Corrugated single layer templates for molecules: From <Emphasis Type="Italic">h</Emphasis>-BN nanomesh to graphene based quantum dot arrays

Functional nano-templates enable self-assembly of otherwise impossible arrangements of molecules. A particular class of such templates is that of sp ² hybridized single layers of hexagonal boron nitride or carbon (graphene) on metal supports. If the substrate and the single layer have a lattice mismatch, superstructures are formed. On substrates like rhodium or ruthenium these superstructures have unit cells with ～3-nm lattice constant. They are corrugated and contain sub-units, which behave like traps for molecules or quantum dots, which are small enough to become operational at room temperature. For graphene on Rh(111) we emphasize a new structural element of small extra hills within the corrugation landscape. For the case of molecules like water it is shown that new phases assemble on such templates, and that they can be used as “nano-laboratories” where many individual processes are studied in parallel. Furthermore, it is shown that the h-BN/Rh(111) nanomesh displays a strong scanning tunneling microscopy-induced luminescence contrast within the 3 nm unit cell which is a way to address trapped molecules and/or quantum dots.     

On general two-scale convergence and its application to the characterization of <Emphasis Type="Italic">G</Emphasis>-limits

We characterize some G-limits using two-scale techniques and investigate a method to detect deviations from the arithmetic mean in the obtained G-limit provided no periodicity assumptions are involved. We also prove some results on the properties of generalized two-scale convergence.     

Comparison of methodologies for determination of residual peracetic acid in wastewater disinfection

The use of peracetic acid (PAA) in the disinfection of sanitary effluents provides an opportunity for the study of analytic methods that permit the determination of the residual concentration of the disinfectant in the effluent. The object of the present study is to compare different methodologies for the determination of residual PAA in concentrations recommended for disinfection of wastewater. The methodologies adopted in this study include three redox titration methods and one spectrophotometric method. Preliminary tests were performed by adding PAA (0.1; 0.5; 1.0; 5.0 and 10.0?mg?L^?1) to distilled water, and later reevaluated by applying the same concentrations of the disinfectant in wastewater. The results obtained were statistically evaluated and showed that the concentrations between 0.5 and 10?mg?L^?1 of PAA could be determined both by the cerimetric/iodometric titration method and by the spectrophotometric method using DPD chromophore with catalase. For concentrations between 0.1 and 0.5?mg?L^?1, only the spectrophotometric method provided satisfactory results.     

Random hypergraph coloring algorithms and the weak chromatic number

We present a hypergraph coloring algorithm and analyze its performance in spaces of random hypergrpahs. In these spaces the number of colors used by our algorithm is almost surely within a small constant factor (less than 2) of the weak chromatic number of the hypergraph. This also establishes new upper and lower bounds for the weak chromatic number of uniform hypergraphs.     

Thermal stability, oxygen non-stoichiometry and transport properties of LaNi0.6Fe0.4O3

Thermal stability, oxygen non-stoichiometry and electrical conductivity of LaNi_0.6Fe_0.4O_3−δ were investigated in the temperature region of 20-1000 °C in Ar/O₂ gas flows at oxygen partial pressures between 0.5 and 21,000 Pa. Diffusion mobility was measured in Ar/O₂ gas flow at pO₂ = 18 Pa. Crystal structure of this compound was found to be stable at the mentioned experimental conditions. LaNi_0.6Fe_0.4O_3−δ is a p-type semiconductor with metallic type conductivity above 150 °C at the investigated pO₂ range. Two different (fast and slow) oxygen exchange areas on the temperature-pO₂ diagram were established, which are due to two different oxygen anion positions in the double B-site mixed perovskite structure. Oxygen non-stoichiometry in the fast oxygen exchange region reaches about 0.005 of oxygen atomic index. Chemical diffusion and oxygen surface exchange coefficients do not vary at 600-800 °C, but show visible increase above 800-850 °C.     

Carbazole-based cyano-stilbene highly fluorescent microcrystals

Aggregation-induced enhanced emission (AIEE) is reported for 1-cyano-trans-1,2-bis-(4-carbazolyl)phenylethylene (CN-CPE). The weak luminescence of dilute CN-CPE solutions is enhanced upon aggregate formation into 2-3 μm sized crystals. In contrast to general observations, crystal formation of CN-CPE causes a blue-shift in emission and enhances the intensity. X-ray crystallographic analysis revealed that key factors causing high luminescence efficiency in the crystal are a lack of strong cofacial π-π alignment and the existence of the strong supramolecular interactions due to the intermolecular H-bonding. These factors seem to be responsible for the AIEE phenomenon as molecules of CN-CPE are held in a rigid twisted conformation, thereby increasing the fluorescence intensity in the solid or aggregated states. Accordingly, conformational twisting in the crystal packing process may be responsible for the unusual emission blue-shift in the aggregate.     

Structure of oriented polyacrylonitrile films

Infrared dichroic measurements, refined to apply to Systems of low orientation, have been used to determine the structure of uniplanar and biaxially drawn polyacrylonitrile films. Orientation results in an alignment of the molecular chains with some degree of unkinking of the molecule. Preferential orientation of the nitrile side groups occurs due to the intermolecular dipolar attractions. Contrary to previous work, the results indicate that this dipolar interaction yields nitrile groups less well oriented than the chains with respect to the direction of draw.     

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

Commonly used rating scales and tests have been found lacking reliability and validity, for example in neurodegenerative diseases studies, owing to not making recourse to the inherent ordinality of human responses, nor acknowledging the separability of person ability and item difficulty parameters according to the well-known Rasch model. Here, we adopt an information theory approach, particularly extending deployment of the classic Brillouin entropy expression when explaining the difficulty of recalling non-verbal sequences in memory tests (i.e., Corsi Block Test and Digit Span Test): a more ordered task, of less entropy, will generally be easier to perform. Construct specification equations (CSEs) as a part of a methodological development, with entropy-based variables dominating, are found experimentally to explain (r =R2 = 0.98) and predict the construct of task difficulty for short-term memory tests using data from the NeuroMET (n = 88) and Gothenburg MCI (n = 257) studies. We propose entropy-based equivalence criteria, whereby different tasks (in the form of items) from different tests can be combined, enabling new memory tests to be formed by choosing a bespoke selection of items, leading to more efficient testing, improved reliability (reduced uncertainties) and validity. This provides opportunities for more practical and accurate measurement in clinical practice, research and trials.     

Significance of Protein–Substrate Hydrogen Bonding for the Selectivity of P450-Catalysed Oxidations

P450_cin and P450_cam are bacterial cytochromes P450 that specifically hydroxylate bicyclic monoterpenes. Protein–substrate H bonding has been previously proposed as crucial in the selectivity of P450_cin oxidations, but not as essential for P450_cam. To examine the difference in importance of H bonds in these two model P450s, the P450-catalysed oxidation products from thiocamphor were compared. Surprisingly, both P450s oxidised thiocamphor predominantly to the corresponding S-oxides, in contrast to previous reports, and this is the first report of P450-catalysed sulfine generation from a thioketone. Additionally, the result emphasised the importance of the protein–substrate H bond to selectivity in both P450_cin and P450_cam. The H bonding in P450_cam was re-examined using camphane, another substrate for which the protein–substrate H bond is absent. The results indicated that both H bonding and hydrophobic interactions between substrate and protein play a role in selectivity. Interestingly, the protein–substrate H bond was not a factor in substrate affinity for the enzyme.