The accuracy of laser wavelength meters

The experimentally obtained accuracy and principal limitations of laser wavelength meters based on two different interferometric designs are discussed. Methods of calibrating these instruments and some experiments for testing their accuracy are presented. Finally, a comparison is given between different kinds of Lambda meters.     

The nucleophilic aromatic photosubstitution in photoaffinity labelling. A model study of a cycloheximide derivative.

The photoreactions of several 4-nitrocatechol ethers with the relatively hard nucleophile methylamine occurs at the $\text{meta}$ position respect to the nitro group. A derivative of the antibiotic cycloheximide carrying a 4-nitrocatechol ether moiety reacts with methylamine affording an $\text{in vitro}$ model for photoaffinity labelling.     

Theoretical study of pyridine and 4,4'-bipyridine adsorption on the lewis acid sites of alumina surfaces based on ab initio and density functional cluster calculations

The interactions of pyridine and 4,4'-bipyridine with the Lewis acid sites of alumina surfaces are investigated using ab initio and density functional calculations. Four cluster models of different sizes and shapes are chosen to represent the Lewis acid sites: three hydrogenated clusters Al(OH)(3), Al(4)O(9)H(6), and Al(10)O(21)H(12) and one non-hydrogenated cluster Al(4)O(6). The Hartree-Fock (HF) and B3LYP approaches with two basis sets 6-31G and 6-31+G are used to calculate the geometries, the electronic structures, the vibrational frequencies, and the adsorption energies of the complexes formed upon interaction of pyridine or 4,4'-bipyridine ligands on the cluster surfaces. Electronic structures are determined by the electrostatic potential (ESP) analysis of charges. Adsorption energies are calculated with corrections made for zero-point energies (ZPE) and basis set superposition error (BSSE). The ESP analysis of atomic charges reveals that the charge-transfer effects are more important in Lewis complexes formed with Al(4)O(6) cluster than in those formed with hydrogenated clusters Al(OH)(3), Al(4)O(9)H(6), and Al(10)O(21)H(12). The significantly larger charge transferred from pyridine or 4,4'-bipyridine ligand to Al(4)O(6) cluster should increase the adsorption energy of these complexes. Consequently, at all levels of calculation, the adsorption energies of pyridine and 4,4'-bipyridine complexed to Al(4)O(6) cluster ( approximately 46 kcal/mol), which compare very well to experiment, are strongly larger than those obtained for both pyridine and 4,4'-bipyridine ligands complexed to Al(OH)(3) (32 kcal/mol), Al(4)O(9)H(6) (24 kcal/mol) and Al(10)O(21)H(12) (25 kcal/mol) clusters. The corrected adsorption energy is found to be insensitive to basis set and electron correlation effects. It essentially depends on the ionic character of the cluster model rather than on its size. For 4,4'-bipyridine complexes, similar results to those obtained for pyridine are found, and the geometry and the amount of charge of the unbound pyridyl ring are unchanged upon complexation. The calculated vibrational frequencies and frequency shifts are little sensitive to the size and shape of the cluster model. The two ring stretching modes 8a and 19b of pyridine and 4,4'-bipyridine observed in the 1400-1600 cm(-1) region are the most affected modes upon adsorption, in good agreement with the available infrared and Raman data.     

Metal concentrations in scleractinean corals determined by instrumental neutron activation analysis and atomic absorption spectrometry

Five species of scleractinean corals, extracted from the Northern Havana reef, were studied by INAA and AAS. Selected specimens were sectioned in foot, center and head parts before pulverization procedure. INAA for different irradiation and decay time regimes in a reactor allowed the determination of: Na, Mg, Al, Cl, Sc, Cr, Co, Th, Lu, Eu, Ce, Hf, La and Sr. AAS was performed in a Pye Unicam Model 929 spectrometer. Cu, Mn, Ni, Zn, and Fe were detected. Ca concentration in all species was also established. Obtained Metal-Calcium ratios for Sr, Cu, Zn, Cr, Co, Fe, Mn, Ni and Sc are compared with reported values.     

Encapsulated Pd nanocrystals supported by nanoline-structured SrTiO3(001)

Palladium nanocrystals were grown on a nanostructured SrTiO(3)(001) surface and annealed in ultrahigh vacuum at 620 degrees C. This leads to the so-called strong metal-support interaction (SMSI) state, characterized by encapsulation of the metal clusters with an oxide layer. Scanning tunneling microscopy (STM) of the oxide adlayer on the Pd(111) cluster surface reveals two superstructures with different lattice parameters and crystallographic rotations. Interpretation of the STM images is most readily achieved via noncommensurate TiO(x)() surface layers which result in two distinct Moiré patterns.     

Random Forests and Networks Analysis

Wilson (Proceedings of the twenty-eight annual acm symposium on the theory of computing, pp. 296–303, 1996) in the 1990s described a simple and efficient algorithm based on loop-erased random walks to sample uniform spanning trees and more generally weighted trees or forests spanning a given graph. This algorithm provides a powerful tool in analyzing structures on networks and along this line of thinking, in recent works (Avena and Gaudillière in A proof of the transfer-current theorem in absence of reversibility, in Stat. Probab. Lett. 142, 17–22 (2018); Avena and Gaudillière in J Theor Probab, 2017.  https://doi.org/10.1007/s10959-017-0771-3; Avena et al. in Approximate and exact solutions of intertwining equations though random spanning forests, 2017. arXiv:1702.05992v1; Avena et al. in Intertwining wavelets or multiresolution analysis on graphs through random forests, 2017. arXiv:1707.04616, to appear in ACHA (2018)) we focused on applications of spanning rooted forests on finite graphs. The resulting main conclusions are reviewed in this paper by collecting related theorems, algorithms, heuristics and numerical experiments. A first foundational part on determinantal structures and efficient sampling procedures is followed by four main applications: (1) a random-walk-based notion of well-distributed points in a graph, (2) a framework to describe metastable-like dynamics in finite settings by means of Markov intertwining dualities, (3) coarse graining schemes for networks and associated processes, (4) wavelets-like pyramidal algorithms for graph signals.