Effect of γ-radiation on the phase transition temperature of Li0.5(NH4)0.5SO4

Polycrystalline lithium-ammonium sulphate samples were subjected to X-ray diffraction analysis for determining the lattice parameters of the prepared mixed crystals. The compositions of the samples were determined using X-ray microanalysis.

The Li_0.5(NH₄)_0.5SO₄ samples were irradiated with different doses of γ-radiation in order to investigate the effect of this ionizing radiation on the phase transition temperatures T_c1 and T_c2. The temperature dependence of the d.c. resistivity ρ_d.c. and dielectric constant of irradiated samples showed (i) a shift of T_c1 to higher temperatures; (ii) a shift of T_c2 to lower temperatures; and (iii) the appearance of a new anomaly near 128°C at moderately high γ-doses. The mechanisms giving rise to this behaviour are discussed.     

Study on the optically linear birefringence and dichroism properties of Fe3O4 magnetic nanoparticles

We adopt an improved co-precipitation method to prepare the Fe₃O₄ magnetic nanoparticles (MNPs). Influence factors such as the reaction temperature, the pH value of the solution, and the Fe³⁺/Fe²⁺ molar concentration are considered. Via the transmission electronic microscope and X-ray diffractometry, we characterize the dispersibility and size of the products. The reaction temperature and the pH value of the solution have a great influence in the dispersibility and size of MNPs. The diameter of Fe₃O₄ MNP, produced under Fe³⁺/Fe²⁺ molar concentration of 0.25 mole/l and molar ratio of 1.9:1, the reaction temperature is 80 °C, and the pH value reaches 9, is close to 11 nm. Above all, considering the variation of molar concentrations in Fe³⁺/Fe²⁺, the linear birefringence and dichroism of the kerosene-based ferrofluids are investigated by a Stokes polarimeter.     

Photoluminescence in γ-irradiated α-quartz investigated by synchrotron radiation

We report an experimental investigation of the photoluminescence, under excitation by synchrotron radiation within the absorption band at 7.6 eV, induced in γ-irradiated α-quartz. Two emissions centered at 4.9 and 2.7 eV are observed at low temperature: the former decreases above 40 K, whereas the second band exhibits an initial slight increase and its quenching is effective above 100 K. Furthermore, the decay kinetics of both emissions occur in a time scale of nanoseconds: at T=17.5 K we measured a lifetime τ1.0 ns for the photoluminescence at 4.9 eV and τ3.6 ns for that at 2.7 eV. These results give new insight on the optical properties associated with defects peculiar of crystalline matrix, also on the basis of their comparison with previous studies on silica.     

Volatile metal β-diketonates — new precursors for the sonochemical synthesis of nanosized materials — sonolysis of thorium(IV) β-diketonates

Ultrasonic irradiation (22 kHz, Ar atmosphere) of Th(IV) β-diketonates Th(HFAA)₄ and Th(DBM)₄, where HFAA and DBM are hexafluoroacetylacetone and dibenzoylmethane respectively, causes them to decompose in hexadecane solutions, forming solid thorium compounds. The first-order rate constants for Th(IV) β-diketonate degradation were found to be (9.3±0.8)×10⁻³ for Th(HFAA)₄ and (3.8±0.4)×10⁻³ min⁻¹ for Th(DBM)₄, (T=92°C, I=3 W cm⁻²). The rate of the sonochemical reaction increased with the rising β-diketonate volatility and decreased with the rising hydrocarbon solvent vapor pressure. Solid sonication products consisted of a mixture of thorium carbide ThC₂ and Th(IV) β-diketonate partial degradation products. The average ThC₂ particle size was estimated to be about 2 nm. ThC₂ formation was attributed to the high-temperature reaction occurring within the cavitating bubble. The thorium β-diketonate partial degradation products formed in the liquid reaction zones surrounding the cavitating bubbles.     

Polarized light of 193 nm induced birefringence reduction fiber gratings

A polarizer of 193 nm was fabricated with several silicon plates which were mounted so as to incident the UV light of 193 nm by Brewster angle. Its transmission rate is 60% and the polarization extinction ratio is 20:1. Compared with using natural 193 nm light, the high isotropic enhancement of Yb³⁺-doped fiber phase-shifted distributed feedback (DFB) lasers was found by using the 193 nm polarized light, of which the UV polarization lies in the plane of the irradiating beams and the fiber axis.     

