Unsteady bipolar diffusion charging in aerosol neutralisers: A non-dimensional approach to predict charge distribution equilibrium behaviour

High total particle concentration and small particle size are common features of aerosols encountered in the field of aerosol-based nanotechnology that can potentially lead to non-equilibrium issues in the neutraliser upon SMPS characterisation, resulting in large errors in size distribution measurements. Experiments show that the commonly assumed n⋅tn⋅t product rule fails to predict equilibrium behaviour in aerosol neutralisers under these conditions, as it does not capture the influence of total particle concentration and particle size. The aim of this work is to provide an equilibrium indicator that identifies situations where equilibrium is not reached in the neutraliser as a function of residence time, ion generation rate, total particle concentration, and particle size. Bipolar diffusion charging equations are solved numerically in a one-dimensional model first, and a non-dimensional analysis of the results is carried out in order to map equilibrium behaviour as a function of two non-dimensional groups, the non-dimensional ion concentration, and the non-dimensional neutraliser residence time. Solving the three-dimensional form of the charging equations in the geometry of the neutraliser then enables one to find good agreement in terms of equilibrium behaviour between experiments and predictions from the non-dimensional model. The three-dimensional model captures the complexity of the physics of unsteady particle charging inside a neutraliser. This work then discusses this as a new approach to non-equilibrium behaviour prediction in neutralisers, providing a tool supplementing the n⋅t product rule that can be used in practice.The authors express their thanks to Cambustion ltd. for the loan of the TSI 3077A neutraliser. The project was supported by the EPSRC Cambridge NanoDTC, EP/G037221/1, the Cambridge Home EU Scholarship Scheme (CHESS Fund) and the Schiff Foundation Studentships.This is the final published version. It was first made available by Elsevier at http://www.sciencedirect.com/science/article/pii/S0021850215000440#

Exploring relation types for literature-based discovery

Objective Literature-based discovery (LBD) aims to identify “hidden knowledge” in the medical literature by: (1) analyzing documents to identify pairs of explicitly related concepts (terms), then (2) hypothesizing novel relations between pairs of unrelated concepts that are implicitly related via a shared concept to which both are explicitly related. Many LBD approaches use simple techniques to identify semantically weak relations between concepts, for example, document co-occurrence. These generate huge numbers of hypotheses, difficult for humans to assess. More complex techniques rely on linguistic analysis, for example, shallow parsing, to identify semantically stronger relations. Such approaches generate fewer hypotheses, but may miss hidden knowledge. The authors investigate this trade-off in detail, comparing techniques for identifying related concepts to discover which are most suitable for LBD. Materials and methods A generic LBD system that can utilize a range of relation types was developed. Experiments were carried out comparing a number of techniques for identifying relations. Two approaches were used for evaluation: replication of existing discoveries and the “time slicing” approach.1 Results Previous LBD discoveries could be replicated using relations based either on document co-occurrence or linguistic analysis. Using relations based on linguistic analysis generated many fewer hypotheses, but a significantly greater proportion of them were candidates for hidden knowledge. Discussion and Conclusion The use of linguistic analysis-based relations improves accuracy of LBD without overly damaging coverage. LBD systems often generate huge numbers of hypotheses, which are infeasible to manually review. Improving their accuracy has the potential to make these systems significantly more usabl

Diquarks and antiquarks in exotics: a menage a trois and a menage a quatre

A menage a trois is very different from an ordinary family. Similarly, exotic hadrons with both qq and qbar q pairs have important color-space correlations that are completely absent in ordinary mesons and baryons. The presence of both types of pairs requires attention to the basic QCD physics that the q qbar interaction is much stronger than the qq interaction. This new physics in multiquark systems produces color structures totally different from those of normal hadrons, for example the ud system is utterly unlike the ud diquark in the uds Lambda baryon. The color-space correlations produce unusual experimental properties in tetraquarks with heavy quark pairs which may be relevant for newly discovered mesons like the X(3872) resonance. Tetraquark masses can be below the two-meson threshold for sufficiently high quark masses. A simple model calculation shows the b q bbar ubar and b q cbar qbar tetraquarks below the B Bbar and B Dbar thresholds. Some of these states have exotic electric charge and their decays might have striking signatures involving monoenergetic photons and/or pions.Comment: Journal version (PLB

Heavy quark spin selection rule and the properties of the X(3872)

The properties of the resonance X(3872) are discussed under the assumption that this resonance is dominantly a `molecular' $J^{PC}=1^{++}$ state of neutral $D$ and $D^*$ mesons. It is argued that in these properties should dominate the states with the total spin of the charmed quark-antiquark pair equal to one. As a practical application of this observation the ratio of the rates of the decays $X \to \pi^0 \chi_{cJ}$ for different $J$ is predicted. It is also pointed out that the total rate of these decays is likely to be comparable to that of the observed transitions $X \to \pi^+ \pi^- J\psi$ and $X \to \pi^+ \pi^- \pi^0 J\psi$. The decays of the X into light hadrons and its production in hadronic processes are also briefly discussed.Comment: 7 page

Pilot Safety Evaluation of Varenicline for the Treatment of Methamphetamine Dependence.

