Integral energy spectrum of primary cosmic rays at high energies

The integral energy spectrum of primary cosmic rays has been obtained. In the energy range (2.4×10³−1.1×10⁵ GeV), the spectrum of all nuclei is consistent with a power law of indexγ=1.55±0.06 and the flux of all nuclei is:N(⩾E ₀)⋍(5.1±1.8)×10⁻¹×E ₀ ^−1.55 particles/cm² sterad. sec., whereE ₀ is in GeV. The spectrum of primaryα-particles in the energy range (4.4×10³−4.8×10⁴) GeV is also consistent with a power law of indexγ=1.71±0.12 and the flux is:N(⩾E ₀)=(4.2±1.4)×10⁻¹×E ₀ ^−1.71 , particles per cm² sterad. sec, whereE ₀ is in GeV.     

Experiment on the production and separation of the pulsed reflective discharge gas-metal plasma

A proprietary way of introducing a working substance to be separated into a reflective-discharge magnetoplasma separator is experimentally verified. The efficiency of working substance delivery using this sputtering mechanism providing a plasma density on the order of 10¹⁴ cm⁻³ is demonstrated. The sputtering yield of the substance being separated achieves (2.6–2.8) × 10⁻² atoms/ion depending on the amount of particles in the discharge. Simultaneously, the minimal separation coefficient for light and heavy particles in a rotating plasma subjected to E × H crossed fields is estimated.     

Angular characteristics of processes of electron detachment from negative ions and hydrogen atoms in gases

The results of experimental measurement of spatial-angular distributions of hydrogen particles (H⁻, H⁰, H⁺) obtained in scattering of a collimated ribbon beam of H⁻ ions and H⁰(1s) atoms in He, Ar, Kr, Xe, H₂, O₂, and CO₂ gas targets for certain values of energy in the range from 0.6 to 15 MeV are reported. The experimental setup and the measurement procedure with an angular resolution of 5×10⁻⁶ rad are described. The angular characteristics of measured distributions, i.e., full width at half maximum and standard deviation, were determined. It is shown that the shape of distribution for a beam of hydrogen atoms produced by neutralization of H⁻ ions in a gas target varies with the type and thickness of the target, and the angular spread is smallest for the H₂ target. The variations in the shape of distribution are due to the contribution of scattering processes without changing the charge of particles.     

Mechanistic investigation into antibacterial behaviour of suspensions of ZnO nanoparticles against <Emphasis Type="Italic">E. coli</Emphasis>

Aqueous suspensions containing 4.45 × 10⁻⁵ − 1.25 × 10⁻³ M ZnO particles exhibit a strong antibacterial activity against E. coli under the dark conditions. The dominant mechanisms of such antibacterial behaviour are found to be either or both of chemical interactions between hydrogen peroxide and membrane proteins, and chemical interactions between other unknown chemical species generated due to the presence of ZnO particles with the lipid bilayer. The effect of direct physical interactions between nanoparticles and biological cells are found to play a relatively small role under the conditions of this study.     

Silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone)

This article describes a method for silica coating of Co–Pt alloy nanoparticles prepared in the presence of poly(vinylpyrrolidone) (PVP) as a stabilizer. The Co–Pt nanoparticles were prepared in an aqueous solution at 25–80 °C from CoCl₂ (3.0 × 10⁻⁴ M), H₂PtCl₆ (3.0 × 10⁻⁴ M), PVP (0–10 g/L), and NaBH₄ (4.8 × 10⁻³–2.4 × 10⁻² M). The silica coating was performed for the Co–Pt nanoparticle colloid containing the PVP ([Co] = [Pt] = 3.0 × 10⁻⁵ M) at 25 °C in (1/4) (v/v) water/ethanol solution with tetraethoxyorthosilicate (TEOS) (7.2 × 10⁻⁵–7.2 × 10⁻³ M) and ammonia (0.1–1.0 M). Silica particles, which had an average size of 43 nm and contained multiple cores of Co–Pt nanoparticles with a size of ca. 8 nm, were produced at 1.4 × 10⁻³ M TEOS and 0.5 M ammonia after the preparation of Co–Pt nanoparticles at 80 °C, 5 g/L PVP, and 2.4 × 10⁻² M NaBH₄. Their core particles were fcc Co–Pt alloy crystallites. Their saturation magnetization was 2.0-emu/g sample, and their coercive field was 12 Oe.     

