Reduction of deltaic channel mobility by tidal action under rising relative sea level

As Holocene river deltas continue to experience sea-level rise, sediment carried by distributary channels counteracts delta-plain drowning. Many deltas worldwide are subject to tidal action, which strongly affects the morphology of distributary channels and could also influence their mobility. Here we show, through physical laboratory experiments, that distributary-channel mobility can be dramatically reduced in systems affected by tides in comparison to an identical system with no tides, and that the mobility of distributary channels decreases as the ratio of tidal to fluvial energy increases. This effect occurs even if new accommodation space is created by rising relative sea level. By analyzing synthetic stratigraphy derived from both digital elevation data and time-lapse photography, we show also that the reduction of channel mobility in tidal deltas increases channel stacking and connectivity in the stratigraphic record

Investigating the mobility habits of electric bike owners through GPS data

This paper investigates the mobility habits of electric bike owners as well as their preferred routes. Through a GPS tracking campaign conducted in the city of Ghent (Belgium) we analyze the mobility habits (travel distance, time spent, speed) during the week of some e-bike users. Moreover, we propose the results of our map matching, based on the Hausdorff criterion, and preliminary results on the route choice of our sample. We strongly believe that investigating the behavior of electric bikes’ owners can help us in better understanding how to incentivize the use of this mode of transport. First results show that the trips with a higher travel distance are performed during the working days. It could be easily correlated with the daily commuting trips (home-work). Moreover, the results of our map-matching highlight how 61% of the trips are performed using the shortest path

Shredding of Environmental Signals by Sediment Transport

Landscapes respond to climate, tectonic motions and sea level, but this response is mediated by sediment transport. Understanding transmission of environmental signals is crucial for predicting landscape response to climate change, and interpreting paleo-climate and tectonics from stratigraphy. Here we propose that sediment transport can act as a nonlinear filter that completely destroys (“shreds”) environmental signals. This results from ubiquitous thresholds in sediment transport systems; e.g., landsliding, bed load transport, and river avulsion. This “morphodynamic turbulence” is analogous to turbulence in fluid flows, where energy injected at one frequency is smeared across a range of scales. We show with a numerical model that external signals are shredded when their time and amplitude scales fall within the ranges of morphodynamic turbulence. As signal frequency increases, signal preservation becomes the exception rather than the rule, suggesting a critical re-examination of purported sedimentary signals of external forcing

Unveiling E-bike potential for commuting trips from GPS traces

Common goals of sustainable mobility approaches are to reduce the need for travel, to facilitate modal shifts, to decrease trip distances and to improve energy efficiency in the transportation systems. Among these issues, modal shift plays an important role for the adoption of vehicles with fewer or zero emissions. Nowadays, the electric bike (e-bike) is becoming a valid alternative to cars in urban areas. However, to promote modal shift, a better understanding of the mobility behaviour of e-bike users is required. In this paper, we investigate the mobility habits of e-bikers using GPS data collected in Belgium from 2014 to 2015. By analysing more than 10,000 trips, we provide insights about e-bike trip features such as: distance, duration and speed. In addition, we offer a deep look into which routes are preferred by bike owners in terms of their physical characteristics and how weather influences e-bike usage. Results show that trips with higher travel distances are performed during working days and are correlated with higher average speeds. Usage patterns extracted from our data set also indicate that e-bikes are preferred for commuting (home-work) and business (work related) trips rather than for recreational trips

Changing stroke mortality trends in middle-aged people: an age-period-cohort analysis of routine mortality data in persons aged 40 to 69 in England

Background: In the UK, overall stroke mortality has declined. A similar trend has been seen in coronary heart disease, although recent reports suggest this decline might be levelling off in middle-aged adults. Aim: To investigate recent trends in stroke mortality among those aged 40–69 years in England. Methods: The authors used routine annual aggregated stroke death and population data for England for the years 1979–2005 to investigate time trends in gender-specific mortalities for adults aged 40 to 69 years. The authors applied log-linear modelling to isolate effects attributable to age, linear ‘drift’ over time, time period and birth cohort. Results; Between 1979 and 2005, age-standardised stroke mortality aged 40 to 69 years dropped from 93 to 30 per 100 000 in men and from 62 to 18 per 100 000 in women. Mortality was higher in older age groups, but the difference between the older and younger age groups appears to have decreased over time for both sexes. Modelling of the data suggests an average annual reduction in stroke deaths of 4.0% in men and 4.3% in women, although this decrease has been particularly marked in the last few years. However, we also observed a relative rate increase in mortality among those born since the mid-1940s compared with earlier cohorts; this appears to have been sustained in men, which explains the levelling off in the rate of mortality decline observed in recent years in the younger middle-aged. Conclusions: If observed trends in middle-aged adults continue, overall stroke mortalities may start to increase again

