Radical-Initiated Reaction of Methyl Linoleate with Dialkyl Phosphites

The addition of dialkyl phosphite (methyl, ethyl and n‐butyl) to methyl linoleate (MeLin) double bonds was investigated. The reaction proved to be more challenging than the analogous reaction with methyl oleate (MeOl), due to inhibition of the radical reaction by the bis‐allylic hydrogens of MeLin and the lower reactivity of MeLin double bonds. However, we demonstrated that this self‐inhibition problem can be solved by simply keeping the MeLin reagent at low concentrations, while keeping the dialkyl phosphite at high concentrations. For optimization of the reaction, four different radical initiators were investigated: dilauroyl peroxide (LP), 2,2′‐azobis(2‐methylpropionitrile) (AIBN), tert‐butyl perbenzoate (t‐BP), and tert‐butyl peroxide (TOOT). The initiators were used at temperatures that provided a half‐life of 10 h: 64, 64, 104, and 125 °C respectively for LP, AIBN, t‐BP, and TOOT. The tests showed the reaction to be faster at higher temperatures, but transesterification of the ester groups was also observed at elevated temperatures. t‐BP was chosen as an optimal initiator for carrying the reaction. The apparent order of reactivity of the dimethyl, diethyl and di‐n‐butyl phosphites (Me >Et >n‐Bu) towards MeLin was due to differences in their molar volumes. When the concentrations of dialkyl phosphite were kept the same, the order reversed (n‐Bu > Et~Me). GC–MS spectra of the resulting phosphonates are reported and the main fragments assigned.     

Synthesis and Characterization of Phosphonates from Methyl Linoleate and Vegetable Oils

Phosphonates were synthesized on a medium scale (~200 g) from three lipids—methyl linoleate (MeLin), high‐oleic sunflower oil (HOSO) and soybean oil (SBO), and three dialkyl phosphites—methyl, ethyl and n‐butyl, using a radical initiator. A staged addition of the lipid and the initiator was used to achieve good yields. Good results were observed with MeLin (94–99% conversions of the double bonds, as determined by NMR, and 83–99% isolated yields) and HOSO (99–100% NMR conversions, 87–96% isolated yields) using tert‐butyl perbenzoate as the initiator. With SBO, benzoyl peroxide was used as the initiator, due to its capability to generate radicals at a higher rate at slightly lower temperatures, and thus to shorten the reaction time. Conversions of 91–93% (by NMR) and isolated yields of 80–94% were achieved. The progress of the reaction was monitored with GC–MS. The products were characterized using ¹H, ¹³C and ³¹P NMR, IR and gel permeation chromatography. A prolonged reaction led to some transesterification between the carboxylic and phosphite ester groups. Conditions favoring higher reaction rates led to the formation of more oligomers and benzoate fatty ester byproducts. The benzoate fatty ester byproducts were formed by the attack of a benzoate radical on a double bond. The more double bonds that were present per lipid molecule, the more oligomers were formed: MeLin 2–8%, HOSO 3–9% and SBO 8–29%.     

Extraction modeling and activities of antioxidants from pomegranate marc

To develop value-added antioxidants from the peel and seeds of pomegranate marc, a by-product after pomegranate juice processing, the effects of drying before extraction and processing parameters on the extraction kinetics and product properties were systematically studied using water as an environmental friendly solvent for the extraction. The results showed that the drying process did not significantly affect the yield, content, and activity of antioxidants from either the peel or seeds. The antioxidants extracted from the peel had higher yield and content than those from the seeds. The yield and content of antioxidants increased with reduced particle size and increased water/sample ratio and temperature, but antioxidant activity was low when extraction temperature was high. By considering the antioxidant activity and operation cost, the recommended extraction conditions were peel particle size of 0.2 mm, water/peel ratio of 50/1 (w/w), temperature of 25 °C, and extraction time of 2 min, which gave the high antioxidant yield (11.5%) and content (22.9%), and DPPH scavenging activity of 6.2 g/g. Kinetic models were successfully developed for describing the extraction processes with different processing parameters.     

Enhanced Sintering of Yttrium-Doped Barium Zirconate by Addition of ZnO

The influence of transition metal oxides additives, especially zinc oxide, on the densification and electrical properties of doped barium zirconate have been examined. With the use of zinc oxide as a sintering aid, BaZr_0.85Y_0.15O_3–δ was readily sintered to above 93% of theoretical density at 1300°C. Scanning electron microscopic investigations showed Zn accumulation in the intergranular regions. Thermogravimetric analysis of the material under flowing CO₂ showed ZnO-modified barium zirconate to exhibit excellent chemical stability. The conductivity, as measured by A.C. impedance spectroscopy under H₂O saturated nitrogen, was slightly lower than that of unmodified barium zirconate. Electromotive force measurements under fuel cell conditions revealed the total ionic transport number to be ∼0.9 at 600°C. The combination of electrical and chemical properties and good sinterability render ZnO-modified barium zirconate an excellent candidate for reduced temperature solid oxide fuel cell applications.     

