4,887 research outputs found
Fabrication and characterization of graphene hydrogel via hydrothermal approach as a scaffold for preliminary study of cell growth
BACKGROUND:
Three-dimensional assembly of graphene hydrogel is rapidly attracting the interest of researchers because of its wide range of applications in energy storage, electronics, electrochemistry, and waste water treatment. Information on the use of graphene hydrogel for biological purposes is lacking, so we conducted a preliminary study to determine the suitability of graphene hydrogel as a substrate for cell growth, which could potentially be used as building blocks for biomolecules and tissue engineering applications.
METHODS:
A three-dimensional structure of graphene hydrogel was prepared via a simple hydrothermal method using two-dimensional large-area graphene oxide nanosheets as a precursor.
RESULTS:
The concentration and lateral size of the graphene oxide nanosheets influenced the structure of the hydrogel. With larger-area graphene oxide nanosheets, the graphene hydrogel could be formed at a lower concentration. X-ray diffraction patterns revealed that the oxide functional groups on the graphene oxide nanosheets were reduced after hydrothermal treatment. The three-dimensional graphene hydrogel matrix was used as a scaffold for proliferation of a MG63 cell line.
CONCLUSION:
Guided filopodia protrusions of MG63 on the hydrogel were observed on the third day of cell culture, demonstrating compatibility of the graphene hydrogel structure for bioapplications
Returning home: heritage work among the Stl'atl'imx of the Lower Lillooet River Valley
This article focusses on heritage practices in the tensioned landscape of the Stlâatlâimx (pronounced Stat-lee-um) people of the Lower Lillooet River Valley, British Columbia, Canada. Displaced from their traditional territories and cultural traditions through the colonial encounter, they are enacting, challenging and remaking their heritage as part of their long term goal to reclaim their land and return âhomeâ. I draw on three examples of their heritage work: graveyard cleaning, the shifting âofficialâ/âunofficialâ heritage of a wagon road, and marshalling of the mountain named Nsvqâts (pronounced In-SHUCK-ch) in order to illustrate how the past is strategically mobilised in order to substantiate positions in the present. While this paper focusses on heritage in an Indigenous and postcolonial context, I contend that the dynamics of heritage practices outlined here are applicable to all heritage practices
Local threshold field for dendritic instability in superconducting MgB2 films
Using magneto-optical imaging the phenomenon of dendritic flux penetration in
superconducting films was studied. Flux dendrites were abruptly formed in a 300
nm thick film of MgB2 by applying a perpendicular magnetic field. Detailed
measurements of flux density distributions show that there exists a local
threshold field controlling the nucleation and termination of the dendritic
growth. At 4 K the local threshold field is close to 12 mT in this sample,
where the critical current density is 10^7 A/cm^2. The dendritic instability in
thin films is believed to be of thermo-magnetic origin, but the existence of a
local threshold field, and its small value are features that distinctly
contrast the thermo-magnetic instability (flux jumps) in bulk superconductors.Comment: 6 pages, 6 figures, submitted to Phys. Rev.
Why Some Interfaces Cannot be Sharp
A central goal of modern materials physics and nanoscience is control of
materials and their interfaces to atomic dimensions. For interfaces between
polar and non-polar layers, this goal is thwarted by a polar catastrophe that
forces an interfacial reconstruction. In traditional semiconductors this
reconstruction is achieved by an atomic disordering and stoichiometry change at
the interface, but in multivalent oxides a new option is available: if the
electrons can move, the atoms don`t have to. Using atomic-scale electron energy
loss spectroscopy we find that there is a fundamental asymmetry between
ionically and electronically compensated interfaces, both in interfacial
sharpness and carrier density. This suggests a general strategy to design sharp
interfaces, remove interfacial screening charges, control the band offset, and
hence dramatically improving the performance of oxide devices.Comment: 12 pages of text, 6 figure
Quasiparticle spectra in the vicinity of a d-wave vortex
We discuss the evolution of the local quasiparticle spectral density and the
related tunneling conductance measurable by the scanning tunneling microscope,
as a function of distance r and angle \theta from the vortex core in a
d_{x^2-y^2} superconductor. We consider the effects of electronic disorder and
of a strongly anisotropic tunneling matrix element, and show that in real
materials they will likely obscure the ~1/r asymptotic tail in the zero-bias
tunneling conductance expected from the straightforward semiclassical analysis.
