96 research outputs found
The macro-environment for liquid biofuels in the US mass media, science and government
The purpose of this study is to investigate under which dimensions the macro-environment for liquid biofuels has been structured during time, respectively by science, mass media, and government in Germany, and how these three social expressions related to each other. Research was carried out on German official government documents, mass media news, and scientific papers on the topic âliquid biofuelsâ. Text Mining was used to extract knowledge from their content. The results indicate that in configurating the macro-environment for liquid biofuels there is some degree of proximity between media and government, less between media and science, and the least between government and scienc
The macro-environment for liquid biofuels in the German science, mass, media and government
The purpose of this study is to investigate under which dimensions the macro-environment for liquid biofuels has been structured during time, respectively by science, mass media, and government in Germany, and how these three social expressions related to each other. Research was carried out on German official government documents, mass media news, and scientific papers on the topic 'liquid biofuels'. Text Mining was used to extract knowledge from their content. The results indicate that in configurating the macro-environment for liquid biofuels there is some degree of proximity between media and government, less between media and science, and the least between government and science
Exact results for the Barabasi model of human dynamics
Human activity patterns display a bursty dynamics, with interevent times
following a heavy tailed distribution. This behavior has been recently shown to
be rooted in the fact that humans assign their active tasks different
priorities, a process that can be modeled as a priority queueing system [A.-L.
Barabasi, Nature 435, 207 (2005)]. In this work we obtain exact results for the
Barabasi model with two tasks, calculating the priority and waiting time
distribution of active tasks. We demonstrate that the model has a singular
behavior in the extremal dynamics limit, when the highest priority task is
selected first. We find that independently of the selection protocol, the
average waiting time is smaller or equal to the number of active tasks, and
discuss the asymptotic behavior of the waiting time distribution. These results
have important implications for understanding complex systems with extremal
dynamics.Comment: 4 pages, 4 figures, revte
Role of Activity in Human Dynamics
The human society is a very complex system; still, there are several
non-trivial, general features. One type of them is the presence of power-law
distributed quantities in temporal statistics. In this Letter, we focus on the
origin of power-laws in rating of movies. We present a systematic empirical
exploration of the time between two consecutive ratings of movies (the
interevent time). At an aggregate level, we find a monotonous relation between
the activity of individuals and the power-law exponent of the interevent-time
distribution. At an individual level, we observe a heavy-tailed distribution
for each user, as well as a negative correlation between the activity and the
width of the distribution. We support these findings by a similar data set from
mobile phone text-message communication. Our results demonstrate a significant
role of the activity of individuals on the society-level patterns of human
behavior. We believe this is a common character in the interest-driven human
dynamics, corresponding to (but different from) the universality classes of
task-driven dynamics.Comment: 5 pages, 6 figures. Accepted by EP
Carbon footprint in different beef production systems on a southern Brazilian farm: a case study.
The carbon footprint (CF) of beef production is one of the most widely discussed environmental issues within the current agricultural community due to its association with climate change. Because of these relevant and serious concerns, the beef cattle industry is under increasing pressure to reduce production or implement technological changes with significant consequences in terms of beef marketing. The goals of this study were to evaluate the CF per 1 kg of live weight gain (LWG) at the farm gate for different beef production systems in the southern part of Brazil. Aberdeen Angus beef-bred cattle were assigned to one of seven categories: natural grass; improved natural grass; natural grass plus ryegrass; improved natural grass plus sorghum; cultivated ryegrass and sorghum; natural grass supplemented with protein mineralised salt; and natural grass supplemented with protein-energetic mineralised salt. Monte Carlo analysis was employed to analyse the effect of variations of dry matter intake digestibility (DMID), total digestible nutrients (TDN) and crude protein (CP) parameters in methane (CH4) enteric, CH4 manure, nitrous oxide (N2O) manure and N2O N-fertiliser. The method used was a comparative life cycle assessment (LCA) centred on the CF. The CF varied from 18.3 kg CO2 equivalent/kg LWG for the ryegrass and sorghum pasture system to 42.6 kg CO2 equivalent/kg LWG for the natural grass system, including the contributions of cows, calves and steers. Among all grassland-based cattle farms, production systems with DMID from 52 to 59% achieved the lowest CO2 emissions and the highest feed conversion rate, thereby generating lower CH4 and N2O emissions per production system. Because the feed intake and feed conversion rate are one of the most important production parameters in beef cattle production with an obvious risk of data uncertainty, accurate feed data, which include quantity and quality, are important in estimates of CF for LWG. The choice of adequate feeding strategies to mitigate greenhouse gas (GHG) emissions may result in better environmental advantages
Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH): process evaluation of a randomised controlled trial intervention
Abstract
Background
The Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH) trial tested a family intervention to reduce screen-based sedentary behaviour in overweight children. The trial found no significant effect of the intervention on childrenâs screen-based sedentary behaviour. To explore these null findings, we conducted a pre-planned process evaluation, focussing on intervention delivery and uptake.
Methods
SWITCH was a randomised controlled trial of a 6-month family intervention to reduce screen time in overweight children aged 9â12 years (nâ=â251). Community workers met with each childâs primary caregiver to deliver the intervention content. Community workers underwent standard training and were monitored once by a member of the research team to assess intervention delivery. The primary caregiver implemented the intervention with their child, and self-reported intervention use at 3 and 6Â months. An exploratory analysis determined whether child outcomes at 6Â months varied by primary caregiver use of the intervention.
