446 research outputs found
Uptake and Diffusion of Ions in Organically Synthesized Porous Carbon for Battery Anode Applications
Organically synthesized porous carbon (OSPC-1) has a high lithium uptake of 748 mA h g-1, demonstrating that it is a strong contender as an anode material for lithium-ion batteries. Simulations of the lithium uptake on models generated of OSPC-1 gave values close to the experimentally obtained data. Thus, we assess the potential of OSPC-1 for use as an anode material in batteries of sodium, potassium, magnesium, and calcium. We find ion uptakes of 770, 386, 158, and 774 mA h g-1 for Li+, Na+, K+, and Ca2+, respectively. We also study the diffusive capabilities of ions through the OSPC-1 structure via means of active diffusion. The lithium ions were able to diffuse at a greater rate, followed by the divalent ions, Mg2+ and Ca2+, and the monovalent ions, Na+ and K+. All these ions were able to diffuse completely through the OSPC-1 structure with the diffusion rate being dependent on the ionic radius of the ion, coupled with the valency of the ion. Therefore, we show that OSPC-1 also has great potential as an anode material for Na+, K+, Mg2+, and Ca2+ batteries
Services diagnostic and needs assessment study
Liberalisation of trade in services and associated domestic reforms is fundamental to the realisation of the ASEAN Economic Community (AEC). However, this requires real (âon the groundâ) liberalisation, not simply âon paperâ liberalisation in the form of commitments under the ASEAN Framework Agreement on Services (AFAS), a sideshow in services liberalisation. The decision by leaders to form an AEC covering also the free flow of services has put the emphasis very much on ensuring each ASEAN Member State (AMS) removes restrictions affecting trade in services (including related foreign investment) and implement related reforms.
However, the diagnostic analysis presented in this Services Diagnostic and Needs Assessment Study (SDNAS), including in the in-country reports, suggests this is not happening, or at least is going very slowly, especially when set against the adopted start date for the AEC of 2015. Hence, key and effective technical assistance and capacity building is needed to advance âon the groundâ liberalisation of services and related reforms. The in-country fieldwork and other analysis undertaken in the SDNAS helped identify constraints and provided a list of potential technical assistance and capacity building projects to help address them, both from a primarily cross-cutting but also a sectoral perspective.
The SDNAS has also adopted an economic framework based on the fundamental benefits of unilateral liberalisation and a strategic structured approach, to identify key areas (âumbrellasâ) needing technical assistance and capacity building activities, such as strengthening the evidence base, promoting transparency, developing strategies and planning, and raising understanding and awareness. Key activity clusters were also identified within these three âumbrellasâ, such as policy analysis, services policy visions, and organisations for dialogues, respectively.
Individual priority technical assistance and capacity building project proposals within these clusters were determined using a cost-benefit analytical approach.
The SNDAS importantly recommends the need to re-balance much of the technical assistance and capacity building activities away from being directed at servicing the AFAS trade negotiations and focusing on âon-paperâ liberalisation towards efforts to build transparency and fundamental support for services trade liberalisation and related reforms in AMS. This is what is required to achieve the necessary âon-the-groundâ changes to achieve the AEC. This is consistent with international experience that significant âon-the-groundâ services liberalisation and related reforms requires unilateral efforts, and that trade negotiations have generally failed to deliver such changes.
With this in mind, the SNDAS has developed and recommended a number of detailed proposed technical assistance and capacity building project templates
Design and characterization of AmLi neutron sources for the LZ experiment
In this paper we describe the development, testing, and characterization of
three low-emission rate AmLi neutron sources. The sources are used to calibrate
the nuclear recoil response of the LUX-ZEPLIN (LZ) dark matter experiment. The
sources' neutron emission rate was measured using He proportional tubes.
