Polyelectrolyte complexes of glycol chitosan with some polysaccharides. II. Electrical conductivity

The dc electrical conductivity of films of the polyelectrolyte complexes of glycol chitosan (GlChi) with the sodium salts of dextran sulfate (DS), carboxymethyl cellulose (CMC), polygalacturonic acid (GalUA)_n, and alginic acid (AlgA) was measured at temperatures above and below room temperature. The maximum field strength in the thinnest film used amounted to 3 × 10⁴ V/cm. A plot of normalized current against the reciprocal of the absolute temperature revealed two regions with different slopes, and activation energies in these two regions have been obtained for all the complexes. The activation energies in the high-temperature region vary from 0.85 to 1.18 eV and in the low-temperature region from 0 to 0.22 eV. Reasons are given to show that the conductivity is probably ionic. Near room temperature, the current–voltage relation is almost linear in the GlChi–DS complex, while in the other three complexes the current varies as a power n of the voltage with the value of n ranging from 1.7 to 2.5. A rise in temperatures causes an increase in the slope of the log I vs log V plot in GlChi–DS and GlChi–CMC complexes. The nonlinear current–voltage relation is ascribed to a space-charge-limited conductivity.     

Study of optical properties of electropolymerized melanin films by photopyroelectric spectroscopy

Photopyroelectric (PPE) spectroscopy, in the 350–1,075 nm wavelength range, was used to study the optical properties of electropolymerized melanin films on indium tin oxide (ITO) coated glass. The PPE intensity signal as a function of the wavelength λ, V _n(λ) and its phase F _n(λ) were independently measured. Using the PPE signal intensity and the thermal and optical properties of the pyroelectric detector, we were able to calculate the optical absorption coefficient β of melanin in the solid-state. We believe this to be the first such measurement of its kind on this material. Additionally, we found an optical gap in these melanin films at 1.70 eV.     

Vacancy clustering and diffusion in germanium using kinetic lattice Monte Carlo simulations

We investigated vacancy-assisted self-diffusion in germanium by means of kinetic lattice Monte Carlo (KLMC) simulations below the melting temperature, for a vacancy concentration of 1 × 10¹⁸/cm³. At higher temperatures, fewer clusters formed, but there was less variation in the number of clusters than at lower temperatures as the time increased. Equilibrium diffusivities in the clustering region were 10² lower than those of free vacancies in the initial stage of KLMC simulations. They were expressed according to three temperature regimes: 6.5 × 10^? 4 exp(–0.35/k _B T) cm²/s at temperatures above 1100 K, 5.2 × 10⁵ exp(–2.32/k _B T) cm²/s at temperatures of 900–1100 K and 6.0 × 0^–7 exp(–0.19/k _B T) cm²/s at temperatures below 900 K. The effective mean migration energy, 1.1 eV, closely coincided with that of the 1.0–1.2 eV in experiments and was very different from the migration energy of the free vacancy.     

Optical Properties of Ferroelectric Epitaxial K0.5Na0.5NbO3 Films in Visible to Ultraviolet Range

The complex index of refraction in the spectral range of 0.74 to 4.5 eV is studied by variable-angle spectroscopic ellipsometry in ferroelectric K_0.5Na_0.5NbO₃ films. The 20-nm-thick cube-on-cube-type epitaxial films are grown on SrTiO₃(001) and DyScO₃(011) single-crystal substrates. The films are transparent and exhibit a significant difference between refractive indices Δn = 0.5 at photon energies below 3 eV. The energies of optical transitions are in the range of 3.15–4.30 eV and differ by 0.2–0.3 eV in these films. The observed behavior is discussed in terms of lattice strain and strain-induced ferroelectric polarization in epitaxial perovskite oxide films.     

Studies of Electronic Excitations of Rectangular ZnO Nanorods by Electron Energy-Loss Spectroscopy

Electronic excitations of single ZnO rectangular nanorod have been investigated by electron energy-loss spectroscopy in conjunction with scanning transmission electron microscopy (STEM-EELS). We focus primarily on the surface excitations greatly enhanced at the grazing incidence parallel to the surfaces of ZnO nanorods. An uncommon kind of surface excitation known as surface exciton polaritons occurring near interband transitions is found to dominate in the spectral range between the band gap at 3.4 eV and the surface plasmon peak at 15.8 eV. In addition, the dielectric function of ZnO up to 25 eV has also been derived from the bulk excitation spectra using the Kramers–Kronig analysis on a single nanorod. Theoretical EELS simulations are also compared with the experimental results and good agreements are obtained.     

