Partially coherent tunneling through a series of barriers: Inelastic scattering versus pure dephasing

Within the Buttiker dephasing model, the backscattering in the dephasing process is eliminated by setting a proper boundary condition. Explicit expression is carried out for the effective total tunneling probability in the presence of multiple pure dephasing scatterers with partial coherence. The derived formula is illustrated analytically by various limiting cases, and numerically for its application in tunneling through multibarrier systems.

Transport property in narrow barrier GaAs/AlAs superlattice under hydrostatic pressure

The current-voltage (I-V) characteristics of a doped weakly coupled GaAs/AlAs superlattice (SL) with narrow barriers are measured under hydrostatic pressure from 1 bar to 13.5 kbar at both 77 and 300 K. The experimental results show that, contrary to the results in SL with wide barriers, the plateau in the I-V curve at 77 K does not shrink with increasing pressure, and becomes wider after 10.5 kbar. It is explained by the fact that the E-Gamma 1-E-Gamma 1 resonance peak is higher than the E-Gamma 1-E-X1 resonance peak. At 300 K, however, because of the more important contribution of the nonresonant component to the current, the plateau shrinks with increasing pressure. (C) 1999 American Institute of Physics. [S0021-8979(99)02008-3].

Transport in the middle atmosphere

An overview is provided of the current understanding of transport in the middle atmosphere. Over the past quarter century this subject has evolved from a basic recognition of the Brewer-Dobson circulation to a detailed appreciation of many key features of transport such as the stratospheric surf zone, mixing barriers and the dynamics of filamentation. Whilst the elegant theoretical framework for middle atmosphere transport that emerged roughly twenty years ago never fulfilled its promise, useful phenomenological models have been developed together with innovative diagnostic methods. These advances were made possible by the advent of plenty of satellite and aircraft observations of long-lived chemical species together with developments in data assimilation and numerical modeling, and have been driven in large measure by the problem of stratospheric ozone depletion. This review is primarily focused on the stratosphere, where both the interest and the knowledge are the greatest, but a few remarks are also made on the mesosphere.

Localization of deep water formation: role of atmospheric moisture transport and geometrical constraints on ocean circulation

A series of coupled atmosphere–ocean–ice aquaplanet experiments is described in which topological constraints on ocean circulation are introduced to study the role of ocean circulation on the mean climate of the coupled system. It is imagined that the earth is completely covered by an ocean of uniform depth except for the presence or absence of narrow barriers that extend from the bottom of the ocean to the sea surface. The following four configurations are described: Aqua (no land), Ridge (one barrier extends from pole to pole), Drake (one barrier extends from the North Pole to 35°S), and DDrake (two such barriers are set 90° apart and join at the North Pole, separating the ocean into a large basin and a small basin, connected to the south). On moving from Aqua to Ridge to Drake to DDrake, the energy transports in the equilibrium solutions become increasingly “realistic,” culminating in DDrake, which has an uncanny resemblance to the present climate. Remarkably, the zonal-average climates of Drake and DDrake are strikingly similar, exhibiting almost identical heat and freshwater transports, and meridional overturning circulations. However, Drake and DDrake differ dramatically in their regional climates. The small and large basins of DDrake exhibit distinctive Atlantic-like and Pacific-like characteristics, respectively: the small basin is warmer, saltier, and denser at the surface than the large basin, and is the main site of deep water formation with a deep overturning circulation and strong northward ocean heat transport. A sensitivity experiment with DDrake demonstrates that the salinity contrast between the two basins, and hence the localization of deep convection, results from a deficit of precipitation, rather than an excess of evaporation, over the small basin. It is argued that the width of the small basin relative to the zonal fetch of atmospheric precipitation is the key to understanding this salinity contrast. Finally, it is argued that many gross features of the present climate are consequences of two topological asymmetries that have profound effects on ocean circulation: a meridional asymmetry (circumpolar flow in the Southern Hemisphere; blocked flow in the Northern Hemisphere) and a zonal asymmetry (a small basin and a large basin).

Exploring the barriers and enablers to attendance at rural cardiac rehabilitation programs

Objective: The objectives of this study were to: (i) identify local barriers and enablers to the uptake of hospital-based cardiac rehabilitation (CR) programs, and (ii) identify preferred alternatives for the delivery of CR.

Design: A questionnaire administered by local CR coordinators and focus groups facilitated by the research team.

Setting: Six regional hospitals in south-west Victoria offering hospital-based CR programs.

Participants: Patients and their carers referred to and eligible for local CR programs; health professionals working within local CR programs.

