Dual-jet plasmatron for medical applications

We present a design for a dual-jet arc plasmatron operating at a frequency of 66 kHz in an argon flow at atmospheric pressure. We present the results of determination of the temperature, electron concentration, and electrode erosion obtained by atomic emission spectral analysis. The proposed convenient design for a dualjet plasmatron and the low erosion of the copper electrodes in the plasma make it possible to use it for medical purposes. Report given at the Fifth International Conference on Plasma Physics and Plasma Technologies (PPPT-5), 18–22 September 2006, Minsk, Belarus. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 1, pp. 139–140, January–February, 2007.     

Effects of irradiation parameters on metal surface erosion by pulsed ion beams

Potential application of high-power ion beams of submicrosecond and microsecond durations with the initial particle energy from 50 to 1000 keV and power density 10⁷–10⁹ W/cm² to ensure metal surface erosion are investigated. Evaporation is treated as a major erosion mechanism and the erosion coefficient is taken as an efficiency indicator. Dependences of the erosion coefficients of several metals on beam parameters obtained via calculations using a technique based on the solution of thermal conductivity equation with phase transitions are presented. The ion species, their initial energy, current pulse duration and power density are used as the beam parameters controlling the result of irradiation. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 49–54, August, 2007.     

Formation of compression erosion plasma fluxes of a given composition in dense gases

This article presents the results of experimental investigations of compression erosion plasma fluxes of a given composition determined by the material of the internal electrode; the fluxes have been obtained for the first time in air at atmospheric pressure. It is shown that a compression erosion plasma flux possesses marked absorption in the visible spectral region. The basic thermodynamic parameters of these fluxes were determined with the use of a two-channel system of recording plasma radiation. Reported at the International Conference on Plasma Physics and Plasma Technologies, Minsk, September 15–19, 1997. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 2, pp. 229–233, March–April, 2000.     

Drell–Yan diffraction: breakdown of QCD factorization

We consider the diffractive Drell–Yan process in proton–(anti)proton collisions at high energies in the color dipole approach. The calculations are performed at forward rapidities of the leptonic pair. The effect of eikonalization of the universal “bare” dipole–target elastic amplitude in the saturation regime takes into account the principal part of the gap survival probability. We present predictions for the total and differential cross sections of the single-diffractive lepton-pair production at RHIC and LHC energies. We analyze implications of the QCD factorization breakdown in the diffractive Drell–Yan process, which is caused by a specific interplay of the soft and hard interactions, resulting in rather unusual properties of the corresponding observables.     

Study of metal-supported carbon matrix as a high-capacity anode for Li-ion battery

Tin–graphite composite with 20 wt. % metal content as well as its structural and electrochemical characteristics are presented. Synthetic graphite—super flake type—was used as object for the modification experiment. Chemical reduction was applied for the loading process, which was carried out under inert argon atmosphere. Composite with specific morphology and improved electrochemical behavior was prepared. The obtained material shows higher discharge capacity as well as increased initial charge–discharge coulomb efficiency, compared with the unmodified one. The supporting metal morphology, the type of graphite, and the preparation process taken together generally affect the improvement of the electrochemical performance. This work was presented at the 11th Euro Conference on Science and Technology of Ionics, Batz-sur-Mer, France, Sept. 9–15, 2007.     

Multilayer coaxial fiber dielectric elastomers for actuation and sensing

A simple dip-coating technique was employed to manufacture coaxial actuators with multiple layers of alternating dielectric and conducting layers. A thin rubber string was coated with an electrode–insulator–electrode structure, giving rise to a thin, fiber-like actuator with coaxial geometry. The process was repeated to achieve a compact multilayer actuator with up to three coaxial dielectric layers. Mechanical and electromechanical characterization of the actuators is presented, showing actuation strains up to 8% and proper voltage–thickness scaling behavior. Also presented is a capacitance vs. extension plot, demonstrating that these structures can be used for compact and accurate capacitive strain sensing.     

Comment on ‘Stationary perfect fluid solutions with differential rotation’

We vindicate our results in Mars and Senovilla (Phys Rev D 54, 6166–6180, 1996), which have been recently put in doubt or misunderstood in García and Ulloa (Gen Rel Grav 39, 1639–1650, 2007). In particular, we maintain that there indeed exist axially symmetric differentially rotating perfect-fluid solutions satisfying all energy conditions within the family of solutions presented in Senovilla (Class Quant Grav 9, L167–L169, 1992). We remark that the existence of an axis of symmetry can never be “re-interpreted” as the existence of a Killing horizon, and vice versa. We prove that such horizons are simply impossible for the perfect fluids within the family, and that regular axes of symmetry (or curvature singularities) are the only possibilities. Other inaccuracies or misunderstandings appeared in García and Ulloa (Gen Rel Grav 39, 1639–1650, 2007) are clarified.     

