Toward Open-Closed String Theoretical Description of Rolling Tachyon

We consider how the time-dependent decay process of an unstable D-brane should be described in the full (quantum) open-closed string theory. It is argued that the system, starting from the unstable D-brane configuration, will evolve in time into the time-independent open string tachyon vacuum configuration which we assume to be finite, with the total energy conserved. As a concrete realization of this idea, we construct a toy model describing the open and closed string tachyons which admits such a time-dependent solution. The structure of our model has some resemblance to that of open-closed string field theory.Comment: 1+10 pages, 6 figures. v2: a reference adde

Gauge Invariant Operators and Closed String Scattering in Open String Field Theory

Using the recent proposal for the observables in open string field theory, we explicitly compute the coupling of closed string tachyon and massless states with the open string states up to level two. Using these couplings, we then calculate the tree level S-matrix elements of two closed string tachyons or two massless states in the open string field theory. Up to some contact terms, the results reproduce exactly the corresponding amplitudes in the bosonic string theory.Comment: 13 pages, Latex file; v2: numerical coefficients fixed, conclusions unchanged, ref. adde

Tachyon Kink on non-BPS Dp-brane in the General Background

This paper is devoted to the study of the tachyon kink on the worldvolume of a non-BPS Dp-brane that is embedded in general background, including NS-NS two form B and also general Ramond-Ramond field. We will explicitly show that the dynamics of the kink is described by the equations of motion that arrise from the DBI and WZ action for D(p-1)-brane.Comment: 28 page

Translesion synthesis in mammalian cells

DNA damage blocks the progression of the replication fork. In order to circumvent the damaged bases, cells employ specialized low stringency DNA polymerases, which are able to carry out translesion synthesis (TLS) past different types of damage. The five polymerases used in TLS in human cells have different substrate specificities, enabling them to deal with many different types of damaged bases. PCNA plays a central role in recruiting the TLS polymerases and effecting the polymerase switch from replicative to TLS polymerase. When the fork is blocked PCNA gets ubiquitinated. This increases its affinity for the TLS polymerases, which all have novel ubiquitin-binding motifs, thereby facilitating their engagement at the stalled fork to effect TLS

ATR-mediated phosphorylation of DNA polymerase η is needed for efficient recovery from UV damage

DNA polymerase η (polη) belongs to the Y-family of DNA polymerases and facilitates translesion synthesis past UV damage. We show that, after UV irradiation, polη becomes phosphorylated at Ser601 by the ataxia-telangiectasia mutated and Rad3-related (ATR) kinase. DNA damage–induced phosphorylation of polη depends on its physical interaction with Rad18 but is independent of PCNA monoubiquitination. It requires the ubiquitin-binding domain of polη but not its PCNA-interacting motif. ATR-dependent phosphorylation of polη is necessary to restore normal survival and postreplication repair after ultraviolet irradiation in xeroderma pigmentosum variant fibroblasts, and is involved in the checkpoint response to UV damage. Taken together, our results provide evidence for a link between DNA damage–induced checkpoint activation and translesion synthesis in mammalian cells

Accelerator system for the PRISM based muon to electron conversion experiment

The next generation of lepton flavor violation experiments need high intensity and high quality muon beams. Production of such beams requires sending a short, high intensity proton pulse to the pion production target, capturing pions and collecting the resulting muons in the large acceptance transport system. The substantial increase of beam quality can be obtained by applying the RF phase rotation on the muon beam in the dedicated FFAG ring, which was proposed for the PRISM project.This allows to reduce the momentum spread of the beam and to purify from the unwanted components like pions or secondary protons. A PRISM Task Force is addressing the accelerator and detector issues that need to be solved in order to realize the PRISM experiment. The parameters of the required proton beam, the principles of the PRISM experiment and the baseline FFAG design are introduced. The spectrum of alternative designs for the PRISM FFAG ring are shown. Progress on ring main systems like injection and RF are presented. The current status of the study and its future directions are discussed.Comment: Studies performed within the PRISM Task Force initiativ