Characterization of the Valence and Conduction Band Levels of n = 1 2D Perovskites: A Combined Experimental and Theoretical Investigation

This study presents a combined experimental and theoretical study of the electronic structure of two 2D metal halide perovskite films. Ultraviolet and inverse photoemission spectroscopies are performed on solution‐processed thin films of the n = 1 layered perovskite butylammonium lead iodide and bromide, BA₂PbI₄ and BA₂PbBr₄, characterized by optical absorption and X‐ray diffraction, to determine their valence and conduction band densities of states, transport gaps, and exciton binding energies. The electron spectroscopy results are compared with the densities of states determined by density functional theory calculations. The remarkable agreement between experiment and calculation enables a detailed identification and analysis of the organic and inorganic contributions to the valence and conduction bands of these two hybrid perovskites. The electron affinity and ionization energies are found to be 3.1 and 5.8 eV for BA₂PbI₄, and 3.1 and 6.5 eV for BA₂PbBr₄. The exciton binding energies are estimated to be 260 and 300 meV for the two materials, respectively. The 2D lead iodide and bromide perovskites exhibit significantly less band dispersion and a larger density of states at the band edges than the 3D analogs. The effects of using various organic ligands are also discussed.     

Dynamics of the implosion of a tungsten wire array onto the central aluminum wire

Results are presented from the studies of the magnetic implosion of a tungsten wire liner onto an aluminum wire at currents of 2.0–2.6 MA. The experiments were carried out in the S-300 high-power pulsed facility at the Russian Research Centre Kurchatov Institute. The liner is composed of 50 wires 6 μm in diameter and 1 cm in length, which are equally spaced on a circle 1 cm in diameter. An aluminum wire 120 μm in diameter is positioned at the array axis. The liner implosion was accompanied by the generation of VUV and soft X-ray emission. The parameters of the pinch plasma produced during the liner implosion onto the aluminum wire were determined from the time-resolved spectral measurements by a five-channel polychromator. The ion and electron densities turned out to be equal to n _i≈4×10¹⁹ cm⁻³ and n _e≈4×10²⁰ cm⁻³, respectively, and the electron temperature was T _e≈40 eV. The radiation energy measured in the range 50–600 eV was 2–10 kJ. The sources of soft X-ray emission in hydrogen-and helium-like aluminum lines were the bright spots and local objects (clouds) formed in the plasma corona at an electron temperature of 200–500 eV and electron density of 10²¹–10²² cm⁻³. The possibility of both the generation of an axial magnetic field during the liner implosion and the conversion of the energy of this field into soft X-ray emission is discussed. __________ Translated from Fizika Plazmy, Vol. 28, No. 6, 2002, pp. 514–521. Original Russian Text Copyright ? 2002 by Bakshaev, Blinov, Dan'ko, Ivanov, Klír, Korolev, Kravárik, Krása, Kubeš, Tumanov, Chernenko, Chesnokov, Shashkov, Juha.     

Effects of hydrocarbon additions on gas-liquid mass transfer coefficients in biphasic bioreactors

The effects of aliphatic hydrocarbons (n-hexadecane andn-dodecane) on the volumetric oxygen mass transfer coefficient (k _L a) were studied in flat alveolar airlift reactor and continuous stirred tank reactors (CSTRs). In the flat alveolar airlift reactor, high aeration rates (>2 vvm) were required in order to obtain efficient organic-aqueous phase dispersion and reliablek _L a measurements. Addition of 1% (v/v)n-hexadecane orn-dodecane increased thek _l a 1.55-and 1.33-fold, respectively, compared to the control (superficial velocity: 25.8×10⁻³ m/s, sparger orifice diameter: 0.5 mm). Analysis of the gas-liquid interfacial areaa and the liquid film mass transfer coefficientk _L suggests that the observedk _L a increase was a function of the media's liquid film mass transfer. Addition of 1% (v/v)n-hexadecane orn-dodecane to analogous setups using CSTRs led to ak _L a increase by a factor of 1.68 and 1.36, respectively (superficial velocity: 2.1×10⁻³ m/s, stirring rate: 250 rpm). These results propose that low-concentration addition of oxygen-vectors to aerobic microbial cultures has additional benefit relative to incubation in purely aqueous media.     

