Electronic structure of C60 on Au(887)

We present an analysis of the electronic structure of C60 adsorbed on a vicinal Au(111) surface at different fullerene coverages using photoemission, x-ray absorption, and scanning tunneling microscopy/spectroscopy (STS). STS provides a straightforward determination of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels with respect to the Fermi energy. At C60 coverages of 0.5 and 1 ML a 2.7 eV wide HOMO-LUMO gap is found. The near-edge x-ray absorption fine structure (NEXAFS) spectrum for the 0.5 ML C60 nanomesh structure displays a significant intensity at the low energy side of the LUMO exciton peak, which is explained as due to absorption into HOMO-LUMO gap states localized at individual C60 cluster edges. From 0.5 to 1 ML we observe a rigid shift of the HOMO-LUMO peaks in the STS spectra and an almost complete quenching of the gap states feature in NEXAFS.     

Surface plasmon resonance study on HIV-1 integrase strand transfer activity

Understanding the molecular mechanism of HIV-1 integrase (IN) activity is critical to find functional inhibitors for an effective AIDS therapy. A robust, fast, and sensitive method for studying IN activity is required. In this work, an assay for real-time label-free monitoring of the IN activity based on surface plasmon resonance was developed. This assay enabled direct monitoring of the integration of a viral doubled-stranded (ds) DNA into the host genome. The strand transfer reaction was detected by using two different DNA targets: supercoiled plasmid (pUC 19) and short palindrome oligonucleotide. The effect of the length of the DNA target on the possibility to monitor the actual process of the strand transfer reaction is discussed. The surface density of integrated ds-DNA was determined. IN binding to the oligonucleotide complexes and model DNA triplexes in the presence of various divalent ions as metal cofactors was investigated as well. The assay developed can serve as an important analytical tool to search for potential strand transfer reaction inhibitors as well as for the study of compounds interfering with the binding of ds long terminal repeats–IN complexes with the host DNA. HIV-1 integrase strand transfer activity was monitored in real time using a multichannel surface plasmon resonance biosensor. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

TiO2 microsphere-based metamaterials exhibiting effective magnetic response in the terahertz regime

The static magnetic structure of a single shape-defective Ni₈₀Fe₂₀ nanowire has been investigated by magnetic force microscopy (MFM). The result shows that defects of the shape of the nanowire have an effect on the magnetic state of the nanowire. In order to check the influence of defects of the shape on the magnetic state, a micromagnetic simulation and a MFM image simulated computation are introduced. Two model systems are studied: (I) model?I: no defects of the shape is present and (II) model?II: the defects of the shape are introduced into the ends of the nanowire. The simulated computation result of model?II is in good agreement with experimental results for the single Ni₈₀Fe₂₀ nanowire. It may have important significance for guiding in sample preparation and application.     

The Role of Entropy in Construct Specification Equations (CSE) to Improve the Validity of Memory Tests: Extension to Word Lists

Metrological methods for word learning list tests can be developed with an information theoretical approach extending earlier simple syntax studies. A classic Brillouin entropy expression is applied to the analysis of the Rey’s Auditory Verbal Learning Test RAVLT (immediate recall), where more ordered tasks—with less entropy—are easier to perform. The findings from three case studies are described, including 225 assessments of the NeuroMET2 cohort of persons spanning a cognitive spectrum from healthy older adults to patients with dementia. In the first study, ordinality in the raw scores is compensated for, and item and person attributes are separated with the Rasch model. In the second, the RAVLT IR task difficulty, including serial position effects (SPE), particularly Primacy and Recency, is adequately explained (Pearson’s correlation R=0.80) with construct specification equations (CSE). The third study suggests multidimensionality is introduced by SPE, as revealed through goodness-of-fit statistics of the Rasch analyses. Loading factors common to two kinds of principal component analyses (PCA) for CSE formulation and goodness-of-fit logistic regressions are identified. More consistent ways of defining and analysing memory task difficulties, including SPE, can maintain the unique metrological properties of the Rasch model and improve the estimates and understanding of a person’s memory abilities on the path towards better-targeted and more fit-for-purpose diagnostics.     

Use of ionic membranes in the fractionation of water-alcohol mixtures by the pervaporation process

Five membranes, constituted of ionic chains grafted onto inert matrix, were studied in pervaporation of water - ethanol mixtures of different compositions. The permeability and selectivity of all five membranes showed a marked dependence on the nature of the counter-ions. Water permeates preferentially through all the types of membrane and counter-ions, except the protonated carboxylate membrane. For cation exchange membranes with alcaline counter-ions, the selectivity decreases in the following sequence: K+<Na+<Li+<H+. The permeability of the sulfonate membrane follows the reversed sequence, while that of the carboxylate membrane follows the same sequence, i.e. there is no trade-off between permeability and selectivity for the latter membrane. The anion-exchange (quaternized amine) membrane behaved similarly to the sulfonate membrane, i.e. the permeability and the selectivity vary in opposite directions. An attempt to interpret the influence of the nature of counter-ions on the basis of physico-chemical properties of the ion pairs was made.     

Simulated diffraction on TiN coatings with gradients

A method of computer simulated X-ray diffraction patterns has been applied to TiN coatings assuming different gradients of lattice parameters, microstrain or grain size in the direction normal to the substrate surface. The generated diffraction patterns have been compared with experimental ones and a possibility of real occurrence of such gradients is discussed. This method is superior to the methods based on intensity weighted average quantities which do not take into account actual profiles of diffraction peaks.     

Scanning Tunneling Spectroscopy of Lithium-Decorated Graphene

Lithium decoration of graphene on SiC(0001) is achieved in a surface science approach by intercalation and adsorption of the alkali metal. Spectroscopy of the differential conductance with a scanning tunneling microscope at the Li-decorated graphene surfaces does not give rise to a pairing gap at the Fermi energy, which may be expected because of the previously predicted superconducting phase [Profeta et al., Nat. Phys. 2012 , 8, 131]. Rather, pronounced gaps in the spectroscopic data of intercalated samples reflect the excitation of graphene phonons. Rationales that possibly explain this discrepancy between experimental findings and theoretical predictions are suggested.