2,640 research outputs found
Analytic, Group-Theoretic Density Profiles for Confined, Correlated N-Body Systems
Confined quantum systems involving identical interacting particles are to
be found in many areas of physics, including condensed matter, atomic and
chemical physics. A beyond-mean-field perturbation method that is applicable,
in principle, to weakly, intermediate, and strongly-interacting systems has
been set forth by the authors in a previous series of papers. Dimensional
perturbation theory was used, and in conjunction with group theory, an analytic
beyond-mean-field correlated wave function at lowest order for a system under
spherical confinement with a general two-body interaction was derived. In the
present paper, we use this analytic wave function to derive the corresponding
lowest-order, analytic density profile and apply it to the example of a
Bose-Einstein condensate.Comment: 15 pages, 2 figures, accepted by Physics Review A. This document was
submitted after responding to a reviewer's comment
Homeless drug users' awareness and risk perception of peer "Take Home Naloxone" use â a qualitative study
BACKGROUND
Peer use of take home naloxone has the potential to reduce drug related deaths. There appears to be a paucity of research amongst homeless drug users on the topic. This study explores the acceptability and potential risk of peer use of naloxone amongst homeless drug users. From the findings the most feasible model for future treatment provision is suggested.
METHODS
In depth face-to-face interviews conducted in one primary care centre and two voluntary organisation centres providing services to homeless drug users in a large UK cosmopolitan city. Interviews recorded, transcribed and analysed thematically by framework techniques.
RESULTS
Homeless people recognise signs of a heroin overdose and many are prepared to take responsibility to give naloxone, providing prior training and support is provided. Previous reports of the theoretical potential for abuse and malicious use may have been overplayed.
CONCLUSION
There is insufficient evidence to recommend providing "over the counter" take home naloxone" to UK homeless injecting drug users. However a programme of peer use of take home naloxone amongst homeless drug users could be feasible providing prior training is provided. Peer education within a health promotion framework will optimise success as current professionally led health promotion initiatives are failing to have a positive impact amongst homeless drug users
On Approximation of the Eigenvalues of Perturbed Periodic Schrodinger Operators
This paper addresses the problem of computing the eigenvalues lying in the
gaps of the essential spectrum of a periodic Schrodinger operator perturbed by
a fast decreasing potential. We use a recently developed technique, the so
called quadratic projection method, in order to achieve convergence free from
spectral pollution. We describe the theoretical foundations of the method in
detail, and illustrate its effectiveness by several examples.Comment: 17 pages, 2 tables and 2 figure
On the Matter of Time
Drawing on several disciplinary areas, this article considers diverse cultural concepts of time, space, and materiality. It explores historical shifts in ideas about time, observing that these have gone full circle, from visions in which time and space were conflated, through increasingly divergent linear understandings of the relationship between them, to their reunion in contemporary notions of space-time. Making use of long-term ethnographic research and explorations of the topic of Time at Durham Universityâs Institute of Advanced Study (2012â13), the article considers Aboriginal Australian ideas about relationality and the movement of matter through space and time. It asks why these earliest explanations of the cosmos, though couched in a wholly different idiom, seem to have more in common with the theories proposed by contemporary physicists than with the ideas that dominated the period between the Holocene and the Anthropocene. The analysis suggests that such unexpected resonance between these oldest and newest ideas about time and space may spring from the fact that they share an intense observational focus on material events. Comparing these vastly different but intriguingly compatible worldviews meets interdisciplinary aims in providing a fresh perspective on both of them
Incompatible sets of gradients and metastability
We give a mathematical analysis of a concept of metastability induced by
incompatibility. The physical setting is a single parent phase, just about to
undergo transformation to a product phase of lower energy density. Under
certain conditions of incompatibility of the energy wells of this energy
density, we show that the parent phase is metastable in a strong sense, namely
it is a local minimizer of the free energy in an neighbourhood of its
deformation. The reason behind this result is that, due to the incompatibility
of the energy wells, a small nucleus of the product phase is necessarily
