What Oxidation State of Iron Determines the Amethyst Colour?

A colourless quartz crystal doped with ⁵⁷Fe³⁺ was obtained by hydrothermal synthesis in an NH₄F solution. The crystal was transformed into violet amethyst by gamma-irradiation. The change in colour was accompanied by changes in the Mössbauer spectrum that can be interpreted as the conversion of trivalent iron into the tetravalent state: Fe³⁺→Fe⁴⁺.

     

“CMB-Slow” or How to Determine Cosmological Parameters by Hand?

I derive analytically the spectrum of the CMB fluctuations. The final result for C _l is presented in terms of elementary functions with an explicit dependence on the basic cosmological parameters. This result is in a rather good agreement with CMBFAST for a wide range of parameters around concordance model. This allows us to understand the physical reasons for dependence of the particular features of the CMB spectrum on the basic cosmological parameters and to estimate the possible accuracy of their determination. I also analyze the degeneracy of the spectrum with respect to certain combinations of the cosmological parameters.     

Measuring the speed of sound of quintessence

Quintessence, a time-varying energy component that may account for the accelerated expansion of the universe, can be characterized by its equation of state and sound speed. In this paper, we show that if the quintessence density is at least 1% of the critical density at the surface of last scattering the cosmic microwave background anisotropy can distinguish between models whose sound speed is near the speed of light versus near zero, which could be useful in distinguishing competing candidates for dark energy.     

Inflation Without Potential

Due to the importance of inflation, considerable effort has gone into developingdifferent inflationary scenarios. In most of them inflation is driven by aself-interacting scalar field. Here we discuss an alternative way to implement aninflationary stage provided by noncanonical kinetic terms in the action for thescalar field.     

Measurements of reduced mobility of standard compounds by high resolving power ion mobility spectrometer in remote laboratories

An atmosphere pressure ion mobility spectrometer is described. Both electrospray and corona discharge ion sources were used. Increased up to 100 resolving power allows obtaining higher selectivity and potentially widens application area. Satisfactory reproducibility of measured reduced mobility is required for improving reliability of identification including interlaboratory reproducibility of measured reduced mobility. Results of measurement were shown for the samples containing compounds proposed earlier as standards, those were measured in remote laboratories. Measured reduced mobility for 2,6-di(tert-butyl)pyridine amounted 1.48 cm²/V · sec for the measurements where corona discharge was used, and 1.46 cm²/V · sec for the measurements, where electrospray ionization was used. Both values are in a good agreement with a value 1.48 cm²/V · sec obtained earlier on the previous version of the instrument. Values of reduced mobility calculated by results of measurements accomplished in Munich for tetraethylammonium iodide, tetra-pentylammonium iodide and tetraoctylammonium bromide amounted correspondingly 1.77, 1.10, and 0.64 cm²/V · sec when electrospray ionization was used. The data are in a very good agreement with the values obtained earlier on the previous version of the instrument in remote laboratory.     

Numerical Simulation of the Yield of α Particles and Neutrons from the 11B(p, 3α) and 11B(p,n)11C Nuclear Reactions Induced by Intense Picosecond Laser Radiation

Journal of Experimental and Theoretical Physics - The yields of alpha particles and neutrons from the promising 11B(p, 3α) fusion reaction and the reference 11B(p, n)11C nuclear reaction,...     

Bi-SQUID arrays and parallel SQIF structures for active electrically small antennas

The basic physics of the development of broadband active electrically small superconductive antennas for the subgigahertz and gigahertz frequency ranges, based on series arrays with cells characterized by a highly linear voltage response to the magnetic component B of an electromagnetic signal, are under consideration. As such cells, bi-SQUIDs and cells based on two parallel SQIF structures that are differentially connected are proposed. Series arrays of cells with linear voltage response, including an antenna prototype, are fabricated using standard niobium technology with a critical current density of Josephson junctions of 4.5 kA/cm² and are studied experimentally. The data obtained allow estimation of the achievable dV/dB conversion factor and the sensitivity ??B for an antenna integrated with a magnetic flux converter, placed on an available area of 3.3 × 3.3 mm of a chip 5 × 5 mm in size. These values are found to be 10 ??V/nT and 20 fT/Hz^1/2, respectively. The conversion factor increases in proportion with the area a ² occupied by the antenna with a square flux converter, and the sensitivity is improved as a ^?3/2.