Determination of the negative hydrogen ion concentration in a cesium-hydrogen discharge

The concentration N _H ⁻ of negative hydrogen ions in a low-voltage cesium-hydrogen discharge plasma N _H ⁻ is determined from experiments with laser radiation absorption caused by the photodetachment of electrons from the H⁻ ions. The resolution of a setup measuring the relative absorption is ≥10⁻⁵ for a signal-to-noise ratio of ∼10⁻² or less. A heated-cathode diode is used to initiate the discharge at a voltage of U≤10 V and a current density of j≤5 A/cm² (hydrogen pressure p _{H 2} is equal to several torr, and the cesium concentration in the plasma N _Cs ⁽⁰⁾ ∼10¹⁴ cm⁻³). The absorption due to the photoionization of excited Cs atoms is shown to be negligible. The measured concentration N _H ⁻ of the H⁻ ions is 10¹²–10¹³ cm⁻³. Experimental results are consistent with the theory.     

MeV particles from laser-initiated processes in ultra-dense deuterium D(−1)

Fast particles from laser-induced processes in ultra-dense deuterium D(−1) are studied. The time of flight shows very fast particles, with energy above MeV. Such particles can be delayed or prevented from reaching the detector by inserting thin or thick metal foils in the beam to the detector. This distinguishes them from energetic photons which pass through the foils without delays. Due to the ultra-high density in D(−1) of 10²⁹cm⁻³, the range for 3 MeV protons in this material is only 700 pm. The fast particles ejected and detected are thus mainly deuterons and protons from the surface of the material. MeV particles are expected to signify fusion processes D+D in the material. The number of fast particles released is determined using the known gain of the photomultiplier. The total number of fast particles formed, assuming isotropic emission, is less than 10⁹ per laser pulse at < 200 mJ pulse energy and intensity 10¹²W cm⁻². A fast shockwave with 30keV u⁻¹ kinetic energy is observed.     

Near IR laser light visualizators using nonlinear GaSe and other layered crystallites

Two methods of preparation of the devices for visualization of pulsed and continuous near-IR (near infrared) are described and the results of conversion of pulsed and continuous IR (800–1360 nm) laser radiation into the visible range of spectra (400–680 nm) by using a transparent substrate covered with the particles (including nanoparticles) of effective nonlinear materials of GaSe _x S_{1 − x} (0.2 ≤ x ≤ 0.8) are presented. Converted light can be detected in transmission or reflection geometry as a visible spot corresponding to the real size of the incident laser beam. Developed device structures can be used for checking if the laser is working or not, for optical adjustment, for visualization of distribution of laser radiation over the cross of the beam and for investigation of the content of the laser radiation. Low energy (power density) limit for visualization of the IR laser pulses with 2–3 ps duration for these device structures are: between 4.6–2.1 μJ (3 × 10⁻⁴−1 × 10⁻⁴ W/cm²) at 1200 nm; between 8.4–2.6 μJ (4.7 × 10⁻⁴−1.5 × 10⁻⁴ W/cm²) at 1300 nm; between 14.4–8.1 μJ (8.2 × 10⁻⁴–4.6 × 10⁻⁴ W/cm²) at 1360 nm. Threshold damage density is more than 10 MW/cm² at λ = 1060 nm, pulse duration τ = 35 ps. The results are compared with commercially existing laser light visualizators.     

