Orientational ordering and spatial distribution of Janus nanoparticles in lamellae diblock copolymers

Orientational ordering and spatial distribution of rod-like Janus nanoparticles in the lamellae diblock copolymers has been considered using a molecular theory based on simple model of Janus particle with two different interaction centres located at the particle ends. Order parameter and concentration profiles of Janus nanoparticles have been calculated numerically for different values of the nanoparticle length. It has been found that Janus nanoparticles are mainly located in the boundary region between the domains and are orientationally ordered in that region with a high orientational order parameter. This orientational order is induced by the interface and is determined by the different affinities of the two ends of the Janus particle with respect to the monomers of different domains. Comparison with block copolymers doped with symmetric nanoparticles indicates that polymer nanocomposites with Janus particles are expected to possess much larger dielectric anisotropy and thus can be considered as promising anisotropic nanomaterials which can be aligned by the external electric field

Three in one : mesogenic aromatic acid as a liquid crystal matrix, a chiral dopant in liquid crystals and a stabilizer for nanoparticles

Studies of thermodynamics of the N*-I phase transitions and optical properties of the new liquid crystal - (R)-2-[4″-(trans-4-butylcyclohexyl)-2′-chloro-p-terphenyl-4-oxy] propanoic acid are carried out. The aim of these studies is to analyze the capabilities of that liquid crystal to simultaneously serve as a matrix for inorganic semiconductor nanoparticles (NP) as well as a chiral dopant for liquid crystals and a chiral ligand stabilizing the surface of CdSe NPs. The chiral doping of a nematic liquid crystal was proven by the measurements of selective transmittance of the visible light. The embedding of NPs in a nematic liquid crystal leads to the increase in TN⁎I, which is explained by the shape anisotropy of the NPs. The anisotropy of the ligand shell may result from the interaction between the ligand and LC matrix inducing the change of the spherical shape of the shell toward the ellipsoidal one. TN⁎I of the liquid crystal matrix of (R)-2-[4″-(trans-4-butylcyclohexyl)-2′-chloro-p-terphenyl-4-oxy] propanoic acid (R-MPA) decreases with the embedding of NPs stabilized by the same ligands, which is in a good agreement with prior experimental results and theory, but there exists a considerable quantitative difference

Composites of the cBN–Si₃N₄ system reinforced by SiCw for turning tools

The cBN–Si₃N₄–SiCw composites with different SiCw contents up to 20 vol % have been produced at high pressure of 8.0 GPa and high temperature of 2500 K. It has been defined that the Young modulus of the composites were within 740–846 GPa, the Vickers hardness and fracture toughness values were 37.5–42.0 GPa and 11.4–12.9 MPa∙m¹/², respectively. An important feature of the composite microstructure is the breaking of SiCw as a result of HPHT action. It has been shown that at the addition of 10 vol % SiCw to the structure of a cBN–Si₃N₄ composite the interrupted turning of hardened steel results in the flank wear reduction up to 20%.В условиях высокого давления 8,0 ГПа и высокой температуры 2500 К были получены композиты cBN–Si₃N₄–SiCw с различным содержанием компоненты SiCw до 20 % (по объему). Модуль Юнга находится в интервале 740–846 ГПа. Твердость по Викерсу и трещиностойкость соответственно имеют значения в интервале 37,5–42,0 ГПа и 11,4–12,9 МПа∙м¹/². Характерной особенностью микроструктуры композита является наличие разрушенных SiC-усов, как результат воздействия высокого давления. Разработана методика тестирования образцов при прерывистом точении. Испытания образцов при прерывистом точении высокотвердых сталей показывают, что добавка SiC-усов в количестве 10 % (по объему) в структуре композита cBN–Si₃N₄–SiCw приводит к снижению износа режущей кромки до 20 %.В умовах високого тиску 8,0 ГПа і високої температури 2500 К було отримано композити cBN–Si₃N₄–SiCw з різним вмістом компоненти SiCw до 20 % (за об’ємом). Модуль Юнга знаходиться в інтервалі 740–846 ГПа. Твердість за Вікерсом і тріщиностійкість відповідно мають значення в інтервалі 37,5–42,0 ГПа і 11,4– 12,9 МПа∙м¹/². Характерною особливістю мікроструктури композиту є наявність зруйнованих SiC-вусів, як результат впливу високого тиску. Розроблено методику тестування зразків при переривчастому точінні. Випробування зразків при переривчастому точінні високотвердих сталей показують, що добавка SiC-вусів в кількості 10 % (за об’ємом) у структурі композиту cBN–Si₃N₄–SiCw приводить до зниження зносу ріжучої кромки до 20 %

New precise determination of the \tau lepton mass at KEDR detector

The status of the experiment on the precise $\tau$ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the $\tau^+\tau^-$ cross section behaviour around the production threshold. The preliminary result based on 6.7 pb$^{-1}$ of data is $m_{\tau}=1776.80^{+0.25}_{-0.23} \pm 0.15$ MeV. Using 0.8 pb$^{-1}$ of data collected at the $\psi'$ peak the preliminary result is also obtained: $\Gamma_{ee}B_{\tau\tau}(\psi') = 7.2 \pm 2.1$ eV.Comment: 6 pages, 8 figures; The 9th International Workshop on Tau-Lepton Physics, Tau0

Search for narrow resonances in e+ e- annihilation between 1.85 and 3.1 GeV with the KEDR Detector

We report results of a search for narrow resonances in e+ e- annihilation at center-of-mass energies between 1.85 and 3.1 GeV performed with the KEDR detector at the VEPP-4M e+ e- collider. The upper limit on the leptonic width of a narrow resonance Gamma(R -> ee) Br(R -> hadr) < 120 eV has been obtained (at 90 % C.L.)