Despite the worldwide extent of methamphetamine dependence, no medication has been shown to effectively treat afflicted individuals. One relatively unexplored approach is modulation of cholinergic system function. Animal research suggests that enhancement of central cholinergic activity, possibly at nicotinic acetylcholine receptors (nAChRs), can reduce methamphetamine-related behaviors. Further, preliminary findings indicate that rivastigmine, a cholinesterase inhibitor, may reduce craving for methamphetamine after administration of the drug in human subjects. We therefore performed a double-blind, placebo-controlled, crossover pilot study of the safety and tolerability of varenicline in eight methamphetamine-dependent research subjects. Varenicline is used clinically to aid smoking cessation, and acts as a partial agonist at α4β2 nAChRs with full agonist properties at α7 nAChRs. Oral varenicline dose was titrated over 1 week to reach 1 mg bid, and then was co-administered with 30 mg methamphetamine, delivered in ten intravenous infusions of 3 mg each. Varenicline was found to be safe in combination with IV methamphetamine, producing no cardiac rhythm disturbances or alterations in vital sign parameters. No adverse neuropsychiatric sequelae were detected either during varenicline titration or following administration of methamphetamine. The results suggest that varenicline warrants further investigation as a potential treatment for methamphetamine dependence

Wrapping interactions and the genus expansion of the 2-point function of composite operators

We perform a systematic analysis of wrapping interactions for a general class of theories with color degrees of freedom, including N=4 SYM. Wrapping interactions arise in the genus expansion of the 2-point function of composite operators as finite size effects that start to appear at a certain order in the coupling constant at which the range of the interaction is equal to the length of the operators. We analyze in detail the relevant genus expansions, and introduce a strategy to single out the wrapping contributions, based on adding spectator fields. We use a toy model to demonstrate our procedure, performing all computations explicitly. Although completely general, our treatment should be particularly useful for applications to the recent problem of wrapping contributions in some checks of the AdS/CFT correspondence.Comment: 41 pages, LaTeX, 12 figures, minor changes, final version in NP

Quantum Dissipation and Decoherence via Interaction with Low-Dimensional Chaos: a Feynman-Vernon Approach

We study the effects of dissipation and decoherence induced on a harmonic oscillator by the coupling to a chaotic system with two degrees of freedom. Using the Feynman-Vernon approach and treating the chaotic system semiclassically we show that the effects of the low dimensional chaotic environment are in many ways similar to those produced by thermal baths. The classical correlation and response functions play important roles in both classical and quantum formulations. Our results are qualitatively similar to the high temperature regime of the Caldeira-Leggett model.Comment: 31 pages, 4 figure

Fredholm-Lagrangian-Grassmannian and the Maslov index

We explain the topology of the space, so called, Fredholm-Lagrangian-Grassmannain and the quantity ``Maslov index'' for paths in this space based on the standard theory of Functional Analysis. Our standing point is to define the Maslov index for arbitrary paths in terms of the fundamental spectral property of the Fredholm operators, which was first recognized by J. Phillips and used to define the ``Spectral flow''. We tried to make the arguments to be all elementary and we summarize basic facts for this article from Functional Analysis in the Appendix.Comment: 64 pages, no figur

The New Heavy Mesons: A Status Report

A survey of the experimental, phenomenological, and theoretical status of the new heavy mesons is presented. States discussed are the $B_c$, $h_c$, $\eta_c'$, $D_s(2317)$, $D_s(2460)$, X(3872), X(3940), Y(3940), Z(3930), and Y(4260). Quark models for spectra, strong decays, and hadronic interactions are reviewed and used to interpret the new states. New results for strong decay models, bound state decays, mesonic molecules, properties of the X(3872), and the chiral doublet model are also presented.Comment: 62 page, 40 figs, 16 tables. v3 corrects typos, adds references. Version to appear in Physics Report

“SOY IGUAL QUE VOSOTRAS. SOLO ME APARTA UN SIGNO ARBITRARIO Y TERRIBLE…”: FEMINISMO, NACIONALISMO Y MALINCHISMO EN LA JUDITH (1952) DE ROSARIO CASTELLANOS

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