Inertial deposition of nanoparticle chain aggregates: Theory and comparison with impactor data for ultrafine atmospheric aerosols

Nanoparticle chain aggregates (NCAs) are often sized and collected using instruments that rely on inertial transport mechanisms. The instruments size segregate aggregates according to the diameter of a sphere with the same aerodynamic behavior in a mechanical force field. A new method of interpreting the aerodynamic diameter of NCAs is described. The method can be used to calculate aggregate surface area or volume. This is useful since inertial instruments are normally calibrated for spheres, and the calibrations cannot be directly used to calculate aggregate properties. A linear relationship between aggregate aerodynamic diameter and primary particle diameter based on published Monte-Carlo drag calculations is derived. The relationship shows that the aggregate aerodynamic diameter is independent of the number of primary particles that compose an aggregate, hence the aggregate mass. The analysis applies to aggregates with low fractal dimension and uniform primary particle diameter. This is often a reasonable approximation for the morphology of nanoparticles generated in high temperature gases. An analogy is the use of the sphere as an approximation for compact particles. The analysis is applied to the collection of NCAs by a low-pressure impactor. Our results indicate the low-pressure impactor collects aggregates with a known surface area per unit volume on each stage. Combustion processes often produce particles with aggregate structure. For diesel exhaust aggregates, the surface area per unit volume calculated by our method was about twice that of spheres with diameter equal to the aerodynamic diameter. Measurements of aggregates collected near a major freeway and at Los Angeles International Airport (LAX) were made for two aerodynamic cutoff diameter diameters (d _a,50), 50 and 75 nm. (Aerodynamic cutoff diameter refers to the diameter of particles collected with 50% efficiency on a low-pressure impactor stage.) Near-freeway aggregates were probably primarily a mixture of diesel and internal combustion engine emissions. Aggregates collected at LAX were most likely present as a result of aircraft emissions. In both measurements, the aggregate aerodynamic diameters calculated from the primary particle diameter were fairly close to the stage cutoff diameter. The number of primary particles per aggregate varied one order of magnitude for particles depositing on the same stage. The average aggregate surface area per unit volume was 2.41 × 10⁶ cm⁻¹ and 2.59 × 10⁶ cm⁻¹ (50 nm d _a,50) and 1.81 × 10⁶ cm⁻¹ and 1.68 × 10⁶ cm⁻¹ (75 nm d _a,50) for near-freeway and LAX measurements, respectively. These preliminary measurements are consistent with values calculated from theory.     

Encapsulation of iron nanoparticles in alginate biopolymer for trichloroethylene remediation

Nanoscale zero-valent iron (NZVI) particles (10–90 nm) were encapsulated in biodegradable calcium-alginate capsules for the first time for application in environmental remediation. Encapsulation is expected to offers distinct advances over entrapment. Trichloroethylene (TCE) degradation was 89–91% in 2 h, and the reaction followed pseudo first order kinetics for encapsulated NZVI systems with an observed reaction rate constant (k _obs) of 1.92–3.23 × 10⁻² min⁻¹ and a surface normalized reaction rate constant (k _sa) of 1.02–1.72 × 10⁻³ L m⁻² min⁻¹. TCE degradation reaction rates for encapsulated and bare NZVI were similar indicating no adverse affects of encapsulation on degradation kinetics. The shelf-life of encapsulated NZVI was found to be four months with little decrease in TCE removal efficiency.     

Precipitation of gold nanoparticles on the quartz surface modified by titanium (IV) butoxide

Gold nanoparticles have been precipitated on the surface of quartz slides covered with titanium (IV) butoxide. UV irradiation of modified quartz slides immersed into water solutions of hydrogen tetrachloroaurate of different concentrations (2.5 × 10⁻⁴–1.0 × 10⁻² M) has been used for this purpose. Properties of produced samples have been investigated by UV–Vis spectroscopy, IR spectroscopy, SEM-EDX, TGA, and AFM. According to the obtained data, produced gold particles are distributed on modified quartz surface very uniformly and the average size of gold particles is about 30–50 nm.     

Nonlinear optical parameters of colloidal silver at various stages of aggregation

The Z-scan method is used to study the variation in the nonlinear susceptibility χ⁽³⁾ (−gw; ω, ω, −ω) and nonlinear refractive index of colloidal silver with the degree of aggregation under the action of picosecond and nanosecond radiation (λ=1064 nm). The values of χ⁽³⁾ for aggregated silver that are defined by Kerr nonlinearity and thermal self-focusing are found to be −1.5×10⁻¹⁴ and −4.4×10⁻¹¹ esu, respectively. The time evolution of the picosecond pulses passing through the colloid is investigated.     