Main outcomes measures: CR attendees and decliners demographics, patient and health professional perceived factors which contribute to enabling hospital-based CR attendance, patient and health professional perceived barriers to CR attendance, and receptiveness and preferences for alternative modes of CR delivery.

Results: This study identified distance to travel to hospital-based CR programs the only statistically significant factor in determining uptake of CR. Easy access to transport (63%) and to a lesser extent family support (49%) and work flexibility (43%) were the primary enablers to attendance. Of the 97 study participants, 38% were receptive to alternative CR methods such as programs in outlying communities, evening facility-based programs, home and GP based programs, telephone support and a patient manual/workbook.

Conclusions: The results of this study provide valuable information for designing strategies to increase utilisation and improve patient acceptability of existing hospital-based CR programs. It provides a basis for pilot testing alternative modes of CR program delivery for cardiac patients in rural areas unable to access hospital-based CR.

Motivational readiness for active commuting by university students : incentives and barriers

Issue addressed: Walking for transport can contribute significantly to health enhancing physical activity. We examined the associations of stages of motivational readiness for active transport with perceived barriers and incentives to walking to and from university among students. Methods: Mail-back surveys were completed by 781 students in a regional university in southeast Queensland. They identified one of eight options on motivational readiness for active commuting, which were then classified as: pre-contemplation; contemplation-preparation; or, action-maintenance. Open-ended questions were used to identify relevant barriers and incentives. Logistic regressions were used to examine the barriers and incentives that distinguished between those at different stages of motivational readiness. Results: Barriers most frequently reported were long travel distances, inconvenience and time constraints. Incentives most frequently reported were shorter travel distance, having more time, supportive infrastructure and better security. Those not considering active commuting (pre-contemplation) were significantly more likely to report shorter travel distance as an incentive compared to those in contemplation-preparation. Those in contemplation-preparation were significantly more likely to report lack of motivation, inadequate infrastructure, shorter travel distance and inconvenience as barriers; and, having more time, supportive infrastructure, social support and incentive programs as encouragement. Conclusions: Different barriers and incentives to walking to or from university exist for students in the different stages of motivational readiness for active commuting. Interventions targeted specifically to stage of motivational readiness may be potentially helpful in increasing activity levels, through active transport.

Getting the complete picture : combining parental and child data to identify the barriers to social inclusion for children living in low socio-economic areas

Background: Childhood mental health problems are prevalent in Australian children (14–20%). Social exclusion is a risk factor for mental health problems, whereas being socially included can have protective effects. This study aims to identify the barriers to social inclusion for children aged 9–12 years living in low socio-economic status (SES) areas, using both child-report and parent-report interviews.

Methods: Australian-born English-speaking parents and children aged 9–12 years were sampled from a low SES area to participate in semi-structured interviews. Parents and children were asked questions around three prominent themes of social exclusion; exclusion from school, social activities and social networks.

Results: Many children experienced social exclusion at school, from social activities or within social networks. Overall, nine key barriers to social inclusion were identified through parent and child interviews, such as inability to attend school camps and participate in school activities, bullying and being left out, time and transport constraints, financial constraints and safety and traffic concerns. Parents and children often identified different barriers.

Discussion: There are several barriers to social inclusion for children living in low SES communities, many of which can be used to facilitate mental health promotion programmes. Given that parents and children may report different barriers, it is important to seek both perspectives.

Conclusion: This study strengthens the evidence base for the investments and action required to bring about the conditions for social inclusion for children living in low SES communities.

Barriers experienced by Asians in accessing injury-related services and compensations

Introduction: The Accident Compensation Corporation (ACC) administers New Zealand’s (NZ) accident compensation scheme. Asians in NZ are apparently under-serviced by ACC and may be experiencing barriers to accessing services. This study identifies barriers that Asians in NZ face in accessing ACC’s injury-related services and compensations.

Methods: By utilising a qualitative research design, 113 Chinese, Korean, Indian, and South East Asian participants residing in Auckland, NZ were recruited through maximum variation and purposive snowball sampling. Data were gathered during 2006 through 22 individual in-depth interviews and 14 focus group discussions based on semi-structured interview schedules. Interviewees included Asian general practitioners, traditional health providers, users and non-users of injury-related services, case managers and Asian community leaders. Data were analysed using a general inductive approach.

Findings: Results show that personal/cultural characteristics such as age, gender, English language competence, injury-related language competence, differing Asian worldviews, and consequent help-seeking behaviours act as barriers to accessing services and entitlements. This is exacerbated by logistical and environmental factors such as cost, transport, time, inadequate interpretation and translation services, as well as institutional barriers such as lack of information about services, culturally inappropriate services, discriminatory attitudes and employment risks.

