387 research outputs found
Hexagonal convection patterns in atomistically simulated fluids
Molecular dynamics simulation has been used to model pattern formation in
three-dimensional Rayleigh--Benard convection at the discrete-particle level.
Two examples are considered, one in which an almost perfect array of
hexagonally-shaped convection rolls appears, the other a much narrower system
that forms a set of linear rolls; both pattern types are familiar from
experiment. The nature of the flow within the convection cells and quantitative
aspects of the development of the hexagonal planform based on automated polygon
subdivision are analyzed. Despite the microscopic scale of the system,
relatively large simulations with several million particles and integration
timesteps are involved.Comment: 4 pages, 6 figures (color figures have low resolution, high
resolution figures available on author's website) Minor changes to text. To
appear in PRE (Rapid Comm
Kindlin-3 loss curbs chronic myeloid leukemia in mice by mobilizing leukemic stem cells from protective bone marrow niches.
Kindlin-3 (K3)-mediated integrin adhesion controls homing and bone marrow (BM) retention of normal hematopoietic cells. However, the role of K3 in leukemic stem cell (LSC) retention and growth in the remodeled tumor-promoting BM is unclear. We report that loss of K3 in a mouse model of chronic myeloid leukemia (CML) triggers the release of LSCs from the BM into the circulation and impairs their retention, proliferation, and survival in secondary organs, which curbs CML development, progression, and metastatic dissemination. We found de novo expression of cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) on CML-LSCs but not normal hematopoietic stem cells and this enabled us to specifically deplete K3 with a CTLA-4-binding RNA aptamer linked to a K3-siRNA (small interfering RNA) in CTLA-4+ LSCs in vivo, which mobilized LSCs in the BM, induced disease remission, and prolonged survival of mice with CML. Thus, disrupting interactions of LSCs with the BM environment is a promising strategy to halt the disease-inducing and relapse potential of LSCs
SPUTTER DEPTH PROFILING OF OPTICAL WAVEGUIDES USING SECONDARY ION MASS SPECTROMETRY
The technique of sputter depth profiling by means of secondary ion mass spectrometry
of samples with high resistivity is reviewed. As examples we discuss optical waveguides made
in lithium niobate by titanium indiffusion and implantation and also yttrium iron garnet
waveguides grown by liquid phase epitaxy on gadolinium gallium garnet. Depth profiling of
these waveguide structures has been performed and the necessary precautions to prevent
charging by the primary ion beam are discussed. In some cases, coating with a metallic layer
is adequate, but a more universal method is charge neutralization by an additional electron
beam
Extreme multiplicity in cylindrical Rayleigh-B\'enard convection: I. Time-dependence and oscillations
Rayleigh-Benard convection in a cylindrical container can take on many
different spatial forms. Motivated by the results of Hof, Lucas and Mullin
[Phys. Fluids 11, 2815 (1999)], who observed coexistence of several stable
states at a single set of parameter values, we have carried out simulations at
the same Prandtl number, that of water, and radius-to-height aspect ratio of
two. We have used two kinds of thermal boundary conditions: perfectly
insulating sidewalls and perfectly conducting sidewalls. In both cases we
obtain a wide variety of coexisting steady and time-dependent flows
Pattern Formation as a Signature of Quantum Degeneracy in a Cold Exciton System
The development of a Turing instability to a spatially modulated state in a
photoexcited electron-hole system is proposed as a novel signature of exciton
Bose statistics. We show that such an instability, which is driven by kinetics
of exciton formation, can result from stimulated processes that build up near
quantum degeneracy. In the spatially uniform 2d electron-hole system, the
instability leads to a triangular lattice pattern while, at an electron-hole
interface, a periodic 1d pattern develops. We analyze the mechanism of
wavelength selection, and show that the transition is abrupt (type I) for the
uniform 2d system, and continuous (type II) for the electron-hole interface.Comment: 5 pages, 3 figure
The Spatio-Temporal Structure of Spiral-Defect Chaos
We present a study of the recently discovered spatially-extended chaotic
state known as spiral-defect chaos, which occurs in low-Prandtl-number,
large-aspect-ratio Rayleigh-Benard convection. We employ the modulus squared of
the space-time Fourier transform of time series of two-dimensional shadowgraph
images to construct the structure factor .
This analysis is used to characterize the average spatial and temporal scales
of the chaotic state. We find that the correlation length and time can be
described by power-law dependences on the reduced Rayleigh number .
