5,453 research outputs found
Resistive Anomalies at Ferromagnetic Transitions Revisited: the case of SrRuO_3
We show that recent resistivity data on SrRuO_3 for T->T_c are consistent
with conventional theory when corrections to scaling are included and a small
shift in T_c is allowed.Comment: 2 pages, 1 figure; revte
STM imaging of impurity resonances on BiSe
In this paper we present detailed study of the density of states near defects
in BiSe. In particular, we present data on the commonly found
triangular defects in this system. While we do not find any measurable
quasiparticle scattering interference effects, we do find localized resonances,
which can be well fitted by theory once the potential is taken to be extended
to properly account for the observed defects. The data together with the fits
confirm that while the local density of states around the Dirac point of the
electronic spectrum at the surface is significantly disrupted near the impurity
by the creation of low-energy resonance state, the Dirac point is not locally
destroyed. We discuss our results in terms of the expected protected surface
state of topological insulators.Comment: 5 pages, 6 figure
An Inversion Method for Measuring Beta in Large Redshift Surveys
A precision method for determining the value of Beta= Omega_m^{0.6}/b, where
b is the galaxy bias parameter, is presented. In contrast to other existing
techniques that focus on estimating this quantity by measuring distortions in
the redshift space galaxy-galaxy correlation function or power spectrum, this
method removes the distortions by reconstructing the real space density field
and determining the value of Beta that results in a symmetric signal. To remove
the distortions, the method modifies the amplitudes of a Fourier plane-wave
expansion of the survey data parameterized by Beta. This technique is not
dependent on the small-angle/plane-parallel approximation and can make full use
of large redshift survey data. It has been tested using simulations with four
different cosmologies and returns the value of Beta to +/- 0.031, over a factor
of two improvement over existing techniques.Comment: 16 pages including 6 figures Submitted to The Astrophysical Journa
Non-linear Response of the trap model in the aging regime : Exact results in the strong disorder limit
We study the dynamics of the one dimensional disordered trap model presenting
a broad distribution of trapping times , when an
external force is applied from the very beginning at , or only after a
waiting time , in the linear as well as in the non-linear response regime.
Using a real-space renormalization procedure that becomes exact in the limit of
strong disorder , we obtain explicit results for many observables,
such as the diffusion front, the mean position, the thermal width, the
localization parameters and the two-particle correlation function. In
particular, the scaling functions for these observables give access to the
complete interpolation between the unbiased case and the directed case.
Finally, we discuss in details the various regimes that exist for the averaged
position in terms of the two times and the external field.Comment: 27 pages, 1 eps figur
Light Induced Melting of Colloidal Crystals in Two Dimensions
We demonstrate that particles confined to two dimensions (2d) and subjected
to a one-dimensional (1d) periodic potential exhibit a rich phase diagram, with
both ``locked floating solids'' and smectic phases. The resulting phases and
phase transitions are studied as a function of temperature and potential
strength. We find reentrant melting as a function of the potential strength.
Our results lead to universal predictions consistent with recent experiments on
2d colloids in the presence of a laser-induced 1d periodic potential.Comment: 4 pages, 3 figures, also available at http://cmtw.harvard.edu/~fre
Space Place Prime
Space Place Prime is public engagement and education software for use on iPad. It targets a multi-generational audience with news, images, videos, and educational articles from the Space Place Web site and other NASA sources. New content is downloaded daily (or whenever the user accesses the app) via the wireless connection. In addition to the Space Place Web site, several NASA RSS feeds are tapped to provide new content. Content is retained for the previous several days, or some number of editions of each feed. All content is controlled on the server side, so features about the latest news, or changes to any content, can be made without updating the app in the Apple Store. It gathers many popular NASA features into one app. The interface is a boundless, slidable- in-any-direction grid of images, unique for each feature, and iconized as image, video, or article. A tap opens the feature. An alternate list mode presents menus of images, videos, and articles separately. Favorites can be tagged for permanent archive. Face - book, Twitter, and e-mail connections make any feature shareable
A new method for tracking of motor skill learning through practical application of Fitts’ law
This article is made available through the Brunel Open Access Publishing Fund.A novel upper limb motor skill measure, task productivity rate (TPR) was developed integrating speed and spatial error, delivered by a practical motor skill rehabilitation task (MSRT). This prototype task involved placement of 5 short pegs horizontally on a spatially configured rail array. The stability of TPR was tested on 18 healthy right-handed adults (10 women, 8 men, median age 29 years) in a prospective single-session quantitative within-subjects study design. Manipulations of movement rate 10% faster and slower relative to normative states did not significantly affect TPR, F(1.387, 25.009) = 2.465, p = .121. A significant linear association between completion time and error was highest during the normative state condition (Pearson's r = .455, p < .05). Findings provided evidence that improvements in TPR over time reflected motor learning with possible changes in coregulation behavior underlying practice under different conditions. These findings extend Fitts’ law theory to tracking of practical motor skill using a dexterity task, which could have potential clinical applications in rehabilitation
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