Conclusion: It is evident that Asians living in NZ are experiencing several cultural, environmental and institutional barriers to accessing ACC services. There is clearly a need for more culturally relevant information and injury-related services if Asian immigrants’ use of such services and entitlements is to be increased.

Promoting active transport to school : evaluation of the Ride2School program

This study involved an evaluation of the Ride2School program, promoting active transport to school. The study found inconsistent evidence of a program impact, and identified the importance of addressing barriers to active transport among individual schools, parents and students; and building the capacity of schools to implement active transport initiatives.

Regulation to create environments conducive to physical activity : understanding the barriers and facilitators at the Australian State Government level

Introduction Policy and regulatory interventions aimed at creating environments more conducive to physical activity (PA) are an important component of strategies to improve population levels of PA. However, many potentially effective policies are not being broadly implemented. This study sought to identify potential policy/regulatory interventions targeting PA environments, and barriers/facilitators to their implementation at the Australian state/territory government level.

Methods In-depth interviews were conducted with senior representatives from state/territory governments, statutory authorities and non-government organisations (n = 40) to examine participants': 1) suggestions for regulatory interventions to create environments more conducive to PA; 2) support for preselected regulatory interventions derived from a literature review. Thematic and constant comparative analyses were conducted.

Results Policy interventions most commonly suggested by participants fell into two areas: 1) urban planning and provision of infrastructure to promote active travel; 2) discouraging the use of private motorised vehicles. Of the eleven preselected interventions presented to participants, interventions relating to walkability/cycling and PA facilities received greatest support. Interventions involving subsidisation (of public transport, PA-equipment) and the provision of more public transport infrastructure received least support. These were perceived as not economically viable or unlikely to increase PA levels. Dominant barriers were: the powerful ‘road lobby’, weaknesses in the planning system and the cost of potential interventions. Facilitators were: the provision of evidence, collaboration across sectors, and synergies with climate change/environment agendas.

Conclusion This study points to how difficult it will be to achieve policy change when there is a powerful ‘road lobby’ and government investment prioritises road infrastructure over PA-promoting infrastructure. It highlights the pivotal role of the planning and transport sectors in implementing PA-promoting policy, however suggests the need for clearer guidelines and responsibilities for state and local government levels in these areas. Health outcomes need to be given more direct consideration and greater priority within non-health sectors.

Patterns and perceptions of physical activity and sedentary time in male transport drivers working in regional Australia

 Abstract

Objective: To objectively measure physical activity (PA) patterns and sedentary time, and explore perceptions of workplace PA opportunities in regional male transport workers.

Methods: A multi-method study involving 28 drivers (52.4±9.69years) working at a bus company in South-East Queensland, Australia. PA was measured using accelerometers (n=23) to determine the proportion of time spent in sedentary (<150 cpm), light (151–2,689 cpm) and moderate+ (≥2,690 cpm) intensity categories. Paired sample t-tests were used to evaluate differences between categories on a workday/off-workday (n=16), and during work/non-work time (n=15). Interviews were conducted with 28 drivers and six managers to explore perceptions and ideas relating to workplace PA opportunities.

Results: Sedentary time was significantly higher on off-work (64% of wear time) than work (52%) days (p<0.05), while the opposite was the case for light intensity time (off-workday=33%; workday=44%; p<0.05). On workdays, sedentary time was significantly lower when employees were working (44%) than when not working (60%; p<0.05). No significant differences were found for time spent in moderate+ PA. Driver perceptions indicated that PA opportunities (walking club and corporate gym membership) were being adopted by some drivers. However, at this depot, perceived health issues and organisational barriers (shift work and irregular driving routines), tended to preclude some drivers from engaging with these opportunities.

Conclusions: Findings contest the notion that a sedentary occupation such as driving necessitates an inactive work environment.

Implications: This research informs ongoing intervention efforts to target inactive drivers who are struggling to take advantage of existing workplace-related PA opportunities.