Structural analysis of value creation in software service platforms

As software service platforms grow in number of users and variety of service offerings, it raises the question of how this phenomenon impacts the value obtained by users. This paper identifies system usability, service variety, and personal connectivity to be the major determinants that contribute to the value offered to users on mobile software service platforms. A structural equation model, which is based on utility theory, technology acceptance theory, and the theory of network externalities, has been constructed from seven observed constructs, reflecting the three determinants and the user value. The lower bound of user value is estimated through the user’s willingness-to-pay for services and the user’s willingness to spend time on using services. For the validation, a co-variance-based structural equation analysis has been conducted on online survey data of 210 users of mobile service platforms (e.g., Android, iOS). The results show that the number of services used and the number of active user connections were found to be the strongest constructs explaining user value. Perceived usefulness did not explain user value as much. In total, they can explain 49 % of the value that the user receives from the platform. The implication of this result is that users’ value from a software service platform cannot be explained by the technology acceptance model itself. Instead, an approach that, as used in this research, of integrating network externality theory, utility theory, and technology acceptance theory is necessary.     

Platelet aggregation induced by a monoclonal antibody to the A1 domain of von Willebrand factor

Shear-induced platelet aggregation (SIPA) involves von Willebrand Factor (vWF) binding to platelet glycoprotein (GP)Ib at high shear stress, followed by the activation of alphaIIb beta3. The purpose of this study was to determine the vWF sequences involved in SIPA by using monoclonal antibodies (MoAbs) to vWF known to interfere with its binding to GPIb and to alphaIIb beta3. Washed platelets were exposed to shear rates between 100 and 4,000 seconds-1 in a rotational viscometer. SIPA was quantitated by flow cytometry as the disappearance of single platelets (DSP) in the sheared sample in the presence of vWF, relative to a control in the absence of shear and vWF. At a shear rate of 4,000 seconds-1, DSP was increased from 5.9% +/- 3.5% in the absence of vWF to 32.7% +/- 6.3% in the presence of vWF. This increase in SIPA was not associated with an elevation of P-selectin expression. vWF-dependent SIPA was completely abolished by MoAb 6D1 to GPIb and partially inhibited by MoAb 10E5 to alphaIIb beta3. Three MoAbs to vWF were compared for their effect on SIPA at 4,000 seconds-1 in the presence of vWF: MoAb 328, known to block vWF binding to GPIb in the presence of ristocetin, MoAb 724 blocking vWF binding to GPIb in the presence of botrocetin, and MoAb 9, an inhibitor of vWF binding to alphaIIbbeta3. Similar to the effect of MoAb 6D1, MoAb 328 completely inhibited the effect of vWF, whereas MoAb 9 had a partial inhibitory effect, as MoAb 10E5 did. In contrast, MoAb 724, as well as its F(ab')2 fragments, promoted shear-dependent platelet aggregation (165% of the DSP value obtained in the absence of MoAb 724), indicating that MoAb 724 was responsible for an enhanced aggregation, which was independent of binding to the platelet Fcgamma receptor. In addition, the enhancement of aggregation induced by MoAb 724 was abrogated by MoAb 6D1 or 10E5 to the level of SIPA obtained in the presence of vWF incubated with a control MoAb to vWF. Finally, the activating effect of MoAb 724 was also found under static conditions at ristocetin concentrations too low to induce platelet aggregation. Our results suggested that on binding to a botrocetin-binding site on vWF, MoAb 724 mimics the effect of botrocetin by inducing an active conformation of vWF that is more sensitive to shear stress or to low ristocetin concentration.     

电池托架有限元分析与轻量化研究

以8 t平台纯电底盘电池托架为研究对象,基于有限元分析,对其强度性能进行了评估,研究了使用高强钢和结构优化等轻量化方法.结果表明:该轻量化方法实现了降重54 kg,经过强度评估后满足设计要求,为纯电底盘的轻量化设计提供了一条可行的途径.     

Black-box modeling of passive systems by rational function approximation

In this paper, a rational interpolation approach is used to approximate the transfer function of passive systems characterized by sampled data. Orthogonal polynomials are used to improve the numerical stability of the ill-conditioned Vandermonde-like interpolation matrix associated with the ordinary power series. First, the poles of the system are obtained by efficiently and accurately transforming the coefficients of the orthogonal polynomials to the ordinary power series using Clenshaw's recurrence algorithm. Then, the residues are solved in real or in complex conjugate pairs to insure a physically realizable system. Finally, the passivity of the system is enforced by applying certain constraints on the poles and residues of the system. The performances of the three most common orthogonal polynomials, Legendre and Chebyshev of the first and second kinds, are also compared to that of the power series.     

Strain differences in maintenance of cocaine self-administration and their relationship to novelty activity responses.

The authors previously demonstrated that Fischer 344 (F344) and Lewis inbred rats differ in acquisition of cocaine self-administration. Other studies show that acquisition and maintenance of drug self-administration are predicted by locomotor activity in a novel environment among outbred Sprague-Dawley rats. The present study was designed to determine whether this relationship extended to F344 and Lewis rats. In Experiment 1, F344, Lewis, and Sprague-Dawley rats were trained to self-administer cocaine and tested with several doses under fixed- and progressive-ratio schedules of reinforcement. Self-administered infusions and ineffective active lever presses--those emitted during infusion and time-out periods--were assessed. In Experiment 2, separate sets of rats of each strain were examined for locomotor responses (distance traveled and center time) under novelty conditions. Results show that F344 rats self-administer more cocaine than Lewis or Sprague-Dawley rats under both schedules and emit more ineffective lever presses--a possible measure of craving. Strain comparisons of locomotor responses suggest that center time, not activity, relates to self-administration behavior. Maintenance studies of cocaine self-administration rather than acquisition may better reflect vulnerability to addiction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)