Experimental delta evolution in tidal environments: Morphologic response to relative sea\u2010level rise and net deposition

Tide-influenced deltas are among the largest depositional features on Earth and are ecologically and economically im-portant as they support large populations. However, the continued rise in relative sea level threatens the sustainability of these land-scapes and calls for new insights on their morphological response. While field studies of ancient deposits allow for insight into deltaevolution during times of eustatic adjustment, tide-influenced deltas are notoriously hard to identify in the rock record. We present asuite of physical experiments aimed at investigating the morphological response of tide-influenced deltas subject to relative sea-levelrise. We show that increasing relative tidal energy changes the response of the delta because tides effectively act to remove fluviallydeposited sediment from the delta topset. This leads to enhanced transgression, which we quantify via a new methodology for com-paring shoreline transgression rates based on the concept of a\u2018transgression anomaly\u2019relative to a simple reference case. We alsoshow that stronger tidal forcing can create composite deltas where distinct land-forming processes dominate different areas of thedelta plain, shaping characteristic morphological features. The net effect of tidal action is to enhance seaward transfer of bedloadsediment, resulting in greater shoreline transgression compared to identical, yet purely fluvial, deltaic systems that exhibit static oreven regressive shorelines

Influences on student decisions to enrol in higher-level mathematics courses

Addressing the participation rates in senior secondary mathematics courses in Australian schools remains a critically important issue. In this paper, the authors report on quantitative findings from a study in which all year 11 and year 12 (aged 17–18 years) Australian Tertiary Admissions Ranking (ATAR) students in Western Australia were invited to participate. The aim was to explore the perceptions of these students regarding their enrolment in higher-level mathematics courses. Data from 1633 students were collected using a survey instrument comprised of 12, 5-point, Likert-scale items. Data were analysed by applying two statistical procedures: calculating frequencies of the 12 items in the scale and examining associations with demographic characteristics and individual items through generalised linear modelling. Analyses indicated most students agreed that other courses of study were more attractive, with almost half indicating that they did not like mathematics. In addition, approximately half of the students said that they did not need to enrol in any mathematics course for ATAR or for university entrance. Significant findings were also identified for gender, school type, and school gender. The knowledge gained from this research is valuable in understanding students’ reasons for choosing not to enrol in higher-level mathematics courses when they have the option to do so and, more broadly, to address persistently low or declining participation rates in these areas of study

Bottomonium spectrum at finite temperature

We investigate the modification of S and P wave states in the bottomonium spectrum above and below the deconfinement crossover temperature through their spectral functions obtained from the maximum entropy method. Anisotropic ensembles with $N_f=2+1$ Wilson clover fermions with tadpole-improvement are used while the bottom quark is treated with an improved non-relativistic action. We observe significant modifications of the P wave $\chi_{b1}$ ground state directly above the crossover temperature, $T_c$, while the S wave $\Upsilon$ ground state remains relatively unchanged up to temperatures of almost $2T_c$. This evidence supports earlier conclusions from our FASTSUM collaboration of the immediate dissociation of the P wave states above $T_c$ and the survival of the S wave ground states up to $2T_c$.Comment: presented at the 31st International Symposium on Lattice Field Theory (Lattice 2013), 29 July - 3 August 2013, Mainz, German

The bottomonium spectrum at finite temperature from Nf=2+1N_f=2+1 lattice QCD

We present results on the bottomonium spectrum at temperatures above and below the deconfinement crossover temperature, $T_c$, from dynamical lattice QCD simulations. The heavy quark is treated with a non-relativistic effective field theory on the lattice and serves as a probe of the hot medium. Ensembles with a finer spatial lattice spacing and a greater range of temperatures below $T_c$ than those previously employed by this collaboration are used. In addition, there are $N_f=2+1$ flavours of Wilson clover quark in the sea with $M_\pi\approx400$ MeV and we perform a more careful tuning of the bottom quark mass in this work. We calculate the spectral functions of S and P wave bottomonium states using the maximum entropy method and confirm earlier findings on the survival of the ground state S wave states up to at least $2T_c$ and the immediate dissociation of the P wave states above $T_c$.Comment: 17 pages, 11 figure