12,829 research outputs found
Numerical simulation of solid tumor blood perfusion and drug delivery during the “vascular normalization window” with antiangiogenic therapy
This Article is provided by the Brunel Open Access Publishing Fund - Copyright @ 2011 Hindawi PublishingTo investigate the influence of vascular normalization on solid tumor blood perfusion and drug delivery, we used the generated blood vessel network for simulations. Considering the hemodynamic parameters changing after antiangiogenic therapies, the results show that the interstitial fluid pressure (IFP) in tumor tissue domain decreases while the pressure gradient increases during the normalization window. The decreased IFP results in more efficient delivery of conventional drugs to the targeted cancer cells. The outcome of therapies will improve if the antiangiogenic therapies and conventional therapies are carefully scheduled
The curvature-induced gauge potential and the geometric momentum for a particle on a hypersphere
For a particle that is constrained to freely move on a hypersurface, the
curvature of the surface can induce a gauge potential; and for a particle on
the hypersphere, the gauge potential derived from the \textit{generalized
angular momentum algebra }on it has been known long before (J. Math. Phys.
\textbf{34}(1993)2827). We demonstrate that the momentum for the particle on
the hyperspherecan be the geometric one which obey commutation relations , in which is the
Planck's constant, and () symbolizes the th component
of the geometric momentum, and specifies the th component of the
angular momentum containing the spin-curvature coupling, and denotes the
radius of the dimensional hypersphere.Comment: 6 pages, no figur
Mathematical Modelling of a Brain Tumour Initiation and Early Development: A Coupled Model of Glioblastoma Growth, Pre-Existing Vessel Co-Option, Angiogenesis and Blood Perfusion
We propose a coupled mathematical modelling system to investigate glioblastoma growth in response to dynamic changes in chemical and haemodynamic microenvironments caused by pre-existing vessel co-option, remodelling, collapse and angiogenesis. A typical tree-like architecture network with different orders for vessel diameter is designed to model pre-existing vasculature in host tissue. The chemical substances including oxygen, vascular endothelial growth factor, extra-cellular matrix and matrix degradation enzymes are alculated based on the haemodynamic environment which is obtained by coupled modelling of intravascular blood flow with interstitial fluid flow. The haemodynamic changes, including vessel diameter and permeability, are introduced to reflect a series of pathological characteristics of abnormal tumour vessels including vessel dilation, leakage, angiogenesis, regression and collapse. Migrating cells are included as a new phenotype to describe the migration behaviour of malignant tumour cells. The simulation focuses on the avascular phase of tumour development and stops at an early phase of angiogenesis. The model is able to demonstrate the
main features of glioblastoma growth in this phase such as the formation of pseudopalisades, cell migration along the host vessels, the pre-existing vasculature co-option, angiogenesis and remodelling. The model also enables us to examine the influence of initial conditions and local environment on the early phase of glioblastoma growth.The authors like to thank Mr. Justin Halls for his kind help on manuscript preparation. This research is supported by the National Basic Research Program of China (973 Program) (No. 2013CB733800), the National Nature Science Foundation of China (No. 11302050, No. 11272091), the Nature Science Foundation of Jiangsu Province (No. BK20130593)
Creation of Entanglement between Two Electron Spins Induced by Many Spin Ensemble Excitations
We theoretically explore the possibility of creating spin entanglement by
simultaneously coupling two electronic spins to a nuclear ensemble. By
microscopically modeling the spin ensemble with a single mode boson field, we
use the time-dependent Fr\"{o}hlich transformation (TDFT) method developed most
recently [Yong Li, C. Bruder, and C. P. Sun, Phys. Rev. A \textbf{75}, 032302
(2007)] to calculate the effective coupling between the two spins. Our
investigation shows that the total system realizes a solid state based
architecture for cavity QED. Exchanging such kind effective boson in a virtual
process can result in an effective interaction between two spins. It is
discovered that a maximum entangled state can be obtained when the velocity of
the electrons matches the initial distance between them in a suitable way.
Moreover, we also study how the number of collective excitations influences the
entanglement. It is shown that the larger the number of excitation is, the less
the two spins entangle each other.Comment: 8 pages, 4 figure
Spin injection from the Heusler alloy Co_2MnGe into Al_0.1Ga_0.9As/GaAs heterostructures
Electrical spin injection from the Heusler alloy Co_2MnGe into a p-i-n
Al_0.1Ga_0.9As/GaAs light emitting diode is demonstrated. A maximum
steady-state spin polarization of approximately 13% at 2 K is measured in two
types of heterostructures. The injected spin polarization at 2 K is calculated
to be 27% based on a calibration of the spin detector using Hanle effect
measurements. Although the dependence on electrical bias conditions is
qualitatively similar to Fe-based spin injection devices of the same design,
the spin polarization injected from Co_2MnGe decays more rapidly with
increasing temperature.Comment: 8 pages, 4 figure
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