Stereochemistry of the aza-Michael reaction with natural alantolactones

Hydrogenated 3-aminomethylnaphtho[2,3-b]furan-2-ones were synthesized by the reaction of natural alantolactones with pharmacophoric amines. Determination of the newly formed asymmetric center configuration by two-dimensional NMR data is presented. The structure of the obtained compounds was proved by X-ray structural analysis.     

Characterization of structure and dynamics of an aqueous scandium(iii) ion by an extended ab initio QM/MM molecular dynamics simulation

Hydration structure and dynamics of an aqueous Sc(iii) solution were characterized by means of an extended ab initio quantum mechanical/molecular dynamical (QM/MM) molecular dynamics simulation at Hartree-Fock level. A monocapped trigonal prismatic structure composed of seven water molecules surrounding scandium(iii) ion was proposed by the QM/MM simulation including the quantum mechanical effects for the first and second hydration shells. The mean Sc(iii)-O bond length of 2.14 ? was identified for six prism water molecules with one capping water located at around 2.26 ?, reproducing well the X-ray diffraction data. The Sc(iii)-O stretching frequency of 432 cm(-1) corresponding to a force constant of 130 N m(-1), evaluated from the enlarged QM/MM simulation, is in good agreement with the experimentally determined value of 430 cm(-1) (128 N m(-1)). Various water exchange processes in the second hydration shell of the hydrated Sc(iii) ion predict a mean ligand residence time of 7.3 ps.     

Theoretical study of the properties of adsorbed oxygen complexes on a Si(100) surface

The results from quantum-chemical calculations of the properties of adsorbed oxygen complexes on a Si(100) surface are presented. Semi-empirical MNDO quantum-chemical modeling, implemented in the MOPAC software package, is used to model the physicochemical properties and estimate the energy parameters. The dependences of the total energy of the silicon cluster-oxygen system are calculated in dependence on the location of oxygen in the Si(100) surface layer, and the geometrical and electron characteristics of the equilibrium states of a cluster with adsorbed oxygen.     

Experimental determination of the electron screening potential energy for the d(d, n)3He Reaction in ZrD2 and D2O in the ultralow energy region

This work is devoted to measuring of the values of the astrophysical S-factors and electron screening potential energy for a d(d,n)³He reaction occurring at ultralow energies in zirconium deuteride ZrD₂ (3.5–7.0 keV) and heavy water D₂O (2.2–6.0 keV). The experiment was performed on the Hall pulsed plasma accelerator at the TPU Nuclear Physics Institute (Tomsk) with ZrD₂ and D₂O targets produced by the magnetron sputtering of zirconium in a deuterium environment and heavy water freezing-out on a copper support, respectively. A χ ² analysis of the dependence of the neutron yields and astrophysical S-factors for the dd reaction on the deuteron collision energy E revealed that the upper bounds of the electron screening potential energy for interacting deuterons in ZrD₂ and D₂O and of the astrophysical S-factors at the deuteron collision energy E = 0 were U _e (ZrD₂) < 30 eV, U _e (D₂O) < 25 eV, S(0) = (57.2 ± 3.9) keV · b (ZrD₂), S(0) = (58.6 ± 3.6) keV · b (D₂O) at the 90% confidence level.     

Dosimetric evaluation of alanine-in-glass dosimeters at clinical dose levels using high-energy X-rays from a linear accelerator

