Self-organization of a system of dipole particles according to the keesom model

Self-organization of dipolar hard spherical particles at low temperatures was studied using the Monte Carlo method. Configurations of the principal stable structures formed by the particles upon the destabilization of homogeneous distribution were described. The possibility of the formation of structural domains of different symmetries and sizes commensurate with the volume of the system under certain circumstances was demonstrated. The dipole moment of the domains thus formed is considerably higher than that of the entire system. The existence of dipole interactions in the model apparently leads to the appearance of layered structures. The results we obtained can be used in the development of biotechnologies involving the use of synthetic magnetic particles for targeted delivery of chemotherapeutics into an affected organ, as contrast agents in magnetic resonance imaging, and for the studies of magnitotaxis mechanisms.     

Electroabsorption and oppositely directed built-in fields in a photovoltaic organic heterostructure

The directions and intensities of local electric fields spontaneously built into organic nanoscale structures of Schottky-diode type, indium tin oxide (ITO)-CuPc-Al and ITO-C₆₀-Al, with donor and acceptor layers of copper phthalocyanine (CuPc) and fullerene (C₆₀) have been investigated using an improved spectral electroabsorption technique. It is established that, in the absence of external field and illumination, the built-in fields in the bulk of these structures are directed differently: from Al to ITO in the case of CuPc and from ITO to Al in the case of C₆0. The best studied photovoltaic heterostructure ITO-CuPc-C₆0-Al contains simultaneously strong built-in fields in CuPc and C₆₀ layers, with strengths of about 15 and ?22 V/μm, respectively. A high (on the order of 10^?3 C/m²) positive space charge arises at the donor-acceptor interface, and the oppositely directed fields may either increase or reduce the efficiency of light-energy converters, depending on the heterostructure parameters.     

On the Efficiency of Particle Injection into the Damping Ring of the Budker Institute of Nuclear Physics

The efficiency of injection from a linear accelerator into the damping ring of the BINP injection complex has been experimentally studied. The estimations of the injection efficiency are in good agreement with the experimental results. Our method of increasing the capture efficiency can enhance the productivity of the injection complex by a factor of 1.5–2.     

Stark effect and photoconductivity of fullerene С<Subscript>70</Subscript> measured on samples with a submicron electrode grating and sandwich geometry

The electroabsorption (Stark effect) and photoconductivity of polycrystalline fullerene C₇₀ in thinfilm samples with radically different geometries (sample 1 with interdigital Cr electrodes and sandwichlike sample 2 with SnO₂ and Al electrodes) have been investigated. It is noteworthy that sample 1 is a submicron grating with 0.88-µm gaps between electrodes. When measuring electroabsorption and photoconductivity, the external voltage does not exceed 4 V. It was assumed that the small gap size may significantly affect the polycrystalline film morphology and surface effects and, as a consequence, the electroabsorption and charge carrier mobility. However, the results of the Stark effect measurements on samples with different geometries differ by only 25%, whereas the spectral photoconductivity values differ by factors of 1–2.5. The increase in photoconductivity may be related to the decrease in the carrier mobility in the sandwich sample or the increase in the number of carriers under the influence of atmospheric oxygen in the surface layer of C₇₀ sample with interdigital electrodes.     

Modulation of galactic cosmic rays and its traces in isotopic tracks on the Earth and the moon

The high-altitude track of the rates of production of cosmogenic isotopes ¹⁴С, ¹⁰Be and ³⁶Cl in the Earth’s atmosphere under the action of galactic cosmic rays is calculated using different intranuclear cascade models in the GEANT4 environment. Inferences based on these models are discussed in comparison to the available experimental data on these isotopes.     

Search for production of invisible final states in single-photon decays of Υ(1S)

We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A?, or a pair of dark matter particles, χχ. Both A? and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π?π?Υ(1S) and look for events with a single energetic photon and significant missing energy. We find no evidence for such processes in the mass range m(A?) ≤ 9.2 GeV and m(χ) ≤ 4.5 GeV in the sample of 98 × 10? Υ(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.     

Investigation of condensed products of graphite evaporation in an electric arc in argon and helium atmosphere

The composition of products formed in the discharge chamber at the synthesis of nanostructures by arc discharge was investigated. The fullerene soot obtained in an argon atmosphere was shown to contain at least three structural phases: amorphous carbon, fullerenes, and graphitized particles. In the process of thermal desorption, the water and oxygen adsorbed from the atmosphere, as well as carbon oxides generated at the oxidation evolve from the argon soot. By the reactivity, the fullerene black obtained in different buffer gases form a series: special helium, argon, usual helium. The cathode deposit of the arc discharge in argon, as in helium, contains multiwall nanotubes in its soft parts.     

Absorption technology of fine cleaning of nitrogen trifluoride from tetrafluoromethane

Scientific basis and equipment design of the industrial absorption technology of fine cleaning of nitrogen trifluoride from tetrafluoromethane are elaborated. Experimental investigations were performed on a laboratory installation, and the examination of results of absorption cleaning on the pilot plant was carried out. The final content of tetrafluoromethane, 10 ppm, in nitrogen trifluoride was attained.     

HSQC-ADEQUATE: an investigation of data requirements

Utilizing ¹³C‐¹³C connectivity networks for the assembly of carbon skeletons from HSQC‐ADEQUATE spectra was recently reported. HSQC‐ADEQUATE data retain the resonance multiplicity information of the multiplicity‐edited GHSQC spectrum and afford a significant improvement in the signal‐to‐noise (s/n) ratio relative to the 1,1‐ADEQUATE data used in the calculation of the HSQC‐ADEQUATE spectrum by unsymmetrical indirect covariance (UIC) processing methods. The initial investigation into the computation of HSQC‐ADEQUATE correlation plots utilized overnight acquisition of the 1,1‐ADEQUATE data used for the calculation. In this communication, we report the results of an investigation of the reduction in acquisition time for the 1,1‐ADEQUATE data to take advantage of the s/n gain during the UIC processing to afford the final HSQC‐ADEQUATE correlation plot. Data acquisition times for the 1,1‐ADEQUATE spectrum can be reduced to as little as a few hours, while retaining excellent s/n ratios and all responses contained in spectra computed from overnight data acquisitions. Concatenation of multiplicity‐edited GHSQC and 1,1‐ADEQUATE data also allows the interrogation of submilligram samples with 1,1‐ADEQUATE data when using spectrometers equipped with 1.7‐mm Micro CryoProbes ?. Copyright © 2011 John Wiley & Sons, Ltd.