β‐Elimination of an aziridine to an allylic amine: a mechanistic study

The base‐induced rearrangement of aziridines has been examined using a combination of calculations and experiment. The calculations show that the substituent on nitrogen is a critical feature that greatly affects the favorability of both α‐deprotonation, and β‐elimination to form an allylic amine. Experiments were carried out to determine whether E2‐like rearrangement to the allylic amine with lithium diisopropyl amide (LDA) is possible. N‐tosyl aziridines were found to deprotonate on the tosyl group, preventing further reaction. A variety of N‐benzenesulfonyl aziridines having both α‐ and β‐protons decomposed when treated with LDA in either tetrahydrofuran or hexamethylphosphoramide. However, when α‐protons were not present, allylic amine was formed, presumably via β‐elimination. Copyright © 2011 John Wiley & Sons, Ltd.     

Relative stabilities and molecular structures of the isomeric enol ethers and carboxylic esters derived from α‐acetyl‐γ‐butyrolactone and α‐acetyl‐δ‐valerolactone

Recently recorded ¹⁷O NMR spectra of compounds studied in a previous work (Taskinen E. Acta Chem. Scand. 1985; B39 : 489–494) dealing with the thermodynamics of isomerization of the enol ethers of α‐acetyl‐γ‐butyrolactone reveal an error in compound identification, caused by an unexpected isomerization reaction during the synthetic procedure. Thus, acid‐catalyzed treatment of the lactone with HC(OR)₃ in the respective alcohol ROH is shown to lead initially to the desired enol ethers which, however, are gradually isomerized to a mixture of the enol ethers and an ester of 2‐methyl‐4,5‐dihydrofuran‐3‐carboxylic acid. As a result, only one of the two isomeric compounds detected in the previous equilibration study was the expected enol ether (the thermodynamically more stable E isomer) of α‐acetyl‐γ‐butyrolactone, while the other, dominating species was the respective carboxylic ester. In the present work, the evidence provided by the ¹⁷O NMR spectra is presented, and the relative stabilities of the isomeric compounds are discussed on the basis of computational enthalpy data. The treatment is also extended to the respective isomeric compounds derived from α‐acetyl‐δ‐valerolactone. Copyright © 2007 John Wiley & Sons, Ltd.     

Determination of microquantities of Be in samples using α-sensitive track etch detectors

A new technique of determining Be content in samples using 4.66 MeV γ-rays is proposed. This energy range is sufficient to knock out the neutron from the ⁹Be nucleaus and to excite the first 2.9 MeV level of the ⁸Be nuclei. 1.5 MeV alpha particles are registered by means of CR-39 or cellulose nitrate detectors. Alpha particles produced in the reaction of γ-rays with Li nuclei which are contained in samples may cause the background. The latter is excluded by heating of samples before irradiation for Li molecules to be evaporated. ¹¹B nuclei do not produce alpha particles at the energy range of γ-rays presented above.The results obtained in the experiments of determining Be content in natural beryl crystal samples are in good agreement with their known chemical composition. Microparticles containing Beryllium were found in soil samples from the Ust-Kamenogorsk are deposit region, which contains 10⁻³ − 10⁻⁴ g/g of Be. The sensitivity of the method is 10⁻⁶ g/g of Be in solids.     

Properties of Si δ-layers embedded in GaAs

An ultrathin, a few monolayers (MLs) thick Si δ-layer, has been embedded in GaAs. The Si δ-layer properties have been electrically and structurally characterized. A conductivity transition has been observed, when going from free carrier transport in thin (1 ML) ordered δ-layers to the disordered conditions for Si δ-layers thicker than 4 MLs. Two novel emission bands are observed in photoluminescence (PL) for Si δ-layers in the width range 1–4 MLs, but solely at below bandgap excitation. The pronounced 2D properties of these δ-layers have been clearly demonstrated by an observed blue shift of the PL characterization as the thickness of the Si δ-layer is reduced. The so-derived results on the transition energies and the electronic structure are in good agreement with theoretical predictions obtained by a self-consistent approach.     

