14,232 research outputs found
Magnetic properties of PdAs2O6: a dilute spin system with an unusually high N\'eel temperature
The crystal structure and magnetic ordering pattern of PdAs2O6 were
investigated by neutron powder diffraction. While the magnetic structure of
PdAs2O6 is identical to the one of its isostructural 3d-homologue NiAs2O6, its
N\'{e}el temperature (140 K) is much higher than the one of NiAs2O6 (30 K).
This is surprising in view of the long distance and indirect exchange path
between the magnetic Pd ions. Density functional calculations yield
insight into the electronic structure and the geometry of the exchange-bond
network of both PdAs2O6 and NiAs2O6, and provide a semi-quantitative
explanation of the large amplitude difference between their primary exchange
interaction parameters
Helicoidal magnetic order in a clean copper oxide spin chain compound
We report susceptibility, specific heat, and neutron diffraction measurements
on NaCuO, a spin-1/2 chain compound isostructural to LiCuO,
which has been extensively investigated. Below 13 K, we find a long-range
ordered, incommensurate magnetic helix state with a propagation vector similar
to that of LiCuO. In contrast to the Li analogue, substitutional
disorder is negligible in NaCuO. We can thus rule out that the helix is
induced by impurities, as was claimed on the basis of prior work on
LiCuO. A spin Hamiltonian with frustrated longer-range exchange
interactions provides a good description of both the ordered state and the
paramagnetic susceptibility.Comment: 4 pages, 4 figures Improved Fig.1 and 4. Minor rephrasing. Reference
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Bond breaking in vibrationally excited methane on transition metal catalysts
The role of vibrational excitation of a single mode in the scattering of
methane is studied by wave packet simulations of oriented CH4 and CD4 molecules
from a flat surface. All nine internal vibrations are included. In the
translational energy range from 32 up to 128 kJ/mol we find that initial
vibrational excitations enhance the transfer of translational energy towards
vibrational energy and increase the accessibility of the entrance channel for
dissociation. Our simulations predict that initial vibrational excitations of
the asymmetrical stretch (nu_3) and especially the symmetrical stretch (nu_1)
modes will give the highest enhancement of the dissociation probability of
methane.Comment: 4 pages REVTeX, 2 figures (eps), to be published in Phys. Rev. B.
(See also arXiv:physics.chem-ph/0003031). Journal version at
http://publish.aps.org/abstract/PRB/v61/p1565
Does a smile matter if the person Is not real?: the effect of a smile and stock photos on persona perceptions
We analyze the effect of using smiling/non-smiling and stock photo/non-stock photo pictures in persona profiles on four key persona perceptions, including credibility, likability, similarity, and willingness to use. For this, we collect data from an experiment with 2,400 participants using a 16-item survey instrument and multiple persona profile treatments of which half have a smiling photo/stock photo and half do not. The results from structural equation modeling, supplemented by a qualitative analysis, show that a smile enhances the perceived similarity with the persona, similar personas are more liked, and that likability increases the willingness to use a persona. In contrast, the use of stock photos decreases the perceived similarity with the persona as well as persona credibility, both of which are significant predictors to a willingness to use a persona. These professionally crafted stock-photos seem to diminish the sense of identification with the persona. The above effects are consistent across the tested ages, genders, and races of the persona picture, although the effect sizes tend to be small. The results suggest that persona creators should use smiling pictures of real people to evoke positive perceptions toward the personas. In addition to presenting quantitative evidence on the predictors of willingness to use a persona, our research has implications for the design of persona profiles, showing that the picture choice influences individuals’ persona perceptions even when the other persona information is identical.info:eu-repo/semantics/acceptedVersio
Persona transparency: analyzing the impact of explanations on perceptions of data-driven personas
Computational techniques are becoming more common in persona development. However, users of personas may question the information in persona profiles because they are unsure of how it was created. This problem is especially vexing for data-driven personas because their creation is an opaque algorithmic process. In this research, we analyze the effect of increased transparency–i.e., explanations of how the information in data-driven personas was produced–on user perceptions. We find that higher transparency through these explanations increases the perceived completeness and clarity of the personas. Contrary to our hypothesis, the perceived credibility of the personas decreases with the increased transparency, possibly due to the technical complexity of the persona profiles disrupting the facade of the personas being real people. This finding suggests that explaining the algorithmic process of data-driven persona creation involves a “transparency trade-off”. We also find that the gender of the persona affects the perceptions, with transparency increasing perceived completeness and empathy of the female persona, but not for the male persona. Therefore, transparency may specifically assist in the acceptance of female personas. We provide practical implication for persona creators regarding transparency in persona profiles.info:eu-repo/semantics/acceptedVersio
Toxic text in personas: An experiment on user perceptions
When algorithms create personas from social media data, the personas can become noxious via automatically including toxic comments. To investigate how users perceive such personas, we conducted a 2 Ă— 2 user experiment with 496 participants that showed participants toxic and non-toxic versions of data-driven personas. We found that participants gave higher credibility, likability, empathy, similarity, and willingness-to-use scores to non-toxic personas. Also, gender affected toxicity perceptions in that female toxic data-driven personas scored lower in likability, empathy, and similarity than their male counterparts. Female participants gave higher perceptions scores to non-toxic personas and lower scores to toxic personas than male participants. We discuss implications from our research for designing data-driven personas.info:eu-repo/semantics/publishedVersio
Ab initio study of canted magnetism of finite atomic chains at surfaces
By using ab initio methods on different levels we study the magnetic ground
state of (finite) atomic wires deposited on metallic surfaces. A
phenomenological model based on symmetry arguments suggests that the
magnetization of a ferromagnetic wire is aligned either normal to the wire and,
generally, tilted with respect to the surface normal or parallel to the wire.
