Synthesis of a carbon-14 analog of 11-(Piperazin-1-yl)-5<Emphasis Type="Italic">H</Emphasis>-dibenzo[<Emphasis Type="Italic">b</Emphasis>,<Emphasis Type="Italic">e</Emphasis>][1,4]diazepine using microwave irradiation

11-(Piperazin-1-yl)-5H-dibenzo[b,e][1,4]diazepine labeled with ¹⁴C in 11-position was synthesized via four-step pathway from anthranilic acid-[carboxyl-¹⁴C] using microwave irradiation.     

The Activation Energy <Emphasis Type="Italic">U</Emphasis>(<Emphasis Type="Italic">T</Emphasis>,<Emphasis Type="Italic">H</Emphasis>) in Y-based Superconductors

Based on the Arrhenius equation, a method to calculate the activation energy from the resistance transition is proposed for high temperature superconductors. This method is applied to the Y-based superconductors. The activation energy is found to be U(T,H)∼(1−T/T _c )^4.8(H/H ₀)^−3.8 of YBCO crystal, and U(T,H)∼(1−T/T _c )^3.3(H/H ₀)^−2.2 of Er doped MTG YBCO crystal, respectively. With the obtained activation energy U(T,H), the lower part of the experimental curve ρ(T,H) and its derivative can be reproduced.      

The search for novel superhard and incompressible materials on the basis of higher borides of <Emphasis Type="Italic">s</Emphasis>, <Emphasis Type="Italic">p</Emphasis>, <Emphasis Type="Italic">d</Emphasis> metals

The state of the art in the search for novel superhard and (or) incompressible materials on the basis of higher borides of s, p, d metals has been briefly reviewed. The information has been considered about experimental and theoretical studies of the following groups of borides: diborides of 4d, 5d heavy metals (Tc, Ru, Rh, Re, Os, and Ir), hexagonal tetraborides with the WB₄-type structure, and AMB₁₄ borides (where A, M are s, p metals) as well as of a number of related systems.     

Synthesis of a carbon-14 analog of 8-chloro-11- (4-methyl-1-piperazinyl)-11-[<Superscript>14</Superscript>C]-5<Emphasis Type="Italic">H</Emphasis>-dibenzo[<Emphasis Type="Italic">b,e</Emphasis>][1,4]diazepine (clozapine) using microwave irradiation

8-Chloro-11-(4-methylpiperazin-1-yl)-5H-dibenzo[b,e][1,4]diazepine labeled with ¹⁴C in 11-position was synthesized in four steps from [carboxyl-¹⁴C]anthranilic acid using microwave irradiation with good overall radiochemical yield.     

Long-wavelength photodiodes based on <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-GaInAsSb/<Emphasis Type="Italic">p</Emphasis>-AlGaAsSb heterostructures

Photodiodes sensitive in the wavelength ranges 1–2.5 μm and 1–4.8 μm at room temperature have been created on the basis of n-GaSb/n-GaInAsSb/p-AlGaAsSb double-junction heterostructures of two types. The broadband photosensitivity of the diode structures of both types is indicative of the complete separation of photogenerated electron-hole pairs in the staggered n-p heterojunction (n-GaInAsSb/p-AlGaAsSb). The noise characteristics of photodetectors based on the proposed diode structures have been studied. Prospects of the use of these devices in thermophotovoltaic cells for low-temperature radiation sources are considered.     

Impact-ionization-stimulated electroluminescence in isotype <Emphasis Type="Italic">n</Emphasis>-GaSb/<Emphasis Type="Italic">n</Emphasis>-AlGaAsSb/<Emphasis Type="Italic">n</Emphasis>-GaInAsSb heterostructures

We have studied electroluminescence in n-GaSb/n-AlGaAsSb/n-GaInAsSb heterostructures with isotype heterojunctions, in which the quantum efficiency of emission is increased due to the additional production of electron-hole pairs as a result of the impact ionization that takes place near the heterointerface. The impact ionization in such heterostructures is possible due to the presence of deep wells in the energy band structure.     

