Studies of tocopherol dimers from soybean oil by reaction gas chromatography

Reaction gas chromatography was found to be helpful in elucidating structures of tocopherol dimers. By this method γ- and δ-tocopherols were determined as monomers derived from tocopherol dimers, after isolation of the latter compounds from soybean oil. It was shown that gas chromatographic determination of tocopherols, as performed by injection of total unsaponifiables from soybean oil, will give results too high; the eluted tocopherols will account for both tocopherol monomers and dimers.     

Conjunctive grammars and alternating pushdown automata

In this paper we introduce a variant of alternating pushdown automata, synchronized alternating pushdown automata, which accept the same class of languages as those generated by conjunctive grammars.     

Digital collaborative learning in elementary and middle schools as a function of individualistic and collectivistic culture: The role of ICT coordinators' leadership experience,students' collaboration skills,and sustainability

The purpose of this study was to examine the influence of online collaborative learning experiences on students' digital collaboration skills and on the sustainability of e-collaboration in schools' culture—comparing individualistic versus collectivistic cultures. In addition, we explored how the leadership experience of schools' ICT coordinators was predicted by their sense of professionalism and cognitive, emotional and social aspects of perceived learning (PL), while leading the collaborative projects. The participants were ICT coordinators from 513 Israeli schools; 214 of whom were Hebrew-speakers, and 299 Arabic-speakers. The participants were asked to complete an online questionnaire, which included multiple-choice and open-ended questions. The results showed significant differences between a variety of the coordinator-related variables as a function of learning culture (more individualistic vs.more collectivistic). Coordinators' leadership experience was a powerful predictor of students' digital collaboration skills, but did not predict the sustainability of e-collaboration. Coordinators' emotional PL predicted the sustainability of collaboration in both schools with more individualistic and with more collectivistic learning cultures. The implications of the findings for educational theory and practise are discussed.     

CIBJO机构向会员传授珠宝营销知识

国际珠宝联盟(CIBJO)大会将于2007年3月12-15日在南非的开普敦举行。其间,CIBJO的市场与教育机构将开展一系列培训活动,向珠宝商们传授一些有效的珠宝营销手段以面对日益激烈的市场竞争。现在的消费者比以往更具辨识能力与知识以及具有更多的需求,而其它奢侈品牌的快速崛起也明     

Should I stay or should I switch? A cost–benefit analysis of voluntary language switching in young and aging bilinguals.

Bilinguals spontaneously switch languages in conversation even though laboratory studies reveal robust cued language switching costs. The authors investigated how voluntary-switching costs might differ when switches are voluntary. Younger (Experiments 1–2) and older (Experiment 3) Spanish–English bilinguals named pictures in 3 conditions: (a) dominant-language only, (b) nondominant-language only, and (c) using “whatever language comes to mind” (in Experiment 2, “using each language about half the time”). Most bilinguals, particularly balanced bilinguals, voluntarily mixed languages even though switching was costly. Unlike with cued switching, voluntary switching sometimes facilitated responses, switch costs were not greater for the dominant language, and age effects on language mixing and switching were limited. This suggests that the freedom to mix languages voluntarily allows unbalanced and older bilinguals to function more like balanced and younger bilinguals. Voluntary switch costs reveal an expanded role for inhibitory control in bilingual language production and imply a mandatory separation by language in bilingual lexical selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A New Low Temperature Device for High Resolution, In Situ Measurement and Control of Submicron Gaps

We have developed a device to investigate finite-size scaling of the thermal expansion coefficient in liquid helium near the lambda transition. Motivated by the need for a range of well known, uniform, sub-micron gaps with constant surface conditions, we have built a variable-gap parallel-plate capacitor that can be adjusted in situ. We measure the gap at three points using laser interferometry. A careful choice of the material and thickness of the reflecting surfaces results in asymmetric fringes, for which both exceptional sensitivity and a high contrast ratio can be achieved simultaneously. Both the gap size and its uniformity are actively controlled using voice coil actuators. This design has a number of additional benefits: the gap can be kept closed until low temperature use, data can be collected for all gaps with no thermal cycling, and no spacers are needed to establish the gap.     

Effects of a supportive or an unsupportive audience on biological and psychological responses to stress.