We also give a prediction for the tunneling conductance anisotropy around the
vortex core and establish a connection to the structure of the tunneling matrix
element.Comment: 9 pages REVTeX + 5 PostScript figures. For related work and info
visit http://www.pha.jhu.edu/~fran
Testing maximal electron and muon neutrino oscillations with sub-GeV SuperKamiokande atmospheric neutrino data
Motivated by the Exact Parity Model and other theories, the hypothesis that
each of the known neutrinos oscillates maximally with a sterile partner has
been put forward as an explanation of the atmospheric and solar neutrino
anomalies. We provide detailed predictions for muon and electron flux ratios
induced in the Kamiokande and SuperKamiokande detectors by sub-GeV atmospheric
neutrinos. Several different, carefully chosen cuts on momentum and zenith
angle are proposed, emphasizing the role of up-down flux asymmetries.Comment: LaTeX, 8 figures, 17 pages, version to appear in Phys. Rev. D Rapid
Communication
The Cyprinodon variegatus genome reveals gene expression changes underlying differences in skull morphology among closely related species
Genes in durophage intersection set at 15 dpf. This is a comma separated table of the genes in the 15 dpf durophage intersection set. Given are edgeR results for each pairwise comparison. Columns indicating whether a gene is included in the intersection set at a threshold of 1.5 or 2 fold are provided. (CSV 13ĂÂ kb
Comparing and contrasting the and solutions to the atmospheric neutrino problem with SuperKamiokande data
The and solutions to the
atmospheric neutrino problem are compared with SuperKamiokande data. The
differences between these solutions due to matter effects in the Earth are
calculated for the ratio of -like to -like events and for up-down flux
asymmetries. These quantities are chosen because they are relatively
insensitive to theoretical uncertainties in the overall neutrino flux
normalisation and detection cross-sections and efficiencies. A
analysis using these quantities is performed yielding ranges which
are approximately given by and for
for the and solutions, respectively. Values of smaller than about
eV are disfavoured for the
solution, suggesting that future long baseline experiments should see a
positive signal if this scenario is the correct one.Comment: revtex, 22 pages, 12 figure
Top Quark Physics at the Tevatron
The discovery of the top quark in 1995, by the CDF and D0 collaborations at
the Fermilab Tevatron, marked the dawn of a new era in particle physics. Since
then, enormous efforts have been made to study the properties of this
remarkable particle, especially its mass and production cross section. In this
article, we review the status of top quark physics as studied by the two
collaborations using the p-pbar collider data at sqrt(s) = 1.8 TeV. The
combined measurement of the top quark mass, m_t = 173.8 +- 5.0 GeV/c^2, makes
it known to a fractional precision better than any other quark mass. The
production cross sections are measured as sigma (t-tbar) = 7.6 -1.5 +1.8 pb by
CDF and sigma (t-tbar) = 5.5 +- 1.8 pb by D0. Further investigations of t-tbar
decays and future prospects are briefly discussed.Comment: 119 pages, 59 figures, 17 tables Submitted to Int. J. Mod. Phys. A
Fixed some minor error
Super-Kamiokande atmospheric neutrino data, zenith distributions, and three-flavor oscillations
We present a detailed analysis of the zenith angle distributions of
atmospheric neutrino events observed in the Super-Kamiokande (SK) underground
experiment, assuming two-flavor and three-flavor oscillations (with one
dominant mass scale) among active neutrinos. In particular, we calculate the
five angular distributions associated to sub-GeV and multi-GeV \mu-like and
e-like events and to upward through-going muons, for a total of 30 accurately
computed observables (zenith bins). First we study how such observables vary
with the oscillation parameters, and then we perform a fit to the experimental
data as measured in SK for an exposure of 33 kTy (535 days). In the two-flavor
mixing case, we confirm the results of the SK Collaboration analysis, namely,
that \nu_\mu\nu_\tau oscillations are preferred over \nu_\mu\nu_e,
and that the no oscillation case is excluded with high confidence. In the
three-flavor mixing case, we perform our analysis with and without the
additional constraints imposed by the CHOOZ reactor experiment. In both cases,
the analysis favors a dominance of the \nu_\mu\nu_\tau channel. Without
the CHOOZ constraints, the amplitudes of the subdominant \nu_\munu_e and
\nu_e\nu_\tau transitions can also be relatively large, indicating that,
at present, current SK data do not exclude sizable \nu_e mixing by themselves.
After combining the CHOOZ and SK data, the amplitudes of the subdominant
transitions are constrained to be smaller, but they can still play a
nonnegligible role both in atmospheric and other neutrino oscillation searches.
In particular, we find that the \nu_e appearance probability expected in long
baseline experiments can reach the testable level of ~15%.Comment: 35 pages (RevTeX), including 20 ps figures (with epsfig.sty
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