Some t-Homogeneous Sets of Permutations

Perpendicular Arrays are orderedcombinatorial structures, which recently have found applicationsin cryptography. A fundamental construction uses as ingredientscombinatorial designs and uniformly t-homogeneoussets of permutations. We study the latter type of objects. Thesemay also be viewed as generalizations of t-homogeneousgroups of permutations. Several construction techniques are given.Here we concentrate on the optimal case, where the number ofpermutations attains the lower bound. We obtain several new optimalsuch sets of permutations. Each example allows the constructionof infinite families of perpendicular arrays.     

A new family of 4-designs

We construct a family of simple 4-designs with parameters 4 – (2 ^f + 1, 6, 10),f odd.     

Mapping dynamical heterogeneity in structural glasses to correlated fluctuations of the time variables

Dynamical heterogeneities--strong fluctuations near the glass transition--are believed to be crucial to explain much of the glass transition phenomenology. One hypothesis for their origin is that they emerge from soft (Goldstone) modes associated with a broken continuous symmetry under time reparametrizations. To test this hypothesis, we use numerical simulation data to construct coarse grained observables and decompose their fluctuations into two transverse components associated with the postulated soft modes and a longitudinal component unrelated to them. We find that as temperature is lowered and time scales are increased, the time reparametrization fluctuations become increasingly dominant, and that their correlation volumes grow together with those of the dynamical heterogeneities, while the correlation volumes for longitudinal fluctuations remain small.     

Experimental proposal for the generation of entangled photon triplets by third-order spontaneous parametric downconversion in optical fibers

We present an experimental proposal for the generation of photon triplets based on third-order spontaneous parametric downconversion in thin optical fibers. Our analysis includes expressions for the quantum state, which describes the photon triplets and for the generation rate in terms of all experimental parameters. We also present, for a specific source design, numerically calculated generation rates.     

The application of "double isolation" in Fourier transform ion cyclotron resonance sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry to remove labile isobaric impurities

This study reports the application of "double isolation" in sustained off-resonance irradiation collisionally-induced dissociation tandem mass spectrometry (SORI-CID-MS/MS) to remove radio- frequency (RF) fragment ions of very close mass isobaric ions (0.02 m/z apart). Analyses were performed with a fraction of a biological extract isolated from a macroalgae containing the mycosporine-like amino acid asterina-330. Direct isolation of the precursor ion by narrowing the isolation window proved ineffective as it impinged upon the required ion thus substantially reducing its intensity. By increasing the correlated sweep time, ejection efficiency of the isolation was improved, but caused the unwanted side-effect of RF fragmentation of labile ions. Finally, by skipping the ion activation step and performing a second isolation (in the MS(3) module) the RF fragments from the first isolation were removed leaving a very pure isolation of the required precursor ion and allowed a very clean CID fragmentation. We demonstrated that the m/z 272.1351 ion is derived from the loss of NH(3) from m/z 289.1620 isobaric impurity and is not related to asterina-330. This application represents a powerful tool to remove unwanted ions in the MS/MS spectrum that result from fragmentation of isobaric ions.     

Facile approach to graphene oxide and poly(N-vinylcarbazole) electro-patterned films

A facile approach of making scalable nanocomposite and electro-patterned films using graphene oxide (GO) and poly(N-vinylcarbazole) (PVK) is reported. The method involves the layering of polystyrene colloidal templates, electrodeposition of the composite film on template array, and finally removal of the sacrificial templates to reveal the patterned GO-PVK arrays.     

Integrating virtual screening and combinatorial chemistry for accelerated drug discovery

Virtual screening is increasingly being used in drug discovery programs with a growing number of successful applications. Experimental methodologies developed to speed up the drug discovery processes include high-throughput screening and combinatorial chemistry. The complementarities between computational and experimental screenings have been recognized and reviewed in the literature. Computational methods have also been used in the combinatorial chemistry field, in particular in library design. However, the integration of computational and combinatorial chemistry screenings has been attempted only recently. Combinatorial libraries (experimental or virtual) represent a notable source of chemically related compounds. Advances in combinatorial chemistry and deconvolution strategies, have enabled the rapid exploration of novel and dense regions in the chemical space. The present review is focused on the integration of virtual and experimental screening of combinatorial libraries. Applications of virtual screening to discover novel anticancer agents and our ongoing efforts towards the integration of virtual screening and combinatorial chemistry are also discussed.     

On the interpretation of IETS spectra of a small organic molecule

We have investigated vibrational spectra of nitrobenzene molecules adsorbed on Cu(111) by low temperature inelastic electron tunneling spectroscopy. This molecule, which should support 39 internal modes, only gives rise to seven peaks in the spectra. We outline a comparison with ensemble IR data and interpret the small number of vibrational peaks by the superposition of a multitude of almost isoenergetic vibrational modes. The non-detectability of further modes cannot be understood in terms of symmetry considerations. Additional modes in the spectra are attributed to external molecular-metal vibrations.     

Fast and simple method for determination of fatty acid methyl esters (FAME) in biodiesel blends using X-ray spectrometry

The determination of fatty acid methyl esters (FAME) in diesel fuel blends is an important aspect of production and blending process as well as quality control of distribution operations. In this study, energy-dispersive X-ray fluorescence spectrometer (EDXRF) is used for the first time for determination of FAME in biodiesel blends. The principle of the method is based on intensity difference of X-ray radiation scattered from hydrocarbons and from FAME. The experiment shows that coherent and incoherent radiation, commonly applied for evaluation of the average atomic number of the sample with light matrix, cannot be applied for FAME determination. However, the application of scattered continuous radiation gives excellent correlation between FAME concentration and intensity of scattered radiation. The best results are obtained if continuum is collected in the range of energy between 10.5 and 15.0 keV for rhodium X-ray tube, operated at 35 kV. Linear relationship between the FAME concentration and the inverse of scattered continuous radiation is obtained with the correlation coefficients of 0.999. Standard deviation of measurement is ca. 0.46% (v/v) of FAME and detection limit is 1.2% (v/v) for 600 s counting time and 50% dead-time loss using Si-PIN detector. The investigation shows that crucial issue in determination of FAME in biodiesel blends using EDXRF spectrometer is the precision of measurements resulting from the counting statistics. Therefore, much better results (0.20% (v/v) standard deviation and 0.52% (v/v) detection limit) can be expected if higher intensity of primary radiation is applied and X-ray spectrum is collected by silicon drift detector of high input count rate. For concentration of FAME from 10 to 100% (v/v), the differences between reference method (Fourier transform infrared spectrometry) and the proposed method usually do not exceed 1% (v/v) of FAME. The proposed method is fast, simple and enables FAME determination in wide range of concentration up to 100% of FAME without any sample treatment.