Erosion of the GaAs target under irradiation by a high-power pulsed ion beam

The results of examination of the GaAs-target erosion under irradiation by a high-power pulsed ion beam are reported. In the experiments, use was made of a high-power pulsed ion source with the following parameters: ion energy — 250 keV, target current density — 350 A/cm², pulse duration — 80 ns, target energy density — up to 7 J/cm². The target erosion coefficient and its dependence on the number of successive pulses are measured. It is found that the surface roughness parameter is increased with the number of successive beam pulses. A regular structure of surface relief is observed to form in the case where the number of pulses > 20–40. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 66–70, January, 2007.     

Detection of carbon nanostructures in carburized chromium-iron spinel

It is established that nanostructures of various modifications are formed in a chromium-iron spinel matrix in the process of hydrocarbon pyrolysis at temperatures T = 600–850 °C. Investigations carried out by the methods of electron microscopy, x-ray diffraction analysis, infrared spectroscopy, and electron paramagnetic resonance demonstrate that nanosystems of three types: graphite crystallites with sizes of 6–22 nm, multilayered nanotubes, and plate carbon fibers are presented in the spinel matrix. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 87–92, January, 2007.     

Domain walls in a generalized Chern–Simons model

In this paper we study the structure of one dimensional topological solitons in a generalized Abelian-Higgs Chern–Simons model where the kinetic term is non-canonical. We present an example of an analytical self-dual electrically charged soliton solution which has a finite momentum per unit length along its direction. We compared the physical properties of our soliton with those for wall of Jackiw–Lee–Weinberg wall presented in Jackiw et al. (Phys. Rev. D 42:3488, 1990) to conclude that the non-canonical kinetic term can make the wall “thicker” redistributing uniformly the momentum flow along it.     

The azimuthal dependent oxidation process on Cu(110) by energetic oxygen molecules

We report a study on the oxidation process induced by a hyperthermal oxygen molecular beam (HOMB) on Cu(110) using X-ray photoemission spectroscopy in conjunction with a synchrotron radiation source. The oxidation process induced by energetic O₂ beams on Cu(110), depending on the azimuthal angle of incidence, suggests that the –Cu–O– added row structure has a role in inhibiting adsorption as a steric obstacle for incident O₂ molecules.     

Molecular relaxation effects in hydrogen chloride photoacoustic detection

A photoacoustic (PA) sensor has been developed to monitor hydrogen chloride at sub-ppm level in the 1740-nm region. The system was designed to control the process in the novel low-water-peak optical fiber manufacturing process. Relaxation effects in hydrogen chloride PA detection in oxygen–helium and nitrogen–helium gas mixtures are presented, showing that the generation of the PA signal is strongly affected by the ratio of these substances. In addition, the role of water vapor in the PA signal is investigated.     

Dynamics of plasma formation during quasicontinuous laser irradiation of metals in high-pressure nitrogen atmospheres

This is a study of target destruction and the dynamics of surface plasma formation during the interaction of quasicontinuous laser radiation (λ = 1.06 μm, q = 1–7 MW/cm², τ ∼ 1.5 msec) with D16T duraluminum and bismuth in nitrogen atmospheres at pressures p = 1–20 atm. High speed photography and spectroscopy of the erosion plasma flare are used to determine the onset time for vaporization of the target, as well as the times of appearance of erosion and nitrogen plasmas for different gas pressures and laser energy fluxes q. The emergence of the plasma front from the vapor zone into the surrounding nitrogen is detected experimentally and the properties of the nitrogen plasma are studied.     

Low threshold current density, low resistance oxide-confined VCSEL fabricated by a dielectric-free approach

We present the fabrication process and experimental results of 850-nm oxide-confined vertical cavity surface emitting lasers (VCSELs) fabricated by using dielectric-free approach. The threshold current of 0.4 mA, which corresponds to the threshold current density of 0.5 kA/cm², differential resistance of 76 Ω, and maximum output power of more than 5 mW are achieved for the dielectric-free VCSEL with a square oxide aperture size of 9 μm at room temperature (RT). L–I–V characteristics of the dielectric-free VCSEL are compared with those of conventional VCSEL with the similar aperture size, which indicates the way to realize low-cost, low-power consumption VCSELs with extremely simple process. Preliminary study of the temperature-dependent L–I characteristics and modulation response of the dielectric-free VCSEL are also presented.     

