Improvement of the Delsarte Bound for τ-Designs When It Is Not the Best Bound Possible

In this paper the problem for improvement of the Delsarte bound for -designs is investigated. Two main results are presented. Firstly, necessary and sufficient conditions for improving the bound are proved. We define test functions with the property that they are negative if and only if the Delsarte bound D(phmmat;, ) can be improved by linear programming. Then we investigate the infinite polynomial metric spaces and give exact intervals, when the Delsarte bound is not the best linear programming bound possible. Secondly, we derive a new bound for the infinite PMS. Analytical forms of the extremal polynomials of degree + 2 for non-antipodal PMS and of degree + 3 for antipodal PMS are given. The new bound is investigated in different asymptotical processes for infinite PMS. When and n grow simultaneously to infinity our bound is better than Delsarte bound.     

Metastable isonitrosyl structure of the nitroprusside anion confirmed by nuclear inelastic scattering

Nuclear inelastic scattering (NIS) measurements were performed on a guanidium nitroprusside ((CN(3)H(6))(2)[Fe(CN)(5)NO], GNP) monocrystal at 77 K after the sample was illuminated with blue light (450 nm) at 50 K to populate the two metastable states, MS(1) and MS(2), of the nitroprusside anion. A second measurement was performed at 77 K after warming up the illuminated crystal to 250 K where the metastable states decay to the groundstate. The measured spectra were compared with simulated NIS spectra that were calculated by using density functional methods. Comparison of measured and simulated spectra provides strong evidence for the isonitrosyl structure of the metastable MS(1) state proposed by Carducci et al. (Carducci, M. D.; Pressprich, M. R.; Coppens, P. J. Am. Chem. Soc. 1997, 119, 2669-2678).     

Whirlwind: a new cryptographic hash function

A new cryptographic hash function Whirlwind is presented. We give the full specification and explain the design rationale. We show how the hash function can be implemented efficiently in software and give first performance numbers. A detailed analysis of the security against state-of-the-art cryptanalysis methods is also provided. In comparison to the algorithms submitted to the SHA-3 competition, Whirlwind takes recent developments in cryptanalysis into account by design. Even though software performance is not outstanding, it compares favourably with the 512-bit versions of SHA-3 candidates such as LANE or the original CubeHash proposal and is about on par with ECHO and MD6.     

Investigation of Ag nanoparticles produced by nanosecond pulsed laser ablation in water

A study is presented of the properties of Ag nanoparticles produced by nanosecond pulsed laser ablation in twice-distilled water. An Ag target was immersed in the liquid and irradiated by the fundamental, second, third and fourth harmonics of a Nd:YAG laser system to create different colloids. Two specific boundary values of the laser fluence were applied for each wavelength. The properties of the nanoparticles at different wavelengths of the laser radiation were examined. The characterization of the colloids was performed immediately after their fabrication. Spherical and spherical-like shapes of the nanoparticles created were established. The formation of nanowires was observed when the second and the third harmonics of the laser were used. It is connected with self-absorption of the incident laser light from the already-created nanoparticles and depends also on the laser fluence. The size distribution of the nanoparticles is estimated by transmission electron microscopy. Generally, their mean size and standard deviation decreased as the wavelength of the incident laser light was increased and increased with the increase of the laser fluence. The substantial discrepancy between the results already commented on for both characteristics considered and others, obtained by dynamic light scattering, is discussed. The structure of the nanoparticles was established to be single and polycrystalline, and the phase composition in both cases is identified as consisting of cubic silver. The nanoparticles are slightly oxidized.     

Characterization of Ag and Au nanoparticles created by nanosecond pulsed laser ablation in double distilled water

Pulsed laser ablation of Ag and Au targets, immersed in double-distilled water is used to synthesize metallic nanoparticles (NPs). The targets are irradiated for 20 min by laser pulses at different wavelengths—the fundamental and the second harmonic (SHG) (λ = 1064 and 532 nm, respectively) of a Nd:YAG laser system. The ablation process is performed at a repetition rate of 10 Hz and with pulse duration of 15 ns. Two boundary values of the laser fluence for each wavelength under the experimental conditions chosen were used—it varied from several J/cm² to tens of J/cm². Only as-prepared samples were measured not later than two hours after fabrication. The NPs shape and size distribution were evaluated from transmission electron microscopy (TEM) images. The suspensions obtained were investigated by optical transmission spectroscopy in the near UV and in the visible region in order to get information about these parameters. Spherical shape of the NPs at the low laser fluence and appearance of aggregation and building of nanowires at the SHG and high laser fluence was seen. Dependence of the mean particle size at the SHG on the laser fluence was established. Comments on the results obtained have been also presented.     

ChemInform Abstract: Metastable Isonitrosyl Structure of the Nitroprusside Anion Confirmed by Nuclear Inelastic Scattering.

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