Molecular orientation and morphology of contact printed α-quaterthiophene films on gold

We present contact printing as a technique to deposit α-quaterthiophene (α-4T) films from the solid phase onto gold. The molecular orientation and morphology of both the printed film and the original polycrystalline α-4T film on silica were investigated with low energy ion scattering (LEIS), atomic force microscopy (AFM), X-ray diffraction (XRD) and optical microscopy. We show that the strong interaction between clean gold and α-4T induces a drastic change in the molecular orientation and morphology of a 380 nm thick α-4T film. On gold the α-4T molecules are orientated with the thiophene rings parallel to the substrate and form rod-like crystallites (typically 13×1.3 μm²), whereas on silica α-4T molecules stand almost upright and form large cobblestone-like crystallites (typical diameter 10 μm). Exposure of α-4T to a low energy ion beam (dose <1×10¹⁴ 3 keV ³He⁺ ions/cm²) prior to printing causes polymerisation, which decreases the ability to print and alters the morphology of the printed film.     

The Effect of ζ‐Potential and Hydrodynamic Size on Nanoparticle Interactions in Hydrogels

The ζ‐potential and hydrodynamic size (d_h) of nanoparticles (NPs) are systematically controlled by capping gold NPs (AuNPs) with polymers having different charges and treating them in NaCl solutions of diverse concentrations. Interactions between AuNPs in hydrogel are caused by chemical reactions induced by 1,4‐dithiothreitol. The effect of ζ‐potential is clear, as negatively charged AuNPs can be aggregated in neutral agarose gel, but the amount of aggregation is significantly affected by the magnitude of the negative surface charge on the AuNPs. However, all positively charged AuNPs show negligible aggregation in agarose gel with slightly negative polarity. The effect of d_h on AuNP aggregation is different from that of ζ‐potential. Although AuNPs with small d_h generally show more aggregation than those with large d_h, the amount of AuNP capping layer is critical. Thus, the amount of polymer present on NP surface needs to be considered to investigate the effect of d_h on AuNP aggregation. Through extended Derjaguin, Landau, Verwey, Overbeek (XDLVO) theory, it is shown that the charges of the AuNPs and the hydrogel, as well as the d_h of the NPs, are related to electrostatic repulsion and steric hindrance, which affect AuNP aggregation in hydrogel.     

The effect of low-dose β-blockade on performance anxiety in singers

Thirteen singing students received placebo or 20 mg of nadolol prior to their end-of-semester jury performance. The performance was repeated 48 h later with the cross-over drug regimen. Subjects' musical performances were evaluated by a panel of judges (comprised of the subjects' voice faculty). No statistically significant difference could be detected in the overall quality of the performance whether students were taking drug or placebo. Although the small number of subjects in this study precludes a definitive conclusion, these data, together with previous information, lead us to suggest that β-blockers are not useful in coping with nervousness in singing students.     

Raman spectroscopic study of serum albumins: an effect of proton‐ and γ‐irradiation

Raman spectroscopy was applied to analyse structural changes in serum albumins (bovine serum albumin, BSA; human serum albumin, HSA) following proton and γ‐irradiation (0.5, 5 and 50 Gy). Characteristic Raman bands of both polypeptide backbone and amino acid residues were sensitive to irradiation. Significant damage of HSA/BSA was observed only at the highest dose (50 Gy). Raman spectra confirmed radiation‐induced denaturation, destruction of helical structures and aggregation of serum albumins. The differences in the dose‐dependent effects of proton and γ‐radiation on studied proteins are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

The Raman spectrum of the γ′‐V2O5 polymorph: a combined experimental and DFT study

Structure and vibrational dynamics of γ′‐V₂O₅ synthesized from a pristine γ‐LiV₂O₅ sample via a chemical oxidation route was studied by means of Raman spectroscopy and quantum‐chemical calculations. The calculations based on density functional theory reliably reproduce the experimental structure of the γ′‐V₂O₅ lattice. The calculated Raman spectrum agrees remarkably well with the experimental one. Making use of the agreement, a complete assignment of Raman bands to vibrations of particular structural units is proposed. The comparison of Raman spectra and structural features of α‐V₂O₅ and γ′‐V₂O₅ polymorphs allowed establishing reliable ‘structure–spectrum’ correlations and identifying Raman peaks characteristic for different structural units. Copyright © 2015 John Wiley & Sons, Ltd.     

