Synthesis of Carbon Fibers in the Decomposition of Acetylene and Propane–Butane Mixture in a Plasma Jet

Carbon fibers are prepared during the conversion of acetylene and propane–butane mixture in a jet of the helium and argon plasma without using catalysts. The synthesis is carried out in a plasma jet reactor. The synthesis products are studied by electron microscopy, synchronous thermal analysis and energy dispersive X-ray spectroscopy. The effect of the synthesis parameters on the structure and properties of the carbon fibers prepared in the volume is established. When the propane–butane mixture is decomposed in an inert medium, conditions are found for the synthesis of cylindrical carbon nanofibers of a tortuous shape with a diameter of up to 20 nm and a length-to-diameter ratio of up to 1000. The decomposition of acetylene at 350 Torr produces nanofibers formed by a chain of straight cylinders with a diameter of up to 20 nm, and cylindrical fibers are synthesized in the form of spirals of up to 200 nm in diameter at 150 Torr.     

Braking of a “Magnetized” Sphere in a Hypersonic Rarefied Plasma Flow

The dependence of the drag coefficient of a “magnetized” (with a self-generated magnetic field) sphere on the ratio of the magnetic pressure to the gas dynamic pressure in a hypersonic rarefied plasma flow is determined experimentally. The dependences are obtained for a wide range of angles between the vectors of the incident flow velocity and the magnetic field, as well as between the velocity vectors of the incident hypersonic plasma flow and a subsonic plasma jet injected from the surface of the sphere. It is shown that the injection of a subsonic plasma jet from the surface of a “magnetized” sphere in a hypersonic rarefied plasma flow increases its drag coefficient by several times in comparison with an “unmagnetized” sphere.     

Diamond Film Synthesis with a DC Plasma Jet： Effect of the Contacting Interface between Substrate and Base on the Substrate Temperature

The contacting interface between the substrate and water-cooled base is vital to the substrate temperature during diamond films deposition by a DC （direct current） plasma jet. The effects of the solid contacting area,conductive materials and fixing between the substrate and the base were investigated without affecting the other parameters. Experimental results indicated that the preferable solid contacting area was more than 60% of total contacting areal; the particular Sn-Pb alloy was more suitable for conducting heat and the concentric fixing ring was a better setting for controlling the substrate temperature. The result was explained in terms of the variable thermal contact resistance at the interface between substrate and base. The diamond films were analyzed by scanning electron microscopy （SEM） for morphology, X-ray diffraction （XRD） for the intensity of characteristic spectroscopy and Raman spectroscopy for structure.     

Shannon's entropy as a measure of the “life” of the literature of a discipline

The paper is divided in two parts. Part I deals with the novel use of the concept ofentropy H (measured in nepers) of the ageT of references cited in the literature of a specialty, and the derived parameterS=exp(H) (measured in years). We have proposed to useS (orH) as a measure of the obsolescence of the literature. The concept of entropy comes from the Theory of Information (Shannon) where its mathematical properties have been widely studied and are thus available.H andS have been calculated for the log-normal probability density functions (which model the empirical distributions ofT) of some IEEE journals and for the 58-year collection of an electronics journal, and then they have been compared to the total utility function, this latter defined in the literature. Part II recalls and discusses the mean residual life,M(T), and the expected lifeE(T), of a reference of ageT (concepts borrowed from lifetime data analysis). Besides their intrinsic applications, another possible application of these concepts may be in defining quantitatively the age of historical papers. Examples taken from the literatures of the XX and XIX centuries have been reported.Paper presented at the Fourth International Conference on Bibliometrics, Informetrics and Scientometrics in Berlin (Germany), September 11–15, 1993.     

Investigation of the Serviceability of the Heat Shield of the Orbital Aircraft “Buran” under the Conditions of Radiant Heating on Solar Plants

We have investigated the serviceability of the heatinsulating tiles of the orbital aircraft Buran under radiant heating on an SGU7 solar plant with a mirror concentrator 5 m in diameter. Cycles of aerodynamic heating with a duration of 20 min were simulated. For the total number of cycles for different materials from 20 to 85, the efficiency and serviceability of TZMKtype materials with different coats have been corroborated. The results obtained agree with the test data obtained on gasdynamic (power consumption 1 MW) and radiation (250 kW) test beds, which enables such tests to be recommended for use at preliminary stages in powersaving and ecologically harmless solar furnaces.     

