17O and 33S nuclear magnetic shielding of sulfur trioxides from the experimental measurements and theoretical calculations

In a recent ¹⁷O NMR spectra of liquid sulfur trioxide, several unexpected peaks appeared with the temperature‐dependent integrated peak ratio. In order to interpret NMR spectra and assign peaks to possible molecular structures, the theoretical quantum mechanical density functional theory and Møller–Plesset second‐order perturbation theory calculations were performed. It is suggested that in the liquid sulfur trioxide, apart from monomeric SO₃, a significant amount of (SO₃)₃ cyclic trimers should appear. No theoretical data support hypothesis on (SO₃)₂ dimers formation. Copyright © 2014 John Wiley & Sons, Ltd.     

Delayed resonator with acceleration feedback – Complete stability analysis by spectral methods and vibration absorber design

This paper deals with the problem of active vibration suppression using the concept of delayed resonator (DR) absorber with acceleration feedback. A complete dynamic analysis of DR and its coupling with a single degree of freedom mechanical system are performed. Due to the presence of a delay in the acceleration feedback, the dynamics of the resonator itself, as well as the dynamics of combined system are of ‘neutral’ character. On this system, spectral methods are applied to perform a complete stability analysis. Particularly, the method of cluster treatment of characteristic roots is used to determine stability boundaries in the space of the resonator parameters. Based on this analysis, a methodology to select the resonator parameters is proposed in order to guarantee desirable suppression characteristics and to provide safe stability margins. An example case study is included to demonstrate these analytical results.     

Reoxidation of uranium in electrolytically reduced simulated oxide fuel during residual salt distillation

Apoptosis is one of the fundamental phenomena behind successful radiation and chemotherapy treatments. Non-invasive imaging of apoptosis can offer an early diagnosis of disease and the true efficiency of an ongoing treatment procedure. The present study describes an attempt to develop ^99mTc-labeled 2-methyl-2-pentylmalonic acid ([^99mTc] 8) as a new SPECT based apoptosis imaging agent. An optimized chemical and radiosynthesis procedure provided desired product [^99mTc] 8 with high radiochemical yield (84%, n = 3) and radiochemical purity (>99%) as determined by radio HPLC. Biodistribution data indicated that the radiotracer has a rapid clearance from blood and other background tissues. High testes accumulation confirmed the ability of the radiotracer to detect testicular apoptosis in mice.

     

A new type of cation‐exchange polymeric microspheres with pendant methylenethiol groups

Synthesis and characterization of the new styrene microspheres with pendant methylenethiol groups are presented. At the first stage, the polymeric matrices were obtained by the suspension–emulsion polymerization of monomers: styrene (St) with 2,3‐(2‐hydroxy‐3‐methacryloyloxypropoxy)naphthalene (NAF.DM) or (bis[4(2‐hydroxy‐3‐methacryloyloxypropoxy)phenyl]sulfide (BES.DM) or divinylbenzene (DVB). At the second stage, the modification of the sythesized matrices was performed as follows: the matrices were reacted with paraformaldehyde in the presence of hydrochloric acid forming chloromethyl derivatives. Next, by reaction with thiourea, a thiouronium salt was obtained, and then the hydrolysis with NaOH solution and acidification with HCl were carried out. Finally, microspheres with –CH₂SH groups on their surface were obtained. The –SH group content (elemental analysis), thermal properties (thermogravimetric analysis), Fourier transform infrared as well as the swelling characteristics of the functional microspheres were examined. The surface texture was also visualized by the atomic force microscopy (AFM) method. The obtained polymers were screened towards sorption of Cu(II) ions. It was found that a better correlation between the experimental Cu(II) uptake and the theoretical curves predicted by the Langmuir or Freundlich models is obtained in the case of the DVB–St–SH polymer. In the case of the BES.DM–St–SH and 2,3‐NAF–St–SH ones, the Freundlich model corresponded quite well to the experimental data. Copyright © 2013 John Wiley & Sons, Ltd.     

The influence of oxidation number of sulfur on the polymerization and thermo-mechanical properties of dimethacrylate copolymers

Structure and characterization of the sulfur-containing monomers bis[4(2-hydroxy-3-methacryloyloxypropoxy)phenyl]sulfide (S·DM), bis[4(2-hydroxy-3-methacryloyloxypropoxy)phenyl]sulfinyl (SO·DM), bis[4(2-hydroxy-3-methacryloyloxypropoxy)phenyl]sulfonyl (SO₂·DM), and their photopolymerization with N-vinyl-2-pyrrolidone (NVP) are presented. The monomers were obtained in the reaction of derivatives of aromatic diols with 2-(chloromethyl)oxirane in the two-phase liquid/liquid system, including organic and aqueous phases. Next, esterification of the obtained diglycidyl ether was carried out with the use of methacrylic acid. Photopolymerization of the compositions (S·DM, SO·DM, SO₂·DM and NVP) and the initiator (Irgacure 651) was carried out. The influence of oxidation number of sulfur on the properties of the obtained copolymers was studied. The following properties were determined: density, glass transition temperature, Young’s modulus, hardness and tensile strength. Additionally, dynamic-mechanical and thermal properties were investigated. Thermal properties of copolymers under different conditions (in air, in nitrogen and in helium) were tested.     

Photoelectrocatalytic decomposition of gaseous isopropanol in a polymer electrolyte photoreactor

A photoelectrochemical reactor constructed as a proton exchange membrane fuel cell was utilized to electrochemically enhance the photocatalytic decomposition of gas-phase isopropanol. Nafion membrane was employed to serve as solid electrolyte to establish an electrochemical circuit for the gaseous photocatalytic reaction. The electrical current density of photoanode was found to correspond to the variation of the applied bias and relative humidity of the inlet gas. Photocatalytic decomposition rate was remarkably increased by 20 % by applying a bias potential of 5 V. The effect of relative humidity exhibited multiple effects for membrane conductivity of Nafion and efficiency of photocatalytic decomposition reaction.