Development of a large area gas photomultiplier with GEM/μ\muPIC

We are developing a new photon detector with micro pattern gaseous detectors. A semitransparent CsI photocathode is combined with 10cm$\times$10cm GEM/$\mu$PIC for the first prototype which is aimed for the large liquid Xe detectors. Using Ar+C$_2$H$_6$ (10%) gas, we achieved the gas gain of $10^5$ which is enough to detect single photoelectron. We, then, irradiated UV photons from a newly developed solid scintillator, LaF$_3$(Nd), to the detector and successfully detected single photoelectron.Comment: Poster presentation at ICHEP08 Philadelphia, USA, July 2008. 3 pages, LaTeX, 4 eps figure

Real-time observation of X-ray-induced intramolecular and interatomic electronic decay in CH2I2

The increasing availability of X-ray free-electron lasers (XFELs) has catalyzed the development of single-object structural determination and of structural dynamics tracking in realtime. Disentangling the molecular-level reactions triggered by the interaction with an XFEL pulse is a fundamental step towards developing such applications. Here we report real-time observations of XFEL-induced electronic decay via short-lived transient electronic states in the diiodomethane molecule, using a femtosecond near-infrared probe laser. We determine the lifetimes of the transient states populated during the XFEL-induced Auger cascades and find that multiply charged iodine ions are issued from short-lived (similar to 20 fs) transient states, whereas the singly charged ones originate from significantly longer-lived states (similar to 100 fs). We identify the mechanisms behind these different time scales: contrary to the short-lived transient states which relax by molecular Auger decay, the long-lived ones decay by an interatomic Coulombic decay between two iodine atoms, during the molecular fragmentation

Experimental Evaluation of the Density of Water in a Cell by Raman Microscopy

We report direct observation of a spatial distribution of water molecules inside of a living cell using Raman images of the O–H stretching band of water. The O–H Raman intensity of the nucleus was higher than that of the cytoplasm, indicating that the water density is higher in the nucleus than that in the cytoplasm. The shape of the O–H stretching band of the nucleus differed from that of the cytoplasm but was similar to that of the balanced salt solution surrounding cells, indicating less crowded environments in the nucleus. The concentration of biomolecules having C–H bonds was also estimated to be lower in the nucleus than that in the cytoplasm. These results indicate that the nucleus is less crowded with biomolecules than the cytoplasm

Embedding a Metal-Binding Motif for Copper Transporter into a Lipid Bilayer by Cu(I) Binding

Peptide–lipid interactions are widely involved with biologically significant phenomena, including the pathogenic mechanisms of protein misfolding diseases and transmembrane protein folding. In this paper, the interaction of the cysteine/tryptophan (Cys/Trp) motif, which is a metal-binding motif of copper transporter (Ctr) proteins, with a lipid bilayer was studied using fluorescence and circular dichroism (CD) spectroscopy. The binding of Cu­(I) to the Cys/Trp motif induced a large red-edge excitation shift in the Trp fluorescence, indicating that the Trp residue is located inside the lipid bilayer following complexation of Cu­(I) with the Cys/Trp motif. The Stern–Volmer quenching of the Trp fluorescence also supported the Cu­(I) binding peptide embedding in the lipid bilayer. The measurement of the CD spectra indicated the increase in β-sheet content of the Cys/Trp motif peptide as a result of Cu­(I) binding. These results lead to the conclusion that complexation with Cu­(I) induces the change in the secondary structure of the Cys/Trp motif, which results in the peptide embedding in the lipid bilayer. Cu­(I)-induced enhancement of the lipid affinity is discussed in terms of the mechanism for copper transport by Ctr

Time-Resolved Structured Illumination Microscopy for Phase Separation Dynamics of Water and 2-Butoxyethanol Mixtures: Interpretation of "Early Stage" Involving Micelle-Like Structures

Phase separation dynamics of a water/2-butoxyethanol (2BE) mixture was studied with newly developed time-resolved structured illumination microscopy (SIM). Interestingly, an employed hydrophobic fluorescent probe for SIM showed spectral shifts up to 500 ns after a laser-induced temperature jump, which suggests 2BE micellar-like aggregates become more hydrophobic at the initial stage of phase separation. This hydrophobic environment in 2BE aggregates, probably due to the ejection of water molecules, continued up to at least 10 μs. Time-resolved SIM and previously reported light scattering data clearly showed that the size of a periodic structure remained constant (ca. 300 nm) from 3 to 10 μs, and then the growth of periodic structures having the self-similarity started. We think that the former and the latter processes correspond to "early stage" (concentration growth) and "late stage" (size growth), respectively, in phase separation dynamics. Here we suggest that, in the early stage, the entity to bear 2BE phase be water-poor 2BE aggregates, and the number density of these aggregates would simply increase in time.status: publishe

Phase Separation Dynamics of a Binary Fluid with a Closed-Loop Phase Diagram

status: publishe