A theoretical study of the structural phases of Group 5B - 6B metals and their transport properties

In order to predict the stable and metastable phases of the bcc metals in the block of the Periodic Table defined by groups 5B to 6B and periods 4 to 6, as well as the structure dependence of their transport properties, we have performed full potential computations of the total energies per unit cell as a function of the c/a ratio at constant experimental volume. In all cases, a metastable body centered tetragonal (bct) phase was predicted from the calculations. The total energy differences between the calculated stable and metastable phases ranged from 0.09 eV/cell (vanadium) to 0.39 eV/cell (tungsten). The trends in resistivity as a function of structure and atomic number are discussed in terms of a model of electron transport in metals. Theoretical calculations of the electrical resistivity and other transport properties show that bct phases derived from group 5B elements are more conductive than the corresponding bcc phases, while bct phases formed from group 6B elements are less conductive than the corresponding bcc phases. Special attention is paid to the phases of tantalum where we show that the frequently observed beta phase is not a simple tetragonal distortion of bcc tantalum

Olympic legacy and cultural tourism: Exploring the facets of Athens' Olympic heritage

This study examines the effects of the Olympic Games on Athens’ cultural tourism and the city’s potential to leverage the Olympic legacy in synergy with its rich heritage in order to enhance its tourism product during the post-Games period. In doing so, a qualitative and interpretive approach was employed. This includes a literature review on Athens’ 2004 Olympics to identify the sport facilities and regeneration projects, which constitute the Olympic legacy and heritage. Based on that, an empirical analysis was undertaken, by collecting official documents about the 2004 Olympics, and conducting five semi-structured interviews with tourism/administrative officials. The findings indicate that the Olympiad contributed significantly to Athens’ built and human heritage, revealing the dimensions of new venues/facilities, infrastructure, transportation and aesthetic image of the city, and human capital enhancement. Hence, the Games affected to the multifaceted representation and reconstruction of the city’s identity and cultural heritage. However, the potential afforded from the post-Olympic Athens remains unrealised due to lack of strategic planning/management. The study concludes that there is a need to develop cross-leveraging synergies between the Olympic legacy and cultural tourism for the host city. Finally, a strategic planning framework for leveraging post-Games Olympic tourism is suggested in order to maximise the benefits of Olympic legacy and heritage in a host city’s tourism development

Testing fluvial erosion models using the transient response of bedrock rivers to tectonic forcing in the Apennines, Italy

The transient response of bedrock rivers to a drop in base level can be used to discriminate between competing fluvial erosion models. However, some recent studies of bedrock erosion conclude that transient river long profiles can be approximately characterized by a transport‐limited erosion model, while other authors suggest that a detachment‐limited model best explains their field data. The difference is thought to be due to the relative volume of sediment being fluxed through the fluvial system. Using a pragmatic approach, we address this debate by testing the ability of end‐member fluvial erosion models to reproduce the well‐documented evolution of three catchments in the central Apennines (Italy) which have been perturbed to various extents by an independently constrained increase in relative uplift rate. The transport‐limited model is unable to account for the catchments’response to the increase in uplift rate, consistent with the observed low rates of sediment supply to the channels. Instead, a detachment‐limited model with a threshold corresponding to the field‐derived median grain size of the sediment plus a slope‐dependent channel width satisfactorily reproduces the overall convex long profiles along the studied rivers. Importantly, we find that the prefactor in the hydraulic scaling relationship is uplift dependent, leading to landscapes responding faster the higher the uplift rate, consistent with field observations. We conclude that a slope‐ dependent channel width and an entrainment/erosion threshold are necessary ingredients when modeling landscape evolution or mapping the distribution of fluvial erosion rates in areas where the rate of sediment supply to channels is low

For the benefit of all? Developing a critical perspective in mega-event leverage

The purpose of this article is to bring to light the need for developing a critical leveraging perspective on mega-events and propose a research agenda that extends the focus of the leverage concept towards this direction. Current research on leverage focuses on the attainment and magnification of mega-event outcomes. A critical lens of inquiry however is needed to move forward and take into account the influence of power structures and social-ordering processes on developing and implementing strategic leveraging programs. Such a perspective can help examine if and how the benefits of mega-events are fairly delivered to host communities, equally distributed among stakeholders and then sustained, while negative impacts are minimised. Ten research themes are brought forward to help build a robust ground for a critical mega-event leveraging perspective

Prime movers : mechanochemistry of mitotic kinesins

Mitotic spindles are self-organizing protein machines that harness teams of multiple force generators to drive chromosome segregation. Kinesins are key members of these force-generating teams. Different kinesins walk directionally along dynamic microtubules, anchor, crosslink, align and sort microtubules into polarized bundles, and influence microtubule dynamics by interacting with microtubule tips. The mechanochemical mechanisms of these kinesins are specialized to enable each type to make a specific contribution to spindle self-organization and chromosome segregation

Influence of the Tibetan Plateau uplift on the Asian monsoon-arid environment evolution

As one of the most important geological events in Cenozoic era, the uplift of the Tibetan Plateau (TP) has had profound influences on the Asian and global climate and environment evolution. During the past four decades, many scholars from China and abroad have studied climatic and environmental effects of the TP uplift by using a variety of geological records and paleoclimate numerical simulations. The existing research results enrich our understanding of the mechanisms of Asian monsoon changes and interior aridification, but so far there are still a lot of issues that need to be thought deeply and investigated further. This paper attempts to review the research on the influence of the TP uplift on the Asian monsoon-arid environment, summarize three types of numerical simulations including bulk-plateau uplift, phased uplift and sub-regional uplift, and especially to analyze regional differences in responses of climate and environment to different forms of tectonic uplifts. From previous modeling results, the land-sea distribution and the Himalayan uplift may have a large effect in the establishment and development of the South Asian monsoon. However, the formation and evolution of the monsoon in northern East Asia, the intensified dryness north of the TP and enhanced Asian dust cycle may be more closely related to the uplift of the main body, especially the northern part of the TP. In this review, we also discuss relative roles of the TP uplift and other impact factors, origins of the South Asian monsoon and East Asian monsoon, feedback effects and nonlinear responses of climatic and environmental changes to the plateau uplift. Finally, we make comparisons between numerical simulations and geological records, discuss their uncertainties, and highlight some problems worthy of further studying

