6,860 research outputs found
A Microscopic Mechanism for Muscle's Motion
The SIRM (Stochastic Inclined Rods Model) proposed by H. Matsuura and M.
Nakano can explain the muscle's motion perfectly, but the intermolecular
potential between myosin head and G-actin is too simple and only repulsive
potential is considered. In this paper we study the SIRM with different complex
potential and discuss the effect of the spring on the system. The calculation
results show that the spring, the effective radius of the G-actin and the
intermolecular potential play key roles in the motion. The sliding speed is
about calculated from the model which well agrees with
the experimental data.Comment: 9 pages, 6 figure
Tunable hybrid surface waves supported by a graphene layer
We study surface waves localized near a surface of a semi-infinite dielectric
medium covered by a layer of graphene in the presence of a strong external
magnetic field. We demonstrate that both TE-TM hybrid surface plasmons can
propagate along the graphene surface. We analyze the effect of the Hall
conductivity on the disper- sion of hybrid surface waves and suggest a
possibility to tune the plasmon dispersion by the magnetic field.Comment: 3 pages, 3 figure
Plastic flow and failure resistance of metallic glass: Insight from \u3cem\u3ein situ\u3c/em\u3e compression of nanopillars
We report in situ nanocompression tests of Cu-Zr-Al metallic glass (MG) pillars in a transmission electron microscope. This technique is capable of spatially and temporally resolving the plastic flow in MGs. The observations reveal the intrinsic ability of fully glassy MGs to sustain large plastic strains, which would otherwise be preempted by catastrophic instability in macroscopic samples and conventional tests. The high ductility in volume-limited MGs and the sample size effects in suppressing the rapid failure common to MGs are analyzed by modeling the evolution of the collectivity of flow defects toward localization
On the global well-posedness of a class of Boussinesq- Navier-Stokes systems
In this paper we consider the following 2D Boussinesq-Navier-Stokes systems
\partial_{t}u+u\cdot\nabla u+\nabla p+ |D|^{\alpha}u &= \theta e_{2}
\partial_{t}\theta+u\cdot\nabla \theta+ |D|^{\beta}\theta &=0 \quad with
and . When , , where is an explicit function
as a technical bound, we prove global well-posedness results for rough initial
data.Comment: 23page
The Double-Time Green's Function Approach to the Two-Dimensional Heisenberg Antiferromagnet with Broken Bonds
We improved the decoupling approximation of the double-time Green's function
theory, and applied it to study the spin- two-dimensional
antiferromagnetic Heisenberg model with broken bonds at finite temperature. Our
decoupling approximation is applicable to the spin systems with spatial
inhomogeneity, introduced by the local defects, over the whole temperature
region. At low temperatures, we observed that the quantum fluctuation is
reduced in the neighborhood of broken bond, which is in agreement with previous
theoretical expectations. At high temperatures our results showed that the
quantum fluctuation close to the broken bond is enhanced. For the two parallel
broken bonds cases, we found that there exists a repulsive interaction between
the two parallel broken bonds at low temperatures.Comment: Revtex, 6 pages, 5 Postscript figures (include
miR-9 and miR-124 synergistically affect regulation of dendritic branching via the AKT/GSK3β pathway by targeting Rap2a
A single microRNA (miRNA) can regulate expression of multiple proteins, and expression of an individual protein may be controlled by numerous miRNAs. This regulatory pattern strongly suggests that synergistic effects of miRNAs play critical roles in regulating biological processes. miR-9 and miR-124, two of the most abundant miRNAs in the mammalian nervous system, have important functions in neuronal development. In this study, we identified the small GTP-binding protein Rap2a as a common target of both miR-9 and miR-124. miR-9 and miR-124 together, but neither miRNA alone, strongly suppressed Rap2a, thereby promoting neuronal differentiation of neural stem cells (NSCs) and dendritic branching of differentiated neurons. Rap2a also diminished the dendritic complexity of mature neurons by decreasing the levels of pAKT and pGSK3β. Our results reveal a novel pathway in which miR-9 and miR-124 synergistically repress expression of Rap2a to sustain homeostatic dendritic complexity during neuronal development and maturation
Mesoscale magnetism at the grain boundaries in colossal magnetoresistive films
We report the discovery of mesoscale regions with distinctive magnetic
properties in epitaxial LaSrMnO films which exhibit
tunneling-like magnetoresistance across grain boundaries. By using
temperature-dependent magnetic force microscopy we observe that the mesoscale
regions are formed near the grain boundaries and have a different Curie
temperature (up to 20 K {\it higher}) than the grain interiors. Our images
provide direct evidence for previous speculations that the grain boundaries in
thin films are not magnetically and electronically sharp interfaces. The size
of the mesoscale regions varies with temperature and nature of the underlying
defect.Comment: 4 pages of text, 4 figure
Temperature Dependence of Low-Lying Electronic Excitations of LaMnO_3
We report on the optical properties of undoped single crystal LaMnO_3, the
parent compound of the colossal magneto-resistive manganites. Near-Normal
incidence reflectance measurements are reported in the frequency range of
20-50,000 cm-1 and in the temperature range 10-300 K. The optical conductivity,
s_1(w), is derived by performing a Kramers-Kronig analysis of the reflectance
data. The far-infrared spectrum of s_1(w) displays the infrared active optical
phonons. We observe a shift of several of the phonon to high frequencies as the
temperature is lowered through the Neel temperature of the sample (T_N = 137
K). The high-frequency s_1(w) is characterized by the onset of absorption near
1.5 eV. This energy has been identified as the threshold for optical
transitions across the Jahn-Teller split e_g levels. The spectral weight of
this feature increases in the low-temperature state. This implies a transfer of
spectral weight from the UV to the visible associated with the paramagnetic to
antiferromagnetic state. We discuss the results in terms of the double exchange
processes that affect the optical processes in this magnetic material.Comment: 7 pages, 5 figure
Surface patterning of carbon nanotubes can enhance their penetration through a phospholipid bilayer
Nanotube patterning may occur naturally upon the spontaneous self-assembly of
biomolecules onto the surface of single-walled carbon nanotubes (SWNTs). It
results in periodically alternating bands of surface properties, ranging from
relatively hydrophilic to hydrophobic, along the axis of the nanotube. Single
Chain Mean Field (SCMF) theory has been used to estimate the free energy of
systems in which a surface patterned nanotube penetrates a phospholipid
bilayer. In contrast to un-patterned nanotubes with uniform surface properties,
certain patterned nanotubes have been identified that display a relatively low
and approximately constant system free energy (10 kT) as the nanotube traverses
through the bilayer. These observations support the hypothesis that the
spontaneous self-assembly of bio-molecules on the surface of SWNTs may
facilitate nanotube transduction through cell membranes.Comment: Published in ACS Nano http://pubs.acs.org/doi/abs/10.1021/nn102763
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