LCLS Ultrafast Science Instruments:Conceptual Design Report

The Stanford Linear Accelerator Center (SLAC), along with Argonne National Laboratory (ANL), Lawrence Livermore National Laboratory (LLNL), and the University of California at Los Angeles (UCLA), is constructing a Free-Electron Laser (FEL) facility, which will operate in the wavelength range 1.5 nm - 0.15 nm. This FEL, the Linac Coherent Light Source (LCLS), utilizes the SLAC linac and will produce sub-picosecond pulses of short wavelength X-rays with very high peak brightness and almost complete transverse coherence. The final one-third of the SLAC linac will be used as the source of electrons for the LCLS. The high energy electrons will be transported across the SLAC Research Yard, into a tunnel which will house a long undulator. In passing through the undulator, the electrons will be bunched by the force of their own synchrotron radiation and produce an intense, monochromatic, spatially coherent beam of X-rays. By varying the electron energy, the FEL X-ray wavelength will be tunable from 1.5 nm to 0.15 nm. The LCLS will include two experimental halls as well as X-ray optics and infrastructure necessary to create a facility that can be developed for research in a variety of disciplines such as atomic physics, materials science, plasma physics and biosciences. This Conceptual Design Report, the authors believe, confirms the feasibility of designing and constructing three X-ray instruments in order to exploit the unique scientific capability of this new LCLS facility. The technical objective of the LCLS Ultrafast Science Instruments (LUSI) project is to design, build, and install at the LCLS three hard X-ray instruments that will complement the initial instrument included in the LCLS construction. As the science programs advance and new technological challenges appear, instrumentation needs to be developed and ready to conquer these new opportunities. The LCLS instrument concepts have been developed in close consultation with the scientific community through a series of workshops team meetings and focused reviews. In particular, the LUSI project instruments have been identified as meeting the most urgent needs of the scientific community based on the advice of the LCLS Scientific Advisory Committee (SAC) in response to an open call for letters of intent (LOI) from the breadth of the scientific community

Heterochromatin and the molecular mechanisms of 'parent-of-origin' effects in animals.

Twenty five years ago it was proposed that conserved components of constitutive heterochromatin assemble heterochromatinlike complexes in euchromatin and this could provide a general mechanism for regulating heritable (cell-to-cell) changes in gene expressibility. As a special case, differences in the assembly of heterochromatin-like complexes on homologous chromosomes might also regulate the parent-of-origin-dependent gene expression observed in placental mammals. Here, the progress made in the intervening period with emphasis on the role of heterochromatin and heterochromatin-like complexes in parent-of-origin effects in animals is reviewed