6,370 research outputs found
Gene Expression Profile Changes After Short-activating RNA-mediated Induction of Endogenous Pluripotency Factors in Human Mesenchymal Stem Cells
It is now recognized that small noncoding RNA sequences have the ability to mediate transcriptional activation of specific target genes in human cells. Using bioinformatics analysis and functional screening, we screened short-activating RNA (saRNA) oligonucleotides designed to target the promoter regions of the pluripotency reprogramming factors, Kruppel-like factor 4 (KLF4) and c-MYC. We identified KLF4 and c-MYC promoter-targeted saRNA sequences that consistently induced increases in their respective levels of nascent mRNA and protein expression in a time- and dose-dependent manner, as compared with scrambled sequence control oligonucleotides. The functional consequences of saRNA-induced activation of each targeted reprogramming factor were then characterized by comprehensively profiling changes in gene expression by microarray analysis, which revealed significant increases in mRNA levels of their respective downstream pathway genes. Notably, the microarray profile after saRNA-mediated induction of endogenous KLF4 and c-MYC showed similar gene expression patterns for stem cell- and cell cycle-related genes as compared with lentiviral vector-mediated overexpression of exogenous KLF4 and c-MYC transgenes, while divergent gene expression patterns common to viral vector-mediated transgene delivery were also noted. The use of promoter-targeted saRNAs for the activation of pluripotency reprogramming factors could have broad implications for stem cell research
Quantum transport at the Dirac point: Mapping out the minimum conductivity from pristine to disordered graphene
The phase space for graphene's minimum conductivity is
mapped out using Landauer theory modified for scattering using Fermi's Golden
Rule, as well as the Non-Equilibrium Green's Function (NEGF) simulation with a
Monte Carlo sampling over impurity distributions. The resulting `fan diagram'
spans the range from ballistic to diffusive over varying aspect ratios (),
and bears several surprises. {The device aspect ratio determines how much
tunneling (between contacts) is allowed and becomes the dominant factor for the
evolution of from ballistic to diffusive regime. We find an
increasing (for ) or decreasing () trend in vs.
impurity density, all converging around at the dirty
limit}. In the diffusive limit, the {conductivity} quasi-saturates due to the
precise cancellation between the increase in conducting modes from charge
puddles vs the reduction in average transmission from scattering at the Dirac
Point. In the clean ballistic limit, the calculated conductivity of the lowest
mode shows a surprising absence of Fabry-P\'{e}rot oscillations, unlike other
materials including bilayer graphene. We argue that the lack of oscillations
even at low temperature is a signature of Klein tunneling
Strength, Toughness, Damage And Fatigue Of Rock
Assessment of rock mechanical properties depends on sample size and testing methodologies. Even for samples cored from the same rock outcrop the difference in properties appears to be sensitive to the local thermal and stress histories of the rock structure. Variations in the fracture toughness, unconfined compressive strength and tensile strength of a suite of granite samples, when tested using different procedures, are discussed in terms of experimental errors of the loading system as well as the thermal history
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