Millennial slip rates along the eastern Kunlun fault: Implications for the dynamics of intracontinental deformation in Asia

The role of major strike-slip faults in the Indo-Asian collision zone is central to our understanding of the ways in which continental crust and lithosphere deform in response to continental collision. We investigated how slip varies along the eastern segments of the Kunlun fault in northeastern Tibet. Millennial slip rates were determined based on landforms that are offset by the fault and that were dated using a combination of 14 C and cosmogenic radionuclide exposure dating techniques. We developed estimates for slip rates at four new locations along the fault in addition to four previously published sites. All of these sites are located along the eastern 300 km of the fault system, and our results reveal a systematic eastward decrease in slip rate along this portion of the fault since the late Pleistocene. This displacement gradient is consistent with the termination of the Kunlun fault near ~102°E. Coincident variations in fault slip rates and geometry reflect complex kinematics along the fault zone. Although other faults exist in the region, our observations suggest that none of these accomplishes transfer of slip from the primary Kunlun fault system. Instead, we interpret that either the eastern Kunlun fault is relatively young and propagating eastward, or that left-lateral slip is absorbed by interaction of the fault zone with regional rotation of the eastern fault tip. Both of these scenarios contrast with previous interpretations and indicate that the Kunlun fault does not accommodate the eastward extrusion of the central Tibetan Plateau lithosphere

Slip rate gradients along the eastern Kunlun fault

Whether strike-slip fault systems in Eurasia accomplish eastward extrusion of Tibetan crust and lithosphere depends largely on the kinematics of deformation at the fault tip. Here we present new slip rate determinations using millennial-scale geomorphic markers from sites along the easternmost segment of the Kunlun fault in north central Tibet. This fault system represents one of the major strike-slip faults within the Indo-Asian collision zone, has been argued to exhibit uniform slip rates along much of its length, and plays a central role in models for eastward extrusion of Tibetan lithosphere. Displaced fluvial terrace risers along tributaries of the Yellow River, coupled with 14C ages of terrace material, provide constraints on slip rates over late Pleistocene to Holocene time. Results indicate that slip rates decrease systematically along the eastern ∼150 km of the fault from > 10 to <2 mm/yr. These data challenge the view that slip along the Kunlun fault remains uniform along the entire length of the fault and instead reveal gradients in displacement similar to those expected at fault tips. Moreover, slip along the fault appears to terminate within the thickened crust of the plateau, and therefore any extrusion of Tibetan lithosphere accomplished by slip along the Kunlun fault must be absorbed by internal deformation of the plateau surrounding the fault tip

Perceptions of trekking tourism and social and environmental change in Nepal's Himalayas

The Himalayas are among the world’s youngest mountain ranges. In addition to the geologic processes of mountain building and erosion, they are also highly vulnerable to human influenced change, occurring at local, national, regional, and international scales. A photo-elicitation methodology is employed to show how residents perceive those changes from historical perspectives, as well as their current conditions and impacts on their daily lives. Nepal’s Khumbu region has undergone major social and environmental transformations since the 1960s when international trekking first began to influence the area's economy. The current perceptions of Khumbu residents of these changes is assessed through photo-elicitation interviews. Their responses are placed in the historical context of: (i) institutional and political changes, much of which have been driven by national government policies; (ii) social and economic changes, for which the tourism economy has been central; and (iii) environmental changes, reflecting the impacts of resource management and climate change. The mostly positive perceptions of Khumbu residents toward how their region has changed reflects general improvements in the physical and cultural landscapes of the Khumbu over time, as well as its continuing geographic isolation, which has helped to slow the rate of globalization, while also keeping the region a dynamic and popular tourist destination

Age and African-American race impact the validity and reliability of the asthma control test in persistent asthmatics

Abstract Background The Asthma Control Test (ACT) is widely used to assess asthma control, yet the validity and reliability of the test have not been specifically evaluated in adolescents or African-Americans. We conducted a prospective psychometric study of the ACT in African-American (AA) and non-African-American (nAA) adolescents with persistent asthma, with emphasis on the clinical utility of the test for medical decision making. Methods Participants completed the ACT and performed spirometry. A physician conducted a guidelines-based assessment of asthma control, blinded to the ACT score. Study procedures were repeated 6–8 weeks later. The ACT-based asthma control assessment was compared to physician assessment. Results For baseline and follow-up visits, internal consistency, as measured using Cronbach’s alpha, was 0.80 and 0.81 in AA teens and 0.80 and 0.83 in nAA teens. Intraclass correlation coefficients were 0.59 and 0.76 in AA and nAA teens, respectively, with stable asthma control over time. Agreement between ACT and physician assessment was moderate in AA teens and fair in nAA teens. An ACT score of ≤19 showed reduced sensitivity for not well controlled asthma in both groups, while a score of ≤21 had the greatest area under the ROC curve. ACT scores were marginally responsive to change in control status. Conclusions Concerns for the ACT’s ability to detect uncontrolled asthma in adolescents emphasizes the need for a more comprehensive evaluation of asthma control in clinical settings. A higher threshold ACT score to define not well controlled asthma may be needed if the ACT is to be used for medical decision making. Trial registration ClinicalTrials.gov: NCT02671643 , NCT02662413