464 research outputs found
On the eigenvalues of a specially rank-r updated complex matrix
AbstractIn this paper, an alternatively simpler proof to an eigenvalue theorem of a specially structured rank-r updated complex matrix is presented and also its characteristic polynomial is explicitly determined by Leverrier’s algorithm for m–D system
State‐of‐the‐Art Nonprobabilistic Finite Element Analyses
The finite element analysis of a mechanical system is conventionally performed in the context of deterministic inputs. However, uncertainties associated with material properties, geometric dimensions, subjective experiences, boundary conditions, and external loads are ubiquitous in engineering applications. The most popular techniques to handle these uncertain parameters are the probabilistic methods, in which uncertainties are modeled as random variables or stochastic processes based on a large amount of statistical information on each uncertain parameter. Nevertheless, subjective results could be obtained if insufficient information unavailable and nonprobabilistic methods can be alternatively employed, which has led to elegant procedures for the nonprobabilistic finite element analysis. In this chapter, each nonprobabilistic finite element analysis method can be decomposed as two individual parts, i.e., the core algorithm and preprocessing procedure. In this context, four types of algorithms and two typical preprocessing procedures as well as their effectiveness were described in detail, based on which novel hybrid algorithms can be conceived for the specific problems and the future work in this research field can be fostered
Elementary building blocks of graphene-nanoribbon-based electronic devices
Graphene nanoribbon junction based electronic devices are proposed in this letter. Nonequilibrium Green's function calculations show that nanoribbon junctions tailored from single layer graphene with different edge shapes and widths can act as metal/semiconductor junctions and quantum dots can be implemented. In virtue of the possibilities of patterning monolayer graphene down to atomic precision, these structures, quite different from the previously reported two-dimensional bulk graphene or carbon nanotube devices, are expected to be used as the building blocks of the future nanoelectronics. © 2007 American Institute of Physics.published_or_final_versio
Viscous damping of nanobeam resonators: humidity, thermal noise and the paddling effect
The nanobeam resonator is the key mechanical component in the
nano-electromechanical system. In addition to its high frequency originating
from its low dimension, the performance is significantly influenced by the
circumstances, especially at nanoscale where a large surface area of the
material is exposed. Molecular dynamics simulations and theoretical analysis
are used for a quantitative prediction on the damping behavior, such as the
critical damping condition and lifetime, of nanobeam resonators that directly
maps the fluid-structure properties and interaction information into dynamical
behaviors. We show here how the humidity defines the critical damping condition
through viscous forces, marking the transition from under-damping to
over-damping regime at elevated humidity. Novel phenomena such as the thermal
fluctuation and paddling effects are also discussed.Comment: 15 pages, 5 figure
Experimental Study of the Effects of Marrow Mesenchymal Stem Cells Transfected with Hypoxia-Inducible Factor-1α Gene
Objective. To construct the eukaryotic expression
vector hypoxia-inducible factor
1α-pcDNA3.1 and to investigate its transfective efficiency into
mesenchymal stem cells (MSCs) in vitro and the expression of
HIF-1α gene in MSCs.
Methods. mRNA of Wistar Rats' myocardial cells
was extracted, and cDNA was synthesized with Reverse Transcription
Kit, HIF-1α was
amplified by polymerase chain reaction (PCR), and constructed into
pcDNA3.1. Transfected
HIF-1α-pcDNA3.1 into MSCs by liposome mediated method. The expression
of HIF-1α in the
cells was detected by Western Blot Analysis and ELISA.
Results. Eukaryotic expression vector
HIF-1α-pcDNA3.1 was constructed successfully. Analyzed by flow
cytometer, The MSCs' surfaces mark were CD44+, SH3(CD73)+,
CD34−, CD45− and the CD44+ cells and SH3(CD73)+ cells were
94.7% and 97.3%, respectively, showing the high purity of
the cultured MSCs. After inducing, the cultured MSCs can
differentiate into osteoblasts and adipocytes successfully. In
HIF-1α gene
transfected MSCs, the expression of
HIF-1α mRNA and
HIF-1α protein were
both increased obviously. Conclusion.
HIF-1α was cloned
successfully.
HIF-1α-pcDNA3.1 can be transfected into MSCs by liposome-mediated
method effectively and which resulting stable expression of
HIF-1α in transfected
MSCs
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