Determination of traces of Zn, Cd, Pb and Cu in white sugar by anodic stripping voltammetry and a modified oxygen-flask combustion technique

Anodic stripping voltammetry with a hanging-drop mercury electrode is used for determination of traces of Zn, Cd, Pb and Cu in white sugar. The sample (1.5 g) is decomposed by ignition in oxygen in a specially modified system.     

The ( n,d )-Krull Property over Domains Arising from Pullbacks

In this work we investigate the transfer of the (n,d)-Krull property between domains arising from pullbacks. As an application, we construct a new class of non-coherent domains which are (0,d)-Krull domains, not (0,d ? 1)-Krull domains, and where the Krull dimension equals d + 1.     

Synthesis of new spiro‐[isothiochromene‐3,5′‐isoxazolidin]‐4(1H)‐ones

A series of seven new 2′,3′,4′‐substituted spiro[isothiochromene‐3,5′‐isoxazolidin]‐4(1H)‐ones ( 7‐13 ) has been prepared in the reaction of benzylidene(phenyl)azane oxide ( 5 ) or benzylidene(methyl)azane oxide ( 6 ) with (3Z)‐3‐(4‐substituted‐benzylidene)‐1H‐isothio‐ chromen‐4(3H)‐one ( 1‐4 ). The reaction occurs by a 1,3‐dipolar cycloaddition mechanism that leads to the regiospecific formation of various spiroisoxazolidines ( 7‐13 ).     

Novel Copolymers of Styrene. 11. Ring-Substituted 2-Cyano-3-phenyl-2-propenamides

Novel electrophilic trisubstituted ethylene monomers, halo ring-disubstituted 2-cyano-3-phenyl-2-propenamides, RPhCH = C(CN)CONH₂, where R is 2,3-difluoro, 2,4-difluoro, 2,5-difluoro, 2,6-difluoro, 3,4-difluoro, 3,5-difluoro, 2-chloro-4-fluoro, 3-chloro-2-fluoro, 3-chloro-4-fluoro were prepared and copolymerized with styrene. The monomers were synthesized by potassium hydroxide catalyzed Knoevenagel condensation of ring-substituted benzaldehydes and cyanoacetamide, and characterized by CHN elemental analysis, IR, ¹H- and ¹³C-NMR. Novel copolymers of the ethylenes and styrene were prepared at equimolar monomer feed composition by solution copolymerization in the presence of a radical initiator, ABCN at 70°C. The composition of the copolymers was calculated from nitrogen analysis, and the structures were analyzed by IR, ¹H- and ¹³C-NMR, GPC, DSC, and TGA. High T_g of the copolymers in comparison with that of polystyrene indicates a substantial decrease in chain mobility of the copolymer due to the high dipolar character of the trisubstituted ethylene monomer unit. Decomposition of the copolymers in nitrogen occurred in two steps, first in the 200–500°C range with residue (10–14 wt%), which then decomposed in the 500–800°C range.     

High-resolution infrared and millimeterwave spectra of the v3=1 vibrational state of NF3 at 907 cm

The ν₃^±1 perpendicular band of ¹⁴NF₃ ( cm⁻¹) has been studied with a resolution of 2.5 × 10⁻³ cm⁻¹, and 3682 infrared (IR) transitions (J_max=55, K_max=45) have been assigned. These transitions were complemented by 183 millimeterwave (MMW) rotational lines (J_max=25, K_max=19) in the 150–550 GHz region (precision 50–100 kHz). The kl=+1 level reveals a strong A₁/A₂ splitting due to the l(2,2) rotational interaction (q=−4.05 × 10⁻³ cm⁻¹) while the kl=−2 and +4 levels exhibit small A₁/A₂ splittings due to l(2,−4) and l(0,6) rotational interactions. All these splittings were observed by both experimental methods. Assuming the v₃=1 vibrational state as isolated, a Hamiltonian model of interactions in the D reduction, with l(2,−1) rotational interaction (r=−1.96 × 10⁻⁴ cm⁻¹) added, accounted for the observations. A set of 26 molecular constants reproduced the IR observations with σ_IR=0.175 × 10⁻³ cm⁻¹ and the MMW data with σ_MMW=134 kHz. The Q reduction was also performed and found of comparable quality while the QD reduction behaved poorly. This may be explained by a predicted Coriolis interaction between v₃=1 and v₁=1 (A₁, 1032.001 cm⁻¹) which induces a slow convergence of the Hamiltonian in the QD reduction but has no major influence on the other reductions. The experimental equilibrium structure could be calculated as: r_e(N–F)=1.3676 Å and (FNF)=101.84°.     

A new formulation and error analysis for vibrating dam-reservoir systems with upstream transmitting boundary conditions

This paper proposes and validates a new formulation to investigate the dynamic response of dam-reservoir systems with upstream transmitting boundary conditions (TBCs). The mathematical derivations are provided for the new formulation as well as for exact and various approximate TBCs. The developed analytical equations can be solved numerically to assess the accuracy of a given TBC and determine the associated error independently of FEM or BEM modeling of the reservoir. The method is first validated in the case of semi-infinite reservoirs and an excellent agreement is obtained against classical techniques. The paper presents a fundamental understanding of the behavior of various TBCs and a systematic identification of their influence on the system's dynamic response, considering: (i) dam flexibility, (ii) water compressibility, (iii) reservoir bottom wave absorption, (iv) reservoir truncation length, and (v) excitation frequency. The new method is used to obtain exact error estimators to evaluate the effects of various TBCs on the dam-reservoir first resonant frequency and hydrodynamic forces acting on the dam upstream face. The proposed formulation can be programmed easily and used efficiently for rigorous assessment of classical or newly developed TBCs for vibrating dam-reservoir systems or similar fluid-structure problems.