The Discrete Evolution Model of Bak and Sneppen is Conjugate to the Classical Contact Process

Two fundamental models of critical phenomena are connected. We show that the discrete Bak–Sneppen evolution model is conjugate to the classical contact process. This holds in discrete and continuous time, on all graphs and for random as well as for deterministic choice of neighbors. Thus the extensive theory for the contact process applies to the discrete Bak–Sneppen model, too.     

A response to Murshed et al., J Nanopart Res (2010) 12:2007–2010

This brief communication provides a response to Murshed et al. (J Nanopart Res 12:2007–2010, 2010). We acknowledge that three of the equations in our original article (Doroodchi et al. J Nanopart Res 11:1501–1507, 2009) contained minor typographical errors. However, we confirm that these misprinted equations have no bearing on the results presented within that article. In addition, we would like to clarify that we do not challenge the methodology of Leong et al. (J Nanopart Res 8:245–254, 2006). Instead, we repeated their analysis using a more general form for the temperature field with continuity imposed across the particle–nanolayer–liquid interfaces and found that the solution reduces to the Renovated-Maxwell model.     

Fabrication of optical disk mastering using electron beam and embossing process

For the requirement of higher storage capacity of an optical disk, it is a good choice to shorten pit length and linewidth. However, the conventional laser beam mastering is difficult to fabricate smaller pit length and linewidth because of the optical diffraction limit. In order to solve this problem, optical disk mastering using electron beam lithography is presented. The process parameters of the electron beam mastering such as beam current, constant linear stage velocity, developing time, and focus distance are discussed in this research. In the experiments, it was found that the focus distance is an important parameter to fabricate nano-linewidth. The experimental results reveal that the 10 μm variance in focus distance causes about 12% variation in linewidth. The photoresist with nano-pattern defined by eletron beam was transferred into metal Ni–Co (Nickel–Cobalt) mold by electroplating process. The Ni–Co mold with hardness larger than Vicker Hardness (Hv) 650 was developed. Then, with the Ni–Co mold, LIGA (German: Lithographie GaVanoformung Abformung) process was applied to replicate high-density optical disk. The Ni–Co mold is served as a master for hot embossing process to transfer the nano-pattern onto PMMA sheet. Since the feature size is in nano-meter range, the study presents an innovative demolding mechanism to demold the master from the PMMA sheet without damaging the nano-meter structure. A spiral nano-groove with 112 nm in linewidth and 80 nm in depth has been successfully fabricated about 50 Gbytes storage capacity.     

Raman study of oxidation-reduction dispersion of silver

We have examined the process of redox dispersion of silver, using a solution simultaneously containing an oxidizing agent (potassium ferricyanide) and a reducing agent (sodium borohydride). We have studied the changes over time in the Raman spectra of the indicated solution when no silver particles are present and when such particles are added to the solution. We have established that the silver particles have a catalytic effect on the reaction between potassium ferricyanide and sodium borohydride, kinetically slowed down in alkaline medium. The original silver particles (1–20 μm) undergo redox dispersion as a result, and Ag particles are formed with sizes 1–10 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 182–186, March–April, 2006.     

Complex oscillations in a system of coupled autogenerators with phase control

We study dynamical modes and bifurcations in a two-loop self-oscillatory system with phase control. The evolution of self-excited oscillations as a function of the initial frequency detuning is presented. This work was presented at the Summer Workshop “Dynamic Days” (Nizhny Novgorod, June 30–July 2, 1998). Institute of Applied Mathematics and Cybernetics, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 41, No. 12, pp. 1604–1611, December, 1998.     

Midrapidity production of secondaries in pp collisions at RHIC and LHC energies in the quark–gluon string model

We consider the phenomenological implications of the assumption that baryons are systems of three quarks connected through a gluon string junction. The transfer of baryon number in rapidity space due to the string junction propagation is considered in detail. At high energies this process leads to a significant effect on the net baryon production in hN collisions at midrapidities. The numerical results for midrapidity inclusive densities of different secondaries in the framework of the quark–gluon string model are in reasonable agreement with the experimental data. One universal value, λ≃0.25, for the strangeness suppression parameter correctly describes the yield ratios of Λ/p, Ξ/Λ, and Ω/Ξ. The predictions for pp collisions at LHC energies are also presented. PACS 25.75.Dw