accompanied by a stressed transition layer whose energetic cost exceeds the
energy lowering capacity of the nucleus. We define and characterize
incompatible sets of matrices, in terms of which the transition layer estimate
at the heart of the proof of metastability is expressed. Finally we discuss
connections with experiment and place this concept of metastability in the
wider context of recent theoretical and experimental research on metastability
and hysteresis.Comment: Archive for Rational Mechanics and Analysis, to appea
Determination of Inter-Phase Line Tension in Langmuir Films
A Langmuir film is a molecularly thin film on the surface of a fluid; we
study the evolution of a Langmuir film with two co-existing fluid phases driven
by an inter-phase line tension and damped by the viscous drag of the underlying
subfluid. Experimentally, we study an 8CB Langmuir film via digitally-imaged
Brewster Angle Microscopy (BAM) in a four-roll mill setup which applies a
transient strain and images the response. When a compact domain is stretched by
the imposed strain, it first assumes a bola shape with two tear-drop shaped
reservoirs connected by a thin tether which then slowly relaxes to a circular
domain which minimizes the interfacial energy of the system. We process the
digital images of the experiment to extract the domain shapes. We then use one
of these shapes as an initial condition for the numerical solution of a
boundary-integral model of the underlying hydrodynamics and compare the
subsequent images of the experiment to the numerical simulation. The numerical
evolutions first verify that our hydrodynamical model can reproduce the
observed dynamics. They also allow us to deduce the magnitude of the line
tension in the system, often to within 1%. We find line tensions in the range
of 200-600 pN; we hypothesize that this variation is due to differences in the
layer depths of the 8CB fluid phases.Comment: See (http://www.math.hmc.edu/~ajb/bola/) for related movie
Properties of continuous Fourier extension of the discrete cosine transform and its multidimensional generalization
A versatile method is described for the practical computation of the discrete
Fourier transforms (DFT) of a continuous function given by its values
at the points of a uniform grid generated by conjugacy classes
of elements of finite adjoint order in the fundamental region of
compact semisimple Lie groups. The present implementation of the method is for
the groups SU(2), when is reduced to a one-dimensional segment, and for
in multidimensional cases. This simplest case
turns out to result in a transform known as discrete cosine transform (DCT),
which is often considered to be simply a specific type of the standard DFT.
Here we show that the DCT is very different from the standard DFT when the
properties of the continuous extensions of these two discrete transforms from
the discrete grid points to all points are
considered. (A) Unlike the continuous extension of the DFT, the continuous
extension of (the inverse) DCT, called CEDCT, closely approximates
between the grid points . (B) For increasing , the derivative of CEDCT
converges to the derivative of . And (C), for CEDCT the principle of
locality is valid. Finally, we use the continuous extension of 2-dimensional
DCT to illustrate its potential for interpolation, as well as for the data
compression of 2D images.Comment: submitted to JMP on April 3, 2003; still waiting for the referee's
Repor
Numerical Integration of Nonlinear Wave Equations for General Relativity
A second-order numerical implementation is given for recently derived
nonlinear wave equations for general relativity. The Gowdy T cosmology is
used as a test bed for studying the accuracy and convergence of simulations of
one-dimensional nonlinear waves. The complete freedom in space-time slicing in
the present formulation is exploited to compute in the Gowdy line-element.
Second-order convergence is found by direct comparison of the results with
either analytical solutions for polarized waves, or solutions obtained from
Gowdy's reduced wave equations for the more general unpolarized waves. Some
directions for extensions are discussed.Comment: 19 pages (LaTex), 3 figures (ps
Association of human cytomegalovirus proteins IRS1 and TRS1 with the viral DNA polymerase accessory subunit UL44
Multiple proteins interacting with DNA polymerases orchestrate DNA replication. Human cytomegalovirus (HCMV) encodes a DNA polymerase that includes the presumptive processivity factor UL44. UL44 is structurally homologous to the eukaryotic DNA polymerase processivity factor proliferating cell nuclear antigen (PCNA), which interacts with numerous proteins. Previous proteomic analysis has identified the HCMV protein IRS1 as a candidate protein interacting with UL44. Nuclease-resistant reciprocal co-immunoprecipitation of UL44 with IRS1 and with TRS1, which has an amino terminus identical to that of IRS1, was observed from lysate of cells infected with viruses expressing epitope-tagged UL44, epitope-tagged IRS1 or epitope-tagged TRS1. Western blotting of protein immunoprecipitated from infected cell lysate indicated that epitope-tagged IRS1 and TRS1 do not associate simultaneously with UL44. Glutathione S-transferase pull-down experiments indicated that IRS1 and TRS1 interact with UL44 via a region that is identical in both proteins. Taken together, these data suggest that IRS1 and TRS1 may compete for association with UL44 and may affect UL44 function differentially