These power laws have as yet no theoretical explanation.Comment: RevTex 38 pages with 13 figures. Due to their large size, some
figures are stored as separate gif images. The paper with included hi-res eps
figures (981kb compressed, 3.5Mb uncompressed) is available at
ftp://mobydick.physics.utoronto.ca/pub/MBCA96.tar.gz An mpeg movie and
samples of data are also available at
ftp://mobydick.physics.utoronto.ca/pub/. Paper submitted to Physica
MTSS1 is a critical epigenetically regulated tumor suppressor in CML
Chronic myeloid leukemia (CML) is driven by malignant stem cells that can persist despite therapy. We have identified Metastasis suppressor 1 (Mtss1/MIM) to be downregulated in hematopoietic stem and progenitor cells from leukemic transgenic SCLtTA/Bcr-Abl mice and in patients with CML at diagnosis, and Mtss1 was restored when patients achieved complete remission. Forced expression of Mtss1 decreased clonogenic capacity and motility of murine myeloid progenitor cells and reduced tumor growth. Viral transduction of Mtss1 into lineage depleted SCLtTA/Bcr-Abl bone marrow cells decreased leukemic cell burden in recipients, and leukemogenesis was reduced upon injection of Mtss1 overexpressing murine myeloid 32D cells. Tyrosine kinase inhibitor (TKI) therapy and reversion of Bcr-Abl expression increased Mtss1 expression but failed to restore it to control levels. CML patient samples revealed higher DNA methylation of specific Mtss1 promoter CpG sites that contain binding sites for Kaiso and Rest transcription factors. In summary, we identified a novel tumor suppressor in CML stem cells that is downregulated by both Bcr-Abl kinase-dependent and -independent mechanisms. Restored Mtss1 expression markedly inhibits primitive leukemic cell biology in vivo, providing a therapeutic rationale for the Bcr-Abl-Mtss1 axis to target TKI resistant CML stem cells in patients
Repairing Family Law
Scholars in the burgeoning field of law and emotion have paid surprisingly little attention to family law. This gap is unfortunate because law and emotion has the potential to bring great insights to family law. This Article begins to fill this void, and inaugurate a larger debate about the central role of emotion in family law, by exploring the intriguing and significant consequences for the regulation of families that flow from a theory of intimacy first articulated by psychoanalytic theorist Melanie Klein. According to Klein, individuals love others, inevitably transgress against those they love out of hate and aggression, feel guilt about the transgression, and then seek to repair the damage. This Article argues that the legal process embodied in the substance, procedure, and practice of traditional family law is at odds with the human process of love, hate, guilt, and reparation. In contexts as far ranging as divorce, child welfare, and adoption, family law is predicated on a binary model of love and hate, with no accounting for guilt and the drive to reparation. This Love-Hate Model actively thwarts the cycle of intimacy, greatly diminishing the opportunity for repair in familial relationships. In short, reparation as a normative goal receives far too little attention in family law. Although several important reforms have begun to move family law away from the Love-Hate Model, these reforms are undertheorized and incomplete and sometimes actively challenged. An overarching theory is needed both to undergird current reforms and to encourage others, thus moving family law more fully in a reparative direction. To replace the prevailing Love-Hate Model, this Article proposes a Reparative Model of family law that would recognize the full cycle of emotions and facilitate the reparative drive. A Reparative Model would modify the substance of family law to recognize the ongoing relationships that often persist even after legal relationships are altered. It would reform the process of family law by de-emphasizing adversarial decisionmaking. And it would change the practice of family law by reconceiving the role of the family law attorney. Ultimately, the Reparative Model yields new perspectives on a range of theoretical and practical problems in contemporary family law, providing a framework for the law to account for the full, and complex, emotional reality of familial relationships
Transition from the Couette-Taylor system to the plane Couette system
We discuss the flow between concentric rotating cylinders in the limit of
large radii where the system approaches plane Couette flow. We discuss how in
this limit the linear instability that leads to the formation of Taylor
vortices is lost and how the character of the transition approaches that of
planar shear flows. In particular, a parameter regime is identified where
fractal distributions of life times and spatiotemporal intermittency occur.
Experiments in this regime should allow to study the characteristics of shear
flow turbulence in a closed flow geometry.Comment: 5 pages, 5 figure
Onset of Surface-Tension-Driven Benard Convection
Experiments with shadowgraph visualization reveal a subcritical transition to
a hexagonal convection pattern in thin liquid layers that have a free upper
surface and are heated from below. The measured critical Marangoni number (84)
and observation of hysteresis (3%) agree with theory. In some experiments,
imperfect bifurcation is observed and is attributed to deterministic forcing
caused in part by the lateral boundaries in the experiment.Comment: 4 pages. The RevTeX file has a macro allowing various styles. The
appropriate style is "mypprint" which is the defaul
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