Correction to: Synthesis and characterization of a biopolymer of glycerol and macadamia oil

Journal of Thermal Analysis and Calorimetry - In the original publication of the article, the Figures 6, 7, and 8 are in disagreement with their figure captions. Moreover, in the result...     

Thiopyran route to polypropionates: exploiting and overcoming double stereodifferentiation and mutual kinetic enantioselection in aldol couplings of chiral fragments

The aldol reaction of tetrahydro-4H-thiopyranone with 1,4-dioxa-8-thiaspiro[4.5]decane-6-carboxaldehyde (I) gives four possible diastereomeric adducts (II). Aldol reactions of I with each of the diastereomers of II and their corresponding methoxymethyl ethers III via the Ti enolates were investigated. Using racemic reactants, reactions with II proceeded with high levels of mutual kinetic enantioselection (MKE) and double stereodifferentiation (DS) to give one of the eight possible bisaldol adducts. Similar reactions of III proceeded with low levels of MKE and DS and gave two bisaldol adducts, one from each of the possible combinations of enantiomeric reactants. By extension, 11 of the 20 possible diastereomers of the bisaldol adduct could be obtained selectively. These adducts are useful for polypropionate synthesis.     

Coumarin 314 free radical cation: formation, properties, and reactivity toward phenolic antioxidants

We have explored the photogeneration of the coumarin 314 radical cation by using nanosecond laser excitation at wavelengths longer than 400 nm in benzene, acetonitrile, dichloromethane, and aqueous media. In addition, time-resolved absorption spectroscopy measurements allowed detection of the triplet excited state of coumarin 314 (C(314)) with a maximum absorption at 550 nm in benzene. The triplet excited state has a lifetime of 90 μs in benzene. It is readily quenched by oxygen (k(q) = 5.0 × 10(9) M(-1) s(-1)). From triplet-triplet energy transfer quenching experiments, it is shown that the energy of this triplet excited state is higher than 35 kcal/mol, in accord with the relatively large singlet oxygen quantum yield (Φ(Δ) = 0.25). However, in aqueous media, the coumarin triplet was no longer observed, and instead of that, a long-lived (160 μs in air-equilibrated solutions) free radical cation with a maximum absorbance at 370 nm was detected. The free radical cation generation, which has a quantum yield of 0.2, occurs by electron photoejection. Moreover, density functional theory (DFT) calculations indicate that at least 40% of the electronic density is placed on the nitrogen atom in aqueous media, which explains its lack of reactivity toward oxygen. On the other hand, rate constant values close to the diffusion rate limit in water (>10(9) M(-1) s(-1)) were found for the quenching of the C(314) free radical cation by phenolic antioxidants. The results have been interpreted by an electron-transfer reaction between the phenolic antioxidant and the radical cation where ion pair formation could be involved.     

Rapid determination of ketanserin in serum by synchronous scanning fluorometry combined with derivative spectroscopy

The work reports a rapid method for the determination of ketanserin in serum which employs new fluorescence spectroscopy techniques. The detection limit was 0.006 μg/ml (ppm). The interference effects of other pharmaceutical compounds commonly used in clinical medicine on the determinations of ketanserin were also investigated and the results demonstrate well the enhanced selectivity of the new techniques described.     

地震力冲击下梁桥桥台的非线性动力分析

提出了梁桥岸墩与桥板间预留空隙（变温伸缩用）时桥身与桥台的有限无非线性动力分析模型，给出了模拟墩顶橡胶支承、土压力基底摩擦力及可闭合空隙的特殊非线性单元，从而分析了地震时在桥板冲击作用下整个桥梁上部结构及桥台的非线性动力性能及安全度，并与计算桥台抗剪安全系数的简化能量法所给出的桥台滑移量做了数值对比     

Local diameters of compact planar sets

Given a compact setS?E² andP ₁ εS, we consider sequencesP _i , 1<i<∞, such that $$h_i : = \left\| {P_i - P_{i + 1} } \right\| = \mathop {\max }\limits_{R \in S} \left\| {P_i - R} \right\|$$ . Callh=limh _i a local diameter ofS. It is realized by a line segmentPQS. In relation toD(S), the ordinary diameter ofS, we determine (with and without certain angular constraints) how smallh can be. For example, ifA, B ε S and the line segmentAB is a diameter ofS, we determine best possible lower bounds for ∥P?Q∥/∥A?B∥ in terms of the smallest angle formed by the lines extendingPQ andAB. Local diameters arise from the problem of computing generalized transfinite diameters. Moreover, information about local diameters provides both upper and lower bounds on the isoperimetric quotient ofS.     

Quadrupole-based mass spectrometric evaluation of isotope ratios of carbon dioxide in expired air from mice and men following the administration of 13C-methyl methionine

A method is described for the measurement of the isotopic ratio of ¹³CO₂/¹²CO₂ in expired air from individual mice and from humans by means of a quadrupole-based mass spectrometer system. Following the administration of ¹³C-methyl methionine or another appropriately labeled substrate, the ¹³C portion of the molecule is converted to ¹³CO₂. The ¹³CO₂ enters the carbonate pool(s) and is ultimately eliminated in the expired air where it is available for analysis. The expired air is transported by a small pump from the subject to a digital valve which provides for the alternate influx of expired air and standard into the mass spectrometer for 30 or 60 seconds each, respectively. The inlet consists of a control valve connected to a microbore stainless steel tube, and can be adjusted manually to achieve a source pressure of 4 X 10^?5 torr. The correction factors for drift in sensitivity and in the mass axis are generated by repeated, automatic analysis of the running standard and relating those measurements to values generated for the standard during the first minutes of the experiment. Each measurement of an isotopic ratio in expired air is corrected by an amount determined by the standard immediately preceding it. Precision for the measurements of both sample and standard ratios is ±0.2%. The technique should prove useful in assessing the metabolism, of substrates that are converted to CO₂ and may find utility as a diagnostic tool for certain diseases and metabolic disorders.     

Measurements of the generalized electric and magnetic polarizabilities of the proton at low Q2 using the virtual-compton-scattering reaction

The mean square polarizability radii of the proton have been measured for the first time in a virtual-Compton-scattering experiment performed at the MIT-Bates out-of-plane scattering facility. Response functions and polarizabilities obtained from a dispersion analysis of the data at Q2 = 0.057 GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory. The data support the dominance of mesonic effects in the polarizabilities.     

Tungsten(V) dimeric thio-complexes with dithiocarbamate ligands

The syntheses of four new tungsten(V) dimeric thio-complexes with disulphido bridge are reported. The complexes have been identified by IR and electronic spectra, magnetic susceptibilities and analytical data. On the basis of the physical measurements we propose these complexes the following formula W₂S₄(Rdtc)₂, where dtc = dithiocarbamate and R = morpholine, piperidine, N-ethylaniline and N,N-methylcyclohexyl. The low values of magnetic moments show a WW interaction. IR spectral results support a bidentate ligand behaviour and show a band in the 550-525 cm^?1 region, that we attribute to a W  S bond.