4,127 research outputs found
Dehydrative etherification reactions of glycerol with alcohols catalyzed by recyclable nanoporous aluminosilicates: telescoped routes to glyceryl ethers
Catalytic
strategies for the efficient transformation of abundant
sustainable bioderived molecules, such as glycerol, into higher value
more useful products is an important research goal. In this study,
we demonstrate that atom efficient dehydrative etherification reactions
of glycerol with activated alcohols are effectively catalyzed by nanoporous
aluminosilicate materials in dimethylcarbonate (DMC) to produce the
corresponding 1-substituted glyceryl ethers in high yield. By carrying
out the reaction in acetone, it is possible to capitalize on the ability
of these materials to catalyze the corresponding acetalization reaction,
allowing for the development of novel, telescoped acetalization-dehydrative
etherification reaction sequences to selectively produce protected
solketal derivatives. These materials also catalyze the telescoped
reaction of glycerol with <i>tert</i>-butanol (TBA) in acetone
to produce the corresponding solketal mono <i>tert</i>-butyl
ether product in high yield, providing a potential route to convert
glycerol directly into a useful and sustainable fuel additive
A new criteria for zero quantum discord
We propose a new criterion to judge zero quantum discord for arbitrary
bipartite states. A bipartite quantum state has zero quantum discord if and
only if all blocks of its density matrix are normal matrices and commute with
each other. Given a bipartite state with zero quantum discord, how to find out
the set of local projectors, which do not disturb the whole state after being
imposed on one subsystem, is also presented. A class of two-qubit X-state is
used to test the criterion, and an experimental scheme is proposed to realize
it. Consequently, we prove that the positive operator-valued measurement can
not extinguish the quantum correlation of a bipartite state with nonzero
quantum discord.Comment: 10 pages, 1 figur
Preparation of Biomass-Derived Furfuryl Acetals by Transacetalization Reactions Catalyzed by Nanoporous Aluminosilicates
Nanoporous aluminosilicate materials efficiently catalyze the formation of furaldehyde dimethyl acetal directly from methanol in high yields and in short reaction times. The facile nature of this reaction has led to the development of a telescoped protocol in which the acyclic acetal is produced in situ and subsequently functions as a substrate for a transacetalization reaction with glycerol to produce the corresponding dioxane and dioxolane products, which are potentially useful biofuel additives. These products are generated in high yield without the requirement for high reaction temperatures of prolonged reaction times, and the aluminosilicate catalysts are operationally simple to produce, are effective with either purified furaldehyde or crude furaldehyde, and are fully recyclable
Psychometric Properties of the Young Children's Participation and Environment Measure
AbstractObjectiveTo evaluate the psychometric properties of the newly developed Young Children's Participation and Environment Measure (YC-PEM).DesignCross-sectional study.SettingData were collected online and by telephone.ParticipantsConvenience and snowball sampling methods were used to survey caregivers of children (N=395, comprising children with [n=93] and without [n=302] developmental disabilities and delays) between the ages of 0 and 5 years (mean age ± SD, 35.33±20.29mo) and residing in North America.InterventionsNot applicable.Main Outcome MeasuresThe YC-PEM includes 3 participation scales and 1 environment scale. Each scale is assessed across 3 settings: home, daycare/preschool, and community. Data were analyzed to derive estimates of internal consistency, test-retest reliability, and construct validity.ResultsInternal consistency ranged from .68 to .96 and .92 to .96 for the participation and environment scales, respectively. Test-retest reliability (2–4wk) ranged from .31 to .93 for participation scales and from .91 to .94 for the environment scale. One of 3 participation scales and the environment scale demonstrated significant group differences by disability status across all 3 settings, and all 4 scales discriminated between disability groups for the daycare/preschool setting. The participation scales exhibited small to moderate positive associations with functional performance scores.ConclusionsResults lend initial support for the use of the YC-PEM in research to assess the participation of young children with disabilities and delays in terms of (1) home, daycare/preschool, and community participation patterns; (2) perceived environmental supports and barriers to participation; and (3) activity-specific parent strategies to promote participation
Nanoporous aluminosilicate catalyzed Friedel–Crafts alkylation reactions of indoles with aldehydes and acetals
Nanoporous aluminosilicate materials efficiently catalyze Friedel-Crafts reactions of indoles to produce bisindolylalkane products. These reactions proceed rapidly and in high yields when acetals are used in place of the more commonly used carbonyl reagents. It is possible to capitalise on the large difference in the rates of reaction observed with aldehydes and acetals to develop a tandem acetalization-Friedel-Crafts protocol in which the acetal is generated in situ and undergoes subsequent reaction. © 2011 The Royal Society of Chemistry
Development of bone marrow lesions is associated with adverse effects on knee cartilage while resolution is associated with improvement - a potential target for prevention of knee osteoarthritis: a longitudinal study
INTRODUCTION: To examine the relationship between development or resolution of bone marrow lesions (BMLs) and knee cartilage properties in a 2 year prospective study of asymptomatic middle-aged adults. METHODS: 271 adults recruited from the Melbourne Collaborative Cohort Study, underwent a magnetic resonance imaging scan (MRI) of their dominant knee at baseline and again approximately 2 years later. Cartilage volume, cartilage defects and BMLs were determined at both time points. RESULTS: Among 234 subjects free of BMLs at baseline, 33 developed BMLs over 2 years. The incidence of BMLs was associated with progression of tibiofemoral cartilage defects (OR 2.63 (95% CI 0.93, 7.44), P = 0.07 for medial compartment; OR 3.13 (95% CI 1.01, 9.68), P = 0.048 for lateral compartment). Among 37 subjects with BMLs at baseline, 17 resolved. Resolution of BMLs was associated with reduced annual loss of medial tibial cartilage volume (regression coefficient -35.9 (95%CI -65, -6.82), P = 0.02) and a trend for reduced progression of medial tibiofemoral cartilage defects (OR 0.2 (95% CI 0.04, 1.09), P = 0.06). CONCLUSIONS: In this cohort study of asymptomatic middle-aged adults the development of new BMLs was associated with progressive knee cartilage pathology while resolution of BMLs prevalent at baseline was associated with reduced progression of cartilage pathology. Further work examining the relationship between changes and BML and cartilage may provide another important target for the prevention of knee osteoarthritis
Assessing Trade-Offs in Large Marine Protected Areas
Large marine protected areas (LMPAs) are increasingly being established and have a high profile in marine conservation. LMPAs are expected to achieve multiple objectives, and because of their size are postulated to avoid trade-offs that are common in smaller MPAs. However, evaluations across multiple outcomes are lacking. We used a systematic approach to code several social and ecological outcomes of 12 LMPAs. We found evidence of three types of trade-offs: trade-offs between different ecological resources (supply trade-offs); trade-offs between ecological resource conditions and the well-being of resource users (supply-demand trade-offs); and trade-offs between the well-being outcomes of different resource users (demand trade-offs). We also found several divergent outcomes that were attributed to influences beyond the scope of the LMPA. We suggest that despite their size, trade-offs can develop in LMPAs and should be considered in planning and design. LMPAs may improve their performance across multiple social and ecological objectives if integrated with larger-scale conservation efforts. © 2018 Davies et al
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