A Decision Support Tool for the Selection of Promoting Actions to Encourage Collaboration in Projects for the Agriculture Sector
[EN] Development and innovation agencies promote consortiums of agricultural stakeholders to collaborate in the proposal of projects for public calls. To achieve this partnerships, these agencies should select between different promoting actions to be performed with two objectives: maximize the number of project proposals presented and minimize the resources invested. To support agencies with these decisions, a computer tool based on a multi-objective integer linear programming model is proposed. To deal with the two objectives the weighting sum method is implemented. The model is validated in different scenarios by means a realistic case of an agency in Brittany (France). The results show the conflict between the two objectives considered and the dependency of the solutions on the scenarios defined. As a conclusion it can be stated that: 1) decision-makers should be careful in defining the weights of each objective and 2) the impact of the different promoting actions on the level of stakeholdersÂż participation should be precisely estimated.The authors acknowledge the support of the project 691249, RUCAPS: "Enhancing and implementing knowledge based ICT solutions within high risk and uncertain conditions for agriculture production systems", funded by the European UnionÂżs research and innovation programme under the H2020 Marie SkÂżodowska-Curie Actions.Alemany DĂaz, MDM.; AlarcĂłn Valero, F.; PĂ©rez Perales, D.; Guyon, C. (2020). A Decision Support Tool for the Selection of Promoting Actions to Encourage Collaboration in Projects for the Agriculture Sector. IFIP Advances in Information and Communication Technology. 598:534-545. https://doi.org/10.1007/978-3-030-62412-5_44S534545598European Comission Funded Programs. https://ec.europa.eu/programmes/horizon2020Zoie, C., Radulescu, M.: Decision analysis for the project selection problem under risk. IFAC Proc. 34(8), 445â450 (2001)Sadi-Nezhad, S.: A state-of-art survey on project selection using MCDM techniques. J. Project Manage. 2, 1â10 (2017)Caballero, H.C., Chopra, S., Schmidt, E.K.: Project portfolio selection using mathematical programming and optimization methods. In: Paper presented at PMIÂź Global Congress 2012âNorth America, Vancouver, British Columbia, Canada, Newtown Square, PA, Project Management Institute (2012)Ahmad, B., Haq, I.: Project selection techniques, relevance and applications in Pakistan. Int. J. Technol. Res. 4, 52â60 (2016)Inuiguchi, M., RamıÌk, J.: Possibilistic linear programming: a brief review of fuzzy mathematical programming and a comparison with stochastic programming in portfolio selection problem. Fuzzy Sets Syst. 111(1), 3â28 (2000)Stewart, R., Mohamed, S.: IT/IS projects selection using multi-criteria utility theory. Log. Inf. Manage. 15(4), 254â270 (2002)Alzober, W., Yaakub, A.R.: Integrated model for MCDM: selection contractor in Malaysian construction industry. In: Applied Mechanics and Materials 548, pp. 1587â1595. Trans Tech Publications (2014)Adhikary, P., Roy, P.K., Mazumdar, A.: Optimal renewable energy project selection: a multi-criteria optimization technique approach. Global J. Pure Appl. Math. 11(5), 3319â3329 (2015)Strang, K.D.: Portfolio selection methodology for a nuclear project. Project Manage. J. 42(2), 81â93 (2011)Benjamin, C.O.: A linear goal-programming model for public-sector project selection. J. Oper. Res. Soc. 36(1), 13â23 (1985)Coronado, J.R., Pardo-Mora, E.M., Valero, M.: A multi-objective model for selection of projects to finance new enterprise SMEs in Colombia. J. Ind. Eng. Manage. 4(3), 407â417 (2011)Mat, N.A.C., Cheung, Y.: Partner selection: criteria for successful collaborative network. In: 20th Australian Conference on Information Systems, pp. 631â641 (2009)Camarinha-Matos, L.M., Afsarmanesh, H.: Collaborative Networks. In: Wang, K., Kovacs, G.L., Wozny, M., Fang, M. (eds.) PROLAMAT 2006. IIFIP, vol. 207, pp. 26â40. Springer, Boston, MA (2006). https://doi.org/10.1007/0-387-34403-9_4PaixĂŁo, M., Sbragia, R., Kruglianskas, I.: Factors for selecting partners in innovation projectsâevidences from alliances in the Brazilian petrochemical leader. Rev. Admin. Innov. SĂŁo Paulo 11(2), 241â272 (2014)Duisters, D., Duysters, G., de Man, A.P.: The partner selection process: steps, effectiveness, governance. Ann. Hematol. 2, 7â25 (2011)Zhang, X.: Criteria for selecting the private-sector partner in public-private partnerships. J. Constr. Eng. Manage. 131(6), 631â644 (2005
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