Synthesis of a “clickable” Angiopep-conjugated p-coumaric acid for brain-targeted delivery

Overexpression of free radicals in the brain is emerging as important markers in the etiology of neurodegenerative diseases including Parkinson’s disease, Alzheimer’s disease, and stroke. Numerous antioxidants with protective effect on neuronal injuries under oxidative stress are often limited to penetrate the blood–brain barrier (BBB). Angiopep-2 is the ligand of low-density lipoprotein receptor-related protein expressed on the BBB possessing high transcytosis capacity and parenchymal accumulation. In this study, novel Angiopep-conjugated p-coumaric acid (3) was synthesized, using the Click chemistry, as a potential antioxidant for the protection of the brain under oxidative stress. The clickable Angiopep (3) was synthesized by Cu(I)-catalyzed 1,3-dipolar cycloaddition reaction of the terminal acetylene-modified Angiopep and azide of p-coumaric acid. The Angiopep-conjugated compound (3) showed antioxidant potency and non-cytotoxic effect toward brain endothelial cells (BECs). Obviously, the penetration and BECs protection of 3 were higher than that of the unconjugated p-coumaric acid. The results establish the bio-conjugation of antioxidant and Angiopep with enhanced protective effect on the BECs under oxidative stress. The findings provide great potential for the development of neurotherapeutics with increased brain penetration.     

Dynamics of Stoneley Waves at the “Water–Water-Saturated or Gas Hydrate-Saturated Sand” Interface

Journal of Engineering Physics and Thermophysics - The process of propagation of the Stoneley wave at the “water–water saturated or gas hydrate-saturated sand” interface is...     

The “meaning” of citation in the context of a scientifically peripheral country

This paper reports an investigation into the referencing pattern of Brazilian agricultural scientists. The study was based on the use of both quantitative data-citations appearing in a sizeable sample of articles published by these scientists—and qualitative data-interviews with a large number of scientists who authored the source, papers. The aim was to explore the extent to which citation counts may be taken as valid indicators of the quality, influence or impact of published scientific knowledge in the general context of a scientifically peripheral country. The findings presented confirm the view that in this context, citation patterns are significantly influenced by factors external to the scientific realm and, thus, reflect neither simply the quality, influence nor even the impact of the research work referred to.     

Comment on “optimum depth of the information pit on the data surface of a compact disk”

A novel design of HD–DVD optical pick-up head is proposed. The geometrical size of the pick-up head is reduced by using a combined system of a Penta prism and an aspherical lens. Such a combined system can replace the mirror and collimating lens in a conventional pick-up head, to achieve a miniature HD–DVD pick-up head.     

Extended region of “anomalous” acceleration in the cathode jet of a vacuum discharge

It is observed that “anomalous” acceleration of ions in a pulsed vacuum discharge is initiated at a certain distance from the surface of the cathode and takes place in the bulk of the cathode jet. It is established that the average ion energy increases as the length l of the discharge gap increases. Pis’ma Zh. Tekh. Fiz. 24, 66–70 (February 26, 1998)     

Motion of a “drift island” in a toroidal magnetic confinement device with Coulomb scattering of the particles

A resonant drift trajectory of a charged-particle in a magnetic field (a “drift island”) can be used to remove high-energy impurities from a thermonuclear plasma and to introduce (inject) high-energy particles into the plasma. As a rule, these effects are studied neglecting the Coulomb scattering, i.e., in the collisionless approximation. In the present letter, the effect of Coulomb scattering of a particle with a resonant trajectory by plasma particles is studied. The conditions under which the drift resonance is maintained are found, i.e., the plasma densities and plasma density profiles for which the “drift island” can still move over the transverse section of the plasma are determined. Pis’ma Zh. Tekh. Fiz. 25, 19–27 (September 26, 1999)     

A discussion on “On the solution of a class of fuzzy system of linear equations”

The paper is a discussion on the results obtained by Salkuyeh in the article (Sādhānā 40(2):369–377, 2015). Salkuyeh considers the solution of the fuzzy system of linear equations (FSLE) and gives numerical examples where the results of FSLE are calculated. It was shown that the results by Salkuyeh are not full solutions and do not satisfy equivalent forms of the analysed FSLE. The paper presents a multidimensional approach to finding the solution of the FSLE. On the basis of the notation of the horizontal fuzzy number, a full solution that satisfies the FSLE and its equivalent forms is obtained.     

Examination of the Polymorphism of Piroxicam in Connection with the Preparation of a New “Soft-Patch” Type Pharmaceutical Dosage Form

The influence of different solvents (propylene glycol, glycerol, ethanol), as well as different technological procedures (melting, rapid and slow cooling), on the formation of polymorphous piroxicam modifications was examined in the course of the elaboration of a “soft-patch” type of semisolid pharmaceutical dosage form. The thermodynamical behavior, some physicochemical properties (such as melting point, dissolution rate), and infrared (IR) spectrum of the formed (needle and cubic) crystal modifications were studied, and the possibilities of their formation and their avoidance were examined.