The 1/<Emphasis Type="Italic">f</Emphasis> spectrum of acoustic cavitation

The fluctuations of a response signal during acoustic cavitation in water in an ultrasonic field were studied by photometry of the transmitted laser radiation. In a broad range of frequencies, the spectral density of photocurrent fluctuations exhibits the 1/f behavior and their amplitude distribution function has a bimodal character. Coarsening of the scale of the experimental time series makes the bimodal character more pronounced and reveals the scale invariance of fluctuations.     

Speed of sound in <Emphasis Type="Italic">n</Emphasis>-hexane, <Emphasis Type="Italic">n</Emphasis>-octane, <Emphasis Type="Italic">n</Emphasis>-decane,and <Emphasis Type="Italic">n</Emphasis>-hexadecane in the liquid state

This paper describes an improved experimental facility for measuring the speed of sound in liquids with an accuracy of up to 0.1%. Measurements of the speed of sound in liquid n-hexane, n-octane, n-decane, and n-hexadecane at temperatures of 298–433 K and pressures of 0.1–100 MPa have been made. It has been shown that in the possible comparison range the obtained values of the speed of sound are in good agreement with the literature data. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 732–736, July–August, 2008.     

Body distribution of poly(<Emphasis Type="SmallCaps">d</Emphasis>,<Emphasis Type="SmallCaps">l</Emphasis>-lactide-<Emphasis Type="Italic">co</Emphasis>-glycolide) copolymer degradation products in rats

Poly (d,l-lactide-co-glycolide) (PLGA) copolymers are among the few synthetic polymers approved for human use, but the biocompatibility of PLGA-derived oligomers and particles remains questionable. Here, high molecular weight PLGA (Mw = 32,000) was radiolabeled with ¹²⁵I in chloroform solution, and the body distribution of PLGA copolymer degradation products was examined following subcutaneous implantation of round ¹²⁵I-PLGA films on the back of Sprague Dawley rats. Autoradiographic images of the PLGA implant taken at 2, 4, 6, 8, 10, and 12 weeks revealed that the central portion of the film degraded much more rapidly than the marginal portions. Examination of the body compartment distribution at these time points revealed that over one-half of the radioactivity was recovered from skin. The remaining radioactivity was concentrated in the blood, liver, and kidneys. Radioactivity steadily appeared in the blood and remained elevated up to 12 weeks after implantation, while the liver to kidney distribution began to decrease after 6 weeks. Cumulatively, these results indicate that the clearance of degraded particles and fragments from the implantation site is extremely delayed. Moreover, the degraded particles and fragments were selectively concentrated in the liver and kidneys, following release of degraded products into the bloodstream from the implantation site.     

Project of laser-pumped quantum <Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">X</Emphasis></Subscript> magnetometer

The possibility of creating a new scheme of a laser-pumped quantum magnetometric device based on a double-beam M _X magnetometer is considered. The proposed system ensures the simultaneous measurement of the modulus of the Earth’s magnetic field vector (with an absolute accuracy of 0.02 nT) and two angles of deviation of this vector with an absolute accuracy and sensitivity of not worse than 0.4″ (0.1 nT) at a measurement time of τ = 1 s. In contrast to the known analogous systems, the proposed scheme does not require generating additional magnetic fields.     

