We propose a system to produce multiple spin reversals of a polarized proton beam based on orbit-steerer dipoles already installed in the Nuclotron, a superconducting synchrotron at the Joint ...Institute for Nuclear Research, when the latter operates in the spin-transparency regime. The beam momentum of 3.54 GeV/
c
corresponds to the integer spin resonance
. We report the results of numerical simulation of the proton spin dynamics pertinent to the acceleration up to
, including the adiabatic capture of spins by navigators and the subsequent multiple spin flips. A feasibility of the pilot experiment to verify our approach with the current magnetic lattice of the Nuclotron is discussed. To preserve the beam polarization during the crossing of integer resonances we propose to employ intentional resonance-strength enhancements effected by controlled variations of the beam orbit during acceleration.
Carbon nanotubes are among the most widely used nanosystems, and stability of carbon nanotube suspensions is critical for nanotechnology and environmental science. Remaining in aqueous environment ...alone misses important factors that regulate colloidal stability in the presence of electrolytes. Indeed, introduction of (80–95) vol % organic solvents leads to sharp changes in suspension properties depending on the solvent. For example, the critical coagulation concentrations for a given inorganic or organic coagulating ion can change by 2 orders of magnitude when going from dimethyl sulfoxide to acetonitrile. We establish and explain these trends by Lewis acid–base interactions and show that a strong interaction extending beyond the standard theory of aggregation plays an important role.
Bimetallic alumina and ceria supported Pt–Co catalysts were prepared via the decomposition of a Co(H₂O)₆Pt(NO₂)₄·2H₂O double complex salt. Catalysts were tested in CO preferential oxidation (PROX). ...PtCo/Al₂O₃ catalyst exhibited high activity and selectivity. It provided the CO conversion higher than 80% and selectivity above 60% in the temperature interval 90–165°C at WHSV of 260,000cm³g⁻¹h⁻¹ and O₂/CO ratio of 0.6. XRD and TEM analysis indicated the formation of a platinum-rich Pt–Co alloy nanoparticles supported over alumina surface.
We report the results of experimental studies of the photoelectric properties of a
p–i–n
GaAs photodiode with InAs/GaAs(001) double asymmetric quantum dots (DAQDs) grown by self-assembling in the ...metal–organic vapor-phase epitaxy process. Three peaks were observed in the dependence of the photocurrent on the reverse bias measured at monochromatic photoexcitation of the DAQDs at the wavelength corresponding to the energy of interband optical transitions between the ground hole and electron states in the larger quantum dots (QDs). These peaks were related to the tunneling of the photoexcited electrons between the QDs, including a dissipative one (with emission and absorption of optical phonons). The experimental results agree qualitatively with the theoretical field dependence of the probability of 1D dissipative tunneling between QDs.
A spin navigator based on correcting dipoles has been proposed to manipulate the directions of protons spins in experiments at the Nuclotron synchrotron (JINR, Dubna). The polarization is controlled ...by means of the controllable distortion of the beam closed orbit by correcting dipoles, which ensures the significant enhancement of the action of the navigator on the spins of particles. A method has been proposed to measure the coherent effect of the lattice imperfection on the spin dynamics by the navigator. An idea of a spin compensator based on correcting dipoles is presented, which allows one to eliminate the effect of the lattice imperfection on the polarization. The proposed navigator and spin compensator make it possible to perform a series of experiments at the Nuclotron to verify a new polarization control technique called the spin transparency mode. The results are relevant for experiments with polarized beams in the spin transparency regime at the NICA (Dubna, Russia) and EIC (Brookhaven, United States) and the COSY synchrotron (Julich, Germany).
Experimental data on burning rates and surface temperatures have been shown to allow deriving unique information on decomposition kinetics of energetic materials at high temperatures, provided ...combustion of these materials occurs in the condensed phase. In the paper, kinetic parameters of the leading reaction on combustion of four solid rocket propellant oxidizers: ammonium perchlorate (AP), ammonium nitrate (AN), ammonium dinitramide (ADN), and hydrazine nitroformate (HNF), as well as six energetic fillers: 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), bicyclo-1,3,5,7-tetranitro-l,3,5,7-tetraazacyclooctane (bicyclo-HMX), hexanitrohexaazaisowurtzitane (CL-20), 3,3′-diamino-4,4′-azofurazan (DAAzF), and 3-nitro-l,2,4-triazole-5-one (NTO) are evaluated from available combustion data.
