Narrow band laser-generated surface acoustic waves using a formed source in the ablative regime

A narrow band laser-generated acoustic signal was created using a 4-element lenticular array. This arrangement of the array produces an acoustical signal with frequency content that is compatible with the response of a noncontact and remote broadband receiver, such as a capacitive air-coupled transducer. To support the experimental observations, a simplified concept is presented to explain the effect of a line array source on the frequency content of a surface acoustic wave. The analytical model solution for the wave front shape is derived from the point load solution of Lamb's problem that represents the displacement of a surface acoustic wave generated by an ablative line array. The distribution function, which was used for the model to represent the laser light energy, was tailored to depict the actual energy distribution that illuminates the lenticular array. Filtering functions are applied to the resultant surface displacement function to retain frequencies similar to those detected by the broadband 50 kHz-2.25 MHz receiver. The theoretical model showed good agreement with experimental results.     

The critical re-evaluation of the aromatic/antiaromatic nature of Ti3(CO)3: a missed opportunity?

The nature of bonding and aromaticity of Ti(3)(CO)(3), a mill-shaped metal-carbonyl complex, is studied carefully. A unique bonding mechanism between metal and carbonyl groups is found in this species. Ti(3)(CO)(3) is an example of a metal-carbonyl complex with prominent metal to carbonyl donation. Moreover, it is proven that not only is Ti(3)(CO)(3) not an antiaromatic complex but also it is the first synthesized example of d-block, σ+π aromatic species. A quick survey among the first row of transition metals in the periodic table shows that other local minima with similar structures and aromaticity are present and Ti(3)(CO)(3) is the first synthesized species of an unknown family.     

Investigation of multibaryonic resonances with strangeness equal to and different from zero

Results on a search for Λp, ΛΛ, Λpp, K^op, pp, 3p and 4p resonances are presented. The Λp effective-mass spectrum reveals three significant peaks (more than 4 s.d.) at 2058, 2127 and 2252 MeV. The first two peaks are shown to be due to effects of the negative Λp and Σp scattering lengths respectively, whereas the third peak is interpreted as a Λp resonance of (2251.4 ± 3.9) MeV mass and Λ = (21.1 ± 5.4) MeV full width. The two enhancements observed in the ΛΛ effective-mass spectrum may be due to the effect of the negative ΛΛ scattering length and to a ΛΛ resonance of ～2370 MeV mass. No enhancements in other effective-mass spectra are observed. The results of this work suggest a condition for the possibility of resonance formation depending on the total hypercharge of the system considered.     

The two-component quantum theory of atoms in molecules (TC-QTAIM): foundations

The foundations of the two-component quantum theory of atoms in molecules (TC-QTAIM) are addressed in this contribution. In this regard, the theory is presented in an axiomatic manner and the main theorems describing regional properties of atoms in molecules are considered in detail. This is an extension of the orthodox quantum theory of atoms in molecules (QTAIM) for dealing with non-adiabatic wavefunctions of usual molecules as well as extracting the regional quantum structure of exotic species from the corresponding wavefunctions. The best examples of the latter are positronic and muonic species. The computational study of a model system consisting of a clamped lithium nucleus, four electrons, and a positively charged quantum particle carrying a unit of positive charge with a variable mass, m = 200–10¹³ m _e, supplements the theoretical argument demonstrating unambiguously that the TC-QTAIM analysis yields reasonable results. It reveals that the contribution of the positively charged particle in the topological analysis and basin properties is non-negligible. Most importantly, it is demonstrated that by increasing the mass of the positive particle, the TC-QTAIM analysis tends toward the QTAIM analysis of the lithium hydride system considered within the clamped nucleus paradigm. This result seems to indicate that the orthodox QTAIM is just the asymptote of the TC-QTAIM, the latter encompasses the former. Thus, one may claim that the TC-QTAIM is a unified framework for the AIM analysis of vast variety of quantum systems.     

Gas-chromatographic fatty-acid fingerprints and partial least squares modeling as a basis for the simultaneous determination of edible oil mixtures

Partial least squares modeling and gas-chromatographic fatty-acid fingerprints are reported as a method for the simultaneous determination of cottonseed, olive, soybean and sunflower edible oil mixtures. In this work, two sets of three- and four-component combinations of oils were prepared, hydrolyzed and the obtained free fatty acids analyzed by gas chromatography (GC) without any further derivatization. The normalized percentages of the myristic (14:0), palmitic (16:0), palmitoleic (16:1), stearic (18:0), oleic (18:1), linoleic (18:2) and linolenic (18:3) acids were chromatographically measured in samples and used for constructing calibration matrix. The cross-validation method was used to select the number of factors and the proposed methods were validated by using two sets of synthetic oil mixture samples. The relative standard error for each oil in mixture samples was less than 10%. This approach allows determining possible adulteration in each of the four edible oils.