1,019 research outputs found
Glutaraldehyde-crosslinking for improved copper absorption selectivity and chemical stability of polyethyleneimine coatings
Nano-thin coatings of glutaraldehyde (GA)-crosslinked polyethyleneimine (PEI) are extremely selective and effective in binding copper from seawater. Here it was demonstrated that GA-PEI performs significantly different from PEI. The copper-selectivity of self-assembled PEI coatings on silicon substrates was greatly improved by GA-crosslinking. After submersion in artificial seawater containing 200 ppb copper and equimolar amounts of 11 competing ions only copper and trace amounts of Zn were detected in the GA-crosslinked coatings, while for non-crosslinked PEI there was about 30% Zn present relative to copper. The coatings were demonstrated to be highly stable under acidic conditions and retained their copper-binding selectivity after repeated cycles of binding and acid-mediated elution. After self-assembly of the GA-crosslinked coating on mesoporous diatomaceous earth particles, significant amounts of copper could be extracted from 200 ppb in artificial seawater and eluted under acidic pH
Cu K-edge XANES: polymer, organic, inorganic spectra, and experimental considerations
In pursuit of design and characterisation of Cu adsorbing in thin films, we present data from a large variety of Cu-K edge X-ray Absorption Near Edge Spectroscopy (XANES) spectra obtained from organic and inorganic standards. Additionally, we have explored the impact of beam damage inducing redox alterations. Polymer nanoparticles were tested against films to produce higher concentration samples while maintaining high surface area to bulk effects. Spectra from nanoparticles were highly comparable to thin films of ~8 nm thickness, implying comparable contributions by surface effects on copper association. Finally, we observed no impact on Cu XANES spectra from vitrification with dimethyl sulfoxide to produce amorphous frozen, hydrated samples. The spectra should act as a valuable resource in assisting the design of experiments and identification of copper associations
Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling
A planar slab of negative index material works as a superlens with
sub-diffraction-limited imaging resolution, since propagating waves are focused
and, moreover, evanescent waves are reconstructed in the image plane. Here, we
demonstrate a superlens for electric evanescent fields with low losses using
perovskites in the mid-infrared regime. The combination of near-field
microscopy with a tunable free-electron laser allows us to address precisely
the polariton modes, which are critical for super-resolution imaging. We
spectrally study the lateral and vertical distributions of evanescent waves
around the image plane of such a lens, and achieve imaging resolution of
wavelength/14 at the superlensing wavelength. Interestingly, at certain
distances between the probe and sample surface, we observe a maximum of these
evanescent fields. Comparisons with numerical simulations indicate that this
maximum originates from an enhanced coupling between probe and object, which
might be applicable for multifunctional circuits, infrared spectroscopy, and
thermal sensors.Comment: 20 pages, 6 figures, published as open access article in Nature
Communications (see http://www.nature.com/ncomms/
A latent trait look at pretest-posttest validation of criterion-referenced test items
Since Cox and Vargas (1966) introduced their pretest-posttest validity index for criterion-referenced test items, a great number of additions and modifications have followed. All are based on the idea of gain scoring; that is, they are computed from the differences between proportions of pretest and posttest item responses. Although the method is simple and generally considered as the prototype of criterion-referenced item analysis, it has many and serious disadvantages. Some of these go back to the fact that it leads to indices based on a dual test administration- and population-dependent item p values. Others have to do with the global information about the discriminating power that these indices provide, the implicit weighting they suppose, and the meaningless maximization of posttest scores they lead to. Analyzing the pretest-posttest method from a latent trait point of view, it is proposed to replace indices like Cox and Vargas’ Dpp by an evaluation of the item information function for the mastery score. An empirical study was conducted to compare the differences in item selection between both methods
Experimental evaluation of vibrotactile training mappings for dual-joystick directional guidance
Two joystick-based teleoperation is a common method for controlling a remote machine or a robot. Their use could be counter-intuitive and could require a heavy mental workload. The goal of this paper is to investigate whether vibrotactile prompts could be used to trigger dual-joystick responses quickly and intuitively, so to possibly employ them for training. In particular, we investigate the effects of: (1) stimuli delivered either on the palm or on the back of the hand, (2) with attractive and repulsive mappings, (3) with single and sequential stimuli. We find that 38 participants responded quicker and more accurately when stimuli were delivered on the back of the hand, preferred to move towards the vibration. Sequential stimuli led to intermediate responses in terms of speed and accuracy
Past Achievements and Future Challenges in 3D Photonic Metamaterials
Photonic metamaterials are man-made structures composed of tailored micro- or
nanostructured metallo-dielectric sub-wavelength building blocks that are
densely packed into an effective material. This deceptively simple, yet
powerful, truly revolutionary concept allows for achieving novel, unusual, and
sometimes even unheard-of optical properties, such as magnetism at optical
frequencies, negative refractive indices, large positive refractive indices,
zero reflection via impedance matching, perfect absorption, giant circular
dichroism, or enhanced nonlinear optical properties. Possible applications of
metamaterials comprise ultrahigh-resolution imaging systems, compact
polarization optics, and cloaking devices. This review describes the
experimental progress recently made fabricating three-dimensional metamaterial
structures and discusses some remaining future challenges
Nonlinear Localization in Metamaterials
Metamaterials, i.e., artificially structured ("synthetic") media comprising
weakly coupled discrete elements, exhibit extraordinary properties and they
hold a great promise for novel applications including super-resolution imaging,
cloaking, hyperlensing, and optical transformation. Nonlinearity adds a new
degree of freedom for metamaterial design that allows for tuneability and
multistability, properties that may offer altogether new functionalities and
electromagnetic characteristics. The combination of discreteness and
nonlinearity may lead to intrinsic localization of the type of discrete
breather in metallic, SQUID-based, and symmetric metamaterials. We
review recent results demonstrating the generic appearance of breather
excitations in these systems resulting from power-balance between intrinsic
losses and input power, either by proper initialization or by purely dynamical
procedures. Breather properties peculiar to each particular system are
identified and discussed. Recent progress in the fabrication of low-loss,
active and superconducting metamaterials, makes the experimental observation of
breathers in principle possible with the proposed dynamical procedures.Comment: 19 pages, 14 figures, Invited (Review) Chapte
Research opportunities for argumentation in social networks
Nowadays, many websites allow social networking between their users in an
explicit or implicit way. In this work, we show how argumentation schemes theory can
provide a valuable help to formalize and structure on-line discussions and user opinions in
decision support and business oriented websites that held social networks between their users.
