37,685 research outputs found
Some integral inequalities on time scales
In this paper, some new integral inequalities on time scales are presented by
using elementarily analytic methods in calculus of time scales.Comment: 8 page
The correlations between the twin kHz QPO frequencies of LMXBs
We analyzed the recently published kHz QPO data in the neutron star low-mass
X-ray binaries (LMXBs), in order to investigate the different correlations of
the twin peak kilohertz quasi-eriodic oscillations (kHz QPOs) in bright Z
sources and in the less luminous Atoll sources. We find that a power-law
relation \no\sim\nt^{b} between the upper and the lower kHz QPOs with
different indices: 1.5 for the Atoll source 4U 1728-34 and
1.9 for the Z source Sco X-1. The implications of our results for
the theoretical models for kHz QPOs are discussed.Comment: 6 pages, accepted by MNRA
Isolated Galaxies versus Interacting Pairs with MaNGA
We present preliminary results of the spectral analysis on the radial
distributions of the star formation history in both, a galaxy merger and a
spiral isolated galaxy observed with MaNGA. We find that the central part of
the isolated galaxy is composed by older stellar population (2 Gyr) than
in the outskirts (7 Gyr). Also, the time-scale is gradually larger from 1
Gyr in the inner part to 3 Gyr in the outer regions of the galaxy. In the case
of the merger, the stellar population in the central region is older than in
the tails, presenting a longer time-scale in comparison to central part in the
isolated galaxy. Our results are in agreement with a scenario where spiral
galaxies are built from inside-out. In the case of the merger, we find evidence
that interactions enhance star formation in the central part of the galaxy.Comment: 7 pages, 2 figures. Proceedings of the EWASS-2015 special session
Sp3, accepted for publication in Special Issue "3D View on Interacting and
Post-Interacting Galaxies from Clusters to Voids" of open access journal
"Galaxies
A one-step procedure to probe the viscoelastic properties of cells by Atomic Force Microscopy
The increasingly recognised importance of viscoelastic properties of cells in pathological conditions requires rapid development of advanced cell microrheology technologies. Here, we present a novel Atomic Force Microscopy (AFM)-microrheology (AFM2) method for measuring the viscoelastic properties in living cells, over a wide range of continuous frequencies (0.005 Hz ~ 200 Hz), from a simple stress-relaxation nanoindentation. Experimental data were directly analysed without the need for pre-conceived viscoelastic models. We show the method had an excellent agreement with conventional oscillatory bulk-rheology measurements in gels, opening a new avenue for viscoelastic characterisation of soft matter using minute quantity of materials (or cells). Using this capability, we investigate the viscoelastic responses of cells in association with cancer cell invasive activity modulated by two important molecular regulators (i.e. mutation of the p53 gene and Rho kinase activity). The analysis of elastic (G′(ω)) and viscous (G″(ω)) moduli of living cells has led to the discovery of a characteristic transitions of the loss tangent (G″(ω)/G′(ω)) in the low frequency range (0.005 Hz ~ 0.1 Hz) that is indicative of the capability for cell restructuring of F-actin network. Our method is ready to be implemented in conventional AFMs, providing a simple yet powerful tool for measuring the viscoelastic properties of living cells
Nanostructuring lithium niobate substrates by focused ion beam milling
We report on two novel ways for patterning Lithium Niobate (LN) at
submicronic scale by means of focused ion beam (FIB) bombardment. The first
method consists of direct FIB milling on LiNbO3 and the second one is a
combination of FIB milling on a deposited metallic layer and subsequent RIE
(Reactive Ion Etching) etching. FIB images show in both cases homogeneous
structures with well reproduced periodicity. These methods open the way to the
fabrication of photonic crystals on LiNbO3 substrates
Peer Evaluation of Video Lab Reports in a Blended Introductory Physics Course
The Georgia Tech blended introductory calculus-based mechanics course
emphasizes scientific communication as one of its learning goals, and to that
end, we gave our students a series of four peer-evaluation assignments intended
to develop their abilities to present and evaluate scientific arguments. Within
these assignments, we also assessed students' evaluation abilities by comparing
their evaluations to a set of expert evaluations. We summarize our development
efforts and describe the changes we observed in student evaluation behavior.Comment: 4 pages, 1 table, 2 figures, submitted to Summer 2014 PERC
Proceeding
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