This study presents the first dosimetric evaluation of the alanine-in-glass dosimeter in radiation therapy. The dosimeter is composed of a Pyrex glass tube filled with pure polycrystalline alanine. 6 MV X-ray beams from a linear accelerator were used to irradiate the dosimeter in a solid water phantom to therapy-level doses ranging from 0 to 30 Gy. An X-band electron paramagnetic resonance (EPR) spectrometer was utilized to measure the absorbed dose of the dosimeter. The doses measured by the dosimeter were compared to those from ion chamber dosimetry. It was found that the dosimeter exhibited a linear response in the dose range from 0.1 to 30 Gy. The deviation between measured and delivered doses was 0.11% over the 0.5–30 Gy range, whereas the deviation increased to about 25% at 0.1 Gy. The lowest detectable dose with an acceptable deviation limit of 5% or less was found to be 0.3 Gy. The inaccuracy in measurements at low doses can be attributed to background signals and instrument noise. The accuracy can be improved by proper selection of measurement conditions and better optimization of equipment. The findings of this study show that the alanine-in-glass dosimeter is suitable for dose measurements with acceptable accuracy down to 0.3 Gy. The dosimeter is therefore has the potential to be employed in radiotherapy applications and quality control procedures.     

Use of Sodium Borohydride in Electrodeposition of Nickel-Boron Coatings

Russian Journal of Applied Chemistry - Possibility was found of using the sodium borohydride additive in technologies for electrodeposition of nickel-boron coatings with various compositions and...     

环硅氧烷负离子乳液聚合中活性中心浓度的变化规律

以八甲基环四硅氧烷(D4)为单体,十二烷基二甲基苄基氢氧化铵(BDAH)为乳化剂兼催化剂,进行环硅氧烷负离子乳液聚合,采用凝胶色谱(GPC)测定聚合产物的转化率及分子量.在此基础上,分析基元反应,提出活性中心生成机理,并应用环硅氧烷开环聚合普适动力学模型计算乳液聚合平衡之前的活性中心浓度变化规律.结果发现,聚合温度较低时,活性中心浓度随时间逐渐增加,最终恒定;聚合温度较高时,活性中心浓度随时间仅单调递增.结果与机理相符.     

Microfluidic Nanomaterial Synthesis and In Situ SAXS,WAXS, or SANS Characterization: Manipulation of Size Characteristics and Online Elucidation of Dynamic Structural Transitions

With the ability to cross biological barriers, encapsulate and efficiently deliver drugs and nucleic acid therapeutics, and protect the loaded cargos from degradation, different soft polymer and lipid nanoparticles (including liposomes, cubosomes, and hexosomes) have received considerable interest in the last three decades as versatile platforms for drug delivery applications and for the design of vaccines. Hard nanocrystals (including gold nanoparticles and quantum dots) are also attractive for use in various biomedical applications. Here, microfluidics provides unique opportunities for the continuous synthesis of these hard and soft nanomaterials with controllable shapes and sizes, and their in situ characterization through manipulation of the flow conditions and coupling to synchrotron small-angle X-ray (SAXS), wide-angle scattering (WAXS), or neutron (SANS) scattering techniques, respectively. Two-dimensional (2D) and three-dimensional (3D) microfluidic devices are attractive not only for the continuous production of monodispersed nanomaterials, but also for improving our understanding of the involved nucleation and growth mechanisms during the formation of hard nanocrystals under confined geometry conditions. They allow further gaining insight into the involved dynamic structural transitions, mechanisms, and kinetics during the generation of self-assembled nanostructures (including drug nanocarriers) at different reaction times (ranging from fractions of seconds to minutes). This review provides an overview of recently developed 2D and 3D microfluidic platforms for the continuous production of nanomaterials, and their simultaneous use in in situ characterization investigations through coupling to nanostructural characterization techniques (e.g., SAXS, WAXS, and SANS).     

Passive Adsorbers Based on Carbon Materials and Their Comparison for Estimating the Oil and Gas Potentials of Rocks

Journal of Analytical Chemistry - Adsorbents used to analyze air for concentrations of various organic compounds with their subsequent determination by thermal desorption gas...     

Production of Magnetic Carbon Materials during Decomposition of Iron Salts Deposited on a Porous Carbon Matrix

Russian Journal of Applied Chemistry - A method is proposed for producing a magnetic carbon material based on the deposition of a labile iron compound on a carbon matrix and its subsequent...