Energetics,kinetics and dynamics of self-interstitial clusters in bcc tungsten

The configuration, slipping and rotation of self-interstitial atoms cluster along <111> crystal orientation with different sizes in a tungsten are investigated systematically with molecular dynamics. It is found that (I) the SIA clusters with high symmetry are always favoured; (II) the SIA clusters can undergo one-dimensional fast migration along <111> direction, and their migration barriers are no more than 0.07?eV, which is expected due to the strong interaction in the SIA clusters; (III) the rotation energy barriers of the SIA clusters are rather high and they are basically positively correlated with the size of the cluster. For example, the reorientation barrier is 0.66?eV for 1 SIA, 1.2–1.8?eV for SIA_n (2?≤?n?≤?5) clusters and over 2.7?eV for SIA_n (6?≤?n?≤?7) clusters. Compared with slipping of SIA clusters, is an infrequent event, especially for larger SIAs cluster, the vast majority SIAs cluster would have already recombination with vacancies or annihilates at surface and grain boundary through slipping before rotation, which explained that there are very low density of SIAs cluster found in the experiment.     

Binding study of lysozyme with Al(III) using chemiluminescence analysis

The binding behavior of lysozyme with Al(III) is described using luminol as a luminescence probe by flow injection–chemiluminescence (FI–CL) analysis. It was found that the CL intensity of the luminol–lysozyme reaction could be markedly enhanced by Al(III), and the increase in CL intensity was linear with the Al(III) concentration over the range 0.3–30.0 pg mL^?1, with a detection limit of 0.1 pg mL^?1 (3σ). Based on the interaction model of lysozyme with Al(III), lg[(I ? I₀)/(2I₀ ? I)] = lgK + nlg[M], the binding constant K = 6.84 × 10⁶ L mol^–1 and the number of binding sites (n) = 0.76. The relative standard deviations were 3.2, 2.4 and 2.0% for 10.0, 20.0 and 30.0 pg mL^?1 Al(III) (n = 7), respectively. This new method was successfully applied to continuous, quantitative monitoring of picogram level Al(III) in human saliva following oral intake of compound aluminum hydroxide tablets. It was found that Al(III) in saliva reached a maximum of 101.2 ng mL^?1 at 3.0 h. The absorption rate constant k_a, elimination rate constant k and half‐life time t_1/2 of Al(III) were 1.378 h^?1, 0.264 h^?1 and 2.624 h, respectively. Copyright © 2013 John Wiley & Sons, Ltd.     

Thermally stimulated luminescence glow curve structure of β‐irradiated CaB4O7:Dy

Thermally stimulated luminescence glow curves of CaB₄O₇:Dy samples after β‐irradiation showed glow peaks at ~335, 530 and 675 K, with a heating rate of 2 K/s. The main peak at 530 K was analyzed using the T_max–T_stop method and was found to be composed of at least five overlapping glow peaks. A curve‐fitting program was used to perform computerized glow curve deconvolution (CGCD) analysis of the complex peak of the dosimetric material of interest. The kinetic parameters, namely activation energy (E) and frequency factor (s), associated with the main glow peak of CaB₄O₇:Dy at 520 K were evaluated using peak shape (PS) and isothermal luminescence decay (ILD) methods. In addition, the kinetics was determined to be first order (b =1) by applying the additive dose method. The activation energies and frequency factors obtained using PS and ILD methods are calculated to be 0.72 and 0.72 eV and 8.76 × 10⁵ and 1.44 × 10⁶/s, respectively. Copyright © 2014 John Wiley & Sons, Ltd.     

Structural,Morphological, and Optical Properties of Nanocrystalline (Bi2O3)1−x:(TiO2)x Thin Films for Transparent Electronics

The fabrication of low cost and eco-friendly transparent electronics using metal oxide semiconductors is still a challenging task. In this work, transparent nanocrystalline (Bi₂O₃)_1−x:(TiO₂)_x thin films were synthesized using a pulsed laser deposition technique (PLD); XRD analysis shows the films have polycrystalline structure of monoclinic Bi₂O₃; morphological and topographical properties were analyzed by SEM and AFM showing the films have smooth surfaces with RMS roughness (4.26–7.37 nm) with micro-and nano-spheres (2 μm to 23 nm); the optical properties were analyzed by Uv-Vis spectrometer and revealed high transmittance in the visible range; the best results were obtained at x = 0.05 where the highest crystallinity, highest transmittance (> 82%), and highest band gap (3.769 eV) were achieved; and empirical models have been proposed to estimate the band gap and Bi–O bond lengths as a function of TiO₂ concentration with excellent coincidence with the experimental data.

