5,178 research outputs found
Quantum Manifestation of Elastic Constants in Nanostructures
Generally, there are two distinct effects in modifying the properties of
low-dimensional nanostructures: surface effect (SS) due to increased
surface-volume ratio and quantum size effect (QSE) due to quantum confinement
in reduced dimension. The SS has been widely shown to affect the elastic
constants and mechanical properties of nanostructures. Here, using Pb nanofilm
and graphene nanoribbon as model systems, we demonstrate the QSE on the elastic
constants of nanostructures by first-principles calculations. We show that
generally QSE is dominant in affecting the elastic constants of metallic
nanostructures while SS is more pronounced in semiconductor and insulator
nanostructures. Our findings have broad implications in quantum aspects of
nanomechanics
Water, waste, energy and food nexus in Brazil: Identifying a resource interlinkage research agenda through a systematic review
The resource nexus consists of a framework to address interlinkages between natural resources and systems that provide water, energy, food and waste management. It transcends traditional assessments conducted in “silos”, raising trade-offs and synergies that are rarely acknowledged. The nexus framework is intrinsically context-specific, as each respective region has particularities in terms of critical interlinkages. Brazil is the world's eighth largest economy [1] and is heavily reliant on natural resources. This paper considers Brazil to be a textbook case for nexus research that identifies critical interlinkages that are neglected by literature, which is typically based on single-resource analysis. It proposes a research agenda to advance resource nexus assessments and improve resource governance in Brazil. We propose a novel method for nexus research, systematically reviewing geographical context-specific papers in relevant single nexus dimensions and establishing resource interlinkages that characterise research gaps and policy priorities. We found that 36% of practices reviewed involve more than one resource at a time, characterising interlinkages not analysed by the literature. Lastly, selected quantitative indicators were used to identify critical interlinkages by analysing the representativeness of practices in the national context, and the relevance of synergies or trade-offs for Brazil. Critical interlinkages in Brazil were found to be irrigation for energy crop expansion (water, food and energy); transport biofuels and fuelwood (water, energy, food); deforestation for new pasture (water, energy, food); and hydropower generation (water and energy). These are, therefore, priorities for future nexus research and for efforts to address synergies and trade-offs in resource governance
TRAIP regulates replication fork recovery and progression via PCNA
published_or_final_versio
Active optical clock based on four-level quantum system
Active optical clock, a new conception of atomic clock, has been proposed
recently. In this report, we propose a scheme of active optical clock based on
four-level quantum system. The final accuracy and stability of two-level
quantum system are limited by second-order Doppler shift of thermal atomic
beam. To three-level quantum system, they are mainly limited by light shift of
pumping laser field. These limitations can be avoided effectively by applying
the scheme proposed here. Rubidium atom four-level quantum system, as a typical
example, is discussed in this paper. The population inversion between
and states can be built up at a time scale of s.
With the mechanism of active optical clock, in which the cavity mode linewidth
is much wider than that of the laser gain profile, it can output a laser with
quantum-limited linewidth narrower than 1 Hz in theory. An experimental
configuration is designed to realize this active optical clock.Comment: 5 page
Exploring the Eastern Frontier: A First Look at Mobile App Tracking in China
Many mobile apps are integrated with mobile advertising and tracking services running in the background to collect information for tracking users. Considering China currently tops mobile traffic growth globally, this paper aims to take a first look at China’s mobile tracking patterns from a large 4G network. We observe the dominance of the top popular domestic trackers and the pervasive tracking on mobile apps. We also discover a very well-connected tracking community, where the non-popular trackers form many local communities with each community tracking a particular category of mobile apps. We further conclude that some trackers have a monopoly on specific groups of mobile users and 10% of users upload Personally Identifiable Information (PII) to trackers (with 90% of PII tracking flows local to China). Our results consistently show a distinctive mobile tracking market in China. We hope the results can inform users and stakeholders on the interplay between mobile tracking and potential security and privacy issues
- …