Precise Measurement of Muon Capture on the Proton

The aim of the μCap experiment is a 1% measurement of the singlet capture rate Λ _S for the basic electro-weak reaction μ + p → n + ν_μ. This observable is sensitive to the weak form-factors of the nucleon, in particular to the induced pseudoscalar coupling constant g _P . It will provide a rigorous test of theoretical predictions based on the Standard Model and effective theories of QCD. The present method is based on high precision lifetime measurements of μ⁻ in hydrogen gas and the comparison with the free μ⁺ lifetime. The μ⁻ experiment will be performed in ultra-clean, deuterium-depleted H₂ gas at 10 bar. Low density compared to liquid H₂ is chosen to avoid uncertainties due to ppμ formation. A time projection chamber acts as a pure hydrogen active target. It defines the muon stop position in 3D and detects rare background reactions. Decay electrons are tracked in cylindrical wire-chambers and a scintillator array covering 75% of 4π. This revised version was published online in August 2006 with corrections to the Cover Date.     

抗坏血酸有机锗倍半氧化物的合成及抗癌活性研究

通过三氯锗仿与抗坏血酸分子的加成反应,合成了一种新型有机锗倍半氧化物,产物的结构通过元素分析、IR及UV光谱等方法进行了表征．生物活性实验表明合成物对小鼠S-180肿瘤生长具有显著的抑制作用．     

Reversible attachment of perylenediimide fluorophore to glass surfaces via strong hydrogen-bonding

Chemical immobilization of a triethoxysilyl-functionalized hydrogen-bonding ureido-[2-(4-pyrimidone)] tetraplex produced interaction sites on a glass substrate that allowed association with a perylenediimide-functionalized tetraplex, providing noncovalent links of the fluorophore to the surface. The association between the self-complementary molecules was exceptionally strong, both in solution and at the surface, such that effective hydrogen-bonding was retained after repeated solvent washes.     

Evaluation of noncovalent interactions between peptides and polyether compounds via energy-variable collisionally activated dissociation

Energy-variable collisionally activated dissociation (CAD) was used to analyze noncovalent interactions of protonated peptide/polyether complexes in a quadrupole ion trap complexes were formed with a series of four polyether host molecules and thirteen peptide molecules. Comparison of dissociation thresholds revealed correlations between the gas-phase basicities of the peptides and polyether molecules and the onset of dissociation. The dissociation thresholds of complexes containing the tripeptides or pentapeptides were inversely proportional to the gas-phase basicities of the sites of protonation of the peptides. Intramolecular hydrogen bonding of the pentapeptides affected the observed dissociation thresholds as well. The dissociation thresholds also scaled proportionally to the gas-phase basicities of the polyethers in the complexes, and the importance of the conformational flexibility of the polyether ligand was confirmed for one of the histidine-containing tripeptide complexes.     

Measurements of the electric form factor of the neutron up to Q2=3.4 GeV2 using the reaction 3He(e,e'n)pp

The electric form factor of the neutron was determined from studies of the reaction 3He(e,e'n)pp in quasielastic kinematics in Hall A at Jefferson Lab. Longitudinally polarized electrons were scattered off a polarized target in which the nuclear polarization was oriented perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons that were registered in a large-solid-angle detector. More than doubling the Q2 range over which it is known, we find G(E)(n)=0.0236±0.0017(stat)±0.0026(syst), 0.0208±0.0024±0.0019, and 0.0147±0.0020±0.0014 for Q(2)=1.72, 2.48, and 3.41 GeV2, respectively.     

Heterogeneous oxidization of graphene nanosheets damages membrane

Graphene-based materials exhibit unique properties that have been sought to utilize for various potential applications. Many studies suggest that graphene-based materials can be cytotoxic, which may be attributed to destructive effects on cell membranes.However, there still are conflicting results regarding interactions between graphene-based materials and lipid membranes. Here,through cryo-electron microscopy(Cryo-EM) and dye-leakage experiments along with in silico methods, we found that graphene oxide nanosheets induce significant membrane damage, while the effect of pristine graphene is negligible. We revealed the importance of heterogeneous oxidization of graphene-based nanosheets in damaging vesicle membranes. Moreover, that not only the oxidization degree but also the oxidization loci and membrane tension play important roles in the cytotoxicity of the graphene-based nanosheets.     

A new property of frieze patterns

Landauer [Journal of Geometry 6, 155–183 (1975)] gives a 10 × 10 frieze table of which he observes that the last row consists of the negative squares of the last column. The present note generalizes and explains this phenomenon.The author is indebted to Memorial University of Newfoundland for the use of their facilities while preparing this paper.