     

Electric dichroism studies on ferriheme– and ferroheme–poly(L-lysine) complexes at pH 9–12

Transient electric dichroism has been measured for the ferriheme–poly(L -lysine)[(Lys)_n], ferroheme–(Lys)_n, and ferroheme–(Lys)_n–carbon monoxide (CO) solutions at pH 9–12. The Soret absorption maximum in electronic spectrum (λ), the reduced linear dichroism (ρ_∞) at complete orientation and the calculated angle (?) between the porphyrin plane of a bound heme and the oriented polymer axis are determined for the following complexes: a ferriheme–(Lys)_n complex at pH 9.5–10.5 (λ = 420 nm, ρ_∞ = 0.50, and ? = 19°), a ferroheme–(Lys)_n complex at pH 9.5–10.2 (λ = 432 nm, ρ_∞ = 0.77, and ? = 0°), and a ferroheme–(Lys)_n–CO complex at pH 9.25 (λ = 430 nm, ρ_∞ = 0.38, and ? = 24°). Based on the above data, the validity of the structures of heme–(Lys)_n complexes proposed by other investigators is discussed.     

Species abundance distributions in neutral models with immigration or mutation and general lifetimes

We consider a general, neutral, dynamical model of biodiversity. Individuals have i.i.d. lifetime durations, which are not necessarily exponentially distributed, and each individual gives birth independently at constant rate λ. Thus, the population size is a homogeneous, binary Crump–Mode–Jagers process (which is not necessarily a Markov process). We assume that types are clonally inherited. We consider two classes of speciation models in this setting. In the immigration model, new individuals of an entirely new species singly enter the population at constant rate μ (e.g., from the mainland into the island). In the mutation model, each individual independently experiences point mutations in its germ line, at constant rate θ. We are interested in the species abundance distribution, i.e., in the numbers, denoted I _n (k) in the immigration model and A _n (k) in the mutation model, of species represented by k individuals, k = 1, 2, . . . , n, when there are n individuals in the total population. In the immigration model, we prove that the numbers (I _t (k); k ≥ 1) of species represented by k individuals at time t, are independent Poisson variables with parameters as in Fisher’s log-series. When conditioning on the total size of the population to equal n, this results in species abundance distributions given by Ewens’ sampling formula. In particular, I _n (k) converges as n → ∞ to a Poisson r.v. with mean γ/k, where γ : = μ/λ. In the mutation model, as n → ∞, we obtain the almost sure convergence of n ⁻¹ A _n (k) to a nonrandom explicit constant. In the case of a critical, linear birth–death process, this constant is given by Fisher’s log-series, namely n ⁻¹ A _n (k) converges to α ^k /k, where α : = λ/(λ + θ). In both models, the abundances of the most abundant species are briefly discussed.     

Binding of caffeine with caffeic acid and chlorogenic acid using fluorescence quenching,UV/vis and FTIR spectroscopic techniques

The interactions of caffeine (CF) with chlorogenic acid (CGA) and caffeic acid (CFA) were investigated by fluorescence quenching, UV/vis and Fourier transform infrared (FTIR) spectroscopic techniques. The results of the study indicated that the fluorescence quenching between caffeine and hydroxycinnamic acids could be rationalized in terms of static quenching or the formation of non‐fluorescent CF–CFA and CF–CGA complexes. From fluorescence quenching spectral analysis, the quenching constant (K_SV), quenching rate constant (k_q), number of binding sites (n), thermodynamic properties and conformational changes of the interaction were determined. The quenching constants (K_SV) between CF and CGA, CFA are 1.84 × 10⁴ and 1.04 × 10⁴ L/mol at 298 K and their binding site n is ~ 1. Thermodynamic parameters determined using the Van't Hoff equation indicated that hydrogen bonds and van der Waal's forces have a major role in the reaction of caffeine with caffeic acid and chlorogenic acid. The 3D fluorescence, UV/vis and FTIR spectra also showed that the binding of CF with CFA and CGA induces conformational changes in CFA and CGA. Copyright © 2015 John Wiley & Sons, Ltd.     

Utilization of normal alkanes by yeasts

A stable mixed yeast culture designated as Culture 4, consisting of Candida intermedia and Candida lipolytica was investigated. The culture was judged stable based on uniformity of fermentation results and the nearly constant ratio of the two organisms at the completion of fermentations. However, the ratio of the two organisms at different times during the fermentation was not determined. The mixed culture grew more rapidly on n-alkanes than did C. intermedia; C. lipolytica did not grow on unsupplemented mineral salt–n-alkane medium. Solid n-alkanes were dissolved in 2,6,0,14-tetramethylpentadecane (pristane) for investigation as carbon sources. With Culture 4, on n-alkanes ranging from pentadecane (C₁₅) through octacosane (C₂₈), cell yields were 74.2–89.5%; generation times were 3.0–8.0 hr. during the exponential growth phase. The fastest growth rates and highest cell yields were obtained with docosane (C₂₂) as substrate. The cells obtained contained 6.75–8.81% nitrogen and 1.9–13.4% lipid. Crude protein yields were 34.4–47.6%. The oxidation of n-alkanes by C. intermedia was studied manometrically with resting whole cells. The alkaneoxidizing system of this organism appears to be constitutive and nonspecific for alkane substrates.     