<Emphasis Type="Italic">p</Emphasis>-AgCoO<Subscript>2</Subscript>/<Emphasis Type="Italic">n</Emphasis>-ZnO heterojunction diode grown by rf magnetron sputtering

P-type transparent semiconducting AgCoO₂ thin films were deposited by rf magnetron sputtering of sintered AgCoO₂ target. The AgCoO₂ films grown by rf sputtering were highly c-axis oriented showing only (001) reflections in the X-ray diffraction pattern unlike in the case of amorphous films grown by pulsed laser deposition (PLD). The bulk powder of AgCoO₂ was synthesized by hydrothermal process. The optical bandgap was estimated as 4·15 eV and has a transmission of about 50% in the visible region. The temperature dependence of conductivity shows a semiconducting behaviour. The positive sign of Seebeck coefficient (+220 μVK⁻¹) indicates p-type conductivity. Transparent p-n heterojunction on glass substrate was fabricated by rf magnetron sputtering of p-AgCoO₂ and n-type ZnO: Al thin films. The structure of the diode was glass/ITO/n-ZnO/p-AgCoO₂. The junction between p-AgCoO₂ and n-ZnO was found to be rectifying.     

Nernst Signal in High-<Emphasis Type="Italic">T</Emphasis><Subscript><Emphasis Type="Italic">c</Emphasis></Subscript> Superconductors

The time-dependent Ginzburg–Landau equation with thermal noise is used to calculate the Nernst signal e _N , describing the Nernst effect, in type-II superconductor in the vortex-liquid regime. The Gaussian method used is an elaboration of the Hartree–Fock method. An additional assumption often made in analytical calculations that only the lowest Landau level significantly contributes to physical quantities of interest in the high-field limit is lifted by including all the Landau levels. The values of e _N are in good quantitative agreement with experimental data for temperature close to T _c on Bi₂Sr₂CaCu₂O_8+δ and Bi₂Sr₂Ca₂Cu₃O_10+δ .     

Electrical and photoelectric properties of electrodeposited <Emphasis Type="Italic">n</Emphasis>-Si/<Emphasis Type="Italic">n</Emphasis>-Cd<Subscript>1 - <Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>x</Subscript>S heterojunctions

n-Si/n-Cd_{1 - x} Zn_xS heterojunctions are produced by electrodepositing Cd_{1 - x} Zn_xS (0 x 0.6) films on silicon substrates, and their electrical and photoelectric properties are studied. The results demonstrate that the spectral response of the heterojunctions depends strongly on the film composition and heat-treatment conditions. The highest photosensitivity is achieved at x = 0.6 by heat treatment at 350°C for 7 min: V _OC = 0.5 V and I _SC = 3.8 mA/cm² under illumination of 1500 lx at 300 K.Translated from Neorganicheskie Materialy, Vol. 41, No. 3, 2005, pp. 276–280.Original Russian Text Copyright © 2005 by Mamedov, Gasanov, Amirova.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Determination of <Emphasis Type="Italic">P</Emphasis>,<Emphasis Type="Italic">T</Emphasis>-conditions developed at high-temperature shock compression of silicon nitride in planar recovery ampoules

We performed experiments on shock compression up to pressures of 36 and 50 GPa of mixed samples of silicon nitride and potassium bromide, placed between copper plates that serve as walls of a recovery ampoule. For comparison, similar experiments were carried out by the conventional compression of a mixture of silicon nitride and copper powder. The loading of the samples was fulfilled by means of aluminum flyers accelerated by products of explosion to a few kilometers per second. The pressure profiles prior to a shock wave entering the sample and after its runout were measured with the use of manganin sensors. It is found that for the configurations of the experimental assembly used, the pressure in the samples, accumulated by circulating the shock wave, reaches the desired value before unloading. Based on estimates of the rate of heat transfer between the components, it is shown that thermal equilibrium can be set during the existence of high pressure in the mixed samples. Within the framework of the single-temperature medium model, the equations of state of the samples are derived, and the temperatures of their shock compression are calculated. Using these equations, we performed numerical simulations that showed good agreement with the experimental data.     

