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.     

Effect of spatial heterogeneity on level of rejuvenation in Ni80P20 metallic glass

Understanding the relation between spatial heterogeneity and structural rejuvenation is one of the hottest topics in the field of metallic glasses (MGs). In this work, molecular dynamics (MD) simulation is implemented to discover the effects of initial spatial heterogeneity on the level of rejuvenation in the Ni$_{80}$P$_{20 }$MGs. For this purpose, the samples are prepared with cooling rates of $10^{10}$ K/s-$10^{12}$ K/s to make glassy alloys with different atomic configurations. Firstly, it is found that the increase in the cooling rate leads the Gaussian-type shear modulus distribution to widen, indicating the aggregations in both elastically soft and hard regions. After the primary evaluations, the elastostatic loading is also used to transform structural rejuvenation into the atomic configurations. The results indicate that the sample with intermediate structural heterogeneity prepared with 10$^{11}$ K/s exhibits the maximum structural rejuvenation which is due to the fact that the atomic configuration in an intermediate structure contains more potential sites for generating the maximum atomic rearrangement and loosely packed regions under an external excitation. The features of atomic rearrangement and structural changes under the rejuvenation process are discussed in detail.     

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.     

A study of some parameters relevant to the response of harwell PMMA dosimeters to gamma and electron irradiation

The effects on the radiation response of Harwell polymethylmethacrylate (PMMA) dosimeters of dose-rate, radiation type, temperature during irradiation and post-irradiation storage, and post-irradiation stability, are of importance to the operators of commercial irradiation facilities.

This paper describes recent studies of the effects of some of these parameters on the radiation response of Harwell Red 4034, Amber 3042, and Gammachrome YR Perspex dosimeters, and provides data on batch to batch variation and shelf-life.