From a first principles point of view, this simple model can be best related
to the so--called magnetic force theorem calculations being often used to
explore magnetic anisotropy energies of bulk and surface systems. The second
theoretical approach we use to search for the canted magnetic ground state is
first principles adiabatic spin dynamics extended to the case of fully
relativistic electron scattering. First, for the case of two adjacent Fe atoms
an a Cu(111) surface we demonstrate that the reduction of the surface symmetry
can indeed lead to canted magnetism. The anisotropy constants and consequently
the ground state magnetization direction are very sensitive to the position of
the dimer with respect to the surface. We also performed calculations for a
seven--atom Co chain placed along a step edge of a Pt(111) surface. As far as
the ground state spin orientation is concerned we obtain excellent agreement
with experiment. Moreover, the magnetic ground state turns out to be slightly
noncollinear.Comment: 8 pages, 5 figures; presented on the International Conference on
Nanospintronics Design and Realizations, Kyoto, Japan, May 2004; to appear in
J. Phys.: Cond. Matte
H_2 Absorption and Fluorescence for Gamma Ray Bursts in Molecular Clouds
If a gamma ray burst with strong UV emission occurs in a molecular cloud,
there will be observable consequences resulting from excitation of the
surrounding H2. The UV pulse from the GRB will pump H2 into
vibrationally-excited levels which produce strong absorption at wavelengths <
1650 A. As a result, both the prompt flash and later afterglow will exhibit
strong absorption shortward of 1650 A, with specific spectroscopic features.
Such a cutoff in the emission from GRB 980329 may already have been observed by
Fruchter et al.; if so, GRB 980329 was at redshift 3.0 < z < 4.4 . BVRI
photometry of GRB 990510 could also be explained by H2 absorption if GRB 990510
is at redshift 1.6 < z < 2.3. The fluorescence accompanying the UV pumping of
the H2 will result in UV emission from the GRB which can extend over days or
months, depending on parameters of the ambient medium and beaming of the GRB
flash. The 7.5-13.6 eV fluorescent luminosity is \sim 10^{41.7} erg/s for
standard estimates of the parameters of the GRB and the ambient medium.
Spectroscopy can distinguish this fluorescent emission from other possible
sources of transient optical emission, such as a supernova.Comment: 13 pages, including 4 figures. submitted to Ap.J.(Letters
Using artificially generated pictures in customer-facing systems: an evaluation study with data-driven personas
We conduct two studies to evaluate the suitability of artificially generated facial pictures for use in a customer-facing system using data-driven personas. STUDY 1 investigates the quality of a sample of 1,000 artificially generated facial pictures. Obtaining 6,812 crowd judgments, we find that 90% of the images are rated medium quality or better. STUDY 2 examines the application of artificially generated facial pictures in data-driven personas using an experimental setting where the high-quality pictures are implemented in persona profiles. Based on 496 participants using 4 persona treatments (2 Ă— 2 research design), findings of Bayesian analysis show that using the artificial pictures in persona profiles did not decrease the scores for Authenticity, Clarity, Empathy, and Willingness to Use of the data-driven personas.info:eu-repo/semantics/publishedVersio
Transient behavior in Single-File Systems
We have used Monte-Carlo methods and analytical techniques to investigate the
influence of the characteristics, such as pipe length, diffusion, adsorption,
desorption and reaction rates on the transient properties of Single-File
Systems. The transient or the relaxation regime is the period in which the
system is evolving to equilibrium. We have studied the system when all the
sites are reactive and when only some of them are reactive. Comparisons between
Mean-Field predictions, Cluster Approximation predictions, and Monte Carlo
simulations for the relaxation time of the system are shown. We outline the
cases where Mean-Field analysis gives good results compared to Dynamic
Monte-Carlo results. For some specific cases we can analytically derive the
relaxation time. Occupancy profiles for different distribution of the sites
both for Mean-Field and simulations are compared. Different results for slow
and fast reaction systems and different distribution of reactive sites are
discussed.Comment: 18 pages, 19 figure
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