347 research outputs found
Osteocyte isolation and culture methods.
The aim of this paper is to present several popular methods for in vitro culture of osteocytes and osteocyte cell lines. Osteocytes are located extremely suitably within the calcified bone matrix to sense mechanical signals, and are equipped with a multitude of molecular features that allow mechanosensing. However, osteocytes are more than specialized mechanosensing cells. Several signaling molecules are preferentially produced by osteocytes, and osteocytes hold a tight reign over osteoblast and osteoclast formation and activity, but also have a role as endocrine cell, communicating with muscles or organs as remote as the kidneys. In order to facilitate further research into this fascinating cell type, three protocols will be provided in this paper. The first protocol will be on the culture of mouse (early) osteocyte cell lines, the second on the isolation and culture of primary mouse bone cells, and the third on the culture of fully embedded human osteocytes within their own three-dimensional bone matrix
Theory of the tunneling resonances of the bilayer electron systems in strong magnetic field
We develop a theory for the anomalous interlayer conductance peaks observed
in bilayer electron systems at nu=1. Our model shows the that the size of the
peak at zero bias decreases rapidly with increasing in-plane magnetic field,
but its location is unchanged. The I-V characteristic is linear at small
voltages, in agreement with experimental observations. In addition we make
quantitative predictions for how the inter-layer conductance peaks vary in
position with in-plane magnetic field at high voltages. Finally, we predict
novel bi-stable behavior at intermediate voltages.Comment: 5 pages, 2 figure
A tachyonic scalar field with mutually interacting components
We investigate the tachyonic cosmological potential in two
different cases of the quasi-exponential expansion of universe and discuss
various forms of interaction between the two components---matter and the
cosmological constant--- of the tachyonic scalar field, which leads to the
viable solutions of their respective energy densities. The distinction among
the interaction forms is shown to appear in the diagnostic. Further,
the role of the high- and low-redshift observations of the Hubble parameter is
discussed to determine the proportionality constants and hence the correct form
of matter--cosmological constant interaction.Comment: 14 page
Solitons in polarized double layer quantum Hall systems
A new manifestation of interlayer coherence in strongly polarized double
layer quantum Hall systems with total filling factor
in the presence of a small or zero tunneling is theoretically
predicted. It is shown that moving (for small tunneling) and spatially
localized (for zero tunneling) stable pseudospin solitons develop which could
be interpreted as mobile or static charge-density excitations.
The possibility of their experimental observation is also discussed.Comment: Phys. Rev. B (accepted
High-Yield of CD34+ Cells With Bortezomib-Based Mobilization Regimen Is Associated With Specific Genomic Expression Patterns, Decrease in SDF-1 Plasma Levels and Up-Regulation of CXCR4 in Multiple Myeloma (MM) Patients
Gibbs' paradox and black-hole entropy
In statistical mechanics Gibbs' paradox is avoided if the particles of a gas
are assumed to be indistinguishable. The resulting entropy then agrees with the
empirically tested thermodynamic entropy up to a term proportional to the
logarithm of the particle number. We discuss here how analogous situations
arise in the statistical foundation of black-hole entropy. Depending on the
underlying approach to quantum gravity, the fundamental objects to be counted
have to be assumed indistinguishable or not in order to arrive at the
Bekenstein--Hawking entropy. We also show that the logarithmic corrections to
this entropy, including their signs, can be understood along the lines of
standard statistical mechanics. We illustrate the general concepts within the
area quantization model of Bekenstein and Mukhanov.Comment: Contribution to Mashhoon festschrift, 13 pages, 4 figure
Spin dynamics in high-mobility two-dimensional electron systems
Understanding the spin dynamics in semiconductor heterostructures is highly
important for future semiconductor spintronic devices. In high-mobility
two-dimensional electron systems (2DES), the spin lifetime strongly depends on
the initial degree of spin polarization due to the electron-electron
interaction. The Hartree-Fock (HF) term of the Coulomb interaction acts like an
effective out-of-plane magnetic field and thus reduces the spin-flip rate. By
time-resolved Faraday rotation (TRFR) techniques, we demonstrate that the spin
lifetime is increased by an order of magnitude as the initial spin polarization
degree is raised from the low-polarization limit to several percent. We perform
control experiments to decouple the excitation density in the sample from the
spin polarization degree and investigate the interplay of the internal HF field
and an external perpendicular magnetic field. The lifetime of spins oriented in
the plane of a [001]-grown 2DES is strongly anisotropic if the Rashba and
Dresselhaus spin-orbit fields are of the same order of magnitude. This
anisotropy, which stems from the interference of the Rashba and the Dresselhaus
spin-orbit fields, is highly density-dependent: as the electron density is
increased, the kubic Dresselhaus term becomes dominant and reduces the
anisotropy.Comment: 13 pages, 6 figure
Bias-voltage induced phase-transition in bilayer quantum Hall ferromagnets
We consider bilayer quantum Hall systems at total filling factor in
presence of a bias voltage which leads to different filling factors
in each layer. We use auxiliary field functional integral approach to study
mean-field solutions and collective excitations around them. We find that at
large layer separation, the collective excitations soften at a finite wave
vector leading to the collapse of quasiparticle gap. Our calculations predict
that as the bias voltage is increased, bilayer systems undergo a phase
transition from a compressible state to a phase-coherent state {\it
with charge imbalance}. We present simple analytical expressions for
bias-dependent renormalized charge imbalance and pseudospin stiffness which are
sensitive to the softening of collective modes.Comment: 12 pages, 5 figures. Minor changes, one reference adde
Nucleon deformation in finite nuclei
The deformation of a nucleon embedded in various finite nuclei is considered
by taking into account the distortion of the chiral profile functions under the
action of an external field representing the nuclear density. The baryon charge
distribution of the nucleon inside light, medium-heavy and heavy nuclei is
discussed. The mass of the nucleon decreases as it is placed deeper inside the
nucleus and reaches its minimum at the center of the nucleus. We discuss the
quantization of non-spherical solitons and its consequences for the mass
splitting of the delta states. We show that bound nucleons acquire an intrinsic
quadrupole moment due to the deformation effects. These effects are maximal for
densities of nuclei about \rho(R)\sim 0.3...0.35 \rho(0). We also point out
that scale changes of the electromagnetic radii can not simply be described by
an overall swelling factor.Comment: 29 pp, REVTeX, 8 figures, more detailed discussion on quantization
and intrinsic quadrupole moments, references adde
Interlayer Exchange Interactions, SU(4) Soft Waves and Skyrmions in Bilayer Quantum Hall Ferromagnets
The Coulomb exchange interaction is the driving force for quantum coherence
in quantum Hall systems. We construct a microscopic Landau-site Hamiltonian for
the exchange interaction in bilayer quantum Hall ferromagnets, which is
characterized by the SU(4) isospin structure. By taking a continuous limit, the
Hamiltonian gives rise to the SU(4) nonlinear sigma model in the
von-Neumann-lattice formulation. The ground-state energy is evaluated at
filling factors . It is shown at that there are 3
independent soft waves, where only one soft wave is responsible for the
coherent tunneling of electrons between the two layers. It is also shown at
that there are 3 independent skyrmion states apart from the
translational degree of freedom. They are CP skyrmions enjoying the
spin-charge entanglement confined within the \LLL.Comment: 12 pages, 2 figure
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