The regulation of miRNAs is critical to the definition of cell identity and behavior in normal physiology and disease. To date, the dynamics of miRNA degradation and the mechanisms involved in remain largely obscure, in particular, in higher organisms. Here, we developed a pulse-chase approach based on metabolic RNA labeling to calculate miRNA decay rates at genome-wide scale in mammalian cells. Our analysis revealed heterogeneous miRNA half-lives, with many species behaving as stable molecules (T 1/2 > 24 h), while others, including passenger miRNAs and a number (25/129) of guide miRNAs, are quickly turned over (T 1/2 = 4-14 h). Decay rates were coupled with other features, including genomic organization, transcription rates, structural heterogeneity (isomiRs), and target abundance, measured through quantitative experimental approaches. This comprehensive analysis highlighted functional mechanisms that mediate miRNA degradation, as well as the importance of decay dynamics in the regulation of the miRNA pool under both steady-state conditions and during cell transitions.

Mathematical modeling and analysis of 3D epithelial structures indicate that epithelial growth can take place far from mechanical equilibrium, depending on cell–cell and cell–ECM contact, cell division, cortical contractility, and cell motility.

In this paper we employ a gaussian expansion within the finite-U slave-bosons formalism to investigate the momentum structure of the electron-phonon vertex function in the Hubbard model as function of U and n. The suppression of large momentum scattering and the onset a small-q peak structure, parametrized by a cut-off qc, are shown to be essentially ruled by the band narrowing factor ZMF due to the electronic correlation. A phase diagram of ZMF and qc in the whole U -n space is presented. Our results are in more than qualitative agreement with a recent numerical analysis and permit to understand some anomalous features of the Quantum Monte Carlo data.PACS numbers: 71.10. Fd,71.27.+a,71.45.Lr In the past months a variety of experiments have pointed out an important role of the electron-phonon (el-ph) interaction in many physical properties of the cuprates. 1,2,3 These recent findings have triggered a renewed interest for a theoretical understanding of the elph properties in strongly correlated systems.One of the most remarkable effects of the strong electronic correlation on the el-ph properties is a to favor forward (small q) scattering in the electron-phonon vertex, q being the exchanged phonon momentum. This feature was investigated in the past by means of analytical techniques based on slave-bosons or X-operators. 4,5,6,7 The assumption of forward scattering predominance within an el-ph framework was shown to explain in a natural way several anomalous properties of cuprates as the difference between transport and superconducting el-ph coupling constants, 6 the linear temperature behaviour of the resistivity, 8 the d-wave symmetry of the superconducting gap. 7,9 Small q scattering selection was shown moreover to be responsible in a natural way for high-T c superconductivity within the context of the nonadiabatic superconductivity. 10 So far, this important feature was analyzed only by means of analytical approaches in the U = ∞ limit and a definitive confirm of it based on numerical methods was lacking. The charge response at finite U was addressed in Refs. 11,12, which however focused only on q = 0 susceptibilities. With these motivations in a recent paper Huang et al have addressed this issue in the twodimensional Hubbard model with generic U by using Quantum Monte Carlo (QMC) techniques on a 8×8 cluster. 13 Their results provide a good agreement with the previous analytical studies and represent an important contribution to assess the relevance of el-ph interaction in correlated system.In this paper we employ the slave-boson techniques to investigate the evaluation of the momentum structure of the el-ph vertex interaction as function of the Hubbard repulsion U . While the previous analytical studies were limited to the U = ∞ limit, 4,5,6,7 we were able in this way to evaluate the small momenta selection in the whole phase diagram of parameters U -n, where n is the electron filling. In particular we show that the predominance of small q scattering is strongly dependent on the closeness of the system to t...

We introduce a novel random field Ising model, grounded on experimental observations, to assess the importance of metric correlations in cortical circuits in vitro. Metric correlations arise from both the finite axonal length and the heterogeneity in the spatial arrangement of neurons. The experiments consider the response of neuronal cultures to an external electric stimulation for a gradually weaker connectivity strength between neurons, and in cultures with different spatial configurations. The model can be analytically solved in the metric-free, mean-field scenario. The presence of metric correlations precipitates a strong deviation from the mean field. Null models of the same networks that preserve the distribution of connections recover the mean field. Our results show that metric-inherited correlations in spatial networks dominate the connectivity blueprint, mask the actual distribution of connections, and may emerge as the asset that shapes network dynamics.