Congestion pricing and active transport - evidence from five opportunities for natural experiment

Congestion pricing schemes have been implemented in cities worldwide as a means of addressing externalities associated with inefficient price signals in transport systems. Limited evidence exists however on the secondary impacts of these schemes, which may include both environmental and health benefits associated with a resultant reduction in motor vehicle usage. There is increasing recognition that transport behaviours may play a role as opportunistic population level targets to reduce physical inactivity. Yet limited evidence currently exists on the effectiveness of transport interventions, such as congestion pricing schemes, for improving physical activity levels.This study aims to examine the physical activity effects of congestion pricing, with the health benefits of physical activity well established. Congestion pricing schemes implemented internationally were considered as 'natural experiments' and evidence of modal shift from vehicle to active forms of transport or physical activity effect was reviewed. Twelve studies were included from a search of peer-reviewed and 'grey' literature, with overall evidence for a physical activity or modal shift effect considered weak. The quality of the available evidence was also considered to be low.This is not to say that congestion pricing schemes may not have important secondary physical activity related health benefits. Instead, this review highlights the paucity of evidence that has been collected from real-world implementation of congestion pricing schemes. Given the growing recognition of the importance of distal mediators and determinants of health and the need for an 'all-of-government' approach more and better quality evidence of effectiveness of transport interventions for a broad range of outcomes, including health, is required. Significant barriers to the collection of such evidence exist, with strategies for overcoming some of these barriers identified. Only with a better understanding of the full range of potential health impacts can transport policy be fully utilised as a tool for population health.

Essays on the general equilibrium effects of barriers to trade on economic growth, foreign trade and the location of economic activity in Brazil

This work presents a fully operational interstate CGE model implemented for the Brazilian economy that tries to quantify both the role of barriers to trade on economic growth and foreign trade performance and how the distribution of the economic activity may change as the country opens up to foreign trade. Among the distinctive features embedded in the model, modeling of external scale economies, port efficiency and land-maritime transport costs provides an innovative way of dealing explicitly with theoretical issues related to integrated regional systems. In order to illustrate the role played by the quality of infrastructure and geography on the country‟s foreign and interregional trade performance, a set of simulations is presented where barriers to trade are significantly reduced. The relative importance of trade policy, port efficiency and land-maritime transport costs for the country trade relations and regional growth is then detailed and quantified, considering both short run as well as long run scenarios. A final set of simulations shed some light on the effects of liberal trade policies on regional inequality, where the manufacturing sector in the state of São Paulo, taken as the core of industrial activity in the country, is subjected to different levels of external economies of scale. Short-run core-periphery effects are then traced out suggesting the prevalence of agglomeration forces over diversion forces could rather exacerbate regional inequality as import barriers are removed up to a certain level. Further removals can reverse this balance in favor of diversion forces, implying de-concentration of economic activity. In the long run, factor mobility allows a better characterization of the balance between agglomeration and diversion forces among regions. Regional dispersion effects are then clearly traced-out, suggesting horizontal liberal trade policies to benefit both the poorest regions in the country as well as the state of São Paulo. This long run dispersion pattern, on one hand seems to unravel the fragility of simple theoretical results from recent New Economic Geography models, once they get confronted with more complex spatially heterogeneous (real) systems. On the other hand, it seems to capture the literature‟s main insight: the possible role of horizontal liberal trade policies as diversion forces leading to a more homogeneous pattern of interregional economic growth.

Effect of robust torus on the dynamical transport

In the present work, we quantify the fraction of trajectories that reach a specific region of the phase space when we vary a control parameter using two symplectic maps: one non-twist and another one twist. The two maps were studied with and without a robust torus. We compare the obtained patterns and we identify the effect of the robust torus on the dynamical transport. We show that the effect of meandering-like barriers loses importance in blocking the radial transport when the robust torus is present.

Physical inactivity and related barriers: A study in a community dwelling of older brazilians

This study sought to investigate the prevalence of physical inactivity and related barriers in older Brazilian adults. A cross-sectional, population-based study was conducted, and a stratified random sampling procedure was used. A total of 359 older adults were interviewed. The long version of the International Physical Activity Questionnaire (IPAQ) and the Questionnaire of Barriers to Physical Activity Practice were used to assess physical activity level and barriers, respectively. No statistically significant difference was observed on the prevalence of physical inactivity in either gender or age groups. Regarding barriers, the proportion of 9 out of 22 barriers was statistically significant between men and women. Self-reported physical inactivity/activity in older Brazilian adults continues to be a concern. Uncommonly, older males reported a higher prevalence of physical inactivity compared to their counterparts. Additionally, physical inactivity prevalence continued to increase with the aging process. Yet, personal barriers such as lack of time and poor health were strongly associated with physical inactivity. The results of this study may help health professionals and public policy makers to better address the issues related to a healthy lifestyle among older adults and promote physical activity among Brazilian older adults and in other countries with similar characteristics. © 2012 Sebastião Gobbi et al.