The Sensitive Determination of Nucleic Acids Using Fluorescence Enhancement of Eu<Superscript>3+</Superscript>-BenzoylacetoneCetyltrimethylammonium Bromide-Nucleic Acid System

A new quantitative method for micro amounts of nucleic acids in aqueous solution is proposed using Eu³⁺-benzoylacetone (BA) complex as fluorescent probe in the presence of cetyltrimethyl-ammonium bromide (CTMAB). Under the optimum condition, the ratio of the fluorescence intensities with and without nucleic acids is proportional to the concentration of nucleic acid in the range of 1.0 × 10⁻⁹ to 5.0 × 10⁻⁶ g/mL for herring sperm DNA (hsDNA), 3.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g/mL for calf thymus DNA(ctDNA) and 8.0 × 10⁻⁹ to 1.0 × 10⁻⁶ g/mL for yeast RNA (yRNA), and their detection limits are 0.33, 0.21 and 0.99 ng/mL, respectively. Actual sample (DNA of Arabidopsis thaliana) was determined satisfactorily. In addition, the interaction mechanism is also investigated.     

Polarisation conductivity of the O2,Pt/Zr(Y)O2 and H2-H2O, Pt/Zr(Y)O2 electrodes

Pt electrodes with defined contact geometries were studied by using impedance spectroscopy. The specific polarisation conductivity per unit length of the three-phase boundary was determined. It is found to be 1 × 10⁻⁴ S·cm⁻¹ at 977 °C in an atmosphere of “pure” hydrogen with an oxygen partial pressure of 10⁻²⁰ atm at 1000 °C. Investigations carried out in an atmosphere of pure oxygen revealed a pronounced dependence of the polarisation conductivity on the electrode history. The polarisation conductivity was found to be in a range of 2 × 10⁻⁴ to 6.5 × 10⁻⁴ S·cm⁻¹ at a temperature of 977 °C. It was possible to estimate the area of the electrolyte surface which takes part in the electrode reaction. The real exchange current density was determined.     

Thin TiO2 grown by metal–organic chemical vapor deposition on (NH4)2S x -treated InP

The electrical characteristics of thin TiO₂ films prepared by metal–organic chemical vapor deposition grown on a p-type InP substrate were studied. For a TiO₂ film of 4.7 nm on InP without and with ammonium sulfide treatment, the leakage currents are 8.8×10⁻² and 1.1×10⁻⁴ A/cm² at +2 V bias and 1.6×10⁻¹ and 8.3×10⁻⁴ A/cm² at −2 V bias. The lower leakage currents of TiO₂ with ammonium sulfide treatment arise from the improvement of interface quality. The dielectric constant and effective oxide charge number density are 33 and 2.5×10¹³ cm², respectively. The lowest mid-gap interface state density is around 7.6×10¹¹ cm⁻² eV⁻¹. The equivalent oxide thickness is 0.52 nm. The breakdown electric field increases with decreasing thickness in the range of 2.5 to 7.6 nm and reaches 9.3 MV/cm at 2.5 nm.     

Spectrofluorimetric Assessment of Chlorzoxazone and Ibuprofen in Pharmaceutical Formulations by using Eu-Tetracycline HCl Optical Sensor Doped in Sol–Gel Matrix

A novel, simple, sensitive and selective spectrofluorimetric method was developed for the determination of trace amounts of chlorzoxazone and Ibuprofen in pharmaceutical tablets using optical sensor Eu-Tetracycline HCl doped in sol–gel matrix. The chlorzoxazone or Ibuprofen can remarkably enhance the luminescence intensity of Eu-Tetracycline HCl complex doped in a sol–gel matrix in dimethylformamide (DMF) at pH 9.7 and 6.3, respectively, λ_ex = 400 nm. The enhancing of luminescence intensity peak of Eu-Tetracycline HCl complex at 617 nm is proportional to the concentration of chlorzoxazone or Ibuprofen a result that suggested profitable application as a simple optical sensor for chlorzoxazone or Ibuprofen assessment. The dynamic ranges found for the determination of chlorzoxazone and Ibuprofen concentration are 5 × 10⁻⁹–1 × 10⁻⁴ and 1 × 10⁻⁸–7 × 10⁻⁵ mol L⁻¹, and the limit of detection (LOD) and quantitation limit of detection (LOQ) are 3.1 × 10⁻¹⁰ , 9.6 × 10⁻¹⁰ and 5.6 × 10⁻¹⁰, 1.7 × 10⁻⁹ mol L⁻¹, respectively.     