Raman spectroscopic study on sodium hyaluronate: an effect of proton and γ irradiation

Raman spectroscopy was applied to the analysis of structural changes in lyophilised sodium hyaluronate after proton and γ irradiation (0.5, 5, 50, 100, 200 and 600 Gy). Characteristic Raman bands of the polysaccharide were sensitive to irradiation. Significant damage was observed at doses of 50 Gy or higher. The spectral changes confirmed radiation‐induced loss of native solution conformation, destruction of primary structure, fragmentation, cross‐linking and elimination of functional groups. Differences in the effects of proton and γ radiation on sodium hyaluronate are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

Tautomeric equilibria analysis of β‐ketoamides by mass spectrometry

Mass spectrometric evidence of tautomerism is reported for β‐ketoamides. The most abundant tautomers are ketoamido and Z‐enolamido (both forming internal hydrogen bonds). The influence of temperature on the enol/keto abundance ratios is studied in order to estimate the enthalpy difference for tautomeric equilibria. Theoretical calculations have been done in order to support experimental determinations. There are consistent trends between theoretical and experimental data: Enolization is favored by electron‐withdrawing substiuents, bulky groups in α position and temperature increase. Copyright © 2012 John Wiley & Sons, Ltd.     

Changes in electrical properties in α- and γ-exposed PADC track detector

The changes in the dielectric properties and temperature dependence of the d.c. conductivity of α-exposed poly allyl diglycol carbonate (PADC) have been studied. On α-irradiation the dielectric constant (′) as a function of frequency has been found to decrease significantly. The temperature dependence of resistivity in pristine and γ-irradiated samples is of the form ρ(T)=ρ_∝ exp(T₀/T) which can be attributed to conduction of thermally generated carriers. In case of (γ+α) irradiated samples the temperature dependence of resistivity is of the form ρ(T)=ρ_∝ exp(T₀/T)^1/2 which is due to one-dimensional hopping of carriers.     

DFT study the interaction of β‐cyclodextrin with benzyl azide and phenyl acetylene in synthesis of 1,2,3‐triazoles

The phenyl acetylene and benzyl azide cycloaddition reaction in water in the presence of β‐cyclodextrin (β‐CD) as a phase transfer catalyst (PTC) can get a better yield in a shorter time. The interaction between β‐CD and phenyl acetylene or benzyl azide plays an important role in this reaction. This paper studies the complexes of β‐CD with phenyl acetylene and benzyl azide using density functional theory (DFT) method. In order to find out the orientations of guests in the cavity of β‐CD, binding energy and deformation energy are investigated, and the calculated results are confirmed by ¹H nuclear magnetic resonance (¹HNMR). The data from single point energy indicate that the inclusion complexes can improve the solubilities of phenyl acetylene and benzyl azide in water. The ¹³C and ¹⁵N spectra show that the most obvious variation concentrates on C₆ and C₈ of phenyl acetylene and N₁₅ of benzyl azide in complexes. Mulliken charge and frontier orbital are employed for revealing the charge distribution. The effect of β‐CD is discussed in terms of the calculated parameters. Copyright © 2014 John Wiley & Sons, Ltd.     

Inclusion complexes of estrone and estradiol with β‐cyclodextrin: Voltammetric and HPLC studies

The interaction of estrone and estradiol with β‐cyclodextrins (βCD) was investigated by differential pulse voltammetry (DPV) and high‐performance liquid chromatography (HPLC) in mixed media. The co‐solvent influence on the tendency of these estrogens to form inclusion complexes with βCD was examined. Thus, acetonitrile (MeCN) and ethanol (EtOH) were used in a mixed aqueous medium containing phosphate buffer. The association constant of the inclusion complexes (K_a) of estrone and estradiol with βCD were determined in two different media by using both voltammetric and chromatographic techniques. Estradiol was found to bind to βCD with higher affinities than estrone, irrespective of the medium. We have also found a clear influence of the co‐solvent on the K_a value, which means a competition of co‐solvent molecules with estrogens for binding to the cavity of βCD. Consequently, interaction between βCD and the steroids is weakened when acetonitrile is used. Copyright © 2007 John Wiley & Sons, Ltd.