media campaign on back pain beliefs and its potential influence on management of low back pain in general practice

Study Design. Quasi-experimental, nonrandomized, nonequivalent, parallel group-controlled study involving before and after telephone surveys of the general population and postal surveys of general practitioners was conducted, with an adjacent state used as a control group.


Objectives. To evaluate the effectiveness of a population-based intervention designed to alter beliefs about back pain, influence medical management, and reduce disability and workers’ compensation–related costs.


Summary of Background Data. A multimedia campaign begun during 1997 in Victoria, Australia, positively advised patients with back pain to stay active and exercise, not to rest for prolonged periods, and to remain at work.


Methods. The campaign’s impact on population beliefs about back pain and fear-avoidance beliefs was measured in telephone surveys, and the effect of the campaign on the potential management of low back pain by general practitioners was assessed by eliciting their likely approach to two hypothetical scenarios in mailed surveys. Demographically identical population groups in Victoria and the control state, New South Wales, were surveyed at three times: before, during, and after intervention in Victoria.


Results. The studies were completed by 4730 individuals in the general population and 2556 general practitioners. There were large statistically significant improvements in back pain beliefs over time in Victoria (mean scores on the Back Beliefs Questionnaire, 26.5, 28.4, and 29.7), but not in New South Wales (26.3, 26.2, and 26.3, respectively). Among those who reported back pain during the previous year, fear-avoidance beliefs about physical activity improved significantly in Victoria (mean scores on the Fear-Avoidance Beliefs Questionnaire for physical activity, 14, 12.5, and 11.6), but not in New South Wales (13.3, 13.6, and 12.7, respectively). General practitioners in Victoria reported significant improvements over time in beliefs about back pain management, as compared with their interstate colleagues. There were statistically significant interactions between state and time for 7 of 10 responses on management of acute low back pain, and for 6 of 10 responses on management of subacute low back pain.


Conclusion. A population-based strategy of providing positive messages about back pain improves the beliefs of the general population and general practitioners about back pain and appears to influence medical management.

Emotional growth: helping children and families 'bounce back'

Background: Depression is becoming increasingly prevalent in young people and is occurring earlier. General practitioners are prescribing antidepressants more frequently for this group, yet they are usually not the answer to the problem. Objective: This article examines the increase in prevalence rates of childhood and adolescent depression. We draw on recent research into resilience and positive psychology to suggest guidelines for the GP in helping young people and their parents develop better coping skills in the short term, and greater resilience in the long term. Discussion: Resilience is the ability to bounce back after encountering difficulties, negative events, hard times or adversity and to be able to return to the original level of emotional wellbeing. It is the capacity to maintain a healthy and fulfilling life despite adversity. Young people who have the skills to be resilient have a lower likelihood of becoming depressed or suicidal and a higher likelihood of maintaining emotional wellbeing. Self efficacy, optimistic and helpful thinking, and maintaining a success orientation are all important skills in being resilient.