Vacuum‐Assisted Growth of Low‐Bandgap Thin Films (FA0.8MA0.2Sn0.5Pb0.5I3) for All‐Perovskite Tandem Solar Cells

All‐perovskite multijunction photovoltaics, combining a wide‐bandgap (WBG) perovskite top solar cell (E_G ≈1.6–1.8 eV) with a low‐bandgap (LBG) perovskite bottom solar cell (E_G < 1.3 eV), promise power conversion efficiencies (PCEs) >33%. While the research on WBG perovskite solar cells has advanced rapidly over the past decade, LBG perovskite solar cells lack PCE as well as stability. In this work, vacuum‐assisted growth control (VAGC) of solution‐processed LBG perovskite thin films based on mixed Sn–Pb perovskite compositions is reported. The reported perovskite thin films processed by VAGC exhibit large columnar crystals. Compared to the well‐established processing of LBG perovskites via antisolvent deposition, the VAGC approach results in a significantly enhanced charge‐carrier lifetime. The improved optoelectronic characteristics enable high‐performance LBG perovskite solar cells (1.27 eV) with PCEs up to 18.2% as well as very efficient four‐terminal all‐perovskite tandem solar cells with PCEs up to 23%. Moreover, VAGC leads to promising reproducibility and potential in the fabrication of larger active‐area solar cells up to 1 cm².     

Infrared studies of stereoregularity of copoly(γ-benzyl-D,L-glutamate) by the polymerization of the N-carboxylic anhydride

The D and L copolymerizations of γ-benzyl glutamate N-carboxylic anhydride (NCA) were carried out by two different initiators, n-butylamine and sodium methoxide. The stereoregularity of the polymer was examined by infrared spectroscopy in the region 700–200 cm^?1. A remarkable difference was found between the polymers obtained by these initiators in the region 450–400 cm^?1. In the polymer obtained with sodium methoxide as initiator, the 409-cm^?1 peak assigned to local α-helical conformation was not greatly affected by the amount of the L -form, but in the polymer obtained by n-butylamine this peak was much affected by the variation of L -content. This indicates that the stereo-selectivity of the polymerization in the sodium methoxide initiated system is higher than that in the n-butylamine initiated system.     

Models of Chance when Measuring Interrater Agreement with Kappa

Two measures of reliability for nominal scales are compared: Coefficient Kappa and k_n, a modification suggested for agreement matrices with free marginals. It is illustrated that the evaluation of two rater's agreement may come to a contradictory conclusion, depending on whether k or k_n is used. On the basis of the underlying chance models it is concluded that k and k_n cannot be interpreted in the same manner. Specifically when raters disagree, the two measures can be widely discrepant.     

Coenzyme models. IV. Effect of polymer micelles on rate and equilibrium of addition of cyanide ion to N-substituted 3-carboxamidopyridinium ions.

The water-soluble poly(1-vinyl-2-ethylimidazole) quaternized with ethyl bromide and lauryl bromide was prepared; lauryl group content, 8.8 mol% (L-9), 28.9 mol% (L-29), and 40.9 mol% (L-41). The λ_max value of methyl orange near 460 nm shifted to shorter wavelengths (417–433 nm) in the aqueous solution of L-29 and L-41, and the intrinsic viscosity of L-29 was more than ten times smaller than that of L-9. The rate and equilibrium constants (k_? and K) for addition of cyanide ion to the N-substituted 3-carboxamidopyridinium ions were studied at 30°C, where N-substituents employed were n-propyl, n-hexyl, benzyl, 2,6-dichlorobenzyl, and n-lauryl. The kinetic parameters for n-lauryl-3-carboxamidopyridinium were markedly increased in the presence of L-29 and L-41 and with increasing polymer concentrations (84-fold for k_? and 7800-fold for K), especially at low ionic strength, whereas L-9 decelerated the addition reaction. These distinct behaviors mean that L-29 and L-41 are classified as micellelike polymers and L-9 as a polyelectrolytelike polymer. However, L-29 depressed the rate of the forward reaction for benzyl-3-carboxamidopyridinium, acting like a simple polyelectrolyte. Therefore, the polymer micelle can provide both the microenvironments characteristic of polyelectrolytes and micelles, depending on the hydrophobicity of substrates.