Binding energies of Si 2<Emphasis Type="Italic">p</Emphasis> and Co 3<Emphasis Type="Italic">p</Emphasis> electrons in cobalt silicides

The binding energies of Si 2p and Co 3p core-shell electrons in four stable cobalt silicides (Co₃Si, Co₂Si, CoSi, and CoSi₂) have been determined by high-resolution photoelectron spectroscopy using synchrotron radiation. The silicides were formed by solid-state epitaxy under identical conditions on Si(100), Si(110), and Si(111) faces of silicon single crystals.     

Thermodynamic modeling of BC<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>N<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript> chemical vapor deposition from mixtures of <Emphasis Type="Italic">N</Emphasis>-trimethylborazine and nitrogen

Thermodynamic modeling of the chemical vapor deposition of boron-carbonitride-based films in the B-C-N-H-O system using mixtures of N-trimethylborazine and nitrogen is carried out for reduced pressures (13.3 and 1.33 Pa) and a wide temperature range (300–1300 K). The source of oxygen impurities in this system is a residual pressure of 0.40 Pa. The results indicate that films of various compositions can be grown. The conditions for the deposition of BC _x N _y films are identified.     

Inference with progressively censored <Emphasis Type="Italic">k</Emphasis>-out-of-<Emphasis Type="Italic">n</Emphasis> system lifetime data

A system with n independent components which works if and only if a least k of its n components work is called a k-out-of-n system. For exponentially distributed component lifetimes, we obtain point and interval estimators for the scale parameter of the component lifetime distribution of a k-out-of-n system when the system failure time is observed only. In particular, we prove that the maximum likelihood estimator (MLE) of the scale parameter based on progressively Type-II censored system lifetimes is unique. Further, we propose a fixed-point iteration procedure to compute the MLE for k-out-of-n systems data. In addition, we illustrate that the Newton–Raphson method does not converge for any initial value. Finally, exact confidence intervals for the scale parameter are constructed based on progressively Type-II censored system lifetimes.     

Synthesis,growth, optical,mechanical and electrical properties of <Emphasis Type="Italic">L</Emphasis>-lysine <Emphasis Type="Italic">L</Emphasis>-lysinium dichloride nitrate (<Emphasis Type="Italic">L</Emphasis>-LLDN) single crystal

Semi-organic nonlinear optical material, L-lysine L-lysinium dichloride nitrate (2C₆H₁₅N₂O₂⁺_{2}^{+} · H⁺ · NO₃^-_{3}^{-} · 2Cl⁻) was synthesized at room temperature. Single crystals of L-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies. The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The frequency and temperature dependence of dielectric constant (ε _r), dielectric loss (tan δ) and a.c. conductivity (σ _ac) were also measured.     

Nonlinear <Emphasis Type="Italic">p</Emphasis>-ary Sequences

Low correlation p-ary sequences with p an odd prime are constructed. They are obtained as Gray images of codewords of a subcode of the generalized Kerdock codes over the ring _p². They can be shown to be nonlinear in some precise sense. The research of this author is partially supported by NUS-ARF research grant R-146-000-029-112 and DSTA research grant R-394-000-011-422.This research was done while this author was visiting Temasek Laboratories and Department of Mathematics, NUS. The author thanks them for their hospitality.Keywords:Galois rings, Gray map, Kerdock code, CDMA.     

<Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">n</Emphasis> junctions in ZnO implanted with group V ions

n-Type ZnO〈Ga〉 films were implanted with 150-keV N⁺ (As⁺) ions to a dose of 7 × 10¹⁵ cm⁻² and then annealed in atomic oxygen at different temperatures. p-Type conductivity was obtained at annealing temperatures in the range 770–870 K. The parameters of the p-type layers were determined by photoluminescence spectroscopy, secondary ion mass spectrometry, and Hall effect measurements. According to the Hall data, the p-type layers had a resistivity of ∼30 Ω cm, carrier mobility of ∼2 cm²/(V s), and carrier concentration of ∼10¹⁸ cm⁻³. The electroluminescence spectra of the p-n junctions produced by ion implantation showed a band at 440 nm, due to recombination via donor-acceptor pairs.