► High-nitrogen energetic materials DHT and BTATz. ► First stage of DHT decomposition is redox process. ► Preliminary reactions of tetrazole isomerization during BTATz decomposition is the reason of ...the large observable activation energy. ► Unique information on decomposition kinetics of energetic materials at high temperatures. ► Explanation of the unusual DHT combustion behavior.
The thermal stability of 3,6-dihydrazino-1,2,4,5-tetrazine (DHT) and 3,6-bis(1H-1,2,3,4-tetrazol-5-ylimino)-1,2,4,5-tetrazine (BTATz) have been examined by isothermal and nonisothermal methods. The research conducted allow considering that the first stage of DHT decomposition is an unique, from viewpoint of thermal decomposition, redox process, in which tetrazine ring is reduced by hydrazine group forming diaminodihydrotetrazine and molecular nitrogen. In the case of BTATz, the decomposition begins with less thermostable tetrazole fragments, which captures the tetrazine ring also. The presence of preliminary reactions of isomerization during tetrazole ring decomposition is the reason for the large observable activation energy of decomposition (240.6kJ/mol or 57.5kcal/mol) in the temperature interval 250–334°C. In the combustion wave at higher temperatures, the activation energy of BTATz decomposition has considerably lower value (128.4kJ/mol or 30.7kcal/mol), which is close to theoretically calculated one.
Burning characteristics of DHT and BTATz have been investigated. The temperature distribution in the combustion waves of DHT and BTATz have been measured at low pressures, which allows obtaining the surface temperature dependence vs. pressure. The research conducted allow considering that the burning of investigated compounds controls by a combustion model with leading reaction in the condensed phase.
The Pt
0.5
Со
0.5
/SiO
2
catalyst has been prepared by the decomposition of a Pt(NH
3
)
4
Co(C
2
O
4
)
2
(H
2
O)
2
. 2H
2
O binary complex salt supported in the pores of SiO
2
pellets. It has been ...shown by a complex of physical and chemical methods that Pt
0.5
Со
0.5
/SiO
2
contains alloy nanoparticles with an average composition Pt0.5Co0.5. The catalytic properties of Pt
0.5
Со
0.5
/SiO
2
are studied in the preferential oxidation of СО in the reaction mixtures with various compositions. It was found that Pt
0.5
Со
0.5
/SiO
2
has a high selectivity and makes it possible to decrease the outlet concentration of CO to a level of <10 ppm, and the presence of СО
2
and/or Н
2
О in the reaction mixture almost does not affect its catalytic properties. The structure of the catalyst is stable under the conditions of preferential CO oxidation.
Abstract
We report on the results of experimental studies of the photocurrent (PC) of photodiodes based on GaAs
p-i-n
structures with InAs/GaAs(001) double asymmetric quantum dot (DAQD) arrays ...obtained by self-assembling in the process of low-pressure metal-organic vapor phase epitaxy (LP-MOVPE). Three peaks were observed in the dependence of the PC on the reverse bias, measured under photoexcitation with a photon energy equal to the energy of the interband ground state transition in larger InAs QDs. These peaks were attributed to photoexcitation of electrons from the ground hole states in larger QDs into the ground electron states followed by resonant dissipative (with absorption or emission of optical phonons) and conservative tunneling into the GaAs conduction band via the ground electron states in smaller QDs. The PC dependence on the bias voltage agrees qualitatively with the theoretical field dependence of the probability of 1D dissipative tunneling between the QDs.
•TKX-50 enthalpy of formation proved to be much less than published values.•TKX-50 is not an extremely powerful energetic material, surpassing common explosives.•Decomposition of TKX-50 is determined ...by decomposition of constituent hydroxylamine.•The burning of TKX-50 obeys the condensed-phase combustion mechanism.
The physico-chemical characterization (thermal decomposition under non- and isothermal conditions, enthalpy of formation, burning behavior and flame structure) of a new explosive dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate is detailed. Combustion studies have shown that TKX-50 burns slightly faster than HMX and approaches the burning rate of CL-20. The combustion of TKX-50 has been shown to obey mechanism with the leading reaction in the condensed phase. The rates of TKX-50 decomposition in both solid and liquid phases proved to be slightly higher than the corresponding rates of decomposition of RDX. Decomposition of TKX-50 is determined by decomposition of free hydroxylamine formed in the reaction of dissociation of the salt. An intermediate decomposition product is ammonium salt of 5,5′-bis(2-hydroxytetrazole), which further decomposes in the second stage at elevated temperatures. The enthalpy of formation of TKX-50 has been measured with the help of bomb calorimetry, however the resulting value is quite different from the enthalpy reported earlier.
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