Measurement of \Gamma_{ee}(J/\psi)*Br(J/\psi->e^+e^-) and \Gamma_{ee}(J/\psi)*Br(J/\psi->\mu^+\mu^-)

The products of the electron width of the J/\psi meson and the branching fraction of its decays to the lepton pairs were measured using data from the KEDR experiment at the VEPP-4M electron-positron collider. The results are \Gamma_{ee}(J/\psi)*Br(J/\psi->e^+e^-)=(0.3323\pm0.0064\pm0.0048) keV, \Gamma_{ee}(J/\psi)*Br(J/\psi->\mu^+\mu^-)=(0.3318\pm0.0052\pm0.0063) keV. Their combinations \Gamma_{ee}\times(\Gamma_{ee}+\Gamma_{\mu\mu})/\Gamma=(0.6641\pm0.0082\pm0.0100) keV, \Gamma_{ee}/\Gamma_{\mu\mu}=1.002\pm0.021\pm0.013 can be used to improve theaccuracy of the leptonic and full widths and test leptonic universality. Assuming e\mu universality and using the world average value of the lepton branching fraction, we also determine the leptonic \Gamma_{ll}=5.59\pm0.12 keV and total \Gamma=94.1\pm2.7 keV widths of the J/\psi meson.Comment: 7 pages, 6 figure

Measurement of main parameters of the \psi(2S) resonance

A high-precision determination of the main parameters of the \psi(2S) resonance has been performed with the KEDR detector at the VEPP-4M e^{+}e^{-} collider in three scans of the \psi(2S) -- \psi(3770) energy range. Fitting the energy dependence of the multihadron cross section in the vicinity of the \psi(2S) we obtained the mass value M = 3686.114 +- 0.007 +- 0.011 ^{+0.002}_{-0.012} MeV and the product of the electron partial width by the branching fraction into hadrons \Gamma_{ee}*B_{h} = 2.233 +- 0.015 +- 0.037 +- 0.020 keV. The third error quoted is an estimate of the model dependence of the result due to assumptions on the interference effects in the cross section of the single-photon e^{+}e^{-} annihilation to hadrons explicitly considered in this work. Implicitly, the same assumptions were employed to obtain the charmonium leptonic width and the absolute branching fractions in many experiments. Using the result presented and the world average values of the electron and hadron branching fractions, one obtains the electron partial width and the total width of the \psi(2S): \Gamma_{ee} =2.282 +- 0.015 +- 0.038 +- 0.021 keV, \Gamma = 296 +- 2 +- 8 +- 3 keV. These results are consistent with and more than two times more precise than any of the previous experiments

Pion condensation of quark matter in the static Einstein universe

In the framework of an extended Nambu--Jona-Lasinio model we are studying pion condensation in quark matter with an asymmetric isospin composition in a gravitational field of the static Einstein universe at finite temperature and chemical potential. This particular choice of the gravitational field configuration enables us to investigate phase transitions of the system with exact consideration of the role of this field in the formation of quark and pion condensates and to point out its influence on the phase portraits. We demonstrate the effect of oscillations of the thermodynamic quantities as functions of the curvature and also refer to a certain similarity between the behavior of these quantities as functions of curvature and finite temperature. Finally, the role of quantum fluctuations for spontaneous symmetry breaking in the case of a finite volume of the universe is shortly discussed.Comment: RevTex4; 15 pages, 10 figure

RF system of the race-track microtron – recuperator for high power free electron laser

A brief description of the RF system of 100 MeV race-track microtron-recuperator being built in Novosibirsk for the Free Electron Laser project at Siberian center of Photochemistry research is presented. The frequency of RF system is 180.4 MHz. The RF system consists of 2 parts: the RF system of 2 MeV injector and the RF system of microtron. The injector RF system includes 3 RF cavities - one buncher cavity and two accelerating cavities. RF cavities are driven by a 2.5 kW amplifier and two high power single-tube 130 kW RF amplifiers respectively. The RF system of microtron includes 16 RF cavities operating at a gap voltage of 850kV each. Two 4-tubes power amplifiers supply the RF power of 600 kW each to the cavities via distribution feeders. In the high power amplifier stages the tetrodes GU-101A are used. The control system controls the amplitude and phase of RF voltage in the cavities and provides signals for synchronization of the electron gun. The results of the operation of the injector RF system and status of large RF system for the microtron are discussed