27,809 research outputs found
Customers' need for uniqueness theory versus brand congruence theory: the impact on satisfaction with social network sites
Social media brands may experience a lack of competitiveness and attraction due to the silent negative increase of customers' need for uniqueness (NFU). This is the result of a tension between the theory of brand congruence, that most brands endeavor to establish with their customers, and the theory of consumers' NFU, that many consumers aim to fulfill, that has not been previously examined. Whilst the theory of brand congruence states that consumers have a favorable attitude towards brands that greatly match their self-concept (brand similarity), the theory of uniqueness, when brand similarity is shared with others, generates avoidance of similarities with others, leading to a reduction in engagement and satisfaction. Social media platforms including Facebook are at risk from customers' NFU which significantly reduces users' satisfaction, hence reducing the attractiveness and usage of Facebook. To examine this, the paper identifies the paradox of similarity in relation to both theories and examines the relationship between consumers' socialization within Social Network Sites (SNSs), brand similarity, consumers' need for uniqueness, and consumers' satisfaction with the SNS. The conceptual model was tested using data from 341 consumers in the US. The findings show that whilst satisfaction with the SNS is enhanced by brand similarity and friend liking, it is undermined by customers' need for uniqueness. Implications for online brand communities and SNSs (Facebook) are discussed and guidance for future research is provided
Two-dimensional magnetism in the pnictide superconductor parent material SrFeAsF probed by muon-spin relaxation
We report muon-spin relaxation measurements on SrFeAsF, which is the parent
compound of a newly discovered iron-arsenic-fluoride based series of
superconducting materials. We find that this material has very similar magnetic
properties to LaFeAsO, such as separated magnetic and structural transitions
(TN = 120 K, Ts = 175 K), contrasting with SrFe2As2 where they are coincident.
The muon oscillation frequencies fall away very sharply at TN, which suggests
that the magnetic exchange between the layers is weaker than in comparable
oxypnictide compounds. This is consistent with our specific heat measurements,
which find that the entropy change S = 0.05 J/mol/K largely occurs at the
structural transition and there is no anomaly at TN.Comment: 4 pages, 3 figure
Coronal mass ejections, magnetic clouds, and relativistic magnetospheric electron events: ISTP
The role of high-speed solar wind streams in driving relativistic electron acceleration within the Earth\u27s magnetosphere during solar activity minimum conditions has been well documented. The rising phase of the new solar activity cycle (cycle 23) commenced in 1996, and there have recently been a number of coronal mass ejections (CMEs) and related “magnetic clouds” at 1 AU. As these CME/cloud systems interact with the Earth\u27s magnetosphere, some events produce substantial enhancements in the magnetospheric energetic particle population while others do not. This paper compares and contrasts relativistic electron signatures observed by the POLAR, SAMPEX, Highly Elliptical Orbit, and geostationary orbit spacecraft during two magnetic cloud events: May 27–29, 1996, and January 10–11, 1997. Sequences were observed in each case in which the interplanetary magnetic field was first strongly southward and then rotated northward. In both cases, there were large solar wind density enhancements toward the end of the cloud passage at 1 AU. Strong energetic electron acceleration was observed in the January event, but not in the May event. The relative geoeffectiveness for these two cases is assessed, and it is concluded that large induced electric fields (∂B/∂t) caused in situ acceleration of electrons throughout the outer radiation zone during the January 1997 event
On the evaluation formula for Jack polynomials with prescribed symmetry
The Jack polynomials with prescribed symmetry are obtained from the
nonsymmetric polynomials via the operations of symmetrization,
antisymmetrization and normalization. After dividing out the corresponding
antisymmetric polynomial of smallest degree, a symmetric polynomial results. Of
interest in applications is the value of the latter polynomial when all the
variables are set equal. Dunkl has obtained this evaluation, making use of a
certain skew symmetric operator. We introduce a simpler operator for this
purpose, thereby obtaining a new derivation of the evaluation formula. An
expansion formula of a certain product in terms of Jack polynomials with
prescribed symmetry implied by the evaluation formula is used to derive a
generalization of a constant term identity due to Macdonald, Kadell and Kaneko.
Although we don't give the details in this work, the operator introduced here
can be defined for any reduced crystallographic root system, and used to
provide an evaluation formula for the corresponding Heckman-Opdam polynomials
with prescribed symmetry.Comment: 18 page
Direct imaging of a digital-micromirror device for configurable microscopic optical potentials
Programable spatial light modulators (SLMs) have significantly advanced the
configurable optical trapping of particles. Typically, these devices are
utilized in the Fourier plane of an optical system, but direct imaging of an
amplitude pattern can potentially result in increased simplicity and
computational speed. Here we demonstrate high-resolution direct imaging of a
digital micromirror device (DMD) at high numerical apertures (NA), which we
apply to the optical trapping of a Bose-Einstein condensate (BEC). We utilise a
(1200 x 1920) pixel DMD and commercially available 0.45 NA microscope
objectives, finding that atoms confined in a hybrid optical/magnetic or
all-optical potential can be patterned using repulsive blue-detuned (532 nm)
light with 630(10) nm full-width at half-maximum (FWHM) resolution, within 5%
of the diffraction limit. The result is near arbitrary control of the density
the BEC without the need for expensive custom optics. We also introduce the
technique of time-averaged DMD potentials, demonstrating the ability to produce
multiple grayscale levels with minimal heating of the atomic cloud, by
utilising the high switching speed (20 kHz maximum) of the DMD. These
techniques will enable the realization and control of diverse optical
potentials for superfluid dynamics and atomtronics applications with quantum
gases. The performance of this system in a direct imaging configuration has
wider application for optical trapping at non-trivial NAs.Comment: 9 page
Pollution in the open oceans: 2009-2013
This review of pollution in the open oceans updates a report on this topic prepared by GESAMP five years previously (Reports and Studies No. 79, GESAMP, 2009). The latter report, the first from GESAMP focusing specifically on the oceans beyond the 200 m depth contour, was prepared for purposes of the Assessment of Assessments, the preparatory phase of a regular process for assessing the state of the marine environment, led jointly by the United Nations Environment Programme (UNEP) and the Intergovernmental Oceanographic Commission (UNESCO-IOC)
Huygens-Fresnel-Kirchhoff construction for quantum propagators with application to diffraction in space and time
We address the phenomenon of diffraction of non-relativistic matter waves on openings in absorbing screens. To this end, we expand the full quantum propagator, connecting two points on the opposite sides of the screen, in terms of the free particle propagator and spatio-temporal properties of the opening. Our construction, based on the Huygens-Fresnel principle, describes the quantum phenomena of diffraction in space and diffraction in time, as well as the interplay between the two. We illustrate the method by calculating diffraction patterns for localized wave packets passing through various time-dependent openings in one and two spatial dimensions
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