Results
Monitoring indicated that community workers delivered all core intervention components to primary caregivers. However, two thirds of primary caregivers reported using any intervention component âsometimesâ or less frequently at both time points, suggesting that intervention uptake was poor. Additionally, analyses indicated no effect of primary caregiver intervention use on child outcomes at 6Â months, suggesting the intervention itself lacked efficacy.
Conclusions
Poor uptake, and the efficacy of the intervention itself, may have played a role in the null findings of the SWITCH trial on health behaviour and body composition.
Trial registration
The trial was registered in the Australian and New Zealand Clinical Trials Registry (no.
ACTRN12611000164998
); registration date: 10/02/2011
Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH): process evaluation of a randomised controlled trial intervention
Abstract
Background
The Screen Time Weight-loss Intervention Targeting Children at Home (SWITCH) trial tested a family intervention to reduce screen-based sedentary behaviour in overweight children. The trial found no significant effect of the intervention on childrenâs screen-based sedentary behaviour. To explore these null findings, we conducted a pre-planned process evaluation, focussing on intervention delivery and uptake.
Methods
SWITCH was a randomised controlled trial of a 6-month family intervention to reduce screen time in overweight children aged 9â12 years (nâ=â251). Community workers met with each childâs primary caregiver to deliver the intervention content. Community workers underwent standard training and were monitored once by a member of the research team to assess intervention delivery. The primary caregiver implemented the intervention with their child, and self-reported intervention use at 3 and 6Â months. An exploratory analysis determined whether child outcomes at 6Â months varied by primary caregiver use of the intervention.
Results
Monitoring indicated that community workers delivered all core intervention components to primary caregivers. However, two thirds of primary caregivers reported using any intervention component âsometimesâ or less frequently at both time points, suggesting that intervention uptake was poor. Additionally, analyses indicated no effect of primary caregiver intervention use on child outcomes at 6Â months, suggesting the intervention itself lacked efficacy.
Conclusions
Poor uptake, and the efficacy of the intervention itself, may have played a role in the null findings of the SWITCH trial on health behaviour and body composition.
Trial registration
The trial was registered in the Australian and New Zealand Clinical Trials Registry (no.
ACTRN12611000164998
); registration date: 10/02/2011
Modeling bursts and heavy tails in human dynamics
Current models of human dynamics, used from risk assessment to
communications, assume that human actions are randomly distributed in time and
thus well approximated by Poisson processes. We provide direct evidence that
for five human activity patterns the timing of individual human actions follow
non-Poisson statistics, characterized by bursts of rapidly occurring events
separated by long periods of inactivity. We show that the bursty nature of
human behavior is a consequence of a decision based queuing process: when
individuals execute tasks based on some perceived priority, the timing of the
tasks will be heavy tailed, most tasks being rapidly executed, while a few
experiencing very long waiting times. We discuss two queueing models that
capture human activity. The first model assumes that there are no limitations
on the number of tasks an individual can hadle at any time, predicting that the
waiting time of the individual tasks follow a heavy tailed distribution with
exponent alpha=3/2. The second model imposes limitations on the queue length,
resulting in alpha=1. We provide empirical evidence supporting the relevance of
these two models to human activity patterns. Finally, we discuss possible
extension of the proposed queueing models and outline some future challenges in
exploring the statistical mechanisms of human dynamics.Comment: RevTex, 19 pages, 8 figure
Priority queues with bursty arrivals of incoming tasks
Recently increased accessibility of large-scale digital records enables one
to monitor human activities such as the interevent time distributions between
two consecutive visits to a web portal by a single user, two consecutive emails
sent out by a user, two consecutive library loans made by a single individual,
etc. Interestingly, those distributions exhibit a universal behavior,
, where is the interevent time, and or 3/2. The universal behaviors have been modeled via the
waiting-time distribution of a task in the queue operating based on priority;
the waiting time follows a power law distribution with either or 3/2 depending on the detail of
queuing dynamics. In these models, the number of incoming tasks in a unit time
interval has been assumed to follow a Poisson-type distribution. For an email
system, however, the number of emails delivered to a mail box in a unit time we
measured follows a powerlaw distribution with general exponent . For
this case, we obtain analytically the exponent , which is not
necessarily 1 or 3/2 and takes nonuniversal values depending on . We
develop the generating function formalism to obtain the exponent ,
which is distinct from the continuous time approximation used in the previous
studies.Comment: 19 pages, 5 figure
Hybrid quantum circuit with a superconducting qubit coupled to a spin ensemble
We report the experimental realization of a hybrid quantum circuit combining
a superconducting qubit and an ensemble of electronic spins. The qubit, of the
transmon type, is coherently coupled to the spin ensemble consisting of
nitrogen-vacancy (NV) centers in a diamond crystal via a frequency-tunable
superconducting resonator acting as a quantum bus. Using this circuit, we
prepare arbitrary superpositions of the qubit states that we store into
collective excitations of the spin ensemble and retrieve back later on into the
qubit. These results constitute a first proof of concept of spin-ensemble based
quantum memory for superconducting qubits.Comment: 13 pages, 4 figures, plus supplementary informatio
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