Emergent Specializations in a Commodity Market: A Multi-Agent Model—Graduate Student Best Paper Award, CASOS 2001 Conference

It has been observed in many instances that markets have a tendency to segment themselves into distinct sub-markets. This paper presents a multi-agent model that illustrates emergent market segmentation. The model illustrates the way local optimization processes result in an emergent global improvement of social welfare.     

Observation of a spin 4 neutral meson with 2 GeV mass decaying in π° π°

The invariant mass spectrum of neutral meson states from π^?p interactions at 40 GeV/c incident momentum has been investigated in a high statistics experiment performed at the 70 GeV IHEP accelerator. To detect the high energy photons coming from the produced neutral states, a hodoscope spectrometer with a computer on-line was used. A clear structure on the mass spectrum of dipions produced in the reaction π^?p→π°π°n is observed at 2 GeV. The decay angular distributions show in this mass region the variation with mass typical of a state with a spin J = 4. The mass of the observed meson is found to be M = (2020±30)MeV and the estimate of the full width is (180±60) MeV.     

Correlation of Aerosol Scattering Lidar and Laser Strainmeter Signals during Earth’s Crust Deformations

Lidar sensing of tectonic aerosol fluctuations in the laser strainmeter–interferometer tunnel during 2017.12–2018.05 at the Schultz cape (131°9′8″ E, 42°34′6″ N) near Vladivostok was performed for the first time to our knowledge. A negative correlation of laser interferometer and aerosol lidar signals was observed during low-frequency Earth crust deformations.     

A chemical placebo: NaCl as an effective, cheapest, non-acidic and greener catalyst for Biginelli-type 3,4-dihydropyrimidin-2(1H)-ones (-thiones) synthesis

Despite prior reports of several really effective catalytic and non-catalytic approaches towards Biginelli’s 3,4-dihydropyrimidin-2(1H)-ones, an overwhelming number of new catalysts for the Biginelli reaction have been recently published. Most of the catalysts are somewhat exotic, expensive, harmful and even uneffective in the absence of acidic additives. Herein we reduce the “yet-another-one-catalyst” idea to absurdity by proposing NaCl promotes the reaction that actually requires no catalyst, neither rare nor expensive.     

Raman spectroscopic study of the tautomeric composition of adenine in water

An experimental and theoretical study of the tautomeric composition of adenine (Ade) in water using Raman spectroscopy is reported. Experimental resonance Raman spectra of adenine at excitation wavelengths of 200, 218, and 266 nm were compared with quantum-mechanical calculations of N(9)H- and N(7)H-adenine tautomers and their cations. Both theoretical and experimental studies of nonresonance Raman spectra (457 nm excitation) of adenine were also performed for comparison. A satisfactory agreement of the calculated results with the experimental data was obtained. The Raman spectra are interpreted, and the basic regularities of the Raman intensity distribution are explained. On the basis of the analysis performed, the tautomeric composition of adenine in water is revealed. It is shown that the Ade-N(9),N(1)H(+) cation is the predominant form and that some neutral forms of Ade-N(9)H and Ade-N(7)H tautomers exist in water at pH 3.     

Voltammetric Determination of Purine Bases Using a Carbon Electrode Modified With Hybrid Silica Film

Hybrid silica films containing cation‐exchange polyelectrolytes were designed and used to modify a glassy carbon electrode (GCE) for voltammetric determination of purine bases. Hybrid silica‐polyelectrolyte films synthesised in the presence of adenine as structure directed component have demonstrated enhanced sorption capacity to purine base. The anodic peaks of adenine and guanine at a hybrid film‐modified GCE were observed at +1.55 and +1.1 V, respectively, in phosphate buffer solution at pH 3.5. Oxidation currents of adenine and guanine were proportional to their concentration in the range of 0.02–0.50 mM, with a detection limit of 0.015 mM. The developed method was used to determine adenine in adenosine triphosphate and purine bases in hydrolyzed solutions of DNA and demonstrated good metrological characteristics.     

Laser ablation of alloys: Selective evaporation model

A mechanism of non-stoichiometric laser ablation is proposed and experimentally verified for multicomponent alloys. The analysis of four-component bronze samples in various excitation modes and the recorded laser plasma spectra revealed that disproportion of plasma elements during laser evaporation arises from selective evaporation of components at the heating-melting-evaporation stage. Correction coefficients proportional to the work function of the alloy component vapor in the heating-melting-evaporation cycle are calculated for the plasma spectrum. Correction procedure for the spectral lines leads to a good agreement of the measured sample composition with the tabulated data. To check that the proposed approach is universal, aluminum alloys and iron alloys (high-alloy stainless steels) are analyzed. It is found that selective evaporation for aluminum alloys is lower than for bronzes. Evaporation selectivity was insignificant for stainless steels. The proposed mechanism for selective evaporation during laser ablation and correction of the plasma spectrum make it unnecessary to use a standard in the quantitative elemental analysis of complex bronze and aluminum alloy samples.     

Transformations of the Spectrum of an Optical Phonon Excited in Raman Scattering in the Bulk of Diamond by Ultrashort Laser Pulses with a Variable Duration

JETP Letters - A spontaneous Raman signal at the frequency of the triply degenerate optical phonon of diamond is observed in the photoluminescence spectrum under the pre-filamentation excitation of...     

A sensitive probe for the detection of Zn(II) by time-resolved fluorescence

A new, highly sensitive fluorescent sensor for Zn(II) ion (a tris(2-pyridylmethyl)amine derivative) shows very strong binding and Zn(II) concentration-dependent biexponential time-resolved fluorescence (TRF) decay profiles that can be used for ratiometric estimates of Zn(II) concentrations. The ligand-metal complexes were characterized in solution by spectroscopic techniques and in the solid state by X-ray crystallography. The TRF studies revealed that the sensor aggregates in the absence of Zn(II) in a ligand concentration-dependent manner, a complication that is discerned by TRF but not by steady-state fluorescence ratiometric sensing techniques. It is shown that the same TRF methods are highly useful for monitoring Zn(II) concentrations in A549 epithelial lung cells in vitro and that the results were consistent with those in solution.     

Divergent synthesis of (quinoxalin-2-yl)-1,3-oxazines and pyrimido[1,6-a]quinoxalines via the cycloaddition reaction of acyl(quinoxalinyl)ketenes

A facile synthetic approach towards two distinct quinoxaline-based heterocyclic scaffolds has been developed from the cycloaddition of acyl(quinoxalinyl)ketenes with carbodiimides. The described reaction represents the first example of a divergent synthesis based on acyl(quinoxalinyl)ketenes providing (quinoxalin-2-yl)-1,3-oxazines or pyrimido[1,6-a]quinoxalines depending on the type of the acyl substituent in the ketenes. The key reactants, acyl(quinoxalinyl)ketenes, are generated in situ via the thermal decarbonylation of readily available pyrroloquinoxaline oxo-derivatives. The proposed diversity-oriented synthesis provides facile access to a library of skeletally diverse pharmaceutically interesting quinoxaline-based heterocycles from inexpensive reagents.