Cosmic rays and random magnetic traps.

The spatial distribution of cosmic ray (CR) particles in the interstellar medium (ISM) is of major importance in radio astronomy, where its knowledge is essential for the interpretation of observations, and in theoretical astrophysics, where CRs contribute to the structure and dynamics of the ISM. Local inhomogeneities in interstellar magnetic field strength and structure can affect the local diffusivity and ensemble dynamics of the CR particles. Magnetic traps (regions between magnetic mirrors located on the same magnetic line) can lead to especially strong and persistent features in the CR spatial distribution.

Quantification of the morphological characteristics of hESC colonies.

The maintenance of the undifferentiated state in human embryonic stem cells (hESCs) is critical for further application in regenerative medicine, drug testing and studies of fundamental biology. Currently, the selection of the best quality cells and colonies for propagation is typically performed by eye, in terms of the displayed morphological features, such as prominent/abundant nucleoli and a colony with a tightly packed appearance and a well-defined edge. Using image analysis and computational tools, we precisely quantify these properties using phase-contrast images of hESC colonies of different sizes (0.

Endothelial Differentiation G Protein-Coupled Receptor 5 Plays an Important Role in Induction and Maintenance of Pluripotency.

Direct reprogramming of human somatic cells toward induced pluripotent stem cells holds great promise for regenerative medicine and basic biology. We used a high-throughput small interfering RNA screening assay in the initiation phase of reprogramming for 784 genes belonging to kinase and phosphatase families and identified 68 repressors and 22 effectors. Six new candidates belonging to the family of the G protein-coupled receptors (GPCRs) were identified, suggesting an important role for this key signaling pathway during somatic cell-induced reprogramming.

Productivity of Premodern Agriculture in the Cucuteni-Trypillia Area.

We present paleoeconomy reconstructions for premodern agriculture, selecting, wherever required, features and parameter values specific for the Cucuteni-Trypillia cultural unity (CTU; 5,400-2,700 BC, mostly the territory of modern Ukraine, Moldova, and Romania). We verify the self-consistency and viability of the archaeological evidence related to all major elements of the agricultural production cycle within the constraints provided by environmental and technological considerations. The starting point of our analysis is the paleodiet structure suggested by archaeological data, stable isotope analyses of human remains, and palynology studies in the CTU area.

The near-eastern roots of the Neolithic in South Asia.

The Fertile Crescent in the Near East is one of the independent origins of the Neolithic, the source from which farming and pottery-making spread across Europe from 9,000 to 6,000 years ago at an average rate of about 1 km/yr. There is also strong evidence for causal connections between the Near-Eastern Neolithic and that further east, up to the Indus Valley. The Neolithic in South Asia has been far less explored than its European counterpart, especially in terms of absolute (14)C) dating; hence, there were no previous attempts to assess quantitatively its spread in Asia.

Bayesian inference for a wave-front model of the neolithization of Europe.

We consider a wave-front model for the spread of neolithic culture across Europe, and use Bayesian inference techniques to provide estimates for the parameters within this model, as constrained by radiocarbon data from southern and western Europe. Our wave-front model allows for both an isotropic background spread (incorporating the effects of local geography) and a localized anisotropic spread associated with major waterways. We introduce an innovative numerical scheme to track the wave front, and use Gaussian process emulators to further increase the efficiency of our model, thereby making Markov chain Monte Carlo methods practical.

Reconnecting flux-rope dynamo.

We develop a model of the fluctuation dynamo in which the magnetic field is confined to thin flux ropes advected by a multiscale model of turbulence. Magnetic dissipation occurs only via reconnection of the flux ropes. This model can be viewed as an implementation of the asymptotic limit R_{m}-->infinity for a continuous magnetic field, where magnetic dissipation is strongly localized to small regions of strong-field gradients.

Dynamo action in Möbius flow.

We demonstrate that flows of conducting fluid along a Möbius strip and related surfaces are hydromagnetic dynamos, i.e., they can produce an exponentially growing magnetic field from an infinitesimal seed.

Magnetic structures produced by the small-scale dynamo.

Small-scale dynamo action has been obtained for a flow previously used to model fluid turbulence, where the sensitivity of the magnetic field parameters to the kinetic energy spectrum can be explored. We apply quantitative morphology diagnostics, based on the Minkowski functionals, to magnetic fields produced by the kinematic small-scale dynamo to show that magnetic structures are predominantly filamentary rather than sheetlike. Our results suggest that the thickness, width, and length of the structures scale differently with magnetic Reynolds number as R(m)(-2/(1-s)) and R(m)(-0.

Nonlinear states of the screw dynamo.

The self-excitation of magnetic field by a spiral Couette flow between two coaxial cylinders is considered. We solve numerically the fully nonlinear, three-dimensional magnetohydrodynamic (MHD) equations for magnetic Prandtl numbers P(m) (ratio of kinematic viscosity to magnetic diffusivity) between 0.14 and 10 and kinematic and magnetic Reynolds numbers up to about 2000.