The sources' gamma emissions were characterized using a high-purity germanium
(HPGe) detector. Source-validated GEANT4 Monte Carlo simulations allowed to
calibrate the Ge and neutron detector responses.Comment: 20 pages, 13 figures, 4 tables, revised manuscripts after
accommodating the reviewer's comment
Facile synthesis of organically synthesized porous carbon using a commercially available route with exceptional electrochemical performance
Organically synthesized porous carbon (OSPC) is a subclass of conjugated microporous polymer materials that have shown potential applications as anodes in ion batteries. However, a challenging, low-yielding, multistep synthetic route (the A method) has hindered further exploration of this exciting family. Here, OSPC-1 has been synthesized via an alternative, efficient one-pot method from commercially available reagents (the B method), hereafter referred to as OSPC-1b in contrast to OSPC-1a, where it is synthesized via the A method. Characterization revealed the same polymer structure and the highest surface area to date of an OSPC (or OSPC analogue) family member for OSPC-1b with 909 m2 gâ1. OSPC-1b was tested as an anode for Li-ion batteries, demonstrating the same high capacity, fast charging, resistance to degradation, and inhibition of the formation of dangerous lithium dendrites as OSPC-1a. Furthermore, the electrochemical properties of OSPC-0 were evaluated for the first time, agreeing with previously predicted values, giving scope for the design and targeting of specific properties
Conceivable security risks and authentication techniques for smart devices
With the rapidly escalating use of smart devices and fraudulent transaction of usersâ data from their devices, efficient and reliable techniques for authentication of the smart devices have become an obligatory issue. This paper reviews the security risks for mobile devices and studies several authentication techniques available for smart devices. The results from field studies enable a comparative evaluation of user-preferred authentication mechanisms and their opinions about reliability, biometric authentication and visual authentication techniques
Artificial Synthesis of Conjugated Microporous Polymers via Sonogashira-Hagihara Coupling
Amorphous network materials are becoming increasingly important with applications, for example, as supercapacitors, battery anodes, and proton conduction membranes. The design of these materials is hampered by the amorphous nature of the structure and sensitivity to synthetic conditions. Here, we show that through artificial synthesis, fully mimicking the catalytic formation cycle, and full synthetic conditions, we can generate structural models that can fully describe the physical properties of these amorphous network materials. This opens up pathways for the rational design where complex structural influences, such as the solvent and catalyst choice, can be taken into account
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The surface temperatures of Earth: steps towards integrated understanding of variability and change
Surface temperature is a key aspect of weather and climate, but the term may refer to different quantities that play interconnected roles and are observed by different means. In a community-based activity in June 2012, the EarthTemp Network brought together 55 researchers from five continents to improve the interaction between scientific communities who focus on surface temperature in particular domains, to exploit the strengths of different observing systems and to better meet the needs of different communities. The workshop identified key needs for progress towards meeting scientific and societal requirements for surface temperature understanding and information, which are presented in this community paper. A "whole-Earth" perspective is required with more integrated, collaborative approaches to observing and understanding Earth's various surface temperatures. It is necessary to build understanding of the relationships between different surface temperatures, where presently inadequate, and undertake large-scale systematic intercomparisons. Datasets need to be easier to obtain and exploit for a wide constituency of users, with the differences and complementarities communicated in readily understood terms, and realistic and consistent uncertainty information provided. Steps were also recommended to curate and make available data that are presently inaccessible, develop new observing systems and build capacities to accelerate progress in the accuracy and usability of surface temperature datasets
Modular and predictable assembly of porous organic molecular crystals
Nanoporous molecular frameworks are important in applications such as separation, storage and catalysis. Empirical rules exist for their assembly but it is still challenging to place and segregate functionality in three-dimensional porous solids in a predictable way. Indeed, recent studies of mixed crystalline frameworks suggest a preference for the statistical distribution of functionalities throughout the pores rather than, for example, the functional group localization found in the reactive sites of enzymes. This is a potential limitation for 'one-pot' chemical syntheses of porous frameworks from simple starting materials. An alternative strategy is to prepare porous solids from synthetically preorganized molecular pores. In principle, functional organic pore modules could be covalently prefabricated and then assembled to produce materials with specific properties. However, this vision of mix-and-match assembly is far from being realized, not least because of the challenge in reliably predicting three-dimensional structures for molecular crystals, which lack the strong directional bonding found in networks. Here we show that highly porous crystalline solids can be produced by mixing different organic cage modules that self-assemble by means of chiral recognition. The structures of the resulting materials can be predicted computationally, allowing in silico materials design strategies. The constituent pore modules are synthesized in high yields on gram scales in a one-step reaction. Assembly of the porous co-crystals is as simple as combining the modules in solution and removing the solvent. In some cases, the chiral recognition between modules can be exploited to produce porous organic nanoparticles. We show that the method is valid for four different cage modules and can in principle be generalized in a computationally predictable manner based on a lock-and-key assembly between modules
WMO Assessment of Weather and Climate Mortality Extremes: Lightning, Tropical Cyclones, Tornadoes, and Hail
A World Meteorological Organization (WMO) Commission for Climatology international panel was convened to examine and assess the available evidence associated with five weather-related mortality extremes: 1) lightning (indirect), 2) lightning (direct), 3) tropical cyclones, 4) tornadoes, and 5) hail. After recommending for acceptance of only events after 1873 (the formation of the predecessor of the WMO), the committee evaluated and accepted the following mortality extremes: 1) âhighest mortality (indirect strike) associated with lightningâ as the 469 people killed in a lightning-caused oil tank fire in Dronka, Egypt, on 2 November 1994; 2) âhighest mortality directly associated with a single lightning flashâ as the lightning flash that killed 21 people in a hut in Manica Tribal Trust Lands, Zimbabwe (at time of incident, eastern Rhodesia), on 23 December 1975; 3) âhighest mortality associated with a tropical cycloneâ as the Bangladesh (at time of incident, East Pakistan) cyclone of 12â13 November 1970 with an estimated death toll of 300 000 people; 4) âhighest mortality associated with a tornadoâ as the 26 April 1989 tornado that destroyed the Manikganj district, Bangladesh, with an estimated death toll of 1300 individuals; and 5) âhighest mortality associated with a hailstormâ as the storm occurring near Moradabad, India, on 30 April 1888 that killed 246 people. These mortality extremes serve to further atmospheric science by giving baseline mortality values for comparison to future weather-related catastrophes and also allow for adjudication of new meteorological information as it becomes available
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