Effect of a magnetic field on the rate of etching of silicon dioxide in a CF4 + O2 plasma

A near-electrode nonuniform magnetic field crossed with an electric field is found to strongly affect the rate of etching of silicon dioxide on glass substrates in a CF₄ + O₂ plasma when the Larmor frequency (≈10⁹ s⁻¹) is much higher than the frequency of collisions of an electron with surrounding plasma particles (≈10⁶ s⁻¹) and the frequency of the applied rf electric field (≈10⁷ s⁻¹). The confinement of electrons by the magnetic field in the immediate vicinity of the substrate surface to be treated increases the rate of generation of chemically active particles, which increases the etching rate of silicon dioxide.     

Generation of the third harmonic in fullerene-containing polyimide films by picosecond radiation of the Nd: YAG laser

The results of the studies on the transformation of the frequency of laser radiation in polyimide films doped by C₇₀ are presented. The nonlinear susceptibility (χ⁽³⁾) of polyimide 6B films with various concentrations of C₇₀ is studied by third-harmonic generation. At a wavelength of 1064 nm, the value of χ⁽³⁾(−3ω; ω, ω, ω) is 9×10⁻¹³ esu. The effect of the nonlinear variation in the refractive index of the fullerene-containing films on the phase matching between the pumping and third-harmonic waves is analyzed. The third harmonic of the Nd: YAG laser radiation was generated with the efficiencies 6×10⁻⁶ and 10⁻⁶ in the films with the C₇₀ concentration of 0.5 and 0.2%, respectively.     

Effect of photoexcitation on the electrical performance of ZnS: Mn thin-film electroluminescent structures

It is shown that the kinetics of the charge and current passing through a thin-film electroluminescent emitter, as well as the I-V characteristics of the emitter, greatly diverge under blue, red, and IR pulsed illumination with photon energies of ≈2.6, ≈1.9, and ≈1.3 eV, respectively, and a photon flux density of 4×10¹⁴–3×10¹⁵ mm⁻² s⁻¹. Results obtained indicate that, during the operation of the emitter, deep centers associated presumably with V _Zn ²⁻ zinc vacancies and V _S ⁺ and V _S ²⁺ sulfur vacancies exchange charge. These centers lie above the valence band by ≈1.1, ≤1.9, and ≤1.3 eV, respectively. Their concentrations are estimated as (3–4)×10¹⁶ cm⁻³ for V _Zn ²⁻ and V _S ⁺ and ≈1.5×10¹⁶ cm⁻³ for V _S ²⁺ . It is demonstrated that positive and negative space charges forming in the near-anode and near-cathode regions of the phosphor layer specify the electric performance of the emitters.     

Microstructure of Cu<Subscript>60</Subscript>Zr<Subscript>20</Subscript>Ti<Subscript>20</Subscript> bulk metallic glass rolled at different strain rates

The structural evolution of Cu₆₀Zr₂₀Ti₂₀ bulk metallic glass during rolling at different strain rates and cryogenic temperature was investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and high-resolution transmission electron microscopy (HRTEM). It is revealed that the deformation-induced transformation is strongly dependent on the strain rate. At the lowest experimental strain rate of 1.0×10⁻⁴ s⁻¹, no phase transformation occurs until the highest deformation degree reaches 95%. In a strain rate range of 5.0×10⁻⁴−5.0×10⁻² s⁻¹, phase separation occurs in a high deformation degree. As the strain rate reaches 5.0×10⁻¹ s⁻¹, phase separation and nanocrystallization concur. The critical deformation degree for occurrence of phase transformation decreases with the strain rate increasing. Supported by the National Natural Science Foundation of China (Grant No. 50471016)