Chemical screen for epigenetic barriers to single allele activation of Oct4

Here we utilized the chromatin in vivo assay (CiA) mouse platform to directly examine the epigenetic barriers impeding the activation of the CiA:Oct4 allele in mouse embryonic fibroblasts (MEF)s when stimulated with a transcription factor. The CiA:Oct4 allele contains an engineered EGFP reporter replacing one copy of the Oct4 gene, with an upstream Gal4 array in the promoter that allows recruitment of chromatin modifying machinery. We stimulated gene activation of the CiA:Oct4 allele by binding a transcriptional activator to the Gal4 array. As with cellular reprograming, this process is inefficient with only a small percentage of the cells re-activating CiA:Oct4 after weeks. Epigenetic barriers to gene activation potentially come from heavy DNA methylation, histone deacetylation, chromatin compaction, and other posttranslational marks (PTM) at the differentiated CiA:Oct4 allele in MEFs. Using this platform, we performed a high-throughput chemical screen for compounds that increased the efficiency of activation. We found that Azacytidine and newer generation histone deacetylase (HDAC) inhibitors were the most efficient at facilitating directed transcriptional activation of this allele. We found one hit form our screen, Mocetinostat, improved iPSC generation under transcription factor reprogramming conditions. These results separate individual allele activation from whole cell reprograming and give new insights that will advance tissue engineering

Effects of Fermi energy, dot size and leads width on weak localization in chaotic quantum dots

Magnetotransport in chaotic quantum dots at low magnetic fields is investigated by means of a tight binding Hamiltonian on L x L clusters of the square lattice. Chaoticity is induced by introducing L bulk vacancies. The dependence of weak localization on the Fermi energy, dot size and leads width is investigated in detail and the results compared with those of previous analyses, in particular with random matrix theory predictions. Our results indicate that the dependence of the critical flux Phi_c on the square root of the number of open modes, as predicted by random matrix theory, is obscured by the strong energy dependence of the proportionality constant. Instead, the size dependence of the critical flux predicted by Efetov and random matrix theory, namely, Phi_c ~ sqrt{1/L}, is clearly illustrated by the present results. Our numerical results do also show that the weak localization term significantly decreases as the leads width W approaches L. However, calculations for W=L indicate that the weak localization effect does not disappear as L increases.Comment: RevTeX, 8 postscript figures include

Quantum Breaking Time Scaling in the Superdiffusive Dynamics

We show that the breaking time of quantum-classical correspondence depends on the type of kinetics and the dominant origin of stickiness. For sticky dynamics of quantum kicked rotor, when the hierarchical set of islands corresponds to the accelerator mode, we demonstrate by simulation that the breaking time scales as $\tau_{\hbar} \sim (1/\hbar)^{1/\mu}$ with the transport exponent $\mu > 1$ that corresponds to superdiffusive dynamics. We discuss also other possibilities for the breaking time scaling and transition to the logarithmic one $\tau_{\hbar} \sim \ln(1/\hbar)$ with respect to $\hbar$

Lagrangian Klein bottles in R^{2n}

It is shown that the n-dimensional Klein bottle admits a Lagrangian embedding into R^{2n} if and only if n is odd.Comment: V.2 - explicit formula for the Luttinger-type surgery; V.3 - section 3 corrected, section 6 expanded; 6 page

Electronic structure of nuclear-spin-polarization-induced quantum dots

We study a system in which electrons in a two-dimensional electron gas are confined by a nonhomogeneous nuclear spin polarization. The system consists of a heterostructure that has non-zero nuclei spins. We show that in this system electrons can be confined into a dot region through a local nuclear spin polarization. The nuclear-spin-polarization-induced quantum dot has interesting properties indicating that electron energy levels are time-dependent because of the nuclear spin relaxation and diffusion processes. Electron confining potential is a solution of diffusion equation with relaxation. Experimental investigations of the time-dependence of electron energy levels will result in more information about nuclear spin interactions in solids

The effect of near-surface plastic deformation on the hot corrosion and high temperature corrosion-fatigue response of a nickel-based superalloy

Surface treatments such as shot peening to inhibit fatigue crack initiation are essential processes when designing gas turbine components for aerospace applications. It is therefore crucial to understand the effects of shot peening in representative service environments. Here, the influence of surface treatment on the high temperature corrosion fatigue response of a polycrystalline nickel-based superalloy is considered, an area that has not previously been explored. Two shot peening conditions; 110H 7A 200% and 330H 7A 200%, along with a polished surface were chosen. Specimens were salted and exposed to SO2 gas during fatigue testing at 700 °C. A range of novel techniques including SEM, EBSD and axial chromatism profilometry were used to analyse the near surface cold work and surface condition before and after testing. EBSD local misorientation maps, paired with an increase in corrosion-fatigue life, suggest that a greater depth of cold work produced by the smaller shot size (110H), is providing a significant benefit in terms of hot corrosion and corrosion-fatigue performance. This paper concludes that the presence of a substantial layer of cold work is required to account for any metal loss due to the effects of hot corrosion. It is also evident that cold work hinders fatigue crack initiation and delays the onset of pit to crack transition

Moments of Nucleon Light Cone Quark Distributions Calculated in Full Lattice QCD

Moments of the quark density, helicity, and transversity distributions are calculated in unquenched lattice QCD. Calculations of proton matrix elements of operators corresponding to these moments through the operator product expansion have been performed on $16^3 \times 32$ lattices for Wilson fermions at $\beta = 5.6$ using configurations from the SESAM collaboration and at $\beta = 5.5$ using configurations from SCRI. One-loop perturbative renormalization corrections are included. At quark masses accessible in present calculations, there is no statistically significant difference between quenched and full QCD results, indicating that the contributions of quark-antiquark excitations from the Dirac Sea are small. Close agreement between calculations with cooled configurations containing essentially only instantons and the full gluon configurations indicates that quark zero modes associated with instantons play a dominant role. Naive linear extrapolation of the full QCD calculation to the physical pion mass yields results inconsistent with experiment. Extrapolation to the chiral limit including the physics of the pion cloud can resolve this discrepancy and the requirements for a definitive chiral extrapolation are described.Comment: 53 Pages Revtex, 26 Figures, 9 Tables. Added additional reference and updated referenced data in Table I