Although social support is related to substantial benefits for health and well-being, research has uncovered qualifications to its benefits. In a test of the psychological and biological impact of an audience on responses to laboratory stress challenges, 183 participants going through the Trier Social Stress Test experienced either (a) an unsupportive audience, (b) a supportive audience, or (c) no audience. Both audience conditions produced significantly stronger cortisol, heart rate, and blood pressure responses to the stress tasks, relative to the no-audience control, even though the supportive audience was rated as supportive. Contrary to hypotheses offered by several theories, these effects were not moderated by self-esteem, individual differences in psychological resources, or baseline social support. Psychological resources and baseline social support were, however, tied to more beneficial biological and psychological profiles at baseline and at recovery in some cases. It was concluded that when one must perform stressful tasks in front of an audience, evaluative concerns may outweigh the potential benefits of a supportive audience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactivity of substituted benzotrichlorides toward granular iron, Cr(II), and an iron(II) porphyrin: A correlation analysis

Cross-correlations of rate constants between a system of interest and a better-defined one have become popular as a tool in studying transformations of organic pollutants. A slope of unity (if the correlation is conducted on a log-log basis) in such plots has been invoked as evidence of a common mechanism. To explore this notion, benzotrichloride and several of its substituted analogues were reacted with Cr(H2O)6(2+), an iron(II) porphyrin (iron meso-tetra(4-carboxyphenyl)porphine chloride, Fe(II)TCP), and granular iron. The first two reductants react with organohalides by dissociative inner sphere single-electron transfer, while mechanism(s) for organohalide reduction by granular iron are still debated. Apartfrom sterically hindered compounds, good correlations were obtained in comparing any two systems, although slopes (on a log-log basis) deviated from unity. We argue that a slope of unity is neither necessary nor sufficient evidence of a common mechanism. Overall rate constants may be composite entities, consisting in part of rate or equilibrium constants for adsorption onto surfaces or for precursor formation in solution; these components may differ between systems in their susceptibility to substituent effects. Cross-correlations may prove useful in predicting reactivity in the absence of steric effects, but additional evidence is required in deducing reaction mechanisms.     

Green tea catechins as brain-permeable, natural iron chelators-antioxidants for the treatment of neurodegenerative disorders

Neurodegeneration in Parkinson's, Alzheimer's, or other neurodegenerative diseases appears to be multifactorial, where a complex set of toxic reactions, including oxidative stress (OS), inflammation, reduced expression of trophic factors, and accumulation of protein aggregates, lead to the demise of neurons. One of the prominent pathological features is the abnormal accumulation of iron on top of the dying neurons and in the surrounding microglia. The capacity of free iron to enhance and promote the generation of toxic reactive oxygen radicals has been discussed numerous times. The observations that iron induces aggregation of inert alpha-synuclein and beta-amyloid peptides to toxic aggregates have reinforced the critical role of iron in OS-induced pathogenesis of neurodegeneration, supporting the notion that a combination of iron chelation and antioxidant therapy may be one significant approach for neuroprotection. Tea flavonoids (catechins) have been reported to possess divalent metal chelating, antioxidant, and anti-inflammatory activities, to penetrate the brain barrier and to protect neuronal death in a wide array of cellular and animal models of neurological diseases. This review aims to shed light on the multipharmacological neuroprotective activities of green tea catechins with special emphasis on their brain-permeable, nontoxic, transitional metal (iron and copper)-chelatable/radical scavenger properties.     

Albumin Nanoshell Encapsulation of Near‐Infrared‐Excitable Rare‐Earth Nanoparticles Enhances Biocompatibility and Enables Targeted Cell Imaging

The use of traditional fluorophores for in vivo imaging applications is limited by poor quantum yield, poor tissue penetration of the excitation light, and excessive tissue autofluorescence, while the use of inorganic fluorescent particles that offer a high quantum yield is frequently limited due to particle toxicity. Rare‐earth‐doped nanoparticles that utilize near‐infrared upconversion overcome the optical limitations of traditional fluorophores, but are not typically suitable for biological application due to their insolubility in aqueous solution, lack of functional surface groups for conjugation of biomolecules, and potential cytotoxicity. A new approach to establish highly biocompatible and biologically targetable nanoshell complexes of luminescent rare‐earth‐doped NaYF₄ nanoparticles (REs) excitable with 920–980 nm near‐infrared light for biomedical imaging applications is reported. The approach involves the encapsulation of NaYF₄ nanoparticles doped with Yb and Er within human serum albumin nanoshells to create water‐dispersible, biologically functionalizable composite particles. These particles exhibit narrow size distributions around 200 nm and are stable in aqueous solution for over 4 weeks. The albumin shell confers cytoprotection and significantly enhances the biocompatibility of REs even at concentrations above 200 µg REs mL^?1. Composite particles conjugated with cyclic arginine‐glycine‐aspartic acid (cRGD) specifically target both human glioblastoma cell lines and melanoma cells expressing α_vβ₃ integrin receptors. These findings highlight the promise of albumin‐encapsulated rare‐earth nanoparticles for imaging cancer cells in vitro and the potential for targeted imaging of disease sites in vivo.