Fractal heterogeneity in minimal matrix models of scars modulates stiff-niche stem-cell responses via nuclear exit of a mechanorepressor.

Scarring is a long-lasting problem in higher animals, and reductionist approaches could aid in developing treatments. Here, we show that copolymerization of collagen I with polyacrylamide produces minimal matrix models of scars (MMMS), in which fractal-fibre bundles segregate heterogeneously to the hydrogel subsurface. Matrix stiffens locally-as in scars-while allowing separate control over adhesive-ligand density.

Cell rigidity and shape override CD47's "self"-signaling in phagocytosis by hyperactivating myosin-II.

A macrophage engulfs another cell or foreign particle in an adhesive process that often activates myosin-II, unless the macrophage also engages "marker of self" CD47 that inhibits myosin. For many cell types, adhesion-induced activation of myosin-II is maximized by adhesion to a rigid rather than a flexible substrate. Here we demonstrate that rigidity of a phagocytosed cell also hyperactivates myosin-II, which locally overwhelms self-signaling at a phagocytic synapse.

Developmental control of the melanocortin-4 receptor by MRAP2 proteins in zebrafish.

The melanocortin-4 receptor (MC4R) is essential for control of energy homeostasis in vertebrates. MC4R interacts with melanocortin receptor accessory protein 2 (MRAP2) in vitro, but its functions in vivo are unknown. We found that MRAP2a, a larval form, stimulates growth of zebrafish by specifically blocking the action of MC4R.

Performance of a short "magnetic bottle" electron spectrometer.

In this article, a newly constructed electron spectrometer of the magnetic bottle type is described. The instrument is part of an apparatus for measuring the electron spectra of free clusters using synchrotron radiation. Argon and helium outer valence photoelectron spectra have been recorded in order to investigate the characteristic features of the spectrometer.

Nonregenerative natural resources in a sustainable system of energy supply.

Following the lead of the European Union in introducing binding measures to promote the use of regenerative energy forms, it is not unreasonable to assume that the global demand for combustible raw materials for energy generation will be reduced considerably in the second half of this century. This will not only have a favourable effect on the CO(2) concentration in the atmosphere, but will also help preserve fossil fuels-important as raw materials in the chemical industry-for future generations. Nevertheless, associated with the concomitant massive shift to regenerative energy forms, there will be a strong demand for other exhaustible raw materials, in particular metals, some of which are already regarded as scarce.

Autoionization mediated by electron transfer.

Electron-electron coincidence spectra of Ar-Kr clusters after photoionization have been measured. An electron with the kinetic energy range from 0 to approximately 1 eV is found in coincidence with the Ar 3s cluster photoelectron. The low kinetic energy electron can be attributed to an Ar + Kr+ + Kr+ final state which forms after electron transfer mediated decay.

Interatomic Coulombic decay in mixed NeKr clusters.

We report the occurrence of interatomic Coulombic decay (ICD) in mixed NeKr clusters. A well-defined feature ranging from 9 to 12 eV in kinetic energy is observed in coincidence with the Ne 2s photoelectrons. It derives from an ICD process, in which an initial Ne 2s vacancy is filled by a Ne 2p electron and an electron is emitted from a 4p level on a neighboring Kr atom.

Separating the vibrationally resolved Auger decay channels for a CO core hole state.

The K-VV Auger spectrum of carbon monoxide (CO) excited by C 1s photoionization has been investigated with a novel electron-electron coincidence setup. The energy resolution is sufficiently high to resolve the vibrational energy levels of the core-ionized intermediate state and of most dicationic final states in the two-dimensional electron energy map. We demonstrate how the influence of vibrational states on a molecular Auger spectrum can be accessed experimentally without the constraint of averaging over all intermediate state energies.