Two real case studies are studied and analysed. Then, guidelines to enhance social decision
support and recommendations with argumentation are provided.This work summarises results of the authors joint research, funded by an STMS of the Agreement Technologies COST Action 0801, by the Spanish government grants [CONSOLIDER-INGENIO 2010 CSD2007-00022, and TIN2012-36586-C03-01] and by the GVA project [PROMETEO 2008/051].Heras Barberá, SM.; Atkinson, KM.; Botti Navarro, VJ.; Grasso, F.; Julian Inglada, VJ.; Mcburney, PJ. (2013). Research opportunities for argumentation in social networks. Artificial Intelligence Review. 39(1):39-62. doi:10.1007/s10462-012-9389-0S3962391Amgoud L (2009) Argumentation for decision making. Argumentation in artificial intelligence. Springer, BerlinAnderson P (2007) What is Web 2.0? Ideas, technologies and implications for education. JISC Iechnology and Standards Watch reportBentahar J, Meyer CJJ, Moulin B (2007) Securing agent-oriented systems: an argumentation and reputation-based approach. 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Springer, Berlin, pp 403–422García AJ, Dix J, Simari GR (2009) Argument-based logic programming. Argumentation in artificial intelligence. Springer, BerlinGolbeck J (2006) Generating predictive movie recommendations from trust in social networks. In: Proceedings of the fourth international conference on trust management, LNCS, vol 3986, 93–104Gordon T, Prakken H, Walton D (2007) The Carneades model of argument and burden of proof. Artif Intell 171(10–15):875–896Guha R, Kumar R, Raghavan P, Tomkins A (2004) Propagating trust and distrust. In: Proceedings of the 13th international conference on, World Wide Web, pp 403–412Heras S, Navarro M, Botti V, Julián V (2009) Applying dialogue games to manage recommendation in social networks. In: Proceedings of the 6th international workshop on argumentation in multi-agent aystems, ArgMASHeras S, Atkinson K, Botti V, Grasso F, Julián V, McBurney P (2010a) How argumentation can enhance dialogues in social networks. In: Proceedings of the 3rd international conference on computational models of argument, COMMA, vol 216, pp 267–274Heras S, Atkinson K, Botti V, Grasso F, Julián V, McBurney P (2010b) Applying argumentation to enhance dialogues in social networks. In: ECAI 2010 workshop on computational models of natural argument, CMNA, pp 10–17Karacapilidis N, Tzagarakis M (2007) Web-based collaboration and decision making support: a multi-disciplinary approach. Web-Based Learn Teach Technol 2(4):12–23Kim D, Benbasat I (2003) Trust-related arguments in internet stores: a framework for evaluation. J Electron Commer Res 4(2):49–64Kim D, Benbasat I (2006) The effects of trust-assuring arguments on consumer trust in internet stores: application of Toulmin’s model of argumentation. Inf Syst Rese 17(3):286–300Laera L, Tamma V, Euzenat J, Bench-Capon T, Payne T (2006) Reaching agreement over ontology alignments. In: Proceedings of the 5th international semantic web conference (ISWC 2006)Lange C, Bojãrs U, Groza T, Breslin J, Handschuh S (2008) Expressing argumentative discussions in social media sites. In: Social data on the web (SDoW2008) workshop at the 7th international semantic web conferenceLinden G, Smith B, York J (2003) Amazon.com recommendations: item-to-item collaborative filtering. IEEE Internet Comput 7(1):76–80Linden G, Hong J, Stonebraker M, Guzdial M (2009) Recommendation algorithms, online privacy and more. Commun ACM, 52(5)Mika P (2007) Ontologies are us: a unified model of social networks and semantics. J Web Semant 5(1):5–15Montaner M, López B, de la Rosa JL (2002) Opinion-based filtering through trust. In: Cooperative information agents VI, LNCS, vol 2446, pp 127–144Ontañón S, Plaza E (2008) Argumentation-based information exchange in prediction markets. 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The challenges faced in the design, conduct and analysis of surgical randomised controlled trials
Randomised evaluations of surgical interventions are rare; some interventions have been widely
adopted without rigorous evaluation. Unlike other medical areas, the randomised controlled trial
(RCT) design has not become the default study design for the evaluation of surgical interventions.
Surgical trials are difficult to successfully undertake and pose particular practical and methodological challenges. However, RCTs have played a role in the assessment of surgical innovations and there is scope and need for greater use. This article will consider the design, conduct and analysis of an RCT of a surgical intervention. The issues will be reviewed under three
headings: the timing of the evaluation, defining the research question and trial design issues.
Recommendations on the conduct of future surgical RCTs are made. Collaboration between
research and surgical communities is needed to address the distinct issues raised by the assessmentof surgical interventions and enable the conduct of appropriate and well-designed trials.The Health Services Research Unit is funded by the Scottish Government Health DirectoratesPeer reviewedPublisher PD
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